DIETARY-LIPID PROFILE IS A DETERMINANT OF TISSUE PHOSPHOLIPID FATTY-ACID COMPOSITION AND RATE OF WEIGHT-GAIN IN RATS

Modifications in membrane fatty acid composition and insulin action are possible through dietary intervention. We examined the metabolic fate of (n-3) fatty acids in male Wistar rats, using three isocaloric, high fat diets. The ET-L, OL-L and SAF-L diets contained edible tallow, olive oil and safflower oil, respectively, with identical amounts of (n-3) fatty acids as linseed oil. Despite isocaloric feeding, weight gain was lower (P < 0.001) in rats fed the more highly saturated ET-L diet (69 +/- 8 g) than in those fed either the high (n-9) fatty acid OL-L diet (93 +/- 2 g) or the high (n-6) fatty acid SAF-L diet (108 +/- 4 g). Analysis of red quadricep fatty acid composition revealed phospholipid (n-3) fatty acid levels in the ET-L-fed group (21.6 +/- 0.8 g/100 g fatty acids) to be significantly higher than in either the OL-L-fed (17.7 +/- 0.6 g/100 g fatty acids, P < 0.05) or SAF-L-fed (15.3 +/- 0.7 g/100 g fatty acids, P < 0.05) group. A similar pattern was observed in other muscles and white adipose tissue. A follow-up study using C-14-labeled (n-3) fatty acids in the diet showed greater (n-3) fatty acid incorporation in the ET-L-fed group relative to the other two groups and conversely lower (CO2)-C-14 production than in the SAF-L-fed group. These results demonstrate that metabolic fate of dietary fatty acids is strongly influenced by the overall fatty acid profile of the diet. The functional consequences are seen in the differing rates of weight gain despite equal intakes, with tissue (n-3) fatty acid apparently protective against weight gain. Because obesity is a powerful predictor of insulin resistance, these results have implications for dietary treatment of diabetes.