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ABSTRACT

Sodium–glucose co-transporter-2 (SGLT2) inhibitors are an emerging class of agents for use in the treatment of type 2 diabetes mellitus (T2DM). Inhibition of SGLT2 leads to improved glycemic control through increased urinary glucose excretion (UGE). In this study, a biologically based pharmacokinetic/pharmacodynamic (PK/PD) model of SGLT2 inhibitor-mediated UGE was developed. The derived model was used to characterize the acute PK/PD relationship of the SGLT2 inhibitor, dapagliflozin, in rats. The quantitative translational pharmacology of dapagliflozin was examined through both prospective simulation and direct modeling of mean literature data obtained for dapagliflozin in healthy subjects. Prospective simulations provided time courses of UGE that were of consistent shape to clinical observations, but were modestly biased toward under prediction. Direct modeling provided an improved characterization of the data and precise parameter estimates which were reasonably consistent with those predicted from preclinical data. Overall, these results indicate that the acute clinical pharmacology of SGLT2 inhibitors in healthy subjects can be reasonably well predicted from preclinical data through rational accounting of species differences in pharmacokinetics, physiology, and SGLT2 pharmacology. Because these data can be generated at the earliest stages of drug discovery, the proposed model is useful in the design and development of novel SGLT2 inhibitors. In addition, this model is expected to serve as a useful foundation for future efforts to understand and predict the effects of SGLT2 inhibition under chronic administration and in other patient populations.

Background

The kidney plays an important role in glucose metabolism, and has been considered a target for therapeutic intervention. The sodium-glucose cotransporter type 2 (SGLT2) mediates most of the glucose reabsorption from the proximal renal tubule. Inhibition of SGLT2 leads to glucosuria and provides a unique mechanism to lower elevated blood glucose levels in diabetes. The purpose of this review is to explore the physiology of SGLT2 and discuss several SGLT2 inhibitors which have clinical data in patients with type 2 diabetes.

Methods

We performed a PubMed search using the terms “SGLT2” and “SGLT2 inhibitor” through April 10, 2012. Published articles, press releases, and abstracts presented at national and international meetings were considered.

Results

SGLT2 inhibitors correct a novel pathophysiological defect, have an insulin-independent action, are efficacious with glycosylated hemoglobin reduction ranging from 0.5% to 1.5%, promote weight loss, have a low incidence of hypoglycemia, complement the action of other antidiabetic agents, and can be used at any stage of diabetes. They are generally well tolerated. However, due to side effects, such as repeated urinary tract and genital infections, increased hematocrit, and decreased blood pressure, appropriate patient selection for drug initiation and close monitoring after initiation will be important. Results of ongoing clinical studies of the effect of SGLT2 inhibitors on diabetic complications and cardiovascular safety are crucial to determine the risk-benefit ratio. A recent decision by the Committee for Medicinal Products for Human Use of the European Medicines Agency has recommended approval of dapagliflozin for the treatment of type 2 diabetes as an adjunct to diet and exercise, in combination with other glucose-lowering medicinal products, including insulin, and as a monotherapy for metformin-intolerant patients. Clinical research also remains to be carried out on the long-term effects of glucosuria and other potential effects of SGLT2 inhibitors, especially in view of the observed increase in the incidence of bladder and breast cancer. SGLT2 inhibitors represent a promising approach for the treatment of diabetes, and could potentially be an addition to existing therapies.

Thirty-six patients with type 2 diabetes mellitus (T2DM) were randomized 1:1:1 to receive a once-daily oral dose of placebo or 150 or 300 mg of the dual SGLT1/SGLT2 inhibitor LX4211 for 28 days. Relative to placebo, LX4211 enhanced urinary glucose excretion by inhibiting SGLT2-mediated renal glucose reabsorption; markedly and significantly improved multiple measures of glycemic control, including fasting plasma glucose, oral glucose tolerance, and HbA1c; and significantly lowered serum triglycerides. LX4211 also mediated trends for lower weight, lower blood pressure, and higher glucagon-like peptide-1 levels. In a follow-up single-dose study in 12 patients with T2DM, LX4211 (300 mg) significantly increased glucagon-like peptide-1 and peptide YY levels relative to pretreatment values, probably by delaying SGLT1-mediated intestinal glucose absorption. In both studies, LX4211 was well tolerated without evidence of increased gastrointestinal side effects. These data support further study of LX4211-mediated dual SGLT1/SGLT2 inhibition as a novel mechanism of action in the treatment of T2DM.

Background

Glucagon-like peptide (GLP-1) analogues are a new class of drugs used in the treatment of type 2 diabetes. They are given by injection, and regulate glucose levels by stimulating glucose-dependent insulin secretion and biosynthesis, suppressing glucagon secretion, and delaying gastric emptying and promoting satiety. This systematic review aims to provide evidence on the clinical effectiveness of the GLP-1 agonists in patients not achieving satisfactory glycaemic control with one or more oral glucose lowering drugs.

Methods

MEDLINE, EMBASE, the Cochrane Library and Web of Science were searched to find the relevant papers. We identified 28 randomised controlled trials comparing GLP-1 analogues with placebo, other glucose-lowering agents, or another GLP-1 analogue, in patients with type 2 diabetes with inadequate control on a single oral agent, or on dual therapy. Primary outcomes included HbA1c, weight change and adverse events.

Results

Studies were mostly of short duration, usually 26 weeks. All GLP-1 agonists reduced HbA1c by about 1% compared to placebo. Exenatide twice daily and insulin gave similar reductions in HbA1c, but exenatide 2 mg once weekly and liraglutide 1.8 mg daily reduced it by 0.20% and 0.30% respectively more than glargine. Liraglutide 1.2 mg daily reduced HbA1c by 0.34% more than sitagliptin 100 mg daily. Exenatide and liraglutide gave similar improvements in HbA1c to sulphonylureas. Exenatide 2 mg weekly and liraglutide 1.8 mg daily reduced HbA1c by more than exenatide 10 μg twice daily and sitagliptin 100 mg daily. Exenatide 2 mg weekly reduced HbA1c by 0.3% more than pioglitazone 45 mg daily.

Exenatide and liraglutide resulted in greater weight loss (from 2.3 to 5.5 kg) than active comparators. This was not due simply to nausea. Hypoglycaemia was uncommon, except when combined with a sulphonylurea. The commonest adverse events with all GLP-1 agonists were initial nausea and vomiting. The GLP-1 agonists have some effect on beta-cell function, but this is not sustained after the drug is stopped.

Conclusions

GLP-1 agonists are effective in improving glycaemic control and promoting weight loss.

Sodium/glucose cotransporter 2 (SGLT2) inhibitors are oral hypoglycemic agents used to treat patients with diabetes mellitus. SGLT2 inhibitors block reabsorption of filtered glucose by inhibiting SGLT2, the primary glucose transporter in the proximal tubular cell (PTC), leading to glycosuria and lowering of serum glucose. We examined the renoprotective effects of the SGLT2 inhibitor empagliflozin to determine whether blocking glucose entry into the kidney PTCs reduced the inflammatory and fibrotic responses of the cell to high glucose. We used an in vitro model of human PTCs. HK2 cells (human kidney PTC line) were exposed to control 5 mM, high glucose (HG) 30 mM or the profibrotic cytokine transforming growth factor beta (TGFβ1; 0.5 ng/ml) in the presence and absence of empagliflozin for up to 72 h. SGLT1 and 2 expression and various inflammatory/fibrotic markers were assessed. A chromatin immunoprecipitation assay was used to determine the binding of phosphorylated smad3 to the promoter region of the SGLT2 gene. Our data showed that TGFβ1 but not HG increased SGLT2 expression and this occurred via phosphorylated smad3. HG induced expression of Toll-like receptor-4, increased nuclear deoxyribonucleic acid binding for nuclear factor kappa B (NF-κB) and activator protein 1, induced collagen IV expression as well as interleukin-6 secretion all of which were attenuated with empagliflozin. Empagliflozin did not reduce high mobility group box protein 1 induced NF-κB suggesting that its effect is specifically related to a reduction in glycotoxicity. SGLT1 and GLUT2 expression was not significantly altered with HG or empagliflozin. In conclusion, empagliflozin reduces HG induced inflammatory and fibrotic markers by blocking glucose transport and did not induce a compensatory increase in SGLT1/GLUT2 expression. Although HG itself does not regulate SGLT2 expression in our model, TGFβ increases SGLT2 expression through phosphorylated smad3.

OBJECTIVE

Although initially effective, sulfonylureas are associated with poor glycemic durability, weight gain, and hypoglycemia. Dapagliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), reduces hyperglycemia by increasing urinary glucose excretion independent of insulin and may cause fewer of these adverse effects. We compared the efficacy, safety, and tolerability of dapagliflozin with the sulfonylurea glipizide in patients with type 2 diabetes inadequately controlled with metformin monotherapy.

RESEARCH DESIGN AND METHODS

This 52-week, double-blind, multicenter, active-controlled, noninferiority trial randomized patients with type 2 diabetes (baseline mean HbA1c, 7.7%), who were receiving metformin monotherapy, to add-on dapagliflozin (n = 406) or glipizide (n = 408) up-titrated over 18 weeks, based on glycemic response and tolerability, to ≤10 or ≤20 mg/day, respectively.

RESULTS

The primary end point, adjusted mean HbA1c reduction with dapagliflozin (−0.52%) compared with glipizide (−0.52%), was statistically noninferior at 52 weeks. Key secondary end points: dapagliflozin produced significant adjusted mean weight loss (−3.2 kg) versus weight gain (1.2 kg; P < 0.0001) with glipizide, significantly increased the proportion of patients achieving ≥5% body weight reduction (33.3%) versus glipizide (2.5%; P < 0.0001), and significantly decreased the proportion experiencing hypoglycemia (3.5%) versus glipizide (40.8%; P < 0.0001). Events suggestive of genital infections and lower urinary tract infections were reported more frequently with dapagliflozin compared with glipizide but responded to standard treatment and rarely led to study discontinuation.

CONCLUSIONS

Despite similar 52-week glycemic efficacy, dapagliflozin reduced weight and produced less hypoglycemia than glipizide in type 2 diabetes inadequately controlled with metformin. Long-term studies are required to further evaluate genital and urinary tract infections with SGLT2 inhibitors.

There is a recognized need for new treatment options for type 2 diabetes mellitus (T2DM). Recovery of glucose from the glomerular filtrate represents an important mechanism in maintaining glucose homeostasis and represents a novel target for the management of T2DM. Recovery of glucose from the glomerular filtrate is executed principally by the type 2 sodium-glucose cotransporter (SGLT2). Inhibition of SGLT2 promotes glucose excretion and normalizes glycemia in animal models. First reports of specifically designed SGLT2 inhibitors began to appear in the second half of the 1990s. Several candidate SGLT2 inhibitors are currently under development, with four in the later stages of clinical testing. The safety profile of SGLT2 inhibitors is expected to be good, as their target is a highly specific membrane transporter expressed almost exclusively within the renal tubules. One safety concern is that of glycosuria, which could predispose patients to increased urinary tract infections. So far the reported safety profile of SGLT2 inhibitors in clinical studies appears to confirm that the class is well tolerated. Where SGLT2 inhibitors will fit in the current cascade of treatments for T2DM has yet to be established. The expected favorable safety profile and insulin-independent mechanism of action appear to support their use in combination with other antidiabetic drugs. Promotion of glucose excretion introduces the opportunity to clear calories (80–90 g [300–400 calories] of glucose per day) in patients that are generally overweight, and is expected to work synergistically with weight reduction programs. Experience will most likely lead to better understanding of which patients are likely to respond best to SGLT2 inhibitors, and under what circumstances.

There is a recognized need for new treatment options for type 2 diabetes mellitus (T2DM). Recovery of glucose from the glomerular filtrate represents an important mechanism in maintaining glucose homeostasis and represents a novel target for the management of T2DM. Recovery of glucose from the glomerular filtrate is executed principally by the type 2 sodium-glucose cotransporter (SGLT2). Inhibition of SGLT2 promotes glucose excretion and normalizes glycemia in animal models. First reports of specifically designed SGLT2 inhibitors began to appear in the second half of the 1990s. Several candidate SGLT2 inhibitors are currently under development, with four in the later stages of clinical testing. The safety profile of SGLT2 inhibitors is expected to be good, as their target is a highly specific membrane transporter expressed almost exclusively within the renal tubules. One safety concern is that of glycosuria, which could predispose patients to increased urinary tract infections. So far the reported safety profile of SGLT2 inhibitors in clinical studies appears to confirm that the class is well tolerated. Where SGLT2 inhibitors will fit in the current cascade of treatments for T2DM has yet to be established. The expected favorable safety profile and insulin-independent mechanism of action appear to support their use in combination with other antidiabetic drugs. Promotion of glucose excretion introduces the opportunity to clear calories (80–90 g [300–400 calories] of glucose per day) in patients that are generally overweight, and is expected to work synergistically with weight reduction programs. Experience will most likely lead to better understanding of which patients are likely to respond best to SGLT2 inhibitors, and under what circumstances.

Introduction

Dapagliflozin is a first-in-class sodium-glucose transporter 2 (SGLT2) inhibitor under investigation for the treatment of type 2 diabetes mellitus. A thorough QTc study was conducted, according to International Conference on Harmonization E14 guidelines, to characterize the effect of dapagliflozin on cardiac repolarization.

Methods

The present study was a double-blind, four-period, placebo-controlled crossover study at a single-center inpatient clinical pharmacology unit. The study enrolled 50 healthy men who were randomized to receive sequences of single doses of dapagliflozin 150 mg, dapagliflozin 20 mg, moxifloxacin 400 mg, and placebo. The sequences were randomized based on the Williams design for a cross-over study to reduce the “carryover” effects from drug-to-drug even with sufficient washout periods. Digital 12-lead electrocardiograms were recorded at nine time points over 24 hours in each period. QT intervals were corrected for heart rate using a study-specific correction factor (QTcX) and Fridericia’s formula.

Results

For dapagliflozin, the upper bound of the one-sided 95% confidence interval (CI) for time-matched, placebo-subtracted, baseline adjusted QTc intervals (ΔΔQTc) was <10 ms. ΔΔQTc was independent of dapagliflozin concentrations. No QTc thresholds >450 ms or QTc increases >30 ms were observed. Moxifloxacin increased the mean QTcX interval by 7.7 ms (lower bound 90% CI, 6.2 ms) over 1–4 hours after dosing, confirming assay sensitivity.

Conclusion

Dapagliflozin, at supratherapeutic doses, does not have a clinically significant effect on the QT interval in healthy subjects.

Introduction

Dapagliflozin is a first-in-class sodium-glucose transporter 2 (SGLT2) inhibitor under investigation for the treatment of type 2 diabetes mellitus. A thorough QTc study was conducted, according to International Conference on Harmonization E14 guidelines, to characterize the effect of dapagliflozin on cardiac repolarization.

Methods

The present study was a double-blind, four-period, placebo-controlled crossover study at a single-center inpatient clinical pharmacology unit. The study enrolled 50 healthy men who were randomized to receive sequences of single doses of dapagliflozin 150 mg, dapagliflozin 20 mg, moxifloxacin 400 mg, and placebo. The sequences were randomized based on the Williams design for a cross-over study to reduce the “carryover” effects from drug-to-drug even with sufficient washout periods. Digital 12-lead electrocardiograms were recorded at nine time points over 24 hours in each period. QT intervals were corrected for heart rate using a study-specific correction factor (QTcX) and Fridericia’s formula.

Results

For dapagliflozin, the upper bound of the one-sided 95% confidence interval (CI) for time-matched, placebo-subtracted, baseline adjusted QTc intervals (ΔΔQTc) was <10 ms. ΔΔQTc was independent of dapagliflozin concentrations. No QTc thresholds >450 ms or QTc increases >30 ms were observed. Moxifloxacin increased the mean QTcX interval by 7.7 ms (lower bound 90% CI, 6.2 ms) over 1–4 hours after dosing, confirming assay sensitivity.

Conclusion

Dapagliflozin, at supratherapeutic doses, does not have a clinically significant effect on the QT interval in healthy subjects.

Background

Canagliflozin is a sodium glucose co-transporter (SGLT) 2 inhibitor in clinical development for the treatment of type 2 diabetes mellitus (T2DM).

Methods

14C-alpha-methylglucoside uptake in Chinese hamster ovary-K cells expressing human, rat, or mouse SGLT2 or SGLT1; 3H-2-deoxy-d-glucose uptake in L6 myoblasts; and 2-electrode voltage clamp recording of oocytes expressing human SGLT3 were analyzed. Graded glucose infusions were performed to determine rate of urinary glucose excretion (UGE) at different blood glucose (BG) concentrations and the renal threshold for glucose excretion (RTG) in vehicle or canagliflozin-treated Zucker diabetic fatty (ZDF) rats. This study aimed to characterize the pharmacodynamic effects of canagliflozin in vitro and in preclinical models of T2DM and obesity.

Results

Treatment with canagliflozin 1 mg/kg lowered RTG from 415±12 mg/dl to 94±10 mg/dl in ZDF rats while maintaining a threshold relationship between BG and UGE with virtually no UGE observed when BG was below RTG. Canagliflozin dose-dependently decreased BG concentrations in db/db mice treated acutely. In ZDF rats treated for 4 weeks, canagliflozin decreased glycated hemoglobin (HbA1c) and improved measures of insulin secretion. In obese animal models, canagliflozin increased UGE and decreased BG, body weight gain, epididymal fat, liver weight, and the respiratory exchange ratio.

Conclusions

Canagliflozin lowered RTG and increased UGE, improved glycemic control and beta-cell function in rodent models of T2DM, and reduced body weight gain in rodent models of obesity.

Objective To assess the effect of targeting intensive glycaemic control versus conventional glycaemic control on all cause mortality and cardiovascular mortality, non-fatal myocardial infarction, microvascular complications, and severe hypoglycaemia in patients with type 2 diabetes.

Design Systematic review with meta-analyses and trial sequential analyses of randomised trials.

Data sources Cochrane Library, Medline, Embase, Science Citation Index Expanded, LILACS, and CINAHL to December 2010; hand search of reference lists and conference proceedings; contacts with authors, relevant pharmaceutical companies, and the US Food and Drug Administration.

Study selection Randomised clinical trials comparing targeted intensive glycaemic control with conventional glycaemic control in patients with type 2 diabetes. Published and unpublished trials in all languages were included, irrespective of predefined outcomes.

Data extraction Two reviewers independently assessed studies for inclusion and extracted data related to study methods, interventions, outcomes, risk of bias, and adverse events. Risk ratios with 95% confidence intervals were estimated with fixed and random effects models.

Results Fourteen clinical trials that randomised 28 614 participants with type 2 diabetes (15 269 to intensive control and 13 345 to conventional control) were included. Intensive glycaemic control did not significantly affect the relative risks of all cause (1.02, 95% confidence interval 0.91 to 1.13; 28 359 participants, 12 trials) or cardiovascular mortality (1.11, 0.92 to 1.35; 28 359 participants, 12 trials). Trial sequential analyses rejected a relative risk reduction above 10% for all cause mortality and showed insufficient data on cardiovascular mortality. The risk of non-fatal myocardial infarction may be reduced (relative risk 0.85, 0.76 to 0.95; P=0.004; 28 111 participants, 8 trials), but this finding was not confirmed in trial sequential analysis. Intensive glycaemic control showed a reduction of the relative risks for the composite microvascular outcome (0.88, 0.79 to 0.97; P=0.01; 25 600 participants, 3 trials) and retinopathy (0.80, 0.67 to 0.94; P=0.009; 10 793 participants, 7 trials), but trial sequential analyses showed that sufficient evidence had not yet been reached. The estimate of an effect on the risk of nephropathy (relative risk 0.83, 0.64 to 1.06; 27 769 participants, 8 trials) was not statistically significant. The risk of severe hypoglycaemia was significantly increased when intensive glycaemic control was targeted (relative risk 2.39, 1.71 to 3.34; 27 844 participants, 9 trials); trial sequential analysis supported a 30% increased relative risk of severe hypoglycaemia.

Conclusion Intensive glycaemic control does not seem to reduce all cause mortality in patients with type 2 diabetes. Data available from randomised clinical trials remain insufficient to prove or refute a relative risk reduction for cardiovascular mortality, non-fatal myocardial infarction, composite microvascular complications, or retinopathy at a magnitude of 10%. Intensive glycaemic control increases the relative risk of severe hypoglycaemia by 30%.

SGLT2 (for “Sodium GLucose coTransporter” protein 2) is the major protein responsible for glucose reabsorption in the kidney and its inhibition has been the focus of drug discovery efforts to treat type 2 diabetes. In order to better clarify the human tissue distribution of expression of SGLT2 and related members of this cotransporter class, we performed TaqMan™ (Applied Biosystems, Foster City, CA, USA) quantitative polymerase chain reaction (PCR) analysis of SGLT2 and other sodium/glucose transporter genes on RNAs from 72 normal tissues from three different individuals. We consistently observe that SGLT2 is highly kidney specific while SGLT5 is highly kidney abundant; SGLT1, sodium-dependent amino acid transporter (SAAT1), and SGLT4 are highly abundant in small intestine and skeletal muscle; SGLT6 is expressed in the central nervous system; and sodium myoinositol cotransporter is ubiquitously expressed across all human tissues.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s13300-010-0006-4 and is accessible for authorized users.

SGLT2 (for “Sodium GLucose coTransporter” protein 2) is the major protein responsible for glucose reabsorption in the kidney and its inhibition has been the focus of drug discovery efforts to treat type 2 diabetes. In order to better clarify the human tissue distribution of expression of SGLT2 and related members of this cotransporter class, we performed TaqMan™ (Applied Biosystems, Foster City, CA, USA) quantitative polymerase chain reaction (PCR) analysis of SGLT2 and other sodium/glucose transporter genes on RNAs from 72 normal tissues from three different individuals. We consistently observe that SGLT2 is highly kidney specific while SGLT5 is highly kidney abundant; SGLT1, sodium-dependent amino acid transporter (SAAT1), and SGLT4 are highly abundant in small intestine and skeletal muscle; SGLT6 is expressed in the central nervous system; and sodium myoinositol cotransporter is ubiquitously expressed across all human tissues.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s13300-010-0006-4 and is accessible for authorized users.

The treatment of diabetes has been mainly focused on maintaining normal blood glucose concentrations. Insulin and hypoglycemic agents have been used as standard therapeutic strategies. However, these are characterized by limited efficacy and adverse side effects, making the development of new therapeutic alternatives mandatory. Inhibition of glucose reabsorption in the kidney, mediated by SGLT1 or SGLT2, represents a promising therapeutic approach. Therefore, the aim of the present study was to evaluate the effect of thioglycosides on human SGLT1 and SGLT2. For this purpose, stably transfected Chinese hamster ovary (CHO) cells expressing human SGLT1 and SGLT2 were used. The inhibitory effect of thioglycosides was assessed in transport studies and membrane potential measurements, using α-methyl-glucoside uptake and fluorescence resonance energy transfer, respectively. We found that some thioglycosides inhibited hSGLT more strongly than phlorizin. Specifically, thioglycoside I (phenyl-1'-thio-β-D-glucopyranoside) inhibited hSGLT2 stronger than hSGLT1 and to a larger extent than phlorizin. Thioglycoside VII (2-hydroxymethyl-phenyl-1'-thio-β-D-galacto-pyranoside) had a pronounced inhibitory effect on hSGLT1 but not on hSGLT2. Kinetic studies confirmed the inhibitory effect of these thioglycosides on hSGLT1 or hSGLT2, demonstrating competitive inhibition as the mechanism of action. Therefore, these thioglycosides represent promising therapeutic agents for the control of hyperglycemia in patients with diabetes.

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are a novel class of glucuretic, antihyperglycemic drugs that target the process of renal glucose reabsorption and induce glucuresis independently of insulin secretion or action. In patients with type 2 diabetes mellitus, SGLT2 inhibitors have been found to consistently reduce measures of hyperglycemia, including hemoglobin A1c, fasting plasma glucose, and postprandial glucose, throughout the continuum of disease. By inducing the renal excretion of glucose and its associated calories, SGLT2 inhibitors reduce weight and have the potential to be disease modifying by addressing the caloric excess that is believed to be one of the root causes of type 2 diabetes mellitus. Additional benefits, including the possibility for combination with insulin-dependent antihyperglycemic drugs, a low potential for hypoglycemia, and the ability to reduce blood pressure, were anticipated from the novel mechanism of action and have been demonstrated in clinical studies. Mechanism-related risks include an increased incidence of urinary tract and genital infections and the possibility of over-diuresis in volume-sensitive patients. Taken together, the results of Phase III clinical studies generally point to a positive benefit-risk ratio across the continuum of diabetes patients. To date, data on dapagliflozin, a selective SGLT2 inhibitor in development, demonstrate that the kidney is an efficacious and safe target for therapy, and that SGLT2 inhibition may have benefits for patients with type 2 diabetes mellitus beyond glycemic control.

OBJECTIVE

Inhibition of the Na+-glucose cotransporter type 2 (SGLT2) is currently being pursued as an insulin-independent treatment for diabetes; however, the behavioral and metabolic consequences of SGLT2 deletion are unknown. Here, we used a SGLT2 knockout mouse to investigate the effect of increased renal glucose excretion on glucose homeostasis, insulin sensitivity, and pancreatic β-cell function.

RESEARCH DESIGN AND METHODS

SGLT2 knockout mice were fed regular chow or a high-fat diet (HFD) for 4 weeks, or backcrossed onto the db/db background. The analysis used metabolic cages, glucose tolerance tests, euglycemic and hyperglycemic clamps, as well as isolated islet and perifusion studies.

RESULTS

SGLT2 deletion resulted in a threefold increase in urine output and a 500-fold increase in glucosuria, as well as compensatory increases in feeding, drinking, and activity. SGLT2 knockout mice were protected from HFD-induced hyperglycemia and glucose intolerance and had reduced plasma insulin concentrations compared with controls. On the db/db background, SGLT2 deletion prevented fasting hyperglycemia, and plasma insulin levels were also dramatically improved. Strikingly, prevention of hyperglycemia by SGLT2 knockout in db/db mice preserved pancreatic β-cell function in vivo, which was associated with a 60% increase in β-cell mass and reduced incidence of β-cell death.

CONCLUSIONS

Prevention of renal glucose reabsorption by SGLT2 deletion reduced HFD- and obesity-associated hyperglycemia, improved glucose intolerance, and increased glucose-stimulated insulin secretion in vivo. Taken together, these data support SGLT2 inhibition as a viable insulin-independent treatment of type 2 diabetes.

Objective To determine all cause mortality and deaths from cardiovascular events related to intensive glucose lowering treatment in people with type 2 diabetes.

Design Meta-analysis of randomised controlled trials.

Data sources Medline, Embase, and the Cochrane database of systematic reviews.

Study selection Randomised controlled trials that assessed the effect of intensive glucose lowering treatment on cardiovascular events and microvascular complications in adults (≥18 years) with type 2 diabetes.

Data extraction Primary end points were all cause mortality and death from cardiovascular causes. Secondary end points were severe hypoglycaemia and macrovascular and microvascular events.

Synthesis of results Results are reported as risk ratios with 99% confidence intervals. Statistical heterogeneity between trials was assessed with χ², τ², and I2 statistics. A fixed effect model was used to assess the effect on the outcomes of intensive glucose lowering versus standard treatment. The quality of clinical trials was assessed by the Jadad score.

Results 13 studies were included. Of 34 533 patients, 18 315 received intensive glucose lowering treatment and 16 218 standard treatment. Intensive treatment did not significantly affect all cause mortality (risk ratio 1.04, 99% confidence interval 0.91 to 1.19) or cardiovascular death (1.11, 0.86 to 1.43). Intensive therapy was, however, associated with reductions in the risk of non-fatal myocardial infarction (0.85, 0.74 to 0.96, P<0.001), and microalbuminuria (0.90, 0.85 to 0.96, P<0.001) but a more than twofold increase in the risk of severe hypoglycaemia (2.33, 21.62 to 3.36, P<0.001). Over a treatment period of five years, 117 to 150 patients would need to be treated to avoid one myocardial infarction and 32 to 142 patients to avoid one episode of microalbuminuria, whereas one severe episode of hypoglycaemia would occur for every 15 to 52 patients. In analysis restricted to high quality studies (Jadad score >3), intensive treatment was not associated with any significant risk of reductions but resulted in a 47% increase in risk of congestive heart failure (P<0.001).

Conclusions The overall results of this meta-analysis show limited benefits of intensive glucose lowering treatment on all cause mortality and deaths from cardiovascular causes. We cannot exclude a 9% reduction or a 19% increase in all cause mortality and a 14% reduction or a 43% increase in cardiovascular death. The benefit:risk ratio of intensive glucose lowering treatment in the prevention of macrovascular and microvascular events remains uncertain. The harm associated with severe hypoglycaemia might counterbalance the potential benefit of intensive glucose lowering treatment. More double blind randomised controlled trials are needed to establish the best therapeutic approach in people with type 2 diabetes.

Background

Many children with type 1 diabetes have poor glycaemic control. Since the Diabetes Control and Complications Trial (DCCT) showed that tighter control reduces complication rates, there has been more emphasis on intensified insulin therapy. We know that patients and families are afraid of hypoglycaemia. We hypothesised that fear of hypoglycaemia might take precedence over concern about long-term complications, and that behaviour to avoid hypoglycaemia might be at the cost of poorer control, and aimed to evaluate the effectiveness of any interventions designed to prevent that. The objective of this review was to systematically review studies concerning the extent and consequences of fear of hypoglycaemia in parents of children under 12 years of age with type 1 diabetes, and interventions to reduce it.

Methods

Data Sources: MEDLINE, EMBASE, PsycINFO, The Cochrane Library, Web of Science, meeting abstracts of EASD, ADA and Diabetes UK, Current Controlled Trials, ClinicalTrials.gov, UK CRN, scrutiny of bibliographies of retrieved papers and contact with experts in the field.

Inclusions: Relevant studies of any design of parents of children under 12 years of age with Type 1 diabetes were included. The key outcomes were the extent and impact of fear, hypoglycaemia avoidance behaviour in parents due to parental fear of hypoglycaemia in their children, the effect on diabetes control, and the impact of interventions to reduce this fear and hypoglycaemia avoidance behaviour.

Results

Eight articles from six studies met the inclusion criteria. All were cross sectional studies and most were of good quality. Parental fear of hypoglycaemia, anxiety and depression were reported to be common. There was a paucity of evidence on behaviour to avoid hypoglycaemia, but there were some suggestions that higher than desirable blood glucose levels might be permitted in order to avoid hypoglycaemia. No studies reporting interventions to reduce parental fear of hypoglycaemia were found.

Conclusions

The evidence base was limited. Parents of children with Type 1 diabetes reported considerable parental fear of hypoglycaemia, affecting both parental health and quality of life. There is some suggestion that hypoglycaemia avoidance behaviours by parents might adversely affect glycaemic control. Trials of interventions to reduce parental anxiety and hypoglycaemia avoidance behaviour are needed. We suggest that there should be a trial of structured education for parents of young children with Type 1 diabetes.

Background

Intestinal transport exhibits distinct diurnal rhythmicity. Understanding the mechanisms behind this may reveal new therapeutic strategies to modulate intestinal function in disease states such as diabetes and obesity, as well as short bowel syndrome. Although diurnal rhythms have been amply documented for several intestinal transporters, the complexity of transepithelial transport has precluded definitive attribution of rhythmicity in glucose uptake to a single transporter. To address this gap, we assessed temporal changes in glucose transport mediated by the Na+/glucose co-transporter SGLT1.

Methods

SGLT1 expression was assessed at 4 times during the day: ZT3, ZT9, ZT15 and ZT21 (ZT, Zeitgeber time; lights-on at ZT0; n=8/ time). SGLT1 activity, defined as glucose uptake sensitive to the specific SGLT1 inhibitor phloridzin, was measured in everted intestinal sleeves. Changes in Sglt1 expression were assessed by real-time PCR and immunoblotting.

Results

Glucose uptake was significantly higher at ZT15 in jejunum (p<0.05 vs. ZT3). Phloridzin significantly reduced glucose uptake and completely abolished its rhythmicity. Sglt1 mRNA levels were significantly higher at ZT9 and ZT15 in jejunum and ileum respectively (p<0.05 vs. ZT3), while SGLT1 protein levels were significantly higher at ZT15 in jejunum (p<0.05 vs. ZT3).

Conclusions

Our results definitively link diurnal changes in intestinal glucose uptake capacity to changes in both SGLT1 mRNA and protein. These findings suggest that modulation of transporter expression would enhance intestinal function and provides an impetus to elucidate the mechanisms underlying diurnal rhythmicity in transcription. Modulation of intestinal function would benefit the management of malnutrition as well as diabetes and obesity.

Objective To determine whether psychological interventions have any effect on glycaemic control in people with type 1 diabetes.

Design Systematic review and meta-analysis of psychological therapies to assess their effectiveness in improving glycaemic control in type 1 diabetes.

Data sources Medline, PsycINFO, Embase, and Cochrane central register of controlled trials searched to September 2004.

Review methods All included studies were randomised controlled trials in children (including adolescents) or adults with type 1 diabetes that evaluated the effect of a psychological therapy (counselling, cognitive behaviour therapy, family systems therapy, and psychodynamic therapy) on control of diabetes. Data were extracted on sample size, age, duration of diabetes, type of psychological therapy, its mode of delivery, and type of intervention in control group.

Main outcome measures Glycaemic control measured by percentage of glycated haemoglobin and psychological distress. Pooled standardised effect sizes were calculated.

Results 29 trials were eligible for the systematic review and 21 trials for the meta-analysis. In the 10 studies of children and adolescents included in the meta-analysis, the mean percentage of glycated haemoglobin was significantly reduced in those who had received a psychological intervention compared with those in the control group (pooled standardised mean difference -0.35 (95% confidence interval -0.66 to -0.04), equivalent to a 0.48% (0.05% to 0.91%) absolute reduction in glycated haemoglobin. In the 11 studies in adults the pooled standardised mean difference was -0.17 (-0.45 to 0.10), equivalent to 0.22% (-0.13% to 0.56%) absolute reduction in glycated haemoglobin. Psychological distress was significantly lower in the intervention groups in children and adolescents (pooled standardised effect size -0.46, -0.83 to -0.10) but not in adults (-0.25, -0.51 to 0.01).

Conclusion Psychological treatments can slightly improve glycaemic control in children and adolescents with diabetes but have no effect in adults.

To clarify the physiological role of Na+-d-glucose cotransporter SGLT1 in small intestine and kidney, Sglt1−/− mice were generated and characterized phenotypically. After gavage of d-glucose, small intestinal glucose absorption across the brush-border membrane (BBM) via SGLT1 and GLUT2 were analyzed. Glucose-induced secretion of insulinotropic hormone (GIP) and glucagon-like peptide 1 (GLP-1) in wild-type and Sglt1−/− mice were compared. The impact of SGLT1 on renal glucose handling was investigated by micropuncture studies. It was observed that Sglt1−/− mice developed a glucose-galactose malabsorption syndrome but thrive normally when fed a glucose-galactose–free diet. In wild-type mice, passage of d-glucose across the intestinal BBM was predominantly mediated by SGLT1, independent the glucose load. High glucose concentrations increased the amounts of SGLT1 and GLUT2 in the BBM, and SGLT1 was required for upregulation of GLUT2. SGLT1 was located in luminal membranes of cells immunopositive for GIP and GLP-1, and Sglt1−/− mice exhibited reduced glucose-triggered GIP and GLP-1 levels. In the kidney, SGLT1 reabsorbed ∼3% of the filtered glucose under normoglycemic conditions. The data indicate that SGLT1 is 1) pivotal for intestinal mass absorption of d-glucose, 2) triggers the glucose-induced secretion of GIP and GLP-1, and 3) triggers the upregulation of GLUT2.

This study examines the conformations of the Na+/glucose cotransporter (SGLT1) during sugar transport using charge and fluorescence measurements on the human SGLT1 mutant G507C expressed in Xenopus oocytes. The mutant exhibited similar steady-state and presteady-state kinetics as wild-type SGLT1, and labeling of Cys507 by tetramethylrhodamine-6-maleimide had no effect on kinetics. Our strategy was to record changes in charge and fluorescence in response to rapid jumps in membrane potential in the presence and absence of sugar or the competitive inhibitor phlorizin. In Na+ buffer, step jumps in membrane voltage elicited presteady-state currents (charge movements) that decay to the steady state with time constants τmed (3–20 ms, medium) and τslow (15–70 ms, slow). Concurrently, SGLT1 rhodamine fluorescence intensity increased with depolarizing and decreased with hyperpolarizing voltages (ΔF). The charge vs. voltage (Q-V) and fluorescence vs. voltage (ΔF-V) relations (for medium and slow components) obeyed Boltzmann relations with similar parameters: zδ (apparent valence of voltage sensor) ≈ 1; and V0.5 (midpoint voltage) between −15 and −40 mV. Sugar induced an inward current (Na+/glucose cotransport), and reduced maximal charge (Qmax) and fluorescence (ΔFmax) with half-maximal concentrations (K0.5) of 1 mM. Increasing [αMDG]o also shifted the V0.5 for Q and ΔF to more positive values, with K0.5's ≈ 1 mM. The major difference between Q and ΔF was that at saturating [αMDG]o, the presteady-state current (and Qmax) was totally abolished, whereas ΔFmax was only reduced 50%. Phlorizin reduced both Qmax and ΔFmax (Ki ≈ 0.4 μM), with no changes in V0.5's or relaxation time constants. Simulations using an eight-state kinetic model indicate that external sugar increases the occupancy probability of inward-facing conformations at the expense of outward-facing conformations. The simulations predict, and we have observed experimentally, that presteady-state currents are blocked by saturating sugar, but not the changes in fluorescence. Thus we have isolated an electroneutral conformational change that has not been previously described. This rate-limiting step at maximal inward Na+/sugar cotransport (saturating voltage and external Na+ and sugar concentrations) is the slow release of Na+ from the internal surface of SGLT1. The high affinity blocker phlorizin locks the cotransporter in an inactive conformation.

MAP17 is a membrane-associated protein that is overexpressed in human tumors. Because the expression of MAP17 increases reactive oxygen species (ROS) generation through SGLT1 in cancer cells, in the present work, we investigated whether MAP17 and/or SGLT1 might be markers for the activity of treatments involving oxidative stress, such as cisplatin or radiotherapy. First, we confirmed transcriptional alterations in genes involved in the oxidative stress induced by MAP17 expression in HeLa cervical tumor cells and found that Hela cells expressing MAP17 were more sensitive to therapies that induce ROS than were parental cells. Furthermore, MAP17 increased glucose uptake through SGLT receptors. We then analyzed MAP17 and SGLT1 expression levels in cervical tumors treated with cisplatin plus radiotherapy and correlated the expression levels with patient survival. MAP17 and SGLT1 were expressed in approximately 70% and 50% of cervical tumors of different types, respectively, but they were not expressed in adenoma tumors. Furthermore, there was a significant correlation between MAP17 and SGLT1 expression levels. High levels of either MAP17 or SGLT1 correlated with improved patient survival after treatment. However, the patients with high levels of both MAP17 and SGLT1 survived through the end of this study. Therefore, the combination of high MAP17 and SGLT1 levels is a marker for good prognosis in patients with cervical tumors after cisplatin plus radiotherapy treatment. These results also suggest that the use of MAP17 and SGLT1 markers may identify patients who are likely to exhibit a better response to treatments that boost oxidative stress in other cancer types.

OBJECTIVE

Dapagliflozin, a highly selective inhibitor of the renal sodium-glucose cotransporter-2, increases urinary excretion of glucose and lowers plasma glucose levels in an insulin-independent manner. We evaluated the efficacy and safety of dapagliflozin in treatment-naive patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This was a 24-week parallel-group, double-blind, placebo-controlled phase 3 trial. Patients with A1C 7.0–10% (n = 485) were randomly assigned to one of seven arms to receive once-daily placebo or 2.5, 5, or 10 mg dapagliflozin once daily in the morning (main cohort) or evening (exploratory cohort). Patients with A1C 10.1–12% (high-A1C exploratory cohort; n = 73) were randomly assigned 1:1 to receive blinded treatment with a morning dose of 5 or 10 mg/day dapagliflozin. The primary end point was change from baseline in A1C in the main cohort, statistically tested using an ANCOVA.

RESULTS

In the main cohort, mean A1C changes from baseline at week 24 were −0.23% with placebo and −0.58, −0.77 (P = 0.0005 vs. placebo), and −0.89% (P < 0.0001 vs. placebo) with 2.5, 5, and 10 mg dapagliflozin, respectively. Signs, symptoms, and other reports suggestive of urinary tract infections and genital infection were more frequently noted in the dapagliflozin arms. There were no major episodes of hypoglycemia. Data from exploratory cohorts were consistent with these results.

CONCLUSIONS

Dapagliflozin lowered hyperglycemia in treatment-naive patients with newly diagnosed type 2 diabetes. The near absence of hypoglycemia and an insulin-independent mechanism of action make dapagliflozin a unique addition to existing treatment options for type 2 diabetes.