Pomegranate metabolite urolithin A improved heart function in male mice with stiff hearts by up to 80 percent

"As much as 80 percent" is a ceiling. It is the largest of the improvements in heart-function measures reported in the King's College London press release, set against untreated mice with stiff, failing hearts ^[3]. Untreated animals from the same model are the right control. The press account does not say which measure moved by 80 percent, how many animals were in each group, or what dose they received.

The experiment has two halves, and each covers a gap in the other ^[6]. The mice supply a whole heart in a living body. In them, urolithin A reduced scarring and helped the heart relax properly between beats, and pressure inside the heart eased as a result ^[7]. Human heart tissue grown from stem cells answers a narrower question: does the effect show up in human cells at all? It did. Treated tissue contracted and relaxed faster ^[8]. Lab-grown tissue tests heart muscle on its own, outside a body ^[6].

The protein the team names is PKGI-alpha. It is involved in lowering blood pressure and in helping the heart relax after a beat ^[9]. ScienceAlert's account says urolithin A "likely" acts through it ^[8]. Joseph Burgoyne, the cardiovascular scientist who is the study's senior author, put it more firmly. "Our findings identify a completely new therapeutic target and show that urolithin A can activate this pathway to improve heart relaxation and reduce disease severity," he said ^[10].

The target fits the disease. In HFpEF the heart squeezes normally but is too stiff to relax as it refills ^[5]. Many established heart failure drugs help a weakened heart keep pumping, a problem these patients do not have, and few treatments exist for this form ^[11]. In these experiments urolithin A acted on relaxation ^[7]. "Despite its growing burden, treatment options remain limited because the disease is complex and varies considerably between patients," Burgoyne said ^[18].

All the mice were male, though women tend to suffer from HFpEF more than men ^[12]. Earlier preclinical studies suggest male and female rodent hearts respond differently to metabolic and hypertensive stress, so it is unclear whether these results extend to females, according to ScienceAlert ^[13].

The human evidence for urolithin A that does exist is early and concerns something else: helping the body remove aged or damaged parts of cells, as ScienceAlert describes it ^[17]. Burgoyne drew the line on diet himself. "While there isn't enough evidence to suggest that people should eat pomegranates to treat heart failure, these findings raise the possibility that dietary approaches that enhance urolithin A production may help alleviate this condition," he said ^[14].

James Leiper, director of research at the British Heart Foundation, which funded the work ^[4], made the same point. "While these findings are promising, the benefits have so far been seen in animals and engineered human tissue, so clinical trials involving people are needed to test if this approach is effective for patients," Leiper said ^[15]. Settling whether the compound helps patients will take a randomized controlled trial with a large and diverse group of participants, ScienceAlert reports ^[16].