High fat intake with monounsaturated fatty acids, but not n6 polyunsaturated fatty acid, increases activity of key mitochondrial oxidative enzymes in the heart

Abstract

Evidence suggests that a high fat intake may be beneficial for cardiovascular health, though optimal dietary fatty acid composition is unclear. In this study, we compare the effects of a standard low fat diet (STD, 15% energy from fat) to high fat diets (40% energy from fat) comprised of monounsaturated fat (MUFA, oleate (18:1)), n6 polyunsaturated fat (PUFA, linoleic acid (18:2n6)), or saturated fat (SAT, palmitate and stearate (16:0 and 18:0)). Male rats (n=13–14/group) were fed the STD diet until 16 weeks of age and then assigned to dietary treatment for 15 weeks. Cardiac function was assessed by echocardiography and left ventricle (LV) pressure measurements and was unaffected by diet. Mitochondria were isolated from the LV and show no impact of dietary treatment on mitochondrial yield or respiration with lipid and nonlipid substrates. Mitochondrial oxidative enzyme activity in whole tissue dramatically increased with MUFA compared to STD. Citrate synthase activity increased from 105±15 μmol/g/min in STD to 157±14 in MUFA (P<0.05 vs STD and PUFA), with no significant effect in PUFA (107±9) or SAT (130±11). Similar changes occurred with aconitase and long chain acyl‐CoA dehydrogenase activities. In summary, a high fat diet did not adversely impact cardiac function, increased activity of mitochondrial oxidative enzymes of the TCA cycle and fatty acid oxidation, and did not affect mitochondrial function.