Effects of Chronic and Acute Grape Consumption on Gene Expression of Inflammatory Mediators in PBMC

Abstract

Studies have demonstrated that polyphenol‐rich foods offer protection against chronic metabolic diseases caused by inflammation and oxidative stress. We investigated whether consumption of grapes alters expression of inflammatory pathway genes and transcription factors in a chronic and acute setting. In this double‐blind, crossover trial, 20 obese subjects (BMI 37.0 ± 9.9) were randomized to consume either 60 g of freeze‐dried whole grape powder (Grape) daily (297 mg polyphenols) or matched placebo (C) daily (0 mg polyphenols) for 4 weeks separated by a 2‐week washout. Acute study days at the beginning of each intervention consisted of a high fat, high carbohydrate meal challenge (1,036 kcal, 31 g protein, 107 g carbohydrate, 54 g fat) accompanied by Grape or C consumption. Peripheral blood mononuclear cells (PBMCs) were isolated from fasted blood on acute study days and at postprandial time points 1, 3, and 5 hr. Fasted blood PBMCs were isolated at the end of each chronic, 4‐week intervention. Gene expression was assessed using real‐time quantitative PCR. Relative expression levels of target genes were calculated using the comparative CT method following normalization to the endogenous reference gene GAPDH. Expression of TNFα, NF‐κB, and IκBα genes in PBMCs shows no significant differences for Grape vs. C after 4 weeks of chronic consumption. Preliminary data examining expression of the same genes in the acute setting are inconclusive. Initial results indicate that grape consumption does not impact gene expression in inflammatory pathways; however additional genes must be investigated. (Supported by the California Table Grape Commission and USDA CRIS CA‐S*‐NTR‐6316‐H)