Molecularly imprinted polymers for sensing/depleting human serum albumin (HSA): A critical review of recent advances and current challenges

Human serum albumin (HSA) is an essential biomacromolecule in the blood circulatory system because it carries numerous molecules, including fatty acids (FAs), bilirubin, metal ions, hormones, and different pharmaceuticals, and plays a significant role in regulating blood osmotic pressure. Fluctuations in HSA levels in human biofluids, particularly urine and serum, are associated with several disorders, such as elevated blood pressure, diabetes mellitus (DM), liver dysfunction, and a wide range of renal diseases. Thus, the ability to quickly and accurately measure HSA levels is important for the rapid identification of these disorders in human populations. Molecularly imprinted polymers (MIPs), well known as artificial antibodies (Abs), have been extensively used for the quantitative detection of small molecules and macromolecules, especially HSA, in recent decades. This review highlights major challenges and recent developments in the application of MIPs to detect HSA in artificial and real samples. The fabrication and application of various MIPs for the depletion of HSA are also discussed, as well as different MIP preparation approaches and strategies for overcoming obstacles that hinder the development of MIPs with high efficiency and recognition capability for HSA determination/depletion.

Protein-templated copper nanoclusters for fluorimetric determination of human serum albumin

Copper nanoclusters (CuNCs) are attractive for their unique optical properties, providing sensitive fluorescent detection of several kinds of targets even in complex matrices. Their ability in growing on suitable protein and nucleic acid templates make CuNCs efficient optical reporters to be exploited in bioanalysis. In this work, we report the specific and sensitive determination of human serum albumin (HSA) in human serum (HS) and urine via CuNCs fluorescence. HSA is the most abundant protein in plasma, and plays a key role in the early diagnosis of serious pathological conditions such as albuminuria and albuminemia. Recently, HSA has become clinically central also as a biomarker to assess severity, progression, and prognosis of various cancers. We report the controlled and reproducible growth of CuNCs directly on the target analyte, HSA, which results in a fine dose-dependent fluorescent emission at 405 nm. The protocol is optimized in water, and then applied to serum and urine specimens, without matrix pretreatment. The method linearly responds within the whole concentration of clinical interest, with a sensitivity of 1.8 ± 0.1 × 10^-3 g L^-1 and 0.62 ± 0.03 × 10^-3 g L^-1 in serum and urine, respectively, and excellent reproducibility (CV_av% ca. 3% for both). The assay is designed to have a single protocol working for both matrices, with recovery of 95% (HS) and 96% (urine). The stability of the fluorescence after CuNCs formation was tested over 3 days, displaying good results (yet higher in urine than in serum).

Review: Detection and quantification of proteins in human urine

Extensive medical research showed that patients, with high protein concentration in urine, have various kinds of kidney diseases, referred to as proteinuria. Urinary protein biomarkers are useful for diagnosis of many health conditions – kidney and cardio vascular diseases, cancers, diabetes, infections. This review focuses on the instrumental quantification (electrophoresis, chromatography, immunoassays, mass spectrometry, fluorescence spectroscopy, the infrared spectroscopy, and Raman spectroscopy) of proteins (the most of all albumin) in human urine matrix. Different techniques provide unique information on what constituents of the urine are. Due to complex nature of urine, a separation step by electrophoresis or chromatography are often used for proteomics study of urine. Mass spectrometry is a powerful tool for the discovery and the analysis of biomarkers in urine, however, costs of the analysis are high, especially for quantitative analysis. Immunoassays, which often come with fluorescence detection, are major qualitative and quantitative tools in clinical analysis. While Infrared and Raman spectroscopies do not give extensive information about urine, they could become important tools for the routine clinical diagnostics of kidney problems, due to rapidness and low-cost. Thus, it is important to review all the applicable techniques and methods related to urine analysis. In this review, a brief overview of each technique's principle is introduced. Where applicable, research papers about protein determination in urine are summarized with the main figures of merits, such as the limit of detection, the detectable range, recovery and accuracy, when available.

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Urinary protein biomarkers are useful for diagnosis of many conditions: kidney and cardio vascular diseases, cancers.

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Liquid chromatography – mass spectroscopy is a powerful tool for urine proteomics, but used mostly in science.

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Immunoassays are widely used in both clinical and bio-analytical laboratories.

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IR and Raman spectroscopies are promising tools for diagnostics of urine due to low-cost and rapidness.

Glycosuria amount in response to hyperglycaemia and risk for diabetic kidney disease and related events in Type 1 diabetic patients

BACKGROUND

Hyperglycaemia impairs tubulo-glomerular feedback. We tested whether variable tubulo-glomerular feedback during hyperglycaemia contributes to renal risk heterogeneity seen in Type 1 diabetes.

METHODS

During the period 1990-92, we studied the tubulo-glomerular feedback in Type 1 diabetic patients at high or low renal risk [21 of 54 with glomerular hyperfiltration and/or microalbuminuria against 11 of 55 with normal glomerular filtration rate (GFR) and urinary albumin despite uncontrolled diabetes]. The GFR, effective renal plasma flow, mean arterial pressure and fractional reabsorptions of glucose, osmols, sodium and lithium were measured sequentially during normo- and hyperglycaemia. All patients were followed up until 2016 for incident proteinuria, estimated GFR <60 mL/min/1.73 m2, doubling of serum creatinine, end-stage renal disease or all-cause death.

RESULTS

Glycaemia increased from 6.1 ± 1.3 to 15.1 ± 1.9 mmol/L in both high-risk and low-risk patients. Glycosuria was lower in the high- versus low-risk patients: 0.34 ± 0.25 versus 0.64 ± 0.44 mmol/min (P = 0.03). Both groups displayed similar kidney function during normoglycaemia. Hyperglycaemia increased more importantly GFR and fractional reabsorptions, and pre-glomerular vasodilatation in the high- than in the low-risk patients (all P < 0.05). Over 21 years, 31.5% high- versus 12.7% low-risk patients developed endpoints (adjusted P = 0.006). In a multi-adjusted survival analysis of patients having undergone renal tests, each 0.10 mmol/min glycosuria during hyperglycaemia reduced the outcome risk by 0.72 (95% confidence interval 0.49-0.97, P = 0.03).

CONCLUSIONS

Reduced tubulo-glomerular feedback and glycosuria during hyperglycaemia indicate high renal risk for Type 1 diabetic patients. Inter-individual variability in tubulo-glomerular feedback activity determines renal risk in Type 1 diabetes.

Electrochemical Quantification of Glycated and Non-glycated Human Serum Albumin in Synthetic Urine

A polymer-based electrode capable of specific detection of human serum albumin, and its glycated derivatives, is described. The sensor is constructed from a glass microscope slide coated with a synthesized, polythiophene film bearing a protected, iminodiacetic acid motif. The electrode surface is then further elaborated to a functional biosensor through deprotection of the iminodiacetic acid, followed by metal-affinity immobilization of a specific and high-affinity, albumin ligand. Albumin was then quantified in buffer and synthetic urine via electrochemical impedance spectroscopy. Glycated albumin was next bound to a boronic acid-modified, single-cysteine dihydrofolate reductase variant to quantify glycation ratios by square-wave voltammetry. The platform offers high sensitivity, specificity, and reproducibility in an inexpensive arrangement. The detection limits exceed the requirements for intermediate-term glycemic control monitoring in diabetes patients at 5 and 1 nM for albumin and its glycated forms, respectively.

Plasma proprotein-convertase-subtilisin/kexin type 9 (PCSK9) and cardiovascular events in type 2 diabetes

AIM

To investigate whether plasma concentrations of proprotein-convertase-subtilisin/kexin type 9 (PCSK9) were associated with cardiovascular (CV) events in two cohorts of patients with type 2 diabetes mellitus.

METHODS

We considered patients from the DIABHYCAR (n = 3137) and the SURDIAGENE (n = 1468) studies. Baseline plasma PCSK9 concentration was measured using an immunofluorescence assay. In post hoc, but preplanned, analyses we assessed the relationship between PCSK9 and the following endpoints: (1) a combined endpoint of major CV events: CV death, non-fatal myocardial infarction (MI), stroke and heart failure-related hospital admission; (2) a composite of all CV events: MI, stroke, heart failure-related hospital admission, coronary/peripheral angioplasty or bypass, CV death; (3) MI; (4) stroke/transient ischaemic attack (TIA); and (5) CV death.

RESULTS

In the DIABHYCAR study, plasma PCSK9 tertiles were associated with the incidence of MI, all CV events and stroke/TIA (P for trend <.05). In adjusted Cox analysis, plasma PCSK9 was associated, independently of classic risk factors, with the incidence of major CV events (hazard ratio [HR] for 1-unit increase of log[PCSK9] 1.28 [95% confidence interval {CI} 1.06-1.55]), the incidence of MI (HR 1.66 [95% CI 1.05-2.63]), and the incidence of all CV events (HR 1.22 [95% CI 1.04-1.44]), but not with CV death. Plasma PCSK9 was not associated with the incidence of CV disease in the participants of the SURDIAGENE study with high CV risk treated with statins and insulin.

CONCLUSIONS

We found that PCSK9 was inconsistently associated with CV events in populations with type 2 diabetes. The association may depend on the level of CV risk and the background treatment.

Impact of morbid obesity on the kidney function of patients with type 2 diabetes

AIMS

Type 2 diabetes and obesity impair kidney function. We examined their respective contributions to urinary albumin excretion (UAE) and glomerular filtration rate (GFR) in patients with type 2 diabetes and morbid obesity.

METHODS

Cross-sectional, monocentric study of kidney function in patients with type 2 diabetes classified into four body mass index (BMI) stages: non-obese (<25 kg/m(2), n=157); overweight (25 to <30, n=311); obesity (30 to <40, n=310); and morbid obesity (≥40, n=77), with 84 similarly staged controls without diabetes. UAE classes were defined as normal (<30 μg/mg creatinine), microalbuminuria (30-299), or macroalbuminuria (≥300) from 3 consecutive urine samples. GFR was measured by (51)Cr EDTA plasma disappearance (adjusted and unadjusted to 1.73 m(2) body surface area, as obesity increases body surface).

RESULTS

Participants with type 2 diabetes had same age, diabetes duration, and HbA1c across BMI stages. UAE was higher in participants with type 2 diabetes (p<0.0001), and increased with obesity stages (p<0.0001). After adjustment for age, sex, systolic blood pressure and type 2 diabetes status, morbid obesity was associated with a risk of microalbuminuria (OR 1.99, 95%CI 1.35-2.98, p=0.0007) and macroalbuminuria (OR 2.33, 95%CI 1.25-4.22, p=0.006). The body surface adjusted GFR was lower in patients with type 2 diabetes than in controls (p<0.0001), and declined with obesity stages, contrary to controls. An interaction of diabetes and obesity was seen with unadjusted GFR values (p=0.002).

CONCLUSIONS

Morbid obesity interacts with type 2 diabetes to aggravate UAE and GFR. Treatment strategies should focus on both conditions to protect kidney function in these patients.

Plasma copeptin and renal outcomes in patients with type 2 diabetes and albuminuria

OBJECTIVE

Plasma copeptin, a surrogate for vasopressin, was associated with albuminuria in population-based studies. These associations are consistent with the effect of vasopressin on albuminuria observed in humans and rodents. The objective of this study was to determine whether plasma copeptin is an independent marker of risk of renal events in people with type 2 diabetes and albuminuria.

RESEARCH DESIGN AND METHODS

We studied 3,101 participants of the DIABHYCAR trial (6-year follow-up) with type 2 diabetes and albuminuria. A renal event was defined as doubling of serum creatinine or development of end-stage renal disease.

RESULTS

During follow-up, 86 renal events occurred in 76 subjects (2.45%). Incidences by tertiles of baseline plasma copeptin were 1.06% (T1), 1.45% (T2), and 4.84% (T3). They were 2.43% (T1), 5.11% (T2), and 11.81% (T3) for the subset of subjects with macroalbuminuria at baseline (n = 729). Hazard ratio for plasma copeptin tertiles as a risk for renal events was 4.79 (95% CI, 2.48-9.24; P < 0.0001; for T3 vs. T1). In a stepwise regression analysis, urinary albumin excretion and plasma copeptin remained positively associated and HDL cholesterol and estimated glomerular filtration rate were inversely associated with the incidence of renal events. These independent predictors explained ∼18% of the variance of the outcome. The yearly variations of estimated glomerular filtration rate by copeptin tertiles were -1.43 ± 0.51 (T1), -2.29 ± 0.49 (T2), and -3.52 ± 0.44 mL/min/1.73 m2 per year (T3) (P = 0.005) in subjects with macroalbuminuria.

CONCLUSIONS

Plasma copeptin may help to identify subjects with diabetic chronic kidney disease who are at high risk for renal function decline.

Allelic variations in superoxide dismutase-1 (SOD1) gene and renal and cardiovascular morbidity and mortality in type 2 diabetic subjects

BACKGROUND

Oxidative stress is involved in the pathophysiology of renal and cardiovascular complications of diabetes. Superoxide dismutase (SOD) enzymes play a major role in detoxification of reactive oxygen species and protection against oxidative stress. Associations of SOD1 gene variants with diabetic nephropathy were reported in patients with type 1 diabetes. We investigated associations of allelic variations in SOD1 gene with nephropathy and cardiovascular complications in patients with type 2 diabetes.

METHODS

Seven SNPs in SOD1 region were analyzed in 3744 type 2 European Caucasian diabetic patients from the DIABHYCAR (a 6-year prospective study) and DIABHYCAR_GENE cohorts. Odds ratios or hazard ratios for prevalence and incidence of diabetic nephropathy and cardiovascular events were estimated.

RESULTS

We observed an association of rs1041740 with the prevalence of microalbuminuria at baseline (OR 1.51, 95% CI 1.10-2.10, p=0.01). No association with the incidence of renal events (doubling of the serum creatinine levels or the requirement of hemodialysis or renal transplantation) or cardiovascular events (myocardial infarction or stroke) was observed during follow-up. However, three variants were associated with increased risk of death from cardiovascular causes (sudden death, fatal myocardial infarction or stroke) during the follow-up: rs9974610 (HR 0.64, 95% CI 0.46-0.88, p=0.005), rs10432782 (HR 1.71, 95% CI 1.16-2.48, p=0.007) and rs1041740 (HR 1.78, 95% CI 1.10-2.78, p=0.02).

CONCLUSIONS

Our results are consistent with a major role for SOD1 in the mechanisms of cardiovascular protection against oxidative stress in type 2 diabetic subjects.

Allelic variations in superoxide dismutase-1 (SOD1) gene are associated with increased risk of diabetic nephropathy in type 1 diabetic subjects

BACKGROUND

Oxidative stress is involved in the pathophysiology of diabetic nephropathy. The superoxide dismutase (SOD) enzymes play a major role in detoxification of reactive oxygen species and have a protective effect against diabetic nephropathy. We investigated associations of allelic variations in SOD1 gene with nephropathy in patients with type 1 diabetes.

METHODS

Seven SNPs in SOD1 region were analyzed in 1285 type 1 European Caucasian diabetic patients from the SURGENE prospective study (n=340; ten year follow-up), and the Genesis France-Belgium (n=501) and GENEDIAB (n=444) cross-sectional studies. Cox proportional hazards and logistic regression analyses were used to estimate hazard ratios or odds ratios for incidence and prevalence of diabetic nephropathy.

RESULTS

In the SURGENE study, the T-allele of rs1041740 was associated with the prevalence of incipient (OR 5.75, 95% CI 1.78-19.39, p=0.004) and established/advanced nephropathy at baseline (OR 8.95, 95% CI 1.51-58.42, p=0.02), and with the incidence of incipient nephropathy during follow-up (HR 1.46, 95% C.I. 1.13-1.90, p=0.004). The variant was also associated with decreased estimated glomerular filtration rate (eGFR) throughout the study. In cross-sectional study of Genesis/GENEDIAB cohorts, the G-allele of rs17880135 was associated with incipient (OR 7.53, 95% CI 2.30-25.45, p=0.001), established (OR 6.04, 95% CI 1.52-23.91, p=0.01) and advanced nephropathy (OR 10.03, 95% CI 2.95-35.44, p=0.0003).

CONCLUSIONS

SOD1 allelic variations were associated with the prevalence of diabetic nephropathy, with the incidence of microalbuminuria and with decreased eGFR in type 1 diabetic subjects. These results are consistent with an implication of oxidative stress in the pathophysiology of diabetic nephropathy and with the major role for antioxidant enzymes as a mechanism of renal protection.

Assessment of proteinuria

Proteinuria is a strong predictor of adverse cardiovascular and kidney events, and an accurate assessment of proteinuria is important for the evaluation and management of CKD. Total urinary protein can be assessed using dipstick, precipitation, and electrophoresis methods. Urinary albumin, the predominant urinary protein in most proteinuric kidney diseases, can be assessed using an albumin-specific dipstick, immunochemical techniques, and size-exclusion high-performance liquid chromatography. Urine albumin may be immune-reactive, immune-unreactive, fragmented, and biochemically modified, and laboratory techniques have variable abilities to detect different types of albumin. Urine specimen for proteinuria assessment can either be obtained from a timed-collection or a spot urine sample. Spot urine protein- or albumin-to-creatinine ratios are preferred to a 24-hour urine sample in routine practice. Assessment of albuminuria rather than proteinuria is more clinically meaningful in patients with diabetic kidney disease, and proteinuria and albuminuria assessments both have a role in nondiabetic kidney disease and in general population screening. As measurement and sampling procedures for proteinuria assessment have yet not been standardized, it is important for physicians to be aware of different types of urinary proteins, albumins, laboratory techniques, and urine sampling methods.

Assessment of Liver Function Using Hybrid Neuro-Fuzzy Model of Blood Albumin

This paper presents an assessment of liver function using novel neuro-fuzzy model of blood albumin level (BA). The developed model that is used to predict the BA consists of four inputs: Asparate Aminotransferace (AST), Alkaline Phosphate (ALP), Total Bilirubin (T. Bil.) and Total Protein (T. Prot.), which are measured in any routine liver function test. The proposed BA model was trained using 211 measured data and a root-mean square error (RMSE) of 0.29 for 100 epochs was achieved. The performance of the developed BA model was validated using 57 testing data sets and RMSE of 0.34 for 100 epochs was achieved. The correlation coefficient (CC) between the predicted and measured values of blood albumin is statistically significant (CC=0.83), which ensures the efficiency and accuracy of developed fuzzy model for predicting BA. The main clinical benefit of this model is that it improves the assessment capabilities of liver diseases and can be used as an integral part of any medical expert system denoted for assessment and diagnosis of liver disorders.

First morning voids are more reliable than spot urine samples to assess microalbuminuria

Measurement of urinary albumin excretion (UAE) in a 24-h collection is the gold standard method to determine the presence of microalbuminuria. We sought to compare more practical alternatives--measurement of urinary albumin concentration (UAC) or albumin:creatinine ratio (ACR)--in a first morning void or in a spot urine sample with this gold standard. We asked 241 participants of a prospective cohort study to make three 24-h urine collections, a first morning void, and a spot urine sample. Regression analysis showed that the ACR in a first morning void best agreed with 24-h UAE. The prevalence of microalbuminuria determined by data from a first morning void (7.5%, whether by UAC or ACR) nearly equaled the prevalence of microalbuminuria determined by 24-h UAE (10.0%), whereas the prevalence was higher when determined by spot urine samples (25.4% for UAC and 22.4% for ACR; both P < 0.001 versus 24-h UAE). The intraindividual coefficients of variation of the ACR in a first morning void and 24-h UAE were similar (19%). Intraindividual coefficients of variations of all other measurements of albuminuria were significantly greater. In conclusion, measurement of albuminuria in a first morning void, preferably as the ACR, is more reliable than a spot urine sample to diagnose and monitor microalbuminuria.

Prognostic value of nocturnal blood pressure and reverse-dipping status on the occurrence of cardiovascular events in hypertensive diabetic patients

AIM

To assess whether reverse-dipping status is associated with cardiovascular (CV) events such as CV death, myocardial infarction (MI) or stroke in diabetic patients with hypertension.

METHODS

A total of 97 diabetic patients underwent their first ambulatory blood pressure monitoring (ABPM 1). "Reverse dippers" were defined as patients with a nighttime systolic and/or diastolic blood pressure (BP) greater than daytime systolic and/or diastolic BP. Other patients were called "others". A second ABPM (ABPM 2) was done after a median delay of 2.6 years. Patients were then followed for a further 2.9-year median period (total median follow-up: 5.5 years).

RESULTS

After ABPM 1, CV events occurred in 53% of the reverse dippers (n=15) and in 29% of the others (n=82). Kaplan-Meier curves showed significant differences between the two groups (P=0.003). Mean nighttime systolic BP on ABPM 1 was 148+/-23 mmHg and 142+/-19 mmHg in patients who did and did not experience a CV event, respectively. With Cox analysis adjusted for confounders, a 10 mmHg increase in nighttime systolic BP was associated with a 35% increase in the risk of a CV event (hazard ratio [HR]: 1.35, P=0.003). The HR for a CV event in reverse- versus nonreverse-dipping status was 2.79 (P=0.023). After ABPM 2, the relationship between the reverse-dipping status and occurrence of CV events was no longer evident (P=0.678). Nighttime systolic BP remained predictive of CV events (P=0.001).

CONCLUSION

These findings suggest that nighttime systolic BP per se appeared to be a stronger predictor of an excess risk of CV events compared with reverse-dipping status.

A rapid and sensitive immunoresonance scattering spectral assay for microalbumin

BACKGROUND

Microalbuminuria (MAU) is the earliest clinical finding for renal disease and a risk factor for hypertensive cardiovascular disease. Several methods, including enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), immunoturbidimetry (IT), immunonephelometry (IN), chemiluminescence immunoassay (CLIA), fluorescence immunoassay (FIA) and time-resolved fluorescence (TRF) have been applied for detection of MAU. However, the resonance scattering (RS) spectral assay, based on the immunoreaction and its resonance scattering effect, has not been reported.

METHOD

In the presence of 75 mg/l polyethylene glycol (PEG), the immunoreaction of microalbumin (Malb) and its goat anti-human Malb antibody took place specifically in pH 4.4 buffer solution and aggregated to form immunocomplex particles that exhibit a strongest resonance scattering peak at 488 nm, and it was used to assay of Malb.

RESULTS

The RS intensity at 488 nm (DeltaI) was proportional to the Malb concentration (C) in the range of 0.03-0.96 mg/l, the regression equation was DeltaI=116.0C-2.1, the detection limit was 0.02 mg/l. Urine samples from 20 healthy subjects were assayed by this assay. The results were in agreement with those obtained with IT.

CONCLUSION

This assay has been applied to detection of Malb in real samples, with simplicity, rapidity, high sensitivity and good selectivity.

A combination of magnetic permeability detection with nanometer-scaled superparamagnetic tracer and its application for one-step detection of human urinary albumin in undiluted urine

A rapid (6.5 min) and simple one-step magnetic immunoassay (MIA) has been developed for analysis of human urinary albumin in near patient settings. Polyclonal rabbit anti-human albumin was used as a capture antibody and monoclonal mouse anti-human albumin as a detection antibody in a two-site immunometric assay requiring no additional washing procedures. The polyclonal anti-human albumin was conjugated to silica microparticles (solid phase) and the monoclonal antibody to dextran-coated nanoscaled superparamagnetic particles (tracer). Quantification of human albumin in undiluted urine was performed by adding 2 microL urine to a measuring vial containing solid-phase, superparamagnetic tracer and reaction buffer and then inverting the vial by hand for 20 s. The measuring vial was allowed to stand for 6 min prior to detection, in order for the solid-phase sediment to form at the bottom of the vial. Lastly, the measuring vial was placed into a magnetic permeability detector, which measured the enrichment of superparamagnetic tracer in the sediment due to complex formation with human albumin. Total analysis time was 6.5 min. A linear response was obtained for 0-400 mg/L albumin with a detection limit of 5 mg/L. The total coefficient of variation (CV) was 11% calculated from four consecutive runs on a urine sample containing 11.1 mg/L human albumin during 3 consecutive days. Human urinary albumin analysis was performed on 149 patient samples using the MIA technique and the obtained results showed good correlation with the hospital immunoturbidimetric reference method (y = 1.004x + 4.01, R2 = 0.978, N = 149) and a commercially available point of care albumin analysis provided by HemoCue Inc. (y = 0.98x + 5.8, R2 = 0.833, N = 90).

Modulation of the renal response to ACE inhibition by ACE insertion/deletion polymorphism during hyperglycemia in normotensive, normoalbuminuric type 1 diabetic patients

ACE inhibition protects kidney function, but ACE insertion/deletion (I/D) polymorphism affects renal prognosis in type 1 diabetic patients. ACE genotype may influence the renal benefits of ACE inhibition. We studied the impact of ACE I/D polymorphism on the renal hemodynamic changes induced by ACE inhibition in type 1 diabetes. We studied renal hemodynamics (glomerular filtration rate [GFR], effective renal plasma flow [ERPF], filtration fraction [GFR/ERPF], mean arterial pressure [MAP], and total renal resistances [MAP/ERPF]) repeatedly during normoglycemia and then hyperglycemia in 12 normotensive, normoalbuminuric type 1 diabetes and the II genotype (associated with nephroprotection) versus 22 age- and sex-matched subjects with the ACE D allele after three randomly allocated 2- to 6-week periods on placebo, 1.25 mg/day ramipril, and 5 mg/day ramipril in a double-blind, cross-over study. During normoglycemia, the hemodynamic changes induced by ramipril were similar in both genotypes. During hyperglycemia, the changes induced by ramipril were accentuated in the II genotype group and attenuated dose dependently in the D allele group (treatment-genotype interaction P values for ERPF, 0.018; MAP, 0.018; and total renal resistances, 0.055). These results provide a basis to different renal responses to ACE inhibition according to ACE genotype in type 1 diabetes.

Increased plasma adiponectin concentrations are associated with microangiopathy in type 1 diabetic subjects

AIMS/HYPOTHESIS

Insulin resistance is related to an increased risk of diabetic retinopathy and nephropathy in type 1 diabetes. Patients with insulin resistance and/or macrovascular disease have abnormally low levels of adiponectin. The aim of this study was to investigate the relationships between adiponectin and renal and retinal diabetic complications in type 1 diabetic patients.

METHODS

In this 6-year prospective follow-up observational study, we evaluated the severity of retinopathy at baseline and determined the incident risk of microalbuminuria in 126 normoalbuminuric patients with type 1 diabetes. Each patient was age- and sex-matched to two non-diabetic control subjects.

RESULTS

Plasma adiponectin concentrations were significantly higher in diabetic subjects than in control subjects (p < 0.0001). The adiponectin concentration was significantly higher in patients with severe diabetic retinopathy than in those without (39.1+/-14.0 vs 29.0+/-13.0 microg/ml, p = 0.0005). The 18 patients who developed persistent microalbuminuria had higher adiponectin concentrations than the other patients (35.8+/-14.5 vs 30.6+/-13.7 microg/ml). Increased adiponectin concentrations were independently associated with the occurrence of microalbuminuria (p = 0.0158) after adjustment for baseline urinary albumin concentration (p = 0.004), sex (p = 0.0054), blood pressure (NS) and metabolic control (NS).

CONCLUSIONS/INTERPRETATION

The elevated adiponectin concentrations observed in subjects with microvascular disease may indicate an altered regulation of this adipocytokine in patients with complications associated with type 1 diabetes.

Different patterns of insulin resistance in relatives of type 1 diabetic patients with retinopathy or nephropathy: the Genesis France-Belgium Study

OBJECTIVE

Insulin resistance may be a risk factor for diabetic microangiopathy, which may have a familial component. We carried out a family-based study to determine which components of the insulin resistance syndrome are associated with diabetic retinopathy and nephropathy in type 1 diabetes.

RESEARCH DESIGN AND METHODS

The Genesis France-Belgium Study is a multicenter binational study designed to investigate the genetic factors involved in the microvascular complications of type 1 diabetes using a family-based design. Probands were type 1 diabetic patients with diabetic retinopathy (classified as background, preproliferative, or proliferative) and possibly diabetic nephropathy (absent, incipient, established, or advanced). The insulin resistance score of their first-degree relatives was calculated according to their BMI and history of arterial hypertension, lipid disorders, and type 2 diabetes.

RESULTS

The insulin resistance score of relatives was positively correlated with the albumin excretion rate (P = 0.0009) and fasting plasma glucose (P = 0.0003) and HbA(1c) (P < 0.0001) concentrations. This score was higher in the relatives of probands with than in those without diabetic nephropathy (P = 0.0370). Similarly, it was higher in relatives of subjects with proliferative diabetic retinopathy than in those of probands without, even after controlling for subjects with versus without diabetic nephropathy (P = 0.0379). However, the components of the insulin resistance score in relatives differed according to the severity of diabetic retinopathy or nephropathy in the probands. Obesity and history of arterial hypertension were most common in relatives of probands with proliferative diabetic retinopathy, whereas obesity and history of lipid disorders were most common in the relatives of probands with diabetic nephropathy.

CONCLUSIONS

Familial insulin resistance segregates with diabetic complications: lipid disorders and obesity segregate with diabetic nephropathy, whereas arterial hypertension and obesity segregate with diabetic retinopathy.

Equivalence of indapamide SR and enalapril on microalbuminuria reduction in hypertensive patients with type 2 diabetes

OBJECTIVES

To test whether microalbuminuria in patients with type 2 diabetes and hypertension is primarily dependent on the severity of hypertension, and to compare the effectiveness of two antihypertensive drugs with opposite effects on the renin-angiotensin system [the diuretic, indapamide sustained release (SR), and an angiotensin-converting enzyme inhibitor, enalapril] in reducing microalbuminuria.

DESIGN

A multinational, multicentre, controlled, double-blind, double-dummy, randomized, two-parallel-groups study over 1 year.

METHODS

After a 4-week placebo run-in period, 570 patients (ages 60.0 +/- 9.9 years, 64% men) with type 2 diabetes, essential hypertension [systolic blood pressure (SBP) 140-180 mmHg, and diastolic blood pressure (DBP) < 110 mmHg], and persistent microalbuminuria (20-200 microg/min) were allocated randomly to groups to receive indapamide SR 1.5 mg (n = 284) or enalapril 10 mg (n = 286) once a day. Amlodipine, atenolol, or both were added, if necessary, to achieve the target blood pressure of 140/85 mmHg.

RESULTS

There was a significant reduction in the urinary albumin : creatinine ratio. Mean reductions were 35% [95% confidence interval (CI) 24 to 43] and 39% (95% CI 30 to 47%) in the indapamide SR and enalapril groups, respectively. Equivalence was demonstrated between the two groups [1.08 (95% CI 0.89 to 1.31%); P = 0.01]. The reductions in mean arterial pressure (MAP) were 16.6 +/- 9.0 mmHg for the indapamide SR group and 15.0 +/- 9.1 mmHg for the enalapril group (NS); the reduction in SBP was significantly greater (P = 0.0245 ) with indapamide SR. More than 50% of patients in each group required additional antihypertensive therapy, with no differences between groups. Both treatments were well tolerated.

CONCLUSIONS

Indapamide-SR-based therapy is equivalent to enalapril-based therapy in reducing microalbuminuria with effective blood pressure reduction in patients with hypertension and type 2 diabetes.

Transforming growth factor-beta 1 production is correlated with genetically determined ACE expression in congenic rats: a possible link between ACE genotype and diabetic nephropathy

Genetic background appears to modulate the development of diabetic vascular complications. In particular, polymorphisms in the ACE gene have been associated with diabetic nephropathy and, in some studies, macrovascular complications. However, the links between ACE gene polymorphism and factors implicated in diabetes complications remain unknown. The aim of this study was to determine whether the ACE genotype could modify factors, such as transforming growth factor (TGF)-beta 1, involved in the complications of diabetes. For this purpose, congenic rats (L.BNAce10), differing from the LOU strain in only a small segment of chromosome 10 containing the ACE locus, were generated. These congenic rats have plasma ACE levels twice as high as the donor strain. Diabetes was induced in rats of both strains, and its effects on ACE and TGF-beta 1 expressions were evaluated in lungs and kidneys. In lung, the main source of ACE production, ACE mRNA levels and activity were higher in L.BNAce10 rats than in LOU rats. Diabetes increased ACE lung expression in rats of both strains in a similar manner. TGF-beta 1 expression was also higher in lungs of L.BNAce10 compared with LOU rats and was also increased by diabetes. Furthermore, a strong correlation was found between TGF-beta 1 and ACE expressions. In renal arterioles, ACE and TGF-beta mRNA expressions were higher in L.BNAce10 rats than LOU rats (both diabetic and nondiabetic). In these vessels, there was also a correlation between ACE and TGF-beta 1 expressions. Urine TGF-beta 1 concentration depended on the genotype and was further increased by diabetes. These results show that TGF-beta 1 expression is correlated with ACE expression and suggest that this growth factor could be a link between ACE gene polymorphism and diabetic vascular complications.

A rapid, simple measurement of human albumin in whole blood using a fluorescence immunoassay (I)

BACKGROUND

Human serum albumin (HSA) is the most abundant plasma protein and plays key a role in metabolism. The variation in albumin concentration provides valuable information related to metabolic diseases and diagnostic application.

METHODS

We constructed two assay systems to quantify the albumin concentration. The immunoassay used a fluorescence (FL) dye to detect albumin in samples and employed the conventional chromatography as a separation system. The assay system consists of an anti-HSA-mAb or an HSA immobilized test strip in a disposable cartridge, a fluorescence-labeled detector buffer and a laser-fluorescence scanner. We mixed the sample with detector, loaded it onto a cartridge, incubated it for 10 min and measured the concentration of albumin in a laser-fluorescence scanner. We examined the comparability of assay with an automated BCG dye binding method using a Hitachi 747 biochemical analyzer.

RESULTS

The correlation of coefficient between AT/AC as converted from the relative fluorescence units (RFU) and albumin concentration displayed reasonable reliability in both the competition and the inhibition assay systems (r = 0.998). Using the Bland-Altman difference plot analysis, we observed an acceptable agreement between two methods, the fluorescence immunochromatography assay (FL-ICA) and the automated BCG dye-binding method of a Hitachi biochemical analyzer, over the clinical relevant range of HSA concentrations. The coefficient of variation (CV) of within- and between-run variation in the immunoassay system was < 8% and the recovery fell within 5% in each control sample. In addition to its reliable analytical performance, the assay with whole blood can be completed in 12 min using a one-step operation without any pretreatment.

CONCLUSION

The developed immunoassay system using fluorescence dye and lateral-flow chromatography is a simple, fast and reliable method for quantifying the albumin concentration in whole blood.

Description of microangiopathy in children with type 1 diabetes mellitus: a 19-year retrospective study

BACKGROUND

The aim of the study was to estimate the outcome of patients with type 1 diabetes followed in a university hospital in the paediatric department and then in the adult diabetic department for at least 10 years.

METHODS

We made a retrospective analysis of 50 patients (28 women and 22 men) with type 1 diabetes with disease duration of 19 +/- 6 years and analysed whether retinopathy and nephropathy had progressed, had remained unchanged or had improved or normalised.

RESULTS

The mean age of diabetes onset was 8 +/- 4 years (1-16). Ketoacidosis revealed diabetes in 36% of the children. Mean HbA(1c) was 8.6 +/- 1.8%, and was over 8.5% in 34% of the patients. The mean age at onset of puberty (Tanner stage II) was 12 +/- 1 years in girls and 13 +/- 1 years in boys. Mean HbA(1c) was 7.9 +/- 1.2% during the year before onset of puberty and 8.7 +/- 1.1% in the following 3 years, corresponding to a 10% pubertal increase in HbA(1c). Retinopathy was seen in 50% of the patients at a mean age of 22 +/- 5 years, 15 +/- 6 years after onset of diabetes. Mean HbA(1c) was 9.7 +/- 1.6% in patients with proliferative retinopathy, 9.0 +/- 1.5% in patients with non proliferative retinopathy, and 8.1 +/- 1.3% in those without (p=0.02, proliferative versus no retinopathy, p > 0.05 non proliferative versus no retinopathy). Microalbuminuria was diagnosed in 26% of the patients. Mean HbA(1c) was 9.3 +/- 2.1% in patients with microalbuminuria versus 8.1 +/- 1.3% in those with normoalbuminuria (p=0.02).

CONCLUSIONS

Glycemic control was similar in patients with non proliferative retinopathy and those without. Proliferative retinopathy and nephropathy were both related to the level of glycemic control.

Incidence of diabetic nephropathy in Type 1 diabetic patients in Spain: 'Estudio Diamante'

AIMS

To determine the prevalence and the incidence of diabetic nephropathy in Type 1 diabetes mellitus in Spain and to investigate the risk factors for the development of microalbuminuria.

METHODS

One thousand five hundred and two patients with Type 1 diabetes mellitus were prospectively followed in 15 hospital diabetes outpatient clinics in Spain. Blood pressure, body weight, HbA(1c), total cholesterol, HDL-cholesterol, triglycerides, plasma creatinine and urinary albumin excretion (UAE) were determined every 3-5 months.

RESULTS

A total of 1225 patients (624 males and 601 females), age 30.7+/-9.3 years with diabetes duration of 14.1+/-9.1 years completed 4.3 (4.0-5.1) years of follow-up. At baseline 14.2 (95% CI 12.3-16.3)% of patients had microalbuminuria, 5.1 (3.9-6.4)% macroalbuminuria and 3.4 (2.5-4.6)% kidney failure. During follow-up the annual incidence of microalbuminuria was 2.7 (2.2-3.2)%. In a multiple logistic regression analysis the predictors of progression to microalbuminuria were initial UAE, HbA(1c), diabetes duration, smoking, and HDL-cholesterol <0.9 mmol/l.

CONCLUSIONS

The prevalence and incidence of diabetic nephropathy in Spain are comparable to data obtained in similar studies carried out in other countries. The development of microalbuminuria is associated not only with glycaemic control and hypertension, but also to the control of other risk factors such as dyslipaemia and smoking.

Association of urinary albumin concentration with casual and ambulatory blood pressure: a similar relationship in normotensive and hypertensive subjects

BACKGROUND

The urinary albumin level has been found to be positively correlated with blood pressure in hypertensive patients. To our knowledge, this relationship has not been evaluated in normotensive subjects and compared with that in hypertensives using casual and ambulatory blood pressure measurements.

METHODS

In this cross-sectional study, a cohort of 234 normotensive and hypertensive participants wore an ambulatory blood pressure monitor for 24 h, standardized casual blood pressure measurements being taken. The urinary albumin concentration was determined by the dipstick Micral Test. The bivariate and multivariate relationship between urinary albumin concentration and demographic and blood pressure measures was investigated using correlational and regression analyses.

RESULTS

The prevalence of microalbuminuria was significantly greater in the hypertensive than normotensive participants. The urinary albumin concentration was positively associated with both casual and ambulatory measures of blood pressure in both the normotensive and hypertensive subsamples, stronger correlations being found for systolic blood pressure. The relationship between systolic blood pressure and urinary albumin concentration was similar in the normotensive and hypertensive subsamples.

CONCLUSIONS

These findings confirm earlier reports of the greater prevalence of microalbuminuria in patients with hypertension than in normotensive participants, as well as those reporting a continuous relationship in hypertensive participants. This study extends prior research to a normotensive subsample, in whom a similar relationship of blood pressure to microalbuminuria, using both ambulatory and casual measures of blood pressure, was found. Future research should investigate the causal direction of this relationship.

Autoregulated glomerular filtration rate during candesartan treatment in hypertensive type 2 diabetic patients

BACKGROUND

Impaired autoregulation of the glomerular filtration rate (GFR) implies disturbances in the downstream transmission of the systemic blood pressure into the glomerulus, leading to capillary hypertension or hypotension dependent of the level of blood pressure. The impact on renal autoregulation of different antihypertensive drugs in animals has been elucidated, whereas information in humans is lacking.

METHODS

A randomized, double-blind crossover study with candesartan cilexetil 16 mg o.d. and placebo was performed in 17 hypertensive type 2 diabetic patients without nephropathy. Each treatment arm lasted four weeks. On the last day, GFR (single shot [51Cr] EDTA plasma clearance technique for 4 hours) was measured twice between 8 a.m. and 5 p.m., first without clonidine and then after an intravenous injection of clonidine 75 microg. Blood pressure (Takeda TM2420, A&D, Tokyo, Japan) was measured every ten minutes, and the urinary albumin excretion rate (UAER) was measured by ELISA during each GFR determination.

RESULTS

Candesartan induced a mean (SE) reduction in mean arterial blood pressure (MABP) of 6 (2) mm Hg (P < 0.02) and had a tendency to reduce UAER (P = 0.07), while GFR remained unchanged (95 vs. 93 mL/min/1.73 m2). Clonidine reduced MABP with 17 (2) versus 16 (1) mm Hg during placebo versus candesartan 16 mg o.d., respectively (NS). GFR diminished in average from 95 (3) to 92 (4) mL/min/1.73 m2 with placebo (NS), and from 93 (3) to 89 (4) mL/min/1.73 m2 during treatment with candesartan (NS). The mean difference (95% CI) in the changes in GFR between the examination with placebo and with candesartan was 0.1 (-5.5 to 5.8) mL/min/1.73 m2 (NS).

CONCLUSION

Candesartan reduces blood pressure without adversely altering the preserved ability to autoregulate GFR in hypertensive type 2 diabetic patients without nephropathy.

Apolipoprotein E gene polymorphism is not a strong risk factor for diabetic nephropathy and retinopathy in Type I diabetes: case-control study

BACKGROUND

The gene encoding apolipoprotein E (APOE) has been proposed as a candidate gene for vascular complications in Type I diabetes. This study aimed to investigate the influence of three-allelic variations in the APOE gene for the development of diabetic retinopathy and nephropathy.

RESULTS

Neither APOE alleles frequencies or APOE genotypes frequencies differed between Type I diabetic groups either with or without nephropathy. Similar results were found for patients with and without diabetic retinopathy.

CONCLUSIONS

APOE gene polymorphism does not determine genetic susceptibility for the development of diabetic retinopathy in Type I diabetes patients. Association between APOE gene polymorphism and diabetic nephropathy may be weak or moderate, but not strong.

Prognostic value of angiotensin-I converting enzyme I/D polymorphism for nephropathy in type 1 diabetes mellitus: a prospective study

Angiotensin-I converting enzyme (ACE) regulates renal hemodynamics. Its insertion/deletion (I/D) polymorphism, which determines most of ACE interindividual variance, was proposed as a genetic marker for diabetic nephropathy. A substitution (M235T) polymorphism in angiotensinogen (AGT) may interact with ACE I/D polymorphism for the risk of diabetic nephropathy, but their prognostic values have to be established by follow-up studies. A total of 310 type 1 diabetes mellitus patients who attended the diabetic clinic in Angers (France) took part in a prospective, observational, follow-up study. Glycohemoglobin, BP, plasma creatinine, and urinary albumin excretion were determined periodically. Nephropathy was classified as absent, incipient (microalbuminuria), established (proteinuria), advanced (plasma creatinine > or = 150 micromol/L), and terminal (renal replacement therapy). The main end point was the occurrence of a renal event defined as the progression to a higher stage of diabetic nephropathy. At baseline, 251 (81%) patients had no nephropathy, 35 (11%) had incipient nephropathy, 18 (6%) had established nephropathy, and 6 (2%) had advanced nephropathy. The ACE I/D and M235T AGT polymorphisms were in Hardy-Weinberg equilibrium in the patients. The median duration of follow-up was 6 yr (range, 2 to 9 yr). The occurrence of renal events was significantly influenced by ACE genotype (log-rank II versus ID versus DD, P < 0.03) with a dominant deleterious effect of the D allele: ID or DD versus II (adjusted hazard ratio, 5.0; 95% confidence interval, 1.5 to 16.6). Other contributors were high glycohemoglobin and systolic BP. In the patients who initially were free of nephropathy, baseline plasma ACE concentration was higher in patients who progressed to microalbuminuria (571 +/- 231 versus 466 +/- 181 microg/L; P = 0.0032); the D allele independently favored the occurrence of incipient nephropathy (adjusted hazard ratio, 4.5; 95% confidence interval, 1.1 to 19.4); other contributors were male gender, baseline systolic BP, and urinary albumin excretion. The AGT M235T polymorphism was not associated with renal events. The D allele of the ACE I/D polymorphism is an independent risk factor for both the onset and the progression of diabetic nephropathy in type 1 diabetes mellitus patients.

The impact of glycaemic control on autoregulation of glomerular filtration rate in patients with non-insulin dependent diabetes

The ability of the kidney to maintain constancy of glomerular filtration rate (GFR) over a wide range of renal perfusion pressures is termed autoregulation. Defective autoregulation of GFR has been demonstrated in patients with diabetic and non-diabetic nephropathy and in streptozotocin diabetic rats during hyperglycaemia. Information on the potential impact of acute changes in glycaemic control on autoregulation of GFR in diabetic patients is lacking. Therefore the aim of our study was to evaluate the effect of acute lowering of blood pressure (BP) on GFR during normoglycaemia and hyperglycaemia. We investigated 14 (12m/2f) normoalbuminuric patients with non-insulin dependent diabetes (NIDDM). The patients were examined in random order on two separate days with blood glucose (BG)<10 mmol/L or with BG>15 mmol/L. GFR (single shot [51Cr] EDTA plasma clearance technique) was measured twice each day; first without clonidine (baseline) followed by intravenous injection of clonidine 100-150 microg. We measured BG (One Touch 2), and BP (Takeda TM2420) several times during each GFR measurement. Clonidine reduced mean arterial blood pressure with 20 (1.4) vs. 16 (1.2) mmHg (mean (SE)) with BG<10mmol/L and with BG>15 mmol/L, respectively (p=0.053). GFR diminished in average from 92 (3.1) to 86 (3.7) ml/min/1.73m2 with BG<10 mmol/L (p<0.05), and from 102 (4.1) to 98 (4.2) ml/min/1.73 m2 with BG> 15 mmol/L, NS. Mean difference between changes in GFR (95% confidence interval) between the examination with BG<10 mmol/L and with BG>15 mmol/L were 2.3 (-1.3 to 5.9) ml/min/1.73 m2 (NS). The mean BG during normoglycaemia was 6.9 (0.3) vs.16.9 (0.4) during hyperglycaemia.

CONCLUSION

Our study suggests that acute changes in glycaemic control have no detectable effect on autoregulation of GFR in NIDDM patients. Hyperglycaemia enhances GFR.

The non-insulin-dependent diabetes, hypertension, microalbuminuria or proteinuria, cardiovascular events, and ramipril (DIABHYCAR) study: design, organization, and patient recruitment. DIABHYCAR Study Group

The non-insulin-dependent DIABetes, HYpertension, microalbuminuria or proteinuria, CARdiovascular events, and Ramipril (DIABHYCAR) study is a randomized, prospective, double-blind, placebo-controlled, multicenter international trial of the ACE inhibitor ramipril (1.25 mg/day) in patients with type II diabetes and micro- or macroalbuminuria. The main outcome of the study is the time to first occurrence of either death from a cardiovascular origin, including sudden death, nonfatal myocardial infarction, stroke, or congestive heart failure, or requirement of hemodialysis or renal transplantation. The study was launched in France in early 1995 with the participation of general practitioners only, but had to be extended to 15 other countries in 1997 due to difficulties in recruitment. Since 2.5 years after the beginning of the trial the observed event rate was much less than anticipated, it was decided to increase recruitment and follow-up duration and to include congestive heart failure in the definition of the main outcome to keep the study power at a satisfactory level. Recruitment ended on April 1, 1998 with 4937 randomized patients. Following the early discontinuation for efficacy of another study of ramipril in high cardiovascular risk patients, the Heart Outcomes Prevention Evaluation study (HOPE), the second interim analysis of DIABHYCAR was performed early (when 406 instead of 500 patients presented a main outcome) and the Data Safety and Monitoring Board recommended that the study continue. Follow-up is planned to end on March 31, 2001.

Renal involvement in type 1 (IDDM) diabetes in Spain. ESTUDIO DIAMANTE

Diabetic nephropathy (DN) is a major complication of diabetes with a significant repercussion in health care with few epidemiological data available in Spain. The aim of this multicenter cross-sectional study was to establish the prevalence of renal involvement in a large group of patients with type 1 (insulin-dependent) diabetes and evaluate several risk factors related to its development. One thousand eight hundred twenty-two patients (921 males, mean age: 30.5 +/- 9.7 years, diabetes duration 14.1 +/- 9.2 years) from the Endocrinology Units of 18 Spanish hospitals were included in this study. Urinary albumin excretion (UAE), plasma creatinine, lipid profile, HbA1c, and family history of hypertension and nephropathy, smoking, arterial blood pressure and BMI were evaluated. The prevalence of microalbuminuria, established nephropathy (patients with macroalbuminuria and those with renal failure) and hypertension was 14.1, 8.5 and 11.3%, respectively. On logistic regression analysis, using the presence or absence of established nephropathy as variable, smoking (P = 0.0005), years of diabetes evolution (P < 0.00005), diastolic blood pressure (P < 0.00005), HbA1c (P < 0.00005) and triglycerides (P = 0.0008) were included in the model. When analyzing patients with microalbuminuria vs those with normoalbuminuria the variables included were smoking (P = 0.005), diastolic blood pressure (P = 0.0026), years of diabetes evolution (P < 0.00005) and HbA1c (P < 0.00005). prevalence of diabetic nephropathy DN in type 1 (insulin-dependent) diabetes in Spain is similar to that observed ther European countries. The association between diabetic nephropathy DN and hypertension, lipid disorders and metabolic control is confirmed and smoking appears to be an additional risk factor to be considered in diabetic care.

Development and validation of a particle-enhanced turbidimetric inhibition assay for urine albumin on the Dade aca® analyzer

The measurement of urine albumin now has a well-established role in the monitoring of patients with diabetes mellitus. We have developed a particle-enhanced immunoturbidimetric inhibition assay for urine albumin on the Dade aca® analyzer. The inhibition approach removes any of the potential antigen excess difficulties that could be expected from the wide clinical range of urine albumin, but retains the sensitivity advantages of latex-enhanced immunoturbidimetry. Human serum albumin (HSA) is covalently attached to 40-nm poly(chloromethyl)styrene-modified latex particles. This reagent, along with monoclonal antibody to HSA, is aliquoted into the aca reagent pack along with polyethylene glycol 8000 in a tablet form (giving a final reaction concentration of 15 g/L). A 150 mmol/L phosphate buffer, pH 7.8, is used to fill the reagent pack in the instrument and the agglutination reaction is monitored at 340 nm. The sample volume is 100 μL and the calibration curve covers the range 2–250 mg/L. Evaluation of commercial scale reagents against the Beckman Array nephelometric immunoassay system gave a Deming regression correlation of aca = 0.87 × Beckman + 8.5,r = 0.995, n = 145. Mean analytical recovery was 104 ± 4.5%, n = 20, and there was no evidence of a lack of parallelism. Interassay precision was 8.8% at 10.0 mg/L and &lt;2.5% at &gt;65 mg/L. Calibrator stability was in excess of 60 days. A small reference range study (24-h urine collections, n = 27) gave a mean of 5.6 mg/L with a range of 0.5–16.2 mg/L. Analytical sensitivity (2.5 SD from zero) was 0.40 mg/L.

Microalbuminuria in type 2 diabetes: an independent predictor of cardiovascular mortality

BACKGROUND

Microalbuminuria has been shown to be associated with cardiovascular mortality in type 2 diabetic subjects. It is unclear to what extent this is due to the increased prevalence of other cardiac risk factors.

AIMS

To examine the relationship of urine albumin excretion to cardiovascular mortality and to determine its status as an independent risk factor.

METHODS

In a prospective longitudinal study from 1986-1993 we followed 666 type 2 diabetic subjects from a diabetes outpatient service. Cardiovascular risk factors including urine albumin concentration were measured at study entry. Cox proportional hazards regression was used to determine risk factors for mortality. The hazard ratios of microalbuminuria and macroalbuminuria for all cause, cardiovascular and coronary heart disease mortality were determined after accounting for other cardiac risk factors including blood pressure, glycated haemoglobin, total cholesterol, HDL cholesterol, triglycerides, urea, smoking, body mass index, patient age and disease duration.

RESULTS

The prevalence of urine albumin of 30-300 mg/L at study entry was 31.7%. A total of 167 deaths occurred (80 from cardiovascular disease). Mortality hazard ratios in subjects with urine albumin of 30-300 mg/L as compared to < 30 mg/L, adjusted for age, sex and other cardiovascular risk factors were 1.77 (95% CI 1.22-2.57, p = 0.002) for all causes, 2.34 (95% CI 1.38-3.99, p = 0.002) for cardiovascular and 1.78 (95% CI 0.97-3.26, p = 0.061) for coronary heart disease (CHD) mortality. Other factors significantly associated with cardiovascular mortality included diastolic blood pressure, HDL cholesterol and glycated haemoglobin. Total cholesterol and log triglyceride were significantly associated with CHD mortality. Disease duration, age at diagnosis, smoking and body mass index were not related to cardiovascular or CHD mortality.

CONCLUSIONS

We confirm microalbuminuria as an independent predictor of mortality in type 2 diabetes despite its association with a number of conventional cardiovascular risk factors.

Epidemiology of renal involvement in type II diabetics (NIDDM) in Catalonia. The Catalan Diabetic Nephropathy Study Group

The aim of this cross-sectional study was to establish the prevalence of renal involvement and to identify associations with its most important possible risk factors in a group of patients with Type II diabetes mellitus, representative of the population living in Catalonia. One thousand two hundred and three patients (47% males, mean age: 61 +/- 6 years, diabetes duration 9 +/- 6 years) were studied. Overnight urine samples were collected to determine urinary albumin excretion (UAE). If UAE was > 15 micrograms/min, a new 24-h urine collection for UAE measurement to establish the existence of microalbuminuria (20-200 micrograms/min) or macroalbuminuria (> 200 micrograms/min) was obtained. Clinic and metabolic evaluations were also performed. The prevalence (%) of microalbuminuria, macroalbuminuria and hypertension were, respectively, 23. 1, 5.4 and 42. In comparison with normoalbuminurics, patients with microalbuminuria were predominately male (P < 0.03), with a significantly higher systolic (P < 0.001) and diastolic (P < 0.001) blood pressure and body mass index (P < 0.001). The prevalence of smokers (former + current) was higher in patients with microalbuminuria (43 vs 32%, P < 0.025). Moreover, patients with nephropathy had more prevalence of retinopathy (P < 0.001), neuropathy (P < 0.001), peripheral angiopathy (P < 0.001) and coronary disease (P < 0.001). The prevalence of microalbuminuria in Type II diabetes in Catalonia is similar to that observed in other european countries. The existence of microalbuminuria is associated with several diabetic complications, as well as tobacco consumption and obesity.

Microalbuminuria in 411 untreated individuals with established hypertension, white coat hypertension, and normotension

We compared urinary albumin excretion in normotensive subjects and patients with white coat and established hypertension. The study involved prospective comparison of office blood pressure, daytime ambulatory blood pressure, and urinary albumin excretion in consecutive patients (n = 284) who were selected from general practice with newly diagnosed mild to moderate hypertension before the institution of pharmacologic antihypertensive therapy. All patients had a diastolic office blood pressure above 90 mm Hg; 173 had a consistently elevated diastolic blood pressure (established hypertension), and 111 had an average daytime ambulatory blood pressure below 90 mm Hg (white coat hypertension). A sample of 127 subjects drawn from the Danish national register served as a normotensive control group. The main outcome measure was the ratio of early morning urinary albumin to creatinine. This ratio differed significantly among the three groups, being (on a molar basis) 21 +/- 69 x 10(-6) in the normotensive subjects, 22 +/- 39 x 10(-6) in the white coat hypertensive patients, and 51 +/- 177 x 10(-6) in patients with established hypertension. The difference remained significant after correction for covariables. The ratio of early morning urinary albumin to creatinine was weakly but significantly correlated to blood pressure, was more pronounced for ambulatory than for office measurements, was more pronounced for systolic than for diastolic pressure, and was more pronounced for hypertensive than for normotensive individuals. The ratio was as reproducible a measure as 24-hour albumin excretion. We conclude that white coat hypertensive patients have less renal involvement than patients with established hypertension but more than a normotensive control group.

Epidemiology of microalbuminuria in the general population

Microalbuminuria in the general population is associated with recognized risk factors for cardiovascular disease such as hypertension, hyperglycemia, hyperinsulinemia, and hyperlipidemia; and it is an independent predictor of subsequent cardiovascular mortality in hypertensive, diabetic, and elderly populations. Although different methods have been used for measuring and expressing urinary albumin excretion and a variety of cutoff levels have been used for defining microalbuminuria, prevalence of microalbuminuria appears to be higher in non-Europeans (8%-28%) than in Europeans (2%-10%). However, because of the large within-individual variability of urinary albumin excretion and the relatively low prevalence of microalbuminuria, large studies are required to detect statistically significant associations between albuminuria and cardiovascular risk factors. Evidence presented here supports the proposition that microalbuminuria represents a marker of cardiovascular disease risk in nondiabetic individuals as well as diabetic individuals. Moreover, because of a high sensitivity of the test and because albuminuria is a concomitant of many forms of renal disease, microalbuminuria also has a role in detecting patients with renal involvement associated with essential hypertension, lupus erythematosus, women with pre-eclampsia, and subjects with unsuspected primary and secondary nephropathies.

Fecal excretion of alpha 1-antitrypsin in patients with Crohn's disease. A comparison of nephelometry and radial immunodiffusion

A comparison is made of two methods for quantifying fecal alpha 1-antitrypsin (A1ATF): nephelometry (NPL) (the method habitually employed in our laboratory), and radial immunodiffusion (RID). A method is also described for extracting A1ATF from single 24-hr stool samples. The normal A1ATF values were initially established in 25 healthy controls, followed by quantification of the protein in 30 patients with Crohn's disease, with the aim of evaluating the sensitivity and specificity of the test in assaying A1ATF and alpha 1-antitrypsin fecal clearance (CLAT). The precision of the measurement method and its applicability to the A1ATF extraction process are also evaluated. The ranges of normal A1ATF and CLAT values were found to be 0-42.2 mg/24 hr and 0-12.6 ml/24 hr, respectively; sensitivity was in turn 83% and 80% for A1ATF and CLAT, respectively, with a specificity of 100% in both cases. A good correlation was observed between the A1ATF quantifications afforded by RID and NPL in both the controls and patients with Crohn's disease (r = 0.917 and 0.997, respectively). We consider that A1ATF quantification is a rapid, safe, and reproducible method that is well tolerated by the patient.

A prospective study of several potential biologic markers for early prediction of the development of preeclampsia

OBJECTIVE

The purpose of this study was to prospectively evaluate the predictive performance of several potential biologic markers of preeclampsia used alone or in combination.

STUDY DESIGN

A prospective cohort of 1366 nulliparous women was followed up longitudinally on three occasions during pregnancy. The predictive performance of the tests, used either alone or in combination (stepwise multiple logistic regression), was assessed and compared with that of the mean arterial pressure.

RESULTS

Preeclampsia occurred in 109 of the pregnant women. At a specificity of 80% the sensitivity and the positive and negative predictive values for mean arterial pressure (at a threshold of 87 mm Hg) were 46.6%, 23.5%, and 92.0%, respectively, and the corresponding values for a multiple logistic model at 15 to 24 weeks that included some biologic markers, as well as the mean arterial pressure, were 57.1%, 26.9%, and 93.7%, respectively.

CONCLUSION

Preeclampsia can be predicted by a combination of simple biologic tests with a performance similar to second-trimester mean arterial pressure. However, this procedure is insufficient in terms of clinical usefulness.

Comparison of reduction in microalbuminuria by enalapril and hydrochlorothiazide in normotensive patients with insulin dependent diabetes

OBJECTIVE

To compare the effects of sodium depletion and of angiotensin I converting enzyme inhibition on microalbuminuria in insulin dependent diabetes.

DESIGN

Randomised, double blind, double dummy parallel study of normotensive diabetic patients with persistent microalbuminuria (30-300 mg/24 h) treated with enalapril or hydrochlorothiazide for one year after a three month, single blind placebo period.

SETTING

Diabetic clinic in a tertiary referral centre.

PATIENTS

10 diabetic patients with low microalbuminuria (30-99 mg/24 h) and 11 with high microalbuminuria (100-300 mg/24 h).

INTERVENTIONS

11 subjects (six with low microalbuminuria, five with high microalbuminuria) were given enalapril 20 mg plus placebo hydrochlorothiazide once daily and 10 (four with low microalbuminuria, six with high microalbuminuria) hydrochlorothiazide 25 mg plus placebo enalapril once daily.

MAIN OUTCOME MEASURES

Monthly assessment of urinary albumin excretion and mean arterial pressure; plasma active renin and aldosterone concentrations and renal function studies at 0, 6, and 12 months.

RESULTS

Median urinary albumin excretion decreased from 59 (range 37-260) to 38 (14-146) mg/24 h with enalapril and from 111 (33-282) to 109 (33-262) mg/24 h with hydrochlorothiazide (analysis of variance, p = 0.0436). During the last three months of treatment with enalapril five patients had persistent normoalbuminuria (2-3 times below 30 mg/24 h), five low microalbuminuria, and one high microalbuminuria; in the hydrochlorothiazide group one had normoalbuminuria, three low microalbuminuria, and six high microalbuminuria (chi 2 test = 6.7; p = 0.03). Mean arterial pressure did not differ before (98 (SD 7) with enalapril v 97 (9) mm Hg with hydrochlorothiazide) or during treatment (88 (7) with enalapril v 90 (7) mm Hg with hydrochlorothiazide (analysis of variance, p = 0.5263)). Glomerular filtration rate did not vary. The aldosterone to active renin ratio was decreased by angiotensin I converting enzyme inhibition and increased by sodium depletion, showing treatment efficacy.

CONCLUSION

Angiotensin I converting enzyme inhibition by enalapril effectively reduces microalbuminuria in normotensive diabetic patients whereas hydrochlorothiazide is not effective. Changes in blood pressure and activity of the renin-angiotensin-aldosterone system may contribute to these different effects.

Semi-quantitative determination of microalbuminuria by urinary dipstick

Microalbuminuria predicts subsequent clinical nephropathy and mortality in diabetic patients. This study was undertaken to determine the usefulness of a new immunochemical urinary dipstick test (Micral-Test, Boehringer Mannheim, GmbH Mannheim, Germany) in identifying urinary albumin concentrations within the microalbuminuric range (urinary albumin concentration 20-200 mg/L). Twenty-four hour urine specimens were collected from 298 consecutive diabetic outpatients. Micral-Test was performed by two laboratory scientists blinded to each other's results and those of radioimmunoassay (RIA) and immunoturbidimetry on the same specimen. When compared with RIA, Micral-Test had an overall sensitivity of 92.2%, specificity of 92.3% and positive predictive value of 86.4%. However, at the threshold value of 20 mg/1 Micral-Test showed false positive results in 37.8% of samples when compared with RIA. Similar results were obtained when Micral-Test was compared with immunoturbidimetry. We conclude that Micral-Test is a useful screening method for the detection of microalbuminuria. We suggest that positive tests be confirmed by a timed urine collection using established methodology and that patients whose Micral-Test is negative be subjected to annual retesting.

Glomerular hyperfiltration in type I, type II, and secondary diabetes

Glomerular hyperfiltration, a risk factor for diabetic nephropathy, has been reported in type I insulin-dependent diabetics, but it is not clear if it occurs in other types of diabetes. To ascertain the prevalence of glomerular hyperfiltration in various types of diabetes, we measured glomerular filtration rate (GFR) in 158 diabetics (91 type I, 36 type II without insulin treatment, 20 type II with insulin treatment, and 11 subjects with diabetes secondary to chronic pancreatitis), and classified them as hyper-, normo-, or hypofiltration according to values measured in 36 age-match controls. After elimination of subjects with overt renal disease or hypertension, glomerular hyperfiltration was detected in 35% of the type I diabetics, 32% of the type II diabetics without insulin treatment, one subject with chronic pancreatitis, and one type II diabetics with insulin treatment. Glomerular hyperfiltration was associated with high blood glucose in type I, insulin-dependent diabetics, and with a high apolipoprotein B/A1 ratio in type II, non-insulin-dependent diabetics without insulin treatment. In all subjects with glomerular hyperfiltration, GFR values and urinary albumin excretion were positively related (r = 0.33; n = 34; p = 0.05). Glomerular hyperfiltration is detectable among all types of diabetics.

Urinary zinc and its relationships with microalbuminuria in type I diabetics

We investigated whether zincuria is associated with microalbuminuria in type I (insulin-dependent) diabetics (IDDM). In 169 IDDM, 215 overnight urine samples were collected for simultaneous assay of zinc and albumin. In 76 samples with excessive microalbuminuria (greater than 15 mg/L), zincuria was higher than in the 139 other samples (0.83 +/- 0.06 vs 0.58 +/- 0.03 mg/L p less than 0.001), though zincuria and microalbuminuria were not significantly correlated. An exercise provocation test was performed in 78 IDDM. Although microalbuminuria increased, zincuria did not change during the test. Another group of 83 IDDM underwent urinary zinc determination over a period of 1 h of recumbency. The 48 patients who had a zincuria higher than the mean + 2 SD of control values had higher microalbuminuria at rest (48 +/- 16 micrograms/min vs 12 +/- 2 p less than 0.01) and after exercise (111 +/- 33 vs 42 +/- 14 p less than 0.02) than the remaining 35 subjects. Both subgroups did not differ for zinc intake and zincemia. Thus, incipient nephropathy as detected by the measurement of microalbuminuria is associated with a highly significant increase in zinc excretion, which is not proportional to albumin leakage, nor is it amplified during exercise. Hyperzincuria is not explained by an increase in zinc intake and does not result in hypozincemia.

Factors associated with diabetic microangiopathy: a study of 157 type I (insulin-dependent) diabetic patients

The relation between poor glycemic control and the development of diabetic microangiopathy has long been recognized. However hyperglycemia alone cannot account for the striking heterogeneity of diabetic patients regarding the presence or absence of microangiopathic lesions. This study was therefore designed to determine the prevalence of retinopathy, nephropathy, and neuropathy, and to identify the factors respectively associated with these lesions. In 157 patients with type I (insulin-dependent) diabetes, the following parameters were recorded: sex, age, duration of diabetes, body mass index, fasting plasma glucose, HbA1c, blood pressure, antihypertensive treatment, tobacco consumption, urinary albumin excretion, plasma creatinine, and presence of retinopathy and neuropathy. One-half of these patients had retinopathy, 32% neuropathy, and 29% nephropathy. Patients with nephropathy exhibited concomitantly high prevalences of retinopathy (69%) and neuropathy (49%). Among patients with retinopathy, 39% had nephropathy; 79% of those with neuropathy had concomitant retinopathy. For each microangiopathic localization, patients with the disease had significantly higher values (p less than 0.05) than those without for duration of diabetes, prevalence of hypertension, and systolic blood pressure. Stepwise logistic regression analysis showed that the following were independent predictive factors of each localization: for nephropathy, systolic blood pressure; for retinopathy, duration of diabetes; and for neuropathy, duration of diabetes, age, and HbA1c.