Subcellular Distribution of Cholesterol and Sphingolipids in Rat Hepatocytes

Abstract

Hepatocytes are central in energy and lipid homeostasis of mammals and as such are key players in maintaining and regulating serum cholesterol levels. In addition, hepatocytes produce bile, which has detergent properties and is the main product of cholesterol metabolism. The canalicular membrane is the site of bile formation and needs protective mechanisms against the detergent properties of bile. One such mechanism could be a specific lipid composition. We therefore aimed to use a targeted lipidomics approach to determine simultaneously the cholesterol and sphingolipid composition of the organelles involved in lipid synthesis in hepatocytes. Subcellular organelles were isolated from rat liver with standard methodologies and lipids were analyzed by either electrospray ionization mass spectrometry (glycerophospholipids and sphingolipids) or gas chromatography coupled mass spectrometry (sterols). Our data indicate that there is a distinct difference in cholesterol and sphingolipid content in the organelle fractions. Highest cholesterol content is found in basolateral plasma membranes and in the Golgi fraction, while endoplasmic reticulum displays a low cholesterol content. A high proportion of sphingomyelin is present in basolateral plasma membranes, smooth endoplasmic reticulum and in the Golgi apparatus. Ceramide content is higher in basolateral membranes compared to organelles and the canalicular plasma membrane. Glucosylceramide levels are very low and are mostly found in Golgi fractions. Our preliminary data so far show a parallel distribution of cholesterol and sphingolipids in subcellular fractions of rat hepatocytes.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.