Peroxisome Proliferator-activated Receptor-gamma Coactivator-1 mRNA Research Articles

Effects of inducible hypothermia on expressions of PGC-1 and SHP in rat model of hemorrhagic shock

Objective To investigate the effects of inducible hypothermia on expressions of peroxisome proliferator activated receptor gamma coactivator-1 (PGC-1) and small heterodimer partner (SHP) in rat model of hemorrhagic shock. Methods SD rats were randomly(random number) divided into three groups: control (C), normothermia (N) and hypothermia (H). Exsanguination was carried out in rats by continuously drawing out venous blood (25 mL/kg) over 15 minutes to establish hemorrhagic shock model. Then, rectal temperatures of rats were maintained by body surface cooling to 32℃ in H group and by body surface warming to 38℃ in N group, respectively. After a shock period of 60 minutes, rats received the infusion of whole blood of their own and lactated Ringer's solution (1∶2) treatment for 60 min. Rats were warmed to 38℃ by body surface warming and monitored for 3 h after resuscitation. Hematocrit(Hct), base excess (BE), lactate (Lac), and glucose (Glu) were recorded before modeling and after different lengths of hemorrhagic shock period (HSP). The expressions of PGC-1 mRNA and SHP mRNA and the levels of their protein in liver were tested by real-time reverse transcription polymerase chain reaction (qRT-PCR) and western blotting, respectively. Results The H group had lower lactate levels and higher BE levels than the N group [(6.3±2.1) vs. (10.4±1.5) and (-4.7±2.5) vs. (-9.0±3.2)] (P< 0.05). At 72 hours after modeling, there were four survivors in the N group and seven survivors in the H group (P< 0.05, Log Rank). The expressions of PGC-1 mRNA and SHP mRNA increased in N group. Hypothermia resuscitation down-regulated PGC-1 mRNA expression, meanwhile, increased expression of SHP mRNA. Both Hypothermia and Normothermia resuscitation increased SHP protein levels, but decreased PGC-1 protein levels. Conclusions Inducible hypothermia ameliorated acidosis and energy metabolism imbalance through adaptive regulation in PGC-1 and SHP. Key words: Hemorrhagic shock; Inducible hypothermia; Peroxisome proliferator activated receptor gamma coactivator-1; Small heterodimer partner; Western blotting; Real-time reverse transcription polymerase chain reaction; Rat; Liver

IUGR alters postnatal rat skeletal muscle peroxisome proliferator-activated receptor-gamma coactivator-1 gene expression in a fiber specific manner.

Uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) increase the risk of insulin resistance in humans and rats. Aberrant skeletal muscle lipid metabolism contributes to the pathogenesis of insulin resistance. Peroxisome proliferator-activated receptor-gamma co-activator-1 (PGC-1) is a transcriptional co-activator that affects gene expression of key lipid metabolizing enzymes such as carnitine palmitoyl-transferase I (mCPTI). Because gene expression of lipid metabolizing enzymes is altered in IUGR postnatal skeletal muscle, and we hypothesized that PGC-1 expression would be similarly affected. To prove this hypothesis, bilateral uterine artery ligation and sham surgery were used to produce IUGR and control rats respectively. Western Blotting demonstrated that PGC-1 hind limb skeletal muscle protein levels were increased in perinatal and postnatal IUGR rats. Conventional RT-PCR demonstrated that PGC-1 mRNA levels were similarly increased in perinatal hind limb skeletal muscle and juvenile extensor digitorum longus (EDL), but were decreased in juvenile soleus. Because a gender specific trend was noted in PGC-1 mRNA levels, real time RT-PCR was used for further differentiation. Real time RT-PCR revealed that changes in postnatal skeletal muscle PGC-1 expression were more marked in male IUGR rats versus female IUGR rats. Down stream targets of PGC-1 followed a similar pattern of expression. We conclude that PGC-1 expression is altered in rat IUGR skeletal muscle and speculate that it contributes to the pathogenesis of insulin resistance in the IUGR rat.

Alterations of PPARα and its coactivator PGC-1 in cisplatin-induced acute renal failure

In this study we examined whether a recently characterized coactivator of Peroxisome proliferator activated receptor alpha (PPARalpha), Peroxisome proliferator activated receptor-gamma-coactivator-1 (PGC-1) plays a role in the regulation of fatty acid oxidation during cisplatin-induced nephrotoxicity. Studies in mouse kidneys used quantitative reverse transcription-polymerase chain reaction (RT-PCR) to measure peroxisomal acyl coenzyme A (acyl-CoA) and PGC-1 mRNA levels and in situ hybridization to localize PGC-1 mRNA. Studies in LLCPK1 cells used quantitative RT-PCR and biochemical assays to measure mRNA levels and enzyme activities of peroxisomal acyl-CoA, mitochondrial carnitine palmitoyl transferase (CPT) and PGC-1. Eletrophoretic mobility shift assays (EMSA) and Western blot analysis of nuclear extracts, and transient transfection of PGC-1 were used to examine the effect of cisplatin on PPARalpha-regulated fatty acid oxidation. Cisplatin decreased mRNA levels of peroxisomal acyl-CoA enzyme in mouse kidney and also reduced the mRNA levels and enzyme activities of acyl-CoA and mitochondrial CPT-1 in LLCPK1 cells. DNA-protein binding studies demonstrated that exposure to cisplatin reduces PPARalpha/retinoid X receptor (RXRalpha) binding activity. Immunoblotting studies demonstrated that cisplatin had no effect on nuclear levels of PPARalpha or RXRalpha protein. In situ hybridization studies in mouse kidney demonstrated the localization of PGC-1 mRNA to proximal tubules and thick ascending limb of Henley (TALH) cells. Cisplatin diminished the expression of PGC-1 mRNA levels in mouse kidney and also in LLCPK1 cells. Transient expression of PGC-1 shows the nuclear localization of PGC-1 protein and increased PPARalpha transcriptional activity in LLCPK1 cells. These results demonstrate that cisplatin deactivates PPARalpha by reducing its DNA binding activity and the availability of its tissue specific coactivator PGC-1.