RESUMEN
BACKGROUND: While folic acid (FA) is widely used to treat elevated total homocysteine (tHcy), promoting vascular health by reducing vascular oxidative stress and modulating endothelial nitric oxide synthase, the optimal daily dose and individual variation by MTHFR C677T genotypes have not been well studied. Therefore, this study aimed to explore the efficacy of eight different FA dosages on tHcy lowering in the overall sample and by MTHFR C677T genotypes. METHODS: This multicentered, randomized, double-blind, controlled clinical trial included 2697 eligible hypertensive adults with elevated tHcy (≥ 10 mmol/L) and without history of stroke and cardiovascular disease. Participants were randomized into eight dose groups of FA combined with 10 mg enalapril maleate, taken daily for 8 weeks of treatment. RESULTS: The intent to treat analysis included 2163 participants. In the overall sample, increasing FA dosage led to steady tHcy reduction within the FA dosing range of 0-1.2 mg. However, a plateau in tHcy lowering was observed in FA dose range of 1.2-1.6 mg, indicating a ceiling effect. In contrast, FA doses were positively and linearly associated with serum folate levels without signs of plateau. Among MTHFR genotype subgroups, participants with the TT genotype showed greater efficacy of FA in tHcy lowering. CONCLUSIONS: This randomized trial lent further support to the efficacy of FA in lowering tHcy; more importantly, it provided critically needed evidence to inform optimal FA dosage. We found that the efficacy of FA in lowering tHcy reaches a plateau if the daily dosage exceeds 1.2 mg, and only has a small gain by increasing the dosage from 0.8 to 1.2 mg. GOV IDENTIFIER: NCT03472508 (Registration Date: March 21, 2018).
Asunto(s)
Ácido Fólico , Genotipo , Homocisteína , Metilenotetrahidrofolato Reductasa (NADPH2) , Humanos , Ácido Fólico/administración & dosificación , Ácido Fólico/sangre , Homocisteína/sangre , Femenino , Masculino , Método Doble Ciego , Persona de Mediana Edad , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Hipertensión/tratamiento farmacológico , Relación Dosis-Respuesta a Droga , Anciano , Enalapril/administración & dosificación , Enalapril/farmacología , Adulto , Hiperhomocisteinemia/tratamiento farmacológico , Hiperhomocisteinemia/sangreRESUMEN
The relationship of folic acid supplementation with the risk of cancer remains inconclusive. We aimed to evaluate the effects of folic acid supplementation on cancer incidence among adults with hypertension without history of stroke or myocardial infarction (MI) in the China Stroke Primary Prevention Trial (CSPPT). A total of 20,702 hypertensive adults without history of stroke or MI, stratified by MTHFR C677T genotypes(CC, CT and TT), were randomly assigned to receive double-blind daily treatment with a single pill containing 10 mg enalapril and 0.8 mg folic acid(n = 10,348) or a pill containing 10 mg enalapril alone(n = 10,354). During a median treatment duration of 4.5 years, cancer occurred in 116 participants(1.12%) in the enalapril-folic acid group versus 116 participants(1.12%) in the enalapril group (HR, 1.00; 95%CI, 0.77-1.29). There was also no significant difference in the HRs for specific types of cancer(esophageal, gastric, breast, lung, colorectal, head and neck, liver and gynecologic cancer or lymphoma) or cancer mortality(HR, 1.05; 95%CI, 0.69-1.58). For participants not receiving folic acid treatment (enalapril only group), MTHFR 677 TT genotype was an independent predictor of total cancer risk compared to CC genotype (HR, 1.86; 95%CI, 1.07-3.22). Consistently, a beneficial effect was observed in participants with MTHFR TT genotype and low folate levels (<9.0 ng/mL; HR, 0.47; 95%CI, 0.24-0.94). There is no evidence that 0.8 mg daily folic acid supplementation can increase the risk of cancer incidence among adults with hypertension without history of stroke or MI in China. Our data suggest a protective effect in participants with MTHFR TT genotype and low folate levels.