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Molecular and Cellular Biology, June 2005, p. 5146-5157, Vol. 25, No. 12
0270-7306/05/$08.00+0     doi:10.1128/MCB.25.12.5146-5157.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Overexpression of Glucose-6-Phosphate Dehydrogenase Is Associated with Lipid Dysregulation and Insulin Resistance in Obesity

School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea

Received 16 September 2004/ Returned for modification 20 October 2004/ Accepted 11 March 2005

Glucose-6-phosphate dehydrogenase (G6PD) produces cellular NADPH, which is required for the biosynthesis of fatty acids and cholesterol. Although G6PD is required for lipogenesis, it is poorly understood whether G6PD in adipocytes is involved in energy homeostasis, such as lipid and glucose metabolism. We report here that G6PD plays a role in adipogenesis and that its increase is tightly associated with the dysregulation of lipid metabolism and insulin resistance in obesity. We observed that the enzymatic activity and expression levels of G6PD were significantly elevated in white adipose tissues of obese models, including db/db, ob/ob, and diet-induced obesity mice. In 3T3-L1 cells, G6PD overexpression stimulated the expression of most adipocyte marker genes and elevated the levels of cellular free fatty acids, triglyceride, and FFA release. Consistently, G6PD knockdown via small interfering RNA attenuated adipocyte differentiation with less lipid droplet accumulation. Surprisingly, the expression of certain adipocytokines such as tumor necrosis factor alpha and resistin was increased, whereas that of adiponectin was decreased in G6PD overexpressed adipocytes. In accordance with these results, overexpression of G6PD impaired insulin signaling and suppressed insulin-dependent glucose uptake in adipocytes. Taken together, these data strongly suggest that aberrant increase of G6PD in obese and/or diabetic subjects would alter lipid metabolism and adipocytokine expression, thereby resulting in failure of lipid homeostasis and insulin resistance in adipocytes.

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