The trans-ancestral genomic architecture of glycemic traits

Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 x 10(-8)), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution. A trans-ancestry meta-analysis of GWAS of glycemic traits in up to 281,416 individuals identifies 99 novel loci, of which one quarter was found due to the multi-ancestry approach, which also improves fine-mapping of credible variant sets.Peer reviewe

Can the association of adult lung function with weight in early life be explained by early life factors?

IntroductionWeight in early life is known to be associated with forced vital capacity (FVC) in adulthood, but whether it is also associated with airflow obstruction (FEV1/FVC) in adulthood is unclear. The observed association between weight in early life and lung function could be confounded by maternal risk factors, such as maternal smoking. Therefore, we examine whether maternal factors might explain this association.MethodsUsing linear regression among 3,832 participants of the Northern Finland Birth Cohort 1966, we examined the association of adult lung function (FVC and FEV1/FVC) with weight in early life (birth weight and weight gain in the first year of life). We then tested whether this association could be explained by maternal factors (maternal weight, height, BMI, age, smoking, education, socio-economic status and parity) by adjusting for them.ResultsFVC was positively associated with birth weight and weight gain. FEV1/FVC was not associated with birth weight and was negatively associated with weight gain. Mean FVC in adulthood (95%CI) increased by 86mL (51,121) and 24mL (7.7, 40) for each kilogram increase in birth weight and weight gain, respectively. One kg increase in weight gain was associated with a reduction of 0.003 units (-0.004,-0.001) of FEV1/FVC. Although several maternal factors were associated with both adult lung function and weight in early life, adjusting for them did not substantially alter the results.ConclusionAdult lung function and weight in early life were both associated with several early life factors, but these did not explain the association between adult lung function and weight in early life.<br/

Does in utero exposure to synthetic glucocorticoids influence birthweight, head circumference and birth length? A systematic review of current evidence in humans

Synthetic glucocorticoids are the mainstay treatment for stimulating lung maturation in threatened preterm delivery. Animal studies suggest that in utero exposure to glucocorticoids leads to a reduction in birth size. Smaller birthweight has been associated with higher risk of many chronic diseases. Therefore, the authors undertook a systematic review of human studies examining the association between synthetic glucocorticoid treatment and birth size. Medline, EMBASE, PubMed, Cochrane, Google scholar and Institute of Life Science databases were searched for studies published between 1978 and 2009 investigating the association between synthetic glucocorticoids and birthweight, head circumference, birth length and ponderal index. All studies controlling for gestational age were examined. Seventeen studies were included in the analysis. Nine out of 17 studies reported a reduction in birthweight (range 12–332 g), five of nine a reduction of head circumference (range 0.31–1.02 cm) and two of four a reduction of 0.8 cm in birth length. Despite methodological inconsistencies and limitations that impede clear conclusions, the evidence suggests an association between in utero exposure to synthetic glucocorticoids and reduced birth size

The association of genotype-based inbreeding coefficient with a range of physical and psychological human traits

Across animal species, offspring of closely related mates exhibit lower fitness, a phenomenon called inbreeding depression. Inbreeding depression in humans is less well understood because mating between close relatives is generally rare and stigmatised, confounding investigation of its effect on fitness-relevant traits. Recently, the availability of high-density genotype data has enabled quantification of variation in distant inbreeding in 'outbred' human populations, but the low variance of inbreeding detected from genetic data in most outbred populations means large samples are required to test effects, and only a few traits have yet been studied. However, it is likely that isolated populations, or those with a small effective population size, have higher variation in inbreeding and therefore require smaller sample sizes to detect inbreeding effects. With a small effective population size and low immigration, Northern Finland is such a population. We make use of a sample of ∼5,500 'unrelated' individuals in the Northern Finnish Birth Cohort 1966 with known genotypes and measured phenotypes across a range of fitness-relevant physical and psychological traits, including birth length and adult height, body mass index (BMI), waist-to-hip ratio, blood pressure, heart rate, grip strength, educational attainment, income, marital status, handedness, health, and schizotypal features. We find significant associations in the predicted direction between individuals' inbreeding coefficient (measured by proportion of the genome in runs of homozygosity) and eight of the 18 traits investigated, significantly more than the one or two expected by chance. These results are consistent with inbreeding depression effects on a range of human traits, but further research is needed to replicate and test alternative explanations for these effects

Prediction of childhood obesity by infancy weight gain: an individual-level meta-anlysis

To assess the predictive ability of infant weight gain on subsequent obesity we performeda meta-analysis of individual-level data on 47 661 participants from 10 cohortstudies from the UK, France, Finland, Sweden, the US and Seychelles. For eachindividual, weight SD scores at birth and age 1 year were calculated using the sameexternal reference (British 1990). Childhood obesity was defined by InternationalObesity Task Force criteria. Each +1 unit increase in weight SD scores between 0 and1 year conferred a twofold higher risk of childhood obesity (odds ratio = 1.97 [95%confidence interval (CI) 1.83, 2.12]), and a 23% higher risk of adult obesity (oddsratio = 1.23 [1.16, 1.30]), adjusted for sex, age and birthweight. There was little heterogeneitybetween studies. A risk score for childhood obesity comprising weight gain0–1 year, mother’s body mass index, birthweight and sex was generated in a random50% selection of individuals from general population cohorts with available information(n = 8236); this score showed moderate predictive ability in the remaining 50%sample (area under receiving operating curve = 77% [95% CI 74, 80%]). A separate riskscore for childhood overweight showed similar predictive ability (area under receivingoperating curve = 76% [73, 79%]). In conclusion, infant weight gain showed a consistentpositive association with subsequent obesity. A risk score combining birthweightand infant weight gain (or simply infant weight), together with mother’s body massindex and sex may allow early stratification of infants at risk of childhood obesity

Liver Function and Risk of Type 2 Diabetes: Bidirectional Mendelian Randomization Study.

Liver dysfunction and type 2 diabetes (T2D) are consistently associated. However, it is currently unknown whether liver dysfunction contributes to, results from, or is merely correlated with T2D due to confounding. We used Mendelian randomization to investigate the presence and direction of any causal relation between liver function and T2D risk including up to 64,094 T2D case and 607,012 control subjects. Several biomarkers were used as proxies of liver function (i.e., alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase [ALP], and γ-glutamyl transferase [GGT]). Genetic variants strongly associated with each liver function marker were used to investigate the effect of liver function on T2D risk. In addition, genetic variants strongly associated with T2D risk and with fasting insulin were used to investigate the effect of predisposition to T2D and insulin resistance, respectively, on liver function. Genetically predicted higher circulating ALT and AST were related to increased risk of T2D. There was a modest negative association of genetically predicted ALP with T2D risk and no evidence of association between GGT and T2D risk. Genetic predisposition to higher fasting insulin, but not to T2D, was related to increased circulating ALT. Since circulating ALT and AST are markers of nonalcoholic fatty liver disease (NAFLD), these findings provide some support for insulin resistance resulting in NAFLD, which in turn increases T2D risk.The Fenland Study is funded by the Wellcome Trust and the Medical Research Council (Grant number: MC_U106179471 and MC_UU_12015/1)

Liver Function and Risk of Type 2 Diabetes: Bidirectional Mendelian Randomization Study.

Liver dysfunction and type 2 diabetes (T2D) are consistently associated. However, it is currently unknown whether liver dysfunction contributes to, results from, or is merely correlated with T2D due to confounding. We used Mendelian randomization to investigate the presence and direction of any causal relation between liver function and T2D risk including up to 64,094 T2D case and 607,012 control subjects. Several biomarkers were used as proxies of liver function (i.e., alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase [ALP], and γ-glutamyl transferase [GGT]). Genetic variants strongly associated with each liver function marker were used to investigate the effect of liver function on T2D risk. In addition, genetic variants strongly associated with T2D risk and with fasting insulin were used to investigate the effect of predisposition to T2D and insulin resistance, respectively, on liver function. Genetically predicted higher circulating ALT and AST were related to increased risk of T2D. There was a modest negative association of genetically predicted ALP with T2D risk and no evidence of association between GGT and T2D risk. Genetic predisposition to higher fasting insulin, but not to T2D, was related to increased circulating ALT. Since circulating ALT and AST are markers of nonalcoholic fatty liver disease (NAFLD), these findings provide some support for insulin resistance resulting in NAFLD, which in turn increases T2D risk.The Fenland Study is funded by the Wellcome Trust and the Medical Research Council (Grant number: MC_U106179471 and MC_UU_12015/1)