Cell Metabolism

Post-meal activity can attenuate glucose excursions; however, the exact magnitude of this effect remains unquantified, and guidance is rarely personalized to the meal occasion. We linked Human Phenotype Project diet logs, continuous glucose monitoring and wearable step counts to test whether glycemic risk estimated before activity occurs can prioritize post-meal movement. An activity-blind PPGR model trained on 391,214 PPGR-valid meals from 9,561 participants generated pre-activity meal scores. Among 55,949 step-linked meals from 1,627 adults without diabetes, higher 0-120-min post-meal steps were associated with lower within-participant PPGR (-53.0 mg/dL*min per 1 s.d. higher log steps; 95% CI, -64.2 to -41.7), with larger adjusted PPGR iAUC contrasts at 1,501-2,500 observed steps (-154.4 mg/dL*min versus 0-50 steps). Associations were stronger among participants with higher glycemic-adiposity burden and after meals with higher predicted PPGR. A held-out pre-activity step-response ranking concentrated larger inverse step-PPGR associations (-79.1 top versus -15.0 mg/dL*min bottom quintile), providing a testable strategy for prediction-guided, post-meal movement prompts.

Type 2 diabetes is linked to systemic inflammation driven by metabolic stress and aging. Although pancreatic inflammation associated with these factors is well documented, the dynamics of immune cell populations and their molecular changes remain poorly understood. We characterized immune cell alterations in the pancreas and pancreatic islets during Western diet (WD) feeding and aging using imaging mass cytometry (IMC) and single-cell RNA sequencing (scRNA-seq). Spatial and transcriptional analyses were performed to define immune cell subtype composition, activation states, and inferred cell-cell communication programs under metabolic and age-related stress conditions. Our analyses identified expansion of an F4/80low macrophage subtype and activated effector-like CD8+ T cells throughout the pancreas during WD feeding and aging. Within pancreatic islets, single-cell RNA sequencing identified a type 1 interferon-responsive macrophage population with low F4/80 expression that expanded during overnutrition. Notably, the type 1 interferon responses elicited by these stressors diverged: aging was associated with a more canonical type 1 interferon response, whereas overnutrition induced a broader response that included STAT3-associated transcriptional programs. We further provide evidence for enhanced cytokine-mediated communication between macrophages and a CD8+ cytotoxic T-cell population under overnutrition and aging. These findings show that metabolic stress and aging remodel pancreatic inflammation through overlapping but distinct immune mechanisms, involving expansion of F4/80low macrophages, activation of divergent type 1 interferon programs, and enhanced macrophage-CD8+ T-cell communication. Together, these findings suggest that distinct therapeutic approaches may be required to preserve islet function in type 2 diabetes driven by metabolic stress versus aging.

During an immune response, metabolism changes dramatically. Metabolites are oxidized to power immune cell functions, serve as building blocks for proliferation, and act as effectors to regulate pathogen or host cells. Though metabolic changes in cultured cells have been studied extensively, metabolism changes in vivo are less understood. Here, we measured metabolomic changes across six mouse tissues in three models of immune activation: CpG-DNA cytokine storm, lymphocytic choriomeningitis virus infection, and polyI:C viral mimetic injection; and carried out metabolomics in cultured macrophages activated with different stimuli. We found most metabolomic changes were exclusive to either inflamed tissues or cultured macrophages, although itaconate was strongly induced in both contexts. We then mechanistically dissected the role of the soluble sialic acid N-glycolylneuraminic acid, which is highly induced in inflamed tissues yet only modestly in cultured macrophages. This metabolite rises in tissues in different models of inflammation, and the analogous human metabolite, N-acetylneuraminic acid, is increased in human patients experiencing inflammation. We found that N-glycolylneuraminic acid is produced in CD11b+ myeloid cells by cleavage of protein-bound sialic acid. However, blocking its production did not affect CpG-DNA liver inflammation or LCMV infection in mice. Therefore, these experiments identify soluble sialic acid as a conserved biomarker of inflammation in mice and humans and highlight the differences in metabolism between in vitro and in vivo models of inflammation.

Background Homeostatic and hedonic brain circuits regulate eating behavior but also shape how food memories are encoded and retrieved. Objective We examined neural correlates during food memory encoding and retrieval during functional MRI before and after a 14-day prebiotic intervention in a preregistered, double-blind crossover trial (NCT03829189). Design 55 healthy adults with overweight (19 females, age 28{+/-}6.5, BMI 25-30 kg/m2) underwent 3 Tesla task-based functional MRI before and after dietary intervention of prebiotic (30g inulin/day) or equicaloric placebo for 14 days. Peripheral metabolic, short-chain fatty acids (SCFA), and microbial markers using 16S rRNA analysis were assessed in fasting blood and feces. Results Food memory was enhanced by assigned reward value and engaged brain activity in hedonic regions, including the nucleus accumbens, orbitofrontal cortex, caudate, cingulate, dorsomedial prefrontal cortex, and ventral tegmental area, as well as homeostatic and memory-related such as the hypothalamus and the hippocampus. Higher neural activations during food encoding were related to higher Actinobacteriota abundance, fecal SCFA acetate, and creatinine levels, and lower ghrelin levels. Activations in reward-related and homeostatic brain areas partially correlated with insulin, glucagon-like peptide-1, leptin, and thyroid-stimulating hormone levels. Neural activations related to food memory decreased after prebiotic intervention. The prebiotic supplementation induced decrease of hippocampal activity during food encoding related to changes in gut microbiota Firmicutes abundance. Conclusions This study indicates that neuronal food-related memory processes depend on homeostatic and hedonic brain signals modulated by the gut-brain axis. Our findings raise implications for the treatment of obesity and substance use disorder.

Type 1 diabetes (T1D) involves immune-mediated destruction of pancreatic {beta}-cells, yet current disease-modifying therapies mainly target immunity without enhancing {beta}-cell resilience. We show selective neuropeptide Y4 receptor (Y4R) agonism protects {beta}-cells while reshaping islet immunity across T1D models. Multi-modal localisation using cell sorting, qPCR, RNAscope and fluorescent ligand competition demonstrated predominant Y4R expression and functional accessibility on mouse and human {beta}-cells. Selective Y4R agonism was non-toxic and did not impair islet network integrity, Ca{superscript 2} dynamics, glucose-stimulated insulin secretion or systemic glucose tolerance. Y4R activation conferred cytoprotection against inflammatory cytokines, streptozotocin, lipotoxicity and ER stress, reducing caspase-3/7 activation and {beta}-cell loss whilst sustaining insulin release and promoting proliferation in both mouse and human islets. Bulk RNA-seq revealed a coordinated {beta}-cell resilience programme characterised by reinforced identity and insulin processing, KEAP1-NFE2L2-driven antioxidative and proteostatic activation, and suppression of EIF2 signalling and associated biosynthetic and ER stress pathways. Concurrently, Y4R agonism dampened pathogenic chemokine and cytokine networks, including CXCL10, CCL3/4/7 and IL-6, while preserving IL-2 and Foxp3 signals, thereby limiting CD8 T cell, CD4 T cell and macrophage chemotaxis toward cytokine-stressed islets. Reduced immune-cell recruitment was conserved in a fully human immune-islet system, where Y4R activation significantly attenuated IL-2-activated human PBMC migration and invasion toward cytokine-stressed human islets. In a stringent NY8.3 CD8 T cell adoptive-transfer model, systemic Y4R agonism significantly delayed diabetes onset. These data position Y4R as a {beta}-cell-centric therapeutic target coupling intrinsic resilience with local immune modulation, offering a complementary approach for {beta}-cell preservation in T1D and islet replacement therapies. Graphical abstractThe selective Y4 receptor agonist K22 binds {beta}-cell-enriched NPY4R in mouse and human islets, activates a {beta}-cell resilience programme that preserves insulin secretion under inflammatory and metabolic stress, and simultaneously dampens islet chemokine output, thereby limiting innate and adaptive immune-cell recruitment and delaying autoimmune diabetes onset. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/736290v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@11af8d3org.highwire.dtl.DTLVardef@1c60d37org.highwire.dtl.DTLVardef@18dd142org.highwire.dtl.DTLVardef@1a56cdb_HPS_FORMAT_FIGEXP M_FIG C_FIG

Pathologic white adipose tissue (WAT) remodeling, characterized by fibrosis, inflammation, and adipocyte dysfunction, is a hallmark and driver of metabolic disease in obesity1. Here, we show that legacy effects of early physiological or pharmacological interventions driving adaptive adipose remodeling can mitigate maladaptive WAT remodeling and metabolic dysfunction when developing obesity later in life. Cold exposure or beta3-adrenergic receptor (beta3AR) agonism (CL316,243) induced thermogenic remodeling of WAT in male mice. After a prolonged recovery at room temperature, trained epididymal WAT reverted to an energy-storing state but retained a population of adipocytes resembling metabolically flexible visceral adipocytes found in human metabolically healthy obesity. The legacy of the antecedent treatment conferred lasting protection against glucose intolerance when later developing high fat diet (HFD)-induced obesity, with insulin sensitivity persisting for at least 20 weeks of overnutrition. This metabolic resilience was accompanied by healthy epididymal WAT expansion with reduced fibrosis and inflammation. Our findings demonstrate that short-term interventions, without genetic manipulation, can train adipose tissue, enhancing its long-term plasticity and conferring durable protection against future obesity-associated insulin resistance.

The release of glucagon from pancreatic alpha cells is a core component of hypoglycaemic counter regulation. Several mechanisms regulate glucagon release including paracrine control by neighbouring cell types, and changes in extracellular glucose. While the inhibitory effect of glucose on glucagon secretion is well established, the exact way in which glucose metabolism contributes to alpha cell function remains unclear. Here, we use live-cell imaging of the redox potential in alpha cells within intact islets to investigate whether non-mitochondrial glucose metabolism contributes to the potentiation of glucagon secretion at low glucose. Our findings show that increased glucose metabolism through the pentose phosphate pathway elevates the cytosolic redox potential in alpha cells. Using a combination of antioxidant treatment and pre-incubation in 5 mM glucose, we find that the cytosolic redox potential affects PKA activity in alpha cells and that changes in whole body redox state affects the counterregulatory response in mice. These findings indicate that prior glucose-driven redox potential charging is essential for maintaining glucagon secretion at low glucose.

Type 2 diabetes (T2D) arises from distinct diabetogenic mechanisms, but whether these mechanisms differ in their associations with hallmarks of aging remains unclear. We analyzed 449,505 UK Biobank and 374,973 All of Us participants using an overall T2D polygenic score (oPS) and eight partitioned polygenic scores (pPSs) representing distinct T2D-related mechanisms. Across organ systems, 81 age-related diseases were assigned to nine hallmarks of aging. UK Biobank analyses used Cox regression for incident hallmark-level outcomes, and All of Us analyses used logistic regression for prevalent hallmark-level outcomes. In both cohorts, the oPS was associated with disease burden across hallmarks, whereas pPS associations varied by mechanism. The obesity pPS showed the strongest and most consistent associations, while other insulin-resistance-related pPSs, including the lipodystrophy pPS, showed more modest positive associations. Beta-cell dysfunction pPS associations were close to null across hallmarks. Obesity pPS-hallmark associations were significantly attenuated after adjustment for BMI, and lipodystrophy pPS-hallmark associations after adjustment for triglyceride-to-HDL cholesterol ratio (TG/HDL-C), a marker of insulin resistance. These findings suggest that adiposity and insulin resistance, indexed by BMI and TG/HDL-C, may act as modifiable factors in the T2D genetic burden on aging hallmarks.

In the pathologically and clinically heterogeneous neurodegenerative disorder amyotrophic lateral sclerosis (ALS), objective biochemical predictors of survival are essential to handle complexity in clinical trials, enrich clinical decision-making and interrogate the biology of disease progression. In this longitudinal study, we performed high-depth proximity extension assay proteomics using 1,095 samples of serum (N=851) and CSF (N=244) from 426 people with ALS, with orthogonal replication in an external cohort of 349 people with ALS. Age- and sex-adjusted Cox analysis identified 57 proteins in serum, including neurofilament light chain (NEFL) and peripherin, as well as five proteins in CSF, including tropomyosin 3 (TPM3) that were associated with survival (FDR-adjusted p<0.05). Penalised Cox regression identified a panel of 9 serum proteins - including NEFL, peripherin, TNF receptor superfamily member 27 (EDA2R) and calcitonin - that reflect the extent of disease as well as the progression rate, improving survival prediction compared with models using clinical parameters and NEFL. Joint modelling identified associations between the longitudinal trajectories of serum EDA2R and calcitonin with survival, highlighting their potential role in measuring disease progression. This work indicates the utility of multiple proteins reflecting diverse biological pathways in refining survival stratification and highlights systemic factors in ALS progression.

Nearly half of patients with advanced lung cancer develop cachexia, a debilitating syndrome that worsens prognosis. We conducted longitudinal clinical and plasma proteomic profiling of 67 patients with non-small cell lung cancer, with and without cachexia, during first-line treatment. Patients with cachexia at diagnosis exhibited elevated risk of hospitalization and treatment-delaying toxicity. At diagnosis, 128 plasma proteins were upregulated and 67 downregulated in cachectic relative to non-cachectic patients. Longitudinal assessments of body composition, physical performance, metabolism, clinical outcomes, and nutritional risk revealed distinct fat and muscle wasting phenotype trajectories. 71 proteins were associated with fat loss, 92 with muscle loss, and 177 with concurrent muscle and weight loss. We identified and functionally validated 8 plasma proteins linked to muscle loss and adverse clinical outcomes. In a separate cohort of 147 patients with advanced pancreatic cancer receiving the interleukin-6 (IL-6) inhibitor tocilizumab, pharmacological suppression of serum amyloid A (SAA) levels following IL-6 inhibition suggests a systemic IL-6-SAA axis. These results collectively highlight SAA1 and SAA2 as IL-6-driven, cachexia-associated factors that reduce human myotube width. These findings uncover new potential therapeutic targets for cachexia.

Stem-cell-derived {beta}-like-cells (SC{beta}-cells) provide a promising platform for diabetes modelling and cell replacement therapy, but their incomplete functional maturation remains a challenge. Here, we compared immature SC{beta}-cells to human primary {beta}-cells utilizing a multi-omic, single-cell framework integrating patch-clamp electrophysiology with scRNA sequencing (patch-seq), regulatory network inference, and functional phenotyping. Despite low insulin secretion and reduced insulin content, SC{beta}-cells displayed larger Na+ and Ca2+ currents and depolarization-induced exocytosis. Ultrastructural and metabolic profiling revealed immature insulin granules, altered mitochondrial morphology, elevated basal respiration and proton leak, and diminished spare respiratory capacity and glucose-responsive metabolism. Patch-seq linked exocytotic activity in SC{beta}-cells to oxidative phosphorylation and MYC target programs, consistent with incomplete terminal differentiation, whereas SC{beta}-cells expressing higher levels of mature identity markers showed reduced ion channel hyperactivity. Multi-omics profiling showed that electrophysiological features in SC{beta}-cells were embedded in transcriptional programs distinct from those of primary {beta}-cells and other endocrine cells. Network control theory nominated SREBP1, an endoplasmic reticulum tethered transcription factor regulating cholesterol and lipid homeostasis, as a promising candidate involved in this immature state. Inhibition of cholesterol trafficking increased SREBF1 expression and shifted metabolic and transcriptional features towards a more mature {beta}-like state. These data identify potential targets and pathways that can be leveraged to improve SC{beta}-cell maturation and validate cholesterol and lipid homeostasis through the SREBP1 axis as one such candidate.

The liver- cell axis is a finely tuned biological rheostat that regulates whole body amino acid availability. Pancreatic cells secrete glucagon that regulates amino acid catabolism through gluconeogenesis and ureagenesis, yet the mechanisms linking amino acid levels to cell growth and function are not fully understood. Here, we identify glutaminase, the enzyme that catalyzes glutamine catabolism, as a critical cell regulator. Glutaminase is highly enriched in cells across species. cell expression of glutaminase is required for nutrient-dependent mTORC1 activation, suppression of AMPK signaling, and sustained expression of the glutamine transporter SLC38A5. This establishes a feed-forward loop linking glutamine metabolism to amino acid sensing and growth. Reduced glutaminase activity impairs dynamic glucagon secretion in response to low glucose and amino acids. Together, these findings highlight the importance of glutamine metabolism in cell growth and hormone secretion and suggest it may play a role in cell adaptation to hyperaminoacidemia.

Cytokine production is a core function of effector T cells, yet the mechanisms that regulate cytokine output during an immune response remain incompletely understood. Here, we identify citrate compartmentalization as a cellular mechanism by which CD8+ T cells couple cytokine production to glucose availability. Under glucose-replete conditions, citrate transport from the mitochondria to the cytosol by the citrate carrier SLC25A1 suppresses calcium-dependent transcription factor activity in effector T cells. Either reducing glucose availability or blocking the exchange of citrate across the mitochondrial membrane raises free cytosolic calcium, thereby driving nuclear localization of Nuclear Factor of Activated T cells (NFAT)-family transcription factors and sustaining cytokine production. As a calcium-chelating metabolite, we show that citrate buffers free cytosolic calcium, thereby linking calcium-dependent signaling to mitochondrial fuel oxidation. We also identify signatures of this regulatory mechanism across hundreds of human cancer cell lines, where there are negative associations between citrate-derived metabolites and calcium-dependent transcriptional programs, and within the spatial organization of human tumors. These findings identify cytosolic citrate as a broadly conserved metabolic rheostat coupling glucose availability to calcium signaling. By adding calcium signaling to the known functions regulated by SLC25A1, our work reveals a mechanism by which mitochondria adaptively tune cytokine expression and other calcium-dependent programs in response to local metabolic conditions, such as nutrients that are available within a tissue or tumor.

Adipose tissue harbors a significant population of regulatory T (Treg) cells that enforce immune homeostasis, yet whether Tregs function as an immunometabolic checkpoint to directly regulate core adipocyte signaling programs remains incompletely defined. Here we show that adipose Tregs function as a dominant, time-dependent checkpoint on {beta}-adrenergic signal-driven lipolytic program and signal transduction in adipocytes. Our integrated scRNA-seq, flow cytometry, and phosphoproteomics data show that prolonged adrenergic stimulation induces a progressive attenuation of activation of key lipase hormone-sensitive lipase (HSL) that coincides with Treg depletion in circulation and accumulation within white adipose tissue. Genetic perturbations establish Treg-derived interleukin-10 (IL-10) as the key mediator of this brake. IL-10 signaling through adipocyte IL-10R suppresses adrenergic HSL activation and rewires downstream signaling nodes that govern catecholamine responsiveness, lipolysis, and systemic energy homeostasis. Mechanistically, IL-10R engages a STAT3-dependent transcriptional program that induces the G-protein regulators RGS2 and RGS3, diminished PKA flux to HSL that reinforces suppression of the HSL activation state and lipolysis. Together, these findings define an adrenergic-immune feedback circuit in which Tregs fine tune the amplitude and duration of catecholamine responsiveness in adipocytes, establishing immune control of a core lipolytic pathway with implications for obesity-associated adipose dysfunction.

Insulin production is a cardinal feature of pancreatic {beta} cells. Studies in rodents show that {beta} cells can switch between low and high insulin gene activity states and that elevated insulin production makes {beta} cells more vulnerable to stresses associated with diabetes. In people, genetically elevated insulin production increases the risk of type 1 diabetes. Via effects on obesity, hyperinsulinemia contributes to the pathogenesis of type 2 diabetes. Here, we characterize {beta} cells in low and high INS gene activity states sorted from primary human islets transduced with INS-GFP adenovirus and differentiated INS-EGFP knock-in embryonic stem cells (SC{beta} cells). We profile {beta} cell function, protein synthesis, resilience to diabetes associated stress, single {beta} cell transcriptomes and their co-activity networks, and purified {beta} cell proteomes. We show that human {beta} cells transition between distinct states. High INS cells have elevated maturity marker mRNAs and proteins, increased protein translation, are larger, but also more susceptible to cell death when exposed to diabetes-relevant stresses. We also catalogue thousands of differences in proteins in high INS stem cell-derived {beta} cells compared directly with high INS primary {beta} cells. Our study improves our understanding of the delicate balance between insulin production and {beta} cell resilience and guides the engineering of better {beta} cells. Blurbtranscriptional, proteomic, and functional analyses of insulin gene expression states in human {beta} cells from donor islets and stem cells Key findingsO_LIWe identify high and low INS gene activity states in human insulin-producing cells from donor islets and embryonic stem cell differentiations. C_LIO_LIWe characterize the relationship between insulin production and fragility, demonstrating that increased insulin production comes at a cost of reduced resilience to multiple stresses. C_LIO_LIFunctional, transcriptomic, and proteomic analyses identify similarities and differences between how primary and stem cell-derived {beta} cells manage stress and insulin production. C_LIO_LIWe report a comprehensive side-by-side proteomic analysis of purified primary and stem cell- derived {beta} cells in the high INS state and identify differences in protein production and secretion machinery, providing a roadmap for making better {beta} cells. C_LI

Alzheimer's disease (AD) unfolds over decades preceding cognitive symptoms, and measuring the full scope of its molecular complexity remains difficult. Blood-based biomarkers of amyloid, phosphorylated tau, astrocytic reactivity and neuroaxonal injury including A{beta}42/40, p-tau181, p-tau217, GFAP and NfL enable scalable assessment of AD-related pathology and associated processes but capture only a narrow slice of the systemic biology ultimately shaping disease progression. Here we link these increasingly routine clinical assays to the plasma proteome using multi-omic linear modeling to resolve functional heterogeneity in AD progression. In 484 older adults spanning normal cognition, mild cognitive impairment (MCI) and AD, we derived proteomic signatures for each key biomarker across more than 6,000 proteins, uncovering overlapping and distinct biological processes and cell types implicated in AD with robust signal across proteomic modalities. From these we built continuous progression-focused functional modules that were consistently preserved across 12 independent cohorts comprising 11,042 participants from the Global Neurodegeneration Proteomics Consortium and that associated with cognitive decline, diagnosis and AD-relevant biology. A synaptic vesicle module marked apparent neuronal resilience as much as 5 years before estimated symptom onset. We show routine and accessible plasma measures can be leveraged to recover reproducible, biologically distinct progression modules that improve characterization of heterogeneous AD and have practical value for risk stratification, trial enrichment, or treatment monitoring.

Stress involves the activation of cellular, physiological, and emotional processes that cost energy--nothing is free in biology. In mammals, the stress response involves hormone release, including norepinephrine (NE), which increases energy expenditure. To quantify the energetic cost of NE signaling in a simple cellular system, we interrogated the dose (0-10 M NE) and time-dependent (up to 10 hours) effects of adrenergic signaling in primary human fibroblasts. Oxygen consumption rates (OCR, reflecting ATP generated by mitochondria) and extracellular acidification rate (ECAR, reflecting ATP generated by glycolysis) were measured continuously using extracellular flux analysis, allowing us to estimate the ATP turnover rates, and thus cellular energy expenditure. Within the first 18 minutes (early phase), glycolysis increases up to 47% whereas respiration decreased 2-5%. Both parameters normalized within 1-2 hours for low NE concentrations. This was followed by an increase in oxidative phosphorylation (OxPhos), peaking around 9-12% by 2-6 hours (mid or late-phase). These minutes-to-hours data reveal the temporal dynamics whereby NE increases cellular energy expenditure in fibroblasts. Blocking OxPhos with oligomycin or piericidin A abolished OxPhos changes post-NE addition while conserving the glycolytic response. Withdrawal of glucose from the media significantly dampened the absolute rise in ECAR in response to NE, and instead increased OxPhos, revealing the metabolic flexibility in fibroblasts. Finally, cells with genetic defects impairing OxPhos exhibited a 50% blunted NE-driven metabolic response, consistent with the existence of an energy constraint in mitochondrial diseases. In summary, we have resolved the dynamics and flexible bioenergetic recalibrations associated with NE-driven hypermetabolism in primary human fibroblasts. Mapping the nature and magnitude of these recalibrations in humans would advance our understanding of the potential energetic forces underlying the damage to health by chronic stress.

Neurons can utilize either glucose or lactate, yet fuel selection during periods of activity remains unresolved. By combining optical monitoring of cytosolic pyruvate and NADH with mathematical modelling, we systematically evaluated mitochondrial fuelling in cultured neurons and acute brain slices. Under substrate concentrations typical of resting brain tissue, neurons rely almost exclusively on glucose, with a minor contribution from pyruvate. However, when extracellular lactate rises to levels mimicking tissue activity, glycolysis is inhibited and lactate becomes a major substrate, irrespective of ongoing neuronal activity. Ultimately, neuronal fuel selection is dictated not by internal energy demand, but by extracellular lactate availability, which fluctuates with local glial metabolism and systemic states such as exercise. These findings redefine our understanding of short-term metabolic flexibility in the brain and underscore the significant yet understudied role of extracellular pyruvate.

Macrophages clear excess host and microbial debris to restore homeostasis in inflamed tissues, yet the regulation and molecular fate of phagocytosed lipids during innate immune training remains largely unexplored. Leveraging stable isotope tracing of 13C-labeled bacteria, we establish an experimental framework to track microbe-to-host lipid transfer and define the fates of microbial lipids in macrophages in vitro and in vivo. While naive macrophages scavenge phagocytosed bacterial fatty acids into the host lipidome, TLR4-trained macrophages direct flux to mitochondria for {beta}-oxidation or lipid droplets in the context of mitochondrial dysfunction. While TLR4 signaling increases ACOD1 expression to produce itaconate that throttles TCA flux, trained macrophages produce IL-10 that reduces ACOD1 to sustain bacterial lipid disposal and promote resolution. These findings reveal an IL-10/ACOD1 regulatory axis in trained macrophages that reprograms lipid metabolism to optimally reestablish tissue homeostasis post-inflammation.

High-fat, high-sucrose (HFHS) diets are established risk factors for obesity. In the intestine, sucrose is hydrolyzed into glucose and fructose, with fructose being taken up by epithelial cells and phosphorylated by ketohexokinase (KHK). We hypothesized that KHK is required for the obesogenic effects of HFHS diets and performed genetic and pharmacologic experiments in mice using diet-induced obesity (DIO) models. We show that genetic loss of KHK prevents HFHS-induced weight gain and intestinal villus elongation. Moreover, pharmacologic inhibition of KHK (KHKi) promotes weight and fat loss during continued HFHS feeding in DIO mice and enhances weight loss and weight maintenance during and after incretin-mimetic therapy. The anti-obesogenic effects of KHKi were associated with delayed intestinal lipid absorption, reprogramming of lipid metabolism in the distal intestinal epithelium, and reduced absorption of unsaturated dietary fats. Together, these findings identify fructose metabolism as a key regulator of intestinal lipid handling and suggest that fructose promotes obesity, in part, by enhancing intestinal lipid absorption and metabolism.