ELEVATION OF THE MITOCHONDRIAL OXIDATIVE ACTIVITY OF RAT-LIVER BY LONG-TERM INTAKE OF A HIGH-FAT DIET BASED ON BEEF TALLOW OR SAFFLOWER OIL

Using rats we examined the effects on liver mitochondrial functions of the long-term intake of a high-fat diet based on beef tallow or saffl ower oil. Forty-eight rats were divided into three dietary groups: a l ow-fat diet group and two high-fat ones (beef tallow and safflower oil ). The low-fat diet provided 7, 73, and 20% of the total energy as fat , carbohydrate, and protein, respectively; and two high-fat diets, 45, 35, and 20% of energy, respectively. Rats were isoenergetically fed t he appropriate diet for 4 months. The state-3 respiration of the mitoc hondria was significantly higher in the two high-fat diet groups than in the low-fat diet group, when both succinate and beta-hydroxybutyrat e were used as substrates for the respiration. However, there was no d ifference between the two high-fat diet groups. The groups were ranked in terms of cytochrome a content in their mitochondria as follows: lo w-fat diet group < beef tallow diet group < safflower oil diet group. The citrate synthase activity of the liver was also significantly high er in the two high-fat diet groups than in the low-fat one, but no dif ference was obtained between the two former. However, the mitochondria l DNA concentration in liver was not different among the three dietary groups, From these results, we conclude that long-term intake of high -fat diets increases the oxidative activity of liver mitochondria and that differences in the type of dietary fatty acids do not markedly al ter mitochondrial functions.