Effect of high percentage medium-chain triglyceride diet on mucosal adaptation following massive bowel resection in rats.

Patients undergoing massive small bowel resection for a variety of conditions develop severe nutrient malabsorption which gradually improves through mucosal hyperplasia in the remaining small intestine. Following massive small bowel resection, patients are generally fed elemental diets, often containing high concentrations of medium-chain triglycerides. We evaluated the effect of high percentage medium-chain triglyceride feeding on mucosal adaptation following massive small bowel resection in rats. Twenty 150-g Sprague-Dawley rats were subjected to 60% jejunoileal resection. Another 20 animals received sham operations. One-half of each group were fed a diet containing 83% of the fat as medium-chain triglycerides, the remainder were fed a diet containing 40% medium-chain triglycerides. Animals were pair-fed for 2 wk and subsequently killed. The remaining bowel was removed and unidirectional glucose and leucine uptake were measured using isolated sacs. Mucosal wet weight, protein, and sucrase content were determined. Animals fed medium-chain triglycerides demonstrated decreased mucosal weight in the proximal bowel, decreased mucosal sucrase activity in the proximal bowel, and decreased mucosal leucine uptake in the distal bowel. While medium-chain triglycerides offer an advantage to patients with short bowel syndrome because they are easily absorbed, they may not stimulate the same degree of mucosal adaptation following resection as long-chain triglyceride feedings.

Effect of casein versus casein hydrolysate on mucosal adaptation following massive bowel resection in infant rats.

Little is known concerning the effects of elemental diets on bowel adaptation following massive resection. Fourteen of 28 Sprague-Dawley rats (40-45 g) were subjected to a 60% jejunoileal resection. Seven of the resected animals and seven sham-operated controls were then placed on a diet containing all protein in the form of casein hydrolysate. The remaining seven resected animals and seven sham-operated controls were placed on a comparable diet in which all the protein was casein. Each control animal was paired with a resected animal. After 2 weeks, unidirectional glucose and leucine transport was determined from intestinal sacs made from the proximal 3 cm and distal 3 cm of the remaining bowel. The midportion was used for the determination of mucosal weight and protein and sucrase content. When expressed as a percent increase over control values per centimeter of bowel, only sucrase levels were significantly elevated in the distal bowel in casein hydrolysate-versus casein-fed animals. The mucosal protein level, mucosal weight, and glucose uptake did not differ from control values when expressed as a percent change. Leucine uptake was significantly decreased in casein hydrolysate-fed animals when compared to that in casein-fed animals in both the proximal and distal bowel, again when expressed as a percent change from the control values. The administration of protein in the form of casein hydrolysate following massive bowel resection does not adversely affect mucosal hyperplasia occurring after resection but may have an adverse effect on the enhancement of amino acid absorption.

Potential for mucosal adaptation following massive small bowel resection in 3-week-old versus 8-week-old rats.

In order to determine the relative capacity for bowel adaptation in young versus older rats, 60% bowel resections were performed in seven 3-week-old and seven 8-week-old rats. These animals were then pair-fed with control animals that had undergone sham operations, and after 2 weeks, all animals were killed. Segments of remaining jejunum, midileum, and distal ileum were removed, and mucosa was scraped free using a glass slide. Mucosal wet weight, protein, RNA, DNA, and sucrase content were measured. Data were expressed as percent increase of each mucosal parameter in resected as opposed to control animals, and the two age groups were compared by unpaired t test. When data were examined per centimeter of bowel, increases in all parameters in each segment were substantially greater in the older animals, suggesting that older animals have a greater capacity for mucosal adaptation following massive bowel resection than do young animals. These findings correlate well with clinical experience which suggests that infants with massive bowel resection may require years of parenteral nutrition before total enteral nutrition is possible.