The medication rosiglitazone (Avandia) controls diabetics’ blood sugar by binding to the PPAR gamma receptor in fat cells, doctors have known. Now new research shows that these receptors also exist in arteries, where they may help protect against heart disease, Dr. Ronald E. Law and colleagues at the University of California at Los Angeles School of Medicine report in the March 21, 2000, Circulation. The study was a preclinical in vitro study using both human and rat tissue.
Previous studies had “been divided as to [the receptor's] presence in the artery wall,” although they did show that it existed in other types of tissue, Dr. Law said.
By binding to the artery receptors, the medication may lower diabetics’ risk of clogged arteries, including restenosis (when an artery is blocked again after angioplasty), the team reports. Rosiglitazone treats type 2 diabetes, which begins in adulthood, and not type 1, which usually begins in childhood.
If an artery is damaged even slightly, such as from atherosclerosis or after angioplasty, the tissue increases production of growth factors that cause cells in the area to multiply and migrate. Such cell activity is dangerous, because it can lead to artery walls getting thicker. However, when the researchers exposed artery smooth muscle cells to the diabetes medication, the cells failed to multiply or migrate, the team reports. The drugs may slow the build-up of fatty substances along the artery wall.
What the PPAR gamma receptor normally does other than bind with diabetes drugs is unclear, Dr. Law told Mediconsult. “We don’t really understand what normally turns these receptors on, or what their role is in tissue other than…to make more fat cells, he said.
The team also tested another diabetes drug, troglitazone (Rezulin), but it was taken off the market in March 2000, because of possible dangerous side effects. Both drugs are part of the thiazolidinedione (TZD) class of drugs that control blood sugar levels in people with type 2 diabetes.
Commenting on the study, Dr. Andrew P. Levy, M.D., Ph.D, at the Technion Faculty of Medicine, and Medical Advisor for HeartInfo, says that, “The new TZD drugs described above will help patients with type 2 control their glucose levels. The precise mechanism as to how these drugs achieve their effect is not entirely clear. More research is required to fully understand their mode of action, but their efficacy is indisputable.”