Nutrient absorption

Interesting advances occurred recently in nutrient absorption. Kinetics of triacylglycerol appearance in endoplasmic reticulum, Golgi apparatus, and l ymph support the hypothesis that endoplasmic reticulum-to-Golgi transport i s rate-limiting for lipid absorption. Apolipoprotein B does not appear nece ssary :for initial formation of chylomicron-sized lipid particles in the en doplasmic reticulum, but rather for their movement out of the endoplasmic r eticulum and to the Golgi, If peptides are protected from luminal proteolys is by fatty acylation, or if a nonpeptide drug, acyclovir, is esterified wi th valine to enhance bioavailability, the peptides nevertheless are absorbe d by peptide transporters, Experimental conditions needed to use human ilea l mucosa for in vitro absorption studies are described. Intestinal mucosa c ontains leptin receptors, and leptin inhibits galactose absorption, suggest ing a new site for leptin's modulation of body mass. The enhancer element f or the apoB gene is located much farther from its structural gene in the in testine than in the liver.