Sodium–Glucose Cotransporter Inhibitors: Effects on Renal and Intestinal Glucose Transport

Abstract

Type 2 diabetes is a chronic disease with disabling micro-and macrovascular complications that lead to excessive morbidity and premature mortality. It affects hundreds of millions of people and imposes an undue economic burden on populations across the world. Although insulin resistance and insulin secretory defects play a major role in the pathogenesis of hyperglycemia, several other metabolic defects contribute to the initiation/worsening of the diabetic state. Prominent among these is increased renal glucose reabsorption, which is maladaptive in patients with diabetes. Instead of an increase in renal glucose excretion, which could ameliorate hyperglycemia, there is an increase in renal glucose reabsorption, which helps sustain hyperglycemia in patients with diabetes. The sodium-glucose cotransporter (SGLT) 2 inhibitors are novel antidiabetes agents that inhibit renal glucose reabsorption and promote glucosuria, thereby leading to reductions in plasma glucose concentrations. In this article, we review the long journey from the discovery of the glucosuric agent phlorizin in the bark of the apple tree through the animal and human studies that led to the development of the current generation of SGLT2 inhibitors.It took nearly 200 years from the isolation of phlorizin, a chemical found in apple tree bark that inhibits sodium-glucose cotransporters (SGLTs) (1), to the approval of the first medications inhibiting SGLTs for treatment of type 2 diabetes (T2D). During this time, several SGLTs were discovered and the roles of SGLT1 and SGLT2 in intestinal and renal glucose reabsorption have been elucidated in studies in genetically manipulated rodents, humans with SGLT gene mutations, healthy humans, and humans with diabetes (Fig. 1). This review provides an overview of the basic and clinical research that led to the translation of the initial findings of increased glucosuria with phlorizin to the development and approval of SGLT inhibitors and a summary of the clinical trial results obtained to date. Identification, Distribution, and In Vitro Characterization of the SGLT InhibitorsIn the 1980s and 1990s, Wright and colleagues cloned SGLT1 (2) and SGLT2 (2,3) and did much of the in vitro characterization, demonstrating that SGLT1 has a higher affinity for glucose than SGLT2 (K m for glucose ;0.4 mmol/L and 2 mmol/L, respectively), whereas SGLT2 has a higher capacity (4). SGLT1 is expressed at high levels in the intestine and is also expressed in the kidney, heart, and skeletal muscle, whereas SGLT2 is expressed almost exclusively in the kidney (4). Renal SGLT2 expression is increased in hyperglycemic rodents (5,6) and in humans with T2D (7). Intestinal SGLT1 expression is regulated by diet and other factors (8) and is

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“…376 Inhibition of SGLT2 results in increased glucose transport to the distal nephron with reduction in renal hyperfiltration 377 and lowering of the serum glucose threshold for renal reabsorption of glucose leading to excretion of 80–100 grams of glucose per day. 376 Three drugs in this class have been approved by the FDA for the treatment of diabetes: dapagliflozin, canagliflozin, and empagliflozin. Several other drugs in this class are in development.…”

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“…2 These drugs are designed to inhibit sodium-glucose cotransporter 2 (SGLT2), which is located in the S1 segment of the proximal tubule. Previous phase 2 and phase 3 studies have shown that administration of SGLT2 inhibitors augments urinary glucose and sodium excretion and decreases glycated hemoglobin A1c (HbA1c), body weight, and BP in patients with type 2 diabetes.…”

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