Diabetes Metab J > Volume 40(4); 2016 > Article
Han: Roles of Reactive Oxygen Species on Insulin Resistance in Adipose Tissue

Abstract

Obesity resulting from the delivery of an excess amount of energy to adipose tissue from glucose or free fatty acids is associated with insulin resistance and adipose tissue inflammation. Reactive oxygen species (ROS) have been implicated as contributors to both the onset and the progression of insulin resistance. ROS can be generated by overloading the mitochondrial oxidative phosphorylation system, and also by nicotinamide adenine dinucleotide phosphate oxidases (NOX) produced by either adipocytes, which only produce NOX4, or by macrophages, which produce mainly NOX2. The source of the ROS might differ in the early, intermediate and late stages of obesity, switching from NOX4-dependence in the early phases to NOX2-dependence, in the intermediate phase, and transiting to mitochondria-dependence later in the time course of obesity. Thus, depending on the stage of obesity, ROS can be generated by three distinct mechanisms: i.e., NOX4, NOX2, and mitochondria. In this review, we will discuss whether NOX4-, NOX2-, and/or mitochondria-derived ROS is/are causal in the onset of adipocyte insulin resistance as obesity progresses. Moreover, we will review the pathophysiological roles of NOX4, NOX2, and mitochondria-derived ROS on adipose tissue inflammation.

INTRODUCTION

Many lines of evidence support the proposal that visceral obesity is strongly associated with features of the metabolic/insulin resistance syndrome, and that obesity predicts the development of both type 2 diabetes and cardiovascular disease (CVD) [1,2,3]. Obesity is associated with a chronic low-grade inflammation [4,5,6], as evidenced by an increase in circulating inflammatory markers, such as C-reactive protein, serum amyloid A (SAA), and interleukin 6 [7,8,9]. The presence of systemic inflammation in visceral obesity has been linked to an increased risk of developing CVD and type 2 diabetes [10,11,12]. Obesity results when there is an imbalance between energy ingested and energy expended [13]. A relative excess of energy (either genetic or diet-induced) results in two major cellular features; adipocyte expansion and infiltration of inflammatory cells into adipose tissue in both mice and humans [14,15,16]. Adipocytes and macrophages both generate inflammatory molecules, which lead to insulin resistance and systemic inflammation. Certain saturated free fatty acids (SFAs; laurate, myristate, and palmitate) increase inflammatory genes in adipocytes [17]. These events are associated with the generation of reactive oxygen species (ROS) and nuclear factor κB (NF-κB) transactivation. Excess glucose and/or certain SFAs increased ROS generation and NF-κB translocation [17]. Treatment with the antioxidants, N-acetyl cysteine, catalase and superoxide dismutase (SOD) repressed ROS generation and NF-κB translocation stimulated by excess glucose 4tate, and decreased inflammatory gene expression [17]. Thus, glucose- and palmitate-stimulated ROS generation appears to play an important role in adipocyte inflammation. Although several mechanisms such as endoplasmic reticulum (ER) stress, hypoxia, and adipocyte death have been reported to be related to adipocyte inflammation during obesity [18,19], ROS generation is upstream of ER stress and apoptosis of adipocyte occurs at later stages of obesity [18,20]. ROS is a key-modulator that activates the initial the sequence of events that leads to adipose tissue inflammation. The relative contribution of ROS derived from different sources in adipocytes during the progression of obesity remains unknown. Therefore, as a first step, our review has been chosen to focus on the role of various sources of ROS generated in adipose tissue on inflammation and insulin resistance.

ROS GENERATION AND OBESITY

Chronic ROS production has recently been suggested to be an important contributor to the pathogenesis of obesity-associated insulin resistance [21,22]. Physiologically, ROS is required for differentiation of adipocytes [23,24]. These physiological ROS exist for short time and are well regulated by insulin signaling. Our review focuses on the pathophysiological roles of ROS in adipocytes inflammation; i.e., the effects of prolonged ROS generation by excess nutrients and the effect of ROS unregulated by insulin signaling. ROS in visceral adipose tissue are significantly increased in genetically obese mice and mice made obese by consumption of a high-fat diet [25]. The direct relationship between ROS generation and obesity is still not entirely clear. ROS can be generated by adipocytes during metabolism of excess nutrients. ROS also can be generated by macrophages, which accumulate in adipose tissue in obesity. Therefore, it is important to understand the source of ROS during the progression of obesity. In the early insulin sensitive state, energy flux from nutrient excess flows into lipogenesis, in which excess glucose and free fatty acid (FFA) are used for triglyceride synthesis by adipocytes. In the insulin sensitive state, insulin activates the insulin receptor tyrosine kinase which leads to stimulation of insulin receptor substrate proteins and phosphatidylinositol 3-kinase (PI3-kinase) [26]. Next, PI3-kinase activates downstream protein kinases, including Akt/protein kinase B [26,27]. Consequently, these events increase intracellular glucose uptake into adipocytes via insulin-stimulated translocation of glucose transporter 4 molecules to the cell membrane [27]. In this state, FFA are stored as triglyceride by activating the production of proteins involved in lipid metabolism/uptake, including lipoprotein lipase, fatty acid transport protein, and acetyl CoA-synthase [28]. However, it is totally unknown whether these ROS casually trigger the insulin resistance, or are a casual bystander of insulin resistance in adipocytes. Thus, although much is known about energy flux in adipocytes during the progression of obesity, little is known as to whether this energy flux leads to differences in the generation of ROS in the early and late stages of obesity, nor is there a good understanding of the potential pathophysiological roles of ROS derived in these stages.

ROS AND NOX4 IN THE EARLY STAGES OF OBESITY

We previously have shown that excess glucose and palmitate are not metabolized to a major extent via mitochondrial oxidation. Instead excess nutrients activate nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) [29]. Members of the NOX family are membrane-bound enzyme complexes that transfer electrons from NADPH to oxygen, generating superoxide. This short lived, non-membrane permeable ROS is converted, to a longer lived membrane permeable ROS, hydrogen peroxide by SOD [30] or spontaneously. The NOX family has seven isoforms, NOX1, NOX2, NOX3, NOX4, NOX5, dual oxidase 1 (DUOX1), and DUOX2, which are strongly conserved in mammals and are widely expressed in various tissues [31]. NOX1 to 3 require additional cytosolic activators (p47phox, p67phox, NADPH oxidase organizer 1) whereas NOX4 is constitutively active and independent of an activator protein (AP) [31,32,33]. NOX5 and DUOX1/2 need intracellular calcium to activate ROS generation [34,35]. It is therefore assumed that NOX1 to 3 mediates short-term effects, while NOX4 is responsible for long term effects. We have found that NOX4 is the major NOX isoform in cultured murine and human adipocytes [29]. Moreover, silencing NOX4 decreased ROS generation stimulated by excess glucose as well as palmitate, leading to inhibition of monocyte chemoattractant protein-1 and SAA3 expression in vitro [29]. Thus, NOX4-derived ROS may be a common mediator induced by both excess glucose and palmitate in adipocytes (Fig. 1). Other studies showed that NOX4 activity increases in the adipose tissue with diet-induced obesity (DIO), and NOX inhibitor, apocynin treatment reduces ROS generation [25]. However, whether NOX4-derived ROS itself can promote the onset of insulin resistance in adipocytes during the progression of obesity is unknown and needs to be investigated.
The pentose phosphate pathway (PPP) generates NADPH and pentose from the 6 carbon glucose and is a major source of cellular NADPH. Glucose-6 phosphate dehydrogenase (G6PD) is the rate-limiting enzyme in the PPP. Recent studies indicate that G6PD expression is upregulated in adipose tissue in genetic and DIO, and that its overexpression is associated with increased adipocyte inflammation and ROS generation [36,37]. Other studies have shown that treatment with dehydroepiandrosterone (DHEA), a G6PD inhibitor, reduces obesity in Zucker diabetic fatty rats [38]. We found that NADPH content and PPP activity were increased by excess glucose, but not by palmitate in 3T3-L1 adipocytes [29]. Moreover, G6PD inhibitors, DHEA and 6-aminonicotinamide, or silencing G6PD all inhibited ROS generation and monocyte chemotactic factor gene expression by both high glucose and palmitate in 3T3-L1 adipocytes [29]. These studies support the concept that PPP and G6PD could be modulators or mediators of adipose tissue inflammation (Fig. 1). During the initial stage of energy access, we hypothesize that adipocytes will continue to actively store triglycerides derived from excess nutrients, and will demonstrate increased PPP activity and NADPH content, which lead to NOX4-derived ROS generation (Fig. 1).
However, whole body NOX4 deficiency has been reported to worsen adipose tissue inflammation in a model of DIO in mice [39]. Since NOX4 activity is essential for pre-adipocyte differentiation to adipocytes [23], blunted adipogenesis in the absence of NOX4 would reduce the number of adipocytes, allowing the remaining adipocytes to become more hypertrophic, thereby leading to adipose tissue inflammation. Indeed, expression of adipogenesis genes (peroxisome proliferator-activated receptor γ [PPARγ] and CCAAT-enhancer-binding protein α [C/EBPα]) was inhibited in whole body NOX4 knockout mice [39]. Therefore, it is imperative to investigate the alteration of NOX4 activity in mice during the pathophysiological progression of obesity where adipogenesis is intact, and to study the effect of adipocyte-specific deficiency of NOX4.

ROS AND NOX2 IN THE INTERMEDIATE STAGES OF OBESITY

Another potentially important source of ROS in obesity is from macrophages that are recruited and accumulate in obese adipose tissue. Obesity provokes changes in T-cell subsets and increases the infiltration and accumulation of activated macrophages in adipose tissue [40,41,42]. These recruited and activated immune cells can promote the generation of ROS by NOX2, which is predominately expressed activated in T-cells and macrophages [43]. Immune cells in the inflammatory environment created by obesity could generate NOX2-derived ROS. Whole body deficiency of NOX2 shows attenuation of adipose tissue inflammation and insulin resistance in mice fed a high fat diet [44]. This implies that NOX2 from immune cells may play a role in adipose tissue inflammation in the intermediate stages of obesity. However, whether these NOX2-dervied ROS itself has effects in adipose tissue inflammation and can promote the onset of insulin resistance in adipocytes during the progression of obesity is unknown and needs to be investigated.

ROS AND MITOCHONDRIA IN THE LATE STAGES OF OBESITY

The mitochondrial electron transport chain is a primary site for ROS production. ROS generation is accelerated when the flow of electrons through the electron transport chain is overload, resulting in leakage of electrons. Overloaded mitochondria mainly produce superoxide, which can signal intracellularly, leading to a pro-inflammatory signaling cascade that includes NF-κB and AP-1 activation [45,46]. Although glucose excess presumably drives the overflow of electrons in mitochondria, other energy sources in adipocytes are preferred in the late stages of obesity since uptake of glucose is limited by the insulin resistance of adipocytes. When glucose consumption is reduced by insulin resistance, adipocytes start to use FFA from triglyceride stores for energy (Fig. 2). This alteration of energy flux into β-oxidation could overwhelm the capacity of mitochondria, leading to leakage of electrons (Fig. 2).
When pro-inflammatory macrophages accumulate in adipose tissue as a result of the NOX4-mediated generation of macrophage chemoattractants by adipocytes, the inflammatory environment induced by these macrophages will be expected to result in adipocyte insulin resistance [47]. With the advent of sufficient insulin resistance, adipocytes will stop storing additional triglycerides, will utilize stored fatty acids from triglycerides, and will show evidence of decreased PPP activity and NADPH content. At such times, adipocyte-derived NOX4 might have a limited role in ROS generation and adipose tissue inflammation. Instead, mitochondria will now take the place of NOX4 and play a pivotal role in ROS generation and adipose tissue inflammation (Fig. 2). In support of this hypothesis are studies that show the production of pro-inflammatory cytokines and macrophage chemoattractants by adipocytes at an early time point (1 week), while adipose tissue insulin resistance occurs much later (after 14 weeks) during the development of DIO in mice [48,49]. These studies also show that even though some infiltration of macrophages occur at early time points, massive infiltration of macrophage happens much later (after 12 weeks) [49]. Thus, these studies strongly suggest that adipocytes become insulin resistant during the later stages of obesity, while adipocytes are insulin sensitive during the early stages of obesity. Recent studies also have reported that fasting and caloric restriction in mice in which insulin signaling is disturbed and β-oxidation of FFA is increased in adipocytes, results in the generation of chemoattractants and an increase of macrophage accumulation in adipose tissue [50,51]. These studies support that mitochondria and β-oxidation of fatty acids might lead to ROS generation. Therefore, we hypothesize that mitochondria-derived ROS accounts for massive macrophage accumulation, worsening insulin resistance and systemic inflammation during the late stages of obesity (Fig. 2). Also, we hypothesize that a temporal transition of the source of ROS between NOX4 and mitochondria as obesity progresses is responsible for conversion to a more insulin resistant phase of obesity.

CONCLUSIONS

An overall role of distinct sources of ROS for adipose tissue inflammation is that (1) in the early stages of obesity, NOX4-derived ROS from adipocytes provoke the onset of insulin resistance and initiates the recruitment of immune cells in adipose tissue, (2) in the intermediate stages of obesity, NOX2-derived ROS from infiltrated immune cells worsens adipocyte insulin resistance and adipose tissue inflammation, and (3) in the late stages of obesity, mitochondria-derived ROS from adipocytes maintain the adipose tissue inflammation and insulin resistance. We summarize how these three distinct sources of ROS might affect adipocyte insulin resistance and adipose tissue inflammation in the early, intermediate, and late stages of obesity (Fig. 3).
Several large clinical trials have failed to show any beneficial effects of consumption of antioxidant supplements in the prevention of insulin resistance [52,53,54,55]. Nevertheless, from studies in obese mice there is increasing evidence that antioxidant might be beneficial in attenuating insulin resistance and restoring insulin signaling. For example, the antioxidant manganese tetrakis porphyrin and the cell permeable small-peptide antioxidant SS31 (D-Arg-2',6'-dimethyltyrosine-Lys-Phe-NH2) improve insulin sensitivity without altering body weight in a genetic and DIO mice [43,56]. Moreover, transgenic mice overexpressing SOD2 exhibit improvements in glucose tolerance and insulin sensitivity resulting from consumption of a high fat diet [57]. A discrepancy between basic research and clinical studies may be due to the fact that we have yet to address the importance of the timing of ROS generation, the source of ROS, and tissue specific effects of ROS. Findings out these discrepancies would be likely to have important translational implications related to the development of antioxidants targeting NOX4- or mitochondria-derived ROS in different stages of obesity.

ACKNOWLEDGMENTS

This work was supported in part by National Institutes of Health grants HL092969, 094352, DK-035816, and a Beginning Grant-in-Aid from the American Heart Association.

NOTES

CONFLICTS OF INTEREST: No potential conflict of interest relevant to this article was reported.

REFERENCES

1. Janssen I, Katzmarzyk PT, Ross R. Body mass index, waist circumference, and health risk: evidence in support of current National Institutes of Health guidelines. Arch Intern Med 2002;162:2074-2079.
crossref pmid
2. Hubert HB, Feinleib M, McNamara PM, Castelli WP. Obesity as an independent risk factor for cardiovascular disease: a 26-year follow-up of participants in the Framingham Heart Study. Circulation 1983;67:968-977.
crossref pmid
3. Wang CC, Goalstone ML, Draznin B. Molecular mechanisms of insulin resistance that impact cardiovascular biology. Diabetes 2004;53:2735-2740.
crossref pmid
4. Bulló M, Garcia-Lorda P, Megias I, Salas-Salvado J. Systemic inflammation, adipose tissue tumor necrosis factor, and leptin expression. Obes Res 2003;11:525-531.
crossref
5. Maachi M, Pieroni L, Bruckert E, Jardel C, Fellahi S, Hainque B, Capeau J, Bastard JP. Systemic low-grade inflammation is related to both circulating and adipose tissue TNFalpha, leptin and IL-6 levels in obese women. Int J Obes Relat Metab Disord 2004;28:993-997.
crossref pmid
6. Cancello R, Clement K. Is obesity an inflammatory illness? Role of low-grade inflammation and macrophage infiltration in human white adipose tissue. BJOG 2006;113:1141-1147.
crossref
7. Ouchi N, Kihara S, Funahashi T, Nakamura T, Nishida M, Kumada M, Okamoto Y, Ohashi K, Nagaretani H, Kishida K, Nishizawa H, Maeda N, Kobayashi H, Hiraoka H, Matsuzawa Y. Reciprocal association of C-reactive protein with adiponectin in blood stream and adipose tissue. Circulation 2003;107:671-674.
crossref
8. Poitou C, Viguerie N, Cancello R, De Matteis R, Cinti S, Stich V, Coussieu C, Gauthier E, Courtine M, Zucker JD, Barsh GS, Saris W, Bruneval P, Basdevant A, Langin D, Clement K. Serum amyloid A: production by human white adipocyte and regulation by obesity and nutrition. Diabetologia 2005;48:519-528.
crossref
9. Fried SK, Bunkin DA, Greenberg AS. Omental and subcutaneous adipose tissues of obese subjects release interleukin-6: depot difference and regulation by glucocorticoid. J Clin Endocrinol Metab 1998;83:847-850.
crossref pmid
10. Lebovitz HE. Insulin resistance: a common link between type 2 diabetes and cardiovascular disease. Diabetes Obes Metab 2006;8:237-249.
crossref
11. Sowers JR. Obesity as a cardiovascular risk factor. Am J Med 2003;115(Suppl 8A):37S-41S.
crossref
12. Bray GA. Risks of obesity. Endocrinol Metab Clin North Am 2003;32:787-804.
crossref
13. Bray GA, Paeratakul S, Popkin BM. Dietary fat and obesity: a review of animal, clinical and epidemiological studies. Physiol Behav 2004;83:549-555.
crossref pmid
14. Wellen KE, Hotamisligil GS. Obesity-induced inflammatory changes in adipose tissue. J Clin Invest 2003;112:1785-1788.
crossref
15. Xu H, Barnes GT, Yang Q, Tan G, Yang D, Chou CJ, Sole J, Nichols A, Ross JS, Tartaglia LA, Chen H. Chronic inflammation in fat plays a crucial role in the development of obesity-related insulin resistance. J Clin Invest 2003;112:1821-1830.
crossref
16. Weisberg SP, McCann D, Desai M, Rosenbaum M, Leibel RL, Ferrante AW Jr. Obesity is associated with macrophage accumulation in adipose tissue. J Clin Invest 2003;112:1796-1808.
crossref pmid pmc
17. Yeop Han C, Kargi AY, Omer M, Chan CK, Wabitsch M, O'Brien KD, Wight TN, Chait A. Differential effect of saturated and unsaturated free fatty acids on the generation of monocyte adhesion and chemotactic factors by adipocytes: dissociation of adipocyte hypertrophy from inflammation. Diabetes 2010;59:386-396.
crossref
18. Strissel KJ, Stancheva Z, Miyoshi H, Perfield JW 2nd, DeFuria J, Jick Z, Greenberg AS, Obin MS. Adipocyte death, adipose tissue remodeling, and obesity complications. Diabetes 2007;56:2910-2918.
crossref
19. Gregor MF, Hotamisligil GS. Thematic review series: adipocyte biology. Adipocyte stress: the endoplasmic reticulum and metabolic disease. J Lipid Res 2007;48:1905-1914.
crossref
20. Kawasaki N, Asada R, Saito A, Kanemoto S, Imaizumi K. Obesity-induced endoplasmic reticulum stress causes chronic inflammation in adipose tissue. Sci Rep 2012;2:799
crossref
21. Houstis N, Rosen ED, Lander ES. Reactive oxygen species have a causal role in multiple forms of insulin resistance. Nature 2006;440:944-948.
crossref
22. Evans JL, Goldfine ID, Maddux BA, Grodsky GM. Oxidative stress and stress-activated signaling pathways: a unifying hypothesis of type 2 diabetes. Endocr Rev 2002;23:599-622.
crossref pmid
23. Schröder K, Wandzioch K, Helmcke I, Brandes RP. Nox4 acts as a switch between differentiation and proliferation in preadipocytes. Arterioscler Thromb Vasc Biol 2009;29:239-245.
crossref pmid
24. Tormos KV, Anso E, Hamanaka RB, Eisenbart J, Joseph J, Kalyanaraman B, Chandel NS. Mitochondrial complex III ROS regulate adipocyte differentiation. Cell Metab 2011;14:537-544.
crossref pmid pmc
25. Furukawa S, Fujita T, Shimabukuro M, Iwaki M, Yamada Y, Nakajima Y, Nakayama O, Makishima M, Matsuda M, Shimomura I. Increased oxidative stress in obesity and its impact on metabolic syndrome. J Clin Invest 2004;114:1752-1761.
crossref pmid pmc
26. Kahn BB, Flier JS. Obesity and insulin resistance. J Clin Invest 2000;106:473-481.
crossref pmid pmc
27. Summers SA, Whiteman EL, Birnbaum MJ. Insulin signaling in the adipocyte. Int J Obes Relat Metab Disord 2000;24(Suppl 4):S67-S70.
crossref
28. Smith U, Axelsen M, Carvalho E, Eliasson B, Jansson PA, Wesslau C. Insulin signaling and action in fat cells: associations with insulin resistance and type 2 diabetes. Ann N Y Acad Sci 1999;892:119-126.
crossref pmid
29. Han CY, Umemoto T, Omer M, Den Hartigh LJ, Chiba T, LeBoeuf R, Buller CL, Sweet IR, Pennathur S, Abel ED, Chait A. NADPH oxidase-derived reactive oxygen species increases expression of monocyte chemotactic factor genes in cultured adipocytes. J Biol Chem 2012;287:10379-10393.
crossref pmid pmc
30. Bedard K, Krause KH. The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology. Physiol Rev 2007;87:245-313.
crossref pmid
31. Kawahara T, Quinn MT, Lambeth JD. Molecular evolution of the reactive oxygen-generating NADPH oxidase (Nox/Duox) family of enzymes. BMC Evol Biol 2007;7:109
crossref pmid pmc
32. Martyn KD, Frederick LM, von Loehneysen K, Dinauer MC, Knaus UG. Functional analysis of Nox4 reveals unique characteristics compared to other NADPH oxidases. Cell Signal 2006;18:69-82.
crossref pmid
33. Ambasta RK, Kumar P, Griendling KK, Schmidt HH, Busse R, Brandes RP. Direct interaction of the novel Nox proteins with p22phox is required for the formation of a functionally active NADPH oxidase. J Biol Chem 2004;279:45935-45941.
crossref pmid
34. Bánfi B, Molnar G, Maturana A, Steger K, Hegedus B, Demaurex N, Krause KH. A Ca(2+)-activated NADPH oxidase in testis, spleen, and lymph nodes. J Biol Chem 2001;276:37594-37601.
crossref pmid
35. Dupuy C, Ohayon R, Valent A, Noel-Hudson MS, Deme D, Virion A. Purification of a novel flavoprotein involved in the thyroid NADPH oxidase. Cloning of the porcine and human cdnas. J Biol Chem 1999;274:37265-37269.
crossref pmid
36. Park J, Rho HK, Kim KH, Choe SS, Lee YS, Kim JB. Overexpression of glucose-6-phosphate dehydrogenase is associated with lipid dysregulation and insulin resistance in obesity. Mol Cell Biol 2005;25:5146-5157.
crossref pmid pmc
37. Park J, Choe SS, Choi AH, Kim KH, Yoon MJ, Suganami T, Ogawa Y, Kim JB. Increase in glucose-6-phosphate dehydrogenase in adipocytes stimulates oxidative stress and inflammatory signals. Diabetes 2006;55:2939-2949.
crossref pmid
38. Cleary MP, Zisk JF. Anti-obesity effect of two different levels of dehydroepiandrosterone in lean and obese middle-aged female Zucker rats. Int J Obes 1986;10:193-204.
pmid
39. Li Y, Mouche S, Sajic T, Veyrat-Durebex C, Supale R, Pierroz D, Ferrari S, Negro F, Hasler U, Feraille E, Moll S, Meda P, Deffert C, Montet X, Krause KH, Szanto I. Deficiency in the NADPH oxidase 4 predisposes towards diet-induced obesity. Int J Obes (Lond) 2012;36:1503-1513.
crossref
40. Nishimura S, Manabe I, Nagasaki M, Eto K, Yamashita H, Ohsugi M, Otsu M, Hara K, Ueki K, Sugiura S, Yoshimura K, Kadowaki T, Nagai R. CD8+ effector T cells contribute to macrophage recruitment and adipose tissue inflammation in obesity. Nat Med 2009;15:914-920.
crossref
41. Olefsky JM, Glass CK. Macrophages, inflammation, and insulin resistance. Annu Rev Physiol 2010;72:219-246.
crossref pmid
42. Hotamisligil GS. Inflammation and metabolic disorders. Nature 2006;444:860-867.
crossref pmid
43. Dang PM, Stensballe A, Boussetta T, Raad H, Dewas C, Kroviarski Y, Hayem G, Jensen ON, Gougerot-Pocidalo MA, El-Benna J. A specific p47phox -serine phosphorylated by convergent MAPKs mediates neutrophil NADPH oxidase priming at inflammatory sites. J Clin Invest 2006;116:2033-2043.
crossref pmid pmc
44. Pepping JK, Freeman LR, Gupta S, Keller JN, Bruce-Keller AJ. NOX2 deficiency attenuates markers of adiposopathy and brain injury induced by high-fat diet. Am J Physiol Endocrinol Metab 2013;304:E392-E404.
crossref pmid
45. Kaul N, Forman HJ. Activation of NF kappa B by the respiratory burst of macrophages. Free Radic Biol Med 1996;21:401-405.
crossref pmid
46. Iles KE, Dickinson DA, Watanabe N, Iwamoto T, Forman HJ. AP-1 activation through endogenous H(2)O(2) generation by alveolar macrophages. Free Radic Biol Med 2002;32:1304-1313.
crossref pmid
47. Suganami T, Ogawa Y. Adipose tissue macrophages: their role in adipose tissue remodeling. J Leukoc Biol 2010;88:33-39.
crossref pmid
48. Kim F, Pham M, Maloney E, Rizzo NO, Morton GJ, Wisse BE, Kirk EA, Chait A, Schwartz MW. Vascular inflammation, insulin resistance, and reduced nitric oxide production precede the onset of peripheral insulin resistance. Arterioscler Thromb Vasc Biol 2008;28:1982-1988.
crossref pmid pmc
49. Lee YS, Li P, Huh JY, Hwang IJ, Lu M, Kim JI, Ham M, Talukdar S, Chen A, Lu WJ, Bandyopadhyay GK, Schwendener R, Olefsky J, Kim JB. Inflammation is necessary for long-term but not short-term high-fat diet-induced insulin resistance. Diabetes 2011;60:2474-2483.
crossref
50. Kosteli A, Sugaru E, Haemmerle G, Martin JF, Lei J, Zechner R, Ferrante AW Jr. Weight loss and lipolysis promote a dynamic immune response in murine adipose tissue. J Clin Invest 2010;120:3466-3479.
crossref pmid pmc
51. Edgel KA, McMillen TS, Wei H, Pamir N, Houston BA, Caldwell MT, Mai PO, Oram JF, Tang C, Leboeuf RC. Obesity and weight loss result in increased adipose tissue ABCG1 expression in db/db mice. Biochim Biophys Acta 2012;1821:425-434.
crossref pmid
52. Kataja-Tuomola M, Sundell JR, Mannisto S, Virtanen MJ, Kontto J, Albanes D, Virtamo J. Effect of alpha-tocopherol and beta-carotene supplementation on the incidence of type 2 diabetes. Diabetologia 2008;51:47-53.
pmid
53. Song Y, Cook NR, Albert CM, Van Denburgh M, Manson JE. Effects of vitamins C and E and beta-carotene on the risk of type 2 diabetes in women at high risk of cardiovascular disease: a randomized controlled trial. Am J Clin Nutr 2009;90:429-437.
crossref
54. Liu S, Lee IM, Song Y, Van Denburgh M, Cook NR, Manson JE, Buring JE. Vitamin E and risk of type 2 diabetes in the women's health study randomized controlled trial. Diabetes 2006;55:2856-2862.
crossref pmid
55. Czernichow S, Couthouis A, Bertrais S, Vergnaud AC, Dauchet L, Galan P, Hercberg S. Antioxidant supplementation does not affect fasting plasma glucose in the Supplementation with Antioxidant Vitamins and Minerals (SU.VI.MAX) study in France: association with dietary intake and plasma concentrations. Am J Clin Nutr 2006;84:395-399.
pmid
56. Anderson EJ, Lustig ME, Boyle KE, Woodlief TL, Kane DA, Lin CT, Price JW 3rd, Kang L, Rabinovitch PS, Szeto HH, Houmard JA, Cortright RN, Wasserman DH, Neufer PD. Mitochondrial H2O2 emission and cellular redox state link excess fat intake to insulin resistance in both rodents and humans. J Clin Invest 2009;119:573-581.
crossref pmid pmc
57. Hoehn KL, Salmon AB, Hohnen-Behrens C, Turner N, Hoy AJ, Maghzal GJ, Stocker R, Van Remmen H, Kraegen EW, Cooney GJ, Richardson AR, James DE. Insulin resistance is a cellular antioxidant defense mechanism. Proc Natl Acad Sci U S A 2009;106:17787-17792.
crossref pmid pmc
Fig. 1

Hypothesis for a mechanism by which excess glucose and saturated free fatty acids (SFAs) affect reactive oxygen species (ROS) generation in adipocytes in early stages of obesity. Excess glucose generates ROS via the pentose phosphate pathway, rather than by overloading mitochondrial oxidative phosphorylation, while SFA generate ROS following activating, Toll-like receptor 4 (TLR4) or lipid rafts. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) might be the common mediator of ROS generation by both excess glucose and SFAs. ROS generated by both glucose and SFA activate nuclear factor κB (NF-κB). LR, lipid raft; SAA3, serum amyloid A3; MCP-1, monocyte chemoattractant protein-1.

dmj-40-272-g001.jpg
Fig. 2

Hypothesis for a mechanism by which mitochondrial β-oxidation of free fatty acid (FFA) from triglyceride stores affects reactive oxygen species (ROS) generation in adipocytes in the late stage of obesity. Uptake of excess glucose and FAA are inhibited, resulting in a decrease of pentose phosphate pathway and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) activity. FFA from fat stores overload mitochondrial oxidative phosphorylation and generate ROS. Mitochondria-derived ROS activate nuclear factor κB. IR, insulin receptor; IRS, insulin receptor substrate; GLUT4, glucose transporter 4; LPL, lipoprotein lipase; FATP, fatty acid transport protein; HSL, hormone-sensitive lipase.

dmj-40-272-g002.jpg
Fig. 3

Scheme of all mechanisms by which these three distinct sources of reactive oxygen species (ROS) might affect adipocyte insulin resistance and adipose tissue inflammation. NOX, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase.

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