Age- and brain region-specific effects of dietary vitamin K on myelin sulfatides

Dysregulation of myelin sulfatides is a risk factor for cognitive decline with age. Vitamin K is present in high concentrations in the brain and has been implicated in the regulation of sulfatide metabolism. Our objective was to investigate the age-related interrelation between dietary vitamin K and sulfatides in myelin fractions isolated from the brain regions of Fischer 344 male rats fed one of two dietary forms of vitamin K: phylloquinone or its hydrogenated form, 2',3'-dihydrophylloquinone {(dK),} for 28 days. Both dietary forms of vitamin K were converted to menaquinone-4 {(MK-4)} in the brain. The efficiency of dietary {dK} conversion to {MK-4} compared to dietary phylloquinone was lower in the striatum and cortex, and was similar to that in the hippocampus. There were significant positive correlations between sulfatides and {MK-4} in the hippocampus (phylloquinone-supplemented diet, 12 and 24 months; {dK-supplemented} diet, 12 months) and cortex (phylloquinone-supplemented diet, 12 and 24 months). No significant correlations were observed in the striatum. Furthermore, sulfatides in the hippocampus were significantly positively correlated with {MK-4} in serum. This is the first attempt to establish and characterize a novel animal model that exploits the inability of dietary {dK} to convert to brain {MK-4} to study the dietary effects of vitamin K on brain sulfatide in brain regions controlling motor and cognitive functions. Our findings suggest that this animal model may be useful for investigation of the effect of the dietary vitamin K on sulfatide metabolism, myelin structure and behavior functions.