Ewendt Franz, Lehmann Anne, Wodak Maximilian F, Stangl Gabriele I
Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, 06120 Halle, Germany.
NutriCARD Competence Cluster for Nutrition and Cardiovascular Health, Dornburger Str. 25, 07743 Jena, Germany.
Biomedicines. 2023 May 12;11(5):1432. doi: 10.3390/biomedicines11051432.
Sclerostin is a protein secreted by osteocytes whose encoding gene is regulated by mechanical stimuli, cytokines, and all- retinoic acid (ATRA) and mediates antianabolic effects on bone formation as an inhibitor of the canonical Wnt/β-catenin pathway. Interestingly, skeletal muscle has recently been identified as another source of sclerostin, suggesting that the musculature may play an important role in maintaining bone mass. However, regulators of muscular expression are virtually unknown. This study investigates the influence of ATRA and the provitamin A derivative beta-carotene (β-C) on sclerostin synthesis in muscle cells. The impact of ATRA, its synthetic analog TTNPB, and β-C on transcription was analyzed by qRT-PCR in C2C12 myotubes and the secreted sclerostin protein by ELISA. ATRA strongly increases the sclerostin synthesis in C2C12 myotubes in a dose-dependent manner. The stimulating effect of ATRA and TTNPB on is largely reduced in the presence of the retinoic acid receptor inhibitor AGN193109. β-C also increases the expression, but this effect vanishes when β-C is coincubated with beta-carotene 15,15'-monooxygenase 1 (BCMO1)-specific siRNA. Thus, ATRA is a potent stimulator of sclerostin release in muscle cells. β-C can also increase mRNA abundance, but this effect depends on the conversion to a retinoid.
硬化蛋白是一种由骨细胞分泌的蛋白质，其编码基因受机械刺激、细胞因子和全反式维甲酸（ATRA）调控，并作为经典Wnt/β-连环蛋白信号通路的抑制剂介导对骨形成的抗合成代谢作用。有趣的是，骨骼肌最近被确定为硬化蛋白的另一个来源，这表明肌肉组织可能在维持骨量方面发挥重要作用。然而，肌肉表达的调节因子几乎完全未知。本研究调查了ATRA和维生素A原衍生物β-胡萝卜素（β-C）对肌肉细胞中硬化蛋白合成的影响。通过qRT-PCR分析了ATRA及其合成类似物TTNPB和β-C对C2C12肌管转录的影响，并通过ELISA分析了分泌的硬化蛋白。ATRA以剂量依赖性方式强烈增加C2C12肌管中的硬化蛋白合成。在存在视黄酸受体抑制剂AGN193109的情况下，ATRA和TTNPB的刺激作用大大降低。β-C也增加了硬化蛋白的表达，但当β-C与β-胡萝卜素15,15'-单加氧酶1（BCMO1）特异性siRNA共同孵育时，这种作用消失。因此，ATRA是肌肉细胞中硬化蛋白释放的有效刺激剂。β-C也可以增加硬化蛋白mRNA丰度，但这种作用取决于向类视黄醇的转化。
