Effect of dietary phytosterols on cell proliferation and protein kinase C activity in rat colonic mucosa

Molecular characterization and transcriptional regulation analysis of the Torreya grandis squalene synthase gene involved in sitosterol biosynthesis and drought response

The kernel of Torreya grandis cv. 'Merrillii' (Cephalotaxaceae) is a rare nut with a variety of bioactive compounds and a high economic value. β-sitosterol is not only the most abundant plant sterol but also has various biological effects, such as antimicrobial, anticancer, anti-inflammatory, lipid-lowering, antioxidant, and antidiabetic activities. In this study, a squalene synthase gene from T. grandis, TgSQS, was identified and functionally characterized. TgSQS encodes a deduced protein of 410 amino acids. Prokaryotic expression of the TgSQS protein could catalyze farnesyl diphosphate to produce squalene. Transgenic Arabidopsis plants overexpressing TgSQS showed a significant increase in the content of both squalene and β-sitosterol; moreover, their drought tolerance was also stronger than that of the wild type. Transcriptome data from T. grandis seedlings showed that the expression levels of sterol biosynthesis pathway-related genes, such as HMGS, HMGR, MK, DXS, IPPI, FPPS, SQS, and DWF1, increased significantly after drought treatment. We also demonstrated that TgWRKY3 directly bound to the TgSQS promoter region and regulated its expression through a yeast one-hybrid experiment and a dual luciferase experiment. Together, these findings demonstrate that TgSQS has a positive role in β-sitosterol biosynthesis and in protecting against drought stress, emphasizing its importance as a metabolic engineering tool for the simultaneous improvement of β-sitosterol biosynthesis and drought tolerance.

Phytochemicals in Cancer Treatment and Cancer Prevention-Review on Epidemiological Data and Clinical Trials

Phytochemicals are a non-nutritive substances that are present in plants and contribute significantly to their flavor and color. These biologically active compounds are classified into five major groups, namely phenolics, carotenoids, organosulfur compounds, nitrogen-containing compounds, and alkaloids, and are known for their potential health benefits in the prevention of various diseases, including cancer. The purpose of this review article is to explore the potential therapeutic benefits of the dietary phytochemicals, such as flavonoids, phenolic acids, phytosterols, carotenoids, and stilbenes, in cancer treatment and prevention based on the epidemiological studies and clinical trials. Although the majority of epidemiological studies report a significant advantage of the heightened phytochemical consumption and increased serum levels of these compounds, linking increased exposure with a lower cancer risk across most cancer types, these effects could not be replicated in the most available clinical trials. In fact, many of these trials were withdrawn early due to a lack of evidence and/or risk of harm. Despite the strong anticancer effect of phytochemicals, as well as their proven efficacy in multiple epidemiological studies, there is still a great need for human studies and clinical trials, with great caution regarding the safety measures. This review article provides an overview of the epidemiological and clinical evidence supporting the potential chemopreventive and anticancer properties of phytochemicals, with a focus on the need for further research in this area.

Medicinal Potential of Heterocyclic Compounds from Diverse Natural Sources for the Management of Cancer

Natural products form a significant portion of medicinal agents that are currently used for the management of cancer. All these natural products have unique structures along with diverse action mechanisms with the capacity to interact with different therapeutic targets of several complex disorders. Although plants contribute as a major source of natural products with anti-cancer potential, the marine environment and microbes have also bestowed some substantial chemotherapeutic agents. A few examples of anti-cancer agents of natural origin include vincristine, vinblastine, paclitaxel, camptothecin and topotecan obtained from plants, bryostatins, sarcodictyin and cytarabine from marine organisms and bleomycin and doxorubicin from micro-organisms (dactinomycin, bleomycin and doxorubicin). The incredible diversity in the chemical structures and biological properties of compounds obtained from million species of plants, marine organisms and microorganisms present in nature has commenced a new era of potential therapeutic anti-cancer agents.

The Phytosterol Peniocerol Inhibits Cell Proliferation and Tumor Growth in a Colon Cancer Xenograft Model

Objective: This study aimed to evaluate the cytotoxic activity of peniocerol against human colon cancer cell lines and its antitumor effect in vivo in a xenograft model using nu/nu mice.

Materials and Methods: SW-620, HCT-15, and HCT-116 colon cancer cell lines were treated with peniocerol for cytotoxicity by crystal violet technique. Cell apoptosis induction was detected by flow cytometry, and the antitumor activity of peniocerol was evaluated in a xenograft model of HCT-116 in nu/nu mice. After treatment, the effect of peniocerol was analyzed in histological sections of tumors by immunohistochemistry using DAPI, anti-PCNA, and PARP-1 antibodies.

Results: Peniocerol inhibited cell growth and induced apoptosis in vitro in a time and dose-dependent manner. Besides, peniocerol administration (30 or 15 mg/kg) inhibited tumor growth and induced apoptosis in the xenograft mice. The lack of peniocerol toxicity was proved by a biochemical blood analysis of healthy nu/nu mice administrated with this sterol.

Conclusions: Our results proved that peniocerol induces apoptosis in vitro and in vivo assays.

Phytosterols and Triterpenoids for Prevention and Treatment of Metabolic-related Liver Diseases and Hepatocellular Carcinoma

Background:

Liver ailments are among the leading causes of death; they originate from viral infections, chronic alcoholism, and autoimmune illnesses, which may chronically be precursors of cirrhosis; furthermore, metabolic syndrome may worsen those hepatopathies or cause Non-alcoholic Fatty Liver Disease (NAFLD) that may advance to non-alcoholic steatohepatitis (NASH). Cirrhosis is the late-stage liver disease and can proceed to hepatocellular carcinoma (HCC). Pharmacological treatment options for liver diseases, cirrhosis, and HCC, are limited, expensive, and not wholly effective. The use of medicinal herbs and functional foods is growing around the world as natural resources of bioactive compounds that would set the basis for the development of new drugs.

Review and Conclusion:

Plant and food-derived sterols and triterpenoids (TTP) possess antioxidant, metabolic-regulating, immunomodulatory, and anti-inflammatory activities, as well as they are recognized as anticancer agents, suggesting their application strongly as an alternative therapy in some chronic diseases. Thus, it is interesting to review current reports about them as hepatoprotective agents, but also because they structurally resemble cholesterol, sexual hormones, corticosteroids and bile acids due to the presence of the steroid nucleus, so they all can share pharmacological properties through activating nuclear and membrane receptors. Therefore, sterols and TTP appear as a feasible option for the prevention and treatment of chronic metabolic-related liver diseases, cirrhosis, and HCC.

The relationship between nut intake and risk of colorectal cancer: a case control study

BACKGROUND

Nut consumption is known to reduce the risk of obesity, diabetes mellitus, and cardiovascular disease. However, in previous studies, portion sizes and categories of nut consumption have varied, and few studies have assessed the association between colorectal cancer risk and nut consumption. In this study, we investigated the relationship between nut consumption and colorectal cancer risk.

METHODS

A case-control study was conducted among 923 colorectal cancer patients and 1846 controls recruited from the National Cancer Center in Korea. Information on dietary intake was collected using a semi-quantitative food frequency questionnaire with 106 items, including peanuts, pine nuts, and almonds (as 1 food item). Nut consumption was categorized as none, < 1 serving per week, 1-3 servings per week, and ≥3 servings per week. A binary logistic regression model was used to estimate odds ratios (OR) and their 95% confidence intervals (CI) for the association between nut consumption and colorectal cancer risk, and a polytomous logistic regression model was used for sub-site analyses.

RESULTS

High nut consumption was strongly associated with reduced risk of colorectal cancer among women (adjusted ORs: 0.30, 95%CI: 0.15-0.60 for the ≥3 servings per week group vs. none). A similar inverse association was observed for men (adjusted ORs: 0.28, 95% CI: 0.17-0.47). In sub-site analyses, adjusted ORs (95% CIs) comparing the ≥3 servings per week group vs none were 0.25 (0.09-0.70) for proximal colon cancer, 0.39 (0.19-0.80) for distal colon cancer, and 0.23 (0.12-0.46) for rectal cancer among men. An inverse association was also found among women for distal colon cancer (OR: 0.13, 95% CI: 0.04-0.48) and rectal cancer (OR: 0.40, 95% CI: 0.17-0.95).

CONCLUSIONS

We found a statistically significant association between high frequency of nut consumption and reduced risk of colorectal cancer. This association was observed for all sub-sites of the colon and rectum among both men and women, with the exception of proximal colon cancer for women.

Daucosterol Inhibits the Proliferation, Migration, and Invasion of Hepatocellular Carcinoma Cells via Wnt/β-Catenin Signaling

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. The purpose of this study was to determine the effects of daucosterol on HCC by investigating Wnt/β-catenin signaling. In this study, HepG2 and SMMC-7721 cells were treated with varying concentrations of daucosterol, and the corresponding inhibitory effects on HCC cells were examined via CCK-8 assays. Cell migration and invasion abilities were detected via transwell assays. β-Catenin and phospho (p)-β-catenin levels were analyzed via western blotting. Our results showed that daucosterol reduced the proliferation, migration, and invasion capacities of HCC cells in a concentration-dependent manner. In addition, daucosterol reduced the levels of β-catenin and p-β-catenin in HepG2 and SMMC-7721 cells. Furthermore, the Wnt signaling pathway inhibitor SB-216763 was used to treat HepG2 and SMMC-7721 cells with daucosterol. Our results showed that co-treatment with daucosterol and SB-216763 abolished the effects of daucosterol on cell inhibition ratios, cell migration, and cell invasion. These findings indicated that daucosterol inhibited cell migration and invasion in HCC cells via the Wnt/β-catenin signaling pathway. Therefore, our study highlights the use of daucosterol as a promising therapeutic strategy for HCC treatment.

In vitro evaluation of Pandanus amaryllifolius ethanol extract for induction of cell death on non-hormone dependent human breast adenocarcinoma MDA-MB-231 cell via apoptosis

BACKGROUND

Our previous study had shown that P. amaryllifolius was able to selectively inhibit cell proliferation of hormone independent breast cancer cell line MDA-MB-231. To understand the mode of killing and mechanism of action for P. amaryllifolius, the ethanol extract was evaluated for their alteration of cell cycle progression, PS externalization, DNA fragmentation and expression of anti/pro-apoptotic related protein.

RESULTS

Cell cycle progression analysis, Annexin V and Tunel assays suggested that IC50 of P. amaryllifolius ethanol extract induced G0/G1 cell cycle arrest, PS externalization and DNA fragmentation. On the other hand, ELISA for cytochrome c, caspase-3/7, 8 and 9 indicated that apoptosis was contributed by mitochondrial cytochrome c release via induction of caspase 3/7, 9, and p53 was associated with the suppression of XIAP in P. amaryllifolius treated MDA-MB-231 cells.

CONCLUSION

Our findings suggest that P. amaryllifolius ethanol extract induced apoptosis on hormone independent breast cancer cell line MDA-MB-231.

Phytochemicals and cancer risk: a review of the epidemiological evidence

A number of epidemiological studies have investigated associations between various phytochemicals and cancer risk. Phytoestrogens and carotenoids are the two most commonly studied classes of phytochemicals; phytosterols, isothiocyanates, and chlorophyll also have been investigated, although to a much lesser extent. Because there have been no systematic reviews of the literature on all phytochemicals and cancer risk to date, this article systematically reviews 96 published epidemiological studies that examined associations between phytochemicals and cancer risk. Most studies found null associations between individual phytochemicals and cancer risk at various sites. In addition, results from past studies have been largely inconsistent, and observed associations have been of relatively modest magnitude. The most consistent protective effects were observed for higher levels--dietary intake, serum, plasma, or urinary metabolites--of β-carotene and renal cell cancer, β-cryptoxanthin and lung cancer, isothiocyanates and lung cancer, isothiocyanates and gastrointestinal cancer, lignans and postmenopausal breast cancer, and flavonoids and lung cancer. Although elevated risk of certain cancers with higher levels of certain phytochemicals was observed, an insufficient pool of studies examining the same associations or inconsistent findings across studies limit the ability to conclude that any one phytochemical increases cancer risk. Additional research is needed to support previously identified associations in cases where only one study has examined a particular relationship. Importantly, continued research efforts are needed to evaluate the cumulative and interactive effects of numerous phytochemicals and phytochemical-rich foods on cancer risk.

In vitro cytotoxicity of Strobilanthes crispus ethanol extract on hormone dependent human breast adenocarcinoma MCF-7 cell

Background

Strobilanthes crispus has been traditionally used as antidiabetic, anticancer, diuretic, antilytic and laxative agent. However, cytotoxicity and antiproliferative effect of S. crispus is still unclear.

Results

Strobilanthes cripus was able to reduce cell viability and proliferation in MTT and BrdU assays. Both cell cycle progression and Tunel assay suggested that IC₅₀ of S. crispus ethanol extract induced sub-G1 cell cycle phase, and DNA fragmentation. On the other hand, translocation of mitochondria cytochrome c release, induction of caspase 3/7 and p53 while suppress XIAP on treated MCF-7 cell were also observed in this study.

Conclusion

Our findings suggest that S. crispus ethanol extract induced apoptosis and DNA fragmentation on hormone dependent breast cancer cell line MCF-7 via mitochondria dependent p53 apoptosis pathway.

Kenaf seed supercritical fluid extract reduces aberrant crypt foci formation in azoxymethane-induced rats

Kenaf (Hibiscus cannabinus) a plant of the family Malvaceae, is a valuable fiber plant native to India and Africa. Kenaf seeds contain alpha-linolenic acid, phytosterol such as β-sitosterol, vitamin E and other antioxidants with chemopreventive properties. In the present study we examined the hypothesis that kenaf seed 'supercritical fluid extract' (SFE) extract could suppress the early colon carcinogenesis in vivo by virtue of its bioactive compounds. To accomplish this goal, 60 male rats were randomly assigned to 5 groups which were (1) negative control group [not induced with azoxymethane (AOM)]; (2) positive control group (induced with AOM but received no treatment); (3) group treated with 500 mg/kg kenaf seed SFE extract; (4) group treated with 1000 mg/kg kenaf seed SFE extract; (5) group treated with 1500 mg/kg kenaf seed SFE extract. At 7 weeks of age, all rats except the negative control group received 15 mg/kg of AOM injection subcutaneously once a week for 2 weeks. Rats were euthanized at 13 weeks of the experiment. Number of ACF (mean±SD) ranged from 84.4±4.43 to 179.5±12.78 in group 2, 3, 4, 5. ACF reductions compared with the untreated group were 45.3, 51.4 and 53.1% in rats fed with 500, 1000 and 1500 mg/kg body weight, respectively. There were no significant differences in weight gain among groups. Our finding indicates that kenaf seed SFE extract reduced AOM-induced ACF in Sprague-Dawley male rats.

Modulation of signal transduction in cancer cells by phytosterols

Phytosterols are biofactors found enriched in plant foods such as seeds, grains, and legumes. Their dietary consumption is associated with numerous health benefits. Epidemiologic and experimental animal studies indicate that phytosterols are cancer chemopreventive agents particularly against cancers of the colon, breast, and prostate. Phytosterols impede oncogenesis and prevent cancer cell proliferation and survival. The molecular mechanisms underlying these beneficial actions involve effects on signal transduction processes which regulate cell growth and apoptosis. Phytosterols increase sphingomyelin turnover, ceramide formation, and liver X receptor activation. In concert, these actions slow cell cycle progression, inhibit cell proliferation, and activate caspase cascades and apoptosis in cancer cells.

Beta-sitosterol inhibits cell growth and induces apoptosis in SGC-7901 human stomach cancer cells

Beta-sitosterol is an important phytosterol found in plant food. It has been shown to have antiproliferative effects on cancers of the colon, breast, and prostate, but its effect on stomach cancer cells in vitro is unknown. Proliferation, cytotoxicity, and apoptosis in SGC-7901 human stomach cancer cells were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, clone formation, lactate dehydrogenase (LDH) leakage assay, acridine orange (AO)/ethidium bromide (EB) double staining, 4',6-diamidine-2'-phenylindole dihydrochloride (DAPI) staining, comet assay, and Western blotting. The results showed that beta-sitosterol suppresses the proliferation and induces the cell cytotoxicity of SGC-7901 stomach cancer cells in a time- and dose-dependent manner. Cells treated with different concentrations of beta-sitosterol also showed changes typical of apoptosis: morphological changes, DNA damage, increased expression of pro-caspase-3 and bax (p < 0.05), and activation of pro-caspase-3 and suppression of bcl-2 expression (p < 0.05). This study therefore revealed that beta-sitosterol significantly inhibits the growth and induces the apoptosis of SGC-7901 human stomach cancer cells in vitro. The decrease of the bcl-2/bax ratio and DNA damage may be the critical mechanisms of apoptosis induced by beta-sitosterol in SGC-7901 human stomach cancer cells.

Suppression of implanted MDA-MB 231 human breast cancer growth in nude mice by dietary walnut

Walnuts contain components that may slow cancer growth including omega 3 fatty acids, phytosterols, polyphenols, carotenoids, and melatonin. A pilot study was performed to determine whether consumption of walnuts could affect growth of MDA-MB 231 human breast cancers implanted into nude mice. Tumor cells were injected into nude mice that were consuming an AIN-76A diet slightly modified to contain 10% corn oil. After the tumors reached 3 to 5 mm diameter, the diet of one group of mice was changed to include ground walnuts, equivalent to 56 g (2 oz) per day in humans. The tumor growth rate from Day 10, when tumor sizes began to diverge, until the end of the study of the group that consumed walnuts (2.9 +/- 1.1 mm(3)/day; mean +/- standard error of the mean) was significantly less (P > 0.05, t-test of the growth rates) than that of the group that did not consume walnuts (14.6 +/- 1.3 mm(3)/day). The eicosapentaenoic and docosahexaenoic acid fractions of the livers of the group that consumed walnuts were significantly higher than that of the group that did not consume walnuts. Tumor cell proliferation was decreased, but apoptosis was not altered due to walnut consumption. Further work is merited to investigate applications to cancer in humans.

Phytosterols as anticancer compounds

Phytochemicals have been proposed to offer protection against a variety of chronic ailments including cardiovascular diseases, obesity, diabetes, and cancer. As for cancer protection, it has been estimated that diets rich in phytochemicals can significantly reduce cancer risk by as much as 20%. Phytosterols are specific phytochemicals that resemble cholesterol in structure but are found exclusively in plants. Phytosterols are absorbed from the diet in small but significant amounts. Epidemiological data suggest that the phytosterol content of the diet is associated with a reduction in common cancers including cancers of the colon, breast, and prostate. The means by which dietary phytosterols may be achieving these effects is becoming clearer from molecular studies with tumorigenic research models. Phytosterols affect host systems potentially enabling more robust antitumor responses, including the boosting of immune recognition of cancer, influencing hormonal dependent growth of endocrine tumors, and altering sterol biosynthesis. In addition, phytosterols have effects that directly inhibit tumor growth, including the slowing of cell cycle progression, the induction of apoptosis, and the inhibition of tumor metastasis. This review summarizes the current state of knowledge regarding the anticancer effects of phytosterols.

Peanut consumption and reduced risk of colorectal cancer in women: A prospective study in Taiwan

AIM: To examine whether peanut consumption is associated with a reduced risk of colorectal cancer in a prospective cohort with a 10-year follow-up.

METHODS: In 1990-1992, residents (12 026 men and 11 917 women aged 30 to 65 years) in 7 townships, Taiwan, were interviewed and recruited into a cancer-screening cohort and annually followed up. Colorectal cancer cases in this cohort were identified from cancer registry and death certificates. Incidence rates of this disease by the end of 2001 were calculated by gender for the primary study variable and covariates. The dietary intake was assessed by means of weekly food frequency measures, including frequently consumed food groups and folk dishes including sweet potato, bean products, peanut products, pickled foodstuffs, nitrated or smoked foodstuffs.

RESULTS: During the study period, 107 new colorectal cancer cases (68 men and 39 women) were confirmed. The multivariate Cox’s proportional hazard model showed that the relative risk (RR) of peanut consumption was 0.73 [95% confidence interval (CI) = 0.44-1.21] for men and 0.42 (95% CI = 0.21-0.84) for women. However, frequent intake of pickled foodstuffs was harmful for women (RR = 2.15, 95% CI = 0.99-4.65). The risk of colorectal cancer was also elevated among cigarette smokers but not significant (P < 0.05).

CONCLUSION: This study suggests that frequent intake of peanut and its products may reduce colorectal cancer risk in women, demonstrating the anti-proliferating effect of peanut intake.

Effects of different phytosterol analogs on colonic mucosal cell proliferation in hamsters

OBJECTIVE

The aim of this study was to investigate the effects of different phytosterols and their analogs on colonic mucosal cell proliferation in hamsters.

METHOD

Hamsters (n=70) were randomly assigned to seven groups after a 2-week acclimation and fed the experimental diet for 5 weeks. Diets included (i) the semipurified diet with no cholesterol (Con), (ii) the Con diet plus 0.25% cholesterol (Ch-con), or the Ch-con diet with (iii) 1% phytosterols (Ste), (iv) 1% phytostanols (Sta), (v) 1.76% sterol esters (esterified to fish oil, SteF), (vi) 0.71% stanol esters (esterified to ascorbic acid [disodium ascorbyl phytostanol phosphate, FM-VP4], 0.7% StaA) and (vii) 1.43% stanol esters (1.4% StaA), respectively. After 5 weeks on experimental diet, hamsters were sacrificed, and colons were collected. Colonic mucosal cell proliferation was measured by immunohistochemistry using monoclonal antibodies against antigen Ki-67.

RESULTS

Colonic mucosal cell proliferation was 21.4% (P<.01) lower in the 0.7%, but not 1.4%, StaA relative to the Ch-con group. In addition, a lower (-13.9%) cell proliferation was observed in the SteF group in comparison to the Ch-con group; however, this difference achieved only a borderline level of statistical significance (P=.069). No differences were observed between Con and Ch-con, as well as among Ste, Sta, 1.4% StaA and Ch-con treatments.

CONCLUSION

Plant stanols esterified to ascorbic acid may possess anticarcinogenic properties in the colon by suppressing colonic mucosa cell proliferation; however, this effect was not observed with free plant sterols or stanols.

Kimchi and an Active Component, β-Sitosterol, Reduce Oncogenic H-Rasv12-Induced DNA Synthesis

The Korean fermented vegetable food, kimchi, has been demonstrated to have anticancer functional properties. This study examined the effect of kimchi samples, methanol extracts of commercially grown baechu cabbage kimchi (CK) and organically grown baechu cabbage kimchi (OK), as well as the dichloromethane fraction (DCM fr.) from CK, and the active compound (AC), which has been identified as largely beta-sitosterol, from DCM fr., on the Ras-dependent signaling pathway. CK, OK, and DCM fr. exhibited a greater inhibition against the proliferation of Rat2 fibroblasts transformed with Ras(v12) (HO6) than parental Rat2 fibroblasts. In addition, OK and DCM fr. showed a higher inhibitory effect than CK. Furthermore, we employed the single-cell microinjection technique, combined with 3-bromo-5'-deoxyuridine incorporation, to examine the effects of kimchi samples on DNA synthesis induced by microinjected oncogenic Ras(v12). When the DCM fr. and AC were used to treat Rat1 fibroblasts overexpressing human insulin receptors (HIRc-B) and microinjected with oncogenic H-Ras(v12), the DNA synthesis of injected cells was decreased, suggesting that kimchi might block the signaling pathway of oncogenic Ras(v12), thus preventing the proliferation of transformed cells. This study provides additional evidence that kimchi and its active components, including beta-sitosterol, have potential in both the prevention and treatment of cancer, and presents convincing evidence that the anticancer effects may be a result of an inhibition of Ras oncogene signaling.

Effects of lyophilized black raspberries on azoxymethane-induced colon cancer and 8-hydroxy-2'-deoxyguanosine levels in the Fischer 344 rat

This study examined the effects of lyophilized black raspberries (BRB) on azoxymethane (AOM)-induced aberrant crypt foci (ACF), colon tumors, and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in male Fischer 344 rats. AOM was injected (15 mg/kg body wt i.p.) once per week for 2 wk. At 24 h after the final injection, AOM-treated rats began consuming diets containing 0%, 2.5%, 5%, or 10% (wt/wt) BRB. Vehicle controls received 5% BRB or diet only. Rats were sacrificed after 9 and 33 wk of BRB feeding for ACF enumeration and tumor analysis. ACF multiplicity decreased 36%, 24%, and 21% (P < 0.01 for all groups) in the 2.5%, 5%, and 10% BRB groups, respectively, relative to the AOM-only group. Total tumor multiplicity declined 42%, 45%, and 71% (P < 0.05 for all groups). Although not significant, a decrease in tumor burden (28%, 42%, and 75%) was observed in all BRB groups. Adenocarcinoma multiplicity decreased 28%, 35%, and 80% (P < 0.01) in the same treatment groups. Urinary 8-OHdG levels were reduced by 73%, 81%, and 83% (P < 0.01 for all groups). These results indicate that BRB inhibit several measures of AOM-induced colon carcinogenesis and modulate an important marker of oxidative stress in the Fischer 344 rat.

Plant sterol intakes and colorectal cancer risk in the Netherlands Cohort Study on Diet and Cancer

BACKGROUND

Plant sterols in vegetable foods might prevent colorectal cancer.

OBJECTIVE

The objective was to study plant sterol intakes in relation to colorectal cancer risk in an epidemiologic study.

DESIGN

The study was performed within the framework of the Netherlands Cohort Study on Diet and Cancer in 120852 subjects who completed a baseline questionnaire in 1986. After 6.3 y of follow-up, 620 colon and 344 rectal cancer cases were detected. A case-cohort approach was used to calculate confounder-adjusted rate ratios (RRs) and their 95% CIs for quintiles of plant sterol intake.

RESULTS

The total mean (+/-SD) intake of campesterol, stigmasterol, beta-sitosterol, campestanol, and beta-sitostanol was 285 +/- 97 mg/d. Major contributors to plant sterol intake were bread (38%), vegetable fats (26%), and fruit and vegetables (21%). For men, there was no clear association between intake of any of the plant sterols and colon cancer risk when age, smoking, alcohol use, family history of colorectal cancer, education level, and cholecystectomy were controlled for. Adjustment for energy did not alter the result. For rectal cancer, adjustment for energy resulted in positive associations between risk and campesterol and stigmasterol intakes. For women, there was no clear association between intake of any of the plant sterols and colorectal cancer risk.

CONCLUSION

A high dietary intake of plant sterols was not associated with a lower risk of colon and rectal cancers in the Netherlands Cohort Study on Diet and Cancer.

Phytosterols have an unfavourable effect on bacterial activity and no evident protective effect on colon carcinogenesis

The effects of physiological dietary phytosterol supplements on intestinal microflora activity and faecal sterols and their capacity to protect rats fed a normal or high saturated fatty-acid diet against tumour development were studied. A group of 80 female Wistar rats were fed an 8% lipid diet for 4 weeks (adaptation period) and then randomly assigned in a factorial experimental design study to diets containing 8% or 24% hydrogenated coconut oil, with or without a 24-mg/day/rat phytosterol supplement. They were instilled intrarectally with saline or methyl-nitroso-urea (MNU). Faecal sterol output was analysed for one week each month. Pathological analysis was done at the end of the 30-week experiment. Animals treated with MNU and given phytosterol supplements had tumour frequencies (8/20) similar to those not fed phytosterols (11/20). The fat-supplemented diet had no significant influence. Colonic glands were found in area of lymphoid follicles in all the groups, but were more frequent in rats on high-fat diets (P < 0.01). The coprostanol and the cholesterol excretion of the phytosterol-supplemented rats was significantly enhanced. Therefore phytosterols have an unfavourable effect on bacterial activity. These data confirm the capacity of phytosterols to decrease cholesterol absorption, but indicate that a large excess of phytosterol must be avoided until further research on its effects on carcinogenesis has been done.

Measurement variability of plasma beta-sitosterol and campesterol, two new biomarkers for cancer prevention

Phytosterols are plant sterols that are structurally similar to cholesterol and are characterized by anti-carcinogenic and anti-atherogenic properties. Beta-sitosterol and campesterol are the predominant phytosterols in blood. The present study aimed to analyse the reproducibility and overtime reliability of plasma beta-sitosterol and campesterol measurements. In order to study the reproducibility of the measurement (technical variability), three healthy premenopausal women donated a sample of their blood. Each blood sample was subdivided into six aliquots and analysed within the same run by the same laboratory technician. The intraclass correlation coefficients (ICCs) of the assay for plasma beta-sitosterol and campesterol were 0.88 and 0.94 (95% confidence intervals low bounds (95% CI(low)) were 0.66 and 0.82), respectively. To study the reliability of beta-sitosterol and campesterol measurement over time, seven premenopausal women were recruited. Over a 6-month period, each woman provided a fasting blood sample once a month at the same time of day, and the same numerical day of the luteal phase of her menstrual cycle (between the 20th and 24th day of her menstrual cycle). All plasma samples from the same individual were processed together at the same time by the same technician at the end of the 6-month period. The overtime ICCs of plasma beta-sitosterol and campesterol were 0.91 (95% CI(low) 0.49) and 0.58 (95% CI(low) 0.31), respectively. The high reproducibility and good overtime reliability of plasma beta-sitosterol and campesterol measurements indicate that they may be suitable for potential clinical and population-based studies on cancer prevention.

Peanuts as a source of beta-sitosterol, a sterol with anticancer properties

Work from our laboratory, as well as others, suggests a protective role of phytosterols (PS), especially beta-sitosterol, from colon, prostate, and breast cancer. Asians and vegetarians consume higher amounts of PS than Western societies. The latter societies have a higher incidence of these cancers than Asians and vegetarians. The aim of this study was to evaluate peanuts and its products as sources of PS in the American diet. Roasted peanuts contain 61-114 mg PS/100 g depending on the peanut variety, 78-83% of which is in the form of beta-sitosterol. Unrefined peanut oil contains 207 mg PS/100 g, which is similar to that of the US Department of Agriculture Nutrient Database. This value is higher than that of unrefined olive oil. Refining these oils results in reduction in PS concentration in the oil. This loss is greater in the case of olive oil than peanut oil. Further refining, such as deodorization, results in significant loss in PS, but hydrogenation after refining has a minimal effect on PS loss. Peanut butter, which represents 50% of the peanuts consumed in the United States, contains 144-157 mg PS/100 g. Peanut flour, which results from partial removal of oil from peanuts, contains 55-60 mg PS/100 g. The data suggest that peanuts and its products, such as peanut oil, peanut butter, and peanut flour, are good sources of PS.

Plant sterols and their derivatives: the current spread of results

Whereas the cholesterol-lowering action of plant sterols and their derivatives has been well established, more recent results have produced new information concerning the similar effects of various mixtures and dose-response relationships. Moreover, although these materials have generally been viewed as safe for long-term use in almost all sectors of the population, some concerns remain regarding the impact of phytosterol consumption on other lipid-soluble nutrients, which need to be further addressed. Further work is also required to define the relationship between plant sterol consumption, circulating sterol levels, and risk of certain cancers.

Phytosterols as anticancer dietary components: evidence and mechanism of action

Phytosterols (PS) or plant sterols are structurally similar to cholesterol. The most common PS are beta-sitosterol, campesterol and stigmasterol. Epidemiologic and experimental studies suggest that dietary PS may offer protection from the most common cancers in Western societies, such as colon, breast and prostate cancer. This review summarizes the findings of these studies and the possible mechanisms by which PS offer this protection. These include the effect of PS on membrane structure and function of tumor and host tissue, signal transduction pathways that regulate tumor growth and apoptosis, immune function of the host and cholesterol metabolism by the host. In addition, suggestions for future studies to fill the gaps in our knowledge have been given.

Effect of sterols and fatty acids on growth and triglyceride accumulation in 3T3-L1 cells

Epidemiologic studies suggest a role of dietary fat in the development of obesity. Populations that consume Western diets have a higher incidence of obesity than do those that consume a vegetarian type diet such as Asians. Because dietary fats are made up mostly of triglyceride with minor lipids such as sterols, the objective of this study was to examine the effect of different fatty acids, the main component of triglycerides, and sterols on cell growth and triglyceride accumulation in 3T3-L1 cells. These cells are being used as an in vitro model for studying obesity because upon differentiation in culture they accumulate triglycerides. Cells were seeded at 5,000 cells/cm(2) and supplemented with 0, 3, 10, or 30 microM of oleic acid, elaidic acid, or docosahexaenoic acid (DHA). Similarly, cells were supplemented with 0, 2, 8, or 16 microM of cholesterol, beta-sitosterol (SIT), or campesterol. Cell growth was measured by cell counting. Cellular triglycerides were measured by the Oil Red O method. In some experiments, fatty acids were combined with sterols and growth and triglyceride content were assessed as described. Both DHA and SIT had inhibitory effects on 3T3-L1 cell growth. However, SIT was more potent than DHA in this regard. The combination of SIT and oleic acid was the most potent in inhibiting cell growth and increasing cellular triglyceride content. It is concluded that cell growth and triglyceride accumulation in 3T3-L1 cells is influenced by fatty acid and sterols. When used alone, DHA and SIT inhibit cell growth. SIT was more effective in this process than was DHA. There was an interaction between fatty acids and sterols. The most effective combination inhibiting cell growth and triglyceride concentration was the combination of SIT and oleic acid. This combination reduced cell growth and increased triglyceride accumulation. These data suggest that diets rich in both monounsaturated fatty acids and phytosterols may play a role in controlling obesity.

Safety evaluation of phytosterol esters. Part 4. Faecal concentrations of bile acids and neutral sterols in healthy normolipidaemic volunteers consuming a controlled diet either with or without a phytosterol ester-enriched margarine

A study was conducted in 12 healthy males and 12 females (mean age 36 years) to assess the impact of a margarine enriched with phytosterol esters on faecal concentrations of bile acids and sterols. During the run-in period, volunteers consumed 40 g of a control margarine for 21 consecutive days if male, and for 28 days if female. Half of the volunteers were then randomly allocated to consume the control margarine for another 21 or 28 days, respectively. The remaining subjects consumed 40 g of a margarine containing 8.6 g vegetable oil phytosterol (46% (w/w) beta-sitosterol, 26% campesterol, 20% stigmasterol). Throughout the total study subjects consumed the same diet adjusted for individual energy requirements. The phytosterol ester-enriched spread significantly enhanced faecal neutral sterol concentrations from about 40 mg/g to 190 mg/g dry weight faeces. Faecal neutral sterol metabolites increased from about 30 mg/g to about 50 mg/g. The major parent sterols excreted were cholesterol, sitosterol, campesterol and stigmasterol. Sitosterol, campesterol and stigmasterol comprised 28%, 15% and 12% of the total faecal neutral sterols, reflecting the composition of the sterol enriched margarine. The major sterol metabolites excreted were metabolites formed by, predominantly, oxidation at the 3-position and metabolites saturated at the 5,6 position in a beta-configuration. Faecal secondary bile acid concentration was reduced by vegetable oil sterols from 7.6 mg/g dry faeces to 6.0 mg/g. Consumption of vegetable oil phytosterols slightly but significantly increased the faecal concentration of 4-cholesten-3-one. However, 4-cholesten-3-one concentration remained very low (< 2 mg/g) and in line with values reported in the literature for subjects fed high or low fat diets. No sterol oxides could be detected in the faeces. We conclude that in healthy adult males and females a high intake of vegetable oil phytosterol esters does increase the amount of neutral sterols in the faeces, as expected, but does not result in the increased formation of bile acids or sterol metabolites.

beta-Sitosterol activates the sphingomyelin cycle and induces apoptosis in LNCaP human prostate cancer cells

Epidemiological evidence has shown that men consuming a low-fat, high-fiber diet containing high amounts of plant products have a lower risk of prostate cancer than men consuming a Western diet. One of the main differences between these two diets is the type of dietary fat, including dietary sterols. This study was undertaken to compare the effect of two dietary sterols on prostate cancer cells in vitro. beta-Sitosterol (SIT), the most common plant sterol, and cholesterol, an animal sterol, were compared for effect on LNCaP cell growth, differentiation, apoptosis, and sphingomyelin cycle intermediates. Cells were treated for up to seven days with sterols delivered by a cyclodextrin vehicle. Compared with cholesterol, SIT (16 microM) decreased growth by 24% and induced apoptosis fourfold, which was accompanied by cell rounding and a 50% increase in ceramide production. No effect was observed on differentiation as measured by prostate-specific antigen and prostatic acid phosphatase, although total acid phosphatase increased with SIT treatment for up to seven days. The results suggest that the decrease in cell number and increase in apoptosis associated with SIT treatment are mediated by activating the sphingomyelin cycle.

Effect of dietary phytosterols on rat tissue lipids

The present study was designed to examine the incorporation of phytosterols (PS) in membranes and tissues of rats fed a diet containing 2% PS in the presence of 0.2% cholic acid for 22 days. The control diet contained 12 mg PS/100 g compared with 2,012 mg/100 g. Liver, kidney, testis, and prostate microsomes, plasma, and epididymal fat pads were examined for sterols. Fatty acid composition and phospholipid pattern were also examined in some tissues. The PS diet resulted in a fivefold increase in plasma PS compared with controls. PS was found to accumulate in adipose tissue and liver microsomes in rats fed the PS-supplemented diet. There was no effect of PS incorporation on microsomal cholesterol content, except in the testes, in which dietary PS reduced cholesterol content by 25%. Dietary PS increased 20:4n-6 and 22:5n-3 fatty acids in membranes of the liver, testis, and prostate but decreased 16:1 in liver microsomes. PS incorporation had no effect on the phospholipid pattern of the liver and testis.