SIRT1 and obesity due to melanocortin 4 receptor deficiency: Moreover, proanthocyanidin extracts derived from CB leaves can exhibit anti-obesity activity owing to the upregulation of SIRT1 and the consequent deacetylation of PPAR- γ together with C/EBP- α downregulation and BMP4 upregulation to increase brown fat levels in a high-fat diet-induced rat model of obesity (Zhou, Chen & Ye, 2017).