School Of Veterinary Medicine
Non Technical Summary
Methods have to be developed to determine what happens to the blood and muscle concentrations when a compound is administered that is now being recognized by regulatory agencies as ?gene doping?. Gene doping is the administration of a molecule or protein that will alter gene expression in a way that will enhance athletic performance. New compounds are being developed to provide a therapeutic benefit for patients with heart disease and cancer by altering gene expression. However, these same compounds used in healthy athletes (humans and racehorses) can also provide an advantage in competition, and are illegal. The research proposed in this project focuses on one such compound: the nucleoside, AICAR. AICAR increases the endurance of mice in the complete absence of exercise training. AICAR may do this by increasing vasodilatation, by increasing skeletal muscle glucose metabolism, and/or by causing long-term changes in skeletal muscle gene expression similar to those observed due to training. The goal of this research is to develop a method for the detection of AICAR usage in the racehorse. In order to detect if AICAR has been administered, we need to determine how much AICAR is present in the blood of normal horses. Next, we intravenously and intramuscularly. Completion of this project is expected to provide the data necessary for us to identify horses that have been treated with AICAR, and will provide better understanding of the effects of AICAR administered to horses.
Animal Health Component
Research Effort Categories
Goals / Objectives
AICAR (5-amino-4-imidazolecarboxamide riboside) is produced endogenously as an intermediate in the purine biosynthetic pathway. When administered exogenously, AICAR activates AMP-activated protein kinase (AMPK), which has been shown to increase exercise endurance in sedentary mice (500 mg/kg/day i.p. for 4 weeks; Narcar 2008), and is now in Phase II Human Clinical trials for the treatment of . AMPK is endogenously activated by an increase in the AMP/ATP ratio. Activation of AMPK creates a metabolic shift at the transcriptional level by down regulating ATP consuming processes and upregulating ATP producing processes. AICAR is rapidly internalized by cells and phosphorylated to become ZMP, an AMP mimetic (Corton, 1995). Binding of ZMP to the AMP binding site in AMPK causes a conformational change, which allows for phosphorylation of Thr 172 and activation of the kinase (reviewed by McGee 2010). In muscle cells, activation of the kinase increases ATP availability via increased fatty acid metabolism, increased glucose uptake via the transporter GLUT4, and increased vascular supply by the phosphorylation and activation of endothelial nitric oxide synthase (reviewed by McGee 2010). Because of these effects, WADA banned the use of AICAR and classified its use as "gene doping" in 2002 (need ref from Thomas 2010 paper). The effect of AICAR administration to equids is unknown. The hypothesis to be tested by the proposed studies are that the use of AICAR in Equids is a form of gene doping.
AICAR (5-amino-4-imidazolecarboxamide riboside) is produced endogenously as an intermediate in the purine biosynthetic pathway. AICAR is rapidly internalized by the cells and phosphorylated to become an adenosine monophosphate (AMP) mimetic called ZMP, which activates AMP-activated protein kinase (AMPK). AMPK has emerged as a key regulator of skeletal muscle oxidative function, including metabolic enzyme expression, mitochondrial biogenesis and angiogenesis. AMPK mediates these processes primarily through alterations in gene expression and based on this action its use is classified as "gene doping". When administered exogenously, AICAR alters muscle gene expression, and increased exercise endurance by approximately 44% in sedentary untrained mice. This drug is being investigated for its therapeutic value for the treatment of metabolic disorders in humans therefore it is available for use in the horse. The goals of this study are: 1. Develop an analytical method to detect/quantify AICAR and phosphorylated AICAR (ZMP) in plasma and RBC's. 2. Establish AICAR and ZMP reference values for normal healthy, racing and non-racing horses by analysing plasma from resting, training, and post-race populations of intact males, geldings, and female horses. 3. Determine the natural decay of ACAIR (endogenous pharmacokinetics) following maximal treadmill exercise. 4. Determine if variations in plasma concentrations exist based on gender, age, level of training, type of training, and physical activity. 5. Describe the pharmacokinetics, renal excretion, and bioavailabity of AICAR following administration. 6. Identify biomarkers which are up-regulated after administration of exogenous AICAR. 7. Determine if gene up-regulation occurs in horses.