FGFR1 and type 1 diabetes mellitus: Plasma FGF21 level in WT diabetic mice significantly decreased at 1, 2 and 4 months after diabetes onset (Fig.1C), which was accompanied by obvious trend of cardiac FGFR1 mRNA level up-regulation at 1 and 2 months after DM onset (Fig.1D), indicating that type 1 diabetes systematically down-regulation of FGF21 resulted in its receptor compensative up-regulation in cardiac tissue.