[Uncertain effects of folic acid on disorders other than neural-tube defects].
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Animals↗
Biomedical subjects
Y M Smulders
Publications and source records attributed to Y M Smulders.
[The cost per year of life gained: trends and internal contradictions].
Recently, a Dutch advisory committee to the Ministry of Health presented a report proposing criteria for health insurance coverage. A central role has been given to the criterion of cost per quality-adjusted life year (QALY) associated with medical interventions. The proposal is to limit the health-insurance coverage of such costs to 80,000 euro per QALY gained. Previously, 20,000 euro was generally considered a reasonable critical level for QALY-cost, whether for preventive or for curative interventions. Although a higher cut-off-level is now proposed by the advisory committee, recent cardiovascular prevention guidelines propose treatment criteria that are associated with much lower QALY costs, sometimes as low as 1,000 euro. With respect to financial considerations, the central role of QALY costs has been replaced in these prevention guidelines by national health budget implications. For individual patient care, these apparently opposing trends in the role and financial appreciation of QALYs have complex repercussions.
Cost-Benefit Analysis↗
[Health effects of fish oil and fish oil supplements: consumption advice sustained].
Omega-3 fatty acids are thought to have beneficial effects on atherosclerosis. Recently, the results ofa systematic review on the health effects of omega-3 fatty acids were published. The risk of cardiovascular death in subjects randomised to taking omega-3 fats was not significantly decreased: relative risk = 0.87 (95% CI: 0.73-1.03). In a 2004 Cochrane review, the same authors concluded that there was a significant beneficial effect on total mortality, combined cardiovascular endpoints and cancer. Inclusion of the recent 'Diet and reinfarction trial' (DART-2-trial) had a decisive negative effect on the results of the recent meta-analysis. Excluding this study resulted in a relative risk of cardiovascular death of 0.83 (95% CI: 0.75-0.91). Since the DART-2 study had methodological shortcomings, it still appears that recommending sufficient intake of omega-3 fatty acids is justifiable, preferably by eating fish but ifnecessary by using fish oil supplements, especially for patients at high risk of cardiovascular disease.
Cardiovascular Diseases↗
Cellular folate vitamer distribution during and after correction of vitamin B12 deficiency: a case for the methylfolate trap.
Haematological sequellae of vitamin B12 deficiency are attributed to disturbed DNA synthesis, but vitamin B12 itself plays no role in DNA biosynthesis. A proposed explanation for this is the methylfolate trap hypothesis. This hypothesis states that B12 deficiency impairs overall folate metabolism because 5-methyltetrahydrofolate (5MTHF) becomes metabolically trapped. This trap results from the fact that 5MTHF can neither be metabolised via the methionine synthase pathway, nor can it be reconverted to its precursor, methylenetetrahydrofolate. Other manifestations of the methylfolate trap include cellular folate loss because of shorter 5MTHF polyglutamate chains and global hypomethylation. The methylfolate trap has never been demonstrated in humans. We describe a patient with B12 deficiency who was homozygous for the common methylenetetrahydrofolate reductase (MTHFR) C677T mutation. We analysed red blood cell (RBC) folate vitamers and global DNA methylation by liquid chromatography (LC) in combination with tandem mass spectrometry, and 5MTHF polyglutamate length by LC-electrochemical detection. Compared to post-B12 supplementation values, homocysteine was higher (52.9 micromol/l vs. 16.8 micromol/l), RBC folate was lower (268.92 nmol/l vs. 501.2 nmol/l), the 5MTHF fraction of RBC folate was much higher (94.5% vs. 67.4%), polyglutamate chain length was shorter (more tetra- and pentaglutamates), and global DNA methylation was 22% lower. This is the first time that virtually all features of the methylfolate trap hypothesis have been demonstrated in a human with vitamin B12 deficiency.
Chromatography, Liquid↗
No effect of B vitamins on ADMA levels in patients at increased cardiovascular risk.
OBJECTIVE: Asymmetric dimethylarginine (ADMA) is a recently identified potent cardiovascular risk factor. ADMA levels are increased in hyperhomocysteinaemia and the metabolism of ADMA is linked with that of homocysteine in several ways. Treatment with B vitamins effectively reduces homocysteine levels, but studies investigating the effect on ADMA levels are scarce and show conflicting results. In this study we evaluated the effect of treatment with B vitamins on ADMA levels in two high cardiovascular risk populations. METHODS: In study I, 110 siblings of patients with clinical atherosclerotic disease and postmethionine hyperhomocysteinaemia were treated with 5 mg of folic acid and 250 mg of pyridoxine or placebo, and were analysed after 1 year. In study II, 41 patients with type 2 diabetes and mild hyperhomocysteinaemia were analysed after 6 months treatment with 5 mg of folic acid or placebo. RESULTS: A correlation between baseline homocysteine and ADMA levels was found, which was partly due to confounding by renal function. Homocysteine levels decreased by 43% in study I and by 28% in study II. In both studies, treatment with B vitamins had no effect at all on ADMA, arginine/ADMA ratio and SDMA levels. This result was confirmed in multiple linear regression analyses with adjustment for baseline values and gender. CONCLUSIONS: Our studies indicate that B vitamins, despite causing a substantial reduction in plasma homocysteine levels, have no beneficial effect on ADMA levels.
Adolescent↗
Vascular type of Ehlers-Danlos syndrome in a patient with ruptured aneurysm of the splenic artery.
A 39-year-old woman presented with a ruptured aneurysm of the splenic artery. The postoperative course was complicated by poor wound healing. This, in combination with a history of easy bruising and joint hypermobility, made us consider a connective tissue disease as underlying cause. The vascular type of Ehlers-Danlos syndrome was diagnosed by identifying collagen III deficiency and the corresponding gene mutation in cultured fibroblasts from a skin biopsy.
Adult↗
[Aortic involvement in patients with temporal arteritis and polymyalgia rheumatica].
In 4 patients with temporal arteritis or polymyalgia rheumatica, women aged 60, 57, 83 and 73 years respectively, signs of aortic involvement were established. The first patient presented with signs of systemic inflammation without signs of temporal arteritis or aortitis. In the second, an acute symptomatic thoracoabdominal aneurysm developed. In the third, temporal arteritis was associated with chronic progressive dilatation ofthe thoracic aorta. The fourth developed signs of intermittent claudication of the extremities. The clinical manifestations in all patients were attributed to chronic inflammation of the aorta caused by giant cell arteritis. Aortic giant cell arteritis frequently accompanies temporal arteritis, but is rarely diagnosed. Up to 75% of patients with temporal arteritis may have some degree of aortic involvement. Thoracic aneurysms, complicated by rupture or dissection, are the most serious complications. Aortic disease associated with signs of systemic inflammation should trigger the suspicion of giant cell arteritis. Corticosteroids are the most important part of treatment. Three patients recovered following treatment; the first two received an endoprosthesis; in the woman aged 83 years, this was not technically possible; she died after 1.5 years.
Adrenal Cortex Hormones↗
[Statins: for the time being, do not as a rule prescribe the maximum dose].
Several large clinical trials have demonstrated the ability of statins to lower the risk of cardiovascular disease and mortality. An unresolved issue, however, has been the appropriate dose of statin therapy. High-dose statins lower LDL-cholesterol more efficiently, but it remains questionable whether they reduce morbidity and mortality more than lower doses. Recently, two large clinical trials have been published that address these issues. The 'Treat to new targets' trial appears most relevant for clinical practice. In this trial, high-dose atorvastatin (80 mg per day) was more effective in reducing cardiovascular events than low-dose atorvastatin (10 mg per day) in patients whose LDL-cholesterol level was previously lowered to 3.4 mmol/l or less with the 10-mg dose. However, overall mortality did not differ due to increased mortality from noncardiac causes in the high-dose group. These findings raise important questions regarding safety and the indications for high-dose statins. Further studies are needed to resolve these issues. In the mean time, it seems reasonable to reserve high-dose statin therapy for patients who are at a very high cardiovascular risk, for example those with a history of recurrent cardiovascular events.
Anticholesteremic Agents↗
S-adenosylmethionine and 5-methyltetrahydrofolate are associated with endothelial function after controlling for confounding by homocysteine: the Hoorn Study.
OBJECTIVE: To explore to what extent homocysteine, S-adenosylmethionine (SAM), S-adenosylhomocysteine, total folate, 5-methyltetrahydrofolate (5-MTHF), vitamin B12, and vitamin B6 are associated with endothelium-dependent, flow-mediated vasodilation (FMD), and whether these associations are stronger in individuals with diabetes or other cardiovascular risk factors. METHODS AND RESULTS: In this population-based study of 608 elderly people, FMD and endothelium-independent nitroglycerin-mediated dilation (NMD) were ultrasonically estimated from the brachial artery (absolute change in diameter [mum]). High SAM and low 5-MTHF were significantly associated with high and low FMD, respectively (linear regression coefficient, [95% confidence interval]): 48.57 microm (21.16; 75.98) and -32.15 microm (-59.09; -5.20), but high homocysteine was not (-15.11 microm (-42.99; 12.78). High SAM and low 5-MTHF were also significantly associated with high and low NMD, respectively. NMD explained the association of 5-MTHF with FMD but not of SAM. No interactions were observed for diabetes or cardiovascular risk factors. CONCLUSIONS: In this elderly population, both SAM and 5-MTHF are associated with endothelial and smooth muscle cell function. The effect of homocysteine on endothelial function is relatively small compared with SAM and 5-MTHF. The relative impact of SAM, 5-MTHF, and homocysteine, and the mechanisms through which these moieties may affect endothelial and smooth muscle cell function need clarification.
Aged↗
[6S]5-methyltetrahydrofolate or folic acid supplementation and absorption and initial elimination of folate in young and middle-aged adults.
OBJECTIVES: To assess the effects of supplementation with the diastereoisomer of 5-methyltetrahydrofolate ([6S]5-methylTHF), as an alternative supplement for folic acid, on folate absorption and elimination, in two age groups. DESIGN: A randomized, double-blind intervention study. SUBJECTS: A total of 12 young (<30 y) and 12 middle-aged (> or =50 y) healthy volunteers were recruited. METHODS: Volunteers were randomized to receive daily supplementation with 400 mug folic acid or equimolar amounts of [6S]5-methylTHF during 5 weeks. Before and after supplementation, absorption and initial elimination were calculated following oral [(2)H(2)]folic acid test doses using isotope kinetics in plasma. RESULTS: Folic acid absorption was lower in the middle-aged as compared to the young adults, both before (P = 0.03) and after (P = 0.05) supplementation. In the young adults, absorption decreased by 22% after [6S]5-methylTHF and increased by 21% after folic acid (P = 0.02). In the other age group, no such changes were found. The folate rate constant of elimination increased after folic acid supplementation in the young (+50%; P = 0.05) but not in the middle-aged (+18%; P = 0.5) adults. CONCLUSIONS: Young adults show increased folate turnover after folic acid supplementation relative to the effect of [6S]5-methylTHF supplementation. Similar differences are not observed in middle-aged adults, in whom folic acid absorption was found to be lower as compared to the young adults. SPONSORSHIP: Financial support was received from the European Union 5th Framework Programme (Grant QLRT-1999-00576).
Adult↗
Homocysteine levels are not associated with cardiovascular autonomic function in elderly Caucasian subjects without or with type 2 diabetes mellitus: the Hoorn Study.
OBJECTIVE: Homocysteine and cardiovascular autonomic function are both predictors of cardiovascular disease and death, particularly in patients with diabetes. The mechanism by which homocysteine causes disease is unknown. The objective of our study was to determine whether hyperhomocysteinaemia is associated with impaired cardiovascular autonomic function in an age-, sex-, and glucose tolerance-stratified sample of an elderly Caucasian population. METHODS: We studied 609 subjects, 252 with normal glucose metabolism, 173 with impaired glucose metabolism, and 184 with type 2 diabetes. Cardiac cycle duration (RR interval) and continuous finger arterial pressure were measured under three conditions: during (i) spontaneous breathing, (ii) six deep breaths over 1 min, and (iii) an active change in position from lying to standing. From these readings, 10 parameters of autonomic function were assessed (three Ewing tests, six heart rate variability tests and one test of baroreflex sensitivity). These 10 measurements were summarized in a single cardiovascular autonomic dysfunction score (CADS). RESULTS: Comparing values of autonomic function measures in the lowest versus the highest quartile of homocysteine revealed no significant association between homocysteine level and autonomic function in the whole study group, nor in the individual glucose tolerance groups. Multiple adjustment for age, sex, waist-to-hip ratio, serum creatinine, use of antihypertensives and fasting insulin, confirmed this result. We found no evidence of effect modification of glucose tolerance status on the association between homocysteine and autonomic dysfunction (P for interaction for CADS = 0.79). CONCLUSIONS: There is no evidence for an association between homocysteine levels and cardiovascular autonomic function in either diabetic or nondiabetic subjects. Cardiovascular autonomic dysfunction does not help explain why hyperhomocysteinaemia is related to cardiovascular mortality.
Age Factors↗
[Old and new scoring systems for assessing cardiovascular risks: problems with the validity, the precision and the homogenicity of the risk categories].
Scoring systems for cardiovascular-risk assessment are increasingly being used to identify patients suitable for primary prevention measures. However, the quality of risk-score systems is threatened by (a) external invalidity, which can be partly compensated for by calibration of the score, (b) risk-score model imprecision, reflected by wide confidence intervals for the risk estimate, and (c) risk-category heterogeneity resulting from the random spread of known and unknown risk factors that are unaccounted for in the scoring system. The commonly used Framingham risk score is limited by imprecision and marked risk-category heterogeneity. The recently published SCORE risk model is probably more precise, but lacks homogenous risk categories. To prevent large scale undertreatment of patients at high cardiovascular risk, the commonly used risk threshold for initiating primary preventative treatment should be lowered.
Cardiovascular Diseases↗
5-Methyltetrahydrofolic acid and folic acid measured in plasma with liquid chromatography tandem mass spectrometry: applications to folate absorption and metabolism.
We describe a liquid chromatography (LC) tandem mass spectrometry (MS-MS) method for the determination of 5-methyltetrahydrofolic acid (5-methylTHF) and folic acid concentrations and enrichments in human plasma. It was used to study absorption and initial metabolism in five volunteers with two simultaneously administered oral test doses ([(13)C(6)]folic acid in capsules and [(2)H(2)]folic acid in a drink). [(13)C(5)]5-methylTHF and [(2)H(4)]folic acid were used as internal standards. Plasma samples (2 ml) were purified using folate binding protein affinity columns, followed by a concentration step. After LC separation, folates were detected using positive electrospray ionization MS-MS under multiple reaction monitoring conditions. Calibrations were linear for 5-methylTHF over the range 1.2 x 10(-11) (=limit of detection) to 3.2 x 10(-7)mol/L and for folic acid over the range 5 x 10(-10) (=limit of detection) to 4.5 x 10(-8)mol/L. For 5-methylTHF concentration in plasma, intraassay coefficient of variation was within 8.6% (and for unlabeled 5-methylTHF it was within 2.8%) and interassay coefficient of variation was within 9.0%. For folic acid concentrations these coefficient of variations were within 7.5% and within 6.5%, respectively. The [(13)C(6)] and [(2)H(2)] isotopomers of folic acid and 5-methylTHF were measured in the plasma of each volunteer for 8h. After accounting for the time delay due to capsule opening, the modeling results showed no significant differences in absorption time, first pass effect, and elimination rate in the folic acid test doses in capsule or drink. We conclude that LC-MS-MS offers increased sensitivity for quantification of plasma concentrations and enrichments of 5-methylTHF and folic acid and is applicable to stable-isotope studies in humans.
Administration, Oral↗
[Gallstones following considerable weight loss and recommendations for their prevention].
Obesity is an increasing public health problem. As a consequence, many people attempt to lose weight by dieting or participation in weight loss programmes. Weight loss is associated with an increased risk of symptomatic gallstones. Preventive measures include keeping the rate of weight loss below 1.5 kg per week, and providing a fat intake of at least 7 g a day. If it is expected that the rate of weight loss will be faster or difficult to control, for example after bariatric surgery, prophylaxis with ursodeoxycholic acid may be considered.
Cholagogues and Choleretics↗
[Diastolic heart failure].
Diastolic heart failure is predominantly a disease of the elderly: at the age of 70 years, almost half of all patients with heart failure have diastolic heart failure. Hypertension and obesity are common underlying disorders in patients with diastolic heart failure. Patients with diastolic heart failure have an equal, or only slightly better, prognosis in terms of mortality compared to patients with systolic heart failure. Echocardiography can distinguish diastolic heart failure from systolic heart failure. Patients with heart failure and a normal ejection fraction almost certainly have a diastolic dysfunction. There is a lack of reliable data about the optimal medicinal treatment strategy for patients with diastolic heart failure. Angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and (non-dihydropyridine) calcium antagonists have therapeutic potential. Digoxin may be contraindicated.
Adrenergic beta-Antagonists↗
[Continuous subcutaneous infusion in palliative care, an undervalued method].
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Fluid Therapy↗
Plasma homocysteine and S-adenosylmethionine in erythrocytes as determinants of carotid intima-media thickness: different effects in diabetic and non-diabetic individuals. The Hoorn Study.
OBJECTIVE: Hyperhomocysteinemia is a risk factor for atherothrombosis. Through unknown mechanisms, individuals with type 2 diabetes appear particularly susceptible. We determined whether components of homocysteine metabolism are associated with intima-media thickness in individuals with and without type 2 diabetes. METHODS AND RESULTS: In a cross-sectional design, we studied 231 Caucasian individuals, 60.6% having type 2 diabetes. We measured fasting homocysteine, vitamin B6 and vitamin B12 in plasma, and folate, S-adenosylmethionine and S-adenosylhomocysteine in plasma and erythrocytes. A homocysteine concentration >12 micromol/l was associated with a greater intima-media thickness of +0.07 mm (95% CI, +0.01 to +0.13; P=0.03) among diabetic individuals and of -0.004 mm (95%CI, -0.08 to +0.07; P=0.92) among non-diabetic individuals. An erythrocyte S-adenosylmethionine concentration above >4000 nmol/l was associated with a smaller intima-media thickness of -0.04 mm (95%CI, -0.10 to +0.02; P=0.17) for diabetic individuals versus -0.12 mm (95%CI, -0.20 to -0.36; P=0.005) for non-diabetic individuals. CONCLUSIONS: With regard to carotid intima-media thickness, individuals with diabetes appear more susceptible to the detrimental effects of homocysteine than non-diabetic individuals. In addition, diabetic individuals may lack the protective effect on the vascular wall conferred by high concentrations of S-adenosylmethionine. These findings may help explain why hyperhomocysteinemia is an especially strong risk factor for atherothrombosis among individuals with type 2 diabetes.
Aged↗
S-adenosylhomocysteine and the ratio of S-adenosylmethionine to S-adenosylhomocysteine are not related to folate, cobalamin and vitamin B6 concentrations.
BACKGROUND: It is unclear whether homocysteine itself is causal in the pathogenesis of cardiovascular disease. Alternatively or additionally, the association between homocysteine and cardiovascular disease may be because of its metabolic precursor, S-adenosylhomocysteine, or of the ratio of S-adenosylmethionine to S-adenosylhomocysteine. Therefore, it is relevant to know how these moieties are interrelated, and whether, as is the case for homocysteine, they are influenced by blood levels of folate, cobalamin or vitamin B6. DESIGN: We cross-sectionally studied a population-based cohort of 97 Caucasian subjects aged 60-85 years. Concentrations of homocysteine, S-adenosylhomocysteine, S-adenosylmethionine, folate, cobalamin and vitamin B6 were measured in fasting blood samples. RESULTS: In multiple regression analysis, homocysteine was associated with vitamin B12 (per 50 pmol L-1 increase of cobalamin, change in homocysteine, -0.70 mmol L-1; 95% CI, -1.30 to -0.10 mmol L-1) and folate (per 100 nmol L-1 increase in erythrocyte folate, change in homocysteine, -0.68 mmol L-1; 95% CI -1.28 to -0.08 mmol L-1). S-adenosylhomocysteine, S-adenosylmethionine and the ratio of S-adenosylmethionine to S-adenosylhomocysteine were not associated with serum folate, cobalamin or vitamin B6, nor with erythrocyte folate. Furthermore, plasma homocysteine showed a negative correlation with the ratio of S-adenosylmethionine to S-adenosylhomocysteine in plasma (r = -0.27; P < 0.01) but not in erythrocytes. CONCLUSIONS: In contrast to homocysteine, the plasma concentrations of S-adenosylhomocysteine and the ratio of S-adenosylmethionine to S-adenosylhomocysteine were not associated with the folate, cobalamin and vitamin B6 concentrations in the present study. If these precursors in part explain why homocysteine is associated with cardiovascular disease, homocysteine-lowering treatment with B vitamins may be less effective than currently expected, at least in an elderly population.
Aged↗