Microsomal Triglyceride Transfer Protein: From Lipid Metabolism to Metabolic Diseases.

Microsomal triglyceride transfer protein (MTP) was first identified as an endoplasmic reticulum (ER) resident protein that helps in the transfer of neutral lipids to nascent apolipoprotein B (apoB). Its critical role in the assembly and secretion of apoB-containing lipoproteins was identified in abetalipoproteinemia patients who have mutations in MTP and completely lack apoB-containing lipoproteins in the circulation. It has been established now that MTP not only is involved in the transfer of neutral lipids but also plays a role in cholesterol ester and cluster of differentiation 1d (CD1d) biosynthesis. Besides neutral lipids, MTP may also help in the transfer of sphingolipids such as ceramides and sphingomyelin to the apoB-containing lipoproteins. MTP is a multifunctional protein, and its deregulation during pathophysiological conditions gives rise to different metabolic conditions. This book chapter discusses the physiological role and regulation of MTP to maintain the homeostasis of lipids and lipoproteins. It also reviews the regulation of MTP during certain pathophysiological conditions and provides a brief overview of therapeutic interventions that can be possibly used to target its activity or expression to alleviate some of these metabolic diseases.