Diabetes treatment by conversion of gut epithelial cells to insulin-producing cells.

Insulin-deficient (type 1) diabetes is treated by providing insulin to maintain euglycemia. The current standard of care is a quasi-closed loop integrating automated insulin delivery with a continuous glucose monitoring sensor. Cell replacement technologies are advancing as an alternative treatment and have been tested as surrogates to cadaveric islets in transplants. In addition, immunomodulatory treatments to delay the onset of type 1 diabetes in high-risk (stage 2) individuals have gained regulatory approval. We have pioneered a cell conversion approach to restore insulin production through pharmacological conversion of intestinal epithelial cells into insulin-producing cells. We have advanced this approach along a translational trajectory through the discovery of small molecule forkhead box protein O1 inhibitors. When administered to different rodent models of insulin-deficient diabetes, these inhibitors have resulted in robust glucose-lowering responses and generation of insulin-producing cells in the gut epithelium. We review past work and delineate a path to human clinical trials.

Chemical induction of gut ß-like-cells by combined FoxO1/Notch inhibition as a glucose-lowering treatment for diabetes.

OBJECTIVE: Lifelong insulin replacement remains the mainstay of type 1 diabetes treatment. Genetic FoxO1 ablation promotes enteroendocrine cell (EECs) conversion into glucose-responsive ß-like cells. Here, we tested whether chemical FoxO1 inhibitors can generate ß-like gut cells. METHODS: We used Ngn3-or Villin-driven FoxO1 ablation to capture the distinctive developmental effects of FoxO1 on EEC pool. We combined FoxO1 ablation with Notch inhibition to enhance the expansion of EEC pool. We tested the ability of an orally available small molecule of FoxO1 inhibitor, Cpd10, to phenocopy genetic ablation of FoxO1. We evaluated the therapeutic impact of genetic ablation or chemical inhibition of FoxO1 on insulin-deficient diabetes in Ins2Akita/+ mice. RESULTS: Pan-intestinal epithelial FoxO1 ablation expanded the EEC pool, induced ß-like cells, and improved glucose tolerance in Ins2Akita/+ mice. This genetic effect was phenocopied by Cpd10. Cpd10 induced ß-like cells that released insulin in response to glucose in gut organoids, and this effect was enhanced by the Notch inhibitor, DBZ. In Ins2Akita/+ mice, a five-day course of either Cpd10 or DBZ induced intestinal insulin-immunoreactive ß-like cells, lowered glycemia, and increased plasma insulin levels without apparent adverse effects. CONCLUSION: These results provide proof of principle of gut cell conversion into ß-like cells by a small molecule FoxO1 inhibitor, paving the way for clinical applications.

A FOXO1-dependent transcription network is a targetable vulnerability of mantle cell lymphomas.

Targeting lineage-defined transcriptional dependencies has emerged as an effective therapeutic strategy in cancer treatment. Through screening for molecular vulnerabilities of mantle cell lymphoma (MCL), we identified a set of transcription factors (TFs) including FOXO1, EBF1, PAX5, and IRF4 that are essential for MCL propagation. Integrated chromatin immunoprecipitation and sequencing (ChIP-Seq) with transcriptional network reconstruction analysis revealed FOXO1 as a master regulator that acts upstream in the regulatory TF hierarchy. FOXO1 is both necessary and sufficient to drive MCL lineage commitment through supporting the lineage-specific transcription programs. We further show that FOXO1, but not its close paralog FOXO3, can reprogram myeloid leukemia cells and induce B-lineage gene expression. Finally, we demonstrate that cpd10, a small molecule identified from an enriched FOXO1 inhibitor library, induces a robust cytotoxic response in MCL cells in vitro and suppresses MCL progression in vivo. Our findings establish FOXO1 inhibition as a therapeutic strategy targeting lineage-driven transcriptional addiction in MCL.

FOXO1 inhibition synergizes with FGF21 to normalize glucose control in diabetic mice.

OBJECTIVE: Forkhead box protein O1 (FOXO1) plays a key role in regulating hepatic glucose production, but investigations of FOXO1 inhibition as a potential therapeutic approach have been hampered by a lack of selective chemical inhibitors. By profiling structurally diverse FOXO1 inhibitors, the current study validates FOXO1 as a viable target for the treatment of diabetes. METHODS: Using reporter gene assays, hepatocyte gene expression studies, and in vivo studies in mice, we profiled our leading tool compound 10 and a previously characterized FOXO1 inhibitor, AS1842856 (AS). RESULTS: We show that AS has significant FOXO1-independent effects, as demonstrated by testing in FOXO1-deficient cell lines and animals, while compound 10 is highly selective for FOXO1 both in vitro and in vivo and fails to elicit any effect in genetic models of FOXO1 ablation. Chronic administration of compound 10 improved insulin sensitivity and glucose control in db/db mice without causing weight gain. Furthermore, chronic compound 10 treatment combined with FGF21 led to synergistic glucose lowering in lean, streptozotocin-induced diabetic mice. CONCLUSIONS: We show that the widely used AS compound has substantial off-target activities and that compound 10 is a superior tool molecule for the investigation of FOXO1 function. In addition, we provide preclinical evidence that selective FOXO1 inhibition has potential therapeutic benefits for diabetes as a monotherapy or in combination with FGF21.

Discovery of LY3325656: A GPR142 agonist suitable for clinical testing in human.

The discovery and optimization of a novel series of GPR142 agonists are described. These led to the identification of compound 21 (LY3325656), which demonstrated anti-diabetic benefits in pre-clinical studies and ADME/PK properties suitable for human dosing. Compound 21 is the first GPR142 agonist molecule advancing to phase 1 clinic trials for the treatment of Type 2 diabetes.

GPR142 prompts glucagon-like Peptide-1 release from islets to improve ß cell function.

OBJECTIVE: GPR142 agonists are being pursued as novel diabetes therapies by virtue of their insulin secretagogue effects. But it is undetermined whether GPR142's functions in pancreatic islets are limited to regulating insulin secretion. The current study expands research on its action. METHODS AND RESULTS: We demonstrated by in situ hybridization and immunostaining that GPR142 is expressed not only in ß cells but also in a subset of α cells. Stimulation of GPR142 by a selective agonist increased glucagon secretion in both human and mouse islets. More importantly, the GPR142 agonist also potentiated glucagon-like peptide-1 (GLP-1) production and its release from islets through a mechanism that involves upregulation of prohormone convertase 1/3 expression. Strikingly, stimulation of insulin secretion and increase in insulin content via GPR142 engagement requires intact GLP-1 receptor signaling. Furthermore, GPR142 agonist increased ß cell proliferation and protected both mouse and human islets against stress-induced apoptosis. CONCLUSIONS: Collectively, we provide here evidence that local GLP-1 release from α cells defines GPR142's beneficial effects on improving ß cell function and mass, and we propose that GPR142 agonism may have translatable and durable efficacy for the treatment of type 2 diabetes.

Hepatic GALE Regulates Whole-Body Glucose Homeostasis by Modulating Tff3 Expression.

Transcripts of key enzymes in the Leloir pathway of galactose metabolism in mouse livers are significantly increased after chronic high-fat/high-sucrose feeding. UDP-galactose-4-epimerase (GALE) is the last enzyme in this pathway that converts UDP-galactose to UDP-glucose and was previously identified as a downstream target of the endoplasmic reticulum (ER) stress effector spliced X-box binding protein 1, suggesting an interesting cross talk between galactose and glucose metabolism in the context of hepatic ER stress and whole-body metabolic fitness. However, its specific role in glucose metabolism is not established. Using an inducible and tissue-specific mouse model, we report that hepatic overexpression of Gale increases gluconeogenesis from pyruvate and impairs glucose tolerance. Conversely, genetic reduction of Gale in liver improves glucose tolerance. Transcriptional profiling identifies trefoil factor 3 (Tff3) as one of the downstream targets of GALE. Restoration of Tff3 expression corrects glucose intolerance in Gale-overexpressing mice. These studies reveal a new link between hepatic GALE activity and whole-body glucose homeostasis via regulation of hepatic Tff3 expression.

Connexin 43 Mediates White Adipose Tissue Beiging by Facilitating the Propagation of Sympathetic Neuronal Signals.

"Beige" adipocytes reside in white adipose tissue (WAT) and dissipate energy as heat. Several studies have shown that cold temperature can activate pro-opiomelanocortin-expressing (POMC) neurons and increase sympathetic neuronal tone to regulate WAT beiging. WAT, however, is traditionally known to be sparsely innervated. Details regarding the neuronal innervation and, more importantly, the propagation of the signal within the population of "beige" adipocytes are sparse. Here, we demonstrate that beige adipocytes display an increased cell-to-cell coupling via connexin 43 (Cx43) gap junction channels. Blocking of Cx43 channels by 18α-glycyrrhetinic acid decreases POMC-activation-induced adipose tissue beiging. Adipocyte-specific deletion of Cx43 reduces WAT beiging to a level similar to that observed in denervated fat pads. In contrast, overexpression of Cx43 is sufficient to promote beiging even with mild cold stimuli. These data reveal the importance of cell-to-cell communication, effective in cold-induced WAT beiging, for the propagation of limited neuronal inputs in adipose tissue.

GPR142 Controls Tryptophan-Induced Insulin and Incretin Hormone Secretion to Improve Glucose Metabolism.

GPR142, a putative amino acid receptor, is expressed in pancreatic islets and the gastrointestinal tract, but the ligand affinity and physiological role of this receptor remain obscure. In this study, we show that in addition to L-Tryptophan, GPR142 signaling is also activated by L-Phenylalanine but not by other naturally occurring amino acids. Furthermore, we show that Tryptophan and a synthetic GPR142 agonist increase insulin and incretin hormones and improve glucose disposal in mice in a GPR142-dependent manner. In contrast, Phenylalanine improves in vivo glucose disposal independently of GPR142. Noteworthy, refeeding-induced elevations in insulin and glucose-dependent insulinotropic polypeptide are blunted in Gpr142 null mice. In conclusion, these findings demonstrate GPR142 is a Tryptophan receptor critically required for insulin and incretin hormone regulation and suggest GPR142 agonists may be effective therapies that leverage amino acid sensing pathways for the treatment of type 2 diabetes.

GPR142 Agonists Stimulate Glucose-Dependent Insulin Secretion via Gq-Dependent Signaling.

GPR142 is an islet-enriched G protein-coupled receptor that has been investigated as a novel therapeutic target for the treatment of type 2 diabetes by virtue of its insulin secretagogue activity. However, the signaling pathways downstream of GPR142 and whether its stimulation of insulin release is glucose-dependent remain poorly characterized. In this study, we show that both native and synthetic GPR142 agonists can activate Gq as well as Gi signaling when GPR142 is recombinantly expressed in HEK293 cells. However, in primary pancreatic islets, a native cellular system, the insulin secretagogue activity of GPR142 agonists only requires Gq activation. In addition, our results show that stimulation of insulin secretion by GPR142 in pancreatic islets is strictly glucose-dependent.

Identification and characterization of sebaceous gland atrophy-sparing DGAT1 inhibitors.

Inhibition of Diacylglycerol O-acyltransferase 1 (DGAT1) has been a mechanism of interest for metabolic disorders. DGAT1 inhibition has been shown to be a key regulator in an array of metabolic pathways; however, based on the DGAT1 KO mouse phenotype the anticipation is that pharmacological inhibition of DGAT1 could potentially lead to skin related adverse effects. One of the aims in developing small molecule DGAT1 inhibitors that target key metabolic tissues is to avoid activity on skin-localized DGAT1 enzyme. In this report we describe a modeling-based approach to identify molecules with physical properties leading to differential exposure distribution. In addition, we demonstrate histological and RNA based biomarker approaches that can detect sebaceous gland atrophy pre-clinically that could be used as potential biomarkers in a clinical setting.

Diacylglycerol acyltransferase-1 (DGAT1) inhibition perturbs postprandial gut hormone release.

Diacylglycerol acyltransferase-1 (DGAT1) is a potential therapeutic target for treatment of obesity and related metabolic diseases. However, the degree of DGAT1 inhibition required for metabolic benefits is unclear. Here we show that partial DGAT1 deficiency in mice suppressed postprandial triglyceridemia, led to elevations in glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) only following meals with very high lipid content, and did not protect from diet-induced obesity. Maximal DGAT1 inhibition led to enhanced GLP-1 and PYY secretion following meals with physiologically relevant lipid content. Finally, combination of DGAT1 inhibition with dipeptidyl-peptidase-4 (DPP-4) inhibition led to further enhancements in active GLP-1 in mice and dogs. The current study suggests that targeting DGAT1 to enhance postprandial gut hormone secretion requires maximal inhibition, and suggests combination with DPP-4i as a potential strategy to develop DGAT1 inhibitors for treatment of metabolic diseases.

Pancreatic ß cell dedifferentiation as a mechanism of diabetic ß cell failure.

Diabetes is associated with ß cell failure. But it remains unclear whether the latter results from reduced ß cell number or function. FoxO1 integrates ß cell proliferation with adaptive ß cell function. We interrogated the contribution of these two processes to ß cell dysfunction, using mice lacking FoxO1 in ß cells. FoxO1 ablation caused hyperglycemia with reduced ß cell mass following physiologic stress, such as multiparity and aging. Surprisingly, lineage-tracing experiments demonstrated that loss of ß cell mass was due to ß cell dedifferentiation, not death. Dedifferentiated ß cells reverted to progenitor-like cells expressing Neurogenin3, Oct4, Nanog, and L-Myc. A subset of FoxO1-deficient ß cells adopted the α cell fate, resulting in hyperglucagonemia. Strikingly, we identify the same sequence of events as a feature of different models of murine diabetes. We propose that dedifferentiation trumps endocrine cell death in the natural history of ß cell failure and suggest that treatment of ß cell dysfunction should restore differentiation, rather than promoting ß cell replication.

Butyrate and propionate protect against diet-induced obesity and regulate gut hormones via free fatty acid receptor 3-independent mechanisms.

Short-chain fatty acids (SCFAs), primarily acetate, propionate, and butyrate, are metabolites formed by gut microbiota from complex dietary carbohydrates. Butyrate and acetate were reported to protect against diet-induced obesity without causing hypophagia, while propionate was shown to reduce food intake. However, the underlying mechanisms for these effects are unclear. It was suggested that SCFAs may regulate gut hormones via their endogenous receptors Free fatty acid receptors 2 (FFAR2) and 3 (FFAR3), but direct evidence is lacking. We examined the effects of SCFA administration in mice, and show that butyrate, propionate, and acetate all protected against diet-induced obesity and insulin resistance. Butyrate and propionate, but not acetate, induce gut hormones and reduce food intake. As FFAR3 is the common receptor activated by butyrate and propionate, we examined these effects in FFAR3-deficient mice. The effects of butyrate and propionate on body weight and food intake are independent of FFAR3. In addition, FFAR3 plays a minor role in butyrate stimulation of Glucagon-like peptide-1, and is not required for butyrate- and propionate-dependent induction of Glucose-dependent insulinotropic peptide. Finally, FFAR3-deficient mice show normal body weight and glucose homeostasis. Stimulation of gut hormones and food intake inhibition by butyrate and propionate may represent a novel mechanism by which gut microbiota regulates host metabolism. These effects are largely intact in FFAR3-deficient mice, indicating additional mediators are required for these beneficial effects.

Increased atherosclerosis and endothelial dysfunction in mice bearing constitutively deacetylated alleles of Foxo1 gene.

Complications of atherosclerosis are the leading cause of death of patients with type 2 (insulin-resistant) diabetes. Understanding the mechanisms by which insulin resistance and hyperglycemia contribute to atherogenesis in key target tissues (liver, vessel wall, hematopoietic cells) can assist in the design of therapeutic approaches. We have shown that hyperglycemia induces FoxO1 deacetylation and that targeted knock-in of alleles encoding constitutively deacetylated FoxO1 in mice (Foxo1(KR/KR)) improves hepatic lipid metabolism and decreases macrophage inflammation, setting the stage for a potential anti-atherogenic effect of this mutation. Surprisingly, we report here that when Foxo1(KR/KR) mice are intercrossed with low density lipoprotein receptor knock-out mice (Ldlr(-/-)), they develop larger aortic root atherosclerotic lesions than Ldlr(-/-) controls despite lower plasma cholesterol and triglyceride levels. The phenotype is unaffected by transplanting bone marrow from Ldlr(-/-) mice into Foxo1(KR/KR) mice, indicating that it is independent of hematopoietic cells and suggesting that the primary lesion in Foxo1(KR/KR) mice occurs in the vessel wall. Experiments in isolated endothelial cells from Foxo1(KR/KR) mice indicate that deacetylation favors FoxO1 nuclear accumulation and exerts target gene-specific effects, resulting in higher Icam1 and Tnfα expression and increased monocyte adhesion. The data indicate that FoxO1 deacetylation can promote vascular endothelial changes conducive to atherosclerotic plaque formation.

InsR/FoxO1 signaling curtails hypothalamic POMC neuron number.

Insulin receptor (InsR) signaling through transcription factor FoxO1 is important in the development of hypothalamic neuron feeding circuits, but knowledge about underlying mechanisms is limited. To investigate the role of InsR/FoxO1 signaling in the development and maintenance of these circuits, we surveyed the pool of hypothalamic neurons expressing Pomc mRNA in different mouse models of impaired hypothalamic InsR signaling. InsR ablation in the entire hypothalamus did not affect Pomc-neuron number at birth, but resulted in a 25% increase, most notably in the middle arcuate nucleus region, in young adults. Selective restoration of InsR expression in POMC neurons in these mice partly reversed the abnormality, resulting in a 10% decrease compared to age-matched controls. To establish whether FoxO1 signaling plays a role in this process, we examined POMC neuron number in mice with POMC-specific deletion of FoxO1, and detected a 23% decrease in age-matched animals, consistent with a cell-autonomous role of InsR/FoxO1 signaling in regulating POMC neuron number, distinct from its established role to activate Pomc transcription. These changes in Pomc cells occurred in the absence of marked changes in humoral factors or hypothalamic NPY neurons.

Proatherogenic abnormalities of lipid metabolism in SirT1 transgenic mice are mediated through Creb deacetylation.

Dyslipidemia and atherosclerosis are associated with reduced insulin sensitivity and diabetes, but the mechanism is unclear. Gain of function of the gene encoding deacetylase SirT1 improves insulin sensitivity and could be expected to protect against lipid abnormalities. Surprisingly, when transgenic mice overexpressing SirT1 (SirBACO) are placed on atherogenic diet, they maintain better glucose homeostasis, but develop worse lipid profiles and larger atherosclerotic lesions than controls. We show that transcription factor cAMP response element binding protein (Creb) is deacetylated in SirBACO mice. We identify Lys136 is a substrate for SirT1-dependent deacetylation that affects Creb activity by preventing its cAMP-dependent phosphorylation, leading to reduced expression of glucogenic genes and promoting hepatic lipid accumulation and secretion. Expression of constitutively acetylated Creb (K136Q) in SirBACO mice mimics Creb activation and abolishes the dyslipidemic and insulin-sensitizing effects of SirT1 gain of function. We propose that SirT1-dependent Creb deacetylation regulates the balance between glucose and lipid metabolism, integrating fasting signals.

Hormonal regulation of hepatic glucose production in health and disease.

We review mechanisms that regulate production of glucose by the liver, focusing on areas of budding consensus, and endeavoring to provide a candid assessment of lingering controversies. We also attempt to reconcile data from tracer studies in humans and large animals with the growing compilation of mouse knockouts that display changes in glucose production. A clinical hallmark of diabetes, excessive glucose production remains key to its treatment. Hence, we attempt to integrate emerging pathways into the broader goal to rejuvenate the staid antidiabetic pharmacopeia.

Reconstitution of insulin action in muscle, white adipose tissue, and brain of insulin receptor knock-out mice fails to rescue diabetes.

Type 2 diabetes results from an impairment of insulin action. The first demonstrable abnormality of insulin signaling is a decrease of insulin-dependent glucose disposal followed by an increase in hepatic glucose production. In an attempt to dissect the relative importance of these two changes in disease progression, we have employed genetic knock-outs/knock-ins of the insulin receptor. Previously, we demonstrated that insulin receptor knock-out mice (Insr(-/-)) could be rescued from diabetes by reconstitution of insulin signaling in liver, brain, and pancreatic ß cells (L1 mice). In this study, we used a similar approach to reconstitute insulin signaling in tissues that display insulin-dependent glucose uptake. Using GLUT4-Cre mice, we restored InsR expression in muscle, fat, and brain of Insr(-/-) mice (GIRKI (Glut4-insulin receptor knock-in line 1) mice). Unlike L1 mice, GIRKI mice failed to thrive and developed diabetes, although their survival was modestly extended when compared with Insr(-/-). The data underscore the role of developmental factors in the presentation of murine diabetes. The broader implication of our findings is that diabetes treatment should not necessarily target the same tissues that are responsible for disease pathogenesis.

Diabetes in mice with selective impairment of insulin action in Glut4-expressing tissues.

OBJECTIVE: Impaired insulin-dependent glucose disposal in muscle and fat is a harbinger of type 2 diabetes, but murine models of selective insulin resistance at these two sites are conspicuous by their failure to cause hyperglycemia. A defining feature of muscle and fat vis-à-vis insulin signaling is that they both express the insulin-sensitive glucose transporter Glut4. We hypothesized that diabetes is the result of impaired insulin signaling in all Glut4-expressing tissues. RESEARCH DESIGN AND METHODS: To test the hypothesis, we generated mice lacking insulin receptors at these sites ("GIRKO" mice), including muscle, fat, and a subset of Glut4-positive neurons scattered throughout the central nervous system. RESULTS: GIRKO mice develop diabetes with high frequency because of reduced glucose uptake in peripheral organs, excessive hepatic glucose production, and ß-cell failure. CONCLUSIONS: The conceptual advance of the present findings lies in the identification of a tissue constellation that melds cell-autonomous mechanisms of insulin resistance (in muscle/fat) with cell-nonautonomous mechanisms (in liver and ß-cell) to cause overt diabetes. The data are consistent with the identification of Glut4 neurons as a distinct neuroanatomic entity with a likely metabolic role.