Suboptimal maternal nutrition and body composition are implicated in metabolic disease risk in adult offspring. We hypothesized that modest disruption of glucose homeostasis previously observed in young adult sheep offspring from ewes of a lower body condition score (BCS) would deteriorate with age, due to changes in skeletal muscle structure and insulin signaling mechanisms. Ewes were fed to achieve a lower (LBCS, n = 10) or higher (HBCS, n = 14) BCS before and during pregnancy. Baseline plasma glucose, glucose tolerance and basal glucose uptake into isolated muscle strips were similar in male offspring at 210 ± 4 weeks. Vastus total myofiber density (HBCS, 343 ± 15; LBCS, 294 ± 14 fibers/mm2, P < .05) and fast myofiber density (HBCS, 226 ± 10; LBCS 194 ± 10 fibers/mm2, P < .05), capillary to myofiber ratio (HBCS, 1.5 ± 0.1; LBCS 1.2 ± 0.1 capillary:myofiber, P < .05) were lower in LBCS offspring. Vastus protein levels of Akt1 were lower (83% ± 7% of HBCS, P < .05), and total glucose transporter 4 was increased (157% ± 6% of HBCS, P < .001) in LBCS offspring, Despite the reduction in total myofiber density in LBCS offspring, glucose tolerance was normal in mature adult life. However, such adaptations may lead to complications in metabolic control in an overabundant postnatal nutrient environment.
glucose uptake; myofibers; type 2 diabetes; maternal body condition; skeletal muscle
Maternal vitamin D deficiency has been associated with reduced offspring bone mineral accrual. Retinoid-X Receptor-alpha (RXRA) is an essential cofactor in the action of 1,25(OH)2-vitamin D, and RXRA methylation in umbilical cord DNA has been associated with later offspring adiposity. We tested the hypothesis that RXRA methylation in umbilical cord DNA collected at birth is associated with offspring skeletal development, assessed by dual-energy X-ray absorptiometry, in a population-based mother-offspring cohort (Southampton Women’s Survey). Relationships between maternal plasma 25(OH)-vitamin D concentrations and cord RXRA methylation were also investigated. In 230 children aged 4 years, higher % methylation at 4 out of 6 RXRA CpG sites measured was correlated with lower offspring % bone mineral content (%BMC) (β=−0.02 to −0.04%/SD, p=0.002 to 0.043) and BMC corrected for body size (β=−2.1 to −3.4g/SD, p=0.002 to 0.047), with a further site associated with %BMC only. Similar relationships for %BMC were observed in a second independent cohort (n=64). Maternal free 25(OH)-vitamin D index was negatively associated with methylation at one of these RXRA CpG sites (β=−3.3 SD/unit, p=0.03). In addition to the mechanistic insights afforded by associations between maternal free 25(OH)-vitamin D index, RXRA methylation in umbilical cord DNA, and childhood BMC, such epigenetic marks in early life might represent novel biomarkers for adverse bone outcomes in the offspring.
Epigenetic; methylation; umbilical cord; RXRA; vitamin D; DXA
Reduced fetal growth associates with endothelial dysfunction and cardiovascular risk in both young and adult offspring and the nitric oxide (NO) system has been implicated in these effects. Epigenetic processes are likely to underlie such effects, but there is to date no evidence that endothelial dysfunction in early life results from epigenetic processes on key genes in the NO system, such as NOS3 (eNOS) and ARG2 (arginase-2). We determined basal DNA methylation status in NOS3 and ARG2 promoters, and DNA methyltransferase 1 (DNMT1) effect on eNOS and arginase-2 expression using human endothelial cells isolated from umbilical arteries (HUAEC) and veins (HUVEC) from control and intrauterine growth restricted (IUGR) fetuses. Compared with cells from control pregnancies, eNOS protein and mRNA levels were increased in HUAEC, but decreased in HUVEC, from IUGR, while arginase-2 levels were increased in IUGR-HUVEC. The NOS3 promoter showed a decrease in DNA methylation at CpG -352 in IUGR-HUAEC, and an increase in IUGR-HUVEC, when compared with control cells. Methylation in the hypoxia response element of the NOS3 promoter was increased in IUGR-HUAEC and decreased in HUVEC. Methylation in the AGR2 promoter in IUGR-HUVEC was decreased in a putative HRE, and without changes in IUGR-HUAEC. Silencing of DNMT1 expression normalized eNOS expression in IUGR endothelial cells, and restored the normal response to hypoxia in HUVEC, without effects on arginase-2. This data suggest that eNOS expression in IUGR-derived endothelial cells is programmed by altered DNA methylation, and can be reversed by transient silencing of the DNA methylation machinery.
fetal programming; intrauterine growth restriction; human endothelial cells; eNOS; NOS3; arginase-2; DNA methylation
We examined macrophyte-environment relationships in shallow lakes located within the Prairie Parkland and Laurentian Mixed Forest provinces of Minnesota. Environmental variables included land cover within lake watersheds, and within-lake, water and sediment characteristics. CCA indicated that sediment fraction smaller than 63 μm (f<63), open water area, turbidity, and percent woodland and agricultural cover in watersheds were significant environmental variables explaining 36.6% of variation in macrophyte cover. When Province was added to the analysis as a spatial covariate, these environmental variables explained 30.8% of the variation in macrophyte cover. CCA also indicated that pH, f<63, percent woodland cover in watersheds, open water area, emergent vegetation area, and organic matter content were significant environmental variables explaining 43.5% of the variation in macrophyte biomass. When Province was added to the analysis as a spatial covariate, these environmental variables explained 39.1% of the variation in macrophyte biomass. The f<63 was the most important environmental variable explaining variation for both measures of macrophyte abundance (cover and biomass) when Province was added as a spatial covariate to the models. Percent woodland in watersheds, turbidity, open water area, and Ca+Mg explained 34.5% of the variation in macrophyte community composition. Most species showed a negative relationship with turbidity and open water area except for Potamogeton richardsonii, Stuckenia pectinata, and filamentous algae. Our study further demonstrates the extent to which macrophyte abundance and community composition are related to site- and watershed-scale variables including lake morphology, water and sediment characteristics, and percent land cover of adjacent uplands.
aquatic macrophyte; canonical correspondence analysis; multivariate; land cover; ordination; sediment; shallow lake
Sub-optimal maternal nutrition and body composition are implicated in metabolic disease risk in adult offspring. We hypothesized that modest disruption of glucose homeostasis previously observed in young adult sheep offspring from ewes of a lower body condition score (BCS) would deteriorate with age, due to changes in skeletal muscle structure and insulin signalling mechanisms. Ewes were fed to achieve a lower (L, n=10) or higher (H, n=14) BCS before and during pregnancy. Baseline plasma glucose, glucose tolerance and basal glucose uptake into isolated muscle strips was similar in male offspring at 210±4 weeks. Vastus total myofibre density (HBCS, 343±15; LBCS, 294±14 fibres/mm2, p<0.05) and fast myofibre density (HBCS, 226±10; LBCS 194±10 fibres/mm2, p<0.05), capillary to myofibre ratio (HBCS, 1.5±0.1; LBCS 1.2±0.1 capillary:myofibre, p<0.05) were lower in LBCS offspring. Vastus protein levels of Akt1 were lower (83±7% of HBCS, p<0.05), and total GLUT-4 was increased (157±6% of HBCS, p<0.001) in LBCS offspring, Despite the reduction in total myofibre density in LBCS offspring, glucose tolerance was normal in mature adult life. However such adaptations may lead to complications in metabolic control in an overabundant postnatal nutrient environment.
Glucose uptake; myofibres; type 2 diabetes; maternal body condition; skeletal muscle
Epidemiological and experimental studies suggest early nutrition has long-term effects on susceptibility to obesity, cardiovascular and metabolic diseases. Small and large animal models confirm the influence of different windows of sensitivity, from fetal to early postnatal life, on offspring phenotype. We showed previously that undernutrition in sheep either during the first month of gestation or immediately after weaning induces differential, sex-specific changes in adult metabolic and cardiovascular systems. The current study aims to determine metabolic and molecular changes that underlie differences in lipid and glucose metabolism induced by undernutrition during specific developmental periods in male and female sheep. Ewes received 100% (C) or 50% nutritional requirements (U) from 1–31 days gestation, and 100% thereafter. From weaning (12 weeks) to 25 weeks, offspring were then fed either ad libitum (CC, UC) or were undernourished (CU, UU) to reduce body weight to 85% of their individual target. From 25 weeks, all offspring were fed ad libitum. A cohort of late gestation fetuses were studied after receiving either 40% nutritional requirements (1–31 days gestation) or 50% nutritional requirements (104–127 days gestation). Post-weaning undernutrition increased in vivo insulin sensitivity, insulin receptor and glucose transporter 4 expression in muscle, and lowered hepatic methylation at the delta-like homolog 1/maternally expressed gene 3 imprinted cluster in adult females, but not males. Early gestational undernutrition induced lower hepatic expression of gluconeogenic factors in fetuses and reduced in vivo adipose tissue insulin sensitivity in adulthood. In males, undernutrition in early gestation increased adipose tissue lipid handling mechanisms (lipoprotein lipase, glucocorticoid receptor expression) and hepatic methylation within the imprinted control region of insulin-like growth factor 2 receptor in adulthood. Therefore, undernutrition during development induces changes in mechanisms of lipid and glucose metabolism which differ between tissues and sexes dependent on the period of nutritional restriction. Such changes may increase later life obesity and dyslipidaemia risk.
Fetal and early postnatal development constitutes the most vulnerable time period of human life in regard to adverse effects of environmental hazards. Subtle effects during development can lead to functional deficits and increased disease risk later in life. The hypothesis stating that environmental exposures leads to altered programming and, thereby, to increased susceptibility to disease or dysfunction later in life has garnered much support from both experimental and epidemiological studies. Similar observations have been made on the long-term impact of nutritional unbalance during early development. In an effort to bridge the fields of nutritional and environmental developmental toxicity, the Society of Toxicology sponsored this work. This report summarizes novel findings in developmental toxicity as reported by select invited experts and meeting attendees. Recommendations for the application and improvement of current and future research efforts are also presented.
developmental origins of health and disease; developmental toxicity; early-life exposure.
Poor prenatal nutrition, acting through epigenetic processes, induces persistent changes in offspring phenotype. We investigated the effect of maternal fat intake on polyunsaturated fatty acid (PUFA) status and on the epigenetic regulation of Fads2, encoding Δ6 desaturase (rate limiting in PUFA synthesis), in the adult offspring. Rats (n=6 per dietary group) were fed either 3.5% (w/w), 7% (w/w) or 21% (w/w) butter or fish oil (FO) from 14 days preconception until weaning. Offspring (n=6 males and females per dietary group) were fed 4% (w/w) soybean oil until postnatal day 77. 20:4n-6 and 22:6n-3 levels were lower in liver phosphatidylcholine (PC) and phosphatidylethanolamine and plasma PC (all P<.0001) in offspring of dams fed 21% than 3.5% or 7% fat regardless of type. Hepatic Fads2 expression related inversely to maternal dietary fat. Fads2 messenger RNA expression correlated negatively with methylation of CpGs at −623, −394, −84 and −76 bases relative to the transcription start site (all P<.005). Methylation of these CpGs was higher in offspring of dams fed 21% than 3.5% or 7% fat; FO higher than butter. Feeding adult female rats 7% fat reduced 20:4n-6 status in liver PC and Fads2 expression and increased methylation of CpGs −623, −394, −84 and −76 that reversed in animals switched from 7% to 4% fat diets. These findings suggest that fat exposure during development induces persistent changes, while adults exhibit a transient response, in hepatic PUFA status in offspring through epigenetic regulation of Fads2. Thus, epigenetic regulation of Fads2 may contribute to short- and long-term regulation of PUFA synthesis.
Maternal dietary fat; Early life programming; Liver; Arachidonic acid; Docosahexaenoic acid; Δ6 desaturase
The genes encoding nuclear receptors comprise multiple 5′untranslated exons, which give rise to several transcripts encoding the same protein, allowing tissue-specific regulation of expression. Both human and mouse peroxisome proliferator activated receptor (PPAR) α genes have multiple promoters, although their function is unknown. Here we have characterised the rat PPARα promoter region and have identified three alternative PPARα transcripts, which have different transcription start sites owing to the utilisation of distinct first exons. Moreover these alternative PPARα transcripts were differentially expressed between adipose tissue and liver. We show that while the major adipose (P1) and liver (P2) transcripts were both induced by dexamethasone, they were differentially regulated by the PPARα agonist, clofibric acid, and leptin. Leptin had no effect on the adipose-specific P1 transcript, but induced liver-specific P2 promoter activity via a STAT3/Sp1 mechanism. Moreover in Wistar rats, leptin treatment between postnatal day 3–13 led to an increase in P2 but not P1 transcription in adipose tissue which was sustained into adulthood. This suggests that the expression of the alternative PPARα transcripts are in part programmed by early life exposure to leptin leading to persistent change in adipose tissue fatty acid metabolism through specific activation of a quiescent PPARα promoter. Such complexity in the regulation of PPARα may allow the expression of PPARα to be finely regulated in response to environmental factors.
People who were small at birth and had poor infant growth have an increased risk of adult cardiovascular disease, osteoporosis and type 2 diabetes, particularly if their restricted early growth is followed by increased childhood weight gain. These relations extend across the normal range of birth size in a graded manner, so reduced size is not a prerequisite. In addition larger birth size is associated with risks of obesity and type 2 diabetes. The associations appear to reflect developmental plastic responses made by the fetus and infant based on cues about the environment, influenced by maternal characteristics including diet, body composition, stress and exercise levels. These responses involve epigenetic processes which modify the offspring’s phenotype. Vulnerability to ill-health results if the environment in infancy, childhood and later life is mismatched to the phenotype induced in development, informed by the developmental cues. This mismatch may arise through unbalanced diet or body composition of the mother, or change in lifestyle factors between generations. These insights offer new possibilities for early diagnosis and prevention of chronic disease.
Nutrition; fetal growth; metabolic disease; epigenetics
Our previous work has shown associations between childhood adiposity and perinatal methylation status of several genes in umbilical cord tissue, including endothelial nitric oxide synthase (eNOS). There is increasing evidence that eNOS is important in bone metabolism; we therefore related the methylation status of the eNOS gene promoter in stored umbilical cord to childhood bone size and density in a group of 9-year old children.
We used Sequenom MassARRAY to assess the methylation status of 2 CpGs in the eNOS promoter, identified from our previous study, in stored umbilical cords of 66 children who formed part of a Southampton birth cohort and who had measurements of bone size and density at age 9 years (Lunar DPXL DXA instrument).
Percentage methylation varied greatly between subjects. For one of the two CpGs, eNOS chr7:150315553+, after taking account of age and sex there was a strong positive association between methylation status and the child’s whole body bone area (r=0.28,p=0.02), bone mineral content (r=0.34,p=0.005) and areal bone mineral density (r=0.34,p=0.005) at age 9 years. These associations were independent of previously documented maternal determinants of offspring bone mass.
Our findings suggest an association between methylation status at birth of a specific CpG within the eNOS promoter and bone mineral content in childhood. This supports a role for eNOS in bone growth and metabolism and implies that its contribution may at least in part occur during early skeletal development.
Epigenetic; methylation; umbilical cord; eNOS; DXA
The discharge of complex mixtures of nutrients, organic micropollutants, and antibiotic resistance genes from treated municipal wastewater into freshwater systems are global concerns for human health and aquatic organisms. Antibiotic resistance genes (ARGs) are genes that have the ability to impart resistance to antibiotics and reduce the efficacy of antibiotics in the systems in which they are found. In the rural community of Grand Marais, Manitoba, Canada, wastewater is treated passively in a sewage lagoon prior to passage through a treatment wetland and subsequent release into surface waters. Using this facility as a model system for the Canadian Prairies, the two aims of this study were to assess: (a) the presence of nutrients, micropollutants (i.e., pesticides, pharmaceuticals), and ARGs in lagoon outputs, and (b) their potential removal by the treatment wetland prior to release to surface waters in 2012.
As expected, concentrations of nitrogen and phosphorus species were greatest in the lagoon and declined with movement through the wetland treatment system. Pharmaceutical and agricultural chemicals were detected at concentrations in the ng/L range. Concentrations of these compounds spiked downstream of the lagoon following discharge and attenuation was observed as the effluent migrated through the wetland system. Hazard quotients calculated for micropollutants of interest indicated minimal toxicological risk to aquatic biota, and results suggest that the wetland attenuated atrazine and carbamazepine significantly. There was no significant targeted removal of ARGs in the wetland and our data suggest that the bacterial population in this system may have genes imparting antibiotic resistance.
The results of this study indicate that while the treatment wetland may effectively attenuate excess nutrients and remove some micropollutants and bacteria, it does not specifically target ARGs for removal. Additional studies would be beneficial to determine whether upgrades to extend retention time or alter plant community structure within the wetland would optimize removal of micropollutants and ARGs to fully characterize the utility of these systems on the Canadian Prairies.
Sewage lagoon; Wastewater; Treatment wetland; Antibiotic resistance genes; Pesticides; Pharmaceuticals
To determine the impact of maternal and post-weaning consumption of a high fat diet on endothelium-dependent vasorelaxation and redox regulation in adult male mouse offspring.
Female C57BL6J mice were fed an obesogenic high fat diet (HF, 45% kcal fat) or standard chow (C, 21% kcal fat) pre-conception and throughout pregnancy and lactation. Post-weaning, male offspring were continued on the same diet as their mothers or placed on the alternative diet to give 4 dietary groups (C/C, HF/C, C/HF and HF/HF) which were studied at 15 or 30 weeks of age.
There were significant effects of maternal diet on offspring body weight (p<0.004), systolic blood pressure (p = 0.026) and endothelium-dependent relaxation to ACh (p = 0.004) and NO production (p = 0.005) measured in the femoral artery. With control for maternal diet there was also an effect of offspring post-weaning dietary fat to increase systolic blood pressure (p<0.0001) and reduce endothelium-dependent relaxation (p = 0.022) and ACh-mediated NO production (p = 0.007). There was also a significant impact of age (p<0.005). Redox balance was perturbed, with altered regulation of vascular enzymes involved in ROS/NO signalling.
Maternal consumption of a HF diet is associated with changes in vascular function and oxidative balance in the offspring of similar magnitude to those seen with consumption of a high fat diet post-weaning. Further, this disadvantageous vascular phenotype is exacerbated by age to influence the risk of developing obesity, raised blood pressure and endothelial dysfunction in adult life.
The global burden of diabetes and other non-communicable diseases is rising dramatically worldwide and is causing a double poor health burden in low- and middle-income countries. Early life influences play an important part in this scenario because maternal lifestyle and conditions such as gestational diabetes and obesity affect the risk of diabetes in the next generation. This indicates important periods during the lifecourse when interventions could have powerful affects in reducing incidence of non-communicable diseases. However, interventions to promote diet and lifestyle in prospective parents before conception have not received sufficient attention, especially in low- and middle-income countries undergoing socio-economic transition.
Interventions to produce weight loss in adults or to reduce weight gain in pregnancy have had limited success and might be too late to produce the largest effects on the health of the child and his/her later risk of non-communicable diseases. A very important factor in the prevention of the developmental component of diabetes risk is the physiological state in which the parents enter pregnancy. We argue that the most promising strategy to improve prospective parents’ body composition and lifestyle is the promotion of health literacy in adolescents. Multiple but integrated forms of community-based interventions that focus on nutrition, physical activity, family planning, breastfeeding and infant feeding practices are needed. They need to address the wider social economic context in which adolescents live and to be linked with existing public health programmes in sexual and reproductive health and maternal and child health initiatives.
Interventions aimed at ensuring a healthy body composition, diet and lifestyle before pregnancy offer a most effective solution in many settings, especially in low- and middle-income countries undergoing socio-economic transition. Preparing a mother, her partner and her future child for “the 1000 days”, whether from planned or unplanned conception would break the cycle of risk and demonstrate benefit in the shortest possible time. Such interventions will be particularly important in adolescents and young women in disadvantaged groups and can improve the physiological status of the fetus as well as reduce the prevalence of pregnancy conditions such as gestational diabetes mellitus which both predispose to non-communicables diseases in both the mother and her child. Pre-conception interventions require equipping prospective parents with the necessary knowledge and skills to make healthy lifestyle choices for themselves and their children. Addressing the promotion of such health literacy in parents-to-be in low- and middle-income countries requires a wider social perspective. It requires a range of multisectoral agencies to work together and could be linked to the issues of women’s empowerment, to reproductive health, to communicable disease prevention and to the Millennium Development Goals 4 and 5.
Adolescents; Diabetes; Health literacy; Interventions; Life-course; Non-communicable diseases; Gestational diabetes mellitus; Obesity
Constraints on lake communities are complex and are usually studied by using limited combinations of variables derived from measurements within or adjacent to study waters. While informative, results often provide limited insight about magnitude of simultaneous influences operating at multiple scales, such as lake- vs. watershed-scale. To formulate comparisons of such contrasting influences, we explored factors controlling the abundance of predominant aquatic invertebrates in 75 shallow lakes in western Minnesota, USA. Using robust regression techniques, we modeled relative abundance of Amphipoda, small and large cladocera, Corixidae, aquatic Diptera, and an aggregate taxon that combined Ephemeroptera-Trichoptera-Odonata (ETO) in response to lake- and watershed-scale characteristics. Predictor variables included fish and submerged plant abundance, linear distance to the nearest wetland or lake, watershed size, and proportion of the watershed in agricultural production. Among-lake variability in invertebrate abundance was more often explained by lake-scale predictors than by variables based on watershed characteristics. For example, we identified significant associations between fish presence and community type and abundance of small and large cladocera, Amphipoda, Diptera, and ETO. Abundance of Amphipoda, Diptera, and Corixidae were also positively correlated with submerged plant abundance. We observed no associations between lake-watershed variables and abundance of our invertebrate taxa. Broadly, our results seem to indicate preeminence of lake-level influences on aquatic invertebrates in shallow lakes, but historical land-use legacies may mask important relationships.
Among primates, human neonates have the largest brains but also the highest proportion of body fat. If placental nutrient supply is limited, the fetus faces a dilemma: should resources be allocated to brain growth, or to fat deposition for use as a potential postnatal energy reserve? We hypothesised that resolving this dilemma operates at the level of umbilical blood distribution entering the fetal liver. In 381 uncomplicated pregnancies in third trimester, we measured blood flow perfusing the fetal liver, or bypassing it via the ductus venosus to supply the brain and heart using ultrasound techniques. Across the range of fetal growth and independent of the mother's adiposity and parity, greater liver blood flow was associated with greater offspring fat mass measured by dual-energy X-ray absorptiometry, both in the infant at birth (r = 0.43, P<0.001) and at age 4 years (r = 0.16, P = 0.02). In contrast, smaller placentas less able to meet fetal demand for essential nutrients were associated with a brain-sparing flow pattern (r = 0.17, p = 0.02). This flow pattern was also associated with a higher degree of shunting through ductus venosus (P = 0.04). We propose that humans evolved a developmental strategy to prioritize nutrient allocation for prenatal fat deposition when the supply of conditionally essential nutrients requiring hepatic inter-conversion is limited, switching resource allocation to favour the brain if the supply of essential nutrients is limited. Facilitated placental transfer mechanisms for glucose and other nutrients evolved in environments less affluent than those now prevalent in developed populations, and we propose that in circumstances of maternal adiposity and nutrient excess these mechanisms now also lead to prenatal fat deposition. Prenatal developmental influences play important roles in the human propensity to deposit fat.
This White Paper highlights the developmental period as a plastic phase, which allows the organism to adapt to changes in the environment to maintain or improve reproductive capability in part through sustained health. Plasticity is more prominent prenatally and during early postnatal life, i.e., during the time of cell differentiation and specific tissue formation. These developmental periods are highly sensitive to environmental factors, such as nutrients, environmental chemicals, drugs, infections and other stressors. Nutrient and toxicant effects share many of the same characteristics and reflect two sides of the same coin. In both cases, alterations in physiological functions can be induced and may lead to the development of non-communicable conditions. Many of the major diseases – and dysfunctions – that have increased substantially in prevalence over the last 40 years seem to be related in part to developmental factors associated with either nutritional imbalance or exposures to environmental chemicals. The Developmental Origins of Health and Disease (DOHaD) concept provides significant insight into new strategies for research and disease prevention and is sufficiently robust and repeatable across species, including humans, to require a policy and public health response. This White Paper therefore concludes that, as early development (in utero and during the first years of postnatal life) is particularly sensitive to developmental disruption by nutritional factors or environmental chemical exposures, with potentially adverse consequences for health later in life, both research and disease prevention strategies should focus more on these vulnerable life stages.
Environmental exposure; Fetal development; Non-communicable disease; Nutritional requirements; Prenatal exposure delayed effects
Fixed genomic variation explains only a small proportion of the risk of adiposity. In animal models, maternal diet alters offspring body composition, accompanied by epigenetic changes in metabolic control genes. Little is known about whether such processes operate in humans.
RESEARCH DESIGN AND METHODS
Using Sequenom MassARRAY we measured the methylation status of 68 CpGs 5′ from five candidate genes in umbilical cord tissue DNA from healthy neonates. Methylation varied greatly at particular CpGs: for 31 CpGs with median methylation ≥5% and a 5–95% range ≥10%, we related methylation status to maternal pregnancy diet and to child’s adiposity at age 9 years. Replication was sought in a second independent cohort.
In cohort 1, retinoid X receptor-α (RXRA) chr9:136355885+ and endothelial nitric oxide synthase (eNOS) chr7:150315553+ methylation had independent associations with sex-adjusted childhood fat mass (exponentiated regression coefficient [β] 17% per SD change in methylation [95% CI 4–31], P = 0.009, n = 64, and β = 20% [9–32], P < 0.001, n = 66, respectively) and %fat mass (β = 10% [1–19], P = 0.023, n = 64 and β =12% [4–20], P = 0.002, n = 66, respectively). Regression analyses including sex and neonatal epigenetic marks explained >25% of the variance in childhood adiposity. Higher methylation of RXRA chr9:136355885+, but not of eNOS chr7:150315553+, was associated with lower maternal carbohydrate intake in early pregnancy, previously linked with higher neonatal adiposity in this population. In cohort 2, cord eNOS chr7:150315553+ methylation showed no association with adiposity, but RXRA chr9:136355885+ methylation showed similar associations with fat mass and %fat mass (β = 6% [2–10] and β = 4% [1–7], respectively, both P = 0.002, n = 239).
Our findings suggest a substantial component of metabolic disease risk has a prenatal developmental basis. Perinatal epigenetic analysis may have utility in identifying individual vulnerability to later obesity and metabolic disease.
Severe acute malnutrition in childhood manifests as oedematous (kwashiorkor, marasmic kwashiorkor) and non-oedematous (marasmus) syndromes with very different prognoses. Kwashiorkor differs from marasmus in the patterns of protein, amino acid and lipid metabolism when patients are acutely ill as well as after rehabilitation to ideal weight for height. Metabolic patterns among marasmic patients define them as metabolically thrifty, while kwashiorkor patients function as metabolically profligate. Such differences might underlie syndromic presentation and prognosis. However, no fundamental explanation exists for these differences in metabolism, nor clinical pictures, given similar exposures to undernutrition. We hypothesized that different developmental trajectories underlie these clinical-metabolic phenotypes: if so this would be strong evidence in support of predictive adaptation model of developmental plasticity.
We reviewed the records of all children admitted with severe acute malnutrition to the Tropical Metabolism Research Unit Ward of the University Hospital of the West Indies, Kingston, Jamaica during 1962–1992. We used Wellcome criteria to establish the diagnoses of kwashiorkor (n = 391), marasmus (n = 383), and marasmic-kwashiorkor (n = 375). We recorded participants' birth weights, as determined from maternal recall at the time of admission. Those who developed kwashiorkor had 333 g (95% confidence interval 217 to 449, p<0.001) higher mean birthweight than those who developed marasmus.
These data are consistent with a model suggesting that plastic mechanisms operative in utero induce potential marasmics to develop with a metabolic physiology more able to adapt to postnatal undernutrition than those of higher birthweight. Given the different mortality risks of these different syndromes, this observation is supportive of the predictive adaptive response hypothesis and is the first empirical demonstration of the advantageous effects of such a response in humans. The study has implications for understanding pathways to obesity and its cardio-metabolic co-morbidities in poor countries and for famine intervention programs.
Nutrition during development affects risk of future cardiovascular disease. Relatively little is known about whether the amount and type of fat in the maternal diet affect vascular function in the offspring. To investigate this, pregnant and lactating rats were fed either 7%(w/w) or 21%(w/w) fat enriched in either18:2n-6, trans fatty acids, saturated fatty acids, or fish oil. Their offspring were fed 4%(w/w) soybean oil from weaning until day 77. Type and amount of maternal dietary fat altered acetylcholine (ACh)-mediated vaso-relaxation in offspring aortae and mesenteric arteries, contingent on sex. Amount, but not type, of maternal dietary fat altered phenylephrine (Pe)-induced vasoconstriction in these arteries. Maternal 21% fat diet decreased 20:4n-6 concentration in offspring aortae. We investigated the role of Δ6 and Δ5 desaturases, showing that their inhibition in aortae and mesenteric arteries reduced vasoconstriction, but not vaso-relaxation, and the synthesis of specific pro-constriction eicosanoids. Removal of the aortic endothelium did not alter the effect of inhibition of Δ6 and Δ5 desaturases on Pe-mediated vasoconstriction. Thus arterial smooth muscle 20:4n-6 biosynthesis de novo appears to be important for Pe-mediated vasoconstriction. Next we studied genes encoding these desaturases, finding that maternal 21% fat reduced Fads2 mRNA expression and increased Fads1 in offspring aortae, indicating dysregulation of 20:4n-6 biosynthesis. Methylation at CpG −394 bp 5′ to the Fads2 transcription start site predicted its expression. This locus was hypermethylated in offspring of dams fed 21% fat. Pe treatment of aortae for 10 minutes increased Fads2, but not Fads1, mRNA expression (76%; P<0.05). This suggests that Fads2 may be an immediate early gene in the response of aortae to Pe. Thus both amount and type of maternal dietary fat induce altered regulation of vascular tone in offspring though differential effects on vaso-relaxation, and persistent changes in vasoconstriction via epigenetic processes controlling arterial polyunsaturated fatty acid biosynthesis.