Effects of fasting and refeeding on jejunal morphology and cellular activity in rats in relation to depletion of body stores

Background: Intestinal mucosa atrophy following a period of starvation characterized by the mobilization of fat stores for energy expenditure ( phase II) worsen after a long fast marked by an increase in protein catabolism ( phase III). However, the morphology of the jejunum is completely restored after 3 days of refeeding. The aim of this study was to determine the mechanisms involved in the rapid jejunal restoration following the critical phase III. Methods: Jejunal structure was observed through conventional and environmental scanning electron microscopy, whilst cellular dynamics were studied using classical optic microscopy tools and immunohistochemistry. Results: Mucosal structural atrophy during fasting proved to worsen over the two phases. During phase II, apoptosis is still present at the tip of the villi, the number of mitosis in crypts showed a 30% decrease and a transient drop in cell migration is observed. During phase III, however, an 85% rise in mitosis was noticed along with an increase in cell migration and the disappearance of apoptotic cells at the villus tips. This increased cell renewal continues after food ingestion. Conclusions: Starved rats appeared to be in a phase of energy sparing in phase II, with depressed cellular events in the intestinal mucosa. In phase III, however, the preservation of functional cells and the early increase in crypt cell proliferation should prepare the mucosa to refeeding and could explain why jejunal repairs are complete after 3 days of refeeding following either phase II or phase III.