[Correlation between short chain fatty acids in saliva and salivary microbiota in patients with laryngopharyngeal reflux disease].

Objective: This study aimed to compare short-chain fatty acid (SCFA) levels in saliva between patients with laryngopharyngeal reflux disease (LPRD) and healthy controls, and to explore the relationship between these SCFAs and the salivary microbiota. Methods: A retrospective case-control study was conducted, enrolling 36 patients with laryngopharyngeal reflux disease (LPRD) who visited the Department of Otorhinolaryngology Head and Neck Surgery, the Eighth Medical Center, Chinese PLA General Hospital between February and November 2023. All patients were diagnosed via pharyngeal pH monitoring. The LPRD group included 30 males and 6 females, aged 20-53 years (30.61±7.83 years). In addition, 39 healthy volunteers were recruited as the control group, comprising 25 males and 14 females, aged 18-58 years (28.64±7.97 years). Unstimulated mixed saliva samples were collected from all participants. Concentrations of eight SCFAs (acetic acid, propionic acid, isobutyric acid, butyric acid, valeric acid, isovaleric acid, hexanoic acid, and heptanoic acid) in saliva were quantified using gas chromatography-mass spectrometry (GC-MS). Salivary DNA was extracted, followed by amplification and sequencing of the 16S rRNA gene to analyze the microbiota composition at the genus level. The SCFA concentrations and the differences in bacterial species between the LPRD and control groups were compared, and the correlation between SCFA concentrations and the relative abundance of different bacterial genera in the salivary microbiota was analyzed. All statistical analyses were performed using R version 3.6.1 and SPSS version 26.0, while, microbiome analyses were conducted using R language. Results: Salivary hexanoic acid concentration was significantly higher in the LPRD group than in the control group [(29.50±19.61) ng/ml vs. (10.15±3.65) ng/ml; t=-2.72, P<0.05]. Significant differences in the relative abundance of 17 bacterial genera were observed between the two groups (P<0.05), including Prevotella, Butyrivibrio, Streptococcus, and Actinomyces. Correlation analysis revealed that hexanoic acid concentration was significantly positively correlated with the abundance of Butyrivibrio (γ=0.73, P<0.05) and Streptococcus (γ=0.78, P<0.05), while showing a significant negative correlation with Actinomyces (γ=-0.73, P<0.05). Conclusion: Elevated salivary hexanoic acid levels may be associated with the development of LPRD. Dysbiosis of the salivary microbiota might contribute to LPRD pathogenesis by altering the concentrations of SCFA, particularly hexanoic acid.