About 25% of people within the general population are insulin resistant, increasing the risk for type 2 diabetes (T2D) and metabolic disease. Transcriptomic analysis of iPS cells differentiated into myoblasts (iMyos) from insulin resistant (I-Res) versus insulin sensitive (I-Sen) non-diabetic individuals reveals 306 genes increased and 271 genes decreased in expression in iMyos from insulin resistant donors with differences of 2-folds or more. Over 30 of the genes changed in I-Res iMyos are associated with T2D by SNP polymorphisms and functionally linked to insulin action and control of metabolism. Interestingly, we also identified >1500 differences in gene expression that were dependent on sex of the cell donor, some of which modified the insulin resistance effects. Many of these sex-differences were associated with increased DNA methylation in cells from females and reversed by 5-azacytidine. By contrast, the insulin sensitivity differences were not reversed and thus appear to reflect genetic or methylation-independent epigenetic effects.
Nida Haider, C. Ronald Kahn
Pancreatic beta-cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair beta-cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion are similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on beta-cell mRNA translation. Prior to induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also of mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex-vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our study uncovered a translational regulatory circuit during beta-cell glucose toxicity that impairs expression of proteins with critical roles in beta-cell function.
Abigael Cheruiyot, Jennifer Hollister-Lock, Brooke A. Sullivan, Hui Pan, Jonathan M. Dreyfuss, Susan Bonner-Weir, Jean E. Schaffer
Glycogen storage disease type III (GSDIII) is a rare inborn error of metabolism affecting liver, skeletal muscle, and heart due to mutations of the AGL gene encoding for the glycogen debranching enzyme (GDE). No curative treatment exists for GSDIII. The 4.6 kb GDE cDNA represents the major technical challenge toward the development of a single recombinant adeno-associated virus (rAAV)-derived vector gene therapy strategy. Using information on GDE structure and molecular modeling, we generated multiple truncated GDEs retaining activity. Among them, an N-terminal-truncated mutant ∆Nter2-GDE had a similar efficacy in vivo compared to the full-size enzyme. A rAAV vector expressing ∆Nter2-GDE allowed significant glycogen reduction in heart and muscle of Agl–/– mice three months after intravenous injection, as well as normalization of histology features and restoration of muscle strength. Similarly, glycogen accumulation and histological features were corrected in a recently generated Agl–/– rat model. Finally, transduction with rAAV vectors encoding ∆Nter2-GDE corrected glycogen accumulation in an in vitro human skeletal muscle cellular model of GSDIII. In conclusion, our results demonstrated the ability of a single rAAV vector expressing a functional mini-GDE transgene to correct the muscle and heart phenotype in multiple models of GSDIII, supporting its clinical translation to GSDIII patients.
Antoine Gardin, Jérémy Rouillon, Valle Montalvo-Romeral, Lucille Rossiaud, Patrice Vidal, Romain Launay, Mallaury Vie, Youssef Krimi Benchekroun, Jérémie Cosette, Bérangère Bertin, Tiziana La Bella, Guillaume Dubreuil, Justine Nozi, Louisa Jauze, Romain Fragnoud, Nathalie F. Daniele, Laetitia Van Wittenberghe, Jérémy Esque, Isabelle André, Xavier Nissan, Lucile Hoch, Giuseppe Ronzitti
While the poor prognosis of glioblastoma arises from the invasion of a subset of tumor cells, little is known of the metabolic alterations within these cells that fuel invasion. We integrated spatially addressable hydrogel biomaterial platforms, patient site-directed biopsies, and multi-omics analyses to define metabolic drivers of invasive glioblastoma cells. Metabolomics and lipidomics revealed elevations in the redox buffers cystathionine, hexosylceramides, and glucosyl ceramides in the invasive front of both hydrogel-cultured tumors and patient site-directed biopsies, with immunofluorescence indicating elevated reactive oxygen species (ROS) markers in invasive cells. Transcriptomics confirmed upregulation of ROS-producing and response genes at the invasive front in both hydrogel models and patient tumors. Amongst oncologic ROS, H2O2 specifically promoted glioblastoma invasion in 3D hydrogel spheroid cultures. A CRISPR metabolic gene screen revealed cystathionine gamma-lyase (CTH), which converts cystathionine to the non-essential amino acid cysteine in the transsulfuration pathway, to be essential for glioblastoma invasion. Correspondingly, supplementing CTH knockdown cells with exogenous cysteine rescued invasion. Pharmacologic CTH inhibition suppressed glioblastoma invasion, while CTH knockdown slowed glioblastoma invasion in vivo. Our studies highlight the importance of ROS metabolism in invasive glioblastoma cells and support further exploration of the transsulfuration pathway as a mechanistic and therapeutic target.
Joseph H. Garcia, Erin A. Akins, Saket Jain, Kayla J. Wolf, Jason Zhang, Nikita Choudhary, Meeki Lad, Poojan Shukla, Jennifer Rios, Kyounghee Seo, Sabraj A. Gill, William H. Carson, Luis R. Carrete, Allison C. Zheng, David R. Raleigh, Sanjay Kumar, Manish K. Aghi
Interplay between energy-storing white adipose cells and thermogenic beige adipocytes contributes to obesity and insulin resistance. Irrespective of specialized niche, adipocytes require the activity of the nuclear receptor PPARγ for proper function. Exposure to cold or adrenergic signaling enriches thermogenic cells though multiple pathways that act synergistically with PPARγ; however, the molecular mechanisms by which PPARγ licenses white adipose tissue to preferentially adopt a thermogenic or white adipose fate in response to dietary cues or thermoneutral conditions are not fully elucidated. Here, we show that a PPARγ/long noncoding RNA (lncRNA) axis integrates canonical and noncanonical thermogenesis to restrain white adipose tissue heat dissipation during thermoneutrality and diet-induced obesity. Pharmacologic inhibition or genetic deletion of the lncRNA Lexis enhances uncoupling protein 1–dependent (UCP1-dependent) and -independent thermogenesis. Adipose-specific deletion of Lexis counteracted diet-induced obesity, improved insulin sensitivity, and enhanced energy expenditure. Single-nuclei transcriptomics revealed that Lexis regulates a distinct population of thermogenic adipocytes. We systematically map Lexis motif preferences and show that it regulates the thermogenic program through the activity of the metabolic GWAS gene and WNT modulator TCF7L2. Collectively, our studies uncover a new mode of crosstalk between PPARγ and WNT that preserves white adipose tissue plasticity.
Zhengyi Zhang, Ya Cui, Vivien Su, Dan Wang, Marcus J. Tol, Lijing Cheng, Xiaohui Wu, Jason Kim, Prashant Rajbhandari, Sicheng Zhang, Wei Li, Peter Tontonoz, Claudio J. Villanueva, Tamer Sallam
The G protein-coupled receptor 84 (GPR84), a medium-chain fatty acid receptor, has garnered attention because of its potential involvement in a range of metabolic conditions. However, the precise mechanisms underlying this effect remain elusive. Our study has shed light on the pivotal role of GPR84, revealing its robust expression and functional significance within the brown adipose tissue (BAT). Mice lacking GPR84 exhibited increased lipid accumulation in BAT, rendering them more susceptible to cold exposure, and displaying reduced BAT activity compared to their wild-type counterparts. Our in vitro experiments with primary brown adipocytes from GPR84 knockout mice revealed diminished expression of thermogenic genes and reduced O2 consumption. Furthermore, the application of the GPR84 agonist 6-OAU counteracted these effects, effectively reinstating the brown adipocyte activity. These compelling in vivo and in vitro findings converge to highlight mitochondrial dysfunction as the primary cause of BAT anomalies in GPR84 knockout mice. The activation of GPR84 induced an increase in intracellular Ca2+ levels, which intricately influences mitochondrial respiration. By modulating mitochondrial Ca2+ levels and respiration, GPR84 has emerged as a potent molecule involved in BAT activity. These findings suggested that GPR84 is a potential therapeutic target for invigorating BAT and ameliorating metabolic disorders.
Xuenan Sun, Yu A. An, Vivian A. Paschoal, Camila O. De Souza, May-yun Wang, Lavanya Vishvanath, Lorena M.A. Bueno, Ayanna S. Cobb, Joseph A. Nieto Carrion, Madison E. Ibe, Chao Li, Harrison A. Kidd, Shiuhwei Chen, Wenhong Li, Rana K. Gupta, Da Young Oh
Why apolipoprotein AV (APOA5) deficiency causes hypertriglyceridemia has remained unclear, but we suspected that the underlying cause was reduced amounts of lipoprotein lipase (LPL) in capillaries. By routine immunohistochemistry, we observed reduced LPL staining of heart and brown adipose tissue (BAT) capillaries in Apoa5–/– mice. Also, after an intravenous injection of LPL-, CD31-, and GPIHBP1-specific monoclonal antibodies, the binding of LPL antibodies to heart and BAT capillaries (relative to CD31 or GPIHBP1 antibodies) was reduced in Apoa5–/– mice. LPL levels in the postheparin plasma were also lower in Apoa5–/– mice. We suspected that a recent biochemical observation—that APOA5 binds to the ANGPTL3/8 complex and suppresses its capacity to inhibit LPL catalytic activity—could be related to the low intracapillary LPL levels in Apoa5–/– mice. We showed that an ANGPTL3/8-specific monoclonal antibody (IBA490) and APOA5 normalize plasma triglyceride levels and intracapillary LPL levels in Apoa5–/– mice. We also showed that ANGPTL3/8 detaches LPL from HSPGs and GPIHBP1 on the surface of cells and that the LPL detachment is blocked by IBA490 and APOA5. Our studies explain the hypertriglyceridemia in Apoa5–/– mice and further illuminate the molecular mechanisms that regulate plasma triglyceride metabolism.
Ye Yang, Anne P. Beigneux, Wenxin Song, Le Phuong Nguyen, Hyesoo Jung, Yiping Tu, Thomas A. Weston, Caitlyn M. Tran, Katherine Xie, Rachel G. Yu, Anh P. Tran, Kazuya Miyashita, Katsuyuki Nakajima, Masami Murakami, Yan Q. Chen, Eugene Y. Zhen, Joonyoung R. Kim, Paul H. Kim, Gabriel Birrane, Peter Tontonoz, Michael Ploug, Robert J. Konrad, Loren G. Fong, Stephen G. Young
Glycogen storage disease type 1a (GSD1a) is caused by a congenital deficiency of glucose-6-phosphatase-alpha (G6Pase-α, encoded by G6PC), primarily associated with life-threatening hypoglycemia. Although strict dietary management substantially improves the life expectancy, patients still suffer from intermittent hypoglycemia and develop hepatic complications. Emerging therapies utilizing new modalities such as adeno-associated virus and mRNA with lipid nanoparticles are under development for GSD1a, but potentially require complicated glycemic management throughout life. Here, we present a oligonucleotide-based therapy to produce intact G6Pase-α from a pathogenic human variant, G6PC c.648G>T, the most prevalent variant in East Asia causing aberrant splicing of G6PC. DS-4108b, a splice-switching oligonucleotide, was designed to correct this aberrant splicing, especially in liver. A generated mouse strain with homozygous knock-in of this variant well reflected the pathophysiology of GSD1a patients. DS-4108b recovered hepatic G6Pase activity through splicing correction and prevented hypoglycemia and various hepatic abnormalities in the mice. Moreover, DS-4108b exhibited long-lasting efficacy for more than 12 weeks in the mice with a single dose and favorable pharmacokinetics and tolerability in mice and monkeys. Taking these findings together, this oligonucleotide-based therapy could provide a sustainable and curative therapeutic option under easy disease management for GSD1a patients with G6PC c.648G>T.
Kentaro Ito, Go Tajima, Chikako Kamisato, Miyuki Tsumura, Mitsuhiro Iwamoto, Yukiko Sekiguchi, Yukinobu Numata, Kyoko Watanabe, Yoshiyuki Yabe, Satomi Kanki, Yusuke Fujieda, Koichi Goto, Yoshitaka Sogawa, Masataka Oitate, Hiroyuki Nagase, Shinnosuke Tsuji, Tomohiro Nishizawa, Masayo Kakuta, Takeshi Masuda, Yoshiyuki Onishi, Makoto Koizumi, Hidefumi Nakamura, Satoshi Okada, Masafumi Matsuo, Kiyosumi Takaishi
The comprehensive assessment of long-term effects of reducing intake of energy (CALERIE-II; NCT00427193) clinical trial established that caloric restriction (CR) in humans lowers inflammation. The identity and mechanism of endogenous CR-mimetics that can be deployed to control obesity-associated inflammation and diseases are not well understood. Our studies have found that 2 years of 14% sustained CR in humans inhibits the expression of the matricellular protein, secreted protein acidic and rich in cysteine (SPARC), in adipose tissue. In mice, adipose tissue remodeling caused by weight loss through CR and low-protein diet feeding decreased, while high-fat diet–induced (HFD-induced) obesity increased SPARC expression in adipose tissue. Inducible SPARC downregulation in adult mice mimicked CR’s effects on lowering adiposity by regulating energy expenditure. Deletion of SPARC in adipocytes was sufficient to protect mice against HFD-induced adiposity, chronic inflammation, and metabolic dysfunction. Mechanistically, SPARC activates the NLRP3 inflammasome at the priming step and downregulation of SPARC lowers macrophage inflammation in adipose tissue, while excess SPARC activated macrophages via JNK signaling. Collectively, reduction of adipocyte-derived SPARC confers CR-like metabolic and antiinflammatory benefits in obesity by serving as an immunometabolic checkpoint of inflammation.
Seungjin Ryu, Olga Spadaro, Sviatoslav Sidorov, Aileen H. Lee, Sonia Caprio, Christopher Morrison, Steven R. Smith, Eric Ravussin, Irina Shchukina, Maxim N. Artyomov, Yun-Hee Youm, Vishwa Deep Dixit
Background: Proglucagon can be processed to Glucagon-Like Peptide-1 (GLP-1) within the islet but its contribution to islet function in humans remains unknown. We sought to understand whether ‘pancreatic’ GLP-1 alters islet function in humans and whether this is affected by type 2 diabetes.Methods: We therefore studied individuals with and without type 2 diabetes on 2 occasions in random order. On one occasion exendin 9-39, a competitive antagonist of the GLP-1 Receptor (GLP1R), was infused, while on the other saline was infused. The tracer dilution technique ([3-3H] glucose) was used to measure glucose turnover during fasting and during a hyperglycemic clamp.Results: Exendin 9-39 increased fasting glucose concentrations; fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed. In people with type 2 diabetes fasting glucagon concentrations were markedly elevated and persisted despite hyperglycemia. This impaired suppression of endogenous glucose production by hyperglycemia. These data show that GLP1R blockade impairs islet function, implying that intra-islet GLP1R activation alters islet responses to glucose and does so to a greater degree in people with type 2 diabetes.
Andrew A. Welch, Rahele A. Farahani, Aoife M. Egan, Marcello C. Laurenti, Maya Zeini, Max Vella, Kent R. Bailey, Claudio Cobelli, Chiara Dalla Dalla Man, Aleksey Matveyenko, Adrian Vella