Identification of an Anti-Diabetic, Orally Available Small Molecule That
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Clinical and Translational Report Identification of an Anti-diabetic, Orally Available Small Molecule that Regulates TXNIP Expression and Glucagon Action Graphical Abstract Authors Lance A. Thielen, Junqin Chen, Gu Jing, ..., Praveen Sethupathy, Jason K. Kim, Anath Shalev Correspondence [email protected] In Brief Here, Thielen et al. show that a newly designed, orally available small molecule inhibited pancreatic islet TXNIP expression, glucagon secretion, hepatic glucagon action, glucose production, and steatosis, and exhibited strong anti- diabetic effects in mouse models of type 1 and type 2 diabetes, promising a distinct and innovative diabetes treatment approach. Highlights d The small molecule SRI-37330 inhibits TXNIP expression in mouse and human islets d SRI-37330 decreases glucagon secretion and action and blocks hepatic glucose output d Oral SRI-37330 reverses obesity- and STZ-induced diabetes and hepatic steatosis in mice d Its antidiabetic effects and safety profile make SRI-37330 an attractive drug candidate Thielen et al., 2020, Cell Metabolism 32, 1–13 September 1, 2020 ª 2020 Elsevier Inc. https://doi.org/10.1016/j.cmet.2020.07.002 ll Please cite this article in press as: Thielen et al., Identification of an Anti-diabetic, Orally Available Small Molecule that Regulates TXNIP Expression and Glucagon Action, Cell Metabolism (2020), https://doi.org/10.1016/j.cmet.2020.07.002 ll Clinical and Translational Report Identification of an Anti-diabetic, Orally Available Small Molecule that Regulates TXNIP Expression and Glucagon Action Lance A. Thielen,1 Junqin Chen,1 Gu Jing,1 Omar Moukha-Chafiq,2 Guanlan Xu,1 SeongHo Jo,1 Truman B. Grayson,1 Brian Lu,1 Peng Li,3 Corinne E. Augelli-Szafran,2 Mark J. Suto,2 Matt Kanke,4 Praveen Sethupathy,4 Jason K. Kim,5 and Anath Shalev1,6,* 1Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USA 2Drug Discovery Division, Southern Research, Birmingham, AL 35205, USA 3School of Nursing, University of Alabama at Birmingham, Birmingham, AL 35294, USA 4Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA 5Program in Molecular Medicine and Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA 6Lead Contact *Correspondence: [email protected] https://doi.org/10.1016/j.cmet.2020.07.002 SUMMARY Diabetes is characterized by hyperglycemia, loss of functional islet beta cell mass, deficiency of glucose- lowering insulin, and persistent alpha cell secretion of gluconeogenic glucagon. Still, no therapies that target these underlying processes are available. We therefore performed high-throughput screening of 300,000 compounds and extensive medicinal chemistry optimization and here report the discovery of SRI-37330, an orally bioavailable, non-toxic small molecule, which effectively rescued mice from streptozotocin- and obesity-induced (db/db) diabetes. Interestingly, in rat cells and in mouse and human islets, SRI-37330 in- hibited expression and signaling of thioredoxin-interacting protein, which we have previously found to be elevated in diabetes and to have detrimental effects on islet function. In addition, SRI-37330 treatment in- hibited glucagon secretion and function, reduced hepatic glucose production, and reversed hepatic steato- sis. Thus, these studies describe a newly designed chemical compound that, compared to currently available therapies, may provide a distinct and effective approach to treating diabetes. INTRODUCTION and Orci, 1975). Insufficient production of the glucose-lowering hormone insulin and high levels of the gluconeogenic hormone Type 2 diabetes (T2D) has become a worldwide epidemic and glucagon combine to exacerbate the hyperglycemia that is the poses major therapeutic challenges. Over the last several de- hallmark of T2D, leading to a vicious cycle of glucose toxicity cades, it has been recognized as a bihormonal disease distin- that furthers beta cell dysfunction (Poitout and Robertson, guished by the combination of hypoinsulinemia due to loss of 2002). However, while T2D management has improved signifi- functional pancreatic beta cell mass and hyperglucagonemia cantly over the years, therapies that target these underlying pro- due to persistent alpha-cell-mediated glucagon secretion (Unger cesses are still lacking. Context and Significance The global health problem of diabetes is getting worse, but therapies that target the underlying causes are still lacking. By screening 300,000 small molecules, researchers at Birmingham, Alabama identified a compound that downregulates the detrimental, pro-diabetic protein TXNIP in mouse and human pancreatic islets. When given orally to mice, this small mole- cule also lowered serum levels of glucagon, a counter-regulatory hormone to insulin that is elevated in diabetes and in- creases blood glucose levels. Furthermore, the compound prevented fatty liver, inhibited unnecessary glucose production by the liver, and reversed diabetes in different mouse models of type 1 and type 2 diabetes. Compared to currently available drugs, this compound may therefore provide an effective and highly promising new approach to diabetes therapy. Cell Metabolism 32, 1–13, September 1, 2020 ª 2020 Elsevier Inc. 1 Please cite this article in press as: Thielen et al., Identification of an Anti-diabetic, Orally Available Small Molecule that Regulates TXNIP Expression and Glucagon Action, Cell Metabolism (2020), https://doi.org/10.1016/j.cmet.2020.07.002 ll Clinical and Translational Report We previously identified thioredoxin-interacting protein regulated, whereas the insulin-like growth factor-1 receptor (TXNIP) as the top glucose-induced gene in a human islet gene (IGF-1R), which recently was found to inhibit TXNIP expression expression microarray study (Shalev et al., 2002) and as a critical (Nagaraj et al., 2018), was upregulated. In addition, V-MAF avian link between glucose toxicity and beta cell loss (Chen et al., musculoaponeurotic fibrosarcoma oncogene homolog A 2008b), suggesting that this arrestin protein may play an impor- (MAFA), an insulin transcription factor previously shown to be tant role in T2D. Indeed, TXNIP expression is not only upregu- downregulated by TXNIP (Xu et al., 2013), was upregulated by lated by glucose (Minn et al., 2005; Shalev et al., 2002); it is our TXNIP inhibitor. Similarly, Bcl-2-like 1 (BCL2L1), which is also increased in different mouse models of T2D and in human involved in the control of beta cell apoptosis and increased in islets from individuals with diabetes (Chen et al., 2008a, 2008b; beta-cell-specific TXNIP knockout mice (Chen et al., 2008a), Minn et al., 2005; Xu et al., 2013). Moreover, genetic TXNIP dele- and connective tissue growth factor (CTGF), which is involved tion has been shown to protect mice from diabetes and has in developmental beta cell proliferation (Riley et al., 2015) and beneficial effects on islet biology (Chen et al., 2008a; Lerner upregulated by TXNIP inhibition (Wu et al., 2018), were both up- et al., 2012; Xu et al., 2013). Together, this suggested that TXNIP regulated in response to SRI-37330. Finally, we also observed inhibition may represent an attractive novel approach to T2D lower expression of the inflammasome, NACHT, LRR, and PYD treatment, but no specific TXNIP inhibitors were available. The domain-containing protein 1 (NLRP1), consistent with the fact goal of the present studies was therefore to identify an orally that TXNIP has been shown to promote inflammasome activa- bioavailable, small molecule TXNIP inhibitor and test its effects tion (Zhou et al., 2010). in human islets and different mouse models of diabetes. We have previously shown that TXNIP expression, especially in the context of high glucose and diabetes, is regulated via a RESULTS AND DISCUSSION distinct E-box motif in the TXNIP promoter that is well conserved across species (Cha-Molstad et al., 2009; Minn et al., 2005). We High-throughput screening of 300,000 small molecules and therefore next investigated whether SRI-37330 confers its ef- several medicinal chemistry iterations, modifications, and opti- fects through this element. Indeed, while human TXNIP promoter mizations led to the identification of SRI-37330 (Figure 1A), a deletions of over 1,000 bp did not diminish the inhibitory effects lead compound, based on its efficacy of inhibiting TXNIP expres- of SRI-37330 as assessed by luciferase activity, mutation of the sion, its pharmacokinetic properties, favorable safety profile, E-box motif completely blunted these effects (Figure 2A). More- and lack of off-target liabilities at least in the currently available over, this E-box motif was able to confer SRI-37330 responsive- panel (Table S1A). Transient transfection experiments showed ness to a heterologous SV40 promoter (Figure 2B). Furthermore, that SRI-37330 inhibited the activity of the human TXNIP pro- chromatin immunoprecipitation revealed that SRI-37330 effec- moter in INS-1 cells by 70% (Figure 1B), consistent with inhibi- tively inhibited polymerase II (Pol II) binding to the E-box motif re- tion at the transcriptional level. SRI-37330 also inhibited endog- gion of the TXNIP promoter, but not to an upstream TXNIP pro- enous TXNIP mRNA expression as shown by seven-point dose- moter region or to an established Pol II binding site in insulin response qRT-PCR assays (Figure 1C), revealing an IC50 of receptor