Grifola frondosa polysaccharide Ameliorates Inflammation and Insulin Resistance by Regulating Macrophage Polarization of liver in Type 2 Diabetes Mellitus Rats

Type 2 diabetes mellitus (T2DM) is a common metabolic disease characterized by a lack of insulin secretion, insulin resistance (IR), and hyperglycemia. Given its high prevalence and multifarious complications, diabetes is globally ranked as the third leading cause of mortality. It is critical to discover efficient medication substitutes in order to lessen the drawbacks and adverse effects of traditional diabetes medication therapy. Previous studies have shown that Grifola frondosa polysaccharide (GFP) have the positive effects in regulating blood glucose and insulin resistance, but the understanding of its regulatory mechanism is still limited. Therefore, this study aimed to investigate the effects of GFP on liver inflammation induced by a high-fat diet (HFD) combined with streptozotocin (STZ) in type 2 diabetic rats and to explore its possible mechanisms. The results showed that GFP intervention reduced weight loss and hyperglycemia symptoms, as well as lowered FINS, HOMA-IR, IPGTT-AUC, and IPITT-AUC to different degrees in T2DM rats. At the same time, after GFP intervention, the secretion level of inflammatory factors (TNF-, IL-1{beta}, MCP-1) was down-regulated and the secretion level of anti-inflammatory factor (IL-10) was up-regulated in the liver tissue of T2DM rats. Furthermore, GFP reduced macrophage infiltration in liver tissue, inhibited macrophage M1-type polarization, and promoted M2-type polarization. These results suggest that GFP intervention could attenuate the hepatic inflammatory response in T2DM rats; possible mechanisms for this effect include hepatic macrophage infiltration and M1/M2 polarization. Summary statementThis study revealed the improvement effect of GFP on hepatic inflammation and insulin resistance in T2DM rats and to explore the possible key roles of hepatic macrophages and their potential mechanisms.