Oral glucose‐stimulated serum C‐peptide predicts successful switching from insulin therapy to liraglutide monotherapy in Japanese patients with type 2 diabetes and renal impairment

AIMS/INTRODUCTION In Japan, liraglutide was recently approved for patients with type 2 diabetes. To our knowledge, there are no markers predicting successful switching from insulin therapy to liraglutide monotherapy in Japanese patients with type 2 diabetes and renal impairment. We therefore assessed clinical characteristics predicting successful switching. MATERIALS AND METHODS We analyzed 21 patients with type 2 diabetes and estimated glomerular filtration rates <60 mL/min/1.73 m(2) receiving long-term insulin in Shiga University of Medical Science Hospital, Otsu, Shiga, Japan. Their β-cell function was assessed by measuring urinary C-peptide and C-peptide immunoreactivity (CPR) index, along with glucagon loading and oral glucose tolerance tests. Blood glucose concentration and blood pressure were measured daily before and after switching from insulin to liraglutide, and glycated hemoglobin (HbA1c; National Glycohemoglobin Standardization Program) was assessed 12 weeks after switching to liraglutide. RESULTS Baseline HbA1c was significantly lower in successfully switched than in unsuccessfully switched patients. CPR index, urinary C-peptide concentration and 6-min post-glucagon increment in CPR (ΔCPR) did not differ significantly in the two groups. ΔCPR 120 min after 75 g oral glucose was significantly higher in successfully than unsuccessfully switched patients. Mean blood glucose concentrations before breakfast, after breakfast, before lunch and after dinner were significantly lower in successfully switched patients. HbA1c did not change significantly in either group. CONCLUSIONS Measurement of oral glucose-stimulated ΔCPR120 min is recommended when considering switching Japanese type 2 diabetes patients with renal impairment from insulin to liraglutide monotherapy.