Diabetes, Obese
Conditions
Keywords
insulin resistance
Brief summary
The purpose of this study is determine if you have too much fat in your body that it will decrease the conversion of food energy into energy that your body can use.
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. The purpose of this study is to determine whether experimental lipid oversupply decreases mitochondrial respiratory function. We will use mitochondrial respiration studies in vitro and mass spectrometry and proteomics analysis to test the hypothesis that experimental lipid oversupply: 1. Decreases mitochondrial respiration in response to lipid fuels. 2. Reduces abundance of mitochondrial proteins. 3. Alters phosphorylation of proteins in the electron transport chain. 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 2 times. On study Day 1 subjects will be screened with a medical history and physical exam, and a 75 g oral glucose tolerance test, measure body fat percentage, and an electrocardiogram (EKG). On Study Day 2, subjects will report to the clinic after an overnight fast. Female subjects will take a urine pregnancy test. A muscle biopsy will be performed to take a small sample from one thigh. A lipid infusion will be performed for 5 hours (60 ml/hr), with blood samples taken at 8 intervals during the infusion. At the end of the 5 hour period, a second muscle biopsy will be taken from the other thigh. The fat infusion will stop, subjects will be given lunch and allowed to leave the clinic.
Interventions
OTHERLipid infusion and muscle biopsies
Subjects will undergo a baseline muscle biopsy, a lipid infusion for 5 hours (60 ml/hr), and a muscle biopsy after the lipid infusion.
Sponsors
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Mayo Clinic
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
21 Years to 55 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Mitochondrial Respiration | Study Day 2, muscle biopsy approximately 6 hours after lipid infusion initiation | Mitochondrial respiration will be measured by micropolarography. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Protein Concentration of Mitochondria | Study Day 2, muscle biopsy approximately 6 hours after lipid infusion initiation | Protein concentration will be determined 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. |
| Phosphorylation of proteins | Study Day 2, muscle biopsy approximately 6 hours after lipid infusion initiation | Phosphopeptides will be measured by mass spectrometry. |
Countries
United States
Outcome results
None listed