Effect of canagliflozin, a sodium glucose co-transporter 2 (SGLT2) inhibitor, on bacteriuria and urinary tract infection in subjects with type 2 diabetes enrolled in a 12-week, phase 2 study.

OBJECTIVE: To examine the effects of canagliflozin, a sodium glucose co-transporter 2 inhibitor that lowers blood glucose by increasing urinary glucose excretion (UGE), on asymptomatic bacteriuria and urinary tract infections (UTIs). RESEARCH DESIGN AND METHODS: In a randomized, double-blind, placebo-controlled, multicenter, dose-ranging phase 2 study, subjects with type 2 diabetes with inadequate glycemic control while receiving metformin were enrolled and randomized to one of seven arms - placebo; canagliflozin doses 50 mg, 100 mg, 200 mg, 300 mg daily, or 300 mg twice daily; and sitagliptin 100 mg daily - for 12 weeks. CLINICAL TRIAL REGISTRATION: This study is registered under Clinicaltrials.gov identification number NCT00642278. RESULTS: Canagliflozin increased renal glucose excretion by 35.4-61.6 mg/mg creatinine in the five dose groups. In the placebo group renal glucose excretion was increased by 1.9 mg/mg creatinine, and in the sitagliptin group it decreased by 1.9 mg/mg creatinine. Asymptomatic bacteriuria (ASB) were present in 6.4% of canagliflozin and 6.5% of placebo/sitagliptin (control) subjects at randomization and, at 12 weeks, in 7.7% and 6.3% of subjects, respectively (odds ratio [OR] 1.23; 95% confidence interval [CI], 0.45-3.89). For subjects with initially negative urine cultures at baseline, 3 out of 82 (3.7%) who received controls and 10 out of 207 (4.8%) who received canagliflozin developed bacteriuria (p = 0.76) at week 12. There were 21 adverse event (AE) reports of UTI; 16 (5.0%) in canagliflozin subjects and 5 (3.8%) in control subjects (OR 1.31; 95% CI, 0.45-4.68). CONCLUSIONS: In this trial, when compared with control subjects, canagliflozin increased UGE but was not associated with increased bacteriuria or AE reports of UTI. However, further studies enrolling larger numbers of subjects with longer term exposure to canagliflozin will be necessary to more fully understand the impact of this agent on the risk of developing UTI.

Canagliflozin improves glycaemic control over 28 days in subjects with type 2 diabetes not optimally controlled on insulin.

AIM: Canagliflozin is a sodium-glucose co-transporter 2 (SGLT2) inhibitor that is being investigated for the treatment of type 2 diabetes mellitus (T2DM). METHODS: This was a randomized, double-blind, placebo-controlled, parallel-group, 28-day study conducted at two sites, in 29 subjects with T2DM not optimally controlled on insulin and up to one oral antihyperglycaemic agent. Subjects were treated with canagliflozin 100 mg QD or 300 mg twice daily (BID) or placebo. Safety, tolerability, pharmacokinetic characteristics and pharmacodynamic effects of canagliflozin were examined. Glucose malabsorption following a 75-g oral glucose challenge was also examined. RESULTS: Canagliflozin pharmacokinetics were dose-dependent, and the elimination half-life ranged from 12 to 15 h. After 28 days, the renal threshold for glucose excretion was reduced; urinary glucose excretion was increased; and A1C, fasting plasma glucose and body weight decreased in subjects administered canagliflozin (A1C reductions: 0.19% with placebo, 0.73% with 100 mg QD, 0.92% with 300 mg BID; body weight changes: 0.03 kg increase with placebo, 0.73 kg reduction with 100 mg QD, 1.19 kg reduction with 300 mg BID). Glucose malabsorption was not observed with canagliflozin treatment. There were no deaths, serious adverse events or severe hypoglycaemic episodes. The incidence of adverse events was similar across groups. There were no clinically meaningful changes in routine laboratory safety tests, vital signs or electrocardiograms. CONCLUSION: In subjects receiving insulin and oral antihyperglycaemic therapy, canagliflozin was well tolerated without evidence for glucose malabsorption, had pharmacokinetic characteristics consistent with once-daily dosing, and improved glycaemic control.

Vascular endothelial growth factor-induced retinal permeability is mediated by protein kinase C in vivo and suppressed by an orally effective beta-isoform-selective inhibitor.

Increased vascular permeability and excessive neovascularization are the hallmarks of endothelial dysfunction, which can lead to diabetic macular edema and proliferative diabetic retinopathy in the eye. Vascular endothelial growth factor (VEGF) is an important mediator of ocular neovascularization and a known vasopermeability factor in nonocular tissues. In these studies, we demonstrate that intravitreal injection of VEGF rapidly activates protein kinase C (PKC) in the retina at concentrations observed clinically, inducing membrane translocation of PKC isoforms alpha, betaII, and delta and >threefold increases in retinal vasopermeability in vivo. The effect of VEGF on retinal vascular permeability appears to be mediated predominantly by the beta-isoform of PKC with >95% inhibition of VEGF-induced permeability by intravitreal or oral administration of a PKC beta-isoform-selective inhibitor that did not inhibit histamine-mediated effects. These studies represent the first direct demonstration that VEGF can increase intraocular vascular permeability through activation of PKC in vivo and suggest that oral pharmacological therapies involving PKC beta-isoform-selective inhibitors may prove efficacious for the treatment of VEGF-associated ocular disorders such as diabetic retinopathy.

Phorbol ester stimulated Cip1 expression in p53-negative leukemic cells.

In differentiating leukemic cells, cyclin-dependent kinase interacting protein (Cip1) is induced and stimulates a G(1) arrest. TPA treated U937 monoblastoid cells expressed Cip1, hypophosphorylated retinoblastoma protein (Rb), arrested in G(1) and differentiated. PKC-zeta cells are U937 cells that overexpress the zeta isoform and display alterations in endogenous PKC isoform expression. TPA treated PKC-zeta cells undergo apoptosis without differentiating. TPA treated PKC-zeta cells express Cip1 and display substantial hypophosphorylation of Rb but fail to arrest in G(1). Thus, a novel phorbol ester dependent signalling pathway exists in which Cip1 induction is associated with the absence of a G(1) arrest and induction of apoptosis rather than differentiation.

2-Chloroadenosine prevents phorbol ester-induced depletion of protein kinase C in porcine coronary artery.

In this study we investigated the role of the adenosine analogue 2-chloroadenosine (CAD) in the regulation of protein kinase C (PKC) in porcine coronary artery. Arterial rings were contracted with endothelin-1 (ET-1; 10(-10) to 10(-7) M) and phorbol 12,13-dibutyrate (PDBu; 10(-7) M) after incubating them for 1 and 2 days with PDBu (200 nM) in the presence and absence of CAD (10(-4) M). Chronic exposure to PDBu alone attenuated ET-1-induced contractions, while inclusion of CAD during incubation protected against the PDBu-induced blunting of ET-1-induced contraction. Similarly, PDBu (10(-7) M)-induced contraction of the arterial rings was attenuated upon chronic incubation with PDBu, and once again, inclusion of CAD showed an improved response to PDBu-induced contraction when compared with PDBu alone. Incubation with PDBu (200 nM) for 20 min caused the PKC translocation from cytosol to membrane, whereas CAD totally blocked this translocation. Chronic (1 and 2 days) incubation with PDBu caused a substantial depletion of PKC activities in cytosol and membrane. The presence of CAD protected the PDBu-induced depletion of PKC in both cytosol and membrane. To replete PKC, after incubation with the drugs, the arteries were incubated in the absence of drugs for another 2 days. Arteries incubated with PDBu in the presence and absence of CAD recovered significantly in their response to ET-1 as well as PDBu. These results indicate that CAD protects against the PDBu-induced activation and depletion of PKC in porcine coronary artery.

Effects of insulin and phorbol esters on subcellular distribution of protein kinase C isoforms in rat adipocytes.

Effects of insulin and phorbol esters on subcellular distribution of protein kinase C (PKC) isoforms were examined in rat adipocytes. Both agonists provoked rapid decreases in cytosolic, and/or increases in membrane, immunoreactive PKC-alpha, PKC-beta, PKC-gamma, and PKC-epsilon. Effects of phorbol esters on PKC-alpha redistribution to the plasma membrane, however, were much greater than those of insulin. In contrast, insulin, but not phorbol esters, stimulated the translocation of PKC-beta to the plasma membrane, and provoked changes in PKC-zeta redistribution. Neither agonist altered subcellular distribution of PKC-delta, which was detected only in membrane fractions. Our findings indicate that insulin and phorbol esters have overlapping and distinctly different effects on the subcellular redistribution of specific PKC isoforms.

Effects of insulin on diacylglycerol/protein kinase-C signalling and glucose transport in rat skeletal muscles in vivo and in vitro.

Insulin treatment in vivo provoked rapid dose-related increases in diacylglycerol content and/or translocation of protein kinase-C (PKC) from cytosol to membranes in rat soleus and gastrocnemius muscles. These effects were apparent with 1) insulin doses that provoked submaximal and maximal increases in glucose utilization, and 2) glucose-stimulated endogenous insulin secretion. Insulin-stimulated PKC translocation was evident when PKC was assayed by 1) histone or protamine phosphorylation after PKC purification by Mono Q column chromatography, and 2) immunoblotting for PKC beta and PKC epsilon. Dose-related effects of insulin on PKC translocation were also observed in the rat soleus in vitro, and this was associated with increased phosphorylation of 40- and 80-kilodalton proteins, which were also phosphorylated by phorbol ester treatment. A role for diacylglycerol-PKC signalling in insulin-stimulated glucose transport was suggested by studies of [3H]2-deoxyglucose ([3H]2-DOG) uptake in the rat soleus in vitro in that 1) PKC translocation and 2-DOG uptake were correlated; and 2) stimulatory effects of insulin and phorbol esters on 2-DOG uptake were apparently nonadditive.

Effect of phorbol esters on cytosolic protein kinase C content and activity in the human monoblastoid U937 cell.

12-O-Tetradecanoylphorbol-13-acetate (TPA) stimulates the human monoblastoid U937 cell to differentiate into a mature monocyte/macrophage-like cell. Since TPA may produce cellular responses by activating protein kinase C, the effects of TPA on kinase activity in the U937 cell were investigated. Brief exposures (less than or equal to 60 min) to TPA dramatically diminished protein kinase C-dependent phosphorylation of histone and endogenous substrates. However, using a peptide substrate corresponding to residues 720-737 of protein kinase C-epsilon, Ca2(+)-, phospholipid-, and diacylglycerol-dependent kinase activity was reduced only modestly after exposure to TPA. This phospholipid-dependent kinase activity coeluted on DEAE chromatography with protein kinase C. Examination of cytosolic protein kinase C content by Western blot analysis demonstrated a moderate decline in kinase content after TPA treatment. The decline was due primarily to loss of an 80-kDa species with preservation of a 76-kDa protein. The immunoreactive 76-kDa protein observed after TPA treatment comigrated on DEAE chromatography with the kinase activity phosphorylating the protein kinase C-epsilon peptide and had an elution profile similar to protein kinase C derived from untreated cells. Using antisera recognizing the catalytic and regulatory domains of the kinase, no evidence for proteolytic degradation of protein kinase C was observed. Although incubation of extracts from vehicle and TPA-treated cells inhibited the activity of partially purified protein kinase C, the degree of inhibition was similar in the two extracts. These findings suggest that TPA markedly diminishes protein kinase C-dependent phosphorylation of histone and endogenous substrates in part by altering kinase substrate specificity. These observations provide evidence for a novel post-translational process that can modulate protein kinase C-dependent phosphorylation.

The metabolite 1 alpha,25-dihydroxyvitamin D3 enhances lymphokine-mediated activation of the oxidative metabolism of the U937 cell line and phosphorylation of a 48-kD respiratory burst-associated protein.

U937 cells respond to a variety of stimuli with increased differentiation as manifested by reduced growth, increased adherence, increased expression of several surface receptors, and increased capacity for phagocytosis and formation of reactive oxygen intermediates. In the present study the effects of lymphocyte conditioned media, recombinant interferon-gamma (IFN-gamma), and 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) on the ability to form reactive oxygen intermediates by U937 cells were measured by using the luminol-dependent luminescence (LDL) assay. Neither 1,25(OH)2D3 alone nor IFN-gamma alone enhanced competence for phorbol myristate acetate-stimulated LDL. Cells were capable of moderate LDL after exposure to lymphocyte conditioned media, and this was enhanced by 1,25(OH)2D3 (10(-8) mol/L) and other vitamin D metabolites at higher concentrations. This effect was not secondary to accelerated production of myeloperoxidase, which is important in the LDL assay. Enhanced phorbol myristate acetate-stimulated phosphorylation of a 48-kd substrate was observed in 32P-labeled intact cells treated with 1,25(OH)2D3 alone or in combination with IFN-gamma. Treatment of cells with IFN-gamma or lymphocyte conditioned media did not alter phosphorylation. These results support the concept that 1,25(OH)2D3 plays a role in phagocyte differentiation and activation beyond the effects of lymphokines. Protein kinase C-mediated phosphorylation reactions may be necessary for the ability of U937 cells to reduce O2 and required for maximal activity under some conditions of incubation.