The Fatty Acid Desaturation Index in Human Plasma: Comparison of Different Analytical Methodologies for the Evaluation of Dietary Effects

Abstract

Abstract (252 words) Background: Stearoyl-CoA Desaturase (SCD1) plays a role in the development of obesity and related conditions, such as insulin resistance, and potentially also in neurological and heart diseases. The activity of SCD1 can be monitored using the desaturation index (DI), the ratio of product (16:1n-7 and 18:1n-9) to precursor (16:0 and 18:0) fatty acids. Here we analyzed the DI in the plasma total triglyceride fraction and very low density lipoproteins (VLDL) in volunteers on a high carbohydrate diet using a dual ultra-high pressure liquid chromatography – mass spectrometry (UHPLC-MS) strategy. Methods: One assay was based on a simple extraction followed by neutral loss triglyceride – fatty acid analysis, the other on saponification of triglycerides followed by fatty acid analysis (specific for the position of the double bond within monosaturated fatty acids (MUFA). Both assays were applied to the isolated VLDL or to the plasma total triglyceride fraction. Assays were compared using plasma from a study in which 8 lean and obese healthy individuals received a high carbohydrate diet for 3 days. Results: All assays showed acceptable accuracies (75-125) and precisions (<20%) for the analysis of fatty acids in VLDL and plasma. Analysis of human plasma samples revealed increased DI (up to 136% of control, p< 0.05 after a high carbohydrate diet of 3 days. Conclusion: Only the specific fatty acid UHPLC-MS analysis of human plasma VLDL samples reflects the complete biological pathway and showed that a significant increase in DI and associated SCD1 activity –in healthy individuals after just 3 days of high carbohydrate diet