Effects of Exercise Training Intensity on Fitness and Insulin Sensitivity in African Americans

East Carolina University52 enrolled

Overview

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.

Interventions

Moderate intensity exercise training (MOD-INT)BEHAVIORAL

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)

High Intensity exercise training (HI-INT)BEHAVIORAL

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

Eligibility

Sex: ALLMin age: 35 YearsMax age: 65 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * African American * Body mass index 30-45 kg/m2 * sedentary/low active (step count ≤ 6,500 step/day) * capable and willing to give written informed consent and understand exclusion criteria * willingness to accept group assignment from randomization * No resistance training and no structured aerobic exercise for \> 20 minutes per day, 3+ days per week, for the last 6 months * conditions that are contraindicated for exercise training Exclusion Criteria: * Resting blood pressure \> 180 mm Hg systolic and/or \>100 mm Hg diastolic; individuals on blood pressure medications meeting the blood pressure criteria are eligible * Diagnosis of type 1 or 2 diabetes, and/or fasting glucose \>125 mg/dL * Medication for the treatment of type 1 or type 2 diabetes * Bariatric surgery including gastric banding or bypass (potential effects on energy intake) * Factors that may limit adherence to intervention or affect conduct of the trial * Unable or unwilling to communicate with staff * Failure to complete run-in or baseline testing * Hospitalization for depression or severe mental illness in the last 6 months * Not physically capable of performing the exercise required of the study protocol * Consuming more than 14 alcoholic beverages per week * Plan to be away from the Pitt County area more than 3 weeks in the next 3 months * Lack support from a primary health care provider or family members * Significant weight loss in the past year (\> 20 pounds) or are currently using weight loss medications. * Current diagnosis of schizophrenia, other psychotic disorders, or bipolar disorder * Another member of the household who is currently a participant or staff member of this study * Other temporary intervening event, such as sick spouse, or bereavement * Other medical, psychiatric, or behavioral limitations that may interfere with study participation or the ability to follow the intervention protocol * Underlying diseases or conditions likely to limit lifespan and/or affect the safety of the intervention * Cancer requiring treatment in the past 5 years with anything but excellent prognosis * Self-reported HIV, tuberculosis, Hepatitis B, or Hepatitis C * History or evidence of serious arrhythmias, cardiomyopathy, congestive heart failure, aortic aneurism, myocardial infarction or heart transplantation * Renal disease: urine protein \> 100 mg/dl, serum creatinine ≥ 1.5 mg/dl or currently receiving dialysis. * Auto-immune diseases (such as Lupus, Multiple Sclerosis, Graves' disease, or Rheumatoid arthritis) * Chronic obstructive lung disease, peripheral vascular disease or angina that limits ability to follow exercise protocol * History of stroke or transient ischemic attack * History of vascular aneurysms * History of bleeding disorders * Pregnancy or plans to become pregnant * Dieting or plans to diet, or in a weight loss program * Any other medical condition or disease that is life threatening or that can interfere with or be aggravated by exercise.

Outcomes

Primary Outcomes

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

Secondary Outcomes

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

Effects of Exercise Training Intensity on Fitness and Insulin Sensitivity in African Americans

Overview

Conditions

Interventions

Eligibility

Locations (1)

Outcomes

Primary Outcomes

Secondary Outcomes