Exploring the Molecular Mechanisms of Dietary EPA+DHA in Mitigating Chemotherapy-Induced Skeletal Muscle Dysfunction: Insights from Multi-Omics Analysis
Creators: Isesele, Peter O
Publisher: name: University of Alberta Library
Year: 2024

<p>Skeletal muscle undergoes profound changes during tumor growth and chemotherapy treatment in cancer patients, characterized by muscle atrophy, weakness, and myosteatosis. It is increasingly recognized that alongside targeting cancer cells, chemotherapy exerts deleterious effects on muscle health. In experimental and clinical studies, dietary fish oil, rich in omega-3 fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), reduces chemotherapy-associated myosteatosis and enables the maintenance of muscle mass, but the underlying mechanisms remain unclear. The aim of this study was to understand the mechanisms underlying chemotherapy-induced changes and how the provision of dietary EPA+DHA counteracts these changes. Fischer 344 rats bearing the Ward colon tumor were fed a semi-purified diet resembling a Westernized diet. The experimental design consisted of rats divided into different groups. All groups, except the healthy group (HEALTHY, n=8), received tumor implantation. After two weeks of tumor growth, one group (TUMOR, n=8) that did not receive chemotherapy was euthanized. The remaining tumor-bearing rats received chemotherapy (Irinotecan, CPT-11 + 5-fluorouracil, 5-FU) and were euthanized after two cycles of chemotherapy (CONTROL, n=8 for each cycle) on a control diet or switched to a diet containing EPA+DHA (4.3 g/100 g of diet) in the form of purified fish oil at the start of chemotherapy (FISH OIL, n=8 for each cycle). This experimental setup was employed to investigate the effects of chemotherapy and dietary EPA+DHA on the transcriptomic profile of skeletal muscle. Genome-wide mRNA profiling was carried out on the skeletal muscle using Next Generation Sequencing (NGS). For further examination of acute effects and the sequence of events leading to observed changes in the skeletal muscle, the same experimental design was applied with slight modifications. All other tumor-bearing rats received chemotherapy and were euthanized four days after the start of chemotherapy (CONTROL Day 4, n=8) or eight days after (CONTROL Day 8, n=8) on a control diet or switched to a diet containing EPA+DHA (4.3 g/100 g of diet) in the form of purified fish oil at the start of chemotherapy for four days (FISH OIL Day 4, n=8) or eight days (FISH OIL Day 8, n=8) post-chemotherapy. Rats were euthanized on various days post-chemotherapy (days 0, 2, 4, and 8, and after two cycles of chemotherapy), and skeletal muscle (gastrocnemius) samples were collected for subsequent analyses. Fatty acid composition was analyzed by gas chromatography, cytokines were assessed using Meso Scale Discovering. Oxylipins, lipidomic profiling, and proteomic analysis were carried out using LC-MS/MS/MS. <br>
Rats that were given chemotherapy while on the control diet showed significant changes in gene expression, leading to disruptions in biological functions related to muscle morphology development, and cell death, while dietary EPA+DHA primarily suppressed pathways associated with leukocyte extravasation signaling. Linoleic acid and arachidonic acid were increased in muscle phospholipids following chemotherapy administration in rats on a control diet and were mitigated by feeding fish oil to enrich EPA and DHA in most muscle phospholipid species. Moreover, chemotherapy-induced elevation of the pro-inflammatory 9- and 13-hydroxyoctadecadienoic acids (HODEs) oxylipins derived from linoleic acid in rats on a control diet was mitigated by dietary EPA+DHA. Dietary EPA+DHA also increased the levels of anti-inflammatory oxylipins derived from DHA, such as 14-, 16-, and 17-hydroxydocosahexaenoic acids (HDoHEs). The presence of tumor induced disruptions to muscle by decreasing proteins involved in mitochondrial function, lipid oxidation, and protein synthesis, which were further exacerbated in rats that received chemotherapy on a control diet. However, dietary EPA+DHA increased proteins associated with mitochondrial function and electron transport, suggesting enhanced mitochondrial biogenesis and function while also increasing proteins involved in protein synthesis, potentially promoting muscle anabolism and counteracting chemotherapy-induced catabolic effects. One of the significant contributions of this study is the elucidation of dietary EPA+DHA as a promising therapeutic intervention for mitigating chemotherapy-induced muscle dysfunction in cancer. Through modulation of pathways of immune extravasation, lipid oxidation, mitochondria function,  and protein synthesis, dietary EPA+DHA demonstrates the capacity to enhance cellular energetics, promote muscle anabolism, and attenuate cellular and lipid-mediated inflammation within skeletal muscle tissue. This offers a novel approach to supportive care strategies to improve the overall well-being and treatment outcomes of cancer patients undergoing chemotherapy</p>