Differential Effects of Saturated and Monounsaturated Fatty Acids on Chylomicron Secretion and Expression of Key Genes That Regulate Intestinal Lipid Metabolism in Insulin Resistant Subjects

The overaccumulation of apolipoprotein (apo)B-48-containing lipoproteins of intestinal origin observed in patients with insulin-resistance is now thought to be attributable to both elevated intestinal production and reduced clearance of these lipoproteins. Substantial evidence exists indicating that elevated plasma levels of these lipoproteins are associated with increased cardiovascular disease (CVD) risk. Therefore, reduction of atherogenic plasma triglyceride-rich lipoproteins à (TRL) levels of intestinal origin appears to be crucial to improve CVD risk associated with insulin-resistance. In this regard, there is some evidence that the clinical recommendation to replace dietary saturated fatty acids (SFAs) by monounsaturated fatty acids (MUFAs) reduces CVD risk in the general population. Although the beneficial impact of PUFAs on CVD risk has been related primarily to favorable changes in plasma LDL-cholesterol levels, recent data suggest that chronic MUFA consumption may also exert beneficial effects on CVD risk by reducing postprandial lipemia. The impact of substituting SFAs by MUFAs on postprandial lipid response may be of even greater significance in dyslipidemic patients with insulin-resistance among whom intestinal TRLs represent a large proportion of the atherogenic lipoproteins. The general objective of the proposed research is to investigate how dietary MUFAs in place of SFAs modify intestinal lipoprotein metabolism in men and women with dyslipidemia associated with insulin-resistance. The investigators hypothesize that the intestinal secretion of apoB-48-containing lipoproteins will be lower following a diet rich in MUFAs than after consuming a diet rich in SFAs. The investigators also hypothesize that substitution of SFAs by MUFAs will be associated with significant alterations in expression of key genes and proteins involved in intestinal lipoprotein metabolism.