Felippe Mousovich-Neto1, Marina Souza Matos1, Anna Carolina Rego Costa2, Ricardo Augusto de Melo Reis2, Georgia Correa Atella3, Leandro Miranda-Alves4, Denise P Carvalho1, Luisa Andrea Ketzer5, Vânia Maria Corrêa da Costa1. 1. Laboratório de Fisiologia Endócrina Doris Rosenthal, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil. 2. Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil. 3. Laboratório de Bioquímica de Lipídeos e Lipoproteínas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil. 4. Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil. 5. Núcleo Multidisciplinar de Pesquisa UFRJ-Xerém em Biologia, Campus Duque de Caxias, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil.
Abstract
NEW FINDINGS: What is the central question of this study? Does glucocorticoid excess disrupt brown adipose tissue (BAT) phenotype and function? What is the main finding and its importance? Glucocorticoid excess induced an extensive remodelling of interscapular BAT, resulting in a white-like phenotype in association with metabolic disturbances. Glucocorticoids might be an important modulator of BAT physiology and BAT may have a role in pathophysiology of metabolic disturbances induced by glucocorticoid excess. ABSTRACT: In mammals, brown adipose tissue (BAT) is centrally involved in energy metabolism. To test the hypothesis that glucocorticoid excess disrupts BAT phenotype and function, male Wistar rats were treated with corticosterone in drinking water for 21 days. To confirm induction of glucocorticoid excess and metabolic disturbances, adrenal weight, corticotrophin releasing hormone mRNA levels and corticosterone serum levels were measured and a glucose tolerance test and serum triacylglycerol analyses were performed. Adipose tissue deposits were excised, weighed and evaluated by a set of biochemical, histological and molecular procedures, including thin-layer chromatography, histochemistry, immunohistochemistry, quantitative real-time polymerase chain reaction, high-resolution oxygraphy, ATP synthesis and enzymatic activity measurements. The approach was successful in induction of glucocorticoid excess and metabolic disturbances. Lower body weight and increased adiposity were observed in corticosterone-treated rats. Interscapular brown adipose tissue (iBAT) showed higher sensitivity to glucocorticoids than other fat deposits. The treatment induced lipid accumulation, unilocular rearrangement, increased collagen content and decreased innervation in iBAT. Furthermore, expression of Prdm16 (P < 0.05), Ucp1 (P <0.05) and Slc7a10 (P <0.05) mRNA decreased, while expression of Fasn (P <0.05) and Lep (P <0.05) mRNA increased in brown adipose tissue. Also, the levels of UCP1 diminished (P <0.001, 2.5-fold). Finally, lower oxygen consumption (P <0.05), ATP synthesis (P <0.05) and mitochondrial content (P <0.05) were observed in iBAT of glucocorticoid-treated rats. Glucocorticoid excess induced an extensive remodelling of interscapular brown adipose tissue, resulting in a white-like phenotype in association with metabolic disturbances.
NEW FINDINGS: What is the central question of this study? Does glucocorticoid excess disrupt brown adipose tissue (BAT) phenotype and function? What is the main finding and its importance? Glucocorticoid excess induced an extensive remodelling of interscapular BAT, resulting in a white-like phenotype in association with metabolic disturbances. Glucocorticoids might be an important modulator of BAT physiology and BAT may have a role in pathophysiology of metabolic disturbances induced by glucocorticoid excess. ABSTRACT: In mammals, brown adipose tissue (BAT) is centrally involved in energy metabolism. To test the hypothesis that glucocorticoid excess disrupts BAT phenotype and function, male Wistar rats were treated with corticosterone in drinking water for 21 days. To confirm induction of glucocorticoid excess and metabolic disturbances, adrenal weight, corticotrophin releasing hormone mRNA levels and corticosterone serum levels were measured and a glucose tolerance test and serum triacylglycerol analyses were performed. Adipose tissue deposits were excised, weighed and evaluated by a set of biochemical, histological and molecular procedures, including thin-layer chromatography, histochemistry, immunohistochemistry, quantitative real-time polymerase chain reaction, high-resolution oxygraphy, ATP synthesis and enzymatic activity measurements. The approach was successful in induction of glucocorticoid excess and metabolic disturbances. Lower body weight and increased adiposity were observed in corticosterone-treated rats. Interscapular brown adipose tissue (iBAT) showed higher sensitivity to glucocorticoids than other fat deposits. The treatment induced lipid accumulation, unilocular rearrangement, increased collagen content and decreased innervation in iBAT. Furthermore, expression of Prdm16 (P < 0.05), Ucp1 (P <0.05) and Slc7a10 (P <0.05) mRNA decreased, while expression of Fasn (P <0.05) and Lep (P <0.05) mRNA increased in brown adipose tissue. Also, the levels of UCP1 diminished (P <0.001, 2.5-fold). Finally, lower oxygen consumption (P <0.05), ATP synthesis (P <0.05) and mitochondrial content (P <0.05) were observed in iBAT of glucocorticoid-treated rats. Glucocorticoid excess induced an extensive remodelling of interscapular brown adipose tissue, resulting in a white-like phenotype in association with metabolic disturbances.