Antibody Research Laboratories, Kyowa Hakko Kirin Co. Ltd., Tokyo 194-8533, Japan.
Biochem Biophys Res Commun. 2010 Jul 30;398(3):513-8. doi: 10.1016/j.bbrc.2010.06.110. Epub 2010 Jul 1.
Alpha-Klotho (alphaKl) regulates mineral metabolism such as calcium ion (Ca(2+)) and inorganic phosphate (Pi) in circulation. Defects in mice result in clinical features resembling disorders found in human aging. Although the importance of transmembrane-type alphaKl has been demonstrated, less is known regarding the physiological importance of soluble-type alphaKl (salphaKl) in circulation.
The aims of this study were: (1) to establish a sandwich ELISA system enabling detection of circulating serum salphaKl, and (2) to determine reference values for salphaKl serum levels and relationship to indices of renal function, mineral metabolism, age and sex in healthy subjects.
We successively developed an ELISA to measure serum salphaKl in healthy volunteers (n=142, males 66) of ages (61.1+/-18.5year). The levels (mean+/-SD) in these healthy control adults were as follows: total calcium (Ca; 9.46+/-0.41mg/dL), Pi (3.63+/-0.51mg/dL), blood urea nitrogen (BUN; 15.7+/-4.3mg/dL), creatinine (Cre; 0.69+/-0.14mg/dL), 1,25 dihydroxyvitamin D (1,25(OH)(2)D; 54.8+/-17.7pg/mL), intact parathyroid hormone (iPTH; 49.2+/-20.6pg/mL), calcitonin (26.0+/-12.3pg/mL) and intact fibroblast growth factor (FGF23; 43.8+/-17.6pg/mL). Serum levels of salphaKl ranged from 239 to 1266pg/mL (mean+/-SD; 562+/-146pg/mL) in normal adults. Although salphaKl levels were not modified by gender or indices of mineral metabolism, salphaKl levels were inversely related to Cre and age. However, salphaKl levels in normal children (n=39, males 23, mean+/-SD; 7.1+/-4.8years) were significantly higher (mean+/-SD; 952+/-282pg/mL) than those in adults (mean+/-SD; 562+/-146, P<0.001). A multivariate linear regression analysis including children and adults in this study demonstrated that salphaKl correlated negatively with age and Ca, and positively with Pi. Finally, we measured a serum salphaKl from a patient with severe tumoral calcinosis derived from a homozygous missense mutation of alpha-klotho gene. In this patient, salphaKl level was notably lower than those of age-matched controls.
We established a detection system to measure human serum salphaKl for the first time. Age, Ca and Pi seem to influence serum salphaKl levels in a normal population. This detection system should be an excellent tool for investigating salphaKl functions in mineral metabolism.
阿尔法-klotho（alphaKl）调节钙（Ca(2+)）和无机磷（Pi）等矿物质在循环中的代谢。老鼠的缺陷导致其表现出类似于人类衰老的临床特征。尽管跨膜型 alphaKl 的重要性已经得到证实，但对于循环中可溶性型 alphaKl（salphaKl）的生理重要性知之甚少。
本研究的目的是：（1）建立一种可检测循环血清 slphaKl 的夹心 ELISA 系统，（2）确定健康受试者血清 slphaKl 水平的参考值及其与肾功能、矿物质代谢、年龄和性别的关系。
我们成功地为健康志愿者（n=142，男性 66 岁）建立了一种检测血清 slphaKl 的 ELISA 系统。这些健康对照组成年人的水平（均值+/-标准差）如下：总钙（Ca；9.46+/-0.41mg/dL）、Pi（3.63+/-0.51mg/dL）、血尿素氮（BUN；15.7+/-4.3mg/dL）、肌酐（Cre；0.69+/-0.14mg/dL）、1,25 二羟维生素 D（1,25(OH)(2)D；54.8+/-17.7pg/mL）、完整甲状旁腺激素（iPTH；49.2+/-20.6pg/mL）、降钙素（26.0+/-12.3pg/mL）和完整成纤维细胞生长因子（FGF23；43.8+/-17.6pg/mL）。正常成年人的血清 slphaKl 水平为 239-1266pg/mL（均值+/-标准差；562+/-146pg/mL）。尽管 slphaKl 水平不受性别或矿物质代谢指标的影响，但 slphaKl 水平与 Cre 和年龄呈负相关。然而，正常儿童（n=39，男性 23 名，均值+/-标准差；7.1+/-4.8 岁）的 slphaKl 水平明显高于成年人（均值+/-标准差；562+/-146，P<0.001）。本研究中包括儿童和成年人的多元线性回归分析表明，salphaKl 与年龄和 Ca 呈负相关，与 Pi 呈正相关。最后，我们测量了一名严重肿瘤性钙质沉着症患者的血清 slphaKl，该患者的 alpha-klotho 基因突变是纯合错义突变。在这名患者中，salphaKl 水平明显低于年龄匹配的对照组。
我们首次建立了一种检测人血清 slphaKl 的检测系统。年龄、Ca 和 Pi 似乎会影响正常人群的血清 slphaKl 水平。该检测系统应该是研究 slphaKl 在矿物质代谢中的功能的理想工具。
