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Emotional profile of female rats showing binge eating behavior
Physiology & Behavior 163 (2016) 136–143
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Emotional profile of female rats showing binge eating behavior Valentina Satta a, Maria Scherma a, Elisa Giunti a, Roberto Collu a, Liana Fattore b,c, Walter Fratta a,c, Paola Fadda a,c,⁎ a b c
Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, (CA), 09042, Italy Neuroscience Institute, Section of Cagliari, National Research Council, Monserrato, (CA), 09042, Italy Centre of Excellence “Neurobiology of Dependence”, University of Cagliari, Cagliari, Italy
H I G H L I G H T S • • • •
Binge eating behavior was induced in female rats by providing limited access to margarine. Emotional profile of rats were evaluated by mean of behavioral mazes. Bingeing rats were less anxious and depressed after margarine consumption We provide evidence of an altered emotional states in bingeing female rats.
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Article history: Received 22 February 2016 Received in revised form 18 April 2016 Accepted 10 May 2016 Available online 11 May 2016 Keywords: Binge eating disorder Food intake High fat diet Anxiety Depression Compulsive-like behavior
a b s t r a c t Binge eating disorder (BED) is characterized by uncontrolled consumption of a large amount of food in a brief period of time. A large body of evidence has shown that BED can be a chronic condition associated with elevated psychiatric comorbidity, including depression and anxiety, and compulsive behavior. In this study we used an animal model of BED in which binge eating behavior was induced in female rats by providing limited access to high fat diet (margarine) to investigate the emotional traits of bingeing animals before and after the binge-like consumption of margarine. Using the plus maze test to disclose a potential anxious phenotype, we found that bingeing rats are much more anxious before the access to margarine, and that this condition is significantly reduced after its consumption. Conversely, no difference was detected between bingeing rats in the marble burying test before and after access to margarine. Yet, the number of marbles buried by bingeing rats before margarine consumption was significantly higher than control groups thus suggesting a compulsive-like trait. In the forced swimming test, bingeing rats showed a decrease in depression-like behavior after the consumption of margarine. Altogether, our findings demonstrate the occurrence of an altered emotional state in female rats showing binge eating behavior. © 2016 Elsevier Inc. All rights reserved.
1. Introduction According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), binge eating disorder (BED) is now recognized as a specific eating disorder [1]. It is characterized by binge eating episodes, defined as rapid and excessive consumption of food in a short period of time, along with loss of control and psychological distress. Food consumed during binge episodes is typically highly palatable, with high fat or sugar content and consequently rich in calories. In BED, binge episodes are typically not associated with inappropriate compensatory behaviors (such as vomiting, excessive physical activity, ⁎ Corresponding author at: Department of Biomedical Science, Section of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria di Monserrato, 09042 Monserrato, (CA), Italy. E-mail address: [email protected] (P. Fadda).
http://dx.doi.org/10.1016/j.physbeh.2016.05.013 0031-9384/© 2016 Elsevier Inc. All rights reserved.
and laxative use) aimed to counteract the excessive intake of calories. Therefore, bingeing people incur a higher risk of weight gain which, in the majority of them (approximately 70%), leads to obesity [1–4]. BED has a high social impact. Epidemiological studies revealed that BED is the most widespread eating disorder with an estimated 1.9% lifetime prevalence in the general population [5]. Like other eating disorders, BED is more prevalent in females, with males representing 30– 40% of the cases [6]. BED can become a chronic disease characterized by frequent exacerbations or relapses and high psychiatric comorbidity [5,7,8]. A clear link between BED and psychiatric comorbidity is reported by several clinical studies showing that binge eaters have a significant higher rate of major depression [9] and anxiety disorders than people without BED [10–13]. Notably, individuals with psychiatric comorbidities may have a more severe form of BED [14]. It is well documented that binge eating episodes are maintained via negative reinforcement, such as reduction of
V. Satta et al. / Physiology & Behavior 163 (2016) 136–143
negative emotional states [15,16]. As reported by many binge eaters, ingestion of large amounts of food, especially highly palatable foods, during binge episodes produces an immediate feeling of well-being and reduces the negative emotional states present before overeating. This feeling of well-being is only temporary as negative states take over again after bingeing thus creating a vicious cycle [16–18]. Further, patients with BED showed increased food-related impulsivity in comparison with weight-matched and normal-weight controls, which may contribute to uncontrolled and excessive food intake and maintenance of binge eating behavior [19]. In order to understand the aberrant eating pattern underlying BED, animal models of binge eating behavior have been developed [20,21]. In fact, intermittent access to highly palatable food can induce compulsive overeating in rodents that remains stable over prolonged periods of time [22–24]. Similar to bingeing humans, animals consumed a large quantity of palatable food in the absence of hunger since they are never food deprived [25]. Although only partially, some of the psychological aspects of BED can be evaluated in animals by means of widely validated behavioral paradigms able to analyze anxiety- and depression like traits, social impairment and obsessive-compulsive behavior [26]. Using the limited access protocol in which binge-type eating is induced in female rats by providing sporadic and time-limited access to an optional source of dietary fat (margarine), this study aimed to characterize the neurobehavioral profile of binge rats before and after the binge-like margarine consumption, in order to make a comparison with the human condition. This characterization included tests of spontaneous locomotor activity, elevated plus-maze behavior (to detect anxiety), marble burying (index of compulsive-like behavior and/or anxiety-like behavior) and forced swimming test (to detect a depression-like phenotype). 2. Materials and methods 2.1. Animals Forty two female Sprague Dawley rats (Harlan Nossan, Udine, Italy) weighing 185–200 g at the start of the study (60–65 days old) were used in this study. Animals were individually housed in a climate-controlled animal room (21 ± 2 °C temperature; 60% humidity) under a reversed 12 h light/dark cycle (lights on 12:00 a.m.) with standard rat chow and water ad libitum. All experiments were approved by the local Animal Care Committee and carried out in strict accordance with the E.C. Regulations for Animal Use in Research (CEE No. 86/609). 2.2. Diets High-fat diet (Margarine, Gradina Unilever Italia Mkt.): 70% kcal from fat, b1% kcal from carbohydrate, containing 6.5 kcal/g. Standard rat chow (Safe, France): 3% kcal from fat, 61% kcal from carbohydrate, 16% kcal from protein, 0% moisture, containing 2.9 kcal/g.
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• Control (CTRL): chow and water were available ad libitum. Margarine was not provided at any time of the study. All rats were maintained on their respective diet protocol for the entire study. Margarine and/or standard chow consumed by each diet group were measured on Mondays, Wednesdays and Fridays (MWF) before and after the 2 h period access to margarine. As shown in Fig. 1, once binge-type eating behavior was stable (4th week) behavioral tests started and were completed within four weeks. 2.4. Behavioral tests Behavioral tests were performed 1.5 h before (pre-binge) and 1.5 h after (post-binge) the 2 h margarine access on Fridays. Animals from each diet group (N = 14 per diet group) were randomly assigned to two different groups to perform tests during the pre-binge (N = 7) and the post-binge phase (N = 7) and were maintained on their respective group for the entire study. Considering that margarine was provided 2 h prior to the start of the dark cycle, in the pre-binge phase, tests were carried out during the light cycle in a room illuminated by a neon lamp (50 Lux), while in the post-binge phase, tests were carried out during the dark cycle in a room dimly illuminated by a red lamp (3 Lux). 2.4.1. Spontaneous locomotor activity (LA) Apparatus and procedure were as described previously [28]. Rats were individually placed into the center of transparent Plexiglas cages (42 cm × 30 cm × 60 cm) fitted with two sets of 16 photocells located at right angles to each other, projecting horizontal infrared beams 2.5 cm apart and 4 cm above the cage floor and a further set of 16 horizontal beams which height could be adapted to the size of the animals. Cumulative horizontal and vertical movement counts were recorded for 30 min by Digiscan Animal Activity Analyser Software (Omnitech Eletronics, USA) and assessed in 10 min intervals. 2.4.2. Elevated plus maze (EPM) The apparatus consisted of two opposite closed (50 × 10 × 40 cm) and open (50 × 10 cm) arms forming a plus shaped maze. The structure was elevated to a height of 50 cm from the floor. All four arms were connected at right angle at a central area where animals were placed (facing an open arm) and were left free to explore the maze for 5 min (300 s). During a 5 min test period, the following behavioral measures were recorded: - number of open and closed arm entries - time spent in the open and closed arms. Closed arms entries were used as a measure of locomotor activity. The percentage (%) of time spent in the open arms [expressed as: time spent in open arms / total time(300 s) × 100] and the percentage (%) of open arms entries [expressed as: open-arms entries / total arm entries × 100] were used as anxiety measures.
2.3. Experimental procedures The general procedure was carried out as described previously [27]. After one week of adaptation, margarine was provided during a single overnight period to prevent neophobia. Rats were then matched by body weight and margarine intake and divided into three groups which correspond to the following diet conditions: • Low restriction (LR): chow and water were available ad libitum. In addition, animals were given 2 h (h) access to a separate bowl of margarine introduced into the home cage every day of the week. • High restriction (HR): chow and water were available ad libitum. In addition, animals were given 2 h access to a separate bowl of margarine introduced into the home cage on Mondays, Wednesdays and Fridays. Animals were given access to margarine in the light phase starting 2 h prior to the start of the dark cycle [27].
2.4.3. Marble burying test (MBT) The marble burying test was conducted according to Andersen and colleagues [29] with some modifications. Rats were individually placed in a transparent acrylic cage (54 × 20 × 34.5 cm), without food and water. Twenty-four clear glass marbles (1 cm diameter), distributed on top of 5-cm-deep fresh spruce wood bedding, were evenly spaced in six lines along the short wall of the cage. Individual subjects were placed in the test cage and their behavior was monitored for 30 min through an Any-Maze apparatus and video recorded by a camera placed 1.5 m above the cage. The number of marbles buried for at least 2/3 was counted by the experimenters and the results were expressed as the number of marbles covered by sawdust. New bedding was used for each animal, and marbles were cleaned with a 70% ethanol solution between animals.
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Fig. 1. Schematic representation of the experimental schedule.
2.4.4. Forced swim test (FST) The forced swim test, a behavioral test in which the animals are forced to swim without possibility of escaping [30], was carried out in two different days. On the first day, rats were placed to swim for 15 min (pre-test session) in a clear plastic cylinder (50 cm height, 25 cm diameter) filled with water (24 ± 1 °C) to a height of 30 cm. After 24 h, rats were tested again for 5 min under the same conditions (test session). Pretest and test sessions were video recorded (Any maze software) to quantify the following behavioral parameters: - immobility, defined as the time (sec) spent by the animal in a floating state, in absence of any active movement with the only exception of those necessary for keeping its head above the water to breath; - swimming, defined as the time (sec) spent in active horizontal swimming; - climbing, defined as the time (sec) spent in upward directed movements of the forepaws along the cylinder walls.
At the end of each swimming session, animals were dried and returned to home cages. 2.5. Statistical analyses Data from the induction of binge-type eating are expressed as mean kcal of margarine and chow (1-block week: MWF) ± SEM during the 2 h access period. Data were analyzed by two-way analysis of variance (ANOVA) for repeated measures with diet group and week as factors, and week as a repeated factor. Data from behavioral experiments are presented as mean ± SEM and were analyzed by two-way ANOVA analysis with the two factors being diet as a between-subjects factor and time as within-subjects factor (pre- and post-binge phase). Within each phase, the differences between diet groups were analyzed by two-way ANOVA (with the two factors being diet as a between-subjects factor and time (blocks of 10 min each) for locomotor activity) or by one-way ANOVA with diet as a between-subjects factor. Post-hoc comparisons, when appropriate, were performed by Newman-Keuls multiple comparison test or Bonferroni test. Finally, within each diet group, the unpaired Student's t-test was performed to verify whether the animals assigned to the two subgroups to perform behavioral tests during the pre-binge and the post-binge phase were significantly different from each other. In all cases, differences with a P value b 0.05 were considered significant. 3. Results 3.1. Induction of binge-type eating As expected [27], intermittent access to margarine leads HR group to consume a significantly higher amount of margarine than LR group during the three days of limited access. Two-way ANOVA showed significant diet × week interaction [F(7,182) = 2.73, P = 0.0102].
Specifically, margarine consumption in HR and LR groups became significantly different by the third week and remained stable throughout the duration of the study (post-hoc 3rd–8th week: P b 0.001) (see Fig. 2A). With respect to chow consumption during the 2 h limited access period, two-way ANOVA revealed a significant effect of diet group [F(2,273) = 12.84, P b 0.0001]. Subsequent individual one-way ANOVA within each week, showed that both LR and HR groups consumed significantly less chow than CTRL group [1st week: F(2,39) = 8.397, P = 0.0009, (P b 0.01, post hoc test); 2nd week: F(2,39) = 8.164, P = 0.0011, (P b 0.01, post hoc test); 3rd week F(2,39) = 3.849, P = 0.0298, (P b 0.05, post hoc test); 4th week F(2,39) = 3.369, P = 0.0447, (P b 0.05, post hoc test); 5th week F(2,39) = 5.381, P = 0.0091, (P b 0.05, post hoc test); 7th week F(2,39) = 4.935, P = 0.0123, (P b 0.05, post hoc test); 8th week F(2,39) = 6.338, P = 0.0041, (P b 0.01, post hoc test)](see Fig. 2B). When looking at the daily total intake of margarine and/or chow consumed by each diet group (Fig. 2C), two-way ANOVA detected a significant dietgroup × week interaction [F(14,273) = 2.01, P = 0.0170]. Post hoc analysis showed that HR group displayed higher daily total intake than LR and CTRL groups by the 2nd week of the study (2nd week, 3rd week, 4th week, 5th week , 6th week and 8th week: P b 0.001; 7th week: P b 0.01). With regard to the body weight, two-way ANOVA revealed a significant diet group x week interaction [F(14, 273) = 2.014, P = 0.0170]. Post hoc analysis indicated that HR group weighed more than CTRL group by the 5th week of the study (5th and 6th weeks: P b 0.05; 7th week P b 0.001; 8th week: P b 0.01). Yet, no difference between HR and LR groups as well as between CTRL and LR groups was detected (Fig. 2D). 3.2. Behavioral tests 3.2.1. Spontaneous locomotor activity (LA) Fig. 3 shows the general locomotor activity of the three experimental groups during the pre- and post-binge phases. On total horizontal beam breaks, two-way ANOVA revealed no significant effect of diet group [F (2.18) = 0.40, P = 0.6747] and time (pre- and post-binge phase) [F (1.18) = 0.03, P = 0.8540] as well as no significant effect of diet group × time (pre- and post-binge phase) interaction [F(2,18) = 0.92, P = 0.4166] (Fig. 3A). A similar scenario was observed on total vertical beam breaks: two-way ANOVA revealed no significant effect of diet group [F(2,18) = 0.47, P = 0.6327] and time (pre- and post-binge phase) [F(1,18) = 1.23, P = 0.2811] as well as no significant effect of diet group x time (pre- and post-binge phase) interaction [F(2,18) = 0.35, P = 0.7116] (Fig. 3B). These data suggested that all groups of animals had similar spontaneous locomotor activity and explorative behavior during the pre- and post-binge phases. The analysis of time course of data within each phase, showed only a significant effect of time on both horizontal (two-way ANOVA pre-binge: F(2,36) = 127.36, P b 0.0001; post-binge: F(2,36) = 137.74, P b 0.0001) and vertical beam breaks (two-way ANOVA pre-binge: F(2,36) = 26.13, P b 0.0001; post-binge: F(2,36) = 25.80, P b 0.0001) (Fig. 3C, D, E and F). This indicates that all three experimental groups animals habituated to the arenas over time and their overall activity decreased.
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Fig. 2. Induction of binge-type eating. Data are presented as mean Kcal (1-bar represents week: MWF) ± SEM of n = 14 animals per diet group. (A) Margarine intake: HR group (black bar) with limited access to margarine 3 days a week consumed more margarine than LR group (grey bar) with daily access to margarine (two way ANOVA: §P b 0.001 vs LR). (B) Chow intake: LR group and HR group consumed less chow than CTRL group (one way ANOVA: *P b 0.05 and #P b 0.01 vs CTRL). (C) Daily total intake: during the limited access HR group displayed higher total intake than LR and CTRL groups by the 2nd week of the study (two way ANOVA: 2nd–6th weeks and 8th week: §P b 0.001; 7th week: #P b 0.01). (D) Body weight: HR group weighed more than the CTRL group by the 5th week of the study (5th and 6th weeks: *P b 0.05; 7th week: §P b 0.001; 8th week: #P b 0.01). Not significant differences were found between HR and LR groups, nor between CTRL and LR groups.
3.2.2. Elevated plus maze (EPM) The entries in the close arms during the pre- and post-binge phases of the three experimental groups are presented in Fig. 4A. Two-way ANOVA revealed no significant effect of diet group [F(2,18) = 0.06, P = 0.9445] and time (pre- and post-binge phase) [F(1,18) = 0.01, P = 0.9642] as well as no significant effect of diet group x time (preand post-binge phase) interaction [F(2,18) = 0.40, P = 0.6768]. Considering the % of time spent in open arms, two-way ANOVA revealed a significant effect of diet group [F(2,18) = 8.92, P = 0.0020] and time (preand post-binge phase) [F(1,18) = 4.43, P = 0.0493], and no group × day interaction [F(2,18) = 0.06, P = 0.9445] (Fig. 4B). Subsequent individual one-way ANOVA within each phase, showed a significant diet effect between subjects [pre-binge: F(2,18) = 4.446, P = 0.0270; post-binge [F(2,18) = 7.357, P = 0.0042]. Post hoc analysis of data showed that, during the pre-binge phase, LR group spent significantly more time in the open-arms compared to both CTRL and HR groups (P b 0.05) but did not detect any difference between CTRL and HR groups. Conversely, in the post-binge phase, post hoc analysis of data only showed that the time spent in open arms by LR group was significantly higher as compared with the CTRL group (P b 0.01). A further analysis of data, highlighted that in the post-binge phase the HR group spent more time in the open arms compared to CTRL [unpaired Student's t-test: t(12) = 2.604 P = 0.0231]. Moreover, the analysis of the behavior of HR group in the two different phases, revealed that the rats spent significantly more time in the open arms during the post-binge phase compared to pre-binge phase [unpaired Student's t-test: t(12) = 3.621,
P = 0.0035]. As regard the % of open arms entries, two-way ANOVA analysis of data revealed a significant effect of diet group [F(2,18) = 5.84, P = 0.0111] and time (pre- and post-binge phase) [F(1,18) = 7.87, P = 0.0117], and no group × day interaction [F(2,18) = 0.27, P = 0.7656] (Fig. 4C). Individual one-way ANOVA within each phase showed a significant diet effect between subjects during the pre-binge [F(2,18) = 4.015, P = 0.0361]: post hoc analysis revealed that LR group made significantly more entries compared to CTRL and HR groups (P b 0.05). On the contrary, in the post-binge phase, individual one-way ANOVA did not detected significant difference between diet groups [F(2,18) = 1.760, P = 0.2004]. Within the HR group, the unpaired Student's t-test showed a significant increase in the number of entries in the open arms during the post-binge phase compared to pre-binge phase [t(12) = 2.397, P = 0.0337]. 3.2.3. Marble burying test (MB) Data from marble burying test are illustrated in Fig. 5. Two-way ANOVA analysis of the number of buried marbles revealed a significant effect of diet group [F(2,18) = 7.10, P = 0.0053] and time (pre- and post-binge phase) [F(1,18) = 39.35, P b 0.0001], and no group × day interaction [F(2,18) = 2.32, P = 0.1270]. During the pre-binge phase, subsequent individual one-way ANOVA revealed significant differences between diet groups [F(2,18) = 12.38, P = 0.0004]. Post-hoc analysis showed that the number of marbles buried by the HR group was significantly higher compared to both CTRL and LR groups (P b 0.001). On the other hand, during the post-binge phase, no significant differences were
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Fig. 3. Evaluation of spontaneous locomotor activity. Data are presented as mean ± SEM of N = 7 animals per diet group. (A) Total horizontal beam breaks, and (B) Total vertical beam breaks were analyzed during the 30 min session, in the pre-binge (white bars) and post-binge (black bars) phases. There were no significant differences between groups. (C) Time course of horizontal beam breaks, and (D) vertical beam breaks in the pre-binge phase. (E) Time course of horizontal beam breaks, and (F) vertical beam breaks in the post-binge phase. Data were analyzed in 10 min-blocks. Not significant differences were found between diet groups.
found in the number of marbles buried between the three experimental groups [one-way ANOVA: F(2,18) = 0.0565, P = 0.6396]. Within each experimental group, the unpaired Student's t-test showed that CTRL and LR groups buried a significantly higher number of marbles during the post-binge phase compared to pre-binge phase [unpaired Student's t-test, CTRL group: t(12) = 4.163, P b 0.01; LR group t(12) = 4.506,
P b 0.01]. No significant difference in the HR group was found when comparing pre and post-binge phases [t(12) = 2.085, P = 0.0589]. 3.2.4. Forced swim test (FST) In the FST, regarding the duration of immobility, two-way ANOVA revealed significant effect of time (pre- and post-binge phase)
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Fig. 4. Evaluation of anxiety-like behavior analyzed by elevated plus maze. Data are presented as mean ± SEM of N = 7 animals per diet group. (A) Number of closed-arm entries: there were no significant differences between groups. (B) % of time spent in open arms: LR group spent significantly more time in the open-arms compared to both CTRL and HR groups during the pre-binge (white bars) (one way ANOVA: *P b 0.05) and compared to CTRL group during the post-binge (black bars) (one way ANOVA: #P b 0.01); HR group spent significantly more time in the open-arms during the post-binge (black bars) compared to CTRL group (unpaired Student's t-test: φP b 0.05); HR group spent significantly more time in the open-arms during the post-binge (black bars) compared to the pre-binge (white bars) (unpaired Student's t-test: δP b 0.001). (C) % of open arm entries: LR group made significantly more entries compared with CTRL and HR groups during the pre-binge (white bars) (one way ANOVA: *P b 0.05); HR showed a significant increase in the number of entries in the open arms during the post-binge (black bars) compared to pre-binge (white bars) (unpaired Student's t-test: θP b 0.05).
[F(1,18) = 17.86, P = 0.0005] and no significant effect of diet group [F(2,18) = 0.35, P = 0.7199] and of diet group × time (pre- and postbinge phase) interaction [F(2,18) = 1.40, P = 0.2716] (Fig. 6A). Indeed, subsequent individual one-way ANOVA within each phase did not detected significant differences between the experimental groups during pre-binge and post-binge phases on this parameter analyzed [prebinge phase: immobility F(2,18) = 0.8970, P = 0.4253; post-binge phase: immobility F(2,18) = 0.6045]. However, intra-group analysis of immobility behavior during the two phases revealed that both LR and HR groups significantly decreased time spent immobility during the post-binge phase compared to the pre-binge phase (unpaired Student's t-test, LR: t(12) = 2.190, P b 0.05; HR: t(12) = 3.582, P b 0.01) (Fig.6A). Considering the swimming behavior, two-way ANOVA revealed no significant effect of diet group [F(2,18) = 1.20, P = 0.3239] and time (pre- and post-binge phase) [F(1,18) = 0.90, P = 0.3554] as well as no significant effect of diet group x time (preand post-binge phase) interaction [F(2,18) = 0.76, P = 0.4824] (Fig. 6B). Finally, two-way ANOVA analysis of climbing revealed significant effect of time (pre- and post-binge phase) [F(1,18) = 19.10, P = 0.0004] and no significant effect of diet group [F(2,18) = 0.20, P = 0.8221] and of diet group × time (pre- and post-binge phase) interaction [F(2,18) = 1.50, P = 0.2499] (Fig. 6C). Intra-group analysis of climbing behavior during the two phases revealed that HR group significantly increased time spent in climbing during the post-binge compared to the pre-binge phase (unpaired Student's t-test: t(12) =
Fig. 5. Evaluation of obsessive-compulsive-like behavior analyzed by marble burying test. Data are presented as mean ± SEM of N = 7 animals per diet group. The number of marbles buried by the HR group was significantly higher compared to both CTRL and LR groups during the pre-binge phase (white bars) (one way ANOVA: §P b 0.001). CTRL and LR group significantly increase the number of marbles during the post-binge (black bars) compared to the pre-binge (white bars) (unpaired Student's t test #P b 0.01).
3.487, P b 0.01). No significant difference in the CTRL and LR groups was found when comparing pre and post-binge phases. 4. Discussion Binge eaters typically displayed altered emotional states when approaching food or soon after its ingestion. The goal of the present study was to characterize the emotional behavior profile of bingeing rats by evaluating depression- and anxiety-like states and obsessive/ compulsive traits before and after access to palatable food. We used a validated animal model of BED, in which binge eating behavior is induced by providing an intermittent (3 days/week) and limited (2 h) access to a palatable food (vegetable margarine) in no food deprived rats (HR group) [22,27]. We confirmed that in HR group intake of margarine escalates over several weeks that of animals with continuous access to margarine (LR group), and that this excessive intake remains stable for the entire duration of the experiment. No difference was found in the locomotor activity when both LR and HR groups were compared to the CTRL group during the pre and postbinge phases as well as within each group in the two phases considered. This suggests that all the group differences observed in the behavioral tests described below were not due to changes in the locomotor activity. The EPM test, commonly used to disclose a potential anxious phenotype, revealed that the HR group displayed significantly higher levels of anxiety-like behavior in the pre-binge phase compared to the postbinge phase. The fact that this condition is reduced after the consumption of margarine suggests that this palatable food may have had an anxiolytic effect. The HR group had access to margarine on Mondays, Wednesdays and Fridays while the LR group, which was housed in the same room, had access to this palatable food every day. This means that in the days of no access to margarine, HR group could only smell it. This condition could be considered very stressful and leads animals showing binge eating behavior to increase their levels of anxiety until they have again access to the highly palatable food. In agreement, Cifani and colleagues [31], showed that the exposure to a familiar palatable food, in conditions in which the animal can see and smell it but cannot get access to it, is a stressful determinant for the rat. Also, it has been demonstrated that consumption of palatable foods rich in sugar and fat is considered to lower the stress response [32,33]. On the other hand, the fact that the LR group shows a less anxious behavior in both phases is in agreement with previous studies that showed that rats subjected continuously to a high fat diet highlighted less anxiety than rats fed a low fat diet or chow in the EPM [34,35]. The effect of a high fat diet on anxiety seems to be related to the capacity of regulate the hypothalamic-pituitary adrenal (HPA) axis activity [33,35,36]. In agreement with Blasio et al. [37], EPM data also showed that HR group did not differ
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Fig. 6. Evaluation of depressive-like behavior analyzed by forced swim test. Data are presented as mean ± SEM of N = 7 animals per diet group. (A) time (s) spent in immobility: intragroup analysis showed that during the two phases both LR and HR groups significantly decreased the immobility time during the post-binge phase (black bars) compared to the pre-binge phase (white bars) (unpaired Student's t-test: δP b 0.05; #P b 0.01). (B) time (s) spent in swimming: there were no significant differences between groups. (C) time (s) spent in climbing: HR showed a significant increase in the time spent in climbing during the post-binge (black bars) compared to pre-binge (white bars) (unpaired Student's t-test: θP b 0.05).
from CTRL in the percent of time spent in the open arms during the prebinge phase, when withdrawn from the palatable food. In contrast, Cottone et al. [38,39] demonstrated that female rats that intermittently had access to a highly palatable diet showed a significant anxiogeniclike behavior during withdrawal from it. This discrepancy could be due to the different protocol used to induce the binge eating behavior (rat strains, diets, post-withdrawal time points) and/or to the fact that under our conditions, the % of open arm time is very low in both CTRL and HR groups, which may prevent to detect an anxiogenic-like behavior in the binge group. In the forced swim test, the most widely used test of antidepressant action [40], we found that in the HR group the immobility time was significantly reduced in the post-binge phase compared to pre-binge indicating a reduction of the depression-like state. The same effect on the immobility duration has been observed in the LR group emphasizing a consistent antidepressant-like effect of margarine. On the contrary, no difference in this parameter has been detected in the CTRL group, in which margarine was not provided at any time. Moreover, only the HR group showed a significant increase in the climbing behavior. The capacity to reduce immobility and selectively increase climbing without affecting swimming appear to be typical of antidepressants such as desipramine, a selective norepinephrine reuptake inhibitor [41]. In agreement with our data, it has been recently demonstrated that withdrawal from chronic, intermittent access to highly palatable food induce signs of depression-like behaviors in rats and this condition was abolished by renewing access to the highly palatable diet [42]. Moreover, highfat diet selectively protected against the depressive-like effects induced by unpredictable chronic psychosocial stress in mice [43]. Lastly, longterm postpartum anxiety and depression-like behavior in mother rats subjected to maternal separation are ameliorated by palatable high fat diet [44]. On the other hand, other studies demonstrated that the chronic consumption of high-fat food induced obesity is associated with a depressive-like phenotype [45,46]. It is important to emphasize that the contrasting findings in these studies might be due to species related differences (mice vs rats) or to procedural differences. In the marble burying test, used as a model of obsessive compulsive behavior [47], the number of marbles buried by the HR group in the prebinge phase was significantly higher compared to CTRL and LR groups suggesting a compulsive-like trait. It is well documented that intermittent and limited access to a palatable food might lead to withdrawal symptoms, when the palatable food is not available, that is important for the induction and maintenance of the binge eating behavior [23, 24]. This emotional negative state may cause the occurrence of compulsive-like trait similar to what has been observed with drugs of abuse [23, 24,48–49]. Indeed, it has been demonstrated that rats with intermittent access to preferred food, showed a compulsive-like behavior since they persisted to accept punishments when access to preferred food pellets
was paired with mild electrical foot shocks [23]. Thus, our data on marble test during the pre-binge phase can be interpreted as a symptom of withdrawal from the palatable diet since margarine access for the binge group was every 48h during the week. However, in the post-binge phase, no difference was found between the three experimental groups. It should be noted that, the number of marbles buried by the HR group was similar to that of the pre-binge phase, demonstrating that a compulsive-like trait is still present after the consumption of margarine. On the contrary, both CTRL and LR groups showed a significant increase in the number of marble buried as compared to the behavior in the prebinge phase. As assessed in both EPM and open filed test, we did not find differences in general locomotor activity between the three experimental groups, thus it is unlikely that changes in locomotor activity due to the different experimental conditions in the two phases, could have contributed in any meaningful way. However, differences in testing room conditions must be considered. All together our findings provide evidence of an emotional state in the HR group that is attenuated after the consumption of margarine in a manner similar to the human condition. U.S. Food and Drug Administration (FDA) has not yet approved an official drug for the treatment of BED [50]. This eating disorder requires a multidisciplinary approach to analyze various aspects: psychotherapies (cognitive behavior therapy (CBT), interpersonal therapy and self-help strategies) that are effective for reducing binge eating episodes, but not all patients respond adequately, and pharmacotherapy which must take account of the common comorbidities of binge eating, such as depression and anxiety [50]. Our results clearly suggest that the limited access model can mimic several translational aspects of BED such as anxiety and depression and can be used in the evaluation of potential preclinical therapeutic interventions aimed to achieve therapeutics goals. Conflict of interest All authors declare no conflicts of interest. Acknowledgements This work was financially supported by Grant from the Italian Ministry of University and Scientific Research (FAR DM28141 del 21/11/2005 and Progetti di Ricerca a rilevante InteresseNazionale, PRIN 2010), by Fondazione Banco di Sardegna (Prot.U627.2013/AI.551MGB) and by Department of Biomedical Sciences Project (RICDIP_2012_Fratta_01), University of Cagliari. Valentina Satta was supported by Programma Master and Back (Percorsi di Rientro, edizione 2010/2011, Codice: PRR-MABA2011-19275), Regione Autonoma della Sardegna.
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References [1] American Psychiatric Association (APA), Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5™), American Psychiatric Association, Arlington, VA, 2013. [2] R.L. Spitzer, S. Yanovski, T. Wadden, R. Wing, M.D. Marcus, A. Stunkard, et al., Binge eating disorder: its further validation in a multisite study, Int. J. Eat. Disord. 13 (1993) 137–153. [3] Z. Cooper, C.G. Fairburn, Refining the definition of binge eating disorder and nonpurging bulimia nervosa, Int. J. Eat. Disord. 34 (2003) 89–95. [4] R.A. Grucza, T.R. Przybeck, C.R. Cloninger, Prevalence and correlates of binge eating disorder in a community sample, Compr. Psychiatry 48 (2007) 124–131. [5] R.C. Kessler, P.A. Berglund, W.T. Chiu, A.C. Deitz, J.I. Hudson, V. Shahly, et al., The prevalence and correlates of binge eating disorder in the World Health Organization World Mental Health Surveys, Biol. Psychiatry 73 (2013) 904–914. [6] J.I. Hudson, E. Hiripi, H.G. Jr Pope, R.C. Kessler, The prevalence and correlates of eating disorders in the National Comorbidity Survey Replication, Biol. Psychiatry 61 (2007) 348–358. [7] C.M. Grilo, M.A. White, R.M. Masheb, DSM-IV psychiatric disorder comorbidity and its correlates in binge eating disorder, Int. J. Eat. Disord. 42 (2009) 228–234. [8] D.V. Sheehan, B.K. Herman, The psychological and medical factors associated with untreated binge eating disorder, Prim. Care Companion CNS Disord. 17 (2015). [9] C.F. Telch, E. Stice, Psychiatric comorbidity in women with binge eating disorder: prevalence rates from a non-treatment-seeking sample, J. Consult. Clin. Psychol. 66 (1998) 768–776. [10] S.Z. Yanovski, J.E. Nelson, B.K. Dubbert, R.L. Spitzer, Association of binge eating disorder and psychiatric comorbidity in obese subjects, Am. J. Psychiatry 150 (1993) 1472–1479. [11] D.E. Wilfley, M.A. Friedman, J.Z. Dounchis, R.I. Stein, R.R. Welch, S.A. Ball, Comorbid psychopathology in binge eating disorder: relation to eating disorder severity at baseline and following treatment, J. Consult. Clin. Psychol. 68 (2000) 641–649. [12] K.N. Javaras, H.G. Pope, J.K. Lalonde, J.L. Roberts, Y.I. Nillni, N.M. Laird, et al., Co-occurrence of binge eating disorder with psychiatric and medical disorders, J. Clin. Psychiatry 69 (2008) 266–273. [13] R.E. Peterson, S.J. Latendresse, L.T. Bartholome, C.S. Warren, N.C. Raymond, Binge eating disorder mediates links between symptoms of depression, anxiety, and caloric intake in overweight and obese women, J. Obes. 2012 (2012) 407103. [14] C.B. Peterson, K.B. Miller, S.J. Crow, P. Thuras, J.E. Mitchell, Subtypes of binge eating disorder based on psychiatric history, Int. J. Eat. Disord. 38 (2005) 273–276. [15] R.H. Striegel-Moore, F.A. Dohm, H.C. Kraemer, G.B. Schreiber, C.B. Taylor, S.R. Daniels, Risk factors for binge-eating disorders: an exploratory study, Int. J. Eat. Disord. 40 (2007) 481–487. [16] K.P. De Young, J.M. Lavender, S.A. Wonderlich, R.D. Crosby, S.G. Engel, J.E. Mitchell, et al., Moderators of post-binge eating negative emotion in eating disorders, J. Psychiatr. Res. 47 (2013) 323–338. [17] E.L. Gibson, The psychobiology of comfort eating: implications for neuropharmacological interventions, Behav. Pharmacol. 23 (2012) 442–460. [18] P. Monteleone, M. Maj, Dysfunctions of leptin, ghrelin, BDNF and endocannabinoids in eating disorders: beyond the homeostatic control of food intake, Psychoneuroendocrinology 38 (2013) 312–330. [19] K. Schag, M. Teufel, F. Junne, H. Preissl, M. Hautzinger, S. Zipfel, K.E. Giel, Impulsivity in binge eating disorder: food cues elicit increased reward responses and disinhibition, PLoS One 8 (2013) 76542. [20] R.L. Corwin, N.M. Avena, M.M. Boggiano, Feeding and reward: perspectives from three rat models of binge eating, Physiol. Behav. 104 (2011) 87–97. [21] S.F. Kim, Animal models of eating disorders, Neuroscience 211 (2012) 2–12. [22] R.L. Corwin, A. Buda-Levin, Behavioral models of binge-type eating, Physiol. Behav. 82 (2004) 123–130. [23] A. Rossetti, G. Spena, O. Halfon, B. Boutrel, Evidence for a compulsive-like behavior in rats exposed to alternate access to highly preferred palatable food, Addict. Biol. 19 (2014) 975–985. [24] R. Dore, M. Valenza, X. Wang, K.C. Rice, V. Sabino, P. Cottone, The inverse agonist of CB1 receptor SR141716 blocks compulsive eating of palatable food, Addict. Biol. 19 (2014) 849–861. [25] M.D. Marcus, M.A. Kalarchian, Binge eating in children and adolescents, Int. J. Eat. Disord. 34 (2003) 47–57. [26] S. Hancock, M.C. Olmstead, Animal model of eating disorder, animal models of drug addiction, Neuromethods 53 (2011) 207–234.
143
[27] M. Scherma, L. Fattore, V. Satta, F. Businco, B. Pigliacampo, S.R. Goldberg, et al., Pharmacological modulation of the endocannabinoid signalling alters binge-type eating behaviour in female rats, Br. J. Pharmacol. 169 (2013) 820–833. [28] M.S. Spano, L. Fattore, F. Cadeddu, W. Fratta, P. Fadda, Chronic cannabinoid exposure reduces phencyclidine-induced schizophrenia-like positive symptoms in adult rats, Psychopharmacology 225 (2013) 531–542. [29] S. Andersen, E. Greene-Colozzi, K.C. Sonntag, A novel, multiple symptom model of obsessive-compulsive like behaviours in animals, Biol. Psychiatry 68 (2010) 741–747. [30] R.D. Porsolt, G. Anton, N. Blavet, M. Jalfre, Behavioural despair in rats: a new model sensitive to antidepressant treatments, Eur. J. Pharmacol. 47 (1978) 379–391. [31] C. Cifani, C. Polidori, S. Melotto, R. Ciccocioppo, M. Massi, A preclinical model of binge eating elicited by yo-yo dieting and stressful exposure to food: effect of sibutramine, fluoxetine, topiramate, and midazolam, Psychopharmacology 204 (2009) 113–125. [32] M.F. Dallman, Stress-induced obesity and the emotional nervous system, Trends Endocrinol. Metab. 21 (2010) 159–165. [33] N. Pecoraro, F. Reyes, F. Gomez, A. Bhargava, M.F. Dallman, Chronic stress promotes palatable feeding, which reduces signs of stress: feed forward and feedback effects of chronic stress, Endocrinology 145 (2004) 3754–3762. [34] A. Prasad, C. Prasad, Short-term consumption of a diet rich in fat decreases anxiety response in adult male rats, Physiol. Behav. 60 (1996) 1039–1042. [35] A.D. McNeilly, C.A. Stewart, C. Sutherland, D.J. Balfour, High fat feeding is associated with stimulation of the hypothalamic-pituitary-adrenal axis and reduced anxiety in the rat, Psychoneuroendocrinology 52 (2015) 272–280. [36] M.F. Dallman, N. Pecoraro, S.F. Akana, S.E. La Fleur, F. Gomez, H. Houshyar, et al., Chronic stress and obesity: a new view of ‘comfort food’, Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 11696–11701. [37] A. Blasio, K.C. Rice, V. Sabino, P. Cottone, Characterization of a shortened model of diet alternation in female rats: effects of the CB1 receptor antagonist rimonabant on food intake and anxiety-like behavior, Behav. Pharmacol. 25 (2014) 609–617. [38] P. Cottone, V. Sabino, M. Roberto, M. Bajo, L. Pockros, J.B. Frihauf, et al., CRF system recruitment mediates dark side of compulsive eating, Proc. Natl. Acad. Sci. U. S. A. 106 (2009) 20016–20020. [39] P. Cottone, V. Sabino, L. Steardo, E.P. Zorrilla, Consummatory, anxiety-related and metabolic adaptations in female rats with alternating access to preferred food, Psychoneuroendocrinology 2009 (34) (2009) 38–49. [40] V. Krishnan, E.J. Nestler, Linking molecules to mood: new insight into the biology of depression, Am. J. Psychiatry 167 (2010) 1305–1320. [41] J.F. Cryan, R.J. Valentino, I. Lucki, Assessing substrates underlying the behavioral effects of antidepressants using the modified rat forced swimming test, Neurosci. Biobehav. Rev. 29 (2005) 547–569. [42] A. Iemolo, M. Valenza, L. Tozier, C.M. Knapp, C. Kornetsky, L. Steardo, et al., Withdrawal from chronic, intermittent access to a highly palatable food induces depressive-like behavior in compulsive eating rats, Behav. Pharmacol. 23 (2012) 593–602. [43] B.C. Finger, T.G. Dinan, J.F. Cryan, High-fat diet selectively protects against the effects of chronic social stress in the mouse, Neuroscience 192 (2011) 351–360. [44] J. Maniam, M.J. Morris, Long-term postpartum anxiety and depression-like behavior in mother rats subjected to maternal separation are ameliorated by palatable high fat diet, Behav. Brain Res. 208 (2010) 72–79. [45] S. Sharma, S. Fulton, Diet-induced obesity promotes depressive-like behaviour that is associated with neural adaptations in brain reward circuitry, Int. J. Obes. 37 (2013) 382–389. [46] S. Sharma, M.F. Fernandes, S. Fulton, Adaptations in brain reward circuitry underlie palatable food cravings and anxiety induced by high-fat diet withdrawal, Int. J. Obes. 37 (2013) 1183–1191. [47] A. Woods-Kettelberger, S. Kongsamut, C.P. Smith, J.T. Winslow, R. Corbett, Animal models with potential applications for screening compounds for the treatment of obsessive-compulsive disorder, Expert Opin. Investig. Drugs 6 (1997) 1369–1381. [48] C. Colantuoni, P. Rada, J. McCarthy, C. Patten, N.M. Avena, A. Chadeayne, B.G. Hoebel, Evidence that intermittent, excessive sugar intake causes endogenous opioid dependence, Obes. Res. 10 (2002) 478–488. [49] C.H. Wideman, G.R. Nadzam, H.M. Murphy, Implications of an animal model of sugar addiction, withdrawal and relapse for human health, Nutr. Neurosci. 8 (2005) 269–276. [50] S.L. McElroy, A.I. Guerdjikova, N. Mori, A.M. O'Melia, Current pharmacotherapy options for bulimia nervosa and binge eating disorder, Expert. Opin. Pharmacother. 13 (2012) 2015–2026.
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Physiology & Behavior journal homepage: www.elsevier.com/locate/phb
Emotional profile of female rats showing binge eating behavior Valentina Satta a, Maria Scherma a, Elisa Giunti a, Roberto Collu a, Liana Fattore b,c, Walter Fratta a,c, Paola Fadda a,c,⁎ a b c
Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato, (CA), 09042, Italy Neuroscience Institute, Section of Cagliari, National Research Council, Monserrato, (CA), 09042, Italy Centre of Excellence “Neurobiology of Dependence”, University of Cagliari, Cagliari, Italy
H I G H L I G H T S • • • •
Binge eating behavior was induced in female rats by providing limited access to margarine. Emotional profile of rats were evaluated by mean of behavioral mazes. Bingeing rats were less anxious and depressed after margarine consumption We provide evidence of an altered emotional states in bingeing female rats.
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Article history: Received 22 February 2016 Received in revised form 18 April 2016 Accepted 10 May 2016 Available online 11 May 2016 Keywords: Binge eating disorder Food intake High fat diet Anxiety Depression Compulsive-like behavior
a b s t r a c t Binge eating disorder (BED) is characterized by uncontrolled consumption of a large amount of food in a brief period of time. A large body of evidence has shown that BED can be a chronic condition associated with elevated psychiatric comorbidity, including depression and anxiety, and compulsive behavior. In this study we used an animal model of BED in which binge eating behavior was induced in female rats by providing limited access to high fat diet (margarine) to investigate the emotional traits of bingeing animals before and after the binge-like consumption of margarine. Using the plus maze test to disclose a potential anxious phenotype, we found that bingeing rats are much more anxious before the access to margarine, and that this condition is significantly reduced after its consumption. Conversely, no difference was detected between bingeing rats in the marble burying test before and after access to margarine. Yet, the number of marbles buried by bingeing rats before margarine consumption was significantly higher than control groups thus suggesting a compulsive-like trait. In the forced swimming test, bingeing rats showed a decrease in depression-like behavior after the consumption of margarine. Altogether, our findings demonstrate the occurrence of an altered emotional state in female rats showing binge eating behavior. © 2016 Elsevier Inc. All rights reserved.
1. Introduction According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), binge eating disorder (BED) is now recognized as a specific eating disorder [1]. It is characterized by binge eating episodes, defined as rapid and excessive consumption of food in a short period of time, along with loss of control and psychological distress. Food consumed during binge episodes is typically highly palatable, with high fat or sugar content and consequently rich in calories. In BED, binge episodes are typically not associated with inappropriate compensatory behaviors (such as vomiting, excessive physical activity, ⁎ Corresponding author at: Department of Biomedical Science, Section of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria di Monserrato, 09042 Monserrato, (CA), Italy. E-mail address: [email protected] (P. Fadda).
http://dx.doi.org/10.1016/j.physbeh.2016.05.013 0031-9384/© 2016 Elsevier Inc. All rights reserved.
and laxative use) aimed to counteract the excessive intake of calories. Therefore, bingeing people incur a higher risk of weight gain which, in the majority of them (approximately 70%), leads to obesity [1–4]. BED has a high social impact. Epidemiological studies revealed that BED is the most widespread eating disorder with an estimated 1.9% lifetime prevalence in the general population [5]. Like other eating disorders, BED is more prevalent in females, with males representing 30– 40% of the cases [6]. BED can become a chronic disease characterized by frequent exacerbations or relapses and high psychiatric comorbidity [5,7,8]. A clear link between BED and psychiatric comorbidity is reported by several clinical studies showing that binge eaters have a significant higher rate of major depression [9] and anxiety disorders than people without BED [10–13]. Notably, individuals with psychiatric comorbidities may have a more severe form of BED [14]. It is well documented that binge eating episodes are maintained via negative reinforcement, such as reduction of
V. Satta et al. / Physiology & Behavior 163 (2016) 136–143
negative emotional states [15,16]. As reported by many binge eaters, ingestion of large amounts of food, especially highly palatable foods, during binge episodes produces an immediate feeling of well-being and reduces the negative emotional states present before overeating. This feeling of well-being is only temporary as negative states take over again after bingeing thus creating a vicious cycle [16–18]. Further, patients with BED showed increased food-related impulsivity in comparison with weight-matched and normal-weight controls, which may contribute to uncontrolled and excessive food intake and maintenance of binge eating behavior [19]. In order to understand the aberrant eating pattern underlying BED, animal models of binge eating behavior have been developed [20,21]. In fact, intermittent access to highly palatable food can induce compulsive overeating in rodents that remains stable over prolonged periods of time [22–24]. Similar to bingeing humans, animals consumed a large quantity of palatable food in the absence of hunger since they are never food deprived [25]. Although only partially, some of the psychological aspects of BED can be evaluated in animals by means of widely validated behavioral paradigms able to analyze anxiety- and depression like traits, social impairment and obsessive-compulsive behavior [26]. Using the limited access protocol in which binge-type eating is induced in female rats by providing sporadic and time-limited access to an optional source of dietary fat (margarine), this study aimed to characterize the neurobehavioral profile of binge rats before and after the binge-like margarine consumption, in order to make a comparison with the human condition. This characterization included tests of spontaneous locomotor activity, elevated plus-maze behavior (to detect anxiety), marble burying (index of compulsive-like behavior and/or anxiety-like behavior) and forced swimming test (to detect a depression-like phenotype). 2. Materials and methods 2.1. Animals Forty two female Sprague Dawley rats (Harlan Nossan, Udine, Italy) weighing 185–200 g at the start of the study (60–65 days old) were used in this study. Animals were individually housed in a climate-controlled animal room (21 ± 2 °C temperature; 60% humidity) under a reversed 12 h light/dark cycle (lights on 12:00 a.m.) with standard rat chow and water ad libitum. All experiments were approved by the local Animal Care Committee and carried out in strict accordance with the E.C. Regulations for Animal Use in Research (CEE No. 86/609). 2.2. Diets High-fat diet (Margarine, Gradina Unilever Italia Mkt.): 70% kcal from fat, b1% kcal from carbohydrate, containing 6.5 kcal/g. Standard rat chow (Safe, France): 3% kcal from fat, 61% kcal from carbohydrate, 16% kcal from protein, 0% moisture, containing 2.9 kcal/g.
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• Control (CTRL): chow and water were available ad libitum. Margarine was not provided at any time of the study. All rats were maintained on their respective diet protocol for the entire study. Margarine and/or standard chow consumed by each diet group were measured on Mondays, Wednesdays and Fridays (MWF) before and after the 2 h period access to margarine. As shown in Fig. 1, once binge-type eating behavior was stable (4th week) behavioral tests started and were completed within four weeks. 2.4. Behavioral tests Behavioral tests were performed 1.5 h before (pre-binge) and 1.5 h after (post-binge) the 2 h margarine access on Fridays. Animals from each diet group (N = 14 per diet group) were randomly assigned to two different groups to perform tests during the pre-binge (N = 7) and the post-binge phase (N = 7) and were maintained on their respective group for the entire study. Considering that margarine was provided 2 h prior to the start of the dark cycle, in the pre-binge phase, tests were carried out during the light cycle in a room illuminated by a neon lamp (50 Lux), while in the post-binge phase, tests were carried out during the dark cycle in a room dimly illuminated by a red lamp (3 Lux). 2.4.1. Spontaneous locomotor activity (LA) Apparatus and procedure were as described previously [28]. Rats were individually placed into the center of transparent Plexiglas cages (42 cm × 30 cm × 60 cm) fitted with two sets of 16 photocells located at right angles to each other, projecting horizontal infrared beams 2.5 cm apart and 4 cm above the cage floor and a further set of 16 horizontal beams which height could be adapted to the size of the animals. Cumulative horizontal and vertical movement counts were recorded for 30 min by Digiscan Animal Activity Analyser Software (Omnitech Eletronics, USA) and assessed in 10 min intervals. 2.4.2. Elevated plus maze (EPM) The apparatus consisted of two opposite closed (50 × 10 × 40 cm) and open (50 × 10 cm) arms forming a plus shaped maze. The structure was elevated to a height of 50 cm from the floor. All four arms were connected at right angle at a central area where animals were placed (facing an open arm) and were left free to explore the maze for 5 min (300 s). During a 5 min test period, the following behavioral measures were recorded: - number of open and closed arm entries - time spent in the open and closed arms. Closed arms entries were used as a measure of locomotor activity. The percentage (%) of time spent in the open arms [expressed as: time spent in open arms / total time(300 s) × 100] and the percentage (%) of open arms entries [expressed as: open-arms entries / total arm entries × 100] were used as anxiety measures.
2.3. Experimental procedures The general procedure was carried out as described previously [27]. After one week of adaptation, margarine was provided during a single overnight period to prevent neophobia. Rats were then matched by body weight and margarine intake and divided into three groups which correspond to the following diet conditions: • Low restriction (LR): chow and water were available ad libitum. In addition, animals were given 2 h (h) access to a separate bowl of margarine introduced into the home cage every day of the week. • High restriction (HR): chow and water were available ad libitum. In addition, animals were given 2 h access to a separate bowl of margarine introduced into the home cage on Mondays, Wednesdays and Fridays. Animals were given access to margarine in the light phase starting 2 h prior to the start of the dark cycle [27].
2.4.3. Marble burying test (MBT) The marble burying test was conducted according to Andersen and colleagues [29] with some modifications. Rats were individually placed in a transparent acrylic cage (54 × 20 × 34.5 cm), without food and water. Twenty-four clear glass marbles (1 cm diameter), distributed on top of 5-cm-deep fresh spruce wood bedding, were evenly spaced in six lines along the short wall of the cage. Individual subjects were placed in the test cage and their behavior was monitored for 30 min through an Any-Maze apparatus and video recorded by a camera placed 1.5 m above the cage. The number of marbles buried for at least 2/3 was counted by the experimenters and the results were expressed as the number of marbles covered by sawdust. New bedding was used for each animal, and marbles were cleaned with a 70% ethanol solution between animals.
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Fig. 1. Schematic representation of the experimental schedule.
2.4.4. Forced swim test (FST) The forced swim test, a behavioral test in which the animals are forced to swim without possibility of escaping [30], was carried out in two different days. On the first day, rats were placed to swim for 15 min (pre-test session) in a clear plastic cylinder (50 cm height, 25 cm diameter) filled with water (24 ± 1 °C) to a height of 30 cm. After 24 h, rats were tested again for 5 min under the same conditions (test session). Pretest and test sessions were video recorded (Any maze software) to quantify the following behavioral parameters: - immobility, defined as the time (sec) spent by the animal in a floating state, in absence of any active movement with the only exception of those necessary for keeping its head above the water to breath; - swimming, defined as the time (sec) spent in active horizontal swimming; - climbing, defined as the time (sec) spent in upward directed movements of the forepaws along the cylinder walls.
At the end of each swimming session, animals were dried and returned to home cages. 2.5. Statistical analyses Data from the induction of binge-type eating are expressed as mean kcal of margarine and chow (1-block week: MWF) ± SEM during the 2 h access period. Data were analyzed by two-way analysis of variance (ANOVA) for repeated measures with diet group and week as factors, and week as a repeated factor. Data from behavioral experiments are presented as mean ± SEM and were analyzed by two-way ANOVA analysis with the two factors being diet as a between-subjects factor and time as within-subjects factor (pre- and post-binge phase). Within each phase, the differences between diet groups were analyzed by two-way ANOVA (with the two factors being diet as a between-subjects factor and time (blocks of 10 min each) for locomotor activity) or by one-way ANOVA with diet as a between-subjects factor. Post-hoc comparisons, when appropriate, were performed by Newman-Keuls multiple comparison test or Bonferroni test. Finally, within each diet group, the unpaired Student's t-test was performed to verify whether the animals assigned to the two subgroups to perform behavioral tests during the pre-binge and the post-binge phase were significantly different from each other. In all cases, differences with a P value b 0.05 were considered significant. 3. Results 3.1. Induction of binge-type eating As expected [27], intermittent access to margarine leads HR group to consume a significantly higher amount of margarine than LR group during the three days of limited access. Two-way ANOVA showed significant diet × week interaction [F(7,182) = 2.73, P = 0.0102].
Specifically, margarine consumption in HR and LR groups became significantly different by the third week and remained stable throughout the duration of the study (post-hoc 3rd–8th week: P b 0.001) (see Fig. 2A). With respect to chow consumption during the 2 h limited access period, two-way ANOVA revealed a significant effect of diet group [F(2,273) = 12.84, P b 0.0001]. Subsequent individual one-way ANOVA within each week, showed that both LR and HR groups consumed significantly less chow than CTRL group [1st week: F(2,39) = 8.397, P = 0.0009, (P b 0.01, post hoc test); 2nd week: F(2,39) = 8.164, P = 0.0011, (P b 0.01, post hoc test); 3rd week F(2,39) = 3.849, P = 0.0298, (P b 0.05, post hoc test); 4th week F(2,39) = 3.369, P = 0.0447, (P b 0.05, post hoc test); 5th week F(2,39) = 5.381, P = 0.0091, (P b 0.05, post hoc test); 7th week F(2,39) = 4.935, P = 0.0123, (P b 0.05, post hoc test); 8th week F(2,39) = 6.338, P = 0.0041, (P b 0.01, post hoc test)](see Fig. 2B). When looking at the daily total intake of margarine and/or chow consumed by each diet group (Fig. 2C), two-way ANOVA detected a significant dietgroup × week interaction [F(14,273) = 2.01, P = 0.0170]. Post hoc analysis showed that HR group displayed higher daily total intake than LR and CTRL groups by the 2nd week of the study (2nd week, 3rd week, 4th week, 5th week , 6th week and 8th week: P b 0.001; 7th week: P b 0.01). With regard to the body weight, two-way ANOVA revealed a significant diet group x week interaction [F(14, 273) = 2.014, P = 0.0170]. Post hoc analysis indicated that HR group weighed more than CTRL group by the 5th week of the study (5th and 6th weeks: P b 0.05; 7th week P b 0.001; 8th week: P b 0.01). Yet, no difference between HR and LR groups as well as between CTRL and LR groups was detected (Fig. 2D). 3.2. Behavioral tests 3.2.1. Spontaneous locomotor activity (LA) Fig. 3 shows the general locomotor activity of the three experimental groups during the pre- and post-binge phases. On total horizontal beam breaks, two-way ANOVA revealed no significant effect of diet group [F (2.18) = 0.40, P = 0.6747] and time (pre- and post-binge phase) [F (1.18) = 0.03, P = 0.8540] as well as no significant effect of diet group × time (pre- and post-binge phase) interaction [F(2,18) = 0.92, P = 0.4166] (Fig. 3A). A similar scenario was observed on total vertical beam breaks: two-way ANOVA revealed no significant effect of diet group [F(2,18) = 0.47, P = 0.6327] and time (pre- and post-binge phase) [F(1,18) = 1.23, P = 0.2811] as well as no significant effect of diet group x time (pre- and post-binge phase) interaction [F(2,18) = 0.35, P = 0.7116] (Fig. 3B). These data suggested that all groups of animals had similar spontaneous locomotor activity and explorative behavior during the pre- and post-binge phases. The analysis of time course of data within each phase, showed only a significant effect of time on both horizontal (two-way ANOVA pre-binge: F(2,36) = 127.36, P b 0.0001; post-binge: F(2,36) = 137.74, P b 0.0001) and vertical beam breaks (two-way ANOVA pre-binge: F(2,36) = 26.13, P b 0.0001; post-binge: F(2,36) = 25.80, P b 0.0001) (Fig. 3C, D, E and F). This indicates that all three experimental groups animals habituated to the arenas over time and their overall activity decreased.
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Fig. 2. Induction of binge-type eating. Data are presented as mean Kcal (1-bar represents week: MWF) ± SEM of n = 14 animals per diet group. (A) Margarine intake: HR group (black bar) with limited access to margarine 3 days a week consumed more margarine than LR group (grey bar) with daily access to margarine (two way ANOVA: §P b 0.001 vs LR). (B) Chow intake: LR group and HR group consumed less chow than CTRL group (one way ANOVA: *P b 0.05 and #P b 0.01 vs CTRL). (C) Daily total intake: during the limited access HR group displayed higher total intake than LR and CTRL groups by the 2nd week of the study (two way ANOVA: 2nd–6th weeks and 8th week: §P b 0.001; 7th week: #P b 0.01). (D) Body weight: HR group weighed more than the CTRL group by the 5th week of the study (5th and 6th weeks: *P b 0.05; 7th week: §P b 0.001; 8th week: #P b 0.01). Not significant differences were found between HR and LR groups, nor between CTRL and LR groups.
3.2.2. Elevated plus maze (EPM) The entries in the close arms during the pre- and post-binge phases of the three experimental groups are presented in Fig. 4A. Two-way ANOVA revealed no significant effect of diet group [F(2,18) = 0.06, P = 0.9445] and time (pre- and post-binge phase) [F(1,18) = 0.01, P = 0.9642] as well as no significant effect of diet group x time (preand post-binge phase) interaction [F(2,18) = 0.40, P = 0.6768]. Considering the % of time spent in open arms, two-way ANOVA revealed a significant effect of diet group [F(2,18) = 8.92, P = 0.0020] and time (preand post-binge phase) [F(1,18) = 4.43, P = 0.0493], and no group × day interaction [F(2,18) = 0.06, P = 0.9445] (Fig. 4B). Subsequent individual one-way ANOVA within each phase, showed a significant diet effect between subjects [pre-binge: F(2,18) = 4.446, P = 0.0270; post-binge [F(2,18) = 7.357, P = 0.0042]. Post hoc analysis of data showed that, during the pre-binge phase, LR group spent significantly more time in the open-arms compared to both CTRL and HR groups (P b 0.05) but did not detect any difference between CTRL and HR groups. Conversely, in the post-binge phase, post hoc analysis of data only showed that the time spent in open arms by LR group was significantly higher as compared with the CTRL group (P b 0.01). A further analysis of data, highlighted that in the post-binge phase the HR group spent more time in the open arms compared to CTRL [unpaired Student's t-test: t(12) = 2.604 P = 0.0231]. Moreover, the analysis of the behavior of HR group in the two different phases, revealed that the rats spent significantly more time in the open arms during the post-binge phase compared to pre-binge phase [unpaired Student's t-test: t(12) = 3.621,
P = 0.0035]. As regard the % of open arms entries, two-way ANOVA analysis of data revealed a significant effect of diet group [F(2,18) = 5.84, P = 0.0111] and time (pre- and post-binge phase) [F(1,18) = 7.87, P = 0.0117], and no group × day interaction [F(2,18) = 0.27, P = 0.7656] (Fig. 4C). Individual one-way ANOVA within each phase showed a significant diet effect between subjects during the pre-binge [F(2,18) = 4.015, P = 0.0361]: post hoc analysis revealed that LR group made significantly more entries compared to CTRL and HR groups (P b 0.05). On the contrary, in the post-binge phase, individual one-way ANOVA did not detected significant difference between diet groups [F(2,18) = 1.760, P = 0.2004]. Within the HR group, the unpaired Student's t-test showed a significant increase in the number of entries in the open arms during the post-binge phase compared to pre-binge phase [t(12) = 2.397, P = 0.0337]. 3.2.3. Marble burying test (MB) Data from marble burying test are illustrated in Fig. 5. Two-way ANOVA analysis of the number of buried marbles revealed a significant effect of diet group [F(2,18) = 7.10, P = 0.0053] and time (pre- and post-binge phase) [F(1,18) = 39.35, P b 0.0001], and no group × day interaction [F(2,18) = 2.32, P = 0.1270]. During the pre-binge phase, subsequent individual one-way ANOVA revealed significant differences between diet groups [F(2,18) = 12.38, P = 0.0004]. Post-hoc analysis showed that the number of marbles buried by the HR group was significantly higher compared to both CTRL and LR groups (P b 0.001). On the other hand, during the post-binge phase, no significant differences were
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Fig. 3. Evaluation of spontaneous locomotor activity. Data are presented as mean ± SEM of N = 7 animals per diet group. (A) Total horizontal beam breaks, and (B) Total vertical beam breaks were analyzed during the 30 min session, in the pre-binge (white bars) and post-binge (black bars) phases. There were no significant differences between groups. (C) Time course of horizontal beam breaks, and (D) vertical beam breaks in the pre-binge phase. (E) Time course of horizontal beam breaks, and (F) vertical beam breaks in the post-binge phase. Data were analyzed in 10 min-blocks. Not significant differences were found between diet groups.
found in the number of marbles buried between the three experimental groups [one-way ANOVA: F(2,18) = 0.0565, P = 0.6396]. Within each experimental group, the unpaired Student's t-test showed that CTRL and LR groups buried a significantly higher number of marbles during the post-binge phase compared to pre-binge phase [unpaired Student's t-test, CTRL group: t(12) = 4.163, P b 0.01; LR group t(12) = 4.506,
P b 0.01]. No significant difference in the HR group was found when comparing pre and post-binge phases [t(12) = 2.085, P = 0.0589]. 3.2.4. Forced swim test (FST) In the FST, regarding the duration of immobility, two-way ANOVA revealed significant effect of time (pre- and post-binge phase)
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Fig. 4. Evaluation of anxiety-like behavior analyzed by elevated plus maze. Data are presented as mean ± SEM of N = 7 animals per diet group. (A) Number of closed-arm entries: there were no significant differences between groups. (B) % of time spent in open arms: LR group spent significantly more time in the open-arms compared to both CTRL and HR groups during the pre-binge (white bars) (one way ANOVA: *P b 0.05) and compared to CTRL group during the post-binge (black bars) (one way ANOVA: #P b 0.01); HR group spent significantly more time in the open-arms during the post-binge (black bars) compared to CTRL group (unpaired Student's t-test: φP b 0.05); HR group spent significantly more time in the open-arms during the post-binge (black bars) compared to the pre-binge (white bars) (unpaired Student's t-test: δP b 0.001). (C) % of open arm entries: LR group made significantly more entries compared with CTRL and HR groups during the pre-binge (white bars) (one way ANOVA: *P b 0.05); HR showed a significant increase in the number of entries in the open arms during the post-binge (black bars) compared to pre-binge (white bars) (unpaired Student's t-test: θP b 0.05).
[F(1,18) = 17.86, P = 0.0005] and no significant effect of diet group [F(2,18) = 0.35, P = 0.7199] and of diet group × time (pre- and postbinge phase) interaction [F(2,18) = 1.40, P = 0.2716] (Fig. 6A). Indeed, subsequent individual one-way ANOVA within each phase did not detected significant differences between the experimental groups during pre-binge and post-binge phases on this parameter analyzed [prebinge phase: immobility F(2,18) = 0.8970, P = 0.4253; post-binge phase: immobility F(2,18) = 0.6045]. However, intra-group analysis of immobility behavior during the two phases revealed that both LR and HR groups significantly decreased time spent immobility during the post-binge phase compared to the pre-binge phase (unpaired Student's t-test, LR: t(12) = 2.190, P b 0.05; HR: t(12) = 3.582, P b 0.01) (Fig.6A). Considering the swimming behavior, two-way ANOVA revealed no significant effect of diet group [F(2,18) = 1.20, P = 0.3239] and time (pre- and post-binge phase) [F(1,18) = 0.90, P = 0.3554] as well as no significant effect of diet group x time (preand post-binge phase) interaction [F(2,18) = 0.76, P = 0.4824] (Fig. 6B). Finally, two-way ANOVA analysis of climbing revealed significant effect of time (pre- and post-binge phase) [F(1,18) = 19.10, P = 0.0004] and no significant effect of diet group [F(2,18) = 0.20, P = 0.8221] and of diet group × time (pre- and post-binge phase) interaction [F(2,18) = 1.50, P = 0.2499] (Fig. 6C). Intra-group analysis of climbing behavior during the two phases revealed that HR group significantly increased time spent in climbing during the post-binge compared to the pre-binge phase (unpaired Student's t-test: t(12) =
Fig. 5. Evaluation of obsessive-compulsive-like behavior analyzed by marble burying test. Data are presented as mean ± SEM of N = 7 animals per diet group. The number of marbles buried by the HR group was significantly higher compared to both CTRL and LR groups during the pre-binge phase (white bars) (one way ANOVA: §P b 0.001). CTRL and LR group significantly increase the number of marbles during the post-binge (black bars) compared to the pre-binge (white bars) (unpaired Student's t test #P b 0.01).
3.487, P b 0.01). No significant difference in the CTRL and LR groups was found when comparing pre and post-binge phases. 4. Discussion Binge eaters typically displayed altered emotional states when approaching food or soon after its ingestion. The goal of the present study was to characterize the emotional behavior profile of bingeing rats by evaluating depression- and anxiety-like states and obsessive/ compulsive traits before and after access to palatable food. We used a validated animal model of BED, in which binge eating behavior is induced by providing an intermittent (3 days/week) and limited (2 h) access to a palatable food (vegetable margarine) in no food deprived rats (HR group) [22,27]. We confirmed that in HR group intake of margarine escalates over several weeks that of animals with continuous access to margarine (LR group), and that this excessive intake remains stable for the entire duration of the experiment. No difference was found in the locomotor activity when both LR and HR groups were compared to the CTRL group during the pre and postbinge phases as well as within each group in the two phases considered. This suggests that all the group differences observed in the behavioral tests described below were not due to changes in the locomotor activity. The EPM test, commonly used to disclose a potential anxious phenotype, revealed that the HR group displayed significantly higher levels of anxiety-like behavior in the pre-binge phase compared to the postbinge phase. The fact that this condition is reduced after the consumption of margarine suggests that this palatable food may have had an anxiolytic effect. The HR group had access to margarine on Mondays, Wednesdays and Fridays while the LR group, which was housed in the same room, had access to this palatable food every day. This means that in the days of no access to margarine, HR group could only smell it. This condition could be considered very stressful and leads animals showing binge eating behavior to increase their levels of anxiety until they have again access to the highly palatable food. In agreement, Cifani and colleagues [31], showed that the exposure to a familiar palatable food, in conditions in which the animal can see and smell it but cannot get access to it, is a stressful determinant for the rat. Also, it has been demonstrated that consumption of palatable foods rich in sugar and fat is considered to lower the stress response [32,33]. On the other hand, the fact that the LR group shows a less anxious behavior in both phases is in agreement with previous studies that showed that rats subjected continuously to a high fat diet highlighted less anxiety than rats fed a low fat diet or chow in the EPM [34,35]. The effect of a high fat diet on anxiety seems to be related to the capacity of regulate the hypothalamic-pituitary adrenal (HPA) axis activity [33,35,36]. In agreement with Blasio et al. [37], EPM data also showed that HR group did not differ
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Fig. 6. Evaluation of depressive-like behavior analyzed by forced swim test. Data are presented as mean ± SEM of N = 7 animals per diet group. (A) time (s) spent in immobility: intragroup analysis showed that during the two phases both LR and HR groups significantly decreased the immobility time during the post-binge phase (black bars) compared to the pre-binge phase (white bars) (unpaired Student's t-test: δP b 0.05; #P b 0.01). (B) time (s) spent in swimming: there were no significant differences between groups. (C) time (s) spent in climbing: HR showed a significant increase in the time spent in climbing during the post-binge (black bars) compared to pre-binge (white bars) (unpaired Student's t-test: θP b 0.05).
from CTRL in the percent of time spent in the open arms during the prebinge phase, when withdrawn from the palatable food. In contrast, Cottone et al. [38,39] demonstrated that female rats that intermittently had access to a highly palatable diet showed a significant anxiogeniclike behavior during withdrawal from it. This discrepancy could be due to the different protocol used to induce the binge eating behavior (rat strains, diets, post-withdrawal time points) and/or to the fact that under our conditions, the % of open arm time is very low in both CTRL and HR groups, which may prevent to detect an anxiogenic-like behavior in the binge group. In the forced swim test, the most widely used test of antidepressant action [40], we found that in the HR group the immobility time was significantly reduced in the post-binge phase compared to pre-binge indicating a reduction of the depression-like state. The same effect on the immobility duration has been observed in the LR group emphasizing a consistent antidepressant-like effect of margarine. On the contrary, no difference in this parameter has been detected in the CTRL group, in which margarine was not provided at any time. Moreover, only the HR group showed a significant increase in the climbing behavior. The capacity to reduce immobility and selectively increase climbing without affecting swimming appear to be typical of antidepressants such as desipramine, a selective norepinephrine reuptake inhibitor [41]. In agreement with our data, it has been recently demonstrated that withdrawal from chronic, intermittent access to highly palatable food induce signs of depression-like behaviors in rats and this condition was abolished by renewing access to the highly palatable diet [42]. Moreover, highfat diet selectively protected against the depressive-like effects induced by unpredictable chronic psychosocial stress in mice [43]. Lastly, longterm postpartum anxiety and depression-like behavior in mother rats subjected to maternal separation are ameliorated by palatable high fat diet [44]. On the other hand, other studies demonstrated that the chronic consumption of high-fat food induced obesity is associated with a depressive-like phenotype [45,46]. It is important to emphasize that the contrasting findings in these studies might be due to species related differences (mice vs rats) or to procedural differences. In the marble burying test, used as a model of obsessive compulsive behavior [47], the number of marbles buried by the HR group in the prebinge phase was significantly higher compared to CTRL and LR groups suggesting a compulsive-like trait. It is well documented that intermittent and limited access to a palatable food might lead to withdrawal symptoms, when the palatable food is not available, that is important for the induction and maintenance of the binge eating behavior [23, 24]. This emotional negative state may cause the occurrence of compulsive-like trait similar to what has been observed with drugs of abuse [23, 24,48–49]. Indeed, it has been demonstrated that rats with intermittent access to preferred food, showed a compulsive-like behavior since they persisted to accept punishments when access to preferred food pellets
was paired with mild electrical foot shocks [23]. Thus, our data on marble test during the pre-binge phase can be interpreted as a symptom of withdrawal from the palatable diet since margarine access for the binge group was every 48h during the week. However, in the post-binge phase, no difference was found between the three experimental groups. It should be noted that, the number of marbles buried by the HR group was similar to that of the pre-binge phase, demonstrating that a compulsive-like trait is still present after the consumption of margarine. On the contrary, both CTRL and LR groups showed a significant increase in the number of marble buried as compared to the behavior in the prebinge phase. As assessed in both EPM and open filed test, we did not find differences in general locomotor activity between the three experimental groups, thus it is unlikely that changes in locomotor activity due to the different experimental conditions in the two phases, could have contributed in any meaningful way. However, differences in testing room conditions must be considered. All together our findings provide evidence of an emotional state in the HR group that is attenuated after the consumption of margarine in a manner similar to the human condition. U.S. Food and Drug Administration (FDA) has not yet approved an official drug for the treatment of BED [50]. This eating disorder requires a multidisciplinary approach to analyze various aspects: psychotherapies (cognitive behavior therapy (CBT), interpersonal therapy and self-help strategies) that are effective for reducing binge eating episodes, but not all patients respond adequately, and pharmacotherapy which must take account of the common comorbidities of binge eating, such as depression and anxiety [50]. Our results clearly suggest that the limited access model can mimic several translational aspects of BED such as anxiety and depression and can be used in the evaluation of potential preclinical therapeutic interventions aimed to achieve therapeutics goals. Conflict of interest All authors declare no conflicts of interest. Acknowledgements This work was financially supported by Grant from the Italian Ministry of University and Scientific Research (FAR DM28141 del 21/11/2005 and Progetti di Ricerca a rilevante InteresseNazionale, PRIN 2010), by Fondazione Banco di Sardegna (Prot.U627.2013/AI.551MGB) and by Department of Biomedical Sciences Project (RICDIP_2012_Fratta_01), University of Cagliari. Valentina Satta was supported by Programma Master and Back (Percorsi di Rientro, edizione 2010/2011, Codice: PRR-MABA2011-19275), Regione Autonoma della Sardegna.
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References [1] American Psychiatric Association (APA), Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5™), American Psychiatric Association, Arlington, VA, 2013. [2] R.L. Spitzer, S. Yanovski, T. Wadden, R. Wing, M.D. Marcus, A. Stunkard, et al., Binge eating disorder: its further validation in a multisite study, Int. J. Eat. Disord. 13 (1993) 137–153. [3] Z. Cooper, C.G. Fairburn, Refining the definition of binge eating disorder and nonpurging bulimia nervosa, Int. J. Eat. Disord. 34 (2003) 89–95. [4] R.A. Grucza, T.R. Przybeck, C.R. Cloninger, Prevalence and correlates of binge eating disorder in a community sample, Compr. Psychiatry 48 (2007) 124–131. [5] R.C. Kessler, P.A. Berglund, W.T. Chiu, A.C. Deitz, J.I. Hudson, V. Shahly, et al., The prevalence and correlates of binge eating disorder in the World Health Organization World Mental Health Surveys, Biol. Psychiatry 73 (2013) 904–914. [6] J.I. Hudson, E. Hiripi, H.G. Jr Pope, R.C. Kessler, The prevalence and correlates of eating disorders in the National Comorbidity Survey Replication, Biol. Psychiatry 61 (2007) 348–358. [7] C.M. Grilo, M.A. White, R.M. Masheb, DSM-IV psychiatric disorder comorbidity and its correlates in binge eating disorder, Int. J. Eat. Disord. 42 (2009) 228–234. [8] D.V. Sheehan, B.K. Herman, The psychological and medical factors associated with untreated binge eating disorder, Prim. Care Companion CNS Disord. 17 (2015). [9] C.F. Telch, E. Stice, Psychiatric comorbidity in women with binge eating disorder: prevalence rates from a non-treatment-seeking sample, J. Consult. Clin. Psychol. 66 (1998) 768–776. [10] S.Z. Yanovski, J.E. Nelson, B.K. Dubbert, R.L. Spitzer, Association of binge eating disorder and psychiatric comorbidity in obese subjects, Am. J. Psychiatry 150 (1993) 1472–1479. [11] D.E. Wilfley, M.A. Friedman, J.Z. Dounchis, R.I. Stein, R.R. Welch, S.A. Ball, Comorbid psychopathology in binge eating disorder: relation to eating disorder severity at baseline and following treatment, J. Consult. Clin. Psychol. 68 (2000) 641–649. [12] K.N. Javaras, H.G. Pope, J.K. Lalonde, J.L. Roberts, Y.I. Nillni, N.M. Laird, et al., Co-occurrence of binge eating disorder with psychiatric and medical disorders, J. Clin. Psychiatry 69 (2008) 266–273. [13] R.E. Peterson, S.J. Latendresse, L.T. Bartholome, C.S. Warren, N.C. Raymond, Binge eating disorder mediates links between symptoms of depression, anxiety, and caloric intake in overweight and obese women, J. Obes. 2012 (2012) 407103. [14] C.B. Peterson, K.B. Miller, S.J. Crow, P. Thuras, J.E. Mitchell, Subtypes of binge eating disorder based on psychiatric history, Int. J. Eat. Disord. 38 (2005) 273–276. [15] R.H. Striegel-Moore, F.A. Dohm, H.C. Kraemer, G.B. Schreiber, C.B. Taylor, S.R. Daniels, Risk factors for binge-eating disorders: an exploratory study, Int. J. Eat. Disord. 40 (2007) 481–487. [16] K.P. De Young, J.M. Lavender, S.A. Wonderlich, R.D. Crosby, S.G. Engel, J.E. Mitchell, et al., Moderators of post-binge eating negative emotion in eating disorders, J. Psychiatr. Res. 47 (2013) 323–338. [17] E.L. Gibson, The psychobiology of comfort eating: implications for neuropharmacological interventions, Behav. Pharmacol. 23 (2012) 442–460. [18] P. Monteleone, M. Maj, Dysfunctions of leptin, ghrelin, BDNF and endocannabinoids in eating disorders: beyond the homeostatic control of food intake, Psychoneuroendocrinology 38 (2013) 312–330. [19] K. Schag, M. Teufel, F. Junne, H. Preissl, M. Hautzinger, S. Zipfel, K.E. Giel, Impulsivity in binge eating disorder: food cues elicit increased reward responses and disinhibition, PLoS One 8 (2013) 76542. [20] R.L. Corwin, N.M. Avena, M.M. Boggiano, Feeding and reward: perspectives from three rat models of binge eating, Physiol. Behav. 104 (2011) 87–97. [21] S.F. Kim, Animal models of eating disorders, Neuroscience 211 (2012) 2–12. [22] R.L. Corwin, A. Buda-Levin, Behavioral models of binge-type eating, Physiol. Behav. 82 (2004) 123–130. [23] A. Rossetti, G. Spena, O. Halfon, B. Boutrel, Evidence for a compulsive-like behavior in rats exposed to alternate access to highly preferred palatable food, Addict. Biol. 19 (2014) 975–985. [24] R. Dore, M. Valenza, X. Wang, K.C. Rice, V. Sabino, P. Cottone, The inverse agonist of CB1 receptor SR141716 blocks compulsive eating of palatable food, Addict. Biol. 19 (2014) 849–861. [25] M.D. Marcus, M.A. Kalarchian, Binge eating in children and adolescents, Int. J. Eat. Disord. 34 (2003) 47–57. [26] S. Hancock, M.C. Olmstead, Animal model of eating disorder, animal models of drug addiction, Neuromethods 53 (2011) 207–234.
143
[27] M. Scherma, L. Fattore, V. Satta, F. Businco, B. Pigliacampo, S.R. Goldberg, et al., Pharmacological modulation of the endocannabinoid signalling alters binge-type eating behaviour in female rats, Br. J. Pharmacol. 169 (2013) 820–833. [28] M.S. Spano, L. Fattore, F. Cadeddu, W. Fratta, P. Fadda, Chronic cannabinoid exposure reduces phencyclidine-induced schizophrenia-like positive symptoms in adult rats, Psychopharmacology 225 (2013) 531–542. [29] S. Andersen, E. Greene-Colozzi, K.C. Sonntag, A novel, multiple symptom model of obsessive-compulsive like behaviours in animals, Biol. Psychiatry 68 (2010) 741–747. [30] R.D. Porsolt, G. Anton, N. Blavet, M. Jalfre, Behavioural despair in rats: a new model sensitive to antidepressant treatments, Eur. J. Pharmacol. 47 (1978) 379–391. [31] C. Cifani, C. Polidori, S. Melotto, R. Ciccocioppo, M. Massi, A preclinical model of binge eating elicited by yo-yo dieting and stressful exposure to food: effect of sibutramine, fluoxetine, topiramate, and midazolam, Psychopharmacology 204 (2009) 113–125. [32] M.F. Dallman, Stress-induced obesity and the emotional nervous system, Trends Endocrinol. Metab. 21 (2010) 159–165. [33] N. Pecoraro, F. Reyes, F. Gomez, A. Bhargava, M.F. Dallman, Chronic stress promotes palatable feeding, which reduces signs of stress: feed forward and feedback effects of chronic stress, Endocrinology 145 (2004) 3754–3762. [34] A. Prasad, C. Prasad, Short-term consumption of a diet rich in fat decreases anxiety response in adult male rats, Physiol. Behav. 60 (1996) 1039–1042. [35] A.D. McNeilly, C.A. Stewart, C. Sutherland, D.J. Balfour, High fat feeding is associated with stimulation of the hypothalamic-pituitary-adrenal axis and reduced anxiety in the rat, Psychoneuroendocrinology 52 (2015) 272–280. [36] M.F. Dallman, N. Pecoraro, S.F. Akana, S.E. La Fleur, F. Gomez, H. Houshyar, et al., Chronic stress and obesity: a new view of ‘comfort food’, Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 11696–11701. [37] A. Blasio, K.C. Rice, V. Sabino, P. Cottone, Characterization of a shortened model of diet alternation in female rats: effects of the CB1 receptor antagonist rimonabant on food intake and anxiety-like behavior, Behav. Pharmacol. 25 (2014) 609–617. [38] P. Cottone, V. Sabino, M. Roberto, M. Bajo, L. Pockros, J.B. Frihauf, et al., CRF system recruitment mediates dark side of compulsive eating, Proc. Natl. Acad. Sci. U. S. A. 106 (2009) 20016–20020. [39] P. Cottone, V. Sabino, L. Steardo, E.P. Zorrilla, Consummatory, anxiety-related and metabolic adaptations in female rats with alternating access to preferred food, Psychoneuroendocrinology 2009 (34) (2009) 38–49. [40] V. Krishnan, E.J. Nestler, Linking molecules to mood: new insight into the biology of depression, Am. J. Psychiatry 167 (2010) 1305–1320. [41] J.F. Cryan, R.J. Valentino, I. Lucki, Assessing substrates underlying the behavioral effects of antidepressants using the modified rat forced swimming test, Neurosci. Biobehav. Rev. 29 (2005) 547–569. [42] A. Iemolo, M. Valenza, L. Tozier, C.M. Knapp, C. Kornetsky, L. Steardo, et al., Withdrawal from chronic, intermittent access to a highly palatable food induces depressive-like behavior in compulsive eating rats, Behav. Pharmacol. 23 (2012) 593–602. [43] B.C. Finger, T.G. Dinan, J.F. Cryan, High-fat diet selectively protects against the effects of chronic social stress in the mouse, Neuroscience 192 (2011) 351–360. [44] J. Maniam, M.J. Morris, Long-term postpartum anxiety and depression-like behavior in mother rats subjected to maternal separation are ameliorated by palatable high fat diet, Behav. Brain Res. 208 (2010) 72–79. [45] S. Sharma, S. Fulton, Diet-induced obesity promotes depressive-like behaviour that is associated with neural adaptations in brain reward circuitry, Int. J. Obes. 37 (2013) 382–389. [46] S. Sharma, M.F. Fernandes, S. Fulton, Adaptations in brain reward circuitry underlie palatable food cravings and anxiety induced by high-fat diet withdrawal, Int. J. Obes. 37 (2013) 1183–1191. [47] A. Woods-Kettelberger, S. Kongsamut, C.P. Smith, J.T. Winslow, R. Corbett, Animal models with potential applications for screening compounds for the treatment of obsessive-compulsive disorder, Expert Opin. Investig. Drugs 6 (1997) 1369–1381. [48] C. Colantuoni, P. Rada, J. McCarthy, C. Patten, N.M. Avena, A. Chadeayne, B.G. Hoebel, Evidence that intermittent, excessive sugar intake causes endogenous opioid dependence, Obes. Res. 10 (2002) 478–488. [49] C.H. Wideman, G.R. Nadzam, H.M. Murphy, Implications of an animal model of sugar addiction, withdrawal and relapse for human health, Nutr. Neurosci. 8 (2005) 269–276. [50] S.L. McElroy, A.I. Guerdjikova, N. Mori, A.M. O'Melia, Current pharmacotherapy options for bulimia nervosa and binge eating disorder, Expert. Opin. Pharmacother. 13 (2012) 2015–2026.