Long-chain polyunsaturated fatty acids in plasma lipids of obese children.

Fatty acid composition of plasma phospholipids (PL), triglycerides (TG), and sterol esters (STE) was determined by high-resolution capillary gas-liquid chromatography in 22 obese children (age: 13.7 +/- 1.4 y, body weight relative to normal weight for height: 170 +/- 24%, mean +/- SD) and compared with data obtained in 25 age-matched healthy controls. There were no differences in the levels of linoleic acid (LA, C18:2n-6) in any of the plasma fractions from obese children and the controls. Obese children exhibited significantly higher values of arachidonic acid (AA, C20:4n-6) than controls both in PL (12.6 [2.4] vs. 8.3 [1.4], % wt/wt, [median (interquartile range)], P < 0.001) and STE (7.3 [1.8] vs. 6.0 [1.1], P < 0.05). Similarly, obese children showed higher values than controls for dihomo-gamma-linoleic acid (DHGLA, C20:3n-6) in PL (4.0 [0.5] vs. 3.0 [0.6], P < 0.001), TG (0.4 [0.1] vs. 0.2 [0.1], P < 0.001), and STE (0.9 [0.1] vs. 0.7 [0.1], P < 0.01), and for gamma-linolenic acid (C18:3n-6) in STE (1.1 [0.2] vs. 0.8 [0.2], P < 0.001). The AA/LA ratios were higher in obese children than in controls in PL (0.68 [0.16] vs. 0.42 [0.09], P < 0.0005) and STE (0.16 [0.04] vs. 0.12 [0.02], P < 0.05), whereas the AA/DHGLA ratios were lower in TG of obese children than in controls (3.40 [0.64] vs. 5.10 [1.75], P < 0.005). Plasma glucose concentrations were inversely related to AA in TG (r = 0.53, P < 0.05), and plasma TG concentrations were inversely related to AA in PL and STE (r = -0.49, P < 0.05 and r = -0.48, P < 0.05) and to the AA/DHGLA ratios in PL (r = -0.57, P < 0.01), TG (r = -0.56, P < 0.01), and STE (r = -0.56, P < 0.01). We conclude that the significantly higher values of n-6 long-chain polyunsaturated fatty acids (LCP) in plasma lipids of obese children than in age-matched controls may be caused by an enhanced activity of delta 6-desaturation, and we speculate that elevated fasting immunoreactive insulin seen in obese children (19.4 +/- 8.0 microU/mL) may stimulate synthesis of n-6 LCP fatty acids.