mRNA LEVELS OF PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS AND THEIR COACTIVATORS ARE AFFECTED BY GLUCOSE DEPRIVATION AND OLEATE IN HUMAN HEPATOMA HepG2 CELLS

Abstract

Aims: Very modest changes in mRNA stability can aff ect critical points in cellular energy pathways. The aim of this study was to investigate the impact of energy abundant substrates on peroxisome proliferator-activated receptors (PPARs) and PPAR-γ coactivators (PGCs) mRNA's steady-state levels.Methods: Quantitative RT-PCR study was performed to assess the eff ect of zero or normal (5 mmol/l) glucose and/or oleic acid (0.3 mmol/l) on mRNA levels of (PPARs) (PGCs) in HepG2 cells.Results: PGC-1α mRNA was signifi cantly upregulated in glucose deprived cells (123 % of the control level; p < 0.05), while PGC-1β mRNA was signifi cantly enhanced in oleate-fed cells (134 % and 160 % of control levels for zero glucose plus oleate and normal glucose plus oleate, respectively; p < 0.05) during the 0.5 h incubation. Upon the 4 h incubation, PPAR-γ1 and PGC-1α mRNAs were signifi cantly elevated in cells lacking glucose (142 % and 163 % of control levels, respectively; p < 0.05). Oleate signifi cantly suppressed PPAR-α and PGC-1β mRNA levels in glucose-deprived cells (58 % and 49 % of control levels, respectively; p < 0.05). PPAR-γ1 and -γ2 mRNAs were signifi cantly superinduced when the cells were treated with cycloheximide, whereas PPAR-α and PGC-1α and-1β mRNAs were destabilized. Upon actinomycin D treatment, glucose shortage signifi cantly stabilized PPAR-α mRNA, while PGC-1α mRNA was destabilized by oleate in glucose-deprived cells.Conclusions: Our fi ndings provide evidence that transcriptional processes that are under the control of energetic substrates are interconnected with concurrent translational processes that can change stability of mRNAs.

Glucose deprivation, oxidative stress and peroxisome proliferator-activated receptor-α (PPARA) cause peroxisome proliferation in preimplantation mouse embryos

“…In different cells and with different stimuli, phosphorylation can activate or deactivate PPARA (Gelman et al 2005). Supporting these results, there is evidence that glucose deprivation stabilizes PPARA mRNA, reducing its degradation, and increases mRNA levels for PPARGC1A, a major co-activator of PPARA (Bogdanova et al 2007). Several groups have reported upregulation of PPARA activity in response to fasting (Sterchele et al 1996, Hashimoto et al 2000, Escher et al 2001, Sugden et al 2001 and in sheep, maternal nutrient restriction between 28 and 80 days gestation induced PPARA expression in offspring (Bispham et al 2005.…”

Hypolipidemic effect of oleanolic acid is mediated by the miR‐98‐5p/PGC‐1β axis in high‐fat diet‐induced hyperlipidemic mice

“…Although PGC-1b robustly regulates many downstream target genes, the transcriptional activity of this coactivator can also be modulated by post-transcriptional and posttranslational modifications that positively or negatively modulate its capacity to recruit chromatin-remodeling complexes and turn gene transcription on. First, mRNA stability of PGC-1b can be affected by oleate (48) and OA, as shown in Fig. 4B.…”

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.

“…Cell culture and treatments. HepG2 cells (American Type Culture Collection, Rockville, MD, USA) were treated as described previously (Bogdanova et al, 2007;Poczatkova et al, 2007) with minor modifications. Briefly, the cells were grown to about 80 % confluence in EMEM supplemented with 10 % fetal bovine serum (FBS), 1 mmol/l sodium pyruvate, 2 mmol/l lglutamine, and 50 IU/ml penicillin/streptomycin in a humidified 5 % CO 2 /95 % air atmosphere at 37 °C.…”

“…Total RNA was extracted from 10 6 cells using the High Pure RNA Isolation kit, and mRNA was reverse-transcribed using the Transcriptor First Strand cDNA Synthesis kit (both from Roche). Primers (Table 1; Bogdanova et al, 2007;Poczatkova et al, 2007) were synthesized by Metabion International (Martinsried, Germany). CynA, GAPDH, and HPRT genes were used as the reference (housekeeping) genes (Table 1).…”

“…As a part of our recent efforts to examine cellular mechanisms responsible for nutrient effects, we have described effects of glucose shortage that caused significant changes in PPAR-γ1 and PGC-1α mRNA levels in human hepatoma-derived HepG2 cells incubated under the constant ambient hormonal milieu (Bogdanova et al, 2007;Poczatkova et al, 2007). In the present quantitative real-time RT-PCR study we administered glucose in a supranormal concentration (30 mmol/l), without or with oleate (0.3 mmol/l), to reveal changes of PPAR-α, -γ1, -γ2, PGC-1α and -1β mRNA levels in the HepG2 in vitro model.…”