SOD3 Is Secreted by Adipocytes and Mitigates High-Fat Diet-Induced Obesity, Inflammation, and Insulin Resistance

Aims: To study the expression and regulatory role of SOD3 in adipocytes and adipose tissue. Results: SOD3 expression was determined in various tissues of adult C57BL/6J mice, human adipose tissue and epididymal adipose tissue, subcutaneous adipose tissue and brown adipose tissue of high-fat diet (HFD)-induced obese mice. SOD3 expression and release were evaluated in adipocytes differentiated from primary human preadipocytes and murine bone marrow-derived mesenchymal stem cells (BM-MSCs). The regulatory role for SOD3 was determined by SOD3 lentivirus knockdown in human adipocytes and global sod3 knockout (KO) mice. SOD3 was expressed at high levels in white adipose tissue, and adipocytes were the main cells expressing SOD3 in adipose tissue. SOD3 expression was significantly elevated in adipose tissue of HFD-fed mice. Moreover, SOD3 expression and release were markedly increased in differentiated human adipocytes and adipocytes differentiated from mouse BM-MSCs compared with undifferentiated cells. In addition, SOD3 silencing in human adipocytes increased expression of genes involved in lipid metabolic pathways such as PPAR γ and SREBP1c and promoted the accumulation of triglycerides. Finally, global sod3 KO mice were more obese and insulin resistant with enlarged adipose tissue and increased triglyceride accumulation. Innovation: Our data showed that SOD3 is secreted from adipocytes and regulates lipid metabolism in adipose tissue. This important discovery may open up new avenues of research for the cytoprotective role of SOD3 in obesity and its associated metabolic disorders. Conclusion: SOD3 is a protective factor secreted by adipocytes in response to HFD-induced obesity and regulates adipose tissue lipid metabolism.