Biochemical basis of oligofructose-induced hypolipidemia in animal models.

Oligofructose (OFS), a mixture of nondigestible/fermentable fructooligosaccharides, decreases serum triacylglycerol (TAG) when it is included in the standard, fiber-free or high fat diet of rats. This paper summarizes in vivo and in vitro data to establish a biochemical mechanism underlying the hypolipidemic effect of OFS. When OFS is added to the standard (carbohydrate-rich) diet of rats at the dose of 10 g/100 g, a TAG-lowering action occurs as a consequence of a reduction of de novo liver fatty acid synthesis. The depression in the activity of all lipogenic enzymes and fatty acid synthase mRNA suggests that OFS modifies the gene expression of lipogenic enzymes. Through its modulation of de novo lipogenesis, OFS can protect against liver lipid accumulation induced by providing 10% fructose-enriched water for 48 h. OFS also significantly decreases serum insulin and glucose, which are both known to participate in the nutritional regulation of lipogenesis. It also increases the intestinal production of incretins, namely, glucose-dependent insulinotropic peptide and glucagon-like peptide 1. This latter phenomenon results mainly from promotion of intestinal tissue proliferation by oligofructose fermentation end-products. Collectively, a link likely exists between the modulation of hormone and incretin production by OFS, and its antilipogenic effect.

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 concentration and the hepatic release of VLDL-triglycerides in rats. Because glucose, insulin, insulin-like growth factor I (IGF-I) and gut peptides [i.e., glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)]) are factors involved in the metabolic response to nutrients, this paper analyzes their putative role in the hypolipidemic effect of oligofructose. Male Wistar rats were fed a nonpurified diet with or without 10% oligofructose for 30 d. Glucose, insulin, IGF-I and GIP concentrations were measured in the serum of rats after eating. GIP and GLP-1 contents were also assayed in small intestine and cecal extracts, respectively. A glucose tolerance test was performed in food-deprived rats. Serum insulin level was significantly lower in oligofructose-fed rats both after eating and in the glucose tolerance test, whereas glycemia was lower only in the postprandial state. 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 increase in GLP-1 concentration. This latter incretin could be involved in the maintenance of glycemia despite a lower insulinemia in the glucose tolerance test in oligofructose-fed rats. We discuss also the role of hormonal changes in the antilipogenic effect of oligofructose.

Oligofructose modulates lipid metabolism alterations induced by a fat-rich diet in rats.

The aim of this study was to test the hypothesis that non-digestible fructans, namely oligofructose (OFS), are able to decrease post-prandial lipaemia in rats fed a high-fat diet composed of 10% lard, 4% corn oil and 0.15% cholesterol. Male Wistar rats were divided into three groups: group 1 was fed a standard low-fat diet (AO4), group 2 received the high-fat diet (HF) and group 3 received 10% (w/w) OFS in the HF diet (HF-OFS) for 3 weeks. The OFS supplementation reduced post-prandial triglyceridaemia by more than 50%, compared to both AO4 and HF groups. It also protected rats against the increase in free cholesterol serum level induced by the HF diet. The OFS did not prevent the HF-induced hepatic accumulation of triglycerides, phospholipids and cholesterol; however, histochemical analysis showed smaller lipid droplets in the liver of HF-OFS rats as compared to HF rats. Our results suggest that, when given in HF diet, OFS decreases serum triglycerides through an extra-hepatic event, namely by enhancing triglyceride-rich lipoprotein catabolism.