Exercise Performance and Skeletal Muscles in Patients With Advanced Chagas Disease

Chagas heart disease is associated with decreased physical activity levels: A cross-sectional analysis

Background

Studies evaluating physical activity (PA) levels in individuals with Chagas disease (CD) are still scarce. The present study aimed to evaluate PA levels in CD individuals and examine their association with Chagas heart disease (ChHD).

Methods

We included patients with CD regularly followed in a reference center for treatment of infectious diseases. PA levels were assessed using the short version of the International Physical Activity Questionnaire (IPAQ). ChHD was determined following the Brazilian Consensus on Chagas Disease. The association between ChHD and levels of PA (total, walking, moderate, and vigorous) as a continuous variable was fitted using generalized linear models. Logistic regression models were fitted to evaluate the association between ChHD and meeting WHO's PA recommendations.

Results

Among the 361 participants included in the analysis (60.7 ± 10.7 years; 56.2 % women), 58.1 % (n = 210) complied with the WHO's PA recommendations. After adjustments for potential confounders, regression analyses revealed that ChHD without heart failure was significantly associated with reduced vigorous PA (Exp β 0.32 95 % CI 0.10 to 0.98). ChHD with heart failure had significantly lower levels of total (Exp β 0.61 95 % CI 0.44 to 0.84) and moderate (Exp β 0.59 95 % CI 0.39 to 0.89) PA. ChHD with heart failure had a lower odd of meeting the PA recommendation in comparison to those with no cardiac involvement (OR 0.48 95 % CI 0.24 to 0.97).

Conclusions

We found low levels of PA among individuals with CD. Presence of ChHD (mainly with HF) was associated with decreased levels of PA.

Dynamics of Trypanosoma cruzi infection in hamsters and novel association with progressive motor dysfunction

Chagas disease is a zoonosis caused by the protozoan parasite Trypanosoma cruzi. Clinical outcomes range from long-term asymptomatic carriage to cardiac, digestive, neurological and composite presentations that can be fatal in both acute and chronic stages of the disease. Studies of T. cruzi in animal models, principally mice, have informed our understanding of the biological basis of this variability and its relationship to infection and host response dynamics. Hamsters have higher translational value for many human infectious diseases, but they have not been well developed as models of Chagas disease. We transposed a real-time bioluminescence imaging system for T. cruzi infection from mice into female Syrian hamsters (Mesocricetus auratus). This enabled us to study chronic tissue pathology in the context of spatiotemporal infection dynamics. Acute infections were widely disseminated, whereas chronic infections were almost entirely restricted to the skin and subcutaneous adipose tissue. Neither cardiac nor digestive tract disease were reproducible features of the model. Skeletal muscle had only sporadic parasitism in the chronic phase, but nevertheless displayed significant inflammation and fibrosis, features also seen in mouse models. Whereas mice had normal locomotion, all chronically infected hamsters developed hindlimb muscle hypertonia and a gait dysfunction resembling spastic diplegia. With further development, this model may therefore prove valuable in studies of peripheral nervous system involvement in Chagas disease.

Inspiratory muscle endurance is similarly reduced in the early and late stages of chronic Chagas heart disease

OBJECTIVE

Inspiratory muscle strength (IMS) appears to be reduced in subjects with chronic Chagas heart disease (CHD), especially in the presence of heart failure (HF). However, only one study about IMS and inspiratory muscle endurance (IME) in those with CHD without heart failure is available. This study aimed to compare IMS and IME in subjects with CHD in the presence and absence of HF.

METHODS

This is a cross-sectional study in which 30 CHD adult patients were divided into CHD-CC group (initial phase of CHD, without HF; n = 15) and CHD-HF group (advanced phase of CHD, with HF; n = 15). We assessed IMS by maximum inspiratory pressure (MIP) and IME by incremental (Pthmax) and constant load (TLim) tests. Reduced IMS and IME were considered by predicted MIP values <70% and Pthmax/MIP <75%, respectively.

RESULTS

Inspiratory muscle weakness (IMW) was more frequent in CHD-HF than in CHD-CC (46.7% vs. 13.3%; p = 0.05), and both groups had high frequencies of reduced IME (93.3% CHD-CC vs. 100.0% CHD-HF; p = 0.95). Age-adjusted logistic regression analysis using HF as a dependent variable showed that HF was associated with an increased chance of IMW compared with the CHD-CC group (OR = 7.47; p = 0.03; 95% CI 1.20-46.19).

CONCLUSION

This study suggests that, in patients with CHD, HF is associated with IMW, and that reduction of IME is already present in the initial phase, similar to the advanced phase with HF.

Comparative analysis of health-related fitness in patients with acute versus chronic Chagas disease

INTRODUCTION

Although Chagas disease causes high levels of morbidity, the muscle function and tolerance to physical activity in Chagas disease patients are still not completely understood.

OBJECTIVE

To compare health-related fitness of patient groups with acute Chagas disease versus chronic Chagas disease.

MATERIALS AND METHODS

We conducted a cross-sectional study involving 18 patients. The data were obtained from patient´s records, and functional capacity was measured with the sixminute walk test, the peripheral muscle strength with handgrip strength, and respiratory muscle strength using the maximum inspiratory pressure and the maximum expiratory pressure.

RESULTS

The 18 patients were divided in two groups: acute Chagas disease (n=9) and chronic Chagas disease (n=9). The distance walked in the six-minute walk test was lower than the predicted distance walked in both groups (p < 0.0001). The maximum expiratory pressure was lower than the predicted one (p = 0.005), and statistically significant for chronic Chagas disease patients (p = 0.02). Heart rate increased faster in the chronic Chagas disease group within the first two minutes of the six-minute walk test (p = 0.04). The sixminute walk test in the acute Chagas disease group presented a strong correlation with peripheral muscle strength (p = 0.012) and maximum inspiratory pressure (p = 0.0142), while in the chronic Chagas disease group, only peripheral muscle strength and maximum inspiratory pressure were correlated (p = 0.0259).

CONCLUSION

The results suggest lowered functional capacity and reduced respiratory and peripheral muscle strength in patients with Chagas disease, although no differences were observed between groups. The early increase in heart rate during exercise in the chronic Chagas disease group implies a greater myocardial overload.

Inspiratory Muscle Strength in Chagas Cardiomyopathy: A Systematic Scoping Review

The increase in inflammatory markers associated with persistent chronic fibrosing myocarditis, a characteristic of chronic Chagas disease, can result in a reduction in inspiratory muscle strength (IMS) in Chagas cardiomyopathy (CC). However, literature in this field is still scarce. This review aimed to map and summarize the evidence regarding IMS in patients with CC. The inclusion criteria included reports with adult participants with a CC diagnosis, with or without heart failure (HF). The core concept examined was the maximum inspiratory pressure evaluated in the untrained and trained groups in the pre-training period. The context was open, including but not limited to hospitals and health centers. Two authors independently identified eligible studies and extracted the data. Descriptive synthesis was used as the primary strategy for analyzing the results. Nine studies (five clinical trials, three cross-sectional, and one cohort) were included. The CC classification differed among the studies, with no mention of HF in five and no CC staging specification in six. IMS was assessed using a manovacuometer, and only six studies analyzed and interpreted the data concerning the predicted values. The CC population with HF appeared to have impaired IMS. All studies involved only Brazilian volunteers. In conclusion, randomized clinical trials evaluating IMS and the effects of inspiratory muscle training need to be conducted to better understand the prevalence and risk of inspiratory muscle weakness in the CC population, as well as the effects of training. Such studies should be conducted at different stages of CC in different populations and countries.

The prognostic value of the Incremental Shuttle Walk Test in Chagas cardiomyopathy

PURPOSE

To verify the value of the Incremental Shuttle Walk Test (ISWT) distance to identify patients with Chagas cardiomyopathy (ChC) at risk of adverse cardiovascular events.

METHODS

Fifty-two patients with ChC (51 ± 6 years) were evaluated by ISWT, echocardiography, Cardiopulmonary Exercise Testing, and Human Activity Profile (HAP) Questionnaire. Patients were prospectively followed for 44 ± 10 months. The combined endpoint was cardiac death/heart transplant/stroke. The prognostic value of ISWT was verified by the Cox regression, and the ISWT was adjusted for age, sex, left ventricular ejection fraction (LVEF), and minute ventilation/carbon dioxide production relationship (VE/VCO₂ slope).

RESULTS

At the final follow-up, 11 patients (21%) had experienced the endpoint event. When adjusted for age, sex, LVEF, and VE/VCO₂ slope, only ISWT distance (HR 0.99, 95% confidence interval (CI): 0.98-0.99; p = 0.026) and VE/VCO₂ slope (HR 0.93, 95% CI: 0.87-0.99; p = 0.044) remained as independent predictors of adverse cardiovascular events in patients with ChC. The optimal cutoff point for identifying poor prognosis was the ISWT distance less than 440 m (AUC = 0.72). There was a significant difference (p = 0.032) in the number of events between the groups with low ISWT distance (≤440 m) and high (>440 m) ISWT distance.

CONCLUSIONS

The ISWT is a valuable tool with potential value in the prognostic evaluation of patients with ChC.Implications for rehabilitationPatients with Chagas cardiomyopathy showed functional impairment since the early stages of heart disease.The Incremental Shuttle Walk Test (ISWT) can be a valuable and inexpensive tool in the risk stratification of the patients.The ISWT distance is an independent predictor of adverse cardiovascular event.The ISWT distance of 440m is the optimal cut-off point in the identification of patients at risk for adverse cardiovascular events.

Effect of exercise training on cardiovascular autonomic and muscular function in subclinical Chagas cardiomyopathy: a randomized controlled trial

PURPOSE

Patients with chronic chagasic cardiomyopathy with preserved ventricular function present with autonomic imbalance. This study evaluated the effects of exercise training (ET) in restoring peripheral and cardiac autonomic control and skeletal muscle phenotype in patients with subclinical chronic chagasic cardiomyopathy.

METHODS

This controlled trial (NCT02295215) included 24 chronic chagasic cardiomyopathy patients who were randomized www.random.org/lists/ into two groups: those who underwent exercise training (n = 12) and those who continued their usual activities (n = 12). Eight patients completed the exercise training protocol, and 10 patients were clinically followed up for 4 months. Muscular sympathetic nerve activity was measured by microneurography and muscle blood flow (MBF) using venous occlusion plethysmography. The low-frequency component of heart rate variability in normalized units (LFnuHR) reflects sympathetic activity in the heart, and the low-frequency component of systolic blood pressure variability in normalized units reflects sympathetic activity in the vessels. The infusion of vasoactive drugs (phenylephrine and sodium nitroprusside) was used to evaluate cardiac baroreflex sensitivity, and a vastus lateralis muscle biopsy was performed to evaluate atrogin-1 and MuRF-1 gene expression.

RESULTS

The baroreflex sensitivity for increases (p = 0.002) and decreases (p = 0.02) in systolic blood pressure increased in the ET group. Muscle blood flow also increased only in the ET group (p = 0.004). Only the ET group had reduced resting muscular sympathetic nerve activity levels (p = 0.008) and sympathetic activity in the heart (LFnu; p = 0.004) and vessels (p = 0.04) after 4 months. Regarding skeletal muscle, after 4 months, participants in the exercise training group presented with lower atrogin-1 gene expression than participants who continued their activities as usual (p = 0.001). The reduction in muscular sympathetic nerve activity was positively associated with reduced atrogin-1 (r = 0.86; p = 0.02) and MuRF-1 gene expression (r = 0.64; p = 0.06); it was negatively associated with improved baroreflex sensitivity both for increases (r = -0.72; p = 0.020) and decreases (r = -0.82; p = 0.001) in blood pressure.

CONCLUSIONS

ET improved cardiac and peripheral autonomic function in patients with subclinical chagasic cardiomyopathy. ET reduced MSNA and sympathetic activity in the heart and vessels and increased cardiac parasympathetic tone and baroreflex sensitivity. Regarding peripheral muscle, after 4 months, patients who underwent exercise training had an increased cross-sectional area of type I fibers and oxidative metabolism of muscle fibers, and decreased atrogin-1 gene expression, compared to participants who continued their activities as usual. In addition, the reduction in MSNA was associated with improved cardiac baroreflex sensitivity, reduced sympathetic cardiovascular tone, and reduced atrogin-1 and MuRF-1 gene expression.

TRIAL REGISTRATION

ID: NCT02295215. Registered in June 2013.

Muscle mass, muscle strength, and functional capacity in patients with heart failure of Chagas disease and other aetiologies

Aims

Patients with Chagas disease and heart failure (HF) have a poor prognosis similar to that of patients with ischaemic or dilated cardiomyopathy. However, the impact of body composition and muscle strength changes in these aetiologies is still unknown. We aimed to evaluate these parameters across aetiologies in two distinct cohort studies [TESTOsterone‐Heart Failure trial (TESTO‐HF; Brazil) and Studies Investigating Co‐morbidities Aggravating Heart Failure (SICA‐HF; Germany)].

Methods and results

A total of 64 male patients with left ventricular ejection fraction ≤40% were matched for body mass index and New York Heart Association class, including 22 patients with Chagas disease (TESTO‐HF; Brazil), and 20 patients with dilated cardiomyopathy and 22 patients with ischaemic heart disease (SICA‐HF; Germany). Lean body mass (LBM), appendicular lean mass (ALM), and fat mass were assessed by dual energy X‐ray absorptiometry. Sarcopenia was defined as ALM divided by height in metres squared <7.0 kg/m² (ALM/height²) and handgrip strength cut‐off for men according to the European Working Group on Sarcopenia in Older People. All patients performed maximal cardiopulmonary exercise testing. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Chagasic and ischaemic patients had lower total fat mass (16.3 ± 8.1 vs. 19.3 ± 8.0 vs. 27.6 ± 9.4 kg; P < 0.05) and reduced peak oxygen consumption (VO₂) (1.17 ± 0.36 vs. 1.15 ± 0.36 vs. 1.50 ± 0.45 L/min; P < 0.05) than patients with dilated cardiomyopathy, respectively. Chagasic patients showed a trend towards decreased LBM when compared with ischaemic patients (48.3 ± 7.6 vs. 54.2 ± 6.3 kg; P = 0.09). Chagasic patients showed lower handgrip strength (27 ± 8 vs. 37 ± 11 vs. 36 ± 14 kg; P < 0.05) and FBF (1.84 ± 0.54 vs. 2.75 ± 0.76 vs. 3.42 ± 1.21 mL/min/100 mL; P < 0.01) than ischaemic and dilated cardiomyopathy patients, respectively. There was no statistical difference in the distribution of sarcopenia between groups (P = 0.87). In addition, FBF correlated positively with LBM (r = 0.31; P = 0.012), ALM (r = 0.25; P = 0.046), and handgrip strength (r = 0.36; P = 0.004). In a logistic regression model using peak VO₂ as the dependent variable, haemoglobin (odds ratio, 1.506; 95% confidence interval, 1.043–2.177; P = 0.029) and ALM (odds ratio, 1.179; 95% confidence interval, 1.011–1.374; P = 0.035) were independent predictors for peak VO₂ adjusted by age, left ventricular ejection fraction, New York Heart Association, creatinine, and FBF.

Conclusions

Patients with Chagas disease and HF have decreased fat mass and exhibit reduced peripheral blood flow and impaired muscle strength compared with ischaemic HF patients. In addition, patients with Chagas disease and HF show a tendency to have greater reduction in total LBM, with ALM remaining an independent predictor of reduced functional capacity in these patients. The percentage of patients affected by sarcopenia was equal between groups.

Six-minute walk test and incremental shuttle walk test in the evaluation of functional capacity in Chagas heart disease

Chagas heart disease (CHD) leads to a progressive functional impairment. Field tests, as the 6-min walk test (6MWT) and the incremental shuttle walk test (ISWT), may be inexpensive approaches in the evaluation of functional capacity of these patients. The present study was addressed to compare the 6MWT and the ISWT measures, and to determine the accuracy of these tests in the identification of functional impairment in patients with CHD. Thirty-five patients with CHD (47.1±8.2 years, NYHA I–III) were evaluated by echocardiography, cardiopulmonary exercise test (CPET), 6MWT, and ISWT. Correlations between the CPET (peak oxygen uptake [peak VO2] and the ratio between ventilation and the carbon dioxide production [VE/VCO2 slope]) and the field tests (walking distances) were also performed. The receiver operating characteristic (ROC) curve was selected to identify the best distances related to identify those patients with functional impairment. There was no difference between distances walked during the 6MWT and ISWT (P=0.694). The Bland-Altman analysis showed good agreement between the field tests. Both 6MWT and ISWT correlated with peak VO2 (r=0.577, P<0.001 and r=0.587, P<0.001, respectively) and ISWT correlated with VE/VCO2 slope (r=−0.339, P=0.003). The cutoff distances of 6MWT and ISWT to identify patients with peak VO2 less than 20 mL/kg/min were 520 m and 400 m, respectively, with no difference between the areas under ROC curves (P=0.276). Both the 6MWT and the ISWT demonstrated accuracy in identify functional impairment in patients with CHD, being useful tools for the risk stratification of these patients.

Parasite control and skeletal myositis in Trypanosoma cruzi-infected and exercised rats

Non-pharmacological strategies have been rarely described in the treatment of infectious diseases. Although exercise training has been recently incorporated in the clinical management of Chagas disease, the rationale basis that supports this indication is poorly understood. Thus, we investigated the effect of an aerobic exercise on the parasitism, inflammation and oxidative tissue damage in a murine model of Trypanosoma cruzi-induced skeletal myositis. Wistar rats were randomized into four groups: trained not infected (TNI) and infected (TI), sedentary not infected (SNI) and infected (SI). A running training program was administered 5days/week for 9 weeks. Then, infected animals were inoculated with T. cruzi and followed up for another 9 weeks. Exercise training induced beneficial adaptations by increasing time to fatigue and lactate threshold in TNI and TI animals. SI animals presented higher parasitemia, skeletal muscle parasitism, cell necrosis, leukocyte infiltration, cytokines levels, reactive oxygen species and nitric oxide production, thiobarbituric acid reactive substances, carbonyl proteins, myosin heavy chain I depletion, and increased catalase (CAT) and superoxide dismutase (SOD) activities. Beyond attenuation in all these variables, TI animals showed reduced TNF-α, CCL-2/MCP-1 and CX3CL1, and increased IL-10 muscle levels. Furthermore, these animals presented higher CAT and SOD activities and reduced lipid and protein oxidation. Taken together, our findings indicated that exercise training induced a protective phenotype in T. cruzi-infected mice, enhancing host defenses against the parasite and attenuating the pathological remodeling associated with skeletal myositis, aspects potentially associated to an improved immunological and redox balance in infected animals.

Mitochondrial dysfunction in skeletal muscle during experimental Chagas disease

Trypanosoma cruzi invasion and replication in cardiomyocytes and other tissues induce cellular injuries and cytotoxic reactions, with the production of inflammatory cytokines and nitric oxide, both sources of reactive oxygen species. The myocyte response to oxidative stress involves the progression of cellular changes primarily targeting mitochondria. Similar alterations could be taking place in mitochondria from the skeletal muscle; if that is the case, a simple skeletal muscle biopsy would give information about the cardiac energetic production that could be used as a predictor of the chagasic cardiopathy evolution. Therefore, in the present paper we studied skeletal muscle mitochondrial structure and the enzymatic activity of citrate synthase and respiratory chain complexes I to IV (CI-CIV), in Albino Swiss mice infected with T. cruzi, Tulahuen strain and SGO Z12 and Lucky isolates, along the infection. Changes in the mitochondrial structure were detected in 100% of the mitochondria analyzed from the infected groups: they all presented at least 1 significant abnormality such as increase in their matrix or disorganization of their cristae, which are probably related to the enzymatic dysfunction. When we studied the Krebs cycle functionality through the measurement of the specific citrate synthase activity, we found it to be significantly diminished during the acute phase of the infection in Tulahuen and SGO Z12 infected groups with respect to the control one; citrate synthase activity from the Lucky group was significantly increased (p<0.05). The activity of this enzyme was reduced in all the infected groups during the chronic asymptomatic phase (p<0.001) and return to normal values (Tulahuen and SGO Z12) or increased its activity (Lucky) by day 365 post-infection (p.i.). When the mitochondrial respiratory chain was analyzed from the acute to the chronic phase of the infection through the measurement of the activity of complexes I to IV, the activity of CI remained similar to control in Tulahuen and Lucky groups, but was significantly augmented in the SGO Z12 one in the acute and chronic phases (p<0.05). CII increased its activity in Tulahuen and Lucky groups by day 75 p.i. and in SGO Z12 by day 365 p.i. (p<0.05). CIII showed a similar behavior in the 3 infected groups, remaining similar to control values in the first two stages of the infection and significantly increasing later on (p<0.0001). CIV showed an increase in its activity in Lucky throughout all stages of infection (p<0.0001) and an increase in Tulahuen by day 365days p.i. (p<0.0001); SGO Z12 on the other hand, showed a decreased CIV activity at the same time. The structural changes in skeletal muscle mitochondria and their altered enzyme activity began in the acute phase of infection, probably modifying the ability of mitochondria to generate energy; these changes were not compensated in the rest of the phases of the infection. Chagas is a systemic disease, which produces not only heart damage but also permanent skeletal muscle alterations.

[Heart rate variability: analysis of time-domain indices in patients with chronic Chagas disease before and after an exercise program]

Chagas disease (CD) is an infection caused by the protozoan flagellate Trypanosoma cruzi, and transmitted by insects of the genera Triatoma, Rhodnius and Panstrongylus. The heart is affected to varying degrees by inflammatory and destructive lesions in atrial and ventricular myocardial fibers. Several studies have demonstrated the benefits of exercise in patients with congestive heart failure (CHF), including reduced sympathetic tone and increased parasympathetic tone, the result of reduced epinephrine and norepinephrine levels, both at rest and during exercise, including at submaximal levels. It has been hypothesized that the increase in sympathetic arousal during exercise improves peripheral muscle metabolism.

OBJECTIVES

The objectives of this study were to select patients with chronic Chagas cardiomyopathy (CCC) with dysautonomia on 24-h Holter monitoring, assess autonomic function after rehabilitation, and determine whether it resulted in reduced daytime levels of SDNN and increased daytime and nighttime levels of pNN50 and rMSSD.

METHODS

We analyzed time-domain indices of heart rate variability through 24-h Holter monitoring before and after a supervised exercise program. We studied 18 CCC patients (five men), mean age 57.33±9.73 years, followed at the CD outpatient clinic of the National Institute of Cardiology and IPEC/Fiocruz in Rio de Janeiro, Brazil, between April 2009 and November 2010. The following tests were used to assess the severity of CCC: clinical examination, functional evaluation by cardiopulmonary stress testing, electrocardiogram and conventional Doppler echocardiography. The exams were performed within a month of the start and end of the exercise program, which consisted of 60-min sessions of aerobic exercise on a treadmill and resistance training three times a week for six months. The goal was to reach the patients' heart rate target zone during training, and their rating of perceived exertion was assessed by the modified Borg scale.

RESULTS

There were no statistically significant differences (p>0.05) in SDNN, pNN50 and rMSSD, probably due to the large standard deviation observed, patients' poor adherence to the program and their low socioeconomic status, resulting in a small sample, and the short duration of the program.

CONCLUSION

Heart rate variability parameters in patients with CCC did not undergo statistically significant changes after a six-month cardiac rehabilitation program.

Depressive symptoms and disability in chagasic stroke patients: impact on functionality and quality of life

INTRODUCTION

Chagas disease (CD) is associated with stroke, which can result in significant long-term disability. Stroke has also been associated with depressive symptoms, which affect functional performance and quality of life (QOL). Few data are available on the effect of chagasic stroke on functional performance and QOL.

OBJECTIVES

This study aimed to investigate the correlation of stroke disability and depressive symptoms with functional performance and QOL in chagasic stroke patients.

METHODS

In this cross-sectional study, stroke sequelae were assessed using the Modified Rankin Stroke Scale (MRSS), depressive symptoms using the Beck Depression Inventory (BDI), functional performance using the Barthel Index (BI), and QOL using the WHOQOL-BREF.

RESULTS

Twenty-one patients with CD and a previous diagnosis of stroke were included. There was a correlation between the MRSS score and the BI score (r=-0.663, p=0.003), but not the scores of the WHOQOL-BREF subscales. The BDI score was correlated with the WHOQOL-BREF subscale scores (Physical: r=-0.733, p=0.001; Psychological: r=-0.581, p=0.012; Social: r=-0.713, p=0.001; Environmental: r=-0.659, p=0.003). However, the BDI score was not associated with the BI score (r=0.279, p=0.262).

CONCLUSIONS

QOL in patients with CD appears to be influenced more by depressive symptoms than by the motor-associated consequences of stroke. Conversely, motor sequelae impair the functionality of the patient more than depressive symptoms.

Trypanosoma cruzi infection alters glucose metabolism at rest and during exercise without modifying the morphology of pancreatic islets in rats

This study investigated the effects of Trypanosoma cruzi infection on pancreatic morphology and glucose metabolism at rest and during exercise. Wistar rats were randomized into control (CG=10) and infected (IG=10) groups. The IG animals were inoculated with T. cruzi Y strain (300,000 trypomastigotes/50 g). After 9 weeks, the animals were subjected to glucose (OGTT) and insulin (ITT) tolerance tests and a treadmill running protocol. Blood glucose, lactate and time to fatigue were determined. After euthanasia, the pancreases were removed for morphological and biochemical analyses. The IG presented abnormal glucose kinetics in OGTT and a similar glucose curve in ITT compared to the CG. During the exercise test, the IG showed anticipation of time to fatigue. At the point of fatigue, no difference was found in blood glucose and lactate between the groups. There was a significant correlation between lactate levels and the time to fatigue. The IG presented marked pancreatic inflammation, fibrosis and protein oxidation. The number of β cells in the IG animals was not reduced. T. cruzi infection impaired pancreas morphology and glucose metabolism at rest and during exercise in rats, which could constitute an additional mechanism in the induction of exercise intolerance in Chagas' disease.

Exercício físico aeróbico em mulheres com doença de Chagas

INTRODUÇÃO: A forma cardíaca da doença de Chagas causa modificações orgânicas e funcionais, sendo o exercício físico aeróbio uma alternativa de proposta terapêutica. OBJETIVO: avaliar o exercício físico aeróbio em mulheres com doença de Chagas crônica. MATERIAIS E MÉTODOS: Quatorze mulheres com doença de Chagas na faixa etária entre 40 e 60 anos, classe I da New York Heart Association (NYHA) foram divididas em dois grupos. Sete no G1 que realizaram exercício físico, com duas sessões diárias semanais por seis semanas e sete no G2 sem tal intervenção. O efeito do exercício físico foi avaliado por 27 variáveis fisioterapêuticas e ergoespirométricas no tempo zero (T0) e após seis semanas (T6). RESULTADO: No T6 em relação ao T0 a avaliação fisioterapêutica mostrou diferenças significativas na pressão arterial sistólica, no pico do fluxo expiratório, nas pressões inspiratória e expiratória máximas e na frequência cardíaca. Na ergoespirometria houve aumento significativo no DP máximo, no MET máximo, no estágio do protocolo de Bruce, no VO2 máximo, na duração do teste e na distância percorrida para as participantes de G1 e apenas na duração do teste para G2. Para G1 foi ainda observada em T6 uma diminuição significativa do duplo produto na intensidade moderada e alta na mesma carga de esforço. CONCLUSÃO: O treinamento aeróbio de curto período, de simples aplicação e com supervisão pode ser realizado com segurança, aumentando a tolerância ao exercício em pacientes com doença de Chagas crônica classe I da NYHA.

Effects of Trypanosoma cruzi infection on myocardial morphology, single cardiomyocyte contractile function and exercise tolerance in rats

The aim of this study was to investigate the effects of Trypanosoma cruzi (T. cruzi) infection on myocardial morphology, single cardiomyocyte contractile function and exercise tolerance in rats. Adult Wistar rats were randomized into control (n = 14) and infected (n = 14) groups. Infected animals were inoculated with T. cruzi Y strain (300,000 trypomastigotes/50 g body weight). After 9 weeks, the animals were subjected to a treadmill running protocol. Then, the right atrium (RA) and left ventricle (LV) were removed for morphological and cell contractile evaluation. The infected animals exhibited a significant reduction in distance travelled, total time to fatigue and workload. In addition, these animals had hypertrophy, increased myocardial cellularity, and an increase in the proportion of collagen and blood vessels. RA and LV myocytes from infected animals showed marked contractile dysfunction under basal conditions and a reduced contractile response to β-adrenergic stimulation. The workload of infected animals was correlated closely with the amplitude of cell shortening of RA and LV myocytes. T. cruzi infection influenced the myocardial morphology and the mechanical properties of RA and LV single myocytes negatively and reduced exercise tolerance. Single cardiomyocyte contractile dysfunction could constitute an additional mechanism of cardiac impairment and reduced exercise tolerance in this infection.

Regulation of muscle growth by pathogen-associated molecules

Skeletal muscle demonstrates great plasticity in response to environmental and hormonal factors including pathogen-associated molecules, inflammatory cytokines, and growth factors. These signals impinge on muscle by forcing individual muscle fibers to either grow or atrophy. We recently demonstrated that skeletal muscle cells express multiple Toll-like receptors (TLR) that recognize bacterial cell wall components, such as lipopolysaccharide (LPS). Exposure of myocytes to LPS and other TLR ligands initiates an inflammatory response culminating in the autocrine production of cytokines and NO by NO synthase (NOS)2. The TLR signal through protein kinases that phosphorylate and promote the degradation of an inhibitory protein that normally retains the transcription factor, nuclear factor kappaB (NFkappaB), in the cytoplasm. Phosphorylation and degradation of the inhibitor of NFkappaB allows for translocation of NFkappaB to the nucleus and activation of inflammatory genes. Overexpression of a constitutively active inhibitor of NFkappaB kinase in skeletal muscle causes severe wasting, and we found that inhibitors of either the phosphorylation of IkappaB or its proteolytic degradation prevent TLR ligand-induced expression of cytokines and NOS2. The combination of LPS and interferon gamma dramatically enhances the magnitude and duration of LPS-stimulated NOS2 expression and reduces protein translation. Lipopolysaccharide and interferon gamma also downregulates signaling from the mammalian target of rapamycin, a kinase that directs changes in cell size. Inhibitors of NOS block the fall in muscle cell protein synthesis and restore translational signaling, indicating that activation of the NOS2-NO pathway is responsible for the observed decrease in muscle protein synthesis. Our work provides a molecular explanation for reduced muscle growth during infection. Muscle is largely self-sufficient because it expresses receptors, signaling pathways, and effectors to regulate its own size. Prolonged activation of NFkappaB and NOS2 have emerged as detrimental facets of the immune response in muscle. The interplay between inflammatory components and growth factor signaling clearly places muscle at the interface between growth and immunity.

Trypanosoma cruzi infection induces proliferation of vascular smooth muscle cells

Trypanosoma cruzi infection causes cardiomyopathy and vasculopathy. Previous studies have demonstrated that infection of human umbilical vein endothelial and smooth muscle cells resulted in activation of extracellular signal-regulated kinase (ERK). In the present study, smooth muscle cells were infected with trypomastigotes, and immunoblot analysis revealed an increase in the expression of cyclin D1 and proliferating cell nuclear antigen (PCNA), important mediators of smooth muscle cell proliferation. Interestingly, after infection, the expression of caveolin-1 was reduced in both human umbilical vein endothelial cells and smooth muscle cells. Immunoblot and immunohistochemical analyses of lysates of carotid arteries obtained from infected mice revealed increased expression of PCNA, cyclin D1, its substrate, phospho-Rb (Ser780), and phospho-ERK1/2. The expression of the cyclin-dependent kinase inhibitor p21(Cip1/Waf1), caveolin-1, and caveolin-3 was reduced in carotid arteries obtained from infected mice. There was an increase in the abundance of pre-pro-endothelin-1 mRNA in the carotid artery and aorta from infected mice. The ET(A) receptor was also elevated in infected arteries. ERK activates endothelin-1, which in turn exerts positive feedback activating ERK, and cyclin D1 is a downstream target of both endothelin-1 and ERK. There was significant incorporation of bromodeoxyuridine into smooth muscle cell DNA when treatment was with conditioned medium obtained from infected endothelial cells. Taken together, these data suggest that T. cruzi infection stimulates smooth muscle cell proliferation and is likely a result of the upregulation of the ERK-cyclin D1-endothelin-1 pathway.