Biomarkers are anatomical characteristics or naturally occurring measurable molecules indicating physiological or pathological state of an individual. These biomarkers have the potential to detect or predict diseases at an early stage, which is particularly beneficial in timely management of common complications of radiation therapy done in head and neck cancer treatment regime. Xerostomia is one of the most common oral complaints of radiation therapy. Saliva has an abundance of protein biomarkers; however, those related to post-radiation therapy xerostomia need to be explored further. Textural and imaging-based biomarkers are helpful in predicting xerostomia in such patients. This narrative review provides an account of salivary protein and imaging-based biomarkers of radiation therapy-induced xerostomia in head and neck cancer patients.
Xerostomia is a subjective condition of dryness of the oral cavity that may lead to several oral problems deteriorating oral health-related quality of life. This study aimed to (1) determine the prevalence of xerostomia, (2) compare the general health status, unstimulated salivary flow rate, and oral health-related quality of life in xerostomics and non-xerostomics, and (3) investigate the potential of salivary aquaporin-3 (AQP-3) as a screening biomarker for xerostomia in patients with periodontal disease. Demographics and systemic health data were collected from 109 healthy participants, 20 to 55 years old, with Community Periodontal Index (CPI) score ≥ 3. For subjective assessment of xerostomia, Shortened Xerostomia Inventory (SXI) was used. For objective assessment of xerostomia, unstimulated salivary flow rate was measured. Shortened Oral Health Impact Profile (S-OHIP) was utilized for oral health-related quality of life assessment. The collected saliva samples were processed and stored at -80°C. Quantification of salivary AQP-3 protein was done with enzyme-linked immunosorbent assay. Xerostomia was reported in 78% of the subjects based on SXI score. Median concentration of AQP-3 was significantly higher in xerostomics compared to non-xerostomics, p = 0.001. Moreover, oral health-related quality of life was significantly poor in xerostomics compared to non-xerostomics, p = 0.002. Furthermore, there were significant correlations between AQP-3 and SXI (r = 0.21, p = 0.025), AQP-3 and S-OHIP (r = 0.2, p = 0.042), S-OHIP and SXI (r = 0.37, p < 0.001), unstimulated salivary flow rate and random blood glucose level (r = 0.32, p = 0.001), and body mass index and mean arterial pressure (r = 0.44, p < 0.001). Regression analysis showed that body mass index, CPI score 3, and salivary AQP-3 were suitable predictors for presence of xerostomia. AQP-3 could be a potential screening biomarker for xerostomia in patients with periodontal disease for its early identification may help improve oral health-related quality of life of the individuals.
Inflammatory biomarkers are molecules that can offer vital information on the intricate chain of happenings and molecular processes underpinning the pathophysiology of any inflammatory disease. They can be measured in various biological samples such as blood, urine, or saliva, and are used as indicators of the presence and severity of inflammation. Measuring salivary inflammatory biomarkers is a non-invasive and relatively easy way to monitor inflammation, and it has been shown to be a useful tool in the diagnosis and management of various oral and systemic inflammatory diseases. Irisin is a novel anti-inflammatory protein and its implication and diagnostic role in inflammation have been widely studied; however, not much have been studied in oral inflammation per se. Irisin is predominantly downregulated in several inflammatory conditions, including obesity, type 2 diabetes, periodontitis, and cardiovascular diseases. This suggests that irisin may be involved in the inflammatory process, but more research is needed, especially of salivary irisin to understand its precise role. Overall, the role of irisin as an inflammatory biomarker is still an area of active research, and more studies are needed to determine its diagnostic and therapeutic potential. This review highlights the diagnostic and therapeutic potential of irisin in various systemic and oral inflammatory conditions.