Study Title:

Quercetin is Effective at Lowering White Adipose Tissue Inflammation

Study Abstract

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-1β, 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.

Study Information

Chuang CC, Martinez K, Xie G, Kennedy A, Bumrungpert A, Overman A, Jia W, McIntosh MK.
Quercetin is equally or more effective than resveratrol in attenuating tumor necrosis factor-{alpha}-mediated inflammation and insulin resistance in primary human adipocytes.
Am J Clin Nutr
2010 December
Department of Nutrition, University of North Carolina-Greensboro, Greensboro, NC, USA

Full Study

http://ajcn.nutrition.org/content/92/6/1511.long