Berries are a rich dietary source of bioactive polyphenols, including flavonoids, such as anthocyanins(1). Dietary flavonoids are known to chelate Cu2+ and are known to alter the uptake of metal ions in human intestinal Caco-2 cells(2, 3). However, little is known about the effects of dietary polyphenols on the expression of genes involved in the Cu-uptake pathway in the human intestine. The present study investigated the influence of a flavonoid-rich berry-extract on the expression of the following genes which co-ordinate the intestinal uptake of Cu: the cell surface metalloreductase (DCYTB); the Cu importers, divalent metal ion transporter (DMT1) and Cu transporter 1 (CTR1); the intracellular Cu chaperone (HAH1) and metallothionein (MT); the Cu transporting ATPases (ATP7A and ATP7B)(4).
Human intestinal Caco-2 cells, cultured for 19 d, were treated for 16 h with a flavonoid-rich berry-extract (OptiBerry; InterHealth Nutraceuticals, Benicia, CA, USA) at a final concentration of 0.125% (w/v). RNA was isolated for quantitative RT–PCR. All gene expression data were normalised to 18S and GAPDH as housekeeping genes and presented as mean normalised expression ratios ±SEM. Statistical significance was determined by Student's t test with significance indicated at P⩽0.05 (n 12).
Following treatment with the berry extract there were significant decreases in DMT1 (0.73±0.08, P<0.04), CTR1 (0.67±0.06, P<0.01), HAH1 (0.82±0.06, P<0.03) and ATP7B (0.72±0.05, P<0.001) mRNA expression (Fig. 1). The mRNA expression of the other genes did not change significantly in response to the berry-extract treatment.
These results indicate that berry flavonoids influence the expression of components of the Cu-uptake pathway. Studies are in progress to investigate the biological relevance of the observed effects in relation to berry consumption and the bioavailability of dietary Cu.