Birth weight of offspring, maternal pre-pregnancy characteristics, and mortality of mothers: the Jerusalem perinatal study cohort

Obesity risk in young adults from the Jerusalem Perinatal Study (JPS): the contribution of polygenic risk and early life exposure

BACKGROUND/OBJECTIVES

The effects of early life exposures on offspring life-course health are well established. This study assessed whether adding early socio-demographic and perinatal variables to a model based on polygenic risk score (PRS) improves prediction of obesity risk.

METHODS

We used the Jerusalem Perinatal study (JPS) with data at birth and body mass index (BMI) and waist circumference (WC) measured at age 32. The PRS was constructed using over 2.1M common SNPs identified in genome-wide association study (GWAS) for BMI. Linear and logistic models were applied in a stepwise approach. We first examined the associations between genetic variables and obesity-related phenotypes (e.g., BMI and WC). Secondly, socio-demographic variables were added and finally perinatal exposures, such as maternal pre-pregnancy BMI (mppBMI) and gestational weight gain (GWG) were added to the model. Improvement in prediction of each step was assessed using measures of model discrimination (area under the curve, AUC), net reclassification improvement (NRI) and integrated discrimination improvement (IDI).

RESULTS

One standard deviation (SD) change in PRS was associated with a significant increase in BMI (β = 1.40) and WC (β = 2.45). These associations were slightly attenuated (13.7-14.2%) with the addition of early life exposures to the model. Also, higher mppBMI was associated with increased offspring BMI (β = 0.39) and WC (β = 0.79) (p < 0.001). For obesity (BMI ≥ 30) prediction, the addition of early socio-demographic and perinatal exposures to the PRS model significantly increased AUC from 0.69 to 0.73. At an obesity risk threshold of 15%, the addition of early socio-demographic and perinatal exposures to the PRS model provided a significant improvement in reclassification of obesity (NRI, 0.147; 95% CI 0.068-0.225).

CONCLUSIONS

Inclusion of early life exposures, such as mppBMI and maternal smoking, to a model based on PRS improves obesity risk prediction in an Israeli population-sample.

Perinatal exposures and adolescence overweight: The role of shared maternal-offspring pathways

BACKGROUND AND AIMS

Early life exposures affect offspring health across the life-course. We aimed to examine whether prevalent perinatal exposures and obstetric complications are independently associated with offspring overweight in adolescence. We then assessed whether shared maternal-offspring pathways drive the association of perinatal exposures with offspring overweight.

METHODS

Using data from the Jerusalem Perinatal Study birth cohort, two perinatal scores were constructed: obstetric complications (OC) and prevalent perinatal exposures (PPE) scores. PPE score, generated by principal component analysis, included three primary components. Logistic regressions were used to assess associations of scores with offspring overweight, with and without adjustment for maternal life-course survival.

RESULTS

OC and PPE scores were independently associated with offspring overweight (OROC = 1.15, 95%CI:1.07,1.25; ORPPE1- SEP and lifestyle = 0.85, 95%CI:0.79,0.91; ORPPE2- Maternal body size = 1.20, 95%CI: 1.13,1.28; ORPPE3-Fetal growth = 1.18, 95%CI:1.11,1.26). Maternal survival was associated with offspring overweight (OR = 1.38, 95%CI:1.08,1.76), yet introducing PPE score to the same model attenuated this association (OR = 1.16, 95%CI:0.90, 1.49). When OC score and maternal survival were included in the same model, their associations with offspring overweight remained unchanged.

CONCLUSIONS

Mother-offspring shared factors, captured by maternal life-course survival, underlie the effect of prevalent perinatal exposures on offspring overweight. However, the effect of obstetric complications was independent, highlighting the contribution of additional pathways.

Obesity Prediction in Young Adults from the Jerusalem Perinatal Study: Contribution of Polygenic Risk and Early Life Exposures

We assessed whether adding early life exposures to a model based on polygenic risk score (PRS) improves prediction of obesity risk. We used a birth cohort with data at birth and BMI and waist circumference (WC) measured at age 32. The PRS was composed of SNPs identified in GWAS for BMI. Linear and logistic models were used to explore associations with obesity-related phenotypes. Improvement in prediction was assessed using measures of model discrimination (AUC), and net reclassification improvement (NRI). One SD change in PRS was associated with a significant increase in BMI and WC. These associations were slightly attenuated (13.7%-14.2%) with the addition of early life exposures to the model. Also, higher maternal pre-pregnancy BMI was associated with increase in offspring BMI and WC (p<0.001). For prediction obesity (BMI ≥ 30), the addition of early life exposures to the PRS model significantly increase the AUC from 0.69 to 0.73. At an obesity risk threshold of 15%, the addition of early life exposures to the PRS model provided a significant improvement in reclassification of obesity (NRI, 0.147; 95% CI 0.068-0.225). We conclude that inclusion of early life exposures to a model based on PRS improves obesity risk prediction in an Israeli population-sample.

Preterm delivery and long term mortality in women: national cohort and co-sibling study

OBJECTIVES

To examine the long term mortality associated with preterm delivery in a large population based cohort of women, and to assess for potential confounding by shared familial factors.

DESIGN

National cohort study.

SETTING

Sweden.

PARTICIPANTS

All 2 189 477 women with a singleton delivery in 1973-2015.

MAIN OUTCOME MEASURES

All cause and cause specific mortality up to 2016, identified from nationwide death records. Cox regression was used to calculate hazard ratios while adjusting for confounders, and co-sibling analyses assessed the potential influence of unmeasured shared familial (genetic and environmental) factors.

RESULTS

In 50.7 million person years of follow-up, 76 535 (3.5%) women died (median age at death was 57.6). In the 10 years after delivery, the adjusted hazard ratio for all cause mortality associated with preterm delivery (<37 weeks) was 1.73 (95% confidence interval 1.61 to 1.87), and when further stratified was 2.20 (1.63 to 2.96) for extremely preterm delivery (22-27 weeks), 2.28 (2.01 to 2.58) for very preterm delivery (28-33 weeks), 1.52 (1.39 to 1.67) for late preterm delivery (34-36 weeks), and 1.19 (1.12 to 1.27) for early term delivery (37-38 weeks) compared with full term delivery (39-41 weeks). These risks declined but remained significantly raised after longer follow-up times: for preterm versusfull term births, 10-19 years after delivery, the adjusted hazard ratio was 1.45 (95% confidence interval 1.37 to 1.53); 20-44 years after delivery, the adjusted hazard ratio was 1.37 (1.33 to 1.41). These findings did not seem to be attributable to shared genetic or environmental factors within families. Several causes were identified, including cardiovascular and respiratory disorders, diabetes, and cancer.

CONCLUSIONS

In this large national cohort of women, the findings suggested that preterm and early term delivery were independent risk factors for premature mortality from several major causes. These associations declined over time but remained raised up to 40 years later.

Female offspring birth weight is associated with Body Mass Index, waist circumference and metabolic syndrome in Latin American women at 10-years postpartum

AIMS

We aimed to assess whether female offspring birth weight (BW) is associated with anthropometric and metabolic outcomes in Chilean mothers at 10-years postpartum.

METHODS

We assessed data from 396 Chilean mother-daughter pairs participating in the longitudinal Chilean Growth and Obesity Cohort (GOCS) and Determinants of Breast Cancer Risk (DERCAM) studies. Multivariate linear and logistic regression models were performed to associate female offspring BW with maternal Body Mass Index (BMI), waist circumference, type 2 diabetes mellitus, metabolic syndrome and its components at 10-years postpartum.

RESULTS

At 10-years postpartum, 69% of mothers were overweight, 65% had central adiposity and 26% had metabolic syndrome. Adjusted linear regression models showed associations between female offspring BW and (1) maternal BMI (%Δ GM = 4.46; 95% CI 0.25-8.85); and (2) waist circumference (%Δ GM = 3.25; 95% CI 0-6.60). Adjusted logistic regression models showed associations between female offspring BW and (1) maternal metabolic syndrome (OR = 3.48; 95% CI 1.50-8.11); (2) central adiposity (OR = 2.37; 95% CI 1.08-5.22); and (3) hypertriglyceridemia (OR = 3.19; 95% CI 1.40-7.23).

CONCLUSIONS

Female offspring BW was associated with maternal anthropometric and metabolic outcomes at 10-years postpartum. Our findings add to the emerging evidence that offspring BW might be a potential indicator for future maternal anthropometric and metabolic risks.

Offspring birth weight and cardiovascular mortality among parents: the role of cardiovascular risk factors

An inverse association between offspring birth weight (BW) and higher risk of parental cardiovascular disease (CVD) mortality and morbidity has been reported. Shared environmental, genetic and intrauterine factors may be responsible for explaining these associations. We studied the role of parental CVD risk factors in the association between offspring BW and CVD mortality among mothers and fathers. All births registered in Medical Birth Registry Norway (1967–2012) were linked to three health surveys, National Educational Registry and Cause of Death Registry. Number of births with information of parental CVD risk factors available for the analyses was 1,006,557 (520,670 for mothers and 485,887 for fathers). Cox proportional hazards regression models were used, following CVD deaths in parents from 1974 to 2012. An inverse association between offspring BW and CVD mortality was observed among both parents: hazard ratio 1.60 (1.44–1.75) for mothers and 1.16 (1.10–1.23) for fathers. Among mothers, adjustment for smoking, triglycerides and diabetes reduced the risk to 1.36 (1.25–1.52), 1.57 (1.43–1.73) and 1.58 (1.43–1.79), respectively. Adjustment for diastolic blood pressure (DBP) and systolic blood pressure (SBP) both reduced the risk to 1.53 (1.37–1.66). Among fathers, adjustments for smoking, DBP, SBP reduced the risk to 1.08 (1.02–1.15), 1.13 (1.06–1.19) and 1.14 (1.08–1.22), respectively. Triglycerides and diabetes both reduced the risk to 1.15 (1.09–1.12). Our results indicate that shared environmental factors might be important in the association. A stronger association in mothers suggest that intrauterine factors also are at play.

Conjoint Associations of Gestational Diabetes and Hypertension With Diabetes, Hypertension, and Cardiovascular Disease in Parents: A Retrospective Cohort Study

The conjoint association of gestational diabetes mellitus (GDM) and gestational hypertension (GH) with cardiometabolic disease has not been well studied. We evaluated a combined GDM/GH risk indicator in both mothers and fathers because of shared spousal behaviors and environments. In the present population-based retrospective cohort study, GH was identified in matched pairs of mothers with GDM or without GDM (matched on age group, health region, and year of delivery) who had singleton live births in Quebec, Canada (1990–2007). A total of 64,232 couples were categorized based on GDM/GH status (neither, either, or both). Associations with diabetes, hypertension, and a composite of cardiovascular disease (CVD) and mortality were evaluated using Cox proportional hazard models (from 12 weeks postpartum to March 2012). Compared with having neither GDM nor GH, having either was associated with incident diabetes (hazard ratio (HR) = 14.7, 95% confidence interval (CI): 12.9, 16.6), hypertension (HR = 1.9, 95% CI: 1.8, 2.0), and CVD/mortality (HR = 1.4, 95% CI: 1.2, 1.7). We found associations of greater magnitude among participants who had both (for diabetes, HR = 36.9, 95% CI: 26.0, 52.3; for hypertension, HR = 5.7, 95% CI: 4.9, 6.7; and for CVD/mortality, HR = 2.4, 95% CI: 1.6, 3.5). Associations with diabetes were also observed in fathers (for either, HR = 1.2, 95% CI: 1.1, 1.3; for both, HR = 1.8, 95% CI: 1.4, 2.3). In conclusion, we found associations of a combined GDM/GH indicator with cardiometabolic disease in mothers and with diabetes in fathers, with stronger associations when both GDM and GH were present.

Study of resilience and environmental adversity in midlife health (STREAM)

PURPOSE

The Jerusalem study of resilience and environmental adversity in midlife health (STREAM) was established to examine the prevalence of common mental and physical health issues in mid-adulthood in the inner city of Jerusalem, and to examine their association with lifespan psychosocial factors of vulnerability and resilience.

METHOD

Participants were 811 randomly selected individuals from 7000 individuals who were born and grew up in inner-Jerusalem. Participants were 34-44 years old during first wave of STREAM assessment. Initial telephone surveys took place in 2007-2008 and participants were followed-up for a second survey 1 year later. Upon funding, a new wave is planned for 2017-2018. Survey topics comprised common health problems (e.g., type 2 diabetes/migraine), health markers (e.g., BMI), and psychiatric vulnerabilities (e.g., anxiety, post-traumatic stress, depressive symptoms, psychosis). Other measures included socioeconomic status, creativity, life style behavior (e.g., smoking, exercise), social contact and adaptation to change. Survey data were retrospectively merged with data of national registry sources that included adverse psychosocial factors, psychiatric and social measures assessed across all developmental stages through midlife. This includes data available on birth factors, school achievement and adjustment, cognitive and behavioral functioning during young adulthood, psychiatric hospitalizations, immigration and socioeconomic status.

RESULTS

Results on health outcomes of the first STREAM wave indicate that prevalence rates of health problems are comparable to recent World Mental Health Surveys.

CONCLUSIONS

Apart from measures on adverse psychosocial factors, STREAM provides a cohort to examine resilience to developing health problems and having a poor health and functional outcome.

Grandparental morbidity and mortality patterns are associated with infant birth weight in the Lifeways cross-generation cohort study 2001-2010

The association of infants' birth weight with maternal cardiovascular morbidity (CVD) and mortality substantiates the foetal origins hypothesis. Few studies to date have investigated grandparent-infant risk association. We prospectively examined this relationship in the Lifeways three-generation familial cohort, contrasting lineage and gender differences to understand mechanisms of intergenerational risk transmission. In 2001, a cohort of 1082 families was established at antenatal stage. A total of 539 families (n = 539 infants) had both a participating grandparent (n = 1054) and information on infants' gestational age. At baseline, grandparents provided their diagnosed CVD status and 79% also underwent a cardiovascular risk factors assessment. In 2005, general practitioners provided an update for 61% grandparents. In 2010, a search of civil register confirmed 77 grandparental deaths in 539 families. Grandchildren's birth weight and grandparental cardiovascular risk factors associations were examined with linear regressions. Grandparental CVD associations were analysed using ANCOVA. Cox proportional hazard ratios (HR) were calculated for all-cause mortality associations. Models were adjusted for infants', mothers' and grandparents' demographic, anthropometric and socio-behavioural characteristics, as appropriate. The paternal grandfathers' (PGF) systolic blood pressure (mmHg) [β (95% CI) = 6.6 (0.8 - 12.5); P = 0.03] and paternal grandmothers' serum triglycerides (mmol/l) [β (95% CI) = 78.8 (7.0 - 150.7); P = 0.03] were linearly predictive of infants' birth weight, which was not observed for maternal grandparents. Mean birth weight for infants of maternal grandmothers with diabetes {-272.7 [(-499.7) - (-45.6)] g; P = 0.02} or stroke {-292.1 [(-544.5) - (-39.6)] g; P = 0.02} was lower than those without diabetes or stroke, a pattern not observed for paternal grandparents. Whereas PGFs' mortality was significantly associated with infants' high birth weight (≥4000 g) [HR (95% CI) = 4.9 (1.2 - 19.9); P = 0.03], maternal grandparents' mortality showed a converse pattern with infants' low birth weight (<2500 g) [HR (95% CI) = 1.7 (0.4 - 8.2); P = 0.7], although not statistically significant. These findings suggest that intergenerational transmission of risk differs in maternal and paternal lines.

Premature aging of leukocyte DNA methylation is associated with type 2 diabetes prevalence

Background

Type 2 diabetes mellitus (T2D) is highly prevalent in Middle-Eastern and North African Arab populations, but the molecular basis for this susceptibility is unknown. Altered DNA methylation levels were reported in insulin-secreting and responding tissues, but whether methylation in accessible tissues such as peripheral blood is associated with T2D risk remains an open question. Age-related alteration of DNA methylation level was reported in certain methylation sites, but no association with T2D has been shown. Here we report on a population-based study of 929 men and women representing the East Jerusalem Palestinian (EJP) Arab population and compare with the findings among Israeli Ashkenazi Jews. This is the first reported epigenetic study of an Arab population with a characteristic high prevalence of T2D.

Results

We found that DNA methylation of a prespecified regulatory site in peripheral blood leukocytes (PBLs) is associated with impaired glucose metabolism and T2D independent of sex, body mass index, and white blood cell composition. This CpG site (Chr16: 53,809,231-2; hg19) is located in a region within an intron of the FTO gene, suspected to serve as a tissue-specific enhancer. The association between PBL hypomethylation and T2D varied by age, revealing differential patterns of methylation aging in healthy and diabetic individuals and between ethnic groups: T2D patients displayed prematurely low methylation levels, and this hypomethylation was greater and occurred earlier in life among Palestinian Arabs than Ashkenazi Jews.

Conclusions

Our study suggests that premature DNA methylation aging is associated with increased risk of T2D. These findings should stimulate the search for more such sites and may pave the way to improved T2D risk prediction within and between human populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0069-1) contains supplementary material, which is available to authorized users.

Antenatal Care Services Utilization in Yobe State, Nigeria: Examining Predictors and Barriers

OBJECTIVE

In Nigeria, wide disparities exist between the different parts of the country, with the states in the North East zone having poor health resources. The objective of this study is to assess whether women's biological, sociocultural, and economic characteristics are associated with utilization of ante natal care services as measured by number of antenatal care (ANC) visits in Yobe State.

METHODS

This is a secondary data analysis of the 2008 Nigeria Demographic and Health Survey with records from 33,385 women between 15-49 years who had given birth between January 2003 and December 2008 in Yobe State. Bivariate Pearson's Chi square test and two stages of Multivariate regression analysis were conducted.

RESULTS

Women with at least primary level education (adjusted OR (AOR) = 2.40; CI 1.24 - 4.67), belonging to professional employment category (AOR = 12.07; CI 0.19 - 75.74) and those who had access to skilled health workers (AOR = 5.13; CI 2.50 - 10.52) are more likely to make the required number of ANC visits compared to those who are illiterates, unemployed and had no access to skilled health workers.

CONCLUSION AND GLOBAL HEALTH IMPLICATIONS

This study demonstrated that educational level, family wealth income, and availability of skilled health worker were consistently associated with the number of ANC visits even after controlling for covariates. These three covariates are in tandem with the Millenium Development Goals (MDG) 1 - eradication of extreme poverty and hunger; MDG 2 - universal basic education; MDG 3 - gender equality; and MDG 4 - maternal mortality. There is the need for inter-sectoral holistic intervention approach.

Maternal obesity and occurrence of fetal macrosomia: a systematic review and meta-analysis

OBJECTIVE

To determine a precise estimate for the contribution of maternal obesity to macrosomia.

DATA SOURCES

The search strategy included database searches in 2011 of PubMed, Medline (In-Process & Other Non-Indexed Citations and Ovid Medline, 1950-2011), and EMBASE Classic + EMBASE. Appropriate search terms were used for each database. Reference lists of retrieved articles and review articles were cross-referenced.

METHODS OF STUDY SELECTION

All studies that examined the relationship between maternal obesity (BMI ≥30 kg/m(2)) (pregravid or at 1st prenatal visit) and fetal macrosomia (birth weight ≥4000 g, ≥4500 g, or ≥90th percentile) were considered for inclusion.

TABULATION, INTEGRATION, AND RESULTS

Data regarding the outcomes of interest and study quality were independently extracted by two reviewers. Results from the meta-analysis showed that maternal obesity is associated with fetal overgrowth, defined as birth weight ≥ 4000 g (OR 2.17, 95% CI 1.92, 2.45), birth weight ≥4500 g (OR 2.77,95% CI 2.22, 3.45), and birth weight ≥90% ile for gestational age (OR 2.42, 95% CI 2.16, 2.72).

CONCLUSION

Maternal obesity appears to play a significant role in the development of fetal overgrowth. There is a critical need for effective personal and public health initiatives designed to decrease prepregnancy weight and optimize gestational weight gain.

Associations of maternal pre-pregnancy and gestational body size with offspring longitudinal change in BMI

OBJECTIVES

Studies demonstrate associations between changes in obesity-related phenotypes and cardiovascular risk. Although maternal pre-pregnancy BMI (mppBMI) and gestational weight gain (GWG) may be associated with adult offspring adiposity, no study has examined associations with obesity changes. Associations of mppBMI and GWG with longitudinal change in offspring's BMI (ΔBMI) were examined, and whether associations are explained by offspring genetics was assessed.

METHODS

A birth cohort of 1400 adults, with data at birth, age 17 and 32 years was used. After genotyping offspring, genetic scores, predictive of exposures and outcome were created, and linear regression models with and without scores were fit to examine the associations of mppBMI and GWG with ΔBMI.

RESULTS

A one SD change in mppBMI and GWG was associated with a 0.83 and a 0.75 kg/m² increase in ΔBMI, respectively. The association between mppBMI and offspring ΔBMI was slightly attenuated (12%) with the addition of genetic scores. In the GWG model, a significant substantial 28.2% decrease in the coefficient was observed.

CONCLUSIONS

This study points to an association between maternal excess weight in pregnancy and offspring BMI change from adolescence to adulthood. Genetic factors may account, in part, for GWG/ΔBMI association. These findings broaden observations that maternal obesity-related phenotypes have long-term consequences for offspring health.

Association between number of children and mortality of mothers: results of a 37-year follow-up study

PURPOSE

To examine the association between parity and long-term, all-cause mortality and mortality owing to specific causes in women.

METHODS

This prospective population-based study included 40,454 mothers who gave birth in Western Jerusalem, Israel, to 125,842 children and were followed for an average of 37 years after the birth of their first child. Cox proportional hazards models were used to evaluate long-term total and specific-cause mortality of women by their parity.

RESULTS

We found a U-shaped relationship between the number of offspring and risk of all-cause mortality in mothers. After adjustment for sociodemographic characteristics and maternal health and obstetric conditions, higher mortality rates were observed for mothers of 1 child (hazard ratio [HR], 1.18; 95% confidence interval [CI], 1.04-1.4), mothers of 5 to 9 children (HR, 1.21; 95% CI, 1.09-1.33), and mothers of 10 or more children (HR, 1.49; 95% CI, 1.12-1.99) compared with mothers of 2 to 4 children. Mortality risk from specific causes including coronary disease, circulatory disease, and cancer were increased for multiparous women.

CONCLUSIONS

In this long-term follow-up study, there was an association between number of children and mortality risk for mothers. These findings suggest that maternal pregnancies and postnatal characteristics as reflected by number of children may have consequences for long-term maternal health.

Associations of maternal prepregnancy body mass index and gestational weight gain with adult offspring cardiometabolic risk factors: the Jerusalem Perinatal Family Follow-up Study

BACKGROUND

Accumulating evidence demonstrates that both maternal prepregnancy body mass index (mppBMI) and gestational weight gain (GWG) are associated with adult offspring adiposity. However, whether these maternal attributes are related to other cardiometabolic risk factors in adulthood has not been comprehensively studied.

METHODS AND RESULTS

We used a birth cohort of 1400 young adults born in Jerusalem who had extensive archival data and clinical information at 32 years of age to prospectively examine the associations of mppBMI and GWG with adiposity and related cardiometabolic outcomes. Greater mppBMI, independently of GWG and confounders, was significantly associated with higher offspring BMI, waist circumference, systolic and diastolic blood pressures, insulin, and triglycerides and with lower high-density lipoprotein cholesterol. For example, the effect sizes were translated to nearly 5 kg/m(2) higher mean BMI, 8.4 cm higher waist circumference, 0.13 mmol/L (11.4 mg/dL) higher triglycerides, and 0.10 mmol/L (3.8 mg/dL) lower high-density lipoprotein cholesterol among offspring of mothers within the upper mppBMI quartile (mppBMI >26.4 kg/m(2)) compared with the lower quartile (mppBMI <21.0 kg/m(2)). GWG, independently of mppBMI, was positively associated with offspring adiposity; differences of 1.6 kg/m(2) in BMI and 2.4 cm in waist were observed when offspring of mothers in the upper (GWG >14 kg) and lower (GWG <9 kg) quartiles of GWG were compared. Further adjustment for offspring adiposity attenuated the observed associations to the null.

CONCLUSIONS

Maternal size both before and during pregnancy is associated with cardiometabolic risk factors in young adult offspring. The associations appear to be driven mainly by offspring adiposity. Future studies that explore mechanisms underlying the intergenerational cycle of obesity are warranted to identify potentially novel targets for cardiometabolic risk-reduction interventions.

Genome-wide survey reveals predisposing diabetes type 2-related DNA methylation variations in human peripheral blood

Inter-individual DNA methylation variations were frequently hypothesized to alter individual susceptibility to Type 2 Diabetes Mellitus (T2DM). Sequence-influenced methylations were described in T2DM-associated genomic regions, but evidence for direct, sequence-independent association with disease risk is missing. Here, we explore disease-contributing DNA methylation through a stepwise study design: first, a pool-based, genome-scale screen among 1169 case and control individuals revealed an excess of differentially methylated sites in genomic regions that were previously associated with T2DM through genetic studies. Next, in-depth analyses were performed at selected top-ranking regions. A CpG site in the first intron of the FTO gene showed small (3.35%) but significant (P = 0.000021) hypomethylation of cases relative to controls. The effect was independent of the sequence polymorphism in the region and persists among individuals carrying the sequence-risk alleles. The odds of belonging to the T2DM group increased by 6.1% for every 1% decrease in methylation (OR = 1.061, 95% CI: 1.032-1.090), the odds ratio for decrease of 1 standard deviation of methylation (adjusted to gender) was 1.5856 (95% CI: 1.2824-1.9606) and the sensitivity (area under the curve = 0.638, 95% CI: 0.586-0.690; males = 0.675, females = 0.609) was better than that of the strongest known sequence variant. Furthermore, a prospective study in an independent population cohort revealed significant hypomethylation of young individuals that later progressed to T2DM, relative to the individuals who stayed healthy. Further genomic analysis revealed co-localization with gene enhancers and with binding sites for methylation-sensitive transcriptional regulators. The data showed that low methylation level at the analyzed sites is an early marker of T2DM and suggests a novel mechanism by which early-onset, inter-individual methylation variation at isolated non-promoter genomic sites predisposes to T2DM.

Birth weight, maternal body mass index, and early childhood growth: a prospective birth cohort study in China

BACKGROUND

The relations of birth weight and maternal body mass index (BMI) to overweight remain unresolved. We prospectively examined the relations of birth weight with various anthropometric measures at age 3 to 6 years, the effect of maternal BMI, and the patterns of these relations in an analysis using 9 birth weight categories.

METHODS

The subjects were 210 172 singleton infants born alive with a gestational age ≥ 28 weeks between October 1993 and December 1996; the subjects were followed up in 2000. Birth weight, maternal height and weight, and other relevant information were measured or collected prospectively. Overweight and underweight were defined by using National Center for Health Statistics/World Health Organization reference data. Logistic regression models were used to estimate relative risks. Analyses stratified by quartile of maternal BMI were performed to examine the effects of maternal BMI on the associations of birth weight with overweight and underweight.

RESULTS

Birth weight was linearly associated with height, weight, and BMI at age 3-6 years. Adjustment for maternal BMI did not alter this association. Birth weight was positively associated with overweight and negatively associated with underweight. The relation curves for both overweight and underweight resembled half of a flat parabolic curve. The associations for overweight and underweight were slightly stronger for the highest and lowest quartiles of maternal BMI, respectively.

CONCLUSIONS

Higher birth weight is associated with an increased risk for childhood overweight, and lower birth weight with an increased risk for underweight. The associations between birth weight and early childhood anthropometric growth measures could not explained by maternal BMI.