BACKGROUND: n-3 PUFA have shown potential anti-obesity and insulin-sensitising properties. However, the mechanisms involved are not clearly established.

METHOD: 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.

STUDY: 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.

RESULTS: 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 (P = 0·09), 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 PPARγ gene expression (P < 0·001), and also to the increase in apoptosis (P < 0·05) found in rats fed with a control diet. TNFα 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.

CONCLUSION: Adiposity-corrected adiponectin plasma levels were increased by EPA. These actions on both TNFα and adiponectin could explain the beneficial effects of EPA on insulin resistance induced by the cafeteria diet.