Effects of Mixed Nuts on Colonic Cell Proliferation and Ptgs2 and Rela Gene Expression

Nut consumption is associated with lower risk of colorectal cancer (CRC). Previously, single nut varieties have been investigated but there is limited research on the consumption of a nut mixture and the underlying mechanisms. This study examined mixed nut consumption's effect on colonic cell proliferation, apoptosis, and gene expression involved in CRC.

Thirty 21-day old Sprague Dawley rats were divided into three groups: control (no nuts), pistachio or mixed nut for 8 weeks. Ki-67 quantitative immunostaining was used to mark proliferative cells and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay for apoptotic cells. Real-time quantitative polymerase chain reaction analysis was used to determine colonic gene expression of prostaglandin endoperoxide synthase 2 (Ptgs2), nuclear factor kappa-B p65 subunit (Rela), cyclin D1 (Ccnd1), peroxisome proliferator-activated receptor gamma (Pparg), O⁶-methylguanine-DNA-methyltransferase (Mgmt), 8-oxoguanine glycosylase (Ogg1), superoxide dismutase (Sod), and catalase (Cat).

DNA damage, determined using 8-oxo-deoxyguanosin, was found to be lower in the mixed nut group only (p<0.05). Differences in proliferation and apoptosis among all three groups were not significant. Lower levels of the inflammatory marker, Ptgs2, were observed between the pistachio group and the control (p=0.035). The pistachio and mixed nut groups had lower levels of Rela compared to the control (p=0.029). Differences among diets for Ccnd1, Pparg, Mgmt, Ogg1, Sod, and Cat were not significant.

Mixed nut consumption reduced DNA damage possibly via down-regulation of Rela inflammation gene expression without changes to colonic cell proliferation and apoptosis.