Targeting glutamine synthesis inhibits stem cell adipogenesis in vitro

Velickovic, Ksenija; Lugo Leija, Hilda Anaid; Surrat, Amal; Kim, Dong-Hyun; Sacks, Harold; Symonds, Michael E.; Sottile, Virginie

Abstract

Background/Aims: Glutamine is the most abundant amino acid in the body and has a metabolic role as a precursor for protein, amino sugar and nucleotide synthesis. After glucose, glutamine is the main source of energy in cells and has recently been shown to be an important carbon source for de novo lipogenesis. Glutamine is synthesized by the enzyme glutamine synthetase, a mitochondrial enzyme that is active during adipocyte differentiation suggesting a regulatory role in this process. The aim of our study was therefore to investigate whether glutamine status impacts on differentiation of adipocytes and lipid droplet accumulation.

Methods: Mouse mesenchymal stem cells (MSCs) were submitted to glutamine deprivation (i.e. glutamine-free adipogenic medium in conjunction with irreversible glutamine synthetase inhibitor, methionine sulfoximine – MSO) during differentiation and their response compared with MSCs differentiated in glutamine-supplemented medium (5, 10 and 20 mM). Differentiated MSCs were assessed for lipid content using Oil Red O (ORO) staining and gene expression was analysed by qPCR. Intracellular glutamine levels were determined using a colorimetric assay, while extracellular glutamine was measured using liquid chromatography-mass spectrometry (LC-MS).

Results: Glutamine deprivation largely abolished adipogenic differentiation and lipid droplet formation. This was accompanied with a reduction in intracellular glutamine concentration, and downregulation of gene expression for classical adipogenic markers including PPARγ. Furthermore, glutamine restriction suppressed isocitrate dehydrogenase 1 (IDH1) gene expression, an enzyme which produces citrate for lipid synthesis. In contrast, glutamine supplementation promoted adipogenic differentiation in a dose-dependent manner.

Conclusion: These results suggest that the glutamine pathway may have a previously overlooked role in adipogenesis. The underlying mechanism involved the glutamine-IDH1 pathway and could represent a potential therapeutic strategy to treat excessive lipid accumulation and thus obesity.

Citation

Velickovic, K., Lugo Leija, H. A., Surrat, A., Kim, D.-H., Sacks, H., Symonds, M. E., & Sottile, V. (2020). Targeting glutamine synthesis inhibits stem cell adipogenesis in vitro. Cellular Physiology and Biochemistry, 54(5), 917-927. https://doi.org/10.33594/000000278

• Journal Article Type: Article
• Acceptance Date: Sep 7, 2020
• Online Publication Date: Sep 19, 2020
• Publication Date: Sep 19, 2020
• Deposit Date: Sep 21, 2020
• Publicly Available Date: Sep 21, 2020
• Journal: Cellular Physiology and Biochemistry
• Print ISSN: 1015-8987
• Publisher: Karger Publishers
• Peer Reviewed: Peer Reviewed
• Volume: 54
• Issue: 5
• Pages: 917-927
• DOI: https://doi.org/10.33594/000000278
• Public URL: https://nottingham-repository.worktribe.com/output/4918334
• Publisher URL: https://www.cellphysiolbiochem.com/Articles/000278/