Increased Amino Acid Absorption Mediated by Lacticaseibacillus rhamnosus IDCC 3201 in High-Protein Diet-Fed Mice

Abstract

The use of dietary protein products has increased with interests in health promotion, and demand for sports supplements. Among various protein sources, milk protein is one of the most widely employed, given its economic and nutritional advantages. However, recent studies have revealed that milk protein undergoes fecal excretion without complete hydrolysis in the intestines. To increase protein digestibility, heating and drying were implemented; however, these methods reduce protein quality by causing denaturation, aggregation, and chemical modification of amino acids. In the present study, we observed that Lacticaseibacillus rhamnosus IDCC 3201 actively secretes proteases that hydrolyze milk proteins. Furthermore, we showed that co-administration of milk proteins and L. rhamnosus IDCC 3201 increased the digestibility and plasma concentrations of amino acids in a high-protein diet mouse model. Thus, food supplementation of L. rhamnosus IDCC 3201 can be an alternative strategy to increase the digestibility of proteins.

Keywords: Lacticaseibacillus rhamnosus; Probiotics; high-protein diet; milk protein; proteolysis.

Fig. 1. Proteolytic activity of Lacticaseibacillus rhamnosus IDCC 3201, Streptococcus thermophilus IDCC 2201, and Enterococcus faecium IDCC 2102 in pea protein and skim milk agar medium.

(A) One representative clear zone data set for three independent experiments. (B) Each value is an average of triplicate experiments with data presented as mean ± standard deviation (SD). (*, p < 0.05; **, p < 0.01 vs. L. rhamnosus IDCC 3201 in pea protein and ##, p < 0.01 vs. L. rhamnosus IDCC 3201 in skim milk).

Fig. 2. Mouse experiment co-administering a high-protein diet with Lacticaseibacillus rhamnosus IDCC 3201.

Fig. 3. Seven amino acids as serum biomarkers for amino acid absorption in the high protein diet mouse model treated with Lacticaseibacillus rhamnosus IDCC 3201.

The concentration of 7 amino acids in serum after HPD diet treatment or L. rhamnosus IDCC 3201 administration. ND: Normal diet group; HPD: High-protein diet group; HPD + L. rhamnosus IDCC 3201 (HPD + LLrh; 5×10⁷ CFU/day); HPD + L. rhamnosus IDCC 3201 (HPD + HLrh; 5×10⁸ CFU/day). Data values are expressed as mean ± standard deviation (SD). (*, p < 0.05; **, p < 0.01; ***, p < 0.001).