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Tissues store excess nutrients as triglyceride or glycogen, but how these reserves are sensed and communicate remains poorly understood. Here we identify molecular players orchestrating this metabolic balance during fat depletion. We show fat body (FB)-specific depletion of fatty acyl-CoA synthase FASN1 in Drosophila causes near-complete fat loss and metabolic remodeling that dramatically elevates glycogen storage and carbohydrate metabolism. Proteomics and metabolomics identify key factors necessary for rewiring including glycolysis enzymes and target-of-brain-insulin (tobi). FASN1-deficient flies are viable but starvation sensitive, oxidatively stressed, and infertile. We also identify CG10824/cDIP as upregulated in FASN1-depleted Drosophila. cDIP is a leucine-rich-repeat protein with homology to secreted adipokines that fine-tune energy signaling, and is required for fly development in the absence of FASN1. Collectively, we show fat-depleted Drosophila rewire their metabolism to complete development, and identify cDIP as a putative new cytokine that signals fat insufficiency and may regulate energy homeostasis.

Metabolomic profiling is instrumental in understanding the systemic and cellular impact of inborn errors of metabolism (IEMs), monogenic disorders caused by pathogenic genomic variants in genes involved in metabolism. This study encompasses untargeted metabolomics analysis of plasma from 474 individuals and fibroblasts from 67 subjects, incorporating healthy controls, patients with 65 different monogenic diseases, and numerous undiagnosed cases. We introduce a web application designed for the in-depth exploration of this extensive metabolomics database. The application offers a user-friendly interface for data review, download, and detailed analysis of metabolic deviations linked to IEMs at the level of individual patients or groups of patients with the same diagnosis. It also provides interactive tools for investigating metabolic relationships and offers comparative analyses of plasma and fibroblast profiles. This tool emphasizes the metabolic interplay within and across biological matrices, enriching our understanding of metabolic regulation in health and disease. As a resource, the application provides broad utility in research, offering novel insights into metabolic pathways and their alterations in various disorders.

Fatty acid synthase (FASN) maintains de novo lipogenesis (DNL) to support rapid growth in most proliferating cancer cells. Lipogenic acetyl-coenzyme A (CoA) is primarily produced from carbohydrates but can arise from glutamine-dependent reductive carboxylation. Here, we show that reductive carboxylation also occurs in the absence of DNL. In FASN-deficient cells, reductive carboxylation is mainly catalyzed by isocitrate dehydrogenase-1 (IDH1), but IDH1-generated cytosolic citrate is not utilized for supplying DNL. Metabolic flux analysis (MFA) shows that FASN deficiency induces a net cytosol-to-mitochondria citrate flux through mitochondrial citrate transport protein (CTP). Previously, a similar pathway has been shown to mitigate detachment-induced oxidative stress in anchorage-independent tumor spheroids. We further report that tumor spheroids show reduced FASN activity and that FASN-deficient cells acquire resistance to oxidative stress in a CTP- and IDH1-dependent manner. Collectively, these data indicate that by inducing a cytosol-to-mitochondria citrate flux, anchorage-independent malignant cells can gain redox capacity by trading off FASN-supported rapid growth., Competing Interests: Declaration of interests R.D. is a founder and advisor at Atavistik Bio and serves on the scientific advisory boards of Agios Pharmaceuticals and Vida Ventures., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Analyzing the metabolic dependencies of tumor cells is vital for cancer diagnosis and treatment. Here, we describe a protocol for 13 C-stable glucose and glutamine isotope tracing in mice HER2+ breast cancer brain metastatic lesions. We describe how to inject cancer cells intracardially to generate brain metastatic lesions in mice. We then detail how to perform 13 C-stable isotope infusion in mice with established brain metastasis. Finally, we outline steps for sample collection, processing for metabolite extraction, and analyzing mass spectrometry data. For complete details on the use and execution of this protocol, please refer to Parida et al. (2022)., Competing Interests: R.J.D. is a founder of Atavistik Biosciences and an advisor for Agios Pharmaceuticals, Nirogy Therapeutics, and Vida Ventures., (© 2022 The Author(s).)

Tumor cells have devised unique metabolic strategies to garner enough nutrients to sustain continuous growth and cell division. Oncogenic mutations may alter metabolic pathways to unlock new sources of energy, and cells take the advantage of various scavenging pathways to ingest material from their environment. These changes in metabolism result in a metabolic profile that, in addition to providing the building blocks for macromolecules, can also influence cell signaling pathways to promote tumor initiation and progression. Understanding what pathways tumor cells use to synthesize the materials necessary to support metabolic growth can pave the way for new cancer therapeutics. Potential strategies include depriving tumors of the materials needed to grow or targeting pathways involved in dependencies that arise by virtue of their altered metabolis., (© 2019 New York Academy of Sciences.)

The oxidative pentose phosphate pathway (oxiPPP) contributes to cell metabolism through not only the production of metabolic intermediates and reductive NADPH but also inhibition of LKB1-AMPK signaling by ribulose-5-phosphate (Ru-5-P), the product of the third oxiPPP enzyme 6-phosphogluconate dehydrogenase (6PGD). However, we found that knockdown of glucose-6-phosphate dehydrogenase (G6PD), the first oxiPPP enzyme, did not affect AMPK activation despite decreased Ru-5-P and subsequent LKB1 activation, due to enhanced activity of PP2A, the upstream phosphatase of AMPK. In contrast, knockdown of 6PGD or 6-phosphogluconolactonase (PGLS), the second oxiPPP enzyme, reduced PP2A activity. Mechanistically, knockdown of G6PD or PGLS decreased or increased 6-phosphogluconolactone level, respectively, which enhanced the inhibitory phosphorylation of PP2A by Src. Furthermore, γ-6-phosphogluconolactone, an oxiPPP byproduct with unknown function generated through intramolecular rearrangement of δ-6-phosphogluconolactone, the only substrate of PGLS, bound to Src and enhanced PP2A recruitment. Together, oxiPPP regulates AMPK homeostasis by balancing the opposing LKB1 and PP2A., (Copyright © 2019 Elsevier Inc. All rights reserved.)

mTOR, the mammalian target of rapamycin, integrates growth factor and nutrient signals to promote a transformation from catabolic to anabolic metabolism, cell growth, and cell cycle progression. Phosphatidic acid (PA) interacts with the FK506-binding protein-12-rapamycin-binding (FRB) domain of mTOR, which stabilizes both mTOR complexes: mTORC1 and mTORC2. We report here that mTORC1 and mTORC2 are activated in response to exogenously supplied fatty acids via the de novo synthesis of PA, a central metabolite for membrane phospholipid biosynthesis. We examined the impact of exogenously supplied fatty acids on mTOR in KRas-driven cancer cells, which are programmed to utilize exogenous lipids. The induction of mTOR by oleic acid was dependent upon the enzymes responsible for de novo synthesis of PA. Suppression of the de novo synthesis of PA resulted in G 1 cell cycle arrest. Although it has long been appreciated that mTOR is a sensor of amino acids and glucose, this study reveals that mTOR also senses the presence of lipids via production of PA., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)

This study sought to investigate the effects of mechanical unloading on myocardial energetics and the metabolic perturbation of heart failure (HF) in an effort to identify potential new therapeutic targets that could enhance the unloading-induced cardiac recovery. The authors prospectively examined paired human myocardial tissue procured from 31 advanced HF patients at left ventricular assist device (LVAD) implant and at heart transplant plus tissue from 11 normal donors. They identified increased post-LVAD glycolytic metabolites without a coordinate increase in early, tricarboxylic acid (TCA) cycle intermediates. The increased pyruvate was not directed toward the mitochondria and the TCA cycle for complete oxidation, but instead, was mainly converted to cytosolic lactate. Increased nucleotide concentrations were present, potentially indicating increased flux through the pentose phosphate pathway. Evaluation of mitochondrial function and structure revealed a lack of post-LVAD improvement in mitochondrial oxidative functional capacity, mitochondrial volume density, and deoxyribonucleic acid content. Finally, post-LVAD unloading, amino acid levels were found to be increased and could represent a compensatory mechanism and an alternative energy source that could fuel the TCA cycle by anaplerosis. In summary, the authors report evidence that LVAD unloading induces glycolysis in concert with pyruvate mitochondrial oxidation mismatch, most likely as a result of persistent mitochondrial dysfunction. These findings suggest that interventions known to improve mitochondrial biogenesis, structure, and function, such as controlled cardiac reloading and conditioning, warrant further investigation to enhance unloading-induced reverse remodeling and cardiac recovery.

Objectives: To identify risk factors for recurrent urinary tract infection (UTI) and renal scarring in children who have had 1 or 2 febrile or symptomatic UTIs and received no antimicrobial prophylaxis., Methods: This 2-year, multisite prospective cohort study included 305 children aged 2 to 71 months with vesicoureteral reflux (VUR) receiving placebo in the RIVUR (Randomized Intervention for Vesicoureteral Reflux) study and 195 children with no VUR observed in the CUTIE (Careful Urinary Tract Infection Evaluation) study. Primary exposure was presence of VUR; secondary exposures included bladder and bowel dysfunction (BBD), age, and race. Outcomes were recurrent febrile or symptomatic urinary tract infection (F/SUTI) and renal scarring., Results: Children with VUR had higher 2-year rates of recurrent F/SUTI (Kaplan-Meier estimate 25.4% compared with 17.3% for VUR and no VUR, respectively). Other factors associated with recurrent F/SUTI included presence of BBD at baseline (adjusted hazard ratio: 2.07 [95% confidence interval (CI): 1.09-3.93]) and presence of renal scarring on the baseline (99m)Tc-labeled dimercaptosuccinic acid scan (adjusted hazard ratio: 2.88 [95% CI: 1.22-6.80]). Children with BBD and any degree of VUR had the highest risk of recurrent F/SUTI (56%). At the end of the 2-year follow-up period, 8 (5.6%) children in the no VUR group and 24 (10.2%) in the VUR group had renal scars, but the difference was not statistically significant (adjusted odds ratio: 2.05 [95% CI: 0.86-4.87])., Conclusions: VUR and BBD are risk factors for recurrent UTI, especially when they appear in combination. Strategies for preventing recurrent UTI include antimicrobial prophylaxis and treatment of BBD., (Copyright © 2015 by the American Academy of Pediatrics.)

Importance: Postdischarge treatment of acute osteomyelitis in children requires weeks of antibiotic therapy, which can be administered orally or intravenously via a peripherally inserted central catheter (PICC). The catheters carry a risk for serious complications, but limited evidence exists on the effectiveness of oral therapy., Objective: To compare the effectiveness and adverse outcomes of postdischarge antibiotic therapy administered via the PICC or the oral route., Design, Setting, and Participants: We performed a retrospective cohort study comparing PICC and oral therapy for the treatment of acute osteomyelitis. Among children hospitalized from January 1, 2009, through December 31, 2012, at 36 participating children's hospitals, we used discharge codes to identify potentially eligible participants. Results of medical record review confirmed eligibility and defined treatment group allocation and study outcomes. We used within- and across-hospital propensity score-based full matching to adjust for confounding by indication., Interventions: Postdischarge administration of antibiotics via the PICC or the oral route., Main Outcomes and Measures: The primary outcome was treatment failure. Secondary outcomes included adverse drug reaction, PICC line complication, and a composite of all 3 end points., Results: Among 2060 children and adolescents (hereinafter referred to as children) with osteomyelitis, 1005 received oral antibiotics at discharge, whereas 1055 received PICC-administered antibiotics. The proportion of children treated via the PICC route varied across hospitals from 0 to 100%. In the across-hospital (risk difference, 0.3% [95% CI, -0.1% to 2.5%]) and within-hospital (risk difference, 0.6% [95% CI, -0.2% to 3.0%]) matched analyses, children treated with antibiotics via the oral route (reference group) did not experience more treatment failures than those treated with antibiotics via the PICC route. Rates of adverse drug reaction were low (<4% in both groups) but slightly greater in the PICC group in across-hospital (risk difference, 1.7% [95% CI, 0.1%-3.3%]) and within-hospital (risk difference, 2.1% [95% CI, 0.3%-3.8%]) matched analyses. Among the children in the PICC group, 158 (15.0%) had a PICC complication that required an emergency department visit (n = 96), a rehospitalization (n = 38), or both (n = 24). As a result, the PICC group had a much higher risk of requiring a return visit to the emergency department or for hospitalization for any adverse outcome in across-hospital (risk difference, 14.6% [95% CI, 11.3%-17.9%]) and within-hospital (risk difference, 14.0% [95% CI, 10.5%-17.6%]) matched analyses., Conclusions and Relevance: Given the magnitude and seriousness of PICC complications, clinicians should reconsider the practice of treating otherwise healthy children with acute osteomyelitis with prolonged intravenous antibiotics after hospital discharge when an equally effective oral alternative exists.