Abstract

Background

Vitamin B12 deficiency among patients with heart failure (HF) may have been underestimated. High serum levels of methylmalonic acid (MMA) have been identified in several studies as an early indicator of vitamin B12 deficiency. Furthermore, MMA seems to constitute a biomarker of oxidative stress and mitochondrial dysfunction. Data regarding vitamin B12 and MMA in patients with HF are scarce. The aim of this study was to investigate vitamin B12 and MMA serum levels in HF patients.

Methods

105 consecutive patients admitted to our hospital with symptoms and signs of acute decompensated HF were included in the study. Demographic and clinical characteristics, as well as comorbidities and medical treatment before hospital admission were recorded. Transthoracic echocardiography was performed in all patients. Blood samples were collected during the first 24 hours of hospitalization and complete blood count, biochemical biomarkers, vitamin B12, N-terminal prohormone of brain natriuretic peptide and MMA levels were measured. A total of 51 healthy individuals constituted the control group.

Results

43.8% of HF patients had elevated MMA levels, but only 10.5% had overt vitamin B12 deficiency, defined as cobalamin serum levels below 189 pg/ml. Mean MMA level was higher in HF patients vs controls (33.0±9.6 vs 19.3±6.3 ng/ml; p<0.001). This difference remained significant when adjusted for age, sex, vitamin B12 and folate serum levels and kidney function (B =14.7 (9.6-19.7); p<0.001). MMA levels were higher in patients with acutely decompensated chronic HF compared with newly diagnosed acute HF (34.7±10.5 vs 30.7±7.8 ng/ml; p=0.036). Correlation analysis revealed significantly negative correlation between MMA and B12 levels only in patients without comorbidities.

Conclusion

HF patients have elevated MMA levels, independently of age, gender, HF category or comorbidities, possibly indicating subclinical vitamin-B12 deficiency. Further research is needed to investigate subclinical vitamin-B12 deficiency in HF patients or clarify whether MMA constitutes a biomarker of oxidative stress.