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Estimation of the Metabolic Changes in Short-Chain Fatty Acids Absorbed in the Large Intestine Using The 13C-SCFAs Breath Test: a Review

Tomihiro MIYADA,1,* Kiyoshi MIURA1

1Graduate School of Health Science and Technology,Kawasaki University of Medical Welfare

Short-chain fatty acids (SCFAs),such as acetate,propionate,and n-butyrate,are produced by intestinal bacteria via the metabolization of fermentable substrates. SCFAs are immediately absorbed and consumed as energy; they also provide many benefits to the host. Of note,epigenetic regulation may be related to the beneficial effects of SCFAs. We measured the changes in metabolism and other functions (e.g.,absorption rate) using a 13C-SCFA breath test. Particularly,we monitored the metabolic changes in intracecally infused 13C-SCFAs in rats,based on the notion that the differences in expired 13CO2 may reflect the differences in absorption and post-absorptive metabolism of SCFAs in the large intestine. In addition,we successfully estimated the changes in the propionate pathway breakdown via application of the novel 13CO2 gas analysis in Caenorhabditis elegans after administration of 13C-propionate. Importantly,this analysis in nematodes may contribute to a better understanding of the physiological effects of SCFAs. This review summarizes recent findings on metabolic changes in the context of SCFAs absorbed in the large intestine in humans and other mammals. The effects of epigenetic modulations in gene expression induced by propionate in the context of metabolic pathways in C. elegans are also discussed.
Key Words: short-chain fatty acids,13C breath test,propionate,vitamin B12C. elegans