Glycerol Kinase Overexpression Suppresses Lipid Synthesis but Increases Mitochondrial Membrane Potential and Thermogenesis Activity in Adipocytes

Abstract

Obesity and type 2 diabetes mellitus are among the main factors contributing to the increase in mortality and disability in the modern world. Therefore, it is a priority to develop new methods, including genetic and cellular engineering, to create ectopic thermogenic fat depots capable of dissipating excess energy. In this study, we overexpressed glycerol kinase (GK), a key enzyme of the futile triacylglycerol cycle (TAG cycle) to generate thermogenic adipocytes. The protein-coding sequence of GK was amplified from the mouse liver mRNA and delivered to adipocytes by lentiviral transduction. Adipocyte metabolism was analyzed by radioisotope monitoring of [³H]- and [¹⁴C]-labelled glucose analogues. Mitochondrial membrane potential, thermogenesis, and lipid droplet morphology were assessed using fluorescent probes JC-1, ERthermAC, and BODIPY493/503, respectively. Lentiviral delivery of the GK gene increases mRNA expression 130-fold and protein levels by 30% in adipocytes. GK overexpression enhances glucose uptake by adipocytes and suppresses fatty acids synthesis and re-esterification without altering lipid droplet morphology. Increase in the glucose uptake upon GK overexpression is associated with increase in the mitochondrial potential and stimulation of thermogenesis. GK overexpression improves metabolic profile of the adipocytes, which could contribute to elimination of metabolic disorders associated with obesity by increasing utilization of the glucose excess during thermogenesis. Nevertheless, the detailed mechanisms underlying stimulation of these processes require further investigation.