Search

Background/Aims Maternal obesity is associated with fertility disorders, obstetric complications, and development of metabolic syndrome in offspring. The recommendation to overweight or obese women is to lose weight before pregnancy, but the impact of these prescriptions on the offspring health is insufficiently studied. Previous results on late-term mice fetuses have shown that maternal obesity leads to fetal growth restriction and to the modification of epigenetic machinery-related gene expression in fetal liver and placenta. Moreover, fetuses from the preconceptional weight loss maternal group normalize their growth, but some fetal genes stay differentially expressed. Method We analysed the metabolic phenotype of offspring born to control (CTRL), obese (OB) or weight loss after diet-induced obesity (WL) mothers. To highlight a possible conditioning effect, offspring were either fed a control (CD) or a high fat diet (HFD). Their metabolism and olfactory behavior were monitored for up to 6 months. Then, we analyzed the metabolome of three tissues involved in food intake and nutrient management (liver, olfactory bulb and hypothalamus) in male adult offspring. Results Multiple Factorial Analysis integration of offspring phenotypic data showed a major influence of the post-weaning diet and pointed a difference in HFD-fed males according to their maternal group (OB vs WL). This confirmed a sex-dependant metabolic conditioning by the maternal environment. The olfactory sensitivity, measured by electro-olfactogram, was reduced in WL male offspring, whatever the postnatal diet. The metabolomics study annotated 278, 258 and 200 metabolites in the liver, olfactory bulb and hypothalamus respectively. Again, the post-weaning diet had a major effect in the three tissues but interestingly, the maternal group also influenced the hepatic metabolome of adult offspring. Conclusions These data, integrating metabolism, olfactory behavior and metabolome, provide new and original information on the effects of preconceptional maternal metabolic status in the offspring health conditioning upon diet challenges.

Since the 90’s, obesity became pandemic. Nutritional environment has an important impact during development, leading to the later onset of non-communicable diseases. Maternal environment may affect offspring development through epigenetic mechanisms, regulating gene expression and microbiota, which is a major actor of metabolism. In order to reduce fertility troubles and obstetrical complications caused by obesity, it is now recommended for women who plan a pregnancy to lose weight before conception. However, the long-term effects of this preconception weight loss are not well described in the literature. We aim to identify whether maternal weight loss prior to conception can prevent the development of metabolic syndrome at the adult age. We previously highlighted in a mouse model the high sensitivity of the epigenetic machinery gene expression, and particularly histone acetylation pathway, to maternal obesity. Preconceptional weight loss appears beneficial for fetal growth, but some effects of previous obesity were retained in offspring transcriptome. During my PhD, I will precise:- the offspring phenotype using metabolomics of adult liver, olfactory bulb and hypothalamus (LC-HRMS),- the epigenomic analysis by an histone acetylation study in fetal liver (ChIP-seq,- the microbiota component with an analysis of maternal and offspring gut microbiota (16S rRNA-seq).The correlation of metabolic parameters, epigenomic state and gut microbiota will give us information about the mechanisms of maternal diet’s effects and their participation to adult health conditioning.

International audience; The grey mouse lemur ( Microcebus murinus) is an arboreal primate originating from Madagascar, where it faces environmental conditions with strong contrasts between summer and winter seasons, in particular for food and water availability. Seasonal varia-tions result in adaptive response inducing energetic metabolism and behavioral changes that are fully reproducible in captivity. Characterized by its great phenotypic fiexibility, this primate appears as an interest­ ing mode!to evaluate the raies of epigenetic me-chanisms in modulating the adaptive responses to environmental modifications. In order to determine the impact of nutritional stress on epigenetic mechanisms, we submitted adult male mouse lemurs to either a control diet (CTL; ad libitum; N=6) or to an energetic challenge (CR; 40% calorie restriction; N=6) for 5 weeks, at the end of the winter season. Animals were then monitored for body mass, food intake, core temperature, metabolic performances and glucose tolerance. Liver biopsies were also performec\ before and after the experimental period, for both control and challenged animals. While calorie restriction had no major effect on body weight, core temperature· or metabolic performance, we observed an improvement of glucose tolerance in CR animals. We further investigated whether this result could be reflected at the epigenetic level. In a first approach, we focusecl on liver global DNA methylation. RNA and DNA were coextracted and DNA methylation measured by LUlMA (luminometric methylation as-say). Global liver DNA methylation was 65% ± 3% in Microcebus murinus. This level was not modified by the season and not affected by calorie restriction. Additional stuclies are needed to understand the molecular mechanisms that underlie the physiological changes displayed in response to environmental changes in the mouse lemur. A specific emphasis could be made on DNA methylation of gene promoters involved in lipid and glucose metabolism. This preliminary project challenges the role of epigenetic plasticity in adaptive processes and highlights the role that might play the mouse lemur as an animal model to decipher the mechanisms underlying phenotypic flexibility.

National audience; Preconceptional or inter-pregnancy weight loss is often recommenclecl to obese future mothers as a preventive action to protect offspring clevelopment from deleterious effects of endocrine impairments du-ring pregnancy and lactation. However, the benefits of such a maternal weight control on offspring long-term health remain poorly investigated. Olfactory sensitivity and associated behaviours are influenced by the metabolic status (1-2). Ils alteration has been described in varions diet-induced inoclels of metabolic imbalances, such as diet-induced obesity (3) and calorie restriction (4) or in bariatric surgery studies (5). As maternal environment could impact progeny health at long-term according to the known DOHaD concept, we investigated the effect of pre-gestational maternal weight control on off­ spring olfactory sensitivity in a mouse model recently developed (6): Mice were either fed with a control diet (CD) , a high-fat diet (HFD) or a HFD switched to a CD one 2 months before conception to induce a weight loss (WL) . After birth, pups were divided in two groups at weaning and were fed with CD or HFD for 5 months. Metabolic measures revealed clear-cut endocrine differences in offspring reflecting their diet status. Animals were tested for their olfactory-based behaviour in a buriecl cookie test and a 2-hole board olfactory preference test. The post-weaning diet predominantly influenced pu p's olfactory sensitivity and preferences as compared to the maternal one. Interestingly, maternal weight loss didn't prevent the development of olfactory impairments observed as early as after 3 weeks uncler a HFD, i.e. much before the appearance of endocrine alterations in the offspring. Surprisingly, we observed that peripheral olfactory mucosa neuronal response was clearly diminished in the electro-olfactograms recorded after 5 months of diet in offspring barn from WL mothers regardless the postweaning diet, compared to those born from CD and HFD mothers. We conclude that post-weaning cliet recommendations are essential to optimize the preventive effect of a pre-gestational or gestational weight loss on the development of olfactory impairments that could participate to food intake deregulation. If the maternal preconceptional weight loss only partially counteracts post-weaning diet consequences, its intergenerational eff'ect on peripheral olfactory sensi-tivity should be further investigated at molecular level.

International audience; Research question Non-genetic heritability of susceptibility to chronic diseases is often different between male and female. The environmental factors to which an individual is exposed can leave an epigenetic footprint that dictates the coordinate expression of genes. A crucial period is the early development, when the epigenome is reprogrammed and therefore particularly sensitive to the environment. The sexual dimorphism results from the chromosomal sex (XX/XY) before gonad differentiation and a later-on complex mix of hormones and X/Y-linked genes regulating autosomal genes. The early exposure interacts with this subtle superposition, leading to specific reactions, adaptation and outcomes for men and women. Methods With several mouse model of maternal high-fat diet exposure, we demonstrate a striking sexual dimorphism of programming trajectories in different tissues (particularly placenta and liver) in response to the same environmental challenge. Results and Conclusion Our findings provide proof-of-concept that the epigenetic marks and modifiers may be part of the sex-specific causal variables. Their study represents a novel approach to identify sex-specific mechanisms in the origins of health and disease. The discovery of such factors should help physicians and patients anticipate disease susceptibility and may help the development of different preventative and treatment strategies precisely adapted to males and females.

International audience

International audience; Research question: The non-genetic heritability of susceptibility to chronic diseases is often different between males and females. The environment factors can leave epigenetic footprints on the DNA that dictate a coordinated expression of genes. A crucial period is the early development, when the epigenome is being reprogrammed and therefore particularly sensitive to the environment. Sexual dimorphism stems from the chromosomal sex (XX/XY) before gonad differentiation and from a later-on complex mix of hormones and X/Y-linked genes regulating autosomal genes. Early exposure interacts with these hormonal and genetic factors, leading to specific reactions, adaptations and outcomes for men and women. Methods: With several mouse models of maternal high-fat diet exposure, we demonstrate a striking sexual dimorphism of programming trajectories in different tissues, particularly placenta and liver, in response to the same environmental challenge. Results and Conclusion: Our findings provide proof-of-concept that epigenetic marks and modifiers may be part of the variables that causes sex-specific. This represents a novel approach to identify sex-specific mechanisms in the origins of health and disease. The discovery of such factors should help physicians and patients anticipate disease susceptibility and may help the development of prevention and treatment strategies precisely adapted to males and females.

International audience

National audience; An increasing number of childbearing age women are overweight or obese. Current recommendations include a preconceptional weight loss (WL) of 5 to 10% to reach a normal pre-pregnancy body mass index. Although there is evidence that preconceptional WL reduces pregnancy complications but can induce growth retardation or preterm delivery , the long-term consequences on offspring health remain unknown. ln the light of the Developmental Origins of Health and Disease (DOHaD) hypothesis, maternal pre-pregnancy weight trajectories could have beneficial, neutral or detrimental long-term effects on offspring• Our aim was to investigate the outcomes of preconception WL in obese C57BL/6J female mice on offspring susceptibility to an obesogenic diet in later life. Female mice of the WL group were led a High-Fat Diet (HFD) for two months and a control diet (CD) for the following two months. Two control groups consisted in: Lean and Obese Control (LC and OC), receiving either the CD or HFD diet for four months and during gestation/lactation. At weaning, offspring were led either a HFD or a CD. Weight, calorie intake, glucose metabolism and body composition were followed until sacrifice at 6 months. No significant differences were observed preweaning between LC and WL offspring for weight and glycaemia. As for OC offspring, they had a higher body weight and lasting hyperglycemia. Sexual dimorphism was observed alter weaning for all parameters studied and as adults, all HFD-fed offspring had an increased body weight, adiposity and lasting hyperglycemia, independently of maternal group. ln our model, the offspring phenotype relies mainly on the postweaning diet. Despite abundant literature on in utero exposure to a one paper reported the absence of association between offspring parameters and preconception HFD. More investigations are needed to complete this phenotyping and at epigenetic levels to draw conclusions about maternal preconception trajectory effects on offspring health.

National audience; More and more women of childbearing age are overweight or obese. To reduce infertility and Obstetric complications, weight loss is recommended. However, whether this weight loss has positive or deleterious consequences on fetal growth and the long-term health of the children remains to be clarified. Our aim was to develop a mice model of preconceptional maternal weight loss (WL) for further studies within the framework of the DOHaD field, with relevance to human. C57BL/6J female mice received a high-fat diet (HFD) for two months, then a control diet (CD) for Two months. Body weight and food intake were recorded twice a week. At 2 and 4 months, lasting glycemia, insulin and cholesterol were measured and glucose metabolism determined with oral glucose tolerance test (OGTT). Mice were mated with males under a CD and their weight gain was followed during gestation. Control mothers received a CD (lean control) or HFD (obese control) during preconceptionallgestation/lactation period. Alter offspring weaning, maternal adipose tissues, liver, kidneys and heart were weighed to evaluate maternal body composition and adiposity. Alter 2 months on a HFD, females showed a significant weight gain compared to CD-led mice, were hyperglycemic, glucose intolerant and hypercholesterolemic. Alter two months on a CD, normalization of weight, carbohydrate and lipid metabolism was observed. At the end of lactation, WL females body composition was not distinguishable from lean control. A switch from HFD to a CD induce a massive WL with normalisation of metabolic state and body composition in obese females. This model is therefore suitable to investigate effects of maternal ponderal trajectories or massive preconceptional loss such as that induced by bariactric surgery in human obese patients on offspring development and their long-term health and the underlying molecular mechanisms.

National audience; Whether the currently recommended preconceptional weight loss (WL) for obese women is beneficial/detrimental for fetoplacental development remains poorly explored and even less on the long term. Obesity, even if corrected before conception, and the WL processes could be "memorized" via epigenetic mechanisms perturbing expression of key developmental genes leading to altered fetal programming. Our aim was to investigate the effects of maternal WL alter diet-induced obesity on feto­placental development and on gene expression in male and female mice offspring. During the preconception period, female C57BI/6J mice were led a high-fat diet (HFD) for two months, leading to obesity and then a control die! (CD) for two months, leading to a complete WL. ln parallel, obese control group (OC) was led a HFD and lean control group (LC) a CD throughout the preconceptional period and gestation. At embryonic day 18 (E18.5), OC fetuses presented intrauterine growth retardation (IUGR), while WL fetuses, despite maternal weight normalization before conception, showed a significantly decreased weight at term which was intermediate between OC and LC fetuses. Placental weight was not affected by diet. Gene expression of 60 epigenetic machinery and 30 key developmental genes was analysed in the placental labyrinth and fetal liver using RTq-PCR Taqman custom array card. Expression of several epigenetic machinery genes was altered in OC fetuses. ln WL fetuses the level of expression of some genes was restored to the level of LC fetuses while ether genes showed similar profiles as in OC fetuses. Thus correction of maternal obesity by nutritional intervention in the preconceptional period only partially protects the offspring from IUGR. We show that modulation of the histone acetylation-deacetylation switch could play a role in fetal programming. Further studies at the genome-wide level will elucidate the epigenetic targets and mechanisms of placental/fetal programming triggered by maternal ponderal trajectories.

National audience