Are β3 -adrenoceptor gene polymorphisms relevant for urology?

AIMS

β₃ -adrenoceptors (ARs) are an important drug target for the treatment of overactive bladder syndrome (OAB) and are under investigation for other indications. The human β₃ -AR gene is polymorphic; an exchange of amino acid tryptophan (Trp) for arginine (Arg) in position 64 of the receptor protein is the most frequent and best-studied polymorphism. A narrative review on the impact of β₃ -AR polymorphisms on urological disease and its treatment is presented.

RESULTS

Two out of four studies have reported that the 64Arg allele was found more frequently in subjects with OAB than in healthy controls. A large study in a highly selective population (men undergoing prostatectomy for cancer treatment) did not confirm this. On the other hand, studies examining symptom severity typically found little difference between 64Arg and 64Trp carriers. In vitro studies with endogenously expressed β₃ -AR reported a decreased lipolytic response in human adipose tissue. Studies with heterologously expressed receptors sometimes found a decreased responsiveness to agonists including β₃ -AR agonists, but others did not confirm that.

CONCLUSIONS

The overall evidence points to carriers of the 64Arg genotype expressing fewer and/or hypofunctional β₃ -ARs and being associated with the presence of OAB but such findings were only detected inconsistently. If this hypofunctionality exists, the consequences may be of insufficient magnitude to allow a robust detection. Only adequately powered studies comparing responses with a β₃ -AR agonist in 64Arg carriers versus wild-type patients can address this.

Functional Polymorphism in the ADRB3 Gene, Encoding the Beta-3 Adrenergic Receptor, and Response to Intra-Detrusor Injection of Botulinum Toxin-A in Women with Overactive Bladder

BACKGROUND

There are reports suggesting an association between the rs4994 polymorphism in the ADRB3 gene encoding the beta-3 adrenergic receptor and OAB risk in females. The injection of botulinum toxin-A into the bladder wall is recommended as a possible treatment for OAB patients in whom first-line therapies have failed. The aim of our study was to analyze the possible association between the ADRB3:rs4994 polymorphism and the patient-perceived response to a single intra-detrusor injection of botulinum toxin-A in Polish women with overactive bladder.

METHODS

The study group consisted of 115 consecutive female patients with OAB. The response to botulinum toxin-A was evaluated at three months after injection, as absolute or relative reductions in OAB symptoms or in scores from questionnaires ICIQ-OAB (parts A and B) and ICIQ-LUTS-QoL (parts A and B). ADRB3:rs4994 variants were identified by the sequencing of genomic DNA extracted from buccal swabs.

RESULTS

There were no statistically significant differences between ADRB3:rs4994 [T];[T] homozygotes and [T];[C]+[C];[C] subjects for absolute or relative reductions in symptoms or in scores from all four questionnaire parts at three months after the injection of botulinum toxin-A.

CONCLUSIONS

Our results do not support the hypothesis that ADRB3:rs4994 polymorphism is associated with the response to the intra-detrusor injection of botulinum toxin-A in Polish females with overactive bladder.

Association Between Trp64Arg Polymorphism of Beta-3 Adrenergic Receptor Gene and Susceptibility to Overactive Bladder: A Meta-Analysis

Objective: Some studies have been carried out to investigate the association between Trp64Arg polymorphism in beta-3 adrenergic receptor gene (ADRB3) and susceptibility to overactive bladder (OAB), but the results remain inconsistent. We carried out a meta-analysis to acquire a more accurate estimation.

Methods: All eligible studies were searched in PubMed, Web of Science, Embase, and Cochrane Library. Pooled odds ratios, with 95% confidence intervals, were assessed for the association using fixed and random effects models.

Results: The overall results of this meta-analysis demonstrated that there might be an association between Trp64Arg polymorphism and susceptibility to OAB in allele model, dominant model, and heterozygote comparison with a relative risk of 2.00 (95% CI 1.36–2.93), 2.13 (95% CI 1.20–3.76), and 2.07 (95% CI: 1.13–3.79), respectively. However, in the recessive model and homozygote comparison, no significant association between ESR1 Trp64Arg polymorphism and susceptibility to OAB was observed, with a relative risk of 2.47 (95% CI 0.63–9.73) and 3.12 (95% CI: 0.79–12.35), respectively. Based on trail sequential analysis, the results turned out to be true positive in the allele model, false positive in the dominant model and heterozygote comparison, and negative in the recessive model and homozygote comparison, respectively.

Conclusion: Our analysis indicated that Trp64Arg polymorphisms in ADRB3 might increase the risk of OAB twice in the allele model, but further well-designed studies with large sample sizes are required to confirm the present findings in other modes and comparisons.

Association of gene polymorphisms with women urinary incontinence

Aim of study was set to investigate the association of women urinary incontinence (UI) with serotonin receptor HTR2A T102C and beta 3-adrenergic receptor ADRB3 Trp64Arg genes polymorphisms. The study included 110 women with Urge, Stress, and Mixed UI types and the control group – 105 continent women. Both groups have filled in the ICIQ-FLUTS questionnaire and their blood genotyping was performed. Urge UI subgroup was older and had higher body mass index (BMI) in comparison to other UI types and control group. More than half of all women had family history of UI in Stress UI and Mixed UI subgroups. The frequency of HTR2A T102C gene polymorphism’s minor allele C and genotype CC was significantly more expressed in Urge UI subgroup, as compared with control group (C-77.3 vs 58.7%, p = 0.007 and CC-57.6 vs 31.1%, p = 0.015). The ADRB3 Trp64Arg gene polymorphism did not differ between groups. The regression analysis revealed CC genotype (OR = 3.06, 95% CI: 1.11–8.43; p = 0.030) and allele C (OR = 2.53, 95% CI: 1.16–5.53; p = 0.020) were risk factors for development of Urge UI. We conclude that HTR2A T102C gene polymorphism affected the development of Urge UI.

Association between the Trp64Arg polymorphism of the ADRB3 gene and overactive bladder

BACKGROUND

The β₃ -adrenergic receptor (ADRB3) is very important in the regulation of the human detrusor muscle function. The well-known tryptophan64arginine polymorphism of the ADRB3 gene alters the response of the receptor to various stimuli, including adrenalin and noradrenalin, and may increase the susceptibility to develop overactive bladder (OAB). Therefore, this study was performed to determine whether ADRB3 Trp64Arg polymorphism is associated with the pathophysiology of OAB syndrome.

METHODS

The study group (n = 150) consists of 72 patients with OAB and 78 controls without OAB. Venous blood samples were taken from all participants to analyze the ADRB3 gene Trp64Arg polymorphism using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay. We compared the distribution of Trp64Arg polymorphism and symptom severity in both OAB and non-OAB subjects using χ² test and Mann-Whitney's U test, respectively.

RESULTS

The frequency of the 64Arg variant (heterozygous plus homozygous) in OAB and non-OAB subjects was 15.3% and 14.1%, respectively. There was no statistically significant difference between the OAB and non-OAB groups in regard to the distribution frequency of ADRB3 Trp64Arg polymorphism. The total frequency (OAB + non-OAB, 76 women and 74 men) of the Arg64 variant allele was 5.9% and 10.8% in women and in men, respectively. Although the frequency of the Arg64 variant was nearly twofold higher in men compared to women, the difference was not statistically significant.

CONCLUSIONS

These results demonstrated that the ADRB3 Trp64Arg polymorphism is not significantly associated with OAB syndrome in a sample of Turkish OAB patients.

The effect of β3-adrenoceptor gene polymorphisms on lower urinary tract function in males

PURPOSE

To clarify the role of Trp64Arg polymorphisms of the gene encoding the β₃-adrenoceptor for lower urinary tract function in males, the present study investigated the association between the Trp64Arg polymorphisms and lower urinary tract symptoms (LUTS) and function.

METHODS

This prospective observational study included patients who underwent robot-assisted radical prostatectomy. Before surgery, blood samples were collected, and analyses of β₃-adrenoceptor gene polymorphism were performed using the real-time polymerase chain reaction. The present cohort was divided into patients with wild type (Trp64Trp) and with variant type (Trp64Arg + Arg64Arg), and LUTS and lower urinary tract function before surgery were compared between them.

RESULTS

Wild type was found in 247 patients, with variant type in 129. There were no significant differences in LUTS between the two groups. Residual urine volume (PVR) (wild type: variant type = 47 ± 53 mL: 58 ± 77 mL, P = 0.04) and voiding time on uroflowmetry (wild type: variant type = 29 ± 15 s: 33 ± 17 s, P = 0.04) were significantly increased in the variant type.

CONCLUSION

The Trp64Arg variant of the β₃-adrenoceptor gene significantly increased PVR and voiding time in men. However, it was not significantly associated with the emergence of LUTS. Thus, since the effect of β₃-adrenoceptor gene polymorphisms on the genitourinary organs might be weak, whether men possess the Trp64Arg variant of the β₃-adrenoceptor gene might not critically affect urinary quality of life, but modestly affect the lower urinary tract function.

Research progress of single nucleotide polymorphism in stress urinary incontinence

Stress urinary incontinence (SUI), as one of the manifestations of pelvic floor dysfunction diseases with high incidence, seriously affects women's physical and mental health and quality of life. The etiology and pathogenesis of SUI are complex and not yet completely clear, now believed to be involved with environmental factors, genetic factors and cross-cutting factors between the two. SUI genetic susceptibility may be related to single nucleotide polymorphism. This article reviews the current studies on SUI-related single nucleotide polymorphisms.

Genetic variants and expression changes in urgency urinary incontinence: A systematic review

Aim

To perform a systematic review summarizing the knowledge of genetic variants, gene, and protein expression changes in humans and animals associated with urgency urinary incontinence (UUI) and to provide an overview of the known molecular mechanisms related to UUI.

Methods

A systematic search was performed on March 2, 2020, in PubMed, Embase, Web of Science, and the Cochrane library. Retrieved studies were screened for eligibility. The risk of bias was assessed using the ROBINS‐I (human) and SYRCLE (animal) tool. Data were presented in a structured manner and in the case of greater than five studies on a homogeneous outcome, a meta‐analysis was performed.

Results

Altogether, a total of 10,785 records were screened of which 37 studies met the inclusion criteria. Notably, 24/37 studies scored medium‐high to high on risk of bias, affecting the value of the included studies. The analysis of 70 unique genes and proteins and three genome‐wide association studies showed that specific signal transduction pathways and inflammation are associated with UUI. A meta‐analysis on the predictive value of urinary nerve growth factor (NGF) levels showed that increased urinary NGF levels correlate with UUI.

Conclusion

The collective evidence showed the involvement of two molecular mechanisms (signal transduction and inflammation) and NGF in UUI, enhancing our understanding of the pathophysiology of UUI. Unfortunately, the risk of bias was medium‐high to high for most studies and the value of many observations remains unclear. Future studies should focus on elucidating how deficits in the two identified molecular mechanisms contribute to UUI and should avoid bias.

Urinary Biomarkers in Overactive Bladder: Revisiting the Evidence in 2019

CONTEXT

In overactive bladder (OAB), after an initial outbreak of research, it is more consensual that biomarkers may be better used to phenotype patients. Herein, we revisit this topic, including some of the most promising biomarkers.

OBJECTIVE

To provide a comprehensive analysis of the actual role of biomarkers in OAB.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted, including the most relevant articles published in the last 15 yr, on nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), adenosine triphosphate (ATP), genomics, and microbiota as OAB biomarkers. Articles with no full text available or not written in English were excluded. Additional reviews were included.

EVIDENCE SYNTHESIS

Urinary NGF, BDNF, and ATP are increased in many OAB patients. These biomarkers can help identify OAB phenotypes and select the ideal candidates for new therapies directed to neurotrophic and purinergic pathways. Circulating urinary miRNA may be useful for establishing the ideal moment for bladder outlet obstruction relief and will eventually lead to the development of therapeutic agents that inhibit or reverse fibrotic pathways in the bladder. Urinary microbiota seems to be related to OAB symptoms, in particular urgency urinary incontinence, and may have strong implications in the prevention, diagnosis, and treatment of OAB.

CONCLUSIONS

In the future, physicians may consider the use of biomarkers to identify distinct OAB phenotypes, with distinct causal mechanisms, selecting patients for specific target therapies with expected better outcomes.

PATIENT SUMMARY

Overactive bladder biomarkers can be useful for phenotype patients and for selecting more effective target therapies.

Role of β-3 adrenergic receptor polymorphism in overactive bladder

AIMS

Women with overactive bladder (OAB) have a higher frequency of a single-nucleotide polymorphism (SNP) at codon 64 of the β-3 adrenergic receptor gene (ADRB3). Since the SNP results in an amino acid substitution that could theoretically alter receptor protein function, we hypothesized that those with the SNP would display greater OAB symptom severity. Therefore we aimed to compare OAB severity between women with this SNP and women with the wild type genotype.

METHODS

A retrospective cohort study was performed in women with bothersome OAB from two academic institutions. Banked blood samples were tested for the codon 64 SNP. Women were divided into two groups based on genotype: wild-type (WT) and heterozygous (HZ). We compared mean OAB Symptom Severity questionnaire (OAB-q) scores between groups using t tests. Linear regression was performed to control for potential confounders.

RESULTS

Of the 303 women with OAB, 254 (83.8%) had the WT genotype, and 49 (16.2%) the HZ genotype. There were no homozygous women for the rare allele. The majority were Caucasian (86%) and non-Hispanic (97%). There were no significant differences in mean OAB-q symptom severity scores (WT 21.2 ± 7 vs HZ 22.0 ± 6.6; P = 0.49) and quality of life scores (WT 39.6 ± 15.5 vs HZ 39.1 ± 16.6; P = 0.83) between groups. These remained nonsignificant in a linear regression model.

CONCLUSIONS

In a predominantly non-Hispanic, Caucasian population of women with bothersome OAB, symptom severity was not related to ADRB3 codon 64 SNP genotype.

β3-Adrenoceptor agonists for overactive bladder syndrome: Role of translational pharmacology in a repositioning clinical drug development project

β3-Adrenoceptor agonists were originally considered as a promising drug class for the treatment of obesity and/or type 2 diabetes. When these development efforts failed, they were repositioned for the treatment of the overactive bladder syndrome. Based on the example of the β3-adrenoceptor agonist mirabegron, but also taking into consideration evidence obtained with ritobegron and solabegron, we discuss challenges facing a translational pharmacology program accompanying clinical drug development for a first-in-class molecule. Challenges included generic ones such as ligand selectivity, species differences and drug target gene polymorphisms. Challenges that are more specific included changing concepts of the underlying pathophysiology of the target condition while clinical development was under way; moreover, a paucity of public domain tools for the study of the drug target and aspects of receptor agonists as drugs had to be addressed. Nonetheless, a successful first-in-class launch was accomplished. Looking back at this translational pharmacology program, we conclude that a specifically tailored and highly flexible approach is required. However, several of the lessons learned may also be applicable to translational pharmacology programs in other indications.

Systematic review and metaanalysis of genetic association studies of urinary symptoms and prolapse in women

OBJECTIVE

Family studies and twin studies demonstrate that lower urinary tract symptoms and pelvic organ prolapse are heritable. This review aimed to identify genetic polymorphisms tested for an association with lower urinary tract symptoms or prolapse, and to assess the strength, consistency, and risk of bias among reported associations.

STUDY DESIGN

PubMed and HuGE Navigator were searched up to May 1, 2014, using a combination of genetic and phenotype key words, including "nocturia," "incontinence," "overactive bladder," "prolapse," and "enuresis." Major genetics, urology, and gynecology conference abstracts were searched from 2005 through 2013. We screened 889 abstracts, and retrieved 78 full texts. In all, 27 published and 7 unpublished studies provided data on polymorphisms in or near 32 different genes. Fixed and random effects metaanalyses were conducted using codominant models of inheritance. We assessed the credibility of pooled associations using the interim Venice criteria.

RESULTS

In pooled analysis, the rs4994 polymorphism of the ADRB3 gene was associated with overactive bladder (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.7-3.6; n = 419). The rs1800012 polymorphism of the COL1A1 gene was associated with prolapse (OR, 1.3; 95% CI, 1.0-1.7; n = 838) and stress urinary incontinence (OR, 2.1; 95% CI, 1.4-3.2; n = 190). Other metaanalyses, including those for polymorphisms of COL3A1,LAMC1,MMP1,MMP3, and MMP9 did not show significant effects. Many studies were at high risk of bias from genotyping error or population stratification.

CONCLUSION

These metaanalyses provide moderate epidemiological credibility for associations of variation in ADRB3 with overactive bladder, and variation of COL1A1 with prolapse. Clinical testing for any of these polymorphisms cannot be recommended based on current evidence.