Changing glomerular filtration with progression from impaired glucose tolerance to Type II diabetes mellitus

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

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.

The Michigan O'Brien Kidney Research Center: transforming translational kidney research through systems biology

Research on kidney diseases is being transformed by the rapid expansion and innovations in omics technologies. The analysis, integration, and interpretation of big data, however, have been an impediment to the growing interest in applying these technologies to understand kidney function and failure. Targeting this urgent need, the University of Michigan O'Brien Kidney Translational Core Center (MKTC) and its Administrative Core established the Applied Systems Biology Core. The Core provides need-based support for the global kidney community centered on enabling incorporation of systems biology approaches by creating web-based, user-friendly analytic and visualization tools, like Nephroseq and Nephrocell, guiding with experimental design, and processing, analysis, and integration of large data sets. The enrichment core supports systems biology education and dissemination through workshops, seminars, and individualized training sessions. Meanwhile, the Pilot and Feasibility Program of the MKTC provides pilot funding to both early-career and established investigators new to the field, to integrate a systems biology approach into their research projects. The relevance and value of the portfolio of training and services offered by MKTC are reflected in the expanding community of young investigators, collaborators, and users accessing resources and engaging in systems biology-based kidney research, thereby motivating MKTC to persevere in its mission to serve the kidney research community by enabling access to state-of-the-art data sets, tools, technologies, expertise, and learning opportunities for transformative basic, translational, and clinical studies that will usher in solutions to improve the lives of people impacted by kidney disease.

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.

Sex-specific clinical outcomes of impaired glucose status: A long follow-up from the Tehran Lipid and Glucose Study

AIMS

To investigate the sex-specific associations of prediabetes with major clinical outcomes including incident type 2 diabetes, chronic kidney disease, hypertension, coronary heart disease, stroke and all-cause mortality.

METHODS

Among 8498 Iranian adults from the Tehran Lipid and Glucose Study, aged ≥30 years and without diagnosed type 2 diabetes, gender-interactions were assessed for each outcome, followed by sex-separated multivariate-adjusted Cox proportional hazard models to calculate hazard ratios and 95% confidence intervals (CIs) of different prediabetes categories, including impaired fasting glucose (IFG), defined by the American Diabetes Association (ADA) and World Health Organization (WHO), as fasting plasma glucose of 5.6-6.9 mmol/L and 6.1-6.9 mmol/L, respectively, and impaired glucose tolerance, defined as 2-h post challenge plasma glucose of 7.8-11 mmol/L.

RESULTS

Sex-specific associations existed for men between IFG-ADA and chronic kidney disease (hazard ratio: 1.28, 95% CI 0.99-1.65; p_interaction = 0.008) and between IFG-WHO and stroke (hazard ratio: 2.15, 95% CI 1.08-4.27; p_interaction = 0.21); and for women between IFG-ADA and hypertension (hazard ratio: 1.24, 95% CI 1.04-1.48; p_interaction = 0.06) and between impaired glucose tolerance and coronary heart disease (hazard ratio: 1.57, 95% CI 1.14-2.16; p_interaction = 0.05). Among both genders, all prediabetes definitions were associated with type 2 diabetes but none with mortality.

CONCLUSIONS

The hazards of prediabetes definitions may differ between genders depending on the outcome of interest. IFG-WHO among men and impaired glucose tolerance among women are particularly important because of their association with incident stroke and coronary heart disease, respectively. Considering these sex differences could improve personalized management of prediabetes.

Prediabetes and Risk of Glomerular Hyperfiltration and Albuminuria in the General Nondiabetic Population: A Prospective Cohort Study

BACKGROUND

The role of prediabetes as a risk factor for hyperfiltration and albuminuria in persons who do not develop diabetes is unclear. The lack of evidence is mainly due to the difficulty of accurately assessing the glomerular filtration rate (GFR) in the near-normal range of GFR. We investigated whether prediabetes is an independent risk factor for glomerular hyperfiltration and high-normal urinary albumin-creatinine ratio (ACR) using measured GFR (mGFR) rather than estimated GFR.

STUDY DESIGN

Prospective cohort study based on the Renal Iohexol Clearance Survey in Tromsø 6 (RENIS-T6) and the RENIS Follow-Up Study. Median observation time was 5.6 years.

SETTING & PARTICIPANTS

A representative sample of 1,261 persons without diabetes mellitus (DM) from the general population aged 50 to 62 years.

PREDICTOR

Prediabetes defined by fasting glucose and hemoglobin A1c according to levels suggested by the American Diabetes Association (preDMADA) and the International Expert Committee of 2009 (preDMIEC).

OUTCOMES

Change in mGFR; hyperfiltration defined as mGFR>90th percentile adjusted for age, sex, weight, and height; and high-normal ACR (>10mg/g) at follow-up.

MEASUREMENTS

GFR was measured with iohexol clearance.

RESULTS

Baseline fasting glucose, hemoglobin A1c, and both definitions of prediabetes were predictors of higher mGFR at follow-up and lower annual mGFR decline in multivariable-adjusted regression analyses. Participants with preDMIEC had an OR for hyperfiltration of 1.95 (95% CI, 1.20-3.17) and for high-normal ACR of 1.83 (95% CI, 1.04-3.22) at follow-up. We adjusted for cardiovascular risk factors including ambulatory blood pressure at baseline and change in use of antihypertensive medication between baseline and follow-up.

LIMITATIONS

Only middle-aged white patients participated. There is no consensus on how to define glomerular hyperfiltration.

CONCLUSIONS

Our findings imply an independent role of prediabetes in the development of glomerular hyperfiltration and albuminuria. Prediabetes might be a target for early treatment to prevent chronic kidney disease in chronic hyperglycemia.

Comparison of serum cystatin C, serum creatinine, measured GFR, and estimated GFR to assess the risk of kidney failure in American Indians with diabetic nephropathy

BACKGROUND

We compared values of baseline serum cystatin C (SCysC), serum creatinine (SCr), and measured glomerular filtration rate (mGFR) for predicting end-stage renal disease (ESRD) in patients with type 2 diabetes and elevated albuminuria.

STUDY DESIGN

Observational longitudinal study.

SETTING & PARTICIPANTS

Pima Indians with type 2 diabetes and elevated albumin-creatinine ratio (ACR ≥30 mg/g).

PREDICTORS

Baseline SCysC, SCr, and mGFR.

OUTCOMES & MEASUREMENTS

Individuals were followed up from their first examination with diabetes and ACR ≥30 mg/g until December 2010, onset of ESRD, or death, whichever came first. Incidence rates adjusted for age and sex were computed by Mantel-Haenszel stratification. The abilities of SCysC, SCr, and mGFR values to predict ESRD were compared with receiver operating characteristic curves.

RESULTS

Of 234 Pima Indians with a mean age of 42.8 years who were followed up for a median of 10.7 (range, 0.6-21.3) years, 68 (29%) developed ESRD. The incidence of ESRD was significantly higher in patients in the lowest versus highest tertile of 1/SCysC (incidence rate ratio, 2.43; 95% CI, 1.31-4.50). By contrast, mGFR and 1/SCr had J-shaped associations with ESRD. In unadjusted analyses, 1/SCysC had the highest area under the receiver operating characteristic curve (AUROC; 0.719 ± 0.035) and mGFR had the lowest (0.585 ± 0.042; P < 0.001); the AUROC for 1/SCr was intermediate (0.672 ± 0.040; P = 0.1 and P = 0.03 vs 1/SCysC and mGFR, respectively). In analyses adjusted for age, sex, diabetes duration, height, weight, hemoglobin A1c level, and ACR, 1/SCysC had the highest AUROC (0.845 ± 0.026). Models with mGFR or 1/SCr alone had similar AUROCs (P = 0.9) and both were lower than the model with 1/SCysC alone (P = 0.02 and P = 0.03, respectively).

LIMITATIONS

The predictive values of the filtration markers are limited to the extent that their precision is based on a single measurement.

CONCLUSIONS

SCysC level was a better predictor of ESRD than mGFR or SCr level in Pima Indians with type 2 diabetes and elevated albuminuria.

Epidemiology of diabetic kidney disease

The increasing prevalence of diabetes has led to DKD becoming the leading cause of ESRD in many regions. The economic cost of DKD will grow to prohibitive amounts unless strategies to prevent its onset or progression are urgently implemented. In type 1 and type 2 diabetes, the presence of microalbuminuria and macroalbuminuria confers increased risk of developing ESRD and of death. Comparison of recent studies with earlier historical studies shows that the incidence of ESRD and death has decreased in DKD. Increased risk of albuminuria has been identified in certain non-European ethnic groups. However, the initial concept of progression of DKD as an albuminuric phenotype involving development of microalbuminuria, macroalbuminuria, and then ESRD has had to be modified. Albumin excretion frequently regresses, and GFR can decline without abnormality in albumin excretion. There is emerging evidence that changes in renal function occurring early in the course of diabetes predict future outcomes. The major challenges are to prevent DKD onset, to detect it early, and to improve DKD outcomes globally.

Early renal function decline in type 2 diabetes

BACKGROUND AND OBJECTIVES

Early decline in GFR may reflect progressive kidney disease in type 1 diabetes, but its predictive value in type 2 diabetes is uncertain.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this longitudinal study, GFR was measured serially over approximately 4.0 years in 195 Pima Indians with type 2 diabetes. Renal function decline (RFD) was defined during this initial period by an average GFR loss ≥3.3%/yr, as defined previously in type 1 diabetes. Subsequently, participants were followed for up to 17.8 years to ESRD onset, death, or December 31, 2010, whichever came first.

RESULTS

RFD prevalence during the initial period was 32% in 68 participants with normal baseline albuminuria (albumin/creatinine ratio [ACR] < 30 mg/g), 42% in 88 with microalbuminuria (ACR 30 to <300 mg/g), and 74% in 39 with macroalbuminuria (ACR ≥300 mg/g; P<0.001). The cumulative incidence of ESRD 10 years after the initial period was 41% in those with RFD and 15% in those without (P<0.001); 41 of the 49 ESRD cases (83.7%) occurred in participants who had or developed macroalbuminuria during the initial period. When adjusted for age, sex, diabetes duration, and hemoglobin A1c, the ESRD hazard rate was 4.78 times (95% confidence interval, 2.39-9.58) as high in those with RFD as in those without; further adjustment for albuminuria attenuated this association (hazard ratio, 1.79; 95% confidence interval, 0.82-3.91).

CONCLUSIONS

In type 2 diabetes, loss of GFR often occurs before the onset of macroalbuminuria, but a decline predictive of ESRD is strongly dependent on progression to macroalbuminuria.

Overview of the importance of glycaemic control for cardiovascular events in the in-and out-patient setting

Worldwide prevalence of diabetes mellitus in the adult population is increasing and when explicitly searched within specific groups of patients, as those presenting cardiovascular disease (CVD), dysglycaemia is detected in about three-quarters of the patients. Dysglycaemia alone is a major risk factor for microvascular and macrovascular complications that impair quality of life and diminish survival. The coexistence of CVD and dysglycaemia in the same individual increases its cardiovascular risk considerably. Since a significant proportion of dysglycaemic individuals develop vascular damage and the disturbed glucose metabolism remains undetected until the first cardiovascular event, there is imperative need for improved strategies for glucometabolic health assessment and management in patients with CVD. The present review has the aim to discuss the importance of glycaemic control for future cardiovascular events starting from the in-hospital setting and continuing to long-term management based on available literature and recently updated international guidelines.

Relation of low glomerular filtration rate to metabolic disorders in individuals without diabetes and with normoalbuminuria

BACKGROUND AND OBJECTIVES

Microalbuminuria increases cardiovascular risk and is considered a metabolic disorder. Low glomerular filtration rate is also associated with increased cardiovascular risk, but the relation of low glomerular filtration rate to metabolic disorders is not well understood.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Designed as a cross-sectional, epidemiologic study, the Insulin Resistance Atherosclerosis Study was conducted in four centers: San Antonio (Texas), San Luis Valley (Colorado), and Oakland and Los Angeles (California). The Modification of Diet in Renal Disease equation was used to classify individuals without diabetes and with normoalbuminuria (n = 856; age 40 to 69 yr) by the presence or absence of low glomerular filtration rate (<60 ml/min per 1.73 m(2)). A direct marker of insulin resistance, the insulin sensitivity index, was measured by the frequently sampled intravenous glucose tolerance test.

RESULTS

Low glomerular filtration rate was related to hypertension and the metabolic syndrome. Low glomerular filtration rate was associated with fasting insulin concentration and insulin sensitivity index. Low glomerular filtration rate was also associated with insulin concentration after adjustment for potential determinants of glomerular filtration rate but was not associated with insulin sensitivity index.

CONCLUSIONS

Low glomerular filtration rate is associated with increased insulin concentration in individuals without diabetes and with normoalbuminuria. Longitudinal analyses are needed to determine whether insulin concentration (insulin resistance) precedes the deterioration of renal function.

Risk for cardiovascular outcomes among subjects with atherosclerotic cardiovascular disease and greater-than-normal estimated glomerular filtration rate

BACKGROUND AND OBJECTIVES

Estimating equations for calculating glomerular filtration rate (eGFR) occasionally identify patients with elevated eGFR, yet the prognostic significance remains to be determined. This study sought to define the association of an elevated eGFR on the risk for death and cardiovascular outcomes among subjects with atherosclerotic cardiovascular disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data from 8941 subjects who had a history of atherosclerotic vascular disease and were enrolled in the Blockade of the Glycoprotein IIb/IIIa Receptor to Avoid Vascular Occlusion trial were analyzed. Time to the composite end point of death, congestive heart failure, myocardial infarction, or stroke was modeled using Cox proportion hazards regression. Glomerular filtration rate was estimated using the Modification of Diet in Renal Disease and Cockcroft-Gault formulas.

RESULTS

Compared with subjects with eGFR of 100 to 125 ml/min per 1.73 m2, subjects with eGFR > or = 125 (n = 462) were younger, female, and nonwhite. In addition, subjects with an elevated eGFR were more likely to have diabetes and congestive heart failure. In adjusted analyses, every 10-ml/min per 1.73 m2 decrease in eGFR < 100 was associated with a 13% increased hazard for the composite end point. In addition, every 10-ml/min per 1.73 m2 increase in eGFR > or = 100 was associated with a 9% increased hazard for the composite end point.

CONCLUSIONS

In individuals with a history of vascular disease, the relationship between eGFR and cardiovascular outcomes may be parabolic, with increased risk among patients with both reduced and elevated eGFR.

An increasing trend in the incidence of type 1 diabetes mellitus in children aged 0-14 years in Romania--ten years (1988-1997) EURODIAB study experience

AIM

To assess the incidence of type 1 diabetes mellitus (DM1) in Romanian children aged 0-14 years using EURODIAB Study methodology.

METHODS

Data were collected for a 10-year interval (1988-1997) for the whole country, using the capture-recapture method.

RESULTS

We registered 1,418 newly diagnosed patients. The mean total incidence rate was 3.051/100,000/year. There was a wide geographic variation (6.71-fold) between the highest and the lowest incidence rates in different districts. We noticed a progressive increase of age-specific incidence rates from 1.43/100,000/year for the 0-4 year age subgroup to 4.37/100,000/year (10-14 years). The annual mean incidence rate rose from 1.91/100,000/year (1988) to 3.94/100,000/year (1996).

CONCLUSIONS

Romania is one of the European countries with the lowest incidence rates (3.051/100,000/year) for DM1 in children. There was an evident increasing trend of DM1 incidence in children between 1988 and 1997, with an annual increase of 7.57%.

Avaliação quanto à presença de microalbuminúria e hiperfiltração glomerular no estágio de tolerância à glicose diminuída

Na fase de tolerância à glicose diminuída (TGD) já estão presentes vários distúrbios metabólicos característicos do diabetes mellitus tipo 2 e fatores de risco que predispõem à vasculopatia. Nosso objetivo foi o de verificar se indivíduos de nossa população, com TGD e normotensos, apresentam elevação da excreção urinária de albumina (EUA) e da depuração de creatinina (D Cr). Teste oral de tolerância à glicose padrão com dosagem de insulina foi realizado, classificando os participantes em dois grupos: com TGD e com tolerância à glicose normal (TGN). Urina do período noturno foi utilizada para a determinação da EUA (imunoturbidimetria) e da D Cr. Os dois grupos não diferiram quanto à EUA e à D Cr. A freqüência de microalbuminúria foi de 21,1 e 3,3%, respectivamente, para os grupos com TGD e TGN (NS). Concluímos que, nesta amostra da população brasileira, indivíduos com TGD, normotensos e com resistência à insulina não apresentaram microalbuminúria e hiperfiltração glomerular.