Influence of Prior Walking on Postprandial Metabolism and Endothelial Function.
Condition: Diabetes Mellitus, Type 2; Cardiovascular Diseases; Endothelial Dysfunction; Insulin Resistance; Oxidative Stress
MeSH terms: Cardiovascular Diseases; Diabetes Mellitus, Type 2; Insulin Resistance
Study type: Interventional

Summary: 
      The present study will investigate the effect of prior walking on postprandial metabolism and
      endothelial function in healthy South Asian and White European women.

      Participants will complete two, 2-day trials in a random, crossover design separated by at
      least 3 weeks to control for the menstrual cycle phase.

      On day 1, participants will either rest or complete a 60 minute walk at 60% maximal oxygen
      uptake. On day 2, participants will arrive at 08:00 having fasted overnight and a baseline
      venous blood sample and endothelial function measurement will be taken. Participants will
      consume a high-fat breakfast and lunch and 12 subsequent venous blood samples will be taken
      throughout the day at standardised intervals to measure a variety of coronary heart disease
      risk markers. A second endothelial function measurement will be completed 2 hours after the
      breakfast. Blood pressure will be measured every hour.

      It is expected that the South Asian participants will have impaired metabolism and
      endothelial function compared to their European counterparts but the bout of exercise
      performed on day 1 will mitigate these responses.
    

Detailed description: 
      South Asian individuals have a higher-than-average risk of coronary heart disease. The
      reasons for this are unclear, but physical inactivity and/or poor responsiveness to exercise
      may play a role.

      Previous research from our laboratory has shown that coronary heart disease risk markers in
      the postprandial period are elevated in South Asian men, but acute exercise was equally, if
      not more, effective for reducing these risk markers in South Asian than White European men.
      However, the effect of acute exercise on coronary heart disease risk markers has not been
      examined in South Asian women.

      Therefore, the purpose of the present study is to compare the effect of acute exercise on
      endothelial function and coronary heart disease risk markers in women of South Asian versus
      White European descent.

      On visit 1, participants will attend the laboratory to undergo preliminary assessments and to
      be familiarised with the laboratory environment and study procedures. Specifically, health
      status, habitual physical activity, dietary habits and anthropometric data (height, weight,
      waist and hip circumference, body fat) will be collected. Two preliminary exercise tests will
      be performed as follows: 1) submaximal-incremental treadmill walking test and 2) incremental
      treadmill running test to exhaustion to measure maximal oxygen uptake.

      On visit 2, participants will undergo a magnetic resonance imaging (MRI) scan to quantify
      regional body composition comprising abdominal subcutaneous adipose tissue, visceral adipose
      tissue, liver fat percentage, thigh intramuscular adipose tissue and thigh muscle volume.

      On visits 3-6 participants will complete two, 2-day trials in a random, crossover design
      seperated by at least 3 weeks to control for the menstrual cycle phase. On day 1 of both
      trials, participants will arrive fasted at 08:00 and a baseline blood sample, blood pressure
      and endothelial function measurement will be taken. Participants will consume a standardised
      high fat breakfast at 09:00 and lunch at 13:00. At 15:30 the participants will walk for 60
      minutes at 60% maximal oxygen uptake and complete a second endothelial function measurement
      at 16:45. Participants will leave the laboratory with a standardised evening meal to consume
      before 22:00. The control trial will be the same, except no exercise will be performed.

      On day 2, participants will arrive at 08:00 having fasted overnight for 10h (except plain
      water). A cannula will be inserted into the antecubital vein for collection of venous blood
      samples. Blood pressure will be measured at 08:00 (0h) and again at hourly intervals
      throughout the day. Endothelial function will measured at 08:15 (0.25h) and again at 3h. At
      0h, a fasting blood sample will be collected. Subsequent venous blood samples will be
      collected at 1.5, 1.75, 2, 3, 4, 5, 5.5, 5.75, 6, 7, 8 and 9h. Participants will consume a
      standardised high fat breakfast at 1h and a standardised high fat lunch at 5h. The meals
      consist of 57% fat, 32% carbohydrate and 11% protein. The meals provide 14.3 kcal per kg of
      body mass.

      Participants will rest in the laboratory throughout day 2 of both the exercise and control
      trials.
    

Intervention name(s): Exercise
Intervention type(s): Behavioral
Intervention description(s): A 60 minute walk at 60% maximal oxygen uptake.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Prevention