Different solubility dietary fibers regulate thermogenesis in rats through modulating adipose tissue activity and colonic Clostridiales

Dietary fibers are classified into soluble and insoluble dietary fibers according to different solubility, which play different physiological roles. The study aimed to investigate the mechanism of dietary fiber solubility affecting thermogenesis and gut microbiota in rats. Twenty-four Sprague Dawley male rats were selected and divided randomly into 3 treatments. Dietary treatments included diet without dietary fiber (CON), control diet supplemented with 10 % inulin (SDF) and control diet supplemented with 10 % cellulose (IDF). The results showed that rats in the SDF group gained less body weight and had lower feed intake ( P  < 0.001). The glucose tolerance of rats fed SDF and IDF was significantly improved ( P  < 0.05). Compared with the CON group, the mRNA expression of thermogenesis-related genes CIDEA, HOXC8 and TMEM26 in inguinal white adipose tissue of rats in the SDF group and IDF group was significantly activated ( P  < 0.05). The expression of brown adipose tissue thermogenesis-related proteins UCP1, CIDEA and HOXC8 in rats of SDF group was significantly increased ( P  < 0.01). The abundance of Faecalibaculum and Gemmiger at the genus level, which both belonged to the order Clostridiales in the SDF group, was significantly increased ( P  < 0.001). In conclusion, both SDF and IDF can regulate body thermogenesis by promoting browning of white adipose tissue. Particularly, SDF was able to further promote thermogenesis in rats by increasing the expression of UCP1 protein in brown adipose tissue and modulating the abundance of order Clostridium.