The role of C16:0 ceramide in the development of obesity and type 2 diabetes: CerS6 inhibition as a novel therapeutic approach

Abstract

Objective Ectopic fat deposition is associated with increased tissue production of ceramides. Recent genetic mouse studies suggest that specific sphingolipid C16:0 ceramide produced by ceramide synthase 6 (CerS6) plays an important role in the development of insulin resistance. However, the therapeutic potential of CerS6 inhibition not been demonstrated. Therefore, we pharmacologically investigated the selective ablation of CerS6 using antisense oligonucleotides (ASO) in obese insulin resistance animal models. Methods We utilized ASO as therapeutic modality, CerS6 ASO molecules designed and synthesized were initially screened for in-vitro knock-down (KD) potency and cytotoxicity. ASOs with >85% inhibition of CerS6 mRNA were selected for further investigations. Most promising ASOs verified for in-vivo KD efficacy in healthy mice. CerS6 ASO (AAGATGAGCCGCACC) was found most active with hepatic reduction of CerS6 mRNA expression. Prior to longitudinal metabolic studies, we performed a dose titration target engagement analysis with CerS6 ASO in healthy mice to select the optimal dose. Next, we utilized leptin deficiency ob/ob and high fat diet (HFD) induced obese mouse models for pharmacological efficacy study. Results CerS6 expression were significantly elevated in the liver and brown adipose, this was correlated with significantly elevated C16:0 ceramide concentrations in plasma and liver. Treatment with CerS6 ASO selectively reduced CerS6 expression by ∼90% predominantly in the liver and this CerS6 KD resulted in a significant reduction of C16:0 ceramide by about 50% in both liver and plasma. CerS6 KD resulted in lower body weight gain and accompanied by a significant reduction in whole body fat and fed/fasted blood glucose levels (1% reduction in HbA1c). Moreover, ASO-mediated CerS6 KD significantly improved oral glucose tolerance (during oGTT) and mice displayed improved insulin sensitivity. Thus, CerS6 appear to play an important role in the development of obesity and insulin resistance. Conclusions Our investigations identified specific and selective therapeutic valid ASO for CerS6 ablation in in-vivo. CerS6 should specifically be targeted for the reduction of C16:0 ceramides, that results in amelioration of insulin resistance, hyperglycemia and obesity. CerS6 mediated C16:0 ceramide reduction could be a potentially attractive target for the treatment of insulin resistance, obesity and type 2 diabetes.

Lipids, inflammasomes, metabolism, and disease

“…164 Ceramide production is associated with an inflammatory response during obesity-induced diabetes. [165][166][167] In agreement, stimulation of LPS-primed BMDMs with ceramide results in caspase-1 cleavage and IL-1β secretion 168 ( Figure 3). Elevated NLRP3 activity in adipose tissue macrophages, in turn, triggers T cell activation and, thereby, impairs insulin sensitivity.…”

Analysis of urinary sphingolipids using liquid chromatography‐tandem mass spectrometry in diabetic nephropathy

“…In the present study, however, the urinary C18:0-to-C16:0, C20:0-to-C16:0, C22:0-to-C16:0, C24:0-to-C16:0 and C22:0-to-C20:0 ratios were significantly lower in the diabetes patients than the control participants ( Figure S4), whereas the C22:0-to-C20:0 ratio was higher in patients with stage 3 diabetic nephropathy. These findings suggest that the modulation of ceramide metabolism by diabetic nephropathy might differ between serum and urine, and that the modulation of urinary ceramide levels by diabetic nephropathy might be different depending on ceramide classes; urinary Cer C16:0 levels might be modulated by the pathogenesis of early diabetic nephropathy 34 , and Cer C22:0 levels might be influenced by the progressed diabetic nephropathy. One of the mechanisms for this unique modulation of very long-chain ceramide species in urine might involve the class of ceramide synthase (CerS) expressed in the kidney.…”

Icosabutate Exerts Beneficial Effects Upon Insulin Sensitivity, Hepatic Inflammation, Lipotoxicity, and Fibrosis in Mice

“…The comparable effect of pioglitazone and icosabutate on glucose tolerance in response to a glucose load is remarkable, given that icosabutate does not target PPAR‐γ (as evidenced by lack of effect on plasma adiponectin and body weight, in addition to lack of PPAR‐γ or PPAR‐δ activity in vitro [in vitro data not shown]). Reductions in hepatic lipid species known to aggravate insulin sensitivity such as AA metabolites, DAG, and ceramides could potentially explain icosabutate's potent effects on glycemic control, and/or activation of ω‐3‐sensitive G‐protein–coupled receptors …”