HTR1B, ADIPOR1, PPARGC1A, and CYP19A1 and obesity in a cohort of Caucasians and African Americans: an evaluation of gene-environment interactions and candidate genes

Association between MCU Gene Polymorphisms with Obesity: Findings from the All of Us Research Program

Obesity is a public health crisis, and its prevalence disproportionately affects African Americans in the United States. Dysregulation of organelle calcium homeostasis is associated with obesity. The mitochondrial calcium uniporter (MCU) complex is primarily responsible for mitochondrial calcium homeostasis. Obesity is a multifactorial disease in which genetic underpinnings such as single-nucleotide polymorphisms (SNPs) may contribute to disease progression. The objective of this study was to identify genetic variations of MCU with anthropometric measurements and obesity in the All of Us Research Program.

METHODS

We used an additive genetic model to assess the association between obesity traits (body mass index (BMI), waist and hip circumference) and selected MCU SNPs in 19,325 participants (3221 normal weight and 16,104 obese). Eleven common MCU SNPs with a minor allele frequency ≥ 5% were used for analysis.

RESULTS

We observed three MCU SNPs in self-reported Black/African American (B/AA) men, and six MCU SNPs in B/AA women associated with increased risk of obesity, whereas six MCU SNPs in White men, and nine MCU SNPs in White women were protective against obesity development.

CONCLUSIONS

This study found associations of MCU SNPs with obesity, providing evidence of a potential predictor of obesity susceptibility in B/AA adults.

Nicotine Impairs the Anti-Contractile Function of Perivascular Adipose Tissue by Inhibiting the PPARγ-Adiponectin-AdipoR1 Axis

Nicotine is an addictive compound found in cigarette smoke that leads to vascular dysfunction and cardiovascular diseases. Perivascular adipose tissue (PVAT) exerts an anti-contractile effect on the underlying vasculature through the production of adipokines, such as adiponectin, which acts on adiponectin receptors 1 (adipoR1) to cause vasorelaxation. Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor that regulates adiponectin gene expression and PVAT development. This study aimed to determine the effect of nicotine on the anti-contractile function of PVAT via the PPARγ-adiponectin-adipoR1 axis. Male Sprague Dawley rats were divided into a control group (given normal saline), a nicotine group (given 0.8 mg/kg of nicotine), and a nicotine + PPARγ agonist group (given nicotine and 5 mg/kg of telmisartan). Thoracic aorta PVAT was harvested after 21 days of treatment. The results showed that nicotine reduced the anti-contractile effect of PVAT on the underlying thoracic aorta. Nicotine also decreased the gene and protein expression of PPARγ, adiponectin, and adipoR1 in PVAT. Treatment with telmisartan restored the anti-contractile effect of PVAT and increased the gene and protein expression of PPARγ, adiponectin, and adipoR1 in PVAT. In conclusion, nicotine attenuates the anti-contractile function of PVAT through inhibition of the PPARγ-adiponectin-adipoR1 axis.

Serotonin system genes contribute to the susceptibility to obesity in Black adolescents

OBJECTIVE

The importance of the central and peripheral serotonin systems in regulating energy balance and obesity development has been highlighted in animal models. Yet, the role of both serotonin systems has not been systematically assessed in humans. The purpose of this study was to investigate the association of genes within both serotonin systems with obesity outcomes in black adolescents.

METHODS

African-American adolescents (n = 1052) whose mothers participated the Memphis New Mother's Study were assessed. In total, 110 polymorphisms mapped to 10 serotonin genes were examined for their associations with standardized body mass index (BMI-z) scores and waist circumferences using generalized estimating equation models.

RESULTS

Over 39% of adolescents were overweight or had obesity. Three single nucleotide polymorphisms (SNPs) within TPH2, HTR3B, and SLC6A4, were significantly associated with BMI-z scores (p < 1.7 × 10-3). Two SNPs in TPH2 were nominally associated with waist circumferences. One SNP in HTR2C was associated with BMI-z scores (p = 0.001) and waist circumferences (p = 0.005) only in girls. Tissue-specific expression indicates that three identified genes are predominantly expressed in the brain.

CONCLUSION

The central serotonin system may play a key role in obesity development in black adolescents. Future studies are warranted to explore additional serotonin system genes and their potential obesogenic mechanisms in humans.

Interaction of Neighborhood and Genetic Risk on Waist Circumference in African-American Adults: A Longitudinal Study

BACKGROUND

Understanding determinants of metabolic risk has become a national priority given the increasingly high prevalence rate of this condition among U.S. adults.

PURPOSE

This study's aim was to assess the impact of gene-by-neighborhood social environment interactions on waist circumference (WC) as a primary marker of metabolic risk in underserved African-American adults. Based on a dual-risk model, it was hypothesized that those with the highest genetic risk and who experienced negative neighborhood environment conditions would demonstrate higher WC than those with fewer risk factors.

METHODS

This study utilized a subsample of participants from the Positive Action for Today's Health environmental intervention to improve access and safety for walking in higher-crime neighborhoods, who were willing to provide buccal swab samples for genotyping stress-related genetic pathways. Assessments were conducted with 228 African-American adults at baseline, 12, 18, and 24 months.

RESULTS

Analyses indicated three significant gene-by-environment interactions on WC outcomes within the sympathetic nervous system (SNS) genetic pathway. Two interactions supported the dual-risk hypotheses, including the SNS genetic risk-by-neighborhood social life interaction (b = -0.11, t(618) = -2.02, p = .04), and SNS genetic risk-by-informal social control interaction (b = -0.51, t(618) = -1.95, p = .05) on WC outcomes. These interactions indicated that higher genetic risk and lower social-environmental supports were associated with higher WC. There was also one significant SNS genetic risk-by-neighborhood satisfaction interaction (b = 1.48, t(618) = 2.23, p = .02) on WC that was inconsistent with the dual-risk pattern.

CONCLUSIONS

Findings indicate that neighborhood and genetic factors dually influence metabolic risk and that these relations may be complex and warrant further study.

TRIAL REGISTRATION

NCT01025726.

Genome-wide admixture mapping of DSM-IV alcohol dependence, criterion count, and the self-rating of the effects of ethanol in African American populations

African Americans (AA) have lower prevalence of alcohol dependence and higher subjective response to alcohol than European Americans. Genome-wide association studies (GWAS) have identified genes/variants associated with alcohol dependence specifically in AA; however, the sample sizes are still not large enough to detect variants with small effects. Admixture mapping is an alternative way to identify alcohol dependence genes/variants that may be unique to AA. In this study, we performed the first admixture mapping of DSM-IV alcohol dependence diagnosis, DSM-IV alcohol dependence criterion count, and two scores from the self-rating of effects of ethanol (SRE) as measures of response to alcohol: the first five times of using alcohol (SRE-5) and average of SRE across three times (SRE-T). Findings revealed a region on chromosome 4 that was genome-wide significant for SRE-5 (p value = 4.18E-05). Fine mapping did not identify a single causal variant to be associated with SRE-5; instead, conditional analysis concluded that multiple variants collectively explained the admixture mapping signal. PPARGC1A, a gene that has been linked to alcohol consumption in previous studies, is located in this region. Our finding suggests that admixture mapping is a useful tool to identify genes/variants that may have been missed by current GWAS approaches in admixed populations.

Functional polymorphisms and transcriptional analysis in the 5' region of the human serotonin receptor 1B gene (HTR1B) and their associations with psychiatric disorders

BACKGROUND

The 5-hydroxytryptamine 1B receptor (5-HT1B) plays an essential role in the serotonin (5-HT) system and is widely involved in a variety of brain activities. HTR1B is the gene encoding 5-HT1B. Genome-wide association studies have shown that HTR1B polymorphisms are closely related to multiple mental and behavioral disorders; however, the functional mechanisms underlying these associations are unknown. This study investigated the effect of several HTR1B haplotypes on regulation of gene expression in vitro and the functional sequences in the 5' regulatory region of HTR1B to determine their potential association with mental and behavioral disorders.

METHODS

Six haplotypes consisting of rs4140535, rs1778258, rs17273700, rs1228814, rs11568817, and rs130058 and several truncated fragments of the 5' regulatory region of HTR1B were transfected into SK-N-SH and HEK-293 cells. The relative fluorescence intensities of the different haplotypes and truncated fragments were detected using a dual-luciferase reporter assay system.

RESULTS

Compared to the major haplotype T-G-T-C-T-A, the relative fluorescence intensities of haplotypes C-A-T-C-T-A, C-G-T-C-T-A, C-G-C-A-G-T, and C-G-T-A-T-A were significantly lower, and that of haplotype C-G-C-A-G-A was significantly higher. Furthermore, the effects of the rs4140535T allele, the rs17273700C-rs11568817G linkage combination, and the rs1228814A allele made their relative fluorescence intensities significantly higher than their counterparts at each locus. Conversely, the rs1778258A and rs130058T alleles decreased the relative fluorescence intensities. In addition, we found that regions from - 1587 to - 1371 bp (TSS, + 1), - 1149 to - 894 bp, - 39 to + 130 bp, + 130 to + 341 bp, and + 341 to + 505 bp upregulated gene expression. In contrast, regions - 603 to - 316 bp and + 130 to + 341 bp downregulated gene expression. Region + 341 to + 505 bp played a decisive role in gene transcription.

CONCLUSIONS

HTR1B 5' regulatory region polymorphisms have regulatory effects on gene expression and potential correlate with several pathology and physiology conditions. This study suggests that a crucial sequence for transcription is located in region + 341 ~ + 505 bp. Regions - 1587 to - 1371 bp, - 1149 to - 894 bp, - 603 to - 316 bp, - 39 to + 130 bp, and + 130 to + 341 bp contain functional sequences that can promote or suppress the HTR1B gene expression.

Polymorphism of IL6 receptor gene is associated with ischaemic stroke in patients with metabolic syndrome

The interleukin 6 receptor (IL6R) gene has been shown to locate in the chromosome 1q21 associated with metabolic syndrome (MetS), a condition related to the augmented risk of ischaemic stroke (IS), cardiovascular diseases and all-cause mortality. The aim of this study was to assess the relationship between IL6R gene polymorphisms and IS in patients with MetS in the Chinese Han population. We designed a case-control study enrolling 447 patients with MetS plus IS and 438 patients with MetS alone. Tag single nucleotide polymorphisms (SNPs) of the IL6R gene were determined by a fine-mapping strategy and genotyped using SNPscan technology. A logistic regression model was used to analzse the associations between the genetic variations in IL6R and the risk of IS in MetS patients. The linkage disequilibrium (LD) analysis was performed and four gamete rules were used to define the block. The haplotypes was reconstructed by the SNPstats software. Two SNPs were significantly related to the risk of IS in MetS patients after adjusting for potential confounders as follows: regarding rs12083537, the GG genotype and the GA genotype decreased the risk of IS in the MetS patients compared with the IS risk in the patients with the AA genotype (multivariate-adjusted, P = 0.005); and regarding rs8192284, the CC genotype and the AC genotype decreased the risk of IS compared with the IS risk in the patients with the AA genotype (multivariate-adjusted, P = 0.004). Strong LD was existed in block 2 and the haplotype analysis showed that compared with the ACCG haplotype, the ATCT haplotype (adjusted OR 1.700; 95% CI 1.246-2.319; P = 0.001) increased the risk of IS in the MetS patients. The analysis of the SNP-SNP interactions showed that rs8192284 was the most influential contributor to the risk of IS in the MetS patients. Our results indicate that rs12083537 and rs8192284 in the IL6R gene might be related to the risk of IS in MetS patients.

The importance of gene-environment interactions in human obesity

The worldwide obesity epidemic has been mainly attributed to lifestyle changes. However, who becomes obese in an obesity-prone environment is largely determined by genetic factors. In the last 20 years, important progress has been made in the elucidation of the genetic architecture of obesity. In parallel with successful gene identifications, the number of gene-environment interaction (GEI) studies has grown rapidly. This paper reviews the growing body of evidence supporting gene-environment interactions in the field of obesity. Heritability, monogenic and polygenic obesity studies provide converging evidence that obesity-predisposing genes interact with a variety of environmental, lifestyle and treatment exposures. However, some skepticism remains regarding the validity of these studies based on several issues, which include statistical modelling, confounding, low replication rate, underpowered analyses, biological assumptions and measurement precision. What follows in this review includes (1) an introduction to the study of GEI, (2) the evidence of GEI in the field of obesity, (3) an outline of the biological mechanisms that may explain these interaction effects, (4) methodological challenges associated with GEI studies and potential solutions, and (5) future directions of GEI research. Thus far, this growing body of evidence has provided a deeper understanding of GEI influencing obesity and may have tremendous applications in the emerging field of personalized medicine and individualized lifestyle recommendations.

A multianalytical approach to evaluate the association of 55 SNPs in 28 genes with obesity risk in North Indian adults

OBJECTIVES

The aim of the study was to investigate the association of 55 SNPs in 28 genes with obesity risk in a North Indian population using a multianalytical approach.

METHODS

Overall, 480 subjects from the North Indian population were studied using strict inclusion/exclusion criteria. SNP Genotyping was carried out by Sequenom Mass ARRAY platform (Sequenom, San Diego, CA) and validated Taqman^® allelic discrimination (Applied Biosystems^® ). Statistical analyses were performed using SPSS software version 19.0, SNPStats, GMDR software (version 6) and GENEMANIA.

RESULTS

Logistic regression analysis of 55 SNPs revealed significant associations (P < .05) of 49 SNPs with BMI linked obesity risk whereas the remaining 6 SNPs revealed no association (P > .05). The pathway-wise G-score revealed the significant role (P = .0001) of food intake-energy expenditure pathway genes. In CART analysis, the combined genotypes of FTO rs9939609 and TCF7L2 rs7903146 revealed the highest risk for BMI linked obesity. The analysis of the FTO-IRX3 locus revealed high LD and high order gene-gene interactions for BMI linked obesity. The interaction network of all of the associated genes in the present study generated by GENEMANIA revealed direct and indirect connections. In addition, the analysis with centralized obesity revealed that none of the SNPs except for FTO rs17818902 were significantly associated (P < .05).

CONCLUSIONS

In this multi-analytical approach, FTO rs9939609 and IRX3 rs3751723, along with TCF7L2 rs7903146 and TMEM18 rs6548238, emerged as the major SNPs contributing to BMI linked obesity risk in the North Indian population.

The association of cigarette smoking and alcohol drinking with body mass index: a cross-sectional, population-based study among Chinese adult male twins

Background

Obesity is a multifactorial abnormality which has an underlying genetic control but requires environmental influences to trigger. Numerous epidemiological studies have examined the roles of physical inactivity and dietary factors in obesity development. Interactions between obesity-related genes and these lifestyles have also been confirmed. However, less attention has been paid to these complex relationship between cigarette smoking, alcohol drinking and obesity. The purpose of this study was to assess whether cigarette smoking and alcohol drinking were associated with body mass index (BMI), and whether these lifestyle factors modified the genetic variance of BMI.

Methods

Subjects were twins recruited through the Chinese National Twin Registry, aged 18 to 79 years, and the sample comprised 6121 complete male twin pairs. Information on height, weight, cigarette smoking and alcohol drinking status were assessed with self-report questionnaires. The associations of cigarette smoking and alcohol drinking with BMI were evaluated by linear regression models. Further, structure equation models were conducted to estimate whether cigarette smoking and alcohol drinking status modified the degree of genetic variance of BMI.

Results

After adjustment for a variety of socio-demographic and lifestyle factors, former smokers had higher BMI (β = 0.475; 95 % CI, 0.196 to 0.754) whereas moderate to heavy smokers had lower BMI (β = −0.115; 95 % CI, −0.223 to −0.007) when compared with nonsmokers. BMI decreased with increased cigarette pack-years (β = −0.008; 95 % CI, −0.013 to −0.003). These effects still existed substantially in within-MZ twin pair analyses. By contrast, current alcohol drinking had no significant influence on BMI when additionally controlled for shared factors in within-pair analyses. Genetic modification by alcohol drinking was statistically significant for BMI (β = −0.137; 95 % CI, −0.215 to −0.058), with the intake of alcohol decreasing the additive genetic component of BMI.

Conclusions

Cigarette smoking was negatively associated with BMI independent of genetic influences. The influence of genes on BMI was moderated by alcohol drinking, such that for individuals who were regular drinkers, genetic factors became less influential. Our findings highlight gene-alcohol interaction in finding candidate genes of BMI and elucidating the etiological factors of obesity.

Genetic polymorphism at Val80 (rs700518) of the CYP19A1 gene is associated with body composition changes in women on aromatase inhibitors for ER (+) breast cancer

OBJECTIVE

Polymorphisms in the CYP19A1 (aromatase) gene influence disease-free survival and bone loss in patients taking aromatase inhibitors (AIs) for estrogen receptor-positive (ER+) breast cancers. Because AI use results in severe estrogen deficiency that may lead to changes in body composition, the aim of this study was to determine the effect of the rs700518 polymorphism in the CYP19A1 gene on the changes in body composition among postmenopausal women who were treated with AIs for ER+ breast cancer.

PATIENTS AND METHODS

This was a 1-year prospective study of changes in body composition in postmenopausal women who were initiated on third-generation AIs for ER+ breast cancer. Body composition was measured by dual-energy absorptiometry at 6 and 12 months, serum estradiol by radioimmunoassay, and genotyping by a TaqMan single-nucleotide polymorphism allelic discrimination assay.

RESULTS

Eighty-two women could provide at least one follow-up body composition measurement. Women with the GG genotype for the rs700518 (G/A at Val80) developed a significant increase in truncal fat mass index (P=0.03) and a significant decrease in fat-free mass index (P=0.01) at 12 months relative to patients carrying the A allele (GA/AA). There was no significant difference in the changes in estradiol levels among the genotypes.

CONCLUSION

Patients with the GG genotype for the rs700518 polymorphism in the CYP19A1 gene are at risk for significant loss of fat-free mass and increase in truncal fat with AI therapy. Whether there are associated metabolic abnormalities and whether changes would persist with long-term AI therapy need to be confirmed in a larger study with a longer duration of follow-up.

The IL6R gene polymorphisms are associated with sIL-6R, IgE and lung function in Chinese patients with asthma

BACKGROUND

sIL-6R is involved in a variety of inflammatory diseases. The present study analyzed the potential associations between two IL6R gene polymorphisms (rs2228145 and rs12083537) and asthma in a Han Chinese population.

METHODS

A cohort of 394 patients and 395 healthy controls were genotyped to detect the two polymorphisms using SNaPshot. In 66 asthma patients and 49 controls, peripheral eosinophil and serum immunoglobulin E (IgE) levels were determined using a routine blood test, and sIL-6R levels were measured by ELISA.

RESULTS

No statistically significant differences were detected between the patients and controls in the distribution of the two independent IL6R polymorphisms (p>0.05). However, rs2228145 C and rs12083537 G were significantly associated with decreased lung function in patients with asthma; the rs2228145 A-C variant was also associated with increased sIL-6R and IgE levels. In addition, sIL-6R levels were positively associated with IgE and inversely associated with lung function in patients with asthma.

CONCLUSIONS

Our results provide evidence that rs2228145 C and rs12083537 G are associated with poor lung function in patients with asthma. Furthermore, the rs2228145 A-C variant is associated with levels of sIL-6R and IgE.

Health Disparities and Delayed Health care among Older Adults in California: A Perspective from Race, Ethnicity, and Immigration

OBJECTIVES

To examine racial/ethnic/immigration disparities in health and to investigate the relationships among race/ethnic/immigration status, delayed health care, and health of the elderly.

DESIGN AND SAMPLE

Responses from 13,508 people aged 65 and above were analyzed based on the California Health Interview Survey (CHIS) 2011-2012.

MEASURES

Key variables include race/ethnicity/immigration status, health outcome, and delayed health care. Age, gender, education, work status, and annual family income are used as covariates.

RESULTS

The findings indicate that Whites (regardless of country of birth) and U.S.-born Asians enjoy better health than Latinos, African-Americans, and Foreign-born Asians. Foreign-born Asians and foreign-born Latinos have the poorest self-reported health and mental health, respectively. Delayed use of health care is negatively associated with both self-reported health and mental health status.

CONCLUSIONS

Health disparities exist among older adult populations; the combined effects of minority and immigrant status can be approximated from the results in this study. Health care accessibility and the quality of care should be promoted in minority/immigrant populations. Public health nurses have a strong potential to aide in reducing health disparities among an aging American population that continues to exhibit increasing racial/ethnic diversity.

Interaction of smoking and obesity susceptibility loci on adolescent BMI: The National Longitudinal Study of Adolescent to Adult Health

BACKGROUND

Adolescence is a sensitive period for weight gain and risky health behaviors, such as smoking. Genome-wide association studies (GWAS) have identified loci contributing to adult body mass index (BMI). Evidence suggests that many of these loci have a larger influence on adolescent BMI. However, few studies have examined interactions between smoking and obesity susceptibility loci on BMI. This study investigates the interaction of current smoking and established BMI SNPs on adolescent BMI. Using data from the National Longitudinal Study of Adolescent to Adult Health, a nationally-representative, prospective cohort of the US school-based population in grades 7 to 12 (12-20 years of age) in 1994-95 who have been followed into adulthood (Wave II 1996; ages 12-21, Wave III; ages 18-27), we assessed (in 2014) interactions of 40 BMI-related SNPs and smoking status with percent of the CDC/NCHS 2000 median BMI (%MBMI) in European Americans (n = 5075), African Americans (n = 1744) and Hispanic Americans (n = 1294).

RESULTS

Two SNPs showed nominal significance for interaction (p < 0.05) between smoking and genotype with %MBMI in European Americans (EA) (rs2112347 (POC5): β = 1.98 (0.06, 3.90), p = 0.04 and near rs571312 (MC4R): β 2.15 (-0.03, 4.33) p = 0.05); and one SNP showed a significant interaction effect after stringent correction for multiple testing in Hispanic Americans (HA) (rs1514175 (TNNI3K): β 8.46 (4.32, 12.60), p = 5.9E-05). Stratifying by sex, these interactions suggest a stronger effect in female smokers.

CONCLUSIONS

Our study highlights potentially important sex differences in obesity risk by smoking status in adolescents, with those who may be most likely to initiate smoking (i.e., adolescent females), being at greatest risk for exacerbating genetic obesity susceptibility.

Resistance to high-fat diet-induced obesity in male heterozygous Pprc1 knockout mice

Peroxisome proliferator-activated receptor gamma, co-activator-related 1 (Pprc1) is the third member of the Pgc1 family. Other than the well-characterized Pgc1a and Pgc1b that act as regulators of mitochondrial biogenesis and oxidative metabolism, the function of Pprc1 in vivo is rarely reported, due to embryonic lethality of whole-body Pprc1 knockout mice. To investigate the biological and physiological function of Pprc1 in metabolic processes, male Pprc1(+/-) mice fed with a high fat diet (HFD) showed resistance to diet-induced obesity with a decrease of adipose tissue in Pprc1(+/-) mice, which was a result of elevated energy expenditure. In skeletal muscle of Pprc1(+/-) mice, Pprc1 level showed haplo-insufficiency with down-regulation of Pgc1b and Pgc1a, whereas in adipose tissue, Pprc1 expression remained normal, with significant compensatory increase of other Pgc1 family members to induce an up-regulation of respiratory chain genes. Taken together, as the first report on the metabolic roles of Pprc1 in vivo, these results indicated an elevated basal metabolic rate and lipid metabolic alteration of male Pprc1(+/-) mice on HFD, suggesting the significant role of Pprc1 in controlling mitochondrial gene expression and energy metabolic processes, synergistically with Pgc1a and Pgc1b.

Gray and white matter structures in the midcingulate cortex region contribute to body mass index in Chinese young adults

Overweight and obesity are rapidly becoming a central public health challenge around the world. Previous studies have suggested that elevated Body Mass Index (BMI) might be associated with structural changes in both gray and white matter, but this association is still not well understood. The present study aimed to investigate the relationship between BMI and brain structure with a relatively large sample of young adults (N = 336) in a small age range (20 ± 1 years). Voxel-based morphometry results showed significant negative correlations between BMI and gray-matter volumes in the midcingulate cortex (MCC), left orbital frontal cortex, and left ventromedial prefrontal cortex. There was also a significant negative correlation between BMI and white matter integrity as indexed by fractional anisotropy in bilateral cingulum. Further tractography analysis showed a significant negative correlation between BMI and the number of fibers passing the MCC region. Regression analysis showed that gray matter and white matter in these regions both contributed to the variance of BMI. These results remained significant even when analysis was restricted to the subjects with normal weights. Finally, we found that decision-making ability (as assessed by the Iowa Gambling Task) mediated the association between the structure of the MCC (a region responsible for impulse control and decision making) and BMI. These results shed light on the structural neural basis of weight variations.

Moderate to vigorous physical activity interactions with genetic variants and body mass index in a large US ethnically diverse cohort

BACKGROUND

Little is known about the interaction between genetic and behavioural factors during lifecycle risk periods for obesity and how associations vary across race/ethnicity.

OBJECTIVE

The objective of this study was to examine joint associations of adiposity-related single-nucleotide polymorphisms (SNPs) and moderate to vigorous physical activity (MVPA) with body mass index (BMI) in a diverse adolescent cohort.

METHODS

Using data from the National Longitudinal Study of Adolescent Health (n = 8113: Wave II 1996; ages 12-21, Wave III; ages 18-27), we assessed interactions of 41 well-established SNPs and MVPA with BMI-for-age Z-scores in European Americans (EA; n = 5077), African-Americans (AA; n = 1736) and Hispanic Americans (HA; n = 1300).

RESULTS

Of 97 assessed, we found nominally significant SNP-MVPA interactions on BMI-for-age Z-score in EA at GNPDA2 and FTO and in HA at LZTR2/SEC16B. In EA, the estimated effect of the FTO risk allele on BMI-for-age Z-score was lower (β = -0.13; 95% confidence interval [CI]: 0.08, 0.18) in individuals with ≥5 vs. <5 (β = 0.24; CI: 0.16, 0.32) bouts of MVPA per week (P for interaction 0.02). Race/ethnicity-pooled meta-analysis showed nominally significant interactions for SNPs at TFAP2B, POC5 and LYPLAL1.

CONCLUSIONS

High MVPA may attenuate underlying genetic risk for obesity during adolescence, a high-risk period for adult obesity.

Common variation at PPARGC1A/B and change in body composition and metabolic traits following preventive interventions: the Diabetes Prevention Program

AIMS/HYPOTHESIS

PPARGC1A and PPARGCB encode transcriptional coactivators that regulate numerous metabolic processes. We tested associations and treatment (i.e. metformin or lifestyle modification) interactions with metabolic traits in the Diabetes Prevention Program, a randomised controlled trial in persons at high risk of type 2 diabetes.

METHODS

We used Tagger software to select 75 PPARGCA1 and 94 PPARGC1B tag single-nucleotide polymorphisms (SNPs) for analysis. These SNPs were tested for associations with relevant cardiometabolic quantitative traits using generalised linear models. Aggregate genetic effects were tested using the sequence kernel association test.

RESULTS

In aggregate, PPARGC1A variation was strongly associated with baseline triacylglycerol concentrations (p = 2.9 × 10(-30)), BMI (p = 2.0 × 10(-5)) and visceral adiposity (p = 1.9 × 10(-4)), as well as with changes in triacylglycerol concentrations (p = 1.7 × 10(-5)) and BMI (p = 9.9 × 10(-5)) from baseline to 1 year. PPARGC1B variation was only associated with baseline subcutaneous adiposity (p = 0.01). In individual SNP analyses, Gly482Ser (rs8192678, PPARGC1A) was associated with accumulation of subcutaneous adiposity and worsening insulin resistance at 1 year (both p < 0.05), while rs2970852 (PPARGC1A) modified the effects of metformin on triacylglycerol levels (p(interaction) = 0.04).

CONCLUSIONS/INTERPRETATION

These findings provide several novel and other confirmatory insights into the role of PPARGC1A variation with respect to diabetes-related metabolic traits.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00004992.

Mitochondrial alteration in type 2 diabetes and obesity: an epigenetic link

The growing epidemic of type 2 diabetes mellitus (T2DM) and obesity is largely attributed to the current lifestyle of over-consumption and physical inactivity. As the primary platform controlling metabolic and energy homeostasis, mitochondria show aberrant changes in T2DM and obese subjects. While the underlying mechanism is under extensive investigation, epigenetic regulation is now emerging to play an important role in mitochondrial biogenesis, function, and dynamics. In line with lifestyle modifications preventing mitochondrial alterations and metabolic disorders, exercise has been shown to change DNA methylation of the promoter of PGC1α to favor gene expression responsible for mitochondrial biogenesis and function. In this article we discuss the epigenetic mechanism of mitochondrial alteration in T2DM and obesity, and the effects of lifestyle on epigenetic regulation. Future studies designed to further explore and integrate the epigenetic mechanisms with lifestyle modification may lead to interdisciplinary interventions and novel preventive options for mitochondrial alteration and metabolic disorders.

Association and interaction analysis of PPARGC1A and serum uric acid on type 2 diabetes mellitus in Chinese Han population

BACKGROUND

Peroxisome proliferator-activated receptor gamma coactivator-1α (PPARGC1A/ PGC-1α) is a ligand-activated transcription factor belonging to the nuclear hormone receptor superfamily. The activity of PGC-1α or genetic variations in the gene encoding the enzyme may contribute to individual variations in mitochondrial function and insulin resistance or diabetes. The objective of this study was to assess the extent to which PPARGC1A (rs8192678) and serum uric acid (UA) and its interaction impact on T2DM susceptibility in Chinese Han population.

METHOD

We conducted a study in a cohort that included 1166 T2DM patients and 1135 controls, and was genotyped for the presence of the PPARGC1A rs8192678 polymorphisms. Genotyping was performed by iPLEX technology. The association between rs8192678 or UA and T2DM was assessed by univariate and multivariate logistic regression (MLR) analysis controlling for confounders. The interaction between rs8192678 and UA for T2DM susceptibility was also assessed by MLR analysis.

RESULTS

The generalized linear regression analysis failed to show an association between the PPARGC1A rs8192678 polymorphisms and T2DM. Interestingly, the present study provided data suggesting that the minor A-allele of PPARGC1A (rs8192678) had a protective effect against T2DM in subjects with higher level of UA (ORint =1.50 95% CI: 1.06-2.12 for allele and P = 0.02, ORint =1.63 95% CI: 1.17-2.26 for genotype and P = 0.004).

CONCLUSION

The combination of higher level of UA and PPARGC1A (rs8192678) was an independent predictor for T2DM.

Models of interinstitutional partnerships between research intensive universities and minority serving institutions (MSI) across the Clinical Translational Science Award (CTSA) consortium

Health disparities are an immense challenge to American society. Clinical and Translational Science Awards (CTSAs) housed within the National Center for Advancing Translational Science (NCATS) are designed to accelerate the translation of experimental findings into clinically meaningful practices and bring new therapies to the doorsteps of all patients. Research Centers at Minority Institutions (RCMI) program at the National Institute on Minority Health and Health Disparities (NIMHD) are designed to build capacity for biomedical research and training at minority serving institutions. The CTSA created a mechanism fostering formal collaborations between research intensive universities and minority serving institutions (MSI) supported by the RCMI program. These consortium-level collaborations activate unique translational research approaches to reduce health disparities with credence to each academic institutions history and unique characteristics. Five formal partnerships between research intensive universities and MSI have formed as a result of the CTSA and RCMI programs. These partnerships present a multifocal approach; shifting cultural change and consciousness toward addressing health disparities, and training the next generation of minority scientists. This collaborative model is based on the respective strengths and contributions of the partnering institutions, allowing bidirectional interchange and leveraging NIH and institutional investments providing measurable benchmarks toward the elimination of health disparities.

Defining the environment in gene-environment research: lessons from social epidemiology

In this article, we make the case that social epidemiology provides a useful framework to define the environment within gene-environment (G × E) research. We describe the environment in a multilevel, multidomain, longitudinal framework that accounts for upstream processes influencing health outcomes. We then illustrate the utility of this approach by describing how intermediate levels of social organization, such as neighborhoods or schools, are key environmental components of G × E research. We discuss different models of G × E research and encourage public health researchers to consider the value of including genetic information from their study participants. We also encourage researchers interested in G × E interplay to consider the merits of the social epidemiology model when defining the environment.

Variation at the melanocortin 4 receptor gene and response to weight-loss interventions in the diabetes prevention program

OBJECTIVE

To assess associations and genotype × treatment interactions for melanocortin 4 receptor (MC4R) locus variants and obesity-related traits.

DESIGN AND METHODS

Diabetes prevention program (DPP) participants (N = 3,819, of whom 3,356 were genotyped for baseline and 3,234 for longitudinal analyses) were randomized into intensive lifestyle modification (diet, exercise, weight loss), metformin or placebo control. Adiposity was assessed in a subgroup (n = 909) using computed tomography. All analyses were adjusted for age, sex, ethnicity and treatment.

RESULTS

The rs1943218 minor allele was nominally associated with short-term (6 month; P = 0.032) and long-term (2 year; P = 0.038) weight change. Eight SNPs modified response to treatment on short-term (rs17066856, rs9966412, rs17066859, rs8091237, rs17066866, rs7240064) or long-term (rs12970134, rs17066866) reduction in body weight, or diabetes incidence (rs17066829) (all Pinteraction < 0.05).

CONCLUSION

This is the first study to comprehensively assess the role of MC4R variants and weight regulation in a weight loss intervention trial. One MC4R variant was directly associated with obesity-related traits or diabetes; numerous other variants appear to influence body weight and diabetes risk by modifying the protective effects of the DPP interventions.

Clinical and genetic predictors of weight gain in patients diagnosed with breast cancer

Background:

Post-diagnosis weight gain in breast cancer patients has been associated with increased cancer recurrence and mortality. Our study was designed to identify risk factors for this weight gain and create a predictive model to identify a high-risk population for targeted interventions.

Methods:

Chart review was conducted on 459 breast cancer patients from Northwestern Robert H. Lurie Cancer Centre to obtain weights and body mass indices (BMIs) over an 18-month period from diagnosis. We also recorded tumour characteristics, demographics, clinical factors, and treatment regimens. Blood samples were genotyped for 14 single-nucleotide polymorphisms (SNPs) in fat mass and obesity-associated protein (FTO) and adiponectin pathway genes (ADIPOQ and ADIPOR1).

Results:

In all, 56% of patients had >0.5 kg m^–2 increase in BMI from diagnosis to 18 months, with average BMI and weight gain of 1.9 kg m^–2 and 5.1 kg, respectively. Our best predictive model was a primarily SNP-based model incorporating all 14 FTO and adiponectin pathway SNPs studied, their epistatic interactions, and age and BMI at diagnosis, with area under receiver operating characteristic curve of 0.85 for 18-month weight gain.

Conclusion:

We created a powerful risk prediction model that can identify breast cancer patients at high risk for weight gain.

Genetic polymorphism at Val80 (rs700518) of the CYP19A1 gene is associated with aromatase inhibitor associated bone loss in women with ER + breast cancer

PURPOSE

Polymorphisms in the CYP19A1 (aromatase) gene have been reported to influence disease-free survival and the incidence of musculoskeletal complaints in patients taking aromatase inhibitors (AIs) for estrogen receptor positive (ER+) breast cancer. Bone loss and fractures are well-recognized complications from AI therapy. The objective of this study is to determine the influence of polymorphisms in the CYP19A1 gene on bone loss among patients taking aromatase inhibitors for ER+ breast cancer.

PATIENTS AND METHODS

The subjects consisted of 97 postmenopausal women with ER+ breast cancer who were initiated on third-generation AIs. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry at baseline and at 6 and 12 months. Twenty-four hour urine N-telopeptide (NTX) was measured by Elisa and serum estradiol was measured by ultrasensitive radioimmunoassay at baseline, and at 6 months. Genotyping was done by Taqman SNP allelic discrimination assay.

RESULTS

Women with the AA genotype for the rs700518 (G/A at Val(80)) developed significant bone loss at the lumbar spine and the total hip at 12 months relative to patients carrying the G allele (GA/GG); both p = 0.03. There was a borderline greater increase in urinary NTX in those with the AA genotype compared to patients with the G allele, p = 0.05; but no significant difference in changes in estradiol levels among the genotypes.

CONCLUSION

Patients with the AA genotype for the rs700518 polymorphism in the CYP19A1 gene are at risk for AI-associated bone loss and deserve close follow-up during long-term AI therapy.

Role of ethnicity in antipsychotic-induced weight gain and tardive dyskinesia: genes or environment?

Aim: This study explored the role of self-reported ethnicity and genetic ancestry on antipsychotic (AP)-induced weight gain and tardive dyskinesia (TD) in schizophrenia. Patients & methods: Ethnicity was determined by self-report as well as Structure analysis of 190 SNPs selected from HapMap3, genotyped using a customized Illumina BeadChip. Age, gender, baseline weight and AP response using Brief Psychiatric Rating Scale were assessed. Multivariate regression models for AP-induced weight gain and TD, based on the Abnormal Involuntary Movement Scale were constructed. Results: African–American ethnicity (self-report, p = 0.021 and Structure analysis, p = 0.042) predicted AP-induced weight gain but not TD (self-report, p = 0.408 and Structure analysis, p = 0.714). Conclusion: Self-reported African–American ethnicity seemed to better predict AP-induced weight gain in schizophrenia compared with genetic ancestry, suggesting a possible role of environmental in addition to genetic factors. Future larger studies are needed to clarify specific gene–environment mechanisms mediating the effect of ethnicity on AP-induced weight gain.

Original submitted 1 January 2013; Revision submitted 17 June 2013

Interactions of genetic and environmental risk factors with respect to body fat mass in children: results from the ALSPAC study

OBJECTIVE

To evaluate if percentile-specific effects of genetic, environmental and lifestyle obesity risk factors on body mass index (BMI) might reflect gene-environment interactions with respect to the development of overweight.

DESIGN AND METHODS

Retrospective study with data of 2,346 children from the Avon Longitudinal Study of Parents and Children (ALSPAC), using quantile regression with body fat mass index (FMI) for children at the age of 9 years as outcome variable. We assessed interactions of an "obesity-risk-allele-score" with environmental and nutritional factors.

RESULTS

There was no evidence of interactions between the obesity-risk-allele score and the environmental variables except for maternal overweight. However, we found a significant interaction with respect to intake of mono- and polyunsaturated fatty acids at the age of 7. In children with low intake, genetic risk was associated with increasing effect sizes by FMI percentile.

CONCLUSIONS

Our results suggest an interaction between a low dietary content of unsaturated fatty acids and genetic risk factors for overweight on FMI. This effect is likely to be stronger in children with higher FMI.

Genetic variations in the serotoninergic system contribute to body-mass index in Chinese adolescents

OBJECTIVE

Obesity has become a worldwide health problem in the past decades. Human and animal studies have implicated serotonin in appetite regulation, and behavior genetic studies have shown that body mass index (BMI) has a strong genetic component. However, the roles of genes related to the serotoninergic (5-hydroxytryptamine,5-HT) system in obesity/BMI are not well understood, especially in Chinese subjects.

SUBJECTS AND DESIGN

With a sample of 478 healthy Chinese volunteers, this study investigated the relation between BMI and genetic variations of the serotoninergic system as characterized by 136 representative polymorphisms. We used a system-level approach to identify SNPs associated with BMI, then estimated their overall contribution to BMI by multiple regression and verified it by permutation.

RESULTS

We identified 12 SNPs that made statistically significant contributions to BMI. After controlling for gender and age, four of these SNPs accounted for 7.7% additional variance of BMI. Permutation analysis showed that the probability of obtaining these findings by chance was low (p = 0.015, permuted for 1000 times).

CONCLUSION

These results showed that genetic variations in the serotoninergic system made a moderate contribution to individual differences in BMI among a healthy Chinese sample, suggesting that a similar approach can be used to study obesity.

No conclusive evidence for association of polymorphisms in the adiponectin receptor 1 gene, AdipoR1, with common obesity

AdipoR1 is one of the adiponectin receptors which are important for adiponectin signaling. Because adiponectin is a candidate gene for common obesity, it is also hypothesized that variations in AdipoR1 may be involved in the development of complex obesity. Therefore, we designed an association study for the AdipoR1 gene. We performed a case-control association study including 1,021 obese subjects (mean age 42 ± 12 years; mean BMI 38.2 ± 6.2 kg/m²) and 226 lean, healthy individuals (mean age 36 ± 7 years; mean BMI 22.1 ± 1.7 kg/m²). Nine tagSNPs were selected to cover the entire AdipoR1 gene and surrounding 7 kb region (based on HapMap data). TagSNPs were genotyped using AcycloPrime-Fluorescence Polarization (FP) SNP Detection kits and TaqMan Pre-Designed SNP Genotyping assays according to manufacturer's protocols. We found that the rs1075399 non-reference allele decreases obesity risk by 45 % in men only [odds ratio (OR) = 0.55, 95 % CI 0.35-0.87, nominal P = 0.010]. However, after Bonferroni correction for multiple testing, this association is lost. None of the other tagSNPs were associated with obesity when studying the entire population, nor when looking at men and women separately. Quantitative analysis of the effect of each SNP on height, weight, and BMI revealed that none of the tagSNPs are associated with weight or BMI. We report here that we found no decisive evidence for association between AdipoR1 tagSNPs and complex obesity in our Belgian Caucasian population.

Gene-Lifestyle Interactions in Obesity

Obesity is a complex multifaceted disease resulting from interactions between genetics and lifestyle. The proportion of phenotypic variance ascribed to genetic variance is 0.4 to 0.7 for obesity and recent years have seen considerable success in identifying disease-susceptibility variants. Although with the advent of genome-wide association studies the list of genetic variants predisposing to obesity has significantly increased the identified variants only explain a fraction of disease heritability. Studies of gene-environment interactions can provide more insight into the biological mechanisms involved in obesity despite the challenges associated with such designs. Epigenetic changes that affect gene function without DNA sequence modifications may be a key factor explaining interindividual differences in obesity, with both genetic and environmental factors influencing the epigenome. Disentangling the relative contributions of genetic, environmental and epigenetic marks to the establishment of obesity is a major challenge given the complex interplay between these determinants.