Evaluation of insulin and inflammatory pathways in skeletal muscle tissue of adult rats, offspring of rats with true endodontic-periodontal lesions

Abstract

Fetal programming suggests that adverse stimuli when applied during early fetal development can alter offspring metabolism, increasing the risk of disease in adulthood. Studies have shown that both maternal periodontal disease (PD) and apical periodontitis (AP) in rats promote insulin resistance (IR) in their adult offspring. However, studies investigated the effects of maternal endodontic-periodontal lesions (EPL) on offspring health are scarce and, in these cases, the impact could be even more. The pulp and periodontium are known to have a close bond, and are intimately connected by anatomical structures such as the apical foramen, accessory canals, and dentinal tubules, which may interfere with each other's health. True EPL is an inflammatory process that extends to the pulp and periodontal tissue simultaneously, each with its origin. In addition, these pathologies, evaluated in isolation, are associated with increased tumor necrosis factor-alpha (TNF-alpha) that can stimulate IkappaB kinase (IKK) and c-Jun N-terminal protein kinase (JNK), which promote phosphorylation of insulin receptor substrate 1 (IRS-1) in serine residues, resulting in attenuation of the insulin signal (IS), contributing to IR in adult offspring. In this context, it has become essential to investigate if true EPL can promote more insulin resistance in its adult offspring. In view of this, the aim of this study will be to evaluate in female rats with LEP: 1) bone markers such as tartrate-resistant acid phosphatase (TRAP) and osteocalcin (OCN) at the site of maternal injuries. In addition, the aims of this study will be to evaluate in adult rats, offspring of rats with LEP: 1) glycemia and insulinemia; 2) insulin signaling pathway; 3) inflammatory pathway in the gastrocnemius muscle (GM). Therefore, the 28 Wistar rats (2 months old) will be distributed in 4 groups: 1) control rats; 2) rats with a AP induced in the first right upper molar; 3) rats with an induced PD in the right upper second molar; 4) rats with LEP, in which PD will be induced in the upper right second molar, and AP in the upper right first molar. The AP will be induced by exposing the pulp tissue to the oral environment, using a carbon steel drill with a 0.1 mm sphere at the end. PD will be induced by ligation with sterile silk thread. After 30 days of inducing oral inflammation, rats from all groups will be placed for mating with healthy rats. After weaning, the mother rats will be sacrificed and the hemimaxyls (on the right side) will be collected to perform the following experiment: 1) evaluation of bone markers such as tartrate-resistant acid phosphatase (TRAP) and osteocalcin (OCN) at the lesion by immunohistochemistry technique. When male offspring of all rats completet 75 days, the experiments will be performed: 1) glycemia and insulinemia, followed by the calculation of the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR); 2) total TNF-a content in GM; 3) evaluation of pp185 (IRS-1) tyrosine phosphorylation status and IRS-1 serine phosphorylation status in GM; 4) JNK and IKKa/b phosphorylation status in GM by Western blotting method. Statistical analysis will be performed by analysis of variance, followed by the Tukey test. Immunohistochemical analyzes will be performed using Kruskal Wallis' non-parametric statistical test. (p <0.05). (AU)