The effects of physiological and pharmacological weight loss on adiponectin and leptin mRNA levels in the rat epididymal adipose tissue

Available online at www.sciencedirect.com

European Journal of Pharmacology 579 (2008) 433 – 438 www.elsevier.com/locate/ejphar

The effects of physiological and pharmacological weight loss on adiponectin and leptin mRNA levels in the rat epididymal adipose tissue Ebrahim K. Naderali a,⁎, Sameer Fatani a , Monica Telles b , Leif Hunter a a

Neuroendocrine & Obesity Biology Unit, School of Clinical Sciences, University of Liverpool, Daluby Street, Liverpool L69 3GA, UK b Department of Physiology, Federal Sāo Paulo University, Sāo Paulo, Brazil Received 12 June 2007; received in revised form 29 October 2007; accepted 10 November 2007 Available online 23 November 2007

Abstract In subjects with obesity, diabetes and coronary artery disease, circulating levels of leptin increased while that of adiponectin is decreased. In this study we have investigated effects of physiological and pharmacological weight reduction on leptin and adiponectin mRNA expression. Wistar rats were fed either standard laboratory chow for 16 weeks (chow-fed) or given a fat-enriched, glucose-enriched diet (diet-fed) for 8 weeks. After 8 weeks, diet-fed group was subdivided into three subgroups, namely, an untreated obese, or were returned to chow diet, or treated with fenofibrate for further 8 week. After 16 weeks, compared with chow-fed group, diet-fed rats had significantly higher body weight, epididymal fat pad mass, and plasma levels of insulin, leptin, adiponectin, non-esterified fatty acids and triglycerides (P b 0.001, for all). Moreover, untreated obese rats had significantly (P b 0.01, for both) raised levels of Ob mRNA but reduced adiponectin mRNA levels in epididymal fat pads compared with chow-fed group. These changes were corrected by chronic removal of the high-energy diet and fenofibrate treatment. These findings indicate that physiological or pharmacological lowering of body weight together with circulating plasma lipids play a significant role in leptin and adiponectin synthesis and metabolism. © 2007 Elsevier B.V. All rights reserved. Keywords: Obesity; Weight loss Adiponectin; Leptin mRNA; Fenofibrate

1. Introduction Higher energy intake together with sedentary life style has increased prevalence of obesity in developed countries. Obesity per se, which is characterised by an increase in adipose tissue mass, is strongly associated with type 2 diabetes and increased cardiovascular morbidity and mortality (Nakamura et al., 1994; Flegal et al., 2002). Researches of the past decade have shown that adipose tissue is not merely an energy storage organ, but it also has an important endocrine function, secreting an array of proteins known as adipokines that include leptin (Bouloumie et al., 1998), and adiponectin (Hu et al., 1996; Nakano et al., 1996). Adiponectin improves insulin sensitivity, decreases plasma glucose and non-esterified fatty acid levels (Fruebis et al., 2001; Berg et al., 2001,2002; Combs et al., 2002), while increasing fatty acid utilization in muscle (Yamauchi et al., 2001). Moreover, adiponectin inhibits monocyte adhesion to endothelial cells and ⁎ Corresponding author. Tel.: +44 1517064108; fax: +44 1517065626. E-mail address: [email protected] (E.K. Naderali). 0014-2999/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2007.11.026

lipid accumulation in human monocyte-derived macrophages in vitro (Ouchi et al., 1999, 2001) pointing to its anti-atherogenic effect. Although adiponectin is mainly synthesised and released from white adipose tissue, yet its circulating levels are paradoxically reduced in human obese subjects (Arita et al., 1999) and in those with the metabolic syndrome (Weyer et al., 2001). In contrast, plasma leptin, the product of Ob gene, levels are increased in obesity and insulin resistance states (Paolisso et al., 1999; Naderali et al., 2001), and is associated with increased risk of cardiovascular diseases (Soderberg et al., 1999; Wallace et al., 2001). Furthermore, a significant weight loss by gastric surgery increases plasma adiponectin while decreasing leptin levels in morbidly obese subjects leading to improved insulin sensitivity (Kopp et al., 2005; Ballantyne et al., 2005), whereas a moderate weight loss by increasing energy expenditure fails to correct plasma adiponectin levels (Mousavinasab et al., 2005) in high calorie diet-fed subjects. Therefore, the aim of this study was to investigate the effects of physiological and pharmacological weight loss on adiponectin and leptin levels and their mRNA expression in dietary-obese rats.

434

E.K. Naderali et al. / European Journal of Pharmacology 579 (2008) 433–438

2. Materials and methods 2.1. Animals and experimental protocol Adult male Wistar rats (n = 28) were randomly assigned to a chow-fed group (n = 7) or a diet-fed group (n = 21). Chow-fed groups were fed on standard pelleted laboratory chow (CRM Biosure, Cambridge, UK), which provided 60% of energy as carbohydrate, 30% as protein and 10% as fat, while ‘diet-fed’ group were fed a highly palatable fat-enriched, glucose-enriched diet consisting of 33% (by weight) ground chow, 33% Nestlĕ condensed milk, 7% sucrose and 27% water. This provided 65% of energy as carbohydrate, 19% as protein and 16% as fat. All animals had free access to water and were housed individually under controlled environmental conditions (19– 22 °C; 30–40% humidity) and a 12-hour light/dark cycle (lights on at 07:00 h). Chow-fed group remained on their respective diet for 16 weeks, while after 8 weeks diet-fed animals were subdivided into three subgroups. Highly palatable diet was removed from one group (n = 7) and the standard chow was reintroduced (diet-to-chow) for further 8 weeks. Another group was given fenofibrate in the presence of palatable diet (fenofibrate-treated n = 7; 50 mg/kg/day), and the third group (untreated obese group, n = 7), which remained on palatable diet was given vehicle (1% carboxymethyl cellulose at 1 ml/kg body weight; Sigma, Pool, UK) by oral gavage, daily for further 8 weeks. The rats were terminated by CO2 inhalation after 2 h of fasting, and the epididymal fat mass and the gastrocnemius muscle were dissected and weighed. Epididymal tissues were then snap frozen immediately in liquid nitrogen and stored at − 70 °C before RNA isolation and Northern blotting. Blood was collected by cardiac puncture into cold heparinized tubes. The plasma was also immediately separated by centrifugation before being frozen at − 40 °C for later measurements of blood analytes. Plasma glucose concentration was determined using a glucose oxidase method (Boehringer Mannheim) while nonesterified fatty acid and triglycerides levels were measured using commercially diagnostic kits (Roche Diagnostic; and Sigma diagnostic, respectively). Insulin, leptin and adiponectin concentrations were measured by radioimmunoassay kits (Pharmacia/Upjohn Diagnostics; and Linco Research, Biogenesis, UK). All procedures were in accordance with the University of Liverpool and current UK legislations. 2.2. RNA isolation and Northern blotting Adiponectin and leptin mRNA levels in epididymal adipose tissues were measured by Northern blotting using oligonucleotide probes in conjunction with a chemiluminescence procedure (Trayhurn and Duncan 1994). Total RNA was extracted from each epididymal fat depot using Trizol® (Gibco, UK) according to the manufacturer's instructions. The RNA concentration was determined from the absorbance at 260 nm. Aliquots of 20 μg of RNA were fractionated by size on a 1% agarose-formaldehyde gel, blotted on to a positively charged membrane (Roche) overnight and then cross-linked under UV light. The membrane

was pre-hybridized in Easyhyb® solution (Roche) at 42 °C for 1 h and hybridized in the same solution with a digoxigenin endlabeled 30-mer antisense oligonucleotide probe for rat adiponectin and leptin at 42 °C overnight. The sequence of the antisense oligonucleotide probes employed were: 5′GTTGCAGTGGAATTTGCCAGTGCTGCCGTCA-3 for adiponectin; the sequences of the oligonucleotides for leptin and 18S rRNA were as described previously (Trayhurn et al., 1995). Following post-hybridization washes, the membrane was incubated with an antibody against digoxigenin (Fab fragment; Roche) for 30 min and then with the chemiluminescence substrate CDP-Star (0.25 mM; Tropix, USA) for 10 min at room temperature. Signals were collected by exposure of the membrane to X-ray film for 15–20 min at room temperature. The blots were stripped and re-probed sequentially with digoxigenin end-labeled oligonucleotides for leptin mRNA and 18S rRNA. Autoradiographs were quantitated by densitometry with image-analysis software (NIH Image). The abundance of a specific mRNA was expressed as the ratio of the target mRNA/ 18S rRNA signals. 2.3. Data interpretations and statistical analysis Normal distribution of data was tested using Shapiro Wilk W test. Data are expressed as mean ± S.E.M. Statistical significance was tested using the Student ‘t-test’ or repeated-measures analysis of variance ANOVA; Bonferroni t-test), as appropriate. Results were considered statistically significant at the P b 0.05 levels. 3. Results 3.1. Body weight and metabolic data Diet-fed animals progressively gained more weight than their chow-fed counterparts, such that after 8 weeks, diet-fed animals had significantly higher body weight than chow-fed controls (Table 1). By 16 weeks, the magnitude of weight increase was higher in untreated obese group than fenofibrateTable 1 Physiological and metabolic characteristics of the four experimental groups

Body weight •Initial •Mid-study •Terminal Epididymal fat-pad mass (g) Gastrocnemius muscle mass (g) Plasma glucose (mM) Plasma insulin (μg/l) Plasma triacylglyceride (mM) Plasma NEFA (mM)

Chow-fed

Untreated

Fenofibrate Diet-to-chow treated

191 ± 3 497 ± 9 567 ± 8 5.7 ± 0.5

190 ± 1 568 ± 15a 695 ± 20a 11.0 ± 1.1a

– 562 ± 14a 585 ± 14bc 6.9 ± 0.6b

– 566 ± 16a 600 ± 18bc 6.7 ± 0.6b

3.1 ± 0.1

3.2 ± 0.1

3.1 ± 0.1

3.3 ± 0.1

11.5 ± 1.1 13.9 ± 0.3 10.5 ± 0.3 12.7 ± 0.4 1.4 ± 0.2 3.6 ± 0.8a 1.2 ± 0.1b 1.5 ± 0.2b a b 0.78 ± 0.05 1.54 ± 0.18 0.63 ± 0.06 0.90 ± 0.05b 0.42 ± 0.02 0.49 ± 0.02a 0.30 ± 0.03b 0.44 ± 0.03b

Data are mean ± SEM for n = 7 on each group. a: P b 0.001 vs lean control, and b: P b 0.001 vs untreated, c: P b 0.05 vs lean control.

E.K. Naderali et al. / European Journal of Pharmacology 579 (2008) 433–438

treated and diet-to-chow groups; nevertheless all three groups had significantly higher total body weight than lean chow-fed controls. The induction of obesity was more evident in untreated obese group signified by a higher epididymal fat mass (P b 0.001) than chow-fed control group (Table 1). Epididymal

435

fat masses in fenofibrate-treated and diet-to-chow groups were comparable to that of chow-fed group, but were significantly (P b 0.05) lower than that of untreated obese rats. Compared with the chow-fed group, untreated diet-fed rats had significantly higher plasma levels of insulin, triglycerides and nonesterified fatty acid (for all, P b 0.001) while glucose concentrations were comparable between the two groups. Moreover, fenofibrate-treatment or removal of high-energy diet restored plasma insulin, triglycerides and non-esterified fatty acid levels to that of control values (Table 1). Untreated dietary-induced obese animals had significantly higher terminal leptin and adiponectin (P b 0.01 and P b 0.05, respectively) than control chow-fed groups. Fenofibrate-treatment or removal of high-energy diet, lowered plasma leptin levels comparable to lean chow-fed groups, but circulating adiponectin levels were remained significantly higher than chow-fed groups (fenofibrate-treated: P b 0.01); diet-to-chow: P b 0.05) (Fig. 1). 3.2. Adiponectin and leptin mRNA levels in epididymal adipose tissue 3.2.1. Ob mRNA levels Northern blotting of epididymal adipose tissue indicated a significant (P b 0.01) increase of Ob mRNA levels in animals that were diet-fed for 16 weeks compared to their chow-fed counterparts (Fig. 1). Removal of high-energy diet and fenofibrate-treatment markedly lowered Ob mRNA. In fact, Ob mRNA levels in fenofibrate-treated rats were significantly (P b 0.05) lower than that of chow-fed controls (Fig. 1). 3.2.2. Adiponectin mRNA levels There was a marked and significant (P b 0.01) reduction in adiponectin mRNA levels in epididymal fat of untreated dietfed rats compared with chow-fed group. Moreover, removal of high-energy diet or fenofibrate-treatement markedly (P b 0.05) augmented adiponectin mRNA levels compared with untreated obese group (Fig. 1). 4. Discussion Since the initial description of leptin and adiponectin, numerous studies have aimed to examine the relationship of these hormones to various pathophysiological conditions that include obesity, diabetes, atherosclerosis and hypertension (Arita et al., 1999; Paolisso et al., 1999; Soderberg et al., Fig. 1. The effects of removal of high-energy diet (DC) and fenofibratetreatment (Feno; 50 mg/kg/day) on a) plasma leptin levels (upper panel) and Ob mRNA (lower panel) levels and b) plasma adiponectin levels (upper panel) and adiponectin mRNA (lower panel) levels in rat epididymal fat pads. Middle panels are representative of Northern blotting of epididymal tissues from chowfed (C), vehicle (V), diet-to-chow (DC) and fenofibrate-treated (F) groups. The lower panels are quantitative analysis of absorbance unit (AU) intensity of Northern blotting. Data are presented as mean ± SEM for n = 7 for each group. Animals in chow and vehicle groups were maintained in their respective diets throughout the 16 weeks study period. ⁎ P b 0.01 vs chow-fed; ψ Pb 0.05 vs chow-fed; π P b 0.05 vs vehicle.

436

E.K. Naderali et al. / European Journal of Pharmacology 579 (2008) 433–438

1999; Ouchi et al., 2001; Wallace et al., 2001; Berg et al., 2002; Miczke et al., 2006). Although the exact physiological role of adiponectin is not fully clear yet, inhibition of TNFα production and subsequent effects on vascular adhesion molecules (Ouchi et al., 1999; Ouchi et al., 2000; Okamoto et al., 2000), as well as alteration of glucose metabolism and improvement of insulin sensitivity (Hu et al., 2007) have been proposed as its cardioprotective effects. Furthermore, down regulation of adiponectin gene expression and subsequent hypoadiponectinemia in obesity and type 2 diabetes (Statnick et al., 2000) and ob/ob mice (Hu et al., 1996) is thought to have a role in the development of insulin resistance and hyperinsulinemia (Weyer et al., 2001). A more imprecise picture has been painted for the role of leptin in pathophysiological conditions. While some reported an association between higher leptin levels and increased cardiovascular diseases (Soderberg et al., 1999; Naderali et al., 2001; Wallace et al., 2001), others have reported vasodilatory effect of leptin, suggesting a cardioprotective role for leptin (Fruhbeck 1999; Lembo et al., 2000). In this study, a 93% increase in fat pad mass together with a 40% increase in fasting plasma leptin, and a 157% rise in fasting plasma insulin concentrations in untreated diet-fed rats, points to the development of obesity and insulin resistance, respectively. Northern blotting of epididymal adipose tissues from untreated obese group indicated a marked increase in Ob mRNA level, further arguing for the development of obesity in these animals. Although terminal body weight of animals in fenofibrate-treated and diet-to-chow groups remained higher than that of the chow-fed rats, fenofibrate-treatment or removal of high-energy diet significantly attenuated body weight gain and consequently lowered terminal fat pad mass, as well as circulating plasma levels of triglycerides and non-esterified fatty acid, suggesting correction of diet- and/or obesity-induced metabolic abnormalities. Moreover, compared with untreated obese animals, Northern blotting analysis showed a significant reduction of epididymal Ob mRNA levels in diet-to-chow and fenofibrate-treated groups. This in turn, translated into a marked decrease in circulating plasma leptin levels in both diet-to-chow and fenofibrate-treated animals, further stressing a role for the removal of high-energy diet and/or fenofibrate-treatment in the management of dietary-induced metabolic abnormalities. Similar findings have also been reported in healthy human and obese subjects. A number of studies have reported that a 4 week reduced caloric diet intake markedly decreases circulating plasma leptin levels in healthy volunteers (Wolfe et al., 2004), while in obese patients a 10 week restriction of caloric intake is required for a significant reduction in circulating plasma leptin levels (Arvidsson et al., 2004). Moreover, fenofibrate-treatment of hypertriglyceridemic type 2 diabetic patients for 3 months significantly lowers not only hypertriglyceridaemia but also insulin and leptin levels (Damci et al., 2003). Numerous human studies have reported a marked reduction of adiponectin mRNA and its plasma levels in obesity (Kern et al., 2003), type 2 diabetes (Monzillo et al., 2003), and gestational diabetic patients (Ranheim et al., 2004), while a weight reduction in these subjects is associated with an increase in plasma adiponectin mRNA and circulating plasma adipo-

nectin levels (Monzillo et al., 2003; Ranheim et al., 2004). Weight loss as well as restricted calorie intake rather than fat/ carbohydrate ratio appears to play a key role in maintaining plasma adiponectin levels (Kopp et al., 2005; Ballantyne et al., 2005; Mousavinasab et al., 2005; Viguerie et al., 2005). Furthermore fenofibrate treatment of hypertriglyceridemic patients improves insulin sensitivity and increases adiponectin levels (Koh et al., 2005). Studies of adiponectin mRNA expression in obese animals have also shown a similar picture to that of human obesity, however, in contrast to findings in human subjects (Monzillo et al., 2003; Ranheim et al., 2004), there is no change or a paradoxical increase in plasma adiponectin levels in obese animals despite a marked decrease in adiponectin mRNA levels (Naderali et al., 2003; Yang et al., 2004; Velkoska et al., 2005; Barnea et al., 2006). In this study high-energy diet-induced obesity, resulted in a marked reduction of epididymal adiponectin mRNA, indicating a pronounced down regulation of mRNA expression in untreated dietaryobese rats. However, circulating adiponectin concentrations in obese animals were significantly higher than that of chow-fed group. Taken together our findings and those reported from other animal studies (Naderali et al., 2003; Barnea et al., 2006) indicate existence of, species specific controlling mechanism(s) in the synthesis and metabolism of adiponectin, which ultimately determines its plasma levels. It is possible that reduction in adiponectin mRNA levels that results in lowering adiponectin protein synthesis acts as a negative feed back mechanism. This in turn inhibits adiponectin metabolism leading to the accumulation of circulating adiponectin levels in untreated obese animals. This physiological feed back mechanism may have a counter regulatory response aiming to reduce cardiovascular diseases (Mallamaci et al., 2002). However, this hypothesis merits further investigation. Compared with untreated obese animals, removal of highenergy diet and fenofibrate treatment augmented epididymal adiponectin mRNA levels, indicating an up regulation of mRNA expression in these two groups. The mechanism(s) of adiponectin mRNA up regulation is unclear. It is possible that a chain of events, which may include: a) weight loss per se resulting in a reduced adiposity, b) reduction in circulating plasma lipids, namely triglycerides and non-esterified fatty acid, and c) a reduced plasma leptin levels, may have determinant roles in controlling adiponectin mRNA expression. Previous reports have shown a positive association between weight loss (Gustafson et al., 2003), and a negative association between plasma triglycerides (Naderali et al., 2003; Yang et al., 2004), and adiponectin mRNA, while leptin's role in synthesis and secretion of adiponectin has been equivocal (Kern et al., 2003; Gustafson et al., 2003; Gavrila et al., 2003; Arvidsson et al., 2004). In our study, animals in diet-to-chow and fenofibratetreated groups had higher plasma adiponectin levels similar to that of untreated obese group. This in turn makes it difficult to ascertain whether the rise in plasma adiponectin levels in these two groups is due to an increase in adiponectin mRNA expression or to a decrease in adiponectin metabolism and clearance. However, marked reduction in adiposity, improvement of insulin sensitivity and reduced plasma triacylglyceride

E.K. Naderali et al. / European Journal of Pharmacology 579 (2008) 433–438

and non-esterified fatty acid levels point to the hypothesis that increased plasma adiponectin levels in diet-to-chow and fenofibrate-treated animals may be due to increased adiponectin mRNA and its activity. Overall, our study indicates that dietary-obesity down regulates adiponectin mRNA while up regulating Ob mRNA expression. Although, up regulation of Ob mRNA translates to increased plasma leptin levels, down regulation of adiponectin mRNA expression does not translate to a decreased plasma adiponectin levels. In fact, there is a paradoxical rise in plasma adiponectin levels in dietary-obese rats. However, physiological and pharmacological weight loss leading to an improvement of insulin sensitivity and lowering of plasma lipid profile reduces Ob mRNA and augments adiponectin mRNA expressions, thus lowering leptin and increasing adiponectin synthesis leading to changes in their circulating levels. Therefore, weight loss per se as a result of removal of high-energy diet and fenofibrate treatment, or a change in plasma triacylglyceride and nonesterified fatty acid levels may affect adipose tissues, thereby affecting leptin and adiponectin production and/or their metabolism. Acknowledgements This study was supported by a grant from British Heart Foundation (FS/02/002). EKN is a BHF Research Fellow. The authors also would like to thank Dr C. Bing for her invaluable input throughout the manuscript. References Arita, Y., Kihara, S., Ouchi, N., Takahashi, M., Maeda, K., Miyagawa, J., Hotta, K., Shimomura, I., Nakamura, T., Miyaoka, K., Kuriyama, H., Nishida, M., Yamashita, S., Okubo, K., Matsubara, K., Muraguchi, M., Ohmoto, Y., Funahashi, T., Matsuzawa, Y., 1999. Paradoxial decrease of an adiposespecific protein, adiponectin, in obesity. Biochem. Biophys. Res. Commun. 257, 79–83. Arvidsson, E., Viguerie, N., Andersson, I., Verdich, C., Langin, D., Arner, P., 2004. Effects of different hypocaloric diets on protein secretion from adipose tissue of obese women. Diabetes 53, 1966–1971. Ballantyne, G.H., Gumbs, A., Modlin, I.M., 2005. Changes in insulin resistance following bariatric surgery and the adipoinsular axis: role of the adipocytokines, leptin, adiponectin and resistin. Obes. Surg. 15, 692–699. Barnea, M., Shamay, A., Stark, A.H., Madar, Z., 2006. A high-fat diet has a tissue-specific effect on adiponectin and related enzyme expression. Obesity 14, 2145–2153. Berg, A.H., Combs, T.P., Du, X., Brownlee, M., Scherer, P.E., 2001. The adipocyte-secreted protein Acrp30 enhances hepatic insulin action. Nat. Med. 7, 947–953. Berg, A.H., Combs, T.P., Scherer, P.E., 2002. ACRP30/adiponectin: an adipokine regulating glucose and lipid metabolism. Trends Endocrinol. Metab. 13, 84–89. Bouloumie, A., Drexler, H.C., Lafontan, M., Busse, R., 1998. Leptin, the product of Ob gene, promotes angiogenesis. Circ. Res. 83, 1059–1066. Combs, T.P., Wanger, J.A., Berger, J., Doebber, T., Wang, W.J., Zhang, B.B., Tanen, M., Berg, A.H., O'Rahilly, S., Savage, D.B., Chatterjee, K., Weiss, S., Larson, P.J., Gottesdiener, K.M., Gertz, B.J., Charron, M.J., Scherer, P.E., Moller, D.E., 2002. Induction of adipocyte complement-related protein of 30 kD by PPARγ agonist: a potential mechanism of insulin sensitisation. Endocrinology 143, 998–1007. Damci, T., Tatliagac, S., Osar, Z., Ilkova, H., 2003. Fenofibrate treatment is associated with better glycemic control and lower serum leptin and insulin

437

levels in type 2 diabetic patients with hypertriglyceridemia. Eur. J. Intern. Med. 14, 357–360. Flegal, K.M., Carroll, M.D., Ogden, C.L., Johnson, C.L., 2002. Prevalence and trends in obesity among US adults, 1999–2000. JAMA 288, 1723–1727. Fruebis, J., Tsao, T.S., Javorschi, S., Ebbets-Reed, D., Erickson, M.R., Yen, F.T., Bihain, B.E., Lodish, H.F., 2001. Proteolytic cleavage product of 30kDa adipocyte complement-related protein increases fatty acid oxidation in muschle and causes weight loss in mice. Proc. Natl. Acad. Sci. 98, 2005–2010. Fruhbeck, G., 1999. Pivotal role of nitric oxide in the control of blood pressure after leptin administration. Diabetes 48, 903–908. Gavrila, A., Chan, J.L., Yiannakouris, N., Kontogianni, M., Miller, L.C., Orlova, C., Mantzoros, C.S., 2003. Serum adiponectin levels are inversely associated with overall and central fat distribution but are not directly regulated by acute fasting or leptin administration in humans: cross-sectional and interventional studies. J. Clin. Endocrinol. Metab. 88, 4823–4831. Gustafson, B., Jack, M.M., Cushman, S.W., Smith, U., 2003. Adiponectin gene activation by thiazolidinediones requires PPAR gamma 2, but not C/EBP alpha-evidence for differential regulation of the aP2 and adiponectin genes. Biochem. Biophys. Res. Commun. 308, 933–939. Hu, E., Liang, P., Spiegelman, B.M., 1996. AdipoQ is a novel adipocyte-spesific gene dysregulated in obesity. J. Biol. Chem. 271, 10679–10703. Hu, X., She, M., Hou, H., Li, Q., Shen, Q., Luo, Y., Yin, W., 2007. Adiponectin decreases plasma glucose and improves insulin sensitivity in diabetic swine. Acta. Biochim. Biophys. Sin. 39, 131–136. Kern, P.A., Di Gregorio, G.B., Lu, T., Rassouli, N., Ranganathan, G., 2003. Adiponectin expression from human adipose tissue: relation to obesity, insulin resistance, and tumor necrosis factor-alpha expression. Diabetes 52, 1779–1785. Koh, K.K., Han, S.H., Quon, M.J., Yeal Ahn, J., Shin, E.K., 2005. Beneficial effects of fenofibrate to improve endothelial dysfunction and raise adiponectin levels in patients with primary hypertriglyceridemia. Diabetes Care 28, 1419–1424. Kopp, H.P., Krzyzanowska, K., Mohlig, M., Spranger, J., Pfeiffer, A.F., Schernthaner, G., 2005. Effects of marked weight loss on plasma levels of adiponectin, markers of chronic subclinical inflammation and insulin resistance in morbidly obese women. Int. J. Obes. Relat. Metab. Disord. 29, 766–771. Lembo, G., Vecchione, C., Fratta, L., Marino, G., Trimarco, V., d'Amati, G., Trimarco, B., 2000. Leptin induces direct vasodilation through distinct endothelial mechanisms. Diabetes 49, 293–297. Mallamaci, F., Zoccali, C., Cuzzola, F., Tripepi, G., Cutrupi, S., Parlongo, S., Tanaka, S., Ouchi, N., Kihara, S., Funahashi, T., Matsuzawa, Y., 2002. Adiponectin in essential hypertension. J. Nephrol. 15, 507–511. Miczke, A., Szulinska, M., Bogdanski, P., Pupek-Musialik, D., 2006. Does a relationship exist between plasma adiponectin concentration and selected parameters of metabolic syndrome? Pol. Merkur. Lek. 21, 170–172. Monzillo, L.U., Hamdy, O., Horton, E.S., Ledbury, S., Mullooly, C., Jarema, C., Porter, S., Ovalle, K., Moussa, A., Mantzoros, C.S., 2003. Effect of lifestyle modification on adipokine levels in obese subjects with insulin resistance. Obes. Res. 11, 1048–1054. Mousavinasab, F., Tahtinen, T., Jokelainen, J., Koskela, P., Vanhala, M., Oikarinen, J., Keinanen-Kiukaanniemi, S., 2005. Lack of increase of serum adiponectin concentrations with a moderate weight loss during six months on a high-caloric diet in military service among a young male Finnish population. Endocrine 26, 65–70. Naderali, E.K., Brwon, M.J., Pickavance, L.C., Wilding, J.P.H., Doyle, P.J., Williams, G., 2001. Dietary obesity in the rat induces endothelial dysfunction without causing insulin resistance: a possible role for triacylglycerols. Clin. Sci. 101, 499–506. Naderali, E.K., Estadella, D., Rocha, M., Pickavance, L.C., Fatani, S., Denis, R.G., Williams, G., 2003. A fat-enriched, glucose-enriched diet markedly attenuates adiponectin mRNA levels in rat epididymal adipose tissue. Clin Sci. 105, 403–408. Nakamura, T., Tokunaga, K., Shimomura, I., Nishida, M., Yoshida, S., Kotani, K., Islam, A.H., Keno, Y., Kobatake, T., Nagai, Y., 1994. Contribution of visceral fat accumulation to the development of coronary artery disease in non-obese men. Atherosclerosis 107, 239–246.

438

E.K. Naderali et al. / European Journal of Pharmacology 579 (2008) 433–438

Nakano, Y., Tobe, T., Choi-Miura, N.H., Mazda, T., Tomita, M., 1996. Isolation and characterization of GBP28, a novel gelatin-binding protein purified from human plasma. J. Biochem. 120, 803–812. Okamoto, Y., Arita, Y., Nishida, M., Muraguchi, M., Ouchi, N., Takahashi, M., Igura, T., Inui, Y., Kihara, S., Nakamura, T., Yamashita, S., Miyagawa, J., Funahashi, T., Matsuzawa, Y., 2000. An adipocyte-derived plasma protein, adiponectin, adheres to injured vascular walls. Horm. Metab. Res. 32, 47–50. Ouchi, N., Kihara, S., Arita, Y., Maeda, K., Kuriyama, H., Okamoto, Y., Hotta, K., Nishida, M., Takahashi, M., Nakamura, T., Yamashita, S., Funahashi, T., Matsuzawa, Y., 1999. Novel modulator for endothelial adhesion moleculesadipocyte-derived plasma protein adiponectin. Circulation 100, 2473–2476. Ouchi, N., Kihara, S., Arita, Y., Okamoto, Y., Maeda, K., Kuriyama, H., Hotta, K., Nishida, M., Takahashi, M., Muraguchi, M., Ohmoto, Y., Nakamura, T., Yamashita, S., Funahashi, T., Matsuzawa, Y., 2000. Adiponectin, an adipocyte-derived plasma protein, inhibits endothelial NK-kappa B signalling through a cAMP-dependent pathway. Circulation 102, 1296–1301. Ouchi, N., Kihara, S., Arita, Y., Nishida, M., Matsuyama, A., Okamoto, Y., Ishigami, M., Kuriyama, H., Kishida, K., Nishizawa, H., Hotta, K., Muraguchi, M., Ohmoto, Y., Yamashita, S., Funahashi, T., Matsuzawa, Y., 2001. Adipocyte-derived plasma protein, adiponectin, suppresses lipid accumulation and class A scavenger receptor expression in human momocyte-derived macrophages. Circulation 103, 1057–1063. Paolisso, G., Tagliamonte, M.R., Galderisi, M., Zito, G.A., Petrocelli, A., Carella, C., de Divitiis, O., Varricchio, M., 1999. Plasma leptin level is associated with myocardial wall thickness in hypertensive insulin-resistant men. Hypertension 34, 1047–1052. Ranheim, T., Haugen, F., Staff, A.C., Braekke, K., Harsem, N.K., Drevon, C.A., 2004. Adiponectin is reduced in gestational diabetes mellitus in normal weight women. Acta. Obstet. Gynecol. Scand. 83, 341–347. Soderberg, S., Ahren, B., Jansson, J.H., Johnson, O., Hallmans, G., Asplund, K., Olsson, T., 1999. Leptin is associated with increased risk of myocardial infarction. J. Intern. Med. 246, 409–418. Statnick, M.A., Beavers, L.S., Conner, L.J., Corominola, H., Johnson, D., Hammond, C.D., Rafaeloff-Phail, R., Seng, T., Suter, T.M., Sluka, J.P., Ravussin, E., Gadski, R.A., Caro, J.F., 2000. Decreased expression of apM1 in omental and subcutaneous adipose tissue of human with type 2 diabetes. Int. J. Reprod. Diabetes Res. 1, 51–58. Trayhurn, P., Duncan, J.S., 1994. Rapid chemiluminescent detection of the mRNA for uncoupling protein in brown adipose tissue by northern

hybridization with a 32-mer oligonucleotide end-labelled with digoxigenin. Int. J. Obes. Relat. Metab. Disord. 18, 449–452. Trayhurn, P., Duncan, J.S., Rayner, D.V., 1995. Acute cold-induced suppression of ob (obese) gene-expression in white adipose-tissue of mice-mediation by the sympathetic system. Biochem. J. 311, 729–733. Velkoska, E., Cole, T.J., Morris, M.J., 2005. Early dietary intervention: longterm effects on blood pressure, brain neuropeptide Y, and adiposity markers. Am. J. Physiol. Endocrinol. Metab. 288, E1236–E1243. Viguerie, N., Vidal, H., Arner, P., Holst, C., Verdich, C., Avizou, S., Astrup, A., Saris, W.H., Macdonald, I.A., Klimcakova, E., Clement, K., Martinez, A., Hoffstedt, J., Sorensen, T.I., Langin, D., 2005. Nutrient-gene interactions in human obesity-implications for dietary guideline (NUGENOB) project. Adipose tissue gene expression in obese subjects during low-fat and high-fat hypocaloric diets. Diabetologia 48, 123–131. Wallace, A.M., McMahon, A.D., Packard, C.J., Kelly, A., Shepherd, J., Gaw, A., Sattar, N., 2001. Plasma leptin and the risk of cardiovascular disease in the west of Scotland coronary prevention study (WOSCOPS). Circulation 104, 3052–3056. Weyer, C., Funahashi, T., Tanaka, S., Hotta, K., Matsuzawa, Y., Pratley, R.E., Tataranni, P.A., 2001. Hypoadiponectinemia in obesity and type 2 diabetes: close association with insulin resistance and hyperinsulinemia. J. Clin. Endocrinol. Metab. 86, 1930–1935. Wolfe, B.E., Jimerson, D.C., Orlova, C., Mantzoros, C.S., 2004. Effect of dieting on plasma leptin, soluble leptin receptor, adiponectin and resistin levels in healthy volunteers. Clin. Endocrinol. 61, 332–338. Yamauchi, T., Kamon, J., Waki, H., Terauchi, Y., Kubota, N., Hara, K., Mori, Y., Ide, T., Murakami, K., Tsuboyama-Kasaoka, N., Ezaki, O., Akanuma, Y., Gavrilova, O., Vinson, C., Reitman, M.L., Kagechika, H., Shudo, K., Yoda, M., Nakano, Y., Tobe, K., Nagai, R., Kimura, S., Tomita, M., Froguel, P., Kadowaki, T., 2001. The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity. Nat. Med. 7, 941–946. Yang, B., Brown, K.K., Chen, L., Carrick, K.M., Clifton, L.G., McNulty, J.A., Winegar, D.A., Strum, J.C., Stimpson, S.A., Pahel, G.L., 2004. Serum adiponectin as a biomarker for in vivo PPARgamma activation and PPARgamma agonist-induced efficacy on insulin sensitization/lipid lowering in rats. BMC Pharmacol. 4, 23.