[Epigenetics and Nutrition: maternal nutrition impacts on placental development and health of offspring]. / Epigénétique et Nutrition : impacts de l'alimentation maternelle sur le développement placentaire et la santé de la descendance.

The environment, defined broadly by all that is external to the individual, conditions the phenotype during development, particularly the susceptibility to develop non-communicable diseases. This notion, called Developmental Origins of Health and Disease (DOHaD), is based on numerous epidemiological studies as well as animal models. Thus, parental nutrition and obesity can predispose the offspring to develop metabolic and cardiovascular diseases in adulthood. The known underlying mechanisms include an altered development of tissues that adapt to maternal metabolic condition, and a placental dysfunction, which in turn impacts fetal growth and development. Epigenetic mechanisms modulate gene expression without affecting the DNA sequence itself. The main epigenetic marks are DNA methylation and histone post-translational modifications. These marks are erased and set-up during gametogenesis and development in order to ensure cellular identity. Therefore, they can lead to a memorisation of early environment and induce long-term alteration of cell and tissue functions, which will condition the susceptibility to non-communicable diseases. The placenta is a programming agent of adult disease. The environment, such as smoking or psychosocial stress, is able to modify epigenetic processes in placenta, such as small RNA expression and DNA methylation. We showed that placenta is sensitive to maternal obesity and maternal nutrition, in terms of histology, transcription and epigenetic marks. A clear sexual dimorphism is remarkable in the placental response to maternal environment. In adulthood, the phenotype is also different between males and females. Epigenetic mechanisms could underlie this differential response of males and females to the same environment. The DOHaD can no longer be ignored in Biology of Reproduction. The prevention of non-communicable diseases must take this new paradigm into account. Research will allow a better comprehension of the mechanisms of this early conditioning and the marked sexual dimorphism it is associated to.

Developmental conditioning of the vasculature.

There is increasing evidence from epidemiological and experimental animal studies that the early life environment, of which nutrition is a key component, acts through developmental adaptive responses to set the capacity of cardiovascular and metabolic pathways to respond to physiological and pathophysiological challenges in later life. One finding that is consistent to both population studies and animal models is the propensity for such effects to induce endothelial dysfunction throughout the vascular tree, including the microvasculature. Obesity, type 2 diabetes and hypertension are associated with changes in microvascular function affecting multiple tissues and organs. These changes may be detected early, often before the onset of macrovascular disease and the development of end organ damage. Suboptimal maternal nutrition and fetal growth result in reduced microvascular perfusion and functional dilator capacity in the offspring, which together with microvascular rarefaction and remodeling serve to limit capillary recruitment, reduce exchange capacity and increase diffusion distances of metabolic substrates; they also increase local and overall peripheral resistance. This article explores how a developmentally conditioned disadvantageous microvascular phenotype may represent an important and additional risk factor for increased susceptibility to the development of cardio-metabolic disease in adult life and considers the cell signaling pathways associated with microvascular dysfunction that may be "primed" by the maternal environment. As the microvasculature has been shown to be a potential target for early therapeutic and lifestyle intervention, this article also considers evidence for the efficacy of such strategies in humans and in animal models of the developmental origins of health and disease.

Critical periods of increased fetal vulnerability to a maternal high fat diet.

BACKGROUND: Fetal adaptations to high fat (HF) diet in utero (IU) that may predispose to Metabolic Syndrome (MetS) in adulthood include changes in fetal hepatic gene expression. Studies were performed to determine whether maternal exposure to HF diet at different stages during pregnancy had different effects on the fetus, including hepatic gene expression. METHODS: Female wild type mice were fed either a HF or breeding chow (C) for 2 wks prior to mating. The experimental groups were composed of embryonic day (e) 18.5 fetuses obtained from WT female mice that were fed HF (HF, 35.5% fat) or breeding chow (C, 9.5% fat) for 2 wk before mating until e9.5 of pregnancy (periconception-midpregnancy). At e9.5 dams were switched to the opposite diet (C-HF or HF-C). RESULTS: Exposure to HF diet throughout pregnancy reduced maternal weight gain compared to C diet (p < 0.02 HF vs. C). HF-C dams had significantly decreased adiponectin levels and litter size when compared to C-HF (p < 0.02 HF-C vs C-HF). Independent of the timing of exposure to HF, fetal weight and length were significantly decreased when compared to C diet (HF, C-HF and HF-C vs. C p < 0.02). HF diet during the second half of pregnancy increased expression of genes in the fetal liver associated with fetal growth (C-HF vs C p < 0.001), glucose production (C-HF vs C p < 0.04), oxidative stress and inflammation (C-HF vs C p < 0.01) compared to C diet. CONCLUSIONS: This model defines that there are critical periods during gestation in which the fetus is actively shaped by the environment. Early exposure to a HF diet determines litter size while exposure to HF during the second half of pregnancy leads to dysregulation of expression of key genes responsible for fetal growth, hepatic glucose production and oxidative stress. These findings underscore the importance of future studies designed to clarify how these critical periods may influence future risk of developing MetS later in life.

[Developmental programming of metabolic diseases--a review of studies on experimental animal models]. / Programowanie rozwojowe chorób metabolicznych--przeglad wyników badan na zwierzecych modelach doswiadczalnych.

Growth and development in utero is a complex and dynamic process that requires interaction between the mother organism and the fetus. The delivery of macro--and micronutrients, oxygen and endocrine signals has crucial importance for providing a high level of proliferation, growth and differentiation of cells, and a disruption in food intake not only has an influence on the growth of the fetus, but also has negative consequences for the offspring's health in the future. Diseases that traditionally are linked to inappropriate life style of adults, such as type 2 diabetes, obesity, and arterial hypertension, can be "programmed" in the early stage of life and the disturbed growth of the fetus leads to the symptoms of the metabolic syndrome. The structural changes of some organs, such as the brain, pancreas and kidney, modifications of the signaling and metabolic pathways in skeletal muscles and in fatty tissue, epigenetic mechanisms and mitochondrial dysfunction are the basis of the metabolic disruptions. The programming of the metabolic disturbances is connected with the disruption in the intrauterine environment experienced in the early and late gestation period. It causes the changes in deposition of triglycerides, activation of the hormonal "stress axis" and disturbances in the offspring's glucose tolerance. The present review summarizes experimental results that led to the identification of the above-mentioned links and it underlines the role of animal models in the studies of this important concept.

Lipotoxicity and the role of maternal nutrition.

Intrauterine malnutrition predisposes the offspring towards the development of type 2 diabetes and cardiovascular disease. To explain this association, the Developmental Origins of Health and Disease hypothesis was introduced, meaning that subtle environmental changes during embryonic and foetal development can influence post-natal physiological functions. Different mechanisms, including epigenetics, are thought to be involved in this foetal programming, but the link between epigenetics and disease is missing. There is increasing evidence that ectopic lipid accumulation and/or lipotoxicity is induced by foetal programming. The aim of this review is to provide insights into the mechanisms underlying lipotoxicity through programming, which contributes to the increase in hepatic and cardiac metabolic risk.

Foetal and placental 11ß-HSD2: a hub for developmental programming.

Foetal growth restriction (FGR), reflective of an adverse intrauterine environment, confers a significantly increased risk of perinatal mortality and morbidity. In addition, low birthweight associates with adult diseases including hypertension, metabolic dysfunction and behavioural disorders. A key mechanism underlying FGR is exposure of the foetus to glucocorticoids which, while critical for foetal development, in excess can reduce foetal growth and permanently alter organ structure and function, predisposing to disease in later life. Foetal glucocorticoid exposure is regulated, at least in part, by the enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2), which catalyses the intracellular inactivation of glucocorticoids. This enzyme is highly expressed within the placenta at the maternal-foetal interface, limiting the passage of glucocorticoids to the foetus. Expression of 11ß-HSD2 is also high in foetal tissues, particularly within the developing central nervous system. Down-regulation or genetic deficiency of placental 11ß-HSD2 is associated with significant reductions in foetal growth and birth weight, and programmed outcomes in adulthood. To unravel the direct significance of 11ß-HSD2 for developmental programming, placental function, neurodevelopment and adult behaviour have been extensively investigated in a mouse knockout of 11ß-HSD2. This review highlights the evidence obtained from this mouse model for a critical role of feto-placental 11ß-HSD2 in determining the adverse programming outcomes.

The microvasculature: a target for nutritional programming and later risk of cardio-metabolic disease.

There is compelling evidence that microvascular deficits affecting multiple tissues and organs play an important role in the aetiopathogenesis of cardio-metabolic disease. Furthermore, both in humans and animal models, deficits in small vessel structure and function can be detected early, often before the onset of macrovascular disease and the development of end-organ damage that is common to hypertension and obesity-associated clinical disorders. This article considers the growing evidence for the negative impact of an adverse maternal diet on the long-term health of her child, and how this can result in a disadvantageous vascular phenotype that extends to the microvascular bed. We describe how structural and functional modifications in the offspring microcirculation during development may represent an important and additional risk determinant to increase susceptibility to the development of cardio-metabolic disease in adult life and consider the cell-signalling pathways associated with endothelial dysfunction that may be 'primed' by the maternal environment. Published studies were identified that reported outcomes related to the microcirculation, endothelium, maternal diet and vascular programming using NCBI PubMed.gov, MEDLINE and ISI Web of Science databases from 1980 until April 2013 using pre-specified search terms. Information extracted from over 230 original reports and review articles was critically evaluated by the authors for inclusion in this review.

[Gestational diabetes: diagnosis, short and long term management]. / Le diabète gestationnel : diagnostic et prise en charge à court et à long terme.

Universal consensus on the diagnosis methods and thresholds has long been lacking. The recently published Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study has been used to confirm the link between hyperglycemia and materno-fetal complications. Consequently, in France, the Société francophone du diabète (SFD) and the Collège national des gynécologues et obstétriciens français (CNGOF) proposed an expert consensus on gestational diabetes mellitus for clinical practice. Fasting blood glucose should be measured at the first visit during early pregnancy for women with risk factors to identify the women with pregestational diabetes. It is proposed a selective screening on risk factors rather than universal screening. Specific treatment of gestational diabetes reduced materno-fetal complications compared to the absence of therapy. Women with a history of gestational diabetes mellitus are characterized by a high risk of type 2 diabetes mellitus.

Glucocorticoid excess and the developmental origins of disease: two decades of testing the hypothesis--2012 Curt Richter Award Winner.

Low birthweight, a marker of an adverse in utero environment, is associated with cardiometabolic disease and brain disorders in adulthood. The adaptive changes made by the fetus in response to the intra-uterine environment result in permanent changes in physiology, structure and metabolism, a phenomenon termed early life programming. One of the key hypotheses to explain programming, namely over exposure of the developing fetus to glucocorticoids, was proposed nearly two decades ago, following the observation that the fetus was protected from high glucocorticoid levels in the mother by the actions of the placental barrier enzyme, 11ß-hydroxysteroid dehydrogenase, which converts active glucocorticoids into inactive products. Numerous mechanistic studies in animal models have been carried out to test this hypothesis using manipulations to increase maternal glucocorticoids. Overall, these have resulted in offspring of lower birthweight, with an activated hypothalamic-pituitary-adrenal (HPA) axis and an adverse metabolic profile and behavioural phenotype in adulthood. Altered glucocorticoid activity or action is a good candidate mechanism in humans to link low birthweight with cardiometabolic and brain disorders. We have carried out detailed studies in men and women showing that high levels of endogenous glucocorticoids, or treatment with exogenous glucocorticoids, is associated with an adverse metabolic profile, increased cardiovascular disease and altered mood and cognitive decline. Our laboratory carried out the first translational studies in humans to test the glucocorticoid hypothesis, firstly demonstrating in studies of adult men and women, that low birthweight was associated with high fasting cortisol levels. We went on to dissect the mechanisms underlying the high fasting cortisol, demonstrating activation of the HPA axis, with increased cortisol responses to stimulation with exogenous adrenocorticotrophin hormone, lack of habituation to the stress of venepuncture, and increased cortisol responses to psychosocial stress. We have developed new dynamic tests to dissect the mechanisms regulating HPA axis central negative feedback sensitivity in humans, and demonstrated that this may be altered in obesity, one component of the metabolic syndrome. There are now studies in humans demonstrating that high circulating levels of maternal cortisol during pregnancy correlate negatively with birthweight, suggesting that excess glucocorticoids can by-pass the placental barrier. Deficiencies in the barrier enzyme, potentially increasing fetal glucocorticoid exposure, can also arise in association with maternal stress, malnutrition and disease, and can be inhibited by consumption of liquorice, which contains glycyrrhizin, an HSD inhibitor. Importantly, studies in humans have now demonstrated that high maternal cortisol in pregnancy and/or inhibition of HSD2 are associated with programmed outcomes in childhood including higher blood pressure, behavioural disorders as well as altered brain structure. We are investigating this further, using novel magnetic resonance imaging techniques to study the developing fetal brain in utero. The translational studies in support of the glucocorticoid hypothesis, and demonstrating that glucocorticoids are both mediators and targets of programming, are exciting and raise the question of whether this information can be used to identify those individuals most at risk of later life disease. In a recent study we showed that alterations in DNA methylation at genes important in regulating cortisol levels, tissue glucocorticoid action, blood pressure and fetal growth, are present in adulthood in association with both early life parameters and cardiometabolic risk factors. These preliminary data add to the limited literature in humans indicating a persisting epigenetic link between early life events and subsequent disease risk. Such findings open novel avenues for further exploration of the contribution of glucocorticoids to later life disease.

Developmental origins of non-communicable disease: implications for research and public health.

This White Paper highlights the developmental period as a plastic phase, which allows the organism to adapt to changes in the environment to maintain or improve reproductive capability in part through sustained health. Plasticity is more prominent prenatally and during early postnatal life, i.e., during the time of cell differentiation and specific tissue formation. These developmental periods are highly sensitive to environmental factors, such as nutrients, environmental chemicals, drugs, infections and other stressors. Nutrient and toxicant effects share many of the same characteristics and reflect two sides of the same coin. In both cases, alterations in physiological functions can be induced and may lead to the development of non-communicable conditions. Many of the major diseases - and dysfunctions - that have increased substantially in prevalence over the last 40 years seem to be related in part to developmental factors associated with either nutritional imbalance or exposures to environmental chemicals. The Developmental Origins of Health and Disease (DOHaD) concept provides significant insight into new strategies for research and disease prevention and is sufficiently robust and repeatable across species, including humans, to require a policy and public health response. This White Paper therefore concludes that, as early development (in utero and during the first years of postnatal life) is particularly sensitive to developmental disruption by nutritional factors or environmental chemical exposures, with potentially adverse consequences for health later in life, both research and disease prevention strategies should focus more on these vulnerable life stages.

Genetic selection of embryos that later develop the metabolic syndrome.

THE BARKER HYPOTHESIS: Is an excellent explanation of the process where human and animal foetuses exposed to malnutrition, either by maternal malnutrition or placental insufficiency, are metabolically programmed, with selective stunting of cell differentiation and organ growth. With the postnatal excess of nutrition observed in developed countries, this irreversible programming causes metabolic syndrome, including obesity, type 2 diabetes, and hypertension. Metabolic programming involves epigenetic changes including imprinting which might be transmitted through more than one generation rather than being completely re-set or erased during reproduction. The Barker hypothesis was supported by epidemiological data that recognised no excess fetal or postnatal mortality when pregnant women were starved during the Dutch famine in World War II. This argued against the "thrifty genotype" theory introduced in 1962, which proposed that starvation selected against members of the population with less "thrifty" genes, but the survivors who had "thrifty" genes developed metabolic syndrome if they were subsequently over-nourished. EMBRYONIC/FETAL SELECTION: Embryos or early foetuses could be selected very early in pregnancy on the basis of their genotype, by maternal malnutrition, hypertension, obesity or other causes of placental insufficiency. The genotype that allows embryos, or cells within them, to survive a less hospitable environment in the decidua after implantation might contribute to the later development of metabolic syndrome. This article hypothesises that an adverse intrauterine environment, caused by maternal malnutrition or placental insufficiency, kills a proportion of embryos and selects a surviving population of early embryos whose growth in utero is retarded by their genotype, their environment or a combination of both. The metabolic syndrome follows if the offspring is over-nourished later in life. The embryonic selection hypothesis presented here could be tested by using single nucleotide polymorphism (SNP) microarrays to study adults who had a history of intrauterine growth retardation (IUGR) and subsequent metabolic syndrome. Their SNP array could be compared with their parents and unaffected unrelated or related controls. If there were no selection based on a "thrifty genotype", all parental sequences would be expected to appear in their surviving children, whether or not they had IUGR or developed metabolic syndrome. SNP sequences present in parents or controls but missing from adult offspring with metabolic syndrome who had IUGR, could be associated with or linked to genes that influence susceptibility to metabolic syndrome. This hypothesis proposes that missing genotypes would be lost if the embryos that inherited them died very early in pregnancy.

[Disturbances of carbohydrate metabolism and factors stimulating its development in ontogenesis].

The review contains comprehencive literature data about the effect of unfavourable factors on forming of islet's apparatus of pancreas and the development of disturbances of carbohydrate metabolism in ontogenesis. The analyses of current sources showed that the effect of unfavourable factors in embrional period and early childhood defines the development of some disturbances of carbohydrate metabolism in adult life. In the process of ontogenesis the combination of the reduction of islet's apparatus functional activity and risk factors (age, abundant weight, stress, hypodinamia) can lead to the development of metabolic syndrome, diabetes mellitus and obesity.

Prenatal origin of obesity and their complications: Gestational diabetes, maternal overweight and the paradoxical effects of fetal growth restriction and macrosomia.

Pregestational (PGDM) and gestational (GDM) diabetes may be associated with a variety of fetal effects including increased rate of spontaneous abortions, intrauterine fetal death, congenital anomalies, neurodevelopmental problems and increased risk of perinatal complications. Additional problems of concern are fetal growth disturbances causing increased or decreased birth weight. Optimal control of maternal blood glucose is known to reduce these changes. Among the long lasting effects of these phenomena are a high rate of overweight and obesity at childhood and a high tendency to develop the "metabolic syndrome" characterized by hypertension, cardio-vascular complications and type 2 diabetes. Similarly, maternal overweight and obesity during pregnancy or excessive weight gain are also associated with increased obesity and complications in the offspring. Although there are different causes for fetal growth restriction (FGR) or for fetal excessive growth (macrosomis), paradoxically both are associated with the "metabolic syndrome" and its long term consequences. The exact mechanism(s) underlying these long term effects on growth are not fully elucidated, but they involve insulin resistance, fetal hyperleptinemia, hypothalamic changes and most probably epigenetic changes. Preventive measures to avoid the metabolic syndrome and its complications seem to be a tight dietary control and physical activity in the children born to obese or diabetic mothers or who had antenatal growth disturbances for other known or unknown reasons.

The metabolic syndrome: common origins of a multifactorial disorder.

The metabolic syndrome (MetS) represents a combination of cardiometabolic risk determinants including obesity (central adiposity), insulin resistance, glucose intolerance, dyslipidaemia, non-alcoholic fatty liver disease and hypertension. MetS is rapidly increasing in prevalence worldwide as a consequence of the continued obesity "epidemic", and as a result will have a considerable impact on the global incidence of cardiovascular disease and type 2 diabetes. Currently, there is debate concerning whether the risk of cardiovascular disease is greater in patients diagnosed with MetS than that of the sum of the individual risk factors. At present, no unifying origin that can explain the pathogenesis of MetS has been identified and therefore no unique pharmacological treatment is available. This review summarises and critically evaluates the current clinical and scientific evidence supporting the existence of MetS as a multifactorial endocrine disease, for which maternal nutrition may be a common pathogenic mechanism. In addition, we suggest that ectopic fat accumulation (such as visceral and hepatic fat accumulation) and the proinflammatory state are central to the development of the MetS.

[The transgenerational mechanisms in developmental programming of metabolic diseases]. / Mecanismos transgeneracionales en el desarrollo de enfermedades metabólicas.

Human epidemiological and experimental animal studies have shown that suboptimal environments in the womb and during early neonatal life alter growth and may program offspring susceptibility to lifelong health problems. One of the most interesting and significant feature of developmental programming is the evidence that adverse consequences of altered intrauterine environments can be passed from first generation to second generation offspring. To obtain the transgenerational phenotype, a negative environment is required during fetal or early neonatal life, the physiologic phenotype or disease can be transmitted through the germ line and the subsequent generations are not directly exposed to the environmental factor. The hypothesis has become well accepted by compelling animal studies that define the outcome of specific challenges such as: 1) nutrient restriction or overfeeding during pregnancy and lactation; 2) uterine blood flow restriction; 3) fetal exposure to inappropriately high levels of glucocorticoids, and 4) experimental maternal diabetes. Maternal protein restriction in the rat adversely affects glucose metabolism of male and female second generation offspring in a gender and developmental time window-specific manner. Other studies have proved transgenerational passage of effects resulting from treatment of pregnant rats with dexamethasone by either maternal or paternal lines. First generation female diabetic offspring of F0 rats treated with streptozotocin during pregnancy had F2 offspring with altered glucose and carbohydrate metabolism. The studies suggest that the mechanisms involved in developmental programming are likely epigenetic rather than due to DNA sequence mutations. Many individuals all over the world experience undernutrition, stress, hyperglycemia and other negative environmental factors during pregnancy and/or lactation. Insult during this critical period of development may induce malprogramming and adversely alter not only the F1 generation but also future generations. Preventing or treating these conditions will help to minimize the risk of transmission of metabolic diseases to future generations.

Intrauterine growth restriction in a rodent model and developmental programming of the metabolic syndrome: a critical appraisal of the experimental evidence.

Research on intrauterine growth restriction (IUGR) and subsequent development of obesity, type 2 diabetes and the metabolic syndrome is rapidly expanding, and potential implications for primary prevention are considerable. We have critically appraised one of the experimental animal models frequently used as mimic of human fetal growth restriction, which involves bilateral ligation of the uterine artery in rats (Lig). Our experimental study showed that Lig performed on day 17 of pregnancy neither leads to IUGR nor to neonatal catch-up growth, an important pathogenetic co-factor in humans. Meta-analysis of the literature revealed domination by studies in which Lig pups with IUGR were actively selected. Accordingly, publication bias is evident (p=0.007). Altered placental perfusion--the main cause of IUGR in humans in Western countries--neither led to IUGR nor to neonatal catch-up growth in Lig offspring, i.e., to none of the etiological factors of the human 'small baby syndrome'. Appropriate and reproducible rodent models of IUGR through decreased placental flow remain to be established to uncover the pathophysiological basis of the 'small baby syndrome'. This may lead to new strategies of primary prevention of diabetes, obesity, and the metabolic syndrome.

Programmed metabolic syndrome: prenatal undernutrition and postweaning overnutrition.

Maternal nutrient restriction results in intrauterine growth restriction (IUGR) newborns that develop obesity despite normal postweaning diet. The epidemic of metabolic syndrome is attributed to programmed "thrifty phenotype" and exposure to Western diets. We hypothesized that programmed IUGR newborns would demonstrate greater susceptibility to obesity and metabolic abnormalities in response to high-fat diet. From day 10 to term gestation and lactation, control pregnant rats received ad libitum (AdLib) food, whereas study rats were 50% food restricted (FR). Cross-fostering techniques resulted in three offspring groups: control (AdLib/AdLib), FR during pregnancy (FR/AdLib), and FR during lactation (AdLib/FR). At 3 weeks, offspring were weaned to laboratory chow or high-fat calorie diet (9% vs. 17% calorie as fat). Body composition, appetite hormones, and glucose and lipid profiles were determined in 9-mo-old male and female offspring. High-fat diet had no effect on body weight of AdLib/AdLib, but significantly increased weights of FR/AdLib and AdLib/FR offspring. High-fat diet significantly increased body fat, reduced lean body mass, and accentuated plasma leptin but not ghrelin levels in both sexes in all groups. In males, high-fat diet caused a significant increase in glucose levels in all three groups with increased insulin levels in AdLib/AdLib and AdLib/FR, but not in FR/AdLib. In females, high-fat diet had no effect on glucose but significantly increased basal insulin among all three groups. High-fat diet caused hypertriglyceridemia in all three groups although only food-restricted females exhibited hypercholesterolemia. Sex and offspring phenotype-associated effects of high-fat diet indicate differing pathophysiologic mechanisms that require specific therapeutic approaches.