Altered regulation of lipid and glucose homeostasis, most often in the setting of insulin resistance and obesity, is central to the pathogenesis of common disorders including non-alcoholic fatty liver disease (NAFLD). Because current management options remain limited, the discovery of new metabolic pathways will serve to identify novel opportunities for pharmacologic intervention. This research proposal addresses the unanswered question of whether membrane phospholipids regulate nutrient homeostasis. Our long-term goal is to understand how phospholipid-mediated metabolic control can be leveraged for therapeutic purposes. The objective of this research is to determine the molecular mechanisms whereby sensing of membrane phosphatidylcholine composition by phosphatidylcholine transfer protein (PC-TP) is translated into metabolic control within the liver and oxidative tissues. The central hypothesis is that key regulatory events occur when PC-TP binds specific membrane phosphatidylcholines and then activates thioesterase superfamily member 2 (Them2). The rationale is that the mechanisms of a phosphatidylcholine-sensing pathway should yield new insights into insulin resistance and its complications, including NAFLD. Guided by extensive preliminary data, the central hypothesis will be tested in three specific aims: 1) Demonstrate that Them2 plays a central role in PC-TP-mediated regulation of hepatic lipid and glucose metabolism;2) Determine the mechanisms by which PC-TP and Them2 limit thermogenesis in brown fat;and 3) Define the influence of phosphatidylcholine molecular species on binding and activation of Them2 by PC-TP.
In Aim 1, hyperinsulinemic euglycemic clamp, as well as triglyceride turnover studies in newly created Them2-/- mice will test functions of Them2 downstream of PC-TP. Additional mechanistic insights will be gleaned from experiments in cultured primary mouse hepatocytes, as wel as HEK 293T cells in which expression of endogenous Them2 and PC-TP are silenced using siRNAs.
Aim 2 will utilize indirect calorimetry, as well as cultured primary brown adipocytes in order to assess whether PC-TP-Them2 interactions limit mitochondrial fatty acid oxidation. Cultured brown adipocytes wil also be used to evaluate whether PC-TP-Them2 interactions reduce norepinephrine signaling by increasing oxidative stress.
In Aim 3, control of PC-TP- Them2 interactions by individual phosphatidylcholine molecular species will be quantified by pulldown assays, surface plasmon resonance and the fatty acyl-CoA thioesterase activity of Them2. The interacting domains of PC-TP and Them2 will be identified by mutational analysis employing a mammalian two-hybrid assay system. Overall, this proposal will elucidate mechanisms of phosphatidylcholine-mediated regulation of lipid and glucose metabolism, which is significant because the fatty acyl composition of the membrane phosphatidylcholines varies in health and disease. These studies are expected to identify new therapeutic targets for the management of for NAFLD, type 2 diabetes and other obesity-associated disorders.

Public Health Relevance

The proposed research is relevant to public health because the discovery of a phospholipid-dependent pathway that controls lipid and glucose homeostasis is expected to provide new insights into the pathogenesis of insulin resistance and its complications, including non-alcoholic fatty liver disease. The proposed studies are relevant to the mission of the NIDDK because they are expected to identify new therapeutic targets for the management of common disorders related to diabetes and obesity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK056626-14
Application #
8452126
Study Section
Special Emphasis Panel (ZRG1-DKUS-C (04))
Program Officer
Sherker, Averell H
Project Start
1999-12-01
Project End
2015-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
14
Fiscal Year
2013
Total Cost
$462,134
Indirect Cost
$186,288
Name
Brigham and Women's Hospital
Department
Type
DUNS #
030811269
City
Boston
State
MA
Country
United States
Zip Code
02115
Imai, Norihiro; Cohen, David E (2018) Trimming the Fat: Acetyl-CoA Carboxylase Inhibition for the Management of NAFLD. Hepatology 68:2062-2065
Xu, Xu; Krumm, Christopher; So, Jae-Seon et al. (2018) Preemptive Activation of the Integrated Stress Response Protects Mice From Diet-Induced Obesity and Insulin Resistance by Fibroblast Growth Factor 21 Induction. Hepatology 68:2167-2181
Ji, Yan-Xiao; Huang, Zan; Yang, Xia et al. (2018) The deubiquitinating enzyme cylindromatosis mitigates nonalcoholic steatohepatitis. Nat Med 24:213-223
Mina, Amir I; LeClair, Raymond A; LeClair, Katherine B et al. (2018) CalR: A Web-Based Analysis Tool for Indirect Calorimetry Experiments. Cell Metab 28:656-666.e1
Ersoy, Baran A; Maner-Smith, Kristal M; Li, Yingxia et al. (2018) Thioesterase-mediated control of cellular calcium homeostasis enables hepatic ER stress. J Clin Invest 128:141-156
Staffas, Anna; Burgos da Silva, Marina; Slingerland, Ann E et al. (2018) Nutritional Support from the Intestinal Microbiota Improves Hematopoietic Reconstitution after Bone Marrow Transplantation in Mice. Cell Host Microbe 23:447-457.e4
Desai, Anal; Alves-Bezerra, Michele; Li, Yingxia et al. (2018) Regulation of fatty acid trafficking in liver by thioesterase superfamily member 1. J Lipid Res 59:368-379
Alves-Bezerra, Michele; Li, Yingxia; Acuña, Mariana et al. (2018) Thioesterase Superfamily Member 2 Promotes Hepatic VLDL Secretion by Channeling Fatty Acids into Triglyceride Biosynthesis. Hepatology :
Alves-Bezerra, Michele; Cohen, David E (2017) Triglyceride Metabolism in the Liver. Compr Physiol 8:1-8
Palmer, Colin J; Bruckner, Raphael J; Paulo, Joao A et al. (2017) Cdkal1, a type 2 diabetes susceptibility gene, regulates mitochondrial function in adipose tissue. Mol Metab 6:1212-1225

Showing the most recent 10 out of 75 publications