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

Exercise Study

PURPOSE: To examine the effects of exercise and energy balance on blood glucose responses to meals. The findings from this study will advance our understanding about the impact of exercise and nutrition on blood glucose control, which may lead to targeted strategies for preventing/treating insulin resistance and related diseases..

ELIGIBILITY: This study is limited to healthy men and women who are between the ages of 18-40 years old and have a Body Mass Index [BMI] = 20-30 kg/m2.  Participants must not have any evidence or history of cardiovascular or metabolic disease.  Female participants must not be pregnant, actively breastfeeding, or menopausal.  No racial or ethnic group will be excluded.

SCREENING PROCEDURES

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.  You will come to the Substrate Metabolism Laboratory at the University of Michigan where we will measure your height and weight, perform an exercise fitness test on a stationary bike, and will also measure your lean body mass and percent body fat using bioelectrical impedance analysis (BIA). This involves you standing on a scale with electrodes at the heels. Currents are sent through the body and the BIA measures resistance to current, which is proportional to lean body mass. You will not be able to feel the current, and it is not harmful. This procedure takes less than 5 minutes.  You will also be asked to complete a brief physical activity questionnaire and health fitness pre-participation screening questionnaire.

STUDY SUMMARY:

If you are eligible for the study and you decide to participate, you will be asked to return to the Substrate Metabolism Laboratory to complete two 5-day study trials. We will continuously monitor your blood sugar levels over an 88-hour period (from 4:00 PM on one day until 8:00 AM four days later).  You will come into the Substrate Metabolism Laboratory to have two continuous glucose monitors (CGM) placed on trial 1, or one CGM placed on trial 2. The placement of the CGM devices involves inserting a very thin flexible tube (resembling a short strand of fishing line) under the skin of your abdomen, near your belly button.  The thin tube is inserted under your skin with the assistance of a small needle. If you feel discomfort of from this procedure, it will be very mild and very brief (1-2 seconds). Immediately after placement of the CGM device (which takes only a few seconds) there should be only minimal, if any sensation from the very thin tube that will remain just beneath your skin. On top of your skin, the CGM device itself is slightly larger than a quarter, and it will be attached to your skin with sterile adhesive tape.  These devices will allow us to continuously measure your blood sugar levels during each of the trials. After placement of the CGM device(s) you will be discharged to resume your normal lifestyle during this 88-hour collection period.  You will be asked to measure your blood sugar 4 times each day during the period using a simple finger stick and a blood glucose monitor similar to what diabetics use to measure their blood sugar multiple times each day.  You will be provided with all of the supplies you need and instructions on how to perform this simple blood test. During the time in which we are monitoring your blood sugar with the CGM device(s), you will be provided with all of the food you will eat on those days, and you will be required to eat at very specific times each day. You will log the exact time of each meal for confirmation.

On the afternoon of the third day of each study trial period, you come to the Substrate Metabolism Laboratory to complete an exercise session. You will exercise at a moderate intensity on a stationary bike for approximately one hour; this intensity is similar to a jog during which you should be able to carry a conversation. You will return to the Substrate Metabolism in the morning of the fifth day of each study trial to have the CGM sensor(s) removed.

COMPENSATION: For your completion of in the study, you will receive a total of $30.  You will not receive compensation for the initial screening tests.  If you do not complete the entire study, you will be compensated at a rate of $10 for each hour spent in the laboratory; this does not include the time spent in the screening tests.

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

Exercise and Overeating Study:

PURPOSE. The primary purpose of this study is to examine the effects of 1-week of overeating on important clinical metabolic health outcomes (e.g., glucose tolerance, blood lipid profile, and blood pressure) and factors regulating the structure and metabolic function of fat tissue. This study will determine how regular exercise during this overeating period impacts these responses.

SUMMARY. If you are eligible, and decide to participate, you will take part in two identical study trials.  One is scheduled before and the other is scheduled after 1 week of overeating controlled by the study team.  Participants who exercise regularly will be instructed to exercise the day before their first study trial – and they will be required to exercise during 6 of the 7 days of the overeating period (including the day before their second study trial).  Participants who do not regularly exercise (no planned physical activity) will remain inactive until the completion of both study trials.    

  • Before each study trial.  If you are a regular exerciser, you will be asked to come to the Substrate Metabolism Laboratory in the afternoon before each of the 2 study trials to exercise in the lab for 45min at a moderate intensity. The evening before the study trial, all subjects will need to eat a standardized dinner meal and snack.  You must eat the meal and snack at specific times as indicated to you by the research staff.   After eating the snack, you will need to fast (no food or beverages – besides water) overnight.  
  • During each study trial.  You will arrive at the Substrate Metabolism Laboratory at 7:00AM and will rest quietly for approximately 30 min.  After which, we will measure your resting blood pressure and your resting metabolic rate.  An intravenous catheter (IV) will then be placed in a vein of your hand or forearm for blood sampling.  We will then collect a small sample of your fat tissue in your abdomen with a needle.  Next, you will drink a sweet sugar solution for an Oral Glucose Tolerance Test (OGTT) and we will collect blood samples every 15 min for 3 hours.  After this 3 hour test, the IV catheter will be removed and you will be provided breakfast and discharged (around 11:00 AM).

ELIGIBLE. This study is limited to healthy men and women, 18-40 years old, who are a normal weight.  For this study, obesity is measured by Body Mass Index [BMI] = 20-30kg/m2. We will recruit two different groups matched for BMI: 1) individuals who do not exercise, and 2) those who exercise regularly (i.e. at least 5 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.  Female participants must not be pregnant, actively breastfeeding, or menopausal.  No racial or ethnic group will be excluded.  

SCREENING PROCEDURES.  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.  You will come to the Substrate Metabolism Laboratory at the University of Michigan where we will measure your height and weight, perform an exercise fitness test on a stationary bike, and will also measure your percent body fat using a procedure in which you are weighed on a scale underwater.  You will also be asked to complete a brief physical activity questionnaire.

COMPENSATION. You will receive $200 for completion of the study.  You will not receive compensation for the initial screening tests.  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 does not include the time spent in the pre-screening tests or pre-study exercise sessions.

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

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.