Influence of dietary cholesterol and stress on the metabolism of linoleic acid: Δ6-desaturase activity vs. product/precursor ratios

Abstract

Δ6-desaturase is a membrane bound enzyme located in a pivotal position within the Essential Fatty Acid metabolic pathway. Changes in the activity of Δ6-desaturase affect the cellular provision of long chain polyunsaturated fatty acids and therefore factors that influence this enzyme are considered relevant to disease processes. This study investigated the effects of social isolation stress and cholesterol supplementation in a rodent model using two methods to estimate Δ6-desaturase activity, namely, a direct method measuring liver microsomal Δ6-desaturase activity and an indirect method measuring product?precursor ratio from tissue fatty acid compositions. Liver Δ6-desaturase activity was significantly decreased by isolation (-14%) and increased by cholesterol feeding (+9%). Liver microsomal phospholipid fatty acid composition and the associated product?precursor ratios for Δ6-desaturase did not relate to the changes observed in Δ6 desaturase activity. These results indicate that tissue fatty acid compositions should be viewed with caution in terms of their appropriateness as a surrogate for measuring Δ6-desaturase activity.