Abstract
This article describes the application of in vivo 13C-nuclear magnetic resonance (NMR) spectroscopy and gas chromatography (GC)-combustion-isotope ratio mass spectrometry to the study of brain uptake and metabolism of polyunsaturated fatty acids in the suckling rat model. NMR spectroscopy is uniquely suited to the noninvasive detection of nonradioactive metabolites in living animals. We applied this approach to the noninvasive detection of 13C-arachidonate in brain and liver of living suckling rats but found that technical limitations in our model, mainly poor signal-to-noise, largely prevent useful results at this time. However, in a tracer study using simultaneous doses of 13C-γ-linolenate and 13C-arachidonate, 13C-NMR of tissue lipid extracts quantitatively demonstrated a 10-fold greater (liver) or 17-fold greater (brain) accumulation of pre-formed vs newly synthesized arachidonate. GC-combustion-isotope ratio mass spectrometry was used to trace the utilization of [U-13C]-α-linolenate into three products in the brain: docosahexaenoate, cholesterol, and palmitate. The rationale was that although α-linolenate is used in de novo lipogenesis, the quantitative importance of this pathway is unknown. Our results in the suckling rat show that 2–13% of carbon from [U-13C]-α-linolenate appearing in brain lipids is in docosahexaenoate while the rest is in brain lipids synthesized de novo. Overall, these results indicate that the suckling rat brain prefers pre-formed to newly synthesized arachidonate and that α-linolenate is readily utilized in brain lipid synthesis. These methods are suited to comparative studies of the metabolism of polyunsaturates and they support previous observations that the metabolism of some polyunsaturates such as α-linolenate extends well beyond the traditional desaturation-chain elongation pathway.
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Bourre J-M., Pascal G., Durand G., Masson M., Dumont O., and Piciotti M. (1984) Alterations in the fatty acid composition of rat beain cells (neurons, astrocytes, oligodendrocytes) and of subcellular fractions (myelin, synaptosomes) induced by a diet devoid of n-3 fatty acids. J. Neurochem. 43, 342–348.
Crawford M. A., Casperd N. M., and Sinclair A. J. (1976) The long chain metabolites of linoleic and linolenic acids in liver and brain in herbivores and carnivores. Comp. Biochem. Physiol. 54B, 395–401.
Cunnane S. C. (1996) Recent studies on the synthesis, β-oxidation and deficiency of linoleate and α-linolenate: are essential fatty acids more aptly named indispensable or conditionally indispensable fatty acids? Can. J. Physiol. Pharmacol. 74, 629–639.
Cunnane S. C. and Anderson M. A. (1997) The majority of linoleate is partitioned to wards oxidation or storage in visceral fat in the growing rat. J. Nutr. 127, 146–152.
Cunnane S. C., Chen Z. Y., and Yang J. (1993) Low zinc intake increases apparent oxidation of linoleic and α-linolenic acids in the pregnant rat. Can. J. Physiol. Pharmacol. 71, 205–210.
Cunnane S. C., Francescutti V., Brenna J. T., and Crawford M. A. (2000) Breast-fed infants achieve a higher rate of brain and whole body docosahexaenoate accumulation than formula-fed infants not consuming dietary docosahexenoate. Lipids 35, 105–111.
Cunnane S. C., Moine G., Likhodii S. S., Vogt J., Corso T. N., Brenna J. T., et al. (1997) [3-13C]-γ-linolenate: A new probe for 13C-NMR studies of arachidonic acid synthesis in the suckling rat. Lipids 32, 211–217.
Cunnane S. C., Williams S. C. R., Bell J. D., Brookes S., Craig K., Iles R. A., and Crawford M. A. (1994) Utilization of [U-13C]-polyunsaturated fatty acids in the synthesis of long chain fatty acids and cholesterol accumulating in the neonatal rat brain. J. Neurochem. 62, 2429–2436.
Dhopeshwarkar G. A. and Subramanian C. (1975) Metabolism of linolenic acid in the developing brain. 1. Incorporation of radioactivity from [1-14C]-linolenic acid into brain fatty acids. Lipids 10, 238–241.
Edmond J., Higa T. A., Korsak R. A., Bergner E. A., and Lee W. N. P. (1998) Fatty acid transport and utilization for the developing brain. J. Neurochem. 70, 1227–1234.
Farquharson J., Cockburn F., Patrick W. A., Jamieson E. C., and Logan R. W. (1992) Infant cerebral cortex phospholipid fatty acid composition and diet. Lancet 340, 810–813.
Goodman K. J. and Brenna J. T. (1992) High sensitivity tracer detection using high precision gas chromotography-combustion-isotope ratio mass spectrometry and highly enriched [U-13C]-labelled precursors. Anal. Chem. 64, 1088–1095.
Likhodii S. S. and Cunnane S. C. (1999) Uptake of 13C-arachidonate and γ-linolenate by the brain and liver of the suckling rat observed using 13C-NMR. J. Neurochem. 72, 2548–2555.
Lucas A., Stafford M., Morley R., Abbott R., Stephenson T., MacFayden U., et al. (1999) Efficacy and safety of long chain polyunsaturated fatty acid supplementation of infant formula milk: a randomized trial. Lancet 354, 1948–1954.
Menard C. R., Goodman K. J., Corso T. N., Brenna J. T., and Cunnane S. C. (1998) Recycling of carbon into lipids synthesized de novo is a quantitatively important pathway of [U-13C]-α-linolenate utilization in the developing rat brain. J. Neurochem. 71, 2151–2158.
Moore S. A., Yoder E., Murphy S., Dutton G. R., and Spector A. A. (1991) Astrocytes, not neurons, produce docosahexaenoic acid (22;6n-3) and arachidonic acid (20;4n-6). J. Neurochem. 56, 518–524.
Sheaff-Greiner R. C., Zhang Q., Goodman K. J., Guissani D. A., Nathanielsz P. W., and Brenna J. T. (1996) Linoleate, α-linolenate and docosahexaenoate recycling into saturated and monounsaturated fatty acids is a major pathway in pregnant or lactating adults and fetal or infant rhesus monkeys. J. Lipid Res. 37, 2675–2686.
Sheaff-Greiner R. C., Winter J., Nathanielsz P. W., and Brenna J. T. (1997) Brain docosahexaenoate accretion in fetal baboons: bioequivalence of dietary α-linolenic and docosahexaenoic acids. Pediatr. Res. 42, 826–834.
Sinclair A. J. (1975) Incorporation of radioactive polyunsaturated fatty acids into liver and brain of the developing rat. Lipids 10, 175–184.
Su H. H., Bernardo L., Mirmiran M., Ma X. H., Corso T. N., Nathanielsz P. W., and Brenna J. T. (1999) Bioequivalence of dietary α-linolenic and docosahexaenoic acids as sources of docosahexaenoate accretion in brain and associated organs of neonatal baboons. Pediatr. Res. 45, 1–7.
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Cunnane, S.C., Nadeau, C.R. & Likhodii, S.S. NMR and isotope ratio mass spectrometry studies of in vivo uptake and metabolism of polyunsaturates by the developing rat brain. J Mol Neurosci 16, 173–180 (2001). https://doi.org/10.1385/JMN:16:2-3:173
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DOI: https://doi.org/10.1385/JMN:16:2-3:173