Islet β-Cell Function Following 4.4-Year Insulin Injection in Chinese Elderly Patients with Type 2 Diabetes Mellitus

Abstract Background The aim of this study was to scrutinize changes of islet β-cell function in Chinese elderly patients with type 2 diabetes mellitus (T2DM) after insulin versus oral anti-diabetic (OAD) treatments. Methods In this prospective study, islet β-cell function was determined by oral glucose tolerance test-derived fasting C-peptide, maximal C-peptide, C-peptide area under the curve (AUC c-pep ) and fasting c-pep /fasting glu , maximal c-pep /maximal glu , AUC c-pep /AUC glu . Differences in β-cell function indices between baseline and follow-up were compared among insulin monotherapy, OAD monotherapy and combined therapies. Results From 2009 to 2017, 419 elderly patients (men: 51.1%) with T2DM (insulin monotherapy, n=105; OAD monotherapy, n=172; insulin + OAD, n=142) had undergone baseline and follow-up β-cell function assessment after a mean observation of 4.4 (range, 3.0 - 7.2) years. Overall, islet β-cell function indices were decreased in all the three groups: insulin (fasting C-peptide: p=0.002; maximal C-peptide: p=0.005; fasting c-pep /fasting glu : p=0.015; maximal c-pep /maximal glu : p=0.031), OAD (fasting C-peptide: p=0.026; maximal C-peptide: p=0.013; fasting c-pep /fasting glu : p=0.025; maximal c-pep /maximal glu : p=0.029), insulin + OAD (fasting C-peptide: p<0.001; maximal C-peptide: p<0.001; fasting c-pep /fasting glu : p=0.015; maximal c-pep /maximal glu : p=0.019). No significant differences of reduction were observed among the three groups regarding the fasting C-peptide (p=0.437), fastingc-pep/fastingglu (p=0.598), maximalc-pep/maximalglu (p=0.756), AUCc-pep (p=0.856) and AUCc-pep/AUCglu (p=0.912). However, the OAD treatment group had showed a less reduction level over insulin or insulin + OAD treatment. Conclusions In Chinese elderly patients with T2DM, islet β-cell function indices progressively decline regardless of insulin supplement or insulin plus OAD treatments. However, patients with OAD monotherapy may provide better β-cell function preservation than the insulin treatments.