Vitamin K1 alleviates streptozotocin-induced type 1 diabetes by mitigating free radical stress, as well as inhibiting NF-κB activation and iNOS expression in rat pancreas

Vitamin K2 in Health and Disease: A Clinical Perspective

Vitamins are essential organic compounds that vary widely in chemical structure and are vital in small quantities for numerous biochemical and biological functions. They are critical for metabolism, growth, development and maintaining overall health. Vitamins are categorised into two groups: hydrophilic and lipophilic. Vitamin K (VK), a lipophilic vitamin, occurs naturally in two primary forms: phylloquinone (VK1), found in green leafy vegetables and algae, and Menaquinones (VK2), present in certain fermented and animal foods and widely formulated in VK supplements. This review explores the possible factors contributing to VK deficiency, including dietary influences, and discusses the pharmacological and therapeutic potential of supplementary VK2, examining recent global clinical studies on its role in treating diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, cardiovascular disease, chronic kidney disease, diabetes, neurodegenerative disorders and cancers. The analysis includes a review of published articles from multiple databases, including Scopus, PubMed, Google Scholar, ISI Web of Science and CNKI, focusing on human studies. The findings indicate that VK2 is a versatile vitamin essential for human health and that a broadly positive correlation exists between VK2 supplementation and improved health outcomes. However, clinical data are somewhat inconsistent, highlighting the need for further detailed research into VK2's metabolic processes, biomarker validation, dose-response relationships, bioavailability and safety. Establishing a Recommended Daily Intake for VK2 could significantly enhance global health.

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 relationship between vitamin K and T2DM: a systematic review and meta-analysis

Background: Previous studies have shown the potential role of vitamin K supplementation in the prevention and treatment of many diseases. However, the effect of vitamin K supplementation on blood glucose remains controversial. The purpose of this study was to assess the effects of vitamin K supplementation on glycemia-related indicators, including Fasting Blood Sugar (FBS), Fasting Insulin (FINS) and Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The potential association between vitamin K and type 2 diabetes mellitus (T2DM) risk was also evaluated. Methods: Up to April 2023, Cochrane, PubMed, Web of Science, Medline and EMBASE databases were searched to assess the effects of vitamin K on blood glucose and the risk of developing T2DM. Results: A meta-analysis of seven studies (813 participants) found vitamin K supplementation significantly reduced FBS (SMD = -0.150 mg dl-1, 95% CI = -0.290, -0.010 mg dl-1) and HOMA-IR (SMD = -0.200, 95% CI = -0.330, -0.060), but not FINS. Five studies with a total of 105 798 participants were included in the meta-analysis of the association between vitamin K and T2DM. The results showed that vitamin K was associated with the reduced risk of developing T2DM (HR = 0.79, 95% CI [0.71-0.88], P < 0.001). Conclusion: The meta-analysis demonstrated that vitamin K supplementation had a significant effect on the regulation of FBS and HOMA-IR in the population. Moreover, vitamin K was associated with the reduced risk of developing T2DM. Considering some limitations found in this study, additional data from large clinical trials are needed.

Anacardium occidentale leaves extract and riboceine mitigate hyperglycemia through anti-oxidative effects and modulation of some selected genes associated with diabetes

Background

Diabetes mellitus (DM) is one of the leading causes of death globally and complications of DM have become a major health concern. Anacardium occidentale is a plant widely recognized for its hypoglycemic properties and traditionally used in developing nations as remedy for DM treatment. Riboceine is a supplement that enhances production of glutathione and known for its vital role in supporting cellular function. This study was designed to evaluate the antidiabetic and antioxidant potential of riboceine and ethanolic extract of A. occidentale leaves in streptozotocin (STZ)-induced diabetic rats.

Method

Twenty-nine adult male Wistar rats were induced with DM intraperitoneally using a single dose of STZ (70 mg/kg). The STZ-induced rats were divided into groups and administered the same dose (100 mg/kg) of A. occidentale leaves extract and riboceine via gastric gavage at the dose (100 mg/kg) for seventeen days while metformin (40 mg/kg) was used as positive control. Fasting blood glucose and weight of the model rats were examined periodically. Activities of total protein, creatinine, urea, antioxidants (SOD, GSH and GPX), and level of serum insulin were determined. Expression of diabetes related genes including pancreas (Insulin, pdx-1, P16NK4A, and Mki-67), Liver (FAS, ACC, and GFAT) and KIM-1 genes were also determined.

Results

Data showed that treatment of STZ-induced diabetic rats with A. occidentale and riboceine at the same dose significantly (p < 0.05) ameliorated hyperglycemic effects by improving hepatic and renal functions and antioxidants, preventing hepatic fat accumulation by downregulation of ACC, FAS and GFAT expression, improving β-cell functions through up-regulation of pancreatic insulin, P16NK4A, Mki-67 and pdx-1 expression. Induction of diabetes upregulated mRNA expression of KIM-1, which was ameliorated after treatment of the rats with A. occidentale and riboceine.

Conclusion

The results obtained in this study demonstrate significant antidiabetic properties of ethanolic extract of A. occidentale and riboceine.

Vitamin K and the Visual System-A Narrative Review

Vitamin K occupies a unique and often obscured place among its fellow fat-soluble vitamins. Evidence is mounting, however, that vitamin K (VK) may play an important role in the visual system apart from the hepatic carboxylation of hemostatic-related proteins. However, to our knowledge, no review covering the topic has appeared in the medical literature. Recent studies have confirmed that matrix Gla protein (MGP), a vitamin K-dependent protein (VKDP), is essential for the regulation of intraocular pressure in mice. The PREDIMED (Prevención con Dieta Mediterránea) study, a randomized trial involving 5860 adults at risk for cardiovascular disease, demonstrated a 29% reduction in the risk of cataract surgery in participants with the highest tertile of dietary vitamin K1 (PK) intake compared with those with the lowest tertile. However, the specific requirements of the eye and visual system (EVS) for VK, and what might constitute an optimized VK status, is currently unknown and largely unexplored. It is, therefore, the intention of this narrative review to provide an introduction concerning VK and the visual system, review ocular VK biology, and provide some historical context for recent discoveries. Potential opportunities and gaps in current research efforts will be touched upon in the hope of raising awareness and encouraging continued VK-related investigations in this important and highly specialized sensory system.

Dysbiosis in Patients with Chronic Kidney Disease: Let Us Talk About Vitamin K

PURPOSE OF REVIEW

This narrative review aimed to summarize the current evidence on the connection between dysbiosis and vitamin K deficiency in patients with chronic kidney disease (CKD). The presence of dysbiosis (perturbations in the composition of the microbiota) has been described in several non-communicable diseases, including chronic kidney disease, and it has been hypothesized that dysbiosis may cause vitamin K deficiency. Patients with CKD present both vitamin K deficiency and gut dysbiosis; however, the relationship between gut dysbiosis and vitamin K deficiency remains to be addressed.

RECENT FINDINGS

Recently, few studies in animals have demonstrated that a dysbiotic environment is associated with low production of vitamin K by the gut microbiota. Vitamin K plays a vital role in blood coagulation as well as in the cardiovascular and bone systems. It serves as a cofactor for γ-glutamyl carboxylases and thus is essential for the post-translational modification and activation of vitamin K-dependent calcification regulators, such as osteocalcin, matrix Gla protein, Gla-rich protein, and proteins C and S. Additionally, vitamin K executes essential antioxidant and anti-inflammatory functions. Dietary intake is the main source of vitamin K; however, it also can be produced by gut microbiota. This review discusses the effects of uremia on the imbalance in gut microbiota, vitamin K-producing bacteria, and vitamin K deficiency in CKD patients, leading to a better understanding and raising hypothesis for future clinical studies.

Phoenixin 14 ameloriates pancreatic injury in streptozotocin-induced diabetic rats by alleviating oxidative burden

Phoenixin-14 (PNX) is a neuropeptide that has been shown to prevent oxidative damage and stimulates insulin secretion. We investigated the effects of PNX on pancreatic injury induced by streptozotocin (STZ), and nicotinamide (NAD). Male Sprague-Dawley rats, in control (C) and diabetic (STZ) groups, were treated with either saline, or PNX (0.45 nmol/kg, or 45 nmol/kg) daily for 3 days 1 week after STZ injection. Fasting blood glucose (FBG) and gastric emptying rate (GER) were measured. Tissue and blood samples were collected. PNX treatments prevented pancreatic damage and β cell loss. Increased luminol and lucigenin levels in the pancreas, ileum and liver tissues of STZ groups were alleviated by PNX treatment in pancreatic and ileal tissues. PNX0.45 decreased FBG without any change in insulin blood level and pancreatic mRNA. GER increased in all diabetic rats while PNX0.45 delayed GER only in the C group. PNX diminishes pancreatic damage and lowers FBG by reducing oxidative load.

Insights into new therapeutic approaches for the treatment and management of polycystic ovary syndrome: An updated review

BACKGROUND

Polycystic ovary syndrome (PCOS) is a long-term, highly prevalent, complex heterogeneous, polygenic endocrine disorder characterized by both metabolic and reproductive disorders. It affects 6-23% of reproductive age women globally.

OBJECTIVE

This review aims to facilitate an understanding of novel PCOS management approaches and highlights the results from relevant interventional studies from animal and human studies.

METHODS

Manual search on PubMed, Cochrane, Scopus databases was performed for relevant articles, preclinical and clinical trials based on related keywords.

RESULTS

According to a multitude of studies, PCOS has evolved over time, but a substantial lag remains in management approaches. New insights into the cross-talk between muscle, brain, fat, and ovaries pointed out new therapeutic targets. This review has highlighted the efficacy of a wide spectrum of novel therapeutic agents [Phosphodiesterase-4 Inhibitors, Glucagon-like peptide-1 receptor agonists, nutritional supplements (Vitamins D and K, omega-3, prebiotics, probiotics and synbiotics), fecal microbiota transplantation (FMT) and intestinal cytokine IL-22] as PCOS therapeutic options. These novel therapies combine anti-inflammatory, insulin sensitizing, anti-obesity, and restoration of the gut microbiota and thus hold the potential to address the basic pathogenic mechanisms of PCOS.

CONCLUSION

Exhaustive, multicentric and multiethnic studies are vital to generate a network of normative data to better figure out the PCOS trajectory and change prognostic outcomes. Preclinical and clinical data is warranted to corroborate the new therapeutics and direct health care resources accordingly.

The effect of menaquinone-7 supplementation on dp-ucMGP, PIVKAII, inflammatory markers, and body composition in type 2 diabetes patients: a randomized clinical trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a common disorder that is characterized by chronic hyperglycemia and chronic inflammation, which also have a reinforcing effect on each other. The present research studied the effects of menaquinone (MK-7) supplementation on serum dp-ucMGP (dephospho uncarboxylated Matrix Gla Protein), PIVKAII (Prothrombin Induced by Vitamin K Absence), inflammatory markers and body composition indices in type 2 diabetes mellitus (T2DM) patients.

METHODS

This 12-week double-blind placebo-controlled randomized clinical trial allocated 60 T2DM patients equally into a MK-7 (200 mcg/day) group or a placebo group. All patients also received dietary advice at the beginning of study and their dietary intakes were checked using a 3-day food record. The body composition of each patient was also measured and their vitamin K status was assessed using the ELISA method to measure serum dp-ucMGP and PIVKAII. In addition, inflammatory status indices were also measured, including hsCRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6) and TNF-α (tumor necrosis factor alpha). All measurements were made both before and after the intervention period.

RESULTS

In total 45 patients completed the trial (MK-7 group = 23 and placebo group = 22). The calorie and macronutrient intake of the two groups were similar pre and post intervention. There were statistically significant increases in dietary vitamin K intake for both groups over the course of the study (p < 0.05), but the intergroup differences were not significant. The body composition indices (i.e., body fat percentage, fat mass, fat free mass, muscle mass, bone mass and total body water) were not significantly different between groups or across the trial. The serum levels of the vitamin K markers, PIVKAII and dp-ucMGP, decreased significantly in the MK-7 group over the course of the study (p < 0.05), but there was no decrease in the placebo group. However, after adjusting for the baseline levels and changes in vitamin K intake, the between group differences were only significant for PIVKAII (p < 0.05). Following the intervention, the serum levels of the inflammatory markers (hsCRP, IL-6, and TNF-α) were significantly lower in the MK-7 group (p < 0.05), but not in the placebo group. However, the between group differences in the inflammatory markers were not statistically significant.

CONCLUSIONS

Although further studies are needed, it appears that MK-7 supplementation can be effective in improving PIVKAII levels, but not for improving dp-ucMGP, inflammatory status or the body composition indices of T2DM patients.

TRIAL REGISTRATION NUMBER

This study was prospectively registered at the Iranian Registry of Clinical Trials on the 20th of May 2019 (ID: IRCT20100123003140N22).

Exogenous Vitamins K Exert Anti-Inflammatory Effects Dissociated from Their Role as Substrates for Synthesis of Endogenous MK-4 in Murine Macrophages Cell Line

Vitamins K exert a range of activities that extend far beyond coagulation and include anti-inflammatory effects, but the mechanisms involved in anti-inflammatory action remain unclear. In the present study, we showed that various forms of exogenous vitamins-K1, K3, K2 (MK-4, MK-5, MK-6 and MK-7)-regulated a wide scope of inflammatory pathways in murine macrophages in vitro, including NOS-2, COX-2, cytokines and MMPs. Moreover, we demonstrated for the first time that macrophages are able to synthesise endogenous MK-4 on their own. Vitamins with shorter isoprenoid chains-K1, K3 and MK-5-exhibited stronger anti-inflammatory potential than vitamins with longer isoprenoid chains (MK-6 and MK-7) and simultaneously were preferably used as a substrate for MK-4 endogenous production. Most interesting, atorvastatin pretreatment inhibited endogenous MK-4 production but had no impact on the anti-inflammatory activity of vitamins K. In summary, our results demonstrate that macrophages are able to synthesise endogenous MK-4 using exogenous vitamins K, and statin inhibits this process. However, the anti-inflammatory effect of exogenous vitamins K was independent of endogenous MK-4 synthesis.

Metabolomics-related nutrient patterns at seroconversion and risk of progression to type 1 diabetes

OBJECTIVE

Our aim was to elucidate the role of diet in type 1 diabetes (T1D) by examining combinations of nutrient intake in the progression from islet autoimmunity (IA) to T1D.

METHODS

We measured 2457 metabolites and dietary intake at the time of seroconversion in 132 IA-positive children in the prospective Diabetes Autoimmunity Study in the Young. IA was defined as the first of two consecutive visits positive for at least one autoantibody (insulin, GAD, IA-2, or ZnT8). By December 2018, 40 children progressed to T1D. Intakes of 38 nutrients were estimated from semiquantitative food frequency questionnaires. We tested the association of each metabolite with progression to T1D using multivariable Cox regression. Nutrient patterns that best explained variation in candidate metabolites were identified using reduced rank regression (RRR), and their association with progression to T1D was tested using Cox regression adjusting for age at seroconversion and high-risk HLA genotype.

RESULTS

In stepwise selection, 22 nutrients significantly predicted at least two of the 13 most significant metabolites associated with progression to T1D, and were included in RRR. A nutrient pattern corresponding to intake lower in linoleic acid, niacin, and riboflavin, and higher in total sugars, explained 18% of metabolite variability. Children scoring higher on this metabolite-related nutrient pattern at seroconversion had increased risk for progressing to T1D (HR = 3.17, 95%CI = 1.42-7.05).

CONCLUSIONS

Combinations of nutrient intake reflecting candidate metabolites are associated with increased risk of T1D, and may help focus dietary prevention efforts.

Beneficial Effects of Vitamin K Status on Glycemic Regulation and Diabetes Mellitus: A Mini-Review

Type 2 diabetes mellitus is a chronic disease that is characterized by hyperglycemia, insulin resistance, and dysfunctional insulin secretion. Glycemic control remains a crucial contributor to the progression of type 2 diabetes mellitus as well as the prevention or delay in the onset of diabetes-related complications. Vitamin K is a fat-soluble vitamin that plays an important role in the regulation of the glycemic status. Supplementation of vitamin K may reduce the risk of diabetes mellitus and improve insulin sensitivity. This mini-review summarizes the recent insights into the beneficial effects of vitamin K and its possible mechanism of action on insulin sensitivity and glycemic status, thereby suppressing the progression of diabetes mellitus.

The Inhibitory Roles of Vitamin K in Progression of Vascular Calcification

Vitamin K is a fat-soluble vitamin that is indispensable for the activation of vitamin K-dependent proteins (VKDPs) and may be implicated in cardiovascular disease (CVD). Vascular calcification is intimately associated with CV events and mortality and is a chronic inflammatory process in which activated macrophages promote osteoblastic differentiation of vascular smooth muscle cells (VSMCs) through the production of proinflammatory cytokines such as IL-1β, IL-6, TNF-α, and oncostatin M (OSM) in both intimal and medial layers of arterial walls. This process may be mainly mediated through NF-κB signaling pathway. Vitamin K has been demonstrated to exert anti-inflammatory effects through antagonizing NF-κB signaling in both in vitro and in vivo studies, suggesting that vitamin K may prevent vascular calcification via anti-inflammatory mechanisms. Matrix Gla protein (MGP) is a major inhibitor of soft tissue calcification and contributes to preventing both intimal and medial vascular calcification. Vitamin K may also inhibit progression of vascular calcification by enhancing the activity of MGP through facilitating its γ-carboxylation. In support of this hypothesis, the procalcific effects of warfarin, an antagonist of vitamin K, on arterial calcification have been demonstrated in several clinical studies. Among the inactive MGP forms, dephospho-uncarboxylated MGP (dp-ucMGP) may be regarded as the most useful biomarker of not only vitamin K deficiency, but also vascular calcification and CVD. There have been several studies showing the association of circulating levels of dp-ucMGP with vitamin K intake, vascular calcification, mortality, and CVD. However, additional larger prospective studies including randomized controlled trials are necessary to confirm the beneficial effects of vitamin K supplementation on CV health.

A systematic review on the mechanisms of vitamin K effects on the complications of diabetes and pre-diabetes

Diabetes mellitus and pre-diabetes are prevalent endocrine disorders associated with substantial morbidity and premature mortality. Vitamin K is known to have several beneficial effects on complications of diabetes and pre-diabetes. However, systematic consolidation of evidence is required to quantify these effects in order to inform clinical practice and research. A systematic search in PubMed, Scopus, Embase, ProQuest, and Google Scholar databases was undertaken from database inception up to October 2018 to evaluate functional roles of different forms of vitamin K on diabetes and pre-diabetes. From 3,734 identified records, nine articles met the inclusion criteria and were evaluated. Vitamin K supplementation was found to be associated with significant reductions in blood glucose (six studies), increased fasting serum insulin (four studies), reduced hemoglobin A1c (three studies), reduced homeostatic model assessment-insulin resistance index (HOMA-IR) (two studies), and increased ß-cell function (two studies) in diabetic animal studies. Following 2-hour oral glucose tolerance test, vitamin K supplementation was observed to be effective in reducing blood glucose and insulin levels in the pre-diabetic population. However, no evidence of effect was observed for fasting blood sugar, insulin, HOMA-IR, and homeostatic model assessment-β-cell function index (two studies). A statistically significant effect was also noted with vitamin K in improving dyslipidemia (three studies) as well as oxidative stress and inflammatory markers (five studies) in diabetic animals. In conclusion, clinical trials and animal studies confirm that vitamin K supplementation may improve both clinical features and complications of diabetes and pre-diabetes. However, quantification of clinical efficacy in the pre-diabetic population and among individuals with comorbidities requires further investigation.

Effects of MK-7 Supplementation on Glycemic Status, Anthropometric Indices and Lipid Profile in Patients with Type 2 Diabetes: A Randomized Controlled Trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a prevalent disorder which accounts for 90-95% of diabetic patients. The aim of this study was to assess the effects of menaquinone (MK-7) supplementation on glycemic indices, anthropometric indices and lipid profile, among patients with T2DM.

METHODS

In this double-blind placebo-controlled randomized clinical trial, 60 men and women with T2DM were allocated equally into either the MK-7 (200 µg/day) or the placebo group. Physical activity level and dietary intake were assessed using the international physical activity questionnaire-short form (IPAQ-SF) and a 3-day food record, pre- and post-intervention. Anthropometric measures, blood pressure, glycemic indices and lipid profile including fasting blood sugar (FBS), hemoglobin A1c (HBA1C), fasting insulin (FI), homeostatic model assessment insulin resistance index (HOMA-IR), triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) were measured at baseline and after twelve weeks.

RESULTS

Forty-five patients completed the trial. There were no significant between-group differences for calorie intake, macronutrient intake, physical activity level or anthropometric measures at baseline and at the end of the study. Dietary vitamin K intake increased significantly at the end of the study in the MK-7 (p: 0.02) and placebo (p: 0.001) groups, but intergroup differences were not significant (p: 0.86). FBS (p: 0.01), HbA1c (p: 0.002), fasting insulin (p: 0.01) and HOMA-IR (p: 0.007) decreased significantly in the MK-7 group. Furthermore, after adjustment for the baseline values and changes of vitamin K intake at the end of study, FBS and HbA1C showed significant intergroup changes, and they were significantly lower in the MK-7 group compared to the placebo group. Lipid profile (TG, TC, LDL-C, HDL-C and LDL-C/HDL-C) did not change significantly within or between groups.

CONCLUSION

MK-7 supplementation seems to be effective in the improvement of glycemic indices, but not the lipid profile of patients with T2DM.

CLINICAL TRIAL REGISTRATION

The present study was prospectively registered at the Iranian Registry of Clinical Trials on May 2019 (ID: IRCT20100123003140N22).

The Biological Impacts of Sitagliptin on the Pancreas of a Rat Model of Type 2 Diabetes Mellitus: Drug Interactions with Metformin

Sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, is a beneficial class of antidiabetic drugs. However, a major debate about the risk of developing pancreatitis is still existing. The aim of the work was to study the histological and immunohistochemical effects of sitagliptin on both endocrine and exocrine pancreases in a rat model of type 2 diabetes mellitus and to correlate these effects with the biochemical findings. Moreover, a possible synergistic effect of sitagliptin, in combination with metformin, was also evaluated. Fifty adult male rats were used and assigned into five equal groups. Group 1 served as control. Group 2 comprised of untreated diabetic rats. Group 3 diabetic rats received sitagliptin. Group 4 diabetic rats received metformin. Group 5 diabetic rats received both combined. Treatments were given for 4 weeks after the induction of diabetes. Blood samples were collected for biochemical assay before the sacrification of rats. Pancreases were removed, weighed, and were processed for histological and immunohistochemical examination. In the untreated diabetic group, the islets appeared shrunken with disturbed architecture and abnormal immunohistochemical reactions for insulin, caspase-3, and inducible nitric oxide synthase (iNOS). The biochemical findings were also disturbed. Morphometrically, there was a significant decrease in the islet size and islet number. Treatment with sitagliptin, metformin, and their combination showed an improvement, with the best response in the combined approach. No evidence of pancreatic injury was identified in the sitagliptin-treated groups. In conclusion, sitagliptin had a cytoprotective effect on beta-cell damage. Furthermore, the data didn't indicate any detrimental effects of sitagliptin on the exocrine pancreas.

Vitamin K1 prevents diabetic cataract by inhibiting lens aldose reductase 2 (ALR2) activity

This study investigated the potential of vitamin K1 as a novel lens aldose reductase inhibitor in a streptozotocin-induced diabetic cataract model. A single, intraperitoneal injection of streptozotocin (STZ) (35 mg/kg) resulted in hyperglycemia, activation of lens aldose reductase 2 (ALR2) and accumulation of sorbitol in eye lens which could have contributed to diabetic cataract formation. However, when diabetic rats were treated with vitamin K1 (5 mg/kg, sc, twice a week) it resulted in lowering of blood glucose and inhibition of lens aldose reductase activity because of which there was a corresponding decrease in lens sorbitol accumulation. These results suggest that vitamin K1 is a potent inhibitor of lens aldose reductase enzyme and we made an attempt to understand the nature of this inhibition using crude lens homogenate as well as recombinant human aldose reductase enzyme. Our results from protein docking and spectrofluorimetric analyses clearly show that vitamin K1 is a potent inhibitor of ALR2 and this inhibition is primarily mediated by the blockage of DL-glyceraldehyde binding to ALR2. At the same time docking also suggests that vitamin K1 overlaps at the NADPH binding site of ALR2, which probably shows that vitamin K1 could possibly bind both these sites in the enzyme. Another deduction that we can derive from the experiments performed with pure protein is that ALR2 has three levels of affinity, first for NADPH, second for vitamin K1 and third for the substrate DL-glyceraldehyde. This was evident based on the dose-dependency experiments performed with both NADPH and DL-glyceraldehyde. Overall, our study shows the potential of vitamin K1 as an ALR2 inhibitor which primarily blocks enzyme activity by inhibiting substrate interaction of the enzyme. Further structural studies are needed to fully comprehend the exact nature of binding and inhibition of ALR2 by vitamin K1 that could open up possibilities of its therapeutic application.

Prophylactic role of vitamin K supplementation on vascular inflammation in type 2 diabetes by regulating the NF-κB/Nrf2 pathway via activating Gla proteins

There is no previous study that has examined the relationship between circulating vitamin K1 (VK1) and vascular inflammation in type 2 diabetes (T2D). This study aims to examine the hypothesis that circulating VK1 deficiency may be associated with higher inflammation and insulin resistance in T2D patients and that VK1 supplementation regulates the NF-κB/Nrf2 pathway via activating VK-dependent Gla proteins and reduces vascular inflammation. The results showed that plasma VK1 levels were significantly lower and MCP-1, fasting glucose, HbA1c, and insulin resistance (HOMA-IR) were significantly higher in T2D patients compared to those in the controls. The lower levels of VK1 in T2D patients were significantly and inversely correlated with MCP-1 and HOMA-IR, which suggests that VK1 supplementation may reduce the vascular inflammation and insulin resistance in T2D. Using a high fat diet-fed T2D mice model this study further demonstrated that VK1 supplementation (1, 3, 5 μg per kg BW, 8 weeks) dose-dependently decreased the body weight gain, glucose intolerance, fasting glucose, glycated hemoglobin, HOMA-IR, and cytokine secretion (MCP-1 and IL-6) in T2D mice. Further cell culture studies showed that VK1 supplementation (1, 5, or 10 nM) decreased NF-κB phosphorylation and MCP-1 secretion and increased Nrf2 protein expression in high glucose (HG, 25 mM)-treated monocytes. Signal silencing studies with GGCX siRNA again depicted the role of VK-dependent Gla proteins in mediating the effect of VK1 on vascular inflammation in HG-treated cells. In conclusion, this study suggests that circulating VK1 has a positive effect in lowering vascular inflammation in T2D by regulating NF-κB/Nrf2 transcription factors via activating VK-dependent Gla proteins.

Beneficial role of vitamin K supplementation on insulin sensitivity, glucose metabolism, and the reduced risk of type 2 diabetes: A review

Micronutrients are gaining acceptance as an important nutritional therapy for the prevention and/or management of diabetes and its associated health risks. Although a very small quantity of micronutrients are required for specific functions in our bodies, moderate deficiencies can lead to serious health issues. Impaired insulin sensitivity and glucose intolerance play a major role in the development of diabetic pathophysiology. Vitamin K is well known for its function in blood coagulation. Moreover, several human studies reported the beneficial role of vitamin K supplementation in improving insulin sensitivity and glucose tolerance, preventing insulin resistance, and reducing the risk of type 2 diabetes (T2 D). Both animal and human studies have suggested that vitamin K-dependent protein (osteocalcin [OC]), regulation of adipokine levels, antiinflammatory properties, and lipid-lowering effects may mediate the beneficial function of vitamin K in insulin sensitivity and glucose tolerance. This review for the first time provides an overview of the currently available preclinical and clinical evidences on the effect of vitamin K supplementation in the management of insulin sensitivity and glucose tolerance. The outcome of this review will increase understanding for the development of a novel adjuvant therapy to achieve better control of glycemia and improve the lives of diabetic patients.

Effect of Streptozotocin on Plasma Insulin Levels of Rats and Mice: A Meta-analysis Study

BACKGROUND:

In the studies focusing on diabetic organisms, Streprozotocine (STZ) is a frequently used agent to induce diabetes in rats and mice. However the current studies do not represent practical importance of their statistical findings. For showing practical importance of the differences in plasma insulin levels of diabetic rats and mice induced by STZ, there should be a statistical synthesis regarding statistical findings of the studies.

AIM:

The purpose of this study is to make a meta-analysis of the studies on the effect of STZ on plasma insulin levels in diabetic rats and mice.

MATERIALS AND METHODS:

In this study 39 effect sizes (37 studies) about levels of plasma insulin were analyzed by calculating individual effect sizes (d) and mean effect size.

RESULTS:

The effect sizes were between -13.7 and +65.3 and the mean effect size value (+9.33) represented a large effect indicating that STZ was an effective agent to significantly decrease plasma insulin levels of diabetic rats and mice.

CONCLUSION:

It can be said that the differences in plasma insulin levels between STZ-applied and no application groups has a practical importance in making animal model of diabetes.