Glomerular hyperfiltration: definitions, mechanisms and clinical implications

Associations of CKD risk factors and longitudinal changes in urine biomarkers of kidney tubules among women living with HIV

BACKGROUND

Novel urine biomarkers have enabled the characterization of kidney tubular dysfunction and injury among persons living with HIV, a population at an increased risk of kidney disease. Even though several urine biomarkers predict progressive kidney function decline, antiretroviral toxicity, and mortality in the setting of HIV infection, the relationships among the risk factors for chronic kidney disease (CKD) and urine biomarkers are unclear.

METHODS

We assessed traditional and infection-related CKD risk factors and measured 14 urine biomarkers at baseline and at follow-up among women living with HIV in the Women's Interagency Health Study (WIHS). We then used simultaneously adjusted multivariable linear regression models to evaluate the associations of CKD risk factors with longitudinal changes in biomarker levels.

RESULTS

Of the 647 women living with HIV in this analysis, the majority (67%) were Black, the median age was 45 years and median follow-up time was 2.5 years. Each traditional and infection-related CKD risk factor was associated with a unique set of changes in urine biomarkers. For example, baseline hemoglobin a1c was associated with worse tubular injury (higher interleukin [IL]-18), proximal tubular reabsorptive dysfunction (higher α1-microglobulin), tubular reserve (lower uromodulin) and immune response to injury (higher chitinase-3-like protein-1 [YKL-40]). Furthermore, increasing hemoglobin a1c at follow-up was associated with further worsening of tubular injury (higher kidney injury molecule-1 [KIM-1] and IL-18), as well as higher YKL-40. HCV co-infection was associated with worsening proximal tubular reabsorptive dysfunction (higher β2-microglobulin [β2m]), and higher YKL-40, whereas HIV viremia was associated with worsening markers of tubular and glomerular injury (higher KIM-1 and albuminuria, respectively).

CONCLUSIONS

CKD risk factors are associated with unique patterns of biomarker changes among women living with HIV, suggesting that serial measurements of multiple biomarkers may help in detecting and monitoring kidney disease in this setting.

Maintaining proteostasis under mechanical stress

Cell survival, tissue integrity and organismal health depend on the ability to maintain functional protein networks even under conditions that threaten protein integrity. Protection against such stress conditions involves the adaptation of folding and degradation machineries, which help to preserve the protein network by facilitating the refolding or disposal of damaged proteins. In multicellular organisms, cells are permanently exposed to stress resulting from mechanical forces. Yet, for long time mechanical stress was not recognized as a primary stressor that perturbs protein structure and threatens proteome integrity. The identification and characterization of protein folding and degradation systems, which handle force-unfolded proteins, marks a turning point in this regard. It has become apparent that mechanical stress protection operates during cell differentiation, adhesion and migration and is essential for maintaining tissues such as skeletal muscle, heart and kidney as well as the immune system. Here, we provide an overview of recent advances in our understanding of mechanical stress protection.

Male renal functions are associated with serum short- and medium-chain chlorinated paraffins in residents from Jinan, China

BACKGROUND

Chlorinated paraffins (CPs) are contaminants ubiquitously detected in environmental samples, and reports addressing CPs in human samples are expanding. While CP exposure was suggested to impair kidney function by in vivo/in vitro experiments, epidemiological evidence is lacking.

OBJECTIVE

To examine the associations between serum total short-chain CP and medium-chain CP concentrations (∑SCCPs and ∑MCCPs) with human kidney function.

METHODS

The study samples were obtained from 387 participants living in Jinan, North China. We quantified ∑SCCPs and ∑MCCPs in serum samples and evaluated the kidney function of included subjects by estimated glomerular filtration rate (eGFR). The associations between serum ∑SCCPs, ∑MCCPs and eGFR were estimated using multivariable linear regression and logistic regression. The possible gender-dependent effects were studied by stratified analysis.

RESULTS

After adjusting for age, education, smoking status, drinking status, body mass index (BMI), family history of chronic kidney disease (CKD), fasting serum glucose, systolic blood pressure and diastolic blood pressure, higher concentrations of serum ∑SCCPs and ∑MCCPs were associated with higher male eGFR (β = 3.13 mL/min/1.73 m² per one ln-unit increase of serum ∑SCCPs, 95%CI: 1.72, 4.54, p = 0.016; β = 3.52 mL/min/1.73 m² per one ln-unit increase of serum ∑MCCPs, 95%CI: 1.89, 5.17, p = 0.011). Associations between serum ∑SCCPs, ∑MCCPs and female eGFR were null. Comparing higher (above the median serum CP levels) vs. lower exposure groups, serum ∑SCCPs and ∑MCCPs were associated with an elevated risk of glomerular hyperfiltration (GH, eGFR ≥ 135 mL/min/1.73 m²), which was associated with glomerular damage and represented as an early stage of chronic kidney disease (OR = 2.98; 95% CI: 1.24, 4.71 for SCCPs; OR = 3.25; 95% CI: 1.20, 5.29 for MCCPs).

CONCLUSIONS

Our study suggests that male serum ∑SCCPs and ∑MCCPs are associated with an increased risk of GH, indicating early-stage kidney impairment.

The Association between Glomerular Diameter and Secondary Focal Segmental Glomerulosclerosis in Chronic Kidney Disease

INTRODUCTION

When nephron loss occurs, the glomerular filtration rate (GFR) is suggested to be maintained by glomerular hypertrophy, but excessive hypertrophy can rather lead to the formation of focal segmental glomerulosclerosis (FSGS), thereby causing progressive kidney damage. However, it is not clear how much glomerular hypertrophy leads to the formation of FSGS. We examined the association between glomerular diameter and FSGS lesions in chronic kidney disease (CKD) patients.

METHODS

We recruited 77 patients who underwent renal biopsy during 2016-2017; however, those identified with primary FSGS and glomerulonephritis with active glomerular lesion were excluded. We evaluated the maximal glomerular diameter (Max GD), an indicator of glomerular size, in each renal biopsy specimen and examined its association with FSGS lesion.

RESULTS

The median age, blood pressure, and estimated GFR of the patients were 53 years, 122/70 mm Hg, and 65 mL/min/1.73 m2, respectively. The optimal cutoff threshold of Max GD for predicting the presence of FSGS lesions, assessed by receiver operating characteristic curve analysis, was determined to be at 224 μm (area under the curve, 0.81; sensitivity, 81%; specificity, 72%). Multivariate logistic regression analyses demonstrated that Max GD ≥224 μm was significantly associated with the presence of FSGS lesions, independent of other confounding factors (odds ratio, 11.70; 95% confidence interval, 1.93-70.84).

DISCUSSION/CONCLUSION

Glomerular hypertrophy (Max GD ≥224 μm) has been associated with FSGS lesions in CKD patients and may reflect the limits of the compensatory process.

The Na/K-ATPase Signaling and SGLT2 Inhibitor-Mediated Cardiorenal Protection: A Crossed Road?

In different large-scale clinic outcome trials, sodium (Na⁺)/glucose co-transporter 2 (SGLT2) inhibitors showed profound cardiac- and renal-protective effects, making them revolutionary treatments for heart failure and kidney disease. Different theories are proposed according to the emerging protective effects other than the original purpose of glucose-lowering in diabetic patients. As the ATP-dependent primary ion transporter providing the Na⁺ gradient to drive other Na⁺-dependent transporters, the possible role of the sodium–potassium adenosine triphosphatase (Na/K-ATPase) as the primary ion transporter and its signaling function is not explored.

Is acute kidney injury after laparoscopic adrenalectomy related to the progression of chronic kidney disease in patients with primary aldosteronism?

Purpose

This study was conducted to investigate the predictors of kidney outcome after laparoscopic adrenalectomy in patients with primary aldosteronism (PA).

Materials and Methods

We retrospectively reviewed the medical records of 74 patients who underwent unilateral adrenalectomy for the treatment of PA from January 2011 to December 2019. Patient characteristics and serial data on postoperative changes in kidney function were analyzed and compared between the two groups according to the presence of acute kidney injury (AKI). Postoperative AKI was defined as a decline in the estimated glomerular filtration rate (eGFR) of >50% or an increase in the serum creatinine level of ≥0.3 mg/dL at 1 week after surgery compared with perioperative levels. Chronic kidney disease (CKD) was defined as an eGFR < 60 mL/min/1.73 m² present for 3 months.

Results

Nineteen patients (25.7%) had postoperative AKI. Patients who experienced postoperative AKI had higher aldosterone-to-renin ratios, higher rates of dyslipidemia, and more left ventricular hypertrophy than did patients without postoperative AKI (p=0.015, 0.036, and 0.033, respectively). Twenty-eight patients (37.8%) had CKD at 6 months after surgery, including 15 patients who had newly progressed to CKD postoperatively. In the multivariate regression analysis of patients without preoperative CKD, the only independent predictor of the progression to CKD was preoperative albuminuria (p=0.007).

Conclusions

In this study, one-quarter of the patients had postoperative AKI after unilateral adrenalectomy for the treatment of PA. However, postoperative AKI was not directly correlated with CKD progression. Preoperative albuminuria was an independent predictor of the progression of CKD.

Novel kidney injury biomarkers in a large cohort of children with sickle cell anemia

Aim: The aim of this study was to compare novel kidney injury biomarkers in sickle cell anemia (SCA) children with and without albuminuria or glomerular hyperfiltration. Materials & methods: A total of 358 Brazilian children with SCA were studied. Fifteen kidney injury biomarkers in urine were measured. Albuminuria was defined as urine albumin/creatinine ratio >100 mg/g. Glomerular hyperfiltration was defined as estimated glomerular filtration rate ≥140 ml/min/1.73 m². Results: After adjustment for age, sex and modifying therapies in use, EGF and collagen IV urinary levels were associated with albuminuria. Renin and clusterin levels were associated with hyperfiltration. Conclusion: Levels of novel kidney injury biomarkers were associated with albuminuria and hyperfiltration in Brazilian children with SCA, suggesting concomitant structural and functional abnormalities.

Chronic Inflammation in Chronic Kidney Disease Progression: Role of Nrf2

Despite recent advances in the management of chronic kidney disease (CKD), morbidity and mortality rates in these patients remain high. Although pressure-mediated injury is a well-recognized mechanism of disease progression in CKD, emerging data indicate that an intermediate phenotype involving chronic inflammation, oxidative stress, hypoxia, senescence, and mitochondrial dysfunction plays a key role in the etiology, progression, and pathophysiology of CKD. A variety of factors promote chronic inflammation in CKD, including oxidative stress and the adoption of a proinflammatory phenotype by resident kidney cells. Regulation of proinflammatory and anti-inflammatory factors through NF-κB- and nuclear factor, erythroid 2 like 2 (Nrf2)-mediated gene transcription, respectively, plays a critical role in the glomerular and tubular cell response to kidney injury. Chronic inflammation contributes to the decline in glomerular filtration rate (GFR) in CKD. Whereas the role of chronic inflammation in diabetic kidney disease (DKD) has been well-elucidated, there is now substantial evidence indicating unresolved inflammatory processes lead to fibrosis and eventual end-stage kidney disease (ESKD) in several other diseases, such as Alport syndrome, autosomal-dominant polycystic kidney disease (ADPKD), IgA nephropathy (IgAN), and focal segmental glomerulosclerosis (FSGS). In this review, we aim to clarify the mechanisms of chronic inflammation in the pathophysiology and disease progression across the spectrum of kidney diseases, with a focus on Nrf2.

Optimizing Diet to Slow CKD Progression

Due to the unique role of the kidney in the metabolism of nutrients, patients with chronic kidney disease (CKD) lose the ability to excrete solutes and maintain homeostasis. Nutrient intake modifications and monitoring of nutritional status in this population becomes critical, since it can affect important health outcomes, including progression to kidney failure, quality of life, morbidity, and mortality. Although there are multiple hemodynamic and metabolic factors involved in the progression and prognosis of CKD, nutritional interventions are a central component of the care of patients with non-dialysis CKD (ND-CKD) and of the prevention of overweight and possible protein energy-wasting. Here, we review the reno-protective effects of diet in adults with ND-CKD stages 3-5, including transplant patients.

Enteropeptidase inhibitor SCO-792 effectively prevents kidney function decline and fibrosis in a rat model of chronic kidney disease

Background

Inhibiting enteropeptidase, a gut serine protease regulating protein digestion, suppresses food intake and ameliorates obesity and diabetes in mice. However, the effects of enteropeptidase inhibition on kidney parameters are largely unknown. Here, we evaluated the chronic effects of an enteropeptidase inhibitor, SCO-792, on kidney function, albuminuria and kidney pathology in spontaneously hypercholesterolaemic (SHC) rats, a rat chronic kidney disease (CKD) model.

Methods

SCO-792, an orally available enteropeptidase inhibitor, was administered [0.03% and 0.06% (w/w) in the diet] to 20-week-old SHC rats showing albuminuria and progressive decline in glomerular filtration rate (GFR) for five weeks. The effects of SCO-792 and the contribution of amino acids to these effects were evaluated.

Results

SCO-792 increased the faecal protein content, indicating that SCO-792 inhibited enteropeptidase in SHC rats. Chronic treatment with SCO-792 prevented GFR decline and suppressed albuminuria. Moreover, SCO-792 improved glomerulosclerosis and kidney fibrosis. Pair feeding with SCO-792 (0.06%) was less effective in preventing GFR decline, albuminuria and renal histological damage than SCO-792 treatment, indicating the enteropeptidase-inhibition-dependent therapeutic effects of SCO-792. SCO-792 did not affect the renal plasma flow, suggesting that its effect on GFR was mediated by an improvement in filtration fraction. Moreover, SCO-792 increased hydrogen sulphide production capacity, which has a role in tissue protection. Finally, methionine and cysteine supplementation to the diet abrogated SCO-792-induced therapeutic effects on albuminuria.

Conclusions

SCO-792-mediated inhibition of enteropeptidase potently prevented GFR decline, albuminuria and kidney fibrosis; hence, it may have therapeutic potential against CKD.

Hemodynamic and biological correlates of glomerular hyperfiltration in sickle cell patients before and under renin-angiotensin system blocker

Glomerular hyperfiltration alone or associated with albuminuria is a well-known feature of sickle cell associated nephropathy. Though, glomerular hyperfiltration is currently considered to be related to a high renal plasma flow and chronic hemolysis, cardiac output influence on measured glomerular filtration rate (mGFR) have not been investigated so far. Thirty seven homozygous sickle cell patients (SCA) from the RAND study investigated before and under angiotensin converting enzyme inhibitor (ACEI) were included. Both mGFR and cardiac index (CI) were high (> 110 ml/min/1.73 m² and > 3.5 l/m² in 81% and 97% of cases) with low systemic vascular resistance (SVR) (< 700 dynes/s/cm^-5) in 38% of cases. mGFR association with CI and SVR were significant at baseline (respectively ρ: 0.44, p = 0.008 and ρ: - 0.37, p = 0.02) and under ACEI (p = 0.007 and 0.01 respectively), in accordance with previous data showing that hyperfiltration was linked to an increased glomerular perfusion and a glomerulomegaly rather than increased capillary hydrostatic pressure. Of notice, after adjustment on CI, mGFR remained associated with reticulocyte count and albuminuria under ACEI (p = 0.006 and 0.02 respectively). Our results suggest that hyperfiltration is tightly linked to an increased cardiac output which may account for an increased renal blood flow. Chronic hemolysis could be a relevant factor accounting for hyperfiltration potentially acting on glomerular enlargement which appears as a key factor. Our data suggest that cardiac output assessment is a relevant tool in the routine management and monitoring of SCA nephropathy.

Modeling the Glomerular Filtration Barrier and Intercellular Crosstalk

The glomerulus is a compact cluster of capillaries responsible for blood filtration and initiating urine production in the renal nephrons. A trilaminar structure in the capillary wall forms the glomerular filtration barrier (GFB), composed of glycocalyx-enriched and fenestrated endothelial cells adhering to the glomerular basement membrane and specialized visceral epithelial cells, podocytes, forming the outermost layer with a molecular slit diaphragm between their interdigitating foot processes. The unique dynamic and selective nature of blood filtration to produce urine requires the functionality of each of the GFB components, and hence, mimicking the glomerular filter in vitro has been challenging, though critical for various research applications and drug screening. Research efforts in the past few years have transformed our understanding of the structure and multifaceted roles of the cells and their intricate crosstalk in development and disease pathogenesis. In this review, we present a new wave of technologies that include glomerulus-on-a-chip, three-dimensional microfluidic models, and organoids all promising to improve our understanding of glomerular biology and to enable the development of GFB-targeted therapies. Here, we also outline the challenges and the opportunities of these emerging biomimetic systems that aim to recapitulate the complex glomerular filter, and the evolving perspectives on the sophisticated repertoire of cellular signaling that comprise the glomerular milieu.

Association between plasma aldosterone and markers of tubular and glomerular damage in primary aldosteronism

OBJECTIVE

Although renal impairments are observed in patients with primary aldosteronism (PA), the association between plasma aldosterone concentration (PAC) and specific structural kidney damage remains unknown. Thus, we analysed the association between PAC, and markers of glomerular and tubular damage.

DESIGN

This was a retrospective cross-sectional study of 96 PA patients, in which we analysed the association between PAC and markers of kidney damage, including urinary albumin-creatinine ratio (ACR) for glomerular damage, and urinary liver fatty acid-binding protein (L-FABP), N-acetyl-β-D-glucosaminidase (NAG) and β2-microglobulin (β2-MG) for tubular damage. In addition, we evaluated the association between PAC and N-terminal pro-brain natriuretic peptide (NT-proBNP) as a marker for body fluid volume.

RESULTS

Urinary ACR, L-FABP, NAG, β2-MG and NT-proBNP significantly correlated with PAC. PAC (<415 pmol/L, 415-550, 550-740, 740 <)-based quartile analysis revealed that both elevated markers of kidney damage and NT-proBNP could be observed in PA patients with a PAC over 550 pmol/L. Logistic regression analysis showed that PAC was significantly associated with a risk of both microalbuminuria and lowered eGFR (<60 mL/min/1.73 m² ), with its optimal cut-offs for predicting each, 558 and 594 pmol/L, respectively.

CONCLUSIONS

Increased PAC, especially over 550 pmol/L, is associated with excessive damage to the tubule and glomerulus.

Skeletal endocrinology: where evolutionary advantage meets disease

The regulation of whole-body homeostasis by the skeleton is mediated by its capacity to secrete endocrine signaling molecules. Although bone-derived hormones confer several adaptive benefits, their physiological functions also involve trade-offs, thus eventually contributing to disease. In this manuscript, we discuss the origins and functions of two of the best-studied skeletal mediators, fibroblast growth factor 23 and osteocalcin, in an evolutionary context. Moreover, we provide a theoretical framework seeking to explain the broad involvement of these two hormones in amniote physiology as well as their potential to fuel the development and progression of diseases. Vice versa, we outline which perturbations might be amenable to manipulation of these systems and discuss limitations and ongoing challenges in skeletal endocrine research. Finally, we summarize unresolved questions and potential future studies in this thriving field.

Nocturnal hypoxemia severity influences the effect of CPAP therapy on renal renin-angiotensin-aldosterone system activity in humans with obstructive sleep apnea

STUDY OBJECTIVES

Nocturnal hypoxemia (NH) in obstructive sleep apnea (OSA) is associated with renal renin-angiotensin-aldosterone system (RAAS) up-regulation and loss of kidney function. Continuous positive airway pressure (CPAP) therapy is associated with RAAS down-regulation, though the impact of NH severity remains unknown. We sought to determine whether NH severity alters the effect of CPAP on renal hemodynamics and RAAS activity in humans.

METHODS

Thirty sodium-replete, otherwise healthy, OSA participants (oxygen desaturation index ≥ 15 h-1) with NH (SpO2 < 90% ≥ 12%/night) were studied pre- and post-CPAP (>4 h/night∙4 weeks). NH severity was characterized as moderate (mean SpO2[MSpO2] ≥ 90%; N = 15) or severe (MSpO2 < 90%; N = 15). Glomerular filtration rate (GFR), renal plasma flow (RPF), and filtration fraction (FF) were measured at baseline and in response to angiotensin-II (3 ng/kg/min∙30 min, 6 ng/kg/min∙30 min), a marker of RAAS activity.

RESULTS

Pre-CPAP, baseline renal hemodynamics did not differ by NH severity. Pre-CPAP, severe NH participants demonstrated blunted GFR (Δ30 min, -9 ± 4 vs 1 ± 3 mL/min, p = 0.021; Δ60 min, -5 ± 5 vs 8 ± 5 mL/min, p = 0.017) and RPF (Δ30 min, -165 ± 13 vs -93 ± 19 mL/min, p = 0.003; Δ60 min, -208 ± 18 vs -112 ± 22 mL/min, p = 0.001; moderate vs severe) responses to angiotensin-II. Post-CPAP, severe NH participants demonstrated maintained GFR (112 ± 5 vs 108 ± 3 mL/min, p = 0.9), increased RPF (664 ± 35 vs 745 ± 34 mL/min, p = 0.009), reduced FF (17.6 ± 1.4 vs 14.9 ± 0.6%, p = 0.009), and augmented RPF responses to Angiotensin-II (Δ30 min, -93 ± 19 vs -138 ± 16 mL/min, p = 0.009; Δ60 min, -112 ± 22 vs -175 ± 20 mL/min, p = 0.001; pre- vs post-CPAP), while moderate participants were unchanged.

CONCLUSIONS

Correction of severe, but not moderate, NH with CPAP therapy was associated with improved renal hemodynamics and decreased renal RAAS activity in humans with OSA.

Obstetric and long-term graft outcomes in pregnant kidney transplant recipients: A single-center experience

BACKGROUND

Kidney transplantation (KT) is the best option for many women with end-stage renal disease desiring pregnancy. The aim of this study was to investigate obstetric and graft outcomes among KT recipient women in our center.

METHODS

Maternal and fetal data were assessed in 29 pregnancies of 18 female KT recipients. Each patient was matched with two controls without pregnancy history for factors known to affect graft function. According to pre-pregnancy levels, serum creatinine and eGFR slope in the gestational and postpartum periods were calculated as percentages.

RESULTS

The main maternal and fetal complications were preeclampsia (38%) and preterm births (38%), respectively. Pregnancy (odds ratio [OR]: 5.09; p = .02), proteinuria in the third trimester (OR: 5.52; p = .02), proteinuria in postpartum third months (OR: 7.4; p = .008) and stable creatinine levels in the first 6 months of pregnancy (OR: 11.25 p = .03) were associated with graft dysfunction. Postpartum first year eGFR decline (-16.8% vs. -6.7%; p = .04) and second-year eGFR decline (-18.5% vs. -8.3%; p = .04) were significantly higher in the pregnancy group than those matched controls.

CONCLUSION

Pregnancy after KT is associated with high rates of maternal and fetal complications. The sustained decline of eGFR may suggest an increased risk of graft loss compared to recipients with similar clinical characteristics.

Levels of angiotensin-converting enzyme 1 and 2 in serum and urine of children with Sickle Cell Disease

Introduction:

Sickle cell nephropathy begins in childhood and presents early increases in glomerular filtration, which, over the long term, can lead to chronic renal failure. Several diseases have increased circulating and urinary angiotensin-converting enzyme (ACE) activity, but there is little information about changes in ACEs activity in children with sickle cell disease (SCD).

Objective:

We examined circulating and urinary ACE 1 activity in children with SCD.

Methods:

This cross-sectional study compared children who were carriers of SCD with children who comprised a control group (CG). Serum and urinary activities of ACE were evaluated, as were biochemical factors, urinary album/creatinine rates, and estimated glomerular filtration rate.

Results:

Urinary ACE activity was significantly higher in patients with SCD than in healthy children (median 0.01; range 0.00-0.07 vs median 0.00; range 0.00-0.01 mU/mL·creatinine, p < 0.001. No significant difference in serum ACE activities between the SCD and CG groups was observed (median 32.25; range 16.2-59.3 vs median 40.9; range 18.0-53.4) mU/m`L·creatinine, p < 0.05.

Conclusion:

Our data revealed a high urinary ACE 1 activity, different than plasmatic level, in SCD patients suggesting a dissociation between the intrarenal and systemic RAAS. The increase of urinary ACE 1 activity in SCD patients suggests higher levels of Ang II with a predominance of classical RAAS axis, that can induce kidney damage.

Impact of kidney hyperfiltration on concentrations of selected perfluoroalkyl acids among US adults for various disease groups

Data from the National Health and Nutrition Examination Survey (N = 6141) for the years 2003-2016 for US adults were analyzed to evaluate the impact of glomerular hyperfiltration on the observed concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid, perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) for several disease groups. Hyperfiltrators were defined as having an estimated glomerular filtration rate (eGFR) ≥ 110 mL/min/1.73 m², and normal filtrators were defined as those having an eGFR between 90 and 110 mL/min/1.73 m². The seven disease groups for which the data were analyzed were as follows: those (i) without any diseases; (ii) with hypertension only; (iii) with albuminuria only; (iv) with anemia only; (v) with diabetes only; (vi) with hypertension and one or more of diabetes, anemia, and albuminuria; and (vii) with two or more of diabetes, anemia, and albuminuria without hypertension. For almost every PFAA, for all seven disease groups except the albuminuria only group, hyperfiltrators had lower adjusted geometric means (AGM) than normal filtrators. For example, for the disease group with hypertension only, for PFOS, the AGMs for hyperfiltrators and normal filtrators were 8.3 and 10.6 ng/mL, respectively, for the total population. For the group with albuminuria only, normal filtrators were found to have higher AGMs than hyperfiltrators for the total population and males. For example, for PFHxS, the AGMs for normal and hyperfiltrators were 0.98 and 1.05 ng/mL, respectively, for the total population. For females, these AGMs for normal and hyperfiltrators were 0.96 and 0.86 ng/mL respectively. Males usually had higher AGMs than females, but the reverse was also true occasionally. Usually, male-female differences were substantially narrower for normal filtrators than hyperfiltrators. Irrespective of the filtration status, the disease group with hypertension only had the highest AGMs for every PFAA. AGMs for the anemia only group were the lowest for every PFAA as compared with other disease groups among hyperfiltrators.

Evaluation of renal injury in children with a solitary functioning kidney

Objective

Children with a solitary functioning kidney have an increased risk of developing renal injury that is hypothesized to be caused by glomerular hyperfiltration. In this study, we aimed to assess the early signs of renal injury and ambulatory blood pressure profiles in children with a solitary functioning kidney.

Materials and Methods

Data of children with normal office blood pressure measurement and a solitary functioning kidney were reviewed (serum creatinine and urine albumin and β2 microglobulin excretions), and 23 age-, weight-, and height-matched healthy children were considered as a control group. The size of the kidney was measured by renal ultrasound, and the presence of compensatory hypertrophy was calculated for all the subjects. Also, the subjects were additionally assessed for blood pressure (BP) pattern and the presence of hypertension by 24-hambulatory blood pressure monitoring.

Results

The solitary functioning kidney demonstrated compensatory hypertrophy in 36 out of the patients (86%) at a mean age of 14.0 (SD 3.0) years. Increased urine albumin and β2 microglobulinuria, which are signs of kidney damage, were found in 7 (17%) and 5(12%) patients. Compared with the controls, patients had significantly higher mean blood pressure standard deviation scores (p>0,001), and ambulatory blood pressure monitoring identified masked hypertension in 7 (17%) children and prehypertension in 6 (14%) patients. Therefore, renal injury, defined as the presence of hypertension and/or albuminuria and/or β2 microglobulinuria and/or hypertension, was present in 36% of all children with a solitary functioning kidney.

Conclusion

Children with a solitary functioning kidney need prolonged follow-up to detect early signs of renal injury and prevent end-organ damage later in life. Ambulatory blood pressure monitoring is an essential tool in the diagnosis and clinical management of solitary functioning kidney patients.

The Assessment of the Usefulness of Selected Markers in the Diagnosis of Chronic Kidney Disease in Children

INTRODUCTION

The kidney deterioration, which starts in childhood often leads to end-stage renal failure in the future. Therefore, searching for an early, sensitive, and specific biomarkers became a paramount for chronic kidney disease diagnosis. The aim of this study was the assessment of markers: KIM-1, FGF-23, NAG, NGAL, and uromodulin for diagnosis of preclinical phase of the disease in children.

PATIENTS AND METHODS

59 children (15 boys, 44 girls from 6 months to 17 years old) with kidney disorders, which had clinical indications for renoscintigraphy, were included in the study. All patients were divided depending on the result of renoscintigraphy (renal scarring vs normal kidney picture) and depending on the level of estimated glomerular filtration rate (glomerular hyperfiltration vs normal filtration rate). The concentration of uromoduline, KIM-1, FGF-23, NAG, and NGAL in serum and of NGAL and uromoduline in urine were measured in all studied groups.

RESULTS

The children with glomerular hyperfiltration had a statistically significantly higher serum values of FGF-23 and NGAL than the children with normal filtration rate (P < .05). There were no statistically significant differences in serum concentrations of tested markers in children with renal scars in comparison to children with normal renal image. There was no statistically significant difference in the concentration of tested markers in urine.

CONCLUSIONS

The study confirmed the possible usefulness of FGF-23 and NGAL in detecting the preclinical-stage of renal disease associated with glomerular hyperfiltration in children. The study do not allow to indicate markers, which could be useful in the early diagnosis of kidney damage visible in the scintigraphic examination.

A kidney perspective on the mechanism of action of sodium glucose co-transporter 2 inhibitors

Sodium glucose co-transporter (SGLT) 2 inhibitors reduce the risk of kidney failure in patients with and without type 2 diabetes (T2D). Although the precise underlying mechanisms for these nephroprotective effects are incompletely understood, various hypotheses have been proposed including reductions in intraglomerular pressure through restoration of tubuloglomerular feedback, blood pressure reduction and favorable effects on vascular function, reduction in tubular workload and hypoxia, and metabolic effects resulting in increased autophagy. Here, we review these mechanisms, which may also explain the beneficial effects of SGLT2 inhibitors on kidney function in patients without T2D.

Acute kidney damage by PM2.5 exposure in a rat model

PM2.5 exposure is associated with a glomerular filtration rate (GFR) reduction, and renal tissue damage. The goal of this study was demonstrate the acute effect of PM2.5 on the kidney. Male rats were acutely exposed to PM2.5 or filtered air. Blood pressure was mesure and early kidney biomarkers were evaluated in serum and urine samples, and also IL-1β, IL-6 and TNFα were determined. Oxidative biomarkers, angiotensin/bradykinin-related proteins, KIM-1, IL-6 and histology were determined. Blood pressure, GFR, and early kidney damage biomarkers increase together with oxidative biomarkers and angiotensin/bradykinin endocrine-related proteins increased after exposure to PM2.5. Urinary IL-6 increased after exposure to PM2.5, whereas in kidney cortex decreased. Histological changes were observed and accompanied by the induction of KIM-1. Acute exposure to PM2.5 not decline kidney function. However, it can induce early kidney damage biomarkers, oxidative stress, inflammation and angiotensin mediators, which perhabs culminates in a lose of renal function.

The Rationale and Evidence for SGLT2 Inhibitors as a Treatment for Nondiabetic Glomerular Disease

Background

Recent studies show that sodium-glucose cotransporter 2 inhibitors (SGLT2i), originally approved for glycemic control in patients with type 2 diabetes, also exert renoprotective effects independently from effects on dysglycemia. Moreover, recent work indicates that SGLT2i treatment may be effective in patients with nondiabetic chronic kidney disease, including primary and secondary glomerular diseases.

Summary

SGLT2i lower blood glucose by blocking glucose resorption in the early renal proximal tubule through the glucose transporter, SGLT2, leading to enhanced urinary glucose excretion. Recent studies indicate that SGLT2i may have pleiotropic effects on cells other than proximal tubular cells. SGLT2i reduce the glomerular workload by decreasing the intraglomerular pressure, thus ameliorating hyperfiltration, if present, and may also decrease systemic blood pressure. SGLT2i may also act directly on endothelial cells, possibly via modulating the effects of adhesion molecules and reducing inflammatory cytokines and reactive oxygen species. SGLT2i may have direct anti-inflammatory and antifibrotic effects on renal tubules. Some reports suggest direct protective effects on podocytes and mesangial cells as well. Here, we provide a review of the potential mechanisms of renoprotection, therapeutic utility, and potential side effects of SGLT2i in patients with nondiabetic glomerular diseases, based on data from studies carried out in cells, experimental animals, and humans.

Key Messages

SGLT2i may be a promising addition to the glomerular disease treatment armamentarium. However, it is unclear at what point of the natural history of specific glomerular diseases (whether this is immune or nonimmune mediated) SGLT2i can be beneficial. Additionally, further studies are needed to assess the long-term efficacy and safety of SGLT2i in patients with nondiabetic glomerular diseases.

A dose-escalating toxicology study of the candidate biologic ELP-VEGF

Vascular Endothelial Growth Factor (VEGF), a key mediator of angiogenesis and vascular repair, is reduced in chronic ischemic renal diseases, leading to microvascular rarefaction and deterioration of renal function. We developed a chimeric fusion of human VEGF-A₁₂₁ with the carrier protein Elastin-like Polypeptide (ELP-VEGF) to induce therapeutic angiogenesis via targeted renal VEGF therapy. We previously showed that ELP-VEGF improves renal vascular density, renal fibrosis, and renal function in swine models of chronic renal diseases. However, VEGF is a potent cytokine that induces angiogenesis and increases vascular permeability, which could cause undesired off-target effects or be deleterious in a patient with a solid tumor. Therefore, the current study aims to define the toxicological profile of ELP-VEGF and assess its risk for exacerbating tumor progression and vascularity using rodent models. A dose escalating toxicology assessment of ELP-VEGF was performed by administering a bolus intravenous injection at doses ranging from 0.1 to 200 mg/kg in Sprague Dawley (SD) rats. Blood pressure, body weight, and glomerular filtration rate (GFR) were quantified longitudinally, and terminal blood sampling and renal vascular density measurements were made 14 days after treatment. Additionally, the effects of a single administration of ELP-VEGF (0.1-10 mg/kg) on tumor growth rate, mass, and vascular density were examined in a mouse model of breast cancer. At doses up to 200 mg/kg, ELP-VEGF had no effect on body weight, caused no changes in plasma or urinary markers of renal injury, and did not induce renal fibrosis or other histopathological findings in SD rats. At the highest doses (100-200 mg/kg), ELP-VEGF caused an acute, transient hypotension (30 min), increased GFR, and reduced renal microvascular density 14 days after injection. In a mouse tumor model, ELP-VEGF did not affect tumor growth rate or tumor mass, but analysis of tumor vascular density by micro-computed tomography (μCT) revealed significant, dose dependent increases in tumor vascularity after ELP-VEGF administration. ELP-VEGF did not induce toxicity in the therapeutic dosing range, and doses one hundred times higher than the expected maximum therapeutic dose were needed to observe any adverse signs in rats. In breast tumor-bearing mice, ELP-VEGF therapy induced a dose-dependent increase in tumor vascularity, demanding caution for potential use in a patient suffering from kidney disease but with known or suspected malignancy.

Clinical Management of Children with a Congenital Solitary Functioning Kidney: Overview and Recommendations

CONTEXT

A congenital solitary functioning kidney (cSFK) is a common developmental defect that predisposes to hypertension and chronic kidney disease (CKD) as a consequence of hyperfiltration. Every urologist takes care of patients with a cSFK, since some will need lifelong urological care or will come with clinical problems or questions to an adult urologist later in life.

OBJECTIVE

We aim to provide clear recommendations for the initial clinical management and follow-up of children with a cSFK.

EVIDENCE ACQUISITION

PubMed and EMBASE were searched to identify relevant publications, which were combined with guidelines on related topics and expert opinion.

EVIDENCE SYNTHESIS

Initially, cSFK diagnosis should be confirmed and risk factors for kidney injury should be identified using ultrasound. Although more research into early predictors of kidney injury is needed, additional congenital anomalies of the kidney or urinary tract and absence of compensatory kidney hypertrophy have repeatedly been associated with a worse prognosis. The role of voiding cystourethrography and antibiotic prophylaxis remains controversial, and is complicated by the exclusion of children with a cSFK from studies. A yearly follow-up for signs of kidney injury is recommended for children with a cSFK. As masked hypertension is prevalent, annual ambulatory blood pressure measurement should be considered. During puberty, an increasing incidence of kidney injury is seen, indicating that long-term follow-up is necessary. If signs of kidney injury are present, angiotensin converting enzyme inhibitors are the first-line drugs of choice.

CONCLUSIONS

This overview points to the urological and medical clinical aspects and long-term care guidance for children with a cSFK, who are at risk of hypertension and CKD. Monitoring for signs of kidney injury is therefore recommended throughout life. Large, prospective studies with long-term follow-up of clearly defined cohorts are still needed to facilitate more risk-based and individualized clinical management.

PATIENT SUMMARY

Many children are born with only one functioning kidney, which could lead to kidney injury later in life. Therefore, a kidney ultrasound is made soon after birth, and other investigations may be needed as well. Urologists taking care of patients with a solitary functioning kidney should realize the long-term clinical aspects, which might need medical management.

Renoprotective effects of sodium-glucose cotransporter-2 inhibitors and underlying mechanisms

PURPOSE OF REVIEW

Emerging data have demonstrated that sodium-glucose cotransporter-2 (SGLT2) inhibitors prevent cardiovascular events, especially heart failure-associated endpoints. Cardiovascular outcome trials have also suggested their renoprotective effects. One large clinical trial investigated renal primary endpoints and demonstrated that SGLT2 inhibitors slowed the progression of diabetic kidney disease (DKD). This review summarizes clinical trial data on renal outcomes and discusses potential underlying mechanisms.

RECENT FINDINGS

The EMPA-REG, CANVAS, and DECLARE-TIMI 58 studies revealed that SGLT2 inhibitors reduce the risk of cardiovascular events and concomitantly suggested that these drugs slow the progression of kidney disease in type 2 diabetes. The CREDENCE trial on patients with high-risk type 2 diabetes and chronic kidney disease demonstrated that canagliflozin treatment reduced the relative risk of a composite outcome, including end-stage kidney disease, serum creatinine doubling, and renal/cardiovascular death, by 30% in these patients. Animal experiments revealed that oxidative stress, inflammation, fibrosis, and tubuloglomerular feedback are underlying renoprotective mechanisms behind SGLT2 inhibitors.

SUMMARY

Recent clinical trials have established the renoprotective effects of SGLT2 inhibitors. Further investigations on mechanisms of these renoprotective effects will provide deeper insights and understanding of pathogenetic properties of DKD.

Nephrotic range proteinuria associated with focal segmental glomerulosclerosis reversed with pioglitazone therapy in a patient with Dunnigan type lipodystrophy

Familial partiallipodystrophy (FPLD)is a rare disorder associated withsevere insulin resistance, hypertriglyceridemia, lowserumHDLcholesterol and proteinuricrenaldisease. Although proteinuric renal disease is not common among in patients with partial lipodystrophy, we report a patient with Dunnigan type FPLD complicated by nephrotic syndrome which resolved following treatment with thePPARγagonist pioglitazone, CPAP, diet, and exercise.

Biomarkers of kidney injury among children in a high-risk region for chronic kidney disease of uncertain etiology

BACKGROUND

Mesoamerican Nephropathy (MeN), a form of chronic kidney disease of uncertain etiology, is a leading cause of death in Central America. The disease often presents in young adult male agricultural workers and progresses rapidly. Given the young age at presentation, we hypothesized that children in Central America experience subclinical kidney injury prior to working life.

METHODS

We assessed specimens from a cross-sectional study of youth, aged 7-17 years, predominantly residing in a high-risk region of Nicaragua (n = 210). We evaluated urinary concentrations and risk factors for kidney injury biomarkers neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), interleukin-18 (IL-18), monocyte chemoattractant protein 1 (MCP-1), and chitinase-3-like protein 1 (YKL-40). We evaluated the association between biomarkers and contemporaneous eGFR and compared biomarker concentrations with reference values from healthy children in other countries.

RESULTS

Median uNGAL, uIL-18, and uKIM-1 concentrations exceeded healthy reference values. A one-year increase in age was associated with 40% increase in odds of being in the highest quartile of uNGAL (OR 1.4; (95%CI 1.2, 1.5); p < 0.0001). Youth who reported ever experiencing dysuria had 2.5 times the odds of having uNGAL concentrations in the top quartile (OR 2.5; (95%CI 1.4, 4.6); p = 0.003). Girls had significantly higher concentrations of all biomarkers than boys. Nine percent of children demonstrated low eGFR (≤ 100 ml/min/1.73 m²), while 29% showed evidence of hyperfiltration (eGFR ≥ 160 ml/min/1.73 m²), both potentially indicative of renal dysfunction.

CONCLUSIONS

Children residing in regions of Nicaragua at high risk for MeN may experience subclinical kidney injury prior to occupational exposures.

Renal outcomes and all-cause death associated with sodium-glucose co-transporter-2 inhibitors versus other glucose-lowering drugs (CVD-REAL 3 Korea)

AIMS

To investigate the effectiveness of sodium-glucose co-transporter-2 (SGLT2) inhibitors on the risk of progression to end-stage renal disease (ESRD) and all-cause mortality in a broad range of patients with type 2 diabetes (T2D) using a Korean nationwide cohort.

MATERIALS AND METHODS

Using data from the Korean National Health Insurance Service database from January 2014 to December 2017, a total of 701 674 patients were identified with T2D. We divided these patients into new users of SGLT2 inhibitors and new users of other glucose-lowering drugs (oGLDs). Using propensity scores, patients in the two groups were matched 1:1. We assessed the risk of ESRD and all-cause death.

RESULTS

There were 45 016 patients in each group, and baseline characteristics were well balanced between the groups. The patients' mean age was 58.1 ± 10.6 years and mean estimated glomerular filtration rate (eGFR) was 89.2 ± 27.4 mL/min/1.73m² , and 8% of patients had proteinuria. We identified 167 incident ESRD cases and 1070 all-cause deaths during follow-up. Use of SGLT2 inhibitors versus oGLDs was associated with a lower risk of ESRD (hazard ratio [HR] 0.47, 95% confidence interval [CI] 0.34 to 0.65) and all-cause death (HR 0.82, 95% CI 0.73 to 0.93). In a subgroup analysis by eGFR, initiation of SGLT2 inhibitor treatment, compared with oGLD treatment, was associated with lower risk of progression to ESRD among patients with eGFR 60 to 90 mL/min/1.73m² and those with eGFR < 60 mL/min/1.73m² , and a lower risk of all-cause death was associated with SGLT2 inhibitors versus oGLDs in patients with eGFR ≥90 and 60 to 90 mL/min/1.73m² .

CONCLUSION

In this large nationwide study of Korean patients with T2D, initiation of SGLT2 inhibitors versus oGLDs was associated with lower risk of ESRD and all-cause death.

Treatment of Refractory Hypertension with Timely Angioplasty in Total Renal Artery Occlusion with Atrophic Kidney

Angioplasty for cases of chronic total occlusion of renal artery with/without atrophic kidney is generally not recommended. We herein report a 57-year-old man who presented with renin-mediated refractory hypertension caused by occlusion of a unilateral renal artery leading to kidney atrophy (length: 69 mm). Angioplasty favorably achieved blood pressure control with normalized renin secretion and enlargement of the atrophic kidney to 85 mm. Timely angioplasty can be beneficial in select patients, even with an atrophic kidney and total occlusion, especially in cases with deterioration of hypertension within six months and the presence of collateral perfusion to the affected kidney.

Glomerular hyperfiltration with hyperglycemia in the spontaneously diabetic Torii (SDT) fatty rat, an obese type 2 diabetic model

Glomerular hyperfiltration is observed in an early stage of kidney diseases including diabetic nephropathy. A better understanding of pathophysiological changes in glomerular hyperfiltration is essential for development of new therapies to prevent kidney disease progression. In this study, we investigated glomerular changes including glomerular filtration rate (GFR) and glomerular size in the Spontaneously Diabetic Torii (SDT) fatty rat, an obese type 2 diabetic model, and we also evaluated pharmacological effects of the sodium glucose cotransporter 2 inhibitor dapagliflozin on the renal lesions. Dapagliflozin was administered to SDT fatty rats from 5 to 17 weeks of age. Blood and urinary biochemical parameters were periodically measured. GFR was determined by transdermal GFR monitor at 16 weeks of age and histopathological analysis was performed at 17 weeks of age. SDT fatty rat developed severe hyperglycemia and exhibited pathophysiological abnormalities in the kidney, such as an increased GFR, glomerular hypertrophy and tissue lesions. Dapagliflozin achieved good glycemic control during the experimental period, inhibited the increase in GFR, and improved histopathological abnormalities in tubules. These results suggest that the SDT fatty rat is a useful model for analyzing the pathogenesis of diabetic nephropathy during its early stage and dapagliflozin improves not only hyperglycemia but also glomerular hyperfiltration and tubule lesions in SDT fatty rat.

Beneficial effects on kidney during treatment with sodium-glucose cotransporter 2 inhibitors: proposed role of ketone utilization

Modestly elevated circulating levels of the ketone β-hydroxybutyrate (βOHB) during treatment with sodium-glucose cotransporter 2 (SGLT2) inhibitors cause different beneficial effects on organs and cells, depending on the succinyl-CoA:3-ketoacid CoA transferase (SCOT) level. In the failing heart, SCOT is highly expressed/up-regulated, and thus, βOHB may be an energy source, in addition to fat and glucose oxidation. However, SCOT is not highly expressed/down-regulated in the kidney, and thus, βOHB may cause different beneficial effects, rather than acting as an alternative energy source in patients with chronic kidney disease (CKD). βOHB is an endogenous and specific inhibitor of class I histone deacetylases (HDACs) and the NLRP3 inflammasome, accumulates in the kidney because of its decreased utilization as an energy source due to the down-regulation of SCOT, and may induce beneficial effects such as inhibiting inflammation, oxidative stress, and fibrosis. In addition to restoring tubulo-glomerular feedback and improving renal proximal tubule oxygenation, SGLT2 inhibitors may play a renoprotective role by way of βOHB in patients with CKD.

Mitochondrial Dysfunction and Diabetic Nephropathy: Nontraditional Therapeutic Opportunities

Diabetic nephropathy (DN) is a progressive microvascular diabetic complication. Growing evidence shows that persistent mitochondrial dysfunction contributes to the progression of renal diseases, including DN, as it alters mitochondrial homeostasis and, in turn, affects normal kidney function. Pharmacological regulation of mitochondrial networking is a promising therapeutic strategy for preventing and restoring renal function in DN. In this review, we have surveyed recent advances in elucidating the mitochondrial networking and signaling pathways in physiological and pathological contexts. Additionally, we have considered the contributions of nontraditional therapy that ameliorate mitochondrial dysfunction and discussed their molecular mechanism, highlighting the potential value of nontraditional therapies, such as herbal medicine and lifestyle interventions, in therapeutic interventions for DN. The generation of new insights using mitochondrial networking will facilitate further investigations on nontraditional therapies for DN.

The Effects of Cardiometabolic Factors on the Association Between Serum Uric Acid and Chronic Kidney Disease in Chinese Middle-Aged and Older Population: A Mediation Analysis

INTRODUCTION

To explore whether dyslipidemia, hyperglycemia or hypertension has mediating effect on the association between serum uric acid (SUA) and the development of chronic kidney disease (CKD).

METHODS

We conducted a mediation analysis to explore the potential mediating effects of systolic blood pressure (SBP), diastolic blood pressure (DBP), blood glucose, triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) on the association between SUA and estimated glomerular filtration rate (eGFR). The data were obtained from China Health and Retirement Longitudinal Study (CHARLS), covering 5,762 individuals.

RESULTS

SUA had a negative dose-response total effect on eGFR (β -3.11, 95% CI -3.40 to -2.82, P-value<0.001). The linear regression between SUA and seven potential mediators indicated that blood glucose (β 0.80, 95% CI 0.18 to 1.42, P-value=0.012), TG (β 10.01, 95% CI 8.22 to 11.79, P-value<0.001), TC (β 2.64, 95% CI 1.83 to 3.45, P-value<0.001), HDL-C (β -0.27, 95% CI -0.52 to -0.02, P-value=0.034) and LDL-C (β 1.15, 95% CI 0.49 to 1.80, P-value=0.001) all had significant dose-response association with SUA, but SBP and DBP showed no significant association with SUA. In terms of the association between potential mediators and eGFR, only TG (β 0.003, 95% CI -0.001 to 0.01, P-value=0.117) and HDL-C (β 0.01, 95% CI -0.02 to 0.04, P-value=0.444) did not have significant linear association with eGFR. The linear regression showed that SUA was directly associated with eGFR (P-value<0.001).

CONCLUSIONS

This study supported that the association between SUA and the risk of CKD was not mediated by hypertension, hyperglycemia or dyslipidemia.

The minimum-mortality estimated glomerular filtration rate percentile shifts upward in the aged population: a nationwide population-based study

Background

The estimated glomerular filtration rate (eGFR) is a biomarker not only for kidney function, but also for major clinical outcomes. We aimed to evaluate the patterns of mortality across the entire eGFR percentile spectrum using a population-based dataset.

Methods

We retrospectively reviewed the National Health Insurance Service (NHIS) database for people who received nationwide health check-ups from 2009 to 2012. Subjects who were ≥45 years old and had one or more serum creatinine values available were included in the study. The primary outcome was all-cause mortality as a function of eGFR percentile.

Results

The middle-aged group (45–64 years) showed a U-shaped pattern of association between eGFR percentile and all-cause mortality. The minimum-mortality eGFR percentile was shifted upward in the elderly group (≥65 years). Specifically, the minimum-mortality eGFR percentiles were the 28th percentile (83.8 mL/min/1.73 m²) for middle-aged males, the 63rd percentile (86.2 mL/min/1.73 m²) for elderly males, the 42nd percentile (102.8 mL/min/1.73 m²) for middle-aged females and the 75th percentile (90.1 mL/min/1.73 m²) for elderly females. Diabetes and hypertension shifted the minimum-mortality eGFR percentile upward in the middle-aged group. This pattern was attenuated in the elderly group.

Conclusions

The eGFR percentile showing minimum mortality moves upward in the aged population as well as patients with diabetes and hypertension, which might reduce the clinical significance of hyperfiltration. Risk stratification for mortality should be approached differently according to the specific conditions of the patient group.

Effects of fermented red bean extract on nephropathy in streptozocin-induced diabetic rats

Background

The antioxidant effects of Bacillus subtilis-fermented red bean (natto-red bean) extract (NRBE) in young (6 weeks old) Sprague–Dawley rats and aged (12 months old) mice had been reported previously.

Objective

To evaluate the antioxidant and anti-inflammatory effects of NRBE in the kidneys of streptozocin-induced diabetic rats.

Design

Normal control rats and diabetic rats were orally gavaged with saline and low-dose NRBE (100 mg/kg body weight [BW]), medium-dose NRBE (200 mg/kg BW), and high-dose NRBE (500 mg/kg BW), for 12 weeks and then sacrificed. Concentration of fasting glucose, adiponectin, renal function markers, antioxidative markers, and pro-inflammatory markers were measured.

Results

Oral administration of 50% ethanolic extract of NRBE with a dosage of 100 mg/kg BW, 200 mg/kg BW, or 500 mg/kg BW could improve the symptoms of kidney enlargement and renal function. Supplementation of NRBE can effectively inhibit the formation of renal reactive oxygen species and advanced-glycation end-products and increase renal glutathione content and serum adiponectin. A low dose of NRBE (100 mg/kg BW) decreased fasting blood sugar and renal interleukin (IL)-6 expression. Serum C-reactive protein, renal tumor necrosis factor-α, and monocyte chemoattractant protein-1 concentrations were decreased, and renal superoxide dismutase activity was increased in the medium-dose NRBE group. Twenty-four hour creatinine clearance and urinary albumin excretion also improved by medium-dose NRBE supplementation. In NRBE, total phenols and flavonoids were 6.3 mg gallic acid equivalent/g and 12.02 mg rutin equivalent/g, respectively, and kampherol was the major active antioxidant compound.

Conclusion

This study demonstrated that appropriate amount of NRBE, 200 mg/kg BW in rats, could prevent diabetic nephropathy by improving antioxidant status and inhibiting inflammation in renal tissue.

Development of glomerular hyperfiltration, a multiphasic phenomenon

The trajectory of glomerular filtration rate (GFR) in relation to glomerular hyperfiltration (GHF) has been unknown. It was evaluated retrospectively in 23,982 GHF-free health examinees who were followed for 2-10 yr (mean: 5.1 yr). GFR was estimated by the serum creatinine concentration, and GHF was defined as age- and sex-specific estimated GFR (eGFR) ≥ 95% of the Japanese general population. The temporal profile of eGFR was plotted in a GHF-centered way, which was fitted to a random coefficient linear mixed model. Of the 23,982 subjects, 797 and 23,185 subjects developed or did not develop GHF, respectively, so that they were termed as the GHF₍₊₎ and GHF_(-) groups. At baseline, median eGFR was significantly elevated in the GHF₍₊₎ group compared with in the GHF_(-) group: 94.1 versus 77.3 mL/min/1.73 m² (P < 0.001). Elevation of basal eGFR lasted for a mean (SD) of 3.3 (1.9) yr in the GHF₍₊₎ group; mean eGFR then rose to the GHF range, which was 108.5 mL/min/1.73 m². The eGFR decline after the peak was steeper in the GHF₍₊₎ group than in the GHF_(-) group: -0.984 versus -0.497 mL/min/1.73 m²/yr (P < 0.001). Baseline eGFR, but no other variable, well predicted incident GHF, with an area under the receiver operating characteristic curve of 0.87 (95% confidence interval: 0.86-0.88). In conclusion, GHF occurs as a chronic, multiphasic phenomenon: initially with a sustained GFR elevation for years, followed by a GFR surge to the GHF range, which was accompanied by accelerated GFR declining.

Novel antihypertensive action of rutin is mediated via inhibition of angiotensin converting enzyme/mineralocorticoid receptor/angiotensin 2 type 1 receptor (ATR1) signaling pathways in uninephrectomized hypertensive rats

Hypertension is the most common cardiovascular disease that affects approximately 26% of adult population, worldwide. Rutin is one of the important flavonoids that is consumed in the daily diet, and found in many food items, vegetables, and beverages. Uninephrectomy (UNX) of the left kidney was performed, followed by induction of hypertension. The rats were randomly divided into four groups of 10 rats: group 1-Sham-operated rats; group 2-UNX rats, group 3-UNX-L-NAME (40 mg/kg) plus rutin (100 mg/kg bwt), and groups 4-UNX-L-NAME plus lisinopril (10 mg/kg bwt), orally for 3 weeks. Results revealed significant heightening of arterial pressure and oxidative stress indices, while hypertensive rats treated with rutin had lower expressions of angiotensin converting enzyme (ACE) and mineralocorticoid receptor in uninephrectomized rats. Together, rutin as a novel antihypertensive flavonoid could provide an unimaginable benefits for the management of hypertension through inhibition of angiotensin converting enzyme and mineralocorticoid receptor. PRACTICAL APPLICATIONS: Hypertension has been reported to be the most common cardiovascular disease, affecting approximately 26% of the adult population worldwide with predicted prevalence to increase by 60% by 2025. Recent advances in phytomedicine have shown flavonoids to be very helpful in the treatment of many diseases. Flavonoids have been used in the treatment and management of cardiovascular diseases, obesity and hypertension. The study revealed that rutin, a known flavonoid inhibited angiotensin converting enzyme (ACE), angiotensin 2 type 1 receptor (ATR1), and mineralocorticoid receptor (MCR), comparable to the classic ACE inhibitor, Lisinopril, indicating the novel antihypertensive property of rutin. Therefore, flavonoids such as rutin found in fruits and vegetables could, therefore, serve as an antihypertensive drug regimen. Combining all, functional foods rich in flavonoids could be used as potential therapeutic candidates for managing uninephrectomized hypertensive patients.

Nutrient-dense protein as a primary dietary strategy in healthy ageing: please sir, may we have more?

A progressive decrement in muscle mass and muscle function, sarcopoenia, accompanies ageing. The loss of skeletal muscle mass and function is the main feature of sarcopoenia. Preventing the loss of muscle mass is relevant since sarcopoenia can have a significant impact on mobility and the quality of life of older people. Dietary protein and physical activity have an essential role in slowing muscle mass loss and helping to maintain muscle function. However, the current recommendations for daily protein ingestion for older persons appear to be too low and are in need of adjustment. In this review, we discuss the skeletal muscle response to protein ingestion, and review the data examining current dietary protein recommendations in the older subjects. Furthermore, we review the concept of protein quality and the important role that nutrient-dense protein (NDP) sources play in meeting overall nutrient requirements and improving dietary quality. Overall, the current evidence endorses an increase in the daily ingestion of protein with emphasis on the ingestion of NDP choices by older adults.

HbA1c and Aortic Calcification Index as Noninvasive Predictors of Pre-Existing Histopathological Damages in Living Donor Kidney Transplantation

We previously reported that allografts from living donors may have pre-existing histopathological damages, defined as the combination of interstitial fibrosis (ci), tubular atrophy (ct), and arteriolar hyalinosis (ah) scores of ≧1, according to the Banff classification. We examined preoperative characteristics to identify whether the degree of these damages was related to metabolic syndrome-related factors of donors. We conducted a single-center cross-sectional analysis including 183 living kidney donors. Donors were divided into two groups: chronic change (ci + ct ≧ 1 &cap; ah ≧ 1, n = 27) and control (n = 156). Preoperative characteristics, including age, sex, blood pressure, hemoglobin A1c (HbA1c), aortic calcification index (ACI), and psoas muscle index (PMI), were analyzed. Comparing the groups, the baseline estimated glomerular filtration rate was not significantly different; however, we observed a significant difference for ACI (p = 0.009). HbA1c (p = 0.016) and ACI (p = 0.006) were independent risk factors to predict pre-existing histopathological damages, whereas PMI was not. HbA1c correlated with ct scores (p = 0.035), and ACI correlated with ci (p = 0.005), ct (p = 0.021), and ah (p = 0.017). HbA1c and ACI may serve as preoperative markers for identifying pre-existing damages on the kidneys of living donors.

Renal growth slope in children with congenital and acquired solitary functioning kidneys

Purpose

This study aimed to analyze the renal growth slope in children with congenital and acquired solitary functioning kidneys.

Methods

This retrospective study included all renal ultrasonography examinations performed in children in the agenesis, multicystic dysplastic kidney (MCDK), or nephrectomy group between September 2002 and February 2019. We reviewed the images and recorded the contralateral kidney size only when there was no focal lesion. Linear mixed model or piecewise linear mixed model analyses with a time point of 24 months of age were performed.

Results

There were 132 patients, including 26 patients in the agenesis group, 35 in the MCDK group, and 71 in the nephrectomy group. The nephrectomy group showed the largest baseline kidney size (7.4 cm vs. 5.3 cm in the agenesis group [P<0.001] and 5.2 cm in the MCDK group [P<0.001]) and the smallest overall growth slope (0.04 cm/mo vs. 0.06 cm/mo in the agenesis group [P=0.004] and 0.07 cm/mo in the MCDK group [P<0.001]). However, considering the time point of 24 months for reaching adult renal function, there were significant changes in slope, from 0.1 cm/mo before 24 months of age to 0.03 cm/mo after 24 months of age in all three groups (P<0.001), without a significant difference among the groups.

Conclusion

Significant changes were found in the renal growth slope before and after 24 months of age, with no significant difference between congenital and acquired solitary functioning kidneys.

Sodium-glucose cotransporter 2 inhibitors: extending the indication to non-diabetic kidney disease?

This year the medical community was pleasantly surprised by the results of the first large outcome trial that primarily examined the renal effects of the sodium-glucose cotransporter 2 (SGLT2) inhibitor canagliflozin (CANA) in subjects with diabetes and impaired kidney function. The Evaluation of the Effects of Canagliflozin on Renal and Cardiovascular Outcomes in Participants With Diabetic Nephropathy (CREDENCE) trial showed that CANA, relative to placebo, reduces the risk for end-stage renal disease, doubling of creatinine or renal death by 34% [hazard ratio 0.66 (95% confidence interval 0.53–0.81]. These effects were consistent across baseline estimated glomerular filtration rate (eGFR) and haemoglobin A1c subgroups. In this review we combine the results of the CREDENCE trial with those of several cardiovascular outcome trials with SGLT2 inhibitors and show that, unexpectedly, patients with lower eGFR levels may have greater benefit with respect to cardiovascular outcome than patients with normal kidney function. The cardio- and renoprotective effects of SGLT2 inhibitors seem to be independent of their glucose-lowering effects, as shown in several post hoc analyses. In this review we discuss the alleged mechanisms of action that explain the beneficial effects of this novel class of drugs. Moreover, we discuss whether these findings indicate that this class of drugs may also be beneficial in non-diabetic chronic kidney diseases.

Renal hyperfiltration as a risk factor for chronic kidney disease: A health checkup cohort study

Introduction

Renal hyperfiltration (RHF) has been found to be an independent predictor of adverse cardiovascular outcome. However, it remains uncertain whether it is precursor of chronic kidney disease (CKD) in a healthy population.

Materials and methods

To determine relative risks and identify the predictor of incident proteinuria and decline of estimated glomerular filtration rate (eGFR) in subjects with RHF. A total of 55,992 subjects aged ≥20 years who underwent health check-up during 2004–2017 were included. Among them, 16,946 subjects who completed at least two health checkups were analyzed.

Results

A total of 949 (5.6%) subjects developed proteinuria and 98 (0.6%) subjects showed ≥ 30% of eGFR decline. The risk of incident proteinuria was significantly higher in those with RHF (RR: 1.644; 95% CI: 1.064–2.541). Those with RHF showed 8.720 fold (95% CI: 4.205–18.081) increased risk for ≥30% decline. ESR, CRP, and monocyte count showed reversed J shaped curve according to the increase of eGFR. The adjusted mean of monocyte count was significantly higher in participants with eGFR ≥90ml/min/1.73m² or < 60ml/min/1.73m² compared to that in patients with eGFR 75-89ml/min/1.73m². Compared to subjects with the lowest tertile of monocyte and no RHF, those with the highest tertile of monocyte count in the RHF group had 3.314-fold (95% CI: 1.893–5.802) higher risk of incident proteinuria and 3.822-fold (95% CI, 1.327–11.006) risk of 30% eGFR decline.

Conclusions

RHF had significantly increased risk of developing proteinuria and CKD in healthy subjects. Higher monocyte count might be used as a predictor of CKD in subjects with RHF.

Dietary Protein Intake and Single-Nephron Glomerular Filtration Rate

High protein intake can increase glomerular filtration rate (GFR) in response to excretory overload, which may exacerbate the progression of kidney disease. However, the direct association between glomerular hemodynamic response at the single-nephron level and dietary protein intake has not been fully elucidated in humans. In the present study, we evaluated nutritional indices associated with single-nephron GFR (SNGFR) calculated based on corrected creatinine clearance (SNGFR_Cr). We retrospectively identified 43 living kidney donors who underwent enhanced computed tomography and kidney biopsy at the time of donation at Jikei University Hospital in Tokyo from 2007 to 2018. Total nephron number was estimated with imaging-derived cortical volume and morphometry-derived glomerular density. SNGFR_Cr was calculated by dividing the corrected creatinine clearance by the number of non-sclerosed glomeruli (Nglom_NSG). The mean (± standard deviation) Nglom_NSG/kidney and SNGFR_Cr were 685,000 ± 242,000 and 61.0 ± 23.9 nL/min, respectively. SNGFR_Cr was directly associated with estimated protein intake/ideal body weight (p = 0.005) but not with body mass index, mean arterial pressure, albumin, or sodium intake. These findings indicate that greater protein intake may increase SNGFR and lead to glomerular hyperfiltration.

Sickle Cell Nephropathy and Associated Factors among Asymptomatic Children with Sickle Cell Anaemia

BACKGROUND

Sickle cell nephropathy (SCN) is a serious complication of sickle cell anaemia (SCA) with asymptomatic onset in childhood and possible progression to chronic kidney disease (CKD). In Southeast Nigeria, few studies have evaluated renal function in paediatric SCA patients for early detection of renal impairment and early intervention to reduce morbidity and mortality. Therefore, this study evaluated the renal function of paediatric SCA patients in a steady state based on glomerular filtration rate and urinalysis findings (proteinuria and haematuria).

METHODS

A cross-sectional study of consecutively recruited sixty haemoglobin SS (HbSS) children in a steady state and sixty age- and sex-matched haemoglobin AA (HbAA) controls aged 2-18 years was done. Renal function of HbSS subjects was evaluated using estimated glomerular filtration rate (eGFR) which was compared with healthy HbAA subjects. The prevalence of significant proteinuria and haematuria, its association with eGFR, and the effect of past sickle cell crisis (in the preceding 24 months) on renal function were also evaluated.

RESULTS

Mean eGFR was significantly higher in HbSS subjects than in the HbAA subjects (p = 0.001) and decreased with age. Significant proteinuria and haematuria were more prevalent in the HbSS group (3.4% and 6.7%, respectively) compared to the HbAA subjects (0% and 0%, respectively) (p = 0.496 and 0.119, respectively). No significant association was observed between eGFR and proteinuria (p = 1.000) or haematuria (p = 1.000). There was a positive correlation between eGFR and frequency of past painful crisis that required hospitalization (r = 0.138, p = 0.295) and between eGFR and frequency of blood transfusion (r = 0.679, p ≤ 0.001).

CONCLUSIONS

Asymptomatic paediatric HbSS (SCA) patients had higher mean eGFR indicating an increased risk of nephropathy. There was no association between eGFR and proteinuria or haematuria. Frequent sickle cell crises especially one requiring transfusion were positively correlated with hyperfiltration.

The role of kidney biopsy in diagnosis of preeclampsia in kidney transplant patients

OBJECTIVE

The aim of this report is to review two patients who developed proteinuria in pregnancy after kidney transplant in order to highlight the importance of maintaining a broad differential and the diagnostic utility of kidney biopsy in this clinical scenario.

METHODS

Two cases of women with kidney transplants who presented with proteinuria in pregnancy are described and the literature is reviewed.

RESULTS

In both cases, a kidney biopsy allowed for prompt diagnosis and treatment.

CONCLUSION

Kidney biopsy should be considered an important diagnostic tool in this clinical scenario.

ABBREVIATIONS

ACE: angiotensin-converting enzyme; ESKD: end-stage kidney disease; FSGS: focal segmental glomerulosclerosis; RAAS: renin aldosterone angiotensin system.

Estimation of Intraglomerular Pressure Using Invasive Renal Arterial Pressure and Flow Velocity Measurements in Humans

Significance Statement

Increased intraglomerular pressure is an important contributor to the pathogenesis and progression of CKD in patients with hypertension and diabetes. This study used an adapted Windkessel model to estimate overall renal arterial resistance, arterial compliance, and intraglomerular pressure based on intrarenal pressure and flow velocity measurements in patients undergoing angiography. The mean intraglomerular pressure was consistent with values in non-human primates. It decreased following hyperemia with efferent exceeding afferent dilatation and had significant positive correlation with perfusion pressure and diabetes. The current model and its derived parameters provide a new research technique to assess the renal hemodynamic effects of therapeutic interventions.

Background

Glomerular hyperfiltration resulting from an elevated intraglomerular pressure (Pglom) is an important cause of CKD, but there is no feasible method to directly assess Pglom in humans. We developed a model to estimate Pglom in patients from combined renal arterial pressure and flow measurements.

Methods

We performed hemodynamic measurements in 34 patients undergoing renal or cardiac angiography under baseline conditions and during hyperemia induced by intrarenal dopamine infusion (30 μg/kg). For each participant during baseline and hyperemia, we fitted an adapted three-element Windkessel model that consisted of characteristic impedance, compliance, afferent resistance, and Pglom.

Results

We successfully analyzed data from 28 (82%) patients. Median age was 58 years (IQR, 52–65), median eGFR was 95 ml/min per 1.73 m2 (IQR, 74–100) using the CKD-EPI formula, 30% had microalbuminuria, and 32% had diabetes. The model showed a mean Pglom of 48.0 mm Hg (SD=10.1) at baseline. Under hyperemia, flow increased by 88% (95% CI, 68% to 111%). This resulted in a 165% (95% CI, 79% to 294%) increase in afferent compliance and a 13.1-mm Hg (95% CI, 10.0 to 16.3) decrease in Pglom. In multiple linear regression analysis, diabetes (coefficient, 10.1; 95% CI, 5.1 to 15.1), BMI (0.99 per kg/m2; 95% CI, 0.38 to 1.59), and renal perfusion pressure (0.42 per mm Hg; 95% CI, 0.25 to 0.59) were significantly positively associated with baseline Pglom.

Conclusions

We constructed a model on the basis of proximal renal arterial pressure and flow velocity measurements that provides an overall estimate of glomerular pressure and afferent and efferent resistance in humans. The model provides a novel research technique to evaluate the hemodynamics of CKD on the basis of direct pressure and flow measurements.

Clinical Trial registry name and registration number

Functional HEmodynamics in patients with and without Renal Artery stenosis (HERA), NL40795.018.12 at the Dutch national trial registry (toetsingonline.nl).

An evaluation of preterm kidney size and function over the first two years of life

BACKGROUND

We carried out a study to determine the impact of prematurity on kidney development in the first 2 years of life.

METHODS

In this prospective study, extremely preterm neonates (gestation < 28 weeks) were recruited and underwent assessments at 6, 12, and 24 months of age. A cohort of neonates born term were also recruited and followed up for 24 months. The primary outcomes measured in this study were total kidney volume (TKV) and estimated glomerular filtration rate (eGFR); albuminuria and blood pressure measurements (all provided as mean (standard deviation)) were the secondary outcomes.

RESULTS

Fifty-three premature and 31 term neonates (control) were recruited. At the age of 24 months (corrected age), infants born preterm had significantly smaller TKV (56.1 (9.4) vs. 64.8 (10.2) mL; P = 0.006). There was no difference in eGFR. These preterm infants were smaller (11.25 (1.53) vs. 12.9 (1.8) kg; P = 0.002) and shorter (83.8 (3.0) vs. 86.3 (3.4) cm; P = 0.02) when compared with the control group. At 6, 12, and 18 months respectively, preterm infants had, relative to their height, significantly smaller kidney volumes (0.54 (0.1) vs. 0.59 (0.1) mL/cm, P = 0.05; 0.61 (0.1) vs.0.71 (0.1) mL/cm, P = 0.003; and 0.67 (0.1) vs.0.76 (0.1) mL/cm, P = 0.006).

CONCLUSIONS

Relative to body length, TKV in premature infants is smaller. Since length reflects adult body proportions more accurately than BSA, TKV to height ratio may be a more important measure in the child. Despite smaller TKV (and therefore fewer nephrons), infants born prematurely achieve similar eGFRs in the first 24 months of life, probably due to single-nephron hyperfiltration.