We have reviewed the literature and have identified more than 100 diseases or conditions that are associated with raised concentrations of plasma total homocysteine. The commonest associations are with cardiovascular diseases and diseases of the central nervous system, but a large number of developmental and age‐related conditions are also associated. Few other disease biomarkers have so many associations. The clinical importance of these associations becomes especially relevant if lowering plasma total homocysteine by B vitamin treatment can prevent disease and so improve health. Five diseases can at least in part be prevented by lowering total homocysteine: neural tube defects, impaired childhood cognition, macular degeneration, primary stroke, and cognitive impairment in the elderly. We conclude from our review that total homocysteine values in adults of 10 μmol/L or below are probably safe, but that values of 11 μmol/L or above may justify intervention. Homocysteine is more than a disease biomarker: it is a guide for the prevention of disease.

It is agreed that disease-modification is the most desirable approach to tackling dementia (1), but we are often told that it is not yet feasible and that “no disease modifying therapy has proven effective in clinical trials” (2). The purpose of our Editorial is to show that disease-modification is not only feasible but that there is good evidence that it has already been achieved in subjects with Mild Cognitive Impairment (MCI).

In rats, dietary restriction of the cysteine precursor methionine suppresses hepatic stearoyl-CoA desaturase (SCD)-1 expression and activity, whereas cysteine supplementation reverses these effects. In 2 independent cohorts: Hordaland Health Study (HUSK; N=2021, aged 71–74y), Norway, and Hoorn study (N=686, aged 50–87y), Netherlands, we examined the cross-sectional associations of plasma sulfur-containing compounds (SCC; methionine, S-adenosylmethionine, S-adenosylhomocysteine, homocysteine, cystathionine, total cysteine (tCys), glutathione and cysteinylglycine) with SCD-16 index (16:1n-7/16:0), estimated from fatty acid profiles of total plasma or serum lipids. Only tCys was consistently associated with SCD-16 index after adjustments for sex and age (HUSK: partial r=0.14; Hoorn: partial r=0.11, P<0.001 for both), and after further adjustments for other SCC, body fat, diet, exercise and plasma lipids (HUSK: partial r=0.07, P=0.004; Hoorn: partial r=0.12, P=0.013). Together with animal data showing an effect of dietary cysteine on SCD1, our results suggest a role for cysteine in SCD1 regulation in humans.

Lower circulating polyunsaturated fatty acids (PUFAs) may induce loss of heart function. We investigated whether lower concentrations of n-3 and n-6 PUFAs were associated with less favourable echocardiographic measures and higher heart rate in older Caucasians, cross-sectionally and after 7 years of follow-up. We used data from the Hoorn Study, a population-based cohort. Cross-sectional data were available for 621 participants and longitudinal data for 336 participants. Mean age was 68.6±6.8 years at baseline. We performed linear regression analyses using n-3 and n-6 PUFAs quartiles—assayed by gas liquid chromatography—with left ventricular ejection fraction (LVEF), left ventricular mass index, left atrial volume index and heart rate. In multivariable analyses (regression coefficient (95% confidence interval)), the lowest eicosapentaenoic acid and docosahexaenoic acid quartiles compared with the highest quartiles were cross-sectionally associated with lower LVEF. Lower eicosapentaenoic acid and docosahexaenoic acid concentrations were associated with higher heart rate: 3.7 b.p.m. (1.5, 6.0; P for trend <0.001) and 3.4 b.p.m. (1.2, 5.6; P for trend 0.001), respectively. Multivariate longitudinal analyses showed a significant trend across quartiles for alpha-linolenic acid in relation to LVEF. The lowest linoleic acid quartile was significantly associated with a decreased LVEF of −4.0% compared with the highest quartile. This study found no strong evidence of longitudinal associations of eicosapentaenoic acid and docosahexaenoic acid with echocardiographic measures, however, lower concentrations of alpha-linolenic acid and linoleic acid were associated with decreased LVEF. These results provide evidence for a potential protective role of alpha-linolenic acid and linoleic acid in relation to systolic function.

Background and aim: Sulfur amino acids are recognized as potent modulators of lipid metabolism. Plasma total cysteine (tCys) is associated with fat mass, obesity and serum LDL-cholesterol and apolipoprotein (Apo)-B in large population studies. It is not known how fasting plasma concentrations of cysteine precursors and products relate to these associations in humans, given that sulfur-containing compounds (SCC) influence rodent weight gain and serum lipids.Methods and results: We investigated the cross-sectional associations of fasting plasma SCC (methionine, total homocysteine, cystathionine, tCys, taurine and total glutathione) with BMI and fasting serum lipids and apolipoproteins in 854 men and women with and without cardiovascular disease (CVD).In multiple linear regression analysis adjusted for age, gender, CVD and other SCC, neither methionine, taurine, nor total glutathione was associated with BMI. Plasma taurine was, however, inversely related to HDL-cholesterol (partial r = -0.12, p = 0.004) and its associated apoA1 (partial r = -0.18, p < 0.001). Plasma cystathionine correlated positively with triglycerides and BMI, while tCys positively correlated with total cholesterol, LDL-cholesterol (partial r = 0.20, p < 0.001) and its associated apoB. The associations of SCC with serum lipids were independent of BMI. tCys was also independently associated with BMI (partial r = 0.20, p < 0.001) after adjustment for other SCC, glucose, lipids and apolipoproteins.Conclusions: Fasting tCys is associated with BMI independently of metabolically related SCC. Elevation of plasma SCC is generally associated with an unfavorable lipid profile. The negative relations of plasma taurine with HDL-C and apoA1 deserve further investigation. (C) 2011 Elsevier B.V. All rights reserved.

Ebbing M., B circle divide naa K.H., Arnesen E., Ueland P.M., Nordrehaug J.E., Rasmussen K., Nj circle divide lstad I., Nilsen D.W., Refsum H., Tverdal A., Vollset S.E., Schirmer H., Bleie circle divide., Steigen T., Midttun circle divide., Fredriksen A., Pedersen E.R., Nygard O. (From the Departments of 1Heart Disease, Haukeland University Hospital, Bergen; Heart Disease, University Hospital of North Norway; Department of Community Medicine, University of Troms circle divide, Troms circle divide; Institute of Medicine, University of Bergen, Bergen; Department of Clinical Medicine, University of Troms circle divide, Troms circle divide; Department of Cardiology, Stavanger University Hospital, Stavanger; Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK; Division of Epidemiology, the Norwegian Institute of Public Health, Oslo; Department of Public Health and Primary Health Care, University of Bergen; Bevital AS, Bergen; Norway) Combined Analyses and Extended Follow-Up of Two Randomized Controlled Homocysteine-Lowering B-Vitamin Trials. J Intern Med 2010; 268: 367-382.Objectives.In the Norwegian Vitamin Trial and the Western Norway B Vitamin Intervention Trial, patients were randomly assigned to homocysteine-lowering B-vitamins or no such treatment. We investigated their effects on cardiovascular outcomes in the trial populations combined, during the trials and during an extended follow-up, and performed exploratory analyses to determine the usefulness of homocysteine as a predictor of cardiovascular outcomes.Design.Pooling of data from two randomized controlled trials (1998-2005) with extended post-trial observational follow-up until 1 January 2008.Setting.Thirty-six hospitals in Norway.Subjects.6837 patients with ischaemic heart disease.Interventions.One capsule per day containing folic acid (0.8 mg) plus vitamin B12 (0.4 mg) and vitamin B6 (40 mg), or folic acid plus vitamin B12, or vitamin B6 alone or placebo.Main outcome measures.Major adverse cardiovascular events (MACEs; cardiovascular death, acute myocardial infarction or stroke) during the trials and cardiovascular mortality during the extended follow-up.Results.Folic acid plus vitamin B12 treatment lowered homocysteine levels by 25% but did not influence MACE incidence (hazard ratio, 1.07; 95% CI, 0.95-1.21) during 39 months of follow-up, or cardiovascular mortality (hazard ratio, 1.12; 95% CI, 0.95-1.31) during 78 months of follow-up, when compared to no such treatment. Baseline homocysteine level was not independently associated with study outcomes. However, homocysteine concentration measured after 1-2 months of folic acid plus vitamin B12 treatment was a strong predictor of MACEs.Conclusion.We found no short- or long-term benefit of folic acid plus vitamin B12 on cardiovascular outcomes in patients with ischaemic heart disease. Our data suggest that cardiovascular risk prediction by plasma total homocysteine concentration may be confined to the homocysteine fraction that does not respond to B-vitamins.

OBJECTIVES:To investigate the relationship between markers of vitamin B(12) status and brain volume loss per year over a 5-year period in an elderly population. METHODS:A prospective study of 107 community-dwelling volunteers aged 61 to 87 years without cognitive impairment at enrollment. Volunteers were assessed yearly by clinical examination, MRI scans, and cognitive tests. Blood was collected at baseline for measurement of plasma vitamin B(12), transcobalamin (TC), holotranscobalamin (holoTC), methylmalonic acid (MMA), total homocysteine (tHcy), and serum folate. RESULTS:The decrease in brain volume was greater among those with lower vitamin B(12) and holoTC levels and higher plasma tHcy and MMA levels at baseline. Linear regression analysis showed that associations with vitamin B(12) and holoTC remained significant after adjustment for age, sex, creatinine, education, initial brain volume, cognitive test scores, systolic blood pressure, ApoE epsilon4 status, tHcy, and folate. Using the upper (for the vitamins) or lower tertile (for the metabolites) as reference in logistic regression analysis and adjusting for the above covariates, vitamin B(12) in the bottom tertile (<308 pmol/L) was associated with increased rate of brain volume loss (odds ratio 6.17, 95% CI 1.25-30.47). The association was similar for low levels of holoTC (<54 pmol/L) (odds ratio 5.99, 95% CI 1.21-29.81) and for low TC saturation. High levels of MMA or tHcy or low levels of folate were not associated with brain volume loss. CONCLUSION:Low vitamin B(12) status should be further investigated as a modifiable cause of brain atrophy and of likely subsequent cognitive impairment in the elderly.

Background and objective: Elevated homocysteine has been associated with a higher prevalence of cerebral white-matter lesions and infarcts, and worse cognitive performance. This raises the question whether factors involved in homocysteine metabolism, such as vitamin B12, are also related to these outcomes. This study examined the association of several markers of vitamin B12 status with cerebral white-matter lesions, infarcts and cognition. Methods: The study evaluated the association of plasma concentrations of vitamin B12, methylmalonic acid, holotranscobalamin and transcobalamin saturation with cerebral white-matter lesions and infarcts at baseline and cognition at baseline and during follow-up among 1019 non-demented elderly participants of the population-based Rotterdam Scan Study. Analyses were adjusted for several potential confounders, including homocysteine and folate concentration. Results: Poorer vitamin B12 status was significantly associated with greater severity of white-matter lesions, in particular periventricular white-matter lesions, in a concentration-related manner. Adjustment for common vascular risk factors (including blood pressure, smoking, diabetes and intima media thickness) did not alter the associations. Adjustment for homocysteine and folate modestly weakened the associations. No association was observed for any of the studied markers of vitamin B12 status with presence of brain infarcts and baseline cognition or cognitive decline during follow-up. Conclusions: These results indicate that vitamin B12 status in the normal range is associated with severity of white-matter lesions, especially periventricular lesions. Given the absence of an association with cerebral infarcts, it is hypothesised that this association is explained by effects on myelin integrity in the brain rather than through vascular mechanisms.

Objectives.  A high level of total homocysteine (tHcy) is a risk marker for cardiovascular disease (CVD), and is related to inflammation. We wanted to test the effect of homocysteine‐lowering B‐vitamin therapy, as used in the Western Norway B‐vitamin Intervention Trial (WENBIT), on inflammatory markers associated with atherosclerosis.