PPARγ agonist-induced alterations in Δ6-desaturase and stearoyl-CoA desaturase 1:Role of MEK/ERK1/2 pathway

AIM:To investigate the effect of MEK/ERK1/2 pathway on peroxisome proliferator-activated receptors(PPARγ)agonist-induced alterations in Δ6-desaturase(Δ6D)and stearoyl-CoA desaturase 1(SCD1)in hepatocellular carcinoma cell line HepG2.METHODS:HepG2 cells cultured in RPMI-1640 were exposed to the commonly used ERK1/2 pathway inhibitor PD98059 and PPARγ agonist,pioglitazone.Total RNA was isolated and reverse transcribed from treated cells.Changes in gene expression and metabolites ratio,as activity index for Δ6D and SCD1,were then determined using reverse transcriptionpolymerase chain reaction and gas liquid chromatography,respectively.RESULTS:The expression of both Δ6D(P = 0.03)and SCD1(P = 0.01)increased following PD98059 treatment,with a higher impact on SCD1(24.5%vs 62.5%).Although pioglitazone increased the mRNA level(1.47 ± 0.10 vs 0.88 ± 0.02,P = 0.006)and activity index(1.40 ± 0.07 vs 0.79 ± 0.11,P < 0.001)of Δ6D,no such changes have been observed for SCD1 activity index in pioglitazone-treated cells.SCD1 gene expression(+26.4%,P = 0.041)and activity index(+52.8%,P = 0.035)were significantly increased by MEK inhibition in the presence of pioglitazone,as compared with pioglitazone alone and control cells.However,the response of Δ6D expression and activity index to pioglitazone was unaffected by incubation with PD98059.CONCLUSION:PPARγ and ERK1/2 signaling pathway affect differentially and may have inhibitory crosstalk effects on the genes expression of 6D and SCD1,and subsequently on their enzymatic activities.

Natural products,PGC-1α,and Duchenne muscular dystrophy

Peroxisome proliferator-activated receptorγ(PPARγ)is a transcriptional coactivator that binds to a diverse range of transcription factors.PPARγcoactivator 1(PGC-1)coactivators possess an extensive range of biological effects in different tissues,and play a key part in the regulation of the oxidative metabolism,consequently modulating the production of reactive oxygen species,autophagy,and mitochondrial biogenesis.Owing to these findings,a large body of studies,aiming to establish the role of PGC-1 in the neuromuscular system,has shown that PGC-1 could be a promising target for therapies targeting neuromuscular diseases.Among these,some evidence has shown that various signaling pathways linked to PGC-1αare deregulated in muscular dystrophy,leading to a reduced capacity for mitochondrial oxidative phosphorylation and increased reactive oxygen species(ROS)production.In the light of these results,any intervention aimed at activating PGC-1 could contribute towards ameliorating the progression of muscular dystrophies.PGC-1αis influenced by different patho-physiological/pharmacological stimuli.Natural products have been reported to display modulatory effects on PPARγactivation with fewer side effects in comparison to synthetic drugs.Taken together,this review summarizes the current knowledge on Duchenne muscular dystrophy,focusing on the potential effects of natural compounds,acting as regulators of PGC-1α.