Glycaemic variability and hypoglycaemia are associated with C-peptide levels in insulin-treated type 2 diabetes

AIM: The aim of the study was to evaluate the association between C-peptide levels, glycaemic variability and hypoglycaemia in patients with insulin-treated type 2 diabetes (T2D).

METHODS: A total of 98 patients with T2D treated with basal-bolus insulin were enrolled in a cross-sectional study. Glycaemic variability and hypoglycaemia were assessed from continuous glucose monitoring (CGM) data recorded over 6 days: Glycemic variability was assessed by calculating the mean coefficient of variation (CV), while hypoglycemia was defined as sensor glucose levels???3.9?mmol/L or?<?3.0?mmol/L. Fasting C-peptide and fasting glucose were measured on day 1.

RESULTS: Low levels of fasting C-peptide correlated with higher CV (r?=?-0.53, P?<?0.0001). In a multivariate regression model with HbA1c, body mass index, diabetes duration and total daily insulin dose, only C-peptide was significantly associated with CV. Patients with???1 episode of hypoglycaemia had significantly lower median C-peptide levels than patients without hypoglycaemia (274 (136-620) pmol/L vs. 675 (445-1013) pmol/L, respectively; P?=?0.0004). Also, 17 patients clinically diagnosed with T2D had detectable glutamic acid decarboxylase (GAD) antibodies (??5?U/mL). These GAD-positive patients had significantly lower fasting C-peptide, higher CV and greater frequency of hypoglycaemia than GAD-negative patients.

CONCLUSION: In patients with insulin-treated T2D, low levels of C-peptide are associated with greater glycaemic variability and higher risk of hypoglycaemia, suggesting that C-peptide levels should be taken into consideration when optimizing insulin treatment and assessing hypoglycaemia risk.