An increase in hepatic glucose production (HGP) represents a key feature of type 2 diabetes. This deficiency in metabolic control of glucose production critically depends on enhanced signaling through hepatic glucagon receptors (GCGRs). Here, we have demonstrated that selective inactivation of the GPCR-associated protein β-arrestin 2 in hepatocytes of adult mice results in greatly increased hepatic GCGR signaling, leading to striking deficits in glucose homeostasis. However, hepatocyte-specific β-arrestin 2 deficiency did not affect hepatic insulin sensitivity or β-adrenergic signaling. Adult mice lacking β-arrestin 1 selectively in hepatocytes did not show any changes in glucose homeostasis. Importantly, hepatocyte-specific overexpression of β-arrestin 2 greatly reduced hepatic GCGR signaling and protected mice against the metabolic deficits caused by the consumption of a high-fat diet. Our data support the concept that strategies aimed at enhancing hepatic β-arrestin 2 activity could prove useful for suppressing HGP for therapeutic purposes.
Lu Zhu, Mario Rossi, Yinghong Cui, Regina J. Lee, Wataru Sakamoto, Nicole A. Perry, Nikhil M. Urs, Marc G. Caron, Vsevolod V. Gurevich, Grzegorz Godlewski, George Kunos, Minyong Chen, Wei Chen, Jürgen Wess
Epidemiologic and animal studies implicate overconsumption of fructose in the development of nonalcoholic fatty liver disease, but the molecular mechanisms underlying fructose-induced chronic liver diseases remain largely unknown. Here, we have presented evidence supporting the essential function of the lipogenic transcription factor carbohydrate response element–binding protein (ChREBP) in mediating adaptive responses to fructose and protecting against fructose-induced hepatotoxicity. In WT mice, a high-fructose diet (HFrD) activated hepatic lipogenesis in a ChREBP-dependent manner; however, in Chrebp-KO mice, a HFrD induced steatohepatitis. In Chrebp-KO mouse livers, a HFrD reduced levels of molecular chaperones and activated the C/EBP homologous protein–dependent (CHOP-dependent) unfolded protein response, whereas administration of a chemical chaperone or Chop shRNA rescued liver injury. Elevated expression levels of cholesterol biosynthesis genes in HFrD-fed Chrebp-KO livers were paralleled by an increased nuclear abundance of sterol regulatory element–binding protein 2 (SREBP2). Atorvastatin-mediated inhibition of hepatic cholesterol biosynthesis or depletion of hepatic Srebp2 reversed fructose-induced liver injury in Chrebp-KO mice. Mechanistically, we determined that ChREBP binds to nuclear SREBP2 to promote its ubiquitination and destabilization in cultured cells. Therefore, our findings demonstrate that ChREBP provides hepatoprotection against a HFrD by preventing overactivation of cholesterol biosynthesis and the subsequent CHOP-mediated, proapoptotic unfolded protein response. Our findings also identified a role for ChREBP in regulating SREBP2-dependent cholesterol metabolism.
Deqiang Q. Zhang, Xin Tong, Kyle VanDommelen, Neil Gupta, Kenneth Stamper, Graham F. Brady, Zhuoxian Meng, Jiandie D. Lin, Liangyou Y. Rui, M. Bishr Omary, Lei Yin
Obesity increases sympathetic nerve activity (SNA) via activation of proopiomelanocortin neurons in the arcuate nucleus (ArcN), and this action requires simultaneous withdrawal of tonic neuropeptide Y (NPY) sympathoinhibition. However, the sites and neurocircuitry by which NPY decreases SNA are unclear. Here, using designer receptors exclusively activated by designer drugs (DREADDs) to selectively activate or inhibit ArcN NPY neurons expressing agouti-related peptide (AgRP) in mice, we have demonstrated that this neuronal population tonically suppresses splanchnic SNA (SSNA), arterial pressure, and heart rate via projections to the paraventricular nucleus (PVN) and dorsomedial hypothalamus (DMH). First, we found that ArcN NPY/AgRP fibers closely appose PVN and DMH presympathetic neurons. Second, nanoinjections of NPY or an NPY receptor Y1 (NPY1R) antagonist into PVN or DMH decreased or increased SSNA, respectively. Third, blockade of DMH NPY1R reversed the sympathoinhibition elicited by selective, DREADD-mediated activation of ArcN NPY/AgRP neurons. Finally, stimulation of ArcN NPY/AgRP terminal fields in the PVN and DMH decreased SSNA. Considering that chronic obesity decreases ArcN NPY content, we propose that the ArcN NPY neuropathway to the PVN and DMH is pivotal in obesity-induced elevations in SNA.
Zhigang Shi, Christopher J. Madden, Virginia L. Brooks
Somatostatin secreted by pancreatic δ cells mediates important paracrine interactions in Langerhans islets, including maintenance of glucose metabolism through the control of reciprocal insulin and glucagon secretion. Disruption of this circuit contributes to the development of diabetes. However, the precise mechanisms that control somatostatin secretion from islets remain elusive. Here, we found that a super-complex comprising the cullin 4B-RING E3 ligase (CRL4B) and polycomb repressive complex 2 (PRC2) epigenetically regulates somatostatin secretion in islets. Constitutive ablation of CUL4B, the core component of the CRL4B-PRC2 complex, in δ cells impaired glucose tolerance and decreased insulin secretion through enhanced somatostatin release. Moreover, mechanistic studies showed that the CRL4B-PRC2 complex, under the control of the δ cell–specific transcription factor hematopoietically expressed homeobox (HHEX), determines the levels of intracellular calcium and cAMP through histone posttranslational modifications, thereby altering expression of the Cav1.2 calcium channel and adenylyl cyclase 6 (AC6) and modulating somatostatin secretion. In response to high glucose levels or urocortin 3 (UCN3) stimulation, increased expression of cullin 4B (CUL4B) and the PRC2 subunit histone-lysine N-methyltransferase EZH2 and reciprocal decreases in Cav1.2 and AC6 expression were found to regulate somatostatin secretion. Our results reveal an epigenetic regulatory mechanism of δ cell paracrine interactions in which CRL4B-PRC2 complexes, Cav1.2, and AC6 expression fine-tune somatostatin secretion and facilitate glucose homeostasis in pancreatic islets.
Qing Li, Min Cui, Fan Yang, Na Li, Baichun Jiang, Zhen Yu, Daolai Zhang, Yijing Wang, Xibin Zhu, Huili Hu, Pei-Shan Li, Shang-Lei Ning, Si Wang, Haibo Qi, Hechen Song, Dongfang He, Amy Lin, Jingjing Zhang, Feng Liu, Jiajun Zhao, Ling Gao, Fan Yi, Tian Xue, Jin-Peng Sun, Yaoqin Gong, Xiao Yu
Patients with coronary artery disease (CAD) are at high risk for reactivation of the varicella zoster virus (VZV) and development of herpes zoster (HZ). Here, we found that macrophages from patients with CAD actively suppress T cell activation and expansion, leading to defective VZV-specific T cell immunity. Monocyte-derived and plaque-infiltrating macrophages from patients with CAD spontaneously expressed high surface density of the immunoinhibitory ligand programmed death ligand-1 (PD-L1), thereby providing negative signals to programmed death-1+ (PD-1+) T cells. We determined that aberrant PD-L1 expression in patient-derived macrophages was metabolically controlled. Oversupply of the glycolytic intermediate pyruvate in mitochondria from CAD macrophages promoted expression of PD-L1 via induction of the bone morphogenetic protein 4/phosphorylated SMAD1/5/IFN regulatory factor 1 (BMP4/p-SMAD1/5/IRF1) signaling pathway. Thus, CAD macrophages respond to nutrient excess by activating the immunoinhibitory PD-1/PD-L1 checkpoint, leading to impaired T cell immunity. This finding indicates that metabolite-based immunotherapy may be a potential strategy for restoring adaptive immunity in CAD.
Ryu Watanabe, Tsuyoshi Shirai, Hong Namkoong, Hui Zhang, Gerald J. Berry, Barbara B. Wallis, Benedikt Schaefgen, David G. Harrison, Jennifer A. Tremmel, John C. Giacomini, Jörg J. Goronzy, Cornelia M. Weyand
Tumor recurrence is the leading cause of breast cancer–related death. Recurrences are largely driven by cancer cells that survive therapeutic intervention. This poorly understood population is referred to as minimal residual disease. Here, using mouse models that faithfully recapitulate human disease together with organoid cultures, we have demonstrated that residual cells acquire a transcriptionally distinct state from normal epithelium and primary tumors. Gene expression changes and functional characterization revealed altered lipid metabolism and elevated ROS as hallmarks of the cells that survive tumor regression. These residual cells exhibited increased oxidative DNA damage, potentiating the acquisition of somatic mutations during hormonal-induced expansion of the mammary cell population. Inhibition of either cellular fatty acid synthesis or fatty acid transport into mitochondria reduced cellular ROS levels and DNA damage, linking these features to lipid metabolism. Direct perturbation of these hallmarks in vivo, either by scavenging ROS or by halting the cyclic mammary cell population expansion, attenuated tumor recurrence. Finally, these observations were mirrored in transcriptomic and histological signatures of residual cancer cells from neoadjuvant-treated breast cancer patients. These results highlight the potential of lipid metabolism and ROS as therapeutic targets for reducing tumor recurrence in breast cancer patients.
Kristina M. Havas, Vladislava Milchevskaya, Ksenija Radic, Ashna Alladin, Eleni Kafkia, Marta Garcia, Jens Stolte, Bernd Klaus, Nicole Rotmensz, Toby J. Gibson, Barbara Burwinkel, Andreas Schneeweiss, Giancarlo Pruneri, Kiran R. Patil, Rocio Sotillo, Martin Jechlinger
Genetic variants at the solute carrier family 39 member 8 (
Wen Lin, David R. Vann, Paschalis-Thomas Doulias, Tao Wang, Gavin Landesberg, Xueli Li, Emanuela Ricciotti, Rosario Scalia, Miao He, Nicholas J. Hand, Daniel J. Rader
Glucocorticoid steroids such as prednisone are prescribed for chronic muscle conditions
such as Duchenne muscular dystrophy, where their use is associated with prolonged
ambulation. The positive effects of chronic steroid treatment in muscular dystrophy are
paradoxical because these steroids are also known to trigger muscle atrophy. Chronic
steroid use usually involves once-daily dosing, although weekly dosing in children has
been suggested for its reduced side effects on behavior. In this work, we tested steroid
dosing in mice and found that a single pulse of glucocorticoid steroids improved
sarcolemmal repair through increased expression of annexins A1 and A6, which mediate
myofiber repair. This increased expression was dependent on glucocorticoid response
elements upstream of annexins and was reinforced by the expression of forkhead box O1
(FOXO1). We compared weekly versus daily steroid treatment in mouse models of acute muscle
injury and in muscular dystrophy and determined that both regimens provided comparable
benefits in terms of annexin gene expression and muscle repair. However, daily dosing
activated atrophic pathways, including F-box protein 32 (
Mattia Quattrocelli, David Y. Barefield, James L. Warner, Andy H. Vo, Michele Hadhazy, Judy U. Earley, Alexis R. Demonbreun, Elizabeth M. McNally
Natalia Rakova, Kento Kitada, Kathrin Lerchl, Anke Dahlmann, Anna Birukov, Steffen Daub, Christoph Kopp, Tetyana Pedchenko, Yahua Zhang, Luis Beck, Bernd Johannes, Adriana Marton, Dominik N. Müller, Manfred Rauh, Friedrich C. Luft, Jens Titze
Natriuretic regulation of extracellular fluid volume homeostasis includes suppression of the renin-angiotensin-aldosterone system, pressure natriuresis, and reduced renal nerve activity, actions that concomitantly increase urinary Na+ excretion and lead to increased urine volume. The resulting natriuresis-driven diuretic water loss is assumed to control the extracellular volume. Here, we have demonstrated that urine concentration, and therefore regulation of water conservation, is an important control system for urine formation and extracellular volume homeostasis in mice and humans across various levels of salt intake. We observed that the renal concentration mechanism couples natriuresis with correspondent renal water reabsorption, limits natriuretic osmotic diuresis, and results in concurrent extracellular volume conservation and concentration of salt excreted into urine. This water-conserving mechanism of dietary salt excretion relies on urea transporter–driven urea recycling by the kidneys and on urea production by liver and skeletal muscle. The energy-intense nature of hepatic and extrahepatic urea osmolyte production for renal water conservation requires reprioritization of energy and substrate metabolism in liver and skeletal muscle, resulting in hepatic ketogenesis and glucocorticoid-driven muscle catabolism, which are prevented by increasing food intake. This natriuretic-ureotelic, water-conserving principle relies on metabolism-driven extracellular volume control and is regulated by concerted liver, muscle, and renal actions.
Kento Kitada, Steffen Daub, Yahua Zhang, Janet D. Klein, Daisuke Nakano, Tetyana Pedchenko, Louise Lantier, Lauren M. LaRocque, Adriana Marton, Patrick Neubert, Agnes Schröder, Natalia Rakova, Jonathan Jantsch, Anna E. Dikalova, Sergey I. Dikalov, David G. Harrison, Dominik N. Müller, Akira Nishiyama, Manfred Rauh, Raymond C. Harris, Friedrich C. Luft, David H. Wassermann, Jeff M. Sands, Jens Titze