Introduction:
Ceramide, a sphingolipid, has a causal role in metabolic diseases and as a predictive marker of cardiovascular disease (CVD). Ceramides containing saturated acyl tails of 16 and 18 carbons are considered particularly deleterious, due to frequent association with metabolic diseases and negative CVD outcomes. Ceramide synthase (CerS), the enzyme which catalyses ceramide production, has six isoforms, each demonstrating unique fatty-acid substrate preference and tissue localisation. Selective pharmacological inhibition of CerS isoforms which produce deleterious ceramides, could potentially prevent metabolic disease and CVD. Our study aims to examine the cellular and metabolic effects of a novel ceramide synthase inhibitor, ET2.39.
Methods:
HEK293 cells were treated with ET2.39 and the effects on ceramide levels and cell viability were evaluated. Oral pharmacokinetics of ET2.39 was determined in mouse plasma via targeted liquid chromatography-mass spectrometry (LC-MS). A 12 week high-fat diet (HFD) study was undertaken with C57BL/6 mice provided Chow, HFD, or HFD + ET2.39 (~5 mg/kg/day) and physiological measurements (weight gain, fat and lean mass, glucose tolerance) taken throughout. Radiolabelled substrate oxidation assays were performed on fresh tibialis and liver. Lipids extracted from cells and snap-frozen mouse tissues were analysed via targeted LC-MS.
Results and Conclusions:
At 1mM ET2.39 significantly inhibited ceramide production in HEK293 cells, without any impact on cell viability. In mice, oral delivery of 5 mg/kg ET2.39 resulted in a peak plasma concentration of 58 nM at 8 hours, with the half-life determined to be 20 hrs. Administration of ET2.39 in the diet did not prevent HFD-induced weight gain or glucose intolerance, despite some effects on hepatic substrate oxidation and marked decreases in C18:0 ceramide levels in heart (20% lower) and quadriceps (55% lower). Overall, ET2.39 had limited metabolic effects in mice fed a long-term HFD, but was able to prevent deleterious ceramide accumulation in key metabolic tissues.