Effects of amino acid supplementation on left ventricular remodeling in patients with chronic heart failure with decreased systolic function and diabetes mellitus: rationale and design of a magnetic resonance imaging study

Autophagy in heart disease: a strong hypothesis for an untouched metabolic reserve

Autophagy is a conserved catabolic process for long-lived proteins and organelles and is primarily responsible for nonspecific degradation of redundant or faulty cell components. Although autophagy has been described as the cell's major adaptive strategy in response to metabolic challenges, its influence on the cell's energy profile is poorly understood. In the myocardium, autophagy is active at basal levels and is crucial for maintaining its contractile function. Defects in the autophagic machinery cause cardiac dysfunction and heart failure. In this paper we propose that (1) autophagy contributes significantly to the metabolic balance sheet of the heart. (2) Increased autophagy contributes to an improved myocardial energy profile through changing the cardiac substrate preference. (3) Substrates generated through autophagy give rise to an alternative for ATP production with an oxygen-sparing effect. These elements identify autophagy in a new context of myocardial metabolic interregulation, which we discuss in the settings of myocardial infarction, heart failure and the diabetic heart. It is hoped that the hypothesis presented can lead to new insights aimed at exploiting autophagy to improve existing metabolic-based therapy in heart disease.

More than bricks and mortar: comments on protein and amino acid metabolism in the heart

Few cardiologists have considered that constituents of the heart muscle cells are in a continuous state of flux. The proteins of sarcomeres, mitochondria, membranes, the cytosol, and even ribosomes and the cell nucleus, are continuously degraded and remade. Schoenheimer's concept of the "dynamic state of body constituents," has received relatively little attention in the world of cardiovascular research, at least not until recently. We propose that the term nutrition of the heart extends well beyond the supply of energy-providing substrates and includes the supply of amino acids, micronutrients, and regulators of protein synthesis and degradation. This short article is written to make the reader think in broad concepts.

Insulin status differentially affects energy transduction in cardiac mitochondria from male and female rats

AIM

The incidence of coronary heart diseases (CHD), congestive heart failure (CHF) and myocardial infarction is higher in diabetic patients than in non-diabetic groups, with these incidences being more in women than in the men. Hence, we examined involvement of mitochondrial energy transduction functions.

METHODS

Mitochondrial energy metabolism in cardiomyopathy was studied using streptozotocin (STZ)-diabetic male and female rats as the model system. Effects of insulin treatment were also evaluated.

RESULTS

The body and heart weights decreased in both male and female diabetic rats. Insulin treatments resulted in significant increase in the body and heart weights in the female rats. Mitochondrial respiration rates with all the substrates tested decreased in diabetic condition in both males and females. Treatment with two dose-regimens of insulin had differential restorative effect on mitochondrial substrate oxidation in the males but caused hyper-stimulation in the females. Diabetic state brought about 19% decrease in the cytochrome aa(3) content in the female rats. Treatment with 0.6 units of insulin significantly increased the cytochrome contents in general in both the sexes whereas higher dose (1.0 unit) caused decrease in the cytochromes content in the females. Diabetic state resulted in decreased dehydrogenases activities; insulin treatments had differential effect on the dehydrogenase activity in the males and the females. The results suggest that insulin treatment-induced hyper-stimulation of respiration in female rats may lead to increased production of reactive oxygen species. Besides, increased formation of advanced glycosylated end products may further lead to increased risk of CHF and CHD.

CONCLUSIONS

The results suggest that differential effects of STZ-diabetes and insulin treatments in the female rats than in males may be the underlying cause for increased incidence of diabetic cardiomyopathies in the females.