Cis trans 18 2n 6

Total lipids were extracted from the plasma samples and converted to their methyl ester equivalents as described previously (12 (link), 22 (link)), and analyzed using an Agilent 7820A GC using flame ionization detection on a SP-2560 polar fused silica capillary column (100 m × 0.25 mm × 0.2 μm; Supelco Inc., PA, USA) with nitrogen as the carrier gas (12 (link)). The FA peaks were identified by comparing retention times with those of a standard mixture of GLC-68A, GLC-481B, GLC-532, GLC-744 (Nu-Chek Prep), 37 FAME, trans 16:1n-7, trans 18:1n-7, trans 18:1n-9, and cis/trans 18:2n-6 (all obtained from Supelco Inc., or Sigma). 13:0 free fatty acid (10 μg) was added as an internal standard. FA composition was expressed as the weight of a percentage of the total weight of carbon-12 to carbon-24 FAs (wt%). The estimated desaturase activity was calculated using the ratio of FA in plasma (11 (link), 17 (link), 23 (link)); SCD1(16) activity = (16:1n-7/16:0), SCD1(18) activity = (18:1n-9/18:0), D5D activity = (20:4n-6/20:3n-6), and D6D activity = (20:3n-6/18:2n-6).

Plasma FA methyl esters were prepared as described previously (Moser et al., 1999) [24 (link)]. Briefly, 200 μl plasma and 10 μg C13:0 as an internal standard were mixed with 1 ml methanol/methylene chloride 3:1 (v/v). Subsequently, 200 μl of acetyl chloride, were added and the samples were placed in a 75°C water bath for 1 h. After cooling down, 4 ml of 7% potassium carbonate and 2 ml hexane were added, and samples were mixed and centrifuged for 10 min at 3000 rpm at room temperature. The plasma sample in hexane layer was dried using nitrogen gas and analyzed with Agilent 7820A GC using flame ionization detection on a SP-2560 polar fused silica capillary column (100 m x 0.25 mm x 0.2 μm, Supelco Inc.) with nitrogen as carrier gas. The oven temperature program was initially set to 60°C for 1 min, then increased by 25°C per minute to 160°C, then increased by 2°C per minute to 240°C for 10 min, and finally increased by 5°C per minute to 245°C for 5 min. The FA peaks were identified by comparing retention times from our samples with retention times of a standard mixture of GLC-68A, GLC-481, GLC-532, GLC-744 (Nu-Chek Prep), 37 FAME, cis/trans 18:2n-6 and cis/trans 18:3n-3, (all from SUPELCO). The FA composition was expressed as the weight of a percentage of the total weight of carbon 12 to carbon 24 FAs (wt%). http://dx.doi.org/10.17504/protocols.io.h6hb9b6