Association between lifetime smoking and cutaneous squamous cell carcinoma: A 2-sample Mendelian randomization study.

Background/Purpose: Cutaneous squamous cell carcinoma (cSCC) is one of the most common malignancies worldwide. While several environmental risk factors for cSCC are well established, there is conflicting evidence on cigarette smoking (and its potential causal effect) and cSCC risk. Furthermore, it is unclear if these potential associations represent causal, modifiable risk factors for cSCC development. This study aims to assess the nature of the associations between cigarette smoking traits (smoking initiation, amount smoked, and lifetime smoking exposure) and cSCC risk using two-sample Mendelian randomization analyses. Methods: Genetic instruments, based on common genetic variants associated with cigarette smoking traits (P < 5 × 10-8), were derived from published genome-wide association studies (GWASs). For cSCC, we used GWAS summary statistics from the Kaiser Permanente GERA cohort (7701 cSCC cases and 60,167 controls; all non-Hispanic Whites). Results: We found modest evidence that genetically determined lifetime smoking was associated with cSCC (inverse-variance weighted method: OR[95% CI] = 1.47[1.09-1.98]; P = .012), suggesting it may be a causal risk factor for cSCC. We did not detect any evidence of association between genetically determined smoking initiation or amount smoked and cSCC risk. Conclusion: Study findings highlight the importance of smoking prevention and may support risk-stratified cSCC screening strategies based on carcinogen exposure and other genetic and clinical information.

Multi-ancestry genome-wide meta-analysis identifies novel basal cell carcinoma loci and shared genetic effects with squamous cell carcinoma.

Basal cell carcinoma (BCC) is one of the most common malignancies worldwide, yet its genetic determinants are incompletely defined. We perform a European ancestry genome-wide association (GWA) meta-analysis and a Hispanic/Latino ancestry GWA meta-analysis and meta-analyze both in a multi-ancestry GWAS meta-analysis of BCC, totaling 50,531 BCC cases and 762,234 controls from four cohorts (GERA, Mass-General Brigham Biobank, UK Biobank, and 23andMe research cohort). Here we identify 122 BCC-associated loci, of which 36 were novel, and subsequently fine-mapped these associations. We also identify an association of the well-known pigment gene SLC45A2 as well as associations at RCC2 and CLPTM1L with BCC in Hispanic/Latinos. We examine these BCC loci for association with cutaneous squamous cell carcinoma (cSCC) in 16,407 SCC cases and 762,486 controls of European ancestry, and 33 SNPs show evidence of association. Our study findings provide important insights into the genetic basis of BCC and cSCC susceptibility.

Association of Behavioral and Clinical Risk Factors With Cataract: A Two-Sample Mendelian Randomization Study.

Purpose: To investigate the association of genetically determined primary open-angle glaucoma (POAG), myopic refractive error (RE), type 2 diabetes (T2D), blood pressure (BP), body mass index (BMI), cigarette smoking, and alcohol consumption with the risk of age-related cataract. Methods: To assess potential causal effects of clinical or behavioral factors on cataract risk, we conducted two-sample Mendelian randomization analyses. Genetic instruments, based on common genetic variants associated with risk factors at genome-wide significance (P < 5 × 10-8), were derived from published genome-wide association studies (GWAS). For age-related cataract, we used GWAS summary statistics from our previous GWAS conducted in the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort (28,092 cataract cases and 50,487 controls; all non-Hispanic whites) or in the UK Biobank (31,852 cataract cases and 428,084 controls; all European-descent individuals). We used the inverse-variance weighted (IVW) method as our primary source of Mendelian randomization estimates and conducted common sensitivity analyses. Results: We found that genetically determined POAG and mean spherical equivalent RE were significantly associated with cataract risk (IVW model: odds ratio [OR] = 1.04; 95% confidence interval [CI], 1.01-1.08; P = 0.018; per diopter more hyperopic: OR = 0.92; 95% CI, 0.89-0.93; P = 6.51 × 10-13, respectively). In contrast, genetically determined T2D, BP, BMI, cigarette smoking, or alcohol consumption were not associated with cataract risk (P > 0.05). Conclusions: Our results provide evidence that genetic risks for POAG and myopia may be causal risk factors for age-related cataract. These results are consistent with previous observational studies reporting associations of myopia with cataract risk. This information may support population cataract risk stratification and screening strategies.

Genetic diversity fuels gene discovery for tobacco and alcohol use.

Tobacco and alcohol use are heritable behaviours associated with 15% and 5.3% of worldwide deaths, respectively, due largely to broad increased risk for disease and injury1-4. These substances are used across the globe, yet genome-wide association studies have focused largely on individuals of European ancestries5. Here we leveraged global genetic diversity across 3.4 million individuals from four major clines of global ancestry (approximately 21% non-European) to power the discovery and fine-mapping of genomic loci associated with tobacco and alcohol use, to inform function of these loci via ancestry-aware transcriptome-wide association studies, and to evaluate the genetic architecture and predictive power of polygenic risk within and across populations. We found that increases in sample size and genetic diversity improved locus identification and fine-mapping resolution, and that a large majority of the 3,823 associated variants (from 2,143 loci) showed consistent effect sizes across ancestry dimensions. However, polygenic risk scores developed in one ancestry performed poorly in others, highlighting the continued need to increase sample sizes of diverse ancestries to realize any potential benefit of polygenic prediction.

Genome-wide association study of actinic keratosis identifies new susceptibility loci implicated in pigmentation and immune regulation pathways.

Actinic keratosis (AK) is a common precancerous cutaneous neoplasm that arises on chronically sun-exposed skin. AK susceptibility has a moderate genetic component, and although a few susceptibility loci have been identified, including IRF4, TYR, and MC1R, additional loci have yet to be discovered. We conducted a genome-wide association study of AK in non-Hispanic white participants of the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort (n = 63,110, discovery cohort), with validation in the Mass-General Brigham (MGB) Biobank cohort (n = 29,130). We identified eleven loci (P < 5 × 10-8), including seven novel loci, of which four novel loci were validated. In a meta-analysis (GERA + MGB), one additional novel locus, TRPS1, was identified. Genes within the identified loci are implicated in pigmentation (SLC45A2, IRF4, BNC2, TYR, DEF8, RALY, HERC2, and TRPS1), immune regulation (FOXP1 and HLA-DQA1), and cell signaling and tissue remodeling (MMP24) pathways. Our findings provide novel insight into the genetics and pathogenesis of AK susceptibility.

A large multiethnic GWAS meta-analysis of cataract identifies new risk loci and sex-specific effects.

Cataract is the leading cause of blindness among the elderly worldwide and cataract surgery is one of the most common operations performed in the United States. As the genetic etiology of cataract formation remains unclear, we conducted a multiethnic genome-wide association meta-analysis, combining results from the GERA and UK Biobank cohorts, and tested for replication in the 23andMe research cohort. We report 54 genome-wide significant loci, 37 of which were novel. Sex-stratified analyses identified CASP7 as an additional novel locus specific to women. We show that genes within or near 80% of the cataract-associated loci are significantly expressed and/or enriched-expressed in the mouse lens across various spatiotemporal stages as per iSyTE analysis. Furthermore, iSyTE shows 32 candidate genes in the associated loci have altered gene expression in 9 different gene perturbation mouse models of lens defects/cataract, suggesting their relevance to lens biology. Our work provides further insight into the complex genetic architecture of cataract susceptibility.

Cigarette smoking behaviors and the importance of ethnicity and genetic ancestry.

Cigarette smoking contributes to numerous diseases and is one of the leading causes of death in the United States. Smoking behaviors vary widely across race/ethnicity, but it is not clear why. Here, we examine the contribution of genetic ancestry to variation in two smoking-related traits in 43,485 individuals from four race/ethnicity groups (non-Hispanic white, Hispanic/Latino, East Asian, and African American) from a single U.S. healthcare plan. Smoking prevalence was the lowest among East Asians (22.7%) and the highest among non-Hispanic whites (38.5%). We observed significant associations between genetic ancestry and smoking-related traits. Within East Asians, we observed higher smoking prevalence with greater European (versus Asian) ancestry (P = 9.95 × 10-12). Within Hispanic/Latinos, higher cigarettes per day (CPD) was associated with greater European ancestry (P = 3.34 × 10-25). Within non-Hispanic whites, the lowest number of CPD was observed for individuals of southeastern European ancestry (P = 9.06 × 10-5). These associations remained after considering known smoking-associated loci, education, socioeconomic factors, and marital status. Our findings support the role of genetic ancestry and socioeconomic factors in cigarette smoking behaviors in non-Hispanic whites, Hispanic/Latinos, and East Asians.

Genetic ancestry, skin pigmentation, and the risk of cutaneous squamous cell carcinoma in Hispanic/Latino and non-Hispanic white populations.

Although cutaneous squamous cell carcinoma (cSCC) is one of the most common malignancies in individuals of European ancestry, the incidence of cSCC in Hispanic/Latinos is also increasing. cSCC has both a genetic and environmental etiology. Here, we examine the role of genetic ancestry, skin pigmentation, and sun exposure in Hispanic/Latinos and non-Hispanic whites on cSCC risk. We observe an increased cSCC risk with greater European ancestry (P = 1.27 × 10-42) within Hispanic/Latinos and with greater northern (P = 2.38 × 10-65) and western (P = 2.28 × 10-49) European ancestry within non-Hispanic whites. These associations are significantly, but not completely, attenuated after considering skin pigmentation-associated loci, history of actinic keratosis, and sun-protected versus sun-exposed anatomical sites. We also report an association of the well-known pigment variant Ala111Thr (rs1426654) at SLC24A5 with cSCC in Hispanic/Latinos. These findings demonstrate a strong correlation of northwestern European genetic ancestry with cSCC risk in both Hispanic/Latinos and non-Hispanic whites, largely but not entirely mediated through its impact on skin pigmentation.

The Polygenic and Monogenic Basis of Blood Traits and Diseases.

Blood cells play essential roles in human health, underpinning physiological processes such as immunity, oxygen transport, and clotting, which when perturbed cause a significant global health burden. Here we integrate data from UK Biobank and a large-scale international collaborative effort, including data for 563,085 European ancestry participants, and discover 5,106 new genetic variants independently associated with 29 blood cell phenotypes covering a range of variation impacting hematopoiesis. We holistically characterize the genetic architecture of hematopoiesis, assess the relevance of the omnigenic model to blood cell phenotypes, delineate relevant hematopoietic cell states influenced by regulatory genetic variants and gene networks, identify novel splice-altering variants mediating the associations, and assess the polygenic prediction potential for blood traits and clinical disorders at the interface of complex and Mendelian genetics. These results show the power of large-scale blood cell trait GWAS to interrogate clinically meaningful variants across a wide allelic spectrum of human variation.

Genome-wide Genotyping of Cerebral Cavernous Malformation Type 1 Individuals to Identify Genetic Modifiers of Disease Severity.

Familial cerebral cavernous malformation type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and characterized by brain lesions that can cause hemorrhagic strokes, seizures, and neurological deficits. Carriers of the same genetic mutation can present with variable symptoms and severity of disease, suggesting the influence of modifier factors. Genetic modifiers of CCM1 disease severity have been recently identified and included common genetic variants in inflammatory, immune response, and oxidative stress genes and pathways. Here, we describe the genotyping of CCM1 patients with the same gene mutation (Q455X) using a high-throughput genotyping array optimized for individuals of Hispanic/Latino ancestry. We then review the quality control steps following the genome-wide genotyping. Genome-wide genotyping of larger cohorts of CCM1 patients might reveal additional genetic variants contributing to the disease severity of CCM1.

Genetic and environmental factors underlying keratinocyte carcinoma risk.

Recent large-scale GWAS and large epidemiologic studies have accelerated the discovery of genes and environmental factors that contribute to the risk of keratinocyte carcinoma (KC), which includes basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). This Review summarizes the genomic regions associated with SCC and BCC risk, examines the genetic overlap between SCC and BCC, and discusses biological pathways involved in SCC and BCC development. Next, we review environmental factors that are associated with KC risk, including those that are shared between SCC and BCC as well as others that associated with only one type of KC. We conclude with a critical appraisal of current research and potential directions for future research.

Functional validity, role, and implications of heavy alcohol consumption genetic loci.

High alcohol consumption is a risk factor for morbidity and mortality, yet few genetic loci have been robustly associated with alcohol intake. Here, we use U.K. Biobank (n = 125,249) and GERA (n = 47,967) datasets to determine genetic factors associated with extreme population-level alcohol consumption and examine the functional validity of outcomes using model organisms and in silico techniques. We identified six loci attaining genome-wide significant association with alcohol consumption after meta-analysis and meeting our criteria for replication: ADH1B (lead SNP: rs1229984), KLB (rs13130794), BTF3P13 (rs144198753), GCKR (rs1260326), SLC39A8 (rs13107325), and DRD2 (rs11214609). A conserved role in phenotypic responses to alcohol was observed for all genetic targets available for investigation (ADH1B, GCKR, SLC39A8, and KLB) in Caenorhabditis elegans. Evidence of causal links to lung cancer, and shared genetic architecture with gout and hypertension was also found. These findings offer insight into genes, pathways, and relationships for disease risk associated with high alcohol consumption.

Association studies of up to 1.2 million individuals yield new insights into the genetic etiology of tobacco and alcohol use.

Tobacco and alcohol use are leading causes of mortality that influence risk for many complex diseases and disorders1. They are heritable2,3 and etiologically related4,5 behaviors that have been resistant to gene discovery efforts6-11. In sample sizes up to 1.2 million individuals, we discovered 566 genetic variants in 406 loci associated with multiple stages of tobacco use (initiation, cessation, and heaviness) as well as alcohol use, with 150 loci evidencing pleiotropic association. Smoking phenotypes were positively genetically correlated with many health conditions, whereas alcohol use was negatively correlated with these conditions, such that increased genetic risk for alcohol use is associated with lower disease risk. We report evidence for the involvement of many systems in tobacco and alcohol use, including genes involved in nicotinic, dopaminergic, and glutamatergic neurotransmission. The results provide a solid starting point to evaluate the effects of these loci in model organisms and more precise substance use measures.

Common Mitochondrial Haplogroups and Cutaneous Squamous Cell Carcinoma Risk.

Background: Cutaneous squamous cell carcinoma (cSCC) is the second most common cancer in United States, and its incidence is substantially higher in men than women, but the reasons for the difference are unknown. We explored whether common mitochondrial DNA (mtDNA) haplogroups, which have been associated with cancer risk, and in particular squamous cell carcinoma risk arising in other organs, could explain this biological sex difference in cSCC susceptibility.Methods: We performed a retrospective cohort study using data from the Genetic Epidemiology Research in Adult Health and Aging cohort composed of 67,868 non-Hispanic white subjects (7,701 cSCC cases and 60,167 controls). Genotype information on >665,000 SNPs was generated using Affymetrix Axiom arrays designed to maximize genome-wide coverage, and 102 high-quality mtDNA SNPs were used to determine mtDNA haplogroups. Associations between each mtDNA haplogroup and cSCC risk were evaluated by logistic regression analysis adjusting for age, sex, and population stratification using ancestry principal components.Results: cSCC was more common in men (15.4% vs. 8.4% for women). Nine common mtDNA haplogroups (frequency ≥1%) were identified in addition to the most common haplogroup, H, used as the reference group. No association with cSCC risk was detected for any of the mtDNA haplogroups or overall or sex-stratified analyses.Conclusions: Common mitochondrial variation is not associated with cSCC risk.Impact: This well-powered study refutes the hypothesis that common mitochondrial haplogroups play a role in the differential sex predilection of cSCCs. Cancer Epidemiol Biomarkers Prev; 27(7); 838-41. ©2018 AACR.

Cytochrome P450 and matrix metalloproteinase genetic modifiers of disease severity in Cerebral Cavernous Malformation type 1.

BACKGROUND: Familial Cerebral Cavernous Malformation type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and characterized by multiple brain lesions. CCM lesions manifest across a range of different phenotypes, including wide differences in lesion number, size and susceptibility to intracerebral hemorrhage (ICH). Oxidative stress plays an important role in cerebrovascular disease pathogenesis, raising the possibility that inter-individual variability in genes related to oxidative stress may contribute to the phenotypic differences observed in CCM1 disease. Here, we investigated whether candidate oxidative stress-related cytochrome P450 (CYP) and matrix metalloproteinase (MMP) genetic markers grouped by superfamilies, families or genes, or analyzed individually influence the severity of CCM1 disease. METHODS: Clinical assessment and cerebral susceptibility-weighted magnetic resonance imaging (SWI) were performed to determine total and large (≥5mm in diameter) lesion counts as well as ICH in 188 Hispanic CCM1 patients harboring the founder KRIT1/CCM1 'common Hispanic mutation' (CCM1-CHM). Samples were genotyped on the Affymetrix Axiom Genome-Wide LAT1 Human Array. We analyzed 1,122 genetic markers (both single nucleotide polymorphisms (SNPs) and insertion/deletions) grouped by CYP and MMP superfamily, family or gene for association with total or large lesion count and ICH adjusted for age at enrollment and gender. Genetic markers bearing the associations were then analyzed individually. RESULTS: The CYP superfamily showed a trend toward association with total lesion count (P=0.057) and large lesion count (P=0.088) in contrast to the MMP superfamily. The CYP4 and CYP8 families were associated with either large lesion count or total lesion count (P=0.014), and two other families (CYP46 and the MMP Stromelysins) were associated with ICH (P=0.011 and 0.007, respectively). CYP4F12 rs11085971, CYP8A1 rs5628, CYP46A1 rs10151332, and MMP3 rs117153070 single SNPs, mainly bearing the above-mentioned associations, were also individually associated with CCM1 disease severity. CONCLUSIONS: Overall, our candidate oxidative stress-related genetic markers set approach outlined CYP and MMP families and identified suggestive SNPs that may impact the severity of CCM1 disease, including the development of numerous and large CCM lesions and ICH. These novel genetic risk factors of prognostic value could serve as early objective predictors of disease outcome and might ultimately provide better options for disease prevention and treatment.

Polymorphisms in inflammatory and immune response genes associated with cerebral cavernous malformation type 1 severity.

BACKGROUND: Familial cerebral cavernous malformation type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and characterized by multiple brain lesions that often result in intracerebral hemorrhage (ICH), seizures, and neurological deficits. Carriers of the same genetic mutation can present with variable symptoms and severity of disease, suggesting the influence of modifier factors. Evidence is emerging that inflammation and immune response play a role in the pathogenesis of CCM. The purpose of this study was to investigate whether common variants in inflammatory and immune response genes influence the severity of familial CCM1 disease, as manifested by ICH and greater brain lesion count. METHODS: Hispanic CCM1 patients (n=188) harboring the founder Q455X 'common Hispanic mutation' (CHM) in the KRIT1 gene were analyzed at baseline. Participants were enrolled between June 2010 and March 2014 either through the Brain Vascular Malformation Consortium (BVMC) study or through the Angioma Alliance organization. Clinical assessment and cerebral susceptibility-weighted magnetic resonance imaging were performed to determine ICH as well as total and large (≥5 mm in diameter) lesion counts. Samples were genotyped on the Affymetrix Axiom Genome-Wide LAT1 Human Array. We analyzed 830 variants in 56 inflammatory and immune response genes for association with ICH and residuals of log-transformed total or large lesion count adjusted for age at enrollment and gender. Variants were analyzed individually or grouped by sub-pathways or whole pathways. RESULTS: At baseline, 30.3% of CCM1-CHM subjects had ICH, with a mean ± standard deviation (SD) of 60.1±115.0 (range 0-713) for total lesions and 4.9±8.7 (range 0-104) for large lesions. The heritability estimates explained by all autosomal variants were 0.20 (SE=0.31), 0.81 (SE=0.17), and 0.48 (SE=0.19), for ICH, total lesion count, and large lesion count, respectively. TGFBR2 rs9823731 was significantly associated with ICH as well as with the total and large lesion counts (p≤0.017). Further, IL-4 rs9327638, CD14 rs778588, IL-6R rs114660934 and MSR1 rs62489577 were associated with two markers of disease severity. Finally, the whole pathway was associated with total lesion count (p=0.005) with TLR-4 rs10759930, CD14 rs778588, IL-6R rs114660934 and IGH rs57767447 mainly bearing this association. Eicosanoid signaling, extracellular pattern recognition, and immune response sub-pathways were also associated with the total lesion count. CONCLUSIONS: These results suggest that polymorphisms in inflammatory and immune response pathways contribute to variability in CCM1 disease severity and might be used as predictors of disease severity. In particular, TGFBR2 rs9823731 was associated with all three markers of CCM1 disease severity tested, suggesting that TGFBR2 might be a key participant in the mechanism underlying CCM1 disease severity and phenotype variability. However, further longitudinal studies in larger sample sizes are needed to confirm these findings.

Association of cardiovascular risk factors with disease severity in cerebral cavernous malformation type 1 subjects with the common Hispanic mutation.

BACKGROUND: Cerebral cavernous malformations (CCM) are enlarged vascular lesions affecting 0.1-0.5% of the population worldwide and causing hemorrhagic strokes, seizures, and neurological deficits. Familial CCM type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and is characterized by multiple brain lesions whose number and size increase with age. The number of lesions varies widely for unknown reasons, even among carriers of similar ages with the same mutation. The purpose of this study was to investigate whether cardiovascular (CV) risk factors influence potential markers of familial CCM1 disease severity, such as lesion count and history of intracerebral hemorrhage. METHODS: We analyzed baseline data from 185 Hispanic subjects, enrolled in the Brain Vascular Malformation Consortium study between June 2010 and March 2013. All subjects were carriers of the founder Q455X 'Common Hispanic Mutation' (CHM) in the KRIT1 gene, and had a clinical diagnosis of CCM or had an affected first- or second-degree relative with CCM. We performed a cross-sectional study, collecting detailed clinical information of CCM1-CHM subjects and cerebral susceptibility-weighted magnetic resonance imaging to assess lesion count. Linear or logistic regression analysis of log-lesion count or history of intracerebral hemorrhage and CV risk factors (age, gender, obesity, diabetes, hypertension, hyperlipidemia and smoking status) and related quantitative traits (body mass index, glycosylated hemoglobin levels, blood pressure, lipids levels and pack-years of cigarette smoking) was performed accommodating familial clustering. RESULTS: CCM1-CHM subjects were mainly female (63.8%) and symptomatic at presentation (63.2%). Lesion count was highly variable (mean ± SD: 57.7 ± 110.6; range: 0-713); 90% of CCM1-CHM subjects had multiple lesions at enrollment. Age (p < 0.001) was positively correlated with lesion count and male gender (p = 0.035) was associated with a greater number of lesions. Obesity (p = 0.001) and higher body mass index (p = 0.002) were associated with fewer lesions. No association with hypertension was detected, however, systolic blood pressure (p = 0.002) was associated with fewer lesions. No significant association with lesion count was observed for diabetes, hyperlipidemia, smoking status or for related quantitative traits. History of intracerebral hemorrhage was not significantly associated with any CV risk factors, however, we found borderline associations of hemorrhage with obesity (p = 0.062), systolic blood pressure (p = 0.083) and pack-years of cigarette smoking (p = 0.055). After correction for multiple testing, age and obesity remained significantly associated with lesion count in CCM1-CHM subjects. CONCLUSIONS: These results suggest that several CV risk factors explain some of the variability in lesion count in Hispanic CCM1-CHM subjects. Although age, gender, obesity, body mass index and systolic blood pressure may influence familial CCM1 disease severity, further longitudinal studies in larger sample sizes are essential to confirm these findings.

Dysfunction of lipid sensor GPR120 leads to obesity in both mouse and human.

Free fatty acids provide an important energy source as nutrients, and act as signalling molecules in various cellular processes. Several G-protein-coupled receptors have been identified as free-fatty-acid receptors important in physiology as well as in several diseases. GPR120 (also known as O3FAR1) functions as a receptor for unsaturated long-chain free fatty acids and has a critical role in various physiological homeostasis mechanisms such as adipogenesis, regulation of appetite and food preference. Here we show that GPR120-deficient mice fed a high-fat diet develop obesity, glucose intolerance and fatty liver with decreased adipocyte differentiation and lipogenesis and enhanced hepatic lipogenesis. Insulin resistance in such mice is associated with reduced insulin signalling and enhanced inflammation in adipose tissue. In human, we show that GPR120 expression in adipose tissue is significantly higher in obese individuals than in lean controls. GPR120 exon sequencing in obese subjects reveals a deleterious non-synonymous mutation (p.R270H) that inhibits GPR120 signalling activity. Furthermore, the p.R270H variant increases the risk of obesity in European populations. Overall, this study demonstrates that the lipid sensor GPR120 has a key role in sensing dietary fat and, therefore, in the control of energy balance in both humans and rodents.

Gene-centric analysis of serum cotinine levels in African and European American populations.

To date, most genetic association studies of tobacco use have been conducted in European American subjects using the phenotype of smoking quantity (cigarettes per day). However, smoking quantity is a very imprecise measure of exposure to tobacco smoke constituents. Analyses of alternate phenotypes and populations may improve our understanding of tobacco addiction genetics. Cotinine is the major metabolite of nicotine, and measuring serum cotinine levels in smokers provides a more objective measure of nicotine dose than smoking quantity. Previous genetic association studies of serum cotinine have focused on individual genes. We conducted a genetic association study of the biomarker in African American (N=365) and European American (N=315) subjects from the Coronary Artery Risk Development in Young Adults study using a chip containing densely-spaced tag SNPs in ∼2100 genes. We found that rs11187065, located in the non-coding region (intron 1) of insulin-degrading enzyme (IDE), was the most strongly associated SNP (p=8.91 × 10(-6)) in the African American cohort, whereas rs11763963, located on chromosome 7 outside of a gene transcript, was the most strongly associated SNP in European Americans (p=1.53 × 10(-6)). We then evaluated how the top variant association in each population performed in the other group. We found that the association of rs11187065 in IDE was also associated with the phenotype in European Americans (p=0.044). Our top SNP association in European Americans, rs11763963 was non-polymorphic in our African American sample. It has been previously shown that psychostimulant self-administration is reduced in animals with lower insulin because of interference with dopamine transmission in the brain reward centers. Our finding provides a platform for further investigation of this, or additional mechanisms, involving the relationship between insulin and self-administered nicotine dose.