Interestingly, emerging evidence also suggests that FGF21 positively regulates a variety of cellular processes and improves various metabolic abnormalities, as it markedly promotes glucose uptake in cultured adipocytes [57], enhances pancreatic β cell function and insulin secretion [58], upregulates fatty acid oxidation and insulin sensitivity, and improves hepatic steatosis and glycemic control [58,59,60]. Here, INS is linked to fatty liver disease.