Understanding the pathogenesis of the metabolic syndrome is paramount to eliminating it. Hepatic metabolic dysfunction associated wifh inadequate substrate oxidation, lipid accumulation, and dyslipidemia is a hallmark of metabolic syndrome as it is evident early in its development and is associated with the severity of other symptoms. It has been speculated that liver metabolic dysfunction is a causative step in the natural progression to metabolic syndrome. Despite the central role of liver metabolism to overall "metabolic health," the mechanism for its effectiveness in healthy physically active states, the factors responsible for dysfunction, and the means to correct dysfunction are poorly understood. The protocols that comprise the extended funding period focus on three Specific Aims that are a continuation of innovative work conducted in the current funding cycle. The Speciic Aims will test in lean and high fat fed mice whether (a) the activation of hepatic energy sensors (AMPK, sirtuins, hypoxia inducible factors) are protective against insulin resistance; (b) the extracellular matrix conveys a spatial barrier or signaling event that contributes to the impaired energetics and nutrient fluxes of insulin resistance;and (c) the hepatic adaptations to high fat feeding and physical activity are AMPK-dependent. The regulation of hepatic metabolism will be studied using surgical, experimental, and isotopic tools that allow well controlled studies to be conducted in the unstressed conscious mouse. Highly innovative approaches will allow the Aims to be addressed with unprecedented resolution of a spectrum of pathophysiological events. We have developed a new, highly innovative, and comprehensive method for measurement of nutrient fluxes in the liver using stable isotopes of glucose, water, and proprionate. Hepatic ECM will be characterized by using a novel proteomic method designed to focus on the ECM, immunohistochemistry, polysaccharide binding protein, and transmission electron microscopy. The ongoing and planned studies provide mechanisms by which environniental factors (diet and exercise) interact with genes to cause or rescue hepatic metabolic dysregulation. The results of these studies will introduce new avenues to our understanding and treatment of metabolic diseases.

Public Health Relevance

The metabolic syndrome is an epidemic in Western Culture. Hepatic metabolic dysfunction associated with lipid accumulation and dyslipidemia is evident early in its development and is associated with the severity of other symptoms. It has been speculated that liver metabolic dysfunction is a causative step in progression to metabolic syndrome. These studies will define how liver metabolism is regulated in the healthy liver and wherfi .<^itfis of dvsfunction lie in the nathonfinesi.q of metaholic .syndrome, in.siilin resistance, and diabetes.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Method to Extend Research in Time (MERIT) Award (R37)
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Special Emphasis Panel (NSS)
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Laughlin, Maren R
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Vanderbilt University Medical Center
Schools of Medicine
United States
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