The clinical importance of nephron mass

Kidney volume-to-birth weight ratio as an estimate of nephron endowment in extremely low birth weight preterm infants

In humans, nephrogenesis is completed by 32-36 weeks gestation, with a highly variable total number of nephrons, ranging from 200,000 to over 2 million. Premature birth disrupts the development and maturation of the kidneys, leading to a reduction in the final number of nephrons. Due to significant genetic variability in the number of nephrons among individuals, it is crucial to identify premature infants with fewer nephrons at birth as early as possible. These infants are more susceptible to developing renal failure with advancing age compared to those with a higher nephron endowment. Bedside ultrasound, an effective and non-invasive tool, is practical for identifying newborns with a lower nephron count. However, renal volume alone cannot reliably indicate the number of nephrons due to substantial variability at birth, influenced by gestational age when nephron maturation is incomplete. This variability in kidney volumes persists as newborns grow. In this observational study we hypothesize that the relationship between renal volume and birth weight may serve as an indicator of nephron endowment in premature infants with birth weight less than 1000 g. This finding could represent the basis for defining appropriate surveillance protocols and developing targeted therapeutic approaches.

Non-contrast-enhanced magnetic resonance urography for measuring split kidney function in pediatric patients with hydronephrosis: comparison with renal scintigraphy

BACKGROUND

Split kidney function (SKF) is critical for treatment decision in pediatric patients with hydronephrosis and is commonly measured using renal scintigraphy (RS). Non-contrast-enhanced magnetic resonance urography (NCE-MRU) is increasingly used in clinical practice. This study aimed to investigate the feasibility of using NCE-MRU as an alternative to estimate SKF in pediatric patients with hydronephrosis, compared to RS.

METHODS

Seventy-five pediatric patients with hydronephrosis were included in this retrospective study. All patients underwent NCE-MRU and RS within 2 weeks. Kidney parenchyma volume (KPV) and texture analysis parameters were obtained from T2-weighted (T2WI) in NCE-MRU. The calculated split KPV (SKPV) percent and texture analysis parameters percent of left kidney were compared with the RS-determined SKF.

RESULTS

SKPV showed a significant positive correlation with SKF (r = 0.88, p < 0.001), while inhomogeneity was negatively correlated with SKF (r =  - 0.68, p < 0.001). The uncorrected and corrected prediction models of SKF were established using simple and multiple linear regression. Bland-Altman plots demonstrated good agreement of both predictive models. The residual sum of squares of the corrected prediction model was lower than that of the uncorrected model (0.283 vs. 0.314) but not statistically significant (p = 0.662). Subgroup analysis based on different MR machines showed correlation coefficients of 0.85, 0.95, and 0.94 between SKF and SKPV for three different scanners, respectively (p < 0.05 for all).

CONCLUSIONS

NCE-MRU can be used as an alternative method for estimating SKF in pediatric patients with hydronephrosis when comparing with RS. Specifically, SKPV proves to be a simple and universally applicable indicator for predicting SKF.

Hypertension in children with congenital anomalies of the kidney and urinary tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of childhood chronic kidney disease (CKD). We hypothesized that hypertension varies across CAKUT categories and increases the risk of CKD.

METHODS

This was a retrospective cohort study and included cases with a multicystic dysplastic kidney (MCDK, n = 81), unilateral kidney agenesis (UKA, n = 47), kidney hypoplasia (KH, n = 130), and posterior urethral valves (PUV, n = 75). Hypertension was defined as systolic or diastolic blood pressure ≥ 95th percentile for age, sex and height, and CKD as an estimated glomerular filtration rate < 60 ml/min/1.73 m2, both at 2 consecutive clinic visits at least 3 months apart.

RESULTS

Sixty-two (19%) out of 333 cases developed hypertension, with significant difference according to CAKUT type. Patients with smaller kidney size (7.7 vs. 8.3, p = 0.045), kidney anomalies in addition to the primary diagnosis (aCAKUT) (53 vs. 38%, p = 0.03), proteinuria (46 vs. 12%, p < 0.001), and CKD (51 vs. 23%, p < 0.001) were more likely to develop hypertension. When adjusted for kidney size, the diagnoses of PUV (OR 10.9, 95%CI 3.0, 40.5), UKA (OR 6.4, 95%CI 1.6, 24.9) and KH (OR 4.2, 95%CI 1.1, 16.1), and aCAKUT (OR 2.1, 95%CI 1.2, 3.9) were independent risk factors for hypertension. Hypertension increased the risk of developing CKD by twofold (HR 1.9, 95%CI 1.19, 2.94).

CONCLUSION

Hypertension is common in children with CAKUT and increases the risk of CKD. These findings will aid in the development of a standardized clinical pathway for the care of hypertensive children with CAKUT.

Associations of MRI-derived kidney volume, kidney function, body composition and physical performance in ≈38 000 UK Biobank participants: a population-based observational study

Background

Kidney volume is used as a predictive and therapeutic marker for several clinical conditions. However, there is a lack of large-scale studies examining the relationship between kidney volume and various clinicodemographic factors, including kidney function, body composition and physical performance.

Methods

In this observational study, MRI-derived kidney volume measurements from 38 526 UK Biobank participants were analysed. Major kidney volume-related measures included body surface area (BSA)-adjusted total kidney volume (TKV) and the difference in bilateral kidneys. Multivariable-adjusted linear regression and cubic spline analyses were used to explore the association between kidney volume-related measures and clinicodemographic factors. Cox or logistic regression was used to identify the risks of death, non-kidney cancer, myocardial infarction, ischaemic stroke and chronic kidney disease (CKD).

Results

The median of BSA-adjusted TKV and the difference in kidney volume were 141.9 ml/m2 [interquartile range (IQR) 128.1-156.9] and 1.08-fold (IQR 1.04-1.15), respectively. Higher BSA-adjusted TKV was significantly associated with higher estimated glomerular filtration rate {eGFR; β = 0.43 [95% confidence interval (CI) 0.42-0.44]; P < .001}, greater muscle volume [β = 0.50 (95% CI 0.48-0.51); P < .001] and greater mean handgrip strength [β = 0.15 (95% CI 0.13-0.16); P < .001] but lower visceral adipose tissue volume [VAT; β = -0.09 (95% CI -0.11 to -0.07); P < .001] in adjusted models. A greater difference in bilateral kidney volumes was associated with lower eGFR, muscle volume and physical performance but with higher proteinuria and VAT. Higher BSA-adjusted TKV was significantly associated with a reduced risk of CKD [odds ratio (OR) 0.7 (95% CI 0.63-0.77); P < .001], while a greater difference in kidney volume was significantly associated with an increased risk of CKD [OR 1.13 (95% CI 1.07-1.20); P < .001].

Conclusion

Higher BSA-adjusted TKV and lower differences in bilateral kidney volumes are associated with higher kidney function, muscle volume and physical performance and a reduced risk of CKD.

A Holistic Framework for the Evaluation of Kidney Function in a Gender-Diverse Landscape

The most commonly used equations to estimate glomerular filtration rate incorporate a binary male-female sex coefficient, which has important implications for the care of transgender, gender-diverse, and nonbinary (TGD) people. Whether "sex assigned at birth" or a binary "gender identity" is most appropriate for the computation of estimated glomerular filtration rate (eGFR) is unknown. Furthermore, the use of gender-affirming hormone therapy (GAHT) for the development of physical changes to align TGD people with their affirmed gender is increasingly common, and may result in changes in serum creatinine and cystatin C, the biomarkers commonly used to estimate glomerular filtration rate. The paucity of current literature evaluating chronic kidney disease (CKD) prevalence and outcomes in TGD individuals on GAHT makes it difficult to assess any effects of GAHT on kidney function. Whether alterations in serum creatinine reflect changes in glomerular filtration rate or simply changes in muscle mass is unknown. Therefore, we propose a holistic framework to evaluate kidney function in TGD people. The framework focuses on kidney disease prevalence, risk factors, sex hormones, eGFR, other kidney function assessment tools, and the mitigation of health inequities in TGD people.

Exposure to Chinese famine and the risk of hyperuricemia in later life: a population-based cross-sectional study

Background

Limited studies have investigated the relationship between famine exposure and the risk of hyperuricemia in later life. Consequently, the primary purpose of the current study was to examine the potential association between exposure to Chinese famine and hyperuricemia, as well as any gender disparities in this relationship.

Method

The data were obtained from the China PEACE (China Patient-Centered Evaluative Assessment of Cardiac Events) Million Persons Project in Rongchang. The study participants were enrolled into different cohorts based on their birthdates: the fetal-exposed cohort (born between 1959 and 1962), the childhood-exposed cohort (born between 1949 and 1958), the adolescence-exposed cohort (born between 1941 and 1948), and the non-exposed cohorts (born between 1963 and 1974). The potential association between famine exposure and hyperuricemia was assessed using binary logistic regression models.

Results

A total of 6,916 individuals were enrolled in the current study with an average age of 60.11 ± 9.22 years, out of which 3,544 were women. After adjusting for confounding factors, fetal (OR = 0.530, 95% CI: 0.411-0.0.683), childhood (OR = 0.642, 95% CI: 0.494-0.833) exposure to the Chinese famine for men was negatively associated with hyperuricemia. Conversely, exposure to the Chinese famine during fetal (OR = 2.144, 95% CI: 1.622-2.834), childhood (OR = 1.485, 95% CI: 1.105-1.997), and adolescence (OR = 1.967, 95% CI: 1.465-2.641) for women was positively associated with hyperuricemia. Furthermore, the impact of famine on hyperuricemia that has been observed in exposed women might be intensified by the presence of dyslipidemia, abdominal obesity, and overweight/obesity.

Conclusion

Women exposed to the Chinese famine during fetal, childhood, and adolescence were positively associated with hyperuricemia, while men exhibited a negative association during fetal and childhood. Additionally, the effect of famine on hyperuricemia in exposed women appears to be intensified by the presence of dyslipidemia, abdominal obesity, and overweight/obesity.

Methylation analysis by targeted bisulfite sequencing in large for gestational age (LGA) newborns: the LARGAN cohort

BACKGROUND

In 1990, David Barker proposed that prenatal nutrition is directly linked to adult cardiovascular disease. Since then, the relationship between adult cardiovascular risk, metabolic syndrome and birth weight has been widely documented. Here, we used the TruSeq Methyl Capture EPIC platform to compare the methylation patterns in cord blood from large for gestational age (LGA) vs adequate for gestational age (AGA) newborns from the LARGAN cohort.

RESULTS

We found 1672 differentially methylated CpGs (DMCs) with a nominal p < 0.05 and 48 differentially methylated regions (DMRs) with a corrected p < 0.05 between the LGA and AGA groups. A systems biology approach identified several biological processes significantly enriched with genes in association with DMCs with FDR < 0.05, including regulation of transcription, regulation of epinephrine secretion, norepinephrine biosynthesis, receptor transactivation, forebrain regionalization and several terms related to kidney and cardiovascular development. Gene ontology analysis of the genes in association with the 48 DMRs identified several significantly enriched biological processes related to kidney development, including mesonephric duct development and nephron tubule development. Furthermore, our dataset identified several DNA methylation markers enriched in gene networks involved in biological pathways and rare diseases of the cardiovascular system, kidneys, and metabolism.

CONCLUSIONS

Our study identified several DMCs/DMRs in association with fetal overgrowth. The use of cord blood as a material for the identification of DNA methylation biomarkers gives us the possibility to perform follow-up studies on the same patients as they grow. These studies will not only help us understand how the methylome responds to continuum postnatal growth but also link early alterations of the DNA methylome with later clinical markers of growth and metabolic fitness.

The molecular and cellular anatomy of a fetal programming defect - the impact of low protein diet on the developing kidney

Low nephron number correlates with the development of hypertension and chronic kidney disease later in life. While intrauterine growth restriction caused by maternal low protein diet (LPD) is thought to be a significant cause of reduced nephron endowment in impoverished communities, its influence on the cellular and molecular processes which drive nephron formation are poorly understood. We conducted a comprehensive characterization of the impact of LPD on kidney development using tomographic and confocal imaging to quantify changes in branching morphogenesis and the cellular and morphological features of nephrogenic niches across development. These analyses were paired with single-cell RNA sequencing to dissect the transcriptional changes that LPD imposes during renal development. Differences in the expression of genes involved in metabolism were identified in most cell types we analyzed, yielding imbalances and shifts in cellular energy production. We further demonstrate that LPD impedes branching morphogenesis and significantly reduces the number of pretubular aggregates - the initial precursors to nephron formation. The most striking observation was that LPD changes the developmental trajectory of nephron progenitor cells, driving the formation of a partially committed cell population which likely reflects a failure of cells to commit to nephron formation and which ultimately reduces endowment. This unique profile of a fetal programming defect demonstrates that low nephron endowment arises from the pleiotropic impact of changes in branching morphogenesis and nephron progenitor cell commitment, the latter of which highlights a critical role for nutrition in regulating the cell fate decisions underpinning nephron endowment.

Significance Statement

While a mother's diet and behavior can negatively impact the number of nephrons in the kidneys of her offspring, the root cellular and molecular drivers of these deficits have not been rigorously explored. In this study we use advanced imaging and gene expression analysis in mouse models to define how a maternal low protein diet, analogous to that of impoverished communities, results in reduced nephron endowment. We find that low protein diet has pleiotropic effects on metabolism and the normal programs of gene expression. These profoundly impact the process of branching morphogenesis necessary to establish niches for nephron generation and change cell behaviors which regulate how and when nephron progenitor cells commit to differentiation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION

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

Investigation of Kidney Morphology and Somatotype Components in Early-Stage Kidney Patients

Objectives

The aim of this study is to examine the kidney morphology and somatotype components of adult patients with early-stage chronic kidney disease (CKD).

Methods

The sample consisted of 46 individuals with early-stage CKD (26 men and 20 women, mean age=45.92±16.53 years). The pathological subjects were compared with a control group consisting of 46 healthy subjects (28 men and 18 women, mean age=41.96±11.48 years). The Heath-Carter method was used to determine somatotype components. Abdominal computed tomography (CT) of patients with Stage 2 CKD and healthy volunteers taken within the past 3 months was scanned to determine kidney morphology. Kidney measurements were performed on CTs (length, width, depth, and volume of kidney).

Results

Kidney patients (mean somatotype: 6.33-5.37-0.6) were less ectomorphic and more endomorphic than the controls (mean somatotype: 4.35-4.40-3.02). Moderate effect size (ES) was found in endomorphy (ES=0.87; p=0.035) and ectomorphy (ES=1.08; p=0.012) between groups. No significant difference was observed in the kidney morphology (ES=0.04-0.19; p>0.05).

Conclusion

In the early-stage CKD, kidney morphology may not be the distinguishing factor. On the other hand, patients differed significantly in terms of endomorph components. Being overweight can also be one of the negative findings for kidney disease. Somatotype classification could be a suitable tool for monitoring kidney disease.

The NOS/NO System in Renal Programming and Reprogramming

Nitric oxide (NO) is a gaseous signaling molecule with renoprotective properties. NO can be produced in NO synthase (NOS)-dependent or -independent manners. NO deficiency plays a decisive role in chronic kidney disease (CKD). Kidney development can be affected in response to adverse intrauterine conditions that induce renal programming, thereby raising the risk of developing CKD in adulthood. Conversely, detrimental programming processes could be postponed or halted prior to the onset of CKD by early treatments, namely reprogramming. The current review provides an overview of the NOS/NO research performed in the context of renal programming and reprogramming. NO deficiency has been increasingly found to interact with the different mechanisms behind renal programming, such as oxidative stress, aberrant function of the renin-angiotensin system, disturbed nutrient-sensing mechanisms, dysregulated hydrogen sulfide signaling, and gut microbiota dysbiosis. The supplementation of NOS substrates, the inhibition of asymmetric dimethylarginine (ADMA), the administration of NO donors, and the enhancement of NOS during gestation and lactation have shown beneficial effects against renal programming in preclinical studies. Although human data on maternal NO deficiency and offspring kidney disease are scarce, experimental data indicate that targeting NO could be a promising reprogramming strategy in the setting of renal programming.

Acute kidney injury in infants hospitalized for viral bronchiolitis

We investigated prevalence of and factors associated with acute kidney injury (AKI) in a group of patients hospitalized with viral bronchiolitis. We retrospectively enrolled 139 children (mean age = 3.2 ± 2.1 months; males = 58.9%) hospitalized for viral bronchiolitis in a non-pediatric intensive care unit (PICU) setting. The Kidney Disease/Improving Global Outcomes creatinine criterion was used to diagnose AKI. We estimated basal serum creatinine by back-calculating it by Hoste (age) equation assuming that basal eGFR were the median age-based eGFR normative values. Univariate and multivariate logistic regression models were used to explore associations with AKI. Out of 139 patients, AKI was found in 15 (10.8%). AKI was found in 13 out of 74 (17.6%) patients with and in 2 out of 65 (3.1%) without respiratory syncytial virus (RSV) infection (p = 0.006). No patient required renal replacement therapies, while 1 out of 15 (6.7%) developed AKI stage 3, 1 (6.7%) developed AKI stage 2, and 13 (86.6%) developed AKI stage 1. Among the 15 patients with AKI, 13 (86.6%) reached the maximum AKI stage at admission, 1 (6.7%) at 48 h, and 1 (6.7%) at 96 h. At multivariate analysis, birth weight < 10th percentile (odds ratio, OR = 34.1; 95% confidence interval, CI = 3.6-329.4; p = 0.002), preterm birth (OR = 20.3; 95% CI = 3.1-129.5; p = 0.002), RSV infection (OR = 27.0; 95% CI = 2.6-279.9; p = 0.006), and hematocrit levels > 2 standard deviation score (SDS) (OR = 22.4; 95% CI = 2.8-183.6; p = 0.001) were significantly associated with AKI.

CONCLUSION

About 11% of patients hospitalized with viral bronchiolitis in a non-PICU setting develop an AKI (frequently mild in degree). Preterm birth, birth weight < 10th percentile, hematocrit levels > 2SDS, and RSV infection are significantly associated with AKI in the setting of viral bronchiolitis.

WHAT IS KNOWN

• Viral bronchiolitis affects children in the first months of life and in 7.5% of cases it can be complicated by acute kidney injury (AKI). • No studies investigated associations with AKI in infants hospitalized for viral bronchiolitis.

WHAT IS NEW

• About 11% of patients hospitalized with viral bronchiolitis can develop an AKI (frequently mild in degree). • Preterm birth, birth weight <10th percentile, hematocrit levels > 2 standard deviation score, and respiratory syncytial virus infection are associated with AKI development in infants with viral bronchiolitis.

A girl with membranous nephropathy associated with ventriculoperitoneal shunt infection

Glomerulopathy associated with shunt infection is commonly membranoproliferative glomerulonephritis, whereas the causative organisms of secondary membranous nephropathy are usually viruses. We report a case of membranous nephropathy associated with shunt infection. The patient was born at 29-week gestation with a birth weight of 1178 g. Ventriculoperitoneal shunt surgery had been performed for congenital hydrocephalus. Thereafter, she had experienced seven shunt infections. At the age 13 years, proteinuria was detected in a school urinary screening. Urinalysis at our hospital demonstrated 3 + protein and 3 + blood. Laboratory testing demonstrated a serum creatinine 0.5 m/dl, albumin 2.5 g/dl, C-reactive protein (CRP) 13.7 mg/dl, and C3 182 mg/dl. Prior to repeat urinalysis, the patient developed vomiting and was admitted with suspected shunt infection. On admission, her body temperature was 36.0 ºC. Physical examination was unremarkable other than small stature and a palpable mass in the left upper quadrant. Urinalysis demonstrated 2 + protein and 1 + blood with no cells or casts. The urinary protein excretion was 3 g/day. Abnormal laboratory tests included erythrocyte sedimentation rate 102 mm/hr, CRP 11.67 mg/dl, IgG 2442 mg/dl, C3 177 mg/dl, and C4 44 mg/dl. Antibiotic therapy was initiated for a presumptive diagnosis of shunt infection and the shunt catheter was removed. Cultures obtained after antibiotic administration were negative. Proteinuria persisted after control of the shunt infection. Histology of a renal biopsy demonstrated membranous nephropathy with diffuse granular IgG staining and subepithelial deposits. Three possible pathomechanisms for her membranous nephropathy were considered.

Lupus nephropathy beyond immunosuppression: Searching for nephro and cardioprotection

Renal involvement in systemic lupus erythematosus (SLE) represents one of the most frequent organ manifestations, often leading to end-stage kidney disease (ESKD). Several therapies have been tested in patients with lupus nephritis (LN) to prevent further organ damage. The effectiveness of immunosuppressive therapy as a treatment for LN is abundant, supported by multiple clinical trials that have shown its efficacy in preventing the development of chronic kidney disease (CKD). In addition to immunosuppressive therapy, several traditional and recent therapies aimed at nephroprotection in patients with proteinuric chronic kidney disease are gaining importance in the setting of LN. Thus, immunosuppressive therapy should be accompanied by nephro- and cardioprotective measures to control cardiovascular risk factors and proteinuria to ensure a better renal prognosis. Despite this, the literature on these specific measures is relatively scarce, with recommendations focused on the blockade of the renin-angiotensin-aldosterone system (RAAS). This review explores the pharmacological options available for cardiovascular and renal protection outside the usual treatment schemes.

The Association Between Adult Height and Stroke Incidence in Japanese Men and Women: A Population-based Case-Control Study

BACKGROUND

No studies have examined the associations between adult height and ischemic stroke subtypes.

METHODS

We conducted a population-based case-control study that included 2,451 thrombotic and 687 embolic stroke cases, as well as 1,623 intracerebral and 768 subarachnoid hemorrhage cases without history of stroke aged 40-79 years, and the same number of sex- and age-matched controls. Cases and controls were grouped according to the quintile cut-off values of height in controls, and the third quintile, which was approximately the average height group, was used as the reference group. Height divided by one standard deviation of height in controls was also examined as a continuous variable. The analyses were carried out separately for participants aged 40-59 years and 60-79 years.

RESULTS

In both younger and older men, height was linearly inversely associated with total and thrombotic strokes, and the shortest quintile compared to the reference group was associated with increased risks of these strokes. Although height was linearly inversely associated with embolic stroke and intracerebral hemorrhage in younger men, the shortest quintile did not show increased risks of these strokes. Height did not seem to be associated with total stroke and any stroke subtypes in younger women. In contrast, the tallest quintile was significantly associated with increased risks of total stroke and intracerebral hemorrhage, and height tended to be positively associated with these strokes in older women.

CONCLUSION

We reported the associations between adult height and ischemic stroke subtypes for the first time, which differed according to sex and age group.

Testican-2 Is Associated with Reduced Risk of Incident ESKD

BACKGROUND

Testican-2 was recently identified as a podocyte-derived protein that is released into circulation by the kidneys and is positively correlated with eGFR and eGFR slope. However, whether higher testican-2 levels are associated with lower risk of ESKD is unknown.

METHODS

Aptamer-based proteomics assessed blood testican-2 levels among participants in the African American Study of Kidney Disease and Hypertension (AASK, n =703), the Chronic Renal Insufficiency Cohort (CRIC) study ( n =3196), and the Atherosclerosis Risk in Communities (ARIC) study ( n =4378). We compared baseline characteristics by testican-2 tertile and used Cox proportional hazards models to study the association of testican-2 with incident ESKD.

RESULTS

Higher testican-2 levels were associated with higher measured GFR (mGFR) in AASK, higher eGFR in the CRIC and ARIC studies, and lower albuminuria in all cohorts. Baseline testican-2 levels were significantly associated with incident ESKD in Cox proportional hazards models adjusted for age, sex, and race (model 1) and model 1+mGFR or eGFR+comorbidities (model 2). In model 3 (model 2+proteinuria), the associations between testican-2 (per SD increase) and incident ESKD were AASK (hazard ratio [HR]=0.84 [0.72 to 0.98], P =0.023), CRIC (HR=0.95 [0.89 to 1.02], P =0.14), ARIC (HR=0.54 [0.36 to 0.83], P =0.0044), and meta-analysis (HR=0.92 [0.86 to 0.98], P =0.0073).

CONCLUSIONS

Across three cohorts spanning >8000 individuals, testican-2 is associated with kidney health and prognosis, with higher levels associated with reduced risk of ESKD.

CT volumetry performs better than nuclear renography in predicting estimated renal function one year after living donation

The evaluation of split renal function (SRF) is a critical issue in living kidney donations and can be evaluated using nuclear renography (NR) or computerized tomography (CT), with unclear comparative advantages. We conducted this retrospective study in 193 donors to examine the correlation of SRF assessed by NR and CT volumetry and compared their ability to predict remaining donor renal function at 1 year, through multiple approaches. A weak correlation between imaging techniques for evaluating the percentage of the remaining kidney volume was found in the global cohort, with an R² = 0.15. However, the Bland-Altman plot showed an acceptable agreement (95% of the difference between techniques falling within - 8.51 to 6.11%). The predicted and observed eGFR one year after donation were calculated using the CKD-EPI, and CG/BSA equations. CT volume showed a better correlation than NR for both formulas (adjusted R² of 0.42. and 0.61 vs 0.37 and 0.61 for CKD-EPI and CG/ BSA equations, respectively). In non-nested modeling tests, CT volumetry was significantly superior to NR for both equations. CT volumetry performed better than NR in predicting the estimated renal function of living donors at 1-year, independently from the eGFR equation.

Nephrons, podocytes and chronic kidney disease: Strategic antihypertensive therapy for renoprotection

Chronic kidney disease (CKD) is one of the strongest risk factors for hypertension, and hypertension can exacerbate the progression of CKD. Thus, the management of CKD and antihypertensive therapy are inextricably linked. Research over the past decades has shown that the human kidney is more diverse than initially thought. Subjects with low nephron endowment are at increased risk of developing CKD and hypertension, which is consistent with the theory of the developmental origins of health and disease. Combined with other lifetime risks of CKD, hypertension may lead to a vicious cycle consisting of podocyte injury, glomerulosclerosis and further loss of nephrons. Of note, recent studies have shown that the number of nephrons correlates well with the number of podocytes, suggesting that these two components are intrinsically linked and may influence each other. Both nephrons and podocytes have no or very limited regenerative capacity and are destined to decrease throughout life. Therefore, one of the best strategies to slow the progression of CKD is to maintain the "numbers" of these essential components necessary to preserve renal function. To this end, both the achievement of an optimal blood pressure and a maximum reduction in urinary protein excretion are essential. Lifestyle modifications and antihypertensive drug therapy must be carefully individualized to address the potential diversity of the kidneys.

Perinatal Oxidative Stress and Kidney Health: Bridging the Gap between Animal Models and Clinical Reality

Oxidative stress arises when the generation of reactive oxygen species or reactive nitrogen species overwhelms antioxidant systems. Developing kidneys are vulnerable to oxidative stress, resulting in adult kidney disease. Oxidative stress in fetuses and neonates can be evaluated by assessing various biomarkers. Using animal models, our knowledge of oxidative-stress-related renal programming, the molecular mechanisms underlying renal programming, and preventive interventions to avert kidney disease has grown enormously. This comprehensive review provides an overview of the impact of perinatal oxidative stress on renal programming, the implications of antioxidant strategies on the prevention of kidney disease, and the gap between animal models and clinical reality.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Mapping single-nephron filtration in the isolated, perfused rat kidney using magnetic resonance imaging

The kidney has an extraordinary ability to maintain glomerular filtration despite natural fluctuations in blood pressure and nephron loss. This is partly due to local coordination between single-nephron filtration and vascular perfusion. An improved understanding of the three-dimensional (3-D) functional coordination between nephrons and the vasculature may provide a new perspective of the heterogeneity of kidney function and could inform targeted therapies and timed interventions to slow or prevent the progression of kidney disease. Here, we developed magnetic resonance imaging (MRI) tools to visualize single-nephron function in 3-D throughout the isolated perfused rat kidney. We used an intravenous slow perfusion of a glomerulus-targeted imaging tracer [cationized ferritin (CF)] to map macromolecular dynamics and to identify glomeruli in 3-D, followed by a bolus of a freely filtered tracer (gadolinium diethylenetriamine penta-acetic acid) to map filtration kinetics. There was a wide intrakidney distribution of CF binding rates and estimated single-nephron glomerular filtration rate (eSNGFR) between nephrons. eSNGFR and CF uptake rates did not vary significantly by distance from the kidney surface. eSNGFR varied from ∼10 to ∼100 nL/min throughout the kidney. Whole single-kidney GFR was similar across all kidneys, despite differences in the distributions eSNGFR of and glomerular number, indicating a robust adaptive regulation of individual nephrons to maintain constant single-kidney GFR in the presence of a natural variation in nephron number. This work provides a framework for future studies of single-nephron function in the whole isolated perfused kidney and experiments of single-nephron function in vivo using MRI.NEW & NOTEWORTHY We report MRI tools to measure and map single-nephron function in the isolated, perfused rat kidney. We used imaging tracers to identify nephrons throughout the kidney and to measure the delivery and filtration of the tracers at the location of the glomeruli. With this technique, we directly measured physiological parameters including estimated single-nephron glomerular filtration rate throughout the kidney. This work provides a foundation for new studies to simultaneously map the function of large numbers of nephrons.

Role of GSTM1 in Hypertension, CKD, and Related Diseases across the Life Span

Over 20 years after the introduction of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, CKD remains a major public health burden with limited therapeutic options to halt or slow kidney disease progression at all ages. The consensus is that oxidative stress contributes to CKD development and progression. Yet, to date, there is no clear evidence that broad use of antioxidant therapy provides a beneficial effect in CKD. Understanding the specific pathophysiologic mechanisms in those who are genetically most susceptible to oxidative stress is a crucial step to inform therapy in an individualized medicine approach, considering differing exposures and risks across the life span. Glutathione-S-transferase μ 1 (GSTM1) is a phase 2 enzyme involved in inactivation of reactive oxygen species and metabolism of xenobiotics. In particular, those with the highly prevalent GSTM1 null genotype (GSTM1[0/0]) may be more susceptible to kidney disease progression, due to impaired capacity to handle the increased oxidative stress burden in disease states, and might specifically benefit from therapy that targets the redox imbalance mediated by loss of the GSTM1 enzyme. In this review, we will discuss the studies implicating the role of GSTM1 deficiency in kidney and related diseases from experimental rodent models to humans, from the prenatal period through senescence, and the potential underlying mechanism.

Plant-Based Diets Improve Maternal-Fetal Outcomes in CKD Pregnancies

Reducing protein intake in patients with chronic kidney disease (CKD) limits glomerular stress induced by hyperfiltration and can prevent the progression of kidney disease; data in pregnancy are limited. The aim of this study is to analyze the results obtained in CKD patients who followed a plant-based moderately protein-restricted diet during pregnancy in comparison with a propensity-score-matched cohort of CKD pregnancies on unrestricted diets. A total of 52 CKD pregnancies followed up with a protein-restricted plant-based diet (Torino, Italy) were matched with a propensity score based on kidney function and proteinuria with CKD pregnancies with unrestricted protein intake (Cagliari Italy). Outcomes included preterm (<37 weeks) and very preterm (<34 weeks) delivery and giving birth to a small-for-gestational-age baby. The median age in our cohort was 34 years, 63.46% of women were primiparous, and the median body mass index (BMI) was 23.15 kg/m² with 13.46% of obese subjects. No statistical differences were found between women on a plant-based diet and women who were not in terms of age, parity, BMI, obesity, CKD stage, timing of referral, or cause of CKD. No differences were found between the two groups regarding the week of delivery. However, the combined negative outcome (birth before 37 completed gestational weeks or birth-weight centile <10) occurred less frequently in women following the diet than in women in the control group (61.54% versus 80.77%; p = 0.03). The lower risk was confirmed in a multivariable analysis adjusted for renal function and proteinuria (OR: 0.260 [Q1:0.093-Q3:0.724]; p = 0.010), in which the increase in proteinuria from the first to the last check-up before delivery was lower in patients on plant-based diets (median from 0.80 to 1.87 g/24 h; p: ns) than in controls (0.63 to 2.39 g/24 h p <0.0001). Plant-based, moderately protein-restricted diets in pregnancy in patients with CKD are associated with a lower risk of preterm delivery and small-for-gestational-age babies; the effect may be mediated by better stabilization of proteinuria.

Omics profiling identifies the regulatory functions of the MAPK/ERK pathway in nephron progenitor metabolism

Nephron endowment is defined by fetal kidney growth and crucially dictates renal health in adults. Defects in the molecular regulation of nephron progenitors contribute to only a fraction of reduced nephron mass cases, suggesting alternative causative mechanisms. The importance of MAPK/ERK activation in nephron progenitor maintenance has been previously demonstrated, and here, we characterized the metabolic consequences of MAPK/ERK deficiency. Liquid chromatography/mass spectrometry-based metabolomics profiling identified 42 reduced metabolites, of which 26 were supported by in vivo transcriptional changes in MAPK/ERK-deficient nephron progenitors. Among these, mitochondria, ribosome and amino acid metabolism, together with diminished pyruvate and proline metabolism, were the most affected pathways. In vitro cultures of mouse kidneys demonstrated a dosage-specific function for pyruvate in controlling the shape of the ureteric bud tip, a regulatory niche for nephron progenitors. In vivo disruption of proline metabolism caused premature nephron progenitor exhaustion through their accelerated differentiation in pyrroline-5-carboxylate reductases 1 (Pycr1) and 2 (Pycr2) double-knockout kidneys. Pycr1/Pycr2-deficient progenitors showed normal cell survival, indicating no changes in cellular stress. Our results suggest that MAPK/ERK-dependent metabolism functionally participates in nephron progenitor maintenance by monitoring pyruvate and proline biogenesis in developing kidneys.

Risk factors for childhood chronic kidney disease: a population-based study

BACKGROUND

The population-based prevalence and risk factors of childhood chronic kidney disease (CKD) are not well-defined. We ascertained childhood CKD epidemiology and perinatal risk factors, based on a large computerized medical record database that covers most of southern Israel's population.

METHODS

Pre- and post-natal records of 79,374 eligible children (with at least one serum creatinine test) born during 2001-2015 were analyzed. "Ever-CKD" was defined as ≥ 2 estimated glomerular filtration rate (eGFR) values < 60 ml/min/1.73 m² beyond age 2 years, more than 3 months apart. The last CKD status was determined on March 2019.

RESULTS

Of 82 (0.1%) patients with ever-CKD, 35 (42.7%) had their first abnormal eGFR identified already at age 2 years. In multiple logistic regression analysis, congenital anomalies of kidney and urinary tract (CAKUT)-related diagnoses, glomerulopathy, maternal oligohydramnios, small for gestational age, prematurity (under 34 weeks), post-term delivery, and small for gestational age at birth were significant risk factors for ever-CKD (odds ratio (95% confidence interval): 44.34(26.43-74.39), 64.60(32.42-128.70), 5.54(3.01-10.19), 2.02(1.25-3.28), 4.45(2.13-9.28), 2.96(1.28-6.86 and 2.02(1.25-3.28), respectively). Seventy children with ever-CKD (85.4%) had a depressed eGFR (< 90 ml/min/1.73 m²) on the last assessment (current-CKD), yielding a prevalence of 882/million.

CONCLUSIONS

CKD is more prevalent among children in southern Israel than previously reported, even after excluding those with aborted-CKD. Prenatal conditions increase the risk to develop CKD in childhood. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information.

Kidney Injuries and Evolution of Chronic Kidney Diseases Due to Neonatal Hyperoxia Exposure Based on Animal Studies

Preterm birth interrupts the development and maturation of the kidneys during the critical growth period. The kidneys can also exhibit structural defects and functional impairment due to hyperoxia, as demonstrated by various animal studies. Furthermore, hyperoxia during nephrogenesis impairs renal tubular development and induces glomerular and tubular injuries, which manifest as renal corpuscle enlargement, renal tubular necrosis, interstitial inflammation, and kidney fibrosis. Preterm birth along with hyperoxia exposure induces a pathological predisposition to chronic kidney disease. Hyperoxia-induced kidney injuries are influenced by several molecular factors, including hypoxia-inducible factor-1α and interleukin-6/Smad2/transforming growth factor-β, and Wnt/β-catenin signaling pathways; these are key to cell proliferation, tissue inflammation, and cell membrane repair. Hyperoxia-induced oxidative stress is characterized by the attenuation or the induction of multiple molecular factors associated with kidney damage. This review focuses on the molecular pathways involved in the pathogenesis of hyperoxia-induced kidney injuries to establish a framework for potential interventions.

Programming by maternal obesity: a pathway to poor cardiometabolic health in the offspring

There is an ever increasing prevalence of maternal obesity worldwide such that in many populations over half of women enter pregnancy either overweight or obese. This review aims to summarise the impact of maternal obesity on offspring cardiometabolic outcomes. Maternal obesity is associated with increased risk of adverse maternal and pregnancy outcomes. However, beyond this exposure to maternal obesity during development also increases the risk of her offspring developing long-term adverse cardiometabolic outcomes throughout their adult life. Both human studies and those in experimental animal models have shown that maternal obesity can programme increased risk of offspring developing obesity and adipose tissue dysfunction; type 2 diabetes with peripheral insulin resistance and β-cell dysfunction; CVD with impaired cardiac structure and function and hypertension via impaired vascular and kidney function. As female offspring themselves are therefore likely to enter pregnancy with poor cardiometabolic health this can lead to an inter-generational cycle perpetuating the transmission of poor cardiometabolic health across generations. Maternal exercise interventions have the potential to mitigate some of the adverse effects of maternal obesity on offspring health, although further studies into long-term outcomes and how these translate to a clinical context are still required.

Early-life exposure to the Chinese famine and risk of hyperuricaemia in adult females in Qingdao

Two population-based cross-sectional surveys involving randomly selected Chinese adults aged 35-74 years were conducted in Qingdao, China in 2006 and 2009. Nine thousand fifty-five subjects from the two surveys were grouped into four birth groups of fetal/infant exposed (born between 1 January 1959 and 31 December 1962), childhood exposed (born between 1 January 1950 and 31 December 1958), adolescence exposed (born between 1 January 1942 and 31 December 1949) and the unexposed (born before 1941 and after 1963). Multivariate logistic regression models were used to calculate the OR and 95 % CI of hyperuricaemia in different exposed groups. Overall, famine exposure in the fetal/infant period, childhood and adolescence was not associated with adulthood hyperuricaemia (all P > 0·05). In females, childhood exposed group (OR = 1·59, 95 % CI 1·25, 2·02) and adolescence exposed group (OR = 1·74, 95 % CI 1·30, 2·33) both had higher risks to have hyperuricaemia in adult. However, this difference was not found in fetal/infant exposed group. In males, no significant relation was observed in any famine exposed group (all P > 0·05). Exposure to famine in childhood and adolescence is associated with an increased risk of hyperuricaemia for adulthood of females, but not in males. Adequate nutrition during early life appears to be beneficial to prevent hyperuricaemia of adult females.

Effects of Prematurity and Growth Restriction on Adult Blood Pressure and Kidney Volume

Gaining insight into the complex cycle of renal programming and its early-life clinical associations is essential to understand the origins of kidney disease. Prematurity and intrauterine growth restriction are associated with low nephron endowment. This increases the risk of developing hypertension and chronic kidney disease later in life. There is appreciable evidence to support mechanistic links between low nephron endowment secondary to intrauterine events and kidney size, kidney function, and blood pressure in postnatal life. A clear understanding of the cycle of developmental programming and consequences of fetal insults on the kidney is critical. In addition, the impact of events in the early postnatal period (accelerated postnatal growth, development of obesity, exposure to nephrotoxins) on the cardiovascular system and blood pressure of individuals born prematurely or with low birth weight is discussed. In summary, this review draws attention to the concepts of renal programming and nephron endowment and underscores the associations between intrauterine growth restriction, prematurity, and its clinical consequences in adult life.

Growth control of the kidney

The functional mass of kidney tissue in an adult is an important determinant of human health. Kidney formation during development is an essential determinant of the final nephron endowment of the adult organ, and no evidence has been reported that mice or humans are able to generate new nephrons after the developmental period. Mechanisms controlling organ growth after development are essential to establish the final adult organ size. The potential for organ growth is maintained in adult life and the size of one kidney may be significantly increased by loss of the contralateral kidney. The mouse has provided a model system for investigators to critically explore genetic, cell biological, and hormonal control of developmental and juvenile kidney growth. This article reviews three basic aspects of kidney size regulation: (1) Mechanisms that control nephron formation and how these are altered by the cessation of nephrogenesis at the end of the developmental period. (2) Applicability of the general model for growth hormone-insulin like growth factor control to kidney growth both pre- and postnatally. (3) Commonalities between mechanisms of juvenile kidney growth and the compensatory growth that is stimulated in adult life by reduction of kidney mass. Understanding the mechanisms that determine set-points for cell numbers and size in the kidney may inform ongoing efforts to generate kidney tissue from stem cells.

Comparison of tomographic kidney volumes measured by semi-automatic segmentation method with scintigraphic split renal function in predicting posttransplant kidney functions

INTRODUCTION

In this study, it was aimed to compare scintigraphic split renal function (SRF) and computed tomographic (CT) kidney volumes by semi-automatic segmentation method in predicting graft functions after kidney transplantation.

METHODS

112 patients (77 males, 35 females) who had a living donor kidney transplant between 2015 and 2017 in our center were included in the study. While SRF was calculated with technetium-99m-diethylenetriaminepentaacetic acid (^99m Tc-DTPA) scintigraphy, CT angiography was used for volumetric calculations.

RESULTS

CT-volumetric measurements, especially renal cortical volume (RCV:103.8 ± 20 mL) and ratio to body mass index (RCV/BMI:4.45±1.3) were found to be more significant than ^99m Tc-DTPA-SRF in predicting graft functions. The correlations between SRF and RCV with 6th month eGFR (rSRF:0.052, rRCV:0.317, p=0.041) and 1st year eGFR (rSRF:0.104, rRCV:0.374, p=0.033) were found to be more significant in favor of RCV. The correlation between SRF/BMI and RCV/BMI with 1st, 6th and 12th month eGFR (respectively, p=0.02/0.048/0.024) were found to be more significant in favor of RCV/BMI. Although univariate analysis showed a significant relationship between most volumetric measurements and 1st year graft functions, in multivariate analysis only RCV (OR: 1.04(1.01-1.07), p=0.023) and RCV/BMI (OR: 2.5(1.27-5.39), p=0.013) showed a significant relationship between graft functions.

CONCLUSION

In our study, it was shown that CT-based renal volumetric measurements, especially RCV and RCV/BMI, predicted graft functions more strongly than scintigraphic ^99m Tc-DTPA-SRF. This article is protected by copyright. All rights reserved.

Chronic Kidney Disease and Gut Microbiota: What Is Their Connection in Early Life?

The gut–kidney interaction implicating chronic kidney disease (CKD) has been the focus of increasing interest in recent years. Gut microbiota-targeted therapies could prevent CKD and its comorbidities. Considering that CKD can originate in early life, its treatment and prevention should start in childhood or even earlier in fetal life. Therefore, a better understanding of how the early-life gut microbiome impacts CKD in later life and how to develop ideal early interventions are unmet needs to reduce CKD. The purpose of the current review is to summarize (1) the current evidence on the gut microbiota dysbiosis implicated in pediatric CKD; (2) current knowledge supporting the impact of the gut–kidney axis in CKD, including inflammation, immune response, alterations of microbiota compositions, short-chain fatty acids, and uremic toxins; and (3) an overview of the studies documenting early gut microbiota-targeted interventions in animal models of CKD of developmental origins. Treatment options include prebiotics, probiotics, postbiotics, etc. To accelerate the transition of gut microbiota-based therapies for early prevention of CKD, an extended comprehension of gut microbiota dysbiosis implicated in renal programming is needed, as well as a greater focus on pediatric CKD for further clinical translation.

Low Birthweight as a Risk Factor for Non-communicable Diseases in Adults

According to studies undertaken over the past 40 years, low birthweight (LBW) is not only a significant predictor of perinatal death and morbidity, but also increases the risk of chronic non-communicable diseases (NCDs) in adulthood. The purpose of this paper is to summarize the research on LBW as a risk factor for NCDs in adults. The Barker hypothesis was based on the finding that adults with an LBW or an unhealthy intrauterine environment, as well as a rapid catch-up, die due to NCDs. Over the last few decades, terminology such as thrifty genes, fetal programming, developmental origins of health and disease (DOHaD), and epigenetic factors have been coined. The most common NCDs include cardiovascular disease, diabetes mellitus type 2 (DMT2), hypertension (HT), dyslipidemia, proteinuria, and chronic kidney disease (CKD). Studies in mothers who experienced famine and those that solely reported birth weight as a risk factor for mortality support the concept. Although the etiology of NCD is unknown, Barry Brenner explained the notion of a low glomerular number (nGlom) in LBW children, followed by the progression to hyperfiltration as the physiopathologic etiology of HT and CKD in adults based on Guyton's renal physiology work. Autopsies of several ethnic groups have revealed anatomopathologic evidence in fetuses and adult kidneys. Because of the renal reserve, demonstrating renal function in proportion to renal volume in vivo is more difficult in adults. The greatest impact of these theories can be seen in pediatrics and obstetrics practice.

How good is a living donor? Systematic review and meta-analysis of the effect of donor demographics on post kidney transplant outcomes

Background and Aims

Living donor kidneys are considered the best quality organs. In the attempt to expand the donor pool, the donor’s age, sex and body mass index (BMI) might be considered as potential determinants of the kidney transplant outcomes, and thus guide recipient selection. We aimed to investigate the effects of donor demographics on kidney function, graft and recipient survival, delayed graft function (DGF) and acute rejection (AR).

Methods

Systematic review and meta-analysis. EMBASE, MEDLINE, Web of Science, BIOSIS, CABI, SciELO and Cochrane were searched using algorithms. NHBLI tools were used for risk of bias assessment. Mean difference (MD), standardized mean difference (SMD), and risk ratio (RR) were calculated in Revman 5.4

Results

Altogether, 5129 studies were identified by the search algorithm; 47 studies met the inclusion criteria and were analyzed. No significant difference in recipient 1-year survival was found between recipients of donors aged < 50 vs donors aged > 50 (RR = 0.65 95% CI: 0.1–4.1), and recipients of donors aged < 60 vs donors aged > 60 (RR = 0.81 95% CI: 0.3–2.3). Graft survival was significantly higher in recipients of grafts from donors aged < 60. Risk of AR (RR = 0.62 95% CI: 0.5–0.8) and DGF (RR = 0.28 95% CI: 0.1–0.9) were significantly lower in recipients of grafts from donors aged < 60. One-year serum creatinine was significantly lower in recipients from donors aged < 60 years compared to donors aged > 60 years (MD = 0.3 mg/dl 95% CI: 0.1–0.9), although there was high heterogeneity. Recipients of grafts from male donors had lower 1-year serum creatinine (MD = 0.12 mg/dl 95% CI: 0.2–0.1) and higher eGFR compared to recipients of female donors (p < 0.00001). Donor obesity increased the incidence of delayed graft function but not acute rejection (RR = 0.66 95% CI: 0.32–1.34).

Conclusions

Older donor age was associated with worse post-transplant outcomes and recipients of male donors had better 1-year eGFR. Donor obesity affects the incidence of delayed graft function, but not the incidence of acute rejection in recipients.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01231-7.

Estimating Nephron Number from Biopsies: Impact on Clinical Studies

BACKGROUND

Accumulating evidence supports an association between nephron number and susceptibility to kidney disease. However, it is not yet possible to directly measure nephron number in a clinical setting. Recent clinical studies have used glomerular density from a single biopsy and whole kidney cortical volume from imaging to estimate nephron number and single nephron glomerular filtration rate. However, the accuracy of these estimates from individual subjects is unknown. Furthermore, it is not clear how sample size or biopsy location may influence these estimates. These questions are critical to study design, and to the potential translation of these tools to estimate nephron number in individual subjects.

METHODS

We measured the variability in estimated nephron number derived from needle or virtual biopsies and cortical volume in human kidneys declined for transplantation. We performed multiple needle biopsies in the same kidney, and examined the three-dimensional spatial distribution of nephron density by magnetic resonance imaging. We determined the accuracy of a single-kidney biopsy to predict the mean nephron number estimated from multiple biopsies from the same kidney.

RESULTS

A single needle biopsy had a 15% chance and virtual biopsy had a 60% chance of being within 20% of the whole-kidney nephron number. Single needle biopsies could be used to detect differences in nephron number between large cohorts of several hundred subjects.

CONCLUSIONS

The number of subjects required to accurately detect differences in nephron number between populations can be predicted on the basis of natural intrakidney variability in glomerular density. A single biopsy is insufficient to accurately predict nephron number in individual subjects.

Management of the congenital solitary kidney: consensus recommendations of the Italian Society of Pediatric Nephrology

In recent years, several studies have been published on the prognosis of children with congenital solitary kidney (CSK), with controversial results, and a worldwide consensus on management and follow-up is lacking. In this consensus statement, the Italian Society of Pediatric Nephrology summarizes the current knowledge on CSK and presents recommendations for its management, including diagnostic approach, nutritional and lifestyle habits, and follow-up. We recommend that any antenatal suspicion/diagnosis of CSK be confirmed by neonatal ultrasound (US), avoiding the routine use of further imaging if no other anomalies of kidney/urinary tract are detected. A CSK without additional abnormalities is expected to undergo compensatory enlargement, which should be assessed by US. We recommend that urinalysis, but not blood tests or genetic analysis, be routinely performed at diagnosis in infants and children showing compensatory enlargement of the CSK. Extrarenal malformations should be searched for, particularly genital tract malformations in females. An excessive protein and salt intake should be avoided, while sport participation should not be restricted. We recommend a lifelong follow-up, which should be tailored on risk stratification, as follows: low risk: CSK with compensatory enlargement, medium risk: CSK without compensatory enlargement and/or additional CAKUT, and high risk: decreased GFR and/or proteinuria, and/or hypertension. We recommend that in children at low-risk periodic US, urinalysis and BP measurement be performed; in those at medium risk, we recommend that serum creatinine also be measured; in high-risk children, the schedule has to be tailored according to kidney function and clinical data.

Dichotomous responses to chronic fetal hypoxia lead to a predetermined aging phenotype

Hypoxia-induced intrauterine growth restriction increases the risk for cardiovascular, renal and other chronic diseases in adults, representing thus a major public health problem. Still, not much is known about the fetal mechanisms that predispose these individuals to disease. Using a previously validated mouse model of fetal hypoxia and bottom-up proteomics we characterize the response of the fetal kidney to chronic hypoxic stress. Fetal kidneys exhibit a dichotomous response to chronic hypoxia, comprising on the one hand cellular adaptations that promote survival (glycolysis, autophagy, and reduced DNA and protein synthesis), but on the other processes that induce a senescence-like phenotype (infiltration of inflammatory cells, DNA damage, and reduced proliferation). Importantly, chronic hypoxia also reduces the expression of the anti-aging proteins klotho and Sirt6, a mechanism that is evolutionary conserved between mice and humans. Taken together, we uncover that predetermined aging during fetal development is a key event in chronic hypoxia, establishing a solid foundation for Barker's hypothesis of fetal programming of adult diseases. This phenotype is associated with a characteristic biomarker profile in tissue and serum samples, exploitable for detecting and targeting accelerated aging in chronic hypoxic human diseases.

Ultrasound-Based Renal Parenchymal Area and Kidney Function Decline in Infants With Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract are the leading cause of chronic kidney disease in children. Noninvasive imaging biomarkers that predict chronic kidney disease progression in early infancy are needed. We performed a pilot study nested in the prospective Chronic Kidney Disease in Children cohort study to determine the association between renal parenchymal area (RPA) on first post-natal renal ultrasound and change in estimated glomerular filtration rate (eGFR) in children with congenital anomalies of the kidney and urinary tract. Among 14 participants, 78.6% were males, the median age at the time of the ultrasound was 3.4 months (interquartile range, 1.3-7.9 mo), and the median total RPA z-score at baseline was -1.01 (interquartile range, -2.39 to 0.52). After a median follow-up period of 7.4 years (interquartile range, 6.8-8.2 y), the eGFR decreased from a median of 49.4 mL/min per 1.73 m² at baseline to 29.4 mL/min per 1.73 m², an annual eGFR percentage decrease of -4.68%. Lower RPA z-scores were correlated weakly with a higher annual decrease in eGFR (Spearman correlation, 0.35; 95% confidence interval, -0.25 to 0.76). This pilot study shows the feasibility of obtaining RPA from a routine ultrasound and suggests that a lower baseline RPA may be associated with a greater decrease in eGFR over time. Further studies with larger patient cohorts are needed to confirm this association.

BET Proteins Regulate Expression of Osr1 in Early Kidney Development

In utero renal development is subject to maternal metabolic and environmental influences affecting long-term renal function and the risk of developing chronic kidney failure and cardiovascular disease. Epigenetic processes have been implicated in the orchestration of renal development and prenatal programming of nephron number. However, the role of many epigenetic modifiers for kidney development is still unclear. Bromodomain and extra-terminal domain (BET) proteins act as histone acetylation reader molecules and promote gene transcription. BET family members Brd2, Brd3 and Brd4 are expressed in the nephrogenic zone during kidney development. Here, the effect of the BET inhibitor JQ1 on renal development is evaluated. Inhibition of BET proteins via JQ1 leads to reduced growth of metanephric kidney cultures, loss of the nephron progenitor cell population, and premature and disturbed nephron differentiation. Gene expression of key nephron progenitor transcription factor Osr1 is downregulated after 24 h BET inhibition, while Lhx1 and Pax8 expression is increased. Mining of BRD4 ChIP-seq and gene expression data identify Osr1 as a key factor regulated by BRD4-controlled gene activation. Inhibition of BRD4 by BET inhibitor JQ1 leads to downregulation of Osr1, thereby causing a disturbance in the balance of nephron progenitor cell self-renewal and premature differentiation of the nephron, which ultimately leads to kidney hypoplasia and disturbed nephron development. This raises questions about the potential teratogenic effects of BET inhibitors for embryonic development. In summary, our work highlights the role of BET proteins for prenatal programming of nephrogenesis and identifies Osr1 as a potential target of BET proteins.

Ability of volume measures of hydronephrosis to predict need for surgery and evaluate renal function in children with ureteropelvic junction obstruction

OBJECTIVE

To explore the efficacy of quantitative renal volume measures on magnetic resonance urography images in predicting need for surgery among children with ureteropelvic junction obstruction and their ability to evaluate renal function.

METHODS

A total of 88 cases of hydronephrosis in 50 patients were collected between 1 April 2018 and 31 March 2020, including 30 operated kidney and 58 unoperated kidney cases. Clinical data were collected, and quantitative analysis of magnetic resonance urography was performed. Renal volume, hydronephrosis volume and the volume ratio of hydronephrosis (hydronephrosis volume/renal volume) were measured and calculated. We analyzed the relationships between the above indices in the two groups and compared these with renal function.

RESULTS

Compared with the unoperated kidney group, hydronephrosis volume, renal volume and hydronephrosis volume/renal volume of the operated kidney group increased significantly. Hydronephrosis volume (area under the curve 0.972, 95% confidence interval 0.943-1.000; P < 0.001) and hydronephrosis volume/renal volume (area under the curve 0.968, 95% confidence interval 0.939-0.998; P < 0.001) were superior to ultrasonography and renal function examination in predicting the probability of surgery, and their sensitivity values (hydronephrosis volume/renal volume: 96.67%; hydronephrosis volume: 93.33%) were higher than those of the renal function test (50%). There was a significant difference among different renal function groups in the pairwise comparison of hydronephrosis volume and hydronephrosis volume/renal volume (P < 0.05).

CONCLUSION

Quantitative volume measures of hydronephrosis by magnetic resonance urography had a greater ability to predict need for surgery than ultrasonography and dynamic renal imaging, and it can be used as method by which to evaluate surgery. Hydronephrosis volume and hydronephrosis volume/renal volume have greater predictive ability, and play an important role in the deterioration of renal function.

Risk Due to ABO Incompatibility and Donor-Recipient Weight Mismatch in Living Donor Kidney Transplantation: A National Cohort Study

The effect of donor-recipient weight mismatch is not well established in ABO-incompatible living donor kidney transplantation (LDKT). A total of 2584 LDKT patients in the Korean Organ Transplantation Registry were classified into four groups according to the presence or absence of ABO incompatibility and donor-recipient weight mismatch (donor-to-recipient weight ratio (DRWR) < 0.8). In a multivariable Cox analysis, the combination of ABO incompatibility and DRWR incompatibility (n = 124) was an independent risk factor for graft survival (HR = 2.73, 95% CI = 1.11-6.70) and patient survival (HR = 3.55, 95% CI = 1.39-9.04), whereas neither factor alone was a significant risk factor for either outcome. The combination of ABO incompatibility and DRWR incompatibility was not an independent risk factor for biopsy-proven graft rejection (HR = 1.27, 95% CI = 0.88-1.82); however, it was an independent risk factor for pneumonia (HR = 2.94, 95% CI = 1.64-5.57). The mortality rate due to infection was higher among patients with both ABO incompatibility and DRWR incompatibility than among patients with neither factor or with either factor alone. The combination of ABO incompatibility and DRWR incompatibility was an independent risk factor for graft and patient survival after LDKT, whereas neither factor alone significantly affected graft or patient survival. Thus, donor-recipient weight matching should be cautiously considered in LDKT with ABO incompatibility.

Birth Weight Is Associated With Kidney Size in Middle-Aged Women

Introduction

Low birth weight (LBW) is associated with increased risk of kidney disease due to lower nephron endowment leading to hyperfiltration and subsequent nephron loss. Kidney size is commonly used as a proxy for nephron number. We compared kidney volume measured by magnetic resonance imaging (MRI) with measured glomerular filtration rate (mGFR) in adults with either normal birth weight (NBW) or low birth weight (LBW).

Methods

Healthy individuals aged 42 to 52 years with LBW (1100−2300 g) and NBW (3500 −4000 g) were invited to participate. The GFR was measured using plasma clearance of iohexol. Kidney volume was measured on magnetic resonance images using axial T2 images and coronal T1 images with fat saturation without contrast enhancement; calculations were performed according to the ellipsoid formula π/6 × length × width × depth.

Results

We included 102 individuals (54 LBW and 48 NBW). Total kidney volume was 302 ± 51 ml for female NBW vs 258 ± 48 ml for female LBW individuals (P = 0.002). For male individuals, total kidney volume was 347 ± 51 ml vs. 340 ± 65 ml (P = 0.7). The mGFR was significantly associated with kidney volume, with r = 0.52 (P < 0.001) for women and r = 0.39 (P = 0.007) for men. A mediation analysis showed that the association between birth weight and mGFR (significant in total sample and women) was mediated by kidney volume.

Conclusion

Healthy female individuals born with LBW have smaller kidneys than healthy females born with NBW. The previously shown associations between LBW and lower mGFR in adult women might be explained by smaller kidney volume.

Adverse Impact of Environmental Chemicals on Developmental Origins of Kidney Disease and Hypertension

Chronic kidney disease (CKD) and hypertension are becoming a global health challenge, despite developments in pharmacotherapy. Both diseases can begin in early life by so-called "developmental origins of health and disease" (DOHaD). Environmental chemical exposure during pregnancy can affect kidney development, resulting in renal programming. Here, we focus on environmental chemicals that pregnant mothers are likely to be exposed, including dioxins, bisphenol A (BPA), phthalates, per- and polyfluoroalkyl substances (PFAS), polycyclic aromatic hydrocarbons (PAH), heavy metals, and air pollution. We summarize current human evidence and animal models that supports the link between prenatal exposure to environmental chemicals and developmental origins of kidney disease and hypertension, with an emphasis on common mechanisms. These include oxidative stress, renin-angiotensin system, reduced nephron numbers, and aryl hydrocarbon receptor signaling pathway. Urgent action is required to identify toxic chemicals in the environment, avoid harmful chemicals exposure during pregnancy and lactation, and continue to discover other potentially harmful chemicals. Innovation is also needed to identify kidney disease and hypertension in the earliest stage, as well as translating effective reprogramming interventions from animal studies into clinical practice. Toward DOHaD approach, prohibiting toxic chemical exposure and better understanding of underlying mechanisms, we have the potential to reduce global burden of kidney disease and hypertension.

The First Thousand Days: Kidney Health and Beyond

The global burden of chronic kidney disease (CKD) is rising. A superior strategy to advance global kidney health is required to prevent and treat CKD early. Kidney development can be impacted during the first 1000 days of life by numerous factors, including malnutrition, maternal illness, exposure to chemicals, substance abuse, medication use, infection, and exogenous stress. In the current review, we summarize environmental risk factors reported thus far in clinical and experimental studies relating to the programming of kidney disease, and systematize the knowledge on common mechanisms underlying renal programming. The aim of this review is to discuss the primary and secondary prevention actions for enhancing kidney health from pregnancy to age 2. The final task is to address the potential interventions to target renal programming through updating animal studies. Together, we can enhance the future of global kidney health in the first 1000 days of life.

Obesity and metabolic syndrome induce hyperfiltration, glomerulomegaly, and albuminuria in obese ovariectomized female mice and obese male mice

OBJECTIVE

Obese patients with metabolic syndrome have a high risk of chronic kidney disease. The prevalence of obesity, metabolic syndrome, and insulin resistance increase in women after menopause, as does the risk of chronic kidney disease. This may indicate an interaction between obesity, metabolic syndrome, and menopause in the induction of renal damage. However, the pathogenesis of kidney disease in postmenopausal obese women is poorly understood.

METHODS

We investigated the interaction of an obesogenic diet and menopause on renal dysfunction in ovariectomized and non-ovariectomized lean (n = 8 and 17) and obese (n = 12 and 20) female mice. Obese (n = 12) and lean (n = 10) male mice were also studied. Glucose metabolism, insulin resistance, and kidney function were evaluated with gold standards procedures. Changes in kidney histology and lipid deposition were analyzed. Females had a lower number of glomeruli than males at baseline.

RESULTS

Only female ovariectomized obese animals developed insulin resistance, hyperglycemia, and kidney damage, evidenced as glomerulomegaly, glomerular hyperfiltration, and increased urinary albumin excretion, despite a similar increase in weight than obese non-ovariectomized female mice. Male obese mice developed hyperglycemia, insulin resistance, and hyperfiltration without major renal histological changes. Males on high fat diet showed higher renal lipid content and females on high fat diet (ovariectomized or non-ovariectomized) showed higher total cholesterol content than males.

CONCLUSIONS

In mice, there is a clear interplay between obesity, metabolic syndrome, and menopause in the induction of kidney damage.

Image analysis techniques to map pyramids, pyramid structure, glomerular distribution, and pathology in the intact human kidney from 3-D MRI

Kidney pathologies are often highly heterogeneous. To comprehensively understand kidney structure and pathology, it is critical to develop tools to map tissue microstructure in the context of the whole, intact organ. Magnetic resonance imaging (MRI) can provide a unique, three-dimensional view of the kidney and allows for measurements of multiple pathological features. Here, we developed a platform to systematically render and map gross and microstructural features of the human kidney based on three-dimensional MRI. These features include pyramid number and morphology as well as the associated medulla and cortex. In a subset of these kidneys, we also mapped individual glomeruli and glomerular volumes using cationic ferritin-enhanced MRI to report intrarenal heterogeneity in glomerular density and size. Finally, we rendered and measured regions of nephron loss due to pathology and individual glomerular volumes in each pyramidal unit. This work provides new tools to comprehensively evaluate the kidney across scales, with potential applications in anatomic and physiological research, transplant allograft evaluation, biomarker development, biopsy guidance, and therapeutic monitoring. These image rendering and analysis tools could eventually impact the field of transplantation medicine to improve longevity matching of donor allografts and recipients and reduce discard rates through the direct assessment of donor kidneys.NEW & NOTEWORTHY We report the application of cutting-edge image analysis approaches to characterize the pyramidal geometry, glomerular microstructure, and heterogeneity of the whole human kidney imaged using MRI. This work establishes a framework to improve the detection of microstructural pathology to potentially facilitate disease monitoring or transplant evaluation in the individual kidney.

The Effect of Gender-Affirming Hormone Therapy on Serum Creatinine in Transgender Individuals

OBJECTIVE

To describe the changes in serum creatinine (Cr) levels after the initiation of gender-affirming hormone therapy (GAHT) in transgender individuals to better understand the expected changes and interpretation of laboratory values in this population.

METHODS

A retrospective chart review of all adult transgender patients initiated on GAHT at Mayo Clinic from January 2011 to October 2019 was completed. Laboratory values were obtained prior to initiating GAHT and at 3, 6, and 12 months after initiating GAHT. Baseline Cr values were compared with Cr values at 3, 6, and 12 months after initiating GAHT in transgender men (TM) on testosterone and transgender women (TW) on estradiol and antiandrogens.

RESULTS

A total of 84 TW (median age of 30 years) and 24 TM (median age of 23 years) were included for analysis. Following a matched pair analysis of TW, Cr values were found to be significantly decreased by -0.03 at 3 months (P = .04), -0.10 at 6 months (P < .01), and -0.07 at 12 months (P < .01) compared with baseline values. Following a matched pair analysis of TM, Cr values were found to be significantly increased, on average, by 0.14 at 3 months (P = .04), 0.21 at 6 months (P = .016), and 0.15 at 12 months (P = .003) compared with baseline values.

CONCLUSION

In TW and TM, a change in Cr level was seen as early as 3 months toward their affirmed gender after initiating GAHT. Clinicians can use Cr levels established at 6 months as new baseline values, as these changes continue to persist up to 12 months.

Do children with solitary or hypofunctioning kidney have the same prevalence for masked hypertension?

BACKGROUND

Having a low nephron number is a well-known risk factor for hypertension. There is an inverse relationship between the filtration surface area and systemic hypertension. A significant percentage of masked hypertension can be detected in children with nephron loss by ambulatory blood pressure monitoring (ABPM).

METHODS

We prospectively investigated ABPM results of children having reduced kidney mass with normal office blood pressures (BPs) and kidney function. Forty-three children with congenital solitary kidney (group 1), 11 children with acquired solitary kidney (group 2), and 76 children with hypofunctioning kidney (group 3) were compared with age, gender, and BMI-matched healthy control group (group 4). The dietary salt intake of 76 patients was evaluated as salt equivalent (g/day). The primary endpoint was change from baseline in mean 24-h ABPM variables and the proportion of patients with masked hypertension when assessed by ABPM.

RESULTS

The masked hypertension ratio of all patients was 12.3% when assessed with ABPM. Night hypertension was significantly higher in all patient groups than in the control group (p = 0.01). Diastolic BP loads of groups 1 and 3 were higher than in controls (p = 0.024). Systolic BP loads were higher only in group 1 than in the control group (p = 0.003). The dietary salt equivalent of patients in group 1 correlated positively with 24-h SBP and mean arterial pressure (MAP) values. Patients with excessive dietary salt intake in group 1 had a significantly higher diastolic BP load than those without excessive salt intake in group 1 (p = 0.002).

CONCLUSIONS

Masked hypertension can be seen in children with a solitary kidney or when one of the kidneys is hypofunctioning. Systolic BP loads are higher in children with congenital solitary kidney, and salt intake correlates with systolic BP profiles especially in those. Our results suggest that being born with a congenital solitary kidney increases predisposition to hypertension and salt sensitivity.