Monocarboxylate transporters facilitate succinate uptake into brown adipocytes.

Uptake of circulating succinate by brown adipose tissue (BAT) and beige fat elevates whole-body energy expenditure, counteracts obesity and antagonizes systemic tissue inflammation in mice. The plasma membrane transporters that facilitate succinate uptake in these adipocytes remain undefined. Here we elucidate a mechanism underlying succinate import into BAT via monocarboxylate transporters (MCTs). We show that succinate transport is strongly dependent on the proportion that is present in the monocarboxylate form. MCTs facilitate monocarboxylate succinate uptake, which is promoted by alkalinization of the cytosol driven by adrenoreceptor stimulation. In brown adipocytes, we show that MCT1 primarily facilitates succinate import. In male mice, we show that both acute pharmacological inhibition of MCT1 and congenital depletion of MCT1 decrease succinate uptake into BAT and consequent catabolism. In sum, we define a mechanism of succinate uptake in BAT that underlies its protective activity in mouse models of metabolic disease.

Monocarboxylate transporters facilitate succinate uptake into brown adipocytes.

Uptake of circulating succinate by brown adipose tissue (BAT) and beige fat elevates whole body energy expenditure, counteracts obesity, and antagonizes systemic tissue inflammation in mice. The plasma membrane transporters that facilitate succinate uptake in these adipocytes remain undefined. Here we elucidate a mechanism underlying succinate import into BAT via monocarboxylate transporters (MCTs). We show that succinate transport is strongly dependent on the proportion of it present in the monocarboxylate form. MCTs facilitate monocarboxylate succinate uptake, which is promoted by alkalinization of the cytosol driven by adrenoreceptor stimulation. In brown adipocytes, we show that MCT1 primarily facilitates succinate import, however other members of the MCT family can partially compensate and fulfill this role in the absence of MCT1. In mice, we show that acute pharmacological inhibition of MCT1 and 2 decreases succinate uptake into BAT. Conversely, congenital genetic depletion of MCT1 alone has little effect on BAT succinate uptake, indicative of additional transport mechanisms with high capacity in vivo . In sum, we define a mechanism of succinate uptake in BAT that underlies its protective activity in mouse models of metabolic disease.

Architecture of the outbred brown fat proteome defines regulators of metabolic physiology.

Brown adipose tissue (BAT) regulates metabolic physiology. However, nearly all mechanistic studies of BAT protein function occur in a single inbred mouse strain, which has limited the understanding of generalizable mechanisms of BAT regulation over physiology. Here, we perform deep quantitative proteomics of BAT across a cohort of 163 genetically defined diversity outbred mice, a model that parallels the genetic and phenotypic variation found in humans. We leverage this diversity to define the functional architecture of the outbred BAT proteome, comprising 10,479 proteins. We assign co-operative functions to 2,578 proteins, enabling systematic discovery of regulators of BAT. We also identify 638 proteins that correlate with protection from, or sensitivity to, at least one parameter of metabolic disease. We use these findings to uncover SFXN5, LETMD1, and ATP1A2 as modulators of BAT thermogenesis or adiposity, and provide OPABAT as a resource for understanding the conserved mechanisms of BAT regulation over metabolic physiology.

Mitochondrial uncouplers induce proton leak by activating AAC and UCP1.

Mitochondria generate heat due to H+ leak (IH) across their inner membrane1. IH results from the action of long-chain fatty acids on uncoupling protein 1 (UCP1) in brown fat2-6 and ADP/ATP carrier (AAC) in other tissues1,7-9, but the underlying mechanism is poorly understood. As evidence of pharmacological activators of IH through UCP1 and AAC is lacking, IH is induced by protonophores such as 2,4-dinitrophenol (DNP) and cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP)10,11. Although protonophores show potential in combating obesity, diabetes and fatty liver in animal models12-14, their clinical potential for treating human disease is limited due to indiscriminately increasing H+ conductance across all biological membranes10,11 and adverse side effects15. Here we report the direct measurement of IH induced by DNP, FCCP and other common protonophores and find that it is dependent on AAC and UCP1. Using molecular structures of AAC, we perform a computational analysis to determine the binding sites for protonophores and long-chain fatty acids, and find that they overlap with the putative ADP/ATP-binding site. We also develop a mathematical model that proposes a mechanism of uncoupler-dependent IH through AAC. Thus, common protonophoric uncouplers are synthetic activators of IH through AAC and UCP1, paving the way for the development of new and more specific activators of these two central mediators of mitochondrial bioenergetics.

Sub-growth-inhibitory concentrations of omadacycline inhibit Staphylococcus aureus haemolytic activity in vitro.

OBJECTIVES: To evaluate the effect of sub-growth-inhibitory concentrations of omadacycline on Staphylococcus aureus ATCC 10832 haemolytic activity in vitro. METHODS: Following determination of the MICs of omadacycline and comparator antibiotics, the strain was grown in the presence of individual antibiotics and the percentage of haemolysis assayed; 'washout' experiments were performed with omadacycline only. RESULTS: Omadacycline inhibited S. aureus haemolytic activity in vitro at sub-growth-inhibitory concentrations. Inhibition was maintained at least 4 h after removal of extracellular drug. CONCLUSIONS: Omadacycline's in vitro potency and suppression of virulence factors might contribute to its efficacy in the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia caused by virulent strains of S. aureus. This finding could be relevant for other organisms and virulence factors that depend on new protein synthesis.

Cysteine 253 of UCP1 regulates energy expenditure and sex-dependent adipose tissue inflammation.

Uncoupling protein 1 (UCP1) is a major regulator of brown and beige adipocyte energy expenditure and metabolic homeostasis. However, the widely employed UCP1 loss-of-function model has recently been shown to have a severe deficiency in the entire electron transport chain of thermogenic fat. As such, the role of UCP1 in metabolic regulation in vivo remains unclear. We recently identified cysteine-253 as a regulatory site on UCP1 that elevates protein activity upon covalent modification. Here, we examine the physiological importance of this site through the generation of a UCP1 cysteine-253-null (UCP1 C253A) mouse, a precise genetic model for selective disruption of UCP1 in vivo. UCP1 C253A mice exhibit significantly compromised thermogenic responses in both males and females but display no measurable effect on fat accumulation in an obesogenic environment. Unexpectedly, we find that a lack of C253 results in adipose tissue redox stress, which drives substantial immune cell infiltration and systemic inflammatory pathology in adipose tissues and liver of male, but not female, mice. Elevation of systemic estrogen reverses this male-specific pathology, providing a basis for protection from inflammation due to loss of UCP1 C253 in females. Together, our results establish the UCP1 C253 activation site as a regulator of acute thermogenesis and sex-dependent tissue inflammation.

In vivo CRISPR base editing of PCSK9 durably lowers cholesterol in primates.

Gene-editing technologies, which include the CRISPR-Cas nucleases1-3 and CRISPR base editors4,5, have the potential to permanently modify disease-causing genes in patients6. The demonstration of durable editing in target organs of nonhuman primates is a key step before in vivo administration of gene editors to patients in clinical trials. Here we demonstrate that CRISPR base editors that are delivered in vivo using lipid nanoparticles can efficiently and precisely modify disease-related genes in living cynomolgus monkeys (Macaca fascicularis). We observed a near-complete knockdown of PCSK9 in the liver after a single infusion of lipid nanoparticles, with concomitant reductions in blood levels of PCSK9 and low-density lipoprotein cholesterol of approximately 90% and about 60%, respectively; all of these changes remained stable for at least 8 months after a single-dose treatment. In addition to supporting a 'once-and-done' approach to the reduction of low-density lipoprotein cholesterol and the treatment of atherosclerotic cardiovascular disease (the leading cause of death worldwide7), our results provide a proof-of-concept for how CRISPR base editors can be productively applied to make precise single-nucleotide changes in therapeutic target genes in the liver, and potentially in other organs.

UCP1 governs liver extracellular succinate and inflammatory pathogenesis.

Non-alcoholic fatty liver disease (NAFLD), the most prevalent liver pathology worldwide, is intimately linked with obesity and type 2 diabetes. Liver inflammation is a hallmark of NAFLD and is thought to contribute to tissue fibrosis and disease pathogenesis. Uncoupling protein 1 (UCP1) is exclusively expressed in brown and beige adipocytes, and has been extensively studied for its capacity to elevate thermogenesis and reverse obesity. Here we identify an endocrine pathway regulated by UCP1 that antagonizes liver inflammation and pathology, independent of effects on obesity. We show that, without UCP1, brown and beige fat exhibit a diminished capacity to clear succinate from the circulation. Moreover, UCP1KO mice exhibit elevated extracellular succinate in liver tissue that drives inflammation through ligation of its cognate receptor succinate receptor 1 (SUCNR1) in liver-resident stellate cell and macrophage populations. Conversely, increasing brown and beige adipocyte content in mice antagonizes SUCNR1-dependent inflammatory signalling in the liver. We show that this UCP1-succinate-SUCNR1 axis is necessary to regulate liver immune cell infiltration and pathology, and systemic glucose intolerance in an obesogenic environment. As such, the therapeutic use of brown and beige adipocytes and UCP1 extends beyond thermogenesis and may be leveraged to antagonize NAFLD and SUCNR1-dependent liver inflammation.

Omadacycline vs moxifloxacin in adults with community-acquired bacterial pneumonia.

OBJECTIVE: Community-acquired bacterial pneumonia (CABP) is a major clinical burden worldwide. In the phase III OPTIC study (NCT02531438) in CABP, omadacycline was found to be non-inferior to moxifloxacin for investigator-assessed clinical response (IACR) at post-treatment evaluation (PTE, 5-10 days after last dose). This article reports the efficacy findings, as specified in the European Medicines Agency (EMA) guidance. METHODS: Patients were randomized 1:1 to omadacycline 100 mg intravenously (every 12 h for two doses, then every 24 h) with optional transition to 300 mg orally after 3 days, or moxifloxacin 400 mg intravenously (every 24 h) with optional transition to 400 mg orally after 3 days. The total treatment duration was 7-14 days. The primary endpoint for EMA efficacy analysis was IACR at PTE in patients with Pneumonia Patient Outcomes Research Team (PORT) risk class III and IV. RESULTS: In total, 660 patients were randomized as PORT risk class III and IV. Omadacycline was non-inferior to moxifloxacin at PTE. The clinical success rates were 88.4% and 85.2%, respectively [intent-to-treat population; difference 3.3; 97.5% confidence interval (CI) -2.7 to 9.3], and 92.5% and 90.5%, respectively (clinically evaluable population; difference 2.0; 97.5% CI 3.2-7.4). Clinical success rates with omadacycline and moxifloxacin were similar against identified pathogens and across key subgroups. CONCLUSIONS: Omadacycline was non-inferior to moxifloxacin for IACR at PTE, with high clinical success across pathogen types and patient subgroups.

Safety and efficacy of omadacycline for treatment of community-acquired bacterial pneumonia and acute bacterial skin and skin structure infections in patients with mild-to-moderate renal impairment.

BACKGROUND: Many antibiotics require dosage adjustments in patients with renal impairment. In Phase III studies, omadacycline was non-inferior to moxifloxacin and linezolid in adults with community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSI), respectively. This analysis evaluated efficacy and safety measures from three omadacycline studies by patient renal function. METHODS: Patients were stratified as having normal renal function (creatinine clearance >89 mL/min), mild renal impairment (creatinine clearance 60-89 mL/min) or moderate renal impairment (creatinine clearance <60 mL/min); creatine clearance ≤30 mL/min (severe renal impairment) was an exclusion criterion. Efficacy endpoints were clinical success at the early clinical response (ECR) and post-treatment evaluation (PTE) time-points. Safety was evaluated as treatment-emergent adverse events (TEAEs) and laboratory measures. RESULTS: This subgroup analysis included 773 patients with CABP and 1339 patients with ABSSSI in intent-to-treat (ITT) and modified ITT populations, respectively. Clinical success rates were high at ECR and PTE across the studies (CABP 75-90%; ABSSSI 74-95%), and broadly similar between treatments, irrespective of renal function. Rates of TEAEs in patients with ABSSSI ranged from 33% to 52%, and were similar across renal function groups. In patients with CABP, higher rates were observed in patients with moderate renal impairment (56-61%) compared with patients with normal renal function or mild renal impairment (35-49%). The most common TEAEs were nausea and vomiting. CONCLUSIONS: Clinical success was similar across renal function groups, indicating no notable difference in the efficacy of omadacycline in patients with mild or moderate renal impairment. Omadacycline and comparators displayed similar safety profiles. CLINICALTRIALS. GOV REGISTRY: OPTIC (NCT02531438); OASIS-1 (NCT02378480); OASIS-2 (NCT02877927).

pH-Gated Succinate Secretion Regulates Muscle Remodeling in Response to Exercise.

In response to skeletal muscle contraction during exercise, paracrine factors coordinate tissue remodeling, which underlies this healthy adaptation. Here we describe a pH-sensing metabolite signal that initiates muscle remodeling upon exercise. In mice and humans, exercising skeletal muscle releases the mitochondrial metabolite succinate into the local interstitium and circulation. Selective secretion of succinate is facilitated by its transient protonation, which occurs upon muscle cell acidification. In the protonated monocarboxylic form, succinate is rendered a transport substrate for monocarboxylate transporter 1, which facilitates pH-gated release. Upon secretion, succinate signals via its cognate receptor SUCNR1 in non-myofibrillar cells in muscle tissue to control muscle-remodeling transcriptional programs. This succinate-SUCNR1 signaling is required for paracrine regulation of muscle innervation, muscle matrix remodeling, and muscle strength in response to exercise training. In sum, we define a bioenergetic sensor in muscle that utilizes intracellular pH and succinate to coordinate tissue adaptation to exercise.

Facultative protein selenation regulates redox sensitivity, adipose tissue thermogenesis, and obesity.

Oxidation of cysteine thiols by physiological reactive oxygen species (ROS) initiates thermogenesis in brown and beige adipose tissues. Cellular selenocysteines, where sulfur is replaced with selenium, exhibit enhanced reactivity with ROS. Despite their critical roles in physiology, methods for broad and direct detection of proteogenic selenocysteines are limited. Here we developed a mass spectrometric method to interrogate incorporation of selenium into proteins. Unexpectedly, this approach revealed facultative incorporation of selenium as selenocysteine or selenomethionine into proteins that lack canonical encoding for selenocysteine. Selenium was selectively incorporated into regulatory sites on key metabolic proteins, including as selenocysteine-replacing cysteine at position 253 in uncoupling protein 1 (UCP1). This facultative utilization of selenium was initiated by increasing cellular levels of organic, but not inorganic, forms of selenium. Remarkably, dietary selenium supplementation elevated facultative incorporation into UCP1, elevated energy expenditure through thermogenic adipose tissue, and protected against obesity. Together, these findings reveal the existence of facultative protein selenation, which correlates with impacts on thermogenic adipocyte function and presumably other biological processes as well.

A Quantitative Tissue-Specific Landscape of Protein Redox Regulation during Aging.

Mammalian tissues engage in specialized physiology that is regulated through reversible modification of protein cysteine residues by reactive oxygen species (ROS). ROS regulate a myriad of biological processes, but the protein targets of ROS modification that drive tissue-specific physiology in vivo are largely unknown. Here, we develop Oximouse, a comprehensive and quantitative mapping of the mouse cysteine redox proteome in vivo. We use Oximouse to establish several paradigms of physiological redox signaling. We define and validate cysteine redox networks within each tissue that are tissue selective and underlie tissue-specific biology. We describe a common mechanism for encoding cysteine redox sensitivity by electrostatic gating. Moreover, we comprehensively identify redox-modified disease networks that remodel in aged mice, establishing a systemic molecular basis for the long-standing proposed links between redox dysregulation and tissue aging. We provide the Oximouse compendium as a framework for understanding mechanisms of redox regulation in physiology and aging.

Once-daily oral omadacycline versus twice-daily oral linezolid for acute bacterial skin and skin structure infections (OASIS-2): a phase 3, double-blind, multicentre, randomised, controlled, non-inferiority trial.

BACKGROUND: Pathogen resistance and safety concerns limit oral antibiotic options for the treatment of acute bacterial skin and skin structure infections (ABSSSI). We aimed to compare the efficacy and safety of once-daily oral omadacycline, an aminomethylcycline antibiotic, versus twice-daily oral linezolid for treatment of ABSSSI. METHODS: In this phase 3, double-blind, randomised, non-inferiority study, eligible adults with ABSSSI at 33 sites in the USA were randomly assigned (1:1) to receive omadacycline (450 mg orally every 24 h over the first 48 h then 300 mg orally every 24 h) or linezolid (600 mg orally every 12 h) for 7-14 days. Randomisation was done via an interactive response system using a computer-generated schedule, and stratified by type of infection (wound infection, cellulitis or erysipelas, or major abscess) and receipt (yes or no) of allowed previous antibacterial treatment. Investigators, funders, and patients were masked to treatment assignments. Primary endpoints were early clinical response, 48-72 h after first dose, in the modified intention-to-treat (mITT) population (randomised patients without solely Gram-negative ABSSSI pathogens at baseline), and investigator-assessed clinical response at post-treatment evaluation, 7-14 days after the last dose, in the mITT population and clinically evaluable population (ie, mITT patients who had a qualifying infection as per study-entry criteria, received study drug, did not receive a confounding antibiotic, and had an assessment of outcome during the protocol-defined window). The safety population included randomised patients who received any amount of study drug. We set a non-inferiority margin of 10%. This study is registered with ClinicalTrials.gov, NCT02877927, and is complete. FINDINGS: Between Aug 11, 2016, and June 6, 2017, 861 participants were assessed for eligibility. 735 participants were randomly assigned, of whom 368 received omadacycline and 367 received linezolid. Omadacycline (315 [88%] of 360) was non-inferior to linezolid (297 [83%] of 360) for early clinical response (percentage-point difference 5·0, 95% CI -0·2 to 10·3) in the mITT population. For investigator-assessed clinical response at post-treatment evaluation, omadacycline was non-inferior to linezolid in the mITT (303 [84%] of 360 vs 291 [81%] of 360; percentage-point difference 3·3, 95% CI -2·2 to 9·0) and clinically evaluable (278 [98%] of 284 vs 279 [96%] of 292; 2·3, -0·5 to 5·8) populations. Mild to moderate nausea and vomiting were the most frequent treatment-emergent adverse events in omadacycline (111 [30%] of 368 and 62 [17%] of 368, respectively) and linezolid (28 [8%] of 367 and 11 [3%] of 367, respectively) groups. INTERPRETATION: Once-daily oral omadacycline was non-inferior to twice-daily oral linezolid in adults with ABSSSI, and was safe and well tolerated. Oral-only omadacycline represents a new treatment option for ABSSSI, with potential for reduction in hospital admissions and cost savings. FUNDING: Paratek Pharmaceuticals.

H+ transport is an integral function of the mitochondrial ADP/ATP carrier.

The mitochondrial ADP/ATP carrier (AAC) is a major transport protein of the inner mitochondrial membrane. It exchanges mitochondrial ATP for cytosolic ADP and controls cellular production of ATP. In addition, it has been proposed that AAC mediates mitochondrial uncoupling, but it has proven difficult to demonstrate this function or to elucidate its mechanisms. Here we record AAC currents directly from inner mitochondrial membranes from various mouse tissues and identify two distinct transport modes: ADP/ATP exchange and H+ transport. The AAC-mediated H+ current requires free fatty acids and resembles the H+ leak via the thermogenic uncoupling protein 1 found in brown fat. The ADP/ATP exchange via AAC negatively regulates the H+ leak, but does not completely inhibit it. This suggests that the H+ leak and mitochondrial uncoupling could be dynamically controlled by cellular ATP demand and the rate of ADP/ATP exchange. By mediating two distinct transport modes, ADP/ATP exchange and H+ leak, AAC connects coupled (ATP production) and uncoupled (thermogenesis) energy conversion in mitochondria.

Pharmacokinetics, Safety, and Clinical Outcomes of Omadacycline in Women with Cystitis: Results from a Phase 1b Study.

Omadacycline, an aminomethylcycline antibiotic, is approved as once-daily intravenous (i.v.) and oral (p.o.) monotherapy for acute bacterial skin and skin structure infections and for community-acquired bacterial pneumonia, and it is under development for treatment of urinary tract infection (UTI). This is a phase 1b, randomized, open-label study of omadacycline in women with cystitis (defined as UTI symptoms and a positive urine leukocyte esterase test). Patients received omadacycline for 5 days (group 1: 200 mg intravenously on day 1, then 300 mg orally every 24 h [q24h]; group 2: 300 mg orally every 12 h [q12h] on day 1, then 300 mg orally q24h; group 3: 450 mg orally q12h on day 1, then 450 mg orally q24h). Blood and urine samples were collected over 5 days. Investigator-assessed clinical response was determined at end of treatment (EOT; day 6) and posttreatment evaluation (PTE; 5 to 9 days after last dosing). A total of 31 women were treated. At steady state (day 5), the range of mean omadacycline urine concentrations over 24 h across the groups was 17.94 to 48.12 µg/ml. The most common treatment-emergent adverse events were gastrointestinal (including nausea [60% to 73%] and vomiting [20% to 40%]) and were generally mild and transient. Investigator-determined clinical success was observed in 94% and 84% of patients at EOT and PTE, respectively, with similar results across groups. A favorable microbiological response at PTE was observed in 78% of patients who had a baseline pathogen. Omadacycline is partially excreted in urine and appears to be safe and well tolerated. These preliminary results indicate that omadacycline warrants further evaluation in larger controlled UTI studies.

Omadacycline for Acute Bacterial Skin and Skin-Structure Infections.

BACKGROUND: Acute bacterial skin and skin-structure infections are associated with substantial morbidity and health care costs. Omadacycline, an aminomethylcycline antibiotic that can be administered once daily either orally or intravenously, is active against pathogens that commonly cause such infections, including antibiotic-resistant strains. METHODS: In this double-blind trial, we randomly assigned adults with acute bacterial skin and skin-structure infections (in a 1:1 ratio) to receive omadacycline (100 mg given intravenously every 12 hours for two doses, then 100 mg given intravenously every 24 hours) or linezolid (600 mg given intravenously every 12 hours). A transition to oral omadacycline (300 mg every 24 hours) or oral linezolid (600 mg every 12 hours) was allowed after 3 days; the total treatment duration was 7 to 14 days. The primary end point was an early clinical response at 48 to 72 hours, defined as survival with a reduction in lesion size of at least 20% without rescue antibacterial therapy. A secondary end point was an investigator-assessed clinical response at the post-treatment evaluation 7 to 14 days after the last dose, with clinical response defined as survival with resolution or improvement in signs or symptoms of infection to the extent that further antibacterial therapy was unnecessary. For both end points, the noninferiority margin was 10 percentage points. RESULTS: In the modified intention-to-treat population, omadacycline (316 patients) was noninferior to linezolid (311 patients) with respect to early clinical response (rate of response, 84.8% and 85.5%, respectively; difference, -0.7 percentage points; 95% confidence interval [CI], -6.3 to 4.9). Omadacycline also was noninferior to linezolid with respect to investigator-assessed clinical response at the post-treatment evaluation in the modified intention-to-treat population (rate of response, 86.1% and 83.6%, respectively; difference, 2.5 percentage points; 95% CI, -3.2 to 8.2) and in the clinical per-protocol population (96.3% and 93.5%, respectively; difference, 2.8 percentage points; 95% CI, -1.0 to 6.9). In both groups, the efficacy of the trial drug was similar for methicillin-susceptible and methicillin-resistant Staphylococcus aureus infections. Adverse events were reported in 48.3% of the patients in the omadacycline group and in 45.7% of those in the linezolid group; the most frequent adverse events in both groups were gastrointestinal (in 18.0% and 15.8% of the patients in the respective groups). CONCLUSIONS: Omadacycline was noninferior to linezolid for the treatment of acute bacterial skin and skin-structure infections and had a similar safety profile. (Funded by Paratek Pharmaceuticals; OASIS-1 ClinicalTrials.gov number, NCT02378480 .).

Omadacycline for Community-Acquired Bacterial Pneumonia.

BACKGROUND: Omadacycline, a new once-daily aminomethylcycline antibiotic agent that can be administered intravenously or orally, reaches high concentrations in pulmonary tissues and is active against common pathogens that cause community-acquired bacterial pneumonia. METHODS: In a double-blind trial, we randomly assigned (in a 1:1 ratio) adults with community-acquired bacterial pneumonia (Pneumonia Severity Index risk class II, III, or IV) to receive omadacycline (100 mg intravenously every 12 hours for two doses, then 100 mg intravenously every 24 hours), or moxifloxacin (400 mg intravenously every 24 hours). A transition to oral omadacycline (300 mg every 24 hours) or moxifloxacin (400 mg every 24 hours), respectively, was allowed after 3 days; the total treatment duration was 7 to 14 days. The primary end point was early clinical response, defined as survival with improvement in at least two of four symptoms (cough, sputum production, pleuritic chest pain, and dyspnea) and no worsening of symptoms at 72 to 120 hours, without receipt of rescue antibacterial therapy. A secondary end point was investigator-assessed clinical response at a post-treatment evaluation 5 to 10 days after the last dose, with clinical response defined as resolution or improvement in signs or symptoms to the extent that further antibacterial therapy was unnecessary. A noninferiority margin of 10 percentage points was used. RESULTS: The intention-to-treat population included 386 patients in the omadacycline group and 388 patients in the moxifloxacin group. Omadacycline was noninferior to moxifloxacin for early clinical response (81.1% and 82.7%, respectively; difference, -1.6 percentage points; 95% confidence interval [CI], -7.1 to 3.8), and the rates of investigator-assessed clinical response at the post-treatment evaluation were 87.6% and 85.1%, respectively (difference, 2.5 percentage points; 95% CI, -2.4 to 7.4). Adverse events that emerged after treatment initiation were reported in 41.1% of the patients in the omadacycline group and 48.5% of the patients in the moxifloxacin group; the most frequent events were gastrointestinal (10.2% and 18.0%, respectively), and the largest difference was for diarrhea (1.0% and 8.0%). Twelve deaths (8 in the omadacycline group and 4 in the moxifloxacin group) occurred during the trial. CONCLUSIONS: Omadacycline was noninferior to moxifloxacin for the treatment of community-acquired bacterial pneumonia in adults. (Funded by Paratek Pharmaceuticals; OPTIC ClinicalTrials.gov number, NCT02531438 .).

Accumulation of succinate controls activation of adipose tissue thermogenesis.

Thermogenesis by brown and beige adipose tissue, which requires activation by external stimuli, can counter metabolic disease1. Thermogenic respiration is initiated by adipocyte lipolysis through cyclic AMP-protein kinase A signalling; this pathway has been subject to longstanding clinical investigation2-4. Here we apply a comparative metabolomics approach and identify an independent metabolic pathway that controls acute activation of adipose tissue thermogenesis in vivo. We show that substantial and selective accumulation of the tricarboxylic acid cycle intermediate succinate is a metabolic signature of adipose tissue thermogenesis upon activation by exposure to cold. Succinate accumulation occurs independently of adrenergic signalling, and is sufficient to elevate thermogenic respiration in brown adipocytes. Selective accumulation of succinate may be driven by a capacity of brown adipocytes to sequester elevated circulating succinate. Furthermore, brown adipose tissue thermogenesis can be initiated by systemic administration of succinate in mice. Succinate from the extracellular milieu is rapidly metabolized by brown adipocytes, and its oxidation by succinate dehydrogenase is required for activation of thermogenesis. We identify a mechanism whereby succinate dehydrogenase-mediated oxidation of succinate initiates production of reactive oxygen species, and drives thermogenic respiration, whereas inhibition of succinate dehydrogenase supresses thermogenesis. Finally, we show that pharmacological elevation of circulating succinate drives UCP1-dependent thermogenesis by brown adipose tissue in vivo, which stimulates robust protection against diet-induced obesity and improves glucose tolerance. These findings reveal an unexpected mechanism for control of thermogenesis, using succinate as a systemically-derived thermogenic molecule.