Differentiation of glomerular, tubular, and normal proteinuria: determinations of urinary excretion of β2-microglobulin, albumin, and total protein

A low molecular weight beta(2)-globulin (beta(2)-microglobulin), albumin, and total protein were measured in concentrated 24-hr urine specimens from 20 healthy subjects and 30 patients with clinical proteinuria of glomerular or tubular type. Classification of proteinuria was made on the basis of clinical diagnosis and size distribution of urinary proteins after gel chromatography. The molecular radii (Stokes' radii) of beta(2)-microglobulin and albumin, estimated by gel chromatography, were 15 A and 35 A.The average 24-hr urinary excretion in healthy subjects was 0.12 mg for beta(2)-microglobulin, 10 mg for albumin, and 80 mg for total protein. The patients with renal glomerular disorders had normal or only somewhat increased excretion of beta(2)-microglobulin, despite considerably increased excretion of albumin and total protein. Most of the patients with tubular dysfunction excreted large amounts of beta(2)-microglobulin, although they excreted normal or only slightly increased amounts of albumin and only moderately increased quantities of total protein. Consequently, the ratio or urinary albumin/urinary beta(2)-microglobulin was high in glomerular proteinuria (1100: 14,200), intermediate in normal proteinuria (33: 163), and low in tubular proteinuria (1.0: 13.3). Determinations of urinary clearances of beta(2)-microglobulin and albumin in four healthy subjects and 11 patients indicated that increased excretions of the two proteins were associated with increased clearances. The results suggest that quantitative determinations of urinary beta(2)-microglobulin and urinary albumin may be useful for detecting disorders of the renal handling of plasma proteins. The findings also seem to suggest a selective tubular reabsorption of the two proteins.Estimates on sera revealed a close correlation between serum levels of beta(2)-microglobulin and creatinine and also a greatly raised serum concentration of beta(2)-microglobulin after bilateral nephrectomy.     

Urinary excretion of albumin and beta 2-microglobulin in a population from an area where Balkan nephropathy is endemic.

The urinary excretion of albumin and beta 2-microglobulin in a population of 294 persons, living in an area where Balkan nephropathy is endemic, has been studied. In fifty-six (about 19%) of the subjects the beta 2-microglobulin concentration was above the +2 SD level for a reference group of healthy individuals from non-endemic areas. Albumin elevation was found in forty-four (about 15%) of the cases. In twenty-one of the subjects the urinary concentration of both beta 2-microglobulin and albumin were increased, in sixteen of these cases the relationship between the two proteins was consistent with tubular proteinuria. An increased beta 2-microglobulin excretion is considered to be a sign of Balkan nephropathy. Radioimmunoassay of the protein is sensitive enough to detect tubular proteinuria at an early stage and is suggested as a suitable screening test for the disease.     

Diuresis-dependent excretions of low-molecular mass proteins in urine: beta 2-microglobulin, lysozyme, and ribonuclease

An investigation was carried out into how the low-molecular mass proteins beta 2-microglobulin, lysozyme, and ribonuclease were excreted over 8 h after high fluid intake (22 ml/kg of body weight in 15 min). With increasing urine flow rate the amount of lysozyme excreted per hour or per millimole creatinine increased more markedly than that of beta 2-microglobulin while at the same time the excretion rate of ribonuclease decreased. The effect of urinary flow upon the excretion rates of the various low-molecular mass proteins has to be considered as a preanalytical factor when these proteins are used as indicators of tubular dysfunction.     

Renal glomerular and tubular impairment during strenuous exercise in young women

Creatinine, total protein, albumin and beta2-microglobulin were measured in the urine of fifteen healthy women before and after strenuous short-term exercise. The heavy intermittent load produced an increased urinary excretion of total protein, albumin and beta2-microglobulin, while creatinine was unaffected. The renal clearance of albumin and beta2-microglobulin showed very high values after stopping the exercise. However, 45 min after the end of exercise, total protein returned to initial values while albumin and beta2-microglobulin remained high. The urinary ratio between beta2-microglobulin and albumin is higher in urine collected after exercise than in normal proteinuria. This implies that post-exercise proteinuria is of glomerular and tubular origin.     

Urinary excretion of complement C3d in patients with renal diseases

INTRODUCTION: Complement-mediated tubular injury may play an important role in the progression of renal diseases. C3d is a presumed marker of complement activation. Its precursor C3dg has been detected in the urine of patients with membranous nephropathy. However, little is known of the renal handling of C3d or its excretion in other renal diseases. METHODS: We measured the urinary excretion of albumin, IgG, beta2-microglobulin (beta2m), and of complement C3d in patients with tubulo-interstitial nephritis (TIN; n= 8), in patients with membranous nephropathy (n = 35) and in patients with nonmembranous glomerular diseases (23 nonproliferative and 21 proliferative). Fractional excretions (FE) were calculated using creatinine clearance as marker of GFR. RESULTS: C3d was not measurable in the urine of the healthy controls, but was detectable in seven out of eight of the TIN patients (median excretion 0.11 mU min-1, range 0.006-2.4 mU min-1). In these patients the urinary excretion of beta2m was clearly elevated (median 26.6 micro g min-1, range 1.0-103 micro g min-1). The FE of C3d correlated with the FE of beta2microglobulin (r = 0.83, P = 0.01), and their ratio amounted to 0.03 (range 0.003-0.06), a value in agreement with the expected sieving coefficient. Urine C3d was detectable in all but three of the patients with glomerular diseases (median excretion 0.36 mU min-1, range 0.004-7.9 mU min-1); C3d-excretion did not differ between the three subgroups of patients with glomerular diseases. FEC3d correlated with FEIgG (r = 0.88, P < 0.01). The ratio FEC3d/FEbeta2m was 0.78 (range 0.04-9.99). Selected patients with membranous nephropathy were re-analyzed after (partial) remission of proteinuria. Reduction of proteinuria resulted in a decrease of C3d excretion. CONCLUSION: Urinary excretion of C3d is elevated in patients with TIN, most likely as a mere consequence of decreased tubular reabsorption. In patients with glomerular diseases urinary excretion of C3d is increased and related to proteinuria, independent of the underlying glomerular disease. In these patients there is evidence of increased local formation of C3d.     

氯沙坦对2型糖尿病肾病患者尿转化生长因子β1的影响

目的通过检测糖尿病肾病患者尿转化生长因子β1(TGFβ1水平,探讨患者肾脏纤维化状况及氯沙坦对肾脏纤维化的影响。方法检测33例2型糖尿病肾病患者氯沙坦(50 mg/d×8周治疗前后24 h尿蛋白、尿肌酐,尿TGFβ1和肌酐。尿TGFβ1检测方法为ELISA法。20例健康志愿者的尿液标本作为对照组。结果糖尿病肾病患者尿TGFβ1明显高于正常对照组,经氯沙坦治疗后尿TGFβ1浓度明显下降(P<0.001。尿TGFβ1浓度变化与尿蛋白变化具有相关性(P<0.01)。结论氯沙坦通过降低糖尿病肾病患者尿TGFβ1水平发挥抗肾脏纤维化作用,这是氯沙坦延缓糖尿病肾病进展的机制之一,这一表现先于蛋白尿的减少。     

Urinary excretion of angiotensin-converting enzyme in NIDDM patients with nephropathy

Twenty-four-hour urinary excretion of angiotensin-converting enzyme (ACE) was investigated in relation to that of albumin and beta 2-microglobulin (beta 2M) in 25 non-insulin-dependent diabetes mellitus (NIDDM) patients without nephropathy, 13 NIDDM patients with incipient nephropathy, 18 NIDDM patients with overt nephropathy, and 14 nondiabetic subjects. NIDDM patients without nephropathy and nondiabetic subjects were similar in albumin, beta 2M, and ACE excretion. NIDDM patients with incipient nephropathy had elevated albumin excretion (P less than .01) and similar beta 2M and ACE excretion compared with nondiabetic subjects. On the other hand, NIDDM patients with overt nephropathy had elevated albumin, beta 2M, and ACE excretion compared with nondiabetic subjects (P less than .01). In all NIDDM patients studied, a positive correlation was found between ACE excretion and albumin excretion (r = 0.76, P less than .001) or beta 2M excretion (r = 0.52, P less than .01). These data suggest that elevated ACE excretion in NIDDM patients with overt nephropathy may be reflective of renal tubular damage.     

Factors affecting the urinary excretion of albumin in insulin-dependent diabetes

To determine the specificity of the urine excretion of albumin as a measure of glomerular permeability in early insulin-dependent diabetic nephropathy, the effect of variable glomerular filtration and urine flow rates on albumin, beta 2-microglobulin excretion, and the fractional renal clearance of neutral dextran (Stokes Einstein Radius 24-46 A) was examined. Five insulin-dependent diabetic subjects with normal glomerular permeability (albumin excretion less than 30 micrograms/min) and one with elevated albumin excretion (195 micrograms/min) were studied pre and post strict glucose control with constant subcutaneous insulin infusion for 7 days. The albumin excretion in the 5 subjects never exceeded 30 micrograms/min during wide variations in glomerular filtration and urine flow rates. A positive correlation between beta 2-microglobulin excretion and urine flow (r = 0.81), and glomerular filtration (r = 0.77) rates was observed. In contrast, albumin excretion showed no correlation, indicating different factors affect the excretion rate of albumin and beta 2-microglobulin. Therefore, elevated albumin excretion (greater than 30 micrograms/min) in insulin-dependent diabetes is due to increased glomerular permeability and not changes in glomerular filtration and urine flow rates, and the albumin/ beta 2-microglobulin ratio may not be a valid indicator of changing glomerular permeability. The fractional neutral dextran clearances remained unchanged with variation in glomerular filtration and urine flow rates. The sieving curve was identical in all subjects for neutral dextran 40 A, the size of albumin, suggesting that reduced glomerular charge selectivity may contribute to increased albuminuria in progressive diabetic glomerulosclerosis.     

A sandwich enzyme immunoassay of human growth hormone in serum using anti-human growth hormone IgG-beta-D-galactosidase conjugate

The specificity, sensitivity and stability of beta 2-microglobulin (beta 2-m) and retinol-binding protein (RBP) in urine as indices of tubular proteinuria were compared. In vitro experiments show that RBP in urine is stable down to pH 4.5, whereas beta 2-m degrades below pH 5.5. This was confirmed by the relationships between pH and the concentration of both proteins in the urines from 150 healthy subjects. Urinary RBP was independent of pH (r = 0.125) but in contrast at pH below 6, beta 2-m concentration was inversely correlated with pH (r = 0.54, p less than 0.05). The comparison of urinary excretion of RBP and beta 2-m in 68 patients with renal diseases shows that in absence of a pH effect, the sensitivity and specificity of both proteins as indices of tubular proteinuria are rather similar. Therefore, in view of its greater stability in urine, RBP appears to be a more practical and reliable index of proximal tubular function than beta 2-m.     

血D-二聚体、纤维蛋白原、同型半胱氨酸测定在糖尿病肾病中的意义

目的 探讨血D-二聚体（DD）、纤维蛋白原（FIB）、同型半胱氨酸（Hcy）测定在早期糖尿病肾病中的临床意义.方法 选择已确诊的2型糖尿病患者141例,健康对照组46例,测定清晨空腹血DD、FIB、Hcy水平.并同时收集糖尿病患者24h尿液进行尿微量白蛋白（mALB）测定,按照其24h尿白蛋白排泄率分为正常蛋白尿组（mALB≤30mg/24h）及微量蛋白尿组（mALB30-300mg/24h）.结果 2型糖尿病患者DD、FIB在正常蛋白尿组已升高;微量蛋白尿组三项指标均显著高于对照组,差异具有统计学意义（P〈0.01）,且三项联合检测阳性率明显高于单项检测.结论 联合检测DD、FIB、Hcy水平对观察糖尿病患者病情发展变化及提高糖尿病早期肾脏损伤的检出率具有重要的临床意义.     

Behaviour of urinary excretion of lysozyme in renal diseases and in urinary tract infections (author's transl)]

Urinary excretion of lysozyme was investigated in a group of 66 patients with various renal diseases, nephrolitiasis and urinary tract infections. The results obtained demonstrate that the amount of the enzyme excreted is related to the entity of tubular damage whereas is not with glomerular damage. No correlation was found between lysozyme excretion neither to the degree of proteinuria neither to the amount of leukocytes and bacteria in the urine. In patients with urinary infections urinary lysozyme increases only when there is a tubular injury of some entity. In 90 pediatric patients with urinary infection and pyelonephritis lysozyme in the urine was found only in two cases. Therefore urinary lysozyme determination cannot be considered for the detection of early tubular injury and is not a helpful diagnostic tool in urinary tract infections.     

Renal excretion of proteins and enzymes in workers exposed to cadmium

The proteinuria rate and the relative clearances of beta 2-microglobulin, orosomucoid, albumin, transferrin and IgG were measured in forty-two workers exposed to cadmium and in seventy-seven control workers. A tubular type proteinuria with an increased excretion of beta 2-microglobulin and often also a glomerular type proteinuria with an increased excretion of orosomucoid, albumin, transferrin and IgG were observed mainly in workers exposed to cadmium for more than 25 years and whose cadmium concentration in blood exceeded 1 microgram Cd/100 ml and that in urine 10 microgram Cd/g creatinine. The glomerular dysfunction was also suggested by an increased plasma level of beta 2-microglobulin and creatinine. Both tubular and glomerular impairments occurred with the same prevalence and were not necessarily associated. The increased release of beta-galactosidase by the kidney suggested that cadmium can damage some epithelial cells.     

血清同型半胱氨酸等指标联合检测对糖尿病肾病的临床价值

目的探讨血清同型半胱氨酸、血清胱抑素C和尿β2-微球蛋白联合检测对糖尿病肾病的临床价值。方法将102例糖尿病肾病患者按尿液清蛋白排泄率分为A、B、C 3组：正常清蛋白组（A组,n=42）、微量清蛋白组（B组,n=35）、大量清蛋白组（C组,n=25）,同时以20例健康人作为健康对照组。分别检测血清同型半胱氨酸、血清胱抑素C、尿液清蛋白和尿β2-微球蛋白水平,对检测结果采用SAS统计软件进行统计学处理作对比分析。结果糖尿病肾病患者各组间血清同型半胱氨酸、血清胱抑素C和尿β2-微球蛋白检测值比较差异均有统计学意义（P〈0.01）。102例糖尿病肾病患者血清同型半胱氨酸、血清胱抑素C和尿β2-微球蛋白检测值采用多元线性相关分析呈正相关（r为0.250,0.410,0.365;P〈0.01）。结论血清同型半胱氨酸、血清胱抑素C和尿β2-微球蛋白联合检测可以推断糖尿病肾病的损害程度,更全面地评价早期糖尿病肾损害,提示临床应早期干预血清同型半胱氨酸水平。     

Dissociation between urinary pyrraline and pentosidine concentrations in diabetic patients with advanced nephropathy

It has been reported that the concentrations of both pyrraline and pentosidine, well-characterized advanced glycation end products, are increased in the urine of diabetic patients. To determine factors that influence the urinary excretion of pyrraline or pentosidine, we compared pyrraline or pentosidine concentrations with glycemic-control indexes, urinary albumin excretion, and urinary β2-microglobulin in patients with type 2 diabetes. The study was conducted in 39 age-matched healthy control subjects and 50 diabetic patients, including 22 patients with normoalbuminuria, 15 with microalbuminuria, and 13 with macroalbuminuria. Both urinary pyrraline and pentosidine were measured in early-morning urine specimens with the use of high-pressure liquid chromatography. The urinary pentosidine concentration was significantly higher in diabetic patients than in control subjects (P < .01). In contrast, the urinary pyrraline concentration was significantly lower in diabetic patients than in control subjects (P < .001). Urinary pentosidine concentrations were greater in diabetic patients with macroalbuminuria and microalbuminuria than in those with normoalbuminuria. However, urinary pyrraline concentrations were significantly lower in diabetic patients with advanced nephropathy. Both the hemoglobin A_1c (HbA_1c) and the preceding year's mean HbA_1c were lower in patients with macroalbuminuria than in those with normoalbuminuria or microalbuminuria. Urinary pyrraline, but not pentosidine, showed a significantly positive correlation with the preceding year's mean HbA_1c (P<0.01). Multivariate analysis disclosed that urinary β-2-microglobulin was independently correlated with the urinary concentrations of pentosidine and pyrraline (P < .05 for both). We conclude that the urinary concentration of pentosidine is greater in diabetic patients with overt nephropathy, whereas the urinary pyrraline concentration is significantly lower in diabetic patients with overt nephropathy. Because urinary pyrraline is more directly influenced by glycemia than by pentosidine, the difference in glycemic control among diabetic patients with various grades of nephropathy may be responsible for a dissociation between urinary pyrraline and pentosidine concentrations in patients with overt diabetic nephropathy.     

糖尿病患者尿微量清蛋白、尿β_2-微球蛋白、糖化血红蛋白及血脂联合检测的临床意义

目的分析糖尿病患者的尿微量清蛋白、β2-微球蛋白、糖化血红蛋白及血脂含量,以观察其与糖尿病肾脏微血管病变的相关性。方法糖尿病患者根据尿微量清蛋白(mALb)分为两组:(1)糖尿病肾病组,晨尿高微量清蛋白(20mg/L)30例;(2)无糖尿病肾病组,晨尿正常微量清蛋白(20mg/L))33例。结果晨尿高微量清蛋白组的尿β2-微球蛋白、糖化血红蛋白及胆固醇含量显著高于晨尿正常微量清蛋白组,两组间差异有统计学意义。结论尿微量清蛋白(mALb)及尿β2-微球蛋白是糖尿病早期肾小球及肾小管损伤的标志物,肾病微血管病变程度与HbA1c的增高有关,血脂异常可增加糖尿病患者肾病微血管病变的危险性。联合检测对糖尿病肾病的早期预防诊断及治疗有重要的临床意义。     

尿微量白蛋白/肌酐比值对糖尿病肾病早期诊断价值

目的 探讨尿微量白蛋白/肌酐比值在糖尿病肾病早期诊断中的价值.方法 选取确诊为2型糖尿病患者293例和体检健康体检者70例,对其尿微量白蛋白/肌酐比值（晨起空腹及随机）、24小时尿微量白蛋白定量、尿微量白蛋白排泄率、尿素氮、血肌酐、尿常规等临床资料进行回顾性分析,观察上述不同检测方法对糖尿病早期诊断灵敏度.结果 晨起、随机尿微量白蛋白/肌酐值与尿微量白蛋白排泄率（urine albumin excretion rateUAER）、24 h尿微量白蛋白定量成显著正相关,晨起空腹尿ACR与UAER、24小时尿微量白蛋白定量的相关系数分别为r＝0.936（P＜0 01）,r＝0.906,（P＜0.01）;随机尿ACR与UAER和24h尿微量白蛋白相关系数分别为r＝0.756（P＜0.01）,r＝0.738,（P＜0.01）.2型糖尿病组尿ACR阳性组和阴性组之间比较尿蛋白、血肌酐、尿素氮水平无统计学差异,P＞0.05.将血肌酐、尿素氮、尿ACR诊断糖尿病肾病敏感性比较,尿ACR阳性率显著高于前两者,P＜0.01.结论 晨起空腹及随机尿微量白蛋白/肌酐比值两者均可以作为糖尿病肾病早期诊断的敏感指标.     

Urinary excretion of beta 2-microglobulin in myeloma patients

The levels of beta 2-microglobulin in urine and serum were determined in 39 patients with myelomatosis. In 25 patients the serum beta 2-microglobulin was elevated, and in seven of the patients with increased serum beta-microglobulin the urinary excretion of the protein was also increased. It was concluded that the increased urine beta-microglobulin indicates a renal tubular disorder.     

Urinary alpha1-microglobulin as a marker of nephropathy in type 2 diabetic Asian subjects in Singapore

OBJECTIVE: This study examines urinary alpha(1)-microglobulin as a marker of early nephropathy in type 2 diabetic Chinese, Malays, and Asian Indians in Singapore. RESEARCH DESIGN AND METHODS: A cross-sectional study was performed on 590 consecutive type 2 diabetic patients (296 males, 294 females) who were on routine follow-up at a primary care clinic. Information was obtained from interviews, case notes, and blood and urine samples. Because the distribution of urinary alpha(1)-microglobulin levels was highly skewed, these levels were log-transformed, and geometric means were calculated. There was correction for variability in urine flow by dividing by urine creatinine levels, given as mg/mmol urine creatinine, and adjustment for confounding variables. RESULTS: Urinary alpha(1)-microglobulin was higher in men than in women and was directly related to age, but no ethnic differences were apparent. It was directly related to duration of diabetes, with adjusted geometric means of 1.19 and 1.43 mg/mmol urine creatinine for a duration of <10 and > or =10 years, respectively (P = 0.07). Urinary alpha(1)-microglobulin was highest in patients on insulin, followed by those on oral medication and then those on diet alone (adjusted geometric means: 1.47, 1.36, and 0.86 mg/mmol urine creatinine, respectively; P = 0.01). Levels were also higher in patients with poor glucose control, as measured by HbA(1c), fasting plasma glucose, and 2-h postprandial plasma glucose (P < 0.01 for each). Urinary alpha(1)-microglobulin was directly related to albuminuria, with adjusted geometric means for normoalbuminuria, microalbuminuria, and macroalbuminuria of 1.06, 1.47, and 4.72 mg/mmol urine creatinine, respectively (P < 0.01). However, of patients with normoalbuminuria, 33.6% had raised urinary alpha(1)-microglobulin. Likewise, of patients with normal urinary alpha(1)-microglobulin, 27.6% had albuminuria. CONCLUSIONS: Urinary alpha(1)-microglobulin was related to duration, severity, and control of diabetes. Urinary alpha(1)-microglobulin and albumin were directly related, but in some patients, one was present in the absence of the other. Hence, in addition to albuminuria (which measures glomerular dysfunction), urinary alpha(1)-microglobulin (which measures proximal tubular dysfunction) is useful for the early detection of nephropathy in diabetic subjects.     

醛固酮受体拮抗剂治疗糖尿病肾病的临床研究

目的:探讨应用醛固酮受体拮抗剂能否改善糖尿病肾病患者的炎症病变、减少糖尿病肾病患者的蛋白尿排泄。方法:采用前瞻性随机对照方法,对糖尿病肾病(Ⅲ、Ⅳ期)患者60例,按照1:1分为治疗组(螺内酯)和对照组(安慰剂),予ACEI类或AT1RA类的药物治疗基础上加用螺内酯片(20mg/d)或安慰剂,共治疗12周。检测治疗前后24h尿微量白蛋白、尿单核细胞趋化蛋白-1(MCP-1)、肾功能等情况。结果:治疗后两组的肌酐清除率均较治疗前升高,但治疗组治疗前后比较差异有非常显著性(59.4±13.4,61.2±13.5,P=0.000)。两组治疗前后的24h尿微量白蛋白及尿MCP-1比较差异均有显著性(P<0.05),但治疗组治疗前后24h尿微量白蛋白及尿MCP-1比较差异有非常显著性(1450.13±1369.84,779.33±656.57,P=0.001;39.69±9.71,32.79±6.74,P=0.000)。治疗前后二者定量呈明显正相关。结论:醛固酮受体拮抗剂能改善糖尿病肾病患者的炎症病变,明显减少蛋白尿排泄,延缓了糖尿病肾病的进展。     

Measurement of urinary retinol-binding protein by enzyme-linked immunosorbent assay, and its application to detection of tubular proteinuria

An enzyme-linked immunosorbent assay (ELISA) for urinary retinol-binding protein (RBP) has been developed and compared with urinary beta 2-microglobulin for the detection of tubular proteinuria. The assay has a working range of 10 to 250 micrograms of RBP per liter of urine. The within-assay CV was 3.2-7.1%, the between-assay CV 12.5%. A control population of 118 male subjects gave a geometric mean urinary RBP concentration of 7.7 micrograms per millimole of creatinine and a 95th centile of 22 micrograms per millimole of creatinine. Comparison of urinary RBP and beta 2-microglobulin concentrations in 80 control subjects and 117 subjects exposed to cadmium fumes gave correlations of r = 0.59 and 0.91, respectively. Of the 117 subjects exposed to cadmium fumes, 103 gave both RBP and beta 2-microglobulin concentrations on the same side of the upper 95th centile values of 22 and 38 micrograms per millimole of creatinine for RBP and beta 2-microglobulin respectively (Chi-square analysis p less than 0.001), demonstrating that RBP and beta 2-microglobulin detect tubular proteinuria with equal sensitivity and specificity. ELISA and an established latex immunoassay gave well-correlated results.