Role of sodium-glucose cotransporter 2 (SGLT 2) inhibitors in the treatment of type 2 diabetes

The molecular mechanism of ion-dependent gating in secondary transporters

LeuT-like fold Na-dependent secondary active transporters form a large family of integral membrane proteins that transport various substrates against their concentration gradient across lipid membranes, using the free energy stored in the downhill concentration gradient of sodium ions. These transporters play an active role in synaptic transmission, the delivery of key nutrients, and the maintenance of osmotic pressure inside the cell. It is generally believed that binding of an ion and/or a substrate drives the conformational dynamics of the transporter. However, the exact mechanism for converting ion binding into useful work has yet to be established. Using a multi-dimensional path sampling (string-method) followed by all-atom free energy simulations, we established the principal thermodynamic and kinetic components governing the ion-dependent conformational dynamics of a LeuT-like fold transporter, the sodium/benzyl-hydantoin symporter Mhp1, for an entire conformational cycle. We found that inward-facing and outward-facing states of Mhp1 display nearly the same free energies with an ion absent from the Na2 site conserved across the LeuT-like fold transporters. The barrier separating an apo-state from inward-facing or outward-facing states of the transporter is very low, suggesting stochastic gating in the absence of ion/substrate bound. In contrast, the binding of a Na2 ion shifts the free energy stabilizing the outward-facing state and promoting substrate binding. Our results indicate that ion binding to the Na2 site may also play a key role in the intracellular thin gate dynamics modulation by altering its interactions with the transmembrane helix 5 (TM5). The Potential of Mean Force (PMF) computations for a substrate entrance displays two energy minima that correspond to the locations of the main binding site S1 and proposed allosteric S2 binding site. However, it was found that substrate's binds to the site S1 ∼5 kcal/mol more favorable than that to the site S2 for all studied bound combinations of ions and a substrate.

Novel hypothesis to explain why SGLT2 inhibitors inhibit only 30-50% of filtered glucose load in humans

Inhibitors of sodium-glucose cotransporter 2 (SGLT2) are a novel class of antidiabetes drugs, and members of this class are under various stages of clinical development for the management of type 2 diabetes mellitus (T2DM). It is widely accepted that SGLT2 is responsible for >80% of the reabsorption of the renal filtered glucose load. However, maximal doses of SGLT2 inhibitors fail to inhibit >50% of the filtered glucose load. Because the clinical efficacy of this group of drugs is entirely dependent on the amount of glucosuria produced, it is important to understand why SGLT2 inhibitors inhibit <50% of the filtered glucose load. In this Perspective, we provide a novel hypothesis that explains this apparent puzzle and discuss some of the clinical implications inherent in this hypothesis.

Characterization of renal glucose reabsorption in response to dapagliflozin in healthy subjects and subjects with type 2 diabetes

OBJECTIVE

To examine the effect of dapagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, on the major components of renal glucose reabsorption (decreased maximum renal glucose reabsorptive capacity [TmG], increased splay, and reduced threshold), using the pancreatic/stepped hyperglycemic clamp (SHC) technique.

RESEARCH DESIGN AND METHODS

Subjects with type 2 diabetes (n=12) and matched healthy subjects (n=12) underwent pancreatic/SHC (plasma glucose range 5.5-30.5 mmol/L) at baseline and after 7 days of dapagliflozin treatment. A pharmacodynamic model was developed to describe the major components of renal glucose reabsorption for both groups and then used to estimate these parameters from individual glucose titration curves.

RESULTS

At baseline, type 2 diabetic subjects had elevated TmG, splay, and threshold compared with controls. Dapagliflozin treatment reduced the TmG and splay in both groups. However, the most significant effect of dapagliflozin was a reduction of the renal threshold for glucose excretion in type 2 diabetic and control subjects.

CONCLUSIONS

The SGLT2 inhibitor dapagliflozin improves glycemic control in diabetic patients by reducing the TmG and threshold at which glucose is excreted in the urine.

Canagliflozin lowers postprandial glucose and insulin by delaying intestinal glucose absorption in addition to increasing urinary glucose excretion: results of a randomized, placebo-controlled study

OBJECTIVE

Canagliflozin, a sodium glucose cotransporter (SGLT) 2 inhibitor, is also a low-potency SGLT1 inhibitor. This study tested the hypothesis that intestinal canagliflozin levels postdose are sufficiently high to transiently inhibit intestinal SGLT1, thereby delaying intestinal glucose absorption.

RESEARCH DESIGN AND METHODS

This two-period, crossover study evaluated effects of canagliflozin on intestinal glucose absorption in 20 healthy subjects using a dual-tracer method. Placebo or canagliflozin 300 mg was given 20 min before a 600-kcal mixed-meal tolerance test. Plasma glucose, (3)H-glucose, (14)C-glucose, and insulin were measured frequently for 6 h to calculate rates of appearance of oral glucose (RaO) in plasma, endogenous glucose production, and glucose disposal.

RESULTS

Compared with placebo, canagliflozin treatment reduced postprandial plasma glucose and insulin excursions (incremental 0- to 2-h area under the curve [AUC0-2h] reductions of 35% and 43%, respectively; P < 0.001 for both), increased 0- to 6-h urinary glucose excretion (UGE0-6h, 18.2 ± 5.6 vs. <0.2 g; P < 0.001), and delayed RaO. Canagliflozin reduced AUC RaO by 31% over 0 to 1 h (geometric means, 264 vs. 381 mg/kg; P < 0.001) and by 20% over 0 to 2 h (576 vs. 723 mg/kg; P = 0.002). Over 2 to 6 h, canagliflozin increased RaO such that total AUC RaO over 0 to 6 h was <6% lower versus placebo (960 vs. 1,018 mg/kg; P = 0.003). A modest (∼10%) reduction in acetaminophen absorption was observed over the first 2 h, but this difference was not sufficient to explain the reduction in RaO. Total glucose disposal over 0 to 6 h was similar across groups.

CONCLUSIONS

Canagliflozin reduces postprandial plasma glucose and insulin by increasing UGE (via renal SGLT2 inhibition) and delaying RaO, likely due to intestinal SGLT1 inhibition.

Advances in pharmacologic therapies for type 2 diabetes

Type 2 diabetes (T2DM) is a multi-causal, heterogeneous and progressive cardiometabolic condition, with an increasing prevalence worldwide. T2DM is associated with multiple comorbidities that may impact patients' quality of life. Treatment is multifactorial, but pharmacologic treatment of hyperglycemia is still regarded as the mainstay of diabetes management. Current established therapies include metformin, sulfonylurea agents and insulin, the long-term use of which was associated with reduced micro- and macrovascular events in the United Kingdom Prospective Diabetes Study. Despite major recent advances in diabetes care, a large proportion of patients remain in poor glycemic control, necessitating the development of new therapeutic options. The recently published position statement of the American Diabetes Association and European Association for the Study of Diabetes for the management of hyperglycemia in T2DM has accommodated this wider range of therapy choices, as it is less prescriptive and advocates an individualized treatment approach, taking into account many relevant patient- and disease-related factors. This review summarizes the updates on various established agents as well as the recent developments with regard to incretin-based therapies, inhibitors of the renal tubular sodium-glucose-linked-transporter-2 and ultra-long acting basal insulin formulations.

A randomized, open-label, crossover study to evaluate the pharmacokinetics of empagliflozin and linagliptin after coadministration in healthy male volunteers

BACKGROUND

Empagliflozin is an oral, potent, and selective inhibitor of sodium glucose cotransporter 2, inhibition of which reduces renal glucose reabsorption and results in increased urinary glucose excretion. Linagliptin is an oral inhibitor of dipeptidyl peptidase-4 approved for the treatment of type 2 diabetes in the United States, Europe, Japan, and Canada. Due to their complementary modes of action, there is a good rationale to combine empagliflozin with linagliptin to improve glycemic control in patients with type 2 diabetes.

OBJECTIVE

This study was conducted to investigate the pharmacokinetics of empagliflozin and linagliptin after coadministration in healthy volunteers.

METHODS

This was an open-label, randomized, multiple-dose, crossover study with 3 treatments in 2 treatment sequences. Sixteen healthy male subjects received treatment A (empagliflozin 50 mg once daily [QD] for 5 days), treatment B (empagliflozin 50 mg QD and linagliptin 5 mg QD for 7 days), and treatment C (linagliptin 5 mg QD for 7 days) in sequence AB then C, or sequence C then AB.

RESULTS

Sixteen healthy male subjects aged between 18 and 50 years with a body mass index of 18.5 to 29.9 kg/m(2) were included in the study. Linagliptin total exposure (AUC over a uniform dosing interval τ at steady state geometric mean ratio [GMR], 1.03 [90% CI, 0.96-1.11]) and peak exposure (C(max) at steady state GMR, 1.01 [90% CI, 0.87-1.19) exposure was unaffected by coadministration of empagliflozin. Empagliflozin total exposure (AUC over a uniform dosing interval τ at steady state GMR, 1.02 [90% CI, 0.97-1.07]) was unaffected by coadministration of linagliptin. There was a reduction in empagliflozin peak exposure (C(max) at steady state GMR, 0.88 [90% CI, 0.79-0.99]) when linagliptin was coadministered that was not considered clinically meaningful. No adverse events were reported during the coadministration period. No hypoglycemia was reported. Empagliflozin and linagliptin were well tolerated.

CONCLUSION

These data support the coadministration of empagliflozin and linagliptin without dose adjustments. European Union Drug Regulating Authorities Clinical Trials Registration: EudraCT 2008-006089-27.

Safety, tolerability, pharmacokinetics and pharmacodynamics following 4 weeks' treatment with empagliflozin once daily in patients with type 2 diabetes

AIM

To investigate the safety, tolerability, pharmacokinetics and pharmacodynamics of empagliflozin in patients with type 2 diabetes following oral administration of 10, 25 or 100 mg doses once daily over 28 days.

METHODS

A total of 78 patients were assigned to empagliflozin 10 mg (n = 16), 25 mg (n = 16) or 100 mg (n = 30) or placebo (n = 16) for 28 days. Assessments included adverse events (AEs) and pharmacokinetic and pharmacodynamic endpoints.

RESULTS

Empagliflozin exposure increased dose-proportionally over the dose range 10-100 mg and showed linear pharmacokinetics with respect to time. Urinary glucose excretion (UGE) increased from baseline to day 1 by 74, 90 and 81 g with empagliflozin 10, 25 and 100 mg, respectively. The increases in UGE were maintained over 28 days with multiple dosing. Virtually no change in UGE was observed in the placebo group. Significant reductions from baseline in mean daily plasma glucose and fasting plasma glucose were observed with empagliflozin compared with placebo. The incidence of AEs was similar in the empagliflozin and placebo groups (50.0, 56.3 and 66.7% with empagliflozin rising doses and 62.5% with placebo). The most frequently reported AEs were pollakiuria (10.3%), nasopharyngitis (9.0%), constipation (9.0%) and headache (7.7%).

CONCLUSIONS

Oral administration of empagliflozin at doses of 10, 25 or 100 mg once daily over 28 days resulted in significant increases in UGE and reductions in blood glucose compared with placebo, and were well tolerated in patients with type 2 diabetes.

Dapagliflozin for the treatment of type 2 diabetes

INTRODUCTION

Despite the availability of many antihypreglycemic agents, many patients with type 2 diabetes (T2DM) fail to achieve the glycemic treatment goal, primarily due to progressive beta-cell dysfunction, and increased risk of hypoglycemia.

AREAS COVERED

The aim of the present article is to review the efficacy and safety of dapagliflozin , a novel antihyperglycemic drug that lowers the plasma glucose concentration by the inhibition of renal sodium-glucose cotransport, in lowering the plasma glucose concentration and the HbA1c in T2DM patents. This review summarizes the published data about the mechanism of action and clinical efficacy of dapagliflozin in lowering the HbA1c in patients with T2DM. It also discusses additional non-glycemic benefits of dapagliflozin and the safety profile of the drug.

EXPERT OPINION

Dapagliflozin is effective in lowering the plasma glucose concentration in patients with T2DM with a good safety profile. Because of its unique mechanism of action, dapagliflozin can be utilized in combination with all other antihyperglycemic agents and at all stages of the disease.

Personalized management of hyperglycemia in type 2 diabetes: reflections from a Diabetes Care Editors' Expert Forum

In June 2012, 13 thought leaders convened in a Diabetes Care Editors' Expert Forum to discuss the concept of personalized medicine in the wake of a recently published American Diabetes Association/European Association for the Study of Diabetes position statement calling for a patient-centered approach to hyperglycemia management in type 2 diabetes. This article, an outgrowth of that forum, offers a clinical translation of the underlying issues that need to be considered for effectively personalizing diabetes care. The medical management of type 2 diabetes has become increasingly complex, and its complications remain a great burden to individual patients and the larger society. The burgeoning armamentarium of pharmacological agents for hyperglycemia management should aid clinicians in providing early treatment to delay or prevent these complications. However, trial evidence is limited for the optimal use of these agents, especially in dual or triple combinations. In the distant future, genotyping and testing for metabolomic markers may help us to better phenotype patients and predict their responses to antihyperglycemic drugs. For now, a personalized ("n of 1") approach in which drugs are tested in a trial-and-error manner in each patient may be the most practical strategy for achieving therapeutic targets. Patient-centered care and standardized algorithmic management are conflicting approaches, but they can be made more compatible by recognizing instances in which personalized A1C targets are warranted and clinical circumstances that may call for comanagement by primary care and specialty clinicians.

Validation of a novel method for determining the renal threshold for glucose excretion in untreated and canagliflozin-treated subjects with type 2 diabetes mellitus

CONTEXT

The stepwise hyperglycemic clamp procedure (SHCP) is the gold standard for measuring the renal threshold for glucose excretion (RT(G)), but its use is limited to small studies in specialized laboratories.

OBJECTIVE

The objective of the study was to validate a new method for determining RT(G) using data obtained during a mixed-meal tolerance test (MMTT) in untreated and canagliflozin-treated subjects with type 2 diabetes mellitus (T2DM).

DESIGN

This was an open-label study with 2 sequential parts.

SETTING

The study was performed at a single center in Germany.

PATIENTS

Twenty-eight subjects with T2DM were studied.

INTERVENTIONS

No treatment intervention was given in part 1. In part 2, subjects were treated with canagliflozin 100 mg/d for 8 days. In each part, subjects underwent an MMTT and a 5-step SHCP on consecutive days.

MAIN OUTCOME MEASURES

For both methods, RT(G) was estimated using measured blood glucose (BG) and urinary glucose excretion (UGE); estimated glomerular filtration rates were also used to determine RT(G) during the MMTT. The methods were compared using the concordance correlation coefficient and geometric mean ratios.

RESULTS

In untreated and canagliflozin-treated subjects, the relationship between UGE rate and BG was well described by a threshold relationship. Good agreement was obtained between the MMTT-based and SHCP-derived RT(G) values. The concordance correlation coefficient (for all subjects) was 0.94; geometric mean ratios (90% confidence intervals) for RT(G) values (MMTT/SHCP) were 0.93 (0.89-0.96) in untreated subjects and 1.03 (0.78-1.37) in canagliflozin-treated subjects. Study procedures and treatments were generally well tolerated in untreated and canagliflozin-treated subjects.

CONCLUSIONS

In both untreated and canagliflozin-treated subjects with T2DM, RT(G) can be accurately estimated from measured BG, UGE, and estimated glomerular filtration rates using an MMTT-based method.

Renal glucose handling: impact of chronic kidney disease and sodium-glucose cotransporter 2 inhibition in patients with type 2 diabetes

OBJECTIVE

Ipragliflozin, a sodium-glucose cotransporter 2 inhibitor, stimulates glycosuria and lowers glycemia in patients with type 2 diabetes (T2DM). The objective of this study was to assess the pharmacodynamics of ipragliflozin in T2DM patients with impaired renal function.

RESEARCH DESIGN AND METHODS

Glycosuria was measured before and after a single ipragliflozin dose in 8 nondiabetic subjects and 57 T2DM patients (age 62 ± 9 years, fasting glucose 133 ± 39 mg/dL, mean ± SD) with normal renal function (assessed as the estimated glomerular filtration rate [eGFR]) (eGFR1 ≥90 mL · min(-1) · 1.73 m(-2)), mild (eGFR2 ≥60 to <90), moderate (eGFR3 ≥30 to <60), or severe reduction in eGFR (eGFR4 ≤15 to <30).

RESULTS

Ipragliflozin significantly increased urinary glucose excretion in each eGFR class (P < 0.0001). However, ipragliflozin-induced glycosuria declined (median [IQR]) across eGFR class (from 46 mg/min [33] in eGFR1 to 8 mg/min [7] in eGFR4, P < 0.001). Ipragliflozin-induced fractional glucose excretion (excretion/filtration) was 39% [27] in the T2DM patients (pooled data), similar to that of the nondiabetic subjects (37% [17], P = ns). In bivariate analysis of the pooled data, ipragliflozin-induced glycosuria was directly related to eGFR and fasting glucose (P < 0.0001 for both, r(2) = 0.55), predicting a decrement in 24-h glycosuria of 15 g for each 20 mL/min decline in eGFR and an increase of 7 g for each 10 mg/dL increase in glucose above fasting normoglycemia.

CONCLUSIONS

In T2DM patients, ipragliflozin increases glycosuria in direct, linear proportion to GFR and degree of hyperglycemia, such that its amount can be reliably predicted in the individual patient. Although absolute glycosuria decreases with declining GFR, the efficiency of ipragliflozin action (fractional glucose excretion) is maintained in patients with severe renal impairment.

In vitro-in vivo correlation of the inhibition potency of sodium-glucose cotransporter inhibitors in rat: a pharmacokinetic and pharmacodynamic modeling approach

To evaluate the relationship between the in vitro and in vivo potency of sodium-glucose cotransporter (SGLT) inhibitors, a pharmacokinetic and pharmacodynamic (PK-PD) study was performed using normal rats. A highly selective SGLT2 inhibitor, tofogliflozin, and four other inhibitors with different in vitro inhibition potency to SGLT2 and selectivity toward SGLT2, versus SGLT1 were used as test compounds, and the time courses for urinary glucose excretion (UGE) and the plasma glucose and compound concentrations were monitored after administration of the compounds. A PK-PD analysis of the UGE caused by SGLT inhibition was performed on the basis of a nonlinear parallel tube model that took into consideration the consecutive reabsorption by different glucose transport properties of SGLT2 and SGLT1. The model adequately captured the time course of cumulative UGE caused by SGLT inhibition; then, the in vivo inhibition constants (Ki) of inhibitors for both SGLT1 and SGLT2 were estimated. The in vivo selectivity toward SGLT2 showed a good correlation with the in vitro data (r = 0.985; P < 0.05), with in vivo Ki values for SGLT2 in the range of 0.3-3.4-fold the in vitro data. This suggests that in vitro inhibition potency to both SGLT2 and SGLT1 is reflected in vivo. Furthermore, the complementary role of SGLT1 to SGLT2 and how selectivity toward SGLT2 affects the inhibitory potency for renal glucose reabsorption were discussed using the PK-PD model.

SGLT2 inhibition: a novel prospective strategy in treatment of diabetes mellitus

The role of the kidney in glucose homeostasis and the potential of the kidney as a therapeutic target in type 2 diabetes is little appreciated. Hyperglycemia is an important pathogenic component in the development of microvascular and macrovascular complications in type 2 diabetes mellitus. Inhibition of renal tubular glucose re-absorption that leads to glycosuria has been proposed as a new mechanism to attain normoglycemia and thus prevent and diminish these complications, thus representing an innovative therapeutic strategy for the treatment of hyperglycemia and/or obesity in patients with type 1 or type 2 diabetes by enhancing glucose and energy loss through the urine. Sodium glucose co-transporter 2 (SGLT2) has a key role in re-absorption of glucose in kidney. Competitive inhibitors of SGLT2 have been discovered and a few of them have also been advanced in clinical trials for the treatment of diabetes.

Why Do SGLT2 inhibitors inhibit only 30-50% of renal glucose reabsorption in humans?

Sodium glucose cotransporter 2 (SGLT2) inhibition is a novel and promising treatment for diabetes under late-stage clinical development. It generally is accepted that SGLT2 mediates 90% of renal glucose reabsorption. However, SGLT2 inhibitors in clinical development inhibit only 30-50% of the filtered glucose load. Why are they unable to inhibit 90% of glucose reabsorption in humans? We will try to provide an explanation to this puzzle in this perspective analysis of the unique pharmacokinetic and pharmacodynamic profiles of SGLT2 inhibitors in clinical trials and examine possible mechanisms and molecular properties that may be responsible.

A novel SGLT is expressed in the human kidney

Selective inhibitors of sodium-glucose cotransporter 2 (SGLT2)-mediated reabsorption of glucose in the proximal tubule of the kidney are being developed for the treatment of diabetes. SGLT2 shares high degree of homology with SGLT3; however, very little is known about the expression and functional role of SGLT3 in the human kidney. Indeed, the SGLT2 inhibitors that are currently in clinical trials might affect the expression and/or the activity of SGLT3. Therefore, the present study examined the expression of SGLT3 mRNA and protein in human kidney and in a human proximal tubule HK-2 cell line. The results indicated that human SGLT3 (hSGLT3) message and protein are expressed both in vivo and in vitro. We also studied the activity of hSGLT3 protein following its over-expression in mammalian kidney-derived COS-7 cells and in HK-2 cells treated with the imino sugar deoxynojirimycin (DNJ), a potent agonist of hSGLT3. Over-expression of hSGLT3 in COS-7 cells increased intracellular sodium concentration by 3-fold without affecting glucose transport. Activation of hSGLT3 with DNJ (50μM) increased sodium uptake in HK-2 cells by 5.5 fold and this effect could be completely blocked with SGLT inhibitor phlorizin (50μM). These results suggest that SGLT3 is expressed in human proximal tubular cells where it serves as a novel sodium transporter. Up-regulation of the expression of SGLT3 in the proximal tubule in diabetic patients may contribute to the elevated sodium transport in this segment of the nephron that has been postulated to promote hyperfiltration and renal injury.

Loss of insulin-induced activation of TRPM6 magnesium channels results in impaired glucose tolerance during pregnancy

Hypomagnesemia affects insulin resistance and is a risk factor for diabetes mellitus type 2 (DM2) and gestational diabetes mellitus (GDM). Two single nucleotide polymorphisms (SNPs) in the epithelial magnesium channel TRPM6 (V(1393)I, K(1584)E) were predicted to confer susceptibility for DM2. Here, we show using patch clamp analysis and total internal reflection fluorescence microscopy, that insulin stimulates TRPM6 activity via a phosphoinositide 3-kinase and Rac1-mediated elevation of cell surface expression of TRPM6. Interestingly, insulin failed to activate the genetic variants TRPM6(V(1393)I) and TRPM6(K(1584)E), which is likely due to the inability of the insulin signaling pathway to phosphorylate TRPM6(T(1391)) and TRPM6(S(1583)). Moreover, by measuring total glycosylated hemoglobin (TGH) in 997 pregnant women as a measure of glucose control, we demonstrate that TRPM6(V(1393)I) and TRPM6(K(1584)E) are associated with higher TGH and confer a higher likelihood of developing GDM. The impaired response of TRPM6(V(1393)I) and TRPM6(K(1584)E) to insulin represents a unique molecular pathway leading to GDM where the defect is located in TRPM6.

Efficacy and safety of SGLT2 inhibitors in the treatment of type 2 diabetes mellitus

In addition to its central role in the development of microvascular complications, hyperglycemia plays an important role in the pathogenesis of type 2 diabetes mellitus (T2DM) by means of glucotoxicity. Thus, effective glycemic control not only reduces the incidence of microvascular complications but also corrects the metabolic abnormalities that contribute to the progression of the disease. Progressive β-cell failure and multiple side effects, including hypoglycemia and weight gain, associated with many current therapies present obstacles to the achievement of optimal and durable glycemic control in subjects with T2DM. Most recently, inhibitors of the renal sodium-glucose cotransporter have been developed to reduce the plasma glucose concentration by producing glucosuria. Because the mechanism of action of these oral antidiabetic agents is independent of β-cell function and tissue sensitivity to insulin, they improve glycemic control while avoiding hypoglycemia and promoting weight loss. In this review, we summarize the available data concerning the mechanism of action, efficacy, and safety of this novel antidiabetic class of therapeutic agents.

The management of type 2 diabetic patients with hypoglycaemic agents

Type 2 Diabetes Mellitus (T2DM) is characterized by chronic hyperglycemia with disturbance in carbohydrate, lipid, and protein metabolism due to insulin resistance and beta cell dysfunction. Epidemiological studies have confirmed a global pandemic of T2DM, which has created an enormous burden on society, with regard to morbidity, mortality, and health care expenditures. Life style modifications are fundamental not only in early stages of disease management but need to be intensified as disease progresses. United Kingdom Prospective Diabetes Study (UKPDS) has demonstrated the progressive nature of T2DM, and as disease progresses, a combination agents-oral antidiabetic drugs (OAD) and insulin-are needed in order to maintain good sugar control. The general consensus of HbA1c target for most patients is less than 7%, and various guidelines and algorithms have provided guidance in patient management to keep patient at goal. As our understanding of pathophysiological defects advances, targeting treatment at underlying defects not only enables us to achieve HbA1c goal but also reduces morbidities, mortalities, and progression of the disease. Traditional oral agents like metformin and sulfonylureas have failed to arrest the progression of T2DM. New agents such as TZD, DPP-4 inhibitor, and SGLT-2 may increase our armamentariums against T2DM.

SGLT2 inhibition in diabetes mellitus: rationale and clinical prospects

This Review covers the rationale, physiological consequences and clinical application of pharmacological sodium-glucose cotransporter 2 (SGLT2) inhibition. In patients with type 2 diabetes mellitus, in whom renal glucose reabsorption might be upregulated, orally active, selective SGLT2 inhibitors improve glycaemic control to a therapeutically useful extent. Chronic administration of several SGLT2 inhibitors dose-dependently lowers HbA(1c) levels by 0.5-1.5% without causing hypoglycaemia. The unique mechanism of action of SGLT2 inhibitors-which does not hinge upon β-cell function or tissue insulin sensitivity-means that they can exert their antihyperglycaemic effects in combination with any other oral antidiabetic drug as well as insulin. Available phase III studies confirm a good tolerability profile. Weight loss owing to urinary calorie leakage may be less than expected, but the negative energy balance offers a valuable clinical benefit. Offloading of sodium can assist blood pressure control. The progressive loss of efficacy in patients with reduced glomerular function will have to be balanced against the possibility of renal protection. The safety issues of genitourinary infections and cancer risk requires careful, proactive monitoring and analysis of robust exposure data, particularly in elderly, frail patients and in patients with impaired kidney function and/or high cardiovascular/cancer risk, who represent an increasing fraction of the population with diabetes mellitus.

Diabetes in Zucker diabetic fatty rat

Male Zucker diabetic fatty fa/fa (ZDF) rats develop obesity and insulin resistance at a young age, and then with aging, progressively develop hyperglycemia. This hyperglycemia is associated with impaired pancreatic β-cell function, loss of pancreatic β-cell mass, and decreased responsiveness of liver and extrahepatic tissues to the actions of insulin and glucose. Of particular interest are the insights provided by studies of these animals into the mechanism behind the progressive impairment of carbohydrate metabolism. This feature among others, including the development of obesity- and hyperglycemia-related complications, is common between male ZDF rats and humans with type 2 diabetes associated with obesity. We discuss the diabetic features and complications found in ZDF rats and why these animals are widely used as a genetic model for obese type 2 diabetes.