Hypoxia during the expansion of adipocytes is known to contribute both to the secretion of multiple inflammation-related adipokines as well as to obesity. We therefore investigated the nature of protein changes Occurring in adipocytes during hypoxia by observation of the intracellular proteins that are expressed in 3T3-L1 adipocytes. Lysates were utilized for quantitative proteome analysis using isobaric tags for relative and absolute quantitation (iTRAQ) combined with peptide separation by multi-dimensional liquid chromatography. Antioxidants and elongation factors, as well as glycolytic enzymes were increased in hypoxic adipocytes. These changes were supported by similar changes Suggested by real-time PCR. The proteins showing changes are all potential targets for revering the mechanism behind the phenomenon of induction of obese adipocytes by hypoxia. This Study can therefore aid in defining the proteomic changes that occur in adipocytes in response to oxygen stress, and can further characterize adipocyte metabolism and adaptation to low oxygen conditions. (C) 2009 Elsevier Inc. All rights reserved.