Management of acute myocardial infarction

Dietary Branched-Chain Amino Acids Modify Postinfarct Cardiac Remodeling and Function in the Murine Heart

BACKGROUND

Branched-chain amino acids (BCAAs), which are derived from the diet, are markedly elevated in cardiac tissue following myocardial infarction (MI). Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling.

METHODS

To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, we fed mice a low or a high BCAA diet for 2 weeks before MI and for 4 weeks after MI. Cardiac structural and functional changes were evaluated by echocardiography, gravimetry, and histopathological analyses. Immunoblotting was used to evaluate the effects of BCAAs on isolated cardiac myofibroblast differentiation.

RESULTS

The low BCAA diet decreased circulating BCAA concentrations by >2-fold when compared with the high BCAA diet. Although neither body weights nor heart masses were different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. The low BCAA diet preserved stroke volume and cardiac output after MI, whereas the high BCAA diet promoted progressive decreases in cardiac function. Although BCAAs were required for myofibroblast differentiation in vitro, cardiac fibrosis, scar collagen topography, and cardiomyocyte cross-sectional area were not different between the dietary groups; however, male mice fed the high BCAA diet had longer cardiomyocytes and higher capillary density compared with the low BCAA group.

CONCLUSIONS

A low BCAA diet mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI in mice, with dietary effects more prominent in males.

Dietary Branched Chain Amino Acids Modify Post-Infarct Cardiac Remodeling and Function in the Murine Heart

Introduction

Branch-chain amino acids (BCAA) are markedly elevated in the heart following myocardial infarction (MI) in both humans and animal models. Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling. We hypothesize that lowering dietary BCAA levels prevents adverse cardiac remodeling after MI.

Methods and Results

To assess whether altering dietary BCAA levels would impact circulating BCAA concentrations, mice were fed a low (1/3×), normal (1×), or high (2×) BCAA diet over a 7-day period. We found that mice fed the low BCAA diet had >2-fold lower circulating BCAA concentrations when compared with normal and high BCAA diet feeding strategies; notably, the high BCAA diet did not further increase BCAA levels over the normal chow diet. To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, male and female mice were fed either the low or high BCAA diet for 2 wk prior to MI and for 4 wk after MI. Although body weights or heart masses were not different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. Echocardiographic assessments revealed that the low BCAA diet preserved stroke volume and cardiac output for the duration of the study, while the high BCAA diet led to progressive decreases in cardiac function. Although no discernible differences in cardiac fibrosis, scar collagen topography, or cardiomyocyte cross-sectional area were found between the dietary groups, male mice fed the high BCAA diet showed longer cardiomyocytes and higher capillary density compared with the low BCAA group.

Conclusions

Provision of a diet low in BCAAs to mice mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI, with dietary effects more prominent in males.

Thrombosis and cardiovascular disease

The early stages of venous thrombosis originate at selective sites of reduced blood flow in the apices of venous valves. Stagnation of venous flow results in the formation of a platelet-fibrin thrombus, which serves as the nidus for thrombus propagation. Stasis alone, however, does not result in thrombosis necessarily. The presence of activated coagulation factors is essential. The major predisposing factors to venous thrombus are activation of blood coagulation and venous stasis. In contrast to venous thrombus formation, vascular abnormalities are the most important causative factor in arterial thrombosis.