DeMambro Victoria E, Tian Li, Karthik Vivin, Rosen Clifford J, Guntur Anyonya R
Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME, USA.
Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA.
Bone Rep. 2023 Jul 24;19:101705. doi: 10.1016/j.bonr.2023.101705. eCollection 2023 Dec.
Parathyroid hormone acts through its receptor, PTHR1, expressed on osteoblasts, to control bone remodeling. Metabolic flexibility for energy generation has been demonstrated in several cell types dependent on substrate availability. Recent studies have identified a critical role for PTH in regulating glucose, fatty acid and amino acid metabolism thus stimulating both glycolysis and oxidative phosphorylation. Therefore, we postulated that PTH stimulates increased energetic output by osteoblasts either by increasing glycolysis or oxidative phosphorylation depending on substrate availability. To test this hypothesis, undifferentiated and differentiated MC3T3E1C4 calvarial pre-osteoblasts were treated with PTH to study osteoblast bioenergetics in the presence of exogenous glucose. Significant increases in glycolysis with acute ∼1 h PTH treatment with minimal effects on oxidative phosphorylation in undifferentiated MC3T3E1C4 in the presence of exogenous glucose were observed. In differentiated cells, the increased glycolysis observed with acute PTH was completely blocked by pretreatment with a Glut1 inhibitor (BAY-876) resulting in a compensatory increase in oxidative phosphorylation. We then tested the effect of PTH on the function of complexes I and II of the mitochondrial electron transport chain in the absence of glycolysis. Utilizing a novel cell plasma membrane permeability mitochondrial (PMP) assay, in combination with complex I and II specific substrates, slight but significant increases in basal and maximal oxygen consumption rates with 24 h PTH treatment in undifferentiated MC3T3E1C4 cells were noted. Taken together, our data demonstrate for the first time that PTH stimulates both increases in glycolysis and the function of the electron transport chain, particularly complexes I and II, during high energy demands in osteoblasts.
甲状旁腺激素通过其在成骨细胞上表达的受体PTHR1发挥作用，以控制骨重塑。能量产生的代谢灵活性已在几种依赖底物可用性的细胞类型中得到证实。最近的研究已经确定了甲状旁腺激素在调节葡萄糖、脂肪酸和氨基酸代谢方面的关键作用，从而刺激糖酵解和氧化磷酸化。因此，我们推测甲状旁腺激素通过根据底物可用性增加糖酵解或氧化磷酸化来刺激成骨细胞增加能量输出。为了验证这一假设，我们用甲状旁腺激素处理未分化和分化的MC3T3E1C4颅盖前成骨细胞，以研究在外源葡萄糖存在下成骨细胞的生物能量学。在外源葡萄糖存在的情况下，对未分化的MC3T3E1C4进行约1小时的急性甲状旁腺激素处理，观察到糖酵解显著增加，而对氧化磷酸化的影响最小。在分化细胞中，急性甲状旁腺激素处理后观察到的糖酵解增加被Glut1抑制剂（BAY - 876）预处理完全阻断，导致氧化磷酸化的代偿性增加。然后，我们在没有糖酵解的情况下测试了甲状旁腺激素对线粒体电子传递链复合体I和II功能的影响。利用一种新型的细胞质膜通透性线粒体（PMP）检测方法，结合复合体I和II的特异性底物，我们注意到在未分化的MC3T3E1C4细胞中，24小时甲状旁腺激素处理后基础和最大耗氧率略有但显著增加。综上所述，我们的数据首次证明，在成骨细胞高能量需求期间，甲状旁腺激素刺激糖酵解增加以及电子传递链的功能，特别是复合体I和II。
