GLP‑1 improves palmitate‑induced insulin resistance in human skeletal muscle via SIRT1 activity

• Published in: International journal of molecular medicine 2019-09, Vol.44 (3), p.1161-1171
• Main Authors: Jeon, Ja Young, Choi, Sung-E, Ha, Eun Suk, Lee, Han Byeol, Kim, Tae Ho, Han, Seung Jin, Kim, Hae Jin, Kim, Dae Jung, Kang, Yup, Lee, Kwan-Woo
• Format: Article
• Language: English
• Subjects: Adenosine monophosphate; Biotechnology industries; Cyclic adenosine monophosphate; Endoplasmic reticulum; Exenatide; Fatty acids; Glucagon; Glucose; Glucose metabolism; Homeostasis; Insulin resistance; Investigations; Kinases; Messenger RNA; Metabolism; Musculoskeletal system; Peptides; Pharmaceutical industry; Protein kinases; Proteins; RNA; Scientific equipment industry; Skeletal muscle; Type 2 diabetes
• ISSN: 1107-3756; 1791-244X
• DOI: 10.3892/ijmm.2019.4272

The present study investigated whether glucagon like peptide-1 (GLP-1) improves glucose uptake through glucose transporter type 4 (GLUT4), mediated by the activation of sirtuin 1 (SIRT1), in skeletal muscle cells with palmitate induced-insulin resistance. The levels of glucose uptake, GLUT4, protein kinase A (PKA), and cyclic adenosine monophosphate (cAMP) were determined in human skeletal muscle myotubes (HSMMs) exposed to palmitate and GLP-1. Then, to determine whether PKA/cAMP were downstream signals of GLP-1, a PKA inhibitor was used. To determine whether SIRT-1 contributes to GLP-1 action in HSMMs with palmitate-induced insulin resistance, the levels of peroxisome proliferator-activated receptor [gamma] coactivator 1[alpha] (PGC1[alpha]) deacetylation and SIRT-1 activity were assessed using a SIRT1 inhibitor and small interfering RNA (siRNA). The phosphorylation levels of protein kinase B (Akt) and insulin receptor substrate 1 (IRS-1) as insulin signaling pathways, were assessed in GLP-1-treated HSMMs exposed to palmitate. The influence of SIRT1 on the GLP-1-induced activation of insulin signaling pathway was determined using a SIRT1 inhibitor. GLP-1 restored the palmitate-induced reductions in the levels of glucose uptake, GLUT4 mRNA, GLUT4 promoter activity, and GLUT4 protein in HSMMs. PKA and cAMP, as GLP-1 downstream signals, played a role in this process. GLP-1 increased the deacetylation levels of PGC1[alpha], and stimulated SIRT1 in HSMMs. Moreover, the SIRT1 inhibitor and siRNA of SIRT1 suppressed the effect of GLP-1 on GLUT4 expression in HSMMs exposed to palmitate. The SIRT1 inhibitor also prevented the GLP-1-induced phosphorylation of IRS-1 and Akt in palmitate-treated HSMMs. The present findings suggest that in palmitate-induced insulin-resistant HSMM, GLP-1 activates SIRT1 through the PKA/cAMP pathway, which in turn enhances glucose uptake through GLUT4 and the insulin signaling pathway.