Maternal nutrition, low nephron number and arterial hypertension in later life

Various Organ Damages in Rats with Fetal Growth Restriction and Their Slight Attenuation by Bifidobacterium breve Supplementation

Children with fetal growth restriction (FGR) and its resultant low birthweight (LBW) are at a higher risk of developing various health problems later in life, including renal diseases, metabolic syndrome, and sarcopenia. The mechanism through which LBW caused by intrauterine hypoperfusion leads to these health problems has not been properly investigated. Oral supplementation with probiotics is expected to reduce these risks in children. In the present study, rat pups born with FGR-LBW after mild intrauterine hypoperfusion were supplemented with either Bifidobacterium breve (B. breve) or a vehicle from postnatal day 1 (P1) to P21. Splanchnic organs and skeletal muscles were evaluated at six weeks of age. Compared with the sham group, the LBW-vehicle group presented significant changes as follows: overgrowth from infancy to childhood; lighter weight of the liver, kidneys, and gastrocnemius and plantaris muscles; reduced height of villi in the ileum; and increased depth of crypts in the jejunum. Some of these changes were milder in the LBW-B.breve group. In conclusion, this rat model could be useful for investigating the mechanisms of how FGR-LBW leads to future health problems and for developing interventions for these problems. Supplementation with B. breve in early life may modestly attenuate these problems.

Histone deacetylases 1 and 2 target gene regulatory networks of nephron progenitors to control nephrogenesis

Our studies demonstrated the critical role of Histone deacetylases (HDACs) in the regulation of nephrogenesis. To better understand the key pathways regulated by HDAC1/2 in early nephrogenesis, we performed chromatin immunoprecipitation sequencing (ChIP-Seq) of HDAC1/2 on isolated nephron progenitor cells (NPCs) from mouse E16.5 kidneys. Our analysis revealed that 11,802 (40.4%) of HDAC1 peaks overlap with HDAC2 peaks, further demonstrates the redundant role of HDAC1 and HDAC2 during nephrogenesis. Common HDAC1/2 peaks are densely concentrated close to the transcriptional start site (TSS). GREAT Gene Ontology analysis of overlapping HDAC1/2 peaks reveals that HDAC1/2 are associated with metanephric nephron morphogenesis, chromatin assembly or disassembly, as well as other DNA checkpoints. Pathway analysis shows that negative regulation of Wnt signaling pathway is one of HDAC1/2's most significant function in NPCs. Known motif analysis indicated that Hdac1 is enriched in motifs for Six2, Hox family, and Tcf family members, which are essential for self-renewal and differentiation of nephron progenitors. Interestingly, we found the enrichment of HDAC1/2 at the enhancer and promoter regions of actively transcribed genes, especially those concerned with NPC self-renewal. HDAC1/2 simultaneously activate or repress the expression of different genes to maintain the cellular state of nephron progenitors. We used the Integrative Genomics Viewer to visualize these target genes associated with each function and found that HDAC1/2 co-bound to the enhancers or/and promoters of genes associated with nephron morphogenesis, differentiation, and cell cycle control. Taken together, our ChIP-Seq analysis demonstrates that HDAC1/2 directly regulate the molecular cascades essential for nephrogenesis.

Novel intrauterine growth retardation model: effects of maternal subtotal nephrectomy on neonates

Changes in body weight (BW), systolic blood pressure (SBP), and localization of renin in the kidneys of neonates born to normal mothers (C neonates) or to five-sixths (5/6) nephrectomized (2/3 left kidney and right kidney) mothers (Nx neonates) were studied. Maternal 5/6 nephrectomy caused weight loss in neonates but no differences in SBP or renin localization. Culling Nx neonates to a litter of 3 at 1 day after birth resulted in growth catching up with C neonates from 3 weeks old and increases in both SBP and renin-positive cells in neonatal kidney. These findings revealed that maternal 5/6 nephrectomy results in low-birth-weight neonates and that these neonates are at increased risk of metabolic syndrome by catch-up growth.

Insights into the Mechanisms of Fetal Growth Restriction-Induced Programming of Hypertension

In recent decades, both clinical and animal studies have shown that fetal growth restriction (FGR), caused by exposure to adverse uterine environments, is a risk factor for hypertension as well as for a variety of adult diseases. This observation has shaped and informed the now widely accepted theory of developmental origins of health and disease (DOHaD). There is a plethora of evidence supporting the association of FGR with increased risk of adult hypertension; however, the underlying mechanisms responsible for this correlation remain unclear. This review aims to explain the current advances in the field of fetal programming of hypertension and a brief narration of the underlying mechanisms that may link FGR to increased risk of adult hypertension. We explain the theory of DOHaD and then provide evidence from both clinical and basic science research which support the theory of fetal programming of adult hypertension. In addition, we have explored the underlying mechanisms that may link FGR to an increased risk of adult hypertension. These mechanisms include epigenetic changes, metabolic disorders, vascular dysfunction, neurohormonal impairment, and alterations in renal physiology and function. We further describe sex differences seen in the developmental origins of hypertension and provide insights into the opportunities and challenges present in this field.

Metabolic programming of nephron progenitor cell fate

Metabolic pathways are one of the first responses at the cellular level to maternal/fetal interface stressors. Studies have revealed the previously unrecognized contributions of intermediary metabolism to developmental programs. Here, we provide an overview of cellular metabolic pathways and the cues that modulate metabolic states. We discuss the developmental and physiological implications of metabolic reprogramming and the key role of metabolites in epigenetic and epiproteomic modifications during embryonic development and with respect to kidney development and nephrogenesis.

Increasing mTORC1 Pathway Activity or Methionine Supplementation during Pregnancy Reverses the Negative Effect of Maternal Malnutrition on the Developing Kidney

BACKGROUND

Low nephron number at birth is associated with a high risk of CKD in adulthood because nephrogenesis is completed in utero. Poor intrauterine environment impairs nephron endowment via an undefined molecular mechanism. A calorie-restricted diet (CRD) mouse model examined the effect of malnutrition during pregnancy on nephron progenitor cells (NPCs).

METHODS

Daily caloric intake was reduced by 30% during pregnancy. mRNA expression, the cell cycle, and metabolic activity were evaluated in sorted Six2 NPCs. The results were validated using transgenic mice, oral nutrient supplementation, and organ cultures.

RESULTS

Maternal CRD is associated with low nephron number in offspring, compromising kidney function at an older age. RNA-seq identified cell cycle regulators and the mTORC1 pathway, among other pathways, that maternal malnutrition in NPCs modifies. Metabolomics analysis of NPCs singled out the methionine pathway as crucial for NPC proliferation and maintenance. Methionine deprivation reduced NPC proliferation and lowered NPC number per tip in embryonic kidney cultures, with rescue from methionine metabolite supplementation. Importantly, in vivo, the negative effect of caloric restriction on nephrogenesis was prevented by adding methionine to the otherwise restricted diet during pregnancy or by removing one Tsc1 allele in NPCs.

CONCLUSIONS

These findings show that mTORC1 signaling and methionine metabolism are central to the cellular and metabolic effects of malnutrition during pregnancy on NPCs, contributing to nephrogenesis and later, to kidney health in adulthood.

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.

Prenatal therapeutics and programming of cardiovascular function

Cardiovascular diseases (CVD) are a leading cause of mortality worldwide. Despite recognizing the importance of risk factors in dictating CVD susceptibility and onset, patient treatment remains a challenging endeavor. Increasingly, the benefits of prevention and mitigation of risk factors earlier in life are being acknowledged. The developmental origins of health and disease posits that insults during specific periods of development can influence long-term health outcomes; this occurs because the developing organism is highly plastic, and hence vulnerable to environmental perturbations. By extension, targeted therapeutics instituted during critical periods of development may confer long-term protection, and thus reduce the risk of CVD in later life. This review provides a brief overview of models of developmental programming, and then discusses the impact of perinatal therapeutic interventions on long-term cardiovascular function in the offspring. The discussion focuses on bioactive food components, as well as pharmacological agents currently approved for use in pregnancy; in short, those agents most likely to be used in pregnancy and early childhood.

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.

Perinatal and childhood exposure to environmental chemicals and blood pressure in children: a review of literature 2007-2017

Exposure to environmental chemicals during periods of renal development from embryogenesis to birth and through childhood can inform critical windows of nephrotoxicity, including changes in childhood blood pressure. This review assessed recent studies that examined the relationship of air pollution, metals, and other organic pollutants with children's blood pressure outcomes. We restricted this review to peer-reviewed studies published in English between January 2007 and July 2017. We identified a total of 36 articles that estimated associations with childhood blood pressure, of which 14 studies examined the effects of air pollution, 10 examined metals, and 12 examined other organic pollutants including phthalates (n = 4), Bisphenol A (n = 3), polychlorinated biphenols (n = 2), organophosphate pesticides (n = 2), or perfluoroalkyl acids (n = 1). Similar to the established relationship between tobacco smoke exposure and childhood blood pressure, the majority of studies that examined air pollutants, particularly exposure to PM10 and PM2.5, reported associations with increased childhood blood pressure. The literature reported conflicting evidence for metals, and putative evidence of the effects of exposure to phthalates, Bisphenol A, polychlorinated biphenols, and pesticides. Overall, our review underscores the need for additional studies that assess the impact of nephrotoxicant exposure during early life, particularly the perinatal period, and blood pressure in childhood.

A new model for fetal programming: maternal Ramadan-type fasting programs nephrogenesis

The effect of maternal Ramadan-type fasting (RTF) on the outcome of pregnancy, kidney development and nephron number in male rat offspring was investigated in current study. Pregnant rats were given food and water ad libitum during pregnancy (control) or restricted for 16 h per day (RTF). Kidney structure was examined during fetal life, at birth, and in early and late adulthood. Maternal body weight, food intake, relative food intake and plasma glucose levels were significantly lower (P<0.001) in the RTF group. Litter and pup weights also were significantly lower (P<0.05) in the RTF group at birth, with no difference in the litter size. The RTF group had a longer gestation, delayed nephrogenesis with less well-differentiated glomeruli, more connective tissue, fewer medullary rays, an increase in the nephrogenic zone/cortical zone ratio, and significant increase (P<0.001) in kidney apoptosis at birth. On the other hand, maternal fasting reduced nephron number (by ~31%) with unchanged kidney and total glomerular volumes. Mean glomerular volume was significantly higher in RTF offspring. Assessment of renal structure revealed mild glomerulosclerosis with enlarged lobulated glomeruli in the renal cortex and high interstitial fibrosis in the medulla of RTF kidneys. Taken together, gestational fasting delays nephrogenesis and reduces nephron number in the kidneys of the offspring, that could be partially owing to increased apoptosis.

Transplacental Nutrient Transport Mechanisms of Intrauterine Growth Restriction in Rodent Models and Humans

Although the causes of intrauterine growth restriction (IUGR) have been intensively investigated, important information is still lacking about the role of the placenta as a link from adverse maternal environment to adverse pregnancy outcomes of IUGR and preterm birth. IUGR is associated with an increased risk of cardiovascular, metabolic, and neurological diseases later in life. Determination of the most important pathways that regulate transplacental transport systems is necessary for identifying marker genes as diagnostic tools and for developing drugs that target the molecular pathways. Besides oxygen, the main nutrients required for appropriate fetal development and growth are glucose, amino acids, and fatty acids. Dysfunction in transplacental transport is caused by impairments in both placental morphology and blood flow, as well as by factors such as alterations in the expression of insulin-like growth factors and changes in the mTOR signaling pathway leading to a change in nutrient transport. Animal models are important tools for systematically studying such complex events. Debate centers on whether the rodent placenta is an appropriate tool for investigating the alterations in the human placenta that result in IUGR. This review provides an overview of the alterations in expression and activity of nutrient transporters and alterations in signaling associated with IUGR and compares these findings in rodents and humans. In general, the data obtained by studies of the various types of rodent and human nutrient transporters are similar. However, direct comparison is complicated by the fact that the results of such studies are controversial even within the same species, making the interpretation of the results challenging. This difficulty could be due to the absence of guidelines of the experimental design and, especially in humans, the use of trophoblast cell culture studies instead of clinical trials. Nonetheless, developing new therapy concepts for IUGR will require the use of animal models for gathering robust data about mechanisms leading to IUGR and for testing the effectiveness and safety of the intervention among pregnant women.

Regulation of Nephron Progenitor Cell Self-Renewal by Intermediary Metabolism

Nephron progenitor cells (NPCs) show an age-dependent capacity to balance self-renewal with differentiation. Older NPCs (postnatal day 0) exit the progenitor niche at a higher rate than younger (embryonic day 13.5) NPCs do. This behavior is reflected in the transcript profiles of young and old NPCs. Bioenergetic pathways have emerged as important regulators of stem cell fate. Here, we investigated the mechanisms underlying this regulation in murine NPCs. Upon isolation and culture in NPC renewal medium, younger NPCs displayed a higher glycolysis rate than older NPCs. Inhibition of glycolysis enhanced nephrogenesis in cultured embryonic kidneys, without increasing ureteric tree branching, and promoted mesenchymal-to-epithelial transition in cultured isolated metanephric mesenchyme. Cotreatment with a canonical Wnt signaling inhibitor attenuated but did not entirely block the increase in nephrogenesis observed after glycolysis inhibition. Furthermore, inhibition of the phosphatidylinositol 3-kinase/Akt self-renewal signaling pathway or stimulation of differentiation pathways in the NPC decreased glycolytic flux. Our findings suggest that glycolysis is a pivotal, cell-intrinsic determinant of NPC fate, with a high glycolytic flux supporting self-renewal and inhibition of glycolysis stimulating differentiation.

Adult Consequences of Extremely Preterm Birth: Cardiovascular and Metabolic Diseases Risk Factors, Mechanisms, and Prevention Avenues

Extremely preterm babies are exposed to various sources of injury during critical stages of development. The extremely preterm infant faces premature transition to ex utero physiology and undergoes adaptive mechanisms that may be deleterious in the long term because of permanent alterations in organ structure and function. Perinatal events can also directly cause structural injury. These disturbances induce morphologic and functional changes in their organ systems that might heighten their risks for later adult chronic diseases. This review examines the pathophysiology of programming of long-term health and diseases after preterm birth and associated perinatal risk factors.

Epigenetic Mechanisms of Transmission of Metabolic Disease across Generations

Both human and animal studies indicate that environmental exposures experienced during early life can robustly influence risk for adult disease. Moreover, environmental exposures experienced by parents during either intrauterine or postnatal life can also influence the health of their offspring, thus initiating a cycle of disease risk across generations. In this Perspective, we focus on epigenetic mechanisms in germ cells, including DNA methylation, histone modification, and non-coding RNAs, which collectively may provide a non-genetic molecular legacy of prior environmental exposures and influence transcriptional regulation, developmental trajectories, and adult disease risk in offspring.

Optimising the use of medicines to reduce acute kidney injury in children and babies

The majority of medications in children are administered in an unlicensed or off-label manner. Paediatricians are obliged to prescribe using the limited evidence available. The 2007 EU regulation on the use of paediatric drugs means pharmaceutical companies are now obliged to (and receive incentives for) contributing to paediatric drug data and carrying out paediatric clinical trials. This is important, as the efficacy and adverse effect profiles of medicines vary across childhood. Additionally, there are significant age-related changes in the pharmacodynamic and pharmacokinetic activity of many drugs. This may be related to physiological (differential expressions of cytochrome P450 enzymes or variable glomerular filtration rates at different ages for example) and psychological (increasing autonomy and risk perception in teenage years) changes. Increasing numbers of children are surviving life-threatening childhood conditions due to medical advances. This means there is an increasing population who are at risk of the consequences of the long-term, early exposure to nephrotoxic agents. The kidney is an organ that is particularly vulnerable to damage as a consequence of drugs. Drug-induced acute kidney injury (AKI) episodes in children and babies are principally due to non-steroidal anti-inflammatory drugs, antibiotics or chemotherapeutic agents. The renal tubules are vulnerable to injury because of their concentrating ability and high-energy hypoxic environment. This review focuses on drug-induced AKI and the methods to minimise its effect, including general management plus the role of child-specific pharmacokinetic data, the use of pharmacogenomics and early detection of AKI using urinary biomarkers and electronic triggers.

Fetal and organ development at gestational days 45, 90, 135 and at birth of lambs exposed to under- or over-nutrition during gestation,. Transl Anim Sci 2017;1:16-25. [PMID: 32704626 PMCID: PMC7235467 DOI: 10.2527/tas2016.0002]

To determine the effects of poor maternal nutrition on offspring body and organ growth during gestation, pregnant Western White-faced ewes (n = 82) were randomly assigned into a 3 × 4 factorial treatment structure at d 30.2 ± 0.2 of gestation (n = 5 to 7 ewes per treatment). Ewes were individually fed 100% (control), 60% (restricted) or 140% (over) of NRC requirements for TDN. Ewes were euthanized at d 45, 90 or 135 of gestation or underwent parturition (birth) and tissues were collected from the offspring (n = 10 to 15 offspring per treatment). Offspring from control, restricted and overfed ewes are referred to as CON, RES and OVER, respectively. Ewe data were analyzed as a completely randomized design and offspring data were analyzed as a split-plot design using PROC MIXED. Ewe BW did not differ at d 30 (P ≥ 0.43), however restricted ewes weighed less than overfed and overfed were heavier than controls at d 45, and restricted weighed less and overfed were heavier than controls at d 90 and 135 and birth (P ≤ 0.05). Ewe BCS was similar at d 30, 45 and 90 (P ≤ 0.07), however restricted ewes scored lower than control at d 135 and birth (P ≤ 0.05) and over ewes scored higher than control at d 135 (P ≤ 0.05) but not at birth (P = 0.06). A maternal diet by day of gestation interaction indicated that at birth the body weight (BW) of RES offspring was less than CON and OVER (P ≤ 0.04) and heart girth of RES was smaller than CON and OVER (P ≤ 0.004). There was no interaction of maternal diet and day of gestation on crown-rump, fetal, or nose occipital length, or orbit or umbilical diam. (P ≥ 0.31). A main effect of maternal diet indicated that the RES crown-rump length was shorter than CON and OVER (P ≤ 0.05). An interaction was observed for liver, kidney and renal fat (P ≤ 0.02). At d 45 the liver of RES offspring was larger than CON and OVER (P ≤ 0.002), but no differences observed at d 90, 135 or birth (P ≥ 0.07). At d 45, the kidneys of OVER offspring were larger than CON and RES (P ≤ 0.04), but no differences observed at d 90, 135 or birth (P ≥ 0.60). At d 135, OVER had more perirenal fat than CON and RES (P ≤ 0.03), and at birth RES had more perirenal fat than CON and OVER (P ≤ 0.04). There was no interaction observed for offspring heart weight, length or width, kidney length, adrenal gland weight, loin eye area or rib width (P ≥ 0.09). In conclusion, poor maternal nutrition differentially alters offspring body size and organ growth depending on the stage of gestation.

Fetal Alcohol Exposure Alters Blood Flow and Neurological Responses to Transient Cerebral Ischemia in Adult Mice

BACKGROUND

Prenatal alcohol exposure (PAE) can result in physical and neurocognitive deficits that are collectively termed "fetal alcohol spectrum disorders" (FASD). Although FASD is associated with lifelong intellectual disability, the mechanisms mediating the emergence of secondary mental health and physical disabilities are poorly understood. Based on our previous data showing that maternal ethanol (EtOH) exposure in mice resulted in an immediate reduction in cranially directed fetal blood flow, we hypothesized that such exposure would also result in persistent alterations in cranially directed blood flow in the prenatally alcohol-exposed (PAE) adult. We also hypothesized that PAE adults exposed to an acute cerebrovascular insult would exhibit more brain damage and neurobehavioral impairment compared to non-PAE adult controls.

METHODS

Pregnant C57BL/6 mice were exposed to EtOH, 3 g/kg, or water by intragastric gavage. Blood flow in carotid, renal, and femoral arteries was assessed by ultrasound imaging in PAE and control adults at 3, 6, and 12 months of age. To mimic ischemic stroke in young adult populations, 3-month-old PAE and control animals were subject to transient middle cerebral artery occlusion (MCAo) and subsequently assessed for behavioral recovery, stroke infarct volume, and brain cytokine profiles.

RESULTS

PAE resulted in a significant age-related decrease in blood acceleration in adult mice, specifically in the carotid artery. A unilateral transient MCAo resulted in equivalent cortico-striatal damage in both PAE and control adults. However, PAE adult mice exhibited significantly decreased poststroke behavioral recovery compared to controls.

CONCLUSIONS

Our data collectively show that PAE adult mice exhibit a persistent, long-term loss of cranially directed blood flow, and decreased capacity to compensate for brain trauma due to acute-onset adult diseases like ischemic stroke.

Spontaneous one-kidney rats are more susceptible to develop hypertension by DOCA-NaCl and subsequent kidney injury compared with uninephrectomized rats

There is little clinical data of how hypertension may influence individuals with nephron deficiency in the context of being born with a single kidney. We recently developed a new rat model (the heterogeneous stock-derived model of unilateral renal agenesis rat) that is born with a single kidney and exhibits progressive kidney injury and decline in kidney function with age. We hypothesized that DOCA-salt would induce a greater increase in blood pressure and therefore accelerate the progression of kidney injury in rats born with a solitary kidney compared with rats that have undergone unilateral nephrectomy. Time course evaluation of blood pressure, kidney injury, and renal hemodynamics was performed in the following six groups of animals from weeks 13 to 18: 1) DOCA-treated rats with a solitary kidney (DOCA+S group), 2) placebo-treated rats with a solitary kidney, 3) DOCA-treated control rats with two kidneys (DOCA+C group), 4) placebo-treated control rats with two kidneys, 5) DOCA-treated rats with two kidneys that underwent uninephrectomy (DOCA+UNX8 group), and 6) placebo-treated rats with two kidneys that underwent uninephrectomy. DOCA+S rats demonstrated a significant rise (P < 0.05) in blood pressure (192 ± 4 mmHg), proteinuria (205 ± 31 mg/24 h), and a decline in glomerular filtration rate (600 ± 42 μl·min(-1)·g kidney weight(-1)) relative to the DOCA+UNX8 (173 ± 3 mmHg, 76 ± 26 mg/24 h, and 963 ± 36 μl·min(-1)·g kidney weight(-1)) and DOCA+C (154 ± 2 mmHg, 7 ± 1 mg/24 h, and 1,484 ± 121 μl·min(-1)·g kidney weight(-1)) groups. Placebo-treated groups showed no significant change among the three groups. An assessment of renal injury markers via real-time PCR/Western blot analysis and histological analysis was concordant with the measured physiological parameters. In summary, congenital solitary kidney rats are highly susceptible to the induction of hypertension compared with uninephrectomized rats, suggesting that low nephron endowment is an important driver of elevated blood pressure, hastening nephron injury through the transmission of elevated systemic blood pressure and thereby accelerating decline in kidney function.

Maternal protein restriction that does not have an influence on the birthweight of the offspring induces morphological changes in kidneys reminiscent of phenotypes exhibited by intrauterine growth retardation rats

Severe restriction of maternal protein intake to 6-8% protein diet results in intrauterine growth retardation (IUGR), low birthweight and high risk of metabolic syndrome in the adult life of the offspring. However, little information is available on the effects of maternal protein restriction on offspring under the conditions that does not have an influence on their birthweight of the offspring,. In the present study, pregnant rats were kept on a diet consisting of either 9% (low-protein, Lp rats) or 18% (normal-protein, Np rats) protein by weight/volume/etc. After birth, both Lp and Np rats were kept on a diet containing 18% protein. Neonatal body weight was significantly lower in Lp rats compared to Np rats from 4 days to 5 weeks after birth. While glomerular number per unit volume (1 mm(3) ) of the kidney (Nv) was comparable between Lp and Np rats 4 weeks after birth, the Nv was significantly decreased in Lp rats at 20 weeks after birth. Four and 20 weeks after birth, glomerular sclerosis index, interstitial fibrosis score, and ratio of ED1-positive cell ratio were all significantly higher in Lp compared to Np rats. Transforming growth factor-β1-positive cells were observed in the distal tubules in the kidney of 4- and 20-week-old Lp rats kidneys, but not in those of age-matched Np rats. Altogether, these findings revealed that maternal protein restriction that does not have an influence on the birthweight of the offspring, induces similar changes as those seen in the kidneys of IUGR neonates.

p53 Enables metabolic fitness and self-renewal of nephron progenitor cells

Contrary to its classic role in restraining cell proliferation, we demonstrate here a divergent function of p53 in the maintenance of self-renewal of the nephron progenitor pool in the embryonic mouse kidney. Nephron endowment is regulated by progenitor availability and differentiation potential. Conditional deletion of p53 in nephron progenitor cells (Six2Cre(+);p53(fl/fl)) induces progressive depletion of Cited1(+)/Six2(+) self-renewing progenitors and loss of cap mesenchyme (CM) integrity. The Six2(p53-null) CM is disorganized, with interspersed stromal cells and an absence of a distinct CM-epithelia and CM-stroma interface. Impaired cell adhesion and epithelialization are indicated by decreased E-cadherin and NCAM expression and by ineffective differentiation in response to Wnt induction. The Six2Cre(+);p53(fl/fl) cap has 30% fewer Six2(GFP(+)) cells. Apoptotic index is unchanged, whereas proliferation index is significantly reduced in accordance with cell cycle analysis showing disproportionately fewer Six2Cre(+);p53(fl/fl) cells in the S and G2/M phases compared with Six2Cre(+);p53(+/+) cells. Mutant kidneys are hypoplastic with fewer generations of nascent nephrons. A significant increase in mean arterial pressure is observed in early adulthood in both germline and conditional Six2(p53-null) mice, linking p53-mediated defects in kidney development to hypertension. RNA-Seq analyses of FACS-isolated wild-type and Six2(GFP(+)) CM cells revealed that the top downregulated genes in Six2Cre(+);p53(fl/fl) CM belong to glucose metabolism and adhesion and/or migration pathways. Mutant cells exhibit a ∼ 50% decrease in ATP levels and a 30% decrease in levels of reactive oxygen species, indicating energy metabolism dysfunction. In summary, our data indicate a novel role for p53 in enabling the metabolic fitness and self-renewal of nephron progenitors.

Influence of gestational salt restriction in fetal growth and in development of diseases in adulthood

Recent studies reported the critical role of the intrauterine environment of a fetus in growth or the development of disease in adulthood. In this article we discussed the implications of salt restriction in growth of a fetus and the development of growth-related disease in adulthood. Salt restriction causes retardation of fatal growth or intrauterine death thereby leading to low birth weight or decreased birth rate. Such retardation of growth along with the upregulation of the renin angiotensin system due to salt restriction results in the underdevelopment of cardiovascular organs or decreases the number of the nephron in the kidney and is responsible for onset of hypertension in adulthood. In addition, gestational salt restriction is associated with salt craving after weaning. Moreover, salt restriction is associated with a decrease in insulin sensitivity. A series of alterations in metabolism due to salt restriction are probably mediated by the upregulation of the renin angiotensin system and an epigenetic mechanism including proinflammatory substances or histone methylation. Part of the metabolic disease in adulthood may be programmed through such epigenetic changes. The modification of gene in a fetus may be switched on through environment factors or life style after birth. The benefits of salt restriction have been assumed thus far; however, more precise investigation is required of its influence on the health of fetuses and the onset of various diseases in adulthood.

Effects of maternal subtotal nephrectomy on the development of the fetal kidney: A morphometric study

The present study was designed to explore if maternal subtotal (5/6) nephrectomy affects the development of fetal rat kidneys using morphometric methods and examining whether there are any apoptotic changes in the fetal kidney. To generate 5/6 nephrectomized model rats, animals underwent 2/3 left nephrectomy on gestation day (GD) 5 and total right nephrectomy on GD 12. The fetal kidneys were examined on GDs 16 and 22. A significant decrease in fetal body weight resulting from maternal 5/6 nephrectomy was observed on GD 16, and a significant decrease in fetal renal weight and fetal body weight caused by maternal nephrectomy was observed on GD 22. Maternal 5/6 nephrectomy induced a significant increase in glomerular number, proximal tubular length, and total proximal tubular volume of fetuses on GD 22. Maternal 5/6 nephrectomy resulted in an increase in the number of apoptotic cells in the metanephric mesenchyme of the kidney on GD 16, and in the collecting tubules on GD 22. These findings suggest that maternal 5/6 nephrectomy stimulates the development of the fetal kidney while suppressing fetal growth.

Aging in the Canine Kidney

Given the irreversible nature of nephron loss, aging of the kidney is of special interest to diagnostic and toxicologic pathologists. There are many similarities among histologic lesions in aged human and canine kidneys, including increased frequency of glomerulosclerosis, interstitial fibrosis, and tubular atrophy. Unfortunately, there are few studies in which renal tissue from aged healthy dogs was adequately examined with advanced diagnostics—namely, transmission electron microscopy and immunofluorescence—so age-associated changes in canine podocytes and glomerular basement membranes are poorly characterized. An age-associated decrease in the glomerular filtration rate in humans and dogs (specifically small breed dogs) has been documented. Although lesions in aged rats and mice differ somewhat from those of aged dogs and humans, the knowledge gained from rodent models is still vital to elucidating the pathogenesis of age-associated renal disease. Many novel molecules implicated in renal aging have been identified through genetically modified rodent models and transcriptomic and proteomic analysis of human kidneys. These molecules represent intriguing therapeutic targets and diagnostic biomarkers. Likewise, influencing critical pathways of cellular aging, such as telomere shortening, cellular senescence, and autophagy, could improve renal function in the elderly.

Effects of moderate global maternal nutrient reduction on fetal baboon renal mitochondrial gene expression at 0.9 gestation

Early life malnutrition results in structural alterations in the kidney, predisposing offspring to later life renal dysfunction. Kidneys of adults who were growth restricted at birth have substantial variations in nephron endowment. Animal models have indicated renal structural and functional consequences in offspring exposed to suboptimal intrauterine nutrition. Mitochondrial bioenergetics play a key role in renal energy metabolism, growth, and function. We hypothesized that moderate maternal nutrient reduction (MNR) would adversely impact fetal renal mitochondrial expression in a well-established nonhuman primate model that produces intrauterine growth reduction at term. Female baboons were fed normal chow diet or 70% of control diet (MNR). Fetal kidneys were harvested at cesarean section at 0.9 gestation (165 days gestation). Human Mitochondrial Energy Metabolism and Human Mitochondria Pathway PCR Arrays were used to analyze mitochondrially relevant mRNA expression. In situ protein content was detected by immunohistochemistry. Despite the smaller overall size, the fetal kidney weight-to-body weight ratio was not affected. We demonstrated fetal sex-specific differential mRNA expression encoding mitochondrial metabolite transport and dynamics proteins. MNR-related differential gene expression was more evident in female fetuses, with 16 transcripts significantly altered, including 14 downregulated and 2 upregulated transcripts. MNR impacted 10 transcripts in male fetuses, with 7 downregulated and 3 upregulated transcripts. The alteration in mRNA levels was accompanied by a decrease in mitochondrial protein cytochrome c oxidase subunit VIc. In conclusion, transcripts encoding fetal renal mitochondrial energy metabolism proteins are nutrition sensitive in a sex-dependent manner. We speculate that these differences lead to decreased mitochondrial fitness that contributes to renal dysfunction in later life.

Role of the kidney in the fetal programming of adult cardiovascular disease: an update

It is well established that an adverse in utero environment can impinge upon fetal development and place the offspring on a track leading to future cardiovascular disease. Significantly, this may occur in the absence of any outward manifestations at birth. In this brief review, we focus on potential renal mechanisms that lead to adaptations in glomerular and tubular function that initiate hypertension of developmental origin and examine potential therapeutic interventions. This report updates recent data in this field.

Clinicopathological assessment of the nephron number

Recent studies have demonstrated much larger variability in the total number of nephrons in normal populations than previously suspected. In addition, it has been suggested that individuals with a low nephron number may have an increased lifetime risk of hypertension or renal insufficiency, emphasizing the importance of evaluating the nephron number in each individual. In view of the fact that all previous reports of the nephron number were based on analyses of autopsy kidneys, the identification of surrogate markers detectable in living subjects is needed in order to enhance understanding of the clinical significance of this parameter. In this review, we summarize the clinicopathological factors and findings indicating a reduction in the nephron number, focusing particularly on those found at the time of a preserved renal function.

Early life influences kidney function at age 63-64 years, but so does adult body size: results from the newcastle thousand families birth cohort

BACKGROUND

It is suggested that impaired fetal growth can affect kidney development, resulting in fewer glomeruli being formed and reduced kidney function later in life. The aim of this study was to investigate early life variables in relation to adult kidney function, and compare these to the influence of later life variables.

METHODS

Detailed information was collected prospectively regarding 1,142 babies, born in 1947 in Newcastle upon Tyne. At the age of 63-64 years, 335 participants had serum creatinine successfully measured and completed a lifestyle questionnaire. These measurements were used to calculate their estimated glomerular filtration rate (eGFR).

RESULTS

Body mass index (BMI) and being female were significantly negatively associated with eGFR. Birth weight was significantly positively associated with eGFR. In sex-specific analyses, BMI and cigarette smoking remained significant for males (n = 154), with a near significant association for birth weight, whereas none of the variables remained significant for females (n = 181).

CONCLUSIONS

The findings suggest that sex, size at birth and BMI may be important variables influencing adult kidney function. However, as only a small amount of variance in eGFR was explained by these variables, additional longitudinal studies would be beneficial for assessing lifecourse influences on kidney function.

Developmental cigarette smoke exposure: kidney proteome profile alterations in low birth weight pups

The Brenner hypothesis states that a congenital reduction in nephron number predisposes to adult-onset hypertension and renal failure. The reduction in nephron number induced by proportionally smaller kidney mass may predispose offspring to glomerular hyperfiltration with maturity onset obesity. Developmental cigarette smoke exposure (CSE) results in intrauterine growth retardation with a predisposition to obesity and cardiovascular disease at maturity. Utilizing a mouse model of 'active' developmental CSE (gestational day [GD] 1-postnatal day [PD] 21; cotinine>50 ng/mL) characterized by persistently smaller offspring with proportionally decreased kidney mass, the present study examined the impact of developmental CSE on the abundance of proteins associated with cellular metabolism in the kidney. Following cessation of CSE on PD21, kidney tissue was collected from CSE and Sham exposed pups for 2D-SDS-PAGE based proteome profiling with statistical analysis by partial least squares-discriminant analysis (PLS-DA) with affected molecular pathways identified by ingenuity pathway analysis. Proteins whose expression in the kidney were affected by developmental CSE belonged to the inflammatory disease, cell to cell signaling/interaction, lipid metabolism, small molecule biochemistry, cell cycle, respiratory disease, nucleic acid and carbohydrate metabolism networks. The present findings indicate that developmental CSE alters the kidney proteome. The companion paper details the liver proteome alterations in the same offspring.

Glomerular number and size variability and risk for kidney disease

PURPOSE OF REVIEW

This review discusses current understandings of variability in glomerular number and size, and the implications for renal health.

RECENT FINDINGS

The quantitative microanatomy of the normal human kidney varies widely. Of greatest significance, total nephron number varies at least 13-fold, and several genes and environmental factors that regulate human nephron endowment have been identified. Full or partial deletion of more than 25 genes in mice has been shown to result in renal hypoplasia and, when measured, reduced nephron endowment. Many more will likely be identified. As would be expected, some gene abnormalities increase nephron endowment above that found in control mice. Glomerular volume also varies widely, both between and within kidneys, and increased heterogeneity of glomerular volume within kidneys is associated with risk factors for kidney disease, including birth weight, age, race, body size and hypertension.

SUMMARY

Data from several human populations indicate that the quantitative microanatomy of the human kidney varies considerably: total glomerular number varies at least 13-fold, mean glomerular volume varies up to seven-fold and the volumes of individual glomeruli within single kidneys can vary as much as eight-fold. Human glomerular number, size and size distribution are being found to correlate with risk factors for kidney disease. The genetic and fetal environmental regulators of nephrogenesis, and thereby nephron endowment, are being rapidly identified and will provide the bases for future clinical interventions. In contrast, the molecular regulation of glomerular size remains unclear.