MTOR and obesity due to melanocortin 4 receptor deficiency: Specifically, in preclinical models of obesity, leptin induces cardiomyocyte hypertrophy, while stimulating fibroblast proliferation and collagen synthesis mediated by the production of galectin-3, transforming growth factor-beta (TGF-β), and connective tissue growth factor production (CTGF) through oxidative stress increased by the activation of the mechanistic target of the rapamycin (mTOR) pathway [24].