Ceramide Synthase 6 (CerS6), the enzyme generating C16-ceramide, has been implicated in cellular stress response, and targeting this enzyme protected mice from diet-induced weight gain and metabolic dysfunction. We investigated the metabolomic response to high fat diet in mouse liver and plasma in CerS6 WT and KO mice. Upon weaning, male WT and KO mice were placed on either a control (Ctrl) or a high fat (HFD) diet for 16 weeks. Animals underwent body composition assessment then were fasted for 4 hours before euthanasia and tissue collection. Snap-frozen liver and plasma samples were subjected to untargeted metabolomic analysis by commercial service provider MetabolonR. Metabolomics analysis revealed that CerS6 knockout induced changes in every major liver metabolic pathway. A significant decrease in nearly every sphingolipid with a C16 acyl chain was noted in both liver and plasma of CerS6 KO mice. On Ctrl diet KO mice demonstrated few differences from the WT in hepatic phosphatidylcholine (PC), phosphatidylethanolamines (PE), and glycosyl-PE, whereas CerS6 KO mice fed HFD showed significantly elevated concentrations of many of these lipids. In plasma, PC concentrations were significantly lower in CerS6 KO mice fed the Ctrl diet while PE levels were significantly lower in CerS6 KO mice fed a HFD, indicating a differential response to diet and genotype in plasma versus liver. In addition to lipids, CerS6 KO mice also demonstrated differences in metabolism of several amino acids in both liver and plasma, with more changes on HFD. Importantly, significant changes in glycolysis intermediates as well as TCA cycle metabolites were observed in CerS6 KO mice. Several glycolytic intermediates were elevated in CerS6 KO mice on HFD in the liver and on both diets in the plasma. TCA cycle metabolites were significantly elevated in the plasma of CerS6 KO mice on HFD but reduced in liver. Of note, CerS6-deficient mice had dramatically elevated bile acids both in liver and plasma compared to WT, but HFD decreased the differences.
Our study confirmed previous observations that CerS6 knockout protects from diet induced weight gain. New metabolomics data demonstrated that disruption of the C16-ceramide production by CerS6 alters multiple metabolic pathways: lipids, amino acids, and carbohydrates. These changes could alter the cellular energetics and contribute to whole-body protection from diet induced weight gain.