Curcumin ameliorates hepatic steatosis and insulin resistance through the JNK2/FOXO1/Bcl6 axis and regulate the intestinal flora structure

Abstract Curcumin, a polyphenol extracted from the plant turmeric rhizoma, is well known for its strong antioxidant capacity and beneficial effects on the treatment of obesity induced by a high-fat diet in mice. However, the exact mechanism of action by which it improves obesity remains elusive. We hypothesize that curcumin exerts its anti-obesity effects on high-fat-diet (HFD) induced obesity through both direct effects on metabolic pathways and indirect effects on metabolism by improving the intestinal flora structure. The aim of this study was to investigate the effect of curcumin on the biological phenotype of HFD-induced obese mice, to determine the related metabolic pathways and to determine whether the intestinal flora is involved. C57BL/6 mice were fed a HFD for 8 weeks and then gavaged with 200 mg/kg curcumin or the same volume of vehicle for 16 weeks. The body weight, blood glucose level, blood lipid level, insulin resistance and oxidative stress level of the mice were detected to determine the effect of the treatment on lipid metabolism. Liver transcriptome analysis combined with qPCR and cell experiments revealed that curcumin improves hepatic steatosis and insulin resistance in mice fed a high-fat diet by downregulating the JNK2/FOXO1/Bcl6 axis. Curcumin treatment can regulate the composition and structure of gut microbiota in high-fat diet-fed mice, increase gut microbiota diversity, and increase the relative abundance of beneficial bacteria such as Coriobacteriaceae, Mailhella, Faecalibaculum, Phocaeicola vulgatus, Parvibacter vulgatus, and Bacteroides intestinalis, which are associated with obesity and metabolic disorders, while reducing the relative abundance of harmful bacteria such as Alistipes, Oscillibacter, Lactobacillus johnsonii, and Acutalibacter muris. In conclusion, curcumin ameliorated hepatic steatosis and insulin resistance in HFD-fed mice by down-regulating hepatic JNK2/FOXO1/Bcl6 axis and altering the composition and structure of gut microbiota.