Suppression of PPAR-gamma attenuates insulin-stimulated glucose uptake by affecting both GLUT1 and GLUT4 in 3T3-L1 adipocytes.
Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) plays a critical role in regulating insulin sensitivity and glucose homeostasis. In this study, we identified highly efficient small interfering RNA (siRNA) sequences and used lentiviral short hairpin RNA and electroporation of siRNAs to deplete PPAR-gamma from 3T3-L1 adipocytes to elucidate its role in adipogenesis and insulin signaling. We show that PPAR-gamma knockdown prevented adipocyte differentiation but was not required for maintenance of the adipocyte differentiation state after the cells had undergone adipogenesis. We further demonstrate that PPAR-gamma suppression reduced insulin-stimulated glucose uptake without affecting the early insulin signaling steps in the adipocytes. Using dual siRNA strategies, we show that this effect of PPAR-gamma deletion was mediated by both GLUT4 and GLUT1. Interestingly, PPAR-gamma-depleted cells displayed enhanced inflammatory responses to TNF-alpha stimulation, consistent with a chronic anti-inflammatory effect of endogenous PPAR-gamma. In summary, 1) PPAR-gamma is essential for the process of adipocyte differentiation but is less necessary for maintenance of the differentiated state, 2) PPAR-gamma supports normal insulin-stimulated glucose transport, and 3) endogenous PPAR-gamma may play a role in suppression of the inflammatory pathway in 3T3-L1 cells.
Liao
Wei
W
Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA 92093, USA.
Nguyen
M T Audrey
MT
Yoshizaki
Takeshi
T
Favelyukis
Svetlana
S
Patsouris
David
D
Imamura
Takeshi
T
Verma
Inder M
IM
Olefsky
Jerrold M
JM
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000502:physiology*; D051275:Glucose Transporter Type 4 / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D047495:PPAR gamma / Q000037:antagonists & inhibitors* / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology*
D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin; D047495:PPAR gamma; D034741:RNA, Small Interfering; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; D005947:Glucose