Measurement Of Peak C-Peptide At Diagnosis Informs Glycemic Control But Not Hypoglycemia In Adults With Type 1 Diabetes
Abstract Context High residual C-peptide in longer duration type 1 diabetes associates with fewer hypoglycemic events and reduced glycemic variability. Little is known about the impact of C-peptide close-to-diagnosis. Objective Using continuous glucose monitoring (CGM) data from a study of newly diagnosed adults with type 1 diabetes, we aimed to explore if variation in C-peptide close-to-diagnosis influenced glycemic variability and risk of hypoglycemia. Design We studied newly diagnosed adults with type 1 diabetes who wore a Dexcom G4 CGM for 7 days as part the EXTOD study. We examined the relationship between peak stimulated C-peptide and glycemic metrics of variability and hypoglycemia for 36 CGM traces from 23 participants. Results For every 100 pmol/l increase in peak C-peptide, percentage time spent range 3.9-10 mmol/l was increased by 2.4% [95% CI: 0.5,4.3], p=0.01) with a reduction in time spent in level 1 hyperglycemia (> 10 mmol/l) and level 2 hyperglycemia (> 13.9 mmol/l) by 2.6% [95% CI: -4.9, -0.4, p=0.02) and 1.3% [95% CI: -2.7, -0.006], p= 0.04) respectively. Glucose levels were on average lower by 0.19 mmol/l ([95 % CI: -0.4,0.02], p=0.06) and standard deviation reduced by 0.14 [95% CI: -0.3, -0.02], p=0.02). Hypoglycemia was not common in this group and no association was observed between time spent in hypoglycemia (p=0.97) or hypoglycemic risk (p=0.72). There was no association between peak C-peptide and insulin dose adjusted HbA1c (IDAA1c, p=0.45). Conclusions C-peptide associates with time spent in normal glucose range and with less hyperglycemia, but not risk of hypoglycemia in newly diagnosed people with type 1 diabetes.