Abstract Background This study aimed to investigate whether retinal fractal dimension (D f ), a measure of microvascular branching complexity from fundus images, together with plasma metabolites, can help identify pathways linking microvascular changes to cardiovascular disease (CVD) events. Methods We analyzed longitudinal data from a subset of 4,781 participants from the Comprehensive cohort of the Canadian Longitudinal Study on Aging (CLSA), free of CVD at baseline (mean age 58.74 ± 8.39; 47% male), and with 811 plasma metabolites measured at baseline and retinal imaging. Total, arterial and venular D f were derived from fundus photographs using the Vessel Assessment and Measurement Platform for Images of the Retina. Incident CVD was defined as one or more of self-reported physician-diagnosed myocardial infarction, angina, coronary heart disease, stroke, transient ischemic attack, or peripheral vascular disease during follow-up. Regression models tested associations among D f , plasma metabolites and incident CVD. Results Over a median follow-up of 5.75 years (IQR 5.48-6.04), 546 participants (11.42%) developed CVD. Higher total, arterial and venular D f were associated with lower CVD risk in unadjusted analyses (Odds Ratio (OR)=0.62, 95% CI:0.53-0.72 for total D f ; OR=0.78, 95% CI:0.70-0.86 for arterial D f ; OR=0.74, 95% CI:0.67-0.82 for venular D f ). Total D f demonstrated the strongest predictive value for incident CVD but not independently of established CVD risk factors. Nine plasma metabolites, including amino acids, lipids, and xenobiotics, were associated with both incident CVD and one D f measure (p < 0.05), with cotinine and hydroxycotinine satisfying a false discovery rate adjustment (q < 0.05). Consistent with these findings the Total Nicotine Equivalent (TNE-3) was also associated with both lower arterial D f and increased CVD risk. Conclusions Retinal microvascular complexity is associated with incident CVD. Nicotine metabolism from tobacco smoking exposures emerged as the strongest association linking microvascular changes and CVD events. Clinical Perspective What is New? Lower retinal branching complexity, as measured through D f , is significantly associated with incident cardiovascular disease (CVD) in unadjusted analyses. In a population-based sample, we found nine plasma metabolites associated with both retinal vascular complexity and incident CVD, but only nicotine metabolites were significant after multiple testing correction. Nicotine metabolites, particularly cotinine and hydroxycotinine, remained significantly associated with incident CVD even after adjustment for self-reported smoking status. What Are the Clinical Implications? Retinal D f measures could be used as a predictor of CVD event, although not independently of age and traditional cardiovascular risk factors. Microvascular changes may lie on the pathway linking nicotine metabolites to CVD events. Plasma nicotine metabolites may provide additional cardiovascular risk information beyond self-reported smoking, reflecting individual exposure, metabolism and passive smoke exposure.

Introduction Peripheral artery disease (PAD) affected approximately 800 000 Canadians aged 25 years or older in 2015 and it poses a substantial risk of lower extremity amputation (LEA). While clinical risk factors for amputation are well-established, the impact of social determinants of health (SDoH) on amputation risk remains unclear, particularly in a Canadian context.Objectives This systematic review aims to: (1) synthesise evidence on the associations between multilevel SDoH domains and LEA (both major and/or minor) risk in Canadian PAD patients including intersectional effects of race and ethnicity with another SDoH domain, and (2) evaluate the statistical methodologies used in the researched literature to inform future study design and analysis approaches.Methods and analysis We will systematically search MEDLINE, Embase, EmCare, Global Health, Cumulative Index to Nursing and Allied Health Literature and Web of Science for studies examining SDoH and LEA in Canadian patients with PAD (including chronic limb-threatening ischaemia which is a severe form of PAD). Date limits for each database will be from inception through December 2025. SDoH will be categorised using a modified Healthy People 2030 SDoH framework under six domains: economic stability, education, food, neighbourhood and physical environment, healthcare system and community and social context. Two reviewers will independently screen titles, abstracts and full texts, with discrepancies resolved by a third reviewer. Data will be extracted on study characteristics, SDoH measures, outcomes and statistical methods. Risk of bias will be assessed using RoB 2 for randomised trials, ROBINS-I for non-randomised studies of interventions and ROBINS-E for studies investigating exposures. A narrative synthesis, and where data permit, a Bayesian hierarchical meta-analysis using both effect size and contingency table approaches will be conducted. Statistical heterogeneity will be explored through subgroup analyses and meta-regression, examining study design, SDoH measurement approaches and population characteristics.Ethics and dissemination As a systematic review and meta-analysis, ethics approval is not required. For institutional oversight, we provide the contact of Dr Sonia Anand (Associate Vice-President, Global Health, McMaster University; anands@mcmaster.ca). Results will be reported following PRISMA guidelines and disseminated through a peer-reviewed publication.PROSPERO registration number CRD420251115759.

BACKGROUND:Air pollution is a risk factor for dementia, but its role in early cognitive dysfunction is not clear. We aimed to investigate the association of air pollution with cognitive function, and the role of cardiovascular risk factors and greenspace in this association. METHODS:The CAHHM (Canadian Alliance for Healthy Hearts and Minds Cohort Study) is a cohort of Canadian adults recruited between 2014 and 2018, for whom averages of exposures to NO2 and fine particulate matter were estimated for 5 years before recruitment. Outcomes included the Montréal Cognitive Assessment and Digit Symbol Substitution Test for cognitive function, and magnetic resonance imaging-measured covert vascular brain injury. Generalized linear mixed models assessed pollutant associations with outcomes in this cross-sectional analysis. RESULTS:A total of 6878 adults participated in the study, with a mean age of 57.6 years (SD=8.8), and 55.6% were women. Mean (SD; range) 5-year pollutant concentrations preceding enrollment for fine particulate matter were 6.9 μg/m3 (2.0 [1.8-11.2]), and for NO2 were 12.9 parts per billion (5.9 [0.9-33.9]). In adjusted models, a 5 μg/m3 higher fine particulate matter concentration was associated with 0.44 points lower Montréal Cognitive Assessment (95% CI, -0.62 to -0.25) and 1.31 points lower Digit Symbol Substitution Test (95% CI, -2.41 to -0.22) scores. A 5 parts per billion higher NO2 concentration was associated with 0.12 points lower Montréal Cognitive Assessment (95% CI, -0.17 to -0.07) and 0.38 points lower Digit Symbol Substitution Test (95% CI, -0.70 to -0.05) scores. A 5 parts per billion higher NO2 concentration was associated with higher odds of covert vascular brain injury (adjusted odds ratio, 1.08 [95% CI, 1.00-1.17]). Cardiovascular risk factors and greenspace did not change these associations. CONCLUSIONS:Fine particulate matter and NO2 were associated with lower cognitive function scores in middle-aged adults living in Canada, independent of cardiovascular risk factors. Our results warrant longitudinal follow-up to study the impact of air pollution on cognitive decline.

Gestational diabetes (GDM) confers an increased risk of future type-2 diabetes (T2D). We aimed to identify determinants of the progression of GDM to T2D in South Asian women and develop a precision prognostics model for potential future clinical application. This study included 247 South Asian women with GDM from the prospective South Asian Birth Cohort (START) study in Ontario, Canada. Metabolomics was performed on 2nd trimester fasting serum samples by multisegment injection−capillary electrophoresis−mass spectrometry. We determined incidence of postpartum T2D through validated diagnostic codes using health administrative data. We used multivariable logistic regression to identify predictors of incident T2D through backward elimination. We assessed diagnostic performance of models using area under the receiver operating characteristic curve (AUC ROC) and 5-fold cross-validation to assess model stability. Of 247 South Asian women diagnosed with GDM with a mean age of 30.9 years and median total follow-up of 9.7 years, 45 (18.2

Background: More than one in five Canadians (6.5 million people) do not have a family doctor or nurse practitioner they see regularly. Access gaps are greater among immigrants and marginalized populations, who face systemic, cultural, and language barriers to care. Objectives: To evaluate access to primary care provider and dentist among residents of a neighborhood with a high proportion of visible minorities in Hamilton, ON. Methods: Between 2022 and 2024, adults living in Riverdale, a neighbourhood in the city of Hamilton, Ontario in which 51% families were born outside the country, were invited to participate in a cross-sectional survey. Determinants of access to these services were identified using multivariable logistic regression modelling. Results. 930 people completed the survey. Of these, 48% were not born in Canada. The median age of participants was 39 years, with a median time living in Canada of 28 years. Of those who responded, 79.6% had a primary care provider; and 57.1% had a dentist. In multivariable models, living in Canada < 5 years (OR = 0.10; 95% CI: 0.05, 0.20), male sex (OR= 0.56; 95%CI: 0.38, 0.82) and being unmarried (OR = 0.41; 95% CI: 0.27, 0.64) were associated with lower odds of having a primary care provider. Living in Canada for < 5 years (OR = 0.20; 95% CI: 0.11, 0.35), male sex (OR =0.74; 95% CI: 0.55, 0.99), and employment while living below the poverty line (OR=0.50; 95% CI: 0.29, 0.90) were linked to lower access to dental care. Conclusion: In a neighborhood with high proportion of visible minority newcomers in Hamilton, ON, 20% of those surveyed did not have access to a primary care provider, and 43% did not have access to a dentist. Access to primary care was lowest amongst newcomers (within 5 years), men, and those who are unmarried.  ### Competing Interest Statement Dr. Sonia S. Anand has received paid consultancy fees and speaking honoraria from Novartis. No other authors declare any competing interest for this work. ### Funding Statement The SCORE! team gratefully acknowledges the contributions and efforts of the community members, families, community partners and local organization leaders in Riverdale whose efforts were integral to the success of this research. This work was funded by the Public Health Agency of Canada in the form of a grant to SSA [2223-HQ-000007], and by the Juravinski Research Institute and McMaster Children's Hospital & McMaster University Department of Pediatrics through support awarded to GW. SSA received funding for a post-doctoral fellow from Novartis and GW received graduate student funding from the Faculty of Health Sciences (McMaster University). SSA is supported by the Heart and Stroke Foundation Chair in Population Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics approval was obtained from the Hamilton Integrated Research Ethics Board HiREB (15028). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Requests for data may be made to the corresponding author. As this is one project of several within the overall funded work, data may not be available until all funded studies are completed.

Background Marked differences in birth weight (BW) between South Asian and White European-origin populations are well-documented and pose public health concerns. Methods We analyzed fetal BW, the fat mass (FM), and fat-free mass (FFM) components in South Asian (n=938) and White European (n=3,044 and 804) newborns from three Canadian birth cohorts, examining the contribution of 16 maternal factors to observed BW differences using epidemiological and Mendelian randomization analyses. Findings South Asian newborns had on average, a significantly lower BW (3.3±0.4kg) than White Europeans (3.5±0.5kg), even after accounting for birth length (p<0.001). FFM was the primary driver of this difference, contributing to 0.22kg lower BW (p<2.2E-16), while FM had a significant but weaker counteracting effect of 0.01kg higher BW in South Asians (p=0.006). Five maternal factors demonstrated a direct maternal genetic influence: pre-pregnancy weight primarily increased BW via FFM, it also had a non-negligible increasing effect on FM. On the other hand, maternal glucose and gestational diabetes mellitus (GDM) causally increased BW through FM accumulation. Maternal height had a minimal effect only on FFM. After adjusting for these 5 maternal predictors, roughly 50% of the ethnic difference in BW (0.1kg; 95% CI: 0.067-0.13kg) was accounted for. Interpretation Different maternal factors influence specific components of BW. Targeting body fat reduction and maternal glucose regulation in South Asian mothers may help reduce the intergenerational transmission of increased FM and its associated adverse health outcomes. Funding This study was funded by the Canadian Institutes of Health Research DOHaD Team Grant: MWG-146332. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the Canadian Institutes of Health Research DOHaD Team Grant: MWG-146332. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical approval was obtained independently from the Hamilton Integrated Research Ethics Board (HiREB): CHILD (REB 07-2929) and START (REB 10-640). CHILD was additionally approved by the respective Human Research Ethics Boards at McMaster University, the Universities of Manitoba, Alberta, and British Columbia, and the Hospital for Sick Children. Legal guardians of each participant provided written informed consent. Written informed consent was obtained from the parent/guardian (participating mother) for each study separately. We also have now obtained additional ethics board approval from HiREB (REB 16592) for using the data from the two cohorts together without additional consent from the participants. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The PGS data used to derive the PGS are available from the PGS catalog with reference number shown in Table S3. Data collected for this study, including individual participant data and data dictionary defining each field in the dataset, are available to researchers who provide a proposal detailing intended analyses, pending access approval by the NutriGen Alliance Team. CHILD study data can be separately requested from the CHILDdb database. Access can be initiated through https://childstudy.ca/childdb/.

OBJECTIVE:The present study sought to synthesize available evidence for the association of ambient air pollutants on overweight and obesity and other commonly used anthropometric measurements. METHODS:We searched five databases (OVID Medline, Embase, PubMed, Web of Science, and LILAC) and grey literature till December 2024. We included studies that met all of the following criteria in the review: participants ≥18 years and reported an association between PM2.5, NO2, O3 or SO2 and at least one of the outcomes of interest and an observational study design. Two independent reviewers assessed the eligibility of articles and extracted the data. Meta-analyses were conducted using the random-effects model for outcomes with ≥2 studies. Risk of bias and evidence certainty were assessed using the JBI tools and OHAT, and GRADE frameworks. FINDINGS:Based on meta-analysis of 41 included studies (n ≈ 150 to 3,900,000), PM2.5 was associated with 0.93 kg/m2 (95 % CI [0.69, 1.16]), 1.17 cm (95 % CI [0.58, 1.75]) and 1.60 % (95 % CI [0.75 to 2.45]) higher body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) respectively. Similarly, increment of PM2.5 and NO2 was associated with change in BMI and WC and increased risk of general and abdominal obesity. The results regarding O3 and SO2 were inconsistent. The certainty of the evidence ranged from very low to high. CONCLUSIONS:PM2.5 and NO2 levels were positively correlated with most of the obesity-related outcomes emphasizing the importance of considering environmental factors in public health strategies to manage obesity. However, more longitudinal studies are needed to establish causality and inform public health.

Importance:Measures of childhood adiposity merit investigation, particularly in individuals of South Asian descent. Objective:To investigate prenatal and childhood factors associated with the trajectory of adiposity in South Asian children, and the cumulative contribution of modifiable factors, such as diet and physical activity, on this trajectory. Design, Setting, and Participants:This cohort study was a prospective analysis of the South Asian Birth Cohort (START; 2011-2015) for discovery; and the Family Atherosclerosis Monitoring In Early Life (FAMILY; 2002-2009) in Ontario, Canada, and the Born in Bradford (BiB; 2008-2009) cohort in Bradford, UK, for validation. Mother-child pairs included 903 South Asian individuals (START), 675 White European individuals (FAMILY), and 1593 individuals (BiB), of which 52% were South Asian. Analysis was conducted from March 2020 to September 2024. Exposure:Maternal, infancy, and early childhood exposures. Main Outcomes and Measures:Adiposity, assessed by the sum of subscapular and triceps skinfold thicknesses (SSF) from birth to 3 years, aggregated to a single measure as total area under the growth curve (AUC for SSF); multivariable linear regression models to identify determinants of AUC for SSF; and a cumulative score to assess joint contribution of modifiable risk factors to AUC for SSF. Results:START included 903 children (456 female [50.5%]; mean [SD] maternal age, 30.2 [4.0] years; maternal mean [SD] prepregnancy body mass index [BMI], 23.8 [4.50]). Maternal sum of skinfold thicknesses (β = 0.80 [95% CI, 0.30-1.30] per 10 mm), gestational weight gain (β = 0.38 [95% CI, 0.02-0.74] per 5 kg), a health-conscious diet score (β = -0.68 [95% CI, -1.26 to -0.10] per 1 SD), and infant breastfeeding for the first year (β = -1.68 [95% CI, -2.94 to -0.42), as well as physical activity (β = -0.33 [95% CI, -0.57 to -0.09] per 30-min/d) and screen time (β = 0.49 [95% CI, 0.18-0.81] per 30-min/d) were each independently associated with AUC for SSF. These 6 early-life modifiable factors combined into a single score had a direct, graded association between number of factors and AUC for SSF (P for trend < .001). In the validation cohorts, maternal BMI, breastfeeding, and child physical activity were replicated and showed a similar graded association with AUC for SSF (P for trend < .001) when combined. Conclusions and Relevance:In this cohort study of South Asian children, 6 modifiable factors were associated with lower adiposity and combined into a single score. This score may be useful in clinical and public health settings to help mitigate childhood obesity in South Asian individuals and beyond.

Objectives Long-term exposure to air pollution has been associated with higher risk of cardiovascular mortality. Less is known about the association of air pollution with initial development of cardiovascular disease. Herein, the association between low-level exposure to air pollutants and subclinical carotid atherosclerosis in adults without known clinical cardiovascular disease was investigated. Design Cross-sectional analysis within a prospective cohort study. Setting The Canadian Alliance for Healthy Hearts and Minds Cohort Study; a pan-Canadian cohort of cohorts. Participants Canadian adults (n = 6645) recruited between 2014-2018 from the provinces of British Columbia, Alberta, Ontario, Quebec, and Nova Scotia, were studied, for whom averages of exposures to nitrogen dioxide (NO2), ozone (O-3), and fine particulate matter (PM2.5) were estimated for the years 2008-2012. Main outcome measure Carotid vessel wall volume (CWV) measured by magnetic resonance imaging (MRI). Results In adjusted linear mixed models, PM2.5 was not consistently associated with CWV (per 5 mu g/m(3) PM2.5; adjusted estimate = -8.4 mm(3); 95% Confidence Intervals (CI) -23.3 to 6.48; p = 0.27). A 5 ppb higher NO2 concentration was associated with 11.8 mm(3) lower CWV (95% CI -16.2 to -7.31; p<0.0001). A 3 ppb increase in O-3 was associated with 9.34 mm(3) higher CWV (95% CI 4.75 to 13.92; p<0.0001). However, the coarse/insufficient O-3 resolution (10 km) is a limitation. Conclusions In a cohort of healthy Canadian adults there was no consistent association between PM2.5 or NO2 and increased CWV as a measure of subclinical atherosclerosis by MRI. The reasons for these inconsistent associations warrant further study.

A mother’s intrauterine environment influences her health and that of her offspring, at birth and in the future. Herein, we present an overview of our Canadian Institutes of Health Research (CIHR)-funded grant “Understanding the impact of maternal and infant nutrition on infant/child health”—set within The NutriGen Birth Cohort Alliance. NutriGen is a consortium of four Canadian prospective birth cohorts representing >5000 mother–child pairs of diverse ethnic groups including South Asians, White Europeans, and Indigenous peoples. We summarize our objectives and main findings on outcomes of maternal diet, gestational diabetes, birth weight, cardiometabolic health, the microbiome, and epigenetic modifications. We append this work with 10 key messages when conducting multiethnic research and review our knowledge translation products. We describe the clinical impact of our research on maternal and child health and conclude with future directions on biomarker discovery, expansion to other ethnic groups, and interventions for high-risk populations.

Background:Maternal smoking has been linked to adverse health outcomes in newborns but the extent to which it impacts newborn health has not been quantified through an aggregated cord blood DNA methylation (DNAm) score. Here, we examine the feasibility of using cord blood DNAm scores leveraging large external studies as discovery samples to capture the epigenetic signature of maternal smoking and its influence on newborns in White European and South Asian populations.Methods:We first examined the association between individual CpGs and cigarette smoking during pregnancy, and smoking exposure in two White European birth cohorts (n=744). Leveraging established CpGs for maternal smoking, we constructed a cord blood epigenetic score of maternal smoking that was validated in one of the European-origin cohorts (n=347). This score was then tested for association with smoking status, secondary smoking exposure during pregnancy, and health outcomes in offspring measured after birth in an independent White European (n=397) and a South Asian birth cohort (n=504).Results:Several previously reported genes for maternal smoking were supported, with the strongest and most consistent association signal from the GFI1 gene (6 CpGs with p<5 × 10-5). The epigenetic maternal smoking score was strongly associated with smoking status during pregnancy (OR = 1.09 [1.07, 1.10], p=5.5 × 10-33) and more hours of self-reported smoking exposure per week (1.93 [1.27, 2.58], p=7.8 × 10-9) in White Europeans. However, it was not associated with self-reported exposure (p>0.05) among South Asians, likely due to a lack of smoking in this group. The same score was consistently associated with a smaller birth size (–0.37±0.12 cm, p=0.0023) in the South Asian cohort and a lower birth weight (–0.043±0.013 kg, p=0.0011) in the combined cohorts.Conclusions:This cord blood epigenetic score can help identify babies exposed to maternal smoking and assess its long-term impact on growth. Notably, these results indicate a consistent association between the DNAm signature of maternal smoking and a small body size and low birth weight in newborns, in both White European mothers who exhibited some amount of smoking and in South Asian mothers who themselves were not active smokers.Funding:This study was funded by the Canadian Institutes of Health Research Metabolomics Team Grant: MWG-146332.

Epigenetic modifications, particularly DNA methylation (DNAm) in cord blood, are an important biological marker of how external exposures during gestation can influence the in-utero environment and subsequent offspring development. Despite the recognized importance of DNAm during gestation, comparative studies to determine the consistency of these epigenetic signals across different ethnic groups are largely absent. To address this gap, we first performed epigenome-wide association studies (EWAS) of gestational age (GA) using newborn cord blood DNAm comparatively in a white European (n = 342) and a South Asian (n = 490) birth cohort living in Canada. Then, we capitalized on established cord blood epigenetic GA clocks to examine the associations between maternal exposures, offspring characteristics and epigenetic GA, as well as GA acceleration, defined as the residual difference between epigenetic and chronological GA at birth. Individual EWASs confirmed 1,211 and 1,543 differentially methylated CpGs previously reported to be associated with GA, in white European and South Asian cohorts, respectively, with a similar distribution of effects. We confirmed that Bohlin’s cord blood GA clock was robustly correlated with GA in white Europeans (r = 0.71; p = 6.0 × 10–54) and South Asians (r = 0.66; p = 6.9 × 10–64). In both cohorts, Bohlin’s clock was positively associated with newborn weight and length and negatively associated with parity, newborn female sex, and gestational diabetes. Exclusive to South Asians, the GA clock was positively associated with the newborn ponderal index, while pre-pregnancy weight and gestational weight gain were strongly predictive of increased epigenetic GA in white Europeans. Important predictors of GA acceleration included gestational diabetes mellitus, newborn sex, and parity in both cohorts. These results demonstrate the consistent DNAm signatures of GA and the utility of Bohlin’s GA clock across the two populations. Although the overall pattern of DNAm is similar, its connections with the mother's environment and the baby's anthropometrics can differ between the two groups. Further research is needed to understand these unique relationships.

Background: Diet is known to affect the gut microbiota and the serum metabolome in adults, but this has not been fully explored in infants. Infancy is an important developmental period that may influence a person's long-term health. Infant development can be affected by diet, which also interacts with the developing gut microbiota.Objectives: This study aimed to explore the associations between diet, the gut microbiota, and the serum metabolome of 1-y-old infants with the overarching goal of identifying serum biomarkers of diet and/or the gut microbiota.Methods: We derived dietary patterns of 1-y-old infants (n = 182) participating in the Canadian South Asian Birth Cohort (START) study. We compared gut microbiota a-diversity and 8-diversity and taxa relative abundance from 16S rRNA gene profiles with dietary patterns (PERMANOVA, Envfit) and investigated diet-serum metabolite associations using a multivariate analysis (partial least squares-discriminant analysis) and univariate analysis (t test). We explored the effect of nondietary factors on diet-serum metabolite relationships by incorpo-rating diet, the gut microbiota, and maternal, perinatal, and infant characteristics in a multivariable forward stepwise regression. We replicated this analysis in White European infants, from the CHILD Cohort Study (n = 81).Results: A dietary pattern characterized by formula consumption and negatively associated with breastfeeding most strongly predicted variation in the gut microbiota (R2 = 0.109) and serum metabolome (R2 = 0.547). Breastfed participants showed higher abundance of microbes from the genera Bifidobacterium (3.29 log2-fold) and Lactobacillus (7.93 log2-fold) and higher median concentrations of the me-tabolites S-methylcysteine (1.38 mu M) and tryptophan betaine (0.43 mu M) than nonbreastfed participants. Formula consuming infants showed higher median concentrations of branched-chain/aromatic amino acids (average 48.3 mu M) than non-formula-consuming infants.Conclusions: Formula consumption and breastfeeding most strongly predicted the serum metabolites of 1-y-old infants, even when the gut microbiota, solid food consumption, and other covariates were considered.

Introduction Globally, the prevalence of obesity tripled from 1975 to 2016. There is evidence that air pollution may contribute to the obesity epidemic through an increase in oxidative stress and inflammation of adipose tissue. However, the impact of air pollution on body weight at a population level remains inconclusive. This systematic review and meta-analysis will estimate the association of ambient air pollution with obesity, distribution of ectopic adipose tissue, and the incidence and prevalence of non-alcoholic fatty liver disease among adults.Methods and analysis The study will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for conduct and reporting. The search will include the following databases: Ovid Medline, Embase, PubMed, Web of Science and Latin America and the Caribbean Literature on Health Sciences, and will be supplemented by a grey literature search. Each article will be independently screened by two reviewers, and relevant data will be extracted independently and in duplicate. Study-specific estimates of associations and their 95% Confidence Intervals will be pooled using a DerSimonian and Laird random-effects model, implemented using the RevMan software. The I2 statistic will be used to assess interstudy heterogeneity. The confidence in the body of evidence will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.Ethics and dissemination As per institutional policy, ethical approval is not required for secondary data analysis. In addition to being published in a peer-reviewed journal and presented at conferences, the results of the meta-analysis will be shared with key stakeholders, health policymakers and healthcare professionals.PROSPERO registration number CRD42023423955.

Background Childhood obesity is a global health concern and can lead to lifetime cardiometabolic disease. New advances in metabolomics can provide biochemical insights into the early development of obesity, so we aimed to characterize serum metabolites associated with overweight and adiposity in early childhood and to stratify associations by sex. Methods Nontargeted metabolite profiling was conducted in the Canadian CHILD birth cohort (discovery cohort) at age 5 years ( n = 900) by multisegment injection-capillary electrophoresis-mass spectrometry. Clinical outcome was defined using novel combined measures of overweight (WHO-standardized body mass index ≥ 85th percentile) and/or adiposity (waist circumference ≥ 90th percentile). Associations between circulating metabolites and child overweight/adiposity (binary and continuous outcomes) were determined by multivariable linear and logistic regression, adjusting for covariates and false discovery rate, and by subsequent sex-stratified analysis. Replication was assessed in an independent replication cohort called FAMILY at age 5 years ( n = 456). Results In the discovery cohort, each standard deviation (SD) increment of branched-chain and aromatic amino acids, glutamic acid, threonine, and oxoproline was associated with 20–28% increased odds of overweight/adiposity, whereas each SD increment of the glutamine/glutamic acid ratio was associated with 20% decreased odds. All associations were significant in females but not in males in sex-stratified analyses, except for oxoproline that was not significant in either subgroup. Similar outcomes were confirmed in the replication cohort, where associations of aromatic amino acids, leucine, glutamic acid, and the glutamine/glutamic acid ratio with childhood overweight/adiposity were independently replicated. Conclusions Our findings show the utility of combining measures of both overweight and adiposity in young children. Childhood overweight/adiposity at age 5 years has a specific serum metabolic phenotype, with the profile being more prominent in females compared to males.

Evidence supports a complex interplay of gut microbiome and host metabolism as regulators of obesity. The metabolic phenotype and microbial metabolism of host diet may also contribute to greater obesity risk in children early in life. This study aimed to identify features that discriminated overweight/obese from normal weight infants by integrating gut microbiome and serum metabolome profiles. This prospective analysis included 50 South Asian children living in Canada, selected from the SouTh Asian biRth cohorT (START). Serum metabolites were measured by multisegment injection-capillary electrophoresis-mass spectrometry and the relative abundance of bacterial 16S rRNA gene amplicon sequence variant was evaluated at 1 year. Cumulative body mass index (BMIAUC) and skinfold thickness (SSFAUC) scores were calculated from birth to 3 years as the total area under the growth curve (AUC). BMIAUC and/or SSFAUC >85th percentile was used to define overweight/obesity. Data Integration Analysis for Biomarker discovery using Latent cOmponent (DIABLO) was used to identify discriminant features associated with childhood overweight/obesity. The associations between identified features and anthropometric measures were examined using logistic regression. Circulating metabolites including glutamic acid, acetylcarnitine, carnitine, and threonine were positively, whereas γ-aminobutyric acid (GABA), symmetric dimethylarginine (SDMA), and asymmetric dimethylarginine (ADMA) were negatively associated with childhood overweight/obesity. The abundance of the Pseudobutyrivibrio and Lactobacillus genera were positively, and Clostridium sensu stricto 1 and Akkermansia were negatively associated with childhood overweight/obesity. Integrative analysis revealed that Akkermansia was positively whereas Lactobacillus was inversely correlated with GABA and SDMA, and Pseudobutyrivibrio was inversely correlated with GABA. This study provides insights into metabolic and microbial signatures which may regulate satiety, energy metabolism, inflammatory processes, and/or gut barrier function, and therefore, obesity trajectories in childhood. Understanding the functional capacity of these molecular features and potentially modifiable risk factors such as dietary exposures early in life may offer a novel approach for preventing childhood obesity.

Introduction This study aimed to identify serum metabolomic signatures associated with gestational diabetes mellitus (GDM), and to examine if ethnic-specific differences exist between South Asian and white European women. Research design and methods Prospective cohort study with a nested case–control analysis of 600 pregnant women from two Canadian birth cohorts; using an untargeted approach, 63 fasting serum metabolites were measured and analyzed using multisegment injection-capillary electrophoresis-mass spectrometry. Multivariate logistic regression modeling was conducted overall and by cohort. Results The proportion of women with GDM was higher in South Asians (27.1%) compared with white Europeans (17.9%). Several amino acid, carbohydrate, and lipid pathways related to GDM were common to South Asian and white European women. Elevated circulating concentrations of glutamic acid, propionylcarnitine, tryptophan, arginine, 2-hydroxybutyric acid, 3-hydroxybutyric acid, and 3-methyl-2-oxovaleric acid were associated with higher odds of GDM, while higher glutamine, ornithine, oxoproline, cystine, glycine with lower odds of GDM. Per SD increase in glucose concentration, the odds of GDM increased (OR=2.07, 95% CI 1.58 to 2.71), similarly for metabolite ratios: glucose to glutamine (OR=2.15, 95% CI 1.65 to 2.80), glucose to creatinine (OR=1.79, 95% CI 1.39 to 2.32), and glutamic acid to glutamine (OR=1.46, 95% CI 1.16 to 1.83). South Asians had higher circulating ratios of glucose to glutamine, glucose to creatinine, arginine to ornithine, and citrulline to ornithine, compared with white Europeans. Conclusions We identified a panel of serum metabolites implicated in GDM pathophysiology, consistent in South Asian and white European women. The metabolic alterations leading to larger ratios of glucose to glutamine, glucose to creatinine, arginine to ornithine, and citrulline to ornithine in South Asians likely reflect the greater burden of GDM among South Asians compared with white Europeans.

Lipidomics aims to comprehensively analyze a diverse range of lipid classes in complex biological samples, including non-esterified fatty acids and glycerophospholipids. Methods developed for quantitative lipid profiling over the past 70 years have closely mirrored technological advances in analytical instrumentation involving separation science and mass spectrometry (MS). Nonaqueous capillary electrophoresis (CE) offers a viable high-efficiency microseparation platform for resolving water-insoluble compounds using a conductive electrolyte in a compatible organic solvent or miscible organic solvent mixture typically containing a low fraction of water in solution. In 2013, the authors' group first introduced a multiplexed separation method for high-throughput metabolite analyses based on multisegment injection–CE–MS, which incorporates a serial injection of seven or more samples within a single run. Metabolome coverage is expanded to encompass hundreds of ionic lipids in blood or tissue sample extracts and thus is no longer limited to polar/hydrophilic metabolites using aqueous-based CE–MS methods.

Background Long-term exposure to air pollution, even at levels below regulatory standards, has been associated with higher risk of cardiovascular-related mortality. Less is known about the association of air pollution and initial development of CVD in low-exposure settings in generally healthy human populations. Objective In the Canadian Alliance for Healthy Hearts and Minds Cohort Study (CAHHM), we aimed to investigate the association between low-level exposure to key air pollutants and subclinical carotid atherosclerosis in adults without known clinical CVD. To date, the association of ambient air pollution and atherosclerosis measured by magnetic resonance imaging (MRI) has not been studied. Methods We studied 6,645 Canadian adults recruited between 2014-2018 from the provinces of British Columbia, Alberta, Ontario, Quebec, and Nova Scotia, for whom average long-term exposures to nitrogen dioxide (NO 2 ), ozone (O 3 ), and fine particulate matter (PM 2.5 ) were estimated for five years prior to the start of CAHHM recruitment, and who underwent MRI to assess carotid vessel wall volume (CWV). Linear mixed models were used to quantify associations between each air pollutant and CWV adjusting for individual-level and community-level risk factors for CVD. Secondary analyses included region-specific stratification and modeling the effect of one pollutant on CWV within low, medium, and high levels of a second pollutant to test for interactions. Results Higher PM 2.5 was nominally associated with lower CWV (quintile 5: 893.3 mm 3 , quintile 1: 908.8 mm 3 ; p-trend =0.05), but this was not robust in region-stratified analysis. Higher NO 2 was associated with lower CWV (quintile 5: 889.5 mm 3 , quintile 1: 918.6 mm 3 ; p-trend <.0001). Higher O 3 was associated with higher CWV (quintile 5: 925.4 mm 3 , quintile 1: 899.7 mm 3 ; p-trend =0.02). NO 2 emerged as a consistent effect modifier of both PM 2.5 and O 3. Conclusion In a cohort of generally healthy adults living in Canada, a country with relatively low levels of air pollution, exposure to NO 2 was negatively associated, and O 3 was positively associated with CWV as a measure of subclinical atherosclerosis by MRI, while associations to PM 2.5 were inconsistent. The reasons for these associations warrant further study.