Tag, you're it: G-ICAT identifies p120-cysteine glutathionylation triggering E-cadherin destabilization.

Current methods have limited ability in directly quantifying the extent of glutathionylation on specific protein-cysteines. In this issue of Cell Chemical Biology, Ahn et al.1 report G-ICAT (glutathione-based isotope-coded affinity tag), aimed at addressing this limitation. G-ICAT identifies Cysteine-692 within p120-catenin-a member of cadherin complex essential for cell-cell-contact maintenance-where C692-specific glutathionylation promotes E-cadherin destabilization.

Development of fluorous boronic acid catalysts integrated with sulfur for enhanced amidation efficiency.

A thermally stable, fluorous sulfur-containing boronic acid catalyst has been developed and was shown to efficiently promote dehydrative condensation between carboxylic acids and amines under environmentally friendly conditions. The methodology can be applied to aliphatic, aromatic and heteroaromatic acids as well as primary and secondary amines. N-Boc protected amino acids were also successfully coupled in good yields with very little racemization. The catalyst could be reused four times with no significant loss of activity.

Alkyltriphenylphosphonium turns naphthoquinoneimidazoles into potent membrane depolarizers against mycobacteria.

Due to its central role in energy generation and bacterial viability, mycobacterial bioenergetics is an attractive therapeutic target for anti-tuberculosis drug discovery. Building upon our work on antimycobacterial dioxonaphthoimidazoliums that were activated by a proximal positive charge and generated reactive oxygen species upon reduction by Type II NADH dehydrogenase, we herein studied the effect of a distal positive charge on the antimycobacterial activity of naphthoquinoneimidazoles by incorporating a trialkylphosphonium cation. The potency-enhancing properties of the linker length were affirmed by structure-activity relationship studies. The most active compound against M. tb H37Rv displayed good selectivity index (SI = 34) and strong bactericidal activity in the low micromolar range, which occurred through rapid bacterial membrane depolarization that resulted in depletion of intracellular ATP. Through this work, we demonstrated a switch of the scaffold's mode-of-action via relocation of positive charge while retaining its excellent antibacterial activity and selectivity.

Fasting increases susceptibility to acute myocardial ischaemia/reperfusion injury through a sirtuin-3 mediated increase in fatty acid oxidation.

Fasting increases susceptibility to acute myocardial ischaemia/reperfusion injury (IRI) but the mechanisms are unknown. Here, we investigate the role of the mitochondrial NAD+-dependent deacetylase, Sirtuin-3 (SIRT3), which has been shown to influence fatty acid oxidation and cardiac outcomes, as a potential mediator of this effect. Fasting was shown to shift metabolism from glucose towards fatty acid oxidation. This change in metabolic fuel substrate utilisation increased myocardial infarct size in wild-type (WT), but not SIRT3 heterozygous knock-out (KO) mice. Further analysis revealed SIRT3 KO mice were better adapted to starvation through an improved cardiac efficiency, thus protecting them from acute myocardial IRI. Mitochondria from SIRT3 KO mice were hyperacetylated compared to WT mice which may regulate key metabolic processes controlling glucose and fatty acid utilisation in the heart. Fasting and the associated metabolic switch to fatty acid respiration worsens outcomes in WT hearts, whilst hearts from SIRT3 KO mice are better adapted to oxidising fatty acids, thereby protecting them from acute myocardial IRI.

Functionalized Dioxonaphthoimidazoliums: A Redox Cycling Chemotype with Potent Bactericidal Activities against Mycobacterium tuberculosis.

Disruption of redox homeostasis in mycobacteria causes irreversible stress induction and cell death. Here, we report the dioxonaphthoimidazolium scaffold as a novel redox cycling antituberculosis chemotype with potent bactericidal activity against growing and nutrient-starved phenotypically drug-resistant nongrowing bacteria. Maximal potency was dependent on the activation of the redox cycling quinone by the positively charged scaffold and accessibility to the mycobacterial cell membrane as directed by the lipophilicity and conformational characteristics of the N-substituted side chains. Evidence from microbiological, biochemical, and genetic investigations implicates a redox-driven mode of action that is reliant on the reduction of the quinone by type II NADH dehydrogenase (NDH2) for the generation of bactericidal levels of the reactive oxygen species (ROS). The bactericidal profile of a potent water-soluble analogue 32 revealed good activity against nutrient-starved organisms in the Loebel model of dormancy, low spontaneous resistance mutation frequency, and synergy with isoniazid in the checkerboard assay.

Antimalarial N 1,N 3-Dialkyldioxonaphthoimidazoliums: Synthesis, Biological Activity, and Structure-activity Relationships.

Here we report the nanomolar potencies of N 1,N 3-dialkyldioxonaphthoimidazoliums against asexual forms of sensitive and resistant Plasmodium falciparum. Activity was dependent on the presence of the fused quinone-imidazolium entity and lipophilicity imparted by the N1/N3 alkyl residues on the scaffold. Gametocytocidal activity was also detected, with most members active at IC50 < 1 µM. A representative analog with good solubility, limited PAMPA permeability, and microsomal stability demonstrated oral efficacy on a humanized mouse model of P. falciparum.

Proximal Tubular Cell-Specific Ablation of Carnitine Acetyltransferase Causes Tubular Disease and Secondary Glomerulosclerosis.

Proximal tubular epithelial cells are highly energy demanding. Their energy need is covered mostly from mitochondrial fatty acid oxidation. Whether derailments in fatty acid metabolism and mitochondrial dysfunction are forerunners of tubular damage has been suggested but is not entirely clear. Here we modeled mitochondrial overload by creating mice lacking the enzyme carnitine acetyltransferase (CrAT) in the proximal tubules, thus limiting a primary mechanism to export carbons under conditions of substrate excess. Mice developed tubular disease and, interestingly, secondary glomerulosclerosis. This was accompanied by increased levels of apoptosis regulator and fibrosis markers, increased oxidative stress, and abnormal profiles of acylcarnitines and organic acids suggesting profound impairments in all major forms of nutrient metabolism. When mice with CrAT deletion were fed a high-fat diet, kidney disease was more severe and developed faster. Primary proximal tubular cells isolated from the knockout mice displayed energy deficit and impaired respiration before the onset of pathology, suggesting mitochondrial respiratory abnormalities as a potential underlying mechanism. Our findings support the hypothesis that derailments of mitochondrial energy metabolism may be causative to chronic kidney disease. Our results also suggest that tubular injury may be a primary event followed by secondary glomerulosclerosis, raising the possibility that focusing on normalizing tubular cell mitochondrial function and energy balance could be an important preventative strategy.

Metabolomic correlates of aerobic capacity among elderly adults.

BACKGROUND: Aerobic capacity is a powerful predictor of cardiovascular disease and all-cause mortality, and it declines with advancing age. HYPOTHESIS: Since physical activity alters body metabolism, metabolism markers will likely differ between subjects with high vs low aerobic capacities. METHODS: Community-based participants without physician-diagnosed heart disease, stroke or cancer underwent same-day multimodal assessment of cardiovascular function (by echocardiography and magnetic resonance feature tracking of left atrium) and aerobic capacity by peak oxygen uptake (VO2 ) metrics. Associations between VO2 and cardiovascular and metabolomics profiles were studied in adjusted models including standard covariates. RESULTS: We studied 141 participants, of whom 82 (58.2%) had low VO2 , while 59 (41.8%) had high VO2 . Compared to participants with high VO2 , participants with low VO2 had more adverse cardiovascular parameters, such as lower ratio of peak velocity flow in early diastole to peak velocity flow in late diastole by atrial contraction of >0.8 (76% vs 35%, adjusted odd ratio [OR] = 4.1, 95% confidence interval [CI] [1.7-9.5], P = 0.001) and lower left atrial conduit strain (11.3 ± 4.0 vs 15.6 ± 6.1%, adjusted OR = 1.1, 95% CI [1.002-1.3], P = 0.045). High VO2 was associated with lower accumulation of wide-spectrum acyl-carnitines (OR = 0.6, 95% CI [0.4-0.9], P = 0.013), alanine (OR = 0.1, 95% CI [0.01-0.9], P = 0.044) and glutamine /glutamate (OR = 0.1, 95% CI [0.01-0.5], P = 0.007), compared to low VO2. CONCLUSION: Elderly adults with low VO2 have adverse cardiovascular and metabolic parameters compared to their counterparts with high VO2 . Combined cardiac and metabolomics phenotyping may be a promising tool to provide insights into physiological states, useful for tracking future interventions related to physical activity among community cohorts.

Dissecting Clinical and Metabolomics Associations of Left Atrial Phasic Function by Cardiac Magnetic Resonance Feature Tracking.

Among community cohorts, associations between clinical and metabolite factors and complex left atrial (LA) phasic function assessed by cardiac magnetic resonance (CMR) feature tracking (FT) are unknown. Longitudinal LA strain comprising reservoir strain (εs), conduit strain (εe) and booster strain (εa) and their corresponding peak strain rates (SRs, SRe, SRa) were measured using CMR FT. Targeted mass spectrometry measured 83 circulating metabolites in serum. Sparse Principal Component Analysis was used for data reduction. Among community adults (n = 128, 41% female) (mean age: 70.5 ± 11.6 years), age was significantly associated with εs (ß = -0.30, p < 0.0001), εe (ß = -0.3, p < 0.0001), SRs (ß = -0.02, p < 0.0001), SRe (ß = 0.04, p < 0.0001) and SRe/SRa (ß = -0.01, p = 0.012). In contrast, heart rate was significantly associated with εa (ß = 0.1, p = 0.001) and SRa (ß = -0.02, p < 0.0001). Serine was significantly associated with εs (ß = 10.1, p = 0.015), SRs (ß = 0.5, p = 0.033) and SRa (ß = -0.9, p = 0.016). Citrulline was associated with εs (ß = -4.0, p = 0.016), εa (ß = -3.4, p = 0.002) and SRa (ß = 0.4, p = 0.019). Valine was associated with ratio of SRe:SRa (ß = -0.4, p = 0.039). Medium and long chain dicarboxyl carnitines were associated with εs (ß = -0.6, p = 0.038). Phases of LA function were differentially associated with clinical and metabolite factors. Metabolite signals may be used to advance mechanistic understanding of LA disease in future studies.

Metabolomic profile of arterial stiffness in aged adults.

BACKGROUND: Increasing arterial stiffness is an important contributor to declining cardiovascular health in ageing. Changes in whole-body fuel metabolism could be related to alterations in arterial stiffness in ageing adults. METHODS: Targeted high-performance liquid and gas chromatography mass spectrometry were used to measure 84 circulating metabolites in a group of community elderly adults ( n = 141, 58% men; mean age = 70.6 ± 11.2 years) without cardiovascular disease. In basic and adjusted models, we correlated the measured metabolites to carotid-femoral pulse wave velocity assessed by applanation tonometry. RESULTS: Age ( ß = 0.10, p < 0.0001), smoking status ( ß = 1.32, p = 0.02), dyslipidemia ( ß = 1.22, p = 0.01), central systolic blood pressure ( ß = 0.05, p < 0.0001), central mean arterial pressure ( ß = 0.04, p = 0.03) and central pulse pressure ( ß = 0.05, p < 0.0001) were significantly associated with pulse wave velocity. Amino acids such as histidine, methionine and valine correlated with pulse wave velocity. In multivariable models adjusted for clinical covariates, only Factor 5, comprising the medium- and long-chain dicarboxyl and hydroxyl acylcarnitines was independently associated with pulse wave velocity ( ß = 0.24, p = 0.015). CONCLUSION: An upstream metabolic perturbation comprising medium- and long-chain dicarboxyl and hydroxyl acylcarnitines, likely reflecting changes in cellular fatty acid oxidation, was associated with arterial stiffness among aged adults. This advances mechanistic understanding of arterial stiffness among aged adults before clinical disease.

A Role for Ceramides, but Not Sphingomyelins, as Antagonists of Insulin Signaling and Mitochondrial Metabolism in C2C12 Myotubes.

The accumulation of sphingolipids in obesity leads to impairments in insulin sensitivity and mitochondrial metabolism, but the precise species driving these defects is unclear. We have modeled these obesity-induced effects in cultured C2C12 myotubes, using BSA-conjugated palmitate to increase synthesis of endogenous sphingolipids and to inhibit insulin signaling and oxidative phosphorylation. Palmitate (a) induced the accumulation of sphingomyelin (SM) precursors such as sphinganine, dihydroceramide, and ceramide; (b) inhibited insulin stimulation of a central modulator of anabolic metabolism, Akt/PKB; (c) inhibited insulin-stimulated glycogen synthesis; and (d) decreased oxygen consumption and ATP synthesis. Under these conditions, palmitate failed to alter levels of SMs, which are the most abundant sphingolipids, suggesting that they are not the primary intermediates accounting for the deleterious palmitate effects. Treating cells with a pharmacological inhibitor of SM synthase or using CRISPR to knock out the Sms2 gene recapitulated the palmitate effects by inducing the accumulation of SM precursors and impairing insulin signaling and mitochondrial metabolism. To profile the sphingolipids that accumulate in obesity, we performed lipidomics on quadriceps muscles from obese mice with impaired glucose tolerance. Like the cultured myotubes, these tissues accumulated ceramides but not SMs. Collectively, these data suggest that SM precursors such as ceramides, rather than SMs, are likely nutritional antagonists of metabolic function in skeletal muscle.