Effects of a grape-supplemented diet on proliferation and Wnt signaling in the colonic mucosa are greatest for those over age 50 and with high arginine consumption

Abstract

A diet rich in fruits and vegetables, and a grape-derived compound, resveratrol, have been linked to a reduced incidence of colon cancer. In vitro and in vivo, resveratrol suppresses Wnt signaling, a pathway constitutively activated in over 85 % of colon cancers.Thirty participants were placed on a low resveratrol diet and subsequently allocated to one of three groups ingesting 1/3-to-1 lb (0.15-0.45 kg) of grapes per day for 2 weeks. Dietary information was collected via 24-h recall. Colon biopsies for biomarker analysis were obtained pre- and post-grape and evaluated for the expression of Wnt pathway target genes and for markers of proliferation by RT-PCR and immunohistochemistry.Participants lost an average of 2 · 6 lb (1.2 kg, p = 0 · 0018) during the period of grape ingestion. The expression of CyclinD1 (p < 0 · 01), AXIN2, CD133 (p = 0 · 02) and Ki67 (p = 0 · 002) were all reduced after grape ingestion. Individuals over 50 years of age and those with high dietary arginine consumption had increased basal expression of CyclinD1, AXIN2, cMYC and CD133 (p value range 0 · 04 to <0 · 001) that, following grape ingestion, were reduced to levels seen in younger participants.The reduction in Wnt signaling and mucosal proliferation seen following short-term ingestion of 1/3-1 lb (0.15-0.45 kg) of grapes per day may reduce the risk of mutational events that can facilitate colon carcinogenesis. The potential benefit is most marked for high-risk older individuals and individuals whose diet is high in arginine intake. Dietary grape supplementation may play a role in colon cancer prevention for high-risk individuals.

Fig. 1

Schematic of the clinical trial design. The controlled reservatrol diet was maintained throughout the 4 week period. Grape ingestion occurred during the final 2 weeks

Fig. 2

Change in individual (a) and mean (b) weights for the 30 participants from pre-grape ingestion timepoint to the post-grape ingestion timepoint. Grape ingestion significantly reduced expression as measured by qRT-PCR of CyclinD1 (c) and CD133 (e) with a non-statistically significant reduction in AXIN2 (d). However, CyclinD1 and AXIN2 levels in colonic mucosa were strongly correlated with each other both pre-grape ingestion (h) and post-grape ingestion (i). Ki67 expression was also reduced following grape ingestion (f). This was measured by calculating the percentage of positively staining cells in the lower 1/3 of colonic crypts (g; representative photomicrograph—green represents positive immunofluorescence). *p < 0 · 05; ** p < 0 · 01; *** p < 0 · 005

Fig. 3

Differences in expression of CyclinD1 (a), AXIN2 (b), cMYC (c) and CD133 (d) in participants below age 50 and 50 years old and above. Prior to grape ingestion, older individuals had significantly higher levels of CyclinD1, AXIN2, cMYC and CD133 than individuals aged 18–49. Grape ingestion in participants aged 50 and above led to a reduction in the expression CyclinD1 (p < 0 · 01), AXIN2, cMYC and CD133. Levels of CyclinD1 and AXIN2 in participants aged 50 and above were reduced to levels seen prior to grape ingestion in 18–49 year olds. While reduced after grape ingestion, the level of expression of cMYC and CD133 in participants aged 50 and above remained significantly elevated when compared to the pre-grape ingestion levels of 18–49 year olds. *p < 0 · 05; **p < 0 · 01; ***p < 0 · 001

Fig. 4

Differences in expression of CyclinD1 (a), AXIN2 (b), cMYC (c) and CD133 (d) in participants with high baseline arginine consumption and those with low baseline arginine consumption. Individuals with high arginine intake had significantly higher expression of each of these markers. In those with high arginine intake, grape ingestion led to a statistically significant reduction in CyclinD1 expression to levels seen in those with low arginine intake. Grape intervention did not significantly change the expression of CyclinD1 in participants with low initial arginine intake. *P < 0 · 05; **p < 0 · 01; ***p < 0 · 005