Lactoferrin potentially facilitates glucose regulation and enhances the incretin effect

Lactoferrin (Lf) is known for its physiologically pleiotropic properties. In this study, we investigated whether Lf affects glycemic regulation, including glucose absorption from the small intestine. Bovine Lf (bLf, 100 mg/kg body mass) was administered to rats by intraperitoneal injection before intravenous (intravenous glucose tolerance test, IVGTT) or oral glucose administration (oral glucose tolerance test, OGTT). With IVGTT, bLf pretreatment had no significant effect on plasma levels of glucose or insulin. With OGTT, the bLf treatment group tended to show lower plasma levels of glucose than the control group at and after the 15 min peak, and decreased levels of plasma glucose at 180 min. The change in plasma levels of insulin from 0 to 30 min was higher in the bLf treatment group than in the control group. Total plasma glucose-dependent insulinotropic polypeptide (GIP) was lowered at 60 min by the bLf treatment, while an immediate increase in total plasma glucagon-like peptide-1 (GLP-1) was observed within the bLf group undergoing OGTT. In addition, bLf was associated with an increase in the amount of glucose absorbed into the everted jejunum sac. These results suggest that Lf could suppress hyperglycemia, accompanied by elevated plasma levels of insulin via transiently accelerating GLP-1 secretion, and that Lf even enhances glucose absorption from the small intestine.