African Americans are at a substantially greater type 2 diabetes risk compared to Caucasians; however, very little data are available on the effects of exercise training on type 2 diabetes risk factors in at risk African Americans. The present proposal will evaluate the effects of 6 months of moderate versus vigorous intensity aerobic exercise training on fitness, insulin sensitivity, mitochondrial capacity, skeletal muscle oxidative/insulin sensitivity markers, adiposity, and quality of life in African Americans.
African Americans have a much greater risk of type 2 diabetes compared to Caucasians in the United States. Similarly, recent evidence has emerged that fitness level, a major risk factor for type 2 diabetes also tends to be lower in African Americans. Many scientific studies have shown that exercise training has a beneficial impact on fitness levels and a variety of other type 2 diabetes risk factors such as the reduction of glucose/insulin levels, and body fat Importantly, studies performed in mostly Caucasian populations suggest that exercise training at a vigorous intensity may promote greater improvements in type 2 diabetes risk factors compared to moderate intensity exercise, which may suggest that it has greater promise in reducing type 2 diabetes risk. However, few exercise training studies compare the health benefits of different exercise training programs (such as exercise intensity) in African Americans, which is clinically important due to their greater type 2 diabetes risk, and that fact that they are less likely to meet public health recommendations for physical activity compared to their Caucasian counterparts. The High Intensity exercise to Promote Accelerated improvements in CardiorEspiratory fitness (HI-PACE) study will evaluate the effect of exercise intensity on cardiorespiratory fitness (CRF) and insulin sensitivity in obese (BMI: 30-45) African Americans (40-65 yrs.) with at least 1 additional T2D risk factor. Participants (n=60) will be recruited in collaboration with the ECU Center for Health Disparities, and subsequently randomized to moderate intensity (MOD-INT, n=20) or high intensity (HIGH-INT, n=20) aerobic exercise training, or to a control group (CON, n=20) for 24 weeks. Supervised exercise training will be performed at a heart rate associated with \~50% and \~75% of VO2 max in the MOD-INT and the HIGH-INT groups, respectively at the same exercise volume of 600 MET-minutes per week (consistent with public health recommendations). The primary outcome is the change in CRF, which will be assessed at baseline, mid-intervention, and follow-up. Insulin sensitivity will be measured via an intravenous glucose tolerance test at baseline and follow-up. Other secondary measures include mitochondrial oxidative capacity using infrared and measurements on muscle biopsies (PGC-1α and other indices of mitochondrial content), the expression of a protein involved with insulin action (GLUT-4 expression) in skeletal muscle as well as systemic inflammation, adiposity, quality of life and exercise enjoyment measures.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
52
Participants in the MOD-INT group will exercise at the heart rate associated with 45-55% VO2 max. The exercise volume will be 600 MET-minutes per week, which is consistent with current public health guidelines (500-1,000 MET-minutes)
Participants in the HI-INT group will exercise at the heart rate associated with 70-80% VO2 max (heart rate ranges will be updated at mid-intervention CRF assessment). The exercise volume will be 600 MET-minutes per week, which is consistent with current public health guidelines (500-1,000 MET-minutes)3
East Carolina University
Greenville, North Carolina, United States
Change in Cardiorespiratory Fitness
Fitness will be measured using a modified Balke protocol on a treadmill. Participants will walk at an initial speed of 2.0 mph with 0% grade for the first 3 minutes after which the treadmill speed will increase to 3.0 mph for the next 3 minutes. The treadmill grade will be increased by 2.5% every 3 minutes until volitional exhaustion. Maximal oxygen consumption (Liters of O2 per minute) will be measured using a True Max 2400 Metabolic Measurement Cart (Parvomedics, Salt Lake City Utah).
Time frame: Baseline and 24 weeks
Change in Body Fat Percentage
Dual-energy X-ray absorptiometry will be used to measure changes in body fat percentage
Time frame: Baseline and 24 weeks
Change in Body Weight
Weight will be measured using a calibrated scale. Weight will be measured in kg
Time frame: Baseline and 24 weeks
Change in Waist Circumference
Waist circumference will be measured at the natural waist (midway between the inferior border of the rib cage and the superior aspect of the iliac crest) with a Gulick tape measure. Both landmarks (the inferior border of the ribcage and the superior aspect of the iliac crest) will be marked and the distance will be measured to determine the appropriate measurement site. Staff will confirm that: 1) the measurement tape remains horizontal; 2) the tape touches the entire circumference of the participant; 3) abdominal tissue is not compressed; 3) the tape measure is not within abdominal folds; 4) the measurement is taken at the end of normal respiration. The measurement will be repeated an additional time, and the reported value will be the average of these measurements. Both measurements must be within 0.5 cm to be considered acceptable for data purposes.
Time frame: Baseline and 24 weeks
Change in Low Density Lipoprotein
Low density lipoprotein will be measured from a fasting blood sample
Time frame: Baseline and 24 Weeks
Change in High Density Lipoprotein
High density lipoprotein will be measured from a fasted blood sample
Time frame: Baseline and 24 Weeks
Changes in Total Cholesterol
Total Cholesterol will be measured in a fasting blood sample
Time frame: Baseline and 24 weeks
Change in Triglycerides
Triglyceride levels will be measured from a fasting blood sample
Time frame: Baseline and 24 Weeks
Change in Systemic Inflammation
High sensitivity c-reactive protein will be measured at baseline and follow-up
Time frame: Baseline and 24 weeks
Change in Fasting Glucose
Fasting glucose will be measured from a fasting blood sample
Time frame: Baseline and 24 Weeks
Change in Insulin
Fasting insulin value will be measured from a blood sample
Time frame: Baseline and 24 Weeks
Change in Insulin Sensitivity
Insulin sensitivity will be measured using an intravenous glucose tolerance test
Time frame: Baseline and 24 weeks
Change in Arterial Stiffness
Arterial stiffness will be measured using pulse wave velocity.
Time frame: Baseline and 24 weeks
Change in Mitochondrial Enzymes
Mitochondrial enzymes (citrate synthase, pgc1aplha and complex1-5)
Time frame: Baseline and 24 weeks
Change in Quality of Life
Quality of life (QOL) will be measured by the short form health survey (SF-36). SF36 consists of 36 questions that measure patient's HRQoL in 8 domains: physical functioning (PF), role-physical (RP), bodily pain (BP), general health (GH) that represent the physical HRQoL, vitality (VT), social functioning (SF), role-emotional (RE), and mental health (MH) that represent the mental HRQoL. Each domain is scored from 0 (worst health status) to 100 (best health status).
Time frame: Baseline and 24 weeks
Change in Quality of Life (Mental Health and Physical Health Summary Scores)
The SF-36 also produces a measure of overall physical health (physical component score \[PCS\]) and overall mental health (mental component score \[MCS\]). Scoring of these items are standardized using means and standard deviations from the general US population. Aggregate PCS and MCS scores are standardized using a linear T-Score transformation to have a mean of 50 and a standard deviation of 10. A higher score indicates better quality of life and a lower score indicates worsened quality of life.
Time frame: Baseline to 24 Weeks
Changes in Physical Activity Levels
Participants will wear an ActivPal accelerometer for seven consecutive days, 24-hrs/day. The change in steps will be be evaluated from baseline to 24 weeks
Time frame: Baseline and 24 Weeks
Change in Dietary Composition
Food Frequency Questionnaire (FFQ) contains approximately 105 items grouped by categories and is completed for both frequency of consumption as well as portion size selections by the individual. The questionnaire, upon completion, provides estimated daily intake values for selected nutrients (kilocalories, macronutrients, and micronutrients) and provides information on food group servings.
Time frame: Baseline and 24 weeks
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