IRS1 and obesity due to melanocortin 4 receptor deficiency: Low-grade chronic inflammation associated with obesity correlates with insulin resistance [7,8], particularly tumour necrosis factor α (TNFα), secreted by adipocytes and adipose tissue macrophages, impairs the insulin signalling via serine phosphorylation of insulin receptor substrate 1 (IRS1), reducing glucose transporter 4 (GLUT4) membrane expression, therefore decreasing glucose entry into cells [9,10].