MTOR and obesity due to melanocortin 4 receptor deficiency: Another cGMP-producing enzyme is GUCY2C; its inactivation is linked to diet-induced obesity and has been suggested to contribute to the onset of colorectal cancer by upregulation of proliferation AKT/mTOR signalling while suppressing mitochondrial function in mouse intestinal epithelial cells and human colorectal cancer cells [125–127].