FERMENTABLE DIETARY FIBER INCREASES GLP-1 SECRETION AND IMPROVES GLUCOSE-HOMEOSTASIS DESPITE INCREASED INTESTINAL GLUCOSE-TRANSPORT CAPACITY IN HEALTHY DOGS

Ileal proglucagon gene expression and postprandial plasma concentratio ns of proglucagon-derived peptides are reported to change with the typ e and quantity of dietary fiber ingested by rats. Within the intestine , proglucagon encodes several proglucagon-derived peptides known to mo dulate intestinal absorption capacity and pancreatic insulin secretion . To determine whether the chronic ingestion of fermentable dietary fi ber regulates the expression and synthesis of proglucagon-derived pept ides in the distal intestine to modulate glucose homeostasis, the foll owing study was conducted: 16 adult dogs (23 +/- 2 kg) were fed isoene rgetic, isonitrogenous diets containing a mixture of high fermentable dietary fibers (HFF) or low fermentable (LFF) wood cellulose for 14 d in a randomized cross-over design. Food was withheld for 16 h before a n oral glucose tolerance test was conducted supplying 2 g of glucose/k g body wt, and peripheral blood was collected via a hind-leg catheter at 0, 15, 30, 45, 60, 90 and 120 min for plasma glucose, insulin and g lucagon-like peptide-1(7-36)NH, (GLP-1) analyses. Intestinal samples w ere collected after the second dietary treatment. Ileal proglucagon mR NA, intestinal (GLP-1) concentrations and the integrated area under th e curves (AUC) for plasma GLP-1 and insulin were greater and plasma gl ucose AUC was reduced when dogs were fed the HFF diet compared to the LFF diet (P < 0.05). Intestinal villi heights, brush border and basola teral glucose transporter protein abundance and jejunal transport capa cities were significantly greater when dogs were fed the HFF diet than when fed the LFF diet. In conclusion, improvements in glucose homeost asis are observed in healthy dogs when they ingest fermentable fibers.