Postexercise Glycemic Control in Type 1 Diabetes Is Associated With Residual β-Cell Function

Objective: To investigate the impact of residual β-cell function on continuous glucose monitoring (CGM) outcomes following acute exercise in people with type 1 diabetes (T1D). Research design and methods: Thirty participants with T1D for ≥3 years were recruited. First, participants wore a blinded CGM unit for 7 days of free-living data capture. Second, a 3-h mixed-meal test assessed stimulated C-peptide and glucagon. Peak C-peptide was used to allocate participants into undetectable (Cpepund 200 pmol/L) C-peptide groups. Finally, participants completed 45 min of incline treadmill walking at 60% VO2peak followed by a further 48-h CGM capture. Results: CGM parameters were comparable across groups during the free-living observation week. In the 12- and 24-h postexercise periods (12 h and 24 h), the Cpephigh group had a significantly greater amount of time spent with glucose 3.9-10 mmol/L (12 h, 73.5 ± 27.6%; 24 h, 76.3 ± 19.2%) compared with Cpeplow (12 h, 43.6 ± 26.1%, P = 0.027; 24 h, 52.3 ± 25.0%, P = 0.067) or Cpepund (12 h, 40.6 ± 17.0%, P = 0.010; 24 h, 51.3 ± 22.3%, P = 0.041). Time spent in hyperglycemia (12 h and 24 h glucose >10 and >13.9 mmol/L, P < 0.05) and glycemic variability (12 h and 24 h SD, P < 0.01) were significantly lower in the Cpephigh group compared with Cpepund and Cpeplow. Change in CGM outcomes from pre-exercise to 24-h postexercise was divergent: Cpepund and Cpeplow experienced worsening (glucose 3.9-10 mmol/L: -9.1% and -16.2%, respectively), with Cpephigh experiencing improvement (+12.1%) (P = 0.017). Conclusions: Residual β-cell function may partially explain the interindividual variation in the acute glycemic benefits of exercise in individuals with T1D. Quantifying C-peptide could aid in providing personalized and targeted support for exercising patients.This article is available to RD&E staff via NHS OpenAthens (subject to any publisher embargo). Click on the Publisher URL, and log in with NHS OpenAthens if prompted.This study was funded by the Diabetes Research and Wellness Foundation (SCA/OF/12/15) award to D.J.W. CGM equipment was provided by an equipment award to D.J.W. by Medtronic UK.accepted version, submitted versio