Investigating the Association between Catechol-O-Methyltransferase Gene Activity and Pain Perception in South African Patients with Different Temporomandibular Disorders Diagnoses

Abstract

Background: Temporomandibular disorders (TMD) affect a significant portion of the population, with profound psychological, behavioral, and social repercussions. Recent investigations have explored the genetic basis underlying pain perception in individuals with TMD, aiming to elucidate the role of specific genetic factors in modulating the condition. Notably, genetic variations have been implicated in the pathogenesis of TMD, particularly genes involved in pain perception pathways. One of the primary candidates is the Catechol-O-Methyltransferase (COMT) gene, which plays a crucial role in the catecholaminergic system and has been associated with the regulation of nociceptive processes. This study seeks to investigate the correlation between COMT gene activity and pain perception among South African patients diagnosed with varying forms of TMD. Methodology: In this study, a total of 196 participants were enrolled, comprising 97 patients diagnosed with TMD and 99 control participants. The control group was meticulously matched with the TMD group for age, gender, and ethnicity. Data collection involved clinical and radiological investigations, and saliva sampling. The English version of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I was utilized to evaluate all TMD participants, focusing on standard diagnostic measures based on clinical signs and symptoms of TMD, which primarily describe common physical manifestations of the disorder. Genomic DNA was extracted from saliva samples, enabling the analysis of single-nucleotide polymorphisms (SNPs) in the COMT gene, specifically targeting polymorphisms rs165774, rs9332377, rs6269, rs4646310, rs165656, and rs4680. Results: The current study demonstrated a pronounced gender disparity, with 80.41% of the participants being female and 19.59% male, suggesting that women in South Africa either exhibit a higher susceptibility to TMD or are more likely to seek treatment for the condition compared to men. The highest prevalence of TMD was observed in the white population (58.76%). Additionally, over 65% of TMD patients were diagnosed with at least two Axis I diagnoses, a figure that increased to 89% for those diagnosed with three Axis I diagnoses. The findings further indicated significant associations between several single-nucleotide polymorphisms (SNPs) in the Catechol-O-Methyltransferase (COMT) gene—specifically rs165656, rs9332377, rs4646310, rs6269, and rs165774—and both TMD and TMD-related pain. Myofascial pain with referral and myalgia showed a strong association with the COMT SNPs rs9332377 and rs4646310. Furthermore, COMT SNP rs4646310 was also associated with disability related to TMD. Conclusions: This study substantiates the hypothesis that pain is prevalent in a considerable proportion of patients affected by TMD. Furthermore, the findings reveal a significant association between COMT gene activity and pain perception in South African patients diagnosed with TMD.