Empagliflozin, a novel potent and selective SGLT-2 inhibitor, improves glycaemic control alone and in combination with insulin in streptozotocin-induced diabetic rats, a model of type 1 diabetes mellitus.

AIM: Sodium glucose cotransporter-2 (SGLT-2) is key to reabsorption of glucose in the kidney. SGLT-2 inhibitors are in clinical development for treatment of type 2 diabetes mellitus (T2DM). The mechanism may be of value also in the treatment of type 1 diabetes mellitus (T1DM). This study investigated effects of the SGLT-2 inhibitor, empagliflozin, alone and in combination with insulin, on glucose homeostasis in an animal model of T1DM. METHODS: Sprague-Dawley rats were administered a single intraperitoneal injection of streptozotocin (STZ; 60 mg/kg). Acutely, STZ rats received two doses of insulin glargine with or without empagliflozin, and blood glucose was measured. In a subchronic study, STZ rats received empagliflozin alone, one or two insulin-releasing implants or a combination of one implant and empagliflozin over 28 days; blood glucose and HbA(1c) were measured. RESULTS: In the acute setting, empagliflozin in combination with 1.5 IU insulin induced a similar glucose-lowering effect as 6 IU insulin. Both interventions were more efficacious than monotherapy with 1.5 IU insulin. In the subchronic study, 12-h blood glucose profile on day 28 in the combination group was lower than with one implant, and similar to two implants. Plasma HbA(1c) was improved in the combination group and in animals with two implants. CONCLUSIONS: Empagliflozin reduced blood glucose levels in a T1DM animal model. Empagliflozin combined with low-dose insulin showed comparable glucose-lowering efficacy to treatment with high-dose insulin. Our data suggest that empagliflozin is an efficacious adjunctive-to-insulin therapy with the clinical potential for the treatment of T1DM.

Empagliflozin, a novel selective sodium glucose cotransporter-2 (SGLT-2) inhibitor: characterisation and comparison with other SGLT-2 inhibitors.

AIMS: Empagliflozin is a selective sodium glucose cotransporter-2 (SGLT-2) inhibitor in clinical development for the treatment of type 2 diabetes mellitus. This study assessed pharmacological properties of empagliflozin in vitro and pharmacokinetic properties in vivo and compared its potency and selectivity with other SGLT-2 inhibitors. METHODS: [(14)C]-alpha-methyl glucopyranoside (AMG) uptake experiments were performed with stable cell lines over-expressing human (h) SGLT-1, 2 and 4. Two new cell lines over-expressing hSGLT-5 and hSGLT-6 were established and [(14)C]-mannose and [(14)C]-myo-inositol uptake assays developed. Binding kinetics were analysed using a radioligand binding assay with [(3)H]-labelled empagliflozin and HEK293-hSGLT-2 cell membranes. Acute in vivo assessment of pharmacokinetics was performed with normoglycaemic beagle dogs and Zucker diabetic fatty (ZDF) rats. RESULTS: Empagliflozin has an IC(50) of 3.1 nM for hSGLT-2. Its binding to SGLT-2 is competitive with glucose (half-life approximately 1 h). Compared with other SGLT-2 inhibitors, empagliflozin has a high degree of selectivity over SGLT-1, 4, 5 and 6. Species differences in SGLT-1 selectivity were identified. Empagliflozin pharmacokinetics in ZDF rats were characterised by moderate total plasma clearance (CL) and bioavailability (BA), while in beagle dogs CL was low and BA was high. CONCLUSIONS: Empagliflozin is a potent and competitive SGLT-2 inhibitor with an excellent selectivity profile and the highest selectivity window of the tested SGLT-2 inhibitors over hSGLT-1. Empagliflozin represents an innovative therapeutic approach to treat diabetes.

Long-term treatment with empagliflozin, a novel, potent and selective SGLT-2 inhibitor, improves glycaemic control and features of metabolic syndrome in diabetic rats.

Empagliflozin is a potent, selective sodium glucose co-transporter-2 inhibitor that is in development for the treatment of type 2 diabetes. This series of studies was conducted to assess the in vivo pharmacological effects of single or multiple doses of empagliflozin in Zucker diabetic fatty rats. Single doses of empagliflozin resulted in dose-dependent increases in urinary glucose excretion and reductions in blood glucose levels. After multiple doses (5 weeks), fasting blood glucose levels were reduced by 26 and 39% with 1 and 3 mg/kg empagliflozin, respectively, relative to vehicle. After 5 weeks, HbA1c levels were reduced (from a baseline of 7.9%) by 0.3 and 1.1% with 1 and 3 mg/kg empagliflozin, respectively, versus an increase of 1.1% with vehicle. Hyperinsulinaemic-euglycaemic clamp indicated improved insulin sensitivity with empagliflozin after multiple doses versus vehicle. These findings support the development of empagliflozin for the treatment of type 2 diabetes.

Tumor necrosis factor alpha induces the expression of the nuclear protein p8 via a novel NF kappaB binding site within the promoter.

p8 is a widely expressed HMG-I/Y-like transcription factor which is involved in regulating cell proliferation and tissue stress. Several studies describe a strong upregulation of p8 expression during inflammatory processes like pancreatitis and LPS-induced sepsis. Here we demonstrate that TNFalpha, which is an important inducer of innate defence against gram-negative bacteria, significantly stimulates p8 protein production in H4IIE rat hepatoma cells within 2 hours. Since a putative NF kappaB motif has been described, we further tested whether TNFalpha stimulates p8 expression via activation of NF kappaB. We characterized the TNFalpha-induced binding of NF kappaB to this motif. We show that the TNFalpha-induced NF kappaB pathway contributes to the induction of p8 during pancreatitis and LPS-induced inflammation.

Expression of thyroid hormone receptor isoform alpha1 in pancreatic islets.

Thyroid hormone receptors (TR) mediate the action of thyroid hormones. Genetic studies revealed that the individual TR isoforms possess different functions. In the present paper we studied the expression of the isoforms TRalpha1 and TRbeta1 in the murine pancreatic islet. TRalpha1 and TRbeta1 mRNA transcripts and proteins were detected in islets using reverse transcription-polymerase chain reaction and Western blotting analyses, respectively. In immunohistochemical studies individual cells in the periphery of islets were labelled using an anti-TRalpha1 antibody. No labelled cells were detected in the exocrine pancreas. A similar staining pattern was obtained with an anti-glucagon antibody, but not with an anti-insulin antibody, which suggests that TRalpha1 is mainly expressed in alpha-cells. In order to address a potential function of TRalpha1 in this cell type, the regulation of glucagon gene expression by triiodothyronine was studied in a glucagon-producing cell line by Northern blot analysis and transient transfection assays using glucagon promoter luciferase fusion gene constructs. In these assays, triiodothyronine did not regulate the glucagon mRNA level or the glucagon promoter activity. The predominant localization of TRalpha1 in pancreatic alpha-cells suggests that this receptor isoform mediates a specific, yet unknown, function of thyroid hormones in this cell type.

Basal level glucose-6-phosphatase gene transcription requires binding sites for Sp family proteins within the gene promoter.

The significance of two regions (SpA: -19 to -11 and SpB: -63 to -55) within the human glucose-6-phosphatase (G6Pase) gene promoter for gene expression was examined. The mutation of SpA and SpB together, but not alone, decreased G6Pase promoter activity. Electromobility shift assays showed that SpA and SpB were able to bind the transcription factors Sp1 and Sp3.

Phorbol ester-induced activation of mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase and extracellular-signal-regulated protein kinase decreases glucose-6-phosphatase gene expression.

Glucose-6-phosphatase (G6Pase) plays a central role in blood glucose homoeostasis, and insulin suppresses G6Pase gene expression by the activation of phosphoinositide 3-kinase (PI 3-kinase). Here, we show that the phorbol ester PMA decreases both basal and dexamethasone/cAMP-induced expression of a luciferase gene under the control of the G6Pase promoter in transiently transfected H4IIE hepatoma cells. This regulation was suppressed by the inhibitors of the mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase (MEK), PD98059 and U0126, but not by the inhibitor of PI 3-kinase, LY294002. The co-expression of a constitutively active mutant of MEK mimicked the regulation of G6Pase promoter activity by PMA. The effect of PMA on both basal and induced G6Pase gene transcription was impaired by the overexpression of a dominant negative MEK construct, as well as by the expression of mitogen-activated protein kinase phosphatase-1. The mutation of the forkhead-binding sites within the insulin-response unit of the G6Pase promoter, which decreases the effect of insulin on G6Pase gene expression, did not alter the regulation of gene expression by PMA. The data show that PMA decreases G6Pase gene expression by the activation of MEK and extracellular-signal regulated protein kinase. With that, PMA mimics the effect of insulin on G6Pase gene expression by a different signalling pathway.

Regulation of glucose-6-phosphatase gene expression by protein kinase Balpha and the forkhead transcription factor FKHR. Evidence for insulin response unit-dependent and -independent effects of insulin on promoter activity.

Glucose-6-phosphatase plays an important role in the regulation of hepatic glucose production, and insulin suppresses glucose-6-phosphatase gene expression. Recent studies indicate that protein kinase B and Forkhead proteins contribute to insulin-regulated gene expression in the liver. Here, we examined the role of protein kinase B and Forkhead proteins in mediating effects of insulin on glucose-6-phosphatase promoter activity. Transient transfection studies with reporter gene constructs demonstrate that insulin suppresses both basal and dexamethasone/cAMP-induced activity of the glucose-6-phosphatase promoter in H4IIE hepatoma cells. Both effects are partially mimicked by coexpression of protein kinase Balpha. Coexpression of the Forkhead transcription factor FKHR stimulates the glucose-6-phosphatase promoter activity via interaction with an insulin response unit (IRU), and this activation is suppressed by protein kinase B. Coexpression of a mutated form of FKHR that cannot be phosphorylated by protein kinase B abolishes the regulation of the glucose-6-phosphatase promoter by protein kinase B and disrupts the ability of insulin to regulate the glucose-6-phosphatase promoter via the IRU. Mutation of the insulin response unit of the glucose-6-phosphatase promoter also prevents the regulation of promoter activity by FKHR and protein kinase B but only partially impairs the ability of insulin to suppress both basal and dexamethasone/cAMP-stimulated promoter function. Taken together, these results indicate that signaling by protein kinase B to Forkhead proteins can account for the ability of insulin to regulate glucose-6-phosphatase promoter activity via the IRU and that other mechanisms that are independent of the IRU, protein kinase B, and Forkhead proteins also are important in mediating effects of in insulin on glucose-6-phosphatase gene expression.