Nondiabetic consequences of obesity on kidney

Abatacept Decreases Renal T-cell Infiltration and Renal Inflammation and Ameliorates Progressive Renal Injury in Obese Dahl Salt-sensitive Rats Before Puberty

ABSTRACT

Prepubertal obesity is growing at an alarming rate and is now considered a risk factor for renal injury. Recently, we reported that the early development of renal injury in obese Dahl salt-sensitive (SS) leptin receptor mutant (SS LepR mutant) rats was associated with increased T-cell infiltration and activation before puberty. Therefore, the current study investigated the effect of inhibiting T-cell activation with abatacept on the progression of renal injury in young obese SS LepR mutant rats before puberty. Four-week-old SS and SS LepR mutant rats were treated with IgG or abatacept (1 mg/kg; ip, every other day) for 4 weeks. Abatacept reduced the renal infiltration of T cells by almost 50% in SS LepR mutant rats. Treatment with abatacept decreased the renal expression of macrophage inflammatory protein-3 alpha while increasing IL-4 in SS LepR mutant rats without affecting SS rats. While not having an impact on blood glucose levels, abatacept reduced hyperinsulinemia and plasma triglycerides in SS LepR mutant rats without affecting SS rats. We did not observe any differences in the mean arterial pressure among the groups. Proteinuria was markedly higher in SS LepR mutant rats than in SS rats throughout the study, and treatment with abatacept decreased proteinuria by about 40% in SS LepR mutant rats without affecting SS rats. We observed significant increases in glomerular and tubular injury and renal fibrosis in SS LepR mutant rats versus SS rats, and chronic treatment with abatacept significantly reduced these renal abnormalities in SS LepR mutant rats. These data suggest that renal T-cell activation contributes to the early progression of renal injury associated with prepubertal obesity.

Metformin reduces insulin resistance and attenuates progressive renal injury in prepubertal obese Dahl salt-sensitive rats

Prepubertal obesity is currently an epidemic and is considered as a major risk factor for renal injury. Previous studies have demonstrated that insulin resistance contributes to renal injury in obesity, independent of diabetes. However, studies examining the relationship between insulin resistance and renal injury in obese children are lacking. Recently, we reported that progressive renal injury in Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) rats was associated with insulin resistance before puberty. Therefore, the aim of the present study was to examine whether decreasing insulin resistance with metformin will reduce renal injury in SSLepRmutant rats. Four-wk-old SS and SSLepRmutant rats were separated into the following two groups: 1) vehicle and 2) metformin (300 mg/kg/day) via chow diet for 4 wk. Chronic administration of metformin markedly reduced insulin resistance and dyslipidemia in SSLepRmutant rats. We did not detect any differences in mean arterial pressure between vehicle and metformin-treated SS and SSLepRmutant rats. Proteinuria was significantly greater in SSLepRmutant rats versus SS rats throughout the study, and metformin administration significantly reduced proteinuria in SSLepRmutant rats. At the end of the protocol, metformin prevented the renal hyperfiltration observed in SSLepRmutant rats versus SS rats. Glomerular and tubular injury and renal inflammation and fibrosis were significantly higher in vehicle-treated SSLepRmutant rats versus SS rats, and metformin reduced these parameters in SSLepRmutant rats. These data suggest that reducing insulin resistance with metformin prevents renal hyperfiltration and progressive renal injury in SSLepRmutant rats before puberty and may be therapeutically useful in managing renal injury during prepubertal obesity.NEW & NOTEWORTHY Childhood/prepubertal obesity is a public health concern that is associated with early signs of proteinuria. Insulin resistance has been described in obese children. However, studies investigating the role of insulin resistance during childhood obesity-associated renal injury are limited. This study provides evidence of an early relationship between insulin resistance and renal injury in a rat model of prepubertal obesity. These data also suggest that reducing insulin resistance with metformin may be renoprotective in obese children.

Bariatric Surgery in Severely Obese Kidney Donors Before Kidney Transplantation: A Retrospective Study

BACKGROUND

Bariatric surgery (BS) is the optimal approach for sustained weight loss and may alter donation candidacy in potential donors with obesity. We evaluated the long-term effects of nephrectomy after BS on metabolic profile, including body mass index, serum lipids and diabetes, and kidney function of donors.

METHODS

This was a single-center retrospective study. Live kidney donors who underwent BS before nephrectomy were matched for age, gender, and body mass index with patients who underwent BS alone and with donors who underwent nephrectomy alone. Estimated glomerular filtration rate (eGFR) was calculated according to Chronic Kidney Disease Epidemiology Collaboration and adjusted to individual body surface area to create absolute eGFR.

RESULTS

Twenty-three patients who underwent BS before kidney donation were matched to 46 controls who underwent BS alone. At the last follow-up, the study group showed significantly worse lipid profile with low-density lipoprotein of 115 ± 25 mg/dL versus the control group with low-density lipoprotein of 99 ± 29 mg/dL ( P  = 0.036) and mean total cholesterol of 191 ± 32 versus 174 ± 33 mg/dL ( P  = 0.046). The second control group of matched nonobese kidney donors (n = 72) had similar serum creatinine, eGFR, and absolute eGFR as the study group before nephrectomy and 1 y after the procedure. At the end of follow-up, the study group had significantly higher absolute eGFR compared with the control group (86 ± 21 versus 76 ± 18 mL/min; P  = 0.02) and similar serum creatinine and eGFR.

CONCLUSIONS

BS before live kidney donation is a safe procedure that could increase the donor pool and improve their health in the long run. Donors should be encouraged to maintain their weight and avoid adverse lipid profile and hyperfiltration.

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.

Chronic treatment with IL-25 increases renal M2 macrophages and reduces renal injury in obese Dahl salt-sensitive rats during the prepubescent stage

Recently, we have reported that the early progression of proteinuria in the obese Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) strain was associated with increased renal macrophage infiltration before puberty. Macrophages can be divided into two distinct phenotypes: M1 (proinflammatory) and M2 (anti-inflammatory). Moreover, previous studies have demonstrated that interleukin (IL)-25 converts resting macrophages and M1 into M2. Therefore, the present study examined whether treatment with IL-25 would reduce the early progression of renal injury in SSLepRmutant rats by increasing renal M2. We also investigated the impact of IL-25 on M2 subtypes: M2a (wound healing/anti-inflammatory), M2b (immune mediated/proinflammatory), M2c (regulatory/anti-inflammatory), and M2d (tumor associated/proangiogenic). Four-wk-old SS and SSLepRmutant rats were treated with either control (IgG) or IL-25 (1 µg/day ip every other day) for 4 wk. The kidneys from SSLepRmutant rats displayed progressive proteinuria and renal histopathology versus SS rats. IL-25 treatment had no effect on these parameters in SS rats. However, in the SSLepRmutant strain, proteinuria was markedly reduced after IL-25 treatment. Chronic treatment with IL-25 significantly decreased glomerular and tubular injury and renal fibrosis in the SSLepRmutant strain. Although the administration of IL-25 did not change total renal macrophage infiltration in both SS and SSLepRmutant rats, IL-25 increased M2a by >50% and reduced M1 by 60% in the kidneys of SSLepRmutant rats. Overall, these data indicate that IL-25 reduces the early progression of renal injury in SSLepRmutant rats by inducing M2a and suppressing M1 and suggest that IL-25 may be a therapeutic target for renal disease associated with obesity. NEW & NOTEWORTHY For the past few decades, immune cells and inflammatory cytokines have been demonstrated to play an important role in the development of renal disease. The present study provides strong evidence that interleukin-25 slows the early progression of renal injury in obese Dahl salt-sensitive rats before puberty by increasing systemic anti-inflammatory cytokines and renal M2a macrophages.

Neutralizing MIP3α Reduces Renal Immune Cell Infiltration and Progressive Renal Injury in Young Obese Dahl Salt-Sensitive Rats

Recently, we reported that the early progression of renal injury in obese Dahl salt-sensitive leptin receptor mutant (SSLepRmutant) rats was associated with increased macrophage inflammatory protein 3-α (MIP3α) expression prior to puberty. Therefore, this study tested the hypothesis that MIP3α plays a role in recruiting immune cells, thereby triggering renal inflammation and early progressive renal injury in SSLepRmutant rats prior to puberty. Four-week-old Dahl salt-sensitive (SS) and SSLepRmutant rats either served as control (IgG; intraperitoneal, every other day) or received MIP3α-neutralizing antibody (MNA; 100 µg/kg) for 4 weeks. MNA reduced circulating and renal MIP3α levels and proinflammatory immune cells by 50%. Although MNA treatment did not affect blood glucose and plasma cholesterol levels, MNA markedly decreased insulin resistance and triglyceride levels in SSLepRmutant rats. We observed no differences in mean arterial pressure (MAP) between SS and SSLepRmutant rats, and MNA had no effect on MAP in either strain. Proteinuria was significantly increased in SSLepRmutant rats versus SS rats over the course of the study. Treatment with MNA markedly decreased proteinuria in SSLepRmutant rats while not affecting SS rats. Also, MNA decreased glomerular and tubular injury and renal fibrosis in SSLepRmutant rats while not affecting SS rats. Overall, these data indicate that MIP3α plays an important role in renal inflammation during the early progression of renal injury in obese SSLepRmutant rats prior to puberty. These data also suggest that MIP3α may be a novel therapeutic target to inhibit insulin resistance and prevent progressive proteinuria in obese children. SIGNIFICANCE STATEMENT: Childhood obesity is increasing at an alarming rate and is now being associated with renal disease. Although most studies have focused on the mechanisms of renal injury associated with adult obesity, few studies have examined the mechanisms of renal injury involved during childhood obesity. In the current study, we observed that the progression of renal injury in obese Dahl salt-sensitive leptin receptor mutant rats was associated with an increase in MIP3α, a chemokine, before puberty, and inhibition of MIP3α markedly reduced renal injury.

Body Composition and Cardiovascular Risk Factors in a Paediatric Population

The aim of our study was to evaluate associations between body composition parameters and several clinical parameters. A total of 206 children and adolescents (120 male, 86 female) were prospectively included. Body impedance measurement was performed in all participants. During the hospital work-up, several clinical parameters such as anthropometric measurements and laboratory and ultrasound findings were obtained and correlated to body composition parameters. There was a significant association between body composition parameters and anthropometric measurements, systolic blood pressure, insulin levels, serum creatinine, urate, liver function tests, triglycerides, cholesterols and apolipoproteins, homocysteine, vitamin D and proteins in 24-h urine. Body composition differed by gender, between participants with and without hepatic steatosis and between patients with and without left ventricular hypertrophy. Interestingly, body composition did not correlate with diastolic blood pressure, pulse wave velocity and intima media thickness. This study showed that several clinical parameters are associated with body composition in children. Obesity and body composition play an important role in the development of other cardiovascular risk factors and are not dependent on fat mass alone, and the latter might be used for cardiovascular risk determination.

Obesity Related Glomerulopathy in Adolescent Women: The Effect of Body Surface Area

Background

Adolescent obesity, a risk factor for cardiorenal morbidity in adulthood, has reached epidemic proportions. Obesity-related glomerulopathy (ORG) has an early reversible stage of hyperfiltration. Age-appropriate formulae for eGFR, which are standardized to ideal body surface area (BSA) and provide assessment of kidney function in ml/min/1.73 m², may underestimate prevalence of early ORG. We investigated whether adjusting eGFR to actual BSA more readily identifies early ORG.

Methods

We studied a cohort of 22,417 young individuals, aged 12-21 years, from a New York metropolitan multi-institutional electronic health records clinical database. eGFR was calculated in two ways: BSA-standardized eGFR, and absolute eGFR. Hyperfiltration was defined above a threshold of 135 ml/min per 1.73 m² or 135 ml/min, respectively. The prevalence of hyperfiltration according to each formula was assessed in parallel to creatinine clearance.

Results

Serum creatinine values and hyperfiltration prevalence according to BSA-standardized eGFR were similar, 13%-15%, across body mass index (BMI) groups. The prevalence of hyperfiltration determined by absolute eGFR differed across BMI groups: underweight, 2%; normal weight, 6%; overweight, 17%; and obese, 31%. This trend paralleled the rise in creatinine clearance across BMI groups.

Conclusions

Absolute eGFR more readily identifies early ORG than the currently used formulae, which are adjusted to a standardized BSA and are not representative of current population BMI measures. Using absolute eGFR in clinical practice and research may improve the ability to identify, intervene, and reverse early ORG, which has great importance with increasing obesity rates.

Prenatal blood lead levels and reduced preadolescent glomerular filtration rate: Modification by body mass index

BACKGROUND

For the developing kidney, the prenatal period may represent a critical window of vulnerability to environmental insults resulting in permanent nephron loss. Given that the majority of nephron formation is complete in the 3rd trimester, we set out to test whether 1) prenatal lead exposure is associated with decreased preadolescent kidney function and 2) whether preadolescent obesity acts synergistically with early life lead exposure to reduce kidney function.

METHODS

Our study included 453 mother-child pairs participating in the PROGRESS birth cohort. We assessed prenatal blood lead levels (BLLs) in samples collected in the 2nd and 3rd trimesters and at delivery, as well as tibial and patellar bone lead measures assessed one-month postpartum. Preadolescent estimated glomerular filtration rate (eGFR) was derived from serum levels of creatinine and/or cystatin C measured at age 8-12 years. We applied linear regression to assess the relationship between prenatal bone and BLL with preadolescent eGFR, and adjusted for covariates including age, sex, BMI z-score, indoor tobacco smoke exposure, and socioeconomic status. We also examined sex-specific associations and tested for effect modification by BMI status.

RESULTS

We observed null associations between prenatal lead exposure and eGFR. However, in interaction analyses we found that among overweight children, there was an inverse association between BLL (assessed at 2nd and 3rd trimester and at delivery) and preadolescent eGFR. For example, among overweight participants, a one ln-unit increase in 2nd trimester BLL was associated with a 10.5 unit decrease in cystatin C-based eGFR (95% CI: -18.1, -2.8; p = 0.008). Regardless of lead exposure, we also observed null relationships between BMI z-score and eGFR overall, as well as among overweight participants. However, among participants with preadolescent obesity, we observed a significant 5.9-unit decrease in eGFR. We observed no evidence of sex-specific effects.

CONCLUSIONS

Our findings, if confirmed in other studies, suggest a complex interplay between the combined adverse effects of adiposity and perinatal lead exposure as they relate to adolescent kidney function. Future studies will assess kidney function and adiposity trajectories through adolescence to better understand environmental risk factors for kidney function decline.

Assessment of urinary podocalyxin as a marker of glomerular injury in obesity-related kidney disease in children and adolescents with obesity compared to urinary albumin creatinine ratio

Obesity increases the risk of chronic kidney disease in children. Our aim was to assess urinary podocalyxin (PCX) in children and adolescents with obesity as a potential marker of obesity-related kidney disease (ORKD). The current case-control study included 128 children with obesity compared to 60 non-obese age and sex matched controls. Study population were subjected to full history taking as well as thorough physical examination. Urine samples for albumin creatinine ratio (uACR) and PCX were collected from the study population as well as blood samples for assessment of serum creatinine and fasting lipid profile. A statistically significant difference was found between cases and controls regarding urinary PCX (P < .001) and uACR (P = .021). A statistically significant positive correlation was found between uACR and weight SD score (SDS), body mass index SDS, waist circumference, estimated glomerular filtration rate, triglycerides (TG) as well as urinary PCX, whilst urinary PCX correlated significantly with obesity duration and uACR. Cases with microalbuminuria had a statistically significant higher waist circumference, waist-hip ratio, fat percentage, TG and urinary PCX compared to those with normal uACR (P = .042, .034, .05, .018 and .036 respectively). Urinary PCX showed 83.3% sensitivity and 74% specificity in detection of albuminuria. Urinary PCX was increased significantly in children with obesity making it a potential sensitive marker of ORKD in children.

Role of glomerular filtration rate-modifying drugs in the development of anticoagulant-related nephropathy

Introduction

Anticoagulant‐related nephropathy (ARN), that was described in humans first as warfarin‐related nephropathy, is characterized by acute kidney injury and red blood cell (RBC) tubular casts in the kidney. 5/6 nephrectomy (5/7NE) rats treated with warfarin or dabigatran show changes in kidney function and morphology that are similar to human disease. The role of glomerular filtration rate (GFR) in the pathogenesis of ARN is not clear. The aim of these studies was to elucidate the role of GFR in the pathogenesis of dabigatran‐induced ARN in 5/6NE rats.

Methods

5/6NE rats were treated per os with 150 mg/kg/day dabigatran alone or with drugs that lower (enalapril, 1.5 mg/kg/day) or increase (albuterol, 4.0 mg/kg/day) GFR for 7 days. Changes in coagulation and kidney function were recorded daily. Kidney morphology was evaluated on day 7 after the treatment.

Results

Dabigatran resulted in activated partial thromboplastin time increase that was not affected by GFR‐modifying drugs. Blood pressure was significantly lower in 5/6NE rats treated with enalapril and dabigatran as compared to dabigatran alone. The GFR was decreased by 35% in enalapril/dabigatran‐ and increased by 26% in albuterol/dabigatran‐treated animals. There were no changes in serum creatinine, hematuria or urinary kidney injury molecule (KIM‐1) levels when GFR‐modifying drugs were added to dabigatran. All dabigatran‐treated animals had RBC casts in the kidney regardless of the GFR modification.

Conclusions

GFR does not play a significant role in the dabigatran‐induced acute kidney injury in 5/6 nephrectomy model in rats. Based in these data, modification of GFR in patients with ARN is not warranted.

Altered renal hemodynamics is associated with glomerular lipid accumulation in obese Dahl salt-sensitive leptin receptor mutant rats

The present study examined whether development of renal injury in the nondiabetic obese Dahl salt-sensitive leptin receptor mutant (SS^LepRmutant) strain is associated with elevations in glomerular filtration rate and renal lipid accumulation. Baseline mean arterial pressure at 6 wk of age was similar between Dahl salt-sensitive wild-type (SS_WT) and SS^LepRmutant rats. However, by 18 wk of age, the SS^LepRmutant strain developed hypertension, while the elevation in mean arterial pressure was not as severe in SS_WT rats (192 ± 4 and 149 ± 6 mmHg, respectively). At baseline, proteinuria was fourfold higher in SS^LepRmutant than SS_WT rats and remained elevated throughout the study. The early development of progressive proteinuria was associated with renal hyperfiltration followed by a decline in renal function over the course of study in the SS^LepRmutant compared with SS_WT rats. Kidneys from the SS^LepRmutant strain displayed more glomerulosclerosis and glomerular lipid accumulation than SS_WT rats. Glomeruli were isolated from the renal cortex of both strains at 6 and 18 wk of age, and RNA sequencing was performed to identify genes and pathways driving glomerular injury. We observed significant increases in expression of the influx lipid transporters, chemokine (C-X-C motif) ligand 16 (Cxcl16) and scavenger receptor and fatty acid translocase (Cd36), respectively, and a significant decrease in expression of the efflux lipid transporter, ATP-binding cassette subfamily A member 2 (Abca2; cholesterol efflux regulatory protein 2), in SS^LepRmutant compared with SS_WT rats at 6 and 18 wk of age, which were validated by RT-PCR analysis. These data suggest an association between glomerular hyperfiltration and glomerular lipid accumulation during the early development of proteinuria associated with obesity.

Urinary prostaglandin E2 is a biomarker of early adaptive hyperfiltration in solitary functioning kidney

INTRODUCTION

Hyperfiltration is a major contributor to progression of chronic kidney disease (CKD) in diabetes, obesity and in individuals with solitary functioning kidney (SFK). We have proposed hyperfiltration-induced injury as a continuum of overlapping glomerular changes caused by increased biomechanical forces namely, fluid flow shear stress (FFSS) and tensile stress. We have shown that FFSS is elevated in animals with SFK and, it upregulates prostaglandin E₂ (PGE₂), cyclooxygenase-2 and PGE₂ receptor EP2 in cultured podocytes and in uninephrectomized mice. We conceptualized urinary PGE₂ as a biomarker of early effects of hyperfiltration-induced injury preceding microalbuminuria in individuals with SFK. We studied children with SFK to validate our hypothesis.

METHODS

Urine samples from children with SFK and controls were analyzed for PGE₂, albumin (glomerular injury biomarker) and epidermal growth factor (EGF, tubular injury biomarker). Age, gender, and Z-scores for height, weight, BMI, and blood pressure were obtained.

RESULTS

Children with SFK were comparable to controls except for lower BMI Z-scores. The median values were elevated in SFK compared to control for urine PGE₂ [9.1 (n = 57) vs. 5.7 (n = 72), p = 0.009] ng/mgCr and albumin [7.6 (n = 40) vs. 7.0 (n = 41), p = 0.085] μg/mgCr, but not for EGF [20098 (n = 44) vs. 18637 (n = 44), p = 0.746] pg/mgCr. Significant increase in urinary PGE₂ (p = 0.024) and albumin (p = 0.019) but not EGF (p = 0.412) was observed using additional regression modeling. These three urinary analytes were independent of each other.

CONCLUSION

Increased urinary PGE₂ from elevated SNGFR and consequently increased FFSS during early stage of CKD precedes overt microalbuminuria and is a biomarker for early hyperfiltration-induced injury in individuals with SFK.

Childhood obesity: Aetiology, comorbidities, and treatment

Obesity is currently considered a global epidemic, and its implications in mortality and morbidity in a paediatric patient and in adulthood are increasingly important. The objective of this article is to review in detail the definition of obesity according to age group, and, in turn, the epidemiology of this entity worldwide and in South America. Available evidence about pathophysiology and, additionally, associated comorbidities are reported in some of the most important and clinically relevant body systems. The recommendations on pharmacological and nonpharmacological management through changes in lifestyle and relevant aspects of bariatric surgery in the paediatric population are also described.

Impact of obesity as an independent risk factor for the development of renal injury: implications from rat models of obesity

Diabetes and hypertension are the major causes of chronic kidney disease (CKD). Epidemiological studies within the last few decades have revealed that obesity-associated renal disease is an emerging epidemic and that the increasing prevalence of obesity parallels the increased rate of CKD. This has led to the inclusion of obesity as an independent risk factor for CKD. A major complication when studying the relationship between obesity and renal injury is that cardiovascular and metabolic disorders that may result from obesity including hyperglycemia, hypertension, and dyslipidemia, or the cluster of these disorders [defined as the metabolic syndrome, (MetS)] also contribute to the development and progression of renal disease. The associations between hyperglycemia and hypertension with renal disease have been reported extensively in patients suffering from obesity. Currently, there are several obese rodent models (high-fat diet-induced obesity and leptin signaling dysfunction) that exhibit characteristics of MetS. However, the available obese rodent models currently have not been used to investigate the impact of obesity alone on the development of renal injury before hypertension and/or hyperglycemia. Therefore, the aim of this review is to describe the incidence and severity of renal disease in these rodent models of obesity and determine which models are suitable to study the independent effects obesity on the development and progression of renal disease.

Restricted nutrition-induced low birth weight, low number of nephrons and glomerular mesangium injury in Japanese quail

Insufficient nutrition during the perinatal period causes structural alterations in humans and experimental animals, leading to increased vulnerability to diseases in later life. Japanese quail, Coturnix japonica, in which partial (8-10%) egg white was withdrawn (EwW) from eggs before incubation had lower birth weights than controls (CTs). EwW birds also had reduced hatching rates, smaller glomeruli and lower embryo weight. In EwW embryos, the surface condensate area containing mesenchymal cells was larger, suggesting that delayed but active nephrogenesis takes place. In mature EwW quail, the number of glomeruli in the cortical region (mm2) was significantly lower (CT 34.7±1.4, EwW 21.0±1.2); capillary loops showed focal ballooning, and mesangial areas were distinctly expanded. Immunoreactive cell junction proteins, N-cadherin and podocin, and slit diaphragms were clearly seen. With aging, the mesangial area and glomerular size continued to increase and were significantly larger in EwW quail, suggesting compensatory hypertrophy. Furthermore, apoptosis measured by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling analysis was higher in EwWs than in CTs on embryonic day 15 and postnatal day 4 (D4). Similarly, plasma glucocorticoid (corticosterone) was higher (P<0.01) on D4 in EwW quail. These results suggest that although nephrogenic activity is high in low-nutrition quail during the perinatal period, delayed development and increased apoptosis may result in a lower number of mature nephrons. Damaged or incompletely mature mesangium may trigger glomerular injury, leading in later life to nephrosclerosis. The present study shows that birds serve as a model for 'fetal programming,' which appears to have evolved phylogenetically early.

Configuring a Better Estimation of Kidney Size in Obese Children and Adolescents

Background

Obesity ignites numerous health and psychosocial problems and is associated with various comorbidities. Body mass index (BMI) is also independently associated with improved risk for numerous kidney disorders. As renal length is considered a vital parameter in the clinical assessment of renal patients, normal renal length has to be defined in accordance to BMI.

Objectives

The aim of this study was to define normal kidney length in obese children, comparing ultrasound measurements of the kidney length in obese and non-obese children and adolescents, in order to reduce unnecessary evaluations for nephromegaly.

Patients and Methods

Fifty obese children and adolescents and 50 non-obese children and adolescents, aged 1-19 years, were selected from patients of pediatric clinics in two hospitals (Rasoul-e-Akram and Shahid Fahmideh) in Tehran between June 2010 and 2012. After the nephrologist’s and endocrinologist’s approval, the largest longitudinal renal dimension was measured in deep inspiration position by abdomino-pelvic ultrasonography in both groups.

Results

It was revealed that both kidneys in obese group were significantly larger than in control group (P = 0.044 and 0.040, respectively). Obesity status, height and age were proven to be significant and independent predictors of length of both kidneys. In both groups length of left kidney was significantly larger than that of right kidney (P < 0.001).

Conclusions

A specific standard cut-point limit or norm gram has to be formulated for obese children and adolescents in order to facilitate the diagnosis of kidney diseases, including organomegaly, in these patients.

Zinc delays the progression of obesity-related glomerulopathy in mice via down-regulating P38 MAPK-mediated inflammation

OBJECTIVE

Obesity, particularly child obesity, is one of the most common public health problems in the world and raises the risk of end-stage renal disease. Zinc (Zn) is essential for multiple organs in terms of normal structure and function; however, effects of Zn deficiency or supplementation among young individuals with obesity have not been well studied.

METHODS

Weaned mice were fed high-fat diets (HFD) with varied contents of Zn (Zn deficient, adequate, and supplemented) for 3 or 6 months. This study examined associations between renal pathogenesis and dietary Zn levels, specifically assessing inflammatory pathways by utilizing P38 MAPK inhibitor SB203580.

RESULTS

HFD feeding induced typical syndromes of obesity-related renal disorders, which worsened by Zn marginal deficiency. The progression of obesity-related renal disorders was delayed by Zn supplementation. HFD induced renal inflammation, reflected by increased P38 MAPK phosphorylation along with increases of inflammatory cytokines MCP-1, IL-1β, IL-6, and TNF-α. P38 MAPK inhibition prevented renal pathological changes in mice fed with HFD and HFD/Zn deficiency.

CONCLUSIONS

P38 MAPK mediated the renal inflammatory responses, which played a central role in the pathogenesis of HFD-induced renal disorders. Zn could delay the progression of obesity-related kidney disease by down-regulating P38 MAPK-mediated inflammation.

'Adipaging': ageing and obesity share biological hallmarks related to a dysfunctional adipose tissue

The increasing ageing of our societies is accompanied by a pandemic of obesity and related cardiometabolic disorders. Progressive dysfunction of the white adipose tissue is increasingly recognized as an important hallmark of the ageing process, which in turn contributes to metabolic alterations, multi-organ damage and a systemic pro-inflammatory state ('inflammageing'). On the other hand, obesity, the paradigm of adipose tissue dysfunction, shares numerous biological similarities with the normal ageing process such as chronic inflammation and multi-system alterations. Accordingly, understanding the interplay between accelerated ageing related to obesity and adipose tissue dysfunction is critical to gain insight into the ageing process in general as well as into the pathophysiology of obesity and other related conditions. Here we postulate the concept of 'adipaging' to illustrate the common links between ageing and obesity and the fact that, to a great extent, obese adults are prematurely aged individuals.

Association between obesity measures and albuminuria: A population-based study

AIMS

The effects of obesity on the micro vascular diseases have drawn much attention. The aim of the study was to investigate the relationship between obesity measures and albuminuria in Chinese population.

METHODS

We conducted a population-based cross-sectional study in 8600 subjects aged 40 years or older from a community in Guangzhou. Urinary albumin excretion and creatinine were measured and urinary albumin-to-creatinine ratio (ACR) was calculated as urinary albumin divided by creatinine. Low-grade albuminuria was classified as the highest quartile of ACR in participants without increased urinary albumin excretion. Increased urinary albumin excretion was defined according to the ACR ranges greater or equal than 30 mg/g.

RESULTS

Pearson's correlation analysis and multivariate linear regression analysis revealed that body mass index (BMI), waist circumference and body fat content were significantly correlated with ACR (all P<0.01). Prevalence of low-grade albuminuria and increased urinary albumin excretion gradually increased across the BMI, waist circumference and body fat content quartiles (all P for trend<0.0001). Compared with participants in quartile 1 of BMI, waist circumference and body fat content, participants in quartile 4 had increased prevalence of low-grade albuminuria and increased urinary albumin excretion in logistic regression analysis after adjustment for age, sex, physical activity, fasting plasma glucose, triglycerides, low-density lipoprotein cholesterol and HbA1c (all P<0.05).

CONCLUSION

Obesity measures are associated with urinary albumin excretion in middle-aged and elderly Chinese.

Proteinuria rebound in IgA nephropathy associated with obesity-related glomerulopathy

IgA nephropathy (IgAN), the most prevalent primary chronic glomerulonephritis worldwide, has three major risk factors: hypertension, proteinuria >1 g/day, and severe renal lesions. Obesity also portends a poor prognosis. A Japanese boy with IgAN showed nephrotic syndrome at presentation. Pathological features resembled those of membranoproliferative glomerulonephritis (MPGN), although IgA deposition differed from MPGN and IgAN. Combination therapy improved renal lesions, but rebound deterioration of proteinuria occurred in this patient, who had marked obesity and hypertension. Serial kidney biopsy specimens were compatible with obesity-related glomerulopathy (ORG). Rebound proteinuria was apparently attributable to ORG rather than relapse and flaring up of IgAN.

The effect of obesity and type 1 diabetes on renal function in children and adolescents

BACKGROUND

Early signs of renal complications can be common in youths with type 1 diabetes (T1D). Recently, there has been an increasing interest in potential renal complications associated with obesity, paralleling the epidemics of this condition, although there are limited data in children.

HYPOTHESIS

Obese children and adolescents present signs of early alterations in renal function similar to non-obese peers with T1D.

SUBJECTS

Eighty-three obese (age: 11.6 ± 3.0 yr), 164 non-obese T1D (age: 12.4 ± 3.2 yr), and 71 non-obese control (age: 12.3 ± 3.2 yr) children and adolescents were enrolled in the study.

METHODS

Anthropometric parameters and blood pressure were measured. Renal function was assessed by albumin excretion rate (AER), serum cystatin C, creatinine and estimated glomerular filtration rate (e-GFR), calculated using the Bouvet's formula.

RESULTS

Obese and non-obese T1D youths had similar AER [8.9(5.9-10.8) vs. 8.7(5.9-13.1) µg/min] and e-GFR levels (114.8 ± 19.6 vs. 113.4 ± 19.1 mL/min), which were higher than in controls [AER: 8.1(5.9-8.7) µg/min, e-GFR: 104.7 ± 18.9 mL/min]. Prevalence of microalbuminuria and hyperfiltration was similar between obese and T1D youths and higher than their control peers (6.0 vs. 8.0 vs. 0%, p = 0.02; 15.9 vs. 15.9 vs. 4.3%, p = 0.03, respectively). Body mass index (BMI) z-score was independently related to e-GFR (r = 0.328; p < 0.001), and AER (r = 0.138; p = 0.017). Hemoglobin A1c (HbA1c) correlated with AER (r = 0.148; p = 0.007) but not with eGFR (r = 0.041; p = 0.310).

CONCLUSIONS

Obese children and adolescents show early alterations in renal function, compared to normal weight peers, and they have similar renal profiles than age-matched peers with T1D.

Diabetic Kidney Disease: A Syndrome Rather Than a Single Disease

The term "diabetic kidney" has recently been proposed to encompass the various lesions, involving all kidney structures that characterize protean kidney damage in patients with diabetes. While glomerular diseases may follow the stepwise progression that was described several decades ago, the tenet that proteinuria identifies diabetic nephropathy is disputed today and should be limited to glomerular lesions. Improvements in glycemic control may have contributed to a decrease in the prevalence of glomerular lesions, initially described as hallmarks of diabetic nephropathy, and revealed other types of renal damage, mainly related to vasculature and interstitium, and these types usually present with little or no proteinuria. Whilst glomerular damage is the hallmark of microvascular lesions, ischemic nephropathies, renal infarction, and cholesterol emboli syndrome are the result of macrovascular involvement, and the presence of underlying renal damage sets the stage for acute infections and drug-induced kidney injuries. Impairment of the phagocytic response can cause severe and unusual forms of acute and chronic pyelonephritis. It is thus concluded that screening for albuminuria, which is useful for detecting "glomerular diabetic nephropathy", does not identify all potential nephropathies in diabetes patients. As diabetes is a risk factor for all forms of kidney disease, diagnosis in diabetic patients should include the same combination of biochemical, clinical, and imaging tests as employed in non-diabetic subjects, but with the specific consideration that chronic kidney disease (CKD) may develop more rapidly and severely in diabetic patients.

Impact of obesity on kidney function and blood pressure in children

In recent years, obesity has become an increasingly important epidemic health problem in children and adolescents. The prevalence of the overweight status in children grew from 5% to 11% from 1960s to 1990s. The epidemic of obesity has been paralleled by an increase in the incidence of chronic kidney disease (CKD) and hypertension. Results of several studies have demonstrated that obesity and metabolic syndrome were independent predictors of renal injury. The pathophysiology of obesity related hypertension is complex, including activation of sympathetic nervous system, renin angiotensin aldosterone system, hyperinsulinemia and inflammation. These same mechanisms likely contribute to the development of increased blood pressure in children. This review summarizes the recent epidemiologic data linking obesity with CKD and hypertension in children, as well as the potential mechanisms.

Obese children and adolescents have elevated nighttime blood pressure independent of insulin resistance and arterial stiffness

BACKGROUND

Insulin resistance has been related to elevated blood pressure (BP) in obese children and may adversely affect the vasculature by arterial stiffening. The objective was to investigate whether daytime and nighttime BP were elevated and related to insulin resistance and arterial stiffness in obese children and adolescents.

METHODS

Ninety-two obese patients aged 10-18 years were compared with 49 healthy control individuals. Insulin resistance was measured as the homeostatic assessment model (HOMA), and arterial stiffness was measured as carotid-femoral pulse wave velocity (cfPWV).

RESULTS

Mean ± SD daytime systolic BP (SBP) (obese: 125±8.3mm Hg; control: 121±10.1mm Hg; P = 0.03) and nighttime SBP (obese: 108±10.7mm Hg; control: 102±8.2mm Hg; P = 0.0001) were higher in the obese group when compared with the control group. No difference was found in daytime diastolic BP (DBP), whereas nighttime DBP (obese: 60±6.6mm Hg; control: 57±4.8mm Hg; P = 0.001) and night-to-day BP ratios were higher in the obese group. Nighttime SBP was related to BMI z score (β = 6.0; 95% confidence interval (CI) = 2.9-9.1; P = 0.0002) and waist/height ratio (β = 36.7; 95% CI = 5.6-67.9; P = 0.02) in the obese group. HOMA index (obese: median = 3.7, interquartile range (IQR) = 2.3-6.0; control: median = 2.6, IQR = 1.8-3.4; P = 0.002) was higher, whereas cfPWV (obese: 4.8±0.8 m/s; control: 5.1±0.6 m/s; P = 0.03) was lower in the obese group. CfPWV was not related to logHOMA index. In multiple regression analyses, the higher nighttime BP in the obese group was independent of logHOMA and cfPWV.

CONCLUSIONS

Obese children had a higher nighttime BP when compared with the control group independently of insulin resistance and arterial stiffness. No relationship was found between insulin resistance and arterial stiffness. CLINICAL TRIAL REGISTRATION Clinicaltrials.gov identifier NCT01310088.

Two children with obesity-related glomerulopathy identified in a school urinary screening program

The incidence of obesity-related glomerulopathy (ORG) has increased over the last decade, but there have been few reports on ORG in Japanese children. Reported herein are two children with ORG identified on school urinary screening (SUS). Patient 1 was a 12-year-old boy in whom proteinuria was first detected on SUS. His body mass index (BMI) was 33.8 kg/m(2) and he had hypertension and hyperuricemia. Patient 2, a 10-year-old boy, also had proteinuria identified on SUS. His BMI was 34.8 kg/m(2) , and he had fatty liver, hyperuricemia, and hypercholesterolemia. Both were diagnosed with ORG based on obesity, proteinuria, and renal pathological findings. After treatment, including candesartan, food restriction and physical exercise, urinary protein excretion was decreased in both cases. We believe that such school urinary screening programs may be effective for the early identification and treatment of children with ORG.

Metabolic syndrome in children with chronic kidney disease and after renal transplantation

Visceral obesity and metabolic abnormalities typical for metabolic syndrome (MS) are the new epidemic in adolescence. MS is not only the risk factor for cardiovascular disease but also for chronic kidney disease (CKD). Thus, there are some reasons to recognize MS as a new challenge for pediatric nephrologists. First, hypertensive and diabetic nephropathy, the main causes of CKD in adults, both share the same pathophysiological abnormalities associated with visceral obesity and insulin resistance and have their origins in childhood. Secondly, as the obesity epidemic also affects children with CKD, MS emerges as the risk factor for progression of CKD. Thirdly, metabolic abnormalities typical for MS may pose additional risk for cardiovascular morbidity and mortality in children with CKD. Finally, although the renal transplantation reverses uremic abnormalities it is associated with an exposure to new metabolic risk factors typical for MS and MS has been found to be the risk factor for graft loss and cardiovascular morbidity after renal transplantation. MS is the result of imbalance between dietary energy intake and expenditure inducing disproportionate fat accumulation. Thus, the best prevention and treatment of MS is physical activity and maintenance of proper relationship between lean and fat mass.

Abdominal obesity is associated with albuminuria in women: the 2011 Korea National Health and Nutrition Examination Survey

BACKGROUND

The effects of obesity on the kidney, apart from diabetes or hypertension, have not drawn much attention. Moreover, only a few studies have reported the relationship between obesity status and albuminuria in Asian countries, including South Korea. Therefore, this study aimed to investigate the association between obesity status and albuminuria in Korean adults.

METHODS

We analyzed data from the 2011 Korea National Health and Nutrition Examination Survey. Of the 4,979 subjects included in the general-population group, 3,274 were sorted into a nondiabetic and nonhypertensive population group. Obesity status was measured by body mass index and waist circumference. Albuminuria was defined as a urine albumin-to-creatinine ratio ≥30 mg/g.

RESULTS

Abdominally obese women were at higher risk for albuminuria than were women without abdominal obesity both in the general population (odds ratio [OR], 95% confidence interval [CI]: 2.08 [1.04-4.16]) and in the nondiabetic and nonhypertensive population (OR [95% CI]: 6.96 [2.34-20.64]) after further adjustment for confounders. Among generally nonobese women, abdominally obese women were at higher risk for albuminuria than were women without abdominal obesity both in the general population (OR [95% CI]: 2.82 [1.51-5.29]) and in the nondiabetic and nonhypertensive population (OR [95% CI]: 5.32 [1.47-19.22]).

CONCLUSION

Abdominal obesity is associated with an increased risk for albuminuria in Korean women, independently of diabetes or hypertension. Screening for abdominal obesity, especially in women, may therefore provide earlier identification of individuals at risk for developing renal disease and cardiovascular disease, even those who are nondiabetic and nonhypertensive.

Low birthweight and premature birth are risk factors for podocytopenia and focal segmental glomerulosclerosis

BACKGROUND

Recent reports suggest that low birthweight (LBW) is a risk factor for kidney diseases, including focal segmental glomerulosclerosis (FSGS), although the underlying pathological mechanism remains unknown. Podocyte loss triggers glomerulosclerosis; however, whether FSGS in LBW children is associated with podocytopenia is unclear.

METHODS

We reviewed the birthweights and gestational age of all patients who underwent renal biopsies from 1995 to 2011 at our Institute. Sixteen patients had FSGS, of which 6 (37.5%) had LBW; this LBW rate was significantly higher than the overall LBW rate in Japan (9.7%). The incidence of LBW was also high in patients with minimal change nephrotic syndrome (MCNS; 12.5%). The glomerular cell numbers in biopsy sections were calculated using computer image analysis and compared with FSGS of normal birthweight (NBW-FSGS). Biopsy specimens from age-matched patients with MCNS were also compared. Wilms' tumor-1 (WT1) immunohistochemistry was performed to enumerate the podocytes.

RESULTS

All patients in the LBW-FSGS group were also preterm, with an average gestational age of 25.8 weeks. The number of podocytes per glomerulus in the LBW-FSGS patients was 34 and 24% lower as compared to that in the MCNS patients (p < 0.01) and the NBW-FSGS patients (p < 0.05), respectively. Similar results were observed for the WT1-positive glomerular cell number.

CONCLUSION

LBW and premature birth were associated with FSGS development. The possibility that LBW and premature birth may be predisposing factors for severe podocytopenia in children with FSGS warrants further investigation.

Structural renal changes in obesity and diabetes

Overweight, obesity, and associated diseases represent an emerging problem, not only in Western countries but also in the developing world. They are now characterized as epidemic diseases. Obesity is particularly serious because its incidence in children and adolescents increased dramatically: it is estimated that in the United States every eighth adolescent suffers from obesity, which in the long run may reduce life expectancy in the population. Apart from cardiovascular disease (ie, blood pressure, stroke, and coronary heart disease), kidney diseases also have been shown to be associated with obesity. Epidemiologic studies have indicated that obesity can be a risk factor of chronic kidney disease irrespective of the presence or absence of diabetes, arterial hypertension, and other comorbidities. More evidence is accumulated on the link between chronic kidney disease in obesity and abnormalities in adipokine secretion (hyperleptinemia, lack of adiponectin), activation of the renin-angiotensin system, chronic inflammation, endothelial dysfunction, lipid accumulation, impaired renal hemodynamics, and diminished nephron number related to body mass. In general, obesity is known to aggravate the course of many primary renal diseases such as glomerulonephritides, but also impairs renal function after kidney transplantation. Microalbuminuria, proteinuria, hyperfiltration, and impaired renal function are associated with obesity. Histologically, secondary focal segmental sclerosis has been shown to be caused particularly by obesity. Of practical purpose for clinical nephrology, loss of body weight either by lifestyle modification or bariatric surgery improves albuminuria and hyperfiltration in obese patients, making renal disease in obesity accessible for prevention programs. This review specifically addresses the pathogenesis and morphology of renal functional and particularly structural changes in obesity and associated renal disease such as diabetic nephropathy.

Limited value of routine microalbuminuria assessment in multi-ethnic obese children

BACKGROUND

To determine the prevalence of microalbuminuria and its association with cardiometabolic risk factors in a multi-ethnic cohort of overweight and obese children.

CASE-DIAGNOSIS/TREATMENT

A retrospective analysis of prospectively collected data was performed using data from 408 overweight and obese children (age 3-19 years). In addition to administering an oral glucose tolerance test, we measured anthropometric variables, plasma lipid levels, alanine aminotransferase and the urinary albumin/creatinine ratio (ACR). Microalbuminuria was defined as an ACR of between 2.5 and 25 mg/mmol in boys and 3.5 and 25 mg/mmol in girls. In total, only 11 (2.7 %) of the children analyzed presented with microalbuminuria, with no differences between ethnic groups, sex or in the prevalence of hypertension compared to the children with normoalbuminuria. After adjustment for confounders, the body mass index Z-score tended to be different between the group with microalbuminuria versus that without (3.6 vs. 3.2, respectively; P = 0.054). ACR was not associated with hypertension, impaired glucose tolerance, high triglycerides or low high-density lipoprotein-cholesterol.

CONCLUSIONS

In a large multi-ethnic cohort of overweight and obese children, we found a low prevalence of microalbuminuria (11 children, 2.7 %), and in this small number of individuals, we found no association with any of the cardiometabolic risk factors assessed. Therefore, our data do not support the routine measurement of microalbuminuria in asymptomatic overweight and obese children and adolescents.

Leptin as a link between the immune system and kidney-related diseases: leading actor or just a coadjuvant?

Food intake and nutritional status modify the physiological responses of the immune system to illness and infection and regulate the development of chronic inflammatory processes, such as kidney disease. Adipose tissue secretes immune-related proteins called adipokines that have pleiotropic effects on both the immune and neuroendocrine systems, linking metabolism and immune physiology. Leptin, an adipose tissue-derived adipokine, displays a variety of immune and physiological functions, and participates in several immune responses. Here, we review the current literature on the role of leptin in kidney diseases, linking adipose tissue and the immune system with kidney-related disorders. The modulation of this adipose hormone may have a major impact on the treatment of several immune- and metabolic-related kidney diseases.

Obesity-induced renal impairment is exacerbated in interleukin-6-knockout mice

AIM

Interleukin-6 (IL-6) is secreted from adipose tissue and thought to contribute to obesity-related disorders. The aim of this study was to assess if IL-6-knockout (IL-6-/-) mice would develop obesity-induced renal impairment.

METHODS

Wild-type (WT) and IL-6-/- mice were high-fat fed (HFF) for 16 weeks to induce obesity. At the end of the study, renal function was measured via albumin/creatinine ratio and serum creatinine levels, using enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC). Glomerulosclerotic index (GSI) was scored in periodic acid Schiff-stained sections and collagen IV accumulation was assessed by immunohistochemistry. Renal cortical tumour growth factor beta (TGF-β(1) ) activity and monocyte chemotactic protein-1 (MCP-1) levels were measured via ELISA.

RESULTS

Renal IL-6 concentrations were increased with obesity. Although both WT HFF and IL-6-/- HFF mice exhibited renal impairment as measured by increased serum creatinine and urinary albumin/creatinine ratios, this was exacerbated in IL-6-/- mice. Obese mice had renal activation of cortical TGF-β(1) , which was also higher in IL-6-/- mice. Collagen IV staining was not affected by obesity. GSI was increased with obesity in both WT and IL-6-/- mice.

CONCLUSION

Obese IL-6-/- mice demonstrated renal functional and structural abnormalities above that seen in obese WT mice. We suggest that absence or low IL-6 levels may be an important accelerating factor implicated in the development and progression of obesity-induced renal disease.

Evaluation of microalbuminuria in obese children and its relation to metabolic syndrome

Several epidemiologic studies have clearly demonstrated that obesity increases the risk of kidney diseases. We have attempted to evaluate the association of obesity with albuminuria, an early marker of kidney disease, among obese children and its relation to metabolic syndrome. This study included 150 obese children. Blood pressure, fasting blood glucose, plasma insulin and the lipid profile were assessed. The homeostasis model assessment of insulin resistance (HOMA-IR) was used to calculate in vivo insulin resistance. Urinary albumin and creatinine were estimated. Microalbuminuria was detected in 22 (14.7%) of the obese children. Waist circumference, blood pressure, triglyceride, low-density lipoprotein (LDL), insulin resistance and fasting blood glucose were significantly higher in obese children with microalbuminuria than in those with normoalbuminuria and showed significant positive correlations with microalbuminuria. High-density lipoprotein (HDL) was significantly lower in obese children with microalbuminuria than in those with normoalbuminuria, with a significant negative correlation with microalbuminuria. We found that body mass index, abdominal obesity, hypertension, impaired fasting glucose level and insulin resistance significantly increased the odds of microalbuminuria in the obese children enrolled in this study. Moreover, high triglyceride, high LDL and low HDL were significantly associated with microalbuminuria. In our patient group, childhood obesity was a risk factor for the development of microalbuminuria, which in turn was significantly associated with metabolic syndrome and its different constituents.

Adiponectin action: a combination of endocrine and autocrine/paracrine effects

The widespread physiological actions of adiponectin have now been well characterized as clinical studies and works in animal models have established strong correlations between circulating adiponectin level and various disease-related outcomes. Thus, conventional thinking attributes many of adiponectin's beneficial effects to endocrine actions of adipose-derived adiponectin. However, it is now clear that several tissues can themselves produce adiponectin and there is growing evidence that locally produced adiponectin can mediate functionally important autocrine or paracrine effects. In this review article we discuss regulation of adiponectin production, its mechanism of action via receptor isoforms and signaling pathways, and its principal physiological effects (i.e., metabolic and cardiovascular). The role of endocrine actions of adiponectin and changes in local production of adiponectin or its receptors in whole body physiology is discussed.

Impact of obesity on childhood kidney

Obese patients are known to have greater risks to develop hypertension, coronary vascular disease, and insulin resistance, and more attention has been recently paid to the impact of obesity on kidney. This study was conducted to investigate whether obese children have higher risk of renal injury as well as adults. Eighteen hundred and thirty school children aged 6-14 years with abnormal urinary findings on thrice occasions detected by the screening program for renal disease in Japan were enrolled. Of them, 27 children with nephritis or suspected nephritis diagnosed by persistent proteinuria with hematuria were compared to 588 without urinary abnormalities regarding their body mass index (BMI), blood pressure (BP), and serum level of total cholesterol. BMI and systolic BP (mmHg) were significantly higher in the former than in the latter. As a result, obesity may be associated with the development of renal injury even in childhood.

Implications for kidney disease in obese children and adolescents

Increasing attention has been focused on the implications of obesity in adults on the development of kidney disease, but data on the obese pediatric population are lacking. The aim of this study was to investigate whether changes in various renal function indexes/markers, as expressed by the glomerular filtration rate [GFR, as estimated by the Schwartz formula (eGFR)], serum cystatin C (CysC) level, albumin excretion rate (AER), and modifications in nitric oxide (NO; an important modulator of renal function and morphology), urinary isoprostanes (markers of oxidative stress), and blood pressure (BP), can be detected in obese children and adolescents when compared to normal weight controls. Blood and urinary samples were collected to evaluate markers of renal function, serum and urinary NO, and urinary isoprostanes in 107 obese Caucasian subjects and 50 controls. Ambulatory BP monitoring (ABPM) was performed in all cases. Obesity was expressed by the body mass index standard deviation score (SDS-BMI), and insulin resistance by the homeostasis model assessment of insulin resistance (HOMA-IR). CysC and eGFR did not significantly differ between the two groups; AER was increased in obese children. CysC and GFR were related to HOMA-IR, and AER was related to HOMA-IR and SDS-BMI. Obese subjects had reduced NO levels and increased urinary isoprostanes and BP measurements; all three parameters were related to SDS-BMI and insulin resistance. ABPM showed an increased incidence of hypertension and non-dipping in the obese group. Based on our comparison of obese and nonobese children, we conclude that renal involvement is not an early clinically evident manifestation of adiposity in childhood, since no overt changes in eGFR and only a mild albuminuria were detected. A longer exposure to obesity is probably needed before renal function impairment appears.

Microalbuminuria in normal Korean children

PURPOSE

Although microalbuminuria is known as a predictor of clinical nephropathy and cardiomyopathy, few studies have investigated the incidence and reference range of microalbuminuria in healthy children. This study aimed to establish a reference range and to study the age-related trend for spot urine microalbumin/creatinine ratio in a Korean pediatric population.

MATERIALS AND METHODS

352 healthy children were studied from July 2007 through March 2010. Height, weight, serum creatinine, spot urine microalbumin/creatinine ratio, and glomerular filtration rate (GFR) were obtained for each subject. We divided the study population into 5 groups according to age, and compared the spot urine microalbumin/creatinine ratio with other variables using one-way analysis of variance (ANOVA), regression analysis and Pearson's correlation analysis.

RESULTS

In this study, the data showed that the spot urine microalbumin/creatinine ratio decreased with age: 1-12 months, 22.72 ± 13.80 mg/mmol (2SD: 3.33-54.40 mg/mmol); 13-28 months, 16.34 ± 9.58 mg/mmol (2SD: 3.16-35.19 mg/mmol); 29-48 months, 13.12 ± 9.74 mg/mmol (2SD: 3.01-41.57 mg/mmol); 4-6 years, 10.58 ± 8.13 mg/mmol (2SD: 0.00-30.19 mg/mmol); and 7-19 years, 5.13±5.44 mg/mmol (2SD: 0.45-14.45 mg/mmol). The spot urine microalbumin/creatinine ratio showed correlation with age, height, height z-score, weight, weight z-score, GFR, body mass index (BMI) and body surface area (BSA).

CONCLUSION

The spot urine microalbumin/creatinine ratio in normal Korean children decreased with age. This ratio could potentially be used to establish reference ranges and cutoff values for Korean children and to predict nephropathy and cardiomyopathy.

Weight loss: a neglected intervention in the management of chronic kidney disease

PURPOSE OF REVIEW

Obesity is being increasingly implicated as an independent risk factor for the development of chronic kidney disease (CKD), raising the question whether reversing obesity can be utilized as a mainstay or an adjunct therapy for CKD and possibly for its prevention. The purpose of this review is to examine the impact of treatment of obesity on renal outcomes.

RECENT FINDINGS

Many observations have pointed to improvement in renal parameters following weight loss. In fact, both surgical and nonsurgical approaches appear to be effective at reducing blood pressure and proteinuria. Weight loss has also been shown to lower glomerular filtration rate (GFR) in obese patients, not an insignificant benefit considering that intra-glomerular hypertension and the subsequent hyperfiltration in the setting of obesity might be a main driver for the development of CKD.

SUMMARY

Urinary protein excretion, blood pressure, and GFR improve with surgical and nonsurgical weight loss interventions. Whether improvements in these surrogate outcomes after weight loss actually translate into a reduction in the risk of CKD or amelioration in the rate of progression of established CKD is yet to be determined.

Weight loss and proteinuria: systematic review of clinical trials and comparative cohorts

BACKGROUND

Obesity is a risk factor for the progression of chronic kidney disease (CKD). The impact of weight loss on proteinuria and renal function is less clear. We aimed to determine the effect of intentional weight loss on proteinuria and kidney function.

METHODS

Three bibliographic databases including Medline, Cochrane and SCUPOS as well as reference list of articles were searched. We included randomized and non-randomized controlled trials as well as single-arm trials published in English through May 2009 which examined urinary protein among obese or overweight adults before and after weight loss interventions including dietary restriction, exercise, anti-obesity medications and bariatric surgery. Study characteristics and methodological quality of trials were assessed.

RESULTS

Five hundred twenty-two subjects from five controlled and eight uncontrolled trials were included. Weight loss interventions were associated with decreased proteinuria and microalbuminuria by 1.7 g [95% confidence interval (95% CI), 0.7 to 2.6 g] and 14 mg (95% CI, 11 to 17 mg), respectively (P < 0.05). Meta-regression showed that, independent of decline in mean arterial pressure, each 1 kg weight loss was associated with 110 mg (95% CI, 60 to 160 mg, P < 0.001) decrease in proteinuria and 1.1 mg (95% CI, 0.5 to 2.4 mg, P = 0.011) decrease in microalbuminuria, respectively. The decrease was observed across different designs and methods of weight loss. Only bariatric surgery resulted in a significant decrease in creatinine clearance.

CONCLUSIONS

Weight loss is associated with decreased proteinuria and microalbuminuria. There were no data evaluating the durability of this decrease or the effect of weight loss on CKD progression.

The effect of obesity on kidney length in a healthy pediatric population

Over the past decade, the percentage of children who are obese has rapidly increased. As weight has been shown to correlate strongly with the size of various organs, we have observed that obese children have larger kidneys than their normal-weight counterparts. This study sought to quantify this observation by establishing the normal limits of renal length for this population. We examined 204 healthy patients seen for benign hematuria between January 2000 and May 2008. Both right and left kidney lengths significantly correlated with age, height, weight, body mass index and body surface area in our obese patients (n = 59). Height was also found to be a significant predictor of kidney length, in the obese group, by multiple linear regression analysis and was used to create renal length nomograms for the obese pediatric population (P < 0.01). According to this analysis, obese patients had significantly larger kidneys than those of normal-weight patients (P < 0.01). By defining the normal limits of renal length for this group, unnecessary evaluation for nephromegaly will be avoided.

Renal volume and function in school-age children born preterm or small for gestational age

Impaired renal development during foetal life is a proposed mechanism for adult hypertension in people born small. Whether preterm birth contributes to such adverse development is still unclear. We investigated the selective contributions from foetal growth restriction or preterm birth to renal function and volume in children with low birth weight. Three groups of 9 to 12-year-old children were studied: those born at < 32 gestational weeks (preterm, n = 39), those born at term but small for gestational age (SGA, n = 29) and those born at the term appropriate for gestational age (controls, n = 37). We estimated renal function by calculating glomerular filtration rate (GFR) and by measuring urinary proteins. Volumetric ultrasound of the kidneys was performed in 86 children (preterm, n = 33; SGA, n = 25; controls, n = 29). Estimated glomerular filtration rate (eGFR) and urinary protein patterns were similar between the groups. Kidney volume (preterm 162 ml (31); SGA 163 ml (26) and controls 182 ml (47)) was smaller in the preterm group than in the controls, but the difference was not significant when adjusted for body surface area, gender and age (P = 0.25). Total renal volume correlated to birth weight (r = 0.23, P = 0.03). No significant differences were found in renal function or volume between the three groups at school age.

Hypertension and microalbuminuria in children with congenital solitary kidneys

AIM

According to the hyperfiltration hypothesis, a low nephron endowment will lead to hyperfiltration in the remaining glomeruli and is associated with systemic hypertension, proteinuria and glomerulosclerosis. Being born with one functioning kidney instead of two, for instance because of unilateral renal agenesis or multicystic dysplastic kidney, is a cause of congenital renal mass reduction.

METHODS

In order to study the effect of congenital renal mass reduction on renal function and blood pressure, a retrospective chart review of 66 patients at the Pediatric Renal Center of the VU University Medical Center was performed. As intrauterine growth restriction is associated with a low nephron endowment, the additional effect of birthweight was also studied.

RESULTS

A total of 50% of patients with congenital renal mass reduction is found to be hypertensive, using anti-hypertensive drugs, and/or having microalbuminuria (>20 mug/min). Patients born small for gestational age have significantly smaller kidneys and lower estimated glomerular filtration rate than patients with a normal birthweight.

CONCLUSIONS

We conclude that microalbuminuria and/or hypertension is present in 50% of patients with congenital solitary kidneys, which warrants a systematic follow-up of blood pressure, proteinuria and renal function in all patients with congenital solitary functioning kidneys, especially in patients with a low birthweight.

Obesity, diabetes, and chronic kidney disease

Similar to diabetes, obesity is associated with the early onset of glomerulomegaly, hemodynamic changes of a hyperfiltering kidney, and increased albuminuria, which are potentially reversible with weight loss. However, the pathologic lesions of focal segmental glomerulosclerosis in experimental models of sustained obesity, and in obese humans presenting with massive proteinuria, are different from those of classic diabetic nephropathy. In addition, several observational, cross-sectional, and longitudinal studies document obesity as an independent risk factor for the onset, aggravated course, and poor outcomes of chronic kidney disease, even after adjustment for confounding comorbidities, including diabetes and hypertension, the two major causes of chronic kidney disease.