Mitochrondrial Dysfunction: Role in Metabolic Syndrome

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The goal of this program is understand the role of mitochondrial dysfunction on insulin resistance and other related metabolic disorders in humans. The program involves collaborative interactions between members of several departments, and is organized into three projects supported by three core facilities. Expertise in the fields of clinical physiology, biochemistry, human genetics, cell & molecular biology and nuclear magnetic resonance spectroscopy (MRS) will focus on the role of mitochondrial dysfunction in human disease. We will address the following questions: (1) Is mitochondrial dysfunction responsible for fat accumulation in muscle/liver and insulin resistance in young lean normorglycemic offspring of parents with type 2 diabetes (IR offspring), (2) What genes are responsible for reduced mitochondrial activity/content in IR offspring and families with hypertension and hyperlipidemia which appears to be due to a novel homoplasmic mutation in a mitochondrial tRNA/ile. (3) is brain mitochonddal metabolism affected in these patients as well as in insulin resistant elderly subjects? These questions will be addressed by collaborative interactions between the Principal Investigators of these 3 projects, which are as follows: (Project 1) - Dr. Shulman will address the role of mitochondrial dysfunction in the pathogenesis of insulin resistance in IR offspring. This project builds on preliminary data by his group demonstrating that these individuals have increased intramyocellular lipid content, which can be attributed to reduced mitochondrial activity. This project will further explore mitochondrial function in liver and muscle of these individuals using 13C/31p/1H MRS in combination with direct examination of muscle tissue by cellular and molecular approaches to directly quantify mitochondrial content, insulin signaling and protein phosphorylation using a novel LC/MSIMS approach, (Project 2) - Dr. Lifton will examine nuclear and mitochondrial DNA in muscle biopsy samples obtained from IR offspring and insulin sensitive control subjects that have been characterized in Project #1 in order to identify genes responsible for reduced mitochondrial function/content and insulin resistance. This project will examine the hypothesis that alterations in genes regulating mitochonddal biogenesis are responsible for insulin resistance. This project will also further characterize patients with hypertension and hyperlipidemia which preliminary data by his group suggests is caused by a novel homoplasmic mutation in a mitochondrial tRNA/ ile. (Project 3) - Dr, Rothman will employ novel C/31P MRS techniques to examine brain mitochondrial function in: 1) healthy elderly volunteers who have recently been shown to be insulin resistant due to mitochondrial dysfunction, 2) patients with the novel mitochondrial tRNA/ ile mutation associated with hypertension and hypedipidemia identified in Project 2, and 3) insulin resistant offspring of parents with type 2 diabetes identified in Project 1. These three projects will be supported by an Administrative Core (Core A) to coordinate the project as a whole, a Clinical Core (Core B) and a MRS/MRI Core (Core C). The program is coordinated by frequent meetings of the program faculty and research workers bdnging together these diverse approaches to address a common goal.