PPARGC1A and obesity due to melanocortin 4 receptor deficiency: The expression of PGC1-α in β-cells is induced by extracellular signals including facilitators of GSIS, such as glucagon-like peptide-1(GLP-1) and cAMP, and stressors that impair β-cell function such as streptozotocin, glucocorticoids, obesity, cold exposure, and glucolipotoxicity (47–50).