a1 Department of Physiological Sciences, University of Stellenbosch, Stellenbosch, 7600, South Africa
a2 Faculty of Applied Sciences, Cape Peninsula University of Technology, Cape Town, South Africa
a3 Department of Biomedical Sciences, University of Stellenbosch, Stellenbosch, South Africa
We have previously shown that dietary red palm oil (RPO) supplementation improves functional recovery in hearts subjected to ischaemia–reperfusion. However, little knowledge exists concerning the effects of RPO supplementation of a high-cholesterol diet on ischaemia–reperfusion injury. The signalling mechanisms responsible for RPO's effects in the presence of cholesterol also remain to be elucidated. Therefore, the aim of the present study was to examine the effects of RPO, given with a high-cholesterol diet, on mitogen-activated protein kinase (MAPK) phosphorylation and apoptosis. Long–Evans rats were fed a control diet, a control diet containing 2 % cholesterol, or a control diet containing 2 % cholesterol and 7 g RPO per kg (CRPO) for 5 weeks. Hearts were excised and mounted on an isolated working heart perfusion apparatus. Cardiac function was measured after which hearts were freeze-clamped and used to assess MAPK phosphorylation and to evaluate apoptosis. Cholesterol supplementation caused a poor aortic output (AO) recovery compared with the control group (35·5 (sem 6·2) v. 55·4 (sem 2·5) %), but when RPO was added, the percentage AO increased significantly. The cholesterol group's poor AO was associated with a significant increase in p38-MAPK phosphorylation, whereas the CRPO-supplemented group showed as significant reduction in p38-MAPK phosphorylation when compared with the cholesterol-supplemented group. This significant reduction in p38-MAPK was also associated with reduced apoptosis as indicated by significant reductions in caspase-3 and poly(ADP-ribose) polymerase cleavage.
(Received June 12 2006)
(Revised November 06 2006)
(Accepted November 06 2006)
Abbreviations: ERK, extracellular signal-regulated protein kinase; JNK, c-Jun NH2-terminal kinase; MAPK, mitogen-activated-protein kinase; PARP, poly(ADP-ribose) polymerase; RPO, red palm oil; Tris, tri(hydroxymethyl)-aminomethane