Division of Nephrology and Hypertension, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, USA.
Nephrol Dial Transplant. 2010 Dec;25(12):3970-7. doi: 10.1093/ndt/gfq316. Epub 2010 Jun 7.
Increased serum phosphate is associated with cardiovascular disease. Compared with whites, blacks have significantly higher serum phosphate and increased risk of hyperphosphataemia in health and chronic kidney disease (CKD). While population-based studies suggest that diminished urinary phosphorus excretion in blacks may explain these differences, few physiological studies explored the potential mechanisms. The aim of this study was to examine racial differences in postprandial urinary mineral ion excretion in health and in CKD.
Twenty-eight healthy (18 white and 10 black) and 19 CKD (9 white and 10 black) subjects consumed a standardized meal; after which, blood and urine samples were collected for 4 h for measurement of phosphate, calcium, parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23).
Although serum phosphate did not differ by race, blacks had ∼30% lower postprandial fractional excretion of phosphate than whites in health (P < 0.001) and CKD (P = 0.02). Similarly, blacks had ∼35% lower fractional excretion of calcium in health (P = 0.02) and CKD (P = 0.3). Moreover, the postprandial response in serum calcium among CKD subjects differed by race (P = 0.03), with serum calcium significantly decreasing in whites but not blacks.
Blacks had lower fractional excretion of phosphate than whites despite similar levels of PTH and FGF23 in health and in CKD, suggesting racial variability in renal sensitivity to phosphaturic hormones. Furthermore, blacks defend postprandial serum calcium more effectively than whites in CKD. Further studies are needed to define the mechanisms underlying these observations and evaluate whether racial differences in mineral ion handling may contribute to disparities in CKD outcomes.
血清磷酸盐水平升高与心血管疾病有关。与白人相比，黑人的血清磷酸盐水平明显更高，且在健康人群和慢性肾脏病（CKD）患者中发生高磷酸盐血症的风险增加。尽管基于人群的研究表明，黑人的尿磷排泄减少可能解释了这些差异，但很少有生理学研究探讨潜在的机制。本研究旨在检查健康人群和 CKD 患者餐后尿矿物质离子排泄的种族差异。
28 名健康（18 名白人，10 名黑人）和 19 名 CKD（9 名白人，10 名黑人）受试者食用标准化餐食；4 小时后采集血样和尿样，以测量磷酸盐、钙、甲状旁腺激素（PTH）和成纤维细胞生长因子 23（FGF23）。
尽管血清磷酸盐无种族差异，但黑人在健康人群和 CKD 患者中的餐后磷酸盐分数排泄率比白人低约 30%（P<0.001）。同样，黑人在健康人群和 CKD 患者中的钙分数排泄率低约 35%（P=0.02）。此外，CKD 患者的餐后血清钙反应存在种族差异（P=0.03），白人的血清钙显著降低，而黑人则没有。
尽管健康人群和 CKD 患者的 PTH 和 FGF23 水平相似，但黑人的磷酸盐分数排泄率低于白人，这表明肾脏对磷排泄激素的敏感性存在种族差异。此外，黑人在 CKD 中更有效地维持餐后血清钙。需要进一步研究来确定这些观察结果的机制，并评估矿物质离子处理的种族差异是否可能导致 CKD 结局的差异。
