INS and major depressive disorder: Compared to the placebo, the vitamin D and probiotic co-supplementation resulted in significant improvements in beck depression inventory total score, beck anxiety inventory scores, and general health questionnaire scores as well as significant reductions in serum insulin HOMA-IR, and serum 25-OH-vitamin D, the quantitative insulin sensitivity check index, serum HDL-cholesterol levels, C-reactive protein (CRP), plasma nitric oxide (NO), and plasma total antioxidant capacity (TAC).