Vitamin K-dependent gamma-carboxylation of the 1,25-dihydroxyvitamin D3 receptor

Role of Vitamin K in Intestinal Health

Intestinal diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancer (CRC) generally characterized by clinical symptoms, including malabsorption, intestinal dysfunction, injury, and microbiome imbalance, as well as certain secondary intestinal disease complications, continue to be serious public health problems worldwide. The role of vitamin K (VK) on intestinal health has drawn growing interest in recent years. In addition to its role in blood coagulation and bone health, several investigations continue to explore the role of VK as an emerging novel biological compound with the potential function of improving intestinal health. This study aims to present a thorough review on the bacterial sources, intestinal absorption, uptake of VK, and VK deficiency in patients with intestinal diseases, with emphasis on the effect of VK supplementation on immunity, anti-inflammation, intestinal microbes and its metabolites, antioxidation, and coagulation, and promoting epithelial development. Besides, VK-dependent proteins (VKDPs) are another crucial mechanism for VK to exert a gastroprotection role for their functions of anti-inflammation, immunomodulation, and anti-tumorigenesis. In summary, published studies preliminarily show that VK presents a beneficial effect on intestinal health and may be used as a therapeutic drug to prevent/treat intestinal diseases, but the specific mechanism of VK in intestinal health has yet to be elucidated.

The combination effect of vitamin K and vitamin D on human bone quality: a meta-analysis of randomized controlled trials

BACKGROUND

Previous studies did not draw a consistent conclusion about the effects of vitamin K combined with vitamin D on human skeletal quality.

METHOD AND FINDINGS

A comprehensive search on Web of Science, PubMed, Embase and the Cochrane Library (from 1950 to February 2020) and bibliographies of relevant articles was undertaken, with the meta-analysis of eight randomized controlled trials (RCTs) including a total of 971 subjects. Vitamin K combined with vitamin D significantly increased the total bone mineral density (BMD): the pooled effect size was 0.316 [95% CI (confidence interval), 0.031 to 0.601]. A significant decrease in undercarboxylated osteocalcin (-0.945, -1.113 to -0.778) can be observed with the combination of vitamin K and D. Simultaneously, subgroup analysis showed that K2 or vitamin K (not specified) supplement was less than 500 μg d-1, which when combined with vitamin D can significantly increase the total BMD compared with the control group fed a normal diet or the group with no treatment (0.479, 0.101 to 0.858 and 0.570, 0.196 to 0.945).

CONCLUSIONS

The combination of vitamin K and D can significantly increase the total BMD and significantly decrease undercarboxylated osteocalcin, and a more favorable effect is expected when vitamin K2 is used.

Analysis of Risk Factors Affecting Incidence of Osteoporosis and Fragility Fractures in Liver Transplant Recipients

Background

Fragility fractures caused by osteoporosis are common complications seen in recipients of organ transplantation who survive long term. Although many risk factors have been identified for osteoporosis after organ transplantation, none of them have been recognized as the main cause of development of the condition. Several studies have examined vitamin D receptor (VDR) gene single-nucleotide polymorphisms (SNPs) for their influence on bone mineral density (BMD) and fracture risk, but with variable results. We aimed to elucidate the risk factors that affect incidence of osteoporosis and fragility fractures in liver transplant recipients.

Material/Methods

In this study, we monitored incidence of fragility fracture and osteoporosis in 45 patients who had been evaluated with dual-energy X-ray absorptiometry (DXA) after liver transplantation. We also analyzed the association between VDR SNPs such as BsmI, ApaI, FokI, and TaqI with osteoporosis and fracture incidence in 27 patients in our cohort in whom SNPs were evaluated and DXA performed after liver transplantation.

Results

Osteoporosis was diagnosed in 17 of 45 patients in whom BMD was measured after liver transplantation. Of the patients with osteoporosis, 15 (88.2%) subsequently had fragility fractures. The incidence of postoperative osteoporosis was significantly higher in the recipients who had alcoholic liver cirrhosis as their primary disease. Interestingly, there were significantly more patients with a homozygous BsmI GG genotype in the group diagnosed with osteoporosis.

Conclusions

Our study suggests that patients who undergo liver transplantation and have alcoholic liver cirrhosis or the BsmI GG genotype may be at increased risk for osteoporosis. Further research is necessary to confirm these findings.

The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review

Vitamins D and K are both fat-soluble vitamins and play a central role in calcium metabolism. Vitamin D promotes the production of vitamin K-dependent proteins, which require vitamin K for carboxylation in order to function properly. The purpose of this review is to summarize available evidence of the synergistic interplay between vitamins D and K on bone and cardiovascular health. Animal and human studies suggest that optimal concentrations of both vitamin D and vitamin K are beneficial for bone and cardiovascular health as supported by genetic, molecular, cellular, and human studies. Most clinical trials studied vitamin D and K supplementation with bone health in postmenopausal women. Few intervention trials studied vitamin D and K supplementation with cardiovascular-related outcomes. These limited studies indicate that joint supplementation might be beneficial for cardiovascular health. Current evidence supports the notion that joint supplementation of vitamins D and K might be more effective than the consumption of either alone for bone and cardiovascular health. As more is discovered about the powerful combination of vitamins D and K, it gives a renewed reason to eat a healthy diet including a variety of foods such as vegetables and fermented dairy for bone and cardiovascular health.

Calcium and vitamin D in obesity

New and more effective nutritional measures are urgently needed for the prevention of obesity. The role of Ca and vitamin D in obesity has been recently implicated. Low Ca intake and low vitamin D status have been linked with an increased risk of obesity in epidemiological studies; however, clinical intervention trials designed to test this association have produced controversial results. The suggested anti-obesity mechanisms of Ca and vitamin D include the regulation of adipocyte death (apoptosis), adipogenesis and lipid metabolism. Dietary Ca has been also shown to increase faecal fat excretion. The potential role of Ca and vitamin D in shifting energy balance towards a more negative state is an area of considerable interest. Ultimately, a review of recent research findings does not allow the reaching of a definitive conclusion that increasing Ca intake and rising vitamin D status will influence fat mass and body weight or decrease the risk of obesity and overweight.

Dietary phylloquinone depletion and repletion in postmenopausal women: effects on bone and mineral metabolism

INTRODUCTION

Vitamin K has been implicated in increased bone fracture risk. Despite a potential role of vitamin K in bone, little is known about the effects of altered dietary phylloquinone intake on the underlying components of bone and mineral metabolism.

METHODS

A 84-day in-house dietary phylloquinone (vitamin K) depletion-repletion study was undertaken in 21 postmenopausal women (mean age: 70 years) to assess the effects of altered vitamin K status on intestinal calcium (Ca) absorption, urinary and serum Ca and phosphorus (P), serum calcemic hormones, and serum biomarkers of bone turnover [osteocalcin and N-telopeptide type 1 collagen cross-links (NTx)] and the response to 1,25-dihydroxyvitamin D treatment (1 microg/dayx7 d).

RESULTS

The group receiving calcitriol treatment (n=11) had higher Ca absorption, urinary Ca, urinary and serum P and serum osteocalcin and lower serum parathyroid hormone (PTH). There were no significant effects of acute (4-week) phylloquinone depletion on response to 1,25-dihydroxyvitamin D treatment or on measures of bone formation or mineral metabolism. However, phylloquinone treatment had a significant effect (p<0.04) on serum NTx. Phylloquinone repletion, up to five times (450 microg phylloquinone per day) the currently recommended adequate intake level of dietary phylloquinone for women, significantly reduced serum NTx (16.8+/-0.9 nmol bone collagen equivalents (BCE) per liter following repletion vs 18.4+/-1.1 nmol BCE per liter following depletion; p<0.01).

CONCLUSIONS

These findings suggest that altering vitamin K status in postmenopausal women by manipulating phylloquinone intake does not have an acute affect on intestinal Ca absorption, renal mineral excretion, or bone formation, but high phylloquinone intake may modestly reduce bone resorption. The impact of high phylloquinone intake on bone mineral density and fracture risk needs to be ascertained in randomized clinical trials.

Osteoporosis after liver transplantation

Osteoporosis remains a serious potential complication of liver transplantation, although its incidence may be significantly reduced by the use of lower doses of glucocorticoids. Additional factors likely to contribute to its pathogenesis include other immunosuppressive agents, particularly cyclosporin A and FK506, vitamin D insufficiency, secondary hyperparathyroidism, hypogonadism and pre-existing bone disease. Bone density assessment and spinal X-rays should be performed before transplantation to assess subsequent fracture risk and vitamin D and gonadal status assessed. Measures should be taken to optimise bone health prior to transplantation; in those with low bone mineral density and/or previous fragility fracture, prophylaxis against bone loss after transplantation should be considered. Although anti-fracture efficacy has not been established for any agent there is evidence, mainly in patients undergoing other forms of solid organ transplantation, that repeated infusions of pamidronate may be effective in preventing bone loss.

Combination of 22-oxa-1,25-dihydroxyvitamin D(3), a vitamin D(3) derivative, with vitamin K(2) (VK2) synergistically enhances cell differentiation but suppresses VK2-inducing apoptosis in HL-60 cells

We originally reported that vitamin K(2) (VK2) effectively induces apoptosis in various types of primary cultured leukemia cells and leukemia cell lines in vitro. In addition, VK2 was shown to induce differentiation of leukemia cells when the cells were resistant against VK2-inducing apoptosis. A novel synthetic vitamin D(3)derivative, 22-oxa-1,25-dihydroxyvitamin D(3) (OCT: oxacarcitriol) shows a more potent differentiation-inducing ability among myeloid leukemia cells in vitro with much lesser extent of the induction of hypercalcemia in vivo as compared to the effects of 1alpha,25(OH)(2)D(3). In the present study, we focused on the effects of a combination of OCT plus VK2 on leukemia cells. Treatment of HL-60 cells with OCT for 72 h induces monocytic differentiation. A combination of OCT plus VK2 dramatically enhances monocytic differentiation as assessed by morphologic features, positivity for non-specific esterase staining, and cell surface antigen expressions. This combined effect far exceeds the maximum differentiation induction ability at the optimal concentrations of either OCT or VK2 alone. In addition, pronounced accumulation of the cells in the G0/G1 phase is observed by combined treatment with OCT plus VK2 as compared with each vitamin alone. In contrast to cell differentiation, caspase-3 activation and apoptosis induction in response to VK2 are significantly suppressed in the presence of OCT in HL-60 cells. These data suggest that monocytic differentiation and apoptosis induction of HL-60 cells are inversely regulated. Furthermore, pronounced induction of differentiation by combined treatment with VK2 plus OCT was also observed in four out of six cases of primary cultured acute myeloid leukemia cells in vitro, suggesting that VK2 plus OCT might be a potent combination for the differentiation-based therapy for acute myeloid leukemias.

Effect of Dietary Vitamin K1 on Selected Plasma Characteristics and Bone Ash in Young Turkeys Fed Diets Adequate or Deficient in Vitamin D3

Three experiments were conducted to determine the effect of dietary vitamin K1 (K1) on selected plasma characteristics and bone ash in poults. In Experiment 1, diets were supplemented with 0, 0.5, 1.0, or 2.0 mg of K1/kg. All diets contained 1,650 IU of vitamin D3 (D3)/kg. Dietary K1 had no effect on tibia ash at 7 d or incidence of a severe, rickets-like condition. Tibia ash of poults fed 2.0 mg of K1/kg, however, was greater at 14 d of age than that of poults fed the basal diet. Dietary inclusion of 0.5 mg of K1/kg was as effective as 1 or 2 mg of K1/kg in reducing plasma prothrombin time. In Experiment 2, a 2 x 4 factorial arrangement was used consisting of 1,650 or 550 IU of D3/kg and 0.1, 0.45, 1.0, and 2.0 mg of K1/kg. Dietary D3 and K1 had no effect on bone ash. Dietary inclusion of 0.1 mg of K1/kg seemed to be enough to minimize plasma prothrombin time. In Experiment 3, dietary treatments consisted of a control (1,650 IU of D3 and 2.0 mg of K1/kg) and K1 concentrations of 0, 0.37, 2.28, or 5.33 mg/kg in diets containing 275 IU of D3/kg. Poults fed the low-D3 diet without K1 consumed less feed, gained less weight, and had increased plasma alkaline phosphatase activity, decreased inorganic phosphorus level, and decreased tibia ash (P < 0.05) compared with those of poults fed the control diet. Feed intake and body weight gain were improved, plasma alkaline phosphatase activity decreased, and plasma inorganic phosphorus increased or tended to increase when poults were fed the low-D3 diet supplemented with 0.37 or 2.88 mg of K1/kg compared with poults fed the low-D3 diet without K1 supplementation. Tibia ash of poults fed the low-D3 diet was not affected by K1 supplementation. The results of this research show that dietary K1 concentration had little, if any, effect on bone development in 1- to 14-d-old turkeys.

Influence of a single treatment with vitamin E or K (hormonal imprinting) of neonatal rats on the sexual behavior of adults

The effect of a single neonatal treatment (imprinting) with vitamin E or vitamin K1 on the sexual activity of three-month old rats, was studied. In female animals vitamin E treatment significantly lowered the Meyerson index and lordosis quotient, among males there were significantly more inactive animals and no multiple ejaculations could be observed. Vitamin K1 treatment caused only slight changes in the same direction, in both sexes. Considering also earlier results concerning vitamin A and D neonatal treatments (alterations in receptor binding capacity, sex hormone levels and sexual behavior), and receptorial changes caused by neonatal vitamin E and K1 treatments, the present experiment also calls attention to the lifelong effects of perinatal treatment with lipid soluble vitamins.

Pharmacological modulation of nerve growth factor synthesis: a mechanistic comparison of vitamin D receptor and beta(2)-adrenoceptor agonists

Increasing nerve growth factor (NGF) in the PNS is a rational strategy for treating certain neurodegenerative disorders. The present studies were undertaken to compare two compounds, a vitamin D(3) analogue (CB1093) with minimal calcaemic effects, and clenbuterol, a long-acting beta(2)-adrenoceptor agonist, both of which induce NGF synthesis in vivo. Clenbuterol caused significant increases in both NGF mRNA and protein in 3T3 cells; with maxima at 10 nM and at 8-12 h exposure. Effects of clenbuterol on NGF mRNA were antagonized by propranolol. Mobility shift assays on whole cell extracts showed that clenbuterol increased AP1 binding in 3T3 cells prior to increasing NGF synthesis. Clenbuterol was without effect on NGF mRNA levels in L929 cells, whereas CB1093 caused significant increases in both NGF mRNA and protein levels in both 3T3 and L929 cells. Stimulation was almost maximal at 24 h exposure and was sustained for at least 72 h. The magnitude of the increase was much greater in L929 (700% increase) than in 3T3 cells (80%). Binding to the vitamin D nuclear receptor (VDR), which acts as a transcription factor itself, was increased as early as 30 min after exposure to of CB1093 and maintained up to 24 h. Increased VDR binding preceded increased NGF mRNA. A 150% increase in AP-1 binding was also evident. This study demonstrates that CB1093 and clenbuterol stimulate NGF levels in vitro and that AP-1 binding could be a commonality between the mechanism of NGF induction of these two compounds.

Rat oligodendrocytes express the vitamin D(3) receptor and respond to 1,25-dihydroxyvitamin D(3)

The present study investigates the presence of vitamin D receptor (VDR) in cells of the rat oligodendrocyte (OL) lineage. VDR transcripts were detected by in situ hybridization in a fraction of rat OL in secondary cultures. The VDR protein was shown to be co-localized in cells that are also recognized by an anti-myelin basic protein (MBP) antibody. Likewise, in vivo, VDR-positive cells were found in the brain white matter, such as the internal capsule of the striatum or the corpus callosum but also in the spinal cord. At least part of these positive cells in vivo correspond to OL, since they were co-stained by an anti-carbonic anhydrase II antiserum. Northern blot analyses of the CG-4 OL cell line demonstrated that the VDR transcripts are already found in the O-2A precursors. There was a two-fold increase in the relative abundance of these transcripts in differentiated OL or in type-2 astrocytes. 1, 25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] increased the pool of transcripts encoding its own receptor, the VDR. The hormone also enhanced the abundance of the mRNA of the nerve growth factor (NGF) and of its low-affinity receptor, the p75(NTR) protein. By contrast, the hormone had no effect on the levels of MBP or proteolipid protein (PLP) mRNA. This finding suggests that unlike retinoic acid (RA) or thyroid hormone, 1,25-(OH)(2)D(3) has no regulatory action on the synthesis of myelin proteins.

Effect of single neonatal vitamin K1 treatment (imprinting) on the binding capacity of thymic glucocorticoid and uterine estrogen receptors of adolescent and adult rats

Neonatal single treatment with vitamin K1 (50 microg/animal) significantly increased the density (Bmax) of thymic glucocorticoid receptors of the adolescent (6 weeks old) and uterine estrogen receptors of adult (10 weeks old) females. The same tendency was observed in the thymus of males and adult females, however without significance. Receptor affinity was (not significantly) influenced in the same direction. Considering that the steroid receptor imprinting effect of vitamins A and D as well as the imprinting-like effect of vitamin E was demonstrated earlier, the ability for neonatal steroid receptor imprinting of the whole lipid-soluble vitamin group is now justified.

Calbindins decreased after space flight

Exposure of the body to microgravity during space flight causes a series of well-documented changes in Ca2+ metabolism, yet the cellular and molecular mechanisms leading to these changes are poorly understood. Calbindins, vitamin D-dependent Ca2+ binding proteins, are believed to have a significant role in maintaining cellular Ca2+ homeostasis. In this study, we used biochemical and immunocytochemical approaches to analyze the expression of calbindin-D28k and calbindin-D9k in kidneys, small intestine, and pancreas of rats flown for 9 d aboard the space shuttle. The effects of microgravity on calbindins in rats from space were compared with synchronous Animal Enclosure Module controls, modeled weightlessness animals (tail suspension), and their controls. Exposure to microgravity resulted in a significant and sustained decrease in calbindin-D28k content in the kidney and calbindin-D9k in the small intestine of flight animals, as measured by enzyme-linked immunosorbent assay (ELISA). Modeled weightlessness animals exhibited a similar decrease in calbindins by ELISA. Immunocytochemistry (ICC) in combination with quantitative computer image analysis was used to measure in situ the expression of calbindins in the kidney and the small intestine, and the expression of insulin in pancreas. There was a large decrease of immunoreactivity in renal distal tubular cell-associated calbindin-D28k and in intestinal absorptive cell-associated calbindin-D9k of space flight and modeled weightlessness animals compared with matched controls. No consistent difference in pancreatic insulin immunoreactivity between space flight, modeled weightlessness, and controls was observed. Regression analysis of results obtained by quantitative ICC and ELISA for space flight, modeled weightlessness animals, and their controls demonstrated a significant correlation. These findings after a short-term exposure to microgravity or modeled weightlessness suggest that a decreased expression of calbindins may contribute to the disorders of Ca2+ metabolism induced by space flight.

1,25-dihydroxyvitamin D3 regulates the synthesis of nerve growth factor in primary cultures of glial cells

The effect of 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3) on nerve growth factor (NGF) synthesis was investigated in primary cultures of astrocytes prepared from brain of neonatal rats. 1,25-(OH)2 D3 elicited a dose-dependent increase of NGF mRNA with a maximal effect at 10(-7) M, which persisted for at least 48 h. Northern blot analysis revealed an expression of the vitamin D3 receptor (VDR) gene in primary glial cells. Treatment of cells with 1,25-(OH)2 D3 led to an increase in the VDR mRNA levels. Similar results were obtained in C6 glioma cells. Exposure of primary glial cells to 10(-8) M 1,25-(OH)2 D3 caused only a 2-fold increase of the levels of cell-secreted NGF after 3 days of treatment. However, a 5-fold increase was observed three days after a second addition of vitamin D3. Likewise, a pretreatment with lower doses of hormone such as 10(-10) M or 10(-9) M enhanced the responsiveness of the cells to a 24 h treatment with 10(-8) M hormone. It appears, therefore, that the duration of the treatment influences the level of synthesis of NGF, possibly as a consequence of the increase of the VDR gene expression. The specificity of 1,25-(OH)2 D3 is supported by the fact that a concentration of 10(-7) M of an another vitamin D3 metabolite, 24,25-(OH)2 D3, had no effect on NGF synthesis. Several lines of evidence indicate that astrocytes constitute the major cell type responsive to 1,25-(OH)2 D3 in primary cultures of glial cells.(ABSTRACT TRUNCATED AT 250 WORDS)