PTPN1 and obesity due to melanocortin 4 receptor deficiency: Moreover, it is worth noting that low-grade inflammation is a feature of both T2DM and obesity, and the expression of PTP1B was shown to be linked to that of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukins IL-1 and IL-6 [30,31].