A combined¹H-NMR spectroscopy- and mass spectrometry-based metabolomic study of the PPAR-α null mutant mouse defines profound systemic changes in metabolism linked to the metabolic syndrome

Abstract

The mobilization of triacylglycerides from storage in adipocytes to the liver is a vital response to the fasting state in mammalian metabolism. This is accompanied by a rapid translational activation of genes encoding mitochondrial, microsomal, and peroxisomal beta-oxidation in the liver, in part under the regulation of peroxisome proliferator-activated receptor-alpha (PPAR-alpha). A failure to express PPAR-alpha results in profound metabolic perturbations in muscle tissue as well as the liver. These changes represent a number of deficits that accompany diabetes, dyslipidemia, and the metabolic syndrome. In this study, the metabolic role of PPAR-alpha has been investigated in heart, skeletal muscle, liver, and adipose tissue of PPAR-alpha null mice at 1 mo of age using metabolomics. To maximize the coverage of the metabolome in these tissues, (1)H-NMR spectroscopy, magic angle spinning (1)H-NMR spectroscopy, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry were used to examine metabolites in aqueous tissue extracts and intact tissue. The data were analyzed by the multivariate approaches of principal components analysis and partial least squares. Across all tissues, there was a profound decrease in glucose and a number of amino acids, including glutamine and alanine, and an increase in lactate, demonstrating that a failure to express PPAR-alpha results in perturbations in glycolysis, the citric acid cycle, and gluconeogenesis. Furthermore, despite PPAR-alpha being weakly expressed in adipose tissue, a profound metabolic perturbation was detected in this tissue.

1H NMR-based Metabonomic Analysis of Metabolic Changes in Streptozotocin-induced Diabetic Rats

“…The metabolic alterations observed at different time-points suggest that time-dependent in vivo effects occur during the earlier period after STZ injection, which was in accord with a previous study for examining the metabolic differences between acute (72 h) and chronic (14 d) STZ-induced diabetes. 41 These time-dependent alterations might contribute to some differences between our observations and those of Zhang et al 20 Furthermore, being consistent with a previous study using the 11-week-old Zucker diabetic rat and PPAR-α null mice model, 42,43 the concentrations of several glucogenic amino acids were also decreased, indicative of higher rates of gluconeogenesis.…”

Protective mechanisms of resveratrol against ischemia-reperfusion-induced damage in hearts obtained from Zucker obese rats: the role of GLUT-4 and endothelin

“…In fact, GLUT-4 repression has profound changes in cardiac dysfunction and arrhythmias with accelerated apoptotic cell death. Although it was not the aim of our investigation, it is interesting to note that it is unlikely that all of the observed cardiac protection by resveratrol occurred directly via PPAR-␣ target, and GLUT-4 gene repression or expression is probably also modulated via PPAR-␣-independent transcriptional regulatory pathways linked to alteration in cellular energy metabolism (4,6).…”

Alterations in carbohydrate metabolism and its regulation in PPARα null mouse hearts

“…Before this study, there had been only a few studies that had investigated substrate fuel utilization and its regulation in PPAR␣ null mouse hearts (3,9,27,30,37), none of which had specifically examined the utilization and/or regulation of CHOs for energy production or anaplerosis. Using our ex vivo working heart model, we documented the impact of an increase in workload induced by raising the preload from 12 to 15 mmHg, which remains in the physiological range.…”