IGF-1 related gene expression in colon and reduced IGF-1 serum levels: studies in the voluntary rat exercise model

Insulin/insulin-like growth factor actions play an essential role in association with colon cancer prevention by physical exercise. For this reason, we investigated some IGF-1 associated parameters in the colon mucosa after using our voluntary long-term exercise (12 weeks) animal model including 20 male Wistar rats (exercise group=EX). 9 rats served as a control group (CO). mRNA levels of IGF-1, IGF-1R and IGFBP3 in the colon mucosa were detected via Real-Time RT-PCR and IGF-1 hormone serum levels were measured via enzyme immunoassay. At the end, we distinguished 3 running groups: a low running distance (L-EX, <2629m/night), a middle running distance (M-EX, 3003–7458m/night) and a high running distance (H-EX, >8314m/night) group. In response to the voluntary exercise M-EX and H-EX showed significant higher heart masses and lower body weights compared to the CO. Gene expression analysis of IGF-1, IGF-1R and IGFBP3 in the colon mucosa showed no significant regulations but revealed some trends (Fig. 1).

[Fig. 1]

In contrast, hormone levels of all distinguished exercise groups were significantly lower compared to the CO. Correlation analysis showed significant positive correlations between IGF-1 hormone level and body weight (r=0.4) and negative correlations between BW and running distances (r=-0.5). In summary, this is the first study investigating colon gene expression after physical activity. The positive relationship between body weight and serum IGF-1 level and the negative correlation between running distance and body weight indicate that exercise-induced body weight reductions may decrease levels of blood IGF-1 and may thereby induce relevant pathways for the colon cancer prevention by physical exercise. In addition, modulations of the IGF-1 related gene expression in the colon mucosa seem to be independent from the IGF-1 serum levels.