SIRT5 and obesity due to melanocortin 4 receptor deficiency: SIRT5 has been also proposed to regulate chondrocyte metabolism, including amino acid metabolism, the tricarboxylic acid cycle (TCA) cycle and glycolysis, and the SIRT5-mediated protein lysine malonylation (Mak) pathway was proven to regulate chondrocyte cellular metabolism in obesity-associated OA development [27].