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]

Abstract

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.