Estimation of Adropin and Irisin levels in saliva and serum in generalized periodontitis patients with and without Type 2 Diabetes mellitus (T2DM)

Diabetes mellitus is a disease associated with a series of symptoms and etiologies ranging from a cell-mediated autoimmune disease to a non-autoimmune metabolic disorder. Insulin secretion can be inhibited by proinflammatory cytokines causing dysregulation of beta cells and ultimately to Type 2 Diabetes mellitus (T2DM). Periodontitis can contribute to adipose tissue inflammation and subsequent systemic insulin resistance. Periodontitis and T2DM have common mechanisms that are associated with altered immune-inflammatory responses at local and systemic levels.

Adropin is a multifunctional peptide, which, being primarily secreted by the liver and brain, modulates the metabolic homeostasis of the heart, vasculature, kidney, and skeletal muscles in connection with nutrition status. Adropin exerts its biological effects through binding with three distinct membrane receptors, which seem to be responsible for various modulations of target tissue metabolism. The favourable effects of adropin on vascular structure and function are mediated by vascular endothelial growth factor (VEGF) via binding with VEGF receptor 2 (VEGFR2). Periodontal lesions are associated with activation of pathological angiogenesis and a high number of newly formed blood vessels. The gingival epithelium activates the angiogenic chain reaction in the connective compartment through VEGFR2 via VEGF secretion. Adropin activates the glucose transporter 4 receptor through its Akt phosphorylation and improves glucose metabolism. It also inhibits inflammation by suppressing the production of several pro-inflammatory cytokines (tumour necrosis factor alpha, C-reactive protein, and interleukin-6). However, the clinical significance of adropin levels in different patient populations remains unclear.

Irisin a novel myokine discovered in 2012, is a secreted peptide that is C-terminally cleaved from fibronectin type III domain-containing protein 5 (FNDC5) in the skeletal muscles and released into the bloodstream. Lack of physical exercise, obesity, and insulin resistance (IR) have been consistently considered as high-risk factors for T2DM. It is released by skeletal muscles during physical exercise. Circulating irisin levels are negatively associated with IR. Irisin modulates the inflammatory response in pathologies which are associated with constant chronic inflammation such as Type 2 diabetes mellitus (T2DM) and periodontitis. Although there is evidence suggesting the role of irisin in promoting osteogenic differentiation and matrix secretion of Periodontal ligament cells (PDLCs) cultured in vitro, little is known about the effects of irisin on inflamed periodontal tissues, including the alveolar bone and local host cells under diabetic conditions.

To the best of our knowledge there are no studies investigating the relationship between  Adropin and Irisin levels in periodontal disease and T2DM. Hence, the aim of this study is to comparatively evaluate salivary and serum levels of  Adropin and Irisin levels in generalized periodontitis and T2DM.