Substrate Metabolism Laboratory Studies

Overview
 

Research in the Substrate Metabolism Laboratory focuses on the health effects of exercise and/or diet on the regulation of metabolism in obesity and obesity-related disease (like diabetes). Descriptions of our current research projects, as well as some of our other recent studies are provided below.

You may have been directed to this webpage because you are interested in participating in one of our research studies. If you are interested in any of the studies, please complete the general screening questionnaire (you can find the link to the questionnaire for each study below each study description). If eligible, you will be contacted by the Study Coordinator (Suzette Howton) via email to set up a screening appointment. If you would like further information, you may also email SML Studies at smlstudies@umich.edu.

 

Studies Currently Recruiting Research Subjects

High Intensity Interval Training (HIIT) Study

Do you want to start exercising? You may be eligible to participate in a research study investigating the effects of continuous and interval exercise on health and fitness!

Who can participate?

  •     Men & women 18-40 years of age
  •     Classified as overweight  (Body Mass Index 30-40 kg/m2)
  •     Weight Stable (+/- 6 pounds for past 6 months)
  •     Non-smoker who is relatively healthy
  •     Do not currently participate in regular exercise

You will undergo/receive:

  • 12 weeks of supervised exercise training (4x/week)
  • Body composition analyses
  • 1 overnight hospital visit before and 2 overnight hospital visits after training with blood sampling and metabolic testing
  • Up to $550 compensation upon completion the study
  • A free Activity Monitor to track your physical activity

STUDY DETAILS:

Preliminary Screening – Before participating in the study, you will undergo a screening visit at the Michigan Clinical Research Unit (MCRU) at the Michigan Medicine Cardiovascular Center (CVC). This appointment should take about 1.5 hours to complete and will include a resting electrocardiogram (EKG), a pre-participation screening questionnaire and a detailed medical history survey.

If you are deemed eligible based on the results of the preliminary screening, you will be enrolled into our study. The study consists of four (4) distinct phases:

  • Baseline Testing:  We want to assess your current level of health and fitness. We will measure your:  aerobic fitness with a bike test, body composition, blood sugar control, resting metabolic rate, and blood lipid profile. These tests will involve blood sampling and we will obtain a small piece of muscle from your thigh, and small piece of fat from your stomach. You will be required to stay in the hospital overnight in order for us to obtain some of the important measures of your health.
  • Exercise training:  You will undergo 12 weeks of supervised exercise training (4x/week) at the University of Michigan Central Campus Recreation Building (CCRB). You will be performing aerobic-type exercise (i.e. cycling, running, elliptical – you choose!). Depending on what group you are randomized into, you will perform your prescribed exercise in an interval or continuous manner. We also provide all participants with a free Activity Monitor to track your physical activity! 
  • Body weight will be recorded before every supervised exercise training session.   If body weight changes 4-5 pounds from your initial weight, you will consult with our research dietitian for strategies to maintain weight during this 3-month exercise training period. 
  • NOTE: After the 12 weeks of supervised exercise training, weight maintenance is not required. Diet will not be controlled during the 9-month follow-up testing portion of the study.  
  • Post-training Testing: We will perform all of the same tests that we did at baseline testing described above in order to see how your health and fitness has changed after 12 weeks of exercise training.  This will involve two overnight hospital stays which are scheduled 3 days apart.
  • Follow-up Testing: After your 12 weeks (3 months) of supervised training, we want to see if you keep performing the exercise on your own OR if you stop exercising once the supervised training is over. You will be asked to return to our lab a few times over the next 9 months so that we can monitor this.
  • NOTE: It is completely up to you whether or not you keep exercising and/or maintain your weight during this time. We are solely interested in monitoring your choice and exercise habits.  

To sign up to screen for this study, select “High Intensity Interval Training (HIIT) Study” on our general online screening questionnaire.

Protection Against Insulin Resistance (PAIR) Study

PURPOSE: Insulin resistance is a major contributor to the development of several obesity-related diseases. Despite the common link between obesity and insulin resistance, as many as one-third of obese adults appear to be “protected” against insulin resistance. Our preliminary findings indicate that insulin resistance can vary considerably even in a population of obese adults who are very similar in terms of the magnitude and distribution of their adiposity. The overall goal of this project is to identify factors that “protect” some obese adults from becoming insulin resistant. Identifying mechanisms that help protect some obese adults from developing insulin resistance could lead to novel, targeted therapeutic and/or preventative strategies for obese adults who are insulin resistant.

ELIGIBILTY: Participants must be healthy men and women ages 18-45 who are healthy, non-exercisers (no planned exercise/physical activity).  We will be recruiting obese individuals. For this study, obese individuals will have a Body Mass Index [BMI] = 30-40 kg/m2 and a waist circumference of 88-98 cm for women and 100-110 cm for men.  Participants must be weight stable (± 5 lbs. in the past month), must not be taking any medications known to affect their metabolism, and must not have any evidence and/or history of cardiovascular or metabolic diseases.  Female participants must not be pregnant, actively breast feeding, or menopausal.  No racial or ethnic group will be excluded.

SUMMARY:

SCREENING PROCEDURES

Participants will undergo a battery of initial screening tests including: a detailed health history and physical examination, a physical activity questionnaire, and a body composition assessment (using a Lunar DPX, DEXA Scanner).  All women will undergo a urine pregnancy test.

GENERAL STUDY DESIGN

To avoid potential confounding hormonal effects, all women will be studied in the early follicular phase of their menstrual cycle.  You will be advised of what you should be eating in the 3 days leading up to your hospital visit to maintain your weight.   You will also complete a three day food journal before your hospital visit.

You will be admitted to the Michigan Clinical Research Unit (MCRU) in the morning after a 12-hour, overnight fast.  After arrival, you will rest quietly in your room for about 30 minutes.  We will then measure your resting metabolic rate for about 20 minutes with a see-through Plexiglas canopy placed over your head.  After this test, an intravenous (IV) catheter will be placed in your forearm vein for the infusions and a second IV will be placed in your hand vein of the opposite arm for blood sampling.  This IV catheter is a very small flexible tube that remains in your vein throughout the study, and eliminates the need to poke you with a needle every time we collect a blood sample. 

After your IV placement, we will begin tracer-labeled glucose, or “sugar,” infusion.  We will then remove a small sample of muscle from your thigh.  This muscle biopsy procedure involves numbing a nickel-sized portion of the skin of your thigh with a local anesthetic, making a small incision (1/4 inch), and removing a small piece of muscle (approximately the size of 2-3 grains of rice).  The incision will then be closed with a piece of sterile tape. We will also obtain a small sample of fat tissue from the area just underneath the skin near your belly button. This procedure involves numbing a small region of skin near your belly button with a local anesthetic, using a needle a small amount of fat tissue is removed from underneath your skin.  During the procedure you will feel some pinching and pulling, but it should not be very painful.  The injury resulting from the muscle and fat tissue biopsies is rather minor.  You will likely have some bruising and mild soreness, but it should not prevent you from performing your general daily activities. 

Approximately 2.5 hours after admission, we will begin the tracer-labeled fat infusion.  The tracer-labeled fats we are infusing occur naturally in your body.  By injecting a slightly greater amount of this substance than you already have in your body we will be able to measure the rate of fat breakdown and fat burning. After about 50 minutes of the infusion, three blood samples will be obtained in 5 min intervals from your hand vein that has been placed in a heated hand box. 

After, we will begin a hyperinsulinemic-euglycemic clamp procedure (a procedure to measure your body’s sensitivity to insulin).  During this procedure we will infuse insulin and glucose through the IV in your forearm and we will collect blood samples every 5 minutes for the duration of the procedure to monitor your blood glucose and blood insulin concentrations.  This procedure is designed to last 2 hours.  We will change the infusion rate of glucose accordingly to ensure that your blood sugar is maintained at a healthy/normal level.  We will also infuse a small amount of potassium to make sure your potassium concentrations remain at healthy/normal levels.  About 30 minutes after starting this procedure to measure your body’s sensitivity to insulin, we will collect another sample of muscle from your thigh and fat tissue from the area just underneath the skin near your belly button.  After completing the hyperinsulinemic-euglycemic clamp procedure, you will be provided a meal, and we will continue to monitor your blood glucose concentration until stable. 

When your vital signs are stable, we will also measure your percent body fat using a Dual Energy X-ray Absorptiometry (DEXA) and intra-abdominal fat by Magnetic resonance imaging (MRI).  When your DEXA scan and MRI tests have been completed, you will be discharged from the hospital. Depending on scheduling, however, the DEXA scan and MRI tests may be performed on a separate occasion from your study trial admission.

COMPENSATION: If you are eligible to participate in the study trial after completing the initial physical screening, you will receive $200 upon completion of the "clinical study trial".  If, after being admitted to the MCRU for the study trial you are unable to complete the entire study trial, you will be compensated at a rate of $10 per hour that you have participated in the study trial (time in the hospital).  This $10 per hour compensation does not include the time spent during the initial physical screening tests.

To sign up to screen for this study, select “PAIR” study on our our general online screening questionnaire.

Iron and Metabolic Health Study

Would you like to participate in a study that would improve our understanding of the relationship between iron in the body and insulin resistance?

 

We are looking for men and women who are:

  • Age 18-40 years
  • Overweight or obese (classified with a Body Mass Index of 27-40 kg/m2)
  • Weight Stable (+/- 6 pounds for past 6 months)
  • Non-tobacco or e-cigarette users
  • Not taking medications or supplements known to affect metabolism or inflammation
  • Relatively healthy with no evidence/history of metabolic diseases or anemia

General blood donation eligibility requirements must be met to participate. Individuals who have donated blood within the past 12 months will be excluded.  

Women must have regularly occurring menses and be premenopausal. Pregnant or actively lactating women will be excluded.

STUDY DETAILS:

 

Initial Screening – Before participating in the study, you will undergo a physical screening that will include a health history, a food frequency, and a physical activity questionnaire.  We will also obtain your height/weight and take a small sample of blood to measure your hemoglobin concentration. This appointment will take about 1 hour and will take place at the Substrate Metabolism Laboratory (SML) located in the Central Campus Recreation Building (CCRB) at the University of Michigan.  

If you are deemed eligible based on the results of the initial screening, you will be enrolled into our study. The study consists of four (4) distinct phases:

  1. Body Composition Assessment: We will measure your body composition using Dual Energy X-ray Absorptiometry (DEXA scan). Women will provide a urine sample for a urine pregnancy test prior to the DEXA scan.  This visit will take about 30 minutes and will take place at the Michigan Clinical Research Unit (MCRU) located in the Michigan Medicine Cardiovascular Center (CVC).
  2. Baseline Trial:  We want to assess your current level of health.  During this trial we will measure: body weight, resting blood pressure, fat metabolism, insulin sensitivity, and blood lipid profile. These tests will involve blood sampling and we will obtain a small piece of fat from your stomach. You will be required to stay in the hospital for approximately 8 hours.  At this appointment, the study team will provide you with a scale to weigh yourself at home on a daily basis.

NOTE: You will be required to maintain your weight from the baseline trial until the completion of the post-blood donation trial.  If your body weight changes ±4.5 pounds from your baseline trial weight, our research dietitian will provide strategies to help you return to the weight that you measured at your baseline trial.

  1. Blood Donation: You will donate blood about 1 week after your baseline trial at a blood donation center of your choice.  Between 24- and 72-hours following the blood donation, you will return to the SML so we can measure your hemoglobin concentration.  
  2. Post-blood Donation Trial: We will perform all of the same tests that we did at baseline testing described above in order to see how your health has changed after the blood donation.  

PARTICIPATION INCENTIVES: You will receive a total of $300 upon completion of the entire study.  You will not receive compensation for the initial screening, body composition test, or blood donation.  If you do not complete the entire study, you will be compensated at a rate of $10 for each hour spent in the hospital for the study trials.  

To sign up to screen for this study, select “Iron and Metabolic Health Study” on our general screening questionnaire.

Exercise and Fat Cells Study

PURPOSE: The purpose of this study is to measure changes in the cellular composition of adipose tissue after one session of endurance exercise.

ELIGIBLE: This study is limited to healthy men and women, 18-40 years old, who are either a normal weight or overweight (Body Mass Index [BMI] 20-25 or 27-35 kg/m2). We are recruiting people who exercise regularly (i.e. at least 3 days/week of aerobic/cardiovascular exercise for 30-60min/session at moderate and vigorous intensities).  Participants must be weight stable (± 5 lbs. in the past 1 month), must not be taking any medications that affect your metabolism, must not have any evidence or history of cardiovascular or metabolic disease, and must not use tobacco or e-cigarettes.  Female participants must not be pregnant, actively breastfeeding, or menopausal. No racial or ethnic group will be excluded.

PRELIMINARY TESTING: Before participating in the study trial, you will be asked to take part in some tests to determine if you are eligible for the study.  After an overnight fast, you will come to the Substrate Metabolism Laboratory (SML) at the University of Michigan where we will measure your height, weight, body composition, resting metabolic rate, and blood pressure. You will perform an exercise fitness test on a treadmill, and we will measure your insulin sensitivity.  You will also complete a brief physical activity questionnaire and a cardiovascular disease risk questionnaire as part of the preliminary testing.

EXPERIMENTAL TRIAL: If you are eligible, and decide to participate, you will take part in two experimental trials during which we will collect blood and fat tissue samples.  

  • Before each experimental trial (“Pre-trial Visit”). You will be instructed to perform your last regular exercise session 2 days before each experimental  trial. The evening before each experimental trial, you will need report to the SML for a Pre-trial Visit.  Before the “control” experimental trial (non-exercise), you will rest in the lab for one hour. For the “exercise” experimental trial, you will exercise on a treadmill for 1 hour at a moderate intensity.  Following these one hour interventions, you will eat a standardized dinner at a specific time and then will be required to fast overnight.
  • During each experimental trial. The following morning after each pre-trial visit, you will arrive at the Substrate Metabolism Laboratory and will rest quietly for approximately 30 min.  After resting, we will collect a blood sample and take a small sample of fat tissue from your abdomen with a needle. You will then be provided with snacks and discharged.  

COMPENSATION: You will receive $150 for completion of the entire study ($75 for the completion of each experimental trial.  If you do not complete the study you will be compensated at a rate of $10 per hour that you have participated in the study (time in the laboratory). This includes the time to complete the Oral Glucose Tolerance Test, but does not include the time spent completing the other preliminary tests.


To sign up to screen for this study, select “Exercise and Fat Cells Study” on our general screening questionnaire.