The aim of this study was to investigate the influence of short-term submaximal postprandial exercise on plasma glucose concentrations in tightly controlled ...
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ontinuous Subcutaneous Insulin Infusion and Postprandial Exercise in Tightly Controlled Type I (Insuluvdependent) Diabetic Patients MARIELLA TROVATI, M.D., QUIRICO CARTA, M.D., FRANCO CAVALOT, M.D., SARA VITALI, M.D., GABRIELLA PASSARINO, Ph.D., GIUSEPPE ROCCA, M.D., GIORGIO EMANUELLI, M.D., AND GIANFRANCO LENT1, M.D.
The aim of this study was to investigate the influence of short-term submaximal postprandial exercise on plasma glucose concentrations in tightly controlled insulin-dependent diabetic patients treated by means of continuous subcutaneous insulin infusion (CSII). Two hours after breakfast, five diabetic patients and five healthy control subjects followed this protocol: 30 min of mild exercise, 30 min rest, 30 min of moderate exercise, 150 min rest. Serial determinations of plasma glucose, free insulin, and growth hormone (GH) were made. Similar control studies without exercise were also performed. In the diabetic patients, analysis of variance and covariance did not reveal any significant difference between the 2-h postbreakfast concentrations of plasma glucose and free insulin and postexercise values. A significant GH increase was observed after the exercise periods. Plasma glucose and insulin concentrations throughout the exercise study were not significantly different from the control study concentrations. Plasma free insulin concentrations of the diabetic patients were higher than the concentrations of healthy subjects. We conclude that CSII-treated, tightly controlled, insulin-dependent diabetic patients performing short-term mild and moderate exercises 2 and 3 h after breakfast do not have a high risk of hypoglycemia in spite of mild hyperinsulinemia. DIABETES CARE 1984; 7:327-30.
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n exercise-induced decrease in plasma glucose in insulin-treated diabetic patients is a phenomenon described since the beginning of the insulin era1 and extensively investigated in numerous
studies.2"5 The pathophysiologic mechanisms causing the decrease in plasma glucose are generally considered to be the lack of an exercise-induced decrease in the plasma insulin concentrations, which occurs in healthy subjects.6 Together with the simultaneous increase in glucose utilization by exercising muscles, this could account for the impaired increase in endogenous glucose production, which causes the decrease in plasma glucose concentration.7 A recent study of insulin-infused healthy subjects showed that a mild fixed hyperinsulinemia did not inhibit the exercise-induced increase of splanchnic glucose production, allowing a steady-state glucose above the hypoglycemic range when the pre-exercise plasma glucose concentrations were at a low set point (about 4 mmol/L),8 suggesting that "mild peripheral hyperinsulinemia (which results from systemic insulin delivery systems) would not, of itself, cause hypoglycemia during moderate exercise."8
We planned the present study to investigate in tightly controlled insulin-dependent diabetic patients whether continuous subcutaneous insulin infusion (CSII) could avoid excessive exercise-induced plasma glucose decreases to hypoglycemic levels not only in the postabsorptive state, as has been recently described,9 but also postprandially. SUBJECTS, MATERIALS, AND METHODS
Informed consent was obtained from five insulin-dependent male diabetic patients, whose clinical data are reported in Table 1. No patient showed signs of macroangiopathy, microangiopathy, nephropathy, or neuropathy when investigated by means of clinical examination, EKG, funduscopy, fluoroangiography, proteinuria, urea and creatinine clearances, EMG, and tests for autonomic neuropathy. All patients had very low urinary C-peptide concentrations (
