Discipline: Biological Sciences
Ryan Shaw - University of the Virgin Islands
Co-Author(s): Sayeepriyadarshini Anakk, University of Illinois at Urbana-Champaign, Urbana, Illinois
Bile acids are amphipathic molecules that are components of bile that facilitate absorption, and the transport of biological molecules in mammals and vertebrates. The delicate balance of bile acids is regulated by genes present in the liver and intestines and is kept in check by proteins called nuclear receptors. Alterations in these genes can cause disturbance in bile acid homeostasis and accumulation of bile acids in the liver leading to the development of cholestasis. The nuclear receptor of interest in this study is SHP (Small Heterodimer Partner), which is a transcriptional repressor expressed in the liver. SHP is known to inhibit the genes responsible for bile acid synthesis such as CYP7A1 and CYP8B1. Apart from synthesis, SHP can also modulate bile acid transport and excretion showing its involvement in maintaining bile acid homeostasis. By specifically deleting SHP in the hepatocyte, we were able to identify the crucial role of SHP in maintaining bile acid homeostasis in the liver cells. Wild type mice and SHPKO mice were fed either a normal chow diet or a 1% cholic acid(CA)to see how bile acid homeostasis was altered when excessive amounts of bile acids were present in the liver of SHPKO mice. cDNA of mice livers was used in order to quantify the expression of bile acid synthesis, transport and excretion genes in the liver. The liver samples were also sectioned and stained for protein Ki-67 in order to evaluate the effect of SHP on proliferation of the liver cells. The goal of this project was to evaluate the role of SHP in regulating the accumulation of bile acids in the liver as well as SHP’s ability to regulate the relative expression of bile acid synthesis, transport and excretion genes in the liver, and lastly evaluate SHP’s effect on proliferation in the liver. We hypothesized that the liver specific knock-out of nuclear receptor SHP would result in the upregulation of bile acid synthesis genes and increase in the overall quantity of bile acid present in the liver. The bile acid negative feedback loop regulated by nuclear receptors FXR and SHP is absent in SHPKO mice as bile acid synthesis gene expression is still significantly high when there is an excess of bile acids in the system. Bile acid transport genes NTCP and BSEP exhibit an increasing trend of expression and bile acid excretion gene SULT2A1 expression is also significantly increased in SHPKO mice on a 1%CA diet. Nuclear receptors FXR and LXR levels are not altered in any of the tested mice groups. Cellular proliferation was significantly increased in SHPKO mice on the 1%CA diet indicating the loss of SHP and a state of increased bile acids triggers increased cellular proliferation. Data depicting the quantity of bile acids in the livers of SHPKO mice is still under analysis. Overall our data suggests that the loss of SHP promote secretion and sulphation of BAs and thus may be beneficial in preventing cholestasis.
Funder Acknowledgement(s): HBCU-RISE Grant No. 5R25GM061325
Faculty Advisor: Sayeepriyadarshini Anakk, email@example.com
Role: For this project, I performed the RNA extraction and cDNA synthesis from mice livers. I also embedded and sectioned the mice livers that were provided for me along with the staining of each sample. I used the cDNA that I prepared from the mice livers to perform qPCRs and statistically analyse the gene expression in each of the samples. The last portion of the project that I performed was the colorimetric bile acid assay.