Limiting dysfunctional neutrophilic inflammation whilst preserving effective immunity requires a better understanding of the processes that dictate neutrophil function in the tissues. Quantitative mass-spectrometry identified how inflammatory murine neutrophils regulated expression of cell surface receptors, signal transduction networks and metabolic machinery to shape neutrophil phenotypes in response to hypoxia. Through the tracing of labelled amino acids into metabolic enzymes, pro-inflammatory mediators and granule proteins we demonstrated that ongoing protein synthesis shapes the neutrophil proteome. To maintain energy supplies in the tissues, neutrophils consumed extracellular proteins to fuel central carbon metabolism. The physiological stresses of hypoxia and hypoglycaemia, characteristic of inflamed tissues, promoted this extra-cellular protein scavenging with activation of the lysosomal compartment further driving exploitation of the protein rich inflammatory milieu. This study provides a comprehensive map of neutrophil proteomes, analysis of which has led to the identification of active catabolic and anabolic pathways which enable neutrophils to sustain synthetic and effector functions in the tissues.
Emily R. Watts, Andrew J.M. Howden, Tyler Morrison, Pranvera Sadiku, Jens L. Hukelmann, Alex von Kriegsheim, Bart Ghesquière, Fiona Murphy, Ananda S. Mirchandani, Duncan C. Humphries, Robert Grecian, Eilise M. Ryan, Patricia Coelho, Giovanny Rodriguez-Blanco, Tracie M. Plant, Rebecca S. Dickinson, Andrew J. Finch, Wesley Vermaelen, Doreen A. Cantrell, Moira K.B. Whyte, Sarah R. Walmsley
The protein kinases IKK-epsilon and TBK1 are activated in liver and fat in mouse models of obesity. We have previously demonstrated that treatment with the IKK-epsilon/TBK1 inhibitor, amlexanox, produces weight loss and relieves insulin resistance in obese animals and patients. While amlexanox treatment caused a transient reduction in food intake, long-term weight loss was attributable to increased energy expenditure via FGF21-dependent beiging of WAT. Amlexanox increased FGF21 synthesis and secretion in several tissues. Interestingly, while hepatic secretion determined circulating levels, it was dispensable for regulating energy expenditure. In contrast, adipocyte-secreted FGF21 may have acted as an autocrine factor that leads to adipose tissue browning and weight loss in obese mice. Moreover, increased energy expenditure was an important determinant of improved insulin sensitivity by amlexanox. Conversely, the immediate reductions in fasting blood glucose observed with acute amlexanox treatment were mediated by suppression of hepatic glucose production via the activation of STAT3 by adipocyte-secreted IL-6. These findings demonstrate that amlexanox improved metabolic health via FGF21 action in adipocytes to increase energy expenditure via WAT beiging, and an endocrine role of adipocyte-derived IL-6 to decrease gluconeogenesis via hepatic STAT3 activation, thereby producing a coordinated improvement in metabolic parameters.
Shannon M. Reilly, Mohammad Abu-Odeh, Magdalene Ameka, Julia H. DeLuca, Meghan C. Naber, Benyamin Dadpey, Nima Ebadat, Andrew V. Gomez, Xiaoling Peng, BreAnne Poirier, Elyse Walk, Matthew J. Potthoff, Alan R. Saltiel
Although cancer cells are frequently faced with nutrient- and oxygen-poor microenvironment, elevated hexosamine-biosynthesis pathway (HBP) activity and protein O-GlcNAcylation (a nutrient sensor) contribute to rapid growth of tumor and are emerging hallmarks of cancer. Inhibiting O-GlcNAcylation could be a promising anti-cancer strategy. The gluconeogenic enzymes phosphoenolpyruvate carboxykinase 1 (PCK1) was downregulated in hepatocellular carcinoma (HCC). However, little is known about the potential role of PCK1 in enhanced HBP activity and HCC carcinogenesis under glucose-limited conditions. In this study, PCK1 knockout markedly enhanced the global O-GlcNAcylation levels under low glucose condition. Mechanistically, metabolic reprogramming in PCK1-loss hepatoma cells led to oxaloacetate accumulation and increased de novo UTP synthesis contributing to uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) biosynthesis. Meanwhile, deletion of PCK1 also resulted in AMPK-GFAT1 axis inactivation promoting UDP-GlcNAc synthesis for elevated O-GlcNAcylation. Notably, lower expression of PCK1 promoted CHK2 threonine 378 O-GlcNAcylation counteracting its stability and dimer formation, increasing CHK2-dependent Rb phosphorylation and HCC cell proliferation. Moreover, aminooxyacetic acid hemihydrochloride and 6-diazo-5-oxo-L-norleucine blocked HBP-mediated O-GlcNAcylation and suppressed tumor progression in liver-specific Pck1-knockout mice. We reveal a link between PCK1 depletion and hyper-O-GlcNAcylation that underlies HCC oncogenesis and suggest therapeutic targets for HCC that act by inhibiting O-GlcNAcylation.
Jin Xiang, Chang Chen, Rui Liu, Dongmei Gou, Lei Chang, Haijun Deng, Qingzhu Gao, Wanjun Zhang, Lin Tuo, Xuanming Pan, Li Liang, Jie Xia, Luyi Huang, Ke Yao, Bohong Wang, Zeping Hu, Ailong Huang, Kai Wang, Ni Tang
X-linked adrenoleukodystrophy (ALD) is a progressive neurodegenerative disease caused by mutations in ABCD1, the peroxisomal very long-chain fatty acid (VLCFA) transporter. ABCD1 deficiency results in accumulation of saturated VLCFAs. A drug screen using a phenotypic motor assay in a zebrafish ALD model identified chloroquine as the top hit. Chloroquine increased expression of stearoyl-CoA desaturase-1 (scd1), the enzyme mediating fatty acid saturation status, suggesting that a shift towards mono-unsaturated fatty acids relieved toxicity. In human ALD fibroblasts chloroquine also increased SCD1 levels and reduced saturated VLCFAs. Conversely, pharmacological inhibition of SCD1 expression led to an increase in saturated VLCFAs, and CRISPR knockout of scd1 in zebrafish mimicked the motor phenotype of ALD zebrafish. Importantly, saturated VLCFAs caused ER stress in ALD fibroblasts whereas mono-unsaturated VLCFA did not. In parallel, we used liver X receptor (LXR) agonists to increase SCD1 expression, causing a shift from saturated towards mono-unsaturated VLCFA, and normalizing phospholipid profiles. Finally, Abcd1-/y mice receiving LXR agonist in their diet had VLCFA reductions in ALD-relevant tissues. These results suggest that metabolic rerouting of saturated to mono-unsaturated VLCFAs may alleviate lipid toxicity, a strategy that may be beneficial in ALD and other peroxisomal diseases in which VLCFAs play a key role.
Quentin Raas, Malu-Clair van de Beek, Sonja Forss-Petter, Inge M.E. Dijkstra, Abigail DeSchiffart, Briana C. Freshner, Tamara J. Stevenson, Yorrick R.J. Jaspers, Liselotte M. Nagtzaam, Ronald J.A. Wanders, Michel van Weeghel, Joo-Yeon Engelen-Lee, Marc Engelen, Florian Eichler, Johannes Berger, Joshua L. Bonkowsky, Stephan Kemp
Aberrant lipid metabolism promotes the development of skeletal muscle insulin resistance, but the exact identity of lipid-mediated mechanisms relevant to human obesity remains unclear. A comprehensive lipidomic analysis of primary myocytes from lean insulin-sensitive (LN) and obese insulin-resistant (OB) individuals revealed several species of lysophospholipids (lyso-PL) that were differentially-abundant. These changes coincided with greater expression of lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme involved in phospholipid transacylation (Lands cycle). Strikingly, mice with skeletal muscle-specific knockout of LPCAT3 (LPCAT3-MKO) exhibited greater muscle lyso-PC/PC, concomitant with improved skeletal muscle insulin sensitivity. Conversely, skeletal muscle-specific overexpression of LPCAT3 (LPCAT3-MKI) promoted glucose intolerance. The absence of LPCAT3 reduced phospholipid packing of cellular membranes and increased plasma membrane lipid clustering, suggesting that LPCAT3 affects insulin receptor phosphorylation by modulating plasma membrane lipid organization. In conclusion, obesity accelerates the skeletal muscle Lands cycle, whose consequence might induce the disruption of plasma membrane organization that suppresses muscle insulin action.
Patrick J. Ferrara, Xin Rong, J. Alan Maschek, Anthony R.P. Verkerke, Piyarat Siripoksup, Haowei Song, Thomas D. Green, Karthickeyan C. Krishnan, Jordan M. Johnson, John Turk, Joseph A. Houmard, Aldons J. Lusis, Micah J. Drummond, Joseph M. McClung, James E. Cox, Saame R. Shaikh, Peter Tontonoz, William L. Holland, Katsuhiko Funai
Sepsis is a leading cause of death in critical illness, and its pathophysiology varies depending on preexisting medical conditions. Here we identified nonalcoholic fatty liver disease (NAFLD) as an independent risk factor for sepsis in a large clinical cohort and showed a link between mortality in NAFLD-associated sepsis and hepatic mitochondrial and energetic metabolism dysfunction. Using in vivo and in vitro models of liver lipid overload, we discovered a metabolic coordination between hepatocyte mitochondria and liver macrophages that express triggering receptor expressed on myeloid cells-2 (TREM2). Trem2-deficient macrophages released exosomes that impaired hepatocytic mitochondrial structure and energy supply because of their high content of miR-106b-5p, which blocks Mitofusin 2 (Mfn2). In a mouse model of NAFLD-associated sepsis, TREM2 deficiency accelerated the initial progression of NAFLD and subsequent susceptibility to sepsis. Conversely, overexpression of TREM2 in liver macrophages improved hepatic energy supply and sepsis outcome. This study demonstrates that NAFLD is a risk factor for sepsis, providing a basis for precision treatment, and identifies hepatocyte-macrophage metabolic coordination and TREM2 as potential targets for future clinical trials.
Jinchao Hou, Jue Zhang, Ping Cui, Yingyue Zhou, Can Liu, Xiaoliang Wu, Yun Ji, Sicong Wang, Baoli Cheng, Hui Ye, Liqi Shu, Kai Zhang, Di Wang, Jielin Xu, Qiang Shu, Marco Colonna, Xiangming Fang
Skeletal muscle is a major determinant of systemic metabolic homeostasis that plays a critical role in glucose metabolism and insulin sensitivity. By contrast, despite being a major user of fatty acids, and evidence that muscular disorders can lead to abnormal lipid deposition (e.g., nonalcoholic fatty liver disease in myopathies), our understanding of skeletal muscle regulation of systemic lipid homeostasis is not well understood. Here we show that skeletal muscle Krüppel-like factor 15 (KLF15) coordinates pathways central to systemic lipid homeostasis under basal conditions and in response to nutrient overload. Mice with skeletal muscle–specific KLF15 deletion demonstrated (a) reduced expression of key targets involved in lipid uptake, mitochondrial transport, and utilization, (b) elevated circulating lipids, (c) insulin resistance/glucose intolerance, and (d) increased lipid deposition in white adipose tissue and liver. Strikingly, a diet rich in short-chain fatty acids bypassed these defects in lipid flux and ameliorated aspects of metabolic dysregulation. Together, these findings establish skeletal muscle control of lipid flux as critical to systemic lipid homeostasis and metabolic health.
Liyan Fan, David R. Sweet, Domenick A. Prosdocimo, Vinesh Vinayachandran, Ernest R. Chan, Rongli Zhang, Olga Ilkayeva, Yuan Lu, Komal S. Keerthy, Chloe E. Booth, Christopher B. Newgard, Mukesh K. Jain
Tauopathies display a spectrum of phenotypes from cognitive to affective behavioral impairments; however, mechanisms promoting tau pathology and how tau elicits behavioral impairment remain unclear. We report a unique interaction between polyamine metabolism, behavioral impairment, and tau fate. Polyamines are ubiquitous aliphatic molecules that support neuronal function, axonal integrity, and cognitive processing. Transient increases in polyamine metabolism hallmark the cell’s response to various insults, known as the polyamine stress response (PSR). Dysregulation of gene transcripts associated with polyamine metabolism in Alzheimer’s disease (AD) brains were observed, and we found that ornithine decarboxylase antizyme inhibitor 2 (AZIN2) increased to the greatest extent. We showed that sustained AZIN2 overexpression elicited a maladaptive PSR in mice with underlying tauopathy (MAPT P301S; PS19). AZIN2 also increased acetylpolyamines, augmented tau deposition, and promoted cognitive and affective behavioral impairments. Higher-order polyamines displaced microtubule-associated tau to facilitate polymerization but also decreased tau seeding and oligomerization. Conversely, acetylpolyamines promoted tau seeding and oligomers. These data suggest that tauopathies launch an altered enzymatic signature that endorses a feed-forward cycle of disease progression. Taken together, the tau-induced PSR affects behavior and disease continuance, but may also position the polyamine pathway as a potential entry point for plausible targets and treatments of tauopathy, including AD.
Leslie A. Sandusky-Beltran, Andrii Kovalenko, Devon S. Placides, Kevin Ratnasamy, Chao Ma, Jerry B. Hunt Jr., Huimin Liang, John Ivan T. Calahatian, Camilla Michalski, Margaret Fahnestock, Laura J. Blair, April L. Darling, Jeremy D. Baker, Sarah N. Fontaine, Chad A. Dickey, Joshua J. Gamsby, Kevin R. Nash, Erin Abner, Maj-Linda B. Selenica, Daniel C. Lee
The relationship between adiposity and metabolic health is well established. However, very little is known about the fat depot, known as paracardial fat (pCF), located superior to and surrounding the heart. Here, we show that pCF remodels with aging and a high-fat diet and that the size and function of this depot are controlled by alcohol dehydrogenase 1 (ADH1), an enzyme that oxidizes retinol into retinaldehyde. Elderly individuals and individuals with obesity have low ADH1 expression in pCF, and in mice, genetic ablation of Adh1 is sufficient to drive pCF accumulation, dysfunction, and global impairments in metabolic flexibility. Metabolomics analysis revealed that pCF controlled the levels of circulating metabolites affecting fatty acid biosynthesis. Also, surgical removal of the pCF depot was sufficient to rescue the impairments in cardiometabolic flexibility and fitness observed in Adh1-deficient mice. Furthermore, treatment with retinaldehyde prevented pCF remodeling in these animals. Mechanistically, we found that the ADH1/retinaldehyde pathway works by driving PGC-1α nuclear translocation and promoting mitochondrial fusion and biogenesis in the pCF depot. Together, these data demonstrate that pCF is a critical regulator of cardiometabolic fitness and that retinaldehyde and its generating enzyme ADH1 act as critical regulators of adipocyte remodeling in the pCF depot.
Jennifer M. Petrosino, Jacob Z. Longenecker, Srinivasagan Ramkumar, Xianyao Xu, Lisa E. Dorn, Anna Bratasz, Lianbo Yu, Santosh Maurya, Vladimir Tolstikov, Valerie Bussberg, Paul M.L. Janssen, Muthu Periasamy, Michael A. Kiebish, Gregg Duester, Johannes von Lintig, Ouliana Ziouzenkova, Federica Accornero
Adipose thermogenesis is repressed in obesity, reducing the homeostatic capacity to compensate for chronic overnutrition. Inflammation inhibits adipose thermogenesis, but little is known about how this occurs. Here we show that the innate immune transcription factor IRF3 is a strong repressor of thermogenic gene expression and oxygen consumption in adipocytes. IRF3 achieves this by driving expression of the ubiquitin-like modifier ISG15, which becomes covalently attached to glycolytic enzymes, thus reducing their function and decreasing lactate production. Lactate repletion is able to restore thermogenic gene expression, even when the IRF3-ISG15 axis is activated. Mice lacking ISG15 phenocopy mice lacking IRF3 in adipocytes, as both have elevated energy expenditure and are resistant to diet-induced obesity. These studies provide a deep mechanistic understanding of how the chronic inflammatory milieu of adipose tissue in obesity prevents thermogenic compensation for overnutrition.
Shuai Yan, Manju Kumari, Haopeng Xiao, Christopher Jacobs, Shihab Kochumon, Mark Jedrychowski, Edward Chouchani, Rasheed Ahmad, Evan D. Rosen