13C-methionine breath tests for mitochondrial liver function assessment

Area of Science:

• Hepatology
• Biochemistry
• Medical Diagnostics

Background:

• The 13C-methionine breath test is a non-invasive method for assessing human hepatic mitochondrial function.
• Two forms of 13C-labeled methionine, [methyl-13C]-methionine and L-methionine-1-13C, are used for breath analysis.

Purpose of the Study:

• To compare the efficacy of two differently 13C-labeled methionines in evaluating mitochondrial oxidation.
• To assess performance under basal conditions and after acute oxidative stress induced by ethanol.

Main Methods:

• 15 healthy males ingested [methyl-13C]-methionine, with breath samples collected over 120 minutes.
• After a 48-hour interval, the test was repeated 30 minutes post-ethanol ingestion.
• A week later, subjects underwent the same protocol using L-methionine-1-13C as the substrate.

Main Results:

• Basal conditions: L-methionine-1-13C yielded a higher cumulative 13CO2 recovery (%cum-dose) than [methyl-13C]-methionine (10.25% vs 4.07%, p < 0.01).
• After ethanol ingestion, both methionines showed decreased %cum-dose at 60 and 120 minutes.
• L-methionine-1-13C showed a significantly lower %cum-dose post-ethanol compared to [methyl-13C]-methionine at 120 minutes (5.03% vs 2.16%, p < 0.01).

Conclusions:

• The L-methionine-1-13C breath test appears more reliable for assessing mitochondrial function compared to [methyl-13C]-methionine.
• This enhanced reliability is attributed to a larger amount of labeled carbon reaching the Krebs cycle with L-methionine-1-13C.