Combination of the anthocyanidins malvidin and peonidin attenuates lipopolysaccharide-mediated inflammatory gene expression in primary human adipocytes.

We recently demonstrated that California table grapes and a methanol-extractable, polyphenol-rich fraction decreased adiposity, insulin resistance, or markers of inflammation in high-fat fed mice. Malvidin and peonidin glycosides were the 2 most abundant anthocyanins in the polyphenol-rich fraction. We hypothesized that a blood borne combination of anthocyanidins malvidin and peonidin derived from intestinal ß-glycosidase metabolism of these 2 anthocyanins are responsible, in part, for the beneficial health effects observed in vivo. Therefore, we supplemented primary human adipocytes with malvidin or peonidin, alone or together, followed by acute lipopolysaccharide (LPS) treatment. Neither peonidin nor malvidin alone consistently decreased the expression of several inflammatory genes. However, supplementing adipocytes with an equal combination of malvidin plus peonidin followed by LPS treatment decreased the mRNA levels of interleukin (IL)-6, IL-1ß, IL-8, monocyte chemoattractant protein-1, toll-like receptor-2, tumor necrosis factor alpha, cyclooxygenase-2, and interferon gamma-induced protein-10. The highest combination dose of malvidin plus peonidin decreased or increased the expression of protein tyrosine phosphatase-1B and hormone sensitive lipase, respectively, genes encoding proteins associated with insulin resistance or lipolysis. These data indicate that a combination of malvidin plus peonidin have potentiating interactions that reduce inflammatory gene expression; however, in vivo studies are needed to support these in vitro data.

Nutrient Regulation: Conjugated Linoleic Acid's Inflammatory and Browning Properties in Adipose Tissue.

Obesity is the most widespread nutritional disease in the United States. Developing effective and safe strategies to manage excess body weight is therefore of paramount importance. One potential strategy to reduce obesity is to consume conjugated linoleic acid (CLA) supplements containing isomers cis-9, trans-11 and trans-10, cis-12, or trans-10, cis-12 alone. Proposed antiobesity mechanisms of CLA include regulation of (a) adipogenesis, (b) lipid metabolism, (c) inflammation, (d) adipocyte apoptosis, (e) browning or beiging of adipose tissue, and (f) energy metabolism. However, causality of CLA-mediated responses to body fat loss, particularly the linkage between inflammation, thermogenesis, and energy metabolism, is unclear. This review examines whether CLA's antiobesity properties are due to inflammatory signaling and considers CLA's linkage with lipogenesis, lipolysis, thermogenesis, and browning of white and brown adipose tissue. We propose a series of questions and studies to interrogate the role of the sympathetic nervous system in mediating CLA's antiobesity properties.

Differential effects of grape powder and its extract on glucose tolerance and chronic inflammation in high-fat-fed obese mice.

The objective of this study was to determine the anti-inflammatory properties of grape powder (GP) or GP extract (GE) and examine (1) which polyphenol metabolites in GE were bioavailable, (2) the impact of GP and GE on glucose tolerance and inflammation in obese mice, and (3) if bioavailable polyphenols in GE decrease markers of inflammation in primary adipocytes. In experiment 1, C57BL/6J mice were gavaged with GE and serum polyphenols were measured. In experiment 2, mice were fed high-fat diets supplemented with 3% GP or 0.02% GE for 18 weeks and markers of inflammation were measured. In experiment 3, human adipocytes were treated with the bioavailable polyphenols quercetin 3-O-glucoside (Q3G) or quercetin 3-O-glucuronide (Q3GN) and markers of inflammation were measured. Serum Q3G and Q3GN increased at 1 h post-GE gavage and decreased thereafter. GP supplementation improved glucose tolerance at 5 weeks and decreased markers of inflammation ∼20-50% in serum and adipose tissue at 18 weeks. Q3G, but not Q3GN, attenuated TNFα-mediated inflammatory gene expression ∼30-40% in human adipocytes, possibly by suppressing c-Jun-NH(2) terminal kinase and c-Jun activation. In summary, (1) Q3G and Q3GN are bioavailable polyphenols in GE, (2) GP acutely improves glucose tolerance and chronically reduces markers of inflammation in obese mice, and (3) Q3G reduces several markers of inflammation in human adipocytes.

JNK inhibition by SP600125 attenuates trans-10, cis-12 conjugated linoleic acid-mediated regulation of inflammatory and lipogenic gene expression.

Supplementation with a mixture of trans-10, cis-12 (t10,c12) and cis-9, trans-11 (c9,t11) isomers of conjugated linoleic acid (CLA), or t10,c12 CLA alone, reduces body weight and fat deposition in animals and some humans. However, these anti-obesity actions of t10,c12 CLA are routinely accompanied by increased markers of inflammation and insulin resistance. Thus, we examined the extent to which blocking c-Jun NH2-terminal kinase (JNK) signaling using the JNK inhibitor SP600125 attenuated markers of inflammation and insulin resistance in primary human adipocytes treated with t10,c12 CLA. SP600125 attenuated t10,c12 CLA-mediated phosphorylation of cJun and increased protein levels of activating transcription factor (ATF) 3, two downstream targets of JNK. SP600125 attenuated t10,c12 CLA-mediated induction of inflammatory genes, including interleukin (IL)-6, IL-8, IL-1ß, ATF3, monocyte chemoattractant protein (MCP)-1, and cyclooxygenase-2. Consistent with these data, SP600125 prevented t10,c12 CLA-mediated secretion of IL-8, IL-6, and MCP-1. SP600125 prevented t10,c12 CLA suppression of lipogenic genes including peroxisome proliferator activated receptor gamma, liver X receptor, sterol regulatory element binding protein, acetyl-CoA carboxylase, and stearoyl-CoA desaturase. Additionally, SP600125 blocked t10,c12 CLA-mediated induction of suppressor of cytokine synthesis-3 and suppression of adiponectin and insulin-dependent glucose transporter 4 mRNA levels. Collectively, these data suggest that JNK signaling plays an important role in t10,c12 CLA-mediated regulation of inflammatory and lipogenic gene expression in primary cultures of human adipocytes.

Potential mechanisms by which polyphenol-rich grapes prevent obesity-mediated inflammation and metabolic diseases.

Obesity and metabolic disease-related health problems (e.g., type 2 diabetes, atherosclerosis, and hypertension) are the most prevalent nutrition-related issues in the United States. An emerging feature of obesity and type 2 diabetes is their linkage with chronic inflammation that begins in white adipose tissue and eventually becomes systemic. One potential strategy to reduce inflammation and insulin resistance is consumption of polyphenol-rich foods like grapes or their by-products, which have anti-inflammatory properties. Polyphenols commonly found in grape products have been reported to reduce inflammation by (a) acting as an antioxidant or increasing antioxidant gene or protein expression, (b) attenuating endoplasmic reticulum stress signaling, (c) blocking proinflammatory cytokines or endotoxin-mediated kinases and transcription factors involved in metabolic disease, (d) suppressing inflammatory- or inducing metabolic-gene expression via increasing histone deacetylase activity, or (e) activating transcription factors that antagonize chronic inflammation. Thus, polyphenol-rich grape products may reduce obesity-mediated chronic inflammation by multiple mechanisms, thereby preventing metabolic diseases.

Grape powder extract attenuates tumor necrosis factor α-mediated inflammation and insulin resistance in primary cultures of human adipocytes.

Grapes are rich in phenolic phytochemicals that possess anti-oxidant and anti-inflammatory properties. However, the ability of grape powder extract (GPE) to prevent inflammation and insulin resistance in human adipocytes caused by tumor necrosis factor α (TNFα), a cytokine elevated in plasma and white adipose tissue (WAT) of obese, diabetic individuals, is unknown. Therefore, we examined the effects of GPE on markers of inflammation and insulin resistance in primary cultures of newly differentiated human adipocytes treated with TNFα. We found that GPE attenuated TNFα-induced expression of inflammatory genes including interleukin (IL)-6, IL-1ß, IL-8, monocyte chemoattractant protein (MCP)-1, cyclooxygenase (COX)-2 and Toll-like receptor (TLR)-2. GPE attenuated TNFα-mediated activation of extracellular signal-related kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK) and activator protein-1 (AP-1, i.e., c-Jun). GPE also attenuated TNFα-mediated IκBα degradation and nuclear factor-kappa B (NF-κB) activity. Finally, GPE prevented TNFα-induced expression of protein tyrosine phosphatase (PTP)-1B and phosphorylation of serine residue 307 of insulin receptor substrate-1 (IRS-1), which are negative regulators of insulin sensitivity, and suppression of insulin-stimulated glucose uptake. Taken together, these data demonstrate that GPE attenuates TNFα-mediated inflammation and insulin resistance in human adipocytes, possibly by suppressing the activation of ERK, JNK, c-Jun and NF-κB.

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

BACKGROUND: Quercetin and trans-resveratrol (trans-RSV) are plant polyphenols reported to reduce inflammation or insulin resistance associated with obesity. Recently, we showed that grape powder extract, which contains quercetin and trans-RSV, attenuates markers of inflammation in human adipocytes and macrophages and insulin resistance in human adipocytes. However, we do not know how quercetin and trans-RSV individually affected these outcomes. OBJECTIVE: The aim of this study was to examine the extent to which quercetin and trans-RSV prevented inflammation or insulin resistance in primary cultures of human adipocytes treated with tumor necrosis factor-α (TNF-α)-an inflammatory cytokine elevated in the plasma and adipose tissue of obese, diabetic individuals. DESIGN: Cultures of human adipocytes were pretreated with quercetin and trans-RSV followed by treatment with TNF-α. Subsequently, gene and protein markers of inflammation and insulin resistance were measured. RESULTS: Quercetin, and to a lesser extent trans-RSV, attenuated the TNF-α-induced expression of inflammatory genes such as interleukin (IL)-6, IL-1ß, IL-8, and monocyte chemoattractant protein-1 (MCP-1) and the secretion of IL-6, IL-8, and MCP-1. Quercetin attenuated TNF-α-mediated phosphorylation of extracellular signal-related kinase and c-Jun-NH2 terminal kinase, whereas trans-RSV attenuated only c-Jun-NH2 terminal kinase phosphorylation. Quercetin and trans-RSV attenuated TNF-α-mediated phosphorylation of c-Jun and degradation of inhibitory κB protein. Quercetin, but not trans-RSV, decreased TNF-α-induced nuclear factor-κB transcriptional activity. Quercetin and trans-RSV attenuated the TNF-α-mediated suppression of peroxisome proliferator-activated receptor γ (PPARγ) and PPARγ target genes and of PPARγ protein concentrations and transcriptional activity. Quercetin prevented the TNF-α-mediated serine phosphorylation of insulin receptor substrate-1 and protein tyrosine phosphatase-1B gene expression and the suppression of insulin-stimulated glucose uptake, whereas trans-RSV prevented only the TNF-α-mediated serine phosphorylation of insulin receptor substrate-1. CONCLUSION: These data suggest that quercetin is equally or more effective than trans-RSV in attenuating TNF-α-mediated inflammation and insulin resistance in primary human adipocytes.

Trans-10, cis-12 conjugated linoleic acid antagonizes ligand-dependent PPARgamma activity in primary cultures of human adipocytes.

We previously demonstrated that trans-10, cis-12 (10,12) conjugated linoleic acid (CLA) causes human adipocyte delipidation, insulin resistance, and inflammation in part by attenuating PPARgamma target gene expression. We hypothesized that CLA antagonizes the activity of PPARgamma in an isomer-specific manner. 10,12 CLA, but not cis-9, trans-11 (9,11) CLA, suppressed ligand-stimulated activation of a peroxisome proliferator response element-luciferase reporter. This decreased activation of PPARgamma by 10,12 CLA was accompanied by an increase in PPARgamma and extracellular signal-related kinase (ERK)1/2 phosphorylation, followed by decreased PPARgamma protein levels. To investigate if 10,12 CLA-mediated delipidation was preventable with a PPARgamma ligand (BRL), cultures were treated for 1 wk with 10,12 CLA or 10,12 CLA + BRL and adipogenic gene and protein expression, glucose uptake, and triglyceride (TG) were measured. BRL cosupplementation completely prevented 10,12 CLA suppression of adipocyte fatty acid-binding protein, lipoprotein lipase, and perilipin mRNA levels without preventing reductions in PPARgamma or insulin-dependent glucose transporter 4 (GLUT4) expression, glucose uptake, or TG. Lastly, we investigated the impact of CLA withdrawal in the absence or presence of BRL for 2 wk. CLA withdrawal did not rescue CLA-mediated reductions in adipogenic gene and protein expression. In contrast, BRL supplementation for 2 wk following CLA withdrawal rescued mRNA levels of PPARgamma target genes. However, the levels of PPARgamma and GLUT4 protein and TG were only partially rescued by BRL. Collectively, we demonstrate for the first time, to our knowledge, that 10,12 CLA antagonizes ligand-dependent PPARgamma activity, possibly via PPARgamma phosphorylation by ERK.