Effect of hypoxia on metabolic markers and gene expression HIF-1 α in adipocytes

Abstract

Background: Docosahexaenoic acid (DHA; omega-3 fatty acid) has been reported to have potential anti-obesity properties. Hypoxia is a condition that results from the excessive expansion of white adipose tissue resulting in obesity-related conditions including insulin resistance, inflammation and oxidative stress. Methods: The objective of this study was to test the effects of DHA on the hypoxia responses (1.0 % for 24 hours) of 3T3-L1 adipocytes with a focus on oxidative stress, inflammation, and mitochondrial function, and antioxidant status. Cell viability, reactive oxygen species (ROS) and apoptosis were measured by flow cytometry. The metabolic parameters such as lactate, glycerol release, glucose uptake and adenosine triphosphate (ATP) content were measured by fluorometer. The expression of (hypoxia inducible factor 1 α; HIF-1 α) and the secretion of adipocytokines were evaluated by qPCR (quantitative polymerase chain reaction) and ELISA (enzyme linked immunosorbant assay). Results: Under hypoxia conditions, DHA treatment resulted in significant changes in all critical parameters of adipocyte biology including HIF-1α RNA expression (decreased by 50%), decreased lactate and glycerol release (66% and 25% respectively), and reactive oxygen species (ROS) production (decreased by 15%), while glucose uptake was decreased by 25% accompnied by decreased secretion of pro-inflammatory markers (Interleukin 6 IL-6, 31% reduction) , macrophage chemoattractant protein 1 MCP-1 (38% reduction) and leptin (14% reduction), and increased adiponectin secretion (by 45%). The exposure of adipocytes to 1% hypoxia significantly alters the transcript of hypoxia genes, and other genes involved in glucose (GLUT1, GLUT4) and lipid (PPAR-γ) metabolism, and is also linked to anaerobic metabolism with apoptosis and increased oxidative stress. Conclusion: Data indicate that DHA can exert potential anti-hypoxia effects by reducing the secretion of inflammatory adipocytokines, oxidative stress, lipolysis and apoptosis. This may ameliorate the deleterious effects of excess adiposity.