Tissue Concentrations of Vitamin K and Expression of Key Enzymes of Vitamin K Metabolism Are Influenced by Sex and Diet but Not Housing in C57Bl6 Mice.

BACKGROUND: There has been limited characterization of biological variables that impact vitamin K metabolism. This gap in knowledge can limit the translation of data obtained from preclinical animal studies to future human studies. OBJECTIVE: The purpose of this study was to determine the effects of diet, sex, and housing on serum, tissue, and fecal vitamin K concentrations and gene expression in C57BL6 mice during dietary vitamin K manipulation. METHODS: C57BL6 4-mo-old male and female mice were randomly assigned to conventional or suspended-wire cages and fed control [1400 ± 80 µg phylloquinone (PK)/kg] or deficient (31 ± 0.45 µg PK/kg) diets for 28 d in a factorial design. PK and menaquinone (MK) 4 plasma and tissue concentrations were measured by HPLC. Long-chain MKs were measured in all matrices by LC-atmospheric pressure chemical ionization-mass spectrometry. Gene expression was quantified by reverse transcriptase-polymerase chain reaction in the liver, brain, kidney, pancreas, and adipose tissue. RESULTS: Male and female mice responded differently to dietary manipulation in a tissue-dependent manner. In mice fed the control diet, females had ∼3-fold more MK4 in the brain and mesenteric adipose tissue than did males and 100% greater PK concentrations in the liver, kidney, and mesenteric adipose tissue than did males. In mice fed the deficient diet, kidney MK4 concentrations were ∼4-fold greater in females than in males, and there were no differences in other tissues. Males and females differed in the expression of vitamin K expoxide reductase complex 1 (Vkorc1) in mesenteric adipose tissue and the pancreas and ubiA domain-containing protein 1 (Ubiad1) in the kidney and brain. There was no effect of housing on serum, tissue, or fecal concentrations of any vitamin K form. CONCLUSIONS: Vitamin K concentrations and expression of key metabolic enzymes differ between male and female mice and in response to the dietary PK concentration. Identifying factors that may impact study design and outcomes of interest is critical to optimize study parameters examining vitamin K metabolism in animal models.

Level of undercarboxylated osteocalcin in reproductive Thai females.

Osteocalcin is a vitamin K dependent protein requiring vitamin K as a cofactor for the enzyme gamma glutamyl carboxylase which converts the glutamate residues at 17, 21, 24 position of the molecule into gamma carboxyglutamate or Gla residues. The carboxylation makes immature osteocalcin or undercarboxylated osteocalcin (ucOC) into mature osteocalcin which enhances calcium binding in bone. The level of undercarboxylated osteocalcin is recognized as a marker of vitamin K2 bone. The level of undercarboxylated osteocalcin is recognized as a marker of vitamin K2 in blood necessary for this process. Mature osteocalcin has a higher affinity for hydroxyapatite than undercarboxylated osteocalcin. Foreign studies have shown that ucOC level is increased in elderly women and postmenopausal women in comparison with young, healthy, reproductive women and level of ucOC is also the marker to predict the risk of hip fracture. The standard value of undercarboxylated osteocalcin in Thai women is not available. The aim of the present study was to find the level of ucOC in reproductive Thai females. 357 healthy female volunteers who had regular menstruation, 20-50 years of age, average age 38.5 years old. The volunteers had no intake of any kind of medicine affecting bone metabolism before blood examination. The mean value of undercarboxylated osteocalcin is 2.69 ng/ml, median is 2.10_ng/ml standard deviation = 2.02,_standard error = 0.107 with 95% confident interval = 2.485 to 2.906 ng/ml. In the authors previous pilot study in elderly and postmenopausal women, the authors found that the mean of ucOC in Thai elderly and postmenopausal women was higher than that of reproductive women.

Novel mutation in the gamma-glutamyl carboxylase gene resulting in congenital combined deficiency of all vitamin K-dependent blood coagulation factors.

A mutation in the gamma-glutamyl carboxylase gene leading to a combined congenital deficiency of all vitamin K-dependent coagulation factors was identified in a Lebanese boy. He is the first offspring of consanguineous parents and was homozygous for a unique point mutation in exon 11, resulting in the conversion of a tryptophan codon (TGG) to a serine codon (TCG) at amino acid residue 501. Oral vitamin K(1) administration resulted in resolution of the clinical symptoms. Screening of several family members on this mutation with an RFLP technique revealed 10 asymptomatic members who were heterozygous for the mutation, confirming the autosomal recessive pattern of inheritance of this disease. In 50 nonrelated normal subjects, the mutation was not found. This is the second time a missense mutation in the gamma-glutamyl carboxylase gene is described that has serious impact on normal hemostasis.

Vitamin K-dependent carboxylase: mRNA distribution and effects of vitamin K-deficiency and warfarin treatment.

A cDNA encoding vitamin K-dependent gamma-glutamyl carboxylase was cloned from a human Hep G2 cDNA library. The RNA transcript of the enzyme was found to be widely distributed in various human and rat tissues with liver showing the highest level. The carboxylase transcription in liver was not affected in rats treated with a single dose of warfarin (10 mg/kg) when measured up to 48 hours after the dose, though, at 12 hours, carboxylase activity measured in liver microsomes was elevated 5.4 fold over controls (p < 0.001). In rats fasted for 72 hours there was no affect on transcription in the liver while hepatic carboxylase activity increased 4.1 fold (p < 0.001). These data suggest that the increase in activity of the liver carboxylase in warfarin treated or fasted rats was not regulated by transcription but more likely was due to a posttranscriptional mechanism.

[Activity of menadione reductase and level of cytochrome B5 and P-450 in liver with varying supplies of vitamin K and administration of pelentan to rats]. / Aktivnost' menadionreduktazy i soderzhanie tsitokhormov B5 i P-450 v pecheni pri razlichnoi obespechennosti krys vitaminom K i vvedenii pelentana.

Content of cytochromes b5 and P-450 as well as activity of soluble menadione reductase were estimated in liver microsomes of rats deprived of vitamin K or maintained both on a diet containing excess of vicasol or antivitamin K-pelentan. Deficiency of vitamin K led to an increase in the specific activity of menadione reductase and in content of the cytochrome P-450. Administration of antivitamin K did not alter these parameters but caused an increase in the content of cytochrome b5, which was not changed in vitamin K deficiency. Dissimilar effects of alimentary deficiency in vitamin K and of pelentan administration suggest that administration of antivitamins K (although it allowed to discover alterations developed via the system of vitamin K-dependent carboxylation) could not be completely identified with alimentary vitamin K deficiency.

[Activity of enzymes participating in xenobiotic metabolism and the condition of microsomal membranes of rat liver in vitamin K deficiency]. / Aktivnost' fermentov, uchastvuiushchikh v metabolizme ksenobiotikov, i sostoianie mikrosomal'nykh membran pecheni krys pri defitsite vitamina K.

Alimentary deficiency or vitamin K (vitamin K-poor diet) as well as the vitamin deficiency resulting from sinkumar administration are accompanied by a decreased activity of microsomal demethylases, hydroxylase, NADH- and nNADPH-reductases of dichlorophenolindophenol and neotrazolium. The activity of cytosolic enzymes (only glutathione-S-transferases, aryl- and allyl esterases) is diminished in a lesser degree. Vitamin K deficiency does not significantly interfere with the effect of the xenobiotic metabolism enzyme inducer (phenobarbital) or the cytochrome P-450 inhibitor (cobalt chloride). The changes in the enzyme activity result in a decrease of acetanilide biotransformation. A possible reason for the observed changes in the activity of microsomal enzymes is the weakening of hydrophobic and polar interactions in microsomal membranes. This hypothesis was confirmed by experiments with the use of membrane perturbants as well as by solubilization of membrane-bound enzymes.

[Activity of various enzymes of energy metabolism in the rat kidney and intestines in vitamin D and K deficiency]. / Aktivnost' nekotorykh fermentov énergeticheskogo obmena pochek i kishechnika krys pri defitsite vitaminov D i K.

The vitamin D and K deficiency was studied for its effect on creatine kinase, phosphorylase and alkaline phosphatase activity of rat kidneys and intestinal mucosa. The results show that creatine kinase and phosphorylase activity of kidneys varies depending on the content of these vitamins, e.g. it is activated with vitamin D depletion irrespective of the vitamin K status and remains unchanged with the deficiency of vitamin K alone. In this case the vitamin D deficiency affects kidney phosphorylase and intestinal mucosa differently. Data obtained and those available in literature permit suggesting that the deficiency of the same vitamin may exert a different action on the activity of isoforms of such enzymes as creatine kinase and phosphorylase.

[The effect of vitamin K deficiency in rats on various enzyme systems participating in energy metabolism]. / Vliianie nedostatochnosti vitamina K u krys na nekotorye fermentnye sistemy, uchastvuiushchie v énergoobespechenii.

In alimentary deficiency of vitamin K in rats, accompanied by an increase in the prothrombin time by 30%, activity of kidney creatine kinase and of blood serum alkaline phosphatase was unaltered, while the activity of alkaline phosphatase in small intestinal mucose was decreased by 20% and that of creatine kinase from skeletal muscles--by 10%. In vitamin K-deprived animals the rate of coupling between respiration and mitochondrial phosphorylation was decreased, which might be due to alteration in the NADH-dehydrogenase complex. Menadion reductase activity and cyanide-resistant respiration of mitochondria were unaltered in presence of menadion. Palmitic acid effectively activated of mitochondrial respiration in vitamin K-deprived animals (contrary to the control rats). This effect appears to occur as a result of structural alterations in mitochondria depending on vitamin K level in the organelles.

[The effect of vitamin K on the activity of glycolysis and pentose phosphate cycle enzymes]. / Vliianie vitamina K na aktivnost' fermentov glikoliza i pentozofosfatnogo tsikla.

Effect of naphthoquinone levels on the activity of enzymes involved in glycolysis and pentose phosphate cycles was studied in male rats. Under conditions of primary and secondary K-avitaminosis the enzymatic activity, limiting these cycles, (aldolase of fructose-1,6-diphosphate, glucose phosphate isomerase and glucose-6-phosphate dehydrogenase) was increased, while the mitochondrial glutamate dehydrogenase activity was decreased. As a result of metabolic transformations under conditions of K-avitaminosis (primary and secondary) concentration of DNA in the animal tissues was lowered.

In vivo effects of beta-lactam antibiotics and heterocyclic thiol compounds on vitamin K-dependent carboxylation activity and blood coagulation factors in vitamin K-deficient rats.

The in vivo effects of heterocyclic thiol compounds, corresponding to the 3'-position substituents of several beta-lactam antibiotics, on blood coagulation factors and on liver microsomal gamma-glutamylcarboxylation (gamma-carboxylation) activity were evaluated in rats maintained on a vitamin K-deficient diet. These rats, when compared to normal control animals, exhibited hypoprothrombinemic changes: prolongation of both prothrombin time and activated partial thromboplastin time, decreases in factor VII and plasma prothrombin, and increases in PIVKA II (descarboxyprothrombin) both in plasma and liver. They also displayed a marked increase in liver microsomal gamma-carboxylation activity. These blood coagulation variables could be altered markedly by administering various heterocyclic thiol compounds to the vitamin K-deficient rats, although these compounds did not inhibit gamma-carboxylation activity in an assay system using phylloquinone. A similar pattern of alteration was observed when some beta-lactam antibiotics were administered. Increased microsomal gamma-carboxylation activity in antibiotic-treated vitamin K-deficient rats was normalized by the administration of vitamin K, concomitant with the recovery of blood coagulation variables to the normal range. The results indicate that antibiotic-induced hypoprothrombinemia in vivo is not caused by inhibition of enzymes of the gamma-carboxylation system, such as vitamin K reductase and gamma-glutamylcarboxylase, but is related to the endogenous vitamin K level.

Vitamin K-dependent carboxylase: possible role of the substrate "propeptide" as an intracellular recognition site.

The liver microsomal vitamin K-dependent carboxylase catalyzes the posttranslational conversion of specific glutamate residues to gamma-carboxyglutamate residues in a limited number of proteins. A number of these proteins have been shown to contain a homologous basic amino acid-rich "propeptide" between the leader sequence and the amino terminus of the mature protein. Plasmids encoding protein C, a vitamin K-dependent protein, containing or lacking a propeptide region were constructed and the protein was expressed in Escherichia coli. The protein products were assayed as substrates in an in vitro vitamin K-dependent carboxylase system. Only proteins containing a propeptide region were substrates for the enzyme. These data support the hypothesis that this sequence of the primary gene product is an important recognition site for this processing enzyme.

Oxygen dependence of vitamin K-dependent carboxylase and vitamin K epoxidase.

A study of the oxygen requirements of the rat liver microsomal vitamin K-dependent carboxylase and vitamin K 2,3-epoxidase indicated that both enzymes had a Km for O2 in the range 60-80 microM. This value was not influenced by vitamin concentration, alterations in carboxylase substrate, Mn2+, or dithiothreitol, and is consistent with the hypothesis that both activities are catalyzed by the same enzyme.

[Tissue lipolytic activity with various vitamin K and E allowances in white rats]. / Lipoliticheskaia aktivnost' tkanei pri razlichnoi obespechennosti belykh krys vitaminami K i E.

Experiments on white male rats were performed to study the activity of tissue lipase (pH 6.8-7.2) and lipoprotein lipase (pH 8.5) in the liver, skeletal muscles and kidneys depending on the body supply with vitamins K and E. It was established that in rats with food K-avitaminosis, liver and skeletal muscle lipase and lipoprotein lipase and kidney lipoprotein lipase were activated. The analogous changes in the activity of the test enzymes were discovered in animals given antivitamins K - hydroxycoumarins (e.g. pelentan). The exception to the rule was lipase (pH 6.8-7.2) of the kidneys. E-avitaminosis was accompanied by alterations in the activity of the test enzymes in the liver, skeletal muscles and kidneys.

Prothrombin biosynthesis: characterization of processing events in rat liver microsomes.

Plasma and hepatic microsomal forms of rat prothrombin have been compared by sodium dodecyl sulfate-polyacrylamide electrophoresis and isoelectric focusing. The major prothrombin species that accumulated in the microsomes of rats treated with warfarin had a molecular weight of 78 500 and a pI in 8 M urea of 6.3-6.5. Plasma prothrombin had a molecular weight of 83 500 and a pI of 5.3-5.7. Microsomes from normal rat liver contain a second pool of precursor with a molecular weight of 83 500, and digestion with the glycosidase Endo H indicated that this form has been processed to contain complex carbohydrates, while the Mr 78 500 form is a high mannose form and is the substrate for the vitamin K dependent carboxylase. Treatment of rats with tunicamycin revealed that glycosylation was not essential for carboxylation or secretion from the liver. Comparison of the aglyco forms of prothrombin and its precursors suggests that the intracellular forms contain a basic, Mr approximately 1500 peptide that is missing from the plasma form of prothrombin.

Vitamin K-dependent carboxylase: effect of detergent concentrations, vitamin K status, and added protein precursors on activity.

Activity of the rat liver microsomal vitamin K-dependent carboxylase has been studied at various concentrations of detergent. The activity which could be solubilized by 0.25% Triton X-100 was low but could be greatly increased if vitamin K-deficient rats were given vitamin K a few minutes before they were killed. At higher concentrations of Triton, more activity was solubilized and this effect was not seen. In vitro carboxylation of endogenous microsomal proteins was decreased by 80-90% if vitamin K was administered 1 min before rats were killed, but the amount of assayable prothrombin precursor was decreased by only 20%. Decarboxylated vitamin K-dependent rat plasma proteins were not substrates for the carboxylase and did not influence peptide carboxylase activity significantly. Purified microsomal prothrombin precursors did, however, stimulate carboxylation of peptide substrate and were used as a substrate for the carboxylase in a preparation from precursor depleted vitamin K-deficient rats.

Localization of renal vitamin K-dependent gamma-glutamyl carboxylase to tubule cells.

The renal vitamin K-dependent gamma-glutamyl carboxylase was present in microsomes prepared from the renal cortex as well as the inner and outer medulla of several species. When glomeruli were isolated from either dog or rat renal cortex, microsomes prepared from these glomeruli were devoid of carboxylase activity. Proximal tubules were isolated from rabbit renal cortex; microsomes derived from these tubules had easily measurable carboxylase activity. The experiments demonstrate that the vitamin K-dependent gamma-glutamyl carboxylase is located in renal tubule cells. Since the enzyme is found not only in cortex but also inner and outer medulla, its distribution is not restricted to specific tubule segments.

Vitamin K-dependent carboxylase. Stoichiometry of carboxylation and vitamin K 2,3-epoxide formation.

Crude rat liver microsomal preparations catalyze a reduced vitamin K- and oxygen-dependent carboxylation of peptide-bound glutamyl residues to gamma-carboxyglutamyl residues. The same preparations convert reduced vitamin K to its 2,3-epoxide. The stoichiometry of this relationship has been investigated. At saturating concentrations of CO2, equal amounts of vitamin K 2,3-epoxide and gamma-carboxyglutamic acid are formed. As the CO2 concentration is lowered, this ratio shifts to a large excess of epoxide. Alterations in glutamyl substrate concentration or Mn2+ concentration cause equal alterations in both activities, while addition of KCN stimulated epoxidation and inhibited carboxylation. The release of 3H from a gamma-[3H]glutamyl substrate was tightly coupled to epoxide formation, and both of these activities were inhibited by glutathione peroxidase. These data are consistent with a reaction mechanism in which an oxygenated form of vitamin K activates the substrate glutamyl residue by hydrogen removal in a reaction that is coupled to vitamin K epoxide formation.