Genetic polymorphisms of human beta-adrenergic receptor genes and their association with obesity

The prevalent rates of overweight and obesity are steadily increasing all over the world. Previous studies of some candidate genes have indicated that most of the genes are associated with obesity in human adipose tissue. As much as 40% of the variations in body mass could be attributed to genetic difference. The beta-adrenergic receptor (beta-AR) plays a major role in the regulation of energy balance in humans. A high sympathetic nervous system activity has been shown to be associated with obesity and is believed to have pathogenetic relevance. Several common single nucleotide polymorphisms (SNPs) including Gly389Arg in beta(1)-AR, Gln27Glu in beta(2)-AR, and Trp64Arg in beta(3)-AR in humans could alter receptor function and these variations of beta-ARs were shown to have certain association with obesity. Here we summarize the genetic polymorphisms of human beta-ARs and their potential impacts to obesity.

Postprandial plasma lipid levels are influenced by the interaction of functional polymorphisms in the microsome triglyceride transfer protein and beta3 adrenergic receptor genes

BACKGROUND

The effects of polymorphisms in the genes encoding microsome triglycerides transfer protein (MTP) and beta3-adrenergic receptor (beta3-AR) on lipid and glucose metabolism were investigated.

MATERIAL/METHOD

Clinical phenotypes related to lipid and glucose metabolism were evaluated during dietary loading (17 g of fat, 750 Cal) and glucose loading (75 g glucose). MTP and beta3-AR genotypes were determined by restriction fragment length polymorphism.

RESULTS

Subjects with the Arg64 beta3-AR gene (Arg+) polymorphism showed significantly higher fasting (FTG) and postprandial (PTG) triglyceride levels, fasting plasma glucose (FPG), fasting plasma immuno-reactive insulin (FIRI) and HOMA-R in comparison with Trp64 homozygotes. Subjects with the T allele (T +) of MTP -164T/G polymorphism (with T allele) showed significantly lower levels of FPG, FIRI, HOMA-R and PTG than did subjects without the T allele (T-). To evaluate the interaction of the polymorphisms, we divided our subjects into four groups. T-/Arg-, T-/Arg+, T+/Arg- and T+/Arg+. In these four groups, only T-/Arg+ showed significantly higher PTG levels. Plasma glucose levels were significantly higher at 60 and 120 min after oral glucose loading in in the T-/Arg+ subjects.

CONCLUSIONS

In this study, we identified an example of genotypic interactions that influence the clinical phenotype in multi-factorial diseases.

[Relationship of beta(3)-adrenergic receptor polymorphism with metabolic syndrome and oxidative stress parameters in postmenopausal women]

INTRODUCTION

Some studies indicate, that the Trp(64)/Arg(64) polymorphism of beta(3)-adrenergic receptor (ADRB3) is associated with obesity, insulin resistance and earlier onset of type 2 diabetes mellitus. The aim of our study was evaluation of frequency of this ADRB3 polymorphism and his association with metabolic syndrome parameters and oxidative stress in postmenopausal women.

MATERIAL AND METHODS

We performed the study among 94 women, aged 50-60, selected randomly from Wroclaw city population. Estimation of anthropometric parameters, densitometry (total body fat, android and gynoid deposits--using DPX(+) Lunar, USA device) and biochemical estimations such as lipid profile, glucose, insulin, estradiol and FSH serum level (using commercial kits) were carried out. Oxidative stress was estimated by measurement of thiobarbituric-reactive substances (TBARS) serum concentration, using Yagi method, on spectrofluorimeter Perkin-Elmer LS55. Blood for analysis was collected before, direct after and 6 h after the 30-minutes physical test using cycloergometer. ADRB3 genotyping was performed by PCR and mini-sequencing using ABI 310 sequencer (Applied Biosystems).

RESULTS

The frequency of Trp(64)/Arg(64) genotype in investigated population was 15.8%. The Arg(64)/Arg(64) genotype had only one woman. Women bearing Trp(64)/Arg(64) genotype showed higher mean serum level of triglycerides and lower serum level of HDL-cholesterol in comparison to women bearing Trp(64)/Trp(64) genotype, however without statistical significance (p > 0.05) (respectively, means +/- SD for triglycerides: 140.3 +/- 64.1 vs. 113.9 +/- 56.2 mg/dl; and for HDL-cholesterol: 60.9 +/- 11.9 vs. 67.0 +/- 16.9 mg/dl). Both groups did not differ in any other investigated anthropometric nor biochemical parameter.

CONCLUSIONS

1. The Trp(64)/Arg(64) polymorphism of beta(3)-adrenergic receptor could be associated with lipid profile disorders observed in metabolic syndrome in postmenopausal women, however it should be explained basing on the study with more included subjects. 2. The Trp(64)/Arg(64 )polymorphism of beta(3)-adrenergic receptor has no influence on oxidative stress intensification after standardized physical effort in postmenopausal women.

beta2- and beta3-Adrenoceptor polymorphisms relate to subsequent weight gain and blood pressure elevation in obese normotensive individuals

High blood pressure (BP) is a major determinant of cardiovascular events in obesity. The beta2- and beta3-adrenoceptor polymorphisms are associated with obesity and hypertension. In the present study, we examine the relationships of beta2- and beta3-adrenoceptor polymorphisms with further weight gain-induced BP elevation in obese subjects. Changes in BP, body weight, total body fat-mass, waist-to-hip ratio, plasma norepinephrine (NE) and leptin levels, and beta2(Arg16Gly)- and beta3(Trp64Arg)-adrenoceptor polymorphisms were measured periodically over a 5-year period in 55 entry obese (body mass index [BMI]> or =25.0 kg/m(2)) normotensive (BP<140/90 mmHg) men. BP elevation and weight gain were defined as > or =10% increases from entry levels over 5 years in mean BP or BMI. Obese subjects with weight gain, BP elevation or weight gain-induced BP elevation had higher frequencies of the Gly16 allele of Arg16GIy and Arg64 allele of Trp64Arg. Subjects carrying the Gly16 or Arg64 alleles had significantly greater total fat-mass and waist-to-hip ratio at entry and over a 5-year period compared to the subjects who did not carry these polymorphisms. Subjects carrying the Gly16 allele had similar levels of plasma NE, higher levels of plasma leptin and a lower slope of the regression lines between plasma leptin and NE levels. Those carrying the Arg64 allele had higher plasma NE levels at entry and over a 5-year period compared to the subjects without the Arg64 allele, but plasma leptin levels and slopes were similar. The findings demonstrate that the Arg64 allele of the beta3-adrenoceptor polymorphisms relates to weight gain-induced BP elevation accompanying high plasma NE (heightened sympathetic activity) in obese men. The Gly16 allele of the beta2-adrenoceptor polymorphisms links to weight gain-induced BP elevation associated with leptin resistance. beta2- and beta3-adrenoceptor polymorphisms could predict the future BP elevation and further weight gain-induced BP elevation in originally obese subjects.

Effect of β-Blockers on β3-Adrenoceptor Expression in Chronic Heart Failure

OBJECTIVES

To investigate the expression of beta(3)-adrenoceptors in rats with chronic heart failure, and to explore the effect of beta-blockers on beta(3)-adrenoceptor expression.

MATERIALS AND METHODS

Thirty-two male Wistar rats were divided into Sham (n = 10) and heart failure (n = 22) groups. The heart failure group was treated with normal saline (Heart Failure Control, n = 6), Metoprolol (n = 8) or Carvedilol (n = 8) for 3 months.

RESULTS

The left ventricular end systolic pressure (LVESP) and the absolute values of maximal rate of rise and fall of left ventricular pressure (+/-dP/dt max) in the heart failure group were lower than in the Sham group (P < 0.01), whereas the left ventricular end diastolic pressure (LVEDP) was higher (P < 0.01). The LVESP and dP/dtmax in the Carvedilol group were higher than the Metoprolol group whereas LVEDP was lower (P < 0.01). The left ventricular mass index (LVMI) in the Carvedilol group was less than the Metoprolol and Heart Failure Control groups (P < 0.01). The level of beta(3)-adrenoceptor expression in the study groups was significantly higher than the Sham group (P < 0.01). beta(3)-adrenoceptor expression in the Carvedilol group was lower than the Heart Failure Control and Metoprolol groups (P < 0.01).

CONCLUSION

beta(3)-adrenoceptor expression is increased in the failing ventricles in rats. Carvedilol is more effective than Metoprolol for improving the hemodynamics and in attenuating ventricular remodeling after heart failure. Carvedilol, rather than Metoprolol, diminishes beta(3)-adrenoceptor expression in the failing ventricles.

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.

Association of beta3 adrenergic receptor and peroxisome proliferator-activated receptor gamma 2 polymorphisms with insulin sensitivity: a twin study

OBJECTIVE

To study the effect of beta3 adrenergic receptor (beta3AR) Trp64Arg and peroxisome proliferator activated receptor gamma 2 (PPARgamma2) Prol2Ala polymorphisms on insulin resistance.

METHODS

One hundred and eight dizygotic twin pairs were enrolled in this study. Microsatellite polymorphism was used to diagnose zygosity of twins. Insulin sensitivity was estimated with logarithm transformed homeostasis model assessment (HOMA). PCR-RFLP analysis was performed to detect the variants. As a supplement to the sib-pair method, identity by state (IBS) was used to analyze the association of polymorphisms with insulin sensitivity.

RESULTS

The genotype frequencies of Trp64Trg, Trp64Arg, and Arg64Arg were 72.3%, 23.8%, and 3.9%, respectively, while the genotype frequencies of Prol2Pro, Prol2Ala, and Alal2Ala were 89.9%, 9.6%, and 0.5%, respectively. For beta3AR Trp64Arg the interclass co-twin correlations of Waist-to-hip ratio (WHR), blood glucose (GLU), and insulin (INS), homeostasis model assessment insulin resistance index (HOMA-IR) of the twin pairs sharing 2 alleles of IBS were greater than those sharing 0-1 allele of IBS, and HOMA-IR had statistic significance. For PPARgamma2 Pro12Ala most traits of twin pairs sharing 2 alleles of IBS had greater correlations and statistic significance in body mass index (BMI), WHR, percent of body fat (PBF) and GLU, but there were low correlations of either insulin or HOMA-IR of twin pairs sharing 1 or 2 alleles of IBS. The combined effects of the two variations showed less squared significant twin-pair differences of INS and HOMA-IR among twins sharing 4 alleles of IBS.

CONCLUSIONS

Beta3AR Trp64Arg and PPARgamma2 Pro12Ala polymorphisms might be associated with insulin resistance and obesity, and there might be slight synergistic effects between this two gene loci, and further studies are necessary to confirm this finding.

In vitro and in vivo pharmacological characterization of ethyl-4-[trans-4-[((2S)-2-hydroxy-3-[4-hydroxy-3[(methylsulfonyl)amino]-phenoxy]propyl) amino]cyclohexyl]benzoate hydrochloride (SAR150640), a new potent and selective human beta3-adrenoceptor agonist for the treatment of preterm labor

Ethyl-4-[trans-4-[((2S)-2-hydroxy-3-[4-hydroxy-3[(methylsulfonyl)amino] phenoxy]propyl) amino]cyclohexyl]benzoate hydrochloride (SAR150640) was characterized as a new potent and selective beta(3)-adrenoceptor agonist for the treatment of preterm labor. SAR150640 and its major metabolite, the corresponding acid 4-[trans-4-[((2S)-2-hydroxy-3-[4-hydroxy-3[(methylsulfonyl) amino] phenoxy]propyl)amino]cyclohexyl]benzoic acid (SSR500400), showed high affinity for beta(3)-adrenoceptors (K(i) = 73 and 358 nM) and greater potency than (-)-isoproterenol in increasing cAMP production in membrane preparations from human neuroblastoma cells (SKNMC), which express native beta(3)-adrenoceptors (pEC(50) = 6.5, 6.2, and 5.1, respectively). SAR150640 and SSR500400 also increased cAMP production in membrane preparations from human uterine smooth muscle cells (UtSMC), which also express native beta(3)-adrenoceptors (pEC(50) = 7.7 and 7.7, respectively). In these cells, SAR150640 dose-dependently inhibited oxytocin-induced intracellular Ca(2+) mobilization and extracellular signal-regulated kinase 1/2 phosphorylation. SAR150640 and SSR500400 had no beta(1)- or beta(2)-agonist or antagonist activity in guinea pig atrium and trachea, or in human isolated atrium and bronchus preparations. Both compounds concentration-dependently inhibited spontaneous contractions in human near-term myometrial strips, with greater potency than salbutamol and 4-[3-[(1,1-dimethylethyl)-amino]-2-hydroxypropoxy]-1,3-dihydro-2H-benzimidazol-2-one hydrochloride (CGP12177) (pIC(50) = 6.4, 6.8, 5.9, and 5.8, respectively), but with similar potency to (-)-isoproterenol and atosiban (oxytocin/vasopressin V(1)a receptor antagonist). SAR150640 also inhibited the contractions induced by oxytocin and prostaglandin F(2alpha). In vivo, after intravenous administration, SAR150640 (1 and 6 mg/kg), but not atosiban (6 mg/kg), dose-dependently inhibited myometrial contractions in conscious unrestrained female cynomolgus monkeys, with no significant effects on heart rate or blood pressure. In contrast, salbutamol (50 and 250 microg/kg) had no inhibitory effect on uterine contractions, but it dose-dependently increased heart rate. These findings indicate a potential for the therapeutic use of SAR150640 in mammals during preterm labor.

LEPR, ADBR3, IRS-1 and 5-HTT genes polymorphisms do not associate with obesity

Obesity is a growing problem and is associated with numerous medical conditions. In several genes coding for molecules involved in the regulation of body weight (fat mass) and thermogenesis, polymorphisms have been reported which possibly modify human obesity risk. The aim of this study was to determine the incidence of the following polymorphisms in the following genes in 262 obese (BMI > or = 30) and 138 control (BMI < or = 25) subjects: leptin receptor (LEPR)-Gln223Arg, B3-adrenergic receptor (B3-AR)-Trp64Arg, serotonin transporter (5-HTT)--a 44-base pair insertion/deletion functional polymorphism in the 5-HTTLPR and insulin receptor substrate-1 (IRS-1)-Gly972Arg. Our hypothesis was that these polymorphisms would occur more frequently in the obese population. The polymorphisms were determined by polymerase chain reaction (PCR) and restriction genotyping in study population. In our results, no strong associations were observed between BMI status and these polymorphisms. Weak, though significant, association coefficients obtained with HTT and LEPR loci indicate that the genotype numbers at these loci may depend on BMI status to some extent.

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.

The association between hyperuricemia and the Trp64Arg polymorphism of the beta-3 adrenergic receptor

The object of this study was to determine the association of Trp64Arg polymorphism with hyperuricemia. This study is an age-matched, case-controlled study of 203 hyperuricemic and 203 normouricemic men. The frequency of genotypes was compared between the two groups. Possible confounding metabolic variables were included in a multiple logistic regression model for multivariate adjustment. The genotype frequencies of Trp64Trp, Trp64Arg, and Arg64Arg in hyperuricemic and normouricemic groups are respectively 130, 69, and 4 (64.0%, 34.0%, 2.0%) and 154, 45, and 4 (75.9%, 22.2%, 2.0%) (P = 0.029, Chi-square test). Simple logistic regression analysis indicated that the Trp64Arg genotype is significantly associated with hyperuricemia (OR = 1.816, 95% CI (1.167-2.827), P = 0.008). Multivariate analysis for controlling metabolic effects also showed a significant association with the occurrence of hyperuricemia (OR = 1.937, 95% CI (1.149-3.266), P = 0.013). Trp64Arg polymorphism of the beta-3 adrenergic receptor may be independently associated with hyperuricemia in males.

Tools to study beta3-adrenoceptors

Beta(3)-adrenoceptors mediate some of the effects of catecholamines on tissues such as blood vessels or the urinary bladder and are putative targets for the treatment of diseases such as the overactive bladder syndrome. Progress in the understanding of the presence, function, and regulation of beta(3)-adrenoceptors has been hampered by a lack of highly specific tools. "Classical" beta(3)-adrenoceptor agonists such as BRL 37,344 [(R*, R*)-(+/-)-4[2-[(3-chlorophenyl)-2-hydroxyethyl) amino] propyl] phenoxyacetic acid] and CGP 12,177 [(+/-)-4-(3-t-butylamino-2-hydroxypropoxy)benzimidazol-2-one] are only partial agonists in many settings, have limited selectivity over other beta-adrenoceptor subtypes, and may additionally act on receptors other than beta-adrenoceptors. More efficacious and more selective agonists have been reported and, in some cases, are in clinical development but are not widely available for experimental studies. The widely used antagonist SR 59,230 [3-(2-ethylphenoxy)-1-[(1,S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanoloxalate] is not selective for beta(3)-adrenoceptors, at least in humans, and may actually be a partial agonist. Radioligands, which are suitable either for the selective labeling of beta(3)-adrenoceptors or for the nonselective labeling of all beta-adrenoceptor subtypes, are also missing. beta(3)- and beta(1)/beta(2) double knockout mice have been reported, but their usefulness for extrapolations in humans is questionable based upon major differences between humans and rodents with regard to the ligand recognition and expression profiles of beta(3)-adrenoceptors. While the common availability of more selective agonists and antagonists at the beta(3)-adrenoceptor is urgently awaited, the limitations of the currently available tools need to be considered in studies of beta(3)-adrenoceptor for the time being.

Beta3-adrenoceptors in urinary bladder

The beta-adrenoceptor (AR) is currently classified into beta(1), beta(2), and beta(3) subtypes. A third subtype, beta(3)-AR, was first identified in adipose tissue, but has also been identified in smooth muscle tissue, particularly in the gastrointestinal tract and urinary bladder smooth muscle. There is a predominant expression of beta(3)-AR messenger RNA (mRNA) in human bladder, with 97% of total beta-AR mRNA being represented by the beta(3)-AR subtype and only 1.5 and 1.4% by the beta(1)-AR and beta (2)-AR subtypes, respectively. Moreover, the presence of beta(1)-, beta(2)-, and beta(3)-AR mRNAs in the urothelium of human bladder has been identified. The distribution of beta-AR subtypes mediating detrusor muscle relaxation is species dependent, the predominant subtype being the beta(3)-AR in humans. Recent studies have suggested that cAMP-dependent routes are not exclusive mechanisms triggering the beta-AR-mediated relaxation of smooth muscle. It has been demonstrated in rats detrusor muscle that cAMP plays a greater role in beta-adrenergic relaxation against basal tone than against KCl-induced tone and that conversely calcium-activated K(+) channels (BKca channels) play a greater role under the latter circumstances. In rat models, beta(3)-AR agonists increase bladder capacity without influencing bladder contraction and have only weak cardiovascular side effects. Although this evidence points toward the clinical utility of beta(3)-AR agonists as therapy for overactive bladder (OAB), pharmacological differences exist between rat and human beta(3)-ARs. Development of compounds with high selectivity for the human beta(3)-AR, identified by screening techniques using cell lines transfected with the human beta(1)-, beta(2)-, and beta(3)-AR genes, may mitigate against such problems. The association between the tryptophan 64 arginine polymorphism in the beta(3)-AR gene and idiopathic OAB is discussed.

Alterations of beta3-adrenoceptors expression and their myocardial functional effects in physiological model of chronic exercise-induced cardiac hypertrophy

Physical training induces cardiovascular autonomic nervous system regulation adaptations, which could result from beta adrenergic receptor (AR) modifications. Among them, beta(3 )AR alterations have been recently reported but their functional effect remained to discuss. To explain the beta(3) AR gene expression in relation to function, we simultaneously studied the left ventricle (LV) beta(3) AR mRNA and protein levels and the myocardial functional effects of a beta(3) AR agonist following physical training. Forty rats were assigned to either a control (C; N = 20) or a trained (T; N = 20) group. The treadmill running protocol was performed for 8 weeks. Histological measurements on LV slices were quantified. The beta(3) AR mRNA abundance was studied with RT-PCR and beta(3) AR protein density with Western-Blot analysis. Myocardial functional effects of a beta(3) AR agonist, BRL37344 (10(-8) M), were studied in Langendorff-perfused hearts. Histological data confirmed the adapted patterns of the physiological cardiac hypertrophy observed in T (P < 0.01), with a significant increase in arteries density (P < 0.01) and an unchanged collagen concentration. The beta(3) AR protein density was increased in T (154 +/- 38% in T vs. 100 +/- 24% in C; P < 0.05), but no change was noted concerning the beta(3) AR mRNA level. After BRL37344 perfusion LVDP, +dP/dT and -dP/dT, in C (P < 0.01), and only +dP/dT in T (P < 0.05) were decreased. Moreover, all LV hemodynamic parameters were more altered after BRL37344 in C than in T (P < 0.01).Thus, in this physiological model of cardiac hypertrophy, an increase of beta(3) AR density without beta(3) AR mRNA alteration was observed. Classical negative myocardial lusitropic and inotropic effects induced by a specific agonist of beta(3) AR were diminished in trained rats.

Polymorphisms of insulin receptor substrate 1 and beta3-adrenergic receptor genes in gestational diabetes and normal pregnancy

Gestational diabetes mellitus (GDM) is considered an important risk factor for the development of type 2 diabetes mellitus. We studied possible relations between GDM and both insulin receptor substrate 1 (IRS-1) (Gly972Arg) and beta3-adrenergic receptor (ADRB3 Trp64Arg, beta3-AR) gene mutations, considered potential modifying factors in the etiology of type 2 diabetes mellitus. We evaluated the 2 gene mutations in late gestation in 627 pregnant women, all studied using the glucose challenge test, followed (in positive tests) by the oral glucose tolerance test (100 g, Carpenter and Coustan [J Obstet Gynecol. 1982;144:768-773] criteria) We diagnosed 309 women with GDM, 41 with gestational impaired glucose tolerance and 277 normal pregnant women. Age, family history of diabetes, prepregnancy body mass index, weight gain during pregnancy, plasma glucose levels, hemoglobin A1c, islet autoantibody levels, and insulin treatment during pregnancy were all evaluated. All pregnant women were genotyped for IRS-1 (Gly972Arg) and beta3-AR (ADRB3 Trp64Arg) polymorphisms. The frequency of IRS-1 gene polymorphism was significantly higher in women with GDM than in women with a normal glucose tolerance (NGT) (P = .039), and there was a significant trend (P = .032) in the increasing frequency of mutant allele Arg from NGT > gestational impaired glucose tolerance > GDM. The search for beta3-AR gene polymorphism showed no significant differences between women with GDM and women with NGT. The X-Arg genotype of IRS-1 was significantly associated with a positive family history of diabetes in NGT (P = .006) and neared significance in GDM (P = .057). Moreover, we found that NGT carriers of both polymorphisms had a higher prepregnancy body mass index than carriers of the IRS-1 variant alone (P = .0034), the beta3-AR variant alone (P = .039), or neither (P = .048), suggesting a possible synergistic effect of the 2 gene polymorphisms. These results suggest that the IRS-1 genetic polymorphism is involved in the occurrence of gestational diabetes, as well as type 2 diabetes mellitus.

Comparison of three radioligands for the labelling of human β-adrenoceptor subtypes

We have compared the ability of three radioligands, [(125)I]-cyanopindolol, [(3)H]-CGP 12,177 and [(3)H]-dihydroalprenolol, to label the three human beta-adrenoceptor subtypes. Saturation and competition binding experiments were performed using membrane preparations from Chinese hamster ovary cells stably transfected with the three subtypes. While [(3)H]-CGP 12,177 had very similar affinity for beta(1)- and beta(2)-adrenoceptors (about 40 pM), [(125)I]-cyanopindolol and [(3)H]-dihydroalprenolol had 4- to 6-fold higher affinity for beta(2)- as compared to beta(1)-adrenoceptors (10 vs 45 and 187 vs 1,021 pM, respectively). The affinity of [(125)I]-cyanopindolol at beta(3)-adrenoceptors was considerably lower (440 pM) than at the other two subtypes. The beta(3)-adrenoceptor affinity of [(3)H]-CGP 12,177 and [(3)H]-dihydroalprenolol was so low that it could not be estimated within the tested range of radioligand concentrations (up to 4,000 pM and 30,000 pM for [(3)H]-CGP 12,177 and [(3)H]-dihydroalprenolol, respectively). We conclude that all three radioligands are ill-suited to label beta(3)-adrenoceptors, particularly in preparations co-expressing multiple subtypes. In the absence of alternatives, [(125)I]-cyanopindolol appears the least unsuitable to label beta(3)-adrenoceptors. There is a need for high-affinity radioligands which are either selective for beta(3)-adrenoceptors or reasonably non-selective among all three beta-adrenoceptor subtypes.

β3-Adrenergic eNOS stimulation in left ventricular murine myocardium

This study investigates mechanisms underlying β3-adrenergic activation of the endothelial nitric oxide synthase (eNOS) in myocardial tissue of wild-type (WT) and β3-adrenoceptor knockout (β3-KNO) mice, in the absence and presence of BRL 37344 (BRL), the preferential β3-adrenoceptor selective agonist. Nitric oxide (NO)-liberation was measured after the application of BRL (10 µmol/L), using fluorescence dye diaminofluorescein (DAF), in left ventricular cardiac preparations. Phosphorylation of eNOSSer1177, eNOSThr495, eNOSSer114, and eNOS translocation, and alterations of 8-isoprostaglandin F2α (a parameter for reactive oxygen radical generation), after application of BRL (10 µmol/L), were studied using immunohistochemical stainings in isolated, electrically stimulated (1 Hz) right atrial (RA) and left ventricular (LV) myocardium. An increased NO release after BRL application (10 µmol/L) was observed in the RA and LV myocardial tissue of WT mice, but not in β3-KNO mice. This NO liberation in WT mice was paralleled by an increased eNOSSer1177, but not eNOSThr495, phosphorylation. A cytosolic eNOS translocation was observed after the application of BRL (10 µmol/L) only in the RA myocardial tissue of WT mice. A BRL (10 µmol/L)-dependent increase in eNOSSer114 phosphorylation was observed only in the LV myocardial tissue of WT mice; this was paralleled by an increase in 8-isoprostaglandin F2α. In murine myocardium, 3 β3-adrenoceptor-dependent activation pathways for eNOS exist (i.e., a translocation and phosphorylation of eNOSSer1177 and eNOSSer114). These pathways are used in a regional-dependent manner. β3-adrenergic oxygen-derived free radical production might be important in situations of enhanced β3-adrenoceptor activation, as has been described in human heart failure.

Polymorphism at the ?3-adrenergic receptor (ADRB3) locus of Merino sheep and its association with lamb mortality

Beta3-adrenergic receptors are predominantly found on the surface of adipocytes and are major mediators of the lipolytic and thermogenic effects of high catecholamine concentrations. Recently, variation in the ovine beta3-adrenergic receptor (ADRB3) gene has been reported to be associated with lamb survival. In this study, polymerase chain reaction-single strand conformational polymorphism analysis of part of the ADRB3 intron was used to genotype 4488 Merino lambs born at 10 farms throughout the South Island of New Zealand. Univariate and multivariate odds ratios for each allele revealed a significant association of the E allele with cdd survival and of the D allele with mortality. This variation at the ADRB3 locus may assist in the genetic selection for survival in Merino sheep.

Differential coupling of beta3A- and beta3B-adrenergic receptors to endogenous and chimeric Galphas and Galphai

Chimeric G proteins made by replacing the COOH-terminal heptapeptide of G(alpha)q with the COOH-terminal heptapeptide of G(alpha)s or G(alpha)i were used to assess the relative coupling of beta(3)-adrenergic receptor (beta(3)-AR) splice variants (beta(3A) and beta(3B)) to G(alpha)s and G(alpha)i. The G(alpha)q/s and G(alpha)q/i chimeras transformed the response to receptor activation from regulation of adenylyl cyclase to mobilization of intracellular calcium (Ca(2+)(i)). Complementary high-throughput and single-cell approaches were used to evaluate agonist-induced coupling of the receptor to the G protein chimeras. In cells stably transformed with rat beta(3)-AR, transfected with the G protein chimeras, and evaluated using a scanning fluorometer, beta(3)-AR-induced coupling to G(alpha)q/s produced a rapid eightfold increase in Ca(2+)(i) followed by a slow decay to levels 25% above baseline. G(alpha)q/i also linked rat beta(3)-AR to mobilization of Ca(2+)(i) in a similar time- and agonist-dependent manner, but the net 2.5-fold increase in Ca(2+)(i) was only 30% of the response obtained with G(alpha)q/s. Activation of the rat beta(3)-AR also increased GTP binding to endogenous G(alpha)i threefold in membranes from CHO cells stably transformed with the receptor. A complementary single-cell imaging approach was used to assess the relative coupling of mouse beta(3A)- and beta(3B)-AR to G(alpha)i under conditions established to produce equivalent agonist-dependent coupling of the receptor splice variants to G(alpha)q/s and to increases in intracellular cAMP through endogenous G(alpha)s. The beta(3A)- and beta(3B)-AR coupled equivalently to G(alpha)q/i, but the temporal patterns of Ca(2+)(i) mobilization indicated that coupling was significantly less efficient than coupling to G(alpha)q/s. Collectively, these findings indicate less efficient but equivalent coupling of beta(3A)- and beta(3B)-AR to G(alpha)i vs. G(alpha)s and suggest that differential expression of the splice variants would not produce local differences in signaling networks linked to beta(3)-AR activation.

Increased Ca2+ sensitivity and protein expression of SERCA 2a in situations of chronic beta3-adrenoceptor deficiency

This study investigated the influence of chronic beta(3)-adrenoceptor deficiency on myocardial function. Therefore, we investigated Ca(2+)-regulatory proteins, SERCA 2a activity, and myofibrillar and mitochondrial function in hearts of wild-type (WT, n=7) and beta(3)-adrenoceptor knockout mice (beta(3)-KNO, n=7). Morphometric heart analysis showed no difference between WT and beta(3)-KNO. No alterations were observed for the protein expression of the ryanodine receptor or phospholamban. However, in beta(3)-KNO mice, protein expression of SERCA 2a and phospholamban phosphorylation were significantly increased. These changes were accompanied by an increased SERCA 2a activity in beta(3)-KNO. Alterations in phospholamban phosphorylation were independent of alterations in beta(1)/beta(2)-adrenoceptor distribution and protein expression of G proteins in beta(3)-KNO. Measurement of myofibrillar Ca(2+) sensitivity showed no difference in the Ca(2+)/force relation for WT and beta(3)-KNO. The same seems to hold true for mitochondrial function since the protein expressions of cytochrome c, uncoupling protein 3 and cytochrome c oxidase subunit IV were similar in WT and beta(3)-KNO. The conclusion is that depression of beta(3)-adrenergic stimulation may modulate the protein expression of SERCA 2a and phospholamban phosphorylation, thereby improving sarcoplasmic reticulum Ca(2+) uptake. Thus, beta(3)-adrenergic depression may be a therapeutic aim in situations of impaired SERCA 2a activity, e.g. for the treatment of heart failure.

Clinical features of nonalcoholic steatohepatitis in Japan: Evidence from the literature

Metabolic syndrome, that is, obesity, hypertension, hyperlipidemia, and insulin resistance with hyperinsulinemia, is a new disease entity prevailing worldwide, and nonalcoholic steatohepatitis (NASH) is believed to be a hepatic expression of this syndrome. NASH is characterized by zone 3-dominant hepatic steatosis with ballooned hepatocytes and Mallory bodies, zone 3 pericellular and perivenular fibrosis with or without bridging fibrosis, and lobular inflammatory cell infiltration. Indeed, 90% of NASH has been revealed to be complicated by visceral obesity, and two-thirds of NASH patients fulfill the criteria of metabolic syndrome. Therefore, a variety of lifestyle-related diseases such as obesity, hypertension, hyperlipidemia, and diabetes mellitus may share the same background. NASH is most prevalent and well characterized in Caucasians; however, little is known about its occurrence in Asia-Oceania, because obesity has not been frequent in countries in these areas. Obesity is expected to become a serious social problem in Asia-Oceania in the next two decades, so we need to prevent a corresponding increase of NASH. For that purpose, we need to know much about not only NASH but also ourselves. To elucidate the status of NASH in Japan, recent progress in the study of NASH in Japan is reviewed in this article.

Beta3-adrenergic receptor gene, body mass index, bone mineral density and fracture risk in elderly men and women: the Dubbo Osteoporosis Epidemiology Study (DOES)

Background

Recent studies have suggested that the Arg allele of β3-adrenergic receptor (ADRB3) gene is associated with body mass index (BMI), which is an important predictor of bone mineral density (BMD) and fracture risk. However, whether the ADRB3 gene polymorphism is associated with fracture risk has not been investigated. The aim of study was to examine the inter-relationships between ADRB3 gene polymorphisms, BMI, BMD and fracture risk in elderly Caucasians.

Methods

Genotypes of the ADRB3 gene were determined in 265 men and 446 women aged 60+ in 1989 at entry into the study, whose BMD were measured by DXA (GE Lunar, WI USA) at baseline. During the follow-up period (between 1989 and 2004), fractures were ascertained by reviewing radiography reports and personal interviews.

Results

The allelic frequencies of the Trp and the Arg alleles were 0.925 and 0.075 respectively, and the relative frequencies of genotypes Trp/Trp, Trp/Arg and Arg/Arg 0.857, 0.138 and 0.006 respectively. There was no significant association between BMI and ADRB3 genotypes (p = 0.10 in women and p = 0.68 in men). There was also no significant association between ADRB3 genotypes and lumbar spine or femoral neck BMD in either men and women. Furthermore, there were no significant association between ADRB3 genotypes and fracture risk in both women and men, either before or after adjusting for and, BMD and BMI.

Conclusion

The present data suggested that in Caucasian population the contribution of ADRB3 genotypes to the prediction of BMI, BMD and fracture risk is limited.

Beta 3 adrenergic receptor Trp64Arg polymorphism and manifestation of coronary artery disease in Arabs

The substitution of tryptophan (Trp) by arginine (Arg) at position 64 in the beta3-adrenoceptor (beta3-AR) gene has been associated with obesity, diabetes mellitus, and coronary artery disease (CAD). We have investigated whether the Trp64Arg polymorphism is associated with the manifestation of CAD or one of its important risk factors, such as obesity, diabetes mellitus, elevated cholesterol and triglyceride levels, or hypertension in the Arab population. All participating subjects were genotyped for this polymorphism using the polymerase chain reaction followed by enzymatic digestion and sequencing. In the angiographed normal control subjects (n=495), 90.3% were homozygous Trp/Trp, 9.5% were heterozygous Trp/Arg, and 0.2% were homozygous for the Arg/Arg genotype, compared to 87%, 12.3%, and 0.7%, respectively, among angiographically confirmed CAD patients (n=981). There was no statistical difference in the distribution of genotypes or allele frequencies between the CAD and control groups. We carried out a stepwise logistic regression analysis to study the possible combined effect of the genotypes and other risk factors on CAD. All variables were retained in the model, with p values of 0.014, 0.006, 0.005, < 0.001, 0.045, 0.002, < 0.001, and 0.016 for genotype, diabetes mellitus, sex, family history of CAD, obesity, myocardial infarction, smoking, and age, respectively. In conclusion, the Trp64Arg polymorphism of the beta3-AR gene does not represent an independent risk factor for CAD in Arabs. However, in the presence of other CAD risk factors, this polymorphism may be used as a predictor of CAD.