The effects of vitamin K-rich green leafy vegetables on bone metabolism: A 4-week randomised controlled trial in middle-aged and older individuals

Effects of vitamin K supplementation on bone mineral density at different sites and bone metabolism in the middle-aged and elderly population

Aims

This meta-analysis and systematic review aimed to comprehensively investigate the effects of vitamin K supplementation on bone mineral density (BMD) at various sites and bone metabolism in middle-aged and older adults.

Methods

The databases of PubMed, Web of Science, and Cochrane Library were thoroughly searched from inception to July 2023.

Results

The results revealed that vitamin K supplementation increased BMD at the lumbar spine (p = 0.035). Moreover, the pooled effects demonstrated a notable increase in carboxylated osteocalcin (cOC) (p = 0.004), a decrease in uncarboxylated osteocalcin (ucOC) (p < 0.001), and no significant effect on total osteocalcin (tOC) (p = 0.076). Accordingly, the ratio of cOC to ucOC (p = 0.002) significantly increased, while the ratio of ucOC to tOC decreased (p = 0.043). However, there was no significant effect of vitamin K supplementation on other bone metabolism markers, such as cross-linked telopeptide of type 1 collagen (NTx), bone alkaline phosphatase (BAP), and procollagen I N-terminal propeptide (PINP). Subgroup analysis revealed that vitamin K notably enhanced bone health in females by increasing lumbar spine BMD (p = 0.028) and decreasing ucOC (p < 0.001). Vitamin K, especially vitamin K2, exhibited effects on maintaining or increasing lumbar spine BMD, and influencing the balance of cOC and ucOC.

Conclusion

This review suggests that the beneficial effects of vitamin K supplementation on bone health primarily involve enhancing the carboxylation of OC rather than altering the total amount of OC.

The role of bone in energy metabolism: A focus on osteocalcin

Understanding the mechanisms involved in whole body glucose regulation is key for the discovery of new treatments for type 2 diabetes (T2D). Historically, glucose regulation was largely focused on responses to insulin and glucagon. Impacts of incretin-based therapies, and importance of muscle mass, are also highly relevant. Recently, bone was recognized as an endocrine organ, with several bone proteins, known as osteokines, implicated in glucose metabolism through their effects on the liver, skeletal muscle, and adipose tissue. Research efforts mostly focused on osteocalcin (OC) as a leading example. This review will provide an overview on this role of bone by discussing bone turnover markers (BTMs), the receptor activator of nuclear factor kB ligand (RANKL), osteoprotegerin (OPG), sclerostin (SCL) and lipocalin 2 (LCN2), with a focus on OC. Since 2007, some, but not all, research using mostly OC genetically modified animal models suggested undercarboxylated (uc) OC acts as a hormone involved in energy metabolism. Most data generated from in vivo, ex vivo and in vitro models, indicate that exogenous ucOC administration improves whole-body and skeletal muscle glucose metabolism. Although data in humans are generally supportive, findings are often discordant likely due to methodological differences and observational nature of that research. Overall, evidence supports the concept that bone-derived factors are involved in energy metabolism, some having beneficial effects (ucOC, OPG) others negative (RANKL, SCL), with the role of some (LCN2, other BTMs) remaining unclear. Whether the effect of osteokines on glucose regulation is clinically significant and of therapeutic value for people with insulin resistance and T2D remains to be confirmed.

The investigation of connection between anticoagulant therapy and vitamin K homologues in human determined by LC-MS/MS

Aim: Differences are existed in the bioactivity among various vitamin K (VK) forms. To investigate the correlation between clinical parameters of initial anticoagulation and plasma levels of VK1 and VK2 (MK-4 and MK-7), it was necessary to establish a quantitative method for simultaneous determination.Materials & methods: Plasma samples in cardiovascular patients were extracted by cyclohexane and analyzed using a C18 column. Baseline concentrations of VK1, MK-4 and MK-7 were 0.98 ± 0.52 ng/ml, 0.45 ± 0.13 ng/ml and 0.65 ± 0.31 ng/ml, respectively. The concentrations of MK-7 and total VKs were significantly relevant to INR0, respectively (p = 0.010 and p = 0.048, respectively).Conclusion: Thus, when adjusting anticoagulation dosage, concentrations of various VK homologues might be considered.

Vitamin K: Infection, Inflammation, and Auto-Immunity

Vitamin K (VK) comprises a group of substances with chlorophyll quinone bioactivity and exists in nature in the form of VK1 and VK2. As its initial recognition originated from the ability to promote blood coagulation, it is known as the coagulation vitamin. However, based on extensive research, VK has shown potential for the prevention and treatment of various diseases. Studies demonstrating the beneficial effects of VK on immunity, antioxidant capacity, intestinal microbiota regulation, epithelial development, and bone protection have drawn growing interest in recent years. This review article focuses on the mechanism of action of VK and its potential preventive and therapeutic effects on infections (eg, asthma, COVID-19), inflammation (eg, in type 2 diabetes mellitus, Alzheimer's disease, Parkinson's disease, cancer, aging, atherosclerosis) and autoimmune disorders (eg, inflammatory bowel disease, type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis). In addition, VK-dependent proteins (VKDPs) are another crucial mechanism by which VK exerts anti-inflammatory and immunomodulatory effects. This review explores the potential role of VK in preventing aging, combating neurological abnormalities, and treating diseases such as cancer and diabetes. Although current research appoints VK as a therapeutic tool for practical clinical applications in infections, inflammation, and autoimmune diseases, future research is necessary to elucidate the mechanism of action in more detail and overcome current limitations.

The Interconnection Between Muscle and Bone: A Common Clinical Management Pathway

Often observed with aging, the loss of skeletal muscle (sarcopenia) and bone (osteoporosis) mass, strength, and quality, is associated with reduced physical function contributing to falls and fractures. Such events can lead to a loss of independence and poorer quality of life. Physical inactivity (mechanical unloading), especially in older adults, has detrimental effects on the mass and quality of bone as well as muscle, while increases in activity (mechanical loading) have positive effects. Emerging evidence suggests that the relationship between bone and muscle is driven, at least in part, by bone-muscle crosstalk. Bone and muscle are closely linked anatomically, mechanically, and biochemically, and both have the capacity to function with paracrine and endocrine-like action. However, the exact mechanisms involved in this crosstalk remain only partially explored. Given older adults with lower bone mass are more likely to present with impaired muscle function, and vice versa, strategies capable of targeting both bone and muscle are critical. Exercise is the primary evidence-based prevention strategy capable of simultaneously improving muscle and bone health. Unfortunately, holistic treatment plans including exercise in conjunction with other allied health services to prevent or treat musculoskeletal disease remain underutilized. With a focus on sarcopenia and osteoporosis, the aim of this review is to (i) briefly describe the mechanical and biochemical interactions between bone and muscle; (ii) provide a summary of therapeutic strategies, specifically exercise, nutrition and pharmacological approaches; and (iii) highlight a holistic clinical pathway for the assessment and management of sarcopenia and osteoporosis.

Fruit and Vegetable Consumption and the Risk of Bone Fracture: A Grading of Recommendations, Assessment, Development, and Evaluations (GRADE)-Assessed Systematic Review and Dose-Response Meta-Analysis

Researchers have examined the link between consuming fruit and vegetables and the incidence of fractures for many years. Nevertheless, their findings have been unclear. Furthermore, the dose-dependent relationship has not been examined, and the level of certainty in the evidence was not evaluated. We carried out a dose-dependent meta-analysis examining the relation between fruit and vegetables intake and fracture incidence. PubMed, Web of Sciences, and Scopus were searched until April 2023 for cohort studies evaluating the relation between fruit and vegetables and fracture incidence. Summary relative risks (RRs) were computed from complied data by applying random effects analysis. To examine the level of evidence, we utilized the approach called the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Ten cohort studies comprising 511,716 individuals were entered. There was a nonsignificant relation between fruit and vegetables, as well as only fruit intake and any fracture risk. In contrast, high versus low analysis presented that vegetables consumption was linked to a 16% decrease in any type of fracture incidence (RR 0.84; 95% confidence interval [CI], 0.75 to 0.95; I 2 = 83.1%; n = 6). Also, per one serving/day (200 g/day) increments in vegetables consumption, there was a 14% decline in the fracture risk (RR 0.86; 95% CI, 0.77 to 0.97; I 2 = 84.7%; n = 5; GRADE = moderate). With moderate certainty, a greater consumption of only vegetables, but not total fruit and vegetables or only fruit, might reduce the risk of fracture. These associations were also evident in dose-response analysis. Large intervention trials are demanded to approve our findings. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The Potential of Vitamin K as a Regulatory Factor of Bone Metabolism-A Review

Vitamin K (VK), a fat-soluble vitamin, is essential for the clotting of blood because of its role in the production of clotting factors in the liver. Moreover, researchers continue to explore the role of VK as an emerging novel bioactive molecule with the potential function of improving bone health. This review focuses on the effects of VK on bone health and related mechanisms, covering VK research history, homologous analogs, dietary sources, bioavailability, recommended intake, and deficiency. The information summarized here could contribute to the basic and clinical research on VK as a natural dietary additive and drug candidate for bone health. Future research is needed to extend the dietary VK database and explore the pharmacological safety of VK and factors affecting VK bioavailability to provide more support for the bone health benefits of VK through more clinical trials.

Anti-Aging Activity and Modes of Action of Compounds from Natural Food Sources

Aging is a natural and inescapable phenomenon characterized by a progressive deterioration of physiological functions, leading to increased vulnerability to chronic diseases and death. With economic and medical development, the elderly population is gradually increasing, which poses a great burden to society, the economy and the medical field. Thus, healthy aging has now become a common aspiration among people over the world. Accumulating evidence indicates that substances that can mediate the deteriorated physiological processes are highly likely to have the potential to prolong lifespan and improve aging-associated diseases. Foods from natural sources are full of bioactive compounds, such as polysaccharides, polyphenols, carotenoids, sterols, terpenoids and vitamins. These bioactive compounds and their derivatives have been shown to be able to delay aging and/or improve aging-associated diseases, thereby prolonging lifespan, via regulation of various physiological processes. Here, we summarize the current understanding of the anti-aging activities of the compounds, polysaccharides, polyphenols, carotenoids, sterols, terpenoids and vitamins from natural food sources, and their modes of action in delaying aging and improving aging-associated diseases. This will certainly provide a reference for further research on the anti-aging effects of bioactive compounds from natural food sources.

Higher Dietary Vitamin K Intake is Associated with Better Physical Function and Lower Long-Term Injurious Falls Risk in Community-Dwelling Older Women

BACKGROUND

In recent years, a potential beneficial role of Vitamin K in neuromuscular function has been recognised. However, the optimal dietary intake of Vitamin K to support muscle function in the context of falls prevention remains unknown.

OBJECTIVE

To examine the relationship of dietary Vitamin K1 and K2 with muscle function and long-term injurious fall-related hospitalisations in older women.

DESIGN

Cohort study.

PARTICIPANTS

1347 community-dwelling older Australian women ≥70 years.

MEASUREMENTS

A new Australian Vitamin K nutrient database, supplemented with published data, was used to calculate Vitamin K1 and K2 intake from a validated food frequency questionnaire at baseline (1998). Muscle function (grip strength and timed-up-and-go; TUG) as well plasma Vitamin D status (25OHD) were also assessed at baseline. Fall-related hospitalisations over 14.5 years were obtained from linked health records. Multivariable-adjusted logistic regression and Cox-proportional hazard models were used to analyse the data.

RESULTS

Over 14.5 years of follow-up (14,774 person-years), 535 (39.7%) women experienced a fall-related hospitalisation. Compared to women with the lowest Vitamin K1 intake (Quartile 1, median 49 µg/d), those with the highest intake (Quartile 4, median 120 µg/d) had 29% lower odds (OR 0.71 95%CI 0.52-0.97) for slow TUG performance (>10.2 s), and 26% lower relative hazards of a fall-related hospitalisation (HR 0.74 95%CI 0.59-0.93) after multivariable adjustment. These associations were non-linear and plateaued at moderate intakes of ~70-100 µg/d. There was no relation to grip strength. Vitamin K2 intakes were not associated with muscle function or falls.

CONCLUSION

A higher habitual Vitamin K1 intake was associated with better physical function and lower long-term injurious falls risk in community-dwelling older women. In the context of musculoskeletal health, Vitamin K1 found abundantly in green leafy vegetables should be promoted.

Dietary Vitamin K1 intake is associated with lower long-term fracture-related hospitalization risk: the Perth longitudinal study of ageing women

This study examined the association between dietary Vitamin K1 intake with fracture-related hospitalizations over 14.5 years in community-dwelling older Australian women (n = 1373, ≥70 years). Dietary Vitamin K1 intake at baseline (1998) was estimated using a validated food frequency questionnaire and a new Australian Vitamin K nutrient database, which was supplemented with published data. Over 14.5 years, any fracture (n = 404, 28.3%) and hip fracture (n = 153, 10.7%) related hospitalizations were captured using linked health data. Plasma Vitamin D status (25OHD) and the ratio of undercarboxylated osteocalcin (ucOC) to total osteocalcin (tOC) from serum was assessed at baseline. Estimates of dietary Vitamin K1 intake were supported by a significant inverse association with ucOC : tOC; a marker of Vitamin K status (r = -0.12, p < 0.001). Compared to women with the lowest Vitamin K1 intake (Quartile 1, <61 μg d^-1), women with the highest Vitamin K1 intake (Quartile 4, ≥99 μg d^-1) had lower hazards for any fracture- (HR 0.69 95%CI 0.52-0.91, p < 0.001) and hip fracture-related hospitalization (HR 0.51 95%CI 0.32-0.79, p < 0.001), independent of 25OHD levels, as part of multivariable-adjusted analysis. Spline analysis suggested a nadir in the relative hazard for any fracture-related hospitalizations at a Vitamin K1 intake of approximately 100 μg day^-1. For hip fractures, a similar relationship was apparent. Higher dietary Vitamin K1 is associated with lower long-term risk for any fracture- and hip fracture-related hospitalizations in community-dwelling older women.

Role of Vitamin K in Chronic Kidney Disease: A Focus on Bone and Cardiovascular Health

Chronic kidney disease (CKD) is commonly associated with vitamin K deficiency. Some of the serious complications of CKD are represented by cardiovascular disease (CVD) and skeletal fragility with an increased risk of morbidity and mortality. A complex pathogenetic link between hormonal and ionic disturbances, bone tissue and metabolism alterations, and vascular calcification (VC) exists and has been defined as chronic kidney disease–mineral and bone disorder (CKD-MBD). Poor vitamin K status seems to have a key role in the progression of CKD, but also in the onset and advance of both bone and cardiovascular complications. Three forms of vitamin K are currently known: vitamin K1 (phylloquinone), vitamin K2 (menaquinone), and vitamin K3 (menadione). Vitamin K plays different roles, including in activating vitamin K-dependent proteins (VKDPs) and in modulating bone metabolism and contributing to the inhibition of VC. This review focuses on the biochemical and functional characteristics of vitamin K vitamers, suggesting this nutrient as a possible marker of kidney, CV, and bone damage in the CKD population and exploring its potential use for promoting health in this clinical setting. Treatment strategies for CKD-associated osteoporosis and CV disease should include vitamin K supplementation. However, further randomized clinical studies are needed to assess the safety and the adequate dosage to prevent these CKD complications.

Change in Circulating Undercarboxylated Osteocalcin (ucOCN) Is Associated With Fat Accumulation in HIV-Seropositive Women

BACKGROUND

Bone mineral density loss and fat accumulation are common in people living with HIV. The bone-derived hormone, undercarboxylated osteocalcin (ucOCN) regulates fat metabolism. We investigated the relationship between ucOCN change and body fat change among perimenopausal/postmenopausal HIV-seronegative and HIV-seropositive women on long-term antiretrovirals.

METHODS

Perimenopausal and postmenopausal women enrolled in the Women's Interagency HIV Study MSK substudy underwent trunk and total fat assessment by dual energy x-ray absorptiometry (DXA) at study enrollment (index visit) and again 2 years later. Circulating ucOCN and cOCN were also measured at the index and 2-year visits. The correlation between the 2-year change in ucOCN and cOCN and change in trunk and total fat was assessed as a function of HIV serostatus using linear regression modeling. Multivariate linear regression assessed the association between ucOCN and cOCN change and total and trunk fat change after adjusting for sociodemographic variables. Linear regression models restricted to HIV-seropositive women were performed to examine the contributions of HIV-specific factors (index CD4 count, viral load, and combined antiretroviral therapy use) on the associations.

RESULTS

Increased ucOCN over the 2-year follow-up was associated with less trunk and total fat accumulation in models adjusting for HIV serostatus and participants sociodemographics, whereas there was no association with cOCN and the fat parameters. None of the HIV-specific factors evaluated influenced the association between ucOCN and fat parameters.

CONCLUSION

The current study suggests that increases in ucOCN are associated with decreased fat accumulation in HIV-seronegative and HIV-seropositive postmenopausal women on long-term antiretroviral therapy.

The Role of Vitamin K in Humans: Implication in Aging and Age-Associated Diseases

As human life expectancy is rising, the incidence of age-associated diseases will also increase. Scientific evidence has revealed that healthy diets, including good fats, vitamins, minerals, or polyphenolics, could have antioxidant and anti-inflammatory activities, with antiaging effects. Recent studies demonstrated that vitamin K is a vital cofactor in activating several proteins, which act against age-related syndromes. Thus, vitamin K can carboxylate osteocalcin (a protein capable of transporting and fixing calcium in bone), activate matrix Gla protein (an inhibitor of vascular calcification and cardiovascular events) and carboxylate Gas6 protein (involved in brain physiology and a cognitive decline and neurodegenerative disease inhibitor). By improving insulin sensitivity, vitamin K lowers diabetes risk. It also exerts antiproliferative, proapoptotic, autophagic effects and has been associated with a reduced risk of cancer. Recent research shows that protein S, another vitamin K-dependent protein, can prevent the cytokine storm observed in COVID-19 cases. The reduced activation of protein S due to the pneumonia-induced vitamin K depletion was correlated with higher thrombogenicity and possibly fatal outcomes in COVID-19 patients. Our review aimed to present the latest scientific evidence about vitamin K and its role in preventing age-associated diseases and/or improving the effectiveness of medical treatments in mature adults ˃50 years old.

Osteocalcin and vascular function: is there a cross-talk?

Background

The bone-derived protein osteocalcin (OC), in its undercarboxylated (ucOC) form, has a beneficial effect on energy metabolism and may be a future therapeutic target for metabolic diseases. Increasing evidence suggests a link between ucOC and cardiovascular disease (CVD) development; however, the exact relationship is conflicting and unclear.

Scope of review

The aim of this review was to summarise the current research examining the interaction between OC and vascular dysfunction, the initiating stage in the development of atherosclerosis and CVD.

Major conclusions

In humans, the association between OC and vascular function is inconsistent. Several studies report that total OC (tOC) is associated with adverse function or beneficial function, whereas others report that tOC and ucOC has no effect on vascular function. The conflicting data are likely due to several methodological inconsistencies, in particular the lack of studies reporting circulating ucOC levels. In animal models, the direct administration of ucOC to isolated blood vessels ex vivo produced minimal changes in endothelial function, but importantly, no adverse responses. Finally, in human endothelial and vascular smooth muscle cells, ucOC treatment did not influence classical markers of cellular function, including endothelin-1, vascular adhesion molecule-1 and monocyte chemoattractant protein-1 after exposure to high glucose and inflammatory conditions. The lack of adverse effects in ex vivo and in vitro studies suggests that ucOC may be targeted as a future therapeutic for metabolic diseases, without the risk of detrimental effects in the vasculature. However, further studies are needed to confirm these findings and to investigate whether there is a direct beneficial influence of ucOC.

•

ucOC is implicated in the regulation of glucose homeostasis; but its role in the vasculature has been minimally reported.

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Studies which examine the association between ucOC and vascular function in humans often report inconsistent outcomes.

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In addition, ex vivo and in vitro studies have reported that ucOC likely does not directly regulate endothelial function.

•

ucOC may be targeted as a therapeutic treatment for metabolic diseases without a risk of adverse effects in the vasculature.

Higher Undercarboxylated to Total Osteocalcin Ratio Is Associated With Reduced Physical Function and Increased 15-Year Falls-Related Hospitalizations: The Perth Longitudinal Study of Aging Women

Evidence from animal models suggests that undercarboxylated osteocalcin (ucOC) is involved in muscle mass maintenance and strength. In humans, the ucOC to total (t)OC ratio may be related to muscle strength and perhaps physical function and falls risk, but data are limited. We tested the hypothesis that ucOC and ucOC/tOC ratio are associated with muscle function (muscle strength and physical function) in older women and 15-year falls-related hospitalizations. Serum tOC and ucOC were assessed in 1261 older women (mean age 75.2 ± 2.7 years) forming the Perth Longitudinal Study of Aging Women (1998 to 2013). Timed-up-and-go (TUG) and grip strength were assessed at baseline and at 5 years. Falls-related hospitalizations (14.5-year follow-up) were captured by the Hospital Morbidity Data Collection, via the Western Australian Data Linkage System. At baseline, women with higher ucOC/tOC ratio (quartile 4) had slower TUG performance compared with quartile 1 (~0.68 seconds, p < .01). Grip strength and 5-year change of TUG and grip were not different (p > .05) between quartiles. Fear of falling limiting house, outdoor, and combined activities was significantly different across quartiles (p < .05). Higher ucOC/tOC was significantly associated with poorer TUG performance at baseline and 5-year change in performance, increased walking aid use, and fear of falling (all p < .05). Higher ucOC was related to lower grip strength at baseline (p < .05) but not 5-year change in strength. Those with the highest ucOC/tOC had greater falls-related hospitalizations (unadjusted log rank, p = .004) remaining significant after adjusting for key variables (hazard ratio [HR] = 1.31, 95% confidence interval [CI] 1.09-1.57, p = .004). We identified a large proportion of older women with high ucOC/tOC ratio who had reduced physical function, including its long-term decline and increased risk of falls-related hospitalizations. Early identification of women at higher risk can enable prevention and intervention strategies to occur, reducing risk for injurious falls. © 2020 American Society for Bone and Mineral Research (ASBMR)..

Association between Circulating Osteocalcin and Cardiometabolic Risk Factors following a 4-Week Leafy Green Vitamin K-Rich Diet

<b><i>Background:</i></b> Evidence suggests that lower serum undercarboxylated osteocalcin (ucOC) may be negatively associated with cardiometabolic health. We investigated whether individuals with a suppression of ucOC following an increase in dietary vitamin K1 exhibit a relative worsening of cardiometabolic risk factors. <b><i>Materials and Methods:</i></b> Men (<i>n</i> = 20) and women (<i>n</i> = 10) aged 62 ± 10 years participated in a randomized, controlled, crossover study. The primary analysis involved using data obtained from participants following a high vitamin K1 diet (HK; 4-week intervention of increased leafy green vegetable intake). High and low responders were defined based on the median percent reduction (30%) in ucOC following the HK diet. Blood pressure (resting and 24 h), arterial stiffness, plasma glucose, lipid concentrations, and serum OC forms were assessed. <b><i>Results:</i></b> Following the HK diet, ucOC and ucOC/tOC were suppressed more (<i>p</i> &#x3c; 0.01) in high responders (41 and 29%) versus low responders (12 and 10%). The reduction in ucOC and ucOC/tOC was not associated with changes in blood pressure, arterial stiffness, plasma glucose, or lipid concentrations in the high responders (<i>p</i> &#x3e; 0.05). <b><i>Discussion/Conclusion:</i></b> Suppression of ucOC via consumption of leafy green vegetables has no negative effects on cardiometabolic health, perhaps, in part, because of cross-talk mechanisms.