title: Effect of altered dietary n-3 fatty acid intake upon plasma lipid fatty acid composition, conversion of [13C]alpha-linolenic acid to longer-chain fatty acids and partitioning towards beta-oxidation in older men.
abstract: The effect of increased dietary intakes of alpha-linolenic acid (ALNA) or eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 2 months upon plasma lipid composition and capacity for conversion of ALNA to longer-chain metabolites was investigated in healthy men (52 (SD 12) years). After a 4-week baseline period when the subjects substituted a control spread, a test meal containing [U-(13)C]ALNA (700 mg) was consumed to measure conversion to EPA, docosapentaenoic acid (DPA) and DHA over 48 h. Subjects were then randomised to one of three groups for 8 weeks before repeating the tracer study: (1) continued on same intake (control, n 5); (2) increased ALNA intake (10 g/d, n 4); (3) increased EPA+DHA intake (1.5 g/d, n 5). At baseline, apparent fractional conversion of labelled ALNA was: EPA 2.80, DPA 1.20 and DHA 0.04 %. After 8 weeks on the control diet, plasma lipid composition and [(13)C]ALNA conversion remained unchanged compared with baseline. The high-ALNA diet resulted in raised plasma triacylglycerol-EPA and -DPA concentrations and phosphatidylcholine-EPA concentration, whilst [(13)C]ALNA conversion was similar to baseline. The high-(EPA+DHA) diet raised plasma phosphatidylcholine-EPA and -DHA concentrations, decreased [(13)C]ALNA conversion to EPA (2-fold) and DPA (4-fold), whilst [(13)C]ALNA conversion to DHA was unchanged. The dietary interventions did not alter partitioning of ALNA towards beta-oxidation. The present results indicate ALNA conversion was down-regulated by increased product (EPA+DHA) availability, but was not up-regulated by increased substrate (ALNA) consumption. This suggests regulation of ALNA conversion may limit the influence of variations in dietary n-3 fatty acid intake on plasma lipid compositions.
authors.affiliation: Institute of Human Nutrition, University of Southampton, UK. g.c.burdge@soton.ac.uk
authors.forename: Graham C
authors.initials: GC
authors.lastname: Burdge
authors.forename: Yvonne E
authors.initials: YE
authors.lastname: Finnegan
authors.forename: Anne M
authors.initials: AM
authors.lastname: Minihane
authors.forename: Christine M
authors.initials: CM
authors.lastname: Williams
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Wootton
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000008:administration & dosage / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage / Q000378:metabolism; D005227:Fatty Acids / Q000097:blood; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage; D006801:Humans; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D017962:alpha-Linolenic Acid / Q000008:administration & dosage* / Q000378:metabolism*
chemical_list: D004042:Dietary Fats, Unsaturated; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D008055:Lipids; D017962:alpha-Linolenic Acid; D002245:Carbon Dioxide; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; C026219:docosapentaenoic acid