Vitamin E supplementation and oxidative stress in obese individuals

Nutrition Research Newsletter,  March, 2007  

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There is a good deal of evidence suggesting that chronic oxidant stress is important in the development of cardiovascular diseases and insulin resistance. Obesity is a risk factor for the development of insulin resistance, diabetes, and cardiovascular disease and is associated with increased oxidative stress as indicated by increased production and plasma concentrations of 8-isoprostanes. Amounts of 8-isoprostane in the plasma and urine are regarded as the best indices of lipid peroxidation and oxidative stress that are currently available. Isoprostanes are bioactive and induce vasoconstriction, platelet adhesion, and macrophage scavenger receptors and matrix metalloproteinase activity. These compounds are present in atherosclerotic lesions, and isoprostane formation is increased in persons with coronary artery disease independently of other risk factors. Thus, a decrease in isoprostane production may attenuate risk of developing cardiovascular disease.

There is evidence that oxidative stress deceases the concentration of circulating adiponectin. Plasma adiponectin concentrations are inversely associated with formation of 8-isoprostanes. Adiponectin is secreted from adipose tissue and is thought to be an important regulator of insulin sensitivity.

Short-term supplementation with pharmacological doses of vitamin E decreases 8-isoprostane formation in subjects under increased oxidative stress as a result of disease. However, there is little information on the effect of longer-term supplementation with high-dose vitamin E on plasma 8-isoprostane and adiponectin concentrations in obesity.

A recent investigation measured 8-isoprostane and adiponectin concentrations in plasma samples to determine the effect of 6-month supplementation with high-dose vitamin E on these variables in overweight individuals. Subjects included 86 individuals aged 31 to 65 years with a BMI of > 27 kg/[m.sup.2]. Following a one-month run-in period, participants were randomized by block randomization with stratification for sex to receive 800 IU of natural vitamin E or matching placebo daily for three months. At the end of this period, the dose of vitamin E was increased to 1200 IU/day with a matching increase in placebo. Subjects were instructed to maintain their usual lifestyle during the study. At baseline and at three and six months, blood was taken, and anthropometric measurements and capsule counts to assess compliance to supplementation were made. Plasma 8-isoprostane and adiponectin concentrations were measured at baseline and three and six months.

During six months of supplementation with vitamin E, plasma vitamin E concentration increased significantly (p < 0.001) by 76%, and plasma 8-isoprostane concentrations decreased significantly (-11%, p = 0.03), whereas plasma adiponectin concentrations did not change significantly.

These findings suggest that supplementation with high dose vitamin E reduces oxidative stress in overweight and obese individuals.

W. Sutherland, P. Manning, R. Walker, et al. Vitamin E supplementation and plasma 8-isoprostane and adiponectin in overweight subjects. Obesity; 15:386-391 (February 2007). [Correspondence: Wayne Sutherland, Medicine Section, Department of Medical and Surgical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand. Email:wayne.Sutherland@stonebow.otago.ac.na].

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