Impact of reduced hepatic ceramide levels in high-fat diet mice on glucose metabolism

Dysregulation of insulin action in hepatocytes, common in obesity, significantly contributes to insulin resistance, type 2 diabetes, and metabolic syndrome. Previous research highlights ceramides' role in these conditions. This study explores the impact of ceramides by silencing the serine palmitoyltransferase (Sptlc2) gene, crucial for the initial ceramide biosynthesis, using hydrodynamic gene delivery. Male C57BL/6 mice were randomly divided into three groups: one on a low-fat diet (LFD) receiving scrambled shRNA plasmids, another on a high-fat diet (HFD) with scrambled shRNA plasmids, and a third on HFD with a plasmid targeting Sptlc2. Analyses included RT-PCR for gene expression, western blot for protein levels, and UHPLC/MS/MS for lipid profiling. Glucose metabolism was evaluated via oral glucose tolerance tests, homeostatic model assessment of insulin resistance, and glucose-6-phosphate analysis. Results showed that HFD induces insulin resistance by inhibiting insulin signaling and increasing active lipid levels in hepatocytes. Sptlc2 silencing reduced ceramide accumulation, improving insulin signaling and glucose metabolism. Notably, ceramide synthesis inhibition did not significantly affect other lipid levels, highlighting ceramide's critical role in hepatic insulin resistance.