Dimai H P, Porta S, Wirnsberger G, Lindschinger M, Pamperl I, Dobnig H, Wilders-Truschnig M, Lau K H
Department of Endocrinology, University of Graz Medical School, Austria.
J Clin Endocrinol Metab. 1998 Aug;83(8):2742-8. doi: 10.1210/jcem.83.8.5015.
This study examined the effects of daily oral magnesium (Mg) supplementation on bone turnover in 12 young (27-36 yr old) healthy men. Twelve healthy men of matching age, height, and weight were recruited as the control group. The study group received orally 15 mmol Mg (Magnosolv powder, Asta Medica) daily in the early afternoon with 2-h fasting before and after Mg intake. Fasting blood and second void urine samples were collected in the early morning on days 0, 1, 5, 10, 20, and 30, respectively. Total and ionized Mg2+ and calcium (Ca2+), and intact PTH (iPTH) levels were determined in blood samples. Serum biochemical markers of bone formation (i.e. C-terminus of type I procollagen peptide and osteocalcin) and resorption (i.e. type I collagen telopeptide) and urinary Mg level adjusted for creatinine were measured. In these young males, 30 consecutive days of oral Mg supplementation had no significant effect on total circulating Mg level, but caused a significant reduction in the serum ionized Mg+ level after 5 days of intake. The Mg supplementation also significantly reduced the serum iPTH level, which did not appear to be related to changes in serum Ca2+ because the Mg intake had no significant effect on serum levels of either total or ionized Ca2+. There was a strong positive correlation between serum iPTH and ionized Mg2+ (r = 0.699; P < 0.001), supporting the contention that decreased serum iPTH may be associated with the reduction in serum ionized Mg2+. Mg supplementation also reduced levels of both serum bone formation and resorption biochemical markers after 1-5 days, consistent with the premise that Mg supplementation may have a suppressive effect on bone turnover rate. Covariance analyses revealed that serum bone formation markers correlated negatively with ionized Mg2+ (r = -0.274 for type I procollagen peptide and -0.315 for osteocalcin), but not with iPTH or ionized Ca2+. Thus, the suppressive effect on bone formation may be mediated by the reduction in serum ionized Mg2+ level (and not iPTH or ionized Ca2+). In summary, this study has demonstrated for the first time that oral Mg supplementation in normal young adults caused reductions in serum levels of iPTH, ionized Mg2+, and biochemical markers of bone turnover. In conclusion, oral Mg supplementation may suppress bone turnover in young adults. Because increased bone turnover has been implicated as a significant etiological factor for bone loss, these findings raise the interesting possibility that oral Mg supplementation may have beneficial effects in reducing bone loss associated with high bone turnover, such as age-related osteoporosis.
本研究检测了每日口服镁（Mg）补充剂对12名年轻（27 - 36岁）健康男性骨转换的影响。招募了12名年龄、身高和体重匹配的健康男性作为对照组。研究组在午后早些时候口服15 mmol Mg（Magnosolv粉末，阿斯塔制药公司），服药前后均禁食2小时。分别在第0、1、5、10、20和30天清晨采集空腹血和第二次晨尿样本。测定血样中的总镁、离子化镁（Mg2+）和钙（Ca2+）以及完整甲状旁腺激素（iPTH）水平。测量血清骨形成生化标志物（即I型前胶原肽C端和骨钙素）、骨吸收生化标志物（即I型胶原末端肽）以及经肌酐校正的尿镁水平。在这些年轻男性中，连续30天口服镁补充剂对总循环镁水平无显著影响，但在摄入5天后导致血清离子化镁（Mg+）水平显著降低。镁补充剂还显著降低了血清iPTH水平，这似乎与血清Ca2+的变化无关，因为镁摄入对总钙或离子化钙的血清水平均无显著影响。血清iPTH与离子化镁（Mg2+）之间存在强正相关（r = 0.699；P < 0.001），支持血清iPTH降低可能与血清离子化镁（Mg2+）减少有关的观点。镁补充剂在1 - 5天后还降低了血清骨形成和骨吸收生化标志物水平，这与镁补充剂可能对骨转换率有抑制作用的前提一致。协方差分析显示，血清骨形成标志物与离子化镁（Mg2+）呈负相关（I型前胶原肽r = -0.274，骨钙素r = -0.315），但与iPTH或离子化钙（Ca2+）无关。因此，对骨形成的抑制作用可能是由血清离子化镁（Mg2+）水平降低介导的（而非iPTH或离子化钙）。总之，本研究首次证明，正常年轻成年人口服镁补充剂可导致血清iPTH、离子化镁（Mg2+）水平以及骨转换生化标志物降低。综上所述，口服镁补充剂可能抑制年轻成年人的骨转换。由于骨转换增加被认为是骨质流失的一个重要病因，这些发现提出了一个有趣的可能性，即口服镁补充剂可能对减少与高骨转换相关的骨质流失（如年龄相关性骨质疏松症）具有有益作用。
