Effect of transglutaminase cross-linking on the in vivo digestion and absorption characteristics of collagen gel

Abstract

This work was conducted to prepare the transglutaminase (TGase) cross-linked collagen gel (CGL) by using pork skin as raw material, and to systematically investigate its digestive and absorptive properties and serum metabolism regulation in mice. The analysis of peptidomics revealed that CGL exhibited a lower average molecular weight of peptides (803.78 Da) and a higher proportion of small molecular peptides (11.22% of < 500 Da) in the gastric digestion stage, indicating that the crosslinked structure significantly enhanced the hydrolysis efficiency of pepsin. After entering the small intestine, the proportion of small peptides (< 500 Da) in the CGL group decreased compared to the gastric stage, and the number of small peptides in the CGL group decreased compared to the collagen sol (CSL) group, indicating that small peptides in the CGL group were rapidly absorbed in the small intestine stage. Meanwhile, the proportion of peptides in the 500–1000 Da range in the CGL group (53.42%) was higher than that in the CSL group (35.50%), suggesting that intestinal proteases can continuously degrade the large-molecule peptides in the CGL group. This also resulted in the CGL group maintaining a high number of characteristic peptides (161 unique peptides) in the cecum stage. The serum analysis revealed obviously increased collagen peptide counts (205 peptides) and hydroxyproline peptide ratios (93.66%) in the CGL group, with specific peptide segments primarily originating from the cross-linking active sites (Lys644, Gln972). These findings confirm the absorption advantage of the CGL group. In addition, CGL optimized the amino acid absorption pattern by cross-linking modification while maintaining the basic nutritional properties of collagen. The metabolomics results showed that CGL regulated key metabolic pathways such as steroid hormone synthesis, glutathione metabolism and tryptophan metabolic pathway. This study reveals the progressive “gastric degradation - intestinal absorption” mechanism of crosslinked collagen gel. Its unique peptide release pattern and metabolic regulation provide a theoretical basis for developing functional collagen-based products targeting intestinal absorption.

Graphical Abstract