Elevated serum homocysteine as a predictor for vitamin B12 or folate deficiency

Possible Modulation of Vascular Function Measures in Rheumatoid Arthritis by Homocysteine

The effect of homocysteine on cardiovascular diseases is still equivocal, especially in rheumatoid arthritis patients. In this investigation, the association between homocysteine with blood flow and vascular resistance in rheumatoid arthritis was examined. Serum levels of homocysteine were determined in thirty-one rheumatoid arthritis patients and nineteen apparently healthy subjects using ELISA. Additionally, strain-gauge plethysmography was used to determine both forearm blood flow and vascular function at rest and after occlusion. Forearm occlusion blood flow (patients: 21.9 ± 6.55 versus control: 25.5 ± 6.10ml/100mL/min) was lower (p < 0.05) while occlusion vascular resistance (patients: 4.77 ± 2.08 versus controls 3.05 ± 0.96U) was greater (p < 0.01) in rheumatoid arthritis than in the controls. Level of serum homocysteine was similar (p = 0.803) in rheumatoid arthritis group and healthy group. In addition, level of serum homocysteine was correlated with resting blood flow (r = −0.41; p < 0.02) and resting vascular resistance (r = 0.31, p < 0.05) in the patients group. The study confirms altered vascular function in rheumatoid arthritis. Uniquely, the results show that homocysteine was related to resting, but not postischemia, vascular measures. These relationships indicate that homocysteine might impact the vasculature in rheumatoid arthritis.

Glyphosate, pathways to modern diseases III: Manganese, neurological diseases, and associated pathologies

Manganese (Mn) is an often overlooked but important nutrient, required in small amounts for multiple essential functions in the body. A recent study on cows fed genetically modified Roundup(®)-Ready feed revealed a severe depletion of serum Mn. Glyphosate, the active ingredient in Roundup(®), has also been shown to severely deplete Mn levels in plants. Here, we investigate the impact of Mn on physiology, and its association with gut dysbiosis as well as neuropathologies such as autism, Alzheimer's disease (AD), depression, anxiety syndrome, Parkinson's disease (PD), and prion diseases. Glutamate overexpression in the brain in association with autism, AD, and other neurological diseases can be explained by Mn deficiency. Mn superoxide dismutase protects mitochondria from oxidative damage, and mitochondrial dysfunction is a key feature of autism and Alzheimer's. Chondroitin sulfate synthesis depends on Mn, and its deficiency leads to osteoporosis and osteomalacia. Lactobacillus, depleted in autism, depend critically on Mn for antioxidant protection. Lactobacillus probiotics can treat anxiety, which is a comorbidity of autism and chronic fatigue syndrome. Reduced gut Lactobacillus leads to overgrowth of the pathogen, Salmonella, which is resistant to glyphosate toxicity, and Mn plays a role here as well. Sperm motility depends on Mn, and this may partially explain increased rates of infertility and birth defects. We further reason that, under conditions of adequate Mn in the diet, glyphosate, through its disruption of bile acid homeostasis, ironically promotes toxic accumulation of Mn in the brainstem, leading to conditions such as PD and prion diseases.

Red blood cell metabolism under prolonged anaerobic storage

Oxygen dependent modulation of red blood cell metabolism is a long investigated issue. However, the recent introduction of novel mass spectrometry-based approaches lends itself to implement our understanding of the effects of red blood cell prolonged exposure to anaerobiosis. Indeed, most of the studies conducted so far have addressed the short term issue, while the limited body of literature covering a 42 days storage period only takes into account a handful of metabolic parameters (ATP, DPG, glucose, glyceraldehyde 3-phosphate, and lactate). We hereby performed a mass spectrometry-based untargeted metabolomics analysis in order to highlight metabolic species in erythrocyte concentrates stored anaerobically in SAGM additive solutions for up to 42 days, by testing cells on a weekly basis. We could confirm previous evidence about long term anaerobiosis promoting glycolytic metabolism in RBCs and prolonging the conservation of high energy phosphate reservoirs and purine homeostasis. In parallel, we evidenced that, in contrast to aerobic storage, anaerobiosis impairs erythrocyte capacity to cope with oxidative stress by blocking metabolic diversion towards the pentose phosphate pathway, which negatively affects glutathione homeostasis. Therefore, although oxidative stress was less sustained than in aerobically stored counterparts, oxidative stress markers still accumulate over anaerobic storage progression.

Validation of a composite scoring scheme in the diagnosis of folate deficiency in a pediatric and adolescent dialysis cohort

BACKGROUND

Laboratory indices are often poorly diagnostic of folate deficiency (FD). Compared with iron depletion in hemodialysis (HD) populations, the impact of FD is less appreciated. The composite scoring of hematologic indices of FD may facilitate a prompt and accurate diagnosis, and enhance operational research on folic acid therapy.

OBJECTIVE

Our objectives were to (1) validate composite scores of folate diagnostic indices, and (2) determine the reliability index of the diagnostic tool.

METHODS

A cohort of 30 subjects, with a mean age of 16 (SD +/- 3.2 years), on HD and erythropoietin (EPO) for a minimum of 3 months was studied. After a baseline hematologic assessment, routine folates were administered for 6 months. Composite FD scores (FDS) of baseline mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), random distribution width (RDW), and hemoglobin were determined. Validation and reliability statistics were then analyzed, using the quantitative change in red blood cell folate/plasma homocysteine, or EPO requirement after 6 months of folate use, as diagnostic criteria.

RESULTS

The mean FDS for FD and non-FD subsets were 3.0 +/- 1.3 and 1.4 +/- 0.9, respectively (analysis of variance; P = .0001). The correlation coefficient, r(2), between FD total and FDS was 0.61 (P = .001), and the coefficient between 2 (weekly) values of RDW, MCV, MCH, and MCHC was >0.84 (P = .0001). Scoring tools derived from the first (P = .002) and second (P = .01) halves of the laboratory indices remained discriminatory for the FD and non-FD groups. Baseline serum folate is poorly specific for FD, whereas FD score >or=3 had sensitivity, specificity, and positive and negative predictive values close to 90%.

CONCLUSIONS

Composite scoring of erythrocyte indices was predictive of the FD diagnosis, as defined by the quantitative response of red blood cell folate, homocysteine, and EPO dose to folate therapeutic intervention. The diagnostic items yielded a high reliability coefficient. The FDS scheme is a potential tool for the diagnosis and surveillance of FD, particularly in at-risk populations (e.g., dialysis subjects).

The prevalence of folic acid deficiency among adolescent girls living in Edirne, Turkey

PURPOSE

A high incidence of iron-deficiency is a common observation among adolescent girls, whereas only limited data are available regarding the folic acid status of this group. This study was designed to determine the prevalence of biochemical folic acid deficiency in a group of Turkish adolescent girls.

METHODS

We surveyed the serum folic acid, complete blood count, and dietary folic acid intake of Turkish adolescent girls after using three-day self-reported food intakes in urban and rural areas of Edirne, Turkey.

RESULTS

A sample population was composed of 704 adolescent girls; their serum folic acid levels were found to be adequate for 37.6% (> or = 6 ng/mL), marginal for 46% (3 to 5.9 ng/mL), and at deficient levels for 16.3% (< 3 ng/mL). Folic acid deficiencies were found in 20.1% (36 of 179) and 14.7 % (61 of 416) of adolescent girls from rural and urban areas, respectively. Self-reported three-day folic acid intakes were correlated with the corresponding blood values for this nutrient. In the logistic regression analysis, three factors emerged as significant independent predictors of folic acid deficiency: low income (odds ratio [OR]: 2.4, 95% confidence interval [CI]: 1.3-4.2, p < .001), low vitamin C (OR: 1.9, 95% CI: 1.1-3.5, p < .05), and folic acid intake (OR: 4.8, 95% CI: 2.8-8.1, p < .001).

CONCLUSION

Data from the present study may indicate that serum folic acid is low in a group of Turkish adolescent girls. These low values appear to be associated with low income, and low dietary intakes of folic acid and vitamin C.

Homocysteine as a neurotoxin in chronic alcoholism

There is evidence from in vitro and in vivo studies that homocysteine induces neuronal damage and cell loss by both excitotoxicity and different apoptotic processes. Clinical evidence suggest a strong relationship between higher plasma homocysteine levels and brain atrophy in healthy elderly subjects as well as in elderly at risk of and with Alzheimer's disease. Chronic alcoholism leads to elevated plasma homocysteine levels, as shown by clinical investigations and animal experiments. In addition, an association between brain atrophy and increased levels of homocysteine in chronic alcoholism was shown. This may have important implications for the pathogenesis of alcoholism-associated brain atrophy. Furthermore, taking into account that high plasma homocysteine levels are helpful in the prediction of alcohol withdrawal seizures, early anticonvulsive therapy could prevent this severe complication. Homocysteine plays a role in a shared biochemical cascade involving overstimulation of N-methyl-D-aspartate (NMDA) receptors, oxidative stress, activation of caspases, DNA damage, endoplasmic reticulum and mitochondrial dysfunction. These mechanisms are believed to be important in the pathogenesis of both excitotoxicity and apoptotic neurotoxicity. Prospective intervention studies may show whether the incidence of complications of alcohol withdrawal or alcoholism-associated disorders can be reduced by therapeutic measures with early lowering of elevated homocysteine levels (e.g. folate administration). The most important pathophysiological and pathobiochemical features of glutamatergic neurotransmission and of ethanol-induced hyperhomocysteinaemia are reviewed in relation to their excitotoxic and apoptotic potential.

Anemia at the end of life: prevalence, significance, and causes in patients receiving palliative care

While data exist on the prevalence and causes of anemia in defined groups of the elderly, information on palliative care patients is limited. Compared to actively treated oncology patients, for whom anemia treatment has demonstrated improved quality of life and symptom alleviation, studies of treatment outcomes in palliative care patients are limited. Knowledge of the extent and causes of anemia in palliative care patients is needed, as correction of anemia in these patients could potentially improve their physical, emotional, and cognitive functioning. In the present study, clinical data and blood test results of 105 patients meeting specific eligibility criteria were examined to estimate the prevalence of anemia and investigate its causes. Ninety-five (90.5%) patients had advanced cancer. Based on World Health Organization criteria, anemia was found in 77% of men (Hb <130 g/l) and 68.2% of women (Hb <120 g/l). The diagnosis was anemia of chronic disease in 76.7% of women and 46.8% of men. Patients with prostate cancer had a significantly lower mean Hb level (P=0.007) and more evidence of bone metastases (P=0.0007) than those with other cancers. Neutrophil hypersegmentation, suggesting occult folate deficiency, was present in 28.6% of patients, being more common in those with major weight loss (58.3%) than those with moderate (37%) or mild/no weight loss (26%) (P=0.019). The findings suggest that anemia is highly prevalent in the palliative care setting. Although anemia of chronic disease is most common, occult folate deficiency may be more prevalent than previously suspected. The findings suggest that a low serum folate level is an insensitive marker of occult folate deficiency. A randomized controlled trial of folic acid treatment is proposed.

Effects of prostaglandin E1, melatonin, and oxytetracycline on lipid peroxidation, antioxidant defense system, paraoxonase (PON1) activities, and homocysteine levels in an animal model of spinal cord injury

STUDY DESIGN

Investigation of the effects of prostaglandin E1, melatonin, and oxytetracycline on lipid peroxidation, antioxidant and paraoxonase activities, and homocysteine levels in an experimental model of spinal cord injury.

OBJECTIVES

To determine the antioxidant efficacy of prostaglandin E1, melatonin, and oxytetracycline and whether paraoxonase and homocysteine can be used as monitoring parameters in the acute oxidative stress of spinal cord injury.

SUMMARY OF BACKGROUND DATA

Melatonin has been found useful in spinal cord injury in previous studies. No study exists investigating the effects of melatonin, prostaglandin E1, and oxytetracycline as well as the response type of paraoxonase enzyme and homocysteine levels in the acute oxidative stress of spinal cord injury.

METHODS

Sixty-three male albino Wistar rats were anesthetized with 400 mg/kg chloral hydrate and divided into 5 groups. The G1 (n = 7) control group provided the baseline levels. G2-G5 underwent T3-T6 total laminectomies and spinal cord injuries by clip compression at the T4-T5 levels. Medications were applied to G3-G5 right after clip compression. Hence, G2 constituted laminectomy + injury, G3 laminectomy + injury + prostaglandin E1; G4 laminectomy + injury + melatonin, and G5 laminectomy + injury + oxytetracycline groups. Animals were decapitated either the first or fourth hour after injury. Spinal cord tissue and blood malonyldialdehyde and plasma homocysteine levels, plasma glutathione peroxidase, superoxide dismutase, paraoxonase activities were assayed. The SPSS 9.0 program was used for statistical analysis and graphics. Intergroup comparisons were made by Bonferroni corrected Mann Whitney U test (P < 0.025) and intragroups comparisons by Wilcoxon Rank test (P < 0.03).

RESULTS

In injury groups, plasma homocysteine levels decreased and paraoxonase activities increased as erythrocyte superoxide dismutase levels and plasma glutathione peroxidase activities decreased in parallel to increases of tissue and blood malonyldialdehyde levels. These alterations were relatively suppressed by prostaglandin E1, melatonin, and oxytetracycline administrations in varying degrees. Melatonin was the most powerful agent, particularly at the fourth hour. Oxytetracycline was also effective, both at the first and fourth hour. Prostaglandin E1 was effective in comparison to injury group, but not as much as melatonin and oxytetracycline.

CONCLUSIONS

Melatonin and oxytetracycline are effective in preventing lipid peroxidation in spinal cord injury. Paraoxonase and homocysteine can be used in monitoring the antioxidant defense system as well as superoxide dismutase and plasma glutathione peroxidase, both in injury and medicated groups.

Differential relations between cognition and 15N isotopic content of hair in elderly people with dementia and controls

BACKGROUND

Previous researchers have suggested that a vegetarian diet or one rich in fish may protect against Alzheimer's disease (AD). However, assessing diet is difficult in AD patients. (15)N:(14)N isotopic ratios (delta(15)N) of body proteins can estimate long-term dietary habits in a way that does not depend on memory. delta(15)N is high in people who eat a lot of fish and low in vegetarians.

METHODS

To choose between the vegetarian and fish hypotheses of AD, we compared dietary questionnaire reports and delta(15)N of hair samples from AD patients and controls.

RESULTS

Patients' cognitive scores related directly to reported frequency of eating fish and to hair delta(15)N(AIR), but inversely to reported frequency of eating beans. Homocysteine levels related inversely to hair delta(15)N(AIR) in controls, but not in patients. Dietary questionnaire reports accounted for slightly more variance in delta(15)N(AIR) in patients than controls. Therefore, our questionnaire assessed dietary habits as reliably for individuals with AD as for cognitively unimpaired controls.

CONCLUSIONS

A diet rich in fish may ameliorate AD, possibly by lowering homocysteine, but more vegetarian diets do not. In fact, eating beans correlated with worse cognition in AD patients. Further studies should test if restricting the intake of beans slows the progression of AD.

Effects of pinealectomy on the levels and the circadian rhythm of plasma homocysteine in rats

Hyperhomocysteinemia is an independent cardiovascular risk factor. There are several factors including aging that contribute to the development of hyperhomocysteinemia. Nevertheless, the exact mechanisms causing this condition are still debated. We hypothesize that the age-related decrease in melatonin levels may be consequential in hyperhomocysteinemia. Recently, we found that plasma homocysteine (Hcy) levels are increased in pinealectomized (PINX) rats and melatonin reverses this increase. The aim of the present study was to determine if there is a circadian rhythm of plasma Hcy in rats and to examine the effect of pinealectomy on this cycle. Plasma Hcy levels demonstrated a 24-hr rhythm with a peak at 02:00 hr and a nadir at 14:00 hr in both control and PINX rats. Pinealectomy did not change the phase of the rhythm or the nocturnal elevation of plasma Hcy, but it did significantly increase mean plasma Hcy levels compared with those in controls and in rats that were sham pinealectomized (sPINX) (P < 0.05). Melatonin decreases plasma Hcy levels while causing an increase in total glutathione (tGSH). In conclusion, we speculate that decreasing levels of melatonin during aging lead to hyperhomocysteinemia and a decrease in tGSH and the latter may be one of the factors causing hyperhomocysteinemia in the elderly population.

Association between erythrocyte mean corpuscular volume and peripheral arterial disease in male subjects: a case control study

Elevated serum total homocysteine, an established risk factor for peripheral arterial disease, is influenced by the vitamin B12 and folate status. Since these vitamins are inversely correlated with erythrocyte mean corpuscular volume, an investigation of whether mean corpuscular volume is higher in patients with symptomatic peripheral arterial disease than in healthy subjects was performed. Furthermore, a determination of predictors of increased mean corpuscular volume levels in this population free of symptomatic coronary artery disease, cerebrovascular disease, and diabetes mellitus was carried out. From 469 consecutive patients with symptomatic peripheral arterial disease, 100 fulfilled study inclusion criteria. Peripheral arterial disease was confirmed by angiography. One hundred age-matched subjects without peripheral arterial disease as verified by ankle-brachial index measurements >0.9 served as control subjects. Patients with PAD displayed a significantly higher mean corpuscular volume level (94.5 fl) than control subjects (90.9 fl, p<0.001). Logistic regression analysis showed that current smoking status (p<0.001) and mean corpuscular volume (p=0.009), but not total homocysteine or lipid parameters discriminated case control status. In addition, logistic regression analysis revealed a relationship of mean corpuscular volume with smoking (p=0.001), gamma-glutamyltransferase (p<0.001), and total homocysteine (p=0.012). This model predicted mean corpuscular volume values with an accuracy of 83%. Elevated mean corpuscular volume is a predictor of symptomatic peripheral arterial disease in the sample studied. A deficiency of folate and/or vitamin B12 may be responsible for this observation, as indicated by the correlation of mean corpuscular volume with total homocysteine. Due to the additional association of mean corpuscular volume with smoking and gamma-glutamyltransferase, an unhealthy lifestyle with low vitamin intake may cause elevated mean corpuscular volume values in patients with PAD.

Homocysteine and alcoholism

Chronic alcohol consumption can induce alterations in the function and morphology of most if not all brain systems and structures. However, the exact mechanism of brain damage in alcoholics remains unknown. Partial recovery of brain function with abstinence suggests that a proportion of the deficits must be functional in origin (i.e. plastic changes of nerve cells) while neuronal loss from selected brain regions indicates permanent and irreversible damage. There is growing evidence that chronic alcoholism is associated with a derangement in the sulfur amino acid metabolism. Recently, it has been shown that excitatory amino acid (EAA) neurotransmitters and homocysteine levels are elevated in patients who underwent withdrawal from alcohol. Furthermore, it has been found that homocysteine induces neuronal cell damage by stimulating NMDA receptors as well as by producing free radicals. Homocysteine neurotoxicity via overstimulation of N-methyl-D-aspartate receptors may contribute to the pathogenesis of both brain shrinkage and withdrawal seizures linked to alcoholism.

Homocysteine: cholesterol of the 90s?

Homocysteine is a sulfur-containing amino acid generated through the demethylation of methionine. It is largely catabolized by trans-sulfuration to cysteine but it may also be remethylated to methionine. Dubbed 'the cholesterol of the 90s' by the lay press, homocysteine is thought to be thrombophilic and to damage the vascular endothelium. Total plasma homocysteine (tHcy) is now established as a clinical risk factor for coronary artery disease, as well as other arterial and venous occlusive disease in adult populations. Regulation of homocysteine is dependent on nutrient intake, especially folate, vitamins B6 and B12. It is also controlled by common genetic variations (polymorphisms) in how vitamins are utilized as cofactors in the reactions controlling homocysteine metabolism. Moreover, concentrations are age- and sex-dependent and are altered by renal function, hormonal status, drug intake and a variety of other common clinical factors. Considerable care must be taken in assaying tHcy. Plasma should be separated shortly after collection, to avoid artifactual increases due to synthesis by blood cells in vitro. Reference methods have not been validated and criteria for establishing reference ranges should take into account the variable prevalence of physiological hyperhomocysteinemia. Determination of tHcy should probably be limited to centres with relevant expertise and ability to maintain the high degree of precision required for reliable interpretation. Molecular testing for the genetic polymorphisms is still in the research phase but the ease and reliability of molecular diagnosis will speed its introduction into clinical laboratory practice--particularly in relation to diagnosis of thrombophilic disorders. Clinical research initiatives are being driven by the benefit that should be achieved by correction with vitamin supplements, particularly folate and B vitamins, but it must be recognized that prospective controlled studies to validate clinical benefit are only now being initiated. At the moment, it is safe to say that hyperhomocysteinemia is one of the few prevalent biochemical risk factors for thromboembolic disease that might be corrected by vitamin supplements. Such a possibility lies behind the growing momentum to recommend increased supplements of folate and B vitamins to at-risk population and patient groups today.

Homocysteine

Homocysteine is a sulfur-containing amino acid generated through the demethylation of methionine. It is largely catabolized by trans-sulfuration to cysteine, but it may also be remethylated to methionine. Regulation of homocysteine is dependent on nutrient intake, especially folate, vitamins B6 and B12. It is also controlled by individual genetic differences in how vitamins are utilized as cofactors in the reactions controlling homocysteine metabolism. In excess quantities, homocysteine is thought to be thrombophilic and to damage the vascular endothelium. Total plasma homocysteine (tHcy) is now established as a clinical risk factor for coronary artery disease, as well as other arterial and venous occlusive disease in adult populations. These effects are probably related to its role as a teratogen in the pathogenesis of neural tube defects--genetic variants causing hyperhomocysteinemia are associated with both neural tube defects in susceptible pregnancies and with risks for vaso-occlusive disease in later years. Considerable care must be taken in assaying tHcy. Plasma should be separated shortly after collection to avoid artifactual increases due to synthesis by blood cells in vitro. tHcy concentrations must be interpreted in light of the fact that serum albumin, urate, creatinine, and vitamin concentrations may be important analytical covariates. Moreover, concentrations are age- and sex-dependent and are altered by renal function, hormonal status, drug intake, and a variety of other common clinical factors. Why then is homocysteine now of such great clinical and scientific interest? If the homocysteine moiety itself is important in the pathogenesis of vaso-occlusive disease, then simple treatment of hyperhomocysteinemia with vitamins should lead to a significant reduction in disease risk. Such a possibility lies behind the growing momentum to recommend increased supplements of folate and B vitamins to at-risk populations and patient groups today.

Increased plasma levels of homocysteine and other thiol compounds in rheumatoid arthritis women

OBJECTIVES

Since moderate hyperhomocysteinemia is an independent risk factor for vascular disease and physiological thiol compounds mediate Cu2+- and Fe3+-dependent low-density lipoprotein (LDL) oxidation, we have studied the total plasma concentrations of thiol compounds including methionine as precursor of homocysteine in rheumatoid arthritis patients, in which the high mortality found is associated with cardiovascular disease.

DESIGN AND METHODS

Thirty-eight women with rheumatoid arthritis and 25 age-matched control women were studied. Plasma was used to measure thiol compounds and amino acids by HPLC.

RESULTS

Rheumatoid arthritis patients showed significantly higher levels than healthy controls of total plasma homocysteine (17.3 +/- 7.8 vs. 7.6 +/- 1.9; p <0.001), cysteine (293 +/- 61 vs. 201 +/- 45; p < 0.001), cysteinglycine (32.7 +/- 8.3 vs. 22.3 +/- 4.7; p < 0.001) and methionine (25 +/- 9 vs. 18 +/- 3; p < 0.01), whereas total glutathione levels were not increased (4.7 +/- 2.0 vs. 4.1 +/- 1.6).

CONCLUSIONS

The increased levels of thiol compounds found in rheumatoid. arthritis patients may be implicated in the increased incidence of cardiovascular disease found in these patients by means of the toxic effect of homocysteine on endothelium and the increased susceptibility of LDL to oxidation by increased plasma amounts of thiol compounds such as cysteine.

Review article: the diagnosis and treatment of haematinic deficiency in gastrointestinal disease

Deficiency of any of the vitamins and minerals essential for normal erythropoiesis (haematinics), including iron, copper, cobalt, vitamins A, B12, B6, C, E, folic acid, riboflavin and nicotinic acid, may be associated with defective erythropoiesis and anaemia. Iron, vitamin B12 and folate are the haematinics for which deficiency states manifest most often clinically and are the focus of this review. The normal absorption of these haematinics and gastrointestinal causes of their deficiency are described. Investigations, including the use of homocysteine metabolite levels and new techniques such as serum transferrin receptor assays, and treatment of haematinic deficiency are discussed in detail.

Clinical chemistry and molecular biology of homocysteine metabolism: an update

OBJECTIVE

To summarize recent developments in our understanding of homocysteine as a clinically relevant and independent predictor of vaso-occlusive disease (including atherosclerosis and thromboembolism), as an early indicator of folate or cobalamin deficiency, and as a key factor in the pathogenesis of neural tube defects.

METHODS AND RESULTS

To determine total homocysteine, plasma or serum must be separated shortly after collection and subjected to chemical reduction. Reference intervals should take into account the prevalence of physiological hyperhomocystinemia. A common cause of hyperhomocystinemia is a genetic predisposition caused by a polymorphic substitution in the methylenetetrahydrofolate reductase (MTHFR) gene, which can be readily detected by molecular means.

CONCLUSION

Determination of homocysteine and MTHFR testing should be limited to laboratories with relevant expertise and ability to maintain the high degree of precision required for reliable interpretation. Assays should be offered in selected cases with clinical features or laboratory findings suggestive of hyperhomocystinemia, since treatment is simple and may be highly effective.

The significance of subnormal serum vitamin B12 concentration in older people: a case control study

OBJECTIVES

To determine the clinical significance of subnormal serum vitamin B12 concentration in older people by comparing the hematological, neurological, and biochemical findings in patients with subnormal serum B12 with a control group with normal B12 levels.

DESIGN

Clinical and laboratory assessment of hospital patients selected to represent a wide range of serum B12 levels.

SETTING

Patients in the medical wards of two hospitals, one a general hospital and the other a geriatric hospital.

PARTICIPANTS

Ninety-four older patients, 43 with subnormal (< 150 pmol/L) and 51 with normal serum B12 concentrations.

MEASUREMENTS

Mini-Mental State Examination, neurological score, full blood examination, mean neutrophil lobe count; serum B12, holotranscobalamin II, total homocysteine, folate, creatinine and gastrin red folate; parietal cell antibodies, intrinsic factor antibodies.

RESULTS

Of all the measurements, only mean neutrophil lobe count and mean serum total homocysteine were significantly different in the low serum B12 compared with the control group. There was a significant correlation between serum B12 and homocysteine levels. Eighty-eight percent of patients in the test group compared with 76% in the control group showed at least one of the following; elevated serum total homocysteine, neutrophil hypersegmentation, or elevated MCV. This overlap was much reduced when patients with borderline values for serum B12 (150-250 pmol/L) were included in the low B12 group. Most of the older subjects had little or no B12 on transcobalamin II, irrespective of the serum B12 level.

CONCLUSION

Almost 90% of older patients with serum B12 < 150 pmol/L show evidence of tissue vitamin B12 deficiency. Deficiency becomes manifest in older patients at relatively higher concentrations of serum B12 than in younger subjects, possibly because of lower levels of holotranscobalamin II in the older patients.

Folate and homocysteine status and haemolysis in patients treated with sulphasalazine for arthritis

In an attempt to estimate the frequency of folate deficiency and haemolysis in a group of 25 outpatients with arthritis treated with sulphasalazine (SASP), haematological measurements, including plasma total homocysteine (tHcy) which is a sensitive marker of folate deficiency, serum folate (S-folate), erythrocyte (RBC) folate, S-cobalamin and routine indices of haemolysis were performed. No patient had been taking folate-containing vitamins for at least 8 weeks prior to the study. Compared to a group of 72 healthy hospital staff, the median plasma tHcy was significantly higher in the patient group (8.8 mumol 1(-1) vs. 6.8 mumol 1(-1); p = 0.003). Five patients (20%) had plasma tHcy levels that exceeded the upper normal limit of plasma tHcy (median+2 SD of the reference group). Median S-folate was significantly lower in the patient group (6.0 nmol 1(-1) vs. 8.5 nmol 1(-1); p < 0.001), and 11 (44%) patients had depressed S-folate. Only three (12%) patients had RBC folate values below the reference interval. There was no difference in the levels of RBC folate between the two groups. A comparison of S-cobalamin levels in the two groups disclosed a significantly lower level in the patient group. However, no patient had cobalamin deficiency as assessed by S-cobalamin and S-methylmalonate measurements. Thus, it is unlikely that any patient had increased plasma tHcy due to cobalamin deficiency. Of 24 patients having a HbA1c measurement performed, 12 (50%) had decreased levels indicating chronic haemolysis. Only seven (28%) patients had reticulocytosis. HbA1c was positively correlated to haptoglobin levels (r = 0.77; p < 0.001) and negatively correlated to the percentage of reticulocytes (r = -0.50; p = 0.02). The percentage of reticulocytes was negatively correlated to haptoglobin levels (r = -0.42; p = 0.04). The chronic haemolysis of the patients' blood due to SASP might explain the similar RBC folate values in the two groups because of a relatively higher folate content of young erythrocytes. In conclusion, our results support previous findings of folate deficiency and haemolysis occurring in a considerable fraction of patients receiving treatment with SASP. Measurements of plasma tHcy suggest that a substantial number of patients may have folate deficiency at the tissue level.

Metabolite assays in cobalamin and folate deficiency

Cbl and folate are both necessary for the metabolism of HCYS, whereas only Cbl is required for MMA metabolism. During the past decade, analytical methods have been developed that are sensitive enough to detect low levels of MMA and HCYS normally present in the plasma. These methods are sufficiently precise to be used in the clinical laboratory and measurements of the serum levels of the metabolites provide sensitive and specific techniques for the identification of Cbl and folate deficiencies. These techniques constitute an important addition to the battery of diagnostic tests that are available for detecting the vitamin deficiencies and for distinguishing each from the other. By virtue of the role of Cbl and folate in the metabolic pathways that involve MMA and HCYS, levels of both metabolites rise in Cbl deficiency, but only HCYS rises in folate deficiency. During the development of Cbl or folate deficiencies, accumulation of these metabolites in the plasma signals the existence of a condition of biochemical vitamin deficiency of sufficient degree to cause impairment in the metabolic pathways which are dependent on these vitamins. Circulating metabolite levels appear to accurately reflect the nutritional status of the vitamins and a rise in serum metabolite levels is therefore one of the earliest and most reliable indicators of developing Cbl and folate deficiencies. Elevations of serum metabolites above the reference range not only precede a fall in the serum vitamin levels but also show a more consistent correlation with objective evidence of vitamin deficiency than do low blood vitamin levels. The advent of serum metabolite measurements has also made it possible to identify subtle or atypical forms of vitamin deficiency that may be associated with unusual or previously undiscovered disease manifestations. Thus, in patients who display only neurological manifestations of disease, underlying Cbl deficiency may be revealed by the finding of raised serum or urine levels of MMA. Similarly, unsuspected folate deficiency may be disclosed by the finding of a raised serum HCYS. This may have important implications with respect to disease risk, since there is mounting evidence that sub-optimal folate nutritional status may be associated with increased risks of vascular disease, neoplasia and birth defects. Finally, the measurement of serum levels of MMA, HCYS and other metabolites that accumulate in Cbl and folate deficiencies may provide important new insights into the mechanism whereby these vitamin deficiencies lead to different patterns and manifestations of disease.