Targeting PKGIα Cys42 attenuates cardiac dysfunction in heart failure with preserved ejection fraction
A 2026 study published in Science Advances by researchers at King’s College London identified urolithin A as a direct activator of a cardiac relaxation pathway with implications for heart failure treatment. The condition studied is heart failure with preserved ejection fraction (HFpEF), in which the heart pumps blood normally but can’t relax and fill between beats; it accounts for nearly half of all heart failure cases and has no approved pharmacological treatment that improves outcomes. The researchers targeted PKGIα, a protein kinase that governs relaxation in heart muscle cells and blood vessels. A single site on this protein, cysteine 42 (C42), can be chemically modified to switch the kinase on and improve cardiac relaxation, but this mechanism has never been pharmacologically exploited. Researchers screened natural polyphenols for their ability to modify C42, then tested urolithin A across experimental models including a preclinical HFpEF mouse model and human heart tissue engineered from stem cell-derived cardiomyocytes.
Urolithin A directly modified C42 on PKGIα, forming a chemical adduct on the cysteine residue confirmed by mass spectrometry. This mechanism differs from the disulfide dimerization produced by other compounds tested in the same study; urolithin A works by adducting to C42 and disrupting an autoinhibitory region on the protein. The modification activated the kinase and increased phosphorylation of phospholamban, a regulatory protein in heart muscle cells that, when phosphorylated, allows more calcium to be reabsorbed between beats and improves relaxation. In the mouse HFpEF model, 7 days of oral urolithin A improved diastolic function across echocardiographic measures including global longitudinal strain (GLS) and E/e’ ratio, a standard indicator of diastolic filling pressure, and increased running distance. It also reduced fibrosis and cardiac stress markers including ANP (atrial natriuretic peptide). All effects were absent in mice carrying a C42 mutation, confirming the mechanism’s specificity. In human engineered heart tissue, urolithin A improved relaxation time (T20% reduced by 32%) and contraction kinetics without reducing contractile force or triggering arrhythmias.
For the prebiotic and functional ingredient field, the most relevant detail is where urolithin A originates. The study itself cites data showing that a single dose of pomegranate juice or extract raises plasma urolithin A above 2.0 μM within 24 hours, concentrations within the therapeutic range explored here. Urolithin A isn’t present in food directly; it’s produced when gut bacteria ferment ellagitannins, the polyphenols abundant in pomegranate. That conversion is microbiome-dependent: people who lack the bacterial species responsible produce little or no urolithin A regardless of how much they consume. The bacteria involved, including Gordonibacter and Ellagibacter species, are selectively enriched by ellagitannin-containing foods, positioning pomegranate polyphenols as a functional prebiotic substrate in this pathway. This study provides a mechanistically defined cardiovascular endpoint for that process: improved cardiac diastolic function through direct PKGIα activation. Whether dietary polyphenol intake reliably produces therapeutic urolithin A concentrations in a given individual depends on their microbiome, a variable that biotic interventions are positioned to influence. The study’s main limits are the use of male mice only, a single human tissue donor, and the absence of clinical trial data in HFpEF patients.
