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Murphy EJ. Glucose as a carbon source to synthesize palmitate de novo in the adult rodent brain: Adding to the carbon recycling story in the brain. J Neurochem 2022; 161:109-111. [DOI: 10.1111/jnc.15592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/12/2022] [Accepted: 02/12/2022] [Indexed: 11/27/2022]
Affiliation(s)
- Eric J. Murphy
- Department of Biomedical Sciences, School of Medicine and Health Sciences University of North Dakota Grand Forks ND USA
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Abstract
Previous studies have revealed that C20 PUFA are significantly less oxidised to CO₂ in whole-body studies compared with SFA, MUFA and C18 PUFA. The present study determined the extent to which three long-chain PUFA, namely 20:5n-3 EPA, 22:5n-3 docosapentaenoic acid (DPA) and 22:6n-3 DHA, were catabolised to CO₂ or, conversely, incorporated into tissue lipids. Rats were administered a single oral dose of 2·5 μCi [1-¹⁴C]DPA, [1-¹⁴C]EPA, [1-¹⁴C]DHA or [1-¹⁴C]oleic acid (18:1n-9; OA), and were placed in a metabolism chamber for 6 h where exhaled ¹⁴CO₂ was trapped and counted for radioactivity. Rats were euthanised after 24 h and tissues were removed for analysis of radioactivity in tissue lipids. The results showed that DPA and DHA were catabolised to CO₂ significantly less compared with EPA and OA (P<0·05). The phospholipid (PL) fraction was the most labelled for all three n-3 PUFA compared with OA in all tissues, and there was no difference between C20 and C22 n-3 PUFA in the proportion of label in the PL fraction. The DHA and DPA groups showed significantly more label than the EPA group in both skeletal muscle and heart. In the brain and heart tissue, there was significantly less label in the cholesterol fraction from the C22 n-3 PUFA group compared with the C20 n-3 PUFA group. The higher incorporation of DHA and DPA into the heart and skeletal muscle, compared with EPA, suggests that these C22 n-3 PUFA might play an important role in these tissues.
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Castro-Perez JM, Roddy TP, Shah V, McLaren DG, Wang SP, Jensen K, Vreeken RJ, Hankemeier T, Johns DG, Previs SF, Hubbard BK. Identifying Static and Kinetic Lipid Phenotypes by High Resolution UPLC–MS: Unraveling Diet-Induced Changes in Lipid Homeostasis by Coupling Metabolomics and Fluxomics. J Proteome Res 2011; 10:4281-90. [DOI: 10.1021/pr200480g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jose M. Castro-Perez
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Thomas P. Roddy
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - Vinit Shah
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - David G. McLaren
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - Sheng-Ping Wang
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - Kristian Jensen
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - Rob J. Vreeken
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, LACDR, Leiden University, P.O. Box 9502, 2300RA Leiden, The Netherlands
| | - Thomas Hankemeier
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, LACDR, Leiden University, P.O. Box 9502, 2300RA Leiden, The Netherlands
| | - Douglas G. Johns
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - Stephen F. Previs
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
| | - Brian K. Hubbard
- Department of Cardiovascular Diseases − Atherosclerosis Rahway, Merck Research Laboratories, New Jersey 07065, United States
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Comhair TM, Garcia Caraballo SC, Dejong CH, Lamers WH, Köhler SE. Dietary cholesterol, female gender and n-3 fatty acid deficiency are more important factors in the development of non-alcoholic fatty liver disease than the saturation index of the fat. Nutr Metab (Lond) 2011; 8:4. [PMID: 21261989 PMCID: PMC3045875 DOI: 10.1186/1743-7075-8-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 01/24/2011] [Indexed: 12/29/2022] Open
Abstract
Background The central feature of NAFLD is a disturbed fatty-acid metabolism with hepatic lipid accumulation. However, the factors that determine the severity of NAFLD, including the role of nutrition, gender, and plasma lipid levels, remain to be determined. Methods High-fat diets (42 en% fat), containing 0.2% cholesterol, were fed to male and female wild-type and hyperlipidemic APOE2ki C57BL/6J mice for three weeks. The fats were, in order of decreasing saturation, fractionated palm fat (fPF; ~95%), cocoa butter (CB; ~60%), olive oil (OO; ~15%), sunflower oil (SO; ~12%), and high-oleic-acid sunflower oil (hoSO; ~7%). Plasma and liver triglycerides (concentration and composition), liver inflammation (Ccl2, Cd68, Tnf-α mRNA), and infiltration of macrophages (Cd68, Cd11b immunohistochemistry) and neutrophils (Mpo) were quantified. Results Addition of cholesterol to a low-fat diet decreased plasma HDL and increased (V)LDL levels in APOE2ki mice. Plasma cholesterol levels in female, but not male APOE2ki mice correlated significantly with inflammation. Kupffer cells of inflamed livers were swollen. Wild-type mice refused the highly saturated fPF diet. The high-fat CB, OO, and SO diets induced hyperglycemia and a 2-fold increase in hepatic fat content in male, but not female wild-type mice (in females, hepatic fat content was similar to that in males fed a high-fat diet). All high-fat diets induced macrovesicular setatosis. APOE2ki mice were protected against high-fat diet-induced steatosis and hyperglycemia, except when fed a hoSO diet. This diet caused a 5-fold increase in liver triglyceride and mead-acid content, and an increased expression of lipogenic genes, suggesting a deficiency in poly-unsaturated fatty acids. Irrespective of the composition of the high-fat diet, oleic acid was the main triglyceride component of liver fat in wild-type and APOE2ki mouse livers. Liver inflammation was dependent on genotype (APOE2ki > wild type), gender (female > male), and cholesterol content (high > low) of the diet, but not on dietary fat composition. Conclusions Dietary cholesterol plays a determining, independent role in inflammation, especially in female mice. The fatty-acid saturation of the diet hardly affected hepatic steatosis or inflammation.
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Affiliation(s)
- Tine M Comhair
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands.,NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands.,Nutrigenomics Consortium, Top Institute Food and Nutrition, Wageningen, The Netherlands
| | - Sonia C Garcia Caraballo
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands.,NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Cornelis Hc Dejong
- Department of General Surgery, Maastricht University, Maastricht, The Netherlands.,NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Wouter H Lamers
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands.,NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands.,Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - S Eleonore Köhler
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands.,NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University, Maastricht, The Netherlands
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Serum linoleic acid status as a clinical indicator of essential fatty acid status in children with cystic fibrosis. J Pediatr Gastroenterol Nutr 2008; 47:635-44. [PMID: 18955866 PMCID: PMC4482449 DOI: 10.1097/mpg.0b013e31817fb76b] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
BACKGROUND Children with cystic fibrosis (CF) and pancreatic insufficiency (PI) are at increased risk for essential fatty acid (EFA) deficiency. OBJECTIVES To investigate serum markers of EFA status in children with CF and PI and their association with growth, body composition, and lung function. PATIENTS AND METHODS Serum phospholipid fatty acid, growth, and forced expiratory volume at 1 second (FEV1, percentage predicted) status were assessed at baseline and 12 months in 77 children with CF and PI, 7 to 10 years old. Longitudinal mixed-effects models were used to compare associations of the triene:tetraene ratio (ratio of eicosatrienoic acid to arachidonic acid) and serum linoleic acid (as a molar percentage of total serum phospholipid fatty acids, or mol%) with the clinical outcomes. Controls for serum fatty acid were 23 healthy white age- and sex-matched children. RESULTS Children with CF and PI had higher median triene:tetraene ratio and lower linoleic acid than healthy controls. Depending on the triene:tetraene ratio cutoff point used (0.04 or 0.02), either 17% or 52% of the children with CF had EFA deficiency, respectively. Only linoleic acid was significantly and positively associated with z scores for weight, height, body mass index, upper arm muscle area, and FEV1 at baseline. Children with linoleic acid at 21 mol% or higher had significantly better growth and pulmonary status than those with lower concentrations. CONCLUSIONS Serum phospholipid linoleic acid at 21 mol% or higher was associated with better growth, body composition, and FEV1. No clinical outcome associations were found with the triene:tetraene ratio. These findings suggest that linoleic acid concentration was a more clinically relevant biomarker of EFA status than the triene:tetraene ratio in children with CF and PI. Further research is warranted to validate this specific percentage of linoleic acid cutoff point as a new recommendation for clinical use.
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The conditional nature of the dietary need for polyunsaturates: a proposal to reclassify ‘essential fatty acids’ as ‘conditionally-indispensable’ or ‘conditionally-dispensable’ fatty acids. Br J Nutr 2007. [DOI: 10.1017/s0007114500002415] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The term essential fatty acid no longer clearly identifies the fatty acids it was originally used to describe. It would be more informative if the concept of essentiality shifted away from the symptoms arising from the lack of de novo synthesis of linoleate or α-linolenate and towards the adequacy of the capacity for synthesis and conservation of both the parent and the derived long-chain polyunsaturates. For instance, despite the existence of the pathway for synthesis of docosahexaenoate from α-linolenate, the former would be more correctly classified as ‘conditionally indispensable’ because the capacity of the pathway appears insufficient during early development, although it may be sufficient later in life in healthy individuals. Similarly, despite the inability to synthesize linoleate de novo, abundant linoleate stores and its relatively slow turnover in healthy adults probably makes linoleate ‘conditionally dispensable’ for long periods. There are two other anomalies with the terms essential and non-essential fatty acids: (1) under several different experimental circumstances, the C-skeleton of essential fatty acids is avidly used in the synthesis of non-essential fatty acids; (2) to function normally, the brain is required to endogenously synthesize several non-essential fatty acids. As with essential amino acids, which have been reclassified as indispensable or conditionally indispensable, such a change in terminology should lead to an improved understanding of the function and metabolism of polyunsaturates in particular, and long-chain fatty acids in general.
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DeMar JC, Lee HJ, Ma K, Chang L, Bell JM, Rapoport SI, Bazinet RP. Brain elongation of linoleic acid is a negligible source of the arachidonate in brain phospholipids of adult rats. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1050-9. [PMID: 16920015 DOI: 10.1016/j.bbalip.2006.06.006] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Revised: 06/19/2006] [Accepted: 06/20/2006] [Indexed: 10/24/2022]
Abstract
The extent to which the adult brain can derive some of its arachidonic acid (AA) through internalized synthesis from linoleic acid (LA) is uncertain. Thus, we determined for plasma-derived LA in vivo rates for brain incorporation, beta-oxidation, and conversion to AA. Adult male unanesthetized rats, reared on a diet enriched in LA but low in AA, were infused intravenously for 5 min with [1-(14)C]LA. Timed arterial samples were collected until the animals were killed at 5 min and the brain was removed after microwaving. Within plasma lipids, >96% of radioactivity was in the form of unchanged [1-(14)C]LA, but [(14)C]AA was insignificant (<0.2%). Eighty-six percent of brain radioactivity at 5 min was present as beta-oxidation products, whereas the remainder was mainly in 'stable' phospholipid or triglyceride as LA or AA (11 and <1%, respectively). Unesterified unlabeled LA rapidly enters brain from plasma, but its incorporation into brain total phospholipid and triglyceride, in the form of synthesized AA, is <1% of the amount that enters the brain. Thus, in rats fed even a diet containing low amounts of AA, the LA that enters brain is largely beta-oxidized, and is not a major source of AA in brain.
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Affiliation(s)
- James C DeMar
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Building 9, Room 1S 126, Bethesda, MD 20892-1582, USA
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Cunnane SC, Ryan MA, Lin YH, Lim SY, Salem N. Suckling rats actively recycle carbon from alpha-linolenate into newly synthesized lipids even during extreme dietary deficiency of n-3 polyunsaturates. Pediatr Res 2006; 59:107-10. [PMID: 16326997 DOI: 10.1203/01.pdr.0000190569.07991.ed] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Docosahexaenoate is usually considered to be the principal endpoint of alpha-linolenate metabolism in mammals. Nevertheless, several studies over the past 30 y have shown that more carbon from alpha-linolenate is recycled into newly synthesized lipids than is used to make docosahexaenoate. Our objective in this study was to assess carbon recycling from alpha-linolenate in suckling rats made deficient in n-3 polyunsaturated fatty acids (PUFA). Female Long-Evans rats were given a diet deficient in n-3 PUFA at weaning and then bred 8 wk later. Pups from the second generation were nursed by their respective dams and gavaged with 1 mg [U-13C]-alpha-linolenate at 10 d old. Brain and liver were obtained 24 h later, and the fatty acid profiles and 13C enrichment analyzed. Docosahexaenoate was markedly depleted in brain (-82%) and liver (-97%) of the n-3 PUFA-deficient rats. In the controls, 13C enrichment in products of carbon recycling (cholesterol and fatty acids other than n-3 PUFA) exceeded that in docosahexaenoate by 2.4-fold (liver) and 7.5-fold (brain). n-3 PUFA deficiency reduced the ratio of 13C enrichment in products of carbon recycling compared with 13C incorporated into docosahexaenoate by 63% in the brain but not in the liver. Despite severe n-3 PUFA deficiency, carbon recycling still consumed 50% more 13C from alpha-linolenate than went into docosahexaenoate in the liver and 2.8-fold more in the brain. We conclude that carbon recycling is an integral part of neonatal metabolism of alpha-linolenate and is not simply an overflow pathway arising from excess availability of preformed docosahexaenoate.
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Affiliation(s)
- Stephen C Cunnane
- Research Center on Aging, Sherbrooke University Geriatric Institute, Québec, Canada.
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Martins de Lima T, de Oliveira Rodrigues L, Bengtson MH, Sogayar MC, Bezerra CNA, Rebouças NA, Curi R. Identification of genes regulated by oleic acid in Jurkat cells by suppressive subtractive hybridization analysis. FEBS Lett 2004; 576:320-4. [PMID: 15498555 DOI: 10.1016/j.febslet.2004.09.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 08/20/2004] [Accepted: 09/06/2004] [Indexed: 11/17/2022]
Abstract
In this study, the effect of oleic acid (50 microM) on gene expression of Jurkat cells (human T lymphocytes cell line) was examined using the suppressive subtractive hybridization approach. This technique allowed us to identify genes with higher or lower expression after cell treatment with oleic acid as compared to untreated cells. Oleic acid upregulated the expression of the translation elongation factor alpha 1 and ATP synthase 8 and downregulated gp96 (human tumor rejection antigen gp96), heat-shock protein 60 and subtilisin-like protein 4. These results suggest that oleic acid, at plasma physiological concentration, can regulate the expression of important genes to maintain the machinery that ensures cell functioning.
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Affiliation(s)
- Thais Martins de Lima
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 1524, Butantã, São Paulo, SP 05508-900, Brazil
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Cunnane SC. Metabolism of polyunsaturated fatty acids and ketogenesis: an emerging connection. Prostaglandins Leukot Essent Fatty Acids 2004; 70:237-41. [PMID: 14769482 DOI: 10.1016/j.plefa.2003.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This paper summarizes the emerging literature indicating that at least two polyunsaturated fatty acids (PUFA; linoleate, alpha-linolenate) are moderately ketogenic and that via ketone bodies significant amounts of carbon are recycled from these fatty acids into de novo synthesis of lipids including cholesterol, palmitate, stearate and oleate. This pathway (PUFA carbon recycling) is particularly active in several tissues during the suckling period when, depending on the tissue, >200 fold more carbon from alpha-linolenate can be recycled into newly synthesized lipids than is used to make docosahexaenoate. At least in rats, PUFA carbon recycling also occurs in adults and even during extreme linoleate deficiency. Hence, this pathway should be considered an obligatory component of PUFA metabolism. It is still speculative but part of the clinical benefit of the very high fat ketogenic diet in intractable seizures may be achieved by raising plasma levels of PUFA that have anti-seizure effects, especially arachidonate and docosahexaenoate. Hence, in addition to some PUFA being ketogenic substrates, the state of ketosis involves potentially beneficial changes in PUFA homeostasis. Both the molecular controls on these pathways and their clinical significance still need elucidation.
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Affiliation(s)
- Stephen C Cunnane
- Research Center on Aging, Sherbrooke University Geriatric Institute, Sherbrooke QC, Canada J1H 4C4
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McCloy U, Ryan MA, Pencharz PB, Ross RJ, Cunnane SC. A comparison of the metabolism of eighteen-carbon 13C-unsaturated fatty acids in healthy women. J Lipid Res 2003; 45:474-85. [PMID: 14679164 DOI: 10.1194/jlr.m300304-jlr200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Altered use of different dietary fatty acids may contribute to several chronic diseases, including obesity, noninsulin-dependent diabetes mellitus, and cardiovascular disease. However, few comparative data are available to support this link, so the goal of the present study was to compare the metabolism of [(13)C]oleate, [(13)C]alpha-linolenate, [(13)C]elaidate, and [(13)C]linoleate through oxidation and incorporation into plasma lipid fractions and adipose tissue. Each tracer was given as a single oral bolus to six healthy women. Samples were collected over 8 days, and (13)C was analyzed using isotope ratio mass spectrometry. At 9 h postdose, cumulative oxidation was similar for [(13)C]elaidate, [(13)C]oleate, and [(13)C]alpha-linolenate (19 +/- 1%, 20 +/- 4%, and 19 +/- 3% dose, respectively). Significantly lower oxidation of [(13)C]linoleate (12 +/- 4% dose; P < 0.05) was accompanied by its higher incorporation into plasma phospholipids and cholesteryl esters. Abdominal adipose tissue was enriched with [(13)C]alpha-linolenate, [(13)C]elaidate, or [(13)C]linoleate within 6 h. The percentage linoleate in plasma phospholipids correlated positively with [(13)C]linoleate and [(13)C]elaidate oxidation, indicating a potential role of background diet. Conversion of [(13)C]linoleate and [(13)C]alpha-linolenate to longer chain polyunsaturates was a quantitatively minor route of utilization.
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Affiliation(s)
- U McCloy
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 3E2.
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12
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Abstract
The term 'essential fatty acid' is ambiguous and inappropriately inclusive or exclusive of many polyunsaturated fatty acids. When applied most rigidly to linoleate and alpha-linolenate, this term excludes the now well accepted but conditional dietary need for two long chain polyunsaturates (arachidonate and docosahexaenoate) during infancy. In addition, because of the concomitant absence of dietary alpha-linolenate, essential fatty acid deficiency is a seriously flawed model that has probably led to significantly overestimating linoleate requirements. Linoleate and alpha-linolenate are more rapidly beta-oxidized and less easily replaced in tissue lipids than the common 'non-essential' fatty acids (palmitate, stearate, oleate). Carbon from linoleate and alpha-linolenate is recycled into palmitate and cholesterol in amounts frequently exceeding that used to make long chain polyunsaturates. These observations represent several problems with the concept of 'essential fatty acid', a term that connotes a more protected and important fatty acid than those which can be made endogenously. The metabolism of essential and non-essential fatty acids is clearly much more interconnected than previously understood. Replacing the term 'essential fatty acid' by existing but less biased terminology, i.e. polyunsaturates, omega3 or omega6 polyunsaturates, or naming the individual fatty acid(s) in question, would improve clarity and would potentially promote broader exploration of the functional and health attributes of polyunsaturated fatty acids.
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Affiliation(s)
- Stephen C Cunnane
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, 150 College Street, M5S 3E2, Toronto, Canada.
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Cunnane SC, Ryan MA, Nadeau CR, Bazinet RP, Musa-Veloso K, McCloy U. Why is carbon from some polyunsaturates extensively recycled into lipid synthesis? Lipids 2003; 38:477-84. [PMID: 12848297 DOI: 10.1007/s11745-003-1087-8] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We summarize here the evidence indicating that carbon from alpha-linolenate and linoleate is readily recycled into newly synthesized lipids. This pathway consumes the majority of these fatty acids that is not beta-oxidized as a fuel. Docosahexaenoate undergoes less beta-oxidation and carbon recycling than do alpha-linolenate or linoleate, but is it still actively metabolized by this pathway? Among polyunsaturates, arachidonate appears to undergo the least beta-oxidation and carbon recycling, an observation that may help account for the resistance of brain membranes to loss of arachidonate during dietary deficiency of n-6 polyunsaturates. Preliminary evidence suggests that de novo lipid synthesis consumes carbon from alpha-linolenate and linoleate in preference to palmitate, but this merits systematic study. Active beta-oxidation and carbon recycling of 18-carbon polyunsaturates does not diminish the importance of being able to convert alpha-linolenate and linoleate to long-chain polyunsaturates but suggests that a broad perspective is required in studying the metabolism of polyunsaturates in general and alpha-linolenate and linoleate in particular.
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Affiliation(s)
- Stephen C Cunnane
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Canada M5S 3E2.
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Bell MV, Dick JR, Porter AEA. Pyloric ceca are significant sites of newly synthesized 22:6n-3 in rainbow trout (Oncorhynchus mykiss). Lipids 2003; 38:39-44. [PMID: 12669818 DOI: 10.1007/s11745-003-1029-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
In this pulse-chase study, rainbow trout fed a diet containing deuterated (D5) (17,17,18,18,18)-18:3n-3 ethyl ester accumulated D5-22:6n-3 in pyloric ceca to a greater extent than in liver 2 d post-dose. The ratio of newly synthesized D5-22:6n-3 in ceca to that in liver 2 d after feeding D5-18:3n-3 was 4.7 +/- 1.2 when expressed as per mg tissue and 5.2 +/- 2.4 when expressed as per mg protein. The amount of D5-22:6n-3 in ceca then declined whereas that in liver and blood increased, with the ratio of ceca to liver falling to 1.7 and 1.4, respectively, by day 5 and approaching unity by day 9. A crude cecal mucosa fraction contained 123 +/- 50 ng D5-22:6n-3/mg protein/mg D5-18:3n-3 eaten 2 d after feeding the tracer, compared with 35 +/- 21 ng D5-22:6n-3/mg protein/mg D5-18:3n-3 eaten in liver. Three days later the amount in cecal mucosa had fallen by one-third and that in liver had increased threefold. Most of the D5-18:3n-3 was catabolized very rapidly. The ratio of D5-18:3n-3 to 21:4n-6 (a relatively inert FA marker) in the diet was 4.0, but this fell to 0.30 in ceca and ca. 0.8 in liver, blood, and whole carcass one day after feeding. These results indicate that ceca are active in the synthesis of 22:6n-3 and the oxidation of 18:3n-3.
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Affiliation(s)
- M V Bell
- Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, United Kingdom.
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Significant utilization of dietary arachidonic acid is for brain adrenic acid in baboon neonates. J Lipid Res 2002. [DOI: 10.1016/s0022-2275(20)30118-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Broadhurst CL, Wang Y, Crawford MA, Cunnane SC, Parkington JE, Schmidt WF. Brain-specific lipids from marine, lacustrine, or terrestrial food resources: potential impact on early African Homo sapiens. Comp Biochem Physiol B Biochem Mol Biol 2002; 131:653-73. [PMID: 11923081 DOI: 10.1016/s1096-4959(02)00002-7] [Citation(s) in RCA: 207] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The polyunsaturated fatty acid (PUFA) composition of the mammalian central nervous system is almost wholly composed of two long-chain polyunsaturated fatty acids (LC-PUFA), docosahexaenoic acid (DHA) and arachidonic acid (AA). PUFA are dietarily essential, thus normal infant/neonatal brain, intellectual growth and development cannot be accomplished if they are deficient during pregnancy and lactation. Uniquely in the human species, the fetal brain consumes 70% of the energy delivered to it by mother. DHA and AA are needed to construct placental and fetal tissues for cell membrane growth, structure and function. Contemporary evidence shows that the maternal circulation is depleted of AA and DHA during fetal growth. Sustaining normal adult human brain function also requires LC-PUFA.Homo sapiens is unlikely to have evolved a large, complex, metabolically expensive brain in an environment which did not provide abundant dietary LC-PUFA. Conversion of 18-carbon PUFA from vegetation to AA and DHA is considered quantitatively insufficient due to a combination of high rates of PUFA oxidation for energy, inefficient and rate limited enzymatic conversion and substrate recycling. The littoral marine and lacustrine food chains provide consistently greater amounts of pre-formed LC-PUFA than the terrestrial food chain. Dietary levels of DHA are 2.5-100 fold higher for equivalent weights of marine fish or shellfish vs. lean or fat terrestrial meats. Mammalian brain tissue and bird egg yolks, especially from marine birds, are the richest terrestrial sources of LC-PUFA. However, land animal adipose fats have been linked to vascular disease and mental ill-health, whereas marine lipids have been demonstrated to be protective. At South African Capesites, large shell middens and fish remains are associated with evidence for some of the earliest modern humans. Cape sites dating from 100 to 18 kya cluster within 200 km of the present coast. Evidence of early H. sapiens is also found around the Rift Valley lakes and up the Nile Corridor into the Middle East; in some cases there is an association with the use of littoral resources. Exploitation of river, estuarine, stranded and spawning fish, shellfish and sea bird nestlings and eggs by Homo could have provided essential dietary LC-PUFA for men, women, and children without requiring organized hunting/fishing, or sophisticated social behavior. It is however, predictable from the present evidence that exploitation of this food resource would have provided the advantage in multi-generational brain development which would have made possible the advent of H. sapiens. Restriction to land based foods as postulated by the savannah and other hypotheses would have led to degeneration of the brain and vascular system as happened without exception in all other land based apes and mammals as they evolved larger bodies.
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Affiliation(s)
- C Leigh Broadhurst
- US Department of Agriculture, Environmental Chemistry Laboratory, Agricultural Research Service, Beltsville, MD 20705, USA
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Abstract
PURPOSE The AY-9944 (AY)-treated rat is a reproducible and clinically relevant animal model of atypical absence seizures. AY inhibits cholesterol synthesis, but the relation between brain sterol levels and the spontaneously recurrent absence seizures has not been determined. METHODS Long-Evans hooded rats were treated every 6 days from postnatal day (P)2 to P20 with AY (7.5 mg/kg, s.c.) or saline. Electrodes were permanently implanted under pentobarbital anesthesia at P50. Spike-and-wave discharge (SWD) duration and amplitude were quantified at P55. Changes in brain sterols after AY were examined in three different experiments, looking at brain regions (experiment 1), recovery after stopping AY (experiment 2), or gender differences (experiment 3). RESULTS Experiment 1: AY caused spontaneously recurrent slow SWD that lasted 59 times longer and had a 3.2-fold higher amplitude than that in controls. At P55, brain cholesterol was reduced and 7-dehydrocholesterol was increased in all brain regions (p < 0.0001). Experiment 2: Four hundred days after stopping AY-9944 treatment (P420), brain sterol levels had returned to normal levels, but the AY-induced SWD lasted twice as long as at P55. Experiment 3: At P55, AY-induced changes in plasma and liver (but not brain) sterols were significantly more severe in females compared with males. CONCLUSIONS AY-induced seizures appear to be related to AY-induced changes in brain sterols but persisted long after the sterols had returned to normal after the last AY injection. Hence, there appears to be a critical developmental window during which the AY must be given but after which the AY-induced change in brain sterols is no longer essential to sustaining the seizures.
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Affiliation(s)
- Miguel A Cortez
- Division of Neurology, The Brain and Behavior Program, The Hospital for Sick Children, Toronto, Ontario, Canada
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Bell MV, Dick JR, Porter AE. Biosynthesis and tissue deposition of docosahexaenoic acid (22:6n-3) in rainbow trout (Oncorhynchus mykiss). Lipids 2001; 36:1153-9. [PMID: 11768160 DOI: 10.1007/s11745-001-0826-1] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Rainbow trout (Oncorhynchus mykiss) weighing ca. 5 g and previously acclimated for 8 wk on a diet comprising vegetable oil (11%), fish meal (5%), and casein (48%) as the major constituents were fed a pulse of diet containing deuterated (D5) (17,17,18,18,18)-18:3n-3 ethyl ester. The synthesis and tissue distribution of D5-22:6n-3 was determined 3, 7, 14, 24, and 35 d after the pulse. The whole-body accumulation of D5-22:6n-3 was linear over the first 7 d, corresponding to a rate of 0.54 +/- 0.12 microg D5-22:6n-3/g fish/mg D5-18:3n-3 eaten/d. Maximal accretion of D5-22:6n-3 was 4.3 +/- 1.2 microg/g fish/mg of D5-18:3n-3 eaten after 14 d. The amount of D5-22:6n-3 peaked in liver at day 7, in brain and eyes at day 24, and plateaued after day 14 in visceral and eye socket adipose tissue and in the whole fish. The majority of D5-22:6n-3 was found in the carcass (remaining tissues minus the above tissues analyzed separately) at all times. On a per milligram lipid basis, liver and eyes had the highest concentration of D5-22:6n-3. The experimental diet also contained 21:4n-6 ethyl ester as a marker to estimate the amount of food eaten by individual fish. From such estimates it was calculated that the great majority of the D5-tracer was catabolized, with the combined recovery of D5-18:3n-3 plus D5-22:6n-3 being 2.6%. The recovery of 21:4n-6 was 57.6%. The concentration of 22:6n-3 in the fish decreased during the 13-wk period, and the amount of 22:6n-3 synthesized from 18:3n-3 was only about 5% of that obtained directly from the fish meal in the diet.
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Affiliation(s)
- M V Bell
- Institute of Aquaculture, University of Stirling, Scotland, United Kingdom.
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Rapoport SI, Chang MC, Spector AA. Delivery and turnover of plasma-derived essential PUFAs in mammalian brain. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31629-1] [Citation(s) in RCA: 252] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Cunnane S, Trotti D, Ryan M. Specific linoleate deficiency in the rat does not prevent substantial carbon recycling from [14C]linoleate into sterols. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)31974-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Cunnane SC. Commentary on the workshop statement. Essentiality of and recommended dietary intakes for Omega-6 and Omega-3 fatty acids. Prostaglandins Leukot Essent Fatty Acids 2000; 63:139-44. [PMID: 10991770 DOI: 10.1054/plef.2000.0182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- S C Cunnane
- Department of Nutritional Sciences, University of Toronto, Toronto M5S 3E2, Canada
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Cunnane SC, Francescutti V, Brenna JT, Crawford MA. Breast-fed infants achieve a higher rate of brain and whole body docosahexaenoate accumulation than formula-fed infants not consuming dietary docosahexaenoate. Lipids 2000; 35:105-11. [PMID: 10695931 DOI: 10.1007/s11745-000-0501-6] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Docosahexaenoate (DHA) has been increasingly recognized as an important fatty acid for neural and visual development during the first 6 mon of life. One important point of controversy that remains is the degree to which adequate levels of DHA can be acquired from endogenous synthesis in infants vs. what should be provided as dietary DHA. We have approached this problem by a retrospective analysis of published body composition data to estimate the actual accumulation of DHA in the human infant brain, liver, adipose tissue, remaining lean tissue, and whole body. Estimating whether infants can synthesize sufficient DHA required comparison to and extrapolation from animal data. Over the first 6 mon of life, DHA accumulates at about 10 mg/d in the whole body of breast-fed infants, with 48% of that amount appearing in the brain. To achieve that rate of accumulation, breast-fed infants need to consume a minimum of 20 mg DHA/d. Virtually all breast milk provides a DHA intake of at least 60 mg/d. Despite a store of about 1,050 mg of DHA in body fat at term birth and an intake of about 390 mg/d alpha-linolenate (alpha-LnA), the brain of formula-fed infants not consuming DHA accumulates half the DHA of the brain of breast-fed infants while the rest of the body actually loses DHA over the first 6 mon of life. No experimental data indicate that formula-fed infants not consuming DHA are able to convert the necessary 5.2% of alpha-LnA intake to DHA to match the DHA accumulation of breast-fed infants. We conclude that dietary DHA should likely be provided during at least the first 6 mon of life.
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Affiliation(s)
- S C Cunnane
- Department of Nutritional Sciences, University of Toronto, Canada.
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Cunnane SC, Menard CR, Likhodii SS, Brenna JT, Crawford MA. Carbon recycling into de novo lipogenesis is a major pathway in neonatal metabolism of linoleate and alpha-linolenate. Prostaglandins Leukot Essent Fatty Acids 1999; 60:387-92. [PMID: 10471127 DOI: 10.1016/s0952-3278(99)80018-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent reports indicate that recycling of the beta-oxidized carbon skeleton of linoleate and alpha-linolenate into newly synthesized cholesterol and fatty acids in the brain is quantitatively significant in both suckling rats and pre- and postnatally in rhesus monkeys. The recycling appears to occur via ketones which are not only readily produced from these 18 carbon polyunsaturates but are also the main lipogenic precursors for the developing mammalian brain. Since the neonatal rat brain appears not to acquire cholesterol or long chain saturated or monounsaturated fatty acids from the circulation, ketones and ketogenic precursors seem to be crucial for normal brain synthesis of these lipids. Cholesterol is plentiful in brain membranes and it has also been discovered to be the essential lipid adduct of the 'hedgehog' family of proteins, the appropriate expression of which determines normal embryonic tissue patterning and neurological development. Insufficient cholesterol or inappropriate expression of 'sonic hedgehog' has major adverse neurodevelopmental consequences typified in humans by Smith-Lemli-Optiz syndrome. Hence, we propose that the importance of alpha-linolenate and linoleate for normal neural development arises not only from being precursors to longer chain polyunsaturates incorporated into neuronal membranes but, perhaps equally importantly, by being ketogenic precursors needed for in situ brain lipid synthesis.
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Affiliation(s)
- S C Cunnane
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada.
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