Association of bone metabolism with the degree of proteinuria in patients of chronic kidney diseases / 中华肾脏病杂志

ABSTRACT

Objective To study the association of bone metabolism with the degree of proteinuria in patients of chronic kidney diseases (CKD). Methods A total of 71 CKD patients diagnosed as primary glomerulopathy were randomly selected from 2008.1-2009.5 in the First People's Hospital of Shanghai. They were classified into three groups according to proteinuria:group A of 25 patients, proteinuria ＜1.0 g/24 h; group B of 16 patients, proteinuria 1.0-＜3.5 g/24 h;group C of 30 patients, proteinuria ≥ 3.5 g/24 h. Fifty-eight healthy persons were selected from our medical examination center at the same time as control. Serum albumin, calcium, phosphorus,PTH, 25 hydroxy vitamin D3, bone gla protein (BGP), degradation products of C-terminal telopeptides of type I collagen (CTx), 24-h urinary protein excretion, and the ratio of urinary calcium to creatinine (UCa/Cr) were measured. Bone mineral density (BMD) was detected by dualenergy X-ray absorptiometry. Results Compared with control group, serum levels of calcium [(2.23±0.08), (2.13±0.09), (2.04±0.06)vs (2.37±0.12)mmol/L], 25-(OH)D3 [(50.19±6.58), (47.78±6.69), (42.42±10.85) vs (56.34±8.34) nmol/L] were significantly lower and UCa/Cr was significantly higher in A, B, C groups respectively (all P＜0.05). In group B and C, BGP was lower [(18.69±7.35), (16.13±5.76) vs (22.88±6.21) μg/L] and CTx was higher [(413.59±114.93),(516.21±314.25) vs (304.53±234.15) ng/L] (all P＜0.05). BMD was lower only in group C [(1.028±0.090) vs (1.090±0.062) g/cm2, P＜0.05]. Pearson analysis showed that 24-h urinary protein excretion was negatively correlated with serum calcium and 25 hydroxy vitamin D3, and positively correlated with UCa/Cr. UCa/Cr was positively correlated with serum CTx and negatively correlated with BGP. 25-(OH) D3 was positively correlated with BGP and negatively correlated with CTx. Conclusion Bone metabolism disorder exists in CKD patients, presenting the decrease of bone formation and the increase of bone resorption, which is associated with as the degree of proteinuria, especially in patients with nephrotic syndrome.