Heart Enzyme PYGM Shields Against Heart Attack by Boosting Energy and Autophagy
A muscle enzyme that declines in heart attack patients may hold the key to preserving cardiac function after MI.
Summary
Researchers discovered that PYGM, an enzyme controlling how heart muscle breaks down glycogen for energy, drops significantly in heart attack patients and is linked to worse cardiac outcomes. Using mouse models, they showed that restoring PYGM levels through gene therapy dramatically reduced heart damage. The enzyme works through two pathways: boosting energy production via glycolysis and the pentose phosphate pathway, and clearing cellular debris through autophagy by suppressing a protein called thrombospondin-1. When autophagy was blocked, PYGM's protective effects disappeared, confirming autophagy is essential to its mechanism. These findings identify PYGM as a promising therapeutic target for protecting the heart during and after myocardial infarction.
Detailed Summary
Heart attacks remain one of the leading causes of death worldwide, and preserving cardiac function after myocardial infarction (MI) is a critical clinical challenge. A new study published in Circulation identifies PYGM — muscle glycogen phosphorylase — as a key cardioprotective enzyme whose loss worsens outcomes after MI, opening a potential new therapeutic avenue.
PYGM is the rate-limiting enzyme in glycogenolysis, the process by which glycogen stored in muscle is broken down to generate energy. The study found that both circulating PYGM levels in blood plasma and its content within cardiac tissue were significantly reduced in patients with myocardial infarction, and this reduction correlated with impaired heart function.
Using mouse models, researchers demonstrated that knocking out PYGM substantially worsened MI-induced cardiac dysfunction and tissue damage. Conversely, replenishing PYGM via adeno-associated virus (AAV)-mediated gene delivery profoundly reversed these harmful effects. Mechanistically, PYGM enhanced cardiac energy homeostasis by stimulating glycolysis and the pentose phosphate pathway, which also reduced oxidative stress — a major driver of heart cell death after MI.
A second, equally important mechanism involved autophagy — the cellular cleaning process that removes damaged proteins and organelles. PYGM was found to restore impaired autophagic flux in MI-affected hearts by suppressing thrombospondin-1 (Thbs1), a protein that blocks this process. When autophagy was pharmacologically or genetically inhibited, PYGM's protective benefits were abolished. Cardiac-specific knockdown of Thbs1 in PYGM-deficient mice also rescued cardiac function, confirming this pathway's central role.
These findings position PYGM as a dual-action cardioprotective factor, preserving both energy metabolism and cellular quality control. Clinically, restoring PYGM activity — whether through gene therapy, small molecules, or lifestyle interventions — could represent a novel strategy to limit cardiac injury following MI. The study is limited by its preclinical nature and the fact that full mechanistic details are only available in the abstract.
Key Findings
- PYGM levels in blood and heart tissue are significantly reduced in myocardial infarction patients, correlating with worse cardiac function.
- Restoring PYGM via AAV gene therapy in mice profoundly reversed MI-induced heart damage and dysfunction.
- PYGM boosts cardiac energy by activating glycolysis and the pentose phosphate pathway, reducing oxidative stress.
- PYGM restores autophagic flux after MI by suppressing thrombospondin-1 (Thbs1), clearing damaged cellular components.
- Blocking autophagy abolished PYGM's cardioprotective effects, confirming autophagy as essential to its mechanism.
Methodology
The study combined analysis of human cardiac tissue and plasma samples from MI patients with mouse MI models using both PYGM-knockout and AAV-mediated PYGM overexpression. Mechanistic pathways were validated through pharmacological and genetic inhibition of autophagy and cardiac-specific Thbs1 knockdown.
Study Limitations
This summary is based on the abstract only, as the full text is not open access, so complete methodological detail and supplementary data could not be reviewed. The study is preclinical; mouse MI models may not fully replicate human cardiac physiology. Translation to human therapeutic applications will require further clinical investigation.
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