After 18 months of treatment, people with the haptoglobin (Hp) 2-2 gene who took 400 International Units (IU) of vitamin E daily had more than 50 percent fewer heart attacks, strokes, and related deaths than Hp 2-2 patients who took a placebo pill. 40% of individuals with diabetes carry the Hp 2-2 gene.
The researchers will present the results on November 5 at the American Heart Meetings in Orlando, Florida. The full study will appear in the November 21 online edition of the journal Arteriosclerosis, Thrombosis, and Vascular Biology.
Most of the difference came from the reduced number of heart attacks among those taking vitamin E. In the group of 1,434 Hp 2-2 individuals taking part in the study, seven people had a heart attack, compared to 17 who did not take the vitamin. Dr. Andrew Levy, of the Technion Faculty of Medicine, said there were no side effects observed in patients who took vitamin E.
The study suggests that genetic testing for the Hp 2-2 gene "may be useful to identify a large group of diabetes individuals who could potentially derive cardiovascular benefit from a very inexpensive treatment," Levy said.
The finding is a new answer to an old question: can antioxidant vitamins such as vitamin E help prevent heart disease? Previously, cardiologists routinely prescribed vitamin E for their patients, but the practice has dwindled as several major studies in the past decade showed no heart-protective effects and potential harm from vitamin E mega-doses.
However, Levy and colleagues suspected that there might be one group of patients who could benefit from vitamin E: diabetic individuals with a particular variant of the haptoglobin gene. Haptoglobin is a powerful antioxidant protein that stabilizes the iron-rich red blood cell molecule called hemoglobin, preventing inflammation in the walls of arteries.
There are several versions of the haptoglobin gene. In previous studies, Levy and colleagues showed that Hp 2-2 is an inferior antioxidant compared to its genetic siblings, and that this difference is exaggerated in patients with diabetes. The researchers also discovered that diabetic patients with Hp 2-2 are two-to-three times more likely than other diabetics to suffer a cardiovascular event such as a heart attack.
"This version of the gene does not determine whether or not an individual will develop diabetes but rather whether an individual with diabetes is susceptible to developing the devastating complications associated with diabetes such as heart disease, kidney disease or visual loss," Levy noted.
A genetic test for Hp 2-2 is commercially available, said Levy, who is also a consultant for Synvista Therapeutics, which owns a patent on the use of Hp testing to predict diabetic complications. By making a kit, the group hopes to considerably lower the price of testing. According to Levy, the test would cost about $30 and only have to be done only once.