Urinary excretion of glycated albumin in insulin-dependent diabetic patients with normal urinary albumin excretion

Summary Glycation involves both circulating proteins, such as albumin, and structural proteins, such as the components of the glomerular basement membrane. A preferential excretion of glycated albumin (more anionic at physiological pH compared with unmodified plasma albumin) has been reported by some authors, but not by others. We therefore investigated the selectivity index (renal clearance of non-glycated albumin/clearance of glycated albumin) in 25 insulin-dependent diabetic patients with normal urinary albumin excretion and in 19 well-matched control subjects. The selectivity index was significantly higher in diabetic patients than in control subjects: 1.38±0.05 SEMvs 0.98±0.02, p<0.0001. This result is not consistent with a preferential urinary excretion of glycated albumin, at least in normoalbuminuric uncomplicated insulin-dependent diabetic patients.     

Body mass index negatively influences glycated albumin, but not glycated hemoglobin, in diabetic patients

Measurement of serum glycated albumin (GA) is accepted as an alternative method to evaluate chronic glycemic control in diabetic patients in whom measurement of HbA 1c is inadequate for some reason. Although GA levels are known to be influenced by serum albumin turnover besides glycemia, little is known about the physiological and pathological conditions affecting GA levels. This study was aimed to prove the effects of body mass index (BMI) on GA measurement in diabetic patients. We studied 209 patients with type 2 diabetes mellitus whose HbA 1c levels had been stable for at least the past three months. In the study patients HbA 1c and GA levels were found to be correlated to one another. Fasting plasma glucose (FPG) was significantly correlated with HbA 1c and GA. BMI showed a significant negative correlation with GA levels, whereas there was no correlation of BMI with HbA 1c levels. Multivariate regression analyses revealed that only FPG was positively correlated with HbA 1c, while FPG was positively and BMI was negatively correlated with GA. Only BMI was negatively correlated with the ratio of GA to HbA 1c. These results clearly demonstrate that GA levels are negatively influenced by BMI in diabetic patients.     

Normalizing glycated albumin reduces increased urinary collagen IV and prevents renal insufficiency in diabetic db/db mice

Increased excretion of type IV collagen accompanies the accumulation of mesangial matrix, which leads to compromise in the glomerular filtration surface area, during the development of diabetic nephropathy. We postulated that the response of urinary collagen IV would be useful in evaluating possible treatment strategies to arrest the nephropathic process while still at a reversible stage. To test this hypothesis, we examined the effect of a small molecule (22CPPA) that inhibits the formation of glycated albumin, which is causally linked to the pathogenesis of diabetic nephropathy, on collagen IV excretion, albuminuria, and renal function in db/db mice. Compared to nondiabetic db/m mice, db/db animals showed markedly increased urinary collagen IV and albumin, significantly elevated serum glycated albumin and creatinine concentrations, and a significantly reduced creatinine clearance. Treatment of db/db mice with test compound, which normalized glycated albumin concentrations, significantly lowered collagen IV and albumin excretion and ameliorated the fall in creatinine clearance and the rise in serum creatinine despite persistent hyperglycemia. The findings indicate that reduction of elevated collagen IV excretion in diabetes reflects a salutary influence on developing glomerulosclerosis, and that glycated albumin has an important nephropathogenic role that can be therapeutically addressed independent of glycemic status.     

Immunohistochemical localization of glycated protein in diabetic rat kidney

The localization of glycated protein in the kidney of diabetic rats was examined immunohistochemically with antiserum against glucitol-lysine. In diabetic rats the brush border and basement membrane of the proximal convoluted tubules were strongly immunoreactive with the antiserum but in control rats, only the brush border was weakly reactive. The immunoreactive tubules were more abundant in diabetic rats. No immunoreaction was found in any other structures in the kidney. Glycation of the proximal convoluted tubules may be an alteration in diabetic nephropathy.     

血清总胆红素、糖化白蛋白、糖化血红蛋白与糖尿病血管并发症的关系

目的探讨血清总胆红素(TBIL)、糖化白蛋白(GA)、糖化血红蛋白(Hb A1c)与糖尿病血管并发症的关系。方法选取糖尿病患者176例,根据是否有血管并发症分为血管病变组和无血管病变组。测定两组TBIL、GA、Hb A1c等生物化学指标。采用Logistic二元回归分析糖尿病患者血管并发症的影响因素。结果最终纳入血管病变组的有120例,纳入无血管病变组的有56例。两组性别、年龄、体质指数(BMI)比较差异无统计学意义(P0. 05)。与无血管病变组比较,血管病变组患者的病程更长,总胆固醇(TC)、高密度脂蛋白胆固醇(HDLC)、TBIL数值更低,GA、Hb A1c、甘油三酯(TG)和低密度脂蛋白胆固醇(LDLC)数值更高,差异具有统计学意义(P0. 05);进一步二元Logistic回归分析结果显示,Hb A1c水平高、TBIL水平低和病程长是糖尿病血管并发症的独立危险因素(P0. 05)。结论临床应积极关注糖尿病患者的Hb A1c和TBIL水平,注意血管病变的筛查并积极干预,避免严重并发症的发生。     

Introduction of glycated albumin measurement for all blood donors and the prevalence of a high glycated albumin level in Japan

(J Diabetes Invest, doi: 10.1111/j.2040‐1124.2012.00224.x, 2012) Aims/Introduction: The Japanese Red Cross Society introduced measurement of glycated albumin (GA) for all blood donors as a glycemic control marker. The GA levels were examined by sex and age. Materials and Methods: GA was measured in 3.14 million blood donors who donated between April 2009 and March 2010. For the reference range for GA, values that were three times the reference range for glycated hemoglobin (Japan Diabetes Society value) were used. All donors were notified of their GA levels. For repeat donors, a comparison was made between the GA levels at the first and second donations to verify the GA change after notification. Results: The mean GA was significantly lower in males than in females in donors aged <60 years. The mean GAs of both sexes increased with age and reached the same level of 14.8% in their 60s. The percentage of donors with prediabetes/diabetes (GA ≥16.5%) was 2.8% in males and 2.3% in females. In the normal high group (15.6% ≤ GA < 16.5%), the mean GA at the second donation was lower by 0.20% than at the first donation. In 42.4% of these donors, GA decreased to the normal range at the second donation. Conclusions: Overall, 2.7% of otherwise healthy Japanese blood donors had a high GA (GA ≥16.5%). Donor blood screening for GA represents an effective measure to identify people at risk of diabetes. The decrease in the GA level after GA notification might indicate the potential usefulness of this strategy to improve glycemic control among people with high GA.     

糖化白蛋白的临床应用价值

糖化白蛋白(GA)是血液中白蛋白与葡萄糖通过非酶促糖基化反应形成的产物,与血糖水平密切相关。GA水平与白蛋白代谢周期相关,反映近2~3周的平均血糖水平。GA可作为糖尿病诊断、血糖监测、疗效评估的辅助指标,同时对慢性肾脏病变、DR等糖尿病并发症风险具有一定的预测作用。在特定的临床条件下,如接受血液透析治疗的糖尿病、GDM患者,GA的临床应用价值优于HbA1c。     

不同尿白蛋白水平的2型糖尿病患者肾小管相关标志物测定的临床意义

目的 评价不同尿白蛋白水平的2型糖尿病(T2DM)患者的肾小管功能及其与尿白蛋白的相关性.方法 438例T2DM患者按Mongensen分期分为正常白蛋白尿组(112例)、微量白蛋白尿组(106例)、大量白蛋白尿组(114例)、肾功能不全组(106例),另设正常对照组(87例),比较各组尿视黄醇结合蛋白(RBP)、β2-微球蛋白(β2-MG)、N-乙酰-D-氨基葡萄糖苷酶(NAG)/尿肌酐(Ucr)比值和24h尿Tamm-Horsrall蛋白(T-HP)水平.结果 正常白蛋白尿组、微量白蛋白尿组、大量白蛋白尿组、肾功能不全组尿NAG/Ucr(分别为9.48,9.68,9.99,10.12 μ/gcr)、RBP(中位数分别为0.09,0.62,3.02,2.96 mg/L)均高于正常对照组(NAG 9.01 μ/gcr,RBP 0.00 mg/L,P均＜0.01);微量白蛋白尿组、大量白蛋白尿组和肾功能不全组尿β2-MG(中位数分别为0.11,0.12,1.4 mg/L)高于正常对照组(0.09 mg/L,P均＜0.01)及正常白蛋白尿组(0.10 mg/L,P＜0.01或0.05);各组间24 h尿T-HP无显著差异.分别联合检测尿RBP+NAG、RBP+β2-MG、NAG+β2-MG以预测正常白蛋白尿组肾小管损伤,敏感性分别为14.3％,16.1％,26.8％.多元Logistic回归分析显示正常白蛋白尿组近端肾小管功能异常与糖化血红蛋白( Hb)A1c、舒张压、收缩压、糖尿病病程[优势比(OR)分别为2.38,1.25,1.10,1.20]显著相关(P均＜0.05).结论 近端肾小管功能受损可能出现于微量白蛋白尿之前,联合测定尿NAG和β2-MG可敏感反映早期近端肾小管功能损伤,血糖控制差、血压升高、糖尿病病程长是正常白蛋白尿期肾小管损伤的独立危险因素.     

Comparison of glycated albumin (GA) and glycated hemoglobin (HbA1c) in type 2 diabetic patients: usefulness of GA for evaluation of short-term changes in glycemic control

We studied the cross-sectional relationship between GA and HbA1c in 142 type 2 diabetic patients who had an HbA1c level < 7.5% for at least one year without fluctuation by more than 0.5%. We also followed the changes of GA and HbA1c in 18 type 2 diabetic patients for 16 weeks as they progressed from untreated severe hyperglycemia (HbA1c > or = 9.0%) to good glycemic control (HbA1c < or = 6.5%) by intensive insulin treatment. The annual mean levels of GA and HbA1c in the stably controlled patients showed a weak, but significant, correlation (r = 0.23, p<0.001) in the 142 diabetic patients. However, the GA/HbA1c ratio ranged widely from 2.0 to 4.0 showing a normal distribution (2.9 +/- 0.34, M +/- SE), although patients with conditions affecting albumin turnover or RBC lifespan were excluded from the study. The GA/HbA1c ratio was significantly higher when patients were in hyperglycemic than when glycemic control was good (3.5 +/- 0.15 vs. 2.9 +/- 0.07, M +/- SE, p<0.01). GA decreased more rapidly than HbA1c during intensive insulin therapy, but the percent reduction of HbA1c eventually corresponded with that of GA by 16 weeks after the start of treatment. These results demonstrate that, although unknown influences on GA or HbA1c may exist, GA may be a useful marker for monitoring short-term variations of glycemic control during treatment of diabetic patients.     

糖化白蛋白在动脉粥样硬化发生发展中的作用

糖尿病是世界范围内的流行病,与动脉粥样硬化(As)等心血管疾病密切相关。长期高糖环境导致糖尿病患者体内蛋白质、脂肪酸等大分子物质经一系列复杂的非酶糖基化反应形成糖基化终末产物(AGE)。而糖化白蛋白(GA)是AGE的最主要形式,通过与糖基化终末产物受体(RAGE)结合引起氧化应激、炎症、内质网应激等反应,促进动脉粥样硬化进展。因此,深入探究GA致As机制对降低糖尿病患者心血管事件发生率、延缓疾病进程有重大意义。目前,现有相关研究已部分揭示其具体机制,本文就GA在As发生发展中的作用作一综述。     

A new effective method for the evaluation of glycated intact plasma proteins in diabetic subjects

Summary The molecular weights of plasma proteins from healthy subjects and from patients with well-or badly-controlled diabetes mellitus have been determined by use of a matrix-assisted laser desorption ionization method, representing a highly accurate technique for the determination of the molecular weight of large biomolecules. Using this approach, different molecular weights of human serum albumin have been found for healthy (66,572–66,694 dalton) and diabetic (66,785–68,959 dalton) subjects. Such differences can be rationalized as being due to the different number of glucose molecules condensed on the protein and/or their further oxidation products; in the case of our diabetic patients this number is in the range of 1.4–14.8. The data show the high validity and specificity of the technique, which allows us to evaluate, without any protein degradation procedure, the number of glucose molecules condensed on a specific protein and ascertain the relationship of this number to the physiopathogenetic conditions of the subjects studied.Abbreviations AGE Advanced glycation end products - FFI 2-(2 furoyl)-4-(5)-(2 furanyl)-1H imidazole - MALDI matrix-assisted laser desorption/ionization - BSA bovine serum albumin - HSA human serum albumin - HbA_1c glycated haemoglobin - Da dalton - NIDDM non-insulin-dependent diabetes mellitus - keV kiloelectron volts - UV ultraviolet     

Clinical evaluation of amylase-creatinine clearance ratio and amylase isoenzyme clearance in chronic renal failure

Amylase-creatinine clearance ratio (ACCR) and amylase isoenzyme clearance were determined simultaneously in patients with chronic renal failure. ACCR in patients with compensated renal failure (3.5 +/- 0.4%) was not significantly different from normals (2.6 +/- 0.2%), while that in patients with non-compensated renal failure (6.7 +/- 0.4%) was significantly higher than that in normals. Clearance ratio of pancreatic isoamylase (Amylase-1) relative to creatinine clearance (CAmy . 1/Ccr) in patients with both compensated (5.9 +/- 1.0%) and non-compensated (6.8 +/- 0.4%) renal failure was as high as that in patients with acute pancreatitis (6.6 +/- 0.5%). On the other hand, clearance ratio of salivary isoamylase (Amylase-3) relative to creatinine clearance (CAmy . 3/CCr) in patients with compensated renal failure (1.5 +/- 0.3%) was almost the same as that in normals (2.1 +/- 0.1%), while that in patients with non-compensated renal failure was 5.9 +/- 0.7%, which was significantly higher than that in normals. The present study revealed that elevated ACCR in patients with severely impaired renal function was due to the increase of the clearance ratio for both pancreatic and salivary amylase. These facts suggested that glomerular permeability and tubular reabsorption for pancreatic and salivary amylase might play an important role on ACCR in patients with severely impaired renal function.     

Transcapillary escape rate and relative metabolic clearance of glycated and non-glycated albumin in Type 1 (insulin-dependent) diabetes mellitus

Summary The transcapillary escape rate and relative plasma disappearance of glycated and non-glycated albumin were measured in 25 male Type 1 (insulin-dependent) diabetic patients using a double tracer technique. The patients were divided into three groups on the basis of their urinary albumin excretion: group 1, normal albumin excretion (<30 mg/24h) (n=8); group 2, microalbuminuria (30–300 mg/24 h) (n=9); and group 3, clinical nephropathy (>300 mg/24 h) (n=8). Six male age-matched non-diabetic persons served as control subjects. The transcapillary escape rate of glycated albumin was similar in group 1 and control subjects (4.7±2.1 versus 5.1±1.7%), but significantly increased in group2 (7.0±1.7%,p<0.05) and in group 3 (7.9±3.1%,p<0.05). The transcapillary escape rate of glycated albumin was slightly lower than that of non-glycated albumin in all groups, but significant only in normal control subjects. No difference in the catabolic rate of glycated and non-glycated albumin was found. We conclude that the in vivo effects of glycation on the clearance and transcapillary passage of albumin are small and not likely to play any significant role in the development of late diabetic microvascular complications.     

Increased permeability across the blood-nerve barrier of albumin glycated in vitro and in vivo from patients with diabetic polyneuropathy.

The blood-nerve transfer of human plasma albumin glycated with D-glucose was investigated by measuring the permeability coefficient-surface area product (PS) of the blood-nerve barrier to radioiodinated albumin in normal adult rat sciatic nerve. Human albumin (ALB) from normal individuals, freshly isolated by CM-Affi-Gel Blue affinity chromatography, was glycated in vitro for 1, 3, 10, 19, and 30 weeks. Glycated ALB (gALB) was separated from the nonglycated form by boronate-affinity chromatography. The efficiency of this separation was assessed by chromatography of ALB glycated with [14C]glucose and by rechromatography of isolated ALB and gALB after radioiodination. The gALB was also shown to have a higher molecular weight and be completely separated from ALB after SDS/pore gradient electrophoresis in a Tris borate/EDTA buffer. After 1 week of glycation, the gALB PS was 2.2-fold greater than the ALB PS (0.724 +/- 0.063 x 10(-6) vs. 0.328 +/- 0.053 x 10(-6) ml.g-1.s-1; mean +/- SD; P less than 0.0001) and it increased with the time of glycation reaching a maximum value of 16.2-fold greater at 30 weeks (4.656 +/- 1.117 x 10(-6) vs. 0.288 +/- 0.042 x 10(-6) ml.g-1.s-1; mean +/- SD; P less than 0.0001). No change was observed in the residual endoneurial plasma volume. In addition, the PS of gALB isolated from patients with diabetic polyneuropathy was significantly increased (P less than 0.0001) compared to the PS for ALB isolated from the same patients. It is hypothesized that the increased permeability of gALB and presumably other glycated serum components across the blood-nerve barrier, as well as the observed quantitative increase in ALB, IgG, and IgM in sural nerve biopsies from patients with diabetic polyneuropathy contribute to the development of diabetic polyneuropathy over a prolonged period of time by mechanisms that might involve osmotic changes in the nerve microenvironment, direct toxic effects of glycated macromolecules on cells within the endoneurium, or nerve damage by classical immunological mechanisms due to trapping of glycated immunoglobulins within nerve.     

Longitudinal study of urinary albumin excretion in young diabetic patients--Wessex Diabetic Nephropathy Project.

AIMS: This study was established to follow changes in albumin/creatinine ratio (ACR) and to determine the prevalence and degree of progression of microalbuminuria (MA) or of clinical proteinuria (CP) in children with Type 1 diabetes. The study has investigated subjects for up to 12 years in establishing the correlation between MA and gender, age, duration of diabetes and glycated haemoglobin (HbA1c). The study has defined clinical cut-offs for MA in daytime clinic urine samples in young diabetic subjects. METHODS: Three hundred and sixty-one patients were involved in the study, with 221 (61.2%) having over six sets of data. Urine samples were collected at routine annual clinic visits and analysed without prior freezing for ACR. Blood samples were taken for HbA1c measurement. Data including sex, age and duration of diabetes were recorded. RESULTS: A random clinic ACR of < 4.5 mg/mmol (males) and 5.2 mg/mmol (females) creatinine was used as the 'clinical cut-off' to define the presence of MA. The presence of MA was independent of HbA1c and duration of diabetes but appeared be associated with the adolescent years (> 10 years). There was little evidence of progression from normoalbuminuria to MA, or from MA to CP. Of patients aged 10-18 years, 30.9% of males and 40.4% of females had one or more episodes of MA. CONCLUSIONS: Persistent MA and random episodes of MA or CP may be associated with the adolescent years but not with duration of diabetes. Further study will reveal if the substantial increases in ACR sometimes seen during adolescence are predictive of diabetic nephropathy. Clinical cut-offs of < 4.5 and < 5.2 mg/mmol creatinine for males and females, respectively, are suggested for the interpretation of changes in ACR in random urine samples in young people with Type 1 diabetes.     

The ratio of glycated albumin to glycated haemoglobin correlates with insulin secretory function

Objective Although glycated haemoglobin (A1c) levels are similar among patients with type 2 diabetes, the glycated albumin (GA)/A1c ratio varies considerably. On the basis of the hypothesis that endogenous insulin secretion might be correlated with the GA/A1c ratio, we investigated whether insulin secretory function or insulin resistance has different effects on the GA/A1c ratio in patients with type 2 diabetes using the standardized liquid meal test. Design A clinical, retrospective study. Patients and measurements A total of 758 patients with type 2 diabetes ingested a standardized liquid meal (i.e. 500 kcal, 17·5 g fat, 68·5 g carbohydrate and 17·5 g protein). The subjects were divided into two groups: those with GA/A1c ratio <2·5 (n = 414) and those with GA/A1c ratio ≥2·5 (n = 344). We compared the A1c and GA levels, and the GA/A1c ratio and evaluated the relationships between the glycaemic indices and other parameters. Effects of β‐cell function [homeostasis model assessment (HOMA‐β), insulinogenic index (IGI)] and insulin resistance (HOMA‐IR) on the GA/A1c ratio were also examined. Results The GA/A1c ratio was significantly correlated with HOMA‐β, IGI and body mass index (BMI) but not with HOMA‐IR. Furthermore, after adjusting for age, gender, BMI, haemoglobin and albumin levels, the GA/A1c ratio was still inversely correlated with both HOMA‐β and IGI. Conclusions The GA/A1c ratio is significantly correlated with insulin secretory function but not with insulin resistance.     

糖化血清白蛋白检测与糖尿病及其并发症

血糖监测可反映糖尿病患者糖代谢紊乱状态,是糖尿病降血糖治疗过程中不可缺少的重要环节.糖化血清白蛋白(GA)是葡萄糖与血清白蛋白发生非酶糖化反应的产物,反映糖尿病治疗近2～3周内平均血糖水平,在临床上用于评价糖尿病短期血糖控制水平及药物疗效等,具有较高的实用价值.与糖尿病血糖监测的其他指标比较,GA有诸多优势.同时,GA与糖尿病慢性并发症密切相关,对于糖尿病合并多种疾病的患者,GA较糖化血红蛋白(Hb)A1c及糖化血清蛋白(CSP)能够更敏感、更快速、更准确地反映血糖控制水平.     

High-performance liquid chromatographic assay of serum glycated albumin

Summary A method for determination of serum glycated albumin by high-performance liquid chromatography is presented. The system involves anion exchange chromatography to separate albumin and consecutive boronate affinity chromatography to separate glycated and nonglycated albumin. The method is rapid (20 min), precise (coefficient of variation, 0.7–4.9%), requires only a small sample (5 l), and can be automated. Assay of glycated albumin by this method is not influenced by the protein concentration of the sample or the presence of glucose. The variation in glycated albumin values in consecutive samples obtained within a day from diabetic patients (coefficient of variation, 2.02±0.65%) was significantly smaller (p<0.001) than that of values for fructosamine (coefficient of variation, 4.33±2.0%). The values of glycated albumin in normal subjects (20.2±1.6%) were clearly less than those in diabetic patients [39,6±5.4% in 40 Type 1 (insulin-dependent) and 39.4±5.9% in 25 Type 2 (non-insulin-dependent) patients]. The serum glycated albumin level was well correlated with HbA_1c in 65 diabetic patients (r=0.60). Because the life span of albumin in the circulation is short, measurement of glycated albumin should be useful as a short-term index of glycaemic control.