Obesity is a rapidly growing public health problem. However, the underlying mechanisms that lead to excess body fat and that link obesity to its associated pathologies remain poorly understood. Recent work has revealed a role for inflammation in the pathogenesis of chronic metabolic diseases including obesity, type 2 diabetes and cardiovascular disease. In this regard, there is a significant interest in the role that macrophages play in these inflammatory processes. It is known that increased adiposity promotes macrophage infiltration into adipose tissue, maintaining local inflammation and causing insulin resistance. Recent results suggest that macrophages undergo a polarization switch from pro-inflammatory (M1 phenotype) to anti-inflammatory (M2 phenotype) in response to adipocyte-secreted cytokines such as IL-4 and IL-13 and the balance between M1 and M2 determines the final inflammatory outcome and its impact on insulin resistance. However, key questions concerning the different signaling pathways responsible for these inflammatory networks and their relative importance in vivo remain unanswered. Therefore, investigation of the inflammatory pathways activated during obesity could be a promising approach to identifying novel therapeutic targets for diabetes. This grant application focuses on the p62/PKC6 signaling complex, which is formed by the scaffold protein p62 and its PB1-interacting kinase PKC6, and their potential role in obesity-induced inflammation and insulin resistance. It is based on previous results demonstrating that the genetic inactivation of p62 leads to late-onset obesity and insulin resistance, and to an associated systemic hyperinflammatory state. Moreover, the preliminary data show that PKC6-/- mice also develop late-onset obesity suggesting a critical role of the p62/PKC6 complex in the control of adiposity and obesity. Importantly, high-fat diet-fed PKC6-/- mice displayed higher insulin resistance, increased macrophage infiltration in adipose tissue, and an enhanced M1 inflammatory response as compared to equally fed WT mice, despite equal body fat content. These observations led to the hypothesis that PKC6 is a regulator of the macrophage M2 polarization switch. The overall objective of this proposal is to rigorously test the hypothesis that the p62/PKC6 complex is a critical negative regulator of inflammation during obesity and to determine its mechanism of action at the organismal and cellular levels. Therefore, this project is designed to 1) determine the role of p62 and PKC6 in M2 polarization of macrophages, and 2) to determine the in vivo role of PKC6 and p62 in macrophages in obesity and obesity-associated inflammation. This work will increase understanding of the mechanisms involved in the regulation of obesity-induce inflammation and insulin resistance, and, in the long term, will lay the groundwork for the development of novel, more specific therapies for insulin resistance and type 2 diabetes.

Public Health Relevance

Chronic inflammation is causally linked to obesity, insulin resistance and type 2 diabetes. Increased adiposity promotes macrophage infiltration into adipose tissue creating a vicious cycle that perpetuates inflammation and causes insulin resistance. This project will determine how a cell signaling complex assembled by p62/Sqstm1 and PKC6 regulates obesity-associated inflammation and insulin resistance in vivo, laying the groundwork for the development of novel, more specific therapies for obesity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK088107-04
Application #
8258350
Study Section
Integrative Physiology of Obesity and Diabetes Study Section (IPOD)
Program Officer
Abraham, Kristin M
Project Start
2010-04-01
Project End
2014-03-31
Budget Start
2012-04-01
Budget End
2014-03-31
Support Year
4
Fiscal Year
2012
Total Cost
$392,233
Indirect Cost
$176,908
Name
Sanford-Burnham Medical Research Institute
Department
Type
DUNS #
020520466
City
La Jolla
State
CA
Country
United States
Zip Code
92037
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Kim, Ji Young; Valencia, Tania; Abu-Baker, Shadi et al. (2013) c-Myc phosphorylation by PKCýý represses prostate tumorigenesis. Proc Natl Acad Sci U S A 110:6418-23
Linares, Juan F; Duran, Angeles; Yajima, Tomoko et al. (2013) K63 polyubiquitination and activation of mTOR by the p62-TRAF6 complex in nutrient-activated cells. Mol Cell 51:283-96
Ma, Li; Tao, Yongzhen; Duran, Angeles et al. (2013) Control of nutrient stress-induced metabolic reprogramming by PKC? in tumorigenesis. Cell 152:599-611
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Diaz-Meco, Maria T; Moscat, Jorge (2012) The atypical PKCs in inflammation: NF-*B and beyond. Immunol Rev 246:154-67
Moscat, Jorge; Diaz-Meco, Maria T (2011) Feedback on fat: p62-mTORC1-autophagy connections. Cell 147:724-7
Linares, Juan F; Amanchy, Ramars; Greis, Kenneth et al. (2011) Phosphorylation of p62 by cdk1 controls the timely transit of cells through mitosis and tumor cell proliferation. Mol Cell Biol 31:105-17
Sengupta, Amitava; Duran, Angeles; Ishikawa, Eri et al. (2011) Atypical protein kinase C (aPKCzeta and aPKClambda) is dispensable for mammalian hematopoietic stem cell activity and blood formation. Proc Natl Acad Sci U S A 108:9957-62
Moscat, Jorge; Diaz-Meco, Maria T (2011) Fine tuning NF-ýýB: new openings for PKC-ýý. Nat Immunol 12:12-4

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