Evaluation of Calpaine and Caspase-3 expression in skeletal muscle tissue of rats submitted to administration of different glucocorticoids and after supplementation of omega-3 fatty acid (EPA/DHA) associated or not with dexamethasone administration

• Grant number: 17/26320-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): April 01, 2018
• Effective date (End): March 31, 2019
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Principal Investigator: Edmar Zanoteli
• Grantee: Thayane Correa Pereira Brandão
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Muscle atrophy corresponds to a loss of muscle tissue related to pathological or physiological conditions such as cancer, septicemia, immobility, fasting, and the use of glucocorticoids. Exogenous glucocorticoids are one of the most prescribed therapeutic compounds in medical practice. However, they have negative effects on several tissues, including skeletal muscle tissue, acting negatively on the IGF-1 / PI-3K / Akt / mTOR pathway, causing atrophy preferentially in type 2B fibers, activating different degradation pathways such as lysosomal, ubiquitin-proteasome and calpain, however, the previous degradation of protein complexes, such as actin-myosin, for example, is necessary for secondary degradation by other systems. Omega-3 is a fatty acid widely recommended for several benefits such as cardiovascular and central nervous systems, but other studies show deleterious action on muscle tissue in association with glucocorticoids. Further studies also show that omega-3 may influence the influx of Ca ++ by interaction with the GPR120 receptor. Considering this and that the Calpain system is calcium-dependent, it would be of great interest to evaluate whether the administration of omega-3 could thus increase skeletal muscle atrophy in a Calpain-dependent manner considering its interaction with receptor GPR120 and additionally assess the expression of caspase-3 in the muscle degradation induced by different glucocorticoids in equipotent dosage and of dexamethasone in association or not with omega-3. Objective: To evaluate the expression of calpain and caspase-3 in muscle atrophy induced by deflazacort, methylprednisolone and dexamethasone associated or not with the previous supplementation of omega-3 (EPA / DHA) in rats for 10 days. Methodology: 60 animals separated in 2 groups of 30 animals each received omega-3 (EPA / DHA) or vehicle solution for 40 days via gavage. During the last 10 days of the study, dexamethasone (Dx) 1.25mg / kg / day or saline solution was administered subcutaneously to induce muscular atrophy without discontinuation of omega-3s, 20 animals received methylprednisolone (6.7 mg / kg / day) or deflazacort (10 mg / kg / day) for 10 days simultaneously with the administration of dexamethasone, thus constituting 6 groups: Ct (control); n-3 (omega-3); Dx 1.25; Dx1.25 + n-3; MP6 and DC10. From the collected materials (tibial anterior and gastrocnemius muscles) will be made the evaluation of the protein expression of calpain and caspase-3 by Western blotting technique. For evaluation of the cross-sectional area of the fibers and measurement of atrophy by fiber, type will be performed using the mATPase staining technique. This study may provide important insights into the molecular mechanisms that regulate muscle terrorism in the administration of glucocorticoids and dietary supplements such as omega-3.(AU)