Defective gene puts middle aged males at risk

Wednesday 29 October 2008

Defective gene puts middle aged males at risk

Heart disease and heart attacks are the main ‘killers’ in New Zealand, with some 30,000 people being admitted to hospitals every year with heart problems. Now researchers at the University of Otago Christchurch have identified a gene variant which is a key indicator of survivability after angina or heart attack, and which may guide improved treatment for the most vulnerable patients.

“It’s been known for some time that a defective ACE2 gene is associated with high blood pressure, but our research has also clearly linked one variant of this gene to a greater likelihood of mortality after heart attack. This is particularly in middle aged males who have acute coronary syndromes, or reduced flow of blood to the heart,” says lead researcher Dr Barry Palmer.

The University of Otago Christchurch scientists carried out the study over three years on a large cohort of 1075 people (males and females) recruited from Christchurch and Auckland hospitals. They found, after adjusting for variables such as age, that male patients are almost twice as likely to die if they had one particular variant (defective) of the ACE2 gene.

“This is the first time ever that this variant of the ACE2 gene has been identified in terms of survivability,” says Dr Palmer.” It will be useful in terms of other research we’re doing on tailoring heart disease treatment more accurately to the patient.”

“If we can identify those people at greater risk we may be able to do more earlier on in their treatment, and it’s easy enough to identify if someone has this variant of the gene.”

Males are more prone than females to the effects of the ACE2 gene variant which is linked to reduced survival because of their chromosomal make-up. That’s because males have only one copy in each cell of the ACE2 gene on the X chromosome and none on the Y chromosome, whereas females have two X chromosomes.

This means that if a male has a defective ACE2 gene variant there is no complementary chromosome which can compensate for that ineffective gene. Females have an alternative copy of the gene on their second X chromosome which can compensate for the defective ACE2 gene, and provide normal blood pressure to the heart.

In its normal form on the X chromosome the ACE2 gene produces an enzyme which controls blood pressure by influencing hormone levels. It is only when that gene is defective that blood pressure may increase.

Dr Palmer says techniques for analysing links between gene variants and heart disease are advancing rapidly, enhancing understanding and improving treatment for one of our most serious health problems.

This research has been published in the October 2008 issue of the American Heart Jourmal and was funded by the University of Otago, Health Research Council, National Heart Foundation and Maurice and Phyllis Paykel Trust. Recent grants from the Canterbury Medical Research Foundation and Lottery Health are allowing further research on genes from the X chromosome and heart disease to continue.

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