Effects of melatonin treatment on oxidative stress on muscle and inflammation in rats with apical periodontitis submitted to a high-fat diet

Abstract

To understand how obesity triggers numerous physiological dysfunctions, several dietary models are used in animals in order to verify and relate how excessive weight gain affects the health of animals. Numerous chronic diseases related to excess adiposity have been increasing over the years, due to lifestyle. In fact, obesity is a multifactorial condition and one of the main contributors to the development of hypertension, diabetes mellitus, cardiovascular and cerebrovascular diseases and metabolic syndrome. It is important to emphasize that these pathologies are associated with chronic inflammation, which is characterized by the exacerbated production of inflammatory mediators, which are associated with the activation of inflammatory signaling pathways, an increase in free radicals and reactive oxygen species (ROS) that, in imbalance, favors the oxidative stress. Given the close relationship between inflammation and oxidative stress, the role of ROS and antioxidant systems has drawn attention in recent years in the pathogenesis of periodontal tissue injury. Apical periodontitis (AP) is an inflammation that results in the destruction of periradicular tissues, affecting several damages to the dental pulp. As the inflammatory process progresses, the body triggers a series of immune responses, recruiting various classes of immunocompetent cells, intercellular messengers and effector molecules. The therapeutic effects of melatonin in periodontitis have been very well documented in several in vitro studies, in animals and clinical trials, mainly in periodontitis by decreasing bone resorption and elimination of reactive oxygen species. However, there are few studies investigating the effects of apical periodontitis associated with high-fat diet models and melatonin treatment on oxidative stress. Therefore, the aim of this study is to investigate the effects of the association of apical periodontitis, high-fat diet and ME treatment on oxidative stress and inflammation in gastrocnemius muscle in rats. For that, 80 rats (Wistar, males, 60 days old) will be distributed in 8 groups (n= 10): 1) control (CN); 2) PA; 3) HFD; 4) HFD+PA (HFDPA); 5) CN+ME (CNME); 6) PA+ME (PAME); 7) HFD+ME (HFDME); 8) HFD+PA+ME (HFDPAME). Initially the HFD, HFDPA, HFDME and HFDPAME groups will be fed for 107 days with a diet consisting of 45.5% standard chow + 22.7% animal lard + 22.7% vegetable fat + 9% sucrose; the other groups will receive a standard diet. On the 7th day, the PA, HFDPA, PAME and HFDPAME groups will undergo BP induction and, after 70 days, they will receive ME (5 mg/Kg, diluted in drinking water, for 30 days). At the end of treatment, the following parameters will be evaluated: 1) Plasma concentrations of TNF-±, IL-1² and LPS; 2) Evaluation of oxidative stress in the gastroecnemic muscle: a) lipid and protein oxidative damage by measuring the concentrations of carbonyl protein (PC) and thiobarbituric acid reactive substances (TBARs); b) non-enzymatic antioxidant defense by measuring the total non-enzymatic antioxidant capacity (FRAP) and reduced glutathione (GSH) concentrations; c) enzymatic antioxidant defense through the activity of the enzymes Superoxide disumutase (SOD), Catalase (CAT) and Glutathione peroxidase (GPx). Statistical analysis will be performed by ANOVA analysis of variance followed by Tukey's test, the significance level will be 5%. (AU)