Normal Lactational Environment Restores Nephron Endowment and Prevents Hypertension after Placental Restriction in the Rat

Growth restriction in the rat alters expression of metabolic genes during postnatal cardiac development in a sex-specific manner

This study investigated the impact of uteroplacental insufficiency and growth restriction on the expression of genes related to mitochondrial biogenesis, glucose transport, and antioxidant defenses in cardiac tissue at embryonic day 20 (E20) and postnatal days 1, 7, and 35 in male and female Wistar rats (8-10 per group). Bilateral uterine vessel ligation to induce growth restriction (Restricted) or sham surgery was performed at pregnancy day 18. In male and female Controls, expression of most cardiac genes decreased during postnatal life, including genes involved in mitochondrial biogenesis regulation such as PGC-1α, NRF-2, and mtTFA and the glucose transporter GLUT-1 (P < 0.05). However, the pattern of gene expression during cardiac development differed in male and female Restricted rats compared with their respective Controls. These effects of restriction were observed at postnatal day 1, with female Restricted rats having delayed reductions in PGC-1α and GLUT-1, whereas males had exacerbated reductions in PGC-1α and mtTFA (P < 0.05). By day 35, cardiac gene expression in Restricted hearts was similar to Controls, except for expression of the antioxidant enzyme MnSOD, which was significantly lower in both sexes. In summary, during postnatal life male and female Control rats have similar patterns of expression for genes involved in mitochondrial biogenesis and glucose transport. However, following uteroplacental insufficiency these gene expression patterns diverge in males and females during early postnatal life, with MnSOD gene expression reduced in later postnatal life.

Developmental programming of hypertension and kidney disease

A growing body of evidence supports the concept that changes in the intrauterine milieu during "sensitive" periods of embryonic development or in infant diet after birth affect the developing individual, resulting in general health alterations later in life. This phenomenon is referred to as "developmental programming" or "developmental origins of health and disease." The risk of developing late-onset diseases such as hypertension, chronic kidney disease (CKD), obesity or type 2 diabetes is increased in infants born prematurely at <37 weeks of gestation or in low birth weight (LBW) infants weighing <2,500 g at birth. Both genetic and environmental events contribute to the programming of subsequent risks of CKD and hypertension in premature or LBW individuals. A number of observations suggest that susceptibility to subsequent CKD and hypertension in premature or LBW infants is mediated, at least in part, by reduced nephron endowment. The major factors influencing in utero environment that are associated with a low final nephron number include uteroplacental insufficiency, maternal low-protein diet, hyperglycemia, vitamin A deficiency, exposure to or interruption of endogenous glucocorticoids, and ethanol exposure. This paper discusses the effect of premature birth, LBW, intrauterine milieu, and infant feeding on the development of hypertension and renal disease in later life as well as examines the role of the kidney in developmental programming of hypertension and CKD.

Impact of fetal and infant exposure to the Chinese Great Famine on the risk of hypertension in adulthood

BACKGROUND

Famine provides quasi-experimental conditions for testing the hypothesis of "programming" health effects by poor nutrition in early life. It remains uncertain whether early life exposure to famine increases the risk of hypertension in adulthood. There is a lack of data on the relative impact of exposure to famine during fetal development versus infancy (<2 years postnatal). We sought to assess the impact of exposure to the 1959-1961 Chinese Great Famine (the largest in human history) during fetal development and infancy on the risks of hypertension, short stature and obesity in adulthood.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a retrospective cohort study of 12,065 adults (46-53 years of age) born 1957-1964 in the Zhongshan and Nanhai municipalities of Guangdong province, China. Adjusting for socio-demographic and lifestyle characteristics, as compared to subjects who were unexposed to famine, the risk of hypertension was not significantly elevated in subjects exposed to famine during fetal development only overall, but was 1.36-fold higher in those exposed during the first trimester of pregnancy only [adjusted odds ratio (OR) 1.36 (95% confidence intervals 1.03-1.79)], 1.83-fold higher in those exposed during infancy only [adjusted OR 1.83 (1.61-2.08)], and 1.31-fold higher in those exposed during both fetal development and infancy [adjusted OR 1.31 (1.14-1.51)]. Exposure to famine during infancy increased the risk of short stature. Early life exposure to famine did not increase the risk of obesity.

CONCLUSIONS/SIGNIFICANCE

Exposure to the Chinese Great Famine during the first trimester of pregnancy only, or during infancy only, or during both fetal development and infancy increased the risk of hypertension in adulthood, suggesting an important role of changes in exposure to famine during fetal development and from prenatal to early postnatal life in developmental "programming" cardiovascular disease risk.

A rodent model of low- to moderate-dose ethanol consumption during pregnancy: patterns of ethanol consumption and effects on fetal and offspring growth

It is unknown whether low to moderate maternal alcohol consumption adversely affects postnatal health. The aim of the present study was to develop a rodent model of low-moderate-dose prenatal ethanol (EtOH) exposure. Sprague-Dawley rats were fed a liquid diet with or without 6% v/v EtOH throughout gestation and the pattern of dietary consumption determined. Fetal bodyweights and hepatic alcohol-metabolising gene expression were measured on embryonic Day (E) 20 and offspring growth studied until 1 year. At E8 the plasma EtOH concentration was 0.03%. There was little difference in dietary consumption between the two treatment groups. At E20, EtOH-exposed fetuses were significantly lighter than controls and had significantly decreased ADH4 and increased CYP2E1 gene expression. Offspring killed on postnatal Day (PN) 30 did not exhibit any growth deficits. Longitudinal repeated measures of offspring growth demonstrated slower growth in males from EtOH-fed dams between 7 and 12 months of age; a cohort of male pups killed at 8 months of age had a reduced crown-rump length and kidney weight. In conclusion, a liquid diet of 6% v/v EtOH fed to pregnant dams throughout gestation caused a 3-8% reduction in fetal growth and brain sparing, with growth differences observed in male offspring later in life. This model will be useful for future studies on the effects of low-moderate EtOH on the developmental origins of health and disease.

Prenatal programming of hypertension induces sympathetic overactivity in response to physical stress

Small-for-gestational-age infants are known to develop hypertension in adulthood. This prenatal programming of hypertension (PPH) can result from several insults including maternal dietary protein deprivation, uteroplacental insufficiency, and prenatal administration of glucocorticoids. The mechanisms underlying the development of hypertension remain unclear although the sympathetic nervous system has been indirectly implicated. This study was designed to directly measure renal sympathetic nerve activity both at rest and during physical stress in an animal model of PPH. The adult male offspring of rats fed either a 6% (PPH) or 20% protein diet (control) were investigated. Conscious systolic blood pressure measured by tail cuff was significantly higher in PPH compared with control (140 ± 3 versus 128 ± 3 mm Hg; P<0.05). Baseline mean arterial pressure, heart rate, and renal sympathetic activity were not different between groups during isoflurane anesthesia or after decerebration. Physical stress was induced in decerebrate animals by activating the exercise pressor reflex during static muscle contraction. Stimulation of the exercise pressor reflex evoked significantly larger changes from baseline in mean arterial pressure (40 ± 7 versus 20 ± 4 mm Hg; P<0.05), heart rate (19 ± 3 versus 5 ± 1 bpm; P<0.05), and renal sympathetic activity (198 ± 29% versus 68 ± 14%; P<0.05) in PPH as compared with control. The data demonstrate that the sympathetic response to physical stress is markedly exaggerated in PPH and may play a significant role in the development of hypertension in adults born small for gestational age.

Blood pressure follows the kidney: Perinatal influences on hereditary hypertension

Epidemiological and experimental data strongly suggest that cardiovascular diseases can originate from an aberrant environment during fetal development, a phenomenon referred to as perinatal programming. This review will focus on the role of the kidneys in determining blood pressure, and how (re)programming the renal development can persistently ameliorate hereditary hypertension. By combining physiologic and genomic studies we have discovered some candidate pathways suited for (re)programming the development of hypertension. This sets the stage for mechanistic analysis in future studies.

Maturational regression of glomeruli determines the nephron population in normal mice

BACKGROUND

Regression is an important process in the normal development of many organs. In this study, we investigated whether glomerular regression occurs after normal glomerulogenesis and determined the time course for this process.

METHODS

Glomerular number was analyzed in normal mouse kidneys at postnatal day (P)7, P10, P14, P18, P21, P25, and P28 by the gold standard fractionator/dissector method, which involves exhausting the kidney tissue. Vascular regression markers, angiopoietin 2 (ANGPT2), and thrombospondin 1 (THBS1), were examined by immunohistochemistry.

RESULTS

The maximum glomerular number was reached at P7 with 14,051 glomeruli per kidney (95% confidence interval: 12,084-16,018). This peak was followed by a progressive reduction, with a nadir of 11,060 (10,393-11,727) occurring at P18 (P < 0.05 as compared with P7). Thereafter, glomerular number remained constant. Complementary immunohistochemical examination of vascular regression markers showed peak expression of glomerular ANGPT2 and THBS1 at P14.

CONCLUSION

Our study reveals that the tissue- and time-saving Weibel-Gomez method commonly used to assess glomerular number is valid only after P18. The data indicate that regulation of glomerular number by regression occurs in normally maturing mouse kidneys. These findings suggest that the process of glomerular regression could be therapeutically targeted to prevent oligonephronia, which otherwise predisposes to chronic kidney disease.

Increased cardiovascular and renal risk is associated with low nephron endowment in aged females: an ovine model of fetal unilateral nephrectomy

Previously we have shown that ovariectomised (OVX) female sheep have reduced renal function and elevated blood pressure from 6 months of age following fetal uninephrectomy (uni-x) at 100 days of gestation (term = 150 days). In the current study we examined if in intact female sheep the onset of decline in renal function and elevation in blood pressure was prevented. Studies were performed at 1 year, 2 and 5 years of age. Following fetal uni-x at 100 days, intact female sheep had ~30% reduction in glomerular filtration rate (GFR) at 1 year, which did not exacerbate with age (P(treatment) = 0.0001, P(age) = 0.7). In contrast renal blood flow was similar between the treatment groups at 1 year of age but had declined in the uni-x animals at 5 years of age (P(treatment × age) = 0.046). Interestingly, intact uni-x sheep did not develop elevations in arterial pressure until 2 years of age. Furthermore, uni-x animals had a similar capacity to respond to a cardiac challenge at 1 year and 2 years of age, however, cardiac functional reserve was significantly reduced compared to sham group at 5 years of age. Uni-x animals exhibited an increase in left ventricular dimensions at 5 years of age compared to the sham animals and compared to 2 years of age (P(treatment)<0.001, P(treatment × age)<0.001). In conclusion, the onset of renal dysfunction preceded the onset of hypertension in intact female uni-x sheep. Furthermore, this study showed that the intact females are protected from the impact of a reduced nephron endowment on cardiovascular health early in life as opposed to our findings in young male sheep and OVX uni-x female sheep. However, with ageing this protection is lost as evidenced by presence of left ventricular hypertrophy and impaired cardiac function in 5 year old uni-x female sheep.

Pregnancy in aged rats that were born small: cardiorenal and metabolic adaptations and second-generation fetal growth

Uteroplacental insufficiency is associated with adult cardiorenal and metabolic diseases, particularly in males. Pregnancy is the greatest physiological challenge facing women, and those born small are at increased risk of gestational hypertension and diabetes and delivering smaller babies. Increased maternal age is associated with exacerbated pregnancy complications. We hypothesized that pregnancy in aged, growth-restricted females unmasks an underlying predisposition to cardiorenal and metabolic dysfunction and compromises fetal growth. Uteroplacental insufficiency was induced by bilateral uterine vessel ligation (restricted group) or sham surgery (control group) on d 18 of gestation in Wistar Kyoto rats. At 12 mo, growth-restricted F1 female offspring were mated with a normal male. F1 restricted females had elevated systolic blood pressure, before and during pregnancy (+10 mmHg) but normal renal and metabolic pregnancy adaptations. F2 fetal weight was not different between groups. In control and restricted females, advanced maternal age (12 vs. 4 mo) was associated with a reduction in the hypoglycemic response to pregnancy and reduced F2 fetal litter size and body weight. Aged rats born small exhibited mostly normal pregnancy adaptations, although they had elevated blood pressure. Advanced maternal age was associated with poorer fetal outcomes that were not exacerbated by low maternal birth weight.

Effect of prenatal exposure to nicotine on kidney glomerular mass and AT1R expression in genetically diverse strains of rats

Prenatal exposure to maternal cigarette smoking in humans or nicotine in experimental animals is associated with elevated blood pressure in the offspring. This effect may be limited to genetically vulnerable individuals and related to alterations in the kidneys. Here we investigated whether prenatal exposure to nicotine (PEN) alters kidney morphology and gene expression, and whether these effects differ between two genetically distant strains, i.e. spontaneously hypertensive (SHR) and Brown Norway (BN) rats. The results showed that, in SHR but not in BN offspring, PEN decreases kidney glomerular mass and increases renal expression of the angiotensin II type 1b receptor gene; the latter is not mediated through changes in DNA methylation of the proximal promoter of this gene. The results also showed that PEN alters expression of multiple genes involved in the kidney nervous system function, with mostly opposite effects being seen in SHR and BN. These results suggest that, in genetically vulnerable individuals, PEN leads to morphological and molecular changes in the kidneys that may contribute to fetal programming of hypertension.

Long-term alteration in maternal blood pressure and renal function after pregnancy in normal and growth-restricted rats

Intrauterine growth restriction is associated with increased risk of adult cardiorenal diseases. Small birth weight females are more likely to experience complications during their own pregnancy, including pregnancy-induced hypertension, preeclampsia, and gestational diabetes. We determined whether the physiological demand of pregnancy predisposes growth-restricted females to cardiovascular and renal dysfunction later in life. Late gestation bilateral uterine vessel ligation was performed in Wistar-Kyoto rats. At 4 months, restricted and control female offspring were mated with normal males and delivered naturally (ex-pregnant). Regardless of maternal birth weight, at 13 months, ex-pregnant females developed elevated mean arterial pressure (indwelling tail-artery catheter; +6 mm Hg), reduced effective renal blood flow ((14)C-PAH clearance; -23%), and increased renal vascular resistance (+27%) compared with age-matched virgins. Glomerular filtration rate ((3)H-inulin clearance) was not different across groups. This adverse cardiorenal phenotype in ex-pregnant females was associated with elevated systemic (+57%) and altered intrarenal components of the renin-angiotensin system. After pregnancy at 13 months, coronary flow (Langendorff preparation) was halved in restricted females compared with controls, and together with reduced NO excretion, this may increase susceptibility to additional lifestyle challenges. Our results have implications for aging females who have been pregnant, suggesting long-term cardiovascular and renal alterations, with additional consequences for females who were small at birth.

Uteroplacental insufficiency programmes vascular dysfunction in non-pregnant rats: compensatory adaptations in pregnancy

Intrauterine growth restriction is a risk factor for cardiovascular disease in adulthood. We have previously shown that intrauterine growth restriction caused by uteroplacental insufficiency programmes uterine vascular dysfunction and increased arterial stiffness in adult female rat offspring. The aim of this study was to investigate vascular adaptations in growth restricted female offspring when they in turn become pregnant. Uteroplacental insufficiency was induced in WKY rats by bilateral uterine vessel ligation (Restricted) or sham surgery (Control) on day 18 of pregnancy. F0 pregnant females delivered naturally at term. F1 Control and Restricted offspring were mated at 4 months of age and studied on day 20 of pregnancy. Age-matched non-pregnant F1 Control and Restricted females were also studied. Wire and pressure myography were used to test endothelial and smooth muscle function, and passive mechanical wall properties, respectively, in uterine, mesenteric, renal and femoral arteries of all four groups. Collagen and elastin fibres were quantified using polarized light microscopy and qRT-PCR. F1 Restricted females were born 10–15% lighter than Controls (P <0.05). Non-pregnant Restricted females had increased uterine and renal artery stiffness compared with Controls (P <0.05), but this difference was abolished at day 20 of pregnancy. Vascular smooth muscle and endothelial function were preserved in all arteries of non-pregnant and pregnant Restricted rats. Collagen and elastin content were unaltered in uterine arteries of Restricted females. Growth restricted females develop compensatory vascular changes during late pregnancy, such that region-specific vascular deficits observed in the non-pregnant state did not persist in late pregnancy.

Pre-eclampsia and offspring cardiovascular health: mechanistic insights from experimental studies

Pre-eclampsia is increasingly recognized as more than an isolated disease of pregnancy. Women who have had a pregnancy complicated by pre-eclampsia have a 4-fold increased risk of later cardiovascular disease. Intriguingly, the offspring of affected pregnancies also have an increased risk of higher blood pressure and almost double the risk of stroke in later life. Experimental approaches to identify the key features of pre-eclampsia responsible for this programming of offspring cardiovascular health, or the key biological pathways modified in the offspring, have the potential to highlight novel targets for early primary prevention strategies. As pre-eclampsia occurs in 2–5% of all pregnancies, the findings are relevant to the current healthcare of up to 3 million people in the U.K. and 15 million people in the U.S.A. In the present paper, we review the current literature that concerns potential mechanisms for adverse cardiovascular programming in offspring exposed to pre-eclampsia, considering two major areas of investigation: first, experimental models that mimic features of the in utero environment characteristic of pre-eclampsia, and secondly, how, in humans, offspring cardiovascular phenotype is altered after exposure to pre-eclampsia. We compare and contrast the findings from these two bodies of work to develop insights into the likely key pathways of relevance. The present review and analysis highlights the pivotal role of long-term changes in vascular function and identifies areas of growing interest, specifically, response to hypoxia, immune modification, epigenetics and the anti-angiogenic in utero milieu.

Maternal adaptations and inheritance in the transgenerational programming of adult disease

Adverse exposures in utero have long been linked with an increased susceptibility to adult cardio-renal and metabolic diseases. Clear gender differences exist, whereby growth-restricted females, although exhibiting some phenotypic modifications, are often protected from overt disease outcomes. One of the greatest physiological challenges facing the female gender, however, is that of pregnancy; yet little research has focused on the outcomes associated with this, as a potential 'second-hit' for those who were small at birth. We review the limited evidence suggesting that pregnancy may unmask cardio-renal and metabolic disease states and the consequences for long-term maternal health in females who were born small. Additionally, a growing area of research in this programming field is in the transgenerational transmission of low birth weight and disease susceptibility. Pathways for transmission might include an abnormal adaptation to pregnancy by the growth-restricted mother and/or inheritance via the parental germline. Strategies to optimise the pregnancy environment and/or prevent the consequences of inheritance of programmed deficits and dysfunction are of critical importance for future generations.

Renal responses to furosemide are significantly attenuated in male sheep at 6 months of age following fetal uninephrectomy

We have previously shown that fetal uninephrectomy (uni-x) at 100 days of gestation (term = 150 days) in male sheep results in a 30% nephron deficit, reduction in glomerular filtration rate (GFR) and renal blood flow, and elevation in arterial pressure at 6 mo of age. Furthermore, in response to an acute 0.9% saline load, sodium excretion was significantly delayed in uni-x animals leading us to speculate that tubuloglomerular feedback (TGF) activity was reset in uni-x animals. In the present study, we induced TGF blockade by furosemide administration (1.5 mg/kg iv over 90 min) and determined GFR, effective renal plasma flow, and urine and sodium excretion responses in 6-mo-old male sheep. In response to furosemide, a significant diuresis and natriuresis was observed in the sham group; however, the response was significantly delayed and reduced in uni-x animals (both, Ptreatment×time < 0.001). Cummulative urinary and sodium output was significantly less in the uni-x compared with the sham sheep (both, Ptreatment×time < 0.001). GFR was increased in the sham but not the uni-x sheep ( Ptreatment×time < 0.0001). In conclusion, the excretory response to furosemide was attenuated in the uni-x sheep, and this suggests a rightward resetting of the TGF operating point. The TGF mechanism is important in the fine tuning of sodium homeostasis and is likely a contributing factor for the dysfunction in sodium regulation we have previously observed in the uni-x animals.

Normal lactational environment restores cardiomyocyte number after uteroplacental insufficiency: implications for the preterm neonate

A reduced complement of cardiomyocytes in early life can adversely affect life-long cardiac functional reserve. In the present study, using a cross-fostering approach in rats, we examined the contributions of the prenatal and postnatal environments in the programming of cardiomyocyte growth. Rat dams underwent either bilateral uterine vessel ligation (Restricted) or sham surgery (Control) on day 18 of gestation. One day after birth, Control and Restricted pups were cross-fostered onto Control (normal lactation) or Restricted (impaired lactation due to impaired mammary gland formation) mothers. In male offspring, genes involved in cardiomyocyte differentiation, proliferation, hypertrophy and apoptosis were examined at gestational day 20 and postnatal days 1 and 7 to assess effects on cardiomyocyte growth. At postnatal day 7 cardiomyocyte number was determined stereologically. Offspring were examined at age 6 mo for evidence of hypertension and pathological cardiac gene expression. There was an increase in Igf1 and Igf2 mRNA expression in hearts of Restricted pups at gestational day 20. At postnatal day 7, Agtr1a and Agtr1b mRNA expression as well as Bcl2 and Cmyc were elevated in all hearts from offspring that were prenatally or postnatally growth restricted. There was a significant reduction (-29%) in cardiomyocyte number in the Restricted-on-Restricted group. Importantly, this deficit was prevented by optimization of postnatal nutrition (in the Restricted-on-Control group). At 6 mo, blood pressure was significantly elevated in the Restricted-on-Restricted group, but there was no difference in expression of the cardiac hypertrophy, remodeling or angiogenic genes across groups. In conclusion, the findings reveal a critical developmental window, when cardiomyocytes are still proliferating, whereby improved neonatal nutrition has the capacity to restore cardiomyocyte number to normal levels. These findings are of particular relevance to the preterm infant who is born at a time when cardiomyocytes are immature and still dividing.

Cardio-renal and metabolic adaptations during pregnancy in female rats born small: implications for maternal health and second generation fetal growth

Intrauterine growth restriction caused by uteroplacental insufficiency increases risk of cardiovascular and metabolic disease in offspring. Cardio-renal and metabolic responses to pregnancy are critical determinants of immediate and long-term maternal health. However, no studies to date have investigated the renal and metabolic adaptations in growth restricted offspring when they in turn become pregnant. We hypothesised that the physiological challenge of pregnancy in growth restricted females exacerbates disease outcome and compromises next generation fetal growth. Uteroplacental insufficiency was induced by bilateral uterine vessel ligation (Restricted) or sham surgery (Control) on day 18 of gestation in WKY rats and F1 female offspring birth and postnatal body weights were recorded. F1 Control and Restricted females were mated at 4 months and blood pressure, renal and metabolic parameters were measured in late pregnancy and F2 fetal and placental weights recorded. Age-matched non-pregnant Control and Restricted F1 females were also studied. F1 Restricted females were born 10-15% lighter than Controls. Basal insulin secretion and pancreatic β-cell mass were reduced in non-pregnant Restricted females but restored in pregnancy. Pregnant Restricted females, however, showed impaired glucose tolerance and compensatory glomerular hypertrophy, with a nephron deficit but normal renal function and blood pressure. F2 fetuses from Restricted mothers exposed to physiological measures during pregnancy were lighter than Controls highlighting additive adverse effects when mothers born small experience stress during pregnancy. Female rats born small exhibit mostly normal cardio-renal adaptations but altered glucose control during late pregnancy making them vulnerable to lifestyle challenges.

Urine-concentrating defects exacerbate with age in male offspring with a low-nephron endowment

Fetal uninephrectomy (uni-x) in male sheep at 100 days of gestation (term = 150 days) reduces overall nephron endowment without affecting birth weight. Offspring have a lower glomerular filtration rate (GFR) and elevated mean arterial pressure (MAP) at 6 mo of age. This study investigated whether this reduction in renal function was associated with impaired urine-concentrating ability at 6 mo of age and exacerbated with ageing (4 yr) and examined response to 1) nonpressor dose of exogenous arginine vasopressin (AVP; 0.2 μg·kg−1·h−1 iv) and 2) 30 h of water deprivation. Basal MAP was higher in uni-x animals at both ages, and became further elevated with age compared with the sham group (elevation in MAP with age; sham: ∼4 mmHg, uni-x: 9 mmHg, Pgroup × age < 0.01). GFR declined with ageing in both groups with the decrease being greater with age in the uni-x group (further 26%, Pgroup × age < 0.001). In response to AVP infusion, urine osmolality increased in both treatment groups; this response was significantly lower in the uni-x animals and became further reduced with ageing. Uni-x animals had reduced renal expression of vasopressin-2 receptor and aquaporin-2 at both ages ( P < 0.01). The increase in plasma AVP levels in response to dehydration was similar between the treatment groups, suggesting the urine-concentrating defect was associated with these renal gene changes rather than defects in AVP secretion. Renal insufficiency due to a low-nephron endowment increases the risk of hypertension and chronic renal disease and may incur greater vulnerability to physiological challenges such as water deprivation as observed in the uni-x animals.

Short-term exercise training early in life restores deficits in pancreatic β-cell mass associated with growth restriction in adult male rats

Fetal growth restriction is associated with reduced pancreatic β-cell mass, contributing to impaired glucose tolerance and diabetes. Exercise training increases β-cell mass in animals with diabetes and has long-lasting metabolic benefits in rodents and humans. We studied the effect of exercise training on islet and β-cell morphology and plasma insulin and glucose, following an intraperitoneal glucose tolerance test (IPGTT) in juvenile and adult male Wistar-Kyoto rats born small. Bilateral uterine vessel ligation performed on day 18 of pregnancy resulted in Restricted offspring born small compared with sham-operated Controls and also sham-operated Reduced litter offspring that had their litter size reduced to five pups at birth. Restricted, Control, and Reduced litter offspring remained sedentary or underwent treadmill running from 5 to 9 or 20 to 24 wk of age. Early life exercise increased relative islet surface area and β-cell mass across all groups at 9 wk, partially restoring the 60-68% deficit (P < 0.05) in Restricted offspring. Remarkably, despite no further exercise training after 9 wk, β-cell mass was restored in Restricted at 24 wk, while sedentary littermates retained a 45% deficit (P = 0.05) in relative β-cell mass. Later exercise training also restored Restricted β-cell mass to Control levels. In conclusion, early life exercise training in rats born small restored β-cell mass in adulthood and may have beneficial consequences for later metabolic health and disease.

Prenatal programming of hypertension in the rat: effect of postnatal rearing

Background/Aims

Dietary protein deprivation during pregnancy causes hypertension in offspring when they become adults. This study examined if postnatal rearing had an effect on blood pressure and glomerular number in male rats whose mothers were fed either a control diet or a low protein diet.

Methods

Neonates were cross fostered at 1 day of age to a different mother. After birth, all nursing and weaned rats were fed a control diet. Blood pressure and glomerular number were measured in adult offspring.

Results

Control rats cross fostered to another control mother had a lower blood pressure than low protein rats cross fostered to another low protein mother (133 ± 4 vs. 151 ± 4 mm Hg, p < 0.05) and a greater number of glomeruli (28,388 ± 989 vs. 25,045 ± 851, p < 0.05). Fostering pups from the 20% group to mothers that were fed a 6% diet during pregnancy did not cause hypertension or a reduction in the number of glomeruli. However, fostering the 6% group on to mothers that were fed a 20% protein diet during pregnancy resulted in normalization of the blood pressure and number of glomeruli.

Conclusion

The hypertension and reduced glomerular number resulting from prenatal dietary protein deprivation can be normalized by improving the postnatal environment.

Low nephron number and its clinical consequences

Epidemiologic studies now strongly support the hypothesis, proposed over two decades ago, that developmental programming of the kidney impacts an individual's risk for hypertension and renal disease in later life. Low birth weight is the strongest current clinical surrogate marker for an adverse intrauterine environment and, based on animal and human studies, is associated with a low nephron number. Other clinical correlates of low nephron number include female gender, short adult stature, small kidney size, and prematurity. Low nephron number in Caucasian and Australian Aboriginal subjects has been shown to be associated with higher blood pressures, and, conversely, hypertension is less prevalent in individuals with higher nephron numbers. In addition to nephron number, other programmed factors associated with the increased risk of hypertension include salt sensitivity, altered expression of renal sodium transporters, altered vascular reactivity, and sympathetic nervous system overactivity. Glomerular volume is universally found to vary inversely with nephron number, suggesting a degree of compensatory hypertrophy and hyperfunction in the setting of a low nephron number. This adaptation may become overwhelmed in the setting of superimposed renal insults, e.g. diabetes mellitus or rapid catch-up growth, leading to the vicious cycle of on-going hyperfiltration, proteinuria, nephron loss and progressive renal functional decline. Many millions of babies are born with low birth weight every year, and hypertension and renal disease prevalences are increasing around the globe. At present, little can be done clinically to augment nephron number; therefore adequate prenatal care and careful postnatal nutrition are crucial to optimize an individual's nephron number during development and potentially to stem the tide of the growing cardiovascular and renal disease epidemics worldwide.

IUGR in the absence of postnatal "catch-up" growth leads to improved whole body insulin sensitivity in rat offspring

A suboptimal in utero environment leads to fetal adaptations to ensure short-term survival but in the long-term may lead to disease when the postnatal growth does not reflect that in utero. This study examined the effect of IUGR on whole body insulin sensitivity and metabolic activity in adult rats. Female Wistar-Kyoto rats were fed either a normal protein diet (NPD 20% casein) or a low protein diet (LPD; 8.7% casein) during pregnancy and 2 wk of lactation. In offspring at 32 wk of age, indirect calorimetry and dual energy x-ray absorptiometry (DEXA) were performed to assess metabolic activity and body composition. Insulin sensitivity was assessed using a euglycemic-hyperinsulinemic clamp. At 3 d of age, male and female LPD offspring were 23 and 27% smaller than controls, respectively. They remained significantly smaller throughout the experimental period (∼10% smaller at 32 wk). Importantly, there was increased insulin sensitivity in LPD offspring (47% increase in males and 38% increase in females); pancreatic insulin content was normal. Body composition, O2 consumption, respiratory exchange ratio (RER), and locomotor activity were not different to controls. These findings suggest that in the absence of "catch-up" growth IUGR programs for improved insulin sensitivity.

Defining and redefining the nephron progenitor population

It has long been appreciated that the mammalian kidney arises via reciprocal interactions between an epithelial ureteric epithelium and the surrounding metanephric mesenchyme. More recently, lineage tracing has confirmed that the portion of the metanephric mesenchyme closest to the advancing ureteric tips, the cap mesenchyme, represents the progenitor population for the nephron epithelia. This Six2(+)Cited1(+) population undergoes self-renewal throughout nephrogenesis while retaining the potential to epithelialize. In contrast, the Foxd1(+) portion of the metanephric mesenchyme shows no epithelial potential, developing instead into the interstitial, perivascular, and possibly endothelial elements of the kidney. The cap mesenchyme rests within a nephrogenic niche, surrounded by the stroma and the ureteric tip. While the role of Wnt signaling in nephron induction is known, there remains a lack of clarity over the intrinsic and extrinsic regulation of cap mesenchyme specification, self-renewal, and nephron potential. It is also not known what regulates cessation of nephrogenesis, but there is no nephron generation in response to injury during the postnatal period. In this review, we will examine what is and is not known about this nephron progenitor population and discuss how an increased understanding of the regulation of this population may better explain the observed variation in final nephron number and potentially facilitate the reinitiation or prolongation of nephron formation.

Fetal uninephrectomy in male sheep alters the systemic and renal responses to angiotensin II infusion and AT1R blockade

Fetal uninephrectomy (uni-x) at 100 days of gestation results in compensatory nephrogenesis in the remaining kidney, resulting in a 30% reduction in total nephron number in male sheep. Recently, we showed that uni-x males at 6 mo of age have elevated arterial pressure, reduced renal blood flow (RBF), glomerular filtration rate (GFR), and low plasma renin levels (Singh R, Denton K, Bertram J, Jefferies A, Head G, Lombardo P, Schneider-Kolsky M, Moritz K. J Hypertens 27: 386–396, 2009; Singh R, Denton K, Jefferies A, Bertram J, Moritz K. Clin Sci (Lond) 118: 669–680, 2010). We hypothesized this was due to upregulation of the intrarenal renin-angiotensin system (RAS). In this study, renal responses to ANG II infusion and ANG II type 1 receptor (AT1R) blockade were examined in the same 6-mo-old male sheep. Uni-x animals had reduced levels of renal tissue and plasma renin and ANG II. Renal gene expression of renin, and gene and protein levels of AT1R and AT2R, were significantly lower in uni-x animals. In response to graded ANG II infusion, sham animals had the expected decrease in conscious RBF and GFR. Interestingly, the response was biphasic in uni-x sheep, with GFR initially decreasing, but then increasing at higher ANG II doses (34 ± 7%; Pgroup × treatment < 0.001), due to a paradoxical decrease in renal vascular resistance ( Pgroup × treatment < 0.001). In response to AT1R blockade, while GFR and RBF responded similarly between groups, there was a marked increase in sodium excretion in uni-x compared with sham sheep (209 ± 35 vs. 25 ± 12%; P < 0.001). In conclusion, in 6-mo-old male sheep born with a single kidney, these studies demonstrate that this is a low-renin form of hypertension, in which responses to ANG II are perturbed and the intrarenal RAS is downregulated.

Prenatal glucocorticoid exposure in the sheep alters renal development in utero: implications for adult renal function and blood pressure control

Treatment of the pregnant ewe with glucocorticoids early in pregnancy results in offspring with hypertension. This study examined whether glucocorticoids can reduce nephron formation or alter gene expression for sodium channels in the late gestation fetus. Sodium channel expression was also examined in 2-mo-old lambs, while arterial pressure and renal function was examined in adult female offspring before and during 6 wk of increased dietary salt intake. Pregnant ewes were treated with saline (SAL), dexamethasone (DEX; 0.48 mg/h) or cortisol (CORT; 5 mg/h) over days 26–28 of gestation (term = 150 days). At 140 days of gestation, glomerular number in CORT and DEX animals was 40 and 25% less, respectively, compared with SAL controls. Real-time PCR showed greater gene expression for the epithelial sodium channel (α-, β-, γ-subunits) and Na+-K+-ATPase (α-, β-, γ-subunits) in both the DEX and CORT group fetal kidneys compared with the SAL group with some of these changes persisting in 2-mo-old female offspring. In adulthood, sheep treated with dexamethasone or cortisol in utero had elevated arterial pressure and an apparent increase in single nephron glomerular filtration rate, but global renal hemodynamics and excretory function were normal and arterial pressure was not salt sensitive. Our findings show that the nephron-deficit in sheep exposed to glucocorticoids in utero is acquired before birth, so it is a potential cause, rather than a consequence, of their elevated arterial pressure in adulthood. Upregulation of sodium channels in these animals could provide a mechanistic link to sustained increases in arterial pressure in cortisol- and dexamethasone-exposed sheep, since it would be expected to promote salt and water retention during the postnatal period.

A design-based method for estimating glomerular number in the developing kidney

Low glomerular (nephron) endowment has been associated with an increased risk of cardiovascular and renal disease in adulthood. Nephron endowment in humans is determined by 36 wk of gestation, while in rats and mice nephrogenesis ends several days after birth. Specific genes and environmental perturbations have been shown to regulate nephron endowment. Until now, design-based method for estimating nephron number in developing kidneys was unavailable. This was due in part to the difficulty associated with unambiguously identifying developing glomeruli in histological sections. Here, we describe a method that uses lectin histochemistry to identify developing glomeruli and the physical disector/fractionator principle to provide unbiased estimates of total glomerular number (N(glom)). We have characterized N(glom) throughout development in kidneys from 76 rats and model this development with a 5-parameter logistic equation to predict N(glom) from embryonic day 17.25 to adulthood (r(2) = 0.98). This approach represents the first design-based method with which to estimate N(glom) in the developing kidney.

Renal programming: cause for concern?

Development of the kidney can be altered in utero in response to a suboptimal environment. The intrarenal factors that have been most well characterized as being sensitive to programming events are kidney mass/nephron endowment, the renin-angiotensin system, tubular sodium handling, and the renal sympathetic nerves. Newborns that have been subjected to an adverse intrauterine environment may thus begin life at a distinct disadvantage, in terms of renal function, at a time when the kidney must take over the primary role for extracellular fluid homeostasis from the placenta. A poor beginning, causing renal programming, has been linked to increased risk of hypertension and renal disease in adulthood. However, although a cause for concern, increasingly, evidence demonstrates that renal programming is not a fait accompli in terms of future cardiovascular and renal disease. A greater understanding of postnatal renal maturation and the impact of secondary factors (genes, sex, diet, stress, and disease) on this process is required to predict which babies are at risk of increased cardiovascular and renal disease as adults and to be able to devise preventative measures.

Calcium supplementation does not rescue the programmed adult bone deficits associated with perinatal growth restriction

Low birth weight and poor childhood growth program a variety of adult diseases including bone disorders such as osteoporosis. We have previously reported that offspring born small, as a result of uteroplacental insufficiency, have shorter femurs, lower bone mineral content and a bone strength deficit as adults. The aim of this study was to determine the effects of calcium supplementation from adolescence on growth restricted male and female offspring which have a programmed bone deficit. Bilateral uterine vessel ligation (Restricted) or sham surgery (Control) was performed on gestational day 18 in WKY rats to induce uteroplacental insufficiency and growth restriction. At 2 months pups were allocated to one of four diet groups: diet 1-constant normal calcium diet, diet 2-variable normal calcium diet, diet 3-constant high calcium diet, diet 4-variable high calcium diet. Diet groups 1 and 3 were fed their respective diets constantly for the duration of the study. In groups 2 and 4, rats were fed one diet for 5 days, followed by a switch to a low calcium diet for the next 5 days. At 6 months Dual Energy Xray Absorptiometry (DXA) and Peripheral Quantitative Computed Tomography (pQCT) were performed on the right femur. Bone turnover markers were measured at 4 months. Male and female Restricted offspring were born 14% lighter compared to Controls (p<0.05). At 6 months both male and female Restricted offspring remained smaller and had shorter femurs compared to Controls (p<0.05). Restricted males and females had reduced trabecular and cortical content compared to Controls, regardless of diet (p<0.05). Trabecular bone density was lower in Restricted females only (p<0.05). A constant high calcium diet increased cortical BMD in Restricted male and both female groups (p<0.05). Measures of bone geometry indicated that Restricted offspring have narrower bones with preservation of absolute cortical thickness (p<0.05). Importantly, the stress strain index of bone bending strength was lower in male and female Restricted offspring, regardless of diet by up to 9.0% and 7.8%, respectively. DXA results were similar to pQCT results. Being born small, due to uteroplacental insufficiency, programs reduced adult femur length, dimensions and stress strain index. Supplementation with a high calcium diet from adolescence can increase adult cortical bone density in low birth weight males and females, and normal weight females. This increase in bone density was not sufficient to rescue the bone dimension and strength deficits which were programmed in utero, suggesting that the early life environment is critical for bone programming.

Prenatal exposure to alcohol reduces nephron number and raises blood pressure in progeny

Prenatal ethanol exposure is teratogenic, but the effects of ethanol on kidney development and the health of offspring are incompletely understood. Our objective was to investigate the effects of acute ethanol exposure during pregnancy on nephron endowment, mean arterial pressure, and renal function in offspring. We administered ethanol or saline by gavage to pregnant Sprague-Dawley rats on embryonic days 13.5 and 14.5. At 1 month of age, the nephron number was 15% lower and 10% lower in ethanol-exposed males and females, respectively, compared with controls. Mean arterial pressure, measured in conscious animals via indwelling tail-artery catheter, was 10% higher in both ethanol-exposed males and females compared with controls. GFR was 20% higher in ethanol-exposed males but 15% lower in ethanol-exposed females; moreover, males had increased proteinuria compared with controls. Furthermore, embryonic kidneys cultured in the presence of ethanol for 48 hours had 15% fewer ureteric branch points and tips than kidneys cultured in control media. Taken together, these data demonstrate that acute prenatal ethanol exposure reduces the number of nephrons, possibly as a result of inhibited ureteric branching morphogenesis, and that these changes affect adult cardiovascular and renal function.

No juvenile arterial hypertension in sheep multiples despite reduced nephron numbers

Low birth weight is associated with an increased risk of metabolic dysfunction and arterial hypertension in later life. Because of their reduced birth weight twins have been used repeatedly as a natural model to investigate prenatal programming of hypertension. To reveal an early impact of lower nephron endowment on blood pressure, we performed a longitudinal study on lambs from single, twin and triplet pregnancies. The lambs were studied from birth until adulthood, including regular blood analyses, measurements of body weight and blood pressure and post-mortem estimation of glomerular numbers. Relative weight differences between multiples and singletons at birth were -28% for twins and -44% for triplets, respectively. Some lambs showed rapid catch-up growth. Total nephron number of twins and triplets was reduced by 21 and 37% with respect to that of singletons (p < 0.01). However, multiples did not show increased blood pressure within the time frame of this study. No gender-specific effect was observed. Plasma concentrations of creatinine, urea, electrolytes or osmolality also did not differ. Our data indicate that the previously reported postnatal blood pressure differences between sheep multiples and singletons are a time-limited phenomenon. During infancy and adolescence, a reduced nephron number in sheep multiples is neither associated with increased blood pressure nor reflected by plasma parameters.

Genetics of renal hypoplasia: insights into the mechanisms controlling nephron endowment

Renal hypoplasia, defined as abnormally small kidneys with normal morphology and reduced nephron number, is a common cause of pediatric renal failure and adult-onset disease. Genetic studies performed in humans and mutant mice have implicated a number of critical genes, in utero environmental factors and molecular mechanisms that regulate nephron endowment and kidney size. Here, we review current knowledge regarding the genetic contributions to renal hypoplasia with particular emphasis on the mechanisms that control nephron endowment in humans and mice.

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.

Uteroplacental insufficiency programs regional vascular dysfunction and alters arterial stiffness in female offspring

Intrauterine growth restriction caused by uteroplacental insufficiency increases the risk of cardiovascular disease in adulthood. Vascular mechanisms in female offspring are poorly understood. The aim of this study was to investigate the effects of uteroplacental insufficiency on blood pressure, vascular reactivity and arterial stiffness in four vascular beds in female offspring born growth restricted. Uteroplacental insufficiency was induced on day 18 of gestation in Wistar Kyoto rats by bilateral uterine vessel ligation (Restricted) or sham surgery (Controls). Wire and pressure myography were used to test endothelial and smooth muscle function, and passive mechanical wall properties, respectively, in uterine, mesenteric, renal and femoral arteries of 18-month-old female offspring. Collagen and elastin fibres were quantified using circular crossed-polarized light microscopy and quantitative real time polymerase chain reaction. Restricted female offspring were born 10-15% smaller. Restricted females were normotensive, had plasma triglycerides 2-fold elevated and had uterine endothelial dysfunction, attributed to a 23% reduction in the maximal relaxation produced by endothelium-derived hyperpolarizing factor. Uterine artery stiffness was increased, with an augmented proportion of thick and decreased proportion of thin collagen fibres. Vascular reactivity and mechanical wall properties were preserved in mesenteric, renal and femoral arteries in growth restricted females. Female offspring born growth restricted have selective uterine artery endothelial dysfunction and increased wall stiffness. The preserved vascular function in other arteries may explain the lack of hypertension in these females. The uterine artery specific dysfunction has potential implications for impaired pregnancy adaptations and a compromised intrauterine environment of the next generation.

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

A potential role of the intrauterine environment in the development of low nephron number and hypertension in later life has been recently recognized in experimental studies and is also postulated in certain conditions in human beings. Nephrogenesis is influenced by genetic as well as by environmental and in particular maternal factors. In man nephrogenesis, i.e. the formation of nephrons during embryogenesis, takes place from weeks 5 to 36 of gestation with the most rapid phase of nephrogenesis occurring from the mid-2nd trimester until 36 weeks. This 16 week period is a very vulnerable phase where genetic and environmental factors such as maternal diet or medication could influence and disturb nephron formation leading to lower nephron number. Given a constant rise in body mass until adulthood lower nephron number may become "nephron underdosing" and result in maladaptive glomerular changes, i.e. glomerular hyperfiltration and glomerular enlargement. These maladaptive changes may then eventually lead to the development of glomerular and systemic hypertension and renal disease in later life. It is the purpose of this review to discuss the currently available experimental and clinical evidence for factors and mechanisms that could interfere with nephrogenesis with particular emphasis on maternal nutrition. In addition, we discuss the emerging concept of low nephron number being a new cardiovascular risk factor in particular for essential hypertension in later life.

The clinical importance of nephron mass

Abundant evidence supports the association between low birth weight (LBW) and renal dysfunction in humans. Anatomic measurements of infants, children, and adults show significant inverse correlation between LBW and nephron number. Nephron numbers are also lower in individuals with hypertension compared with normotension among white and Australian Aboriginal populations. The relationship between nephron number and hypertension among black individuals is still unclear, although the high incidence of LBW predicts low nephron number in this population as well. LBW, a surrogate for low nephron number, also associates with increasing BP from childhood to adulthood and increasing risk for chronic kidney disease in later life. Because nephron numbers can be counted only postmortem, surrogate markers such as birth weight, prematurity, adult height, reduced renal size, and glomerulomegaly are potentially useful for risk stratification, for example, during living-donor assessment. Because early postnatal growth also affects subsequent risk for higher BP or reduced renal function, postnatal nutrition, a potentially modifiable factor, in addition to intrauterine effects, has significant influence on long-term cardiovascular and renal health.

Review: Sex specific programming: a critical role for the renal renin-angiotensin system

The "Developmental Origins of Health and Disease" hypothesis has caused resurgence of interest in understanding the factors regulating fetal development. A multitude of prenatal perturbations may contribute to the onset of diseases in adulthood including cardiovascular and renal diseases. Using animal models such as maternal glucocorticoid exposure, maternal calorie or protein restriction and uteroplacental insufficiency, studies have identified alterations in kidney development as being a common feature. The formation of a low nephron endowment may result in impaired renal function and in turn may contribute to disease. An interesting feature in many animal models of developmental programming is the disparity between males and females in the timing of onset and severity of disease outcomes. The same prenatal insult does not always affect males and females in the same way or to the same degree. Recently, our studies have focused on changes induced in the kidney of both the fetus and the offspring, following a perturbation during pregnancy. We have shown that changes in the renin-angiotensin system (RAS) occur in the kidney. The changes are often sex specific which may in part explain the observed sex differences in disease outcomes and severity. This review explores the evidence suggesting a critical role for the RAS in sex specific developmental programming of disease with particular reference to the immediate and long term changes in the local RAS within the kidney.

Role of the kidney in the prenatal and early postnatal programming of hypertension

Epidemiologic studies from several different populations have demonstrated that prenatal insults, which adversely affect fetal growth, result in an increased incidence of hypertension when the offspring reaches adulthood. It is now becoming evident that low-birth-weight infants are also at increased risk for chronic kidney disease. To determine how prenatal insults result in hypertension and chronic kidney disease, investigators have used animal models that mimic the adverse events that occur in pregnant women, such as dietary protein or total caloric deprivation, uteroplacental insufficiency, and prenatal administration of glucocorticoids. This review examines the role of the kidney in generating and maintaining an increase in blood pressure in these animal models. This review also discusses how early postnatal adverse events may have repercussions in later life. Causes for the increase in blood pressure by perinatal insults are likely multifactorial and involve a reduction in nephron number, dysregulation of the systemic and intrarenal renin-angiotensin system, increased renal sympathetic nerve activity, and increased tubular sodium transport. Understanding the mechanism for the increase in blood pressure and renal injury resulting from prenatal insults may lead to therapies that prevent hypertension and the development of chronic kidney and cardiovascular disease.

Early postnatal overfeeding induces early chronic renal dysfunction in adult male rats

Low birth weight is associated with an increased risk of hypertension and renal dysfunction at adulthood. Such an association has been shown to involve a reduction of nephron endowment and to be enhanced by accelerated postnatal growth in humans. However, while low-birth-weight infants often undergo catch-up growth, little is known about the long-term vascular and renal effects of accelerated postnatal growth. We surimposed early postnatal overfeeding (OF; reduction of litter size during the suckling period) to appropriate-birth-weight (NBW+OF) and intrauterine growth restriction (IUGR; IUGR+OF) pups, obtained after a maternal gestational low-protein diet. Blood pressure (systolic blood pressure; SBP) and renal function (glomerular filtration rate; GFR) were measured in young and aging offspring. Glomerulosclerosis and nephron number were determined in aging offspring (22 mo). Nephron number was reduced in both IUGR and IUGR+OF male offspring (by 24 and 26%). GFR was reduced by 40% in 12-mo-old IUGR+OF male offspring, and both NBW+OF and IUGR+OF aging male offspring had sustained hypertension (+25 mmHg) and glomerulosclerosis, while SBP and renal function were unaffected in IUGR aging offspring. Female offspring were unaffected. In conclusion, in this experimental model, early postnatal OF in the neonatal period has major long-lasting effects. Such effects are gender dependent. Reduced nephron number alone, associated with IUGR, may not be sufficient to induce long-lasting physiological alterations, and early postnatal OF acts as a "second hit." Early postnatal OF is a suitable model with which to study the long-term effects of postnatal growth in the pathogenesis of vascular disorders and renal disease.

Impact of maternal undernutrition on diabetes and cardiovascular disease risk in adult offspring

Epidemiological, clinical, and experimental observations have led to the hypothesis that the risk of developing chronic diseases in adulthood is influenced not only by genetic and adult lifestyle factors, but also by environmental factors during early life. Low birth weight, a marker of intrauterine stress, has been linked to predisposition to cardiovascular disease (CVD) and diabetes. The compelling animal evidence and significant human data to support this conclusion are reviewed. Specifically, the review discusses the role of maternal nutrition before and during pregnancy, placental insufficiencies and epigenetic changes in the increased predisposition to diabetes and CVD in adult life. The impact of low birth weight and catch-up growth as they pertain to risk of disease in adult life is also discussed. In addition, adult disease risk in the overnourished fetus is also mentioned. Reference is made to some of the mechanisms of the induction of diabetes and CVD phenotype. It is proposed that fetal nutrition, growth and development through efficient maternal nutrition before and during pregnancy could constitute the basis for nutritional strategies for the primary prevention of diabetes and CVD.

Prenatal growth restriction and postnatal growth restriction followed by accelerated growth independently program reduced bone growth and strength

Low birth weight increases the risk of developing adult onset cardiovascular and metabolic diseases. Recently being born small has also been identified as a risk factor for adverse bone growth, development and adult fracture risk. Evidence also suggests that accelerated growth in offspring of normal birth weight, following periods of slowed growth, can also independently program adult diseases. The aim of this study was to determine the relative roles of prenatal and postnatal growth restriction on adult bone characteristics and strength. Bilateral uterine vessel ligation (Restricted) or sham surgery (Control) was performed on gestational day 18 in WKY rats to induce fetal growth restriction. Control, Reduced (reduced Control litter size to match Restricted) and Restricted pups were cross-fostered onto different Control (normal lactation) or Restricted (impaired lactation) mothers 1 day after birth. Femur length, dimensions, strength, mineral content and density were quantified using DXA and pQCT analysis. Markers of bone turnover were measured in offspring at 6 months. Restricted pups were born lighter than Controls with males, not females, remaining smaller than Control-on-Control at 6 months (P<0.05). Pups born of normal weight from a reduced litter suckling on a Restricted mother (Reduced-on-Restricted) grew slowly during lactation then quicker after weaning compared to Controls (P<0.05). Cortical bone mineral content, dimensions and strength were lower in Restricted-on-Restricted and Reduced-on-Restricted offspring compared to Controls with lower density in Reduced-on-Restricted females (P<0.05). The stress strain index of bone bending strength remained lower in the Restricted male offspring when body weight adjustments were made. Cross-fostering Restricted females, but not males, onto mothers with normal lactation (Restricted-on-Control) restored growth and bone parameters to Controls (P<0.05). Being born small, or postnatal growth restriction for normal birth weight offspring followed by accelerated growth, programs bone content and strength deficits. Deficits were corrected by improving postnatal nutrition for females born small, highlighting sex specific programming outcomes and impact of postnatal nutrition. These findings suggest a link between growth restriction and adult bone health with additional studies needed to further explore this link in humans.

Uteroplacental insufficiency causes a nephron deficit, modest renal insufficiency but no hypertension with ageing in female rats

In rats, uteroplacental insufficiency induced by uterine vessel ligation restricts fetal growth and impairs mammary development compromising postnatal growth. In male offspring, this results in a nephron deficit and hypertension which can be reversed by improving lactation and postnatal growth. Here, growth, blood pressure and nephron endowment in female offspring from mothers which underwent bilateral uterine vessel ligation (Restricted) on day 18 of pregnancy were examined. Sham surgery (Control) and a reduced litter group (Reduced at birth to 5, equivalent to Restricted group) were used as controls. Offspring (Control, Reduced, Restricted) were cross-fostered on postnatal day 1 onto a Control (normal lactation) or Restricted (impaired lactation) mother. Restricted-on-Restricted offspring were born small but were of similar weight to Control-on-Control by postnatal day 35. Blood pressure was not different between groups at 8, 12 or 20 weeks of age. Glomerular number was reduced in Restricted-on-Restricted offspring at 6 months without glomerular hypertrophy. Cross-fostering a Restricted pup onto a Control dam resulted in a glomerular number intermediate between Control-on-Control and Restricted-on-Restricted. Blood pressure, along with renal function, morphology and mRNA expression, was examined in Control-on-Control and Restricted-on-Restricted females at 18 months. Restricted-on-Restricted offspring did not become hypertensive but developed glomerular hypertrophy by 18 months. They had elevated plasma creatinine and alterations in renal mRNA expression of transforming growth factor-beta(1), collagen IV (alpha1) and matrix matelloproteinase-9. This suggests that perinatally growth restricted female offspring may be susceptible to onset of renal injury and renal insufficiency with ageing in the absence of concomitant hypertension.