Plasma Vitamin B12 Concentrations Research Articles

The effects of exercise training and acute exercise duration on plasma folate and vitamin B12.

BACKGROUND/OBJECTIVESEnergy production and the rebuilding and repair of muscle tissue by physical activity require folate and vitamin B12 as a cofactor. Thus, this study investigated the effects of regular moderate exercise training and durations of acute aerobic exercise on plasma folate and vitamin B12 concentrations in moderate exercise trained rats.MATERIALS/METHODSFifty rats underwent non-exercise training (NT, n = 25) and regular exercise training (ET, n = 25) for 5 weeks. The ET group performed moderate exercise on a treadmill for 30 min/day, 5 days/week. At the end of week 5, each group was subdivided into 4 groups: non-exercise and 3 exercise groups. The non-exercise group (E0) was sacrificed without exercising and the 3 exercise groups were sacrificed immediately after exercising on a treadmill for 0.5 h (E0.5), 1 h (E1), and 2 h (E2). Blood samples were collected and plasma folate and vitamin B12 were analyzed.RESULTSAfter exercise training, plasma folate level was significantly lower and vitamin B12 concentration was significantly higher in the ET group compared with the NT group (P < 0.05). No significant associations were observed between plasma folate and vitamin B12 concentrations. In both the NT and ET groups, plasma folate and vitamin B12 were not significantly changed by increasing duration of aerobic exercise. Plasma folate concentration of E0.5 was significantly lower in the ET group compared with that in the NT group. Significantly higher vitamin B12 concentrations were observed in the E0 and E0.5 groups of the ET group compared to those of the NT group.CONCLUSIONRegular moderate exercise training decreased plasma folate and increased plasma vitamin B12 levels. However, no significant changes in plasma folate and vitamin B12 concentrations were observed by increasing duration of acute aerobic exercise.

Effect of multi-nutrient insufficiency on markers of one carbon metabolism in young women: response to a methionine load.

Multi-nutrient insufficiencies as a consequence of nutritional and economic factors are common in India and other developing countries. We have examined the impact of multi-nutrient insufficiency on markers of one carbon (1C) metabolism in the blood, and response to a methionine load in clinically healthy young women. Young women from Pune, India (n=10) and Cleveland, USA (n=13) were studied. Blood samples were obtained in the basal state and following an oral methionine load (50 mg/kg of body weight in orange juice). Plasma concentrations of vitamin B12, folate and B6 were measured in the basal state. The effect of methionine load on the levels of methionine, total homocysteine, cysteine, glutathione and amino acids was examined. Indian women were significantly shorter and lighter compared with the American women and had lower plasma concentration of vitamins B12, folate and B6, essential amino acids and glutathione, but higher concentration of total homocysteine. The homocysteine response to methionine load was higher in Indian women. The plasma concentrations of glycine and serine increased in the Indian women after methionine (in juice) load. A significant negative correlation between plasma B6 and homocysteine (r= -0.70), and plasma folate and glycine and serine levels were observed in the Indian group (P<0.05) but not in the American group. Multi-nutrient insufficiency in the Indian women caused unique changes in markers of whole body protein and 1C metabolism. These data would be useful in developing nutrient intervention strategies.

Folate and Vitamin B12 Status in Latin America and the Caribbean: An Update.

Background: The current magnitude of folate and vitamin B12 deficiency in Latin America and the Caribbean is uncertain. To summarize data on plasma or serum vitamin B12 and folate concentrations in Latin America and the Caribbean reported since 1990, a period that covers the era before and after the introduction of folic acid fortification. A systematic review was conducted in 2012 and updated in 2014. Studies and surveys using biochemical biomarkers and conducted in apparently healthy individuals were identified. Folate deficiency in Latin America and the Caribbean appears not to be a public health problem (prevalence < 5%) after the introduction of folic acid fortification. However, there is some indication that high rates of low or marginal vitamin B12 status remain in most locations and across population groups. Adding vitamin B12 as a fortificant with folic acid may be the best strategy in areas where vitamin B12 deficiency is an established concern.

Association between intake of B vitamins and cognitive function in elderly Koreans with cognitive impairment.

BackgroundIt is possible that blood B vitamins level and cognitive function may be affected by dietary intake of these vitamins, no study however has yet been conducted on relationships between B vitamins intake and cognitive function among elderly population in Korea. This study examined the relationship between B vitamins intake and cognitive function among elderly in South Korea.MethodsParticipants consisted of 100 adults with mild cognitive impairment (MCI), 100 with Alzheimer’s disease (AD), and 121 normal subjects. Dietary intake data that included the use of dietary supplements were obtained using a 24-hour recall method by well-trained interviewers. Plasma folate and vitamin B12 concentrations were analyzed by radioimmunoassay, and homocysteine (Hcy) was assessed by a high performance liquid chromatography-fluorescence method.ResultsPlasma levels of folate and vitamin B12 were positively correlated with B vitamins intake; and plasma Hcy was negatively correlated with total intake of vitamin B2, vitamin B6, vitamin B12 and folate. In the AD group, a multiple regression analysis after adjusting for covariates revealed positive relationships between vitamin B2 intake and test scores for the MMSE-KC, Boston Naming, Word Fluency, Word List Memory and Constructional Recall Tests; and between vitamin B6 intake and the MMSE-KC, Boston Naming, Word Fluency, Word List Memory, Word List Recognition, Constructional Recall and Constructional Praxis Tests. Positive associations were observed between vitamin B12 intake and the MMSE-KC, Boston Naming, Constructional Recall and Constructional Praxis Tests, and between folate intake and the Constructional Recall Test. In the MCI group, vitamin B2 intake was positively associated with the MMSE-KC and Boston Naming Test, vitamin B6 intake was positively associated with the Boston Naming Test, and folate intake was positively associated with the MMSE-KC and Word List Memory test. No associations were observed in the normal group.ConclusionThese results suggested that total B vitamins intake is associated with cognitive function in cognitively impaired AD and MCI elderly, and the association is stronger in AD patients.

Low folate levels are associated with reduced risk of colorectal cancer in a population with low folate status.

A diet rich in folate is associated with a reduced colorectal cancer risk, whereas the role of circulating levels is less clear. The aim of this study was to relate prediagnostic plasma folate, vitamin B12, and homocysteine concentrations to the risk of colorectal cancer. This was a prospective case-control study of 331 cases and 662 matched controls nested within the population-based Northern Sweden Health and Disease Study. Median follow-up time from recruitment to diagnosis was 10.8 years. Plasma folate concentrations were positively related to colorectal cancer risk; multivariate odds ratios were 1.62 [95% confidence intervals (CI), 1.08-2.42] and 1.42 (95% CI, 0.94-2.21) for the middle and highest versus lowest tertile, respectively. In subjects with follow-up <10.8 years, a statistically significant doubled risk was observed for the middle and highest versus lowest tertile, whereas findings for longer follow-up times were null. A positive risk relationship was also observed for tumor stage III-IV but not I-II. Plasma vitamin B12 concentrations were inversely associated with rectal cancer risk. Homocysteine was not significantly related to colorectal cancer risk. In this population-based, nested case-control study, low plasma folate concentrations were associated with a reduced colorectal cancer risk. This protective role was mainly observed in subjects with higher tumor stage or shorter follow-up time between recruitment and diagnosis. Low circulating folate status may protect against colorectal cancer or suppress progression of preneoplastic or neoplastic lesions. These findings may have relevance for the ongoing debate about mandatory folic acid fortification of flour.

Low-dose B vitamins supplementation ameliorates cardiovascular risk: a double-blind randomized controlled trial in healthy Chinese elderly.

We investigated whether daily supplementation with low-dose B vitamins in the healthy elderly population improves the Framingham risk score (FRS), a predictor of cardiovascular disease risk. Between 2007 and 2012, a double-blind randomized controlled trial was conducted in a rural area of North China. In all, 390 healthy participants aged 60-74 were randomly allocated to receive daily vitamin C (50 mg; control group) or vitamin C plus B vitamins (400 µg folic acid, 2 mg B6, and 10 µg B12; treatment group) for 12 months. FRSs were calculated for all 390 subjects. Folate and vitamin B12 plasma concentrations in the treatment group increased by 253 and 80%, respectively, after 6 months, stopped increasing with continued supplementation after 12 months and returned to baseline levels 6 months after supplementation cessation. Compared with the control group, there was no significant effect of B vitamin supplementation on FRSs after 6 months (mean difference -0.38; 95% CI -1.06, 0.31; p = 0.279), whereas a significant effect of supplementation was evident after 12 months (reduced magnitude 7.6%; -0.77; 95% CI -1.47, -0.06; p = 0.033). However, this reduction disappeared 6 months after supplementation stopped (-0.07; 95% CI -0.80, 0.66; p = 0.855). The reduction in FRS 12 months after supplementation was more pronounced in individuals with a folate deficiency (10.4%; -1.30; 95% CI -2.54, -0.07; p = 0.039) than in those without (4.1%; -0.38; 95% CI -1.12, 0.36; p = 0.313). B vitamins increased high-density lipoprotein cholesterol by 3.4% after 6 months (0.04; 95% CI -0.02, 0.10; p = 0.155) and by 9.2% after 12 months (0.11; 95 % CI 0.04, 0.18; p = 0.003). Compared with the control group, this change in magnitude decreased to 3.3% (0.04; 95 % CI -0.02, 0.10; p = 0.194) 6 months after supplementation cessation. Daily supplementation with a low-dose of B vitamins for 12 months reduced FRS, particularly in healthy elderly subjects with a folate deficiency. These reduced effects declined after supplementation cessation, indicating a need for persistent supplementation to maintain the associated benefits.

Relationships of maternal folate and vitamin B12 status during pregnancy with perinatal depression: The GUSTO study

Studies in the general population have proposed links between nutrition and depression, but less is known about the perinatal period. Depletion of nutrient reserves throughout pregnancy and delayed postpartum repletion could increase the risk of perinatal depression. We examined the relationships of plasma folate and vitamin B12 concentrations during pregnancy with perinatal depression. At 26th–28th weeks of gestation, plasma folate and vitamin B12 were measured in women from the GUSTO mother-offspring cohort study in Singapore. Depressive symptoms were measured with the Edinburgh Postnatal Depression Scale (EPDS) during the same period and at 3-month postpartum. EPDS scores of ≥15 during pregnancy or ≥13 at postpartum were indicative of probable depression. Of 709 women, 7.2% (n = 51) were identified with probable antenatal depression and 10.4% (n = 74) with probable postnatal depression. Plasma folate concentrations were significantly lower in those with probable antenatal depression than those without (mean ± SD; 27.3 ± 13.8 vs 40.4 ± 36.5 nmol/L; p = 0.011). No difference in folate concentrations was observed in those with and without probable postnatal depression. In adjusted regression models, the likelihood of probable antenatal depression decreases by 0.69 for every unit variation (increase) in folate (OR = 0.69 per SD increase in folate; 95% CI: 0.52, 0.94). Plasma vitamin B12 concentrations were not associated with perinatal depression. Lower plasma folate status during pregnancy was associated with antenatal depression, but not with postnatal depression. Replication in other studies is needed to determine the direction of causality between low folate and antenatal depression. Clinical trial registryNCT01174875.

Plasma Aminothiol Profile and Some of Its Determinants in Apparently Healthy Azorean Subjects

Objectives. To evaluate the plasma aminothiol profile (PAP) and serum gamma-glutamyltransferase (GGT) activity, as well as plasma folate, vitamin B12, and vitamin B6 concentrations, in 326 apparently healthy subjects from the Azores archipelago (Portugal). Also eventual relationships of PAP with conventional risk factors for atherosclerosis were investigated, aiming at the finding of early blood markers of the disease. Design and Methods. This was an observational cross-sectional study, where participants were split into two groups: one with a normal and another with an altered PAP (at least one aminothiol out of its reference concentration range). Results. About 76% of subjects had an altered PAP, mainly due to low glutathione levels (&lt;1.5 μmol/L), mostly associated with normal GGT activity. Prevalence of hyperhomocysteinemia was 10%, where only 33% had some B-vitamin deficiency. The risk for atherosclerosis was more evidenced in subjects exhibiting both deficient GSH concentration and increased serum GGT activity. Conclusions. An altered PAP, namely, when caused by low GSH levels in the absence of alterations in the Hcy, or Cys, or Cys-Gly concentrations and in serum GGT activity, might reveal a subclinical stage of atherogenesis and should be explored as a potential early marker of atherosclerosis.

B-vitamin levels and genetics of hyperhomocysteinemia are not associated with arterial stiffness

Background and aimsHyperhomocysteinemia is associated with arterial stiffness, but underlying pathophysiological mechanisms explaining this association are to be revealed. This study was aimed to explore two potential pathways concerning the one-carbon metabolism. A potential causal effect of homocysteine was explored using a genetic risk score reflecting an individual's risk of having a long-term elevated plasma homocysteine level and also associations with B-vitamin levels were investigated. Methods and resultsBaseline cross-sectional data of the B-PROOF study were used. In the cardiovascular subgroup (n = 567, 56% male, age 72.6 ± 5.6 yrs) pulse wave velocity (PWV) was determined using applanation tonometry. Plasma concentrations of vitamin B12, folate, methylmalonic acid (MMA) and holo transcobalamin (holoTC) were assessed and the genetic risk score was based on 13 SNPs being associated with elevated plasma homocysteine. Associations were examined using multivariable linear regression analysis. B-vitamin levels were not associated with PWV. The genetic risk score was also not associated with PWV. However, the homocysteine–gene interaction was significant (p < 0.001) in the association of the genetic risk score and PWV. Participants with the lowest genetic risk of having long-term elevated homocysteine levels, but with higher measured homocysteine levels, had the highest PWV levels. ConclusionHomocysteine is unlikely to be causally related to arterial stiffness, because there was no association with genetic variants causing hyperhomocysteinemia, whereas non-genetically determined hyperhomocysteinemia was associated with arterial stiffness. Moreover, the association between homocysteine and arterial stiffness was not mediated by B-vitamins. Possibly, high plasma homocysteine levels reflect an unidentified factor, that causes increased arterial stiffness.

Interactions between plasma concentrations of folate and markers of vitamin B12status with cognitive performance in elderly people not exposed to folic acid fortification: the Hordaland Health Study

A combination of high folate with low vitamin B12 plasma status has been associated with cognitive impairment in a population exposed to mandatory folic acid fortification. The objective of the present study was to examine the interactions between plasma concentrations of folate and vitamin B12 markers in relation to cognitive performance in Norwegian elderly who were unexposed to mandatory or voluntary folic acid fortification. Cognitive performance was assessed by six cognitive tests in 2203 individuals aged 72-74 years. A combined score was calculated using principal component analysis. The associations of folate concentrations, vitamin B12 markers (total vitamin B12, holotranscobalamin (holoTC) and methylmalonic acid (MMA)) and their interactions in relation to cognitive performance were evaluated by quantile regression and least-squares regression, adjusted for sex, education, apo-ɛ4 genotype, history of CVD/hypertension and creatinine. Cross-sectional analyses revealed an interaction (P=0·009) between plasma concentrations of folate and vitamin B12 in relation to cognitive performance. Plasma vitamin B12 concentrations in the lowest quartile (<274pmol/l) combined with plasma folate concentrations in the highest quartile (>18·5nmol/l) were associated with a reduced risk of cognitive impairment compared with plasma concentrations in the middle quartiles of both vitamins (OR 0·22, 95% CI 0·05, 0·92). The interaction between folate and holoTC or MMA in relation to cognitive performance was not significant. In conclusion, this large study population unexposed to mandatory folic acid fortification showed that plasma folate, but not plasma vitamin B12, was associated with cognitive performance. Among the elderly participants with vitamin B12 concentrations in the lower range, the association between plasma folate and cognitive performance was strongest.

Association between maternal folate concentrations during pregnancy and insulin resistance in Indian children

Aims/hypothesisIn an Indian birth cohort, higher maternal homocysteine concentration in pregnancy was associated with lower birthweight of the offspring. Lower maternal vitamin B12 and higher folate concentrations were associated with higher offspring insulin resistance. Disordered one-carbon metabolism during early development may increase later metabolic risk. We explored these associations in another birth cohort in India at three age points.MethodsWe measured plasma vitamin B12, folate and homocysteine concentrations at 30 ± 2 weeks’ gestation in 654 women who delivered at one hospital. Neonatal anthropometry was recorded, and the children’s glucose and insulin concentrations were measured at 5, 9.5 and 13.5 years of age. Insulin resistance was estimated using HOMA of insulin resistance (HOMA-IR).ResultsMaternal homocysteine concentrations were inversely associated with all neonatal anthropometric measurements (p < 0.05), and positively associated with glucose concentrations in the children at 5 (30 min; p = 0.007) and 9.5 years of age (120 min; p = 0.02). Higher maternal folate concentrations were associated with higher HOMA-IR in the children at 9.5 (p = 0.03) and 13.5 years of age (p = 0.03). Maternal vitamin B12 concentrations were unrelated to offspring outcomes.Conclusions/interpretationMaternal vitamin B12 status did not predict insulin resistance in our cohort. However, associations of maternal homocysteine and folate concentrations with birth size, and with childhood insulin resistance and glycaemia in the offspring, suggest a role for nutritionally driven disturbances in one-carbon metabolism in fetal programming of diabetes.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-013-3086-7) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Effects of cobalt supplementation and vitamin B12 injections on lactation performance and metabolism of Holstein dairy cows

The objective of this study was to determine lactation performance and metabolism of primiparous and multiparous dairy cows fed different levels and sources (inorganic and organic) of Co or given weekly vitamin B12 injections. Forty-five primi- and multiparous cows at 60d prepartum were blocked by expected calving date, and randomly assigned to 1 of 5 treatments in a randomized complete block design with treatments starting at 60d prepartum. The 5 treatments were (1) no supplemental dietary Co (control, CON), (2) 25mg/d of supplemental dietary Co from Co carbonate (CoCarb), (3) 25mg/d of supplemental dietary Co from Co glucoheptonate (LCoGH), (4) 75mg/d of supplemental dietary Co from Co glucoheptonate (HCoGH), and (5) CON diet plus weekly 10mg i.m. of vitamin B12 injections (IB12). Cows remained on their respective treatment until 150d after calving. Cobalt concentrations (mg/kg of dry matter) in the lactating diets were 1.0, 1.9, 2.3, and 5.1 for CON/IB12, CoCarb, LCoGH, and HCoGH, respectively. Dry matter intake, body weight, and body condition score were not affected by treatment. The LCoGH treatment tended to have greater milk yield than CoCarb, and CON had similar milk yields to the mean of LCoGH and HCoGH. Cobalt supplementation or the use of vitamin B12 injections did not influence plasma or liver measures of energy metabolism. Injections of vitamin B12 increased plasma, liver, and milk vitamin B12 contents. Dietary Co addition did not affect plasma vitamin B12 concentrations; however, it did increase milk vitamin B12 concentrations throughout lactation and liver vitamin B12 at calving with no effect of source or level of Co. Folate status of cows in the study was low and possibly limited the effect of improved vitamin B12 status on lactation performance. Overall, Co supplementation (inorganic and organic) or vitamin B12 injections improved measures of vitamin B12 status, but not lactation performance compared with CON possibly due to Co being above requirements in the CON diet.

Concentration plasmatique élevée de la vitamine B12 : un indicateur des maladies hépatiques ou tumorales

PurposeTo identify the diseases that are associated with a high plasma concentration of vitamin B12 and to measure the strength of this association. Patients and methodsRetrospective study including all admissions between 1st May, 2005 and 30th April, 2008 in the UMAG pole departments (emergency, internal medicine, acute geriatrics and medical intensive care) with a test for plasma vitamin B12. The association between each of medical information system codes (solid tumors, malignant hematologic process, and renal disease) and a high or low vitamin B12 concentration was measured by odds ratios (OR) from logistic models taking into account repeated admissions, with adjustment for age and the weighted Charlson index. ResultsAmong 3702 admissions, 12% had a B12 more than 820pg/ml, 10.4% a B12 less than 180pg/ml and 77.6% a normal B12 concentration. After adjustment for age and the weighted Charlson index, high concentration of vitamin B12 was associated with interstitial renal diseases (OR 2.7; 95% CI: [1.7–4.2]), and cirrhosis or hepatitis (OR 4.3; [2.9–6.4]). After additional adjustment for these parameters, it was still associated with tumors (OR 1.8; [1.2–2.6]), malignant hematologic diseases (OR 2.1; [1.3–3.5]), metastasis (OR 2.9; [1.5–5.9]), liver metastasis (OR 6.2; [2.7–14.5]), liver carcinoma (LC) (OR 3.3; [1.1–10.4]), liver tumors other than LC (OR 4.7; [1.2–17.9]) and lymphoma (OR 3.2; [1.6–6.4]) but not with myeloma (OR 1.9; [0.6–1.4]). Low concentration of B12 was associated with myeloma (OR 2.9; [1.3–6.6]). ConclusionFinding a high plasma concentration of vitamin B12 should lead to a systematic search for a hepatic disease or a tumor, and particularly for a hepatic localization of a tumor.

S-Adenosylmethionine-dependent Protein Methylation Is Required for Expression of Selenoprotein P and Gluconeogenic Enzymes in HepG2 Human Hepatocytes

Cellular methylation processes enable expression of gluconeogenic enzymes and metabolism of the nutrient selenium. Selenium status has been proposed to relate to type II diabetes risk, and plasma levels of selenoprotein P (SEPP1) have been positively correlated with insulin resistance. Increased expression of gluconeogenic enzymes glucose-6-phosphatase (G6PC) and phosphoenolpyruvate carboxykinase 1 (PCK1) has negative consequences for blood glucose management in type II diabetics. Transcriptional regulation of SEPP1 is directed by the same transcription factors that control the expression of G6PC and PCK1, and these factors are activated by methylation of arginine residues. We sought to determine whether expression of SEPP1 and the aforementioned glucoconeogenic enzymes are regulated by protein methylation, the levels of which are reliant upon adequate S-adenosylmethionine (SAM) and inhibited by S-adenosylhomocysteine (SAH). We treated a human hepatocyte cell line, HepG2, with inhibitors of adenosylhomocysteine hydrolase (AHCY) known to increase concentration of SAH before analysis of G6PC, PCK1, and SEPP1 expression. Increasing SAH decreased 1) the SAM/SAH ratio, 2) protein-arginine methylation, and 3) expression of SEPP1, G6PC, and PCK1 transcripts. Furthermore, hormone-dependent induction of gluconeogenic enzymes was reduced by inhibition of protein methylation. When protein-arginine methyltransferase 1 expression was reduced by siRNA treatment, G6PC expression was inhibited. These findings demonstrate that hepatocellular SAM-dependent protein methylation is required for both SEPP1 and gluconeogenic enzyme expression and that inhibition of protein arginine methylation might provide a route to therapeutic interventions in type II diabetes.

Plasma free choline, betaine and cognitive performance: the Hordaland Health Study

Choline and betaine are nutrients involved in one-carbon metabolism. Choline is essential for neurodevelopment and brain function. We studied the associations between cognitive function and plasma concentrations of free choline and betaine. In a cross-sectional study, 2195 subjects (55 % women), aged 70-74 years, underwent extensive cognitive testing including the Kendrick Object Learning Test (KOLT), Trail Making Test (part A, TMT-A), modified versions of the Digit Symbol Test (m-DST), Block Design (m-BD), Mini-Mental State Examination (m-MMSE) and Controlled Oral Word Association Test (COWAT). Compared with low concentrations, high choline (>8·4 μmol/l) was associated with better test scores in the TMT-A (56·0 v. 61·5, P=0·004), m-DST (10·5 v. 9·8, P=0·005) and m-MMSE (11·5 v. 11·4, P=0·01). A generalised additive regression model showed a positive dose-response relationship between the m-MMSE and choline (P=0·012 from a corresponding linear regression model). Betaine was associated with the KOLT, TMT-A and COWAT, but after adjustments for potential confounders, the associations lost significance. Risk ratios (RR) for poor test performance roughly tripled when low choline was combined with either low plasma vitamin B₁₂ (≤257 pmol/l) concentrations (RR(KOLT)=2·6, 95 % CI 1·1, 6·1; RR(m-MMSE)=2·7, 95 % CI 1·1, 6·6; RR(COWAT)=3·1, 95 % CI 1·4, 7·2) or high methylmalonic acid (MMA) (≥3·95 μmol/l) concentrations (RR(m-BD)=2·8, 95 % CI 1·3, 6·1). Low betaine (≤31·1 μmol/l) combined with high MMA was associated with elevated RR on KOLT (RR(KOLT)=2·5, 95 % CI 1·0, 6·2). Low plasma free choline concentrations are associated with poor cognitive performance. There were significant interactions between low choline or betaine and low vitamin B₁₂ or high MMA on cognitive performance.

Nutritional Factors, Homocysteine and C677T Polymorphism of the Methylenetetrahydrofolate Reductase Gene in Algerian Subjects with Cardiovascular Disease

Abstract The C677T variant of methylenetetrahydrofolate reductase (MTHFR), a key enzyme in the remethylation of homocysteine (HCY) to methionine, is a frequent genetic cause of moderate hyperhomocysteinemia (HHCY) among individuals with cardiovascular disease (CVD), and particularly when combined with other factors such as hyperlipidaemia. However, in Algeria the influence of nutrient-gene interactions is not known. The aim of the present study was to explore the influence of age and gender, together with folate status, on the association between the C677T MTHFR polymorphism and plasma total HCY (tHCY) concentrations. This research was carried out as a prospective study on 98 patients hospitalized in the Cardiology Section, University of Sétif, Algeria. Mean age of participants was 57 y (range 20-96 y).The genetic analysis of the MTHFR C677T polymorphism was performed by real-time polymerase chain reaction (PCR) performed on Light Cycler in borosilicate capillaries with MTHFR 677CT polymorphism detection kit. The concentrations of tHCY, folic acid vitamin B12 levels were determined using a competitive immunoassay on the IMMULITE 1000 Analyzers. Plasma total cholesterol, triglycerides, glucose, creatinine and urea concentrations were measured by colorimetric methods. Assays were conducted according to the manufacturers' instructions. Plasma tHCY was significantly higher in the patients with CVD, and HHCY was associated with the presence of mildly elevated serum urea and creatinine (p &lt;0.05). MTHFR gene mutation does not seem to be associated with elevation of plasma tHCY in the studied patients and this lack of correlation could be influenced by the higher folate concentrations in our study. CVD patients with 677CT/TT genotypes had a higher concentration of total cholesterol than those with 677CC genotype (p &lt;0.05). Although, the presence of 677T variant together with hypofolatemia (&lt;15.4 ng/ml) had a more detrimental effect on the level of total cholesterol (p &lt;0.05). Folatemia and vitamin B12 were much higher in 677CC genotype compared to 677CT/TT genotype in CVD subjects without hyperlipidemia (p &lt;0.05). However in patients with hyperlipidemia these values became lower also with 677CC genotype. In conclusion, hyperlipidemia affects the levels of plasma folate and vitamin B12 concentrations independent of mutated MTHFR genotype. The effect of 677T variant on total cholesterol, folate and vitamin B12 concentrations may relate to possible adverse effects of elevated tHCY on lipid profiles and on plasma folate and vitamin B12.

Methyl deficient diet aggravates experimental colitis in rats

Inflammatory bowel diseases (IBD) result from complex interactions between environmental and genetic factors. Low blood levels of vitamin B12 and folate and genetic variants of related target enzymes are associated with IBD risk, in population studies. To investigate the underlying mechanisms, we evaluated the effects of a methyl-deficient diet (MDD, folate, vitamin B12 and choline) in an experimental model of colitis induced by dextran sodium sulphate (DSS), in rat pups from dams subjected to the MDD during gestation and lactation. Four groups were considered (n= 12–16 per group): C DSS− (control/DSS−), D DSS− (deficient/DSS−), C DSS+ (control/DSS+) and D DSS+ (deficient/DSS+). Changes in apoptosis, oxidant stress and pro-inflammatory pathways were studied within colonic mucosa. In rat pups, the MDD produced a decreased plasma concentration of vitamin B12 and folate and an increased homocysteine (7.8 ± 0.9 versus 22.6 ± 1.2 μmol/l, P < 0.001). The DSS-induced colitis was dramatically more severe in the D DSS+ group compared with each other group, with no change in superoxide dismutase and glutathione peroxidase activity, but decreased expression of caspase-3 and Bax, and increased Bcl-2 levels. The mRNA levels of tumour necrosis factor (TNF)-α and protein levels of p38, cytosolic phospolipase A2 and cyclooxygenase 2 were significantly increased in the D DSS+ pups and were accompanied by a decrease in the protein level of tissue inhibitor of metalloproteinases (TIMP)3, a negative regulator of TNF-α. MDD may cause an overexpression of pro-inflammatory pathways, indicating an aggravating effect of folate and/or vitamin B12 deficiency in experimental IBD. These findings suggest paying attention to vitamin B12 and folate deficits, frequently reported in IBD patients.

Child's homocysteine concentration at 2 years is influenced by pregnancy vitamin B12 and folate status.

Longitudinal studies investigating vitamin B12 and folate status of mothers and their offspring will provide a better understanding of intergenerational nutrition. During pregnancy and 2 years (2y) after delivery, we measured plasma vitamin B12 and folate concentrations in 118 women [aged (mean ± s.d.) 22.9 ± 3.9y] who attended a rural (n = 68) or an urban (n = 50) antenatal clinic in Pune, India. Cord blood vitamin B12 and folate were measured, and when the child was 2y total homocysteine (tHcy) was also measured. Demographic and diet measurements were recorded using standard methods. Pregnancy plasma vitamin B12 concentration at 34 weeks was low [median (25th, 75th), 115 (95, 147) pm]; 75% had low status (<150 pm). Plasma folate was high (mean ± s.d., 33 ± 21 nm); one had a folate concentration <7 pm. Cord plasma vitamin B12 and folate concentrations were higher than and positively associated with maternal concentrations. In stepwise regression, higher child vitamin B12 at 2y was predicted (total R 2 15.7%) by pregnancy vitamin B12 (std β 0.201, R 2 7.7%), current consumption of cow's milk (std β 0.194, R 2 3.3%) and whether breast feeding was stopped before 2y (std β -0.234 R 2 7.2%). Child's 2y tHcy concentration was high (11.4 ± 3.6 μm) and predicted by lower pregnancy vitamin B12 (std β -0.206, R 2 4.1%), lack of vitamin supplementation (std β -0.256, R 2 5.6%) in pregnancy and whether currently breastfed (std β 0.268, R 2 8.4%). Low maternal vitamin B12 status in pregnancy and prolonged breast-feeding results in disturbed one-carbon metabolism in offspring at 2y. Supplementation of women of child-bearing age, particularly during pregnancy and lactation, may improve the homocysteine status of these children.

Cobalamin supplementation improves motor development and gastrointestinal reflux in moderately deficient infants

Folate plays a critical role in the prevention of uracil incorporation into DNA and hypomethylation of DNA. This activity is compromised when vitamin B12 concentration is low because methionine synthase activity is reduced, lowering the concentration of S-adenosyl methionine (SAM) which in turn may diminish DNA methylation and cause folate to become unavailable for the conversion of dUMP to dTMP. The most plausible explanation for the chromosome-breaking effect of low folate is excessive uracil misincorporation into DNA, a mutagenic lesion that leads to strand breaks in DNA during repair. Both in vitro and in vivo studies with human cells clearly show that folate deficiency causes expression of chromosomal fragile sites, chromosome breaks, excessive uracil in DNA, micronucleus formation, DNA hypomethylation and mitochondrial DNA deletions. In vivo studies show that folate and/or vitamin B12 deficiency and elevated plasma homocysteine (a metabolic indicator of folate deficiency) are significantly correlated with increased micronucleus formation and reduced telomere length respectively. In vitro experiments indicate that genomic instability in human cells is minimised when folic acid concentration in culture medium is greater than 100 nmol/L. Intervention studies in humans show (a) that DNA hypomethylation, chromosome breaks, uracil incorporation and micronucleus formation are minimised when red cell folate concentration is greater than 700 nmol/L and (b) micronucleus formation is minimised when plasma concentration of vitamin B12 is greater than 300 pmol/L and plasma homocysteine is less than 7.5 μmol/L. These concentrations are achievable at intake levels at or above current recommended dietary intakes of folate (i.e. >400 μg/day) and vitamin B12 (i.e. >2 μg/day) depending on an individual's capacity to absorb and metabolise these vitamins which may vary due to genetic and epigenetic differences.

A higher degree of LINE-1 methylation in peripheral blood mononuclear cells, a one-carbon nutrient related epigenetic alteration, is associated with a lower risk of developing cervical intraepithelial neoplasia

Objective The objective of the study was to evaluate LINE-1 methylation as an intermediate biomarker for the effect of folate and vitamin B12 on the occurrence of higher grades of cervical intraepithelial neoplasia (CIN ≥2). Methods This study included 376 women who tested positive for high-risk human papillomaviruses and were diagnosed with CIN ≥2 (cases) or CIN ≤1 (non-cases). CIN ≥2 (yes/no) was the dependent variable in logistic regression models that specified the degree of LINE-1 methylation of peripheral blood mononuclear cells (PBMCs) and of exfoliated cervical cells (CCs) as the independent predictors of primary interest. In analyses restricted to non-cases, PBMC LINE-1 methylation (≥70% versus <70%) and CC LINE-1 methylation (≥54% versus <54%) were the dependent variables in logistic regression models that specified the circulating concentrations of folate and vitamin B12 as the primary independent predictors. Results Women in the highest tertile of PBMC LINE-1 methylation had 56% lower odds of being diagnosed with CIN ≥2 (odds ratio 0.44, 95% confidence interval 0.24–0.83, P = 0.011), whereas there was no significant association between degree of CC LINE-1 methylation and CIN ≥2 (odds ratio 0.86, 95% confidence interval 0.51–1.46, P = 0.578). Among non-cases, women with supraphysiologic concentrations of folate (>19.8 ng/mL) and sufficient concentrations of plasma vitamin B12 (≥200.6 ng/mL) were significantly more likely to have highly methylated PBMCs compared with women with lower folate and lower vitamin B12 (odds ratio 3.92, 95% confidence interval 1.06–14.52, P = 0.041). None of the variables including folate and vitamin B12 were significantly associated with CC LINE-1 methylation. Conclusion These results suggest that a higher degree of LINE-1 methylation in PBMCs, a one-carbon nutrient-related epigenetic alteration, is associated with a lower risk of developing CIN.