Melatonin improves metabolic syndrome induced by high fructose intake in rats.

In this study, we examined whether melatonin improves metabolic syndrome induced by high fructose intake in male Wistar rats. Feeding of a diet containing 60% fructose (HFD) for 4 or 6 wk caused increased serum insulin, triglyceride, total cholesterol, free fatty acids, uric acid, leptin, and lipid peroxide concentrations as well as hepatic triglyceride and cholesterol concentrations, and relative intra-abdominal fat and liver weights. The 4- or 6-wk HFD feeding reduced serum high-density lipoprotein cholesterol and adiponectin concentrations. The 6-wk HFD feeding increased serum tumor necrosis factor-α concentration and hepatic lipid peroxide concentration and lowered hepatic reduced glutathione concentration. Daily intraperitoneal administration of melatonin (1 or 10mg/kg body weight), starting at 4-wk HFD feeding, attenuated these changes at 6-wk HFD feeding more effectively at its higher dose than at its lower dose. In an oral glucose tolerance test, rats with 4- or 6-wk HFD feeding showed higher serum insulin response curve and normal serum glucose response curve when compared with the corresponding animals that received the control diet. The 4- or 6-wk HFD feeding caused insulin resistance, judging from the scores of HOMR-IR and QUICKI, which are indices of insulin resistance. The daily administered melatonin (1 or 10mg/kg body weight) ameliorated the higher serum insulin response curve in the oral glucose tolerance test and insulin resistance at 6-wk HFD feeding more effectively at its higher dose than at its lower dose. These results indicate that melatonin improves metabolic syndrome induced by high fructose intake in rats.

Kitagawa A ，Ohta Y ，Ohashi K 《-》

Melatonin effect on plasma adiponectin, leptin, insulin, glucose, triglycerides and cholesterol in normal and high fat-fed rats.

Melatonin effect on body weight progression, mean levels and 24-hr pattern of circulating adiponectin, leptin, insulin, glucose, triglycerides and cholesterol were examined in rats fed a normal or a high-fat diet. In experiment 1, rats fed a normal diet were divided into two groups: receiving melatonin (25 μg/mL drinking water) or vehicle for 9 wk. In experiment 2, animals were divided into three groups: two fed with a high-fat diet (35% fat) and melatonin (25 μg/mL) or vehicle in drinking water for 11 wk, while a third group was given a normal diet (4% fat). At the end of experiments, groups of eight rats were killed at six different time intervals throughout a 24-hr period. Melatonin administration for 9 wk decreased body weight gain from the 3rd wk on without affecting food intake. A significant reduction in circulating insulin, glucose and triglyceride mean levels and disrupted daily patterns of plasma adiponectin, leptin and insulin were observed after melatonin. In high fat-fed rats, melatonin attenuated body weight increase, hyperglycemia and hyperinsulinemia, as well as the increase in mean plasma adiponectin, leptin, triglycerides and cholesterol levels. The high-fat diet disrupted normal 24-hr patterns of circulating adiponectin, insulin and cholesterol, the effects on insulin and cholesterol being counteracted by melatonin. Nocturnal plasma melatonin concentration in control and obese rats receiving melatonin for 11 wk attained values 21-24-fold greater than controls. The results indicate that melatonin counteracts some of the disrupting effects of diet-induced obesity in rats.

Ríos-Lugo MJ ，Cano P ，Jiménez-Ortega V ，Fernández-Mateos MP ，Scacchi PA ，Cardinali DP ，Esquifino AI ... -  《-》

Influence of alpha-lipoic acid on lipid peroxidation and antioxidant defence system in blood of insulin-resistant rats.

High fructose feeding induces insulin resistance and hyperinsulinaemia in rats. A role for oxidative stress in the occurrence of insulin resistance has been suggested by several workers. The aim of this study was to investigate the effect of alpha-lipoic acid (LA) on oxidant-antioxidant balance in rats fed on a high-fructose diet that showed characteristic features of insulin resistance. Male Wistar rats weighing 150-170 g were divided into seven groups. The control group received the control diet containing starch. The fructose group was given a high-fructose diet (>60% of total calories). The third and fourth groups were given fructose diet and were administered two different doses of LA at a low dose (35 mg/kg body weight) and high dose (70 mg/kg body weight) using olive oil as vehicle. The fifth group received fructose diet and olive oil. The sixth group received control diet and was administered LA (70 mg/kg body weight). And, the seventh group received the control diet and olive oil. Products of lipid peroxidation and activities of enzymic antioxidants, namely superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase, in red blood cells were assayed. Levels of non-enzymic antioxidants alpha-tocopherol, ascorbic acid and reduced glutathione were determined in plasma. The levels of lipid peroxides, diene conjugates and thiobarbituric acid-reactive substances were significantly higher in fructose-fed rats. Inadequate antioxidant system was observed in high-fructose-fed rats. Treatment of fructose rats mitigated the imbalance between peroxidation and antioxidant defence system at both the doses tested. Increases in glucose, triglycerides, free fatty acids, insulin and insulin resistance were observed in fructose-fed rats. LA administration prevented these alterations and improved insulin sensitivity. Significant positive correlations were obtained between insulin resistance and lipid peroxidation indices. Increased lipid peroxidation and deficient antioxidant system are observed in high-fructose-fed rats. LA administration preserves the antioxidant system and lowers lipid peroxidation. The findings suggest an interrelationship between lipid peroxidation and insulin resistance.

Thirunavukkarasu V ，Anuradha CV 《DIABETES OBESITY & METABOLISM》

Dietary sardine protein lowers insulin resistance, leptin and TNF-α and beneficially affects adipose tissue oxidative stress in rats with fructose-induced metabolic syndrome.

Madani Z ，Louchami K ，Sener A ，Malaisse WJ ，Ait Yahia D ... -  《-》

Effect of feeding grape pomace on selected metabolic parameters associated with high fructose feeding in growing Sprague-Dawley rats.

Khanal RC ，Howard LR ，Rogers TJ ，Wilkes SE ，Dhakal IB ，Prior RL ... -  《-》