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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 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

1. Exercise Dose Response Study:

PURPOSE: To determine the effects of a single session of exercise the body’s ability to control blood sugar and regulate fat metabolism. Impaired regulation of blood sugar can result in diabetes. Our study focuses on the importance of how EACH session of exercise can regulate the ability of body tissues to respond to insulin, which is the main factor responsible to effective removal of sugar from the bloodstream.

SUMMARY: If you are eligible for the study and you decide to participate, you will be asked to perform a minimum of three overnight experiments, on three separate occasions, with the option of participating in an additional two overnight experiments.

During your hospital visits

The afternoon one day before the experiment, you will need to pick up a pre-prepared meal from the General Clinical Research Center (GCRC) in the University of Michigan Hospital. This should be eaten by 7 o’clock that evening. You should not have anything to eat or drink except water after 7 o’clock that evening.

You will be admitted to the hospital in the morning. Females will then be asked to complete a urine pregnancy test. After resting for 30 minutes in your hospital room, we will measure your “basal metabolic rate” for which you will lie flat and breathe normally for about 20 minutes with a see-through Plexiglas canopy placed over your head. You will be provided breakfast at about 9:30AM and Lunch at about 12:30PM. The start time for the exercise portion of the study will be determined by the duration of the exercise, which will vary (between about 45-60 minutes) depending on the trial, all exercise will finish by about 4:00PM. In order for us to measure energy expended and the amount of fat you are burning during exercise, we will periodically ask you to breathe through a mouthpiece so we can collect your expired breath. A nose clip will also be used to prevent air escaping through your nose. You will also be connected to a heart monitor so that your heart activity during this exercise can be evaluated as well. During the trials without exercise you will sit quietly. After the exercise session you will be allowed to shower. An intravenous catheter (IV) will then be placed in a vein of your hand or forearm 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 placing the catheter you will eat a small meal and then blood samples will be obtained from the catheter in your arm every 15 minutes for 2 hours. You will be provided dinner at about 8:00PM and a light snack at 10:00PM, after which you will fast overnight. During the evening we will also place a second IV in a forearm or hand vein for the infusion of tracer-labeled glucose and fat that we will start early the next morning. Throughout your hospital stay you will wear a pedometer, and are limited to 1000 steps for the day.

At 5:00AM the next morning we will begin the tracer-labeled glucose and fat infusions. Blood samples will be taken during the 10 minutes before the start of these infusions and the infusions will continue until you complete the trial at about 11:00AM. At7:00AM, we will once again measure your basal metabolic rate (~20 min). At about 7:30AM, Dr. Horowitz or one of his qualified associates will remove a small muscle sample 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. The injury resulting from the muscle biopsy is very minor and should not prevent you from performing your general daily activities. Between 8:50-9:00AM we will collect some blood samples (in 5 min intervals) and at 9:00AM we will begin 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 periodically to monitor your blood glucose and blood insulin concentrations. 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. This final procedure will take about two hours. However, it is not uncommon for there to be some delays in the timing of these procedures, so we may not complete the study until the early afternoon. Please note that you will not be allowed to eat or drink anything on Day 2 of the study (other than water) until completion of all of these procedures. We should be finished with all of the procedures before 1:00PM, at which time you will be provided a meal.

ELIGIBLE: This research is limited to obese, but otherwise healthy men and women 18-45 years old. For this study, obesity is measured by Body Mass Index [BMI] = 30-45 kg/m2. Participants must be weight stable (± 5 lbs in the past month) and their fasting blood glucose concentration must be <125 mg/dl. Female participants must not be pregnant or have any evidence of cardiovascular or metabolic disease. No racial or ethnic group will be excluded.

COMPENSATION: The payment for the completion of study trials is as follows:

Trial #1: $100
Trial #2: $125
Trial #3: $150
Trial #4 (optional): $175
Trial #5 (optional): $175

You will not receive compensation for the initial screening tests.

To sign up to screen for this study, select "Exercise Dose Response Study" on our general screening questionnaire


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2. Exercisers vs. Non-Exercisers Study:

PURPOSE: The primary purpose of this study is to compare the effects of single session of exercise vs. chronic exercise training on key risk factors associated with Metabolic Syndrome (e.g., glucose tolerance, blood lipid profile, and blood pressure) in overweight adults.

SUMMARY: If you are eligible for the study and you decide to participate, you will be asked to participate in an experiment that will take approximately 3-4 hours of your time (“One-day study”) - with the option of extending your participation into a second day (“Two day study”; total participation time in the laboratory for the “Two day study” is approximately 10 hours).

  • One day study: You will be asked to come to the laboratory at 7AM in the morning for a series of metabolic measurements involving some blood sampling and we will be controlling your diet (see details below).

  • Two day study: If you choose to extend your participation, after we complete the metabolic measurements for the “One-day study” you will be asked exercise on a treadmill in the laboratory for 1 hour at a mild/moderate intensity. You will then be allowed to leave and you will return at 7AM the next morning for the same series of metabolic measurements performed the day before. During these two days, we will collect some blood samples from you and we will control your diet (see details below).

During your lab visit

The afternoon one day before the experiment, you will need to pick up a pre-prepared meal and snack from the Substrate Metabolism Laboratory, located in the basement of the CCRB. You must eat the meal and snack at specific times as indicated to you by the research staff. Other than the foods provided, you should not eat or drink except water until after the experiment is complete.

One Day Trial

You will need to come to the Substrate Metabolism Laboratory at 7:00AM. After you arrive you will rest quietly for approximately 30 min, after which we will measure your resting blood pressure (using standard procedures with a blood pressure cuff) and we will also measure your “resting metabolic rate”. Measuring your resting metabolic rate involves you resting comfortably on your back and breathing normally through a mouthpiece while air is prevented from escaping your nose by a padded nose clip. After these procedures an intravenous catheter (IV) will then be placed in a vein of your hand or forearm 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 obtaining a blood samples you will drink a sweet sugar solution containing 75 grams of glucose in water. We will collect blood samples every 15 min for 2 hours. This procedure is called an “oral glucose tolerance test” (OGTT) and it is a standard procedure used to test for symptoms of diabetes. After this 2 hour test, the IV catheter will be removed and you will be provided breakfast.

Two Day Trial

Day 1: Initial procedures will be identical to the “One Day Trial” listed above. After breakfast you will remain in the lab resting quietly for about 2 hours. During this time you may read, do homework, work on the computer, watch a movie, etc… At noon you will start the exercise portion of the study, you will exercise on a treadmill at a moderate intensity for about one hour. In order for us to measure energy expended and the amount of fat you are burning during exercise, we will periodically ask you to breathe through a mouthpiece so we can collect your expired breath. After the exercise session you will be allowed to shower. You will be provided with lunch, which can be eaten in the lab. After you have finished lunch, we will provide you with monitors that you will wear to measure your blood pressure and your activity level while you are away from the laboratory. We will also provide you with a take home dinner meal that is to be and a light snack that must be eaten at the times specifically indicated by the research staff. You must eat all of the food provided during the study and no other, and drinking water is encouraged. You will need to fast overnight; after you have eaten the snack.

Day 2: You will need to return to the Substrate Metabolism Laboratory at 7:00AM the next morning. You will rest quietly for approximately 30 min after you arrive and then we will perform the same battery of test that you underwent in the morning of Day 1 (i.e., blood pressure, resting metabolic rate, IV catheter placement/blood sampling, OGTT). After the 2 hour OGTT (approximately 10AM) the IV catheter will be removed and you will be free to leave.

ELIGIBLE: This research is limited to overweight, but otherwise healthy men and women 18-40 years old. For this study, overweight is measured by Body Mass Index [BMI] = 27-34 kg/m2. Participants must be weight stable (± 5 lbs in the past 3 months) and not have any evidence of cardiovascular or metabolic disease. Female participants must not be pregnant. No racial or ethnic group will be excluded.

COMPENSATION: You will receive $40 for completion of the One Day Trial. If you choose to participate in a second day of testing you will receive an additional $60. 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.

To sign up for this study, select "Exercisers vs. Non-Exercisers Study" on our general screening questionnaire

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3. Progressive Adaptions to Exercise and Weight Loss Study:

PURPOSE: To determine the effect of low intensity exercise training, with and without weight loss, on the body’s ability to control blood sugar and regulate fat metabolism. Impaired regulation of blood sugar can result in diabetes. Our study focuses on how low intensity exercise training, with and without weight loss, may help regulate the ability of body tissues to respond to insulin, which is the main factor responsible to effective removal of sugar from the bloodstream.

SUMMARY: The first 12 weeks (3 months) of the study you will participate in an exercise program (40min of relatively low intensity exercise, 5-6 days per week) and you will not be allowed to lose weight. After this initial 3 month period, a dietary weight loss program will be added to your exercise routine. You will continue with this exercise + weight loss program until you lose 10% of your initial body weight. In order to evaluate the adaptations that are occurring in your body throughout the program, you will be admitted to the hospital for a battery of metabolic tests at seven different time points throughout the program. Each of these hospital admissions will last ~27 hours, and therefore, they require you to stay overnight in the hospital. The details of the metabolic tests are described in detail below.

During your hospital visits

The afternoon one day before each hospital visit, you will need to pick up a pre-prepared meal from the Michigan Clinical Research Unit (MCRU) in the University of Michigan Cardiovascular Center. This should be eaten by 7 o’clock that evening. You will not have anything to eat or drink except water after 7 o’clock that evening.

On the first day of each hospital admission you will be provided a breakfast and lunch prepared from the MCRU Metabolic Kitchen which will be eaten about 9:30AM and about 12:30PM. Around 5:00PM, you will begin a 40min exercise session on a stationary bike (at approximately 50% of your previously determined maximal aerobic capacity). All metabolic studies will be identical with the exception that you will not exercise during visits #1, #5, or #7. During the trials without exercise you will sit quietly during this time.

An intravenous catheter (IV) will then be placed in a vein of your hand or forearm 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 placing the IV catheter you will eat a small meal around 6:00PM and then blood samples will be obtained from the catheter in your arm every 15 minutes for 2 hours. You will be provided dinner around 8:00PM and a light snack around 10:00PM, after which you will fast overnight. During the evening we will also place a second IV in a forearm or hand vein for infusions that will begin the next morning.

Very early in the morning of the 2nd day of each hospital visit (5AM), we will begin a tracer-labeled glucose infusion. At 6:30AM, we will measure your resting metabolic rate, during this test you will lie relatively flat in your bed and breathe normally for about 20-30 minutes with a see-through Plexiglas canopy placed over your head. At about 7:00AM, Dr. Horowitz or one of his qualified associates will remove a small muscle sample 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 also involves numbing a small region of skin near your belly button and 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 very minor. You will likely have some bruising, but it should not prevent you from performing your general daily activities.

At 8:45AM we will collect some blood samples (in 5 min intervals) and at 9:00AM we will begin 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 periodically to monitor your blood sugar. We will change the infusion rate of glucose accordingly to ensure that your blood sugar is maintained at a healthy/normal level. This final procedure will take about two hours. However, it is not uncommon for there to be some delays in the timing of these procedures, so we may not complete the study until the early afternoon. Please note that you will not be allowed to eat or drink anything on Day 2 of the study (other than water) until completion of all of these procedures. After we are finished with all of the procedures to measure your body’s insulin sensitivity, you will be provided a meal. When your vital signs are stable, you will be discharged from the hospital.

ELIGIBLE: This research is limited to obese, but otherwise healthy men and women 18-45 years old. For this study, obesity is measured by Body Mass Index [BMI] = 30-45 kg/m2. Participants must be weight stable (± 5 lbs in the past 3 months) and must not have any evidence or history of cardiovascular or metabolic disease. Participants fasting blood glucose concentration must be <125 mg/dl, and must have hematocrit blood values >34%. Female participants must not be pregnant, actively breastfeeding, or menopausal. No racial or ethnic group will be excluded.

COMPENSATION: You will receive $700 for completion of the entire study. If you do not complete the entire study you will receive $100 for each overnight visit you do complete. You will not receive compensation for the initial screening tests.

To sign up to screen for this study, select "Progressive Adaptions to Exercise and Weight Loss Study" on our general screening questionnaire


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4. Fatty Metabolism and Insulin Sensitivity Study:

PURPOSE: To compare the relationship between systemic fatty acid availability and insulin sensitivity in obese adults.

SUMMARY: We will perform some metabolic tests on you in the hospital. The total time required to complete these test will be approximately 6-9 hours, all in one day. The details of the metabolic tests are described in detail below.

During your hospital visits

You will be admitted to the Michigan Clinical Research Unit (MCRU) in the University of Michigan Cardiovascular Center at 7:00 AM. After resting quietly in a hospital room for about 30 minutes, we will measure your resting metabolic rate for about 20 minutes with a see-through Plexiglas canopy placed over your head.

At approximately 8:00 AM one intravenous (IV) catheter will be placed in your forearm vein for the infusion of tracer-labeled fat. 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 and collection of a baseline blood sample, we will 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.

Between 8:50-9:00AM we will collect some blood samples from the IV and at 9:00 AM we will begin the tracer-labeled fat infusion. After 45 minutes of the infusion, we collect four more blood samples.

At 10:00 AM we will begin 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 periodically to monitor your blood glucose and blood insulin concentrations. We will change the infusion rate of glucose accordingly to ensure that your blood sugar is maintained at a healthy/normal level. After completing the 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, you will be discharged from the hospital.

ELIGIBLE: Participants must be overweight/obese, non-exercisers (no planned exercise/physical activity) but otherwise healthy men and women ages 18-45 years old. For this study, obesity is measured by Body Mass Index [BMI] = 35-45 kg/m2. 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.

COMPENSATION: You will receive $125 for completion of the study. 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 hospital), this does not include the time spent in the pre-screening tests.

To sign up to screen for this study, select "Fatty Metabolism and Insulin Sensitivity Study" on our general screening questionnaire


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