Published online Jun 7, 2023. doi: 10.3748/wjg.v29.i21.3269
Peer-review started: February 2, 2023
First decision: March 8, 2023
Revised: March 13, 2023
Accepted: May 6, 2023
Article in press: May 6, 2023
Published online: June 7, 2023
The 13C-propionate breath test (PBT) has been studied as a non-invasive diagnostic modality for vitamin B12 (VB12) deficiency by utilizing the role of VB12 as a coenzyme of methylmalonyl-CoA mutase in propionate metabolism. Although alcoholism has been regarded as a risk factor for deficiency, studies on propionate metabolism using the PBT in individuals with alcoholism is limited. Furthermore, conventional PBT requires up to 2 hours of breath collection time, which may undermine its clinical utility.
The scarcity of studies regarding the PBT in alcoholism, and the possibility of improving the clinical utility of the PBT by shortening the breath collection time, motivated us to perform this study.
The aim of this study was to evaluate the change in propionate metabolism due to long-term ethanol consumption in ethanol-fed rats (ERs) as an animal model of chronic alcoholism. We also aimed to evaluate the utility of a faster PBT that requires only 1 hour to collect breath.
The ERs were 18th generation descendants of F344/DuCrj rats that had been bred by replacing standard drinking water with a 16% ethanol solution. A faster PBT was performed by injecting the 13C-propionate aqueous solution from the mouth to the stomach of ERs and control rats (CRs); we collected exhaled gas in bags, and measured the 13CO2/12CO2 isotope ratio using infrared isotope spectrometry. We measured serum VB12 and alanine transaminase (ALT) levels via chemiluminescence immunoassay and the lactate dehydrogenase-ultraviolet method, respectively. We evaluated statistical differences in mean body weight, change in 13CO2 (Δ13CO2‰), peak Δ13CO2‰, and serum VB12 and ALT, between ERs and CRs, and males and females, respectively.
Besides male dominance of body weight (P < 0.001), CRs weighed significantly more than ERs (P < 0.008). The Δ13CO2 reached a peak (Cmax) within 30 min in both sex groups, while males had a significantly higher Cmax and Δ13CO2 at 15-45 min than females (P < 0.05; for all pairs). Enhanced propionate metabolism was observed in male ERs relative to male CRs, and although males had higher serum VB12 levels than females, no prominent differences were observed between the ER and CR groups. Male CRs had notably higher ALT levels than male ERs. These results suggest that chronic ethanol consumption may trigger fatty acid production via intestinal bacteria and changes in gut microbiome composition.
We believe that a faster (1-h) PBT could serve as a substitute for the conventional PBT, as the Δ13CO2 reached a peak (Cmax) within 30 min in both sex groups. We failed to evaluate the usefulness of the faster PBT as a diagnostic modality for VB12 deficiency in the chronic alcoholism rat model; however, our study suggests that instead of inducing alcoholism, chronic consumption of 16% ethanol changed the composition of fatty acids produced by the intestinal flora.
Our study demonstrates the potential utility of the faster PBT as a non-invasive and more convenient modality to evaluate changes in the gut flora associated with ethanol consumption and various other conditions via changes in propionate metabolism.