Paradoxical Stimulation of Hepatic Glucose Production With Dapagliflozin

To determine the role of plasma glucagon and insulin in the rise of endogenous glucose production (EGP) following the SGLT2 inhibition.

The increase in plasma glucagon conc and/or decrease in plasma insulin conc in response to glucosuria is (are) important signal(s) responsible, at least in part, for the increase in EGP, which the investigators anticipate will be derived primarily from the liver. Insulin and glucagon are powerful regulators of HGP. Therefore, the investigators anticipate that, at least in part, an increase in HGP secondary to the rise in plasma glucagon concentration and decrease in plasma insulin concentration in response to dapagliflozin-induced glucosuria will account for the majority of increase in EGP in both NGT and T2DM subjects. This study will define whether the increase in plasma glucagon and/or the decrease in plasma insulin are the trigger to stimulate EGP. Eligible subjects will receive three 5-hour measurements of endogenous glucose production (EGP), which is the biosynthesis of new glucose, with administration of study drug after a 3-hour tracer equilibration period. Hepatic glucose production (HGP), which is the net release of glucose from the liver, will be measured for 5 hours after drug administration to allow sufficient time for a significant increase in HGP above baseline after dapagliflozin administration (10). In study 1, HGP will be measured for 5 hours after dapagliflozin (10 mg) or placebo administration. This is the control study. The investigators expect to observe the "paradoxical" rise in EGP following dapagliflozin. Study 2 will be performed under glucose clamp conditions (i.e. maintaining the plasma glucose concentration stable at each subject's fasting level). This study will define whether the decline in plasma glucose concentration is the trigger to stimulate EGP. Study 3 will be performed under pancreatic clamp conditions (maintaining the plasma glucagon and insulin concentrations constant at the basal level). This study will define whether the increase in plasma glucagon and/or the decrease in plasma insulin are the trigger to stimulate EGP. Subjects will be randomized in a 2:1 ratio; 32 subjects will receive dapagliflozin and 16 subjects will receive placebo. Each study will be performed on a separate day, after a 10-12 hour overnight fast within 1-2 week period. Following studies 1-3, subjects will return for a renal (kidney) MRI-measurement to record kidney size.

Eligibility Criteria:
Inclusion Criteria:

* T2DM according to ADA criteria-HbA1C \< 8.0%
* BMI = 25-35 kg/m2
* Subjects must be in good general health as determined by physical exam, medical history, blood chemistries, CBC, TSH, T4, EKG and urinanalysis
* Body weight has been stable (± 3 lbs) over the preceding three months
* Do not participate in an excessively heavy exercise program
* Taking stable dose (more than 3 months) of monotherapy or combination therapy with metformin and/or a sulfonylurea

Exclusion Criteria:

* Subjects taking drugs known to affect glucose metabolism (other than metformin and sulfonylurea) will be excluded
* Individuals with evidence of proliferative diabetic retinopathy, plasma creatinine \>1.4 females or \>1.5 males, or 24-hour urine albumin excretion \> 300 mg will be excluded