ABCG5 and ABCG8 Are Involved in Vitamin K Transport

Abstract

ATP-binding cassette protein G5 (ABCG5)/ABCG8 heterodimer exports cholesterol from cells, while Niemann–Pick C1-like 1 (NPC1L1) imports cholesterol and vitamin K. We examined whether ABCG5/ABCG8 transports vitamin K similar to NPC1L1. Since high concentrations of vitamin K3 show cytotoxicity, the cytoprotective effects of ABCG5/ABCG8 were examined. BHK cells expressing ABCG5/ABCG8 were more resistant to vitamin K3 cytotoxicity than control cells, suggesting that ABCG5/ABCG8 transports vitamin K3 out of cells. The addition of vitamin K1 reversed the effects of ABCG5/ABCG8, suggesting that vitamin K1 competitively inhibits the transport of vitamin K3. To examine the transport of vitamin K1 by ABCG5/ABCG8, vitamin K1 levels in the medium and cells were measured. Vitamin K1 levels in cells expressing ABCG5/ABCG8 were lower than those in control cells, while vitamin K1 efflux increased in cells expressing ABCG5/ABCG8. Furthermore, the biliary vitamin K1 concentration in Abcg5/Abcg8-deficient mice was lower than that in wild-type mice, although serum vitamin K1 levels were not affected by the presence of Abcg5/Abcg8. These findings suggest that ABCG5 and ABCG8 are involved in the transport of sterols and vitamin K. ABCG5/ABCG8 and NPC1L1 might play important roles in the regulation of vitamin K absorption and excretion.

Nutritional Strategies for Muscle Atrophy: Current Evidence and Underlying Mechanisms

“…[150] The VDR agonist, 1,25-dihydroxyvitamin D3, counteracts muscle atrophy by enhancing the VDR/SIRT1/SIRT3 axis. [151] Therefore, vitamin D supplementation becomes a potential nutritional support strategy for muscle atrophy. [150,152,153] In addition, a series of animal studies have shown that nicotinamide riboside and vitamins B6 and C have the potential to reduce muscle atrophy and promote skeletal muscle growth and repair.…”

Roles of vitamin K‑dependent protein in biomineralization (Review)

“…1C ). In addition, a recent study found that ATP-binding cassette protein G5 (ABCG5)/ABCG8, a heterodimer exporting cholesterol, participates in the excretion of VK from the intestines ( 16 ).…”