Polymorphisms in COMT, ADRB2 and HTR1A genes are associated with temporomandibular disorders in individuals with other arthralgias

Genetically predicted major depression causally increases the risk of temporomandibular joint disorders

Objective

Observational studies have reported that mental disorders are comorbid with temporomandibular joint disorder (TMD). However, the causal relationship remains uncertain. To clarify the causal relationship between three common mental illnesses and TMD, we conduct this Mendelian Randomization (MR) study.

Methods

The large-scale genome-wide association studies data of major depression, bipolar disorder and schizophrenia were retrieved from the Psychiatric Genomics Consortium. The summary data of TMD was obtained from the Finn-Gen consortium, including 211,023 subjects of European descent (5,668 cases and 205,355 controls). The main approach utilized was inverse variance weighting (IVW) to evaluate the causal association between the three mental disorders and TMD. Five sensitivity analyses including MR-Egger, Maximum Likelihood, Weighted median, MR. RAPS and MR-PRESSO were used as supplements. We conducted heterogeneity tests and pleiotropic tests to ensure the robustness.

Results

As shown by the IVW method, genetically determined major depression was associated with a 1.65-fold risk of TMD (95% CI = 1.10-2.47, p < 0.05). The direction and effect size remained consistent with sensitivity analyses. The odds ratios (ORs) were 1.51 (95% CI = 0.24-9.41, p > 0.05) for MR-Egger, 1.60 (95% CI = 0.98-2.61, p > 0.05) for Weighted median, 1.68 (95% CI = 1.19-2.38, p < 0.05) for Maximum likelihood, 1.56 (95% CI = 1.05-2.33, p < 0.05) for MR. RAPS, and 1.65 (95% CI = 1.10-2.47, p < 0.05) for MR-PRESSO, respectively. No pleiotropy was observed (both P for MR-Egger intercept and Global test >0.05). In addition, the IVW method identified no significant correlation between bipolar disorder, schizophrenia and TMD.

Conclusion

Genetic evidence supports a causal relationship between major depression and TMD, instead of bipolar disorder and schizophrenia. These findings emphasize the importance of assessing a patient's depressive status in clinical settings.

The roles of 5-HT in orofacial pain

OBJECTIVES

Acute and chronic orofacial pain are very common and remain a vexing health problem that has a negative effect on the quality of life. Serotonin (5-HydroxyTryptamine, 5-HT) is a kind of monoamine neurotransmitter that is involved in many physiological and pathological processes. However, its role in orofacial pain remains inconclusive. Therefore, this review aims to summarize the recent advances in understanding the effect exerted by 5-HT on the modulation of orofacial pain.

SUBJECTS AND METHODS

An extensive search was conducted on PubMed and Web of Science for pertinent studies focusing on the effects of 5-HT on the modulation of orofacial pain.

RESULTS

In this review, we concisely review how 5-HT mediates orofacial pain, how 5-HT is regulated and how we can translate these findings into clinical applications for the prevention and/or treatment of orofacial pain.

CONCLUSIONS

5-HT plays a key role in the modulation of orofacial pain, implying that 5-HT modulators may serve as effective treatment for orofacial pain. However, further research on the precise mechanisms underlying the modulation of orofacial pain is still warranted.

Single nucleotide polymorphisms and sickle cell disease-related pain: a systematic review

Background

Scientists have speculated genetic variants may contribute to an individual's unique pain experience. Although research exists regarding the relationship between single nucleotide polymorphisms and sickle cell disease-related pain, this literature has not been synthesized to help inform future precision health research for sickle cell disease-related pain. Our primary aim of this systematic review was to synthesize the current state of scientific literature regarding single nucleotide polymorphisms and their association with sickle cell disease-related pain.

Methods

Using the Prisma guidelines, we conducted our search between December 2021-April 2022. We searched PubMed, Web of Science, CINAHL, and Embase databases (1998-2022) and selected all peer-reviewed articles that included reports of associations between single nucleotide polymorphisms and sickle cell disease-related pain outcomes.

Results

Our search yielded 215 articles, 80 of which were duplicates, and after two reviewers (GG, JD) independently screened the 135 non-duplicate articles, we retained 22 articles that met the study criteria. The synthesis of internationally generated evidence revealed that this scientific area remains predominantly exploratory in nature, with only three studies reporting sufficient power for genetic association. Sampling varied across studies with a range of children to older adults with SCD. All of the included articles (n = 22) examined acute pain, while only nine of those studies also examined chronic pain.

Conclusion

Currently, the evidence implicating genetic variation contributing to acute and chronic sickle cell disease-related pain is characterized by modestly powered candidate-gene studies using rigorous SCD-pain outcomes. Effect sizes and directions vary across studies and are valuable for informing the design of future studies. Further research is needed to replicate these associations and extend findings with hypothesis-driven research to inform precision health research.

Polymorphisms in the HTR2A and HTR3A Genes Contribute to Pain in TMD Myalgia

Background: The aim of this study was to investigate if single nucleotide polymorphisms (SNPs) related to monoaminergic neurotransmission, in particular the serotonergic pathway, contribute to pain perception in patients with temporomandibular disorder (TMD) myalgia and if there is a correlation to jaw function as well as psychosocial factors such as stress, anxiety and depression.

Materials and Methods: One hundred and seventeen individuals with TMD myalgia were included. A venous blood or saliva sample was taken for genetic analyses and genotyped regarding HTR2A (rs9316233) HTR3A (rs1062613), HTR3B (rs1176744), SERT (5-HTTLPR) and COMT (rs4680). A clinical examination according to Diagnostic Criteria for TMD (DC/TMD) was performed and axis II data (psychosocial factors) were compared between participants with different genotypes for each gene using Kruskall–Wallis test. The characteristic pain intensity (CPI) was tested for correlations to scores for the Perceived Stress Scale, Generalized Anxiety Disorder, and Patient Health Questionnaires using Spearman's rank correlation test with Bonferroni correction for multiple testing. To further explore data factor analysis was performed to identify latent factors associated to the outcome variables.

Results: Participants carrying at least one copy of the rare allele of the HTR2A (rs9316233) and HTR3A (rs1062613) had higher CPI compared with the participants with the homozygous common genotype (P = 0.042 and P = 0.024, respectively). Correlation analyses showed several significant positive correlations between CPI on one hand, and self-reported psychosocial distress and jaw function on the other hand for several genotypes that mostly were weak to moderate. The factor analysis identified two latent variables. One was positively correlated to the HTR3B gene, jaw function and self-reported parafunctions, and the other was positively correlated to psychological distress and negatively correlated to SERT.

Conclusion: Taken together, the polymorphism rs1062613 in the HTR3A gene contributes to pain intensity in TMD myalgia. This together with positive interactions between pain variables and psychological factors in genotypes strengthens that pain and psychological distress are related. Further research is needed to explore this as well as the influence of gene-to-gene interactions on pain and psychological distress.

Preclinical models of deep craniofacial nociception and temporomandibular disorder pain

Chronic pain in temporomandibular disorder (TMD) is a common health problem. Cumulating evidence indicates that the etiology of TMD pain is complex with multifactorial experience that could hamper the developments of treatments. Preclinical research is a resource to understand the mechanism for TMD pain, whereas limitations are present as a disease-specific model. It is difficult to incorporate multiple risk factors associated with the etiology that could increase pain responses into a single animal. This article introduces several rodent models which are often employed in the preclinical studies and discusses their validities for TMD pain after the elucidations of the neural mechanisms based on the clinical reports. First, rodent models were classified into two groups with or without inflammation in the deep craniofacial tissues. Next, the characteristics of each model and the procedures to identify deep craniofacial pain were discussed. Emphasis was directed on the findings of the effects of chronic psychological stress, a major risk factor for chronic pain, on the deep craniofacial nociception. Preclinical models have provided clinically relevant information, which could contribute to better understand the basis for TMD pain, while efforts are still required to bridge the gap between animal and human studies.

Adrenergic signalling in osteoarthritis

Adrenoceptors (ARs) mediate the effects of the sympathetic neurotransmitters norepinephrine (NE) and epinephrine (E) in the human body and play a central role in physiologic and pathologic processes. Therefore, ARs have long been recognized as targets for therapeutic agents, especially in the field of cardiovascular medicine. During the past decades, the contribution of the sympathetic nervous system (SNS) and particularly of its major peripheral catecholamine NE to the pathogenesis of osteoarthritis (OA) attracted growing interest. OA is the most common degenerative joint disorder worldwide and a disease of the whole joint. It is characterized by progressive degradation of articular cartilage, synovial inflammation, osteophyte formation, and subchondral bone sclerosis mostly resulting in chronic pain. The subchondral bone marrow, the periosteum, the synovium, the vascular meniscus and numerous tendons and ligaments are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers that release NE into the synovial fluid and cells of all abovementioned joint tissues express at least one out of nine AR subtypes. During the past decades, several in vitro studies explored the AR-mediated effects of NE on different cell types in the joint. So far, only a few studies used animal OA models to investigate the contribution of distinct AR subtypes to OA pathogenesis in vivo. This narrative review shortly summarizes the current background knowledge about ARs and their signalling pathways at first. In the second part, we focus on recent findings in the field of NE-induced AR-mediated signalling in different joint tissues during OA pathogenesis and at the end, we will delineate the potential of targeting the adrenergic signalling for OA prevention or treatment. We used the PubMed bibliographic database to search for keywords such as 'joint' or 'cartilage' or 'synovium' or 'bone' and 'osteoarthritis' and/or 'trauma' and 'sympathetic nerve fibers' and/or 'norepinephrine' and 'adrenergic receptors / adrenoceptors' as well as 'adrenergic therapy'.

Abdominal pain in patients with inflammatory bowel disease: association with single-nucleotide polymorphisms prevalent in irritable bowel syndrome and clinical management

BACKGROUND

Abdominal pain is a frequent symptom in patients with inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC). Pain can result from ongoing inflammation or functional disorders imitating irritable bowel syndrome (IBS). Several single-nucleotide polymorphisms (SNPs) have been associated with IBS. However, the impact of IBS genetics on the clinical course of IBD, especially pain levels of patients remains unclear.

METHODS

Data of 857 UC and 1206 CD patients from the Swiss IBD Cohort Study were analysed. We tested the association of the maximum of the abdominal pain item of disease activity indices in UC and CD over the study period with 16 IBS-associated SNPs, using multivariate ANOVA models.

RESULTS

In UC patients, the SNPs rs1042713 (located on the ADRB2 gene) and rs4663866 (close to the HES6 gene) were associated with higher abdominal pain levels (P = 0.044; P = 0.037, respectively). Abdominal pain was not associated with any markers of patient management in a model adjusted for confounders. In CD patients, higher levels of abdominal pain correlated with the number of physician contacts (P < 10^-15), examinations (P < 10^-12), medical therapies (P = 0.023) and weeks of hospitalisation (P = 0.0013) in a multivariate model.

CONCLUSIONS

We detected an association between maximal abdominal pain in UC patients and two IBS-associated SNPs. Abdominal pain levels had a pronounced impact on diagnostic and therapeutic procedures in CD but not in UC patients.

Is catechol-O-methyltransferase gene associated with temporomandibular disorders? A systematic review and meta-analysis

BACKGROUND

Temporomandibular disorder (TMD) is a condition, in which multiple factors act synergistically to determine the outcome of the disorder.

AIM

A systematic review and meta-analysis was conducted to evaluate the association between genetic polymorphisms in catechol-O-methyltransferase (COMT) and TMD.

DESIGN

Observational studies that investigated this association were included. The risk of bias and study quality were evaluated according to the Newcastle-Ottawa tool. The meta-analysis was performed for each polymorphism associated with TMD signs and symptoms.

RESULTS

A total of 1903 articles were identified. Ten remained in the qualitative analysis: six were classified as low risk of bias and four with moderate risk of bias, and three were included in the meta-analysis. The polymorphism rs6269, in the genotypic model (0.65; CI = 0.44-0.97; P = .04) and in the allelic model (0.73; CI = 0.54-0.98; P = .04), was associated with myofascial pain. The rs9332377 was associated with myofascial pain in the genotypic model (2.69; CI = 1.51-4.76; P = .0007) and in the allelic model (1.46; CI = 1.01-2.13; P = .05) and with painful TMD in the genotypic model (2.08; CI = 1.27-3.40; P = .004) and in the allelic model (1.34 CI = 0.98-1.82; P = .06).

CONCLUSION

The polymorphisms in COMT were significantly associated with TMD.

COMT rs4818, pain sensitivity and duration, and alveolar bone grafting of oral clefts

PURPOSE

Verifying whether the mutation in COMT rs4818 could be involved in pain modulation.

METHODS

Thirty-two individuals born with cleft lip and palate that underwent bone graft from the iliac crest bone were assessed at 12, 24, 48, 72 h, and 7 days regarding their pain experience using a visual analogic scale. DNA from each participant was collected from saliva samples, and genotyping of rs4818 was performed using TaqMan chemistry. Overrepresentation of rs4818 alleles was tested using chi-square or Fisher's exact tests with an alpha of 0.05.

RESULTS

Of the 32 individuals, eighteen reported long pain duration, nine reported high pain intensity, and fourteen low pain intensity up to 48 h. No differences were found in the distribution of individuals depending on the reported pain by sex (p = 0.12), age (p = 0.42), or cleft type (p = 0.5). The distribution of COMT r4818 alleles was different depending on the intensity and duration of pain. Carriers of the C wild-type allele were four times more likely to show high pain intensity and duration (odds ratio = 4.29, 95% confidence interval 1.13-16.18), meaning that the G variant allele is protective.

CONCLUSION

COMT rs4818 is associated with postoperative pain after alveolar bone grafting.