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| Author(s): |
Alan Fappi
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2018-06-04 |
| Examining board members: |
Edmar Zanoteli;
Maria Julia Marques;
Anselmo Sigari Moriscot;
Sueli Mieko Oba Shinjo
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| Advisor: | Edmar Zanoteli |
| Abstract | |
Several conditions may be related to muscle atrophy, such as inactivity, aging, septicemia, diabetes, cancer and use of glucocorticoids. In a previous attempt to prevent such glucocorticoid catabolic condition, through the supplementation of omega-3 (N-3), we observed a worsening of muscular atrophy, affecting more types of muscle fibers, usually spared by glucocorticoid, type 1 fibers for example. However, it was not possible to determine the properties of this interaction. Therefore, the objective of this study was to evaluate the action of omega-3 associated with dexamethasone and different glucocorticoids in equipotent dose on body weight; muscle cross-sectional area; fatty acid profile; gene expression of muscle transcription factors and atrogenes (Atrogin-1 and MuRF-1); protein expression of IGF-1/Akt/mTOR, Ras/Raf/MEK/ERK and Myostatin/Smad2/3 pathways components; and expression of glucocorticoid receptors in the skeletal musculature of rats. Methods: Wistar rats given orally or not with omega-3 (100mg/kg/day of EPA) for 40 days received subcutaneous dexamethasone (DX) (2.5 or 1.25mg/kg/day) during the last 10 days of supplementation. For the other glucocorticoids, rats without supplementation received deflazacorte (DC) or methylprednisolone (MP) in dose/volume equivalent to that of dexamethasone (DC 10 or 20mg/kg/day and MP6.7 or 13.3mg/kg/day) for 10 days. Comprising 10 groups: CT, N-3, DX1.25, DX2.5, DX1.25 + N-3, DX2.5 + N-3, MP6, MP13, DC10 and DC20. Through histological, immunohistochemical, real-time PCR and Western blotting, we evaluated the transverse area of the different muscle fibers; the expression of glucocorticoid receptor; the gene expression of atrogenes and transcription factors; protein expression of the IGF-1, Myostatin and MEK/ERK pathways. Results: N-3 administration influenced DEXA atrophy causing increased atrophy in type 1 and 2A fibers, increased protein expression of total FoxO3a, P-Smad3, LC3-II, and REDD-1 gene (mRNA), Atrogin-1/MAFbx isolated omega-3 reduced the expression of P-FoxO3a, PGC1alpha, the amount of arachidonic acid and the expression of IRS-1 mRNA with increased expression of LC3-II. The comparison between glucocorticoids showed that MP13 had a greater impact on body and muscle weight; the DC10 caused less atrophy in 2B fibers in relation to the other glucocorticoids. DX, caused greater impact on total Akt compared to the other glucocorticoids, in P-Akt the DX1,25 group had lower expression to other equipotent dose glucocorticoids. All glucocorticoids affect the expression of P-FOXO3a. In the of ERK1/2 and P-ERK1/2 protein expression, the MP6 was the group with the greatest damage to the phosphorylation in relation to the others in equipotent dose. In the evaluation of the Myostatin/Smad2/3 pathway MP 6, MP13 and DC20 showed higher expression of total Smad2/3 and P-Smad3. The gene expression of REDD-1 and MYOD was increased in the MP6 and MP13 groups compared to the other groups, REDD2 in the DC20 group was lower in relation to the DX2.5 group. Myostatin expression was lower in the DX2.5 and DC20 groups, with DC being the drug with less impact on atrogenes MuRF-1 and Atrogin-1. DX1.25 and DX2.5 caused lower IRS-1 expression among the glucocorticoid groups. Conclusions: Omega-3 may increase muscle atrophy caused by DX in fibers 1 and 2A, possibly related to increased expression of FoxO3a, REDD-1 and Atrogin-1, decreased expression of PGC1alpha and P-FoxO3a, in the amounts of acid arachidonic with increased lysosomal activity. Comparing different glucocorticoids, MP tends to produce a greater impact on body and muscular weights, DC is less harmful to type 2B fibers, however, it predominantly affects type 1 fibers, in the same way as DX in the dosage of 1.25mg/kg/day. DX tends to affect total and phosphorylated Akt expression more than other glucocorticoids. MP affects more the Ras/Raf/MEK/ERK pathway and REDD-1 expression in relation to the other glucocorticoids, and DC and MP show a higher expression of total and phosphorylated Smad2/3 compared to DX after 10 days of administration (AU) | |
| FAPESP's process: | 13/23191-6 - Glucocorticoid effects on molecular pathways related to the muscular trophysm in rats and the effect of omega-3 fatty acid (EPA/DHA) on dexametasone-induced muscle atrophy |
| Grantee: | Alan Fappi |
| Support Opportunities: | Scholarships in Brazil - Doctorate |