INS and gestational diabetes: In summary, dietary fiber fermented by gut microbiota (e.g., Bifidobacterium, Lactobacillus) produces SCFAs including acetate, propionate, and butyrate, which act on FFAR2 and FFAR3 to inhibit histone deacetylases, suppress insulin signaling, activate AMPK, stimulate GLP-1 and insulin secretion, and enhance FFAR2 signaling in pregnancy to stimulate insulin release and pancreatic β-cell proliferation, thereby maintaining glucose homeostasis in gestational diabetes.