FGF21 and hyperinsulinism: The results of the present study support the findings of prospective cohort studies, demonstrating that plasma FGF21 levels and expression of hepatic FGF21 were acutely increased following intake of a high fat-diet for 1 day, and that the increases in plasma FGF21 levels preceded hyperinsulinemia, hyperglycemia, and weight gain in mice fed a high-fat diet.