Dietary carbohydrates and intestinal lipoprotein production.

PURPOSE OF REVIEW

To review new evidence that dietary monosaccharides enhance intestinal chylomicron secretion.

RECENT FINDINGS

There is abundant evidence linking diets that are high in carbohydrate content with hypertriglyceridemia. In addition, epidemiological studies reveal that the increase in dietary sugars and refined carbohydrates are associated with the rising prevalence of the metabolic syndrome and type 2 diabetes. Association studies, however, cannot prove causation. Mechanistic studies to date have focused on the link between carbohydrate ingestion and hepatic very low-density lipoprotein metabolism, with very little appreciation that dietary carbohydrates may also regulate intestinal lipid absorption and chylomicron secretion. We have recently studied this phenomenon in healthy humans and have shown that both glucose and fructose, infused concomitantly with a lipid emulsion directly into the duodenum and under conditions of a pancreatic clamp, stimulate chylomicron particle secretion. There are a paucity of data regarding the cellular and molecular mechanisms of this effect, which remains largely unknown and a matter of speculation.

SUMMARY

Sugar in the diet enhances dietary fat absorption and chylomicron secretion. Whether this phenomenon contributes quantitatively to the well described hypertriglyceridemia that occurs with diets high in carbohydrate and low in fat requires further investigation, as does the underlying cellular mechanism. A thorough understanding of this phenomenon could provide useful information to optimize dietary guidelines.