INSULIN, GLUCAGON-LIKE PEPTIDE-1, GLUCOSE-DEPENDENT INSULINOTROPIC POLYPEPTIDE AND INSULIN-LIKE-GROWTH-FACTOR-I AS PUTATIVE MEDIATORS OF THE HYPOLIPIDEMIC EFFECT OF OLIGOFRUCTOSE IN RATS

The addition of oligofructose as a dietary fiber decreases the serum c oncentration and the hepatic release of VLDL-triglycerides in rats. Be cause glucose, insulin, insulin-like growth factor I (IGF-I) and gut p eptides [i.e., glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)]) are factors involved in the metaboli c response to nutrients, this paper analyzes their putative role in th e hypolipidemic effect of oligofructose. Male Wistar rats were fed a n onpurified diet with or without 10% oligofructose for 30 d. Glucose, i nsulin, IGF-I and GIP concentrations were measured in the serum of rat s after eating. GIP and GLP-1 contents were also assayed in small inte stine and cecal extracts, respectively. A glucose tolerance test was p erformed in food-deprived rats, Serum insulin level was significantly lower in oligofructose-fed rats both after eating and in the glucose t olerance test, whereas glycemia was lower only in the postprandial sta te. IGF-I serum level did not differ between groups. GIP concentration was significantly higher in the serum of oligofructose-fed rats. The GLP-1 cecal pool was also significantly higher. In this study, we have shown that cecal proliferation induced by oligofructose leads to an i ncrease in GLP-1 concentration. This latter incretin could be involved in the maintenance of glycemia despite a lower insulinemia in the glu cose tolerance test in oligofructose-fed rats. We discuss also the rol e of hormonal changes in the antilipogenic effect of oligofructose.