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Abstracts

LE Magazine June 2006
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Homocysteine

Homocysteine, methylenetetrahydrofolate reductase and risk of schizophrenia: a meta-analysis.

Elevated plasma homocysteine concentration has been suggested as a risk factor for schizophrenia, but the results of epidemiological studies have been inconsistent. The most extensively studied genetic variant in the homocysteine metabolism is the 677C>T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, resulting in reduced enzyme activity and, subsequently, in elevated homocysteine. A meta-analysis of eight retrospective studies (812 cases and 2,113 control subjects) was carried out to examine the association between homocysteine and schizophrenia. In addition, a meta-analysis of 10 studies (2,265 cases and 2721 control subjects) on the homozygous (TT) genotype of the MTHFR 677C>T polymorphism was carried out to assess if this association is causal. A 5 micromol/l higher homocysteine level was associated with a 70% (95% confidence interval, CI: 27-129) higher risk of schizophrenia. The TT genotype was associated with a 36% (95% CI: 7-72) higher risk of schizophrenia compared to the CC genotype. The performed meta-analyses showed no evidence of publication bias or excessive influence attributable to any given study. In conclusion, our study provides evidence for an association of homocysteine with schizophrenia. The elevated risk of schizophrenia associated with the homozygous genotype of the MTHFR 677C>T polymorphism provides support for causality between a disturbed homocysteine metabolism and risk of schizophrenia.

Mol Psychiatry. 2006 Feb;11(2):143-9

Homocysteine-Reducing Strategies Improve Symptoms in Chronic Schizophrenic Patients with Hyperhomocysteinemia.

BACKGROUND: An elevated homocysteine level is reported to be a risk factor for several diseases, including Alzheimer's and cerebrovascular disease. Recently, several studies have reported that homocysteine levels are elevated in many schizophrenic patients. Homocysteine levels can be lowered by oral folic acid, B-12, and pyridoxine. METHODS: Forty-two schizophrenic patients with plasma homocysteine levels >15 mumol/L were treated with these vitamins for 3 months and placebo for 3 months in a study with a randomized, double-blind, placebo-controlled, crossover design. RESULTS: Homocysteine levels declined with vitamin therapy compared with placebo in all patients except for one noncompliant subject. Clinical symptoms of schizophrenia as measured by the Positive and Negative Syndrome Scale declined significantly with active treatment compared with placebo. Neuropsychological test results overall, and Wisconsin Card Sort (Categories Completed) test results in particular, were significantly better after vitamin treatment than after placebo. CONCLUSIONS: A subgroup of schizophrenic patients with hyperhomocysteinemia might benefit from the simple addition of B vitamins.

Biol Psychiatry. 2006 Jan 17

Plasma total homocysteine level and bone mineral density: the Hordaland Homocysteine Study.

BACKGROUND: Plasma total homocysteine (tHcy) has been associated with hip fracture but not directly with bone mineral density (BMD). We examined the association of hip BMD with levels of plasma tHcy, folate, and vitamin B12 and the methylenetetrahydrofolate reductase (MTHFR) 677C-->T and 1298A-->C polymorphisms. METHODS: Bone mineral density was measured between 1997 and 2000 in 2,268 men and 3,070 women, aged 47 to 50 and 71 to 75 years, from the Hordaland Homocysteine Study cohort. Low BMD was defined as BMD in the lowest quintile for each sex and age group. Linear, logistic, and generalized additive regression models were used. RESULTS: Plasma levels of tHcy were inversely related to BMD among middle-aged and elderly women (P<.001) but not among men. The multiple adjusted odds ratio for low BMD among subjects with high (>or=15 micromol/L [>or=2.02 mg/L]) compared with low (<9 micromol/L [<1.22 mg/L]) tHcy level was 1.96 (95% confidence interval, 1.40-2.75) for women and was not significant for men. Additional adjustments for plasma folate level or intake of calcium and vitamin D did not substantially alter the results. Plasma folate level was associated with BMD in women only. We observed no association between BMD and vitamin B12 level or the MTHFR polymorphisms. CONCLUSIONS: Elevated tHcy and low folate levels were associated with reduced BMD in women but not in men. These findings suggest that tHcy may be a potential modifiable risk factor for osteoporosis in women.

Arch Intern Med. 2006 Jan 9;166(1):88-94

Evaluation of plasma homocysteine and risk of age-related macular degeneration.

PURPOSE: To assess the relationship between plasma levels of homocysteine and age-related macular degeneration (AMD). DESIGN: Cross-sectional, case-control study. METHODS: Fasting plasma homocysteine levels were measured at two centers in 934 individuals who were participating in an ancillary study of the Age-Related Eye Disease Study. There were 547 cases and 387 control subjects, who were determined by fundus photography. Conditional logistic regression analyses were conducted to assess the association of homocysteine with AMD. RESULTS: Median values of homocysteine were higher among advanced AMD cases (9.51 mmol/l) compared with persons with no AMD (8.81 mmol/l; P = .01). Values of >12 mmol/l vs < or =12 mmol/l were also associated with an increased risk of AMD (P = .023), when controlled for other covariates. CONCLUSION: Results are consistent with a possible small, independent association between higher homocysteine levels and AMD. Homocysteine may be a modifiable risk factor for AMD.

Am J Ophthalmol. 2006 Jan;141(1):201-3

Homocysteine and its determinants in nondialyzed chronic kidney disease patients.

This cross-sectional study aimed to investigate the prevalence of hyperhomocysteinemia, the determinants of plasma total homocysteine concentrations, and the relationship of total homocysteine with nutritional parameters in a sample of patients with chronic kidney disease (CKD) and not yet on dialysis. The study was done with outpatients from the Nephrology Division of the Federal University of Sao Paulo and Oswaldo Ramos Foundation. Sixty-six patients with CKD (70% male; age 58.6+/-15.6 years [mean+/-standard deviation]) with moderate to severe renal impairment (creatinine clearance=29.8+/-14.3 mL/min [0.5+/-0.24 mL/sec]), clinically stable, and older than 18 years were included. A group of 20 healthy subjects from the clinic staff was also studied for reference values for plasma homocysteine, folate, and vitamin B-12 concentration. Fasting blood samples were collected to determine plasma total homocysteine, folate, vitamin B-12, and creatinine. To calculate creatinine clearance, a 24-hour urine collection sample was obtained. The assessment of nutritional status included anthropometric parameters. Pearson correlation, Mann-Whitney test, and multiple linear regression analysis were used for statistical analyses. The main results showed that the concentration of total homocysteine in the patients was significantly increased compared with the healthy subjects (3.4+/-1.7 vs 1.41+/-0.42 mg/L [25.4+/-12.2 vs 10.4+/-3.1 micromol/L]; P<0.001). Plasma folate and plasma vitamin B-12 were in the normal range and did not differ between patients and healthy individuals. A high prevalence of hyperhomocysteinemia (total homocysteine >1.89 mg/L [14 micromol/L]) was found in the patients (89%). Plasma total homocysteine did not correlate with any of the nutritional parameters studied and did not differ between patients in terms of whether they were using or not using folic acid supplementation (3.07+/-1.09 vs 3.55+/-1.78 mg/L [22.7+/-8.1 vs 26.3+/-13.2 micromol/L]; P=0.47), although plasma folate was significantly higher in the supplemented group (12.6+/-3.0 vs 8.0+/-3.6 ng/mL [28.5+/-6.8 nmol/L vs 18.1+/-8.2 nmol/L]; P<0.001). According to the multiple regression analysis, the determinants of total homocysteine were only plasma folate, plasma vitamin B-12, and creatinine clearance (r2=0.20). In conclusion, a high prevalence of hyperhomocysteinemia was found in our sample of nondialyzed patients with CKD. The determinants of total homocysteine levels were plasma folate, plasma vitamin B-12, and creatinine clearance. No association between nutritional parameters and total homocysteine was observed.

J Am Diet Assoc. 2006 Feb;106(2):267-70

Association of plasma homocysteine with coronary artery calcification in different categories of coronary heart disease risk.

OBJECTIVE: To Investigate the association of plasma homocystelne with coronary artery calcification (CAC) in strata based on 10-year risk of coronary heart disease (CHD) in a cohort enriched in persons with hypertension. PARTICIPANTS AND METHODS: Fasting plasma homocystelne was measured by liquid chromatography electrospray tandem mass spectrometry. Coronary artery calcification was measured noninvasively by electron beam computed tomography and CAC score calculated using the method of Agatston et al. The 10-year CHD risk was calculated based on the Framingham risk score. The association of homocysteine with log-transformed CAC score was assessed in the pooled sample and within each risk stratum by linear regression after adjustment for conventional risk factors. RESULTS: In the 1,071 participants studied, homocysteine was associated with CAC quantity (P = .01) after adjustment for CHD risk factors (age, male sex, total and high-density lipoproteln cholesterol, diabetes, history of smoking, body mass Index, and systolic blood pressure), serum creatinine, and statin and hypertension medication use. When the association was assessed in strata based on 10-year CHD risk, homocysteine was significantly (P = .003) associated with CAC quantity in participants at Intermediate 10-year risk of CHD (6%-20%) independent of other risk factors but not in those at lower risk or higher risk. CONCLUSION: Plasma homocysteine is associated with quantity of CAC Independent of CHD risk factors. When studied in categories of 10-year CHD risk, the association was significant in participants at intermediate risk but not in those at low or high risk. Plasma homocysteine levels may have clinical utility as a marker of CHD risk in such individuals.

Mayo Clin Proc. 2006 Feb;81(2):177-82

Serum homocysteine, folate and risk of stroke: Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study.

BACKGROUND: Homocysteine and folate have been suggested to have opposite effects on the risk of stroke, although the results are controversial. DESIGN AND METHODS: The purpose of this study was to assess the effects of serum total homocysteine (tHcy) and serum folate levels on the risk of stroke in a prospective cohort study. The subjects were 1,015 men aged 46-64 years and free of prior stroke, examined in 1991-1993 in the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study. RESULTS: At baseline the mean serum tHcy concentration was 10.9 micromol/l (SD 3.4). During an average follow-up time of 9.6 years, 49 men experienced a stroke, of which 34 were ischaemic. In Cox proportional hazards models, men in the highest tHcy third had a risk factor-adjusted hazard rate ratio (RR) of 2.77 [95% confidence interval (CI): 1.23-6.24] for any stroke and 2.61 (95% CI: 1.02-6.71) for ischaemic stroke, compared with men in the lowest third. The mean baseline serum folate concentration was 10.4 nmol/l (SD 4.1). Men in the highest third of serum folate (>11.2 nmol/l) had an adjusted RR for any stroke of 0.35 (95% CI: 0.14-0.87) and for ischaemic stroke of 0.40 (95% CI: 0.15-1.09), compared with men in the lowest third. CONCLUSION: Elevated serum tHcy is associated with increased risk of all strokes and ischaemic strokes in middle-aged eastern Finnish men free of prior stroke. On the other hand, high serum folate concentration may protect against stroke.

Eur J Cardiovasc Prev Rehabil. 2005 Aug;12(4):369-75

Do maternal folate and homocysteine levels play a role in neurodevelopmental processes that increase risk for schizophrenia?

OBJECTIVE: Evidence from many different lines of research supports the hypothesis that schizophrenia is a disorder of development with etiological factors implicated as early as the second trimester in utero. We suggest that low maternal folate, acting to increase homocysteine levels, may provide a functional link between many of the identified prenatal risk factors and the hypothesized mechanisms whereby neurodevelopmental patterning deviates toward a schizophrenic potential. METHODS: PubMed was searched from the present back to 1963, when elevated homocysteine was identified as a pathogen in homocystinuria as first described by Carson and colleagues (Arch Dis Child 1963;38:425-36). All articles for homocystinuria, homocysteine, folate, and development with schizophrenia were evaluated. RESULTS: The findings from this review support the hypothesis that maternal low folate and high homocysteine levels may provide a potential teratogenic mechanism that increases the risk for developing schizophrenia. CONCLUSION: The potential role of maternal folate deficiency and hyperhomocystinemia in the genesis of schizophrenia would extend the range of their known teratogenic effects. Given the potential for preventive treatment offered by this hypothesis, we believe further investigation into this mechanism is warranted.

Harv Rev Psychiatry. 2005 Jul-Aug;13(4):197-205

Homocysteine as a predictive factor for hip fracture in elderly women with Parkinson's disease.

PURPOSE: Incidence of hip fractures among elderly patients with Parkinson's disease is high. Recent studies have found that levodopa induces hyperhomocysteinemia in Parkinson's disease. Hyperhomocysteinemia is considered to be a risk factor for osteoporotic fractures in elderly men and women. Very high plasma homocysteine levels are a feature of homocystinuria, characterized by the early onset of osteoporosis. To determine the association between plasma homocysteine concentration and the risk of hip fracture in Parkinson's disease patients receiving levodopa, we prospectively studied a cohort of elderly women with Parkinson's disease. METHODS: We studied 199 elderly women with Parkinson's disease receiving levodopa therapy, from whom blood samples had been obtained to measure plasma homocysteine. Age-adjusted incidence rates of hip fractures were calculated for quartiles of plasma homocysteine concentrations. Cox proportional-hazard regression was used to calculate hazard ratios for quartiles of homocysteine values. RESULTS: The mean duration of follow-up was 4.9 years. Hip fractures occurred in 66 patients. The age-adjusted incidence rates per 1,000 person-years for hip fractures, from the lowest to the highest quartile of plasma homocysteine levels, were 1.59 (95% confidence interval [CI], 1.01-2.24), 1.57 (95% CI, 0.98-2.19), 1.21 (95% CI, 0.61-1.72), and 26.98 (95% CI, 16.48-37.24). The risk of hip fractures was greater in the highest quartile than that in the lowest, and the risk was almost 2.4 times higher. CONCLUSION: These findings suggest that the homocysteine concentration is an important risk factor for hip fractures in Parkinson's disease patients receiving levodopa.

Am J Med. 2005 Nov;118(11):1250-5

Homocysteine as a predictive factor for hip fracture in stroke patients.

Risk of hip fractures in stroke patients is higher than that in a reference population. Hyperhomocysteinemia is regarded as a risk factor for ischemic stroke. The high prevalence of osteoporosis among patients with homocystinuria suggests that hyperhomocysteine may also increase the risk of fractures. To determine the association between homocysteine concentration and the risk of hip fractures, we studied a cohort of stroke patients with hemiplegia. Age-adjusted incidence rates of a hip fracture were calculated for quartiles of homocysteine concentrations. Cox proportional-hazard regression was used to calculate hazard ratios for quartiles of homocysteine levels. The initial enrolment of 433 hemiplegic patients with ischemic stroke, older than 65 years old, were followed for up to 10 years. The mean plasma homocysteine concentration at the enrolment was 14.1 +/- 5.2 micromol/L. There were 33 hip fractures among men and 46 among women during the mean follow-up period of 9.0 years. The age-adjusted incidence rates per 1,000 person-years for hip fractures increased almost linearly from 2.89 in the lowest to 27.87 in the highest quartiles of homocysteine levels. We conclude that hyperhomocysteinemia is one of the risk factors for hip fractures in stroke patients.

Bone. 2005 Apr;36(4):721-6

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