Nandy Ananya, Helderman Ron C M, Thapa Santosh, Peck Sun H, Richards Alison, Jayapalan Shobana, Narayani Nikita, Czech Michael P, Rosen Clifford J, Rendina-Ruedy Elizabeth
Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, United States.
Frank H. Netter M.D. School of Medicine, Quinnipiac University, North Haven, CT 06518, United States.
J Bone Miner Res. 2025 Feb 2;40(2):283-298. doi: 10.1093/jbmr/zjae195.
Bone homeostasis within the skeletal system is predominantly maintained by bone formation and resorption, where formation of new bone involves maturation of stromal cells to mineral and matrix secreting mature osteoblasts, which requires cellular energy or adenosine triphosphate. Alterations in systemic metabolism can influence osteoblast function. In line with this, type 2 diabetes mellitus (T2DM), a common metabolic disorder is also associated with reduced bone formation and increased risk of fracture. Impairment in lipid metabolism is one of the key features associated with T2DM-related pathologies in multiple tissues. Therefore, we tested the hypothesis that the reduced bone formation reported in obese murine models of impaired glucose tolerance is a function of disrupted lipid metabolism in osteoblasts. We first confirmed that mice fed a high-fat diet (HFD) have reduced bone microarchitecture along with lower bone formation rates. Interestingly, osteoblasts from obese mice harbor higher numbers of cytosolic lipid droplets along with decreased bioenergetic profiles compared to control cells. Further supporting this observation, bone cortex demonstrated higher total lipid content in HFD fed mice compared to control-fed mice. As a further proof of principle, we generated a novel murine model to conditionally delete Plin2 in osteoblast-progenitor cells using Prrx1-Cre, to enhance lipid droplet breakdown. Our data demonstrate that knocking down Plin2 in an osteoprogenitor specific manner protects from HFD induced osteoblast dysfunction. Furthermore, the mechanism of action involves enhanced osteoblast fatty acid oxidation. In conclusion, the current studies establish that HFD induced glucose intolerance leads to perturbations in osteoblast lipid metabolism, thus causing lower bone formation, which can be protected against by increasing fatty acid oxidation.
骨骼系统内的骨稳态主要通过骨形成和骨吸收来维持,其中新骨形成涉及基质细胞成熟为分泌矿物质和基质的成熟成骨细胞,这需要细胞能量或三磷酸腺苷。全身代谢的改变会影响成骨细胞功能。与此一致的是,2型糖尿病(T2DM)这种常见的代谢紊乱也与骨形成减少和骨折风险增加有关。脂质代谢受损是与T2DM相关的多种组织病理相关的关键特征之一。因此,我们检验了这样一个假设,即糖耐量受损的肥胖小鼠模型中报道的骨形成减少是成骨细胞脂质代谢紊乱的结果。我们首先证实,喂食高脂饮食(HFD)的小鼠骨微结构减少,同时骨形成率降低。有趣的是,与对照细胞相比,肥胖小鼠的成骨细胞含有更多的胞质脂滴,同时生物能量特征降低。进一步支持这一观察结果的是,与对照喂养的小鼠相比,喂食HFD的小鼠骨皮质显示出更高的总脂质含量。作为原理的进一步证明,我们构建了一种新型小鼠模型,使用Prrx1-Cre有条件地删除成骨祖细胞中的Plin2,以增强脂滴分解。我们的数据表明,以成骨祖细胞特异性方式敲低Plin2可保护免受HFD诱导的成骨细胞功能障碍。此外,作用机制涉及增强成骨细胞脂肪酸氧化。总之,目前的研究表明,HFD诱导的糖耐量异常导致成骨细胞脂质代谢紊乱,从而导致骨形成降低,通过增加脂肪酸氧化可以预防这种情况。
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