Because T1D and T2D differ in pathophysiology and underlying risk factors (with T1D being an autoimmune disease, whereas insulin resistance, driven mainly by obesity, is the hallmark of T2D), consistent results for insulin-treated T1D and T2D are suggestive of an insulin therapy effect independent of underlying disease etiology. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.