ABCG5 and ABCG8 Are Involved in Vitamin K Transport

Revisiting the interconnection between lipids and vitamin K metabolism: insights from recent research and potential therapeutic implications: a review

Vitamin K is a lipophilic vitamin, whose absorption, transportation, and distribution are influenced by lipids. The plasma vitamin K level after supplementation is predominantly a lipid-driven effect and independent of existing vitamin K status. However, previous studies examining the efficacy of vitamin K supplementation often overlooked the influence of lipid levels on vitamin K absorption, resulting in inconsistent outcomes. Recent research discovered that impaired transportation of vitamin K2 within uremic high-density lipoproteins (HDL) in individuals with uremia might elucidate the lack of beneficial effects in preventing calcification observed in multiple trials involving menaquinone-7 (MK-7) supplementation among patients with chronic kidney disease. Clinical findings have shown that drugs used to regulate hyperlipidemia interact with the vitamin K antagonist warfarin, because cholesterol and vitamin K share common transport receptors, such as Niemann-Pick C1-like 1 (NPC1L1) and ATP-binding cassette protein G5/G8 (ABCG5/ABCG8), in enterocytes and hepatocytes. Additionally, cholesterol and vitamin K share a common biosynthetic intermediate called geranylgeranyl pyrophosphate (GGPP). It is important to note that statins, which hinder cholesterol synthesis, can also impede vitamin K conversion, ultimately impacting the functionality of vitamin K-dependent proteins. Furthermore, certain studies have indicated that vitamin K supplementation holds potential in managing hyperlipidemia, potentially opening a novel avenue for controlling hyperlipidemia using dietary vitamin K supplements. Therefore, attaining a more comprehensive understanding of the intricate interplay between vitamin K and lipids will yield valuable insights concerning the utilization of vitamin K and lipid regulation.

A polymorphism in ABCA2 is associated with neutropenia induced by capecitabine in Japanese patients with colorectal cancer

PURPOSE

Capecitabine is a prodrug that converts to 5-fluorouracil (5-FU) in three steps. A previous study showed that ABCA2 rs2271862 (C > T) and ABCG5 rs6720173 were associated with increased clearance of 5-FU and 5'-deoxy-5-fluorouridine, respectively, in Spanish patients with colorectal cancer (CRC) (Br J Clin Pharmacol 2021) and reported that ABCA2 rs2271862 was associated with decreased risk of capecitabine-induced neutropenia. Other studies have reported that ABCB1 rs1128503, rs2032592, and rs1045642 were associated with capecitabine-induced toxicity in Spanish CRC patients (Oncotarget 2015, Phamacogenomics 2010). Here, we prospectively examined the effects of ABC transporter genes polymorphisms on capecitabine pharmacokinetics and toxicity.

METHODS

We enrolled patients with postoperative CRC treated with adjuvant capecitabine plus oxaliplatin (CapeOX) and patients with metastatic CRC receiving CapeOX. Pharmacokinetic analysis of the first capecitabine dose (1000 mg/m2) was performed on day 1. We analyzed plasma concentrations of capecitabine and its three metabolites by high-performance liquid chromatography and ABC transporter genes polymorphisms using direct sequencing.

RESULTS

Patients with ABCA2 rs2271862 T/T genotype had significantly lower area under the plasma concentration-time curve of capecitabine, but not of its metabolites, which were divided by the dose of the parent drug, than patients with C/C or C/T genotype (P = 0.0238). Frequency of ≥ grade 2 neutropenia was significantly lower in patients with ABCA2 rs2271862 T/T genotype (P = 0.00915). Polymorphisms in ABCG5 and ABCB1 were not associated with capecitabine pharmacokinetics and toxicity.

CONCLUSIONS

We found that ABCA2 polymorphism was significantly associated with systemic exposure to capecitabine and capecitabine-induced neutropenia in Japanese patients with CRC.