Metabolic underpinnings of the paradoxical net phosphocreatine resynthesis in contracting rat gastrocnemius muscle

AbstractNet phosphocreatine (PCr) resynthesis during muscle contraction is a paradoxical phenomenon because it occurs under conditions of high energy demand. The metabolic underpinnings of this phenomenon were analyzed non-invasively using 31P-magnetic resonance spectroscopy in rat gastrocnemius muscle (n=11) electrically stimulated (7.6 Hz, 6 min duration) in situ under ischemic and normoxic conditions. During ischemic stimulation, [PCr] initially fell to a steady state (9±5% of resting concentration) which was maintained for the last 5 min of stimulation, whereas isometric force production decreased to a non-measurable level beyond 3 min. Throughout normoxic stimulation, [PCr] and force production declined to a steady state after respectively 1 min (5±3% of resting concentration) and 3.25 min (21±8% of initial value) of stimulation. Contrary to the observations under ischemia, a paradoxical net PCr resynthesis was recorded during the last 2 min of normoxic stimulation and was not accompanied by any improvement in force production. These results demonstrate that the paradoxical net PCr resynthesis recorded in contracting muscle relies exclusively on oxidative energy production and could occur in inactivated fibers, similarly to PCr resynthesis during post-exercise recovery

White matter maturation of normal human fetal brain. An in vivo diffusion tensor tractography study

We demonstrate for the first time the ability to determine in vivo and in utero the transitions between the main stages of white matter (WM) maturation in normal human fetuses using magnetic resonance diffusion tensor imaging (DTI) tractography. Biophysical characteristics of water motion are used as an indirect probe to evaluate progression of the tissue matrix organization in cortico-spinal tracts (CSTs), optic radiations (OR), and corpus callosum (CC) in 17 normal human fetuses explored between 23 and 38 weeks of gestation (GW) and selected strictly on minimal motion artifacts. Nonlinear polynomial (third order) curve fittings of normalized longitudinal and radial water diffusivities (Z-scores) as a function of age identify three different phases of maturation with specific dynamics for each WM bundle type. These phases may correspond to distinct cellular events such as axonal organization, myelination gliosis, and myelination, previously reported by other groups on post-mortem fetuses using immunostaining methods. According to the DTI parameter dynamics, we suggest that myelination (phase 3) appears early in the CSTs, followed by the OR and by the CC, respectively. DTI tractography provides access to a better understanding of fetal WM maturation

Inflammatory Multiple-Sclerosis Plaques Generate Characteristic Metabolic Profiles in Cerebrospinal Fluid

International audienceBackgroundMultiple sclerosis (MS), an inflammatory disease of the central nervous system, manifests itself in numerous forms and stages. A number of brain metabolic alterations have been reported for MS patients vs. control subjects. However, metabolite profiles of cerebrospinal fluid (CSF) are not consistent among the published MS studies, most probably due to variations in the patient cohorts studied. We undertook the first investigation of highly homogeneous MS patient cohorts to determine characteristic effects of inflammatory MS plaques on the CSF metabolome, including only patients with clinically isolated syndrome (CIS) with or without inflammatory brain plaques, and controls.Methodology/Principal FindingsCSF obtained by lumbar puncture was analyzed by proton magnetic resonance spectroscopy. 27 metabolites were quantified. Differences between groups of control subjects (n = 10), CIS patients with (n = 21) and without (n = 12) inflammatory plaques were evaluated by univariate statistics and principal component analysis (PCA). Seven metabolites showed statistically significant inter-group differences (p<0.05). Interestingly, a significant increase in β-hydroxyisobutyrate (BHIB) was detected in CIS with vs. without active plaques, but not when comparing either CIS group with control subjects. Moreover, a significant correlation was found, for the first time, between CSF lactate concentration and the number of inflammatory MS brain plaques. In contrast, fructose concentrations were equally enhanced in CIS with or without active plaques. PCA based on all 27 metabolites yielded group-specific clusters.Conclusions/SignificanceCSF metabolic profiles suggest a close link between MS plaque activity in CIS patients on the one hand and organic-acid metabolism on the other. Our detection of increased BHIB levels points to a hitherto unsuspected role for this compound in MS with active plaques, and serves as a basis for further investigation. The metabolic effects described in our study are crucial elements in the explanation of biochemical mechanisms involved in specific MS manifestations

Gender differences in response to cold pressor test assessed with velocity-encoded cardiovascular magnetic resonance of the coronary sinus

BACKGROUND: Gender-specific differences in cardiovascular risk are well known, and current evidence supports an existing role of endothelium in these differences. The purpose of this study was to assess non invasively coronary endothelial function in male and female young volunteers by myocardial blood flow (MBF) measurement using coronary sinus (CS) flow quantification by velocity encoded cine cardiovascular magnetic resonance (CMR) at rest and during cold pressor test (CPT). METHODS: Twenty-four healthy volunteers (12 men, 12 women) underwent CMR in a 3 Tesla MR imager. Coronary sinus flow was measured at rest and during CPT using non breath-hold velocity encoded phase contrast cine-CMR. Myocardial function and morphology were acquired using a cine steady-state free precession sequence. RESULTS: At baseline, mean MBF was 0.63 ± 0.23 mL·g⁻¹·min⁻¹ in men and 0.79 ± 0.21 mL·g⁻¹·min⁻¹ in women. During CPT, the rate pressure product in men significantly increased by 49 ± 36% (p \textless 0.0001) and in women by 52 ± 22% (p \textless 0.0001). MBF increased significantly in both men and women by 0.22 ± 0.19 mL·g⁻¹·min⁻¹ (p = 0.0022) and by 0.73 ± 0.43 mL·g⁻¹·min⁻¹ (p = 0.0001), respectively. The increase in MBF was significantly higher in women than in men (p = 0.0012). CONCLUSION: CMR coronary sinus flow quantification for measuring myocardial blood flow revealed a higher response of MBF to CPT in women than in men. This finding may reflect gender differences in endothelial-dependent vasodilatation in these young subjects. This non invasive rest/stress protocol may become helpful to study endothelial function in normal physiology and in physiopathology

Expression of Cell-Surface Marker ABCB5 Causes Characteristic Modifications of Glucose, Amino Acid and Phospholipid Metabolism in the G3361 Melanoma-Initiating Cell Line

We present a pilot study aimed at determining the effects of expression of ATP-binding cassette member B5 (ABCB5), a previously described marker for melanoma-initiating cells, on cellular metabolism. Metabolic profiles for two groups of human G3361 melanoma cells were compared, i.e. wildtype melanoma cells with intact ABCB5 expression (ABCB5-WT) and corresponding melanoma cell variants with inhibited ABCB5 expression, through shRNA-mediated gene knockdown (ABCB5-KD). A comprehensive metabolomic analysis was performed by using proton and phosphorus NMR spectroscopy of cell extracts to examine water-soluble metabolites and lipids. Parametric and non-parametric statistical analysis of absolute and relative metabolite levels yielded significant differences for compounds involved in glucose, amino acid and phospholipid (PL) metabolism. By contrast, energy metabolism was virtually unaffected by ABCB5 expression. The sum of water-soluble metabolites per total protein was 17% higher in ABCB5-WT vs. ABCB5-KD G3361 variants, but no difference was found for the sum of PLs. Enhanced abundance was particularly pronounced for lactate (+ 23%) and alanine (+ 26%), suggesting an increase in glycolysis and potentially glutaminolysis. Increases in PL degradation products, glycerophosphocholine and glycerophosphoethanolamine (+ 85 and 123%, respectively), and redistributions within the PL pool suggested enhanced membrane PL turnover as a consequence of ABCB5 expression. The possibility of glycolysis modulation by an ABCB5-dependent IL1β-mediated mechanism was supported by functional studies employing monoclonal antibody (mAb)-dependent ABCB5 protein inhibition in wildtype G3361 melanoma cells. Our metabolomic results suggest that the underlying biochemical pathways may offer targets for melanoma therapy, potentially in combination with other treatment forms

A porcine model of heart failure with preserved ejection fraction:magnetic resonance imaging and metabolic energetics

Aims A significant proportion of heart failure (HF) patients have HF preserved ejection fraction (HFpEF). The lack of effective treatments for HFpEF remains a critical unmet need. A key obstacle to therapeutic innovation in HFpEF is the paucity of pre-clinical models. Although several large animal models have been reported, few demonstrate progression to decompensated HF. We have established a model of HFpEF by enhancing a porcine model of progressive left ventricular (LV) pressure overload and characterized HF in this model including advanced cardiometabolic imaging using cardiac magnetic resonance imaging and hyperpolarized carbon-13 magnetic resonance spectroscopy. Methods and results Pigs underwent progressive LV pressure overload by means of an inflatable aortic cuff. Pigs developed LV hypertrophy (50% increase in wall thickness, P <0.001, and two-fold increase in mass compared to sham control, P <0.001) with no evidence of LV dilatation but a significant increase in left atrial volume (P = 0.013). Cardiac magnetic resonance imaging demonstrated T1 modified Look-Locker inversion recovery values increased in 16/17 segments compared to sham pigs (P <0.05-P <0.001) indicating global ventricular fibrosis. Mean LV end-diastolic (P = 0.047) and pulmonary capillary wedge pressures (P = 0.008) were elevated compared with sham control. One-third of the pigs demonstrated clinical signs of frank decompensated HF, and mean plasma BNP concentrations were raised compared with sham control (P = 0.008). Cardiometabolic imaging with hyperpolarized carbon-13 magnetic resonance spectroscopy agreed with known metabolic changes in the failing heart with a switch from fatty acid towards glucose substrate utilization. Conclusions Progressive aortic constriction in growing pigs induces significant LV hypertrophy with cardiac fibrosis associated with left atrial dilation, raised filling pressures, and an ability to transition to overt HF with raised BNP without reduction in LVEF. This model replicates many aspects of clinical HFpEF with a predominant background of hypertension and can be used to advance understanding of underlying pathology and for necessary pre-clinical testing of novel candidate therapies