VITAMIN B12 AND HOMOCYSTEINE LEVELS IN PATIENTS WITH NAFLD: A SYSTEMATIC REVIEW AND METANALYSIS

ABSTRACT BACKGROUND: The vitamin B12 absorption can be affected in patients with nonalcoholic fatty liver disease (NAFLD), and low serum vitamin B12 levels has been related to the high homocysteine (HCY) levels and to the degree of NAFLD. OBJECTIVE: To carry out a systematic review and metanalysis of serum vitamin B12 and HCY levels in patients with NAFLD. METHODS: Original studies including serum vitamin B12 and HCY levels in humans with NAFLD were included. The searches were performed in four databases. RESULTS: 159 studies were identified, and after excluding the duplicates and non-eligible titles, eight original articles were included. Six out of eight showed higher B12 levels in NAFLD patients (404.9±136.2 pg/mL in relation to controls 353.91±117.3 pg/mL). Seven of the eight studies also showed higher HCY levels in NAFLD patients (14.2±3.44 umol/L in relation to controls 11.05±3.6 umol/L). The results for serum vitamin B12 and HCY levels were submitted to metanalysis, showing no difference in the vitamin B12 levels between patients with NAFLD and controls. However, the levels of Hcy were higher in NAFLD patients than in controls. CONCLUSION: There was no relashionship between the vitamin B12 levels and NAFLD. The levels of HCY were significantly higher in patients with NAFLD, suggesting this could be a potential marker for liver damage. RESUMO CONTEXTO: A absorção de vitamina B12 pode ser afetada em pacientes com doença hepática gordurosa não alcoólica (DHGNA), e baixos níveis séricos de vitamina B12 têm sido relacionados a níveis elevados de homocisteína (HCI) ao grau de DHGNA. OBJETIVO: Realizar revisão sistemática e metanálise dos níveis séricos de vitamina B12 e de HCI em pacientes com DHGNA. MÉTODOS: Estudos originais que incluíssem avaliação dos níveis séricos de vitamina B12 e de HCI em humanos com DHGNA foram incluídos. As buscas foram realizadas em quatro bases de dados. RESULTADOS: Foram identificados 159 estudos e, após exclusão das duplicatas e dos não elegíveis, oito artigos originais foram incluídos. Seis dos oito artigos apresentaram níveis mais elevados de vitamina B12 nos pacientes com DHGNA (404,9±136,2 pg/mL) em relação aos controles (353,91±117,3 pg/mL). Sete dos oito estudos determinaram os níveis de HCI, estando aumentados em pacientes com DHGNA (14,2±3,44 umol/L) em relação aos controles (11,05±3,6 umol/L). Os resultados dos níveis séricos de vitamina B12 e HCI foram submetidos à metanálise, mostrando que não há diferença nos ní