Aims: 

Biomarkers are important tools for an understanding of physiological processes or the evaluation of pharmacological responses to therapy, and in this sense, mammalian methanogenesis was earlier considered to be an exclusive indicator of carbohydrate fermentation by the anaerobic gastrointestinal flora. This commonly held notion, however, was challenged when in vitro and in vivo studies revealed the possibility of non-microbial methane formation in anoxic mitochondria and eukaryote cells, in both plants and animals (FASEB J 2003, Plant Cell Environ 2011). In line with this, we have suggested that the methyl groups of the ubiquitous phosphatidylcholine molecule are potential electron acceptors after temporary oxygen deprivation, and in consequence of this, methane may be liberated.

Methods: 

We have investigated this possibility at four experimental levels: (1) in model chemical reactions with choline and its metabolites in the presence of hypoxia and oxygen radical generation, (2) in rat liver mitochondria and mitochondrial subfractions under hypoxic conditions, (3) in endothelial cell cultures with or without oxygen, and (4) in vivo, in experimental animal models of vascular occlusion and reperfusion.

Results: 

Significant methane generation was demonstrated in all four series of experiments (Cell Physiol Biochem 2008; Shock 2008; Environ Chem 2009).

Conclusion: 

Collectively, these results are suggesting that methane generation is a consequence of transient oxygen deprivation in aerobic cells. In this respect, the next question to be answered is whether non-bacterial methane generation is solely a by-product of hypoxia-induced degradation of biomolecules, or it plays a more general role.