Temporal alterations in vascular angiotensin receptors and vasomotor responses in offspring of protein-restricted rat dams

Protein restriction during peripubertal period impairs endothelial aortic function in adult male Wistar rats

Protein restriction during early phases of body development, such as intrauterine life can favor the development of vascular disorders. However, it is not known if peripubertal protein restriction can favor vascular dysfunction in adulthood. The present study aimed to evaluated whether a protein restriction diet during peripubertal period favors endothelial dysfunction in adulthood. Male Wistar rats from postnatal day (PND) 30 until 60 received a diet with either 23% protein (CTR group) or with 4% protein (LP group). At PND 120, the thoracic aorta reactivity to phenylephrine, acetylcholine, and sodium nitroprusside was evaluated in the presence or absence of: endothelium, indomethacin, apocynin and tempol. The maximum response (Rmax) and pD2 (-log of the concentration of the drug that causes 50% of the Rmax) were calculated. The lipid peroxidation and catalase activity were also evaluated in the aorta. The data were analyzed by ANOVA (one or two-ways and Tukey's) or independent t-test; the results were expressed as mean ± S.E.M., p < 0.05. The Rmax to phenylephrine in aortic rings with endothelium were increased in LP rats when compared with the Rmax in CTR rats. Apocynin and tempol reduced Rmax to phenylephrine in LP aortic rings but not in CTR. The aortic response to the vasodilators was similar between the groups. Aortic catalase activity was lower and lipid peroxidation was greater in LP compared to CTR rats. Therefore, protein restriction during the peripubertal period causes endothelial dysfunction in adulthood through a mechanism related to oxidative stress.

Sex-dependent effects of prenatal food and protein restriction on offspring physiology in rats and mice: systematic review and meta-analyses

BACKGROUND

Males and females may experience different effects of early-life adversity on life-long health. One hypothesis is that male foetuses invest more in foetal growth and relatively less in placental growth, and that this makes them susceptible to poor nutrition in utero, particularly if nutrition is reduced part-way through gestation.

OBJECTIVES

Our objectives were to examine whether (1) food and/ or protein restriction in rats and mice has consistent sex-dependent effects, (2) sex-dependency differs between types of outcomes, and (3) males are more severely affected when restriction starts part-way through gestation.

DATA SOURCES

PubMed and Web of Science were searched to identify eligible studies.

STUDY ELIGIBILITY CRITERIA

Eligible studies described controlled experiments that restricted protein or food during gestation in rats or mice, examined physiological traits in offspring from manipulated pregnancies, and tested whether effects differed between males and females.

RESULTS

Our search identified 292 articles, of which the full texts of 72 were assessed, and 65 were included for further synthesis. A majority (50) used Wistar or Sprague-Dawley rats and so these were the primary focus. Among studies in which maternal diet was restricted for the duration of gestation, no type of trait was consistently more severely affected in one particular sex, although blood pressure was generally increased in both sexes. Meta-analysis found no difference between sexes in the effect of protein restriction throughout gestation on blood pressure. Among studies restricting food in the latter half of gestation only, there were again few consistent sex-dependent effects, although three studies found blood pressure was increased in males only. Meta-analysis found that food restriction in the second half of gestation increased adult blood pressure in both sexes, with a significantly greater effect in males. Birthweight was consistently reduced in both sexes, a result confirmed by meta-analysis.

CONCLUSIONS

We found little support for the hypotheses that males are more affected by food and protein restriction, or that effects are particularly severe if nutrition is reduced part-way through gestation. However, less than half of the studies tested for sex by maternal diet interactions to identify sex-dependent effects. As a result, many reported sex-specific effects may be false positives.

Testosterone plays a permissive role in angiotensin II-induced hypertension and cardiac hypertrophy in male rats

Sex hormones contribute to sex differences in blood pressure. Inappropriate activation of the renin-angiotensin system is involved in vascular dysfunction and hypertension. This study evaluated the role of androgens (testosterone) in angiotensin II (Ang II)-induced increase in blood pressure, vascular reactivity, and cardiac hypertrophy. Eight-week-old male Wistar rats underwent sham operation, castration, or castration with testosterone replacement. After 12 weeks of chronic changes in androgen status, Ang II (120 ng/kg per minute) or saline was infused for 28 days via subcutaneous miniosmotic pump, and changes in blood pressure was measured. Vascular reactivity and Ang II receptor levels were examined in mesenteric arteries. Heart weight, cardiac ANP mRNA levels, and fibrosis were also assessed. Ang II infusion increased arterial pressure in intact males. The Ang II-induced increase in hypertensive response was prevented in castrated males. Testosterone replacement in castrated males restored Ang II-induced hypertensive responses. Castration reduced vascular AT1R/AT2R ratio, an effect that was reversed by testosterone replacement. Ang II-induced hypertension was associated with increased contractile response of mesenteric arteries to Ang II and phenylephrine in intact and testosterone-replaced castrated males; these increases were prevented in castrated males. Ang II infusion induced increased left ventricle-to-body weight ratio and ANP mRNA expression, indicators of left ventricular hypertrophy, and fibrosis in intact and testosterone-replaced castrated males, and castration prevented the increase in these parameters caused by Ang II. This study demonstrates that testosterone plays a permissive role in development and maintenance of Ang II-induced vascular dysfunction, hypertension, and cardiac hypertrophy.

Mechanisms of Sex Disparities in Cardiovascular Function and Remodeling

Epidemiological studies demonstrate disparities between men and women in cardiovascular disease prevalence, clinical symptoms, treatments, and outcomes. Enrollment of women in clinical trials is lower than men, and experimental studies investigating molecular mechanisms and efficacy of certain therapeutics in cardiovascular disease have been primarily conducted in male animals. These practices bias data interpretation and limit the implication of research findings in female clinical populations. This review will focus on the biological origins of sex differences in cardiovascular physiology, health, and disease, with an emphasis on the sex hormones, estrogen and testosterone. First, we will briefly discuss epidemiological evidence of sex disparities in cardiovascular disease prevalence and clinical manifestation. Second, we will describe studies suggesting sexual dimorphism in normal cardiovascular function from fetal life to older age. Third, we will summarize and critically discuss the current literature regarding the molecular mechanisms underlying the effects of estrogens and androgens on cardiac and vascular physiology and the contribution of these hormones to sex differences in cardiovascular disease. Fourth, we will present cardiovascular disease risk factors that are positively associated with the female sex, and thus, contributing to increased cardiovascular risk in women. We conclude that inclusion of both men and women in the investigation of the role of estrogens and androgens in cardiovascular physiology will advance our understanding of the mechanisms underlying sex differences in cardiovascular disease. In addition, investigating the role of sex-specific factors in the development of cardiovascular disease will reduce sex and gender disparities in the treatment and diagnosis of cardiovascular disease. © 2019 American Physiological Society. Compr Physiol 9:375-411, 2019.

Fetal programming of the metabolic syndrome

Prenatal development is currently recognized as a critical period in the etiology of human diseases. This is particularly so when an unfavorable environment interacts with a genetic predisposition. The fetal programming concept suggests that maternal nutritional imbalance and metabolic disturbances may have a persistent and intergenerational effect on the health of offspring and on the risk of diseases such as obesity, diabetes, and cardiovascular diseases.

A Low-Protein Diet Enhances Angiotensin II Production in the Lung of Pregnant Rats but not Nonpregnant Rats

Pulmonary angiotensin II production is enhanced in pregnant rats fed a low-protein (LP) diet. Here we assessed if LP diet induces elevations in angiotensin II production in nonpregnant rats and whether Ace expression and ACE activity in lungs are increased. Nonpregnant rats were fed a normal (CT) or LP diet for 8, 12, or 17 days and timed pregnant rats fed for 17 days from Day 3 of pregnancy. Plasma angiotensin II, expressions of Ace and Ace2, and activities of these proteins in lungs, kidneys, and plasma were measured. These parameters were compared among nonpregnant rats or between nonpregnant and pregnant rats fed different diets. Major findings are as follows: (1) plasma angiotensin II levels were slightly higher in the LP than CT group on Days 8 and 12 in nonpregnant rats; (2) expression of Ace and Ace2 and abundance and activities of ACE and ACE2 in lungs, kidneys, and plasma of nonpregnant rats were unchanged by LP diet except for minor changes; (3) the abundance and activities of ACE in lungs of pregnant rats fed LP diet were greater than nonpregnant rats, while those of ACE2 were decreased. These results indicate that LP diet-induced increase in pulmonary angiotensin II production depends on pregnancy.

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

Blunted hypothalamic ghrelin signaling reduces diet intake in rats fed a low-protein diet in late pregnancy

Diet intake in pregnant rats fed a low‐protein (LP) diet was significantly reduced during late pregnancy despite elevated plasma levels of ghrelin. In this study, we hypothesized that ghrelin signaling in the hypothalamus is blunted under a low‐protein diet condition and therefore, it does not stimulate diet intake during late pregnancy. Female Sprague–Dawley rats were fed a normal (CT) or LP diet from Day 1 of pregnancy. On Day 21, 0.5 μg ghrelin was given into the third ventricle (ICV). Diet and water intake at 30, 60, and 120 min after ICV injection was measured. Hypothalami were dissected and analyzed for expression of genes related to appetite regulation (Npy, Agrp, Pomc and Cart) and phosphorylation of AMPK and ACC proteins (downstream proteins of ghrelin receptor activation). Results include: In response to ICV injection of ghrelin, (1) diet intake was significantly lower in LP compared to CT rats; (2) water intake was not affected in LP rats; (3) expression of Npy and Agrp, but not Pomc and Cart, were higher in the hypothalamus of LP compared to CT rats; (4) the abundance of phosphorylated AMPK and the ratio of phosphorylated to total AMPK, but not the abundance of total AMPK, were lower in LP compared to CT rats; (5) the abundance of phosphorylated ACC, but not total ACC, was lower in LP rats. These findings suggest that blunted ghrelin signaling in the hypothalamus of pregnant rats fed a LP diet leads to reduced diet intake and exacerbates gestational protein insufficiency.

Appetite regulation is independent of the changes in ghrelin levels in pregnant rats fed low-protein diet

Gestational protein restriction causes hypertension in the adult offspring. Very little is known about the food intake regulation and ghrelin signaling in pregnant dams fed a low-protein (LP) diet. We hypothesized that diet intake and ghrelin signaling are altered in pregnant rats fed the low-protein diet. Sprague–Dawley rats were fed a control (CT) or LP diet from Day 3 of pregnancy. Diet intake and body weight were monitored daily. Expression of ghrelin production-related genes in the stomach and appetite-related genes in the hypothalamus was analyzed by real-time PCR. Plasma levels of total and active ghrelin, growth hormone and leptin were measured by ELISA. Main results include: (1) Daily diet intake was greater in the LP group than in the CT group in early pregnancy, but substantially lower in late pregnancy; (2) Daily gain in body weight was substantially lower in the LP group in late pregnancy; (3) Expression of ghrelin production-related genes in the stomach and plasma total ghrelin levels were increased in LP group in late pregnancy; (4) Plasma active ghrelin levels were elevated in the LP group at mid-late pregnancy, but growth hormone and leptin levels were uncorrelated with active ghrelin in late pregnancy; and (5) Hypothalamic expression of ghrelin-stimulated genes in LP rats was unassociated with the changes in both plasma ghrelin levels and the diet intake. Taken together, the appetite in LP rats is greater in early pregnancy but reduced at late pregnancy, possibly due to ghrelin insensitivity in appetite regulation.

Intrauterine programming

In mammals, the intrauterine condition has an important role in the development of fetal physiological systems in later life. Suboptimal maternal environment can alter the regulatory pathways that determine the normal development of the fetus in utero, which in post-natal life may render the individual more susceptible to cardiovascular or metabolic adult-life diseases. Changes in the intrauterine availability of nutrients, oxygen and hormones can change the fetal tissue developmental regulatory planning, which occurs genomically and non-genomically and can cause permanent structural and functional changes in the systems, leading to diseases in early years of life and those that particularly become overt in adulthood. In this review we take a brief look at the main elements which program the fetal system development and consequently induce a crucial impact on the cardiovascular, nervous and hormonal systems in adulthood.

Enhanced mesenteric arterial responsiveness to angiotensin II is androgen receptor-dependent in prenatally protein-restricted adult female rat offspring

Gestational protein restriction results in intrauterine growth restriction and hypertension in adult female growth-restricted rats. Enhanced vascular responsiveness to angiotensin II is observed, and blockade of the renin-angiotensin system abolishes hypertension in adult growth-restricted rats, suggesting that the renin-angiotensin system contributes to intrauterine growth restriction-induced hypertension. Moreover, growth-restricted adult rats have higher plasma testosterone levels, and antiandrogen treatment abolishes hypertension, indicating an important role for testosterone. We hypothesized that androgens may play a pivotal role in the enhanced responsiveness to Ang II and hypertension. Female offspring of pregnant rats fed 20% protein (control) or 6% protein diet (protein restricted), at 6 mo of age, were studied. Plasma testosterone and mean arterial pressure in protein-restricted offspring were significantly higher compared to controls. Flutamide treatment (10 mg/kg/day subcutaneously for 10 days) reduced mean arterial pressure in protein-restricted offspring but was without significant effect in controls. Vascular Agtr1/Agtr2 ratio was significantly higher in protein-restricted offspring, an effect that was reversed by flutamide. Flutamide treatment did not have any effect on Agtr1/Agtr2 ratio in controls. Enhanced contractile response to angiotensin II in mesenteric arteries was observed in protein-restricted offspring compared with control. Flutamide treatment reversed the enhanced contractile response to angiotensin II in protein-restricted offspring without significant effect in controls. Vascular reactivity to phenylephrine was similar between the control and protein-restricted offspring with and without flutamide treatment, suggesting that enhanced contractile response and flutamide's reversal effect is specific to angiotensin II. These results suggest that prenatally protein-restricted rats exhibit an enhanced responsiveness to angiotensin II that is testosterone-dependent.

Sex differences in the developmental origins of cardiovascular disease

The Developmental Origins of Health and Disease (DOHaD) proposes that adverse events during early life program an increased risk for cardiovascular disease. Experimental models provide proof of concept but also indicate that insults during early life program sex differences in adult blood pressure and cardiovascular risk. This review will highlight the potential mechanisms that contribute to the etiology of sex differences in the developmental programming of cardiovascular disease.

Gestational protein restriction impairs insulin-regulated glucose transport mechanisms in gastrocnemius muscles of adult male offspring

Type II diabetes originates from various genetic and environmental factors. Recent studies showed that an adverse uterine environment such as that caused by a gestational low-protein (LP) diet can cause insulin resistance in adult offspring. The mechanism of insulin resistance induced by gestational protein restriction is not clearly understood. Our aim was to investigate the role of insulin signaling molecules in gastrocnemius muscles of gestational LP diet-exposed male offspring to understand their role in LP-induced insulin resistance. Pregnant Wistar rats were fed a control (20% protein) or isocaloric LP (6%) diet from gestational day 4 until delivery and a normal diet after weaning. Only male offspring were used in this study. Glucose and insulin responses were assessed after a glucose tolerance test. mRNA and protein levels of molecules involved in insulin signaling were assessed at 4 months in gastrocnemius muscles. Muscles were incubated ex vivo with insulin to evaluate insulin-induced phosphorylation of insulin receptor (IR), Insulin receptor substrate-1, Akt, and AS160. LP diet-fed rats gained less weight than controls during pregnancy. Male pups from LP diet-fed mothers were smaller but exhibited catch-up growth. Plasma glucose and insulin levels were elevated in LP offspring when subjected to a glucose tolerance test; however, fasting levels were comparable. LP offspring showed increased expression of IR and AS160 in gastrocnemius muscles. Ex vivo treatment of muscles with insulin showed increased phosphorylation of IR (Tyr972) in controls, but LP rats showed higher basal phosphorylation. Phosphorylation of Insulin receptor substrate-1 (Tyr608, Tyr895, Ser307, and Ser318) and AS160 (Thr642) were defective in LP offspring. Further, glucose transporter type 4 translocation in LP offspring was also impaired. A gestational LP diet leads to insulin resistance in adult offspring by a mechanism involving inefficient insulin-induced IR, Insulin receptor substrate-1, and AS160 phosphorylation and impaired glucose transporter type 4 translocation.

Prenatal testosterone induces sex-specific dysfunction in endothelium-dependent relaxation pathways in adult male and female rats

Prenatal testosterone (T) exposure impacts postnatal cardiovascular function, leading to increases in blood pressure with associated decreased endothelium-dependent vascular relaxation in adult females. Endothelial function in males is not known. Furthermore, which of the endothelial pathways contributes to endothelial dysfunction and if there exists sex differences are not known. The objective of this study was to characterize the relative contribution of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) to the impaired endothelium-dependent vasodilation in prenatal T-exposed adult males and females. Offspring of pregnant rats treated with T propionate or its vehicle were examined. Telemetric blood pressure levels and endothelium-dependent vascular reactivity were assessed with wire myography. Levels of nitric oxide synthase (NOS3) and Kcnn3 and Kcnn4 channel expression were examined in mesenteric arteries. Mean arterial pressure was significantly higher in T males and females than in controls. Endothelium-dependent acetylcholine relaxation was significantly lower in both T males and females. EDHF-mediated relaxation was specifically blunted in T males (Emax = 48.64% ± 3.73%) compared to that in control males (Emax = 81.71% ± 3.18%); however, NO-mediated relaxation was specifically impaired in T females (Emax = 36.01% ± 4.29%) compared with that in control females (Emax = 54.56% ± 6.37%). Relaxation to sodium nitroprusside and levcromakalim were unaffected with T-treatment. NOS3 protein was decreased in T females but not in T males. Kcnn3 expression was decreased in both T males and females compared to controls. These findings suggest that prenatal T leads to an increase in blood pressure in the adult offspring, associated with blunting of endothelial cell-associated relaxation and that the effects are sex-specific: EDHF-related in males and NO-related in females.

Gestational protein restriction increases angiotensin II production in rat lung

Gestational protein restriction (PR) alters the renin-angiotensin system in uterine arteries and placentas and elevates plasma levels of angiotensin II in pregnant rats. To date, how PR increases maternal plasma levels of angiotensin II remains unknown. In this study, we hypothesize that the expression and/or the activity of angiotensin I converting enzyme (peptidyl-dipeptidase A) 1 (ACE) in lungs, but not kidneys and blood, largely contribute to elevated plasma angiotensin II levels in pregnant rats subject to gestational PR. Time-scheduled pregnant Sprague-Dawley rats were fed a normal or low-protein diet from Day 3 of pregnancy until euthanized at Day 19 or 22. Expressions of Ace and Ace2 (angiotens in I converting enzyme [peptidyl-dipeptidase A] 2) in lungs and kidneys from pregnant rats by quantitative real-time PCR and Western blotting, and the activities of these proteins in lungs, kidneys, and plasma, were measured. The mRNA levels of Ace and Ace2 in lungs were elevated by PR at both Days 19 and 22 of pregnancy. The abundance of ACE protein in lungs was increased, but ACE2 protein was decreased, by PR. The activities of ACE, but not ACE2, in lungs were increased by PR. PR did not change expressions of Ace and Ace2, the activities of both ACE and ACE2 in kidneys, and the abundance and activity of plasma ACE. These findings suggest that maternal lungs contribute to the elevated plasma levels of angiotensin II by increasing both the expression and the activity of ACE in response to gestational PR.