Epigenetic changes in hypothalamic appetite regulatory genes may underlie the developmental programming for obesity in rat neonates subjected to a high-carbohydrate dietary modification

An industrialized diet as a determinant of methylation in the 1F region of the NR3C1 gene promoter

Background

Dietary composition can modify gene expression, favoring the development of chronic diseases via epigenetic mechanisms.

Objective

Our study aimed to investigate the relationship between dietary patterns and NR3C1 gene methylation in users of the Brazilian Public Unified Health System (SUS).

Methods

We recruited 250 adult volunteers and evaluated their socioeconomic status, psychosocial characteristics, lifestyle, and anthropometrics. Peripheral blood was collected and evaluated for cortisol levels, glycemia, lipid profile, and insulin resistance; methylation of CpGs 40-47 of the 1F region of the NR3C1 gene was also measured. Factors associated with degree of methylation were evaluated using generalized linear models (p < 0.05). Lifestyle variables and health variables were included as confounding factors.

Results

The findings of our cross-sectional study indicated an association between NR3C1 DNA methylation and intake of processed foods. We also observed relevant associations of average NR3C1 DNA across the segment analyzed, methylation in component 1 (40-43), and methylation in component 2 (44-47) with a pattern of consumption of industrialized products in relation to BMI, serum cortisol levels, and lipid profile. These results may indicate a relationship between methylation and metabolic changes related to the stress response.

Conclusion

These findings suggest an association of methylation and metabolic alterations with stress response. In addition, the present study highlights the significant role of diet quality as a stress-inducing factor that influences NR3C1 methylation. This relationship is further linked to changes in psychosocial factors, lifestyle choices, and cardiometabolic variables, including glucose levels, insulin resistance, and hyperlipidemia.

Epigenetic programming for obesity and noncommunicable disease: From womb to tomb

Several epidemiological, clinical and experimental studies in recent decades have shown the relationship between exposure to stressors during development and health outcomes later in life. The characterization of these susceptible phases, such as preconception, gestation, lactation and adolescence, and the understanding of factors that influence the risk of an adult individual for developing obesity, metabolic and cardiovascular diseases, is the focus of the DOHaD (Developmental Origins of Health and Disease) research line. In this sense, advancements in molecular biology techniques have contributed significantly to the understanding of the mechanisms underlying the observed phenotypes, their morphological and physiological alterations, having as a main driving factor the epigenetic modifications and their consequent modulation of gene expression. The present narrative review aimed to characterize the different susceptible phases of development and associated epigenetic modifications, and their implication in the development of non-communicable diseases. Additionally, we provide useful insights into interventions during development to counteract or prevent long-term programming for disease susceptibility.

HMBA ameliorates obesity by MYH9- and ACTG1-dependent regulation of hypothalamic neuropeptides

The global epidemic of obesity remains a daunting problem. Here, we report hexamethylene bisacetamide (HMBA) as a potent anti-obesity compound. Peripheral and central administration of HMBA to diet-induced obese mice regulated the expression of hypothalamic neuropeptides critical for energy balance, leading to beneficial metabolic effects such as anorexia and weight loss. We found that HMBA bound to MYH9 and ACTG1, which were required for the anti-obesity effects of HMBA in both NPY-expressing and POMC-expressing neurons. The binding of HMBA to MYH9 and ACTG1 elevated the expression of HEXIM1 and enhanced its interaction with MDM2, resulting in the dissociation of the HEXIM1-p53 complex in hypothalamic cells. Subsequently, the free HEXIM1 and p53 translocated to the nucleus, where they downregulated the transcription of orexigenic NPY, but p53 and acetylated histone 3 upregulated that of anorexigenic POMC. Our study points to a previously unappreciated efficacy of HMBA and reveals its mechanism of action in metabolic regulation, which may propose HMBA as a potential therapeutic strategy for obesity.

Developmental origins of diabetes mellitus: Environmental epigenomics and emerging patterns

Mounting epidemiological evidence indicates that environmental exposures in early life have roles in diabetes susceptibility in later life. Additionally, environmentally induced diabetic susceptibility could be transmitted to subsequent generations. Epigenetic modifications provide a potential association with the environmental factors and altered gene expression that might cause disease phenotypes. Here, we bring the increasing evidence that environmental exposures early in development are linked to diabetes through epigenetic modifications. This review first summarizes the epigenetic targets, including metastable epialleles and imprinting genes, by which the environmental factors can modify the epigenome. Then we review the epigenetics changes in response to environmental challenge during critical developmental windows, gametogenesis, embryogenesis, and fetal and postnatal period, with the specific example of diabetic susceptibility. Although the mechanisms are still largely unknown, especially in humans, the new research methods are now gradually available, and the animal models can provide more in-depth study of mechanisms. These have implications for investigating the link of the phenomena to human diabetes, providing a new perspective on environmentally triggered diabetes risk.

DNA methylation of pck1 might contribute to the programming effects of early high-carbohydrate diets feeding to the glucose metabolism across two generations in zebrafish (Danio rerio)

The purpose of this study is to assess the effects of early high-carbohydrate stimulus on glucose metabolism in zebrafish (Danio rerio) over two generations and explore the mechanisms that explain those nutritional programming effects via epigenetic modifications. The larvae were delivered a high-carbohydrate diet (53.66%) that was used as an early nutritional stimulus from the first feeding to the end of the yolk sac (FF) and 5 days after yolk-sac exhaustion (YE). The larvae (F0) and their offspring (F1) were then both fed the control diet (22.69%) until adulthood (15 weeks), and they were challenged with a high-carbohydrate diet (35.36%) at the 16th week. The results indicated that early stimulus immediately raised the mRNA levels of genes involved in glycolysis and gluconeogenesis. At the end of F0 challenge, both treatment groups decreased the plasma glucose levels, increased the expression levels of glucokinase (gck), and inhibited the mRNA during gluconeogenesis. When challenged in F1, the glucose levels were lower in FF (F1), and the mRNA levels of phosphoenolpyruvate carboxykinase 1 (pck1) were decreased in FF (F1) and YE (F1). Besides, in both experimental groups (F0 and F1), the CpG island of pck1 maintained lower levels of hypermethylated expression from F0 adult, 24 h post-fertilization embryo, to F1 adult. In conclusion, these results indicated that an early high-carbohydrate stimulus could significantly reprogram glucose metabolism in adult zebrafish, that those modifications could be partially transmitted to the next generation, and that the DNA methylation of pck1 might work as a stable epigenetic marker to contribute to those processes.

The metabolic conditioning of obesity: A review of the pathogenesis of obesity and the epigenetic pathways that "program" obesity from conception

Understanding the developmental origins of health and disease is integral to overcome the global tide of obesity and its metabolic consequences, including atherosclerotic cardiovascular disease, type 2 diabetes, hyperlipidemia, and nonalcoholic fatty liver disease. The rising prevalence of obesity has been attributed, in part, to environmental factors including the globalization of the western diet and unhealthy lifestyle choices. In this review we argue that how and when such exposures come into play from conception significantly impact overall risk of obesity and later health outcomes. While the laws of thermodynamics dictate that obesity is caused by an imbalance between caloric intake and energy expenditure, the drivers of each of these may be laid down before the manifestation of the phenotype. We present evidence over the last half-century that suggests that the temporospatial evolution of obesity from intrauterine life and beyond is, in part, due to the conditioning of physiological processes at critical developmental periods that results in maladaptive responses to obesogenic exposures later in life. We begin the review by introducing studies that describe an association between perinatal factors and later risk of obesity. After a brief discussion of the pathogenesis of obesity, including the systemic regulation of appetite, adiposity, and basal metabolic rate, we delve into the mechanics of how intrauterine, postnatal and early childhood metabolic environments may contribute to adult obesity risk through the process of metabolic conditioning. Finally, we detail the specific epigenetic pathways identified both in preclinical and clinical studies that synergistically "program" obesity.

Exploring the evidence for epigenetic regulation of environmental influences on child health across generations

Environmental exposures, psychosocial stressors and nutrition are all potentially important influences that may impact health outcomes directly or via interactions with the genome or epigenome over generations. While there have been clear successes in large-scale human genetic studies in recent decades, there is still a substantial amount of missing heritability to be elucidated for complex childhood disorders. Mounting evidence, primarily in animals, suggests environmental exposures may generate or perpetuate altered health outcomes across one or more generations. One putative mechanism for these environmental health effects is via altered epigenetic regulation. This review highlights the current epidemiologic literature and supporting animal studies that describe intergenerational and transgenerational health effects of environmental exposures. Both maternal and paternal exposures and transmission patterns are considered, with attention paid to the attendant ethical, legal and social implications.

Food intake in early life and epigenetic modifications of pro-opiomelanocortin expression in arcuate nucleus

The prevalence of obesity is increasing in nowadays societies and, despite being a multifactorial disease, it has a significant correlation with food intake. The control of food intake is performed by neurons of the arcuate nucleus of the hypothalamus (ARC), which secret orexigenic and anorexigenic neuropeptides, such as proopiomelanocortin (POMC), under stimulation of, e.g., ghrelin, insulin, and leptin. Insulin, uses inositol 1,4,5-trisphosphate/serine-threonine kinase (IP3/Akt) pathways and stimulates the exclusion of (Forkhead box protein O1) FOXO1 from the nucleus and thereby does the inactivation of the inhibition of POMC expression, while Leptin stimulates signal transducer and activator of transcription 3 (STAT3) phosphorylation and POMC expression. Epigenetic modifications of the synthesis of these neuropeptides can lead to an increased caloric intake, which, in turn, is an important risk factor for obesity and its comorbidities. Epigenetic modifications are reversible, so the search for epigenetic targets has significant scientific and therapeutic appeal. In this review, we synthesize the effect of food intake on the epigenetic modifications of Neuropeptide Y and Pro-opiomelanocortin of ARC and its relationships with obesity development and comorbidities. We found that there is no consensus on the methylation of neuropeptides when the evaluations are carried out in different promoters. Based on reports carried on in the early life in laboratory animals, which is the timeline that the vast majority of author used to study this topic, chronic inflammation, defects in insulin and leptin signaling may be linked to changes occurring in the phosphoinositide 3-kinase/Akt (PI3K/Akt) and/or STAT3/SOCS3 (cytokine signaling 3) pathways. In its turn, the epigenetic modifications related to increased food intake and reduced energy expenditure may be associated with PI3K/Akt and STAT3/SOCS3 signaling disruption and Pro-opiomelanocortin expression.

Fetal betaine exposure modulates hypothalamic expression of cholesterol metabolic genes in offspring cockerels with modification of promoter DNA methylation

In documents, maternal betaine modulates hypothalamic cholesterol metabolism in chicken posthatchings, but it remains unclear whether this effect can be passed on by generations. In present study, eggs were injected with saline or betaine at 2.5 mg/egg, and the hatchlings (F1) were raised under the same condition until sexual maturation. Both the control group and the betaine group used artificial insemination to collect sperm from their cockerels. Fertilized eggs were incubated, and the hatchlings of the following generation (F2) were raised up to 64 D of age. F2 cockerels in betaine group showed significantly (P < 0.05) lower body weight, which was associated with significantly decreased (P < 0.05) hypothalamic content of total cholesterol and cholesterol ester. Concordantly, hypothalamic expression of cholesterol biosynthetic genes, SREBP2 and HMGCR, were significantly downregulated (P < 0.05), together with cholesterol conversion-related and excretion-related genes, CYP46A1 and ABCA1. These changes coincided with a significant downregulation in mRNA expression of regulatory neuropeptides including brain-derived neurotrophic factor, neuropeptide Y, and corticotropin-releasing hormone. Moreover, genes involved in methyl transfer cycle were also modified. Betaine homocysteine methyltransferase (P < 0.05) was downregulated, yet DNA methyltransferase1 tended to be upregulated (P = 0.06). S-adenosyl methionine/S-adenosylhomocysteine ratio was higher in the hypothalamus of betaine-treated F2 cockerels, which was associated with significantly modified CpG methylation on the promoter of those affected genes. These results suggested that betaine might regulate central cholesterol metabolism and hypothalamic expression of genes related to brain function by altering promoter DNA methylation in F2 cockerels.

Epigenetics: Linking Early Postnatal Nutrition to Obesity Programming?

Despite constant research and public policy efforts, the obesity epidemic continues to be a major public health threat, and new approaches are urgently needed. It has been shown that nutrient imbalance in early life, from conception to infancy, influences later obesity risk, suggesting that obesity could result from "developmental programming". In this review, we evaluate the possibility that early postnatal nutrition programs obesity risk via epigenetic mechanisms, especially DNA methylation, focusing on four main topics: (1) the dynamics of epigenetic processes in key metabolic organs during the early postnatal period; (2) the epigenetic effects of alterations in early postnatal nutrition in animal models or breastfeeding in humans; (3) current limitations and remaining outstanding questions in the field of epigenetic programming; (4) candidate pathways by which early postnatal nutrition could epigenetically program adult body weight set point. A particular focus will be given to the potential roles of breast milk fatty acids, neonatal metabolic and hormonal milieu, and gut microbiota. Understanding the mechanisms by which early postnatal nutrition can promote lifelong metabolic modifications is essential to design adequate recommendations and interventions to "de-program" the obesity epidemic.

Cafeteria diet induces progressive changes in hypothalamic mechanisms involved in food intake control at different feeding periods in female rats

We studied the effects of cafeteria diet (CAF) intake from weaning on mRNA levels and DNA methylation state of feeding-related neuropeptides and hormone receptors in individual hypothalamic nuclei at different feeding periods. Four weeks of CAF (short-term) increased energy intake and adiposity, without affecting neuropeptides' expression. Eleven weeks of CAF (medium-term) increased energy intake, adiposity, leptinemia, and body weight, with an orexigenic response of the lateral hypothalamus, paraventricular and ventromedial nuclei, given by upregulation of Orexins, AgRP, and NPY opposed by an anorectic signal of the arcuate nucleus, which displayed a higher POMC expression. The changes in neuropeptidic mRNA levels were related to epigenetic modifications in their promoter regions. Metabolic and molecular changes were intensified after 20 weeks of diet (long-term). The alterations in these hypothalamic brain nuclei could add information about their differential role in food intake control, and how their action is disrupted during the development of obesity.

Epigenetic regulation of POMC; implications for nutritional programming, obesity and metabolic disease

Proopiomelanocortin (POMC) is a key mediator of satiety. Epigenetic marks such as DNA methylation may modulate POMC expression and provide a biological link between early life exposures and later phenotype. Animal studies suggest epigenetic marks at POMC are influenced by maternal energy excess and restriction, prenatal stress and Triclosan exposure. Postnatal factors including energy excess, folate, vitamin A, conjugated linoleic acid and leptin may also affect POMC methylation. Recent human studies suggest POMC DNA methylation is influenced by maternal nutrition in early pregnancy and associated with childhood and adult obesity. Studies in children propose a link between POMC DNA methylation and elevated lipids and insulin, independent of body habitus. This review brings together evidence from animal and human studies and suggests that POMC is sensitive to nutritional programming and is associated with a wide range of weight-related and metabolic outcomes.

A Maternal High-Fat Diet Induces DNA Methylation Changes That Contribute to Glucose Intolerance in Offspring

Scope: Overnutrition in utero is a critical contributor to the susceptibility of diabetes by programming, although the exact mechanism is not clear. In this paper, we aimed to study the long-term effect of a maternal high-fat (HF) diet on offspring through epigenetic modifications. Procedures: Five-week-old female C57BL6/J mice were fed a HF diet or control diet for 4 weeks before mating and throughout gestation and lactation. At postnatal week 3, pups continued to consume a HF or switched to a control diet for 5 weeks, resulting in four groups of offspring differing by their maternal and postweaning diets. Results: The maternal HF diet combined with the offspring HF diet caused hyperglycemia and insulin resistance in male pups. Even after changing to the control diet, male pups exposed to the maternal HF diet still exhibited hyperglycemia and glucose intolerance. The livers of pups exposed to a maternal HF diet had a hypermethylated insulin receptor substrate 2 (Irs2) gene and a hypomethylated mitogen-activated protein kinase kinase 4 (Map2k4) gene. Correspondingly, the expression of the Irs2 gene decreased and that of Map2k4 increased in pups exposed to a maternal HF diet. Conclusion: Maternal overnutrition programs long-term epigenetic modifications, namely, Irs2 and Map2k4 gene methylation in the offspring liver, which in turn predisposes the offspring to diabetes later in life.

Lactational programming of glucose homeostasis: a window of opportunity

The window of lactation is a critical period during which nutritional and environmental exposures impact lifelong metabolic disease risk. Significant organ and tissue development, organ expansion and maturation of cellular functions occur during the lactation period, making this a vulnerable time during which transient insults can have lasting effects. This review will cover current literature on factors influencing lactational programming such as milk composition, maternal health status and environmental endocrine disruptors. The underlying mechanisms that have the potential to contribute to lactational programming of glucose homeostasis will also be addressed, as well as potential interventions to reduce offspring metabolic disease risk.

Maternal overnutrition programs epigenetic changes in the regulatory regions of hypothalamic Pomc in the offspring of rats

Background and objective

Maternal overnutrition has been implicated in affecting the offspring by programming metabolic disorders such as obesity and diabetes, by mechanisms that are not clearly understood. This study aimed to determine the long-term impact of maternal high-fat (HF) diet feeding on epigenetic changes in the offspring’s hypothalamic Pomc gene, coding a key factor in the control of energy balance. Further, it aimed to study the additional effects of postnatal overnutrition on epigenetic programming by maternal nutrition.

Methods

Eight-week-old female Sprague–Dawley rats were fed HF diet or low-fat (LF) diet for 6 weeks before mating, and throughout gestation and lactation. At postnatal day 21, samples were collected from a third offspring and the remainder were weaned onto LF diet for 5 weeks, after which they were either fed LF or HF diet for 12 weeks, resulting in four groups of offspring differing by their maternal and postweaning diet.

Results

With maternal HF diet, offspring at weaning had rapid early weight gain, increased adiposity, and hyperleptinemia. The programmed adult offspring, subsequently fed LF diet, retained the increased body weight. Maternal HF diet combined with offspring HF diet caused more pronounced hyperphagia, fat mass, and insulin resistance. The ARC Pomc gene from programmed offspring at weaning showed hypermethylation in the enhancer (nPE1 and nPE2) regions and in the promoter sequence mediating leptin effects. Interestingly, hypermethylation at the Pomc promoter but not at the enhancer region persisted long term into adulthood in the programmed offspring. However, there were no additive effects on methylation levels in the regulatory regions of Pomc in programmed offspring fed a HF diet.

Conclusion

Maternal overnutrition programs long-term epigenetic alterations in the offspring’s hypothalamic Pomc promoter. This predisposes the offspring to metabolic disorders later in life.

Cafeteria diet differentially alters the expression of feeding-related genes through DNA methylation mechanisms in individual hypothalamic nuclei

We evaluated the effect of cafeteria diet (CAF) on the mRNA levels and DNA methylation state of feeding-related neuropeptides, and neurosteroidogenic enzymes in discrete hypothalamic nuclei. Besides, the expression of steroid hormone receptors was analyzed. Female rats fed with CAF from weaning increased their energy intake, body weight, and fat depots, but did not develop metabolic syndrome. The increase in energy intake was related to an orexigenic signal of paraventricular (PVN) and ventromedial (VMN) nuclei, given principally by upregulation of AgRP and NPY. This was mildly counteracted by the arcuate nucleus, with decreased AgRP expression and increased POMC and kisspeptin expression. CAF altered the transcription of neurosteroidogenic enzymes in PVN and VMN, and epigenetic mechanisms associated with differential promoter methylation were involved. The changes observed in the hypothalamic nuclei studied could add information about their differential role in food intake control and how their action is disrupted in obesity.

Breastfeeding effects on DNA methylation in the offspring: A systematic literature review

BACKGROUND

Breastfeeding benefits both infants and mothers. Recent research shows long-term health and human capital benefits among individuals who were breastfed. Epigenetic mechanisms have been suggested as potential mediators of the effects of early-life exposures on later health outcomes. We reviewed the literature on the potential effects of breastfeeding on DNA methylation.

METHODS

Studies reporting original results and evaluating DNA methylation differences according to breastfeeding/breast milk groups (e.g., ever vs. never comparisons, different categories of breastfeeding duration, etc) were eligible. Six databases were searched simultaneously using Ovid, and the resulting studies were evaluated independently by two reviewers.

RESULTS

Seven eligible studies were identified. Five were conducted in humans. Studies were heterogeneous regarding sample selection, age, target methylation regions, methylation measurement and breastfeeding categorisation. Collectively, the studies suggest that breastfeeding might be negatively associated with promoter methylation of LEP (which encodes an anorexigenic hormone), CDKN2A (involved in tumour suppression) and Slc2a4 genes (which encodes an insulin-related glucose transporter) and positively with promoter methylation of the Nyp (which encodes an orexigenic neuropeptide) gene, as well as influence global methylation patterns and modulate epigenetic effects of some genetic variants.

CONCLUSIONS

The findings from our systematic review are far from conclusive due to the small number of studies and their inherent limitations. Further studies are required to understand the actual potential role of epigenetics in the associations of breastfeeding with later health outcomes. Suggestions for future investigations, focusing on epigenome-wide association studies, are provided.

Neuropeptide Y in Alcohol Addiction and Affective Disorders

Neuropeptide Y (NPY), a neuropeptide highly conserved throughout evolution, is present at high levels in the central nervous system (CNS), as well as in peripheral tissues such as the gut and cardiovascular system. The peptide exerts its effects via multiple receptor subtypes, all belonging to the G-protein-coupled receptor superfamily. Of these subtypes, the Y1 and the Y2 are the most thoroughly characterized, followed by the Y5 subtype. NPY and its receptors have been shown to be of importance in central regulation of events underlying, for example, affective disorders, drug/alcohol use disorders, and energy homeostasis. Furthermore, within the CNS, NPY also affects sleep regulation and circadian rhythm, memory function, tissue growth, and plasticity. The potential roles of NPY in the etiology and pathophysiology of mood and anxiety disorders, as well as alcohol use disorders, have been extensively studied. This focus was prompted by early indications for an involvement of NPY in acute responses to stress, and, later, also data pointing to a role in alterations within the CNS during chronic, or repeated, exposure to adverse events. These functions of NPY, in addition to the peptide's regulation of disease states, suggest that modulation of the activity of the NPY system via receptor agonists/antagonists may be a putative treatment mechanism in affective disorders as well as alcohol use disorders. In this review, we present an overview of findings with regard to the NPY system in relation to anxiety and stress, acute as well as chronic; furthermore we discuss post-traumatic stress disorder and, in part depression. In addition, we summarize findings on alcohol use disorders and related behaviors. Finally, we briefly touch upon genetic as well as epigenetic mechanisms that may be of importance for NPY function and regulation. In conclusion, we suggest that modulation of NPY-ergic activity within the CNS, via ligands aimed at different receptor subtypes, may be attractive targets for treatment development for affective disorders, as well as for alcohol use disorders.

Transgenerational effects of maternal diet on metabolic and reproductive ageing

The early-life environment, in particular maternal diet during pregnancy, influences a wide range of organs and systems in adult offspring. Mounting evidence suggests that developmental programming can also influence health and disease in grand-offspring. Transgenerational effects can be defined as those persisting into an F2 generation, where the F0 mother experiences suboptimal diet during her pregnancy. In this review, we critically examine evidence for transgenerational developmental programming effects in human populations, focusing on metabolic and reproductive outcomes. We discuss evidence from historical cohorts suggesting that grandchildren of women exposed to famine and other dietary alterations during pregnancy may experience increased rates of later health complications than their control counterparts. The methodological difficulties with transgenerational studies in human cohorts are explored. In particular, the problems with assessing reproductive outcomes in human populations are discussed. In light of the relative paucity of evidence available from human cohorts, we consider key insights from transgenerational experimental animal models of developmental programming by maternal diet; data are drawn from a range of rodent models, as well as the guinea-pig and the sheep. The evidence for different potential mechanisms of transgenerational inheritance or re-propagation of developmental programming effects is evaluated. Transgenerational effects could be transmitted through methylation of the gametes via the paternal and maternal lineage, as well as other possible mechanisms via the maternal lineage. Finally, future directions for exploring these underlying mechanisms further are proposed, including utilizing large, well-characterized, prospective pregnancy cohorts that include biobanks, which have been established in various populations during the last few decades.

Neuroendocrinological and Epigenetic Mechanisms Subserving Autonomic Imbalance and HPA Dysfunction in the Metabolic Syndrome

Impact of environmental stress upon pathophysiology of the metabolic syndrome (MetS) has been substantiated by epidemiological, psychophysiological, and endocrinological studies. This review discusses recent advances in the understanding of causative roles of nutritional factors, sympathomedullo-adrenal (SMA) and hypothalamic-pituitary adrenocortical (HPA) axes, and adipose tissue chronic low-grade inflammation processes in MetS. Disturbances in the neuroendocrine systems for leptin, melanocortin, and neuropeptide Y (NPY)/agouti-related protein systems have been found resulting directly in MetS-like conditions. The review identifies candidate risk genes from factors shown critical for the functioning of each of these neuroendocrine signaling cascades. In its meta-analytic part, recent studies in epigenetic modification (histone methylation, acetylation, phosphorylation, ubiquitination) and posttranscriptional gene regulation by microRNAs are evaluated. Several studies suggest modification mechanisms of early life stress (ELS) and diet-induced obesity (DIO) programming in the hypothalamic regions with populations of POMC-expressing neurons. Epigenetic modifications were found in cortisol (here HSD11B1 expression), melanocortin, leptin, NPY, and adiponectin genes. With respect to adiposity genes, epigenetic modifications were documented for fat mass gene cluster APOA1/C3/A4/A5, and the lipolysis gene LIPE. With regard to inflammatory, immune and subcellular metabolism, PPARG, NKBF1, TNFA, TCF7C2, and those genes expressing cytochrome P450 family enzymes involved in steroidogenesis and in hepatic lipoproteins were documented for epigenetic modifications.

Developmental programming of type 2 diabetes: early nutrition and epigenetic mechanisms

PURPOSE OF REVIEW

The environment experienced during critical windows of development can 'programme' long-term health and risk of metabolic diseases such as type 2 diabetes in the offspring. The purpose of this review is to discuss potential epigenetic mechanisms involved in the developmental programming of type 2 diabetes by early nutrition.

RECENT FINDINGS

Maternal and more recently paternal nutrition have been shown to play key roles in metabolic programming of the offspring. Although the exact mechanisms are still not clear, epigenetic processes have emerged as playing a plausible role. Epigenetic dysregulation is associated with several components that contribute to type 2 diabetes risk, including altered feeding behaviour, insulin secretion and insulin action. It may also contribute to transgenerational risk transmission.

SUMMARY

Epigenetic processes may represent a central underlying mechanism of developmental programming of type 2 diabetes. During embryonic and foetal development, extensive epigenetic remodelling takes place not only in somatic but also in primordial germ cells. Therefore, concerns have been raised that epigenetic dysregulation induced by a suboptimal early environment could programme altered phenotypes not only in the first generation but also in the subsequent ones. Characterizing these altered epigenetic marks has great implications for identifying individuals at an increased disease risk as well as potentially leading to novel preventive and treatment strategies.

Regulation of hypothalamic neuropeptides gene expression in diet induced obesity resistant rats: possible targets for obesity prediction?

Several factors play a role in obesity (i.e., behavior, environment, and genetics) and epigenetic regulation of gene expression has emerged as a potential contributor in the susceptibility and development of obesity. To investigate the individual sensitivity to weight gain/resistance, we here studied gene transcription regulation of several hypothalamic neuropeptides involved in the control of energy balance in rats developing obesity (diet-induced obesity, DIO) or not (diet resistant, DR), when fed with a high fat diet. Rats have been followed up to 21 weeks of high fat diet exposure. After 5 weeks high fat diet exposure, the obese phenotype was developed and we observed a selective down-regulation of the orexigenic neuropeptide Y (NPY) and peroxisome proliferator-activated receptor gamma (PPAR-γ) genes. No changes were observed in the expression of the agouti-related protein (AgRP), as well as for all the anorexigenic genes under study. After long-term high fat diet exposure (21 weeks), NPY and PPAR-γ, as well as most of the genes under study, resulted not be different between DIO and DR, whereas a lower expression of the anorexigenic pro-opio-melanocortin (POMC) gene was observed in DIO rats when compared to DR rats. Moreover we observed that changes in NPY and POMC mRNA were inversely correlated with gene promoters DNA methylation. Our findings suggest that selective alterations in hypothalamic peptide genes regulation could contribute to the development of overweight in rats and that environmental factor, as in this animal model, might be partially responsible of these changes via epigenetic mechanism.

Leptin resistance in obesity: An epigenetic landscape

Leptin is an adipocyte-secreted hormone that inhibits food intake and stimulates energy expenditure through interactions with neuronal pathways in the brain, particularly pathways involving the hypothalamus. Intact functioning of the leptin route is required for body weight and energy homeostasis. Given its function, the discovery of leptin increased expectations for the treatment of obesity. However, most obese individuals and subjects with a predisposition to regain weight after losing it have leptin concentrations than lean individuals, but despite the anorexigenic function of this hormone, appetite is not effectively suppressed in these individuals. This phenomenon has been deemed leptin resistance and could be the result of impairments at a number of levels in the leptin signalling pathway, including reduced access of the hormone to its receptor due to changes in receptor expression or changes in post-receptor signal transduction. Epigenetic regulation of the leptin signalling circuit could be a potential mechanism of leptin function disturbance. This review discusses the molecular mechanisms, particularly the epigenetic regulation mechanisms, involved in leptin resistance associated with obesity and the therapeutic potential of these molecular mechanisms in the battle against the obesity pandemic.

Developmental programming of hypothalamic neuronal circuits: impact on energy balance control

The prevalence of obesity in adults and children has increased globally at an alarming rate. Mounting evidence from both epidemiological studies and animal models indicates that adult obesity and associated metabolic disorders can be programmed by intrauterine and early postnatal environment- a phenomenon known as "fetal programming of adult disease." Data from nutritional intervention studies in animals including maternal under- and over-nutrition support the developmental origins of obesity and metabolic syndrome. The hypothalamic neuronal circuits located in the arcuate nucleus controlling appetite and energy expenditure are set early in life and are perturbed by maternal nutritional insults. In this review, we focus on the effects of maternal nutrition in programming permanent changes in these hypothalamic circuits, with experimental evidence from animal models of maternal under- and over-nutrition. We discuss the epigenetic modifications which regulate hypothalamic gene expression as potential molecular mechanisms linking maternal diet during pregnancy to the offspring's risk of obesity at a later age. Understanding these mechanisms in key metabolic genes may provide insights into the development of preventative intervention strategies.

Adult-onset obesity induced by early life overnutrition could be reversed by moderate caloric restriction

Overnutrition during the suckling period (small litter, SL) results in the development of adult-onset obesity. Our aim was to investigate whether two levels of caloric restriction (CR) in the early postweaning period can reverse obese phenotype in SL rats. The normal litter (NL) had 12 pups/dam and SL had 3 male pups/dam from the postnatal day 3 until day 21. After weaning, rats consumed lab chow as indicated: 1) NL and SL groups were on ad libitum regimen up to day 140, 2) another SL group was pair-fed (SL/PF) to NL(∼14% reduction), 3) SL/PF/AL group was pair-fed up to day 94 and then switched to ad libitum feeding, 4) SL/CR group received 24% reduction (moderate CR) in food intake compared with SL, and 5) SL/CR/AL group was on 24% CR up to day 94 and then switched to ad libitum feeding. Pair-feeding reduced body weight gains and serum insulin and leptin levels compared with SL rats, but these parameters were restored to SL levels in the SL/PF/AL rats after switching to ad libitum feeding. Interestingly, the moderate CR normalized these parameters in SL/CR and SL/CR/AL rats compared with NL. The expression of neuropeptide Y, proopiomelanocortin, and leptin receptor returned to control levels in hypothalami from SL/CR and SL/CR/AL rats. These results indicate that appropriate manipulation of energy intake during the early postweaning period could lead to longer-lasting effects on the regulation of body weight homeostasis via reversal of the early preweaning programming effects on the hypothalamic appetite regulation mechanism.