Part 8

Rationale for SGLT2 Inhibitors Inhibit glucose reabsorption in the renal proximal tubule Resultant glucosuria leads to a decline in plasma glucose and reversal of glucotoxicity This therapy is simple and nonspecific Even patients with refractory type 2 diabetes are likely to respond

Fasting Plasma Glucose Pathophysiology of Type 2 Diabetes 10 mmol/L Islet  -cell Impaired Insulin Secretion Insulin Resistance Increased HGP Glucosuria

Fasting Plasma Glucose Pathophysiology of Type 2 Diabetes 10 mmol/L Islet  -cell Impaired Insulin Secretion Insulin Resistance Increased HGP 5 mmol/L Glucosuria

SGLT1 (180 L/day) (900 mg/L)=162 g/day 10% Glucose No Glucose S1 S3 Renal Handling of Glucose SGLT2 90%

Sodium-Glucose Cotransporters SGLT1SGLT2SiteIntestine, kidneyKidney Sugar specificity Glucose or galactoseGlucose Glucose affinity High K m =0.4 mM Low K m =2 mM Glucose transport capacity LowHigh Role Dietary absorption of glucose and galactose Renal glucose reabsorption

Major transporter of glucose in the kidney Low affinity, high capacity for glucose Nearly exclusively expressed in the kidney Responsible for ~90% of renal glucose reabsorption in the proximal tubule Hediger MA, Rhoads DB. Physiol. Rev. 1994;74: S1 Proximal Tubule Na + K+K+ ATPase Glucose GLUT2 Glucose SGLT2 BloodLumen Na + SGLT2 Mediates Glucose Reabsorption in the Kidney

Plasma Glucose Concentration (mmol/L) 155 Glucose Reabsorption and Excretion Splay Excretion Tm G 10 Actual Threshold Reabsorption Theoretical threshold Renal Glucose Handling

Rossetti L, et al. J Clin Invest. 1987;79: Effect of Phlorizin on Insulin Sensitivity in Diabetic Rats: Study Design Rat Group Pancreatectomy / Diabetic Status Phlorizin Meal Tolerance Test I (n=14) Sham Control –+ II (n=19) 90% Diabetes –+ III (n=10) 90% Diabetes ++ IV (n=4) 90% Diabetes + / – days after discontinuation of phlorizin Phlorizin treatment period: 4-5 weeks Diet was same for all groups; body weight was similar across groups at end of study

Fasting Glucose (mmol/L) Diabetes +/- Phlorizin Diabetes + Phlorizin Diabetes Control * Fed Glucose (mmol/L) Diabetes +/- Phlorizin Diabetes + Phlorizin Diabetes Control *P<0.05 vs control and phlorizin. † P<0.001 vs control and phlorizin. Rossetti L, et al. J Clin Invest. 1987;79: Effect of Phlorizin on Fed and Fasting Plasma Glucose in Diabetic Rats † †

Glucose Uptake (mg/kg ∙ min) *P<0.001 vs control and phlorizin. Rossetti L, et al. J Clin Invest. 1987;79: Insulin-Mediated Glucose Uptake in Diabetic Rats Following Phlorizin Treatment Diabetes +/- Phlorizin Diabetes + Phlorizin DiabetesControl * *

Mechanism of Action of SGLT2 Inhibitors Inhibition of SGLT2Reversal of glucotoxicity Insulin sensitivity in muscle ↑ GLUT4 translocation ↑ Insulin signaling Other Insulin sensitivity in liver ↓ Glucose- 6-phosphatase Gluconeogenesis Decreased Cori cycle ↓ PEP carboxykinase  -Cell function

Effect of Phlorizin on  -Cell Function in Diabetic Rats: Study Design Rat Group Pancreactomy / Diabetic Status Phlorizin I Sham Control – II 90% Diabetes – III 90% Diabetes 0.4 g/kg/day Sprague-Dawley male rats weighing g Phlorizin treatment period: 3 weeks Arginine clamp (2 mM); hyperglycemic clamp (≥5.5 mmol/L) Rossetti L, et al. J Clin Invest. 1987;80:

First Phase Second Phase Control Diabetes + Phlorizin Diabetes * * 2 Plasma Insulin (ng/mL ∙ min / g Pancreas) Plasma Insulin Response to Glucose *P<0.001 vs control. Rossetti L, et al. J Clin Invest. 1987;80:

Starke A, et al. Proc Natl Acad Sci. 1985;82:  Glucagon (pg/mL) Glucose Infusion Rate (mg/kg min) Diabetic + Phlorizin Diabetic Plasma Glucagon Concentration in Diabetic Dogs Before and After Phlorizin