Association of Peripheral-type Benzodiazepine Receptor gene Polymorphism with Sleep Bruxism

Objectives: Currently it is thought that sleep bruxism has a close relation to psychological stress. Peripheral-type Benzodiazepine Receptor (PBR) gene polymorphism has attracted attention for a sensitivity to psychological stress, but it is uncertain whether PBR gene polymorphism has an influence on sleep bruxism. Therefore, we examined connections between sleep bruxism and PBR gene polymorphism. Methods: The subjects, 14 males and 6 females with a mean age of 28.9 years, were generally healthy volunteers in this study. We amplified PBR genes using phi 29 DNA polymerase after collection with the oral mucosa cells. We identified polymorphism using direct sequencing after PBR gene amplification by Polymerase Chain Reaction (PCR). Also, we measured masseteric muscle activity during sleep using a portable electromyography for an evaluation of sleep bruxism. Furthermore, two-minute stimulated whole saliva samples were collected from the subjects both before and after sleep. We measured salivary Chromogranin A (CgA) for an index of the psychological stress. Mann-Whitney U-test was used for statistical analysis, and p<0.05 was set as significant. Results: 6 people (30%) were G/A genotypes, and 14 people (70%) were G/G genotypes. The number of the bruxism events was significantly higher with the G/A group than with the G/G group (p<0.05). Changes in the salivary CgA level decreased during sleep for the G/A group, and there was a tendency toward increase in the G/G group. Conclusion: PBR gene polymorphism group (G/A group) could be suggested as a high-risk possibility of the sleep bruxism. In addition, the reduction in the level of the stress biomarker CgA suggests that sleep bruxism might reduce psychological stress during sleep in the G/A group.