Prevalence of the Trp64Arg missense mutation of the beta3-adrenergic receptor gene in Japanese subjects

β3-Adrenergic receptors regulate human brown/beige adipocyte lipolysis and thermogenesis

β3-Adrenergic receptors (β3-ARs) are the predominant regulators of rodent brown adipose tissue (BAT) thermogenesis. However, in humans, the physiological relevance of BAT and β3-AR remains controversial. Herein, using primary human adipocytes from supraclavicular neck fat and immortalized brown/beige adipocytes from deep neck fat from 2 subjects, we demonstrate that the β3-AR plays a critical role in regulating lipolysis, glycolysis, and thermogenesis. Silencing of the β3-AR compromised genes essential for thermogenesis, fatty acid metabolism, and mitochondrial mass. Functionally, reduction of β3-AR lowered agonist-mediated increases in intracellular cAMP, lipolysis, and lipolysis-activated, uncoupling protein 1-mediated thermogenic capacity. Furthermore, mirabegron, a selective human β3-AR agonist, stimulated BAT lipolysis and thermogenesis, and both processes were lost after silencing β3-AR expression. This study highlights that β3-ARs in human brown/beige adipocytes are required to maintain multiple components of the lipolytic and thermogenic cellular machinery and that β3-AR agonists could be used to achieve metabolic benefit in humans.

Genetic predictors of obesity development

The most common reasons that cause obesity are eating disorders (overeating), genetic predisposition, sedentary lifestyle (lack of exercise), disorders of the endocrine system, and environmental factors. There is evidence of an obvious relationship of high consumption of sugary drinks and weight gain. Since 1990, there has been considerable growth in the number of obese people in the first place associated with the promotion of soft drinks. According to a study in Finnish diabetes prevention average physical activity and change of diet (1200-1800 kcal) of total fat intake with less than 30% saturated fat, including less than 10%, leading to long-term loss of excess weight (within 4 years). Many studies have demonstrated the impossibility of a single template approach to the determination of optimal diets for patients with overweight and obesity which has been shown in various studies on gene polymorphisms are associated with obesity, and their interaction. This article provides an overview of current data on the genetics of obesity covering the main provisions of the study of candidate genes, such as PPARG, FABP2, ADRB 2, ADRB3. The role nutrigenetics in the creation of individual programs of weight control and weight loss. But the question of the direct role of genetic factors in the development of obesity remains controversial, since one can not ignore the impact of environmental factors, such as lifestyle, diet, physical activity, stress, and harmful habits. To understand the mechanism of the relationship between genetic factors, environmental factors, and obesity, one needs to carry out research not only on the population level, but also in certain groups of people (ethnic, racial, age).

Association of the beta3-adrenergic receptor Trp64Arg polymorphism with common metabolic traits: studies of 7605 middle-aged white people

AIM/HYPOTHESIS

The functional variant Trp64Arg in the beta(3)-adrenergic receptor has previously been examined for association with obesity and insulin resistance with ambiguous results. For further evaluation the present study examined the impact of the Trp64Arg variant on the pathogenesis of type 2 diabetes and obesity in a relatively large, homogenous study population.

METHODS

The Trp64Arg polymorphism was genotyped in 7605 Danish subjects using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Association was examined in case-control studies of obesity (1529 cases and 6049 controls) and type 2 diabetes (1373 cases and 4742 controls) and quantitative trait analyses among 5822 individuals. Furthermore, the association of Trp64Arg with type 2 diabetes was examined in a meta-analysis.

RESULTS

The Trp64Arg polymorphism was not associated with obesity. However, the Arg-allele was associated with a slightly increased risk of type 2 diabetes (OR1.15 (CI: 1.01-1.31); p=0.04), increased insulin resistance estimated by homeostasis model assessment (p=0.01), higher fasting serum insulin levels (p=0.01), and higher levels of plasma glucose 2-h after glucose ingestion (p=0.02). After sex stratification these associations were only present among women. Furthermore, the Arg-allele was borderline associated with type 2 diabetes in a meta-analysis of the present and 26 previous studies (p=0.06, OR1.27 (CI: 0.99-1.63)) (n=18891).

CONCLUSION/INTERPRETATION

Trp64Arg does not confer an increased risk of obesity among Danes. Yet, in the present study of 7605 Danes the variant is associated with type 2 diabetes and quantitative traits related to type 2 diabetes.

The Trp64Arg polymorphism of the beta3-adrenergic receptor gene is associated with increased small dense low-density lipoprotein in a rural Japanese population: the Mima study

The presence of small dense low-density lipoprotein (sdLDL) is closely associated with an increased risk of developing coronary artery disease. The Trp64Arg polymorphism of the beta(3)-adrenergic receptor (beta(3)-AR) gene is a genetic marker for obesity-related traits. However, any possible association between this polymorphism and sdLDL profiles is unclear. The objective of this study is to investigate the effects of the polymorphism of the beta(3)-AR gene on LDL particle size and sdLDL in a rural Japanese population. Among 277 subjects, body mass index, blood pressure, fasting serum insulin levels, and insulin resistance index (fasting glucose x fasting insulin/405) were determined. The polymorphism of the beta(3)-AR gene was assessed by polymerase chain reaction-restriction fragment length polymorphism using buccal samples. Low-density lipoprotein particle size and sdLDL were measured with the electrophoretic separation of lipoproteins on the LipoPrint System (Quantimetrix, Redondo Beach, CA). The frequency of the beta(3)-AR allele was 0.19. In Arg carriers (Trp/Arg or Arg/Arg), the mean value of LDL particle size was smaller than that of non-Arg carriers (Trp/Trp) (P < .05). The area percentage of sdLDL was higher in Arg carriers (P < .05) than in non-Arg carriers. A multiple regression analysis showed that the area percentage of sdLDL was correlated with the polymorphism of the beta(3)-AR gene (P < .05), independently of age, sex, body mass index, smoking, and insulin resistance index. The present findings suggest that the beta(3)-AR gene polymorphism plays a role in the genetic predisposition to increased sdLDL, independently of insulin resistance.

Metabolic syndrome and ADRB3 gene polymorphism in severely obese patients from South Italy

OBJECTIVE

To evaluate the prevalence of beta(3)-adrenergic receptor (ADRB3) Trp64Arg polymorphism and its relationship with the metabolic syndrome in severe obesity.

DESIGN

Cross-sectional outpatients study.

PATIENTS AND METHODS

In 265 (100 men) severely obese non-diabetic subjects and 78 (25 men) healthy volunteers, genomic DNA was isolated from peripheral leukocytes. In obese patients, plasma concentrations of leptin, lipids, glucose and insulin, the homeostasis model assessment index and blood pressure have been measured. The Trp64Arg mutation was identified with the real-time TaqMan method.

RESULTS

Neither genotype distribution nor allele frequency differed between the two groups. The metabolic syndrome prevalence was 59% in obese subjects, and was higher in men than in women (65 vs 55%: P=0.03). The body mass index (BMI) was related to age tertiles (beta=0.08; P<0.001; multiple linear regression) in Trp64Arg-positive obese subjects.

CONCLUSION

We confirm the high prevalence of the metabolic syndrome among severely obese subjects. ADRB3 polymorphism was significantly related to insulin resistance only in obese male subjects. Moreover, increased BMI was related to age in obese subjects with the ADRB3 polymorphism.

Variation analysis of beta3-adrenergic receptor and melanocortin-4 receptor genes in childhood obesity

BACKGROUND

Decreased energy expenditure and increased food intake are principal causes for obesity. In the present study, genotypes of beta(3)-adrenergic receptor (beta(3)AR) and of melanocortin-4 receptor (MC4R), both of which are believed to have a close link to the cause of obesity, were analyzed and compared with phenotypes of childhood obesity.

METHODS

Thirty-five obese children with moderate to severe obesity were enrolled. Direct sequencing of the MC4R coding region and pinpoint-polymerase chain reaction were used to detect genomic variation in the beta(3)AR gene using peripheral blood-derived DNA.

RESULTS

Allele frequency of Trp64Arg variation in the beta(3)AR gene in the obese subjects was 0.16, which is comparable with that in the healthy general population in eastern Asia. Comparison of phenotypical characteristics did not show a significant difference between Trp/Trp and Trp/Arg subjects. It was notable that body height SD was significantly higher in the Trp/Trp than the Trp/Arg subjects (0.93 +/- 1.0 SD vs 0.07 +/- 1.3 SD, P= 0.03). Annual weight gains were far beyond a hypothetical fat gain in an Arg64 heterozygote with decreased energy consumption, suggesting increased food intake in childhood obesity. There was, however, no variation in the MC4R gene despite thorough sequencing of the entire coding region.

CONCLUSIONS

The Trp64Arg variation in the beta(3)AR gene has no relationship to the degree or the incidence of childhood obesity. The majority of childhood obesity can be characterized as tall stature, more rapid weight gain than that expected by decreased energy expenditure. Further investigation is necessary in regard to the increased food intake as a major cause of childhood obesity.

Genetics of Type 2 diabetes

Type 2 diabetes (T2D) has become a health-care problem worldwide, with the rise in disease prevalence being all the more worrying as it not only affects the developed world but also developing nations with fewer resources to cope with yet another major disease burden. Furthermore, the problem is no longer restricted to the ageing population, as young adults and children are also being diagnosed with T2D. In recent years, there has been a surge in the number of genetic studies of T2D in attempts to identify some of the underlying risk factors. In this review, I highlight the main genes known to cause uncommon monogenic forms of diabetes (e.g. maturity-onset diabetes of the young--MODY--and insulin resistance syndromes), as well as describe some of the main approaches used to identify genes involved in the more common forms of T2D that result from the interaction between environmental risk factors and predisposing genotypes. Linkage and candidate gene studies have been highly successful in the identification of genes that cause the monogenic variants of diabetes and, although progress in the more common forms of T2D has been slow, a number of genes have now been reproducibly associated with T2D risk in multiple studies. These are discussed, as well as the main implications that the diabetes gene discoveries will have in diabetes treatment and prevention.

β3-adrenergic agonists: potential therapeutics for obesity

During the last decade a number of beta3-adrenergic receptor agonists have been advanced to clinical trials. The results of human studies to date have been disappointing with respect to sustained increases in metabolic rate and weight loss. Cloning of beta3-adrenoceptors in a number of species and subsequent pharmacological evaluations revealed these early investigational drugs to be weakly active against the human receptor, suggesting an explanation for the poor performance of these compounds in clinical trials. This information has been integrated into subsequent research efforts resulting in the discovery of agents with activities optimised for the human receptor. This new generation of compounds is in late preclinical/early clinical development and are poised to address the role beta3-adrenoceptor signalling plays in the obese state. Issues related to the potential for beta3-adrenergic agonists to positively impact metabolic parameters in humans are also discussed.

Pharmacogenomics of adrenoceptors

Adrenoceptors (ARs) consist of nine subtypes (alpha(1A)-, alpha(1B)-, alpha(1D)-, beta(1)-, beta(2)-, beta(3)-, alpha(2A)-, alpha(2B)- and alpha(2C)-AR), which are involved in a wide spectrum of physiological functions and are the site of action for a considerable percentage of currently prescribed therapeutics. With the exception of alpha(1D), all AR subtypes are polymorphic with genetic variations in the coding and non-coding regions. This review discusses the biochemical consequences of these genetic variations and their impact in receptor function, disease pathophysiology, and drug response. Pharmacogenomic principles that have been discovered are also discussed.

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.

Difficulty in losing weight by behavioral intervention for women with Trp64Arg polymorphism of the beta3-adrenergic receptor gene

OBJECTIVE

Trp64Arg mutation in the beta(3)-adrenergic receptor (beta(3)AR) gene is relatively common in Japanese people. However, it has not been clear whether persons with Trp64Arg mutation in the beta(3)AR gene tend to have obesity and difficulty in losing weight even with a restricted diet and exercise. We investigated the response of body weight and metabolic factors to behavioral intervention in Japanese women with Trp64Arg mutation in the beta(3)AR gene.

DESIGN

A 3-month behavioral intervention study using a combination of diet and exercise programs.

SUBJECTS

A total of 76 perimenopausal women with no clinical symptoms (age: 54.7+/-7.7 y, body mass index (BMI): 21.0-33.0 kg/m(2)).

MEASUREMENTS

Anthropometric measurements (weight, height, body fat, waist circumference, hip circumference, skin fold, resting energy expenditure and blood pressure) and metabolic measurements (serum levels of cholesterol, triglyceride, phospholipid, nonesterified fatty acid, glucose, insulin and leptin) and determination of the beta(3)AR genotype by polymerase chain reaction followed by BstNI digestion.

RESULTS

At the baseline of BMI, body weight, body fat, waist circumference, hip circumference, the arm skin fold, resting energy expenditure, or blood lipid and glucose profiles, there was no significant difference in participants with/without mutation of the beta(3)AR gene. The intervention yielded a body weight reduction in 69 and 48%, and induced a significant difference in weight loss (-0.74 and -0.01 kg) for women with wild-type and Trp64Arg mutation, respectively. Significant differences of anthropometric parameters were found in body weight, BMI, waist and hip circumferences and blood pressure of wild type by the intervention. However, women with Trp64Arg mutation did not show significant changes in these anthropometric parameters, except for hip circumference. A significant difference was found in high-density lipoprotein cholesterol (HDL-C) and in the low-density lipoprotein cholesterol/HDL-C ratio in both genotypes.

CONCLUSION

The results of the present study suggest that the Trp64Arg mutation of the beta(3)AR gene is associated with difficulty in losing weight through behavioral intervention, although it is not related to obesity-related phenotypes and resting energy expenditure before the intervention.

Association of BMI with the beta3-adrenergic receptor gene polymorphism in Japanese: meta-analysis

OBJECTIVE

To assess the effect of the Trp64Arg polymorphism in the beta3-adrenergic receptor gene (ADRB3) on body mass index (BMI) in the Japanese population.

RESEARCH METHODS AND PROCEDURES

We selected studies that evaluated the association between BMI and ADRB3 polymorphism among Japanese, using MEDLINE and PubMed. After data collection, an extension of ANOVA was performed to assess the differences according to the genotype.

RESULTS

In a total of 35 subgroups including 2316 subjects with the Trp64Arg variant and 4266 subjects without this variant, the weighted mean difference in BMI was 0.26 kg/m(2) (95% confidence interval: 0.18 to 0.42; p < 0.01), indicating that variant carriers exhibited higher BMI than did normal homozygous subjects.

DISCUSSION

Although it is known that the allele frequency of the ADRB3 polymorphism differs among races, this study focuses on the Japanese population, which has a high allele frequency of ADRB3 polymorphism. We assumed that statistical errors would be prevented due to the sufficient number of subjects. In conclusion, the results support the hypothesis that ADRB3 gene polymorphism is associated with BMI.

Beta(3)-adrenergic receptor gene variant is associated with upper body obesity only in obese Japanese-American men but not in women

We investigated gender differences in the relationships between the Trp64Arg variant of the beta(3)-adrenergic receptor (AR) gene in obesity and insulin resistance in nondiabetic subjects. In 476 nondiabetic Japanese-Americans (M/F=204/272), the Trp64Arg variant of the beta(3)-AR gene was examined. The presence or absence of the Trp64Arg mutation was examined in DNA separated from leukocytes in peripheral blood using the PCR-RFLP method. The frequency of abnormal allele of the beta(3)-AR gene was 0.18 for males and 0.17 for females, almost the same as the reported values in Japanese. There was no difference in the frequency of the beta(3)-AR gene variant between obese and non obese subjects for each gender. However, among obese males (body mass index > or =24.2 kg/m(2)), with the beta(3)-AR gene mutation, the waist-to-hip ratio, fasting insulin, 2-h insulin, total insulin, and HOMA, an index of insulin resistance, were all significantly higher than obese males without the mutation. In females, the index of obesity, insulin resistance, or lipid metabolism did not differ significantly between the subjects with or without the beta(3)-AR gene variant either in the obese and non-obese group. We suggest that the beta(3)-AR gene variant is not important as an obesity-inducing factor in Japanese. However, in males, when obesity becomes obvious, the beta(3)-AR gene variant is considered to influence the enhancement of insulin resistance, in association with visceral obesity.

Synergistic effect of polymorphisms of uncoupling protein 1 and beta3-adrenergic receptor genes on autonomic nervous system activity

OBJECTIVE

To investigate the association of the promoter region -3826 A to G polymorphism of the uncoupling protein 1 (UCP1) gene with autonomic nervous system (ANS) activity and the interaction of the polymorphism with the Trp64Arg polymorphism of the beta3 adrenergic receptor (beta3AR).

SUBJECTS

Three-hundred and forty-nine young (mean age 20.4+/-2.1 y old), healthy Japanese males.

MEASUREMENTS

DNA was extracted from whole blood and genotyped by polymerase chain reaction restriction fragment length polymorphism. Plasma glucose, plasma insulin and body mass index (BMI) were measured. Frequency of family history of diabetes or obesity was determined by interview. Subjects randomly chosen from each genotype were examined for ANS activity during supine rest and standing by electrocardiogram power spectral analysis of heart rate variability.

RESULTS

UCP1 or beta3AR polymorphism was not associated with BMI, plasma glucose, plasma insulin and frequency of family history of diabetes or obesity. The inhibitory effect of UCP1 polymorphism on ANS activity was observed only with occurrence of the variant of beta3AR. The very low frequency component associated with thermoregulation in the sympathetic nervous system of homozygotes of UCP1 (GG) at supine rest was significantly lower than normal (AA, 203.2+/-50.3 vs 462.2+/-83.6 ms(2); mean+/-s.e., P=0.021). A higher response to postural change to standing was also observed in both sympathetic and parasympathetic nervous activities of AA than of GG.

CONCLUSION

While UCP1 polymorphism alone does not affect ANS activity, it has a synergistic effect with beta3AR polymorphism in decreasing sympathetic nervous system activity.

Expression of the human beta(3)-adrenergic receptor gene in SK-N-MC cells is under the control of a distal enhancer

Mechanisms of transcriptional regulation of the human beta(3)-adrenergic receptor were studied using SK-N-MC cells, a human neuroblastoma cell line that expresses beta(3)- and beta(1)-adrenergic receptors endogenously. Deletions spanning different portions of a 7-kb 5'-flanking region of the human beta(3)-adrenergic receptor gene were linked to a luciferase reporter and transfected in SK-N-MC, CV-1, and HeLa cells. Maximal luciferase activity was observed when a 200-bp region located between -6.5 and -6.3 kb from the translation start site was present. This region functioned only in SK-N-MC cells. Electrophoretic mobility shift assays of nuclear extracts from SK-N-MC, CV-1, and HeLa cells using double stranded oligonucleotides spanning different portions of the 200-bp region as probes and transient transfection studies revealed the existence of three cis-acting regulatory elements: A) -6.468 kb-AGGTGGACT--6.458 kb, B) -6.448 kb-GCCTCTCTGGGGAGCAGCTTCTCC-6.428 kb, and C) -6.405 kb-20 repeats of CCTT-6.385 kb. These elements act together to achieve full transcriptional activity. Mutational analysis, antibody supershift, and electrophoretic mobility shift assay competition experiments indicated that element A binds the transcription factor Sp1, element B binds protein(s) present only in nuclear extracts from SK-N-MC cells and brown adipose tissue, and element C binds protein(s) present in both SK-N-MC and HeLa cells. In addition, element C exhibits characteristics of an S1 nuclease-hypersensitive site. These data indicate that cell-specific positive cis-regulatory elements located 6.5 kb upstream from the translation start site may play an important role in transcriptional regulation of the human beta(3)-adrenergic receptor. These data also suggest that brown adipose tissue-specific transcription factor(s) may be involved in the tissue-specific expression of the beta(3)-adrenergic receptor gene.

Relationship of the Trp64Arg polymorphism of the beta3-adrenoceptor gene to central adiposity and high blood pressure: interaction with age. Cross-sectional and longitudinal findings of the Olivetti Prospective Heart Study

METHODS

The association of the Trp64Arg polymorphism of the beta3-adrenoceptor (beta3-AR) gene with high blood pressure, central adiposity and other features of the metabolic syndrome was investigated in a large unselected sample of a white male working population in Southern Italy (n = 979).

RESULTS

In the whole population, subjects heterozygous for the Trp64Arg mutation (11.2%) were not different from the homozygous Trp64Trp for any of the variables investigated. However, upon stratification for age, among men in the upper tertile of age (> 53 years), the Trp64Arg genotype was associated with higher waist: hip ratio (0.992 +/- 0.021 versus 0.982 +/- 0.037, P< 0.05), serum uric acid (6.34 +/- 1.50 versus 5.75 +/- 1.30 micromol/l, P < 0.05) and systolic blood pressure (144.3 +/- 19.4 versus 136.9 +/- 18.9 mmHg, P< 0.05) compared with the wild-type homozygotes. Accordingly, in the same age group, the carriers of Trp64Arg genotype were more often in the upper tertile of abdominal adiposity (69.7 versus 43.7%, P< 0.02) and serum uric acid (56.3 versus 34.8%, P < 0.02) and were more often hypertensive (68.6 versus 57.6%, P< 0.058) than the Trp64Trp homozygotes. No such differences were observed in younger age groups. No association was found with fasting serum insulin and the homeostasis model assessment (HOMA) index of insulin resistance. Furthermore, in a subgroup of 457 men for whom retrospective 20-year follow-up data were available, the variant genotype was associated with a higher probability of developing overweight (44.7 versus 27.0%, P < 0.05) and a trend to higher blood pressure (52.6 versus 38.4%, P = 0.09) over 20 years.

CONCLUSION

We conclude that the Trp64Arg variant of the beta3-AR receptor predicts a greater tendency to develop abdominal adiposity and high blood pressure with advancing age.

The beta 3-adrenergic receptor gene and obesity in a population sample of African Americans

OBJECTIVE

To examine the role of the Trp64Arg polymorphism in the beta 3-adrenergic receptor gene and the beta 3-adrenergic receptor gene locus in obesity-related traits in African Americans.

SUBJECTS

A total of 687 individuals representing 193 African American families who were residents of metropolitan Chicago.

MEASUREMENTS

Genotyping of the Trp64Arg polymorphism in the beta 3-adrenergic receptor gene and three microsatellite markers flanking the beta 3-adrenergic receptor gene (ADRB3) locus and measuring various obesity-related traits, including body mass index (BMI), fat-free mass, fat mass, percentage fat mass, waist circumference and serum lipid levels.

RESULTS

The prevalence of obesity (defined as body mass index > or = 30 kg/m(2)) in the population was 27.3% and 51.2% in men and women, respectively. The frequency of the Arg64 allele was 10.0%. Multivariate regression analyses confirmed the existence of a significant contribution of familial variance to each of the five obesity-related traits noted above. Likelihood ratio statistics computed in a multivariate regression analysis failed to demonstrate a significant association between the Arg64 allele and any of the five obesity-related traits. Single and multipoint analyses using extended Haseman--Elston regression analyses failed to demonstrate suggestive evidence of linkage of three microsatellite markers that flank the beta 3-adrenergic receptor gene to BMI, percentage body fat, waist circumference or serum leptin levels.

CONCLUSION

Given the contribution of familial variance to obesity-related traits in this population, neither the null finding for the Arg64 allele nor the lack of evidence of linkage of the ADRB3 locus to obesity-related traits could be attributed to lack of transmissibility of the traits suggesting that neither the Arg64 variant of the beta 3-adrenergic receptor gene nor another genetic variant in or near the ADRB3 locus contribute significantly to familial aggregation of obesity-related traits in African Americans. International Journal of Obesity (2001) 25, 54-60

The Trp64Arg polymorphism of the beta3-adrenergic receptor gene and obesity in Chinese subjects with components of the metabolic syndrome

BACKGROUND

In regions such as Hong Kong, rapid economic development has led to lifestyle alterations characterized by increases in energy and fat intake and reduction in physical activity. These changes have been associated with a dramatic increase in the prevalence of diabetes and related diseases of the metabolic syndrome.

OBJECTIVE

To investigate if a common polymorphism (Trp64Arg) of the beta3-adrenergic receptor gene, previously implicated as predisposing to type 2 diabetes mellitus or obesity in other populations, has a role in the apparent susceptibility of Hong Kong Chinese to diabetes and related disorders.

METHOD

A PCR-based protocol was used to genotype 802 Southern Chinese subjects who were either healthy or had one or more of the metabolic disorders including diabetes, hypertension or dyslipidaemia.

RESULTS

The frequencies of the mutant A allele (12.7%) and AA genotype (1.7%) did not differ, by the chi2 test, in any patient group with diabetes, hypertension or dyslipidaemia, alone or in combination, compared to healthy controls. Using the t-test in the 802 subjects, those carrying the mutant A allele had evidence of increased obesity with a significantly (all P<0.05) higher body mass index (BMI, kg/m2) and also lower HDL-cholesterol. BMI was also elevated in subjects with the A allele in the separate groups with diabetes, dyslipidaemia or hypertension. Stepwise multiple regression showed this polymorphism to be an independent predictor of BMI.

CONCLUSION

These data do not support any direct involvement of the Trp64Arg polymorphism in the development of diabetes, hypertension or dyslipidaemia in Chinese subjects, but do suggest a relationship with obesity.

Association of Trp64Arg polymorphism of the beta3-adrenergic receptor gene and no association of Gln223Arg polymorphism of the leptin receptor gene in Japanese schoolchildren with obesity

OBJECTIVE

To investigate whether Trp64Arg polymorphism of the beta3-adrenergic receptor (beta3-AR) gene and Gln223Arg polymorphism of the leptin receptor (Ob-R) gene are associated with obesity in Japanese schoolchildren.

DESIGN

Population study of participants from a rural town located within 50 km northeast of Tokyo based on school medical examinations.

SUBJECTS

553 Japanese schoolchildren (291 boys and 262 girls) who were 9-15 y old with a mean age of 11.9 +/- 1.8 y.

MEASUREMENTS

DNA was extracted from whole blood and genotyped by PCR-RFLP. Height, weight and blood pressure were measured in school medical examinations. Total cholesterol, triglyceride and HDL-cholesterol concentrations were measured by an autoanalyzer. Obesity index, body mass index (BMI) and LDL-cholesterol concentration were calculated by the respective formulae.

RESULTS

In Trp64Arg polymorphism of the beta3-AR gene, the number of obese subjects with Trp/Arg or Arg/Arg genotypes was significantly higher than that of the non-obese subjects (chi2=5.79, P=0.02). The obesity index of subjects with the Arg/Arg or Arg/Trp genotype was significantly higher than that of those with the Trp/Trp genotype (8.2 +/- 18.7% vs 4.5 +/- 15.8%, P=0.04). Moreover, after adjustments for age and gender, BMI of subjects with the Trp/Arg or Arg/Arg genotype was significantly higher than that of those with the Trp/Trp genotype (19.4 +/- 3.6 kg/m2 vs 18.9 +/- 3.2 kg/m2, P= 0.02). However, no significant differences were observed in the clinical characteristics among the genotype groups of the Ob-R gene.

CONCLUSIONS

Trp64Arg polymorphism of the beta3-AR gene appears to be a genetic risk factor for obesity in Japanese children, but Gln223Arg polymorphism of the Ob-R gene does not appear to be associated with obesity.

No association between body mass index and beta(3)-adrenergic receptor variant (W64R) in children with premature pubarche and adolescent girls with hyperandrogenism

OBJECTIVE

To determine if the Trp(64)Arg (W64R) variant of the beta(3)-adrenergic receptor (ADRB3) could be used as a genetic marker to define risk for polycystic ovary syndrom (PCOS) and/or obesity in children and adolescents.

DESIGN

Association study.

SETTING

Academic research environment.

PATIENT(S)

Children referred for evaluation of premature pubic hair (n = 63), adolescent girls referred for evaluation of hirsutism and/or oligomenorrhea (n = 33), and healthy adult controls (n = 67).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Relationship of body mass index (BMI) to presence or absence of W64R variant and frequency of W64R variant in our patient population.

RESULT(S)

Body mass index (kg/m(2)) was determined for 63 children (55 girls and 8 boys) and 33 adolescent girls. Presence or absence of the W64R variant was assayed by polymerase chain reaction (PCR) amplification followed by allele-specific restriction fragment digest. Twelve subjects and 11 healthy controls were found to be heterozygous for the W64R variant. One subject was found to be homozygous for the W64R variant. Allele frequency for the W64R variant was comparable between patients and controls. Among the patients, mean BMI values were not different between carriers and noncarriers.

CONCLUSION(S)

Although other studies suggest that the W64R variant is associated with the development of obesity and insulin resistance, we cannot demonstrate that it has a major effect on BMI in children with premature pubarche or in adolescent girls with hyperandrogenism. Serial observations are necessary to determine if this variant predicts the development of obesity and/or PCOS in adulthood.

Analysis of beta3 adrenergic receptor gene polymorphism using noninvasive samples obtained at scheduled infant health checkups

Obesity is a risk factor for life-style-related diseases, and is based on three factors: genetic, environmental, and life-style. In adults, it is difficult to achieve and maintain normal body weight, so it is more effective to intervene from infancy to establish weight control. Legally required health checkups in infants of 18 and 36 months present important opportunities for obesity prevention. We consider genetic analysis to be a very important factor for obesity prevention in infancy. However, since health checkups don't involve the collection of blood, genetic analysis is considered difficult. In this study, we attempted the typing of beta3 adrenergic receptor gene polymorphism as a genetic factor from non-invasively obtained samples, buccal mucosa, hair and cerumen in 96 infants at their 18- and 36-month health checkups. Sampling buccal mucosa, hair and cerumen instead of blood caused almost no anxiety to the child or parent, so 94.1% cooperation with sampling was obtained. From buccal mucosa, about 76% of the samples could be used for the typing of polymorphism (81% by enzyme method, 59% by kit method). From hair, about 44% of the samples permitted typing of polymorphism, but from cerumen only about 4% of the samples could be used. Results from buccal mucosa and hair typed about 90% of infant polymorphism. These results suggest that this method would be practical at periodic health checkups, and would probably be applicable to mass screenings for genetic factor analysis for other diseases.

Association of beta3-adrenergic receptor gene polymorphism with insulin resistance in Japanese-American men

The Trp64Arg variant of the beta3-adrenergic receptor (beta3-AR) gene is relatively common in Japanese people. We hypothesized that this variant may be associated with obesity and insulin resistance when combined with a westernized lifestyle. To test this hypothesis, we investigated the relationships between the beta3-AR gene variant and obesity and insulin resistance in Japanese-American men, who are known to have a higher prevalence of type 2 diabetes mellitus (DM). The subjects were 152 Japanese-American men living in Hawaii, 83 with normal glucose tolerance (NGT), 40 with impaired glucose tolerance (IGT), and 29 with DM. The frequency of the Trp64Arg allele of the beta3-AR gene was 0.18, almost identical to that of the mainland Japanese. The prevalence of the Trp64Arg allele was 30.1% in NGT, 35.0% in IGT, and 41.4% in DM subjects (nonsignificant). The Trp64Arg variant of the beta3-AR gene showed no significant relationship with obesity or insulin resistance in NGT subjects. However, fasting and 2-hour insulin levels and insulin resistance as determined by homeostasis model assessment (HOMA) were significantly higher in IGT subjects with the Trp64Arg variant. Although indices of obesity were the same in IGT subjects with and without the Trp64Arg variant, differences in the body mass index (BMI) and percent body fat between NGT and IGT subjects were greater for individuals with the Trp64Arg variant. Thus, there is an association between the Trp64Arg variant of the beta3-AR gene and insulin resistance in Japanese-Americans with IGT.

The Trp64Arg mutation of the adrenergic beta-3 receptor gene impairs insulin secretion: a twin study

AIMS

The physiological role of the adrenergic beta-3 receptor is poorly understood in man but the Trp64Arg mutation of the receptor gene has been related to the insulin resistance syndrome, an earlier onset of diabetes and rapid weight gain. This study set out to examine the effects of the mutation on glycaemic responses after an oral glucose tolerance test.

METHODS

A standard oral glucose tolerance test (75 g glucose) was performed in 196 dizygotic twins. Serum insulin and glucose responses were measured at 0, 30 and 120 min.

RESULTS

In the twins discordant for the mutation (21 pairs), no effects of the mutation were found on the plasma glucose responses. The insulin response given as incremental area under curve (iAUC) (median 13.8 (25-75th percentile 9.3-21.0) vs. 23.3 (14.2-29.2) mmol x l(-1) x min, P<0.021) and the insulinogenic index ((insulin30min - insulin0min)/ (glucose30min - glucose0min)), a measure of the insulin secretory capacity (44 (34-58) vs. 75 (42-124), P<0.006), were considerably lower in the variant type. The results were confirmed when using non-paired statistics on all subjects.

CONCLUSION

It was concluded that the adrenergic beta-3 receptor, in addition to its already known effects, may be involved in the regulation of insulin secretion and that patients with the Trp64Arg mutation present an impaired insulin secretion.

Lipoprotein-genotype associations in Trinidadian neonates

OBJECTIVES

We hypothesized that common variation in the angiotensinogen (AGT), beta-3-adrenergic receptor, intestinal fatty acid-binding protein, serum paraoxonase, paraoxonase-2, hepatic lipase, apolipoprotein E (APOE), and Werner helicase (WRN) genes would be associated with variation in biochemical phenotypes in a previously unstudied neonatal sample.

DESIGN AND METHODS

We examined associations of both nongenetic and genetic variables with plasma lipoprotein traits in neonates from Trinidad.

RESULTS

Among nongenetic variables, we found significant associations between plasma concentrations of: 1) lipoprotein(a) [Lp(a)] and both ethnicity (p = 0.037) and birth weight (p = 0.001); 2) total cholesterol and gender (p = 0.010); 3) triglyceride and birth weight (p = 0.035); and 4) apolipoprotein AI and gender (p = 0.016). Among genetic variables, we found that: 1) common variation on chromosome 1q in AGT codon 235 was significantly associated with variation in plasma apolipoproteins AI (p<0.0001) and B (p = 0.013); 2) common variation in WRN at codon 1367 was significantly associated with variation in plasma Lp(a) (p<0.0001); and 3) common variation in APOE at codons 112 and 158 was significantly associated with variation in plasma triglycerides (p = 0.013).

CONCLUSIONS

The associations with AGT and WRN are novel and may have resulted either from a direct influence of the genetic variants or through linkage disequilibrium with other functional loci, such as the familial combined hyperlipidemia locus on chromosome 1q in the case of AGT. Despite the fact that there are some limitations in making determinations from cord blood, the results suggest that there may be genetic determinants of plasma lipoproteins in neonates.

Genetics of human obesity: lessons from mouse models and candidate genes

Obesity is a common disorder with potentially serious negative implications on health and quality of life and a rising prevalence worldwide, warranting effective treatments. The disorder runs in families, and important knowledge is expected to follow the identification of human obesity genes. Although statistical analysis of inheritance of obesity in humans suggests a large genetic component in obesity, up to 80%, few actual obesity genes have been identified so far. However, a number of obesity causing genes have successfully been cloned from rodents with monogenic forms of obesity, and it is probable that new knowledge in the field of human obesity will result from these findings.

Adrenoceptor genes in human obesity

The genes causing obesity in rodent models have been characterized, but do not seem to be important for human obesity. Recently the putative association between obesity and polymorphism in human beta-adrenergic receptor genes have been studied intensely in the light of the important role of these receptors in the regulation of energy mobilization and utilization. A polymorphism (Trp64Arg) in the beta3-adrenergic receptor gene is associated with obesity (relative risk approximately 2) in some but not all investigations on Caucasian and Japanese populations. When expressed in artificial cell systems, the polymorphism is associated with alterations of the beta -adrenoceptor. The genetic allele variance influences also the native receptor function when measured in isolated human fat cells. The human beta2-adrenoceptor gene shows a high degree of polymorphism. The role of beta2-receptor gene polymorphism for obesity has so far only been investigaed in women. A Gln27Glu variant is markedly associated with obesity with a relative risk for obesity of approximately 7 and odds ratio of approximately 10. Women who are homozygous for 27Glu have approximately 20 kg higher fat mass than controls. Thus, polymorphism in genes coding for different beta-adrenoceptor subtypes may be important for the development of human obesity.

A Trp 64 Arg mutation in the beta3-adrenergic receptor gene is not associated with moderate overweight in Japanese workers

The aim of the present study was to investigate the trend for obesity and the relationship between Trp64Arg mutation in the beta3-adrenergic receptor gene and obesity-related phenotypes in Japanese workers. A total of 658 workers, 483 women and 175 men, responded to this survey. Genomic DNA was prepared from leukocytes, and DNA amplification by polymerase chain reaction was performed using 100 ng genomic DNA. Amplified fragments were digested with BstNI and analyzed by 3% agarose gel electrophoresis. The body mass index (BMI) increased from 21.1 +/- 2.6 to 22.0 +/- 3.0 kg/m2 for women and from 20.9 +/- 2.1 to 22.1 +/- 2.6 kg/m2 for men from 1982 to 1997. Body weight increased 63.3% for women and 67.4% for men over 15 years. The frequency of the Trp64Arg allele was 19.9%, and the frequency of heterozygote and homozygote carriers of the mutation was 32.9% and 3.4%, respectively. Changes in the BMI and body weight over 15 years from 1982 to 1997 did not differ significantly between subjects with or without the mutant allele in either women or men. The BMI was not significantly higher in subjects who were homozygous or heterozygous for the Trp64Arg mutation versus subjects who were homozygous for the normal allele. This mutation of the beta3-adrenergic receptor gene is not likely a major determinant of moderate obesity in the Japanese population.

Trp64Arg variant of the beta3-adrenoceptor and insulin resistance in obese postmenopausal women

There is controversy regarding the role of the Trp64Arg variant of the beta3-adrenergic receptor (beta3AR) gene in the pathogenesis of insulin resistance. The modest effect of the variant as well as differences in study design, gender, age, and genetic background may contribute to divergent results among investigations. Insulin sensitivity (euglycemic clamp and tracers) was measured in 13 obese women (57 +/- 6 yr old) heterozygous for the beta3AR variant and in 14 women (57 +/- 4 yr old) homozygous for the normal gene. Groups were matched for age, body composition, intraabdominal fat, sc abdominal fat, physical activity level, and aerobic capacity. Exogenous glucose infusion during the clamp was significantly lower (P = 0.03) in beta3AR heterozygotes (241 +/- 135 mg/min) vs. normal homozygotes (379 +/- 172 mg/min). Basal endogenous glucose production was not different (P = 0.20) between heterozygotes (175 +/- 27 mg/min) and normal homozygotes (164 +/- 14 mg/min). Endogenous glucose production during hyperinsulinemia was also not different (P = 0.22) between heterozygotes (77 +/- 57 mg/min) and normal homozygotes (56 +/- 16 mg/min). Total glucose disposal adjusted for residual endogenous glucose production was lower (P = 0.049) for heterozygotes (320 +/- 111 mg/min) than for normal homozygotes (441 +/- 183 mg/min). Our results suggest that obese postmenopausal women who are heterozygous for the Trp64Arg variant in the beta3AR gene have greater insulin resistance than age-, body composition-, and physical activity-matched women homozygous for the normal gene.

Association of the Trp64Arg mutation of the beta3-adrenergic receptor with fatty liver and mild glucose intolerance in Japanese subjects

The prevalence of a mutation of the codon for tryptophan 64 to arginine (Trp64Arg) in the beta3-adrenergic receptor gene was investigated by genotyping 261 Japanese subjects. The allelic frequency of this mutation was 0.18. Subjects with the homozygous W64R mutant alleles had a significantly higher prevalence of fatty liver, BMI, serum gamma-glutamyl transpeptidase, and serum leucine amino transpeptidase levels than those without the mutation. Individuals with this mutation also showed a higher fasting blood glucose level than those without this mutation. However, the prevalence of diabetes mellitus was no different between the three groups. These results suggest a potential association of the Trp64Arg mutation with higher morbidity of fatty liver and mild glucose intolerance.

Clinical features associated with the homozygous Trp64Arg mutation of the beta3-adrenergic receptor: no evidence for its association with obesity in Japanese

To characterize the clinical features associated with the Trp64Arg mutation of the beta3-adrenergic receptor (beta3-AR), the effects of this mutation, in particular the homozygous state (Arg/Arg), on obesity, blood pressure, and plasma lipoproteins were investigated in 2 populations: subjects residing on a small isolated island (group 1; n=746) and patients residing in Tokyo who attend a clinic for metabolic diseases (group 2; n=371). The allelic frequency of the Trp64Arg mutation was 23.4% in group 1 and 18.3% in group 2. No significant difference in the body mass index was observed between subjects with 3 different genotypes in each group. There was a trend that the Arg/Arg had higher systolic blood pressure than the Trp/Trp in both groups, but the differences were not statistically significant. The plasma LDL cholesterol levels were significantly lower in Arg/Arg than in Trp/Trp in men from the group 1 cohort (2.82+/-0.84 versus 3.19+/-0.7 mmol/L, P<0.05). These results suggest that the homozygous Trp64Arg mutation is not a major contributing factor for obesity, but potentially contributed to higher systolic blood pressure and low plasma levels of LDL cholesterol in Japanese men.

The Trp64Arg mutation of the beta3-adrenergic receptor is associated with hyperglycemia and current body mass index in Jamaican women

The Trp64Arg mutation of the beta3-adrenergic receptor (beta3-AR) has been linked to earlier onset of non-insulin-dependent diabetes mellitus (NIDDM), insulin resistance, abdominal obesity, and an increased capacity to gain weight in some European and Japanese populations. We studied the prevalence of the mutation and its association with NIDDM and obesity in our population, in which both rates are high, especially in women. The frequency of the homozygous mutation was 1.53%, and of the Arg allele, 10.5%. Rates were similar in men and women. Significantly higher body mass index (BMI), weight, hip circumference, and fasting and postchallenge 2-hour blood glucose concentrations were associated with the presence of the Arg allele in women but not in men. The association with weight and hip measurements and with hyperglycemia was present only in women aged less than 55 years. In multivariate analysis, the mutation was associated with the BMI and sex in a model that also included age. The variation in fasting and 2-hour blood glucose levels was predicted by beta3-AR, gender, age, and BMI. These results suggest that the presence of the mutation contributes to obesity and hyperglycemia in our female population.

The significance of the Trp 64 Arg mutation of the beta3-adrenergic receptor gene in impaired glucose tolerance, non-insulin-dependent diabetes mellitus, and insulin resistance in Japanese subjects

It has been reported that the Trp 64 Arg mutation of the human beta3-adrenergic receptor (beta3-AR) gene is related to an earlier age of onset of non-insulin-dependent diabetes mellitus (NIDDM) and features of insulin resistance and weight gain in morbidly obese patients. However, such findings have not been consistent in varying ethnic populations. In the present study, we investigated the frequency of the Trp 64 Arg mutation of the human beta3-AR gene in Japanese control subjects (n = 253) and in NIDDM (n = 314) and impaired glucose tolerance (IGT) patients (n = 100). We compared the frequency of the mutation with the body-mass index (BMI) in these groups and with the metabolic clearance rate (MCR) of glucose in the NIDDM patients. A Trp 64 Arg mutation was observed in 36.7%, 31.6%, and 37.0% of the control, NIDDM, and IGT subjects, respectively. The frequency of the homozygotes for the mutation was 4.3%, 4.8%, and 3.0%, respectively. Neither the genotype frequency (Trp/Arg, Arg/Arg) nor the frequency of the mutated allele was significantly different among the three groups. The BMI of the subjects with the mutation was not significantly higher than that of the subjects without the mutation in each group. Furthermore, the allele frequency (A) was not different among the subjects with different BMIs (BMI < 22.0, 22.0 < or = BMI < or = 26.4, BMI > 26.4) in each group. In a separate group of NIDDM patients, the MCR of the subjects with intermediate BMIs (22.0 < or = BMI < or = 26.4) with the mutation tended to be lower than that of those without the mutation. In addition, the MCR of the subjects with the mutation in this group was significantly lower compared with that of those with a BMI less than 22. These results indicate that the Trp 64 Arg mutation of the beta3-AR gene may not contribute to the development of NIDDM or be a determinant of obesity in the Japanese population. However, the mutation may contribute to insulin resistance in NIDDM patients with an intermediate BMI.

The human obesity gene map: the 1997 update

An update of the human obesity gene map incorporating published results up to October 1997 is presented. Evidence from Mendelian disorders exhibiting obesity as a clinical feature; single-gene mutation rodent models; quantitative trait loci uncovered in human genome-wide scans and in crossbreeding experiments with mouse, rat, and pig models; association and case-control studies with candidate genes; and linkage studies with genes and other markers is reviewed. All chromosomal locations of the animal loci are converted into human genome locations based on syntenic relationships between the genomes. A complete listing of all of these loci reveals that all but chromosome Y of the 24 human chromosomes are represented. Some chromosomes show at least three putative loci related to obesity on both arms (1, 2, 6, 8, 11, and 20) and several on one chromosome arm only (3p, 4q, 5q, 7q, 12q, 13q, 15q, 15p, 22q, and Xq). Studies reporting negative association and linkage results are also listed, with the exception of the unlinked markers from genome-wide scans.