Increased intestinal absorption of oleic acid with aging in the rat

Changes in nutrient absorption could be responsible for some of the disorders associated with aging. Oleic acid is the most common dietary fatty acid. Therefore, we investigated its absorption by the small intestine of aging rats in vivo. We used a single pass intestinal perfusion technique to study absorption in animals between 6 and 138 weeks of age. Rats less than 70 weeks of age absorbed 14,000 to 15,000 nmol of oleic acid per 100 cm/hr. In contrast, rats 94 weeks of age or older, absorbed 22,000 to 23,000 nmol of oleic acid per 100cm/hr. The 61% increase in oleic acid absorption as the rats aged correlated with a decrease in the resistance of the unstirred water layer from 0.8 to 0.5 min/cm3/100cm. Concomitantly, the surface area of the unstirred water layer increased from 97.1 to 141.2 cm2/100cm. The changes in unstirred water layer resistance and surface area explain the observed increase in absorption of oleic acid with aging. The increased surface area and decreased resistance of the unstirred water layer are both conducive to increased intestinal absorption of this lipid nutrient as the animals aged.