Mecanismos moleculares relacionados à deposição protéica e ao estado redox de aves alimentadas com DL-metionina e submetidas ao estresse térmico

• Autor(a) principal: Del Vesco, Ana Paula
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1586
• topic: Codorna; Antioxidante; Metionina; Estresse oxidativo; Estresse térmico; Frango de corte; Deposição proteica; Nutrigênomica; Brasil.; Quail; Antioxidant; Methionine; Oxidative stress; Thermal stress; Broiler; Protein deposition; Nutrigenomics; Brazil.; Ciências Agrárias; Zootecnia

The growth rate is linked, among other factors, to muscle deposition. The muscle deposition is based on the balance between protein synthesis and degradation, which are partially coordinated by dietary nutrients, hormones related to growth, and complex metabolic pathways involved in muscle and lysosomal degradation. The bird's performance is also affected by environmental conditions to which these animals are exposed. Therefore, the main objective of this study was to evaluate the effect of acute heat stress and methionine supplementation on performance, gene expression, and the redox state in birds, broilers, and quail. Broilers from 1 to 21 days of age and 22 to 42 days of age were divided into three treatments regarding methionine supplementation: without methionine supplementation (MD), recommended level of methionine (DL1), and excess methionine supplementation (DL2). The animals were kept under thermal comfort or exposed to acute heat stress (38ºC for 24 hours, starting at 20 or 41 days of age, depending on the assessed experimental phase). In this experiment, we evaluated, among other parameters, animal performance, some markers of oxidative stress, and the gene expression of the following genes: uncoupling protein (UCP), betaine-homocysteine methyltransferase (BHMT), cystathionine β synthase (CBS), glutathione synthetase (GSS), glutathione peroxidase 7 (GPx 7), insulin-like growth factor 1(IGF-I), growth hormone receptor (GHR), phosphatidylinositol 3-kinase regulatory subunit 1 (PI3KR1), atrogin 1, and cathepsin L2 (CTSL2). We observed that heat stress increased the body temperature and the water intake in broilers at both ages. The heat stress also decreased the ration intake and the body weight gain in the animals. The methionine supplementation also reduced the ration intake, but it increased the body weight gain. We observed that heat stress decreased both the activity of the enzyme creatinine kinase (CK) and the uric acid levels, and increased the activity of the enzyme alanine aminotransferase (ALT). The methionine supplementation decreased the activity of the enzymes aspartate aminotransferase (AST) and ALT, and increased the activity of CK and the uric acid plasmatic concentration. A greater expression of the genes GSS, CBS, GPX 7, atrogin 1, and CTSL2 were observed in birds exposed to heat stress. The methionine supplementation resulted in a lower gene expression of CTSL2, atrogin 1, BHMT, and UCP and also caused a greater gene expression of IGF-I, GHR, GSS, CBS, and GPx 7. The gene expression of BHMT (P<.0001), CBS (P<.0001), GSS (P=0.0036), and GPx 7 (P=0.0375) were affected by the interaction between ambience × diet. A greater BHMT gene expression was observed in animals kept under thermal comfort and fed with the WM diet. Birds kept under heat stress and fed the DL1 and DL2 diets had a greater CBS, GSS, and GPx7 gene expression. In the experiment with quail, we did not evaluate the DL2 diet; however, the results of IGF-I, GHR, and UCP gene expression, animal performance, and the other evaluated plasmatic parameters were similar to those observed in the broiler experiment. In the experiment with quail, we also observed a significantly greater H2O2 production by the animal kept under heat stress for 24 hours, and in animals receiving a diet without methionine supplementation. Higher glutathione (GSH) content was observed in animals that were fed a diet with methionine supplementation and in animals kept under thermal comfort. A greater TBARS level and activity of the catalase enzyme were found in animals kept under heat stress and fed a diet without methionine. A greater glutathione peroxidase activity was observed in animals kept under heat stress and fed a diet with methionine supplementation. All of the results obtained in this study suggest that under thermal comfort, methionine supplementation reduced the damage caused by ROS, which may be related to the increase in the expression and activity of antioxidants. Our results reveal that heat stress increases the body temperature, induces oxidative stress, and induces greater protein proteolysis; methionine supplementation can also attenuate the effects of stress, thereby contributing to a greater expression and activity of elements related to antioxidant activity. This may stimulate protein deposition, which not only ensures greater gene expression related to synthesis, but also ensures the increase in gene expression related to protein degradation.