Validation of bovine glycomacropeptide as an intestinal anti-inflammatory nutraceutical in the lymphocyte-transfer model of colitis

Abstract

Milk κ-casein-derived bovine glycomacropeptide (GMP) exerts immunomodulatory effects. It exhibits intestinal anti-inflammatory activity in chemically induced models of colitis. However, to validate its clinical usefulness as a nutraceutical, it is important to assess its effects in a model with a closer pathophysiological connection with human inflammatory bowel disease. Therefore, in the present study, we used the lymphocyte-transfer model of colitis in mice and compared the effects of GMP in this model with those obtained in the dextran sulphate sodium (DSS) model. GMP (15 mg/d) resulted in higher body-weight gain and a reduction of the colonic damage score and myeloperoxidase (MPO) activity in Rag1(-/-) mice with colitis induced by the transfer of naïve T cells. The colonic and ileal weight:length ratio was decreased by approximately 25%, albeit non-significantly. GMP treatment reduced the percentage of CD4⁺ interferon (IFN)-γ⁺ cells in mesenteric lymph nodes (MLN). The basal production of IL-6 by MLN obtained from the GMP-treated mice ex vivo was augmented. However, concanavalin A-evoked production was similar. The colonic expression of regenerating islet-derived protein 3γ, S100A8, chemokine (C-X-C motif) ligand 1 and IL-1β was unaffected by GMP, while that of TNF-α and especially IFN-γ was paradoxically increased. In the DSS model, GMP also reduced the activity of colonic MPO, but it failed to alter weight gain or intestinal weight:length ratio. GMP augmented the production of IL-10 by MLN cells and was neutral towards other cytokines, except exhibiting a trend towards increasing the production of IL-6. The lower effect was attributed to the lack of the effect of GMP on epithelial cells. In conclusion, GMP exerts intestinal anti-inflammatory effects in lymphocyte-driven colitis.