COMPARISON OF THE MODULATORY INFLUENCE OF MAIZE AND OLIVE OILS AND BUTTER ON METABOLIC RESPONSES TO ENDOTOXIN IN RATS

1. n-3 polyunsaturated fatty acids decrease responses to cytokines and inflammatory agents, The present study examines how different intakes of n-6 and n-9 fatty acids influence the metabolic response to endoto xin in Wistar rats. 2. Weanling male rats were, for 4 weeks, fed diets containing 50, 100 or 200 g/kg fat in the form of maize oil (rich in linoleic acid), butter (poor in linoleic acid, rich in oleic acid) or olive oil (adequate in linoleic acid, rich in oleic acid) or standard laboratory chow. All butter and olive oil diets included 10 g/kg maize oil, in total fat, to avoid essential fatty acid deficiency. 3. Rats subsequently received 800 mu g/kg Escherichia coli endotoxin or steril e saline subcutaneously. Twenty-four hours after injection, the rate o f tissue protein synthesis was measured in liver, lung, kidney, tibial is muscle and spleen by the 'flooding dose' method. Protein and zinc c oncentrations were assayed in all tissues and serum albumin and caerul oplasmin measured. 4. In animals fed chow, protein synthetic rate incr eased by 18%, 29% and 27% in liver, lung and kidney respectively. Tiss ue zinc concentrations increased by 33% in kidney, and tissue protein increased by 17%, 23% and 17% in liver, lung and kidney respectively. Serum caeruloplasmin increased by 60% and albumin concentration fell b y 14%. 5. In animals consuming the 50g/kg maize oil diet, protein synt hetic rate increased by 56%, 36% and 34% in liver, lung and kidney res pectively. Tissue zinc concentration increased by 14%, 15% and 17% in the three tissues respectively, and tissue protein concentration incre ased by 7%, 9% and 51% respectively. Serum caeruloplasmin increased by 172% and albumin concentrations fell by 22%. 6. No change in any para meter occurred in response to endotoxin in rats given diets containing fat predominantly as butter (50 and 100 g/kg), or olive oil (50, 100 and 200 g/kg). 7. In animals fed maize oil diets, responses increased in magnitude in parallel with dietary intake. 8. Responses in rats fed fat (200 g/kg) predominantly as butter were similar to those seen whe n diets contained 50 g/kg fat as maize oil. 9. The data suggest that t he metabolic response to endotoxin is enhanced by n-6 and suppressed b y R9 unsaturated fatty acids. The modulatory influence of fats on resp onses to inflammatory agents may depend on the relative proportions of these substances.