Absorption and metabolism of lipids in rats depend on fatty acid isomeric position

This study determined the effect of dietary (dipalmitoyl) triacylglycerol (TAG) structure on the absorption and metabolism of fat in the presence or absence of cholesterol. Sprague-Dawley male rats weighing ∼180 g were fed diets containing 10 g/100 g diet 1,3-dipalmitoyl-2-oleoyl-glycerol-rich oil (POP) or 1(3),2-dipalmitoyl-3(1)-oleoyl-glycerol-rich oil (PPO), either with or without cholesterol supplementation (0.5 g/100 g diet), for 2 wk. There were no differences in the growth of rats fed the various diets. The apparent absorption efficiency of dietary fat especially the apparent absorption efficiency of palmitic acid, was significantly lower in the POP groups than in the groups fed the PPO diets. The excretion of cholesterol in feces of rats fed the POP diet with cholesterol was significantly greater than those fed the PPO diet containing cholesterol. The excretion of total bile acids in the rats fed cholesterol was significantly greater than in those fed the diets without cholesterol. Liver cholesterol was significantly greater in rats fed cholesterol and was not affected by the TAG structure. Plasma cholesterol was significantly lower in the POP dietary groups than in the PPO groups. These results suggest that the absorption and metabolism of fat depend on the positional isomer of the fatty acid.