Urinary albumin excretion rate and puberty in non-diabetic children and adolescents

Tangled relationship between insulin resistance and microalbuminuria in children with obesity

Childhood obesity represents a complex disease with a well-known cardiometabolic burden including fatty liver, type 2 diabetes, metabolic syndrome, and cardiovascular disease. From a pathogenic point of view, insulin resistance (IR) represents the key factor underlying the spectrum of these obesity consequences. As observed in adults, recent data supported the occurrence of microalbuminuria (MA) as marker of early kidney dysfunction and its potential link with cardiometabolic factors also in children with obesity. In fact, a well-documented pathophysiological hypothesis both in adults and children supported an intimate correlation with the major feature of obesity such as IR through the influence of insulin on renal hemodynamics. Based on the clinical and prognostic relevance of this relationship in daily practice (including an increased risk of chronic kidney disease development overtime), more scientific attention needs to be paid to the evaluation of early kidney damage in children with obesity. In this paper, we attempt to address three debated questions regarding the intriguing liaison between IR and MA in children with obesity: (1) What is the prevalence of pediatric MA? (2) What is the state of art of MA in children with obesity? and (3) Is there a link between IR and MA in children with obesity?

Proteomic Analysis of Hypothalamus and Pituitary Gland in Pre and Postpubertal Brahman Heifers

The hypothalamus and the pituitary gland are directly involved in the complex systemic changes that drive the onset of puberty in cattle. Here, we applied integrated bioinformatics to elucidate the critical proteins underlying puberty and uncover potential molecular mechanisms from the hypothalamus and pituitary gland of prepubertal (n = 6) and postpubertal (n = 6) cattle. Proteomic analysis in the hypothalamus and pituitary gland revealed 275 and 186 differentially abundant (DA) proteins, respectively (adjusted p-value < 0.01). The proteome profiles found herein were integrated with previously acquired transcriptome profiles. These transcriptomic studies used the same tissues harvested from the same heifers at pre- and post-puberty. This comparison detected a small number of matched transcripts and protein changes at puberty in each tissue, suggesting the need for multiple omics analyses for interpreting complex biological systems. In the hypothalamus, upregulated DA proteins at post-puberty were enriched in pathways related to puberty, including GnRH, calcium and oxytocin signalling pathways, whereas downregulated proteins were observed in the estrogen signalling pathway, axon guidance and GABAergic synapse. Additionally, this study revealed that ribosomal pathway proteins in the pituitary were involved in the pubertal development of mammals. The reported molecules and derived protein-protein networks are a starting point for future experimental approaches that might dissect with more detail the role of each molecule to provide new insights into the mechanisms of puberty onset in cattle.

Individual and Environmental Factors Associated with Proteinuria in Korean Children: A Multilevel Analysis

Proteinuria is a significant sign of childhood renal disorders. However, little is known about how sociodemographic and environmental factors are related to the presence of proteinuria among children and adolescents. This paper focuses on the prevalence of proteinuria and its risk factors among children and adolescents. This study conducted a secondary analysis of data from the 2016 Sample Schools Raw Data of Health Examination for School Students (SSRDHESS). Data collected from 27,081 students who had undergone a health screening were analyzed using Chi-square tests, independent t-tests, and multilevel logistic regression analysis. The prevalence of proteinuria was higher in the thin group than in the normal weight group (adjusted odds ratio (aOR) = 1.77; 95% confidence interval (CI) = 1.34–2.33) and lower in the overweight/obese group (aOR = 0.64; 95% CI = 0.51–0.80). Additionally, those in metropolitan and small–medium sized cities had a proteinuria prevalence about 1.5-fold higher than that of those in rural areas (95% CI = 1.08–2.02, 95% CI = 1.19–1.92, respectively). Proteinuria was associated with environmental pollution, including smoking rate, ambient particulate matter and heavy metals in drinking water (aOR = 1.10; 95% CI = 1.01–1.20; aOR = 1.06; 95% CI = 1.01–1.11, aOR = 1.001; 95% CI = 1.0001–1.0015). These results suggest that to improve health management effectiveness, kidney disease prevention efforts for children and adolescents should focus on geographical area and environmental pollution, as well as body weight as individual factors.

Differential prevalence of hematuria and proteinuria with socio-demographic factors among school children in Hualien, Taiwan

BACKGROUND

Pediatric hematuria/proteinuria is a risk factor for chronic kidney disease in later life, and school urinary screening can detect asymptomatic glomerulonephritis in the early stage. This study aimed to evaluate the prevalence of hematuria/proteinuria and its association with different socio-demographic factors among school children in 2013 in Hualien, Taiwan.

METHODS

A cross-sectional study was conducted among first, fourth, and seventh graders. Health examination results and urinalysis data were analyzed. Logistic regression models were used to the simultaneously analyze the association between the prevalence of hematuria/proteinuria and socio-demographic factors.

RESULTS

A total of 9544 students were included. The overall prevalence of hematuria and proteinuria was 4.1% and 5.7%, respectively. Students who were females, of a high grade level, of aboriginal ethnicity, and living in rural areas had higher hematuria risk (all P < 0.001) than other students. Underweight students had low odds ratio (0.53) of hematuria (P < 0.001). Seventh-grade students had higher odds ratio (3.63) of proteinuria than first grade students (P < 0.001). Students with both parents of aboriginal descent had lower odds ratio (0.81) of proteinuria than those with non-aboriginal parents (P = 0.044). Only higher grade level students had significantly higher risk of combined hematuria and light proteinuria (odds ratio: 10.67) and heavy proteinuria with/without hematuria (odds ratio: 3.22) than first graders.

CONCLUSION

Increased hematuria/proteinuria prevalence was noted in our county as compared to prior studies. Hematuria/proteinuria was significantly associated with gender, grade level, body mass index, ethnicity, and residence urbanization. Our data can be used for future longitudinal dataset collection to prevent pediatric renal disorders in Taiwan.

Prevalence and determinants of microalbuminuria in children suffering from sickle cell anemia in steady state

Background

Sickle cell anemia (SCA) is considered a major risk factor for renal complications. The main goal of this study was to determine the frequency of macroalbuminuria and microalbuminuria in Congolese children <18 years of age suffering from Sickle cell anemia and to identify associated factors.

Methods

The cross-sectional study was completed in 150 hemoglobin-SS children (77 boys and 73 girls). Microalbuminuria was defined by a urine albumin:creatinine ratio of 30–299 mg/g.

Results

The mean age of this group was 8.8 ± 4.3 years (range 2–18). Microalbuminuria was found in 27 children (18%). In multivariate logistic regression, only age emerged as a determinant of microalbuminuria odds ratio 1.11 (95% confidence interval 1.00–1.22); P = 0.042].

Conclusions

In our series, only age was a major determinant of the occurrence of microalbuminuria. These results confirm the need for early screening of microalbuminuria in Congolese children suffering from Sickle cell anemia in a context where access to renal and bone marrow transplant is nonexistent.

Practice recommendations for the monitoring of renal function in pediatric non-renal organ transplant recipients

The management of non-renal pediatric solid organ transplant recipients has become complex over the last decade with innovations in immunosuppression and surgical techniques. Post-transplantation follow-up is essential to ensure that children have functioning allografts for as long as possible. CKD is highly prevalent in these patients, often under recognized, and has a profound impact on patient survival. These practice recommendations focus on the early detection and management of hypertension, proteinuria, and renal dysfunction in non-renal pediatric solid organ transplant recipients. We present seven practice recommendations. Renal function should be monitored regularly in organ transplant recipients, utilizing assessment of serum creatinine and cystatin C. GFR should be calculated using the new Schwartz formula. Transplant physicians should also monitor blood pressure using automated oscillometric devices and confirm repeated abnormal measures with manual blood pressure readings and ambulatory 24-h blood pressure monitoring. Proteinuria and microalbuminuria should also be assessed regularly. Referrals to a pediatric nephrologist should be made for non-renal organ transplant recipients with repeated blood pressures >95th percentile using the Fourth Task Force reference intervals, microalbumin/creatinine ratio >32.5 mg/g (3.7 mg/mmol) creatinine on repeated testing and/or GFR <90 mL/min/1.73 m(2) .

Urinalysis in children and adolescents

BACKGROUND

Urinalysis is the most commonly performed biochemical test in infancy and early childhood. The urine sample should be correctly obtained, age-specific aspects should be considered, and age-dependent reference values should be used.

METHOD

This review is based on a selective literature search in electronic databases, textbooks, and guidelines from Germany and abroad on the acquisition of urine samples and the performance of urinalysis in infancy and early childhood.

RESULTS

The timing and mode of acquisition of the urine sample affect the assessment of hematuria, proteinuria, leukocyturia, nitrituria, and the uropathogenic bacterial colony count in the urine culture. Dipstick tests can be used for targeted screening for these features. The test results should be interpreted together with the findings of urine microscopy, the medical history, and the physical examination. Proteinuria should be quantified and differentiated; both of these things can be done either from collected urine or (especially in infants and young children) from a spontaneously voided urine sample, by determination of the protein/creatinine quotient. Orthostatic proteinuria in an adolescent requires no further evaluation or treatment. Hematuria should be characterized as either glomerular or non-glomerular erythrocyturia. Asymptomatic, isolated microhematuria in childhood is not uncommon and often transient; in the absence of a family history, it usually does not require an extensive work-up. Proteinuria combined with hematuria should arouse the suspicion of glomerulonephritis.

CONCLUSION

Urinalysis in infancy and early childhood is a simple and informative diagnostic test as long as the urine sample has been obtained properly and the results are interpreted appropriately for this age group.

Presence of Cardiometabolic Risk Factors Is Not Associated with Microalbuminuria in 14-to-20-Years Old Slovak Adolescents: A Cross-Sectional, Population Study

Introduction

In adults, microalbuminuria indicates generalized endothelial dysfunction, and is an independent risk factor for cardiovascular and all cause mortality. Slovak adults present one of the highest cardiovascular mortality rates in Europe. Thus Slovak adolescents are on a high-risk to develop cardiovascular afflictions early, and screening for microalbuminuria might be useful in early assessment of their cardiovascular risk. We aimed to study the prevalence of microalbuminuria in Slovak adolescents, and the association of urinary albumin-to-creatinine ratio (ACR) to cardiovascular risk factors.

Subjects and methods

Anthropometric data, blood pressure, blood count, glucose homeostasis, lipid profile, renal function, inflammatory status, concentrations of homocysteine and uric acid were determined and associated with ACR in 2 666 adolescents (49.4% boys, 51.6% girls) aged 14-to-20 years. Microalbuminuria was classified as ACR 2.5–25.0 mg/mmol in boys and 3.5–35.0 mg/mmol in girls.

Results

Prevalence of microalbuminuria in both genders reached 3.3%, and did not differ significantly between lean and centrally obese subjects. Girls presented higher ACR than boys (normoalbuminuric: 0.6±0.5 mg/mmol vs. 0.5±0.4 mg/mmol, p>0.001; microalbuminuric: 9.3±7.3 mg/mmol vs. 5.0±3.8 mg/mmol; p>0.001). Microalbuminuric adolescents and those presenting normoalbuminuria within the upper ACR quartile were slimmer than their normoalbuminuric counterparts or adolescents with normoalbuminuria within the lower quartile, respectively. No association between microalbuminuria and cardiovascular risk markers was revealed.

Conclusion

Results obtained in this study do not support our assumption that ACR associates with cardiometabolic risk factors in apparently healthy adolescents. Follow-up studies until adulthood are needed to estimate the potential cardiometabolic risk of apparently healthy microalbuminuric adolescents.

Nephropathy in youth and young adults with type 2 diabetes

The occurrence and progression of nephropathy associated with early onset type 2 diabetes (T2D) is a consequence of the ongoing epidemic of childhood obesity. Minimal evidence regarding treatment effectiveness of renovascular comorbidities in youth with early onset T2D is available, due to the relatively recent emergence of T2D in youth and young adults. Extrapolation of adult therapy guidelines is not an ideal approach to making therapeutic decisions in this population. Evolving management and intervention strategies are based on accumulating longitudinal data from cohorts of well characterized youth and young adults with T2D. The degree of similarity in histologic findings and disease specific characteristics of kidney disease in patients with early onset T2D and albuminuria compared with affected adults is not well characterized. Early aggressive therapies to minimize the impact of nephropathy are indicated as the evidence for best therapies in youth with T2D are further explored.

The association of albumin/creatinine ratio with postoperative AKI in children undergoing cardiac surgery

BACKGROUND AND OBJECTIVES

This study determined if preoperative and postoperative urine albumin/creatinine ratios (ACRs) predict postoperative AKI in children undergoing cardiac surgery (CS).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a three-center, prospective study (2007-2009) of 294 children undergoing CS (n=145 aged <2 years). Urine ACR was measured preoperatively and 0-6 hours after intensive care unit arrival. AKI outcomes were based on the Acute Kidney Injury Network serum creatinine (SCr) criteria (stage 1 AKI, ≥50% or 0.3 mg/dl SCr rise from baseline; and stage 2 or worse AKI, ≥SCr doubling or dialysis). AKI was predicted using preoperative and postoperative ACRs and postoperative ACR performance was compared with other AKI biomarkers.

RESULTS

Preoperative ACR did not predict AKI in younger or older children. In children aged <2 years, first postoperative ACR ≥908 mg/g (103 mg/mmol) predicted stage 2 AKI development (adjusted relative risk, 3.4; 95% confidence interval, 1.2-9.4). In children aged ≥2 years, postoperative ACR ≥169 mg/g (19.1 mg/mmol) predicted stage 1 AKI (adjusted relative risk, 2.1; 95% confidence interval, 1.1-4.1). In children aged ≥2 years, first postoperative ACR improved AKI prediction from other biomarker and clinical prediction models, estimated by net reclassification improvement (P≤0.03), but only when serum cystatin C was also included in the model.

CONCLUSIONS

Postoperative ACR is a readily available early diagnostic test for AKI after pediatric CS that performs similarly to other AKI biomarkers; however, its use is enhanced in children aged ≥2 years and in combination with serum cystatin C.

Chronic kidney disease and albuminuria in children with sickle cell disease

BACKGROUND AND OBJECTIVES

Sickle cell nephropathy begins in childhood and may progress to renal failure. Albuminuria is a sensitive marker of glomerular damage that may indicate early chronic kidney disease (CKD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The aims of this study were to determine the cross-sectional prevalence and clinical correlates of albuminuria and CKD among children with sickle cell disease (SCD). Over a 10-year period (1995 to 2005) 410 pediatric SCD patients ages 2 to 21 years were enrolled: 261 with hemoglobin SS (HbSS) or HbSβ(0) thalassemia (HbSβ(0)) and 149 with HbSC or HbSβ(+) thalassemia (HbSβ(+)). The albumin/creatinine ratio (ACR) of spot-urine specimens and serum creatinine were measured; abnormal albuminuria was defined as urinary ACR ≥ 30 mg/g.

RESULTS

The prevalence of abnormal albuminuria was 20.7% (23.0% in HbSS/HbSβ(0), 16.8% in HbSC/HbSβ(+)). Among HbSS/HbSβ(0), abnormal albuminuria was associated with increasing age and lower baseline hemoglobin. GFR, estimated in 189 patients using the updated Schwartz formula, correlated negatively with age (r = -0.27, P = 0.0002). CKD defined according to the Kidney Disease: Improving Global Outcomes study was present in 26.5% (50 of 189) of patients: stage 1 in 27 (14.8%) and stage 2 in 22 (11.6%). In multivariate analysis, age and HbSC/HbSβ(+) genotype were associated with CKD.

CONCLUSIONS

This is the first study to stage CKD in children with SCD and highlights a high prevalence of albuminuria and glomerular injury early in life. Detecting CKD in childhood could allow for earlier intervention and prevention of renal failure in adulthood.

Microalbuminuria in the paediatric age: current knowledge and emerging questions

The prevalence of microalbuminuria (MA) in children and adolescents differs from the one in adults, and it is estimated to be about 5.7-7.3% in boys and 12.7-15.1% in girls. The percentage is greater in smaller age group, whereas a positive association is found between albumin excretion rate and pubertal development stage in nondiabetic subjects. The data so far suggest that impairment of glucose metabolism, obesity-related proatherosclerotic pathways and the impact of haemodynamic load constitute major determinants of albuminuria development in the early years of life. In everyday practice if persistent MA is present at a young age, especially in the setting of diabetes, further investigation of cardiovascular risk factors, a more careful follow-up and dietary/lifestyle interventions are needed.

CONCLUSION

Although the significance of MA in paediatric essential hypertension has yet to be determined, its role in diabetic children and adolescents is established and albuminuria assessment has been utilized as a screening test for the presence of diabetes-related kidney disease.

Is albuminuria associated with obesity in school children?

BACKGROUND

Different studies in adults have shown that obesity is an independent risk factor for end-stage renal disease.

OBJECTIVE

It was to (i) determine the association between albuminuria and age, gender, BMI, waist circumference (WC), and blood pressure (ii) relate albuminuria to gender and age in healthy school children.

METHODS

Over 1564 students (806 males) aged 9.35 +/- 2.00 yr from 9 elementary schools in Buenos Aires, were examined between April and September 2005. BMI, WC, blood pressure, urinary albumin excretion and albumin/creatinine ratio (ACR) were determined.

RESULTS

Over 220 (14.1%) children were obese (OB), and 300 (19.2%) overweight (OW) using centers for disease control (CDC) norms. Median ACR and urinary albumin levels were higher in normal weight children than in OW/OB children (p < 0.01). Median values for ACR were higher in girls than in boys (p < 0.001). OW/OB proved to be a protective factor against ACR [OR, 0.77 (95% CI 0.64-0.92)], whereas female gender [OR, 2.72 (95% CI 2.13-3.47)] was associated with a higher ACR adjusted for age systolic and diastolic blood pressure in the multiple logistic regression analysis. Therefore, children with OW/OB had 23% lower odds of having ACR >or= III quartile and girls had more than two and half times the risk of having high ACR.

CONCLUSIONS

Our results suggest that OW/OB is inversely associated with childhood albuminuria while female gender is positively associated. Whether the results can be explained by the increased physical activity in lean children should be the subject of future investigations. These results suggest that micro-albuminuria in children may not be a useful tool in the early identification of children at risk for future renal and cardiovascular disease (CVD).

Albuminuria in children

PURPOSE OF REVIEW

Albuminuria is a marker of present and future cardiovascular and renal morbidity, and mortality, in adults. Because the roots of these diseases extend back into childhood, assessment of albuminuria has become relevant to child and adolescent clinical care.

RECENT FINDINGS

Normal levels of albumin excretion in children are well below the cut-off for microalbuminuria. In healthy children, albuminuria relates to fasting insulin, but not blood pressure, BMI, lipid levels, fasting glucose, or insulin resistance. In obese children, albuminuria relates to multiple measures of insulin resistance. In children with type 1 diabetes, hemoglobin A1c seems to be the most consistent clinical predictor of microalbuminuria although multiple mechanisms seem to be involved, including genetic polymorphisms. Children with type 2 diabetes and hypertension already exhibit microalbuminuria.

SUMMARY

When considering the population as a whole, children make ideal subjects in which to study the natural history of albuminuria given their relative lack of multiple morbidities commonly seen in adults. The unfortunate rise in 'adult' diseases in the pediatric age group makes this especially relevant. There is a need for longitudinal studies examining predictors of elevated urinary albumin levels as well as potential treatment strategies.

Albuminuria and insulin resistance in children with biopsy proven non-alcoholic fatty liver disease

Insulin resistance may favor increased urinary albumin excretion (UAE), leading progressively to chronic kidney disease (CKD). A recent study on non-alcoholic fatty liver disease (NAFLD), a condition of insulin resistance, associated this disease with the incidence of CKD in patients with type 2 diabetes. The aim of our study was to determine whether there is an association between insulin resistance and kidney function, based on estimates of UAE and creatinine clearance in children with biopsy-proven NAFLD. Kidney function was assessed in 80 patients with NAFLD and 59 individuals of normal weight matched for age and sex. Insulin resistance was measured by means of the homeostatic model assessment-insulin resistance (HOMA-IR) and limited to NAFLD patients by using the whole-body insulin sensitivity index. The HOMA-IR was found to differ significantly between the two groups (2.69 +/- 1.7 vs. 1.05 +/- 0.45; p = 0.002), while UAE (9.02 +/- 5.8 vs. 8.0 +/- 4.3 mg/24 h; p = 0.9) and creatinine clearance (78 +/- 24 vs. 80 +/- 29 mg/min; p = 0.8) did not. We found a significant but weak inverse correlation between insulin sensitivity and creatinine clearance in NAFLD patients (r (s) = -0.25;p = 0.02). No difference was observed in kidney function between NAFLD children presenting with or without metabolic syndrome, low or normal HDL-cholesterol, and different degrees of histological liver damage (grade of steatosis >or=2, necro-inflammation, and fibrosis). Patients with hypertension had increased levels of UAE (p = 0.04). A longer exposure to insulin resistance may be required to cause the increase in urinary albumin excretion and to enable the detection of the effect of the accelerated atherogenic process most likely occurring in children with fatty liver disease. Longitudinal studies are needed to rule out any causative relationship between insulin resistance and urinary albumin excretion.

Monitoring kidney function and renal disease in children following transplant

This article reviews the currently available tools for measuring glomerular filtration rate (GFR) and early detection of chronic kidney disease in pediatric transplant recipients. GFR measurement remains the mainstay to detect renal dysfunction. Inulin clearance formed the earlier gold standard method to measure GFR. In current clinical practice, it has been replaced by nuclear medicine techniques (51Cr EDTA and 99Tc DTPA isotope clearance studies). GFR estimation based on surrogate markers allows more frequent GFR monitoring in a clinical setting. Serum creatinine has a low sensitivity to detect early renal dysfunction and its muscle mass dependency hampers its clinical utility. The Schwartz formula accounts for age-dependent muscle changes in children, but requires center-specific constants. Cystatin C offers the advantage of a constant production and a higher sensitivity in diagnosing renal dysfunction. Microalbuminuria has been an established screening tool in diabetic renal disease. It offers the advantage of detecting underlying renal damage even before a decrease in GFR. Its diagnostic value in other conditions needs evaluation. Hypertension is known to accelerate the progression of chronic kidney disease. A 24-h ambulatory blood pressure is a useful tool to diagnose hypertension, to quantify blood pressure load and to characterize nocturnal blood pressure dipping. GFR scans, serum creatinine and cystatin C form the cornerstone of currently used tools to evaluate kidney dysfunction.

How to monitor renal function in pediatric solid organ transplant recipients

The aim is to review the tools for early detection of renal dysfunction after pediatric solid organ transplantation. Currently, the most widely used marker for detection of renal dysfunction involves measurement of GFR. Inulin clearance forms the "gold standard" method for measuring GFR; however, nuclear medicine methods ((51)Cr EDTA and (99)Tc DTPA isotope clearance studies) have replaced inulin clearance. The measurement of serum creatinine has a low sensitivity for the early detection of renal damage. The Schwartz formula using patient height and serum creatinine requires center-specific constants and has limitations associated with creatinine determination. These limitations may be overcome using a cystatin C-based GFR estimation. In diabetic nephropathy, and more recently in hemolytic uremic syndrome, microalbuminuria has been established as a useful screening tool for renal damage, while its predictive value in the transplantation setting needs to be established. All transplant recipients should be screened for hypertension. Early referral for ambulatory 24-h blood pressure monitoring and involvement of pediatric nephrologists should be considered. All pediatric solid organ transplant recipients receiving CNI should be screened regularly for high blood pressure and early evidence of renal damage using either GFR scans or cystatin C-based GFR estimations.

Albumin excretion rate in normal adolescents: relation to insulin resistance and cardiovascular risk factors and comparisons to type 1 diabetes mellitus patients

BACKGROUND AND OBJECTIVES

Although albumin excretion rates have been related to cardiovascular morbidity and mortality in both diabetic and nondiabetic adults, little is known about the relation between albuminuria and either cardiovascular risk factors or the insulin resistance syndrome in adolescents. A normal range for albumin excretion in adolescents was established, correlations between albumin excretion and cardiovascular risk factors were evaluated, and albumin excretion in normal adolescents was compared with that in type 1 diabetes mellitus adolescents.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Albumin excretion rate was measured in 368 normal and 175 diabetic adolescents. Multiple regression analysis was used to predict the relation of age, sex, Tanner stage, body mass index, and systolic blood pressure to albumin excretion in both cohorts. In addition, correlations between albumin excretion and age, blood pressure, body mass index, lipids, and measurements of insulin resistance were performed in the normal adolescents.

RESULTS

Mean albumin excretion was significantly lower in normal adolescents (4.0 microg/min) than in type 1 diabetic adolescents (5.0 microg/min). Albumin excretion increased with age in diabetics. Albumin excretion did not significantly correlate with any measure of cardiovascular risk or insulin resistance but did significantly correlate with fasting insulin.

CONCLUSIONS

Albumin excretion rate is not related to insulin resistance or traditional cardiovascular risk factors in adolescence but is related to fasting insulin. Diabetic adolescents have increased albumin excretion compared with normal adolescents.

Diabetic nephropathy in children and adolescents

Type 1 diabetes mellitus (T1DM) commonly occurs in childhood or adolescence, although the rising prevalence of type 2 diabetes mellitus (T2DM) in these age groups is now being seen worldwide. Diabetic nephropathy (DN) develops in 15-20% of subjects with T1DM and in similar or higher percentage of T2DM patients, causing increased morbidity and premature mortality. Although overt DN or kidney failure caused by either type of diabetes are very uncommon during childhood or adolescence, diabetic kidney disease in susceptible patients almost certainly begins soon after disease onset and may accelerate during adolescence, leading to microalbuminuria or incipient DN. Therefore, all diabetics warrant ongoing assessment of kidney function and screening for the earliest manifestations of renal injury. Pediatric health care professionals ought to understand about risk factors, strategy for prevention, method for screening, and treatment of early DN. This review considers each form of diabetes separately, including natural history, risk factors for development, screening for early manifestations, and strategy recommended for prevention and treatment of DN in children and adolescents.

The influence of urinary flow rate in children on excretion of markers used for assessment of renal damage: albumin, gamma-glutamyl transpeptidase, N-acetyl-beta-D -glucosaminidase, and alpha1-microglobulin

The aim of the present study was to examine the influence of urinary flow rate on markers of renal function in children. A sub-study of the New England Children's Amalgam Trial collected 82 pairs of urine samples from children aged 10-16 years: a timed overnight collection and a spot daytime sample collected the following day. These samples were analyzed for albumin, gamma-glutamyl transpeptidase (gamma-GT), N-acetyl-beta-D-glucosaminidase (NAG), alpha1-microglobulin (A1M), and creatinine concentration. Regression analysis was used to model the effect of urinary flow rate in the timed overnight samples. A paired t-test compared concentrations and creatinine-corrected renal markers between overnight and daytime samples. Albumin, gamma-GT, NAG, and A1M excretion rates increased significantly with urinary flow rate. Their corresponding creatinine-corrected markers did not vary significantly with urinary flow rate, but the creatinine-corrected excretions of albumin, gamma-GT, and NAG were significantly higher in daytime samples than in overnight samples, with the same (non-significant) trend for A1M. The influence of urinary flow rate on creatinine-corrected markers of renal function was markedly less than its influence on excretion rates. Therefore, the use of creatinine-corrected markers seems to be a good choice in practice, with the caveat that daytime and overnight samples are not comparable.

Racial differences in microalbumin excretion in healthy adolescents

It has been suggested that "normal" levels of urine albumin excretion rate (AER) may be predictive of an increased risk for progression of hypertension, cardiovascular morbidity, and mortality. No data are available on the effect of race and gender on AER in normal youth. We evaluated AER in timed urine samples in subjects participating in a study of stress-induced pressure natriuresis. A total of 317 healthy, normotensive adolescents aged 15 to 18 years (155 males and 162 females; 216 blacks and 101 whites) participated in a 5-hour testing protocol, which included a 1-hour period of mental stress preceded and followed by a 2-hour rest period. AER (micrograms per minute) was determined after 60 minutes of rest, and log transformation was used to normalize the data. AER was significantly higher in blacks as compared with whites (P=0.006). We also found a race-by-sex interaction, which was driven by the low albumin excretion in white females (P=0.036). Indexing urine albumin to creatinine excretion revealed the same pattern. Among blacks, AER was also higher in subjects who demonstrated impaired stress-induced pressure natriuresis versus those with normal sodium excretion (P=0.024). AER was related to blood pressure only in African-American males. The relative elevation of AER in normotensive black adolescents and the association with impaired pressure natriuresis and blood pressure is noteworthy. These findings suggest that albumin excretion may be a marker for a population at increased risk for the development of vascular and renal injury even before the manifestation of hypertension.

Being overweight modifies the association between cardiovascular risk factors and microalbuminuria in adolescents

OBJECTIVE

The goal was to determine the association between cardiovascular risk factors and microalbuminuria in a nationally representative sample of adolescents and to determine whether being overweight modifies this association.

METHODS

We analyzed cross-sectional data from the National Health and Nutrition Examination Survey (1999-2004) for 2515 adolescents 12 to 19 years of age. Cardiovascular risk factors included abdominal obesity, impaired fasting glucose, diabetes mellitus, insulin resistance, high triglyceride levels, low high-density lipoprotein cholesterol levels, hypertension, smoking, and the metabolic syndrome. Microalbuminuria was defined as a urinary albumin/creatinine ratio of 30 to 299 mg/g in a random morning sample. Overweight was defined as BMI of > or = 95th percentile, according to the Centers for Disease Control and Prevention 2000 growth charts.

RESULTS

Microalbuminuria was present in 8.9% of adolescents. The prevalence of microalbuminuria was higher among nonoverweight adolescents than among overweight adolescents. The median albumin/creatinine ratio decreased with increasing BMI z scores. The association of microalbuminuria with cardiovascular risk factors differed according to BMI category. Among nonoverweight adolescents, microalbuminuria was not associated with any cardiovascular disease risk factor except for overt diabetes mellitus. Among overweight adolescents, however, microalbuminuria was associated with impaired fasting glucose, insulin resistance, hypertension, and smoking, as well as diabetes mellitus.

CONCLUSION

For the majority of adolescents, microalbuminuria is not associated with cardiovascular risk factors. Among overweight adolescents, however, microalbuminuria is associated with cardiovascular risk factors. The prognostic importance of microalbuminuria in overweight and nonoverweight adolescents with regard to future cardiovascular and renal disease needs to be defined in prospective studies conducted specifically in children.

National Kidney Foundation's Kidney Disease Outcomes Quality Initiative clinical practice guidelines for chronic kidney disease in children and adolescents: evaluation, classification, and stratification

OBJECTIVES

A series of new guidelines has been developed by the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative to improve the detection and management of chronic kidney disease (CKD). In most instances of CKD, the earliest manifestations of the disorder may be identified by relatively simple tests. Unfortunately, CKD is often "underdiagnosed," in part because of the absence of a common definition of CKD and a classification of the stages in its progression. The Kidney Disease Outcomes Quality Initiative clinical practice guidelines for CKD evaluation, classification, and stratification provide a basis to remedy these deficits. The specific goals of the guidelines described in this review are to provide: 1) an overview of the clinical practice guidelines as they pertain to children and adolescents, 2) a simple classification of the stages of CKD, and 3) a practical approach to the laboratory assessment of kidney disease in children and adolescents.

METHODS

The guidelines were developed as part of an evidence-based evaluation of CKD and its consequences in patients of all ages. The data that were used to generate the guidelines in this article were extracted from a structured analysis of articles that reported on children with CKD.

RESULTS AND CONCLUSIONS

This review presents the definition and 5-stage classification system of CKD developed by the work group assigned to develop the guidelines, and summarizes the major recommendations regarding the early detection of CKD. Major emphasis is placed on the identification of children and adolescents with CKD by measuring the protein-to-creatinine ratio in spot urine specimens and by estimating the glomerular filtration rate from serum creatinine using prediction equations.

Metabolic characteristics and urine albumin excretion rate in relation to pubertal maturation in Type 1 diabetes

BACKGROUND

The objective of this study was to assess the impact of pubertal maturation on urinary albumin excretion rate (AER) and persistent microalbuminuria, and to identify possible factors affecting urinary AER in adolescents with Type 1 diabetes.

METHODS

One hundred patients aged 9.1-19.0 years with a duration of diabetes of >2 years out of 138 eligible adolescents with Type 1 diabetes from an outpatient diabetes clinic participated in the study, together with 100 healthy controls. A timed overnight urine sample was collected in the hospital, where all the adolescents stayed for 22-24 h, and microalbuminuria was confirmed with at least one consecutive positive sample (AER 20-200 microg/min).

RESULTS

The prevalence of persistent microalbuminuria was 6%. All the patients affected were girls: one prepubertal (T I), one in late puberty (T IV) and three postpubertal (T V). These patients had significantly higher HbA(1c) levels than did the normoalbuminuric girls with Type 1 diabetes. Neither duration of diabetes nor age differed significantly between the two groups. AER increased more conspicuously with pubertal maturation in the boys with Type 1 diabetes than in the control boys, while the girls with diabetes had significantly higher body mass index (BMI) and serum total and LDL cholesterol than did the control girls. HbA(1c) was independently associated with AER in a multiple regression model. Diastolic blood pressure (BP) was elevated in both girls and boys with Type 1 diabetes as compared with healthy adolescents, while no difference was observed between the patients with microalbuminuria and normoalbuminuria.

CONCLUSIONS

Persistent microalbuminuria was mainly observed in late puberty and after puberty among adolescents with Type 1 diabetes. Female sex and poor metabolic control predispose such adolescents to this condition during pubertal maturation.

Detection and management of diabetic glomerulopathy in children and adolescents with insulin-dependent diabetes mellitus: need for improved knowledge and better care

Current modalities of detection and management of incipient diabetic nephropathy in childhood and adolescence are summarized and the open questions outlined. In particular, the predictive value of microalbuminuria for later nephropathy in adolescents is examined. Microalbuminuria is not as strong a predictor as suggested in earlier studies - recent studies show up to 50% of microalbuminuria can revert to normal. We advocate that the association of well-established risk markers and promoters of renal injury, including degree and tracking of albuminuria, glycemic control, blood pressure changes, incipient retinopathy and genetic background, allow more precise assessment of the individual risk of developing nephropathy and the decision to start pharmacological intervention. The major impact of strict glycemic control to prevent the development and progression of diabetic nephropathy is emphasized, as well as the need for a multidisciplinary team to optimize the care of pediatric diabetic patients. We discuss other therapeutic options, i.e. angiotensin-converting enzyme inhibitors (ACE-Is), moderate dietary protein intake, and other drugs. ACE-Is may provide a second line intervention in a well selected, high-risk subgroup of microalbuminuric diabetic adolescents.

Urinary albumin excretion in children: factors related to elevated excretion in the United States population

Past population studies have indicated a higher prevalence of high albumin excretion in children than in adults. In this study, NHANES III United States population data was analyzed to study factors associated with elevated albumin excretion in children 8 to 18 years of age. The analysis confirmed a higher prevalence of albumin values > 30 mg/g creatinine and > 200 mg/g creatinine in children than in adults, and indicated that girls are two to three times more likely to have albumin excretion above these levels than boys. Neither hypertension nor reported diabetes--major factors influencing albumin excretion in adults--accounted for the higher excretion levels in children. The higher excretion levels were not associated with prescription medications or a poor rating of the child's overall health status by a physician. The higher prevalences is influenced by puberty stage and is more likely to occur in children with lower than average body mass index, independent of the relationship with urine creatinine excretion. The increased prevalence of high albumin excretion is probably associated with normal development in children, but an increased susceptibility to chronic diseases in the future among the children with high excretion cannot be ruled out.

The multidimensional nature of renal disease: rates and associations of albuminuria in an Australian Aboriginal community

BACKGROUND

An epidemic of end-stage renal disease (ESRD) is accompanying the rising rates of hypertension, type 2 diabetes and cardiovascular disease among Aborigines in the Northern Territory of Australia. Incidence rates are now 21 times those of nonAboriginal Australians and are doubling every four years. We describe the rates and associations of renal disease in one remote community, which has a current ESRD incidence of 2700 per million, and cardiovascular mortality among the highest in Australia.

METHODS

Between 1992 and 1995 a community-wide screening program was conducted, in which the urinary albumin/creatinine ratio (ACR) was used as the chief renal disease marker. More than 90% of the population ages five and older participated.

RESULTS

Albuminuria was evident in early childhood and increased dramatically with age; 26% of adults had microalbuminuria and 24% had overt albuminuria. All renal failure developed out of a background of overt albuminuria. ACR was significantly correlated with the presence of scabies at screening, with a history of poststreptococcal glomerulonephritis, which is epidemic and endemic in the community, with increasing body wt, blood pressure, glucose, insulin and lipid levels, and with evidence of heavy drinking. ACR was also significantly and inversely correlated with birth weight. As a result of its association with deteriorating hemodynamic and metabolic profiles, increasing ACR was also correlated with increasing cardiovascular risk score. Direct observations showed, and multivariate models predicted, progressive amplification of ACR when multiple risk factors were present simultaneously. Albuminuria also clustered in families.

CONCLUSION

Renal disease in this population is multifactorial, with risk factors related to whole-of-life nutrition, metabolic and hemodynamic profiles, infections, health behaviors, and possibly a family predisposition. Its relationship to low birth weight, and its associations with deteriorating metabolic and hemodynamic profiles, suggest that renal disease is, in part, a component of Syndrome X, which explains the simultaneous increase in metabolic, cardiovascular and renal disease in Aboriginal people. The family clustering might have both environmental and genetic causes, and is under further investigation. Most of the identified risk factors arise out of poverty, disadvantage and accelerated lifestyle change, and the current epidemic can be explained by the confluence of many risk factors in the last few decades. The introduction of effective and sustained programs to address social, economic and educational inequities in all Aboriginal communities, and of screening and renal- and cardiovascular-protective treatment programs for those already afflicted are matters of great urgency.

Normal values of overnight albumin excretion rate in a sample of healthy Italian children and adolescents

The aim of this study was to define normal values of albumin excretion rate (AER) in young people. We measured overnight timed AER (tAER, microgram/min) by a double-antibody radioimmunoassay in 281 healthy Italian children and adolescents (160 M and 121 F), aged 7-19 years. The frequency distribution of tAER deviated from normality, therefore percentiles were used: median and 95th percentile were 2.3 and 6.9 micrograms/min respectively. Log transformed tAER was not related to age or pubertal stage. "Borderline" AER refers to AER higher than normal 95th percentile in non-diabetic subjects but lower than microalbuminuria threshold level. Incipient nephropathy, expressed as "borderline" AER, has been reported in adult IDDM patients, and can be reversed by improving metabolic control. Because incipient diabetic nephropathy may be present in young IDDM patients without microalbuminuria, screening for AER should be recommended for pediatric diabetic patients, also before puberty, in order to detect early renal damage and the "borderline" AER state.

Changes in the urinary excretion of creatinine, albumin and N-acetyl-beta-D-glucosaminidase with increasing age and maturity in healthy schoolchildren

Raised urinary levels of albumin and N-acetyl-beta-D-glucosaminidase (NAG) are predictive of abnormal renal function and excretion of these substances is often expressed as a creatinine ratio. However, it is important to establish normal reference limits of albumin and NAG excretion for comparison of values from patients. For this reason, overnight excretion rates of creatinine, albumin and NAG were determined in timed overnight urine samples from 528 healthy schoolchildren (260 boys, 268 girls; 4-16 years) of normal size. There was a significant correlation with age and puberty for all substances in both sexes (P < 0.01). Peak creatinine excretion occurred at 16 years in boys, at 15 years in girls and at pubertal stage 5 in both sexes. Maximum albumin excretion was seen at 15 years and genital stage 5 in boys and at 16 years and breast stage 4 in girls. Peak NAG excretion occurred earlier, at 14 years and genital stage 4 in boys and at 13 years and breast stage 3 in girls. Boys excreted significantly more creatinine compared with girls before and during puberty (reflecting greater muscle mass) (P < 0.001) while excretion rates for albumin and NAG were similar in both sexes. Height and weight combined accounted for 58% and 29% of the variation in creatinine and NAG excretion respectively, while height alone predicted 20% of variation in albumin excretion.

CONCLUSION

Age and puberty influence the urinary excretion of albumin and NAG while sex has an additional effect on creatinine excretion. The urinary excretion of albumin and NAG in children with renal disorders should be compared with age-related normal ranges while creatinine excretion could be used as a marker of muscle growth.

Indications of low sex hormone binding globulin (SHBG) in young females with type 1 diabetes, and an independent association to microalbuminuria

Sex hormone binding globulin (SHBG) is normally decreased during puberty and inversely related to insulin resistance. Microalbuminuria is rare before puberty in Type 1 diabetes implicating that sex hormones may contribute to its development. We investigated SHBG levels in young females with > 5 years of Type 1 diabetes, and the association to microalbuminuria. Ten diabetic females with, and 15 without microalbuminuria, and 17 healthy controls in pubertal stage 4-5 were compared regarding anthropometric data, fasting serum levels of SHBG, testosterone, insulin, insulin-like growth factor-1 (IGF-1), lipids and lipoproteins. Multiple regression analyses were performed to study variables with independent influences on SHBG and albumin excretion rate (AER), respectively, in Type 1 diabetes. SHBG was lower and testosterone/SHBG ratio higher in normoalbuminuric females with diabetes than in controls. This was further emphasized in diabetic patients with microalbuminuria. IGF-1 was lower in Type 1 diabetes than in controls, and significantly decreased in microalbuminuric as compared to normoalbuminuric diabetic patients. IGF-1 was only correlated to SHBG in healthy controls. In Type 1 diabetes, applying stepwise multiple regression analysis, insulin dose, BMI, and HbA1c had a significant and independent inverse influence on SHBG (r2 = 0.77, p < 0.001). With log AER as the dependent variable, low SHBG, low IGF-1, HbA1c, and age added to the regression (r2 = 0.65, p = 0.004), whereas BMI, insulin dose and blood pressure did not. In conclusion, SHBG is decreased in young females with Type 1 diabetes, influenced by increased insulin requirements, BMI and HbA1c. In turn, low SHBG seems to be independently associated to elevated AER in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary excretion of retinol-binding protein in healthy children and adolescents

Retinol-binding protein (RBP) is a marker of tubular reabsorption in the kidneys. The aim of our study was to investigate urinary RBP excretion in healthy children to obtain reference values related to age and pubertal stage. Overnight samples from 143 subjects (73 girls, 70 boys) aged 10-18 years were investigated. RBP was quantified by a solid-phase sandwich enzyme immunoassay. Both the RBP excretion rate and the RBP/creatinine ratio (RBP/Cr) showed a skewed distribution. The medians and the 5th-95th percentiles were 38 ng/min (15-127) and 9 micrograms/mmol (4-23), respectively. The RBP excretion rate and RBP/Cr ratio were similar in both sexes, and linear multiple regression analysis showed no association with age or pubertal stage, although a weak relationship (r = 0.27) was found between RBP excretion rate and age in boys and RBP/Cr ratio and age (r = -0.28) in girls by simple correlation analysis. The correlation between RBP excretion rate and RBP/Cr ratio was 0.76; the RBP excretion rate and RBP/Cr ratio measured on 2 consecutive days, showed a correlation coefficient of 0.84 and 0.88, respectively. We conclude that overnight RBP excretion in children over 10 years shows a low day-to-day variation and, in practical terms, is independent of age, gender and pubertal stage.