Potato and grape polyphenols, respectively, suppress high-fat diet-elevated oxidative stress/innate inflammation markers in porcine model and induce apoptosis in HCT-116 p53 +/+ and p53 -/- human colon cancer cell lines in vitro

Rationale. In Vitro Study. Bioactive compounds from fruits and vegetables have demonstrated anti-inflammatory, anti-oxidant and anti-cancer properties. Grapes and purple-fleshed potatoes are rich sources of polyphenols. Grape seed extract (GSE) a popular dietary supplement rich in proanthocyanidins, demonstrated anti-cancer properties in a variety of in vitro and in vivo models. Red grapes are rich in resveratrol (RSV), a compound that has shown anti-oxidant, anti-inflammatory and anti-cancer properties in a variety of models including human studies. We previously reported that RSV suppressed proliferation, and induced apoptosis via p53 activation in human colon cancer cell lines HT-29 and SW-480, however, only at high concentration > 75-100 muM. Since bioactive compounds exist as a complex mixture in fruits and vegetables with synergistic or additive chemopreventive/protective actions, we hypothesized that the combination of RSV and GSE would be a more potent mixture with efficacy at lower concentrations.;Animal Study High-fat diet (HFD) consumption is linked to elevated risk for a variety of disorders. HFD elevated oxidative stress and inflammation and provides conducive environment for chronic disorders such as colon cancer. Dietary modification can help reduce risk for such conditions. Indeed, higher consumption of bioactive compounds present in fruits and vegetables are inversely associated with risk for such inflammatory disorders. The potato is the third largest source of phenolic compounds in the human diet after oranges and apples. Purple-fleshed potatoes are rich in anthocyanins and phenolic acids with anti-oxidant and anti-inflammatory properties. Unlike other anthocyanin-rich sources such as blueberries, purple-fleshed potatoes are relatively inexpensive and widely available, but they are almost always consumed in processed form. The overall goal of these studies was to determine the extent to which purple-fleshed potato consumption, even after processing, prevent or reverse HFD elevated oxidative stress and innate inflammatory markers (colon, mesenteric fat and systemic circulation) in a pig model.;Animal Study Experiment Design We hypothesized that consumption of purple-fleshed potatoes, even after processing, will suppress HFD elevated colonic, mesenteric fat and systemic oxidative stress/inflammation markers in the pig model compared to white-fleshed potatoes and HFD control. To test this hypothesis, we performed two studies -- a prevention study where 64 pigs, 3 weeks post-weaning, consumed one of the eight diets: standard diet (SD), HFD and HFD supplemented with raw, baked or chipped purple or white-fleshed potatoes (10 % w/w) for 13 weeks; and a reversal study where pigs (12 weeks on HFD) consumed HFD containing 10/20 % purple or white-fleshed potato chips for additional 5 weeks (n = 8).;Results and Conclusions In Vitro Study Our results demonstrated that RSV (∼ 25 muM) and GSE (35-50 mug/ml) mixture is potent in suppressing proliferation and elevating apoptosis in HCT-116 p53 +/+ human colon cancer cell lines at lower concentrations compared to RSV or GSE alone. RSV potentiated GSE induced p53 dependent apoptosis via mitochondrial apoptotic signaling as evidenced by elevated Bax:Bcl-2 ratio, reactive oxygen species and activated caspase-3. The RSV-GSE combination suppressed proliferation and induced apoptosis even in presence of IGF-1 (elevated during obesity), suggesting its potential role as a chemopreventive agent against IGF-1 promoted colon cancer. Moreover, RSV-GSE did not suppress proliferation or induce apoptosis in normal colonic epithelial cell line CRL-1831, demonstrating its specificity to cancer cells. These results strongly support our hypothesis that combining bioactive compounds like RSV and GSE could provide similar or better anti-colon cancer properties compared to individual compounds at lower concentrations. This lends support to the proposal that combinatorial approach towards colon cancer chemoprevention using bioactive compounds is a feasible approach. However, animal studies using such a RSV-GSE combination is warranted.;Animal Study In the prevention study, only the purple-fleshed potato raw group had significantly lower distal colonic and mesenteric fat oxidative stress (measured using GSH:GSSG ratio, a sensitive marker for oxidative stress) compared to the HFD control. However, all the potato diets consuming animals had suppressed (P < 0.05) distal colonic and mesenteric fat expression of innate inflammatory markers TLR-4, NF-kappaB, and TNF-alpha compared to the HFD control and similar to that of SD control animals. Animals consuming potato diets had significantly suppressed urinary 8-isoprostane (8IP) and DNA adduct 8-OHDG (Enzyme immunoassay), and serum TNF-alpha (ELISA) and IL-1beta (Milliplex immunoassay) compared to the HFD control animals. In the reversal study, the markers of distal colonic and systemic oxidative stress and inflammation were consistently suppressed only in the purple-fleshed potato consuming groups compared to HFD controls (P ≤ 0.05), suggesting that time of intervention is very important. Results from both studies show that only the purple-fleshed potato, even after processing, prevented and reversed HFD elevated oxidative stress/inflammation markers in the distal colon, mesenteric fat and systemic circulation, in the pig -- a human relevant animal model. (Abstract shortened by UMI.).