Evidence suggests an important link between immune cell activation and insulin resistance (IR) in states associated with increases in visceral adipose tissue (AT). The interleukin-12 (IL-12) family of cytokines is particularly relevant given their importance in cell-mediated immune responses and downstream inflammatory gene induction. IL-12 has been shown to be directly involved in the progression of atherosclerosis. Signal transducer and activator of transcription 4 (STAT4), which is activated by IL-12, induces the expression of several major genes linked to inflammation in atherosclerosis and the metabolic syndrome. The central hypothesis is that IL-12/Stat-4 pathway plays a critical role in the induction of IR in visceral and peri-aortic adipose tissue and this will affect the immune response in aortas and further accelerate atherosclerosis.
Aims to address this include:
Aim 1. Determine mechanisms related to IL-12/STAT4 deficiency in hematopoetic and non-hematopoetic cells on protection against obesity induced insulin resistance, and adipose tissue inflammation. Our hypothesis is that STAT4 deficiency prevents IR in diet-induced obesity by changes in T cell abundance and phenotype and macrophage polarization in adipose tissue and by reducing inflammation and improving insulin sensitivity in visceral adipocytes.
Aim 1. 1: Determine the in vivo effect of IL-12 or STAT4 deficiency in the hematopoietic (T cells, NK cells) vs. non-hematopoetic compartment (adipocyte) for the development of IR and obesity.
Aim 1. 2: Determine role of IL-12/STAT4 deficiency on in vivo and in vitro T cell migration in adipose tissue, T cell and macrophage phenotype and polarization and production of pro-inflammatory cytokines.
Aim 1. 3: Mechanistically investigate functional roles of IL-12/STAT4 deficiency in adipocytes on glucose uptake and insulin signaling in response to high fat diet and cytokine stimulation.
Aim 2. Determine effects of IL-12/Stat-4 pathway inhibition on AT inflammation-associated atherosclerosis. What is the specific role of peri-aortic and visceral AT in adipose tissue-related atherosclerosis? Aim 2.1: Examine effects of Stat-4 deficiency on atherosclerosis with and without AT inflammation in Stat -4-/- Ldlr-/- mice fed a diabetogenic diet (DD) to induce IR and DD with additional cholesterol (DDC) to induce atherosclerosis and AT inflammation.
Aim 2. 2: Test the effects of AT inflammation, Stat-4 deficiency on leukocyte recruitment into peri-aortic, visceral AT and aortas.
Aim 2. 3: Determine the involvement of AT inflammation, Stat-4 deficiency and the conditions of AT inflammation-related atherogenesis on local immune response in peri-aortic, visceral AT and aortas.
Aim 2. 4: Investigate effects and specificity of IL-12 inhibition on Stat-4+/+ and Stat-4 deficient model of AT- inflammation accelerated atherosclerosis in mice fed DDC diet. The completed project should identify an innovative therapeutic target that could lead to new treatment to reduce atherosclerosis associated with central obesity insulin resistance and diabetes.
Central obesity is a major independent risk factor for development of serious cardiovascular disease and diabetes. However the mechanism why this occurs is not clear. The proposed research will identify a new target that could lead to new medications to halt the rise of heart attack risks due to obesity and diabetes.
|Lieb, David C; Brotman, Joshua J; Hatcher, Margaret A et al. (2014) Adipose tissue 12/15 lipoxygenase pathway in human obesity and diabetes. J Clin Endocrinol Metab 99:E1713-20|
|Butcher, Matthew J; Hallinger, Daniel; Garcia, Eden et al. (2014) Association of proinflammatory cytokines and islet resident leucocytes with islet dysfunction in type 2 diabetes. Diabetologia 57:491-501|
|Taghavie-Moghadam, Parésa L; Butcher, Matthew J; Galkina, Elena V (2014) The dynamic lives of macrophage and dendritic cell subsets in atherosclerosis. Ann N Y Acad Sci 1319:19-37|
|Luci, Diane K; Jameson 2nd, J Brian; Yasgar, Adam et al. (2014) Synthesis and structure-activity relationship studies of 4-((2-hydroxy-3-methoxybenzyl)amino)benzenesulfonamide derivatives as potent and selective inhibitors of 12-lipoxygenase. J Med Chem 57:495-506|
|Tersey, Sarah A; Maier, Bernhard; Nishiki, Yurika et al. (2014) 12-lipoxygenase promotes obesity-induced oxidative stress in pancreatic islets. Mol Cell Biol 34:3735-45|
|Taylor-Fishwick, D A; Weaver, J R; Grzesik, W et al. (2013) Production and function of IL-12 in islets and beta cells. Diabetologia 56:126-35|
|Imai, Yumi; Dobrian, Anca D; Morris, Margaret A et al. (2013) Islet inflammation: a unifying target for diabetes treatment? Trends Endocrinol Metab 24:351-60|
|Dobrian, Anca D; Galkina, Elena V; Ma, Qian et al. (2013) STAT4 deficiency reduces obesity-induced insulin resistance and adipose tissue inflammation. Diabetes 62:4109-21|
|Imai, Y; Dobrian, A D; Weaver, J R et al. (2013) Interaction between cytokines and inflammatory cells in islet dysfunction, insulin resistance and vascular disease. Diabetes Obes Metab 15 Suppl 3:117-29|
|Cole, Banumathi K; Kuhn, Norine S; Green-Mitchell, Shamina M et al. (2012) 12/15-Lipoxygenase signaling in the endoplasmic reticulum stress response. Am J Physiol Endocrinol Metab 302:E654-65|