The relationship between postprandial C peptide-glucose ratio, beta-cell function and treatment success in type 2 diabetes mellitus

Abstract

Objectives: This study aims to investigate the relationship between postprandial C-peptide-to-glucose ratio (PCGR), β-cell function and successful glycemic glycemic control in type 2 diabetes mellitus (DM) and determine the efficacy and feasibility of the PCGR index in the individualization of diabetes treatment. Materials and methods: This prospective study included a total of 49 patients (17 males, 32 females; mean age: 56±10 years; range, 32 to 75 years) under follow-up in Istanbul Medeniyet University Göztepe Training and Research Hospital Department of Internal Medicine with the diagnosis of type 2 DM between June and December 2016. Patients receiving insulin or insulin secretagogues were excluded. Data including age, sex, weight, height, waist circumference, hip circumference, date of DM diagnosis, serum hemoglobin A1c (HbA1c), and creatinine levels were recorded. All patients underwent a mixed meal test and their fasting blood glucose, C-peptide, postprandial glucose, and C-peptide levels were measured and recorded. Patients with a serum HbA1c level of 7% or lower were considered to have good glycemic control while patients with a serum HbA1c level of higher than 7% were considered to have uncontrolled diabetes. The relationship between C-peptide index (CPI), PCGR index, and parameters related to glycemia and β cell function was investigated. Results: Mean diabetes duration was 6.6±6 years and mean serum HbA1c level was 7.9±1.8%. There was a weak correlation between CPI and Homeostasis Model Assessment-β (HOMA-β), a moderate correlation between fasting C-peptide, delta C-peptide, and HOMA-β, and a strong correlation between fasting C-peptide, postprandial C-peptide, PCGR, and HOMA-β (p<0.05, p<0.05, p<0.001, respectively). There was a moderate negative correlation between postprandial C-peptide, delta C-peptide, fasting C-peptide-to-glucose ratio (FCGR), and serum HbA1c level (p<0.05). There was no correlation between fasting C-peptide and serum HbA1c level while there was a strong negative correlation between PCGR and serum HbA1c level (p<0.001). Comparison of the patient groups with and without glycemic control revealed that mean PCGR was significantly higher in the former group than the latter (p<0.001). Conclusion: We conclude that PCGR is significantly associated with glycemic control and variability. Our data suggest that PCGR is a useful index indicating β-cell function, and it can be used in the individualization of DM treatment.