Over 30% of adult Americans are obese, as defined by a body mass index (BMI) of 30 or greater. BMI is calculated from a person’s height and weight and can be used as an indicator of the probability of developing obesity-related health issues, such as cardiovascular disease and type 2 diabetes.
Diabetes affects millions of people in the United States. Nearly 24 million have the disease and another 57 million are thought to have pre-diabetes, which means they are at greater risk of developing diabetes. Diabetes, which results from problems with the production of insulin or a decreased sensitivity to insulin, causes high levels of sugar to build up in the body. This increase in blood sugar can eventually lead to other serious problems such as heart disease, kidney failure, or blindness.

The heavier a person is, the greater their chance of developing type 2 diabetes. Many studies have shown that waist circumference is the strongest predictor of this. This is the difference between having an ‘apple’ shape or ‘pear’ shape. What is it about waist circumference that is so predictive? The answer might be found in the visceral, or internal, fat that pads the waistline. A major portion of this fat is the omentum, a blanket of internal fat that is attached to the outer edge of the stomach and rests on top of the intestines. This study, led by Naji Abumrad, M.D., professor and chair of General Surgery at Vanderbilt University Medical Center, is examining many of the factors associated with insulin sensitivity, including the effects of removing the omentum along with gastric bypass surgery.
“We have shown the reversal of diabetes through gastric bypass surgery. We know that this surgery leads to significant weight loss and a significant resolution of diabetes. We want to know how the reversal occurs”, Abumrad says. Participants in this study are randomly assigned to either a Roux-en-Y gastric bypass operation with omentum removal or a Roux-en-Y gastric bypass surgery alone. The researchers are comparing the participants' insulin sensitivity before and after the surgery, as well as comparing the participants to one another in order to understand what variables might affect the speed of response to the surgery and to a reversal in type 2 diabetes. In an effort to compare racial differences in type 2 diabetes, the study is seeking African-American and Caucasian participants.
To be a potential participant in this study, you must meet certain inclusion criteria, including, but not limited to having approval for gastric bypass surgery at Vanderbilt University Medical Center and being between the ages of 18 and 65. We do not pay for the costs associated with bariatric surgery, so insurance approval or the ability to self-pay must be considered. Since the operation and study must take place at Vanderbilt, and the complete study period is 2 years, living within a reasonable distance from Nashville, TN is imperative.

There are two different arms of the study. One requires 5 overnight visits to the General Clinical Research Center (GCRC) at Vanderbilt University Medical Center. The first visit must be before you have your operation, then you will return at 1-, 6-, 12-, and 24-months after the operation. The second arm also requires 5 visits (at the same time points as above), but 4 of the 5 involve staying overnight for 2 nights at each visit. The additional night allows for a 24-hour stay in the metabolic chamber in order to measure your energy expenditure. 

Other than the extra day in the metabolic chamber, the two versions of the study are identical. You will report to the GCRC the afternoon or early evening before the study day. You will do some paperwork, have an EKG if over the age of 40, have a pregnancy test if you are a female capable of childbearing, and be fed a standardized meal. The next morning you will have a DEXA scan to measure your body composition, then you will begin the insulin clamp test, which measures how your body uses sugars. You will have IVs inserted into each arm—one for drawing blood at various time points throughout the day, and one for infusing insulin, glucose, potassium and a labeled tracer (which is a small amount of glucose with a radioactive ‘tag’ attached to it that allows us to tell the difference from what your body makes and what we give you). A plexi-glass hood will be placed over your head for about 20 minutes in the morning and again in the afternoon to measure how much air you breathe in and out. This gives us an estimate of your resting energy expenditure. At each of the visits after your operation, a muscle and fat biopsy will be taken from the outer part of your upper thigh, using local anesthesia.

Blood samples and the biopsy tissues will be used to measure how sensitive your body is to insulin, as well as to examine many different hormones and proteins related to energy regulation, inflammation, fat composition, hunger regulation, and gene expression. The total amount of time for the study day is about 10 hours and you are compensated for your participation.

 

For more information, please contact:
 

Pam Marks, MS, RD Phone: 615-343-8389 Email: pamela.a.marks@vanderbilt.edu
Marcy Buckley, RN Phone: 615-343-2243 Email: marcia.h.buckley@vanderbilt.edu