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

Background: Obesity is linked to chronic inflammation in white adipose tissue, which is exacerbated by infiltrating macrophages (MFs). We recently demonstrated that an extract from grape powder (GPE), which is abundant in quercetin (QUE), reduced inflammation in human MFs and prevented MF-mediated inflammation and insulin resistance in human adipocytes. However, we did not know how QUE individually affected these outcomes. Objective and design: We examined the extent to which QUE prevents inflammation in human MFs (that is, differentiated U937 cell line) and cross-talk with human adipocytes (that is, primary cultures of newly differentiated human adipocytes). Methods and results: Treatment of MFs with QUE attenuated the basal expression of inflammatory genes, such as tumor necrosis factor-a, interleukin (IL)-6, IL-8, IL-1b and interferon-g inducible protein-10, and cyclooxygenase-2, a marker of prostaglandin production. QUE also attenuated the abundance of phosphorylated c-Jun N-terminal kinase (JNK) and c-Jun, and IkBa degradation in MFs. Furthermore, conditioned media (CM) obtained from MFs treated with QUE decreased the capacity of this CM to inflame adipocytes and cause insulin resistance as evidenced by decreased: (1) inflammatory gene expression, (2) phosphorylation of JNK and c-Jun, (3) serine residue 307 phosphorylation of insulin receptor substrate (IRS)-1, 4) protein tyrosine phosphatase-1B gene expression and 5) suppression of insulin-stimulated glucose uptake. Conclusion: Taken together, these data suggest that QUE is one of the bioactive components of GPE that prevents inflammation in MFs and MF-mediated insulin resistance in adipocytes.

Inflammation plays a role in trans-10, cis-12 (10,12)-conjugated linoleic acid (CLA)-mediated delipidation and insulin resistance in adipocytes. Given the anti-inflammatory role of resveratrol (RSV), we hypothesized that RSV would attenuate inflammation and insulin resistance caused by 10,12 CLA in human adipocytes. RSV blocked 10,12 CLA induction of the inflammatory response by preventing activation of extracellular signal-related kinase and induction of inflammatory gene expression (i.e., IL-6, IL-8, IL-1b) within 12 h. Similarly, RSV suppressed 10,12 CLA-mediated activation of the inflammatory prostaglandin pathway involving phospholipase A 2 , cyclooxygenase-2, and PGF 2a . In addition, RSV attenuated 10,12 CLA increase of intracellular calcium and reactive oxygen species associated with cellular stress, and activation of stress-related proteins (i.e., activating transcription factor 3, JNK) within 12 h. 10,12 CLA-mediated insulin resistance and suppression of fatty acid uptake and triglyceride content were attenuated by RSV. Finally, 10,12 CLA-mediated decrease of peroxisome proliferator-activated receptor g (PPARg) protein levels and activation of a peroxisome proliferator response element (PPRE) reporter were prevented by RSV. RSV increased the basal activity of PPRE, suggesting that RSV increases PPARg activity. Collectively, these data demonstrate for the first time that RSV prevents 10,12 CLAmediated insulin resistance and delipidation in human adipocytes by attenuating inflammation and cellular stress and increasing PPARg activity. Feeding a mixture of conjugated linoleic acid (CLA) isomers [i.e., trans-10, cis-12 (10,12) CLA and cis-9, trans-11 (9,11) CLA] reduces adiposity in animals (1) and some humans (2). The triglyceride (TG)-lowering properties of CLA appear to be due exclusively to the 10,12 isomer (3-5), and involve decreased uptake and metabolism of glucose and fatty acids (FA)s (6), and increased lipolysis (7) in adipocytes. These anti-obesity properties of 10,12 CLA are dependent on the activation of mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK) (6) and nuclear factor kB (NFkB) (8, 9) in adipocytes. These signaling pathways induced by 10,12 CLA are linked to the induction and secretion of cytokines (8, 9), which are known to antagonize peroxisome proliferator-activated receptor g (PPARg) target gene expression and insulin sensitivity (10-15). Consistent with these data, 10,12 CLA supplementation of humans is associated with hyperglycemia, insulin resistance, elevated levels of inflammatory prostaglandins (PGs) and cytokines, and dyslipidemia (16)(17)(18).Recently, supplementation of mice and 3T3-L1 adipocytes with 10,12 CLA has been shown to activate the integrated stress response (ISR) pathway (19), which is linked to inflammation, insulin resistance, and endoplasmic reticulum (ER) stress (20). Cellular stress can be caused by a relatively disproportional influx of macronutrients that adversely affect organelle function, including the mitoc...

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Obesity-associated inflammation is characterized by recruitment of macrophages (MPhi) into white adipose tissue (WAT) and production of inflammatory cytokines, leading to the development of insulin resistance. The xanthones, alpha- and gamma-mangostin (MG), are major bioactive compounds found in mangosteen that are reported to have antiinflammatory and antioxidant properties. Thus, we examined the efficacy of MG to prevent lipopolysaccharide (LPS)-mediated inflammation in human MPhi (differentiated U937 cells) and cross-talk with primary cultures of newly differentiated human adipocytes. We found that alpha- and gamma-MG attenuated LPS-induced expression of inflammatory genes, including tumor necrosis factor-alpha, interleukin-6, and interferon gamma-inducible protein-10 in a dose-dependent manner in MPhi. We also found that alpha- and gamma-MG attenuated LPS-activated mitogen-activated protein kinases (MAPK) and activator protein (AP)-1, but only gamma-MG reduced nuclear factor-kappaB (NF-kappaB). In addition, alpha- and gamma-MG attenuated LPS suppression of PPARgamma gene expression in a dose-dependent manner. Notably, the ability of MPhi-conditioned media to cause inflammation and insulin resistance in primary cultures of human adipocytes was attenuated by pretreating MPhi with gamma-MG. Taken together, these data demonstrate that MG attenuates LPS-mediated inflammation in MPhi and insulin resistance in adipocytes, possibly by preventing the activation of MAPK, NF-kappaB, and AP-1, which are central to inflammatory cytokine production in WAT.