Objective: To investigate and compare the effects of two common dietary phytosterols, stigmasterol and β-sitosterol, in altering lipid metabolism and attenuating nonalcoholic fatty liver disease (NAFLD). Methods: Stigmasterol and β-sitosterol were administered to mice at 0.4% in a high-fat western-style diet (HFWD) for 17 weeks. Results: Stigmasterol and β-sitosterol significantly ameliorated HFWD-induced fatty liver and metabolic abnormalities, including elevated levels of hepatic total lipids, triacylglycerols, cholesterol and liver histopathology. Both phytosterols decreased the levels of intestinal bile acids, accompanied by markedly increased fecal lipid levels. In addition, they altered the expression of genes involved in lipid metabolism. β-Sitosterol was less effective in affecting most of these parameters. Lipidomic analysis of liver and serum samples showed that stigmasterol prevented the HFWD-induced elevation of some di- and triacylglycerol species and lowering of some phospholipid species. Stigmasterol also decreased serum levels of ceramides. Conclusion: Stigmasterol and β-sitosterol, at a dose corresponding to that suggested for humans by the FDA for lowering cholesterol levels, are shown to alleviate HFWD-induced NAFLD. Stigmasterol was more effective than β-sitosterol, possibly because of its suppression of hepatic lipogenic gene expression and modulation of circulating ceramide levels.

The cancer preventive activity of vitamin E has been extensively discussed, but the activities of specific forms of tocopherols have not received sufficient attention. Herein, we compared the activities of δ-tocopherol (δ-T), γ-T and α-T in a colon carcinogenesis model. Male F344 rats, 7 weeks old, were given 2 weekly subcutaneous injections of azoxymethane (AOM) each at a dose of 15 mg/kg body weight. Starting 1 week before the AOM injection, the animals were maintained on a modified AIN76A diet, or the same diet containing 0.2% of δ-T, γ-T, α-T or a γ-T-rich mixture of tocopherols (γ-TmT), until the termination of the experiment at 8 weeks after the second AOM injection. δ-T treatment showed the strongest inhibitory effect, decreasing the numbers of aberrant crypt foci by 62%. γ-T and γ-TmT were also effective, but α-T was not. Immunohistochemical analysis showed that δ-T and γ-T treatments reduced the levels of 4-hydroxynonenal and nitrotyrosine and the expression of cyclin D1 in the colon, preserved the expression of PPAR-γ, and decreased the serum levels of prostaglandin E2 and 8-isoprostane. Supplementation with 0.2% δ-T, γ-T or α-T increased the respective levels of tocopherols and their side-chain degradation metabolites in the serum and colon tissues. Rather high concentrations of δ-T and γ-T and their metabolites were found in colon tissues. Our study provides the first evidence for the much higher cancer preventive activity of δ-T and γ-T than α-T in a chemically-induced colon carcinogenesis model. It further suggests that δ-T is more effective than γ-T.

To study the effects of stigmasterol and β-sitosterol on high-fat Western diet (HFWD)-induced nonalcoholic fatty liver disease (NAFLD), lipidomic analyses were conducted in liver samples collected after 33 weeks of the treatment. Principal component analysis showed these phytosterols were effective in protecting against HFWD-induced NAFLD. Orthogonal projections to latent structures-discriminate analysis (OPLS-DA) and S-plots showed that triacylglycerols (TGs), phosphatidylcholines, cholesteryl esters, diacylglycerols, and free fatty acids (FFAs) were the major lipid species contributing to these discriminations. The alleviation of NAFLD is mainly associated with decreases in hepatic cholesterol, TGs with polyunsaturated fatty acids, and alterations of free hepatic FFA. In conclusion, phytosterols, at a dose comparable to that suggested for humans by the FDA for the reduction of plasma cholesterol levels, are shown to protect against NAFLD in this long-term (33-week) study.

To develop a relevant mouse model for prostate cancer prevention research, we administered a dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), to CYP1A-humanized mice. In comparison to mouse Cyp1a2, human CYP1A2 preferentially activates PhIP to a proximate carcinogen. Following a single oral dose of PhIP (200 mg/kg body weight), we observed inflammation, atrophy of acini, low-grade prostatic intraepithelial neoplasia (PIN) (after 20 weeks) and high-grade PIN (HgPIN) (after 30 to 50 weeks) in dorso-lateral, ventral and coagulating anterior prostate glands of these mice. These lesions were androgen receptor positive and featured the loss of expression of the basal cell marker p63 and the tumor suppressor PTEN. Similar to human prostate carcinogenesis, glutathione-S-transferase P1 (GSTP1) expression was lost or partially lost in HgPIN. E-Cadherin expression was also lost in HgPIN. The expression of DNA methyltransferase 1 was elevated, possibly to enhance promoter hypermethylation for the silencing of GSTP1 and E-cadherin. Prostate carcinogenesis was promoted by a high-fat stress diet, resulting in HgPIN that developed earlier and in advanced lesions displayed features consistent with carcinoma in situ. This dietary carcinogen-induced prostate cancer model, recapitulating important features of early human prostate carcinogenesis, constitutes a new experimental system for prostate cancer research.