Fat Cell Size in Insulin Resistance

Adipose Cell Size In Human Insulin Resistance

This study, conducted at Stanford University in Palo Alto, California, will examine how insulin metabolism and cardiovascular risk are altered in response to weight loss. Insulin is a natural hormone that causes cells to remove glucose (sugar) from the blood. People who are insulin-sensitive remove glucose efficiently. People who are insulin-resistant require more insulin to remove glucose from the blood.

Adult volunteers will be recruited for this study through advertisements in local newspapers in communities around Stanford University.

Participants will undergo the following tests and procedures:

• Insulin sensitivity testing: Before beginning the study, participants will be tested for insulin sensitivity. For the test, two small catheters (plastic tubes) are placed into two veins - one for infusing glucose, insulin, and sandostatin (a drug that blocks insulin secretion from the pancreas), and one for drawing blood samples. The infusions are done over 3 hours. Blood samples are collected before, during, and at the end of the study to measure how well the cells remove glucose from the blood in response to insulin.
• Research diet: Participants are assigned to a low-calorie diet tailored to the individual's metabolic rate. The diets contain either 40 or 60 percent of total calories as carbohydrates, 40 or 20 percent as fat, and the rest as protein. People with type 2 diabetes who are taking diabetes medicine with have a diet of 45 to 50 percent carbohydrates, 35 to 40 percent fat, and the rest protein.
• Meal profile: Before beginning the diet and after 4 months on the diet, participants are tested for the effects of the various study diets on control of blood sugar and fats. On the day of each test, participants have a physical examination and provide a medical history. Then, a small catheter is placed in a vein. Blood samples are drawn before breakfast and then hourly for up to 8 hours.
• Participants who are diabetic are randomly assigned to take one of three diabetes medications - rosiglitazone, glucophage, or a sulfonylurea compound - to help control blood glucose levels.
• Magnetic resonance imaging: This diagnostic test uses a strong magnetic field and radio waves to show structural and chemical changes in tissues. During the scan, the participant lies on a table in a narrow cylinder containing a magnetic field, wearing ear plugs to muffle loud knocking and thumping sounds that occur during the scanning process. He or she can speak with a staff member via an intercom system at all times during the procedure.

In addition to these procedures, patients may be asked to have a fat cell biopsy. This is done to determine whether insulin-resistant people have fewer fat cells but more fat per cell than insulin-sensitive people. For this test, a small piece of fat tissue is surgically removed, under local anesthetic, from an area of the lower abdomen. With the participant's consent, genetic testing may be done on the fat tissue sample to look for genes that may link central obesity to insulin resistance.

Some participants may be asked to be followed for an additional 3 months after completion of the study for a continued weight loss program. The follow-up includes weekly visits for weight measurements and a review of food records.

Study Overview

• Status: Completed
• Conditions: Obesity

Detailed Description

Little is known about the turnover of adipose cells in the fat depots of normal animals and human subjects. However, microarray analysis of adipose cell gene expression in high risk insulin-resistant human subjects suggests that a reduced rate of adipose cell turnover is associated with enhanced adipose cell size and systemic insulin resistance. New technology now permits a detailed analysis of adipose cell size including the detection of smaller cells which may be in the process of active differentiation. We propose to examine the relationship between adipose cell size distribution and systemic insulin resistance in obese human subjects. Adipose tissue biopsies will be obtained at Stanford University under protocols and consent forms approved by the Stanford University IRB. Only procedures already being performed on subjects under these protocols will be used.

• Study Type: Observational
• Enrollment (Actual): 782

Contacts and Locations

Study Locations

• United States
  • Maryland
    • Bethesda, Maryland, United States, 20892
      • National Institute of Diabetes and Digestive and Kidney Disorders (NIDDK), 9000

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

The NIH is involved with several Stanford protocols that have recruited both males & females between ages of 40-65 years of age who are either overweight patients but generally healthy, those with diabetes and cardiovascular medical conditions and/or are healthy volunteers.

Description

• INCLUSION AND EXCLUSION CRITERIA:

Without regard to gender, race, or socioeconomic status, all subjects will be adult men and women. The racial/ethnic composition of the study population will be reflective of the communities surrounding Stanford University. Subjects will be recruited through placement of advertisements in local newspapers, but no subjects will be seen at NIH.

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort
Healthy volunteers; healthy, non-overweight or other medical conditions
Patients overweight; Those who are generally healthy but overweight
Patients with health conditions; Those with diabetes and cardiovascular disease.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
adipose cell size distribution	to look at role of the to look at role of the fat cell in relation to obesity and insulin resistance, the role of anti-inflammatory helper cells in protecting against insulin resistance, look at effects of overfeeding on fat cells and insulin resistance, measure inflammatory markers (during and after weight loss), quantify production of fat cells, total triglycerides production, and breakdown of fat cells.	end of study

Collaborators and Investigators

• Sponsor: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• Investigators: Principal Investigator: Arthur Sherman, Ph.D., National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Study record dates

Study Major Dates

• Study Start (Actual): September 4, 2003
• Primary Completion (Actual): September 18, 2018
• Study Completion (Actual): August 10, 2020

Study Registration Dates

• First Submitted: June 19, 2006
• First Submitted That Met QC Criteria: June 19, 2006
• First Posted (Estimate): June 21, 2006

Study Record Updates

• Last Update Posted (Actual): August 17, 2020
• Last Update Submitted That Met QC Criteria: August 14, 2020
• Last Verified: August 1, 2020

More Information

Terms related to this study

• Keywords: Obesity; Type 2 Diabetes; Multisizer 3; Signaling; Adipose Cell Turn Over
• Additional Relevant MeSH Terms: Glucose Metabolism Disorders; Metabolic Diseases; Hyperinsulinism; Insulin Resistance
• Other Study ID Numbers: 999903290; 03-DK-N290