Sodium-Glucose Cotransporter Inhibitors: Effects on Renal and Intestinal Glucose Transport: From Bench to Bedside

Effect of Dapagliflozin Treatment on Fluid and Electrolyte Balance in Diabetic Rats

AIM

This study evaluates the effect of dapagliflozin, a SGLT2 inhibitor, on fluid or electrolyte balance and its effect on urea transporter-A1 (UT-A1), aquaporin-2 (AQP2) and Na-K-2Cl cotransporter (NKCC2) protein abundance in diabetic rats.

METHODS

Diabetes mellitus (DM) was induced by injection of streptozotocin into the tail vein. Serum Na+, K+, Cl- concentration, urine Na+, K+, Cl- excretion, blood glucose, urine glucose excretion, urine volume, urine osmolality and urine urea excretion were analyzed after the administration of dapagliflozin. UT-A1, AQP2 and NKCC2 proteins were detected by western blot.

RESULTS

Dapagliflozin treatment decreased blood glucose concentration by 38% at day 7 and by 47% at day 14 and increased the urinary glucose excretion rate compared with the untreated diabetic animals. Increased 24-hour urine volume, decreased urine osmolality and hyponatremia, hypokalemia and hypochloremia observed in diabetic rats were attenuated by dapagliflozin treatment. Western blot analysis showed that UT-A1, AQP2 and NKCC2 proteins are upregulated in DM rats over control rats; dapagliflozin treatment results in a further increase in inner medulla tip UT-A1 protein abundance by 42% at day 7 and by 46% at day 14, but it did not affect the DM-induced upregulation of AQP2 and NKCC2 proteins.

CONCLUSION

Dapagliflozin treatment augmented the compensatory changes in medullary transport proteins in DM. These changes would tend to conserve solute and water even with persistent glycosuria. Therefore, diabetic rats treated with dapagliflozin have a mild osmotic diuresis compared to nondiabetic animals, but this does not result in an electrolyte disorder or significant volume depletion.

New Oral Hypoglycemic Agents and Cardiovascular Risk. Crossing the Metabolic Border

Sodium-glucose cotransporter 2 inhibitors are a novel pharmacological class of oral hypoglycemic agents that lower glucose levels by increasing renal glucose excretion in an insulin-independent manner. However, this seemingly simple mechanism has more complex indirect metabolic effects. The results of randomized clinical trials have shown that these inhibitors effectively lower blood glucose and glycated hemoglobin levels without increasing the risk of hypoglycemia and, at the same time, also reduce bodyweight and systolic blood pressure. In this review, we describe the mechanism of action, efficacy, and safety of currently marketed drugs, as well as other risk factors besides glucose that can potentially be modulated positively. Recent data on empagliflozin showing a significant cardiovascular benefit have compelled us to update knowledge of this new therapeutic class for the treatment of type 2 diabetes.

Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors from Natural Products: Discovery of Next-Generation Antihyperglycemic Agents

Diabetes mellitus is a chronic condition associated with the metabolic impairment of insulin actions, leading to the development of life-threatening complications. Although many kinds of oral antihyperglycemic agents with different therapeutic mechanisms have been marketed, their undesirable adverse effects, such as hypoglycemia, weight gain, and hepato-renal toxicity, have increased demand for the discovery of novel, safer antidiabetic drugs. Since the important roles of the sodium-glucose cotransporter 2 (SGLT2) for glucose homeostasis in the kidney were recently elucidated, pharmacological inhibition of SGLT2 has been considered a promising therapeutic target for the treatment of type 2 diabetes. Since the discovery of the first natural SGLT2 inhibitor, phlorizin, several synthetic glucoside analogs have been developed and introduced into the market. Furthermore, many efforts to find new active constituents with SGLT2 inhibition from natural products are still ongoing. This review introduces the history of research on the development of early-generation SGLT2 inhibitors, and recent progress on the discovery of novel candidates for SGLT2 inhibitor from several natural products that are widely used in traditional herbal medicine.

Pharmacological management of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) affects one-third of the population and two-thirds of patients with obesity or type 2 diabetes (T2DM). Its more aggressive form is known as nonalcoholic steatohepatitis (NASH) and is characterized by hepatocyte necrosis, inflammation and often fibrosis. The presence of fibrosis indicates a more aggressive course and may lead to cirrhosis. Premature mortality in NASH is related to both hepatic (cirrhosis and hepatocellular carcinoma) and extra-hepatic complications, largely cardiovascular disease (CVD). Many therapeutic agents have been tested, but still none approved specifically for NASH. Treatment of NAFLD includes aggressive management of diabetes and cardiovascular risk factors, although the role of controlling hyperglycemia per se in patients with T2DM and NASH remains unknown. Agents tested with some success in non-diabetic patients with NASH include pioglitazone, liraglutide, vitamin E and to a lesser degree, pentoxiphylline. In patients with T2DM and NASH only pioglitazone has shown to significantly improve liver histology, with only a handful of patients with diabetes having been studied with other modalities. This review focuses on available agents for NASH to assist clinicians in the management of these complex patients. Many novel compounds are being studied and will likely make combination therapy for NASH a reality in the future.

Efficacy and safety of titrated canagliflozin in patients with type 2 diabetes mellitus inadequately controlled on metformin and sitagliptin

AIMS

To evaluate the efficacy and safety of titrated canagliflozin, a sodium glucose co-transporter 2 inhibitor, in patients with type 2 diabetes mellitus (T2DM) inadequately controlled on metformin and sitagliptin.

METHODS

In this randomized, double-blind study, patients with T2DM (N = 218) on metformin ≥1500 mg/day and sitagliptin 100 mg received canagliflozin 100 mg or placebo. After 6 weeks, the canagliflozin dose was increased from 100 to 300 mg (or from placebo to matching placebo) if all of the following criteria were met: baseline estimated glomerular filtration rate ≥70 ml/min/1.73 m(2) ; fasting self-monitored blood glucose ≥5.6 mmol/l (≥100 mg/dl); and no volume depletion-related adverse events (AEs) within 2 weeks before dose increase. Endpoints included change in glycated haemoglobin (HbA1c) at week 26 (primary); proportion of patients achieving HbA1c <7.0%; and changes in fasting plasma glucose (FPG), body weight and systolic blood pressure (SBP). Safety was assessed using AE reports.

RESULTS

Overall, 85.4% of patients were titrated to canagliflozin 300 mg or matching placebo (mean ± standard deviation time to titration 6.2 ± 0.8 weeks). At week 26, canagliflozin (pooled 100 and 300 mg) demonstrated superiority in HbA1c reduction versus placebo (-0.91% vs. -0.01%; p < 0.001). Canagliflozin provided significant reductions in FPG, body weight and SBP compared with placebo (p < 0.001). The overall AE incidence was 39.8 and 44.4% for canagliflozin and placebo, respectively. Canagliflozin was associated with an increased incidence of genital mycotic infections.

CONCLUSIONS

Titrated canagliflozin significantly improved HbA1c, FPG, body weight and SBP, and was generally well tolerated over 26 weeks in patients with T2DM as add-on to metformin and sitagliptin.

An overview of the effect of sodium glucose cotransporter 2 inhibitor monotherapy on glycemic and other clinical laboratory parameters in type 2 diabetes patients

Objectives

We aimed to determine the effect of sodium glucose cotransporter 2 (SGLT2) inhibitor monotherapy on glycemic and other clinical laboratory parameters versus other antidiabetic medications or placebo therapy in patients with type 2 diabetes mellitus. In addition, we aimed to investigate the risk of diabetic ketoacidosis associated with SGLT2 inhibitor therapy and evaluate its weight-sparing ability.

Design

Meta-analysis.

Materials and methods

PubMed and MEDLINE were searched to identify eligible studies up to December 2015. Randomized controlled trials that assessed the efficacy and safety of SGLT2 inhibitor monotherapy versus placebo therapy or active control were considered. The Cochrane Collaboration Risk of Bias Tool was used to evaluate quality and bias. The mean difference was used to evaluate the glycemic and other clinical laboratory parameters for SGLT2 inhibitor intervention versus control by drugs or placebo. Similarly, the risk ratio was used to assess adverse events, and the I² was used to evaluate heterogeneity.

Results

SGLT2 inhibitors significantly decreased glycated hemoglobin (HbA1c) (P<0.001), weight (P<0.001), and the low-density lipoprotein/high-density lipoprotein ratio (P=0.03) compared with placebo therapy. No statistically significant changes were found in fasting plasma glucose, 2-hour postprandial glucose, or lipid parameters. Significant changes in the uric acid level were found for SGLT2 inhibitors versus placebo therapy (P=0.005) or active control (P<0.001). Although no significant change in levels of ketones occurred (P=0.93), patients receiving SGLT2 inhibitors were at greater risk of increased ketone bodies. Events suggestive of urinary tract infection and pollakiuria presented the greatest risk for patients receiving SGLT2 inhibitors versus active control or placebo therapy.

Conclusion

SGLT2 inhibitors significantly decreased HbA1c, body weight, and the low-density lipoprotein/high-density lipoprotein ratio and were found to be safe and well tolerated in type 2 diabetes mellitus patients. Further randomized control trials are required to establish their risk for ketoacidosis.

Can a Shift in Fuel Energetics Explain the Beneficial Cardiorenal Outcomes in the EMPA-REG OUTCOME Study? A Unifying Hypothesis

Type 2 diabetes mellitus causes excessive morbidity and premature cardiovascular (CV) mortality. Although tight glycemic control improves microvascular complications, its effects on macrovascular complications are unclear. The recent publication of the EMPA-REG OUTCOME study documenting impressive benefits with empagliflozin (a sodium-glucose cotransporter 2 [SGLT2] inhibitor) on CV and all-cause mortality and hospitalization for heart failure without any effects on classic atherothrombotic events is puzzling. More puzzling is that the curves for heart failure hospitalization, renal outcomes, and CV mortality begin to separate widely within 3 months and are maintained for >3 years. Modest improvements in glycemic, lipid, or blood pressure control unlikely contributed significantly to the beneficial cardiorenal outcomes within 3 months. Other known effects of SGLT2 inhibitors on visceral adiposity, vascular endothelium, natriuresis, and neurohormonal mechanisms are also unlikely major contributors to the CV/renal benefits. We postulate that the cardiorenal benefits of empagliflozin are due to a shift in myocardial and renal fuel metabolism away from fat and glucose oxidation, which are energy inefficient in the setting of the type 2 diabetic heart and kidney, toward an energy-efficient super fuel like ketone bodies, which improve myocardial/renal work efficiency and function. Even small beneficial changes in energetics minute to minute translate into large differences in efficiency, and improved cardiorenal outcomes over weeks to months continue to be sustained. Well-planned physiologic and imaging studies need to be done to characterize fuel energetics-based mechanisms for the CV/renal benefits.

CV Protection in the EMPA-REG OUTCOME Trial: A "Thrifty Substrate" Hypothesis

The striking and unexpected relative risk reductions in cardiovascular (CV) mortality (38%), hospitalization for heart failure (35%), and death from any cause (32%) observed in the EMPA-REG OUTCOME trial using an inhibitor of sodium-glucose cotransporter 2 (SGLT2) in patients with type 2 diabetes and high CV risk have raised the possibility that mechanisms other than those observed in the trial-modest improvement in glycemic control, small decrease in body weight, and persistent reductions in blood pressure and uric acid level-may be at play. We hypothesize that under conditions of mild, persistent hyperketonemia, such as those that prevail during treatment with SGLT2 inhibitors, β-hydroxybutyrate is freely taken up by the heart (among other organs) and oxidized in preference to fatty acids. This fuel selection improves the transduction of oxygen consumption into work efficiency at the mitochondrial level. In addition, the hemoconcentration that typically follows SGLT2 inhibition enhances oxygen release to the tissues, thereby establishing a powerful synergy with the metabolic substrate shift. These mechanisms would cooperate with other SGLT2 inhibition-induced changes (chiefly, enhanced diuresis and reduced blood pressure) to achieve the degree of cardioprotection revealed in the EMPA-REG OUTCOME trial. This hypothesis opens up new lines of investigation into the pathogenesis and treatment of diabetic and nondiabetic heart disease.

Efficacy and safety of canagliflozin in combination with insulin: a double-blind, randomized, placebo-controlled study in Japanese patients with type 2 diabetes mellitus

BACKGROUND

Combination therapy with canagliflozin and insulin was investigated in a prescribed substudy of the canagliflozin Cardiovascular Assessment Study (CANVAS); however, it was not evaluated in Japanese patients with type 2 diabetes mellitus (T2DM). Since the usage profile of insulin therapy and pathologic features of Japanese patients differ from those of Caucasian patients, we determined the clinical benefit of such a combination therapy in Japanese patients.

METHODS

Patients who had inadequate glycemic control despite insulin, diet and exercise therapies were randomized into placebo (n = 70) and canagliflozin 100 mg (n = 76) groups that were administered once daily in addition to their prior insulin therapy in this double-blind, placebo-controlled study. The primary endpoint was the change in glycated hemoglobin (HbA1c) levels from the baseline to week 16.

RESULTS

There was a statistically significant decrease in HbA1c levels from the baseline in the canagliflozin group (-0.97 ± 0.08 %) compared with the placebo group (0.13 ± 0.08 %) at week 16 [last observation carried forward (LOCF)]. The decrease in HbA1c levels in the canagliflozin group was independent of the insulin regimen (premixed, long-acting and long-acting plus rapid- or short-acting). Compared with the placebo group, canagliflozin significantly decreased fasting plasma glucose levels (-34.1 ± 4.8 vs -1.4 ± 5.0 mg/dL) and body weights (-2.13 ± 0.25 vs 0.24 ± 0.26 %), and significantly increased HDL cholesterol (3.3 ± 1.0 vs -0.5 ± 1.0 mg/dL) and HOMA2- %B (10.15 ± 1.37 vs 0.88 ± 1.42 %). The overall incidence of adverse events was similar between the two groups. The incidence and incidence per subject-year exposure of hypoglycemia (hypoglycemic symptoms and/or decreased blood glucose) were slightly higher in the canagliflozin group (40.0 % and 7.97) than in the placebo group (29.6 % and 4.51). However, hypoglycemic events in both groups were mild in severity and dose-reduction of insulin by <10 % from the baseline following hypoglycemic events decreased the incidence per subject-year exposure in the canagliflozin group. The incidence of hypoglycemia between the groups did not differ according to the insulin regimen.

CONCLUSION

Canagliflozin in combination with insulin was effective in improving glycemic control and reducing body weight and well tolerated by Japanese patients with T2DM. Trial Registration ClinicalTrials.gov identifier: NCT02220920.

Clinical Update: Cardiovascular Disease in Diabetes Mellitus: Atherosclerotic Cardiovascular Disease and Heart Failure in Type 2 Diabetes Mellitus - Mechanisms, Management, and Clinical Considerations

Cardiovascular disease remains the principal cause of death and disability among patients with diabetes mellitus. Diabetes mellitus exacerbates mechanisms underlying atherosclerosis and heart failure. Unfortunately, these mechanisms are not adequately modulated by therapeutic strategies focusing solely on optimal glycemic control with currently available drugs or approaches. In the setting of multifactorial risk reduction with statins and other lipid-lowering agents, antihypertensive therapies, and antihyperglycemic treatment strategies, cardiovascular complication rates are falling, yet remain higher for patients with diabetes mellitus than for those without. This review considers the mechanisms, history, controversies, new pharmacological agents, and recent evidence for current guidelines for cardiovascular management in the patient with diabetes mellitus to support evidence-based care in the patient with diabetes mellitus and heart disease outside of the acute care setting.

Treatment of patients with type 2 diabetes and non-alcoholic fatty liver disease: current approaches and future directions

Non-alcoholic fatty liver disease (NAFLD) is reaching epidemic proportions in patients with type 2 diabetes. Patients with NAFLD are at increased risk of more aggressive liver disease (non-alcoholic steatohepatitis [NASH]) and at a higher risk of death from cirrhosis, hepatocellular carcinoma and cardiovascular disease. Dysfunctional adipose tissue and insulin resistance play an important role in the pathogenesis of NASH, creating the conditions for hepatocyte lipotoxicity. Mitochondrial defects are at the core of the paradigm linking chronic excess substrate supply, insulin resistance and NASH. Recent work indicates that patients with NASH have more severe insulin resistance and lipotoxicity compared with matched obese controls with only isolated steatosis. This review focuses on available agents and future drugs under development for the treatment of NAFLD/NASH in type 2 diabetes. Reversal of lipotoxicity with pioglitazone is associated with significant histological improvement, which occurs within 6 months and persists with continued treatment (or for at least 3 years) in patients with prediabetes or type 2 diabetes, holding potential to modify the natural history of the disease. These results also suggest that pioglitazone may become the standard of care for this population. Benefit has also been reported in non-diabetic patients. Recent promising results with glucagon-like peptide 1 receptor agonists have opened another new treatment avenue for NASH. Many agents in Phase 2-3 of development are being tested, aiming to restore glucose/lipid metabolism, ameliorate adipose tissue and liver inflammation, or to inhibit liver fibrosis. By targeting a diversity of relevant pathways, combination therapy in NASH will likely provide greater success in the future. In summary, increased clinical awareness and improved screening strategies (as currently done for diabetic retinopathy and nephropathy) are needed, to translate recent treatment progress into early treatment and improved quality of life for patients with type 2 diabetes and NASH. This review summarises a presentation given at the symposium 'The liver in focus' at the 2015 annual meeting of the EASD. It is accompanied by two other reviews on topics from this symposium (by John Jones, DOI: 10.1007/s00125-016-3940-5 , and by Hannele Yki-Järvinen, DOI: 10.1007/s00125-016-3944-1 ) and a commentary by the Session Chair, Michael Roden (DOI: 10.1007/s00125-016-3911-x ).

Intestinal SGLT1 in metabolic health and disease

The Na(+)-glucose cotransporter 1 (SGLT1/SLC5A1) is predominantly expressed in the small intestine. It transports glucose and galactose across the apical membrane in a process driven by a Na(+) gradient created by Na(+)-K(+)-ATPase. SGLT2 is the major form found in the kidney, and SGLT2-selective inhibitors are a new class of treatment for type 2 diabetes mellitus (T2DM). Recent data from patients treated with dual SGLT1/2 inhibitors or SGLT2-selective drugs such as canagliflozin (SGLT1 IC50 = 663 nM) warrant evaluation of SGLT1 inhibition for T2DM. SGLT1 activity is highly dynamic, with modulation by multiple mechanisms to ensure maximal uptake of carbohydrates (CHOs). Intestinal SGLT1 inhibition lowers and delays the glucose excursion following CHO ingestion and augments glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) secretion. The latter is likely due to increased glucose exposure of the colonic microbiota and formation of metabolites such as L cell secretagogues. GLP-1 and PYY secretion suppresses food intake, enhances the ileal brake, and has an incretin effect. An increase in colonic microbial production of propionate could contribute to intestinal gluconeogenesis and mediate positive metabolic effects. On the other hand, a threshold of SGLT1 inhibition that could lead to gastrointestinal intolerability is unclear. Altered Na(+) homeostasis and increased colonic CHO may result in diarrhea and adverse gastrointestinal effects. This review considers the potential mechanisms contributing to positive metabolic and negative intestinal effects. Compounds that inhibit SGLT1 must balance the modulation of these mechanisms to achieve therapeutic efficacy for metabolic diseases.

Treatment of Nonalcoholic Fatty Liver Disease (NAFLD) in patients with Type 2 Diabetes Mellitus

Nonalcoholic fatty liver disease (NAFLD) is believed to be the most common chronic liver disease, affecting at least one-third of the population worldwide. The more aggressive form is known as nonalcoholic steatohepatitis (NASH) and characterized by hepatocyte necrosis and inflammation. The presence of fibrosis is not uncommon. Fibrosis indicates a more aggressive course and patients with NASH that are at high-risk of cirrhosis and premature mortality, as well as at increased risk of hepatocellular carcinoma (HCC). Patients with type 2 diabetes mellitus (T2DM) are at the highest risk for the development of NASH, even in the setting of normal plasma aminotransferase levels. The presence of dysfunctional adipose tissue in most overweight and obese subjects, combined with insulin resistance, hyperglycemia, and atherogenic dyslipidemia, contribute to their increased cardiovascular risk. Many therapeutic agents have been tested for the treatment of NASH but few studies have focused in patients with T2DM. At the present moment, the only FDA-approved agents that in controlled studies have shown to significantly improve liver histology in patients with diabetes are pioglitazone and liraglutide. Current research efforts are centering on the mechanisms for intrahepatic triglyceride accumulation and for the development of steatohepatitis, the role of mitochondrial dysfunction in NASH, and the impact of improving glycemic control per se on the natural history of the disease. This brief review summarizes our current knowledge on the pharmacological agents available for the treatment of NASH to assist healthcare providers in the management of these challenging patients.