Effect of vitamin K supplementation on insulin sensitivity: a meta-analysis

Menaquinone-7 and its therapeutic potential in type 2 diabetes mellitus based on a Zucker diabetic fatty rat model

Background

Type 2 diabetes mellitus (T2DM) is marked by insulin resistance, low grade chronic inflammation, and endothelial dysfunction. Vitamin K2, especially menaquinone-7 (MK-7), might delay T2DM progression and alleviate its consequences. Hence, this study evaluated the effects of MK-7 on serum and urine markers of diabetes in an animal model of T2DM.

Methods

Hetero- (fa/+, control) and homozygous (fa/fa, diabetic) male Zucker diabetic fatty (ZDF) rats were supplemented or not with MK-7 for 12 weeks. After euthanasia, vitamin K1, menaquinone-4 and MK-7 serum concentrations were analyzed via reversed phase high pressure liquid chromatography. Glucose (serum), fructosamine (serum) and creatinine (serum and urine) levels were assessed photometrically, serum cystatin C and urinary total protein were turbidimetrically determined. Serum transforming growth factor beta 1 (TGF-β1) and procollagen type III N-terminal peptide (PIIINP) were quantified with enzyme-linked immunosorbent assay. Urinary marker proteins were analyzed via sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Nephropathy was assessed histologically.

Results

Supplementation led to significantly elevated MK-7 serum levels and a significant reduction of PIIINP serum levels in both hetero- and homozygous ZDF rats. Additionally, not statistically significant reductions of TGF-β1 serum levels, proteinuria as well as the nephropathy score were observed. In vivo body mass, serum fructosamine, glucose, cystatin C and creatinine levels were unaffected.

Conclusion

MK-7 reduced serum markers of fibrosis, histological features of nephropathy and urinary protein excretion, but failed to affect serum markers of T2DM. The therapeutic potential of MK-7 in T2DM and its mode of action should be further investigated in more detail.

The effect of vitamin K supplementation on cardiovascular risk factors: a systematic review and meta-analysis

Cardiovascular disease (CVD) is one of the most important diseases which controlling its related risk factors, such as metabolic and inflammatory biomarkers, is necessary because of the increased mortality risk of that. The aim of our meta-analysis is to reveal the general effect of vitamin K supplementation on its related risk factors. Original databases were searched using standard keywords to identify all randomized clinical trials (RCTs) investigating the effects of vitamin K on CVD. Pooled weighted mean difference (WMD) and 95 % confidence intervals (95 % CI) were achieved by random-model effect analysis for the best estimation of outcomes. The statistical heterogeneity was determined using the Cochran's Q test and I2 statistics. Seventeen studies were included in this systematic review and meta-analysis. The pooled findings showed that vitamin K supplementation can reduce homeostatic model assessment insulin resistance (HOMA-IR) (WMD: -0⋅24, 95 % CI: -0⋅49, -0⋅02, P = 0⋅047) significantly compared to the placebo group. However, no significant effect was observed on other outcomes. Subgroup analysis showed a significant effect of vitamin K2 supplementation compared to vitamin K1 supplementation on HOMA-IR. However, no significant effect was observed on other variables. Also, subgroup analysis showed no potential effect of vitamin K supplementation on any outcome and omitting any articles did not affect the final results. We demonstrated that supplementation with vitamin K has no effect on anthropometrics indexes, CRP, glucose metabolism, and lipid profile factors except HOMA-IR.

Vitamin K: A vital micronutrient with the cardioprotective potential against diabetes-associated complications

Cardiovascular disease (CVD) remains the leading cause of mortality in patients with type 2 diabetes (T2D). The conventional therapies seem to offer minimal long-term cardioprotection against diabetes-related complications in patients living with T2D. There is a growing interest in understanding the therapeutic effects of food-derived bioactive compounds in protecting or managing these metabolic diseases. This includes uncovering the therapeutic potential of fat-soluble micronutrients such as vitamin K, which are abundantly found in green leafy vegetables. We searched the major electronic databases including PubMed, Web of Sciences, Scopus, Google Scholar and Science direct. The search retrieved randomized clinical trials and preclinical studies, reporting on the impact of vitamin K on CVD-related complications in T2D. The current review updates clinical evidence on the therapeutic benefits of vitamin K by attenuating CVD-risk factors such as blood lipid profiles, blood pressure, as well as markers of oxidative stress and inflammation in patients with T2D. Importantly, the summarized preclinical evidence provides a unique perspective into the pathophysiological mechanisms that could be targeted by vitamin K in the primary prevention of T2D-related complications. Lastly, this review further explores the controversies related to the cardioprotective effects of vitamin K, and also provides the basic information such as the source and bioavailability profile of this micronutrient is covered to highlight its therapeutic potential.

Preparation of Vitamin K2 Mk-7 in a Process of Fermentation of Different Seeds and Cereals by Bacteria Bacillus Subtilis

In this study, 10 different plant materials (seeds/beans) were fermented by Bacillus subtilis var. natto. The influence of the process on vitamin K2 MK-7 content during different fermentation periods was assessed. Fermented plant samples were analyzed by the procedure using HPLC UV/DAD. The fermented sunflower seeds, mung beans and peas appeared to be the most promising plants, reaching values of K2 of 1080.18±55.11 µg/100g, 806.45±60.95 µg/100g and 636.92±59.86 µg/100g, respectively. The experiments showed that extending of the fermentation time to 5–6 days was favorable for the menaquinone-7 yield. The results show that almost all fermented seeds/beans, apart from soybean, can be good source of vitamin K2 MK-7 and represent a new perspective, especially in terms of lower the phytoestrogen content.

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.

Effect of Vitamin K Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis

BACKGROUND

Multiple cross sectional and longitudinal studies reported the benefits of vitamin K intake for management of cardiometabolic risk factors so as to minimize the risk of cardiovascular diseases.

OBJECTIVE

In present systematic review and meta-analysis, we aimed to evaluate the effect of vitamin K supplementation on cardiometabolic risk factors.

METHODOLOGY

A systematic literature search of PubMed, Cochrane central, Clinicaltrials.gov, Google Scholar, Web of Science, EBSCO and Scopus databases was done from inception to November, 2017. A total of 13 trials were selected for inclusion into the present systematic review to evaluate the effect of vitamin K supplementation on cardiometabolic risk factors in healthy or in population at high risk of cardiovascular diseases.

RESULTS

Significant beneficial effects of vitamin K supplementation were found only in case of Creactive protein (p = 0.01) and insulin sensitivity index (p <0.001), while no significant effects of vitamin K supplementation were found in case of total cholesterol (p=0.857), low density lipoprotein - cholesterol (p=0.964), high density lipoprotein - cholesterol (p=0.998), interleukin - 6 (p=0.766), systolic blood pressure (p=0.660), diastolic blood pressure (p=0.818), fasting plasma glucose (p=0.362), fasting plasma insulin (p=0.928) and homeostasis model assessment for insulin resistance (p=0.672).

CONCLUSION

Presently available evidence are insufficient to ascertain the beneficial effects of vitamin K supplementation for the management of cardiometabolic risk factors. In order to explore the true potential of vitamin K supplementation for management of cardiometabolic diseases, large randomized placebo controlled trials are required in population with disturbed cardiometabolic profile. Present systematic review and meta-analysis is registered with PROSPERO (Registration number: CRD42018084608).

Clinical Advances in Immunonutrition and Atherosclerosis: A Review

Atherosclerosis is a chronic low-grade inflammatory disease that affects large and medium-sized arteries and is considered to be a major underlying cause of cardiovascular disease (CVD). The high risk of mortality by atherosclerosis has led to the development of new strategies for disease prevention and management, including immunonutrition. Plant-based dietary patterns, functional foods, dietary supplements, and bioactive compounds such as the Mediterranean Diet, berries, polyunsaturated fatty acids, ω-3 and ω-6, vitamins E, A, C, and D, coenzyme Q10, as well as phytochemicals including isoflavones, stilbenes, and sterols have been associated with improvement in atheroma plaque at an inflammatory level. However, many of these correlations have been obtained in vitro and in experimental animals' models. On one hand, the present review focuses on the evidence obtained from epidemiological, dietary intervention and supplementation studies in humans supporting the role of immunonutrient supplementation and its effect on anti-inflammatory response in atherosclerotic disease. On the other hand, this review also analyzes the possible molecular mechanisms underlying the protective action of these supplements, which may lead a novel therapeutic approach to prevent or attenuate diet-related disease, such as atherosclerosis.

Beneficial Effects of Adiponectin on Glucose and Lipid Metabolism and Atherosclerotic Progression: Mechanisms and Perspectives

Circulating adiponectin concentrations are reduced in obese individuals, and this reduction has been proposed to have a crucial role in the pathogenesis of atherosclerosis and cardiovascular diseases associated with obesity and the metabolic syndrome. We focus on the effects of adiponectin on glucose and lipid metabolism and on the molecular anti-atherosclerotic properties of adiponectin and also discuss the factors that increase the circulating levels of adiponectin. Adiponectin reduces inflammatory cytokines and oxidative stress, which leads to an improvement of insulin resistance. Adiponectin-induced improvement of insulin resistance and adiponectin itself reduce hepatic glucose production and increase the utilization of glucose and fatty acids by skeletal muscles, lowering blood glucose levels. Adiponectin has also β cell protective effects and may prevent the development of diabetes. Adiponectin concentration has been found to be correlated with lipoprotein metabolism; especially, it is associated with the metabolism of high-density lipoprotein (HDL) and triglyceride (TG). Adiponectin appears to increase HDL and decrease TG. Adiponectin increases ATP-binding cassette transporter A1 and lipoprotein lipase (LPL) and decreases hepatic lipase, which may elevate HDL. Increased LPL mass/activity and very low density lipoprotein (VLDL) receptor and reduced apo-CIII may increase VLDL catabolism and result in the reduction of serum TG. Further, adiponectin has various molecular anti-atherosclerotic properties, such as reduction of scavenger receptors in macrophages and increase of cholesterol efflux. These findings suggest that high levels of circulating adiponectin can protect against atherosclerosis. Weight loss, exercise, nutritional factors, anti-diabetic drugs, lipid-lowering drugs, and anti-hypertensive drugs have been associated with an increase of serum adiponectin level.

Vitamin K: a nutrient which plays a little-known role in glucose metabolism

PURPOSE OF REVIEW

Type 2 diabetes is one of the most important public health diseases. Type 2 diabetes pathophysiology involves multiple pathways, in which micronutrients could play a role. Among them, interest has grown concerning vitamin K. The purpose of this review is to expose the latest studies on the role of vitamin K in glucose metabolism, a poorly known function of this vitamin.

RECENT FINDINGS

Animal experimentations and human observational and interventional studies were analyzed to evaluate the role of this vitamin in glucose metabolism. Daily intake of vitamin K seems to improve glucose metabolism and low intakes could be involved in type 2 diabetes pathophysiology. Recent data show that vitamin K could act on glucose metabolism via downstream targets such as osteocalcin, growth arrest-specific 6 protein, and matrix Gla protein.

SUMMARY

This review depicts new insights into the role of vitamin K in glucose metabolism regulation and depicts also the probable mechanisms underlying this association. Further studies will be needed to determine the dose and the duration of vitamin K treatment to achieve the strongest metabolic effect. Maybe the best strategy to improve glucose metabolism would be 'cocktails' of micronutrients associating vitamin K.

Undercarboxylated Osteocalcin: Experimental and Human Evidence for a Role in Glucose Homeostasis and Muscle Regulation of Insulin Sensitivity

Recent advances have indicated that osteocalcin, and in particular its undercarboxylated form (ucOC), is not only a nutritional biomarker reflective of vitamin K status and an indicator of bone health but also an active hormone that mediates glucose metabolism in experimental studies. This work has been supported by the putative identification of G protein-coupled receptor, class C, group 6, member A (GPRC6A) as a cell surface receptor for ucOC. Of note, ucOC has been associated with diabetes and with cardiovascular risk in epidemiological studies, consistent with a pathophysiological role for ucOC in vivo. Limitations of existing knowledge include uncertainty regarding the underlying mechanisms by which ucOC interacts with GPRC6A to modulate metabolic and cardiovascular outcomes, technical issues with commonly used assays for ucOC in serum, and a paucity of clinical trials to prove causation and illuminate the scope for novel health interventions. A key emerging area of research is the role of ucOC in relation to expression of GPRC6A in muscle, and whether exercise interventions may modulate metabolic outcomes favorably in part via ucOC. Further research is warranted to clarify potential direct and indirect roles for ucOC in human health and cardiometabolic diseases.