Department of Biomedical Engineering, Indiana University-Purdue Indianapolis (IUPUI), Indianapolis, Indiana, United States of America.
PLoS One. 2022 Jun 17;17(6):e0270001. doi: 10.1371/journal.pone.0270001. eCollection 2022.
Diabetes mellitus is a metabolic disorder that causes health concerns worldwide. Patients with diabetes exhibit multisystemic symptoms, including loss of bone quality over time. The progressive deterioration of bone promotes failure to withstand damage and increases the risk of fractures. Much of the molecular and metabolic mechanism(s) in diabetic bone remains unclear. In vitro studies suggest that hyperglycemia inhibits mineralization, affecting bone formation and function. In this study, inhibition of osteoblast differentiation was induced using hyperglycemia to assess whether high glucose promotes mitochondrial impairment along with altered bone matrix formation. It was hypothesized that bone energy metabolism would be altered in these cells as calcium deposition, a key phase for bone function, is suppressed. Early passages of osteoblast like MC3T3-E1 cells were differentiated under normal and high glucose conditions. To investigate osteoblast differentiation, we quantified calcium accumulation by alizarin red staining and analyzed immunoblots of key proteins. To assess mitochondrial function, we quantified mitochondrial DNA (mtDNA), detected expression and function of key proteins from the Tricarboxylic (TCA) cycle, measured mitochondrial respiration, and fuel oxidation of alternative nutrients. Results confirmed previous work showing that mineralization was inhibited and AKT expression was reduced in high glucose-treated bone cells. Unexpectedly, high glucose-treated osteoblast cells utilize both mitochondrial respiration and glycolysis to maintain energy demands with partial help of fatty acid for reliance of baseline bioenergetics. These metabolic shifts suggest that hyperglycemia maintain bone metabolic needs in an early differentiated state concurrent to the inhibition in bone matrix formation.
糖尿病是一种代谢紊乱，在全球范围内引起健康问题。糖尿病患者表现出多系统症状，包括随着时间的推移骨质量的丧失。骨的进行性恶化促进了对损伤的抵抗力下降，并增加了骨折的风险。糖尿病患者的许多分子和代谢机制仍不清楚。体外研究表明，高血糖抑制矿化，影响骨形成和功能。在这项研究中，使用高血糖诱导成骨细胞分化抑制来评估高葡萄糖是否促进线粒体损伤以及改变骨基质形成。研究假设这些细胞中的骨能量代谢会发生改变，因为钙沉积（骨功能的关键阶段）受到抑制。成骨细胞样 MC3T3-E1 细胞的早期传代会在正常和高葡萄糖条件下分化。为了研究成骨细胞分化，我们通过茜素红染色定量钙积累，并分析关键蛋白的免疫印迹。为了评估线粒体功能，我们定量了线粒体 DNA（mtDNA），检测三羧酸（TCA）循环中关键蛋白的表达和功能，测量了线粒体呼吸和替代营养物的氧化燃料。结果证实了之前的工作，表明在高葡萄糖处理的骨细胞中，矿化受到抑制，AKT 表达减少。出乎意料的是，高葡萄糖处理的成骨细胞利用线粒体呼吸和糖酵解来维持能量需求，部分依赖脂肪酸来维持基础生物能量。这些代谢变化表明，高血糖在抑制骨基质形成的同时，维持了早期分化状态下的骨代谢需求。
