December 12, 2013
Men’s and Women’s Hearts React Differently to Diabetes Drug
Brett Smith for redOrbit.com - Your Universe Online
In a new study from researchers at at Washington University School of Medicine, the type 2 diabetes drug metformin was found to have different effects on the hearts of men and women, despite managing blood sugar the same in both sexes.
According to the study, which was published in the December issue of the American Journal of Physiology - Heart and Circulatory Physiology, the drug had positive effects on women’s heart health, but male patients saw a change in heart function associated with increased risk for heart failure.
“We saw dramatic sex differences in how the heart responds to the different therapies,” said study author Robert J. Gropler, a professor of radiology at WUStL. “Our study suggests that we need to better define which therapies are optimal for women with diabetes and which ones are optimal for men.”
The pancreas continues to make insulin in patients with type 2 diabetes, but the body isn’t able to effectively use it to draw glucose out of the blood and into the tissues. Type 2 diabetes is also linked to an increased risk for heart failure.
“It is imperative that we gain understanding of diabetes medications and their impact on the heart in order to design optimal treatment regimens for patients,” said study author Dr. Janet B. McGill, also a professor of medicine at WUStL. “This study is a step in that direction.”
In the study, researchers looked at commonly prescribed diabetes drugs in 78 patients. The study participants were divided into one of three groups: those receiving metformin alone, those receiving metformin and rosiglitazone (Avandia) and those receiving metformin plus Lovaza, a form of fish oil.
While metformin reduces glucose production by the liver, rosiglitazone is known to draw free fatty acids out of the blood. Both drugs boost the body’s sensitivity to insulin. Lovaza is prescribed to reduce levels of fatty triglycerides in the blood.
The three groups did not exhibit any major differences in heart metabolism. However, when the patients were divided by sex, the drugs were seen as having different and sometimes opposite effects on heart metabolism.
“The most dramatic difference between men and women is with metformin alone,” Gropler said. “Our data show it to have a favorable effect on cardiac metabolism in women and an unfavorable one in men.”
More specifically, metformin caused men’s hearts to burn less sugar and more fats. According to Gropler, chronic fat burn in the heart leads to negative changes in the heart muscle and potential heart failure.
“Instead of making heart metabolism more normal in men, metformin alone made it worse, looking even more like a diabetic heart,” Gropler said. “But in women, metformin had the desired effect – lowering fat metabolism and increasing glucose uptake by the heart.”
The findings could explain why some trials for diabetes drugs produce conflicting data, the researchers said. Gropler noted his previous research has found differences in how even healthy men’s and women’s hearts metabolize fuel.
“We now know there are sex differences at baseline, both in the metabolism of healthy hearts and in the hearts of patients with diabetes,” Gropler said. “We are adding the message that these sex differences persist in how patients respond to drugs. For patients with diabetes, we are going to have to be more attentive to sex differences when we design therapies.”
Furthermore, the differences in heart metabolism can’t be seen using conventional blood tests, the researchers said.
“This may mean we have to do more complex imaging of the heart to better understand which therapies are best for which patients,” Gropler said.