Five-year prospective study of glomerular filtration rate and albumin excretion rate in normofiltering and hyperfiltering normoalbuminuric NIDDM patients

Machine learning prediction models for diabetic kidney disease: systematic review and meta-analysis

BACKGROUND

Machine learning is increasingly recognized as a viable approach for identifying risk factors associated with diabetic kidney disease (DKD). However, the current state of real-world research lacks a comprehensive systematic analysis of the predictive performance of machine learning (ML) models for DKD.

OBJECTIVES

The objectives of this study were to systematically summarize the predictive capabilities of various ML methods in forecasting the onset and the advancement of DKD, and to provide a basic outline for ML methods in DKD.

METHODS

We have searched mainstream databases, including PubMed, Web of Science, Embase, and MEDLINE databases to obtain the eligible studies. Subsequently, we categorized various ML techniques and analyzed the differences in their performance in predicting DKD.

RESULTS

Logistic regression (LR) was the prevailing ML method, yielding an overall pooled area under the receiver operating characteristic curve (AUROC) of 0.83. On the other hand, the non-LR models also performed well with an overall pooled AUROC of 0.80. Our t-tests showed no statistically significant difference in predicting ability between LR and non-LR models (t = 1.6767, p > 0.05).

CONCLUSION

All ML predicting models yielded relatively satisfied DKD predicting ability with their AUROCs greater than 0.7. However, we found no evidence that non-LR models outperformed the LR model. LR exhibits high performance or accuracy in practice, while it is known for algorithmic simplicity and computational efficiency compared to others. Thus, LR may be considered a cost-effective ML model in practice.

Novel insights in classic versus relative glomerular hyperfiltration and implications on pharmacotherapy

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) assessment and its estimation (eGFR) is a long-lasting challenge in medicine and public health. Current eGFR formulae are indexed for standardized body surface area (BSA) of 1.73 m2, ignoring persons and populations wherein the ratio of BSA or metabolic rate to nephron number might be different, due to increased BSA, increased metabolic rate or reduced nephron number. These equations are based on creatinine, cystatin C or a combination of the two, which adds another confounder to eGFR assessment. Unusually high GFR values, also known as renal hyperfiltration, have not been well defined under these equations.

RECENT FINDINGS

Special conditions such as solitary kidney in kidney donors, high dietary protein intake, obesity and diabetes are often associated with renal hyperfiltration and amenable to errors in GFR estimation. In all hyperfiltration types, there is an increased intraglomerular pressure that can be physiologic, but its persistence over time is detrimental to glomerulus leading to progressive glomerular damage and renal fibrosis. Hyperfiltration might be underdiagnosed due to BSA standardization embedded in the formula. Hence, timely intervention is delayed. Reducing intraglomerular pressure in diabetes can be achieved by SGLT2 inhibitors or low protein diet to reverse the glomerulopathy process.

SUMMARY

Accurate identification of glomerular hyperfiltration as a pre-CKD condition needs accurate estimation of GFR in the above normal range should establish a threshold for timely intervention.

Prediction of 3-year risk of diabetic kidney disease using machine learning based on electronic medical records

BACKGROUND

Established prediction models of Diabetic kidney disease (DKD) are limited to the analysis of clinical research data or general population data and do not consider hospital visits. Construct a 3-year diabetic kidney disease risk prediction model in patients with type 2 diabetes mellitus (T2DM) using machine learning, based on electronic medical records (EMR).

METHODS

Data from 816 patients (585 males) with T2DM and 3 years of follow-up at the PLA General Hospital. 46 medical characteristics that are readily available from EMR were used to develop prediction models based on seven machine learning algorithms (light gradient boosting machine [LightGBM], eXtreme gradient boosting, adaptive boosting, artificial neural network, decision tree, support vector machine, logistic regression). Model performance was evaluated using the area under the receiver operating characteristic curve (AUC). Shapley additive explanation (SHAP) was used to interpret the results of the best performing model.

RESULTS

The LightGBM model had the highest AUC (0.815, 95% CI 0.747-0.882). Recursive feature elimination with random forest and SHAP plot based on LightGBM showed that older patients with T2DM with high homocysteine (Hcy), poor glycemic control, low serum albumin (ALB), low estimated glomerular filtration rate (eGFR), and high bicarbonate had an increased risk of developing DKD over the next 3 years.

CONCLUSIONS

This study constructed a 3-year DKD risk prediction model in patients with T2DM and normo-albuminuria using machine learning and EMR. The LightGBM model is a tool with potential to facilitate population management strategies for T2DM care in the EMR era.

High Estimated Glomerular Filtration Rate Is Associated With Worse Cognitive Performance in the Hypertensive Population: Results From the China H-Type Hypertension Registry Study

Background

Increasing studies have focused on the predictive value of high estimated glomerular filtration rate (eGFR) on cardiovascular diseases and mortality; however, the association between high eGFR with cognitive function is still not established. Thus, this study aimed to determine the co-relationship between high eGFR and cognitive performance in the hypertensive population.

Methods

We conducted a baseline cross-sectional study using data from the China H-type Hypertension Registry study. Mini-Mental State Examination (MMSE) assessment was performed to evaluate the cognitive function scale, and serum creatinine was collected to estimate eGFR level. Different MMSE cutoff values were applied in participants with the various educational background to define dementia: <24 in participants with secondary school and above education setting, <20 in those with primary school, and <17 in illiterate participants.

Results

A total of 9,527 hypertensive adults with mean age 63.7 ± 9.8 years and 67% female gender were analyzed. The eGFR cutoff value of 71.52 ml/min/1.73 m2 was found after adjusting for potential covariates in a threshold effect analysis. The MMSE increased significantly with the increment of eGFR (β, 0.27; 95% CI: 0.12–0.41) in participants with eGFR < 71.52 ml/min/1.73 m2 and decreased (β, −0.28; 95% CI: −0.39 to −0.17) in participants with eGFR ≥ 71.52 ml/min/1.73 m2. Individuals with eGFR ≥ 85 ml/min/1.73 m2 have an elevated risk of cognitive impairment than those with eGFR of 65–75 ml/min/1.73 m2. Subgroup analysis showed that a greater reduction degree of MMSE was observed in female individuals and those who had body mass index (BMI) ≥ 24 kg/m2 among participants with eGFR ≥ 71.52 ml/min/1.73 m2.

Conclusion

Our findings observed an inverted U-shaped relationship between eGFR and cognitive function. Both the low and high levels of eGFR were independently associated with worse cognitive assessment in the hypertensive population.

Conditions, pathogenesis, and progression of diabetic kidney disease and early decliner in Japan

OBJECTIVE

Glomerular filtration rate (GFR) decreases without or prior to the development of albuminuria in many patients with diabetes. Therefore, albuminuria and/or a low GFR in patients with diabetes is referred to as diabetic kidney disease (DKD). A certain proportion of patients with diabetes show a rapid progressive decline in renal function in a unidirectional manner and are termed early decliners. This study aimed to elucidate the prevalence of DKD and early decliners and clarify their risk factors.

RESEARCH DESIGN AND METHODS

This combination cross-sectional and cohort study included 2385 patients with diabetes from 15 hospitals. We defined DKD as a urinary albumin to creatinine ratio (ACR) ≥30 mg/gCr and/or estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m². We classified patients into four groups based on the presence or absence of albuminuria and a decrease in eGFR to reveal the risk factors for DKD. We also performed a trajectory analysis and specified the prevalence and risk factors of early decliners with sequential eGFR data of 1955 patients in five facilities.

RESULTS

Of our cohort, 52% had DKD. Above all, 12% with a low eGFR but no albuminuria had no traditional risk factors, such as elevated glycated hemoglobin, elevated blood pressure, or diabetic retinopathy in contrast to patients with albuminuria but normal eGFR. Additionally, 14% of our patients were early decliners. Older age, higher basal eGFR, higher ACR, and higher systolic blood pressure were significantly associated with early decliners.

CONCLUSIONS

The prevalence of DKD in this cohort was larger than ever reported. By testing eGFR yearly and identifying risk factors in the early phase of diabetes, we can identify patients at high risk of developing end-stage renal disease.

Early Glomerular Hyperfiltration and Long-Term Kidney Outcomes in Type 1 Diabetes: The DCCT/EDIC Experience

BACKGROUND AND OBJECTIVES

Glomerular hyperfiltration has been considered to be a contributing factor to the development of diabetic kidney disease (DKD). To address this issue, we analyzed GFR follow-up data on participants with type 1 diabetes undergoing ¹²⁵I-iothalamate clearance on entry into the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications study.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a cohort study of DCCT participants with type 1 diabetes who underwent an ¹²⁵I-iothalamate clearance (iGFR) at DCCT baseline. Presence of hyperfiltration was defined as iGFR levels ≥140 ml/min per 1.73 m², with secondary thresholds of 130 or 150 ml/min per 1.73 m². Cox proportional hazards models assessed the association between the baseline hyperfiltration status and the subsequent risk of reaching an eGFR <60 ml/min per 1.73 m².

RESULTS

Of the 446 participants, 106 (24%) had hyperfiltration (iGFR levels ≥140 ml/min per 1.73 m²) at baseline. Over a median follow-up of 28 (interquartile range, 23, 33) years, 53 developed an eGFR <60 ml/min per 1.73 m². The cumulative incidence of eGFR <60 ml/min per 1.73 m² at 28 years of follow-up was 11.0% among participants with hyperfiltration at baseline, compared with 12.8% among participants with baseline GFR <140 ml/min per 1.73 m². Hyperfiltration was not significantly associated with subsequent risk of developing an eGFR <60 ml/min per 1.73 m² in an unadjusted Cox proportional hazards model (hazard ratio, 0.83; 95% confidence interval, 0.43 to 1.62) nor in an adjusted model (hazard ratio, 0.77; 95% confidence interval, 0.38 to 1.54). Application of alternate thresholds to define hyperfiltration (130 or 150 ml/min per 1.73 m²) showed similar findings.

CONCLUSIONS

Early hyperfiltration in patients with type 1 diabetes was not associated with a higher long-term risk of decreased GFR. Although glomerular hypertension may be a mechanism of kidney injury in DKD, higher total GFR does not appear to be a risk factor for advanced DKD.

Is hyperfiltration associated with higher urine albumin-to-creatinine ratio at follow up among Indigenous Australians? The eGFR follow-up study

BACKGROUND

Glomerular hyperfiltration is not able to be detected in clinical practice. We assessed whether hyperfiltration is associated with albuminuria progression among Indigenous Australians at high risk of diabetes and kidney disease to determine its role in kidney disease progression.

METHODS

Longitudinal observational study of Indigenous Australians aged ≥18 years recruited from >20 sites, across diabetes and/or kidney function strata. At baseline, iohexol clearance was used to measure glomerular filtration rate (mGFR) and hyperfiltration was defined as (i) a mGFR of ≥125 mL/min/1.73 m², and (ii) an age-adjusted definition, with the top 10% of the mGFR for each 10 year age group at baseline. Baseline and follow-up urine albumin-to-creatinine ratio (uACR) was collected, and linear regression was used to assess the associations of hyperfiltration and uACR at follow up.

RESULTS

407 individuals (33% men, mean age 47 years) were followed-up for a median of 3 years. At baseline, 234 had normoalbuminuria and 173 had albuminuria. Among participants with normoalbuminuria, those with mGFR ≥125 mL/min/1.73 m² had 32% higher uACR at follow-up (p = 0.08), and those with age-adjusted hyperfiltration had 60% higher uACR (p = 0.037) compared to those who had normofiltration. These associations were independent of uACR at baseline, but attenuated by HbA_1c. Associations were stronger among those without than those with albuminuria at baseline.

CONCLUSIONS

Although not available for assessment in current clinical practice, hyperfiltration may represent a marker of subsequent albuminuria progression among individuals who have not yet developed albuminuria.

Associations of renal function with diabetic retinopathy and visual impairment in type 2 diabetes: A multicenter nationwide cross-sectional study

BACKGROUND

Diabetic retinopathy (DR) separately has been noted as a major public health problem worldwide as well. Currently, many studies have demonstrated an association between diabetic nephropathy and DR in type 1 diabetes mellitus (T1DM) patients, but this association is less strong in T2DM. The evidence for an association between renal function and DR and visual impairment among T2DM patients is limited, particularly in the Asian population.

AIM

To assess the association between glomerular filtration rate (GFR) and DR, severe DR, and severe visual impairment among T2DM patients in Thailand.

METHODS

We conducted a nationwide cross-sectional study based on the DM/HT study of the Medical Research Network of the Consortium of Thai Medical Schools. This study evaluated adult T2DM patients from 831 public hospitals in Thailand in the year 2013. GFR was categorized into ≥ 90, 60-89, 30-59 and < 30 mL/min/1.73 m². The association between GFR and DR, severe DR, and severe visual impairment were assessed using multivariate logistic regression.

RESULTS

A total of 13192 T2DM patients with available GFR were included in the analysis. The mean GFR was 66.9 ± 25.8 mL/min/1.73 m². The prevalence of DR, proliferative DR, diabetic macular edema, and severe visual impairment were 12.4%, 1.8%, 0.2%, and 2.1%, respectively. Patients with GFR of 60-89, 30-59 and < 30 mL/min/1.73 m² were significantly associated with increased DR and severe DR when compared with patients with GFR of ≥ 90 mL/min/1.73 m². In addition, increased severe visual impairment was associated with GFR 30-59 and < 30 mL/min/1.73 m².

CONCLUSION

Decreased GFR was independently associated with increased DR, severe DR, and severe visual impairment. GFR should be monitored in diabetic patients for DR awareness and prevention.

Relationship between High Level of Estimated Glomerular Filtration Rate and Contrast-Induced Acute Kidney Injury in Patients who Underwent an Emergency Percutaneous Coronary Intervention

Background

Mounts of studies have shown that low estimated glomerular filtration rate (eGFR) is associated with increased risk of adverse outcomes in patients with coronary artery disease. However, high level of eGFR was less reported. In the study, we aimed to explore the relationship between the baseline eGFR, especially the high level, and contrast-induced acute kidney injury (CI-AKI) in a Chinese population who underwent an emergency percutaneous coronary intervention (PCI).

Methods

Patients who underwent an emergency PCI from 2013 to 2015 were enrolled and divided into five groups as eGFR decreasing. Baseline characteristics were collected and analyzed. The rates of CI-AKI and the composite endpoint (including nonfatal myocardial infarction, revascularization, stroke, and all-cause death) at 6- and 12-month follow-up were compared. Logistic analysis for CI-AKI was performed.

Results

A total of 1061 patients were included and the overall CI-AKI rate was 22.7% (241/1061). The separate rates were 77.8% (7/9) in Group 1 (eGFR ≥120 ml·min^-1·1.73 m^-2), 26.0% (118/454) in Group 2 (120 ml·min^-1·1.73 m^-2> eGFR ≥90 ml·min^-1·1.73m^-2), 18.3% (86/469) in Group 3 (90 ml·min^-1·1.73 m^-2> eGFR ≥60 ml·min^-1·1.73 m^-2), 21.8% (26/119) in Group 4 (60 ml·min^-1·1.73 m^-2> eGFR ≥30 ml·min^-1·1.73 m^-2), and 40.0% (4/10) in Group 5 (eGFR <30 ml·min^-1·1.73 m^-2), with statistical significance (χ² = 25.19, P < 0.001). The rates of CI-AKI in five groups were 77.8%, 26.0%, 18.3%, 21.8%, and 40.0%, respectively, showing a U-typed curve as eGFR decreasing (the higher the level of eGFR, the higher the CI-AKI occurrence in case of eGFR ≥60 ml·min^-1·1.73 m^-2). The composite endpoint rates in five groups were 0, 0.9%, 2.1%, 6.7%, and 0 at 6-month follow-up, respectively, and 0, 3.3%, 3.4%, 16.0%, and 30.0% at 12-month follow-up, respectively, both with significant differences (χ² = 16.26, P = 0.009 at 6-month follow-up, and χ² = 49.05, P < 0.001 at 12-month follow-up). The logistic analysis confirmed that eGFR was one of independent risk factors of CI-AKI in emergency PCI patients.

Conclusions

High level of eGFR might be associated with increased risk of CI-AKI in patients with emergency PCI, implying for future studies and risk stratification in clinical practice.

Long-term prospective observation suggests that glomerular hyperfiltration is associated with rapid decline in renal filtration function: A multiethnic study

AIM

Glomerular hyperfiltration usually occurs early in development of kidney complications in diabetes. To understand hyperfiltration as a marker of renal disease progression in type 2 diabetes mellitus, we aimed to examine association between glomerular hyperfiltration (estimated glomerular filtration rate ⩾ 120 mL/min/1.73 m²) and rapid renal decline (annual estimated glomerular filtration rate loss ⩾ 3 mL/min/1.73 m²).

METHODS

This was a prospective cohort comprising 1014 patients with type 2 diabetes mellitus attending a Diabetes Centre of a regional hospital in 2002-2014. A separate prospective cohort, comprising 491 patients who attended Diabetes Centre or primary-care polyclinics, was used for validation. We performed binary mediation analysis to examine role of hyperfiltration on relationship between baseline haemoglobin A1c and rapid renal decline.

RESULTS

Among patients in discovery cohort, 5.2% had baseline hyperfiltration. Over mean follow-up of 6 years, 22.9% had rapid glomerular filtration rate decline. Baseline hyperfiltration was significantly associated with greater odds of rapid renal decline after adjusting for demographics, diabetes duration and clinical covariates (odds ratio: 2.57; 95% confidence interval: 1.21-5.46; p = 0.014). Similar finding was found in validation cohort (odds ratio: 2.98; 95% confidence interval: 1.06-8.42; p = 0.034). Hyperfiltration significantly accounted for 35.3% of association between increasing baseline haemoglobin A1c and rapid renal decline.

CONCLUSION

Glomerular hyperfiltration is an independent risk factor of rapid renal decline. It mediates the association between increasing haemoglobin A1c and rapid renal decline.

Diabetes and Trajectories of Estimated Glomerular Filtration Rate: A Prospective Cohort Analysis of the Atherosclerosis Risk in Communities Study

OBJECTIVE

To characterize long-term kidney disease trajectories in persons with and without diabetes in a general population.

RESEARCH DESIGN AND METHODS

We classified 15,517 participants in the community-based Atherosclerosis Risk in Communities (ARIC) study by diabetes status at baseline (1987-1989; no diabetes, undiagnosed diabetes, and diagnosed diabetes). We used linear mixed models with random intercepts and slopes to quantify estimated glomerular filtration rate (eGFR) trajectories at four visits over 26 years.

RESULTS

Adjusted mean eGFR decline over the full study period among participants without diabetes was -1.4 mL/min/1.73 m2/year (95% CI -1.5 to -1.4), with undiagnosed diabetes was -1.8 mL/min/1.73 m2/year (95% CI -2.0 to -1.7) (difference vs. no diabetes, P < 0.001), and with diagnosed diabetes was -2.5 mL/min/1.73 m2/year (95% CI -2.6 to -2.4) (difference vs. no diabetes, P < 0.001). Among participants with diagnosed diabetes, risk factors for steeper eGFR decline included African American race, APOL1 high-risk genotype, systolic blood pressure ≥140 mmHg, insulin use, and higher HbA1c.

CONCLUSIONS

Diabetes is an important risk factor for kidney function decline. Those with diagnosed diabetes declined almost twice as rapidly as those without diabetes. Among people with diagnosed diabetes, steeper declines were seen in those with modifiable risk factors, including hypertension and glycemic control, suggesting areas for continued targeting in kidney disease prevention.

Renal Effects of Incretin-Based Diabetes Therapies: Pre-clinical Predictions and Clinical Trial Outcomes

PURPOSE OF REVIEW

The purpose of this review is to correlate predictions based on pre-clinical data with outcomes from clinical trials that examine the effects of incretin-based diabetes treatments on the kidney. The incretin-based treatments include agonists of the glucagon-like peptide 1 receptor (GLP-1R) and inhibitors of the enzyme, dipeptidyl peptidase-4 (DPP-4). In addition, what is known about the incretin-based therapies will be compared to what is known about the renal effects of SGLT2 inhibitors.

RECENT FINDINGS

Large-scale clinical trials have shown that SGLT2 inhibitors reduce albuminuria and preserve estimated glomerular filtration rate (eGFR) in patients with diabetic nephropathy. A concise and plausible hemodynamic mechanism is supported by pre-clinical research on the physiology and pharmacology of SGLT2. Large-scale clinical trials have shown that incretin-based therapies mitigate albuminuria but have not shown beneficial effects on eGFR. Research on the incretin-based therapies has yielded a diverse array of direct effects throughout the body, which fuels speculation as to how these drugs might benefit the diabetic kidney and affect its function(s). But in vivo experiments have yet to confirm that the proposed mechanisms underlying emergent phenomena, such as proximal tubular fluid reabsorption, are the ones predicted by cell and molecular experiments. There may be salutary effects of incretin-based treatments on the diabetic kidney, but the system is complex and not amenable to simple explanation or prior prediction. This contrasts with the renal effects of SGLT2 inhibitors, which can be explained concisely.

Patients with type 2 diabetes having higher glomerular filtration rate showed rapid renal function decline followed by impaired glomerular filtration rate: Japan Diabetes Complications Study

AIMS

The Japan Diabetes Complications Study (JDCS), a nation-wide, multicenter, prospective study of patients with type 2 diabetes, reported that hemoglobin A_1c (HbA_1c), systolic blood pressure, and smoking were risk factors for the onset of macroalbuminuria. This study explored the risk factors for glomerular filtration rate (GFR) decline in the JDCS patients.

METHODS

We examined the 1407 JDCS patients (667 women, mean age 59years, 974 normoalbuminuria, 433 microalbuminuria) whose urinary albumin-to-creatinine ratio (UACR) and estimated GFR (eGFR) were determined at baseline with an 8-year follow-up. We divided all the patients into four groups according to baseline eGFR: G1 (120≤eGFR), G2 (90≤eGFR<120), G3 (60≤eGFR<90), G4 (eGFR<60).

RESULTS

The eGFRs in groups G1 and G2 decreased at follow-up compared to those at the baseline. The risk of annual eGFR decline rate≥3ml/min/1.73m² (rapid decliners) increased as the baseline eGFR increased. Advanced age, high HbA_1c, and UACR, or diabetic retinopathy at baseline were risk factors for the rapid decliners. Especially the G1 group had a significant risk for the rapid decliners. The frequency of the patients with GFR<60ml/min/1.73m² at the follow-up amounted to 31.1% in the rapid decliners, which was higher than 12% in the non-rapid decliners.

CONCLUSIONS

In normo- and microalbuminuric patients with type 2 diabetes, extra careful attention should be paid to patients with eGFR ≥120ml/min/1.73m² to detect cases with rapidly decreased GFR under the normal range.

Glomerular Hyperfiltration in Diabetes: Mechanisms, Clinical Significance, and Treatment

An absolute, supraphysiologic elevation in GFR is observed early in the natural history in 10%-67% and 6%-73% of patients with type 1 and type 2 diabetes, respectively. Moreover, at the single-nephron level, diabetes-related renal hemodynamic alterations-as an adaptation to reduction in functional nephron mass and/or in response to prevailing metabolic and (neuro)hormonal stimuli-increase glomerular hydraulic pressure and transcapillary convective flux of ultrafiltrate and macromolecules. This phenomenon, known as glomerular hyperfiltration, classically has been hypothesized to predispose to irreversible nephron damage, thereby contributing to initiation and progression of kidney disease in diabetes. However, dedicated studies with appropriate diagnostic measures and clinically relevant end points are warranted to confirm this assumption. In this review, we summarize the hitherto proposed mechanisms involved in diabetic hyperfiltration, focusing on ultrastructural, vascular, and tubular factors. Furthermore, we review available evidence on the clinical significance of hyperfiltration in diabetes and discuss currently available and emerging interventions that may attenuate this renal hemodynamic abnormality. The revived interest in glomerular hyperfiltration as a prognostic and pathophysiologic factor in diabetes may lead to improved and timely detection of (progressive) kidney disease, and could provide new therapeutic opportunities in alleviating the renal burden in this population.

Renal and Systemic Effects of Calorie Restriction in Patients With Type 2 Diabetes With Abdominal Obesity: A Randomized Controlled Trial

In individuals with type 2 diabetes with abdominal obesity, hyperfiltration is a risk factor for accelerated glomerular filtration rate (GFR) decline and nephropathy. In this academic, single-center, parallel-group, prospective, randomized, open-label, blinded end point trial, consenting patients with type 2 diabetes aged >18 years, with waist circumference >94 (males) or >80 (females) cm, serum creatinine <1.2 mg/dL, and normoalbuminuria were randomized (1:1) with permuted blocks to 6 months of a 25% calorie restricted (CR) or standard diet (SD). Primary outcome was measured GFR (iohexol plasma clearance). Analyses were by modified intention to treat. At 6 months, GFR significantly decreased in 34 patients on CR and did not change appreciably in 36 on SD. Changes were significantly different between the groups. GFR and body weight reduction were correlated. GFR reduction was larger in hyperfiltering (GFR >120 mL/min) than nonhyperfiltering patients and was associated with BMI, waist circumference, blood pressure, heart rate, HbA_1c, blood glucose, LDL-to-HDL cholesterol ratio, C-reactive protein, angiotensin II, and albuminuria reduction and with increased glucose disposal rate (measured by hyperinsulinemic-euglycemic clamps). Protein and sodium intake and concomitant treatments were similar between the groups. CR was tolerated well. In patients with type 2 diabetes with abdominal obesity, CR ameliorates glomerular hyperfiltration, insulin sensitivity, and other cardiovascular risk factors, effects that might translate into long-term nephro- and cardioprotection.

Predictors of Renal Function Decline in Chinese Patients with Type 2 Diabetes Mellitus and in a Subgroup of Normoalbuminuria: A Retrospective Cohort Study

BACKGROUND

Risk factors related to renal function decline in type 2 diabetes mellitus (T2DM) remain uncertain. This study aimed to investigate risk factors in relation to renal function decline in patients with T2DM and in a subgroup of patients with normoalbuminuria.

METHODS

This study was a retrospective cohort study, which included 451 patients with T2DM aged 63 ± 14 years admitted to a tertiary hospital in Beijing, China, between April and December 2010 and followed up for 6-60 months. Endpoint was renal function decline, defined as estimated glomerular filtration rate less than 60 mL/min 1.73 m² or at least twofold increase of serum creatinine. Cox proportional hazards analysis was used to estimate hazard ratios (HRs) for candidate risk factors of renal function decline.

RESULTS

After a median follow-up of 3.3 years, 94 (20.8%) patients developed renal function decline. Increased age (HR, 1.045; 95% CI, 1.020-1.070), albuminuria (HR, 1.956; 95%CI, 1.271-3.011), mild renal dysfunction (HR, 4.521; 95%CI, 2.734-7.476), hyperfiltration (HR, 3.897; 95%CI, 1.572-9.663), and increased hemoglobin A1c (HR, 1.128; 95%CI, 1.020-1.249) were identified as major risk factors. Among a subgroup of 344 patients with normoalbuminuria at baseline, 53 (15.4%) patients developed renal function decline. Increased age (HR, 1.089; 95%CI, 1.050-1.129), mild renal dysfunction (HR, 4.667; 95%CI, 2.391-9.107), hyperfiltration (HR, 5.677; 95%CI, 1.544-20.872), smoking (HR, 2.886; 95%CI, 1.370-6.082), higher pulse pressure (HR, 1.022; 95%CI, 1.004-1.040), and increased fasting glucose (HR, 1.104; 95%CI, 1.020-1.194) were major risk factors.

CONCLUSIONS

Risk factors of diabetic renal impairment in T2DM should be screened and evaluated at an early stage of diabetes. Albuminuria, mild renal dysfunction, hyperfiltration, increased blood glucose, increased pulse pressure, and smoking were all predictors for diabetic renal impairment and interventions that focus on these risk factors may reduce further decline in renal function.

Clinical predictive factors in diabetic kidney disease progression

Diabetic kidney disease (DKD) represents a major component of the health burden associated with type 1 and type 2 diabetes. Recent advances have produced an explosion of ‘novel’ assay‐based risk markers for DKD, though clinical use remains restricted. Although many patients with progressive DKD follow a classical albuminuria‐based pathway, non‐albuminuric DKD progression is now well recognized. In general, the following clinical and biochemical characteristics have been associated with progressive DKD in both type 1 and type 2 diabetes: increased hemoglobin A1c, systolic blood pressure, albuminuria grade, early glomerular filtration rate decline, duration of diabetes, age (including pubertal onset) and serum uric acid; the presence of concomitant microvascular complications; and positive family history. The same is true in type 2 diabetes for male sex category, in patients following an albuminuric pathway to DKD, and also true for the presence of increased pulse wave velocity. The following baseline clinical characteristics have been proposed as risk factors for DKD progression, but with further research required to assess the nature of any relationship: dyslipidemia (including low‐density lipoprotein, total and high‐density lipoprotein cholesterol); elevated body mass index; smoking status; hyperfiltration; decreases in vitamin D, hemoglobin and uric acid excretion (all known consequences of advanced DKD); and patient test result visit‐to‐visit variability (hemoglobin A1c, blood pressure and high‐density lipoprotein cholesterol). The development of multifactorial ‘renal risk equations’ for type 2 diabetes has the potential to simplify the task of DKD prognostication; however, there are currently none for type 1 diabetes‐specific populations. Significant progress has been made in the prediction of DKD progression using readily available clinical data, though further work is required to elicit the role of several variables, and to consolidate data to facilitate clinical implementation.

Association of estimated glomerular filtration rate with all-cause and cardiovascular mortality: the role of malnutrition-inflammation-cachexia syndrome

BACKGROUND

Previous studies have demonstrated that high estimated glomerular filtration rate (eGFR) is paradoxically associated with an increased risk of mortality, and the association becomes more predominant in older people. However, the role of malnutrition-inflammation-cachexia syndrome (MICS) in the association between eGFR and mortality has never been explored.

METHODS

We conducted a community-based cohort study using data from the Taipei City Elderly Health Examination Database, collected during the period 2001-10. All participants aged ≥65 years were included and stratified by the absence or presence of MICS, which is defined as the presence of at least one of the following markers: body mass index <22 kg/m(2), serum albumin <3.0 mg/dL, or Geriatric Nutritional Risk Index (GNRI) <98. The study endpoints were all-cause and cardiovascular mortality.

RESULTS

A total of 131 354 participants were identified and categorized according to the chronic kidney disease stage based on eGFR. Compared with the reference eGFR of 60-89 mL/min/1.73 m(2), the overall and cardiovascular mortality risks were markedly high in the groups with eGFR of <30 mL/min/1.73 m(2) [overall: adjusted hazard ratio (aHR), 1.86; 95% confidence interval (CI), 1.72-2.00; cardiovascular: aHR, 1.87; 95% CI, 1.60-2.19] and ≥90 mL/min/1.73 m(2) (overall: aHR, 1.23; 95% CI, 1.13-1.34; cardiovascular: aHR, 1.28; 95% CI, 1.06-1.54). In the absence of MICS, high eGFR was associated with lower mortality risk (aHR, 0.71; 95% CI, 0.62-0.80), and the U-shaped relationship disappeared. Subgroup analyses produced consistent results.

CONCLUSIONS

MICS could influence the association observed between high eGFR and mortality in older people, particularly in those with low body mass index, albumin level, GNRI, and very low serum creatinine level.

Hyperfiltration in Indigenous Australians with and without diabetes

BACKGROUND

Hyperfiltration (HF) has been linked to the development of diabetic kidney disease (DKD), but the causative or predictive role of HF in the pathogenesis of DKD still remains unclear. To date, there have been no studies of HF in Indigenous Australians, a population with high rates of both diabetes and end-stage kidney disease. We aimed to compare the characteristics and frequency of HF in Indigenous Australians with and without type 2 diabetes.

METHODS

Indigenous Australian participants, recruited across five pre-defined strata of health, diabetes status and kidney function, had a reference glomerular filtration rate (GFR) measured using plasma disappearance of iohexol [measured GFR(mGFR)] over 4 h. HF was defined in various ways: (i) mGFR > 144 mL/min/1.73 m(2), which is mGFR > 1.96 × SD above the mean of the mGFR in non-diabetic participants with normal albuminuria and normal renal function (mGFR > 90 mL/min/1.73 m(2)); (ii) age-corrected mGFR (>144 mL/min/1.73 m(2)) to account for the effect of ageing on GFR in subjects over 40 years of age with cut-off 1 mL/min/1.73 m(2) lower for every year; (iii) mGFR > 144 mL/min, without correction for body surface area or age, as well as (iv) mGFR > 125 mL/min/1.73 m(2), without adjustment for age.

RESULTS

A total of 383 Indigenous participants, 125 with and 258 without diabetes, with mGFR > 90 mL/min/1.73 m(2) were studied. The proportion of participants with HF was 7% using mGFR > 144 mL/min/1.73 m(2), 11% using the age-adjusted definition, 19% using mGFR > 144 mL/min and 27% using mGFR > 125 mL/min/1.73 m(2). Diabetes was more common in participants with HF (40-74%) compared with normofiltering participants (28-31%), regardless of the definition of HF.

CONCLUSIONS

HF exists in Indigenous Australians with and without diabetes. A greater proportion of participants had diabetes in HF group compared with normofiltration group. Long-term follow-up of this cohort is necessary to determine if HF plays a role in the development of DKD and non-DKD.

Longitudinal Study of the Decline in Renal Function in Healthy Subjects

BACKGROUND

Chronic kidney disease is an important concern in preventive medicine, but the rate of decline in renal function in healthy population is not well defined. The purpose of this study was to determine reference values for the estimated glomerular filtration rate (eGFR) and rate of decline of eGFR in healthy subjects and to evaluate factors associated with this decline using a large cohort in Japan.

METHODS

Retrospective cross-sectional and longitudinal studies were performed with healthy subjects aged ≥18 years old who received a medical checkup. Reference values for eGFR were obtained using a nonparametric method and those for decline of eGFR were calculated by mixed model analysis. Relationships of eGFR decline rate with baseline variables were examined using a linear least-squares method.

RESULTS

In the cross-sectional study, reference values for eGFR were obtained by gender and age in 72,521 healthy subjects. The mean (±SD) eGFR was 83.7±14.7 ml/min/1.73 m2. In the longitudinal study, reference values for eGFR decline rate were obtained by gender, age, and renal stage in 45,586 healthy subjects. In the same renal stage, there was little difference in the rate of decline regardless of age. The decline in eGFR depended on the renal stage and was strongly related to baseline eGFR, with a faster decline with a higher baseline eGFR and a slower decline with a lower baseline eGFR. The mean (±SD) eGFR decline rate was ‒1.07±0.42 ml/min/1.73 m2/year (‒1.29±0.41%/year) in subjects with a mean eGFR of 81.5±11.6 ml/min/1.73 m2.

CONCLUSIONS

The present study clarified for the first time the reference values for the rate of eGFR decline stratified by gender, age, and renal stage in healthy subjects. The rate of eGFR decline depended mainly on baseline eGFR, but not on age, with a slower decline with a lower baseline eGFR.

The Relationship between Estimated Glomerular Filtration Rate and Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment and blindness in working-aged people. Several studies have suggested that glomerular filtration rate (GFR) was correlated with DR. This is a hospital-based study and the aim of it was to examine the relationship between the GFR and DR in patients with type 2 diabetes mellitus (T2DM). We used CKD-EPI equation to estimate GFR and SPSS 19.0 and EmpowerStats software to assess their relationship. Among the 1613 participants (aged 54.75 ± 12.19 years), 550 (34.1%) patients suffered from DR. The multivariate analysis revealed that the risk factors for DR include age (P < 0.001, OR = 0.940), duration of diabetes (P < 0.001, OR = 1.163), hemoglobin A1c (P = 0.007, OR = 1.224), systolic blood pressure (P < 0.001, OR = 1.032), diastolic blood pressure (P = 0.007, OR = 0.953), high density lipoprotein cholesterol (P = 0.024, OR = 3.884), and eGFR (P = 0.010, OR = 0.973). Through stratified analysis and saturation effect analysis, our data suggests that eGFR of 99.4 mL/min or lower might imply the early stage of DR in diabetic patients. Thus, the evaluation of eGFR has clinical significance for the early diagnosis of DR.

The impact of hyperfiltration on the diabetic kidney

More than two decades ago, hyperfiltration (HF) in diabetes was postulated to be a maladaptive response observed early in the course of diabetic kidney disease (DKD), which may eventually predispose to irreversible damage to nephrons and development of progressive renal disease. Despite this, the potential mechanisms leading to renal HF in diabetes are not fully understood, although several hypotheses have been proposed, including alterations in glomerular haemodynamic function and tubulo-glomerular feedback. Furthermore, the role of HF as a causative factor in renal disease progression is still unclear and warrants further prospective longer-term studies. Although HF has been entrenched as the first stage in the classic albuminuric pathway to end-stage renal disease in DKD, and HF has been shown to predict the progression of albuminuria in many, but not all studies, the concept that HF predisposes to the development of chronic kidney disease (CKD) stage 3, that is, glomerular filtration rate (GFR) decline to<60mL/min/1.73m(2), remains to be proved. Further long-term studies of GFR gradients therefore are required to establish whether HF ultimately leads to decreased kidney function, after adjustment for glycaemic control and other confounders. Whether reversal of HF with therapeutic agents is protective against reducing the risk of development of albuminuria and renal impairment is also worth investigating in prospective randomized trials.

Novel urinary biomarkers in early diabetic kidney disease

In diabetic kidney disease, detection of urinary albumin is recommended to aid in diagnosis, evaluate disease severity, and determine effects of therapy. However, because typical histopathologic changes in diabetic kidney disease or early progressive renal decline may occur in patients with normoalbuminuria, urinary albumin may not be sufficient to identify patients with early-stage diabetic kidney disease or to predict its progression. Therefore, intensive efforts have been made to identify novel noninvasive urinary biomarkers to discriminate patients with a higher risk of end-stage renal failure. Because diabetic kidney disease progression is associated with the extent of histologic changes in the glomeruli and the degree of tubulointerstitial changes, urinary biomarkers that accurately reflect the degree of histopathologic damage may be excellent biomarkers. This review article summarizes the clinical significance of new urinary biomarkers in the early detection of diabetic kidney disease.

An epidemiologic model to project the impact of changes in glomerular filtration rate on quality of life and survival among persons with chronic kidney disease

PURPOSE

Predicting the timing and number of end-stage renal disease (ESRD) cases from a population of individuals with pre-ESRD chronic kidney disease (CKD) has not previously been reported. The objective is to predict the timing and number of cases of ESRD occurring over the lifetime of a cohort of hypothetical CKD patients in the US based on a range of baseline estimated glomerular filtration rate (eGFR) values and varying rates of eGFR decline.

METHODS

A three-state Markov model - functioning kidney, ESRD, and death - with an annual cycle length is used to project changes in baseline eGFR on long-term health outcomes in a hypothetical cohort of CKD patients. Using published eGFR-specific risk equations and adjusting for predictive characteristics, the probability of ESRD (eGFR <10), time to death, and incremental cost-effectiveness ratios for hypothetical treatments (costing US$10, $5, and $2/day), are projected over the cohort's lifetime under two scenarios: an acute drop in eGFR (mimicking acute kidney injury) and a reduced hazard ratio for ESRD (mimicking an effective intervention).

RESULTS

Among CKD patients aged 50 years, an acute eGFR decrement from 45 mL/minute to 35 mL/minute yields decreases of 1.6 life-years, 1.5 quality-adjusted life-years (QALYs), 0.8 years until ESRD, and an increase of 183 per 1,000 progressing to ESRD. Among CKD patients aged 60 years, lowering the hazard ratio of ESRD to 0.8 yields values of 0.2, 0.2, 0.2, and 46 per 1,000, respectively. Incremental cost-effectiveness ratios are higher (ie, less favorable) for higher baseline eGFR, indicating that interventions occurring later in the course of disease are more likely to be economically attractive.

CONCLUSION

Both acute kidney injury and slowing the rate of eGFR decline produce substantial shifts in expected numbers and timing of ESRD among CKD patients. This model is a useful tool for planning management of CKD patients.

Dynamic and dual effects of glycated hemoglobin on estimated glomerular filtration rate in type 2 diabetic outpatients

BACKGROUND

Diabetic nephropathy is the leading cause of incident end-stage renal disease in Taiwan. Previous studies on the consistent benefits of glycemic control in diabetic nephropathy focused primarily on delaying microalbuminuria. However, this effect on glomerular filtration rate (GFR) remains controversial. This study aims to establish a model that explains the controversial effects of glycated hemoglobin (HbA1C) on GFR.

METHODS

This retrospective cohort study followed subjects with type 2 diabetes mellitus, who were enrolled between June 2006 and December 2006, for 4 years. The effects of HbA1C on estimated GFR (eGFR) were examined both cross-sectionally and longitudinally. The dual effects of HbA1C on eGFR, and how renal function interferes with these effects, were investigated.

RESULTS

Of the 1,992 subjects enrolled, 1,699 completed the follow-up. HbA1C was positively correlated with eGFR in the cross-sectional study (β coefficient = 1.44, 95% CI: 0.71-2.17, p = 0.0001). In the longitudinal study, higher baseline HbA1C resulted in a greater decline in eGFR. The annual eGFR decline rates were -1.89, -1.29, and -0.68 ml/min/1.73 m(2)/year for baseline HbA1C >9, 7 to ≤9, and ≤7%, respectively. The eGFR value was simultaneously affected by concurrent (β coefficient = 0.78, 95% CI: 0.48-1.08, p < 0.0001) and preceding HbA1C (-0.52, -0.82 to -0.23, p < 0.0001). The positive effects of concurrent HbA1C on eGFR reached statistical significance at all stages of chronic kidney disease (CKD); however, the negative effects of preceding HbA1C only applied to CKD stages 3 and 4.

CONCLUSIONS

We developed a new model that demonstrates how preceding and concurrent HbA1C simultaneously affect eGFR in opposing ways. The dynamic effects varied among different CKD stages. The deterioration in eGFR at CKD stages 3 and 4 may be postponed by intensive glycemic control. Further prospective studies may be necessary to clarify the specific CKD stage(s) that will benefit from intensive glycemic control.

Correlation of high urinary Smad1 level with glomerular hyperfiltration in type 2 diabetes mellitus

The aim of this study was to assess the relationship between urinary Smad1 and glomerular hyperfiltration (GHF) in type 2 diabetes mellitus (T2DM), and to explore the factors related to the urinary Smad1 in T2DM. The reference value of the estimated glomerular filtration rate (eGFR) was determined in 248 healthy individuals. 30 patients with GHF, 58 patients with norm-GFR T2DM, and 24 healthy patients who served as controls were recruited. Urinary Smad1, fasting plasma glucose (FPG), fasting serum C-Peptide (C-P), hemoglobin A1C (HbA1c), cystatin C, and other chemistry laboratory parameters of T2DM participants and controls were measured. Patients with GHF had higher levels of urinary Smad1 than the control group, and those with norm-GFR. For T2DM patients with body mass index, age, and gender adjustments, urinary Smad1 was positively correlated with FPG, HbA1C, and eGFR, but negatively correlated with fasting serum C-P. Multivariate linear regression analysis demonstrated that eGFR, HbA1C, and fasting serum C-P were independently associated with urinary Smad1. High levels of urinary Smad1 were found in GHF patients with T2DM, which may be another potential mechanism of GHF in relation to diabetic nephropathy.

Relationship between BNP level and renal function in diabetic nephropathy with microalbuminuria

AIMS

We examined the relationship between the brain natriuretic peptide (BNP) level and renal function in diabetic nephropathy with microalbuminuria.

METHODS

The subjects were 97 Japanese type 2 diabetes mellitus outpatients with microalbuminuria. Associations between the annual rate of decline in estimated glomerular filtration rate (eGFR) and various metabolic parameters at baseline (BMI, systolic blood pressure, HbA1c, LDL cholesterol, urine albumin-creatinine ratio, BNP and eGFR) were examined.

RESULTS

Among the baseline factors, eGFR and BNP had significant associations with the annual rate of decline in eGFR in Pearson correlation analysis (r=0.295, p=0.003; r=0.223, p=0.028, respectively). Multiple linear regression analysis also showed the significance of baseline eGFR and BNP as independent predictors of renal function (β=0.340, p=0.001; β=0.278, p=0.005, respectively). In multivariate logistic regression analysis, eGFR and BNP were independently associated with the risk of a decline in GFR (p=0.003, p=0.011, respectively). ROC curve analysis showed a cutoff value of BNP is 17.0 pg/mL for predicting a decline in GFR.

CONCLUSIONS

The BNP level at baseline is an independent predictor of the annual rate of decline in eGFR. Therefore, monitoring of BNP can play an important role in management of diabetic nephropathy.

Glomerular hyperfiltration and renal disease progression in type 2 diabetes

OBJECTIVE

To describe the prevalence and determinants of hyperfiltration (glomerular filtration rate [GFR] ≥120 mL/min/1.73 m(2)), GFR decline, and nephropathy onset or progression in type 2 diabetic patients with normo- or microalbuminuria.

RESEARCH DESIGN AND METHODS

We longitudinally studied 600 hypertensive type 2 diabetic patients with albuminuria <200 μg/min and who were retrieved from two randomized trials testing the renal effect of trandolapril and delapril. Target blood pressure (BP) was <120/80 mmHg, and HbA(1c) was <7%. GFR, albuminuria, and glucose disposal rate (GDR) were centrally measured by iohexol plasma clearance, nephelometry in three consecutive overnight urine collections, and hyperinsulinemic euglycemic clamp, respectively.

RESULTS

Over a median (range) follow-up of 4.0 (1.7-8.1) years, GFR declined by 3.37 (5.71-1.31) mL/min/1.73 m(2) per year. GFR change was bimodal over time: a larger reduction at 6 months significantly predicted slower subsequent decline (coefficient: -0.0054; SE: 0.0009), particularly among hyperfiltering patients. A total of 90 subjects (15%) were hyperfiltering at inclusion, and 11 of 47 (23.4%) patients with persistent hyperfiltration progressed to micro- or macroalbuminuria versus 53 (10.6%) of the 502 who had their hyperfiltration ameliorated at 6 months or were nonhyperfiltering since inclusion (hazard ratio 2.16 [95% CI 1.13-4.14]). Amelioration of hyperfiltration was independent of baseline characteristics or ACE inhibition. It was significantly associated with improved BP and metabolic control, amelioration of GDR, and slower long-term GFR decline on follow-up.

CONCLUSIONS

Despite intensified treatment, patients with type 2 diabetes have a fast GFR decline. Hyperfiltration affects a subgroup of patients and may contribute to renal function loss and nephropathy onset or progression. Whether amelioration of hyperfiltration is renoprotective is worth investigating.

The association of genetic variants of type 2 diabetes with kidney function

Type 2 diabetes is highly prevalent and is the major cause of progressive chronic kidney disease in American Indians. Genome-wide association studies identified several loci associated with diabetes but their impact on susceptibility to diabetic complications is unknown. We studied the association of 18 type 2 diabetes genome-wide association single-nucleotide polymorphisms (SNPs) with estimated glomerular filtration rate (eGFR; MDRD equation) and urine albumin-to-creatinine ratio in 6958 Strong Heart Study family and cohort participants. Center-specific residuals of eGFR and log urine albumin-to-creatinine ratio, obtained from linear regression models adjusted for age, sex, and body mass index, were regressed onto SNP dosage using variance component models in family data and linear regression in unrelated individuals. Estimates were then combined across centers. Four diabetic loci were associated with eGFR and one locus with urine albumin-to-creatinine ratio. A SNP in the WFS1 gene (rs10010131) was associated with higher eGFR in younger individuals and with increased albuminuria. SNPs in the FTO, KCNJ11, and TCF7L2 genes were associated with lower eGFR, but not albuminuria, and were not significant in prospective analyses. Our findings suggest a shared genetic risk for type 2 diabetes and its kidney complications, and a potential role for WFS1 in early-onset diabetic nephropathy in American Indian populations.

Changes of the tubular markers in type 2 diabetes mellitus with glomerular hyperfiltration

AIM

To assess whether glomerular hyperfiltration (GHF) could result in renal tubular damage in type 2 diabetes mellitus (T2DM) patients.

METHODS

Reference value of estimated glomerular filtration rate (eGFR) was determined in 248 healthy individuals based on serum CysC levels. GHF was defined as an eGFR exceeding the sex-specific 97.5th percentile in non-diabetic individuals. In the present study, 30 with GHF, 58 with norm-GFR T2DM, and 24 healthy controls were recruited. Tubular markers, such as urinary N-acetyl-β-D-glucosaminidase (NAG) and kidney injury molecule 1 (KIM-1), as well as serum and urinary neutrophil gelatinase-associated lipocalin (NGAL), were measured and compared. The correlation of these markers with eGFR was analyzed in the GHF group.

RESULTS

The GHF group had higher urinary NGAL and KIM-1 levels but lower serum NGAL level than the norm-GFR and control groups. Slightly decreased serum NGAL and increased urinary NGAL levels were also noted in the norm-GFR group compared with those of the controls. There was no statistical difference in the urinary NAG values among the three groups. Correlation analysis showed that eGFR was positively related to fasting blood glucose (FBG), HbA1c, urinary NGAL, and KIM-1, but negatively with serum NGAL in the GHF group.

CONCLUSION

Higher urinary tubular damage markers were found in T2DM patients with GHF than the norm-GFR and control groups, probably a direct proof that GHF is a deleterious factor for diabetic nephropathy.

Higher estimated glomerular filtration rates may be associated with increased risk of adverse outcomes, especially with concomitant proteinuria

The estimated glomerular filtration rate (eGFR) is a powerful predictor of adverse outcomes, but most attention has focused on studies in the setting of reduced eGFR. Here we tested whether patients with an eGFR higher than 60-89.9 ml/min per 1.73 m(2) could also be at elevated risk of adverse outcomes. Further, we tested whether concomitant proteinuria further increases the risk of outcomes among individuals with an eGFR equal to or above 90 ml/min per 1.73 m(2), as it does for those with reduced eGFR. Using data from a population-based outpatient laboratory data set of 1,526,437 patients, we measured adjusted associations between eGFR calculated by the modification of diet in renal disease equation, urine dipstick proteinuria, and adverse clinical outcomes. The adjusted risk of all-cause mortality was lowest at an eGFR of 60-74.9 ml/min per 1.73 m(2) (referent) and increased at both lower and higher levels of eGFR. Specifically, the hazard ratio of death was 3.7 and 1.8 among patients with an eGFR equal to or above 105 and 90-104.9 ml/min per 1.73 m(2), respectively, compared to the referent group. Similar results were seen when the CKD-EPI equation (sensitivity analyses) was used to assess eGFR. Higher levels of eGFR were not associated with the risk of kidney failure or myocardial infarction. Thus, the presence and severity of proteinuria was significantly associated with graded increases in the risk of clinical outcomes for both lower and higher eGFR. We do not know, however, whether the finding at higher eGFR could be due to inadequacies of the eGFR formula at low serum creatinine levels.

Clinical outcome of renal tubular damage in chronic heart failure

AIMS

Both reduced glomerular filtration and increased urinary albumin excretion independently determine outcome in patients with chronic heart failure (HF). However, tubulo-interstitial injury might indicate renal damage, even in the presence of normal glomerular filtration. We studied the relationship between tubular damage, glomerular filtration, urinary albumin excretion, and outcome in HF patients.

METHODS AND RESULTS

In 2130 patients participating in the GISSI-HF trial, we measured urinary albumin-to-creatinine ratio (UACR), estimated glomerular filtration rate (eGFR), and three urinary markers of tubular damage: N-acetyl-beta-D-glucosaminidase (NAG), kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL). We assessed the relationship between the individual tubular damage markers and the combined endpoint of all-cause mortality and HF hospitalizations. Mean age was 67 ± 11 years, and 21% were female. Urinary NAG 13.7 (7.8-22) U/gCr, KIM-1 1939 (671-3871) ng/gCr, and NGAL 36 (14-94) µg/gCr were markedly elevated above normal levels. All individual tubular markers were independently associated with the combined endpoint: NAG: adjusted hazard ratio (HR) 1.22; 95% confidence interval (CI), 1.10-1.36; P< 0.001, KIM-1 HR 1.13; 95% CI, 1.02-1.24; P= 0.018 and NGAL HR 1.10; 95% CI, 1.00-1.20; P= 0.042; all per log standard deviation increase). Even in patients with a normal eGFR, increased tubular markers were related to a poorer outcome. The combination of impaired eGFR, increased UACR, and high NAG was associated with a HR of 3.00; 95% CI, 2.29-3.95; P< 0.001, compared with those without these abnormalities.

CONCLUSION

Tubular damage is related to a poor clinical outcome in HF patients even when eGFR is normal.

The clinical significance of hyperfiltration in diabetes

Glomerular filtration rate is commonly elevated in early diabetes and patients with this symptom are arbitrarily considered to have hyperfiltration. The prevalence of hyperfiltration in type 1 diabetes varies from less than 25% to more than 75%. The corresponding figures in type 2 diabetes are significantly lower, ranging between 0% and more than 40%. Several factors, methodological and biological, may contribute to the wide variation in estimates of hyperfiltration prevalence. Methodological differences in measurement and evaluation of GFR apply in particular to the handling of plasma disappearance curves of filtration markers. Biological factors that may influence GFR in the hyperfiltration range include glycaemic control, diabetes duration, BMI, sex, pubertal status in type 1 diabetes and age in type 2 diabetes. Hyperglycaemia may influence GFR and albuminuria, and may therefore confound the evaluation of hyperfiltration as an independent risk factor for diabetic nephropathy. Adequate assessment of the relationship between glycaemic control, GFR and AER therefore requires serial measurements of all three variables followed by multivariate analysis. A recent meta-analysis of ten type 1 diabetes studies concluded that the presence of hyperfiltration at baseline more than doubled the risk of developing micro- or macroalbuminuria at follow-up. However, not all studies allowed for confounding factors or regression dilution bias. Future studies will therefore need to address the independent role of hyperfiltration, not only in the evolution of albuminuria, but also in the subsequent decline of GFR.

Glomerular hyperfiltration and increased proximal sodium reabsorption in subjects with type 2 diabetes or impaired fasting glucose in a population of the African region

BACKGROUND. Glomerular hyperfiltration (GHF) is a well-recognized early renal alteration in diabetic patients. As the prevalence of GHF is largely unknown in populations in the African region with respect to normal fasting glucose (NFG), impaired fasting glucose (IFG) and type 2 diabetes [diabetes mellitus (DM)], we conducted a cross-sectional study in the Seychelles islands among families including at least one member with hypertension. METHODS. The glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and proximal tubular sodium reabsorption were measured using inulin, p-aminohippurate (PAH) and endogenous lithium clearance, respectively. Twenty-four-hour urine was collected on the preceding day. RESULTS. Of the 363 participants (mean age 44.7 years), 6.6% had IFG, 9.9% had DM and 63.3% had hypertension. The prevalence of GHF, defined as a GFR >140 ml/min, was 17.2%, 29.2% and 52.8% in NFG, IFG and DM, respectively (P trend <0.001). Compared to NFG, the adjusted odds ratio for GHF was 1.99 [95% confidence interval (CI) 0.73-5.44] for IFG and 5.88 (2.39-14.45) for DM. Lithium clearance and fractional excretion of lithium were lower in DM and IFG than NFG (P < 0.001). CONCLUSION. In this population of African descent, subjects with impaired fasting glucose or type 2 diabetes had a high prevalence of GHF and enhanced proximal sodium reabsorption. These findings provide further insight on the elevated incidence of nephropathy reported among African diabetic individuals.

Determinants of decline in glomerular filtration rate in nonproteinuric subjects with or without diabetes and hypertension

BACKGROUND AND OBJECTIVES

This study investigated whether the slope of estimated GFR is different between nonproteinuric subjects with and without diabetes, and what clinical factors are associated with the GFR slope.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

An observational cohort study was performed in 923 subjects, and the predictive value of baseline variables on the GFR slope was investigated.

RESULTS

On the basis of the median 3-yr follow-up and 7 measurements of GFR, GFR slope (%/yr, median and interquartile range) was significantly larger in subjects with diabetes (-2.39 (-4.86 to 0.15), n=729) than in those without diabetes (-1.02 (-4.28 to 1.37), n=194), and this difference remained significant with or without presence of hypertension. After adjustments for confounding factors, predictors of GFR decline were found to be baseline high values of glycosylated hemoglobin A1C(HbA1C), GFR, systolic blood pressure, and low plasma total protein in subjects with diabetes, whereas only the latter two were significant in subjects without diabetes. In subjects with diabetes, the high GFR was accounted for by high HbA1C at baseline, and the predictors of GFR decline differed between those with and without hypertension, or with high and low baseline GFR. Any combination of the predictors showed increased risk for GFR decline.

CONCLUSIONS

GFR slope is substantially affected by multiple factors at various stages. The degree of chronic hyperglycemia is likely to play a crucial role in elevating GFR and accelerating the decline in patients with type 2 diabetes even from the normoalbuminuric stage.

Is hyperfiltration associated with the future risk of developing diabetic nephropathy? A meta-analysis

AIMS/HYPOTHESIS

Glomerular hyperfiltration is a well-established phenomenon occurring early in some patients with type 1 diabetes. However, there is no consistent answer regarding whether hyperfiltration predicts later development of nephropathy. We performed a systematic review and meta-analysis of observational studies that compared the risk of developing diabetic nephropathy in patients with and without glomerular hyperfiltration and also explored the impact of baseline GFR.

METHODS

A systematic review and meta-analysis was carried out. Cohort studies in type 1 diabetic participants were included if they contained data on the development of incipient or overt nephropathy with baseline measurement of GFR and presence or absence of hyperfiltration.

RESULTS

We included ten cohort studies following 780 patients. After a study median follow-up of 11.2 years, 130 patients had developed nephropathy. Using a random effects model, the pooled odds of progression to a minimum of microalbuminuria in patients with hyperfiltration was 2.71 (95% CI 1.20-6.11) times that of patients with normofiltration. There was moderate heterogeneity (heterogeneity test p = 0.05, measure of degree of inconsistency = 48%) and some evidence of funnel plot asymmetry, possibly due to publication bias. The pooled weighted mean difference in baseline GFR was 13.8 ml min(-1) 1.73 m(-2) (95% CI 5.0-22.7) greater in the group progressing to nephropathy than in those not progressing (heterogeneity test p < 0.01).

CONCLUSIONS/INTERPRETATION

In published studies, individuals with glomerular hyperfiltration were at increased risk of progression to diabetic nephropathy using study level data. Further larger studies are required to explore this relationship and the role of potential confounding variables.

High-normal levels of albuminuria predict the development of micro- and macroalbuminuria and increased mortality in Brazilian Type 2 diabetic patients: an 8-year follow-up study

AIM

To analyse the risk factors for the development of micro- and macroalbuminuria and mortality rates in a cohort of normoalbuminuric Type 2 diabetes mellitus (DM) patients.

METHODS

In this prospective study, 193 Type 2 DM patients with urinary albumin excretion (UAE) < 20 microg/min, 96 men (50%), aged 56.5 +/- 9 years, were followed for a mean period of 8 +/- 3 years. UAE and estimated glomerular filtration rate (eGFR; Modification of Diet in Renal Disease) were measured. The outcomes were development of persistent micro- and macroalbuminuria and mortality.

RESULTS

Twenty patients were lost to follow-up. Of the 173 remaining patients, 33 (19%) died. The Cox analysis [hazard ratio (HR), 95% confidence interval] revealed that the baseline significant predictors of mortality were higher UAE [above median (5 microg/min); HR 2.7, 1.2-6.1; P = 0.02], male sex (HR 3.9, 1.7-9.2; P = 0.002), age (HR 1.6, 1.3-1.9; P = 0.0001), and fasting plasma glucose (HR 1.2, 1.1-1.3; P = 0.004). Smoking and eGFR were not significant in this model. Follow-up renal data were available for 158 patients: 34 (22%) progressed to microalbuminuria and seven (4%) to macroalbuminuria, and the baseline predictors were a higher UAE (> 5 microg/min, HR 2.5, 1.2-5.1; P = 0.02), presence of diabetic retinopathy (HR 2.5, 1.3-5.0; P = 0.009), fasting glucose (HR 1.1, 1.0-1.2; P = 0.015), and male sex (HR 2.2, 1.1-4.7; P = 0.04), independently of smoking and hypertension. Lower GFR (HR 0.98, 0.97-1.00; P = 0.07) was of borderline significance.

CONCLUSIONS

In normoalbuminuric Type 2 DM patients, the development of micro- or macroalbuminuria and mortality rates was independently and positively associated with higher levels of albuminuria, although still in the traditionally established normal range.

Normoalbuminuric renal-insufficient diabetic patients: a lower-risk group

OBJECTIVE

About 20% of diabetic patients with chronic kidney disease (CKD) detected from the new American Diabetes Association recommendations (albumin excretion rate >30 mg/24 h or estimated glomerular filtration rate [GFR] <60 ml/min per 1.73 m2) may be normoalbuminuric. Do the characteristics and outcome differ for subjects with and without albuminuria?

RESEARCH DESIGN AND METHODS

A total of 89 patients with diabetes and a modification of diet in renal disease (MDRD) estimated GFR (e-GFR) <60 ml/min per 1.73 m2 underwent a 51Cr-EDTA B-isotopic GFR determination and were followed up for 38 +/- 11 months.

RESULTS

The mean MDRD e-GFR (41.3 +/- 13.1 ml/min per 1.73 m2) did not significantly differ from the i-GFR (45.6 +/- 29.7). Of the subjects, 15 (17%) were normoalbuminuric. Their i-GFR did not differ from the albuminuric rate and from their MDRD e-GFR, although their serum creatinine was lower (122 +/- 27 vs. 160 +/- 71 micromol/l, P < 0.05): 71% would not have been detected by measuring serum creatinine (sCr) alone. They were less affected by diabetic retinopathy, and their HDL cholesterol and hemoglobin were higher (P < 0.05 vs. albuminuric). None of the CKD normoalbuminuric subjects started dialysis (microalbuminuric: 2/36, macroalbuminuric: 10/38) or died (microalbuminuric: 3/36, macroalbuminuric: 7/38) during the follow-up period (log-rank test: P < 0.005 for death or dialysis), and their albumin excretion rate and sCr values were stable after 38 months, whereas the AER increased in the microalbuminuric patients (P < 0.05), and the sCr increased in the macroalbuminuric patients (P < 0.01).

CONCLUSIONS

Although their sCr is usually normal, most of the normoalbuminuric diabetic subjects with CKD according to an MDRD e-GFR below 60 ml/min per 1.73 m2 do really have a GFR below 60 ml/min per 1.73 m2. However, as expected, because of normoalbuminuria and other favorable characteristics, their risk for CKD progression or death is lower.

Are glomerular volume differences between type 1 and type 2 diabetic patients pathologically significant?

The observation that patients with type 2 diabetes tend to have larger glomeruli than patients with type 1 diabetes was first made more than 10 years ago. It has also been noted that type 2 diabetic patients with nephropathy often have more heterogeneous renal function and structure than type 1 patients. However, whether these observations are linked or have any bearing on the progression of nephropathy in the two types of diabetes remains uncertain. Here we put forward several hypotheses as to why glomerular volume in type 1 differs from that in type 2 diabetes. We suggest that although type 1 and type 2 diabetic patients appear to progress through similar stages of diabetic nephropathy, the route they take may differ. Differences in the way in which the glomeruli respond to the diabetic milieu may enable some type 2 diabetic patients to preserve their filtration surface in the face of an expanding mesangium.

Cigarette smoking is associated with low glomerular filtration rate in male patients with type 2 diabetes

OBJECTIVE

The relationship between cigarette smoking and renal dysfunction in diabetes has predominantly been documented in patients with type 1 diabetes. The aim of the present study was to explore the relationship between cigarette smoking and glomerular filtration rate (GFR) in a large cross-sectional study carried out in male subjects with type 2 diabetes. The role of metabolic syndrome in modulating this relationship was also investigated.

RESEARCH DESIGN AND METHODS

One hundred fifty-eight current smokers and 158 never smokers with type 2 diabetes were consecutively recruited. Low GFR was defined as GFR <60 ml/min per 1.73 m(2).

RESULTS

The proportion of patients affected by low GFR was significantly higher in current smokers (20.9 vs. 12.0%, P = 0.03). The adjusted risk (odds ratio [OR]) of low GFR in current smokers was 2.20 (95% CI 1.14-4.26, P = 0.02) and markedly higher in patients from the first tertile of disease duration (4.27 [1.26-14.40], P = 0.02). When metabolic syndrome was added to the statistical model exploring the relationship between smoking and low GFR, the risk of low GFR showed a small change, although it did not become any more significant (1.84 [0.98-3.45], P = 0.06). Current smokers showed even higher free oxygen radical test unit values (560.0 +/- 91.5 vs. 442.7 +/- 87.2, P < 0.0001).

CONCLUSIONS

In a large population of male patients with type 2 diabetes, the risk of low GFR is markedly enhanced by smoking and is at least partially mediated by metabolic syndrome.

Glomerular filtration rate changes in normoalbuminuric and microalbuminuric Type 2 diabetic patients and normal individuals A 10-year follow-up

AIM

To analyze the changes in the glomerular filtration rate (GFR) in a cohort of normoalbuminuric Type 2 diabetic (DM 2) patients and nondiabetic individuals.

METHODS

Sixty-five normoalbuminuric DM 2 patients [urinary albumin excretion rate (UAER) <20 microg/min] and 44 nondiabetic individuals recruited at baseline were followed for a mean period of 10 +/- 1 years. In addition to conventional clinical and metabolic variables, GFR ((51)Cr-EDTA technique) and UAER (immunoturbidimetric method) measurements were performed at baseline and at follow-up. We also evaluated the presence of diabetic retinopathy, hypertension, and cardiovascular disease. Multiple linear regression was performed to assess variables independently associated with GFR evolution in patients with Type 2 diabetes.

RESULTS

Fifty DM 2 patients and 32 nondiabetic individuals were included in the follow-up evaluation. Fourteen out of the 50 patients with Type 2 diabetes developed microalbuminuria. They presented a faster GFR decline (-0.39+/-0.24 ml/min/month; ANOVA, P=.0013) than did persistently normoalbuminuric (-0.16+/-0.16 ml/min/month) and nondiabetic individuals (-0.13+/-0.14 ml/min/month). Multiple linear regression analysis disclosed baseline fasting plasma glucose (FPG) along with the development of microalbuminuria as factors significantly related to a higher GFR decline.

CONCLUSIONS

Persistently normoalbuminuric patients and normal individuals presented a similar degree of GFR reduction related to the aging process. The slope was significantly enhanced in patients who developed microalbuminuria and was influenced by worse baseline glucose control.

Glucose control influences glomerular filtration rate and its prediction in diabetic subjects

OBJECTIVE

Hyperglycemia increases glomerular filtration rate (GFR), but the influence of HbA(1c) (A1C) on GFR and GFR's prediction by recommended equations remains to be determined.

RESEARCH DESIGN AND METHODS

In 193 diabetic patients, we searched for an association between A1C and isotopically measured GFR (51Cr-EDTA) and their predictions by the Cockcroft and Gault formula (CG) and the modification of diet in renal disease (MDRD) equation. Their accuracy for the diagnosis of moderate (GFR <60 ml/min per 1.73 m(2)) or severe (GFR <30 ml/min per 1.73 m(2)) renal failure was compared from receiver operating characteristic (ROC) curves, before and after categorizing the patients as well (A1C <or=8%) or poorly controlled.

RESULTS

The mean GFR was 57.0 +/- 34.8 ml/min per 1.73 m(2) and was well correlated with both estimations (CG r = 0.75, MDRD r = 0.83; P < 0.05). The areas under the ROC curves were higher with the MDRD (P < 0.05). A1C was correlated (P < 0.001) with the GFR (r = 0.29), MDRD (r = 0.38), CG (r = 0.26), and the absolute differences between the GFR and their CG but not MDRD estimations (r = 0.17, P < 0.05). Each +1% A1C was associated with +6.0 ml/min per 1.73 m(2) GFR (CG +5.6, MDRD +5.3). After separating well-controlled (n = 88, A1C 7.0 +/- 0.7%) and poorly controlled (n = 105, 9.6 +/- 1.3%) patients, the diagnostic accuracies were better (P < 0.05) for the MDRD, except for the diagnosis of moderate renal failure in well-controlled patients (NS).

CONCLUSIONS

GFR and its estimations correlate with A1C. Although the relations between GFR and its estimations were not affected by the degree of glucose control, the precision and diagnostic accuracy of the CG formula were diminished for A1C >8%. The MDRD equation was more accurate and robust in diabetic patients with impaired renal function.

Glomerular hyperfiltration in non-proteinuric and non-hypertensive Japanese type 2 diabetic patients

Glomerular hyperfiltration (GHF) may be an important factor in the initiation of glomerular damage and in predisposing diabetic patients to the later development of diabetic nephropathy (DN). Previous reports show wide range of prevalence of GHF in type 2 diabetic patients. This cross-sectional study was designed to determine the prevalence of GHF at an early stage of DN in Japanese type 2 diabetic patients and to investigate the relationships between clinical variables and GHF. We measured the glomerular filtration rate (GFR) using the plasma clearance of iohexol in 56 control subjects and 93 type 2 diabetic patients without hypertension or overt proteinuria. We used Altman's method to calculate the age-adjusted 95% reference ranges for GFR from the data of control subjects and classified GHF in type 2 diabetics from the reference ranges. Hyperfiltrators (defined as GFR > mean GFR + 1.96 S.D. of control subjects) was found in 17% patients (16/93). Other 77 patients (83%) were normofiltrators (defined as GFR< or = mean GFR + 1.96 S.D. of control subjects). GFR values, both in hyperfiltrators and normofiltrators, were 140.5 +/- 14.6 and 98.8 +/- 14.0 ml/min/1.73 m2, respectively. Age, sex, BMI, blood pressure, albumin excretion rate, and frequency of microalbuminuria did not differ between the hyperfiltrators and normofiltrators. Fasting plasma glucose and hemoglobin A1c were significantly higher in the hyperfiltrators than the normofiltrators (P<0.001 and 0.004, respectively). GHF exists among Japanese type 2 diabetic patients with no evidence of overt proteinuria or hypertension. Glycemic control might be a significant determinant of GHF in these patients.

Enhancing the Predictive Value of Urinary Albumin for Diabetic Nephropathy

Diabetic nephropathy (DN) is a growing cause of ESRD despite widely known recommendations for improved glycemic and BP control. Perhaps earlier identification of patients who have diabetes and are at high risk for DN could reverse these epidemiologic trends. Albumin excretion rate (AER), the mainstay of early detection of DN, is not a sufficiently precise predictor of DN risk. Careful family history, smoking history, consideration of absolute versus categorical AER values, more frequent AER measures, ambulatory BP monitoring, precise GFR measurements, diabetic retinopathy assessments, and plasma lipid levels all can add to predictive accuracy for DN. Thus, although further research in DN biomarkers and predictors is greatly needed, a careful integrated evaluation of currently available parameters can improve our ability to predict DN risk in individual patients.