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Metherel AH, Valenzuela R, Klievik BJ, Cisbani G, Rotarescu RD, Gonzalez-Soto M, Cruciani-Guglielmacci C, Layé S, Magnan C, Mutch DM, Bazinet RP. Dietary docosahexaenoic acid (DHA) downregulates liver DHA synthesis by inhibiting eicosapentaenoic acid elongation. J Lipid Res 2024:100548. [PMID: 38649096 DOI: 10.1016/j.jlr.2024.100548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/13/2024] [Accepted: 04/18/2024] [Indexed: 04/25/2024] Open
Abstract
DHA is abundant in brain where it regulates cell survival, neurogenesis and neuroinflammation. DHA can be obtained from the diet or synthesized from alpha-linolenic acid (ALA; 18:3n-3) via a series of desaturation and elongation reactions occurring in the liver. Tracer studies suggest that dietary DHA can downregulate its own synthesis, but the mechanism remains undetermined and is the primary objective of this paper. First, we show by tracing 13C content (δ13C) of DHA via compound-specific isotope analysis (CSIA), that following low dietary DHA, the brain receives DHA synthesized from ALA. We then show that dietary DHA increases mouse liver and serum EPA, which is dependant on ALA. Furthermore, by CSIA we demonstrate that the source of increased EPA is slowed EPA metabolism, not increased DHA retroconversion as previously assumed. DHA feeding alone or with ALA lowered liver elongation of very long-chain (ELOVL2, EPA elongation) enzyme activity despite no change in protein content. To further evaluate the role of ELOVL2, a liver-specific Elovl2 knockout was generated showing that DHA feeding in the presence or absence of a functional liver ELOVL2 yields similar results. An enzyme competition assay for EPA elongation suggests both uncompetitive and non-competitive inhibition by DHA depending on DHA levels. To translate our findings, we show that DHA supplementation in men and women increases EPA levels in a manner dependent on a SNP (rs953413) in the ELOVL2 gene. In conclusion, we identify a novel feedback inhibition pathway where dietary DHA downregulates its liver synthesis by inhibiting EPA elongation.
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Affiliation(s)
- Adam H Metherel
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada.
| | | | - Brinley J Klievik
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Giulia Cisbani
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Ruxandra D Rotarescu
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Melissa Gonzalez-Soto
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | | | - Sophie Layé
- Université de Bordeaux, INRA, Bordeaux INP, NutriNeuro, Bordeaux, France
| | | | - David M Mutch
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Richard P Bazinet
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
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Metherel AH, Klievik BJ, Cisbani G, Smith ME, Cumberford G, Bazinet RP. Blood and tissue docosahexaenoic acid (DHA, 22:6n-3) turnover rates from Ahiflower® oil are not different than from DHA ethyl ester oil in a diet switch mouse model. Biochim Biophys Acta Mol Cell Biol Lipids 2024; 1869:159422. [PMID: 37977491 DOI: 10.1016/j.bbalip.2023.159422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 11/06/2023] [Accepted: 11/07/2023] [Indexed: 11/19/2023]
Abstract
Ahiflower® oil is high in α-linolenic and stearidonic acids, however, tissue/blood docosahexaenoic acid (DHA, 22:6n-3) turnover from dietary Ahiflower oil has not been investigated. In this study, we use compound-specific isotope analysis to determine tissue DHA synthesis/turnover from Ahiflower, flaxseed and DHA oils. Pregnant BALB/c mice (13-17 days) were placed on a 2 % algal DHA oil diet of high carbon-13 content (δ13C) and pups (n = 132) were maintained on the diet until 9 weeks old. Mice were then randomly allocated to a low δ13C-n-3 PUFA diet of either: 1) 4 % Ahiflower oil, 2) 4.35 % flaxseed oil or 3) 1 % fish DHA ethyl ester oil for 1, 3, 7, 14, 30, 60 or 120 days (n = 6). Serum, liver, adipose and brains were collected and DHA levels and δ13C were determined. DHA concentrations were highest (p < 0.05) in the liver and adipose of DHA-fed animals with no diet differences in serum or brain (p > 0.05). Based on the presence or absence of overlapping 95 % C.I.'s, DHA half-lives and synthesis/turnover rates were not different between Ahiflower and DHA diets in the liver, adipose or brain. DHA half-lives and synthesis/turnover rates from flaxseed oil were significantly slower than from the DHA diet in all serum/tissues. These findings suggest that the distinct Ahiflower oil n-3 PUFA composition could support tissue DHA needs at a similar rate to dietary DHA, making it a unique plant-based dietary option for maintaining DHA turnover comparably to dietary DHA.
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Affiliation(s)
- Adam H Metherel
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada.
| | - Brinley J Klievik
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Giulia Cisbani
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Mackenzie E Smith
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Greg Cumberford
- Natures Crops International, Kensington, Prince Edward Island, Canada
| | - Richard P Bazinet
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
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Valenzuela R, Metherel AH, Cisbani G, Smith ME, Chouinard-Watkins R, Klievik BJ, Videla LA, Bazinet RP. Protein concentrations and activities of fatty acid desaturase and elongase enzymes in liver, brain, testicle, and kidney from mice: Substrate dependency. Biofactors 2024; 50:89-100. [PMID: 37470206 DOI: 10.1002/biof.1992] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 07/04/2023] [Indexed: 07/21/2023]
Abstract
The synthesis rates of n-3 and n-6 polyunsaturated fatty acids (PUFAs) in rodents and humans are not agreed upon and depend on substrate availability independently of the capacity for synthesis. Therefore, we aimed to assess the activities of the enzymes for n-3 and n-6 PUFA synthesis pathways in liver, brain, testicle, kidney, heart, and lung, in relation to their protein concentration levels. Eight-week-old Balb/c mice (n = 8) were fed a standard chow diet (6.2% fat, 18.6% protein, and 44.2% carbohydrates) until 14 weeks of age, anesthetized with isoflurane and tissue samples were collected (previously perfused) and stored at -80°C. The protein concentration of the enzymes (Δ-6D, Δ-5D, Elovl2, and Elovl5) were assessed by ELISA kits; their activities were assayed using specific PUFA precursors and measuring the respective PUFA products as fatty acid methyl esters by gas chromatographic analysis. The liver had the highest capacity for PUFA biosynthesis, with limited activity in the brain, testicles, and kidney, while we failed to detect activity in the heart and lung. The protein concentration and activity of the enzymes were significantly correlated. Furthermore, Δ-6D, Δ-5D, and Elovl2 have a higher affinity for n-3 PUFA precursors compared to n-6 PUFA. The capacity for PUFA synthesis in mice mainly resides in the liver, with enzymes having preference for n-3 PUFAs.
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Affiliation(s)
- Rodrigo Valenzuela
- Nutrition Department, Faculty of Medicine, University of Chile, Santiago, Chile
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Adam H Metherel
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Giulia Cisbani
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Mackenzie E Smith
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Raphaël Chouinard-Watkins
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Brinley J Klievik
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Luis A Videla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Richard P Bazinet
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
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Klievik BJ, Tyrrell AD, Chen CT, Bazinet RP. Measuring brain docosahexaenoic acid turnover as a marker of metabolic consumption. Pharmacol Ther 2023:108437. [PMID: 37201738 DOI: 10.1016/j.pharmthera.2023.108437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 05/02/2023] [Accepted: 05/15/2023] [Indexed: 05/20/2023]
Abstract
Docosahexaenoic acid (DHA, 22:6n-3) accretion in brain phospholipids is critical for maintaining the structural fluidity that permits proper assembly of protein complexes for signaling. Furthermore, membrane DHA can by released by phospholipase A2 and act as substrate for synthesis of bioactive metabolites that regulate synaptogenesis, neurogenesis, inflammation, and oxidative stress. Thus, brain DHA is consumed through multiple pathways including mitochondrial β-oxidation, autoxidation to neuroprostanes, as well as enzymatic synthesis of bioactive metabolites including oxylipins, synaptamide, fatty-acid amides, and epoxides. By using models developed by Rapoport and colleagues, brain DHA loss has been estimated to be 0.07-0.26 μmol DHA/g brain/d. Since β-oxidation of DHA in the brain is relatively low, a large portion of brain DHA loss may be attributed to synthesis of autoxidative and bioactive metabolites. In recent years, we have developed a novel application of compound specific isotope analysis to trace DHA metabolism. By the use of natural abundance in 13C-DHA in food supply, we are able to trace brain phospholipid DHA loss in free-living mice with estimates ranging from 0.11 to 0.38 μmol DHA/g brain/d, in reasonable agreement with previous methods. This novel fatty acid metabolic tracing methodology should improve our understanding of the factors that regulate brain DHA metabolism.
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Affiliation(s)
- Brinley J Klievik
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
| | - Aidan D Tyrrell
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
| | - Chuck T Chen
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
| | - Richard P Bazinet
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8.
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Klievik BJ, Metherel AH, Cisbani G, Valenzuela R, Bazinet RP. Novel 13C enrichment technique reveals early turnover of DHA in peripheral tissues. J Lipid Res 2023; 64:100357. [PMID: 36948271 PMCID: PMC10154972 DOI: 10.1016/j.jlr.2023.100357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 03/05/2023] [Accepted: 03/14/2023] [Indexed: 03/24/2023] Open
Abstract
The brain is rich in DHA, which plays important roles in regulating neuronal function. Recently, using compound-specific isotope analysis (CSIA) that takes advantage of natural differences in carbon-13 content (13C/12C ratio or δ13C) of the food supply, we determined the brain DHA half-life. However, due to methodological limitations, we were unable to capture DHA turnover rates in peripheral tissues. In the current study, we applied CSIA via high-precision gas chromatography combustion isotope ratio mass spectrometry (GC/C/IRMS) to determine half-lives of brain, liver, and plasma DHA in mice following a dietary switch experiment. To model DHA tissue turnover rates in peripheral tissues, we added earlier timepoints within the diet switch study and took advantage of natural variations in the δ13C-DHA of algal and fish DHA sources to maintain DHA pool sizes and used an enriched (uniformly labeled 13C) DHA treatment. Mice were fed a fish-DHA diet (control) for 3 months, then switched to an algal-DHA treatment diet, the 13C enriched-DHA treatment diet, or they stayed on the control diet for the remainder of the study time course. In mice fed the algal and 13C enriched-DHA diets, the brain DHA half-life was 47 and 46 days, the liver half-life was 5.6 and 7.2 days, and the plasma half-life was 4.7 and 6.4 days respectively. By using improved methodologies, we calculated DHA turnover rates in the liver and plasma, and our study for the first time, by using an artificially enriched DHA source (very high δ13C), validated its utility in diet switch studies.
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Affiliation(s)
- Brinley J Klievik
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Adam H Metherel
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Giulia Cisbani
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Rodrigo Valenzuela
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Richard P Bazinet
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8.
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