The onset of type 2 diabetes mellitus(T2DM) is based on the insulin resistance and decreasing of insulin secretion. Residual β-cell function is a key factor in achieving optimal glycemic control in patients with type 2 diabetes. Glucagon induces insulin secretion by direcdtly stimulating β-cells, therefore glucagon stimulaton test(GST) is a reliable marker for β-cell function. Fasting C-peptide(CPR)-index(CPR[ng/ml] to glucose[mg/dl] ratio x100; F-CPRI) is used as a marker of insulin secretion. We evaluated the efficacy of postprandial CPR to glucose ratio(P-CPRI) as a tool for evaluating β-cell function. Japanese T2DM patients with inadequte glycemic control(HbA1c>7.0%) were enrolled in the study(n=333, insulin therapy =217). HbA1c, fasting CPR and glucose were measured, and F-CPRI was calculated. Postprandial(120 min after breakfast) CPR and glucose were measured, and P-CPRI was calculated. For the GST, CPR was determinated before and 6 min after 1mg of glucagon injection. GSTδCPR(CPR[6 min] - CPR[0 min]) was calculated. Factors correlated with GSTδCPR were analyzed using simple and multiple stepwise regression analysis. P value<0.was defined as statistically different. F-CPR-index, P-CPR-index and GSTδCPR were 1.42±0.85, 2.26±1.59 and 1.85±1.15, respectively. Simple regression analysis showed that GSTδCPR was significantly correlated with age, height, body weight(BW), BMI, gender, duration of diabetes, diebetic retinopathy, diabetic nephropathy, insulin therapy, F-CPRI and P-CPRI. Multiple stepwise regression analysis revealed that independent factors contributing to GSTδCPR were BW(β=0.331, p<0.001), P-CPRI(β=0.451, p<0.001), duration of diabetes(β= -0.104, p=0.025), diabetic retinopathy(β= -0.127, p=0.004), DPP-4 inhibitor(β= -0.089, p=0.036) and biguanide(β= -0.144, p=0.001). Our date demonstrated that P-CPRI was valuable in assessing β-cell function and can help clinicians in clinical practice.
Y. Matsuhashi: None. S. Chikazawa: None. H. Nakayama: None. M. Murabayashi: None. S. Mizushiri: None. S. Osonoi: None. K. Takahashi: None. H. Otaka: None. M. Yanagimachi: None. H. Murakami: None. M. Daimon: None.