Summarizing these facts, obesity and associated insulin resistance may increase the risk of DR development via several established mechanisms, namely, dyslipidemia hypertension and glucose dysmetabolism as well as some new mechanisms, whose roles still need to be clarified such as leptin, adiponectin, IL-6, TNF-α and ICAM-1. This evidence concerns the gene TNF and obesity due to melanocortin 4 receptor deficiency.