Study on efficient metabolism mechanism of starch in the intestine of carnivorous fish: A case of Monopterus albus

An efficient metabolism of mammals in the intestine is a crucial factor in their dietary starch utilization. Swamp eel (Monopterus albus), a carnivorous fish, has shown a remarkable ability to utilize dietary starch efficiently. However, the specific mechanisms underlying this efficient starch metabolism in the intestine remain poorly understood. Thus, we conducted a study in which juvenile swamp eels (average weight: 12.10 ± 0.03 g) were fed diets with two different starch levels (20 % -NF and 32 % -HF) for a period of 56 days. Subsequently, the intestine and digesta were extracted for analysis. This study showed that there was no significant variety on the activity of digestive enzyme and histological structure in anterior intestine of fish between HF group and NF group. However, HF diets down-regulated the expression of all differentially expressed genes of glycine--tRNA ligase concerned to damage in the most significantly enriched GO function of glycyl-tRNA aminoacylation. Besides, the HF diets significantly increased the genus of Cetobacterium with the function of producing acetic acid. Consistently, the HF diets significantly increased the concentration of short chain fatty acids (SCFA), particularly acetic acid, in the posterior intestine digesta of swamp eel. In summary, our study argued that the enhanced efficiency in utilizing dietary starch by the swamp eel might be attributed to the increased abundance of Cetobacterium and the subsequent production of acetic acid in the posterior intestine.