Betaine dose and treatment intervals in therapy for homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency

Cystathionine beta synthase deficiency and brain edema associated with methionine excess under betaine supplementation: Four new cases and a review of the evidence

CBS deficient individuals undergoing betaine supplementation without sufficient dietary methionine restriction can develop severe hypermethioninemia and brain edema. Brain edema has also been observed in individuals with severe hypermethioninemia without concomitant betaine supplementation. We systematically evaluated reports from 11 published and 4 unpublished patients with CBS deficiency and from additional four cases of encephalopathy in association with elevated methionine. We conclude that, while betaine supplementation does greatly exacerbate methionine accumulation, the primary agent causing brain edema is methionine rather than betaine. Clinical signs of increased intracranial pressure have not been seen in patients with plasma methionine levels below 559 μmol/L but occurred in one patient whose levels did not knowingly exceed 972 μmol/L at the time of manifestation. While levels below 500 μmol/L can be deemed safe it appears that brain edema can develop with plasma methionine levels close to 1000 μmol/L. Patients with CBS deficiency on betaine supplementation need to be regularly monitored for concordance with their dietary plan and for plasma methionine concentrations. Recurrent methionine levels above 500 μmol/L should alert clinicians to check for clinical signs and symptoms of brain edema and review dietary methionine intake. Levels approaching 1000 μmol/L do increase the risk of complications and levels exceeding 1000 μmol/L, despite best dietetic efforts, should be acutely addressed by reducing the prescribed betaine dose.

Betaine in the Brain: Characterization of Betaine Uptake, its Influence on Other Osmolytes and its Potential Role in Neuroprotection from Osmotic Stress

Betaine (N-trimethylglycine), a common osmolyte, has received attention because of the number of clinical reports associating betaine supplementation with improved cognition, neuroprotection and exercise physiology. However, tissue analyses report little accumulation of betaine in brain tissue despite the presence of betaine/GABA transporters (BGT1) at the blood brain barrier and in nervous tissue, calling into question whether betaine influences neuronal function directly or indirectly. Therefore, the focus of this study was to determine what capacity nervous tissue has to accumulate betaine, specifically in the hippocampus, a region of the brain associated with learning and memory and one that is particularly susceptible to damage (e.g., seizure activity). Here we report that hippocampal slices actively accumulate betaine in a time, dose and osmolality dependent manner, resulting in peak intracellular concentrations four times extracellular concentrations within 8 h. Our data also indicate that betaine uptake differentially influences the accumulation of other osmolytes. Under isosmotic conditions, betaine uptake minimally impacted some osmolytes (e.g., glycerylphosphorylcholine and glutamate) while significantly reducing others (taurine, creatine, and myo-inositol). Under osmotic stress (hyperosmotic) conditions, we observed dramatic changes in osmolytes like glycine and glutamine-key players in inhibitory neurotransmission-and little change in osmolytes such as taurine, creatine and myo-inositol when betaine was available. These data suggest that betaine may influence pathways of inhibitory neurotransmitter production/recycling in addition to serving as an osmolyte and metabolic intermediate. In sum, our data provide detailed characterization of betaine uptake in the hippocampus that implicates betaine in the modulation of hippocampal neurophysiology and neuroprotection.

Homocysteine lowering interventions for peripheral arterial disease and bypass grafts

BACKGROUND

Elevated plasma levels of the amino acid homocysteine (hyperhomocysteinaemia) are associated with narrowing or blocking of the arteries (atherosclerosis). Treatment to lower homocysteine levels has been shown to be both effective and cheap in healthy volunteers. However, the impact of reducing homocysteine levels on the progression of atherosclerosis and patency of the vessels after treatment for atherosclerosis is still unknown and forms the basis for this review. This is the second update of a review first published in 2002.

OBJECTIVES

To assess the effects of plasma homocysteine lowering therapy on the clinical progression of disease in people with peripheral arterial disease (PAD) and hyperhomocysteinaemia including, as a subset, those who have undergone surgical or radiological intervention.

SEARCH METHODS

For this update, the Cochrane Peripheral Vascular Disease Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched January 2013) and CENTRAL (2012, Issue 12). Trial databases were searched by the TSC (January 2013) for details of ongoing and unpublished studies. We also searched the reference lists of relevant articles.

SELECTION CRITERIA

Randomised trials in which participants with PAD and hyperhomocysteinaemia were allocated to either homocysteine lowering therapy or no treatment, including participants before and after surgical or radiological interventions.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted the data. Information on adverse events was collected from the trials.

MAIN RESULTS

Two randomised trials with a total of 161 participants were included in this review. The studies did not report on mortality and rate of limb loss. One randomised trial with a total of 133 participants showed that there was a significant improvement in ankle brachial index (ABI) in participants who received folic acid compared with placebo (mean difference (MD) 0.07, 95% confidence interval (CI) 0.04 to 0.11, P < 0.001) and in participants who received 5-methyltetrahydrofolate (5-MTHF) versus placebo (MD 0.05, 95% CI 0.01 to 0.10, P = 0.009). A second trial with a total of 18 participants showed that there was no difference (P non-significant) in ABI in participants who received a multivitamin B supplement (mean ± SEM: 0.7 ± 01) compared with placebo (mean ± SEM: 0.8 ± 0.1). No major events were reported.

AUTHORS' CONCLUSIONS

Currently, no recommendation can be made regarding the value of treatment of hyperhomocysteinaemia in peripheral arterial disease. Further, well constructed trials are urgently required.

The effects of normalizing hyperhomocysteinemia on clinical and operative outcomes in patients with critical limb ischemia

PURPOSE

To assess the outcome of patients with medically treated hyperhomocysteinemia (HHC) requiring intervention for critical limb ischemia (CLI).

METHODS

A parallel observational study was conducted to compare the clinical and revascularization outcomes of CLI patients who received standardized treatment for HHC preoperatively (folic acid and vitamin B12) vs. contemporaneous patients with normal homocysteine levels. The threshold for HHC diagnosis was 13.0 μmol/L. From 2009 to 2011, 169 patients underwent revascularization procedures for CLI. Of these, all 66 patients (40 men; mean age 69.6 ± 11.2 years) with HHC (mean 17.3 μmol/L, range 13.5-34.9) were treated to normalize the homocysteine level prior to lower limb revascularization. The remaining 103 patients (58 men; mean age 72.7±8.1 years) had normal homocysteine levels (8.2 μmol/L, range 5-12.3) before revascularization. The primary endpoint was symptomatic and hemodynamic improvement in the treated HHC group. The secondary endpoints were all-cause survival, binary restenosis, reintervention, amputation-free survival, and major adverse events. The treated HHC cohort was compared to an age/sex-matched historical group of patients with untreated HHC from 2002 to 2006 before HHC pretreatment became routine. All interventions (endovascular, hybrid, and open) were performed by the same surgeon, and the groups were evenly matched.

RESULTS

Patients with HHC were treated for a mean 12.2 days, which significantly reduced their mean homocysteine level after 3 weeks to 10.1 μmol/L (range 6.2-14.4, p<0.05). After revascularization, immediate clinical improvement was similar between normal homocysteine and medically corrected HHC groups. There was no significant difference in time to binary restenosis (p=0.822). Secondary endpoints and all-cause mortality were similar. Multivariate logistic regression showed that untreated HHC was a significant factor for graft occlusion and limb loss (p<0.0001), but medically corrected HHC was no longer predictive of adverse operative outcome.

CONCLUSION

Patients with medically corrected HHC have similar outcomes compared to those with normal homocysteine levels. Thus, aggressively treating HHC with folic acid and vitamin B12 may help enhance the clinical outcome of CLI patients undergoing revascularization.

Double-blind therapeutic trial in Angelman syndrome using betaine and folic acid

Angelman syndrome (AS) is caused by reduced or absent expression of the maternally inherited ubiquitin protein ligase 3A gene (UBE3A), which maps to chromosome 15q11-q13. UBE3A is subject to genomic imprinting in neurons in most regions of the brain. Expression of UBE3A from the maternal chromosome is essential to prevent AS, because the paternally inherited gene is not expressed, probably mediated by antisense UBE3A RNA. We hypothesized that increasing methylation might reduce expression of the antisense UBE3A RNA, thereby increasing UBE3A expression from the paternal gene and ameliorating the clinical phenotype. We conducted a trial using two dietary supplements, betaine and folic acid to promote global levels of methylation and attempt to activate the paternally inherited UBE3A gene. We performed a number of investigations at regular intervals including general clinical and developmental evaluations, biochemical determinations on blood and urine, and electroencephalographic studies. We report herein the data on 48 children with AS who were enrolled in a double-blind placebo-controlled protocol using betaine and folic acid for 1 year. There were no statistically significant changes between treated and untreated children; however, in a small subset of patients we observed some positive trends.

Titration of betaine therapy to optimize therapy in an infant with 5,10-methylenetetrahydrofolate reductase deficiency

Betaine therapy was given for 2 years to a 2-year-old boy with 5,10-methylenetetrahydrofolate reductase deficiency. Used as a methyl donor to lower homocysteine levels through methylation of methionine, betaine has been reported to be effective in treating homocystinuria. Satisfactory biochemical and clinical responses were obtained with the following regimen: betaine started in the newborn period at increasing doses to reach 1 g given six times a day. It is suggested that frequent administration of a moderate dose may provide clinical and biochemical benefit.

Betaine for nonalcoholic fatty liver disease: results of a randomized placebo-controlled trial

Based on animal studies and pilot studies in humans, betaine, a methyl donor for the remethylation of homocysteine, may be a therapeutic agent for nonalcoholic steatohepatitis (NASH). We evaluated the safety and efficacy of betaine for patients with NASH and whether betaine positively modified factors postulated to be "second hits" and underlying mechanisms of NASH. We conducted a randomized placebo-control study of 55 patients with biopsy-proven NASH who received either oral betaine (20 g daily) or placebo for 12 months. Pre- and posttreatment variables were analyzed using the paired t test or Wilcoxon rank test. Treatment groups were comparable at baseline. Of the 35 patients (17 betaine, 18 placebo) who completed the study, 34 patients (16 betaine, 18 placebo) underwent posttreatment liver biopsy. Patients randomized to betaine had a decrease in steatosis grade. No intra- or intergroup differences or changes in nonalcoholic fatty liver disease activity score or fibrosis stage were noted. Elevations of insulin, glucose, and proinflammatory cytokines and the reduced antioxidant status noted in NASH patients did not improve with betaine therapy. The antiinflammatory agent adiponectin was significantly reduced in both groups and did not change with therapy. Lastly, S-adenosylhomocysteine was approximately twice normal and was not reduced by betaine therapy.

CONCLUSION

Compared to placebo, betaine did not improve hepatic steatosis but may protect against worseningsteatosis [corrected]. High-dose betaine supplementation failed to reduce S-adenosylhomocysteine and did not positively affect any of the second hit mechanisms postulated to contribute to NASH that we studied. Although betaine has been proven effective in treating hepatic steatosis in several animal models, translating novel therapeutic options noted in animal studies to humans with NASH will prove challenging.

A study of the treatment of Rett syndrome with folate and betaine

We tested the hypothesis that increasing methyl-group pools might promote transcriptional repression by other methyl-binding proteins or by mutant methyl-CpG-binding protein 2 with altered affinity, ameliorating the clinical features of Rett syndrome. A 12-month, double-blind, placebo-controlled folate-betaine trial enrolled 73 methylCpG-binding protein 2 mutation positive female participants meeting consensus criteria for Rett syndrome. Participants were randomized as young (< age 5 years) or old (>or= age 5 years). Structured clinical assessments occurred at baseline, 3, 6, and 12 months. Primary outcome measures included quantitative evaluation of breathing and hand movements during wakefulness, growth, anthropometry, motor/behavioral function, and qualitative evaluations from electroencephalograms and parent questionnaires. In all, 68 participants completed the study. Objective evidence of improvement was not found. Subjective improvement from parent questionnaires was noted for the <5 years group. This study should inform future treatment trials regarding balancing participants with specific mutations and comparable severity to minimize selection bias.

Prevention of brain disease from severe 5,10-methylenetetrahydrofolate reductase deficiency

Over a four-year period, we collected clinical and biochemical data from five Amish children who were homozygous for missense mutations in 5,10-methylenetetrahydrofolate reductase (MTHFR c.1129C>T). The four oldest patients had irreversible brain damage prior to diagnosis. The youngest child, diagnosed and started on betaine therapy as a newborn, is healthy at her present age of three years. We compared biochemical data among four groups: 16 control subjects, eight heterozygous parents, and five affected children (for the latter group, both before and during treatment with betaine anhydrous). Plasma amino acid concentrations were used to estimate changes in cerebral methionine uptake resulting from betaine therapy. In all affected children, treatment with betaine (534+/-222 mg/kg/day) increased plasma S-adenosylmethionine, improved markers of tissue methyltransferase activity, and resulted in a threefold increase of calculated brain methionine uptake. Betaine therapy did not normalize plasma total homocysteine, nor did it correct cerebral 5-methyltetrahydrofolate deficiency. We conclude that when the 5-methyltetrahydrofolate content of brain tissue is low, dietary betaine sufficient to increase brain methionine uptake may compensate for impaired cerebral methionine recycling. To effectively support the metabolic requirements of rapid brain growth, a large dose of betaine should be started early in life.

Orally administered betaine has an acute and dose-dependent effect on serum betaine and plasma homocysteine concentrations in healthy humans

Betaine, i.e., trimethylglycine, is linked to homocysteine metabolism. A 3-mo daily betaine supplementation decreased even normal plasma total homocysteine (tHcy) concentrations in humans. The pharmacokinetic characteristics and metabolism of betaine in humans have not been investigated in detail. The aim of this study was to assess the pharmacokinetics of orally administered betaine and its acute effect on plasma tHcy concentrations. Healthy volunteers (n = 10; 3 men, 7 women) with normal body weight (mean +/- SD, 69.5 +/- 17.0 kg), 40.8 +/- 12.4 y old, participated in the study. The betaine doses were 1, 3, and 6 g. The doses were mixed with 150 mL of orange juice and ingested after a 12-h overnight fast by each volunteer according to a randomized double-blind crossover design. Blood samples were drawn for 24 h and a 24-h urine collection was performed. Orally administered betaine had an immediate and dose-dependent effect on serum betaine concentration. Single doses of 3 and 6 g lowered plasma tHcy concentrations (P = 0.019 and P < 0.001, respectively), unlike the 1-g dose. After the highest dose, the concentrations remained low during the 24 h of monitoring. The change in plasma tHcy concentration was linearly associated with betaine dose (P = 0.006) and serum betaine concentration (R2 = 0.17, P = 0.025). The absorption and elimination of betaine were dose dependent. The urinary excretion of betaine seemed to increase with an increasing betaine dose, although a very small proportion of ingested betaine was excreted via urine. In conclusion, a single dose of orally administered betaine had an acute and dose-dependent effect on serum betaine concentration and resulted in lowered plasma tHcy concentrations within 2 h in healthy subjects.

Low Dose Betaine Supplementation Leads to Immediate and Long Term Lowering of Plasma Homocysteine in Healthy Men and Women

High plasma homocysteine is a risk for cardiovascular disease and can be lowered through supplementation with 6 g/d of betaine. However, dietary intake of betaine is approximately 0.5-2 g/d. Therefore, we investigated whether betaine supplementation in the range of dietary intake lowers plasma homocysteine concentrations in healthy adults. Four groups of 19 healthy subjects ingested three doses of betaine or placebo daily for 6 wk. A methionine loading test was performed during run in, on d 1 of betaine supplementation, and after 2 and 6 wk of betaine supplementation. Fasting plasma homocysteine after 6-wk daily intakes of 1.5, 3 and 6 g of betaine was 12% (P < 0.01), 15% (P < 0.002) and 20% (P < 0.0001) less than in the placebo group, respectively. Furthermore, the increase in plasma homocysteine after methionine loading on the 1st d of betaine supplementation was 16% (P < 0.06), 23% (P < 0.008) and 35% (P < 0.0002) less than in the placebo group, respectively, and after 6 wk of supplementation was 23% (P < 0.02), 30% (P < 0.003) and 40% (P < 0.0002) less, respectively. Thus, doses of betaine in the range of dietary intake reduce fasting and postmethionine loading plasma homocysteine concentrations. A betaine-rich diet might therefore lower cardiovascular disease risk.

Limited effectiveness of betaine therapy for cystathionine beta synthase deficiency

BACKGROUND

Orally administered betaine (Bet) is regarded as an effective and safe therapy for homocystin-uria. However, even when patients' serum Bet concentrations are increased by supplementation, serum homocysteine (Hcy) concentrations are often not lowered to the normal range. The present study tested the hypothesis that with relatively high serum methionine (Met), serum Hcy does not adequately decrease, even when serum Bet concentrations are potentially therapeutic.

METHODS

The present study examines the relationship between these amino acids by high-performance liquid chromatography (HPLC) in a total of 63 samples obtained over 2 years from two patients with cystathionine beta synthase (CBS) deficiency.

RESULTS

When serum Met was less than 80 micro mol/L (1.2 mg/dL), the treatment reduced serum Hcy to within the normal range. When serum Met exceeded 80 micro mol/L, serum Hcy showed only a limited decrease, despite sufficient doses of Bet (serum concentration, over 250 micro mol/L). The findings of the present study suggest that it is necessary to follow a low methionine diet that keeps serum Met within the normal range when treating patients with homocystinuria due to CBS deficiency when Bet is administered. Homocystinuria is a rare congenital metabolic disease and the data presented in the present paper, although it relates to only two patients, is worth reporting.

Pharmacokinetics of oral betaine in healthy subjects and patients with homocystinuria

AIMS

Large oral doses of betaine have proved effective in lowering plasma homocysteine in severe hyperhomocysteinaemia. The pharmacokinetic characteristics and metabolism of betaine in humans have not been assessed and drug monitoring for betaine therapy is not available. We studied the pharmacokinetics of betaine and its metabolite dimethylglycine (DMG) in healthy subjects and in three patients with homocystinuria.

METHODS

Twelve male volunteers underwent an open-label study. After one single administration of 50 mg betaine kg-1 body weight and during continuous intake of twice daily 50 mg kg-1 body weight, serial blood samples and 24 h urines were collected to determine betaine and DMG plasma concentrations and urinary excretion, respectively. Patients were evaluated after one single dose of betaine.

RESULTS

We found rapid absorption (t(1/2),abs 00.28 h, s.d. 0.17) and distribution (t(1/2), lambda1 00.59 h, s.d. 0.22) of betaine. A Cmax of 0.94 mmol l-1 (s.d. 0.19) was reached after tmax 00.90 h (s.d. 0.33). The elimination half life t(1/2), z was 14.38 h (s.d. 7.17). After repeated dosage, t(1/2), lambda1 (01.77 h, s.d. 0.75) and t(1/2), z (41.17 h, s.d. 13.50) increased significantly (95% CI 0.73, 01.64 h and 19.90, 33.70 h, respectively), whereas absorption remained unchanged. DMG concentrations increased significantly after betaine administration and accumulation occurred to the same extent as with betaine. Renal clearance was low and urinary excretion of betaine was equivalent to 4% of the ingested dose. Distribution and elimination kinetics in homocystinuric patients appeared to be accelerated.

CONCLUSIONS

Betaine plasma concentrations change rapidly after ingestion. Elimination half-life increased during continuous dosing over 5 days. Betaine is mainly eliminated by metabolism. More pharmacokinetic and pharmacodynamic studies in hyperhomocysteinaemic patients are needed to refine the current treatment with betaine.

Betaine supplementation decreases plasma homocysteine concentrations but does not affect body weight, body composition, or resting energy expenditure in human subjects

BACKGROUND

Betaine (trimethylglycine) is found in several tissues in humans. It is involved in homocysteine metabolism as an alternative methyl donor and is used in the treatment of homocystinuria in humans. In pigs, betaine decreases the amount of adipose tissue.

OBJECTIVE

The aim of the study was to examine the effect of betaine supplementation on body weight, body composition, plasma homocysteine concentrations, blood pressure, and serum total and lipoprotein lipids.

DESIGN

Forty-two obese, white subjects (14 men, 28 women) treated with a hypoenergetic diet were randomly assigned to a betaine-supplemented group (6 g/d) or a control group given placebo for 12 wk. The intervention period was preceded by a 4-wk run-in period with a euenergetic diet.

RESULTS

Body weight, resting energy expenditure, and fat mass decreased significantly in both groups with no significant difference between the groups. Plasma homocysteine concentrations decreased in the betaine group ( +/- SD: 8.76 +/- 1.63 micro mol/L at 4 wk, 7.93 +/- 1.52 micro mol/L at 16 wk; P = 0.030 for the interaction of time and treatment). Diastolic blood pressure decreased without a significant difference between the groups. Serum total and LDL-cholesterol concentrations were higher in the betaine group than in the control group (P < 0.05).

CONCLUSION

A hypoenergetic diet with betaine supplementation (6 g daily for 12 wk) decreased the plasma homocysteine concentration but did not affect body composition more than a hypoenergetic diet without betaine supplementation did.

An indirect response model of homocysteine suppression by betaine: optimising the dosage regimen of betaine in homocystinuria

AIMS

To investigate the pharmacokinetics (PK) and pharmacodynamics (PD) of betaine in the treatment of classical homocystinuria due to cystathionine beta-synthase (CbetaS) deficiency with a view to optimizing the dosage regimen.

METHODS

Betaine was given as a single oral dose of 100 mg kg(-1) to six patients (age range 6-17 years) who normally received betaine but whose treatment had been suspended for 1 week prior to the study. Plasma betaine and total homocysteine concentrations were measured by high performance liquid chromatography (h.p.l.c.) at frequent intervals over 24 h. The best-fit PK model was determined using the PK-PD program Win-Nonlin and the concentration-time-effect data analysed by an indirect PD model. Using the PK and PD parameters, simulations were carried out with the aim of optimizing betaine dosage.

RESULTS

Betaine PK was described by both mono- and bi-exponential disposition functions with first order absorption and a lag time. The correlation coefficient between betaine oral clearance and body weight was 0.6. Mean betaine clearance was higher in males than in females (P=0.03). PK-PD simulation indicated minimal benefit from exceeding a twice-daily dosing schedule and a 150 mg kg(-1) day(-1) dosage for betaine.

CONCLUSIONS

PK-PD modelling allows recommendations for optimal dosage of betaine in the treatment of homocystinuria, that have the potential for improved patient compliance and both therapeutic and pharmacoeconomic benefit.

Betaine and homocysteine concentrations in foods

BACKGROUND

Betaine (Bet) supplementation is an effective strategy for dietary treatment of homocystinuria. However,previous reports on diet therapy have only examined methionine (Met)and cystine concentrations, but not those of Bet and homocysteine(Hcy) in food items. We set up a hypothesis that there are some food items, which contain a small amount of Met, but a great amount of Hcy and Bet.

METHODS

We measured Bet and Hcy concentrations in 58 food items, which were regarded as containing low Met.

RESULTS

Products of wheat flour are rich in Bet. The amount of Bet in food items investigated in this study is much smaller than the dose used to treat homocystinuria patients. Vegetables contained little Hcy, however sprouted beans and sprouted alfalfa seeds contained ample Hcy.

CONCLUSION

Patients with homocystinuria do not have to be too concerned about Hcy in food items because the amount is small. Therefore, we encourage homocystinuria patients to continue a low Met diet therapy without anxiety of Hcy and Bet, and if necessary,Bet will be supplemented.

Homocysteine lowering interventions for peripheral arterial disease and bypass grafts

BACKGROUND

Elevated plasma levels of the amino acid homocysteine (hyperhomocysteinaemia) are associated with hardening or blocking of the arteries (atherosclerosis) In addition, there is a poorer prognosis, both in the progression of the disease and outcome after therapy. Treatment to lower homocysteine levels has been shown to be both effective and cheap in healthy volunteers. However, the impact of reducing homocysteine levels on the progression of atherosclerosis and patency of vessels after treatment for atherosclerosis is still unknown and forms the basis for this review.

OBJECTIVES

To assess the effects of plasma homocysteine-lowering therapy on the clinical progression of disease in patients with peripheral arterial disease (PAD) and hyperhomocysteinaemia, including, as a subset, those who have undergone surgical or radiological intervention.

SEARCH STRATEGY

The reviewers (MH,GS) searched the Cochrane Peripheral Vascular Diseases Group trials register, the Cochrane Controlled trials register (2002, Issue 1), MEDLINE, EMBASE and reference lists of relevant articles.

SELECTION CRITERIA

Randomised trials of the treatment of hyperhomocysteinaemia in patients with peripheral arterial disease, before and after surgical or radiological intervention versus no treatment for hyperhomocysteinaemia.

DATA COLLECTION AND ANALYSIS

Two reviewers (MH,GS) independently assessed trial quality and extracted data. Information on adverse events was collected from the trials.

MAIN RESULTS

There are currently no randomised trials available for analysis.

REVIEWER'S CONCLUSIONS

Well constructed trials assessing the impact of the treatment of hyperhomocysteinaemia in patients with peripheral arterial disease are urgently required.

Betaine and homocysteine concentrations in infant formulae and breast milk

BACKGROUND

Early diagnosis and treatment of homocystinuria with methionine-free or low methionine formulae significantly improve prognosis in children found by newborn screening and treated soon after birth. Betaine (Bet) supplementation is also an effective strategy for dietary treatment of homocystinuria. However, previous reports on diet therapy have only examined methionine and cysteine concentrations but not those of Bet and homocysteine (Hcy) in infant diets.

METHODS

We measured Bet and Hcy concentrations in three methionine-free formulae, five infant starter formulae, and 33 samples of human breast milk from 10 mothers.

RESULTS

In methionine-free formulae, Hcy but not Bet was isolated. However, in human breast milk and infant starter formulae, both Bet and Hcy were detected. However, the Bet concentration was not sufficient for the treatment.

CONCLUSIONS

Our study suggests that methionine-free formulae should have Hcy eliminated and be fortified with Bet to the concentration of 150 mg/dL for the treatment of homocystinuria.

Co-administration of equimolar doses of betaine may alleviate the hepatotoxic risk associated with niacin therapy

High-dose niacin has versatile and substantial efficacy for the treatment of hyperlipidemias, but its utility is compromised by various side effects, the most serious of which is liver damage. It is proposed that this hepatotoxicity reflects the high demand for methyl groups imposed by niacin catabolism, leading to a reduction in hepatic levels of S-adenosylmethionine (SAM). Depletion of the hepatic SAM pool has likewise been shown to mediate, at least in part, the hepatotoxic effects of ethanol, methotrexate, and niacinamide. If niacin does indeed decrease SAM, a likely consequence would be a counterproductive elevation of plasma homocysteine. Conceivably, methyl group deficiency, by altering membrane properties of skeletal muscle, also contributes to niacin-induced insulin resistance. Concurrent betaine supplementation - preferably administered as a complex with equimolar amounts of niacin - may represent the most cost-effective way to prevent niacin-mediated depletion of SAM and thus avoid hepatotoxicity (and possibly other adverse effects) while controlling homocysteine. Betaine also merits evaluation as an adjuvant to methotrexate and niacinamide therapies.