Nonalcoholic fatty liver disease (NAFLD) is a common liver disease that affects one-third of the world's population. The first stage of NAFLD is hepatic steatosis, which is characterized by accumulation of fat droplets in the cytoplasm of hepatocytes. Hepatic steatosis further develops into nonalcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). Age and diet/fat intake are risk factors for NAFLD. My laboratory investigates age-associated pathways of NAFLD. We found that two members of the C/EBP family, C/EBP? and C/EBP, as well as the chromatin remodeling protein p300 play a critical role in NAFLD associated with aging. Our findings show that cyclin-dependent kinase 4 (cdk4) phosphorylates C/EBP? at Ser193, triggering formation of the tripartite C/EBP?/-p300 complex. Using four animal models with increased or reduced levels of C/EBP?/-p300 complexes, we found that the C/EBP?/-p300 complex activates expression of five key triglyceride (TG) synthesis enzymes. Triglycerides are the main components of the fat droplets that are accumulated in the hepatocytes of NAFLD patients. This led to our main hypothesis that the development of NAFLD is mediated by up-regulation of the cdk4-C/EBP?-p300- TG pathway and that cdk4 inhibitor-mediated reduction in phosphorylation of C/EBP? at Ser193 will inhibit development of NAFLD. We propose to test this hypothesis using animal models of NAFLD and liver biopsies from patients with NAFLD.
Specific Aim 1 will examine if knock-in mice carrying C/EBP?- S193A, a C/EBP? construct that cannot be phosphorylated by cdk4, are resistant to development of NAFLD. We recently generated these C/EBP?-S193A mice. We will examine if the development of NAFLD that we normally observe with age and under long-term high fat diet conditions will be reduced in C/EBP?-S193A mice.
Specific Aim 2 will test if the inhibition of cdk4 activity by small molecule drugs will inhibit NAFLD. Wild-type mice will be maintained on either high-fat or low-fat diets and treated with inhibitors of cdk4, such as PD0332991. Activity of the cdk4-C/EBP?-p300-TG pathway and development of NAFLD will be compared between un-treated and treated mice.
Specific Aim 3 will determine if the cdk4-C/EBP?-p300-TG synthesis pathway is elevated in patients with NAFLD. Our recent data showed that levels of S193-phosphorylated C/EBP? are increased in mouse models of NAFLD and in NAFLD patients. We will therefore: 1) determine if the expression of cdk4 and its activating partner cyclin D3 are elevated in the livers of patients with NAFLD, 2) determine if levels of C/EBP?-p300 complexes are elevated in NAFLD patient liver samples, and 3) examine if TG synthesis enzyme levels are increased in patients with NAFLD. These proposed studies will provide a basis for the development of a novel cdk4-based therapy for NAFLD. Because the cdk4/6 inhibitor PD033991 is already used in the clinical trials for other diseases, the proposed studies might be quickly translated to treatment of human patients with NAFLD.

Public Health Relevance

Nonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem that affects one-third of adults. In this project, we will determine mechanisms of development of different stages of NAFLD including steatosis, fibrosis, cirrhosis and HCC in patients and in animal models. The ultimate goals are to develop approaches to improve liver functions and healthy life in elderly.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK102597-02
Application #
8990962
Study Section
Cellular Mechanisms in Aging and Development Study Section (CMAD)
Program Officer
Doo, Edward
Project Start
2015-01-01
Project End
2018-12-31
Budget Start
2016-01-01
Budget End
2016-12-31
Support Year
2
Fiscal Year
2016
Total Cost
$315,900
Indirect Cost
$113,400
Name
Cincinnati Children's Hospital Medical Center
Department
Type
DUNS #
071284913
City
Cincinnati
State
OH
Country
United States
Zip Code
45229
Valanejad, Leila; Cast, Ashley; Wright, Mary et al. (2018) PARP1 activation increases expression of modified tumor suppressors and pathways underlying development of aggressive hepatoblastoma. Commun Biol 1:67
Wei, Christina; Stock, Lauren; Schneider-Gold, Christiane et al. (2018) Reduction of Cellular Nucleic Acid Binding Protein Encoded by a Myotonic Dystrophy Type 2 Gene Causes Muscle Atrophy. Mol Cell Biol 38:
D'Souza, Amber M; Jiang, Yanjun; Cast, Ashley et al. (2018) Gankyrin Promotes Tumor-Suppressor Protein Degradation to Drive Hepatocyte Proliferation. Cell Mol Gastroenterol Hepatol 6:239-255
Wei, Christina; Stock, Lauren; Valanejad, Leila et al. (2018) Correction of GSK3? at young age prevents muscle pathology in mice with myotonic dystrophy type 1. FASEB J 32:2073-2085
Timchenko, Nikolai A (2018) Mitochondrial and anabolic pathways in hepatocellular carcinoma. Hepatology 67:823-825
Cast, Ashley; Valanejad, Leila; Wright, Mary et al. (2018) C/EBP?-dependent preneoplastic tumor foci are the origin of hepatocellular carcinoma and aggressive pediatric liver cancer. Hepatology 67:1857-1871
Valanejad, Leila; Lewis, Kyle; Wright, Mary et al. (2017) FXR-Gankyrin axis is involved in development of pediatric liver cancer. Carcinogenesis 38:738-747
Lewis, Kyle; Valanejad, Leila; Cast, Ashley et al. (2017) RNA Binding Protein CUGBP1 Inhibits Liver Cancer in a Phosphorylation-Dependent Manner. Mol Cell Biol 37:
Jin, Jingling; Valanejad, Leila; Nguyen, Thuy Phuong et al. (2016) Activation of CDK4 Triggers Development of Non-alcoholic Fatty Liver Disease. Cell Rep 16:744-56
Jones, Karlie; Wei, Christina; Schoser, Benedikt et al. (2015) Reduction of toxic RNAs in myotonic dystrophies type 1 and type 2 by the RNA helicase p68/DDX5. Proc Natl Acad Sci U S A 112:8041-5

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