342-P: Effects of Sitagliptin on Hypoglycemic Episodes and Counterregulation in Type 2 Diabetic Patients Tightly Titrated with Insulin Glargine

DPP-4 inhibitors may prevent hypoglycemic episodes in insulin-treated type 2 diabetes (T2D), but mechanisms are unclear. 20 T2D patients treated with basal insulin and metformin (± other agents) were recruited for two randomized treatments (placebo or 100 mg/d sitagliptin) in addition to insulin glargine/metformin; 17 completed (3 women, 14 men; age 57 ± 7 yrs.; BMI 28.8 ± 3.9 kg/m²; HbA_1c 7.4 ± 0.7 %). After titrating fasting plasma glucose (PG) to 90-110 mg/dl, patients were observed during a 3-day (d) inpatient period with exposure to oral glucose or lipid loads, strenuous exercise and fasting, while increasing insulin doses to 110, and 120 % of the titrated dose before d 2 and 3, respectively. Hypoglycemic episodes (PG < 70 mg/dl) were identified by measuring venous plasma glucose or symptoms, and prompted the determination of counter-regulatory hormones at the glucose nadir and 30 and 60 min later. After titrating insulin glargine, fasting PG was 112 ± 5 and 107 ± 5 mg/dl with placebo and sitagliptin treatment, respectively. Concentrations of insulin, C-peptide and counterregulatory hormones were similar during both treatments. Hypoglycemic episodes were mainly nocturnal (10 p.m. to 7 a.m.), with a similar PG nadir (65 ± 4 mg/dl) and incidence with placebo and sitagliptin (4.5 ± 3.2 vs. 4.6 ± 3.6 episodes per patient, respectively, p = 0.96). With a similar incidence of daytime (7 a.m. to 10 p.m.) chemical hypoglycemia, the incidence of symptomatic episodes was higher with sitagliptin (0.2 ± 0.4 vs. 0.0 ± 0.0, p = 0.028). Counter-regulatory responses were suppressed by sitagliptin for cortisol (p = 0.022), unchanged for glucagon, HGH, noradrenaline and prolactin, and accentuated for adrenaline (p = 0.022). Our results suggest that sitagliptin treatment augments counter-regulatory responses of adrenaline at minimal degrees of hypoglycemia. This may increase symptoms, in particular during daytime, and may offer opportunities for earlier treatment.