Maternal and fetal genetic effects on birth weight and their relevance to cardio-metabolic risk factors

Parent-of-origin effects in the life-course evolution of cardiometabolic traits

AIMS/HYPOTHESIS

Cardiometabolic traits are heritable, and some display parent-of-origin effects, which indicates preferential inheritance from one parent or parental bias. Most studies of these phenomena have focused on adult populations. We aimed to investigate the heritability and parent-of-origin effects on cardiometabolic traits in a birth cohort with serial measurements to determine whether these patterns emerged early in life.

METHODS

The Pune Maternal Nutrition Study comprises a birth cohort in which offspring and parents were studied from birth and followed up for 24 years. We investigated parent-of-origin effects on cardiometabolic traits cross-sectionally at available timepoints using linear regression, and longitudinally across the life course using mixed-effect regression. Maternal and paternal effects on offspring phenotype were modelled after adjusting for age, sex and BMI. Parent-of-origin effects were calculated based on the difference between maternal and paternal effects. We also investigated these effects in another birth cohort, that of the Pune Children's Study. Genetic parent-of-origin effects were assessed using generalised estimating equations after taking the parental origin of the alleles into account.

RESULTS

Birthweight showed a maternal parent-of-origin effect. At 24 years, maternal bias was seen for some obesity-related traits for daughters, while paternal bias was seen for WHR in sons. A shift from paternal bias at 6 years to maternal bias at 24 years for the skinfold thickness was observed in daughters. Fasting glucose and lipids showed maternal bias at 6, 12 and 24 years. For fasting insulin and HOMA2-S, a negative maternal effect at 6 years transitioned to a positive one at 12 years. For HOMA2-B, a paternal effect at 6 years transitioned to a maternal one at 12 years, and this remained so at 24 years. Some of these findings were also observed in the cohort from the Pune Children's Study. Longitudinal modelling revealed stronger paternal effects over time for fasting insulin and HOMA indices but maternal effects for glucose and lipids, reflecting their cumulative effect over time. Genetic variants at the KCNQ1 locus showed a maternal parent-of-origin effect on birthweight, on HOMA2-B at 12 years, and on lipids at 6 and 12 years.

CONCLUSIONS/INTERPRETATION

Our study provides proof of concept of the existence of parent-of-origin effects on cardiometabolic traits from birth, through childhood and puberty, until adult age. Our results indicate a predominantly maternal influence on intrauterine, pubertal and reproductive-age metabolism in the offspring. While the longitudinal analysis indicated a maternal bias for the macronutrients (glucose and lipids), and a paternal bias for glucose-insulin metabolism, the cross-sectional analysis revealed a transition between parental influence across physiological stages. This dynamic relationship may have its origins in the life-history theory of evolution, and could inform strategies for primordial prevention aimed at curbing the rising burden of cardiometabolic disease. Further studies are needed to determine the mechanisms underlying such effects.

Quantifying the impact of biobanks and cohort studies

Biobanks advance biomedical and clinical research by collecting and offering data and biological samples for numerous studies. However, the impact of these repositories varies greatly due to differences in their purpose, scope, governance, and data collected. Here, we computationally identified 2,663 biobanks and their textual mentions in 228,761 scientific articles, 16,210 grants, 15,469 patents, 1,769 clinical trials, and 9,468 public policy documents, helping characterize the academic communities that utilize and support them. We found a strong concentration of biobank-related research on a few diseases, including obesity, Alzheimer's disease, breast cancer, and diabetes. Moreover, collaboration, rather than citation count, shapes the community's recognition of a biobank. We show that, on average, 41.1% of articles fail to reference any of the biobank's reference papers, but 59.6% include a biobank member as a coauthor. Using a generalized linear model, we identified the key factors that contribute to the impact of a biobank, finding that an impactful biobank tends to be more open to external researchers and that quality data-especially linked medical records-as opposed to large data, correlates with a higher impact in science, innovation, and disease. The collected data and findings are accessible through an open-access web application intended to inform strategies to expand access and maximize the value of these resources.

Fetal/Maternal-Determined Birth Weight and Adulthood Type 2 Diabetes and Its Subtypes: A Mendelian Randomization Study

BACKGROUND

Lower birth weight (BW) might increase the risk of adulthood type 2 diabetes, but its associations with the highly heterogeneous type 2 diabetes subtypes remain to be studied. In addition, whether the associations between lower BW and adulthood type 2 diabetes risks depend on fetal or maternal effect is largely unknown.

METHODS

In this study, we performed a two-sample Mendelian randomization analysis to study the associations between overall, fetal-determined, and maternal-determined BW and the risks of type 2 diabetes and its subtypes, namely mild age-related diabetes (MARD), mild obesity-related diabetes (MOD), severe insulin-deficient diabetes (SIDD), and severe insulin-resistant diabetes (SIRD).

RESULTS

Lower BW was genetically associated with increased risks of type 2 diabetes (odds ratio [OR]: 1.86; 95% CI: 1.53, 2.26), MARD (OR: 2.15; 95% CI: 1.43, 3.23), MOD (OR: 1.75; 95% CI: 1.10, 2.77), SIDD (OR: 1.86; 95% CI: 1.11, 3.10), and SIRD (OR: 1.66; 95% CI: 1.06, 2.60). When examining the fetal-determined genetic effects independently, lower BW remained associated with type 2 diabetes and its subtypes, except for MOD. Using maternal-determined BW-lowering genotypes to proxy for an adverse intrauterine environment provided no evidence that it raised offspring risks of type 2 diabetes.

CONCLUSION

Fetal-determined but not maternal-determined lower BW were associated with increased risks of adulthood type 2 diabetes and its subtypes. Our results underscored the importance of early targeted management among people with a low BW in the prevention of type 2 diabetes.

Nephron number variability in Japanese subjects: an autopsy-based study and its implications for chronic kidney disease: clinical scientist award address 2024

The number of nephrons is a key determinant of blood pressure regulation and chronic kidney disease (CKD) progression. Although traditional estimates suggest approximately one million nephrons per kidney, modern stereological approaches reveal substantial variability, that is influenced by ethnicity, birth weight, and other early life factors. This review evaluates the century-long evolution of nephron number research, variations across racial and ethnic groups, and explores how factors, such as body size, aging, and lifestyle risks, influence nephron endowment. Techniques for nephron quantification, from design-based stereology to emerging in vivo imaging, are also discussed. Recent research suggests markedly lower nephron counts in Japanese populations, especially among individuals with hypertension or CKD. The autopsy-based investigation in the present study included 27 middle-aged to older Japanese men (9 normotensive, 9 hypertensive, and 9 participants with CKD) who underwent dissector-fractionator stereology to quantify non-sclerosed glomeruli. Normotensive men had an average of approximately 640,399 non-sclerosed glomeruli. In contrast, the hypertensive participants had approximately 392,108 non-sclerosed glomeruli and those with CKD had only 268, 043. These findings underscore the potential influence of limited nephron reserves on hypertension and CKD in Japan. Current evidence suggests that nephron number estimates can guide therapeutic decisions and predict CKD outcomes, while advancements in real-time imaging offer potential avenues for non-invasive nephron assessment. Collectively, these developments highlight the central importance of nephron quantity in nephrology and enable targeted interventions aimed at preserving kidney function and mitigating the CKD burden.

Maternal obesity and ancestry distance in influencing birth outcomes

BACKGROUND

Maternal pre-pregnancy obesity has been associated with birth outcomes, but the influence of genetic distance (GD) on this relationship is unclear. Therefore, the objective of this study was to assess the interplay of GD and maternal obesity on birthweight, placental weight, and large for gestational age (LGA).

METHODS

We used data from the NICHD Fetal Growth Studies-Singletons cohort, a prospective cohort study of multi-ancestral pregnant women. GD was estimated using data from 1810 women across four ancestral reference populations. We categorized GD into five quintiles, with quintile one and quintile five representing the closest and farthest distances, respectively. Linear regression models were used to test association between GD and birth outcomes and to estimate the association of interaction of GD and maternal obesity with birth outcomes.

RESULTS

Farther maternal GD from an African reference was significantly associated with higher birthweight and higher odds of LGA, with associations persisting after adjusting for socioeconomic status (SES). The interaction between the third Amerindigenous GD quintile and obesity was significantly associated with a 198 g larger placental weight (95% CI = 51-345, p = 0.009) compared to the first Amerindigenous GD quintile. We also found the interaction between East Asian fourth GD quintile and obesity to be significantly associated with 86.0% lower odds of infants being born LGA (OR = 0.14 g, 95% CI = 0.02-74, p = 0.031) compared to the first quintile. These associations persisted after SES adjustment.

CONCLUSIONS

Interplays between maternal GD from Amerindigenous and East Asian references and pre-pregnancy obesity influence placental weight and risk of LGA. The results underline that consideration of maternal obesity in the context of GD from multiple ancestries and SES may facilitate interventions that will minimize adverse pregnancy outcomes.

CLINICAL TRIAL REGISTRATION

The study has been registered at ClinicalTrials.gov (Trial registration: NCT00912132).

The genetics of low and high birthweight and their relationship with cardiometabolic disease

AIMS/HYPOTHESIS

Low birthweight infants are at increased risk not only of mortality, but also of type 2 diabetes mellitus and CVD in later life. At the opposite end of the spectrum, high birthweight infants have increased risk of birth complications, such as shoulder dystocia, neonatal hypoglycaemia and obesity, and similarly increased risk of type 2 diabetes mellitus and CVD. However, previous genome-wide association studies (GWAS) of birthweight in the UK Biobank have primarily focused on individuals within the 'normal' range and have excluded individuals with high and low birthweight (<2.5 kg or >4.5 kg). The aim of this study was to investigate genetic variation associated within the tail ends of the birthweight distribution, to: (1) see whether the genetic factors operating in these regions were different from those that explained variation in birthweight within the normal range; (2) explore the genetic correlation between extremes of birthweight and cardiometabolic disease; and (3) investigate whether analysing the full distribution of birthweight values, including the extremes, improved the ability to detect genuine loci in GWAS.

METHODS

We performed case-control GWAS analysis of low (<2.5 kg) and high (>4.5 kg) birthweight in the UK Biobank using REGENIE software (Nlow=20,947; Nhigh=12,715; Ncontrols=207,506) and conducted three continuous GWAS of birthweight, one including the full range of birthweights, one involving a truncated GWAS including only individuals with birthweights between 2.5 and 4.5 kg and a third GWAS that winsorised birthweight values <2.5 kg and >4.5 kg. Additionally, we performed bivariate linkage disequilibrium (LD) score regression to estimate the genetic correlation between low/normal/high birthweight and cardiometabolic traits.

RESULTS

Bivariate LD score regression analyses suggested that high birthweight had a mostly similar genetic aetiology to birthweight within the normal range (genetic correlation coefficient [rG]=0.91, 95% CI 0.83, 0.99), whereas there was more evidence for a separate set of genes underlying low birthweight (rG=-0.74, 95% CI 0.66, 0.82). Low birthweight was also significantly positively genetically correlated with most cardiometabolic traits and diseases we examined, whereas high birthweight was mostly positively genetically correlated with adiposity and anthropometric-related traits. The winsorisation strategy performed best in terms of locus detection, with the number of independent genome-wide significant associations (p<5×10-8) increasing from 120 genetic variants at 94 loci in the truncated GWAS to 270 genetic variants at 178 loci, including 27 variants at 25 loci that had not been identified in previous birthweight GWAS. This included a novel low-frequency missense variant in the ABCC8 gene, a gene known to be involved in congenital hyperinsulinism, neonatal diabetes mellitus and MODY, that was estimated to be responsible for a 170 g increase in birthweight amongst carriers.

CONCLUSIONS/INTERPRETATION

Our results underscore the importance of genetic factors in the genesis of the phenotypic correlation between birthweight and cardiometabolic traits and diseases.

Trans-ancestry genome-wide association study of childhood body mass index identifies novel loci and age-specific effects

Over the past 30 years, obesity prevalence has markedly increased globally, including among children. Although genome-wide association studies (GWASs) have identified over 1,000 genetic loci associated with obesity-related traits in adults, the genetic architecture of childhood obesity is less well characterized. Moreover, most childhood obesity GWASs have been restricted to severely obese children, in relatively small sample sizes, and in primarily European-ancestry populations. To identify genetic loci associated with early-childhood body mass index (BMI), we performed GWAS of BMI Z scores in eight ancestrally diverse cohorts: ZOE 2.0 cohort, the Santiago Longitudinal Study (SLS), the Vanderbilt University BioVU biobank, the Geisinger MyCode Health Initiative biobank, Study of Latino (SOL) Youth, Pelotas (Brazil) Birth Cohort, Cameron County Hispanic Cohort (CCHC), and Viva La Familia cohort. We subsequently performed inverse-variance-weighted fixed-effect meta-analysis of these results with previously published GWAS summary statistics of BMI Z scores of children in the Early Growth Genetics (EGG) Consortium and the Norwegian Mother and Child Cohort (MoBa), constituting a final total of 84,804 individuals. We identified 39 genome-wide significant loci associated with childhood BMI, including three putatively novel loci (EFNA5 and DTWD2, RP11-2N5.1 on chromosome 5, and LSM14A on chromosome 19). We also observed a dynamic nature of genetic loci-BMI associations across the life course, with distinct effects across childhood and adulthood, highlighting possible critical periods for early-childhood interventions. These findings strengthen calls for larger population-based studies of children across age strata and across diverse populations.

Examining the association between fetal HLA-C, maternal KIR haplotypes and birth weight

Human birth weight is under stabilizing selection, seeking balance between extremes of high and low, thereby reducing fetal and maternal perinatal mortality risk. Certain combinations of maternal killer immunoglobulin-like receptor (KIR) and paternally derived fetal human leuokocyte antigen-C (HLA-C) alleles were previously associated with higher risk of high and low birth weight in a study with limited sample size (n=1,316). Using recently developed methods to impute HLA and KIR haplotypes using single nucleotide polymorphism (SNP) genotype data, we tested associations of fetal HLA and maternal KIR genotypes with offspring birth weight in a large sample. We imputed KIR haplotypes using the KIR*IMP imputation software in 10,602 mother-offspring pairs of European descent from singleton pregnancies from five studies. Using mixed linear regression models to account for mothers with multiple children, we tested associations between maternal KIR A vs B haplotypes (AA, AB/BA, BB genotypes) as well as copy number of activating receptor gene KIR2DS1 (0, 1, 2 copies of the gene) in the presence of fetal HLA C1/C2 alleles, and offspring birth weight. Associations were analyzed in each cohort before performing a meta-analysis to estimate the interaction effects between maternal KIR and fetal HLA-C2 on birth weight across the entire sample. The KIR haplotypes achieved imputation accuracy estimated at >95% in most of the cohorts. No interaction effects were observed between either the maternal A vs. B haplotype or the maternal KIR2DS1 locus and fetal HLA-C. When specifically trying to replicate the previously associated combination of maternal KIR2DS1 and paternally inherited fetal HLA-C2, there was a negligible change in offspring birth weight for each additional KIR2DS1 allele and HLA-C2 of paternal origin (7g lower birth weight per allele [95% CI: -54, 40], P = 0.78). We found little evidence of association between birth weight and maternal KIR haplotypes or fetal HLA-C2 and were unable to replicate previously reported findings. Our observations reinforce the importance of replication and the use of large sample sizes in the validation of genetic associations.

Preschool age-specific obesity and later-life kidney health: a Mendelian randomization and colocalization study

OBJECTIVES

While the association between obesity and kidney diseases has been found in previous studies, the relationship between preschool-age obesity and later-life kidney health remains unclear, posing challenges for effective interventions in this critical life period.

METHODS

Utilizing the hitherto largest genome-wide association studies, we conducted two-sample mendelian randomization (MR) to estimate the association of preschool age-specific obesity on kidney health and diseases, including blood urea nitrogen (BUN), eGFRcrea, eGFRcys, chronic kidney disease (CKD), IgA nephropathy, and diabetic nephropathy. Then, we applied multivariable Mendelian randomization (MVMR) and stepwise MR to elucidate the role of adult obesity and 12 other potential factors in the pathway between preschool age-specific obesity and kidney health. Finally, we employed colocalization analysis to understand the mechanism of preschool age-specific obesity and kidney damage further by detecting shared causal variants.

RESULTS

Our two-sample MR results indicated that preschool obesity could be associated with kidney health and disease. In addition, we observed a switch in the direction of associations between age-specific body mass index (BMI) and CKD, manifesting as negative associations before 3 years old and positive associations after 3 years old. Furthermore, MVMR and stepwise MR results suggested potential pathways linking preschool obesity to kidney health, involving factors such as adult BMI, circulating high-density lipoprotein cholesterol levels, and circulating C-reactive protein levels. Finally, we detected that preschool-age BMI and kidney function could share causal variants such as rs76111507, rs62107261, rs77165542 in the region of chromosome 2, and rs571312 in the region of chromosome 18.

CONCLUSION

Our study supports the association between preschool obesity and kidney health, emphasizing the role of adult BMI in this relationship. These findings underscore the importance of interventions starting in early childhood and continuing through adulthood to reduce the long-term risk of obesity-related kidney damage.

Genome Wide Association Study (GWAS) Identifies Novel Genetic Loci for Second-Generation Antipsychotics (SGA)-Induced Metabolic Syndrome (MetS)

Second-generation antipsychotics (SGA) are widely used for treating psychiatric disorders; however, their use is associated with an increased risk of metabolic syndrome (MetS). To identify common genetic associations of SGA-induced metabolic syndrome (SGA-MetS), we conducted a genome-wide association study (GWAS) in a diverse patient population within the BioVU and BioMe electronic health records (EHRs)-linked biobanks. Additionally, we performed Mendelian Randomization (MR) analysis to investigate the association between the individual metabolic parameters comprising MetS (body mass index [BMI], fasting glucose, blood pressure, HDL, and triglycerides) and SGA-MetS. The meta-analysis of European ancestry GWAS from BioVU and BioMe (N = 9248) identified a genome-wide signal (rs61900075, β = -0.27, SE = 0.05, p = 1.6 × 10-8) on chromosome 11. Multiple associated variants met the suggestive level of association (p ≤ 10-5) in the PELO-ITGA1 locus on chromosome 5 and were associated among the Hispanic Ancestry within BioMe. The meta-analysis of the African Ancestry patients of BioVU and BioMe (N = 2018) identified multiple genome-wide signals that were functionally mapped to NPPC-DIS3L2 in chromosome 2. Finally, the inverse-variance weighted average MR (BMI: OR = 1.2, 95% CI: 1.1-1.4, p = 0.002) showed that genetically predicted, higher BMI was associated with an increased risk of SGA-MetS. Similar results were seen in the sensitivity analyses using the weighted median and Egger MR. This study identified novel variants for SGA-MetS and suggested a role of BMI in increasing the risk of SGA-MetS. The findings highlight the value of EHR biobanks for identifying the genetics underlying SGA-MetS. The associations in chromosome 2 and 5 will need further replication.

Is early-life obesity associated with kidney cancer in adulthood?-insights from genetic studies

Background

Adult obesity increases the risk of kidney cancer (KIC), yet the link between early body size traits and KIC remains uncertain. This study aimed to investigate the causal relationship between early body size characteristics and KIC, including its subtypes, using Mendelian randomization (MR).

Methods

We utilized data from public genome-wide association study (GWAS) databases on birth weight and body mass index (BMI) across childhood, adolescence, and adulthood as exposure variables, and KIC and its subtypes as outcome variables. A two-way two-sample MR analysis was performed to explore these associations, with the inverse variance weighted (IVW) method as the primary analytical approach and sensitivity analyses to assess result stability.

Results

IVW analysis revealed significant associations between childhood obesity [odds ratio (OR) =1.08, 95% confidence interval (CI): 1.04-1.14, P<0.001], childhood BMI (OR =1.23, 95% CI: 1.07-1.42, P=0.003), adolescent BMI (OR =1.22, 95% CI: 1.07-1.40, P=0.003), and adult BMI (OR =1.75, 95% CI: 1.41-2.17, P<0.001) with increased risk of KIC. Similar associations were observed for clear cell renal cell carcinoma (ccRCC), with childhood obesity (OR =1.09, 95% CI: 1.02-1.15, P=0.007), childhood BMI (OR =1.33, 95% CI: 1.14-1.55, P<0.001), adolescent BMI (OR =1.24, 95% CI: 1.04-1.47, P=0.01), and adult BMI (OR =1.97, 95% CI: 1.51-2.57, P<0.001) significantly linked to higher ccRCC risk. No evidence of reverse causation was found.

Conclusions

This study provides MR evidence supporting a causal association between early-life obesity and KIC. Our findings suggest that reducing obesity in early life may have a potential positive impact on the prevention of KIC.

Effect of obesity on cardiovascular morphofunctional phenotype: Study of Mendelian randomization

BACKGROUND

Obesity is an independent factor for cardiovascular diseases, impacting health across different age groups. cardiovascular magnetic resonance (CMR) imaging is considered the gold standard for noninvasive assessment of cardiovascular structure and function. We conducted a Mendelian randomization (MR) study to explore the associations between obesity-related traits and the clinical pre-phenotype of cardiac and aortic structure and function.

METHODS

Independent genetic variations significantly correlated with adult body mass index, adult waist-to-hip ratio, birth weight, child body mass index, and excess visceral fat were selected as instrumental variables. Eighty-two CMR imaging features were obtained from the UK Biobank Genome-Wide Association Study. These features served as clinical pre-phenotypes, providing early indications of the structure and function of the 4 cardiac chambers and 2 aortic slices. Preliminary analyses were conducted using MR and inverse variance-weighted methods. Causal directions were determined through Steiger filtering and testing, achieving confirmation. Sensitivity analyses were performed using weighted median, MR-Egger, and MR-PRESSO methods.

RESULTS

Adult BMI was positively correlated with left ventricular end-systolic volume, right ventricular end-diastolic volume, right ventricular end-systolic volume, and right ventricular volume per beat. The adult waist-to-hip ratio was inversely proportional to right atrial volume per beat, right atrial maximum volume, right atrial minimum volume, partial regional longitudinal strain, regional peak circumferential strain, and regional radial strain, and positively proportional to partial regional peak circumferential strain and partial end-diastolic local myocardial wall thickness characteristics. Birth weight was positively correlated with maximum right atrial volume, minimum right atrial volume, right atrial volume per beat, right ventricular end-diastolic volume, right ventricular output per beat, maximum area of the ascending aorta, minimum area of the ascending aorta, and negatively correlated with longitudinal strain in some regions. Body mass index in children is positively correlated with left ventricular end-diastolic volume, left ventricular end-systolic volume, left atrial volume per beat, right ventricular end-diastolic volume, and right ventricular volume per beat.

CONCLUSION

This study suggests that obesity may lead to myocardial hypertrophy and dilation of the cardiac chambers and aorta, thereby exerting adverse effects on the cardiovascular system and increasing the susceptibility to HF.

Cohort profile: the Genetics of Glucose regulation in Gestation and Growth (Gen3G) - a prospective prebirth cohort of mother-child pairs in Sherbrooke, Canada, 3-year and 5-year follow-up visits

PURPOSE

Initiated in 2010, the Genetics of Glucose regulation in Gestation and Growth (Gen3G) prospective cohort investigates the pathophysiology of impaired glycaemic regulation in pregnancy and evaluates its impact on both the mothers and her offspring health trajectory. Follow-up visits 3 and 5 years after delivery aimed to investigate pregnancy-related risk factors such as maternal obesity and gestational hyperglycaemia in relation to the mother's metabolic health after pregnancy, and with offspring health outcomes such as risk of obesity and neurodevelopmental problems in early childhood. We also investigated molecular mechanisms involved in the fetal programming of these later health outcomes.

PARTICIPANTS

Of the 1024 women originally recruited in the first trimester of pregnancy, we have targeted the 854 who had complete glucose tolerance test data and the 724 newborns who provided placenta and/or cord blood samples for follow-up recruitment. Of these, 695 mother-child dyads agreed to be contacted for the prospective follow-up visits. 448 and 521 mother-child dyads completed the research visits at 3 and 5 years after delivery respectively.

FINDINGS TO DATE

At both visits, we collected the mother's and child's medical history, lifestyle (using validated questionnaires), sociodemographic status, anthropometric measurements, mother's blood samples, child's saliva samples and growth charts. At the 5-year-old visit, we additionally collected the mother's and child's urine and stool samples and the child's blood samples; we performed a 75 g oral glucose tolerance test in the mothers and assessed the body composition in children using dual-energy X-ray absorptiometry. Using the Gen3G rich longitudinal data set, we have enhanced the understanding of the pathophysiology and characterisation of the heterogeneity of gestational diabetes mellitus, and we have shown that gestational hyperglycaemia and insulin resistance are associated with offspring epigenetics (DNA methylation) variations in the placenta, cord blood and blood at 5 years of age, as well as with offspring anthropometric, metabolic and neurodevelopmental outcomes in early childhood.

FUTURE PLANS

We are currently conducting a prospective follow-up of mothers and their children 12 years after delivery to study how prenatal and early-life metabolic factors may programme childhood adiposity and obesogenic dietary behaviours. This follow-up should be completed by the end of 2026.

Causal effect of life-course adiposity on the risk of respiratory diseases: a Mendelian randomization study

BACKGROUND

There is limited evidence on the causal associations of life-course adiposity with the risk of respiratory diseases. This study aimed to elucidate these associations.

METHODS

Two-sample Mendelian randomization was conducted using genetic instruments of life-course adiposity (including birth weight, childhood BMI, and adulthood adiposity) to estimate their causal effect on respiratory diseases in participants of European ancestry from the UK Biobank, the FinnGen consortium, and other large consortia.

RESULTS

Genetically predicted higher birth weight was associated with decreased risk of acute upper respiratory infections and increased risk of pulmonary embolism, sleep apnea, and lung cancer. Genetically predicted high childhood BMI was associated with increased risk of asthma, COPD, pulmonary embolism, and sleep apnea. However, most of these observed associations were no longer significant after adjusting for adult BMI. Genetically predicted higher adult BMI and WHR were associated with 10 and 4 respiratory diseases, respectively. High adult body fat percentage and visceral adiposity were genetically associated with increased risk of 9 and 11 respiratory diseases, respectively. Consistently, genetically predicted higher whole-body fat mass was associated with increased risk of 8 respiratory diseases.

CONCLUSIONS

This study provides genetic evidence that greater adiposity in childhood and adulthood has a causal effect in increasing the risk of a wide range of respiratory diseases. Furthermore, the effects of childhood obesity on respiratory outcomes may be mediated by adult obesity.

Association and shared biological bases between birth weight and cortical structure

Associations between birth weight and cortical structural phenotypes have been detected; however, the understanding is incomprehensive, and the potential biological bases are not well defined. Leveraging data from genome-wide association studies, we investigated the associations and the shared transcriptomic, proteomic and cellular bases of birth weight and 13 cortical structural phenotypes. Mendelian randomization analyses were performed to examine associations between birth weight and cortical structure. Downstream transcriptome-wide association study (TWAS), proteome-wide association study (PWAS) and summary-based Mendelian randomization (SMR) analyses were utilized to identify the shared cis-regulated gene expressions and proteins. Finally, cell-type expression-specific integration for complex traits (CELLECT) analyses were conducted to explore the enriched cell types. The Mendelian randomization analyses found positive associations between birth weight and global cortical folding index, intrinsic curvature index, local gyrification index, surface area and volume. Downstream transcriptomic-level TWAS and SMR identified three gene expressions both linked to birth weight and at least one cortical structural phenotype (CNNM2, RABGAP1 and CENPW). Parallel PWAS and SMR analyses at the proteomic level identified four proteins linked to both phenotypes (CNNM2, RAB7L1, RAB5B and PPA2), of which CNNM2 was replicated. CELLECT analyses revealed brain cell types enriched in birth weight, including pericytes, inhibitory GABAergic neurons and cerebrovascular cells. These findings support the importance of early life growth to cortical structure, and suggest underlying transcriptomic, proteomic and cellular bases. These results provide intriguing targets for further research into the mechanisms of cortical development.

Haplotype-based analysis distinguishes maternal-fetal genetic contribution to pregnancy-related outcomes

Genotype-based approaches for the estimation of SNP-based narrow-sense heritability ([Formula: see text]) have limited utility in pregnancy-related outcomes due to confounding by the shared alleles between mother and child. Here, we propose a haplotype-based approach to estimate the genetic variance attributable to three haplotypes - maternal transmitted ([Formula: see text]), maternal non-transmitted ([Formula: see text]) and paternal transmitted ([Formula: see text]) in mother-child pairs. We show through extensive simulations that our haplotype-based approach outperforms the conventional and contemporary approaches for resolving the contribution of maternal and fetal effects, particularly when m1 and p1 have different effects in the offspring. We apply this approach to estimate the explicit and relative maternal-fetal genetic contribution to the phenotypic variance of gestational duration and gestational duration-adjusted fetal size measurements at birth in 10,375 mother-child pairs. The results reveal that variance of gestational duration is mainly attributable to m1 and m2 ([Formula: see text]). In contrast, variance of fetal size measurements at birth are mainly attributable to m1 and p1 ([Formula: see text]). Our results suggest that gestational duration and fetal size measurements are primarily genetically determined by the maternal and fetal genomes, respectively. In addition, a greater contribution of m1 as compared to m2 and p1 ([Formula: see text]) to birth length and head circumference suggests a substantial influence of correlated maternal-fetal genetic effects on these traits. Our newly developed approach provides a direct and robust alternative for resolving explicit maternal and fetal genetic contributions to the phenotypic variance of pregnancy-related outcomes.

Causal Effect Between Natural Hair Color and Endometriosis in a European Population: A Two-Sample Mendelian Randomization

Previous observational studies have suggested an association between natural hair color and the risk of endometriosis; however, the causal relationship remains unclear. Here, we conducted a two-sample Mendelian randomization (MR) study to evaluate the potential causal link between natural hair color and endometriosis using 428 single nucleotide polymorphisms (SNPs) as genetic instruments derived from a genomewide meta-analysis comprising over 4511 cases and 227,260 controls of European ancestry. Our findings indicate that dark brown hair is associated with a decreased risk of developing endometriosis (dark brown IVW OR: 0.844, 95% CI [0.725, 0.984], p < .05). Conversely, dark hair color and lighter hair colors (red, blonde, and light brown) did not demonstrate a significant association with endometriosis risk (dark IVW OR: 0.568, 95% CI [0.280, 1.15], p = .117; red IVW OR: 1.058, 95% CI [0.719, 1.558], p = .77; blonde IVW OR: 1.158, 95% CI [0.886, 1.514], p = .28; light brown IVW OR: 1.306, 95% CI [0.978, 1.743], p = .07). These results provide compelling MR evidence supporting a causal association between natural hair color and endometriosis risk. Our findings underscore the need for larger scale studies and randomized controlled trials to delineate the biological mechanisms driving the association between hair color and endometriosis.

Thyroid Hormones in Early Pregnancy and Birth Weight: A Retrospective Study

Background/Objectives: Various factors influence intrauterine growth and birth weight. We investigated the possible association between first-trimester pregnancy thyroid functions and birth weight. Methods: A retrospective observational study was conducted from 31 March 2021 to 30 September 2022. Ninety-eight low-risk pregnant women were evaluated. To obtain a homogeneous population, we included only patients with no maternal or fetal comorbidities. TSH, FT3, and FT4 levels in the first trimester and birth weight were recorded and analyzed. Results: The average maternal age was 33.37 years (IQR = 8.67), with a median BMI of 24.98 kg/m2 (IQR = 5.66). The average gestational week of pregnancy was 39.40 weeks (IQR = 2.10). Linear regression for birth weight according to TSH effects adjusted by sociodemographic and clinical factors did not show any associations between birth weight and TSH, age, ethnicity, BMI, smoking, or weight gain. Pregnancy duration was associated with birth weight: β = 172.027, p-value < 0.001. A negative significant correlation between FT3 and birth weight was found (beta = -118.901 95% CI: -222.942 to -14.859, p = 0.026). Age, ethnicity, BMI, smoking, and weight showed non-significant associations with birth weight. The FT3 scatterplot showed a negative correlation of FT3 levels with birth weight. Higher values of FT3 were associated with a low birth weight (R = -0.22, p = 0.029). Conclusions: Our study, focused on the first trimester, found a negative correlation between FT3 variations and birth weight.

Causal Association of Primary Biliary Cholangitis with Adverse Pregnancy and Neonatal Outcomes: A Two-Sample Mendelian Randomization Study

Background

Primary biliary cholangitis (PBC) is associated with multiple adverse pregnancy events and neonatal outcomes. However, the available observational study evidence results are inconsistent, and causality is unclear.

Methods

We used a two-sample Mendelian randomization (MR) analysis to assess the association between PBC and multiple adverse pregnancy events and neonatal outcomes in a European population. Independent SNPs associated with PBC from genome-wide association studies (GWAS) were selected as instrumental variables. The inverse variance weighting (IVW) method was used as the primary analysis method, supplemented by the remaining four MR analysis methods. Heterogeneity and sensitivity analyses of instrumental variables were examined using Cochrane's Q, MR-PRESSO, MR-Egger, and leave-one-out methods.

Results

IVW estimates indicated that genetically predicted increased PBC was associated with lower birth weight (OR 0.991, 95% CI 0.983 ~ 0.998, P=0.018), decreased gestational age (OR 0.992, 95% CI 0.987 ~ 0.998, P=0.007), and increased risk of preterm birth (OR 1.043, 95% CI 1.007 ~ 1.081, P=0.019) were associated. For birth weight, the OR estimates obtained by weighted median (OR 0.988, 95% CI 0.980 ~ 0.996, P= 0.006) were consistent with IVW. In addition, no significant causal associations were found between genetically predicted PBC and preeclampsia or eclampsia, miscarriage, placental abruption, gestational diabetes mellitus, and postpartum hemorrhage.

Conclusion

Our study reveals that genetically predicted PBC is associated with low birth weight, decreased gestational age, and increased risk of preterm labor in a European population. However, current research does not establish a causal relationship between PBC and adverse pregnancy outcomes.

Preterm Birth and Cardiometabolic Health Trajectories From Birth to Adulthood: The Avon Longitudinal Study of Parents and Children

BACKGROUND

Adults who were born prematurely (<37 weeks' gestation) are at increased cardiovascular disease risk, but it is unclear when in the life course this risk emerges. Our aim was to compare trajectories of multiple cardiometabolic risk factors from childhood to early adulthood between those who had and had not been born preterm.

METHODS AND RESULTS

Multilevel models were used to compare trajectories from early childhood (<9 years) to age 25 years of body mass index, fat and lean mass, systolic and diastolic blood pressure, lipids, glucose, and insulin, between individuals born preterm (N=311-676; range, 25-36 weeks' gestation) and term (N=4973-10 534) in a UK birth cohort study. We also investigated gestational age as a continuum. In children born preterm (versus term), systolic and diastolic blood pressures were higher at age 7 years (mean predicted differences, 0.7 [95% CI, -0.2 to 1.6] mm Hg and 0.6 [95% CI, -0.04 to 1.3] mm Hg, respectively). By age 18 years, the difference in systolic blood pressure persisted (1.9 [95% CI, 0.8-3.1] mm Hg) and in diastolic blood pressure (0.1 [95% CI, -0.7 to 1.0 mm Hg]) disappeared. By age 25 years, this difference in systolic blood pressure began to attenuate towards the null (0.9 [95% CI, -0.5 to 2.3] mm Hg). Participants born preterm (versus term) had lower body mass index between ages 7 and 18 years, but by age 25 years, there was no difference. Fat and lean mass trajectories were consistent with body mass index. High-density lipoprotein cholesterol was higher and triglycerides lower at birth, in those born preterm, but this difference also disappeared by age 25 years. There was no evidence of differences in glucose and insulin.

CONCLUSIONS

Few, modest differences in cardiometabolic health were found in those born preterm versus term. All disappeared by age 25 years, except the small difference in systolic blood pressure. Longer follow-up is needed to establish if and when cardiometabolic health trajectories diverge between these 2 groups.

Infant birth weight in Brazil: A cross-sectional historical approach

In 1888, Brazil became the last country in the Americas to abolish slavery. Historians have outlined the racialized health disparities of people of African descent in the post-abolition period. Epidemiologists have shown that twenty-first-century health disparities continue to mirror patterns from over a century ago. This cross-sectional analysis quantifies health disparities in a post-abolition maternity hospital using infant birth weight. It relies on hospital records on infants delivered between 1922 and 1926 (n = 2845) at the Maternidade Laranjeiras in the city of Rio de Janeiro, Brazil to run linear models assessing differences in infant birth weight by maternal skin color, age, number of pregnancies (parity), and nationality. African ancestry was correlated with lower birth weights. Infants born to Afro-descendant women had birth weights estimated to be 84 g lighter (p-value = 0.002 [95% CI -137, -32]) than infants born to Euro-descendant women. Among Afro-descendant women, infants born to Black (preta) women had birth weights estimated to be 100 g lighter (p-value = 0.001 [95% CI -160, -39]) and infants born to mixed-race (parda) women had birth weights estimated to be 70 g lighter (p-value = 0.022 [95% CI -130, -10]) than infants born to White women. The findings were likely the consequence of slavery's legacy, particularly race-based socioeconomic inequality - including more strenuous work schedules, poorer nutrition, and less sanitary living environments for people of African descent. The findings are consistent with current-day research on racialized health disparities in Brazil and demonstrate the importance of historical findings to public health research.

Kidney disease and reproductive health

Understanding the relationship between reproductive health and kidney function is important to provide holistic care for people living with kidney disease. Chronic kidney disease (CKD) has negative impacts on both male and female fertility owing to factors including inflammation, hormonal dysregulation, reduced ovarian reserve, reduced sperm quality and sexual dysfunction. However, pregnancy is achievable for most cisgender women with kidney disease, including kidney transplant recipients and patients on dialysis. CKD in pregnancy is associated with health risks to the mother and child, including increased risk of progression of kidney disease, hypertensive complications of pregnancy, and neonatal complications including fetal growth restriction, preterm birth and stillbirth. However, with appropriate pre-pregnancy counselling, fertility assessment and support, health optimization, and evidence-based antenatal care, the majority of patients will achieve a good outcome. Medication safety should be reviewed before and during pregnancy and lactation, weighing the risk of disease flare against potential adverse effects on the offspring. Important areas for further research include the optimal timing of delivery and the short- and long-term cardiovascular and renal impacts of pregnancy in patients with CKD, as well as long-term kidney and cardiovascular outcomes in their offspring.

The influence of fetal sex on maternal blood pressure in pregnancy

Background

Pregnancy with a male fetus carries a higher risk of term pre-eclampsia than pregnancy with a female fetus. Based on evidence that maternal blood pressure (BP) may be raised in pregnancies with Beckwith-Wiedemann syndrome (fetal overgrowth), a possible contributing factor to the association between male sex and term pre-eclampsia is that males grow faster, reaching ~130 g higher birth weight, on average, than females. The association between fetal sex and maternal BP in healthy pregnancies is not known. We hypothesized that male sex would be associated with higher maternal BP in healthy pregnancies, and that this association would be explained by birth weight differences between males and females.

Methods and findings

We tested the association between fetal sex and maternal systolic (SBP) and diastolic blood pressure (DBP), measured at ~28 weeks of gestation, in a meta-analysis of five different cohorts of mother-child pairs (n up to 109,842). Maternal BP was analyzed as both a continuous and dichotomized (high BP: yes or no) outcome. Linear regression models were constructed with and without adjustment for birth weight to assess whether any difference in maternal BP was explained by the difference in birth weight between male and female babies. Lastly, we constructed a fetal genetic score for birth weight using 186 own-birth-weight-associated single-nucleotide polymorphisms (SNPs) to test whether birth-weight-raising-alleles in the fetus were associated with maternal BP in pregnancy (n up to 32,232). Both maternal SBP and DBP were higher in pregnancy when carrying a male fetus compared to a female fetus (mean difference 0.35 mmHg [95%CI: 0.15-0.55] and 0.35 mmHg [95%CI: 0.21-0.49], for SBP and DBP, respectively). An independent effect of fetal sex remained when including birth weight but attenuated slightly (0.22 mmHg [95%CI: 0.02-0.42] and 0.31 mmHg [95%CI: 0.17-0.45], for SBP and DBP respectively). A positive effect estimate was found for odds of experiencing high maternal BP given pregnancy with a male fetus, but confidence intervals were wide (OR 1.05 [95%CI: 0.98-1.12]). No evidence for an association was found between a fetal birth weight genetic score and SBP or DBP when conditioned on maternal genotype.

Conclusions

We found strong evidence to support a small effect of male fetal sex on higher maternal BP in pregnancy and that larger fetal size at birth does not contribute to a substantial part of this association. Our findings do not indicate a difference in maternal BP that would warrant changes to routine monitoring in clinical practice but do suggest that male sex may be a contributing risk factor for BP-related complications.

Genetic score associations with birthweight in preterm-born infants compared with term-born infants

Objective

In preterm infants, lower birthweight correlates with a higher risk of neonatal complications. Understanding the factors influencing birthweight in these infants is important as it may guide future antenatal and perinatal care. Genetic variants account for at least one-quarter of variation in birthweight in term-born infants, but the genetic contribution to birthweight in preterm infants is not well understood. We aimed to compare genetic score associations with birthweight in a well-powered sample of preterm infants with those in term-born infants.

Study design

We used linear regression to test the association between birth weight and fetal genetic scores for birthweight (BW-GS) in a total of 1,416 preterm, singleton and 15,253 term, singleton infants. Analyses, adjusted for ancestry principal components were performed within each of 4 datasets and meta-analysed.

Results

In term-born infants: a 1 SD higher BW-GS was associated with a 1.20 (95% CI 1.10-1.29) SD higher birthweight. In preterm infants, there was also strong evidence of association, but with a smaller effect size (0.76SD (0.41-1.11) higher birthweight per 1-SD higher BW-GS). In preterms, when stratifying by gestational duration, we found that the associations strengthened with increasing gestational duration.

Conclusions

Genetic scores composed of variants identified in term-born infants also influenced birthweight in preterm infants. However, the associations had smaller effects in preterms and were weaker at earlier gestations. This suggests that while many of the same genetic factors influence birthweight in preterm and term-born infants, other factors (environmental, placental, different genetic) may be more important in preterms. Future well-powered studies are required to investigate this.

Exploring fetal growth patterns in the second trimester: insights from ultrasound measurements among the Minangkabau Ethnic Group in Indonesia

BACKGROUND

Understanding fetal growth is essential for predicting perinatal outcomes and long-term health implications. This study explores the correlation between ultrasound parameters and gestational age in the Minangkabau ethnic group, focusing on the biometric variables biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and humerus length (HL) during the second trimester.

METHODS

Conducted from December 2020 to December 2021, the research employed a cross-sectional design at the Fetomaternal clinic of Hospital M. Djamil Padang and affiliated hospitals. Pregnant women (n = 600) meeting inclusion criteria were sampled consecutively. Univariate, bivariate (Pearson correlation test), and multivariate (linear regression) analyses were performed using SPSS software.

RESULTS

Demographically, most participants were 21-30 years old, primigravida, with senior high school education, and employed. Fetal biometric measurements displayed increasing variability with gestational age. AC exhibited the strongest correlation (r = 0.95, p < 0.005) with gestational age during the second trimester. The study validated the accuracy of AC in estimating gestational age based on LMP (r = 0.95, p = 0.0001).

CONCLUSION

This study contributes to the understanding of fetal growth dynamics, emphasizing the reliability of ultrasound parameters in estimating gestational age during the second trimester, particularly in the Minangkabau ethnic group. The strong correlation, especially with AC, enhances the precision of due date predictions and refines prenatal care strategies. However, limitations include the study's focus on a single ethnic group, potentially restricting generalizability. Future research should explore fetal growth dynamics across diverse populations, incorporate longitudinal designs to assess growth trajectories, and evaluate additional maternal and environmental factors. Enhanced standardization of AC measurement techniques is also necessary to reduce variability and improve clinical utility.

Effects of the maternal and fetal proteome on birth weight: a Mendelian randomization analysis

Background

Fetal growth is an important indicator of survival, regulated by maternal and fetal genetic and environmental factors. However, little is known about the underlying molecular mechanisms. Proteins play a major role in a wide range of biological processes and could provide key insights into maternal and fetal molecular mechanisms regulating fetal growth.

Method

We used intergenerational two-sample Mendelian randomization to explore the effects of 1,139 maternal and fetal genetically-instrumented plasma proteins on birth weight. We used genome-wide association summary data from the Early Growth Genetics (EGG) consortium (n=406,063 with maternal and/or fetal genotype), with independent replication in the Norwegian Mother, Father and Child Cohort Study (MoBa; n=74,932 mothers and n=62,108 offspring). Maternal and fetal data were adjusted for the correlation between fetal and maternal genotype, to distinguish their independent genetic effects.

Results

We found that higher genetically-predicted maternal levels of NEC1 increased birth weight (mean-difference: 12g (95% CI [6g, 18g]) per 1 standard deviation protein level) as did PRS57 (20g [10g, 31g]) and ULK3 (140g [81g, 199g]). Higher maternal levels of Galectin_4 decreased birth weight (-206g [-299g, -113g]). In contrast, in the offspring, higher genetically-predicted offspring levels of NEC1 decreased birth weight (-10g [-16g, -5g]), alongside sLeptin_R (-8g [-12g, -4g]), and UBS3B (-78g [-116g, -41g]). Higher fetal levels of Galectin_4 increased birth weight (174g [89g, 258g]). We replicated these results in MoBa, and found supportive evidence for shared causal variants from genetic colocalization analyses and protein-protein network associations.

Conclusions

We find strong evidence for causal effects, sometimes in opposing directions, of maternal and fetal genetically-instrumented proteins on birth weight. These provide new insights into maternal and fetal molecular mechanisms regulating fetal growth, involving glucose metabolism, energy balance, and vascular function that could be used to identify new intervention targets to reduce the risk of fetal growth disorders, and their associated adverse maternal and fetal outcomes.

Rare variant associations with birth weight identify genes involved in adipose tissue regulation, placental function and insulin-like growth factor signalling

Investigating the genetic factors influencing human birth weight may lead to biological insights into fetal growth and long-term health. We report analyses of rare variants that impact birth weight when carried by either fetus or mother, using whole exome sequencing data in up to 234,675 participants. Rare protein-truncating and deleterious missense variants are collapsed to perform gene burden tests. We identify 9 genes; 5 with fetal-only effects on birth weight, 1 with maternal-only effects, 3 with both, and observe directionally concordant associations in an independent sample. Four of the genes were previously implicated by GWAS of birth weight. IGF1R and PAPPA2 (fetal and maternal-acting) have known roles in insulin-like growth factor bioavailability and signalling. PPARG, INHBE and ACVR1C (fetal-acting) are involved in adipose tissue regulation, and the latter two also show associations with favourable adiposity patterns in adults. We highlight the dual role of PPARG (fetal-acting) in adipocyte differentiation and placental angiogenesis. NOS3 (fetal and maternal-acting), NRK (fetal), and ADAMTS8 (maternal-acting) have been implicated in placental function and hypertension. To conclude, our analysis of rare coding variants identifies regulators of fetal adipose tissue and fetoplacental angiogenesis as determinants of birth weight, and further evidence for the role of insulin-like growth factors.

Childhood adiposity underlies numerous adult brain traits commonly attributed to midlife obesity

Obese adults are often reported to have smaller brain volumes than their non-obese peers. Whether this represents evidence of accelerations in obesity-driven atrophy or is instead a legacy of developmental differences established earlier in the lifespan remains unclear. This study investigated whether early-life differences in adiposity explain differences in numerous adult brain traits commonly attributed to mid-life obesity. We used a two-sample life course Mendelian randomization study in 37 501 adults recruited to UK Biobank (UKB) imaging centres from 2014, with secondary analyses in 6996 children assessed in the Adolescent Brain Cognitive Development Study (ABCD) recruited from 2018. Exposures were genetic variants for childhood (266 variants) and adult (470 variants) adiposity derived from a genome-wide association study (GWAS) of 407 741 UKB participants. Primary outcomes were: adult total brain volume; grey matter volume, thickness and surface area; white matter volume and hyperintensities; and hippocampus, amygdala and thalamus volumes at mean age 55 in the UKB. Secondary outcomes were equivalent childhood measures collected at mean age 10 in ABCD. In the UKB, individuals who were genetically predicted to have had higher levels of adiposity in childhood were found to have multiple smaller adult brain volumes relative to intracranial volume [e.g. z-score difference in normalized brain volume per category increase in adiposity-95% confidence interval (CI) = -0.20 (-0.28, -0.12); P = 4 × 10-6]. These effect sizes remained essentially unchanged after accounting for birthweight or current adult obesity in multivariable models, whereas most observed adult effects attenuated towards null [e.g. adult z-score (95% CI) for total volume = 0.06 (-0.05, 0.17); P = 0.3]. Observational analyses in ABCD showed a similar pattern of changes already present in those with a high body mass index by age 10 [z-score (95% CI) = -0.10 (-0.13, -0.07); P = 8 × 10-13], with follow-up genetic risk score analyses providing some evidence for a causal effect already at this early age. Sensitivity analyses revealed that many of these effects were likely due to the persistence of larger head sizes established in those who gained excess weight in childhood [childhood z-score (95% CI) for intracranial volume = 0.14 (0.05, 0.23); P = 0.002], rather than smaller brain sizes per se. Our data suggest that the persistence of early-life developmental differences across the life course may underlie numerous neuroimaging traits commonly attributed to obesity-related atrophy in later life.

Lifelong impacts of puberty timing on human plasma metabolic profiles: A metabolome-wide Mendelian randomization study

AIM

The aim was to investigate the causal relationship between puberty timing and plasma metabolites, accounting for birth weight, childhood and adulthood adiposity.

MATERIALS AND METHODS

The meta-analysis of genome-wide association studies (GWAS) for puberty timing was extracted from the ReproGen Consortium, involving 329 345 women of European ancestry. Summary data for 174 plasma metabolites were retrieved from a recently conducted cross-platform GWAS that involved a meta-analysis of three cohort studies (i.e. the Fenland, European Prospective Investigation into Cancer-Norfolk and INTERVAL studies) and three publicly available studies and included up to 86 507 participants. We conducted a two-sample Mendelian randomization (MR) analysis to infer the causal relationship of puberty timing on 174 plasma metabolites, complemented by a two-step and multivariable Mendelian randomization (MVMR) analysis to assess direct and indirect effects. Additionally, summary-level data from the UK Biobank were used for our replication analysis.

RESULTS

The results of the two-sample MR provide moderate evidence supporting a causal relationship between puberty timing and 23 of 174 plasma metabolites (i.e. 7 acylcarnitines, 8 amino acids, 2 biogenic amines and 6 lysophosphatidylcholines). Even after single-nucleotide polymorphisms associated with birth weight and childhood adiposity were excluded, causal effects persisted for 16 metabolites (i.e. 8 acylcarnitines, 4 amino acids, 2 biogenic amines and 2 lysophosphatidylcholines). The two-step MR analysis provided evidence that the relationship between puberty timing and plasma metabolites was mediated by adulthood adiposity. Additionally, moderate evidence emerged for an independent causal effect of puberty timing on 10 metabolites through an MVMR analysis (i.e. 5 acylcarnitines, 2 amino acids, 1 biogenic amine, 1 lysophosphatidylcholine and 1 phosphatidylcholine). Furthermore, the replication analysis suggested the robustness of our results.

CONCLUSIONS

In summary, our study provides compelling evidence that puberty timing has a causal influence on certain plasma metabolites, although this influence is largely mediated by adulthood adiposity.

Cross-sectional relationships of circadian misalignment and rest-activity rhythms with occupational attainment in UK Biobank participants

Circadian misalignment and disrupted rest-activity rhythms have been linked to adverse health and educational outcomes, yet few studies have considered their relationships with economic outcomes. We investigate associations between multiple accelerometer-measured circadian misalignment traits (Composite Phase Deviation and the Sleep Regularity Index) and rest-activity rhythm traits (Inter-daily Stability, Intra-daily variability and relative amplitude), with occupational attainment, measured using the average wage paid to an individual's occupation. We use data from 20 356 UK Biobank participants who wore an accelerometer (2013-16), provided employment data for the year they wore the accelerometer, and supplied covariate data at recruitment (2006-10). We use linear regression, with incremental adjustments for four sets of covariates, and stratify our analysis by sex. Our findings provide mixed evidence on the relationship between circadian misalignment and occupational attainment, varying by the measure of circadian misalignment used, and sex. We find fragmented rest-activity rhythms to be associated with higher occupational attainment, which is counterintuitive. Since circadian misalignment is a modifiable trait, our results suggest potential benefits of policies aimed at reducing circadian misalignment, such as altering work schedules and reducing bright light exposure in the evening. Further research is needed to elucidate the mechanisms through which rest-activity rhythms may impact economic outcomes.

Modifiable factors for irritable bowel syndrome: evidence from Mendelian randomisation approach

ABSTRACT

Background

The potential modifiable factors influencing irritable bowel syndrome (IBS) have not been thoroughly documented. We aimed to systematically investigate the modifiable factors associated with IBS, while accounting for the impact of unobserved confounders and coexisting disorders.

Methods

Genetic correlation and Mendelian randomisation (MR) analyses were integrated to identify potential modifiable factors and coexisting disorders linked to IBS. Subsequently, multiresponse MR (MR2) was employed to further examine these associations. Summary-level genome-wide association data were used. Modifiable factors and coexisting disorders (ie, gastrointestinal and psychiatric disorders) were identified based on evidence from cohort studies and meta-analysis. In all analyses, IBS was the primary outcome, while in the MR2 analysis, coexisting disorders were also treated as outcomes alongside IBS.

Results

Most identified modifiable factors and coexisting disorders exhibited genetic correlations with IBS. MR analyses revealed strong causation between IBS and multisite chronic pain (OR=2.20, 95% CI 1.82 to 2.66), gastro-oesophageal reflux disease (OR=1.31, 95% CI 1.23 to 1.39), well-being spectrum (OR=0.17, 95% CI 0.13 to 0.21), life satisfaction (OR=0.31, 95% CI 0.25 to 0.38), positive affect (OR=0.30, 95% CI 0.24 to 0.37), neuroticism score (OR=1.20, 95% CI 1.16 to 1.25) and depression (OR=1.50, 95% CI 1.37 to 1.66). Additionally, smoking, alcohol frequency, college or university degree, intelligence, childhood maltreatment, frailty index, diverticular disease of the intestine and schizophrenia were suggestively associated with IBS. Robust associations were found between multisite chronic pain and both IBS and coexisting disorders.

Conclusions

Our study identified a comprehensive array of potential modifiable factors and coexisting disorders associated with IBS, supported by genetic evidence, including genetic correlation and multiple MR analyses. The presence of multisite chronic pain may offer a promising avenue for the concurrent prevention of IBS and its coexisting disorders.

Exploring and Accounting for Genetically Driven Effect Heterogeneity in Mendelian Randomization

Mendelian randomization (MR) is a framework to estimate the causal effect of a modifiable health exposure, drug target or pharmaceutical intervention on a downstream outcome by using genetic variants as instrumental variables. A crucial assumption allowing estimation of the average causal effect in MR, termed homogeneity, is that the causal effect does not vary across levels of any instrument used in the analysis. In contrast, the science of pharmacogenetics seeks to actively uncover and exploit genetically driven effect heterogeneity for the purposes of precision medicine. In this study, we consider a recently proposed method for performing pharmacogenetic analysis on observational data-the Triangulation WIthin a STudy (TWIST) framework-and explore how it can be combined with traditional MR approaches to properly characterise average causal effects and genetically driven effect heterogeneity. We propose two new methods which not only estimate the genetically driven effect heterogeneity but also enable the estimation of a causal effect in the genetic group with and without the risk allele separately. Both methods utilise homogeneity-respecting and homogeneity-violating genetic variants and rely on a different set of assumptions. Using data from the ALSPAC study, we apply our new methods to estimate the causal effect of smoking before and during pregnancy on offspring birth weight in mothers whose genetics mean they find it (relatively) easier or harder to quit smoking.

Maternal genomic profile, gestational diabetes control, and Mediterranean diet to prevent low birth weight

Low birth weight (LBW) is associated to poor health outcomes. Its causes include maternal lifestyle, obstetric factors, and fetal (epi)genetic abnormalities. This study aims to increase the knowledge regarding the genetic background of LBW by analyzing its association with a set of 110 maternal variants related to gestational diabetes mellitus, in the setting of a nutritional intervention with Mediterranean diet. The analysis follows a multifactorial approach, including maternal genetic information of 1,642 pregnant women, along with their anthropometric and metabolic characteristics. Binary logistic regression models provided 33 discovery variants associated with LBW that underwent a functional enrichment process to obtain a protein/gene interaction network and 126 enriched terms. Overall, our analysis proves that genetic variants form proximity clusters, grouped into subsets statistically associated with underlying biological processes or other maternal characteristics, which, on their part, allow early prevention of the eventual risk of LBW.

Multi-ancestry GWAS of severe pregnancy nausea and vomiting identifies risk loci associated with appetite, insulin signaling, and brain plasticity

While most pregnancies are affected by nausea and vomiting, hyperemesis gravidarum (HG) is at the severe end of the clinical spectrum and is associated with dehydration, undernutrition, and adverse maternal, fetal, and child outcomes. Herein we performed a multi-ancestry genome-wide association study (GWAS) of severe nausea and vomiting of pregnancy of 10,974 cases and 461,461 controls across European, Asian, African, and Latino ancestries. We identified ten significantly associated loci, of which six were novel (SLITRK1, SYN3, IGSF11, FSHB, TCF7L2, and CDH9), and confirmed previous genome-wide significant associations with risk genes GDF15, IGFBP7, PGR, and GFRAL. In a spatiotemporal analysis of placental development, GDF15 and TCF7L2 were expressed primarily in extra villous trophoblast, and using a weighted linear model of maternal, paternal, and fetal effects, we confirmed opposing effects for GDF15 between maternal and fetal genotype. Conversely, IGFBP7 and PGR were primarily expressed in developing maternal spiral arteries during placentation, with effects limited to the maternal genome. Risk loci were found to be under significant evolutionary selection, with the strongest effects on nausea and vomiting mid-pregnancy. Selected loci were associated with abnormal pregnancy weight gain, pregnancy duration, birth weight, head circumference, and pre-eclampsia. Potential roles for candidate genes in appetite, insulin signaling, and brain plasticity provide new pathways to explore etiological mechanisms and novel therapeutic avenues.

Multi-ancestry Genome Wide Association Study Meta-analysis of Non-syndromic Orofacial Clefts

Non-syndromic orofacial clefts (NSOC) are common craniofacial birth defects, and result from both genetic and environmental factors. NSOC include three major sub-phenotypes: non-syndromic cleft lip with palate (NSCLP), non-syndromic cleft lip only (NSCLO) and non-syndromic cleft palate only (NSCPO), NSCLP and NSCLO are also sometimes grouped as non-syndromic cleft lip with or without cleft palate (NSCL/P) based on epidemiology. Currently known loci only explain a limited proportion of the heritability of NSOC. Further, differences in genetic susceptibility among the sub-phenotypes are poorly characterized. We performed a multi-ancestry GWAS meta-analysis on 44,094 individuals (9,381 cases, 28,510 controls, 2042 case-parent trios and 18 multiplex pedigrees) of East Asian, European, Latin and South American, and African ancestry for both NSOC and subtypes. We identified 50 loci, including 11 novel loci: four loci ( CALD1 , SHH , NRG1 and LINC00320 ) associated with both NSOC and NSCL/P, two loci ( NTRK1 and RUNX1 ) only associated with NSOC, four loci ( HMGCR , PRICKLE1 , SOX9 and MYH9 ) only associated with NSCL/P and one locus ( ALX1 ) specifically associated with NSCLO. Five of the novel loci are located in regions containing genes associated with syndromic orofacial clefts ( SHH , NTRK1, CALD1, ALX1 and SOX9 ); seven of the novel loci are located in regions containing genes-implicated in craniofacial development ( HMGCR, SHH, PRICKLE1, ALX1, SOX9, RUNX1, MYH9 ). Genetic correlation and colocalization analyses revealed an overlap between signals associated with NSCLO, NSCPO and NSCLP, but there were also notable differences, emphasizing the complexity of common and distinct genetic processes affecting lip and palate development.

Exome sequencing of UK birth cohorts

Birth cohort studies involve repeated surveys of large numbers of individuals from birth and throughout their lives. They collect information useful for a wide range of life course research domains, and biological samples which can be used to derive data from an increasing collection of omic technologies. This rich source of longitudinal data, when combined with genomic data, offers the scientific community valuable insights ranging from population genetics to applications across the social sciences. Here we present quality-controlled whole exome sequencing data from three UK birth cohorts: the Avon Longitudinal Study of Parents and Children (8,436 children and 3,215 parents), the Millenium Cohort Study (7,667 children and 6,925 parents) and Born in Bradford (8,784 children and 2,875 parents). The overall objective of this coordinated effort is to make the resulting high-quality data widely accessible to the global research community in a timely manner. We describe how the datasets were generated and subjected to quality control at the sample, variant and genotype level. We then present some preliminary analyses to illustrate the quality of the datasets and probe potential sources of bias. We introduce measures of ultra-rare variant burden to the variables available for researchers working on these cohorts, and show that the exome-wide burden of deleterious protein-truncating variants, S het burden, is associated with educational attainment and cognitive test scores. The whole exome sequence data from these birth cohorts (CRAM & VCF files) are available through the European Genome-Phenome Archive, and here we provide guidance for their use.

Engaging Australian healthcare consumers to determine priorities and consensus for precision medicine approaches to detect non-communicable disease in early life: a modified Delphi study

OBJECTIVES

Research to develop early screening tools to determine an individual's risk of developing adult-onset disease is a growing field. Expectant parents may find themselves with an option in the future to undergo screening to determine not only genetic abnormalities in their child but also their risk of developing adult-onset non-communicable diseases (NCD) such as hypertension, obesity or hypercholesterolaemia. To ensure acceptability and feasibility of new screening tools researchers must work in partnership with healthcare consumers to discern consumers' current understanding and acceptance of these technologies in research and the potential for clinical applications. We sought to engage with healthcare consumers to develop a consensus, using a modified Delphi study design, for the acceptability of (1) screening tools for use within pregnancy that would indicate a child's risk for developing NCD, and (2) targeted early interventions for those identified at a higher risk of developing NCD using precision medicine approaches. The acceptability of future research design and conduct as well as the implications for implementation into routine healthcare were discussed. In addition, participants were asked to rank the non-communicable diseases they believed were of most importance for precision medicine research focus, in line with recent calls for better involvement of healthcare consumers in setting research questions and defining priority areas.

DESIGN

A modified two-stage Delphi study design including an in-person consumer workshop (stage 1) and online follow-up survey (stage 2), was used to evaluate consumer consensus for research to develop precision medicine tools for early detection and potential intervention to reduce onset of NCDs. The acceptability of research design and conduct and future implications for the implementation of newly developed tools into routine healthcare was also addressed.

SETTING AND PARTICIPANTS

We engaged 76 healthcare consumers in 2020, in the Hunter New England Region, New South Wales, Australia. Participants were recruited from existing healthcare consumer organisations, research programmes and healthcare networks through purposeful selection, with a focus on participants having a broad range of experiences and backgrounds to ensure adequate representativeness.

RESULTS AND CONCLUSIONS

Our findings indicate the majority (98%) of participants in our study believe early screening for risk of NCD in their children was acceptable, provided it was equitable and clear pathways for referral and support were available.

Relationship between paternal excessive weight and neonatal anthropometry in a clinical trial of nutritional counseling for pregnant women with overweight

BACKGROUND/OBJECTIVES

Human studies suggest that fathers with obesity influence infant growth and development. This study aimed to evaluate the relationship between paternal body mass index (BMI) and waist circumference (WC) with neonatal anthropometry and adiposity.

METHODS

This study is a cohort nested in a randomized controlled clinical trial of nutritional counseling for pregnant women with overweight. In total, 89 partner-pregnant woman-neonate triads were included. Paternal anthropometric measurements were taken at the time of the interview. Secondary data related to birth were obtained through access to the health information systems. Neonatal skinfold thickness was assessed and the adiposity was estimated using a predictive anthropometric model. Pearson's correlation and adjusted multivariate linear regression models were employed to evaluate the relationship between paternal BMI and WC with neonatal anthropometric measurements and adiposity.

RESULTS

In total, 57.0% of the fathers presented a BMI ≥ 25 kg/m² and 14.6% a waist circumference ≥102 cm. The mean ± SD birth weight of the newborns (g) was 3357 ± 538. Paternal BMI and WC were inversely correlated with head circumference at birth [r = -0.31 (p = 0.004), r = -0.23 (p = 0.03), respectively]. Paternal BMI was also inversely correlated with the birth weight standardized by gestational age (z-score) [r = -0.23 (p = 0.03)]. In adjusted multivariate linear regression models, the paternal BMI (kg/m²) was inversely associated with the head circumference at birth (cm) [β = -0.07 (95% CI -0.15; -0.001) p = 0.04].

CONCLUSION

The data suggest that paternal excessive weight have a negative effect on fetal development, as assessed by anthropometric measurements. The inverse association between paternal BMI and the head circumference at birth was independent of confounders. Future studies with larger sample sizes are necessary to confirm or refute such hypotheses.

Genotypic and phenotypic consequences of domestication in dogs

Runs of homozygosity (ROH) are genomic regions that arise when two copies of identical haplotypes are inherited from a shared common ancestor. In this study, we leverage ROH to identify associations between genetic diversity and non-disease phenotypes in Canis lupus familiaris (dogs). We find significant association between the ROH inbreeding coefficient (FROH) and several phenotypic traits. These traits include height, weight, lifespan, muscled, white coloring of the head and chest, furnishings, and fur length. After correcting for population structure, we identified more than 45 genes across the examined quantitative traits that exceed the threshold for suggestive significance. We observe distinct distributions of inbreeding and elevated levels of long ROH in modern breed dogs compared to more ancient breeds, which aligns with breeding practices during Victorian era breed establishment. Our results highlight the impact of non-additive variation and of polygenicity on complex quantitative phenotypes in dogs due to domestication and the breed formation bottleneck.

Multi-ancestry GWAS of severe pregnancy nausea and vomiting identifies risk loci associated with appetite, insulin signaling, and brain plasticity

While most pregnancies are affected by nausea and vomiting, hyperemesis gravidarum (HG) is at the severe end of the clinical spectrum and is associated with dehydration, undernutrition, and adverse maternal, fetal, and child outcomes. Herein we performed a multi-ancestry genome-wide association study (GWAS) of severe nausea and vomiting of pregnancy of 10,974 cases and 461,461 controls across European, Asian, African, and Latino ancestries. We identified ten significantly associated loci, of which six were novel (SLITRK1, SYN3, IGSF11, FSHB, TCF7L2, and CDH9), and confirmed previous genome-wide significant associations with risk genes GDF15, IGFBP7, PGR, and GFRAL. In a spatiotemporal analysis of placental development, GDF15 and TCF7L2 were expressed primarily in extra villous trophoblast, and using a weighted linear model of maternal, paternal, and fetal effects, we confirmed opposing effects for GDF15 between maternal and fetal genotype. Conversely, IGFBP7 and PGR were primarily expressed in developing maternal spiral arteries during placentation, with effects limited to the maternal genome. Risk loci were found to be under significant evolutionary selection, with the strongest effects on nausea and vomiting mid-pregnancy. Selected loci were associated with abnormal pregnancy weight gain, pregnancy duration, birth weight, head circumference, and pre-eclampsia. Potential roles for candidate genes in appetite, insulin signaling, and brain plasticity provide new pathways to explore etiological mechanisms and novel therapeutic avenues.

Birthweight influences liver structure, function and disease risk: Evidence of a causal association

AIM

Low birthweight is an issue during pregnancy associated with an increased risk of developing liver disease later in life. Previous Mendelian randomisation (MR) studies which explored this issue have not isolated the direct impact of the foetus on birthweight. In the present study, MR was used to assess whether direct foetal effects on birthweight were causally associated with liver structure, function and disease risk independent of intrauterine effects.

MATERIALS AND METHODS

We extracted single nucleotide polymorphisms (SNPs) from genome-wide association studies (GWAS) about direct foetal-affected birthweight (321 223 cases) to conduct univariable and multivariable MR analyses to explore the relationships between birthweight and 4 liver structure measures, 9 liver function measures and 18 liver diseases. A two-step MR analysis was used to further assess and quantify the mediating effects of the mediators.

RESULTS

When isolating direct foetal effects, genetically predicted lower birthweight was associated with a higher risk of non-alcoholic fatty liver disease (NAFLD) (odds ratios [OR], 95% confidence interval [CI]: 1.61, 1.29-2.02, p < 0.001), higher magnetic resonance imaging [MRI] proton density fat fraction (PDFF) and higher serum gamma glutamyltransferase (GGT). Two-step MR identified two candidate mediators that partially mediate the direct foetal effect of lower birthweight on NAFLD, including fasting insulin (proportion mediated: 22.29%) and triglycerides (6.50%).

CONCLUSIONS

Our MR analysis reveals a direct causal association between lower birthweight and liver MRI PDFF, as well as the development of NAFLD, which persisted even after accounting for the potential influence of maternal factors. In addition, we identified fasting insulin and triglycerides as mediators linking birthweight and hepatic outcomes, providing insights for early clinical interventions.

Sex-Specific Effects of Birth Weight on Longitudinal Behavioral Outcomes: A Mendelian Randomization Approach Using Polygenic Scores

Background

It is unclear whether sex differences in behavior arising from birth weight (BW) are genuine because of the cross-sectional nature and potential confounding in previous studies. We aimed to test whether sex differences associated with BW phenotype were reproducible using a Mendelian randomization approach, i.e., association between polygenic score (PGS) for BW and behavior outcomes across childhood and adolescence.

Methods

Using data from the Raine Study, we had 1484 genotyped participants with a total of 6446 Child Behavior Checklist assessments from ages 5 to 17 years. We used BW-PGSs in linear mixed-effect models to predict parentally assessed attention, aggression, and social problems scales; we also derived estimates and significance for a sex-by-genotype interaction. We used a Bonferroni-corrected significance threshold and tested robustness of the results with teacher assessments of behavior and a second PGS.

Results

We found a sex-by-genotype interaction with lower BW-PGSs associated with increased aggression in males compared with females. These findings were consistent across various analyses, including teacher assessments. Surprisingly, a lower BW-PGS showed protective effects in females, while a lower BW phenotype had detrimental effects in males with evidence of a genotype-phenotype mismatch increasing aggression problems in males only.

Conclusions

This study underscores the genuine nature of behavioral sex differences arising from low BW and highlights the sex-dependent and diverging effects of environmental and genetic BW determinants.

LCoRL Regulates Growth and Metabolism

Genome-wide association studies (GWAS) in humans and livestock have identified genes associated with metabolic traits. However, the causality of many of these genes on metabolic homeostasis is largely unclear due to a lack of detailed functional analyses. Here we report ligand-dependent corepressor-like (LCoRL) as a metabolic regulator for body weight and glucose homeostasis. Although GWAS data show that LCoRL is strongly associated with body size, glucose homeostasis, and other metabolic traits in humans and livestock, functional investigations had not been performed. We generated Lcorl knockout mice (Lcorl-/-) and characterized the metabolic traits. We found that Lcorl-/- pups are born smaller than the wild-type (WT) littermates before reaching normal weight by 7 to 9 weeks of age. While aging, Lcorl-/- mice remain lean compared to WT mice, which is associated with a decrease in daily food intake. Glucose tolerance and insulin sensitivity are improved in Lcorl-/- mice. Mechanistically, this stunted growth is linked to a reduction of circulating levels of IGF-1. The expression of the genes downstream of GH signaling and the genes involved in glucose and lipid metabolism are altered in the liver of Lcorl-/- mice. Furthermore, Lcorl-/- mice are protected against a high-fat diet challenge and show reduced exercise capacity in an exercise stress test. Collectively, our results are congruent with many of the metabolic parameters linked to the Lcorl locus as reported in GWAS in humans and livestock.

Controlling for polygenic genetic confounding in epidemiologic association studies

Epidemiologic associations estimated from observational data are often confounded by genetics due to pervasive pleiotropy among complex traits. Many studies either neglect genetic confounding altogether or rely on adjusting for polygenic scores (PGS) in regression analysis. In this study, we unveil that the commonly employed PGS approach is inadequate for removing genetic confounding due to measurement error and model misspecification. To tackle this challenge, we introduce PENGUIN, a principled framework for polygenic genetic confounding control based on variance component estimation. In addition, we present extensions of this approach that can estimate genetically unconfounded associations using GWAS summary statistics alone as input and between multiple generations of study samples. Through simulations, we demonstrate superior statistical properties of PENGUIN compared to the existing approaches. Applying our method to multiple population cohorts, we reveal and remove substantial genetic confounding in the associations of educational attainment with various complex traits and between parental and offspring education. Our results show that PENGUIN is an effective solution for genetic confounding control in observational data analysis with broad applications in future epidemiologic association studies.

DINGO: increasing the power of locus discovery in maternal and fetal genome-wide association studies of perinatal traits

Perinatal traits are influenced by fetal and maternal genomes. We investigate the performance of three strategies to detect loci in maternal and fetal genome-wide association studies (GWASs) of the same quantitative trait: (i) the traditional strategy of analysing maternal and fetal GWASs separately; (ii) a two-degree-of-freedom test which combines information from maternal and fetal GWASs; and (iii) a one-degree-of-freedom test where signals from maternal and fetal GWASs are meta-analysed together conditional on estimated sample overlap. We demonstrate that the optimal strategy depends on the extent of sample overlap, correlation between phenotypes, whether loci exhibit fetal and/or maternal effects, and whether these effects are directionally concordant. We apply our methods to summary statistics from a recent GWAS meta-analysis of birth weight. Both the two-degree-of-freedom and meta-analytic approaches increase the number of genetic loci for birth weight relative to separately analysing the scans. Our best strategy identifies an additional 62 loci compared to the most recently published meta-analysis of birth weight. We conclude that whilst the two-degree-of-freedom test may be useful for the analysis of certain perinatal phenotypes, for most phenotypes, a simple meta-analytic strategy is likely to perform best, particularly in situations where maternal and fetal GWASs only partially overlap.

GWAS shows the genetics behind cell-free DNA and highlights the importance of p.Arg206Cys in DNASE1L3 for non-invasive testing

The properties of cell-free DNA (cfDNA) are intensely studied for their potential as non-invasive biomarkers. We explored the effect of common genetic variants on the concentration and fragmentation properties of cfDNA using a genome-wide association study (GWAS) based on low-coverage whole-genome sequencing data of 140,000 Dutch non-invasive prenatal tests (NIPTs). Our GWAS detects many genome-wide significant loci, functional enrichments for phagocytes, liver, adipose tissue, and macrophages, and genetic correlations with autoimmune and cardiovascular disease. A common (7%) missense variant in DNASE1L3 (p.Arg206Cys) strongly affects all cfDNA properties. It increases the size of fragments, lowers cfDNA concentrations, affects the distribution of cleave-site motifs, and increases the fraction of circulating fetal DNA during pregnancy. For the application of NIPT, and potentially other cfDNA-based tests, this variant has direct clinical consequences, as it increases the odds of inconclusive results and impairs the sensitivity of NIPT by causing predictors to overestimate the fetal fraction.

Estimation of Direct and Indirect Polygenic Effects and Gene-Environment Interactions using Polygenic Scores in Case-Parent Trio Studies

Family-based studies provide a unique opportunity to characterize genetic risks of diseases in the presence of population structure, assortative mating, and indirect genetic effects. We propose a novel framework, PGS-TRI, for the analysis of polygenic scores (PGS) in case-parent trio studies for estimation of the risk of an index condition associated with direct effects of inherited PGS, indirect effects of parental PGS, and gene-environment interactions. Extensive simulation studies demonstrate the robustness of PGS-TRI in the presence of complex population structure and assortative mating compared to alternative methods. We apply PGS-TRI to multi-ancestry trio studies of autism spectrum disorders (Ntrio = 1,517) and orofacial clefts (Ntrio = 1,904) to establish the first transmission-based estimates of risk associated with pre-defined PGS for these conditions and other related traits. For both conditions, we further explored offspring risk associated with polygenic gene-environment interactions, and direct and indirect effects of genetically predicted levels of gene expression and metabolite traits.

No evidence for a causal contribution of bioavailable testosterone to ADHD in sex-combined and sex-specific two-sample Mendelian randomization studies

The higher prevalence of attention-deficit/hyperactivity disorder (ADHD) in males raises the question of whether testosterone is implicated in ADHD risk. However, cross-sectional studies did not identify an association between ADHD and testosterone levels. Mendelian randomization (MR) studies can overcome limitations inherent to association studies, especially of reverse causation and residual confounding. In the current study, sex-combined and sex-specific two-sample MR analyses were conducted to address whether testosterone has a causal influence on ADHD risk. Sex-combined as well as sex-specific target-genetic variants for bioavailable testosterone were derived from a large genome-wide association study (GWAS) on up to 382,988 adult white European UK Biobank study participants. In our sex-specific analyses for ADHD, including data from 14,154 males and 4,945 females with ADHD (17,948 and 16,246 controls respectively), no association between bioavailable testosterone and ADHD risk was found, neither in males (inverse-variance weighted (IVW): beta = 0.09, 95%-CI [-0.10, 0.27]) nor in females (IVW: beta=-0.01, 95%-CI [-0.20, 0.19]). However, in the sex-combined analysis, including 38,691 cases and 186,843 controls, genetically predicted bioavailable testosterone was associated with ADHD risk (IVW: beta = 0.24, 95%-CI [0.09, 0.39]). The inclusion of birth weight and/or SHBG as additional variables in multivariable MR analyses did not alter this result. However, when correcting for potential BMI-driven pleiotropy by a multivariable MR study, all effect estimates for testosterone showed non-significant results. Taken together, no robust evidence for a causal effect of bioavailable testosterone on the risk for ADHD was found.

Unravel the distinct effects of adiposity at different life stages on COVID-19 susceptibility and severity: A life-course Mendelian randomization study

Childhood obesity is widely recognized as a risk factor for numerous health conditions, particularly cardiovascular disease. However, it remains unclear whether childhood adiposity directly affects the risk of COVID-19 in later life. We aimed to investigate the causal effects of early life adiposity on COVID-19 susceptibility and severity. We used genetic instruments from large-scale genome-wide association studies to examine the relationships between birth weight, childhood and adulthood adiposity indicators (including body mass index [BMI], obesity, and body size), and COVID-19 outcomes. Univariable and multivariable Mendelian randomization (MR) analyses were used to obtain the causal estimates. Univariable MR analyses found that childhood BMI and obesity were positively associated with COVID-19 risk and severity in adulthood, however, the significant associations were attenuated to null after further adjusting for adulthood adiposity indicators in multivariable MR analyses. In contrast, our analysis revealed strong evidence of a genetically predicted effect of childhood obesity on COVID-19 hospitalization (OR 1.08, 95% CI: 1.01-1.15, p = 2.12E-2), which remained robust even after adjusting for adulthood obesity and potential lifestyle confounders. Our results highlight the importance of promoting healthy weight management throughout life to reduce the risk of COVID-19.

The onset and the development of cardiometabolic aging: an insight into the underlying mechanisms

Metabolic compromise is crucial in aggravating age-associated chronic inflammation, oxidative stress, mitochondrial damage, increased LDL and triglycerides, and elevated blood pressure. Excessive adiposity, hyperglycemia, and insulin resistance due to aging are associated with elevated levels of damaging free radicals, inducing a proinflammatory state and hampering immune cell activity, leading to a malfunctioning cardiometabolic condition. The age-associated oxidative load and redox imbalance are contributing factors for cardiometabolic morbidities via vascular remodelling and endothelial damage. Recent evidence has claimed the importance of gut microbiota in maintaining regular metabolic activity, which declines with chronological aging and cardiometabolic comorbidities. Genetic mutations, polymorphic changes, and environmental factors strongly correlate with increased vulnerability to aberrant cardiometabolic changes by affecting key physiological pathways. Numerous studies have reported a robust link between biological aging and cardiometabolic dysfunction. This review outlines the scientific evidence exploring potential mechanisms behind the onset and development of cardiovascular and metabolic issues, particularly exacerbated with aging.