SGLT2 inhibitors for primary and secondary prevention of cardiovascular and renal outcomes in type 2 diabetes: a systematic review and meta-analysis of cardiovascular outcome trials.

Sodium-glucose cotransporter-2 (SGLT2) inhibitors, including empagliflozin, dapagliflozin, and canagliflozin, are now widely approved antihyperglycemic therapies. Because of their unique glycosuric mechanism, SGLT2 inhibitors also reduce weight. Perhaps more important are the osmotic diuretic and natriuretic effects contributing to plasma volume contraction, and decreases in systolic and diastolic blood pressures by 4 to 6 and 1 to 2 mm Hg, respectively, which may underlie cardiovascular and kidney benefits. SGLT2 inhibition also is associated with an acute, dose-dependent reduction in estimated glomerular filtration rate by ≈5 mL·min(-1)·1.73 m(-2) and ≈30% to 40% reduction in albuminuria. These effects mirror preclinical observations suggesting that proximal tubular natriuresis activates renal tubuloglomerular feedback through increased macula densa sodium and chloride delivery, leading to afferent vasoconstriction. On the basis of reduced glomerular filtration, glycosuric and weight loss effects are attenuated in patients with chronic kidney disease (estimated glomerular filtration rate 30% reductions in cardiovascular mortality, overall mortality, and heart failure hospitalizations associated with empagliflozin, even though, by design, the hemoglobin A1c difference between the randomized groups was marginal. Aside from an increased risk of mycotic genital infections, empagliflozin-treated patients had fewer serious adverse events, including a lower risk of acute kidney injury. In light of the EMPA-REG OUTCOME results, some diabetes clinical practice guidelines now recommend that SGLT2 inhibitors with proven cardiovascular benefit be prioritized in patients with type 2 diabetes mellitus who have not achieved glycemic targets and who have prevalent atherosclerotic cardiovascular disease. With additional cardiorenal protection trials underway, sodium-related physiological effects of SGLT2 inhibitors and clinical correlates of natriuresis, such as the impact on blood pressure, heart failure, kidney protection, and mortality, will be a major management focus.

Sodium Glucose Cotransporter 2 Inhibitors in the Treatment of Diabetes Mellitus: Cardiovascular and Kidney Effects, Potential Mechanisms, and Clinical Applications

Recently, the U.S. Food and Drug Administration (FDA) issued a Drug Safety Communication that warns of an increased risk of diabetic ketoacidosis (DKA) with uncharacteristically mild to moderate glucose elevations (euglycemic DKA [euDKA]) associated with the use of all the approved sodium–glucose cotransporter 2 (SGLT2) inhibitors (1). This Communication was based on 20 clinical cases requiring hospitalization captured between March 2013 and June 2014 in the FDA Adverse Event Reporting System database. The scarce clinical data provided suggested that most of the DKA cases were reported in patients with type 2 diabetes (T2D), for whom this class of agents is indicated; most likely, however, they were insulin-treated patients, some with type 1 diabetes (T1D). The FDA also identified potential triggering factors such as intercurrent illness, reduced food and fluid intake, reduced insulin doses, and history of alcohol intake. The following month, at the request of the European Commission, the European Medicines Agency (EMA) announced on 12 June 2015 that the Pharmacovigilance Risk Assessment Committee has started a review of all of the three approved SGLT2 inhibitors (canagliflozin, dapagliflozin, and empagliflozin) to evaluate the risk of DKA in T2D (2). The EMA announcement claimed that as of May 2015 a total of 101 cases of DKA have been reported worldwide in EudraVigilance in T2D patients treated with SGLT2 inhibitors, with an estimated exposure over 0.5 million patient-years. No clinical details were provided except for the mention that “all cases were serious and some required hospitalisation. Although [DKA] is usually accompanied by high blood sugar levels, in a number of these reports blood sugar levels were only moderately increased” (2).

With this background, it is very timely that in this issue of Diabetes Care there are two articles on this subject. Erondu et al. (3) report cases of DKA in T2D …

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Euglycemic Diabetic Ketoacidosis: A Predictable, Detectable, and Preventable Safety Concern With SGLT2 Inhibitors

Pharmacologically induced glycosuria elicits adaptive responses in glucose homeostasis and hormone release. In type 2 diabetes (T2D), along with decrements in plasma glucose and insulin levels and increments in glucagon release, sodium-glucose cotransporter 2 (SGLT2) inhibitors induce stimulation of endogenous glucose production (EGP) and a suppression of tissue glucose disposal (TGD). We measured fasting and postmeal glucose fluxes in 25 subjects without diabetes using a double glucose tracer technique; in these subjects and in 66 previously reported patients with T2D, we also estimated lipolysis (from [(2)H5]glycerol turnover rate and circulating free fatty acids, glycerol, and triglycerides), lipid oxidation (LOx; by indirect calorimetry), and ketogenesis (from circulating β-hydroxybutyrate concentrations). In both groups, empagliflozin administration raised EGP, lowered TGD, and stimulated lipolysis, LOx, and ketogenesis. The pattern of glycosuria-induced changes was similar in subjects without diabetes and in those with T2D but quantitatively smaller in the former. With chronic (4 weeks) versus acute (first dose) drug administration, glucose flux responses were attenuated, whereas lipid responses were enhanced; in patients with T2D, fasting β-hydroxybutyrate levels rose from 246 ± 288 to 561 ± 596 µmol/L (P < 0.01). We conclude that by shunting substantial amounts of carbohydrate into urine, SGLT2-mediated glycosuria results in a progressive shift in fuel utilization toward fatty substrates. The associated hormonal milieu (lower insulin-to-glucagon ratio) favors glucose release and ketogenesis.

https://diabetes.diabetesjournals.org/content/diabetes/65/5/1190.full.pdf

Shift to Fatty Substrate Utilization in Response to Sodium-Glucose Cotransporter 2 Inhibition in Subjects Without Diabetes and Patients With Type 2 Diabetes.

The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.

Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men

Type 2 diabetes (T2D) is characterized by chronic hyperglycemia resulting from a deficiency in insulin signaling, because of insulin resistance and/or defects in insulin secretion; it is also associated with increases in glucagon and endogenous glucose production (EGP). Gliflozins, including dapagliflozin, are a new class of approved oral antidiabetic agents that specifically inhibit sodium-glucose co-transporter 2 (SGLT2) function in the kidney, thus preventing renal glucose reabsorption and increasing glycosuria in diabetic individuals while reducing hyperglycemia. However, gliflozin treatment in subjects with T2D increases both plasma glucagon and EGP by unknown mechanisms. In spite of the rise in EGP, T2D patients treated with gliflozin have lower blood glucose levels than those receiving placebo, possibly because of increased glycosuria; however, the resulting increase in plasma glucagon levels represents a possible concerning side effect, especially in a patient population already affected by hyperglucagonemia. Here we demonstrate that SGLT2 is expressed in glucagon-secreting alpha cells of the pancreatic islets. We further found that expression of SLC5A2 (which encodes SGLT2) was lower and glucagon (GCG) gene expression was higher in islets from T2D individuals and in normal islets exposed to chronic hyperglycemia than in islets from non-diabetics. Moreover, hepatocyte nuclear factor 4-α (HNF4A) is specifically expressed in human alpha cells, in which it controls SLC5A2 expression, and its expression is downregulated by hyperglycemia. In addition, inhibition of either SLC5A2 via siRNA-induced gene silencing or SGLT2 via dapagliflozin treatment in human islets triggered glucagon secretion through KATP channel activation. Finally, we found that dapagliflozin treatment further promotes glucagon secretion and hepatic gluconeogenesis in healthy mice, thereby limiting the decrease of plasma glucose induced by fasting. Collectively, these results identify a heretofore unknown role of SGLT2 and designate dapagliflozin an alpha cell secretagogue.

Cédric Beaucamps

Papers

Inhibition of the glucose transporter SGLT2 with dapagliflozin in pancreatic alpha cells triggers glucagon secretion