Biomedical subjects

Kieran Clarke

Publications and source records attributed to Kieran Clarke.

At least 19 recordsLinked to original sources

PubMed2006

Chronic oral ascorbic acid therapy worsens skeletal muscle metabolism in patients with chronic heart failure.

BACKGROUND: Chronic heart failure (CHF) is associated with abnormalities of skeletal muscle metabolism. This may be due to impaired oxygen delivery as a result of endothelial dysfunction. AIMS: We postulated that ascorbic acid would improve oxygen delivery to exercising muscle and improve skeletal muscle metabolism. METHODS: We studied skeletal muscle metabolism using (31)P magnetic resonance spectroscopy in 39 CHF patients. Endothelial function was assessed by changes in pulse wave velocity. Subjects were randomised to receive 4 g ascorbic acid daily for 4 weeks in a placebo-controlled double-blind study. RESULTS: Ascorbic acid significantly increased phosphocreatine utilization during exercise. In addition, glycolytic ATP synthesis increased in the ascorbic acid group (change in rate of ATP synthesis at 1 min -0.21+/-0.76 with placebo, 2.06+/-0.60 following ascorbic acid; p<0.05). Phosphocreatine and ADP recovery after exercise were not changed. The fall in pulse wave velocity during reactive hyperaemia was increased by ascorbic acid from -6.3+/-2.6% to -12.1+/-2.0% (p<0.05). CONCLUSIONS: These findings suggest that ascorbic acid increased both phosphocreatine utilization and glycolytic ATP synthesis during exercise in patients with CHF implying worsened skeletal muscle metabolism despite improvements in endothelial function.

Adenosine Triphosphate↗

PubMed2006

Fatty acid transporter levels and palmitate oxidation rate correlate with ejection fraction in the infarcted rat heart.

OBJECTIVES: Cardiac fatty acid uptake occurs predominantly via sarcolemmal transporter proteins; fatty acid translocase (FAT/CD36), plasma membrane fatty acid binding protein (FABPpm) and fatty acid transporter proteins (FATP) 1 and 6. We hypothesised that levels of the fatty acid transporters would be reduced in the chronically infarcted rat heart, in parallel with reduced dependence on fatty acid utilisation. METHODS AND RESULTS: In vivo left ventricular ejection fractions, measured using echocardiography, were 36% lower in rats six months after coronary artery ligation than in sham-operated control rats. In isolated, perfused, infarcted hearts, 3H-palmitate oxidation was 30% lower, and correlated with in vivo ejection fractions. As myocardial lipid incorporation was also reduced by 25%, total palmitate utilisation was 29% lower in the infarcted rat heart. The protein levels of the cardiac fatty acid transporters were reduced in the infarcted rat heart; FAT/CD36 by 36%, FABPpm by 12%, FATP6 by 21% and FATP1 by 26%, and the cytosolic fatty acid binding protein (cFABP) was 47% lower than in sham-operated rat hearts. Fatty acid transporter levels correlated with both palmitate oxidation rates and cardiac ejection fractions. CONCLUSIONS: Reductions in fatty acid oxidation and lipid incorporation rates were accompanied by downregulation of the cardiac fatty acid transporters. The metabolic shift away from fatty acid utilisation was proportional to the degree of functional impairment in the chronically infarcted rat heart.

Animals↗

PubMed2006

A combined 1H-NMR spectroscopy- and mass spectrometry-based metabolomic study of the PPAR-alpha null mutant mouse defines profound systemic changes in metabolism linked to the metabolic syndrome.

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.

Adipose Tissue↗

PubMed2006

Insulin resistance, abnormal energy metabolism and increased ischemic damage in the chronically infarcted rat heart.

OBJECTIVE: Many patients with heart failure have whole-body insulin resistance and reduced cardiac fluorodeoxyglucose uptake, but whether these metabolic changes have detrimental effects on the heart is unknown. Here, we tested whether there is a link between insulin resistance and ischemic damage in the chronically infarcted Wistar rat heart, postulating that the heart would have decreased insulin sensitivity, with lower GLUT4 glucose transporter protein levels due to high circulating free fatty acid (FFA) concentrations. A decreased capacity for glucose uptake would lower glycolytic adenosine triphosphate (ATP) production and thereby increase ischemic injury in the infarcted heart. METHODS AND RESULTS: In vivo left ventricular ejection fractions, measured using echocardiography, were 40% lower in rats 10 weeks after coronary artery ligation than in sham-operated control rats. Insulin-stimulated D[2-3H]glucose uptake was 42% lower in isolated, perfused, infarcted hearts. Myocardial GLUT4 glucose transporter protein levels were 28% lower in the infarcted hearts and correlated negatively with ejection fractions and with fasting plasma FFA concentrations. Compared with controls, chronically infarcted hearts had 46% lower total glucose uptake and three-fold faster ATP hydrolysis rates, measured using phosphorus-31 nuclear magnetic resonance spectroscopy, during 32-min ischemia at 0.4 ml/min/gww. During reperfusion, recovery of left ventricular developed pressure in infarcted hearts was 42% lower than in control hearts. CONCLUSIONS: Glucose uptake, in response to insulin or ischemia, was lower in the chronically infarcted rat heart and associated with increased circulating FFA concentrations and decreased GLUT4 levels. Thus, infarcted hearts had greater ATP depletion, and consequently incurred greater damage, during ischemia.

Adenosine Triphosphate↗

PubMed2006

Determination of cardiac volumes and mass with FLASH and SSFP cine sequences at 1.5 vs. 3 Tesla: a validation study.

PURPOSE: To compare cardiac cine MR imaging using steady state free precession (SSFP) and fast low angle shot (FLASH) techniques at 1.5 and 3 T, and to establish their variabilities and reproducibilities for cardiac volume and mass determination in volunteers. To assess the feasibility of SSFP imaging in patients at 3 T and to determine comparability to volume data acquired at 1.5 T. MATERIALS AND METHODS: Ten healthy volunteers underwent cardiac magnetic resonance imaging using SSFP and segmented gradient-echo FLASH, using both a 1.5 and a 3 T MR system on the same day. Ten patients with impaired left ventricular (LV) function were also studied at both field strengths with SSFP. RESULTS: For both SSFP and FLASH, field strength had no effect on the quantification of LV and right ventricular (RV) volumes, mass, or function (P > or = 0.05 for field strength for all parameters). At both 1.5 and 3 T, SSFP yielded smaller LV mass (e.g., at 3 T 109 +/- 30 g vs. 142 +/- 37 g; P = 0.011) and larger LV volume (e.g., at 3 T end-diastolic volume 149 +/- 37 mL vs. 133 +/- 31 mL at 5 T; P = 0.041) measurements than FLASH. In patients with reduced LV function, all volume and mass measurements were again similar for SSFP sequences at 1.5 vs. 3 T. In volunteers and patients, measurement variabilities for LV parameters were small for both field strength and sequences, ranging between 3.7% and 10.7% for mass. CONCLUSION: Compared to 1.5 T, cardiac cine MR imaging at 3 T, using either FLASH or SSFP sequences, is feasible and highly reproducible. Field strength does not have an influence on quantification of cardiac volume or mass, but the systematic overestimation of LV mass and underestimation of LV volume by FLASH compared to SSFP is present at both 1.5 and 3 T. Normal values for cardiac volumes and mass established at 1.5 T can be applied to scans obtained at 3 T.

Adult↗

PubMed2006

Modification of myocardial substrate use as a therapy for heart failure.

Despite advances in treatment, chronic heart failure is still associated with significant morbidity and a poor prognosis. The scope for further advances based on additional neurohumoral blockade is small. Effective adjunctive therapies acting via a different cellular mechanism would, therefore, be attractive. Energetic impairment seems to contribute to the pathogenesis of heart failure. The findings from several studies have shown that the so-called metabolic agents could have potential as adjunctive therapies in heart failure. These agents cause a shift in the substrate used by the heart away from free fatty acids, the oxidation of which normally provides around 70% of the energy needed, towards glucose. The oxygen cost of energy generation is lessened when glucose is used as the substrate. In this review we aim to draw attention to the metabolic alteration in heart failure and we present evidence supporting the use of metabolic therapy in heart failure.

Acetanilides↗

PubMed2006

Haemoglobin and flow-mediated vasodilation.

A low [Hb] (Hb concentration) is out-balanced by peripheral vasodilation via mechanisms that are incompletely understood. Peripheral vasodilation is influenced by NO (nitric oxide) released from vascular endothelium in response to increased vessel wall shear stress, and absorption by Hb is the main mechanism by which the bioactivity of NO is disarmed. Thus we propose that graded NO absorption is the mechanism through which a low [Hb] is related to peripheral vasodilation. In the present study, we examined the relationship between [Hb] and FMD (flow-mediated vasodilation; 5 min of cuff ischaemia) of the radial and brachial arteries in 33 normal subjects and in 13 patients with Type II diabetes, known to have impaired NO-mediated vasodilation. The smaller radial artery provided the more sensitive test, as it had a 2-fold larger FMD than the brachial artery (22+/-18% compared with 9+/-18% respectively, in normal subjects; means+/-S.D., P<0.05). FMD of the radial artery had a negative correlation with [Hb] (r(2)=-0.66, P<0.05; n=27). In subjects with [Hb] below and above the median of 14.1 g/dl, the radial artery FMD was 30+/-22% compared with 13+/-12% respectively (P<0.05). In diabetic patients, FMD was lower and a co-variation with [Hb] could not be established. Thus, in normal subjects, NO-mediated endothelium-related vasodilation at least partly out-balanced the 'added burden' of a low [Hb] during post-ischaemic reperfusion.

Adult↗

PubMed2006

CINE-MR imaging of the normal and infarcted rat heart using an 11.7 T vertical bore MR system.

MR imaging is uniquely placed to non-invasively study rodent cardiac structure and function. High-field MR scanners commonly have a vertical bore, and the purpose of this work was to demonstrate CINE-MR imaging in normal and infarcted rat hearts after determining hemodynamic stability when positioned vertically for imaging. Optimisation of imaging parameters was carried out prior to assessment of cardiac function in a group of normal and infarcted rat hearts. Rat hemodynamics were unaltered when vertical for 90 minutes, compared with horizontal measurements and rat cardiac parameters were measured accurately and reproducibly with our optimized CINE-MR protocol. A flip angle of 17.5 degrees was shown to provide optimal contrast for the assessment of structure and function, and, in contrast to our findings in mice, respiratory gating was not found to be essential. Hence, we conclude that vertical bore MR systems can be used to measure in vivo cardiac function in normal and infarcted rat hearts.

Analysis of Variance↗

PubMed2006

Cardiac cine MR-imaging at 3T: FLASH vs SSFP.

The implications of an increase in field strength, from 1.5 T to 3 T, for routine functional cardiac examinations have been systematically investigated. Flip angle optimization was carried out for identical SSFP and FLASH cine imaging sequences at 1.5 T and 3 T, which supported the use of 20 degrees (FLASH 1.5 T and 3 T) and >60 degrees (SSFP 1.5 T and 3 T). The optimized sequences were applied in a study of cardiac function in a group of ten normal volunteers. Both SSFP and FLASH sequences showed significant SNR increases in the myocardium and blood at 3 T compared with 1.5 T, increases of 48% and 30% (myocardium and blood, respectively) for the SSFP sequence and 19% and 13% for the FLASH sequence. The SSFP sequence also showed a significant increase in CNR (22%). Image quality assessment revealed that the SSFP acquisitions were superior to FLASH at both field strengths. Although SSFP contained more artifacts at 3 T, they would not prevent its clinical use. We conclude that cardiac functional examinations at 3 T should use SSFP sequences.

Artifacts↗

PubMed2005

MLP accumulation and remodelling in the infarcted rat heart.

Mutation of cytoskeletal protein genes results in abnormal protein function and causes cardiomyopathy. We hypothesised that cardiac levels of cytoskeletal proteins, such as dystrophin, desmin and muscle LIM protein (MLP), would be altered during remodelling caused by myocardial infarction (MI). We measured left-ventricular morphology, function and cytoskeletal protein levels 10 weeks after coronary artery ligation or sham operation in male Wistar rats. Two-dimensional echocardiography revealed significant impairment of systolic function and decreased ejection fraction in infarcted hearts compared with sham (47+/-5% versus 73+/-4%), commensurate with the development of heart failure. Western blotting was used to measure levels of beta-myosin heavy chain (beta-MyHC), a marker of hypertrophy, and levels of dystrophin, desmin, MLP, beta-tubulin, utrophin and syncoilin, using GAPDH for normalization. Relative to shams, beta-MyHC and MLP levels were increased 1.9-fold and 1.7-fold, respectively, in infarcted rat hearts, whereas the levels of other cytoskeletal proteins were unchanged. Both MLP and desmin protein levels correlated negatively with ejection fraction, with the strongest relation between MLP and ejection fraction (r=-0.95, n=13, p<0.0001). This work suggests that MLP may play an important compensatory role in cardiac remodelling following MI.

Animals↗

PubMed2005

Metabolic modulation with perhexiline in chronic heart failure: a randomized, controlled trial of short-term use of a novel treatment.

BACKGROUND: Chronic heart failure (CHF) is a major cause of morbidity and mortality that requires a novel approach to therapy. Perhexiline is an antianginal drug that augments glucose metabolism by blocking muscle mitochondrial free fatty acid uptake, thereby increasing metabolic efficiency. We assessed the effects of perhexiline treatment in CHF patients. METHODS AND RESULTS: In a double-blind fashion, we randomly assigned patients with optimally medicated CHF to either perhexiline (n=28) or placebo (n=28). The primary end point was peak exercise oxygen consumption (VO2max), an important prognostic marker. In addition, the effect of perhexiline on myocardial function and quality of life was assessed. Quantitative stress echocardiography with tissue Doppler measurements was used to assess regional myocardial function in patients with ischemic CHF. 31P magnetic resonance spectroscopy was used to assess the effect of perhexiline on skeletal muscle energetics in patients with nonischemic CHF. Treatment with perhexiline led to significant improvements in VO2max (16.1+/-0.6 to 18.8+/-1.1 mL . kg(-1) . min(-1); P<0.001), quality of life (Minnesota score reduction from 45+/-5 to 34+/-5; P=0.04), and left ventricular ejection fraction (24+/-1% to 34+/-2%; P<0.001). Perhexiline treatment also increased resting and peak dobutamine stress regional myocardial function (by 15% and 24%, respectively) and normalized skeletal muscle phosphocreatine recovery after exercise. There were no adverse effects during the treatment period. CONCLUSIONS: In patients with CHF, metabolic modulation with perhexiline improved VO2max, left ventricular ejection fraction, symptoms, resting and peak stress myocardial function, and skeletal muscle energetics. Perhexiline may therefore represent a novel treatment for CHF with a good safety profile, provided that the dosage is adjusted according to plasma levels.

Aged↗

PubMed2005

Supranormal myocardial creatine and phosphocreatine concentrations lead to cardiac hypertrophy and heart failure: insights from creatine transporter-overexpressing transgenic mice.

BACKGROUND: Heart failure is associated with deranged cardiac energy metabolism, including reductions of creatine and phosphocreatine. Interventions that increase myocardial high-energy phosphate stores have been proposed as a strategy for treatment of heart failure. Previously, it has not been possible to increase myocardial creatine and phosphocreatine concentrations to supranormal levels because they are subject to tight regulation by the sarcolemmal creatine transporter (CrT). METHODS AND RESULTS: We therefore created 2 transgenic mouse lines overexpressing the myocardial creatine transporter (CrT-OE). Compared with wild-type (WT) littermate controls, total creatine (by high-performance liquid chromatography) was increased in CrT-OE hearts (66+/-6 nmol/mg protein in WT versus 133+/-52 nmol/mg protein in CrT-OE). Phosphocreatine levels (by 31P magnetic resonance spectroscopy) were also increased but to a lesser extent. Surprisingly, CrT-OE mice developed left ventricular (LV) dilatation (LV end-diastolic volume: 21.5+/-4.3 microL in WT versus 33.1+/-9.6 microL in CrT-OE; P=0.002), substantial LV dysfunction (ejection fraction: 64+/-9% in WT versus 49+/-13% in CrT-OE; range, 22% to 70%; P=0.003), and LV hypertrophy (by 3-dimensional echocardiography and magnetic resonance imaging). Myocardial creatine content correlated closely with LV end-diastolic volume (r=0.51, P=0.02), ejection fraction (r=-0.74, P=0.0002), LV weight (r=0.59, P=0.006), LV end-diastolic pressure (r=0.52, P=0.02), and dP/dt(max) (r=-0.69, P=0.0008). Despite increased creatine and phosphocreatine levels, CrT-OE hearts showed energetic impairment, with increased free ADP concentrations and reduced free-energy change levels. CONCLUSIONS: Overexpression of the CrT leads to supranormal levels of myocardial creatine and phosphocreatine, but the heart is incapable of keeping the augmented creatine pool adequately phosphorylated, resulting in increased free ADP levels, LV hypertrophy, and dysfunction. Our data demonstrate that a disturbance of the CrT-mediated tight regulation of cardiac energy metabolism has deleterious functional consequences. These findings caution against the uncritical use of creatine as a therapeutic agent in heart disease.

Animals↗

PubMed2005

Serial high resolution 3D-MRI after aortic banding in mice: band internalization is a source of variability in the hypertrophic response.

Transverse aortic constriction (TAC) is used as a model of left ventricular hypertrophy and failure; however, there is extensive variability in the hypertrophic response. In 43 mice that underwent TAC with a 7-0 polypropylene suture, 13 were identified by echocardiography with initial LV hypertrophy that halted or regressed over time. Post-mortem examination on 7 of these mice found the constricting band to be intact, but partially internalized into the aortic lumen, allowing blood flow around the stenosis. To confirm this prospectively in vivo we then followed 12 mice after TAC for 6 weeks, using a new high resolution 3D-MRI method to measure minimal aortic arch cross-sectional area (CSA). Three of the 12 mice developed a significantly increased aortic CSA (0.31 +/- 0.15 on day 2 vs. 1.11 +/- 0.29 mm2 on day 42; P < 0.05), which was independently confirmed by dissection. These mice had internalized part of the band within the aortic lumen and, by week 6, showed significantly less LV hypertrophy and better systolic function. Nine of the 12 mice showed no change in aortic CSA. Band internalization could be prevented when two banding sutures were placed side-by-side (n = 10). This is the first observation that a significant subset of animals following TAC bypass the stenosis resulting in partial regression of hypertrophy.

Animals↗

PubMed2005

Reduced inotropic reserve and increased susceptibility to cardiac ischemia/reperfusion injury in phosphocreatine-deficient guanidinoacetate-N-methyltransferase-knockout mice.

BACKGROUND: The role of the creatine kinase (CK)/phosphocreatine (PCr) energy buffer and transport system in heart remains unclear. Guanidinoacetate-N-methyltransferase-knockout (GAMT-/-) mice represent a new model of profoundly altered cardiac energetics, showing undetectable levels of PCr and creatine and accumulation of the precursor (phospho-)guanidinoacetate (P-GA). To characterize the role of a substantially impaired CK/PCr system in heart, we studied the cardiac phenotype of wild-type (WT) and GAMT-/- mice. METHODS AND RESULTS: GAMT-/- mice did not show cardiac hypertrophy (myocyte cross-sectional areas, hypertrophy markers atrial natriuretic factor and beta-myosin heavy chain). Systolic and diastolic function, measured invasively (left ventricular conductance catheter) and noninvasively (MRI), were similar for WT and GAMT-/- mice. However, during inotropic stimulation with dobutamine, preload-recruitable stroke work failed to reach maximal levels of performance in GAMT-/- hearts (101+/-8 mm Hg in WT versus 59+/-7 mm Hg in GAMT-/-; P<0.05). (31)P-MR spectroscopy experiments showed that during inotropic stimulation, isolated WT hearts utilized PCr, whereas isolated GAMT-/- hearts utilized P-GA. During ischemia/reperfusion, GAMT-/- hearts showed markedly impaired recovery of systolic (24% versus 53% rate pressure product recovery; P<0.05) and diastolic function (eg, left ventricular end-diastolic pressure 23+/-9 in WT and 51+/-5 mm Hg in GAMT-/- during reperfusion; P<0.05) and incomplete resynthesis of P-GA. CONCLUSIONS: GAMT-/- mice do not develop hypertrophy and show normal cardiac function at low workload, suggesting that a fully functional CK/PCr system is not essential under resting conditions. However, when acutely stressed by inotropic stimulation or ischemia/reperfusion, GAMT-/- mice exhibit a markedly abnormal phenotype, demonstrating that an intact, high-capacity CK/PCr system is required for situations of increased cardiac work or acute stress.

Animals↗

PubMed2005

PPAR-alpha activation required for decreased glucose uptake and increased susceptibility to injury during ischemia.

The transcription of key metabolic regulatory enzymes in the heart is altered in the diabetic state, yet little is known of the underlying mechanisms. The aim of this study was to investigate the role of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) in modulating cardiac insulin-sensitive glucose transporter (GLUT-4) protein levels in altered metabolic states and to determine the functional consequences by assessing cardiac ischemic tolerance. Wild-type and PPAR-alpha-null mouse hearts were isolated and perfused 6 wk after streptozotocin administration or after 14 mo on a high-fat diet or after a 24-h fast. Myocardial d-[2-(3)H]glucose uptake was measured during low-flow ischemia, and differences in GLUT-4 protein levels were quantified using Western blotting. In wild-type mice in all three metabolic states, elevated plasma free fatty acids were associated with lower total cardiac GLUT-4 protein levels and decreased glucose uptake during ischemia, resulting in poor postischemic functional recovery. Although PPAR-alpha-null mice also had elevated plasma free fatty acids, they had neither decreased cardiac GLUT-4 levels nor decreased glucose uptake during ischemia and, consequently, did not have poor recovery during reperfusion. We conclude that elevated plasma free fatty acids are associated with increased injury during ischemia due to decreased cardiac glucose uptake resulting from lower cardiac GLUT-4 protein levels, the levels of GLUT-4 being regulated, probably indirectly, through PPAR-alpha activation.

Animals↗

PubMed2005

Mechanisms of creatine depletion in chronically failing rat heart.

The failing myocardium is characterised by energetic imbalance, reflected by reduced phosphocreatine and creatine content. These changes may contribute to cardiac dysfunction, yet mechanisms of creatine and phosphocreatine depletion are poorly understood. Creatine is taken up by the heart via the creatine transporter. We investigated the mechanisms leading to myocardial creatine depletion in heart failure. Therefore rats were subjected to chronic left coronary artery ligation (MI; n = 36) or to sham operation (sham; n = 25). After 8 weeks, hearts were perfused with 14C-creatine buffer to determine creatine uptake rates via the creatine transporter. Total creatine content was determined by HPLC. Creatine transport in sham hearts followed Michaelis-Menten kinetics with a V(max) of 5.9 +/- 0.5 nmol/min per gww. Heart failure led to a significant 30% decrease in intracellular creatine content and to a significant 26% reduction in creatine uptake (V(max) in MI 4.3 +/- 0.4 nmol/min per gww; P < 0.001 vs. sham). We conclude that depletion of creatine/phosphocreatine content in the failing heart is due to reduced sarcolemmal creatine uptake. The creatine transporter may be a potential therapeutic target to prevent energetic imbalance in heart failure.

Animals↗

PubMed2005

Plasma free fatty acids and peroxisome proliferator-activated receptor alpha in the control of myocardial uncoupling protein levels.

Diabetic patients have abnormal cardiac energy metabolism associated with high plasma free fatty acid (FFA) concentrations. We investigated whether high plasma FFAs increase mitochondrial uncoupling protein (UCP) levels in the mouse heart by activating the nuclear transcription factor peroxisome proliferator-activated receptor (PPAR)alpha. We used Western blotting to measure UCP protein levels in isolated cardiac mitochondria from PPARalpha-/- and diabetic mice. Cardiac UCP2 and UCP3 were significantly lower in the PPARalpha-/- mouse than in the wild type. Treatment with the PPARalpha-specific agonist, WY-14,643, increased cardiac UCP2 and UCP3 levels in wild-type mice but did not alter UCP levels in PPARalpha-/- mice. Inhibition of beta-oxidation with etomoxir increased cardiac UCP2 and UCP3 levels in wild-type mice and UCP2 levels in PPARalpha-/- mice but did not alter UCP3 levels in PPARalpha-/- mice. Streptozotocin treatment, which increased circulating FFAs by 91%, did not alter cardiac UCP2 levels in wild-type or PPARalpha-/- mice but increased UCP3 levels in wild-type, and not in PPARalpha-/-, mice. The diabetic db/db mouse had 50% higher plasma FFA concentrations and elevated cardiac UCP2 and UCP3 protein levels. We conclude that high plasma FFAs activated PPARalpha to increase cardiac UCP3 levels, but cardiac UCP2 levels changed via PPARalpha-dependent and -independent mechanisms.

Animals↗

PubMed2004

Identification of cardiac malformations in mice lacking Ptdsr using a novel high-throughput magnetic resonance imaging technique.

BACKGROUND: Congenital heart defects are the leading non-infectious cause of death in children. Genetic studies in the mouse have been crucial to uncover new genes and signaling pathways associated with heart development and congenital heart disease. The identification of murine models of congenital cardiac malformations in high-throughput mutagenesis screens and in gene-targeted models is hindered by the opacity of the mouse embryo. RESULTS: We developed and optimized a novel method for high-throughput multi-embryo magnetic resonance imaging (MRI). Using this approach we identified cardiac malformations in phosphatidylserine receptor (Ptdsr) deficient embryos. These included ventricular septal defects, double-outlet right ventricle, and hypoplasia of the pulmonary artery and thymus. These results indicate that Ptdsr plays a key role in cardiac development. CONCLUSIONS: Our novel multi-embryo MRI technique enables high-throughput identification of murine models for human congenital cardiopulmonary malformations at high spatial resolution. The technique can be easily adapted for mouse mutagenesis screens and, thus provides an important new tool for identifying new mouse models for human congenital heart diseases.

Animals↗