Evidence for differential effects of glucose and cycloheximide on mRNA levels of peroxisome proliferator-activated receptor- (PPAR-) machinery members: Superinduction of PPAR-gamma1 and -gamma2 mRNAs.
Quantitative real-time RT-PCR study was conducted to reveal the effects of normal (5 mmol/l) and high (30 mmol/l) glucose without or with oleate (0.3 mmol/l) on mRNA levels of peroxisome proliferator-activated receptor- (PPAR-)alpha, -gamma1, -gamma2, and peroxisome proliferator-activated receptor-gamma coactivator- (PGC-)1alpha and -1beta in commercial human hepatoma-derived HepG2 cells maintained under low-serum condition. Significant decrease in PPAR-gamma1 and PGC-1alpha mRNA levels to about 50 % was observed during the first 4 h incubation period. During the next 4 h period, both PPAR-gamma1 and PGC-1alpha mRNAs were partly but significantly restored in high glucose batches. In this period, the presence of the transcriptional inhibitor actinomycin D revealed a significant protective effect of excess glucose on mature PPAR-gamma1 and PGC-1alpha mRNAs. Furthermore, PPAR-gamma1 and -gamma2 mRNAs were differentially superinduced 1.2-2.5 fold in cells upon the administration of the translational inhibitor cycloheximide. When the cells were co-treated with the combination of cycloheximide and actinomycin D, superinduction was completely suppressed, however. Altogether, the experiments revealed, first, an unexpected protective effect of abundant glucose on PPAR-gamma1 and PGC-1alpha mRNAs in HepG2 cells. Second, we demonstrated cycloheximide-induced, transcription-dependent upregulation of mature PPAR-gamma1 and -gamma2 mRNAs in HepG2 cells associated with preferential expression of the PPAR-gamma2 mRNA variant. The results draw attention to as yet unexplored mechanisms involved in the control of PPAR and PGC genes.
Rypka
Miroslav
M
Department of Pathological Physiology, Palacky University, Olomouc, Czech Republic. mirek@tunw.upol.cz <mirek@tunw.upol.cz>
Veselý
Jaroslav
J
D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D014644:Genetic Variation; D005947:Glucose / Q000494:pharmacology*; D056945:Hep G2 Cells; D006801:Humans; D019301:Oleic Acid / Q000494:pharmacology; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
D047495:PPAR gamma; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D019301:Oleic Acid; D003513:Cycloheximide; D005947:Glucose