Probiotic administration in patients with MDD for 8 weeks had beneficial effects on the Beck depression inventory, insulin, homeostasis model assessment of insulin resistance, hs-CRP concentrations, and glutathione concentrations, but did not influence fasting plasma glucose, the homeostatic model assessment of beta cell function, quantitative insulin sensitivity check index, lipid profiles, and total antioxidant capacity levels. The gene discussed is INS; the disease is major depressive disorder.