Irisin Ameliorates Glucolipotoxicity-Associated β-Cell Dysfunction and Apoptosis via AMPK Signaling and Anti-Inflammatory Actions

Abstract

Background/Aims: Islet metabolic disorder and inflammation contribute to the pathogenesis and progression of type 2 diabetes mellitus (T2DM). Irisin is a recently identified adipomyokine with protective effects on metabolic homeostasis and inflammation-suppressing effects in hepatic and vascular cells. The present study examined the effects of irisin on lipid metabolism and inflammation in β cells under glucolipotoxic conditions. Methods: Rat INS-1E β cells and islets isolated from C57BL/6 mice were incubated in glucolipotoxic conditions with or without irisin. Intracellular lipid contents and lipogenic gene expression were determined by enzymatic colorimetric assays and real-time PCR, respectively. Inflammatory status was evidenced by Western blot analysis for the phosphorylation of nuclear factor-κB (NF-κB) p65 and real-time PCR analysis for the expression of pro-inflammatory genes. Results: Irisin reversed glucolipotoxicity-induced intracellular non-esterified fatty acid (NEFA) and triglyceride accumulation, suppressed associated elevations in lipogenic gene expression, and phosphorylated acetyl-CoA-carboxylase (ACC) in INS-1E cells. These demonstrated effects were dependent on irisin-activated adenosine monophosphate-activated protein kinase (AMPK). Meanwhile, AMPK signaling mediated the protective effects of irisin on INS-1E cell insulin secretory ability and survival as well. Additionally, irisin inhibited phosphorylation of NF-κB p65 while decreasing the expression of pro-inflammatory genes in INS-1E cells under glucolipotoxic conditions. Moreover, irisin also improved insulin secretion, inhibited apoptosis, and restored β-cell function-related gene expression in isolated mouse islets under glucolipotoxic conditions. Conclusion: Irisin attenuated excessive lipogenesis in INS-1E cells under glucolipotoxic state through activation of AMPK. Irisin also suppressed overnutrition-induced inflammation in INS-1E cells. Our findings implicate irisin as a promising therapeutic target for the treatment of islet lipid metabolic disorder and islet inflammation in T2DM.

Keywords

• Ins-1E cells
• Insulin
• Islets
• Lipid metabolism
• Nuclear factor-κB
• Pancreas
• Triglyceride
• Diabetes mellitus