title: Fatty acid desaturation index in human plasma: comparison of different analytical methodologies for the evaluation of diet effects.
abstract: Stearoyl-CoA desaturase 1 (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, different analytical strategies were applied to identify the method which best supports SCD1 biology. A novel effective approach was the use of the SCD1-independent fatty acid (16:1n-10) as a negative control. The first approach was based on a simple extraction followed by neutral loss triglyceride fatty acid analysis. The second approach was based on the saponification of triglycerides followed by fatty acid analysis (specific for the position of the double bond within monounsaturated fatty acids (MUFAs)). In addition to the analytical LC-MS assays, different matrices (plasma total triglyceride fraction and the very low-density lipoprotein (VLDL) fraction) were investigated to identify the best for studying changes in SCD1 activity. Samples from volunteers on a high-carbohydrate diet were analyzed. Both ultra HPLC (UHPLC)-MS-based assays showed acceptable accuracies (75-125% of nominal) and precisions (<20%) for the analysis of DI-specific fatty acids in VLDL and plasma. The most specific assay for the analysis of the liver SCD activity was then validated for specificity and selectivity, intra- and interday accuracy and precision, matrix effects, dilution effects, and analyte stability. After 3 days of high-carbohydrate diet, only the specific fatty acids in human plasma VLDL showed a significant increase in DI and associated SCD1 activity.
authors.affiliation: iC42 Integrated Solutions in Systems Biology, University of Colorado, Aurora, CO, 80045-7503, USA, Jost.Klawitter@ucdenver.edu.
authors.forename: Jost
authors.initials: J
authors.lastname: Klawitter
authors.forename: Stephan
authors.initials: S
authors.lastname: Bek
authors.forename: Marjorie
authors.initials: M
authors.lastname: Zakaria
authors.forename: Chenhui
authors.initials: C
authors.lastname: Zeng
authors.forename: Andrea
authors.initials: A
authors.lastname: Hornberger
authors.forename: Richard
authors.initials: R
authors.lastname: Gilbert
authors.forename: Touraj
authors.initials: T
authors.lastname: Shokati
authors.forename: Jelena
authors.initials: J
authors.lastname: Klawitter
authors.forename: Uwe
authors.initials: U
authors.lastname: Christians
authors.forename: K Olaf
authors.initials: KO
authors.lastname: Boernsen
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004032:Diet; D005227:Fatty Acids / Q000097:blood* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008079:Lipoproteins, VLDL / Q000097:blood; D013058:Mass Spectrometry / Q000379:methods*; D015394:Molecular Structure; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D008079:Lipoproteins, VLDL; D013230:Stearoyl-CoA Desaturase