Reduction of n-3 PUFAs, specifically DHA and EPA, and enhancement of peroxisomal beta-oxidation in type 2 diabetic rat heart

Background: There is overwhelming evidence that dietary supplementation with n-3 polyunsaturated fatty acids (PUFAs), mainly EPA (C20:5n-3) and DHA (C22:6n-3), has cardiovascular protective effects on patients with type 2 diabetes mellitus (T2DM) but not on healthy people. Because the T2DM heart increases fatty acid oxidation (FAO) to compensate for the diminished utilization of glucose, we hypothesize that T2DM hearts consume more n-3 PUFAs and, therefore, need more n-3 PUFAs. In the present study, we investigated the changes in cardiac n-3 PUFAs and peroxisomal beta-oxidation, which are responsible for the degradation of PUFAs in a high-fat diet (HFD) and low-dose streptozotocin-(STZ) induced type 2 diabetic rat model. Methods and results: The capillary gas chromatography results showed that all the n-3 (or omega-3) PUFAs, especially DHA (similar to 50%) and EPA (similar to 100%), were significantly decreased, and the n-6/n-3 ratio (similar to 115%) was significantly increased in the hearts of diabetic rats. The activity of peroxisomal beta-oxidation, which is crucial to very-long-chain and unsaturated FA metabolism (including DHA), was significantly elevated in DM hearts. Additionally, the real-time PCR results showed that the mRNA expression of most peroxisomal beta-oxidation key enzymes were up-regulated in T2DM rat hearts, which might contribute to the reduction of n-3 (or omega-3) PUFAs. Conclusion: In conclusion, our results indicate that T2DM hearts consume more n-3 PUFAs, especially DHA and EPA, due to exaggerated peroxisomal beta-oxidation.