Effect of vitamin K in bone metabolism and vascular calcification: A review of mechanisms of action and evidences

Gut Microbiome and Osteoporosis

Gut microbiome refers to the microbes that live in human digestive tract and are symbiotic with the human body. They participate in the regulation of various physiological and pathological processes of the human body and are associated with various diseases. The pathological process of osteoporosis is affected by gut microbes. The molecular mechanisms of osteoporosis mainly include: 1) Intestinal barrier and nutrient absorption (involving SCFAs). 2) Immunoregulation (Th-17 and T-reg cells balance). 3) Regulation of intestinal-brain axis (involving 5-HT). Gut microbes can increase bone mass and improve osteoporosis by inhibiting osteoclast proliferation and differentiation, inducing apoptosis, reducing bone resorption, or promoting osteoblast proliferation and maturation. However, the therapeutic effect of gut microbes on osteoporosis remains to be further proven. At present, some of the findings on the impact of gut microbes on osteoporosis has been applied in clinical, including early diagnosis and intervention of osteoporosis and adjuvant therapy. In this article, we reviewed the molecular mechanisms underlying the regulatory effect of gut microbes on osteoporosis and the clinical practice of using gut microbes to improve bone health.

Non-polyphenolic natural inhibitors of amyloid aggregation

Protein misfolding diseases (PMDs) are chronic and progressive, with no effective therapy so far. Aggregation and misfolding of amyloidogenic proteins are closely associated with the onset and progression of PMDs, such as amyloid-β (Aβ) in Alzheimer's disease, α-Synuclein (α-Syn) in Parkinson's disease and human islet amyloid polypeptide (hIAPP) in type 2 diabetes. Inhibiting toxic aggregation of amyloidogenic proteins is regarded as a promising therapeutic approach in PMDs. The past decade has witnessed the rapid progresses of this field, dozens of inhibitors have been screened and verified in vitro and in vivo, demonstrating inhibitory effects against the aggregation and misfolding of amyloidogenic proteins, together with beneficial effects. Natural products are major sources of small molecule amyloid inhibitors, a number of natural derived compounds have been identified with great bioactivities and translational prospects. Here, we review the non-polyphenolic natural inhibitors that potentially applicable for PMDs treatment, along with their working mechanisms. Future directions are proposed for the development and clinical applications of these inhibitors.

Endocrine roles of vitamin K-dependent- osteocalcin in the relation between bone metabolism and metabolic disorders

Obesity and diabetes are important metabolic diseases and a major public health problem among the world, they have serious health and economic complications. Overweight and obesity are increased risk for deficiency of vitamin particularly shortage of fat soluble-vitamins. Studies reported that vitamin K supplementation reduces oxidative stress and metabolic risk biomarkers for diabetes, as well as reduces progression of insulin resistance. Vitamin K-dependent-protein osteocalcin (bone derived hormone) plays crucial roles in energy metabolism. There is a clear association between circulating vitamin k and dependent-osteocalcin concentrations with obesity and risk of Type 2 diabetes. Osteocalcin through molecular mechanisms improves insulin resistance, lipid and glucose profile, and mediate vitamin K positive effects. Insulin also signals osteocalcin to regulate bone mineralization. Normal carboxylation of vitamin K-dependent proteins/ hormones is a key step in preventing apoptosis and calcification of vascular endothelial cells. A missing relationship between bone, glucose and fat metabolism could clarify and manage many metabolic mechanisms. This review focuses on the physiological relationship between vitamin K-dependent-osteocalcin, metabolic and cardiovascular diseases through some molecular proteins and hormones including adipokines. A better understanding of the mechanism of action of osteocalcin modulated by vitamin K could help in implementing therapeutic drugs to cure metabolic diseases.

Extraction and Determination of Vitamin K1 in Foods by Ultrasound-Assisted Extraction, SPE, and LC-MS/MS

Vitamin K₁ is one of the important hydrophobic vitamins in fat-containing foods. Traditionally, lipase is employed in the determination of vitamin K₁ to remove the lipids, which makes the detection complex, time-consuming, and insensitive. In this study, the determination of vitamin K₁ in fat-containing foods was developed based on ultrasound-assisted extraction (UAE), solid-phase extraction (SPE) combined with liquid chromatography–tandem mass spectrometry (LC-MS/MS). The optimal conditions for extraction of vitamin K₁ were material–liquid ratio of 1:70 (g/mL), extraction temperature of 50 °C, extraction power of 700 W, extraction time of 50 min, material-wash fluid ratio of 1:60 (g/mL), and 8 mL of hexane/anhydrous ether (97:3, v/v) as the elution solvent. Then, vitamin K₁ was analyzed on a ZORBAX SB-C18 column (50 mm × 2.1 mm, 1.8 μm) by gradient elution with water (0.01% formic acid) and methanol (0.01 formic acid + 2.5 mmol/L ammonium formate) as the mobile phase. The limit of detection (LOD) and limit of quantification (LOQ) were 0.05 and 0.16 μg/kg, respectively. Calibration curve was linear over the range of 10–500 ng/mL (R² > 0.9988). The recoveries at three spiked levels were between 80.9% and 119.1%. The validation and application indicated that the proposed method was simple and sensitive in determination of vitamin K₁ in fat-containing foods.

Vitamin K as a Diet Supplement with Impact in Human Health: Current Evidence in Age-Related Diseases

Vitamin K health benefits have been recently widely shown to extend beyond blood homeostasis and implicated in chronic low-grade inflammatory diseases such as cardiovascular disease, osteoarthritis, dementia, cognitive impairment, mobility disability, and frailty. Novel and more efficient nutritional and therapeutic options are urgently needed to lower the burden and the associated health care costs of these age-related diseases. Naturally occurring vitamin K comprise the phylloquinone (vitamin K1), and a series of menaquinones broadly designated as vitamin K2 that differ in source, absorption rates, tissue distribution, bioavailability, and target activity. Although vitamin K1 and K2 sources are mainly dietary, consumer preference for diet supplements is growing, especially when derived from marine resources. The aim of this review is to update the reader regarding the specific contribution and effect of each K1 and K2 vitamers in human health, identify potential methods for its sustainable and cost-efficient production, and novel natural sources of vitamin K and formulations to improve absorption and bioavailability. This new information will contribute to foster the use of vitamin K as a health-promoting supplement, which meets the increasing consumer demand. Simultaneously, relevant information on the clinical context and direct health consequences of vitamin K deficiency focusing in aging and age-related diseases will be discussed.

Concentrations of Circulating Phylloquinone, but Not Cerebral Menaquinone-4, Are Positively Correlated with a Wide Range of Cognitive Measures: Exploratory Findings in Centenarians

BACKGROUND

Vitamin K (VK) exists in the form of phylloquinone (PK) and menaquinones (MKs). Roles of VK on cognitive health in the elderly are emerging, but there is limited evidence on VK uptake and metabolism in human brain.

OBJECTIVES

The primary objective of this study was to characterize VK distribution in brains of an elderly population with varied cognitive function. In addition, associations among circulating (a biomarker of VK intake) and cerebral VK concentrations and cognition were investigated.

METHODS

Serum or plasma (n = 27) and brain samples from the frontal cortex (FC; n = 46) and the temporal cortex (TC; n = 33) were acquired from 48 decedents (aged 98-107 y; 25 demented and 23 nondemented) enrolled in the Georgia Centenarian Study. Both circulating and brain VK concentrations were measured using HPLC with fluorescence detection. Cognitive assessment was performed within 1 y prior to mortality. Partial correlations between serum/plasma or cerebral VK concentrations and cognitive function were performed, adjusting for covariates and separating by dementia and antithrombotic use.

RESULTS

MK-4 was the predominant vitamer in both FC (mean ± SD = 4.92 ± 2.31 pmol/g, ≥89.15% ± 5.09% of total VK) and TC (4.60 ± 2.11 pmol/g, ≥89.71% ± 4.43% of total VK) regardless of cognitive status. Antithrombotic users had 34.0% and 53.9% lower MK-4 concentrations in FC (P < 0.05) and TC (P < 0.001), respectively. Circulating PK was not correlated with cerebral MK-4 or total VK concentrations. Circulating PK concentrations were significantly associated with a wide range of cognitive measures in nondemented centenarians (P < 0.05). In contrast, cerebral MK-4 concentrations were not associated with cognitive performance, either before or after exclusion of antithrombotic users.

CONCLUSIONS

Circulating VK concentrations are not related to cerebral MK-4 concentrations in centenarians. Cerebral MK-4 concentrations are tightly regulated over a range of VK intakes and cognitive function. Circulating PK may reflect intake of VK-rich foods containing other dietary components beneficial to cognitive health. Further investigation of VK uptake and metabolism in the brain is warranted.

Plaque Calcification

Vascular calcification (VC) is strongly associated with all-cause mortality and is an independent predictor of cardiovascular events. Resulting from its complex, multifaceted nature, targeted treatments for VC have not yet been developed. Lipoproteins are well characterized in the pathogenesis of atherosclerotic plaques, leading to the development of plaque regressing therapeutics. Although their roles in plaque progression are well documented, their roles in VC, and calcification of a plaque, are not well understood. In this review, early in vitro data and clinical correlations suggest an inhibitory role for HDL (high-density lipoproteins) in VC, a stimulatory role for LDL (low-density lipoprotein) and VLDL (very low-density lipoprotein) and a potentially causal role for Lp(a) (lipoprotein [a]). Additionally, after treatment with a statin or PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitor, plaque calcification is observed to increase. With the notion that differing morphologies of plaque calcification associate with either a more stable or unstable plaque phenotype, uncovering the mechanisms of lipoprotein-artery wall interactions could produce targeted therapeutic options for VC.

Interactive and Multifactorial Mechanisms of Calcific Vascular and Valvular Disease

Calcific vascular and valvular disease (CVVD) is widespread and has major health consequences. Although coronary artery calcification has long been associated with hyperlipidemia and increased mortality, recent evidence suggests that its progression is increased in association with cholesterol-lowering HMG-CoA reductase inhibitors ('statins') and long-term, high-intensity exercise. A nationwide trial showed no cardiovascular benefit of vitamin D supplements. Controversy remains as to whether calcium deposits in plaque promote or prevent plaque rupture. CVVD appears to occur through mechanisms similar to those of intramembranous, endochondral, and osteophytic skeletal bone formation. New evidence implicates autotaxin, endothelial-mesenchymal transformation, and microRNA and long non-coding RNA (lncRNA) as novel regulatory factors. New therapeutic options are being developed.

Bioactivities and Medicinal Value of Solanesol and Its Accumulation, Extraction Technology, and Determination Methods

Solanesol, an aliphatic terpene alcohol composed of nine isoprene units, is mainly found in solanaceous plants. Particularly, tobacco (Nicotiana tabacum), belonging to the Solanaceae family, is the richest plant source of solanesol, and its leaves have been regarded as the ideal material for solanesol extraction. Since the discovery of solanesol in tobacco, significant progress has been achieved in research on solanesol’s bioactivities, medicinal value, accumulation, extraction technology, and determination methods. Solanesol possesses strong free radical absorption ability and antioxidant activity owing to the presence of several non-conjugated double bonds. Notably, solanesol’s anti-inflammatory, neuroprotective, and antimicrobial activities have been previously demonstrated. Solanesol is a key intermediate in the synthesis of coenzyme Q10, vitamin K2, and the anticancer agent synergiser N-solanesyl-N,N′-bis(3,4-dimethoxybenzyl) ethylenediamine. Other applications of solanesol include solanesol derivative micelles for hydrophobic drug delivery, solanesol-derived scaffolds for bioactive peptide multimerization, and solanesol-anchored DNA for mediating vesicle fusion. Solanesol accumulation in plants is influenced by genetic and environmental factors, including biotic stresses caused by pathogen infections, temperature, illumination, and agronomic measures. Seven extraction technologies and seven determination methods of solanesol are also systematically summarized in the present review. This review can serve as a reference for solanesol’s comprehensive application.

A comparatively study of menaquinone-7 isolated from Cheonggukjang with vitamin K1 and menaquinone-4 on osteoblastic cells differentiation and mineralization

The effect of menaquinone-7 isolated from cheonggukjang was comparatively investigated with vitamin K₁ and menaquinone-4 on cell differentiation and mineralization of the osteoblastic cell line MC3T3-E1. Results indicated that all vitamin K species significantly increased MC3T3-E1 cell proliferation, cellular alkaline phosphatase activity, osteocalcin synthesis, and calcium deposition in a dose-dependent manner. Menaquinone-4 and menaquinone-7 had more potent effects on calcium deposition than vitamin K₁, and their effects were only partly reduced by warfarin (γ-carboxylation inhibitor) treatment, while warfarin abolished the induction activity of vitamin K₁ on calcification. This suggests that vitamin K₁ and K₂ (menaquinone-4 & menaquinone-7) may have different mechanisms in stimulating osteoblast mineralization. In addition, the mRNA expression ratio of osteoprotegerin and the receptor activator of nuclear factor-kB ligand was also dramatically increased by treatment with vitamin K₁ (62%), menaquinone-4 (247%), and menaquinone-7 (329%), suggesting that vitamin K may suppress the formation of osteoclast by up-regulating the ratio of osteoprotegerin/receptor activator of nuclear factor-kB ligand in osteoblasts. These results provide compelling evidence that vitamin K₁, menaquinone-4, and menaquinone-7 all can promote bone health, which might be associated with elevations in the osteoprotegerin/receptor activator of nuclear factor-kB ligand ratio.

A Multi-omics Approach to Unraveling the Microbiome-Mediated Effects of Arabinoxylan Oligosaccharides in Overweight Humans

The use of dietary fiber food supplementation as a strategy to reduce the burden of diet-related diseases is a matter of study given its cost-effectiveness and the positive results demonstrated in clinical trials. This multi-omics assessment, on different biological samples of overweight subjects with signs of metabolic syndrome, sheds light on the early and less evident effects of short-term AXOS intake on intestinal microbiota and host metabolism. We observed a deep influence of AXOS on gut microbiota beyond their recognized bifidogenic effect by boosting concomitantly a wide diversity of butyrate producers and Prevotella copri, a microbial species abundant in non-Westernized populations with traditional lifestyle and diets enriched in fresh unprocessed foods. A comprehensive evaluation of hundreds of metabolites unveiled new benefits of the AXOS intake, such as reducing the plasma ceramide levels. Globally, we observed that multiple effects of AXOS consumption seem to converge in reversing the glucose homeostasis impairment.

Long-term consumption of dietary fiber is generally considered beneficial for weight management and metabolic health, but the results of interventions vary greatly depending on the type of dietary fibers involved. This study provides a comprehensive evaluation of the effects of a specific dietary fiber consisting of a wheat-bran extract enriched in arabinoxylan-oligosaccharides (AXOS) in a human intervention trial. An integrated multi-omics analysis has been carried out to evaluate the effects of an intervention trial with an AXOS-enriched diet in overweight individuals with indices of metabolic syndrome. Microbiome analyses were performed by shotgun DNA sequencing in feces; in-depth metabolomics using nuclear magnetic resonance in fecal, urine, and plasma samples; and massive lipid profiling using mass spectrometry in fecal and serum/plasma samples. In addition to their bifidogenic effect, we observed that AXOS boost the proportion of Prevotella species. Metagenome analysis showed increases in the presence of bacterial genes involved in vitamin/cofactor production, glycan metabolism, and neurotransmitter biosynthesis as a result of AXOS intake. Furthermore, lipidomics analysis revealed reductions in plasma ceramide levels. Finally, we observed associations between Prevotella abundance and short-chain fatty acids (SCFAs) and succinate concentration in feces and identified a potential protective role of Eubacterium rectale against metabolic disease given that its abundance was positively associated with plasma phosphatidylcholine levels, thus hypothetically reducing bioavailability of choline for methylamine biosynthesis. The metagenomics, lipidomics, and metabolomics data integration indicates that sustained consumption of AXOS orchestrates a wide variety of changes in the gut microbiome and the host metabolism that collectively would impact on glucose homeostasis. (This study has been registered at ClinicalTrials.gov under identifier NCT02215343.)

IMPORTANCE The use of dietary fiber food supplementation as a strategy to reduce the burden of diet-related diseases is a matter of study given its cost-effectiveness and the positive results demonstrated in clinical trials. This multi-omics assessment, on different biological samples of overweight subjects with signs of metabolic syndrome, sheds light on the early and less evident effects of short-term AXOS intake on intestinal microbiota and host metabolism. We observed a deep influence of AXOS on gut microbiota beyond their recognized bifidogenic effect by boosting concomitantly a wide diversity of butyrate producers and Prevotella copri, a microbial species abundant in non-Westernized populations with traditional lifestyle and diets enriched in fresh unprocessed foods. A comprehensive evaluation of hundreds of metabolites unveiled new benefits of the AXOS intake, such as reducing the plasma ceramide levels. Globally, we observed that multiple effects of AXOS consumption seem to converge in reversing the glucose homeostasis impairment.

The Role of Vitamin K and Its Related Compounds in Mendelian and Acquired Ectopic Mineralization Disorders

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders.

The role of ENPP1/PC-1 in osteoinduction by calcium phosphate ceramics

In the past decade, calcium phosphate (CaP) ceramics have emerged as alternatives to autologous bone grafts for the treatment of large, critical-sized bone defects. In order to be effective in the regeneration of such defects, ceramics must show osteoinductive behaviour, defined as the ability to induce de novo heterotopic bone formation. While a set of osteoinductive CaP ceramics has been developed, the exact processes underlying osteoinduction, and the role of the physical and chemical properties of the ceramics, remain largely unknown. Previous studies have focused on the role of the transcriptome to shed light on the mechanism of osteoinduction at the mRNA level. To complement these studies, a proteomic analysis was performed to study the behaviour of hMSCs on osteoinductive and non-osteoinductive CaPs. The results of this analysis suggest that plasma cell glycoprotein 1 (PC-1), encoded by the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene, plays a key role in the process of osteoinduction by CaP ceramics. Validation experiments have confirmed that indeed, the mRNA expression of ENPP1 and the production of PC-1 are higher on osteoinductive than on non-osteoinductive CaP ceramics, a trend that was also observed for other osteogenic markers such as bone morphogenetic protein 2 (BMP2) and osteopontin (OPN), but not for alkaline phosphatase (ALP). Our results also showed that the expression of PC-1 is restricted to those cells which are in direct contact with the CaP ceramic surface, plausibly due to the localised depletion of calcium and inorganic phosphate ions from the supersaturated cell culture medium as CaP crystallises on the ceramic surface. Replicating the surface of the osteoinductive ceramic in polystyrene resulted in a significant decrease in ENPP1 expression, suggesting that surface structural properties alone are not sufficient to induce ENPP1 expression. Finally, knocking down ENPP1 expression in hMSCs resulted in increased BMP2 expression, both at the mRNA and protein level, suggesting that ENPP1 is a negative regulator of BMP-2 signalling. Taken together, this study shows, for the first time, that ENPP1/PC-1 plays an important role in CaP-induced osteogenic differentiation of hMSCs and thus possibly osteoinduction by CaP ceramics. Furthermore, we have identified a crucial role for the interfacial (chemical) events occurring on the CaP ceramic surface in the process of osteoinduction. This knowledge can contribute to the development of new bone graft substitutes, with improved osteoinductive potential.

Beneficial Effects of Vitamins K and D3 on Redox Balance of Human Osteoblasts Cultured with Hydroxyapatite-Based Biomaterials

Hydroxyapatite-based biomaterials are commonly used in surgery to repair bone damage. However, the introduction of biomaterials into the body can cause metabolic alterations, including redox imbalance. Because vitamins D3 and K (K1, MK-4, MK-7) have pronounced osteoinductive, anti-inflammatory, and antioxidant properties, it is suggested that they may reduce the adverse effects of biomaterials. The aim of this study was to investigate the effects of vitamins D3 and K, used alone and in combination, on the redox metabolism of human osteoblasts (hFOB 1.19 cell line) cultured in the presence of hydroxyapatite-based biomaterials (Maxgraft, Cerabone, Apatos, and Gen-Os). Culturing of the osteoblasts in the presence of hydroxyapatite-based biomaterials resulted in oxidative stress manifested by increased production of reactive oxygen species and decrease of glutathione level and glutathione peroxidase activity. Such redox imbalance leads to lipid peroxidation manifested by an increase of 4-hydroxynonenal level, which is known to influence the growth of bone cells. Vitamins D3 and K were shown to help maintain redox balance and prevent lipid peroxidation in osteoblasts cultured with hydroxyapatite-based biomaterials. The strongest effect was observed for the combination of vitamin D3 and MK-7. Moreover, vitamins promoted growth of the osteoblasts, manifested by increased DNA biosynthesis. Therefore, it is suggested that the use of vitamins D3 and K may protect redox balance and support the growth of osteoblasts affected by hydroxyapatite-based biomaterials.

Dietary Patterns in Relation to Low Bone Mineral Density and Fracture Risk: A Systematic Review and Meta-Analysis

Low bone mineral density (BMD) and osteoporosis-related fractures constitute a considerable public health burden. Several studies have demonstrated the association between diet and bone health. We performed a systematic review to provide an estimate of the association between different dietary patterns defined through the use of a posteriori methods and fracture or low BMD risk. A literature search on PubMed, Web of Science, and Scopus databases, up to March 2018, was performed to identify all eligible case-control, prospective, or cross-sectional studies involving subjects of both sexes and any age. Random-effects models were used. Heterogeneity and publication bias were evaluated. Stratified analyses were conducted on study characteristics. The meta-analysis includes 20 studies and identifies 3 prevalent dietary patterns: "Healthy," "Milk/dairy," and "Meat/Western." From the 10 studies on fracture, adherence to the "Healthy" pattern reduced the risk, particularly in older people (OR: 0.79; 95% CI: 0.66, 0.95; P = 0.011) and in Eastern countries (OR: 0.64; 95% CI: 0.43, 0.97; P = 0.037), whereas the risk increased with the "Meat/Western" pattern, especially for older people (OR: 1.11; 95% CI: 1.04, 1.18, P = 0.001), in those with hip fractures (OR: 1.15; 95% CI: 1.05, 1.25; P = 0.002), and in Western countries (OR: 1.10; 95% CI: 1.07, 1.14; P < 0.0001). Analyses on low BMD showed a reduced risk in the "Healthy" pattern, particularly for younger people (OR: 0.62; 95% CI: 0.44, 0.89; P = 0.009). The "Meat/Western" pattern increased low BMD risk, especially in older people (OR: 1.31; 95% CI: 1.05, 1.64; P = 0.015). The "Milk/dairy" pattern resulted in the strongest reduction in low BMD risk; when stratifying, this effect remained significant (e.g., older women-OR: 0.57; 95% CI: 0.46, 0.70; P < 0.0001). Nutrition is an important modifiable factor affecting bone health. The "Healthy" and "Milk/dairy" patterns are associated with a reduced risk of low BMD and fracture. In contrast, the "Western" pattern is inversely associated.

Gut Microbiome, Probiotics and Bone: An Updated Mini Review

The gut microbiome is now considered as a large organ that has a direct effect on gastrointestinal tract, immune and endocrine system. There is no evidence that gut microbiota regulates the immune system and is responsible for bone formation and destruction. Probiotics have been shown through the gastrointestinal tract to have a positive effect on the management of the healthy bone. This article discusses the latest data available from PubMed and Scopus databases regarding gut microbiome, probiotics and bone briefly.

Vitamin K and Bone Metabolism: A Review of the Latest Evidence in Preclinical Studies

Bone is a metabolically active tissue that renews itself throughout one's life. Cytokines along with several hormonal, nutritional, and growth factors are involved in tightly regulated bone remodeling. Accordingly, vitamin K as a multifunctional vitamin has been recently deemed appreciable as a topic of research as it plays a pivotal role in maintenance of the bone strength, and it has been proved to have a positive impact on the bone metabolism. Vitamin K exerts its anabolic effect on the bone turnover in different ways such as promoting osteoblast differentiation, upregulating transcription of specific genes in osteoblasts, and activating the bone-associated vitamin k dependent proteins which play critical roles in extracellular bone matrix mineralization. There is also credible evidence to support the effects of vitamin k2 on differentiation of other mesenchymal stem cells into osteoblast. The main objective of the present paper is to comprehensively outline the preclinical studies on the properties of vitamin K and its effects on the bone metabolism. The evidence could shed light on further clinical studies to improve osteogenesis in bone graft surgeries.

Citrofulvicin, an Antiosteoporotic Polyketide from Penicillium velutinum

Citrofulvicin (1), along with its early shunt product fulvionol (2), was characterized as a skeletally unprecedented antiosteoporotic agent from a human sputum-derived fungus Penicillium velutinum. The unique citrofulvicin framework is likely formed by a nonenzymatic intermolecular Diels-Alder cycloaddition between heptaketide-based intermediates. Citrofulvicin and fulvionol were demonstrated to be osteogenic at 0.1 μM in the prednisolone-induced osteoporotic zebrafish.

Skeletogenesis in the Persian sturgeon Acipenser persicus and its correlation with gene expression of vitamin K-dependent proteins during larval development

The present study describes morphological development of the skeleton in the Persian sturgeon Acipenser persicus and discusses the hypothesis that expression of genes encoding vitamin K-dependent proteins (VKDP) might be correlated with the mineralization of skeletal tissues during early development in sturgeons. Results showed that development of cartilage started just after hatching (mean ± S.D., 10·9 ± 0·7 mm in total length, LT ) in the head and notochord, whereas the first signs of mineralization occurred in the dentary and in the dermopalatine and palatopterygoid elements of the upper jaw, coinciding with the onset of exogenous feeding (20·1 ± 1·5 mm LT ). All branchial arch elements developed between 19·3 and 22·3 mm LT , whereas mineralization was only observed in tooth plates associated with the hypobranchial 1 and gill rakers at 20·8 ± 1·5 mm LT and 48·4 ± 6·4 mm LT , respectively. Quantitative real-time PCR showed that transcripts of VKDP genes including bone Gla protein (bgp), matrix Gla protein (mgp) and Gla rich protein (grp) genes were significantly up-regulated during the transition to exogenous feeding, supporting hypotheses about relevance of the above-mentioned genes in chondrogenesis at early developmental stages. The strong mineralization of skeletal elements from 21·5 to 27·3 mm LT (20 days post hatch) was in accordance with the maximal levels of bgp, mgp and grp expression indicating a correlation between development of the skeleton and the expression of VKDP genes. These data are important for evaluating A. persicus larval quality, understanding the influence of rearing biotic and abiotic factors on skeletogenesis and recognizing the occurrence of skeletal deformities in this species.

Association Between Gut Microbiota and Bone Health: Potential Mechanisms and Prospective

CONTEXT

It has been well established that the human gut microbiome plays a critical role in the regulation of important biological processes and the mechanisms underlying numerous complex diseases. Although researchers have only recently begun to study the relationship between the gut microbiota and bone metabolism, early efforts have provided increased evidence to suggest an important association.

EVIDENCE ACQUISITION

In this study, we attempt to comprehensively summarize the relationship between the gut microbiota and bone metabolism by detailing the regulatory effects of the microbiome on various biological processes, including nutrient absorption and the intestinal mucosal barrier, immune system functionality, the gut-brain axis, and excretion of functional byproducts. In this review, we incorporate evidence from various types of studies, including observational, in vitro and in vivo animal experiments, as well as small efficacy clinic trails.

EVIDENCE SYNTHESIS

We review the various potential mechanisms of influence for the gut microbiota on the regulation of bone metabolism and discuss the importance of further examining the potential effects of the gut microbiota on the risk of osteoporosis in humans. Furthermore, we outline some useful tools/approaches for metagenomics research and present some prominent examples of metagenomics association studies in humans.

CONCLUSION

Current research efforts, although limited, clearly indicate that the gut microbiota may be implicated in bone metabolism, and therefore, further exploration of this relationship is a promising area of focus in bone health and osteoporosis research. Although most existing studies investigate this relationship using animal models, human studies are both needed and on the horizon.

Integrative Medicine for Geriatric and Palliative Care

More than 80% of people in the United States who are older than 65 years have 1 or more chronic medical problems, and 50% have 2 or more. The cost of care for the elderly is at least 3 to 4 times that of younger populations and is rapidly growing, mostly because of a lack of preventive approaches and overly medicalized and fragmented care. This article summarizes the most up-to-date evidence for specific integrative modalities for common geriatric conditions, including falls, frailty, osteoporosis, and end-of-life palliative care.

Postmenopausal Osteoporosis: The Role of Lifestyle in Maintaining Bone Mass and Reducing Fracture Risk

Postmenopausal osteoporosis is a significant contributor to morbidity and mortality. Medications can provide effective treatment but their use can be complicated by side effects. This case illustrates the role that diet, supplements, and specific exercises can play in preventing and treating bone loss and reducing fracture risk.

CDKN2A/p16INK4a expression is associated with vascular progeria in chronic kidney disease

Patients with chronic kidney disease (CKD) display a progeric vascular phenotype linked to apoptosis, cellular senescence and osteogenic transformation. This has proven intractable to modelling appropriately in model organisms. We have therefore investigated this directly in man, using for the first time validated cellular biomarkers of ageing (CDKN2A/p16INK4a, SA-β-Gal) in arterial biopsies from 61 CKD patients undergoing living donor renal transplantation. We demonstrate that in the uremic milieu, increased arterial expression of CDKN2A/p16INK4a associated with vascular progeria in CKD, independently of chronological age. The arterial expression of CDKN2A/p16INK4a was significantly higher in patients with coronary calcification (p=0.01) and associated cardiovascular disease (CVD) (p=0.004). The correlation between CDKN2A/p16INK4a and media calcification was statistically significant (p=0.0003) after correction for chronological age. We further employed correlate expression of matrix Gla protein (MGP) and runt-related transcription factor 2 (RUNX2) as additional pathognomonic markers. Higher expression of CDKN2A/p16INK4a, RUNX2 and MGP were observed in arteries with severe media calcification. The number of p16INK4a and SA-β-Gal positive cells was higher in biopsies with severe media calcification. A strong inverse correlation was observed between CDKN2A/p16INK4a expression and carboxylated osteocalcin levels. Thus, impaired vitamin K mediated carboxylation may contribute to premature vascular senescence.