Nature Metabolism

Adipocyte lipid metabolism is coordinated by circadian rhythms, diet, and environmental temperature. Yet how these diverse signals are molecularly integrated remains unknown. Here we show that clock, diet, and temperature cues converge on the orphan mitochondrial transporter, SLC25A34, to orchestrate thermogenic cycling of lipid synthesis and oxidation. During sleep, the clock suppresses Slc25a34 transcription through REV-ERB. Waking, lipid-rich diets, or cold exposure abolish this repression, allowing lipolytic signals to stimulate Slc25a34 expression via PPAR. SLC25A34 then imports oxaloacetate into mitochondria to accelerate the export of substrates used for acetyl-CoA production in the cytosol. This feeds into cytosolic lipid synthesis and transcriptional induction of mitochondrial biogenesis, which collectively promote mitochondrial lipid oxidation. Thus, SLC25A34 confers circadian, dietary, and environmental control of thermogenic metabolism through interorganellar lipid cycling.

Acetyl-CoA is a central metabolite used for lipid synthesis in the cytosol and histone acetylation in the nucleus, among other pathways. The two major precursors to acetyl-CoA in the nuclear-cytoplasmic compartment are citrate and acetate, which are processed to acetyl-CoA by ATP-citrate lyase (ACLY) and acyl-CoA synthetase short-chain 2 (ACSS2), respectively. While some evidence has suggested the existence of additional routes to nuclear-cytosolic acetyl-CoA, such pathways remain poorly defined. To investigate this, we generated cancer cell lines lacking both ACLY and ACSS2. Unexpectedly, and in contrast to observations in fibroblasts, ACLY and ACSS2 double knockout (DKO) cancer cells remain viable and proliferate, maintain pools of cytosolic acetyl-CoA, and are competent to acetylate proteins in both cytosolic and nuclear compartments. Using stable isotope tracing, we show that both glucose and fatty acids feed acetyl-CoA pools and histone acetylation in DKO cells. Moreover, we provide evidence for the carnitine shuttle and carnitine acetyltransferase (CrAT) as a substantial pathway to transfer two-carbon units from mitochondria to cytosol independent of ACLY. Indeed, in the absence of ACLY, glucose can feed fatty acid synthesis in a carnitine responsive and CrAT-dependent manner. This work defines a carnitine-facilitated route to produce nuclear-cytosolic acetyl-CoA, shedding light on the intricate regulation and compartmentalization of acetyl-CoA metabolism

Proliferating cells rely on acetyl-CoA to support membrane biogenesis and acetylation. Several organelle-specific pathways are available for provision of acetyl-CoA as nutrient availability fluctuates, so understanding how cells maintain acetyl-CoA flux under such stresses is critically important. To this end we applied 13C isotope tracing cell lines deficient in these mitochondrial (ATP-citrate lyase; ACLY-), cytosolic, (acetyl-CoA synthetase (ACSS2-), and peroxisomal (peroxisomal biogenesis factor 5; PEX5-) dependent pathways. ACLY knockout in multiple cell lines reduced fatty acid synthesis and increased reliance on extracellular lipids or acetate. Knockout of both ACLY and ACSS2 (DKO) severely stunted but did not entirely block proliferation, suggesting alternate pathways can support acetyl-CoA homeostasis. Metabolic tracing and PEX5 knockout studies link peroxisomal oxidation of exogenous lipids as a major source of acetyl-CoA for lipogenesis and histone acetylation, highlighting a role for inter-organelle crosstalk in supporting cell survival in response to nutrient fluctuations. TeaserWe quantify how acetyl-CoA metabolism is supported by distinct pathways spanning mitochondria, cytosol, and peroxisomes using comprehensive tracing applied to knockout cells.

Protein undernutrition is a global risk factor for impaired growth and neurobehavioral development in children. However, the critical periods, environmental interactions, and maternal versus neonatal influences on programming lasting behavioral abnormalities are poorly understood. In a mouse model of fetal growth restriction, limiting maternal protein intake particularly during pregnancy leads to cognitive and anxiety-like behavioral abnormalities in adult offspring, indicating a critical role for the gestational period. By cross-fostering newborn mice to dams previously exposed to either low protein or standard diet, we find that the adult behavioral impairments require diet-induced conditioning of both fetal development and maternal peripartum physiology, rather than either alone. This suggests that protein undernutrition during pregnancy directly disrupts fetal neurodevelopment and indirectly alters maternal state in ways that interact postnatally to precipitate behavioral deficits. Consistent with this, maternal protein restriction during pregnancy reduces the diversity of the maternal gut microbiome, modulates maternal serum metabolomic profiles, and yields widespread alterations in fetal brain transcriptomic and metabolomic profiles, including subsets of microbiome-dependent metabolites. Depletion of the maternal microbiome in protein-restricted dams further alters fetal brain gene expression and exacerbates neurocognitive behavior in adult offspring, suggesting that the maternal microbiome modifies the impact of gestational protein undernutrition on risk for neurobehavioral impairment in the offspring. To explore the potential for microbiome-targeted interventions, we find that maternal treatment with short chain fatty acids or a cocktail of 10 diet- and microbiome-dependent metabolites each yield differential effects on fetal development and/or postnatal behavior. Results from this study highlight impactful prenatal influences of maternal protein undernutrition on fetal neurodevelopment and adverse neurobehavioral trajectories in offspring, which are mitigated by microbiome-targeted interventions during pregnancy.

Daily light-dark cycles impose predictable environmental fluctuations that require coordinated temporal regulation of cellular physiology. This coordination is mediated by the circadian clock, which operates as a network of tissue oscillators; however, the molecular signals that convey circadian information between organs remain incompletely defined. Here, we identify nicotinic acid riboside (NaR) as a circulating metabolite whose rhythmicity depends on the liver clock. In differentiating 3T3-L1 adipocytes, NaR engages unfolded protein response (UPR) gene programs and modulates adipogenic competence. Proteome-wide stability profiling implicates the prefoldin complex as a molecular target of NaR signaling, linking NaR exposure to altered proteostasis. Functionally, NaR-induced UPR signaling converges on the adipogenic transcription factor CEBPA, which is a central regulator of adipogenesis. Importantly, sustained NaR exposure suppresses adipocyte lipid deposition, whereas temporally restricted NaR stimulation enhances adipogenesis, indicating that NaR acts in a time-dependent manner. Together, these findings identify NaR as a liver clock-controlled circulating metabolite that couples systemic circadian metabolism to adipocyte proteostasis and differentiation, revealing a mechanism by which temporal metabolic signals shape tissue-specific physiological outcomes. HighlightsO_LIThe circadian clock is required for rhythmic regulation of circulating nicotinic acid riboside (NaR). C_LIO_LIThe liver clock is sufficient to generate NaR rhythmicity. C_LIO_LINaR engages the prefoldin complex to regulate unfolded protein response signaling and Cebpa expression. C_LIO_LITime-dependent NaR exposure differentially regulates CEBPA levels and adipocyte lipid deposition. C_LI

The gut microbiota produces metabolites that circulate to host tissues and are increasingly linked to metabolic health, yet the mechanisms by which individual microbial products regulate liver glucose metabolism remain poorly defined. Here, we identify the tryptophan-derived microbial metabolite indole-3-propionic acid (IPA) as a direct modulator of hepatic glucose production. In primary hepatocytes, a focused screen of indole metabolites revealed that several indole-containing compounds suppress glucagon-stimulated glucose output, with IPA emerging as a physiologically relevant candidate. IPA selectively reduced glucose production from mitochondrial-dependent gluconeogenic substrates while largely preserving glycerol-supported glucose production, suggesting that it does not simply shut down gluconeogenesis but instead alters how hepatocytes use metabolic fuels. Mechanistic analyses showed that IPA redirects lactate-derived carbon away from glucose production and reshapes mitochondrial metabolism, including redox balance, ATP availability, and urea cycle-linked metabolic activity. These effects occurred without detectable disruption of proximal insulin or glucagon signaling, supporting a model in which IPA acts primarily through intracellular metabolic remodeling. In mice, endogenous IPA levels varied with nutritional state, and short-term IPA administration improved fasting glycemia and glucose handling in Western diet-fed animals. Finally, microbiome-depleted mice colonized with IPA-producing Clostridium sporogenes displayed increased circulating IPA and improved glucose tolerance compared with mice colonized with an IPA-deficient mutant C. Sporogenes strain. Together, these findings identify IPA as a microbial metabolite that directly connects gut tryptophan metabolism to hepatic mitochondrial function and systemic glucose regulation, highlighting a mechanistic gut-liver pathway with potential therapeutic relevance to metabolic disease.

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.

Forty percent of the US population and 1 in 6 individuals worldwide are obese, and the incidence of this disease is surging globally1,2. Various dietary interventions, including carbohydrate and fat restriction, and more recently amino acid restriction, have been explored to combat this epidemic3-6. We sought to investigate the impact of removing individual amino acids on the weight profiles of mice. Compared to essential amino acid restriction, induction of conditional cysteine restriction resulted in the most dramatic weight loss, amounting to 20% within 3 days and 30% within one week, which was readily reversed. This weight loss occurred despite the presence of substantial cysteine reserves stored in glutathione (GSH) across various tissues7. Further analysis demonstrated that the weight reduction primarily stemmed from an increase in the utilization of fat mass, while locomotion, circadian rhythm and histological appearance of multiple other tissues remained largely unaffected. Cysteine deficiency activated the integrated stress response (ISR) and NRF2-mediated oxidative stress response (OSR), which amplify each other, leading to the induction of GDF15 and FGF21, hormones associated with increased lipolysis, energy homeostasis and food aversion8-10. We additionally observed rapid tissue coenzyme A (CoA) depletion, resulting in energetically inefficient anaerobic glycolysis and TCA cycle, with sustained urinary excretion of pyruvate, orotate, citrate, -ketoglutarate, nitrogen rich compounds and amino acids. In summary, our investigation highlights that cysteine restriction, by depleting GSH and CoA, exerts a maximal impact on weight loss, metabolism, and stress signaling compared to other amino acid restrictions. These findings may pave the way for innovative strategies for addressing a range of metabolic diseases and the growing obesity crisis.

Dihydroxyacetone phosphate (DHAP), glycerol-3-phosphate (Gro3P) and reduced/oxidized nicotinamide adenine dinucleotide (NADH/NAD+) are key metabolites of the Gro3P shuttle system that forms a redox circuit, allowing transfer of reducing equivalents between cytosol and mitochondria. Targeted activation of Gro3P biosynthesis was recently identified as a promising strategy to alleviate reductive stress by promoting NAD+ recycling, including in cells with an impaired mitochondrial complex I. However, because Gro3P constitutes the backbone of triglycerides under some circumstances, its accumulation can lead to excessive fat deposition. Here, we present the development of a novel genetically encoded tool based on a di-domain glycerol-3-phosphate dehydrogenase from algae Chlamydomonas reinhardtii (CrGPDH), which is a bifunctional enzyme that can recycle NAD+ while converting DHAP to Gro3P. In addition, this enzyme possesses an N-terminal domain which cleaves Gro3P into glycerol and inorganic phosphate (Pi) (in humans and other organisms, this reaction is catalyzed by a separate glycerol-3-phosphate phosphatase, a reaction also known as "glycerol shunt"). When expressed in mammalian cells, CrGPDH diminished Gro3P levels and boosted the TCA cycle and fatty acid {beta}-oxidation in mitochondria. CrGPDH expression alone supported proliferation of HeLa cells under conditions of either inhibited activity of the mitochondrial electron transport chain or hypoxia. Moreover, human kidney cancer cells, which exhibit abnormal lipid accumulation, had decreased triglycerides levels when expressing CrGPDH. Our findings suggest that the coordinated boosting of both Gro3P biosynthesis and glycerol shunt may be a viable strategy to alleviate consequences of redox imbalance and associated impaired lipogenesis in a wide repertoire of conditions, ranging from primary mitochondrial diseases to obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD).

Methylene tetrahydrofolate reductase 2 (MTHFD2), the rate-limiting enzyme of mitochondrial one-carbon metabolism, is one of the most highly expressed metabolic enzymes across diverse cancers and lymphoproliferative disorders. However, its exact roles in oncogenic metabolism remain poorly defined. We show that MTHFD2 is a key regulator of mitochondrial energetics in Epstein-Barr virus-transformed B lymphoblastoid cell lines (LCLs), an in vitro model of post-transplant lymphoproliferative disorder (PTLD). We also delineate a role for MTHFD2 in fueling de novo creatine synthesis; MTHFD2 mediates the production of glycine, a necessary substrate for creatine synthesis, through serine catabolism. Aminomethyltransferase (AMT) suppression short-circuits the glycine cleavage system (GCS) to augment LCL mitochondrial glycine levels. Creatine synthesis is hypostatic to mitochondrial one-carbon metabolism; inhibition of creatine synthesis improves LCL fitness only when MTHFD2 is lost. Our findings emplace MTHFD2 at the nexus of amino acid and energy metabolism pathways in LCLs, with potential clinical ramifications for PTLD. Highlights* Complete activation of creatine synthesis in an in vitro cellular model of PTLD * Creatine synthesis is a major sink for mitochondrial 1C-derived glycine * Reverse GCS activity due to AMT deficiency in lymphoblastoid cells * Epistasis between mitochondrial 1C metabolism and creatine synthesis eTOC BlurbLeung et al. demonstrate that MTHFD2 is crucial for creatine synthesis in lymphoproliferative disorders. MTHFD2 supports forward 1C flux through SHMT and drives reverse GCS activity to augment mitochondrial glycine, a substrate for creatine synthesis. Tumor-suppressive effects of creatine synthesis are unmasked with MTHFD2 loss, exhibiting metabolic epistasis.

Coordination between innate immune signaling and glucose metabolism is fundamental to organismal homeostasis, yet despite decades of study linking immunity and metabolism, the mechanisms by which metabolic cells restrain antiviral innate signaling while preserving glycolytic competence during overnutrition remain poorly defined. Here we identify Tetherin (BST2) as a unique cell-intrinsic immunometabolic checkpoint that couples restraint of type I interferon (IFN-I) signaling to preservation of glycolytic capacity in adipocytes. Tetherin localizes to endoplasmic reticulum and organizes an interactome enriched for antiviral sensing regulators and glycolytic control nodes in adipocytes. Mechanistically, Tetherin directly engages the ubiquitin-dependent degradation machinery NDFIP1 and RNF128 to terminate IRF3 activation, thereby limiting pro-inflammatory, anti-glycolytic signaling and protecting adipocytes from metabolic dysfunction. In parallel, multiomics integration reveals that Tetherin also acts as a scaffold that binds and spatially organizes and activates PFKFB3 to increase glycolytic capacity and restrain MAVS-IRF3 innate immune signalling. In vivo, adipocyte-specific loss of Tetherin amplifies high sucrose diet and high-fat-diet-induced glucose intolerance and liver steatosis, whereas overexpression of human Tetherin in adipocyte suppresses obesity-driven interferon signaling, restores glycolytic pathway, and improves metabolic homeostasis. Orthogonal perturbations in cancer and insulinoma cells further confirm an immunometabolic role for Tetherin. Together, these findings define Tetherin as a dual node immunometabolic checkpoint that couples restraint of antiviral innate inflammatory signaling to maintenance of glycolytic competence, thereby safeguarding adipocyte metabolic homeostasis.

Mitochondria and lipid droplets (LDs) are functionally coupled to coordinate fatty acid utilization and storage. However, a comprehensive understanding of mitochondria-LD alliances remains elusive. We have identified a previously unrecognized role for optical atrophy 1 (OPA1), a mitochondrial fusion factor, in the regulation of fatty acid release from LDs. We demonstrated that OPA1s exon 4 adapts an amphipathic helix to target OPA1 to LDs. OPA1 localized to LDs promote fatty acid release by facilitating the recruitment of lipases to LDs. In addition, OPA1s residence on LDs competes with its mitochondrial entry, influencing mitochondria fusion and connectivity. Furthermore, the S158N polymorphism within OPA1s exon 4 exhibiting attenuated fatty acid release from LDs is associated with changes in metabolic traits in pediatric cancer survivors. Altogether, our findings reveal that OPA1 actively mediates fatty acid release from LDs and provide a mechanistic link between OPA1 and human metabolism.

Metformin is a therapeutically versatile biguanide drug primarily prescribed for type II diabetes. Despite its extensive use, the mechanisms underlying many of its clinical effects, including attenuated postprandial glucose excursions, elevated intestinal glucose uptake, and increased production of lactate, Lac-Phe and GDF15, remain unclear. Here, we map these and other clinical effects of metformin to intestine-specific mitochondrial complex I inhibition. Using human metabolomic data and an orthogonal genetics approach in male mice, we demonstrate that metformin suppresses citrulline synthesis, a metabolite generated exclusively by small intestine mitochondria, and increases GDF15 by inhibiting the mitochondrial respiratory chain at complex I. This inhibition co-opts the intestines to function as a glucose sink, driving uptake of excess glucose and converting it to lactate and Lac-Phe. Notably, the glucose-lowering effect of another biguanide, phenformin, and berberine, a structurally unrelated nutraceutical, similarly depends on intestine-specific mitochondrial complex I inhibition, underscoring a shared therapeutic mechanism.

Severe hypoglycemia remains a serious adverse effect of insulin therapy in individuals with diabetes and is linked to cognitive decline, yet the mechanisms by which transient metabolic stress leads to persistent neuronal dysfunction remain poorly defined. Using mouse models of acute severe hypoglycemia and integrated screening, we identified the retrosplenial cortex as a previously unrecognized brain region that is particularly vulnerable to hypoglycemia-induced neuronal damage. This injury is driven by a feedforward interaction between neuron-specific Drp1-dependent mitochondrial fission and microglial IL-1 signaling, as pharmacological or genetic targeting of either pathway suppressed the other, rescued neuronal damage, and reversed cognitive impairment. These findings identify a region-specific neuron-microglia injury circuit that links severe hypoglycemia to cognitive dysfunction and suggest a therapeutic strategy to protect brain function without compromising diabetes management.

4-phosphopantetheinyl (4PP) groups are essential co-factors added to target proteins by phosphopantetheinyl transferase (PPTase) enzymes. Although mitochondrial 4PP-modified proteins have been described for decades, a mitochondrially-localized PPTase has never been found in mammals. We discovered that the cytoplasmic PPTase aminoadipate semialdehyde dehydrogenase phosphopantetheinyl transferase (AASDHPPT) is required for mitochondrial respiration and oxidative metabolism. Loss of AASDHPPT results in failed 4PP modification of the mitochondrial acyl carrier protein and blunted activity of the mitochondrial fatty acid synthesis (mtFAS) pathway. We found that in addition to its cytoplasmic localization, AASDHPPT localizes to the mitochondrial matrix via an N-terminal mitochondrial targeting sequence contained within the first 20 amino acids of the protein. Our data show that this novel mitochondrial localization of AASDHPPT is required to support mtFAS activity and oxidative function. We further identify five variants of uncertain significance in AASDHPPT that are likely pathogenic in humans due to loss of mtFAS activity.

While the earliest pathological signs of cardiovascular disease (CVD) emerge before age 20, current adult-based risk thresholds fail to identify a substantial fraction of high-risk children. With the rising prevalence of childhood obesity, the need for early and sensitive detection of cardiovascular-kidney-metabolic disease (CKMD) risk is paramount to enable timely intervention that can prevent the trajectory toward CVD in later life. To identify early accessible molecular biomarkers of CKMD in children, we measured 25 CKMD phenotypes, spanning liver, adipose, vascular, and dysglycemia traits, linked those to the circulating proteome and built a multi-protein signature of composite CKMD, leveraging data from 273 children and adolescents (13.1 {+/-} 2.7 years; 53% females). We compared these results to the adult CKMD proteome, using data from 685 adults from the same community and 28,257 adults from the UK Biobank. The pediatric CKMD proteome was highly concordant with the adult CKMD proteome, reflecting known and novel mechanisms of pancreatic beta-cell health and insulin sensitivity, liver homeostasis, inflammation, and cholesterol metabolism. Similarly, multi-protein signatures of composite CKMD phenotypes in children were strongly associated with CKMD-related outcomes in both adult populations. Importantly, many proteins linked to pediatric CKMD were modifiable with GLP-1 receptor agonist therapy, associated with adult CKMD-related outcomes in a large-scale proteome-wide association study (PWAS), and exhibited significant variability during development (ages 4-24 years). These findings demonstrate that CKMD develops starting early in life-course continuum, with proteomic profiles linked to future irreversible CVD conditions emerging early in life when they may still be reversible. This highlights a critical opportunity to improve CVD-free longevity through precision medicine diagnosis and intervention in children and adolescents.

Renalase (Rnls), annotated as an oxidase enzyme, is a GWAS gene associated with Type 1 Diabetes (T1D) risk. We previously discovered that Rnls inhibition delays diabetes onset in mouse models of T1D in vivo, and protects pancreatic {beta} cells against autoimmune killing, ER and oxidative stress in vitro. The molecular biochemistry and functions of Rnls are entirely uncharted. Here we find that Rnls inhibition defends against loss of {beta} cell mass and islet dysfunction in chronically stressed Akita mice in vivo. We used RNA sequencing, untargeted and targeted metabolomics and metabolic function experiments in mouse and human {beta} cells and discovered a robust and conserved metabolic shift towards glycolysis, amino acid abundance and GSH synthesis to counter protein misfolding stress, in vitro. Our work illustrates a function for Rnls in mammalian cells, and suggests an axis by which manipulating intrinsic properties of {beta} cells can rewire metabolism to protect against diabetogenic stress.

Alzheimers disease and related tauopathies are escalating public health threats, particularly in the context of obesity and metabolic dysfunction, which accelerate cerebral glucose hypometabolism, tau pathology, neurodegeneration, and cognitive decline. Ketogenic therapies reconfigure systemic fuel metabolism, with emerging evidence for neuroprotection. (R,S)-1,3-butanediol (BD) raises circulating D- and L-{beta}-hydroxybutyrate ({beta}OHB) concentrations. To evaluate whether BD improves cognitive function across dietary contexts, male and female tau-transgenic mice and littermate controls received 10% BD in drinking water for 20 or 30 weeks starting at 6 weeks of age. BD rapidly induced ketosis (1.5-3.0 mM {beta}OHB) in chow-fed mice, with L-{beta}OHB contributing to [~]75% of the circulating {beta}OHB pool. Despite minimal effects of BD on body weight and glucose homeostasis, and no effect on histopathological tau signal, 20-week BD treatment improved memory to control levels in chow-fed female tauopathy mice. Isotope-tracing untargeted metabolomics revealed that BD-treatment differentially affected glucose-derived 13C-enrichment of metabolites in brains of male and female mice. BD-induced cognitive benefits in tau-transgenic mice were abrogated when mice were maintained on BD for 30 weeks on standard chow or when mice were administered BD over 20 weeks while maintained on a high-fat, Western diet, Notably, BD-induced ketosis was blunted in mice consuming Western diet. Moreover, intermittent ketogenic diet-induced ketosis failed to improve cognition in Western diet-fed tauopathy mice. These results suggest BD-induced ketosis extends cognitive benefits in a manner dependent on biological sex and nutritional metabolic status. Taken together, these data contextualize the roles of {beta}OHB as modulators of cognitive resilience in tauopathy.

The hypothalamus and brainstem are key hubs of metabolic control that undergo dynamic molecular adaptations in response to changes in energy availability. This remodeling is associated with changes in the expression and activity of enzymes linked to energy homeostasis but also importantly, lipid metabolism. Given that lipids account for [~]50% of the brains dry weight, it is likely that lipid metabolism is a major determinant of brain function. Therefore, understanding how the hypothalamic and brainstem lipidome adapts to metabolic perturbation is key to understanding tissue function and metabolic health. Here we characterize the remodeling of [~]750 lipid species in mouse hypothalamus and brainstem, as well as the cerebrospinal fluid and plasma, in response to a metabolic challenge (an Ad Libitum-Fasting-Refeeding cycle). We show that around 45% and 36% of lipids in the hypothalamus and brainstem respectively, exhibit reversible, nutritional state-dependent remodeling during this metabolic challenge, and that this remodeling is substantially impacted by long-term high fat diet intervention. Of note, targeted analysis of specific lipids revealed that certain fatty acids were affected by this intervention in the hypothalamus and brainstem, most strikingly defined by the reversible fasting-induced increase in linoleic acid (18:2)-containing phosphatidylcholines in both the hypothalamus and brainstem, an effect that is abolished by high fat diet intervention. Such precise and intervention-specific regulation of linoleic acid (18:2)-containing phosphatidylcholines provides a previously unrecognized role for this lipid in the physiological response to fasting. Thus, these findings demonstrate that the brain lipidome undergoes robust, nutritional state-dependent remodeling, and provide a comprehensive resource for investigating its role in regulating metabolic adaptations.

AbstractsGestational diabetes mellitus (GDM) is a common metabolic complication of pregnancy that is paradoxically associated with both fetal overgrowth and fetal growth restriction (FGR). While maternal hyperglycemia is widely presumed to drive macrosomia through excessive nutrient supply, the mechanisms underlying FGR remain poorly understood. Here, using a mouse model that recapitulates the small-for-gestational-age (SGA) phenotype observed in human GDM pregnancies, we identify placental underdevelopment as a principal driver of FGR. Despite systemic nutrient abundance, hyperglycemic placentas exhibit reduced mass and an increased fetal-to-placental weight ratio, indicative of placental insufficiency. Mechanistically, maternal hyperglycemia induces anabolic metabolic rewiring while suppressing oxidative phosphorylation (OXPHOS), accompanied by upregulation and nuclear redistribution of ATP-citrate lyase (ACLY). ACLY converts glucose-derived carbon into acetyl-CoA in the cytosol and nucleus, thereby coupling glycolytic flux to lipid and hexosamine biosynthesis as well as to global histone hyperacetylation. This hyperacetylation-associated epigenetic reprogramming activates metabolic, innate immune, and inflammatory gene programs while repressing pro-proliferative and anti-apoptotic pathways. Consequently, placental growth is compromised despite nutrient excess. Importantly, activation of the ACLY-acetyl-CoA axis and global histone hyperacetylation is consistently observed in human GDM placentas across diverse birth outcomes, suggesting a conserved metabolic-epigenetic adaptation to maternal hyperglycemia. Together, these findings identify ACLY-dependent acetyl-CoA production as a central metabolic node linking maternal hyperglycemia to chromatin remodeling and placental development control, thereby reshaping fetal growth trajectories.