Synthesis of linoleate and alpha-linolenate by chain elongation in the rat.
The objective was to determine whether rats could synthesize longer chain polyunsaturates from hexadecadienoate (16:2n-6) and hexadecatrienoate (16:3n-3). Rats were gavaged with uniformly 13C-labelled hexadecadienoate or hexadecatrienoate, euthanized 24 h later, and total lipids were extracted from liver and carcass. Gas chromatography/combustion/isotope ratio mass spectrometry was used to measure 13C levels in individual liver, carcass, and whole body fatty acids. 13C Enrichment was present in desaturated and chain-elongated polyunsaturates, including linoleate, arachidonate, alpha-linolenate, and docosahexaenoate at 12-13% of the dose of tracer given. 13C Enrichment from hexadecatrienoate was highest in carcass and liver alpha-linolenate, representing 3.5 and 17.9% of the total alpha-linolenate pool, respectively. For linoleate, arachidonate, or docosahexaenoate, the contribution of 13C did not exceed 0.2% of the total body pool. Green leafy vegetables common in the human diet were shown to contain up to 1.2% of total fatty acids as hexadecadienoate and 11.6% as hexadecatrienoate. Hence, humans consuming green vegetables probably synthesize a small proportion of their total body content of linoleate and alpha-linolenate.
D000818:Animals; D002247:Carbon Isotopes; D004032:Diet; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014675:Vegetables / Q000737:chemistry; D017962:alpha-Linolenic Acid / Q000096:biosynthesis*
D002247:Carbon Isotopes; D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids; D017962:alpha-Linolenic Acid; D019787:Linoleic Acid