Multi-Tracer PET Quantitation of Insulin Action in Muscle (Phase 1, Phase 2, Phase 3, Phase 4)

Obesity Clinical Trial

Official title: Three-Tracer PET Quantitation of Insulin Action in Muscle

Status Completed

Clinical Trial Summary

The purpose of this research is to develop a new method to study insulin action using positron emission tomography (PET). Insulin is the hormone made by your body to control the blood sugar level. We want to develop a way to image (look at) the following three things: 1) how insulin affects blood flow in skeletal muscle 2) how insulin affects glucose (sugar) transport (movement) into muscle, and 3) how insulin affects glucose metabolism (breakdown) in skeletal muscle of healthy individuals. The long term goal will be to later apply this method to the study of metabolic diseases, especially type 2 diabetes mellitus and obesity.

PET imaging is a relatively non-invasive way to obtain a "metabolic picture" of body organs, and has been used successfully to study brain, heart and more recently skeletal muscle. In this research study, we will use PET with as many as four radioactive tracers (markers) to study skeletal muscle glucose transport in healthy volunteers.

Clinical Trial Description

The goal of this proposal is to develop a novel triple-tracer positron emission tomography (PET) method to image in vivo insulin-stimulated tissue perfusion, glucose transport and glucose phosphorylation in skeletal muscle in healthy individuals. The long term goal will be to later apply this model to the study of metabolic diseases, notably type 2 diabetes mellitus (Type 2 DM) and obesity (Ob). While it is often suggested that glucose transport is the rate-controlling step for insulin action, we will test the hypothesis that the control insulin exerts on the uptake of glucose into skeletal muscle is distributed across flow and tissue perfusion, trans-membrane transport and intra-cellular phosphorylation of glucose.

Specific Aim 1. The first specific aim is to develop the triple-tracer PET method for quantitative determinations of tissue perfusion, glucose transport and glucose phosphorylation in skeletal muscle. To measure blood flow and tissue perfusion, we will use 15O-H2O (half-life ~ 2 min; also referred to as 15O-water). To measure glucose transport, we will use 11C-3-O-methyl glucose (half-life ~ 20 min; also referred to as 3-0-MG), an analog that is transported but not phosphorylated or otherwise metabolized. 18F-2-deoxy-2-fluoro-glucose (half-life ~ 109 min; also referred to as FDG), will be used to examine glucose transport and glucose phosphorylation. Because of the differences in half-life of the three positrons (15O, 11C, and 18F), it is feasible to use each of these tracers, in sequence, in the same individual.

Specific Aim 2. The second specific aim is to rigorously test mathematical models to extract quantitative physiological information from dynamic PET imaging. We will test a novel model that specifically addresses the kinetics of substrate delivery within the interstitial space of skeletal muscle (i.e. a 5 rate constant, 4 compartment model with respect to FDG. Model testing will entail use of non-compartmental models e.g. spectral analysis). ;

Study Design

Time Perspective: Prospective

Related Conditions & MeSH terms

• Diabetes
• Obesity

• NCT number: NCT00222885
• Study type: Observational
• Source: University of Pittsburgh
• Status: Completed
• Phase: N/A
• Start date: December 2002
• Completion date: December 2006