We hypothesize that addictive drugs alter cellular lipid pathways in brain and peripheral tissues, and that such alterations influence the transition to compulsive drug use. A corollary of this idea is that peripheral lipid alterations might be used as biomarkers or biosignatures (composite biomarkers) of addiction. The goal of our experiments is to discover, through an unbiased evaluation of the lipidome, abnormalities in lipid function that might be involved in methamphetamine self-administration in rats (a model for human addiction) and identify peripheral biomarker candidates that might be used to screen for exposure and vulnerability to addiction. To achieve this goal, we will take tissue samples from rats at different stages of acquisition of methamphetamine self-administration and subsequent abstinence from the drug. We will then conduct lipidome-wide analyses of the samples using liquid chromatography/mass spectrometry. Finally, we will process the information obtained and integrate it with behavioral and molecular data to generate testable hypotheses on the functional significance of newly described lipid abnormalities. Initial experiments have uncovered multiple lipid alterations in brain and liver tissues from methamphetamine-exposed rats. We have two specific aims.
Aim 1 : To discover lipidomic abnormalities in the brain of rats that self-administer methamphetamine. We will (i) profile the brain lipidome during the acquisition of methamphetamine self-administration and subsequent abstinence from the drug;(ii) explore the mechanisms underlying significant lipid alterations uncovered by our lipidomic work;(iii) test whether such alterations correlate with drug self- administration;and (iv) examine whether lipid abnormalities might be used to monitor the severity of addiction as methamphetamine self-administration progresses from casual, controlled use to compulsive intake in susceptible individuals.
Aim 2 : To discover lipidomic abnormalities in peripheral tissues of rats exposed to methamphetamine, and identify candidate biomarkers for methamphetamine exposure. We will extend the lipidomic analyses conducted in Aim 1 to include peripheral tissues that are readily accessible to biopsy and/or interact metabolically with the brain (blood, skeletal muscle, subcutaneous fat, skin). We will also determine whether pre-existing differences in peripheral lipid profiles may predispose rats toward developing compulsive addiction-like behavior, and thus be potentially useful as antecedent biomarkers for methamphetamine addiction. A systematic and unbiased search of the lipidome to discover abnormalities associated with drug self- administration has yet to be attempted. The proposed studies address this gap and will result, if successful, in the discovery of novel biomarker candidates for addiction. This work will result in the retention of 7 existing jobs and the creation of 4 new jobs.
We propose to conduct a systematic and unbiased search of all lipids (the 'lipidome') in various rat tissues to identify abnormalities associated with methamphetamine addiction and discover early biomarkers for this disease.
