title: Threshold changes in rat brain docosahexaenoic acid incorporation and concentration following graded reductions in dietary alpha-linolenic acid.
abstract: BACKGROUND
  This study tested the dietary level of alpha-linolenic acid (α-LNA, 18:3n-3) required to maintain brain (14)C-Docosahexaenoic acid (DHA, 22:6n-3) metabolism and concentration following graded α-LNA reduction.
  
  
  METHODS
  Fischer-344 (CDF) male rat pups (18-21 days old) were randomized to the AIN-93G diet containing as a % of total fatty acids, 4.6% ("n-3 adequate"), 3.6%, 2.7%, 0.9% or 0.2% ("n-3 deficient") α-LNA for 15 weeks. Rats were intravenously infused with (14)C-DHA to steady state for 5 min, serial blood samples collected to obtain plasma, and brains excised following microwave fixation. Labeled and unlabeled DHA concentrations were measured in plasma and brain to calculate the incorporation coefficient, k*, and incorporation rate, J(in).
  
  
  RESULTS
  Compared to 4.6% α-LNA controls, k* was significantly increased in ethanolamine glycerophospholipids in the 0.2% α-LNA group. Circulating unesterified DHA and brain incorporation rates (J(in)) were significantly reduced at 0.2% α-LNA. Brain total lipid and phospholipid DHA concentrations were reduced at or below 0.9% α-LNA.
  
  
  CONCLUSIONS
  Threshold changes for brain DHA metabolism and concentration were maintained at or below 0.9% dietary α-LNA, suggesting the presence of homeostatic mechanisms to maintain brain DHA metabolism when dietary α-LNA intake is low.
authors: Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA. Electronic address: ataha@ucdavis.edu.
authors: Ameer Y
authors: AY
authors: Taha
authors: Brain Physiology and Metabolism Section, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
authors: Lisa
authors: L
authors: Chang
authors: Brain Physiology and Metabolism Section, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
authors: Mei
authors: M
authors: Chen
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D019587:Dietary Supplements; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D008297:Male; D051381:Rats; D017962:alpha-Linolenic Acid / Q000494:pharmacology*
chemical_list: D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids
keywords: Alpha-linolenic acid; Brain DHA metabolism; Docosahexaenoic acid (DHA); Graded reduction; Polyunsaturated fatty acids (PUFAs); Threshold