Effects of Low Intensity Aerobic Exercise Training on the Microvascular Endothelial Function of Patients With Type 1 Diabetes: a Non-pharmacological Interventional Study

Subjects The present study was performed in accordance with the Helsinki Declaration of 1975, as revised in 2000, and the Institutional Review Board of the University Hospital of the State University of Rio de Janeiro, Brazil approved of this study. Once considered eligible, all subjects read and signed an informed consent document that was approved by the IRB.

Study subjects were recruited among patients who were followed up at a public hospital. Twenty-two individuals with T1D diagnosed for more than 6 years, between 25 and 50 years of age (mean 34 ± 7 years) were included in the study.

The initial clinical evaluation included the patient history and physical examination as well as recording of the following anthropometric data: weight, height, waist circumference and body mass index (BMI). Blood pressure measurements were collected with patients in the supine position after 5 minutes in quiet surroundings; they were repeated twice with two-minute intervals between measurements. All measurements were performed before and after twelve weeks of physical training.

Blood sampling and laboratory tests On the morning scheduled for the evaluation of cutaneous microcirculation, the patients presented in 12-hour fasted conditions for blood collection. Smokers should not have smoked or ingested caffeine from the night before until the completion of tests. The following variables were measured: fasting and postprandial plasma glucose, total cholesterol, LDL and HDL cholesterol, triglycerides, transaminases, high-sensitivity C-reactive protein, gamma-glutamyl transferase, creatine kinase, urea, creatinine, albumin and uric acid by colorimetric reactions with using a Cobas Mira-machine (Roche). Blood samples were collected before and after the physical training period. LDL cholesterol was calculated using Friedewald's formula. Serum samples were kept frozen at -80°C until measurement of the IL-6 levels with a commercial ELISA kit (Cayman Chemical Company, Ann Arbor, MI, USA), according to the manufacturer's instructions.

Physical training The study participants followed an aerobic training protocol targeted at low intensity and corresponding to 45% of the heart rate (HR) reserve [(HRmax - HRrest) x 45% + HRrest]. The exercise sessions were conducted 4 times per week for 12 weeks and included alternating walking and running, in accordance with the patient's fitness level, so that the heart rate reserve was between 40-50%. The heart rate was monitored using heart rate monitors (Polar Electro Oy, Kempele, Finland). In the first four weeks of training, there were additional increments of 10 minutes per session every week to promote gradual progression in the volume of 30 to 60 minutes during the remaining eight weeks.