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Doctoral Thesis
DOI
https://doi.org/10.11606/T.25.2021.tde-28042022-083717
Document
Author
Full name
Mizael Pereira
Institute/School/College
Knowledge Area
Date of Defense
Published
Bauru, 2021
Supervisor
Committee
Oliveira, Rodrigo Cardoso de (President)
Buchaim, Daniela Vieira
Buzalaf, Marilia Afonso Rabelo
Ponce, Jose Burgos
Title in Portuguese
Análise do perfil proteico de músculos e fígado de ratos sob o efeito da dexametasona e Beta-Hidroxi-Beta-metilbutirato
Keywords in Portuguese
Atrofia muscular
Dexametasona
Fígado
Leucina
Músculo esquelético
Abstract in Portuguese
Apesar de alguns efeitos dos glicocorticóides serem necessários às respostas metabólicas durante o estresse, a exposição crônica em altos níveis destes pode apresentar como efeitos colaterais a hiperglicemia, resistência à insulina e também a atrofia muscular. O aumento nos níveis de glicocorticoides estão presentes em diversas condições clínicas e sua administração exógena, tais como tratamentos com altas dosagens de dexametasona, estão presentes em diversos protocolos clínicos. Neste cenário o suplemento -Hidroxi- -metilbutirato (HMB) apresenta-se como uma hipótese bastante promissora para contrapor os efeitos colaterais da dexametasona, por conta de sua ação anticatabólica. Deste modo, o objetivo deste trabalho foi avaliar o perfil proteico em músculos e fígado de ratos sob o efeito do HMB, frente à um modelo agressivo de atrofia muscular induzido por dexametasona. Para isto foram utilizados 24 ratos, machos da linhagem Wistar, com 60 dias, distribuídos nos seguintes grupos: 1) Grupo Experimental Placebo (GEP), n=8, tratados apenas solução salina; 2) Grupo Experimental Dexametasona (GED), n=8, tratados com injeção intraperitoneal de dexametasona (1mg/kg/dia); e 3) Grupo Experimental Dexametasona + HMB (GEDH), n=8, tratados com injeção intraperitoneal de dexametasona (1mg/kg/dia) e gavagem contendo HMB (0,3g/kg/dia). Após os 10 dias de tratamento os animais foram eutanasiados para a coleta dos músculos Sóleo, Extensor longo dos dedos (EDL) e do fígado, com processamento e identificação das proteínas em seguida. No musculo Sóleo, ao comparar GEDxGEP pôde-se observar as proteínas Myosin heavy chain 2, Myosin-4, Myosin-6 e Myosin-7, todas com expressão diminuída no GED em relação ao GEP, enquanto ao comparar GEP ao GEDH também houve diminuição na expressão das miosinas do grupo GEDH. Porém, dentre as isoformas de miosinas identificadas, apenas a Myosin-6, Myosin-7 encontraram-se diminuídas. No músculo EDL, nota-se que GED e GEDH apresentaram diminuição no conteúdo de todos os subtipos de miosinas identificados, e ao comparar GED e GEDH entre si a única isoforma de miosina poupada no GEDH em relação ao GED foi Myosin heavy chain 2. No fígado o tratamento com dexametasona prejudicou a captação de glicose, induziu alteração no sistema do Citocromo P450 e induziu alteração na função mitocondrial que foi sustentada pela diminuição do ATP. Ao final conclui-se que a dexametasona induziu a perda de proteínas contráteis (miosinas) em ambos os músculos. A dosagem de HMB aplicada em nosso estudo foi capaz de evitar parcialmente a perda das miosinas no músculo Sóleo, mas não inibiu a perda de miosinas no músculo EDL. No fígado, a dexametasona induziu alterações de diversas proteínas relacionadas ao metabolismo da glicose, entretanto o HMB não foi capaz de atenuar a glicogenólise hepática induzida pela dexametasona.
Title in English
Analysis of the protein profile in rat muscles and liver under the effect of dexamethasone and Beta-HydroxyBeta-methylbutyrate
Keywords in English
Dexamethasone
Leucine
Liver
Muscular atrophy
Skeletal muscle
Abstract in English
Although some effects of glucocorticoids are necessary for metabolic responses during stress, chronic exposure to high levels of them may have side effects such as hyperglycemia, insulin resistance, and also muscle atrophy. Increased levels of glucocorticoids are present in several clinical conditions and their exogenous administration, such as treatments with high doses of dexamethasone, are present in several clinical protocols. In this sense, the -Hydroxy- -methylbutyrate (HMB) supplement is a very promising hypothesis to counteract the side effects of dexamethasone, due to its anti-catabolic action. Thus, the present study aims to evaluate the protein profile in muscles and liver of rats under the effect of HMB, against an aggressive model of muscle atrophy induced by dexamethasone. For this, 24 male Wistar rats, aged 60 days, were used, distributed in the following groups: 1) Experimental Placebo Group (GEP), n=8, treated only with saline solution; 2) Experimental Dexamethasone Group (GED), n=8, treated with intraperitoneal injection of dexamethasone (1mg/kg/day); and 3) Experimental Group Dexamethasone + HMB (GEDH), n=8, treated with intraperitoneal injection of dexamethasone (1mg/kg/day) and HMB gavage (0.3g/kg/day). After 10 days of treatment, the animals were euthanized to collect the Soleus, Extensor Digitorum Longus (EDL) muscles and liver, followed by processing and identification of proteins. In the Soleus muscle, when comparing GEDxGEP it was possible to observe the proteins Myosin heavy chain 2, Myosin-4, Myosin-6 and Myosin-7, all with decreased expression in GED compared to GEP, while comparing GEP to GEDH there was also a decrease in the expression of myosins of the GEDH group. However, among the identified myosin isoforms, only Myosin-6, Myosin-7 were decreased. In the EDL muscle, it is noted that GED and GEDH showed a decrease in the content of all identified myosin subtypes, and when comparing GED and GEDH with each other, the only myosin isoform spared in GEDH in relation to GED was Myosin heavy chain 2. In the liver, treatment with dexamethasone impaired glucose uptake, induced alteration in the Cytochrome P450 system and induced alteration in mitochondrial function that was sustained by the decrease in ATP. In the end, it was concluded that dexamethasone induced the loss of contractile proteins (myosins) in both muscles. The HMB dosage applied in our study was able to partially prevent the loss of myosins in the Soleus muscle, but it did not inhibit the loss of myosins in the EDL muscle. In the liver, dexamethasone induced changes in several proteins related to glucose metabolism, however HMB was not able to attenuate a dexamethasone-induced hepatic glycogenolysis
 
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Publishing Date
2022-04-29
 
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