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Dietary Fish Oil Does Not Alter Glucose Tolerance in Conscious Rats^1,2,

Department of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada ^* Department of Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada

We examined the effect of dietary fish oil (MaxEPA) and sunflower seed oil on glucose tolerance in male Wistar rats. Semipurified diets containing 100 g oil/kg diet were administered for 30 d. The fish oil diet contained 26 g (n-3) fatty acids, 16 g eicosapentaenoic acid and 10.4 g docosahexaenoic acid/kg diet. Phospholipids from liver, pancreas, and pancreatic islets were enriched in eicosapentaenoic and docosahexaenoic acids by the fish oil diet. In unfed pentobarbital-anesthetized rats, both basal plasma insulin concentration and insulin responses to intravenous glucose were significantly lower for fish oil-fed rats although glucose responses were similar; however, incremental excursions in plasma insulin over the basal concentrations did not differ. Intravenous glucose tolerance was also examined in conscious unfed rats under minimal restraint. Responses of plasma glucose and insulin were similar for fish oil- and sunflower oil-fed groups. Furthermore, in another experiment, intravenous glucose tolerance tests were similar for conscious rats provided with either 100 g fish oil or corn oil/kg nonpurified diet. Thus, glucose-induced insulin secretion is lower in rats fed fish oil than in rats fed sunflower oil, when tests are conducted in pentobarbital-anesthetized animals but not when tests are performed in conscious rats; there was no effect on plasma glucose in either anesthetized or nonanesthetized rats. Therefore, substitution of (n-3) for (n-6) polyunsaturated fatty acids in tissue phospholipids does not alter plasma glucose or insulin in conscious male Wistar rats.

KEY WORDS: • rats • fish oil • insulin • glucose tolerance • (n-3) fatty acids

¹ Presented in part at two conferences: [Behme, M. T., Dupre, J., Holub, B. J. & Philbrick, D. (1988) Fish oil vs. sunflower seed oil: effect of dietary fat on insulin secretion. Proceedings of the 31st Annual Meeting of the Canadian Federation of Biological Societies p. 61 (abs. 075) and Behme, M. T. & Dupre, J. (1989) MaxEPA vs. sunflower seed oil: effect of dietary fat on insulin secretion. Royal College of Physicians and Surgeons of Canada, Edmonton, AB. Clin. Invest. Med. 12: B30: (abs. C-168)].

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence should be addressed.

Manuscript received 1 March 1993. Initial review completed 13 April 1993. Revision accepted 26 July 1993.