Twenty systemically healthy subjects with healthy periodontium and 20 patients with stage III grade B generalized periodontitis were enrolled for this cross-sectional study. The study was performed in accordance with the Helsinki Declaration of 1975, as revised in 2013. Before starting, the informed consent was obtained from all participants which was approved by the human subject's ethics board of Istanbul Medipol University's Faculty of Dentistry for use and access of human subjects in research.For all study subjects, the exclusion criteria were (1) use of contraceptive drugs; (2) use of antibiotics, anti-inflammatory drugs, or immunosuppressants in the last 3 months before the study; (3) alcohol consumption; (4) pregnancy or breastfeeding; (5) taking drugs that could cause side effects such as gingival hypertrophy or hyperplasia; and (6) any periodontal treatments in the 3 months prior to enrollment. All participants were systemically healthy and non-smokers (never smokers).The clinical periodontal parameters (plaque index (PI), probing pocket depth (PD), gingival recession (GR), clinical attachment loss (CAL), and bleeding on probing (BOP)) were recorded on periodontal charts in each patient .For the analysis of irisin and IL-6 specific ELISA Kits (Elabscience, Houston, Texas, USA) were used to determine the molecules in both serum and saliva samples in accordance with the manufacturer's instructions. The minimum detectable doses of irisin and IL-6 for saliva with these assay kits were 1,28 and 13,22 pg/ml, respectively. For serum, minimum detectable irisin dose was 175,43 whereas IL-6 was 0,06 pg/ml. All samples were run in duplicate, and values have been averaged.
Irisin is novel adipomyokine known as a mediator of physical activity that produced mainly by skeletal muscle and adipose tissues. It is cleaved from the fibronectin type III domain-containing protein 5 (FDNC5), which is, in turn, induced by peroxisome proliferator-activated receptor-ɣ co-activator 1-α (PGC-1α). Several studies reported that irisin is related with pathogenesis of many diseases which are known to be associated with periodontal disease such as obesity, diabetes mellitus, rheumatoid arthritis, cardiovascular disease, nonalcoholic fatty liver disease and metabolic bone diseases. There are several studies those have reported that increased IL-6 levels are associated with progression and severity of periodontitis . Recently, it has been shown that irisin is expressed in human periodontal ligament cells (hPDL), dental pulp stem cells and osteoblasts. Also, a few studies revealed that irisin promotes growth, migration and matrix formation in hPDL cells and cementoblast differentiation. To the best our knowledge, there 's one study has been reported that the higher levels of irisin in saliva in patient with chronic periodontitis