Proglucagon messenger ribonucleic acid and intestinal glucose uptake are modulated by fermentable fiber and food intake in diabetic rats

Diabetes is characterized by hyperphagia and increased absorption of nutrients from the small intestine coupled with inadequate insulin secretion. Ingestion of fermentable fiber by non-diabetic rats is associated with increased intestinal proglucagon mRNA and greater postprandial release of glucagon-like peptide (GLP-1). To determine if food intake and fiber fermentability had similar effects on intestinal proglucagon mRNA in diabetic rats, diets containing cellulose (CEL) or rhubarb (RH) were fed to streptozotocin-diabetic Sprague-Dawley rats (Sz-SD), Sz-SD pair-fed to non-diabetic SD controls, and BE diabetic rats (10/treatment) for 14d. Jejunal, ileal and colonic weights were significantly affected by food intake and ileal weight was greater in RH-fed rats. ileal and colonic proglucagon mRNA abundance's were greater in GEL-fed vs. RH-fed rats regardless of food intake and opposite to that observed in non-diabetic rats (1). Diet did not affect intestinal glucose uptakes in vitro except for increased ileal uptake in pair-fed rats eating GEL vs. RH. Jejunal mRNA abundance's for glucose transporters SGLT-1 and GLUT2 were greater in ad lib-fed rats and in RH vs. GEL-fed rats. This study confirms reports that jejunal glucose transport capacity is positively correlated with food intake. Proglucagon gene expression in diabetic rats responds to fermentable fiber but differs from that determined in non-diabetic rats. (C) 2000 Elsevier Science Inc.