In theory, the enzymatic digestion and utilization efficiency of starch in the small intestine are high, but the intestinal starch utilization in ruminants is considerably constrained by insufficient pancreatic amylase secretion. Consequently, deciphering the molecular networks regulating pancreatic exocrine physiology in ruminants and identifying key targets that constrain intestinal starch degradation will enable systematic optimization of precision nutritional regimes.

A research team led by Prof. Tan Zhiliang from the Institute of Subtropical Agriculture, Chinese Academy of Sciences, has systematically confirmed the phenomenon of impaired intestinal starch digestion in ruminants, and have identified the low expression of Cholecystokinin B Receptor (CCKBR) in the Acinar Cells is associated with insufficient starch hydrolysis in ruminants.

Using goats as a model, the team established the first-ever single-cell atlas of the caprine pancreas, revealing cell-type-specific molecular signatures. 

Furthermore, the results of scRNA-seq data showed that insufficient starch hydrolysis in adult goats might be associated with low expression of CCKBR in the acinar cells. Cellular functional assays further demonstrated that low expression of CCKBR in caprine pancreatic acinar cells significantly limit digestive enzyme exocytosis. In addition, inadequate amylase activity could be a limiting factor in starch digestion in ruminants. 

Additionally, the low expression of CCKBR in adult goats, in conjunction with a low distribution of CCK-Ⅰ cells in the duodenum, may jointly lead to a slow response of the intestinal-pancreatic reflex and induce an asynchronous process of food entering the small intestine and releasing of digestive enzymes, which ultimately limits the starch digestibility. 

“Our groundbreaking research findings provide novel mechanistic explanations for the insufficient starch hydrolysis in ruminants”, Dr. He Zhixiong, the co-corresponding author of the paper said, “while identifying CCKBR as a potential therapeutic target for enhancing intestinal nutrient utilization in livestock production of ruminants”.

Contact: Tan Zhiliang

E-mail: zltan@isa.ac.cn

Graphical Abstract (Image by Cheng Yan)