Early glomerulopathy is present in young, type 1 (insulin-dependent) diabetic patients with microalbuminuria

A candidate panel of eight urinary proteins shows potential of early diagnosis and risk assessment for diabetic kidney disease in type 1 diabetes

Diabetic kidney disease (DKD) poses a significant health challenge for individuals with diabetes. At its initial stages, DKD often presents asymptomatically, and the standard for non-invasive diagnosis, the albumin-creatinine ratio (ACR), employs discrete categorizations (normal, microalbuminuria, macroalbuminuria) with limitations in sensitivity and specificity across diverse population cohorts. Single biomarker reliance further restricts the predictive value in clinical settings. Given the escalating prevalence of diabetes, our study uses proteomic technologies to identify novel urinary proteins as supplementary DKD biomarkers. A total of 158 T1D subjects provided urine samples, with 28 (15 DKD; 13 non-DKD) used in the discovery stage and 131 (45 DKD; 40 pDKD; 46 non-DKD) used in the confirmation. We identified eight proteins (A1BG, AMBP, AZGP1, BTD, RBP4, ORM2, GM2A, and PGCP), all of which demonstrated excellent area-under-the-curve (AUC) values (0.959 to 0.995) in distinguishing DKD from non-DKD. Furthermore, this multi-marker panel successfully segregated the most ambiguous group (microalbuminuria) into three distinct clusters, with 80% of subjects aligning either as DKD or non-DKD. The remaining 20% exhibited continued uncertainty. Overall, the use of these candidate urinary proteins allowed for the better classification of DKD and offered potential for significant improvements in the early identification of DKD in T1D populations.

Pros and cons of live kidney donation in prediabetics: A critical review and way forward

There is shortage of organs, including kidneys, worldwide. Along with deceased kidney transplantation, there is a significant rise in live kidney donation. The prevalence of prediabetes (PD), including impaired fasting glucose and impaired glucose tolerance, is on the rise across the globe. Transplant teams frequently come across prediabetic kidney donors for evaluation. Prediabetics are at risk of diabetes, chronic kidney disease, cardiovascular events, stroke, neuropathy, retinopathy, dementia, depression and nonalcoholic liver disease along with increased risk of all-cause mortality. Unfortunately, most of the studies done in prediabetic kidney donors are retrospective in nature and have a short follow up period. There is lack of prospective long-term studies to know about the real risk of complications after donation. Furthermore, there are variations in recommendations from various guidelines across the globe for donations in prediabetics, leading to more confusion among clinicians. This increases the responsibility of transplant teams to take appropriate decisions in the best interest of both donors and recipients. This review focuses on pathophysiological changes of PD in kidneys, potential complications of PD, other risk factors for development of type 2 diabetes, a review of guidelines for kidney donation, the potential role of diabetes risk score and calculator in kidney donors and the way forward for the evaluation and selection of prediabetic kidney donors.

U-shaped relationship between fasting blood glucose and urinary albumin-to-creatinine ratio in the general United States population

Objective

The current controversy surrounding the association between fasting blood glucose (FBG) and albuminuria necessitates further investigation. Hence, the primary objective of this study was to examine the relationship between FBG and urinary albumin-to-creatinine ratio (UACR).

Methods

A cohort of complete data from National Health and Nutrition Examination Survey (NHANES) participants (1999-2020) was analyzed. Linear regression analyses and a generalized additive model explored the association between FBG and UACR. Furthermore, the stability of this relationship across different populations was assessed.

Results

The study involved a total of 20,264 participants who were identified as U.S. citizens. By employing linear regression analysis, a statistically significant relationship was observed between elevated FBG levels and an increase in UACR (P<0.0001). Additionally, using a generalized additive model analysis, a U-shaped correlation between FBG and UACR was identified. Further examination using threshold effect analysis indicated a turning point for FBG at 5.44 mmol/L. A noteworthy finding in multiple populations is the consistent U-shaped association between FBG and UACR, except for individuals with serum uric acid levels ≥420 μmol/L and those who refrain from alcohol consumption.

Conclusion

The general U.S. population has a U-shaped nonlinear relationship between FBG and UACR.

Insulin and glucose-lowering agents for treating people with diabetes and chronic kidney disease

BACKGROUND

Diabetes is the commonest cause of chronic kidney disease (CKD). Both conditions commonly co-exist. Glucometabolic changes and concurrent dialysis in diabetes and CKD make glucose-lowering challenging, increasing the risk of hypoglycaemia. Glucose-lowering agents have been mainly studied in people with near-normal kidney function. It is important to characterise existing knowledge of glucose-lowering agents in CKD to guide treatment.

OBJECTIVES

To examine the efficacy and safety of insulin and other pharmacological interventions for lowering glucose levels in people with diabetes and CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 February 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs looking at head-to-head comparisons of active regimens of glucose-lowering therapy or active regimen compared with placebo/standard care in people with diabetes and CKD (estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2) were eligible.

DATA COLLECTION AND ANALYSIS

Four authors independently assessed study eligibility, risk of bias, and quality of data and performed data extraction. Continuous outcomes were expressed as post-treatment mean differences (MD). Adverse events were expressed as post-treatment absolute risk differences (RD). Dichotomous clinical outcomes were presented as risk ratios (RR) with 95% confidence intervals (CI).

MAIN RESULTS

Forty-four studies (128 records, 13,036 participants) were included. Nine studies compared sodium glucose co-transporter-2 (SGLT2) inhibitors to placebo; 13 studies compared dipeptidyl peptidase-4 (DPP-4) inhibitors to placebo; 2 studies compared glucagon-like peptide-1 (GLP-1) agonists to placebo; 8 studies compared glitazones to no glitazone treatment; 1 study compared glinide to no glinide treatment; and 4 studies compared different types, doses or modes of administration of insulin. In addition, 2 studies compared sitagliptin to glipizide; and 1 study compared each of sitagliptin to insulin, glitazars to pioglitazone, vildagliptin to sitagliptin, linagliptin to voglibose, and albiglutide to sitagliptin. Most studies had a high risk of bias due to funding and attrition bias, and an unclear risk of detection bias.Compared to placebo, SGLT2 inhibitors probably reduce HbA1c (7 studies, 1092 participants: MD -0.29%, -0.38 to -0.19 (-3.2 mmol/mol, -4.2 to -2.2); I2 = 0%), fasting blood glucose (FBG) (5 studies, 855 participants: MD -0.48 mmol/L, -0.78 to -0.19; I2 = 0%), systolic blood pressure (BP) (7 studies, 1198 participants: MD -4.68 mmHg, -6.69 to -2.68; I2 = 40%), diastolic BP (6 studies, 1142 participants: MD -1.72 mmHg, -2.77 to -0.66; I2 = 0%), heart failure (3 studies, 2519 participants: RR 0.59, 0.41 to 0.87; I2 = 0%), and hyperkalaemia (4 studies, 2788 participants: RR 0.58, 0.42 to 0.81; I2 = 0%); but probably increase genital infections (7 studies, 3086 participants: RR 2.50, 1.52 to 4.11; I2 = 0%), and creatinine (4 studies, 848 participants: MD 3.82 μmol/L, 1.45 to 6.19; I2 = 16%) (all effects of moderate certainty evidence). SGLT2 inhibitors may reduce weight (5 studies, 1029 participants: MD -1.41 kg, -1.8 to -1.02; I2 = 28%) and albuminuria (MD -8.14 mg/mmol creatinine, -14.51 to -1.77; I2 = 11%; low certainty evidence). SGLT2 inhibitors may have little or no effect on the risk of cardiovascular death, hypoglycaemia, acute kidney injury (AKI), and urinary tract infection (low certainty evidence). It is uncertain whether SGLT2 inhibitors have any effect on death, end-stage kidney disease (ESKD), hypovolaemia, fractures, diabetic ketoacidosis, or discontinuation due to adverse effects (very low certainty evidence).Compared to placebo, DPP-4 inhibitors may reduce HbA1c (7 studies, 867 participants: MD -0.62%, -0.85 to -0.39 (-6.8 mmol/mol, -9.3 to -4.3); I2 = 59%) but may have little or no effect on FBG (low certainty evidence). DPP-4 inhibitors probably have little or no effect on cardiovascular death (2 studies, 5897 participants: RR 0.93, 0.77 to 1.11; I2 = 0%) and weight (2 studies, 210 participants: MD 0.16 kg, -0.58 to 0.90; I2 = 29%; moderate certainty evidence). Compared to placebo, DPP-4 inhibitors may have little or no effect on heart failure, upper respiratory tract infections, and liver impairment (low certainty evidence). Compared to placebo, it is uncertain whether DPP-4 inhibitors have any effect on eGFR, hypoglycaemia, pancreatitis, pancreatic cancer, or discontinuation due to adverse effects (very low certainty evidence).Compared to placebo, GLP-1 agonists probably reduce HbA1c (7 studies, 867 participants: MD -0.53%, -1.01 to -0.06 (-5.8 mmol/mol, -11.0 to -0.7); I2 = 41%; moderate certainty evidence) and may reduce weight (low certainty evidence). GLP-1 agonists may have little or no effect on eGFR, hypoglycaemia, or discontinuation due to adverse effects (low certainty evidence). It is uncertain whether GLP-1 agonists reduce FBG, increase gastrointestinal symptoms, or affect the risk of pancreatitis (very low certainty evidence).Compared to placebo, it is uncertain whether glitazones have any effect on HbA1c, FBG, death, weight, and risk of hypoglycaemia (very low certainty evidence).Compared to glipizide, sitagliptin probably reduces hypoglycaemia (2 studies, 551 participants: RR 0.40, 0.23 to 0.69; I2 = 0%; moderate certainty evidence). Compared to glipizide, sitagliptin may have had little or no effect on HbA1c, FBG, weight, and eGFR (low certainty evidence). Compared to glipizide, it is uncertain if sitagliptin has any effect on death or discontinuation due to adverse effects (very low certainty).For types, dosages or modes of administration of insulin and other head-to-head comparisons only individual studies were available so no conclusions could be made.

AUTHORS' CONCLUSIONS

Evidence concerning the efficacy and safety of glucose-lowering agents in diabetes and CKD is limited. SGLT2 inhibitors and GLP-1 agonists are probably efficacious for glucose-lowering and DPP-4 inhibitors may be efficacious for glucose-lowering. Additionally, SGLT2 inhibitors probably reduce BP, heart failure, and hyperkalaemia but increase genital infections, and slightly increase creatinine. The safety profile for GLP-1 agonists is uncertain. No further conclusions could be made for the other classes of glucose-lowering agents including insulin. More high quality studies are required to help guide therapeutic choice for glucose-lowering in diabetes and CKD.

Previous Exercise Training Reduces Markers of Renal Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Female Rats

The aim of this study is to evaluate the effects of regular moderate exercise training initiated previously or after induction of diabetes mellitus on renal oxidative stress and inflammation in STZ-induced diabetic female rats. For this purpose, Wistar rats were divided into five groups: sedentary control (SC), trained control (TC), sedentary diabetic (SD), trained diabetic (TD), and previously trained diabetic (PTD). Only the PTD group was submitted to treadmill running for 4 weeks previously to DM induction with streptozotocin (40 mg/kg, i.v). After confirming diabetes, the PTD, TD, and TC groups were submitted to eight weeks of exercise training. At the end of the training protocol, we evaluated the following: glycosuria, body weight gain, plasma, renal and urinary levels of nitric oxide and thiobarbituric acid reactive substances, renal glutathione, and immunolocalization of lymphocytes, macrophages, and nuclear factor-kappa B (NF-κB/p65) in the renal cortex. The results showed that exercise training reduced glycosuria, renal TBARS levels, and the number of immune cells in the renal tissue of the TD and PTD groups. Of note, only previous exercise increased weight gain and urinary/renal NO levels and reduced NF-κB (p65) immunostaining in the renal cortex of the PTD group. In conclusion, our study shows that exercise training, especially when initiated previously to diabetes induction, promotes protective effects in diabetic kidney by reduction of renal oxidative stress and inflammation markers in female Wistar rats.

Nodular glomerulosclerosis and renin angiotensin system in Chinese patients with type 2 diabetes

BACKGROUND

Diabetic nephropathy (DN) is a multifactorial and polygenic disease with nodular glomerulosclerosis (NGS) pathognomonic for diabetes and hypertension. Patients with type 2 diabetes and hypertension have characteristic renin-angiotensin system (RAS) gene polymorphisms.

METHODS AND RESULTS

In this retrospective cohort study, we correlated the presence of NGS with renal function, angiotensin-converting enzyme (ACE) genotypes (DD, DI, and II), angiotensinogen (AGT) genotypes (MM, MT, and TT) and immunohistochemical staining characteristics of RAS components in 847 patients and 172 consecutive autopsy cases with type 2 diabetes. T allele of AGT was associated with macroalbuminuria (P = 0.040). Multitude regression analysis revealed ACE insertion (I)/deletion (D) polymorphism as an independent determinant for estimated glomerular filtration rate (eGFR) less than 60 mL min(-1)·1.73 m(-2) (DD carriers: odds ratio [OR] = 3.46, 95% confidence interval [CI] = 1.08-11.07; DI carriers: OR = 3.51, 95% CI = 1.63-7.56). A significant association between NGS and eGFR less than 60 mL min(-1)·1.73 m(-2) also persisted after adjusting for nonlinear relationship (P < 0.001). In NGS patients, immunoreactivity of angiotensin I converting enzyme 2 (ACE2) significantly decreased in glomeruli with mesangial nodules compared with glomeruli without the mesangial nodules.

CONCLUSIONS

These data suggest associations of ACE D allele with glomerular filtration impairment, and NGS with glomerular ACE2 down-regulation and reduced glomerular filtration in Chinese patients with type 2 diabetes.

Kidney tissue proteomics reveals regucalcin downregulation in response to diabetic nephropathy with reflection in urinary exosomes

Diabetic nephropathy (DN) is a major complication of diabetes mellitus and the most frequent cause of end-stage renal disease. DN progresses silently and without clinical symptoms at early stages. Current noninvasive available markers as albuminuria account with severe limitations (late response, unpredictable prognosis, and limited sensitivity). Thus, it urges the discovery of novel markers to help in diagnosis and outcome prediction. Tissue proteomics allows zooming-in where pathophysiological changes are taking place. We performed a differential analysis of renal tissue proteome in a rat model of early DN by 2-dimensional differential gel electrophoresis and mass spectrometry. Confirmation was performed by Western blot, immunohistochemistry (IHC), and selected reaction monitoring (SRM). Rat urine samples were collected and exosomes were isolated from urine to evaluate if these microvesicles reflect changes directly occurring at tissue level. The protein showing maximum altered expression in rat tissue in response to DN was further analyzed in human kidney tissue and urinary exosomes. Regucalcin protein or senescence marker protein-30 (SMP30) (Swiss-Prot Q03336) was found to be strongly downregulated in DN kidney tissue compared with healthy controls. The same trend was observed in exosomes isolated from urine of control and DN rats. These data were further confirmed in a pilot study with human samples. IHC revealed a significant decrease of regucalcin in human kidney disease tissue vs control kidney tissue, and regucalcin was detected in exosomes isolated from healthy donors' urine but not from kidney disease patients. In conclusion, regucalcin protein expression is reduced in DN kidney tissue and this significant change is reflected in exosomes isolated from urine. Urinary exosomal regucalcin represents a novel tool, which should be explored for early diagnosis and progression monitoring of diabetic kidney disease.

Beneficial effects of previous exercise training on renal changes in streptozotocin-induced diabetic female rats

This study evaluated the effects of aerobic exercise performed both previously and after the induction of diabetes mellitus on changes of renal function and structure in streptozotocin-induced diabetic rats. Female wistar rats were divided into five groups: sedentary control (C + Se); trained control (C + Ex); sedentary diabetic (D + Se); trained diabetic (D + Ex) and previously trained diabetic (D + PEx). The previous exercise consisted of treadmill running for four weeks before the induction of diabetes mellitus. After induction of diabetes mellitus with streptozotocin, the D + PEx, D + Ex and C + Ex groups were submitted to eight weeks of aerobic exercise. At the end of the training protocol, we evaluate the serum glucose, insulin and 17β-estradiol levels, renal function and structure, proteinuria, and fibronectin, collagen IV and transforming growth factor beta 1 (TGF-β1) renal expressions. Induction of diabetes mellitus reduced the insulin and did not alter 17β-estradiol levels, and exercise did not affect any of these parameters. Previous exercise training attenuated the loss of body weight, the blood glucose, the increase of glomerular filtration rate and prevented the proteinuria in the D + PEx group compared to D + Se group. Previous exercise also reduced glomerular hypertrophy, tubular and glomerular injury, as well as the expressions of fibronectin and collagen IV. These expressions were associated with reduced expression of TGF-β1. In conclusion, our study shows that regular aerobic exercise especially performed previously to induction of diabetes mellitus improved metabolic control and has renoprotective action on the diabetic kidney.

Diabetic Kidney Disease: A Syndrome Rather Than a Single Disease

The term "diabetic kidney" has recently been proposed to encompass the various lesions, involving all kidney structures that characterize protean kidney damage in patients with diabetes. While glomerular diseases may follow the stepwise progression that was described several decades ago, the tenet that proteinuria identifies diabetic nephropathy is disputed today and should be limited to glomerular lesions. Improvements in glycemic control may have contributed to a decrease in the prevalence of glomerular lesions, initially described as hallmarks of diabetic nephropathy, and revealed other types of renal damage, mainly related to vasculature and interstitium, and these types usually present with little or no proteinuria. Whilst glomerular damage is the hallmark of microvascular lesions, ischemic nephropathies, renal infarction, and cholesterol emboli syndrome are the result of macrovascular involvement, and the presence of underlying renal damage sets the stage for acute infections and drug-induced kidney injuries. Impairment of the phagocytic response can cause severe and unusual forms of acute and chronic pyelonephritis. It is thus concluded that screening for albuminuria, which is useful for detecting "glomerular diabetic nephropathy", does not identify all potential nephropathies in diabetes patients. As diabetes is a risk factor for all forms of kidney disease, diagnosis in diabetic patients should include the same combination of biochemical, clinical, and imaging tests as employed in non-diabetic subjects, but with the specific consideration that chronic kidney disease (CKD) may develop more rapidly and severely in diabetic patients.

Regression and progression of microalbuminuria in adolescents with childhood onset diabetes mellitus

PURPOSE

Although microalbuminuria is considered as an early marker of nephropathy in diabetic adults, available information in diabetic adolescents is limited. The aim of this study was to investigate prevalence and frequency of regression of microalbuminuria in type 1 (T1DM) and type 2 diabetes mellitus (T2DM) patients with childhood onset.

METHODS

One hundred and nine adolescents (median, 18.9 years; interquartile range (IQR), 16.5-21.0 years) with T1DM and 18 T2DM adolescents (median, 17.9 years; IQR, 16.8-18.4 years) with repeated measurements of microalbuminuria (first morning urine microalbumin/creatinine ratios) were included. The median duration of diabetes was 10.1 (7.8-14.0) years and 5.0 (3.5-5.6) years, respectively, and follow-up period ranged 0.5-7.0 years. Growth parameters, estimated glomerular filtration rate, glycosylated hemoglobin (HbA1c) and lipid profiles were obtained after reviewing medical record in each subject.

RESULTS

The prevalence of microalbuminuria at baseline and evaluation were 21.1% and 17.4% in T1DM, and 44.4% and 38.9% in T2DM. Regression of microalbuminuria was observed in 13 T1DM patients (56.5%) and 3 T2DM patients (37.5%), and progression rate was 10.5% and 20% in T1DM and T2DM respectively. In regression T1DM group, HbA1c at baseline and follow-up was lower, and C-peptide at baseline was higher compared to persistent or progression groups. In T2DM, higher triglyceride was observed in persistent group.

CONCLUSION

Considerable regression of microalbuminuria more than progression in diabetes adolescents indicates elevated urinary microalbumin excretion in a single test does not imply irreversible diabetic nephropathy. Careful monitoring and adequate intervention should be emphasized in adolescents with microalbuminuria to prevent rapid progression toward diabetic nephropathy.

SNP in the genome-wide association study hotspot on chromosome 9p21 confers susceptibility to diabetic nephropathy in type 1 diabetes

AIMS/HYPOTHESIS

Parental type 2 diabetes mellitus increases the risk of diabetic nephropathy in offspring with type 1 diabetes mellitus. Several single nucleotide polymorphisms (SNPs) that predispose to type 2 diabetes mellitus have recently been identified. It is, however, not known whether such SNPs also confer susceptibility to diabetic nephropathy in patients with type 1 diabetes mellitus.

METHODS

We genotyped nine SNPs associated with type 2 diabetes mellitus in genome-wide association studies in the Finnish population, and tested for their association with diabetic nephropathy as well as with severe retinopathy and cardiovascular disease in 2,963 patients with type 1 diabetes mellitus. Replication of significant SNPs was sought in 2,980 patients from three other cohorts.

RESULTS

In the discovery cohort, rs10811661 near gene CDKN2A/B was associated with diabetic nephropathy. The association remained after robust Bonferroni correction for the total number of tests performed in this study (OR 1.33 [95% CI 1.14, 1.56], p = 0.00045, p (36tests) = 0.016). In the meta-analysis, the combined result for diabetic nephropathy was significant, with a fixed effects p value of 0.011 (OR 1.15 [95% CI 1.02, 1.29]). The association was particularly strong when patients with end-stage renal disease were compared with controls (OR 1.35 [95% CI 1.13, 1.60], p = 0.00038). The same SNP was also associated with severe retinopathy (OR 1.37 [95% CI 1.10, 1.69] p = 0.0040), but the association did not remain after Bonferroni correction (p (36tests) = 0.14). None of the other selected SNPs was associated with nephropathy, severe retinopathy or cardiovascular disease.

CONCLUSIONS/INTERPRETATION

A SNP predisposing to type 2 diabetes mellitus, rs10811661 near CDKN2A/B, is associated with diabetic nephropathy in patients with type 1 diabetes mellitus.

Spot urine albumin to creatinine ratio and serum cystatin C are effective for detection of diabetic nephropathy in childhood diabetic patients

Spot urinary albumin to creatinine ratio (ACR) measurement has been suggested as a surrogate to 24-hr urine collection for the assessment of microalbuminuria, and cystatin C (cysC) is known as an advantageous marker for renal function. The aim of this study was to evaluate the clinical values of spot urinary ACR and serum cysC for the assessment of diabetic nephropathy instead of 24-hr urine microalbumin in children and adolescents with diabetes. A total of 113 children and adolescents (age 12-19 yr, M:F = 47:66) with type 1 or 2 diabetes were enrolled. We evaluated the validity of spot urine ACR and serum cysC, and then compared them to 24-hr urine microalbumin and creatinine clearance. Spot urine ACR was correlated with 24-hr urine albumin excretion (R(2) = 0.828, P = 0.001) and creatinine clearance (R(2) = 0.249, P = 0.017). The ROC curve analysis of serum cysC demonstrated higher diagnostic accuracy than that of serum creatinine (AUC 0.732 vs 0.615). Both the measurements of spot urine ACR and serum cysC might better predict the presence of diabetic nephropathy than 24-hr urine microalbumin in childhood diabetic patients.

Research into the structure of the kidney glomerulus--making it count

The renal glomerulus and its components have been intensively studied using microscopy - both light and electron - for decades and much has been learnt about their role in the pathogenesis of chronic kidney diseases such as diabetic nephropathy. In order to get more than purely qualitative information from the images, stereological tools have been applied to obtain unbiased quantitative data and thus allow structural-functional relationships to be explored. These techniques are likely to continue to be used in the coming decades in order to provide vital information about the disease process, complementing knowledge obtained from molecular techniques.

Risk markers of future microalbuminuria and hypertension based on clinical and morphological parameters in young type 1 diabetes patients

BACKGROUND

Nephropathy is a severe complication of type 1 diabetes and develops in 30% of patients. Currently, it is not possible to identify young patients at risk prior to the development of microalbuminuria (MA) and/or hypertension (HT).

OBJECTIVE

To study predictors of MA and/or HT in young normoalbuminuric (NA) patients with type 1 diabetes.

SUBJECTS AND METHODS

Forty-six NA and normotensive (NT) type 1 diabetes patients, regularly followed since onset with checks on metabolic control, kidney function, and MA, were investigated with kidney biopsies and 24-h ambulatory blood pressure measurements (ABPMs) after 10.6 yr of diabetes. The patients were followed another six and a half years with regard to the development of MA and HT.

RESULTS

Fifteen patients developed MA and/or HT during follow-up. The strongest risk markers were poor metabolic control after puberty, high day-time systolic blood pressure (BP), and increased BMT at 10 yr, which explained 62% of the outcome for MA and/or HT at 17 yr duration with 77% sensitivity and 65% specificity. The threshold values were long-term postpubertal HbA(1c) > 8.2%, day-time systolic BP > 130 mmHg, and BMT > 490 nm/1.73 m(2).

CONCLUSIONS

Normoalbuminuric and NT patients at risk of developing MA and HT could be identified and might benefit from an early start of antihypertensive therapy and improvement of metabolic control.

Ultrastructural changes in the glomerular filtration barrier and occurrence of proteinuria in Chinese patients with type 2 diabetic nephropathy

AIM

Diabetic nephropathy (DN) is one of the most important causes of end stage renal disease in the world. Its hallmark is proteinuria. Therefore, we set out to clarify the structural changes that occur in the glomerular filtration barrier in Chinese patients with true type 2 diabetic nephropathy, and to examine the relationship between these structural changes and proteinuria.

METHODS

42 Chinese patients with true T2DN were divided into three groups according to urinary protein excretion. Glomerular volume, endothelial cell density, endothelial cell number, glomerular basement membrane (GBM) width, podocyte density, podocyte number and foot process width were evaluated using light and electron microscopic morphometry.

RESULT

Glomerular volume and endothelial cell number were increased in diabetic patients, but there was no difference between patients with respect to the degree of proteinuria. As proteinuria progressed, endothelial cell density remained unchanged, while the glomerular basement membrane (GBM) and podocyte foot process width increased, podocyte density and number decreased.

CONCLUSIONS

Podocyte and GBM change more obviously during the development of proteinuria. Besides, proteinuria was inversely related to podocyte density, and directly related to GBM and glomerular volume.

Renal tubulointerstitial expansion is associated with endothelial dysfunction and inflammation in type 1 diabetes

OBJECTIVE

Diabetic nephropathy has been considered to be primarily of glomerular origin, but there is now compelling evidence that disruption of the tubulointerstitial architecture determines the outcome of diabetic nephropathy in interplay with the glomerular damage. We investigated whether reactive oxidative species, pro-inflammatory cytokines and endothelial dysfunction were implicated in the progression of tubulointerstitial damage in young subjects with type 1 diabetes.

MATERIAL AND METHODS

In a prospective study, we investigated 18 young subjects (mean age 21 years) with type 1 diabetes and microalbuminuria. Quantitative morphometry concerning glomerular and tubulointerstitial changes was performed at baseline (i.e. mean duration of diabetes 10 years) and 2.5 and 8 years later. Markers of endothelial activation and inflammation, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, tumour necrosis factor-alpha, interleukin-6, interleukin-8 and highly sensitive C-reactive protein were measured at baseline and after 8 years. Tissue plasminogen activator antigen and plasminogen activator inhibitor (PAI-1 activity) and asymmetric dimethylargine (ADMA) were measured at baseline and after 2.5 years.

RESULTS

PAI-1 activity at baseline was a significant independent variable of the 8-year increment in interstitial volume fraction (Vv(Int/cortex)). ADMA/L-arginine ratio at baseline was associated with the increment in Vv(Int/cortex) during 2.5 years (p<0.01), still significant after adjustment for covariates (p = 0.02). No associations between Vv(Int/cortex) and glomerular parameters, HaemoglobinA1c and urinary albumin excretion were observed.

CONCLUSIONS

Biomarkers involved in interstitial volume expansion seem to be different from those of mesangial expansion in early diabetic nephropathy. PAI-1 activity may have a predictive role in the development of the tubulointerstitial expansion.

The effects of candesartan on diabetes glomerulopathy: a double-blind, placebo-controlled trial

Our objective was to study the effects of candesartan on diabetic glomerulopathy in young normoalbuminuric and normotensive patients with type 1 diabetes in a double-blind, placebo-controlled trial. In 13 patients aged 24 years at baseline, we evaluated blood pressure, kidney biopsies and kidney function tests at baseline and after 5 years of treatment. Kidney biopsies were examined with light and electron microscopy, glomerular filtration rate and effective renal plasma flow determined with inulin and para-aminohippuric acid clearances. Two patients in the placebo group needed antihypertensive treatment because they developed microalbuminuria and/or hypertension, but no patient in the candesartan group did. A significant reduction in mesangial matrix volume and mesangial volume occurred in the candesartan group, although changes in morphological parameters were similar between groups. Office blood pressure was significantly lower in the candesartan group at follow-up than in the placebo group. Deterioration in morphological parameters observed in earlier studies of our patients did not become worse during treatment with candesartan or placebo. The effects of candesartan, with reduction in morphological parameters and lowering of blood pressure, might influence future treatment of glomerulopathy in type 1 diabetes patients.

Risk of microalbuminuria and progression to macroalbuminuria in a cohort with childhood onset type 1 diabetes: prospective observational study

OBJECTIVES

To describe independent predictors for the development of microalbuminuria and progression to macroalbuminuria in those with childhood onset type 1 diabetes.

DESIGN

Prospective observational study with follow-up for 9.8 (SD 3.8) years.

SETTING

Oxford regional prospective study.

PARTICIPANTS

527 participants with a diagnosis of type 1 diabetes at mean age 8.8 (SD 4.0) years.

MAIN OUTCOME MEASURES

Annual measurement of glycated haemoglobin (HbA1c) and assessment of urinary albumin:creatinine ratio.

RESULTS

Cumulative prevalence of microalbuminuria was 25.7% (95% confidence interval 21.3% to 30.1%) after 10 years of diabetes and 50.7% (40.5% to 60.9%) after 19 years of diabetes and 5182 patient years of follow-up. The only modifiable adjusted predictor for microalbuminuria was high HbA1c concentrations (hazard ratio per 1% rise in HbA1c 1.39, 1.27 to 1.52). Blood pressure and history of smoking were not predictors. Microalbuminuria was persistent in 48% of patients. Cumulative prevalence of progression from microalbuminuria to macroalbuminuria was 13.9% (12.9% to 14.9%); progression occurred at a mean age of 18.5 (5.8) years. Although the sample size was small, modifiable predictors of macroalbuminuria were higher HbA(1c) levels and both persistent and intermittent microalbuminuria (hazard ratios 1.42 (1.22 to 1.78), 27.72 (7.99 to 96.12), and 8.76 (2.44 to 31.44), respectively).

CONCLUSION

In childhood onset type 1 diabetes, the only modifiable predictors were poor glycaemic control for the development of microalbuminuria and poor control and microalbuminuria (both persistent and intermittent) for progression to macroalbuminuria. Risk for macroalbuminuria is similar to that observed in cohorts with adult onset disease but as it occurs in young adult life early intervention in normotensive adolescents might be needed to improve prognosis.

Amelioration of established diabetic nephropathy by combined treatment with SMP-534 (antifibrotic agent) and losartan in db/db mice

BACKGROUND/AIMS

Diabetic nephropathy is the main cause of end-stage renal disease. Previously we have demonstrated that SMP-534 (an antifibrotic agent) prevents the development of diabetic nephropathy in db/db mouse and that combined treatment with SMP-534 and losartan (antihypertensive agents) markedly prevents the development of diabetic nephropathy compared with single treatment. SMP-534 or losartan was prophylactically administered to db/db mice before the onset of diabetic nephropathy. In the present study, we evaluated the efficacy of combined treatment when administration was started after the onset of diabetic nephropathy.

METHODS

db/db mice were raised untreated until 17 weeks of age, by which time increase of urinary albumin was noted, and then treated with SMP-534 and/or losartan for another 8 weeks. Biochemical and histological analyses were performed at 25 weeks of age.

RESULTS

Combined treatment with SMP-534 and losartan markedly prevented the increase of urinary albumin and ameliorated the progression of mesangial matrix expansion, even when administration was started long after the increase of urinary albumin.

CONCLUSION

The study results indicate that a combination of SMP-534 and losartan might be a valuable therapeutic approach for the treatment of diabetic nephropathy even when administration is started after the onset of diabetic nephropathy.

Aberrant heparan sulfate profile in the human diabetic kidney offers new clues for therapeutic glycomimetics

BACKGROUND

Diabetic nephropathy poses an increasing health problem in the Western world, and research to new leads for diagnosis and therapy therefore is warranted. In this respect, heparan sulfates (HSs) offer new possibilities because crude mixtures of these polysaccharides are capable of ameliorating proteinuria. The aim of this study is to immuno(histo)chemically profile HSs from microalbuminuric kidneys from patients with type 1 diabetes and identify specific structural HS alterations associated with early diabetic nephropathy.

METHODS

Renal cryosections of control subjects and patients with type 1 diabetes were analyzed immunohistochemically by using a set of 10 unique phage display-derived anti-HS antibodies. HS structures defined by relevant antibodies were characterized chemically by means of enzyme-linked immunosorbent assay and probed for growth factor binding and presence in HS/heparin-containing drugs.

RESULTS

In all patients, HS structure defined by the antibody LKIV69 consistently increased in basement membranes of proximal tubules. This structure contained N- and 2-O-sulfates and was involved in fibroblast growth factor 2 binding. It was present in HS/heparin-containing drugs shown to decrease albuminuria in patients with diabetes. The HS structure defined by the antibody HS4C3 increased in the renal mesangium of some patients, especially those who developed macroalbuminuria within 8 to 10 years. This structure contained N- and 6-O-sulfates. For 8 other antibodies, no major differences were observed.

CONCLUSION

Specific structural alterations in HSs are associated with early diabetic nephropathy and may offer new leads for early diagnosis and the rational design of therapeutic glycomimetics.

The course of diabetic glomerulopathy in patients with type I diabetes: a 6-year follow-up with serial biopsies

Diabetic nephropathy is a severe complication and few studies have described the early morphological changes over time. Two kidney biopsies were performed, within a 6-year interval, in 29 primarily normoalbuminuric patients, aged 24 years at the second biopsy. These were examined with light and electron microscopy. Glomerular filtration rate, and effective renal plasma flow were determined with inulin and para-aminohippurate clearances. Urinary albumin excretion rate and the 24 ambulatory blood pressure were determined. Ten patients had developed microalbuminuria and/or hypertension; of these, six were treated with antihypertensive medication for 2 years or more. Significant increases were found in night time diastolic blood pressure and decreases in systolic and diastolic dipping. The glomerular volume, mesangial volume, mesangial matrix volume fraction and foot process width increased significantly. The group that was treated later for complications had the worst long-term metabolic control, thicker basement membranes and larger mesangial matrix and volume at the first biopsy, than the persistent normoalbuminuric group. During the follow-up, the untreated group with complications and the persistent normoalbuminuric group showed an increase in morphological parameters, whereas no progression occurred in the treated patients who also improved their metabolic control. In conclusion, the morphological parameters deteriorated in the normoalbuminuric patients and in those with complications, but were unchanged in the small antihypertensive-treated group with improved metabolic control.

The relationship between microalbuminuria and glomerular filtration rate in young type 1 diabetic subjects: The Oxford Regional Prospective Study

BACKGROUND

The purpose of this study was to examine the relationship between glomerular filtration rate (GFR) measured at 5 years' diabetes duration and annual urine albumin excretion in a prospective cohort of children with type 1 diabetes (T1DM).

METHODS

Three hundred and eight children were followed from diagnosis of T1DM [aged 9.8 years (range 0.4-15.9) for a median duration of 10.9 years (6.0-17.8) with annual assessments comprising measurement of HbA1(c) and 3 urine samples for albumin:creatinine ratio (ACR). GFR was measured in all children at 5 years' diabetes duration.

RESULTS

Two hundred forty-three (78.8%) subjects were normoalbuminuric (MA-) for the duration of the study. At 5 years: 35 (11.4%) subjects had MA (MA+) and 30 (9.7%) subjects were normoalbuminuric but developed MA during subsequent follow-up annual assessments (future MA+). In the future MA+ group compared to the MA+ and MA- groups; GFR was higher (167 vs. 134 vs. 139 mL/min/1.73 m(2), P < 0.002); the prevalence of hyperfiltration (GFR >125 mL/min/1.73 m(2)) was greater (97 vs. 57 vs. 64%, P= 0.006) and HbA1c levels were higher (11.4 vs. 10.8 vs. 9.7%, P < 0.001). The probability (Cox Model) of having hyperfiltration at 5 years' duration was related to puberty (a 1.7-fold increased risk with puberty onset) and poor glycemic control (a 10% increased risk for a 1% increase in HbA1c). Comparing subjects with and without hyperfiltration, prior to the first GFR measurement no difference in ACR levels existed; however, after this time median ACR levels were significantly greater [1.2 (0.1-86.4) vs. 0.9 (0.1-71.6) mg/mmol, P= 0.003], independent of age and HbA1c levels. The probability of developing MA between 5 and 10 years' duration was associated with poor glycemic control (a 30% increased risk for a 1% increase in HbA1c) and higher GFR at 5 years (22% increased risk for a 10 mL/min/1.73 m(2) rise in GFR).

CONCLUSION

Glomerular hyperfiltration is associated with puberty and increasing ACR levels and is predictive of MA independent of HbA1c. This suggests that factors other than poor glycemic control may be involved in the pathogenesis of early diabetic nephropathy and early intervention with medical therapy to reduce GFR may be beneficial even before onset of MA.

Widening of foot processes in normoalbuminuric adolescents with type 1 diabetes

We compared renal morphology in normoalbuminuric adolescents with type 1 diabetes with age-and sex-matched controls. Renal morphological measurements in 46 unselected adolescents with diabetes for approx. 10 years were compared with those in 20 healthy kidney donors. Renal volume estimated by ultra-sound, renal function determined by clearances of inulin and para-aminohippurate, and long-term mean HbA(1c) were measured in the patient group. Basement membrane thickness (BMT), mesangial matrix and capillary volume fractions per glomerulus [V(V)(matrix/glom), V(V)(cap/glom)] were significantly greater in patients than in controls (505 nm, 10.5%, 46.7% vs. 320 nm, 7.9% and 39.3%). The foot processes were wider in patients than in living donors (414 nm vs. 372 nm). There was no difference in mean kidney volume of patients with diabetes and healthy subjects. Glomerular filtration rate, body weight, and slit pore length density explained 60% of the variance in renal volume. After about 10 years' duration of type 1 diabetes, BMT, V(V)(matrix/glom), V(V)(cap/glom), and foot process width were greater in normoalbuminuric adolescents than in healthy controls. This increase in foot processes of normoalbuminuric patients has not been reported before.

Mannose-binding lectin as a predictor of microalbuminuria in type 1 diabetes: an inception cohort study

Inflammation and complement activation via the mannose-binding lectin (MBL) pathway have been suggested to play a role in the pathogenesis of diabetic microvascular complications. The association between the complement-activating protein MBL and the development of persistent microalbuminuria was evaluated in an inception cohort of 286 newly diagnosed type 1 diabetic patients consecutively admitted to the Steno Diabetes Center between 1 September 1979 and 31 August 1984. Serum MBL was measured with an immunofluorometric assay in 270 of the patients (159 men) after 3 years of diabetes duration. During the median (range) follow-up period of 18.0 (1.0-21.8) years, 75 patients subsequently progressed to persistent micro- or macroalbuminuria (urinary albumin excretion rate >30 mg/24 h). In patients with MBL levels above the median (1,597 microg/l), the cumulative incidence of persistent micro- or macroalbuminuria was 41% (CI 31-50) as compared with 26% (CI 17-34) in patients with MBL levels below the median (log-rank test, P = 0.003). In a Cox proportional hazard model with sex and age as fixed covariates, MBL was independently associated with later development of persistent micro- or macroalbuminuria (hazard ratio 1.21 [CI 1.02-1.42] per 1,000 microg/l increase in MBL; P = 0.03) after adjusting for possible confounders. In our study, high levels of MBL early in the course of type 1 diabetes was significantly associated with later development of persistent micro- or macroalbuminuria, suggesting that complement activation initiated by MBL may be involved in the pathogenesis of diabetic microvascular complications.

Predicting the development of diabetic nephropathy and its progression

Diabetes remains the number one cause of end-stage renal disease worldwide. Only about one third of diabetic patients develop nephropathy, and the risk appears to be, in part, genetically determined. In this article, we review clinical and genetic markers for the development and progression of diabetic nephropathy. Microalbuminuria remains the best available predictor of the subsequent development of nephropathy, even though in recent years it has become clear that less than 50% of individuals with type 1 diabetes progress to overt proteinuria over a period of less than 10 years. It is of great interest for early recognition of risk of nephropathy that small elevations in nighttime blood pressure predict microalbuminuria in type 1 diabetes. Genetic markers for diabetic nephropathy have not been conclusively identified. The occurrence of renal events in diabetic patients, however, appears to be influenced by the angiotensin-converting enzyme (ACE) genotype, with a dominant deleterious effect of the D allele (D/D or I/D) versus I/I genotype. Some patients with the DD genotype also appear less susceptible to the renoprotective effects of conventional doses of ACE inhibitors, suggesting that ACE genotyping might be useful in selecting those patients that could benefit from higher doses of ACE inhibitors and more aggressive treatment to prevent or delay disease progression.

Isolate diffuse thickening of glomerular capillary basement membrane: a renal lesion in prediabetes?

A total of 23 patients with proteinuria and isolated ultrastructural diffuse thickening of the glomerular capillary basement membrane were studied, focusing on the possibility of diabetes mellitus, morphometry of the capillary basement membrane, and the comparison with three other groups of patients. These included 14 patients with minimal change nephropathy (MCN), 45 patients with type II diabetes arbitrarily divided into 11 early and 34 late diabetic patients, defined, respectively, as less than 3 and over 5 years history, and 13 patients biopsied for transient mild proteinuria or hematuria, with no evidence of renal disease on follow-up were used as controls. The level of proteinuria and prevalence of hematuria were similar in patients with isolated thick basement membrane and with diabetes. Diabetic retinopathy was present in 10% of early diabetes, 69% of late diabetes, but not in isolated thick basement membrane. Kimmelstiel-Wilson nodules were seen in late diabetes, and not in other patients. Hyaline arteriosclerosis was more common in late diabetes than in early diabetes or isolated thick basement membrane. The basement membrane thickness was similar between controls (371+/-17 nm) and MCN (345+/-16 nm), between patients with isolated thick basement membrane (482+/-69 nm) and early diabetes (457+/-64 nm), but significantly thicker in isolated thick basement membrane as compared to controls and MCN. In patients with isolated thick basement membrane, the basement membrane thickness was not correlated with age, smoking, body weight, hyaline arteriosclerosis, and hypertension. However, blood tests for diabetes were positive in 20% of patients at biopsy, in 44% at 6 months and 70% at 24 months follow-up, while seven patients showed no evidence of diabetes on follow-up. Patients with proteinuria and isolated thick glomerular basement membrane must be differentiated from MCN for therapeutic implications, and specifically managed for its strong association with prediabetes or early diabetes.

Effect of angiotensin II on glomerular structure in streptozotocin-induced diabetic rats

BACKGROUND/AIMS

The streptozotocin (STZ)-induced diabetic rat is a widely used animal model of human diabetic nephropathy. In this model, diabetic nephropathy progresses without significant elevation in blood pressure. Therefore, studies have examined the effect of hypertension in STZ spontaneously hypertensive rats (SHR). This study investigated angiotensin II (Ang II)-induced hypertension in diabetic nephropathy in the STZ-diabetic rat independent of deleterious genetic effects in SHR.

METHODS

Animals were divided as follows: nondiabetic controls (ND; n = 18); diabetic (STZ: 65 mg/kg; n = 16); Ang II-induced hypertensive ND (Ang II: 120 ng/kg/min; n = 9), and hypertensive diabetic rats (n = 18). Systolic blood pressure was measured by the tail-cuff method prior to STZ injection and then weekly. After 3 months, plasma creatinine, and 24-hour urine albumin and creatinine were measured and kidneys harvested for morphometry.

RESULTS

Ang II infusion increased systolic blood pressure in diabetic and ND rats. When combined with diabetes, Ang II increased albumin excretion rate (14-fold, p < 0.05), plasma creatinine (1.5-fold, p < 0.005) worsened creatinine clearance (37%, p < 0.002) and increased glomerular basement membrane width (1.2-fold, p < 0.0001).

CONCLUSION

Ang II caused moderate hypertension and accelerated diabetic nephropathy and glomerular structural changes. The Ang II-infused STZ-diabetic rat is an excellent model to study the deleterious glomerular effects of hypertension on diabetes independent of genetic traits.

Sex difference and possible relationship to microvascular complications of serum prorenin levels in type 2 diabetic patients, measured by a novel antibody-activating direct enzyme kinetic assay

Prorenin, a precursor of renin, was measured in sera from normal subjects and type 2 diabetic patients, using a newly developed antibody-activating direct enzyme kinetic assay. Levels of prorenin were examined in relationship to diabetic microangiopathies. The levels of antibody-activating direct prorenin (AAD-PR) were approximately 1.5-fold higher than levels of prorenin measured by a conventional enzyme-activating method. AAD-PR levels were significantly higher in males than in females and in diabetic patients than in normal subjects. Moreover, AAD-PR levels were higher in diabetic patients with microalbuminuria and even higher in those with macroalbuminuria. In normoalbuminuric diabetic patients, AAD-PR levels were higher in those with retinopathy. Furthermore, a significant positive correlation was seen between the AAD-PR levels and HbA(lc) in normoalbuminuric diabetic subjects without retinopathy. Thus, the determination of circulating serum prorenin measured as AAD-PR is related to glycemia and in type 2 diabetic patients may be a risk marker of diabetic microangiopathy. More studies are necessary to determine whether AAD-PR may actually predict the development of microangiopathy.

Predictors for the development of microalbuminuria and macroalbuminuria in patients with type 1 diabetes: inception cohort study

OBJECTIVE

To evaluate baseline predictors for the development of persistent microalbuminuria and macroalbuminuria prospectively in patients with type 1 diabetes.

DESIGN

Prospective observational study of an inception cohort.

SETTING

Outpatient diabetic clinic in a tertiary referral centre, Gentofte, Denmark.

PARTICIPANTS

286 patients (216 adults) newly diagnosed with type 1 diabetes consecutively admitted to the clinic between 1 September 1979 and 31 August 1984.

MAIN OUTCOME MEASURES

Persistent microalbuminuria and persistent macroalbuminuria.

RESULTS

During the median follow up of 18.0 years (range 1.0-21.5 years), total of 4706 patient years of follow up, 79 of 277 (29%) patients developed persistent microalbuminuria. 27 of 79 progressed further to persistent macroalbuminuria. The cumulative incidence of persistent microalbuminuria and persistent macroalbuminuria was 33.6% (95% confidence interval 27.2% to 40.0%) and 14.6% (8.9% to 20.3%), respectively. Significant predictors for the development of persistent microalbuminuria were a 10-fold increase in urinary albumin excretion rate (relative risk 3.78, 1.57 to 9.13), being male (2.41, 1.43 to 4.06), a 10 mm Hg increase in mean arterial blood pressure (1.38, 1.20 to 1.57), a 1% increase in haemoglobin A1c (1.18, 1.04 to 1.32), and a 1 cm increase in height (0.96, 0.95 to 0.98). 28 patients with microalbuminuria (35%) regressed to normoalbuminuria either transiently (n = 15) or permanently (n = 13).

CONCLUSIONS

Around one third of patients newly diagnosed with type 1 diabetes develop persistent microalbuminuria within the first 20 years of diabetes. Several potentially modifiable risk factors predict the development of persistent microalbuminaria and persistent macroalbuminuria.

ACE inhibitor intervention in Type 1 diabetes with low grade microalbuminuria

Several clinical trials have consistently shown that antihypertensive treatment, particularly with angiotensin-converting enzyme inhibitors (ACE-I) reduces albuminuria in Type 1 diabetic patients. More recently, data on the beneficial effects of ACE-I on the preservation of glomerular filtration rate and renal ultrastructure have emerged. However, in general, these trials have recruited a wide spectrum of diabetics, including some patients with severe albuminuria. Thus, the question of the ideal stage at which to instigate what is likely to be lifelong therapy in young people still remains unanswered. Exercise is known to significantly increase both blood pressure (BP) and urinary albumin excretion (UAE), both of which are important determinants of progression of nephropathy in diabetes. Thus, it is possible that exercise may have an adverse effect on diabetic renal disease. The effects of ACE-I on exercise-BP and exercise-UAE in microalbuminuric Type 1 diabetic patients has not been examined in long-term placebo-controlled studies. In the second part of this two-part review, we examine the effects of the ACE-I, lisinopril, 20 mg o.d. for two years, in comparison with placebo, on UAE, 24-hour ambulatory BP, exercise-BP, exercise-UAE and renal haemodynamics in 22 patients with Type 1 diabetes and low-grade microalbuminuria. We further discuss the effects of ACE-I on nephropathy and other complications of diabetes.

Reversibility of established diabetic glomerulopathy by anti-TGF-beta antibodies in db/db mice

Treatment with a neutralizing anti-transforming growth factor-beta (TGF-beta) antibody can prevent the development of diabetic nephropathy in the db/db mouse, a model of type 2 diabetes. However, it is unknown whether anti-TGF-beta therapy can reverse the histological lesions of diabetic glomerulopathy once they are established. Diabetic db/db mice and their non-diabetic db/m littermates were allowed to grow until 16 weeks of age, by which time the db/db mice had developed glomerular basement membrane (GBM) thickening and mesangial matrix expansion. The mice were then treated with an irrelevant control IgG or a panselective, neutralizing anti-TGF-beta antibody for eight more weeks. Compared with control db/m mice, the db/db mice treated with IgG had developed increased GBM width (16.64+/-0.80 nm vs. 21.55+/-0.78 nm, P<0.05) and increased mesangial matrix fraction (4.01+/-0.81% of total glomerular area vs. 9.55+/-1.04%, P<0.05). However, the db/db mice treated with anti-TGF-beta antibody showed amelioration of GBM thickening (18.40+/-0.72 nm, P<0.05 vs. db/db-IgG) and mesangial matrix accumulation (6.32+/-1.79%, P<0.05 vs. db/db-IgG). Our results demonstrate that inhibiting renal TGF-beta activity can partially reverse the GBM thickening and mesangial matrix expansion in this mouse model of type 2 diabetes. Anti-TGF-beta regimens would be useful in the treatment of diabetic nephropathy.

Blood pressure and cardiac autonomic function in relation to risk factors and treatment perspectives in Type 1 diabetes

The cumulative incidence of diabetic nephropathy in Type 1 diabetes mellitus is in the order of 25 30%. The recognition that elevated blood pressure (BP) is a major factor in the progression of these patients to end-stage renal failure has led to the widespread use of antihypertensive therapy in order to preserve glomerular filtration rate and ultimately to reduce mortality. The routine measurement of microalbuminuria allows early identification of the subgroup of patients at increased risk of developing clinical nephropathy. Microalbuminuric Type 1 diabetic patients show a number of characteristic pathological abnormalities. In addition to elevated BP and abnormal circadian rhythm, there are also associated abnormalities of vagal function, lipid profile and endothelial function, as well as an increased prevalence of retinopathy. The first section of this two-part review focusses on the early changes associated with renal involvement in Type 1 diabetes. It addresses the associations between urinary albumin excretion, glycaemic control, smoking, BP, circadian BP variation, QT interval abnormalities and autonomic function in three groups of patients; those with normoalbuminuria, those progressing towards microalbuminuria and those with established low-grade microalbuminuria.

The early natural history of nephropathy in type 1 diabetes: I. Study design and baseline characteristics of the study participants

This report describes the design and baseline demographic and clinical data in the study of the early natural history of diabetic nephropathy (DN) in type 1 diabetes carried out by the International Diabetic Nephropathy Study Group. The study enrolled 243 patients ages 10-40 years (16.8 +/- 6.0, mean +/- SD) with type 1 diabetes for 2-20 years (8.0 +/- 4.2) at centers in the United States (Minneapolis), Canada (Montreal), and France (Paris). At baseline, all patients were normotensive, none had reduced glomerular filtration rate (GFR), and all but eight were normoalbuminuric (NA). All patients had baseline renal biopsies. During the study, patients will have multiple measurements of blood pressure (BP), renal function, albumin excretion rate (AER), glycemia, and other variables, with repeat renal biopsies planned at 5 years after baseline. The 31.3% of the approached patients who agreed to participate were similar in age, diabetes duration, HbA(1c), AER, and sex to those refusing participation. Age, diabetes duration, HbA(1c), and AER were similar among the three centers, but systolic BP, GFR, renal plasma flow (RPF), and filtration fraction were lower in the Paris center. The 153 patients with hyperfiltration (GFR >130 ml x min(-1) x 1.73 m(-2)) had greater RPF than those with normal GFR. The eight microalbuminuric patients tended to have longer duration of diabetes but were otherwise similar to the NA patients. The role of these and other variables in determining the development rate of the early lesions of DN over the 5 years between biopsies is the central issue under study.

The early natural history of nephropathy in type 1 diabetes: II. Early renal structural changes in type 1 diabetes

Renal structural abnormalities are known to precede the development of proteinuria, hypertension, and reduced renal function in patients with type 1 diabetes. The determinants of these early structural abnormalities are, however, largely unknown. The International Diabetic Nephropathy Study (IDNS) has recruited 243 children and adults (aged 10-40 years) in Montreal, Minneapolis, and Paris to identify and quantify these determinants. All study subjects were normotensive and had normal-to-high glomerular filtration rates (GFRs) and urinary albumin excretion rates (AERs) <100 microg/min at study entry. Only 8 of 243 had an AER > or =20 microg/min (microalbuminuria). Two renal biopsies are obtained at a 5-year intervals, with baseline and follow-up measures of renal function, blood pressure (BP), HbA(1c), plasma lipids, and AER. Herein, we examine the baseline renal biopsy morphometric findings in these subjects and in 87 kidney donor control subjects and explore the associations between findings and clinical and demographic variables. The principal morphometric abnormalities were increased glomerular basement membrane (GBM) width and fractional volume of mesangium [Vv(Mes/glom)] and mesangial matrix [Vv(MM/glom)]. The frequency of these abnormalities increased with increasing duration of diabetes but was observed as early as 2-8 years after onset. Diastolic BP (DBP), but not HbA(1c), was directly associated with these abnormalities. Elevated GFR was associated with only a small increase in peripheral glomerular capillary basement membrane filtration surface density. Center differences were detected in renal structural, renal functional, and BP parameters, especially between the Paris and North American centers. GBM width, Vv(Mes/glom), and Vv(MM/glom) are significantly increased even within a few years of onset of type 1 diabetes. These changes are detectable in normoalbuminuric patients and are related to duration, BP, and study site. Changes in these and other morphometric measures over 5-year follow-up should help clarify the roles of glycemia and other determinants of the rates of development of diabetic nephropathy lesions, as well as their relationships to early changes in BP, albumin excretion, and renal function.

Risk predictors in patients with diabetic nephropathy

Diabetic nephropathy is currently the most common cause of end-stage renal disease in the Western countries. Only approximately one third of patients with type 1 diabetes develop nephropathy; thus, because it is not feasible to aggressively treat all patients, it becomes very important to find early markers in order to identify patients at high nephropathy risk. To date the best available predictor of overt nephropathy is microalbuminuria. In this article we review the validity of microalbuminuria as a predictor of overt nephropathy and consider other markers of nephropathy risk.

Follow-up study of glomerular dimensions and cortical interstitium in microalbuminuric type 1 diabetic patients with or without antihypertensive treatment

BACKGROUND

A decrease in urinary albumin excretion is regularly seen with antihypertensive treatment in patients with diabetic nephropathy. Our study concerns structural data obtained by light microscopy in baseline and follow-up biopsies in antihypertensive treated patients and in a reference group.

METHODS

Microalbuminuric type 1 diabetic patients with diabetes duration of 6-16 years were studied. Two groups, allocated to treatment with either angiotensin-converting enzyme-inhibitor (group 1, n=6) or beta-blocker (group 2, n=6) after the baseline biopsy, were studied in parallel, whereas the reference group (group 3, n=9), without antihypertensive treatment, was part of a previously completed study. The renal plastic-embedded biopsies were serially sectioned (1 microm), the sections being used for determining glomerular volume, vascular pole area, and interstitial space expressed as fraction of tubular cortex.

RESULTS

A significant increase in glomerular volume (P=0.04) was seen in group 3 only. Vascular pole area (VPA) and VPA relative to calculated glomerular surface did not show significant changes in any of the groups, only a tendency to increase in VPA in group 3 (P=0.051). The increase in VPA correlated with systolic blood pressure during the study period (r=0.49, P=0.03). Glomerular volume did not correlate with HbA(1C), current diabetic glomerulopathy, or ensuing worsening of glomerulopathy. In group 3 every case showed an increase in interstitium (P=0.0009), group 2 showed a decrease (P=0.03), and group 1 showed no change. Increase in interstitial fractional volume correlated with diastolic blood pressure during the study (r=0.54, P=0.01).

CONCLUSIONS

In early microalbuminuria, type 1 diabetic patients show glomerular growth, probably compensatory to the developing glomerulopathy. The increase in interstitial volume fraction, demonstrable in early nephropathy, is further augmented over a few years, but is arrested by antihypertensive treatment.

Stereologic methods and their application in kidney research

Stereologic methods are used to obtain quantitative information about three-dimensional structures based on observations from section planes or--to a limited degree--projections. Stereologic methods, which are used in biologic research and especially in the research of normal and pathologic kidneys, will be discussed in this review. Special emphasis will be placed on modern stereologic methods, free of assumptions of the structure, size, and shape, etc., so-called UFAPP (unbiased for all practical purposes) stereologic methods. The basic foundation of all stereology, sampling, will be reviewed in relation to most of the methods discussed. Estimation of error variances and some of the basic problems in stereology will be reviewed briefly. Finally, a few comments will be made about the future directions for stereology in kidney research.

Renal structural changes in insulin-dependent diabetic patients with albuminuria. Comparison of cases with onset of albuminuria after short or long duration

The large interindividual variation in diabetes duration until the onset of nephropathy is partly unexplained. This study was performed to compare renal structure in insulin-dependent (IDDM) patients who had developed signs of nephropathy after a short or long duration of diabetes. Renal biopsies were obtained from 17 IDDM patients, with albumin excretion rate 20-300 microg/min and normal blood pressure. Six patients had <25 years duration ("short-term", early onset of microalbuminuria) and eight patients had duration >30 years ("long-term", late onset of microalbuminuria). Biopsies were obtained 18 months after entry into a study testing the effect of low-dose antihypertensives. Parameters characterizing diabetic glomerulopathy were significantly increased in IDDM patients compared with those in 17 living donors: Basement membrane thickness, mean and (CV): 591 nm (0.17) vs 320 nm (0.12), mesangial volume fraction per glomerulus 0.27 (0.19) vs 0.19 (0.10), matrix volume fraction per glomerulus 0.16 (0.20) vs 0.097 (0.22), matrix star volume 38.5 microm3 (0.43) vs 13.9 microm3 (0.31), (p<10(-4) for each). Comparison of short vs long-term patients showed no significant differences in glomerulopathy parameters, glomerular volume or extracellular material per glomerulus, whereas the fraction of occluded glomeruli was significantly increased in long-term patients. A close correlation obtained between fraction of occluded glomeruli and glomerular filtration rate (r=0.72, p= 0.001). Glomerular occlusion occurred unrelated to the severity of diabetic glomerulopathy. It is suggested that diabetic macroangiopathy and arteriolar hyalinization may play an important role in the renal function of patients with slow development of nephropathy.

The importance of microalbuminuria as an indicator of incipient diabetic nephropathy: therapeutic implications

Nephropathy is the major life-threatening complication of insulin-dependent diabetes mellitus (IDDM). The clinical syndrome is characterized by persistent albuminuria (greater than 300 mg day), a rise in arterial blood pressure, and a relentless decline in glomerular filtration rate leading to end-stage renal failure. The availability of a radioimmunoassay for detecting albumin in low concentrations in urine has allowed the study of urinary albumin excretion rates in diabetics well before clinically persistent proteinuria develops. An albumin excretion rate greater than that in normal subjects and lower than that in macroalbuminuric subjects is called microalbuminuria (range 20-200 microg/min or 30-300 mg/24 h). Although recent studies have challenged the predictive value of microalbuminuria for later development of overt diabetic nephropathy, albumin excretion rate in the microalbuminuric range and its tracking (i.e. annual increase) are still considered reliable markers for prediction of later overt diabetic kidney disease. Overnight urinary collection is preferred for calculation of the rate of albumin excretion, but may be difficult to perform precisely. The albumin:creatinine ratio of the first morning urine sample is a reliable screening method: the microalbuminuric range is considered to be 2.5-25 mg/mmol or 30-300 mg/g (3.5 mg/mol has been proposed as lower limit in females because of their lower creatinine excretion). Irrespective of the procedure used, at least two samples over a 3-6-month period should test positive before microalbuminuria is confirmed and 'persistent microalbuminuria' defined. If the albumin excretion rate is persistently in the microalbuminuric range it is of crucial importance to define strategies and carry out interventions for prevention of decline in kidney function. The goal of achieving the best glycaemic control as early as possible in as many IDDM patients as is safely possible is particularly important in microalbuminuric patients. Although it is unsafe to reduce dietary protein intake drastically, particularly in children and adolescents, moderate decrease of protein intake (i.e. 0.9-1.1/g/kg day) is advisable in diabetic patients from the very beginning of the disease. Timely treatment with an angiotensin-converting enzyme inhibitor, independently of rise in arterial blood pressure, should be considered if improvement of glycaemic control and moderate decrease of dietary protein intake for 6-12 months have failed to reduce the albumin excretion rate. Screening programmes for microalbuminuria and early intervention can substantially modify the natural history of diabetic renal involvement and disease and possibly reduce the incidence of end-stage renal failure.

Microalbuminuria: a marker to increased renal and cardiovascular risk in diabetes mellitus

The presence of persistent microalbuminuria in IDDM is strongly predictive of the future development of end stage renal failure and of cardiovascular disease to a lesser extent. Screening for microalbuminuria is an essential component of modern diabetes practice, as effective antihypertensive therapy, and particularly, the use of angiotensin converting enzyme inhibitors is of proven benefit in retarding progression of renal disease. Cost benefit analysis justifies the expense of microalbuminuria screening programmes and early intervention. It has been estimated that the use of angiotensin converting enzyme inhibitors in microalbuminuric IDDM will save 5200 Pounds-11,000 Pounds per year of life saved. Angiotensin converting enzyme inhibitors are not free of side-effects, and it is therefore essential, given the intrinsic variability of the albumin excretion rate, and the regression to normoalbuminuria of a significant proportion of patients, to confirm the diagnosis of microalbuminuria by repeated measurements prior to the commencement of treatment. The value of intensive glycaemic control is unproven, and further prospective studies are required. There are no proven therapies for the prevention of macrovascular disease in IDDM, although the value of cessation of smoking and aggressive blood pressure control are undoubted in the non-diabetic population. Controversy persists about the value of lipid lowering therapy, especially in young patients, although even in this group there is an increased risk of cardiovascular disease. Microalbuminuria is the strongest known predictor of cardiovascular disease in NIDDM; in contrast to the situation in the non-diabetic population, active lipid lowering therapy is not of proven cardiac benefit, but intervention seems justifiable when taken in the context of the very high prevalence of cardiovascular disease. Microalbuminuria is also predictive of end stage renal disease in NIDDM. Although intervention with angiotensin converting enzyme inhibitors has not been proven to prevent end stage renal disease, stabilisation of albumin excretion rate and creatinine clearance have been demonstrated in normotensive NIDDM, and it seems likely that longer term follow-up studies will confirm the benefit of angiotensin converting enzyme inhibitors in the prevention of end-stage renal disease. The observed predictive power of microalbuminuria as regards both cardiac and renal risk in NIDDM when considered in conjunction with the preliminary results of the benefits of angiotensin converting enzyme inhibition lend further support to the employment of microalbuminuria screening in NIDDM.

Advanced glycation end products in serum predict changes in the kidney morphology of patients with insulin-dependent diabetes mellitus

The biochemical mechanisms that cause the development and progression of diabetic nephropathy are unknown. Advanced glycation end products (AGEs) might play a role, as shown by increased levels of tissue-bound and circulating AGEs that correlate with the severity of diabetic nephropathy. The aim of the present study was to investigate if circulating AGEs predict the progression of morphological pathology in patients with diabetic nephropathy. We have developed an immunoassay to determine serum levels of AGEs. In a prospective clinical trial of young insulin-dependent diabetes mellitus (IDDM) patients with microalbuminuria, kidney biopsies were taken at baseline and after 24 to 36 months. The biopsies were analyzed for structural changes in the glomeruli by quantitative morphometry (electron microscopy). We have retrospectively analyzed serum AGEs. The mean serum level of AGEs at the start of the study was 18.7 U/mL (95% confidence interval [CI], 16.9 to 20.5). A positive correlation between serum AGE levels at the start of study and changes from baseline to follow-up study in basement membrane thickness (r = .56, P < .02) and matrix/glomerular volume fraction (r = .57, P < .02) was demonstrated. In a stepwise regression analysis with changes in the matrix/glomerular volume fraction as the dependent variable, serum AGE levels at the start of the study proved to be a significant independent variable (P < .02), whereas the mean hemoglobin A1c (HbA1c) or HbA1c at the start was not. This study shows that serum AGEs predict the progression of early morphological kidney damage during 2.5 years in patients with IDDM.