Vascular cognitive impairment linked to B vitamin deficiency

In the August 26, 2008 issue of Proceedings of the National Academy of Sciences, researchers at Tufts University's Human Nutrition Research Center on Aging (HNRCA) report that a deficiency of three B vitamins is associated with cognitive dysfunction in mice, as well as adverse effects on the brain's capillaries.

Tufts Friedman School of Nutrition Science and Policy assistant professor Aron Troen, PhD and colleagues fed mice one of two diets designed to result in high homocysteine levels over a ten week period. Elevated plasma homocysteine has been linked with an increased risk of cognitive impairment. The first diet contained a high amount of the amino acid methionine, which metabolizes to homocysteine, and the second diet was deficient in folate, vitamin B6 and vitamin B12, which help convert homocysteine back to methionine. A third group received normal diets.

"Mice fed a diet deficient in folate and vitamins B12 and B6 demonstrated significant deficits in spatial learning and memory compared with normal mice." Dr Troen reported. "The B vitamin-deficient mice also developed plasma homocysteine concentrations that were seven-fold higher than the concentrations observed in mice fed a normal diet."

Dr Troen's team additionally observed reductions in capillary length and density in the brains of mice that received B vitamin deficient diets. Mice that were given high methionine diets experienced similar effects, but to a lesser degree.

"The elevated levels of homocysteine that were associated with vascular cognitive impairment in the mice in our study are comparable to the levels that are associated in older adults with an increased risk for Alzheimer's disease and cerebrovascular disease, the latter of which manifests with conditions such as stroke and atherosclerosis," stated Irwin Rosenberg, MD, who is the director of the Nutrition and Neurocognition Laboratory at the HNRCA. "These findings may indicate that microvascular changes mediate the association between high homocysteine levels and human age-related cognitive decline."
Reported 9/08 LEF.ORG

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