Studies Link Diabetes, Antioxidant Vitamins and Atherosclerosis
Diabetes mellitus is a debilitating disease. Individuals with diabetes face daily challenges to manage blood glucose levels and increased risk of long-term vascular complications affecting the heart and brain. Diabetes is becoming more prevalent worldwide. In addition to the personal burden, the disease is transforming societies. For example, 10% of total UK health resources in 2010/2012 were diabetes-related and these are projected to 17% in 2035/2036.
A new cross-sectional study in 350 individuals with Type 2 diabetes reports greater brain atrophy and cognitive impairment (poorer visuospatial construction, planning, visual memory and speed) versus 363 individuals without diabetes. Why does diabetes affect cognitive function?
As reviewed by Goldenstein and colleagues, oxidative stress is considered to be an important factor in atherosclerotic plaque accumulation. High blood glucose levels glycosylate blood proteins, cause endothelial dysfunction and impair vascular tone. Smoking, hypertension and hyperlipidemia increase oxidation of lipids and their accumulation in macrophages. This contributes to foam cell formation, plaque development in blood vessels, and atherosclerosis. Atherosclerosis is associated with diminished blood flow. Blood flow carries oxygen and nutrients for tissues to function. Individuals with diabetes have a higher incidence of cardiovascular complications such as atherosclerosis than people without diabetes.
Maintaining adequate levels of antioxidant vitamins may be important in maintaining healthy blood vessels. Haptoglobin (HP), a blood protein which helps prevent heme-iron mediated oxidation, is found in three forms. People with diabetes and the HP 2-2 genotype (about 36% of the population) have a significantly greater risk of a non-fatal heart attack or cardiovascular death. Vitamin E supplementation seems to relieve the risk (Vardi et al., 2012). In a new study, Costacou and colleagues measured plasma and urinary markers of oxidative stress in 658 individuals with Type 1 diabetes at 3 times over 20 years. They report α-tocopherol (vitamin E) concentrations were inversely associated with coronary artery disease. Urinary markers of oxidative stress, 15-isoprostane F2t per mg creatinine, was directly associated with coronary artery disease.
These studies suggest that diabetes management is more complicated than maintaining normal blood glucose and cholesterol levels. Emerging evidence suggests that having optimal antioxidant status is also important. Scientists are only beginning to understand the interactions among individual genetics, antioxidant status and cardiovascular risk management.
Hex N, Bartlett C, Wright D, Taylor M, Varley D. Estimating the current and future costs of Type 1 and Type 2 diabetes in the UK, including direct health costs and indirect societal and productivity costs. 2012 Diabetic Med doi:10.1111/j.1464-5491.2012.03698.x
Moran C, Phan TG, Chen J, Blizzard L, Beare R, Venn A, Munch G, Wood AG, Forbes J, Greenaway TM, Pearson S, Srikanth V. Brain atrophy in Type 2 diabetes: Regional distribution and influence on cognition. 2013 Diab Care doi:10.2337/dc13-0143
Goldenstein H, Levy NS, Lipener YT, Levy AP. Patient selection and vitamin E treatment in diabetes mellitus. 2013 Expert Rev Cardiovasc Ther doi://1586/ERC.12.187
Vardi M, Blum S, Levy AP. Haptoglobin genotype and cardiovascular outcomes in diabetes mellitus- natural history of the disease and the effect of vitamin E treatment. Meta-analysis of the medical literature. 2012 Eur J Intern Med doi:10.1016/j.ejim.2012.04.009
Costacou T, Evans RW, Schafer GL, Orchard TJ. Oxidative stress and response in relation to coronary artery disease in Type 1 diabetes. 2013 Diabetes Care doi:10.2337/dc12-2378