Scientific Abstract
Objective
Vitamin K (VK) exists in multiple forms. Plant-based phylloquinone (PK) is considered the predominant dietary VK form. However,recent studies have shown bacterial and animal-based forms of VK, called menaquinones (MKn; n=number of prenyl units in side chain), are prevalent in foods such as dairy, fermented products, and meat, including pork. Bacterially-produced MKn are also synthesized by the gut microbiota. It is unknown if MKn are absorbed and metabolized. The objective of this study was to compare MKn concentrations in blood, tissue, and feces of mice given purified and food-based MKn to mice fed a VK-deficient (VKD, “control”) diet.
Methods
Sixty male and 60 female 10-week old C57BL6 mice were acclimated on a VKD diet. After 4 weeks, mice were randomized to six groups and given a diet containing purified dietary VK forms (“PK”, “MK4”, “MK9”, or an equimolar combination, “Combo”), pork (24% of diet, “Pork”), or maintained on “VKD” diet for 4 weeks. VK forms in diets, blood, tissues, and feces were measured using LC-MS, and compared by diet group and sex using 2-way ANOVA. Bacterial DNA was extracted from fecal samples and sequenced using Illumina HiSeq to analyze bacterial community composition. Differences in composition by sex and diet group were determined using non-parametric PERMANOVA, and bacterial richness was compared by sex and by diet group using Welch’s t-test.
Results
The VK content of the study diets were as follows (in µg/kg diet): control: 20.6 ± 2.0 PK; PK: 3200 ± 932 PK; MK4: 10.2 ± 0.4 PK and 2150 ± 184 MK4; MK9: 9.2 ± 1.6 PK and 3820 ± 598 MK9; Combo: 925 ± 173 PK, 821 ± 130 MK4, and 1310 ± 214 MK9; and Pork: 11.1 ± 0.6 PK, 38.5 ± 7.8 MK4, 34.7 ± 9.8 MK9, and 33.2 ± 10.5 MK10. In all analyzed tissues, tissue accumulation of VK was greater in females as compared to males. VK content of the small intestine and liver reflected vitamin K present in the diet, such that PK, MK4, and MK9 were significantly higher in groups supplemented that form as compared to the control group (all p<0.03). Female mice had significantly higher bacterial richness compared to male mice (Welch’s t-test, t = 2.2699, df = 92.739, p-value = 0.02553) while no significant differences in bacterial richness were observed between dietary regiments.
Conclusions
MKn forms in small intestine and liver reflect dietary MKn intake. There is sex difference for VK forms absorption. Fecal MKn partially reflected intake, but endogenous production of MKn was largely unaffected by dietary VK. Despite abundant endogenous MKn production, tissue VK was low in the control group suggesting tissue accumulation of VK is independent of MKn produced in the gut.
Publications
Taylor & Francis: https://www.tandfonline.com/doi/full/10.1080/19490976.2021.1887721