Proglucagon and glucose transporter mRNA is altered by diet and disease susceptibility in 30-day-old biobreeding (BB) diabetes-prone and normal rats

Modulation of glucagon-like peptide 1 and energy metabolism by inulin and oligofructose: experimental data

Inulin-type fructans have been tested for their capacity to modulate lipid and glucose metabolism in several animal models. Oligofructose (OFS) decreases food intake, fat mass development, and hepatic steatosis in normal and in obese rats; moreover, it exerts an antidiabetic effect in streptozotocin-treated rats and high-fat-fed mice. In most cases, the beneficial effects of OFS are linked to an increase of glucagon-like peptide-1 (GLP-1) level in the portal vein and of GLP-1 and proglucagon mRNA, its precursor, in the proximal colon. In this organ, OFS increases the number of GLP-1-positive L cells by promoting factors (Neurogenin 3 and NeuroD) involved in the differentiation of stem cells into L cells. The chronic administration of GLP-1 receptor antagonist exendin 9-39 totally prevents the beneficial effects of OFS (improved glucose tolerance, fasting blood glucose, glucose-stimulated insulin secretion, insulin-sensitive hepatic glucose production, and reduced body weight gain). Furthermore GLP-1 receptor knockout mice are completely insensitive to the antidiabetic actions of OFS. These findings highlight the potential interest of enhancing endogenous GLP-1 secretion by inulin-type fructans for the prevention/treatment of obesity and type 2 diabetes. Moreover, OFS is also able to modulate other gastrointestinal peptides (such as PYY and ghrelin) that could be involved in the control of food intake. Several studies in humans already support interest in OFS in the control of satiety, triglyceridemia, or steatohepatitis. The link with gut peptides production in humans remains to be proven.

Diabetes-prone BioBreeding rats do not have a normal immune response when weaned to a diet containing fermentable fibre

Diet is known to modulate the development of diabetes in diabetes-prone BioBreeding (BBdp) rats. The objective of the present study was to determine the effect of fermentable fibre (FF) on immune function in BBdp and diabetes-resistant BioBreeding (BBdr) rats after weaning. Weanling BBdp (thirty-six to thirty-eight per diet) and BBdr rats (thirty to thirty-two per diet) were fed a nutritionally complete, semi-purified, casein-based diet containing either cellulose (control diet, 8 % w/w) or FF (3·2 % cellulose+4·8 % w/w inulin). At 35 d, the small intestine was excised and lymphocytes isolated from spleen, mesenteric lymph nodes and Peyer's patches. Feeding FF to both BBdr and BBdp rats affected the production of anti-inflammatory cytokines (P=0·02). In BBdr rats, feeding FF compared with cellulose resulted in an increased small intestinal length (P=0·0031), higher proliferative (stimulation) index from both splenocytes (P=0·001) and mesenteric lymph nodes (P=0·04), and an increased proportion of CD8+ T-cells in the Peyer's patches (P=0·003). We did not observe an effect of diet on the number of IgA-bearing cells in the jejunum from BBdr rats. Feeding FF to BBdp rats did not affect the same parameters. BBdp rats had both a higher proportion of B-cells in the Peyer's patches (P=0·01) and a higher number of IgA+ cells in the jejunum (P=0·0036) when fed a diet containing FF, a response not observed in BBdr rats. We demonstrate that several aspects of the BBdp immune system respond differently than that of BBdr rats when challenged at weaning with FF.

Relation between colonic proglucagon expression and metabolic response to oligofructose in high fat diet-fed mice

Several data suggest that fermentable dietary fiber could play a role in the control of obesity and associated metabolic disorders. The aim of this study was to investigate the putative role of short chain fructo-oligosaccharide (OFS) - a non-digestible oligosaccharide - in mice fed a standard diet and in mice fed two distinct high fat diets inducing metabolic disorders associated to obesity. We confirmed, in mice, several effects previously shown in rats fed a standard diet enriched with OFS, namely an increase in total and empty caecum weight, a significant decrease in epididymal fat mass, and an increase in colonic and portal plasma glucagon-like peptide-1 (GLP-1), a phenomenon positively correlated with a higher colonic proglucagon mRNA level. Curiously, 4-week treatment with OFS added at the same dose induced different effects when added in the two different high fat diets. OFS decreased energy intake, body weight gain, glycemia, and epididymal fat mass only when added together with the high fat-carbohydrate free diet, in which OFS promoted colonic proglucagon expression and insulin secretion. Our results support an association between the increase in proglucagon expression in the proximal colon and OFS effects on glycemia, fat mass development, and/or body weight gain. In conclusion, dietary oligosaccharides would constitute an interesting class of dietary fibers promoting, in certain conditions, endogenous GLP-1 production, with beneficial physiological consequences. This remains to be proven in human studies.

Ontogeny of intestinal nutrient transport

Children born prematurely lack the ability to digest and to absorb nutrients at rates compatible with their nutritional needs. As a result, total parenteral nutrition may need to be given. While this nutritional support may be life-saving, the baby who receives this therapy is exposed to the risks of possible sepsis, catheter dysfunction, and liver disease. The rodent model of postnatal development provides a useful framework to investigate some of the cellular features of human intestinal development. The up-regulation of intestinal gene expression and precocious development of intestinal nutrient absorption can be achieved by providing growth factor(s) or by modifying the composition of the maternal diet during pregnancy and nursing or the weaning diet of the infant. Accelerating the digestive and absorptive functions of the intestine would thereby allow for the maintenance of infant nutrition through oral food intake, and might possibly eliminate the need for, and risks of, total parenteral nutrition. Accordingly, this review was undertaken to focus on the adaptive processes available to the intestine, to identify what might be the signals for and mechanisms of the modified nutrient absorption, and to speculate on approaches that need to be studied as means to possibly accelerate the adaptive processes in ways which would be beneficial to the newborn young.Key words: absorption, adaptation, diet, peptides.