Homocysteine as a risk factor for cardiovascular and related disease: nutritional implications

Homocysteine and Digestive Tract Cancer Risk: A Dose-Response Meta-Analysis

Background

Homocysteine, a key component in one-carbon metabolism, is of great importance in remethylation. Many epidemiologic studies have assessed the association between homocysteine and risk of digestive tract cancer, but the results are inconsistent.

Objective

The objective of our meta-analysis is to assess the association between homocysteine and digestive tract cancer risk.

Methods

Comprehensive searches were performed on the PubMed, Embase, Cochrane, and Web of Science databases up to September 25, 2018, to identify relevant studies. Thirteen studies were included in the meta-analysis. Odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were used to estimate the strength of the relationship between homocysteine and the risk of digestive tract cancer.

Results

The pooled OR of digestive tract cancer risk for patients with the highest categories of blood homocysteine levels versus the lowest categories was 1.27 (95% CI, 1.15, 1.39) with no significant heterogeneity observed (P = 0.798, I ² = 0.0%). Moreover, the dose-response analysis revealed that each 5μmol/L increase in homocysteine increased the incidence of digestive tract cancer by 7%.

Conclusion

Generally, our results indicated that elevated homocysteine was associated with higher risk of digestive tract cancer. That is, homocysteine concentration may be a potential biomarker for occurrence of digestive tract cancer.

Quantification of folate metabolites in serum using ultraperformance liquid chromatography tandem mass spectrometry

Folate deficiency is considered a risk factor for many diseases such as cancer, congenital heart disease and neural tube defects (NTDs). There is a pressing need for more methods of detecting folate and its main metabolites in the human body. Here, we developed a simple, fast and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC/MS/MS) method for the simultaneous quantifications of folate metabolites including folic acid, 5-methyltetrahydrofolate (5-MeTHF), 5-formyltetrahydrofolate (5-FoTHF), homocysteine (Hcy), S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH). The method was validated by determining the linearity (r(2)>0.998), sensitivity (limit of detection ranged from 0.05 to 0.200ng/mL), intra- and inter-day precision (both CV<6%) and recovery (each analyte was >90%). The total analysis time was 7min. Serum samples of NTD-affected pregnancies and controls from a NTD high-risk area in China were analyzed by this method, the NTD serum samples showed lower concentrations of 5-MeTHF (P<0.05) and 5-FoTHF (P<0.05), and higher concentrations of Hcy (P<0.05) and SAH (P<0.05) compared with serum samples from controls, consistent with a previous study. These results showed that the method is sensitive and reliable for simultaneous determination of six metabolites, which might indicate potential risk factors for NTDs, aid early diagnosis and provide more insights into the pathogenesis of NTDs.

Folate: a functional food constituent

Folate, a water-soluble vitamin, includes naturally occurring food folate and synthetic folic acid in supplements and fortified foods. Mammalian cells cannot synthesize folate and its deficiency has been implicated in a wide variety of disorders. A number of reviews have dwelt up on the health benefits associated with increased folate intakes and many countries possess mandatory folate enrichment programs. Lately, a number of studies have shown that high intakes of folic acid, the chemically synthesized form, but not natural folates, can cause adverse effects in some individuals such as the masking of the hematological manifestations of vitamin B(12) deficiency, leukemia, arthritis, bowel cancer, and ectopic pregnancies. As fermented milk products are reported to contain even higher amounts of folate produced by the food-grade bacteria, primarily lactic acid bacteria (LAB), the focus has primarily shifted toward the natural folate, that is, folate produced by LAB and levels of folate present in foods fermented by/or containing these valuable microorganisms. The proper selection and use of folate-producing microorganisms is an interesting strategy to increase "natural" folate levels in foods. An attempt has been made through this review to share information available in the literature on wide ranging aspects of folate, namely, bioavailability, analysis, deficiency, dietary requirements, and health effects of synthetic and natural folate, dairy and nondairy products as a potential source of folate, microorganisms with special reference to Streptococcus thermophilus as prolific folate producer, and recent insight on modulation of folate production levels in LAB by metabolic engineering.

Homocysteine and diabetic retinopathy

OBJECTIVE

Homocysteine is an emerging risk factor for cardiovascular and nondiabetic ocular vaso-occlusive diseases. However, studies of the relationship between homocysteine and diabetic retinopathy have reported inconsistent results. The purpose of this study was to evaluate the relationship between plasma total homocysteine concentration and diabetic retinopathy.

RESEARCH DESIGN AND METHODS

We assessed the homocysteine-retinopathy relationship in 168 men and women with type 2 diabetes in a community-based, cross-sectional study. We photodocumented diabetic retinopathy status and measured plasma total homocysteine concentration using a commercial fluorescence polarization immunoassay enzymatic kit. Data for selected clinical/demographic variables and established risk factors for diabetic retinopathy were obtained from fasting blood samples and an interviewer-assisted lifestyle questionnaire.

RESULTS

A higher mean plasma total homocysteine concentration was observed in diabetic individuals with retinopathy than in those without retinopathy (11.5 mumol/l [95% CI 10.4-12.5] vs. 9.6 mumol/l [9.1-10.2], P = 0.001). Furthermore, the relationship between homocysteine and diabetic retinopathy was not explained by renal dysfunction and was independent of the other major risk factors for diabetic retinopathy (duration of diabetes, A1C, and systolic blood pressure) and determinants of higher homocysteine concentrations (age, sex, and red cell folate) (odds ratio 1.20 [95% CI 1.023-1.41], P = 0.024).

CONCLUSIONS

Plasma total homocysteine concentration may be a useful biomarker and/or a novel risk factor for increased risk of diabetic retinopathy in people with type 2 diabetes.

The essentiality of sulfur is closely related to nitrogen metabolism: a clue to hyperhomocysteinaemia

N and S metabolisms are closely interwoven throughout both the plant and animal kingdoms. The essentiality of S relates to its participation in the structure of S-containing amino acids (SAA), to its inclusion in many sulfonated molecules, and to a myriad of metabolic and catalytic reactions of vital importance. Methionine (Met) is the indispensable SAA supplied by food proteins and its plasma homeostasis is achieved via a number of highly efficient regulatory mechanisms. In all conditions characterised by a negative body protein balance such as in dietary restriction or cytokine-induced hypercatabolic losses, N and S endogenous pools manifest parallel tissue depletion rates. Adaptive conservation of N and S body stores is reached by a functional restraint of the trans-sulfuration cascade, through the depression of cystathionine β-synthase activity. As a result, upstream accumulation of homocysteine favours its re-methylation conversion to Met which helps maintain metabolic pathways of survival value. In addition to the measurement of vitamin indices, that of plasma transthyretin, a sensitive marker of protein nutritional status, is proposed to identify the fluctuations of the total body N component accountable for the alterations of homocysteine concentrations in body fluids.

Combining 2nd-Trimester Maternal Serum Homocysteine Levels and Uterine Artery Doppler for Prediction of Preeclampsia and Isolated Intrauterine Growth Restriction

AIM

To evaluate the efficacy of a combined 2nd-trimester maternal serum homocysteine and uterine artery Doppler screening at 20 weeks of gestation for complications of pregnancy: preeclampsia, isolated intrauterine growth restriction (IUGR), placental abruption, and stillbirths.

METHODS

Consecutive singleton pregnancies without previous risk factors who had homocysteine measured as part of a serum-screening program for trisomy 21 had uterine artery Doppler performed. Sensitivity, specificity, positive and negative predictive values, odds ratio, and positive and negative likelihood ratios for the subsequent development of preeclampsia, isolated IUGR, placental abruption, stillbirth, and preterm delivery were calculated for the following methods (1) homocysteine cut-off level 6.3 micromol/l (95th centile); (2) on Doppler ultrasound bilateral notches with a mean resistance index (RI) >0.55 (50th centile), all unilateral notches with a mean RI >0.65 (80th centile), and absence of notches with a mean RI >0.7 (95th centile), and (3) Doppler ultrasound notch evaluation (bilateral, unilateral, absence as in method 2) combined with the homocysteine cut-off level of 6.3 micromol/l.

RESULTS

By using a logistic regression model, methods 1 and 2 predicted preeclampsia (p < 0.001), isolated IUGR (p < 0.01), and "any complication" (p < 0.01). The sensitivity for prediction of preeclampsia using the combined method (3) was 61.3% for a false-positive rate of 2%, better than that for isolated IUGR (54%) below the 5th centile and "any complication" (56%).

CONCLUSION

This prospective study confirms the potential of a combined method of elevated homocysteine and uterine artery Doppler screening for preeclampsia, isolated IUGR, and any obstetric complication.

Hyperhomocysteinemia, Pregnancy Complications, and the Timing of Investigation

OBJECTIVE

To assess associations between vitamin-dependent homocysteine metabolism and vascular-related pregnancy complications by considering interval between delivery and postpartum investigation and maternal age.

METHODS

Case-control study performed at the University Medical Center Nijmegen in the Netherlands. Patients had experienced pregnancy-induced hypertension (n = 37), preeclampsia (n = 144), hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome (n = 104), recurrent early pregnancy loss (n = 544), abruptio placentae (n = 135), intrauterine growth restriction (n = 144), or intrauterine fetal death (n = 104). Controls comprised 176 women with uncomplicated obstetric histories. Oral methionine loading tests and fasting vitamin profiles were performed more than 6 weeks after delivery. Odds ratios and 95% confidence intervals were calculated after logistic regression analysis.

RESULTS

Hyperhomocysteinemia was associated with an approximately 2-fold to 3-fold increased risk for pregnancy-induced hypertension, abruptio placentae, and intrauterine growth restriction. Cobalamin deficiency was associated with HELLP syndrome, abruptio placentae, intrauterine growth restriction, and intrauterine fetal death. Pyridoxal 5-phosphate deficiency increased the risk for pregnancy-induced hypertension 4-fold. These associations lost their significance after adjustment for time interval and maternal age. High red cell folate was associated with a decreased risk for abruptio placentae and intrauterine growth restriction. An increased creatinine concentration was associated with pregnancy-induced hypertension, preeclampsia, HELLP syndrome, and abruptio placentae.

CONCLUSION

Hyperhomocysteinemia and vitamin deficiencies are largely determined by the interval between delivery and postpartum investigation and by maternal age. Time interval and maternal age should be considered in the risk estimation for vascular-related pregnancy complications.

Elevated plasma homocysteine in early pregnancy: a risk factor for the development of nonsevere preeclampsia

OBJECTIVE

We have recently demonstrated that an elevated plasma homocysteine in early pregnancy is associated with the development of severe preeclampsia. The aim of this study was to determine whether an elevated plasma homocysteine in early pregnancy is also associated with the development of nonsevere preeclampsia.

STUDY DESIGN

Blood was obtained from patients attending for a first antenatal visit. Subjects were asymptomatic women who subsequently developed nonsevere preeclampsia. Controls were matched for parity, gestational age, and date of sample collection. Plasma homocysteine was measured using fluorescence polarization immunoassay.

RESULTS

There were 71 cases of nonsevere preeclampsia sampled at a mean gestational age (+/-SD) of 15.9+/-3.6 weeks and 142 controls at 15.6+/-3.4 weeks. The preeclampsia cases had a mean (+/-SD) homocysteine level of 8.4+/-2.4 micromol/L, whereas controls had a mean homocysteine of 7.07+/-1.5 micromol/L (P</=.0001).

CONCLUSION

Women who develop nonsevere preeclampsia have higher plasma homocysteine levels in early pregnancy compared with women who remain normotensive throughout pregnancy. An elevated plasma homocysteine value in early pregnancy may be associated with a 4-fold increased risk for development of nonsevere preeclampsia.

Determination of 5-methyltetrahydrofolate (13C-labeled and unlabeled) in human plasma and urine by combined liquid chromatography mass spectrometry

The association of folates with the prevention of neural tube defects and reduced risk of other chronic diseases has stimulated interest in the development of techniques for the study of their bioavailability in humans. Stable isotope protocols differentiate between oral and/or intravenous test doses of folate and natural levels of folate already present in the body. An liquid chromatography/mass spectrometry (LC/MS) procedure is described that has been validated for the determination of [13C]5-methyltetrahydropteroyl monoglutamic acid ([13C]5-CH3H4PteGlu) in plasma and urine, following oral dosing of volunteers with different labeled folates. Folate binding protein affinity columns were used for sample purification prior to LC/MS determination. Chromatographic separation was achieved using a Superspher 100RP18 (4 microm) column and mobile phase of 0.1 mol/L acetic acid (pH 3.3):acetonitrile (90:10; 250 microL/min). Selected ion monitoring was conducted on the [M-H](-) ion: m/z 458 and 459 for analyzing 5-CH3H4PteGlu; m/z 464 [M+6-H](-) to determine 5-CH3H4PteGlu derived from the label dose; m/z 444 for analysis of 2H4PteGlu internal standard, and m/z 446 and 478 to confirm that there was no direct absorption of unmetabolized compounds. Calibration was linear over the range 0-9 x 10(-9) mol/L; the limits of detection and quantification were 0.2 x 10(-9) and 0.55 x 10(-9) mol/L, respectively. The mean coefficient of variation of the ratios (m/z 463/458) was 7.4%. The method has potential applications for other key folates involved in one-carbon metabolism.

Elevated plasma homocysteine in early pregnancy: a risk factor for the development of severe preeclampsia

OBJECTIVE

The aim of our study was to determine if an elevated plasma homocysteine level in early pregnancy is associated with the development of severe preeclampsia.

STUDY DESIGN

Blood samples were obtained from patients attending their first antenatal visit. Cases were asymptomatic women who subsequently developed severe preeclampsia. Controls were matched for gestational age and date of sample collection. Plasma homocysteine level was measured by using fluorescence polarization immunoassay.

RESULTS

There were 56 patients with severe preeclampsia from whom blood samples were obtained at a mean (+/-SD) gestation of 15.3 weeks (+/-4.04 weeks) and 112 controls at 14.9 weeks (+/-3.41 weeks). The preeclampsia cases had a mean (+/-SD) homocysteine level of 9.8 micromol/L (+/-3.3 micromol/L), whereas controls had a mean homocysteine level of 8.4 micromol/L (+/-1.9 micromol/L), P < or = .0001.

CONCLUSION

Women who develop severe preeclampsia have higher plasma homocysteine levels in early pregnancy than women who remain normotensive throughout pregnancy. An elevated plasma homocysteine level in early pregnancy can increase the risk of developing severe preeclampsia by almost threefold.

Folates and prevention of disease

Research in the past decade has established that low or inadequate folate status may contribute to congenital malformations and the development of chronic disease in later life. Using an evidence based approach, there are clear guidelines for recommending folic acid supplementation or fortification in certain disease conditions but further proof of its efficacy is required in other circumstances. There is conclusive evidence that maternal periconceptional supplementation with folic acid prevents the majority of NTDs, probably by overcoming one or more genetically inherited metabolic blocks in folate dependent enzymes. Public health efforts to advise women to increase their folate intake have not been successful. As a result, the U.S. government passed legislation to have all flour fortified with folic acid. This intervention has had a dramatic effect on folate status in the U.S. To date, countries of the EU have not adopted mandatory fortification policies. The amino acid homocysteine is an essential intermediate in folate metabolism. Substantial evidence indicates that elevated plasma homocysteine is an independent risk factor for heart disease and stroke. Plasma homocysteine levels can be reduced by folic acid supplements. A food fortification policy would probably be an effective population strategy to reduce plasma homocysteine. However, many experts believe that this would be premature without first showing that such reduction would cause a decrease in the prevalence of cardiovascular disease. The contribution of folate to cancer risk is not well defined although there is reasonable evidence to implicate low folate status in the specific case of colorectal cancer. In particular, long-term folic acid supplementation may reduce risk of colorectal cancer substantially. Various mental disorders including Alzheimer's Disease have been associated with low folate status or elevated plasma homocysteine. While it is hard to determine if this is cause or effect, there is little doubt that if it were true then low dose folic acid intervention would be highly effective.

Metabolism 2000: the emperor needs new clothes

Metabolism is one of the corner stones of nutritional science. As biology enters the post-genomic era and with functional genomics beginning to takeoff, we anticipate that the study of metabolism will play an increasingly important role in helping to link advances made via the reductionist paradigm, that has been so successful in molecular and cellular biology, with those emerging from observational studies in animals and human subjects. A reconstructive metabolically-focused approach offers a timely paradigm for enhancing the elegance of nutritional science. Here we give particular attention to the use of tracers as phenotyping tools and discuss the application of our metaprobe concepts with respect to some novel features of metabolism, including 'underground metabolism', 'metabolic hijacking', 'catalytic promiscuity' and 'moonlighting proteins'. The opportunities for enhancing the study of metabolism by new and emerging technologies, and the importance of the interdisciplinary research enterprise are also touched upon. We conclude that: (1) the metaprobe concepts and approach, discussed herein, potentially yield a quantitative physiological (metabolic) phenotype against which to elaborate partial or focused genotypes; (2) physiological (metabolic) phenotypes which have a whole-body or kinetically-discernible inter-organ tissue-directed metabolic signature are an ideal target for this directed tracer-based definition of the 'functional' genotype; (3) metabolism, probed with tracer tool kits suitable for measuring rates of turnover, change and conversion, becomes in the current sociology of the 'Net', like AOL, Yahoo. Alta Vista, Lycos or Ask Jeeves, the portal for an exploration of the metabolic characteristics of the 'Genomics Internet'.

Evidence that diet modification reduces in vivo oxidant damage

Because few trials have studied the antioxidant effects of diets rather than vitamin supplements, the results of a recent trial that altered fruit, vegetable, and fat intake in healthy adults are especially valuable. The findings support the hypothesis that changing dietary patterns may decrease the risk of atherosclerosis by favorably altering the balance of oxidant defense and damage.