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

Not Applicable

Completed

Conditions: Insulin Resistance
Sedentary Lifestyle
Obesity

Interventions: Behavioral: High Intensity exercise training (HI-INT)
Behavioral: Moderate intensity exercise training (MOD-INT)

Registration Number: NCT02892331

Lead Sponsor: East Carolina University

Brief Summary: 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.

Detailed Description: 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.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 52

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.

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
HIGH-INT	High Intensity exercise training (HI-INT)	High Intensity exercise training (HI-INT) group will exercise at a high aerobic intensity for 24 weeks
MOD-INT	Moderate intensity exercise training (MOD-INT)	The Moderate intensity exercise training (MOD-INT) group will exercise at a moderate aerobic exercise intensity for 24 weeks

Primary Outcome Measures

Name	Time	Method
Change in Cardiorespiratory Fitness	Baseline and 24 weeks	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).

Secondary Outcome Measures

Name	Time	Method
Change in Body Weight	Baseline and 24 weeks	Weight will be measured using a calibrated scale. Weight will be measured in kg
Change in Systemic Inflammation	Baseline and 24 weeks	High sensitivity c-reactive protein will be measured at baseline and follow-up
Change in Fasting Glucose	Baseline and 24 Weeks	Fasting glucose will be measured from a fasting blood sample
Change in Insulin Sensitivity	Baseline and 24 weeks	Insulin sensitivity will be measured using an intravenous glucose tolerance test
Change in Quality of Life (Mental Health and Physical Health Summary Scores)	Baseline to 24 Weeks	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.
Change in High Density Lipoprotein	Baseline and 24 Weeks	High density lipoprotein will be measured from a fasted blood sample
Change in Insulin	Baseline and 24 Weeks	Fasting insulin value will be measured from a blood sample
Change in Dietary Composition	Baseline and 24 weeks	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.
Change in Body Fat Percentage	Baseline and 24 weeks	Dual-energy X-ray absorptiometry will be used to measure changes in body fat percentage
Change in Triglycerides	Baseline and 24 Weeks	Triglyceride levels will be measured from a fasting blood sample
Change in Quality of Life	Baseline and 24 weeks	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).
Changes in Physical Activity Levels	Baseline and 24 Weeks	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
Change in Waist Circumference	Baseline and 24 weeks	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.
Change in Low Density Lipoprotein	Baseline and 24 Weeks	Low density lipoprotein will be measured from a fasting blood sample
Changes in Total Cholesterol	Baseline and 24 weeks	Total Cholesterol will be measured in a fasting blood sample
Change in Mitochondrial Enzymes	Baseline and 24 weeks	Mitochondrial enzymes (citrate synthase, pgc1aplha and complex1-5)
Change in Arterial Stiffness	Baseline and 24 weeks	Arterial stiffness will be measured using pulse wave velocity.