Heart bank might reveal why men and women’s organs fail differently
“We looked at thousands of proteins and breakdown products of proteins,” he said.
“What we found, in essence, was certain enzymes were turned off in the heart, explaining its low energy state. They could potentially be targets in the future – we could turn them back on.”
A protein produced by a gene on the X-chromosome – men have one, women have two – was found at lower levels in male hearts that suffered from decreased blood flow. A compound important to widening blood vessels was also at a low level in male hearts.
TMAO a substance produced by gut bacteria when they digest foods such as red meat – and which has been implicated in clogging arteries – was found in higher levels in male but not female hearts.
The study fills in some of the basic science that might explain why male and female hearts fail in such different ways.
Women have very different heart failure symptoms to men.
Up to 40 per cent of women do not experience chest pain but they are more likely to experience shortness of breath, dizziness and nausea. Their symptoms are often missed in hospital, meaning they are twice as likely to not receive proper treatment.
Many of the proteins found to be at high levels in the sick hearts were associated with inflammation, stress and heart repair.
But surprisingly, the researchers discovered a hormone called thyroxine was inactive in the damaged hearts.
Thyroxine is secreted by the thyroid gland in the neck and is important to energy production in the body.
“It’s a master regulator of metabolism,” said Dr O’Sullivan. It needs to be individually turned on by each organ to work.
None of the hearts studied came from people with known thyroid problems – suggesting something may be going wrong with thyroxine in the heart.
Many heart failure studies are done using animal hearts. But there is only so much you can learn from a heart that is not human.
Dr O’Sullivan’s study was made possible by the decision of a small group of doctors to establish the Sydney Heart Bank in 1989.
At the Charles Perkins Centre at the University of Sydney where the bank is housed, heart samples are placed in liquid-nitrogen “cryopreservation”.
Researchers around the world were initially sceptical that you could learn much from a frozen heart. But those fears proved unfounded.
A long list of molecular-level discoveries have come from the bank, including evidence – against the expectations of the scientific community – that hearts can grow new cells.
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Liam is The Age and Sydney Morning Herald’s science reporter