Artificial Antioxidants
Supplementary Antiradicals May Induce Early Stage Type 2 Diabetes
Oct 19, 2009
A new study was the to show that a high intake of supplementary antioxidants promotes insulin resistance - a precursor of type 2 diabetes. Confusing? Definitely. After all, antioxidants have been construed as health protectors, not the other way around.
Association Between High Antioxidant Intake and Type 2 Diabetes
Dr. Xingen Lee, a Cornell University professor, says: "Although free radicals are known to be harmful and antioxidants helpful, our study suggests that we actually need some free radicals to regulate insulin sensitivity."
To determine the relationship between high antioxidant levels and insulin resistance, Dr. Lee and his team used mice that have been bred to overexpress glutathione peroxidase (an antioxidant enzyme) to up to three times the normal levels. They found that the mice developed hyperglycemia (high blood glucose levels), hyperinsulinemia (high blood insulin concentration), and high blood leptin values. Leptin is a protein produced by fat cells that decreases appetite and increases energy expenditure.The experimental mice were 36% heavier and twice as fat as the control mice. Hyperglycemia, hyperinsulinemia, and obesity characterizes type 2 diabetes. Glutathione peroxidase contains 60% selenium - an antioxidant mineral.
"Most people believe that both selenium and the selenium-containing enzyme are good for health by protecting cells and tissue from oxidation. However, this study suggests that they are a double-edged sword. Antioxidants can be harmful by neutralizing too many free radicals and interfering with insulin signalling, which results in promoting obesity, insulin resistance, and diabetes." He added that their findings are consistent with the results of a recent study of pregnant women which links high levels of glutathione peroxidase, insulin resistance, and gestational diabetes - a type of diabetes that begins or becomes apparent during pregnancy.
The Biological Role of Oxidants (Free Radicals)
Pro-oxidants or "free radicals" are atoms, molecules or ions with unpaired electrons. They are highly unstable and reactive. Superoxide anion, hydrogen peroxide, hydroxyl radical, hydroxyl ion, and singlet oxygen are some examples of reactive oxygen species ROS). Nitric Oxide (NO) is an example of a reactive nitrogen species (RNS).
Reactive oxygen and nitrogen radicals are involved in numerous body processes. They facilitate:
- Intercellular and intracellular signaling. For example, the addition of superoxide or hydrogen peroxide to a variety of cultured cells increases the rate of DNA replication and cell proliferation.
- The body's immune function against infection. White blood cells produce ROS, which destroys harmful bacteria and viruses. Vitamin C (an antioxidant) actually fights infection by producing hydrogen peroxide (an pro-oxidant). Hydrogen peroxide stimulates the production of prostaglandins - substances that function as regulators affecting nearby cells. For example, some progstaglandins cause muscles to relax, dilate blood vessels and promote oxygenation of the blood. Others help muscles to contract, helping to induce labor during childbirth. Still others, sound the alarm "everything's not well!" by inducing fever, inflammation and pain.
- The stimulation of enzyme systems throughout the body. For example, hydrogen peroxide and nitric oxide (a radical nitrogen species) dilates blood vessels, increasing blood flow and the body's distribution and consumption of oxygen.
- The body's sensitivity to insulin signals. A study conducted by Dr. Tiganis and colleagues showed that "physiologic" low levels of ROS may promote the insulin response and weaken insulin resistance early in the progression of type 2 diabetes before obesity and hyperglycemia sets in. In their study, mice that have been bred not to eliminate ROS did not develop insulin resistance after they were fed a high-fat diet. They believe ROS present in muscles enhance insulin action and help reduce blood sugar levels. Dr. Tiganis concluded: "In the case of early type 2 diabetes and the development of insulin resistance, our studies suggests that antioxidants would be bad for you," explaining that under some conditions, treatments that selectively increase pro-oxidants in muscle might even be helpful, if they could be developed.
The Need for Daily Antioxidant Supplementation
Based on their findings, Dr. Tiganis believes that it is probably not a good idea to take daily antioxidant supplements if you are healthy. He said: "Although we need to undertake further studies in humans, our results indicate that the widespread use of antioxidants by the general public as a preventative measure is something that should be discouraged, particularly if you are otherwise healthy." Healthy people should eat a healthy diet and exercise regularly. This is the natural way of making ROS that promotes insulin sensitivity.
References:
Xingen Lei et al. "Dual Roles of Antioxidant Enzymes in Oxidative Stress and Chronic Diseases" Cornell University Plenary Session Proposal SFRBM Annual Meeting February 2009
Tiganis T el al. "Reactive Oxygen Species Enhance Insulin Sensitivity" Cell Metabolism Oct.2009;10(4):260-272
Valko M "Free radicals and antioxidants in normal physiological functions in human disease" Int. J Biochem Cell Biology 2007;39(1):44-84
Whitney EN & Noss SR "Free Radicals" Understanding Nutrition Ninth Edition Wadsworth, CA 2002pp: 336-378
Berkow R (ed) "Diabetes" Merck Manual 1997 pp: 717-723
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