Interaction of fish oil and a glucocorticoid on metabolic responses to an oral glucose load in healthy human subjects

Abstract

Compared with saturated fat, n -3 long-chain PUFA-rich fish oil improves insulin sensitivity in rats. We studied whether n -3 long-chain PUFA could prevent insulin resistance induced by dexamethasone (a glucocorticoid) in healthy human volunteers. A group of eight subjects was studied twice after a 2d dexamethasone treatment, before and after a 3-week supplementation with fish oil (providing daily doses of 1·1g 20:5 n -3 and 0·7g 22:6 n -3). The subjects were studied during the basal state and over the 6h following an oral glucose load (1g/kg). Plasma glucose fluxes were traced with [6,6- 2 H 2 ]glucose and [ 13 C]glucose (naturally 13 C-enriched corn glucose). Substrate oxidation was obtained from indirect calorimetry. Following fish oil supplementation, plasma glucose fluxes and substrate oxidation were maintained despite a 17% reduction ( P <0·05) in the area under the curve of plasma insulin response, suggesting an insulin-sensitizing effect.