CHICAGO, March 31, 2008 (AFP) - A Japanese diabetes drug is the first to help reduce the hardening of the arteries, according to study released Monday, potentially opening up a new way to treat the debilitating disease.

Actos, made by Japan's Taketa laboratory, was compared with the drug Amaryl, manufactured by the French company Sanofi, during 18 months of clinical trials involving 543 patients.

Until now no diabetes drug has proved effective in reducing atherosclerosis, known as hardening of the arteries, said Steven Nissen, head of cardiology at Cleveland Clinic in Ohio and the study's lead author.

'In my view, this is really a breakthrough study,' he said.

He noted atherosclerosis is 'particularly aggressive' in diabetes patients, and 75 percent of deaths from type 2 diabetes, which is most common in adults and is increasingly linked to obesity, are caused by cardio-vascular problems.

'No one has ever shown any diabetes therapy could slow the progression of the disease,' he told the annual meeting of the American College of Cardiology in Chicago, adding that previously, no one drug was much better than another.

Diabetes is currently increasing at 'an alarming rate' in both developed and developing countries, Nissen said.

The study, which was also published in the Journal of the American Medical Association (JAMA), followed patients in 97 clinics in North and South America.

It measured the volume of plaque found in patients' arteries before and after the trials, with the help of an ultra-sound scan.

The group taking Actos had no visible increase in arterial plaque, in fact registering a 0.16 percent reduction, while in the second group prescribed Amaryl, the growth of plaque was up 0.73 percent.

'This study has major implications for how we will treat diabetics with coronary disease in the future,' Nissen said, adding that further studies were needed before making any changes to the standard treatment.

An accompanying editorial pointed out Actos' failings, noting that this group of drugs 'share a common adverse effect on heart failure, and other non-cardiovascular adverse effects, such as bone fractures.'

But Doctors Philippe Gabriel Steg, of the Centre Hospitalier Bichat-Claude Bernard in Paris and editor of JAMA-Francais, and Michel Marre, of the Universite Paris VII, wrote that the trial 'provides a reassuring perspective for patients with type 2 diabetes and high cardiovascular risk.'

Dr Salim Yusuf, professor of medicine at the Population Health Research Institute at McMaster University in Ontario, Canada, told a press conference that patients in the clinical trial had an increased number of fractures.

'We need proper studies in diabetes. This suggests there may be differences in drugs,' he said.