Regulation of PPARgamma function by TNF-alpha

Insulin signalling mechanisms for triacylglycerol storage

Insulin signalling is uniquely required for storing energy as fat in humans. While de novo synthesis of fatty acids and triacylglycerol occurs mostly in liver, adipose tissue is the primary site for triacylglycerol storage. Insulin signalling mechanisms in adipose tissue that stimulate hydrolysis of circulating triacylglycerol, uptake of the released fatty acids and their conversion to triacylglycerol are poorly understood. New findings include (1) activation of DNA-dependent protein kinase to stimulate upstream stimulatory factor (USF)1/USF2 heterodimers, enhancing the lipogenic transcription factor sterol regulatory element binding protein 1c (SREBP1c); (2) stimulation of fatty acid synthase through AMP kinase modulation; (3) mobilisation of lipid droplet proteins to promote retention of triacylglycerol; and (4) upregulation of a novel carbohydrate response element binding protein β isoform that potently stimulates transcription of lipogenic enzymes. Additionally, insulin signalling through mammalian target of rapamycin to activate transcription and processing of SREBP1c described in liver may apply to adipose tissue. Paradoxically, insulin resistance in obesity and type 2 diabetes is associated with increased triacylglycerol synthesis in liver, while it is decreased in adipose tissue. This and other mysteries about insulin signalling and insulin resistance in adipose tissue make this topic especially fertile for future research.

Leucine-rich glioma inactivated 3 associates negatively with adiponectin

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI/epitempin family. We previously reported that LGI3 was expressed in adipose tissues and suppressed adipogenesis through its receptor, ADAM23. We proposed that LGI3 may be a candidate adipokine with pro-inflammatory activity. To investigate the role of LGI3 in adipose tissues, we analyzed cytokine profile in LGI3 knockout mice. Protein array analysis showed that adiponectin was significantly increased in adipose tissues and plasma of LGI3 knockout mice. SiRNA-mediated knockdown of LGI3 increased adiponectin in 3T3-L1 preadipocytes. Treatment of differentiating 3T3-L1 cells with LGI3 protein decreased adiponectin in a dose-dependent manner. High fat diet (HFD)-fed mice showed expression of LGI3 in adipose tissue macrophages in addition to adipocytes that expressed LGI3 in both normal chow-fed and HFD-fed mice. The 60-kDa LGI3 was selectively increased in adipose tissues of HFD mice in which adiponectin was downregulated. Taken together, these results suggested that LGI3 may participate in adipose tissue homeostasis by negatively regulating adiponectin.

Mechanisms of insulin resistance in obesity

Obesity increases the risk for type 2 diabetes through induction of insulin resistance. Treatment of type 2 diabetes has been limited by little translational knowledge of insulin resistance although there have been several well-documented hypotheses for insulin resistance. In those hypotheses, inflammation, mitochondrial dysfunction, hyperinsulinemia and lipotoxicity have been the major concepts and have received a lot of attention. Oxidative stress, endoplasmic reticulum (ER) stress, genetic background, aging, fatty liver, hypoxia and lipodystrophy are active subjects in the study of these concepts. However, none of those concepts or views has led to an effective therapy for type 2 diabetes. The reason is that there has been no consensus for a unifying mechanism of insulin resistance. In this review article, literature is critically analyzed and reinterpreted for a new energy-based concept of insulin resistance, in which insulin resistance is a result of energy surplus in cells. The energy surplus signal is mediated by ATP and sensed by adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Decreasing ATP level by suppression of production or stimulation of utilization is a promising approach in the treatment of insulin resistance. In support, many of existing insulin sensitizing medicines inhibit ATP production in mitochondria. The effective therapies such as weight loss, exercise, and caloric restriction all reduce ATP in insulin sensitive cells. This new concept provides a unifying cellular and molecular mechanism of insulin resistance in obesity, which may apply to insulin resistance in aging and lipodystrophy.

Inflammation links excess fat to insulin resistance: the role of the interleukin-1 family

A growing body of evidence suggests that cytokines of the interleukin-1 (IL-1) family, particularly IL-1β but also IL-1Ra and IL-18, are involved in obesity-associated inflammation. IL-1β is produced via cleavage of pro-IL-1β by caspase-1, which in turn is activated by a multiprotein complex called the inflammasome. The components of the NLRP3 inflammasome are involved in sensing obesity-associated danger signals, both in mice and in human (obese) subjects, with caspase-1 seemingly the most crucial regulator. Autophagy is upregulated in obesity and may function as a mechanism to control IL-1β gene expression in adipose tissue to mitigate chronic inflammation. All these mechanisms are operative in human adipose tissue and appear to be more pronounced in human visceral compared to subcutaneous tissue. In animal studies, blocking caspase-1 activity results in decreased weight gain, decreased inflammation, and improved insulin sensitivity. Human intervention studies with IL-1Ra (anakinra) have reported beneficial effects in patients with diabetes, yet without significant changes in insulin sensitivity. Clearly, the IL-1 family of cytokines, especially IL-1β, plays an important role in obesity-associated inflammation and insulin resistance and may represent a therapeutic target to reverse the detrimental metabolic consequences of obesity.

Regulation of stem cell differentiation in adipose tissue by chronic inflammation

1. Recent studies suggest that a local hypoxic response leads to chronic inflammation in the adipose tissue of obese individuals. The adipose tissue hypoxia may reflect a compensatory failure in the local vasculature system in response to obesity. 2. Studies suggest that inflammation stimulates angiogenesis and inhibits adipocyte activities in a feedback manner within the obese adipose tissue. Adipose-derived stem cells (ASC) are able to differentiate into multiple lineages of progenitor cells for adipocytes, endothelial cells, fibroblasts and pericytes. Differentiation of ASC into those progenitors is regulated by the adipose tissue microenvironment. 3. As a major factor in the microenvironment, inflammation may favour ASC differentiation into endothelial cells through the induction of angiogenic factors. At the same time, inflammation inhibits ASC differentiation into adipocytes by suppressing peroxisome proliferator-activated receptor γ activity and the insulin signalling pathway. In this context, inflammation may serve as a signal mediating the competition between adipocytes and endothelial cells for the limited source of ASC. 4. It is a new concept that inflammation mediates signals in the competition between adipocytes and endothelial cells for the limited ASC in obesity. There is a lot of evidence that inflammation promotes endothelial cell differentiation. However, this activity of inflammation remains to be established in adipose tissue. The present article reviews the literature in support of this conclusion.

Adipokines in inflammation, insulin resistance and cardiovascular disease

1. Obesity is a major determinant of cardiovascular disease (CVD). Studies in the past two decades have shown that adipose tissue is not merely an inert energy reserve of triglycerides, but also an active endocrine organ. 2. Adipose tissue can produce and secrete numerous bioactive peptides and/or proteins termed adipokines. These secretory factors are involved in the regulation of local and systemic inflammation and insulin sensitivity in a paracrine and/or endocrine manner. Inflammation and insulin resistance (IR) play critical roles in the obesity-linked development of CVD, such as atherosclerosis, hypertension and restenosis. 3. In the present minireview, we summarize the relationship between inflammation and IR, as well as their contribution to the development of CVD during adipose tissue dysfunction. In particular, we focus on the effects of various adipokines in pathological processes, which may provide an insight into obesity-linked CVD and facilitate the development of new therapeutic strategies.

Bone marrow-CNS connections: implications in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is the fourth most common cause of blindness in adults. Current therapies, including anti-VEGF therapy, have partial efficacy in arresting the progression of proliferative diabetic retinopathy and diabetic macular edema. This review provides an overview of a novel, innovative approach to viewing diabetic retinopathy as the result of an inflammatory cycle that affects the bone marrow (BM) and the central and sympathetic nervous systems. Diabetes associated inflammation may be the result of BM neuropathy which skews haematopoiesis towards generation of increased inflammatory cells but also reduces production of endothelial progenitor cells responsible for maintaining healthy endothelial function and renewal. The resulting systemic inflammation further impacts the hypothalamus, promoting insulin resistance and diabetes, and initiates an inflammatory cascade that adversely impacts both macrovascular and microvascular complications, including diabetic retinopathy (DR). This review examines the idea of using anti-inflammatory agents that cross not only the blood-retinal barrier to enter the retina but also have the capability to target the central nervous system and cross the blood-brain barrier to reduce neuroinflammation. This neuroinflammation in key sympathetic centers serves to not only perpetuate BM pathology but promote insulin resistance which is characteristic of type 2 diabetic patients (T2D) but is also seen in T1D. A case series of morbidly obese T2D patients with retinopathy and neuropathy treated with minocycline, a well-tolerated antibiotic that crosses both the blood-retina and blood-brain barrier is presented. Our results indicates that minocycine shows promise for improving visual acuity, reducing pain from peripheral neuropathy, promoting weight loss and improving blood pressure control and we postulate that these observed beneficial effects are due to a reduction of chronic inflammation.

The cellular and signaling networks linking the immune system and metabolism in disease

It is now recognized that obesity is driving the type 2 diabetes epidemic in Western countries. Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes and cardiovascular disease, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various cellular and signaling networks that participate in linking the immune and metabolic systems together have contributed to understanding of the pathogenesis of metabolic diseases and may also inform new therapeutic strategies based on immunomodulation. Here we discuss how these various networks underlie the etiology of the inflammatory component of insulin resistance, with a particular focus on the central roles of macrophages in adipose tissue and liver.

A pilot study to evaluate the effect of soy isolate protein on the serum lipid profile and other potential cardiovascular risk markers in moderately hypercholesterolemic Chinese adults

This article examines the effect of soy isolate protein on the serum lipids and other potential cardiovascular risk markers in 90 moderately hypercholesterolemic Chinese adults (64 women and 26 men, aged 25 to 70 years). Fasting blood samples were taken before and after consuming 24 g of protein supplied by soy isolate protein supplement (including 18 g soy protein and 6 g milk protein) or milk protein supplement daily for 8 weeks. Dietary intake was assessed by a 3-day record collected at baseline, week 4, and week 8 of the study. The results indicate that the two kinds of protein can modestly improve serum lipids and markers associated with obesity and inflammation.

PPARγ and Oxidative Stress: Con(β) Catenating NRF2 and FOXO

Peroxisome-proliferator activator receptor γ (PPARγ) is a nuclear receptor of central importance in energy homeostasis and inflammation. Recent experimental pieces of evidence demonstrate that PPARγ is implicated in the oxidative stress response, an imbalance between antithetic prooxidation and antioxidation forces that may lead the cell to apoptotic or necrotic death. In this delicate and intricate game of equilibrium, PPARγ stands out as a central player devoted to the quenching and containment of the damage and to foster cell survival. However, PPARγ does not act alone: indeed the nuclear receptor is at the point of interconnection of various pathways, such as the nuclear factor erythroid 2-related factor 2 (NRF2), Wnt/β-catenin, and forkhead box proteins O (FOXO) pathways. Here we reviewed the role of PPARγ in response to oxidative stress and its interaction with other signaling pathways implicated in this process, an interaction that emerged as a potential new therapeutic target for several oxidative-related diseases.

A low-protein, high-carbohydrate diet increases fatty acid uptake and reduces norepinephrine-induced lipolysis in rat retroperitoneal white adipose tissue

A low-protein, high-carbohydrate (LPHC) diet for 15 days increased the lipid content in the carcass and adipose tissues of rats. The aim of this work was to investigate the mechanisms of this lipid increase in the retroperitoneal white adipose tissue (RWAT) of these animals. The LPHC diet induced an approximately two- and tenfold increase in serum corticosterone and TNF-α, respectively. The rate of de novo fatty acid (FA) synthesis in vivo was reduced (50%) in LPHC rats, and the lipoprotein lipase activity increased (100%). In addition, glycerokinase activity increased (60%), and the phosphoenolpyruvate carboxykinase content decreased (27%). Basal [U-¹⁴C]-glucose incorporation into glycerol-triacylglycerol did not differ between the groups; however, in the presence of insulin, [U-¹⁴C]-glucose incorporation increased by 124% in adipocytes from only control rats. The reductions in IRS1 and AKT content as well as AKT phosphorylation in the RWAT from LPHC rats and the absence of an insulin response suggest that these adipocytes have reduced insulin sensitivity. The increase in NE turnover by 45% and the lack of a lipolytic response to NE in adipocytes from LPHC rats imply catecholamine resistance. The data reveal that the increase in fat storage in the RWAT of LPHC rats results from an increase in FA uptake from circulating lipoproteins and glycerol phosphorylation, which is accompanied by an impaired lipolysis that is activated by NE.

Adipose tissue inflammation and cancer cachexia: possible role of nuclear transcription factors

Cancer cachexia is a multifaceted syndrome whose aetiology is extremely complex and is directly related to poor patient prognosis and survival. Changes in lipid metabolism in cancer cachexia result in marked reduction of total fat mass, increased lipolysis, total oxidation of fatty acids, hyperlipidaemia, hypertriglyceridaemia, and hypercholesterolaemia. These changes are believed to be induced by inflammatory mediators, such as tumour necrosis factor-α (TNF-α) and other factors. Attention has recently been drawn to the current theory that cachexia is a chronic inflammatory state, mainly caused by the host's reaction to the tumour. Changes in expression of numerous inflammatory mediators, notably in white adipose tissue (WAT), may trigger several changes in WAT homeostasis. The inhibition of adipocyte differentiation by PPARγ is paralleled by the appearance of smaller adipocytes, which may partially account for the inhibitory effect of PPARγ on inflammatory gene expression. Furthermore, inflammatory modulation and/or inhibition seems to be dependent on the IKK/NF-κB pathway, suggesting that a possible interaction between NF-κB and PPARγ is required to modulate WAT inflammation induced by cancer cachexia. In this article, current literature on the possible mechanisms of NF-κB and PPARγ regulation of WAT cells during cancer cachexia are discussed. This review aims to assess the role of a possible interaction between NF-κB and PPARγ in the setting of cancer cachexia as well as its significant role as a potential modulator of chronic inflammation that could be explored therapeutically.

A Western-type diet attenuates pulmonary hypertension with heart failure and cardiac cachexia in rats

Western-type diets (WD) constitute risk factors for disease but may have distinct effects in heart failure (HF) with cardiac cachexia (CC). We evaluated hemodynamic, metabolic, and inflammatory effects of short-term WD intake in pulmonary hypertension (PH) with CC. Male Wistar rats randomly received 60 mg · kg(-1) monocrotaline (M) or vehicle (C) and consumed either a 5.4-kcal · g(-1) WD (35% animal fat, 35% simple carbohydrate, 20% protein, 0.4% Na(+)) or a 2.9-kcal · g(-1) (3% vegetable fat, 60% complex carbohydrate, 16% protein, 0.25% Na(+)) normal diet (ND) for 5 wk. Mortality, energy intake, body weight (BW), metabolism, hemodynamics, histology, apoptosis, gene expression, transcription factors, and plasma cytokines were evaluated. Compared with the C-ND group, the M-ND group had PH, HF, and mortality that were significantly attenuated in M-WD. The extent of myocardial remodeling and apoptosis was higher in M-ND than in C-ND but lower in M-WD than in M-ND, while conversely, energy intake, BW, cholesterol, and TG plasma concentrations were lower in M-ND than in C-ND but higher in M-WD than in M-ND. M-ND had increased myocardial NF-κB transcription factor activity, endothelin-1, and cytokine overexpression and higher circulating cytokine concentrations than C-ND, which were lower in M-WD than in M-ND. PPARα activity, however, was lower in M-ND, but not in M-WD, compared with the respective C groups. WD attenuated PH and CC, ameliorating survival, myocardial function, metabolism, and inflammation, through transcription factor modulation, suggesting a beneficial role in CC.

The apoptotic effects of the flavonoid N101-2 in human cervical cancer cells

This study evaluated the anti-cancer effects of a naringenin derivative in human cervical cancer cells. In this study, a synthesized naringenin derivative, diethyl 5,7,4'-trihydroxy flavanone N-phenyl hydrazone (N101-2), inhibited cervical cancer cell growth, whereas naringenin itself exhibited no anti-cancer activity. N101-2 treatment inhibited cancer cell viability in a dose- and time-dependent manner through cell cycle arrest at sub-G1 phase, accompanied by an increase in apoptotic cell death. Expression of cyclins and ppRB was down-regulated, whereas that of CDK inhibitors and p53 increased upon N101-2 treatment. Meanwhile, we detected processing of caspases-8, -9, and -3, cleavage of PARP, as well as Bax up-regulation, which indicates activation of mitochondria-emanated intrinsic apoptosis signaling. Treatment with caspase-8 and -3 inhibitors also recovered cell cycling, and Fas/FasL expression increased in N101-2-treated cervical cancer cells, suggesting that Fas-mediated extrinsic apoptosis signaling was also activated. The tumor suppressor PTEN and its upstream regulator PPARγ were up-regulated with coincident inhibition of PI3K and phospho-Akt after N101-2 treatment. Taken together, we could conclude that N101-2 induces apoptosis by arresting the cell cycle at sub-G1 phase, activating mitochondria-emanated intrinsic and Fas-mediated extrinsic signaling pathways, and inhibiting the PI3K/AKT pathway in CaSki and SiHa human cervical cancer cells.

Arginine decreases peroxisome proliferator-activated receptor-γ activity via c-Jun

We have previously shown in the post ischemic gut that enteral arginine enhanced injury and inflammation via c-Jun/AP-1 and abrogated peroxisome proliferator-activated receptor (PPAR) γ activity. In the current study, we investigated the mechanism by which arginine inhibited PPARγ in vitro in rat small bowel epithelial IEC-6 cells. Arginine repressed PPARγ transcriptional activity in a time and dose-dependent fashion. Furthermore, downregulation of PPARγ by arginine involved phosphorylation of c-Jun that occurred before to changes in PPARγ transcriptional activity. Silencing of c-Jun increased PPARγ beyond that of nonsilenced cells and was not mitigated by arginine. Using a series of blocking studies, we found no relationship between arginine and the ligand-dependent binding site of PPARγ. In conclusion, arginine decreased PPARγ transcriptional activity in small bowel intestinal epithelial cells. These changes are due, in part, to phosphorylation of c-Jun and may explain the deleterious effects of enteral arginine in the post ischemic gut.

Cell-specific effects of TNF-α and IL-1β on alkaline phosphatase: implication for syndesmophyte formation and vascular calcification

Tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate tissue non-specific alkaline phosphatase (TNAP) activity and mineralization in cultures of vascular smooth muscle cells (VSMCs). They are, therefore, considered as stimulators of vascular calcification in the context of atherosclerosis and diabetes type 2. In contrast, although ankylosing spondylitis (AS) leads to the formation of syndesmophytes, which are ectopic ossifications from entheses (where ligaments, tendons and capsules are attached to bone), anti-TNF-α therapies fail to block bone formation in this disease. In this context, our aims were to compare the effects of TNF-α and IL-1β on TNAP activity and mineralization in entheseal cells and VSMCs. Organotypic cultures of mouse ankle entheses were treated or not with TNF-α and IL-1β for 5 days. Micro-computed tomography was performed to determine trabecular bone parameters, and histology to assess TNAP activity and mineralization. Human mesenchymal stem cells cultured in pellets in chondrogenic conditions and human VSMCs were also used to determine the effects of cytokines on TNAP activity and expression, measured by quantitative PCR. In organotypic cultures, TNF-α and IL-1β significantly reduced the tibia BV/TV ratio. They also inhibited TNAP activity in entheseal chondrocytes in situ, and in mouse and human chondrocytes in vitro. In contrast, TNF-α stimulated TNAP expression and activity in human VSMCs. These differences were likely due to cell-specific effects of peroxisome proliferator-activated receptor γ (PPARγ), which is inhibited by TNF-α. Indeed, in human chondrocytes and VSMCs, the PPARγ inhibitor GW-9662 displayed the same opposite effects as TNF-α on TNAP expression. In conclusion, whereas TNF-α and IL-1β stimulate TNAP activity in VSMCs, they inhibit it in entheseal cells in situ and on chondrocytes in vitro. The identification of PPARγ as a likely mediator of cytokine effects deserves consideration for future research on the mechanisms of ectopic ossification.

Inhibition of glyceroneogenesis by histone deacetylase 3 contributes to lipodystrophy in mice with adipose tissue inflammation

We have reported that the nuclear factor-κB (NF-κB) induces chronic inflammation in the adipose tissue of p65 transgenic (Tg) mice, in which the NF-κB subunit p65 (RelA) is overexpressed from the adipocyte protein 2 (aP2) gene promoter. Tg mice suffer a mild lipodystrophy and exhibit deficiency in adipocyte differentiation. To understand molecular mechanism of the defect in adipocytes, we investigated glyceroneogenesis by examining the activity of cytosolic phosphoenolpyruvate carboxykinase (PEPCK) in adipocytes. In aP2-p65 Tg mice, Pepck expression is inhibited at both the mRNA and protein levels in adipose tissue. The mRNA reduction is a consequence of transcriptional inhibition but not alteration in mRNA stability. The Pepck gene promoter is inhibited by NF-κB, which enhances the corepressor activity through activation of histone deacetylase 3 (HDAC3) in the nucleus. HDAC3 suppresses Pepck transcription by inhibiting the transcriptional activators, peroxisome proliferator-activated receptor-γ, and cAMP response element binding protein. The NF-κB activity is abolished by Hdac3 knockdown or inhibition of HDAC3 catalytic activity. In a chromatin immunoprecipitation assay, HDAC3 interacts with peroxisome proliferator-activated receptor-γ and cAMP response element binding protein in the Pepck promoter when NF-κB is activated by TNF-α. These results suggest that HDAC3 mediates NF-κB activity to repress Pepck transcription. This mechanism is responsible for inhibition of glyceroneogenesis in adipocytes, which contributes to lipodystrophy in the aP2-p65 Tg mice.

Quercetin is equally or more effective than resveratrol in attenuating tumor necrosis factor-{alpha}-mediated inflammation and insulin resistance in primary human adipocytes

BACKGROUND

Quercetin and trans-resveratrol (trans-RSV) are plant polyphenols reported to reduce inflammation or insulin resistance associated with obesity. Recently, we showed that grape powder extract, which contains quercetin and trans-RSV, attenuates markers of inflammation in human adipocytes and macrophages and insulin resistance in human adipocytes. However, we do not know how quercetin and trans-RSV individually affected these outcomes.

OBJECTIVE

The aim of this study was to examine the extent to which quercetin and trans-RSV prevented inflammation or insulin resistance in primary cultures of human adipocytes treated with tumor necrosis factor-α (TNF-α)-an inflammatory cytokine elevated in the plasma and adipose tissue of obese, diabetic individuals.

DESIGN

Cultures of human adipocytes were pretreated with quercetin and trans-RSV followed by treatment with TNF-α. Subsequently, gene and protein markers of inflammation and insulin resistance were measured.

RESULTS

Quercetin, and to a lesser extent trans-RSV, attenuated the TNF-α-induced expression of inflammatory genes such as interleukin (IL)-6, IL-1β, IL-8, and monocyte chemoattractant protein-1 (MCP-1) and the secretion of IL-6, IL-8, and MCP-1. Quercetin attenuated TNF-α-mediated phosphorylation of extracellular signal-related kinase and c-Jun-NH₂ terminal kinase, whereas trans-RSV attenuated only c-Jun-NH₂ terminal kinase phosphorylation. Quercetin and trans-RSV attenuated TNF-α-mediated phosphorylation of c-Jun and degradation of inhibitory κB protein. Quercetin, but not trans-RSV, decreased TNF-α-induced nuclear factor-κB transcriptional activity. Quercetin and trans-RSV attenuated the TNF-α-mediated suppression of peroxisome proliferator-activated receptor γ (PPARγ) and PPARγ target genes and of PPARγ protein concentrations and transcriptional activity. Quercetin prevented the TNF-α-mediated serine phosphorylation of insulin receptor substrate-1 and protein tyrosine phosphatase-1B gene expression and the suppression of insulin-stimulated glucose uptake, whereas trans-RSV prevented only the TNF-α-mediated serine phosphorylation of insulin receptor substrate-1.

CONCLUSION

These data suggest that quercetin is equally or more effective than trans-RSV in attenuating TNF-α-mediated inflammation and insulin resistance in primary human adipocytes.

Regulation of energy metabolism by inflammation: a feedback response in obesity and calorie restriction

Caloric restriction (CR), in the absence of malnutrition, delays aging and prevents aging-related diseases through multiple mechanisms. A reduction in chronic inflammation is widely observed in experimental models of caloric restriction. The low inflammation status may contribute to the reduced incidence of osteoporosis, Alzheimer's disease, cardiovascular diseases and cancer in the aging subjects. The association of caloric restriction with low inflammation suggests a role of energy accumulation in the origin of the chronic inflammation. This point is enforced by recent advances in obesity research. Abundant literature on obesity suggests that chronic inflammation is a consequence of energy accumulation in the body. The emerging evidence strongly supports that the inflammatory response induces energy expenditure in a feedback manner to fight against energy surplus in obesity. If this feedback system is deficient (Inflammation Resistance), energy expenditure will be reduced and energy accumulation will lead to obesity. In this perspective, we propose that an increase in inflammation in obesity promotes energy expenditure with a goal to get rid of energy surplus. A decrease in inflammation under caloric restriction contributes to energy saving. Inflammation is a mechanism for energy balance in the body. Inflammation resistance will lead to obesity. We will review the recent literature in support of the viewpoints.

The bovine milk proteome: cherishing, nourishing and fostering molecular complexity. An interactomics and functional overview

Bovine milk represents an essential source of nutrients for lactating calves and a key raw material for human food preparations. A wealth of data are present in the literature dealing with massive proteomic analyses of milk fractions and independent targeted studies on specific groups of proteins, such as caseins, globulins, hormones and cytokines. In this study, we merged data from previous investigations to compile an exhaustive list of 573 non-redundant annotated protein entries. This inventory was exploited for integrated in silico studies, including functional GO term enrichment (FatiGO/Babelomics), multiple pathway and network analyses. As expected, most of the milk proteins were grouped under pathways/networks/ontologies referring to nutrient transport, lipid metabolism and objectification of the immune system response. Notably enough, another functional family was observed as the most statistically significant one, which included proteins involved in the induction of cellular proliferation processes as well as in anatomical and haematological system development. Although the latter function for bovine milk proteins has long been postulated, studies reported so far mainly focused on a handful of molecules and missed the whole overview resulting from an integrated holistic analysis. A preliminary map of the bovine milk proteins interactome was also built up, which will be refined in future as result of the widespread use of quantitative methods in protein interaction studies and consequent reduction of false-positives within associated databases.

Interleukin-15 contributes to the regulation of murine adipose tissue and human adipocytes

An alarming global rise in the prevalence of obesity and its contribution to the development of chronic diseases is a serious health concern. Recently, obesity has been described as a chronic low-grade inflammatory condition, influenced by both adipose tissue and immune cells suggesting proinflammatory cytokines may play a role in its etiology. Here we examined the effects of interleukin-15 (IL-15) on adipose tissue and its association with obesity. Over expression of IL-15 (IL-15tg) was associated with lean body condition whereas lack of IL-15 (IL-15(-/-)) results in significant increase in weight gain without altering appetite. Interestingly, there were no differences in proinflammatory cytokines such as IL-6 and tumor necrosis factor-alpha (TNF-alpha) in serum between the three strains of mice. In addition, there were significant numbers of natural killer (NK) cells in fat tissues from IL-15tg and B6 compared to IL-15(-/-) mice. IL-15 treatment results in significant weight loss in IL-15(-/-) knockout and diet-induced obese mice independent of food intake. Fat pad cross-sections show decreased pad size with over expression of IL-15 is due to adipocyte shrinkage. IL-15 induces weight loss without altering food consumption by affecting lipid deposition in adipocytes. Treatment of differentiated human adipocytes with recombinant human IL-15 protein resulted in decreased lipid deposition. In addition, obese patients had significantly lower serum IL-15 levels when compared to normal weight individuals. These results clearly suggest that IL-15 may be involved in adipose tissue regulation and linked to obesity.

Cytotoxic flavonoids as agonists of peroxisome proliferator-activated receptor gamma on human cervical and prostate cancer cells

We conducted in silico screening for human peroxisome proliferator-activated receptor gamma (hPPARgamma) by performing an automated docking study with 450 flavonoids. Among the eight flavonoids as possible agonists of hPPARgamma, only 3,6-dihydroxyflavone (4) increased the binding between PPARgamma and steroid receptor coactivator-1 (SRC-1), approximately 5-fold, and showed one order higher binding affinity for PPARgamma than a reference compound, indomethacin. The 6-hydroxy group of the A-ring of 3,6-dihydroxyflavone (4) participated in hydrogen-bonding interactions with the side chain of Tyr327, His449, and Tyr473. The B-ring formed a hydrophobic interaction with Leu330, Leu333, Val339, Ile341, and Met364. Therefore, 3,6-dihydroxyflavone is a potent agonist of hPPAR with cytotoxic effects on human cervical and prostate cancer cells.

Dominant processes during human dendritic cell maturation revealed by integration of proteome and transcriptome at the pathway level

Gene expression is commonly used to study the activation of dendritic cells (DCs) to identify proteins that determine whether these cells induce an immunostimulatory or tolerogenic immune response. RNA expression, however, does not necessarily predict protein abundance and often requires large numbers of experiments for statistical significance. Proteomics provides a direct view on protein expression but is costly and time consuming. Here, we combined a comprehensive quantitative proteome and transcriptome analysis on a single batch of immature and cytokine cocktail matured human DCs and integrated resulting data sets at the pathway level. Although overall correlation between differential mRNA and protein expression was low, correlation between components of DC relevant pathways was significantly higher. Differentially expressed proteins and genes partly mapped to identical but also to different pathway components demonstrating that RNA and protein data not only supported but also complemented each other. We identified 5 dominant pathways, which confirmed the importance of cytokines, cell adhesion, and migration in DC maturation and also indicated a fundamental role for lipid metabolism. From these pathways we extracted novel maturation markers that might improve DC vaccine design. For several of the candidate markers we confirmed widespread significance examining DCs from multiple individuals, underscoring the validity of our approach. We conclude that integration of different but related data sets at the pathway level can significantly increase the predictive power of multi "omics" analyses.

Lack of SIRT1 (Mammalian Sirtuin 1) activity leads to liver steatosis in the SIRT1+/- mice: a role of lipid mobilization and inflammation

Mammalian sirtuin 1 (SIRT1) may control fatty acid homeostasis in liver. However, this possibility and underlying mechanism remain to be established. In this study, we addressed the issues by examining the metabolic phenotypes of SIRT1 heterozygous knockout (SIRT1(+/-)) mice. The study was conducted in the mice on three different diets including a low-fat diet (5% fat wt/wt), mediate-fat diet (11% fat wt/wt), and high-fat diet (HFD, 36% fat wt/wt). On low-fat diet, the mice did not exhibit any abnormality. On mediate-fat diet, the mice exhibited a significant increase in hepatic steatosis with elevated liver/body ratio, liver size, liver lipid (triglyceride, glycerol, and cholesterol) content, and liver inflammation. The hepatic steatosis was deteriorated in the mice by HFD. In the liver, lipogenesis was increased, fat export was reduced, and beta-oxidation was not significantly changed. Body weight and fat content were increased in response to the dietary fat. Fat was mainly increased in sc adipose tissue and liver. Inflammation was also elevated in epididymal fat. Whole body energy expenditure and substrate utilization were reduced. Food intake, locomotor activity, and fat absorption were not changed. These data suggest that a reduction in the SIRT1 activity increases the risk of fatty liver in response to dietary fat. The liver steatosis may be a result of increased lipogenesis and reduced liver fat export. The inflammation may contribute to the pathogenesis of hepatic steatosis as well. A reduction in lipid mobilization may contribute to the hepatic steatosis and low energy expenditure.

In vitro study of the effect of diesterified alkoxyglycerols with conjugated linoleic acid on adipocyte inflammatory mediators

Background

Adipocytes contribute to inflammation and the innate immune response through expression of inflammatory mediators. High levels of these mediators have been related to chronic inflammation state and insulin resistance, cardiovascular diseases and diabetes type 2, among other disorders. 3-octadecylglycerol (batyl alcohol) has been described as an inflammatory agent, whereas Conjugated Linoleic Acid (CLA) is considered effective against obesity. In this study we examined the anti-inflammatory activity and mechanisms of modified alkoxyglycerols. Tumor necrosis factor (TNF-α) activated mature adipocytes were used as cellular model of inflammation. Secreted levels and gene expressions of some inflammatory mediators, such as the adipokines, interleukin (IL)-1β, IL-6 and IL-10; and the levels of leptin and adiponectin hormones were quantified in presence and absence of alkoxyglycerols and when human adipocyte cells were or not activated by TNF-α. The aim of this study is to describe the effects of nonesterified alkoxyglycerols, CLA and diesterified alkoxyglycerols with CLA (DEA-CLA) and check if they present beneficial properties using an in vitro model of some chronic diseases related to the inflammatory process, such as obesity, using human mature adipocytes activated with TNF-α.

Results

Our data suggest that DEA-CLA, product of the esterification between the CLA and batyl alcohol, present beneficial effects on adipocytes close to observed and described for CLA (i.e. decrease of IL-1β) and no adverse effects as observed for batyl alcohol (i.e. decrease of IL-10). In addition, DEA-CLA presented similar activity to CLA showing a trend to increase the secreted levels of adiponectin and decreasing the secreted levels of leptin.

Conclusions

CLA and DEA-CLA modify adipocyte inflammatory mediators and also could play a role on energy homeostasis through depletion of leptin levels.

Salicylate inhibits macrophage-secreted factors induced adipocyte inflammation and changes of adipokines in 3T3-L1 adipocytes

Antidiabetic effects of salicylates have been known for years, however the cellular and molecular mechanisms of the hypoglycemic activity are not well elucidated. We examined the effects of salicylate on inflammation-related changes in gene or/and protein expressions of several adipokines in 3T3-L1 adipocytes and of LPS-induced inflammatory factors in RAW 264.7 cell. Especially, we focused our attention on the cross-talk between the macrophages and adipocytes. Exposure to RAW-CM medium resulted in an increase in the gene expression or/and protein secretion of TNF-alpha, IL-6 and resistin, and at the same time, a decrease in the gene expression of PPARgamma and adiponectin in 3T3-L1 adipocytes. Salicylate effectively reversed these changes, and up-regulated glucose consumption in adipocytes. We also found salicylate inhibited phosphorylation of NF-kappaB in RAW-CM-stimulated adipocytes. We conclude salicylate blocks inflammatory process in the pathogenesis of inflammation-related insulin resistance.

Food-derived bioactives as potential regulators of the IL-12/IL-23 pathway implicated in inflammatory bowel diseases

The gene-specific modulation of inflammatory cytokines by food bioactives represents a possible approach to the nutritional or pharmaceutical prevention and treatment of inflammatory bowel disease (IBD). There is evidence for a key role of the interleukin-12beta1/23 receptor (IL-12 Rbeta1/23 R) pathway in IBD, and that reduction of the normal expression of the IL-23 R gene may provide a therapeutic target for this disease. The binding of interleukin-23 (IL-23) to its receptor IL-23 R regulates a newly defined effector T-cell subset, Th17 cells, characterised by the production of interleukin-17 (IL-17) and other cytokines, including tumour necrosis factor-alpha (TNF-alpha). In this study we developed an assay that measured IL-17 and TNF-alpha expression after incubation with specific dietary bioactives in the human T-cell Kit 225. It is anticipated that these changes will reflect differences in IL-23 R production, albeit indirectly. The cell line Kit 225 has similarities to Th17 cells, a subset of T cells producing IL-17 and TNF-alpha, and in initial experiments we demonstrated that the cells express both IL-23 receptor subunits, as well as IL-17 and TNF-alpha genes. Upon verification that stimulation of Kit 225 cells with 1ng/mL IL-23 significantly upregulated IL-17 and TNF-alpha gene expression, and IL-17 production, we supplemented cells with selected food bioactives, caffeic acid phenethyl ester (CAPE), epigallocatechin gallate (EGCG), docosahexaenoic acid (DHA), and linoleic acid (LA), and with phorbol myristate acetate (PMA) and sodium salicylate, used as pro-inflammatory and anti-inflammatory controls, respectively. In both unstimulated cells and after IL-23 stimulation, bioactives modulated the pro-inflammatory cytokines involved in IBD, underlining the possible role of foods in this disease. EGCG and DHA, which significantly inhibited both IL-17 and TNF-alpha expression, appeared particularly interesting.

Uncoupling of inflammation and insulin resistance by NF-kappaB in transgenic mice through elevated energy expenditure

To study the metabolic activity of NF-kappaB, we investigated phenotypes of two different mouse models with elevated NF-kappaB activities. The transcriptional activity of NF-kappaB is enhanced either by overexpression of NF-kappaB p65 (RelA) in aP2-p65 mice or inactivation of NF-kappaB p50 (NF-kappaB1) through gene knock-out. In these models, energy expenditure was elevated in day and night time without a change in locomotion. The mice were resistant to adulthood obesity and diet-induced obesity without reduction in food intake. The adipose tissue growth and adipogenesis were inhibited by the elevated NF-kappaB activity. Peroxisome proliferator-activator receptor gamma expression was reduced by NF-kappaB at the transcriptional level. The two models exhibited elevated inflammatory cytokines (tumor necrosis factor-alpha and interleukin-6) in adipose tissue and serum. However, insulin sensitivity was not reduced by the inflammation in the mice on a chow diet. On a high fat diet, the mice were protected from insulin resistance. The glucose infusion rate was increased more than 30% in the hyperinsulinemic-euglycemic clamp test. Our data suggest that the transcription factor NF-kappaB promotes energy expenditure and inhibits adipose tissue growth. The two effects lead to prevention of adulthood obesity and dietary obesity. The energy expenditure may lead to disassociation of inflammation with insulin resistance. The study indicates that inflammation may prevent insulin resistance by eliminating lipid accumulation.

Rheumatoid arthritis: Disease or syndrome?

Rheumatoid arthritis (RA) has been described in the medical literature for over two hundred years, but its etiology remains unknown. RA displays phenotypic heterogeneity, and it is a relatively prevalent clinical entity: it affects approximately 1% of the population, resulting in enormous pathologic sequelae. Earlier studies targeting the cause(s) of RA suggested potential infectious involvement, whereas more recent reports have focused on a genetic origin of the disease. However, neither infection nor genetics, nor any other single factor is currently accepted as causative of RA. In this article we review studies relating to the etiology of RA, and those of several related matters, and we conclude that the literature indeed does provide insight into the causes underlying the initiation of RA pathogenesis. Briefly, given the remarkable phenotypic variation of RA, especially in its early stages, as well as a number of other characteristics of the condition, we contend that RA is not a discrete clinical entity with a single etiological source. Rather, we argue that it represents a common clinical endpoint for various starting points, each of which is largely guided by as yet poorly understood aspects of the genetic background of the affected individual. Adoption of this alternative view of the origin of RA will have significant consequences for future research and for development of new therapeutic interventions for this burdensome condition.

Antiobesity mechanisms of action of conjugated linoleic acid

Conjugated linoleic acid (CLA), a family of fatty acids found in beef, dairy foods and dietary supplements, reduces adiposity in several animal models of obesity and some human studies. However, the isomer-specific antiobesity mechanisms of action of CLA are unclear, and its use in humans is controversial. This review will summarize in vivo and in vitro findings from the literature regarding potential mechanisms by which CLA reduces adiposity, including its impact on (a) energy metabolism, (b) adipogenesis, (c) inflammation, (d) lipid metabolism and (e) apoptosis.

Hyperglycemia in critical illness: a review

Hyperglycemia is commonplace in the critically ill patient and is associated with worse outcomes. It occurs after severe stress (e.g., infection or injury) and results from a combination of increased secretion of catabolic hormones, increased hepatic gluconeogenesis, and resistance to the peripheral and hepatic actions of insulin. The use of carbohydrate-based feeds, glucose containing solutions, and drugs such as epinephrine may exacerbate the hyperglycemia. Mechanisms by which hyperglycemia cause harm are uncertain. Deranged osmolality and blood flow, intracellular acidosis, and enhanced superoxide production have all been implicated. The net result is derangement of endothelial, immune and coagulation function and an association with neuropathy and myopathy. These changes can be prevented, at least in part, by the use of insulin to maintain normoglycemia.

Peroxisome proliferator-activated receptor and retinoic x receptor in alcoholic liver disease

A growing number of new studies demonstrate that nuclear receptors are involved in the development of alcoholic liver disease (ALD). Ethanol metabolism and RXR/PPAR functions are tightly interconnected in the liver. Several ethanol metabolizing enzymes are potently regulated by RXR and PPARα after alcohol consumption. The increased ethanol metabolism, in turn, leads to alteration of the redox balance of the cells and impairment of RXR/PPAR functions by direct and indirect effects of acetaldehyde, resulting in deranged lipid metabolism, oxidative stress, and release of proinflammatory cytokines. The use of animal models played a crucial role in understanding the molecular mechanisms of ALD. In this paper we summarize the reciprocal interactions between ethanol metabolism and RXR/PPAR functions. In conclusion, RXR and PPAR play a central role in the onset and perpetuation of the mechanisms underling all steps of the clinical progression in ALD.

Enhancement in liver SREBP-1c/PPAR-alpha ratio and steatosis in obese patients: correlations with insulin resistance and n-3 long-chain polyunsaturated fatty acid depletion

Sterol receptor element-binding protein-1c (SREBP-1c) and peroxisome proliferator-activated receptor-alpha (PPAR-alpha) mRNA expression was assessed in liver as signaling mechanisms associated with steatosis in obese patients. Liver SREBP-1c and PPAR-alpha mRNA (RT-PCR), fatty acid synthase (FAS) and carnitine palmitoyltransferase-1a (CPT-1a) mRNA (real-time RT-PCR), and n-3 long-chain polyunsaturated fatty acid (LCPUFA)(GLC) contents, plasma adiponectin levels (RIA), and insulin resistance (IR) evolution (HOMA) were evaluated in 11 obese patients who underwent subtotal gastrectomy with gastro-jejunal anastomosis in Roux-en-Y and 8 non-obese subjects who underwent laparoscopic cholecystectomy (controls). Liver SREBP-1c and FAS mRNA levels were 33% and 70% higher than control values (P<0.05), respectively, whereas those of PPAR-alpha and CPT-1a were 16% and 65% lower (P<0.05), respectively, with a significant 62% enhancement in the SREBP-1c/PPAR-alpha ratio. Liver n-3 LCPUFA levels were 53% lower in obese patients who also showed IR and hipoadiponectinemia over controls (P<0.05). IR negatively correlated with both the hepatic content of n-3 LCPUFA (r=-0.55; P<0.01) and the plasma levels of adiponectin (r=-0.62; P<0.005). Liver SREBP-1c/PPAR-alpha ratio and n-3 LCPUFA showed a negative correlation (r=-0.48; P<0.02) and positive associations with either HOMA (r=0.75; P<0.0001) or serum insulin levels (r=0.69; P<0.001). In conclusion, liver up-regulation of SREBP-1c and down-regulation of PPAR-alpha occur in obese patients, with enhancement in the SREBP-1c/PPAR-alpha ratio associated with n-3 LCPUFA depletion and IR, a condition that may favor lipogenesis over FA oxidation thereby leading to steatosis.

Targets for TNFα-induced lipolysis in gilthead sea bream(Sparus aurata L.) adipocytes isolated from lean and fat juvenile fish

The present study aimed to analyze adiposity heterogeneity and the role of liver X receptor (LXRα) and peroxisome proliferator-activated receptors(PPARs) as targets of tumour necrosis factor-α (TNFα) in gilthead sea bream (Sparus aurata L.). The screening of 20 fish at the beginning of the warm season identified two major groups with fat and lean phenotypes. Fat fish showed increased liver and mesenteric fat depots. This increased adiposity was concurrent in the adipose tissue to enhanced expression of lipoprotein lipase (LPL) whereas mRNA levels of the hormone-sensitive lipase (HSL) remained almost unchanged. The resulting LPL/HSL ratio was thereby highest in fat fish, which suggests that this group of fish has not reached its peak fat storage capacity. This is not surprising given the increased expression of PPARγ in the absence of a counter-regulatory raise of TNFα. However, this lipolytic cytokine exerted dual effects in primary adipocyte cultures that differ within and between lean and fat fish. One set of fat fish did not respond to TNFαtreatment whereas a second set exhibited a lipolytic response (increased glycerol release) that was apparently mediated by the downregulated expression of PPARβ. In lean fish, TNFα exerted a strong and non-transcriptionally mediated lipolytic action. Alternatively, TNFαwould inhibit lipid deposition via the downregulated expression of adipogenic nuclear factors (PPARγ and LXRα). TNFα targets are therefore different in fish with lean and fat phenotypes, which is indicative of the complex network involved in the regulation of fish lipid metabolism.

Curcumin ameliorates renal failure in 5/6 nephrectomized rats: role of inflammation

TNF-α and NF-κB play important roles in the development of inflammation in chronic renal failure (CRF). In hepatic cells, curcumin is shown to antagonize TNF-α-elicited NF-κB activation. In this study, we hypothesized that if inflammation plays a key role in renal failure then curcumin should be effective in improving CRF. The effectiveness of curcumin was compared with enalapril, a compound known to ameliorate human and experimental CRF. Investigation was conducted in Sprague-Dawley rats where CRF was induced by 5/6 nephrectomy (Nx). The Nx animals were divided into untreated (Nx), curcumin-treated (curcumin), and enalapril-treated (enalapril) groups. Sham-operated animals served as a control. Renal dysfunction in the Nx group, as evidenced by elevated blood urea nitrogen, plasma creatinine, proteinuria, segmental sclerosis, and tubular dilatation, was significantly reduced by curcumin and enalapril treatment. However, only enalapril significantly improved blood pressure. Compared with the control, the Nx animals had significantly higher plasma and kidney TNF-α, which was associated with NF-κB activation and macrophage infiltration in the kidney. These changes were effectively antagonized by curcumin and enalapril treatment. The decline in the anti-inflammatory peroxisome proliferator-activated receptor γ (PPARγ) seen in Nx animals was also counteracted by curcumin and enalapril. Studies in mesangial cells were carried out to further establish that the anti-inflammatory effect of curcumin in vivo was mediated essentially by antagonizing TNF-α. Curcumin dose dependently antagonized the TNF-α-mediated decrease in PPARγ and blocked transactivation of NF-κB and repression of PPARγ, indicating that the anti-inflamatory property of curcumin may be responsible for alleviating CRF in Nx animals.

Involvement of TNF-alpha in abnormal adipocyte and muscle sortilin expression in obese mice and humans

AIMS/HYPOTHESIS

Insulin resistance is caused by numerous factors including inflammation. It is characterised by defective insulin stimulation of adipocyte and muscle glucose transport, which requires the glucose transporter GLUT4 translocation towards the plasma membrane. Defects in insulin signalling can cause insulin resistance, but alterations in GLUT4 trafficking could also play a role. Our goal was to determine whether proteins controlling GLUT4 trafficking are altered in insulin resistance linked to obesity.

METHODS

Using real-time RT-PCR, we searched for selected transcripts that were differentially expressed in adipose tissue and muscle in obese mice and humans. Using various adipocyte culture models and in vivo mice treatment, we searched for the involvement of TNF-alpha in these alterations in obesity.

RESULTS

Sortilin mRNA and protein were downregulated in adipose tissue from obese db/db and ob/ob mice, and also in muscle. Importantly, sortilin mRNA was also decreased in morbidly obese human diabetic patients. Sortilin and TNF-alpha (also known as TNF) mRNA levels were inversely correlated in mice and human adipose tissues. TNF-alpha decreased sortilin mRNA and protein levels in cultured mouse and human adipocytes, an effect partly prevented by the peroxisome proliferator-activated receptor gamma activator rosiglitazone. TNF-alpha also inhibited adipocyte and muscle sortilin mRNA when injected to mice.

CONCLUSIONS/INTERPRETATION

Sortilin, an essential player in adipocyte and muscle glucose metabolism through the control of GLUT4 localisation, is downregulated in obesity and TNF-alpha is likely to be involved in this defect. Chronic low-grade inflammation in obesity could thus contribute to insulin resistance by modulating proteins that control GLUT4 trafficking.

Tumor necrosis factor-alpha induces caspase-mediated cleavage of peroxisome proliferator-activated receptor gamma in adipocytes

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent transcription factor that acts as a primary regulator of adipogenesis and controls adipocyte metabolism and insulin action. Increased expression of tumor necrosis factor (TNFalpha) in adipose tissue of obese subjects potently suppresses the expression of PPARgamma and attenuates adipocyte functions. Here we show that PPARgamma is a substrate of caspase-3 and caspase-6 during TNFalpha receptor signaling in adipocytes, and the consequent PPARgamma cleavage disrupts its nuclear localization. TNFalpha treatment of 3T3-L1 adipocytes decreases full-length PPARgamma while increasing the level of a 45-kDa immunoreactive PPARgamma fragment. Specific inhibitors of caspase-3 and caspase-6 attenuate the cleavage of PPARgamma protein in response to TNFalpha in cultured adipocytes. Incubation of nuclear fractions with recombinant caspase-3 and caspase-6 also generates a 45-kDa PPARgamma cleavage product. Dispersion of nuclear PPARgamma to the cytoplasm in response to TNFalpha treatment occurs in parallel with detection of activated caspase-3. We suggest that activation of the caspase cascade by TNFalpha down-regulates PPARgamma protein and PPARgamma-mediated metabolic processes in adipose cells.

Modulation of C-reactive protein, tumor necrosis factor-alpha, and adiponectin by diet, exercise, and weight loss

Chronic disease has been strongly correlated with inflammation resulting from the body's release of inflammatory cytokines as a result of injury or infection. Specific interventions promoting weight loss, exercise, or intake of antioxidants have been used by several investigators in an effort to decrease inflammatory cytokines. C-reactive protein (CRP) is produced by the liver and its role in the development of inflammation has been well established. However, the strong association between CRP and risk for heart disease is a more recent discovery. During the inflammation process, the transcriptional activity of nuclear factor kappaB leads to the increased production of inflammatory cytokines associated with atherosclerosis, including tumor necrosis factor-alpha (TNFalpha). Increased concentrations of TNFalpha have been reported in obese patients; thus, weight loss is considered a key intervention to reduce the concentrations of this cytokine. In contrast to CRP and TNFalpha, adiponectin increases during weight loss and insulin sensitivity. Additionally, lower concentrations of this cytokine have been reported in cardiovascular disease and type-2 diabetes. Recent epidemiological studies and clinical interventions have reported contradictory findings related to dietary or exercise interventions and the resulting alterations in plasma cytokines. Part of the discrepancies may be due to the population studied, the time of the treatment, and the lack of weight loss in some studies. Although it is clear from the literature that these cytokines play a major role in the development of chronic disease, the best strategy to favorably alter the inflammatory response is still debatable.