Myocardial Involvement in Chagas Disease and Insulin Resistance: A Non-Metabolic Model of Cardiomyopathy

Mechanisms behind the high mortality rate in chronic Chagas cardiomyopathy: Unmasking a three-headed monster

Chagas disease is a neglected tropical disease caused by the parasite Trypanosoma cruzi. Chronic Chagas cardiomyopathy (CCC), the most severe form of target organ involvement in Chagas disease, is characterized by a complex pathophysiology and a unique phenotype that differentiates it from other cardiomyopathies, highlighting its worse prognosis compared to other aetiologies of heart failure. The three pathophysiological mechanisms with the largest impact on this differential mortality include rapidly progressive heart failure, a high incidence of stroke, and a high burden of ventricular arrhythmias. However, despite significant advances in understanding the unique molecular circuits underlying these mechanisms, the new knowledge acquired has not been efficiently translated into specific diagnostic and therapeutic approaches for this unique cardiomyopathy. The lack of dedicated clinical trials and the limited CCC-specific risk stratification tools available are evidence of this reality. This review aims to provide an updated perspective of the evidence and pathophysiological mechanisms associated with the higher mortality observed in CCC compared to other cardiomyopathies and highlight opportunities in the diagnostic and therapeutic approaches of the disease.

Fat tissue regulates the pathogenesis and severity of cardiomyopathy in murine chagas disease

Chronic Chagas cardiomyopathy (CCC) caused by a parasite Trypanosoma cruzi is a life-threatening disease in Latin America, for which there is no effective drug or vaccine. The pathogenesis of CCC is complex and multifactorial. Previously, we demonstrated T. cruzi infected mice lose a significant amount of fat tissue which correlates with progression of CCC. Based on this an investigation was undertaken during both acute and chronic T. cruzi infection utilizing the FAT-ATTAC murine model (that allows modulation of fat mass) to understand the consequences of the loss of adipocytes in the regulation of cardiac parasite load, parasite persistence, inflammation, mitochondrial stress, ER stress, survival, CCC progression and CCC severity. Mice were infected intraperitoneally with 5x10⁴ and 10³ trypomastigotes to generate acute and chronic Chagas models, respectively. Ablation of adipocytes was carried out in uninfected and infected mice by treatment with AP21087 for 10 days starting at 15DPI (acute infection) and at 65DPI (indeterminate infection). During acute infection, cardiac ultrasound imaging, histological, and biochemical analyses demonstrated that fat ablation increased cardiac parasite load, cardiac pathology and right ventricular dilation and decreased survival. During chronic indeterminate infection ablation of fat cells increased cardiac pathology and caused bi-ventricular dilation. These data demonstrate that dysfunctional adipose tissue not only affects cardiac metabolism but also the inflammatory status, morphology and physiology of the myocardium and increases the risk of progression and severity of CCC in murine Chagas disease.

An estimated eight million individuals worldwide are chronically infected with Trypanosoma cruzi, the causative agent of Chagas disease (CD). Of these infected individuals, 30% will develop chronic Chagas cardiomyopathy (CCC), a major cause of morbidity and mortality in CD endemic regions for which there is currently no effective drug or vaccine. The molecular mechanisms underlying CCC pathogenesis, progression and severity are complex, multi-factorial and not completely understood. Earlier, it was demonstrated that T. cruzi persists in adipose tissue, alters adipocyte physiology, and causes loss of body fat mass in T. cruzi infected mice with CCC. In this study, the authors examined the role of visceral fat pad (adipose tissue) in regulating the pathogenic signalling in the development and progression of CCC using a fat mass modulatable transgenic mouse CD model. Loss of fat cells increased cardiac lipid load and deregulated cardiac lipid metabolism leading to mitochondrial oxidative stress and endoplasmic reticulum stress and severe CCC. In addition, loss of fat cells increased cardiac parasite load during acute infection and altered immune signalling in the hearts of infected mice during chronic infection. These discoveries underscore the importance of adipose tissue in the development of CCC.

Benznidazole decreases the risk of chronic Chagas disease progression and cardiovascular events: A long-term follow up study

BACKGROUND

Chagas disease (CD) remains an important endemic disease in Latin America. However, CD became globalized in recent decades. The majority of the chronically infected individuals did not receive etiologic treatment for several reasons, among them the most conspicuous is the lack of access to diagnosis. The impact of trypanocidal treatment on CD chronic phase, without cardiac involvement (indeterminate form ICF), is yet to be determined. We aimed to evaluate the effect of trypanocidal treatment with benznidazole (BZN) on the rate of progression to Chagas heart disease in patients with ICF.

METHODS

This is a retrospective cohort observational study including patients with ICF treated with BZN and compared to a group of non-treated patients matched for age, sex, region of origin, and the year of cohort entry. We reviewed the medical charts of all patients followed from May 1987 to June 2020 at the outpatient center of the Evandro Chagas National Institute of Infectious Diseases (INI) of the Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro, Brazil. Patients' follow-up included at least one annual medical visit and one annual electrocardiogram (ECG). Echocardiographic exams were performed at baseline and during the follow-up. Disease progression from ICF to cardiac form was defined by changes in baseline ECG. Cumulative incidence and the incidence rate were described in the incidence analysis. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals for the association between BZN and CD progression, cardiovascular events or death.

FINDINGS

One hundred and fourteen treated patients met the study inclusion criteria. A comparison group of 114 non-treated patients matched for age, sex, region of origin, and the year of cohort entry was also included, totalizing 228 patients. Most patients included in the study were male (70.2%), and their mean age was 31.3 (+7.4) years. Over a median follow-up of 15.1 years (ranging from 1.0 to 32.4), the cumulative CD progression incidence in treated patients was 7.9% vs. 21.1% in the non-treated group (p = 0.04) and the CD progression rate was 0.49 per 1.000 patients/year in treated patients vs. 1.10 per 1.000 patients/year for non-treated patients (p = 0.02). BZN treatment was associated with a decreased risk of CD progression in both unadjusted (HR 0.46; 95%CI 0.21 to 0.98) and adjusted (HR 0.43; 95%CI 0.19 to 0.96) models and with a decreased risk of occurrence of the composite of cardiovascular events only in the adjusted (HR 0.15; 95%CI 0.03 to 0.80) model. No association was observed between BZN treatment and mortality.

INTERPRETATION

In a long-term follow-up, BZN treatment was associated with a decreased incidence of CD progression from ICF to the cardiac form and also with a decreased risk of cardiovascular events. Therefore, our results indicate that BZN treatment for CD patients with ICF should be implemented into clinical practice.