Evaluation of tracer labelled methionine load test in vitamin B-12 deficient adolescent women.

Autor: Bhat DS; Kamalnayan Bajaj Diabetology Research Centre, King Edward Memorial Hospital Research Centre, Pune, India., Gruca LL; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America.; Department of Pathobiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, United States of America., Bennett CD; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America.; Department of Pathobiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, United States of America., Katre P; Kamalnayan Bajaj Diabetology Research Centre, King Edward Memorial Hospital Research Centre, Pune, India., Kurpad AV; St. John's Research Institute, Bangalore, India., Yajnik CS; Kamalnayan Bajaj Diabetology Research Centre, King Edward Memorial Hospital Research Centre, Pune, India., Kalhan SC; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States of America.; Department of Pathobiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, United States of America.
Jazyk: angličtina
Zdroj: PloS one [PLoS One] 2018 May 24; Vol. 13 (5), pp. e0196970. Date of Electronic Publication: 2018 May 24 (Print Publication: 2018).
DOI: 10.1371/journal.pone.0196970
Abstrakt: Background: Methionine loading test (MLT) has been used primarily to identify defects in transsulfuration of homocysteine in cystathionine beta synthase deficiency. It may not be as useful to evaluate remethylation pathway, in vitamin B-12 and folate deficiencies.
Objective: We used tracer isotope labelled MLT to interrogate transsulfuration and remethylation independently in vitamin B-12 deficiency.
Design: We studied vitamin B-12 deficient women with a tracer labelled MLT before and eleven months after treatment with vitamin B-12. The fractional contribution of [13C]homocysteine to breath CO2 was used as a measure of transsulfuration, and difference in the intracellular enrichment of [13C]methionine and that of [C2H3]methionine as a measure of remethylation of homocysteine. Combined pre- and post-treatment results were analyzed to investigate the association between plasma vitamin B-12 concentrations and measures of homocysteine metabolism.
Results: The subjects were 17 years old, with a BMI of 19.4 kg/m2. Treatment with vitamin B-12, 2µg/day increased plasma B-12 from 93 (78.7, 106.2) [median (25th, 75th centiles)] to 161.5 (125.5, 226.2) pmol/L; 44% were below <150pmol/L after treatment. Fasting homocysteine concentration was significantly lower and that of cysteine higher in subjects with B-12 levels >150pmol/L. The tracer estimated transsulfuration of homocysteine was lower and remethylation higher with B-12 levels >150pmol/L when compared with those <150pmol/L.
Conclusions: The tracer labelled MLT in combination with fasting parameters is a robust way to estimate parameters of methionine metabolism and can be used in the field where prime-constant rate infusion studies cannot be done efficiently.
Competing Interests: The authors have declared that no competing interests exist.
Databáze: MEDLINE
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