FGF21 has demonstrated the ability to modulate blood glucose and insulin resistance in mice, effectively reducing lipid levels, blood glucose, and serum insulin, while enhancing insulin sensitivity in diet-induced obesity models, mostly through improved glucose absorption by skeletal muscle and diminished hepatic glucose synthesis (127).FGF21 can affect glucose homeostasis in both insulin-dependent and insulin-independent manners. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.