In the present study, rats were exposed from the 8th week after birth and for the ensuing 8 weeks to diets containing either starch or fructose (64% w/w) and sunflower oil (5%). Two further groups of rats were exposed to the fructose-containing diet with substitution of part (1.6%) of the sunflower diet by an equal amount of either salmon oil rich in long-chain polyunsaturated ω3 fatty acids or safflower oil reach in long-chain polyunsaturated ω6 fatty acids. The insulin content of the islets and their secretory response to D-glucose (5.6, 8.3 and 16.7 mM), to the combination of D-glucose (5.6 mM) and D-fructose (10.0 mM) and to 2-ketoisocaproate (10.0 mM) were then measured. In the sunflower oil-fed rats, the dietary substitution of starch by fructose decreased basal insulin output, lowered the apparent Km for the insulinotropic action of D-glucose and altered the insulinotropic efficiency of the latter hexose relative to that of other nutrients. Some of these secretory perturbations were opposed by the enrichment of the diet in long-chain polyunsaturated fatty acids, especially ω3 fatty acids. It is proposed that these changes in B-cell secretory behaviour may be linked, in part at least, to both the apparent caloric efficiency of each diet, and hence to the regulation of the islet content in endogenous nutrients, and to alteration of insulin sensitivity considered as a major feature of the present animal model of metabolic syndrome.

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