In line with previously reported data (12, 40, 41), this study shows not only an inverse relationship between FGF-21 and HDL-c but also a direct correlation between HDL-c and Vitamin D levels, as we previously reported (42), thus supporting the hypothesis that FGF-21-driven putative protective role against diabetes and obesity may depend on normal Vitamin D and HDL-cholesterol levels. This evidence concerns the gene FGF21 and diabetes mellitus.