Sleep duration and quality in relation to chronic kidney disease and glomerular hyperfiltration in healthy men and women

Background

It is unclear whether sleep duration and quality are associated with chronic kidney disease (CKD) and glomerular hyperfiltration. The aim of this study was to examine the association of sleep duration and quality with CKD and glomerular hyperfiltration in young and middle-aged adults.

Methods

We conducted a cross-sectional study of men and women who underwent a health checkup examination, including assessment of sleep duration and quality (n = 241,607). Chronic kidney disease (CKD) was defined as an estimated glomerular filtration rate (eGFR) less than 60 ml/min/1.73 m², and glomerular hyperfiltration was defined as eGFR above the age-/sex-specific 95^th percentile.

Results

In a multinomial logistic regression analysis adjusting for relevant confounders, the adjusted prevalence ratios for CKD (95% confidence interval) comparing sleep durations of ≤ 5, 6, 8, and 9 hours with 7 hours were 1.22 (0.95–1.55), 0.93 (0.75–1.14), 0.97 (0.75–1.26), and 1.56 (1.06–2.30) in men and 0.98 (0.68–1.43), 1.03 (0.72–1.46), 1.39 (0.97–2.00), and 1.31 (0.78–2.22) in women, respectively. The corresponding prevalence ratios (95% confidence interval) for glomerular hyperfiltration were 1.00 (0.93–1.08), 0.97 (0.91–1.03), 1.03 (0.94–1.13), and 1.39 (1.13–1.72) in men and 1.04 (0.95–1.14), 0.96 (0.90–1.04), 1.11 (1.02–1.20), and 1.28 (1.14–1.45) in women, respectively. Poor subjective sleep quality was associated with glomerular hyperfiltration in men and women.

Conclusion

In this large study of young and middle-aged adults, we found that long sleep duration was associated with CKD and glomerular hyperfiltration. Additionally, poor subjective sleep quality was associated with increased prevalence of glomerular hyperfiltration, suggesting the importance of adequate quantity and quality of sleep for kidney function.

Higher glomerular filtration rate is related to insulin resistance but not to obesity in a predominantly obese non-diabetic cohort

Glomerular hyperfiltration has been associated with obesity, insulin resistance, and systolic blood pressure (SBP). However, previous studies are limited by confounders such as pre-existing diabetes or hypertension, or have used indirect measures of adiposity and insulin sensitivity (IS). Therefore, we examined the relationship between estimated glomerular filtration rate (eGFR) and IS measured by the hyperinsulinaemic euglycaemic clamp in a healthy population on no medications. We performed oral glucose tolerance test (OGTT) and measured % body fat (DEXA), BMI, blood pressure and M-value (hyperinsulinaemic euglycaemic clamp) in 104 individuals (44 females and 60 males). The majority of the study population (n = 89, 85.6%) were classified on their BMI as overweight/obese. eGFR was related to age, BMI, M-value (IS), 2-hour glucose levels post OGTT and white blood cell count (WBC) (all p < 0.05); but not to SBP (p = 0.1) or fasting glucose levels (p = 0.2). After adjustment for gender, BMI, SBP and WBC, the inverse association between eGFR and M-value (p = 0.001), and 2-hour glucose post OGTT (p = 0.02) persisted. In conclusion, although eGFR has been associated with BMI and blood pressure in previous studies, in our healthy population, eGFR was more closely related to markers of glucose metabolism (IS and 2-hour glucose post OGTT) than to BMI and blood pressure.

Characteristics and Impact Factors of Renal Threshold for Glucose Excretion in Patients with Type 2 Diabetes Mellitus

Sodium glucose co-transporter 2 (SGLT-2) inhibitors are newly developed but promising medicine for type 2 diabetes. However, patients with a different renal threshold for glucose excretion (RT(G)) may have a different reaction to this medicine. Therefore, the objective of this study was to investigate the characteristics of RT(G) and its impact factors in patients with type 2 diabetes mellitus (T2DM). The clinical and laboratory data of 36 healthy individuals and 168 in-hospital patients with T2DM were collected and analyzed, RT(G) was calculated using blood glucose (BG) measured by dynamic BG monitoring, urinary glucose excretion (UGE) and estimated glomerular filtration rate (eGFR). The characteristics of RT(G) were investigated. The risk factors for high RT(G) were analyzed using non-conditional logistic regression analysis. Our results found that RT(G) of the T2DM group was higher than that of the healthy individuals (P < 0.05); and 22.22% from the healthy individuals group but 58.33% from the T2DM group had high RT(G). Age, duration of diabetes, body mass index (BMI), and homeostasis model assessment insulin resistance index (HOMA-IR) were independently associated with high RT(G) (P < 0.05). Further stratified analysis revealed that RT(G) in T2DM patients increased with age, duration of diabetes, and BMI. In conclusion, RT(G) is increased in patients with T2DM, especially in those with longer diabetic duration, higher BMI, and those who are older. Therefore, these patients may be more sensitive to SGLT-2 inhibitors.

Hyperfiltration-associated biomechanical forces in glomerular injury and response: Potential role for eicosanoids

Hyperfiltration is a well-known risk factor in progressive loss of renal function in chronic kidney disease (CKD) secondary to various diseases. A reduced number of functional nephrons due to congenital or acquired cause(s) results in hyperfiltration in the remnant kidney. Hyperfiltration-associated increase in biomechanical forces, namely pressure-induced tensile stress and fluid flow-induced shear stress (FFSS) determine cellular injury and response. We believe the current treatment of CKD yields limited success because it largely attenuates pressure-induced tensile stress changes but not the effect of FFSS on podocytes. Studies on glomerular podocytes, tubular epithelial cells and bone osteocytes provide evidence for a significant role of COX-2 generated PGE₂ and its receptors in response to tensile stress and FFSS. Preliminary observations show increased urinary PGE₂ in children born with a solitary kidney. FFSS-induced COX2-PGE₂-EP₂ signaling provides an opportunity to identify targets and, for developing novel agents to complement currently available treatment.

Estimation of the relationship between the polymorphisms of selected genes: ACE, AGTR1, TGFβ1 and GNB3 with the occurrence of primary vesicoureteral reflux

PURPOSE

Etiopathogenesis of VUR is composite and not fully understood. Many data indicate the importance of genetic predisposition. The aim of this study was to establish the relationship of selected polymorphisms: 14094 polymorphism of the ACE, polymorphism rs1800469 of TGFβ-1, rs5443 gene polymorphism of the GNB3 and receptor gene polymorphism rs5186 type 1 AGTR1 with the occurrence of the primary vesicoureteral reflux.

MATERIAL

The study included 190 children: 90 with the primary VUR confirmed with the voiding cystourethrogram and excluded secondary VUR and a control group of 100 children without a history of the diseases of the genitourinary tract.

METHODS

The study was planned in the scheme: "tested case versus control." Genomic DNA was isolated from the leukocytes of peripheral blood samples. The results were statistically analyzed in the Statistica 10 using χ ² test and analysis of the variance Anova.

RESULTS

Any of the four studied polymorphisms showed no difference in the distribution of genotypes between patients with primary vesicoureteral reflux and the control group. In patients with VUR and TT genotype polymorphism rs5443 GNB3 gene, the glomerular filtration rate was significantly higher than in patients with genotype CC or CT.

CONCLUSIONS

(1) No relationship was found between the studied polymorphisms (14094 ACE gene, rs1800469 gene TGFβ1, GNB3 gene rs5443, rs5186 AGTR1 gene) and the occurrence of primary vesicoureteral reflux. (2) TT genotype polymorphism rs5443 GNB3 gene may be a protective factor for the improved renal function in patients with primary vesicoureteral reflux in patients with genotype CC or CT.

Neuropilin1 regulates glomerular function and basement membrane composition through pericytes in the mouse kidney

Neuropilin1 (Nrp1) is a co-receptor best known to regulate the development of endothelial cells and is a target of anticancer therapies. However, its role in other vascular cells including pericytes is emergent. The kidney is an organ with high pericyte density and cancer patients develop severe proteinuria following administration of NRP1B-neutralizing antibody combined with bevacizumab. Therefore, we investigated whether Nrp1 regulates glomerular capillary integrity after completion of renal development using two mouse models; tamoxifen-inducible NG2Cre to delete Nrp1 specifically in pericytes and administration of Nrp1-neutralizing antibodies. Specific Nrp1 deletion in pericytes did not affect pericyte number but mutant mice developed hematuria with glomerular basement membrane defects. Despite foot process effacement, albuminuria was absent and expression of podocyte proteins remained unchanged upon Nrp1 deletion. Additionally, these mice displayed dilation of the afferent arteriole and glomerular capillaries leading to glomerular hyperfiltration. Nidogen-1 mRNA was downregulated and collagen4α3 mRNA was upregulated with no significant effect on the expression of other basement membrane genes in the mutant mice. These features were phenocopied by treating wild-type mice with Nrp1-neutralizing antibodies. Thus, our results reveal a postdevelopmental role of Nrp1 in renal pericytes as an important regulator of glomerular basement membrane integrity. Furthermore, our study offers novel mechanistic insights into renal side effects of Nrp1 targeting cancer therapies.

Is there any Gender Difference in the Association between Obesity, Chronic Kidney Disease and Anemia

Introduction. Nowadays, obesity has emerged as one of the most independent risk factors for chronic kidney disease (CKD) in both economically developed and undeveloped countries. The number of patients requiring dialysis as a consequence of obesity-related renal diseases, such as diabetes mellitus and hypertension, is increasing worldwide. Moreover, obesity has been shown to favorize the risk of cardiovascular diseases (CVD) with premature death due to CKD and/or end-stage renal disease (ESRD). The aim of the study was to investigate the association between obesity [e.g. body mass index (BMI)], kidney function [e.g. glomerular filtration rate (GFR)] and renal anemia in CKD patients.

Methods. Retrospectively, data from the register of 315 pre-dialysis patients with different stages of CKD not on erythropoiesis stimulation agents (ESAs) during the period between 1 Jan 2013-30 June 2013 were used to assess the association between the degree of CKD impairment with the degree of obesity and anemia. The stage and/or progression of CKD was calculated by GFR, while the degree of obesity by the body mass index (BMI). CKD was defined as a glomerular filtration rate (GFR) <60 mL/min per 1.73 m2. Data analysis was performed by means of the simple Microsoft excel program.

Results. Within the study population of 315 CKD patients, 123 were males with mean age of 63.4±1.33 years and 192 females of 57.3±1.2 years. The GFR reduced with the increased BMI in both genders, and majority of patients (n=243) were in CKD stage 3, with a mean GFR of 44.5 ml/min/1.73 m2. The BMI values in female patients with first and second degree of obesity negatively correlated with GFR (r=−0.46, p<0.05). Only female patients with second degree of obesity (BMI of 35-39.9 kg/m2) had a positive correlation between the decreased renal function and reduced Hb levels.

Conclusions. Our study provided an unconditional evidence not only for the presence of an association between the degree of obesity (BMI) and the degree of renal function impairment (GFR), but also an association between the higher BMI and the higher degree of kidney anemia seen in women with second degree of obesity. Further larger scale trials and interventional studies are required to see the effect of body weight reduction on renal function and especially anemia.

Association between prediabetes and risk of chronic kidney disease: a systematic review and meta-analysis

AIMS

To assess the effect of prediabetes (impaired fasting glucose and/or impaired glucose tolerance) on the incidence of chronic kidney disease.

METHODS

PubMed and EMBASE were searched (for studies published up to March 2015). Effects estimated from cohort studies reporting the relationship of prediabetes to incident chronic kidney disease [kidney damage (microalbuminuria, albuminuria or proteinuria) and/or decreased glomerular filtration rate] were pooled using a random-effects model meta-analysis.

RESULTS

Nine cohort studies with a total of 185 452, mainly Asian and white, participants were followed for a total of 835 146 person-years. In eight cohort studies defining impaired fasting glucose as fasting glucose 6.1-6.9 mmol/l, the summary relative risk of chronic kidney disease after adjustment for established risk factors was 1.11 (95% CI 1.02-1.21). When a study defining impaired fasting glucose as fasting glucose 5.6-6.9 mmol/dl was added, the overall relative risk of chronic kidney disease was 1.12 (95% CI 1.02-1.21). Exclusion of the only study with information on impaired glucose tolerance did not change the relative risk (1.12; 95% CI 1.02-1.21). There was no evidence of publication bias (P value for Egger test = 0.12).

CONCLUSION

Prediabetes is modestly associated with an increase in chronic kidney disease risk, but this remains to be robustly confirmed. Chronic kidney disease screening among people with prediabetes, and aggressive management of prediabetes in those with chronic kidney disease may be warranted.

Kidney outcomes three years after bariatric surgery in severely obese adolescents

A significant number of severely obese adolescents undergoing bariatric surgery have evidence of early kidney damage. To determine if kidney injury is reversible following bariatric surgery, we investigated renal outcomes in the Teen-Longitudinal Assessment of Bariatric Surgery cohort, a prospective multicenter study of 242 severely obese adolescents undergoing bariatric surgery. Primary outcomes of urine albumin-to-creatinine ratio and cystatin C-based estimated glomerular filtration rate (eGFR) were evaluated preoperatively and up to 3 years following bariatric surgery. At surgery, mean age of participants was 17 years and median body mass index (BMI) was 51 kg/m². In those with decreased kidney function at baseline (eGFR under 90 mL/min/1.73m²), mean eGFR significantly improved from 76 to 102 mL/min/1.73m² at three-year follow-up. Similarly, participants with albuminuria (albumin-to-creatinine ratio of 30 mg/g and more) at baseline demonstrated significant improvement following surgery: geometric mean of ACR was 74 mg/g at baseline and decreased to 17 mg/g at three years. Those with normal renal function and no albuminuria at baseline remained stable throughout the study period. Among individuals with a BMI of 40 kg/m² and more at follow-up, increased BMI was associated with significantly lower eGFR, while no association was observed in those with a BMI under 40 kg/m². In adjusted analysis, eGFR increased by 3.9 mL/min/1.73m² for each 10-unit loss of BMI. Early kidney abnormalities improved following bariatric surgery in adolescents with evidence of preoperative kidney disease. Thus, kidney disease should be considered as a selection criteria for bariatric surgery in severely obese adolescents who fail conventional weight management.

Temporal stability of chemical hormesis (CH): Is CH just a temporary stop on the road to thresholds and toxic responses?

Chemical hormesis (CH) is currently described as a nonmonotonic, bidirectional dose-response relationship for chemicals, where a stimulatory, (beneficial?) response at low dose or exposure is followed by an inhibitory response at higher doses/exposures (or vice-versa). CH is depicted as U(J)-shaped or inverse U(J)-shaped curves, i.e., curve slopes change sign. Some describe CH as a homeostasis-preserving response; others view CH as adaptive or (pre)conditioning responses to chemical stress. One aspect of CH and stress hormesis in general that has not been researched is its temporal stability, i.e., persistence, particularly in experimental animals and humans having long-term chemical stressing. Once maximized, does the CH response remain operative over the entire time of chemical exposure? One possible reason for the question's neglect is that temporal stability, e.g., 'steady-state hormesis,' has been assumed. Another is that CH temporality is not well understood or has been under-appreciated as to its importance. Available data, mainly for simpler biological systems, describe cases of transitory CH. Other examples, in human and experimental animal studies, show transitory existence of CH and, in some specialized cases, persisting CH. Also, certain disease state-induced hormetic responses are transitory over time in humans. The question requires resolution if CH is to be considered (i) a stable and beneficial or adverse response, (ii) a stable dose-response model competitive with stable threshold and linear, nonthreshold (LNT) dose-response models, and (iii) a model having any impact on, or role in, regulatory and public health policies.

Adrenal, metabolic and cardio-renal dysfunction develops after pregnancy in rats born small or stressed by physiological measurements during pregnancy

KEY POINTS

Women born small are at an increased risk of developing pregnancy complications. Stress may further increase a woman's likelihood for an adverse pregnancy. Adverse pregnancy adaptations can lead to long-term diseases even after her pregnancy. The current study investigated the effects of stress during pregnancy on the long-term adrenal, metabolic and cardio-renal health of female rats that were born small. Stress programmed increased adrenal Mc2r gene expression, a higher insulin secretory response to glucose during intraperitoneal glucose tolerance test (+36%) and elevated renal creatinine clearance after pregnancy. Females that were born small had increased homeostatic model assessment-insulin resistance and elevated systolic blood pressure after pregnancy, regardless of stress exposure. These findings suggest that being born small or being stressed during pregnancy programs long-term adverse health outcomes after pregnancy. However, stress in pregnancy does not exacerbate the long-term adverse health outcomes for females that were born small.

ABSTRACT

Females born small are more likely to experience complications during their pregnancy, including pregnancy-induced hypertension, pre-eclampsia and gestational diabetes. The risk of developing complications is increased by stress exposure during pregnancy. In addition, pregnancy complications may predispose the mother to diseases after pregnancy. We determined whether stress during pregnancy would exacerbate the adrenal, metabolic and cardio-renal dysfunction of growth-restricted females in later life. Late gestation bilateral uterine vessel ligation was performed in Wistar Kyoto rats to induce growth restriction. At 4 months, growth-restricted and control female offspring were mated with normal males. Those allocated to the stressed group had physiological measurements [metabolic cage, tail cuff blood pressure, intraperitoneal glucose tolerance test (IPGTT)] conducted during pregnancy whilst the unstressed groups were unhandled. After the completion of pregnancy, dams were aged to 12 months and blood pressure, and metabolic and renal function were assessed. At 13 months, adrenal glands, pancreases and plasma were collected at post-mortem. Females stressed during pregnancy had increased adrenal Mc2r gene expression (+22%), higher insulin secretory response to glucose during IPGTT (+36%) and higher creatinine clearance (+29%, indicating increased estimated glomerular filtration rate). In contrast, females that were born small had increased homeostatic model assessment-insulin resistance (+54%), increased water intake (+23%), urine output (+44%) and elevated systolic blood pressure (+7%) regardless of exposure to stress. Our findings suggest that low maternal birth weight and maternal stress exposure during pregnancy are both independently detrimental for long-term adrenal, metabolic and cardio-renal health of the mother, although their effects were not exacerbated.

Effect of increased protein intake on renal acid load and renal hemodynamic responses

Increased protein intake versus maltodextrin intake for 4 weeks lowers blood pressure. Concerns exist that high‐protein diets reduce renal function. Effects of acute and 4‐week protein intake versus maltodextrin intake on renal acid load, glomerular filtration rate and related parameters were compared in this study. Seventy‐nine overweight individuals with untreated elevated blood pressure and normal kidney function were randomized to consume a mix of protein isolates (60 g/day) or maltodextrin (60 g/day) for 4 weeks in energy balance. Twenty‐four‐hour urinary potential renal acid load (uPRAL) was compared between groups. A subgroup (maltodextrin N = 27, protein mix N = 25) participated in extra test days investigating fasting levels and postprandial effects of meals supplemented with a moderate protein‐ or maltodextrin‐load on glomerular filtration rate, effective renal plasma flow, plasma renin, aldosterone, pH, and bicarbonate. uPRAL was significantly higher in the protein group after 4 weeks (P ≤ 0.001). Postprandial filtration fraction decreased further after the protein‐supplemented breakfast than after the maltodextrin‐supplemented breakfast after 4 weeks of supplementation (P ≤ 0.001). Fasting and postprandial levels of glomerular filtration rate, effective renal plasma flow, renin, aldosterone, angiotensin‐converting enzyme, pH and bicarbonate did not differ between groups. In conclusion, 4 weeks on an increased protein diet (25% of energy intake) increased renal acid load, but did not affect renal function. Postprandial changes, except for filtration fraction, also did not differ between groups. These data suggest that a moderate increase in protein intake by consumption of a protein mix for 4 weeks causes no (undesirable) effects on kidney function in overweight and obese individuals with normal kidney function.

The Impact of Nonalcoholic Fatty Liver Disease on Renal Function in Children with Overweight/Obesity

The association between nonalcoholic fatty liver disease (NAFLD) and chronic kidney disease has attracted interest and attention over recent years. However, no data are available in children. We determined whether children with NAFLD show signs of renal functional alterations, as determined by estimated glomerular filtration rate (eGFR) and urinary albumin excretion. We studied 596 children with overweight/obesity, 268 with NAFLD (hepatic fat fraction ≥5% on magnetic resonance imaging) and 328 without NAFLD, and 130 healthy normal-weight controls. Decreased GFR was defined as eGFR < 90 mL/min/1.73 m². Abnormal albuminuria was defined as urinary excretion of ≥30 mg/24 h of albumin. A greater prevalence of eGFR < 90 mL/min/1.73 m² was observed in patients with NAFLD compared to those without liver involvement and healthy subjects (17.5% vs. 6.7% vs. 0.77%; p < 0.0001). The proportion of children with abnormal albuminuria was also higher in the NAFLD group compared to those without NAFLD, and controls (9.3% vs. 4.0% vs. 0; p < 0.0001). Multivariate logistic regression analysis revealed that NAFLD was associated with decreased eGFR and/or microalbuminuria (odds ratio, 2.54 (confidence interval, 1.16–5.57); p < 0.05) independently of anthropometric and clinical variables. Children with NAFLD are at risk for early renal dysfunction. Recognition of this abnormality in the young may help to prevent the ongoing development of the disease.

Effect of angiotensin converting enzyme inhibitor on glomerular hyperfiltration in patients with type 1 diabetes

OBJECTIVE

To assess the effect of angiotensin converting enzyme inhibition on glomerular filtration rate (GFR) in normotensive patient with type 1 diabetes.

METHODS

A two year non-placebo control prospective study was conducted after ethical approval at Diabetes Centre of Diabetic Association of Pakistan, a WHO collaborating centre in Karachi, Pakistan. All patients with type 1 diabetes visited the out-patients department from August 2009 till July 2011 and those who fulfilled the inclusion criteria were invited to participate. A total of 121 people aged ≥18 years and ≥ 5 years of diabetes were included. Pregnant and lactating woman and those aged <18 years were excluded. GFR was calculated by using CKD-EPI formula (eGFR) at baseline and after two year. On the basis of estimated GFR, patients at baseline were divided according to KDIGO classification of chronic kidney diseases into, hyperfiltration (eGFR ≥ 100 ml/min) and normal filtration group (eGFR < 100 ml/min). All subjects in hyperfiltration group received ACE inhibitor (treatment group) while patients with normal filtration did not receive ACE inhibitor (control group).

RESULTS

Fifty two patients (43%) were in the treatment and sixty nine (57%) were in the control group. At baseline eGFR, systolic and diastolic blood pressures between groups were non-significantly different. After two years, compared to baseline, eGFR of the treatment group declined and the control group increased significantly. No significant difference in systolic while diastolic blood pressure of the treatment group increased significantly after two years compared to baseline. In contrast both systolic and diastolic blood pressure of control group increased significantly after two years compared to their baseline values.

CONCLUSION

Present study demonstrated that initiation of ACEI in hyperfiltration stage declined GFR and keep blood pressure within normal range.

Association of statin use and the risk of end-stage renal disease: A nationwide Asian population-based case-control study

BACKGROUND

Although experimental models have shown that statins could alleviate glomerular damage and decrease urinary protein excretion, the renal effects of statins remain unclear. A case-control study was conducted using data from Taiwan's National Health Insurance system.

METHODS

An end-stage renal disease (ESRD) group comprising 11,486 patients was established. Each patient was frequency-matched by age, sex, and comorbidities with one person without ESRD from the general population. Logistic regression analysis was performed to estimate the influence of statin use on ESRD risk.

RESULTS

The overall adjusted odds ratios (ORs) of ESRD among patients who received statins was 1.59 (95% confidence interval=1.50-1.68). The raised ESRD risk of statin remained consolidated regardless of statin type (P<.001), except lovastatin. Further, while stratified by cumulative define daily dose, the risk of ESRD increased with accumulative dosage of statins (P for trend<.001).

CONCLUSION

This population-based case-control study showed that statin use might be associated with increased ESRD risks. Large-scale randomized clinical trial encompassing statins of different kinds and populations of different comorbidities would be helpful to clarify the potential ESRD risks of statin users.

Association of sleep duration with kidney function and albuminuria: NHANES 2009-2012

OBJECTIVE

The purpose of this study was to examine the association between self-reported sleep duration and markers of kidney function.

DESIGN

A cross-sectional survey from the 2009-2012 National Health and Nutrition Examination Survey.

SETTING AND PARTICIPANTS

The participants were 8690 adults (e20years) without a previous sleep disorder diagnosis, end-stage kidney failure, or other kidney or liver problems. Subsamples with pre-diabetes and pre-hypertension were examined.

MEASUREMENTS

Participants reported habitual sleep duration, coded as d5, 6, 7, 8, and e9hours per night. Biomarkers of kidney function were determined, including glomerular filtration rate (eGFR) estimated from the Chronic Kidney Disease Epidemiology Collaboration equation, urine albumin-to-creatinine ratio (ACR), microalbuminuria status, and glomerular hyperfiltration status. Weighted and adjusted general linear models assessed associations between sleep duration with eGFR and ACR. Logistic regression analyses evaluated the associations of microalbuminuria and glomerular hyperfiltration status with sleep duration.

RESULTS

Greater eGFR was related to short sleep duration in the total sample and among participants with pre-diabetes. Greater ACR was associated with short and long sleep duration. Short sleep duration (d5hours) was associated with an increased odds for glomerular hyperfiltration (OR, 1.41; 95% CI, 0.97-2.06) and microalbuminuria (OR, 1.31; 95% CI, 0.96-1.79).

CONCLUSIONS

In a US representative sample of adults, self-reported short and long sleep duration were related to higher ACR. Short sleep duration was associated with higher eGFR and microalbuminuria. Research is needed to understand whether these associations indicate increased risk for kidney damage and cardiovascular risk.

The kidney and type 2 diabetes mellitus: therapeutic implications of SGLT2 inhibitors

Understanding the role of the kidneys in type 2 diabetes mellitus (T2DM) has taken on an increased importance in recent years with the arrival of sodium-glucose co-transporter 2 (SGLT2) inhibitors - antihyperglycemic agents (AHAs) that specifically target the kidneys. This review includes an update on the physiology of the kidneys, their role in the pathophysiology of T2DM, and the mechanisms implicated in the development and progression of diabetic kidney disease, such as glomerular hyperfiltration and inflammation. It also discusses renal issues that could influence the choice of AHA for patients with T2DM, including special populations such as patients with concomitant chronic kidney disease. The most recent data published on the clinical efficacy and safety of the SGLT2 inhibitors canagliflozin, dapagliflozin, and empagliflozin and their effects on renal function are presented, showing how the renally mediated mechanisms of action of these agents translate into clinical benefits, including the potential for renoprotection. The observed positive effects of these agents on measures such as glucose control, estimated glomerular filtration rate, albumin-to-creatinine ratio, blood pressure, and body weight in patients both with and without impaired renal function suggest that SGLT2 inhibitors represent an important extension to the diabetes treatment armamentarium.

Dabigatran Plasma Levels in Acute Cerebrovascular Events

BACKGROUND

Oral anticoagulation with dabigatran was shown to be effective for stroke prevention in patients with nonvalvular atrial fibrillation without the need for laboratory monitoring. However, a recent publication based on data of the Randomized Evaluation of Long-Term Anticoagulation Therapy study reported that ischemic stroke and bleeding outcomes are correlated with dabigatran plasma concentration (DPC). DPC was determined at a prespecified time point and correlated with cardiovascular events at any time during follow-up. Because of the known variability of DPC, among others depending on renal function, this approach might compromise data evaluation. We report on dabigatran plasma levels in acute cerebrovascular events.

METHODS

Consecutive patients with acute ischemic stroke (AIS) or intracerebral hemorrhage (ICH) while taking dabigatran were retrospectively identified if admission DPC was available. DPC was determined using the diluted thrombin time (Hemoclot (HYPHEN BioMed, Neuville sur Oise, France)). Creatinine clearance (CrCl) was determined by measuring creatinine in plasma and 24-hour urine.

RESULTS

Fifteen AIS and 4 ICH patients were included. Median DPC on admission was significantly higher in ICH patients than in AIS patients (135 ng/mL [interquartile range {IQR} 79-218] and 69.1 ng/mL [IQR 20.6-85.0], respectively; P = .035). Increased CrCl (values above published normal range) was correlated with lower median DPC (60 ng/mL [IQR 10-69] versus 100 ng/mL [IQR 79-157] in patients with normal CrCl, P = .01).

CONCLUSIONS

Higher DPC was found in ICH patients than in AIS patients in temporal proximity to the event. Both decreased and increased renal functions seem to have an important influence on DPC.

Urinary Extracellular Vesicles: Potential Biomarkers of Renal Function in Diabetic Patients

The aim of this study was to check the relationship between the density of urinary EVs, their size distribution, and the progress of early renal damage in type 2 diabetic patients (DMt2). Patients were enrolled to this study, and glycated hemoglobin (HbA1c) below 7% was a threshold for properly controlled diabetic patients (CD) and poorly controlled diabetic patients (UD). Patients were further divided into two groups: diabetic patients without renal failure (NRF) and with renal failure (RF) according to the Glomerular Filtration Rate. Density and diameter of EVs were determined by Tunable Resistive Pulse Sensing. Additionally, EVs were visualized by means of Transmission and Environmental Scanning Electron Microscopy. Nano-liquid chromatography coupled offline with mass spectrometry (MALDI-TOF-MS/MS) was applied for proteomic analysis. RF had reduced density of EVs compared to NRF. The size distribution study showed that CD had larger EVs (mode) than UD (115 versus 109 nm; p < 0.05); nevertheless the mean EVs diameter was smaller in controls than in the CD group (123 versus 134 nm; p < 0.05). It was demonstrated that EVs are abundant in urine. Albumin, uromodulin, and number of unique proteins related to cell stress and secretion were detected in the EVs fraction. Density and size of urinary EVs reflect deteriorated renal function and can be considered as potential renal damage biomarkers.

Association of Retinoid X Receptor Alpha Gene Polymorphism with Clinical Course of Chronic Glomerulonephritis

Background

Vitamin D (VD), VD binding protein, VD receptor (VDR), and retinoids are involved in pathogenesis of chronic glomerulonephritis (ChGN). We aimed to compare distribution of VD pathway gene polymorphisms in ChGN patients showing glomerular filtration rate (GFR) category 1–3, GFR category 5D, and healthy controls in order to elucidate the role of VD-related polymorphisms in the course of ChGN.

Material/Methods

GFR category 1–3 ChGN patients (n=195), GFR category 5D ChGN patients (n=178), and controls (n=751) underwent testing for polymorphisms of genes encoding VD binding protein (GC, rs2298849, rs7041, rs1155563), VDR (VDR, rs2228570, rs1544410), and retinoid X receptor alpha (RXRA, rs10776909, rs10881578, rs749759).

Results

Among GFR 1–3 subjects possessing TT genotype of RXRA rs10776909, 75% of patients had nephrotic syndrome, and 37.5% had glomerular hyperfiltration defined as GFR >140 ml/min/1.73 m², and, consequently, serum creatinine was lower in these patients compared to the remaining subjects (0.67±0.26 vs. 0.94±0.34, P=0.014). In GFR category 5D ChGN patients, frequencies of RXRA rs10776909 allele T (25% vs. 19%) and CT+TT (46% vs. 34%) were higher compared to frequencies of respective variants in controls (P_trend=0.004, P_genotype=0.008).

Conclusions

RXRA rs10776909 allele T is specifically involved in the pathogenesis of ChGN. This risk allele may be also associated with worse clinical course of ChGN.

Documentation of renal glomerular and tubular impairment and glomerular hyperfiltration in multitransfused patients with beta thalassemia

Urinary albumin to creatinine (ACR) and beta2 microglobulin to creatinine ratios (BCR) are the surrogate and robust markers of renal glomerulopathy and tubulopathy, respectively. These markers predict short-term renal deterioration and mortality in various conditions. We aimed to assess the frequency and predictors of glomerular and tubular defects, renal impairment, and hyperfiltration in 96 adult patients with beta thalassemia intermedia and major. ACR > 300 mg/g creatinine and BCR > 300 μg/g creatinine were used to define the renal glomerular and tubular damages, respectively. Glomerular filtration rate (eGFRcreat) was estimated according to 2009 the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Decreased eGFRcreat was defined as less than 60 mL/min per 1.73 m(2). Renal glomerular and/or tubular defects were observed in about 68.8 % of all patients. Forty percent of patients had glomerular hyperfiltration. None of the patients had a decreased eGFRcreat. T2* value ≤20 msec on cardiac magnetic resonance (cMR) was the only independent predictor of glomerular damage (p = 0.013). Use of alendronate was associated with less renal tubular damage (p = 0.007). Female gender and previous history of splenectomy were the independent predictors of glomerular hyperfiltration in multivariate analysis (p < 0.001 and p = 0.040, respectively). Renal tubular and glomerular damage is frequent in adult patients with thalassemia intermedia and major. T2* value on cMR was the only independent predictor of glomerular damage. However, since we did not explore all the parameters of iron, it is not possible to draw a definite conclusion about the association of cMR and glomerular damage. There is no association with cardiac iron overload/accumulation and tubular damage or hyperfiltration.

Abdominal Adipose Tissue was Associated with Glomerular Hyperfiltration among Non- Diabetic and Normotensive Adults with a Normal Body Mass Index

Glomerular hyperfiltration is recognized as an early marker of progressive kidney dysfunction in the obese population. This study aimed to identify the relationship between glomerular hyperfiltration and body fat distribution measured by computed tomography (CT) in healthy Korean adults. The study population included individuals aged 20-64 years who went a routine health check-up including an abdominal CT scan. We selected 4,378 individuals without diabetes and hypertension. Glomerular filtration rate was estimated using the CKD-EPI equation, and glomerular hyperfiltration was defined as the highest quintile of glomerular filtration rate. Abdominal adipose tissue areas were measured at the level of the umbilicus using a 16-detector CT scanner, and the cross-sectional area was calculated using Rapidia 2.8 CT software. The prevalence of glomerular hyperfiltration increased significantly according to the subcutaneous adipose tissue area in men (OR = 1.74 (1.16-2.61), P for trend 0.016, for the comparisons of lowest vs. highest quartile) and visceral adipose tissue area in women (OR = 2.34 (1.46-3.75), P for trend < 0.001) in multivariate analysis. After stratification by body mass index (normal < 23 kg/m2, overweight ≥ 23 kg/m2), male subjects with greater subcutaneous adipose tissue, even those in the normal BMI group, had a higher prevalence of glomerular hyperfiltration (OR = 2.11 (1.17-3.80), P for trend = 0.009). Among women, the significance of visceral adipose tissue area on glomerular hyperfiltration resulted from the normal BMI group (OR = 2.14 (1.31-3.49), P for trend = 0.002). After menopause, the odds ratio of the association of glomerular hyperfiltration with subcutaneous abdominal adipose tissue increased (OR = 2.96 (1.21-7.25), P for trend = 0.013). Subcutaneous adipose tissue areas and visceral adipose tissue areas are positively associated with glomerular hyperfiltration in healthy Korean adult men and women, respectively. In post-menopausal women, visceral adipose tissue area shows significant positive association with glomerular hyperfiltration as in men.

Effect of Acetazolamide on Obesity-Induced Glomerular Hyperfiltration: A Randomized Controlled Trial

AIMS

Obesity is an important risk factor for the development of chronic kidney disease. One of the major factors involved in the pathogenesis of obesity-associated kidney disease is glomerular hyperfiltration. Increasing salt-delivery to the macula densa is expected to decrease glomerular filtration rate (GFR) by activating tubuloglomerular feedback. Acetazolamide, a carbonic anhydrase inhibitor which inhibits salt reabsorption in the proximal tubule, increases distal salt delivery. Its effects on obesity-related glomerular hyperfiltration have not previously been studied. The aim of this investigation was to evaluate whether administration of acetazolamide to obese non diabetic subjects reduces glomerular hyperfiltration.

MATERIALS AND METHODS

The study was performed using a randomized double-blind crossover design. Obese non-diabetic men with glomerular hyperfiltration were randomized to receive intravenously either acetazolamide or furosemide at equipotent doses. Twelve subjects received the allocated medications. Two weeks later, the same subjects received the drug which they had not received during the first study. Inulin clearance, p-aminohippuric acid clearance and fractional lithium excretion were measured before and after medications administration. The primary end point was a decrease in GFR, measured as inulin clearance.

RESULTS

GFR decreased by 21% following acetazolamide and did not decrease following furosemide. Renal vascular resistance increased by 12% following acetazolamide, while it remained unchanged following furosemide administration. Natriuresis increased similarly following acetazolamide and furosemide administration. Sodium balance was similar in both groups.

CONCLUSIONS

Intravenous acetazolamide decreased GFR in obese non-diabetic men with glomerular hyperfiltration. Furosemide, administered at equipotent dose, did not affect GFR, suggesting that acetazolamide reduced glomerular hyperfiltration by activating tubuloglomerular feedback.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01146288.

First Trimester Urine and Serum Metabolomics for Prediction of Preeclampsia and Gestational Hypertension: A Prospective Screening Study

Hypertensive disorders of pregnancy, including preeclampsia, are major contributors to maternal morbidity. The goal of this study was to evaluate the potential of metabolomics to predict preeclampsia and gestational hypertension from urine and serum samples in early pregnancy, and elucidate the metabolic changes related to the diseases. Metabolic profiles were obtained by nuclear magnetic resonance spectroscopy of serum and urine samples from 599 women at medium to high risk of preeclampsia (nulliparous or previous preeclampsia/gestational hypertension). Preeclampsia developed in 26 (4.3%) and gestational hypertension in 21 (3.5%) women. Multivariate analyses of the metabolic profiles were performed to establish prediction models for the hypertensive disorders individually and combined. Urinary metabolomic profiles predicted preeclampsia and gestational hypertension at 51.3% and 40% sensitivity, respectively, at 10% false positive rate, with hippurate as the most important metabolite for the prediction. Serum metabolomic profiles predicted preeclampsia and gestational hypertension at 15% and 33% sensitivity, respectively, with increased lipid levels and an atherogenic lipid profile as most important for the prediction. Combining maternal characteristics with the urinary hippurate/creatinine level improved the prediction rates of preeclampsia in a logistic regression model. The study indicates a potential future role of clinical importance for metabolomic analysis of urine in prediction of preeclampsia.

Gallic acid ameliorates renal functions by inhibiting the activation of p38 MAPK in experimentally induced type 2 diabetic rats and cultured rat proximal tubular epithelial cells

Diabetic nephropathy (DN) is one of the leading causes of morbidity and mortality in diabetic patients that accounts for about 40% of deaths in type 2 diabetes. p38 mitogen activated protein kinase (p38 MAPK), a serine-threonine kinase, plays an important role in tissue inflammation and is known to be activated under conditions of oxidative stress and hyperglycemia. The role of p38 MAPK has been demonstrated in DN, and its inhibition has been suggested as an alternative approach in the treatment of DN. In the present study, we investigated the nephroprotective effects of an anti-inflammatory phenolic compound, gallic acid (GA, 3,4,5-trihydroxybenzoic acid), in high fat diet/streptozotocin (HFD/STZ) induce type 2 diabetic wistar albino rats. GA (25 mg/kgbw and 50 mg/kgbw, p.o.) treatment for 16 weeks post induction of diabetes led to a significant reduction in the levels of blood glucose, HbA1c, serum creatinine, blood urea nitrogen and proteinuria as well as a significant reduction in the levels of creatinine clearance. GA significantly inhibited the renal p38 MAPK and nuclear factor kappa B (N-κB) activation as well as significantly reduced the levels of renal transforming growth factor beta (TGF-β) and fibronectin. Treatment with GA resulted in a significant reduction in the serum levels of proinflammatory cytokines viz. interleukin 1 beta (IL-1β), IL-6 and tumor necrosis factor alpha (TNF-α). Moreover, GA significantly lowered renal pathology and attenuated renal oxidative stress. In cultured rat NRK 52E proximal tubular epithelial cells, GA treatment inhibited high glucose induced activation of p38 MAPK and NF-κB as well as suppressed proinflammatory cytokine synthesis. The results of the present study provide in vivo and in vitro evidences that the p38 MAPK pathway plays an important role in the pathogenesis of DN, and GA attenuates the p38 MAPK-mediated renal dysfunction in HFD/STZ induced type 2 diabetic rats.

Beat it early: putative renoprotective haemodynamic effects of oral hypoglycaemic agents

Diabetic kidney disease represents a considerable burden; around one-third of patients with type 2 diabetes develop chronic kidney disease. In health, the kidneys play an important role in the regulation of glucose homeostasis via glucose utilization, gluconeogenesis and glucose reabsorption. In patients with diabetes, renal glucose homeostasis is significantly altered with an increase in both gluconeogenesis and renal tubular reabsorption of glucose. Environmental factors, both metabolic (hyperglycaemia, obesity and dyslipidaemia) and haemodynamic, together with a genetic susceptibility, lead to the activation of pro-oxidative, pro-inflammatory and pro-fibrotic pathways resulting in kidney damage. Hyperfiltration and its haemodynamic-driven insult to the kidney glomeruli is an important player in proteinuria and progression of kidney disease towards end-stage renal failure. Control of glycaemia and blood pressure are the mainstays to prevent kidney damage and slow its progression. There is emerging evidence that some hypoglycaemic agents may have renoprotective effects which are independent of their glucose-lowering effects. Sodium-glucose co-transporter-2 (SGLT-2) inhibitors may exert a renoprotective effect by a number of mechanisms including restoring the tubuloglomerular feedback mechanism and lowering glomerular hyperfiltration, reducing inflammatory and fibrotic markers induced by hyperglycaemia thus limiting renal damage. Simultaneous use of an SGLT-2 inhibitor and blockade of the renin-angiotensin-aldosterone system may be a strategy to slow progression of diabetic nephropathy more than either drug alone. The use of dipeptidyl peptidase-4 inhibitors and glucagon-like peptide 1 receptor agonists may exert a renoprotective effect by reducing inflammation, fibrosis and blood pressure. Given the burden of diabetic kidney disease, any additional renoprotective benefit with hypoglycaemic therapy is to be welcomed. Large randomized controlled trials are currently underway investigating if these new anti-diabetic agents can provide renoprotection in diabetes.

Associations between renal hyperfiltration and serum alkaline phosphatase

Renal hyperfiltration, which is associated with renal injury, occurs in diabetic or obese individuals. Serum alkaline phosphatase (ALP) level is also elevated in patients with diabetes (DM) or metabolic syndrome (MS), and increased urinary excretion of ALP has been demonstrated in patients who have hyperfiltration and tubular damage. However, little was investigated about the association between hyperfiltration and serum ALP level. A retrospective observational study of the 21,308 adults in the Korea National Health and Nutrition Examination Survey IV-V databases (2008–2011) was performed. Renal hyperfiltration was defined as exceeding the age- and sex-specific 97.5^th percentile. We divided participants into 4 groups according to their estimated glomerular filtration rate (eGFR): >120, 90–119, 60–89, and <60 mL/min/1.73 m². The participants with eGFR >120 mL/min/1.73 m² showed the highest risk for MS, in the highest ALP quartiles (3.848, 95% CI, 1.876–7.892), compared to the lowest quartile. Similarly, the highest risk for DM, in the highest ALP quartiles, was observed in participants with eGFR >120 ml/min/1.73 m² (2.166, 95% CI, 1.084–4.329). ALP quartiles were significantly associated with albuminuria in participants with eGFR ≥ 60 ml/min/1.73m². The highest ALP quartile had a 1.631-fold risk elevation for albuminuria with adjustment of age and sex. (95% CI, 1.158-2.297, P = 0.005). After adjustment, the highest ALP quartile had a 1.624-fold risk elevation, for renal hyperfiltration (95% CI, 1.204–2.192, P = 0.002). In addition, hyperfiltration was significantly associated with hemoglobin, triglyceride, white blood cell count, DM, smoking, and alcohol consumption (P<0.05). The relationship between serum ALP and metabolic disorders is stronger in participants with an upper-normal range of eGFR. Higher ALP levels are significantly associated with renal hyperfiltration in Korean general population.

Renal functional outcomes after surgery for renal cortical tumors

Historically, radical nephrectomy represented the gold standard for the treatment of small (≤ 4cm) as well as larger renal masses. Recently, for small renal masses, the risk of ensuing chronic kidney disease and end stage renal disease has largely favored nephron-sparing surgical techniques, mainly partial nephrectomy. In this review, we surveyed the literature on renal functional outcomes after partial nephrectomy for renal tumors. The largest randomized control trial comparing radical and partial nephrectomy failed to show a survival benefit for partial nephrectomy. With regards to overall survival, surgically induced chronic kidney disease (GFR < 60 ml/min/ 1.73m²) caused by nephrectomy might not be as deleterious as medically induced chronic kidney disease. In evaluating patients who underwent donor nephrectomy, transplant literature further validates that surgically induced reductions in GFR may not affect patient survival, unlike medically induced GFR declines. Yet, because patients who present with a renal mass tend to be elderly with multiple comorbidities, many develop a mixed picture of medically, and surgically-induced renal disease after extirpative renal surgery. In this population, we believe that nephron sparing surgery optimizes oncological control while protecting renal function.

Use of Dual-Source Computed Tomography to Evaluate Renal Cortical Perfusion in Patients With Essential Hypertension Without Diabetes: Preliminary Results

OBJECTIVES

To assess renal cortical perfusion parameter changes using computed tomography (CT) renal perfusion examination in patients with essential hypertension (EH), especially those with EH-related target organ damage (TOD), and to correlate renal perfusion parameters with clinical and laboratory data.

METHODS

Consecutive patients with EH (without exclusion criteria) and healthy controls underwent 128-slice dual-source CT perfusion imaging. Quantitative perfusion analysis of renal cortex parameters [blood flow (BF), blood volume, time to peak, and mean transit time] was performed.

RESULTS

Ninety-one participants (60 patients with EH, 31 healthy controls) underwent renal perfusion CT imaging, and 84 participants (92.3%) were eligible for perfusion analysis. The BF values were lower in patients with EH than that in controls. Blood flow was correlated with age (P < 0.01), duration of hypertension (P < 0.01), estimated glomerular filtration rate (eGFR; P < 0.01), pulse pressure (P < 0.05), and body mass index (BMI; P < 0.05). Duration of hypertension, eGFR, and BMI were independently associated with BF. No parameter differed between control subjects and those with EH but not. Blood flow was lower in patients with TOD than in control subjects (P < 0.01), but no other parameter differed. Blood flow was lower (P < 0.01) and mean transit time and time to peak were higher (P < 0.05) in the TOD than that in the non-TOD group.

CONCLUSIONS

Essential hypertension, especially EH-related TOD, alters renal cortical perfusion parameters, especially BF. Four-dimensional spiral CT renal perfusion examination showed that duration of hypertension, eGFR, and BMI were independently associated with decreased BF.

Kidney function in severely obese adolescents undergoing bariatric surgery

OBJECTIVE

Determine objective measures of kidney function and analyze factors associated with kidney dysfunction in severely obese adolescents undergoing weight loss surgery were described.

METHODS

Cross-sectional data from 242 adolescent participants in the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study before weight loss surgery were analyzed. Kidney status was assessed by measuring urine albumin creatinine ratio to determine microalbuminuria and by calculating serum cystatin C-based estimated glomerular filtration rate (eGFR) to assess kidney function.

RESULTS

Mean age and median body mass index (BMI) were 17.1 years and 50.5 kg/m(2) , respectively; 76% were females and 65% were non-Hispanic white race. Fourteen percent of the cohort had microalbuminuria, and 3% had macroalbuminuria; 3% had eGFR < 60 ml/min/1.73 m(2) , and 7.1% had eGFR > 150 ml/min/1.73 m(2) . In adjusted analyses, female gender and increasing ferritin levels were significantly associated with the presence of microalbuminuria/macroalbuminuria. Increasing BMI and homeostasis model assessment of insulin resistance values were significantly associated with lower eGFR.

CONCLUSIONS

A significant number of severely obese adolescents undergoing weight loss surgery have evidence of early kidney dysfunction. Longitudinal studies following weight loss surgery in these individuals are needed to determine whether these kidney abnormalities are reversible following weight loss therapy.

Obesity and kidney protection

CONTEXT

Obesity, both directly and indirectly, increases the risk for a variety of disease conditions including diabetes, hypertension, liver disease, and certain cancers, which in turn, decreases the overall lifespan in both men and women. Though the cardiovascular risks of obesity are widely acknowledged, less often identified is the relationship between obesity and renal function.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, PubMed, EBSCO and Web of Science has been searched.

RESULTS

The concept of the "Metabolic Syndrome" helps us to understand this close link between obesity, diabetes, hypertension, and renal dysfunction. An elevated body mass index has shown to be one of the major determinants of glomerular hyperfiltration that lead to the development of chronic kidney disease. Interestingly, weight loss can lead to attenuation of hyperfiltration in severely obese patients suggesting a possible therapeutic option to combat obesity-related hyperfiltration.

CONCLUSIONS

Various treatment strategies had been suggested to decrease impact of obesity on kidneys. These are blood pressure controling, inhibition of the renin-angiotensinaldosterone axis, improving glycemic control, improving dyslipidemia, improving protein uriaand lifestyle modifications. Regardless of the numerous pharmacotherapies, the focus should be on the root cause: obesity.

A longitudinal assessment of the natural rate of decline in renal function with age

BACKGROUND

Cross-sectional studies have long suggested that renal function declines with age. Longitudinal studies regarding this issue are limited.

METHODS

We retrospectively analyzed a database of subjects attending a screening center in Israel between the years 2000-2012. Only subjects with normal estimated glomerular filtration rate (eGFR) were included. eGFR was assessed consequently at 5 or more yearly visits. The rate of decline in GFR with age was assessed in healthy subjects and in subjects with comorbidities.

RESULTS

The cohort included 2693 healthy subjects and 230 subjects with different comorbidities. Mean (±standard error) annual rate of decline in eGFR in healthy subjects was 0.97 ± 0.02 ml/min/year/1.73 m(2). This decline increased significantly from 0.82 ± 0.22 in age-group 20-30 years to 0.84 ± 0.08, 1.07 ± 0.08 and 1.15 ± 0.12 ml/min/year/1.73 m(2) in age groups 31-40, 41-50 and 50 years and older respectively (p < 0.001). No correlation was found between the annual decline in eGFR and body mass index. In subjects with hypertension, diabetes mellitus, impaired fasting glucose or combined comorbidity the decline in eGFR was 1.12 ± 0.12, 0.77 ± 0.16, 0.85 ± 0.17, and 1.18 ± 0.26 ml/min/year/1.73 m(2) respectively.

CONCLUSIONS

This large longitudinal study provides new data on the decrease in eGFR with age. Accurate prediction of the natural rate of GFR decline might be used to distinguish between normally aging kidneys and those with chronic disease. This approach could avoid unnecessary diagnostic procedures in the former and facilitate appropriate treatment in the latter.

The number of metabolic syndrome components is a good risk indicator for both early- and late-stage kidney damage

BACKGROUND AND AIMS

Renal hyperfiltration (early-stage kidney damage) and hypofiltration (late-stage kidney damage) are common in populations at high risk of chronic kidney disease. This study investigated the associations of renal hyperfiltration and hypofiltration with the number of metabolic syndrome (MetS) components.

METHODS AND RESULTS

The study subjects included 205,382 people aged 40-74 years who underwent Specific Health Checkups in Aichi Prefecture, Japan. The prevalence of renal hyperfiltration [estimated glomerular filtration rate (eGFR) above the age-/sex-specific 95th percentile] and hypofiltration (eGFR below the 5th percentile) was compared according to the number of MetS components. We found that the prevalence of both hyperfiltration and hypofiltration increased with increasing number of MetS components (odds ratios for hyperfiltration: 1.20, 1.40, 1.42, 1.41, and 1.77; odds ratios for hypofiltration: 1.07, 1.25, 1.57, 1.89, and 2.21 for one, two, three, four, and five components, respectively, compared with no MetS components). These associations were observed in both normal weight [body mass index (BMI) < 25 kg/m(2)] and overweight (BMI ≥ 25 kg/m(2)) subjects. Renal hyperfiltration was associated with prehypertension and prediabetes, while hypofiltration was associated with dyslipidemia, abdominal obesity, overt hypertension, and overt diabetes.

CONCLUSION

The number of MetS components is a good risk indicator of early- and late-stage kidney damage. Therefore, kidney function should be monitored in subjects with MetS components. MetS components should be treated as early as possible to prevent the development of kidney damage and cardiovascular diseases in people with hyperfiltration, regardless of their body weight.

HIV therapy, metabolic and cardiovascular health are associated with glomerular hyperfiltration among men with and without HIV infection

OBJECTIVE

Diabetes and hypertension, common conditions in antiretroviral-treated HIV-infected individuals, are associated with glomerular hyperfiltration, which precedes the onset of proteinuria and accelerated kidney function decline. In the Multicenter AIDS Cohort Study, we examined the extent to which hyperfiltration is present and associated with metabolic, cardiovascular, HIV and treatment risk factors among HIV-infected men.

DESIGN

Cross-sectional cohort using direct measurement of glomerular filtration rate by iohexol plasma clearance for 367 HIV-infected men and 241 HIV-uninfected men who were free of chronic kidney disease.

METHODS

Hyperfiltration was defined as glomerular filtration rate above 140-1 ml/min per 1.73 m per year over age 40. Multivariate logistic regression was used to estimate the odds ratios (ORs) of prevalent hyperfiltration for metabolic, cardiovascular, HIV and cumulative antiretroviral exposure factors.

RESULTS

Among individuals without chronic kidney disease, the prevalence of hyperfiltration was higher for HIV-infected participants (25%) compared to uninfected participants (17%; P = 0.01). After adjustment, HIV infection remained associated with hyperfiltration [OR 1.70, 95% confidence interval (CI) 1.11-2.61] and modified the association between diabetes and hyperfiltration, such that the association among HIV-uninfected men (OR 2.56, 95% CI 1.33-5.54) was not observed among HIV-infected men (OR 1.19, 95% CI 0.69-2.05). These associations were independent of known risk factors for hyperfiltration. Indicators of hyperglycemia and hypertension were also associated with hyperfiltration as was cumulative zidovudine exposure.

CONCLUSION

Hyperfiltration, a potential modifiable predictor of kidney disease progression, is significantly higher among antiretroviral-treated HIV-infected men. Furthermore, HIV-infection nullifies the association of diabetes and hyperfiltration present in HIV-uninfected men.

Fabrication of 3D Photoresist Structure for Artificial Capillary Blood Vessel

We propose a new method for fabricating artificial capillaries using direct laser writing. IP-L and Ormocomp are tested as photoresist materials. Three different microstructures were fabricated from IP-L: a porous hollow pipe microstructure, a 3 × 3 array of twig microstructures, and an array of hollow twig microstructures. Porous hollow pipe microstructures of different diameters were fabricated from Ormocomp, a biocompatible photoresist. These designs resemble capillaries. IP-L and Ormocomp fabrication parameters, such as laser power, numerical aperture, fabrication time, and fabrication model, are compared. Fabrication time is related to the fabrication model chosen during the direct laser writing process. Combined model fabrication is recommended over solid model fabrication because it results in shorter fabrication time and a more robust microstructure that is more likely to maintain its shape on the substrate after development. Laser power is another important parameter controlling fabrication. IP-L fabrication withstands up to 20 mW of laser power, unlike Ormocomp microstructures, which require laser power of less than 18 mW. IP-L and Ormocomp photoresist stiffness is also evaluated. The fabrication of artificial capillaries is important in developing vascular simulators that enable researchers to understand, for example, blood pressure in the kidney glomerulus.

Sodium glucose cotransporter 2 and the diabetic kidney

PURPOSE OF REVIEW

Reabsorption of glucose in the proximal tubule occurs predominantly via the sodium glucose cotransporter 2 (SGLT2). There has been intense interest in this transporter as a number of SGLT2 inhibitors have entered clinical development. SGLT2 inhibitors act to lower plasma glucose by promoting glycosuria and this review aims to outline the effect on the diabetic kidney of this hypoglycaemic agent.

RECENT FINDINGS

This review provides an overview of recent findings in this area: the transcriptional control of SGLT2 expression in human proximal tubular cells implicates a number of cytokines in the alteration of SGLT2 expression; experimental data show that SGLT2 inhibition may correct early detrimental effects of diabetes by reducing proximal tubular sodium and glucose transport, suggesting a possible renoprotective effect independent of the glucose lowering effects of these agents; and the nonglycaemic effects of SGLT2 inhibitors may have an impact on renal outcomes.

SUMMARY

The available clinical evidence shows consistent reduction in glycaemic parameters and some evidence suggests additional effects including weight loss and mild blood pressure reduction. There are some side effects that warrant further investigation and establishing whether SGLT2 inhibition provides a renal benefit relies on future long-term studies with specific renal end-points.

GFR estimating equations: getting closer to the truth?

The application of serum creatinine and cystatin C in patients with CKD has been limited to using estimated glomerular filtration rate (eGFR). Criteria for choosing the best GFR estimating equation are 1) accuracy in estimating measured GFR, 2) optimal discrimination of clinical outcomes, and 3) association with CKD risk factors and outcomes similar to that of measured GFR. Notably, these criteria are often not in agreement; and while the last criterion is the most important, it has been widely overlooked. The primary problem with eGFR is that the non-GFR determinants of serum creatinine and cystatin C, as well as their surrogates (age, sex, and race), associate with CKD risk factors and outcomes. This leads to a distorted understanding of CKD, though eGFR based on serum creatinine appears to be less biased than eGFR based on cystatin C. Because of this problem, the use of eGFR should be limited to settings where knowing actual GFR is relevant and eGFR is more informative about GFR than serum creatinine or cystatin C alone. Such settings include staging CKD severity by GFR and dosing medications cleared by glomerular filtration. Alternatively, the diagnosis of CKD, the longitudinal progression of CKD, and prognostic models for CKD are settings where serum creatinine and cystatin C can be better applied and interpreted without eGFR.

Renal hyperfiltration in prediabetes confirmed by fasting plasma glucose and hemoglobin A1c

BACKGROUND

The aim of the study was to confirm that glomerular hyperfiltration, an early and reversible stage of kidney damage, is associated in patients with prediabetes and prehypertension.

METHODS

In total, 5003 people aged between 35 and 69 years who had participated in the Shizuoka part of the Japan Multi-Institutional Collaborative Cohort (J-MICC) study took part in the study. Prevalence of hyperfiltration [the estimated glomerular filtration rate (eGFR) above the age- /sex-specific 95th percentile] was compared among different stages of prediabetes [fasting plasma glucose (FPG) < 100, 100-109, 110-125, and ≥126 mg/dL; and/or hemoglobin A1c (HbA1c) < 5.7, 5.7-6.0, 6.1-6.4 and ≥6.5% for no prediabetes, stage 1 prediabetes, stage 2 prediabetes, and overt diabetes, respectively] and prehypertension (blood pressure <120/80, 120-129/80-84, 130-139/85-89, and ≥140/90 mmHg for no prehypertension, stage 1 prehypertension, stage 2 prehypertension, and overt hypertension, respectively).

RESULTS

The prevalence of hyperfiltration increased with increasing stages of prediabetes (odds ratios: 1.25, 1.68, and 2.37 using FPG, and 1.26, 2.15, and 2.45 using HbA1c for stage 1 prediabetes, stage 2 prediabetes, and diabetes, respectively, relative to no prediabetes). Prehypertension, however, was not associated with hyperfiltration.

CONCLUSION

The results confirmed that the prevalence of glomerular hyperfiltration increased with increasing stages (i.e., worsening) of prediabetes. Because both FPG and HbA1c showed similar association with hyperfiltration, either of these can be used to identify subjects who are at increased risk of nephropathy. Therefore, the functioning of kidneys should be monitored in subjects with prediabetes. Prompt treatment of hyperglycemia is necessary in subjects with hyperfiltration to prevent it to cause nephropathy.

The role of dietary protein in blood pressure regulation

PURPOSE OF REVIEW

Despite a considerable amount of research, the blood pressure (BP) lowering effect of dietary proteins is still not fully established. This review discusses the most recent findings on BP lowering of dietary proteins and protein sources, the possible mechanisms and the safety of increasing protein intake.

RECENT FINDINGS

Recent short-term, strictly controlled, randomized clinical trials show a BP lowering effect of increased protein intake. Longer-term trials, however, show inconsistent results. Because all recent trials exchanged carbohydrates, and not fats, for proteins, the question remains whether potential beneficial effects of high protein diets are due to increased protein intake or decreased carbohydrate intake. No clear differences between plant protein and animal protein are found in observational studies, and trials comparing plant versus animal protein are lacking. Different protein sources may lower BP via different mechanisms, which might explain divergent findings. Potential harms of high protein diets are not confirmed in recent trials in healthy persons.

SUMMARY

Increasing dietary protein intake or decreasing carbohydrate intake within reasonable limits may be beneficial for BP. The most and least beneficial protein sources still need to be determined.

Hypertension in obesity: is leptin the culprit?

The number of obese or overweight humans continues to increase worldwide. Hypertension is a serious disease that often develops in obesity, but it is not clear how obesity increases the risk of hypertension. However, both obesity and hypertension increase the risk of cardiovascular diseases (CVD). In this review, we examine how obesity may increase the risk of developing hypertension. Specifically, we discuss how the adipose-derived hormone leptin influences the sympathetic nervous system (SNS), through actions in the brain to elevate energy expenditure (EE) while also contributing to hypertension in obesity.

Limits to chemical hormesis as a dose-response model in health risk assessment

This review presents and discusses the extent to which chemical hormesis meets five important requirements for performance of any dose-response model in the toxicological and regulatory sciences. These include (1) the requirement that there be a documented and accepted mechanistic basis for the dose-response model's plausible role and use in health risk assessment; (2) the requirement that any newly proposed dose-response methodology can be compared with current models as to reliability and scientific validity; (3) the requirement that the underlying reliability and stability of the model be established as to its temporal aspects, that is, minimal temporal lag between stressor contact and biological or toxicological response and temporal stability expressed throughout the prevailing relationship; (4) the requirement that the dose-response model be as broadly applicable as other dose-response methodologies being applied in human health risk assessment; and, (5) the requirement that any dose-response model proposed as default methodology can be characterized as to variability and uncertainty and will have a minimal likelihood of harm to the health of impacted populations. This review includes a brief treatment of definitions of hormesis and its place in nonmonotonic dose-response relationships. Overall, critical evaluation of chemical hormesis as a dose-response model in risk assessment shows it to have significant limits within the five requirements. These limits will impede any acceptance of chemical hormesis as a default approach in health risk assessment.

Microalbuminuria and hyperfiltration in subjects with nephro-urological disorders

BACKGROUND

Microalbuminuria (MA) has been shown to be an early biomarker of renal damage. It is postulated that MA is the early result of hyperfiltration, which could evolve into glomerular sclerosis and renal failure if hyperfiltration is left untreated. We hypothesized that MA is a good indicator of hyperfiltration in children with kidney disorders, obviating the need to calculate the filtration fraction (FF).

METHODS

A total of 155 children or young adults were prospectively included [42 single kidney (SK), 61 vesico-ureteral reflux, 23 obstructive uropathies, 29 other kidney diseases]. We measured inulin, para-aminohippuric acid clearances, FF and MA. Prediction of hyperfiltration was explored by studying the association between the FF and other variables such as urinary albumin (Alb), urinary albumin-creatinine ratio (ACR) and creatinine clearance.

RESULTS

A significant but weak association between urinary Alb or ACR and FF was found in subjects with an SK (Spearman correlation coefficients 0.32 and 0.19, respectively). Multivariate analysis also showed that urinary Alb and ACR significantly predict FF only in subjects with an SK (r(2) = 0.17, P = 0.01 and r(2) = 0.13, P = 0.02, respectively). This holds true only in subjects with an SK and inulin clearance >90 mL/min/1.73 m(2) (r(2) = 0.41, P < 0.001). There was no association between creatinine clearance and FF.

CONCLUSIONS

MA is not associated with FF in our subjects with nephro-urological disorders, except in those with an SK, where the association is weak, indicating that MA is due to other mechanisms than high FF and cannot predict hyperfiltration in such groups.