Effects of Moderate Cycling Exercise on Blood Glucose Regulation Following Successful Clinical Islet Transplantation

Abstract

Context Islet transplantation is effective in preventing hypoglycemia in patients with type 1 diabetes (T1D). However, it is unknown whether transplanted islets regulate plasma glucose concentrations appropriately during and after exercise in human islet transplant recipient (ITxs). Objective To determine the effect of exercise on plasma glucose, insulin, and glucagon concentrations in ITxs compared with control subjects (CONs) without diabetes. Intervention Participants completed two conditions in random order: 45 minutes of aerobic exercise (60% VO 2peak) and 45 minutes of seated rest. Blood samples were drawn at baseline, immediately after exercise or rest, and every 15 minutes throughout a 60-minute recovery period. Postexercise (24 hours) interstitial glucose was monitored with continuous glucose monitoring (CGM). Results Twenty-four participants (12 ITxs, 12 CONs) completed the protocol. Plasma glucose decreased more over time with exercise in ITxs compared with CONs [main effects of treatment (P = 0.019), time (P = 0.001), and group (P = 0.012)]. Plasma glucose was lower during exercise vs rest in ITxs but not CONs [treatment by group interaction (P = 0.028)]. Plasma glucose decreased more during exercise than during rest [treatment by time interaction (P = 0.001)]. One ITx and one CON experienced plasma glucose concentrations <3.5 mmol/L at the end of exercise, both of whom returned above that threshold within 15 minutes. Nocturnal CGM glucose <3.5 mmol/L was detected in two CONs but no ITxs. Conclusion Despite a greater plasma glucose decline during exercise in ITxs, hypoglycemia risk was similar during and after exercise in ITxs compared with CONs.