Intrauterine growth restriction increases blood pressure and central pulse pressure measured with telemetry in aging rats

High Sucrose Ingestion during a Critical Period of Vessel Development Promotes the Synthetic Phenotype of Vascular Smooth Muscle Cells and Modifies Vascular Contractility Leading to Hypertension in Adult Rats

Cardiometabolic diseases, including hypertension, may result from exposure to high sugar diets during critical periods of development. Here, we studied the effect of sucrose ingestion during a critical period (CP) between postnatal days 12 and 28 of the rat on blood pressure, aortic histology, vascular smooth muscle phenotype, expression of metalloproteinases 2 and 9, and vascular contractility in adult rats and compared it with those of adult rats that received sucrose for 6 months and developed metabolic syndrome (MS). Blood pressure increased to a similar level in CP and MS rats. The diameter of lumen, media, and adventitia of aortas from CP rats was decreased. Muscle fibers were discontinuous. There was a decrease in the expression of alpha-actin in CP and MS rat aortas, suggesting a change to the secretory phenotype in vascular smooth muscle. Metalloproteinases 2 and 9 were decreased in CP and MS rats, suggesting that phenotype remains in an altered steady stationary state with little interchange of the vessel matrix. Aortic contraction to norepinephrine did not change, but aortic relaxation was diminished in CP and MS aortas. In conclusion, high sugar diets during the CP increase predisposition to hypertension in adults.

Early Programming of Adult Systemic Essential Hypertension

Cardiovascular diseases are being included in the study of developmental origins of health and disease (DOHaD) and essential systemic hypertension has also been added to this field. Epigenetic modifications are one of the main mechanisms leading to early programming of disease. Different environmental factors occurring during critical windows in the early stages of life may leave epigenetic cues, which may be involved in the programming of hypertension when individuals reach adulthood. Such environmental factors include pre-term birth, low weight at birth, altered programming of different organs such as the blood vessels and the kidney, and living in disadvantageous conditions in the programming of hypertension. Mechanisms behind these factors that impact on the programming include undernutrition, oxidative stress, inflammation, emotional stress, and changes in the microbiota. These factors and their underlying causes acting at the vascular level will be discussed in this paper. We also explore the establishment of epigenetic cues that may lead to hypertension at the vascular level such as DNA methylation, histone modifications (methylation and acetylation), and the role of microRNAs in the endothelial cells and blood vessel smooth muscle which participate in hypertension. Since epigenetic changes are reversible, the knowledge of this type of markers could be useful in the field of prevention, diagnosis or epigenetic drugs as a therapeutic approach to hypertension.

Conflicting Effects of Fetal Growth Restriction on Blood Pressure Between Human and Rat Offspring: A Meta-Analysis

Low birth weight is associated with hypertension. Low birth weight can result from fetal growth restriction (FGR) or prematurity. FGR is postulated to impact blood pressure (BP) by developmental programming. This systematic review and meta-analysis studies BP in human and animal offspring following FGR. Pubmed and Web of Science were searched for studies reporting on BP after placental insufficiency induced FGR compared with normal growth controls. Primary outcome was mean absolute BP difference (ΔBP mm Hg [95% CI]). Meta-analysis was performed using random-effects models. Subgroup analyses were executed on species, sex, age, pregnancy duration, and stress during BP readings. Due to large interspecies heterogeneity, analyses were performed separately for human (n=41) and animal (n=31) studies, the latter restricted to rats (n=27). Human studies showed a ΔBP between FGR and controls of -0.6 mm Hg ([95% CI, -1.7 to 0.6]; I²=91%). Mean ΔBP was -2.6 mm Hg (95% CI, -5.7 to 0.4) in women versus -0.5 mm Hg (95% CI, -3.7 to 2.7) in men. Subgroup analyses did not indicate age, gestational age, and stress during measurements as sources of heterogeneity. In rats, mean BP was 12.0 mm Hg ([95% CI, 8.8-15.2]; I²=81%) higher in FGR offspring. This difference was more pronounced in FGR males (13.6 mm Hg [95% CI, 10.3-17.0] versus 9.1 mm Hg [95% CI, 5.3-12.8]). Subgroup analyses on age showed no statistical interaction. BP readings under restrained conditions resulted in larger BP differences between FGR and control rats (15.3 mm Hg [95% CI, 11.6-18.9] versus 5.7 mm Hg [95% CI, 1.1-10.3]). Rat studies confirm the relation between FGR and offspring BP, while observational studies in humans do not show such differences. This may be due to the observational nature of human studies, methodological limitations, or an absence of this phenomenon in humans. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: CRD42018091819.

Effect of Sucrose Ingestion at the End of a Critical Window that Increases Hypertension Susceptibility on Peripheral Mechanisms Regulating Blood Pressure in Rats. Role of Sirtuins 1 and 3

Susceptibility to develop hypertension may be established during early stages of life that include the intrauterine period, infancy and childhood. We recently showed that blood pressure increased when rats reached adulthood when sucrose was ingested for a short-term critical window from postnatal day 12 to 28 in the rat, which corresponds to days around weaning. Here, we studied several factors that might participate in the increased susceptibility to hypertension when adulthood is reached by analyzing the changes produced at the end of the sucrose ingestion during this critical period. Body weight of the rats at the end of the sucrose period was decreased even if there was an increased ingestion in Kcal. We found an increase in blood pressure accompanied by a decrease in endothelial nitric oxide synthase (eNOS) expression in the aorta. When insulin was administered to rats receiving sucrose, glucose in plasma diminished later than in controls and this slight insulin resistance may reduce nitric oxide synthase action. Oleic acid that modulates eNOS expression was increased, lipoperoxidation was elevated and total non-enzymatic anti-oxidant capacity was decreased. There was also a decrease in SOD2 expression. We also studied the expression of Sirt1, which regulates eNOS expression and Sirt3, which regulates SOD2 expression as possible epigenetic targets of enzyme expression involved in the long- term programming of hypertension. Sirt3 was decreased but we did not find an alteration in Sirt1 expression. We conclude that these changes may underpin the epigenetic programming of increased susceptibility to develop hypertension in the adults when there was exposure to high sucrose levels near weaning in rats.

Short-Term Exposure to High Sucrose Levels near Weaning Has a Similar Long-Lasting Effect on Hypertension as a Long-Term Exposure in Rats

Adverse conditions during early developmental stages permanently modify the metabolic function of organisms through epigenetic changes. Exposure to high sugar diets during gestation and/or lactation affects susceptibility to metabolic syndrome or hypertension in adulthood. The effect of a high sugar diet for shorter time lapses remains unclear. Here we studied the effect of short-term sucrose ingestion near weaning (postnatal days 12 and 28) (STS) and its effect after long-term ingestion, for a period of seven months (LTS) in rats. Rats receiving sucrose for seven months develop metabolic syndrome (MS). The mechanisms underlying hypertension in this model and those that underlie the effects of short-term exposure have not been studied. We explore NO and endothelin-1 concentration, endothelial nitric oxide synthase (eNOS) expression, fatty acid participation and the involvement of oxidative stress (OS) after LTS and STS. Blood pressure increased to similar levels in adult rats that received sucrose during short- and long-term glucose exposure. The endothelin-1 concentration increased only in LTS rats. eNOS and SOD2 expression determined by Western blot and total antioxidant capacity were diminished in both groups. Saturated fatty acids and arachidonic acid were only decreased in LTS rats. In conclusion, a high-sugar diet during STS increases the hypertension predisposition in adulthood to as high a level as LTS, and the mechanisms involved have similarities (participation of OS and eNOS and SOD expression) and differences (fatty acids and arachidonic acid only participate in LTS and an elevated level of endothelin-1 was only found in LTS) in both conditions. Changes in the diet during short exposure times in early developmental stages have long-lasting effects in determining hypertension susceptibility.

Perinatal and long-term effects of maternal uterine artery adenoviral VEGF-A165 gene therapy in the growth-restricted guinea pig fetus

Uterine artery application of adenoviral vascular endothelial growth factor A₁₆₅ (Ad.VEGF-A₁₆₅) gene therapy increases uterine blood flow and fetal growth in experimental animals with fetal growth restriction (FGR). Whether Ad.VEGF-A₁₆₅ reduces lifelong cardiovascular disease risk imposed by FGR remains unknown. Here, pregnant guinea pigs fed 70% normal food intake to induce FGR received Ad.VEGF-A₁₆₅ (1×10¹⁰ viral particles, n = 15) or vehicle ( n = 10), delivered to the external surface of the uterine arteries, in midpregnancy. Ad libitum-fed controls received vehicle only ( n = 14). Litter size, gestation length, and perinatal mortality were similar in control, untreated FGR, and FGR+Ad.VEGF-A₁₆₅ animals. When compared with controls, birth weight was lower in male but higher in female pups following maternal nutrient restriction, whereas both male and female FGR+Ad.VEGF-A₁₆₅ pups were heavier than untreated FGR pups ( P < 0.05, ANOVA). Postnatal weight gain was 10-20% greater in female FGR+Ad.VEGF-A₁₆₅ than in untreated FGR pups, depending on age, although neither group differed from controls. Maternal nutrient restriction reduced heart weight in adult female offspring irrespective of Ad.VEGF-A₁₆₅ treatment but did not alter ventricular wall thickness. In males, postnatal weight gain and heart morphology were not affected by maternal treatment. Neither systolic, diastolic, mean arterial pressure, adrenal weight, nor basal or challenged plasma cortisol were affected by maternal undernutrition or Ad.VEGF-A₁₆₅ in either sex. Therefore, increased fetal growth conferred by maternal uterine artery Ad.VEGF-A₁₆₅ is sustained postnatally in FGR female guinea pigs. In this study, we did not find evidence for an effect of maternal nutrient restriction or Ad.VEGF-A₁₆₅ therapy on adult offspring blood pressure.

Role of renal sympathetic nerve activity in prenatal programming of hypertension

Prenatal insults, such as maternal dietary protein deprivation and uteroplacental insufficiency, lead to small for gestational age (SGA) neonates. Epidemiological studies from many different parts of the world have shown that SGA neonates are at increased risk for hypertension and early death from cardiovascular disease as adults. Animal models, including prenatal administration of dexamethasone, uterine artery ligation and maternal dietary protein restriction, result in SGA neonates with fewer nephrons than controls. These models are discussed in this educational review, which provides evidence that prenatal insults lead to altered sodium transport in multiple nephron segments. The factors that could result in increased sodium transport are discussed, focusing on new information that there is increased renal sympathetic nerve activity that may be responsible for augmented renal tubular sodium transport. Renal denervation abrogates the hypertension in programmed rats but has no effect on control rats. Other potential factors that could cause hypertension in programmed rats, such as the renin-angiotensin system, are also discussed.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

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

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

Childhood kidney outcomes in relation to fetal blood flow and kidney size

Impaired fetal abdominal blood flow may lead to smaller kidneys and subsequent impaired kidney function in later life. In a prospective cohort study among 923 pregnant women and their children, we measured fetal growth, kidney volumes, and umbilical and cerebral artery blood flow (median gestational age of 30.3 weeks; 95% range, 28.5-32.7 weeks). We used a higher umbilical/cerebral artery pulsatility index ratio as an indicator of preferential fetal blood flow to the upper body parts at the expense of the intra-abdominal organs. At a median age of 5.9 years (95% range, 5.7-6.6 years), we measured childhood kidney volumes, creatinine and cystatin C blood levels, microalbuminuria, BP, and eGFR. A preferential fetal blood flow to the upper body parts at the expense of the intra-abdominal organs associated only with a smaller combined kidney volume in childhood. Fetal combined kidney volume positively associated with childhood combined kidney volume and eGFR, and inversely associated with childhood creatinine and cystatin C levels (all P values <0.05), but did not associate with childhood microalbuminuria and BP. Children within the highest tertile of fetal umbilical/cerebral ratio and the lowest tertile of fetal combined kidney volume had the lowest eGFR (difference, -6.36 ml/min per 1.73 m(2); 95% confidence interval, -11.78 to -0.94 compared with children within the middle tertiles). These data suggest that impaired fetal blood to the abdominal organs and smaller fetal kidney size are associated with subclinical changes in kidney outcomes in school-aged children.

Prenatal exposure to dexamethasone in the mouse alters cardiac growth patterns and increases pulse pressure in aged male offspring

Exposure to synthetic glucocorticoids during development can result in later cardiovascular and renal disease in sheep and rats. Although prenatal glucocorticoid exposure is associated with impaired renal development, less is known about effects on the developing heart. This study aimed to examine the effects of a short-term exposure to dexamethasone (60 hours from embryonic day 12.5) on the developing mouse heart, and cardiovascular function in adult male offspring. Dexamethasone (DEX) exposed fetuses were growth restricted compared to saline treated controls (SAL) at E14.5, but there was no difference between groups at E17.5. Heart weights of the DEX fetuses also tended to be smaller at E14.5, but not different at E17.5. Cardiac AT_1aR, Bax, and IGF-1 mRNA expression was significantly increased by DEX compared to SAL at E17.5. In 12-month-old offspring DEX exposure caused an increase in basal blood pressure of ∼3 mmHg. In addition, DEX exposed mice had a widened pulse pressure compared to SAL. DEX exposed males at 12 months had an approximate 25% reduction in nephron number compared to SAL, but no difference in cardiomyocyte number. Exposure to DEX in utero appears to adversely impact on nephrogenesis and heart growth but is not associated with a cardiomyocyte deficit in male mice in adulthood, possibly due to compensatory growth of the myocardium following the initial insult. However, the widened pulse pressure may be indicative of altered vascular compliance.

Pre-weaning growth hormone treatment reverses hypertension and endothelial dysfunction in adult male offspring of mothers undernourished during pregnancy

Maternal undernutrition results in elevated blood pressure (BP) and endothelial dysfunction in adult offspring. However, few studies have investigated interventions during early life to ameliorate the programming of hypertension and vascular disorders. We have utilised a model of maternal undernutrition to examine the effects of pre-weaning growth hormone (GH) treatment on BP and vascular function in adulthood. Female Sprague-Dawley rats were fed either a standard control diet (CON) or 50% of CON intake throughout pregnancy (UN). From neonatal day 3 until weaning (day 21), CON and UN pups received either saline (CON-S, UN-S) or GH (2.5 ug/g/day)(CON-GH, UN-GH). All dams were fed ad libitum throughout lactation. Male offspring were fed a standard diet until the end of the study. Systolic blood pressure (SBP) was measured at day 150 by tail cuff plethysmography. At day 160, intact mesenteric vessels mounted on a pressure myograph. Responses to pressure, agonist-induced constriction and endothelium-dependent vasodilators were investigated to determine vascular function. SBP was increased in UN-S groups and normalised in UN-GH groups (CON-S 121±2 mmHg, CON-GH 115±3, UN-S 146±3, UN-GH 127±2). Pressure mediated dilation was reduced in UN-S offspring and normalised in UN-GH groups. Vessels from UN-S offspring demonstrated a reduced constrictor response to phenylephrine and reduced vasodilator response to acetylcholine (ACh). Furthermore, UN-S offspring vessels displayed a reduced vasodilator response in the presence of L-NG-Nitroarginine Methyl Ester (L-NAME), carbenoxolone (CBX), L-NAME and CBX, Tram-34 and Apamin. UN-GH vessels showed little difference in responses when compared to CON and significantly increased vasodilator responses when compared to UN-S offspring. Pre-weaning GH treatment reverses the negative effects of maternal UN on SBP and vasomotor function in adult offspring. These data suggest that developmental cardiovascular programming is potentially reversible by early life GH treatment and that GH can reverse the vascular adaptations resulting from maternal undernutrition.

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.

Developmental programming of energy balance and its hypothalamic regulation

Developmental programming is an important physiological process that allows different phenotypes to originate from a single genotype. Through plasticity in early life, the developing organism can adopt a phenotype (within the limits of its genetic background) that is best suited to its expected environment. In humans, together with the relative irreversibility of the phenomenon, the low predictive value of the fetal environment for later conditions in affluent countries makes it a potential contributor to the obesity epidemic of recent decades. Here, we review the current evidence for developmental programming of energy balance. For a proper understanding of the subject, knowledge about energy balance is indispensable. Therefore, we first present an overview of the major hypothalamic routes through which energy balance is regulated and their ontogeny. With this background, we then turn to the available evidence for programming of energy balance by the early nutritional environment, in both man and rodent models. A wealth of studies suggest that energy balance can indeed be permanently affected by the early-life environment. However, the direction of the effects of programming appears to vary considerably, both between and within different animal models. Because of these inconsistencies, a comprehensive picture is still elusive. More standardization between studies seems essential to reach veritable conclusions about the role of developmental programming in adult energy balance and obesity.

Pathways linking the early environment to long-term health and lifespan

The intrauterine environment is a major contributor to normal physiological growth and development of an individual. Disturbances at this critical time can affect the long-term health of the offspring. Low birth weight individuals have strong correlations with increased susceptibility to type 2 diabetes and cardiovascular disease in later-life. These observations led to the Thrifty Phenotype Hypothesis which suggested that these associations arose because of the response of a growing fetus to a suboptimal environment such as poor nutrition. Animal models have shown that environmentally induced intrauterine growth restriction increases the risk of a variety of diseases later in life. These detrimental features are also observed in high birth weight offspring from mothers who were obese or consumed a high fat diet during gestation. Recent advances in our understanding of the mechanisms underlying this phenomenon have elucidated several potential candidates for the long-term effects of the early environment on the function and metabolism of a cell. These include: (1) Epigenetic alterations (e.g. DNA methylation and histone modifications), which regulate specific gene expression and can be influenced by the environment, both during gestation and early postnatal life and (2) Oxidative stress that changes the balance between reactive oxygen species generation (e.g. through mitochondrial dysfunction) and antioxidant defense capacity. This has permanent effects on cellular ageing such as regulation of telomere length. Further understanding of these processes will help in the development of therapeutic strategies to increase healthspan and reduced the burden of age-associated diseases.

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.

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.

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.

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.

Hypertension and microalbuminuria in children with congenital solitary kidneys

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Influence of intrauterine growth restriction on renal function in the adult rat

Intrauterine growth restriction (IUGR) has been shown to influence renal development and lead to fewer nephrons. Data on long term renal function after IUGR are limited. We studied the effect on renal function of IUGR in aging rats. IUGR was induced using a model of bilateral uterine artery ligation in pregnant Wistar rats. Renal function was studied at the age of 18 months. In male IUGR rats, estimated glomerular filtration rate was significantly decreased compared to male control rats [1.1 (SD 0.3) 1.7 (SD 0.3) ml x min(-1), p<0.05]. Female IUGR rats showed an increased urinary protein excretion compared with female control rats [84 (SD 73) vs. 12 (SD 13) mg x 24h(-1), p<0.01]. All male rats showed heavy proteinuria (p<0.01 vs. female rats from same experimental group), with no significant differences between the groups. Tubular reabsorption of phosphorus was lower in females, but showed no differences between the experimental groups. In conclusion, IUGR impairs renal function in the rat. It is suggested that a low nephron endowment leads to proteinuria as a sign of glomerular damage, and ends with a decrease in glomerular filtration rate as a sign of glomerular loss.

Intrauterine growth restriction and risk for arterial hypertension: a causal relationship?

AIMS

Intrauterine growth restriction (IUGR) has been demonstrated to have serious consequences for health in adult age. These include an increased risk for metabolic syndrome, pulmonary and cardiovascular disorders. These disorders are in part secondary to the development of arterial hypertension, which has been demonstrated to be more frequent in individuals subjected to restricted intrauterine growth.

METHODS

A review on publications on pathogenesis and epidemiology of hypertension associated to IUGR.

RESULTS

Current concepts for this association include a reduced nephrogenesis and increased arterial stiffness, impaired sympathetic regulation and steroid metabolism secondary to IUGR. Early postnatal risk-modifying factors include among others catch-up growth leading to childhood overweight.

CONCLUSION

IUGR increases the risk of hypertension in adult life. Identifying relevant risk factors for arterial hypertension will be the basis for the development of preventive concepts to be applied for predisposed individuals.

Prenatal high-salt diet in the Sprague-Dawley rat programs blood pressure and heart rate hyperresponsiveness to stress in adult female offspring

Several animal models have been developed to study fetal programming of hypertension. One model involves feeding high-salt (HS) diet to rats before and during pregnancy, during lactation, and after weaning for 10 days. In the present investigation, we limited HS diet to the prenatal period in an attempt to find a narrower critical window for fetal programming. The HS diet did not result in low-birth weight offspring. In the adult offspring, radiotelemetry was used to assess blood pressure and heart rate in the conscious unstressed state. As adults, the HS offspring were not hypertensive compared with normal-salt (NS) control animals. However, the pressor and tachycardic responses to 1-h of restraint were significantly enhanced in HS female offspring, and recovery after restraint was delayed. This was accompanied by an increase in relative expression of corticotropin-releasing hormone (CRH) mRNA in the paraventricular nucleus of the hypothalamus during basal and stressed conditions. There was no augmented stress response or relative increase in CRH mRNA in adult HS male offspring. When challenged with 1 wk of 8% NaCl diet as adults, neither HS male nor female offspring exhibited salt sensitivity compared with NS groups. These data show that a high-salt diet limited to the prenatal period is not sufficient to program hypertension in adult offspring. However, this narrower critical period is sufficient to imprint a lasting hyperresponsiveness to stress, at least in adult female offspring. These data indicate that excessive maternal salt intake during pregnancy can adversely affect the cardiovascular health of adult offspring.

Prenatal programming of nephron number and blood pressure

A low nephron number has been advocated to explain the association between intrauterine growth restriction (IUGR) and hypertension in later life. IUGR not only leads to a low birth weight but is also hypothesized to reprogram nephrogenesis, which results in a low nephron endowment. Several methods are used to estimate the total glomerular number, but only stereological techniques result in accurate (unbiased) and precise (reproducible) data. Several studies, both in humans and animal models that have used these methods indeed revealed that IUGR leads to a low nephron number. According to the hyperfiltration hypothesis, this reduction in renal mass is supposed to lead to glomerular hyperfiltration and hypertension in remnant nephrons with subsequent glomerular injury with proteinuria, systemic hypertension and glomerulosclerosis. Even though IUGR is associated with both a low nephron endowment and an increased risk of hypertension, only circumstantial evidence is available to support the hyperfiltration hypothesis after prenatal programming. A prerequisite for establishment of this association in long-term, prospective follow-up studies is the ability to estimate glomerular numbers in living human beings, for which a further advancement in radiological techniques is necessary. Only then can the association between nephron endowment and blood pressure in humans be studied more conclusively.

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

Uteroplacental insufficiency in the rat restricts fetal growth, impairs mammary development, compromising postnatal growth; and increases adult BP. The roles of prenatal and postnatal nutritional restraint on later BP and nephron endowment in offspring from mothers that underwent bilateral uterine vessel ligation (restricted) on day 18 of pregnancy were examined. Sham surgery (control) and a group of rats with reduced litter size (reduced; litter size reduced at birth to five, equivalent to restricted group) were used as controls. Offspring (control, reduced, and restricted) were cross-fostered on postnatal day 1 onto a control (normal lactation) or restricted (impaired lactation) mother. BP in male offspring was determined by tail cuff at 8, 12, and 20 wk of age, with glomerular number and volume (Cavalieri/Physical Dissector method) and renal angiotensin II type 1 receptor (AT(1)R) mRNA expression (real-time PCR) determined at 6 mo. Restricted-on-restricted male offspring developed hypertension (+16 mmHg) by 20 wk together with a nephron deficit (-26%) and glomerular hypertrophy (P < 0.05). In contrast, providing a normal lactational environment to restricted offspring improved postnatal growth and prevented the nephron deficit and hypertension. Reduced-on-restricted pups that were born of normal weight but with impaired growth during lactation subsequently grew faster, developed hypertension (+16 mmHg), had increased AT(1A)R and AT(1B)R mRNA expression (P < 0.05), but had no nephron deficit. Our study identifies the prenatal and postnatal nutritional environments in the programming of adult hypertension, associated with distinct renal changes. It is shown for the first time that a prenatally induced nephron deficit can be restored by correcting growth restriction during lactation.