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Ameliorative effects of dietary carotenoids on memory deficits in senescence-accelerated mice (SAMP8)
International Congress Series 1260 (2004) 129 – 135
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Ameliorative effects of dietary carotenoids on memory deficits in senescence-accelerated mice (SAMP8) Hiroyuki Suganuma *, Takaaki Hirano, Sachiko Kaburagi, Kiro Hayakawa, Takahiro Inakuma Research Institute, KAGOME Co., Ltd. 17 Nishitomiyama, Nishinasuno-machi, Nasu-gun, Tochigi 329-2762, Japan Received 20 June 2003; received in revised form 26 June 2003; accepted 10 September 2003
Abstract. We previously reported that the dietary ingestion of the red-bell pepper (Capsicum annuum L.) or tomato (Lycopersicon esculentum Mill.) ameliorated the age-related alteration of SAMP8. These vegetable abounds in antioxidative carotenoids, capsanthin and lycopene. We examined the effects of feeding red-bell pepper or capsanthin on the age-related disorders in the senescence-accelerated mouse (SAMP8), a murine model of the accelerated decline in learning ability, and the control SAMR1 mouse. SAMP8 mice that received a diet containing 0.1% (w/w) capsanthin showed a much better memory acquisition in passive avoidance tasks compared to those given the control diet. The ingestion of capsanthin showed no effect on the learning ability of the SAMR1 mice. The activity of choline acetyltransferase (ChAT) in the parietal cortex of SAMP8 mice fed the diet containing capsanthin was potentiated compared to that in those fed the common diet. These observations indicate that the amelioratory effect of the red-bell pepper on the learning impairment in SAMP8 mice is mainly due to capsanthin. The ingestion of lycopene (0.02% (w/w) in the diet) also ameliorated the memory deficits in the SAMP8 mice analogous to the feeding of capsanthin. D 2003 Elsevier B.V. All rights reserved. Keywords: Capsanthin; Lycopene; Memory deficit; Passive avoidance
1. Introduction Free radicals are the most significant environmental factors in several neuronal degeneration processes as well as age-related physiological decline [1]. Many alterations similar to the pathology of aged humans have been reported in the senescence-
Abbreviations: ACh, Acetylcholine; ChAT, Choline acetyltransferase. * Corresponding author. Tel.: +81-287-36-2935; fax: +81-287-39-1038. E-mail address: [email protected] (H. Suganuma). 0531-5131/ D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0531-5131(03)01601-7
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accelerated mouse (SAMP8) brain, and oxidative stress has been shown to be involved in these brain alterations [2]. Thus, the supplementation of antioxidants was suggested to ameliorate the age-related disorders in SAMP8, and it has been reported that the administration of antioxidants prolonged the life span and improved the learning disorders in SAMP8 [3,4]. Carotenoids are widely distributed over the face of the earth mainly in plants, and more than 600 compounds have been recognized. These carotenoids can act as antioxidants by quenching singlet oxygen [5] and scavenging free radicals [6]. We previously reported that the dietary ingestion of the red-bell pepper (Capsicum annuum L.) or tomato (Lycopersicon esculentum Mill.) ameliorated the age-related alteration of SAMP8 [7,8]. These vegetables contain much antioxidative carotenoids, capsanthin and lycopene, respectively. Therefore, we examined the effect of dietary carotenoids on the age-related disorders in SAMP8.
2. Materials and methods 2.1. Animals and diet SAMP8 and SAMR1 mice were originally obtained from The Council for SAM Research, and bred under conventional conditions in our laboratory. They were given a commercially available diet (CE-2, Japan CLEA, Tokyo, Japan) until 6 weeks old. Thereafter, they continuously received the experimental diets in place of the common diet for 3 months. The animals were allowed free access to water and the powdered diets throughout the experiments. The control diet consisted of the following (g/kg): casein, 200; h-cornstarch, 397.486; a-cornstarch, 132; sucrose, 100; soybean oil, 70; cellulose powder, 50; AIN-93G mineral mixture, 35; AIN-93 vitamin mixture, 10; L-cystine, 3; choline bitartrate, 2.5; t-butyl-hydroquinone, 0.014. The composition of the diets containing capsanthin or lycopene resembled the control diet except that 0.1% (w/w) capsanthin or 0.02% (w/w) lycopene replaced the same weight of h-cornstarch. The capsanthin or lycopene (purity >99.0%) was extracted from paprika- or tomato-paste (TAT, Istanbul, Turkey) and purified by HPLC. The experimental procedures used in this study met the standards set forth in the Guidelines for the Care and Use of Laboratory Animals of the Experimental Animal Facility, the Japanese Society of Nutrition and Food Science. 2.2. Grouping We divided the male SAMP8 and SAMR1 mice into two groups, each containing six mice for both experiments 1 and 2. They received the control diet (P8-C, R1-C) or the diet containing 0.1% (w/w) capsanthin (P8-Cap, R1-Cap) in experiment 1 and the control diet (P8-C, R1-C) or the diet containing 0.02% (w/w) lycopene (P8-Ly, R1-Ly) in experiment 2. 2.3. Grading score The degree of senescence was evaluated by a grading score system [9] every month during the feeding experiment.
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2.4. Passive avoidance The learning and memory performances of the mice were assessed at the end of the feeding experiment with a two-compartment step-through passive avoidance apparatus (Ugo Basile, VA, Italy). For the acquisition trials, each mouse was placed in the light chamber and the time before it entered the dark chamber was recorded. When the mouse entered the dark compartment, the door was immediately closed and a 1.2-mA AC scrambled footshock was applied to the floor grid for 3 s. The first retention test was conducted 24 h after the initial acquisition trial, and subsequent trials were performed twice at 24-h intervals. 2.5. Morris water maze test To evaluate the spatial recognition ability of the mice, the Morris water maze test was performed according to a modified version of the method of Zhang et al. [10]. 2.6. Choline acetyltransferase (ChAT) assay In experiment 1, the brains were rapidly removed and dissected into the hippocampus, parietal cortex, frontal cortex and other. The brain ChAT activity was measured in the hippocampus and parietal cortex using the procedure described by Kaneda and Nagatsu [11].
3. Results 3.1. Experiment 1 The mean grading scores of P8-C, P8-Cap, R1-C and R1-Cap at the end of the experiment were 5.73 F 0.23, 6.28 F 0.24, 2.73 F 0.38 and 2.68 F 0.38, respectively. Supplementation with capsanthin was ineffective based on the grading score. The mean avoidance time in the step-through test is presented in Fig. 1. The two groups fed the diet containing 0.1% (w/w) capsanthin showed a better mean avoidance time on day 1 ( p < 0.01) than the group fed the capsanthin-free control diet. In the SAMP8 group, dietary capsanthin significantly prolonged the latency from days 1 to 3 compared with the control diet, but no such effect was observed in the SAMR1 group. In the SAMR1 group, the escape latency of the Morris water maze test became shorter independent of the diet in an alternating succession of trials but no learning effect was observed in the SAMP8 groups. The number of times to cross the goal area in free swimming on day 5 in each group was as follows: P8-C, 0.5 F 0.3; P8-Cap, 1.4 F 0.5; R1-C, 3.0 F 0.4; R1-Cap, 3.2 F 0.6. The number in the SAMR1 group was significantly greater than that in the SAMP8 group ( p < 0.05, Tukey’s test), but supplementation with capsanthin had no effect. The activities of ChAT in the parietal cortex and hippocampus were measured (Fig. 2). The dietary ingestion of capsanthin potentiated the ChAT activity in the parietal cortex in the SAMP8 group but showed no effect in the SAMR1 group. There were no differences in the hippocampal ChAT activity between the four experimental groups.
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Fig. 1. Effects of capsanthin on passive avoidance performance in SAM mice. The latency before footshock on passive avoidance response in each group is shown as the mean F S.E. (n = 6); open columns, P8-C; closed columns, P8-Cap; striped columns, R1-C; gray columns, R1-Cap. When the mouse remained in the light chamber over 9 min, the trial was ended. Significantly different from control; *p < 0.05, **p < 0.01 (Mann – Whitney U-test vs. P8-C).
3.2. Experiment 2 The mean grading score at the end of the feeding experiment in each group was as follows: P8-C, 5.75 F 0.34; P8-Ly, 6.25 F 0.53; R1-C, 2.50 F 0.16; R1-Ly, 2.67 F 0.24, and the dietary lycopene had no effect on the grading score analogous to capsanthin. Only
Fig. 2. Effects of capsanthin on brain ChAT activity in SAM mice. Brain ChAT activities in the parietal cortex and hippocampus in SAM mice are shown. Data are expressed as means F S.E. (n = 6); open columns, P8-C; closed columns, P8-Cap; striped columns, R1-C; gray columns, R1-Cap. Values with different superscripts are significantly different; p < 0.05 (Tukey’s test).
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Fig. 3. Effect of lycopene on passive avoidance performance in SAM mice. The latency before footshock on passive avoidance response in each group is shown as mean F SE (n = 6); open columns, P8-C; closed columns, P8-Ly; striped columns, R1-C; gray columns, R1-Ly. When the mouse remained in the light chamber over 9 min, the trial was ended. Significantly different from control; *p < 0.05, **p < 0.01 (Mann – Whitney U-test vs. P8-C).
in the SAMP8 group did the diet containing 0.02% lycopene significantly prolong the latency on days 1 and 3 ( p < 0.05) compared to the control diet (Fig. 3). In the Morris water maze test, the number of times crossing the goal area in free swimming on day 5 in each group was as follows: P8-C, 0.25 F 0.25; P8-Ly, 1.25 F 0.63; R1-C, 2.50 F 0.89; R1Ly, 4.00 F 1.53, and no obvious effect of the dietary lycopene was observed with regard to spatial learning performances.
4. Discussion We previously reported the beneficial effect of feeding red-bell pepper or tomato on the learning ability in SAMP8 mice [7,8]. This study suggested that these effects by dietary vegetables were caused by the antioxidative carotenoids such as capsanthin and lycopene. After Harman [1] put forward the theory that aging was due to free radicals, oxidative stress has been thought to be responsible for the majority of age-related alterations. Mitochondrial dysfunctions induced by an inefficient hyperactive state in the mitochondrial electron transport system with a concomitant increase in free electron defluxion were shown to be involved in the learning impairments in SAMP8 [12,13]. Capsanthin and lycopene were suggested to be absorbable by feeding vegetable juice to humans [14,15], and inhibited the oxidation of plasma low-density lipoproteins [16]. We could not detect capsanthin or lycopene in the cerebral cortex and there have been few previous reports showing its transport into the brain of rodents. However, the accumulations of h-carotene in the brain were reported not only in humans [17], but also in rats [18]. These results led us to two hypotheses about the effect of capsanthin and lycopene. First, these carotenoids may be transported into the brain where it exerts beneficial effects on the learning
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impairment in SAMP8. Second, they cannot pass the blood – brain barrier but may complement the endogenous antioxidative system and indirectly ameliorate the learning disorder in SAMP8. The enhancement of the ChAT activity in the parietal cortex by dietary capsanthin was observed in SAMP8 but not in SAMR1 analogous to the beneficial effects on the passive avoidance task. These results suggested that the effects of dietary carotenoids were not an enhancement of the brain function but the maintenance of it. In this study, SAMP8 was inferior to SAMR1 regarding the mean latency of the step-through type passive avoidance task and the escape latency of the Morris water maze task, and the ameliorative effect of dietary carotenoids was shown in the former but not in the latter. The ingestion of carotenoids might slightly improve the learning ability in passive avoidance but had no effect on spatial perception. In conclusion, dietary carotenoids attenuated the age-related learning impairment in SAMP8. This beneficial effect may be the result of an antioxidative effect. The mechanism by which carotenoids elicit the beneficial effect in SAMP8 remains to be elucidated. References [1] D.J. Harman, Aging: a theory based on free radical and radiation chemistry, Gerontologia 11 (1956) 298 – 300. [2] J.B. Schulz, R.T. Matthews, T. Klockgether, J. Dichgans, M.F. Beal, The role of mitochondrial dysfunction and neuronal nitric oxide in animal model of neurodegenerative diseases, Mol. Cell. Biochem. 174 (1997) 193 – 197. [3] R. Edamatsu, A. Mori, L. Packer, The spin-trap N-tert-alpha-phenyl-butylnitrone prolongs the life span of the senescence accelerated mouse, Biochem. Biophys. Res. Commun. 211 (1995) 847 – 849. [4] T. Moriguchi, H. Saito, N. Nishiyama, Aged garlic extract prolongs longevity and improves spatial memory deficit in senescence-accelerated mouse, Biol. Pharm. Bull. 19 (1996) 305 – 307. [5] P. Di Mascio, S. Kaiser, H. Sies, Lycopene as the most efficient biological carotenoid singlet oxygen quencher, Arch. Biochem. Biophys. 274 (2) (1989) 532 – 538. [6] J. Terao, Antioxidant activity of beta-carotene-related carotenoids in solution, Lipids 24 (1989) 659 – 661. [7] H. Suganuma, T. Hirano, T. Inakuma, Amelioratory effect of dietary ingestion with red-bell pepper on learning impairment in senescence-accelerated mice (SAMP8), J. Nutr. Sci. Vitaminol. 45 (1999) 143 – 149. [8] H. Suganuma, S. Kaburagi, T. Inakuma, Y. Ishiguro, Amelioratory effect of dietary ingestion of lycopene and tomato rich in lycopene on learning impairment in senescence-accelerated mice (SAMP8), Food Sci. Technol. Res. 8 (2) (2002) 183 – 187. [9] M. Hosokawa, Senescence grading system in mice, Jpn. J. Clin. Pathol. 38 (1990) 539 – 542. [10] Y. Zhang, H. Saito, N. Nishiyama, Thymetomy-induced deterioration of learning and memory in mice, Brain Res. 658 (1994) 127 – 134. [11] N. Kaneda, T. Nagatsu, Highly sensitive assay for choline acetyltransferase activity by high-performance liquid chromatography with electrochemical detection, J. Chromatogr. 341 (1985) 23 – 30. [12] T. Nishikawa, J.A. Takahashi, Y. Fujibayashi, H. Fujisawa, B. Zhu, Y. Nishimura, K. Ohnishi, K. Higuchi, N. Hashimoto, M. Hosokawa, An early stage mechanism of the age-associated mitochondrial dysfunction in the brain of SAMP8 mice; an age-associated neurodegeneration animal model, Neurosci. Lett. 254 (1998) 69 – 72. [13] Y. Fujibayashi, S. Yamamoto, A. Waki, J. Konishi, Y. Yonekura, Increased mitochondrial DNA deletion in the brain of SAMP8, a mouse model for spontaneous oxidative stress brain, Neurosci. Lett. 254 (1998) 109 – 112. [14] S. Oshima, H. Sakamoto, Y. Ishiguro, J. Terao, Accumulation and clearance of capsanthin in blood plasma after the ingestion of paprika juice in men, J. Nutr. 127 (1997) 1475 – 1479.
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[15] H. Sakamoto, S. Oshima, F. Ojima, Y. Ishiguro, M. Ogawa, H. Fukuba, Changes of serum carotenoids and retinol levels after continual ingestion of carrot or tomato juice in human subjects, J. Jpn. Soc. Nutr. Food Sci. 50 (1) (1997) 21 – 24. [16] F. Ojima, H. Sakamoto, Y. Ishiguro, J. Terao, Consumption of carotenoids in photosensitized oxidation of human plasma and plasma low-density lipoprotein, Free Radic. Biol. Med. 15 (1993) 377 – 384. [17] M.M. Mathews-Roth, A.A. Abraham, T.G. Gabuzda, Beta-carotene content of certain organs from two patients receiving high doses of beta-carotene, Clin. Chem. 22 (1976) 922 – 924. [18] S.S. Shapiro, D.J. Mott, L.J. Machlin, Kinetic characteristics of h-carotene uptake and depletion in rat tissue, J. Nutr. 114 (1984) 1924 – 1933.
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Ameliorative effects of dietary carotenoids on memory deficits in senescence-accelerated mice (SAMP8) Hiroyuki Suganuma *, Takaaki Hirano, Sachiko Kaburagi, Kiro Hayakawa, Takahiro Inakuma Research Institute, KAGOME Co., Ltd. 17 Nishitomiyama, Nishinasuno-machi, Nasu-gun, Tochigi 329-2762, Japan Received 20 June 2003; received in revised form 26 June 2003; accepted 10 September 2003
Abstract. We previously reported that the dietary ingestion of the red-bell pepper (Capsicum annuum L.) or tomato (Lycopersicon esculentum Mill.) ameliorated the age-related alteration of SAMP8. These vegetable abounds in antioxidative carotenoids, capsanthin and lycopene. We examined the effects of feeding red-bell pepper or capsanthin on the age-related disorders in the senescence-accelerated mouse (SAMP8), a murine model of the accelerated decline in learning ability, and the control SAMR1 mouse. SAMP8 mice that received a diet containing 0.1% (w/w) capsanthin showed a much better memory acquisition in passive avoidance tasks compared to those given the control diet. The ingestion of capsanthin showed no effect on the learning ability of the SAMR1 mice. The activity of choline acetyltransferase (ChAT) in the parietal cortex of SAMP8 mice fed the diet containing capsanthin was potentiated compared to that in those fed the common diet. These observations indicate that the amelioratory effect of the red-bell pepper on the learning impairment in SAMP8 mice is mainly due to capsanthin. The ingestion of lycopene (0.02% (w/w) in the diet) also ameliorated the memory deficits in the SAMP8 mice analogous to the feeding of capsanthin. D 2003 Elsevier B.V. All rights reserved. Keywords: Capsanthin; Lycopene; Memory deficit; Passive avoidance
1. Introduction Free radicals are the most significant environmental factors in several neuronal degeneration processes as well as age-related physiological decline [1]. Many alterations similar to the pathology of aged humans have been reported in the senescence-
Abbreviations: ACh, Acetylcholine; ChAT, Choline acetyltransferase. * Corresponding author. Tel.: +81-287-36-2935; fax: +81-287-39-1038. E-mail address: [email protected] (H. Suganuma). 0531-5131/ D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0531-5131(03)01601-7
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H. Suganuma et al. / International Congress Series 1260 (2004) 129–135
accelerated mouse (SAMP8) brain, and oxidative stress has been shown to be involved in these brain alterations [2]. Thus, the supplementation of antioxidants was suggested to ameliorate the age-related disorders in SAMP8, and it has been reported that the administration of antioxidants prolonged the life span and improved the learning disorders in SAMP8 [3,4]. Carotenoids are widely distributed over the face of the earth mainly in plants, and more than 600 compounds have been recognized. These carotenoids can act as antioxidants by quenching singlet oxygen [5] and scavenging free radicals [6]. We previously reported that the dietary ingestion of the red-bell pepper (Capsicum annuum L.) or tomato (Lycopersicon esculentum Mill.) ameliorated the age-related alteration of SAMP8 [7,8]. These vegetables contain much antioxidative carotenoids, capsanthin and lycopene, respectively. Therefore, we examined the effect of dietary carotenoids on the age-related disorders in SAMP8.
2. Materials and methods 2.1. Animals and diet SAMP8 and SAMR1 mice were originally obtained from The Council for SAM Research, and bred under conventional conditions in our laboratory. They were given a commercially available diet (CE-2, Japan CLEA, Tokyo, Japan) until 6 weeks old. Thereafter, they continuously received the experimental diets in place of the common diet for 3 months. The animals were allowed free access to water and the powdered diets throughout the experiments. The control diet consisted of the following (g/kg): casein, 200; h-cornstarch, 397.486; a-cornstarch, 132; sucrose, 100; soybean oil, 70; cellulose powder, 50; AIN-93G mineral mixture, 35; AIN-93 vitamin mixture, 10; L-cystine, 3; choline bitartrate, 2.5; t-butyl-hydroquinone, 0.014. The composition of the diets containing capsanthin or lycopene resembled the control diet except that 0.1% (w/w) capsanthin or 0.02% (w/w) lycopene replaced the same weight of h-cornstarch. The capsanthin or lycopene (purity >99.0%) was extracted from paprika- or tomato-paste (TAT, Istanbul, Turkey) and purified by HPLC. The experimental procedures used in this study met the standards set forth in the Guidelines for the Care and Use of Laboratory Animals of the Experimental Animal Facility, the Japanese Society of Nutrition and Food Science. 2.2. Grouping We divided the male SAMP8 and SAMR1 mice into two groups, each containing six mice for both experiments 1 and 2. They received the control diet (P8-C, R1-C) or the diet containing 0.1% (w/w) capsanthin (P8-Cap, R1-Cap) in experiment 1 and the control diet (P8-C, R1-C) or the diet containing 0.02% (w/w) lycopene (P8-Ly, R1-Ly) in experiment 2. 2.3. Grading score The degree of senescence was evaluated by a grading score system [9] every month during the feeding experiment.
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2.4. Passive avoidance The learning and memory performances of the mice were assessed at the end of the feeding experiment with a two-compartment step-through passive avoidance apparatus (Ugo Basile, VA, Italy). For the acquisition trials, each mouse was placed in the light chamber and the time before it entered the dark chamber was recorded. When the mouse entered the dark compartment, the door was immediately closed and a 1.2-mA AC scrambled footshock was applied to the floor grid for 3 s. The first retention test was conducted 24 h after the initial acquisition trial, and subsequent trials were performed twice at 24-h intervals. 2.5. Morris water maze test To evaluate the spatial recognition ability of the mice, the Morris water maze test was performed according to a modified version of the method of Zhang et al. [10]. 2.6. Choline acetyltransferase (ChAT) assay In experiment 1, the brains were rapidly removed and dissected into the hippocampus, parietal cortex, frontal cortex and other. The brain ChAT activity was measured in the hippocampus and parietal cortex using the procedure described by Kaneda and Nagatsu [11].
3. Results 3.1. Experiment 1 The mean grading scores of P8-C, P8-Cap, R1-C and R1-Cap at the end of the experiment were 5.73 F 0.23, 6.28 F 0.24, 2.73 F 0.38 and 2.68 F 0.38, respectively. Supplementation with capsanthin was ineffective based on the grading score. The mean avoidance time in the step-through test is presented in Fig. 1. The two groups fed the diet containing 0.1% (w/w) capsanthin showed a better mean avoidance time on day 1 ( p < 0.01) than the group fed the capsanthin-free control diet. In the SAMP8 group, dietary capsanthin significantly prolonged the latency from days 1 to 3 compared with the control diet, but no such effect was observed in the SAMR1 group. In the SAMR1 group, the escape latency of the Morris water maze test became shorter independent of the diet in an alternating succession of trials but no learning effect was observed in the SAMP8 groups. The number of times to cross the goal area in free swimming on day 5 in each group was as follows: P8-C, 0.5 F 0.3; P8-Cap, 1.4 F 0.5; R1-C, 3.0 F 0.4; R1-Cap, 3.2 F 0.6. The number in the SAMR1 group was significantly greater than that in the SAMP8 group ( p < 0.05, Tukey’s test), but supplementation with capsanthin had no effect. The activities of ChAT in the parietal cortex and hippocampus were measured (Fig. 2). The dietary ingestion of capsanthin potentiated the ChAT activity in the parietal cortex in the SAMP8 group but showed no effect in the SAMR1 group. There were no differences in the hippocampal ChAT activity between the four experimental groups.
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Fig. 1. Effects of capsanthin on passive avoidance performance in SAM mice. The latency before footshock on passive avoidance response in each group is shown as the mean F S.E. (n = 6); open columns, P8-C; closed columns, P8-Cap; striped columns, R1-C; gray columns, R1-Cap. When the mouse remained in the light chamber over 9 min, the trial was ended. Significantly different from control; *p < 0.05, **p < 0.01 (Mann – Whitney U-test vs. P8-C).
3.2. Experiment 2 The mean grading score at the end of the feeding experiment in each group was as follows: P8-C, 5.75 F 0.34; P8-Ly, 6.25 F 0.53; R1-C, 2.50 F 0.16; R1-Ly, 2.67 F 0.24, and the dietary lycopene had no effect on the grading score analogous to capsanthin. Only
Fig. 2. Effects of capsanthin on brain ChAT activity in SAM mice. Brain ChAT activities in the parietal cortex and hippocampus in SAM mice are shown. Data are expressed as means F S.E. (n = 6); open columns, P8-C; closed columns, P8-Cap; striped columns, R1-C; gray columns, R1-Cap. Values with different superscripts are significantly different; p < 0.05 (Tukey’s test).
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Fig. 3. Effect of lycopene on passive avoidance performance in SAM mice. The latency before footshock on passive avoidance response in each group is shown as mean F SE (n = 6); open columns, P8-C; closed columns, P8-Ly; striped columns, R1-C; gray columns, R1-Ly. When the mouse remained in the light chamber over 9 min, the trial was ended. Significantly different from control; *p < 0.05, **p < 0.01 (Mann – Whitney U-test vs. P8-C).
in the SAMP8 group did the diet containing 0.02% lycopene significantly prolong the latency on days 1 and 3 ( p < 0.05) compared to the control diet (Fig. 3). In the Morris water maze test, the number of times crossing the goal area in free swimming on day 5 in each group was as follows: P8-C, 0.25 F 0.25; P8-Ly, 1.25 F 0.63; R1-C, 2.50 F 0.89; R1Ly, 4.00 F 1.53, and no obvious effect of the dietary lycopene was observed with regard to spatial learning performances.
4. Discussion We previously reported the beneficial effect of feeding red-bell pepper or tomato on the learning ability in SAMP8 mice [7,8]. This study suggested that these effects by dietary vegetables were caused by the antioxidative carotenoids such as capsanthin and lycopene. After Harman [1] put forward the theory that aging was due to free radicals, oxidative stress has been thought to be responsible for the majority of age-related alterations. Mitochondrial dysfunctions induced by an inefficient hyperactive state in the mitochondrial electron transport system with a concomitant increase in free electron defluxion were shown to be involved in the learning impairments in SAMP8 [12,13]. Capsanthin and lycopene were suggested to be absorbable by feeding vegetable juice to humans [14,15], and inhibited the oxidation of plasma low-density lipoproteins [16]. We could not detect capsanthin or lycopene in the cerebral cortex and there have been few previous reports showing its transport into the brain of rodents. However, the accumulations of h-carotene in the brain were reported not only in humans [17], but also in rats [18]. These results led us to two hypotheses about the effect of capsanthin and lycopene. First, these carotenoids may be transported into the brain where it exerts beneficial effects on the learning
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impairment in SAMP8. Second, they cannot pass the blood – brain barrier but may complement the endogenous antioxidative system and indirectly ameliorate the learning disorder in SAMP8. The enhancement of the ChAT activity in the parietal cortex by dietary capsanthin was observed in SAMP8 but not in SAMR1 analogous to the beneficial effects on the passive avoidance task. These results suggested that the effects of dietary carotenoids were not an enhancement of the brain function but the maintenance of it. In this study, SAMP8 was inferior to SAMR1 regarding the mean latency of the step-through type passive avoidance task and the escape latency of the Morris water maze task, and the ameliorative effect of dietary carotenoids was shown in the former but not in the latter. The ingestion of carotenoids might slightly improve the learning ability in passive avoidance but had no effect on spatial perception. In conclusion, dietary carotenoids attenuated the age-related learning impairment in SAMP8. This beneficial effect may be the result of an antioxidative effect. The mechanism by which carotenoids elicit the beneficial effect in SAMP8 remains to be elucidated. References [1] D.J. Harman, Aging: a theory based on free radical and radiation chemistry, Gerontologia 11 (1956) 298 – 300. [2] J.B. Schulz, R.T. Matthews, T. Klockgether, J. Dichgans, M.F. Beal, The role of mitochondrial dysfunction and neuronal nitric oxide in animal model of neurodegenerative diseases, Mol. Cell. Biochem. 174 (1997) 193 – 197. [3] R. Edamatsu, A. Mori, L. Packer, The spin-trap N-tert-alpha-phenyl-butylnitrone prolongs the life span of the senescence accelerated mouse, Biochem. Biophys. Res. Commun. 211 (1995) 847 – 849. [4] T. Moriguchi, H. Saito, N. Nishiyama, Aged garlic extract prolongs longevity and improves spatial memory deficit in senescence-accelerated mouse, Biol. Pharm. Bull. 19 (1996) 305 – 307. [5] P. Di Mascio, S. Kaiser, H. Sies, Lycopene as the most efficient biological carotenoid singlet oxygen quencher, Arch. Biochem. Biophys. 274 (2) (1989) 532 – 538. [6] J. Terao, Antioxidant activity of beta-carotene-related carotenoids in solution, Lipids 24 (1989) 659 – 661. [7] H. Suganuma, T. Hirano, T. Inakuma, Amelioratory effect of dietary ingestion with red-bell pepper on learning impairment in senescence-accelerated mice (SAMP8), J. Nutr. Sci. Vitaminol. 45 (1999) 143 – 149. [8] H. Suganuma, S. Kaburagi, T. Inakuma, Y. Ishiguro, Amelioratory effect of dietary ingestion of lycopene and tomato rich in lycopene on learning impairment in senescence-accelerated mice (SAMP8), Food Sci. Technol. Res. 8 (2) (2002) 183 – 187. [9] M. Hosokawa, Senescence grading system in mice, Jpn. J. Clin. Pathol. 38 (1990) 539 – 542. [10] Y. Zhang, H. Saito, N. Nishiyama, Thymetomy-induced deterioration of learning and memory in mice, Brain Res. 658 (1994) 127 – 134. [11] N. Kaneda, T. Nagatsu, Highly sensitive assay for choline acetyltransferase activity by high-performance liquid chromatography with electrochemical detection, J. Chromatogr. 341 (1985) 23 – 30. [12] T. Nishikawa, J.A. Takahashi, Y. Fujibayashi, H. Fujisawa, B. Zhu, Y. Nishimura, K. Ohnishi, K. Higuchi, N. Hashimoto, M. Hosokawa, An early stage mechanism of the age-associated mitochondrial dysfunction in the brain of SAMP8 mice; an age-associated neurodegeneration animal model, Neurosci. Lett. 254 (1998) 69 – 72. [13] Y. Fujibayashi, S. Yamamoto, A. Waki, J. Konishi, Y. Yonekura, Increased mitochondrial DNA deletion in the brain of SAMP8, a mouse model for spontaneous oxidative stress brain, Neurosci. Lett. 254 (1998) 109 – 112. [14] S. Oshima, H. Sakamoto, Y. Ishiguro, J. Terao, Accumulation and clearance of capsanthin in blood plasma after the ingestion of paprika juice in men, J. Nutr. 127 (1997) 1475 – 1479.
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