J Fiamoncini¹, N Turner², S Hirabara³, T Lima¹, A Marçal¹, S Leslie², G Cooney², R Curi^1
1Institute of Biomedical Sciences - University of São Paulo, São Paulo, Brazil
²Garvan Institute of Medical Research, Sydney, Australia
³Universidade Cruzeiro do Sul, São Paulo, Brazil

Objective: In this study, we investigated how different concentrations of fish oil and lard can modulate glucose and lipid homeostasis and affect insulin resistance. The role of peroxisomes in these effects was also evaluated.

Procedure: Swiss mice were fed for 10 weeks on diets containing either fish oil at 4% (NFO) or 45% (HFO) and lard at 4% (NL) or 45% (HL). Glucose and lipid metabolism were studied in liver and muscle.

Results: Fish oil fed animals weighed ~10 % less than corresponding lard-fed animals, and also displayed smaller epididymal and retroperitoneal fat pad (p<0.05). Despite the lean phenotype, fish oil-fed mice showed lower oxygen consumption when compared with the lard fed groups (p<0.01). NFO and HFO exhibited a better response during a Glucose Tolerance Test than lard fed animals (average area under the curve = 375 and 564 for NFO and HFO, vs. 703 and 867 for NL and HL, respectively). Triacylglycerol content and palmitate oxidation rate were not different in muscle across the 4 groups. In contrast, fish oil fed animals exhibited 60% lower triacylglycerol levels in liver than lard-fed counterparts. Furthermore, despite lower complete oxidation of palmitate in liver homogenates from NFO and HFO animals, a ~50% higher level of acid soluble metabolites were generated in these groups. This suggests that peroxisomal fat oxidation was increased. The activity of the key peroxisomal enzyme, acyl-CoA oxidase and other enzymes involved in beta-oxidation were also substantially enhanced in the liver of fish oil fed animals.

Conclusion: The increased acid soluble metabolite production from palmitate and the increased activity of peroxisomal enzymes in the liver of fish oil fed groups, suggest that inefficient peroxisomal metabolism of fatty acids in liver is an important contributor to the lower fat accumulation and better glucose tolerance in n-3 PUFA fed mice.

Keywords: lard, lcPUFA, glucose toleranc, triacylglycerol levels
Schlüsselwörter: Schmalz, lcPUFA, Glucosetoleranz, Triglyzeridspiegel