Dissertations / Theses on the topic 'Fetal origins of adult disease'

Adult exposure to high fat diet (HFD) has been linked to increased risk of musculoskeletal, cardiovascular, and metabolic diseases; however, the contribution of gestational HFD to elevated oxidative stress (OS), perinatal cardiovascular, skeletal, and metabolic dysfunction as well as long-term effects on adult offspring are incompletely understood. Pathophysiologic mechanisms linking gestational HFD, OS, and insulin resistance to perinatal development and adult-onset chronic diseases are explored in the present study, and maternal antioxidant (quercetin) is offered as a potential preventive dietary supplement to reduce fetal and maternal sequelae of HFD. Female C57BL/6 mice were fed â cafeteria-styleâ HFD (including 32.1% saturated fat to mimic a typical fast food menu) with or without quercetin for one month prior to conception, and throughout gestation. HFD dams developed gestational diabetes with significantly increased placental OS and vasculopathy. Neonates were smaller at birth than age-matched controls, and surviving offspring developed type 2 diabetes, hypertension and osteoporosis during adulthood, despite having been fed healthy diet throughout their postnatal life. Additional measures of bone using three-dimensionally reconstructed computed tomographic image analysis (microCT) revealed microarchitectural changes of bone at birth, and at 6 and 12 months postnatally. Fetuses from HFD dams displayed diminished bone mineral density (BMD) and disrupted endochondral and intramembranous ossification with significantly shortened distal limb lengths, as compared to offspring of standard rodent chow dams. Skeletal malformation persisted into adulthood despite the fact that both control and HFD offspring were fed conventional rodent chow throughout postnatal life. The offspring gestationally exposed to HFD showed significant decreased femoral BMD at 6 months of age and dysregulation of distal femoral trabecular architecture at 12 months of age, indicating development of osteoporosis. We were able to reduce incidence of placental vasculopathy, fetal maldevelopment and adult-onset type 2 diabetes, hypertension and osteoporosis with concurrent maternal quercetin supplementation during pregnancy. Collectively, these data suggested that maternal HFD increases placental OS and vascular damage during pregnancy, which are associated with fetal malformation and elevated adult-onset multisystemic chronic diseases. Maternal quercetin supplementation must be further explored as a potential dietary intervention for improved placental integrity, fetal development and lifelong health.
Ph. D.

Background In some cross-sectional epidemiologic studies the shape of the association between serum concentrations of perfluoroalkyl acids (PFAAs) and lipids suggests departures from linearity. Objectives We used statistical approaches allowing for non-linearity to determine associations of prenatal exposures of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) with lipid concentrations. Methods PFAAs were measured in serum from pregnant women collected in 1991–1992 at enrollment in the Avon Longitudinal Study of Parents and Children and lipids in serum from their daughters at ages 7 (n = 111) and 15 (n = 88). The associations of PFAAs with lipids were first explored by cubic splines, followed by piecewise linear regressions by tertiles to obtain regression coefficients (β) and their 95% confidence limits (95% CL) (in mg/dL per 1 ng/mL). Results At age 7, total cholesterol was positively associated with prenatal PFOA concentrations in the lower tertile (β = 15.01; 95% CL = 2.34, 27.69) but not with PFOA concentrations in the middle (β = − 3.63; 95% CL = − 17.43, 10.16) and upper (β = − 1.58; 95% CL = − 4.58, 1.42) tertiles. At age 15, a similar pattern was noted as well. Positive associations between LDL-C and prenatal PFOA concentration in the lower tertile were observed in daughters at ages 7 (β = 14.91; 95% CL = 3.53, 28.12) and 15 (β = 13.93; 95% CL = 0.60, 27.26). LDL-C was not associated with PFOA concentrations in the middle or upper tertile at any age. Neither HDL-C nor triglycerides was associated with prenatal PFOA exposure. Non-linear patterns of association of total cholesterol and LDL-C with prenatal PFOS were less consistently noted. Conclusion Exposure to low levels of PFOA during prenatal development may alter lipid metabolism later in life. Given the small sample size further replication of the association in large independent cohorts is important.

Polycystic ovary syndrome (PCOS) is a common and complex endocrine condition with reproductive and metabolic complications, affecting up to 10% of reproductive-age women. Hyperandrogenemia, ovulatory dysfunction, and luteinising hormone hypersecretion are characteristic traits of PCOS however, it seems that the most concerning long-term key issues are metabolic problems associated with the syndrome, such as hyperinsulinemia, insulin resistance, obesity, dyslipidaemia and non-alcoholic liver disease. Despite the numerous studies on PCOS, its origin and pathophysiology are still not fully understood. However, there is increasing evidence that the adult PCOS phenotype is programmed in fetal life by androgen excess. Exposure to increased levels of testosterone in utero in rodents, sheep and monkeys result in adult reproductive and metabolic pathologies that parallel those seen in PCOS women. Since hyperandrogenemia is a hallmark of PCOS and daughters of PCOS mothers have elevated levels of androgens at birth, it is likely that prenatal androgenisation during early life predispose to the future development of PCOS. Animal models of PCOS provide an opportunity to examine the developmental aetiology and molecular mechanisms underlying the pathogenesis of this condition. Over last 10 years our lab has successfully utilised a well-established ovine model of PCOS, where pregnant ewes were treated with testosterone propionate (TP) through mid-gestation. From this model, we had a large sample bank of fixed and frozen tissues from the fetal, lamb and adolescent prenatally androgenised animals that allowed to carry a broad range of experiments. In addition, a new cohort of prenatally androgenised adult sheep enabled additional in vivo analysis. Past research documented that prenatal androgenisation result in hyperinsulinemia with altered pancreas structure and function, and early fatty liver without difference in body weight in adolescent sheep. This thesis examines the effects and consequences of increased in utero androgen exposure on metabolic dysregulation in adolescent and adult female sheep. During puberty, but not fetal or early life, there was decreased adipogenesis in subcutaneous adipose tissue (SAT), but not visceral adipose tissue (VAT), accompanied by decreased circulating concentrations of fibroblast growth factor 21 (FGF21), leptin and adiponectin, and increased concentrations of fasting free fatty acids (FFA) in prenatally androgenised sheep. This was countered by upregulated expression of FFA transporters in liver. As adults, TP-exposed animals had increased body weight, elevated fasting insulin and FFA concentrations but normal FGF21, leptin and adiponectin levels. Histological analysis revealed that adult TP-exposed animals had SAT hypertrophy, which was associated with increased expression of inflammatory markers and correlated with increased fasting FFA. Therefore, it is likely that impaired preadipocyte differentiation in SAT during adolescence resulted in hypertrophy and inflammation of adult SAT. This consequently lowered capacity of SAT to safely store fat and potentially explains metabolic perturbations observed in PCOS-like female sheep. To further investigate potential causes of obesity in adult PCOS-like sheep postprandial thermogenesis (PPT), an important constituent of energy expenditure, was measured through implantation of datalogger thermometers into interscapular adipose tissue. Adult prenatally androgenised sheep had decreased amplitude of PPT, without difference in basal body temperature, despite receiving the same caloric intake, and independent of obesity. These findings indicate that adult PCOS-like sheep have reduced capacity for energy expenditure, which is mirrored in women with PCOS. This reduced capacity for postprandial thermogenesis was correlated with hyperinsulinemia decreased noradrenaline levels and reduced thermogenic potential of brown and/or beige adipose tissue. This suggests that women with PCOS might be prenatally programmed to become obese. In summary, findings documented in this thesis provide better understanding into the pathophysiology of PCOS from puberty to adulthood and give opportunities for early clinical intervention to ameliorate the metabolic phenotype of PCOS.

Chronic diseases such as osteoporosis, type 2 diabetes, and cardiovascular disease are diseases of long duration, slow progression, and are by far the leading cause of death worldwide. A growing body of evidence links adverse exposures in early development with an increased risk of chronic diseases in adult life. The studies presented in this dissertation sought to exploit this phenomenon to determine the extent to which gestational and lactational exposure to a high fat diet predisposes the offspring to certain diseases in later life and if the eating habits of adult offspring would be able to mitigate or exacerbate these conditions.  In the study presented in Chapter III, dams fed an atherogenic high fat diet prior to conception and throughout gestation and lactation experienced excess hepatic lipid accumulation and poor birth outcome as characterized by smaller litter sizes and higher post-delivery mortality. In the offspring, gestational and lactational exposure to such a diet resulted in growth restriction and skeletal aberrations indicative of osteoporosis, despite being fed a standard rodent diet post-weaning. We propose that dietary-induced hyperlipidemia, along with pregnancy-associated factors, resulted in fatty liver and subsequently reduced litter sizes and increased early mortality, and that the skeletal aberrations seen in the mature offspring represent dietary-induced inhibition of osteogenesis in favor of adipogenesis. In the study presented in Chapter IV, early exposure to a high fat diet resulted in central obesity, elevated lipid levels, hyperglycemia, and additional markers used in the diagnosis of the metabolic syndrome. Altering the diets of the mature offspring demonstrated that the eating habits of adulthood have the potential to mitigate or exacerbate certain metabolic parameters established earlier in life. Mechanisms contributing to the observed metabolic aberrations could include developmental plasticity and mismatch, catch-up growth, and altered programming of the appetite regulatory network. Collectively, this research suggests that early exposure to a fat-rich diet can lead to metabolic and skeletal aberrations in the adult offspring and adds support to the developmental origins of health and disease hypothesis by finding that adverse nutritional exposures in early life can play a role in the chronic diseases of adulthood.

Ph. D.

Although the association between social inequality and poor adult health is well established, the mechanisms by which inequality is translated into poor adult health are less clear. Increasingly, evidence suggests that many adult health problems and health disparities have their origins in early life; the developmental origins of health and disease (DOHaD) hypothesis provides an explanatory mechanism linking adverse early life conditions with permanent structural or functional changes that increase the risk for disease. This hypothesis is consistent with bioarchaeological research noting reduced lifespan among individuals exhibiting signs of childhood stress. The principal aim of this dissertation is to contribute a bioarchaeological perspective to health disparities research by investigating how health disparities can be measured and understood in the past. This study focuses on early life conditions as a source of adult health disparity by examining a skeletal sample for the association between childhood stress and adult longevity; the relationship between childhood stress and the presence of adult health conditions; and sex, ancestry, and regional differences in these relationships. The study sampled 830 age-documented, U.S. born African American males and females and Euro-American males from the Terry and the Hamann-Todd anatomical collections, representing socially-marginalized individuals from the late 19th- to early 20th centuries. Enamel hypoplasia, femoral length, and vertebral neural canal diameters represented childhood stress; skeletal fractures, tibial periostosis, and the diseased, missing, and filled tooth index represented adult health. Longevity was modeled with Kaplan-Meier survival curves and adult health relationships were modeled with logistic regression. Additionally, cause of death data from historic health department publications and the study sample morgue records were examined for disparity in the epidemiological transition from infectious to degenerative cause of death. The study found mixed results for all analyses. There was no reduction in longevity for the presence of enamel hypoplasia, short femoral length, or reduced thoracic neural canal diameter. African American males had statistically significant reduced longevity for small lumbar vertebral neural canal diameters. African American males from the Hamann-Todd Collection and Euro-American males from both collections had significant relationships between vertebral neural canal diameters and adult conditions; these relationships varied among the groups but in most cases demonstrated reduced odds for having the adult condition for individuals with smaller canal diameters. African American females had no differential survival or relationships between variables over the lifecourse. All groups except for the Terry Collection Euro-American males continued to have more infectious disease deaths than degenerative disease deaths. The study results contribute to disparities research by demonstrating that the consequences of childhood stress varied by sex and ancestry and by demonstrating within-population variation in timing of the epidemiological transition. Additionally, the study results support the contention of greater male sensitivity to environmental conditions and contributes evidence supporting the DOHaD hypothesis.

Infant growth is a key indicator of health and a relevant component of paediatric surveillance. Certain growth characteristics are also associated with greater risk for diseases such as obesity and cardiovascular disease. South Asian populations are known to demonstrate poor infant growth and suffer from a high prevalence of non-communicable disease. Relatively little is known about the growth of Pakistani infants, especially following migration. In the United kingdom (UK), infant growth is routinely monitored to detect poor health, and this process produces a repository of largely unutilised data. In 2009, new growth charts, which include a component of the World Health Organisation (WHO) growth standards, were introduced to routine practice. The adoption of prescriptive standards, which are based on breastfed infants living in an unconstrained environment, will have implications for the assessment of growth. To develop and assess the quality of routine growth monitoring data collected in Bradford, UK, so that it can be used to describe the differences in growth between White British and Pakistani infants in the same city. To investigate the factors that influence this growth. To assess the implications of adopting growth standards for practice. The frequency of routine growth monitoring data that are collected at prescribed age periods was assessed. Test-retest growth data were collected from 192 practitioners, and technical error of measurements were calculated. Data on 2464 (boys 51%, White British 45%) infants were submitted to multilevel modelling analysis to produce sex and ethnic specific weight-for-age, abdominal circumference-for-age, head circumference-for-age, and length-for-age growth curves between birth and nine months. Multivariable linear regression models were used to investigate factors that influence size at birth and at nine months. Growth curves were plotted against the WHO standards and the UK 1990 references, Z-scores were calculated, and the relative risks (RR) of underweight, obesity, and poor infant weight gain using the standards compared to the references were assessed. During each prescribed age period for routine growth monitoring generally only 30% to 35% of measurements were recorded. None of the technical error of measurements were excessively large, and coefficients of reliability ranged from 0.96 to 1.00. Multilevel models explained that Pakistani infants were smaller than White British infants, in the first nine months of life, for weight (-210.3g to -321.7g), abdominal circumference (-1.15cm to -0.39cm), head circumference (-0.59cm), and length (-0.32cm). Compared to the WHO standards, infants demonstrated dissimilar weight growth, but similar head circumference and length growth. The common weight growth pattern was slow growth between birth and two months, followed by rapid growth. Using the standards, infants were significantly less likely to be classified as underweight (RR at birth 0.496; 95% Confidence Interval 0.363 to 0.678) and demonstrating poor weight gain from birth to nine months (0.783; 0.644 to 0.952). Growth monitoring data are not collected at prescribed age periods, but following initial training of practitioners are reliable. Integrating research with practice has developed routine data to research calibre and has established protocols to make data more accessible. Pakistani infants were consistently smaller than White British infants, and, despite efforts, the determinants of this phenomenon have not yet been fully elucidated. Growth in weight of infants in Bradford differs significantly from that represented by the WHO standards, and without adequate training of practitioners infant growth may be incorrectly interpreted.

Puerto Rico has the highest prevalence of type 2 diabetes, low birth-weight, and the second highest prevalence of preterm-birth in all the U.S. and its non-incorporated territories. These conditions are related. Birth-weight at both ends of the spectrum and preterm-birth are associated with an increased risk for developing type 2 diabetes and immune-inflammatory dysregulations. Maternal psychosocial stressors during pregnancy have also been recognized as potential risk factors for type 2 diabetes, and have been consistently associated with preterm-birth and low birth-weight across populations. Current evidence points toward epigenetic fetal metabolic-programming as the mechanism that underlies the increased risk for the previously mentioned morbidities. However, the particular psychosocial stressors that may contribute to the high prevalence of low birth-weight and preterm-birth in the population of Puerto Rico have not been well studied.

The present study assesses the relationships between particular psychosocial stressors, socioeconomic status, food insecurity, and birth outcomes. The results of this study show that low-risk pregnancy women were more likely to have babies with a higher ponderal index if they were exposed to stressors during gestation months 5, 6, and 7, or if exposed to "relationship stress" at any time during pregnancy. Women exposed to "financial difficulties" at any time during pregnancy were more likely to deliver babies at an earlier gestational age. Differences in birth outcomes between the exposed and non-exposed women were independent of maternal anthropometric measurements, maternal age at birth, number of previous births, and sex of the baby. Significant differences in birth outcomes were found between categories of father's self-identified and identified by others ethnicity, but sample size within categories was small. Although mothers with children at home had higher levels of food insecurity, and the level of food insecurity was correlated with higher levels of stress, no birth outcome measure was associated with food insecurity.

Some results are atypical in comparison with other populations, and therefore these findings may contribute to the understanding of population differences in the relationship between maternal stress during pregnancy and birth outcomes. The relatively small sample size and strict exclusion criteria of this study may limit the generalizability of the findings. Epidemiological similarities between Puerto Rico and other populations, and the possibility of a higher ponderal index increasing the risk for type 2 diabetes in the population of Puerto Rico need to be examined in future research.

A greater understanding of critical periods of body weight regulation, including pregnancy, may aid in efforts to optimize weight management strategies for the mother and her baby. The gestational period has been implicated to play, in the child, a vital role in the developmental origins of obesity and other cardiometabolic diseases later in life. Therefore, we initially examined existing literature on the role of maternal obesity and its link to pediatric obesity and documented the known underlying physiological mechanisms responsible for this relationship while suggesting potential intervention targets that may improve maternal-fetal outcomes. In a second paper, we aimed to quantify maternal predictors of large for gestational age (LGA) neonates in the Ottawa and Kingston (OaK) birth cohort with specific hypotheses verifying the independent contribution of maternal prepregnancy body mass index (BMI) and excessive gestational weight gain (GWG) to fetal overgrowth. This paper also highlights the clinical utility of the revised 2009 Institute of Medicine GWG guidelines and discusses the potential role of physiological factors underlying the observed associations between BMI, excessive GWG and LGA neonates. As a follow-up to our population-level analysis (i.e., OAK cohort), papers three and four highlight how the insulin-like growth factor (IGF) axis, a vital regulator of growth and development, may be compromised at the molecular level in cases of maternal obesity (paper 3) and excessive GWG (paper 4). In paper 3 we show that maternal obesity is associated with attenuated expression of IGF binding protein-4 (IGFBP4) in umbilical cord blood and discuss how this may preferentially promote fetal adipogenesis. The effects of excessive GWG on IGF axis protein expression are addressed in paper four where we show that excessive weight gain during pregnancy is associated with increased expression of IGFBP3 in maternal circulation in normoglycemic term pregnancies. In this paper we discuss the potential inhibitory role of IGFBP3 on adipogenesis and how it relates to glucose intolerance during pregnancy. Recognizing that both obesity and excessive GWG can alter physiological processes in mother and her baby, appropriate evidence-based interventions are warranted to best optimize outcomes. In paper five, we discuss the results of a study which sought to assess patient information channels and knowledge of nutrition and physical activity during pregnancy with the intent that these findings be applied to best design efficacious strategies that cater to the needs of our target group of pregnant women. In our analysis we show that the majority of pregnant women studied would be willing to participate in a lifestyle intervention for their own personal health and that of their child. Of great interest was the observation that most women were not informed of the importance of pregnancy-specific energy intake, or made aware of their own healthy GWG targets. Additionally, many of the respondents reported receiving no information pertaining to appropriate physical activity recommendations; despite the fact that the vast majority of participants consider this lifestyle modality to be safe during their pregnancy. Finally in paper six, we build on the results of our previous work and evaluate the risks and benefits of physical activity during pregnancy on maternal-fetal outcomes through a review of the literature and note that engaging in non-sedentary pursuits during gestation may aid in maternal weight regulation, protect against metabolic disorders and optimize neonatal birth weight and body composition. Overall, the collective nature of the papers presented in this dissertation provides qualitative and quantitative evidence to support not only the complexity of body weight regulation in the mother and her baby, but also highlights potential avenues for intervention that may improve maternal-fetal outcomes during this critical period.

Introdução: Considerando-se a dificuldade e o elevado custo para o tratamento da obesidade, e seu papel como fator de risco para diversas patologias, sua prevenção mostra-se fundamental, por este motivo, a identificação precoce de fatores de risco evitáveis, como a inadequação do estado nutricional em períodos críticos para a gênese da obesidade, representa um interessante campo para investigação científica. Objetivo: Verificar a relação entre o excesso de peso corporal em adolescentes segundo estado nutricional ao nascer e excesso de peso durante o primeiro ano de vida e no período de repleção da adiposidade. Método: Participaram deste estudo alunos de ambos os sexos matriculados nos quintos e sextos anos de Unidades Escolares no Município de São José dos Campos-SP. A coleta de dados ocorreu em três etapas, a primeira consistiu na avaliação nutricional durante a adolescência, considerando-se as medidas de índice de massa corporal (IMC), circunferências abdominal e do braço e soma das pregas cutâneas triciptal e subescapular. Na segunda etapa foram coletadas informações referentes à escolaridade materna, aleitamento materno e estado nutricional ao nascer por meio de questionário respondido pelos pais. As crianças foram classificadas segundo os índices peso ao nascer por idade gestacional, índice ponderal ao nascer e peso ao nascer. Na última etapa foram obtidas informações de peso e estatura durante a infância nos prontuários de atendimento das Unidades Básicas de Saúde (UBS) do Município. Realizou-se análise de regressão logística para verificar associação entre excesso de peso aos 10 anos de idade, considerada variável dependente e, como variáveis independentes, estado nutricional ao nascer, excesso de peso corporal no primeiro ano de vida e no período de repleção da adiposidade (entre os 5 e 7 anos de idade). As análises foram ajustadas para demais variáveis. Resultados: Os estudantes apresentaram média (desvio-padrão) de 131,3 meses (10,99) de idade. Verificou-se elevada correlação entre o peso e comprimento ao nascer informado pelos responsáveis e registrado no prontuário das UBSs (coeficiente de correlação: 0,95 e 0,98, respectivamente). Com relação ao estado nutricional ao nascer, observou-se que o elevado peso ao nascer e o peso ao nascer pequeno para idade gestacional associaram-se ao excesso de peso corporal no início da adolescência. Foi identificado limiar de associação entre excesso de peso corporal no primeiro ano de vida e aos 10 anos de idade. Também foi encontrada associação entre excesso de peso corporal na adolescência e no período de repleção da adiposidade. Conclusão: Os achados mostram consistência com a hipótese de que períodos críticos do crescimento acarretariam em maior predisposição ao excesso de gordura corporal, identificada no presente estudo no início da adolescência
Introduction: Considering that obesity is a major risk for many diseases as well as the difficulties and elevated costs for its treatment, its prevention and the identification of early avoidable health risks, such as nutritional status in critical periods of life, represent important aspects for scientific investigation. Objective: Verify the relationship between excessive body weight during adolescence according to birth nutrition status and excessive body weight during the first year of life and at the period of adiposity rebound. Method: This study was conducted with schoolchildren of both sexes, enrolled in Public Schools in São José dos Campos - SP (SJC-SP). The data was collected in 3 phases, the first consisted of collecting anthropometric information during adolescence, considering body mass index (BMI), arm and abdominal circumferences and the sum of skin fold thickness (triceps and sub scapular). Information about mother´s education, breastfeeding and birth nutritional status was collected in the second phase through a survey which the parents answered. The children were classified according to birth weight for gestational age, ponderal index and birth weight. In the last phase, information about nutritional status during infancy was obtained from medical registers of primary health units in the city. Logistical regression analyses were made to investigate the association between excessive body weight at 10 years of age, considered as dependent variable and, as independent variables, the nutritional status at time of birth, the first year of age and during the period of adiposity rebound (between 5 and 7 years of age). The analyses were adjusted by other variables. Results: The students presented a mean of 131.3 months of age (10.99). An elevated correlation was observed between parents information about birth weight and length and the information registered at the medical documents of primary health units in the city (Correlation coefficient: 0.95 and 0.98, for weight and for length, respectively). An association between elevated birth weight and birth weight small for gestational age and excessive body weight during adolescence was observed. A weak association between excessive body weight during the first year of life and at 10 years of age was identified. It was also verified association in relation to adiposity during the period of adiposity rebound and excessive weight at 10 years of age. Conclusion: These results show consistency in the hypothesis that the critical period for growth development could predispose to future obesity, identified in the present study during early adolescence

Les problèmes de santé liés à l’alimentation hyperlipidique chez l’humain sont en constante progression. Or, une perturbation de l’environnement fœtal induit chez la descendance une susceptibilité plus grande à développer des maladies à l’âge adulte (DOHad : Developmental Origins of Health and Disease). L’objectif de ce travail de Thèse est d’évaluer, chez le lapin, les conséquences d’une alimentation hypercholestérolémique et hyperlipidique sur le développement embryonnaire, fœtal, et la survenue de troubles métaboliques à long terme.Nous avons nourri des lapines ad libitum avec un régime hypercholéstérolémique (0,2%) et hyperlipidique (8%) (HH) ou un régime témoin (C) à partir de l'âge de 10 (expérience 1) ou de 18 semaines (age de la mise à la reproduction, expérience 2). A la naissance, les portées ont été équilibrées et des croisements effectués pour différencier l'effet de l'alimentation de la mère pendant la gestation et pendant la lactation. Ainsi des lapereaux nés de mères HH ont été allaités par des mères C (groupe HH-C) ou HH (groupe HH-HH) et des lapereaux nés de mère C ont été allaités par des mères C (groupe C-C) ou HH (groupe C-HH). Au cours de l’expérience 1, un retard de croissance intra utérin (RCIU) significatif a été mis en évidence dès 9 jours de gestation par échographie dans le groupe HH (P<0,05). A la naissance, les laperaux étaient significativement plus légers (P<0,05). En raison d’un rattrapage pondéral rapide, il n’existait plus de différence significative au sevrage. Tous les lapins ont alors reçu un aliment témoin distribué ad libitum. A J176, il n’y avait pas de différence de poids entre les groupes HH-HH et HH-C, mais les animaux de ces deux groupes étaient significativement plus lourds que les groupes C-C and C-HH (P<0.05). De plus, la tension artérielle était plus élevée dans le groupe HH-HH par rapport à tous les autres groupes (P<0.05). Au cours de l’expérience 2, de tels effets physiologiques n’ont pas été observés. Les effets physiologiques n'ayant été observés que lorsque le régime avait été commencé avant la gestation, nous avons émis l'hypothèse que l'environnement maternel précoce avait été modifié, entrainant une perturbation du développement embryonnaire à l'origine des conséquences à long terme. l’expression des gènes au moment de la mise en route du génome embryonnaire a été étudié à l’aide d’une puce dédiée. L’analyse transcriptomique a permis de suggérer que certains transcrits étaient présents en quantités différentes. Nous avons montré par qRT-PCR que le régime HH induit une augmentation transitoire de la quantité de transcrit de l’adipophiline (présente à J2 mais pas à J5,5). L’analyse immunohistochimique montre une quantité plus importante de gouttelettes lipidiques localisées près du noyau dans les embryons issus de mères nourries par le régime HH à J5,5 comparé aux témoins. Ces résultats illustrent l’importance de la nutrition avant et pendant la gestation pour la determination de la croissance in utero et postnatale, ainsi que pour le développement de maladies métaboliques à long terme. La nutrition maternelle avant la gestation peut engendrer des modifications d’expression de gènes au moment de la transmission materno embryonnaire
The prevalence of human health problems associated with high-fat diets continues to rise, as does the number of such problems known to be associated with this diet. Disruption of the fetal environment induces in progeny a greater susceptibility to developing diseases in adulthood (DOHad: Developmental Origins of Health and Disease). The objective of the work for this thesis was to assess in rabbits the consequences of a high-cholesterol and high-fat diet on embryonic and fetal development and on the onset of metabolic disorders in the long term.We fed rabbits ad libitum with a high-cholesterol (0.2%) and high-fat (8%) (HH) diet or a control (C) diet, starting at the age of 10 (experiment 1) or 18 weeks (age at which reproduction began, experiment 2).The litters were balanced at birth, and crossings were performed to differentiate the effect of the mother's food during gestation and during lactation. Accordingly, rabbits born to HH mothers were nursed by C (HH-C group) or HH (HH-HH) mothers and those born to C mothers were nursed either by C (C-C) or HH (C-HH) mothers. During experiment 1, ultrasound clearly showed significant intrauterine growth restriction (IUGR) beginning at 9 days of gestation in the HH group (P<0.05). At birth, these rabbits weighed significantly less than their C counterparts (P<0.05). Because of their rapid weight catch-up, the significant difference had disappeared at weaning. All the rabbits thereafter received control food distributed ad libitum. At D176, there was no difference in weight between the HH-HH and HH-C groups but the animals in both these groups were significantly heavier than those in the C-C and C-HH groups (P<0.05). Moreover, blood pressure was higher in the HH-HH group than in any of the other groups (P<0.05). These physiological effects were not observed during experiment 2. Because the physiological effects were observed only when the diet began before gestation, we hypothesized that the early maternal environment been modified, a change that resulted in disruption of embryo development with long-term consequences. We then used a specially designed chip to study gene expression at the maternal to embryonic transition. Transcriptomic analysis suggested that some transcripts were present in different quantities. We showed with qRT-PCR that the HH diet induced a transient augmentation in the quantity of adipophilin transcripts (present at D2 but not at D5.5). The immunohistochemical analysis on D5.5 showed a higher quantity of lipid droplets localized near the nucleus of embryos from mothers fed with the HH diet than in embryos of control mothers. These results illustrate the importance of nutrition before and during pregnancy in the determination of in utero and postnatal growth as well as in the development of metabolic diseases over the long term. Maternal nutrition before conception can engender modifications in gene expression at the moment of the maternal to embryonic transition

The prepartum surge in fetal plasma cortisol, essential for the maturation of organs in mammals and the normal timing of parturition in some species, including sheep, may result from an increase in the molar ratio of adrenocorticotropin (ACTH) to pro-opiomelanocortin (POMC) in the fetal circulation. Related to this, the cleavage of POMC to ACTH by the enzyme, prohormone convertase 1 (PC1), may be influenced by corticotrophin releasing hormone (CRH) stimulation. Accumulating evidence suggests that the capacity of individual corticotrophs to process POMC to ACTH may vary and individual corticotrophs are differentially responsive to CRH. It is not known, however, if there are separate corticotroph subpopulations in the fetal sheep pituitary which can be identified by differential colocalisation of POMC, ACTH and the CRH receptor 1, CRHR₁, nor if changes in the relative proportions of such subpopulations play a role in the molecular mechanisms underlying the overall changes in pituitary function described previously during gestation and in response to suboptimal uterine environments. To investigate these hypotheses, it was first necessary to develop novel methods for the simultaneous immunohistochemical labelling of POMC, ACTH and CRHR₁ in individual cells on sections of fetal sheep pituitary. In addition, I developed and validated an automated method to categorise and count individual cells to increase the quantitative power of this study. Pituitary tissue was collected from control fetuses at 53-55 (n=6), 63-85 (n=6), 110 (n=4), 139-141 (n=4) and 144-145 (n=6) days gestation. Two animal models, known to alter pituitary function in the fetal sheep, were used to investigate corticotrophic adaptations to suboptimal uterine environments. For the maternal periconceptional undernutrition (PCUN) model, maternal feed was reduced to 70% of maintenance requirements from at least 45 days before to 7 days after mating and fetal tissues were collected at 53-55 days gestation (n=7). For the placental restriction (PR) model, the majority of the placental attachment sites were removed in five ewes before mating and fetal tissues were collected at 140 (n=4) and 144 (n=4) days gestation. Pituitary sections were simultaneously labelled with antisera raised against full length POMC, ACTH and CRHR₁ and the proportions of pituitary cells with combinations of antisera were quantified. Four subpopulations of corticotrophs were identified, which expressed either: POMC+ACTH+CRHR₁, ACTH+CRHR₁, POMC+ CRHR₁ or POMConly. There was a significant decrease in the proportion of pituitary cells expressing POMC+ACTH+CRHR₁ between 53-55 and 65-85 days gestation, before an increase at 110 days gestation and a further marked decrease between 139-141 and 144-145 days gestation. In fetuses from the PCUN group, the proportion of pituitary cells expressing POMC+ACTH+CRHR₁ in early gestation was reduced. PR resulted in a significantly higher proportion of corticotrophs expressing POMC+ACTH+CRHR₁ during the prepartum period. This work represents the discovery of the differential expression of POMC, ACTH and CRHR₁ in individual corticotrophs of the fetal sheep pituitary and the first insights into the pituitary adaptations to periconceptional nutrient restriction and placental restriction at the level of individual corticotrophs.
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Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008

The prepartum surge in fetal plasma cortisol, essential for the maturation of organs in mammals and the normal timing of parturition in some species, including sheep, may result from an increase in the molar ratio of adrenocorticotropin (ACTH) to pro-opiomelanocortin (POMC) in the fetal circulation. Related to this, the cleavage of POMC to ACTH by the enzyme, prohormone convertase 1 (PC1), may be influenced by corticotrophin releasing hormone (CRH) stimulation. Accumulating evidence suggests that the capacity of individual corticotrophs to process POMC to ACTH may vary and individual corticotrophs are differentially responsive to CRH. It is not known, however, if there are separate corticotroph subpopulations in the fetal sheep pituitary which can be identified by differential colocalisation of POMC, ACTH and the CRH receptor 1, CRHR₁, nor if changes in the relative proportions of such subpopulations play a role in the molecular mechanisms underlying the overall changes in pituitary function described previously during gestation and in response to suboptimal uterine environments. To investigate these hypotheses, it was first necessary to develop novel methods for the simultaneous immunohistochemical labelling of POMC, ACTH and CRHR₁ in individual cells on sections of fetal sheep pituitary. In addition, I developed and validated an automated method to categorise and count individual cells to increase the quantitative power of this study. Pituitary tissue was collected from control fetuses at 53-55 (n=6), 63-85 (n=6), 110 (n=4), 139-141 (n=4) and 144-145 (n=6) days gestation. Two animal models, known to alter pituitary function in the fetal sheep, were used to investigate corticotrophic adaptations to suboptimal uterine environments. For the maternal periconceptional undernutrition (PCUN) model, maternal feed was reduced to 70% of maintenance requirements from at least 45 days before to 7 days after mating and fetal tissues were collected at 53-55 days gestation (n=7). For the placental restriction (PR) model, the majority of the placental attachment sites were removed in five ewes before mating and fetal tissues were collected at 140 (n=4) and 144 (n=4) days gestation. Pituitary sections were simultaneously labelled with antisera raised against full length POMC, ACTH and CRHR₁ and the proportions of pituitary cells with combinations of antisera were quantified. Four subpopulations of corticotrophs were identified, which expressed either: POMC+ACTH+CRHR₁, ACTH+CRHR₁, POMC+ CRHR₁ or POMConly. There was a significant decrease in the proportion of pituitary cells expressing POMC+ACTH+CRHR₁ between 53-55 and 65-85 days gestation, before an increase at 110 days gestation and a further marked decrease between 139-141 and 144-145 days gestation. In fetuses from the PCUN group, the proportion of pituitary cells expressing POMC+ACTH+CRHR₁ in early gestation was reduced. PR resulted in a significantly higher proportion of corticotrophs expressing POMC+ACTH+CRHR₁ during the prepartum period. This work represents the discovery of the differential expression of POMC, ACTH and CRHR₁ in individual corticotrophs of the fetal sheep pituitary and the first insights into the pituitary adaptations to periconceptional nutrient restriction and placental restriction at the level of individual corticotrophs.
Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008

Low birth weight is associated with an increased risk of impaired glucose tolerance and type 2 diabetes and with signs of increased hypothalamic pituitary adrenal axis activity in later life (1, 2). Low birth usually weight reflects a reduction in fetal growth, which largely depends on an adequate supply of nutrients and oxygen. Variations in supply modify the metabolic and neuroendocrine characteristics of the fetus, which in turn modulate the pattern of functional development as well as growth (3). An adverse fetal environment, evident as low birth weight, is therefore proposed to alter functional development with long term effects for the function and risk of disease in the individual later in life (4, 5). Increased HPAA impairs metabolic homeostasis and could therefore mediate effect of prenatal challenge on later metabolic control (6). It was therefore hypothesised that restriction of fetal growth, increases circulating cortisol and/or alters sensitivity to cortisol, which increases fasting blood glucose, and impairs glucose tolerance in the young adult. Large litter size in the guinea pig is characterised by reduced placental and fetal growth, reduced size at birth and insulin resistance in offspring in later life, providing a suitable model to test this hypothesis. Spontaneous restriction of fetal growth in the guinea pig, evident as small size at birth, was associated with increased salivary cortisol, in both sexes but at different stages of postnatal life. In males, salivary cortisol was increased with small size at birth in early and adult life, but reduced later with ageing. In females however, salivary cortisol was increased in juveniles and in aged adults, possibly reflecting the impact of the oestrus cycle on cortisol production in mature cycling females. Altered activity of the HPGA, which can influence that of the HPAA, has also been reported to be programmed by prenatal restriction. In the guinea pig, salivary testosterone in males increased with age and small size at birth in juveniles, young and aged adults. In females, salivary progesterone increased with age up to 300 days, and decreased with size at birth in the young guinea pig. Although testosterone inhibits HPAA activity, in males, mean salivary cortisol correlated positively with mean salivary testosterone at 100 and 300 days of age. In contrast, progesterone may enhance HPAA activity, and consistent with this, in females, mean salivary progesterone correlated with mean salivary cortisol at 400 days of age. Therefore, salivary testosterone in the male and salivary progesterone in the female guinea pig changes with maturation and has previously reported in this or other species, but small size at birth increases salivary testosterone in males with modest effects in early life in females. This together with the unexpected positive associations of salivary cortisol with testosterone in males, suggests that programming of the HPAA makes little contribution to that of the HPAA as indicated by salivary cortisol. Here we show that low birth weight is associated with increased fasting blood glucose and impaired glucose tolerance in both male and female young adult guinea pigs aged 100 days. Fasting and mean (during IVGTT) plasma cortisol was reduced in low birth weight female adult guinea pigs, and is not vary with size at birth at this age in males. This suggests that circulating cortisol does not contribute to the impaired glycaemia associated with small size at birth in the guinea pig. Glucose tolerance was increasingly impaired in males but not females, as mean plasma cortisol increased. This is consistent with cortisol impairing glycaemia in the guinea pig as in other species, in males at least. To assess the role of cortisol in prentally programmed impairment of glycaemia directly, metyrapone or vehicle containing 24% ethanol was administered to young adult guinea pigs for 3 days. Treatment with the latter impaired fasting blood glucose and glucose tolerance in females and the latter in males compared to a previous IVGTT and this was exacerbated in low birth weight females. Metyrapone prevented this impairment of fasting glycaemia and glucose tolerance in the low birth weight adult female guinea pig and in the male guinea pig regardless of birth weight class. Neither vehicle or metyrapone altered plasma cortisol, before or during a second IVGTT. Limited numbers of animals, particularly females, limited this study however and additional investigation is required. Nevertheless this shows for the first time that inhibition of glucocorticoid synthesis in the guinea pig improves glucose control. Furthermore this suggests that the low birth weight guinea pig may be more sensitive to cortisol, have increased cortisol synthesis or reduced inactivation of cortisol in peripheral tissues, leading to increased local cortisol action. In conclusion, alterations in peripheral HPAA activity in the guinea pig due to restricted fetal growth may contribute to their prenatally programmed development of impaired glucose tolerance as young adults, but the extent of that contribution may vary with age and gender.
Thesis (Ph.D.) -- University of Adelaide, School of Paediatrics and Reproductive Health, 2008

Events around conception such as maternal undernutrition and twinning may have effects on offspring physiology and disease risk in adulthood. Periconceptional undernutrition alters offspring physiology and adult pathology without affecting birth size, while twinning affects birth size and physiology but with inconsistent effects on adult pathology. We investigated the effects of these two periconceptional events and their interaction on maternal cardiovascular adaptation to pregnancy and fetal growth, physiology and endocrinology in late gestation in sheep. Pre and/or postconception undernutrition resulted in increased uterine blood flow in late gestation, but no change in maternal blood volume. Preconception undernutrition alone resulted in a relatively large placenta with a small, slow-growing fetus in late gestation. In contrast, postconception undernutrition alone resulted in a fetus with rapid late-gestation growth that was maintained through a maternal fast. Fetuses of ewes undernourished throughout both periods were similar in growth rate and size to controls. Maternal fasting also demonstrated that plasma levels of C-type natriuretic peptide are acutely and independently regulated by nutrient supply in mother and fetus. Fetuses of ewes undernourished both pre- and postconception had increased glucose disposal following a glucose challenge. Hypothalamic-pituitary-adrenal axis tests in these fetuses showed decreased pituitary adrenocorticotropin hormone response to direct stimulation but increased adrenal response to decreased cortisol negative feedback. Twin fetuses grew more slowly in late gestation than singletons. Twins also had a smaller insulin response to arginine and a greater insulin response to glucose, but periconceptional undernutrition abolished this difference. Twins had suppressed baseline hypothalamic-pituitary-adrenal axis function and decreased adrenal sensitivity compared to singletons, but increased fetal pituitary adrenocorticotropin hormone response to direct stimulation and decreased cortisol negative feedback. These studies suggest that firstly, fetal size is a poor reflection of fetal growth trajectory, physiology and endocrinology. Secondly, pre- and postconception undernutrition affect late-gestation fetal growth in different ways, while undernutrition in both periods alters fetal endocrine status in late gestation. Thirdly, the biology of twin fetal development is fundamentally different from that of singletons, which may explain the inconsistency of the relationship between birth weight and adult disease risk in twins.
Auckland Medical Research Foundation, Health Research Council of New Zealand