PPARG and obesity due to melanocortin 4 receptor deficiency: Variants in the pparγ gene have been linked to severe obesity [201], insulin resistance [54], a decreased risk of T2DM in certain ancestries [202], or an increased risk of T2DM [54], hypercholesterolemia [203], and systemic sclerosis characterized by diffuse fibrosis and vascular abnormalities [204].