Influence of dietary fat quantity and composition on insulin binding to rat intestine

It is presently recommended that the general US population reduce the consumption of dietary lipid in order to reduce the risk of several chronic diseases, although the mechanism(s) through which dietary factors alter cellular function remain unclear. Dietary lipid composition has been shown to alter the plasma membrane lipid composition of adipocytes, muscle and other tissues. These changes in membrane lipid composition have been correlated with altered insulin receptor binding and signal transduction. Insulin receptors are present on mucosal cells of the intestinal tract, although their role in this tissue is not fully understood. We have fed rats diets containing 6, 31.4 or 76% of calories from lard (Protocol 1) and found insulin binding to be increased in the duodenum and decreased in the colon of rats fed the high-fat diet. Additionally, we compared diets containing either 12 or 37.6% of calories from beef tallow (saturated fatty acids or SFA) or corn oil (polyunsaturated fatty acids or PUFA; Protocol 2) and found insulin binding in the jejunum to be significantly decreased by a low SFA or high PUFA diet relative to the low PUFA diet. These results suggest that intestinal insulin receptors are responsive to dietary lipid quantity and quality which may have implications as to the role of dietary factors in modifying nutrient transport and/or risk of intestinal disease.