Intestinal secretion of lipids and lipoproteins during carbohydrate absorption in the rat.

To assess the effects of carbohydrate ingestion on the characteristics and quantities of triglyceride-rich lipoproteins produced by the intestine, mesenteric lymph was collected from rats receiving intraduodenal infusions of saline, sucrose or starch. Lymph total lipid (mg/hour) was greatest during saline infusion, decreased during sucrose and became significantly less (P less than 0.05) during starch infusion. Lipoproteins were isolated from lymph by ultracentrifugation followed by gel filtration chromatography. During saline infusion total lipid in very low density lipoproteins (VLDL) was 2-fold higher than total lipid in chylomicrons; with both carbohydrate infusions this ratio increased to seven. Both carbohydrates significantly lowered the rate of secretion of total lipid as chylomicrons. The VLDL lipid secretion rates during sucrose infusion were equivalent to those during saline, whereas starch infusion tended to decrease VLDL lipid secretion rates. These results suggest that during the process of carbohydrate absorption, carbohydrate does not enhance the flow of intestinal VLDL into the circulation; digestion and absorption of complex carbohydrates in fact may retard the intestinal contribution of triglyceride-rich lipoproteins.