Effects of eicosapentaenoic acid ethyl ester on visfatin and apelin in lean and overweight (cafeteria diet-fed) rats

Previous studies have demonstrated that the n-3 fatty acid EPA improves insulin resistance induced by high-fat diets. The aim of the present study was to investigate the potential role of visfatin and apelin in the insulin-sensitising effects of EPA ethyl ester. The effects of EPA on muscle and adipose GLUT mRNA, as well as on liver glucokinase (GK) and glucose-6-phosphatase (G6Pase) activity, were investigated. Male Wistar rats fed on a standard diet or a high-fat cafeteria diet were daily treated by oral administration with EPA ethyl ester (1 g/kg) for 5 weeks. A significant decrease (P,0·01) in white adipose tissue (WAT) visfatin mRNA levels was found in the cafeteria-fed rats, which was reversed by EPA administration (P,0·05). Moreover, a negative relationship was observed between homeostatic model assessment (HOMA) and the visfatin:total WAT ratio. In contrast, cafeteria-diet feeding caused a significant increase (P,0·01) in apelin mRNA in visceral WAT. EPA increased (P,0·01) apelin gene expression, and a negative relationship between HOMA index with visceral apelin mRNA and serum apelin:total WAT ratio was also observed. EPA treatment did not induce changes in skeletal muscle GLUT1, GLUT4 or insulin receptor mRNA levels. Neither liver GK and G6Pase activity nor the GK:G6Pase ratio was modified by EPA. These data suggest that somehow the insulin-sensitising effects of EPA could be related to its stimulatory action on both visfatin and apelin gene expression in visceral fat, while changes in skeletal muscle GLUT, as well as in hepatic glucose production, are not likely to be the main contributing factors in the improvement in insulin resistance induced by EPA

Eicosapentaenoic acid actions on adiposity and insulin resistance in control and high-fat-fed rats: role of apoptosis, adiponectin and tumour necrosis factor-a[alfa]

n-3 PUFA have shown potential anti-obesity and insulin-sensitising properties. However, the mechanisms involved are not clearly established. The aim of the present study was to assess the effects of EPA administration, one of the n-3 PUFA, on body-weight gain and adiposity in rats fed on a standard or a high-fat (cafeteria) diet. The actions on white adipose tissue lipolysis, apoptosis and on several genes related to obesity and insulin resistance were also studied. Control and cafeteria-induced overweight male Wistar rats were assigned into two subgroups, one of them daily received EPA ethyl ester (1 g/kg) for 5 weeks by oral administration. The high-fat diet induced a very significant increase in both body weight and fat mass. Rats fed with the cafeteria diet and orally treated with EPA showed a marginally lower body-weight gain (P¼0·09), a decrease in food intake (P,0·01) and an increase in leptin production (P,0·05). EPA administration reduced retroperitoneal adipose tissue weight (P,0·05) which could be secondary to the inhibition of the adipogenic transcription factor PPARg gene expression (P,0·001), and also to the increase in apoptosis (P,0·05) found in rats fed with a control diet. TNFa gene expression was significantly increased (P,0·05) by the cafeteria diet, while EPA treatment was able to prevent (P,0·01) the rise in this inflammatory cytokine. Adiposity-corrected adiponectin plasma levels were increased by EPA. These actions on both TNFa and adiponectin could explain the beneficial effects of EPA on insulin resistance induced by the cafeteria diet

Effects of eicosapentaenoic acid ethyl ester on visfatin and apelin in lean and overweight (cafeteria diet-fed) rats

Previous studies have demonstrated that the n-3 fatty acid EPA improves insulin resistance induced by high-fat diets. The aim of the present study was to investigate the potential role of visfatin and apelin in the insulin-sensitising effects of EPA ethyl ester. The effects of EPA on muscle and adipose GLUT mRNA, as well as on liver glucokinase (GK) and glucose-6-phosphatase (G6Pase) activity, were investigated. Male Wistar rats fed on a standard diet or a high-fat cafeteria diet were daily treated by oral administration with EPA ethyl ester (1 g/kg) for 5 weeks. A significant decrease (P,0·01) in white adipose tissue (WAT) visfatin mRNA levels was found in the cafeteria-fed rats, which was reversed by EPA administration (P,0·05). Moreover, a negative relationship was observed between homeostatic model assessment (HOMA) and the visfatin:total WAT ratio. In contrast, cafeteria-diet feeding caused a significant increase (P,0·01) in apelin mRNA in visceral WAT. EPA increased (P,0·01) apelin gene expression, and a negative relationship between HOMA index with visceral apelin mRNA and serum apelin:total WAT ratio was also observed. EPA treatment did not induce changes in skeletal muscle GLUT1, GLUT4 or insulin receptor mRNA levels. Neither liver GK and G6Pase activity nor the GK:G6Pase ratio was modified by EPA. These data suggest that somehow the insulin-sensitising effects of EPA could be related to its stimulatory action on both visfatin and apelin gene expression in visceral fat, while changes in skeletal muscle GLUT, as well as in hepatic glucose production, are not likely to be the main contributing factors in the improvement in insulin resistance induced by EPA

Cardiotrophin-1 is a key regulator of glucose and lipid metabolism

Cardiotrophin-1 (CT-1) is a member of the gp130 family of cytokines. We observed that ct-1(-/-) mice develop mature-onset obesity, insulin resistance, and hypercholesterolemia despite reduced calorie intake. Decreased energy expenditure preceded and accompanied the development of obesity. Acute treatment with rCT-1 decreased blood glucose in an insulin-independent manner and increased insulin-stimulated AKT phosphorylation in muscle. These changes were associated with stimulation of fatty acid oxidation, an effect that was absent in AMPKα2(-/-) mice. Chronic rCT-1 treatment reduced food intake, enhanced energy expenditure, and induced white adipose tissue remodeling characterized by upregulation of genes implicated in the control of lipolysis, fatty acid oxidation, and mitochondrial biogenesis and genes typifying brown fat phenotype. Moreover, rCT-1 reduced body weight and corrected insulin resistance in ob/ob and in high-fat-fed obese mice. We conclude that CT-1 is a master regulator of fat and glucose metabolism with potential applications for treatment of obesity and insulin resistance