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Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant across a Large Range of Dietary α-Linolenic Acid Intakes.
J Nutr. 2017 01; 147(1):37-44.JN

Abstract

BACKGROUND

Docosahexaenoic acid (DHA) is an ω-3 (n-3) polyunsaturated fatty acid (PUFA) thought to be important for brain function. Although the main dietary source of DHA is fish, DHA can also be synthesized from α-linolenic acid (ALA), which is derived from plants. Enzymes involved in DHA synthesis are also active toward ω-6 (n-6) PUFAs to synthesize docosapentaenoic acid n-6 (DPAn-6). It is unclear whether DHA synthesis from ALA is sufficient to maintain brain DHA.

OBJECTIVE

The objective of this study was to determine how different amounts of dietary ALA would affect whole-body DHA and DPAn-6 synthesis rates.

METHODS

Male Long-Evans rats were fed an ALA-deficient diet (ALA-D), an ALA-adequate (ALA-A) diet, or a high-ALA (ALA-H) diet for 8 wk from weaning. Dietary ALA concentrations were 0.07%, 3%, and 10% of the fatty acids, and ALA was the only dietary PUFA that differed between the diets. After 8 wk, steady-state stable isotope infusion of labeled ALA and linoleic acid (LA) was performed to determine the in vivo synthesis-secretion rates of DHA and DPAn-6.

RESULTS

Rats fed the ALA-A diet had an ∼2-fold greater capacity to synthesize DHA than did rats fed the ALA-H and ALA-D diets, and a DHA synthesis rate that was similar to that of rats fed the ALA-H diet. However, rats fed the ALA-D diet had a 750% lower DHA synthesis rate than rats fed the ALA-A and ALA-H diets. Despite enrichment into arachidonic acid, we did not detect any labeled LA appearing as DPAn-6.

CONCLUSIONS

Increasing dietary ALA from 3% to 10% of fatty acids did not increase DHA synthesis rates, because of a decreased capacity to synthesize DHA in rats fed the ALA-H diet. Tissue concentrations of DPAn-6 may be explained at least in part by longer plasma half-lives.

Authors+Show Affiliations

Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and.Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and.Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and.Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and.Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and.Bunge Ltd., New York, NY.Department of Nutritional Sciences, University of Toronto, Toronto, Canada; and richard.bazinet@utoronto.ca.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

27852871

Citation

Domenichiello, Anthony F., et al. "Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant Across a Large Range of Dietary α-Linolenic Acid Intakes." The Journal of Nutrition, vol. 147, no. 1, 2017, pp. 37-44.
Domenichiello AF, Kitson AP, Metherel AH, et al. Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant across a Large Range of Dietary α-Linolenic Acid Intakes. J Nutr. 2017;147(1):37-44.
Domenichiello, A. F., Kitson, A. P., Metherel, A. H., Chen, C. T., Hopperton, K. E., Stavro, P. M., & Bazinet, R. P. (2017). Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant across a Large Range of Dietary α-Linolenic Acid Intakes. The Journal of Nutrition, 147(1), 37-44. https://doi.org/10.3945/jn.116.232074
Domenichiello AF, et al. Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant Across a Large Range of Dietary α-Linolenic Acid Intakes. J Nutr. 2017;147(1):37-44. PubMed PMID: 27852871.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant across a Large Range of Dietary α-Linolenic Acid Intakes. AU - Domenichiello,Anthony F, AU - Kitson,Alex P, AU - Metherel,Adam H, AU - Chen,Chuck T, AU - Hopperton,Kathryn E, AU - Stavro,P Mark, AU - Bazinet,Richard P, Y1 - 2016/11/16/ PY - 2016/03/07/received PY - 2016/04/22/revised PY - 2016/10/18/accepted PY - 2016/11/18/pubmed PY - 2017/6/16/medline PY - 2016/11/18/entrez KW - docosahexaenoic acid KW - kinetics KW - synthesis KW - α-linolenic acid KW - ω-3 PUFA SP - 37 EP - 44 JF - The Journal of nutrition JO - J Nutr VL - 147 IS - 1 N2 - BACKGROUND: Docosahexaenoic acid (DHA) is an ω-3 (n-3) polyunsaturated fatty acid (PUFA) thought to be important for brain function. Although the main dietary source of DHA is fish, DHA can also be synthesized from α-linolenic acid (ALA), which is derived from plants. Enzymes involved in DHA synthesis are also active toward ω-6 (n-6) PUFAs to synthesize docosapentaenoic acid n-6 (DPAn-6). It is unclear whether DHA synthesis from ALA is sufficient to maintain brain DHA. OBJECTIVE: The objective of this study was to determine how different amounts of dietary ALA would affect whole-body DHA and DPAn-6 synthesis rates. METHODS: Male Long-Evans rats were fed an ALA-deficient diet (ALA-D), an ALA-adequate (ALA-A) diet, or a high-ALA (ALA-H) diet for 8 wk from weaning. Dietary ALA concentrations were 0.07%, 3%, and 10% of the fatty acids, and ALA was the only dietary PUFA that differed between the diets. After 8 wk, steady-state stable isotope infusion of labeled ALA and linoleic acid (LA) was performed to determine the in vivo synthesis-secretion rates of DHA and DPAn-6. RESULTS: Rats fed the ALA-A diet had an ∼2-fold greater capacity to synthesize DHA than did rats fed the ALA-H and ALA-D diets, and a DHA synthesis rate that was similar to that of rats fed the ALA-H diet. However, rats fed the ALA-D diet had a 750% lower DHA synthesis rate than rats fed the ALA-A and ALA-H diets. Despite enrichment into arachidonic acid, we did not detect any labeled LA appearing as DPAn-6. CONCLUSIONS: Increasing dietary ALA from 3% to 10% of fatty acids did not increase DHA synthesis rates, because of a decreased capacity to synthesize DHA in rats fed the ALA-H diet. Tissue concentrations of DPAn-6 may be explained at least in part by longer plasma half-lives. SN - 1541-6100 UR - https://www.unboundmedicine.com/medline/citation/27852871/Whole_Body_Docosahexaenoic_Acid_Synthesis_Secretion_Rates_in_Rats_Are_Constant_across_a_Large_Range_of_Dietary_α_Linolenic_Acid_Intakes_ L2 - https://academic.oup.com/jn/article-lookup/doi/10.3945/jn.116.232074 DB - PRIME DP - Unbound Medicine ER -