Influence of Prior Walking on Postprandial Metabolism in Centrally Obese Men
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 centrally obese South Asian and White European men.

      Participants will complete two, 2-day trials in a random, crossover design separated by at
      least a week.

      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 Asians 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.
      It is important to understand the effect of exercise on endothelial function and coronary
      heart disease risk markers in the hope that exercise can be prescribed as an effective
      treatment to mitigate endothelial dysfunction and the risk of heart disease.

      Previous research from the investigators' laboratory has indicated that postprandial
      metabolism is impaired in South Asian men, but this, and other coronary heart disease risk
      markers, can be improved with acute exercise. However, the previous research was conducted in
      apparently healthy South Asian and White European men. The investigators now wish to quantify
      and compare the coronary heart disease risk marker and endothelial function response to acute
      exercise in centrally obese South Asian and White European individuals who are at a higher
      risk for diabetes and cardiovascular disease.

      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. A HbA1c test will be performed to
      check participants are not diabetic. The modified Bruce Treadmill test will be performed to
      predict 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
      separated by at least 1 week. 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