Niemann-Pick C1-Like 1, NPC1L1, is crucial for cholesterol absorption and is the molecular target for ezetimibe, the cholesterol lowering drug. Previous studies showed that NPC1L1 expression is increased in patients with diabetes mellitus contributing to associated hypercholesterolemia. Blocking choelsterol absoprtion with ezetimibe in combination with statins (inhibitors of cholesterol synthesis) has been shown to be more effective than treatment with statins alone in lowering serum cholesterol. Current guidelines recommend aggressive lowering of blood cholesterol in patients with high risk for developing cardiovascular diseases (CVD), such as diabetic patients. Achieving these stringent low targets remains challenging. Since ezetimibe only blocks NPC1L1 activity, decreasing NPC1L1 expression represents an attractive therapeutic approach for further reduction in plasma cholesterol. Therefore, it is critical to delineate cellular pathways involved in decreasing NPC1L1 expression that could be exploited to efficiently reduce the risk for CVD. We have previously shown that NPC1L1 expression is regulated by an epigenetic mechanism involving DNA methylation. However, the role of epigenetic histone modifications in modulating NPC1L1 expression is not known. Our preliminary data showed that the HDAC inhibitors (HDACi) butyrate and valproic acid (VPA) significantly decreased NPC1L1 expression in intestinal Caco2 cells and mouse intestine. Also, siRNA-mediated attenuation of HDAC2 and 3, but not the other isoforms, reduced NPC1L1 expression; however, the underlying molecular mechanisms remain unclear. We hypothesize that specific histone deacetylase isoforms modulate NPC1L1 expression via modifying chromatin structure and/or altering the binding of specific transcription factors to the NPC1L1 gene. We also hypothesize that HDAC inhibitors such as VPA decrease cholesterol absorption and reduce plasma cholesterol in mouse models of hypercholesterolemia. VPA is a widely used drug for the treatment of epilepsy and bipolar disorders. Therefore, it will be important to directly study its effects on cholesterol absorption in humans. However, the current standard method to directly measure cholesterol absorption has limitations in humans as it relies on the use of isotope-labeled cholesterol and laborious laboratory techniques. We are currently inveatigating a novel simple assay that is non-radioactive to evaluate cholesterol transport. Our preliminary data indicate that this method is suitable for assessing NPC1L1 function. We hypothesize that our putative simple non-radioactive approach to measure NPC1L1 function represents a novel method to directly measure cholesterol absorption in living animals. The studies are designed to rigorously examine the hypotheses and address two main objectives.
In Specific Aim 1, our studies are aimed to investigate the effects of attenuating HDAC isoforms on NPC1L1 function, to examine chromatin remodeling of NPC1L1 gene and alterations in binding of transcription factors in intestinal cell lines and enteroids, and to investigate the effects of HDACi on cholesterol absorption in the LDL receptor knockout mice as a model of hypercholesterolemia. Studies proposed in Specific Aim 2 are designed to establish the accuracy of the putative method in measuring cholesterol absorption utilizing NPC1L1 knockout mice and wild type littermates. The studies will also investigate the decrease in cholesterol absorption by HDACi using the new method in mice, providing the basis for future translational studies in humans. Notably, the risk for CVD is significantly higher in the veterans as compared to the general population. Thus, unraveling novel mechanisms involving histone deacetylation to downregulate NPC1L1 expression and establishing novel, state-of-the-art method to measure the associated decrease in cholesterol absorption are timely and directly relevant to improving the health of the veterans.

Public Health Relevance

Diseases associated with hypercholesterolemia such as diabetes mellitus are highly prevalent among the veterans. Hypercholesterolemia is a major risk factor for cardiovascular diseases (CVD) such as coronary heart disease and stroke. Current available therapeutic options are not sufficient in many cases to reduce blood cholesterol and meet the low therapeutic target in patients with high risk for CVD. Therefore, there is a dire need to develop novel and effective approaches to lower blood cholesterol. The proposed studies are focused at investigating mechanisms that could effectively decrease intestinal cholesterol absorption and aid in the development of superior treatment for hypercholesterolemia. The proposed studies are, therefore, relevant to the VA patients as well as the general patient population.

National Institute of Health (NIH)
Veterans Affairs (VA)
Non-HHS Research Projects (I01)
Project #
Application #
Study Section
Gastroenterology (GAST)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Jesse Brown VA Medical Center
United States
Zip Code
Kumar, Anoop; Chatterjee, Ishita; Anbazhagan, Arivarasu N et al. (2018) Cryptosporidium parvum disrupts intestinal epithelial barrier function via altering expression of key tight junction and adherens junction proteins. Cell Microbiol 20:e12830
Kumar, Anoop; Chatterjee, Ishita; Gujral, Tarunmeet et al. (2017) Activation of Nuclear Factor-?B by Tumor Necrosis Factor in Intestinal Epithelial Cells and Mouse Intestinal Epithelia Reduces Expression of the Chloride Transporter SLC26A3. Gastroenterology 153:1338-1350.e3
Muthusamy, Saminathan; Malhotra, Pooja; Hosameddin, Mobashir et al. (2015) N-glycosylation is essential for ileal ASBT function and protection against proteases. Am J Physiol Cell Physiol 308:C964-71
Priyamvada, Shubha; Anbazhagan, Arivarasu N; Gujral, Tarunmeet et al. (2015) All-trans-retinoic Acid Increases SLC26A3 DRA (Down-regulated in Adenoma) Expression in Intestinal Epithelial Cells via HNF-1?. J Biol Chem 290:15066-77
Priyamvada, Shubha; Gomes, Rochelle; Gill, Ravinder K et al. (2015) Mechanisms Underlying Dysregulation of Electrolyte Absorption in Inflammatory Bowel Disease-Associated Diarrhea. Inflamm Bowel Dis 21:2926-35
Nazir, Saad; Kumar, Anoop; Chatterjee, Ishita et al. (2015) Mechanisms of Intestinal Serotonin Transporter (SERT) Upregulation by TGF-?1 Induced Non-Smad Pathways. PLoS One 10:e0120447
Kumar, Anoop; Hecht, Cameron; Priyamvada, Shubha et al. (2014) Probiotic Bifidobacterium species stimulate human SLC26A3 gene function and expression in intestinal epithelial cells. Am J Physiol Cell Physiol 307:C1084-92
Ma, Ke; Malhotra, Pooja; Soni, Vinay et al. (2014) Overactivation of intestinal SREBP2 in mice increases serum cholesterol. PLoS One 9:e84221
Anbazhagan, Arivarasu N; Priyamvada, Shubha; Kumar, Anoop et al. (2014) Translational repression of SLC26A3 by miR-494 in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 306:G123-31
Domingue, Jada C; Ao, Mei; Sarathy, Jayashree et al. (2014) HEK-293 cells expressing the cystic fibrosis transmembrane conductance regulator (CFTR): a model for studying regulation of Cl- transport. Physiol Rep 2:

Showing the most recent 10 out of 16 publications