Publications by authors named "Kenneth Westerman"

Article Synopsis
  • Type 2 diabetes (T2D) genome-wide association studies (GWASs) typically miss rare genetic variants due to limitations in previous imputation methods and insufficient whole-genome sequencing data.
  • In a large-scale study involving over half a million individuals, researchers uncovered 12 new genetic variants linked to T2D, including a rare enhancer variant near the LEP gene that significantly increases risk.
  • The study also analyzed ClinVar variants related to monogenic diabetes, identifying additional rare variants that affect T2D risk and offering new insights into the pathogenicity of certain variants previously deemed uncertain.
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Discovery and translation of gene-environment interactions (GxEs) influencing clinical outcomes is limited by low statistical power and poor mechanistic understanding. Molecular omics data may help address these limitations, but their incorporation into GxE testing requires principled analytic approaches. We focused on genetic modification of the established mechanistic link between dietary long-chain omega-3 fatty acid (dN3FA) intake, plasma N3FA (pN3FA), and chronic inflammation as measured by high sensitivity CRP (hsCRP).

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Article Synopsis
  • * We found 17 genetic loci associated with sleep duration impacting lipid levels, with 10 of them being newly identified and linked to sleep-related disturbances in lipid metabolism.
  • * The research points to potential drug targets that could lead to new treatments for lipid-related issues in individuals with sleep problems, highlighting the connection between sleep patterns and cardiovascular health.
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Although both short and long sleep duration are associated with elevated hypertension risk, our understanding of their interplay with biological pathways governing blood pressure remains limited. To address this, we carried out genome-wide cross-population gene-by-short-sleep and long-sleep duration interaction analyses for three blood pressure traits (systolic, diastolic, and pulse pressure) in 811,405 individuals from diverse population groups. We discover 22 novel gene-sleep duration interaction loci for blood pressure, mapped to 23 genes.

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We examined the associations of vegetarianism with metabolic biomarkers using traditional and genetic epidemiology. First, we addressed inconsistencies in self-reported vegetarianism among UK Biobank participants by utilizing data from two dietary surveys to find a cohort of strict European vegetarians (N = 2,312). Vegetarians were matched 1:4 with nonvegetarians for non-genetic association analyses, revealing significant effects of vegetarianism in 15 of 30 biomarkers.

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Despite the importance of gene-environment interactions (GxEs) in improving and operationalizing genetic discovery, interpretation of any GxEs that are discovered can be surprisingly difficult. There are many potential biological and statistical explanations for a statistically significant finding and, likewise, it is not always clear what can be claimed based on a null result. A better understanding of the possible underlying mechanisms leading to a detected GxE can help investigators decide which are and which are not relevant to their hypothesis.

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Although both short and long sleep duration are associated with elevated hypertension risk, our understanding of their interplay with biological pathways governing blood pressure remains limited. To address this, we carried out genome-wide cross-population gene-by-short-sleep and long-sleep duration interaction analyses for three blood pressure traits (systolic, diastolic, and pulse pressure) in 811,405 individuals from diverse population groups. We discover 22 novel gene-sleep duration interaction loci for blood pressure, mapped to genes involved in neurological, thyroidal, bone metabolism, and hematopoietic pathways.

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Article Synopsis
  • Type 2 diabetes (T2D) has a strong genetic component, and this study examined genetic data from over 1.4 million individuals across diverse populations to identify genetic clusters related to T2D.
  • Researchers used 650 T2D-related genetic variants to categorize individuals into 12 genetic clusters associated with different cardiometabolic traits, revealing variations in risk factors across populations including African, East Asian, and European ancestry.
  • The findings suggest that T2D risk varies by genetic background, with East Asians needing a lower body mass index (BMI) to have a similar T2D risk as Europeans, highlighting the complexity of genetic factors influencing T2D across different ancestries.
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Article Synopsis
  • Large-scale studies on gene-environment interactions often simplify outcomes and covariates to improve data consistency, which can hinder the understanding of complex relationships, such as those between physical activity and HDL cholesterol.* -
  • The study refined a previously identified interaction between the rs295849 genotype and physical activity on HDL cholesterol levels, using datasets from the Women's Genome Health Study, UK Biobank, and Multi-Ethnic Study of Atherosclerosis.* -
  • Findings showed that the interaction effect was stronger when looking at medium-sized HDL particles compared to total HDL cholesterol, highlighting variations based on gender and the specific lipid metrics used.*
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Motivation: statistics from genome-wide association studies enable many valuable downstream analyses that are more efficient than individual-level data analysis while also reducing privacy concerns. As growing sample sizes enable better-powered analysis of gene-environment interactions, there is a need for gene-environment interaction-specific methods that manipulate and use summary statistics.

Results: We introduce two tools to facilitate such analysis, with a focus on statistical models containing multiple gene-exposure and/or gene-covariate interaction terms.

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Background: Individuals with type 2 diabetes (T2D) have an increased risk of coronary artery disease (CAD), but questions remain about the underlying pathology. Identifying which CAD loci are modified by T2D in the development of subclinical atherosclerosis (coronary artery calcification [CAC], carotid intima-media thickness, or carotid plaque) may improve our understanding of the mechanisms leading to the increased CAD in T2D.

Methods: We compared the common and rare variant associations of known CAD loci from the literature on CAC, carotid intima-media thickness, and carotid plaque in up to 29 670 participants, including up to 24 157 normoglycemic controls and 5513 T2D cases leveraging whole-genome sequencing data from the Trans-Omics for Precision Medicine program.

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Article Synopsis
  • - The study identified various genetic subtypes of type 2 diabetes (T2D) by analyzing genetic data from different populations, not just those of European descent.
  • - Researchers found twelve distinct genetic clusters linked to T2D, each associated with unique cardiometabolic traits, and observed differences in polygenic risk scores based on ancestry— notably higher lipodystrophy-related risk in East Asians.
  • - T2D risk was shown to be influenced by BMI thresholds, with East Asians needing a lower BMI for equivalent T2D risk compared to Europeans; adjusting for genetic risk revealed significant differences in BMI thresholds between the groups.
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We identified genetic subtypes of type 2 diabetes (T2D) by analyzing genetic data from diverse groups, including non-European populations. We implemented soft clustering with 650 T2D-associated genetic variants, capturing known and novel T2D subtypes with distinct cardiometabolic trait associations. The twelve genetic clusters were distinctively enriched for single-cell regulatory regions.

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Article Synopsis
  • A meta-analysis was conducted on data from 51,256 cases and 370,487 controls to identify rare genetic variants linked to type 2 diabetes (T2D), discovering 52 novel variants with significant associations.
  • This study highlighted a specific rare missense variant, p.Arg114Trp, that has a strong connection to diabetes risk, influenced by other common genetic risk factors.
  • The findings also indicated that a subset of variants previously listed as possible disease-causing mutations might actually be benign, suggesting a need for reevaluation of these genetic markers in relation to T2D.
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Hyperinsulinemia is a complex and heterogeneous phenotype that characterizes molecular alterations that precede the development of type 2 diabetes (T2D). It results from a complex combination of molecular processes, including insulin secretion and insulin sensitivity, that differ between individuals. To better understand the physiology of hyperinsulinemia and ultimately T2D, we implemented a genetic approach grouping fasting insulin (FI)-associated genetic variants based on their molecular and phenotypic similarities.

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Objective: Clonal hematopoiesis of indeterminate potential (CHIP) is an aging-related accumulation of somatic mutations in hematopoietic stem cells, leading to clonal expansion. CHIP presence has been implicated in atherosclerotic coronary heart disease (CHD) and all-cause mortality, but its association with incident type 2 diabetes (T2D) is unknown. We hypothesized that CHIP is associated with elevated risk of T2D.

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Aims/hypothesis: We sought to quantify the relationship between morning, afternoon or evening physical activity and consistency (e.g. routine) and risk of type 2 diabetes.

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Unlabelled: Few studies have demonstrated reproducible gene-diet interactions (GDIs) impacting metabolic disease risk factors, likely due in part to measurement error in dietary intake estimation and insufficient capture of rare genetic variation. We aimed to identify GDIs across the genetic frequency spectrum impacting the macronutrient-glycemia relationship in genetically and culturally diverse cohorts. We analyzed 33,187 participants free of diabetes from 10 National Heart, Lung, and Blood Institute Trans-Omics for Precision Medicine program cohorts with whole-genome sequencing, self-reported diet, and glycemic trait data.

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A variety of statistical approaches in nutritional epidemiology have been developed to enhance the precision of dietary variables derived from longitudinal questionnaires. Correlation with biomarkers is often used to assess the relative validity of these different approaches, however, validated biomarkers do not always exist and are costly and laborious to collect. We present a novel high-throughput approach which utilizes the modest but importantly non-zero influence of genetic variation on variation in dietary intake to compare different statistical transformations of dietary variables.

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Aims/hypothesis: Type 2 diabetes is highly polygenic and influenced by multiple biological pathways. Rapid expansion in the number of type 2 diabetes loci can be leveraged to identify such pathways.

Methods: We developed a high-throughput pipeline to enable clustering of type 2 diabetes loci based on variant-trait associations.

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Introduction: Disentangling the specific factors that regulate glycemia from prediabetes to normoglycemia could improve type 2 diabetes prevention strategies. Metabolomics provides substantial insights into the biological understanding of environmental factors such as diet. This study aimed to identify metabolomic markers of regression to normoglycemia in the context of a lifestyle intervention (LSI) in individuals with prediabetes.

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Article Synopsis
  • - The study analyzed genetic factors affecting fasting glucose (FG) and fasting insulin (FI) using high-coverage whole genome sequencing from over 23,000 non-diabetic individuals across five different racial and ethnic groups.
  • - Researchers identified eight significant genetic variants linked to FG or FI in known gene regions, while also suggesting associations with additional regions related to metabolic processes.
  • - The project compiled functional annotation resources to help understand the implications of these genetic variations and laid the groundwork for future research on glycemic traits.
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