The objectives of this K08 proposal are: a) To foster the development of critical scientific and professional skills which will allow the candidate, Dr. Omar Mesarwi, to progress toward his goal of becoming an independent physician-scientist, examining the metabolic consequences of obstructive sleep apnea (OSA); and b) To determine how intermittent hypoxia (IH) in OSA may impact the development and progression of nonalcoholic fatty liver disease (NAFLD). Dr. Mesarwi and his mentors at UC San Diego have designed a comprehensive training plan that will afford Dr. Mesarwi new knowledge and research skills in the pathobiology of metabolic dysfunction in OSA. This will be accomplished through extensive laboratory experience and coursework at UC San Diego, which will provide Dr. Mesarwi additional expertise in experimental design, laboratory procedures, data analysis, and scientific communication. OSA is a common condition which is characterized by recurrent upper airway narrowing during sleep, leading to chronic IH. OSA is associated with a more severe NAFLD phenotype, driven by IH. NAFLD is an extremely prevalent condition in which hepatic steatosis and dysregulated glucose metabolism may ultimately lead to cirrhosis, need for transplant, and liver-related death. The mechanisms which link OSA and NAFLD are relatively unknown. Previous animal work has demonstrated that IH exacerbates hepatic steatosis and fibrosis in mice with diet-induced obesity, mirroring findings in human subjects. Hepatic steatosis in experimental NAFLD reduces liver oxygen tension; it is further reduced with superimposed IH. Hepatic steatosis also increases hypoxia inducible factor-1 (HIF-1), a regulator of the cellular response to hypoxia. We have shown that hepatocyte HIF-1 mediates the expression of several key enzymes of fatty acid metabolism in the liver, and the progression of liver fibrosis in experimental NAFLD. Therefore, we hypothesize that IH in OSA may worsen the NAFLD phenotype through HIF-1 activation and its downstream effects. We will test this hypothesis in three Specific Aims: 1) Determine the role of HIF-1 as a mediator of IH- induced hepatic steatosis and dysregulated hepatic glucose metabolism; 2) Determine the role of HIF-1 on IH- induced hepatic fibrosis in mice with experimental NAFLD, and the effect of antisense oligonucleotides targeting HIF-1? in reversing liver fibrosis; and 3) Determine the role of HIF-1 and IH in mediating liver fibrosis in other hepatic cell types. Tools available to us include cell type-specific HIF-1? knockout, which will help localize HIF-1 effects. Major methods for this proposal include co-modeling OSA and NAFLD in rodents, antisense knockdown of hepatic HIF-1?, RNA interference, and whole genome shotgun sequencing (RNA- Seq). Successful implementation of these Specific Aims will provide a rigorous training program for Dr. Mesarwi, laying the groundwork for R01 submission, and will allow us to answer a fundamentally important question about the role of hypoxia and HIF-1 in patients with OSA and NAFLD, and possibly to credential HIF-1 and/or its downstream mediators as therapeutic targets in preventing metabolic derangement in OSA.
Obstructive sleep apnea (OSA) is a common disorder characterized by recurrent upper airway narrowing during sleep, resulting in intermittent hypoxia. The hypoxia of OSA may lead to the development of nonalcoholic fatty liver disease (NAFLD), a disorder which can cause cirrhosis, liver cancer, and early death. We aim to define whether a protein called HIF-1 may play a role in the link between OSA and NAFLD, so that therapeutic advances can be made to target this pathway.
