Figure 2.

The regulation of glucose and lipid homoeostasis via gut microbiota. Functional oligosaccharides promote the growth of probiotics and reverse diversified composition of microbial flora. They also enhance the production of beneficial metabolites such as SCFAs, bile acids, and lactic acid. Subsequently, probiotics and their metabolism products affect glucose and lipid metabolism via numerous metabolic mechanisms. SCFAs bound to GPCRs GPR41 or GPR43 promote the expression of gut hormones such as PYY, GLP-1, and GLP-2. In peripheral tissues, insulin and glucose sensitivity are improved and gluconeogenesis is suppressed. This activation of GPCR influences the balance of lipid synthesis and lipolysis, peroxisome proliferator-activated receptor γ (PPARγ)–related differentiation, and the expression of angiopoietin-like 4. Bile acids control the production of fibroblast growth factor (FGF) 19 and GLP-1 and influence glucose homeostasis through the activation of the nuclear farnesoid X receptor and membrane-bound GPCR in the ileum. Probiotics and their metabolic products influence inflammation, oxidative stress, and intestinal permeability. Intestinal permeability is improved by the integration of gut epithelial cells, adherence to the mucosal surface, and the intestinal mucosal barrier. ZO-1, zonula occludens-1.