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Neuroscience. 2013;255:1-18. doi: 10.1016/j.neuroscience.2013.09.012. Epub 2013 Sep 14.

Metabolomics uncovers dietary omega-3 fatty acid-derived metabolites implicated in anti-nociceptive responses after experimental spinal cord injury.

Author information

1
Center for Health Disparities and Molecular Medicine, Loma Linda University, Loma Linda, CA, United States; Department of Basic Sciences, Loma Linda University, Loma Linda, CA, United States; Department of Pathology and Human Anatomy, Loma Linda University, Loma Linda, CA, United States.

Abstract

Chronic neuropathic pain is a frequent comorbidity following spinal cord injury (SCI) and often fails to respond to conventional pain management strategies. Preventive administration of docosahexaenoic acid (DHA) or the consumption of a diet rich in omega-3 polyunsaturated fatty acids (O3PUFAs) confers potent prophylaxis against SCI and improves functional recovery. The present study examines whether this novel dietary strategy provides significant antinociceptive benefits in rats experiencing SCI-induced pain. Rats were fed control chow or chow enriched with O3PUFAs for 8weeks before being subjected to sham or cord contusion surgeries, continuing the same diets after surgery for another 8 more weeks. The paw sensitivity to noxious heat was quantified for at least 8weeks post-SCI using the Hargreaves test. We found that SCI rats consuming the preventive O3PUFA-enriched diet exhibited a significant reduction in thermal hyperalgesia compared to those consuming the normal diet. Functional neurometabolomic profiling revealed a distinctive deregulation in the metabolism of endocannabinoids (eCB) and related N-acyl ethanolamines (NAEs) at 8weeks post-SCI. We found that O3PUFAs consumption led to a robust accumulation of novel NAE precursors, including the glycerophospho-containing docosahexaenoyl ethanolamine (DHEA), docosapentaenoyl ethanolamine (DPEA), and eicosapentaenoyl ethanolamine (EPEA). The tissue levels of these metabolites were significantly correlated with the antihyperalgesic phenotype. In addition, rats consuming the O3PUFA-rich diet showed reduced sprouting of nociceptive fibers containing CGRP and dorsal horn neuron p38 mitogen-activated protein kinase (MAPK) expression, well-established biomarkers of pain. The spinal cord levels of inositols were positively correlated with thermal hyperalgesia, supporting their role as biomarkers of chronic neuropathic pain. Notably, the O3PUFA-rich dietary intervention reduced the levels of these metabolites. Collectively, these results demonstrate the prophylactic value of dietary O3PUFA against SCI-mediated chronic pain.

KEYWORDS:

1-OG; 1-oleoyl glycerol; 2-AG; 2-PG; 2-arachidonoyl glycerol; 2-palmitoyl glycerol; AEA; Abh4; BBB; Basso, Beattie and Bresnahan; CGRP; DHA; DHEA; DPEA; EG; EPA; EPEA; G3P; GAP43; GC/MS; GDE1; GP-NAEs; HWL; LEA; LPA; MAPK; N-acyl ethanolamines; N-acyl phosphatidyl ethanolamine; NAEs; NAPE; O3PUFAs; PA; PEA; PLD; PLS-DA; SCI; TH; UHPLC/MS/MS(2); arachidonoyl ethanolamine; calcitonin gene-related peptide; chronic pain; dietary fatty acids; docosahexaenoic acid; docosahexaenoyl ethanolamine/synaptamide; docosapentaenoyl ethanolamine; eCBs; eicosapentaenoyl ethanolamine; eicosenoyl glycerol; endocannabinoid metabolome; endocannabinoids; gas chromatography/mass spectrometry; glycerol-3-phosphate; glycerophospho-containing N-acyl ethanolamines; glycerophosphodiesterase; growth-associated protein 43; hindpaw withdrawal latency; linoleyl ethanolamine; lyso-phosphatidic acid; mitogen-activated protein kinase; omega-3 polyunsaturated fatty acids; palmitoyl ethanolamine; partial least square-discriminant analysis; phosphatidic acid; phospholipase A/B or α-β-hydrolase 4; phospholipase D; spinal cord injury; thermal hyperalgesia; ultrahigh performance liquid chromatography/tandem mass spectrometry

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