Senescence-accelerated mouse accumulates dietary triacylglycerols in the intestinal mucosa with aging

Abstract

Conflicting results are obtained with respect to aging-related changes of the absorption and transport of dietary fats. To address this issue, 4-week-old senescence-accelerated mouse (SAMP8) and the resistant strain (SAMR1) were raised on AIN-76 diet containing 5% safflower oil for 1, 3 and 6 months. Apparent fat absorption rate from both strains at all ages examined was greater than 95%. There were no differences in the luminal contents of free fatty acids derived from dietary fats between the strains. There were no strain differences in the mucosal triacylglycerol contents from 2-month-old mice. However, those from the 4- and 7-month-old SAMP8 were 1.5- to 5-fold greater than from the corresponding SAMR1. The triacylglycerol accumulation was mainly seen in the lower half of the intestine, but it was also observed in the upper as well as lower parts from 7-month-old SAMP8. Electron microscopic observation revealed a lot of lipid droplets in the trans-Golgi area of the enterocytes from 7-month-old SAMP8. When mice were treated with Triton WR 1339 prior to administration of [ 3H] triolein, an accumulation of the radioactive lipids in the serum from SAMP8 was less than half of that from SAMR1. These results demonstrate that SAMP8 exhibits an age-related defect in secretion of diet-derived fats from the enterocytes.