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Mechanisms Underlying Metabolic Syndrome in Obesity

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00579813
Recruitment Status : Completed
First Posted : December 24, 2007
Results First Posted : July 12, 2011
Last Update Posted : June 15, 2017
National Institutes of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Information provided by (Responsible Party):
Philip Kern, University of Kentucky

Brief Summary:
The purpose of this study is to better understand the link between obesity and diabetes or pre-diabetes.

Condition or disease Intervention/treatment Phase
Metabolic Syndrome Insulin Resistance Prediabetes Drug: Pioglitazone Phase 4

Detailed Description:

Obesity is the most common and powerful force for creating insulin resistance and metabolic syndrome, however, the molecular basis of this association is not well understood. In this proposal, three independently funded researchers-Philip Kern, MD a clinical investigator, and Charlotte Peterson, PhD and Robert McGehee, PhD, with significant experience in muscle and adipocyte biology, respectively-will formalize a collaborative effort as a natural extension of previous work and shared interests in the fields of obesity, insulin resistance, and tissue lipid accumulation. Our overall hypothesis is that insulin resistance in humans stems largely from ectopic accumulation of intramyocellular lipid (IMCL) during the development of obesity. Further, we hypothesize that excess IMCL accumulation is dependent on secretory proteins derived from a complex interplay between adipocytes and macrophages in adipose tissue. To test these hypotheses, we will examine the interactions among adipocytes, macrophages, and muscle cells isolated and cultured from subjects that are obese with insulin resistance and impaired glucose tolerance (IGT), and from some with Type 2 Diabetes. This study population has elevated IMCL and is at high risk for obesity complications, but avoids the pathophysiologic complications of glucotoxicity. These subjects will be compared to obese subjects with normal glucose tolerance (NGT).

Aim 1 will explore mechanisms that contribute to IMCL and elucidate its role in the development of IGT. Cultured muscle cells will be used to determine whether obese subjects with IGT versus NGT demonstrate intrinsic differences in muscle gene expression and metabolic activity under differing extracellular fatty acid concentrations. Lipid accumulation and oxidation, and insulin-mediated glycogen synthesis and signaling will be assessed.

Aim 2 will determine if the IMCL accumulation is dependent on adipose tissue secretory proteins. We will use co-cultures of adipocytes, myoblasts, and adipose stromal vascular cells to examine IMCL and the development of insulin resistance.

Aim 3 will determine whether the stromal fraction from IGT subjects promotes IMCL more effectively than that from NGT subjects in co-cultures with muscle cells. We will compare the stromal vascular fractions with regard to monocyte/macrophage accumulation and cytokine expression.

Aim 4 will determine if improved glucose tolerance in response to a 10-week treatment with pioglitazone results in decreased IMCL and identify cellular mechanisms involved. Co-culture studies will also be used with muscle and stromal cells, before and after pioglitazone treatment. These experiments will provide mechanistic insight into the link between obesity and muscle function leading to metabolic syndrome.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 70 participants
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Basic Science
Official Title: Mechanisms Underlying Metabolic Syndrome in Obesity
Study Start Date : April 2005
Actual Primary Completion Date : January 2009
Actual Study Completion Date : January 2011

Resource links provided by the National Library of Medicine

Arm Intervention/treatment
No Intervention: 1
Baseline studies (OGTT, DXA, RMR, FSIGT, and biopsies) on normal control subjects. Oral glucose tolerance tests, body composition assessment, resting metabolic rate, insulin sensitivity measurement with the frequently sampled method and Minimal Model. These studies will establish baseline data in lean subjects on adipose tissue gene expression, insulin sensitivity, glucose tolerance, metabolic rate and body composition. There is no intervention.
Active Comparator: 2
Baseline studies (OGTT, DXA, RMR, FSIGT, biopsies), then 10 weeks treatment on Pioglitazone. Baseline tests are repeated at the end of medication treatment. All of the studies described in arm 1 are repeated after treatment. The subjects in this group have impaired glucose tolerance. After the measurement of adipose tissue gene expression, insulin sensitivity, glucose tolerance, metabolic rate and body composition, subjects are treated with pioglitazone, working up to 45 mg/day, for 10 weeks. After this time, adipose tissue gene expression, insulin sensitivity, glucose tolerance, metabolic rate and body composition are repeated.
Drug: Pioglitazone
Pioglitazone 30mg for 2 weeks, then Pioglitazone 45mg for 8 weeks.
Other Name: Actos

Primary Outcome Measures :
  1. Change in Insulin Sensitivity Using FSIGT [ Time Frame: Baseline and 10 weeks ]
    The frequently sampled intravenous glucose tolerance test (FSIGT) involves the injection of IV glucose and the frequent measurement of glucose and insulin.

  2. Effects of Pioglitazone on Changes in BMI [ Time Frame: Baseline and 10 weeks ]
    Body Mass Index (BMI) is measured at baseline, in lean and obese subjects, and after pioglitazone in obese subjects

  3. Changes in Muscle Lipid After Pioglitazone [ Time Frame: At baseline and 10 weeks ]
    Muscle lipid following biopsy using oil red-O staining.

  4. Changes in Fat Inflammation Following Pioglitazone [ Time Frame: Baseline and 10 weeks ]
    macrophages in fat at baseline, in lean and obese participants, and obese after pioglitazone (in obese)

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 65 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • 18-65 years of age
  • BMI 28+
  • diabetes, impaired glucose tolerance or normal glucose tolerance

Exclusion Criteria:

  • AST >2x normal
  • congestive heart failure
  • history of coronary artery disease
  • chronic renal insufficiency (creatinine > 1.4mg/dl)
  • use of gemfibrozil, ACE inhibitors, and angiotensin receptor II blockers, or anticoagulants

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00579813

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United States, Arkansas
University of Arkansas for Medical Sciences
Little Rock, Arkansas, United States, 72205
United States, Kentucky
University of Kentucky
Lexington, Kentucky, United States, 40536
Sponsors and Collaborators
Philip Kern
National Institutes of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Principal Investigator: Philip Kern, MD University of Kentucky
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Responsible Party: Philip Kern, Principal Investigator, University of Kentucky Identifier: NCT00579813    
Other Study ID Numbers: 32677
R01DK071277 ( U.S. NIH Grant/Contract )
First Posted: December 24, 2007    Key Record Dates
Results First Posted: July 12, 2011
Last Update Posted: June 15, 2017
Last Verified: May 2017
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Yes
Plan Description: Data from this study has been published. Individual (deidentified) data will be shared with other investigators upon request to Dr Kern.

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Studies a U.S. FDA-regulated Drug Product: Yes
Studies a U.S. FDA-regulated Device Product: No
Product Manufactured in and Exported from the U.S.: No
Keywords provided by Philip Kern, University of Kentucky:
Additional relevant MeSH terms:
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Metabolic Syndrome
Insulin Resistance
Pathologic Processes
Nutrition Disorders
Body Weight
Glucose Metabolism Disorders
Metabolic Diseases
Hypoglycemic Agents
Physiological Effects of Drugs