Background: Substantial studies have demonstrated that fasting therapy (FT) can inhibit the inflammatory response and improve insulin resistance (IR); however, the underlying mechanisms are still unclear. This study aimed to explore the related mechanisms of intermittent FT for the treatment of IR.
Methods: A rat IR model was established through collaboration of a high-fat diet with streptozotocin (STZ) injection. 8 rats were treated with intermittent FT. A positive control group was treated with metformin (MET). Mouse 3T3-L1 pre-adipocytes were cultured and induced into adipocytes in vitro, and were used as the cellular IR model. Blood insulin, glucose, and homeostatic model assessment (HOMA)-IR index were determined. Enzyme-linked immunosorbent assay (ELISA) and western blotting were used to detect inflammatory markers. Oil Red O staining determined the lipid accumulation. An NLRP3 inflammasome agonist served to investigate the effects of FT on IR in 3T3-L1 adipocytes.
Results: The high levels of blood insulin, glucose, and HOMA-IR induced by high-fat diet and STZ were significantly decreased by FT. The FT also reduced the level of C-reactive protein (CRP), interleukin (IL)-1β, IL-18, caspase-1, and increased the expression of glucose transporter 1 (GLUT1), insulin receptor substrate 1 (IRS1), and IRS2 in both the rat models and 3T3-L1 adipocytes. In addition, FT significantly relieved lipid accumulation in the liver of rats. Application of NLRP3 inflammasome agonist weakened the effect of FT on IR in the IR 3T3-L1 adipocytes.
Conclusions: These results suggest that FT can ameliorate the high-fat diet-and STZ-induced IR in rats through inhibition of NLRP3 inflammasome.
Keywords: Intermittent fasting therapy; NLR pyrin domain containing 3 (NLRP3); inflammation; insulin resistance (IR); type 2 diabetes mellitus.