Obesity is a major risk factor for developing nonalcoholic fatty-liver disease (NAFLD). NAFLD is the most common form of chronic liver disease and closely associated with insulin resistance, ultimately leading to cirrhosis and hepatocellular carcinoma. However, knowledge of the intracellular regulators of obesity-linked fatty-liver disease remains incomplete. Here we showed that hepatic Rho-kinase 1 (ROCK1) drives obesity-induced steatosis in mice through stimulation of de novo lipogenesis. Mice lacking ROCK1 in the liver were resistant to diet-induced obesity due to increased energy expenditure and thermogenic gene expression. Constitutive expression of hepatic ROCK1 was sufficient to promote adiposity, insulin resistance, and hepatic lipid accumulation in mice fed a high-fat diet. Correspondingly, liver-specific ROCK1 deletion prevented the development of severe hepatic steatosis and reduced hyperglycemia in obese diabetic (ob/ob) mice. Of pathophysiologic significance, hepatic ROCK1 was markedly up-regulated in humans with fatty-liver disease and correlated with risk factors clustering around NAFLD and insulin resistance. Mechanistically, we found that hepatic ROCK1 suppresses AMPK activity and a ROCK1-AMPK pathway is necessary to mediate cannabinoid-induced lipogenesis in the liver. Furthermore, treatment with metformin, the most widely used anti-diabetes drug, reduced hepatic lipid accumulation by inactivating ROCK1, resulting in activation of AMPK downstream signaling. Taken together, our findings establish a ROCK1-AMPK signaling axis that regulates de novo lipogenesis, providing a unique target for treating obesity-related metabolic disorders such as NAFLD.
Hu Huang, Seung-Hwan Lee, Inês Sousa-Lima, Sang Soo Kim, Won Min Hwang, Yossi Dagon, Won-Mo Yang, Sungman Cho, Min-Cheol Kang, Ji A Seo, Munehiko Shibata, Hyunsoo Cho, Getachew Debas Belew, Jinhyuk Bhin, Bhavna N. Desai, Min Jeong Ryu, Minho Shong, Peixin Li, Hua Meng, Byung-Hong Chung, Daehee Hwang, Min Seon Kim, Kyong Soo Park, Paula Macedo, Morris White, John Jones, Young-Bum Kim
Sugar- and lipid-derived aldehydes are reactive carbonyl species (RCS) frequently used as surrogate markers of oxidative stress in obesity. A pathogenic role for RCS in metabolic diseases of obesity remains controversial, however, due in part to their highly diffuse and broad reactivity, and to lack of specific RCS-scavenging therapies. Naturally occurring histidine dipeptides (e.g., anserine and carnosine) possess RCS reactivity, but their therapeutic potential in humans is limited by serum carnosinases. Here we present the rational design, characterization and pharmacological evaluation of ‘carnosinol’ (i.e. (2S)-2-(3-amino propanoylamino)-3-(1H-imidazol-5-yl)propanol) a derivative of carnosine with high oral bioavailability that is resistant to carnosinases. Carnosinol displayed a suitable ADMET profile and was determined to have the greatest potency and selectivity toward α,β-unsaturated aldehydes (e.g. 4-hydroxynonenal, HNE, acrolein) among all others so far reported. In rodent models of diet-induced obesity and metabolic syndrome, carnosinol dose-dependently attenuated HNE-adduct formation in liver and skeletal muscle while simultaneously mitigating inflammation, dyslipidemia, insulin resistance, and steatohepatitis. These improvements in metabolic parameters with carnosinol were not due to changes in energy expenditure, physical activity, adiposity or body weight. Collectively, our findings illustrate a pathogenic role for RCS in obesity-related metabolic disorders, and provide validation for a promising new class of carbonyl-scavenging therapeutic compounds rationally derived from carnosine.
Ethan J. Anderson, Giulio Vistoli, Lalage A. Katunga, Katsuhiko Funai, Luca Regazzoni, T. Blake Monroe, Ettore Gilardoni, Luca Cannizzaro, Mara Colzani, Danilo De Maddis, Giuseppe Rossoni, Renato Canevotti, Stefania Gagliardi, Marina Carini, Giancarlo Aldini
The M2 isoform of pyruvate kinase (PKM2) is highly expressed in most cancer cells, and has been studied extensively as a driver of oncogenic metabolism. In contrast, the role of PKM2 in nontransformed cells is little studied, and nearly nothing is known of its role, if any, in quiescent cells. We show here that endothelial cells express PKM2 almost exclusively over PKM1. In proliferating endothelial cells, PKM2 is required to suppress p53 and maintain cell cycle progression. In sharp contrast, PKM2 has a strikingly different role in quiescent endothelial cells, where inhibition of PKM2 leads to degeneration of tight junctions and barrier function. Mechanistically, PKM2 regulates barrier function independently of its canonical activity as a pyruvate kinase. Instead, PKM2 suppresses NF-kB and its downstream target, the vascular permeability factor angiopoietin 2. As a consequence, loss of endothelial cell PKM2 in vivo predisposes mice to VEGF-induced vascular leak, and to severe bacteremia and death in response to sepsis. Together, these data demonstrate new roles of PKM2 in quiescent cells, and highlight the need for caution in developing cancer therapies that target PKM2.
Boa Kim, Cholsoon Jang, Harita Dharaneeswaran, Jian Li, Mohit Bhide, Steven Yang, Kristina Li, Zolt Arany
The glucocorticoid receptor (GR) is a major drug target in inflammatory disease. However, chronic glucocorticoid (GC) treatment leads to disordered energy metabolism, including increased weight gain, adiposity, and hepatosteatosis — all programs modulated by the circadian clock. We demonstrated that while antiinflammatory GC actions were maintained irrespective of dosing time, the liver was significantly more GC sensitive during the day. Temporal segregation of GC action was underpinned by a physical interaction of GR with the circadian transcription factor REVERBa and co-binding with liver-specific hepatocyte nuclear transcription factors (HNFs) on chromatin. REVERBa promoted efficient GR recruitment to chromatin during the day, acting in part by maintaining histone acetylation, with REVERBa-dependent GC responses providing segregation of carbohydrate and lipid metabolism. Importantly, deletion of Reverba inverted circadian liver GC sensitivity and protected mice from hepatosteatosis induced by chronic GC administration. Our results reveal a mechanism by which the circadian clock acts through REVERBa in liver on elements bound by HNF4A/HNF6 to direct GR action on energy metabolism.
Giorgio Caratti, Mudassar Iqbal, Louise Hunter, Donghwan Kim, Ping Wang, Ryan M. Vonslow, Nicola Begley, Abigail J. Tetley, Joanna L. Woodburn, Marie Pariollaud, Robert Maidstone, Ian J. Donaldson, Zhenguang Zhang, Louise M. Ince, Gareth Kitchen, Matthew Baxter, Toryn M. Poolman, Dion A. Daniels, David R. Stirling, Chad Brocker, Frank Gonzalez, Andrew S.I. Loudon, David A. Bechtold, Magnus Rattray, Laura C. Matthews, David W. Ray
The t-SNARE protein SNAP23 conventionally functions as a component of the cellular machinery required for intracellular transport vesicle fusion with target membranes and has been implicated in the regulation of fasting glucose levels, BMI, and type 2 diabetes. Surprisingly, we observed that adipocyte-specific KO of SNAP23 in mice resulted in a temporal development of severe generalized lipodystrophy associated with adipose tissue inflammation, insulin resistance, hyperglycemia, liver steatosis, and early death. This resulted from adipocyte cell death associated with an inhibition of macroautophagy and lysosomal degradation of the proapoptotic regulator BAX, with increased BAX activation. BAX colocalized with LC3-positive autophagic vacuoles and was increased upon treatment with lysosome inhibitors. Moreover, BAX deficiency suppressed the lipodystrophic phenotype in the adipocyte-specific SNAP23-KO mice and prevented cell death. In addition, ATG9 deficiency phenocopied SNAP23 deficiency, whereas ATG7 deficiency had no effect on BAX protein levels, BAX activation, or apoptotic cell death. These data demonstrate a role for SNAP23 in the control of macroautophagy and programmed cell death through an ATG9-dependent, but ATG7-independent, pathway regulating BAX protein levels and BAX activation.
Daorong Feng, Dulguun Amgalan, Rajat Singh, Jianwen Wei, Jennifer Wen, Tszki Peter Wei, Timothy E. McGraw, Richard N. Kitsis, Jeffrey E. Pessin
Prostate cancer is an androgen-dependent disease subject to interactions between the tumor epithelia and its microenvironment. Here, we found epigenetic changes in cancer-associated prostatic fibroblasts (CAF) initiated a cascade of stromal-epithelial interactions. This facilitated lethal prostate cancer growth and development of resistance to androgen signaling deprivation therapy (ADT). We identified that a Ras inhibitor, RASAL3, is epigenetically silenced in human prostatic CAF, leading to oncogenic Ras activity driving macropinocytosis-mediated glutamine synthesis. Interestingly, ADT further promoted RASAL3 epigenetic silencing and glutamine secretion by prostatic fibroblasts. In a orthotopic xenograft model, subsequent inhibition of macropinocytosis and glutamine transport resulted in antitumor effects. Stromal glutamine served as a source of energy through anaplerosis and as a mediator of neuroendocrine differentiation for prostate adenocarcinoma. Antagonizing the uptake of glutamine restored sensitivity to ADT in a castrate resistant xenograft model. In validating these findings, we found that prostate cancer patients on ADT with therapeutic resistance had elevated blood glutamine levels compared to those with therapeutically responsive disease (odds ratio = 7.451, P = 0.02). Identification of epigenetic regulation of RAS activity in prostatic CAF revealed RASAL3 as a sensor for metabolic and neuroendocrine reprogramming in prostate cancer patients failing ADT.
Rajeev Mishra, Subhash Haldar, Veronica Placencio, Anisha Madhav, Krizia Rohena-Rivera, Priyanka Agarwal, Frank Duong, Bryan Angara, Manisha Tripathi, Zhenqiu Liu, Roberta A. Gottlieb, Shawn Wagner, Edwin M. Posadas, Neil A. Bhowmick
Movement of circulating fatty acids (FAs) to parenchymal cells requires their transfer across the endothelial cell (EC) barrier. The multi-ligand receptor cluster of differentiation 36 (CD36) facilitates tissue FA uptake and is expressed in ECs and parenchymal cells such as myocytes and adipocytes. Whether tissue uptake of FAs is dependent on EC or parenchymal cell CD36, or both, is unknown. Using a cell-specific deletion approach, we show that EC, but not parenchymal cell CD36 deletion increased fasting plasma FAs and postprandial triglycerides. EC-Cd36 knockout mice had reduced uptake of radiolabeled long chain FAs into heart, skeletal muscle, and brown adipose tissue; these uptake studies were replicated using [11C]palmitate PET scans. High fat diet-fed EC-CD36 deficient mice had improved glucose tolerance and insulin sensitivity. Both EC and cardiomyocyte (CM) deletion of CD36 reduced heart lipid droplet accumulation after fasting, but CM deletion did not affect heart glucose or FA uptake. Heart expression of several genes modulating glucose metabolism and insulin action increased with EC-CD36 deletion, but decreased with CM deletion. In conclusion, EC CD36 acts as a gatekeeper for parenchymal cell FA uptake, with important downstream effects on glucose utilization and insulin action.
Ni-Huiping Son, Debapriya Basu, Dmitri Samovski, Terri A. Pietka, Vivek S. Peche, Florian Willecke, Xiang Fang, Shui-Qing Yu, Diego Scerbo, Hye Rim Chang, Fei Sun, Svetlana Bagdasarov, Konstantinos Drosatos, Steve T. Yeh, Adam E. Mullick, Kooresh I. Shoghi, Namrata Gumaste, KyeongJin Kim, Lesley-Ann M. Huggins, Tenzin Lhakhang, Nada A. Abumrad, Ira J. Goldberg
Control of cellular metabolism is critical for efficient cell function, although little is known about the interplay between cell subset-specific metabolites in situ, especially in the tumor setting. Here, we determine how a macrophage-specific metabolite, itaconic acid, can regulate tumor progression in the peritoneum. We show peritoneal tumors (B16 melanoma or ID8 ovarian carcinoma) elicited a fatty acid oxidation-mediated increase in oxidative phosphorylation (OXPHOS) and glycolysis in peritoneal tissue-resident macrophages (pResMφ). Unbiased metabolomics identified itaconic acid, the product of Irg1-mediated catabolism of mitochondrial cis-aconitate, among the most highly upregulated metabolites in pResMφ of tumor-bearing mice. Administration of lentivirally-encoded Irg1 shRNA significantly reduced peritoneal tumors. This resulted in reductions in OXPHOS and OXPHOS-driven production of reactive oxygen species (ROS) in pResMφ and ROS-mediated MAP kinase activation in tumor cells. Our findings demonstrate that tumors profoundly alter pResMφ metabolism, leading to the production of itaconic acid, which potentiates tumor growth. Monocytes isolated from ovarian carcinoma patient ascites fluid expressed significantly elevated levels of Irg1. Therefore, Irg1 in pResMφ represents a potential therapeutic target for peritoneal tumors.
Jonathan M. Weiss, Luke C. Davies, Megan Karwan, Lilia Ileva, Michelle K. Ozaki, Robert Y.S. Cheng, Lisa A. Ridnour, Christina M. Annunziata, David A. Wink, Daniel W. McVicar
Jumonji D3 (JMJD3) histone demethylase epigenetically regulates development and differentiation, immunity, and tumorigenesis by demethylating a gene repression histone mark, H3K27-me3, but a role for JMJD3 in metabolic regulation has not been described. SIRT1 deacetylase maintains energy balance during fasting by directly activating both hepatic gluconeogenic and mitochondrial fatty acid β-oxidation genes, but the underlying epigenetic and gene-specific mechanisms remain unclear. In this study, JMJD3 was identified unexpectedly as a gene-specific transcriptional partner of SIRT1 and epigenetically activated mitochondrial β-oxidation, but not gluconeogenic, genes during fasting. Mechanistically, JMJD3, together with SIRT1 and the nuclear receptor PPARα, formed a positive autoregulatory loop upon fasting-activated PKA signaling and epigenetically activated β-oxidation–promoting genes, including Fgf21, Cpt1a, and Mcad. Liver-specific downregulation of JMJD3 resulted in intrinsic defects in β-oxidation, which contributed to hepatosteatosis as well as glucose and insulin intolerance. Remarkably, the lipid-lowering effects by JMJD3 or SIRT1 in diet-induced obese mice were mutually interdependent. JMJD3 histone demethylase may serve as an epigenetic drug target for obesity, hepatosteatosis, and type 2 diabetes that allows selective lowering of lipid levels without increasing glucose levels.
Sunmi Seok, Young-Chae Kim, Sangwon Byun, Sunge Choi, Zhen Xiao, Naoki Iwamori, Yang Zhang, Chaochen Wang, Jian Ma, Kai Ge, Byron Kemper, Jongsook Kim Kemper
BACKGROUND. Recombinant leptin (metreleptin) ameliorates hyperphagia and metabolic abnormalities in leptin-deficient humans with lipodystrophy. We aimed to determine whether metreleptin improves glucose and lipid metabolism in humans when food intake is held constant. METHODS. Patients with lipodystrophy were hospitalized for 19 days with food intake held constant by controlled diet in an inpatient metabolic ward. In a non-randomized cross-over design, previously metreleptin-treated patients (n = 8) were continued on-metreleptin for five days, and off-metreleptin for the next 14 days (withdrawal cohort). This order was reversed in metreleptin-naïve patients (n = 14), who were restudied after six months of metreleptin treatment on an ad libitum diet (initiation cohort). Outcomes included insulin sensitivity by hyperinsulinemic-euglycemic clamp, fasting glucose and triglycerides, lipolysis measured using isotopic tracers, and liver fat by magnetic resonance spectroscopy. RESULTS. With food intake constant, peripheral insulin sensitivity decreased by 41% after stopping metreleptin for 14 days (withdrawal cohort) and increased by 32% after starting metreleptin for 14 days (initiation cohort). In the initiation cohort only, metreleptin decreased fasting glucose by 11%, triglycerides by 41%, and increased hepatic insulin sensitivity. Liver fat decreased from 21.8% to 18.7%. In the initiation cohort, lipolysis did not change independent of food intake, but decreased after six months on metreleptin on an ad libitum diet by 30% (palmitate turnover) to 35% (glycerol turnover). CONCLUSION. Using lipodystrophy as a human model of leptin deficiency and replacement, we showed that metreleptin improves insulin sensitivity, and decreases hepatic and circulating triglycerides, independent of its effects on food intake. TRIAL REGISTRATION. ClinicalTrials.gov, NCT01778556. FUNDING. This research was supported by the intramural research program of the National Institute of Diabetes and Digestive and Kidney Diseases.
Rebecca J. Brown, Areli Valencia, Megan Startzell, Elaine Cochran, Peter J. Walter, H. Martin Garraffo, Hongyi Cai, Ahmed M. Gharib, Ronald Ouwerkerk, Amber B. Courville, Shanna Bernstein, Robert J. Brychta, Kong Y. Chen, Mary Walter, Sungyoung Auh, Phillip Gorden