Regulation of PPAR gamma gene expression by nutrition and obesity in rodents.
The orphan nuclear receptor, peroxisome proliferator-activated receptor (PPAR) gamma, is implicated in mediating expression of fat-specific genes and in activating the program of adipocyte differentiation. The potential for regulation of PPAR gamma gene expression in vivo is unknown. We cloned a partial mouse PPAR gamma cDNA and developed an RNase protection assay that permits simultaneous quantitation of mRNAs for both gamma l and gamma 2 isoforms encoded by the PPAR gamma gene. Probes for detection of adipocyte P2, the obese gene product, leptin, and 18S mRNAs were also employed. Both gamma l and gamma 2 mRNAs were abundantly expressed in adipose tissue. PPAR gamma 1 expression was also detected at lower levels in liver, spleen, and heart; whereas, gamma l and gamma 2 mRNA were expressed at low levels in skeletal muscle. Adipose tissue levels of gamma l and gamma 2 were not altered in two murine models of obesity (gold thioglucose and ob/ob), but were modestly increased in mice with toxigene-induced brown fat ablation uncoupling protein diphtheria toxin A mice. Fasting (12-48 h) was associated with an 80% fall in PPAR gamma 2 and a 50% fall in PPAR gamma mRNA levels in adipose tissue. Western blot analysis demonstrated a marked effect of fasting to reduce PPAR gamma protein levels in adipose tissue. Similar effects of fasting on PPAR gamma mRNAs were noted in all three models of obesity. Insulin-deficient (streptozotocin) diabetes suppressed adipose tissue gamma l and gamma 2 expression by 75% in normal mice with partial restoration during insulin treatment. Levels of adipose tissue PPAR gamma 2 mRNA were increased by 50% in normal mice exposed to a high fat diet. In obese uncoupling protein diphtheria toxin A mice, high fat feeding resulted in de novo induction of PPAR gamma 2 expression in liver. We conclude (a) PPAR gamma 2 mRNA expression is most abundant in adipocytes in normal mice, but lower level expression is seen in skeletal muscle; (b) expression of adipose tissue gamma1 or gamma2 mRNAs is increased in only one of the three models of obesity; (c) PPAR gamma 1 and gamma 2 expression is downregulated by fasting and insulin-deficient diabetes; and (d) exposure of mice to a high fat diet increases adipose tissue expression of PPAR gamma (in normal mice) and induces PPAR gamma 2 mRNA expression in liver (in obese mice). These findings demonstrate in vivo modulation of PPAR gamma mRNA levels over a fourfold range and provide an additional level of regulation for the control of adipocyte development and function.
Vidal-Puig
A
A
Department of Medicine, Beth Israel Hospital, Boston, Massachusetts 02215, USA.
Jimenez-Liñan
M
M
Lowell
B B
BB
Hamann
A
A
Hu
E
E
Spiegelman
B
B
Flier
J S
JS
Moller
D E
DE
D017667:Adipocytes / Q000378:metabolism; D000273:Adipose Tissue / Q000378:metabolism; D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000502:physiology; D000818:Animals; D006051:Aurothioglucose / Q000494:pharmacology; D001483:Base Sequence; D017931:DNA Primers; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D004041:Dietary Fats; D004167:Diphtheria Toxin / Q000633:toxicity; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D020738:Leptin; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009765:Obesity / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D012336:RNA, Ribosomal, 16S / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis*; D012016:Reference Values; D013154:Spleen / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000187:drug effects
D017931:DNA Primers; D004041:Dietary Fats; D004167:Diphtheria Toxin; D020738:Leptin; D011506:Proteins; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D006051:Aurothioglucose