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Vitamin K is an essential nutrient involved in the regulation of blood clotting and tissue mineralization. Vitamin K oxidoreductase (VKORC1) converts vitamin K epoxide into reduced vitamin K, which acts as the co-factor for the γ-carboxylation of several proteins, including coagulation factors produced by the liver. VKORC1 is also the pharmacological target of warfarin, a widely used anticoagulant. Vertebrates possess a VKORC1 paralog, VKORC1-like 1 (VKORC1L1), but until very recently, the importance of VKORC1L1 for protein γ-carboxylation and hemostasis in vivo was not clear. Here, we first review the current knowledge on the structure, function and expression pattern of VKORC1L1, including recent data establishing that, in the absence of VKORC1, VKORC1L1 can support vitamin K-dependent carboxylation in the liver during the pre- and perinatal periods in vivo. We then provide original data showing that the partial redundancy between VKORC1 and VKORC1L1 also exists in bone around birth. Recent studies indicate that, in vitro and in cell culture models, VKORC1L1 is less sensitive to warfarin than VKORC1. Genetic evidence is presented here, which supports the notion that VKORC1L1 is not the warfarin-resistant vitamin K quinone reductase present in the liver. In summary, although the exact physiological function of VKORC1L1 remains elusive, the latest findings clearly established that this enzyme is a vitamin K oxidoreductase, which can support γ-carboxylation in vivo.

Sodium dehydroacetate (Na-DHA), a fungicide used in food, feed, cosmetics, and medicine, has been found to cause coagulation aberration accompanied by the inhibition of vitamin K epoxide reductase (VKOR) in the liver in rats. VKOR complex 1 (VKORC1) and VKORC1 like-1 (VKORC1L1) are two homologous VKOR proteins. Little information is available on the effect of Na-DHA on VKORC1L1 in the liver or VKORC1/VKORC1L1 in extrahepatic tissue and sex differences in Na-DHA metabolism. In the present study, after administration of 200 mg/kg Na-DHA by gavage, significant inhibition of VKORC1 or VKORC1L1 expression in tissues, as well as prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT), were observed. The PT/APTT in the Na-DHA-exposed males were 1.27- to 1.48-fold/1.17- to 1.37-fold, while the corresponding values in the Na-DHA-exposed females were 1.36- to 2.02-fold/1.20- to 1.70-fold. Serum or tissue Na-DHA concentrations were significantly higher in females than in males. The pharmacokinetic parameters (t1/2, Cmax, AUC0∼24 h, and MRT0∼24 h) of Na-DHA in female rats were significantly higher than those in male rats. Furthermore, cytochrome P450 (CYP) activity was investigated using the cocktail probe method. The results revealed that Na-DHA exhibited an inductive effect on CYP1A2, 2D1/2, and 3A1/2 activities by changing the main pharmacokinetic parameters of probe drugs in male rats. However, no significant change in CYP2E1 activity was found. There were sex differences in the metabolism and coagulation in rats exposed to Na-DHA. The lower metabolism and higher blood Na-DHA concentration in females may be the reasons for higher coagulation sensitivity in female rats.

Sodium dehydroacetate (Na-DHA), a fungicide used in food, feed, cosmetics, and medicine, has been found to cause coagulation aberration accompanied by the inhibition of vitamin K epoxide reductase (VKOR) in the liver in rats. VKOR complex 1 (VKORC1) and VKORC1 like-1 (VKORC1L1) are two homologous VKOR proteins. Little information is available on the effect of Na-DHA on VKORC1L1 in the liver or VKORC1/VKORC1L1 in extrahepatic tissue and sex differences in Na-DHA metabolism. In the present study, after administration of 200 mg/kg Na-DHA by gavage, significant inhibition of VKORC1 or VKORC1L1 expression in tissues, as well as prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT), were observed. The PT/APTT in the Na-DHA-exposed males were 1.27- to 1.48-fold/1.17- to 1.37-fold, while the corresponding values in the Na-DHA-exposed females were 1.36- to 2.02-fold/1.20- to 1.70-fold. Serum or tissue Na-DHA concentrations were significantly higher in females than in males. The pharmacokinetic parameters (t1/2, Cmax, AUC0∼24 h, and MRT0∼24 h) of Na-DHA in female rats were significantly higher than those in male rats. Furthermore, cytochrome P450 (CYP) activity was investigated using the cocktail probe method. The results revealed that Na-DHA exhibited an inductive effect on CYP1A2, 2D1/2, and 3A1/2 activities by changing the main pharmacokinetic parameters of probe drugs in male rats. However, no significant change in CYP2E1 activity was found. There were sex differences in the metabolism and coagulation in rats exposed to Na-DHA. The lower metabolism and higher blood Na-DHA concentration in females may be the reasons for higher coagulation sensitivity in female rats. [ABSTRACT FROM AUTHOR]