Submitted on December 27, 2006
Accepted on April 25, 2008
The benefit of medium-chain triglyceride (MCT) therapy on cardiac function of SHR is associated with reversal of metabolic and signaling alterations
Motoyuki Iemitsu1, Nobutake Shimojo2, Seiji Maeda3, Yoko Irukayama-Tomobe4, Satoshi Sakai5, Takeshi Ohkubo6, Yukihisa Tanaka6, and Takashi Miyauchi2*
1 Department of Physical Education, International Pacific University, Okayama, Japan
2 University of Tsukuba, Institute of Clinical Medicine, Tsukuba, Ibaraki, Japan
3 University of Tsukuba, Center for Tsukuba Advanced Research Alliance, Tsukuba, Ibaraki, Japan
4 University of Tsukuba, Institute of Health and Sport Sciences, Tsukuba, Ibaraki, Japan
5 Unversity of Tsukuba, Institute of Clinical Medisine, Tsukuba, Japan
6 NOF Corporation, Tsukuba Research Laboratory, Tsukuba, Ibaraki, Japan
* To whom correspondence should be addressed. E-mail: t-miyauc{at}md.tsukuba.ac.jp.
The spontaneously hypertensive rats (SHR) is a model of cardiomyopathy that displays a genetic defect in the cardiac fatty acid (FA) translocase/CD36, a plasma membrane long-chain FA transporter. Therapy with medium-chain FAs, which do not require CD36-facilitated transport, has been shown to improve cardiac function and hypertrophy in SHR despite persistent hypertension. However, little is known about the underlying molecular mechanisms. The aim of this study was to document the impact of medium-chain triglyceride (MCT) therapy in SHR on the expression level and activity of metabolic enzymes and signaling pathways. Four-week-old male SHR were administered MCT (SHR-MCT) or long-chain triglyceride (SHR-LCT) for 16 weeks. We used WKY rats (WKY-MCT and WKY-LCT) as controls. SHR-MCT displayed improved cardiac dysfunction (assessed by LVEDP and ±dp/dt/p), a shift in the beta/alpha-myosin heavy chain ratio and cardiac hypertrophy in comparison to SHR-LCT without an effect on blood pressure. Administration of MCT of SHR reversed LCT-induced reduction in the cardiac fatty acid metabolic enzymatic activities of long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) and medium-chain acyl-CoA dehydrogenase (MCAD). In SHR-MCT, protein expression and transcriptional regulation of myocardial peroxisome proliferator-activated receptor (PPAR)-alpha, which regulates the transcription of LCHAD and MCAD genes, corresponded to the changes seen in those enzymatic activities. Furthermore, MCT intake caused inhibition of SHR-induced of c-Jun N-terminal kinase (JNK) activation in hearts. Collectively, the observed changes in myocardial activity of metabolic enzymes and signaling pathways may contribute to the improved cardiac dysfunction and hypertrophy in SHR following MCT therapy.
