In vivo alterations in cardiac metabolism and function in the spontaneously hypertensive rat heart

Aims The aim of this work was to use hyperpolarized carbon-13 ( ¹³C) magnetic resonance (MR) spectroscopy and cine MR imaging (MRI) to assess in vivo cardiac metabolism and function in the 15-week-old spontaneously hypertensive rat (SHR) heart. At this time point, the SHR displays hypertension and concentric hypertrophy. One of the cellular adaptations to hypertrophy is a reduction in β-oxidation, and it has previously been shown that in response to hypertrophy the SHR heart switches to a glycolytic/glucose-oxidative phenotype. Methods and results Cine-MRI (magnetic resonance imaging) was used to assess cardiac function and degree of cardiac hypertrophy. Wistar rats were used as controls. SHRs displayed functional changes in stroke volume, heart rate, and late peak-diastolic filling alongside significant hypertrophy (a 56 increase in left ventricular mass). Using hyperpolarized [1- ¹³C] and [2- ¹³C]pyruvate, an 85 increase in ¹³C label flux through pyruvate dehydrogenase (PDH) was seen in the SHR heart and ¹³C label incorporation into citrate, acetylcarnitine, and glutamate pools was elevated in proportion to the increase in PDH flux. These findings were confirmed using biochemical analysis of PDH activity and protein expression of PDH regulatory enzymes. Conclusion sFunctional and structural alterations in the SHR heart are consistent with the hypertrophied phenotype. Our in vivo work indicates a preference for glucose metabolism in the SHR heart, a move away from predominantly fatty acid oxidative metabolism. Interestingly, ¹³C label flux into lactate was unchanged, indicating no switch to an anaerobic glycolytic phenotype, but rather an increased reliance on glucose oxidation in the SHR heart. Published on behalf of the European Society of Cardiology. All rights reserved.