L'infertilité affecte près d'un couple sur 6 en France. L’obésité et l'excès de réserves adipeuses, à l'origine de stress oxydant, sont associés à l'infertilité idiopathique. L’équilibre des concentrations entre les pro et antioxydants est assuré par des enzymes antioxydantes, dont la fonction est partiellement contrôlée par des polymorphismes génétiques. De plus, l'altération des gamètes par le stress oxydant pourrait aussi entraîner des conséquences sur le développement d'infertilité chez la descendance. L'objectif de cette étude était d’évaluer les relations entre l’alimentation, le stress oxydant et l’infertilité à travers une étude cas-témoins chez l’Homme et à l’aide d’un modèle animal. Chez l’Homme, le polymorphisme des enzymes impliquées dans le stress oxydant a été étudié chez 110 individus infertiles et 69 fertiles. Le risque d’infertilité est augmenté chez les hommes porteurs d’au moins un allèle Ala-SOD2 (rs4880) et chez les porteurs, hommes et femmes confondus, de deux allèles G-NOS3 (rs1799983). La prise en compte de ces polymorphismes pourrait permettre d’adapter l’alimentation et/ou la prise d’antioxydants selon le génotype du couple infertile idiopathique. Chez la lapine, une alimentation hyperlipidique administrée dès la période prépubertaire a un impact délétère sur la folliculogénèse avec une réduction du nombre de follicules tertiaires et une atrésie folliculaire augmentée par rapport aux témoins. La fonction de l’axe hypothalamo-hypophysaire est aussi perturbée. Chez les descendantes, on observe une atrésie folliculaire augmentée. Ces résultats indiquent qu'une alimentation déséquilibrée en lipides entraine des dysfonctions de l’axe hypothalamo-hypophyso-gonadique chez la mère et ses filles. / Infertility affects one in 6 couples. Obesity and excess fat, which induce oxidative stress, have been associated with idiopathic infertility. The balance between pro- and antioxidant enzymes is insured by antioxidant enzymes, which activity partly depends on genetic polymorphisms. Moreover, the alteration of gamete quality through oxidative stress may also affect offspring development and fertility. The aim of the project was to evaluate the association between nutrition, oxidative stress and infertility through a case-control study in humans and using a rabbit model. In humans, the genetic polymorphism of enzymes involved in oxidative stress was studied in 110 infertile and 69 fertile individuals. The presence of at least one Ala-SOD2 allele in men and the presence of two G-NOS3 alleles in both men and women increased the risk of infertility. The analysis of these gene polymorphisms in infertile couples may help adapting nutrition and/or antioxidant intake depending on the couple's genotype. Feeding a hyperlipidic diet to female rabbits from the prepubertal period has a detrimental impact on folliculogenesis, with a reduction in tertiary follicles and an increase in atretic follicles numbers in the ovary, together with an alteration of the hypothalamo-pituitary axis. An increased number of atretic follicles was also observed in adult female offspring. Those results highlight the importance of a high fat diet on hypothalamo-pituitary-gonadal function in females and their offspring.

An essential event during early pregnancy is the invasion of trophoblasts into the maternal decidua, which is necessary for proper implantation and establishment of maternal-fetal interface and ultimately allows for proper nutrient exchange and immunological tolerance of the growing fetus. For this invasion to occur, cells originating from the trophectoderm undergo an epithelial to mesenchymal transition to become invasive extravillous trophoblasts and begin invading the uterine decidual tissue. Through the secretion of matrix metalloproteinases and through interactions with many cytokines and cell-adhesion molecules, this well-orchestrated process of trophoblast invasion results in extensive remodeling of the maternal spiral vasculature by the extravillous trophoblasts. Ultimately, the spiral arteries are transformed from high resistance, low flow vessels to low resistance, high flow vessels to allow for adequate perfusion of the placenta and developing fetus. Preeclampsia is a leading cause of maternal morbidity worldwide and is associated with the onset of hypertension and proteinuria, typically after 20 weeks of gestation. While the hypertension typically resolves following delivery of the fetus and placenta, both the mother and growing child are faced with long-term adverse health effects such as the development of cardiovascular disease and metabolic disorders. Preeclampsia is characterized by widespread maternal inflammation and endothelial dysfunction triggered by the secretion of soluble factors from the placenta into the maternal circulation. It is thought that the onset of these adverse systemic conditions is initiated by poor placental perfusion and pathologically hypoxic conditions in the placenta. In many cases of preeclampsia, there is evidence of shallow trophoblast invasion which results in incomplete spiral artery transformation, ultimately leading to poor placental perfusion. However, the exact mechanisms underlying the inadequate extravillous trophoblast invasion and remodeling are incompletely understood. LIN28 is an RNA binding protein that is highly expressed in embryonic stem cells, fetal tissues and many cancers, and was discovered as a regulator of the maturation of the Let-7 family of miRNAs. However, as an RNA binding protein, LIN28 has been shown to interact with thousands of mRNA transcripts, leading to both increased and decreased protein expression, and control of many cellular processes such as differentiation, proliferation, migration, invasion, and cellular metabolism. In vertebrates, LIN28 exists as two highly homologous paralogs, LIN28A and LIN28B, however LIN28B is slightly larger and contains a nuclear localization signal not found in LIN28A. While they both function to inhibit Let-7 maturation, there is evidence to suggest they also have independent functions. Given the primary role of LIN28A and LIN28B in modulating cell metabolism, differentiation and invasion, we hypothesized that LIN28A and/or LIN28B regulates trophoblast differentiation and invasion, and that its dysregulation may contribute to preeclampsia. We found that LIN28B mRNA expression is ~1300-fold higher than LIN28A in human term placenta and is the predominant paralog expressed in human primary cytotrophoblasts, syncytiotrophoblasts, and decidual cells. We also found that LIN28B mRNA and protein levels are significantly reduced in human placentas from preeclamptic pregnancies compared to placentas from normal pregnancies, while LIN28A expression is unchanged. Upon investigation of human first trimester placenta sections, we found that LIN28B is more highly expressed in the invasive extravillous trophoblasts and syncytial sprouts compared to villous trophoblasts. To support this with in vitro evidence, we found that overexpression of LIN28B in human HTR8/SVneo cells resulted in increased proliferation, migration and invasion, while knockdown of LIN28B in JEG3 cells resulted in decreased proliferation. Furthermore, knockdown of LIN28B in JEG3 cells led to decreased expression of SYN-1, ELABELA, and the chromosome 19 miRNA cluster, with accompanying increases in the pro-inflammatory cytokine TNFα and ITGβ4, an integrin enriched on non-invasive trophoblasts. Moreover, culture of JEG3 and BEWO cells in hypoxia resulted in significantly decreased levels of LIN28B mRNA and protein expression, as well as syncytin-1 and ELABELA mRNA levels, while TNFα was increased. These results provide the first evidence that LIN28B is the predominant paralog expressed in human placenta and decreased LIN28B may play a crucial role in PE pathogenesis by reducing trophoblast invasion, syncytialization and by promoting inflammation.

Maternal overweight and obesity (i.e., excess adiposity) are risk factors for adverse pregnancy outcomes and long-term maternal and offspring health impairments that are rooted in placental dysfunction. Factors contributing to placental dysfunction in pregnancies affected by excess adiposity are not fully understood. We hypothesized that impaired remodelling of uterine spiral arteries and enhanced inflammatory signalling at the placental interface related to compositional and functional differences in uterine macrophage and natural killer (NK) cells in early pregnancy would contribute to placental hypoxia and impaired vascular maturation. We tested this hypothesis using a mouse model of periconceptional high-fat, high-sucrose (HFHS) diet-induced excess adiposity. In Chapter 3, we found that HFHS placental tissues were hypoxic and exhibited histological features of malperfusion and inflammation in late gestation. This was accompanied by elevated circulating fetal endocrine and inflammatory mediators. In Chapter 4, we show that diet-induced excess adiposity does not impair spiral artery transformation at mid-gestation but does promote angiogenic and inflammatory shifts related to decidual macrophage and NK cell populations that might contribute to later placental malperfusion. In Chapter 5, we examined the cell-type-specific impacts of excess adiposity using single-cell gene expression analysis. We found that immune and stromal cell populations from HFHS uterine tissues exhibit pro-fibrotic, pro-thrombotic, and potentially immuno-suppressive gene expression changes immediately following embryo implantation. This coincided with immunophenotypic changes in blood monocytes and neutrophils that might be indicative of low-level systemic vascular injury. Overall, our findings indicate that diet-induced excess adiposity can compromise placental perfusion in the absence of impaired spiral artery remodelling. Altered recruitment and activity of uterine immune cells driven by conditions surrounding excess adiposity likely participate in disrupted uteroplacental perfusion, inflammation, and suboptimal placental function. These data provide new insights into the cellular and molecular mechanisms underlying placental dysfunction in pregnancies affected by overweight and obesity. / Thesis / Doctor of Philosophy (PhD)

: L’économie de la filière équine repose aujourd’hui sur la production de chevaux athlètes performants sur le long terme. Le métabolisme de la jument gestante peut programmer le développement du poulain, sa santé à long terme et donc ses performances sportives à l’âge adulte. De nombreuses pratiques d’élevage peuvent modifier le métabolisme maternel, telles que la nutrition durant la gestation, la surnutrition durant la vie de la jument (surpoids et obésité) et le nombre de poulains produits par la jument (parité). L’objectif de ce travail était d’étudier les effets du métabolisme maternel durant la gestation sur la fonction et la structure placentaire à terme, la croissance osseuse, le métabolisme énergétique, l’inflammation systémique et le statut ostéoarticulaire des poulains en croissance. Un premier modèle de perturbation nutritionnelle en fin de gestation a été développé en comparant des juments ayant ingéré uniquement des fourrages au cours de la gestation ou bien des fourrages et des concentrés à partir de la mi-gestation. Ce modèle a permis de montrer que la supplémentation en concentrés altérait le métabolisme glucidique maternel, la fonction placentaire ainsi que le statut ostéoarticulaire et la réponse métabolique à un challenge de surnutrition chez le poulain. D’autre part, une perte d’état trop importante associée à une qualité/quantité de foin insuffisante entrainait un retard de maturité des fonctions de métabolisme énergétique et de reproduction mâle chez les poulains. Un deuxième modèle a ensuite été développé pour étudier l’effet de la primiparité. Cette étude a confirmé que la croissance fœtale des poulains issus des juments primipares était réduite et que ces poulains demeuraient plus petits avec un métabolisme glucidique et une maturation testiculaire retardés par rapport aux poulains issus de juments multipares. Le troisième modèle développé s’est intéressé à l’effet de l’obésité maternelle dès la conception. En effet, la prévalence de surpoids et d’obésité est de plus en plus importante au sein de la filière équine. Ce dernier modèle a permis de montrer que l’obésité maternelle associée à une résistance à l’insuline et une inflammation systémique augmentées entrainait une augmentation de la résistance à l’insuline, de l’inflammation systémique et du développement de lésions d’ostéochondrose chez les poulains. L'ensemble de ces résultats met en avant la relation entre la résistance à l’insuline maternelle, l’inflammation maternelle et le développement de lésions d’ostéochondrose chez les poulains durant la croissance, mais également entre sous-nutrition utérine et retard de maturité. Ces observations vont permettre de développer de nouvelles recommandations nutritionnelles pour les poulinières. / The economy of the equine industry is based on the production of high performance athlete horses. The metabolism of the pregnant mare can program the development of the foal, its long-term health and therefore its athletic performance at adulthood. Many breeding practices can modify maternal metabolism, such as nutrition during pregnancy, overnutrition during the mare's productive life (overweight and obesity) and the number of foals produced by the mare (parity). The aim of this work was to study the effects of maternal metabolism during pregnancy on placental function and structure, as well as bone growth, energy metabolism, systemic inflammation and osteoarticular status in growing foals. In a first approach, mares fed with forage only during gestation were compared to mares fed forage and concentrates from mid-gestation. Supplementation with concentrates altered maternal carbohydrate metabolism and placental function. In weaned foals, the osteoarticular status and the metabolic response to an overnutrition were also affected by the use of concentrates in maternal nutrition. Conversely, mares fed forage only lost body condition, which led to a delay in the post-natal maturation in terms of energy metabolism and testicular function in foals. In a second approach, the effect of primiparity was studied. Foals born to primiparous mares were growth restricted at birth and had a long-term maturational delay in bone growth, carbohydrate metabolism and testicular function. Finally, given the current high prevalence of overweight and obesity in the equine species, the effects of maternal obesity were studied. Maternal obesity associated with increased maternal insulin resistance and systemic inflammation resulted in increased insulin resistance, systemic inflammation, and increased incidence of osteochondrosis in foals. Altogether, these results highlight the relationship between maternal insulin resistance, maternal inflammation and the development of osteochondrosis lesions in foals during growth, but also between in utero undernutrition and maturation delay. These observations will contribute to adjust nutritional recommendations to broodmares.

Epidemiological studies have shown that human adults have a higher chance of developing various metabolic disorders, such as type II diabetes and hypertension, due to maternal under nutrition. The concept that conditions encountered in early development can have far reaching implications for an individual’s adult life is known as the Developmental Origins of Health and Disease (DOHaD) hypothesis. In vitro studies have shown that if the amino acid leucine is not available at a high enough concentration the embryo will not exhibit normal trophectoderm protrusive activity which precedes implantation. The amino acid transport system System B0,+ is the main gateway into these cells for leucine but its expression at the transcription level has never been shown in preimplantation blastocysts. We investigated System B0,+ expression in preimplantation blastocysts from dams fed a control versus a low-protein isocaloric diet (18% and 9% casein, respectively). Using RT-PCR to detect the System B0,+ transcript, ATB0,+, we found that indeed there is expression of this amino acid transporter in the pre-implantation rat blastocyst. Due to the gender-specific nature of many DOHaD phenomena, the blastocysts were sexed using gender specific primers and a nested PCR approach. Quantitative real time PCR (qRT-PCR) results show no significant difference in ATB0,+ expression in blastocysts taken from dams fed either diet (9% n= 56, 18% n = 52; 7 dams from each diet group). Furthermore, separating the data by gender reveals no significant difference in expression. However, while not significant, there does appear to be a trend in the protein restricted blastocysts towards increased transcription of ATB0,+, suggesting System B0,+ may be responding at the transcription level to the diet. This could be part of the predictive adaptive response leading to a reprogrammed phenotype as described by the DOHaD hypothesis. Further work is needed to elucidate System B0,+’s role in developmental programming.

Epidemiological studies have shown that human adults have a higher chance of developing various metabolic disorders, such as type II diabetes and hypertension, due to maternal under nutrition. The concept that conditions encountered in early development can have far reaching implications for an individual’s adult life is known as the Developmental Origins of Health and Disease (DOHaD) hypothesis. In vitro studies have shown that if the amino acid leucine is not available at a high enough concentration the embryo will not exhibit normal trophectoderm protrusive activity which precedes implantation. The amino acid transport system System B0,+ is the main gateway into these cells for leucine but its expression at the transcription level has never been shown in preimplantation blastocysts. We investigated System B0,+ expression in preimplantation blastocysts from dams fed a control versus a low-protein isocaloric diet (18% and 9% casein, respectively). Using RT-PCR to detect the System B0,+ transcript, ATB0,+, we found that indeed there is expression of this amino acid transporter in the pre-implantation rat blastocyst. Due to the gender-specific nature of many DOHaD phenomena, the blastocysts were sexed using gender specific primers and a nested PCR approach. Quantitative real time PCR (qRT-PCR) results show no significant difference in ATB0,+ expression in blastocysts taken from dams fed either diet (9% n= 56, 18% n = 52; 7 dams from each diet group). Furthermore, separating the data by gender reveals no significant difference in expression. However, while not significant, there does appear to be a trend in the protein restricted blastocysts towards increased transcription of ATB0,+, suggesting System B0,+ may be responding at the transcription level to the diet. This could be part of the predictive adaptive response leading to a reprogrammed phenotype as described by the DOHaD hypothesis. Further work is needed to elucidate System B0,+’s role in developmental programming.

O sobrepeso/obesidade é uma condição multifatorial e poligênica que pode resultar em desequilíbrio calórico. Uma vez instalada, a obesidade tende a se manter, de modo que a prevenção figura como principal recurso e, a compreensão das causas, essencial. Este estudo teve o objetivo de avaliar a associação da expressão de genes relacionados à obesidade, inflamação e perfil lipídico em gestantes com sobrepeso/obesidade e eutróficas, na adiposidade dos recém-nascidos. Trata-se de um estudo prospectivo, inserido em estudo coorte de base populacional, realizado em 33 Unidades Básicas de Saúde e em hospital municipal de Araraquara (SP). Foram acompanhadas desde o início do pré-natal até o pós-parto, 78 gestantes, das quais 46 delas eram obesas ou com sobrepeso e 32, eutróficas. Trimestralmente, realizava-se aplicação de questionário digital sociodemográfico, de estilo de vida e morbidade, exames de ultrassonografia e exames de sangue para determinação de: glicemia de jejum, insulina, colesterol total, LDL, HDL, VLDL, triglicérides e PCR-us, hemoglobina glicada e hemograma completo). A análise da expressão gênica materna foi realizada apenas no terceiro trimestre, utilizando o método de extração por fenolclorofórmio para obter RNA a partir do sangue total, e a expressão gênica relativa foi analisada em triplicata por RT-qPCR no equipamento 7500 Fast Real PCR System (Applied Biosystems®, USA). A adiposidade do neonato foi estimada por pletismografia por deslocamento de ar (PEA POD®), na alta hospitalar. O presente estudo é inédito e mostrou que tanto o fator genético (expressão gênica dos genes LEPR, STAT3, PPARG, TLR4, IL6, NFkB e TNF) como fatores nutricionais e metabólicos maternos (IMC pré-gestacional, ganho de peso, HOMA-IR e diabetes mellitus gestacional) estão relacionados com a adiposidade do concepto logo após ao nascimento. O desenvolvimento fetal é um processo biológico complexo, regulado tanto por fatores maternos quanto fetais, incluindo influências genéticas e ambientais. Os mecanismos genéticos influenciam a regulação anti e pró-inflamatória que têm impacto na saúde materna. Expressões de sete dos dez genes investigados mostraram-se estatisticamente associados com a adiposidade do recém-nascido, independente de alguns genes serem mais ou menos expressos em gestantes obesas/sobrepeso. Portanto, o entendimento das diferentes vias do processo inflamatório, imunológico e sinalização da resistência à insulina são intimamente relacionados e dependentes. A elucidação dos fatores envolvidos no início da vida, observados neste estudo, e que podem ser prevenidos no pré-natal, devem ser cruciais para as políticas de saúde pública, na prevenção da obesidade infantil. / Overweight/obesity is a multicausal and polygenic condition that can result in energy imbalance. Once obesity tends to persist, prevention is the more effective strategy and understanding its causes is essential. This study aimed to evaluate the association of the gene expression related to obesity, inflammation and lipid profile in overweight/obese and eutrophic pregnant women and in newborn adiposity. It is a prospective study, inserted in a cohort study with population-based data, which was carried out at 33 Health Units and at a municipal maternity in Araraquara, Sao Paulo, Brazil. Seventy-eight pregnant women were followed since conception until postpartum, of whom 46 were obese or overweight and 32 were eutrophic. Every trimester, a sociodemographic, lifestyle and morbidity questionnaire was applied, ultrasonography and blood tests (fasting glucose, insulin, total cholesterol, LDL, HDL, VLDL, triglycerides and hs-CRP, glycated hemoglobin and complete blood count). The analysis of maternal gene expression was performed only in the third trimester, using the phenolchloroform extraction method to obtain RNA from whole blood, and relative gene expression was analyzed in triplicate by RT-qPCR in the 7500 Fast Real PCR System (Applied Biosystems®, USA). Newborn adiposity was estimated by air displacement plethysmography (PEA POD®) at hospital discharge. As far as we know this is the first study that verified that both genetic factors (LEPR, STAT3, PPARG, TLR4, IL6, NFkB and TNF gene expressions) and maternal nutritional and metabolic factors (pre-gestational BMI, gestational weight gain, HOMA-IR and gestational diabetes) are related to newborn adiposity at birth. Genetic mechanisms that participate in pro and anti-inflammatory regulation impact on maternal health, that may consequently play a role in the complex biological process of fetal development, that depends not only from maternal and fetal factors, but also of genetic and environmental influences. Expression of seven from ten genes investigated were statistically associated with newborn adiposity, regardless that some genes were more and other less expressed in obese/overweight pregnant women. Understanding immune and inflammatory pathways and insulin resistance signaling is crucial because its close association to maternal and newborn obesity, as observed in this study. The elucidation of factors involved in early life, as shown, should guide prenatal care in public health policies to prevent childhood obesity.

Les adaptations du fœtus aux stimuli intra-utérins ont des conséquences immédiates puis à long terme sur sa santé après la naissance. Chez l’équin, ce concept connu sous le nom de DOHaD (Developmental Origins of Health and Disease) a été validé à l’aide de croisements inter-races : la taille de la jument, qui conditionne l’environnement maternel pendant la gestation puis la lactation, a un impact crucial sur la croissance postnatale du poulain, mais aussi sur la sensibilité à l’insuline du nouveau-né. L’ostéochondrose, pathologie du cheval en croissance, est responsable de pertes financières majeures pour la filière équine. Elle a été reliée à des anomalies de l’homéostasie glucidique et son origine anténatale est fortement suspectée. Dans cette thèse, nous avons mesuré l’impact de perturbations expérimentales au cours du développement fœtal sur la croissance, l’homéostasie glucidique et la prédisposition à l’ostéochondrose du poulain jusqu’à l’âge de 1 an ½. Un premier modèle de croissance fœtale augmentée versus restreinte a été obtenu par transferts d’embryons inter-races (« poneys dans traits » versus « selles dans poneys », respectivement). L’environnement maternel « enrichi » de la jument de trait versus restreint de la ponette s’est révélé déterminant dans la régulation de la croissance des différents segments osseux, de l’axe thyréotrope, de la fonction des cellules β pancréatiques, de la sensibilité à l’insuline de l’organisme et de la santé ostéoarticulaire du poulain dès la naissance et jusqu’à 1 an ½. Tout en validant le concept de DOHaD chez l’équin, ce modèle souligne le soin qui doit être apporté à la sélection des juments receveuses dans la pratique du transfert d’embryons. En démontrant l’ampleur des effets post-nataux programmés in utero et pendant la lactation, ce modèle alerte aussi l’éleveur sur la gestion des poulinières et ses impacts à long terme. En ce sens, le second modèle est en adéquation avec les préoccupations d’élevage puisqu’une perturbation de l’environnement nutritionnel du fœtus a été induite en apportant un concentré (orge) dans la ration hivernale de la jument gravide versus des fourrages uniquement. A ce jour, l’impact de cette modification anténatale sur l’homéostasie glucidique du poulain avant sevrage semble limité à la période néonatale, tandis que sa croissance n’est pas du tout affectée. En revanche, sa prédisposition à l’ostéochondrose à l'âge de 6 mois semble être accrue, ce qui ne permet pas de présager de la suite car le statut ostéoarticulaire du poulain âgé de 6 mois reste susceptible d’évoluer jusqu’à 1 an ½. Ces travaux devraient permettre d’ajuster les recommandations nutritionnelles chez les poulinières. / Fetal adaptations to intra-uterine stimuli have immediate and long term effects on the offspring’s health after birth. In equids, this concept known as the DOHaD (Developmental Origins of Health and Disease) was validated using cross-breeding: the mare’s size which affects the fetal environment throughout gestation and then lactation, has a critical impact on the foal’s post-natal growth, as well as on the neonate’s sensitivity to insulin. Osteochondrosis, a pathology of the growing horse, induces heavy financial losses in the equine industry. It has been associated to abnormalities in glucose homeostasis and its antenatal origin is highly suspected. The present research aimed to evaluate the impact of experimental disturbances during fetal development on growth, glucose homeostasis and predisposition to osteochondrosis in the foal until age 1½ year. Increased versus restricted fetal growth was obtained using between-breed embryo transfers (“ponies in draft horses” versus “saddlebreds in ponies”, respectively). The lush environment of the draft mare versus the restricted environment of the pony mare turned out to be critical in the regulation of bone growth, thyroid hormones secretion, β-cells function, insulin sensitivity and the osteoarticular status of the foal from birth to 1½ year of age. This validates the concept of the DOHaD in equids and shows that recipient mares should be carefully selected in embryo transfer practice. By demonstrating the scope of post-natal effects which were programmed in utero and throughout the lactating period, it also alerts the breeder about the importance of broodmare management and its long term impacts. Thus, the second model was developed to address breeders' practices. A disturbance of the nutritional environment of the fetus was induced by supplementing mares in late pregnancy with concentrated feed (barley). So far, only the neonatal foal's glucose homeostasis was affected, whereas all other studied parameters, including growth, were not affected. The foal’s predisposition to osteochondrosis, however, was increased at 6 months of age, which does not preclude that it will affect the animals afterwards since the osteoarticular status of the 6-month-old foal will evolve beyond weaning time. This research could help adjust nutritional recommendations to broodmares.

La nutrition postnatale précoce conditionne la santé du futur adulte du fait de son rôle déterminant dans l’implantation du microbiote intestinal et le développement de la physiologie de l’hôte. L’objectif de mon travail de thèse a été d’évaluer les conséquences de la réintroduction de matière grasse laitière associée ou non au probiotique Lactobacillus fermentum dans des préparations pour nourrissons, sur le microbiote, la physiologie intestinale et le métabolisme de l’adulte, en utilisant le miniporc Yucatan comme modèle de l’Homme. Nos travaux ont montré un renforcement des défenses non spécifiques intestinales chez le jeune et une amélioration des fonctions endocrine et immunitaire intestinales de l’adulte soumis à un régime hyper-énergétique, réduisant ainsi le risque de développer une inflammation et des désordres métaboliques. Ces effets ont été associés à une modification de la digestion des préparations chez le jeune et à une modulation de la composition et de l’activité métabolique du microbiote intestinal. Des effets spécifiques de la matière grasse laitière et de L. fermentum, et d’autres complémentaires, ont été observés, suggérant des mécanismes d’action différents. Les modifications induites par la composition des préparations pour nourrissons étaient site- et âge-spécifiques, le comportement du microbiote caecal se rapprochant du microbiote fécal. En conclusion, l’optimisation des préparations pour nourrissons pourrait passer par l’ajout de matière grasse laitière et du probiotique L. fermentum. / Early postnatal nutrition programs adult health owing to its crucial role in gut microbiota colonization and host physiology development. The objective of my thesis was to investigate the consequences of dairy lipid addition with or without probiotic Lactobacillus fermentum in infant formulas on adult gut microbiota, physiology and metabolism, using Yucatan minipig as a model for humans. We demonstrated increased non-specific intestinal defences in piglets and improved intestinal endocrine and immune functions in adults submitted to a high-energy diet, which may protect them from inflammation and metabolic disorders. These effects were associated in piglets to changes in digestion and gut microbiota composition and metabolism. We observed specific and complementary effects of dairy lipids and L. fermentum, suggesting different mechanisms of action. The infant formula composition had site- and age-specific effects, the caecal microbiota being closer to the faecal one. To conclude, the addition of dairy lipids and L. fermentum in infant formulas is an effective way to improve infant formulas.

Background: Substantial variation exists between ethnicities in both birth weight and the prevalence of obesity-related non-communicable diseases (OR-NCDs). South Asians, who display a reduced birth weight and increased risk of developing these OR-NCDS, have been the focus of much of the research into the developmental origins of health and disease (DOHaD) paradigm. However, little research utilising ultrasonically derived estimates of fetal growth has been conducted. The use of more direct measures of fetal growth may also enable the identification of relationships between patterns of fetal growth with patterns of postnatal growth, explicitly, whether periods of restricted or rapid growth lead to postnatal catch-up or down, respectively. The known differences in birth weight existing between South Asians and White British infants may also have implications for the assessment of neonatal health in these sub-groups when using a population derived birth weight chart, such as the UK-World Health Organisation (UK-WHO). Customised charts, which adjust for maternal variables including ethnicity, have been recommended for clinical practice, yet evidence for their efficacy is varied. Objectives: The aims of this thesis were to: 1) investigate whether fetal growth patterns differ between Pakistani and White British foetuses and determine whether maternal size and demographic variables mediate any such differences; 2) produce a birth weight chart adjusting for ethnicity and compare this to the UK-WHO and customised birth weight charts to determine which chart better identifies neonates at risk of the adverse delivery and neonatal outcomes associated with small-for-gestational-age (SGA) and large-for-gestational age (LGA); 3) identify whether there is evidence of weight growth tracking between fetal and infant periods and determine whether patterns of fetal growth predict patterns of postnatal growth. Methods: All data come from the Born in Bradford (BiB) birth cohort. Objective 1: Multilevel models and fractional polynomials were employed for the modelling of fetal weight, head circumference (HC) and abdominal circumference (AC) growth. Potential mediators of the effect of being of Pakistani origin were entered into the model and the effect on the ethnicity variable was assessed. Objective 2: Ethnic specific birth weight charts (BiB) were constructed using the LMS method. SGA and LGA were defined as a birth weight <10th and >90th relative to the BiB, the UK-WHO or the customised charts. Sensitivity, specificity, positive & negative predictive values and area-under-the curve were calculated for each of the three charts SGA and LGA cut-offs, to assess the predictive ability of each chart for a range of delivery and neonatal outcomes. Objective 3: Multilevel models were employed for the modelling of fetal and postnatal growth. Fitted values were produced at 20, 30, 40 prenatal weeks & 1, 3, 6, 9, 12, 24 postnatal months in both an internal reference and the sample population. Z scores were calculated and conditional Z scores were generated to account for regression to the mean. Growth tracking was defined as change in Z score ≤ 0.67 & ≥ -0.67. Restricted and rapid fetal growth were defined as a change in Z score in the fetal period of <-0.67 and >0.67, respectively. Catch-down and catch-up growth were defined in the same way, except in the postnatal period. ANOVAs were used to test for differences in size and growth by type of fetal growth. Furthermore, logistic regression and a sensitivity and specificity analysis were employed to examine the predictive ability of the type of fetal growth. Results: Objective 1: Pakistani fetuses were significantly smaller and lighter than White British fetuses, throughout gestation. In terms of weight, Pakistani fetuses were approximately 2.25% lighter at 20 weeks, 4.13% at 30 weeks and 5.94% at 40 weeks. The differences in size for AC and HC between the two groups were not as great, with the AC and HC of Pakistani fetuses being approximately 4.1% and 1.25% smaller, respectively, at 40 weeks. Despite these significant differences in size the pattern of growth for HC and weight was not significantly different between the two groups. There was a trend for Pakistani fetuses to display a greater deceleration of growth in the final trimester (figure 4-12). The biggest mediators of the effect of being of Pakistani origin were maternal height and weight. Objective 2: Classifying infants as SGA or LGA by the BiB, UK-WHO or customised charts had low predictive utility for the outcomes under investigation. Despite the fact that the BiB ethnic specific birth weight reference provided significantly better prediction for more outcomes than both the UK-WHO and customised charts in both White British and Pakistani infants, with the exception of shoulder dystocia, AUROC values for all three charts were all below 0.61. Objective 3: The prevalence of tracking within the same centile band from 20 weeks gestation to 2 years was 10.82%. Infants who experienced restricted fetal growth remained significantly lighter than those who had not, for the duration of infancy. In this group however, there was a pattern of greater growth than expected during infancy. This was opposite to the pattern observed in infants who had experienced rapid fetal growth, who exhibited less growth than expected during infancy. However, the ability of the type of fetal growth to predict the pattern of postnatal growth was minimal, with only rapid fetal growth being significantly associated with increased odds of catch-down growth in infancy. Conclusions: No ethnic difference in the pattern of growth was found in terms of the whole body (weight) or in HC. The trend for reduced growth of the AC in Pakistanis may be a result of a reduced growth of the visceral organs during the third trimester, which may lead to both an altered liver metabolism and impaired renal function in post-natal life. Although being small or large at birth may increase the risk of an adverse neonatal outcome, size alone is not sensitive or specific enough with current detection to be a useful clinical tool. The finding that neither restricted nor rapid fetal growth predicted postnatal catch-up growth may suggest that the timing of canalisation is outside of the fetal period. If infant catch-up and down growth are not associated with periods of restricted or rapid fetal growth, the definitions of these growth patterns may need revising.