Nearly half a million people in the UK live with a form of heart failure that has long frustrated doctors, according to King's College London. The heart still pumps, but it has become too stiff to relax and fill properly between beats.
Scientists at the university have found that a natural compound linked to pomegranates may help stiff heart tissue relax. It is a promising new direction for a condition with few treatment options.
It is important to be clear from the start: this is early-stage research. The results come from animal models and engineered human heart tissue in the laboratory. No clinical trials in people have yet tested whether it works for patients.
Readers should not treat pomegranates, pomegranate juice or urolithin A supplements as heart medicine. Anyone living with heart failure should talk to their GP or cardiologist before changing their diet, medication or supplements.
A stiff heart that struggles to fill
The condition is called heart failure with preserved ejection fraction, or HFpEF. "Preserved ejection fraction" means the heart still squeezes out a normal share of blood with each beat. The trouble comes in between beats, when a stiffened heart cannot relax enough to fill up again.
According to King's College London, HFpEF accounts for around half of all heart failure cases. It can cause breathlessness, fatigue, reduced ability to exercise and a poorer quality of life.
HFpEF is hard to treat because many different factors drive it, including ageing, high blood pressure and diabetes. Many standard heart failure treatments are less effective against it, so doctors focus on managing the underlying conditions and recommend lifestyle changes such as weight loss and better blood sugar control.
"This type of heart failure is becoming increasingly common as populations age and rates of obesity and diabetes rise," said Dr Joseph Burgoyne, senior author of the study. "Despite its growing burden, treatment options remain limited because the disease is complex and varies considerably between patients."
What the researchers found
The study, published in Science Advances and funded by the British Heart Foundation, looked at urolithin A. Scientists have become increasingly interested in this compound because of its links to healthy ageing and to mitochondria, the parts of cells that produce energy.
In what the university describes as a research first, the team found that urolithin A activates a protein called PKGIα. This protein plays an important role in blood vessel function and in helping heart muscle relax.
According to the university, urolithin A improved measures of heart function in animal models by up to 80% compared with untreated models. It also reduced fibrosis, the harmful scarring of heart tissue, and limited abnormal enlargement of heart muscle cells.
The researchers then tested the compound on engineered human heart tissue grown from stem cells, a laboratory model that closely mimics real heart muscle. Urolithin A significantly improved how well this tissue relaxed.
The university notes that urolithin A has already been studied in humans and has shown a favourable safety profile. That is not the same as showing that it treats heart failure, and much more research is needed first.
"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," said Dr Burgoyne. "This raises the exciting possibility of developing new treatments that improve clinical outcomes and quality of life for people living with the condition."
Why a pomegranate is not a prescription
Urolithin A is not simply sitting inside the fruit. It is produced in the body, with the help of gut bacteria, after people eat foods such as pomegranates, walnuts and some berries. Eating a pomegranate is therefore not the same as receiving the dose studied in the laboratory.
Dr Burgoyne was clear on this point. "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."
Professor James Leiper, Director of Research at the British Heart Foundation, said HFpEF "can be debilitating". He added that this early-stage study suggests urolithin A "may help to improve the heart tissue's ability to relax and fill with blood between beats."
"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," he said.
"In the meantime, a healthy, balanced diet remains one of the best ways to look after your heart. Eating plenty of fruit and vegetables is linked to better heart health, but it's important to remember that no single food can prevent or treat heart disease on its own."
For the hundreds of thousands of people living with a stiff, struggling heart, that is a measured kind of hope: a new target, and a well-tolerated compound worth testing properly in human trials.
