Cysteamine revisited: repair of arginine to cysteine mutations.

Cysteamine is a small aminothiol endogenously derived from coenzyme A degradation. For some decades, synthetic cysteamine has been employed for the treatment of cystinosis, and new uses of the drug continue to emerge. In this review, we discuss the role of cysteamine in cellular and extracellular homeostasis and focus on the potential use of aminothiols to reconstitute the function of proteins harboring arginine (Arg) to cysteine (Cys) mutations, via repair of the Cys residue into a moiety that introduces an amino group, as seen in basic amino acid residues Lys and Arg. Cysteamine has been utilized in vitro and ex vivo in four different genetic disorders, and thus provides "proof of principle" that aminothiols can modify Cys residues. Other aminothiols such as mercaptoethylguanidine (MEG) with closer structural resemblance to the guanidinium moiety of Arg are under examination for their predicted enhanced capacity to reconstitute loss of function. Although the use of aminothiols holds clinical potential, more studies are required to refine specificity and treatment design. The efficacy of aminothiols to target proteins may vary substantially depending on their specific extracellular and intracellular locations. Redox potential, pH, and specific aminothiol abundance in each physiological compartment are expected to influence the reactivity and turnover of cysteamine and analogous drugs. Upcoming research will require the use of suitable cell and animal models featuring Arg to Cys mutations. Since, in general, Arg to Cys changes comprise about 8% of missense mutations, repair of this specific mutation may provide promising avenues for many genetic diseases.

Arterial stiffness is not associated with bone parameters in an elderly hyperhomocysteinemic population.

Several studies have observed positive associations between bone disease and cardiovascular disease. A potential common pathway is hyperhomocysteinemia; however, to date, there is a lack of data regarding hyperhomocysteinemic populations. Therefore, we examined both cross-sectionally and longitudinally, whether there is an association between bone parameters and arterial stiffness in a hyperhomocysteinemic population, and investigated the potential common role of homocysteine (hcy) level on these associations. Cross-sectional and longitudinal data of the B-PROOF study were used (n = 519). At both baseline and 2-year follow-up we determined bone measures-incident fractures and history of fractures, bone-mineral density (BMD) and quantitative ultrasound (QUS) measurement. We also measured arterial stiffness parameters at baseline-pulse wave velocity, augmentation index and aortic pulse pressure levels with applanation tonometry. Linear regression analysis was used to examine these associations and we tested for potential interaction of hcy level. The mean age of the study population was 72.3 years and 44.3 % were female. Both cross-sectionally and longitudinally there was no association between arterial stiffness measures and BMD or QUS measurements or with incident fractures (n = 16) within the 2-3 years of follow-up. Hcy level did not modify the associations and adjustment for hcy did not change the results. Arterial stiffness was not associated with bone parameters and fractures, and hcy neither acted as a pleiotropic factor nor as a mediator. The potential association between bone and arterial stiffness is therefore not likely to be driven by hyperhomocysteinemia.

MRI and (1)H-MRS in adenosine kinase deficiency.

INTRODUCTION: Adenosine kinase deficiency (ADK deficiency) is a recently described disorder of methionine and adenosine metabolism resulting in a neurological phenotype with developmental delay, muscular hypotonia, and epilepsy as well as variable systemic manifestations. The underlying neuropathology is poorly understood. We have investigated MRI and (1)H-MRS changes in ADK deficiency in order to better understand the in vivo neuropathologic changes of ADK deficiency. METHODS: Systematic evaluation of 21 MRIs from eight patients (age range 9 days-14.6 years, mean 3.9 years, median 2.7 years) including diffusion-weighted imaging in six and (1)H-MRS in five patients. RESULTS: Brain maturation was delayed in the neonatal period and in infancy (6/6), but ultimately complete. White matter changes occurring in five of eight patients were discrete, periventricular, and unspecific (4/5), or diffuse with sparing of optic radiation, corona radiata, and pyramidal tracts (1/5). Choline was low in white matter spectra (3/3), while there was no indication of low creatine in white matter or basal ganglia (5/5), and diffusion was variably decreased or increased. Central tegmental tract hyperintensity was a common finding (6/8), as was supratentorial atrophy (6/8). CONCLUSIONS: MRI changes in ADK deficiency consist of delayed but ultimately completed brain maturation with later onset of mostly unspecific white matter changes and potentially transient central tegmental tract hyperintensity. Immaturity on neonatal MRI is consistent with prenatal onset of disease and reduced choline with lower membrane turnover resulting in delayed myelination and deficient myelin maintenance.

A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase.

Hyperhomocysteinaemia has been identified as a risk factor for cerebrovascular, peripheral vascular and coronary heart disease. Elevated levels of plasma homocysteine can result from genetic or nutrient-related disturbances in the trans-sulphuration or re-methylation pathways for homocysteine metabolism. 5, 10-Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the predominant circulatory form of folate and carbon donor for the re-methylation of homocysteine to methionine. Reduced MTHFR activity with a thermolabile enzyme has been reported in patients with coronary and peripheral artery disease. We have identified a common mutation in MTHFR which alters a highly-conserved amino acid; the substitution occurs at a frequency of approximately 38% of unselected chromosomes. The mutation in the heterozygous or homozygous state correlates with reduced enzyme activity and increased thermolability in lymphocyte extracts; in vitro expression of a mutagenized cDNA containing the mutation confirms its effect on thermolability of MTHFR. Finally, individuals homozygous for the mutation have significantly elevated plasma homocysteine levels. This mutation in MTHFR may represent an important genetic risk factor in vascular disease.

Cellular hypomethylation is associated with impaired nitric oxide production by cultured human endothelial cells.

Hyperhomocysteinemia (HHcy) is a risk factor for vascular disease, but the underlying mechanisms remain incompletely defined. Reduced bioavailability of nitric oxide (NO) is a principal manifestation of underlying endothelial dysfunction, which is an initial event in vascular disease. Inhibition of cellular methylation reactions by S-adenosylhomocysteine (AdoHcy), which accumulates during HHcy, has been suggested to contribute to vascular dysfunction. However, thus far, the effect of intracellular AdoHcy accumulation on NO bioavailability has not yet been fully substantiated by experimental evidence. The present study was carried out to evaluate whether disturbances in cellular methylation status affect NO production by cultured human endothelial cells. Here, we show that a hypomethylating environment, induced by the accumulation of AdoHcy, impairs NO production. Consistent with this finding, we observed decreased eNOS expression and activity, but, by contrast, enhanced NOS3 transcription. Taken together, our data support the existence of regulatory post-transcriptional mechanisms modulated by cellular methylation potential leading to impaired NO production by cultured human endothelial cells. As such, our conclusions may have implications for the HHcy-mediated reductions in NO bioavailability and endothelial dysfunction.

Elevated concentrations of sedoheptulose in bloodspots of patients with cystinosis caused by the 57-kb deletion: implications for diagnostics and neonatal screening.

Cystinosis is an autosomal recessive lysosomal storage disease caused by mutations in CTNS. The most prevalent CTNS mutation is a homozygous 57-kb deletion that also includes an adjacent gene named SHPK (CARKL), encoding sedoheptulokinase. Patients with this deletion have elevated urinary concentrations of sedoheptulose. Using derivatisation with pentafluorobenzyl hydroxylamine and liquid chromatography-tandem mass spectrometry (LC-MS/MS), we developed a new sensitive method for the quantification of sedoheptulose in dried blood spots. This method can be utilized as a quick screening test to detect cystinosis patients homozygous for the 57-kb deletion in CTNS; which is the most common mutation of cystinosis. Sedoheptulose concentrations in the deleted patients were 6 to 23 times above the upper limit for controls. The assessment of sedoheptulose in a bloodspot from a known cystinosis patient homozygous for the 57-kb deletion retrieved from the Dutch neonatal screening program showed that sedoheptulose was already elevated in the neonatal period. There was no overlap in sedoheptulose levels between cystinosis patients homozygous for the 57-kb deletion and cystinosis patients not homozygous for this deletion. Our presented method can be used prior to mutation analysis to detect cystinosis patients homozygous for the 57-kb deletion. We feel that the presented method enables fast (pre)-symptomatic detection of cystinosis patients homozygous for the 57-kb deletion, allowing early treatment.

Serum homocysteine levels in relation to clinical progression in multiple sclerosis.

BACKGROUND: Elevated homocysteine levels are associated with various neurodegenerative diseases and have even been identified as a risk factor for some of these. Homocysteine levels may be elevated in patients with multiple sclerosis (MS) but large studies are lacking and the relation with disease progression remains to be determined. AIM: The aim of the study was to investigate homocysteine levels in patients with MS and in controls, and to study the relationship between homocysteine levels and clinical progression in MS. METHODS: Serum homocysteine levels were compared between MS subtypes (n = 219) and controls (n = 152). Homocysteine levels were associated with baseline and follow-up clinical severity scores. RESULTS: The results showed that serum homocysteine values were similar in patients with MS and controls. Baseline scores on the Expanded Disability Status Scale were higher in patients with secondary progressive MS (SPMS) in the top compared with the bottom quartile of homocysteine levels (p = 0.02). The baseline scores on the Multiple Sclerosis Functional Composite (MSFC) and Paced Auditory Serial Addition Test (PASAT), which measures cognitive functioning, were lower in patients with SPMS in the top compared with the bottom quartile of homocysteine levels (MSFC, p = 0.02; PASAT, p = 0.02). High homocysteine levels were associated with a decline in PASAT scores during follow-up in patients with primary progressive MS (p = 0.009). CONCLUSION: Serum total homocysteine levels are associated with several measures of disease progression in MS but are not elevated in patients with MS compared with controls. The association of homocysteine levels with cognition in patients with progressive MS raises the question of whether homocysteine directly impacts on MS or reflects a more general neurodegenerative process.

Changes in markers of cobalamin status after cessation of oral B-vitamin supplements in elderly people with mild cobalamin deficiency.

Mildly cobalamin-deficient elderly were supplemented with 1000 microg cobalamin (group C, n=34), 1000 microg cobalamin with 400 microg folic acid (group CF, n=31) or a placebo (n=30) for 6 months. Participants provided one single blood sample 3, 5 or 7 months after cessation of supplementation to monitor early changes in plasma concentrations of cobalamin, holotranscobalamin (holoTC) and methylmalonic acid (MMA). At the end of supplementation (groups C+CF), one participant met our criteria for mild cobalamin deficiency, as did 13, 14 and 43% of the participants assessed at respectively 3, 5 and 7 months post-supplementation. Cobalamin and holoTC declined on average with 47 and 56% relative to concentrations at the end of supplementation for the group assessed at 7 months post-supplementation. Essentially similar declines were observed for those participants assessed at 3 and 5 months post-supplementation. Mean MMA concentrations increased by 15% (P=0.07) in those participants assessed at 3 and 5 months post-supplementation, and increased by 50% (P=0.002) in those participants assessed at 7 months post-supplementation. Considering MMA as a sensitive tissue marker for cobalamin status, oral supplementation may afford adequate cobalamin status for a period of up to 5 months after cessation in the majority of participants.

Transsulfuration in an adult with hepatic methionine adenosyltransferase deficiency.

We investigated sulfur and methyl group metabolism in a 31-yr-old man with partial hepatic methionine adenosyltransferase (MAT) deficiency. The patient's cultured fibroblasts and erythrocytes had normal MAT activity. Hepatic S-adenosylmethionine (SAM) was slightly decreased. This clinically normal individual lives with a 20-30-fold elevation of plasma methionine (0.72 mM). He excretes in his urine methionine and L-methionine-d-sulfoxide (2.7 mmol/d), a mixed disulfide of methanethiol and a thiol bound to an unidentified group X, which we abbreviate CH3S-SX (2.1 mmol/d), and smaller quantities of 4-methylthio-2-oxobutyrate and 3-methylthiopropionate. His breath contains 17-fold normal concentrations of dimethylsulfide. He converts only 6-7 mmol/d of methionine sulfur to inorganic sulfate. This abnormally low rate is due not to a decreased flux through the primarily defective enzyme, MAT, since SAM is produced at an essentially normal rate of 18 mmol/d, but rather to a rate of homocysteine methylation which is abnormally high in the face of the very elevated methionine concentrations demonstrated in this patient. These findings support the view that SAM (which is marginally low in this patient) is an important regulator that helps to determine the partitioning of homocysteine between degradation via cystathionine and conservation by reformation of methionine. In addition, these studies demonstrate that the methionine transamination pathway operates in the presence of an elevated body load of that amino acid in human beings, but is not sufficient to maintain methionine levels in a normal range.

Defective cystathionine beta-synthase regulation by S-adenosylmethionine in a partially pyridoxine responsive homocystinuria patient.

We determined the molecular basis of cystathionine beta-synthase (CBS) deficiency in a partially pyridoxine-responsive homocystinuria patient. Direct sequencing of the entire CBS cDNA revealed the presence of a homozygous G1330A transition. This mutation causes an amino acid change from aspartic acid to asparagine (D444N) in the regulatory domain of the protein and abolishes a TaqI restriction site at DNA level. Despite the homozygous mutation, CBS activities in extracts of cultured fibroblasts of this patient were not in the homozygous but in the heterozygous range. Furthermore, we observed no stimulation of CBS activity by S-adenosylmethionine, contrary to a threefold stimulation in control fibroblast extract. The mutation was introduced in an E. coli expression system and CBS activities were measured after addition of different S-adenosylmethionine concentrations (0-200 microM). Again, we observed a defective stimulation of CBS activity by S-adenosylmethionine in the mutated construct, whereas the normal construct showed a threefold stimulation in activity. These data suggest that this D444N mutation interferes in S-adenosylmethionine regulation of CBS. Furthermore, it indicates the importance of S-adenosylmethionine regulation of the transsulfuration pathway in homocysteine homeostasis in humans.

The MTHFR 677C->T polymorphism and the risk of congenital heart defects: a literature review and meta-analysis.

BACKGROUND: Periconceptional folic acid supplementation may protect against congenital heart defects (CHDs). Identification of candidate genes in folate metabolism has suggested that the 677C-->T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene may be particularly associated with the risk of CHDs. AIM: To assess the relationship between MTHFR 677C-->T and CHDs by literature review and meta-analysis. METHODS: Studies were identified by searches of electronic literature for papers focussing on MTHFR 677C-->T and the risk of any type of CHD. Both case-control comparisons and transmission-disequilibrium tests (TDTs) in family-based designs were included. RESULTS: We found 13 eligible studies. Of 10 case-control studies, four focused on the fetal polymorphism, two studied the maternal polymorphism, and a further four investigated both. Three further publications used a family-based association study to assess the effect of the T allele on cardiac development. Overall analysis yielded odds ratios of 1.3 (95%CI 0.97-1.73) and 1.2 (95%CI 0.83-1.74) for fetal and maternal MTHFR TT genotypes, respectively. TDTs revealed no association between fetal 677T allele and CHDs. DISCUSSION: This relatively small meta-analysis found no substantial evidence of increased CHD risk in individuals with MTHFR 677CT and TT genotypes. Heterogeneity regarding population background, study design and type of heart defects complicates the pooling and comparison of the studies. The effect of modification by periconceptional folic acid intake should be taken into account. Further larger studies and well-defined phenotypic subcategory analyses are needed to decide whether the MTHFR 677C-->T polymorphism of the affected child and/or their mother is truly a risk factor for the development of CHDs.

A genome-wide linkage scan for homocysteine levels suggests three regions of interest.

BACKGROUND: An elevated plasma total homocysteine (tHcy) level is a risk factor for many clinical conditions, including vascular disease and venous thrombosis. The tHcy levels are partly determined by genetic factors. Extensive candidate gene studies have identified several genetic variants, including the MTHFR 677C>T, that influence tHcy levels, but so far only part of the genetic variation in tHcy can be explained. OBJECTIVE: In order to identify chromosomal regions that influence tHcy levels, a genome-wide linkage analysis was conducted. PATIENTS/METHODS: Our study population consisted of 13 pedigrees and 469 subjects with data on fasting plasma tHcy levels. A set of 377 markers covering the genome was genotyped in 275 subjects. The variance component linkage method (SOLAR version 2.1.3) was used for the two-point and multipoint linkage analyses. RESULTS: The heritability of the age- and sex-adjusted homocysteine levels was 44%. The multipoint linkage analysis identified one region with suggestive linkage on chromosome 16q (LOD score 1.76; nominal P = 0.0024). Weaker evidence of linkage was found for regions on chromosome 12q (LOD score 1.57; nominal P = 0.0036) and chromosome 13q (LOD score 1.52; nominal P = 0.0041). CONCLUSIONS: In our families the plasma tHcy level was highly heritable. The multipoint linkage analysis identified three regions that showed weak to suggestive linkage to tHcy levels.

No effect of folic acid and methionine supplementation on D4Z4 methylation in patients with facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy (FSHD) is associated with a contraction of the D4Z4 allele on chromosome 4qter. There is also marked DNA hypomethylation of the D4Z4 allele. The DNA hypomethylation may have a central role in the pathogenesis of FSHD. Supplemental folic acid can boost DNA methylation. We evaluated the effect of oral folic acid and methionine supplementation on the methylation level of 4qter D4Z4 alleles in peripheral-blood lymphocytes of nine patients affected with FSHD and six healthy controls. Methylation levels did not change, while recommended serum-folate concentrations were reached.

Oral anticoagulant treatment with coumarin derivatives does not influence plasma homocysteine concentration.

BACKGROUND: High circulating levels of homocysteine are a risk factor for arterial and venous thrombosis. This association has been established in numerous case-control studies. In some of these studies, patients were treated with anticoagulants at the time of venapuncture. It is not clear whether homocysteine concentrations are influenced by anticoagulants. If anticoagulation does, indeed, have an effect on homocysteine levels, it might underestimate or overestimate the possible association of homocysteine levels and vascular disease. METHODS: In this study we used two different groups to investigate the effect of coumarin derivatives on homocysteine concentrations. Homocysteine levels were measured in 40 patients who were on the waiting list for orthopedic surgery and who were expected to receive prophylactic anticoagulant therapy after the operation. Measurements were taken before the operation, as well as during and after coumarin therapy. Homocysteine concentrations were also measured in a second study group consisting of 12 healthy volunteers who were treated with oral anticoagulants. RESULTS: Mean homocysteine concentrations increased by 6% (95% CI 2-10%) during the treatment with coumarin derivatives. This corresponds to a 1 mumol/L increase in homocysteine concentration. After the anticoagulant treatment period, the concentrations decreased again. We determined that this slight increase does not influence the interpretation of epidemiological studies. We also observed no significant effect of anticoagulants on homocysteine concentration after 13 weeks of treatment of healthy volunteers (decrease of 3.6%, or approximately 0.6 micromol/L; 95% CI -17.5-8.5%). CONCLUSION: We conclude that anticoagulation does not influence homocysteine concentrations to any significant degree.

Thiamine (vitamin B1) supplementation does not reduce fasting blood homocysteine concentration in most homozygotes for homocystinuria.

Homozygotes for homocystinuria due to cystathionine synthase (CS) deficiency accumulate homocysteine and methionine in their blood and tissues. High-dose pyridoxin, folic acid, vitamin B12, or betaine are therapeutical options to lower the elevated homocysteine concentration. These compounds stimulate the transsulfuration or remethylation of homocysteine. Despite such treatment, elevated blood homocysteine concentrations may persist in many homocystinurics. Therefore, it is warranted to study alternative regimen to reduce the blood homocysteine concentration in homocystinurics. Apart from entering the transsulfuration pathway, methionine can be catabolized via the transamination pathway, by conversion into 4-methylthio-2-oxobutyrate (MTOB), followed by oxidative decarboxylation of MTOB to 3-methylthiopropionate. Thiamine pyrophosphate, the active form of thiamine, is a cofactor of the supposed rate-limiting oxidative decarboxylation in the transamination of methionine. The effect of thiamine administered in 2 or 3 daily doses of 25 mg orally, was studied in nine homozygote CS deficient patients. Methionine levels decreased in 6 out of 9 patients. In 8 out of 9 patients, however, the levels of plasma homocysteine remained virtually unchanged, as did the serum transamination metabolites in all patients. We conclude that vitamin B1 cannot be used as an additional homocysteine-lowering treatment in most homozygotes for homocystinuria.

Methanethiol and dimethylsulfide formation from 3-methylthiopropionate in human and rat hepatocytes.

This study was designed to investigate the metabolism of methanethiol, and the involvement of methanethiol and its metabolites in the transamination pathway of methionine. Gaseous methanethiol, methanethiol-mixed disulfides and dimethylsulfide were formed from 3-methylthiopropionate, a metabolite in the transamination pathway of methionine, during incubation with human and rat hepatocytes. An increase of the 3-methylthiopropionate concentration resulted in an increased formation of the products, up to a substrate concentration of 4.4 mM. Higher substrate levels resulted in a decreased methanethiol formation, probably due to poisoning of the system. However, in human hepatocytes the formation of dimethylsulfide increased up to a 3-methylthiopropionate concentration of 12.5 mM. The formation of methanethiol, dimethylsulfide and methanethiol-mixed disulfides from 3-methylthiopropionate in hepatocytes of both human and rat support the hypothesis that methanethiol can be formed from methionine via the transamination pathway.

Growth promotion by homocysteine but not by homocysteic acid: a role for excessive growth in homocystinuria or proliferation in hyperhomocysteinemia?

Excessive growth of long bones in patients with homocystinuria is still unexplained and previous work incriminating homocysteic acid could not be confirmed by others. In vitro studies from our laboratory showed that homocysteine stimulated growth in a clonogenic assay. This observation made us study plasma cyclin dependent kinase (CDK), homocyst(e)ine and homocysteic acid in 10 patients with homocystinuria and 20 controls. In addition, homocysteine and homocysteic acid were tested in a clonogenic assay to correlate the growth promoting activity with CDK. Plasma CDK (protein) correlated strongly with homocysteine (r=0.84) but not with homocysteic acid. Supernatants of the clonogenic assay samples showed up to three times higher CDK levels in the presence of homocyst(e)ine but not homocysteic acid. In vitro data and the strong correlation between homocysteine and CDK suggest a role for homocysteine stimulating CDK, the starter of mitosis, with subsequent stimulation of growth.

Evidence for McKusick's hypothesis of deficient collagen cross-linking in patients with homocystinuria.

Osteoporosis occurs commonly in homocystinuria. The underlying pathobiochemical mechanism remains unclear; disturbed cross-linking of collagen has been suggested but this hypothesis has not been fully tested, nor have studies on collagen synthesis been performed. We therefore used recently available noninvasive tests for collagen synthesis and cross-linking to examine 10 patients with homocystinuria. Synthesis of collagen type I and type III was not different from age-matched healthy controls as reflected by comparable plasma levels of carboxyterminal propeptide of type I procollagen (PICP) and of plasma levels of N-terminal propeptide of procollagen type III (PIIINP). Collagen type I cross-links expressed by serum carboxyterminal telopeptide of collagen type I (ICTP) were 1.14 +/- 0.24 micrograms/l in the patient group versus 3.29 +/- 0.32 micrograms/l in the control group. This significant reduction of cross-links in the group with homocystinuria did not correlate with serum homocysteine or homocysteic acid concentrations. Our data clearly indicate that the disturbed cross-linking hypothesis still holds and that the bone manifestations of homocystinuria are not due to deficient collagen synthesis.

Hyperhomocysteinemia: a risk factor for ischemic stroke in children.

BACKGROUND: Moderate hyperhomocysteinemia is a risk factor for arterial vascular disease and venous thrombosis in adults. We performed a case-control study to assess a possible relation between moderate hyperhomocysteinemia and ischemic stroke in Dutch children (age range, 0 to 18 years). METHODS AND RESULTS: We measured plasma total homocysteine levels (tHcy) in 45 patients with ischemic stroke and in 234 controls. Hyperhomocysteinemia was defined as a tHcy above the 95th percentile regression line for the respective age of the controls. Hyperhomocysteinemia was present in 8 (18%) of the 45 patients with ischemic stroke. The odds ratio was 4.4 (95% CI, 1.7 to 11.6). CONCLUSIONS: We conclude that moderate hyperhomocysteinemia is a risk factor for ischemic stroke in children.

Prevalences of hyperhomocysteinemia, unfavorable cholesterol profile and hypertension in European populations.

BACKGROUND: Hyperhomocysteinemia (HHCY) is a risk factor for cardiovascular diseases (CVD). HHCY may interact with hypertension (HTEN) and an unfavorable cholesterol profile (UNFAVCHOL) to alter the risk of CVD. OBJECTIVES: To estimate the prevalences of HHCY (1) isolated and (2) in combination with UNFAVCHOL and/or HTEN in different age categories. To provide information that may improve the screening and treatment of subjects at risk of CVD. DESIGN: Cross-sectional data on 12,541 men and 12,948 women aged 20 + y were used from nine European studies. RESULTS: The prevalence of isolated HHCY was 8.5% in subjects aged 20-40 y, 4.7% in subjects aged 40-60 y and 5.9% in subjects aged over 60 y. When combining all age groups, 5.3% had isolated HHCY and an additional 5.6% had HHCY in combination with HTEN and/or UNFAVCHOL. The combinations of risk factors increased with age and, except for HHCY&UNFAVCHOL, were more prevalent than predicted by chance. Of the young subjects (20-40 y), 24% suffered from one or more of the investigated CVD risk factors. This figure was 75.1% in the old subjects (60+ years). CONCLUSIONS: A substantial number of subjects in selected European populations have HHCY (10.9%). In half of these cases, subjects suffer also from other CVD risk factors like UNFAVCHOL and HTEN. Older people in particular tend to have more than one risk factor. Healthcare professionals should be aware of this when screening and treating older people not only for the conventional CVD risk factors like UNFAVCHOL and HTEN but also HHCY, as this can easily be reduced through increased intake of folic acid via supplement or foods fortified with folic acid.