Salivary biomarkers : diagnostic potential in oral and systemic diseases in epidemiological surveys

Abstract

Human saliva is a fluid with many biological functions, and essential for the maintenance of oral health. Several studies report local and systemic biomarkers appearing in saliva, including electrolytes, blood products, enzymes and tissue destruction molecules, inflammatory markers as well as proteins putatively associated with different diseases. However, the clinical utility of salivary diagnostics for the assessment of oral and systemic disease remains elusive. The general aim of this project was to investigate the utility of salivary biomarkers for diagnostic potential of oral- and systemic diseases in large populations. This thesis consists of two different projects:

(i) Skåne cohort. A cross-sectional study (Studies I and II): 451 individuals were randomly selected and enrolled for these investigations, including 51% women. All participants were asked to complete a questionnaire, a medical history was taken, a clinical examination was made and stimulated saliva samples were collected.

(ii) PAROKRANK sub-cohort (Periodontal disease and the relation to myocardial infarction). (Studies III and IV): A case-control study comprising 400 subjects. In total 200 consecutive patients with a first acute myocardial infarction (AMI) admitted to coronary care units in Sweden from May 2010 to December 2011, and 200 controls without previous AMI, matched for age, gender, residential area were included during the same time period. Dental examinations were performed, blood and stimulated saliva samples were collected eight to ten weeks after the myocardial infarction (MI). Matched controls were examined within one to two weeks after the MI patients.

Study I: The aim of this study was to investigate if selected salivary biomarkers could be used for epidemiological studies for detection of periodontitis. Our findings showed that patients with severe periodontitis had elevated salivary concentrations of interleukin (IL) -1β (IL-1β) and matrix metalloproteinase (MMP) -8 (MMP-8), as well as and increased ratio of MMP-8/ tissue inhibitor of metalloproteinase-1 (TIMP-1).

Study II: The aim of this study was to investigate if certain salivary biomarkers could be used for detection of common systemic inflammatory diseases. The results of our study showed that salivary IL-8 concentrations were higher in patients with bowel disease and subjects who had experience of tumor diseases. MMP-8 levels were elevated in saliva from patients with diabetes, muscle and joint diseases or previously had undergone cardiac surgery.

Study III: The aim of this study was to investigate whether salivary concentrations of selected cardiovascular biomarkers could be used to identify patients with a previous MI and whether such markers, in plasma and saliva, were related to periodontal status. There was no difference between participants with or without MI in regards of N-terminal prohormone of brain natriuretic peptide (NT- pro BNP) and growth differentiation factor-15 (GDF-15) levels in saliva. However, cystatin C, NT- pro BNP and GDC-15 levels were higher in MI patients with other co-morbidities. The levels of cystatin C were lower in saliva from patients with MI. GDF-15 levels correlated with periodontal status in both groups. Further, there was no correlation between plasma and saliva levels.

Study IV: The aim of this study was to explore the levels of the inflammatory markers, MMP-8, MMP-9, TIMP-1 and myeloperoxidase (MPO) in saliva with regards to previous MI and periodontal disease. The analyzed biomarkers correlated significantly with each other and most of the periodontal parameters in both study groups. Salivary MMP-8 and MPO levels were significantly higher in non- MI subjects.

In conclusion, the findings in this project indicates that certain salivary biomarkers have the potential to be used for screening purposes in epidemiological studies related to both oral and systemic diseases. In addition, the selected salivary biomarkers in our studies could be seen as markers for increased local and systemic inflammation.