P38-MAPK and PKB/Akt, Possible Role Players in Red Palm Oil-induced Protection of the Isolated Perfused Rat Heart?

It has been shown that dietary red palm oil (RPO) supplementation improves reperfusion function. However, no exact protective cellular mechanisms have been established. To determine a potential mechanism for functional improvement, we examined the regulation of both mitogen-activated protein kinases (MAPKs) and PKB/Akt in the presence and absence of dietary RPO supplementation in ischemia/reperfusion-induced injury. Wistar rats were fed a control diet or control diet plus 7 g RPO/kg diet for 6 weeks. Hearts were excised and mounted on an isolated working heart perfusion apparatus. Cardiac function was measured before and after hearts were subjected to 25 min of total global ischemia. Hearts subjected to the same conditions were freeze clamped and used to characterize the degree of phosphorylation of extracellular signal-regulated kinase, p38, c-Jun NH(2)-terminal protein kinase (JNK) and PKB/Akt. Dietary RPO supplementation significantly improved aortic output recovery (72.1 +/- 3.2% vs. 54.0 +/- 3.2%, P < .05). This improved aortic output recovery was associated with significant increases in p38 and PKB/Akt phosphorylation during reperfusion when compared with control hearts. Furthermore, a significant decrease in JNK phosphorylation and attenuation of poly(ADP-ribose) polymerase cleavage occurred in the RPO-supplemented group during reperfusion. Our results suggest that dietary RPO supplementation caused differential phosphorylation of the MAPKs and PKB/Akt during ischemia/reperfusion-induced injury. These changes in phosphorylation were associated with improved functional recovery and reduced cleavage of an apoptotic marker, arguing that dietary RPO supplementation may confer protection via the MAPK and PKB/Akt signaling pathways during ischemia/reperfusion-induced injury.