NOS3 and obesity due to melanocortin 4 receptor deficiency: Obesity has also been linked to elevated p53 expression in vascular endothelial cells, which reduces the activation of endothelial nitric oxide synthase (eNOS) and glucose transporter (GLUT)1 in these cells and contributes to suppression of mitochondrial biogenesis and glucose uptake in the skeletal muscle, leading to systemic metabolic dysfunction [41].