Effect of high-dose vitamin E on insulin resistance and associated parameters in overweight subjects.
OBJECTIVE
Markers of oxidative stress and plasma alanine transferase (ALT) levels are increased and circulating antioxidant concentrations are reduced in individuals with insulin resistance. Vitamin E improves glycemic control in people with diabetes. We tested the hypothesis that vitamin E would decrease markers of oxidative stress and plasma ALT levels and improve insulin sensitivity in overweight individuals.


METHODS
Eighty overweight individuals (BMI >27 kg/m(2)) were randomly allocated to receive either 800 IU vitamin E per day or a matching placebo for 3 months. The dose of vitamin E was increased to 1,200 IU per day for a further 3 months.


RESULTS
Plasma peroxides decreased by 27% at 3 months and by 29% at 6 months in the group that received vitamin E and were positively correlated with plasma vitamin E concentrations at the 6-month time point. At 3 months, fasting plasma glucose and insulin concentrations were significantly reduced and homeostasis model assessment increased. These changes were not apparent at 6 months. Plasma ALT concentrations declined significantly throughout the study period.


CONCLUSIONS
In conclusion, these findings indicate that vitamin E improves oxidative stress and hepatocellular function. Although insulin resistance also improves, this effect appears transient.
Manning
Patrick J
PJ
Department of Medical and Surgical Sciences, University of Otago, Private bag, Dunedin, New Zealand. patrickmanning@healthotago.co.nz
Sutherland
Wayne H F
WH
Walker
Robert J
RJ
Williams
Sheila M
SM
De Jong
Sylvia A
SA
Ryalls
Anne R
AR
Berry
Elizabeth A
EA
D000328:Adult; D000368:Aged; D000975:Antioxidants / Q000627:therapeutic use; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis; D004798:Enzymes / Q000097:blood; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000503:physiopathology*; D010919:Placebos; D012016:Reference Values; D014810:Vitamin E / Q000097:blood / Q000627:therapeutic use*
D000975:Antioxidants; D001786:Blood Glucose; D004798:Enzymes; D007328:Insulin; D010919:Placebos; D014810:Vitamin E; D002097:C-Reactive Protein