High risk of ESRD in type 1 diabetes: new strategies are needed to retard progressive renal function decline

Role of the SLIT-ROBO signaling pathway in renal pathophysiology and various renal diseases

SLIT ligand and its receptor ROBO were initially recognized for their role in axon guidance in central nervous system development. In recent years, as research has advanced, the role of the SLIT-ROBO signaling pathway has gradually expanded from axonal repulsion to cell migration, tumor development, angiogenesis, and bone metabolism. As a secreted protein, SLIT regulates various pathophysiological processes in the kidney, such as proinflammatory responses and fibrosis progression. Many studies have shown that SLIT-ROBO is extensively involved in various aspects of kidney development and maintenance of structure and function. The SLIT-ROBO signaling pathway also plays an important role in different types of kidney disease. This article reviews the advances in the study of the SLIT-ROBO pathway in various renal pathophysiological and kidney disorders and proposes new directions for further research in this field.

Establishment and validation of the cut-off values of estimated glomerular filtration rate and urinary albumin-to-creatinine ratio for diabetic kidney disease: A multi-center, prospective cohort study

OBJECTIVE

We aimed to study the cut-off values of estimated glomerular filtration rate (eGFR) and the urinary albumin creatinine ratio (UACR) in the normal range for diabetic kidney disease (DKD).

METHODS

In this study, we conducted a retrospective, observational cohort study included 374 type 2 diabetic patients who had baseline eGFR ≥60 mL/min/1.73 m² and UACR <30 mg/g with up to 6 years of follow-up. The results were further validated in a multi-center, prospective cohort study.

RESULTS

In the development cohort, baseline eGFR (AUC: 0.90, cut-off value: 84.8 mL/min/1.73 m², sensitivity: 0.80, specificity: 0.85) or UACR (AUC: 0.74, cut-off value: 15.5mg/g, sensitivity: 0.69, specificity: 0.63) was the most effective single predictor for DKD. Moreover, compared with eGFR or UACR alone, the prediction model consisted of all of the independent risk factors did not improve the predictive performance (P >0.05). The discrimination of eGFR at the cut-off value of 84.80 mL/min/1.73 m2 or UACR at 15.5mg/g with the largest Youden's index was further confirmed in the validation cohort. The decrease rate of eGFR was faster in patients with UACR ≥15.5mg/g (P <0.05). Furthermore, the decrease rate of eGFR or increase rate of UACR and the incidence and severity of cardiovascular disease (CVD) were higher in patients with eGFR ≤84.8 mL/min/1.73 m² or UACR ≥15.5mg/g (P <0.05).

CONCLUSIONS

In conclusion, eGFR ≤84.8mL/min/1.73 m² or UACR ≥15.5mg/g in the normal range may be an effective cut-off value for DKD and may increase the incidence and severity for CVD in type 2 diabetic patients.

Urinary angiotensinogen antedates the development of stage 3 CKD in patients with type 1 diabetes mellitus

We examined if urinary angiotensinogen (uAOG), a marker of intrarenal renin‐angiotensin system activity, antedates stage 3 chronic kidney disease (CKD) using samples from participants in the Diabetes Control and Complications Trial (DCCT) and later in the Epidemiology of Diabetes Intervention and Complications (EDIC) trial. In a nested case–control design, cases were matched at the outcome visit (eGFR less than 60, 21‐59 mL/min per 1.73 m²) on age, gender, and diabetes duration, with controls: eGFR (95, 75‐119, mL/min per 1.73 m².) Additionally, in an exploratory analysis progressive renal decline (PRD), defined as eGFR loss >3.5 mL/min per 1.73m²/year, was evaluated using only data from EDIC because no progressions were observed during DCCT. At the EDIC visit, which antedated the GFR outcome visit by 2 years (range 1–7years) the median uAOG/creatinine was markedly higher in cases than in controls (13.9 vs. 3.8 ng/mg P = 0.003) whereas at the DCCT visit, which antedated the GFR outcome by 17 to 20 years it was not (2.75 vs. 3.16 ng/mg, respectively). The Odds Ratio for uAOG and CKD stage 3 development was significant after adjusting for eGFR, HbA1c, and systolic blood pressure 1.82 (1.00–3.29) but no longer significant when Albumin Excretion Ratio (AER) was included 1.21 (0.65–2.24).In the PRD analysis, uAOG/creatinine was sixfold higher in participants who experienced PRD than in those who did not (26 vs. 4.0 ng/mg, P = 0.003). The Odds Ratio for uAOG and PRD was significant after adjusting for eGFR, HbA1c, and systolic blood pressure 2.48 (1.46–4.22) but no longer significant when AER was included 1.32 (0.76–2.30). In people with type1 diabetes, a robust increase in uAOG antedates the development of stage 3 CKD but is not superior to AER in predicting this renal outcome. Increased uAOG moreover is associated with PRD, an index of progression to End Stage Kidney Disease (ESKD).

Uric acid is not associated with diabetic nephropathy and other complications in type 1 diabetes

BACKGROUND

To examine the association between plasma uric acid (UA) and the presence of diabetic complications including diabetic nephropathy and cardiovascular risk factors in patients with type 1 diabetes.

METHODS

This study, which is cross-sectional in design, included 676 Caucasian type 1 diabetes patients from the Steno Diabetes Center Copenhagen. Participants with UA within the three lowest sex-specific quartiles were compared with participants with levels in the highest quartile. Unadjusted and adjusted linear regression analyses were applied. Adjustment included sex, age, diabetes duration, body mass index, high-density lipoprotein cholesterol, smoking, haemoglobin A1c, 24-h pulse pressure, urinary albumin excretion rate (UAER), estimated glomerular filtration rate (eGFR) and treatment with renin-angiotensin-aldosterone system blockers.

RESULTS

Of the 676 patients, 372 (55%) were male, mean ± SD age was 55 ± 13 years and eGFR was 82 ± 26 mL/min/1.73 m2. The median UA was 0.30 (interquartile range 0.23-0.37) mmol/L. UA in the upper sex-specific quartile was associated with lower eGFR, higher UAER and carotid-femoral pulse wave velocity and lower 24 h and daytime diastolic blood pressure (BP) in unadjusted analyses (P < 0.001). Moreover, UA in the upper sex-specific quartile was associated with higher nighttime systolic BP and the presence of cardiovascular disease in unadjusted analyses (P ≤ 0.01), but significance was lost after adjustment (P ≥ 0.17). UA was higher across the retinopathy groups [nil (n = 142), simplex (n = 277), proliferative (n = 229) and blind (n = 19)] in unadjusted analyses (P < 0.0001), but not after adjustment (P = 0.12). Patients with an accelerated decline in eGFR (≥3 mL/min/year) had significantly higher UA at baseline (P = 0.006) compared with slow decliners (<3 mL/min/year), but significance was lost after adjustment (P = 0.10).

CONCLUSIONS

In type 1 diabetes patients, higher UA was associated with lower kidney function and other diabetic complications. The association between higher UA and lower eGFR and lower diastolic BP was independent of traditional risk factors.

Risk of end-stage renal disease from chronic kidney disease defined by decreased glomerular filtration rate in type 1 diabetes: A comparison with type 2 diabetes and the effect of metabolic syndrome

BACKGROUND

We estimated the end-stage renal disease (ESRD) risk of chronic kidney disease (CKD) in patients with type 1 diabetes (T1D). The ESRD risk of CKD in patients with T1D was compared with that of CKD in patients without diabetes and with type 2 diabetes (T2D). We also evaluated the predictive value of metabolic syndrome (MetS) for ESRD development in CKD patients with T1D.

MATERIALS AND METHODS

The Korean National Health Insurance Service datasets of preventive health check-ups from 2009 to 2016 were used. The risk of incident ESRD was analysed according to the presence and type of diabetes in CKD (defined as an estimated glomerular filtration rate < 60 mL/min/1.73 m² ) patients aged 20 years or older. Incident ESRD risk according to the presence of MetS was calculated among adult patients with CKD and T1D.

RESULTS

During 10 701 375.84 person-years of follow-up, 43 693 cases of ESRD developed. Hazard ratios (HRs) for incident ESRD from CKD in the T1D group were 2.580 (95% confidence interval [CI], 2.336-2.849) and 9.267 (95% CI, 8.378-10.251) compared with T2D and nondiabetes groups, respectively. In CKD patients with T1D, the presence of MetS increased incident ESRD risk by an HR of 2.023 (95% CI, 1.501-2.727).

CONCLUSIONS

The presence of diabetes increases the risk for ESRD development from CKD. Furthermore, patients with T1D have a higher risk for ESRD incidence from CKD than do patients with T2D in a Korean population. MetS may be a useful predictor for ESRD in CKD patients with T1D.

Preventing Early Renal Loss in Diabetes (PERL) Study: A Randomized Double-Blinded Trial of Allopurinol-Rationale, Design, and Baseline Data

OBJECTIVE

Higher serum uric acid (SUA) is associated with diabetic kidney disease (DKD). Preventing Early Renal Loss in Diabetes (PERL) evaluates whether lowering SUA with allopurinol slows glomerular filtration rate (GFR) loss in people with type 1 diabetes (T1D) and mild to moderate DKD. We present the PERL rationale, design, and baseline characteristics.

RESEARCH DESIGN AND METHODS

This double-blind, placebo-controlled, multicenter trial randomized 530 participants with T1D, estimated GFR (eGFR) of 40-99.9 mL/min/1.73 m², SUA ≥4.5 m/dL, and micro- to macroalbuminuric DKD or normoalbuminuria with declining kidney function (NDKF) (defined as historical eGFR decline ≥3 mL/min/1.73 m²/year) to allopurinol or placebo. The primary outcome is baseline-adjusted iohexol GFR (iGFR) after 3 years of treatment plus a 2-month washout period.

RESULTS

Participants are 66% male and 84% white. At baseline, median age was 52 years and diabetes duration was 35 years, 93% of participants had hypertension, and 90% were treated with renin-angiotensin system inhibitors (median blood pressure 127/71 mmHg). Median HbA_1c was 8%, SUA 5.9 mg/dL, iGFR 68 mL/min/1.73 m², and historical eGFR slope -3.5 mL/min/1.73 m²/year. Compared with participants with albuminuria (n = 419), those with NDKF (n = 94) were significantly older (56 vs. 52 years), had lower HbA_1c (7.7 vs. 8.1%) and SUA (5.4 vs. 6.0 mg/dL), and had higher eGFR (82 vs. 74 mL/min/1.73 m²) and historical eGFR loss (-4.7 vs. -2.5 mL/min/1.73 m²/year). These differences persisted when comparing groups with similar rates of historical eGFR loss.

CONCLUSIONS

PERL will determine the effect of allopurinol on mild to moderate DKD in T1D, with or without albuminuria. Participants with normoalbuminuria and rapid GFR loss manifested many DKD risk factors of those with albuminuria, but with less severity.

Advances in understanding the genetic basis of diabetic kidney disease

Diabetic kidney disease (DKD) is a devastating complication of Type 1 and Type 2 diabetes and leads to increased morbidity and mortality. Earlier work in families has provided strong evidence that heredity is a major determinant of DKD. Previous linkage analyses and candidate gene studies have identified potential DKD genes; however, such approaches have largely been unsuccessful. Genome-wide association studies (GWAS) have made significant contribution in identifying SNPs associated with common complex diseases. Thanks to advanced technology, new analytical approaches, and international research collaborations, many DKD GWASs have reported unique genes, highlighted novel biological pathways and suggested new disease mechanisms. This review summarizes the current state of GWAS technology; findings from GWASs of DKD and its related traits conducted over the past 15 years and discuss the future of this field.

Estimated glomerular filtration rate decline and risk of end-stage renal disease in type 2 diabetes

Background

According to studies by the National Kidney Foundation and Food and Drug Administration, 30% and 40% declines in estimated glomerular filtration rate (eGFR) could be used as surrogate endpoints of end-stage renal disease (ESRD). However, the benefits of using these endpoints in diabetic patients remain unclear.

Methods

This cohort study comprised Japanese patients with type 2 diabetes; those with repeated serum creatinine measurements during a baseline period of 2 years (n = 1868) or 3 years (n = 2001) were enrolled. Subsequent risks of ESRD following eGFR declines were assessed.

Results

In the 2-year baseline analysis, the cumulative prevalence of −20%, −30%, −40%, and −53% changes in eGFR were 23.9%, 11.1%, 6.8%, and 3.7%, respectively. There were 133 cases (7.1%) of subsequent ESRD during a median follow-up period of 6.5 years. In the 3-year baseline analysis, the corresponding proportions were 28.1%, 14.0%, 7.7%, and 3.9%, respectively, with 110 participants (5.5%) reaching ESRD during a median follow-up period of 5.5 years. The adjusted hazard ratios of subsequent ESRD following −53%, −40%, −30%, and −20% changes in eGFR during the 2-year baseline period were 22.9 (11.1–47.3), 12.8 (6.9–23.7), 8.2 (4.3–15.5), and 3.9 (2.2–7.0), respectively when compared with the no changes in eGFR. In the 3-year baseline analysis, the corresponding risks were 29.7 (10.8–81.9), 18.4 (7.6–44.7), 12.8 (5.2–32.2), and 5.4 (2.3–12.8), respectively. In the subgroup analysis, similar trends were observed in patients with macroalbuminuria at baseline.

Conclusions

Declines in eGFR were strongly associated with subsequent risk of ESRD in Japanese type 2 diabetic patients. In addition to 30% and 40% declines, a 20% decline in eGFR over 2 years could be considered as a candidate surrogate endpoint of ESRD in diabetic kidney disease.

Incidence of End-Stage Renal Disease in Patients With Type 1 Diabetes

OBJECTIVE

To investigate how risk of end-stage renal disease (ESRD) among patients with type 1 diabetes has changed over time and further how the risk is affected by age, sex, and time period of diagnosis of diabetes.

RESEARCH DESIGN AND METHODS

A cohort including all patients <30 years old diagnosed with type 1 diabetes in Finland in 1965-2011 was followed until start of renal replacement therapy, death, or end of follow-up at the end of 2013. Altogether, 29,906 patients were included. The main outcome was cumulative risk of ESRD, accounting for death as a competing risk.

RESULTS

The patients were followed up for a median of 20 years. During 616,403 patient-years, 1,543 ESRD cases and 4,185 deaths were recorded. The cumulative risk of ESRD was 2.2% after 20 years and 7.0% after 30 years from the diabetes diagnosis. The relative risk of ESRD was 0.13 (95% CI 0.08-0.22) among patients diagnosed in 1995-2011 compared with those diagnosed in 1965-1979. Patients <5 years old at the time of diagnosis had the lowest risk of ESRD after diagnosis. With the cumulative risk of ESRD estimated from time of birth, the patients aged 5-9 years at diabetes diagnosis were at highest risk.

CONCLUSIONS

The cumulative risk of ESRD has decreased markedly during the past five decades. This highlights the importance of modern treatment of diabetes and diabetic nephropathy.

The role of Slit-Robo signaling in the regulation of tissue barriers

The role of Slit/Robo signaling has extended from initial axon repulsion in the developing nervous system to organ morphogenesis, cancer development and angiogenesis. Slit/Robo signaling regulates similar pathways within these processes. Slit/Robo ensures the homeostasis of the dynamic interaction between cell-cell and cell-matrix interactions. The dysregulation of Slit/Robo signaling damages the tissue barrier, resulting in developmental abnormalities or disease. Here, we summarize how Slit/Robo controls kidney morphogenesis and describe the dual roles of Slit/Robo signaling in the regulation of tumorigenesis and angiogenesis.

Association of prediabetes-associated single nucleotide polymorphisms with microalbuminuria

Increased glycemic exposure, even below the diagnostic criteria for diabetes mellitus, is crucial in the pathogenesis of diabetic microvascular complications represented by microalbuminuria. Nonetheless, there is limited evidence regarding which single nucleotide polymorphisms (SNPs) are associated with prediabetes and whether genetic predisposition to prediabetes is related to microalbuminuria, especially in the general population. Our objective was to answer these questions. We conducted a genomewide association study (GWAS) separately on two population-based cohorts, Ansung and Ansan, in the Korean Genome and Epidemiology Study (KoGES). The initial GWAS was carried out on the Ansung cohort, followed by a replication study on the Ansan cohort. A total of 5682 native Korean participants without a significant medical illness were classified into either control group (n = 3153) or prediabetic group (n = 2529). In the GWAS, we identified two susceptibility loci associated with prediabetes, one at 17p15.3-p15.1 in the GCK gene and another at 7p15.1 in YKT6. When variations in GCK and YKT6 were used as a model of prediabetes, this genetically determined prediabetes increased microalbuminuria. Multiple logistic regression analyses revealed that fasting glucose concentration in plasma and SNP rs2908289 in GCK were associated with microalbuminuria, and adjustment for age, gender, smoking history, systolic blood pressure, waist circumference, and serum triglyceride levels did not attenuate this association. Our results suggest that prediabetes and the associated SNPs may predispose to microalbuminuria before the diagnosis of diabetes mellitus. Further studies are needed to explore the details of the physiological and molecular mechanisms underlying this genetic association.

Knowledge regarding the prevention of chronic kidney disease in hypertensive and diabetic patients: a cross-sectional study

Abstract Introduction: Hypertension (HT) and diabetes mellitus (DM) lead to functional and structural changes in target organs such as the kidneys, characterizing the need for preventive actions to avoid Chronic Kidney Disease (CKD). Objective: To verify cardiologists’ and endocrinologists’ knowledge, indications and practices regarding prevention of CKD in patients with HT and DM. Methods: A cross-sectional study with 14 cardiologists and 5 endocrinologists applying a questionnaire about the conduct of these professionals regarding the prevention of CKD in hypertensive and diabetic patients. Results: One hundred percent of the cardiologists and endocrinologists did not request specific tests for CKD screening (albuminuria and glomerular filtration rate (GFR), although 92.9% of the cardiologists and 60.0% of the endocrinologists report referring hypertensive and diabetic patients with impaired renal function to nephrologists. One hundred percent of the interviewees recognize the importance of physical exercise for their patients; however, only 68.6% of cardiologists and 60% of endocrinologists indicated a physiotherapist and/or physical trainer to implement these exercises. Conclusion: The professionals evaluated in this study do not request microalbuminuria and GFR examinations for hypertensive and diabetic patients as a follow-up routine, despite having found cases of renal function impairment in these patients; in contrast to what is proposed in the guidelines for hypertension and diabetes mellitus. They recognize the importance of physical exercise and report indicating their patients to a physiotherapist and/or physical trainer. We suggest continuing the study in order to ascertain the reasons for their not complying with the respective guidelines.

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.

Progressive renal decline: the new paradigm of diabetic nephropathy in type 1 diabetes

On the basis of extensive studies in Joslin Clinic patients over 25 years, we propose a new model of diabetic nephropathy in type 1 diabetes. In this model, the predominant clinical feature of both early and late stages of diabetic nephropathy is progressive renal decline, not albuminuria. Progressive renal decline (estimated glomerular filtration rate loss >3.5 mL/min/year) is a unidirectional process that develops while patients have normal renal function. It progresses at an almost steady rate until end-stage renal disease is reached, albeit at widely differing rates among individuals. Progressive renal decline precedes the onset of microalbuminuria, and as it continues, it increases the risk of proteinuria. Therefore, study groups ascertained for microalbuminuria/proteinuria are enriched for patients with renal decline (decliners). We found prevalences of decliners in 10%, 32%, and 50% of patients with normoalbuminuria, microalbuminuria, and proteinuria, respectively. Whether the initial lesion of progressive renal decline is in the glomerulus, tubule, interstitium, or vasculature is unknown. Similarly unclear are the initiating mechanism and the driver of progression. No animal model mimics progressive renal decline, so etiological studies must be conducted in humans with diabetes. Prospective studies searching for biomarkers predictive of the onset and rate of progression of renal decline have already yielded positive findings that will help to develop not only accurate methods for early diagnosis but also new therapeutic approaches. Detecting in advance which patients will have rapid, moderate, or minimal rates of progression to end-stage renal disease will be the foundation for developing personalized methods of prevention and treatment of progressive renal decline in type 1 diabetes.

Proteases and protease inhibitors of urinary extracellular vesicles in diabetic nephropathy

Diabetic nephropathy (DN) is one of the major complications of diabetes mellitus (DM), leads to chronic kidney disease (CKD), and, ultimately, is the main cause for end-stage kidney disease (ESKD). Beyond urinary albumin, no reliable biomarkers are available for accurate early diagnostics. Urinary extracellular vesicles (UEVs) have recently emerged as an interesting source of diagnostic and prognostic disease biomarkers. Here we used a protease and respective protease inhibitor array to profile urines of type 1 diabetes patients at different stages of kidney involvement. Urine samples were divided into groups based on the level of albuminuria and UEVs isolated by hydrostatic dialysis and screened for relative changes of 34 different proteases and 32 protease inhibitors, respectively. Interestingly, myeloblastin and its natural inhibitor elafin showed an increase in the normo- and microalbuminuric groups. Similarly, a characteristic pattern was observed in the array of protease inhibitors, with a marked increase of cystatin B, natural inhibitor of cathepsins L, H, and B as well as of neutrophil gelatinase-associated Lipocalin (NGAL) in the normoalbuminuric group. This study shows for the first time the distinctive alterations in comprehensive protease profiles of UEVs in diabetic nephropathy and uncovers intriguing mechanistic, prognostic, and diagnostic features of kidney damage in diabetes.

Leptin monotherapy rescues spermatogenesis in male Akita type 1 diabetic mice

Type 1 diabetes is associated with subfertility in humans. The current treatment for type 1 diabetes, insulin monotherapy, is suboptimal to fully stabilize glycemia, potentially leading to this subfertility. Recent work has demonstrated that treatment with the energy-regulating hormone leptin, alone or in combination with insulin, can more effectively control glycemia in mouse models of type 1 diabetes. Here, we sought to determine whether the fertility defects in a type 1 diabetic mouse model, the Akita mouse, can be rescued with leptin monotherapy in the absence of any exogenous insulin. Akita homozygous mice treated with leptin alone had a larger total body size, testes, and seminal vesicles than their untreated siblings. Leptin treatment prevented testicular degeneration and rescued sperm motility to wild-type levels. Furthermore, sperm obtained from leptin-treated mice could successfully fertilize ooctyes in vitro. Despite completely rescuing spermatogenesis, the critical reproductive hormones LH and testosterone were only modestly higher than in untreated mice, indicating that a minimum threshold of these hormones must be met to maintain spermatogenesis. Cumulatively, these findings implicate the importance of leptin in maintaining fertility and support the use of leptin therapy in the treatment of type 1 diabetes.

Progressive renal decline as the major feature of diabetic nephropathy in type 1 diabetes

Despite almost universal implementation of renoprotective therapies over the past 25 years, the risk of end-stage renal disease (ESRD) in type 1 diabetes (T1D) is not decreasing, and ESRD remains the major cause of excess morbidity and premature mortality [1]. Such a state of affairs prompts a call to action. In this review we re-evaluated the proteinuria-centric model of diabetic nephropathy and showed its deficiencies. On the basis of extensive studies that we have been conducting on the patients attending the Joslin Clinic, we propose that progressive renal decline, not abnormalities in urinary albumin excretion, should be considered as the major feature of disease processes leading to ESRD in T1D. The etiology of diabetic nephropathy should be reconsidered in light of our new findings so our perspective can be broadened regarding new therapeutic targets available for interrupting the progressive renal decline in T1D. Reduction in the loss of glomerular filtration rate, not reduction of albumin excretion rate, should become the measure for evaluating the effectiveness of new therapeutic interventions. We need new accurate methods for early diagnosis of patients at risk of progressive renal decline or, better still, for detecting in advance which patients will have rapid, moderate or minimal rate of progression to ESRD.

Risk for end-stage renal disease over 25 years in the population-based WESDR cohort

OBJECTIVE

In the population-based Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) cohort, we sought to examine whether a decline in the prevalence and incidence of end-stage renal disease (ESRD) was evident with increasing calendar year of type 1 diabetes diagnosis among people followed for 25 years. Factors associated with the hazard of incident ESRD that may mediate a decline were also investigated.

RESEARCH DESIGN AND METHODS

Participants were examined at baseline in 1980 (n = 996) and at 4-25 years of follow-up. ESRD was defined by self-reported renal transplant or dialysis. Cumulative incidence with competing risk of death was determined. Incident ESRD was modeled by period of diagnosis, adjusting for other known risk factors using discrete time hazard models.

RESULTS

When diabetes was diagnosed during 1970-1980, the unadjusted cumulative incidence of ESRD at 25 years was 9.3%. The unadjusted hazard of ESRD was reduced by 70% (P < 0.001), compared with those diagnosed with diabetes in 1922-1969; however, the association was attenuated by glycosylated hemoglobin level (HbA1c), systolic blood pressure, and antihypertensive use (hazard ratio [HR] 0.89 [95% CI 0.55-1.45]). HbA1c, age, and male sex remained associated with ESRD hazard after adjustment for kidney function and proliferative retinopathy.

CONCLUSIONS

A lower incidence of ESRD among those more recently diagnosed with type 1 diabetes was explained by improvements in glycemic and blood pressure control over the last several decades. Intensive diabetes management, especially for glycemic control, remains important even in long-standing diabetes as it may delay the development of ESRD.

Temporal profile of diabetic nephropathy pathologic changes

Diabetic nephropathy, by far, is the most common cause of end stage renal disease in the US and many other countries. In type 1 diabetes, the natural history of diabetic nephropathy is tightly linked to evolution of classic lesions of the disease, namely glomerular basement membrane thickening, increased mesangial matrix, and reduced glomerular filtration surface density. These lesions progress in parallel and correlate with increased albumin excretion rate and reduced glomerular filtration rate across a wide range of renal function. In fact, the vast majority of the variances of albumin excretion and glomerular filtration rates can be explained by these glomerular lesions alone in type 1 diabetic patients. Although, classic lesions of diabetic nephropathy, indistinguishable from those of type 1 diabetes, also occur in type 2 diabetes, renal lesions are more heterogeneous in type 2 diabetic patients with some patients developing more advanced vascular or chronic tubulointerstitial lesions than diabetic glomerulopathy. More research biopsy longitudinal studies, especially in type 2 diabetic patients, are needed to better understand various pathways of renal injury in diabetic nephropathy.

Uric acid lowering to prevent kidney function loss in diabetes: the preventing early renal function loss (PERL) allopurinol study

Diabetic kidney disease causes significant morbidity and mortality among people with type 1 diabetes (T1D). Intensive glucose and blood pressure control have thus far failed to adequately curb this problem and therefore a major need for novel treatment approaches exists. Multiple observations link serum uric acid levels to kidney disease development and progression in diabetes and strongly argue that uric acid lowering should be tested as one such novel intervention. A pilot of such a trial, using allopurinol, is currently being conducted by the Preventing Early Renal Function Loss (PERL) Consortium. Although the PERL trial targets T1D individuals at highest risk of kidney function decline, the use of allopurinol as a renoprotective agent may also be relevant to a larger segment of the population with diabetes. As allopurinol is inexpensive and safe, it could be cost-effective even for relatively low-risk patients, pending the completion of appropriate trials at earlier stages.

Pancreas transplant as treatment to arrest renal function decline in patients with type 1 diabetes and proteinuria

Recent findings from the Diabetes Control and Complications Trial and Epidemiology of Diabetes Interventions and Complications study showed that long-term improved glycemic control in patients with type 1 diabetes with normal renal function and normoalbuminuria can delay development of impaired renal function by at least 6.5 years, although the reduction in the relative risk of end-stage renal disease (ESRD) was not significant. The unanswered question is: can improvement of glycemic control delay the onset of ESRD in patients with established diabetic nephropathy? In this context, pancreas transplantation (PATx) can be considered the most effective intervention to restore normoglycemia. Can this aggressive/experimental intervention be applied to arrest/retard renal function decline? To answer this question, this review summarizes the relevant findings from observational studies conducted in cohorts of patients, followed up for 4 to 15 years, who underwent PATx. These noncontrolled studies provided positive answers to the earlier question, principally concerning a significant decrease in albumin excretion levels. However, current drugs used to prevent rejection could impair renal function, principally in recipients with low pretransplant estimated glomerular filtration rate (ie, <60 mL/min). Unfortunately, all these studies had shortcuts that qualify interpretation of the findings. First, it is unclear how much initial estimated glomerular filtration rate loss results from nephrotoxic effect of antirejection drugs, and how much results from improved glycemia and its impact on the reduction of hyperfiltration. Second, the study designs did not consider the wide variation in rates of renal function loss observed in patients with established nephropathy (ie, one third are nonprogressors, one third are slow progressors, and one third are rapid progressors). Third, all studies were observational in nature and clinical trials are needed to properly evaluate the effectiveness of normalization of hyperglycemia through PATx on postponing the onset of ESRD in type 1 diabetes.

Pre-emptive kidney transplantation to improve survival in patients with type 1 diabetes and imminent risk of ESRD

Despite significant improvements in the treatment of diabetic nephropathy over the past 20 years, patients with type 1 diabetes are at high risk of developing end-stage renal disease and high mortality once end-stage renal disease develops. Type 1 diabetic patients treated with predialysis (pre-emptive) transplantation have a lower death rate than type 1 diabetic patients treated with dialysis. Living donor kidney transplantation is possible before starting dialysis and is associated with better kidney and patient outcomes as compared with transplantation while on dialysis. In addition, a variety of potential donors can be used, not just young, well-matched family members. Through paired kidney donation, blood group ABO-incompatible transplants and transplants across the barrier of anti-human leukocyte antigen antibodies, diabetic patients can receive living donor kidney transplants even if their intended donor is not a good match for them. Despite these expanded options making living donation possible, only a minority of type 1 diabetic patients receive a pre-emptive kidney transplant. Multiple barriers remain that prevent type 1 diabetic patients from enjoying the reduced risk of death afforded by a pre-emptive kidney transplant, including lack of knowledge by primary care physicians, endocrinologists, and nephrologists; late referral for transplantation; patient and family misconceptions about timing of transplantation; and who can be a donor. The vast majority of type 1 diabetic patients are listed for kidney transplantation after the initiation of dialysis. Of these patients, thousands subsequently receive a live donor kidney transplant. We believe that the appropriate agencies and societies should address the barriers to pre-emptive kidney transplantation through nationwide educational initiatives and study the causes of failure to be transplanted before dialysis initiation.

Can improved glycemic control slow renal function decline at all stages of diabetic nephropathy?

Observational studies have shown the strong association between level of glycemic control and the key outcome measure, risk of glomerular filtration rate (GFR) loss rather than subsequent course of albumin excretion, in type 1 diabetes patients at all stages of nephropathy. However, it has not been clear if clinical interventions designed to normalize glycemic control are equally effective at all stages, such as primary prevention in normoalbuminuric patients, secondary prevention in microalbuminuria and macroalbuminuria, or tertiary prevention aimed at slowing or reversing further loss of GFR once impaired. Substantial randomized controlled trial data from the Diabetes Control and Complications Trial and Epidemiology of Diabetes Interventions and Complications exists to support postponement, but not outright prevention, of GFR loss in normoalbuminuric patients. Although secondary and tertiary prevention systematic studies are limited to methodologically insufficient insulin pump and transplantation trials, the reversal of advanced glomerular lesions observed in whole-pancreas transplant recipients who experienced long-term glycemic normalization offers convincing support for further research into glycemic interventions specifically for GFR preservation. In light of existing literature, we encourage the design of secondary and tertiary prevention trials that incorporate biomarker methods for identifying patients at highest risk of GFR loss because interventions to normalize hyperglycemia are resource-intensive and may be applied unnecessarily to clinical populations at low long-term GFR loss risk.

JDRF perspective: bridging the gap-translational research to prevent progression of diabetic nephropathy

For those with type 1 diabetes (T1D), the diagnosis of diabetic nephropathy predicts a significant negative impact on quality of life and mortality risk. Diabetic nephropathy is a huge component of the potential cost of diabetes both to the individual and society. For this reason, JDRF and others have prioritized programs aimed to advance our understanding of diabetic nephropathy and translate findings to benefit patients with T1D. Although the current standard of care has reduced the incidence of diabetic nephropathy, a significant proportion of those with T1D are still at risk for declining renal function and progression to end-stage renal disease. Carefully directed research is needed to discover and translate novel targets and biomarkers for diabetic nephropathy to improve the prognosis and outlook for those with T1D and at risk for end-stage renal disease.

Can existing drugs approved for other indications retard renal function decline in patients with type 1 diabetes and nephropathy?

Mounting evidence from human, animal, and in vitro studies indicates that existing drugs, developed to treat other disorders, also might be effective in preventing or slowing the progression of diabetic nephropathy to end-stage renal disease. Examples of such drugs include the urate-lowering agent allopurinol, the anti-tumor necrosis factor agents etanercept and infliximab, and the immunomodulating drug abatacept. Because some of these medications are already on the market and have been used for a number of years for other indications, they can be tested immediately in human beings for a beneficial effect on renal function in diabetes. Special emphasis should be placed on evaluating the use of these drugs early in the course of diabetic nephropathy when renal damage is most likely to be reversible and interventions can yield the greatest delay to end-stage renal disease.