Importance of small intestine in diabetic hypercholesterolemia

Numerous studies have demonstrated that poor glycemic control is associated with elevated plasma cholesterol levels in diabetic patients. Experiments have shown that cholesterol synthesis is increased in the small intestine of various diabetic animals. This increase is a generalized phenomenon occurring in all segments of the small intestine. Insulin therapy that normalizes blood glucose levels markedly decreases intestinal cholesterol synthesis in diabetic animals to a level similar to that observed in control animals. Studies have suggested that the hyperphagia that accompanies poorly controlled diabetes is the chief stimulus for the increase in intestinal cholesterol synthesis. However, the direct contact of the intestinal mucosa with nutrients is not the sole trigger for increasing cholesterol synthesis in the small intestine, suggesting that circulating and/or neurological factors play a role. The transport of newly synthesized cholesterol, most of which is in the chylomicron lipoprotein fraction, from the intestines to the circulation is increased in diabetic rats. The sterols associated with these chylomicrons are rapidly cleared from the circulation and delivered to the liver. The increased transport of chylomicrons from the intestine to the circulation in diabetic patients could potentially result in several alterations in lipid metabolism that may increase the risk of atherosclerotic vascular disease.