Base teórica: A osteoartrite é uma doença crônica cuja principal característica é a degradação progressiva da cartilagem articular. Além do acometimento articular, frequentemente, os pacientes com osteoartrite apresentam fraqueza e atrofia dos músculos periarticulares. Apesar disso, os mecanismos moleculares envolvidos na perda muscular relacionada à osteoartrite não são conhecidos. Os principais mecanismos já estudados, em outras condições, estão relacionados ao aumento da degradação e à redução da síntese de proteínas musculares e a déficits na ativação das células-satélite, responsáveis pela regeneração muscular. A miostatina, um importante regulador negativo do crescimento da massa muscular, estimula o aumento da degradação e a redução da síntese de proteínas musculares. Por outro lado, MyoD e miogenina, são marcadores de proliferação e de diferenciação de células-satélite, respectivamente. Objetivos: Investigar os mecanismos moleculares envolvidos na perda muscular em um modelo animal de osteoartrite induzida por transecção do ligamento cruzado anterior em ratas. Métodos: Ratas Wistar fêmeas foram alocadas em dois grupos: OA (submetidas à cirurgia de transecção do ligamento cruzado anterior do joelho direito) e SHAM (submetidas à cirurgia fictícia do joelho direito). Durante o período experimental de 12 semanas foram avaliados, semanalmente, o peso corporal e a locomoção exploratória espontânea. Após a eutanásia, foram coletadas as articulações do joelho direito para confirmação do desenvolvimento da doença. Os músculos gastrocnêmio, tibial-anterior e sóleo, da pata posterior direita, foram dissecados, pesados e congelados. O músculo gastrocnêmio foi utilizado para a avaliação da atrofia muscular, através da análise da área seccional da miofibra, e para análise da expressão proteica de miostatina, MyoD e miogenina. Resultados: A locomoção exploratória espontânea, o peso corporal e o peso dos músculos gastrocnêmio, tibial-anterior e sóleo não apresentaram diferença significativa entre os grupos OA e SHAM. A histopatologia da articulação do joelho confirmou o desenvolvimento da doença nos animais do grupo OA. A área do músculo gastrocnêmio demonstrou redução de aproximadamente 10% no grupo OA, em comparação com o grupo SHAM. O grupo OA apresentou aumento na expressão proteica de miostatina e redução na expressão proteica de miogenina. A expressão proteica de MyoD não apresentou diferença entre os grupos. Conclusão: A atrofia do músculo gastrocnêmio presente na osteoartrite induzida por transecção do ligamento cruzado anterior envolve aumento na expressão de miostatina e redução na expressão de miogenina. Nesse modelo, a perda muscular pode estar relacionada à proteólise induzida pelos níveis aumentados de miostatina e ao déficit na diferenciação das células-satélite devido à redução na expressão de miogenina. / Background: Osteoarthritis is a chronic joint disease primarily characterized by cartilage loss. In addition to joint impairment, patients with osteoarthritis often suffer from weakness and atrophy of the periarticular muscles. However, the molecular mechanisms involved in osteoarthritis-related muscle wasting are not known. The main mechanisms studied, in other conditions, are related to increased degradation and reduced synthesis of muscle protein and to deficits in the activation of satellitecells, which are responsible for muscle regeneration. Myostatin, an important negative regulator of muscle growth, stimulates the increase of degradation and the reduction of synthesis of muscle protein. Moreover, MyoD and myogenin are markers of proliferation and differentiation of satellite-cells, respectively. Objective: To investigate the pathways involved in muscle wasting in a model of osteoarthritis induced by anterior cruciate ligament transection (ACL) in rats. Methods: Female Wistar rats were allocated into two groups: OA (submitted to the ACL transection) and SHAM (submitted to surgical procedures without ACL transection). The spontaneous exploratory locomotion and the body weight of animals were evaluated weekly. In the twelfth week after the induction of disease, animals were euthanized and the right knee joints were collected for further confirmation of the disease by histopathology. Gastrocnemius, tibialis-anterior and soleus muscles from right hind paw were dissected, weighed and frozen. Gastrocnemius was used for evaluation of muscle atrophy, by cross-sectional area measurement, and protein expression of myostatin, MyoD and myogenin. Results: Spontaneous exploratory locomotion, body weight and weight of muscles showed no difference between OA and SHAM groups. The histopathology of the knee joints confirmed the development of the disease in animals from OA group. Gastrocnemius area of animals from OA group had a reduction of about 10% compared to animals from SHAM group. Protein expression of myostatin was increased in animals from OA group, while myogenin expression was decreased. MyoD expression was similar in both OA and SHAM groups. Conclusion: Gastrocnemius atrophy in osteoarthritis induced by ACL transection involves increased protein expression of myostatin and decreased protein expression of myogenin. In this model, muscle wasting may be linked to myostatininduced proteolysis and to deficits in satellite-cell differentiation due to decreased expression of myogenin.

Early-lactating dairy cows mobilize body protein, primarily from skeletal muscle, to provide amino acids which are directed towards gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and our hypothesis was that its dietary inclusion could attenuate skeletal muscle wasting by reducing amino acid-driven gluconeogenesis. The major objectives of this study were to delineate the effects of pre- and post-partum PG supplementation in transition dairy cows on whole-body nitrogen (N) balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG (PG). Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress. All measurements were conducted at 3 time intervals starting at d -14 ± 5, d 15 and d 38 relative to calving. Propylene glycol had no effect (P > 0.05) on whole-body N balance, urinary 3-MH excretion, and body composition. However, N balance was lower (P < 0.001) at d 15 and d 38, compared to d -14. Urinary excretion of 3-MH was lower at d -14 than at d 15 (P = 0.01) and d 38 (P = 0.001). Supplemental PG had no effect (P > 0.05) on body weight (BW), and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain (P = 0.96) and 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) (P = 0.54); however, PG supplementation down-regulated mRNA expression for µ-calpain at d 15 (P = 0.02), and tended to down-regulate mRNA expression for ubiquitin at d 15 (P = 0.07) and proteasome 26S subunit-ATPase at d 38 (P = 0.097). Relative to calving, mRNA abundance for m-calpain (P = 0.02) and µ-calpain (P = 0.005) were higher at d 15 compared to d -14 and d 38. Messenger RNA abundance for ubiquitin (P = 0.07) and 14-kDa E2 (P = 0.005) were lower at d 38 compared to d 15. In summary, these results demonstrate that up-regulation of the Ca2+-dependent and ubiquitin-mediated proteolytic pathways are the mechanisms by which skeletal muscle wasting occurs in early-lactating cows. In addition, dietary supplementation with PG may down-regulate some of these proteolytic pathways, thereby potentially attenuating undesirable skeletal muscle wasting.

Early-lactating dairy cows mobilize body protein, primarily from skeletal muscle, to provide amino acids which are directed towards gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and our hypothesis was that its dietary inclusion could attenuate skeletal muscle wasting by reducing amino acid-driven gluconeogenesis. The major objectives of this study were to delineate the effects of pre- and post-partum PG supplementation in transition dairy cows on whole-body nitrogen (N) balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG (PG). Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress. All measurements were conducted at 3 time intervals starting at d -14 ± 5, d 15 and d 38 relative to calving. Propylene glycol had no effect (P > 0.05) on whole-body N balance, urinary 3-MH excretion, and body composition. However, N balance was lower (P < 0.001) at d 15 and d 38, compared to d -14. Urinary excretion of 3-MH was lower at d -14 than at d 15 (P = 0.01) and d 38 (P = 0.001). Supplemental PG had no effect (P > 0.05) on body weight (BW), and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain (P = 0.96) and 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) (P = 0.54); however, PG supplementation down-regulated mRNA expression for µ-calpain at d 15 (P = 0.02), and tended to down-regulate mRNA expression for ubiquitin at d 15 (P = 0.07) and proteasome 26S subunit-ATPase at d 38 (P = 0.097). Relative to calving, mRNA abundance for m-calpain (P = 0.02) and µ-calpain (P = 0.005) were higher at d 15 compared to d -14 and d 38. Messenger RNA abundance for ubiquitin (P = 0.07) and 14-kDa E2 (P = 0.005) were lower at d 38 compared to d 15. In summary, these results demonstrate that up-regulation of the Ca2+-dependent and ubiquitin-mediated proteolytic pathways are the mechanisms by which skeletal muscle wasting occurs in early-lactating cows. In addition, dietary supplementation with PG may down-regulate some of these proteolytic pathways, thereby potentially attenuating undesirable skeletal muscle wasting.

Base teórica: A osteoartrite é uma doença crônica cuja principal característica é a degradação progressiva da cartilagem articular. Além do acometimento articular, frequentemente, os pacientes com osteoartrite apresentam fraqueza e atrofia dos músculos periarticulares. Apesar disso, os mecanismos moleculares envolvidos na perda muscular relacionada à osteoartrite não são conhecidos. Os principais mecanismos já estudados, em outras condições, estão relacionados ao aumento da degradação e à redução da síntese de proteínas musculares e a déficits na ativação das células-satélite, responsáveis pela regeneração muscular. A miostatina, um importante regulador negativo do crescimento da massa muscular, estimula o aumento da degradação e a redução da síntese de proteínas musculares. Por outro lado, MyoD e miogenina, são marcadores de proliferação e de diferenciação de células-satélite, respectivamente. Objetivos: Investigar os mecanismos moleculares envolvidos na perda muscular em um modelo animal de osteoartrite induzida por transecção do ligamento cruzado anterior em ratas. Métodos: Ratas Wistar fêmeas foram alocadas em dois grupos: OA (submetidas à cirurgia de transecção do ligamento cruzado anterior do joelho direito) e SHAM (submetidas à cirurgia fictícia do joelho direito). Durante o período experimental de 12 semanas foram avaliados, semanalmente, o peso corporal e a locomoção exploratória espontânea. Após a eutanásia, foram coletadas as articulações do joelho direito para confirmação do desenvolvimento da doença. Os músculos gastrocnêmio, tibial-anterior e sóleo, da pata posterior direita, foram dissecados, pesados e congelados. O músculo gastrocnêmio foi utilizado para a avaliação da atrofia muscular, através da análise da área seccional da miofibra, e para análise da expressão proteica de miostatina, MyoD e miogenina. Resultados: A locomoção exploratória espontânea, o peso corporal e o peso dos músculos gastrocnêmio, tibial-anterior e sóleo não apresentaram diferença significativa entre os grupos OA e SHAM. A histopatologia da articulação do joelho confirmou o desenvolvimento da doença nos animais do grupo OA. A área do músculo gastrocnêmio demonstrou redução de aproximadamente 10% no grupo OA, em comparação com o grupo SHAM. O grupo OA apresentou aumento na expressão proteica de miostatina e redução na expressão proteica de miogenina. A expressão proteica de MyoD não apresentou diferença entre os grupos. Conclusão: A atrofia do músculo gastrocnêmio presente na osteoartrite induzida por transecção do ligamento cruzado anterior envolve aumento na expressão de miostatina e redução na expressão de miogenina. Nesse modelo, a perda muscular pode estar relacionada à proteólise induzida pelos níveis aumentados de miostatina e ao déficit na diferenciação das células-satélite devido à redução na expressão de miogenina. / Background: Osteoarthritis is a chronic joint disease primarily characterized by cartilage loss. In addition to joint impairment, patients with osteoarthritis often suffer from weakness and atrophy of the periarticular muscles. However, the molecular mechanisms involved in osteoarthritis-related muscle wasting are not known. The main mechanisms studied, in other conditions, are related to increased degradation and reduced synthesis of muscle protein and to deficits in the activation of satellitecells, which are responsible for muscle regeneration. Myostatin, an important negative regulator of muscle growth, stimulates the increase of degradation and the reduction of synthesis of muscle protein. Moreover, MyoD and myogenin are markers of proliferation and differentiation of satellite-cells, respectively. Objective: To investigate the pathways involved in muscle wasting in a model of osteoarthritis induced by anterior cruciate ligament transection (ACL) in rats. Methods: Female Wistar rats were allocated into two groups: OA (submitted to the ACL transection) and SHAM (submitted to surgical procedures without ACL transection). The spontaneous exploratory locomotion and the body weight of animals were evaluated weekly. In the twelfth week after the induction of disease, animals were euthanized and the right knee joints were collected for further confirmation of the disease by histopathology. Gastrocnemius, tibialis-anterior and soleus muscles from right hind paw were dissected, weighed and frozen. Gastrocnemius was used for evaluation of muscle atrophy, by cross-sectional area measurement, and protein expression of myostatin, MyoD and myogenin. Results: Spontaneous exploratory locomotion, body weight and weight of muscles showed no difference between OA and SHAM groups. The histopathology of the knee joints confirmed the development of the disease in animals from OA group. Gastrocnemius area of animals from OA group had a reduction of about 10% compared to animals from SHAM group. Protein expression of myostatin was increased in animals from OA group, while myogenin expression was decreased. MyoD expression was similar in both OA and SHAM groups. Conclusion: Gastrocnemius atrophy in osteoarthritis induced by ACL transection involves increased protein expression of myostatin and decreased protein expression of myogenin. In this model, muscle wasting may be linked to myostatininduced proteolysis and to deficits in satellite-cell differentiation due to decreased expression of myogenin.

Base teórica: A osteoartrite é uma doença crônica cuja principal característica é a degradação progressiva da cartilagem articular. Além do acometimento articular, frequentemente, os pacientes com osteoartrite apresentam fraqueza e atrofia dos músculos periarticulares. Apesar disso, os mecanismos moleculares envolvidos na perda muscular relacionada à osteoartrite não são conhecidos. Os principais mecanismos já estudados, em outras condições, estão relacionados ao aumento da degradação e à redução da síntese de proteínas musculares e a déficits na ativação das células-satélite, responsáveis pela regeneração muscular. A miostatina, um importante regulador negativo do crescimento da massa muscular, estimula o aumento da degradação e a redução da síntese de proteínas musculares. Por outro lado, MyoD e miogenina, são marcadores de proliferação e de diferenciação de células-satélite, respectivamente. Objetivos: Investigar os mecanismos moleculares envolvidos na perda muscular em um modelo animal de osteoartrite induzida por transecção do ligamento cruzado anterior em ratas. Métodos: Ratas Wistar fêmeas foram alocadas em dois grupos: OA (submetidas à cirurgia de transecção do ligamento cruzado anterior do joelho direito) e SHAM (submetidas à cirurgia fictícia do joelho direito). Durante o período experimental de 12 semanas foram avaliados, semanalmente, o peso corporal e a locomoção exploratória espontânea. Após a eutanásia, foram coletadas as articulações do joelho direito para confirmação do desenvolvimento da doença. Os músculos gastrocnêmio, tibial-anterior e sóleo, da pata posterior direita, foram dissecados, pesados e congelados. O músculo gastrocnêmio foi utilizado para a avaliação da atrofia muscular, através da análise da área seccional da miofibra, e para análise da expressão proteica de miostatina, MyoD e miogenina. Resultados: A locomoção exploratória espontânea, o peso corporal e o peso dos músculos gastrocnêmio, tibial-anterior e sóleo não apresentaram diferença significativa entre os grupos OA e SHAM. A histopatologia da articulação do joelho confirmou o desenvolvimento da doença nos animais do grupo OA. A área do músculo gastrocnêmio demonstrou redução de aproximadamente 10% no grupo OA, em comparação com o grupo SHAM. O grupo OA apresentou aumento na expressão proteica de miostatina e redução na expressão proteica de miogenina. A expressão proteica de MyoD não apresentou diferença entre os grupos. Conclusão: A atrofia do músculo gastrocnêmio presente na osteoartrite induzida por transecção do ligamento cruzado anterior envolve aumento na expressão de miostatina e redução na expressão de miogenina. Nesse modelo, a perda muscular pode estar relacionada à proteólise induzida pelos níveis aumentados de miostatina e ao déficit na diferenciação das células-satélite devido à redução na expressão de miogenina. / Background: Osteoarthritis is a chronic joint disease primarily characterized by cartilage loss. In addition to joint impairment, patients with osteoarthritis often suffer from weakness and atrophy of the periarticular muscles. However, the molecular mechanisms involved in osteoarthritis-related muscle wasting are not known. The main mechanisms studied, in other conditions, are related to increased degradation and reduced synthesis of muscle protein and to deficits in the activation of satellitecells, which are responsible for muscle regeneration. Myostatin, an important negative regulator of muscle growth, stimulates the increase of degradation and the reduction of synthesis of muscle protein. Moreover, MyoD and myogenin are markers of proliferation and differentiation of satellite-cells, respectively. Objective: To investigate the pathways involved in muscle wasting in a model of osteoarthritis induced by anterior cruciate ligament transection (ACL) in rats. Methods: Female Wistar rats were allocated into two groups: OA (submitted to the ACL transection) and SHAM (submitted to surgical procedures without ACL transection). The spontaneous exploratory locomotion and the body weight of animals were evaluated weekly. In the twelfth week after the induction of disease, animals were euthanized and the right knee joints were collected for further confirmation of the disease by histopathology. Gastrocnemius, tibialis-anterior and soleus muscles from right hind paw were dissected, weighed and frozen. Gastrocnemius was used for evaluation of muscle atrophy, by cross-sectional area measurement, and protein expression of myostatin, MyoD and myogenin. Results: Spontaneous exploratory locomotion, body weight and weight of muscles showed no difference between OA and SHAM groups. The histopathology of the knee joints confirmed the development of the disease in animals from OA group. Gastrocnemius area of animals from OA group had a reduction of about 10% compared to animals from SHAM group. Protein expression of myostatin was increased in animals from OA group, while myogenin expression was decreased. MyoD expression was similar in both OA and SHAM groups. Conclusion: Gastrocnemius atrophy in osteoarthritis induced by ACL transection involves increased protein expression of myostatin and decreased protein expression of myogenin. In this model, muscle wasting may be linked to myostatininduced proteolysis and to deficits in satellite-cell differentiation due to decreased expression of myogenin.

No description available.

Introdução: A artrite reumatoide é uma doença inflamatória autoimune associada à complicações sistêmicas como fadiga e perda muscular. Perda muscular pode estar relacionada com a ativação do sistema ubiquitina-proteossomo. O objetivo deste trabalho foi avaliar a perda muscular e o evolvimento do proteossomo no modelo de artrite induzida por colágeno (CIA), com ou sem o tratamento de metotrexato ou inibidor de TNF (etanercepte). Métodos: Camundongos DBA1/J machos foram divididos em 4 grupos (n=8 cada): CIA (salina); ETN (etanercepte, 5.5 /) e MTX (metotrexato, 35 /), tratados duas vezes por semana por 6 semanas, e um grupo controle saudável (CO). Tratamentos iniciaram uma semana após a injeção do booster. Escore clínico, edema da pata traseira e peso corporal foram analisados durante o período experimental. Músculo gastrocnêmio (GA) foi pesado após a morte e usado para quantificar a atividade, níveis proteicos e expressão de mRNA das diferentes subunidades do proteossomo através de ensaio fluorogênico, Western blot e rtPCR, respectivamente. Resultados: Tratamentos reduziram o desenvolvimento da doença, observado através do menor escore clínico e edema da pata traseira nos grupos ETN e MTX. ETN apresentou maior peso corporal do que MTX nas semanas 5 e 7. Músculo GA estava aumentado em ETN do que CIA e MTX, um resultado também observado no peso muscular normalizado. As propriedades catalíticas do proteossomo 26S muscular mostraram um aumento na atividade do tipo caspase nos grupos CIA e MTX. Tecidos musculares de animais MTX demonstraram maiores níveis proteicos das subunidades do proteossomo PSMB8 e PSMB9 e maior expressão gênica de Psmb5, Psmb8 e Psmb9. Por outro lado, a expressão de Psmb6 estava diminuída e de Psmb9 estava aumentada em CIA. Conclusões: Apesar de ambos os medicamentos melhorarem o escore da doença, ETN apresentou um afeito anti-artrítico mais forte e foi o único tratamento capaz de prevenir parcialmente a perda muscular. Ao contrário de ETN, CIA e o tratamento com MTX apresentaram perda muscular e atividade e expressão do proteossomo aumentadas. / Background: Rheumatoid arthritis is an autoimmune inflammatory disease associated with systemic complications like fatigue and muscle wasting. Muscle wasting could be related to the activation of the ubiquitin-proteasome system. The aim of this study was to evaluate muscle loss and involvement of the proteasome in collagen-induced arthritis (CIA), with or without treatment with methotrexate or a TNF inhibitor (etanercept). Methods: Male DBA1/J mice were divided into 4 groups (n=8 each): CIA (saline); ETN (etanercept, 5.5 /) and MTX (methotrexate, 35 /), treated twice a week for 6 weeks, and a healthy control group (CO). Treatments started one week after booster injection. Clinical score, hind paw oedema, and body weight were analysed during the experimental period. Gastrocnemius muscles (GA) were weighted after death and used to quantify proteasome activity, protein levels and mRNA expression of its subunits by Western blot and rtPCR, respectively. Results: Treatments slowed disease development, observed through smaller clinical score and hindpaw edema in ETN and MTX groups. ETN presented higher body weight compared to MTX group at weeks 5 and 7. GA weight was heavier in ETN than CIA and MTX, a result also observed in the normalized muscle weight. The catalytic properties of 26S proteasome showed an increase of caspase-like activity in CIA and MTX groups. Muscles tissues of MTX treated animals showed higher protein levels for proteasomal subunits PSMB8 and PSMB9 and higher gene expression for Psmb5, Psmb8 and Psmb9. In contrast, expression of Psmb6 was decreased and of Psmb9 was enhanced in CIA. Conclusions: Although both drugs improved the disease score, ETN presented a stronger anti-arthritic effect and was the only treatment able to partially prevent muscle wasting. In contrast to ETN, CIA and MTX treatment did not prevent muscles loss due to increased proteasome expression and activity.

Introdução: A artrite reumatoide é uma doença inflamatória autoimune associada à complicações sistêmicas como fadiga e perda muscular. Perda muscular pode estar relacionada com a ativação do sistema ubiquitina-proteossomo. O objetivo deste trabalho foi avaliar a perda muscular e o evolvimento do proteossomo no modelo de artrite induzida por colágeno (CIA), com ou sem o tratamento de metotrexato ou inibidor de TNF (etanercepte). Métodos: Camundongos DBA1/J machos foram divididos em 4 grupos (n=8 cada): CIA (salina); ETN (etanercepte, 5.5 /) e MTX (metotrexato, 35 /), tratados duas vezes por semana por 6 semanas, e um grupo controle saudável (CO). Tratamentos iniciaram uma semana após a injeção do booster. Escore clínico, edema da pata traseira e peso corporal foram analisados durante o período experimental. Músculo gastrocnêmio (GA) foi pesado após a morte e usado para quantificar a atividade, níveis proteicos e expressão de mRNA das diferentes subunidades do proteossomo através de ensaio fluorogênico, Western blot e rtPCR, respectivamente. Resultados: Tratamentos reduziram o desenvolvimento da doença, observado através do menor escore clínico e edema da pata traseira nos grupos ETN e MTX. ETN apresentou maior peso corporal do que MTX nas semanas 5 e 7. Músculo GA estava aumentado em ETN do que CIA e MTX, um resultado também observado no peso muscular normalizado. As propriedades catalíticas do proteossomo 26S muscular mostraram um aumento na atividade do tipo caspase nos grupos CIA e MTX. Tecidos musculares de animais MTX demonstraram maiores níveis proteicos das subunidades do proteossomo PSMB8 e PSMB9 e maior expressão gênica de Psmb5, Psmb8 e Psmb9. Por outro lado, a expressão de Psmb6 estava diminuída e de Psmb9 estava aumentada em CIA. Conclusões: Apesar de ambos os medicamentos melhorarem o escore da doença, ETN apresentou um afeito anti-artrítico mais forte e foi o único tratamento capaz de prevenir parcialmente a perda muscular. Ao contrário de ETN, CIA e o tratamento com MTX apresentaram perda muscular e atividade e expressão do proteossomo aumentadas. / Background: Rheumatoid arthritis is an autoimmune inflammatory disease associated with systemic complications like fatigue and muscle wasting. Muscle wasting could be related to the activation of the ubiquitin-proteasome system. The aim of this study was to evaluate muscle loss and involvement of the proteasome in collagen-induced arthritis (CIA), with or without treatment with methotrexate or a TNF inhibitor (etanercept). Methods: Male DBA1/J mice were divided into 4 groups (n=8 each): CIA (saline); ETN (etanercept, 5.5 /) and MTX (methotrexate, 35 /), treated twice a week for 6 weeks, and a healthy control group (CO). Treatments started one week after booster injection. Clinical score, hind paw oedema, and body weight were analysed during the experimental period. Gastrocnemius muscles (GA) were weighted after death and used to quantify proteasome activity, protein levels and mRNA expression of its subunits by Western blot and rtPCR, respectively. Results: Treatments slowed disease development, observed through smaller clinical score and hindpaw edema in ETN and MTX groups. ETN presented higher body weight compared to MTX group at weeks 5 and 7. GA weight was heavier in ETN than CIA and MTX, a result also observed in the normalized muscle weight. The catalytic properties of 26S proteasome showed an increase of caspase-like activity in CIA and MTX groups. Muscles tissues of MTX treated animals showed higher protein levels for proteasomal subunits PSMB8 and PSMB9 and higher gene expression for Psmb5, Psmb8 and Psmb9. In contrast, expression of Psmb6 was decreased and of Psmb9 was enhanced in CIA. Conclusions: Although both drugs improved the disease score, ETN presented a stronger anti-arthritic effect and was the only treatment able to partially prevent muscle wasting. In contrast to ETN, CIA and MTX treatment did not prevent muscles loss due to increased proteasome expression and activity.

Introdução: A artrite reumatoide é uma doença inflamatória autoimune associada à complicações sistêmicas como fadiga e perda muscular. Perda muscular pode estar relacionada com a ativação do sistema ubiquitina-proteossomo. O objetivo deste trabalho foi avaliar a perda muscular e o evolvimento do proteossomo no modelo de artrite induzida por colágeno (CIA), com ou sem o tratamento de metotrexato ou inibidor de TNF (etanercepte). Métodos: Camundongos DBA1/J machos foram divididos em 4 grupos (n=8 cada): CIA (salina); ETN (etanercepte, 5.5 /) e MTX (metotrexato, 35 /), tratados duas vezes por semana por 6 semanas, e um grupo controle saudável (CO). Tratamentos iniciaram uma semana após a injeção do booster. Escore clínico, edema da pata traseira e peso corporal foram analisados durante o período experimental. Músculo gastrocnêmio (GA) foi pesado após a morte e usado para quantificar a atividade, níveis proteicos e expressão de mRNA das diferentes subunidades do proteossomo através de ensaio fluorogênico, Western blot e rtPCR, respectivamente. Resultados: Tratamentos reduziram o desenvolvimento da doença, observado através do menor escore clínico e edema da pata traseira nos grupos ETN e MTX. ETN apresentou maior peso corporal do que MTX nas semanas 5 e 7. Músculo GA estava aumentado em ETN do que CIA e MTX, um resultado também observado no peso muscular normalizado. As propriedades catalíticas do proteossomo 26S muscular mostraram um aumento na atividade do tipo caspase nos grupos CIA e MTX. Tecidos musculares de animais MTX demonstraram maiores níveis proteicos das subunidades do proteossomo PSMB8 e PSMB9 e maior expressão gênica de Psmb5, Psmb8 e Psmb9. Por outro lado, a expressão de Psmb6 estava diminuída e de Psmb9 estava aumentada em CIA. Conclusões: Apesar de ambos os medicamentos melhorarem o escore da doença, ETN apresentou um afeito anti-artrítico mais forte e foi o único tratamento capaz de prevenir parcialmente a perda muscular. Ao contrário de ETN, CIA e o tratamento com MTX apresentaram perda muscular e atividade e expressão do proteossomo aumentadas. / Background: Rheumatoid arthritis is an autoimmune inflammatory disease associated with systemic complications like fatigue and muscle wasting. Muscle wasting could be related to the activation of the ubiquitin-proteasome system. The aim of this study was to evaluate muscle loss and involvement of the proteasome in collagen-induced arthritis (CIA), with or without treatment with methotrexate or a TNF inhibitor (etanercept). Methods: Male DBA1/J mice were divided into 4 groups (n=8 each): CIA (saline); ETN (etanercept, 5.5 /) and MTX (methotrexate, 35 /), treated twice a week for 6 weeks, and a healthy control group (CO). Treatments started one week after booster injection. Clinical score, hind paw oedema, and body weight were analysed during the experimental period. Gastrocnemius muscles (GA) were weighted after death and used to quantify proteasome activity, protein levels and mRNA expression of its subunits by Western blot and rtPCR, respectively. Results: Treatments slowed disease development, observed through smaller clinical score and hindpaw edema in ETN and MTX groups. ETN presented higher body weight compared to MTX group at weeks 5 and 7. GA weight was heavier in ETN than CIA and MTX, a result also observed in the normalized muscle weight. The catalytic properties of 26S proteasome showed an increase of caspase-like activity in CIA and MTX groups. Muscles tissues of MTX treated animals showed higher protein levels for proteasomal subunits PSMB8 and PSMB9 and higher gene expression for Psmb5, Psmb8 and Psmb9. In contrast, expression of Psmb6 was decreased and of Psmb9 was enhanced in CIA. Conclusions: Although both drugs improved the disease score, ETN presented a stronger anti-arthritic effect and was the only treatment able to partially prevent muscle wasting. In contrast to ETN, CIA and MTX treatment did not prevent muscles loss due to increased proteasome expression and activity.

Objectives: Sarcopenia is defined using a variety of different muscle variables, muscle mass adjustment techniques and cut offs for each variable. The objectives of this thesis were to assess how operational differences in sarcopenia definitions impact the agreement between definitions and the association between sarcopenia and health outcomes such as falls. Methods: A list of sarcopenia definitions was developed which captured the combinations of muscle variables, muscle mass adjustment techniques, and cut offs used in the literature based on a systematic review conducted for this thesis. These definitions were applied to participants taking part in the Canadian Longitudinal Study on Aging, a national study of participants aged 45 to 85 years at baseline. The agreement between the definitions and the association of each definition with falls was assessed. Findings: Both the combination of muscle variables as well as the different muscle mass adjustment techniques generally had limited agreement. Sarcopenia definitions including muscle mass and muscle strength were associated with falls in males, but none of the sarcopenia definitions were associated with falls in females. Area under the curve analyses revealed that even sarcopenia definitions associated with more than two times the odds of falling in males, had a small impact on identifying fallers with values ≤0.56. Conclusions: The results of this thesis show that the existing range of definitions used to define sarcopenia are not equivalent based on the limited agreement and inconsistent association of sarcopenia with falls. The results also show that sarcopenia may have limitations as clinically useful diagnosis for identifying fallers with area under the curve values for all definitions showing that the identification of fallers based on sarcopenic status was at best, modestly better than chance alone. / Thesis / Doctor of Philosophy (PhD) / Definitions for sarcopenia differ in terms of which muscle variables are included, how muscle mass is adjusted, and which cut offs to use for each variables. This thesis assessed the impact of different methods of operationalizing sarcopenia on the proportion of sarcopenic participants, agreement between definitions, and the strength of the association between sarcopenia and falls. The variables used to operationalize sarcopenia as well as different techniques for adjusting muscle mass resulted in poor agreement between definitions. In males, these factors impacted which definitions were significantly associated with falls, and in females, sarcopenia was not associated with falls for any definition. For all definitions, sarcopenia status poorly discriminated between those that would or would not fall. Together, these results show that different sarcopenia definitions are not equivalent and that a standard definition is required. However, this thesis also shows that more work is required to determine the clinical utility of sarcopenia.