TRP64ARG polymorphism of the beta 3-adrenergic receptor gene and obesity risk: effect modification by a sedentary lifestyle

Majid H. Non-Synonymous Single-Nucleotide Polymorphisms and Physical Activity Interactions on Adiposity Parameters in Malaysian Adolescents

BACKGROUND

Several non-synonymous single-nucleotide polymorphisms (nsSNPs) have been shown to be associated with obesity. Little is known about their associations and interactions with physical activity (PA) in relation to adiposity parameters among adolescents in Malaysia.

METHODS

We examined whether (a) PA and (b) selected nsSNPs are associated with adiposity parameters and whether PA interacts with these nsSNPs on these outcomes in adolescents from the Malaysian Health and Adolescents Longitudinal Research Team study (n = 1,151). Body mass indices, waist-hip ratio, and percentage body fat (% BF) were obtained. PA was assessed using Physical Activity Questionnaire for Older Children (PAQ-C). Five nsSNPs were included: beta-3 adrenergic receptor (ADRB3) rs4994, FABP2 rs1799883, GHRL rs696217, MC3R rs3827103, and vitamin D receptor rs2228570, individually and as combined genetic risk score (GRS). Associations and interactions between nsSNPs and PAQ-C scores were examined using generalized linear model.

RESULTS

PAQ-C scores were associated with % BF (β = -0.44 [95% confidence interval -0.72, -0.16], p = 0.002). The CC genotype of ADRB3 rs4994 (β = -0.16 [-0.28, -0.05], corrected p = 0.01) and AA genotype of MC3R rs3827103 (β = -0.06 [-0.12, -0.00], p = 0.02) were significantly associated with % BF compared to TT and GG genotypes, respectively. Significant interactions with PA were found between ADRB3 rs4994 (β = -0.05 [-0.10, -0.01], p = 0.02) and combined GRS (β = -0.03 [-0.04, -0.01], p = 0.01) for % BF.

CONCLUSION

Higher PA score was associated with reduced % BF in Malaysian adolescents. Of the nsSNPs, ADRB3 rs4994 and MC3R rs3827103 were associated with % BF. Significant interactions with PA were found for ADRB3 rs4994 and combined GRS on % BF but not on measurements of weight or circumferences. Targeting body fat represent prospects for molecular studies and lifestyle intervention in this population.

Molecular genetics of human obesity: A comprehensive review

Obesity and its related health complications is a major problem worldwide. Hypothalamus and their signalling molecules play a critical role in the intervening and coordination with energy balance and homeostasis. Genetic factors play a crucial role in determining an individual's predisposition to the weight gain and being obese. In the past few years, several genetic variants were identified as monogenic forms of human obesity having success over common polygenic forms. In the context of molecular genetics, genome-wide association studies (GWAS) approach and their findings signified a number of genetic variants predisposing to obesity. However, the last couple of years, it has also been noticed that alterations in the environmental and epigenetic factors are one of the key causes of obesity. Hence, this review might be helpful in the current scenario of molecular genetics of human obesity, obesity-related health complications (ORHC), and energy homeostasis. Future work based on the clinical discoveries may play a role in the molecular dissection of genetic approaches to find more obesity-susceptible gene loci.

Genetic variants influencing effectiveness of exercise training programmes in obesity - an overview of human studies

Frequent and regular physical activity has significant benefits for health, including improvement of body composition and help in weight control. Consequently, promoting training programmes, particularly in those who are genetically predisposed, is a significant step towards controlling the presently increasing epidemic of obesity. Although the physiological responses of the human body to exercise are quite well described, the genetic background of these reactions still remains mostly unknown. This review not only summarizes the current evidence, through a literature review and the results of our studies on the influence of gene variants on the characteristics and range of the body's adaptive response to training, but also explores research organization problems, future trends, and possibilities. We describe the most reliable candidate genetic markers that are involved in energy balance pathways and body composition changes in response to training programmes, such as FTO, MC4R, ACE, PPARG, LEP, LEPR, ADRB2, and ADRB3. This knowledge can have an enormous impact not only on individualization of exercise programmes to make them more efficient and safer, but also on improved recovery, traumatology, medical care, diet, supplementation and many other areas. Nevertheless, the current studies still represent only the first steps towards a better understanding of the genetic factors that influence obesity-related traits, as well as gene variant x physical activity interactions, so further research is necessary.

Influence of ADRB2 Gln27Glu and ADRB3 Trp64Arg polymorphisms on body weight and body composition changes after a controlled weight-loss intervention

The β-2 and β-3 adrenergic receptors (ADRB2 and ADRB3) are thought to play a role in energy expenditure and lipolysis. However, the effects of the ADRB2 glutamine (Gln) 27 glutamic acid (glutamate) (Glu) and ADRB3 tryptophan (Trp) 64 arginine (Arg) polymorphisms on weight loss remain controversial. The aim of this study was to investigate the effect of these polymorphisms on changes in weight and body composition during a controlled weight-loss program. One hundred seventy-three healthy overweight and obese participants (91 women, 82 men) aged 18-50 years participated in a 22-week-long intervention based on a hypocaloric diet and exercise. They were randomly assigned to 1 of 4 groups: strength, endurance, strength and endurance combined, and physical activity recommendations only. Body weight, body mass index (BMI), and body composition variables were assessed before and after the intervention. Genetic analysis was carried out according to standard protocols. No effect of the ADRB2 gene was shown on final weight, BMI, or body composition, although in the supervised male group, Glu27 carriers tended to have greater weight (p = 0.019, 2.5 kg) and BMI (p = 0.019, 0.88 kg/m(2)) reductions than did noncarriers. There seems to be an individual effect of the ADRB3 polymorphism on fat mass (p = 0.004) and fat percentage (p = 0.036), in addition to an interaction with exercise for fat mass (p = 0.038). After the intervention, carriers of the Arg64 allele had a greater fat mass and fat percentage than did noncarriers (p = 0.004, 2.8 kg). In conclusion, the ADRB2 Gln27Glu and ADRB3 Trp64Arg polymorphisms may influence weight loss and body composition, although the current evidence is weak; however, further studies are necessary to clarify their roles.

Behavioral and Environmental Modification of the Genetic Influence on Body Mass Index: A Twin Study

Body mass index (BMI) has a strong genetic basis, with a heritability around 0.75, but is also influenced by numerous behavioral and environmental factors. Aspects of the built environment (e.g., environmental walkability) are hypothesized to influence obesity by directly affecting BMI, by facilitating or inhibiting behaviors such as physical activity that are related to BMI, or by suppressing genetic tendencies toward higher BMI. The present study investigated relative influences of physical activity and walkability on variance in BMI using 5079 same-sex adult twin pairs (70 % monozygotic, 65 % female). High activity and walkability levels independently suppressed genetic variance in BMI. Estimating their effects simultaneously, however, suggested that the walkability effect was mediated by activity. The suppressive effect of activity on variance in BMI was present even with a tendency for low-BMI individuals to select into environments that require higher activity levels. Overall, our results point to community- or macro-level interventions that facilitate individual-level behaviors as a plausible approach to addressing the obesity epidemic among US adults.

Genetic variation at the CYP2C19 gene associated with metabolic syndrome susceptibility in a South Portuguese population: results from the pilot study of the European Health Examination Survey in Portugal

BACKGROUND

Metabolic syndrome (MetS) is a cluster of conditions that occur together, increasing the risk of heart disease, stroke and diabetes. Since pathways implicated in different diseases reveal surprising insights into shared genetic bases underlying apparently unrelated traits, we hypothesize that there are common genetic components involved in the clustering of MetS traits. With the aim of identifying these common genetic components, we have performed a genetic association study by integrating MetS traits in a continuous MetS score.

METHODS

A cross-sectional study developed in the context of the Portuguese Component of the European Health Examination Survey (EHES) was used. Data was collected through a detailed questionnaire and physical examination. Blood samples were collected and biochemical analyses were performed. Waist circumference, blood pressure, glucose, triglycerides and high density lipoprotein cholesterol (HDL) levels were used to compute a continuous MetS score, obtained by Principal Component Analysis. A total of 37 single nucleotide polymorphisms (SNPs) were genotyped and individually tested for association with the score, adjusting for confounding variables.

RESULTS

A total of 206 individuals were studied. Calculated MetS score increased progressively with increasing number of risk factors (P < 0.001). We found a significant association between CYP2C19 rs4244285 and the MetS score not detected using the MetS dichotomic approach. Individuals with the A allelic variant seem to be protected against MetS, displaying a lower MetS score (Mean difference: 0.847; 95%CI: 0.163-1.531; P = 0.015), after adjustment for age, gender, smoking status, excessive alcohol consumption and physical inactivity. An additive genetic effect of GABRA2 rs279871, NPY rs16147 and TPMT rs1142345 in the MetS score variation was also found.

CONCLUSIONS

This is the first report of a genetic association study using a continuous MetS score. The significant association found between the CYP2C19 polymorphism and the MetS score but not with the individual associated traits, emphasizes the importance of lipid metabolism in a MetS common etiological pathway and consequently on the clustering of different cardiovascular risk factors. Despite the sample size limitation of our study, this strategy can be useful to find genetic factors involved in the etiology of other disorders that are defined in a dichotomized way.

Trends of body mass index distribution in schoolchildren in Sendai, Japan, 1989-2003

SUMMARY

Accumulating evidence indicates a strong association between obesity and health problems. Childhood obesity increases the risk of adulthood obesity. Although it is reported that the number of obese children in Japan has increased, it is unclear whether the obesity index distribution pattern has changed. To clarify this distribution pattern, we analyzed the changes in the body mass index (BMI) of primary (6th grade, 12 years old) and junior high (3rd year, 15 years old) schoolchildren in the city of Sendai during the period from 1989 to 2003. Our department has accumulated information on the height and body weight of all the schoolchildren in the city of Sendai. BMI was calculated using both the height and body weight data. The change in median BMI for 15 years had a slightly upward trend every year with both gender and school year. Although the BMI distribution showed that there was little or no change over time in the lower (10th and 25th) percentiles, the increases in the 75th and 90th percentiles were more marked than that in the 50th percentile in primary school children. On the other hand, there was only a small increase in BMI in the 3rd year of junior high school. Our results indicated that the changes in BMI distribution were concentrated at the upper end of the distribution in primary school children. The shifts in the value of high percentiles might be due to effect modification of the corresponding exposure by another environmental exposure or genetic predisposition. It is suggested that the factors causing this change influenced only part of this population, and affected individuals might represent a susceptible subpopulation of the exposed children.:

Physical activity and sex modulate obesity risk linked to 3111T/C gene variant of the CLOCK gene in an elderly population: the SUN Project

Genetic factors may interact with physical activity levels to modify obesity risk. Our aim was to explore the influence of rs1801260 single-nucleotide polymorphism (SNP) (3111T/C) of CLOCK gene on obesity risk, and to examine its potential interaction with lifestyle factors in an elderly population within the SUN ("Seguimiento Universidad de Navarra") Project. Subjects (n = 903, aged 69 ± 6 yrs) were recruited from the SUN Project. DNA was obtained from saliva, whereas lifestyle and dietary data were collected by validated self-report questionnaires. Genotype was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) plus allele discrimination. A significant interaction was observed between the 3111T/C SNP of CLOCK gene and sex for overweight/obesity risk (p for sex × CLOCK interaction <.001). Our results showed that women carrying the C allele of CLOCK gene had a marginally significant lower risk of overweight/obesity compared with noncarrier-TT-subjects (odds ratio [OR]: .61, 95% confidence interval [CI]: .36-1.04; p = .069). Moreover, this association of the C allele with a decreased overweight/obesity risk might be enhanced in those women with a high physical activity level. Women practicing more than 16.8 metabolic equivalent tasks (hours per week) had a significantly lower overweight/obesity risk (OR: .36, 95% CI: .17-.79; p = .011). Furthermore, a significant interaction between the 3111T/C gene variant and physical activity (PA) for overweight/obesity risk was observed but only in women (p for PA × CLOCK interaction <.050). In conclusion, it appears that physical activity levels may act by modifying the association of the 3111T/C SNP (rs1801260) of the CLOCK gene with overweight/obesity risk in elderly women in the SUN Project.

Effect of β(3)-adrenergic receptor gene polymorphism on body weight change in middle-aged, overweight women

OBJECTIVES

To examine the effects of β(3)-adrenergic receptor gene polymorphism on body weight change during a weight reduction program for middle-aged, overweight women with careful consideration of their energy intake and expenditure.

METHODS

DESIGN

Intervention study of weight reduction for 12 weeks in a community setting.

SUBJECTS

Eighty overweight middle-aged women who completed the individualized lifestyle modification program.

MEASUREMENTS

β(3)-adrenergic receptor gene polymorphism was identified by polymerase chain reaction and consecutive restriction fragment-length polymorphism analysis. Anthropometrical parameters, lifestyle factors, blood lipid and glucose levels, physical activity level and energy intake were measured before and at the end of the program.

RESULTS

The numbers of subjects with the Trp64Trp, Trp64Arg, and Arg64Arg genotypes were 45, 30 and 5, respectively. Baseline characteristics among subjects with the 64Arg allele had significantly smaller decrease in body weight and energy intake than those without the 64Arg allele. The change of other clinical characteristics did not differ between the two groups. After adjusting for the %change of energy intake, the %change of body weight did not differ between the two groups.

CONCLUSION

The 64Arg allele of the β(3)-AR gene is not likely to be the factor determining the difficulty in losing body weight in Japanese middle-aged, overweight women. Lifestyle factors, such as the decrease in energy intake, might mask the effect of the 64Arg allele on body weight loss. Specific considerations for the management of energy intake would be needed to promote body weight loss for those with the 64Arg allele.

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

Association Between Body Fat Response to Exercise Training and MultilocusADRGenotypes

OBJECTIVE

To examine the contribution of adrenergic receptor (ADR) gene polymorphisms and their gene-gene interactions to the variability of exercise training-induced body fat response.

RESEARCH METHODS AND PROCEDURES

This was an intervention study that used a volunteer sample of 70 healthy, sedentary men (n = 29) and postmenopausal women (n = 41) 50 to 75 years of age, with a BMI < or = 37 kg/m2, from the Washington, DC, metropolitan area. Participants completed 6 weeks of dietary stabilization (American Heart Association diet) before 24 weeks of supervised aerobic exercise training. Diet was maintained throughout the intervention. Change in percent total body fat, percent trunk fat, and fat mass by DXA in ADR genotype groups (Glu12/Glu9 alpha2b-ADR, Trp64Arg beta3-ADR, and Gln27Glu beta2-ADR) at baseline and after 24 weeks of aerobic exercise training was measured.

RESULTS

In multivariate analysis (covariates: age, gender, and baseline value of phenotype), best fit models for percent total body and trunk fat response to exercise training retained main effects of all three ADR gene loci and the effects of each gene-gene interaction (p = 0.009 and 0.003, respectively). Similarly, there was a trend for the fat mass response model (p = 0.03). The combined genetic factors explained 17.5% of the overall model variability for percent total body fat, 22% for percent trunk fat, and 10% for fat mass.

DISCUSSION

The body fat response to exercise training in older adults is associated with the combined effects of the Glu12/Glu9 alpha2b-, Trp64Arg beta3-, and Gln27Glu beta2-ADR gene variants and their gene-gene interactions.

Obesity and eating behaviour in children and adolescents: contribution of common gene polymorphisms

The prevalence of childhood obesity is increasing in many countries and confers risks for early type 2 diabetes, cardiovascular disease and metabolic syndrome. In the presence of potent 'obesogenic' environments not all children become obese, indicating the presence of susceptibility and resistance. Taking an energy balance approach, susceptibility could be mediated through a failure of appetite regulation leading to increased energy intake or via diminished energy expenditure. Evidence shows that heritability estimates for BMI and body fat are paralleled by similar coefficients for energy intake and preferences for dietary fat. Twin studies implicate weak satiety and enhanced food responsiveness as factors determining an increase in BMI. Single gene mutations, for example in the leptin receptor gene, that lead to extreme obesity appear to operate through appetite regulating mechanisms and the phenotypic response involves overconsumption and a failure to inhibit eating. Investigations of robustly characterized common gene variants of fat mass and obesity associated (FTO), peroxisome proliferator-activated receptor (PPARG) and melanocortin 4 receptor (MC4R) which contribute to variance in BMI also influence the variance in appetite factors such as measured energy intake, satiety responsiveness and the intake of palatable energy-dense food. A review of the evidence suggests that susceptibility to childhood obesity involving specific allelic variants of certain genes is mediated primarily through food consumption (appetite regulation) rather than through a decrease in activity-related energy expenditure. This conclusion has implications for early detection of susceptibility, and for prevention and management of childhood obesity.

Lifestyle modifies the relationship between body composition and adrenergic receptor genetic polymorphisms, ADRB2, ADRB3 and ADRA2B: a secondary analysis of a randomized controlled trial of physical activity among postmenopausal women

Genetic variations in the adrenergic receptor (ADR) have been associated with body composition in cross-sectional studies. Recent findings suggest that ADR variants may also modify body composition response to lifestyle. We assessed the role of ADR variants in body composition response to 12 months of resistance training versus control in previously sedentary postmenopausal women. Randomized trial completers were genotyped for A2B (Glu9/12) by fragment length analysis, and B2 (Gln27Glu) and B3 (Trp64Arg) by TaqMan (n = 148, 54% hormone therapy users). Associations between genotypes and body composition, by dual energy X-ray absorptiometry, were analyzed using univariate models. There was no main effect of individual genes on change in body composition, however, gene x exercise interactions were observed for A2B (Glu9/12) and B2 (Gln27Glu) on change in lean soft tissue (LST, p = 0.02); exercisers on the A2B (Glu9-) background gained LST compared to a loss among controls over 12 months (p < 0.05), with no significant intervention effect on the A2B (Glu9+) background. Similarly, there was a significant LST gain with exercise on the B2 (Glu27+) background compared to loss among controls and no intervention effect on the B2 (Glu27-) background. A non-significant association between total body fat (TBF) and B3 (Trp64Arg) persisted among sedentary controls only when intervention groups were separated (%TBF gain with B3 (Arg64+) carriage, p = 0.03); exercisers lost TBF regardless of genotype. In summary, effect modification by lifestyle was demonstrated on ADRA2B, B2, and B3 genetic backgrounds. Individuals with certain ADR genotypes may be more vulnerable to adverse changes in body composition with sedentary behavior, thus these candidate genes warrant further study.

Interaction between genes and lifestyle factors on obesity

Obesity originates from a failure of the body-weight control systems, which may be affected by changing environmental influences. Basically, the obesity risk depends on two important mutually-interacting factors: (1) genetic variants (single-nucleotide polymorphisms, haplotypes); (2) exposure to environmental risks (diet, physical activity etc.). Common single-nucleotide polymorphisms at candidate genes for obesity may act as effect modifiers for environmental factors. More than 127 candidate genes for obesity have been reported and there is evidence to support the role of twenty-two genes in at least five different populations. Gene-environment interactions imply that the synergy between genotype and environment deviates from either the additive or multiplicative effect (the underlying model needs to be specified to appraise the nature of the interaction). Unravelling the details of these interactions is a complex task. Emphasis should be placed on the accuracy of the assessment methods for both genotype and lifestyle factors. Appropriate study design (sample size) is crucial in avoiding false positives and ensuring that studies have enough power to detect significant interactions, the ideal design being a nested case-control study within a cohort. A growing number of studies are examining the influence of gene-environmental interactions on obesity in either epidemiological observational or intervention studies. Positive evidence has been obtained for genes involved in adiposity, lipid metabolism or energy regulation such as PPARgamma2 (Pro12Ala), beta-adrenoceptor 2 (Gln27Glu) or uncoupling proteins 1, 2 and 3. Variants on other genes relating to appetite regulation such as melanocortin and leptin receptors have also been investigated. Examples of some recently-identified interactions are discussed.

Genetics of obesity

Objective

The aim was to review and update advances in genetics of obesity.

Design

Analysis and interpretation of recent investigations about regulating the energy balance as well as about gene-nutrient interactions and current nutrigenomic research methods.

Background and main statements

Obesity results from a long-term positive energy balance. However, its rising prevalence in developed and developing societies must reflect lifestyle changes, since genetic susceptibility remains stable over many generations. Like most complex diseases, obesity derives from a failure of adequate homoeostasis within the physiological system controlling body weight. The identification of genes that are involved in syndromic, monogenic and polygenic obesity has seriously improved our knowledge of body weight regulation. This disorder may arise from a deregulation at the genetic level (e.g. gene transcription or altered protein function) or environmental exposure (e.g. diet, physical activity, etc.).

Conclusions

In practice, obesity involves the interaction between genetic and environmental factors.

Candidate genes and growth curves for adiposity in African- and European-American youth

OBJECTIVE

Obesity is associated with multiple health problems and often originates in childhood. This study investigated the association of genes with the development of general and central obesity from childhood into adulthood.

DESIGN

Individual growth curves for measures of general adiposity were examined in an 11-year (1987-1998) cohort study. Single-nucleotide polymorphisms (SNPs) in 11 candidate genes were genotyped.

SUBJECTS

Five hundred and twenty-six subjects classified by race (49% African American (AA)), sex (47% male) and socio-economic status (SES).

RESULTS

AA female carriers of the 27Glu allele in the ADRB2 gene had a larger waist circumference (P<0.05). Subjects of high SES with the ApoB 4145Lys allele had a larger mean waist circumference than those without this allele (P<0.05). Only in the presence of an adverse environment (low SES) did carriers of the NOS3 298Asp allele have a larger mean body mass index, waist circumference and sum of skinfolds (P<0.05).

CONCLUSION

These results suggest that several polymorphisms are associated with the mean level of adiposity, with the effects depending on other factors such as race, sex and/or SES.

The ADRB3 Trp64Arg variant and obesity in African-American breast cancer cases

OBJECTIVE

To determine if a missense change at codon 64 of ADRB3 (Trp64Arg), a candidate obesity gene, is associated with obesity and levels of subcutaneous or visceral fat in African-American breast cancer cases. Several observational studies have found that women, who are overweight or obese at the time of diagnosis, as well as those who gain weight after diagnosis, are at greater risk for breast cancer recurrence and death than non-overweight women.

DESIGN

Prospective cohort of breast cancer cases.

SUBJECTS

219 African-American breast cancer patients participating in the Los Angeles component of the Health, Eating, Activity and Lifestyle Study.

MEASURES

ADRB3 Trp64Arg genotype, measures of weight including body mass index (BMI), weight gain (weight 5 years before diagnosis compared with weight at 30 months after diagnosis), obesity (BMI> or =30 kg/m(2)), waist/hip circumference and visceral or subcutaneous fat were determined by magnetic resonance imaging.

RESULTS

African-American women who were homozygous for the ADRB3 wild-type allele had significantly higher mean visceral fat levels than women who carried the variant (P=0.04), and were significantly more likely to be obese (odd ratios (OR)=2.1, 95% confidence interval (CI)=1.1-4.2). The association with obesity was most pronounced among women who were premenopausal (OR=4.8, 95% CI=1.3-18), who received chemotherapy for their breast cancer (OR=6.1, 95% CI=1.8-20), or who were not physically active (OR=3.9, 95% CI=1.5-9.7).

CONCLUSION

The wild-type allele of the ADRB3 missense change was associated with measures of obesity in our sample of African-American women. The association was modified by menopausal status, history of chemotherapy and modest levels of physical activity. These results will need to be confirmed in an independent sample.

A novel missense mutation in ADRB3 increases risk for type 2 diabetes in a Mexican American family

BACKGROUND

The human beta3-adrenergic receptor gene (ADRB3) has been investigated as a candidate gene for diabetes-related traits in many studies. However, the results have been inconsistent so it is unclear whether variation in ADRB3 is a risk factor for type 2 diabetes. We have identified a novel missense mutation of ADRB3 in a single large pedigree of the San Antonio Family Diabetes/Gallbladder Study (SAFDGS) that is located in the first transmembrane domain at amino acid 62 (Ile62Met). The aim of this study was to investigate the association of this mutation in the SAFDGS with risk for diabetes.

METHODS

Variance components-based statistical methods were used to determine association of this mutation with diabetes traits in the SAFDGS. The ADRB3 gene was also resequenced to identify all variants present in this pedigree.

RESULTS

Significant association was observed for the Ile62Met mutation and type 2 diabetes (p = 0.01, relative risk 2.3), an earlier age of onset (p = 0.01) and 2-h glucose measures (p = 0.006) in the single pedigree. Average age and body mass index do not differ between the two genotypic groups. In a recent genome-wide linkage analysis of SAFDGS, we observed suggestive linkage of diabetes to this region at marker D8S1477 (2pt LOD of 2.55). The variance attributed to Ile62Met accounted for nearly all of the family-specific LOD score.

CONCLUSIONS

These results suggest that this variant in ADRB3 is influencing diabetes risk in this Mexican American family and supports a role for alterations of the beta3-adrenergic receptor in the pathogenesis of type 2 diabetes.

Genomics, nutrition, obesity, and diabetes

PURPOSE

To present evidence of genetic and environmental interactions as they relate to nutrition, diabetes, and obesity.

METHODS

A review of seminal literature related to genetics, obesity, and diabetes.

FINDINGS

Multifactorial interactions are important in the development of nutrition-related disorders, but the challenge remains to explain how these interactions are expressed. Treating subpopulations of people might be important and useful to some extent at present, but in the future treating people of given genetic predispositions and other personal and environmental factors will have greater effects on quality-of-life indicators and life expectancies.

CONCLUSIONS

Individualization coupled with multifactorial interactions will lead to new and more effective preventive and treatment modalities of nutrition-related disorders. With obesity and diabetes, genomics will bridge the traditional use of diet, exercise, and weight reduction with other environmental factors, ultimately leading to healthier lives.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.

Genetic and environmental correlations between obesity phenotypes and age at menarche

OBJECTIVE

To assess the extent that the genetic and environmental factors contribute to the phenotypic correlations between obesity traits and age at menarche (AAM), and also to examine the influence of AAM on obesity in both pre- and postmenopausal women.

METHODS

F ive hundred and twelve pedigrees with 2667 Caucasian female subjects from two to four generations were recruited. Fat mass and lean mass (both in kg) were measured by dual-energy X-ray absorptiometry scanner. Body mass index (BMI) (kg/m(2)) was calculated. We performed bivariate quantitative genetic analyses in the total sample containing 2667 Caucasian women. We also selected 206 unrelated premenopausal women and 140 unrelated postmenopausal women from the total sample, and computed the respective phenotypic correlation between obesity and AAM in these two subgroups.

RESULTS

For fat mass, lean mass and BMI, we detected their significant negative genetic correlations with AAM after adjustment for significant covariates, which were -0.3170 (P<0.001), -0.1721 (P<0.05) and -0.3665 (P<0.001), respectively. However, their environmental correlations with AAM were all nonsignificant (P>0.05), ranging from -0.0016 to 0.0192. In the premenopausal subgroup, significant associations were observed between fat mass and AAM (rho=-0.231, P<0.01) as well as between BMI and AAM (rho=-0.257, P<0.01). In the postmenopausal subgroup, no such associations were observed.

CONCLUSION

Our results for the first time suggested that significant phenotypic association between obesity phenotypes and AAM is mainly attributable to shared genetic rather than environmental factors, and AAM may have stronger effects on obesity phenotypes in pre- than in postmenopausal women.

Obesity and colorectal cancer: epidemiology, mechanisms and candidate genes

There is increasing evidence that dysregulation of energy homeostasis is associated with colorectal carcinogenesis. Epidemiological data have consistently demonstrated a positive relation between increased body size and colorectal malignancy, whereas mechanistic studies have sought to uncover obesity-related carcinogenic pathways. The phenomenon of "insulin resistance" or the impaired ability to normalize plasma glucose levels has formed the core of these pathways, but other mechanisms have also been advanced. Obesity-induced insulin resistance leads to elevated levels of plasma insulin, glucose and fatty acids. Exposure of the colonocyte to heightened concentrations of insulin may induce a mitogenic effect within these cells, whereas exposure to glucose and fatty acids may induce metabolic perturbations, alterations in cell signaling pathways and oxidative stress. The importance of chronic inflammation in the pathogenesis of obesity has recently been highlighted and may represent an additional mechanism linking increased adiposity to colorectal carcinogenesis. This review provides an overview of the epidemiology of body size and colorectal neoplasia and outlines current knowledge of putative mechanisms advanced to explain this relation. Family based studies have shown that the propensity to become obese is heritable, but this is only manifest in conditions of excess energy intake over expenditure. Inheritance of a genetic profile that predisposes to increased body size may also be predictive of colorectal cancer. Genomewide scans, linkage studies and candidate gene investigations have highlighted more than 400 chromosomal regions that may harbor variants that predispose to increased body size. The genetics underlying the pathogenesis of obesity are likely to be complex, but variants in a range of different genes have already been associated with increased body size and insulin resistance. These include genes encoding elements of insulin signaling, adipocyte metabolism and differentiation, and regulation of energy expenditure. A number of investigators have begun to study genetic variants within these pathways in relation to colorectal neoplasia, but at present data remain limited to a handful of studies. These pathways will be discussed with particular reference to genetic polymorphisms that have been associated with obesity and insulin resistance.

Association of UCP3 Gene –55C>T Polymorphism and Obesity in a Spanish Population

BACKGROUND/AIMS

The uncoupling protein 3 (UCP3) gene has been suggested as a possible determinant affecting obesity risk given its function in the regulation of energy metabolism. However, available genetic association studies have been inconsistent, which could be attributable to not considering individual lifestyle patterns, such as physical activity, a factor that affects UCP3 expression. The objective of this study was to assess the association between the UCP3 -55C>T polymorphism and the risk of obesity.

METHODS

Case-control study conducted in a sample of Spanish adults. 157 obese subjects (BMI > or = 30) and 150 controls (BMI < 25) participated in the study. UCP3 -55C>T polymorphism was identified by the polymerase chain reaction-restriction fragment length polymorphism methodology.

RESULTS

The odds ratio (OR) for obesity (95% confidence interval [CI]) according to the presence of UCP 3 gene -55C>T polymorphism (heterozygotes and homozygotes merged together), adjusting for age, sex, and recreational physical activity, was 0.61 (0.37-1.00), p = 0.05. Interestingly, this association was only manifest among those with higher recreational physical activity (OR: 0.46, 95% CI 0.21-0.99, p = 0.05) and not among those with lower physical activity (OR: 0.84, 95% CI 0.41-1.70, p = 0.84).

CONCLUSION

UCP3 -55C>T polymorphism carriers have apparently a lower risk of obesity when taking into consideration recreational energy expenditure. Interestingly, this inverse beneficial association may only occur in people with a high level of physical activity.

Association between β-adrenergic receptor polymorphisms and their G-protein-coupled receptors with body mass index and obesity in women: a report from the NHLBI-sponsored WISE study

OBJECTIVES

The beta-adrenergic receptor (betaAR) genes are candidate genes for obesity because of their roles in energy homeostasis and promotion of lipolysis in human adipose tissue. Objective is to determine the association between obesity and polymorphisms in genes of the beta(1)AR (ADRB1), beta(2)AR (ADRB2), beta(3)AR (ADRB3), Gs protein alpha (GNAS1), to which all three beta-receptors couple and the G protein beta3 subunit (GNB3), to which beta(3)ARs couple.

DESIGN

A case-control genetic association study.

SUBJECTS

A total of 643 black or white women enrolled in Women's Ischemia Syndrome Evaluation (WISE) study.

MEASUREMENTS

Genotypes were determined by PCR with single primer extension. Associations between genotype and body mass index (BMI), waist-to-hip ratio (WHR), waist circumference, and obesity were made.

RESULTS

Polymorphisms in the three betaAR genes, GNAS1, and GNB3 were not associated with BMI, WHR, waist circumference, or obesity. Linear and logistic regression analyses found no contribution of either genotype or haplotype with anthropometric measurements or obesity.

CONCLUSIONS

Our study suggests that among American women with suspected coronary heart disease, polymorphisms in the betaARs and their G-protein-coupled receptors do not contribute to increased BMI, WHR, waist circumference, or obesity. Given that 50% of all women die from coronary heart disease, and a higher percentage have heart disease during their lifetime, our results are likely generalizable to many American women.

Gene-gene interaction between PPAR gamma 2 and ADR beta 3 increases obesity risk in children and adolescents

AIMS

Multiple genes are likely to be involved in obesity and these genes may interact with environmental factors to influence obesity risk. Our aim was to explore the synergistic contribution of the two polymorphisms: Pro12Ala of the PPAR gamma 2 gene and Trp64Arg of the ADR beta 3 gene to obesity risk in a Spanish children and adolescent population.

METHODS

We designed a sex- and age-matched case-control study. Participants were 185 obese and 185 control children (aged 5-18 y) from the Navarra region, recruited through Departments of Pediatrics (Hospital Virgen del Camino, Navarra University Clinic and several Primary Health Centers). The obesity criterion (case definition) was BMI above the 97th percentile according to Spanish BMI reference data for age and gender. Anthropometric parameters were measured by standard protocols. The genotype was assessed by PCR-RFLP after digestion with BstUI for PPAR gamma 2 mutation and BstNI for ADR beta 3 variants. Face-to-face interviews were conducted to assess the physical activity. Using a validated physical activity questionnaire, we computed an activity metabolic equivalent index (METs h/week), which represents the physical exercise during the week for each participant. Statistical analysis was performed by conditional logistic regression, taking into account the matching between cases and controls.

RESULTS

Carriers of the polymorphism Pro12Ala of the PPAR gamma 2 gene had a significantly higher obesity risk than noncarriers (odds ratio (OR)=2.18, 95% CI=1.09-4.36) when we adjusted for sex, age and physical activity. Moreover, the risk of obesity was higher (OR=2.59, 95% CI=1.17-5.34) when family history of obesity was also taken into account in the model. The OR for obesity linked to both polymorphisms (PPAR gamma 2 and ADR beta 3) was 5.30 (95% CI=1.08-25.97) when we adjusted for sex, age and physical activity. After adjustment for family history of obesity, the OR for carriers of both polymorphisms was 19.5 (95% CI=2.43-146.8).

CONCLUSIONS

A synergistic effect between polymorphism Pro12Ala of the PPAR gamma 2 gene and Trp64Arg of the ADR beta 3 gene for obesity risk was found in a case-control study including children and adolescents.

Genes, lifestyles and obesity

OBJECTIVE

To review the role of genes and lifestyle factors, particularly dietary habits and physical activity patterns, in obesity risk as well as their potential interactions.

DESIGN AND MEASUREMENTS

A descriptive report of a number of genes definitely ascribed or potentially implicated in excessive fat accumulation leading to obesity as assessed by different research approaches (Mendelian transmission, genetic animal models, epidemiological association/linkage studies and genome-wide scans). Also, the involvement of macronutrient intake and composition (fat/carbohydrate) as well as the role of activity-linked energy expenditure in obesity onset is reviewed.

RESULTS

Examples of the role of the genotype as well as of the dietary macronutrient composition/intake and sedentary/low energy cost of physical activities in obesity prevalence are reported.

CONCLUSIONS

Both genes and everyday life environmental factors such as cultural and social mediated food intake and reduced domestic and living work activities are involved in the obesity pandemia. The occurrence of gene x gene and gene x environmental factors interactions makes it more difficult to interpret the specific roles of genetics and lifestyle in obesity risk.

High-resolution comparative mapping of pig Chromosome 4, emphasizing the FAT1 region

The first quantitative trait locus (QTL) in pigs, FAT1, was found on Chromosome 4 (SSC4) using a Wild Boar intercross. Further mapping has refined the FAT1 QTL to a region with conserved synteny to both human Chromosomes 1 and 8. To both improve the comparative map of the entire SSC4 and to define the specific human chromosome region with conserved synteny to FAT1, we have now mapped 103 loci to pig Chromosome 4 using a combination of radiation hybrid and linkage mapping. The physical data and linkage analysis results are in very good agreement. Comparative analysis revealed that gene order is very well conserved across SSC4 compared to both HSA1 and HSA8. The breakpoint in conserved synteny was refined to an area of about 23 cR on the q arm of SSC4 corresponding to a genetic distance of less than 0.5 cM. Localizations of the centromeres do not seem to have been conserved between the two species. No remnants of the HSA1 centromere were detected on the corresponding region on SSC4 and traces from the centromeric region of SSC4 cannot clearly be revealed on the homologous region on HSA8. This refined SSC4 map and the comparative analysis will be a great aid in the search for the genes underlying the FAT1 locus.

Lack of relationship between beta3-adrenergic receptor gene polymorphism and gestational diabetes mellitus in a Taiwanese population

The Trp64Arg polymorphism of beta(3)-adrenergic receptor (ADRB3) has been reported to be associated with insulin resistance and gestational diabetes mellitus (GDM). The objective of this study is to investigate whether the ADRB3 Arg variant confers susceptibility to GDM in a Taiwanese population. A total of 299 pregnant women (mean +/- SD, 31.1 +/- 4.2 years) was recruited. Two-hour, 75-g oral glucose tolerance tests (OGTT) were conducted at 24 to 31 weeks gestation (28.3 +/- 1.6 weeks). Forty-one GDM subjects and 258 controls with normal glucose tolerance (NGT) level were genotyped for the ADRB3 Trp64Arg polymorphism. The genotype distribution and allele frequency of ADRB3 did not significantly differ between GDM and NGT subjects (9.8% v 14.5%). Body weight gain during pregnancy was not different between ADRB3 genotypes. However, the GDM subjects with the Arg64 variant had higher fasting (P =.04) and postload 120 minutes (P =.03) insulin levels as compared with the GDM subjects with the Trp64Trp allele. In all subjects, the women with the Arg64 allele (n = 76) had significantly higher level of insulin secretion (the ratio of Deltainsulin(60)/Deltaglucose(60)) during OGTT than those without (n = 223) (P =.03) despite similar plasma levels of glucose and insulin in both genotypes. Our results indicated that the ADRB3 Trp64Arg variant is not related to the development of GDM and has no effect on obesity during pregnancy in a Taiwanese population. However, ADRB3 polymorphism might be a possible determinant of insulin resistance.

Higher obesity risk associated with the exon-8 insertion of the UCP2 gene in a Spanish case-control study

OBJECTIVE

We conducted a case-control study to examine the association between the risk of obesity and the exon-8 insertion allele in the UCP2 gene.

METHODS

The case series included 157 subjects with a body mass index greater than 30 kg/m(2) (obesity) and no other major disease except for type 2 diabetes; the control series consisted of 150 healthy subjects with a body mass index less than 25 kg/m(2). In total, 307 subjects between ages 20 and 60 y were screened for the exon-8 insertion allele in the UCP2 gene.

RESULTS

The association between risk of obesity and the UCP2 insertion allele was estimated using multivariate logistic regression. Obesity risk among carriers of the UCP2 insertion allele was slightly higher than among non-carriers (unadjusted odds ratio, 1.42; 95% confidence interval, 0.90 to 2.23); however, when the model was adjusted for sex, age, physical activity, and sedentary lifestyle (hours spent sitting down), a statistically significant odds ratio of obesity (1.94; 95% confidence interval, 1.14 to 3.30; P = 0.01) for carriers of the UCP2 insertion allele was found.

CONCLUSIONS

We found a greater risk of developing obesity among individuals carrying the exon-8 insertion allele in the UCP2 gene, independent of sex, age, physical activity, and sedentary lifestyle, which may partly explain some discrepancies found in the literature.

Autonomic Nervous System Pharmacogenomics: A Progress Report

Pharmacogenetics, the inherited basis for interindividual differences in drug response, has rapidly expanded with the advent of new molecular tools and the sequencing of the human genome, yielding pharmacogenomics. We review here recent ideas and findings regarding pharmacogenomics of components of the autonomic nervous system, in particular, neuronal nicotinic acetylcholine receptors, postsynaptic receptors with which the parasympathetic and sympathetic neurotransmitters, acetylcholine (ACh) and norepinephrine, respectively, interact. The receptor subtypes that mediate these responses, M(1-3) muscarinic cholinergic receptors (mAChRs), and alpha(1A,B,D)-, alpha(2A,B,C)-, and beta(1,2,3)-adrenergic receptors (AR), show highly variable expression of genetic variants; variants of mAChRs and alpha(1)-ARs are relatively rare, whereas alpha(2)-AR and beta-AR subtype variants are quite common. The largest amount of data is available regarding variants of the latter ARs and represents efforts to associate certain receptor genotypes, most commonly, single nucleotide polymorphisms, with particular phenotypes (e.g., cardiovascular and metabolic responses). In vitro and in vivo studies have yielded inconsistent results; definitive conclusions are limited. We identify several conceptual and methodological problems with available data: sample size, ethnicity, tissue differences, coding versus noncoding variants, limited studies of haplotypes, and interaction among variants. Thus, although progress has been made in identifying genetic variation that influences drug response fo autonomic nervous system components, we are still at the early stages of defining the most critical genetic determinants and their role in human physiology and pharmacology.

Estudios sobre la obesidad en genes candidatos

There are more than 430 chromosomic regions with gene variants involved in body weight regulation and obesity development. Polymorphisms in genes related to energy expenditure--uncoupling proteins (UCPs), related to adipogenesis and insulin resistance--hormone-sensitive lipase (HLS), peroxisome proliferator-activated receptor gamma (PPAR gamma), beta adrenergic receptors (ADRB2,3), and alfa tumor necrosis factor (TNF-alpha), and related to food intake--ghrelin (GHRL)--appear to be associated with obesity phenotypes. Obesity risk depends on two factors: a) genetic variants in candidate genes, and b) biographical exposure to environmental risk factors. It is necessary to perform new studies, with appropriate control groups and designs, in order to reach relevant conclusions with regard to gene/environmental (diet, lifestyle) interactions.

Obesity risk is associated with carbohydrate intake in women carrying the Gln27Glu beta2-adrenoceptor polymorphism

Interindividual differences in the response to dietary intake are, in some cases, genotype dependent. Moreover, genotype-environment interactions may appear when the impact of lifestyle factors (e.g., diet) on a phenotype (e.g., BMI > 30 kg/m(2)) differs by genotype. A case-control study (obese subjects vs. normal weight controls) was conducted to assess a possible effect modification on obesity risk of the Gln27Glu polymorphism for the beta(2)-adrenoceptor gene depending on dietary intake. The sample included 159 subjects with BMI > 30 kg/m(2) and 154 controls with BMI < 25 kg/m(2). The allele frequency for the Glu27 polymorphism, as assessed by the polymerase chain reaction-restriction fragment length polymorphism methodology, was 0.40 in cases (obese) and 0.37 in controls (lean), which was similar to that of other Caucasian populations. The dietary intake was estimated by using a previously validated food frequency questionnaire. Obesity incidence was not directly affected by the polymorphism [odds ratio (OR) = 1.40; P = 0.246]. However, a significant interaction (effect modification) between carbohydrate (CHO) intake and the presence of the Glu27 variant in the probability of obesity was apparent. Thus, females with the polymorphism and a higher CHO intake [>49% energy (E)] had a higher obesity risk (OR = 2.56, P = 0.051). The product-term introduced in the logistic model to assess effect modification revealed a marginally significant interaction (P = 0.058) between both factors. Furthermore, a high intake of CHO (E > 49%) was associated with higher insulin levels among women carrying the Gln27Glu polymorphism (P < 0.01). This gene-nutrient interaction emphasizes the importance of examining the outcome of some obesity-related mutations depending on lifestyle (including diet) and may explain the heterogeneity of findings from previous studies.

The human obesity gene map: the 2002 update

This is the ninth update of the human obesity gene map, incorporating published results through October 2002 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and various animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. For the first time, transgenic and knockout murine models exhibiting obesity as a phenotype are incorporated (N = 38). As of October 2002, 33 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and the causal genes or strong candidates have been identified for 23 of these syndromes. QTLs reported from animal models currently number 168; there are 68 human QTLs for obesity phenotypes from genome-wide scans. Additionally, significant linkage peaks with candidate genes have been identified in targeted studies. Seven genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 222 studies reporting positive associations with 71 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. More than 300 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.