Role of Microsomal Triglyceride Transfer Protein (MTP) in Lipid Processing Pathways in Retinal Pigment Epithelium.

Lipid processing in the retinal pigment epithelium (RPE) is important for maintaining the health and function of the neural retina and the RPE itself. One mode of en mass lipid transport from the RPE is apolipoprotein B-containing lipoproteins (Blps), the assembly of which is regulated by microsomal triglyceride transfer protein (MTP). To gain an initial understanding of how the loss of MTP and, thereby, Blp secretion alters other lipid processing pathways in the RPE, we measured the expression of proteins associated with β-oxidation and lipid droplets in mice lacking MTP expression in the RPE (RPEΔMttp) and age-matched controls. Expression of perilipin 2, a lipid droplet-associated protein, nearly doubled in the RPE of RPEΔMttp, and its localization with neutral lipids also increased. Meanwhile, expression of CPT1A, which mediates the transport of fatty acids into the mitochondria for β-oxidation, was unaffected. These results suggest that the loss of Blp assembly alters intracellular lipid storage patterns. Future studies will examine the effects of the loss of RPE-specific MTP expression and Blp secretion on additional lipid processing pathways.