In this study,
milk protein casein was glycated by
oligochitosan through the catalysis of
transglutaminase (TGase) and then hydrolyzed by
trypsin. The obtained glycated
casein hydrolysates (GCNH) were assessed for their anti-inflammatory activities, using the
lipopolysaccharide (LPS)-stimulated rat intestinal epithelial cells (IEC-6) as cell models and the
casein hydrolysates (CNH) without TGase catalysis as controls. The results showed that GCNH had
oligochitosan incorporation and thus possessed a
glucosamine content of 5.74 g/kg
protein. In general, GCNH at dose levels of 25-100 μg/mL could elevate IEC-6 cell growth, and at dose levels of 25-50 μg/mL, they were also able to alleviate the LPS-induced cytotoxicity by increasing cell viability efficiently. Although LPS caused clear
inflammation in the LPS-stimulated cells, GCNH were capable of reducing the secretion of three pro-inflammatory mediators including interleukin-1β (IL-1β),
IL-6, and
tumor necrosis factor-α, or promoting the secretion of two anti-inflammatory mediators like
IL-10 and
transforming growth factor-β, demonstrating their anti-inflammatory activities to the stimulated cells. Moreover, GCNH also could down-regulate the expression of three
inflammation-related
proteins including TLR4, p-p38, and p-p65 in the stimulated cells, and thus possessed a capacity to suppress the phosphorylation of p38 and p65
proteins as well as to inactivate the NF-κB and MAPK signaling pathways. Additionally, a higher GCNH dose level consistently led to higher anti-inflammatory effect in the cells, while GCNH were always more potent than CNH at performing anti-inflammatory function targets. It is thus suggested that the TGase-catalyzed
casein oligochitosan-glycation could enhance the anti-inflammatory activities of
casein hydrolysates efficiently. TGase-catalyzed protein glycation thus might enhance the healthcare function of
protein ingredients in the body.