Maternal overnutrition results in programmed offspring obesity, mediated in part, by hyperphagia. This is remarkably similar to the effects of maternal undernutrition on offspring hyperphagia and obesity. In view of the marked differences in the energy environment of the over and under-nutrition exposures, we studied the expression of select epigenetic modifiers associated with energy imbalance including neurogenic factors and appetite/satiety neuropeptides which are indicative of neurogenic differentiation. HF offspring were exposed to maternal overnutrition (high fat diet; HF) during pregnancy and lactation. We determined the protein expression of energy sensors (mTOR, pAMPK), epigenetic factors (DNA methylase, DNMT1; histone deacetylase, SIRT1/HDAC1), neurogenic factors (Hes1, Mash1, Ngn3) and appetite/satiety neuropeptides (AgRP/POMC) in newborn hypothalamus and adult arcuate nucleus (ARC). Despite maternal obesity, male offspring born to obese dams had similar body weight at birth as Controls. However, when nursed by the same dams, male offspring of obese dams exhibited marked adiposity. At 1 day of age, HF newborn males had significantly decreased energy sensors, DNMT1 including Hes1 and Mash1, which may impact neuroprogenitor cell proliferation and differentiation. This is consistent with increased AgRP in HF newborns. At 6 months of age, HF adult males had significantly increased energy sensors and decreased histone deactylases. In addition, the persistent decreased Hes1, Mash1 as well as Ngn3 are consistent with increased AgRP and decreased POMC. Thus, altered energy sensors and epigenetic responses which modulate gene expression and adult neuronal differentiation may contribute to hyperphagia and obesity in HF male offspring.

Small-for-gestational age (SGA) human newborns have an increased risk of hyperphagia and obesity, as well as a spectrum of neurologic and neurobehavioral abnormalities. We have shown that the SGA hypothalamic (appetite regulatory site) neuroprogenitor cells (NPCs) exhibit reduced proliferation and neuronal differentiation. DNA methylation (DNA methyltransferase; DNMT1) regulates neurogenesis by maintaining NPC proliferation and suppressing premature differentiation. Once differentiation ensues, DNMT1 preferentially promotes neuronal and inhibits astroglial fate. We hypothesized that the programmed dysfunction of NPC proliferation and differentiation in SGA offspring is epigenetically mediated via DNMT1. Pregnant rats received either ad libitum food (Control) or were 50% food-restricted to create SGA offspring. Primary hypothalamic NPCs from 1 day old SGA and Controls newborns were cultured and transfected with nonspecific or DNMT1-specific siRNA. NPC proliferation and protein expression of specific markers of NPC (nestin), neuroproliferative transcription factor (Hes1), neurons (Tuj1) and astrocytes (GFAP) were determined. Under basal conditions, SGA NPCs exhibited decreased DNMT1 and reduced proliferation and differentiation, as compared to Controls. In both SGA and Controls, DNMT1 siRNA in complete media inhibited NPC proliferation, consistent with reduced expression of nestin and Hes1. In differentiation media, DNMT1 siRNA decreased expression of Tuj1 but increased GFAP. In vivo data replicated these findings. In SGA offspring, impaired neurogenesis is epigenetically mediated, in part, via reduction in DNMT1 expression and suppression of Hes1 resulting in NPC differentiation. It is likely that the maturation of regions beyond the hypothalamus (e.g., cerebral cortex, hippocampus) may be impacted, contributing to poor cognitive and neurobehavioral competency in SGA offspring.

Small for gestational age (SGA) offspring exhibit reduced hypothalamic neural satiety pathways leading to programmed hyperphagia and adult obesity. Appetite regulatory site, the hypothalamic arcuate nucleus (ARC) contains appetite (NPY/AgRP) and satiety (POMC) neurons. Using in vitro culture of hypothalamic neuroprogenitor cells (NPC) which form the ARC, we demonstrated that SGA offspring exhibit reduced NPC proliferation and neuronal differentiation. bHLH protein Hes1 promotes NPC self-renewal and inhibits differentiation by repressing neuronal differentiation genes (Mash1, neurogenin3). We hypothesized that Hes1/Mash1 and ultimately ARC neuronal differentiation and expression of NPY/POMC neurons are influenced by SIRT1 which is a nutrient sensor and a histone deacetylase. Control dams received ad libitum food, whereas study dams were 50% food-restricted from pregnancy day 10 to 21 (SGA). In vivo studies showed that SGA newborns and adult offspring had increased protein expression of hypothalamic/ARC SIRT1 and AgRP with decreased POMC. Additionally, SGA newborns had decreased expression of hypothalamic neurogenic factors with reduced in vivo NPC proliferation. In vitro culture of hypothalamic NPCs showed similar changes with elevated SIRT1 binding to Hes1 in SGA newborn. Silencing SIRT1 increased NPC proliferation and Hes1 and Tuj1expression in both Control and SGA NPCs. Although SGA NPC proliferation remained below that of Controls, it was higher than Control NPCs in the absence of SIRT1 siRNA. The direct impact of SIRT1 on NPC proliferation and differentiation were further confirmed with pharmacologic SIRT1 inhibitor and activator. Thus, in SGA newborns elevated SIRT1 induces premature differentiation of NPCs, reducing the NPC pool and cell proliferation.

Background

The obesogenic and diabetogenic effects of the environmental toxin bisphenol A during critical windows of development are well recognized. Liver and skeletal muscle play a central role in the control of glucose production, utilization, and storage.

Objectives

We hypothesized that maternal bisphenol A exposure disrupts insulin signaling in rat offspring liver and skeletal muscle. We determined the protein expression of hepatic and skeletal muscle insulin signaling molecules including insulin receptor beta, its downstream target insulin receptor substrate 1 and glucose transporters (glucose transporter 2, glucose transporter 4), and hepatic glucose-regulating enzymes phosphoenolpyruvate carboxykinase and glucokinase.

Study design

Rat dams had ad libitum access to filtered drinking water (control) or drinking water with bisphenol A from 2 weeks prior to mating and through pregnancy and lactation. Offspring litters were standardized to 4 males and 4 females and nursed by the same dam. At weaning, bisphenol A exposure was removed from all offspring. Glucose tolerance was tested at 6 weeks and 6 months. Liver and skeletal muscle was collected from 3 week old and 10 month old offspring for protein expression (Western blot) of insulin receptor beta, insulin receptor substrate 1, glucose transporter 2, glucose transporter 4, phosphoenolpyruvate carboxykinase, and glucokinase.

Results

Male, but not female, bisphenol A offspring had impaired glucose tolerance at 6 weeks and 6 months. Both male and female adult offspring had higher glucose-stimulated insulin secretion as well as the ratio of stimulated insulin to glucose. Male bisphenol A offspring had higher liver protein abundance of the 200 kDa insulin receptor beta precursor (2-fold), and insulin receptor substrate 1 (1.5-fold), whereas glucose transporter 2 was 0.5-fold of the control at 3 weeks of age. In adult male bisphenol A offspring, the abundance of insulin receptor beta was higher (2-fold) and glucose transporter 4 was 0.8-fold of the control in skeletal muscle. In adult female bisphenol A offspring, the skeletal muscle protein abundance of glucose transporter 4 was 0.4-fold of the control.

Conclusion

Maternal bisphenol A had sex- and tissue-specific effects on insulin signaling components, which may contribute to increased risk of glucose intolerance in offspring. Glucose transporters were consistently altered at both ages as well as in both sexes and may contribute to glucose intolerance. These data suggest that maternal bisphenol A exposure should be limited during pregnancy and lactation.

Abstract Background Small for gestational age (SGA) leads to increased risk of adult obesity and metabolic syndrome. Offspring exposed to 50% maternal food restriction in utero are born smaller than Controls (FR), catch-up in growth by the end of the nursing period, and become obese adults. The objective of the study was to determine stearoyl-CoA desaturase activity (SCD1) and rates of de novo fatty acid synthesis in young FR and Control offspring tissues at the end of the nursing period, as possible contributors to catch-up growth. Methods From gestational day 10 to term, dams fed ad libitum (Control) or were 50% food-restricted to produce small FR pups. Control dams nursed all pups. At postnatal day 1 (p1) and p21, offspring body tissues were analyzed by GC/MS, and desaturation indices of palmitoleate/palmitate and oleate/stearate were calculated. SCD1 gene expression was determined by real-time PCR on adipose and liver. Offspring were enriched with deuterium that was given to dams in drinking water during lactation and de novo synthesis of offspring body tissues was determined at p21. Primary adipocyte cell cultures were established at p21 and exposed to U13C-glucose. Results FR offspring exhibited higher desaturation index in p1 and p21 adipose tissue, but decreased desaturation index in liver at p21. SCD1 gene expression at p21 was correspondingly increased in adipose and decreased in liver. FR subcutaneous fat demonstrated increased de novo synthesis at p21. Primary cell cultures exhibited increased de novo synthesis in FR. Conclusions Adipose tissue is the first site to exhibit increased de novo synthesis and desaturase activity in FR. Therefore, abnormal lipogenesis is already present prior to onset of obesity during the period of catch-up growth. These abnormalities may contribute to future obesity development.

In offspring exposed in utero to a maternal diet high in fat (HF), we have previously demonstrated that despite similar birth weights, HF adult offspring at 6 months of age had significantly higher body weights, greater adiposity, and increased triacylglycerol (TAG) levels as compared to controls. We hypothesized that a maternal HF diet predisposes to offspring adiposity via a programmed increase in the synthesis of monounsaturated fatty acids in the liver and hence increased substrate availability for liver TAG synthesis. We further hypothesized that programmed changes in offspring liver fatty acid metabolism are associated with increased liver expression of the lipogenic enzyme stearoyl-CoA desaturase-1 (SCD-1). Female rats were maintained on a HF diet rich in monounsaturated fatty acids (MUFA) prior to and throughout pregnancy and lactation. After birth, newborns were nursed by the same dam, and all offspring were weaned to control diet. Plasma and liver fatty acid compositions were determined using gas chromatography/mass spectrometry. Fatty acid C16 desaturation indices of palmitoleic/palmitic and (vaccenic + palmitoleic)/palmitic and the C18 desaturation index of oleic/stearic were calculated. Liver protein abundance of SCD-1 was analyzed in newborns and adult offspring. Plasma and liver C16 desaturation indices were decreased in HF newborns, but increased in the adult offspring. Liver SCD-1 expression was increased in the HF adult offspring. These data show that the maternal HF diet during pregnancy and lactation increases offspring liver SCD-1 protein abundance and alters the liver C16 desaturase pathway.

Objective

We determined the potential programming effects of maternal obesity and high-fat (HF) diet during pregnancy and/or lactation on offspring metabolic syndrome.

Study design

A rat model of maternal obesity was created using an HF diet prior to and throughout pregnancy and lactation. At birth, pups were cross-fostered, thereby generating 4 paradigms of maternal diets during pregnancy/lactation: (1) control (Con) diet during pregnancy and lactation (Con/Con), (2) HF during pregnancy and lactation (HF/HF), (3) HF during pregnancy alone (HF/Con), and (4) HF during lactation alone (Con/HF).

Results

Maternal phenotype during pregnancy and the end of lactation evidenced markedly elevated body fat and plasma corticosterone levels in HF dams. In the offspring, the maternal HF diet during pregnancy alone programmed increased offspring adiposity, although with normal body weight, whereas the maternal HF diet during lactation increased both body weight and adiposity. Metabolic disturbances, particularly that of hyperglycemia, were apparent in all groups exposed to the maternal HF diet (during pregnancy and/or lactation), although differences were apparent in the manifestation of insulin resistant vs insulin-deficient phenotypes. Elevated systolic blood pressure was manifest in all groups, implying that exposure to an obese/HF environment is disadvantageous for offspring health, regardless of pregnancy or lactation periods. Nonetheless, the underlying mechanism may differ because offspring that experienced in utero HF exposure had increased corticosterone levels.

Conclusion

Maternal obesity/HF diet has a marked impact on offspring body composition and the risk of metabolic syndrome was dependent on the period of exposure during pregnancy and/or lactation.

Abstract Background Small-for-gestational age (SGA) at birth increases risk of development of adult obesity and insulin resistance. A model of SGA rat offspring has been shown to exhibit increased adipose tissue expression of a key adipogenic transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ), and increased fatty acid de novo synthesis during the nursing period, prior to onset of obesity. PPARγ agonists have been studied for potential use in the prevention of insulin resistance. Moreover, SGA adipocytes exhibit age-dependent differences in lipogenesis as mediated by PPARγ. The effects of PPARγ modulators on lipogenic gene expression and de novo lipogenesis on the age-dependent changes in SGA adipocytes are not known. The objectives of this study were: 1) to determine the adipogenic and lipogenic potential in SGA adipocytes at postnatal day 1 (p1) and day 21 (p21), 2) to determine how the PPARγ activator- and repressor-ligands affect the lipogenic potential, and 3) to determine the fatty acid metabolic response to PPARγ activator-ligand treatment. Methods Primary adipocyte cultures from p1 and p21 SGA and Control male offspring were established from a known maternal food-restriction model of SGA. Cell proliferation and Oil Red O (ORO) staining were quantified. Adipocytes were treated with increasing doses of rosiglitazone or bisphenol-A diglycidyl ether (BADGE). PPARγ and SREBP1 protein expression were determined. De novo lipogenesis with rosiglitazone treatment at p21 was studied using 50% U13C-glucose and gas chromatography/mass spectrometry. Results At p1 and p21, SGA demonstrated increased cell proliferation and increased ORO staining. At p21, SGA demonstrated increased lipogenic gene expression and increased glucose-mediated fatty acid de novo synthesis compared with Controls. In response to rosiglitazone, SGA adipocytes further increased glucose utilization for fatty acid synthesis. SGA lipogenic gene expression demonstrated resistance to BADGE treatment. Conclusions SGA adipocytes exhibit an enhanced adipogenic and lipogenic potential in early postnatal life. By p21, SGA demonstrated resistance to PPARγ repressor-ligand treatment, and selective response to high dose PPARγ activator-ligand treatment in adipogenic and lipogenic gene expression. p21 SGA adipocytes revealed increased fatty acid de novo synthesis through a complex relationship with glucose metabolism.