- Title: Genetics of Brain Structure and Function
Principal Investigator: David Glahn, Ph.D.
Dates: August 1, 2006 - July 31, 2011
The goal of this project is to identify quantitative trait loci associated with variation in brain structure and function. The ultimate promise of this research is the discovery of genes that predispose to brain disorders and mental illnesses. We believe that the analysis of genetic influences on brain structure and function in randomly sampled extended pedigrees will provide significant clues regarding the genes that are involved in both normal and pathological brain function. The focus of the project is on the genetic dissection of quantitative endophenotypes that more directly index the underlying biological basis of brain function than do discrete disease states themselves. To this end, we will perform neuroimaging and conduct neuropsychological examinations on Mexican American individuals who have been part of our ongoing genetic research studies for the past 15 years. All participants were previously genotyped and our plan is to utilize existing genome scan and genome-wide quantitative transcriptomic data for correlation with neuroanatomic and neurocognitive variables. Our specific aims are to: 1) perform high quality brain magnetic resonance imaging and neuropsychological examinations on 1,000 Mexican Americans who are members of approximately 30 large extended families, 2) assess the quantitative genetic architecture of brain-related phenotypes by estimating their heritabilities and their genetic correlations, 3) classify specific brain morphological variables and quantitative leukocyte-derived gene expression measures as endophenotypes related to brain function, 4) localize QTLs influencing variation in the quantitative brain-related phenotypes by performing linkage-based genome scanning using the variance component method, 5) refine the position of localized QTLs and identify positional candidate loci using an objective prioritization strategy that jointly utilizes in silico bioinformatics, genetic, and transcriptional data, and 6) identify the most likely functional variations within the two best positional candidate genes. This project involves coordinated R01 applications from Dr. John Blangero, Southwest Foundation for Biomedical Research, and Drs. David Glahn and Peter Fox, University of Texas Health Science Center at San Antonio. If funded, our data and biomaterials will be incorporated into the NIMH Human Genetics Initiative making them available to qualified researchers in the wider scientific community. Relevance to agency mission: Brain-related mental diseases are a major public health burden whose biology is still largely unknown. By identifying genes involved in brain function and structure, we will provide novel biological candidates for the determinants of such diseases and thus improve potential for intervention.
- Title: Influence of Psychosis on Brain-Behavior Endophenotypes for Bipolar Disorder
Principal Investigator: David C. Glahn, Ph.D.
Dates: May 1, 2008 - January 31, 2013
The aims in this study will (1) develop candidate neurocognitive and neuroimaging endophenotypes for bipolar I disorder (BPI), (2) examine the association of history of psychosis and these brain-behavior markers in BPI patients, and (3) determine if markers are sensitive to liability for psychosis. Thus, the project has two overlapping goals: the development of candidate endophenotypes for BPI broadly and the identification of candidate endophenotypes for psychosis. The ultimate promise of this research is to develop markers that will characterize the biological mechanisms of BPI and facilitate the discovery of genes that predispose the illness. We believe that a comprehensive assessment of neuropsychological functioning and brain structure and function in sibling pairs discordant for bipolar disorder and stratified for psychosis history is a strategically strong first step towards reaching these goals. To this end, we will perform anatomic and functional neuroimaging and conduct neuropsychological examinations on 130 euthymic patients with BPI (65 with history of psychosis), 130 of their unaffected same-sex siblings and 65 unrelated comparison subjects. Markers found to be aberrant in both affected individuals (regardless of history of psychosis) and in their unaffected relatives will be considered candidate endophenotypes for BPI (Aim 1). Neuropsychological and neuroimaging measures that distinguish between BPI patients with and without history of psychosis (Aim 2) and their siblings (Aim 3) will be considered potential endophenotypes for psychosis. Bipolar I disorder represents a significant economic burden and is associated with substantial morbidity and mortality rates. Although it is well established that BPI is substantially heritable, the molecular genetic basis for this illness remains elusive, potentially because of illness complexity, heterogeneity of disease expression, and comorbidity with other disorders that may distort clinical presentation. In the face of evidence that genes predisposing to BPI may be transmitted without expression of the clinical phenotype, interest has arisen in developing endophenotypes for the illness, indicators of processes mediating between genotype and phenotype. Given the high rates of psychosis in BPI and that history of psychosis may alter brain structure and function, we believe that elucidating neurocognitive and neuroimaging endophenotypes for the disorder must account for the potential impact of hallucinations and delusions on these markers. This research will established biomarkers that could improve the identification and treatment of BPI patients and, potentially, patients with psychotic disorders, independent of their formal diagnosis. PUBLIC HEALTH RELEVANCE: Bipolar I disorder is a major public health burden whose biology is still largely unknown. Through the development of brain-behavior markers sensitive to genetic liability for bipolar disorder, the proposed research should significantly aid the discovery of genes that predispose the illness and facilitate the identification of the biological determinants of bipolar disorder. This, in turn, should lead to improved characterization and treatment of bipolar disorder.
- Title: Relationship of Cytokines to Cognitive Functions in HCV
Principal Investigator: Robin C. Hilsabeck, Ph.D.
Dates: July 19, 2007 - July 31, 2009
The candidate is a board certified clinical neuropsychologist with prior research experience examining cognitive functioning of patients with chronic hepatitis C. The research environment includes ample office and laboratory space, computers and testing equipment, administrative and technical personnel, and strong institutional support for devoting at least 75% time to career development in conducting patient-oriented research. The purpose of this application is to provide the candidate with the necessary training in viral neuroimmunology to become an independent researcher capable of investigating the relationship between the immune response and cognitive functioning. Career development will include both didactic and "hands on" training in viral neuroimmunology and research methodology associated with measurement of cytokines. The long-term goal is for the candidate to develop a programmatic line of research that will contribute to the limited understanding of how the immune system influences cognitive functioning. Specific Aims of this project are: 1) to test the hypothesis that higher levels of interferon-alpha (IFN-a), a proinflammatory cytokine, are associated with cognitive dysfunction in patients with chronic hepatitis C infection (CMC) as measured by neuropsychological tests, and 2) to test the hypothesis that higher levels of IFN-a are associated with cognitive dysfunction as indicated by inhibition of complex motor pathways in patients with CMC measured by image-guided, robotically positioned transcranial magnetic stimulation surface electromyography (irTMS-sEMG). CMC infection is associated with significant morbidity and mortality, including mood and cognitive disturbances. To complicate matters further, IFN-a, the primary treatment for CHC, also is associated with mood and cognitive disturbances. While much research has focused on mood disturbances associated with IFN-a therapy, far less attention has been paid to associated cognitive difficulties. In this study, patients with CHC will undergo neuropsychological testing, psychiatric assessment, cytokine measurement, and irTMS-sEMG within 1 month of beginning IFN-a therapy and again after 12 weeks of IFN-a therapy. Changes in cognitive functioning over time will be compared to that of a healthy comparison group tested over the same time interval. Levels of IFN-a and other cytokines in serum also will be examined and related to cognitive functioning. Knowledge gained by examining these relationships will increase understanding of how the immune response affects thinking abilities of patients with CHC and may provide insights into treatments for thinking problems. Additionally, these relationships may be true in patients with other chronic diseases that affect thinking, such as Alzheimer's disease and systemic lupus erythematosus, leading to possible treatments for these patients, as well.
- Title: Regulation of Hepatic and Peripheral Glucose Metabolism
Principal Investigator: Ralph A. DeFronzo, M.D.
Funding: 5R01DK024092-26 Project
Dates: September 1, 2006 - June 30, 2009
Type 2 diabetes mellitus (T2DM) is characterized by defects in insulin action and insulin secretion. Disturbances in free fatty acid (FFA) metabolism also are a characteristic feature of T2DM and are observed in genetically predisposed individuals before the onset of overt diabetes. This raises the interesting possibility that FFA act as metabolic messengers which, when released in increased amounts, impair insulin action in insulin target tissues, i.e., "lipotoxicity". Much evidence also indicates that tissue fat content is increased in T2DM. We hypothesize that tissue lipid overload decreases expression of PGC-1, NRF-1, and multiple mitochondrial genes involved in oxidative phosphorylation. The resultant impairment in mitochondrial function leads to impaired substrate oxidation and accumulation of toxic lipid metabolites that inhibit insulin signaling and cause insulin resistance. In vivo and in vitro studies also suggest that increased hexosamine flux inhibits expression of PGC-1 and multiple mitochondrial genes involved in oxidative phosphorylation, i.e. "glucotoxicity". In the presence of hyperglycemia, an increase in malonyl CoA would be expected to further impair muscle fat and glucose oxidation by inhibiting CPTI, leading to an increase in toxic intracellular lipid metabolites and worsening of the insulin resistance, i.e. "glucolipotoxicity". In the present grant we shall examine the mechanisms of FFA-induced and hyperglycemia-induced insulin resistance. Using the insulin clamp with vastus lateralis muscle biopsy, magnetic resonance spectroscopy, and in vivo and in vitro evaluation of mitochondrial function, we shall examine the effect of elevated plasma FFA alone, increased glucosamine (glucose) alone, and the combination of elevated plasma glucosamine (glucose) plus elevated plasma FFA on whole body (muscle) insulin-stimulated glucose disposal/glucose oxidation/glycogen synthesis, insulin signaling, and mitochondrial gene expression and function in healthy NGT-insulin sensitive subjects. We also will examine the effect of acipimox (a potent inhibitor of lipolysis) and the effect of a highly specific inhibitor of renal tubular (SGLT2) glucose transport (BMS 512148) on the preceding parameters in T2DM subjects. These treatments reduce plasma FFA/deplete lipid from muscle and reduce plasma glucose levels, respectively. Therefore, we hypothesize that these interventions will increase PGC-1/NRF- 1/mitochondrial gene expression, improve mitochondrial function, and enhance insulin sensitivity/secretion. Lastly, we will examine the effect of combined acipimox/BMS 512148 therapy on the above paramters in T2DM. We believe that these studies will yield new insights into the etiology of insulin resistance in T2DM and identify novel therapeutic approaches to reverse the defects in insulin action and restore normoglycemia.
- Title: Mechanisms of Action of TMS-Induced Performance Enhancement
Principal Investigator: Peter T. Fox, M.D.
Funding: VA Merit Award
Dates: July 1, 2006 – June 30, 2010
The long-range purpose of the research program presented here is to study the mechanisms of action by which transcranial magnetic stimulation (TMS) enhances human performance. It is well established that, when properly applied, TMS can alter human performance. The mechanisms of action underlying TMS-induced performance enhancements, both acute and chronic, are not well understood. We hypothesize that the transient performance enhancement induced by single-session TMS is mediated by increased neuronal excitability at the stimulated site (Specific Aim 1), but not by increased connectivity or recruitment (increased activation volume). For multi-session TMS, we hypothesize that TMS adjuvant treatment will increase rate of learning and maximum performance achieved in comparison to motor practice alone, but that TMS alone will not improve either parameter of motor performance (Specific Aim 2). We also hypothesize that adjuvant TMS to SMAhand will have a greater effect on motor learning that adjuvant TMS to M1hand (Specific Aim 2). We hypothesize that for both motor practice alone and TMS adjuvant therapy: 1) rate of learning will be correlated with recruitment (increased activation volume) following Hebbian principles; 2) that absolute performance enhancement will be correlated with increased connectivity; and, 3) increased excitability will not be correlated with either performance variable (Specific Aim 3). This proposal will use several non invasive imaging and eletrophysiological techniques. Functional magnetic resonance imaging (fMRI) will assess alterations in the volume of cortex recruited during performance. TMS and positron emission tomography will be used conjointly (TMS/PET) to detect enhancements in inter-regional connectivity be used to detect alterations in neuronal excitability. These proposed experiments will determine the mechanism(s) of action by which single-session M1-hand TMS enhances motor performance. They will also determine the efficacy multi-session M1-hand and SMA-hand TMS as adjuvants to practice-induced enhancement of motor performance. The research program presented here will create a knowledge base which will inform the rationale development of transcranial magnetic stimulation (TMS) as adjuvant treatment to be used in conjunction with primary therapies in the treatment of neurological, psychiatric and developmental disorders. We predict that the results from the proposed studies will have direct impact on the management of stroke which is the third leading cause of death in the United States. Treatment of residual symptoms of stroke is mainly physical and occupational therapy. Applying TMS as an adjunct to physical therapy will reduce morbidity and improve quality of life of stroke patients. The findings from this study will also shed light on the mechanism of action of TMS that is being used as an adjunct therapy in depression.