Metabolism
Abstract
RNA binding protein Apobec1 Complementation Factor (A1CF) regulates posttranscriptional ApoB mRNA editing but the range of RNA targets and long-term impact of altered A1CF expression on liver function are unknown. Here we studied hepatocyte-specific A1cf transgenic (A1cf +/Tg), A1cf+/Tg Apobec1–/– and A1cf –/– mice fed chow or high fat/high fructose diets using RNA-Seq, RNA-CLIP Seq and tissue microarrays from human hepatocellular cancer (HCC). A1cf +/Tg mice exhibited increased hepatic proliferation and steatosis, with increased lipogenic gene expression (Mogat1, Mogat2, Cidea, Cd36) associated with shifts in polysomal RNA distribution. Aged A1cf +/Tg mice developed spontaneous fibrosis, dysplasia and HCC, which was accelerated on a high fat/fructose diet and independent of Apobec1. RNA-Seq revealed increased expression of mRNAs involved in oxidative stress (Gstm3, Gpx3, Cbr3), inflammatory response (Il19, Cxcl14, Tnfα, Ly6c), extracellular matrix organization (Mmp2, Col1a1, Col4a1), proliferation (Kif20a, Mcm2, Mcm4, Mcm6) with a subset of mRNAs (including Sox4, Sox9, Cdh1) identified in RNA CLIP-Seq. Increased A1CF expression in human HCC correlated with advanced fibrosis and with reduced survival in a subset with nonalcoholic fatty liver disease. In conclusion, we show that hepatic A1CF overexpression selectively alters polysomal distribution and mRNA expression, promoting lipogenic, proliferative and inflammatory pathways leading to HCC.
Authors
Valerie Blanc, Jesse D. Riordan, Saeed Soleymanjahi, Joseph Nadeau, ILKe Nalbantoglu, Yan Xie, Elizabeth A. Molitor, Blair B. Madison, Elizabeth M. Brunt, Jason C. Mills, Deborah C. Rubin, Irene O.L. Ng, Yeonjung Ha, Lewis R. Roberts, Nicholas O. Davidson
Abstract
Particulate matter < 2.5 micrometers (PM2.5) air pollution is the world’s leading environmental risk factor contributing to mortality through cardiometabolic pathways. In this study, we modeled early life exposure using chow-fed C57BL/6J male mice, exposed to real-world inhaled concentrated PM2.5 (~10 times ambient levels / ~60-120ug/m3) or filtered air over 14 weeks. We investigated PM2.5 effects on phenotype, transcriptome and chromatin accessibility, compared the effects with a prototypical high-fat diet (HFD) stimulus, and examined cessation of exposure on reversibility of phenotype. Exposure to PM2.5 impaired glucose and insulin tolerance, reduced energy expenditure and 18FDG-PET uptake in brown adipose tissue. Multiple differentially expressed gene (DEG) clusters in pathways involving metabolism and circadian rhythm were noted in insulin responsive tissues. Although the magnitude of transcriptional change seen with PM2.5 was lower than HFD, the degree of alteration in chromatin accessibility after PM2.5 exposure was significant. A novel chromatin remodeler SMARCA5 (SWI/SNF complex) was regulated in response to PM2.5 with cessation of exposure associated with reversal of insulin resistance, restoration of chromatin accessibility/nucleosome positioning near transcription start sites (TSS) and exposure induced changes in the transcriptome including SMARCA5, indicating pliable epigenetic control mechanisms following exposure cessation.
Authors
Sanjay Rajagopalan, Bongsoo Park, Rengasamy Palanivel, Vinesh Vinayachandran, Jeffrey A. Deiuliis, Roopesh Singh Gangwar, Lopa M. Das, Jinhu Yin, Youngshim Choi, Sadeer Al-Kindi, Mukesh K. Jain, Kasper D. Hansen, Shyam Biswal
Abstract
Recent genome-wide association studies (GWAS) identified DUSP8, a dual-specificity phosphatase targeting MAP kinases, as type 2 diabetes (T2D) risk gene. Here, we unravel Dusp8 as gatekeeper in the hypothalamic control of glucose homeostasis in mice and humans. Male but not female Dusp8 loss-of-function mice, either with global or CRH neuron-specific deletion, had impaired systemic glucose tolerance and insulin sensitivity when exposed to high-fat diet (HFD). Mechanistically, we found impaired hypothalamic–pituitary–adrenal (HPA) axis feedback, blunted sympathetic responsiveness, and chronically elevated corticosterone levels driven by hypothalamic hyperactivation of Jnk signaling. Accordingly, global Jnk1 ablation, AAV-mediated Dusp8 overexpression in the mediobasal hypothalamus, or metyrapone-induced chemical adrenalectomy rescued the impaired glucose homeostasis of obese male Dusp8 KO mice, respectively. The sex-specific role of murine Dusp8 in governing hypothalamic Jnk signaling, insulin sensitivity and systemic glucose tolerance was consistent with fMRI data in human volunteers that revealed an association of the DUSP8 rs2334499 risk variant with hypothalamic insulin resistance in men. Further, expression of DUSP8 was increased in the infundibular nucleus of T2D humans. In summary, our findings suggest the GWAS-identified gene Dusp8 as novel hypothalamic factor that plays a functional role in the etiology of T2D.
Authors
Sonja C. Schriever, Dhiraj G. Kabra, Katrin Pfuhlmann, Peter Baumann, Emily V. Baumgart, Joachim Nagler, Fabian Seebacher, Luke Harrison, Martin Irmler, Stephanie Kullmann, Felipe Corrêa-da-Silva, Florian Giesert, Ruchi Jain, Hannah Schug, Julien Castel, Sarah Martinez, Moya Wu, Hans-Ulrich Häring, Martin Hrabe de Angelis, Johannes Beckers, Timo D. Müller, Kerstin Stemmer, Wolfgang Wurst, Jan Rozman, Rubén Nogueiras, Meri De Angelis, Jeffery D. Molkentin, Natalie Krahmer, Chun-Xia Yi, Mathias V. Schmidt, Serge Luquet, Martin Heni, Matthias H. Tschoep, Paul T. Pfluger
Abstract
Mitochondria have emerged as key actors of innate and adaptive immunity. Mitophagy has a pivotal role in cell homeostasis but its contribution to macrophage functions and host defense remains to be delineated. Here we showed that lipopolysaccharide (LPS) in combination with IFNγ, inhibits PINK1-dependent mitophagy in macrophages through a STAT1-dependent activation of the inflammatory caspases 1 and 11. In addition, we demonstrated that the inhibition of mitophagy triggers classical macrophage activation in a mitochondrial ROS-dependent manner. In a murine model of polymicrobial infection (cecal ligature and puncture, CLP), adoptive transfer of Pink1-deficient bone marrow or pharmacological inhibition of mitophagy promoted macrophage activation which favored bactericidal clearance and lead to a better survival. Reciprocally, mitochondrial uncouplers, that promote mitophagy, reverse LPS/IFNγ-mediated activation of macrophages and lead to immuno-paralysis with impaired bacterial clearance and lowered survival. In critically ill patients, we showed that mitophagy is inhibited in blood monocytes of patients with sepsis as compared to non-septic patients. Overall, this work demonstrates that the inhibition of mitophagy is a physiological mechanism that contributes to the activation of myeloid cells and improves the outcome of sepsis.
Authors
Danish Patoli, Franck Mignotte, Valérie Deckert, Alois Dusuel, Adelie Dumont, Aurelie Rieu, Antoine Jalil, Kevin Van Dongen, Thibaut Bourgeois, Thomas Gautier, Charlene Magnani, Naig Le Guern, Stéphane Mandard, Jean Bastin, Fatima Djouadi, Christine Schaeffer, Nina Guillaumot, Michel Narce, Maxime Nguyen, Julien Guy, Auguste Dargent, Jean-Pierre Quenot, Mickaël Rialland, David Masson, Johan Auwerx, Laurent Lagrost, Charles Thomas
Abstract
Males and females differ in body composition and fat distribution. Using a mouse model that segregates gonadal sex (ovaries and testes) from chromosomal sex (XX and XY), we showed that XX chromosome complement in combination with a high-fat diet led to enhanced weight gain in the presence of male or female gonads. We identified the genomic dosage of Kdm5c, an X chromosome gene that escapes X-chromosome inactivation, as a determinant of the X chromosome effect on adiposity. Modulating Kdm5c gene dosage in XX female mice to levels that are normally present in males reduced body weight, fat content, and food intake to a similar degree as altering the entire X chromosome dosage. In cultured preadipocytes, the levels of KDM5C histone demethylase influenced chromatin accessibility (ATAC-seq), gene expression (RNA-seq), and adipocyte differentiation. Both in vitro and in vivo, Kdm5c dosage influenced gene expression involved in extracellular matrix remodeling, which is critical for adipocyte differentiation and adipose tissue expansion. In humans, adipose tissue KDM5C mRNA levels and KDM5C genetic variants were associated with body mass. These studies demonstrate that the sex-dependent dosage of Kdm5c contributes to male/female differences in adipocyte biology, and highlight X-escape genes as a critical component of female physiology.
Authors
Jenny C. Link, Carrie B. Wiese, Xuqi Chen, Rozeta Avetisyan, Emilio Ronquillo, Feiyang Ma, Xiuqing Guo, Jie Yao, Matthew Allison, Yii-Der I. Chen, Jerome I. Rotter, Julia S. El-Sayed Moustafa, Kerrin S. Small, Shigeki Iwase, Matteo Pellegrini, Laurent Vergnes, Arthur P. Arnold, Karen Reue
Abstract
Fibrinolysis is initiated by tissue-type plasminogen activator (tPA) and inhibited by plasminogen activator inhibitor 1 (PAI-1). In obese humans, plasma PAI-1 and tPA proteins are increased, but PAI-1 dominates, leading to reduced fibrinolysis and thrombosis. To understand tPA–PAI-1 regulation in obesity, we focused on hepatocytes, a functionally important source of tPA and PAI-1 that sense obesity-induced metabolic stress. We showed that obese mice, like humans, had reduced fibrinolysis and increased plasma PAI-1 and tPA, due largely to their increased hepatocyte expression. A decrease in the PAI-1 (SERPINE1) gene corepressor Rev-Erbα increased PAI-1, which then increased the tPA gene PLAT via a PAI-1/LRP1/PKA/p-CREB1 pathway. This pathway was partially counterbalanced by increased DACH1, a PLAT-negative regulator. We focused on the PAI-1/PLAT pathway, which mitigates the reduction in fibrinolysis in obesity. Thus, silencing hepatocyte PAI-1, CREB1, or tPA in obese mice lowered plasma tPA and further impaired fibrinolysis. The PAI-1/PLAT pathway was present in primary human hepatocytes, and associations among PAI-1, tPA, and PLAT in livers from obese and lean humans were consistent with these findings. Knowledge of PAI-1 and tPA regulation in hepatocytes in obesity may suggest therapeutic strategies for improving fibrinolysis and lowering the risk of thrombosis in this setting.
Authors
Ze Zheng, Keiko Nakamura, Shana Gershbaum, Xiaobo Wang, Sherry Thomas, Marc Bessler, Beth Schrope, Abraham Krikhely, Rui-Ming Liu, Lale Ozcan, José A. López, Ira Tabas
Abstract
Skeletal muscle depends on the precise orchestration of contractile and metabolic gene expression programs to direct fiber type specification and to ensure muscle performance. Exactly how such fiber type-specific patterns of gene expression are established and maintained remains unclear, however. Here, we demonstrate that histone mono-methyltransferase MLL4 (KMT2D), an enhancer regulator enriched in slow myofibers, plays a critical role in controlling muscle fiber identity as well as muscle performance. Skeletal muscle-specific ablation of MLL4 in mice resulted in downregulation of the slow-oxidative myofiber gene program, decreased number of type I myofibers, and diminished mitochondrial respiration, which caused reductions in muscle fat utilization and endurance capacity during exercise. Genome-wide ChIP-seq and mRNA-seq analyses revealed that MLL4 directly binds to enhancers and functions as a coactivator of the myocyte enhancer factor 2 (MEF2) to activate transcription of slow-oxidative myofiber genes. Importantly, we also found that the MLL4 regulatory circuit is associated with muscle fiber type remodeling in humans. Thus, our results uncover a pivotal role for MLL4 in specifying structural and metabolic identities of myofibers that govern muscle performance. These findings provide new therapeutic opportunities for enhancing muscle fitness to combat a variety of metabolic and muscular diseases.
Authors
Lin Liu, Chenyun Ding, Tingting Fu, Zhenhua Feng, Ji-Eun Lee, Liwei Xiao, Zhisheng Xu, Yujing Yin, Qiqi Guo, Zongchao Sun, Wanping Sun, Yan Mao, Likun Yang, Zheng Zhou, Danxia Zhou, Leilei Xu, Zezhang Zhu, Yong Qiu, Kai Ge, Zhenji Gan
Abstract
Cachexia, a devastating wasting syndrome characterized by severe weight loss with specific losses of muscle and adipose tissue, is driven by reduced food intake, increased energy expenditure, excess catabolism, and inflammation. Cachexia is associated with poor prognosis and high mortality, and frequently occurs in patients with cancer, chronic kidney disease, infection, and many other illnesses. There is no effective treatment for this condition. Hypothalamic melanocortins have a potent and long-lasting inhibitory effect on feeding and anabolism, and pathophysiological processes increase melanocortin signaling tone leading to anorexia, metabolic changes, and eventual cachexia. We utilized three rat models of anorexia and cachexia (LPS, methylcholanthrene sarcoma, and 5/6 subtotal nephrectomy) to evaluate efficacy of TCMCB07, a synthetic antagonist of the melanocortin-4 receptor. Our data show that peripheral treatment of TCMCB07 with intraperitoneal, subcutaneous, and oral administration increased food intake and body weight, and preserved fat mass and lean mass during cachexia and LPS-induced anorexia. Furthermore, administration of TCMCB07 diminished hypothalamic inflammatory gene expression in cancer cachexia. These results suggest that peripheral TCMCB07 treatment effectively inhibits central melanocortin signaling and therefore stimulates appetite and enhances anabolism, indicating that TCMCB07 is a promising drug candidate to treat cachexia.
Authors
Xinxia Zhu, Michael F. Callahan, Kenneth A. Gruber, Marek Szumowski, Daniel L. Marks
Abstract
The brain has evolved in an environment where food sources are scarce and foraging for food is one of the major challenges for survival of the individual and species. Basic and clinical studies show that obesity/overnutrition leads to overwhelming changes in the brain in animals and humans. However, the exact mechanisms underlying the consequences of excessive energy intake are not well understood. Neurons expressing the neuropeptide hypocretin/orexin (Hcrt) in the lateral/perifonical hypothalamus (LH) are critical for homeostatic regulation, reward seeking, stress response, and cognitive functions. In this study, we examined adaptations in Hcrt cells regulating behavioral responses to salient stimuli in diet-induced obese mice. Our results demonstrated changes in primary cilia, synaptic transmission and plasticity, cellular responses to neurotransmitters necessary for reward seeking and stress responses in Hcrt neurons from obese mice. Activities of neuronal networks in the LH and hippocampus were impaired as a result of decreased hypocretinergic function. The weakened Hcrt system decreased reward seeking while altering responses to acute stress (stress coping strategy), which were reversed by selectively activating Hcrt cells with chemogenetics. Taken together, our data suggest that a deficiency in the Hcrt signaling may be a common cause of behavioral changes (such as lowered arousal, weakened reward seek and altered stress response) in obese animals.
Authors
Ying Tan, Fu Hang, Zhong-Wu Liu, Milan Stoiljkovic, Mingxing Wu, Yue Tu, Wenfei Han, Angela M. Lee, Craig Kelley, Mihaly Hajos, Lingeng Lu, Luis de Lecea, Ivan de Araujo, Marina Picciotto, Tamas L. Horvath, Xiao-Bing Gao
Abstract
Type 2 diabetes mellitus (T2DM) has become an expanding global public health problem. Although the glucocorticoid receptor (GR) is an important regulator of glucose metabolism, the relationship between circulating glucocorticoids (GCs) and the features of T2DM remains controversial. Here, we show that 17-hydroxyprogesterone (17-OHP), an intermediate steroid in the biosynthetic pathway that converts cholesterol to cortisol, binds to and stimulates the transcriptional activity of GR. Hepatic 17-OHP concentrations are increased in diabetic mice and patients due to aberrantly increased expression of Cyp17A1. Systemic administration of 17-OHP or overexpression of Cyp17A1 in the livers of lean mice promoted the pathogenesis of hyperglycemia and insulin resistance, whereas knockdown of Cyp17A1 abrogated metabolic disorders in obese mice. Therefore, our results identify a Cyp17A1/17-OHP/GR–dependent pathway in the liver that mediates obesity-induced hyperglycemia, suggesting that selectively targeting hepatic Cyp17A1 may provide a therapeutic avenue for treating T2DM.
Authors
Yan Lu, E Wang, Ying Chen, Bing Zhou, Jiejie Zhao, Liping Xiang, Yiling Qian, Jingjing Jiang, Lin Zhao, Xuelian Xiong, Zhiqiang Lu, Duojiao Wu, Bin Liu, Jing Yan, Rong Zhang, Huijie Zhang, Cheng Hu, Xiaoying Li
Copyright © 2021 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)