Effects of Low Intensity Aerobic Exercise on the Microvascular Endothelial Function of Patients With Type 1 Diabetes
Condition: Diabetes Mellitus, Type 1
MeSH terms: Diabetes Mellitus; Diabetes Mellitus, Type 1
Study type: Interventional

Summary: 
      Background: The aim of the present study was to evaluate the changes in the microvascular
      density and reactivity in patients with type 1 diabetes (T1D) resulting from low intensity
      chronic exercise training.

      Methods: This study included 22 (34 ± 7 years) consecutive outpatients with T1D and disease
      duration > six years. We used intravital video-microscopy to measure the basal skin capillary
      density as well as capillary recruitment using post-occlusive reactive hyperemia (PORH) in
      the dorsum of the fingers. Endothelium-dependent and -independent vasodilation of the skin
      microcirculation was evaluated in the forearm with a laser Doppler perfusion monitoring
      (LDPM) system in combination with acetylcholine and sodium nitroprusside iontophoresis, PORH
      and local thermal hyperemia.
    

Detailed description: 
      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.

      Capillaroscopy by intra-vital videomicroscopy The capillary density, defined as the number of
      perfused capillaries per mm2 of skin area, was assessed by high-resolution intra-vital color
      microscopy (Moritex, Cambridge, UK) using a video microscopy system with an epi-illuminated
      fiber optic microscope containing a 100-W mercury vapor lamp light source and an M200
      objective with a final magnification of 200X. The dorsum of the non-dominant middle phalanx
      was used for image acquisition, which occurred while the patient sat comfortably in a
      constant temperature environment (23±1°C). Images were acquired and saved for posterior
      off-line analysis using a semi-automatic integrated system (Microvision Instruments, Evry,
      France). The mean capillary density was calculated as the arithmetic mean of the number of
      visible (i.e., spontaneously perfused) capillaries in three contiguous microscopic fields of
      1 mm2 each. A blood pressure cuff was then applied to the patient's arm and inflated to
      suprasystolic pressure (50 mm Hg above systolic arterial pressure) to completely interrupt
      blood flow for three minutes (post-occlusive reactive hyperemia test, PORH test). After cuff
      release, images were again acquired and recorded during the following 60-90 seconds, during
      which a maximal hyperemic response was expected to occur.

      Microvascular reactivity to pharmacological stimulation The microvascular cutaneous
      reactivity was studied by laser Doppler perfusion monitoring (LDPM), a method that has
      previously been standardized and validated. Real-time variations in the cutaneous
      microcirculatory flow were assessed through an LDPM system (wavelength 780 nm; Periflux 5001,
      Perimed AB, Järfälla, Sweden) attached to a pharmacological micro-iontophoresis system
      (PeriIont, Perimed AB). The iontophoresis microelectrodes (PF 383, Perimed) were incorporated
      into the head of the laser probe (PF 481-1, Perimed), and the probe temperature was
      standardized to 32°C to avoid variations in the skin temperature and, consequently, in the
      measurements of microvascular flow. The drug-delivery electrodes were filled with 200 µl of
      1% ACh solution (Sigma Chemical Co., USA) and placed on the ventral surface of the forearm,
      away from visible subcutaneous veins and areas of skin pigmentation. Neutral electrodes for
      current dispersion were placed 15 cm above the infusion electrodes, and reference points were
      marked and annotated to ensure reproducibility during the second examination, which took
      place at the end of the intervention period. After measuring the baseline flow for 5 minutes,
      four equal cumulative doses of ACh (anodal current) were applied at a constant intensity of
      0.1 mA for 10, 20, 40 and 80 seconds, with total charges of 1, 2, 4 and 8 millicoulombs,
      respectively, allowing for a 120-second interval between doses. Recording of the
      microvascular flow induced by ACh was conducted for 10 minutes as follows: 2 minutes for each
      dose and 2 minutes to allow the flow to reach a plateau after the last dose. Using a new
      delivery electrode applied to a different location on the same forearm, four doses of a
      solution of 1% sodium nitroprusside (SNP; Sigma Chemical CO, USA) dissolved in distilled
      water were delivered using a cathodal current (same charges and intervals as for ACh).

      The laser Doppler output, which is semiquantitative, is expressed in arbitrary perfusion
      units (PUs) of output voltage (1 PU = 10 mV) in accordance with general consensus (European
      Laser Doppler Users Groups, London, 1992). An area under the flow response to the ACh curve
      could be defined using the PeriSoft for Windows 2.5 software (Perimed, Järfälla, Sweden);
      this area was quantitatively measured and expressed in PU/s.

      Microvascular reactivity to physiologic stimulation After measuring the resting capillary
      flow for 5 minutes using another laser probe (PF 457, Perimed) that had been positioned at
      the start of the recording session, the PORH test was performed. Following release of the
      pressure, the maximum flow and area under the PORH curve were measured. The mean value of the
      resting flow was considered the basal flow value. When the microvascular flow returned to the
      basal value after the PORH test (typically 5-10 minutes), the maximal skin microvascular
      vasodilatation was investigated with prolonged (20 minutes) local heating of the laser probe
      to 42°C. The baseline microvascular flux value was calculated as described above.

      Statistical analysis The values were expressed as the means ± standard error of the means for
      the variables with a normal distribution and as median (percentiles 25th - 75th) for
      variables with a non-parametric distribution, according to results of the Shapiro-Wilk
      normality test. The data were analyzed by two-tailed paired t tests or the two-tailed
      Wilcoxon signed-rank test, as appropriate. The null hypothesis was rejected at P<0.05.
    

Intervention name(s): Low intensity Exercise
Intervention type(s): Other
Intervention description(s): aerobic exercise training using walking and running
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Exercise training; microvascular rarefaction