The Effect of Pioglitazone on Peroxisome Proliferator-Activated Receptor-γ Target Genes Related to Lipid Storage In Vivo
- Iwona Bogacka, PHD,
- Hui Xie, MS,
- George A. Bray, MD and
- Steven R. Smith, MD
- Address correspondence and reprint requests to Iwona Bogacka, Pennington Biomedical Research Center, 6400 Perkins Rd., Baton Rouge, LA 70808. E-mail: bogackiu{at}pbrc.edu
Abstract
OBJECTIVE—Pioglitazone is a member of the thiazolidinediones (TZDs), insulin-sensitizing agents used to treat type 2 diabetes. The aim of this study was to define the effect of pioglitazone on the expression of genes related to carbohydrate and lipid metabolism in subcutaneous fat obtained from type 2 diabetic patients.
RESEARCH DESIGN AND METHODS—Forty-eight volunteers with type 2 diabetes were divided into two groups treated for 12 weeks with placebo or pioglitazone (30 mg/day). The expression of several genes was quantified by real-time RT-PCR.
RESULTS—Pioglitazone treatment increased the expression of genes involved in glycerol-3-phosphate synthesis. The mRNA expression of PEPCK-C and glycerol-3-phosphate dehydrogenase (GPDH) increased (P < 0.01) in patients treated with pioglitazone. There was no difference in glycerol kinase (GyK) mRNA levels. The expression of genes that regulate fatty acid availability in adipocytes, including lipoprotein lipase (LPL) and acetyl-CoA synthetase (ACS), was higher (P < 0.01) in pioglitazone-treated patients. Pioglitazone stimulated (P < 0.0001) expression of c-Cbl-associated protein (CAP), whereas tumor necrosis factor-α, leptin, resistin, angiopoietin like-4, and 11-β-hydroxysteroid dehydrogenase type 1 (11β HSD 1) were not affected by pioglitazone. The baseline peroxisome proliferator-activated receptor (PPAR)-γ1 mRNA was significantly correlated with mRNA for LPL, CAP, ACS, 11β HSD 1, GyK, fatty acid synthase, leptin, and GPDH, whereas PPAR-γ2 mRNA was correlated with CAP, PEPCK-C, leptin, and GPDH.
CONCLUSIONS—Treatment with pioglitazone increased body weight, and this is associated with upregulation of some, but not all, genes previously demonstrated as “TZD responsive” in subcutaneous fat. The results suggest that TZDs might increase body weight through the upregulation of genes facilitating adipocyte lipid storage in vivo.
- ACS, acetyl-CoA synthetase
- ANGPTL-4, angiopoietin like-4
- CAP, c-Cbl-associated protein
- FAS, fatty acid synthase
- GPDH, glycerol-3-phosphate dehydrogenase
- GyK, glycerol kinase
- 11β HSD 1, 11-β-hydroxysteroid dehydrogenase type 1
- LPL, lipoprotein lipase
- PPAR, peroxisome proliferator-activated receptor
- TZD, thiazolidinedione
Footnotes
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I.B. and H.X. are involved in a project sponsored by Takeda Pharmaceuticals. G.A.B. serves on the scientific advisory board for and has received honoraria and laboratory funding from Takeda Pharmaceuticals. S.R.S. has served as an ad hoc consultant for and has received honoraria and laboratory funding from Takeda Pharmaceuticals.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
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- Accepted March 25, 2004.
- Received January 7, 2004.
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