Metabolism
Abstract
Insulin signaling is a critical determinant of metabolic health, and impairments in insulin action contribute to the development of type 2 diabetes. The kinase Akt is a central mediator of insulin signaling and is required for insulin’s suppression of hepatic glucose output. Although the regulation of Akt by the insulin receptor-PI3K pathway is well understood, there are instances in which signaling downstream of Akt is dissociated from proximal insulin signaling, for example in insulin resistance. Nonetheless, little is known about PI3K-independent mechanisms of Akt regulation. Here, we discovered that hepatocyte manganese concentrations are a key determinant of PI3K-independent Akt function in vivo. We further demonstrated that manganese increases Akt’s catalytic efficiency, and quantitative phosphoproteomics revealed that manganese and insulin act additively to enhance Akt activity. Moreover, we uncovered that hepatic manganese concentrations fluctuate during fasting and feeding via carbohydrate-dependent transcriptional regulation of the manganese efflux transporter Slc30a10. This dynamic metal–signaling axis provides a mechanistic link between nutrient status and Akt activation, and suggests a molecular explanation for the glucose-lowering effects of manganese observed in humans. Our findings establish manganese as a physiologically regulated cofactor for Akt and position metal bioavailability as a previously unrecognized layer of insulin signaling control.
Authors
Jennifer R. Gamarra, Sei Higuchi, Timothy L. Yuan, Yuke Xie, Cong Liu, Niroshan Shanmugarajah, Hang Yang, Meredith O. Kelly, Sarah A. Hannou, Kathrin Schilling, Ana Navas-Acien, Eunhee Choi, Anum Glasgow, Inna I. Astapova, Mark A. Herman, Rebecca A. Haeusler
Abstract
Type 2 (T2) inflammation is a defining feature of asthma and associated with epithelial dysfunction, including goblet cell metaplasia and ciliary loss. Here, we investigated whether T2 inflammation and associated 15 lipoxygenase-1 (15LO1) activity alters mitochondrial metabolism in airway epithelial cells (AECs) and contributes to disease pathophysiology. Freshly isolated AECs from T2-high asthmatic participants exhibited increased oxygen consumption rates (OCR), including elevated basal respiration and proton leak, alongside reduced coupling efficiency compared to T2-low participants. These functional changes were accompanied by increased expression of electron transport chain (ETC) proteins, worse lung function and epithelial phenotypic changes. In vitro, IL-13 stimulation of differentiated AECs recapitulated these findings, inducing higher OCR, increased ETC protein levels, and enhanced proton leak while paradoxically reducing intracellular ATP. These metabolic alterations are associated with increased uncoupling protein 2 (UCP2) expression and goblet cell differentiation. Mechanistically, 15LO1 emerged as a key regulator, as ALOX15 knockdown or pharmacologic inhibition reduced OCR parameters, ETC protein expression, UCP2, and goblet cell markers, without effect on ATP levels, suggesting additional regulatory mechanisms. Collectively, these findings identify a metabolic axis linking T2 inflammation, mitochondrial dysfunction, and airway epithelial metabolism, while highlighting 15LO1-driven mitochondrial uncoupling as a potential therapeutic target in asthma.
Authors
Xiuxia Zhou, Krithika S. Rao, Sruti Shiva, Catharina van Heusden, Qi Wei, Nobuhiko Fukuda, Mayoko Tsuji, Angelina Kendi, Laura R. Bradley, Jinming Zhao, John B. Trudeau, Anuradha Ray, Richard C. Boucher, Sally E. Wenzel
Abstract
Authors
Simeon I. Taylor
Abstract
Authors
Abdualrahman Mohammed Abdualkader, Rami Al Batran
Abstract
Sphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) is a rare condition causing nephrotic syndrome, neuropathy, and other manifestations. SPLIS is caused by mutations in SGPL1, which encodes sphingosine-1-phosphate lyase (SPL), a pyridoxal 5′-phosphate (PLP)-dependent enzyme needed to degrade the bioactive sphingolipid sphingosine-1-phosphate (S1P). Supplementation with the PLP precursor pyridoxine benefits some individuals with PLP-dependent enzymopathies. We investigated whether pyridoxine has therapeutic activity in SPLIS. Neurological improvement, plasma S1P normalization, and increased SPL activity in patient-derived fibroblasts were observed after pyridoxine supplementation in a patient with R222Q-variant SPLIS. Additionally, PLP dose-dependently augmented recombinant R222Q-variant SPL activity. To further explore pyridoxine’s effects, gene editing was employed to create an R222Q-variant SPLIS mouse model. SPLR222Q mice fed pyridoxine-enriched chow lacked obvious phenotypes. However, SPL inactivation, S1P accumulation, proteinuria, and glomerulosclerosis developed in SPLR222Q but not WT mice fed chow with reduced pyridoxine. Ultrastructural analysis and super-resolution microscopy showed podocyte loss and foot process effacement. Transcriptional profiling revealed patterns of cytokine upregulation and extracellular matrix remodeling. Inhibiting S1P production or RhoA/ROCK signaling prevented nephrosis in SPLR222Q mice fed chow lacking pyridoxine. Our findings establish a SPLIS mouse model that recapitulates R222Q-variant SPLIS, demonstrates its responsiveness to pyridoxine, and implicates a S1P/RhoA/ROCK pathway in its pathophysiology. Running Title: Cofactor supplementation in R222Q-variant SPLIS
Authors
Ranjha Khan, Maria L. Allende, Ehtesham Khalid, Joanna Y. Lee, Everett Stone, Max Rodnick-Smith, Audrey Izuhara, Vadym Buncha, Georgina Gyarmati, Janos Peti-Peterdi, Ranya Al-Khaledy, Jeffrey B. Hodgin, Gizachew Tassew, Babak Oskouian, Alina Chen, Yu-Tang Chang, Rachel Zhang, Richard L. Proia, Julie D. Saba
Abstract
Metabolic dysfunction-associated steatohepatitis (MASH) is rising globally despite recent therapeutic advances, highlighting the need to identify new targetable pathways. While dysregulated lipid and amino acid metabolism are established features of MASH, the interplay between these two metabolic pathways remains unexplored. Here, metabolomics of livers from humans and mice with MASH uncovered depletion of lipidated amino acids, where these two distinctive pathways converge. Notably, hepatic levels of N-oleoyl-leucine (C18:1-Leu) were inversely correlated with the severity of MASH-fibrosis. The C18:1-Leu-regulating enzyme, peptidase M20 domain containing 1 (PM20D1), was suppressed in MASH due to attenuated de novo transcription, and stable-isotope tracing confirmed impaired hepatic biosynthesis of C18:1-Leu in MASH. Hepatocyte-specific PM20D1 ablation lowered hepatic C18:1-Leu and exacerbated MASH, whereas hepatocyte-specific PM20D1 overexpression restored C18:1-Leu and ameliorated both MASH progression and established disease. Exogenous administration of C18:1-Leu similarly ameliorated MASH-fibrosis. In silico modeling, transcriptomics, metabolic flux analyses and hepatocyte-specific in vivo manipulations revealed that C18:1-Leu binds and activates peroxisome proliferator-activated receptor alpha to suppress C-C motif chemokine ligand 2, concurrently enhancing fatty acid β-oxidation and attenuating monocyte recruitment to reduce MASH-fibrosis. These findings highlight C18:1-Leu deficiency as a driver and a therapeutic target in MASH-fibrosis, warranting further clinical evaluation.
Authors
Sumit Kumar Anand, Sandeep Das, Fabio Arias, Koral S.E. Richard, Sumati Rohilla, Alia Ghrayeb, M. Peyton McKinney, Lu Wang, Lin Tan, Jibin Ding, Dhananjay Kumar, Nilesh Pandey, Jennifer Lee, Ying Zhao, Suman Mohajan, Gurranna Male, Kelley Nunez, Alexandra C. Finney, Brenna H. Pearson-Gallion, Reethika Gade, Jemiah Maxie, Yu Liu, Harpreet Kaur, Rajan Pandit, Cyrine Ben Dhaou, Joseph Eniafe, Xiaolu Zhang, Zhipeng Liu, Andrew D. Yurochko, Minerva T. Garcia-Barrio, Babak Razani, Fei Chang, Francisco J. Schopfer, Xin Huang, Bishuang Cai, Eyal Gottlieb, Bo Wen, Duxin Sun, Wanqing Liu, Paul T. Thevenot, Ari J. Cohen, Jifeng Zhang, Y. Eugene Chen, A. Wayne Orr, Nirav Dhanesha, Arif Yurdagul Jr., Oren Rom
Abstract
Pharmacologic immunosuppression is essential for preventing organ rejection and controlling autoimmunity, but profoundly impairs humoral immunity, increasing the risk of vaccine failure and infection. The mechanisms by which immunosuppressive therapies disrupt human B cell responses remain poorly defined. Here, we identified dysregulated lipid metabolism as a central determinant of impaired vaccine response in solid organ transplant recipients (SOTRs). Using high-dimensional immune profiling, single-cell transcriptomics, and functional metabolic assays, we found that effective B cell responses required a homeostatic balance between lipid synthesis and fatty acid oxidation. The widely used immunosuppressive agent, mycophenolic acid (MPA) was strongly associated with vaccine non-response and induced excessive lipid synthesis, lipid accumulation, and mitochondrial stress in B cells. In contrast, CD11c+ B cells retained the capacity to differentiate into plasmablasts in the presence of MPA through elevated expression of CPT1A, a mitochondrial fatty acid transporter, and enhanced fatty acid oxidation. These cells were found to be a key feature of early effective vaccine responses in healthy individuals and SOTRs. Notably, pharmacologic inhibition of cholesterol synthesis partially restored plasmablast differentiation in the presence of MPA. These findings identify B cell lipid metabolism as a critical and targetable regulator of human humoral immunity during immunosuppression.
Authors
Elizabeth A. Thompson, Alexis Figueroa, Katerina Roznik, Nicole E. Skinner, Santosh Dhakal, Shuai Li, Luca Biavati, Laura A. Sena, Laila Stoddart, Karli Redinger, Samuel B. Warner, Sabra L. Klein, Nadine Rouphael, Joel N. Blankson, Yolanda Eby, Robert D. Leone, Peter S. Heeger, Mark A. Robien, Christian P. Larsen, Erika L. Pearce, Edward J. Pearce, Hongkai Ji, Andrew H. Karaba, Dorry L. Segev, Aaron A.R. Tobian, William A. Werbel, Andrea L. Cox, Justin R. Bailey
Abstract
GLP-1 receptor agonists (GLP1RAs) effectively reduce feeding to treat obesity, although nausea and other aversive side effects of these drugs can limit their use. Brainstem circuits that promote satiation and mediate the physiological control of body weight can be distinguished from those that cause aversion. It remains unclear whether brainstem Glp1r neurons contribute to the normal regulation of energy balance and whether GLP1RAs control appetite via circuits distinct from those that mediate aversive responses, however. Here, we silenced Glp1r neurons in the nucleus of the solitary tract or area postrema (NTSGlp1r or APGlp1r neurons, respectively) or restored their GLP1R signaling on an otherwise GLP1R-deficient background to determine physiological and pharmacological roles for each neuron population. Although NTSGlp1r neurons contributed to the normal restraint of food intake and body weight, they failed to mediate GLP1RA-dependent weight loss. In contrast, while we detected no role for APGlp1r neurons in physiological feeding, they mediated both the weight-lowering and aversive effects of GLP1RAs. Therefore, while non-aversive NTSGlp1r neurons control physiologic satiation they do not contribute to weight loss during GLP1RA treatment. Rather, APGlp1r neurons mediate both the weight-lowering and aversive effects of GLP1RAs, preventing the separation of their nauseating and weight-loss effects at a circuit level.
Authors
Warren T. Yacawych, Yi Wang, Guoxiang Zhou, Shad Hassan, Cagri Bodur, Elisabeth Walters, John G. Santinga, Frederike Sass, Martin deVaux, Stace Kernodle, Iris Wu, Jenny M. Brown, Dylan M. Belmont-Rausch, Alan C. Rupp, Abigail J. Tomlinson, Zitian Lin, Emma VanTongeren, Anna Secher, Kirsten Raun, Tune H. Pers, Randy J. Seeley, Martin G. Myers Jr., Weiwei Qiu
Abstract
Obesity-associated inflammation impairs pancreatic β-cell function, yet the mechanisms by which immune cells acutely regulate insulin secretion remain poorly defined. Here, we identify myeloid Gq signaling as an immunometabolic node linking macrophage lipid sensing to impaired insulin secretion. Using chemogenetic DREADD-mediated activation of myeloid Gq, we show that acute macrophage Gq activation impairs glucose-stimulated insulin secretion (GSIS) in vivo, whereas myeloid Gαq ablation enhances GSIS. Mechanistically, Gq activation rapidly induced AMPK phosphorylation and sphingolipid remodeling independently of canonical inflammatory cytokines. Macrophage-derived sphingolipids impaired β-cell insulin signaling and GSIS through CD36-PKCζ, while inhibition of CD36, AMPK, or sphingolipid metabolism restored β-cell function. We further identified GPR18, a Gq-coupled endocannabinoid-responsive GPCR, as an upstream regulator. GPR18 activation with N-arachidonoyl glycine (NAGly) recapitulated this phenotype, whereas myeloid Gαq deletion or Gpr18/AMPK silencing abolished it. GPR18 signaling predominantly engaged Gq rather than Gi pathways. In human tissues, GPR18 was enriched in islet macrophages, and NAGly suppressed GSIS in primary human islets. Thus, a conserved macrophage GPR18-Gαq-AMPK-sphingolipid axis dynamically regulates β-cell function and represents a potential therapeutic target in obesity and type 2 diabetes.
Authors
Simran Singh, Ashish Kumar, Sudipta Paul, Mriganka Sarkar, Santhosh Duraisamy, Ganesh Timalsina, Raashidha Farhath, Harender Yadav, Seema Kuldeep, Soumita Bhaumik, Kunj Kumar Prajapati, Saahiba Thaleshwari, Anuj Gargya, Tamojit Santra, Sonal Amit, Rashmi Parihar, Santosh K. Misra, Hamim Zafar, Luiz F. Barella, Michael A. Kalwat, Dharmaraja Allimuthu, Sai Prasad Pydi
Abstract
Metabolic-associated steatohepatitis (MASH) involves hepatocyte damage that cannot be explained solely by lipid accumulation. Here, to discover injury-specific pathways, we focused on a gene of uncertain function, EF-Hand Domain Family Member D1 (EFHD1), identified in human genome-wide association studies of liver injury but not liver fat. We show that EFHD1, a Ca2+-dependent actin crosslinker, stabilizes endoplasmic reticulum–mitochondria contact sites (ERMCS), detecting spatiotemporal coincidence of inter-organellar proximity and ER Ca2+ release. During MASH, EFHD1 upregulation drives pathological mitochondrial fragmentation via excessive contact persistence. This structural failure promotes mitochondrial double-stranded RNA escape and activation of a maladaptive antiviral PKR-associated stress response, a causal relationship also supported by Mendelian randomization in humans. Consequently, inhibiting EFHD1 in human and mouse models blunts hepatocyte damage. These findings identify EFHD1 as a Ca2+-dependent ERMCS stabilizer, reveal a hepatocyte-intrinsic injury pathway, and suggest EFHD1 inhibition as a therapeutic strategy.
Authors
David R. Eberhardt, Emma C. Rekate, Yasmin B. Masini, Hannah E. Duron, David Mollinedo, Adrian M. Velarde, Devorah Stucki, Tara R. Price, Sandra H.J. Lee, Enrique Balderas, Neeraj K. Rai, Ashley R. Bratt, Anthony M. Balynas, Chris J. Stubben, Ryan Bia, Sudipa Maity, Nicolas Hartel, Xue Yin, Andrea Corbin, Anshu Kumari, Dung M. Nguyen, Daisuke Shimura, Vu D. Nguyen, Vishaka Vinod, Kamrul H. Chowdhury, Francisco Verdeguer, Joel Zvick, Patrice N. Mimche, Sihem Boudina, Stavros G. Drakos, Ademuyiwa S. Aromolaran, Sarah Franklin, Vivek Garg, Robin M. Shaw, William L. Holland, Scott A. Summers, Marcus G. Pezzolesi, Jared Rutter, Kimberley J. Evason, Dipayan Chaudhuri
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)