(Recasts throughout, adds byline, interview)

By Julie Steenhuysen

CHICAGO, March 31 (Reuters) - The popular diabetes pill Actos prevented the build-up of fatty deposits in heart arteries in a study of patients with type 2 diabetes, U.S. researchers said on Monday.

They said the Takeda Pharmaceutical Co Ltd <4502.T>drug Actos, known generically as pioglitazone, is the first diabetes therapy shown to reduce the progression of atherosclerosis.

"The results are very striking. In my view, this is really a breakthrough study," Dr. Steven Nissen of the Cleveland Clinic, who led the study, said in an interview.

"No one has ever shown any diabetes therapy could slow the progression of disease. Keep in mind the leading cause of death for diabetics is cardiovascular disease," said Nissen, whose findings were published online in the Journal of the American Medical Association and presented at a meeting of the American College of Cardiology in Chicago.

Diabetics are especially prone to atherosclerosis, which involves the build-up of fat, calcium and other deposits in the arteries.

The study, known as PERISCOPE, compared two types of medications to treat type 2 diabetes -- Actos and glimepiride, an older sulfonylurea drug that is among the most commonly used classes of diabetes therapies.

Actos is in a class of drugs known as thiazolidinediones, a relatively new group of antidiabetic agents that are known to raise the risk of heart failure and bone fractures.

In the current study, Nissen and colleagues compared the two drugs to see how well they reduced progression of atherosclerosis in 543 patients with type 2 diabetes and coronary disease.

The trial took place from 2003-2006 in 97 hospitals in North and South America. The team used intravascular ultrasound to measure fatty deposits inside the arteries.

Patients took glimepiride or pioglitazone for 18 months and their arteries were measured again for plaque build-up.

While plaque increased 0.73 percent in the glimepiride group, it fell 0.16 percent in the pioglitazone group.

The researchers also looked at maximum plaque thickness and saw it increased in the glimepiride group and decreased in the pioglitazone group.

"Evidence for a slowing of disease progression has proven a very challenging end point in recent years with the prominent failure of several promising approaches," Nissen and colleagues wrote in JAMA.

Nissen said a single study is not enough to change medical practice, but it does signal the need for more research on how different diabetes drugs stack up.

Dr. Salim Yusuf of McMaster University in Ontario, Canada, however, noted that patients in the study who took Actos did have a significant number of fractures.

"We need proper studies in diabetes. This suggests there may be differences in drugs. We need to test that," Yusuf told reporters.

(Editing by Maggie Fox)

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