摘要
肥胖是导致许多慢性疾病的主要因素,尤其是胰岛素抵抗和2型糖尿病,约90%的2型糖尿病患者超重或肥胖。脂肪组织增生肥大、脂肪细胞功能受损是肥胖状态时机体最主要的形态、病理改变,可诱发脂肪细胞炎症反应和胰岛素抵抗。1.本研究应用FFA诱导脂肪细胞模型,分析FFA对3T3-L1脂肪细胞内质网应激信号,炎症信号和胰岛素信号传导通路的影响,结果发现:(1)FFA激活脂肪细胞内质网应激反应激酶—双链RNA激活的蛋白激酶样内质网真核翻译起始因子2α激酶[the double-stranded RNA activated protein kinase (PKR)-like endoplasmic reticulum eukaryotic initiation factor 2 alpha(eIF2α)kinase,PERK]和肌醇需要酶1α(inositol-requiring 1 alpha,IRE1α),上调内质网应激标志物-葡萄糖调节蛋白78(glucose-regulated protein 78,GRP78)和剪接型X盒结合蛋白1(spliced form of XBP1,XBP1s)的表达。(2)FFA激活炎症信号通路-核因子κB抑制蛋白激酶β[ inhibator of nuclear factor kappa B(NF-κB)kinaseβ,IKKβ]和c-Jun氮末端激酶(c-Jun N-terminal kinase,JNK);上调炎性细胞因子—TNFα和IL-6的表达水平,并损害脂肪细胞内的胰岛素信号转导。(3)有抑制内质网应激作用的小分子化学伴侣—牛磺熊去氧胆酸(tauroursodeoxycholic acid,TUDCA),能够有效逆转FFA诱导的脂肪细胞炎症反应和胰岛素抵抗,证实FFA通过内质网应激信号通路诱导脂肪细胞发生炎症反应和胰岛素抵抗。2.本研究通过构建的重组腺病毒Ad-hIKKβWT(人野生型IKKβ)、Ad-hIKKβK44M(人失活型IKKβ)、Ad-hIKKβS177ES181E(人活化型IKKβ)转导3T3-L1 CAR脂肪细胞,研究IKKβ过表达对脂肪细胞中各信号传导通路的影响。结果证实:(1)IKKβ过表达导致脂肪细胞发生内质网应激反应、炎症反应和胰岛素抵抗,证实IKKβ是FFA诱导的脂肪细胞内质网应激反应信号通路的重要下游调节分子。(2)IKKβ参与调节脂肪细胞的脂肪代谢过程—促进脂肪细胞的脂解反应,并抑制脂肪合成过程。3.本研究还分析了肥胖小鼠原代脂肪细胞内IKKβ的活化情况,结果证实ob/ob小鼠脂肪细胞中的内源性IKKβ及其磷酸化蛋白的表达同样增加。综上所述,内质网应激和IKKβ是介导FFA诱导的脂肪细胞炎症反应和胰岛素抵抗的重要分子机制。4.本研究的创新点:(1)首次证实内质网应激反应参与调节FFA诱导的脂肪细胞炎症反应和胰岛素抵抗。(2)首次证实在脂肪细胞中,炎性激酶IKKβ具有与FFA相似的作用—诱发内质网应激反应、炎症反应和胰岛素抵抗;证实IKKβ与内质网应激相互作用,将加剧脂肪细胞胰岛素抵抗。(3)首次证实炎性激酶IKKβ对脂肪细胞脂肪代谢的作用—抑制脂肪合成、促进脂肪裂解,加重脂肪细胞胰岛素抵抗。(4)首次证实在ob/ob小鼠原代脂肪细胞中,IKKβ的磷酸化水平和总蛋白含量都明显增加,进一步证实IKKβ是参与调节脂肪细胞肥胖相关炎症反应和胰岛素抵抗发生的重要蛋白分子。
Obesity is the leading risk factor for development of many life threatening diseases, particularly insulin resistance and type 2 diabetes[181, 182]. The hallmark of obesity is massive expansion of fat mass in order to store excessive amount of energy in the form of triglycerides. Stressed adipocytes secrete multiple chemokines and cytokines, which may contribute to the initial adipose macrophage infiltration and impair adipocyte insulin signaling[30, 46, 113, 183, 184]. At a later stage of obesity development, massive infiltrated and activated macrophages become important source for adipose chemokines and cytokines[111, 112]. It is known that cytokines like TNFαand IL-6 can increase adipocyte lipolysis[185]. Increased circulating FFA levels cause insulin resistance in other organs such as liver and muscle. Approaches aimed to reduce adipose inflammation seem to be effective on improving insulin sensitivity in both animal models and in humans. Decreased macrophage infiltration and reduction of inflammatory gene expression in adipose tissue have also been associated with weight loss in obese subjects[186, 187]. Thiazolidinedione (TZD), a class of insulin sensitizing drug that mainly improves adipose insulin sensitivity of type 2 diabetic patients, also has potent anti-inflammatory effects and suppresses adipose macrophage gene expression in vitro and in vivo[188-194]. The fact that fat mass increases prior to macrophage infiltration indicates that lipid overload in adipocytes is the causal factor for adipose inflammation and insulin resistance[113].
Recently, obesity has been shown to cause ER stress in both liver and adipose tissue. Chemical chaperones can effectively alleviate ER stress in liver and adipose tissue as well as reverse systemic insulin resistance and type 2 diabetes in ob/ob mice. Adipose tissue is heterogeneous and contains many cell types. It is unclear whether over-nutrition generates ER stress in adipocytes, a type of cells critical for storage of excessive energy and production of inflammatory cytokines. In order for adipocytes to store excessive amount of lipids, triglycerides derived from diet and de novo synthesis need to be broken down to FFA and glycerol first, then uptaken by adipocytes for reesterification. It is well known that FFA can induce adipocyte inflammation and insulin resistance. However, it remains unclear whether FFA can cause ER stress in adipocytes and whether ER stress plays a role in FFA-induced inflammation and insulin resistance in adipocytes. In the present study, we show that FFA cause ER stress in 3T3-L1 adipocytes. Chemical chaperone can alleviate the adverse effect of FFA on adipocytes. IKKβis an important downstream effecter of FFA-induced ER stress since IKKβoverexpression is sufficient to cause adipocyte inflammation and insulin resistance. Furthermore, activation of IKKβcan also induce ER stress in adipocytes and the expression of endogenous IKKβis elevated in adipocyte of obese mice.
1. The effect of FFA in 3T3-L1 adipocytes
1.1 FFA activate ER stress pathway and inflammatory pathway, suppress insulin pathway in 3T3-L1 adipocytes.
A mixture of FFA was used to treat 3T3-L1 adipocytes and ER stress, inflammation and insulin resistance were examined. FFA treatment caused rapid phosphorylation of both PERK and IRE-1α30 and 60 minutes after treatment (Figure 2.5). Phosphorylation dynamics of both IKKβand JNK is similar to that of PERK and IRE-1α, being strongest at 30 and 60 minutes after FFA treatment and starting to fade away at later time points (Figure 2.6). The expression level of several other ER marker proteins, such as GRP78 and the spliced transcription factor XBP-1 (XBP-1s), peaked at two hours after FFA treatment (P<0.05) (Figure 2.4). In contrast, impairment of insulin signaling, reflected by decreased IR, IRS-1 and Akt phosphorylation, did not reach maximal till three hours post treatment (Figure 2.7). In our previous study, we reported that FFA can induce up-regulation of multiple chemokines in 3T3-L1 adipocytes which peak three hours post treatment under identical conditions (3). These results indicate that FFA can induce ER stress response in 3T3-L1 adipocytes. Activation of ER stress sensor proteins (IRE-1αand PERK) is concurrent with activation of IKKβand JNK but precedes FFA-induced expression of other ER marker proteins (GRP78 and XBP1s), adipocyte chemokine production and maximal impairment of insulin signaling.
1.2 Chemical chaperone TUDCA can reduce FFA-induced inflammation and insulin resistance in 3T3-L1 adipocytes.
It has been reported that chemical chaperones can ameliorate ER stress and improve insulin sensitivity in obese mice as well as tunicamycin and thapsigargin treated liver cells[158, 164]. We next examined whether TUDCA, a well-established chemical chaperone that has been demonstrated to reduce ER stress, can improve FFA-induced adipocyte inflammation and insulin resistance. TUDCA was used to pre-treat 3T3-L1 adipocytes overnight and added again with FFA mixture next day. Pre-treatment with TUDCA effectively reduced FFA-induced phosphorylation on both IKKβand JNK in 3T3-L1 adipocytes (Figure 2.8), indicating that activation of IKKβand JNK by FFA treatment might be at least partially through turning on ER stress response pathway. TNFαand IL-6 are inflammatory cytokines that have been demonstrated to increase in adipose tissue of obese state and impair adipocyte function. TUDCA pre-treatment completely blocked FFA-induced expression of TNFαand IL-6 in 3T3-L1 adipocytes (P<0.05) (Figure 2.9). Furthermore, TUDCA pre-treatment also improved insulin signaling of 3T3-L1 adipocytes in the presence of FFA as demonstrated by increased tyrosine phosphorylation on IRS-1 and serine/threonine phosphorylation on Akt in comparison to vehicle-pretreatment in the presence of FFA (Figure 2C). These results suggest that ER stress pathway is likely an important mediator of FFA-induced inflammation and insulin resistance in adipocytes.
2. The effect of IKKβin adipocytes
2.1 The effect of IKKβin 3T3-L1 CAR adipocytes
2.1.1 Overexpression of IKKβis sufficient to mimic FFA-induced inflammation and insulin resistance in 3T3-L1 CAR adipocytes. To examine whether IKKβis the critical mediator of FFA-induced inflammation and insulin resistance in 3T3-L1 adipocytes, we next over-expressed both wild type (IKKβWT) and the constitutively active human IKKβ(IKKβSE) by adenovirus- mediated gene transfer in 3T3-L1 CAR adipocytes. Catalytically inactive IKKβ(IKKβK44M) and GFP were also expressed as negative controls. Over- expression of hIKKβSE, not IKKβWT, obviously impaired insulin-stimulated phosphorylation of Akt on both threonine 308 and serine 473 (Figure 3.3). In contrast, IKKβoverexpression did not affect insulin-stimulated tyrosine phosphorylation on either IR or IRS-1 (Supplementary figure 2) despite that IRS-1 has been reported to be a direct target of IKKβfor serine phosphorylation[73]. Overexpression of both IKKβWT and IKKβSE significantly increased expression of inflammatory cytokines TNFαand IL-6 (P<0.05) (Figure 3.6) but dramatically decreased expression of insulin-sensitizing hormones leptin and adiponectin (P<0.05)(Figure 3.7). The constitutively active IKKβhas more robust effect on regulating aforementioned genes compared to the wild type IKKβ. Interestingly, overexpression of both IKKβWT and IKKβSE also significantly increased expression of GRP78 and CHOP(P<0.05)(Figure 3.5), indicating that IKKβis not only a downstream effecter for FFA-induced ER stress but it also can induce ER stress. In contrast, overexpression of JNK1 in 3T3-L1 CAR adipocytes increased IL-6 expression but did not have an effect on TNFαexpression (Supplementary figure 1A). These results are consistent with reported literature that plasma IL-6, not TNFα, was reduced in adipose-specific JNK1 knock out mice fed on high fat diet[168].
2.1.2 Overexpression of IKKβhas profound effect on adipocyte lipid metabolism.
One potential reason that adipose inflammation develops in response to lipid load might be to limit excessive fat mass expansion. Indeed, TNFαhas been reported to inhibit adipocyte differentiation and induce lipolysis, both can reduce adipocyte lipid content[185, 195]. Since IKKβoverexpression dramatically increased expression of TNF-α, it is very likely that lipid metabolism is also altered. To determine whether IKKβoverexpression has any effect on lipid metabolism, lipolysis and lipid synthesis were evaluated. The expression of hormone sensitive lipase (HSL), adipocyte triglyceride lipase (AGTL), lipoprotein lipase (LPL) and perilipin are all significantly decreased (P<0.05) (Figure 3.11). Glycerol contents in conditioned media collected from hIKKβWT and hIKKβSE over-expressing 3T3-L1 CAR adipocytes are significantly higher than those from adipocytes over-expressing GFP and IKKβKM (P<0.05) (Figure 3.10), suggesting increased lipolysis upon IKKβoverexpression. The decreased expression of lipases might be a feedback mechanism for adipocytes to control dysregulated lipolysis. Expression level of glut4 is also significantly decreased in 3T3-L1 CAR adipocytes over-expressing IKKβcompared to control cells expressing GFP and inactive IKKβ(P<0.05) (Figure 3.4), indicating potential impairment in insulin-stimulated glucose uptake. IKKβoverexpression also significantly reduced expression of many lipogenic genes (P<0.05) (Figure 3.9) such as stearoyl CoA desaturase 1 (SCD1), fatty acid synthase (FAS), acyl CoA carboxylase 1 (ACC1), Acyl CoA carboxylase 2 (ACC2), mitochondrial glycerol-3-phosphate acyltransferase 1 (GPAT1), and diacylglycerol acyltrans- ferase 1 (DGAT1). The reduced triglyceride contents in hIKKβWT and hIKKβSE over-expressing cells are consistent with decreased expression of lipogenic genes. It remains to be studied whether the effect of IKKβon lipid metabolism is directly achieved through modulating expression of relevant genes or indirectly achieved via increase of TNFαand IL-6 expression.
2.2 Obesity activates IKKβin primary adipocytes.
Our IKKβoverexpression study in L1-CAR adipocytes demonstrated that IKKβis an important player in adipocyte inflammation and insulin resistance. To assess whether expression and phosphorylation status of endogenous IKKβcan be increased in adipocytes of obese mice, primary adipocytes were isolated from 9-week old ob/ob mice and littermate lean controls. Expression of phospho-IKKβwas significantly increased by 147% in adipocytes isolated from ob/ob mice compared to the level in lean mice (Figure 3.12, 3.13). The increase of phospho-IKKβis mainly due to elevated expression of IKKβprotein, which was increased by 151% in adipocytes from ob/ob mice (Figure 3.12, 3.13). In contrast, expression of phospho-IKKαdecreased by 53% in adipocytes from ob/ob mice despite increased expression of IKKαprotein by 17.7% (Figure 3.12, 3.14). These results indicate that IKKβmay play an important role in adipocyte inflammation and insulin resistance in obese state.
Understanding the link between lipid overload and development of adipocyte inflammation and insulin resistance will likely provide useful information for potential new therapeutic directions to treat metabolic syndrome. It is well known that FFA can induce inflammation and insulin resistance in adipocytes but the molecular mechanism is not very clear. ER stress has recently been linked to obesity-related insulin resistance. Despite the solid evidence that ER stress exists in obese adipose tissue, it remained to be studied whether ER stress occurs in adipocyte in response to increased lipid accumulation. In the present study, we have demonstrated that FFA can activate two major ER stress sensing pathways, PERK and IRE-1α. Attenuation of FFA-induced ER stress by chemical chaperone effectively reduced FFA-induced expression of inflammatory cytokines and improved insulin signaling, which was accompanied by reduced IKKβand JNK phosphorylation. These results indicate that ER stress pathway is involved in FFA-induced production of inflammatory factors and impairment of insulin signaling.
Both JNK and IKKβhave been demonstrated to be critical mediators of obesity-related inflammation and insulin resistance. JNK1 deficient mice are protected from the development of obesity-related systemic insulin resistance [77]. Absence of JNK1 in macrophages can also modestly change inflammatory profile in adipose tissue[196]. Heterozygous IKKβknock out mice are protected from developing insulin resistance induced by high fat diet and leptin deficiency[65]. Overexpression of the constitutively active IKKβin the liver causes hepatic and systemic insulin resistance[72].Constitutive activation of IKKβin the hypothalamus impairs central insulin and leptin signaling and suppression of IKKβin the hypothalamus protects from development of obesity and glucose intolerance[197]. Deletion of IKKβin hepatocytes improved high fat diet-induced liver insulin resistance while deficiency of IKKβin myeloid cells renders global insulin sensitivity upon high fat diet[71]. Gain-of-funtion approach was used next to explore whether overexpression of IKKβand JNK can mimic the effect of FFA on causing adipocyte inflammation and insulin resistance. Due to the fact that the constitutively active form of JNK is not available, only wild type JNK1 was over-expressed in 3T3-L1 CAR adipocytes, which increased expression of IL-6 but not TNFα. Overexpression of JNK1WT did not impair insulin signaling (supplementary figure 1B, 1C). In contrast, over- expression of IKKβWT significantly increased expression of both TNFαand IL-6 but was still not sufficient to impair insulin signaling. Overexpression of the constitutively active form of IKKβnot only further increased expression of inflammatory cytokines but also reduced insulin-stimulated Akt phosphorylation. Interestingly, IKKβactivation in adipocytes also induced ER stress as demonstrated by increased expression of GRP78 and CHOP. These data indicate that a certain threshold level of proinflammatory cytokines might be required to damage insulin signaling in adipocytes and constitutive activation of IKKβis sufficient to mimic the effect of FFA on inducing adipocyte inflammation and insulin resistance.
In addition to increasing expression of proinflammatory cytokines, activation of IKKβdrastically repressed expression of leptin and adiponectin, both are important hormones that can modulate systemic insulin sensitivity and energy homeostasis. Overexpression of IKKβalso had profound effect on adipocyte lipid metabolism, such as increasing lipolysis and decreasing triglyceride synthesis. Furthermore, activation of endogenous IKKβhas been observed in primary adipocytes isolated from obese mice. Activation of IKKβin adipocytes during the development of obesity not only likely to influence adipose tissue inflammation profile and lipid storage but also may affect whole body energy metabolism by modulating expression of adipocyte-derived hormones.
引文
[1]Haslam D W, James W P. Obesity. Lancet 2005;366:1197‐1209.
[2]Shi Y, Burn P. Lipid metabolic enzymes: emerging drug targets for the treatment ofobesity. Nat Rev Drug Discov 2004;3:695‐710.
[3]Popkin B M. Will China's nutrition transition overwhelm its health care system andslow economic growth? Health Aff (Millwood) 2008;27:1064‐1076.
[4]Hotamisligil G S. Inflammation and metabolic disorders. Nature 2006;444:860‐867.
[5]Wild S, Roglic G, Green A, et al. H. Global prevalence of diabetes: estimates for theyear 2000 and projections for 2030. Diabetes Care 2004;27:1047‐1053.
[6]Hossain P, Kawar B, El Nahas M. Obesity and diabetes in the developing world‐‐agrowing challenge. N Engl J Med 2007;356:213‐215.
[7]Reaven G M. Pathophysiology of insulin resistance in human disease. Physiol Rev1995;75:473‐486.
[8]Saltiel A R, Kahn C R. Insulin signalling and the regulation of glucose and lipidmetabolism. Nature 2001;414:799‐806.
[9]Chakraborty C. Biochemical and molecular basis of insulin resistance. Curr ProteinPept Sci 2006;7:113‐121.
[10]Gual P, Le Marchand‐Brustel Y, Tanti J F. Positive and negative regulation of insulinsignaling through IRS‐1 phosphorylation. Biochimie 2005;87:99‐109.
[11]Bhattacharya S, Dey D, Roy S S. Molecular mechanism of insulin resistance. J Biosci2007;32:405‐413.
[12]Bak J F, Moller N, Schmitz O, et al. In vivo insulin action and muscle glycogensynthase activity in type 2 (non‐insulin‐dependent) diabetes mellitus: effects of diettreatment. Diabetologia 1992;35:777‐784.
[13]Freidenberg G R, Reichart D, Olefsky J M, et al. Reversibility of defective adipocyteinsulin receptor kinase activity in non‐insulin‐dependent diabetes mellitus. Effect of weightloss. J Clin Invest 1988;82:1398‐1406.
[14]Sims E A, Danforth E, Jr., Horton E S, et al. Endocrine and metabolic effects ofexperimental obesity in man. Recent Prog Horm Res 1973;29: 457‐496.
[15]Feinstein R, Kanety H, Papa M Z, et al. Tumor necrosis factor‐alpha suppressesinsulin‐induced tyrosine phosphorylation of insulin receptor and its substrates. J Biol Chem1993;268:26055‐26058.
[16]Hotamisligil G S, Shargill N S, Spiegelman B M. Adipose expression of tumornecrosis factor‐alpha: direct role in obesity‐linked insulin resistance. Science 1993;259:87‐91.
[17]Fried S K, Bunkin D A, Greenberg A S. Omental and subcutaneous adipose tissuesof obese subjects release interleukin‐6: depot difference and regulation by glucocorticoid. JClin Endocrinol Metab 1998;83:847‐850.
[18]Fukuhara A, Matsuda M, Nishizawa M, et al. Visfatin: a protein secreted byvisceral fat that mimics the effects of insulin. Science 2005;307:426‐430.
[19]Shimomura I, Funahashi T, Takahashi M, et al. Enhanced expression of PAI‐1 invisceral fat: possible contributor to vascular disease in obesity. Nat Med 1996; 2:800‐803.
[20]Steppan C M, Bailey, S T, Bhat S, et al. The hormone resistin links obesity todiabetes. Nature 2001;409:307‐312.
[21]Zhang Y, Proenca R, Maffei M, et al. Positional cloning of the mouse obese geneand its human homologue. Nature 1994;372:425‐432.
[22]Hotamisligil G S, Arner P, Caro J F, et al. Increased adipose tissue expression oftumor necrosis factor‐alpha in human obesity and insulin resistance. J Clin Invest 1995;95:2409‐2415.
[23]Hotamisligil G S. The role of TNFalpha and TNF receptors in obesity and insulinresistance. J Intern Med 1999;245:621‐625.
[24]Uysal K T, Wiesbrock S M, Marino M W, et al. Protection from obesity‐inducedinsulin resistance in mice lacking TNF‐alpha function. Nature 1997; 389:610‐614.
[25]Bernstein L E, Berry J, Kim S, et al. Effects of etanercept in patients with themetabolic syndrome. Arch Intern Med 2006;166:902‐908.
[26]Ryden M, Arner P. Tumour necrosis factor‐alpha in human adipose tissue‐‐ fromsignalling mechanisms to clinical implications. J Intern Med 2007;262:431‐438.
[27]Stephens J M, Lee J, Pilch P F. Tumor necrosis factor‐alpha‐induced insulinresistance in 3T3‐L1 adipocytes is accompanied by a loss of insulin receptor substrate‐1 andGLUT4 expression without a loss of insulin receptor‐mediated signal transduction. J BiolChem 1997;272:971‐976.
[28]Qi C, Pekala PH. Tumor necrosis factor‐alpha‐induced insulin resistance inadipocytes. Proc Soc Exp Biol Med 2000;223:128‐135.
[29]Hotamisligil G S, Budavari A, Murray D, et al. Reduced tyrosine kinase activity ofthe insulin receptor in obesity‐diabetes. Central role of tumor necrosis factor‐alpha. J ClinInvest 1994;94:1543‐1549.
[30]Hotamisligil G S, Murray D L, Choy L N, et al. Tumor necrosis factor alpha inhibitssignaling from the insulin receptor. Proc Natl Acad Sci U S A 1994;91:4854‐4858.
[31]Hotamisligil G S, Peraldi P, Budavari A, et al. IRS‐1‐mediated inhibition of insulinreceptor tyrosine kinase activity in TNF‐alpha‐ and obesity‐induced insulin resistance.Science 1996;271:665‐668.
[32]Peraldi P, Hotamisligil G S, Buurman W A, et al. Tumor necrosis factor (TNF)‐alphainhibits insulin signaling through stimulation of the p55 TNF receptor and activation ofsphingomyelinase. J Biol Chem 1996;271:13018‐13022.
[33]Paz K, Hemi R, LeRoith D, et al. A molecular basis for insulin resistance. Elevatedserine/threonine phosphorylation of IRS‐1 and IRS‐2 inhibits their binding to thejuxtamembrane region of the insulin receptor and impairs their ability to undergoinsulin‐induced tyrosine phosphorylation. J Biol Chem 1997;272:29911‐29918.
[34]Peraldi P, Xu M, Spiegelman B M. Thiazolidinediones block tumor necrosisfactor‐alpha‐induced inhibition of insulin signaling. J Clin Invest 1997;100:1863‐1869.
[35]Muller S, Martin S, Koenig W, et al. Impaired glucose tolerance is associated withincreased serum concentrations of interleukin 6 and co‐regulated acute‐phase proteins butnot TNF‐alpha or its receptors. Diabetologia 2002;45:805‐812.
[36]Pickup J C, Mattock M B, Chusney G D, et al. NIDDM as a disease of the innateimmune system: association of acute‐phase reactants and interleukin‐6 with metabolicsyndrome X. Diabetologia 1997;40:1286‐1292.
[37]Petersen E W, Carey A L, Sacchetti M, et al. Acute IL‐6 treatment increases fattyacid turnover in elderly humans in vivo and in tissue culture in vitro. Am J PhysiolEndocrinol Metab 2005;288:E155‐162.
[38]Tsigos C, Papanicolaou D A, Kyrou I, et al. Dose‐dependent effects of recombinanthuman interleukin‐6 on glucose regulation. J Clin Endocrinol Metab 1997;82:4167‐4170.
[39]Kopp H P, Kopp C W, Festa A, et al. Impact of weight loss on inflammatory proteinsand their association with the insulin resistance syndrome in morbidly obese patients.Arterioscler Thromb Vasc Biol 2003;23:1042‐1047.
[40]Fontana L, Eagon J C, Trujillo M E, et al. Visceral fat adipokine secretion isassociated with systemic inflammation in obese humans. Diabetes 2007;56:1010‐1013.
[41]You T, Yang R, Lyles M F, et al. Abdominal adipose tissue cytokine gene expression:relationship to obesity and metabolic risk factors. Am J Physiol Endocrinol Metab 2005;288:E741‐747.
[42]Klover P J, Zimmers T A, Koniaris L G, et al. Chronic exposure to interleukin‐6causes hepatic insulin resistance in mice. Diabetes 2003;52:2784‐2789.
[43]Klover P J, Clementi A H, Mooney RA. Interleukin‐6 depletion selectively improveshepatic insulin action in obesity. Endocrinology 2005;146:3417‐3427.
[44]De Benedetti F, Alonzi T, Moretta A, et al. Interleukin 6 causes growth impairmentin transgenic mice through a decrease in insulin‐like growth factor‐I. A model for stuntedgrowth in children with chronic inflammation. J Clin Invest 1997;99:643‐650.
[45]Wallenius V, Wallenius K, Ahren B, et al. Interleukin‐6‐deficient mice developmature‐onset obesity. Nat Med 2002;8:75‐79.
[46]Rotter V, Nagaev I, Smith U. Interleukin‐6 (IL‐6) induces insulin resistance in 3T3‐L1adipocytes and is, like IL‐8 and tumor necrosis factor‐alpha, overexpressed in human fatcells from insulin‐resistant subjects. J Biol Chem 2003;278:45777‐45784.
[47]Senn J J, Klover P J, Nowak I A, et al. Interleukin‐6 induces cellular insulinresistance in hepatocytes. Diabetes 2002;51:3391‐3399.
[48]Weigert C, Hennige A M, Lehmann R, et al. Direct cross‐talk of interleukin‐6 andinsulin signal transduction via insulin receptor substrate‐1 in skeletal muscle cells. J BiolChem 2006;281:7060‐7067.
[49]Baldwin A S Jr. The NF‐kappa B and I kappa B proteins: new discoveries andinsights. Annu Rev Immunol 1996;14:649‐683.
[50]Scheidereit C. IkappaB kinase complexes: gateways to NF‐kappaB activation andtranscription. Oncogene 2006;25:6685‐6705.
[51]Mercurio F, Murray B W, Shevchenko A, et al. IkappaB kinase (IKK)‐associatedprotein 1, a common component of the heterogeneous IKK complex. Mol Cell Biol 1999;19:1526‐1538.
[52]Mercurio F, Zhu H, Murray B W, et al. IKK‐1 and IKK‐2: cytokine‐activated IkappaBkinases essential for NF‐kappaB activation. Science 1997;278:860‐866.
[53]Rothwarf D M, Zandi E, Natoli G, et al. IKK‐gamma is an essential regulatorysubunit of the IkappaB kinase complex. Nature 1998;395:297‐300.
[54]Yamaoka S, Courtois G, Bessia C, et al. Complementation cloning of NEMO, acomponent of the IkappaB kinase complex essential for NF‐kappaB activation. Cell1998;93:1231‐1240.
[55]Karin M. How NF‐kappaB is activated: the role of the IkappaB kinase (IKK) complex.Oncogene 1999;18:6867‐6874.
[56]Woronicz J D, Gao X, Cao Z, et al. IkappaB kinase‐beta: NF‐kappaB activation andcomplex formation with IkappaB kinase‐alpha and NIK. Science 1997;278:866‐869.
[57]Delhase M, Hayakawa M, Chen Y, et al. Positive and negative regulation of IkappaBkinase activity through IKKbeta subunit phosphorylation. Science 1999;284:309‐313.
[58]Ling L, Cao Z, Goeddel D V. NF‐kappaB‐inducing kinase activates IKK‐alpha byphosphorylation of Ser‐176. Proc Natl Acad Sci U S A 1998;95:3792‐3797.
[59]Huynh Q K, Boddupalli H, Rouw S A, et al. Characterization of the recombinantIKK1/IKK2 heterodimer. Mechanisms regulating kinase activity. J Biol Chem 2000;275:25883‐25891.
[60]Hacker H, Karin M. Regulation and function of IKK and IKK‐related kinases. SciSTKE 2006;2006:re13.
[61]Li Q, Van Antwerp D, Mercurio F, et al. Severe liver degeneration in mice lackingthe IkappaB kinase 2 gene. Science 1999;284:321‐325.
[62]Takeda K, Takeuchi O, Tsujimura T, et al. Limb and skin abnormalities in micelacking IKKalpha. Science 1999;284:313‐316.
[63]Hu Y, Baud V, Delhase M, et al. Abnormal morphogenesis but intact IKK activationin mice lacking the IKKalpha subunit of IkappaB kinase. Science 1999;284:316‐320.
[64]Ohazama A, Hu Y, Schmidt‐Ullrich R, et al. A dual role for Ikk alpha in toothdevelopment. Dev Cell 2004;6:219‐227.
[65]Yuan M, Konstantopoulos N, Lee J, et al. Reversal of obesity‐ and diet‐inducedinsulin resistance with salicylates or targeted disruption of Ikkbeta. Science 2001;293:1673‐1677.
[66]Jiao P, Xu H. Adipose inflammation: cause or consequence of obesity‐relatedinsulin resistance. Diabetes, Metabolic Syndrome and Obesity 2008;2008:25‐31.
[67]Yin M J, Yamamoto Y, Gaynor R B. The anti‐inflammatory agents aspirin andsalicylate inhibit the activity of I(kappa)B kinase‐beta. Nature 1998;396:77‐80.
[68]Coleman D L. Diabetes‐obesity syndromes in mice. Diabetes 1982;31:1‐6.
[69]Houseknecht K L, Portocarrero C P. Leptin and its receptors: regulators ofwhole‐body energy homeostasis. Domest Anim Endocrinol 1998;15:457‐475.
[70]Rohl M, Pasparakis M, Baudler S, et al. Conditional disruption of IkappaB kinase 2fails to prevent obesity‐induced insulin resistance. J Clin Invest 2004;113:474‐481.
[71]Arkan M C, Hevener A L, Greten F R, et al. IKK‐beta links inflammation toobesity‐induced insulin resistance. Nat Med 2005;11:191‐198.
[72]Cai D, Yuan M, Frantz D F, et al. Local and systemic insulin resistance resulting fromhepatic activation of IKK‐beta and NF‐kappaB. Nat Med 2005;11:183‐190.
[73]Gao Z, Hwang D, Bataille F, et al. Serine phosphorylation of insulin receptorsubstrate 1 by inhibitor kappa B kinase complex. J Biol Chem 2002;277:48115‐48121.
[74]Shoelson S E, Lee J, Goldfine A B. Inflammation and insulin resistance. J Clin Invest2006;116:1793‐1801.
[75]Johnson G L, Nakamura K. The c‐jun kinase/stress‐activated pathway: regulation,function and role in human disease. Biochim Biophys Acta 2007;1773:1341‐1348.
[76]Yang R, Trevillyan J M. c‐Jun N‐terminal kinase pathways in diabetes. Int J BiochemCell Biol 2008;40:2702‐2706.
[77]Hirosumi J, Tuncman G, Chang L, et al. A central role for JNK in obesity and insulinresistance. Nature 2002;420:333‐336.
[78]Tilg H, Moschen A R. Inflammatory mechanisms in the regulation of insulinresistance. Mol Med 2008;14:222‐231.
[79]Jiao P, Xu H. Adipose inflammation: cause or consequence of obesity‐relatedinsulin resistance. Diabetes, Metabolic Syndrome and Obesity 2008;2008:25‐31.
[80]Tuncman G, Hirosumi J, Solinas G, et al. Functional in vivo interactions betweenJNK1 and JNK2 isoforms in obesity and insulin resistance. Proc Natl Acad Sci USA 2006;103:10741‐10746.
[81]Vazquez‐Vela M E, Torres N, Tovar A R. White adipose tissue as endocrine organand its role in obesity. Arch Med Res 2008;39:715‐728.
[82]Villena J A, Roy S, Sarkadi‐Nagy E, et al. Desnutrin, an adipocyte gene encoding anovel patatin domain‐containing protein, is induced by fasting and glucocorticoids: ectopicexpression of desnutrin increases triglyceride hydrolysis. J Biol Chem 2004;279:47066‐47075.
[83]Fredrikson G, Tornqvist H, Belfrage P. Hormone‐sensitive lipase andmonoacylglycerol lipase are both required for complete degradation of adipocytetriacylglycerol. Biochim Biophys Acta 1986;876:288‐293.
[84]Brasaemle D L, Rubin B, Harten I A, et al. Perilipin A increases triacylglycerolstorage by decreasing the rate of triacylglycerol hydrolysis. J Biol Chem 2000;275:38486‐38493.
[85]Egan J J, Greenberg A S, Chang M K, et al. Mechanism of hormone‐stimulatedlipolysis in adipocytes: translocation of hormone‐sensitive lipase to the lipid storagedroplet. Proc Natl Acad Sci U S A 1992;89:8537‐8541.
[86]Sul H S, Wang D. Nutritional and hormonal regulation of enzymes in fat synthesis:studies of fatty acid synthase and mitochondrial glycerol‐3‐phosphate acyltransferase genetranscription. Annu Rev Nutr 1998;18:331‐351.
[87]Park H, Kaushik V K, Constant S, et al. Coordinate regulation of malonyl‐CoAdecarboxylase, sn‐glycerol‐3‐phosphate acyltransferase, and acetyl‐CoA carboxylase byAMP‐activated protein kinase in rat tissues in response to exercise. J Biol Chem 2002;277:32571‐32577.
[88]Yamauchi T, Kamon J, Waki H, et al. The fat‐derived hormone adiponectin reversesinsulin resistance associated with both lipoatrophy and obesity. Nat Med 2001;7:941‐946.
[89]Ran J, Hirano T, Fukui T, et al. Angiotensin II infusion decreases plasma adiponectinlevel via its type 1 receptor in rats: an implication for hypertension‐related insulinresistance. Metabolism 2006;55:478‐488.
[90]Chu NF, Spiegelman D, Hotamisligil GS, et al. Plasma insulin, leptin, and solubleTNF receptors levels in relation to obesity‐related atherogenic and thrombogeniccardiovascular disease risk factors among men. Atherosclerosis 2001;157:495‐503.
[91]Tilg H, Moschen A R. Insulin resistance, inflammation, and non‐alcoholic fatty liverdisease. Trends Endocrinol Metab 2008;19:371‐379.
[92]Berg A H, Combs T P, Du X, et al. The adipocyte‐secreted protein Acrp30 enhanceshepatic insulin action. Nat Med 2001;7:947‐953.
[93]Kershaw E E, Flier J S. Adipose tissue as an endocrine organ. J Clin EndocrinolMetab 2004;89:2548‐2556.
[94]Hotta K, Funahashi T, Arita Y, et al. Plasma concentrations of a novel,adipose‐specific protein, adiponectin, in type 2 diabetic patients. Arterioscler Thromb VascBiol 2000;20:1595‐1599.
[95]Hotta K, Funahashi T, Bodkin N L, et al. Circulating concentrations of the adipocyteprotein adiponectin are decreased in parallel with reduced insulin sensitivity during theprogression to type 2 diabetes in rhesus monkeys. Diabetes 2001;50:1126‐1133.
[96]Weyer C, Funahashi T, Tanaka S, et al. Hypoadiponectinemia in obesity and type 2diabetes: close association with insulin resistance and hyperinsulinemia. J Clin EndocrinolMetab 2001;86:1930‐1935.
[97] Maeda N, Shimomura I, Kishida K, et al. Diet‐induced insulin resistance in micelacking adiponectin/ACRP30. Nat Med 2002;8:731‐737.
[98] Fasshauer M, Kralisch S, Klier M, et al. Adiponectin gene expression and secretionis inhibited by interleukin‐6 in 3T3‐L1 adipocytes. Biochem Biophys Res Commun 2003;301:1045‐1050.
[99]Ouchi N, Kihar S, Arita Y, et al. Novel modulator for endothelial adhesionmolecules: adipocyte‐derived plasma protein adiponectin. Circulation 1999;100:2473‐2476.
[100]Yokota T, Oritani K, Takahashi I, et al. Adiponectin, a new member of the family ofsoluble defense collagens, negatively regulates the growth of myelomonocytic progenitorsand the functions of macrophages. Blood 2000;96:1723‐1732.
[101]La Cava A, Matarese G. The weight of leptin in immunity. Nat Rev Immunol2004;4:371‐379.
[102]Friedman J M, Halaas J L. Leptin and the regulation of body weight in mammals.Nature 1998;395:763‐770.
[103]Mandel M A, Mahmoud A A. Impairment of cell‐mediated immunity in mutationdiabetic mice (db/db). J Immunol 1978;120:1375‐1377.
[104]Halaas J L, Gajiwala KS, Maffei M, et al. Weight‐reducing effects of the plasmaprotein encoded by the obese gene. Science 1995;269:543‐546.
[105]Montague C T, Prins J B, Sanders L, et al. Depot‐related gene expression in humansubcutaneous and omental adipocytes. Diabetes 1998;47:1384‐1391.
[106]Clement K, Vaisse C, Lahlou N, et al. A mutation in the human leptin receptorgene causes obesity and pituitary dysfunction. Nature 1998;392:398‐401.
[107]Farooqi I S, Jebb S A, Langmack G, et al. Effects of recombinant leptin therapy ina child with congenital leptin deficiency. N Engl J Med 1999;341:879‐884.
[108]Muzzin P, Eisensmith R C, Copeland K C, et al. Correction of obesity and diabetesin genetically obese mice by leptin gene therapy. Proc Natl Acad Sci USA 1996;93:14804‐14808.
[109]Gainsford T, Willson T A, Metcalf D, et al. Leptin can induce proliferation,differentiation, and functional activation of hemopoietic cells. Proc Natl Acad Sci USA1996;93:14564‐14568.
[110]Otto T C, Lane M D. Adipose development: from stem cell to adipocyte. Crit RevBiochem Mol Biol 2005;40:229‐242.
[111]Weisber S P, McCann D, Desai M, et al. Obesity is associated with macrophageaccumulation in adipose tissue. J Clin Invest 2003;112: 1796‐1808.
[112]Xu H, Barnes G T, Yang Q, et al. Chronic inflammation in fat plays a crucial role inthe development of obesity‐related insulin resistance. J Clin Invest 2003;112:1821‐1830.
[113]Jiao P, Chen Q, Shah S, et al. Obesity‐related upregulation of monocytechemotactic factors in adipocytes: involvement of nuclear factor‐kappaB and c‐JunNH2‐terminal kinase pathways. Diabetes 2009;58:104‐115.
[114]Kamei N, Tobe K, Suzuki R, et al. Overexpression of monocyte chemoattractantprotein‐1 in adipose tissues causes macrophage recruitment and insulin resistance. J BiolChem 2006;281:26602‐26614.
[115]Kanda H, Tateya S, Tamori Y, et al. MCP‐1 contributes to macrophage infiltrationinto adipose tissue, insulin resistance, and hepatic steatosis in obesity. J Clin Invest2006;116:1494‐1505.
[116]Suganami T, Nishida J, Ogawa Y. A paracrine loop between adipocytes andmacrophages aggravates inflammatory changes: role of free fatty acids and tumor necrosisfactor alpha. Arterioscler Thromb Vasc Biol 2005;25:2062‐2068.
[117]Suganami T, Tanimoto‐Koyama K, Nishida J, et al. Role of the Toll‐like receptor4/NF‐kappaB pathway in saturated fatty acid‐induced inflammatory changes in theinteraction between adipocytes and macrophages. Arterioscler Thromb Vasc Biol 2007;27:84‐91.
[118]Permana P A, Menge C, Reaven P D. Macrophage‐secreted factors induceadipocyte inflammation and insulin resistance. Biochem Biophys Res Commun 2006;341:507‐514.
[119]Ruan H, Hacohen N, Golub TR, et al. Tumor necrosis factor‐alpha suppressesadipocyte‐specific genes and activates expression of preadipocyte genes in 3T3‐L1adipocytes: nuclear factor‐kappaB activation by TNF‐alpha is obligatory. Diabetes2002;51:1319‐1336.
[120]Hajer G R, van Haeften T W, Visseren F L. Adipose tissue dysfunction in obesity,diabetes, and vascular diseases. Eur Heart J 2008;29:2959‐2971.
[121]Schenk S, Saberi M, Olefsky J M. Insulin sensitivity: modulation by nutrients andinflammation. J Clin Invest 2008;118:2992‐3002.
[122]Kahn B B, Flier J S. Obesity and insulin resistance. J Clin Invest 2000;106:473‐481.
[123]Rebrin K, Steil G M, Mittelman S D, et al. Causal linkage between insulinsuppression of lipolysis and suppression of liver glucose output in dogs. J Clin Invest 1996;98:741‐749
[124]Kelley D E, Mokan M, Simoneau J A, et al. Interaction between glucose and freefatty acid metabolism in human skeletal muscle. J Clin Invest 1993;92:91‐98.
[125]Lewis G F, Uffelman K D, Szeto L W, et al. Interaction between free fatty acids andinsulin in the acute control of very low density lipoprotein production in humans. J ClinInvest 1995;95:158‐166.
[126]Zhao T, Hou M, Xia M, et al. Globular adiponectin decreases leptin‐inducedtumor necrosis factor‐alpha expression by murine macrophages: involvement of cAMP‐PKAand MAPK pathways. Cell Immunol 2005;238:19‐30.
[127]Boden G. Obesity and free fatty acids. Endocrinol Metab Clin North Am2008;37:635‐646, viii‐ix.
[128]Itani S I, Ruderman N B, Schmieder F, et al. Lipid‐induced insulin resistance inhuman muscle is associated with changes in diacylglycerol, protein kinase C, andIkappaB‐alpha. Diabetes 2002;51:2005‐2011.
[129]Dey D, Mukherjee M, Basu D, et al. Inhibition of insulin receptor gene expressionand insulin signaling by fatty acid: interplay of PKC isoforms therein. Cell Physiol Biochem2005;16:217‐228.
[130]Jove M, Planavila A, Sanchez R M, et al. Palmitate induces tumor necrosisfactor‐alpha expression in C2C12 skeletal muscle cells by a mechanism involving proteinkinase C and nuclear factor‐kappaB activation. Endocrinology 2006;147:552‐561.
[131]Krebs M, Roden M. Molecular mechanisms of lipid‐induced insulin resistance inmuscle, liver and vasculature. Diabetes Obes Metab 2005;7:621‐632.
[132]Roden M. How free fatty acids inhibit glucose utilization in human skeletalmuscle. News Physiol Sci 2004;19:92‐96.
[133]Schmitz‐Peiffer C, Browne C L, Oakes N D, et al. Alterations in the expression andcellular localization of protein kinase C isozymes epsilon and theta are associated withinsulin resistance in skeletal muscle of the high‐fat‐fed rat. Diabetes 1997;46:169‐178.
[134]Shulman G I. Cellular mechanisms of insulin resistance. J Clin Invest 2000;106:171‐176.
[135]Talukdar I, Szeszel‐Fedorowicz W, Salati L M. Arachidonic acid inhibits the insulininduction of glucose‐6‐phosphate dehydrogenase via p38 MAP kinase. J Biol Chem 2005;280:40660‐40667.
[136]Lobo S, Bernlohr D A. Fatty acid transport in adipocytes and the development ofinsulin resistance. Novartis Found Symp 2007;286:113‐121; discussion 121‐116, 162‐113,196‐203.
[137]Nguyen M T, Satoh H, Favelyukis S, et al. JNK and tumor necrosis factor‐alphamediate free fatty acid‐induced insulin resistance in 3T3‐L1 adipocytes. J Biol Chem 2005;280:35361‐35371.
[138]Van Epps‐Fung M, Williford J, Wells A, et al. Fatty acid‐induced insulin resistancein adipocytes. Endocrinology 1997;138:4338‐4345.
[139]Yi P, Lu F E, Chen G. [Molecular mechanism of berberine in improving insulinresistance induced by free fatty acid through inhibiting nuclear trascription factor‐kappaBp65 in 3T3‐L1 adipocytes]. Zhongguo Zhong Xi Yi Jie He Za Zhi 2007;27:1099‐1104.
[140]Dey D, Pal B C, Biswas T, et al. A Lupinoside prevented fatty acid inducedinhibition of insulin sensitivity in 3T3 L1 adipocytes. Mol Cell Biochem 2007;300:149‐157.
[141]Dobson C M. Protein folding and misfolding. Nature 2003;426:884‐890.
[142]Ellgaard L, Helenius A. ER quality control: towards an understanding at themolecular level. Curr Opin Cell Biol 2001;13:431‐437.
[143]Araki E, Oyadomari S, Mori M. Endoplasmic reticulum stress and diabetesmellitus. Intern Med 2003;42:7‐14.
[144]Zhang K, Kaufman R J. The unfolded protein response: a stress signaling pathwaycritical for health and disease. Neurology 2006;66:S102‐109.
[145]Mori K. Tripartite management of unfolded proteins in the endoplasmicreticulum. Cell 2000;101:451‐454.
[146]Ron D, Walter P. Signal integration in the endoplasmic reticulum unfolded proteinresponse. Nat Rev Mol Cell Biol 2007;8:519‐529.
[147]Schroder M, Kaufman R J. The mammalian unfolded protein response. Annu RevBiochem 2005;74:739‐789.
[148]Schroder M, Kaufman R J. ER stress and the unfolded protein response. MutatRes 2005;569:29‐63.
[149]Sundar Rajan S, Srinivasan V, Balasubramanyam M, et al. Endoplasmic reticulum(ER) stress & diabetes. Indian J Med Res 2007;125:411‐424.
[150]Xu C, Bailly‐Maitre B, Reed J C. Endoplasmic reticulum stress: cell life and deathdecisions. J Clin Invest 2005;115:2656‐2664.
[151]Christis C, Lubsen N H, Braakman I. Protein folding includes oligomerizationexamplesfrom the endoplasmic reticulum and cytosol. FEBS J 2008;275:4700‐4727.
[152]Zhang K, Kaufman R J. From endoplasmic‐reticulum stress to the inflammatoryresponse. Nature 2008;454:455‐462.
[153]Bertolotti A, Zhang Y, Hendershot L M, et al. Dynamic interaction of BiP and ERstress transducers in the unfolded‐protein response. Nat Cell Biol 2000;2:326‐332.
[154]Shen J, Chen X, Hendershot L, et al. ER stress regulation of ATF6 localization bydissociation of BiP/GRP78 binding and unmasking of Golgi localization signals. Dev Cell2002;3:99‐111.
[155]Szegezdi E, Logue S E, Gorman A M, et al. Mediators of endoplasmic reticulumstress‐induced apoptosis. EMBO Rep 2006;7:880‐885.
[156]Harding H P, Zhang Y, Bertolotti A, et al. Perk is essential for translationalregulation and cell survival during the unfolded protein response. Mol Cell 2000;5:897‐904.
[157]Wang X Z, Harding H P, Zhang Y, et al. Cloning of mammalian Ire1 reveals diversityin the ER stress responses. EMBO J 1998;17:5708‐5717.
[158]Ozcan U, Cao Q, Yilmaz E, et al. Endoplasmic reticulum stress links obesity, insulinaction, and type 2 diabetes. Science 2004;306:457‐461.
[159]Urano F, Wang X, Bertolotti A, et al. Coupling of stress in the ER to activation ofJNK protein kinases by transmembrane protein kinase IRE1. Science 2000;287:664‐666.
[160]Harding H P, Zeng H, Zhang Y, et al. Diabetes mellitus and exocrine pancreaticdysfunction in perk‐/‐ mice reveals a role for translational control in secretory cell survival.Mol Cell 2001;7:1153‐1163.
[161]Zhang P, McGrath B, Li S, et al. The PERK eukaryotic initiation factor 2 alphakinase is required for the development of the skeletal system, postnatal growth, and thefunction and viability of the pancreas. Mol Cell Biol 2002;22:3864‐3874.
[162]Gregor M F, Yang L, Fabbrini E, et al. Endoplasmic reticulum stress is reduced intissues of obese subjects after weight loss. Diabetes 2009;58:693‐700.
[163]Mulhern M L, Madson C J, Kador P F, et al. Cellular osmolytes reduce lensepithelial cell death and alleviate cataract formation in galactosemic rats. Mol Vis2007;13:1397‐1405.
[164]Ozcan U, Yilmaz E, Ozcan L, et al. Chemical chaperones reduce ER stress andrestore glucose homeostasis in a mouse model of type 2 diabetes. Science2006;313:1137‐1140.
[165]Gregor M F, Hotamisligil G S. Thematic review series: Adipocyte Biology.Adipocyte stress: the endoplasmic reticulum and metabolic disease. J Lipid Res 2007;48:1905‐1914.
[166]Ross S A, Song X, Burney M W, et al. Efficient adenovirus transduction of 3T3‐L1adipocytes stably expressing coxsackie‐adenovirus receptor. Biochem Biophys Res Commun2003;302:354‐358.
[167]Orlicky D J, DeGregori J, Schaack J. Construction of stable coxsackievirus andadenovirus receptor‐expressing 3T3‐L1 cells. J Lipid Res 2001;42:910‐915.
[168]Sabio G, Das M, Mora A, et al. A stress signaling pathway in adipose tissueregulates hepatic insulin resistance. Science 2008;322:1539‐1543.
[169]Ntambi J M. Regulation of stearoyl‐CoA desaturase by polyunsaturated fattyacids and cholesterol. J Lipid Res 1999;40:1549‐1558.
[170]Ntambi J M, Miyazaki M, Dobrzyn A. Regulation of stearoyl‐CoA desaturaseexpression. Lipids 2004;39:1061‐1065.
[171]Swierczynski J, Goyke E, Korczynska J,et al. Acetyl‐CoA carboxylase and fatty acidsynthase activities in human hypothalamus. Neurosci Lett 2008;444:209‐211.
[172]Coleman R A, Lee D P. Enzymes of triacylglycerol synthesis and their regulation.Prog Lipid Res 2004;43:134‐176.
[173]Gimeno R E, Cao J. Thematic review series: glycerolipids. Mammalian glycerol‐3‐phosphate acyltransferases: new genes for an old activity. J Lipid Res 2008;49:2079‐2088.
[174]Yen C L, Stone S J, Koliwad S, et al. Thematic review series: glycerolipids. DGATenzymes and triacylglycerol biosynthesis. J Lipid Res 2008;49:2283‐2301.
[175]Watt M J, Steinberg G R. Regulation and function of triacylglycerol lipases incellular metabolism. Biochem J 2008;414:313‐325.
[176]Egan J J, Greenberg A S, Chang M K, et al. Control of endogenousphosphorylation of the major cAMP‐dependent protein kinase substrate in adipocytes byinsulin and beta‐adrenergic stimulation. J Biol Chem 1990;265:18769‐18775.
[177]Faber B C, Cleutjens K B, Niessen R L, et al. Identification of genes potentiallyinvolved in rupture of human atherosclerotic plaques. Circ Res 2001;89:547‐554.
[178]Greenberg A S, Egan J J, Wek SA, et al. Perilipin, a major hormonally regulatedadipocyte‐specific phosphoprotein associated with the periphery of lipid storage droplets. JBiol Chem 1991;266:11341‐11346.
[179]Greenberg A S, Egan J J, Wek S A, et al. Isolation of cDNAs for perilipins A and B:sequence and expression of lipid droplet‐associated proteins of adipocytes. Proc Natl AcadSci U S A 1993;90:12035‐12039.
[180]Tansey J T, Sztalryd C, Gruia‐Gray J, et al. Perilipin ablation results in a lean mousewith aberrant adipocyte lipolysis, enhanced leptin production, and resistance todiet‐induced obesity. Proc Natl Acad Sci U S A 2001;98:6494‐6499.
[181]Hill J O, Wyatt H R, Reed G W, et al. Obesity and the environment: where do wego from here? Science 2003;299:853‐855.
[182]Kopelman P G. Obesity as a medical problem. Nature 2000;404:635‐643.
[183]Hrnciar J, Gabor D, Hrnciarova M, et al. [Relation between cytokines (TNF‐alpha,IL‐1 and 6) and homocysteine in android obesity and the phenomenon of insulin resistancesyndromes]. Vnitr Lek 1999;45:11‐16.
[184]Sartipy P, Loskutoff D J. Monocyte chemoattractant protein 1 in obesity andinsulin resistance. Proc Natl Acad Sci U S A 2003;100:7265‐7270.
[185]Green A, Dobias S B, Walters D J, Brasier, AR. Tumor necrosis factor increases therate of lipolysis in primary cultures of adipocytes without altering levels ofhormone‐sensitive lipase. Endocrinology 1994;134:2581‐2588.
[186]Clement K, Viguerie N, Poitou C, et al. Weight loss regulatesinflammation‐related genes in white adipose tissue of obese subjects. FASEB J 2004;18:1657‐1669.
[187]Cancello R, Henegar C, Viguerie N, et al. Reduction of macrophage infiltrationand chemoattractant gene expression changes in white adipose tissue of morbidly obesesubjects after surgery‐induced weight loss. Diabetes 2005;54:2277‐2286.
[188]Ricote M, Li A C, Willson T M, et al. The peroxisome proliferator‐activatedreceptor‐gamma is a negative regulator of macrophage activation. Nature 1998;391:79‐82.
[189]Jiang C, Ting A T, Seed B. PPAR‐gamma agonists inhibit production of monocyteinflammatory cytokines. Nature 1998;391:82‐86.
[190]Marx N, Libby P, Plutzky J. Peroxisome proliferator‐activated receptors (PPARs)and their role in the vessel wall: possible mediators of cardiovascular risk? J Cardiovasc Risk2001;8:203‐210.
[191]Li A C, Brown K K, Silvestre M J, et al. Peroxisome proliferator‐activated receptorgamma ligands inhibit development of atherosclerosis in LDL receptor‐deficient mice. J ClinInvest 2000;106:523‐531.
[192]Ghanim H, Garg R, Aljada A, et al. Suppression of nuclear factor‐kappaB andstimulation of inhibitor kappaB by troglitazone: evidence for an anti‐inflammatory effectand a potential antiatherosclerotic effect in the obese. J Clin Endocrinol Metab2001;86:1306‐1312.
[193]Aljada A, Garg R, Ghanim H, et al. Nuclear factor‐kappaB suppressive andinhibitor‐kappaB stimulatory effects of troglitazone in obese patients with type 2 diabetes:evidence of an antiinflammatory action? J Clin Endocrinol Metab 2001;86:3250‐3256.
[194]Mohanty P, Aljada A, Ghanim H, et al. Evidence for a potent antiinflammatoryeffect of rosiglitazone. J Clin Endocrinol Metab 2004;89:2728‐2735.
[195]Xu H, Sethi J K, Hotamisligil G S. Transmembrane tumor necrosis factor(TNF)‐alpha inhibits adipocyte differentiation by selectively activating TNF receptor 1. J BiolChem 1999;274:26287‐26295.
[196]Vallerie S N, Furuhashi M, Fucho R, et al. A predominant role for parenchymalc‐Jun amino terminal kinase (JNK) in the regulation of systemic insulin sensitivity. PLoS ONE2008;3:e3151.
[197]Zhang X, Zhang G, Zhang H, et al. Hypothalamic IKKbeta/NF‐kappaB and ER stresslink overnutrition to energy imbalance and obesity. Cell 2008;135:61‐73.