PPARs are a unique set of fatty acid regulated transcription factors controlling both lipid metabolism and inflammation.
TL;DR: Understanding is summarized on how transcription factors/receptors connect lipid metabolism to inflammation and some of the novel regulatory mechanisms by which they contribute to homeostasis and certain pathological conditions.
About: This article is published in Biochimica et Biophysica Acta.The article was published on 2011-08-01 and is currently open access. It has received 699 citations till now. The article focuses on the topics: Lipid metabolism & Peroxisome proliferator-activated receptor.
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TL;DR: The molecular mechanisms of the antagonistic signaling between NF-κB and SIRT1 are examined and how this crosstalk controls inflammatory process and energy metabolism is described to induce the appearance of chronic inflammation in metabolic diseases.
683 citations
TL;DR: The protective roles ofPPARs in inflammatory conditions and the therapeutic anti-inflammatory potential of PPAR ligands are discussed.
Abstract: Nuclear receptors (NRs) are ligand-dependent transcription factors whose activation affects genes controlling vital processes. Among them, the peroxisome proliferator-activated receptors (PPARs) have emerged as links between lipids, metabolic diseases, and innate immunity. PPARs are activated by fatty acids and their derivatives, many of which also signal through membrane receptors, thereby creating a lipid signaling network between the cell surface and the nucleus. Tissues that play a role in whole-body metabolic homeostasis, such as adipose tissue, liver, skeletal muscle, intestines, and blood vessel walls, are prone to inflammation when metabolism is disturbed, a complication that promotes type 2 diabetes and cardiovascular disease. This review discusses the protective roles of PPARs in inflammatory conditions and the therapeutic anti-inflammatory potential of PPAR ligands.
548 citations
TL;DR: The importance of SCFAs in shaping and promoting bone marrow hematopoietic precursors in the bone marrow to resolve airway inflammation and to support a healthy homeostasis is highlighted.
439 citations
TL;DR: This review will investigate obese AT biology, initiation of the inflammatory, and insulin resistant environment; and the mechanisms through which dietary anti-inflammatory components/functional nutrients may be beneficial.
Abstract: Obesity and associated chronic inflammation initiate a state of insulin resistance (IR). The secretion of chemoattractants such as MCP-1 and MIF and of cytokines IL-6, TNF-α, and IL-1β, draw immune cells including dendritic cells, T cells, and macrophages into adipose tissue (AT). Dysfunctional AT lipid metabolism leads to increased circulating free fatty acids, initiating inflammatory signaling cascades in the population of infiltrating cells. A feedback loop of pro-inflammatory cytokines exacerbates this pathological state, driving further immune cell infiltration and cytokine secretion and disrupts the insulin signaling cascade. Disruption of normal AT function is causative of defects in hepatic and skeletal muscle glucose homeostasis, resulting in systemic IR and ultimately the development of type 2 diabetes. Pharmaceutical strategies that target the inflammatory milieu may have some potential; however there are a number of safety concerns surrounding such pharmaceutical approaches. Nutritional anti-inflammatory interventions could offer a more suitable long-term alternative; whilst they may be less potent than some pharmaceutical anti-inflammatory agents, this may be advantageous for long-term therapy. This review will investigate obese AT biology, initiation of the inflammatory, and insulin resistant environment; and the mechanisms through which dietary anti-inflammatory components/functional nutrients may be beneficial.
420 citations
Cites background from "PPARs are a unique set of fatty aci..."
...Nevertheless it is impossible to adequately address PPAR functionality in obesity within the current review and this topic was reviewed very comprehensively elsewhere (Stienstra et al., 2007; Varga et al., 2011)....
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TL;DR: There is a distinct need for a review of the literature and additional experimentation to determine the potential for targeting PPARs for cancer therapy and cancer chemoprevention.
Abstract: Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that are involved in regulating glucose and lipid homeostasis, inflammation, proliferation and differentiation. Although all of these functions might contribute to the influence of PPARs in carcinogenesis, there is a distinct need for a review of the literature and additional experimentation to determine the potential for targeting PPARs for cancer therapy and cancer chemoprevention. As PPAR agonists include drugs that are used for the treatment of metabolic diseases, a more complete understanding of the roles of PPARs in cancer will aid in determining any increased cancer risk for patients undergoing therapy with PPAR agonists.
381 citations
References
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TL;DR: Dysfunction of the immune response and metabolic regulation interface can be viewed as a central homeostatic mechanism, dysfunction of which can lead to a cluster of chronic metabolic disorders, particularly obesity, type 2 diabetes and cardiovascular disease.
Abstract: Metabolic and immune systems are among the most fundamental requirements for survival. Many metabolic and immune response pathways or nutrient- and pathogen-sensing systems have been evolutionarily conserved throughout species. As a result, immune response and metabolic regulation are highly integrated and the proper function of each is dependent on the other. This interface can be viewed as a central homeostatic mechanism, dysfunction of which can lead to a cluster of chronic metabolic disorders, particularly obesity, type 2 diabetes and cardiovascular disease. Collectively, these diseases constitute the greatest current threat to global human health and welfare.
7,536 citations
"PPARs are a unique set of fatty aci..." refers background in this paper
...The alternative explanation suggests that chronic caloric overload initiates an inflammatory response that is originated in the adipose tissue [15,16]....
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TL;DR: This work has shown that tissue stress or malfunction induces an adaptive response that is intermediate between the basal homeostatic state and a classic inflammatory response, which is referred to here as para-inflammation.
Abstract: Inflammation underlies a wide variety of physiological and pathological processes. Although the pathological aspects of many types of inflammation are well appreciated, their physiological functions are mostly unknown. The classic instigators of inflammation - infection and tissue injury - are at one end of a large range of adverse conditions that induce inflammation, and they trigger the recruitment of leukocytes and plasma proteins to the affected tissue site. Tissue stress or malfunction similarly induces an adaptive response, which is referred to here as para-inflammation. This response relies mainly on tissue-resident macrophages and is intermediate between the basal homeostatic state and a classic inflammatory response. Para-inflammation is probably responsible for the chronic inflammatory conditions that are associated with modern human diseases.
4,832 citations
"PPARs are a unique set of fatty aci..." refers background in this paper
...Typically, chronic inflammatory reactions develop gradually from an acute reaction if the host is not able to eliminate the inflammatory inducer (for a review of inflammation, see [8])....
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TL;DR: It is reported that thiazolidinediones are potent and selective activators of peroxisome proliferator-activated receptor γ (PPARγ), a member of the nuclear receptor superfamily recently shown to function in adipogenesis, and raised the intriguing possibility that PPARγ is a target for the therapeutic actions of this class of compounds.
3,635 citations
TL;DR: It is shown that PPAR-γ is markedly upregulated in activated macrophages and inhibits the expression of the inducible nitric oxide synthase, gelatinase B and scavenger receptor A genes in response to 15d-PGJ2 and synthetic PPar-γ ligands, suggesting that PPARS and locally produced prostaglandin D2 metabolites are involved in the regulation of inflammatory responses.
Abstract: The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors that is predominantly expressed in adipose tissue, adrenal gland and spleen PPAR-gamma has been demonstrated to regulate adipocyte differentiation and glucose homeostasis in response to several structurally distinct compounds, including thiazolidinediones and fibrates Naturally occurring compounds such as fatty acids and the prostaglandin D2 metabolite 15-deoxy-delta prostaglandin J2 (15d-PGJ2) bind to PPAR-gamma and stimulate transcription of target genes Prostaglandin D2 metabolites have not yet been identified in adipose tissue, but are major products of arachidonic-acid metabolism in macrophages, raising the possibility that they might serve as endogenous PPAR-gamma ligands in this cell type Here we show that PPAR-gamma is markedly upregulated in activated macrophages and inhibits the expression of the inducible nitric oxide synthase, gelatinase B and scavenger receptor A genes in response to 15d-PGJ2 and synthetic PPAR-gamma ligands PPAR-gamma inhibits gene expression in part by antagonizing the activities of the transcription factors AP-1, STAT and NF-kappaB These observations suggest that PPAR-gamma and locally produced prostaglandin D2 metabolites are involved in the regulation of inflammatory responses, and raise the possibility that synthetic PPAR-gamma ligands may be of therapeutic value in human diseases such as atherosclerosis and rheumatoid arthritis in which activated macrophages exert pathogenic effects
3,587 citations
"PPARs are a unique set of fatty aci..." refers background in this paper
...This suggested that liganded PPARγ acted via transrepression of other transcription factors [76]....
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TL;DR: A role for the abnormal regulation of this cytokine in the pathogenesis of obesity-related insulin resistance is suggested as well as the effects of weight reduction by dietary treatment of obesity on the adipose expression of TNF-alpha mRNA.
Abstract: Obesity is frequently associated with insulin resistance and abnormal glucose homeostasis. Recent studies in animal models have indicated that TNF-alpha plays an important role in mediating the insulin resistance of obesity through its overexpression in fat tissue. However, the mechanisms linking obesity to insulin resistance and diabetes in humans remain largely unknown. In this study we examined the expression pattern of TNF-alpha mRNA in adipose tissues from 18 control and 19 obese premenopausal women by Northern blot analysis. TNF-alpha protein concentrations in plasma and in conditioned medium of explanted adipose tissue were measured by ELISA. Furthermore, the effects of weight reduction by dietary treatment of obesity on the adipose expression of TNF-alpha mRNA were also analyzed in nine premenopausal obese women, before and after a controlled weight-reduction program. These studies demonstrated that obese individuals express 2.5-fold more TNF-alpha mRNA in fat tissue relative to the lean controls (P < 0.001). Similar increases were also observed in adipose production of TNF-alpha protein but circulating TNF-alpha levels were extremely low or undetectable. A strong positive correlation was observed between TNF-alpha mRNA expression levels in fat tissue and the level of hyperinsulinemia (P < 0.001), an indirect measure of insulin resistance. Finally, body weight reduction in obese subjects which resulted in improved insulin sensitivity was also associated with a decrease in TNF-alpha mRNA expression (45%, P < 0.001) in fat tissue. These results suggest a role for the abnormal regulation of this cytokine in the pathogenesis of obesity-related insulin resistance.
3,499 citations
"PPARs are a unique set of fatty aci..." refers background in this paper
...The inflammatory reaction make adipocytes and immune cells residing in the adipose tissue produce cytokines and adipokines (such as tumor necrosis alpha (TNFα)) that could lead to impaired glucose tolerance in remote tissues of the body [17]....
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