EFFECT OF DIETARY-FAT CONTENT ON MICROVILLUS IN RAT JEJUNUM

To examine whether dietary manipulation of isoenergic diets might affect microvillar structure of small intestinal epithelial cells, morphological parameters of enterocytes and microvilli in the mid-villus portion of jejunum were determined in the rats fed either high-starch (70 energy%), low-fat (7 energy%) diet or high-fat (73 energy%), low-starch (5 energy%) diet for 7 days. Feeding the high-fat diet produced an increase in the height of villus, in accordance with the elevated jejunal mucosal weight and total protein contents as compared with the high-starch diet. No appreciable change in crypt depth occurred. Scanning electron microscopy of jejunal epithelial cells revealed that the morphometrical parameters of the villus cells were unchanged by the diets, but the microvillar structure of each villus cell was influenced by the diets; the animals fed the high-fat diet exhibited a reduced length (28%) of microvillus with a slight increase (12%) in diameter, showing a significantly reduced surface area of microvilli per enterocyte. The reduction in microvillar surface area of animals fed the high-fat diet was accompanied by the decrease in total proteins of the brush border membranes as well as the decrease in the activities of microvillar stalked disaccharidases, i.e., sucrase-isomaltase and lactase. These results provide an evidence that dietary manipulation, even when diets are ''complete'' in terms of the content of energy, protein, and other micronutrients, can modify the microvillar structure of small intestinal epithelial cells, leading to alterations in the digestive/absorptive surface area of villus cells.