Erythrocyte folate and 5-methyltetrahydrofolate levels decline during 6 months of oral anticoagulation with warfarin

Potential Drug-Nutrient Interactions of 45 Vitamins, Minerals, Trace Elements, and Associated Dietary Compounds with Acetylsalicylic Acid and Warfarin-A Review of the Literature

In cardiology, acetylsalicylic acid (ASA) and warfarin are among the most commonly used prophylactic therapies against thromboembolic events. Drug-drug interactions are generally well-known. Less known are the drug-nutrient interactions (DNIs), impeding drug absorption and altering micronutritional status. ASA and warfarin might influence the micronutritional status of patients through different mechanisms such as binding or modification of binding properties of ligands, absorption, transport, cellular use or concentration, or excretion. Our article reviews the drug-nutrient interactions that alter micronutritional status. Some of these mechanisms could be investigated with the aim to potentiate the drug effects. DNIs are seen occasionally in ASA and warfarin and could be managed through simple strategies such as risk stratification of DNIs on an individual patient basis; micronutritional status assessment as part of the medical history; extensive use of the drug-interaction probability scale to reference little-known interactions, and application of a personal, predictive, and preventive medical model using omics.

High homocysteine and low folate plasma concentrations are associated with cardiovascular events but not bleeding during warfarin treatment

BACKGROUND

Previous studies have shown that homocysteine and folate levels in plasma are associated with risk for cardiovascular events and mortality. The aim of this study was to investigate if plasma concentrations of total homocysteine and folate can predict major bleeding, cardiovascular events, and all-cause mortality in patients being treated with warfarin.

METHODS

In a longitudinal cohort study, 719 patients who were taking warfarin were followed for 3001 treatment years. The following were recorded and classified: major bleeding; cardiovascular events including stroke, arterial emboli, and myocardial infarction (MI); and mortality. Blood samples collected at baseline were analysed for plasma homocysteine and folate levels.

RESULTS

After adjustment for age, C-reactive protein, and creatinine, high homocysteine levels were associated with cardiovascular events [hazard ratio (HR) 1.23 per standard deviation (SD); 95% confidence interval (CI): 1.03-1.47], MI (HR 1.38 per SD; 95% CI: 1.03-1.85), and all-cause mortality (HR 1.41 per SD; 95% CI: 1.19-1.68). The highest tertile of folate compared to the lowest tertile was associated with decreased risk for both cardiovascular events (HR 0.64; 95% CI: 0.43-0.91) and MI (HR 0.45; 95% CI: 0.21-0.97). There was no association between major bleeding and homocysteine or folate levels.

CONCLUSIONS

In patients receiving warfarin treatment, high homocysteine and low folate plasma concentrations are associated with increased risk for cardiovascular events but not major bleeding. For homocysteine levels, there is also an association with all-cause mortality.

The adverse effects of an excessive folic acid intake

Folate is a vital component of a healthy diet, being essential for numerous bodily functions. Deficiency of folate is common, with studies suggesting prevalence of deficiencyas high as 85.5% as was shown in women between the ages of 16 and 49, living in the UK. Causes of folate deficiency range from diet and lifestyle, to pathological and pharmacological processes. Because of the well-known role of folate in prevention of neural tube defects, numerous countries have implemented strategies to increase folate intake, with programs such as mandatory grain fortification. As a result, the intake of folate in these countries is often higher than the recommended dietary allowance for many groups of people. Although folate is believed to be non-toxic, the potential adverse effects of excessive intake of folic acid (synthetic form of folate) have not been highlighted well by authorities to people taking supplements; despite this, many studies have addressed this issue. However, the results of these studies provide discrepant results, leading to confusion as to whether mandatory folic acid fortification should be introduced in other countries. The purpose of this review was to provide a summary of evidence related to high folic acid ingestion and to look at the unwanted effects it may have on the certain groups within the general population.

Elevated homocysteine with pseudo-homozygosity for MTHFR677T as predisposing factors for transient ischemic attacks: a case report

A 21 year old male presented with a history of intermittent, transient neurological events. A brain MRI showed an area of restricted diffusion in keeping with an infarct, and an angiogram demonstrated an intracranial stenosis in the internal carotid artery, consistent with atherosclerosis. Laboratory investigations revealed a highly elevated plasma homocysteine, with low plasma folate and 5-methyltetrahydrofolate and methionine at the lower end of the normal ranges. The homocysteine normalized following treatment with folic acid. Molecular analysis found heterozygosity for the common MTHFR c.665C > T (aka 677C > T) variant and heterozygosity for a c.3G > C nucleotide substitution, which result in the lack of translation from this allele. It is proposed that the loss of p. Met1, coupled with folate deficiency, may be significant for the remethylation process, and may have contributed to the neurological events in this patient. If the two genetic variants are on alternate alleles, the patient would present with pseudo-homozygosity for MTHFR677T. It is probable that the combination of pronounced dietary folate deficiency, an MTHFR 'null allele' and the 677 T variant is sufficient to explain both the moderate hyperhomocysteinaemia and the clinical presentation in this patient. This case highlights the need to investigate other possible mutations in MTHFR, particularly in the absence of homozygous MTHFR 677C > T status in premature cardiovascular events.

Acute renal infarction associated with homozygous methylenetetrahydrofolate reductase mutation C677T and IgA beta-2-glycoprotein antibodies

Arterial thrombosis of the kidney(s) is a rare clinical entity usually presenting as a result of cardioembolic disease, though rare inherited hypercoagulable states have also been implicated. Within this context, both hyperhomocysteinemia triggered by a mutated methylenetetrahydrofolate reductase (MTHFR) gene product and the presence of antiphospholipid antibodies have been separately associated with arterial thrombotic events, including renal artery embolism. We present a case of combined homozygous MTHFR C677T mutation and IgA beta-2-glycoprotein antibody positivity resulting in acute renal infarction and previous silent myocardial infarction. An acute and otherwise unexplained thrombotic event of unusual location always warrants further investigation, which should include testing for hereditary thrombophilic disorders.

Avoidance of Vitamin K-Rich Foods Is Common among Warfarin Users and Translates into Lower Usual Vitamin K Intakes

BACKGROUND

Warfarin users should aim for stable daily vitamin K intakes. However, some studies report that patients are often advised to avoid eating green vegetables. Whether this advice impacts vitamin K intakes is unknown.

OBJECTIVE

Our aim was to describe the nature and sources of vitamin K-related dietary recommendations that patients received at the initiation of warfarin therapy, assess their adherence to these recommendations, and examine whether usual vitamin K intakes vary according to these recommendations.

DESIGN

We conducted a retrospective cohort study with patients enrolled in the Québec Warfarin Cohort Study. Patients were asked to report dietary recommendations they had received at warfarin initiation and their adherence to these recommendations. Usual vitamin K intakes were assessed using a validated semi-quantitative food frequency questionnaire.

PARTICIPANTS/SETTING

Three hundred seventeen patients aged 36 to 97 years who initiated warfarin between 2011 and 2012 and were treated for 12 months or longer with a target international normalized ratio range of 2.0 to 3.0 or 2.5 to 3.5.

STATISTICAL ANALYSES PERFORMED

Patients were classified according to vitamin K-related recommendations reported: limit or avoid vitamin K-rich foods; aim for stable consumption of vitamin K-rich foods; or no vitamin K-related advice. A one-way analysis of covariance was used to compare mean usual vitamin K intakes between patients after adjustment for covariates.

RESULTS

Most patients (68%) reported being advised to limit or avoid vitamin K-rich foods, particularly green vegetables, 10% reported being advised to aim for stable consumption of vitamin K-rich foods, and 22% did not recall receiving any vitamin K-related recommendation. Mean usual vitamin K intakes of patients adhering to the recommendation to limit or avoid vitamin K-rich foods was 35% to 46% lower than those of other patients (P<0.001), a difference resulting almost entirely (82%) from a lower consumption of green vegetables.

CONCLUSIONS

In contrast with current dietary recommendation, most warfarin users reported avoiding vitamin K-rich foods, which translated into lower usual vitamin K intakes.

Plasma and red cell reference intervals of 5-methyltetrahydrofolate of healthy adults in whom biochemical functional deficiencies of folate and vitamin B 12 had been excluded

5-Methyltetrahydrofolate (5-MTHF) is the predominant form of folate and a strong determinant of homocysteine concentrations. There is evidence that suboptimal 5-MTHF availability is a risk factor for cardiovascular disease independent of homocysteine. The analysis of folates remains challenging and is almost exclusively limited to the reporting of “total” folate rather than individual molecular forms. The purpose of this study was to establish the reference intervals of 5-MTHF in plasma and red cells of healthy adults who had been prescreened to exclude biochemical evidence of functional deficiency of folate and/or vitamin B₁₂. Functional folate and vitamin B₁₂ status was assessed by respective plasma measurements of homocysteine and methylmalonic acid in 144 healthy volunteers, aged 19–64 years. After the exclusion of 10 individuals, values for 134 subjects were used to establish the upper reference limits for homocysteine (13 μmol/L females and 15 μmol/L males) and methylmalonic acid (430 nmol/L). Subjects with values below these cutoffs were designated as folate and vitamin B₁₂ replete and their plasma and red cell 5-MTHF reference intervals determined, N = 126: 6.6–39.9 nmol/L and 223–1041 nmol/L, respectively. The application of these intervals will assist in the evaluation of folate status and facilitate studies to evaluate the relationship of 5-MTHF to disease.

The role of dietary vitamin K in the management of oral vitamin K antagonists

Vitamin K antagonists (VKA) have been the mainstay of oral anticoagulant therapy for over 60years. In this review we critically assess the evidence for the importance of vitamin K nutrition during VKA therapy; the methodologies for measuring dietary intakes; the vitamin K intake data in patients on VKA and healthy people; and the experimental evidence for the influence of vitamin K intakes and biochemical measures of vitamin K status on VKA response. Several studies show that dietary intakes of phylloquinone (vitamin K1) are associated to the sensitivity and stability of anticoagulation during initiation and maintenance dosing with low habitual intakes associated with greater instability of the INR and risk of sub-therapeutic anticoagulation. Preliminary evidence suggests that the stability of anticoagulation therapy may be improved by daily vitamin K supplementation, but further studies are needed to find out whether this, or other dietary interventions, can improve anticoagulant control in routine clinical practice.