Widely used diabetes drugs have different effects on men's and women's hearts, a new study suggests.
Researchers examined how three commonly prescribed treatments for type 2 diabetes affected 78 patients who were divided into three groups. One group took metformin alone, the second group took metformin plus rosiglitazone (sold under the brand name Avandia) and the third group took metformin plus Lovaza, a type of fish oil.
Metformin reduces blood sugar production by the liver and improves insulin sensitivity. Rosiglitazone also improves insulin sensitivity and moves free fatty acids out of the blood. Lovaza lowers blood levels of another type of fat called triglycerides.
The researchers found that the drugs had very different and sometimes opposite effects on the hearts of men and women, even as the drugs controlled blood sugar equally well in both genders. The study appears in the December issue of the American Journal of Physiology -- Heart and Circulatory Physiology.
Although metformin had positive heart effects in women, it caused the heart metabolism of men to burn less sugar and more fats. Chronic burning of fat by the heart results in harmful changes that can lead to heart failure, said the researchers, from the Washington University School of Medicine in St. Louis.
"Instead of making heart metabolism more normal in men, metformin alone made it worse, looking even more like a diabetic heart," study senior author Dr. Robert Gropler said in a university news release. "But in women, metformin had the desired effect -- lowering fat metabolism and increasing glucose uptake by the heart."
Taking either rosiglitazone or Lovaza with metformin seemed to reduce some of the negative heart effects of metformin alone in men. Taking rosiglitazone in addition to metformin further improved women's heart metabolism, compared to taking metformin alone.
The addition of Lovaza to metformin did not have a strong effect either way for men or women, the researchers said.
"Our study suggests that we need to better define which therapies are optimal for women with diabetes and which ones are optimal for men," said Gropler, a professor of radiology. The study did not, however, prove a cause-and-effect link between the drug combinations and heart changes. It showed only an association.
-- Robert Preidt
