The Potential Role of Milk-Fat-Globule Membrane (MFGM) Proteins in Regulating the Size of Milk-Lipid Droplets

Abstract

The aim of this thesis was to identify protein factors that may regulate the size of lipid droplets in milk. To address this hypothesis, the relative amounts of specific MFGM proteins on lipid droplets fractionated according to size were measured. Protein amounts were estimated by quantitative western blotting and confocal microscopy. By quantitative confocal microscopy, small lipid droplets (<1.26 um) contained more XOR, BTN, adipophilin (ADPH) and fatty acid binding protein (FABP) per surface area than medium (>1.26 to <2.8 um) or large (>2.8 um) sized droplets. Milk-fat-globule-EFG-8 (MFG-E8) protein was more evenly distributed on small, medium and large droplets. In contrast CD36, in both cow and mouse milk, was concentrated on small droplets and absent from large droplets. Based on these data, we postulate that CD36 possibly association with FABP may have a function in small lipid droplet secretion by localizing excessively on the small lipid droplets.