Metabolomics in Angiotensin II-Induced Cardiac Hypertrophy

Abstract

Abstract-Angiotensin II (Ang II) induces mitochondrial dysfunction. We tested whether Ang II alters the "metabolomic"profile. We harvested hearts from 8-week-old double transgenic rats harboring human renin and angiotensinogen genes (dTGRs) and controls (Sprague-Dawley), all with or without Ang II type 1 receptor (valsartan) blockade. We used gas chromatography coupled with time-of-flight mass spectrometry to detect 247 intermediary metabolites. We used a partial least-squares discriminate analysis and identified 112 metabolites that differed significantly after corrections (false discovery rate q Ͻ0.05). We found great differences in the use of fatty acids as an energy source, namely, decreased levels of octanoic, oleic, and linoleic acids in dTGR (all PϽ0.01). The increase in cardiac hypoxanthine levels in dTGRs suggested an increase in purine degradation, whereas other changes supported an increased ketogenic amino acid tyrosine level, causing energy production failure. The metabolomic profile of valsartan-treated dTGRs more closely resembled Sprague-Dawley rats than untreated dTGRs. Mitochondrial respiratory chain activity of cytochrome C oxidase was decreased in dTGRs, whereas complex I and complex II were unaltered. Mitochondria from dTGR hearts showed morphological alterations suggesting increased mitochondrial fusion. Cardiac expression of the redox-sensitive and the cardioprotective metabolic sensor sirtuin 1 was increased in dTGRs. Interestingly, valsartan changed the level of 33 metabolites and induced mitochondrial biogenesis in Sprague-Dawley rats. Thus, distinct patterns of cardiac substrate use in Ang II-induced cardiac hypertrophy are associated with mitochondrial dysfunction. The finding underscores the importance of Ang II in the regulation of mitochondrial biogenesis and cardiac metabolomics, even in healthy hearts. represents an adaptive and compensatory response to increased workload and represents an independent risk factor of cardiovascular events. Patients with LVH have more strokes, congestive heart failure, and sudden cardiac death compared with those without LVH. 1 The mechanisms are unknown, although angiotensin (Ang) II contributes greatly to the process. Other than the regulatory effects on blood pressure, sodium excretion, and aldosterone secretion, Ang II also induces inflammatory responses and oxidative stress by blood pressure-independent mechanisms. 2-4 Energy metabolism is deranged in LVH, with and without heart failure. 5,6 All 3 of the components of cardiac energy metabolism, namely substrate use, oxidative phosphorylation, and high-energy phosphate metabolism, are affected. Mitochondria generate energy, regulate apoptosis, and produce reactive oxygen species (ROS). Doughan et al 7 showed recently that Ang II induces mitochondrial dysfunction via a protein kinase C-dependent pathway that activates NADPH oxidase and formation of peroxynitrite. Several factors regulate mitochondrial function and biogenesis. ROS, NO, peroxisome proliferatoractivated receptor-␥ coactivator (PGC)...

Metabolomics as a tool for cardiac research

“…The effect of angiotensin II-induced mitochondrial dysfunction and subsequent cardiac hypertrophy in the rat has been investigated by GCxGC-TOF MS. 54 A wide range of metabolic changes were identified in a transgenic model of angiotensin stimulation (where rats had both human renin and angiotensinogen genes), including an increase in hypoxanthine consistent with purine degradation compared with the wild-type strain, as measured by GC-MS.…”

Caloric Restriction Ameliorates Angiotensin II–Induced Mitochondrial Remodeling and Cardiac Hypertrophy

“…Each lane corresponded to one rat and all 4 groups were run on one gel. SIRT1 immunoblotting was performed from nuclear proteins isolated as described elsewhere 12 . OPA1 immunoblotting was performed from mitochondrial proteins.…”

“…Ang II-induced amplification of mitochondrial ROS activates several downstream redox-sensitive signal transduction pathways implicated in cardiac hypertrophy and apoptosis, including p38 mitogen-activated protein kinase, nuclear factor " light chain enhancer" of activated B cells, and calcineurin nuclear factor of activated T cells. 11 We showed recently that Ang II-induced cardiac hypertrophy is associated with mito-chondrial dysfunction, distinct cardiac substrate use, 12 and downregulation of several genes encoding mitochondrial respiratory chain and lipid metabolism. 13 Caloric restriction (CR) extends life span and reduces the incidence of diabetes mellitus, cancer, brain atrophy, and cardiovascular diseases.…”

Levosimendan improves cardiac function and survival in rats with angiotensin II-induced hypertensive heart failure

“…In a separate study, we very recently observed distinct patterns of cardiac substrate utilization and mitochondrial dysfunction in dTGRs. 27 Recently, Koudouna et al 28 showed that levosimendan improved the initial outcome of cardiopulmonary resuscitation in an experimental model of cardiac arrest. We found that lifelong levosimendan treatment was associated with a 58% increase in mean survival time and a 27% increase in median survival time.…”

“…17,18 Cardiac mRNA expression analysis by quantitative real-time reverse transcriptase-PCR Quantitative real-time reverse transcriptase-PCR was performed using the LightCycler instrument (Roche Diagnostics, Neuilly sur Seine, France) for detection of atrial natriuretic peptide (ANP), SERCA2, NCX-1, a-MHC, b-MHC, MCP-1, Bax, PGC-1a and ribosomal 18S mRNA as described elsewhere. 18,27 Briefly, total RNA from the rat hearts were collected using Trizol (Gibco, Invitrogen, Carlsbad, CA, USA), treated with DNAse 1 (deoxyribonuclease 1, Sigma Chemicals, St Louis, MO, USA) and reverse transcribed to cDNA by reverse transcription enzyme (Im-Prom-II reverse transcription system, Promega, Madison, WI, USA). A volume of 1 ml of cDNA was subjected to quantitative real-time PCR for detection of ANP, a-MHC, b-MHC, MCP-1, Bax, PGC-1a and ribosomal 18S mRNA.…”