Neonatal catch up growth increases diabetes susceptibility but improves behavioral and cardiovascular outcomes of low birth weight male mice

Neonatal Leptin Levels Predict the Early Childhood Developmental Assessment Scores of Preterm Infants

Preterm infants have low circulating levels of leptin, a key trophic hormone that influences growth and development. While the clinical importance of prematurity-associated leptin deficiency is undefined, recent preclinical and clinical investigations have shown that targeted enteral leptin supplementation can normalize neonatal leptin levels. We tested the hypothesis that, independent of growth velocity, prematurity-related neonatal leptin deficiency predicts adverse cardiovascular and neurodevelopmental outcomes. In a planned 2-year longitudinal follow-up of 83 preterm infants born at 22 to 32 weeks' gestation, we obtained blood pressures from 58 children and the Ages & Stages Questionnaire (ASQ-3) for 66 children. Based on univariate analysis, blood pressures correlated with gestational age at birth (R = 0.30, p < 0.05) and weight gain since discharge (R = 0.34, p < 0.01). ASQ-3 scores were significantly higher in female than male children. Utilizing best subset regression with Mallows' C_p as the criterion for model selection, higher systolic blood pressure was predicted by rapid postnatal weight gain, later gestation at delivery and male sex (C_p = 3.0, R = 0.48). Lower ASQ-3 was predicted by lower leptin levels at 35 weeks postmenstrual age, earlier gestation at delivery and male sex (C_p = 2.9, R = 0.45). Children that had leptin levels above 1500 pg/mL at 35 weeks postmenstrual age had the highest ASQ-3 scores at 2 years. In conclusion, independent of growth velocity, higher leptin levels at 35 weeks' gestation are associated with better developmental assessment scores in early childhood. While longer-term follow-up of a larger cohort is needed, these findings support investigations that have suggested that targeted neonatal leptin supplementation could improve the neurodevelopmental outcomes of preterm infants.

LRP6 Bidirectionally Regulates Insulin Sensitivity through Insulin Receptor and S6K Signaling in Rats with CG-IUGR

OBJECTIVE

Intrauterine growth restriction followed by postnatal catch-up growth (CG-IUGR) increases the risk of insulin resistance-related diseases. Low-density lipoprotein receptor-related protein 6 (LRP6) plays a substantial role in glucose metabolism. However, whether LRP6 is involved in the insulin resistance of CG-IUGR is unclear. This study aimed to explore the role of LRP6 in insulin signaling in response to CG-IUGR.

METHODS

The CG-IUGR rat model was established via a maternal gestational nutritional restriction followed by postnatal litter size reduction. The mRNA and protein expression of the components in the insulin pathway, LRP6/β-catenin and mammalian target of rapamycin (mTOR)/S6 kinase (S6K) signaling, was determined. Liver tissues were immunostained for the expression of LRP6 and β-catenin. LRP6 was overexpressed or silenced in primary hepatocytes to explore its role in insulin signaling.

RESULTS

Compared with the control rats, CG-IUGR rats showed higher homeostasis model assessment for insulin resistance (HOMA-IR) index and fasting insulin level, decreased insulin signaling, reduced mTOR/S6K/ insulin receptor substrate-1 (IRS-1) serine307 activity, and decreased LRP6/β-catenin in the liver tissue. The knockdown of LRP6 in hepatocytes from appropriate-for-gestational-age (AGA) rats led to reductions in insulin receptor (IR) signaling and mTOR/S6K/IRS-1 serine307 activity. In contrast, LRP6 overexpression in hepatocytes of CG-IUGR rats resulted in elevated IR signaling and mTOR/S6K/IRS-1 serine307 activity.

CONCLUSION

LRP6 regulated the insulin signaling in the CG-IUGR rats via two distinct pathways, IR and mTOR-S6K signaling. LRP6 may be a potential therapeutic target for insulin resistance in CG-IUGR individuals.

IUGR with catch-up growth programs impaired insulin sensitivity through LRP6/IRS-1 in male rats

Intrauterine growth restriction combined with postnatal accelerated growth (CG-IUGR) could lead to long-term detrimental metabolic outcomes characterized by insulin resistance. As an indispensable co-receptor of Wnt signaling, LRP6 plays a critical role in the susceptibility of metabolic disorders. However, whether LRP6 is involved in the metabolic programing is still unknown. We hypothesized that CG-IUGR programed impaired insulin sensitivity through the impaired LRP6-mediated Wnt signaling in skeletal muscle. A CG-IUGR rat model was employed. The transcriptional and translational alterations of the components of the Wnt and the insulin signaling in the skeletal muscle of the male CG-IUGR rats were determined. The role of LRP6 on the insulin signaling was evaluated by shRNA knockdown or Wnt3a stimulation of LRP6. Compared with controls, the male CG-IUGR rats showed an insulin-resistant phenotype, with impaired insulin signaling and decreased expression of LRP6/β-catenin in skeletal muscle. LRP6 knockdown led to reduced expression of the IR-β/IRS-1 in C2C12 cell line, while Wnt3a-mediated LRP6 expression increased the expression of IRS-1 and IGF-1R but not IR-β in the primary muscle cells of male CG-IUGR rats. The impaired LRP6/β-catenin/IGF-1R/IRS-1 signaling is probably one of the critical mechanisms underlying the programed impaired insulin sensitivity in male CG-IUGR.

Central nervous system regulation of organismal energy and glucose homeostasis

Growing evidence implicates the brain in the regulation of both immediate fuel availability (for example, circulating glucose) and long-term energy stores (that is, adipose tissue mass). Rather than viewing the adipose tissue and glucose control systems separately, we suggest that the brain systems that control them are components of a larger, highly integrated, 'fuel homeostasis' control system. This conceptual framework, along with new insights into the organization and function of distinct neuronal systems, provides a context within which to understand how metabolic homeostasis is achieved in both basal and postprandial states. We also review evidence that dysfunction of the central fuel homeostasis system contributes to the close association between obesity and type 2 diabetes, with the goal of identifying more effective treatment options for these common metabolic disorders.

Postnatal Catch-Up Growth Programs Telomere Dynamics and Glucose Intolerance in Low Birth Weight Mice

Low birth weight and rapid postnatal weight gain are independent predictors of obesity and diabetes in adult life, yet the molecular events involved in this process remain unknown. In inbred and outbred mice, this study examines natural intrauterine growth restriction (IUGR) in relation to body weight, telomere length (TL), glucose tolerance, and growth factor gene (Igf1, Igf2, Insr, Igf1r, and Igf2r) mRNA expression levels in the brain, liver, and muscle at 2- and 10 days of age and then at 3- and 9 months of age. At birth, ~15% of the animals showed IUGR, but by 3 and 9 months, half of these animals had regained the same weight as controls without IUGR (recuperated group). At 10 days, there was no difference in TL between animals undergoing IUGR and controls. However, by 3 and 9 months of age, the recuperated animals had shorter TL than the control and IUGR-non recuperated animals and also showed glucose intolerance. Further, compared to controls, Igf1 and Igf2 growth factor mRNA expression was lower in Day 2-IUGR mice, while Igf2r and Insr mRNA expression was higher in D10-IUGR animals. Moreover, at 3 months of age, only in the recuperated group were brain and liver Igf1, Igf2, Insr, and Igf2r expression levels higher than in the control and IUGR-non-recuperated groups. These data indicate that catch-up growth but not IUGR per se affects TL and glucose tolerance, and suggest a role in this latter process of insulin/insulin-like growth signaling pathway gene expression during early development.

Antioxidant Effects of N-Acetylcysteine Prevent Programmed Metabolic Disease in Mice

An adverse maternal in utero and lactation environment can program offspring for increased risk for metabolic disease. The aim of this study was to determine whether N-acetylcysteine (NAC), an anti-inflammatory antioxidant, attenuates programmed susceptibility to obesity and insulin resistance in offspring of mothers on a high-fat diet (HFD) during pregnancy. CD1 female mice were acutely fed a standard breeding chow or HFD. NAC was added to the drinking water (1 g/kg) of the treatment cohorts from embryonic day 0.5 until the end of lactation. NAC treatment normalized HFD-induced maternal weight gain and oxidative stress, improved the maternal lipidome, and prevented maternal leptin resistance. These favorable changes in the in utero environment normalized postnatal growth, decreased white adipose tissue (WAT) and hepatic fat, improved glucose and insulin tolerance and antioxidant capacity, reduced leptin and insulin, and increased adiponectin in HFD offspring. The lifelong metabolic improvements in the offspring were accompanied by reductions in proinflammatory gene expression in liver and WAT and increased thermogenic gene expression in brown adipose tissue. These results, for the first time, provide a mechanistic rationale for how NAC can prevent the onset of metabolic disease in the offspring of mothers who consume a typical Western HFD.

Characterization of Different Commercial Dietary Supplements in the Peri-Weaning Period on Consumption and Growth Performance in C57Bl/6J Mice

Simple Summary

The current study compares two different commercially available nutritional supplements promoted as caloric support for weanlings for acceptability and effect on weight and survival in mouse pups and lactating dams in the peri-weaning phase with standard diet mash or no supplementation. Our aim was to provide an independent characterization of nutritional supplementation on survival and weight gain in a commonly used mouse strain. These factors influence animal welfare and are essential for the success of a general breeding program. Similarly, supplementation in the peri-weaning phase can alter early nutrition depending on type, which can introduce unintentional confounding that affects the reliability of subsequent experimental outcomes. This study was also designed to consider pragmatic aspects including timing, cost-effectiveness, diet composition, and practicality in an effort to identify supplements capable of optimally supporting pup growth and survival for various research applications in diverse animal use programs.

Abstract

This experiment was conducted to investigate the effects of common commercially available dietary supplementation in the peri-weaning period on feed intake, growth, and survival in C57Bl/6J mouse pups and lactating dams. A total of 96 pups and their dams were randomized to the control group or one of three nutritional supplement treatment groups: (i) control group without supplementation, or (ii) weanling-targeted Clear H₂O gel (Gel), (iii) transgenic-targeted Bio-Serv dough (Dough), or (iv) dam diet as a mash (Chow), in the peri-weaning period (from 11 to 28 days). Stool was observed daily for a dye marker indicating supplement consumption. Pups were weaned at 21 days and followed for a total of 42 days. No pup morbidity or mortality was observed. There was a higher proportion of pups consuming dough and gel earlier than chow (p = 0.0091). The majority of treated pups (>95%) were consuming the supplement by day 23 (range 15–23), suggesting interplay between organoleptic properties of the supplement and pup maturity. All groups gained weight, with typical sexual dimorphism observed in the growth curves. Dough treatment led to significantly higher average daily gain in male pups (0.64 ± 0.03 g/d) as compared with controls (0.58 ± 0.03 g/d). The highest average daily gain in all groups was observed pre-weaning between days 21 and 28. Compared with controls, the weight gain slope was significantly higher in the Dough and Chow treatment groups and lower in Gel treatment groups, with a more pronounced effect in males. In this study, the composition of nutritional supplementation was the dominant factor in increasing the growth trend as opposed to energy density. Peri-weaning supplementation with Dough and Chow treatments improved pre- and post-growth performance in a comparable way and was more effective than Gel treatment during adaptation to solid feeding. Proper application of supplements to support weanlings can directly improve welfare and limit unintended experimental variability.

Risk of hypertension following perinatal adversity: IUGR and prematurity

Consistent with the paradigm shifting observations of David Barker and colleagues that revealed a powerful relationship between decreased weight through 2 years of age and adult disease, intrauterine growth restriction (IUGR) and preterm birth are independent risk factors for the development of subsequent hypertension. Animal models have been indispensable in defining the mechanisms responsible for these associations and the potential targets for therapeutic intervention. Among the modifiable risk factors, micronutrient deficiency, physical immobility, exaggerated stress hormone exposure and deficient trophic hormone production are leading candidates for targeted therapies. With the strong inverse relationship seen between gestational age at delivery and the risk of hypertension in adulthood trumping all other major cardiovascular risk factors, improvements in neonatal care are required. Unfortunately, therapeutic breakthroughs have not kept pace with rapidly improving perinatal survival, and groundbreaking bench-to-bedside studies are urgently needed to mitigate and ultimately prevent the tsunami of prematurity-related adult cardiovascular disease that may be on the horizon. This review highlights our current understanding of the developmental origins of hypertension and draws attention to the importance of increasing the availability of lactation consultants, nutritionists, pharmacists and physical therapists as critical allies in the battle that IUGR or premature infants are waging not just for survival but also for their future cardiometabolic health.

Reduction of the PI3K/Akt related signaling activities in skeletal muscle tissues involves insulin resistance in intrauterine growth restriction rats with catch-up growth

Individuals with intrauterine growth retardation (IUGR) are prone to insulin resistance, whereas the underlying molecular mechanisms remain unclear. In this study, we investigated if the PI3K/Akt signaling pathway in skeletal muscle tissues involves insulin resistance in IUGR offsprings, particularly ones with catch-up growth. An IUGR rat model was established by feeding rats an isocaloric (30.50 Kcal/g) diet containing 8% protein (low-protein diet) from day 1 of pregnancy until the birth of their pups. Glucometabolic parameters were measured and compared. Quantitative PCR and western blot were performed to assess mRNA and protein expression changes of the PI3K/Akt related signals in skeletal muscle tissues. Pearson analysis was used to assess the correlation of the PI3K/Akt signaling level and catch-up growth with the insulin resistance index (IRI). The values of fasting plasma glucose, fasting insulin and IRI were significantly higher, whereas insulin sensitivity index was significantly lower in IUGR offsprings than those in the controls. The PI3K mRNA and protein levels as well as the phospho-Akt^Ser473 levels were significantly lower in IUGR offsprings compared to the controls. Reductions of GLUT4 as well as increases of PTEN and nuclear fractional PPARγ were detected in IUGR offsprings. Catch-up growth IUGR rats were positively correlated with insulin resistance and underwent more remarkable alterations of the PI3K, PTEN and GLUT4 expressions. Our results demonstrated that rats born IUGR developed insulin resistance later in life, which was likely mediated by reductions of the PI3K/Akt related signaling activities, particularly in those with excess catch-up growth.

The Placental Transcriptome in Late Gestational Hypoxia Resulting in Murine Intrauterine Growth Restriction Parallels Increased Risk of Adult Cardiometabolic Disease

Intrauterine growth restriction (IUGR) enhances risk for adult onset cardiovascular disease (CVD). The mechanisms underlying IUGR are poorly understood, though inadequate blood flow and oxygen/nutrient provision are considered common endpoints. Based on evidence in humans linking IUGR to adult CVD, we hypothesized that in murine pregnancy, maternal late gestational hypoxia (LG-H) exposure resulting in IUGR would result in (1) placental transcriptome changes linked to risk for later CVD, and 2) adult phenotypes of CVD in the IUGR offspring. After subjecting pregnant mice to hypoxia (10.5% oxygen) from gestational day (GD) 14.5 to 18.5, we undertook RNA sequencing from GD19 placentas. Functional analysis suggested multiple changes in structural and functional genes important for placental health and function, with maximal dysregulation involving vascular and nutrient transport pathways. Concordantly, a ~10% decrease in birthweights and ~30% decrease in litter size was observed, supportive of placental insufficiency. We also found that the LG-H IUGR offspring exhibit increased risk for CVD at 4 months of age, manifesting as hypertension, increased abdominal fat, elevated leptin and total cholesterol concentrations. In summary, this animal model of IUGR links the placental transcriptional response to the stressor of gestational hypoxia to increased risk of developing cardiometabolic disease.

Distinct Cellular Mechanisms Underlie Smooth Muscle Turnover in Vascular Development and Repair

Supplemental Digital Content is available in the text.

Rationale:

Vascular smooth muscle turnover has important implications for blood vessel repair and for the development of cardiovascular diseases, yet lack of specific transgenic animal models has prevented it’s in vivo analysis.

Objective:

The objective of this study was to characterize the dynamics and mechanisms of vascular smooth muscle turnover from the earliest stages of embryonic development to arterial repair in the adult.

Methods and Results:

We show that CD146 is transiently expressed in vascular smooth muscle development. By using CRISPR-Cas9 genome editing and in vitro smooth muscle differentiation assay, we demonstrate that CD146 regulates the balance between proliferation and differentiation. We developed a triple-transgenic mouse model to map the fate of NG2⁺CD146⁺ immature smooth muscle cells. A series of pulse-chase experiments revealed that the origin of aortic vascular smooth muscle cells can be traced back to progenitor cells that reside in the wall of the dorsal aorta of the embryo at E10.5. A distinct population of CD146⁺ smooth muscle progenitor cells emerges during embryonic development and is maintained postnatally at arterial branch sites. To characterize the contribution of different cell types to arterial repair, we used 2 injury models. In limited wire-induced injury response, existing smooth muscle cells are the primary contributors to neointima formation. In contrast, microanastomosis leads to early smooth muscle death and subsequent colonization of the vascular wall by proliferative adventitial cells that contribute to the repair.

Conclusions:

Extensive proliferation of immature smooth muscle cells in the primitive embryonic dorsal aorta establishes the long-lived lineages of smooth muscle cells that make up the wall of the adult aorta. A discrete population of smooth muscle cells forms in the embryo and is postnatally sustained at arterial branch sites. In response to arterial injuries, existing smooth muscle cells give rise to neointima, but on extensive damage, they are replaced by adventitial cells.

Prenatal Food Restriction with Postweaning High-fat Diet Alters Glucose Metabolic Function in Adult Rat Offspring

BACKGROUND AND AIMS

The present study was designed to investigate the effects of prenatal food restriction (PFR) with postweaning high-fat diet (HFD) on glucose metabolic function in adult offspring.

METHODS

Pregnant Wistar rats were given PFR treatment from gestational day 11 to spontaneous delivery. All pups were fed by HFD after weaning. Oral glucose tolerance test (OGTT) was conducted at postnatal week (PW) 20. Rats were decapitated in PW24 to collect liver and pancreas, and expression of hepatic insulin signaling genes were then quantified.

RESULTS

Body weight from PW4 to PW24 in PFR males was lower than those in control males, whereas there was no distinct difference between females. However, body weight gain rates were higher from PW16 to PW24 in PFR males and females. Fasting serum glucose presented no changes, whereas fasting serum insulin decreased in PW20 in PFR pups. Moreover, glucose intolerance only appeared in PFR males, whereas no changes were shown in PFR females in relative values. Serum insulin increased in both PFR groups after OGTT. Remarkable pathological changes were also found in islets from PFR rats. There was an increase in the hepatic mRNA expression of IR in PFR females and of Glut2 in PFR males.

CONCLUSION

PFR with postweaning HFD induced a catch-up growth in body weight, especially in PFR females. Serum insulin decreased in both PFR groups in fasting status. Insulin resistance after OGTT only existed in PFR males, whereas PFR females showed no obvious changes in glucose metabolism.

Prenatal toluene exposure impairs performance in the Morris Water Maze in adolescent rats

Volatile organic solvent abuse continues to be a worldwide health problem, including the neurobehavioral teratogenic sequelae of toluene abuse during pregnancy. Although abuse levels of prenatal toluene exposure can lead to a Fetal Solvent Syndrome, there is little research examining these effects on memory. Consumption of toluene can have detrimental effects on the developing hippocampus which could lead to specific spatial learning and memory deficits. This study used a rat model to determine how prenatal exposure to abuse levels of toluene would affect performance in a spatial learning and memory task, the Morris Water Maze (MWM). Pregnant Sprague-Dawley rats were exposed to 0, 8000 or 12,000ppm (ppm) of toluene for 15min twice daily from gestation day 8 (GD8) through GD20. Male and female offspring (N=104) were observed in the MWM for 5days beginning on postnatal day (PN) 28 and again on PN44. While prenatal toluene-exposed animals did not differ in initial acquisition in the MWM, rats prenatally exposed to 12,000ppm toluene displayed performance deficits during a probe trial and in reversal learning on PN44. Overall, this study indicates that prenatal exposure to repeated inhaled abuse patterns of high concentrations of toluene can impair spatial memory function that persists into adolescence.

Modeling the impact of growth and leptin deficits on the neuronal regulation of blood pressure

The risk of hypertension is increased by intrauterine growth restriction (IUGR) and preterm birth. In the search for modifiable etiologies for this life-threatening cardiovascular morbidity, a number of pathways have been investigated, including excessive glucocorticoid exposure, nutritional deficiency and aberration in sex hormone levels. As a neurotrophic hormone that is intimately involved in the cardiovascular regulation and whose levels are influenced by glucocorticoids, nutritional status and sex hormones, leptin has emerged as a putative etiologic and thus a therapeutic agent. As a product of maternal and late fetal adipocytes and the placenta, circulating leptin typically surges late in gestation and declines after delivery until the infant consumes sufficient leptin-containing breast milk or accrues sufficient leptin-secreting adipose tissue to reestablish the circulating levels. The leptin deficiency seen in IUGR infants is a multifactorial manifestation of placental insufficiency, exaggerated glucocorticoid exposure and fetal adipose deficit. The preterm infant suffers from the same cascade of events, including separation from the placenta, antenatal steroid exposure and persistently underdeveloped adipose depots. Preterm infants remain leptin deficient beyond term gestation, rendering them susceptible to neurodevelopmental impairment and subsequent cardiovascular dysregulation. This pathologic pathway is efficiently modeled by placing neonatal mice into atypically large litters, thereby recapitulating the perinatal growth restriction-adult hypertension phenotype. In this model, neonatal leptin supplementation restores the physiologic leptin surge, attenuates the leptin-triggered sympathetic activation in adulthood and prevents leptin- or stress-evoked hypertension. Further pathway interrogation and clinical translation are needed to fully test the therapeutic potential of perinatal leptin supplementation.

Assessment of Toxicological Perturbations and Variants of Pancreatic Islet Development in the Zebrafish Model

The pancreatic islets, largely comprised of insulin-producing beta cells, play a critical role in endocrine signaling and glucose homeostasis. Because they have low levels of antioxidant defenses and a high perfusion rate, the endocrine islets may be a highly susceptible target tissue of chemical exposures. However, this endpoint, as well as the integrity of the surrounding exocrine pancreas, is often overlooked in studies of developmental toxicology. Disruption of development by toxicants can alter cell fate and migration, resulting in structural alterations that are difficult to detect in mammalian embryo systems, but that are easily observed in the zebrafish embryo model (Danio rerio). Using endogenously expressed fluorescent protein markers for developing zebrafish beta cells and exocrine pancreas tissue, we documented differences in islet area and incidence rates of islet morphological variants in zebrafish embryos between 48 and 96 h post fertilization (hpf), raised under control conditions commonly used in embryotoxicity assays. We identified critical windows for chemical exposures during which increased incidences of endocrine pancreas abnormalities were observed following exposure to cyclopamine (2–12 hpf), Mono-2-ethylhexyl phthalate (MEHP) (3–48 hpf), and Perfluorooctanesulfonic acid (PFOS) (3–48 hpf). Both islet area and length of the exocrine pancreas were sensitive to oxidative stress from exposure to the oxidant tert-butyl hydroperoxide during a highly proliferative critical window (72 hpf). Finally, pancreatic dysmorphogenesis following developmental exposures is discussed with respect to human disease.

Neonatal growth restriction-related leptin deficiency enhances leptin-triggered sympathetic activation and central angiotensin II receptor-dependent stress-evoked hypertension

BACKGROUND

Neonatal growth restriction (nGR) leads to leptin deficiency and increases the risk of hypertension. Previous studies have shown nGR-related hypertension is normalized by neonatal leptin (nLep) and exacerbated by psychological stress. With recent studies linking leptin and angiotensin signaling, we hypothesized that nGR-induced nLep deficiency increases adult leptin sensitivity; leading to leptin- or stress-induced hypertension, through a pathway involving central angiotensin II type 1 receptors.

METHODS

We randomized mice with incipient nGR, by virtue of their presence in large litters, to vehicle or physiologic nLep supplementation (80 ng/g/d). Adult caloric intake and arterial pressure were monitored at baseline, during intracerebroventricular losartan infusion and during systemic leptin administration.

RESULTS

nGR increased leptin-triggered renal sympathetic activation and hypertension with increased leptin receptor expression in the arcuate nucleus of the hypothalamus; all of those nGR-associated phenotypes were normalized by nLep. nGR mice also had stress-related hyperphagia and hypertension, but only the stress hypertension was blocked by central losartan infusion.

CONCLUSION

nGR leads to stress hypertension through a pathway that involves central angiotensin II receptors, and nGR-associated leptin deficiency increases leptin-triggered hypertension in adulthood. These data suggest potential roles for preservation of neonatal growth and nLep supplementation in the prevention of nGR-related hypertension.

Maternal exposure to high-fat and high-fructose diet evokes hypoadiponectinemia and kidney injury in rat offspring

BACKGROUND

Maternal exposure to overnutrition during fetal development contributes to metabolic and renal damage in offspring. Adiponectin plays a protective role against obesity-related renal injury. However, role of adiponectin in renal injury of offspring exposed to maternal overnutrition remains unknown. We addressed the issue.

METHODS

Female Sprague-Dawley rats were fed either a standard (N) or a high-fat and high-fructose (HFF)-diet for 6 weeks before mating, and kept each diet during the gestation and lactation period. After 4 weeks postpartum, all the offspring were fed N diet, and followed by 12 weeks. Kidney weight, urinary albumin excretion, blood pressure, and blood chemistry, including adiponectin and malondialdehyde, a marker of oxidative stress, were evaluated in the offspring.

RESULTS

Compared with N-offspring, serum adiponectin levels of 1-day- and 4-week-old HFF-offspring were significantly lower, the latter of which was inversely associated with malondialdehyde. Kidney weight was significantly decreased in 1-day-old HFF-offspring, whereas increased in 4-week-old HFF-offspring. Urinary albumin excretion levels of HFF-offspring at 8, 12, and 16-week old were significantly higher than those of N-offspring at the same age, whose levels at 16-week old were inversely correlated with plasma adiponectin. Compared with N-offspring, HFF-offspring at 16-week old exhibited glomerulosclerosis, hyperglycemia, and high mean blood pressure associated with reduced podocin and increased transforming growth factor-β1 expression in the kidneys.

CONCLUSIONS

Our present study suggests that exposure to maternal HFF-diet during fetal and early postnatal development induces hypoadiponectinemia in offspring, which might cause renal injury and metabolic derangements later in life.

Oral oestrogen reverses ovariectomy-induced morning surge hypertension in growth-restricted mice

Perinatal growth restriction (GR) is associated with heightened sympathetic tone and hypertension. We have previously shown that naturally occurring neonatal GR programmes hypertension in male but not female mice. We therefore hypothesized that intact ovarian function or post-ovariectomy (OVX) oestrogen administration protects GR female mice from hypertension. Utilizing a non-interventional model that categorizes mice with weanling weights below the tenth percentile as GR, control and GR adult mice were studied at three distinct time points: baseline, post-OVX and post-OVX with oral oestrogen replacement. OVX elicited hypertension in GR mice that was significantly exacerbated by psychomotor arousal (systolic blood pressure at light to dark transition: control 122 ± 2; GR 119 ± 2; control-OVX 116 ± 3; GR-OVX 126 ± 3 mmHg). Oestrogen partially normalized the rising blood pressure surge seen in GR-OVX mice (23 ± 7% reduction). GR mice had left ventricular hypertrophy, and GR-OVX mice in particular had exaggerated bradycardic responses to sympathetic blockade. For GR mice, a baseline increase in baroreceptor reflex sensitivity and high frequency spectral power support a vagal compensatory mechanism, and that compensation was lost following OVX. For GR mice, the OVX-induced parasympathetic withdrawal was partially restored by oestrogen (40 ± 25% increase in high frequency spectral power, P<0.05). In conclusion, GR alters cardiac morphology and cardiovascular regulation. The haemodynamic consequences of GR are attenuated in ovarian-sufficient or oestrogen-replete females. Further investigations are needed to define the role of hormone replacement therapy targeted towards young women with oestrogen deficiency and additional cardiovascular risk factors, including perinatal GR, cardiac hypertrophy and morning surge hypertension.

IUGR with infantile overnutrition programs an insulin-resistant phenotype through DNA methylation of peroxisome proliferator-activated receptor-γ coactivator-1α in rats

BACKGROUND

Intrauterine growth restriction (IUGR) followed by postnatal accelerated growth (CG-IUGR) is associated with long-term adverse metabolic consequences, and an involvement of epigenetic dysregulation has been implicated. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a key orchestrator in energy homeostasis. We hypothesized that CG-IUGR programed an insulin-resistant phenotype through the alteration in DNA methylation and transcriptional activity of PGC-1α.

METHODS

A CG-IUGR rat model was adopted using maternal gestational nutritional restriction followed by infantile overnutrition achieved by reducing the litter size. The DNA methylation was determined by pyrosequencing. The mRNA expression and mitochondrial content were assessed by real-time PCR. The insulin-signaling protein expression was evaluated by western blotting.

RESULTS

Compared with controls, the CG-IUGR rats showed an increase in the DNA methylation of specific CpG sites in PGC-1α, and a decrease in the transcriptional activity of PGC-1α, mitochondrial content, protein level of PI3K and phosphorylated-Akt2 in liver and muscle tissues. The methylation of specific CpG sites in PGC-1α was positively correlated with fasting insulin concentration.

CONCLUSION

IUGR followed by infantile overnutrition programs an insulin-resistant phenotype, possibly through the alteration in DNA methylation and transcriptional activity of PGC-1α. The genetic and epigenetic modifications of PGC-1α provide a potential mechanism linking early-life nutrition insult to long-term metabolic disease susceptibilities.

Challenges and opportunities in developmental integrative physiology

This review explores challenges and opportunities in developmental physiology outlined by a symposium at the 2014 American Physiological Society Intersociety Meeting: Comparative Approaches to Grand Challenges in Physiology. Across animal taxa, adverse embryonic/fetal environmental conditions can alter morphological and physiological phenotypes in juveniles or adults, and capacities for developmental plasticity are common phenomena. Human neonates with body sizes at the extremes of perinatal growth are at an increased risk of adult disease, particularly hypertension and cardiovascular disease. There are many rewarding areas of current and future research in comparative developmental physiology. We present key mechanisms, models, and experimental designs that can be used across taxa to investigate patterns in, and implications of, the development of animal phenotypes. Intraspecific variation in the timing of developmental events can be increased through developmental plasticity (heterokairy), and could provide the raw material for selection to produce heterochrony--an evolutionary change in the timing of developmental events. Epigenetics and critical windows research recognizes that in ovo or fetal development represent a vulnerable period in the life history of an animal, when the developing organism may be unable to actively mitigate environmental perturbations. 'Critical windows' are periods of susceptibility or vulnerability to environmental or maternal challenges, periods when recovery from challenge is possible, and periods when the phenotype or epigenome has been altered. Developmental plasticity may allow survival in an altered environment, but it also has possible long-term consequences for the animal. "Catch-up growth" in humans after the critical perinatal window has closed elicits adult obesity and exacerbates a programmed hypertensive phenotype (one of many examples of "fetal programing"). Grand challenges for developmental physiology include integrating variation in developmental timing within and across generations, applying multiple stressor dosages and stressor exposure at different developmental timepoints, assessment of epigenetic and parental influences, developing new animal models and techniques, and assessing and implementing these designs and models in human health and development.

When early life growth restriction in rats is followed by attenuated postnatal growth: effects on cardiac function in adulthood

PURPOSE

Epidemiological and experimental studies demonstrate that intrauterine growth restriction (IUGR) followed by accelerated postnatal growth leads to increased risk of developing cardiac disease in adulthood. The aim of this study was to examine the effect of early life growth restriction on cardiac structure and function in young adult rats.

METHODS

IUGR was induced in Wistar Kyoto dams through administration of a low protein diet (LPD; 8.7% casein) during pregnancy and lactation; controls received a normal protein diet (NPD; 20% casein). Cardiac function and structure were assessed in female NPD (n = 7) and LPD (n = 7) offspring at 18 weeks of age by echocardiography and pressure-volume techniques, and systolic blood pressure by tail-cuff sphygmomanometry.

RESULTS

LPD offspring remained significantly smaller throughout life compared to controls. There were no differences in the levels of systolic blood pressure, left ventricular cardiac dimensions, heart rate, ejection fraction and fractional shortening of the cardiac muscle between the investigated groups. Aortic peak systolic velocity was significantly reduced in the LPD group (P = 0.02).

CONCLUSION

Our findings support the idea that the programming of adult cardiovascular disease can be prevented or delayed in IUGR offspring when postnatal growth trajectory resembles that of in utero.

Neonatal leptin deficiency reduces frontal cortex volumes and programs adult hyperactivity in mice

Intrauterine growth restriction and premature delivery decrease circulating levels of the neurotrophic hormone leptin and increase the risk of adult psychiatric disease. In mouse models, neonatal leptin replacement normalizes brain growth and improves the neurodevelopmental outcomes of growth restricted mice, but leptin supplementation of well-grown mice decreases adult locomotor activity. We hypothesized isolated neonatal leptin deficiency is sufficient to reduce adult brain volumes and program behavioral outcomes, including hyperactivity. C57Bl/6 pups were randomized to daily injections of saline or PEG-leptin antagonist (LX, 12.5 mg/kg) from postnatal day 4 to 14. After 4 months, fear conditioning and open field testing were performed followed by carotid radiotelemetry for the measurement of baseline activity and blood pressure. Neonatal LX did not significantly increase cue-based fear or blood pressure, but increased adult locomotor activity during assessment in both the open field (beam breaks: control 930 ± 40, LX 1099 ± 42, P<0.01) and the home cage (radiotelemetry counts: control 4.5 ± 0.3, LX 5.6 ± 0.3, P=0.02). Follow-up MRI revealed significant reductions in adult frontal cortex volumes following neonatal LX administration (control 45. 1 ± 0.4 mm(3), LX 43.8 ± 0.4 mm(3), P=0.04). This was associated with a significant increase in cerebral cortex leptin receptor mRNA expression. In conclusion, isolated neonatal leptin deficiency increases cerebral cortex leptin receptor expression and reduces frontal cortex volumes in association with increased adult locomotor activity. We speculate neonatal leptin deficiency may contribute to the adverse neurodevelopmental outcomes associated with perinatal growth restriction, and postnatal leptin therapy may be protective.

Effect of a mixture of bovine milk oligosaccharides, Lactobacillus rhamnosus NCC4007 and long-chain polyunsaturated fatty acids on catch-up growth of intra-uterine growth-restricted rats

AIM

To investigate the effect of a nutritional mixture (bovine milk oligosaccharides, Lactobacillus rhamnosus NCC4007, arachidonic and docosahexaenoic acid) on growth of intrauterine growth-restricted (IUGR) rats.

METHODS

IUGR was induced by maternal food restriction. The offspring (males and females) were assigned to: REF (non-IUGR, no mixture), IUGRc (IUGR, no mixture), or IUGRmx (IUGR, mixture). The mixture was given from day 7 to day 58, when tissues and plasma from half of the animals were collected for hormones, metabolites and microarray analysis. The rest received a high-fat diet (HFD) until day 100. Glucose tolerance was measured at 56 and 98 days, and body fat content at 21, 52 and 97 days.

RESULTS

IUGRmx had the greatest growth during lactation, but from day 22 to day 54, both IUGR groups gained less body weight than the REF (P < 0.05). In the short-term (58 days), IUGRmx tended to be longer (P = 0.06) and had less body fat (P = 0.03) than IUGRc. These differences were not seen after HFD. Microarray analysis of hepatic mRNA expression at 58 and 100 days revealed a gender-dependent treatment effect, and expression of genes related to lipid metabolism was the most affected. Twelve of these genes were selected for studying differences in DNA methylation in the promoter region, for some, we observed age- and gender-related differences but none because of treatment.

CONCLUSION

The nutritional intervention promoted catch-up growth and normalized excessive adiposity in IUGR animals at short-term. The benefits did not extend after a period of HFD. IUGR and early diet had gender-dependent effects on hepatic gene expression.

Obesity in prematurely born children and adolescents: follow up in pediatric clinic

Background

Understanding associated risk for obesity is a prerequisite to develop early life interventions to arrest the increasing epidemic of metabolic syndrome and obesity among preterm born children and adolescents.

Findings

A retrospective review of 160 charts was conducted to determine the associated risk of being obese during childhood and adolescent period in preterm children. Birth weight, gestational age, weight gain, demographics, maternal health, socioeconomics, and clinical factors during early neonatal life were evaluated. The number of obese children increased with age and was observed more in the adolescent population. Obese children were significantly heavier at age 24 months old compared to their peers (p = 0.001). Analysis of associated risk for maternal demographics, maternal age, maternal marital status or race, prenatal factors, maternal substance abuse or diabetes, neonatal factors, weight for gestational age or birth weight did not show any statistically significant risk for future obesity. Duration of gestational age (OR 1.6; p = 0.017) and heavier birth weight (OR 3.2; p = 0.001) were associated with risk of obesity.

Conclusion

Among preterm born babies in the study, the highest risk of developing excessive weight during childhood and adolescent periods are babies born at more advanced gestational age. Strong positive association was found between birth weight and body weight in childhood. By 24 months old, there was a distinguished group of toddlers, who were heavier than their peers and remained with excessive weight as they got older. Primary care pediatricians should draw attention to premature babies, overweight infants and toddlers.

High-fat/fructose feeding during prenatal and postnatal development in female rats increases susceptibility to renal and metabolic injury later in life

Accumulating evidence suggests that both an adverse prenatal and early postnatal environment increase susceptibility to renal and metabolic dysfunction later in life; however, whether exposure to adverse conditions during both prenatal and postnatal development act synergistically to potentiate the severity of renal and metabolic injury remains unknown. Sprague-Dawley rats were fed either a standard diet or a diet high in fat/fructose throughout pregnancy and lactation. After being weaned, female offspring were randomized to either standard diet or the high-fat/high-fructose diet, resulting in the following treatment groups: NF-NF, offspring of mothers fed a standard diet and fed a standard diet postnatally; NF-HF, offspring of mothers fed a standard diet and fed a high-fat/fructose diet postnatally; HF-NF, offspring of mothers fed a high-fat/fructose diet and fed a standard diet postnatally; HF-HF, offspring of mothers fed a high-fat/fructose diet and fed a high-fat/fructose diet postnatally. At the time of euthanasia (17 wk of age), HF-HF offspring weighed 30% more and had 110% more visceral fat than NF-NF offspring. The HF-HF offspring also had elevated blood glucose levels, glucose intolerance, 286% increase in urine albumin excretion, and 60% increase in glomerulosclerosis compared with NF-NF. In addition, HF-HF offspring exhibited a 100% increase in transforming growth factor-β protein expression and 116% increase in the abundance of infiltrated macrophages compared with the NF-NF offspring. These observations suggest that high-fat/fructose feeding during prenatal and throughout postnatal life increases the susceptibility to renal and metabolic injury later in 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.

Superimposition of postnatal calorie restriction protects the aging male intrauterine growth- restricted offspring from metabolic maladaptations

Intrauterine growth restriction (IUGR) results in dysregulated glucose homeostasis and adiposity in the adult. We hypothesized that with aging, these perturbations will wane, and superimposition of postnatal growth restriction (PNGR) on IUGR [intrauterine and postnatal growth restriction (IPGR)] will reverse the residual IUGR phenotype. We therefore undertook hyperinsulinemic-euglycemic clamp, energy balance, and physical activity studies during fed, fasted, and refed states, in light and dark cycles, on postweaned chow diet-fed more than 17-month aging male IUGR, PNGR, and IPGR vs. control (CON) rat offspring. Hyperinsulinemic-euglycemic clamp revealed similar whole-body insulin sensitivity and physical activity in the nonobese IUGR vs. CON, despite reduced heat production and energy expenditure. Compared with CON and IUGR, IPGR mimicking PNGR was lean and growth restricted with increased physical activity, O(2) consumption (VO(2)), energy intake, and expenditure. Although insulin sensitivity was no different in IPGR and PNGR, skeletal muscle insulin-induced glucose uptake was enhanced. This presentation proved protective against the chronologically earlier (5.5 months) development of obesity and dysregulated energy homeostasis after 19 wk on a postweaned high-fat diet. This protective role of PNGR on the metabolic IUGR phenotype needs future fine tuning aimed at minimizing unintended consequences.

Neonatal SSRI Exposure Programs a Hypermetabolic State in Adult Mice

Background. Selective serotonin reuptake inhibitor (SSRI) therapy complicates up to 10% of pregnancies. During therapy, SSRIs exert pleiotropic antidepressant, anorexigenic, and neurotrophic effects. Intrauterine SSRI exposure has been modeled by neonatal administration to developmentally immature rodents, and it has paradoxically elicited features of adult depression. We hypothesized neonatal SSRI exposure likewise programs a rebound hypermetabolic state in adult mice. Methods. C57BL/6 pups were randomized to saline or sertraline (5 mg/kg/d) from P1–P14. Because estrogen increases tryptophan hydroxylase 2 (TPH2) expression, a subset of female mice underwent sham surgery or bilateral ovariectomy (OVX). Metabolic rate was determined by indirect calorimetry. Results. In both male and female mice, neonatal SSRI exposure increased adult caloric intake and metabolic rate. SSRI-exposed female mice had significantly decreased adult weight with a relative increase in brain weight and melatonin excretion, independent of ovarian status. Cerebral cortex TPH2 expression was increased in SSRI-exposed male mice but decreased in OVX SSRI-exposed female mice. Conclusions. SSRI exposure during a critical neurodevelopmental window increases adult caloric intake and metabolic rate. Ovarian status modulated central TPH2 expression, but not adult energy balance, suggesting programmed neural connectivity or enhanced melatonin production may play a more important role in the post-SSRI hypermetabolic syndrome.

Exposure to maternal overnutrition and a high-fat diet during early postnatal development increases susceptibility to renal and metabolic injury later in life

Overnutrition during pre- and postnatal development both confer increased susceptibility to renal and metabolic risks later in life; however, whether they have an additive effect on the severity of renal and metabolic injury remains unknown. The present study tested the hypothesis that a combination of a pre- and postnatal diet high in fat/fructose would exacerbate renal and metabolic injury in male offspring later in life. Male offspring born to high fat/high-fructose-fed mothers and fed a high-fat/high-fructose diet postnatally (HF-HF) had increased urine albumin excretion (450%), glomerulosclerosis (190%), and tubulointerstitial fibrosis (101%) compared with offspring born to mothers fed a standard diet and fed a standard diet postnatally (NF-NF). No changes in blood pressure or glomerular filtration were observed between any of the treatment groups. The HF-HF offspring weighed ∼23% more than offspring born to mothers fed a high-fat/high-fructose diet and fed a normal diet postnatally (HF-NF), as well as offspring born to mothers fed a standard diet regardless of their postnatal diet. The HF-HF rats also had increased (and more variable) blood glucose levels over 12 wk of being fed a high-fat/high-fructose diet. A combination of exposure to a high-fat/high-fructose diet in utero and postnatally increased plasma insulin levels by 140% compared with NF-NF offspring. Our data suggest that the combined exposure to overnutrition during fetal development and early postnatal development potentiate the susceptibility to renal and metabolic disturbances later in life.

Maternal antioxidant blocks programmed cardiovascular and behavioural stress responses in adult mice

Intra-uterine growth restriction is an independent risk factor for adult psychiatric and cardiovascular diseases. In humans, intra-uterine growth restriction is associated with increased placental and fetal oxidative stress, as well as down-regulation of placental 11β-HSD (11β-hydroxysteroid dehydrogenase). Decreased placental 11β-HSD activity increases fetal exposure to maternal glucocorticoids, further increasing fetal oxidative stress. To explore the developmental origins of co-morbid hypertension and anxiety disorders, we increased fetal glucocorticoid exposure by administering the 11β-HSD inhibitor CBX (carbenoxolone; 12 mg·kg-1 of body weight·day-1) during the final week of murine gestation. We hypothesized that maternal antioxidant (tempol throughout pregnancy) would block glucocorticoid-programmed anxiety, vascular dysfunction and hypertension. Anxiety-related behaviour (conditioned fear) and the haemodynamic response to stress were measured in adult mice. Maternal CBX administration significantly increased conditioned fear responses of adult females. Among the offspring of CBX-injected dams, maternal tempol markedly attenuated the behavioural and cardiovascular responses to psychological stress. Compared with offspring of undisturbed dams, male offspring of dams that received daily third trimester saline injections had increased stress-evoked pressure responses that were blocked by maternal tempol. In contrast, tempol did not block CBX-induced aortic dysfunction in female mice (measured by myography and lucigenin-enhanced chemiluminescence). We conclude that maternal stress and exaggerated fetal glucocorticoid exposure enhance sex-specific stress responses, as well as alterations in aortic reactivity. Because concurrent tempol attenuated conditioned fear and stress reactivity even among the offspring of saline-injected dams, we speculate that antenatal stressors programme offspring stress reactivity in a cycle that may be broken by antenatal antioxidant therapy.

Neonatal leptin administration alters regional brain volumes and blocks neonatal growth restriction-induced behavioral and cardiovascular dysfunction in male mice

Premature delivery is often complicated by neonatal growth restriction (GR) and neurodevelopmental impairment. Because global overnutrition increases the risk of adult metabolic syndrome, we sought a targeted intervention. Premature delivery and perinatal GR decrease circulating levels of the neurotrophic hormone leptin. We hypothesized that leptin supplementation would normalize the outcomes of mice with incipient neonatal GR. Pups were fostered into litters of 6 or 12 to elicit divergent growth patterns. Pups in each litter received injections of saline or leptin from d 4 to 14. At 4 mo, mice underwent tail cuff blood pressure measurement, behavioral testing, and MRI. Mice fostered in litters of 12 had decreased weanling weights and leptin levels. Neonatal leptin administration normalized plasma leptin levels without influencing neonatal growth. Leptin replacement also normalized the hypertension, stress-linked immobility, conditioned fear, and amygdala enlargement seen in neonatal growth restricted male mice. In control males, neonatal leptin administration led to hypothalamic enlargement, without overt neurocardiovascular alterations. Female mice were less susceptible to the effects of neonatal GR or leptin supplementation. In conclusion, the effects of neonatal leptin administration are modulated by concurrent growth and gender. In growth restricted male mice, physiologic leptin replacement improves adult neurocardiovascular outcomes.

Neonatal macrosomia is an independent risk factor for adult metabolic syndrome

BACKGROUND

Weight in infancy correlates with risk of type 2 diabetes, hypertension, and obesity in adulthood. Clinical observations have been confounded by obesity-prone genotypes and obesity-linked lifestyles.

OBJECTIVES

To define the effects of isolated neonatal macrosomia in isogenic animals, we compared macrosomic and control C57Bl6 mice co-fostered by healthy dams receiving standard laboratory feed.

METHODS

Naturally occurring neonatal macrosomia was identified by a gender-specific weanling weight above the 90th percentile for the colony. Macrosomic and control mice were phenotyped in adulthood by exercise wheel, tail cuff and intraperitoneal insulin or glucose challenge.

RESULTS

Compared to control males, adult males with a history of neonatal macrosomia had significantly increased body weight, reduced voluntary activity, insulin resistance, fasting hyperinsulinemia, and impaired glucose tolerance. In contrast, adult females with neonatal macrosomia had no significant alteration in body weight or endocrine phenotypes, but did have higher blood pressures and lower heart rates than control females. After these baseline studies, all mice were switched to a hypercaloric, high fat diet (5 kcal/g, 45% of energy as fat). Twenty weeks later, male mice had impaired glucose tolerance and insulin resistance, independent of their weanling weight classification. While on high fat feeds, macrosomic males maintained a significantly higher body weight than control males.

CONCLUSIONS

We conclude that (1) in our murine model, neonatal macrosomia is an independent risk factor of adult metabolic syndrome, and (2) neonatal macrosomia accentuates the sexually dimorphic predisposition of C57Bl6 male mice towards glucose intolerance and C57Bl6 female mice towards hypertension.