CerS1 but Not CerS5 Gene Silencing, Improves Insulin Sensitivity and Glucose Uptake in Skeletal Muscle

Abstract

Skeletal muscle is perceived as a major tissue in glucose and lipid metabolism. High fat diet (HFD) lead to the accumulation of intramuscular lipids, including: long chain acyl-CoA, diacylglycerols, and ceramides. Ceramides are considered to be one of the most important lipid groups in the generation of skeletal muscle insulin resistance. So far, it has not been clearly established whether all ceramides adversely affect the functioning of the insulin pathway, or whether there are certain ceramide species that play a pivotal role in the induction of insulin resistance. Therefore, we designed a study in which the expression of CerS1 and CerS5 genes responsible for the synthesis of C18:0-Cer and C16:0-Cer, respectively, was locally silenced in the gastrocnemius muscle of HFD-fed mice through in vivo electroporation-mediated shRNA plasmids. Our study indicates that HFD feeding induced both, the systemic and skeletal muscle insulin resistance, which was accompanied by an increase in the intramuscular lipid levels, decreased activation of the insulin pathway and, consequently, a decrease in the skeletal muscle glucose uptake. CerS1 silencing leads to a reduction in C18:0-Cer content, with a subsequent increase in the activity of the insulin pathway, and an improvement in skeletal muscle glucose uptake. Such effects were not visible in case of CerS5 silencing, which indicates that the accumulation of C18:0-Cer plays a decisive role in the induction of skeletal muscle insulin resistance.

Insulin sensitivity is preserved in mice made obese by feeding a high starch diet

“…This is similar to the observation in humans where obese, insulin-sensitive individuals have similar levels of Cer18:0 to lean individuals, while obese, insulin-resistant individuals had increased levels ( Tonks et al, 2016 ). Previous studies have also shown Cer18:0 content in muscle to be increased in mice fed a Hi-F diet ( Turner et al, 2013 ; Turpin-Nolan et al, 2019 ; Frangioudakis et al, 2010 ) while reductions of Cer18:0, through deletion of ceramide synthase 1, has been associated with improved glucose tolerance and insulin sensitivity ( Turpin-Nolan et al, 2019 ; Błachnio-Zabielska et al, 2022 ). Our data also showed a negative correlation between skeletal muscle insulin sensitivity (insulin-stimulated glucose uptake) and muscle Cer18:0 levels.…”

Loss of ceramide synthase 5 inhibits the development of experimentally induced aortic valve stenosis

“…Calcification of the AV is a fundamental mechanism in the development of AVS 4,35 . In general, ceramides influence calcification, but the specific role of CerS5 has not been investigated yet 20,31,36 . Our work shows that inhibition of CerS5 leads to reduced calcification of VICs in vitro.…”

“…The impact of ceramides on obesity and lipid metabolism is well studied 14,31,32 . It has been shown that CerS5 is essential to maintain systemic C16 ceramide levels in mice 14 .…”

“…13,15 The impact of ceramides on obesity and lipid metabolism is well studied. 14,31,32 It has been shown that CerS5 is essential to maintain systemic C16 ceramide levels in mice. 14 CerS5 −/− mice are partially protected from an increase in ceramide serum levels due to high-fat diet.…”

Insulin sensitivity is preserved in mice made obese by feeding a high starch diet

“…This is similar to the observation in humans where obese, insulin-sensitive individuals have similar levels of Cer18:0 to lean individuals, while obese, insulin-resistant individuals had increased levels [4]. Previous studies have also shown Cer18:0 content in muscle to be increased in mice fed a HFD [9; 21; 23] and reductions of Cer18:0 through deletion of ceramide synthase 1 (CerS1), has been reported to improve glucose tolerance and insulin sensitivity [21; 24]. Our data also showed a negative correlation between skeletal muscle insulin sensitivity (insulin-stimulated glucose uptake) and muscle Cer18:0 levels.…”