Comparison of long chain and medium chain polyunsaturated n-3 fatty acids for their ability to correct insulin resistance induced by saturated fatty acids in cultured bovine adipocytes

The modern dairy cows, due to intensive selection for higher milk production during past decades, have become more resistant to insulin. Accompanied with DMI depression in per parturient dairy cow, insulin resistance may lead to a massive release of non-esterified fatty acids (NEFA) to bloodstream which might act as a start point for development of other diseases.
The purpose of this study was to investigate potentiality of long chain polyunsaturated fatty acid (LCPUFA) of marine or polyunsaturated fatty acids (PUFA) of plant origin to correct the insulin resistance induced by saturated fatty acids in cultured bovine adipocytes.
Fatty acids from different oils were isolated using KOH and were mixed together with different proportions to obtain the following profiles: 1) saturated fatty acids (SFA); 2); saturated fatty acids6/n-3 PUFA (medium chain) at ratio of 1:1 (SFA-MC1:1)and3) saturated fatty acids n-6/n-3 PUFA (long chain) at ratio of 1:1 (SFA-LC 1:1). Adipocytes were cultured for 48 in the presence of treatments and after the incubation period an epinephrine challenge was applied to stimulate lipolysis. In the adjacent culture plates for each treatment insulin was added along with epinephrine challenge in different concentrations to test sensitivity of adipocytes to insulin. After conducting insulin sensitivity test, a sample was taken from culture media and analyzed for glycerol concentration as an index of lipolysis.
Results indicated that saturated fatty acids effectively induced insulin resistance in adipocytes. Long chain polyunsaturated fatty acids from fish oil had a significant preventive effect on insulin resistance induced by saturated fatty acids so that increasing insulin concentration linearly increased the response of adipocytes to insulin in treatment LC-SFA 1:1. Shorter chain n-3 polyunsaturated fatty acids of plant origin did not show such effects on insulin sensitivity in adipocytes.
n-3 fatty acids from fish oil improved bovine adipocyte sensitivity to insulin but shorter chain n-3 fatty acids did not show this ability.