INS and obesity due to melanocortin 4 receptor deficiency: In obesity, adipose tissue becomes severely dysfunctional, does not store excess energy, causes ectopic fat deposition [26], enhances the levels of free fatty acid metabolites (e.g., ceramide, long-chain fatty acyl Coenzyme A, and di-acyl glycerol) [27], and regulates insulin resistance by constraining the protein-kinase B (PKB) pathway [28].