Importance of colonic bacterial fermentation in short bowel patients - Small intestinal malabsorption of easily digestible carbohydrate

The small intestine's large capacity for glucose absorption and for adaptat ion seems to contradict the reported importance of carbohydrate malabsorpti on in short bowel (SB) patients. The aim of the present study was to invest igate the occurrence of malabsorption in these patients ingesting realistic amounts of carbohydrates. We performed a dose-response study [ingestion of increasing amounts of glucose glucose and complex carbohydrates (boiled ri ce and wheat bread), and the nonabsorbable disaccharide lactulose] in SE pa tients with an intact colon. The hydrogen (H-2) -breath test and changes in serum acetate were used to evaluate colonic fermentation and, thus, indire ctly, the lack of small intestinal carbohydrate assimilation. Blood glucose and plasma insulin were measured to evaluate absorption. Plasma concentrat ions of the ileal brake hormones-glucagon-like peptide-1 (GLP-1) and peptid e tyrosine tyrosine (PYY)-were measured to test whether release of these ho rmones was related to colonic fermentation. Significant amounts of 25 g and 50 g glucose, and of the bread and rice meals were fermented rather than a bsorbed, as judged by the increases in end-expiratory H-2. Serum acetate co ncentrations were significantly higher in SE patients than in healthy contr ols. The orocecal transit times of all test meals ranged from 15 to 120 min . GLP-1 and PYY releases in SE patients were significantly higher than in h ealthy volunteers. They were mutually parallel and paralleled the increase in insulin. They were not related to ongoing fermentation or to intralumina l carbohydrate content per se, but most. probably to absorption of glucose in the distal bowel, In conclusion, well-adapted SE patients had pronounced small intestinal malabsorption of carbohydrate, even after ingestion of sm all amounts of easily absorbable carbohydrates. A fast small intestinal spr eading of carbohydrates, once in the small intestine, and a spill-over to t he colon seem to explain the data best.