Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.
Veterans Affairs Medical Center, Oklahoma City, OK, USA.
Cartilage. 2021 Dec;13(2_suppl):1185S-1199S. doi: 10.1177/1947603521993209. Epub 2021 Feb 11.
Obesity accelerates the development of osteoarthritis (OA) during aging and is associated with altered chondrocyte cellular metabolism. Protein lysine malonylation (MaK) is a posttranslational modification (PTM) that has been shown to play an important role during aging and obesity. The objective of this study was to investigate the role of sirtuin 5 (Sirt5) in regulating MaK and cellular metabolism in chondrocytes under obesity-related conditions.
MaK and SIRT5 were immunostained in knee articular cartilage of obese mice and different aged C57BL6 mice with or without destabilization of the medial meniscus surgery to induce OA. Primary chondrocytes were isolated from 7-day-old WT and mice and treated with varying concentrations of glucose and insulin to mimic obesity. Sirt5-dependent effects on MaK and metabolism were evaluated by western blot, Seahorse Respirometry, and gas/chromatography-mass/spectrometry (GC-MS) metabolic profiling.
MaK was significantly increased in cartilage of mice and in chondrocytes treated with high concentrations of glucose and insulin (GluIns). Sirt5 was increased in an age-dependent manner following joint injury, and Sirt5 deficient primary chondrocytes had increased MaK, decreased glycolysis rate, and reduced basal mitochondrial respiration. GC-MS identified 41 metabolites. Sirt5 deficiency altered 13 distinct metabolites under basal conditions and 18 metabolites under GluIns treatment. Pathway analysis identified a wide range of Sirt5-dependent altered metabolic pathways that include amino acid metabolism, TCA cycle, and glycolysis.
This study provides the first evidence that Sirt5 broadly regulates chondrocyte metabolism. We observed changes in SIRT5 and MaK levels in cartilage with obesity and joint injury, suggesting that the Sirt5-MaK pathway may contribute to altered chondrocyte metabolism that occurs during OA development.
肥胖加速衰老过程中骨关节炎（OA）的发展，并与软骨细胞代谢改变有关。蛋白质赖氨酸丙二酰化（MaK）是一种翻译后修饰（PTM），已被证明在衰老和肥胖过程中发挥重要作用。本研究旨在探讨 Sirtuin 5（Sirt5）在肥胖相关条件下调节软骨细胞 MaK 和细胞代谢中的作用。
用肥胖小鼠和不同年龄的 C57BL6 小鼠的膝关节关节软骨进行 MaK 和 SIRT5 免疫染色，这些小鼠进行内侧半月板手术以诱导 OA。从小鼠中分离出 7 日龄 WT 和 型原代软骨细胞，并使用不同浓度的葡萄糖和胰岛素处理，以模拟肥胖。通过 Western blot、 Seahorse 呼吸测定法和气相/色谱-质谱/质谱（GC-MS）代谢谱分析评估 Sirt5 对 MaK 和代谢的依赖性。
在 型小鼠的软骨和高浓度葡萄糖和胰岛素（GluIns）处理的软骨细胞中，MaK 显著增加。Sirt5 随关节损伤呈年龄依赖性增加，Sirt5 缺陷型原代软骨细胞 MaK 增加、糖酵解率降低、基础线粒体呼吸减少。GC-MS 鉴定出 41 种代谢物。Sirt5 缺陷在基础条件下改变了 13 种不同的代谢物，在 GluIns 处理下改变了 18 种代谢物。途径分析确定了广泛的 Sirt5 依赖的代谢途径改变，包括氨基酸代谢、TCA 循环和糖酵解。
本研究首次提供了 Sirt5 广泛调节软骨细胞代谢的证据。我们观察到肥胖和关节损伤软骨中 SIRT5 和 MaK 水平的变化，表明 Sirt5-MaK 途径可能有助于 OA 发展过程中发生的软骨细胞代谢改变。
