Hyperhomocysteinaemia

Current and Novel Therapeutical Approaches of Classical Homocystinuria in Childhood With Special Focus on Enzyme Replacement Therapy, Liver-Directed Therapy and Gene Therapy

Classical homocystinuria is a hereditary defect of the enzyme cystathionine beta synthase, which is produced in the liver. If this enzyme fails, the synthesis pathway of cysteine from methionine is interrupted, leading to the accumulation of homocysteine in the blood plasma and homocysteine in the urine. After birth, the children are unremarkable except for the characteristic laboratory findings. Symptoms rarely appear before the second year of life. The most common symptom is a prolapse of the crystalline lens. This finding is seen in 70% of untreated 10-year-old affected individuals. As the earliest symptom, psychomotor retardation occurs in the majority of patients already during the first two years of life. Limiting factors in terms of life expectancy are thromboembolism, peripheral arterial disease, myocardial infarction, and stroke. These symptoms are due to the damage to the vessels caused by the elevated amino acid levels. About 30% suffer a thromboembolic event by the age of 20, about half by the age of 30. This review focus on present and new therapeutical approaches like the role of enzyme replacement with presentation of different novel targets in research like pegtibatinase, pegtarviliase, CDX-6512, erymethionase, chaperones, proteasome inhibitors and probiotic treatment with SYNB 1353. Furthermore, we analyze the role of liver-directed therapy with three dimensional (3D) bioprinting, liver bioengineering of liver organoids in vitro and liver transplantation. The role of different gene therapy options to treat and cure this extremely rare disease in childhood will be discussed.

Recurrent dislocation of binocular crystal lenses in a patient with cystathionine beta-synthase deficiency

Background

Ectopia lentis is the common ocular manifestation of homocystinuria resulting from cystathionine beta-synthase (CBS) deficiency which has a high risk of thromboembolic complications.

Case presentation

The present study reports the case of a teenager with recurrent lens dislocation and glaucoma. He was diagnosed with CBS deficiency according to a high level of serum homocysteine and compound heterozygous mutations at two different positions on the CBS gene. Antiglaucoma eyedrops and a mydriatic successfully controlled the intraocular pressure, while oral pyridoxine and betaine uptake lowered the serum homocysteine level effectively.

Conclusions

Children with CBS deficiency may suffer from ectopia lentis, glaucoma and/or amblyopia. We firstly discovered a new mutation of CBS c. 697 T > G which had not been reported before. The patient was pyridoxine responsive and well controlled by medicine.

Clinical, biochemical, radiological, and genetic profile of patients with homocysteine remethylation pathway defect and spastic paraplegia

Objectives:

The objective of this study is to describe the clinical, biochemical, radiological, and genetic profile of patients presenting with progressive spastic paraparesis due to homocysteine remethylation pathway defect.

Methods:

This was a retrospective study conducted by reviewing the medical records of patients with serum homocysteine levels >50 μmol/L between January 2015 and January 2019 at our hospital. We included patients presenting with progressive spastic paraparesis, having serum homocysteine >50 μmol/L with low or normal blood methionine suggesting disorders of homocysteine remethylation. Demographic details, clinical manifestations, biochemical abnormalities, neuroimaging findings, and genetic profile were analyzed.

Results:

A total of seven patients (M: F = 5:2) fulfilled the study eligibility criteria. The mean age at onset of the disease was 13.4 ± 2.4 years (range: 9–17 years). Spastic paraparesis was the presenting manifestation in 4/7 (57.1%) patients. Other manifestations included cognitive decline, poor scholastic performance, behavioral disturbances, seizures, and spastic bladder. Severe hyperhomocysteinemia (>100 μmol/L) was noted in 6/7 (85.7%) patients with median levels of serum homocysteine being 185.7 μmol/L (range: 85.78–338.5 μmol/L). Neuroimaging showed parieto-occipital predominant leukoencephalopathy in 5/7 (71.4%) and diffuse cerebral atrophy in 1/7 (14.2%). Genetic analysis in three patients revealed pathogenic missense variants c.459C >G (p.Ile153Met), c.973C >T (p.Arg325Cys), and c.1031G >T (p.Arg344Met) in MTHFR gene. All the patients received vitamin B12 (injection and oral), folic acid, and pyridoxine and two patients received betaine. At the last follow-up of a median duration of 12 months, there was a good clinical and biochemical response with reduction in the median value of serum homocysteine by 77.5 μmol/L.

Conclusion:

Evaluation of serum homocysteine and blood methionine in adolescents presenting with progressive spastic paraparesis gives clue to a treatable homocysteine remethylation disorders.

Differential Metabolic Pathways and Metabolites in a C57BL/6J Mouse Model of Alcoholic Liver Disease

Background

Alcoholic liver disease (ALD), an important cause of acute or chronic liver injury, results from binge drinking or long-term alcohol consumption. To date, there is no well-established mouse model with a comprehensive metabolic profile that mimics ALD in humans. This study aimed to explore the differential metabolic pathways and related differential metabolites in the liver of an ALD mouse model.

Material/Methods

A C57BL/6J mouse model of ALD was induced by alcohol feeding for 10 days plus binge alcohol feeding. The metabolomic profiles in the liver of the ALD mouse model was detected through ultra-high-pressure liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC/Q-TOF-MS).

Results

A total 35 metabolites were significantly altered during the development of ALD. These metabolites were correlated to multiple metabolic pathways, including purine metabolism, the pentose phosphate pathway, cysteine and methionine metabolism, D-glutamine and D-glutamate metabolism, pyrimidine metabolism, and vitamin B6 metabolism.

Conclusions

The findings of the present study reveal potential biomarkers of ALD, and provide further insights into the pathogenesis of ALD.

Association of Plasma Homocysteine and Macular Edema in Type 2 Diabetes Mellitus

Purpose

The aim of this study was to assess the association of macular edema (ME) with plasma homocysteine, vitamin B6, vitamin B12, and folic acid levels in patients with Type 2 diabetes.

Methods

Sixty-five diabetic subjects with no retinopathy and nonproliferative diabetic retinopathy (NPDR) (no DR, without ME, with ME: 16, 25, 24, respectively), 28 with proliferative diabetic retinopathy (PDR) (with and without ME: 14, 14, respectively), and 19 healthy subjects as control were recruited in this cross-sectional study Plasma homocysteine, vitamin B12, vitamin B6, and folate levels were determined after 8-hour of fasting for all subjects. The levels of serum homocysteine and vitamin B6 were measured using high performance liquid chromatography (HPLC) with fluorescence detection, and the levels of serum vitamin B12 and folic acid were measured by electrochemiluminescence immunoassay.

Results

When diabetic groups with ME were compared with diabetic groups without ME for homocysteine, vitamin B12, vitamin B6, and folic acid, the only significant difference was detected in homocysteine levels (p=0.001). There was no significant difference between NPDR with ME group compared with NPDR without ME group and no DR group for plasma homocysteine, vitamin B12, vitamin B6, and folic acid (p=0.200, p=0.660; p=0.999, p=0.678; p=1.0, p=0.248; p=1.0, p=0.982, respectively). On the other hand, when PDR with ME group was compared with PDR without ME group, there was only significant difference in homocysteine levels (p=0.023).

Conclusions

Mild to moderate elevation of homocysteine may explain the role of vascular dysregulation and endothelial dysfunction in patients with DR. The present study suggests hyperhomocysteinemia may be one of the crucial risk factors for development of ME.

Long-term methionine-diet induced mild hyperhomocysteinemia associated cardiac metabolic dysfunction in multiparous rats

Mild hyperhomocysteinemia (HHcy, clinically defined as less than 30 μmol/L) is an independent cardiovascular disease (CVD) risk factor, and is associated with many complications during pregnancy, such as preeclampsia (PE). The aim of this study was to assess the effect of long-term mild HHcy on cardiac metabolic function of multiparous rats. Female rats were mated 3 to 4 times and were fed with methionine in drinking water to increase plasma Hcy (2.9 ± 0.3 to 10.5 ± 2.3 μmol/L) until termination. This caused significant increase of heart weight/body weight (0.24 ± 0.01 to 0.27 ± 0.01 g/100 g) and left ventricle weight (0.69 ± 0.03 to 0.78 ± 0.01 g). Superoxide production was increased by 2.5-fold in HHcy hearts using lucigenin chemiluminescence. The ability of bradykinin and carbachol to regulate myocardial oxygen consumption (MVO₂) in vitro was impaired by 59% and 66% in HHcy heart, and it was restored by ascorbic acid (AA), tempol, or apocynin (Apo). Protein expression of p22^phox subunit of NAD(P)H oxidase was increased by 2.6-fold, but there were no changes in other NAD(P)H oxidase subunits, NOSs or SODs. Microarray revealed 1518 genes to be differentially regulated (P < 0.05). The mRNA level of NAD(P)H oxidase subunits, NOSs or SODs remained unchanged. In conclusion, long-term mild HHcy increases cardiac superoxide mainly through regulation of p22^phox component of the NAD(P)H oxidase and impairs the ability of NO to regulate MVO₂ in heart of multiparous mothers.

Factors that influence the bleeding phenotype in severe hemophilic patients

Hemophilia A and B are rare, X-linked bleeding disorders resulting from a partial or total deficiency of functionally active coagulation factor VIII or factor IX, respectively. Endogenous factor levels have traditionally been used to characterize the severity of the disorder, with severe hemophilia considered as circulating levels of factor less than 1% of normal. Identifying patients with severe hemophilia is essential to effective treatment, since these patients are at highest risk of spontaneous life or limb-threatening bleeding and disability resulting from repeated joint bleeding and are most likely to benefit from prophylaxis. However, there is variability in bleeding tendency, even among patients with severe hemophilia. This article will review potential modifiers of hemophilia-associated bleeding other than endogenous factor activity, which may influence bleeding tendencies and complications in hemophilic patients considered to have severe hemophilia. These potential modifiers include physiologic factors, such as elements of the hemostatic system; pathophysiologic factors, such as hemophilic arthropathy, associated inflammation, and angiogenesis; and others, such as seasonal variation, body weight, and physical activity.

Homocysteine induces energy imbalance in rat skeletal muscle: is creatine a protector?

Homocystinuria is a neurometabolic disease caused by a severe deficiency of cystathionine beta-synthase activity, resulting in severe hyperhomocysteinemia. Affected patients present several symptoms including a variable degree of motor dysfunction. In this study, we investigated the effect of chronic hyperhomocysteinemia on the cell viability of the mitochondrion, as well as on some parameters of energy metabolism, such as glucose oxidation and activities of pyruvate kinase, citrate synthase, isocitrate dehydrogenase, malate dehydrogenase, respiratory chain complexes and creatine kinase in gastrocnemius rat skeletal muscle. We also evaluated the effect of creatine on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injections of homocysteine (0.3-0.6 µmol/g body weight) and/or creatine (50 mg/kg body weight) from the 6th to the 28th days of age. The animals were decapitated 12 h after the last injection. Homocysteine decreased the cell viability of the mitochondrion and the activities of pyruvate kinase and creatine kinase. Succinate dehydrogenase was increased other evaluated parameters were not changed by this amino acid. Creatine, when combined with homocysteine, prevented or caused a synergistic effect on some changes provoked by this amino acid. Creatine per se or creatine plus homocysteine altered glucose oxidation. These findings provide insights into the mechanisms by which homocysteine exerts its effects on skeletal muscle function, more studies are needed to elucidate them. Although creatine prevents some alterations caused by homocysteine, it should be used with caution, mainly in healthy individuals because it could change the homeostasis of normal physiological functions.

Homocysteine induces oxidative-nitrative stress in heart of rats: prevention by folic acid

Hyperhomocysteinemia is a risk factor for cardiovascular disease, stroke, and thrombosis; however, the mechanisms by which homocysteine triggers these dysfunctions are not fully understood. In the present study, we investigated the effect of chronic hyperhomocysteinemia on some parameters of oxidative stress, namely thiobarbituric acid reactive substances, an index of lipid peroxidation, 2',7'-dichlorofluorescein (H(2)DCF) oxidation, activities of antioxidant enzymes named superoxide dismutase and catalase, as well as nitrite levels in heart of young rats. We also evaluated the effect of folic acid on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injection of homocysteine (0.3-0.6 μmol/g body weight) and/or folic acid (0.011 μmol/g body weight) from their 6th to the 28th day of life. Controls and treated rats were killed 1 h and/or 12 h after the last injection. Results showed that chronic homocysteine administration increases lipid peroxidation and reactive species production and decreases enzymatic antioxidant defenses and nitrite levels in the heart of young rats killed 1 h, but not 12 h after the last injection of homocysteine. Folic acid concurrent administration prevented homocysteine effects probable by its antioxidant properties. Our data indicate that oxidative stress is elicited by chronic hyperhomocystenemia, a mechanism that may contribute, at least in part, to the cardiovascular alterations characteristic of hyperhomocysteinemic patients. If confirmed in human beings, our results could propose that the supplementation of folic acid can be used as an adjuvant therapy in cardiovascular alterations caused by homocysteine.

Predicting diabetic nephropathy using a multifactorial genetic model

Aims

The tendency to develop diabetic nephropathy is, in part, genetically determined, however this genetic risk is largely undefined. In this proof-of-concept study, we tested the hypothesis that combined analysis of multiple genetic variants can improve prediction.

Methods

Based on previous reports, we selected 27 SNPs in 15 genes from metabolic pathways involved in the pathogenesis of diabetic nephropathy and genotyped them in 1274 Ashkenazi or Sephardic Jewish patients with Type 1 or Type 2 diabetes of >10 years duration. A logistic regression model was built using a backward selection algorithm and SNPs nominally associated with nephropathy in our population. The model was validated by using random “training” (75%) and “test” (25%) subgroups of the original population and by applying the model to an independent dataset of 848 Ashkenazi patients.

Results

The logistic model based on 5 SNPs in 5 genes (HSPG2, NOS3, ADIPOR2, AGER, and CCL5) and 5 conventional variables (age, sex, ethnicity, diabetes type and duration), and allowing for all possible two-way interactions, predicted nephropathy in our initial population (C-statistic = 0.672) better than a model based on conventional variables only (C = 0.569). In the independent replication dataset, although the C-statistic of the genetic model decreased (0.576), it remained highly associated with diabetic nephropathy (χ² = 17.79, p<0.0001). In the replication dataset, the model based on conventional variables only was not associated with nephropathy (χ² = 3.2673, p = 0.07).

Conclusion

In this proof-of-concept study, we developed and validated a genetic model in the Ashkenazi/Sephardic population predicting nephropathy more effectively than a similarly constructed non-genetic model. Further testing is required to determine if this modeling approach, using an optimally selected panel of genetic markers, can provide clinically useful prediction and if generic models can be developed for use across multiple ethnic groups or if population-specific models are required.

Plasma homocysteine, vitamin B12 and folate levels in age-related macular degeneration

PURPOSE

The purpose of this study was to investigate the association of age-related macular degeneration (AMD) with plasma homocysteine, vitamin B12, and folate levels.

METHODS

Sixty patients diagnosed with AMD at our clinic between March 2004 and September 2004 were assessed in a prospective cross-sectional study. Plasma homocysteine, vitamin B12, and folate levels taken after 8 h of fasting from 30 patients with exudative AMD and 30 patients with dry AMD were compared with the results of 30 age- and sex-matched healthy participants.

RESULTS

Patients with both exudative and dry types of AMD had significantly higher plasma homocysteine levels (mean 14.19+/-3.11 micromol/l; 13.07+/-2.90 micromol/l respectively) compared with the controls (mean 10.79+/-2.56 micromol/l; (p=0.000 and p=0.008 respectively). Homocysteine levels were higher in the exudative AMD group compared with the dry AMD group, but the difference was not statistically significant (p=0.290). Plasma vitamin B12 levels were found to be significantly lower in the exudative AMD group (289.14+/-113.44 pg/l) compared with the controls (436.17+/-204.12 pg/l) and dry AMD group (443.47+/-190.83 pg/l; (p=0.000). Plasma folate levels were comparable among groups (p=0.106).

CONCLUSION

This study suggests an association between elevated plasma homocysteine and AMD regardless of the subtype. Further controlled prospective studies are needed to investigate the possible role of homocysteine in AMD and the effect of vitamin B12 and folate supplementation in this process.

Portal vein thrombosis: what is the role of genetics?

The aetiology of portal vein thrombosis (PVT) in adults is complex. Risk factors include local precipitating factors and acquired and inherited factors, an area in which there has been much recent progress. Although PVT in the absence of cirrhosis may be regarded as a somewhat different disorder to PVT in the presence of cirrhosis, in both cases most studies support a role of the prothrombin G20210A mutation. Some differences in risk factors observed between different studies may relate partly to referral patterns or study design, although individual patients may develop PVT as a result of differing combinations of risk factors. The demonstration of an inherited thrombophilic mutation in a subset of PVT may ultimately inform clinical management regarding the use and duration of anticoagulation therapy, although there is a need for evidence from randomized-controlled clinical trial data.

Avaliação do polimorfismo no gene da metilenotetrahidrofolato redutase e concentração de folato e vitamina B12 em pacientes portadores do HIV-1 em tratamento com anti-retrovirais

Neste trabalho, investigamos concentração da vitamina B12 e folato, considerando-se a influência dos genótipos da metilenotetrahidrofolato redutase, o perfil imunológico e a terapia antiretroviral utilizada na população brasileira portadora do HIV. Um grupo de 86 indivíduos portadores do HIV-1 e 29 doadores de sangue foram recrutados para compor a casuística. Entre os infectados pelo HIV-1, observou-se menor concentração de B12 no grupo com maior número de linfócitos TCD4+. Não encontramos diferença na distribuição genotípica para as mutações MTHFR C677T e A1298C entre infectados e não infectados pelo HIV-1. Indivíduos portadores do HIV, genótipo C677C, apresentaram concentrações menores de B12 em relação ao grupo controle de mesmo genótipo. A terapia antiretroviral não mostrou qualquer influência nos valores de folato e vitamina B12. Estudos adicionais são necessários para reavaliar a prevalência de menores concentrações de B12 e folato e de hiperhomocisteinemia na população portadora do HIV sob a ótica do uso de HAART e da melhoria na sobrevida dos pacientes.

Chronic methionine load-induced hyperhomocysteinemia enhances rat carotid responsiveness for angiotensin II

The purpose of the present study was to investigate the effects of chronic methionine treatment on vascular smooth muscle contractility for angiotensin II (Ang II). Methionine at 0.1, 1 and 2 g/kg body weight was administered daily in the drinking water for 2, 4, 8 and 16 weeks. Rat carotid rings from control and treated animals were placed in an organ chamber containing Krebs solution. Concentration-response curves for Ang II and potassium chloride (KCl) were determined. Methionine-rich diet enhanced the plasmatic homocysteine concentration, and the magnitude of the contractile response to Ang II was increased in carotid rings from treated animals after 8 and 16 weeks. However, the treatment did not alter KCl-induced contraction. In another set of experiments, the rings were incubated with indomethacin and curves for Ang II were obtained. Exposure of the rings to indomethacin inhibited the enhancement in the contractile response to Ang II. The present findings show that chronic methionine treatment enhances homocysteine plasmatic concentration leading to an enhanced Ang-II-induced contraction, which appears to be related to the release of vasoconstrictor prostanoid(s).

Thrombophilia and pregnancy complications

OBJECTIVE

This systematic review examines the strength of the association between thrombophilia and recurrent pregnancy loss and other serious obstetric complications. Study design Electronic databases and manual bibliography searches were used to identify studies evaluating the association between thrombophilia and pregnancy loss, preeclampsia, fetal growth retardation, and placental abruption.

RESULTS

Thrombophilic disorders are associated with an increased risk of fetal loss in the majority of case control and cohort studies. The risk is increased throughout pregnancy, but may be higher in the second and third trimester. The common pathologic finding of placental infarction suggests unexplained fetal loss may result from uteroplacental insufficiency and thrombosis. Thrombophilic disorders are not consistently associated with preeclampsia, fetal growth retardation, or placental abruption. Preliminary data suggest prophylactic anticoagulation may improve outcome in thrombophilic women with unexplained recurrent fetal loss.

CONCLUSION

Women with thrombophilia have an increased risk of pregnancy loss and possibly other serious obstetric complications, although definition of the magnitude of risk will require prospective longitudinal studies. Preliminary data suggesting prophylactic anticoagulation may improve gestational outcome provide a rationale for prospective randomized trials in thrombophilic women with unexplained recurrent fetal loss.

Effects of the interaction between the C677T 5,10-methylenetetrahydrofolate reductase polymorphism and serum B vitamins on homocysteine levels in pregnant women

OBJECTIVE

The purpose of this study was to investigate the effect of the interaction between the C677T mutation in the 5,10-methylenetetrahydrofolate reductase (MTHFR) genotypes and serum levels of B vitamins on serum homocysteine levels in pregnant women.

DESIGN

A cross-sectional study.

SETTING

Ewha Womans University Hospital, Seoul, Korea.

SUBJECTS

A total of 177 normal pregnant women, 24.6+/-1.1 weeks of gestation, in a 6-month period during 2001-2002.

INTERVENTIONS

Serum vitamin B2, vitamin B6, and homocysteine analyses were conducted using high-performance liquid chromatography methods. Serum folate and vitamin B12 concentrations were determined using a radioimmunoassay kit. MTHFR gene mutation was investigated by the polymerase chain reaction of a genomic DNA fragment.

RESULTS

Serum homocysteine was higher in women with the T/T genotype than those with the C/T or C/C genotype of the MTHFR gene (P<0.05). Serum homocysteine was negatively correlated with serum folate in all MTHFR genotypes (P<0.001), and the correlation between the two serum levels was the strongest in the T/T genotype. Serum homocysteine was higher in the subjects with the T/T MTHFR genotype only when the serum folate was below the median level. Explanatory power of B vitamin status as predictors of serum homocysteine levels was more pronounced in the T/T genotypes (68.5%) compared with the C/T (37.9%) or C/C genotypes (20.6%).

CONCLUSIONS

Serum homocysteine levels in pregnant women varied significantly with MTHFR genotype and the serum B vitamin status. Higher serum folate, vitamin B2, and vitamin B12 concentrations may lessen the MTHFR genotypic effect on serum homocysteine levels.

Inherited Thrombophilia: Impact on Human Reproduction

The development of thrombotic disorders is a major threat for young women during pregnancy. It is one of the main causes of pregnancy-related disorders, which may also result in harm for the conceptus. Successful pregnancies require an even balance of coagulation and fibrinolysis, in order to secure stabilization of the basal plate as well as adequate placental perfusion. Thrombophilia is a laboratory definition for pre-disposing factors of thrombosis, which can be inherited or acquired. Many individuals, who carry a thrombotic defect remain asymptomatic, at least until additional boosting factors arise. The documentation of thrombophilic causes of recurrent miscarriage or pregnancy-related disorders is important, because of availability of effective early treatment. There is a rapidly growing awareness on the relationship of genetic factors influencing hemostasis and pregnancy-related disorders. The aim of our review is to summarize this knowledge, focusing on common genetic variations.

Methylenetetrahydrofolate reductase gene C677T mutation is related to the defects in the internal elastic lamina of the artery wall

BACKGROUND

The C677T mutation of the methylenetetrahydrofolate reductase (MTHFR) gene leads to C/C, C/T and T/T genotypes, which affect the plasma homocysteine concentration in humans. In mini-pigs, high serum homocysteine levels are associated with defects in the internal elastic lamina (IEL) of the artery wall, which are apparently related to the migration of smooth muscle cells into the intima during atherogenesis. We studied the association between the MTHFR genotypes and the number of gaps in the IEL in the wall of the five major abdominal arteries.

MATERIALS AND METHODS

The autopsy study included 123 subjects (90 males and 33 females) aged 18-93. For the light microscopy, a 0.5 cm circular segment of the coeliac, the superior mesenteric, the inferior mesenteric and the renal arteries were cut and embedded in paraffin blocks. The circumference of the IEL, the thickness of the intima and the number of the gaps per millimetre in the IEL were measured by MOP 3 image analysis.

RESULTS

The T-allele carriers (C/T and T/T) of the MTHFR gene had significantly less gaps in the IEL than the subjects with the C/C genotype in the superior mesenteric and in the left renal arteries (2.02 +/- 2.25 vs. 2.53 +/- 1.89, P < 0.04 and 0.56 +/- 1.09 vs. 1.82 +/- 2.66, P < 0.02, respectively). The trend was similar for the coeliac and the right renal arteries.

CONCLUSIONS

Our result suggests that MTHFR polymorphism may be involved in the fragmentation of the IEL.

Plasma homocysteine as a risk factor for dementia and Alzheimer's disease

BACKGROUND

In cross-sectional studies, elevated plasma homocysteine levels have been associated with poor cognition and dementia. Studies of newly diagnosed dementia are required in order to establish whether the elevated homocysteine levels precede the onset of dementia or result from dementia-related nutritional and vitamin deficiencies.

METHODS

A total of 1092 subjects without dementia (667 women and 425 men; mean age, 76 years) from the Framingham Study constituted our study sample. We examined the relation of the plasma total homocysteine level measured at base line and that measured eight years earlier to the risk of newly diagnosed dementia on follow-up. We used multivariable proportional-hazards regression to adjust for age, sex, apolipoprotein E genotype, vascular risk factors other than homocysteine, and plasma levels of folate and vitamins B12 and B6.

RESULTS

Over a median follow-up period of eight years, dementia developed in 111 subjects, including 83 given a diagnosis of Alzheimer's disease. The multivariable-adjusted relative risk of dementia was 1.4 (95 percent confidence interval, 1.1 to 1.9) for each increase of 1 SD in the log-transformed homocysteine value either at base line or eight years earlier. The relative risk of Alzheimer's disease was 1.8 (95 percent confidence interval, 1.3 to 2.5) per increase of 1 SD at base line and 1.6 (95 percent confidence interval, 1.2 to 2.1) per increase of 1 SD eight years before base line. With a plasma homocysteine level greater than 14 micromol per liter, the risk of Alzheimer's disease nearly doubled.

CONCLUSIONS

An increased plasma homocysteine level is a strong, independent risk factor for the development of dementia and Alzheimer's disease.