Jensen Brian, Farach-Carson Mary C, Kenaley Erin, Akanbi Kamil A
Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
Exp Cell Res. 2004 Dec 10;301(2):280-92. doi: 10.1016/j.yexcr.2004.08.030.
We studied the effect of extracellular Ca(2+) concentration (Ca(2+)) on adipocyte differentiation. Preadipocytes exposed to continuous Ca(2+) higher than 2.5 mmol/l accumulated little or no cytoplasmic lipid compared to controls in 1.8 mmol/l Ca(2+). Differentiation was monitored by Oil Red O staining of cytoplasmic lipid and triglyceride assay of accumulated lipid, by RT-PCR analysis of adipogenic markers, and by the activity of glycerol-3-phosphate dehydrogenase (GPDH). Elevated Ca(2+) inhibited expression of peroxisome proliferator-activated receptor gamma, CCAAT/enhancer binding protein alpha, and steroid regulatory binding element protein. High Ca(2+) significantly inhibited differentiation marker expression including adipocyte fatty acid binding protein, and GPDH. The decrease in Pref-1 expression that accompanied differentiation also was prevented by high Ca(2+). Treatment of 3T3-L1 cells with high Ca(2+) did not significantly affect cell number or viability and did not trigger apoptosis. Levels of intracellular Ca(+2) remained unchanged in various Ca(2+). Treatment of 3T3-L1 with pertussis toxin (PTX) partially restored lipid accumulation and increased differentiation markers in cells treated with 5 mmol/l Ca(2+). 'Classical' parathyroid cell Ca(2+) sensing receptors (CaSR) were not detected either by RT-PCR or by Western blotting. These results suggest that continuous exposure to high Ca(2+) inhibits preadipocyte differentiation and that this may involve a G-protein-coupled mechanism mediated by a novel Ca(2+) sensor or receptor.
我们研究了细胞外钙离子浓度（Ca(2+)）对脂肪细胞分化的影响。与处于1.8 mmol/l Ca(2+)的对照组相比，暴露于高于2.5 mmol/l的持续Ca(2+)环境中的前脂肪细胞积累的细胞质脂质很少或没有。通过对细胞质脂质进行油红O染色和对积累的脂质进行甘油三酯测定、通过对脂肪生成标志物进行逆转录聚合酶链反应（RT-PCR）分析以及通过甘油-3-磷酸脱氢酶（GPDH）的活性来监测分化情况。升高的Ca(2+)抑制过氧化物酶体增殖物激活受体γ、CCAAT/增强子结合蛋白α和类固醇调节结合元件蛋白的表达。高Ca(2+)显著抑制包括脂肪细胞脂肪酸结合蛋白和GPDH在内的分化标志物的表达。高Ca(2+)也阻止了伴随分化出现的前脂肪细胞表面蛋白1（Pref-1）表达的降低。用高Ca(2+)处理3T3-L1细胞对细胞数量或活力没有显著影响，也不会引发细胞凋亡。在不同的Ca(2+)条件下，细胞内Ca(+2)水平保持不变。用百日咳毒素（PTX）处理3T3-L1细胞可部分恢复脂质积累，并增加用5 mmol/l Ca(2+)处理的细胞中的分化标志物。通过RT-PCR或蛋白质印迹法均未检测到“经典”的甲状旁腺细胞钙离子感受受体（CaSR）。这些结果表明，持续暴露于高Ca(2+)会抑制前脂肪细胞分化，这可能涉及一种由新型钙离子传感器或受体介导的G蛋白偶联机制。
