Exercise, mTOR Activation, and Potential Impacts on the Liver in Rodents.

The literature offers a consensus on the association between exercise training (ET) protocols based on the adequate parameters of intensity and frequency, and several adaptive alterations in the liver. Indeed, regular ET can reverse glucose and lipid metabolism disorders, especially from aerobic modalities, which can decrease intrahepatic fat formation. In terms of molecular mechanisms, the regulation of hepatic fat formation would be directly related to the modulation of the mechanistic target of rapamycin (mTOR), which would be stimulated by insulin signaling and Akt activation, from the following three different primary signaling pathways: (I) growth factor, (II) energy/ATP-sensitive, and (III) amino acid-sensitive signaling pathways, respectively. Hyperactivation of the Akt/mTORC1 pathway induces lipogenesis by regulating the action of sterol regulatory element binding protein-1 (SREBP-1). Exercise training interventions have been associated with multiple metabolic and tissue benefits. However, it is worth highlighting that the mTOR signaling in the liver in response to exercise interventions remains unclear. Hepatic adaptive alterations seem to be most outstanding when sustained by chronic interventions or high-intensity exercise protocols.

Are lower limb symmetry and self-reported symptoms associated with functional and neuromuscular outcomes in Brazilian adults with anterior cruciate ligament reconstruction? A cross-sectional study.

INTRODUCTION: After anterior cruciate ligament (ACL) reconstruction, determining readiness to return to participation is challenging. The understanding of which neuromuscular performance parameters are associated with limb symmetry and self-reported symptoms may be useful to improve monitoring the rehabilitation towards adequate decision-making to return. OBJECTIVES: To compare the ACL-operated and injury-free lower limbs regarding functional performance; and to investigate whether lower limb strength and functional performance are associated with self-reported symptoms and functional lower limb symmetry. METHOD: Thirty-four participants were included. Functional performance was assessed by using the Y-Balance test, Single-leg Hop, and Functional Movement Screen. An isokinetic dynamometer was used to evaluate the strength levels in open and closed kinetic chains. The functional lower limb symmetry was calculated considering the single-leg hop test results for each lower limb. RESULTS: There were no differences in dynamic balance (Y-Balance) between the operated and injury-free limbs. The operated limb presented a worst performance in the single-leg hop. Self-reported symptoms prevalence and lower limb symmetry were associated with knee extension strength and functional performance (Y-Balance). CONCLUSION: Individuals submitted to ACL-reconstruction presented worse functional performance in the operated limb compared to the injury-free limb. Both knee strength and dynamic balance were associated with limb symmetry and self-reported symptoms.

Etiologia e fisiopatologia da fibromialgia / Etiology and pathophysiology of fibromyalgia

A fibromialgia é uma condição crônica de etiologia desconhecida e desvinculada de marcadores laboratoriais específicos para diagnóstico, devido à pobre caracterização da etiopatogenia. Em geral, as alterações comuns à fibromialgia também são observadas em outras condições de dor crônica, tornando a patogênese controversa entre diferentes condições patológicas. A etiologia desconhecida dificulta o diagnóstico e, consequentemente, repercute em um tratamento não tão eficaz de pacientes com fibromialgia. A restauração de desordens sistêmicas confere amplo espectro de possibilidades terapêuticas com potencial de orientar profissionais a estabelecer metas e métodos de avaliação. Diante disso, essa revisão narrativa se volta para debater hipóteses etiológicas e fisiopatológicas no desenvolvimento da fibromialgia.

Fibromyalgia is a chronic condition of unknown etiology unrelated to specific laboratory markers for diagnosis because of poor etiopathogenesis. In general, the changes common to fibromyalgia are also seen in other chronic pain conditions, making the pathogenesis controversial among different pathological conditions. The unknown etiology makes the diagnosis difficult and consequently has repercussions on a not so effective treatment of patients with fibromyalgia. The restoration of systemic disorders provides a wide spectrum of therapeutic possibilities with the potential to guide professionals in establishing goals and evaluation methods. Therefore, this narrative review discusses the etiological and pathophysiological hypotheses involved in the development of fibromyalgia.

Effects of Creatine Supplementation on the Myostatin Pathway and Myosin Heavy Chain Isoforms in Different Skeletal Muscles of Resistance-Trained Rats.

Creatine has been used to maximize resistance training effects on skeletal muscles, including muscle hypertrophy and fiber type changes. This study aimed to evaluate the impact of creatine supplementation on the myostatin pathway and myosin heavy chain (MyHC) isoforms in the slow- and fast-twitch muscles of resistance-trained rats. Twenty-eight male Wistar rats were divided into four groups: a sedentary control (Cc), sedentary creatine supplementation (Cr), resistance training (Tc), and resistance training combined with creatine supplementation (Tcr). Cc and Tc received standard commercial chow; Cr and Tcr received a 2% creatine-supplemented diet. Tc and Tcr performed a resistance training protocol on a ladder for 12 weeks. Morphology, MyHC isoforms, myostatin, follistatin, and ActRIIB protein expressions were analyzed in soleus and white gastrocnemius portion samples. The results were analyzed using two-way ANOVA and Tukey's test. Tc and Tcr exhibited higher performance than their control counterparts. Resistance training increased the ratio between muscle and body weight, the cross-sectional area, as well as the interstitial collagen fraction. Resistance training alone increased MyHC IIx and follistatin while reducing myostatin (p < 0.001) and ActRIIB (p = 0.040) expressions in the gastrocnemius. Resistance training induced skeletal muscle hypertrophy and interstitial remodeling, which are more evident in the gastrocnemius muscle. The effects were not impacted by creatine supplementation.

Efeitos da crioterapia por imersão sobre o desempenho sensório-motor de esportistas após protocolo de fadiga muscular / Efectos de la crioterapia de inmersión sobre el rendimiento sensoriomotor en deportistas después de unprotocolo de fatiga muscular / Effects of cold-water immersion on sensorimotor performance of sportsmen after muscle fatigue protocol

Objetivo: O objetivo deste trabalho foi avaliar os efeitos da crioterapia por imersão (CI) sobre o desempenho sensório-motor de esportistas apósprotocolo para indução de fadiga muscular localizada. Método: O presente estudo teve caráter experimental e delineamento prospectivo e teve participação de 36 esportistas universitários que foram divididosem três grupos: grupo recuperação passiva (RP), grupo crioterapia por imersão a 5°C (CI5°) e grupo crioterapia por imersão a 10°C (CI10°). Todos osgrupos foram submetidos a protocolo de fadiga de membro inferior dominante em cadeira extensora. Posteriormente, o RP foi mantido em repouso,enquanto os demais grupos foram submetidos à imersão em água gelada a 5°C e 10°C, respectivamente, durante 10 minutos. Para avaliação dodesempenho sensório-motor, foi utilizado o teste de equilíbrio (YBT), que foi realizado antes e no decorrer de 120 minutos após indução de fadiga. Resultados: Embora os resultados absolutos tenham sido similares entre os grupos, em termos relativos (%), o CI5° mostrou menor desempenhosensório-motor do que RP, o que foi mais acentuado no membro não-dominante. Todos os grupos obtiveram maior desempenho no YBT após 120minutos de recuperação, quando comparado aos primeiros momentos de análise. Conclusão: Em conclusão, o protocolo de CI de 5°C durante 10 minutos aplicado após indução de fadiga neuromuscular resultou em menor desempenhosensório-motor no YBT, em comparação com o método de RP.(AU)

Objetivo: El objetivo de este trabajo es evaluar los efectos de la crioterapia (CI) por inmersión sobre el rendimiento sensoriomotor de deportistas tras unprotocolo de inducción de fatiga muscular localizada.Método: El presente estudio tuvo un carácter experimental y diseño prospectivo y contó con la participación de 36 deportistas universitarios que sedividieron en tres grupos: grupo de recuperación pasiva (PR), grupo de crioterapia a 5°C (IC5°) y grupo de crioterapia a 10°C (IC10°). Todos los grupos sesometieron a un protocolo de fatiga de miembros inferiores dominante en una silla de extensión. Posteriormente, la PR se mantuvo en reposo, mientrasque los otros grupos se sumergieron en agua helada a 5°C y 10°C, respectivamente, durante 10 minutos. Para evaluar el desempeño sensoriomotor seutilizó la prueba de equilibrio (YBT), que se realizó antes y durante 120 minutos después de la inducción de fatiga.Resultados: Aunque los resultados absolutos eran similares entre grupos, en términos relativos (%), el IC5° mostró un menor rendimiento sensoriomotorque el PR, que se acentuó más en la extremidad no dominante. Todos los grupos lograron un mayor rendimiento en los YBT 120 minutos de recuperación,en comparación con los primeros momentos de análisis.Conclusión: En conclusión, el protocolo de CI de 5°C durante 10 minutos aplicado después de la inducción de fatiga neuromuscular resultó en un menorrendimiento sensoriomotor en YBT, en comparación con el método de recuperación pasiva.(AU)

Objective: The objective of this investigation was to evaluate the effects of cold-water immersion (CWI) on the sensorimotor performance of youngathletes in response to local muscle fatigue.Method: The present study had prospective experimental design and involved 36 university sportsmen who were divided into three groups: passiverecovery group (PR), cryotherapy group at 5°C (CI5°) and cryotherapy group at 10°C (CI10°). All groups were submitted to a dominant lower limb fatigueprotocol in an extension chair. Subsequently, the PR was kept at rest, while the other groups were immersed in cold-water at 5°C and 10°C, respectively,for 10 minutes. To assess sensorimotor performance, the Y balance test (YBT) was used, which was performed before and during 120 minutes afterfatigue induction.Results: Although the absolute results had been similar among groups, in relative terms (%), the CI5° showed less sensorimotor performance than PR,which was more accentuated in the non-dominant limb. All groups achieved greater performance in the YBT after 120 minutes of recovery, whencompared to the first moments of analysis (p<0.05).Conclusion: In conclusion, postexercise CWI to 5°C for 10 minutes resulted lower sensorimotor performance in YBT, compared to the PR method.(AU)

Effectiveness of aquatic exercise in the treatment of inflammatory arthritis: systematic review.

Spondyloarthritis and rheumatoid arthritis are classified as inflammatory arthritis and represent a significant source of pain and disability. Non-pharmacological intervention with physical exercise is among the therapeutic approaches most used by health professionals. This study aimed to investigate the effectiveness of aquatic exercise in the treatment of inflammatory arthritis. The review was registered on the PROSPERO (CRD42020189602). The databases (PubMed, PEDro, Web of Science, and SciELO) were searched for studies involving adults with inflammatory arthritis and subjected to rehabilitation with aquatic exercise compared to any other control group, from the year 2010 to March 2022. Pain, disease activity, and physical function were regarded as primary outcomes. Two reviewers completed the eligibility screening and data extraction, and disagreements were resolved by a third reviewer. The methodological quality was assessed using the PEDro scale. A total of 5254 studies were identified, and nine articles were included, totalling 604 participants. Regarding pain, two studies showed that aquatic exercise was superior to home exercise. One study showed that disease activity was significantly improved in the aquatic group compared to the land-based exercise and the control groups (no exercise). Two studies reported that therapy containing aquatic exercise was able to improve physical function. Overall, the studies included in this review indicate that aquatic exercise is effective in treating pain, disease activity, and physical function in individuals with inflammatory arthritis. However, further studies carrying stronger evidence should be conducted to determine whether the treatment with aquatic exercise is superior to other types of therapies.

Analysis of high-intensity interval training on bone mineral density in an experimental model of type 2 diabetes.

PURPOSE: To analyze the effect of high-intensity interval training (HIIT) on bone mineral density (BMD) in a model of type 2 diabetes mellitus. METHODS: Thirty-two male, adult, 12-week-old rats (Rattus norvegicus), of the Wistar lineage, were used. The animals induced to the experimental model received a high fat diet for 10 days and, after that period, intraperitoneal injection of streptozotocin (40 mg·kg-1), dissolved in 20 mmol·L-1 sodium citrate solution (pH = 4.5). The experimental group of diabetes was formed by the animals that, 48 h after the injection of streptozotocin, had fasting blood glucose > 250 mg·dL-1). The animals were randomly divided into four groups with eight animals each: HIIT experimental diabetes; HIIT control; sedentary experimental diabetes and sedentary control. The animals in the HIIT group performed an aerobic exercise protocol on a treadmill inclined at an angle of 15° to the horizontal, with interspersed intensity. Five weekly sessions, lasting 49 min each, were held for 6 weeks. The analysis of cortical bone density (CBD) and BMD were performed by X-ray images using the In-Vivo Xtreme II/Bruker system. RESULTS: For CBD and BMD, when comparing diabetes and control groups, a significant difference was seen between groups in relation to HIIT (p = 0.007). Animals submitted and not submitted to HIIT in the same group showed a significant difference between groups in relation to diabetes (p < 0.001). CONCLUSIONS: The HIIT experimental diabetes group had increased CBD and BMD in comparison with the sedentary experimental diabetes group.

Analysis of high-intensity interval training on bone mineral density in an experimental model of type 2 diabetes

Purpose: To analyze the effect of high-intensity interval training (HIIT) on bone mineral density (BMD) in a model of type 2 diabetes mellitus. Methods: Thirty-two male, adult, 12-week-old rats (Rattus norvegicus), of the Wistar lineage, were used. The animals induced to the experimental model received a high fat diet for 10 days and, after that period, intraperitoneal injection of streptozotocin (40 mg·kg­1), dissolved in 20 mmol·L­1 sodium citrate solution (pH = 4.5). The experimental group of diabetes was formed by the animals that, 48 h after the injection of streptozotocin, had fasting blood glucose > 250 mg·dL­1). The animals were randomly divided into four groups with eight animals each: HIIT experimental diabetes; HIIT control; sedentary experimental diabetes and sedentary control. The animals in the HIIT group performed an aerobic exercise protocol on a treadmill inclined at an angle of 15° to the horizontal, with interspersed intensity. Five weekly sessions, lasting 49 min each, were held for 6 weeks. The analysis of cortical bone density (CBD) and BMD were performed by X-ray images using the In-Vivo Xtreme II/Bruker system. Results: For CBD and BMD, when comparing diabetes and control groups, a significant difference was seen between groups in relation to HIIT (p = 0.007). Animals submitted and not submitted to HIIT in the same group showed a significant difference between groups in relation to diabetes (p < 0.001). Conclusions: The HIIT experimental diabetes group had increased CBD and BMD in comparison with the sedentary experimental diabetes group.

Acute effects of different rest intervals between agonist-antagonist paired-sets in the neuromuscular system performance of young adults.

INTRODUCTION: The agonist-antagonist paired-sets (APS) is a resistance training that involves alternating between exercises for agonist/antagonist muscles of a joint, with little or no rest between then. There is evidence that APS is more strenuous than traditional methods, but evidence on the optimal RI between agonist-antagonist actions is unknown. OBJECTIVE: The aim of this study was to compare different rest intervals between agonist-antagonist actions during APS in young adults. METHOD: Fifty healthy men (mean age 23.2 ± 2.8 years; 1.76 ± 0.1m height, 78.03 ± 8.1 kg) were included and performed three different agonist-antagonist paired-sets protocols separated by 72h, consisting of 4 sets of 10 repetitions. The protocols differed in terms of the rest interval between the knee flexion and extension movements: 0s (no rest); 60s and 120s. The rest intervals between exercise sets were standardized at 60s. Total work, peak torque, neuromuscular efficiency, surface EMG amplitude (sEMG, root mean square) and fatigue index obtained by processing of sEMG signal, were compared between rest intervals and exercise sets within each protocol. RESULTS: There were no significant differences between rest intervals for total work, peak torque and neuromuscular efficiency (P > 0.05), but significant differences were found for sEMG and fatigue (P < 0.01), in which the protocol with 60s interval resulted in greater fatigue. CONCLUSION: We showed that peak torque, total work and neuromuscular efficiency were not different between RI. The 60s RI showed a lower sEMG and a greater muscle fatigue. Although there were no significant differences, the NME was higher in the 60s interval.

Cardiovascular health indicators in soccer exercise during adolescence: systematic review.

This review analyzed the studies that evaluated cardiovascular health indicators (blood pressure, waist circumference, heart rate, glucose index and lipid blood) in recreational soccer players during adolescence, and identify possible associated factors. The search was performed in the electronic databases (PubMED, SciELO, LILACS, Scopus, SPORTDiscus and Web of Science). Inclusion criteria were: population composed of children and/or adolescents (10-19 years or average age up to 19 years); studies adolescents engaged in recreational soccer regularly and observational studies with cross-sectional or longitudinal design. The process of analysis of studies involved reading titles, abstracts and full texts. After these phases, seven articles were eligible. Regarding the design, all studies were cross-sectional. Of the total studies included, five presented moderate methodological quality values and two presented low methodological quality values, according to National Heart, Lung, and Blood Institute instrument. The most cardiovascular health indicators used in recreational soccer players during adolescence was waist circumference; three studies analyzed heart rate, two evaluated blood pressure, one analyzed insulin resistance and none of the included studies analyzed lipid profile. Factors associated were analyzed in four studies, being that sedentary time and body mass index (BMI) present association with at least one indicator of cardiovascular health.

Intermittent Fasting Attenuates Exercise Training-Induced Cardiac Remodeling. / Dieta Intermitente Atenua a Remodelação Cardíaca Causada pelo Exercício Físico.

BACKGROUND: The effects of non-pharmacological interventions such as calorie restriction and exercise training on health and prevention of cardiovascular diseases have been investigated in clinical and experimental studies. OBJECTIVE: To analyze the influence of intermittent fasting and exercise training on functional fitness, glycemia and cardiac remodeling. METHODS: Wistar rats (n=60) were randomly divided into four groups: control, exercise training (ET), intermittent fasting (IF) and exercise training plus intermittent fasting (ETI). Over 12 weeks, control and ET animals were fed daily a standard commercial diet ad libitum , while IF and ETI animals were fed every other day. In addition, the ET and ETI groups were submitted to a running protocol on a treadmill. After this period, functional fitness, nutritional parameters and blood glucose levels were analyzed. In addition to heart morphology, myocardial protein expression of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) was assessed by Western-blot. The results were analyzed using two-way ANOVA and Student-Newman-Keuls test. The level of significance considered was 5%. RESULTS: Exercise training increased functional fitness in the ET and ETI groups and promoted cardiac fibrosis. The combination of intermittent fasting and exercise training resulted in a smaller area under the blood glucose curve and reduced cardiomyocyte cross-sectional area and interstitial collagen fraction in the ETI group compared to ET. ERK and JNK expression levels were similar among groups (p>0.05). CONCLUSIONS: Intermittent fasting is associated with improved glucose tolerance and attenuates cardiac remodeling induced by exercise training (Arq Bras Cardiol. 2020; 115(2):184-193).

FUNDAMENTO: A influência de intervenções não farmacológicas como restrição calórica e exercício físico sobre a saúde e prevenção de enfermidades cardíacas tem sido documentada em estudos clínicos e experimentais. OBJETIVO: Analisar a influência da combinação entre dieta intermitente e exercício físico sobre a capacidade funcional, metabolismo glicêmico e remodelação cardíaca. MÉTODOS: Foram utilizados 60 ratos Wistar machos distribuídos em quatro grupos: Controle (C), Exercício Físico (EF), Dieta Intermitente (DI) e Exercício Físico e Dieta Intermitente (EDI). Durante 12 semanas, enquanto C e EF foram tratados diariamente com dieta comercial padrão ad libitum, DI e EDI receberam dieta similar em dias alternados com dias de jejum. Os grupos EF e EDI foram submetidos a protocolo de corrida em esteira rolante. Posteriormente, foram analisadas capacidade funcional, comportamento nutricional e metabolismo glicêmico. Além da morfologia do coração, a expressão proteica das proteínas extracellular signal-regulated kinase (ERK) e c-Jun N-terminal kinase (JNK) no coração foi avaliada por Western-blot. A análise dos resultados foi feita por meio de Two-Way ANOVA e teste de Student-Newman-Keuls. O nível de significância considerado foi de 5%. RESULTADOS: O exercício físico aumentou a capacidade funcional nos grupos EF e EDI, e acarretou fibrose cardíaca. A combinação entre dieta intermitente e exercício físico resultou em menor área sob a curva de glicemia e menores medidas de área e interstício cardíaco no EDI em relação ao EF. A expressão de proteínas ERK e JNK foi similar entre os grupos (p>0,05). CONCLUSÕES: Dieta intermitente se associa com melhor tolerância glicêmica e atenua o processo de remodelação cardíaca decorrente do exercício físico. (Arq Bras Cardiol. 2020; 115(2):184-193).

Dieta Intermitente Atenua a Remodelação Cardíaca Causada pelo Exercício Físico / Intermittent Fasting Attenuates Exercise Training-Induced Cardiac Remodeling

Resumo Fundamento A influência de intervenções não farmacológicas como restrição calórica e exercício físico sobre a saúde e prevenção de enfermidades cardíacas tem sido documentada em estudos clínicos e experimentais. Objetivo Analisar a influência da combinação entre dieta intermitente e exercício físico sobre a capacidade funcional, metabolismo glicêmico e remodelação cardíaca. Métodos Foram utilizados 60 ratos Wistar machos distribuídos em quatro grupos: Controle (C), Exercício Físico (EF), Dieta Intermitente (DI) e Exercício Físico e Dieta Intermitente (EDI). Durante 12 semanas, enquanto C e EF foram tratados diariamente com dieta comercial padrão ad libitum, DI e EDI receberam dieta similar em dias alternados com dias de jejum. Os grupos EF e EDI foram submetidos a protocolo de corrida em esteira rolante. Posteriormente, foram analisadas capacidade funcional, comportamento nutricional e metabolismo glicêmico. Além da morfologia do coração, a expressão proteica das proteínas extracellular signal-regulated kinase (ERK) e c-Jun N-terminal kinase (JNK) no coração foi avaliada por Western-blot. A análise dos resultados foi feita por meio de Two-Way ANOVA e teste de Student-Newman-Keuls. O nível de significância considerado foi de 5%. Resultados O exercício físico aumentou a capacidade funcional nos grupos EF e EDI, e acarretou fibrose cardíaca. A combinação entre dieta intermitente e exercício físico resultou em menor área sob a curva de glicemia e menores medidas de área e interstício cardíaco no EDI em relação ao EF. A expressão de proteínas ERK e JNK foi similar entre os grupos (p>0,05). Conclusões Dieta intermitente se associa com melhor tolerância glicêmica e atenua o processo de remodelação cardíaca decorrente do exercício físico. (Arq Bras Cardiol. 2020; 115(2):184-193)

Abstract Background The effects of non-pharmacological interventions such as calorie restriction and exercise training on health and prevention of cardiovascular diseases have been investigated in clinical and experimental studies. Objective To analyze the influence of intermittent fasting and exercise training on functional fitness, glycemia and cardiac remodeling. Methods Wistar rats (n=60) were randomly divided into four groups: control, exercise training (ET), intermittent fasting (IF) and exercise training plus intermittent fasting (ETI). Over 12 weeks, control and ET animals were fed daily a standard commercial diet ad libitum , while IF and ETI animals were fed every other day. In addition, the ET and ETI groups were submitted to a running protocol on a treadmill. After this period, functional fitness, nutritional parameters and blood glucose levels were analyzed. In addition to heart morphology, myocardial protein expression of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) was assessed by Western-blot. The results were analyzed using two-way ANOVA and Student-Newman-Keuls test. The level of significance considered was 5%. Results Exercise training increased functional fitness in the ET and ETI groups and promoted cardiac fibrosis. The combination of intermittent fasting and exercise training resulted in a smaller area under the blood glucose curve and reduced cardiomyocyte cross-sectional area and interstitial collagen fraction in the ETI group compared to ET. ERK and JNK expression levels were similar among groups (p>0.05). Conclusions Intermittent fasting is associated with improved glucose tolerance and attenuates cardiac remodeling induced by exercise training (Arq Bras Cardiol. 2020; 115(2):184-193)

Bloqueio de Receptores AT1 Melhora o Desempenho Funcional Miocárdico na Obesidade / AT1Receptor Blockade Improves Myocardial Functional Performance in Obesity

Resumo Fundamento A obesidade tem sido associada com ativação crônica do sistema renina-angiotensina-aldosterona e importantes alterações no desempenho cardíaco. Objetivo Avaliar a influência do bloqueio de receptores de angiotensina-II do tipo 1 (AT1) sobre a morfologia e desempenho cardíaco de ratos obesos por dieta Métodos Ratos Wistar (n=48) foram submetidos a dieta controle (2,9 kcal/g) ou hiperlipídica (3,6 kcal/g) durante 20 semanas. Após a 16ª semana, foram distribuídos em quatro grupos: Controle (CO), Obeso (OB), Controle Losartan (CL) e Obeso Losartan (OL). CL e OL receberam losartan (30 mg/kg/dia) na água durante quatro semanas. Posteriormente, foram analisadas composição corporal, pressão arterial sistólica (PAS) e ecocardiograma. A função de músculos papilares foi avaliada em situação basal com concentração de cálcio ([Ca2+]o) de 2,50 mM e após manobras inotrópicas: potencial pós-pausa (PPP), elevação da [Ca2+]o e durante estimulação beta-adrenérgica com isoproterenol. A análise dos resultados foi feita por meio de Two-Way ANOVA e teste de comparações apropriado. O nível de significância considerado foi de 5%. Resultados Embora a alteração da PAS não tenha se mantido ao final do experimento, a obesidade se associou com hipertrofia cardíaca e maior velocidade de encurtamento da parede posterior do ventrículo esquerdo.No estudo de músculos papilares em condição basal, CL mostrou menor velocidade máxima de variação negativa da tensão desenvolvida (-dT/dt) do que CO. O PPP de 60s promoveu menor -dT/dt e pico de tensão desenvolvida (TD) em OB e CL, comparados ao CO, e maior variação relativa de TD e velocidade máxima de variação positiva (+dT/dt) no OL em relação a CL e OB. Sob 1,5, 2,0 e 2,5mM de [Ca2+]o, o grupo OL exibiu maior -dT/dt do que CL. Conclusão Losartan melhora a função miocárdica de ratos com obesidade induzida por dieta. (Arq Bras Cardiol. 2020; 115(1):17-28)

Abstract Background Obesity has been associated with chronic activation of the renin-angiotensin-aldosterone system and with significant changes in cardiac performance. Objective To assess the impact of a blockade of angiotensin-II receptor type 1 (AT1receptor) on morphology and on myocardial functional performance in rats with high-fat diet- induced obesity. Methods Wistar rats (n=48) were submitted to control (2.9 kcal/g) or high-fat (3.6 kcal/g) diet for 20 weeks. After the 16thweek they were divided into four groups: Control (CO), Obese (OB), Control Losartan (CL) and Obese Losartan (OL). CL and OL received losartan (30 mg/kg/day) in drinking water for four weeks. Subsequently, body composition, systolic blood pressure (SBP) and echocardiographic variables were analyzed. Papillary muscle function was assessed at baseline with 2.50 mM calcium concentration ([Ca2+]o) and after inotropic maneuvers: post-pause potentiation (PPP), [Ca2+]oelevation, and during beta-adrenergic stimulation with isoproterenol. Analysis of the results was performed by the Two-Way ANOVA and by the appropriate comparison test. The level of significance was set at 5%. Results Although SBP change had been not maintained at the end of the experiment, obesity was associated with cardiac hypertrophy and with increased left ventricle posterior wall shortening velocity. In the study of papillary muscles in basal condition, CL showed lower developed tension maximum negative variation velocity (-dT/dt) than CO. The 60s PPP promoted lower -dT/dt and maximum developed tension (DT) in OB and CL compared with CO, and higher relative DT variation and maximum positive variation velocity (+dT/dt) in OL compared with CL and OB. Under 1.5, 2.0, and 2.5mM [Ca2+]o, the OL group showed higher -dT/dt than CL. Conclusion Losartan improves myocardial function in high-fat diet-induced obesity. (Arq Bras Cardiol. 2020;115(1):17-28)

AT1Receptor Blockade Improves Myocardial Functional Performance in Obesity. / Bloqueio de Receptores AT1 Melhora o Desempenho Funcional Miocárdico na Obesidade.

Background Obesity has been associated with chronic activation of the renin-angiotensin-aldosterone system and with significant changes in cardiac performance. Objective To assess the impact of a blockade of angiotensin-II receptor type 1 (AT1receptor) on morphology and on myocardial functional performance in rats with high-fat diet- induced obesity. Methods Wistar rats (n=48) were submitted to control (2.9 kcal/g) or high-fat (3.6 kcal/g) diet for 20 weeks. After the 16thweek they were divided into four groups: Control (CO), Obese (OB), Control Losartan (CL) and Obese Losartan (OL). CL and OL received losartan (30 mg/kg/day) in drinking water for four weeks. Subsequently, body composition, systolic blood pressure (SBP) and echocardiographic variables were analyzed. Papillary muscle function was assessed at baseline with 2.50 mM calcium concentration ([Ca2+]o) and after inotropic maneuvers: post-pause potentiation (PPP), [Ca2+]oelevation, and during beta-adrenergic stimulation with isoproterenol. Analysis of the results was performed by the Two-Way ANOVA and by the appropriate comparison test. The level of significance was set at 5%. Results Although SBP change had been not maintained at the end of the experiment, obesity was associated with cardiac hypertrophy and with increased left ventricle posterior wall shortening velocity. In the study of papillary muscles in basal condition, CL showed lower developed tension maximum negative variation velocity (-dT/dt) than CO. The 60s PPP promoted lower -dT/dt and maximum developed tension (DT) in OB and CL compared with CO, and higher relative DT variation and maximum positive variation velocity (+dT/dt) in OL compared with CL and OB. Under 1.5, 2.0, and 2.5mM [Ca2+]o, the OL group showed higher -dT/dt than CL. Conclusion Losartan improves myocardial function in high-fat diet-induced obesity. (Arq Bras Cardiol. 2020;115(1):17-28).