Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2001
Publication Date: N/A
Interpretive Summary: We studied the effects of menhaden oil, rich in omega-3 fatty acids, and corn oil, rich in omega-6 fatty acids on plasma insulin levels and insulin receptors from red blood cell ghosts in female miniature swine. One group of animals was made hypercholesterolemic by feeding cholesterol and lard for two months, the other group served as control. Both groups were fed the experimental diets for 23 weeks and blood samples were collected at regular intervals. We did not observe any significant effect of cholesterol feeding on plasma insulin level. Menhaden oil increased plasma insulin levels compared to corn oil. Cholesterol feeding and menhaden oil had no significant effect on insulin binding to red blood cell membranes. We observed a significant negative correlation- ship between insulin binding and anisotropy (a measure of rigidity of the membrane). Our data suggest that insulin receptors on red blood cells are in a dynamic state and insulin binding is related to the fluidity of the membrane. These data will help medical professionals, dietitians, nutritionists, basic scientists and other health professionals to recommend diets to the general population to reduce the incidence of hyperlipidemia.
Technical Abstract: The effect of fish oil on red blood cell membrane insulin receptors in normal and hypercholesterolemic minipigs was examined. A group of minipigs were made hypercholesterolemic by feeding cholesterol and lard for 2 months; the other group served as controls and was fed stock diet. Both groups were then fed either corn oil or menhaden oil or a mixture of the two for 23 additional weeks. Blood was collected at 0, 2, 4, 12 and 23 weeks after the start of the experimental diets and membranes were prepared from the red blood cells. Insulin binding to red blood cell membranes was measured by radioreceptor assay. Plasma insulin was measured by radioimmunoassasy. Insulin binding to red blood cell membrane was compared with the fluidity of the membrane. There was no significant effect of cholesterol feeding on plasma insulin concentrations. After 23 weeks on experimental diet plasma insulin was significantly higher in minipigs fed menhaden oil compared to those fed corn oil. No such effect was observed in hypercholesterolemic minipigs. No significant effect of either hypercholesterolemia or fish oil was observed on red blood cell insulin binding. Significant negative relationship was observed between insulin binding and anisotropy at 4C for all probes but at 37C significant negative relationship was observed only with polar probes. The data suggest that insulin receptors on erythrocytes are in a dynamic state and that insulin binding is related to the membrane fluidity.