Dapagliflozin Plus Pioglitazone in T1DM

Insulin deficiency, due to autoimmune destruction of beta cells, is the primary factor responsible for the development of T1DM, and insulin replacement therapy is the mainstay for the management of hyperglycemia. However, insulin therapy often is associated with adverse events, including weight gain which promotes insulin resistance leading to an increase in insulin demand. This results in a self-perpetuating vicious cycle whereby the increase in insulin dose causes weight gain that worsens insulin sensitivity, and further enhances insulin requirement. Hyperinsulinemia per se also induces insulin resistance.

To break this cycle, adjunctive therapies have been added to insulin in T1DM patients to lower the plasma glucose concentration. However, the addition of metformin, pioglitazone, and GLP-1 agonists to insulin in T1DM patients have not provided convincing evidence for a clinically meaningful reduction in the HbA1c or significant reduction in daily insulin dose.

SGLT2 inhibitors (SGLT2i) are a novel class of antidiabetic agents which reduce the plasma glucose concentration by inhibiting renal glucose reuptake and producing glucosuria. Because of this unique mechanism of action, which is independent of insulin secretion and insulin action, SGLT2i have proven to be very effective in lowering the plasma glucose concentration in T1DM. Initial proof of concept studies have demonstrated that, compared to placebo, all members of this class (dapagliflozin, empagliflozin, canagliflozin and sotagliflozin) effectively lower the plasma glucose concentration, HbA1c and daily insulin dose in T1DM without increased risk of hypoglycemia. Further, SGLT2i improved cardiovascular risk factors in T1DM by promoting weight loss and decreasing blood pressure.

Despite the promising potential for SGLT2i as adjunctive therapy to insulin in T1DM, recent large clinical trials have demonstrated two important limitations to this therapeutic strategy: First, although the decrease in HbA1c caused by SGLT2i in T1DM patients was statistically significant, the absolute decrease was relatively modest (0.30-0.45%). The investigators, previously have shown that SGLT2i stimulate an increase in the basal rate of hepatic glucose production (HGP) in T2DM patients. This SGLT2i-induced increase in HGP offsets by approximately one half the amount of glucose lost in the urine. Therefore, the investigators have hypothesize that, similar to what they have observed in T2DM patients, the addition of SGLT2i to insulin in T1DM patients stimulates HGP thereby attenuating the decrease in HbA1c. Further, the decrease in daily insulin dose after initiating therapy with SGLT2i in T1DM patients would be expected to enhance the increase in HGP and diminish the decrease in HbA1c. Thus, preventing the increase in HGP caused by SGLT2i in T1DM can be expected to markedly amplify the clinical efficacy of SGLT2i and enhance the reduction in HbA1c.

A second limitation of the use of SGLT2i an adjunct therapy to insulin in T1DM patients is the increase in diabetic ketoacidosis (DKA) risk. In three large clinical trials , the addition of SGLT2i to insulin in T1DM patients was associated with a 3-6% increase in DKA risk (see Table 1 below). Because of the significant morbidity and mortality associated with DKA, the increased DKA risk in T1DM has raised concerns about the use of SGLT2i as an adjunct therapy to insulin in T1DM patients despite their multiple metabolic benefits.

The Investigators previously have demonstrated that SGLT2i cause a significant increase in plasma FFA concentration, fat oxidation and subsequent increase in plasma ketone concentration in T2DM patients (27). Therefore, they hypothesize that in T1DM, SGLT2i cause a similar increase in plasma FFA concentration, fat oxidation and plasma ketone concentration which in certain clinical conditions (e.g. acute illness) can increase the production of ketones and result in the development of DKA. Further, prevention of the increase in plasma FFA concentration will inhibit the increase in plasma ketone concentration and reduce DKA risk associated with SGLT2i use in T1DM patients.

Pioglitazone inhibits lipolysis and markedly decreases the plasma FFA concentration. Further, pioglitazone is a potent inhibitor of HGP. These actions of pioglitazone are due to direct actions of the drug on adipocytes and liver, respectively, are mediated by PPAR gama, and are independent of the plasma insulin and glucagon concentrations. In fact, pioglitazone inhibits lipolysis and HGP in type 2 diabetic patients despite a decrease in plasma insulin concentration. Therefore, the investigators hypothesize that the addition of pioglitazone to SGLT2i in T1DM patients will prevent the rise in HGP caused by SGLT2i and, thereby, augment the decrease in HbA1c. Further, combination therapy with pioglitazone plus SGLT2i will prevent the increase in plasma FFA concentration and subsequent increase in plasma ketone concentration, thus reducing the risk of DKA.