Plant stanols induce intestinal tumor formation by up-regulating Wnt and EGFR signaling in Apc Min mice

Combined Effects of Plant Sterols with Low Ratio of n-6/n-3 Polyunsaturated Fatty Acids against Atherosclerosis in ApoE-/- Mice

The effects of low ratio of n-6/n-3 polyunsaturated fatty acids (PUFA) have been clarified against atherosclerosis. Increasing evidence indicated that plant sterols (PS) have a significant cholesterol-lowering effect. This study explored the effects of PS combined with n-6/n-3 (2:1) PUFA on atherosclerosis and investigated the possible mechanism. In ApoE^-/- mice, the milk fat in high fat diets was replaced with n-6/n-3 (2:1) PUFA alone or supplemented with 6% PS for 16 weeks. Results demonstrated that PS combined with PUFA exerted commentary and synergistic effects on ameliorating atherosclerosis, improving lipid metabolism and lipid deposition in liver, and alleviating inflammatory response. These changes were accompanied with decreased serum TC, TG, LDL-C and increased fecal cholesterol efflux, as well as the lower inflammatory cytokine CRP, IL-6, TNF-α. It is suggested that the underlying mechanism of PS combined with n-6/n-3 (2:1) PUFA promoting the fecal cholesterol efflux may be mediated by liver X receptor α/ATP-binding cassette transporter A1 pathway.

Dietary feeding of freeze-dried whole cranberry inhibits intestinal tumor development in Apcmin/+ mice

It is increasingly perceived that dietary components have been linked with the prevention of intestinal cancer. Cranberry is a rich source of phenolic constituents and non-digestible fermentable dietary fiber, which shows anti-proliferation effect in colorectal cancer cells. Herein, we investigated the efficacy of long-term cranberry diet on intestinal adenoma formation in Apc^min/+ mice. Apc^min/+ mice were fed a basal diet or a diet containing 20% (w/w) freeze-dried whole cranberry powder for 12 weeks, and the number and size of tumors were recorded after sacrifice. Our results showed that cranberry strongly prevented the growth of intestinal tumors by 33.1%. Decreased cell proliferation and increased apoptosis were observed in tumors of cranberry-fed mice. Cranberry diet reduced the expression profile of colonic inflammatory cytokines (IFN-γ, IL-1β and TNF-α) accompanied with increased levels of anti-inflammatory cytokines (IL-4 and IL-10). Moreover, the number of colonic goblet cells and MUC2 production were increased, and the intestinal barrier function was also improved. In addition, cranberry diet increased caecal short chain fatty acids concentrations, and down-regulated epidermal growth factor receptor signaling pathway. These data firstly show the efficacy and associated mechanisms of cranberry diet on intestinal tumor growth in Apc^min/+ mice, suggesting its chemopreventive potential against intestinal cancer.

Western diet enhances intestinal tumorigenesis in Min/+ mice, associating with mucosal metabolic and inflammatory stress and loss of Apc heterozygosity

Western-type diet (WD) is a risk factor for colorectal cancer, but the underlying mechanisms are poorly understood. We investigated the interaction of WD and heterozygous mutation in the Apc gene on adenoma formation and metabolic and immunological changes in the histologically normal intestinal mucosa of Apc^Min/+ (Min/+) mice. The diet used was high in saturated fat and low in calcium, vitamin D, fiber and folate. The number of adenomas was twofold higher in the WD mice compared to controls, but adenoma size, proliferation or apoptosis did not differ. The ratio of the Min to wild-type allele was higher in the WD mice, indicating accelerated loss of Apc heterozygosity (LOH). Densities of intraepithelial CD3ε⁺ T lymphocytes and of mucosal FoxP3⁺ regulatory T cells were higher in the WD mice, implying inflammatory changes. Western blot analyses from the mucosa of the WD mice showed suppressed activation of the ERK and AKT pathways and a tendency for reduced activation of the mTOR pathway as measured in phosphoS6/S6 levels. The expression of pyruvate dehydrogenase kinase 4 was up-regulated in both mRNA and protein levels. Gene expression analyses showed changes in oxidation/reduction, fatty acid and monosaccharide metabolic pathways, tissue organization, cell fate and regulation of apoptosis. Together, our results suggest that the high-risk Western diet primes the intestine to tumorigenesis through synergistic effects in energy metabolism, inflammation and oxidative stress, which culminate in the acceleration of LOH of the Apc gene.

Plant sterol and stanol intake in Finland: a comparison between users and nonusers of plant sterol- and plant stanol-enriched foods

BACKGROUND/ OBJECTIVES: We evaluated plant sterol and stanol (PS) intakes from natural sources and enriched foods in the Finnish population-based national FINDIET 2007 Survey. In addition, we compared the users and nonusers of PS-enriched foods in terms of their characteristics and dietary intake.

SUBJECTS/METHODS

This was a cross-sectional population-based study on 958 men and 1080 women aged 25-74. Users and nonusers of PS-enriched products were compared with respect to sex, age, education, region, cholesterol-lowering medication and cholesterol-lowering diet. Intakes of PS, energy, energy nutrients, fat composition, cholesterol and dietary fibre were calculated on the basis of a 48-h dietary recall. The distribution of PS intake was assessed for the users of enriched products.

RESULTS

PS-enriched foods were used by 9.5% of all subjects. The usage increased significantly with age (P<0.001) and level of education (P=0.01). The usage of enriched products was more common among those following a cholesterol-lowering medication or diet (P<0.001 for both). Among users, the mean intake of PS was 2.2 g/d for men and 1.6 g/d for women, and among nonusers it was 363 mg/d for men and 286 mg/d for women. The majority of users received less than 2 g/d of PS from enrichment, but 20% of users obtained more than 3 g of PS per day.

CONCLUSIONS

The intake of PS can reach several grams in a subgroup of subjects consuming PS-enriched foods. The manufacturers' recommendations on PS-enriched food consumption are not consistently followed, and customer guidance needs to be improved.

Plant sterol feeding induces tumor formation and alters sterol metabolism in the intestine of Apc(Min) mice

Dietary plant sterols reduce the absorption of cholesterol and therefore increase intraluminal cholesterol concentration. We examined how plant sterol esters from functional foods affect intestinal tumorigenesis in tumor-prone adenomatous polyposis coli (Apc)(Min) mice. Feeding plant sterols at 0.8% increased the number of intestinal adenomas, and the effect was significant in female mice. The concentration of mucosal free sitosterol increased by eightfold in plant sterol males and by threefold in plant sterol females when compared with respective controls. The concentration of mucosal free cholesterol was significantly lower in plant sterol males than in control males, and the decrease in free cholesterol was accompanied with a significant increase in nuclear sterol regulatory element binding protein-2. No difference was found in the levels of β-catenin, cyclin D1, epidermal growth factor receptor, extracellular signal-regulated kinase 1/2, or caveolin-1 in either gender after plant sterol feeding. Among all measured parameters, higher levels of estrogen receptor β and free cholesterol in the mucosa were among the strongest predictors of increased intestinal tumorigenesis. In addition, gene expression data showed significant enrichment of up-regulated genes of cell cycle control and cholesterol biosynthesis in plant sterol females. The results indicate that high intake of plant sterols accelerates intestinal tumorigenesis in female Apc (Min)mice; however, the mechanism behind the adverse effect remains to be discovered.