title: Delta-6-desaturase and delta-5-desaturase in human Hep G2 cells are both fatty acid interconversion rate limiting and are upregulated under essential fatty acid deficient conditions.
abstract: Essential fatty acids are interconverted by desaturases and elongases to eicosanoid precursors. In essential fatty acid deficiency (EFAD) an increased hepatic interconversion of linoleic acid (18:2) to arachidonic acid (20:4n-6) has been demonstrated in vivo. We now cultured Hep G2 cells under EFAD conditions. 20:3n-6 appeared in EFAD cells, but also in controls. After adding 14C-18:2 to the medium, interconversion products and their distribution in different lipids were studied by HPLC. When trace amounts 18:2 were incubated, 38% were converted by the EFAD cells after 21 h, vs 6% by controls. 20% was converted to 20:4 by EFAD cells vs 14% by controls. EFAD cells preferentially distributed more 18:2 and conversion products to neutral fats and to phosphatidyl ethanolamine, but less to cardiolipin than controls did, when incubated with trace amount 18:2, but not with 1 mM 18:2. A relative accumulation of radioactivity in 20:3 was observed. In conclusion; in EFAD Hep G2 cells delta-6- and delta-5-desaturase both were found to be upregulated and eicosanoid precursors were distributed more into phosphatidyl ethanolamine. Delta-5-desaturase had a rate limiting property as well as delta-6-desaturase.
authors.affiliation: Department of Internal Medicine, University Hospital, Lund, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Melin
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
mesh_terms: D016718:Arachidonic Acid / Q000378:metabolism; D002460:Cell Line; D000090943:Delta-5 Fatty Acid Desaturase; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D005228:Fatty Acids, Essential / Q000172:deficiency*; D006801:Humans; D007700:Kinetics; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism; D050602:Linoleoyl-CoA Desaturase; D010743:Phospholipids / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000090943:Delta-5 Fatty Acid Desaturase; D005227:Fatty Acids; D005228:Fatty Acids, Essential; D008041:Linoleic Acids; D010743:Phospholipids; D016718:Arachidonic Acid; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase