Methylmalonic Acid and Homocysteine as Indicators of Vitamin B12 Deficiency in Patients with Gastric Cancer after Gastrectomy.

Jongwon Oh,Sae-Mi Lee,Mi-Ryung Chun,Soo-Youn Lee

doi:10.3390/nu11020450

Jongwon Oh, Sae-Mi Lee + Show 2 more

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https://doi.org/10.3390/nu11020450

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Abstract

Vitamin B12 deficiency is a common complication in patients after gastrectomy. Elevated methylmalonic acid (MMA) and homocysteine are better indications of vitamin B12 deficiency than vitamin B12 serum level. We compared MMA and homocysteine levels of patients with gastric cancer after gastrectomy (n = 151) with controls (n = 142) and evaluated the prevalence of vitamin B12 deficiency using MMA and homocysteine in patients. MMA and homocysteine levels were significantly higher (p < 0.05) in patients with gastric cancer after gastrectomy. Of the 151 patients assessed after gastrectomy, 32 patients (21.2%) were vitamin B12 deficient as defined by serum MMA levels > 350 nmol/L, and 8 patients (5.3%) were vitamin B12 deficient as defined by serum homocysteine levels > 15 μmol/L. Both MMA and homocysteine levels were elevated in 7 patients. Among 33 patients with elevated MMA or homocysteine levels, 8 patients (24.2%) were vitamin B12 deficient based on a serum vitamin B12 level < 200 pg/mL. Additionally, levels of MMA and homocysteine were compared pre- and post-gastrectomy in 27 patients. The median MMA level was higher in patients with post-gastrectomy compared to pre-gastrectomy, while the median serum homocysteine level was not significantly different. These results indicate that using serum vitamin B12 levels alone may fail to detect vitamin B12 deficiency. Additional assessments of MMA and homocysteine levels are useful to evaluate possible vitamin B12 deficiency in patients who underwent a gastrectomy, and MMA is a better indicator than homocysteine to detect early changes in vitamin B12 levels.

Highlights

Vitamin B12 is essential for DNA synthesis and maintenance of normal hematologic and neurologic functions [1]
There were no significant differences between gastrectomy patient and healthy control groups in sex, creatinine, total protein, aspartate aminotransferase (AST), and alanine aminotransferase (ALT)
We evaluated the utility of methylmalonic acid (MMA) and homocysteine as follow-up markers after gastrectomy by comparing MMA and homocysteine levels in patients before and after gastrectomy

Summary

Introduction

Vitamin B12 is essential for DNA synthesis and maintenance of normal hematologic and neurologic functions [1]. It acts as a cofactor for two enzymatic reactions: the conversion of methylmalonic acid (MMA) to succinic acid and the synthesis of methionine from homocysteine. Acquired vitamin B12 deficiencies are caused by inadequate dietary intake, malabsorption, or other medical conditions such as pernicious anemia [2]. A gastrectomy is a well-known cause of vitamin B12 deficiency [3]. A gastrectomy results in lack of intrinsic factors and causes gradual depletion of vitamin B12 stores, with deficiency occurring 1–2 years post-surgery [3,4]

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