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Joo Y. Lee

Bio: Joo Y. Lee is an academic researcher from Gwangju Institute of Science and Technology. The author has contributed to research in topics: Signal transduction & TLR4. The author has an hindex of 27, co-authored 40 publications receiving 5033 citations. Previous affiliations of Joo Y. Lee include University of California, Davis & Catholic University of Korea.

Papers
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Journal ArticleDOI
TL;DR: A novel mechanism by which fatty acids modulate signaling pathways and target gene expression is represented by both SFA-induced COX-2 expression and its inhibition by UFAs are mediated through a common signaling pathway derived from Tlr4.

1,189 citations

Journal ArticleDOI
TL;DR: Results demonstrate that inhibition of COX-2 expression by n-3 PUFAs is mediated through the modulation of TLR-mediated signaling pathways, and the beneficial or detrimental effects of different types of dietary fatty acids on the risk of the development of many chronic inflammatory diseases may be in part mediated throughThe modulation ofTLRs.

531 citations

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TL;DR: It is demonstrated that lauric acid activates TLR2 dimers as well as TLR4 for which respective bacterial agonists require acylated fatty acids, whereas DHA inhibits the activation of all TLRs tested.

493 citations

Journal ArticleDOI
TL;DR: The results suggest that saturated and polyunsaturated fatty acids reciprocally modulate the activation of TLR4 and its downstream signaling pathways involving MyD88/IRAK/TRAF6 and PI3K/AKT and further suggest the possibility thatTLR4-mediated target gene expression and cellular responses are also differentially modulated by saturated and uns saturated fatty acids.

492 citations

Journal ArticleDOI
TL;DR: The results presented in this study demonstrate that the saturated fatty acid, lauric acid, up-regulates the expression of costimulatory molecules, MHC class II, and cytokines in bone marrow-derived DCs, implying that TLRs are involved in sterile inflammation and immune responses induced by nonmicrobial endogenous molecules.
Abstract: TLRs provide critical signals to induce innate immune responses in APCs such as dendritic cells (DCs) that in turn link to adaptive immune responses. Results from our previous studies demonstrated that saturated fatty acids activate TLRs, whereas n-3 polyunsaturated fatty acids inhibit agonist-induced TLR activation. These results raise a significant question as to whether fatty acids differentially modulate immune responses mediated through TLR activation. The results presented in this study demonstrate that the saturated fatty acid, lauric acid, up-regulates the expression of costimulatory molecules (CD40, CD80, and CD86), MHC class II, and cytokines (IL-12p70 and IL-6) in bone marrow-derived DCs. The dominant negative mutant of TLR4 or its downstream signaling components inhibits lauric acid-induced expression of a CD86 promoter-reporter gene. In contrast, an n-3 polyunsaturated fatty acid, docosahexaenoic acid, inhibits TLR4 agonist (LPS)-induced up-regulation of the costimulatory molecules, MHC class II, and cytokine production. Similarly, DCs treated with lauric acid show increased T cell activation capacity, whereas docosahexaenoic acid inhibits T cell activation induced by LPS-treated DCs. Together, our results demonstrate that the reciprocal modulation of both innate and adaptive immune responses by saturated fatty acid and n-3 polyunsaturated fatty acid is mediated at least in part through TLRs. These results imply that TLRs are involved in sterile inflammation and immune responses induced by nonmicrobial endogenous molecules. These results shed new light in understanding how types of dietary fatty acids differentially modulate immune responses that could alter the risk of many chronic diseases.

295 citations


Cited by
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Journal ArticleDOI
TL;DR: The pathophysiology seems to be largely attributable to insulin resistance with excessive flux of fatty acids implicated, and a proinflammatory state probably contributes to the metabolic syndrome.

5,810 citations

Journal ArticleDOI
TL;DR: The evolving concept of insulin resistance and T2D as having immunological components and an improving picture of how inflammation modulates metabolism provide new opportunities for using antiinflammatory strategies to correct the metabolic consequences of excess adiposity.
Abstract: Over a hundred years ago, high doses of salicylates were shown to lower glucose levels in diabetic patients. This should have been an important clue to link inflammation to the pathogenesis of type 2 diabetes (T2D), but the antihyperglycemic and antiinflammatory effects of salicylates were not connected to the pathogenesis of insulin resistance until recently. Together with the discovery of an important role for tissue macrophages, these new findings are helping to reshape thinking about how obesity increases the risk for developing T2D and the metabolic syndrome. The evolving concept of insulin resistance and T2D as having immunological components and an improving picture of how inflammation modulates metabolism provide new opportunities for using antiinflammatory strategies to correct the metabolic consequences of excess adiposity.

4,046 citations

Journal ArticleDOI
TL;DR: Diet-induced obesity leads to a shift in the activation state of ATMs from an M2-polarized state in lean animals that may protect adipocytes from inflammation to an M1 proinflammatory state that contributes to insulin resistance.
Abstract: Adipose tissue macrophages (ATMs) infiltrate adipose tissue during obesity and contribute to insulin resistance. We hypothesized that macrophages migrating to adipose tissue upon high-fat feeding may differ from those that reside there under normal diet conditions. To this end, we found a novel F4/80(+)CD11c(+) population of ATMs in adipose tissue of obese mice that was not seen in lean mice. ATMs from lean mice expressed many genes characteristic of M2 or "alternatively activated" macrophages, including Ym1, arginase 1, and Il10. Diet-induced obesity decreased expression of these genes in ATMs while increasing expression of genes such as those encoding TNF-alpha and iNOS that are characteristic of M1 or "classically activated" macrophages. Interestingly, ATMs from obese C-C motif chemokine receptor 2-KO (Ccr2-KO) mice express M2 markers at levels similar to those from lean mice. The antiinflammatory cytokine IL-10, which was overexpressed in ATMs from lean mice, protected adipocytes from TNF-alpha-induced insulin resistance. Thus, diet-induced obesity leads to a shift in the activation state of ATMs from an M2-polarized state in lean animals that may protect adipocytes from inflammation to an M1 proinflammatory state that contributes to insulin resistance.

4,046 citations

Journal ArticleDOI
TL;DR: It is suggested that TLR4 is a molecular link among nutrition, lipids, and inflammation and that the innate immune system participates in the regulation of energy balance and insulin resistance in response to changes in the nutritional environment.
Abstract: TLR4 is the receptor for LPS and plays a critical role in innate immunity. Stimulation of TLR4 activates proinflammatory pathways and induces cytokine expression in a variety of cell types. Inflammatory pathways are activated in tissues of obese animals and humans and play an important role in obesity-associated insulin resistance. Here we show that nutritional fatty acids, whose circulating levels are often increased in obesity, activate TLR4 signaling in adipocytes and macrophages and that the capacity of fatty acids to induce inflammatory signaling in adipose cells or tissue and macrophages is blunted in the absence of TLR4. Moreover, mice lacking TLR4 are substantially protected from the ability of systemic lipid infusion to (a) suppress insulin signaling in muscle and (b) reduce insulin-mediated changes in systemic glucose metabolism. Finally, female C57BL/6 mice lacking TLR4 have increased obesity but are partially protected against high fat diet-induced insulin resistance, possibly due to reduced inflammatory gene expression in liver and fat. Taken together, these data suggest that TLR4 is a molecular link among nutrition, lipids, and inflammation and that the innate immune system participates in the regulation of energy balance and insulin resistance in response to changes in the nutritional environment.

3,301 citations

Journal ArticleDOI
TL;DR: Preliminary results from clinical trials with salicylates and interleukin-1 antagonists support the notion that inflammation participates in the pathogenesis of type 2 diabetes and have opened the door for immunomodulatory strategies for the treatment of T2D that simultaneously lower blood glucose levels and potentially reduce the severity and prevalence of the associated complications of this disease.
Abstract: Components of the immune system are altered in obesity and type 2 diabetes (T2D), with the most apparent changes occurring in adipose tissue, the liver, pancreatic islets, the vasculature and circulating leukocytes. These immunological changes include altered levels of specific cytokines and chemokines, changes in the number and activation state of various leukocyte populations and increased apoptosis and tissue fibrosis. Together, these changes suggest that inflammation participates in the pathogenesis of T2D. Preliminary results from clinical trials with salicylates and interleukin-1 antagonists support this notion and have opened the door for immunomodulatory strategies for the treatment of T2D that simultaneously lower blood glucose levels and potentially reduce the severity and prevalence of the associated complications of this disease.

2,845 citations