Effect of maternal nutrient restriction from early to midgestation on cardiac function and metabolism after adolescent-onset obesity

A Reduction in Antenatal Steroid Dose Was Associated with Reduced Cardiac Dysfunction in a Sheep Model of Pregnancy

Despite widespread use, dosing regimens for antenatal corticosteroid (ACS) therapy are poorly unoptimized. ACS therapy exerts a programming effect on fetal development, which may be associated with an increased risk of cardiovascular disease. Having demonstrated that low-dose steroid therapy is an efficacious means of maturing the preterm lung, we hypothesized that a low-dose steroid exposure would exert fewer adverse functional and transcriptional changes on the fetal heart. We tested this hypothesis using low-dose steroid therapy (10 mg delivered to the ewe over 36 h via constant infusion) and compared cardiac effects with those of a higher dose treatment (30 mg delivered to the ewe over 24 h by intramuscular injection; simulating currently employed clinical ACS regimens). Fetal cardiac function was assessed by ultrasound on the day of ACS treatment initiation. Transcriptomic analyses were performed on fetal myocardial tissue. Relative to saline control, fetuses in the higher-dose clinical treatment group had significantly lower ratios between early diastolic ventricular filling and ventricular filling during atrial systole, and showed the differential expression of myocardial hypertrophy-associated transcripts including βMHC, GADD45γ, and PPARγ. The long-term implications of these changes remain unstudied. Irrespective, optimizing ACS dosing regimens to maximize respiratory benefit while minimizing adverse effects on key organ systems, such as the heart, offers a means of improving the acute and long-term outcomes associated with this important obstetric therapy.

The Potential Role of PPARs in the Fetal Origins of Adult Disease

The fetal origins of adult disease (FOAD) hypothesis holds that events during early development have a profound impact on one’s risk for the development of future adult disease. Studies from humans and animals have demonstrated that many diseases can begin in childhood and are caused by a variety of early life traumas, including maternal malnutrition, maternal disease conditions, lifestyle changes, exposure to toxins/chemicals, improper medication during pregnancy, and so on. Recently, the roles of Peroxisome proliferator-activated receptors (PPARs) in FOAD have been increasingly appreciated due to their wide variety of biological actions. PPARs are members of the nuclear hormone receptor subfamily, consisting of three distinct subtypes: PPARα, β/δ, and γ, highly expressed in the reproductive tissues. By controlling the maturation of the oocyte, ovulation, implantation of the embryo, development of the placenta, and male fertility, the PPARs play a crucial role in the transition from embryo to fetus in developing mammals. Exposure to adverse events in early life exerts a profound influence on the methylation pattern of PPARs in offspring organs, which can affect development and health throughout the life course, and even across generations. In this review, we summarize the latest research on PPARs in the area of FOAD, highlight the important role of PPARs in FOAD, and provide a potential strategy for early prevention of FOAD.

Berberine elevates cardiolipin in heart of offspring from mouse dams with high fat diet-induced gestational diabetes mellitus

Berberine (BBR) is an isoquinoline alkaloid from plants known to improve cardiac mitochondrial function in gestational diabetes mellitus (GDM) offspring but the mechanism is poorly understood. We examined the role of the mitochondrial phospholipid cardiolipin (CL) in mediating this cardiac improvement. C57BL/6 female mice were fed either a Lean-inducing low-fat diet or a GDM-inducing high-fat diet for 6 weeks prior to breeding. Lean and GDM-exposed male offspring were randomly assigned a low-fat, high-fat, or high-fat diet containing BBR at weaning for 12 weeks. The content of CL was elevated in the heart of GDM offspring fed a high fat diet containing BBR. The increase in total cardiac CL was due to significant increases in the most abundant and functionally important CL species, tetralinoleoyl-CL and this correlated with an increase in the expression of the CL remodeling enzyme tafazzin. Additionally, BBR treatment increased expression of cardiac enzymes involved in fatty acid uptake and oxidation and electron transport chain subunits in high fat diet fed GDM offspring. Thus, dietary BBR protection from cardiac dysfunction in GDM exposed offspring involves improvement in mitochondrial function mediated through increased synthesis of CL.

Early-life origins of disparities in chronic diseases among Indigenous youth: pathways to recovering health disparities from intergenerational trauma

Indigenous women and children experience some of the most profound health disparities globally. These disparities are grounded in historical and contemporary trauma secondary to colonial atrocities perpetuated by settler society. The health disparities that exist for chronic diseases may have their origins in early-life exposures that Indigenous women and children face. Mechanistically, there is evidence that these adverse exposures epigenetically modify genes associated with cardiometabolic disease risk. Interventions designed to support a resilient pregnancy and first 1000 days of life should abrogate disparities in early-life socioeconomic status. Breastfeeding, prenatal care and early child education are key targets for governments and health care providers to start addressing current health disparities in cardiometabolic diseases among Indigenous youth. Programmes grounded in cultural safety and co-developed with communities have successfully reduced health disparities. More works of this kind are needed to reduce inequities in cardiometabolic diseases among Indigenous women and children worldwide.

Sex-dimorphic acceleration of pericardial, subcutaneous, and plasma lipid increase in offspring of poorly nourished baboons

Developmental programming by reduced maternal nutrition alters function in multiple offspring physiological systems, including lipid metabolism. We have shown that intrauterine growth restriction (IUGR) leads to offspring cardiovascular dysfunction with an accelerated aging phenotype in our nonhuman primate, baboon model. We hypothesized age-advanced pericardial fat and blood lipid changes. In pregnancy and lactation, pregnant baboons ate ad lib (control) or 70% ad lib diet (IUGR). We studied baboon offspring pericardial lipid deposition with magnetic resonance imaging at 5-6 years (human equivalent 20-24 years), skinfold thickness, and serum lipid profile at 8-9 years (human equivalent 32-36 years), comparing values with a normative life-course baboon cohort, 4-23 years. Increased pericardial fat deposition occurred in IUGR males but not females. Female but not male total cholesterol, low-density lipoprotein, and subcutaneous fat were increased with a trend of triglycerides increase. When comparing IUGR changes to values in normal older baboons, the increase in male apical pericardial fat was equivalent to advancing age by 6 years and the increase in female low-density lipoprotein to an increase of 3 years. We conclude that reduced maternal diet accelerates offspring lipid changes in a sex-dimorphic manner. The interaction between programming and accelerated lipogenesis warrants further investigation.

IUGR decreases cardiomyocyte endowment and alters cardiac metabolism in a sex- and cause-of-IUGR-specific manner

Intrauterine growth restriction (IUGR) increases the risk of ischemic heart disease in adulthood. Studies in rats suggest cardiac vulnerability is more pronounced in males and in offspring that were exposed to hypoxia in utero. Therefore, we aimed to test the hypotheses that 1) IUGR adolescent males, but not females, have fewer cardiomyocytes and altered expression of cardiometabolic genes compared with controls; and 2) IUGR due to hypoxia has a greater effect on these parameters compared with IUGR due to nutrient restriction. IUGR was induced in guinea pigs by maternal hypoxia (MH; 10% O₂, n = 9) or maternal nutrient restriction (MNR; ~30% reduction in food intake, n = 9) in the second half of pregnancy and compared with control ( n = 11). At 120 days of age, postmortem was performed and the left ventricle perfusion fixed for stereological determination of cardiomyocyte number or snap frozen to determine the abundance of cardiometabolic genes and proteins by quantitative RT-PCR and Western blotting, respectively. MH reduced the number of cardiomyocytes in female ( P < 0.05), but not male or MNR, adolescent offspring. Furthermore, IUGR males had decreased expression of genes responsible for fatty acid activation in the sarcoplasm ( FACS) and transport into the mitochondria ( AMPK-a₂ and ACC; P < 0.05) and females exposed to MH had increased activation/phosphorylation of AMP-activated protein kinase-α ( P < 0.05). We postulate that the changes in cardiomyocyte endowment and cardiac gene expression observed in the present study are a direct result of in utero programming, as offspring at this age did not suffer from obesity, hypertension, or left ventricular hypertrophy.

Akt signaling as a mediator of cardiac adaptation to low birth weight

Intrauterine insults, such as poor nutrition and placental insufficiency, can alter cardiomyocyte development, and this can have significant long-term implications for heart health. Consequently, epidemiological studies have shown that low-birth-weight babies have an increased risk of death from cardiovascular disease in adult life. In addition, intrauterine growth restriction can result in increased left ventricular hypertrophy, which is the strongest predictor for poor health outcomes in cardiac patients. The mechanisms responsible for these associations are not clear, but a suboptimal intrauterine environment can program alternative expression of genes such as cardiac IGF-2/H19, IGF-2R and AT₁R through either an increase or decrease in DNA methylation or histone acetylation at specific loci. Furthermore, hypoxia and other intrauterine insults can also activate the IGF-1 receptor via IGF-1 and IGF-2, and the AT₁ receptor via angiotensin signaling pathways; both of which can result in the phosphorylation of Akt and the activation of a range of downstream pathways. In turn, Akt activation can increase cardiac angiogenesis and cardiomyocyte apoptosis and promote a reversion of metabolism in postnatal life to a fetal phenotype, which involves increased reliance on glucose. Cardiac Akt can also be indirectly regulated by microRNAs and conversely can target microRNAs that will eventually affect other specific cardiac genes and proteins. This review aims to discuss our understanding of this complex network of interactions, which may help explain the link between low birth weight and the increased risk of cardiovascular disease in adult life.

Suboptimal maternal nutrition during early-to-mid gestation in the sheep enhances pericardial adiposity in the near-term fetus

Manipulation of the maternal diet at defined stages of gestation influences long-term health by inducing changes in fetal adipose tissue development, characterised as possessing brown and white adipocytes. We determined whether suboptimal maternal nutrition in early-to-mid gestation, followed by ad libitum feeding until term, increases adiposity in the pericardial depot of the sheep fetus. Pericardial adipose tissue was sampled from near-term (140 days) fetuses delivered to mothers fed either 100% (C) or 60% (i.e. nutrient restricted (NR)) of their total metabolisable requirements from 28 to 80 days gestation and then fed ad libitum. Adipose tissue mass, uncoupling protein (UCP) 1 and gene expression of brown and white adipogenic genes was measured. Total visceral and pericardial adiposity was increased in offspring born to NR mothers. The abundance of UCP1 was increased, together with those genes involved in brown (e.g. BMP7 and C/EBPβ) and white (e.g. BMP4 and C/EBPα) adipogenesis, whereas insulin receptor gene expression was downregulated. In conclusion, suboptimal maternal nutrition between early-to-mid gestation followed by ad libitum feeding enhances pericardial adiposity near to term. A combination of raised UCP1 and adipose tissue mass could improve survival following cold exposure at birth. In the longer term, this enhanced adipogenic potential could predispose to greater pericardial adiposity.

A review of fundamental principles for animal models of DOHaD research: an Australian perspective

Epidemiology formed the basis of ‘the Barker hypothesis’, the concept of ‘developmental programming’ and today’s discipline of the Developmental Origins of Health and Disease (DOHaD). Animal experimentation provided proof of the underlying concepts, and continues to generate knowledge of underlying mechanisms. Interventions in humans, based on DOHaD principles, will be informed by experiments in animals. As knowledge in this discipline has accumulated, from studies of humans and other animals, the complexity of interactions between genome, environment and epigenetics, has been revealed. The vast nature of programming stimuli and breadth of effects is becoming known. As a result of our accumulating knowledge we now appreciate the impact of many variables that contribute to programmed outcomes. To guide further animal research in this field, the Australia and New Zealand DOHaD society (ANZ DOHaD) Animals Models of DOHaD Research Working Group convened at the 2nd Annual ANZ DOHaD Congress in Melbourne, Australia in April 2015. This review summarizes the contributions of animal research to the understanding of DOHaD, and makes recommendations for the design and conduct of animal experiments to maximize relevance, reproducibility and translation of knowledge into improving health and well-being.

Excess nutrient supply in early life and its later metabolic consequences

Suboptimal nutrition in early life, both in utero and during infancy, is linked to increased risk of adult obesity and its associated adverse metabolic health problems. Excess nutrient supply during early life can lead to metabolic programming in the offspring. Such overnutrition can occur in the offspring of obese mothers, the offspring of mothers who gain excess weight during gestation, infants of diabetic mothers and infants who undergo rapid growth, particularly weight gain, during early infancy. Postnatal overnutrition is particularly detrimental for infants who are born small for gestational age, who are overfed to attain 'catch-up growth'. Potential mechanisms underlying metabolic programming that results from excess nutrition during early life include resetting of hypothalamic energy sensing and appetite regulation, altered adipose tissue insulin sensitivity and impaired brown adipose tissue function. More detailed understanding of the mechanisms involved in metabolic programming could enable the development of therapeutic strategies for ameliorating its ill effects. Research in this field could potentially identify optimal and appropriate preventative interventions for a burgeoning population at risk of increased mortality and morbidity from obesity and its concomitant metabolic conditions.

Maternal obesity and the developmental programming of hypertension: a role for leptin

Mother-child cohort studies have established that both pre-pregnancy body mass index (BMI) and gestational weight gain are independently associated with cardio-metabolic risk factors in young adult offspring, including systolic and diastolic blood pressure. Animal models in sheep and non-human primates provide further evidence for the influence of maternal obesity on offspring cardiovascular function, whilst recent studies in rodents suggest that perinatal exposure to the metabolic milieu of maternal obesity may permanently change the central regulatory pathways involved in blood pressure regulation. Leptin plays an important role in the central control of appetite, is also involved in activation of efferent sympathetic pathways to both thermogenic and non-thermogenic tissues, such as the kidney, and is therefore implicated in obesity-related hypertension. Leptin is also thought to have a neurotrophic role in the development of the hypothalamus, and altered neonatal leptin profiles secondary to maternal obesity are associated with permanently altered hypothalamic structure and function. In rodent studies, maternal obesity confers persistent sympathoexcitatory hyper-responsiveness and hypertension acquired in the early stages of development. Experimental neonatal hyperleptinaemia in naive rat pups provides further evidence of heightened sympathetic tone and proof of principle that hyperleptinaemia during a critical window of hypothalamic development may directly lead to adulthood hypertension. Insight from these animal models raises the possibility that early-life exposure to leptin in humans may lead to early onset essential hypertension. Ongoing mother-child cohort and intervention studies in obese pregnant women provide a unique opportunity to address associations between maternal obesity and offspring cardiovascular function. The goal of the review is to highlight the potential importance of leptin in the developmental programming of hypertension in obese pregnancy.

Lipotoxicity and the role of maternal nutrition

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

Suboptimal maternal nutrition during early fetal kidney development specifically promotes renal lipid accumulation following juvenile obesity in the offspring

Reduced maternal food intake between early-to-mid gestation results in tissue-specific adaptations in the offspring following juvenile-onset obesity that are indicative of insulin resistance. The aim of the present study was to establish the extent to which renal ectopic lipid accumulation, as opposed to other markers of renal stress, such as iron deposition and apoptosis, is enhanced in obese offspring born to mothers nutrient restricted (NR) throughout early fetal kidney development. Pregnant sheep were fed either 100% (control) or NR (i.e. fed 50% of their total metabolisable energy requirement from 30-80 days gestation and 100% at all other times). At weaning, offspring were made obese and, at approximately 1 year, kidneys were sampled. Triglyceride content, HIF-1α gene expression and the protein abundance of the outer-membrane transporter voltage-dependent anion-selective channel protein (VDAC)-I on the kidney cortex were increased in obese offspring born to NR mothers compared with those born to controls, which exhibited increased iron accumulation within the tubular epithelial cells and increased gene expression of the death receptor Fas. In conclusion, suboptimal maternal nutrition coincident with early fetal kidney development results in enhanced renal lipid deposition following juvenile obesity and could accelerate the onset of the adverse metabolic, rather than cardiovascular, symptoms accompanying the metabolic syndrome.

Suboptimal maternal nutrition affects offspring health in adult life

Suboptimal maternal nutrition during pregnancy is prevalent and compromises fetal development. Physiological and metabolic adaptations made by the fetus to an inadequate, or excess, maternal nutritional environment, may promote immediate survival but are lasting, conferring significantly increased risks of ill health in childhood and adulthood. In addition, such fetal adaptations are particularly detrimental when nutrient supply is no longer constrained in contemporary nutrient rich environments. Given the prevalence of suboptimal maternal nutritional environments during fetal development, effective prevention, early detection and therapeutic interventions to reduce the increased risks on population health must be a health priority. Therefore, the mechanisms of these lasting in utero adaptations are highly relevant to establishing how exposure to a suboptimal nutritional environment impacts on the health of current generations living in an environment challenged by excess nutrition.

Alteration of cardiac glucose metabolism in association to low birth weight: experimental evidence in lambs with left ventricular hypertrophy

OBJECTIVE

Intrauterine growth restriction that results in low birth weight (LBW) has been linked to the onset of pathological cardiac hypertrophy. An altered transition from a fetal to an adult energy metabolism phenotype, with increased reliance on glucose rather than fatty acids for energy production, could help explain this connection. We have therefore investigated cardiac metabolism in relation to left ventricular hypertrophy in LBW lambs, at 21days after birth.

MATERIALS/METHODS

The expression of regulatory molecules involved in cardiac glucose and fatty acid metabolism was measured using real-time PCR and Western blotting. A section of the left ventricle was fixed for Periodic Acid Schiff staining to determine tissue glycogen content.

RESULTS

There was increased abundance of insulin signalling pathway proteins (phospho-insulin receptor, insulin receptor and phospho-Akt) and the glucose transporter (GLUT)-1, but no change in GLUT-4 or glycogen content in the heart of LBW compared to ABW lambs. There was, however, increased abundance of cardiac pyruvate dehydrogenase kinase 4 (PDK-4) in LBW compared to ABW lambs. There were no significant changes in the mRNA expression of components of the peroxisome proliferator activated receptor regulatory complex or proteins involved in fatty acid metabolism.

CONCLUSION

We concluded that LBW induced left ventricular hypertrophy was associated with increased GLUT-1 and PDK-4, suggesting increased glucose uptake, but decreased efficacy for the conversion of glucose to ATP. A reduced capacity for energy conversion could have significant implications for vulnerability to cardiovascular disease in adults who are born LBW.

Pre- and early-postnatal nutrition modify gene and protein expressions of muscle energy metabolism markers and phospholipid Fatty Acid composition in a muscle type specific manner in sheep

We previously reported that undernutrition in late fetal life reduced whole-body insulin sensitivity in adult sheep, irrespective of dietary exposure in early postnatal life. Skeletal muscle may play an important role in control of insulin action. We therefore studied a range of putative key muscle determinants of insulin signalling in two types of skeletal muscles (longissimus dorsi (LD) and biceps femoris (BF)) and in the cardiac muscle (ventriculus sinister cordis (VSC)) of sheep from the same experiment. Twin-bearing ewes were fed either 100% (NORM) or 50% (LOW) of their energy and protein requirements during the last trimester of gestation. From day-3 postpartum to 6-months of age (around puberty), twin offspring received a high-carbohydrate-high-fat (HCHF) or a moderate-conventional (CONV) diet, whereafter all males were slaughtered. Females were subsequently raised on a moderate diet and slaughtered at 2-years of age (young adults). The only long-term consequences of fetal undernutrition observed in adult offspring were lower expressions of the insulin responsive glucose transporter 4 (GLUT4) protein and peroxisome proliferator-activated receptor gamma, coactivator 1α (PGC1α) mRNA in BF, but increased PGC1α expression in VSC. Interestingly, the HCHF diet in early postnatal life was associated with somewhat paradoxically increased expressions in LD of a range of genes (but not proteins) related to glucose uptake, insulin signalling and fatty acid oxidation. Except for fatty acid oxidation genes, these changes persisted into adulthood. No persistent expression changes were observed in BF and VSC. The HCHF diet increased phospholipid ratios of n-6/n-3 polyunsaturated fatty acids in all muscles, even in adults fed identical diets for 1½ years. In conclusion, early postnatal, but not late gestation, nutrition had long-term consequences for a number of determinants of insulin action and metabolism in LD. Tissues other than muscle may account for reduced whole body insulin sensitivity in adult LOW sheep.

Brown adipose tissue growth and development

Brown adipose tissue is uniquely able to rapidly produce large amounts of heat through activation of uncoupling protein (UCP) 1. Maximally stimulated brown fat can produce 300 watts/kg of heat compared to 1 watt/kg in all other tissues. UCP1 is only present in small amounts in the fetus and in precocious mammals, such as sheep and humans; it is rapidly activated around the time of birth following the substantial rise in endocrine stimulatory factors. Brown adipose tissue is then lost and/or replaced with white adipose tissue with age but may still contain small depots of beige adipocytes that have the potential to be reactivated. In humans brown adipose tissue is retained into adulthood, retains the capacity to have a significant role in energy balance, and is currently a primary target organ in obesity prevention strategies. Thermogenesis in brown fat humans is environmentally regulated and can be stimulated by cold exposure and diet, responses that may be further modulated by photoperiod. Increased understanding of the primary factors that regulate both the appearance and the disappearance of UCP1 in early life may therefore enable sustainable strategies in order to prevent excess white adipose tissue deposition through the life cycle.

Early origins of heart disease: low birth weight and determinants of cardiomyocyte endowment

1. World-wide epidemiological and experimental animal studies demonstrate that adversity in fetal life, resulting in intrauterine growth restriction, programmes the offspring for a greater susceptibility to ischaemic heart disease and heart failure in adult life. 2. After cardiogenesis, cardiomyocyte endowment is determined by a range of hormones and signalling pathways that regulate cardiomyocyte proliferation, apoptosis and the timing of multinucleation/terminal differentiation. 3. The small fetus may have reduced cardiomyocyte endowment owing to the impact of a suboptimal intrauterine environment on the signalling pathways that regulate cardiomyocyte proliferation, apoptosis and the timing of terminal differentiation.

In utero programming of later adiposity: the role of fetal growth restriction

Intrauterine growth restriction (IUGR) is strongly associated with obesity in adult life. The mechanisms contributing to the onset of IUGR-associated adult obesity have been studied in animal models and humans, where changes in fetal adipose tissue development, hormone levels and epigenome have been identified as principal areas of alteration leading to later life obesity. Following an adverse in utero development, IUGR fetuses display increased lipogenic and adipogenic capacity in adipocytes, hypoleptinemia, altered glucocorticoid signalling, and chromatin remodelling, which subsequently all contribute to an increased later life obesity risk. Data suggest that many of these changes result from an enhanced activity of the adipose master transcription factor regulator, peroxisome proliferator-activated receptor-γ (PPARγ) and its coregulators, increased lipogenic fatty acid synthase (FAS) expression and activity, and upregulation of glycolysis in fetal adipose tissue. Increased expression of fetal hypothalamic neuropeptide Y (NPY), altered hypothalamic leptin receptor expression and partitioning, reduced adipose noradrenergic sympathetic innervations, enhanced adipose glucocorticoid action, and modifications in methylation status in the promoter of hepatic and adipose adipogenic and lipogenic genes in the fetus also contribute to obesity following IUGR. Therefore, interventions that inhibit these fetal developmental changes will be beneficial for modulation of adult body fat accumulation.

Nutritional regulation of fetal growth and implications for productive life in ruminants

The maternal nutritional and metabolic environment is critical in determining not only the reproductive success but also the long-term health and viability of the offspring. Changes in maternal diet at defined stages of gestation coincident with different stages of development can have pronounced effects on organ and tissue function in later life. This includes adipose tissue for which differential effects are observed between brown and white adipose tissues. One early, critical window of organ development in the ruminant relates to the period covering uterine attachment, or implantation, and rapid placental growth. During this period, there is pronounced cell division within developing organelles in many fetal tissues, leading to their structural development. In sheep, a 50% global reduction in caloric intake over this specific period profoundly affects placental growth and morphology, resulting in reduced placentome weight. This occurs in conjunction with a lower capacity to inactivate maternal cortisol through the enzyme 11β-hydroxysteroid dehydrogenase type 2 in response to a decrease in maternal plasma cortisol in early gestation. The birth weight of the offspring is, however, unaffected by this dietary manipulation and, although they possess more fat, this adaptation does not persist into adulthood when they become equally obese as those born to control fed mothers. Subsequently, after birth, further changes in fat development occur which impact on both glucocorticoid action and inflammatory responses. These adaptations can include changes in the relative populations of both brown and white adipocytes for which prolactin acting through its receptor appears to have a prominent role. Earlier when in utero nutrient restricted (i.e. between early-to-mid gestation) offspring are exposed to an obesogenic postnatal environment; they exhibit an exaggerated insulin response, which is accompanied by a range of amplified and thus, adverse, physiological or metabolic responses to obesity. These types of adaptations are in marked contrast to the effect of late gestational nutrient restriction, which results in reduced fat mass at birth. As young adults, however, fat mass is increased and, although basal insulin is unaffected, these offspring are insulin resistant. In conclusion, changes in nutrient supply to either the mother and/or her fetus can have profound effects on a range of metabolically important tissues. These have the potential to either exacerbate, or protect from, the adverse effects of later obesity and accompanying complications in the resulting offspring.

High multivitamin intakes during pregnancy and postweaning obesogenic diets interact to affect the relationship between expression of PPAR genes and glucose regulation in the offspring

High multivitamin intake (HV) during pregnancy increases body fat and weight and alters glucose and fatty acid metabolism in Wistar rat offspring. This study investigated the expression of peroxisome-proliferator activated receptors (PPARs) genes involved in regulation of glucose and fatty acid metabolism in their tissues. Dams received the AIN-93G diet with either the regular (RV) or 10-fold multivitamins (HV) during pregnancy. Male offspring were weaned to either the RV diet (RV-RV and HV-RV) or an obesogenic diet (RV-Ob and HV-Ob). Gene expression of PPARs in tissues was analyzed by real-time reverse transcriptase polymerase chain reaction. Gestational diet (GD) did not affect PPARs gene expression in offspring at either birth or weaning. In liver, at 14 weeks postweaning, PPAR-γ was 30% lower in the HV-RV and 30% higher in HV-Ob than in the RV-RV group [GD P=.76, postweaning diet (PD) P=.19, interaction P=.02, by two-way analysis of variance]. In muscle, PPAR-α expression was affected by GD and PD (GD P=.05, PD P<.01, interaction P=.07). In adipose tissue, PPAR-α expression was higher in all groups compared to RV-RV (GD P=.25, PD P=.85, interaction P=.03). PPAR-γ mRNA levels correlated with abdominal fat (r=0.45, P<.05) and insulin resistance index (r=0.39, P<.05). In liver, PPAR-γ expression correlated with insulin resistance index in offspring from RV (r=-0.62, P<.05), but not in those from HV dams (r=0.13, P>.05). In conclusion, the HV diet during pregnancy interacts with postweaning diets in determining the expression of PPARs genes in a tissue- and age-dependent manner and uncouples the relationship between these genes and glucose regulation and fat mass in the rat offspring.

Nutrition, epigenetics, and metabolic syndrome

SIGNIFICANCE

Epidemiological and animal studies have demonstrated a close link between maternal nutrition and chronic metabolic disease in children and adults. Compelling experimental results also indicate that adverse effects of intrauterine growth restriction on offspring can be carried forward to subsequent generations through covalent modifications of DNA and core histones.

RECENT ADVANCES

DNA methylation is catalyzed by S-adenosylmethionine-dependent DNA methyltransferases. Methylation, demethylation, acetylation, and deacetylation of histone proteins are performed by histone methyltransferase, histone demethylase, histone acetyltransferase, and histone deacetyltransferase, respectively. Histone activities are also influenced by phosphorylation, ubiquitination, ADP-ribosylation, sumoylation, and glycosylation. Metabolism of amino acids (glycine, histidine, methionine, and serine) and vitamins (B6, B12, and folate) plays a key role in provision of methyl donors for DNA and protein methylation.

CRITICAL ISSUES

Disruption of epigenetic mechanisms can result in oxidative stress, obesity, insulin resistance, diabetes, and vascular dysfunction in animals and humans. Despite a recognized role for epigenetics in fetal programming of metabolic syndrome, research on therapies is still in its infancy. Possible interventions include: 1) inhibition of DNA methylation, histone deacetylation, and microRNA expression; 2) targeting epigenetically disturbed metabolic pathways; and 3) dietary supplementation with functional amino acids, vitamins, and phytochemicals.

FUTURE DIRECTIONS

Much work is needed with animal models to understand the basic mechanisms responsible for the roles of specific nutrients in fetal and neonatal programming. Such new knowledge is crucial to design effective therapeutic strategies for preventing and treating metabolic abnormalities in offspring born to mothers with a previous experience of malnutrition.

The early programming of metabolic health: is epigenetic setting the missing link?

Adult health is dependent, in part, on maternal nutrition and growth during early life, which may independently affect insulin sensitivity, body composition, and overall energy homeostasis. Since the publication of the "thrifty phenotype hypothesis" by Hales and Barker (Diabetologia 1992;35:595-601), animal experiments have focused on establishing the mechanisms involved, which include changes in fetal cortisol, insulin, and leptin secretion or sensitivity. Intrauterine growth retardation can be induced by either prolonged modest changes in maternal diet or by more severe changes in uterine blood supply near to term. These contrasting challenges result in different amounts of cellular stress in the offspring. In addition, shifts in the transcriptional activity of DNA may produce sustained metabolic adaptations. Within tissues and organs that control metabolic homeostasis (eg, hypothalamus, adipose tissue, stomach, skeletal muscle, and heart), a range of phenotypes can be induced by sustained changes in maternal diet via modulation of genes that control DNA methylation and by histone acetylation, which suggests epigenetic programming. We now need to understand how changes in maternal diet affect DNA and how they are conserved on exposure to oxidative stress. A main challenge will be to establish how the dietary environment interacts with the programmed phenotype to trigger the development of metabolic disease. This may aid in the establishment of nutrigenomic strategies to prevent the metabolic syndrome.

Programming research: where are we and where do we go from here?

Convincing evidence has accumulated to show that both pre- and postnatal nutrition preprogram long-term health, well-being, and performance until adulthood and old age. There is a very large potential in the application of this knowledge to promote public health. One of the prerequisites for translational application is to strengthen the scientific evidence. More extensive knowledge is needed (eg, on effect sizes of early life programming in contemporary populations, on specific nutritional exposures, on sensitive time periods in early life, on precise underlying mechanisms, and on potential effect differences in subgroups characterized by, eg, genetic predisposition or sex). Future programming research should aim at filling the existing gaps in scientific knowledge, consider the entire lifespan, address socioeconomic issues, and foster innovation. Research should aim at results suitable for translational application (eg, by leading to health-promoting policies and evidence-based dietary recommendations in the perinatal period). International collaboration and a close research partnership of academia, industry, and small and medium enterprises may strengthen research and innovative potential enhancing the likelihood of translational application. The scientific know-how and methodology available today allow us to take major steps forward in the near future; hence, research on nutritional programming deserves high priority.

The conflicting effects of maternal nutrient restriction and early-life obesity on renal health

Epidemiological and animal studies have demonstrated that early-life nutrition alters the metabolic responses and generates structural changes in complex tissues, such as the kidneys, which may lead to a reduction in the offspring lifespan. Independently, obesity induces a spontaneous low-grade chronic inflammatory response by modulating several of the major metabolic pathways that ultimately compromise long-term renal health. However, the combined effects of maternal nutrition and early-life obesity in the development of renal diseases are far from conclusive. Previous results, using the ovine model, demonstrated that the combination of a reduction in fetal nutrition and juvenile obesity induced a series of adaptations associated with severe metabolic syndrome in the heart and adipose tissue. Surprisingly, exposure to an obesogenic environment in the kidney of those offspring produced an apparent reduction in glomerulosclerosis in relation to age- and weight-matched controls. However, this reduction in cellular apoptosis was accompanied by a rise in glomerular filtration rate and blood pressure of equal intensity when compared with obese controls. The intention of this review is to explain the adaptive responses observed in this model, based on insights into the mechanism of renal fetal programming, and their potential interactions with some of the metabolic changes produced by obesity.

Suboptimal maternal nutrition, during early fetal liver development, promotes lipid accumulation in the liver of obese offspring

Maternal nutrition during the period of early organ development can modulate the offspring's ability to metabolise excess fat as young adults when exposed to an obesogenic environment. This study examined the hypothesis that exposing offspring to nutrient restriction coincident with early hepatogenesis would result in endocrine and metabolic adaptations that subsequently lead to increased ectopic lipid accumulation within the liver. Pregnant sheep were fed either 50 or 100% of total metabolisable energy requirements from 30 to 80 days gestation and 100% thereafter. At weaning, offspring were made obese, and at ∼1 year of age livers were sampled. Lipid infiltration and molecular indices of gluconeogenesis, lipid metabolism and mitochondrial function were measured. Although hepatic triglyceride accumulation was not affected by obesity per se, it was nearly doubled in obese offspring born to nutrient-restricted mothers. This adaptation was accompanied by elevated gene expression for peroxisome proliferator-activated receptor γ (PPARG) and its co-activator PGC1α, which may be indicative of changes in the rate of hepatic fatty acid oxidation. In contrast, maternal diet had no influence on the stimulatory effect of obesity on gene expression for a range of proteins involved in glucose metabolism and energy balance including glucokinase, glucocorticoid receptors and uncoupling protein 2. Similarly, although gene expressions for the insulin and IGF1 receptors were suppressed by obesity they were not influenced by the prenatal nutritional environment. In conclusion, excess hepatic lipid accumulation with juvenile obesity is promoted by suboptimal nutrition coincident with early development of the fetal liver.

Maternal high fat feeding and gestational dietary restriction: effects on offspring body weight, food intake and hypothalamic gene expression over three generations in mice

Excessive gestational weight gain and maternal obesity have both been associated with increased incidence of obesity and metabolic disorder in offspring in both humans and animal models. The objectives of this study were to determine (1) whether mild gestational food restriction during the third trimester (GFR) would alter food intake and growth parameters of offspring, (2) whether effects of GFR depended on diet (high fat [HF] vs chow), (3) whether effects of excessive gestational weight gain (WG) would become magnified across generations, and (4) whether diet and GFR would alter hypothalamic gene expression in adult offspring. Three generations of female C57BL/6 mice were fed chow or HF diet, mated at 11 weeks of age and assigned to ad libitum feeding or 25% GFR. Offspring were fed the same diet as their mothers. Results showed (1) maternal gestational WG was positively correlated with offspring WG. (2) HF offspring weighed less (p<0.01) at weaning (WWT) but gained more during the 8 weeks after weaning than chow-fed offspring (p<0.05), resulting in higher final body weights (BW) (p<0.01). (3) HF males from GFR mothers had higher WWT (p<0.05), but subsequent WG and final BW were less (p<0.05) compared to males from ad lib mothers. (4) In the HF group, GFR also resulted in decreased FI (p<0.05) and FE (p<0.07) in offspring, compared to offspring from ad lib mothers. (5) In generation 3, hypothalamic expression of tyrosine hydroxylase was lower in HF males from GFR mothers compared to HF males from ad lib mothers (p<0.05). In conclusion, gender and maternal GFR had independent effects on growth and FI, and hypothalamic gene expression was dependent on both gender and maternal GFR in HF offspring. Even mild food restriction of obese mothers during pregnancy may have beneficial effects in reducing the risk or degree of obesity in offspring.

Influence of prenatal nutrition and obesity on tissue specific fat mass and obesity-associated (FTO) gene expression

The recent discovery of an association between body composition, energy intake and the fat mass and obesity-associated (FTO) gene represents a promising new therapeutic target in obesity prevention. In a well, pre-established large animal model, we investigated the regulation ofFTOgene expression under conditions either leading to obesity or increased risk of obesity related disorders: i) a sedentary ‘Western’ lifestyle and ii) prenatal exposure to nutrient restriction. Pregnant sheep were either fed to fully meet their nutritional requirements throughout gestation or 50% of this amount from early-to-mid gestation. Following weaning, offspring were either made obese through exposure to a sedentary obesogenic environment or remained lean. A significant positive relationship between placentalFTOgene expression and fetal weight was found at 110 days gestation. In both the newborn and adult offspring, the hypothalamus was the major site ofFTOgene expression. HypothalamicFTOgene expression was upregulated by obesity and was further increased by prenatal nutrient restriction. Importantly, we found a strong negative relationship between the hypothalamicFTOgene expression and food intake in lean animals only that may imply FTO as a novel controller of energy intake. In contrast,FTOgene expression in the heart was downregulated in obese offspring born to nutrient restricted mothers. In addition,FTOgene expression was unaffected by obesity or prenatal diet in insulin-dependent tissues, where it changed with age possibly reflecting adaptations in cellular energetic activity. These findings extend information gained from human epidemiology and provide new insights into the regulation ofin vivoenergy metabolism to prevent obesity.

Nutritional programming of the metabolic syndrome

The primary markers of the metabolic syndrome are central obesity, insulin resistance and hypertension. In this review, we consider the effect of changes in maternal nutrition during critical windows in fetal development on an individual's subsequent predisposition to the metabolic syndrome. The fetal origins of obesity, cardiovascular disease and insulin resistance have been investigated in a wide range of epidemiological and animal studies; these investigations highlight adaptations made by the nutritionally manipulated fetus that aim to maintain energy homeostasis to ensure survival. One consequence of such developmental plasticity may be a long term re-setting of cellular energy homeostasis, most probably via epigenetic modification of genes involved in a number of key regulatory pathways. For example, reduced maternal-fetal nutrition during early gestation to midgestation affects adipose tissue development and adiposity of the fetus by setting an increased number of adipocyte precursor cells. Importantly, clinically relevant adaptations to nutritional challenges in utero may only manifest as primary components of the metabolic syndrome if followed by a period of accelerated growth early in the postnatal period and/or if offspring become obese.

The impact of diet during early life and its contribution to later disease: critical checkpoints in development and their long-term consequences for metabolic health

Changes in maternal diet at different stages of reproduction can have pronounced influences on the health and well-being of the resulting offspring, especially following exposure to an obesogenic environment. The mechanisms mediating adaptations in development of the embryo, placenta, fetus and newborn include changes in the maternal metabolic environment. These changes include reductions in a range of maternal counter-regulatory hormones such as cortisol, leptin and insulin. In the sheep, for example, targeted maternal nutrient restriction coincident with the period of maximal placental growth has pronounced effects on the development of the kidney and adipose tissue. As a consequence, the response of these tissues varies greatly following adolescent-onset obesity and ultimately results in these offspring exhibiting all the symptoms of the metabolic syndrome earlier in young adult life. Leptin administration to the offspring after birth can have some long-term differential effects, although much higher amounts are required to cause a response in small compared with large animal models. At the same time, the responsiveness of the offspring is gender dependent, which may relate to the differences in leptin sensitivity around the time of birth. Increasing maternal food intake during pregnancy, either globally or of individual nutrients, has little positive impact on birth weight but does impact on liver development. The challenge now is to establish which components of the maternal diet can be sustainably modified in order to optimise the maternal endocrine environment through pregnancy, thus ensuring feto–placental growth is appropriate in relation to an individual's gender and body composition.