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Glucose needs drop during high-intensity exercise in type 1 diabetes
In patients with type 1 diabetes, glucose amounts necessary to maintain euglycemia during an exercise session follow an inverted U-shaped trajectory, with no external glucose needed at high-intensity exercise, according to recent findings.
Vinutha B. Shetty, M D, FRACP , a pediatric endocrinologist at Princess Margaret Hospital for Children in Perth, Australia, and colleagues evaluated nine patients with type 1 diabetes (six women; aged 14.6-25 years; mean age, 21.5 years) to determine the association between exercise intensity and glucose needs. Participants underwent euglycemic clamp with the initial insulin infusion rate set at the participant’s lowest basal insulin rate for those on an insulin pump, or at the dose of the long-acting insulin for those on multiple daily injections. Insulin rate was then modified to a level at which no exogenous glucose was required to sustain a stable level of 5 mmol/L to 6 mmol/L.
Vinutha B. Shetty
Participants were randomly assigned on separate days to each of the following tests for 40 minutes or until fatigue: exercise at 35%, 50%, 65% or 80% O2 peak. Glucose infusion was continued throughout exercise and for 2 hours after exercise. Primary outcomes were glucose infusion rate, rate of endogenous glucose appearance and rate of endogenous glucose disappearance.
During exercise, the individual glucose infusion rate needed for maintenance of euglycemia ranged from 0 g/hour to 15 g/hour across all exercise intensities and increased with intensity up to 50% O2 peak (4 g/hour; P < .05) and 65% O2 peak (4.1 g/hour), with the exception of exercise at 80% O2 peak, in which no glucose was required by any participant. In two participants, no glucose was required at any exercise intensity. The individual glucose infusion rate needed to maintain euglycemia during the 2 hours after exercise ranged from 0 g/hour to 10.4 g/hour, and glucose was needed by all patients to maintain euglycemia during the 2-hour recovery period at 65% O2 peak.
Exercise did not prompt a significant change in endogenous glucose appearance during exercise at 35%, 50% and 65% O2 peak, except at the conclusion of exercise at 50% O2 peak, when endogenous glucose appearance was significantly higher than the basal level. Endogenous glucose disappearance increased with increasing exercise intensity, then rapidly dropped to baseline within 30 minutes after exercise. During exercise at 80% O2 peak, both endogenous glucose appearance and disappearance increased significantly, but endogenous glucose disappearance was similar to appearance (P > .05). The levels of epinephrine and norepinephrine increased during all exercise intensities, reaching the highest levels at 80% O2 peak. After exercise, these levels decreased to basal levels within 30 minutes.
“Glucose requirements to maintain euglycemia during exercise performed under basal insulinemic vary markedly between individuals and depend on exercise intensity,” Shetty told Endocrine Today. “The risk of hypoglycemia during and early after exercise are not high when exercise is performed while plasma insulin levels are at close to basal levels, particularly when exercise intensity is elevated. However, [carbohydrate] must be administered post-exercise to maintain stable glycemia during early recovery from exercise performed under basal insulinemic conditions” – by Jennifer Byrne
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Vinutha B. Shetty, MD, FRACP, can be reached at Vinutha.Shetty@health.wa.gov.au.
Disclosure: The researchers report no relevant financial disclosures.