Mitochondrial Dysfunction in Diabetes

Overview

The purpose of this study is to determine whether insulin resistance is accompanied by "exercise resistance". Investigators will use mass spectrometry and proteomics analysis to test the hypothesis is that a bout of exercise that increases mitochondrial protein abundance in lean, healthy individuals is less effective in insulin resistant patients.

Full Title of Study: “PGC-1 and Mitochondrial Dysfunction in Diabetes, Aims 4 & 5″

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Non-Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Basic Science
    • Masking: None (Open Label)
  • Study Primary Completion Date: March 2014

Detailed Description

The investigators' prior research has focused on defining the changes in expression of nuclear encoded mitochondrial genes that predict changes in insulin sensitivity in skeletal muscle, with the goal of defining the molecular mechanisms underlying the connection between mitochondrial dysfunction and insulin resistance in skeletal muscle.

Three groups of subjects will be studied: lean, healthy control subjects (n=12) obese non-diabetic subjects (n=12) and patients with type 2 Diabetes Mellitus (n=12) for a total of 36 subjects. Twenty subjects have completed the study at Arizona State University; the remaining 16 subjects will be accrued at the Mayo Clinic in Arizona.

Subjects will come to the Mayo Clinic 4 times. On Study Day 1 Subjects will be screened with a medical history & physical and a 75 g oral glucose tolerance test to determine if they are eligible for the study. On Study Day 2, subjects will report to the clinic after an overnight fast, undergo a euglycemic clamp (using deuterated glucose) to determine insulin sensitivity, and in addition have a muscle biopsy (basal biopsy for comparison). On Study Day 3, subjects will report to the clinic after an overnight fast, and undergo a Volume Oxygen Maximum (VO_2 max) determination. On Study Day 4, subjects will report to the clinic after an overnight fast to perform an exercise bout with muscle biopsy 30 minutes after the end of exercise. This will be followed by an overnight fast, and an additional muscle biopsy at 24 hours post exercise.

Interventions

  • Behavioral: Exercise and muscle biopsies
    • Subjects will undergo a euglycemic clamp, VO_2 max determination, exercise periods and muscle biopsies.

Arms, Groups and Cohorts

  • Experimental: Obese Non-Diabetic Subjects
    • All subjects on this arm will undergo exercise and muscle biopsies.
  • Experimental: Type 2 Diabetic Subjects
    • All subjects on this arm will undergo exercise and muscle biopsies.
  • Experimental: Healthy Control Subjects
    • All subjects on this arm will undergo exercise and muscle biopsies.

Clinical Trial Outcome Measures

Primary Measures

  • Protein Concentration of Mitochondria
    • Time Frame: Study Day 4 (30 min after exercise) and (24 hours after exercise)
    • Protein concentration will be determined from muscle biopsies by the method of Lowry. 75 micrograms of muscle lysate proteins will be separated on a 10% Sodium Dodecyl Sulfate Polyacrylamide Gel, and then visualized with Coomassie stain. The gel lane will be cut into cubes, digested with trypsin and cleaned, then protein abundance will be determined using spectral counting.

Participating in This Clinical Trial

Inclusion Criteria

1. Subjects must be able to communicate meaningfully with the investigator and must be legally competent to provide written informed consent.

2. Subjects may be of either sex with age as described in each protocol. Female subjects must be non-lactating and will be eligible only if they have a negative pregnancy test throughout the study period.

3. Subjects must range in age as described in each specific protocol.

4. Subjects must have the following laboratory values:

1. Hematocrit ≥ 35 vol%

2. Serum creatinine ≤ 1.6 mg/dl

3. Aspartate Aminotransferase (AST) (SGOT) < 2 times upper limit of normal

4. Alanine Aminotransferase (ALT) (SGPT) < 2 times upper limit of normal

5. Alkaline phosphatase < 2 times upper limit of normal

6. Triglycerides < 150 mg/dl.

7. Prothrombin Time (PT) 11.7 -14.3 seconds (during Intralipid/heparin infusion,PT will be determined to insure that it is < 1.5-2.0 times the normal value.)

8. Partial thromboplastin time (PTT) 23.0-37.0 seconds.

Exclusion Criteria

1. Subjects must not be receiving any of the following medications: thiazide or furosemide diuretics, beta-blockers, or other chronic medications with known adverse effects on glucose tolerance levels unless the patient has been on a stable dose of such agents for the past three months before entry into the study. Subjects may be taking a stable dose of estrogens or other hormonal replacement therapy, if the subject has been on these agents for the prior three months. Subjects taking systemic glucocorticoids are excluded.

2. Subjects with a history of clinically significant heart disease (New York Heart Classification greater than grade II; more than non-specific ST-T wave changes on the EKG), peripheral vascular disease (history of claudication), or pulmonary disease (dyspnea on exertion of one flight or less; abnormal breath sounds on auscultation) will not be studied.

3. Recent systemic or pulmonary embolus, untreated high-risk proliferative retinopathy, recent retinal hemorrhage, uncontrolled hypertension, systolic BP>180, diastolic BP>105, autonomic neuropathy, resting heart rate >100, electrolyte abnormalities.

Gender Eligibility: All

Minimum Age: 21 Years

Maximum Age: 55 Years

Are Healthy Volunteers Accepted: Accepts Healthy Volunteers

Investigator Details

  • Lead Sponsor
    • Mayo Clinic
  • Collaborator
    • National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
  • Provider of Information About this Clinical Study
    • Principal Investigator: Lawrence Mandarino, Ph.D. – Mayo Clinic
  • Overall Official(s)
    • Lawrence Mandarino, Ph.D., Principal Investigator, Mayo Clinic

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