Effects of Exercise on Blood Glucose and Glycemic Variability in Type 2 Diabetic Patients with Dawn Phenomenon

Background. The dawn phenomenon (DP) is the primary cause of difficulty in blood glucose management in type 2 diabetic (T2D) patients, and the use of oral hypoglycemic agents has shown weak efficacy in controlling DP. Thus, this study is aimed at investigating the effect of moderate-intensity aerobic exercise before breakfast on the blood glucose level and glycemic variability in T2D patients with DP. Methods. A total of 20 T2D patients with DP confirmed via continuous glucose monitoring (CGM) participated in the current study. After collecting baseline measurements by CGM as a control, CGM was reinstalled and 30 minutes of moderate-intensity aerobic exercise was performed prior to breakfast. Dawn blood glucose increase, blood glucose levels, and glycemic variability were measured before and after exercise. Results. Dawn blood glucose increase (ΔGlu, 1.25±0.84vs.2.15±1.07, P=0.005), highest blood glucose value before breakfast (Gmax, 8.01±1.16vs. 8.78±1.09, P=0.005), and mean blood glucose (MBG, 7.80±0.97vs. 8.37±0.95, P=0.001) were all lower, and time in range (TIR, 90.75±12.27vs. 83.5±15.41, P=0.015) was higher after exercise than before exercise. Among the glycemic variability indicators, blood glucose standard deviation (SD, 1.1±0.5vs. 1.48±0.63, P=0.001), coefficient of variation (CV, 14.14±5.94vs.17.69±7.46, P=0.006), mean amplitude of glucose excursion (MAGE, 2.71±1.52vs.3.73±1.98, P=0.006), and largest amplitude of glucose excursion (LAGE, 4.97±2.07vs.6.41±2.36, P=0.002) were all decreased following exercise. Conclusions. Acute moderate-intensity aerobic exercise before breakfast reduced the morning rise of blood glucose in T2D patients, partially counteracting DP. Furthermore, exercise significantly reduced blood glucose fluctuations and improved blood glucose control throughout the day. We recommend that T2D patients with DP take moderate-intensity aerobic exercise before breakfast to improve DP and glycemic control.