Alcoholic fatty liver disease (ALD) is one of the primary causes of chronic liver diseases in the United States. In particular, ALD is becoming a prevalent health issue among veterans due to an increase in obesity, diabetes, post-traumatic stress disorder (PTSD), and drug abuse in conjunction with alcohol consumption. Disturbance of circadian rhythmicity is a risk factor for the development of liver and metabolic diseases. However, the association between the liver circadian clock and ALD remains an intriguing but unexplored research area. In addition, the most advanced analytical tools, such as transcriptomics (RNA- seq) and metabolomics (GC/MS), have not been well utilized to study ALD. Nuclear receptors are key liaisons between the molecular clock machinery and metabolic diseases. My laboratory has pioneered major discoveries in the in vivo function of small heterodimer partner (SHP, Nrob2) in hepatic bile acid and lipid metabolism. The proposed study is based on our newly discovered role of SHP in integrating the circadian clock, metabolic network, and the ER stress signaling in the liver. The overall objective is to establish an integrated molecular circadian network in alcohol mediated ER stress response and steatosis. The central hypothesis is that ethanol-binge alters rhythmic SHP expression in the liver, which in turn modulates Npas2 and the downstream targets in the ER stress signaling and lipogenesis pathways. Specifically, we will elucidate how alcohol, SHP and Npas2 coordinately control CHOP and SREBP1c gene transcription, protein stability, and activity, and establish the modulation by alcohol of the entie liver transcriptome and metabolome.
Aim #1 : To elucidate a SHP and alcohol mediated molecular circadian pathway that controls ER stress signaling;
Aim #2 : To determine the effect of liver specific Npas2 knockdown on the ER stress response and steatosis mediated by SHP and ethanol-binge;
and Aim #3 : To establish hepatic circadian transcriptome and metabolome networks interlocked by SHP and ethanol-binge. In addition to our unique in vivo mouse (SHP-/-) and in vitro cell models, new liver Npas2 knockdown mice will be generated and employed for the study. Our approach makes full use of molecular biology, systems biology, and genome wide high throughput analysis (RNA-seq and GC/MS) to address an important scientific question that is directly relevant to the health of veterans. This study is innovative both conceptually and in the implementation of experimental approaches. The planned experimental strategies are comprehensive, yet feasible. This project will uncover for the first time a novel interplay between alcohol and the liver circadian clock to control the ER stress response and hepatic lipid metabolism. The discoveries made from this study are highly likely to enable substantial advances in ALD research, making this project of high clinical significance and translational value.
Both non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (ALD) are major causes of chronic liver diseases in the United States. In particular, ALD is becoming a major health issue among veterans that is associated with the prevalence of obesity, diabetes and behavioral risk factors such as smoking and drug abuse. Growing evidence suggests that disturbance of circadian rhythmicity is a risk factor for the development of liver and metabolic diseases. This study will uncover for the first time the interplays among ethanol consumption, rhythmic expression of genes, oscillation of metabolites, and ER stress signaling mediated by nuclear receptor SHP.
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