Cobalamin dose regimen for maximum homocysteine reduction in end-stage renal disease

High doses of oral folate and sublingual vitamin B12 in dialysis patients with hyperhomocysteinemia

INTRODUCTION

Folic acid and vitamin B12, alone or in combination have been used to reduce homocysteine (Hcy) levels in dialysis patients.

OBJECTIVES

We aimed to assess the efficacy of high doses of oral folate and vitamin B12 in reducing plasma Hcy levels after a 12-week treatment.

PATIENTS AND METHODS

Thirty-two dialysis patients aged 10-324 months screened for hyperhomocysteinuria. Then cases with hyperhomocysteinemia received oral folate 10 mg/day with sublingual methylcobalamin 1 mg/day for 12 weeks. In pre- and post-intervention phases plasma Hcy concentration, serum folate, and vitamin B12 levels were measured. Changes in plasma Hcy, serum folate, and vitamin B12 concentrations were analyzed by paired t tests, and P values < 0.05 were considered significant.

RESULTS

Eighteen (56.2%) patients had hyperhomocysteinuria. Vitamin B12 and folate levels were normal or high in all cases. Two patients were lost due to transplant or irregular drugs consumption. Plasma Hcy levels were reduced in all, and reached normal values in 50%. A statistically significant differences between first Hcy levels with levels after intervention was found (95% CI, 5.1-8.9, P = 0.0001).

CONCLUSION

Oral folate 10 mg/day in combination with sublingual vitamin B12, 1 mg/day can be considered as a favorable treatment for hyperhomocysteinemia in dialysis patients.

Interventions for lowering plasma homocysteine levels in dialysis patients

BACKGROUND

People with end-stage kidney disease (ESKD) have high rates of cardiovascular events. Randomised controlled trials (RCTs) of homocysteine-lowering therapies have not shown reductions in cardiovascular event rates in the general population. However, people with kidney disease have higher levels of homocysteine and may have different mechanisms of cardiovascular disease. We performed a systematic review of the effect of homocysteine-lowering therapies in people with ESKD.

OBJECTIVES

To evaluate the benefits and harms of established homocysteine lowering therapy (folic acid, vitamin B6, vitamin B12) on all-cause mortality and cardiovascular event rates in patients with ESKD.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register to 25 January 2016 through contact with the Information Specialist using search terms relevant to this review.

SELECTION CRITERIA

Studies conducted in people with ESKD that reported at least 100 patient-years of follow-up and assessed the effect of therapies that are known to have homocysteine-lowering properties were included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data using a standardised form. The primary outcome was cardiovascular mortality. Secondary outcomes included all-cause mortality, incident cardiovascular disease (fatal and nonfatal myocardial infarction and coronary revascularisation), cerebrovascular disease (stroke and cerebrovascular revascularisation), peripheral vascular disease (lower limb amputation), venous thromboembolic disease (deep vein thrombosis and pulmonary embolism), thrombosis of dialysis access, and adverse events. The effects of homocysteine-lowering therapies on outcomes were assessed with meta-analyses using random-effects models. Prespecified subgroup and sensitivity analyses were conducted.

MAIN RESULTS

We included six studies that reported data on 2452 participants with ESKD. Interventions investigated were folic acid with or without other vitamins (vitamin B6, vitamin B12). Participants' mean age was 48 to 65 years, and proportions of male participants ranged from 50% to 98%.Homocysteine-lowering therapy probably leads to little or no effect on cardiovascular mortality (4 studies, 1186 participants: RR 0.93, 95% CI 0.70 to 1.22). There was no evidence of heterogeneity among the included studies (I² = 0%). Homocysteine-lowering therapy had little or no effect on all-cause mortality or any other of this review's secondary outcomes. All prespecified subgroup and sensitivity analyses demonstrated little or no difference. Reported adverse events were mild and there was no increase in the incidence of adverse events from homocysteine-lowering therapies (3 studies, 1248 participants: RR 1.12, 95% CI 0.51 to 2.47; I(2) = 0%). Overall, studies were assessed as being at low risk of bias and there was no evidence of publication bias.

AUTHORS' CONCLUSIONS

Homocysteine-lowering therapies were not found to reduce mortality (cardiovascular and all-cause) or cardiovascular events among people with ESKD.

Testing the homocysteine hypothesis in end-stage renal disease: Problems and a possible solution

The homocysteine hypothesis states that circulating homocysteine is a vascular toxin in concentrations that occur in the general population and in renal failure. This hypothesis is currently being tested in the Kidney and End State Renal Disease Study (HOST), but data have emerged since the HOST began that suggest its results will be inconclusive. The crucial treatment component in the HOST is folic acid, but its effect is likely to be lost because the American food supply is now fortified with folic acid. A second concern is that the very high doses of folic acid and pyridoxine being used in the HOST may confound the results. Finally, confounding due to 'reverse epidemiology' was not considered when the HOST was designed. Parenteral vitamin B(12) is a highly promising therapy for homocysteine reduction in end-stage renal disease that merits careful investigation. Clinical trials using it to test the homocysteine hypothesis will avoid the problems inherent in the HOST.

Comparative effects of hydroxocobalamin and cyanocobalamin on plasma homocysteine concentrations in end-stage renal disease

End-stage renal disease (ESRD) is associated with marked hyperhomocysteinemia which is only partially corrected by folic acid and pyridoxine supplementation. We and others have reported that various forms of parenteral cobalamin reduce plasma total homocysteine (tHcy) concentrations of patients with ESRD substantially below the lowest levels attainable with folic acid. We here report a 16-week randomized controlled crossover trial which directly compared the Hcy-lowering effect of intravenous hydroxocobalamin (HC) with that of cyanocobalamin (CC). Folic acid- and vitamin B12-replete maintenance hemodialysis patients were randomly assigned to receive either 1 mg intravenous HC weekly for 8 weeks followed by CC for a further 8 weeks, or CC for 8 weeks followed by HC for 8 weeks. Hydroxocobalamin increased serum cobalamin concentrations 40-fold, whereas CC increased them only 10-fold, but both treatments reduced plasma tHcy concentrations similarly by 33% (P < .001). Crossover to the alternate form of the vitamin greatly affected the serum cobalamin concentration but was without further effect on the plasma tHcy concentration. These results confirm that weekly cobalamin injections lower plasma tHcy concentrations of hemodialysis patients well below the level attainable with folic acid. Hydroxocobalamin and CC are equipotent despite producing very different serum cobalamin concentrations.