Prenatal programming of nephron number and blood pressure

Intrauterine growth restriction alters kidney metabolism at the end of nephrogenesis

BACKGROUND

This study investigated the effect of uteroplacental insufficiency (UPI) on renal development by detecting metabolic alterations in the kidneys of rats with intrauterine growth restriction (IUGR).

METHODS

On gestational day 17, pregnant Sprague Dawley rats were selected and allocated randomly to either the IUGR group or the control group. The IUGR group received a protocol involving the closure of bilateral uterine vessels, while the control group underwent a sham surgery. The rat pups were delivered on gestational day 22 by natural means. Pups were randomly recruited from both the control and IUGR groups on the seventh day after birth. The kidneys were surgically removed to conduct Western blot and metabolomic analyses.

RESULTS

IUGR was produced by UPI, as evidenced by the significantly lower body weights of the pups with IUGR compared to the control pups on postnatal day 7. UPI significantly increased the levels of cleaved caspase-3 (p < 0.05) and BAX/Bcl-2 (p < 0.01) in the pups with IUGR. Ten metabolites exhibited statistically significant differences between the groups (q < 0.05). Metabolic pathway enrichment analysis demonstrated statistically significant variations between the groups in the metabolism related to fructose and mannose, amino and nucleotide sugars, and inositol phosphate.

CONCLUSIONS

UPI alters kidney metabolism in growth-restricted newborn rats and induces renal apoptosis. The results of our study have the potential to provide new insights into biomarkers and metabolic pathways that are involved in the kidney changes generated by IUGR.

Perinatal intermittent hypoxia increases early susceptibility to ANG II-induced hypertension in adult male but not in female Sprague-Dawley rats

Prenatal, perinatal, and adulthood exposure to chronic intermittent hypoxia (IH) increases blood pressure in rodents. Males exposed to chronic IH have higher blood pressure versus females. However, it is unknown if this same-sex difference exists with acute perinatal IH. We tested the hypothesis that acute perinatal IH increases baseline blood pressure and enhances sensitivity to angiotensin II (ANG II)-induced hypertension in male Sprague-Dawley rats. Male and female pups were randomized to control (room air) or IH (10 min of ∼10% O2 for 3 times/day) for the first 8 days of life. IH decreased oxygen saturation, as confirmed via a pulse oximeter. Pups were weaned at postnatal day 21. Blood pressure was measured via telemetry beginning at 14 wk of age and analyzed separately into light and dark phases to assess circadian rhythm. Osmotic minipumps to deliver ANG II were implanted at 15 wk of age. Perinatal IH exposure did not alter baseline blood pressure. One week of ANG II treatment increased blood pressure in light and dark periods in males exposed to IH versus control; there was no effect in females. Blood pressure among the groups was comparable following 2 wk of ANG II infusion. Perinatal IH did not change the circadian rhythm. Following ANG II treatment, indexes of renal injury were measured. Perinatal IH did not alter kidney size, structure, nephron number, or creatinine clearance. These data indicate that acute perinatal IH enhances early ANG II-induced hypertension in males, independent of nephron loss or decreases in body weight or kidney function.NEW & NOTEWORTHY The impact of acute intermittent hypoxia (IH) in early life on blood pressure in adulthood is unknown. This study used a new model exposing female and male rat pups to acute IH in the first 8 days of life, without exposing the dam. Although baseline blood pressure was not altered in adulthood, IH increased susceptibility to angiotensin II hypertension only in males, supporting increased susceptibility of males exposed to IH to a second cardiovascular stressor.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Renal pathology in a mouse model of severe Spinal Muscular Atrophy is associated with downregulation of Glial Cell-Line Derived Neurotrophic Factor (GDNF)

Spinal muscular atrophy (SMA) occurs as a result of cell-ubiquitous depletion of the essential survival motor neuron (SMN) protein. Characteristic disease pathology is driven by a particular vulnerability of the ventral motor neurons of the spinal cord to decreased SMN. Perhaps not surprisingly, many other organ systems are also impacted by SMN depletion. The normal kidney expresses very high levels of SMN protein, equivalent to those found in the nervous system and liver, and levels are dramatically lowered by ~90-95% in mouse models of SMA. Taken together, these data suggest that renal pathology may be present in SMA. We have addressed this using an established mouse model of severe SMA. Nephron number, as assessed by gold standard stereological techniques, was significantly reduced. In addition, morphological assessment showed decreased renal vasculature, particularly of the glomerular capillary knot, dysregulation of nephrin and collagen IV, and ultrastructural changes in the trilaminar filtration layers of the nephron. To explore the molecular drivers underpinning this process, we correlated these findings with quantitative PCR measurements and protein analyses of glial cell-line-derived neurotrophic factor, a crucial factor in ureteric bud branching and subsequent nephron development. Glial cell-line-derived neurotrophic factor levels were significantly reduced at early stages of disease in SMA mice. Collectively, these findings reveal significant renal pathology in a mouse model of severe SMA, further reinforcing the need to develop and administer systemic therapies for this neuromuscular disease.

Temporal Trends of Acute Kidney Injury and Associated Risk Exposures in Extremely Preterm Infants

BACKGROUND AND OBJECTIVES

Neonatal AKI in the preterm population is an under-recognized morbidity. Detecting AKI in preterm infants is important for their long-term kidney health. We aimed to examine the yearly trends of incidence and the related morbidities and care practices affecting the occurrence of neonatal AKI in extremely preterm (gestational age <29 weeks) and very preterm (gestational age 29-32 weeks) infants.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The trends and the related risk factors and care practices of AKI were examined in the extremely preterm (n=434) and very preterm (n=257) infants who were admitted within 14 days after birth from 2005 to 2018 to the University Hospital and had at least two serum creatinine measurements during hospitalization. We defined AKI as a serum creatinine rise of 0.3 mg/dl or more within 48 hours or a 1.5-fold increase within 7 days.

RESULTS

The extremely preterm group had a three-fold higher incidence of AKI (30% versus 10%) than the very preterm group. Among preterm infants with AKI, 92% had one episode of AKI, and 45% experienced stage 2 or 3 AKI; the mean duration of AKI was 12±9 days. Across the 14-year period, the crude incidence of AKI declined markedly from 56% to 17% in the extremely preterm group and from 23% to 6% in the very preterm group. After adjustment, a significant decline of AKI incidence was still observed in the extremely preterm group. The declining AKI in the extremely preterm infants was related to the trends of decreasing incidences of neonatal transfer, prolonged aminoglycoside exposure, prophylactic use of nonsteroidal anti-inflammatory drugs, and sepsis.

CONCLUSIONS

We observed a declining trend in the incidence of neonatal AKI among extremely preterm infants from 2005 to 2018, which may be related to improvement of care practices.

Assessment of nephron number and single-nephron glomerular filtration rate in a clinical setting

Total nephron counts vary widely between individuals and may affect susceptibility to certain diseases, including hypertension and chronic kidney disease. Detailed analyses of whole kidneys collected from autopsy patients remain the only method for accurately counting nephrons in humans, with no equivalent option in living subjects. Current technological advances have enabled estimations of nephron numbers in vivo, particularly the use of total nephron number and whole-kidney glomerular filtration rate to estimate the mean single-nephron glomerular filtration rate. The use of this method would allow physicians to detect dynamic changes in filtration function at the single-nephron level rather than to simply count the number of nephrons that appear to be functioning. Currently available methods for estimating total nephron number in clinical practice have the potential to overcome limitations associated with autopsy analyses and may therefore pave the way for new therapeutic interventions and improved clinical outcomes.

Neonatal Morbidities of Fetal Growth Restriction: Pathophysiology and Impact

Being born small lays the foundation for short-term and long-term implications for life. Intrauterine or fetal growth restriction describes the pregnancy complication of pathological reduced fetal growth, leading to significant perinatal mortality and morbidity, and subsequent long-term deficits. Placental insufficiency is the principal cause of FGR, which in turn underlies a chronic undersupply of oxygen and nutrients to the fetus. The neonatal morbidities associated with FGR depend on the timing of onset of placental dysfunction and growth restriction, its severity, and the gestation at birth of the infant. In this review, we explore the pathophysiological mechanisms involved in the development of major neonatal morbidities in FGR, and their impact on the health of the infant. Fetal cardiovascular adaptation and altered organ development during gestation are principal contributors to postnatal consequences of FGR. Clinical presentation, diagnostic tools and management strategies of neonatal morbidities are presented. We also present information on the current status of targeted therapies. A better understanding of neonatal morbidities associated with FGR will enable early neonatal detection, monitoring and management of potential adverse outcomes in the newborn period and beyond.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

Prenatal lead exposure modifies the effect of shorter gestation on increased blood pressure in children

BACKGROUND

High blood pressure (BP) in childhood is frequently renal in origin and a risk factor for adult hypertension and cardiovascular disease. Shorter gestations are a known risk factor for increased BP in adults and children, due in part to a nephron deficit in children born preterm. As nephrogenesis is incomplete until 36 weeks gestation, prenatal lead exposure occurring during a susceptible period of renal development may contribute to programming for later life renal disease. The relationship between shorter gestation and children's BP has not yet been explored to identify i) critical windows using nonlinear piecewise models or ii) combined with other early life risk factors such as prenatal lead exposure.

OBJECTIVES

(1) To evaluate the nonlinear relationship between lower gestational age and childhood BP measured at 4-6 years of age, and (2) to investigate modification by prenatal lead exposure.

METHODS

In a prospective longitudinal birth cohort, we assessed 565 children between 4 and 6 years of age (mean: 4.8 years) in the PROGRESS cohort in Mexico City, Mexico. Gestational age at delivery was calculated using maternal report of last menstrual period (LMP) and confirmed with Capurro physical examination at birth. We measured pregnant women's blood lead levels (BLLs) in the second trimester via inductively coupled plasma-mass spectrometry and children's BP using an automated device. We performed both linear and nonlinear piecewise regression analyses to examine associations of gestational age with children's BP adjusting for children's age, sex, height, prenatal exposure to smoke, and maternal socioeconomic status. We stratified to assess modification by prenatal lead exposure, and used a data-adaptive approach to identify a lead cutpoint.

RESULTS

Maternal second trimester BLLs ranged from 0.7 to 17.8 μg/dL with 112 (20%) women above the CDC guideline level of 5 μg/dL. In adjusted linear regression models, a one week reduction in gestational age was associated with a 0.5 mm Hg (95%CI: 0.2, 0.8) increase in SBP and a 0.4 mm Hg (95%CI 0.1, 0.6) increase in DBP. Our nonlinear models suggested evidence for different magnitude estimates on either side of an estimated join-point at 35.9 weeks' gestation, but did not reach statistical significance. However, when stratified by prenatal lead exposure, we identified a cutpoint lead level of concern of 2.5 μg/dL that suggested an interaction between gestational age and blood lead. Specifically, for BLLs ≥ 2.5 μg/dL, SBP was 1.6 (95%CI: 0.3, 2.9) mm Hg higher per each week reduction in gestational age among children born before 37.0 weeks; and among children born after 37.0 weeks, this relationship was attenuated yet remained significant [β: 0.9, 95%CI (0.2, 1.6)]. At BLLs below 2.5 μg/dL, there was no appreciable association between lower gestational age and SBP.

CONCLUSIONS

Our findings suggest that shorter gestation combined with higher prenatal lead exposure contributes to a higher risk of increased SBP at 4-6 years of age, particularly among infants born <37 weeks gestation. Our results underscore the importance of preventing prenatal lead exposure - even levels as low as 2.5 μg/dL - especially among pregnant women at risk for preterm birth. Given that high BP in childhood is a risk factor for adult hypertension and cardiovascular disease later in life, these results may have implications that extend across the life span.

Elevated renal tissue oxygenation in premature fetal growth restricted neonates: An observational study

BACKGROUND

Fetal growth restriction (FGR) is associated with an increased risk for kidney disease in later life. Studies reporting on early signs of renal disturbances in FGR are sparse and mostly include invasive measurements, which limit the possibility for early identification and prevention. We aim to investigate whether renal tissue oxygen saturation (rSO2) measured with near-infrared spectroscopy (NIRS) and the derived value fractional tissue oxygen extraction (FTOE) differ between premature FGR and control neonates in the first three days after birth.

METHODS

Nine FGR and seven control neonates born <32 weeks of gestation were included. FGR was defined as biometry

RESULTS

Renal rSO2 was higher in FGR neonates compared to controls (94% vs. 83%; pgroup = 0.002). During the first three days after birth, renal rSO2 decreased in FGR neonates and increased in controls (r = -0.25 vs. r = 0.03; pinteraction = 0.001). Renal FTOE was lower in FGR neonates (0.02 vs. 0.14; pgroup = 0.01) and increased slightly during three days after birth, while it remained stable in controls (r = 0.003 vs. r = -0.0001; pinteraction = 0.001). Renal artery blood flow was similar between groups.

CONCLUSIONS

FGR neonate kidneys showed higher rSO2 as measured with NIRS and lower derived values of FTOE in the first three days after birth. We speculate that this was caused by either a reduced oxygen consumption due to impaired renal maturation or increased renal oxygen supply. How these observations correlate with short- and long-term renal function needs further investigation before renal NIRS can be implemented in screening and prevention in clinical practice.

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Key Words Collapse

MESH Headings

• Female
• Fetal Growth Retardation/metabolism
• Gestational Age
• Humans
• Infant, Newborn
• Infant, Premature
• Intensive Care, Neonatal
• Kidney/blood supply
• Kidney/metabolism
• Male
• Oxygen/analysis
• Oxygen Consumption
• Premature Birth/metabolism
• Renal Circulation
• Spectroscopy, Near-Infrared

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Grants

• Nierstichting
• ZonMw
• Academy Medical Sciences Fund (Koninklijke Nederlandse Akademie van Wetenschappen; KNAW

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Affiliation(s)

Fieke Terstappen Department of Obstetrics, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands Department of Neonatology, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands
Nina D. Paauw Department of Obstetrics, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands
Thomas Alderliesten Department of Neonatology, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands
Jaap A. Joles Department of Nephrology and Hypertension, University Medical Centre Utrecht, University Utrecht, Utrecht, the Netherlands
Daniel C. Vijlbrief Department of Neonatology, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands
A. Titia Lely Department of Obstetrics, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands
Petra M. A. Lemmers Department of Neonatology, Wilhelmina Children’s Hospital Birth Centre, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands

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Low birth weight is a conditioning factor for podocyte alteration and steroid dependance in children with nephrotic syndrome

BACKGROUND

Low birth weight (LBW) is associated with reduced nephron endowment. Clinical-pathologic features of post adaptive focal segmental glomerulosclerosis (FSGS) have been observed in subjects with prematurity and very LBW.

METHODS

We aimed to investigate the correlation between LBW and outcome in a cohort of 89 children with idiopathic nephrotic syndrome (NS) (2-12 years-old at onset, followed for > 3 years), of whom 21 with LBW (birth weight < 10th percentile for gestational age, gender, ethnicity, and maternal parity or birth weight < 2500 g).

RESULTS

Children with NS and LBW were found to have FSGS more frequently than children with normal birth weight (NBW) [8/21 = 38% vs. 4/68 = 6%; odds ratio, OR 7.754 (95% confidence interval, CI 2.184-27.525); χ² = 9.817; p < 0.003]. Children with LBW and cortico-sensitive NS had a greater risk of cortico-dependence (CD) than those with NBW [10/13 = 76.9% vs. 28/63 = 44.4%, OR 4.744 (1.188-18.936); χ² = 4.158; p < 0.05]. Moreover, children with LBW and CDNS needed a greater dose of immunosuppressive drugs than those with NBW [OR 4 (1.153-13.877); χ² = 3.842; p = 0.05].

CONCLUSIONS

LBW children developing NS had higher risk of FSGS and CD, and needed heavier immunosuppressive therapy than those with NBW. These data might suggest a conditioning role for hemodynamic and podocyte changes due to reduced nephron mass in LBW.

Maternal determinants of renal mass and function in the fetus and neonate

The impact of adverse maternal and early gestational issues, ranging from maternal-fetal interactions all the way through to premature birth, are recognized as having influence on the subsequent development of chronic diseases later in life. The development of chronic kidney disease (CKD) as a direct result of early life renal injury or a sequela of diseases such as hypertension or diabetes is a good model example of the potential impact that early life events may have on renal development and lifelong function. The global monetary and human resource cost of CKD is exorbitant. Socio-economic factors, along with other factors (genetic and environmental) may significantly influence the timing and display of phenotypic expression in fetuses and neonates at risk for developing CKD, yet very few of these factors are studied or well understood. In general our focus has been directed at treatment once CKD is established. This strategy has been and remains short-sighted and costly. Earlier understanding of the intrauterine determinants of renal mass development (i.e. environmental "biomes", poor maternal-fetal health, socio-economic factors impacting early life events, diet, access to value based health care and educational opportunities on disease evolution) may allow us an opportunity for earlier intervention. This article aims to provide some foundation for improved understanding of the maternal determinants of renal mass and function in the fetus and neonate.

Prevalence of risk factors for cardiovascular and kidney disease in Brazilian healthy preschool children

AIM

To investigate the prevalence of nutritional parameters of risk for cardiovascular disease (CVD) and kidney diseases in healthy preschool children.

METHODS

This is an observational cross-sectional study with 60 healthy children, of both genders, aged two to six years old and 56 mothers, in Belo Horizonte, Minas Gerais, Brazil. Preschool children and their families with regular activities at public schools were invited to paticipate in the study. The following characteristics were assessed: Socio-demographic condictions, clinical health, anthropometric, biochemical, lifestyle and data on food consumption. The 56 healthy children were divided into two groups, overweight (C1) and non-overweight (C2), as well as their mothers, respectively, in overweight (M1) and non-overweight (M2). Nutritional status was defined according to results obtained through the Anthro^® Software for nutritional analysis.

RESULTS

Thirty-five children were male, with mean age of 4.44 ± 1.0 years old. Eighty-nine percent of them were eutrophic, 86.7% were sedentary and they had five meals a day. Body mass index (BMI) for age and total cholesterol (TC) was higher on C1 (P = 0.0001) and high density lipoprotein cholesterol (HDL-c) was higher on C2. Mothers were 32.5 ± 7.1 years old, mostly married and employed. Eighty-six percent of them were sedentary and 62.5% were overweight with BMI = 26.38 ± 5.07 kg/m². Eighteen percent of the overweight mothers had isolated total hypercholesterolemia (TC levels elevated) and 12.5% had low HDL-c levels. The present study showed an association between overweight and obesity during the preschool years and the correspondent mothers’ nutritional status of overweight and obesity (OR = 4.96; 95%CI: 0.558-44.17). There was a positive correlation between the food risk associated with CVD by children and mothers when their consumption was 4 times/wk (P = 0.049; r = 0.516) or daily (P = 0.000008; r = 0.892).

CONCLUSION

Analyzed children showed high rates of physical inactivity, high serum cholesterol levels and high consumption of food associated with risk for CVD and renal disease. Changes in habits should be encouraged early in kindergarten.

Assessment of glomerular filtration rate in the neonate: is creatinine the best tool?

PURPOSE OF REVIEW

This article answers the question of whether creatinine is the best biomarker for monitoring neonatal glomerular filtration rate (GFR) in view of recent advances in measuring neonatal renal function.

RECENT FINDINGS

We rely largely on serum creatinine for the estimation of GFR in the newborn, even though creatinine is freely exchanged through the placenta. During the first few days of life, the serum creatinine reflects maternal renal function or the maternal creatinine. Back filtration of creatinine in preterm newborns is also a serious limitation. This review summarizes current knowledge on the prenatal and postnatal handling of creatinine as well as that of other, more novel biomarkers of GFR, such as cystatin C (CysC) and β-trace protein (BTP). Only small amounts of CysC cross the placenta, whereas BTP does not cross the placenta at all. However, BTP measurements are not widely available. Recent studies on renal volumetry are also discussed.

SUMMARY

Currently, CysC may be the most suitable marker of neonatal renal function, but its availability is still limited, it is more costly, and the best method of reporting acute kidney injury and neonatal estimated GFR remains to be established.

Statistical analyses in trials for the comprehensive understanding of organogenesis and histogenesis in humans and mice

Statistical analyses based on the quantitative data from real multicellular organisms are useful as inductive-type studies to analyse complex morphogenetic events in addition to deductive-type analyses using mathematical models. Here, we introduce several of our trials for the statistical analysis of organogenesis and histogenesis of human and mouse embryos and foetuses. Multidimensional scaling has been applied to prove the existence and examine the mode of interkinetic nuclear migration, a regulatory mechanism of stem cell proliferation/differentiation in epithelial tubular tissues. Several statistical methods were used on morphometric data from human foetuses to establish the multidimensional standard growth curve and to describe the relation among the developing organs and body parts. Although the results are still limited, we show that these analyses are not only useful to understand the normal and abnormal morphogenesis in humans and mice but also to provide clues that could correlate aspects of prenatal developmental events with postnatal diseases.

Factors associated with a vicious cycle involving a low nephron number, hypertension and chronic kidney disease

It has been reported that there is substantial variation in the nephron number between individuals. Previous studies using autopsy kidneys have demonstrated that a low nephron number, in relation to a low birth weight, may result in hypertension (HTN) and/or chronic kidney disease (CKD). However, recent studies have revealed that the association between a low nephron number and HTN is not a universal finding. This observation indicates that a low nephron number is unlikely to be the sole factor contributing to an elevated blood pressure. In addition to the nephron number, various genetic and congenital factors may contribute to increased susceptibility to HTN and/or CKD in a complex manner. Acquired factors, including aging, obesity and related metabolic abnormalities, and various causes of renal injury, may additionally promote further nephron loss. Such a vicious cycle may induce HTN and/or CKD via the common mechanisms of renal hemodynamic maladaptation.

Protective role of female gender in programmed accelerated renal aging in the rat

The aging kidney exhibits a progressive decline in glomerular filtration rate, accompanied by inflammatory and oxidative damage. We hypothesized that accelerated, age-related progression of renal injury is ovarian hormones-dependant. To address this we used an established model of developmentally programmed accelerated renal aging in the rat, superimposed by ovariectomy to assess interactions between ovarian hormones and the aging process. Under our experimental conditions, we found that kidney function worsens with age, that is GFR reduces over 18 month analyzed time-course and this was worsened by fetal exposure to maternal low-protein diet and absence of estrogen. Reduction in GFR was followed by increases in albuminuria, proteinuria, inflammatory markers, and tissue carbonyls, all suggesting inflammatory response and oxidative stress. This was associated with changes in AGTR2 expression which was greater at 18 months of age compared to earlier time points, but in MLP offspring only. Our studies show an influence of ovarian hormones on programmed accelerated renal aging and the AGTR2 across the lifespan. The main findings are that ovariectomy is a risk factor for increased aging-related renal injury and that this and oxidative damage might be related to changes in AGTR2 expression.

Early-life course socioeconomic factors and chronic kidney disease

Kidney failure or ESRD affects approximately 650,000 Americans, whereas the number with earlier stages of CKD is much higher. Although CKD and ESRD are usually associated with adulthood, it is likely that the initial stages of CKD begin early in life. Many of these pathways are associated with low birth weight and disadvantaged socioeconomic status (SES) in childhood, translating childhood risk into later-life CKD and kidney failure. Social factors are thought to be fundamental causes of disease. Although the relationship between adult SES and CKD has been well established, the role of early childhood SES for CKD risk remains obscure. This review provides a rationale for examining the association between early-life SES and CKD. By collecting data on early-life SES and CKD, the interaction with other periods in the life course could also be studied, allowing for examination of whether SES trajectories (eg, poverty followed by affluence) or cumulative burden (eg, poverty at multiple time points) are more relevant to lifetime CKD risk.

GDNF and MAPK-ERK pathway signaling is reduced during nephrogenesis following maternal under-nutrition

Maternal under-nutrition (MUN) during gestation results in growth-restricted newborns with reduced glomerular number and subsequent hypertension. We investigated dysregulation of glial derived neurotrophic factor (GDNF) and MAPK-ERK (mitogen-activated protein kinase-extracellular signal-regulated protein kinase) signal pathway gene expression following MUN. MUN rats were 50% food restricted from embryonic day 10 till postnatal day 1. Kidneys were harvested at embryonic day (E)20, and postnatal days (P)1 and 21. Kidney protein expression was determined by Western blot. At E20, protein expression of growth factor receptor alpha 1 (GFRα1) and phosphorylated ERK1/2 and mitogen-activated protein kinase kinase (MEK)1/2 were reduced significantly, and immunohistochemistry confirmed reduction of phosphorylated ERK (pERK) with maintenance of pERK localization. Total MEK and ERK were unchanged. At P1, only GFRα1 and pERK1/2 were reduced significantly while at P21, expression of all growth factors except total MEK was unchanged. Total MEK was increased. Glomerular number was decreased by 19% in P21 kidneys and blood pressure was increased in 12-week-old rats. In conclusion, GDNF and MAPK-ERK signaling are dysregulated during active nephrogenesis in fetal and early newborn offspring kidneys in the MUN model. This may be a key mechanism in reduced offspring nephrogenesis and programmed hypertension.

Maternal undernutrition upregulates apoptosis in offspring nephrogenesis

Maternal undernutrition (MUN) results in growth-restricted newborns with reduced nephron numbers that is associated with increased risk of hypertension and renal disease. The total adult complement of nephrons is set during nephrogenesis suggesting that MUN affects the staged development of nephrons in as yet unknown manner. A possible cause may be the increased renal apoptosis; therefore, we investigated whether apoptotic signaling and cell death were increased in MUN rat kidneys. Pregnant rat dams were fed an ad libitum diet [control] or were 50% food restricted (MUN) starting at embryonic day (E) 10. Male offspring kidneys (n = 5 each, MUN and control) were analyzed for mRNA using quantitative PCR (E20) and for protein expression using Western blotting and immunohistochemistry (E20 and postnatal day 1, P1). Apoptosis was measured by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Upregulation of pro-apoptotic protein expression was detected at E20 (Fas receptor, caspase 9) and at P1 (caspase 3, Bax). The anti-apoptotic factor Bcl2 was significantly decreased in P1 kidneys. Kidney TUNEL showed apoptotic nuclei significantly increased in the P1 nephrogenic zone (MUN 3.3 + 0.3 v. C 1.6 + 0.5, P = 0.002). The majority of apoptotic nuclei co-localized to mesenchyme and pretubular aggregates in the nephrogenic zone. Differential regulation of apoptosis in mesenchyme and pretubular aggregates following parturition suggests a mechanism for nephropenia in gestational programming of the kidney.

Simulated growth trajectories and blood pressure in adolescence: Hong Kong's Chinese Birth Cohort

BACKGROUND

Patterns and amounts of growth may determine adult blood pressure. Growth at different phases is correlated and affects current size, making effects on blood pressure difficult to distinguish. We decomposed growth to 13 years into independent associations with blood pressure and estimated how reaching the same size by different routes could affect adolescent blood pressure.

METHODS

Using estimates from partial least squares for the associations of birth weight, height, and BMI at 3 months, growth at 3-9 months, 9-36 months, 3-8 years and 8-13 years and size at 13 years with SBP and DBP in 5247 term births (67% follow-up) from Hong Kong's 'Children of 1997' Birth Cohort, we estimated SBP and DBP at 13 years for 99 simulated growth trajectories resulting in the same size using nonparametric bootstrapping.

RESULTS

High birth weight followed by slower growth was associated with lower SBP in both sexes and DBP in boys. Greater height to 3 years followed by slower height growth was associated with lower SBP in boys. Higher BMI until 9 months followed by slower BMI growth was associated with lower blood pressure in boys.

CONCLUSION

High birth weight or larger early size was associated with lower blood pressure if followed by slower later growth, consistent with the fetal origin hypothesis. However, whether these patterns are due to fetal and infant metabolic programming or to allowing slower growth at periods when rapid growth is harmful is unknown.

Vesicoureteric reflux and reflux nephropathy: from mouse models to childhood disease

Vesicoureteric reflux (VUR) is a common congenital urinary tract defect that predisposes children to recurrent kidney infections. Kidney infections can result in renal scarring or reflux nephropathy defined by the presence of chronic tubulo-interstitial inflammation and fibrosis that is a frequent cause of end-stage renal failure. The discovery of mouse models with VUR and with reflux nephropathy has provided new opportunities to understand the pathogenesis of these conditions and may provide insight on the genes and the associated phenotypes that need to be examined in human studies.

Ultrasonographic study of initial size and postnatal growth of kidneys in preterm infants

BACKGROUND

Preterm birth is known to be associated with risks of impaired nephrogenesis.

OBJECTIVES

To determine the normal range of renal sizes at birth in preterm infants as well as their short-term postnatal renal growth, to assess the correlation between initial renal size and growth parameters at birth and to compare the initial and serial renal sizes between appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) preterm infants.

METHODS

Initial ultrasonography (US) was prospectively performed in 125 preterm infants within the first 72 h of life and every 2 weeks thereafter until a postmenstrual age (PMA) of 37 weeks was reached. Correlation between renal size and growth parameters was investigated. Renal lengths of AGA and SGA preterm infants were compared with those of age-matched fetuses described in the literature.

RESULTS

The renal sizes at birth in preterm infants are presented. Multiple regression analysis showed the strongest correlation between initial renal size and birth weight (p < 0.0001). Initial renal lengths of AGA infants were not significantly different from those of age-matched fetuses at ≥30 weeks' gestational age (GA), whereas those of SGA infants were significantly smaller at ≥28 weeks' GA. Serial renal lengths of SGA infants were significantly smaller than fetal renal lengths at ≥30 weeks' GA.

CONCLUSION

With US, the normal range of initial renal sizes of AGA preterm infants was defined according to GA. In contrast to AGA infants, SGA infants showed smaller initial renal sizes and no significant catch-up growth until a PMA of 37 weeks.

Postnatal dietary omega-3 fatty acid supplementation rescues glucocorticoid-programmed adiposity, hypertension, and hyperlipidemia in male rat offspring raised on a high-fat diet

Fetal glucocorticoid excess programs several adverse outcomes in adult offspring, many of which can be prevented by postnatal, dietary omega-3 (n-3) fatty acids. Here we tested 2 separate hypotheses: 1) a postnatal high-fat diet exacerbates the glucocorticoid-programmed phenotype; and 2) postnatal, dietary n-3 fatty acids rescue programmed outcomes, even in the presence of a high-fat diet challenge. Pregnant Wistar rat dams were either untreated or administered dexamethasone acetate (Dex; 0.5 μg/mL drinking water) from day 13 of pregnancy. Offspring were cross-fostered to untreated mothers and males were weaned onto a standard (Std), high-fat, low n-3 (HF), or high-fat, high n-3 (HFHn-3) diet. Prenatal Dex reduced birth weight (26%) and delayed puberty onset by 1.2 days, irrespective of postnatal diet. Prenatal Dex programmed increased blood pressure in adult offspring, an effect worsened by the postnatal HF diet. Supplementation with high n-3 fatty acids, however, prevented both the Dex and HF-induced increases in blood pressure. Prenatal Dex also programmed increased adiposity, plasma cholesterol, and plasma triglyceride levels at 6 months of age, particularly in those offspring raised on the HF diet. But again, each of these adverse outcomes was rescued by supplementation of the HF diet with n-3 fatty acids. In conclusion, the capacity of n-3 fatty acids to overcome adverse programming outcomes remains evident, even in the presence of a HF diet challenge.

Bmp7 maintains undifferentiated kidney progenitor population and determines nephron numbers at birth

The number of nephrons, the functional units of the kidney, varies among individuals. A low nephron number at birth is associated with a risk of hypertension and the progression of renal insufficiency. The molecular mechanisms determining nephron number during embryogenesis have not yet been clarified. Germline knockout of bone morphogenetic protein 7 (Bmp7) results in massive apoptosis of the kidney progenitor cells and defects in early stages of nephrogenesis. This phenotype has precluded analysis of Bmp7 function in the later stage of nephrogenesis. In this study, utilization of conditional null allele of Bmp7 in combination with systemic inducible Cre deleter mice enabled us to analyze Bmp7 function at desired time points during kidney development, and to discover the novel function of Bmp7 to inhibit the precocious differentiation of the progenitor cells to nephron. Systemic knockout of Bmp7 in vivo after the initiation of kidney development results in the precocious differentiation of the kidney progenitor cells to nephron, in addition to the prominent apoptosis of progenitor cells. We also confirmed that in vitro knockout of Bmp7 in kidney explant culture results in the accelerated differentiation of progenitor population. Finally we utilized colony-forming assays and demonstrated that Bmp7 inhibits epithelialization and differentiation of the kidney progenitor cells. These results indicate that the function of Bmp7 to inhibit the precocious differentiation of the progenitor cells together with its anti-apoptotic effect on progenitor cells coordinately maintains renal progenitor pool in undifferentiated status, and determines the nephron number at birth.

Excess maternal salt intake produces sex-specific hypertension in offspring: putative roles for kidney and gastrointestinal sodium handling

Hypertension is common and contributes, via cardiovascular disease, towards a large proportion of adult deaths in the Western World. High salt intake leads to high blood pressure, even when occurring prior to birth – a mechanism purported to reside in altered kidney development and later function. Using a combination of in vitro and in vivo approaches we tested whether increased maternal salt intake influences fetal kidney development to render the adult individual more susceptible to salt retention and hypertension. We found that salt-loaded pregnant rat dams were hypernatraemic at day 20 gestation (147±5 vs. 128±5 mmoles/L). Increased extracellular salt impeded murine kidney development in vitro, but had little effect in vivo. Kidneys of the adult offspring had few structural or functional abnormalities, but male and female offspring were hypernatraemic (166±4 vs. 149±2 mmoles/L), with a marked increase in plasma corticosterone (e.g. male offspring; 11.9 [9.3–14.8] vs. 2.8 [2.0–8.3] nmol/L median [IQR]). Furthermore, adult male, but not female, offspring had higher mean arterial blood pressure (effect size, +16 [9–21] mm Hg; mean [95% C.I.]. With no clear indication that the kidneys of salt-exposed offspring retained more sodium per se, we conducted a preliminary investigation of their gastrointestinal electrolyte handling and found increased expression of proximal colon solute carrier family 9 (sodium/hydrogen exchanger), member 3 (SLC9A3) together with altered faecal characteristics and electrolyte handling, relative to control offspring. On the basis of these data we suggest that excess salt exposure, via maternal diet, at a vulnerable period of brain and gut development in the rat neonate lays the foundation for sustained increases in blood pressure later in life. Hence, our evidence further supports the argument that excess dietary salt should be avoided per se, particularly in the range of foods consumed by physiologically immature young.

Proximal nephron

The kidney plays a fundamental role in maintaining body salt and fluid balance and blood pressure homeostasis through the actions of its proximal and distal tubular segments of nephrons. However, proximal tubules are well recognized to exert a more prominent role than distal counterparts. Proximal tubules are responsible for reabsorbing approximately 65% of filtered load and most, if not all, of filtered amino acids, glucose, solutes, and low molecular weight proteins. Proximal tubules also play a key role in regulating acid-base balance by reabsorbing approximately 80% of filtered bicarbonate. The purpose of this review article is to provide a comprehensive overview of new insights and perspectives into current understanding of proximal tubules of nephrons, with an emphasis on the ultrastructure, molecular biology, cellular and integrative physiology, and the underlying signaling transduction mechanisms. The review is divided into three closely related sections. The first section focuses on the classification of nephrons and recent perspectives on the potential role of nephron numbers in human health and diseases. The second section reviews recent research on the structural and biochemical basis of proximal tubular function. The final section provides a comprehensive overview of new insights and perspectives in the physiological regulation of proximal tubular transport by vasoactive hormones. In the latter section, attention is particularly paid to new insights and perspectives learnt from recent cloning of transporters, development of transgenic animals with knockout or knockin of a particular gene of interest, and mapping of signaling pathways using microarrays and/or physiological proteomic approaches.

Association of low aerobic fitness with hyperfiltration and albuminuria in men

PURPOSE

The purpose of this study was to evaluate the association of low aerobic fitness (AF), a quantitative phenotype primarily modified by physical activity, with the earlier markers of chronic kidney disease (CKD).

METHODS

Maximum oxygen uptake (VO2max), the best index of AF, was estimated in an apparently healthy population of 34,769 adults without known history of diabetes and/or hypertension, and its association with renal function and albuminuria was analyzed retrospectively. VO2max was estimated using a cycle ergometer. Glomerular filtration rate was estimated with the Modification of Diet in Renal Disease Study equation. Glomerular hyperfiltration was defined as estimated glomerular filtration rate above the age- and sex-specific 97.5th percentile. Albuminuria was detected with dipstick urinalysis on fast morning urine and defined as ≥1+.

RESULTS

VO2max levels were negatively correlated with the odds ratios of glomerular hyperfiltration in men (Ptrend = 0.039), not in women. VO2max was associated with glomerular hyperfiltration in young men (≤ the median age; Ptrend < 0.001), but not in old men. VO2max levels were negatively correlated with the odds ratio of albuminuria in men (Ptrend < 0.001), but not in women. These findings suggest that low AF may be associated with earlier markers of CKD in men. This association was not observed in women.

CONCLUSION

From the results of this study, it can be concluded that low AF may be a possible independent, modifiable risk factor for CKD in men.

Short-term gestation, long-term risk: prematurity and chronic kidney disease

Thanks to remarkable advances in neonatal intensive care, infants who once had little chance for survival can now enter adulthood. Yet the consequences of premature birth or low birth weight (LBW) on nephrogenesis, final nephron number, and long-term kidney function are unclear. This review focuses on the theory, experimental evidence, and observational data that suggest an increased risk of chronic kidney disease (CKD) for infants born prematurely. Many premature and LBW infants begin life with an incomplete complement of immature nephrons. They are then exposed to a variety of external stressors that can hinder ongoing kidney development or cause additional nephron loss such as hemodynamic alterations, nephrotoxic medications, infections, and suboptimal nutrition. Acute kidney injury, in particular, may be a significant risk factor for the development of CKD. According to Brenner's hypothesis, patients with decreased nephron number develop hyperfiltration that results in sodium retention, hypertension, nephron loss, and CKD due to secondary focal segmental glomerulosclerosis. Because the risk of CKD in premature and LBW infants has not been accurately determined, there are no evidence-based recommendations for screening or management. Yet with the first generation of infants from the surfactant era only now reaching adulthood, it is possible that there is already an unrecognized epidemic of CKD. We suggest individualized, risk-based assessments of premature and LBW infants due to the increased risk of CKD and call for additional research into the long-term risk for CKD these infants face.

Risk factors for renal injury in children with a solitary functioning kidney

OBJECTIVE

The hyperfiltration hypothesis implies that children with a solitary functioning kidney are at risk to develop hypertension, proteinuria, and chronic kidney disease. We sought to determine the presenting age of renal injury and identify risk factors for children with a solitary functioning kidney.

METHODS

We evaluated 407 patients for signs of renal injury, defined as hypertension, proteinuria, an impaired glomerular filtration rate, and/or the use of renoprotective medication. Patients were subdivided on the basis of type of solitary functioning kidney and the presence of ipsilateral congenital anomalies of the kidney and urinary tract (CAKUT). The development of renal injury was analyzed with Kaplan-Meier analysis. Risk factors were identified by using logistic regression models.

RESULTS

Renal injury was found in 37% of all children. Development of renal injury increased by presence of ipsilateral CAKUT (odds ratio [OR] 1.66; P = .04) and age (OR 1.09; P < .001). Renal length was inversely associated with the risk to develop renal injury (OR 0.91; P = .04). In all patients, the median time to renal injury was 14.8 years (95% confidence interval 13.7-16.0 years). This was significantly shortened for patients with ipsilateral CAKUT (12.8 years, 95% confidence interval 10.6-15.1 years).

CONCLUSIONS

Our study determines independent risk factors for renal injury in children with a solitary functioning kidney. Because many children develop renal injury, we emphasize the need for clinical follow-up in these patients starting at birth.

Safety in glomerular numbers

A low nephron number is, according to Brenner's hyperfiltration hypothesis, associated with hypertension, glomerular damage and proteinuria, and starts a vicious cycle that ends in renal failure over the long term. Nephron endowment is set during foetal life, and there is no formation of nephrons after 34-36 weeks of gestation, indicating that many factors before that time-point may have an impact on kidney development and reduce nephron numbers. Such factors include maternal malnutrition, stress, diseases, such as diabetes, uteroplacental insufficiency, maternal and neonatal drugs and premature birth. However, other congenital anomalies, such as renal hypoplasia, unilateral renal agenesis or multicystic dysplastic kidney, may also lead to a reduced nephron endowment, with an increased risk for hypertension, renal dysfunction and the need for renal replacement therapy. This review focuses on the causes and consequences of a low nephron endowment and will illustrate why there is safety in glomerular numbers.

Early programming of adult blood pressure in the low birth weight Yucatan miniature pig is exacerbated by a post-weaning high-salt-fat-sugar diet

We previously demonstrated that intra-uterine growth-restricted (IUGR) Yucatan miniature pigs develop modestly elevated blood pressure (BP) as young adults. The present study evaluated the effects of a post-weaning Western-style, high-salt-fat-sugar (HSFS) diet on early programming of BP. IUGR piglets (3 d old, 0·77 (sem 0·04) kg, n 6) were paired with normal weight (NW) same-sex littermates (1·14 (sem 0·03) kg, n 6) and fed milk replacer for 4 weeks. A third littermate was left with the sow (SF; 1·01 (sem 0·05) kg, n 6). When 4 weeks old, all pigs were placed on a HSFS diet ad libitum for 5 h/d. When 11 months old, telemeters were implanted to measure BP in pigs before (4·5 % NaCl) and after (0·5 % NaCl) a 7 d reduced salt challenge. At necropsy, nephron numbers were determined. Before sexual maturity, IUGR pigs had greater relative feed intake (P < 0·05), and experienced catch-up growth with greater adiposity, with correlations between adiposity and BP (P < 0·05). Adult IUGR pigs had 26–34 % fewer nephrons and higher diastolic BP (107·7 (sem 4·9) mmHg, P = 0·044) than NW (97·2 (sem 1·8) mmHg) and SF (98·9 (sem 5·3) mmHg) pigs. Systolic BP was similar among the three groups, but was significantly elevated compared with levels previously reported for a control diet. Salt restriction reduced BP in all groups (P < 0·05), but with no differences (P>0·05) in the degree of salt sensitivity among groups. In conclusion, a post-weaning Western-style diet exacerbates early programming of diastolic BP in Yucatan miniature swine, whereas systolic BP is more sensitive to postnatal diet.

Can we predict hypertension among preterm children?

Prematurity and low birth weight (LBW) cause hypertension (HTN), ischemic heart disease, and obesity in young adults. The objective of the study was to identify risk factors for the development of HTN in children born preterm or at a LBW and to assess pediatricians' awareness of the problem. A retrospective review of 160 cases was conducted. In total, 22% of babies born preterm/LBW developed HTN by age 15 years. The odds of developing HTN were 1.6 times greater for every one standard deviation increase in body mass index. Higher risk posses for those born small for gestational age and under 1000 g. Of the 35 cases of HTN identified, only 31% were recognized as abnormal by the primary care providers. The development of obesity and HTN appear related in preterm/LBW children. Awareness of prematurity or LBW as a risk factor for HTN should be raised among pediatric primary care providers.

Both high and low maternal salt intake in pregnancy alter kidney development in the offspring

In humans, low glomerular numbers are related to hypertension, cardiovascular, and renal disease in adult life. The present study was designed 1) to explore whether above- or below-normal dietary salt intake during pregnancy influences nephron number and blood pressure in the offspring and 2) to identify potential mechanisms in kidney development modified by maternal sodium intake. Sprague-Dawley rats were fed low (0.07%)-, intermediate (0.51%)-, or high (3.0%)-sodium diets during pregnancy and lactation. The offspring were weaned at 4 wk and subsequently kept on a 0.51% sodium diet. The kidney structure was assessed at postnatal weeks 1 and 12 and the expression of proteins of interest at term and at week 1. Blood pressure was measured in male offspring by telemetry from postnatal month 2 to postnatal month 9. The numbers of glomeruli at weeks 1 and 12 were significantly lower and, in males, telemetrically measured mean arterial blood pressure after month 5 was higher in offspring of dams on a high- or low- compared with intermediate-sodium diet. A high-salt diet was paralleled by higher concentrations of marinobufagenin in the amniotic fluid and an increase in the expression of both sprouty-1 and glial cell-derived neutrophic factor in the offspring's kidney. The expression of FGF-10 was lower in offspring of dams on a low-sodium diet, and the expression of Pax-2 and FGF-2 was lower in offspring of dams on a high-sodium diet. Both excessively high and excessively low sodium intakes during pregnancy modify protein expression in offspring kidneys and reduce the final number of glomeruli, predisposing the risk of hypertension later in life.

Renal injury in children with a solitary functioning kidney--the KIMONO study

BACKGROUND

Children with a solitary functioning kidney (SFK) have an increased risk of developing hypertension, albuminuria and chronic kidney disease in later life. This renal injury is hypothesized to be caused by glomerular hyperfiltration that follows renal mass reduction in animal studies. Furthermore, children with an SFK show a high incidence of congenital anomalies of the kidney and urinary tract (CAKUT), which could further compromise renal function.

METHODS

A retrospective study of renal injury markers was performed in 206 children, divided into groups based on the origin of SFK [primary (congenital) SFK (n = 116) and secondary SFK (n = 90)]. Data on ipsilateral CAKUT were stratified separately. For blood pressure, albuminuria and glomerular filtration rate, longitudinal models were additionally developed using generalized estimated equation analysis.

RESULTS

Renal injury, defined as the presence of hypertension and/or albuminuria and/or the use of renoprotective medication, was present in 32% of all children with an SFK at a mean age of 9.5 (SD 5.6) years. Children with ipsilateral CAKUT had higher proportions of renal injury (48.3 versus 24.6%, P < 0.05). Furthermore, longitudinal models showed a decrease in glomerular filtration rate in both groups from the beginning of puberty onwards.

CONCLUSIONS

This large cohort study demonstrates that renal injury is present in children with an SFK at a young age, whereas our longitudinal models show an increased risk for chronic kidney disease in adulthood. Renal injury is even more pronounced in the presence of ipsilateral CAKUT. Therefore, we underline that clinical follow-up of all children with an SFK is needed.

Altered health outcomes in adult offspring of Sprague Dawley and Wistar rats undernourished during early or late pregnancy

BACKGROUND

Birth weight in humans has been inversely associated with adult disease risk. Results of animal studies have varied depending on species, strain, and treatment.

METHODS

We compared birth weight and adult health in offspring following 50% maternal undernutrition on gestation days (GD) 1-15 (UN1-15) or GD 10-21 (UN10-21) in Sprague Dawley and Wistar rats. Offspring from food-deprived dams were weighed and cross-fostered to control dams. Litters were weighed during lactation and initiating at weaning males were fed either control or a high-fat diet. Young and mature adult offspring were evaluated for obesity, blood pressure (BP), insulin response to oral glucose, and serum lipids. Nephron endowment, renal glucocorticoid receptor, and renin-aldosterone-angiotensin system components were measured.

RESULTS

The UN10-21 groups had birth weights lower than controls and transient catch up growth by weaning. Neither strain demonstrated obesity or dyslipidemia following prenatal undernutrition, but long-term body weight deficits occurred in the UN groups of both strains. High-fat diet fed offspring gained more weight than control offspring without an effect of prenatal nutrition. Sprague Dawley were slightly more susceptible than Wistar rats to altered insulin response and increased BP following gestational undernutrition. Nephron endowment in Sprague Dawley but not Wistar offspring was lower in the UN10-21 groups. Glucocorticoid and renin-aldosterone-angiotensin system pathways were not altered.

CONCLUSIONS

The most consistent effect of maternal undernutrition was elevated BP in offspring. Long-term health effects occurred with undernutrition during either window, but the UN10-21 period resulted in lower birth weight and more severe adult health effects.

Early glomerular alterations in genetically determined low nephron number

An association between low nephron number and subsequent development of hypertension in later life has been demonstrated. The underlying pathomechanisms are unknown, but glomerular and postglomerular changes have been discussed. We investigated whether such changes are already present in prehypertensive “glial cell line-derived neurotrophic growth factor” heterozygous mice (GDNF+/−) with lower nephron number. Twenty-six-week-old mice [22 GDNF+/−, 29 C57B6 wild-type control (wt)] were used for in vivo experiments with intra-arterial and tail cuff blood pressure measurements. After perfusion fixation, kidneys were investigated with morphological, morphometric, stereological, and immunohistochemical techniques and TaqMan PCR analysis. As expected at this age, blood pressure was comparable between GDNF+/− and wt. Nephron number per kidney was significantly lower in GDNF+/− than in wt (−32.8%, P < 0.005), and mean glomerular volume was significantly higher (+49.5%, P < 0.001). Renal damage scores, glomerular and tubular proliferation, analysis of intrarenal arteries and peritubular capillaries, expression of relevant tubular transporter proteins, as well as gene expression of profibrotic, proinflammatory, or prohypertensive markers were not significantly different between GDNF+/− and wt. Compensatory glomerular hypertrophy in GDNF+/− was accompanied by higher numbers of endothelial and mesangial cells as well as PCNA-positive glomerular cells, whereas podocyte density was significantly reduced. Further electron microscopic analysis showed marked thickening of glomerular basement membrane. In conclusion, lower nephron number is associated with marked early glomerular structural changes, in particular lower capillary supply, reduced podocyte density, and thickened glomerular basement membrane, that may predispose to glomerular sclerosis.

Maternal undernourished fetal kidneys exhibit differential regulation of nephrogenic genes including downregulation of the Notch signaling pathway

Maternal undernutrition results in offspring nephron number reduction and hypertension that are hypothesized to begin as compensatory changes in fetal gene expression during gestation. To evaluate mechanisms of dysregulated nephrogenesis, pregnant Sprague Dawley rats were 50% food restricted from embryonic day (E) 10 to E20. At E20, fetal male kidneys were examined by microarray analysis. A total of 476 differentially expressed transcripts were detected including those regulating development and differentiation, mitosis and cell cycle, chromatin assembly, and steroid hormone regulation. Differentially regulated genes were detected in MAPK/ERK, Wnt, and Notch signaling pathways. Validation of the microarray results was performed for the Notch signaling pathway, an important pathway in nephron formation. Protein expression of Notch pathway factors by Western blotting showed significantly decreased Notch2 and downstream effector Hey1 protein expression, while Ctbp1 co-repressor was increased. These data together show that maternal undernutrition results in developmental disruption in fetal nephrogenesis gene expression signaling.

Individual variation in organ histogenesis as a causative factor in the developmental origins of health and disease: unnoticed congenital anomalies?

Morphological studies of congenital anomalies have mainly focused on abnormal shape (i.e. malformation) and thus on disturbed organogenesis. However, in regard to postnatal functions of organs that develop through branching mechanisms, organ size is another important morphological feature. These organs consist of a large number of structural and functional units, such as nephrons in the kidney, and the total number of these units, that is approximately proportional to the organ size, has been shown to vary widely among individuals. Organ-specific cells are differentiated and organized to form structural units and realize organ-specific functions during the histogenetic period (i.e. from mid-gestation to the early postnatal period). The total number of units is attained at the end of histogenesis and determines the total functional capacity, including the functional reserve of the organ, and thus may be related to predispositions to postnatal organ-based diseases, because the functional reserve decreases during the course of life and eventually become short of the minimum requirement of each organ. Therefore, it may be hypothesized that a smaller number of units of organs at the end of histogenesis is one of the predisposing factors for postnatal diseases (i.e. a form of unnoticed but late-manifested congenital anomalies), in this era of extended longevity. However, the mechanisms that control the total number of units in each organ during histogenesis and the possible relationship among the numbers of units in different organs remain unknown. Here, we review our trials based on the above hypothesis in order to (1) mathematically analyze the morphometric data of the different organs in fetuses to elucidate relationship among developing organs, (2) analyze the developing neuro-immuno-endocrine network as a series of mechanisms to systemically correlate the histogenesis of multiple organs, and (3) examine the maternal environment, including dietary fat, as a factor to influence histogenesis and thus the predisposition to type 1 diabetes.

Amplification of the association between birthweight and blood pressure with age: the Bogalusa Heart Study

OBJECTIVES

Although low birthweight is associated with elevated blood pressure (BP) levels, whether the strength of this relationship is amplified with age is still debated. This study tested the hypothesis that the magnitude of the birthweight-BP association increases with age from childhood to adulthood.

METHODS

The study cohort included 6251 individuals (64.5% whites and 35.6% blacks, 50.0% males) enrolled in the Bogalusa Heart Study. Individuals were examined 1-15 times for BP from childhood to adulthood, with 24 363 observations. Information on birthweight and gestational age was obtained from Louisiana State birth certificates.

RESULTS

After adjusting for race, sex, age and gestational age, low birthweight (kg) was associated with higher SBP levels (mmHg) in adolescence (aged 12-17 years, regression coefficient β = -0.80, P = 0.004) and adulthood (aged 18-50 years, β = -1.34, P = 0.010). Adjustment for current BMI yielded considerably stronger association. Importantly, the magnitude of the birthweight-SBP relationship, measured as standardized β(unit = SD), was significantly amplified with increasing age, regardless of adjustment for current BMI and race. Further, the strengthened association (the increase in standardized β ranging 0.02-0.12) by adjustment for current BMI was closely related to the BMI-SBP and birthweight-BMI correlations, especially noted in childhood.

CONCLUSION

These findings on the potentiating effect of increasing age on the birthweight-BP relationship suggest that the fetal programming and the increasing cumulative burden with age of unhealthy lifestyle behaviors affect the development of adult hypertension in a synergistic manner.

Renal function and volume of infants born with a very low birth-weight: a preliminary cross-sectional study

AIM

The aim of our study was to compare the function and volumes of kidneys of very low birth-weight (VLBW) and of extremely low birth-weight (ELBW) infants at pre-school ages.

PATIENTS AND METHODS

We did a revision of the neonatal records of infants born in our hospital that weighed < or =1500 g at birth. The children were divided into two groups according to their weight at birth: ELBW (<1000 g) and VLBW (1000-1500 g). At the age of 5.7 +/- 1.4 years, the children underwent clinical, laboratory and ultrasound renal assessments.

RESULTS

Sixty-nine children fulfilled the requirements for the study. The rate of neonatal treatment with aminoglycosides was higher in ELBW preterms. Renal function parameters, i.e. estimated glomerular filtration rate and albuminuria, did not differ between the two groups of children. Urinary alpha1-microglobulin excretion was significantly higher and kidneys were significantly smaller in the ELBW group than in the VLBW group.

CONCLUSION

No impairment or differences in renal parameters were found in pre-school children born ELBW compared with those born with VLBW, except for differences in kidney volume, renal cortical thickness and urinary alpha1-microglobulin excretion. Thus, patients born with ELBW would require a longer follow-up period.

Perinatal nutrient restriction reduces nephron endowment increasing renal morbidity in adulthood: a review

Perinatal malnutrition has been included among the causes of renal disease in adulthood. Here, we consider the relationships between early supply of specific nutrients (such as protein, fat, vitamins and electrolytes) and renal endowment. Prenatal and postnatal nutrition mismatch is also discussed. In addition, this article presents the role of nutrition of both mothers and pre-term infants on nephron endowment, with final practical considerations.

Fetal origins of renal disparities

Epidemiologic studies of populations continue to emerge showing that early-life factors influence the risk of developing several chronic diseases of adulthood. Susceptibility to environmental factors is particularly problematic during renal development, which is not complete until 36 weeks of gestation. Environmental deprivation may lead to adaptations including early growth restriction, whereas late insults may alter the kidney during the final stages of development. Because disparities among those who are more likely to have low birth weight mirrors the disparities observed among those more likely to develop kidney-related disorders, fetal origins have been presumed to explain some of the observed disparities. Although current empiric evidence supports a link between fetal programming and childhood/adult kidney disease, affected pathways may vary by race.