Tocopherols and tocotrienols plasma levels are associated with cognitive impairment

Abstract:

Vitamin E includes 8 natural compounds (4 tocopherols, 4 tocotrienols) with potential neuroprotective activity. α-Tocopherol has mainly been investigated in relation to cognitive impairment.

We examined the relation of all plasma vitamin E forms and markers of vitamin E damage (α-tocopherylquinone, 5-nitro-γ-tocopherol) to mild cognitive impairment (MCI) and Alzheimer's disease (AD). Within the AddNeuroMed-Project, plasma tocopherols, tocotrienols, α-tocopherylquinone, and 5-nitro-γ-tocopherol were assessed in 168 AD cases, 166 MCI, and 187 cognitively normal (CN) people.

Compared with cognitively normal subjects, AD and MCI had lower levels of total tocopherols, total tocotrienols, and total vitamin E. In multivariable-polytomous-logistic regression analysis, both MCI and AD cases had 85% lower odds to be in the highest tertile of total tocopherols and total vitamin E, and they were, respectively, 92% and 94% less likely to be in the highest tertile of total tocotrienols than the lowest tertile. Further, both disorders were associated with increased vitamin E damage.

Low plasma tocopherols and tocotrienols levels are associated with increased odds of MCI and AD.

'Vitamin E' actually includes 8 different substances (4 tocopherols and 4 tocotrienols), all of which have the potential to protect brain cells from damage.  However, most studies of Vitamin E in relation to dementia or age-related cognitive impairment have focused on only one of these, known as alpha-tocopherol.

In this study, the researchers measured all 8 forms of Vitamin E in blood serum, as well as two markers of Vitamin E damage. These measures were taken in 166 patients with mild cognitive impairment (MCI) 168 with Alzheimer's Disease (AD), and 187 people who were cognitively normal (CN).

Both groups of patients (MCI and AD) had lower levels of total tocopherols, total tocotrienols and total Vitamin E compared with the cognitively normal adults.  Additional analyses were then carried out, controlling for many other factors that could potentially influence the results.  People with AD or MCI were 85% less likely to score in the highest third for either total tocopherols or total Vitamin E. They were also more than 90% less likely to be in the top third than the bottom third on total tocotrienols.  In addition, people with either MCI or AD showed significantloy more signs of Vitamin E damage than those who were cognitively normal.

In conclusion, low levels of all forms of Vitamin E, and higher levels of Vitamin E damage were associated with higher odds of having mild cognitive impairment and dementia.