![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824 and * Department of Nutrition, University of Tennessee, Knoxville, TN 37996
1To whom correspondence should be addressed. E-mail: claycom3{at}msu.edu.
 |
ABSTRACT |
|---|
 TOP ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
KEY WORDS: • interleukin-6 • preadipocyte • obesity
An increasing number of studies have shown that circulating levels of interleukin-6 (IL-6)2 are significantly higher in obese humans and animals (1–4). IL-6, a proinflammatory cytokine, is secreted from a variety of tissues, including activated leukocytes, endothelial cells, and adipocytes (5,6). Once secreted, IL-6 acts synergistically with other regulatory factors to affect the development of several chronic diseases such as cardiovascular disease (CVD) and Type 2 diabetes (5,7). For example, IL-6 decreases lipoprotein lipase (LPL) activity, which in turn results in increased circulating lipid levels (7). Further, IL-6 was also shown to induce hepatic C-reactive protein, one of the most sensitive markers of CVD risk (7,8). Moreover, obesity-associated increases in IL-6 levels were shown to be linked to decreased insulin-induced glucose uptake (9,10). Although the exact mechanisms of IL-6–induced decreased insulin sensitivity are not clearly defined, a recent study demonstrated that human subcutaneous fat cells from insulin-resistant subjects have significantly higher levels of IL-6 gene expression, and that IL-6 inhibits insulin action by inhibiting expression of insulin receptor, insulin receptor substrate-1, and glucose transporter type 4 in 3T3-L1 adipocytes (11). Further, IL-6 was shown to decrease insulin sensitivity through suppression of adiponectin mRNA synthesis and secretion (6) and via inhibition of insulin signaling in hepatocytes (12).
Interestingly, studies showed that increased plasma IL-6 levels in obese patients decrease with reduction in body weight and with decreased body adipose tissue mass (13–15). Accordingly, recent studies suggested that adipose tissue might be one of the major sources of IL-6. For example, Mohamed-Ali et al. (16) reported that adipose tissue releases large amounts of IL-6, and Fried et al. (17) demonstrated that IL-6 is released from adipose tissue of obese subjects, with omental adipose tissue producing 3-fold higher levels of IL-6 than subcutaneous adipose tissue. Importantly, Fried et al. (17) also reported that 90% of human adipose IL-6 expression was in the stromal vascular fraction (SVF), although the cellular source was not identified. Adipose tissue is comprised of several different cell types such as fibroblasts, nondifferentiated mesenchymal cells, preadipocytes, and adipocytes (18). However, to our knowledge, no studies have shown which cell types within the adipose tissue contribute the most toward obesity-associated increases in circulating IL-6 levels. Interestingly, when 3T3-L1 preadipocytes were injected into the peritoneal cavity of nude mice, these cells acquired macrophage-like phenotypes and developed high phagocytic activity (19,20). These data suggest that preadipocytes can assume proinflammatory immune cell characteristics and therefore can play a potentially important role in modulating proinflammatory cytokine levels.
In this study, we investigated the extent to which adipocytes contribute to overall increases in obesity-associated IL-6 levels by measuring IL-6 levels of plasma, IL-6 mRNA levels from liver, spleen, and adipose tissue, and IL-6 secretion from peritoneal macrophage in leptin-deficient obese (ob/ob) and lean control mice. We further investigated whether obesity-associated increases in IL-6 expression were due to increased IL-6 secretion from preadipocytes or differentiated adipocytes using both the murine 3T3-L1 cell line as well as primary adipose tissue cells from lean and ob/ob mice.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Leptin, insulin, and glucose measurements. Blood was collected via heart puncture using heparinized tubes. Plasma was prepared, and 100 µL was used in a RIA using a kit purchased from Linco to determine leptin and insulin levels (21). Glucose concentration was measured by the glucose oxidase method (Sigma) (22).
Peritoneal macrophage culture. Peritoneal exudate cells from thioglycollate (3 mL of 2.98% broth for 3 d)-injected lean and ob/ob mice were obtained by peritoneal lavage with cold Ca2+- and Mg2+-free HBSS (Life Technologies). Peritoneal macrophages were collected by centrifugation at 200 x g at 4°C for 10 min followed by resuspension in endotoxin-free RPMI 1640 (Life Technologies) medium supplemented with 10 mmol/L HEPES, 2 mmol/L glutamine (Life Technologies), 105 U/L penicillin, 100 mg/L streptomycin (Life Technologies), and 2% fetal bovine serum (FBS). The cells were plated onto cell culture plates and allowed to adhere for 2 h at 37°C in 5% CO2, at which time nonadherent cells were removed by vigorous washing (23). Cells were then treated with lipopolysaccharide (LPS) for 48 h or insulin (100 nmol/L) or glucose (100 mmol/L) and incubated in serum free media for 12 h. The supernatant was collected and IL-6 secretion was measured by ELISA using mouse IL-6 antibody (BD Biosciences Pharmingen).
Isolation and culture of primary adipose cells.
White adipose tissue was excised from C57BL/6J and ob/ob mice, minced, and digested using collagenase type I (Worthington Biochemical) at 37°C in a shaking water bath for 1 h. Adipose tissue cells were filtered using 100-µm nylon cell strainers (BD Biosciences). Adipocytes were isolated by gentle centrifugation (<500 x g for 1 min), washed twice with DMEM at 37°C, and resuspended with fresh DMEM. The SVF cells containing preadipocytes were then separated from floating primary adipocytes by centrifugation (<500 x g for 5 min). Resulting SVF cell pellets were treated with RBC lysis buffer (Sigma Chemical) for 1 min at room temperature, resuspended in DMEM supplemented with 10% FBS, and centrifuged. SVF cells were plated in a 48-well cell culture plate with 
0.5 x 106 cells/well. Adipocytes were cultured in sterile 6-mL polypropylene tubes. Both SVF cells and adipocytes were stimulated with LPS (200 µg/L) for 12 h before collection of cell culture media followed by IL-6 ELISA. The concentration of secreted IL-6 levels was normalized by DNA fluorescence using a DNA quantitation assay (Stratagene).
3T3-L1 cell culture. 3T3-L1 adipocyte cell lines originally derived from mouse embryo were purchased from the American Type Culture Collection and grown in 12-well plates or 100-mm dishes and cultured in DMEM supplemented with 10% FBS and 1% penicillin/streptomycin (growth medium). 3T3-L1 cells were differentiated into adipocytes according to previously described methods (24). Briefly, 3T3-L1 cells were grown to confluence, supplemented with 250 nmol/L dexamethasone, 25 nmol/L insulin, and 0.5 mmol/L isobutyl methylxanthine for 72 h. Cells were then cultured for an additional 5 d in growth medium. For IL-6 secretion studies, the undifferentiated preadipocytes and differentiated adipocytes were treated with LPS (200 µg/L) for 0, 1, and 3 h for total RNA isolation or treated with LPS (0, 50, 100, and 200 µg/L) for 12 h for IL-6 secretion. For IL-6 expression studies, both the 3T3-L1 preadipocytes and fully differentiated adipocytes were treated with 200 µg/L of LPS for 0, 1, and 3 h
ELISA. 3T3-L1 preadipocytes and adipocytes were treated with 0, 50, 100, or 200 µg/L of LPS for 12 h. The supernatant was immediately frozen at –80°C, and IL-6 concentration measured by ELISA. The results were normalized by fluorescence DNA using a DNA quantitation assay (Stratagene).
Real-time RT-PCR. Cells were harvested to isolate total RNA using Totally RNA Isolation Kit (Ambion). Total RNA (100 ng) was used to measure IL-6 mRNA and 18S-rRNA using real-time PCR methods (PE Applied Biosystems). Total RNA was also isolated from spleen, liver, and adipose tissue of lean and ob/ob mice, and 100 ng total RNA was used to measure IL-6 mRNA, using ABI Prism 7700 Sequence Detection System (PE Applied Biosystems). Probes and primers for IL-6 and 18S, and premixed RT and PCR reagents (40X Multiscribe RNase Inhibitor Mix and TaqMan 2X Universal PCR Master Mix contained in TaqMan One-Step RT-PCR Master Mix Reagents kit) were purchased from PE Applied Biosystems. Data were analyzed using the comparative threshold cycle (CT) method according to the manufacturer’s instructions (PE Applied Biosystems).
Statistical analysis. Data are reported as means ± SEM and were analyzed by Student’s t test and general linear model (GLM) ANOVA using SAS software when appropriate. Differences were considered significant at P < 0.05.
|
RESULTS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
|
|
|
IL-6 expression in primary adipose tissue SVF and in adipocytes. Both basal and LPS-stimulated IL-6 secretion levels were measured in SVF cells that contain preadipocytes and separated adipocytes from adipose tissues of lean and ob/ob mice. Compared with the control treatment, LPS treatment increased IL-6 secretion in both SVF cells and adipocytes of both lean and ob/ob mice (P < 0.001, Fig. 2). Importantly, SVF cells secreted more IL-6 than adipocytes in both lean and ob/ob mice (P < 0.001, Fig. 2). In addition, IL-6 mRNA levels of unstimulated SVF cells of ob/ob mice were higher than in lean mice (real time RT-PCR CT values of SVF cells, 37.44 ± 1.30 in ob/ob vs. 40.00 ± 0.00 in lean mice). Moreover, IL-6 mRNA levels of ob/ob mice were significantly higher in the LPS-stimulated SVF cells compared with adipocytes (data not shown).
|
|
|
|
DISCUSSION |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
(13,14), and IL-6 (16,17). Results from the current study showed that the increased body weight in ob/ob mice was associated with significantly elevated plasma glucose and insulin concentrations compared with control lean mice (Table 1). Accordingly, we hypothesized that obesity-associated increases in plasma IL-6 concentrations may be due to insulin or glucose-induced increases in IL-6 secretion by a variety of cell types. Although macrophages are one of the major sources of IL-6 secretion, our results indicated that peritoneal macrophage secretion of IL-6 in response to glucose, insulin, and LPS treatment cannot account for the obesity-associated increases in plasma IL-6 secretion levels in ob/ob mice. Further, macrophage or macrophage-like cell–containing tissues such as spleen and liver also did not show obesity-related increases in IL-6 mRNA expression. Adipose tissue, however, showed a significantly increased IL-6 mRNA levels. Therefore, we suggest that adipose tissue accounts for the significant difference in plasma IL-6 in ob/ob mice compared with lean control mice. Furthermore, our real-time PCR data showed that CT values were lower in adipose tissue in both lean and ob/ob mice compared with CT values of liver and spleen, suggesting that adipose tissue synthesizes higher levels of IL-6. Differential expression of IL-6 in primary preadipocytes and adipocytes of lean and ob/ob mice were addressed by measuring LPS-induced IL-6 secretion using SVF cells and adipocytes from adipose tissues of both lean and ob/ob mice. To ensure that SVF cells were comprised mainly of preadipocytes, we differentiated SVF cells to adipocytes and used cells that showed >70% differentiation rate (data not shown). Furthermore, using an intracellular staining and fluorescent-activated cell sorting method, we demonstrated that the undifferentiated 3T3-L1 cells used in our experiments expressed >95% of the preadipocyte maker preadipocyte factor-1 (data not shown). The identity of the cells types that are responsible for the remaining 90% of adipose tissue–derived IL-6 is currently unknown. Adipose tissue is comprised of several types of cells such as fibroblasts, nondifferentiated mesenchymal cells, preadipocytes, and adipocytes (18). Adipocytes develop from fibroblast-like preadipocytes within the adipose tissue stromal vascular fraction (26). To date, no studies have investigated whether conversion of precursor cells to preadipocytes contributes significantly to obesity-induced increases in IL-6 levels, although it was suggested that the rate or efficiency of conversion of stem cells to preadipocytes may be one of the important contributors of increased adipose tissue mass (27).
A large body of evidence demonstrates that obesity-associated increases in circulating proinflammatory cytokines, particularly IL-6, can be decreased after a substantial reduction in adipose tissue mass (1–4,13–15). It was also shown that adipose tissue contributes up to 35% of circulating IL-6 (16). Interestingly, only 10% of total circulating adipose tissue–derived circulating IL-6 levels can be accounted for by fully differentiated adipocytes (17).
Increased adipose tissue mass is also due to an increase in adipocyte size and increased conversion of preadipocytes to adipocytes (27,28). The results of our study clearly demonstrate that preadipocytes rather than adipocytes contribute more significantly toward obesity-associated high IL-6 levels. It was shown that a gradual increase in IL-6 secretion by adipocytes occurs throughout the differentiation process (29). Thus we tested whether prolonged culture up to 72 h post-preadipocyte differentiation into adipocytes has any effect on accumulative IL-6 production. LPS stimulated IL-6 secretion in preadipocytes and adipocytes did not differ up to 72 h in culture (data not shown).
The data presented in this study demonstrated that SVF cells secrete significantly higher levels of IL-6 compared with adipocytes. However, a limitation to the study is that other cells within the adipose tissue such as macrophages (F4/80 positive cells) can also secrete IL-6. In the current study, we did not determine which of the 2 cell types contributed more toward elevated levels of plasma IL-6 in ob/ob mice. Interestingly, recent studies showed that macrophage numbers positively and significantly correlate with increased adiposity (30,31), and SVF have significantly higher levels of macrophage cell marker (F4/80) mRNA expression compared with the adipocyte fraction (31). Because our data showed that peritoneal macrophages cannot account for increased plasma IL-6 in ob/ob mice, it seems possible that a locally increased inflammatory environment due to increased adiposity may alter the adipose tissue macrophage IL-6 secretory function.
In summary, the data presented herein demonstrate that adipose tissue may be an important source of obesity-associated increases in plasma IL-6. Further, our results indicate that stromal vascular cells rather than adipocytes contribute more toward obesity-induced increases in IL-6. Further study is required to elucidate the signaling mechanisms underlying obesity-associated IL-6 gene expression.
|
FOOTNOTES |
|---|
Manuscript received 13 February 2004. Initial review completed 13 April 2004. Revision accepted 19 July 2004.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1. Kopp, H. P., Kopp, C. W., Festa, A., Krzyzanowska, K., Kriwanek, S., Minar, E., Roka, R. & Schernthaner, G. (2003) Impact of weight loss on inflammatory proteins and their association with the insulin resistance syndrome in morbidly obese patients. Arterioscler. Thromb. Vasc. Biol. 23:1042-1047.
2. Roytblat, L., Rachinsky, M., Fisher, A., Greemberg, L., Shapira, Y., Douvdevani, A. & Gelman, S. (2000) Raised interleukin-6 levels in obese patients. Obes. Res. 8:673-675.[Medline]
3. Laimer, M., Ebenbichler, C. F., Kaser, S., Sandhofer, A., Weiss, H., Nehoda, H., Aigner, F. & Patsch, J. R. (2002) Markers of chronic inflammation and obesity: a prospective study on the reversibility of this association in middle-aged women undergoing weight loss by surgical intervention. Int. J. Obes. Relat. Metab. Disord. 26:659-662.[Medline]
4. Bastard, J. P., Jardel, C., Bruckert, E., Blondy, P., Capeau, J., Laville, M., Vidal, H. & Halinque, B. (2000) Elevated levels of interleukin-6 are reduced in serum and subcutaneous adipose tissue of obese women after weight loss. J. Clin. Endocrinol. Metab. 85:3338-3342.
5. Pradhan, A. D., Manson, J. E., Rifai, N., Buring, J. E. & Ridker, P. M. (2001) C-reactive protein, interleukin 6, and risk of developing type 2 diabetes mellitus. J. Am. Med. Assoc. 286:327-334.
6. Fasshauer, M., Kralisch, S., Klier, M., Lossner, U., Bluher, M., Klein, J. & Paschke, R. (2003) Adiponectin gene expression and secretion is inhibited by interleukin-6 in 3T3–L1 adipocytes. Biochem. Biophys. Res. Commun. 301:1045-1050.[Medline]
7. Yudkin, J. S., Kumari, M., Humphries, S. E. & Mohamed-Ali, V. (2000) Inflammation, obesity, stress and coronary heart disease: is interleukin-6 the link?. Atherosclerosis 148:209-214.[Medline]
8. Pepys, M. B. & Hirschfield, G. M. (2003) C-reactive protein: a critical update. J. Clin. Investig. 111:1805-1812.[Medline]
9. Kern, P. A., Ranganathan, S., Li, C., Wood, L. & Ranganathan, G. (2001) Adipose tissue necrosis factor and interleukin-6 expression in human obesity and insulin resistance. Am. J. Physiol. 280:E745-E751.
10. Fasshauer, M., Klein, J., Lossner, U. & Paschke, R. (2003) Interleukin-6 mRNA expression is stimulated by insulin, isoproterenol, tumor necrosis factor alpha, growth hormone, and IL-6 in 3T3–L1 adipocytes. Horm. Metab. Res. 35:147-152.[Medline]
11. Rotter, V., Nagaev, I. & Smith, U. (2003) Interleukin-6 (IL-6) induces insulin resistance in 3T3–L1 adipocytes and is, like IL-8 and tumor necrosis factor , overexpressed in human fat cells from insulin resistant subjects. J. Biol. Chem. 278:45777-45784.
12. Senn, J. J., Klover, P. J., Nowak, I. A. & Mooney, R. A. (2002) Interleukin-6 induces cellular insulin resistance in hepatocytes. Diabetes 51:3391-3399.
13. Esposito, K., Pontillo, A., Di Palo, C., Giugliano, G., Masella, M., Marfella, R. & Giugliano, D. (2003) Effect of weight loss and lifestyle changes on vascular inflammatory markers in obese women: a randomized trial. J. Am. Med. Assoc. 289:1799-1804.
14. Bruun, J. M., Verdich, C., Toubro, S., Astrup, A. & Richelsen, B. (2003) Association between measures of insulin sensitivity and circulating levels of interleukin-8, interleukin-6, and tumor necrosis factor-alpha. Effect of weight loss in obese men. Eur. J. Endocrinol. 148:535-542.[Abstract]
15. Ziccardi, P., Nappo, F., Giugliano, G., Esposito, K., Marfella, R., Cioffi, M., D’Andrea, F., Molinari, A. M. & Giugliano, D. (2002) Reduction of inflammatory cytokine concentrations and improvement of endothelial functions in obese women after weight loss over one year. Circulation 105:e9075-e9076.
16. Mohamed-Ali, V., Goodrick, S., Rawesh, A., Katz, D. R., Miles, J. M., Yudkin, J. S., Klein, S. & Coppack, S. W. (1997) Subcutaneous adipose tissue releases interleukin-6, but not tumor necrosis factor-, in vivo. J. Clin. Endocrinol. Metab. 82:4196-4200.
17. Fried, S. K., Bunkin, D. A. & Greenberg, A. S. (1998) Omental and subcutaneous adipose tissues of obese subjects release interleukin-6: depot difference and regulation by glucocorticoid. J. Clin. Endocrinol. Metab. 83:847-850.
18. Ailhaud, G., Grimaldi, P. & Negrel, R. (1992) Cellular and molecular aspects of adipose tissue development. Annu. Rev. Nutr. 12:207-233.[Medline]
19. Guillaume, C., Cousin, B., Emmanuelle, A., Mireille, A., Bacou, F., Penicaud, L. & Casteilla, L. (2003) Preadipocyte conversion to macrophage. J. Biol. Chem. 278:9850-9855.
20. Cousin, B., Andre, M., Casteilla, L. & Penicaud, L. (2001) Altered macrophage-like functions of preadipocytes in inflammation and genetic obesity. J. Cell Physiol. 186:380-386.[Medline]
21. Claycombe, K. J., Xue, B. Z., Mynatt, R. L., Zemel, M. B. & Moustaid-Moussa, N. (2000) Regulation of leptin by agouti. Physiol. Genomics 2:101-105.
22. Standridge, M., Alemzadeh, R., Zemel, M., Koontz, J. & Moustaid-Moussa, N. (2000) Diazoxide down-regulates leptin and lipid metabolizing enzymes in adipose tissue of Zucker rats. FASEB J. 14:455-460.
23. Claycombe, K. J., Wu, D., Nikolova-Karakashian, M., Palmer, H., Beharka, A., Paulson, K. E. & Meydani, S. N. (2002) Ceramide mediates age-associated increase in macrophage cyclooxygenase-2 (COX-2) expression. J. Biol. Chem. 277:30784-30791.
24. Kim, S., Whelan, J., Claycombe, K., Reath, D. B. & Moustaid-Moussa, N. (2002) Angiotensin II increases leptin secretion by 3T3–L1 and human adipocytes via a prostaglandin-independent mechanism. J. Nutr. 132:1135-1140.
25. Esposito, K., Pontillo, A., Ciotola, M., Di Palo, C., Grella, E., Nicoletti, G. & Giugliano, D. (2002) Weight loss reduces interleukin-18 levels in obese women. J. Clin. Endocrinol. Metab. 87:3864-3866.
26. Shahparaki, A., Grunder, L. & Sorisky, A. (2002) Comparison of human abdominal subcutaneous versus omental preadipocyte differentiation in primary culture. Metabolism 51:1211-1215.[Medline]
27. Tomlinson, J. W., Crabtree, N., Clark, P. M., Holder, G., Toogood, A. A., Shackleton, C. H. & Stewart, P. M. (2003) Low-dose growth hormone inhibits 11 beta-hydroxysteroid dehydrogenase type 1 but has no effect upon fat mass in patients with simple obesity. J. Clin. Endocrinol. Metab. 88:2113-2118.
28. Chavey, C., Mari, B., Monthouel, M. N., Bonnafous, S., Anglard, P., Van Obberghen, E. & Tartare-Deckert, S. (2003) Matrix metalloproteinases are differentially expressed in adipose tissue during obesity and modulate adipocyte differentiation. J. Biol. Chem. 278:11888-11896.
29. Vicennati, V., Voterro, A., Friedman, C. & Papanicolaou, D. A. (2002) Hormonal regulation of interleukin-6 production in human adipocytes. Int. J. Obes. 26:905-911.[Medline]
30. Weisberg, S. P., McCann, D., Desai, M., Rosenbaum, M., Leibel, R. L. & Ferrante, A. W. (2003) Obesity is associated with macrophage accumulation in adipose tissue. J. Clin. Investig. 112:1796-1808.[Medline]
31. Xu, H., Barnes, G., Yang, Q., Tan, G., Yang, D., Chou, C., Sole, J., Nichols, A., Ross, J., Tartaglia, L. & Chen, H. (2003) Chronic inflammation in fat plays a crucial role in the development of obesity-related insulin resistance. J. Clin. Investig. 112:1821-1830.[Medline]
This article has been cited by other articles:
|
|
 |
|
  H. R. Zhou, E.-K. Kim, H. Kim, and K. J. Claycombe Obesity-associated mouse adipose stem cell secretion of monocyte chemotactic protein-1 Am J Physiol Endocrinol Metab, November 1, 2007; 293(5): E1153 - E1158. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Chung, K. LaPoint, K. Martinez, A. Kennedy, M. Boysen Sandberg, and M. K. McIntosh Preadipocytes Mediate Lipopolysaccharide-Induced Inflammation and Insulin Resistance in Primary Cultures of Newly Differentiated Human Adipocytes Endocrinology, November 1, 2006; 147(11): 5340 - 5351. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. T. Antunes, A. Gagnon, B. Chen, F. Pacini, T. J. Smith, and A. Sorisky Interleukin-6 release from human abdominal adipose cells is regulated by thyroid-stimulating hormone: effect of adipocyte differentiation and anatomic depot Am J Physiol Endocrinol Metab, June 1, 2006; 290(6): E1140 - E1144. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Chung, J. M. Brown, J. N. Provo, R. Hopkins, and M. K. McIntosh Conjugated Linoleic Acid Promotes Human Adipocyte Insulin Resistance through NF{kappa}B-dependent Cytokine Production J. Biol. Chem., November 18, 2005; 280(46): 38445 - 38456. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Different from adipocytes, P < 0.001 (2-way ANOVA).
