THE hearts of men and women may differ in more than just matters of love. It now seems that the root causes of high blood pressure and other cardiovascular diseases may vary between men and women, which could lead to gender-tailored diagnosis and treatment.
Men and women differ when it comes to their risk of developing high blood pressure, or hypertension. Men are more likely to develop high blood pressure and heart disease at younger ages, while women鈥檚 risk increases after menopause. There is also evidence that women and men respond differently to blood pressure medications, though little is known about why such differences exist.
鈥淢en are more likely to develop hypertension and heart disease at younger ages, while women鈥檚 risk increases after menopause鈥�
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To address this question, Brinda Rana and colleagues at the University of California in San Diego used a database of more than 53,000 people undergoing routine blood pressure checks. They compared the genetic make-up of the men and women with the highest and lowest blood pressures 鈥� excluding those with conditions known to affect it. Out of 35 candidate genes, the researchers found four that were clearly associated with raised blood pressure.
Blood pressure is regulated in two ways: by the kidneys, which influence blood volume, and through the constriction and dilation of blood vessels. Rana鈥檚 team found that the genes most strongly associated with hypertension in women code for beta-1 and alpha-2A receptors on blood vessels, which control vasoconstriction and vasodilation.
In men, two different genes were found to be of greater significance. One codes for a blood vessel receptor called beta-2, which works in a similar way to the beta-1 receptor, but the other codes for a protein called angiotensinogen, which is involved in the regulation of blood volume by the kidneys ().
Since commonly prescribed blood pressure drugs often target different causes of hypertension, the finding could lead to gender-specific drug combinations, says Rana. For example, ACE inhibitors target angiotensinogen, and may therefore be more effective in men, while a medication called clonidine, which blocks the alpha receptors, may be more effective in women. To confirm whether this really is the case, researchers will need to look closely at how men and women of different ages respond to different drugs, says Gordon Huggins, a physician at Tufts University School of Medicine in Boston, who is also studying how genes influence hypertension. 鈥淭his kind of work may help identify what medication is the best first-line treatment for a woman with hypertension who is 60 years old, versus a hypertensive man aged 45,鈥� he says, although other factors such as race may also affect how an individual responds to specific drugs.
Knowing which genes are important in controlling blood pressure in men and women may also help in creating diagnostic tests to measure a person鈥檚 likelihood of developing hypertension, says Rana, who presented at a meeting of the American Physiological Society in Austin, Texas, earlier this week.
Hearts under Acid attack
Sexual equality does not extend to the heart, it seems. Subtle physiological distinctions between the hearts of male and female animals have been identified that could explain differences between the sexes when it comes to preventing and treating heart problems.
Studies in newborns and children have shown that girls are more likely than boys to die after heart surgery. To figure out why this might be, Carin Wittnich and colleagues at the University of Toronto in Ontario, Canada, restricted blood flow to the hearts of newborn piglets for 60 minutes 鈥� as often happens during heart surgery 鈥� and found that female hearts became much more acidic than male hearts. This condition, called acidosis, occurs when the heart runs out of oxygen, resulting in the production of lactic acid and hydrogen ions which fail to flush out because of low blood flow.
Acidosis seriously impedes heart recovery after trauma, as well as causing heart dysfunction further down the road. Studies in adults have also shown women have more difficulty than men in recovering after a heart attack or heart surgery. Increased acidosis may play a part, says Wittnich, although more research is needed to figure out what鈥檚 causing the acid to build up at a faster rate.
Yet while females might have a tougher time recovering from heart trauma, they may be at an advantage when it comes to preventing it. A study in mice by Sebastian Brokat and colleagues at the Centre for Cardiovascular Research in Berlin, Germany, shows that female hearts benefit more from physical activity than male hearts.
Brokat鈥檚 team compared exercise patterns and heart physiology in male and female mice and found that females experienced greater hypertrophy than males 鈥� a beneficial enlargement of heart muscle cells in response to exercise, enabling the heart to pump more efficiently.
The findings from both studies were presented at a meeting of the American Physiological Society in Austin, Texas, earlier this week.
