Changes in Albuminuria But Not GFR are Associated with Early Changes in Kidney Structure in Type 2 Diabetes

Association of podocyte ultrastructural changes with proteinuria and pathological classification in type 2 diabetic nephropathy

AIMS

Podocyte injury plays an essential role in the progression of diabetic nephropathy (DN). The associations between the ultrastructural changes of podocyte with proteinuria and the pathological classification of DN proposed by Renal Pathology Society (RPS) have not been clarified in patients with type 2 diabetic nephropathy (T2DN).

METHODS

We collected 110 patients with kidney biopsy-confirmed T2DN at Peking University First Hospital from 2017 to 2022. The morphometric analysis on the podocyte foot process width (FPW) and podocyte detachment (PD) as markers of podocyte injury was performed, and the correlations between the ultrastructural changes of podocytes with severity of proteinuria and the RPS pathological classification of DN were analyzed.

RESULTS

Mean FPW was significantly broader in the group of T2DN patients with nephrotic proteinuria (565.1 nm) than those with microalbuminuria (437.4 nm) or overt proteinuria (494.6 nm). The cut-off value of FPW (> 506 nm) could differentiate nephrotic proteinuria from non-nephrotic proteinuria with a sensitivity of 75.3% and a specificity of 75.8%. Percentage of PD was significantly higher in group of nephrotic proteinuria (3.2%) than that in microalbuminuria (0%) or overt proteinuria (0.2%). FPW and PD significantly correlated with proteinuria in T2DN (r = 0.473, p < 0.001 and r = 0.656, P < 0.001). FPW and PD correlated with RPS pathological classification of T2DN (r = 0.179, P = 0.014 and r = 0.250, P = 0.001). FPW value was increased significantly with more severe DN classification (P for trend =0.007). The percentage of PD tended to increase with more severe DN classification (P for trend = 0.017).

CONCLUSIONS

Podocyte injury, characterized by FPW broadening and PD, was associated with the severity of proteinuria and the pathological classification of DN.

Lysine and salt-sensitive hypertension

PURPOSE OF REVIEW

Salt-sensitive (SS) hypertension and its associated kidney damage have been extensively studied, yet proper therapeutic strategies are lacking. The interest in altering the metabolome to affect renal and cardiovascular disease has been emerging. Here, we discuss the effect and potential mechanism behind the protective effect of lysine, an essential amino acid, on the progression of SS hypertension.

RECENT FINDINGS

We have recently demonstrated that administering lysine in an SS rodent model can control the progression of hypertension. Both the animal and pilot human studies showed that lysine can efficiently inhibit tubular reabsorption of albumin and protect the kidneys from further damage. In addition, we conducted multilevel omics studies that showed increased lysine conjugation and excretion, leading to the depletion of harmful metabolites and an increase in useful ones.

SUMMARY

Lysine's twofold action involves both mechanically flushing protein from proximal tubules to shield the kidneys and initiating metabolic adaptations in the kidneys. This results in a net positive impact on SS hypertension. While further research is necessary to apply the current findings in clinical settings, this study offers some evidence suggesting that lysine supplementation holds promise as a therapeutic approach for hypertensive kidney disease.

Body mass index modifies the effect of urinary protein-to-creatinine ratio on chronic kidney disease progression

BACKGROUND

This study aimed to determine the association between the urinary protein-to-creatinine ratio (UPCR) and chronic kidney disease (CKD) progression in a cohort study, and to determine whether body mass index (BMI) modifies this association.

METHODS

The study population consisted of 856 hypertensive patients with CKD stages 2-5, enrolled between 2010 and 2011 in Japan. Generalized linear models with a logit link were used to evaluate the independent and combined effects of the UPCR and BMI on CKD progression RESULTS: During a median follow-up of 25 months, 242 patients developed CKD progression during follow-up. A notably higher risk of CKD progression was found in participants in tertiles 2 [odds ratio (OR): 5.46, 95% confidence interval (95% CI): 2.49-11.99] and 3 (OR 27.74, 95% CI 12.34-62.38) comparing with tertiles 1 for UPCR levels. Moreover, an interaction was found between UPCR and BMI on CKD progression (P for interaction = 0.006). Participants in both the highest tertile of UPCR and overweight (UPCR ≥ 248.9 mg/mmol and BMI ≥ 25 kg/m2) had a 45.59-times higher risk of CKD progression compared with those in the lowest tertile of UPCR and nonoverweight (UPCR < 36.2 mg/mmol and BMI < 25 kg/m2) CONCLUSIONS: The present study demonstrates that the combination of elevated UPCR and BMI may contribute to an increased risk of CKD progression.

Insulin resistance before type 2 diabetes onset is associated with increased risk of albuminuria after diabetes onset: A prospective cohort study

AIM

Reduced renal insulin signalling is implicated in the pathogenesis of albuminuria. We sought to investigate whether insulin action and secretion, measured before diabetes onset, are associated with the development of albuminuria after diabetes onset.

MATERIALS AND METHODS

Baseline body composition, insulin sensitivity by hyperinsulinaemic-euglycaemic clamp at submaximal and maximal insulin stimulation (240 and 2400 pmol/m2/min; M-low and M-high), and insulin secretion by intravenous glucose tolerance test [acute insulin response (AIR)] were measured in 170 Southwestern Indigenous American adults who subsequently developed diabetes. After diabetes onset and during the median follow-up of 13.6 years, 81 participants (48%) developed albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g). Separate associations of M-low, M-high and AIR (per 1-SD change) with the risk of albuminuria were assessed by Cox regression models adjusted for age, sex and body fat (%).

RESULTS

Participants who developed albuminuria were of similar age (26.4 ± 5.4 vs. 27.5 ± 6.1 years), sex (46% vs. 48% male), body fat (36.4 ± 7.5 vs. 35.7 ± 7.9%) and AIR [2.3 ± 0.3 vs. 2.3 ± 0.3, pmol/L (log)] as those who did not develop albuminuria but had lower insulin sensitivity [M-low: 0.33 ± 0.08 vs. 0.36 ± 0.12, p = .03; M-high: 0.87 ± 0.11 vs. 0.91 ± 0.12, p = .02; mg/kg-metabolic body size/min (log)]. In separate adjusted models, lower M-low and M-high were both associated with an increased risk for albuminuria [hazard ratio (HR) 1.51, 95% confidence interval (CI) 1.14, 2.00, p = .004; HR 1.31, 95% CI 1.06, 1.63, p = .01), whereas AIR was not (HR 1.15, 95% CI 0.87, 1.56, p = .3).

CONCLUSIONS

Lower insulin sensitivity is associated with the development of albuminuria, suggesting a role for insulin signalling in the pathogenesis of proteinuria.

Angiotensin-converting-enzyme inhibitors and angiotensin receptor blockers for preventing the progression of diabetic kidney disease

BACKGROUND

Guidelines suggest that adults with diabetes and kidney disease receive treatment with angiotensin-converting-enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB). This is an update of a Cochrane review published in 2006.

OBJECTIVES

We compared the efficacy and safety of ACEi and ARB therapy (either as monotherapy or in combination) on cardiovascular and kidney outcomes in adults with diabetes and kidney disease.

SEARCH METHODS

We searched the Cochrane Kidney and Transplants Register of Studies to 17 March 2024 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included studies evaluating ACEi or ARB alone or in combination, compared to each other, placebo or no treatment in people with diabetes and kidney disease.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias and extracted data. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

One hundred and nine studies (28,341 randomised participants) were eligible for inclusion. Overall, the risk of bias was high. Compared to placebo or no treatment, ACEi may make little or no difference to all-cause death (24 studies, 7413 participants: RR 0.91, 95% CI 0.73 to 1.15; I2 = 23%; low certainty) and with similar withdrawals from treatment (7 studies, 5306 participants: RR 1.03, 95% CI 0.90 to 1.19; I2 = 0%; low certainty). ACEi may prevent kidney failure (8 studies, 6643 participants: RR 0.61, 95% CI 0.39 to 0.94; I2 = 0%; low certainty). Compared to placebo or no treatment, ARB may make little or no difference to all-cause death (11 studies, 4260 participants: RR 0.99, 95% CI 0.85 to 1.16; I2 = 0%; low certainty). ARB have uncertain effects on withdrawal from treatment (3 studies, 721 participants: RR 0.85, 95% CI 0.58 to 1.26; I2 = 2%; low certainty) and cardiovascular death (6 studies, 878 participants: RR 3.36, 95% CI 0.93 to 12.07; low certainty). ARB may prevent kidney failure (3 studies, 3227 participants: RR 0.82, 95% CI 0.72 to 0.94; I2 = 0%; low certainty), doubling of serum creatinine (SCr) (4 studies, 3280 participants: RR 0.84, 95% CI 0.72 to 0.97; I2 = 32%; low certainty), and the progression from microalbuminuria to macroalbuminuria (5 studies, 815 participants: RR 0.44, 95% CI 0.23 to 0.85; I2 = 74%; low certainty). Compared to ACEi, ARB had uncertain effects on all-cause death (15 studies, 1739 participants: RR 1.13, 95% CI 0.68 to 1.88; I2 = 0%; low certainty), withdrawal from treatment (6 studies, 612 participants: RR 0.91, 95% CI 0.65 to 1.28; I2 = 0%; low certainty), cardiovascular death (13 studies, 1606 participants: RR 1.15, 95% CI 0.45 to 2.98; I2 = 0%; low certainty), kidney failure (3 studies, 837 participants: RR 0.56, 95% CI 0.29 to 1.07; I2 = 0%; low certainty), and doubling of SCr (2 studies, 767 participants: RR 0.88, 95% CI 0.52 to 1.48; I2 = 0%; low certainty). Compared to ACEi plus ARB, ACEi alone has uncertain effects on all-cause death (6 studies, 1166 participants: RR 1.08, 95% CI 0.49 to 2.40; I2 = 20%; low certainty), withdrawal from treatment (2 studies, 172 participants: RR 0.78, 95% CI 0.33 to 1.86; I2 = 0%; low certainty), cardiovascular death (4 studies, 994 participants: RR 3.02, 95% CI 0.61 to 14.85; low certainty), kidney failure (3 studies, 880 participants: RR 1.36, 95% CI 0.79 to 2.32; I2 = 0%; low certainty), and doubling of SCr (2 studies, 813 participants: RR 1.14, 95% CI 0.70 to 1.85; I2 = 0%; low certainty). Compared to ACEi plus ARB, ARB alone has uncertain effects on all-cause death (7 studies, 2607 participants: RR 1.02, 95% CI 0.76 to 1.37; I2 = 0%; low certainty), withdrawn from treatment (3 studies, 1615 participants: RR 0.81, 95% CI 0.53 to 1.24; I2 = 0%; low certainty), cardiovascular death (4 studies, 992 participants: RR 3.03, 95% CI 0.62 to 14.93; low certainty), kidney failure (4 studies, 2321 participants: RR 1.15, 95% CI 0.67 to 1.95; I2 = 29%; low certainty), and doubling of SCr (3 studies, 2252 participants: RR 1.18, 95% CI 0.85 to 1.64; I2 = 0%; low certainty). Comparative effects of different ACEi or ARB and low-dose versus high-dose ARB were rarely evaluated. No study compared different doses of ACEi. Adverse events of ACEi and ARB were rarely reported.

AUTHORS' CONCLUSIONS

ACEi or ARB may make little or no difference to all-cause and cardiovascular death compared to placebo or no treatment in people with diabetes and kidney disease but may prevent kidney failure. ARB may prevent the doubling of SCr and the progression from microalbuminuria to macroalbuminuria compared with a placebo or no treatment. Despite the international guidelines suggesting not combining ACEi and ARB treatment, the effects of ACEi or ARB monotherapy compared to dual therapy have not been adequately assessed. The limited data availability and the low quality of the included studies prevented the assessment of the benefits and harms of ACEi or ARB in people with diabetes and kidney disease. Low and very low certainty evidence indicates that it is possible that further studies might provide different results.

Baseline Urine Albumin-to-Creatinine Ratio is Associated With Decline of Estimated Glomerular Filtration Rate in Patients Newly Diagnosed With Type 2 Diabetes Mellitus: An Observational 5-year Cohort Study

OBJECTIVE

This study aimed to investigate the association between baseline albuminuria and the progression of diabetic kidney disease (DKD) in patients newly diagnosed with type 2 diabetes mellitus (DM).

METHODS

A retrospective cohort study was conducted among 604 patients aged ≥18 years who were newly diagnosed with type 2 DM between January 2014 and 31 December 2017 at an outpatient clinic in a tertiary hospital in China. The incidence of albuminuria was determined and the associations between albuminuria at baseline and the progression of DKD estimated by estimated glomerular filtration rate slope were evaluated using binary logistic regression analysis.

RESULTS

At diagnosis of type 2 DM, 18.8% of patients had albuminuria, with 17.4% having microalbuminuria and the other 1.4% having macroalbuminuria. During the 5-year follow-up period, patients with albuminuria at the baseline experienced a more rapid decline of estimated glomerular filtration rate over time than patients with normoalbuminuria at baseline (-2.6 vs -1.5 mL/min/1.73 m2 per year, P =.01). Albuminuria at baseline is independently associated with the progression of DKD.

CONCLUSIONS

The prevalence of albuminuria is 18.8% in patients newly diagnosed with type 2 diabetes and the occurrence of albuminuria can predict steeper annual decline in kidney function.

Development of an automated estimation of foot process width using deep learning in kidney biopsies from patients with Fabry, minimal change, and diabetic kidney diseases

Podocyte injury plays a key role in pathogenesis of many kidney diseases with increased podocyte foot process width (FPW), an important measure of podocyte injury. Unfortunately, there is no consensus on the best way to estimate FPW and unbiased stereology, the current gold standard, is time consuming and not widely available. To address this, we developed an automated FPW estimation technique using deep learning. A U-Net architecture variant model was trained to semantically segment the podocyte-glomerular basement membrane interface and filtration slits. Additionally, we employed a post-processing computer vision approach to accurately estimate FPW. A custom segmentation utility was also created to manually classify these structures on digital electron microscopy (EM) images and to prepare a training dataset. The model was applied to EM images of kidney biopsies from 56 patients with Fabry disease, 15 with type 2 diabetes, 10 with minimal change disease, and 17 normal individuals. The results were compared with unbiased stereology measurements performed by expert technicians unaware of the clinical information. FPW measured by deep learning and by the expert technicians were highly correlated and not statistically different in any of the studied groups. A Bland-Altman plot confirmed interchangeability of the methods. FPW measurement time per biopsy was substantially reduced by deep learning. Thus, we have developed a novel validated deep learning model for FPW measurement on EM images. The model is accessible through a cloud-based application making calculation of this important biomarker more widely accessible for research and clinical applications.

Trajectories of eGFR and risk of albuminuria in youth with type 2 diabetes: results from the TODAY cohort study

BACKGROUND

We conducted exploratory analyses to identify distinct trajectories of estimated glomerular filtration rate (eGFR) and their relationship with hyperfiltration, subsequent rapid eGFR decline, and albuminuria in participants with youth-onset type 2 diabetes enrolled in the Treatment Options for type 2 Diabetes in Adolescents and Youth (TODAY) study.

METHODS

Annual serum creatinine, cystatin C, urine albumin, and creatinine measurements were obtained from 377 participants followed for ≥ 10 years. Albuminuria and eGFR were calculated. Hyperfiltration peak is the greatest eGFR inflection point during follow-up. Latent class modeling was applied to identify distinct eGFR trajectories.

RESULTS

At baseline, participants' mean age was 14 years, type 2 diabetes duration was 6 months, mean HbA1c was 6%, and mean eGFR was 120 ml/min/1.73 m2. Five eGFR trajectories associated with different rates of albuminuria were identified, including a "progressive increasing eGFR" group (10%), three "stable eGFR" groups with varying starting mean eGFR, and an "eGFR steady decline" group (1%). Participants who exhibited the greatest peak eGFR also had the highest levels of elevated albuminuria at year 10. This group membership was characterized by a greater proportion of female and Hispanic participants.

CONCLUSIONS

Distinct eGFR trajectories that associate with albuminuria risk were identified, with the eGFR trajectory characterized by increasing eGFR over time associating with the highest level of albuminuria. These descriptive data support the current recommendations to estimate GFR annually in young persons with type 2 diabetes and provide insight into eGFR-related factors which may contribute to predictive risk strategies for kidney disease therapies in youth with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00081328, date registered 2002. A higher resolution version of the Graphical abstract is available as Supplementary information.

[Non-Classical Clinical Types and Pathological Changes of Diabetic Kidney Disease: A Review]

Diabetic kidney disease (DKD) is a common complication of diabetes mellitus and approximately 1/3 of diabetic patients may progress to DKD. A typical early clinical manifestation of DKD is microalbuminuria and patients may present with macroproteinuria accompanied by a decrease in renal function condition as the disease progresses. It is generally believed that the likelihood of a reversal of the disease is reduced after the development of macroproteinuria in patients with DKD, and that eventually some patients' condition may develop into end-stage renal disease (ESRD). Moreover, the thickening of the glomerular basement membrane, mesangial matrix expansion, Kimmelstiel-Wilson (K-W) nodules, and glomerulosclerosis in end-stage diabetes mellitus are typical pathologic changes of DKD. However, some DKD patients, especially those with type 2 diabetes mellitus (T2DM) combined with DKD, may have diverse clinical manifestations, showing variations in disease progression and regression, and manifesting as non-classical types of DKD, such as normoalbuminuric DKD, proteinuria-reduced DKD, and DKD with rapid decline in renal function. In addition, the formation of crescents, a special pathological change, is observed in renal biopsy. However, this issue is currently under-recognized by clinicians and therefore deserves more attention. In order to improve clinicians' understanding of the presentations and pathological changes of non-classical DKD and the level of DKD prevention and treatment in China, we present a preliminary introduction to the clinical phenotypes and pathological changes of non-classical types of DKD in this paper by summarizing the findings of our prior studies as well as domestic and international literature.

Sex Difference in the Association Between Serum Versican and Albuminuria in Patients with Type 2 Diabetes Mellitus

Introduction

Diabetic kidney disease (DKD) is one of the major microvascular complications of diabetes. DKD is associated with oxidative stress and inflammation. Versican (VCAN), a chondroitin sulphate proteoglycan, has been proven to participate in oxidative stress and inflammation. This study aimed to explore the overall and sex-based relationship between serum VCAN levels and albuminuria in patients with type 2 diabetes mellitus (T2DM).

Methods

428 patients with T2DM and 84 healthy individuals were enrolled. Patients with diabetes were separated into normal albuminuria, microalbuminuria, and macroalbuminuria groups, according to their urinary albumin/creatinine ratio (UACR). Serum VCAN levels were tested using an enzyme-linked immunosorbent assay.

Results

Compared with males, female patients were older, and had higher total cholesterol and high-density lipoprotein cholesterol, but lower body mass index, diastolic blood pressure, glycated hemoglobin A1, alanine aminotransferase, urinary albumin (UA), and serum creatinine (SCr) (P < 0.05). The VCAN levels in male patients with T2DM were significantly higher than those in the healthy individuals. Male patients with T2DM with albuminuria (micro and macro) had higher levels of VCAN than in patients with normal albuminuria; the highest level was seen in patients with macroalbuminuria (P < 0.05). In male patients with T2DM, serum VCAN correlated positively with systolic blood pressure, blood urea nitrogen, UA, SCr, and UACR, but correlated negatively with the estimated glomerular filtration rate. The area under the receiver operating characteristic curve of serum VCAN to diagnose albuminuria was 0.702, with a corresponding cut-off value of 0.399 ng/mL (P < 0.001). However, the association between serum VCAN and UACR was not observed in female patients with T2DM.

Conclusion

Serum VCAN levels correlated positively with the severity of albuminuria in male patients with T2DM.

Loss of Glomerular Permselectivity in Type 2 Diabetes Associates With Progression to Kidney Failure

We examined whether defects in glomerular size selectivity in type 2 diabetes are associated with progressive kidney disease. Glomerular filtration rate (GFR) and fractional clearances of dextrans of graded sizes were measured in 185 American Indians. The permselectivity model that best fit the dextran sieving data represented the glomerular capillary as being perforated by small restrictive pores and a parallel population of larger nonrestrictive pores characterized by ω0, the fraction of total filtrate volume passing through this shunt. The hazard ratio (HR) for kidney failure was expressed per 1-SD increase of ω0 by Cox regression after adjusting for age, sex, mean arterial pressure, HbA1c, GFR, and the urine albumin-to-creatinine ratio (ACR). Baseline mean ± SD age was 43 ± 10 years, HbA1c 8.9 ± 2.5%, GFR 147 ± 46 mL/min, and median (interquartile range) ACR 41 (11-230) mg/g. During a median follow-up of 17.7 years, 67 participants developed kidney failure. After adjustment, each 1-SD increment in ω0 was associated with a higher risk of kidney failure (HR 1.55 [95% CI 1.17, 2.05]). Enhanced transglomerular passage of test macromolecules was associated with progression to kidney failure, independent of albuminuria and GFR, suggesting that mechanisms associated with impaired glomerular permselectivity are important determinants of progressive kidney disease.

ARTICLE HIGHLIGHTS

Postprandial glucagon-like peptide 1 secretion is associated with urinary albumin excretion in newly diagnosed type 2 diabetes patients

BACKGROUND

Microalbuminuria is an early and informative marker of diabetic nephropathy. Our study found that microalbuminuria developed in patients with newly diagnosed type 2 diabetes mellitus (T2DM).

AIM

To investigate the association between glucagon-like peptide 1 (GLP-1) and microalbuminuria in newly diagnosed T2DM patients.

METHODS

In total, 760 patients were recruited for this cross-sectional study. The GLP-1 levels during a standard meal test and urinary albumin-creatinine ratio (UACR) were determined.

RESULTS

Patients with microalbuminuria exhibited lower GLP-1 levels at 30 min and 120 min during a standard meal test than patients with normal albuminuria (30 min GLP-1, 16.7 ± 13.3 pmol vs 19.9 ± 15.6 pmol, P = 0.007; 120 min GLP-1, 16.0 ± 14.1 pmol vs 18.4 ± 13.8 pmol, P = 0.037). The corresponding area under the curve for active GLP-1 (AUCGLP-1) was also lower in microalbuminuria patients (2257, 1585 to 3506 vs 2896, 1763 to 4726, pmol × min, P = 0.003). Postprandial GLP-1 levels at 30 min and 120 min and AUCGLP-1 were negatively correlated with the UACR (r = 0.159, r = 0.132, r = 0.206, respectively, P < 0.001). The prevalence of microalbuminuria in patients with newly diagnosed T2DM was 21.7%, which decreased with increasing quartiles of AUCGLP-1 levels (27.4%, 25.3%, 18.9% and 15.8%). After logistic regression analysis adjusted for sex, age, hemoglobin A1c, body mass index, systolic blood pressure, estimated glomerular filtration rate, homeostasis model assessment of insulin resistance, AUC_glucose and AUC_glucagon, patients in quartile 4 of the AUCGLP-1 presented a lower risk of microalbuminuria compared with the patients in quartile 1 (odds ratio = 0.547, 95% confidence interval: 0.325-0.920, P = 0.01). A consistent association was also found between 30 min GLP-1 or 120 min GLP-1 and microalbuminuria.

CONCLUSION

Postprandial GLP-1 levels were independently associated with microalbuminuria in newly diagnosed Chinese T2DM patients.

Diagnostic criteria and etiopathogenesis of type 2 diabetes and its complications: Lessons from the Pima Indians

The Phoenix Epidemiology and Clinical Research Branch of the National Institute of Diabetes and Digestive and Kidney Diseases has conducted prospective studies of diabetes and its complications in the Pima Indians living in Arizona, USA for over 50 years. In this review we highlight areas in which these studies provided vital insights into the criteria used to diagnose type 2 diabetes, the pathophysiologic changes that accompany the development of type 2 diabetes, and the course and determinants of diabetes complications-focusing specifically on diabetic kidney disease. We include data from our longitudinal population-based study of diabetes and its complications, studies on the role of insulin resistance and insulin secretion in the pathophysiology of type 2 diabetes, and in-depth studies of diabetic kidney disease that include measures of glomerular function and research kidney biopsies. We also focus on the emerging health threat posed by youth-onset type 2 diabetes, which was first seen in the Pima Indians in the 1960s and is becoming an increasing issue worldwide.

Albuminuria and Heart Failure: JACC State-of-the-Art Review

Although chronic kidney disease is characterized by low glomerular filtration rate (GFR) or albuminuria, estimated GFR (eGFR) is more widely utilized as a marker of risk profile in cardiovascular diseases, including heart failure (HF). The presence and magnitude of albuminuria confers a strong prognostic association in forecasting risk of incident HF as well as its progression, irrespective of eGFR. Despite the high prevalence of albuminuria in HF, whether it adds incremental prognostic information in clinical practice and serves as an independent risk marker, and whether there are any therapeutic implications of assessing albuminuria in patients with HF is less well-established. In this narrative review, we assess the potential role of albuminuria in risk profiling for development and progression of HF, strengths and limitations of utilizing albuminuria as a risk marker, its ability to serve in HF risk prediction models, and the implications of adopting albuminuria as an effective parameter in cardiovascular trials and practice.

Epigenome-wide meta-analysis identifies DNA methylation biomarkers associated with diabetic kidney disease

Type 1 diabetes affects over nine million individuals globally, with approximately 40% developing diabetic kidney disease. Emerging evidence suggests that epigenetic alterations, such as DNA methylation, are involved in diabetic kidney disease. Here we assess differences in blood-derived genome-wide DNA methylation associated with diabetic kidney disease in 1304 carefully characterised individuals with type 1 diabetes and known renal status from two cohorts in the United Kingdom-Republic of Ireland and Finland. In the meta-analysis, we identify 32 differentially methylated CpGs in diabetic kidney disease in type 1 diabetes, 18 of which are located within genes differentially expressed in kidneys or correlated with pathological traits in diabetic kidney disease. We show that methylation at 21 of the 32 CpGs predict the development of kidney failure, extending the knowledge and potentially identifying individuals at greater risk for diabetic kidney disease in type 1 diabetes.

Molecular programs associated with glomerular hyperfiltration in early diabetic kidney disease

Hyperfiltration is a state of high glomerular filtration rate (GFR) observed in early diabetes that damages glomeruli, resulting in an iterative process of increasing filtration load on fewer and fewer remaining functional glomeruli. To delineate underlying cellular mechanisms of damage associated with hyperfiltration, transcriptional profiles of kidney biopsies from Pima Indians with type 2 diabetes with or without early-stage diabetic kidney disease were grouped into two hyperfiltration categories based on annual iothalamate GFR measurements. Twenty-six participants with a peak GFR measurement within two years of biopsy were categorized as the hyperfiltration group, and 26 in whom biopsy preceded peak GFR by over two years were considered pre-hyperfiltration. The hyperfiltration group had higher hemoglobin A1c, higher urine albumin-to-creatinine ratio, increased glomerular basement membrane width and lower podocyte density compared to the pre-hyperfiltration group. A glomerular 1240-gene transcriptional signature identified in the hyperfiltration group was enriched for endothelial stress response signaling genes, including endothelin-1, tec-kinase and transforming growth factor-β1 pathways, with the majority of the transcripts mapped to endothelial and inflammatory cell clusters in kidney single cell transcriptional data. Thus, our analysis reveals molecular pathomechanisms associated with hyperfiltration in early diabetic kidney disease involving putative ligand-receptor pairs with downstream intracellular targets linked to cellular crosstalk between endothelial and mesangial cells.

Youth versus adult-onset type 2 diabetic kidney disease: Insights into currently known structural differences and the potential underlying mechanisms

Type 2 diabetes (T2D) is a global health pandemic with significant humanitarian, economic, and societal implications, particularly for youth and young adults who are experiencing an exponential rise in incident disease. Youth-onset T2D has a more aggressive phenotype than adult-onset T2D, and this translates to important differences in rates of progression of diabetic kidney disease (DKD). We hypothesize that youth-onset DKD due to T2D may exhibit morphometric, metabolic, and molecular characteristics that are distinct from adult-onset T2D and develop secondary to inherent differences in renal energy expenditure and substrate metabolism, resulting in a central metabolic imbalance. Kidney structural changes that are evident at the onset of puberty also serve to exacerbate the organ’s baseline high rates of energy expenditure. Additionally, the physiologic state of insulin resistance seen during puberty increases the risk for kidney disease and is exacerbated by both concurrent diabetes and obesity. A metabolic mismatch in renal energetics may represent a novel target for pharmacologic intervention, both for prevention and treatment of DKD. Further investigation into the underlying molecular mechanisms resulting in DKD in youth-onset T2D using metabolomics and RNA sequencing of kidney tissue obtained at biopsy is necessary to expand our understanding of early DKD and potential targets for therapeutic intervention. Furthermore, large-scale clinical trials evaluating the duration of kidney protective effects of pharmacologic interventions that target a metabolic mismatch in kidney energy expenditure are needed to help mitigate the risk of DKD in youth-onset T2D.

Genome-wide meta-analysis and omics integration identifies novel genes associated with diabetic kidney disease

AIMS/HYPOTHESIS

Diabetic kidney disease (DKD) is the leading cause of kidney failure and has a substantial genetic component. Our aim was to identify novel genetic factors and genes contributing to DKD by performing meta-analysis of previous genome-wide association studies (GWAS) on DKD and by integrating the results with renal transcriptomics datasets.

METHODS

We performed GWAS meta-analyses using ten phenotypic definitions of DKD, including nearly 27,000 individuals with diabetes. Meta-analysis results were integrated with estimated quantitative trait locus data from human glomerular (N=119) and tubular (N=121) samples to perform transcriptome-wide association study. We also performed gene aggregate tests to jointly test all available common genetic markers within a gene, and combined the results with various kidney omics datasets.

RESULTS

The meta-analysis identified a novel intronic variant (rs72831309) in the TENM2 gene associated with a lower risk of the combined chronic kidney disease (eGFR<60 ml/min per 1.73 m2) and DKD (microalbuminuria or worse) phenotype (p=9.8×10-9; although not withstanding correction for multiple testing, p>9.3×10-9). Gene-level analysis identified ten genes associated with DKD (COL20A1, DCLK1, EIF4E, PTPRN-RESP18, GPR158, INIP-SNX30, LSM14A and MFF; p<2.7×10-6). Integration of GWAS with human glomerular and tubular expression data demonstrated higher tubular AKIRIN2 gene expression in individuals with vs without DKD (p=1.1×10-6). The lead SNPs within six loci significantly altered DNA methylation of a nearby CpG site in kidneys (p<1.5×10-11). Expression of lead genes in kidney tubules or glomeruli correlated with relevant pathological phenotypes (e.g. TENM2 expression correlated positively with eGFR [p=1.6×10-8] and negatively with tubulointerstitial fibrosis [p=2.0×10-9], tubular DCLK1 expression correlated positively with fibrosis [p=7.4×10-16], and SNX30 expression correlated positively with eGFR [p=5.8×10-14] and negatively with fibrosis [p<2.0×10-16]).

CONCLUSIONS/INTERPRETATION

Altogether, the results point to novel genes contributing to the pathogenesis of DKD.

DATA AVAILABILITY

The GWAS meta-analysis results can be accessed via the type 1 and type 2 diabetes (T1D and T2D, respectively) and Common Metabolic Diseases (CMD) Knowledge Portals, and downloaded on their respective download pages ( https://t1d.hugeamp.org/downloads.html ; https://t2d.hugeamp.org/downloads.html ; https://hugeamp.org/downloads.html ).

Urinary Proteomics Identifies Cathepsin D as a Biomarker of Rapid eGFR Decline in Type 1 Diabetes

OBJECTIVE

Understanding mechanisms underlying rapid estimated glomerular filtration rate (eGFR) decline is important to predict and treat kidney disease in type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

We performed a case-control study nested within four T1D cohorts to identify urinary proteins associated with rapid eGFR decline. Case and control subjects were categorized based on eGFR decline ≥3 and <1 mL/min/1.73 m2/year, respectively. We used targeted liquid chromatography-tandem mass spectrometry to measure 38 peptides from 20 proteins implicated in diabetic kidney disease. Significant proteins were investigated in complementary human cohorts and in mouse proximal tubular epithelial cell cultures.

RESULTS

The cohort study included 1,270 participants followed a median 8 years. In the discovery set, only cathepsin D peptide and protein were significant on full adjustment for clinical and laboratory variables. In the validation set, associations of cathepsin D with eGFR decline were replicated in minimally adjusted models but lost significance with adjustment for albuminuria. In a meta-analysis with combination of discovery and validation sets, the odds ratio for the association of cathepsin D with rapid eGFR decline was 1.29 per SD (95% CI 1.07-1.55). In complementary human cohorts, urine cathepsin D was associated with tubulointerstitial injury and tubulointerstitial cathepsin D expression was associated with increased cortical interstitial fractional volume. In mouse proximal tubular epithelial cell cultures, advanced glycation end product-BSA increased cathepsin D activity and inflammatory and tubular injury markers, which were further increased with cathepsin D siRNA.

CONCLUSIONS

Urine cathepsin D is associated with rapid eGFR decline in T1D and reflects kidney tubulointerstitial injury.

Glomerular filtration rate as a kidney outcome of diabetic kidney disease: a focus on new antidiabetic drugs

Diabetes has reached epidemic proportions, both in Korea and worldwide and is associated with an increased risk of chronic kidney disease and kidney failure (KF). The natural course of kidney function among people with diabetes (especially type 2 diabetes) may be complex in real-world situations. Strong evidence from observational data and clinical trials has demonstrated a consistent association between decreased estimated glomerular filtration rate (eGFR) and subsequent development of hard renal endpoints (such as KF or renal death). The disadvantage of hard renal endpoints is that they require a long follow-up duration. In addition, there are many patients with diabetes whose renal function declines without the appearance of albuminuria, measurement of the eGFR is emphasized. Many studies have used GFR-related parameters, such as its change, decline, or slope, as clinical endpoints for kidney disease progression. In this respect, understanding the trends in GFR changes could be crucial for developing clinical management strategies for the prevention of diabetic complications. This review focuses on the clinical implication of the eGFR-related parameters that have been used so far in diabetic kidney disease. We also discuss the use of recently developed new antidiabetic drugs for kidney protection, with a focus on the GFR as clinical endpoints.

Pathophysiological Analysis of Uninephrectomized db/db Mice as a Model of Severe Diabetic Kidney Disease

Diabetic nephropathy, included in diabetic kidney disease (DKD), is the primary disease leading to end-stage renal disease (ESRD) or dialysis treatment, accounting for more than 40% of all patients with ESRD or receiving dialysis. Developing new therapeutics to prevent the transition to ESRD or dialysis treatment requires an understanding of the pathophysiology of DKD and an appropriate animal model for drug efficacy studies. In this study, we investigated the pathophysiology of diabetic kidney disease with type 2 diabetes in uninephrectomized db/db mice. In addition, the nephrectomized db/db mice from 10 weeks to 42 weeks were used to assess the efficacy of long-term administration of the angiotensin-II–receptor antagonist losartan. The blood and urinary biochemical parameters and the blood pressure which is a main pharmacological endpoint of the losartan therapy, were periodically measured. And at the end, histopathological analysis was performed. Uninephrectomized db/db mice clearly developed obesity and hyperglycemia from young age. Furthermore, they showed renal pathophysiological changes, such as increased urinary albumin-creatinine ratio (UACR) (the peak value 3104±986 in 40-week-old mice), glomerular hypertrophy and increased fibrotic areas in the tubulointerstitial tubules. The blood pressure in the losartan group was significantly low compared to the normotensive Vehicle group. However, as expected, Losartan suppressed the increase in UACR (829±500) indicating the medication was sufficient, but the histopathological abnormalities including tubular interstitial fibrosis did not improve. These results suggest that the uninephrectomized db/db mice are useful as an animal model of the severe DKD indicated by the comparison of the efficacy of losartan in this model with the efficacy of losartan in clinical practice.

Structural Lesions on Kidney Biopsy in Youth-Onset and Adult-Onset Type 2 Diabetes

OBJECTIVE

Type 2 diabetes (T2D) is a leading cause of end-stage kidney disease worldwide. Recent studies suggest a more aggressive clinical course of diabetic kidney disease in youth-onset compared with adult-onset T2D. We compared kidney structural lesions in youth- and adult-onset T2D to determine if youth onset was associated with greater early tissue injury.

RESEARCH DESIGN AND METHODS

Quantitative microscopy was performed on kidney tissue obtained from research kidney biopsies in 161 Pima Indians (117 women, 44 men) with T2D. Onset of T2D was established by serial oral glucose tolerance testing, and participants were stratified as youth onset (age <25 years) or adult onset (age ≥25 years). Associations between clinical and morphometric parameters and age at onset were tested using linear models.

RESULTS

At biopsy, the 52 participants with youth-onset T2D were younger than the 109 with adult-onset T2D (39.1 ± 9.9 vs. 51.4 ± 10.2 years; P < 0.0001), but their diabetes duration was similar (19.3 ± 8.1 vs. 17.0 ± 7.8 years; P = 0.09). Median urine albumin-to-creatinine ratio was higher in the youth-onset group (58 [25th-75th percentile 17-470] vs. 27 [13-73] mg/g; P = 0.02). Youth-onset participants had greater glomerular basement membrane (GBM) width (552 ± 128 vs. 490 ± 114 nm; P = 0.002) and mesangial fractional volume (0.31 ± 0.10 vs. 0.27 ± 0.08; P = 0.001) than adult-onset participants. Glomerular sclerosis percentage, glomerular volume, mesangial fractional volume, and GBM width were also inversely associated with age at diabetes onset as a continuous variable.

CONCLUSIONS

Younger age at T2D onset strongly associates with more severe kidney structural lesions. Studies are underway to elucidate the pathways underlying these associations.

Quantitative morphometrics reveals glomerular changes in patients with infrequent segmentally sclerosed glomeruli

AIMS

Detection of one segmentally sclerosed glomerulus (SSG) identifies patients with focal segmental glomerulosclerosis (FSGS) but rare SSGs may be missed in kidney biopsies. It is unknown whether alterations of unaffected glomeruli in patients with infrequent SSG can be detected by quantitative morphometrics.

METHODS

We determined SSG frequency and obtained quantitative morphometrics in glomeruli without a pathologic phenotype in large kidney sections of non-involved kidney tissue from 137 patients undergoing total nephrectomy. We used multivariate modelling to identify morphometrics independently associated with increasing frequency of SSG and Receiver Operator Curve (ROC) analysis to determine the ability of quantitative morphometrics to identify patients with FSGS. We used the geometric distribution to estimate the sensitivity and specificity of a needle biopsy to identify patients with FSGS.

RESULTS

In seventy-one patients (51.8%), at least one SSG was observed, and of those, 39 (54.9%) had an SSG lesion in less than 2% of all glomeruli (mean of 249 glomeruli per specimen). Increasing percent of SSG was independently associated with decreasing podocyte density and increasing mesangial index in multivariate modelling. For infrequent SSG lesions (<1% of glomeruli), kidney biopsy could miss FSGS diagnosis more than 74% of the time, and podocyte density had an area under the curve (AUC) of 0.77, and mesangial index, an AUC of 0.79 to identify patients with FSGS.

CONCLUSIONS

More than half of patients had FSGS, although 30% had infrequent SSG. Quantitative morphometrics in glomeruli without pathology, such as podocyte density and mesangial index, identified patients with infrequent SSG and may serve as clinical markers to identify patients with FSGS.

Combination therapy with artemether and enalapril improves type 1 diabetic nephropathy through enhancing antioxidant defense

Previous studies have demonstrated that both artemether and enalapril are effective in treating diabetic nephropathy (DN). However, the effects and underlying mechanisms of their combination in treating DN remain unknown. The experimental DN model was induced by injecting streptozotocin (STZ) into male C57BL/6J mice. Mice were randomly allocated to the Type 1 diabetes control (T1D-ctrl), STZ, STZ + artemether (STZ + Art), STZ + enalapril (STZ + ACEi), or STZ + artemether + enalapril (STZ + Art + ACEi) group. The interventions lasted for 8 weeks. At the end of the experiment, related urine and serum biochemical values, such as urinary albumin excretion (UAE) and fasting blood glucose (FBG), were measured. In addition, blood pressure (BP) and kidney morphologic changes were also evaluated. The expression of oxidative stress related molecules, such as catalase, acetylated SOD2 (k68) and acetylated SOD2 (k122) in the kidney were measured. Results: combination therapy showed more pronounced effects in reducing UAE, FBG, and BP than any single drug. Typical diabetic kidney injuries, such as heavier kidney weight, and glomerular and tubular hypertrophy, were also further alleviated by combination therapy. Combination therapy also up-regulated the expression of catalase and down-regulated the expression of acetylated SOD2 (k68) and acetylated SOD2 (k122). Combination therapy with artemether and enalapril exhibited renoprotective effects in STZ-induced T1D mice superior to a single drug. The mechanism might be associated with their synergistic effects in enhancing antioxidant defense.

Trajectories of kidney function in diabetes: a clinicopathological update

Diabetic nephropathy has been traditionally diagnosed based on persistently high albuminuria and a subsequent decline in glomerular filtration rate (GFR), which is widely recognized as the classical phenotype of diabetic kidney disease (DKD). Several studies have emphasized that trajectories of kidney function in patients with diabetes (specifically, changes in GFR and albuminuria over time) can differ from this classical DKD phenotype. Three alternative DKD phenotypes have been reported to date and are characterized by albuminuria regression, a rapid decline in GFR, or non-proteinuric or non-albuminuric DKD. Although kidney biopsies are not typically required for the diagnosis of DKD, a few studies of biopsy samples from patients with DKD have demonstrated that changes in kidney function associate with specific histopathological findings in diabetes. In addition, various clinical and biochemical parameters are related to trajectories of GFR and albuminuria. Collectively, pathological and clinical characteristics can be used to predict trajectories of GFR and albuminuria in diabetes. Furthermore, cohort studies have suggested that the risks of kidney and cardiovascular outcomes might vary among different phenotypes of DKD. A broader understanding of the clinical course of DKD is therefore crucial to improve risk stratification and enable early interventions that prevent adverse outcomes.

Intraglomerular Dysfunction Predicts Kidney Failure in Type 2 Diabetes

No longitudinal data link intraglomerular hemodynamic dysfunction with end-stage kidney disease (ESKD) in people with type 2 diabetes (T2D). Afferent (R_A) and efferent (R_E) arteriolar resistance and intraglomerular pressure (P_GLO) are not directly measurable in humans but are estimable from glomerular filtration rate (GFR), renal plasma flow (RPF), blood pressure, hematocrit, and plasma oncotic pressure. We examined the association of the R_A-to-R_E ratio and P_GLO with ESKD incidence in 237 Pima Indian individuals with T2D who underwent serial measures of GFR (iothalamate) and RPF (p-aminohippurate). Their association with kidney structural lesions was also examined in a subset of 111 participants. Of the 237 participants (mean age 42 years, diabetes duration 11 years, and GFR 153 mL/min and median urine albumin-to-creatinine ratio 36 mg/g), 69 progressed to ESKD during a median follow-up of 17.5 years. In latent class analysis, distinct trajectories characterized by increasing R_A-to-R_E ratio (HR 4.60, 95% CI 2.55-8.31) or elevated P_GLO followed by a rapid decline (HR 2.96, 95% CI 1.45-6.02) strongly predicted incident ESKD. P_GLO (R ² = 21%, P < 0.0001) and R_A-to-R_E ratio (R ² = 15%, P < 0.0001) also correlated with mesangial fractional volume, a structural predictor of DKD progression. In conclusion, intraglomerular hemodynamic parameters associated strongly with incident ESKD and correlated with structural lesions of DKD.

Effect of Psychosocial Distress on the Rate of Kidney Function Decline

BACKGROUNDS

Chronic kidney disease is a growing global health problem. Psychosocial stress has been found to induce changes in biological processes and behavioral patterns that increase risks of cardiovascular and metabolic diseases. However, the association between psychosocial stress and kidney function is not well understood.

OBJECTIVE

To evaluate the association between psychosocial stress and kidney function decline.

DESIGN

In this prospective cohort study, psychosocial distress was assessed using the psychosocial well-being index short-form (PWI-SF).

PARTICIPANTS

Data of a total of 7246 participants were retrieved from a community-based cohort (Korean Genome and Epidemiology Study).

MAIN MEASURES

The rate of estimated glomerular filtration rate (eGFR) decline was calculated for each individual. Rapid eGFR decline was defined as a decrease of ≥ 3 mL/min/1.73 m² per year. The presence of kidney disease was defined as eGFR < 60 mL/min/1.73 m² at baseline or proteinuria of higher than trace levels from two consecutive urine test results.

KEY RESULTS

A total of 7246 participants were analyzed. The mean eGFR was 92.1 ± 14.0 mL/min/1.73 m². Rapid eGFR decline was observed in 941 (13.0%) participants during a median follow-up of 11.7 years. When the participants were categorized into tertiles according to PWI-SF score, rapid eGFR decline was more prevalent in the group with the highest PWI-SF score (15.8%) than in the group with the lowest score (12.2%). Multivariate logistic regression analysis revealed that the risk of rapid eGFR decline was significantly increased in the tertile group with the highest PWI-SF score compared to the lowest group (odds ratio, 1.35; 95% confidence interval, 1.15-1.59). This association was maintained even after adjusting for confounding variables and excluding participants with kidney disease.

CONCLUSIONS

Higher levels of psychosocial distress were closely associated with an increased risk of rapid kidney function decline.

Prediabetes is associated with proteinuria development but not with glomerular filtration rate decline: A longitudinal observational study

AIMS

Diabetes is recognized as the leading cause of chronic kidney disease (CKD); however, the association of prediabetes with CKD remains unclear, in particular, the independent effect of prediabetes on proteinuria or estimated glomerular filtration rate (eGFR) has not been evaluated. This study aimed to investigate the associations of prediabetes with the proteinuria development and with eGFR decline separately in the Japanese general population without CKD.

METHODS

Participants who underwent health check-ups in 2014 and had adequate data after 2 years were retrospectively analysed. A total of 405,487 participants without CKD (eGFR, ≥60 ml min^-1  1.73 m^-2 , with negative or trace urinary protein) at baseline were categorized according to fasting plasma glucose as having diabetes (≥126 mg/dl [7.0 mmol/l]), prediabetes (100-125 mg/dl [5.6-6.9 mmol/l]) or normal glucose level (˂100 mg/dl [5.6 mmol/l]). Logistic regression analysis was used to analyse the effects of prediabetes (vs. normal glucose level) on the proteinuria development (urinary protein of ≥1+) and eGFR decline (˂60 ml min^-1  1.73 m^-2 ) after 2 years.

RESULTS

After 2 years, 7037 participants (1.7%) developed proteinuria alone, 19,015 (4.7%) presented eGFR decline alone and 636 (0.2%) showed both proteinuria and eGFR decline. Compared to normal glucose level and adjusting for prognostic factors, prediabetes was independently associated with the proteinuria development (odds ratio [OR] 1.233; 95% confidence interval [CI] 1.170-1.301], whereas prediabetes was not associated with eGFR decline (OR 0.981; 95% CI 0.947-1.017).

CONCLUSIONS

Prediabetes is associated with the proteinuria development but not with eGFR decline in the general population.

Pima Indian Contributions to Our Understanding of Diabetic Kidney Disease

Prospective studies in informative populations are crucial to increasing our knowledge of disease. In this perspective, we describe a half century of studies in an American Indian population that transformed our understanding of kidney disease in type 2 diabetes, now recognized as the leading cause of kidney failure worldwide. Serial examinations conducted for many years that included the collection of data and samples across multiple domains captured an unprecedented volume of clinical, physiologic, morphometric, genomic, and transcriptomic data. This work permitted us to extensively characterize the course and determinants of diabetic kidney disease, its pathophysiologic underpinnings, and important secular trends of urgent concern to populations worldwide, including the emergence of youth-onset type 2 diabetes and its effect on development of diabetic kidney disease in midlife. By combining these data using the tools of integrative biology, we are developing new mechanistic insights into the development and progression of diabetic kidney disease in type 2 diabetes. These insights have already contributed to the identification and successful therapeutic targeting of a novel pathway in DKD. We anticipate that this work will continue to expand our understanding of this complex disease and influence its management in the coming years.

Serum albumin and albuminuria predict the progression of chronic kidney disease in patients with newly diagnosed type 2 diabetes: a retrospective study

Background

Diabetes-related kidney disease is associated with end-stage renal disease and a high mortality rate. However, data on risk factors associated with kidney disease in patients with newly diagnosed type 2 diabetes mellitus (DM) remains insufficient. The aim of the present study was to identify the risk factors significantly associated with chronic kidney disease progression in patients with newly diagnosed type 2 DM.

Methods

We reviewed a total of 254 consecutive patients who were newly diagnosed with type 2 diabetes at Nanjing First Hospital from January to December 2014. They were observed for two years, and baseline and biochemical variables were used to identify significant predictors of kidney failure progression. Kidney failure progression was defined as a ≥ 30% increase in serum creatine level.

Results

The mean age of patients was 58.96 years, 37.4% were women, and 57.1% had hypertension. Kidney function progressed in 40 patients (15.75%). Multivariable logistic regression analyses showed that serum albumin (p = 0.015) and microalbuminuria (p < 0.001) were associated with kidney failure progression in patients with newly diagnosed type 2 DM. Those with lower estimated glomerular filtration rate (eGFR; 30–60 ml/min/1.73 m²) at baseline had lower serum albumin levels compared to those of patients with higher eGFR. The albuminuria levels were higher in patients with lower eGFR than in those with eGFR ≥ 90 ml/min/1.73 m². Receiver operating characteristic curve analysis showed that the area under the curve was 0.754 (95% CI [0.670–0. 0.837]).

Conclusions

The overall rate of chronic kidney disease progression is relatively high, and low serum albumin and high albuminuria levels are associated with kidney failure progression in newly diagnosed diabetic patients.

The HSD17B13 rs72613567 variant is associated with lower levels of albuminuria in patients with biopsy-proven nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Several susceptibility gene variants predisposing to nonalcoholic fatty liver disease (NAFLD) have been identified in chronic kidney disease (CKD). Evidence supports that 17-beta hydroxysteroid dehydrogenase 13 (HSD17B13) rs72613567 plays a role in NAFLD development by affecting lipid homeostasis. Since lipid droplets may accumulate in the kidneys and contribute to renal injury, we investigated the association between the HSD17B13 rs72613567 variant and markers of renal function/injury in NAFLD.

METHODS AND RESULTS

We measured estimated glomerular filtration rate (eGFR), urinary/serum neutrophil gelatinase-associated lipocalin (NGAL), and urinary albumin-to-creatinine ratio (u-ACR) in individuals with biopsy-proven NAFLD. Multivariable regression analyses were undertaken to examine the associations between the HSD17B13 rs72613567 variant and markers of renal function/injury. Individuals were stratified by HSD17B13 rs72613567 genotypes into -/-, A/- and A/A groups. HSD17B13 rs72613567 genotypes were not significantly associated with eGFR and urinary/serum NGAL levels. Conversely, the prevalence of abnormal albuminuria in the A/- + A/A group was lower than in the -/- group (4.92% vs. 19.35%, p = 0.001). Additionally, the mean u-ACR levels were lower among carriers of the A/- or A/A genotypes with coexisting hypertension or diabetes, than among those with the -/- genotype. The risk of abnormal albuminuria (adjusted-odds ratio 0.16, p = 0.001) remained significantly lower in the A/- + A/A group after adjustment for established renal risk factors and histologic severity of NAFLD.

CONCLUSION

HSD17B13 rs72613567: A allele is associated with a lower risk of having abnormal albuminuria, but not with lower eGFR or urinary/serum NGAL levels, in patients with biopsy-proven NAFLD.

DNAm-based signatures of accelerated aging and mortality in blood are associated with low renal function

BACKGROUND

The difference between an individual's chronological and DNA methylation predicted age (DNAmAge), termed DNAmAge acceleration (DNAmAA), can capture life-long environmental exposures and age-related physiological changes reflected in methylation status. Several studies have linked DNAmAA to morbidity and mortality, yet its relationship with kidney function has not been assessed. We evaluated the associations between seven DNAm aging and lifespan predictors (as well as GrimAge components) and five kidney traits (estimated glomerular filtration rate [eGFR], urine albumin-to-creatinine ratio [uACR], serum urate, microalbuminuria and chronic kidney disease [CKD]) in up to 9688 European, African American and Hispanic/Latino individuals from seven population-based studies.

RESULTS

We identified 23 significant associations in our large trans-ethnic meta-analysis (p < 1.43E-03 and consistent direction of effect across studies). Age acceleration measured by the Extrinsic and PhenoAge estimators, as well as Zhang's 10-CpG epigenetic mortality risk score (MRS), were associated with all parameters of poor kidney health (lower eGFR, prevalent CKD, higher uACR, microalbuminuria and higher serum urate). Six of these associations were independently observed in European and African American populations. MRS in particular was consistently associated with eGFR (β =  - 0.12, 95% CI = [- 0.16, - 0.08] change in log-transformed eGFR per unit increase in MRS, p = 4.39E-08), prevalent CKD (odds ratio (OR) = 1.78 [1.47, 2.16], p = 2.71E-09) and higher serum urate levels (β = 0.12 [0.07, 0.16], p = 2.08E-06). The "first-generation" clocks (Hannum, Horvath) and GrimAge showed different patterns of association with the kidney traits. Three of the DNAm-estimated components of GrimAge, namely adrenomedullin, plasminogen-activation inhibition 1 and pack years, were positively associated with higher uACR, serum urate and microalbuminuria.

CONCLUSION

DNAmAge acceleration and DNAm mortality predictors estimated in whole blood were associated with multiple kidney traits, including eGFR and CKD, in this multi-ethnic study. Epigenetic biomarkers which reflect the systemic effects of age-related mechanisms such as immunosenescence, inflammaging and oxidative stress may have important mechanistic or prognostic roles in kidney disease. Our study highlights new findings linking kidney disease to biological aging, and opportunities warranting future investigation into DNA methylation biomarkers for prognostic or risk stratification in kidney disease.

Arteriolar hyalinosis is related to rapid GFR decline and long-standing GFR changes observed on renal biopsies in normo-microalbuminuric type 2 diabetic patients

AIMS

Whether or not renal structural changes, especially arteriolar hyalinosis, are related to the rate of renal functional decline and increase in urinary albumin excretion (UAE) at the early stage of diabetic nephropathy in patients with type 2 diabetes is still unknown. Our previous study determined that arteriolar hyalinosis is an independent risk factor for low GFR. We sought to determine whether arteriolar hyalinosis is also a risk factor for rapidly progressive decline in GFR.

METHODS

We evaluated 22 type 2 diabetic patients with normo- or microalbuminuria who took part in the previous study, to clarify which renal histological factors were associated with changes in UAE and the glomerular filtration rate (GFR) during 11.0 ± 3.0 years of follow-up. Light and electron microscopy-based morphometric analyses were performed to quantitatively evaluate the glomerular and interstitial structural changes.

RESULTS

In all 22 patients, the GFR was significantly decreased from baseline to follow-up, while the UAE did not change markedly between the 2 periods. After 11 ± 3 years of follow-up, the GFR was significantly lower in the rapid decliner group (annual rate of GFR decline ≥3.0%) than in the non-rapid decliner group (p = 0.017). The index of arteriolar hyalinosis (IAH) at baseline in the rapid decliners was significantly larger than in the non-rapid decliners (p = 0.015). The IAH showed a significant negative correlation with the GFR at follow-up (r = 0.50, p = 0.018) and the annual rate in the GFR decline (r = 0.47, p = 0.027) and significant positive correlations with UAE at follow-up (r = 0.46, p = 0.034) and the annual rate in the UAE increase (r = 0.57, p = 0.005). The GFR at follow-up in patients with IAH ≥2.0 was significantly decreased from baseline (p = 0.042) and significantly lower than that of the patients with IAH <2.0 (p = 0.026), which did not decrease significantly from baseline. The frequency of rapid decliners was larger in the IAH ≥2.0 than in the IAH <2.0 patients (p = 0.037).

CONCLUSIONS

Aggravated arteriolar hyalinosis was a risk factor for a rapid GFR decline. This finding might reflect initial changes in early diabetic nephropathy.

The Role of Glomerular Epithelial Injury in Kidney Function Decline in Patients With Diabetic Kidney Disease in the TRIDENT Cohort

Introduction

Although diabetic kidney disease (DKD) is responsible for more than half of all chronic and end-stage kidney disease (ESKD), the association of light (LM) and electron microscopic (EM) structural changes with clinical parameters and prognosis in DKD is incompletely understood.

Methods

This is an interim analysis of 62 patients diagnosed with biopsy-confirmed DKD from the multicenter TRIDENT (Transformative Research in Diabetic Nephropathy) study. Twelve LM and 8 EM descriptors, representing changes in glomeruli, tubulointerstitium, and vasculature were analyzed for their relationship with clinical measures of renal function. Patients were followed every 6 months.

Results

Multivariable linear regression analysis revealed that estimated glomerular filtration rate (eGFR) upon enrollment correlated the best with interstitial fibrosis. On the other hand, the rate of kidney function decline (eGFR slope) correlated the most with glomerular lesions including global glomerulosclerosis and mesangiolysis. Unbiased clustering analysis based on histopathologic data identified 3 subgroups. The first cluster, encompassing subjects with the mildest histologic lesions, had the most preserved kidney function. The second and third clusters had similar degrees of kidney dysfunction and structural damage, but differed in the degree of glomerular epithelial cell and podocyte injury (podocytopathy DKD subtype). Cox proportional hazard analysis showed that subjects in cluster 2 had the highest risk to reach ESKD (hazard ratio: 17.89; 95% confidence interval: 2.13–149.79). Glomerular epithelial hyperplasia and interstitial fibrosis were significant predictors of ESKD in the multivariate model.

Conclusion

The study highlights the association between fibrosis and kidney function and identifies the role of glomerular epithelial changes and kidney function decline.

Acarbose Reduces Low-Grade Albuminuria Compared to Metformin in Chinese Patients with Newly Diagnosed Type 2 Diabetes

PURPOSE

To assess the effect of acarbose in lowering low-grade albuminuria compared to metformin in newly diagnosed Chinese type 2 diabetes (T2DM) patients.

PATIENTS AND METHODS

The Metformin and AcaRbose Clinical Trial was a randomized, open-label trial in newly diagnosed T2DM patients. Participants received 48 weeks of monotherapy with acarbose (100 mg three times a day) or metformin (1500 mg once a day). As the hypoglycemic effect of acarbose and metformin has been evaluated in previous reports. This analysis studied the effect of the two antidiabetic drugs on reducing urinary albumin. The percent change in the urinary albumin/creatinine ratio (uACR) from baseline to week 48 was analyzed, and ANCOVA was employed to establish whether the effect in decreasing uACR was mediated by metabolic improvement.

RESULTS

Acarbose reduced the adjusted mean percent uACR by -31.5% (95% confidence interval [CI] -48.4 to -7.5) compared with metformin. When adjusting for changes in glycated hemoglobin, body weight, systolic blood pressure and triglycerides or changes in area under the curve of glucagon-like peptide 1 (AUCGLP-1) in the standard meal test, the uACR-lowering effect was not attenuated. If stratified by eGFR, blood glucose level, sex or uACR level, the effect of acarbose versus metformin was consistent across subgroups. The proportion of patients with a reduction in uACR of at least 70% was 48.6% in the acarbose group and 34.1% in the metformin group.

CONCLUSION

Acarbose lowered the uACR compared to metformin in newly diagnosed T2DM patients independent of improvements in hyperglycemia, blood pressure, body weight and triglycerides.

Optimal Early Diagnosis and Monitoring of Diabetic Kidney Disease in Type 2 Diabetes Mellitus: Addressing the Barriers to Albuminuria Testing

Chronic kidney disease (CKD) in patients with type 2 diabetes (T2D) is associated with increased risk of end-stage renal disease (ESRD) and cardiovascular disease (CVD). Urine albumin-to-creatinine ratio (UACR) is a sensitive and early indicator of kidney damage, which should be used routinely to accurately assess CKD stage and monitor kidney health. However, this test currently is performed in only a minority of patients with T2D. Here, we review the importance of albuminuria testing and current barriers that hinder patient access to UACR testing and describe solutions to such testing in a community clinical setting.

Metformin Protects against Podocyte Injury in Diabetic Kidney Disease

Metformin is the most commonly prescribed drug for treating type 2 diabetes mellitus (T2D). Its mechanisms of action have been under extensive investigation, revealing that it has multiple cellular targets, either direct or indirect ones, via which it regulates numerous cellular pathways. Diabetic kidney disease (DKD), the serious complication of T2D, develops in up to 50% of the individuals with T2D. Various mechanisms contribute to the development of DKD, including hyperglycaemia, dyslipidemia, oxidative stress, chronic low-grade inflammation, altered autophagic activity and insulin resistance, among others. Metformin has been shown to affect these pathways, and thus, it could slow down or prevent the progression of DKD. Despite several animal studies demonstrating the renoprotective effects of metformin, there is no concrete evidence in clinical settings. This review summarizes the renoprotective effects of metformin in experimental settings. Special emphasis is on the effects of metformin on podocytes, the glomerular epithelial cells that are central in maintaining the glomerular ultrafiltration function.

SARS-CoV-2 receptor networks in diabetic and COVID-19 associated kidney disease

COVID-19 morbidity and mortality is increased in patients with diabetes and kidney disease via unknown mechanisms. SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) for entry into host cells. Since ACE2 is a susceptibility factor for infection, we investigated how diabetic kidney disease (DKD) and medications alter ACE2 receptor expression in kidneys. Single cell RNA profiling of healthy living donor (LD) and DKD kidney biopsies revealed ACE2 expression primarily in proximal tubular epithelial cells (PTEC). This cell specific localization was confirmed by in situ hybridization. ACE2 expression levels were unaltered by exposures to renin angiotensin aldosterone system inhibitors in DKD. Bayesian integrative analysis of a large compendium of public -omics datasets identified molecular network modules induced in ACE2-expressing PTEC in DKD (searchable at hb.flatironinstitute.org/covid-kidney) that were linked to viral entry, immune activation, endomembrane reorganization, and RNA processing. The DKD ACE2-positive PTEC module overlapped with expression patterns seen in SARS-CoV-2 infected cells. Similar cellular programs were seen in ACE2-positive PTEC obtained from urine samples of 13 COVID-19 patients who were hospitalized, suggesting a consistent ACE2-coregulated PTEC expression program that may interact with the SARS-CoV-2 infection processes. Thus SARS-CoV-2 receptor networks can seed further research into risk stratification and therapeutic strategies for COVID-19 related kidney damage.

Renal structure in type 2 diabetes: facts and misconceptions

The clinical manifestations of diabetic nephropathy are similar in type 1 and type 2 diabetes, while the renal lesions may differ. Indeed, diabetic glomerulopathy is the predominant renal lesion in type 1 diabetes, although also tubular, interstitial and arteriolar lesions are present in the advanced stages of renal disease. In contrast, in type 2 diabetes renal lesions are heterogeneous, and a substantial number of type 2 diabetic patients with diabetic kidney disease have mild or absent glomerulopathy with tubulointerstitial and/or arteriolar abnormalities. In addition, a high prevalence of non-diabetic renal diseases, isolated or superimposed on classic diabetic nephropathy lesions have been reported in patients with type 2 diabetes, often reflecting the bias of selecting patients for unusual clinical presentations for renal biopsy. This review focuses on renal structural changes in type 2 diabetes, emphasizing the contribution of research kidney biopsy studies to the understanding of the pathogenesis of DKD and of the structural lesions responsible for the different clinical phenotypes. Also, kidney biopsies could provide relevant information in terms of renal prognosis, and help to understand the different responses to different therapies, especially SGLT2 inhibitors, thus allowing personalized medicine.

Combination of astragaloside IV and ACEi ameliorates renal injuries in db/db mice

Evidences demonstrated that the effect on anti-proteinuria and renal protection of Chinese herbs combination with ACEi or ARB seemed to be better than ACEi or ARB alone. Astragaloside IV could decrease the urinary albumin excretion rate and could protect against renal injuries linking to its anti-oxidation ability. We aimed to investigate the effect of astragaloside IV combined with ACEi on diabetic nephropathy and to explore whether its underlying mechanism is dependent on anti-oxidation. 8-week-old male experiment mice were randomly assigned to five groups: lean wild type (wt) group, db/db group, db/db + astragaloside IV group, db/db + enalapril group, db/db + combination therapy with astragaloside IV and enalapril group. During the experiment, 24 hours urinary albumin, fasting glucose, body weight, and metabolic parameters were monitored in regular intervals. At the end of the study, tail blood pressure, serum H₂O₂, lipid, and liver function were measured and kidney histological injuries were evaluated. Results of the study indicated that combination therapy with astragaloside IV and ACEi further reduced 24 hours urinary albumin excretion rate, blood pressure, and body weight. Combination therapy reduced the foot process width, glomerular base membrane thickness, glomerular tuft cell proliferation, tubular cell atrophy, tubular base membrane thickness, and improved tubular cell proliferation. It modulated the body H₂O₂ metabolism and up-regulated the expression of the catalase in renal cortex. Astragaloside IV combined with ACEi exerted renal protective effects in db/db mice more significantly than their individual used. The mechanism possibly involved their synergistic effects on anti-oxidation.

Accumulation of Globotriaosylceramide in Podocytes in Fabry Nephropathy Is Associated with Progressive Podocyte Loss

BACKGROUND

In males with classic Fabry disease, the processes leading to the frequent outcome of ESKD are poorly understood. Defects in the gene encoding α-galactosidase A lead to accumulation of globotriaosylceramide (GL3) in various cell types. In the glomerular podocytes, accumulation of GL3 progresses with age. Of concern, podocytes are relatively resistant to enzyme replacement therapy and are poorly replicating, with little ability to compensate for cell loss.

METHODS

In this study of 55 males (mean age 27 years) with classic Fabry disease genotype and/or phenotype, we performed unbiased quantitative morphometric electron microscopic studies of biopsied kidney samples from patients and seven living transplant donors (to serve as controls). We extracted clinical information from medical records and clinical trial databases.

RESULTS

Podocyte GL3 volume fraction (proportion of podocyte cytoplasm occupied by GL3) increased with age up to about age 27, suggesting that increasing podocyte GL3 volume fraction beyond a threshold may compromise survival of these cells. GL3 accumulation was associated with podocyte injury and loss, as evidenced by increased foot process width (a generally accepted structural marker of podocyte stress and injury) and with decreased podocyte number density per glomerular volume. Worsening podocyte structural parameters (increasing podocyte GL3 volume fraction and foot process width) was also associated with increasing urinary protein excretion-a strong prognosticator of adverse renal outcomes in Fabry disease-as well as with decreasing GFR.

CONCLUSIONS

Given the known association between podocyte loss and irreversible FSGS and global glomerulosclerosis, this study points to an important role for podocyte injury and loss in the progression of Fabry nephropathy and indicates a need for therapeutic intervention before critical podocyte loss occurs.

Diagnostic utility of protein to creatinine ratio (P/C ratio) in spot urine sample within routine clinical practice

The spot (random) urine protein to creatinine ratio (P/C ratio) is an alternative, fast and simple method of detecting and estimating the quantitative assessment of proteinuria. The aim of the work was to review the literature concerning the usefulness of spot urine P/C ratio evaluation in the diagnosis of proteinuria in the course of kidney disease, hypertension, gestational hypertension, preeclampsia, immunological diseases, diabetes mellitus, and multiple myeloma, and in the diagnosis of proteinuria in children. We searched the PubMed and Google Scholar databases using the following keywords: proteinuria, spot urine protein to creatinine ratio, spot urine P/C ratio, protein creatinine index, PCR (protein to creatinine ratio), P/C ratio and methods, Jaffe versus enzymatic creatinine methods, urine protein methods, spot urine protein to creatinine ratio versus ACR (albumin to creatinine ratio), proteinuria versus albuminuria, limitations of the P/C ratio. More weight was given to the articles published in the last 10-20 years. A spot urine P/C ratio >20 mg/mmol (0.2 mg/mg) is the most commonly reported cutoff value for detecting proteinuria, while a P/C ratio value >350 mg/mmol (3.5 mg/mg) confirms nephrotic proteinuria. The International Society for the Study of Hypertension in Pregnancy recommends a P/C ratio of 30 mg/mmol (0.3 mg/mg) for the classification of proteinuria in pregnant women at risk of preeclampsia. A high degree of correlation was observed between P/C ratio values and the protein concentration in 24-h urine collections. The spot urine P/C ratio is a quick and reliable test that can eliminate the need for a daily 24-h urine collection. However, in doubtful situations, it is still recommended to assess proteinuria in a 24-h urine collection. The literature review indicates the usefulness of the spot P/C ratio in various disease states; therefore, this test should be available in every laboratory. However, the challenge for the primary care physician is to know the limitations of the methods used to determine the protein and creatinine concentrations that are used to calculate the P/C ratio. Moreover, the P/C ratio cutoff used should be determined in individual laboratories because it depends on the patient population and the laboratory methodologies.

Catalpol Ameliorates Podocyte Injury by Stabilizing Cytoskeleton and Enhancing Autophagy in Diabetic Nephropathy

Catalpol, an iridoid glycoside extracted from Rehmannia glutinosa, has been found to ameliorate diabetic nephropathy (DN), but the mechanism has not been clarified. Podocyte injury play a key role in the pathogenesis of DN. This study mainly investigated the protective effect and potential mechanism of catalpol on podocyte injury of DN in vivo and in vitro. The results indicated that the pathological features of DN in mice were markedly ameliorated after treatment with catalpol. Moreover, podocyte foot process effacement, and down-regulation of nephrin and synaptopodin expression in DN mice were also significantly improved after treatment with catalpol. In vitro, catalpol rescued disrupted cytoskeleton and increased migration ratio in podocytes induced by high glucose, the effect might be attributable to the inhibition of RhoA and Cdc42 activities but not Rac1. Furthermore, the impaired podocyte autophagy in DN mice was significantly enhanced after catalpol treatment. And catalpol also enhanced autophagy and lysosome biogenesis in cultured podocytes under high glucose condition. In addition, we found that catalpol could inhibit mTOR activity and promote TFEB nuclear translocation in vivo and in vitro experiments. Our study demonstrated that catalpol could ameliorate podocyte injury in DN, and the protective effect of catalpol might be attributed to the stabilization of podocyte cytoskeleton and the improvement of impaired podocyte autophagy.