Developmental programming: variations in early growth and adult disease

Postnatal persistence of nonhuman primate sex-dependent renal structural and molecular changes programmed by intrauterine growth restriction

BACKGROUND

Poor nutrition during fetal development programs postnatal kidney function. Understanding postnatal consequences in nonhuman primates (NHP) is important for translation to our understanding the impact on human kidney function and disease risk. We hypothesized that intrauterine growth restriction (IUGR) in NHP persists postnatally, with potential molecular mechanisms revealed by Western-type diet challenge.

METHODS

IUGR juvenile baboons were fed a 7-week Western diet, with kidney biopsies, blood, and urine collected before and after challenge. Transcriptomics and metabolomics were used to analyze biosamples.

RESULTS

Pre-challenge IUGR kidney transcriptome and urine metabolome differed from controls. Post-challenge, sex and diet-specific responses in urine metabolite and renal signaling pathways were observed. Dysregulated mTOR signaling persisted postnatally in female pre-challenge. Post-challenge IUGR male response showed uncoordinated signaling suggesting proximal tubule injury.

CONCLUSION

Fetal undernutrition impacts juvenile offspring kidneys at the molecular level suggesting early-onset blood pressure dysregulation.

DNA methylation at the crossroads of gene and environment interactions

DNA methylation is an epigenetic mark involved in regulating genome function and is critical for normal development in mammals. It has been observed that the developmental environment can lead to permanent changes in gene expression and DNA methylation, at least at 'metastable epialleles'. These are defined as regions of the genome that show a variable epigenetic state that is established early in development and maintained through subsequent cell divisions. However, the majority of the known genome does not behave in this manner. Here, we use the developmental origins of adult disease hypothesis to understand environmental epigenomics. Some challenges to studying how DNA methylation is influenced by the environment include identifying DNA methylation changes associated with an environmental exposure in tissues with a complex cellular composition and at genomic regions for which DNA methylation is dynamically regulated in a cell-type specific manner. We also offer a perspective of how emerging technologies may be useful for dissecting the functional contribution of exposure-associated epigenetic changes and highlight recent evidence that suggests that genomic regions that are absent from genome assemblies may be unappreciated hotspots for environmental modulation of the epigenetic state.

Reducing Pup Litter Size Alters Early Postnatal Calcium Homeostasis and Programs Adverse Adult Cardiovascular and Bone Health in Male Rats

The in utero and early postnatal environments play essential roles in offspring growth and development. Standardizing or reducing pup litter size can independently compromise long-term health likely due to altered milk quality, thus limiting translational potential. This study investigated the effect reducing litter size has on milk quality and offspring outcomes. On gestation day 18, dams underwent sham or bilateral uterine vessel ligation surgery to generate dams with normal (Control) and altered (Restricted) milk quality/composition. At birth, pups were cross-fostered onto separate dams with either an unadjusted or reduced litter size. Plasma parathyroid hormone-related protein was increased in Reduced litter pups, whereas ionic calcium and total body calcium were decreased. These data suggest Reduced litter pups have dysregulated calcium homeostasis in early postnatal life, which may impair bone mineralization decreasing adult bone bending strength. Dams suckling Reduced litter pups had increased milk long-chain monounsaturated fatty acid and omega-3 docosahexaenoic acid. Reduced litter pups suckled by Normal milk quality/composition dams had increased milk omega-6 linoleic and arachidonic acids. Reduced litter male adult offspring had elevated blood pressure. This study highlights care must be taken when interpreting data from research that alters litter size as it may mask subtle cardiometabolic health effects.

Angiotensin receptor blockade in juvenile male rat offspring: Implications for long-term cardio-renal health

Inhibition of the renin-angiotensin system in early postnatal life is a potential therapeutic approach to prevent long-term cardiovascular and kidney diseases in individuals born small. We determined the long-term effects of juvenile losartan treatment on cardiovascular and kidney function in control male rat offspring and those exposed to uteroplacental insufficiency and born small. Bilateral uterine vessel ligation (Restricted) or sham (Control) surgery was performed in late gestation in Wistar Kyoto rats. At weaning, male offspring were randomly assigned to receive losartan in their drinking water or drinking water alone from 5 to 8 weeks of age, and followed to 26 weeks of age. Systolic blood pressure and kidney function were assessed throughout the study. Pressure myography was used to assess passive mechanical wall properties in mesenteric and femoral arteries from 26-week-old offspring. Losartan treatment for three weeks lowered systolic blood pressure in both Control and Restricted groups but this difference was not sustained after the cessation of treatment. Losartan, irrespective of birth weight, mildly increased renal tubulointerstitial fibrosis when assessed at 26 weeks of age. Mesenteric artery stiffness was increased by the early losartan treatment, and was associated with increased collagen and decreased elastin content. Losartan also exerted long-term increases in fat mass and decreases in skeletal muscle mass. In this study, untreated Restricted offspring did not develop hypertension, vascular dysfunction or kidney changes as anticipated. Regardless, we demonstrate that short-term losartan treatment in the juvenile period negatively affects postnatal growth, and kidney and vascular parameters in adulthood, irrespective of birth weight. The long-term effects of early-life losartan treatment warrant further consideration in settings where the potential benefits may outweigh the risks; i.e. when programmed adulthood diseases are apparent and in childhood cardiovascular and kidney diseases.

Low-protein diet does not alter reproductive, biochemical, and hematological parameters in pregnant Wistar rats

The aim of this study was to investigate the reproductive, biochemical, and hematological outcomes of pregnant rats exposed to protein restriction. Wistar rat dams were fed a control normal-protein (NP, 17% protein, n=8) or a low-protein (LP, 8% protein, n=14) diet from the 1st to the 20th day of pregnancy. On the 20th day, the clinical signs of toxicity were evaluated. The pregnant rats were then anesthetized and blood samples were collected for biochemical-hematological analyses, and laparotomy was performed to evaluate reproductive parameters. No sign of toxicity, or differences (P>0.05) in body weight gain and biochemical parameters (urea, creatinine, albumin, globulin, and total protein) between NP and LP pregnant dams were observed. Similarly, hematological data, including red blood cell count, white blood cell count, hemoglobin, hematocrit, red blood cell distribution width (coefficient of variation), mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, % lymphocytes, absolute lymphocyte count, platelet count, and mean platelet volume were similar (P>0.05) at the end of pregnancy. Reproductive parameters (the dam-offspring relationship, ovary mass, placenta mass, number of corpora lutea, implantation index, resorption index, and the pre- and post-implantation loss rates) were also not different (P>0.05) between NP and LP pregnant dams. The present data showed that a protein-restricted diet during pregnancy did not alter reproductive, biochemical, and hematological parameters and seems not to have any toxic effect on pregnant Wistar rats.

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

Hypertension and chronic kidney disease (CKD) have a significant impact on global morbidity and mortality. The Low Birth Weight and Nephron Number Working Group has prepared a consensus document aimed to address the relatively neglected issue for the developmental programming of hypertension and CKD. It emerged from a workshop held on April 2, 2016, including eminent internationally recognized experts in the field of obstetrics, neonatology, and nephrology. Through multidisciplinary engagement, the goal of the workshop was to highlight the association between fetal and childhood development and an increased risk of adult diseases, focusing on hypertension and CKD, and to suggest possible practical solutions for the future. The recommendations for action of the consensus workshop are the results of combined clinical experience, shared research expertise, and a review of the literature. They highlight the need to act early to prevent CKD and other related noncommunicable diseases later in life by reducing low birth weight, small for gestational age, prematurity, and low nephron numbers at birth through coordinated interventions. Meeting the current unmet needs would help to define the most cost-effective strategies and to optimize interventions to limit or interrupt the developmental programming cycle of CKD later in life, especially in the poorest part of the world.

Adrenal, metabolic and cardio-renal dysfunction develops after pregnancy in rats born small or stressed by physiological measurements during pregnancy

KEY POINTS

Women born small are at an increased risk of developing pregnancy complications. Stress may further increase a woman's likelihood for an adverse pregnancy. Adverse pregnancy adaptations can lead to long-term diseases even after her pregnancy. The current study investigated the effects of stress during pregnancy on the long-term adrenal, metabolic and cardio-renal health of female rats that were born small. Stress programmed increased adrenal Mc2r gene expression, a higher insulin secretory response to glucose during intraperitoneal glucose tolerance test (+36%) and elevated renal creatinine clearance after pregnancy. Females that were born small had increased homeostatic model assessment-insulin resistance and elevated systolic blood pressure after pregnancy, regardless of stress exposure. These findings suggest that being born small or being stressed during pregnancy programs long-term adverse health outcomes after pregnancy. However, stress in pregnancy does not exacerbate the long-term adverse health outcomes for females that were born small.

ABSTRACT

Females born small are more likely to experience complications during their pregnancy, including pregnancy-induced hypertension, pre-eclampsia and gestational diabetes. The risk of developing complications is increased by stress exposure during pregnancy. In addition, pregnancy complications may predispose the mother to diseases after pregnancy. We determined whether stress during pregnancy would exacerbate the adrenal, metabolic and cardio-renal dysfunction of growth-restricted females in later life. Late gestation bilateral uterine vessel ligation was performed in Wistar Kyoto rats to induce growth restriction. At 4 months, growth-restricted and control female offspring were mated with normal males. Those allocated to the stressed group had physiological measurements [metabolic cage, tail cuff blood pressure, intraperitoneal glucose tolerance test (IPGTT)] conducted during pregnancy whilst the unstressed groups were unhandled. After the completion of pregnancy, dams were aged to 12 months and blood pressure, and metabolic and renal function were assessed. At 13 months, adrenal glands, pancreases and plasma were collected at post-mortem. Females stressed during pregnancy had increased adrenal Mc2r gene expression (+22%), higher insulin secretory response to glucose during IPGTT (+36%) and higher creatinine clearance (+29%, indicating increased estimated glomerular filtration rate). In contrast, females that were born small had increased homeostatic model assessment-insulin resistance (+54%), increased water intake (+23%), urine output (+44%) and elevated systolic blood pressure (+7%) regardless of exposure to stress. Our findings suggest that low maternal birth weight and maternal stress exposure during pregnancy are both independently detrimental for long-term adrenal, metabolic and cardio-renal health of the mother, although their effects were not exacerbated.

Resveratrol partially prevents oxidative stress and metabolic dysfunction in pregnant rats fed a low protein diet and their offspring

Protein restriction in pregnancy produces maternal and offspring metabolic dysfunction potentially as a result of oxidative stress. Data are lacking on the effects of inhibition of oxidative stress. We hypothesized that maternal resveratrol administration decreases oxidative stress, preventing, at least partially, maternal low protein-induced maternal and offspring metabolic dysfunction. In the present study, pregnant wistar rats ate control (C) (20% casein) or a protein-restricted (R) (10% casein) isocaloric diet. Half of each group received resveratrol orally, 20 mg kg(-1) day(-1), throughout pregnancy. Post-delivery, mothers and offspring ate C. Oxidative stress biomarkers and anti-oxidant enzymes were measured in placenta, maternal and fetal liver, and maternal serum corticosterone at 19 days of gestation (dG). Maternal (19 dG) and offspring (postnatal day 110) glucose, insulin, triglycerides, cholesterol, fat and leptin were determined. R mothers showed metabolic dysfunction, increased corticosterone and oxidative stress and reduced anti-oxidant enzyme activity vs. C. R placental and fetal liver oxidative stress biomarkers and anti-oxidant enzyme activity increased. R offspring showed higher male and female leptin, insulin and corticosterone, male triglycerides and female fat than C. Resveratrol decreased maternal leptin and improved maternal, fetal and placental oxidative stress markers. R induced offspring insulin and leptin increases were prevented and other R changes were offspring sex-dependent. Resveratrol partially prevents low protein diet-induced maternal, placental and sex-specific offspring oxidative stress and metabolic dysfunction. Oxidative stress is one mechanism programming offspring metabolic outcomes. These studies provide mechanistic evidence to guide human pregnancy interventions when fetal nutrition is impaired by poor maternal nutrition or placental function.

Pediatric obesity prevention: From naïve examination of energy imbalance towards strategies that influence the competition for nutrient resources among tissues

Current pediatric obesity interventions have collectively yielded relatively unsuccessful results. In this Field of Vision, we present plausible physiologic underpinnings fostering ineffectiveness of conventional strategies grounded in requisite induction of negative energy imbalance. Moreover, such recommendations exacerbate the underlying metabolic dysfunction by further limiting metabolic fuel availability, lowering energy expenditure, and increasing hunger (recapitulating the starvation response amid apparent nutritional adequacy) which precede and promote obesity during growth and development. The qualitative aspects of musculoskeletal system (i.e., endocrine response, muscle functional capacity) are likely to improve metabolic function and increase nutrient delivery and utilization. An intricate and complex system including multiple feedback mechanisms operates to homeostatically regulate energy balance and support optimal body composition trajectories and metabolic health, during growth and development. Thus, ignoring the interdependencies of regulatory growth processes initiates a nuanced understanding of energy regulation and thus misguided attempts at preventive strategies. Importantly, these gains are not dependent upon weight-loss, rather we suggest can be achieved through resistance training. Collectively, optimizing musculoskeletal health via resistance training elicits augmentation of competitive capacity across systems. Further, substantial gains can be achieved in skeletal muscle mass, strength, and functional capacity through resistance training in a relatively short period of time.

Adult exercise effects on oxidative stress and reproductive programming in male offspring of obese rats

Exercise improves health but few data are available regarding benefits of exercise in offspring exposed to developmental programming. There is currently a worldwide epidemic of obesity. Obesity in pregnant women predisposes offspring to obesity. Maternal obesity has well documented effects on offspring reproduction. Few studies address ability of offspring exercise to reduce adverse outcomes. We observed increased oxidative stress and impaired sperm function in rat offspring of obese mothers. We hypothesized that regular offspring exercise reverses adverse effects of maternal obesity on offspring sperm quality and fertility. Female Wistar rats ate chow (C) or high-energy, obesogenic diet (MO) from weaning through lactation, bred at postnatal day (PND) 120, and ate their pregnancy diet until weaning. All offspring ate C diet from weaning. Five male offspring (different litters) ran on a wheel for 15 min, 5 times/week from PND 330 to 450 and were euthanized at PND 450. Average distance run per session was lower in MO offspring who had higher body weight, adiposity index, and gonadal fat and showed increases in testicular oxidative stress biomarkers. Sperm from MO offspring had reduced antioxidant enzyme activity, lower sperm quality, and fertility. Exercise in MO offspring decreased testicular oxidative stress, increased sperm antioxidant activity and sperm quality, and improved fertility. Exercise intervention has beneficial effects on adiposity index, gonadal fat, oxidative stress markers, sperm quality, and fertility. Thus regular physical exercise in male MO offspring recuperates key male reproductive functions even at advanced age: it's never too late.

Adverse prenatal environment and kidney development: implications for programing of adult disease

The 'developmental origins of health and disease' hypothesis suggests that many adult-onset diseases can be attributed to altered growth and development during early life. Perturbations during gestation can be detrimental and lead to an increased risk of developing renal, cardiovascular, metabolic, and neurocognitive dysfunction in adulthood. The kidney has emerged as being especially vulnerable to insult at almost any stage of development resulting in a reduction in nephron endowment. In both humans and animal models, a reduction in nephron endowment is strongly associated with an increased risk of hypertension. The focus of this review is twofold: i) to determine the importance of specific periods during development on long-term programing and ii) to examine the effects of maternal perturbations on the developing kidney and how this may program adult-onset disease. Recent evidence has suggested that insults occurring around the time of conception also have the capacity to influence long-term health. Although epigenetic mechanisms are implicated in mediating these outcomes, it is unclear as to how these may impact on kidney development. This presents exciting new challenges and areas for research.