Plasma insulin-like growth factor I levels in rats are reduced by dietary supplementation of flaxseed or its lignan secoisolariciresinol diglycoside

The What and Who of Dietary Lignans in Human Health: Special Attention to Estrogen Effects and Safety Evaluation

Lignans are a group of phenolic compounds found in plant-based diets. The human body can obtain lignans through diet, which are then metabolized into enterolignans. The enterolignans have been linked to several health benefits, including anticancer, anti-inflammatory, antioxidant effects, and estrogen effects. This review explores the relationship between the estrogenic effects of lignans and health. This review not only considers the estrogen-like activity of lignans but also discusses the safe dosage of lignans at different life stages. In addition, this review also identified other types of bioactive compounds that can act synergistically with lignans to promote health. Studies have shown that lignan administration during pregnancy and lactation reduces the risk of breast cancer in offspring. Further studies are needed to investigate the estrogenic safety effects of lignan on pregnant women and children. Whether lignans combine with other nutrients in complex food substrates to produce synergistic effects remains to be investigated. This review provides a basis for future studies on the safe dose of lignan and recommended dietary intake of lignan. We believe that the acquired as discussed here has implications for developing dietary therapies that can promote host nutrition and modulate estrogenic diseases.

Lignans: a versatile source of anticancer drugs

Background

Cancer is considered as the second deadliest disease globally. Plants have continuously offered unique secondary metabolites with remarkable biological applications. Lignans have gained great importance due to their biological activity. Previous studies revealed that the most remarkable bioactivity of lignan class of molecules is anticancer. They are derived from the oxidative dimerization of two phenylpropanoid units. This review covers the isolated anticancer lignans and their mechanistic aspects.

Main body

A bibliographic investigation was performed by analyzing the information available on anticancer lignans in the internationally accepted scientific databases including Web of Science, SciFinder, PubMed, Scopus, and Google Scholar. In this review we have tried to sum up the isolated anticancerous lignan, its source, active plant part, extract and various cell lines used to establish different studies. Here we have included a total number of 113 natural lignans. Many studies that mainly performed in human cell lines have reported. Very few plants have been evaluated for their in vivo anticancer activity.

Conclusion

It can be concluded that in near future the lignans may be an effective pharmacon for the treatment of cancer. Fruitful areas of future research may be in modifying natural lignans or synthesizing new lignans with structural diversity and potent pharmacological activities. Extensive studies are needed to be done highlighting the mechanism of anticancer action of explored and unexplored plants. The data will definitely attract many researchers to start further experimentation that might lead to the drugs for the cancer treatment.

Graphical Abstract

Discriminatory and cooperative effects within the mouse gut microbiota in response to flaxseed and its oil and lignan components

Gut microbial processing of dietary flaxseed (FS) contributes to its health benefits, but the relative effects of its bioactive components (lignans, omega-3 fatty acids, fiber) on the microbiota are unclear. We investigated the gut microbial compositional and functional responses to whole FS and its isolated components, FS oil (FSO) and secoisolariciresinol diglucoside (SDG) (precursor to microbial-derived enterolignans) to help understand their contribution to whole FS benefits. Cecum content and fecal samples were collected from C57BL/6 female mice fed a basal diet (AIN93G) or isocaloric diets containing 10% FS or 10% FS-equivalent amounts of FSO or SDG for 21 days. Cecal and fecal microbiota composition and predicted genomic functions, and their relationship with serum enterolignans were evaluated. Only FS modified the community structure. Shared- and diet-specific enriched taxa and functions were identified. Carbohydrate and protein processing functions were enriched in FS mice, and there was a positive correlation between select enriched taxa, encompassing fiber degraders and SDG metabolizers, and serum enterolignans. This was not observed in mice receiving isolated FSO and SDG, suggesting that FS fiber supports SDG microbial metabolism. In conclusion, the cooperative activities of a diverse microbiota are necessary to process FS components and, when administered at the amount present in FS, these components may act together to affect SDG-derived enterolignans production. This has implications for the use of FS, FSO and SDG in clinical practice.

Effects of Flaxseed and Its Components on Mammary Gland MiRNome: Identification of Potential Biomarkers to Prevent Breast Cancer Development

Breast cancer is the most common cancer among women worldwide. We previously showed that early-life exposure to flaxseed (FS) or its components, FS oil (FSO) and secoisolariciresinol diglucoside (SDG), affects the mammary gland (MG) and is associated with the reduction of breast cancer risk during adulthood. However, the underlying mechanisms are not understood. This study aimed to investigate the effect of FS, FSO, and SDG on the MG miRNA signature at a late stage of development. Female C57BL/6 mice, 4–5 weeks of age, were randomized into four groups to receive: (i) basal AIN-93G, (ii) 10% FS, (iii) 3.67% FSO, or (iv) 0.15% SDG. After 21 days, the mice were sacrificed and MG miRNAs were profiled. Diet-specific MG miRNA signatures were identified. Deregulated miRNAs were associated with breast cancer and targeted genes involved in MG development, growth, and cancer. The study allowed for the identification of potential biomarkers or novel therapeutic targets to prevent and/or reduce the risk of breast cancer.

Secoisolariciresinol diglucoside is a blood-brain barrier protective and anti-inflammatory agent: implications for neuroinflammation

BACKGROUND

Secoisolariciresinol diglucoside (SDG), the main lignan in flaxseed, is known for its beneficial effects in inflammation, oxidative stress, heart disease, tumor progression, atherosclerosis, and diabetes. SDG might be an attractive natural compound that protects against neuroinflammation. Yet, there are no comprehensive studies to date investigating the effects of SDG on brain endothelium using relevant in vivo and in vitro models.

METHODS

We evaluated the effects of orally administered SDG on neuroinflammatory responses using in vivo imaging of the brain microvasculature during systemic inflammation and aseptic encephalitis. In parallel, the anti-inflammatory actions of SDG on brain endothelium and monocytes were evaluated in vitro blood-brain barrier (BBB) model. Multiple group comparisons were performed by one-way analysis of variance with Dunnet's post hoc tests.

RESULTS

We found that SDG diminished leukocyte adhesion to and migration across the BBB in vivo in the setting of aseptic encephalitis (intracerebral TNFα injection) and prevented enhanced BBB permeability during systemic inflammatory response (LPS injection). In vitro SDG pretreatment of primary human brain microvascular endothelial cells (BMVEC) or human monocytes diminished adhesion and migration of monocytes across brain endothelial monolayers in conditions mimicking CNS inflammatory responses. Consistent with our in vivo observations, SDG decreased expression of the adhesion molecule, VCAM1, induced by TNFα, or IL-1β in BMVEC. SDG diminished expression of the active form of VLA-4 integrin (promoting leukocyte adhesion and migration) and prevented the cytoskeleton changes in primary human monocytes activated by relevant inflammatory stimuli.

CONCLUSION

This study indicates that SDG directly inhibits BBB interactions with inflammatory cells and reduces the inflammatory state of leukocytes. Though more work is needed to determine the mechanism by which SDG mediates these effects, the ability of SDG to exert a multi-functional response reducing oxidative stress, inflammation, and BBB permeability makes it an exciting potential therapeutic for neuroinflammatory diseases. SDG can serve as an anti-inflammatory and barrier-protective agent in neuroinflammation.

Flaxseed Alone or in Combination with Tamoxifen Inhibits MCF-7 Breast Tumor Growth in Ovariectomized Athymic Mice with High Circulating Levels of Estrogen

Flaxseed (FS) is rich in mammalian lignan precursors and α-linolenic acid, which have been suggested as having anticancer effects. Previous studies have shown that 10% FS inhibits the growth of human estrogen–dependent breast cancer (MCF-7) in athymic mice, and it enhances the inhibitory effect of tamoxifen (TAM). This study determined whether the effect of FS, alone or in combination with TAM, is dose dependent, and it explored the potential mechanism of action. Ovariectomized athymic mice with estradiol (E2) supplementation (1.7 mg/pellet, 60-day release) and established MCF-7 tumors were treated with basal diet control (0FS), 5% FS (5FS), 10% FS (10FS), and TAM (TAM/ 0FS; 5 mg/pellet, 60-day release), alone or in combination (TAM/ 5FS and TAM/10FS) for 8 weeks. Compared with control, 5FS and 10FS significantly inhibited tumor growth by 26% and 38%, respectively. TAM/0FS had an effect similar to the 10FS. TAM/ 5FS and TAM/10FS, respectively, induced significant 48% and 43% reductions in tumor size compared with 0FS, and 18% and 10% reductions compared with TAM/0FS. The relative uterine weight was significantly lower in all TAM groups compared with the control. The reduction of tumor growth resulted from decreased cell proliferation and increased cell apoptosis. TAM/ 5FS caused a significantly higher expression of estrogen receptor-α (ERα) compared with 5FS and TAM/0FS, whereas TAM/10FS had a higher ERα than 10FS and TAM/0FS. Compared with the control, progesterone receptor (PgR) expression was significantly reduced in all treatment groups, but insulin-like growth factor-1 (IGF-1) expression was reduced only by 10FS, TAM/5FS and TAM/10FS. Tumor cell proliferation was significantly positively associated with expression of PgR and IGF-1 and negatively associated with apoptosis and ERα. Apoptosis was only associated with ERα. In conclusion, FS inhibited MCF-7 tumor growth in a dose-dependent manner and enhanced the inhibitory effect of TAM due to the modulation of ER and growth factor signal transduction pathways.

Absorption of plant lignans from cereals in an experimental pig model

Plant lignans are diphenolic compounds ingested with whole grains and seeds and converted to enterolignans by the colonic microbiota. In the present study, we investigated absorption and metabolism of plant lignans and enterolignans in vivo after consumption of cereal-based diets. Six pigs fitted with catheters in the mesenteric artery and portal vein and with a flow probe attached to the portal vein along with twenty pigs for quantitative collection of urine were used for this study. The animals were fed bread based on wheat flour low in plant lignans and three lignan-rich breads based on whole-wheat grain, wheat aleurone flour or rye aleurone flour. Plant lignans and enterolignans in plasma were monitored daily at fast after 0-3 d of lignan-rich intake, and on the 4th day of lignan-rich intake a 10-h profile was completed. Urine samples were collected after 11 d of lignan-rich diet consumption. The concentrations of plant lignans were low at fast, and was 1·2-2·6 nmol/l after switching from the low-lignan diet to the lignan-rich diets. However, on the profile day, the concentration and quantitative absorption of plant lignans increased significantly from 33 nmol/h at fast to 310 nmol/h 0-2·5 h after ingestion with a gradual increase in the following periods. Quantitatively, the absorption of plant lignans across diets amounted to 7 % of ingested plant lignans, whereas the urinary excretion of plant lignans was 3 % across diets. In conclusion, there is a substantial postprandial uptake of plant lignans from cereals, suggesting that plant lignans are absorbed from the small intestine.

Potential protective properties of flax lignan secoisolariciresinol diglucoside

Lignans are a group of phytonutrients which are widely distributed in the plant kingdom. Flaxseed is the richest source of providing lignan precursor such as secoisolariciresinol diglucoside (SDG). This article reviews the studies relevant to experimental models in animals and humans demonstrating the possible nutraceutical actions of SDG to prevent and alleviate lifestyle-related diseases. A local and international web-based literature review for this project was carried out to provide information relating to the study. The major key word "SDG" was selected to gather information using the electronic databases pertaining to the current state of flaxseed lignans composition, bioactive compounds, metabolism and to find out their role in terms of chemopreventive action. The extraction methods vary from simple to complex depending on separation, fractionation, identification and detection of the analytes. The majority of studies demonstrate that SDG interferes with the development of different types of diseases like cardiovascular, diabetic, lupus nephritis, bone, kidney, menopause, reproduction, mental stress, immunity, atherosclerosis, hemopoietic, liver necrosis and urinary disorders due to its various biological properties including anti-inflammatory, antioxidant, antimutagenic, antimicrobial, antiobesity, antihypolipidemic and neuroprotective effects. Moreover, SDG has a defending mediator against various cancers by modulating multiple cell signaling pathways. As discussed in this review, SDG has shown therapeutic potential against a number of human diseases and can be recommended for discerning consumers.

Flaxseed: a potential source of food, feed and fiber

Flaxseed is one of the most important oilseed crops for industrial as well as food, feed, and fiber purposes. Almost every part of the flaxseed plant is utilized commercially, either directly or after processing. The stem yields good quality fiber having high strength and durability. The seed provides oil rich in omega-3, digestible proteins, and lignans. In addition to being one of the richest sources of α-linolenic acid oil and lignans, flaxseed is an essential source of high quality protein and soluble fiber and has considerable potential as a source of phenolic compounds. Flaxseed is emerging as an important functional food ingredient because of its rich contents of α-linolenic acid (ALA), lignans, and fiber. Lignans appear to be anti-carcinogenic compounds. The omega-3s and lignan phytoestrogens of flaxseed are in focus for their benefits for a wide range of health conditions and may possess chemo-protective properties in animals and humans. This paper presents a review of literature on the nutritional composition of flaxseed, its health benefits, and disease-prevention qualities, utilization of flaxseed for food, feed, and fiber, and processing of flaxseed.

Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study

Dietary lignan intakes have been associated with reduced breast cancer risks; however, no previous studies have investigated whether lignan intake might be associated with breast cancer survival. We examined the association of dietary lignan intakes with survival in 1122 women with primary, incident, histologically confirmed breast cancer identified between 1996 and 2001, and with vital status determined through December 31, 2006. Diet in the 12-24 months before diagnosis was assessed with an extensive food frequency questionnaire, and potential confounders assessed from an extensive epidemiologic interview and abstracted clinical data. Lignan intake was calculated using published food composition data. Hazard ratios (HR), and 95% confidence intervals (CIs) for dietary lignan intakes with all cause, and breast cancer mortality were estimated using Cox proportional hazards adjusting for age, education, race, total energy intake, tumor stage, and body mass index. Of the 1122 women with complete dietary data, 160 had died by the end of follow-up. Among postmenopausal women only, those in the highest versus lowest quartile of lignan intakes had a statistically significant reduction in the risk of all cause mortality (HR 0.49, 95% CI 0.26-0.91) and a significantly reduced risk of breast cancer mortality (HR 0.29, 95% CI 0.11-0.76). Higher intakes of dried beans (HR 0.61, 95% CI 0.36-1.03), but not fruits, vegetables, or grains, were also weakly associated with overall mortality. In summary, our results suggest that higher lignan intakes may be associated with improved survival among postmenopausal women with breast cancer.

Health effects with consumption of the flax lignan secoisolariciresinol diglucoside

Flaxseed is the richest source of the lignan secoisolariciresinol diglucoside (SDG). After ingestion, SDG is converted to secoisolariciresinol, which is further metabolised to the mammalian lignans enterodiol and enterolactone. A growing body of evidence suggests that SDG metabolites may provide health benefits due to their weak oestrogenic or anti-oestrogenic effects, antioxidant activity, ability to induce phase 2 proteins and/or inhibit the activity of certain enzymes, or by mechanisms yet unidentified. Human and animal studies identify the benefits of SDG consumption. SDG metabolites may protect against CVD and the metabolic syndrome by reducing lipid and glucose concentrations, lowering blood pressure, and decreasing oxidative stress and inflammation. Flax lignans may also reduce cancer risk by preventing pre-cancerous cellular changes and by reducing angiogenesis and metastasis. Thus, dietary SDG has the potential to decrease the incidence of several chronic diseases that result in significant morbidity and mortality in industrialised countries. The available literature, though, makes it difficult to clearly identify SDG health effects because of the wide variability in study methods. However, the current evidence suggests that a dose of at least 500 mg SDG/d for approximately 8 weeks is needed to observe positive effects on cardiovascular risk factors in human patients. Flaxseed and its lignan extracts appear to be safe for most adult populations, though animal studies suggest that pregnant women should limit their exposure. The present review discusses the potential health benefits of SDG in humans, with supporting evidence from animal studies, and offers suggestions for future research.

Vitexins, nature-derived lignan compounds, induce apoptosis and suppress tumor growth

PURPOSE

Lignans such as secoisolariciresinol diglucoside in flaxseed, are metabolizes to bioactive mammalian lignans of END and ENL. Because mammalian lignans have chemical structural similarity to the natural estrogen, they are thought to behave like selective estrogen receptor modulators and therefore have anticancer effect against hormone-related cancers. We isolated a series of lignan compounds, named as Vitexins, from the seed of Chinese herb Vitex Negundo.

EXPERIMENTAL DESIGN

We purified several Vitexin lignan compounds. Cytotoxic and antitumor effects were analyzed in cancer cells and in tumor xenograft models. In vivo metabolism of Vitexins was determined in rat.

RESULTS

Contrasts to the classic lignans, Vitexins were not metabolized to END and ENL. A mixture of Vitexins EVn-50 and purified Vitexin compound 6-hydroxy-4-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-7-methoxy-3, 4-dihydro-2-naphthaldehyde have cytotoxic effect on breast, prostate, and ovarian cancer cells and induces apoptosis with cleavage in poly ADP ribose polymerase protein, up-regulation of Bax, and down-regulation of Bcl-2. This induction of apoptosis seems to be mediated by activation of caspases because inhibition of caspases activity significantly reduced induced apoptosis. We showed a broad antitumor activity of EVn-50 on seven tumor xenograft models including breast, prostate, liver, and cervical cancers. Consistent with in vitro data, EVn-50 treatment induced apoptosis, down-regulated of Bcl-2, and up-regulated Bax in tumor xenografts.

CONCLUSION

Vitexin is a class of nature lignan compounds, whose action and anticancer effect is mediated by the mechanisms different from the classic lignans. Vitexin-induced antitumor effect and cytotoxic activity is exerted through proapoptotic process, which is mediated by a decreased Bcl-2/Bax ratio and activation of caspases.

Lignans and human health

This review focuses on the possible role in human health of the consumption of lignan-rich foods. Most of the plant lignans in human foods are converted by the intestinal microflora in the upper part of the large bowel to enterolactone and enterodiol, called mammalian or enterolignans. The protective role of these compounds, particularly in chronic Western diseases, is discussed. Evidence suggests that fiber- and lignan-rich whole-grain cereals, beans, berries, nuts, and various seeds are the main protective foods. Many factors, in addition to diet, such as intestinal microflora, smoking, antibiotics, and obesity affect circulating lignan levels in the body. Lignan-rich diets may be beneficial, particularly if consumed for life. Experimental evidence in animals has shown clear anticarcinogenic effects of flaxseed or pure lignans in many types of cancer. Many epidemiological results are controversial, partly because the determinants of plasma enterolactone are very different in different countries. The source of the lignans seems to play a role because other factors in the food obviously participate in the protective effects. The results are promising, but much work is still needed in this area of medicine.

Dietary lignans and postmenopausal breast cancer risk by oestrogen receptor status: a prospective cohort study of Swedish women

Among the 51 823 postmenopausal women in the Swedish Mammography Cohort, we investigated breast cancer risk in relation to the FFQ-based estimated lignan intake by oestrogen receptor (ER) and progesterone receptor (PR) subtypes. A significant 17% risk reduction for breast cancer overall in the high lignan quartile was observed, especially among PMH user (P_interaction<0.010), but no heterogeneity across ER/PR subtypes.

Secoisolariciresinol diglucoside induces neovascularization-mediated cardioprotection against ischemia-reperfusion injury in hypercholesterolemic myocardium

Hypercholesterolemia (HC) induced endothelial cell dysfunction and decreased endothelial nitric oxide formation results in impaired angiogenesis and subsequent cardiovascular disorders. Therapeutic angiogenesis is known to be a novel strategy for treatment of patients with ischemic heart disease. We have shown that secoisolariciresinol diglucoside (SDG) is angiogenic as well as cardioprotective against myocardial ischemia. In the present study, we examined the efficacy of SDG in a hypercholesterolemic myocardial infarction (MI) model. The rats were maintained on a normal and high cholesterol diet (2%) for 8 weeks followed by oral administration of SDG (20 mg/kg) for 2 weeks. The rats were divided into four groups (n=24 in each): Control (C); SDG control (SDG); HC; and HC+SDG (HSDG). Isolated hearts subjected to 30 min of global ischemia followed by 120 min of reperfusion were used to measure the cardiac functions, infarct size and to examine the protein expression profile. After treatment, MI was induced by ligating the left anterior descending artery. Echocardiographic parameters were examined 30 days after MI. Significant reduction in total cholesterol, LDL-cholesterol, triglycerides and an increase in HDL-cholesterol levels were observed in HSDG as compared to the HC. Decreased infarct size was observed in the HSDG group (43%) compared to the HC (54%). Increased phosphorylation of endothelial nitric oxide synthase (p-eNOS) (3.1-fold), vascular endothelial growth factor (1.9-fold) and heme oxygenase-1 (2.3-fold) was observed in the HSDG group as compared to the HC group. Significant improvement in left ventricular functions was also observed in the HSDG group as evidenced by increased ejection fraction (55% vs. 45%), fractional shortening (28% vs. 22%) and decreased left ventricular inner diameter in systole (8 vs. 6 mm) in HSDG compared to HC. Moreover, MI model has shown increased capillary density (2531 vs. 1901) and arteriolar density (2.6 vs. 1.8) in SDG-treated rats as compared to the HC. The increased capillary and arteriolar density along with increased left ventricular functions on SDG treatment might be due to increased HO-1, VEGF and p-eNOS expression. In conclusion, our study demonstrates for the first time that SDG treatment reduces ventricular remodeling by neovascularization of the infarcted HC myocardium.

Dietary Flaxseed Interaction With Tamoxifen Induced Tumor Regression in Athymic Mice With MCF-7 Xenografts by Downregulating the Expression of Estrogen Related Gene Products and Signal Transduction Pathways

Our previous short-term study has shown that 10% flaxseed (FS) inhibits the growth of human estrogen dependent estrogen receptor positive breast tumors (MCF-7) xenografts in ovariectomized (OVX) athymic mice and enhances the tumor inhibitory effect of tamoxifen (TAM). This study determined the long-term effect of 5% and 10% FS, with or without TAM, on the growth of MCF-7 xenografts in athymic mice and the potential mechanisms of actions. OVX mice with established MCF-7 tumors were treated with basal diet (control), 5% FS (5FS), 10% FS (10FS), and TAM (5 mg/pellet, 60-day release), alone or in combination, for 16 wk without estrogen supplementation. Tumor growth was monitored weekly. At sacrifice, the tumors were analyzed by immunohistochemistry for cell proliferation, apoptosis, and expression of estrogen-related genes and signal transduction pathways. Both 5FS and 10FS regressed the pretreatment tumor size by over 90% similar to control. TAM initially regressed the tumors but then induced a regrowth; thus, only a final 6% reduction from pretreatment tumor size was achieved, which was attenuated by combining TAM with 10FS but not with 5FS. TAM combined with 10FS regressed tumors to 55% of pretreatment tumor size due to decreased cell proliferation and increased apoptosis. The expressions of cyclin D1, estrogen receptor alpha, human epidermal growth factor receptor 2, and insulin-like growth factor I receptor in the TAM group were significantly reduced when TAM was combined with 5FS or 10FS. In conclusion, after long-term treatment, FS did not stimulate tumor growth and combined with TAM, regressed tumor size in part due to downregulation of the expression of estrogen-related gene products and signal transduction pathways.

Microwave-assisted extraction of the main phenolic compounds in flaxseed

A microwave-assisted extraction (MAE) method has been applied for the first time to the extraction of the main lignan, secoisolariciresinol diglucoside (SDG), and the two most concentrated hydroxycinnamic acid glucosides in flaxseed. The effects of microwave power, extraction time and alkaline treatment were investigated. It was shown that a 3 min MAE resulted in an SDG content of 16.1+/-0.4 mg/g, a p-coumaric acid glucoside content of 3.7+/-0.2 mg/g and a ferulic acid glucoside content of 4.1+/-0.2 mg/g. These values were compared with those obtained using conventional extraction methods and the results demonstrated that MAE was more effective in terms of both yield and time consumption.

Feeding flaxseed oil but not secoisolariciresinol diglucoside results in higher bone mass in healthy rats and rats with kidney disease

Flaxseed's oil and lignan, secoisolariciresinol diglucoside (SDG), are implicated in attainment of health and treatment of renal injury and osteoporosis. To test for these benefits, weanling Han:SPRD-cy rats (n=171) with or without kidney disease were randomized to diets made with either corn oil or flaxseed oil and with or without SDG for 12 weeks. In females, weight was lower with the SDG diet. In males fed flaxseed oil, lean mass was higher and fat % was lower. In both sexes, fat % was lower in diseased rats. Bone mineral content (BMC) and density were higher in rats fed flaxseed oil and lower in diseased rats, additionally; BMC was lower in SDG-supplemented females. The benefit of flaxseed oil on body composition is sex specific but the effect on bone mass is not. Lastly, reduced weight due to early rat kidney disease is not due to loss of lean body mass.

Secoisolariciresinol diglucoside: relevance to angiogenesis and cardioprotection against ischemia-reperfusion injury

Therapeutic angiogenesis represents a novel approach for the prevention and treatment of ischemic heart disease. This study examined a novel method of stimulating myocardial angiogenesis using secoisolariciresinol diglucoside (SDG), a plant lignan isolated from flaxseed. SDG has been shown to decrease serum cholesterol and reduce the extent of atherosclerosis. In the present study, the angiogenic properties of SDG were investigated in three different models. First, in the in vitro model, human coronary arteriolar endothelial cells (HCAEC) treated with SDG (50 and 100 microM) showed a significant increase in tubular morphogenesis compared with control. Western blot analysis indicated an increased expression of vascular endothelial growth factor (VEGF), kinase insert domain-containing receptor (KDR), Flt-1, angiopoietin-1 (Ang-1), Tie-1, and phosphorylated endothelial nitric oxide synthase (p-eNOS) in the SDG-treated cells. Second, in the ex vivo ischemia/reperfusion model, SDG-treated rats (20 mg/kg b.wt./day for 2 weeks orally) showed an increased level of aortic flow and functional recovery after 2 h of reperfusion following 30 min of ischemia compared with the control group [dP/dt (mm Hg/s) of 2110 +/- 35 versus 1752 +/- 62]. SDG reduced infarct size compared with the control group by 32% (38 versus 26%) and also decreased cardiomyocyte apoptosis. Increased protein expression of VEGF, Ang-1, and p-eNOS was also observed in the SDG-treated group. Third, in the in vivo myocardial infarction model, SDG increased capillary density and myocardial function as evidenced by increased fractional shortening and ejection fraction. In conclusion, these results suggest that SDG has potent angiogenic and antiapoptotic properties that may contribute to its cardioprotective effect in ischemic models.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Flaxseed and its components reduce metastasis after surgical excision of solid human breast tumor in nude mice

This study determined the effect of 10% flaxseed (FS) and its components, secoisolariciresinol diglycoside (SDG) and flaxseed oil (FO) alone or in combination (SDG+FO), on the metastasis and recurrence of human breast tumor after excision in nude mice. Mice were injected orthotopically with human breast cancer cells (MDA-MB-435) and fed basal diet (BD). When the tumors reached an average size of 110 mm(2) (0.9 g), surgical excisions were performed, and the mice were assigned to one of five diet groups for 7 weeks. The total incidence of metastasis was significantly lower in the FS, SDG, and SDG+FO groups. Reduced lung and lymph node metastases were observed in the FS and SDG+FO groups. In the FS and FO groups, a greater reduction in lung and total metastases was found when excised tumors were <or=0.9 versus >0.9 g. There was no significant difference in tumor recurrence among groups. In conclusion, FS and its components inhibited tumor metastasis but not tumor recurrence after surgical excision of the primary tumor.

Dietary lignans: potential role in cancer prevention

Recent in vitro, animal, and epidemiological studies suggest that dietary lignans may be chemopreventive, potentially through anti-estrogenic, anti-angiogenic, pro- apoptotic, and anti-oxidant mechanisms. In this article, we review lignan food sources and metabolism, proposed anti-carcinogenic mechanisms, and the evidence for a role of lignans in breast, colon, and prostate cancer prevention from animal and epidemiologic literature. Although a number of in vitro and animal studies support a role for lignan-rich foods and purified lignans in the modulation of cancer events of the breast, prostate, and colon, epidemiological studies, sparse and often retrospective in nature, offer inconsistent findings. The most support for a role of lignans in cancer is observed for premenopausal breast cancer. Additional epidemiological studies that use a prospective design and well-developed food databases and questionnaires are needed to adequately evaluate the role of lignans in cancer prevention.

Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer

PURPOSE

Flaxseed, the richest source of mammalian lignan precursors, has previously been shown to reduce the growth of tumors in rats. This study examined, in a randomized double-blind placebo-controlled clinical trial, the effects of dietary flaxseed on tumor biological markers and urinary lignan excretion in postmenopausal patients with newly diagnosed breast cancer.

EXPERIMENTAL DESIGN

Patients were randomized to daily intake of either a 25 g flaxseed-containing muffin (n = 19) or a control (placebo) muffin (n = 13). At the time of diagnosis and again at definitive surgery, tumor tissue was analyzed for the rate of tumor cell proliferation (Ki-67 labeling index, primary end point), apoptosis, c-erbB2 expression, and estrogen and progesterone receptor levels. Twenty-four-hour urine samples were analyzed for lignans, and 3-day diet records were evaluated for macronutrient and caloric intake. Mean treatment times were 39 and 32 days in the placebo and flaxseed groups, respectively.

RESULTS

Reductions in Ki-67 labeling index (34.2%; P = 0.001) and in c-erbB2 expression (71.0%; P = 0.003) and an increase in apoptosis (30.7%; P = 0.007) were observed in the flaxseed, but not in the placebo group. No significant differences in caloric and macronutrient intake were seen between groups and between pre- and posttreatment periods. A significant increase in mean urinary lignan excretion was observed in the flaxseed group (1,300%; P < 0.01) compared with placebo controls. The total intake of flaxseed was correlated with changes in c-erbB2 score (r = -0.373; P = 0.036) and apoptotic index (r = 0.495; P < 0.004).

CONCLUSION

Dietary flaxseed has the potential to reduce tumor growth in patients with breast cancer.

Dietary flaxseed enhances the inhibitory effect of tamoxifen on the growth of estrogen-dependent human breast cancer (mcf-7) in nude mice

PURPOSE

This study determined the effect of 10% dietary flaxseed (FS) and tamoxifen (TAM), alone and in combination, on the growth of estrogen-dependent human breast cancer (MCF-7) in athymic mice with or without 17beta-estradiol (E2) supplementation.

EXPERIMENTAL DESIGN

Ovariectomized mice received injection with MCF-7 cells, were implanted with an E2 pellet (1.7 mg), and fed the basal diet (BD). When tumor reached approximately 40 mm2, the E2 implant was removed, and mice were randomized to the following groups and maintained at either low (E2 pellet removed) or high E2 level (new E2 pellet implanted) for 6 weeks: (a) positive control with new E2 pellet, fed BD, (b) negative control with no E2 implant, fed BD, (c) TAM group with TAM pellet (5 mg) implant, fed BD, (d) FS group fed 10% FS, (e) FS+TAM group with TAM implant, fed 10% FS. Tumor growth was monitored weekly.

RESULTS

At low E2 level, FS regressed the pretreatment tumor size by 74%. TAM regressed tumor initially but later induced an increase so that the tumor size was finally similar to the pretreatment size. A tumor regression >53% was induced by FS+TAM than by TAM alone. At high E2 level, FS, TAM, and FS+TAM inhibited the tumor growth by 22, 41, and 50%, respectively, compared with the positive control. Decreased tumor size was attributable to reduced tumor cell proliferation and increased apoptosis.

CONCLUSIONS

FS inhibited the growth of human estrogen-dependent breast cancer and strengthened the tumor-inhibitory effect of TAM at both low and high E2 levels.

An update on bioactive plant lignans

Lignans are a class of secondary plant metabolites produced by oxidative dimerization of two phenylpropanoid units. Although their molecular backbone consists only of two phenylpropane (C6-C3) units, lignans show an enormous structural diversity. There is a growing interest in lignans and their synthetic derivatives due to applications in cancer chemotherapy and various other pharmacological effects. This review deals with lignans possessing anticancer, antioxidant, antimicrobial, anti-inflammatory and immunosuppressive activities, and comprises the data reported in more than 100 peer-reviewed articles, so as to highlight the recently reported bioactive lignans that could be a first step towards the development of potential new therapeutic agents.

The inhibitory effect of flaxseed on the growth and metastasisof estrogen receptor negative human breast cancer xenograftsis attributed to both its lignan and oil components

Our previous studies have shown that dietary flaxseed (FS) can reduce the growth and metastasis of human estrogen receptor negative (ER-) breast cancer in nude mice. The aims of our study were to determine (i) whether the tumor inhibitory effect of FS was due to its oil (FO), lignan secoisolariciresinol diglycoside (SDG), or both components, and (ii) whether the effect on tumor growth was related to increased lipid peroxidation. Athymic nude mice were orthotopically injected with ER- breast cancer cells (MDA-MB-435) and 8 weeks later were fed either the basal diet (BD) or BD supplemented with 10% FS, SDG, FO, or combined SDG and FO (SDG + FO) for 6 weeks. The SDG and FO levels were equivalent to the amounts in the 10% FS. Compared to the BD group, the tumor growth rate was significantly lower (p < 0.05) in the FS, FO, and SDG + FO groups, in concordance with decreased cell proliferation and increased apoptosis; however, these did not significantly relate to the lipid peroxidation, indexed as malonaldehyde (MDA), in the primary tumors. Lung metastasis incidence was reduced (16-70%) by all treatments, significantly in the FS and SDG + FO groups. The distant lymph node metastasis was significantly decreased (52%) only in the FO group. Although the total metastasis incidence was lowered (42%) significantly only in the SDG + FO group, all treatment groups did not differ significantly. In conclusion, FS reduced the growth and metastasis of established ER- human breast cancer in part due to its lignan and FO components, and not to lipid peroxidation.

Effect of flax supplementation and growth promotants on lipoprotein lipase and glycogenin messenger RNA concentrations in finishing cattle1

Lipoprotein lipase (LPL) hydrolyzes triacylglycerols into monoacylglycerol and fatty acids, which are taken up by tissues and used for energy. Glycogenin is the core protein on which glycogen molecules are synthesized. There is one molecule of glycogenin per molecule of glycogen in skeletal muscle; therefore, glycogen storage is limited by the amount of glycogenin present in muscle. The objective of this study was to investigate the effect of feeding flaxseed, a source of PUFA, and administering a growth promoter on steady-state LPL and glycogenin mRNA content of muscle in finishing cattle. Sixteen crossbred steers (initial BW = 397 kg), given ad libitum access to a 92% concentrate diet for 28 d, were used in a four-treatment, 2 x 2 factorial experiment, with flaxseed supplementation (0 or 5% of dietary DM) and implanting (not implanted or implanted with Revalor-S) as the main effects. Muscle biopsies were obtained from the LM at 0, 14, and 28 d, and used to quantify LPL and glycogenin mRNA concentrations using real-time quantitative PCR. Implanting with Revalor-S did not affect LPL (P = 0.13) or glycogenin (P = 0.98) mRNA concentrations. A day x flaxseed interaction (P < 0.001) was observed for both LPL and glycogenin mRNA concentrations. No differences (P > 0.10) were observed between 0 and 5% flaxseed supplemented steers; however, at 28 d, nonflaxseed-fed steers had 4.1- and 5.7-fold increases (P < 0.001) over flaxseed steers for LPL and glycogenin mRNA concentrations, respectively. To further evaluate the effects of alpha-linolenic acid (alpha-LA) on LPL and glycogenin mRNA concentrations, muscle satellite cells were isolated from five finishing steers, and different alpha-LA concentrations were applied in culture. The RNA was isolated from the bovine satellite cells. Addition of alpha-LA numerically increased (P = 0.16) the LPL mRNA concentration 48% at 1 microM alpha-LA compared with the control. The expression of glycogenin was increased (P < 0.05) 50% at 1 microM alpha-LA compared with the control. These results suggest that flaxseed supplementation to finishing steers for 28 d decreased gene expression of both LPL and glycogenin compared with not feeding flaxseed. Alterations in local concentrations of these two proteins could affect the ability of muscle to use fatty acids and glucose for energy, and, ultimately, affect carcass quality.

Proposal for a dietary “phytochemical index”

There is ample reason to believe that diets rich in phytochemicals provide protection from vascular diseases and many cancers; direct antioxidant activity as well as modulation of enzyme expression or hormone activity contribute to this effect. Phytochemicals derived from diverse foods presumably can interact additively and (possibly) synergistically; thus, the total dietary load of phytochemicals may have important implications for health. As a means of very roughly quantifying this load, a "phytochemical index" (PI) is proposed, defined as the percent of dietary calories derived from foods rich in phytochemicals. Calories derived from fruits, vegetables (excluding potatoes), legumes, whole grains, nuts, seeds, fruit/vegetable juices, soy products, wine, beer, and cider - and foods compounded therefrom - would be counted in this index. Partial credit could be given for antioxidant-rich extra virgin olive oil. Other added oils, refined sugars, refined grains, potato products, hard liquors, and animal products - regrettably, the chief sources of calories in typical Western diets - would be excluded. Although the PI would provide only a very rough approximation of the quantity or quality of phytochemical nutrition, it nonetheless could aid epidemiologists in exploring the health consequences of diets high in phytochemical-rich plant foods, and could also help clinical nutritionists in their efforts to improve the phytochemical nutrition of their clients.

Effects of flax supplementation and a combined trenbolone acetate and estradiol implant on circulating insulin-like growth factor-I and muscle insulin-like growth factor-I messenger RNA levels in beef cattle1,2

We evaluated effects of a 5% (dry matter basis) ground flaxseed supplement (flax) and a trenbolone acetate and estradiol-17beta implant, Revalor-S, on circulating IGF-I and muscle IGF-I messenger RNA (mRNA). Sixteen crossbred yearling steers (initial BW = 397 kg) were assigned randomly to one of four treatments: 1) flax/implant; 2) nonflax/implant; 3) flax/nonimplant; and 4) nonflax/nonimplant. Serum was harvested from blood collected on d 0 (before implant or flax addition), 14, and 28, and used in subsequent analyses of circulating IGF-I. Biopsy samples (0.5 g) were obtained from the longissimus muscle on d 0, 14, and 28. Total RNA was isolated from the muscle samples, and real-time quantitative-PCR was used to assess relative differences in IGF-I mRNA. Flax supplementation had no effect (P > 0.10) on circulating IGF-I concentrations. Following implantation, sera from implanted steers had 52 and 84% greater (P < 0.05) IGF-I concentrations than sera from nonimplanted steers on d 14 and 28, respectively. On d 28, local muscle IGF-I mRNA levels increased 2.4-fold (P < 0.01) in biopsy samples obtained from implanted compared with nonimplanted steers. Muscle biopsy samples from nonflax cattle had 4.4-fold higher (P < 0.01) levels of IGF-I mRNA than those from flax cattle on d 28. To determine whether a component of flax, alpha-linolenic acid (alphaLA), was directly responsible for IGF-I mRNA down-regulation, we incubated primary cultures of bovine satellite cells, from implanted and nonimplanted steers, in two concentrations of alphaLA (10 nM and 1 microM). An implant x dose interaction (P < 0.05) was observed for IGF-I mRNA concentrations in bovine satellite cells cultured for 72 h with alphaLA. Satellite cells from nonimplanted steers had similar (P > 0.10) IGF-I mRNA concentration regardless of the level of alphaLA exposure; however, satellite cells from implanted steers exposed to 10 nM and 1 microM alphaLA had 2.5- and 2.0-fold greater IGF-I mRNA levels, respectively, than cells from implanted steers that were not exposed to alphaLA (P < 0.05). Administration of a Revalor-S implant increased circulating IGF-I and local muscle IGF-I mRNA concentrations in finishing cattle. However, muscle IGF-I mRNA levels were decreased by flax supplementation. Muscle cell culture experiments suggested that alphaLA was not responsible for the IGF-I mRNA down-regulation.

Randomised controlled short-term intervention pilot study on rye bran bread in prostate cancer

The short-term effects of rye bran bread intake in prostate cancer were investigated. Ten men with conservatively treated prostate cancer were randomised to a daily supplement of 295 g of rye bran bread and eight men to 275 g of wheat bread (control) with similar fibre content for three weeks. Blood samples, ultrasound-guided core biopsies of the prostate, and urine samples were taken. In the rye group, there was a significant increase in plasma enterolactone, and the apoptotic index increased significantly from 2.1% (SD 1.3) to 5.9% (SD 1.8), P<0.005 as measured by a TUNEL index in four cases in the rye group and seven cases in the control group. Besides a significant decrease in weight in both groups, only small changes were observed in plasma concentrations of prostate specific antigen (PSA), circulating sex hormones, excreted oestrogens, insulin-like growth factor (IGF)-I, and in the endothelial fibrinolytical system. High intake of rye bran bread is suggested to increase apoptosis in prostate tumours.

Exposure to flaxseed or its purified lignan during suckling inhibits chemically induced rat mammary tumorigenesis

Previous studies have shown that feeding flaxseed (FS) or its lignan secoisolariciresinol diglucoside (SDG) to rat dams during lactation enhances the differentiation of rat mammary gland in the female offspring. This study determined whether exposure to a diet with 10% FS or SDG (equivalent to the amount in 10% FS) during suckling could protect against 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced rat mammary tumorigenesis later in life. Dams were fed the AIN-93G basal diet (BD) throughout pregnancy. After delivery, dams were randomized to continue on BD or were fed BD supplemented with 10% FS or SDG during lactation. Three-day urine of dams was analyzed for mammalian lignans. After weaning, all offspring were fed BD. At postnatal Days 49 to 51, during proestrus phase, offspring were gavaged with 5 mg of DMBA. At Week 21 post-DMBA administration, compared with the BD group, the FS and SDG groups had significantly lower (P < 0.05) tumor incidence (31.3% and 42.0% lower, respectively), total tumor load (50.8% and 62.5% lower, respectively), mean tumor size (43.9% and 67.7% lower, respectively), and tumor number (46.9% and 44.8% lower, respectively) per rat. There was a significant decreasing trend (P < 0.05) in final tumor weights in rats fed FS or SDG. The high urinary lignan excretion in dams fed with FS or SDG corresponded with the reduced tumor development. The FS and SDG groups did not differ significantly in tumor indices, indicating that the effect of FS is primarily due to its SDG. There were no significant changes in selective reproductive indices measured among dams and offspring. In conclusion, exposure to FS or SDG during suckling suppressed DMBA-induced rat mammary tumorigenesis, suggesting that exposure to lignans at this early stage of mammary gland development reduces susceptibility to mammary carcinogenesis later in life without adverse effects on selective reproductive indices in dams or offspring.

High-performance liquid chromatographic analysis of secoisolariciresinol diglucoside and hydroxycinnamic acid glucosides in flaxseed by alkaline extraction

A HPLC method was developed for the analysis of secoisolariciresinol diglucoside (SDG) and hydroxycinnamic acid glucosides in milled defatted flaxseed flour. Direct extraction by 1 M NaOH for 1 h at 20 degrees C resulted in a higher yield than that obtained by hydrolysis of alcoholic extracts. An internal standard, o-coumaric acid, was used and the method was found to be easy, fast, and with good repeatability. On dry matter basis, different samples of flaxseeds varied considerably in their content of (+)-SDG (11.9-25.9 mg/g), (-)-SDG (2.2-5.0 mg/g), p-coumaric acid glucoside (1.2-8.5 mg/g), and ferulic acid glucoside (1.6-5.0 mg/g).

Estrogen agonists/antagonists may down-regulate growth hormone signaling in hepatocytes--an explanation for their impact on IGF-I, IGFBP-1, and lipoprotein(a)

Estrogen agonists/antagonists, when administered orally, exert a range of effects on hepatic function, some of which are potentially protective. These effects include reduced synthesis of IGF-I and apolipoprotein(a), and increased synthesis of IGFBP-1--shifts which arguably could decrease risk for vascular disease and certain cancers. These effects are diametrically opposite to those of growth hormone (GH), which boosts hepatic production of IGF-I and apolipoprotein(a), while suppressing that of IGFBP-1. Thus, a parsimonious explanation of these phenomena is that oral estrogen blunts the efficiency of GH signaling in the liver. Oral androgenic progestins may have the reverse effect. It may be of particular value to determine whether certain estrogen agonists/antagonists can exert relatively 'hepatospecific' activity when administered orally--thus enabling down-regulation of systemic IGF-I activity and of lipoprotein(a), without however inducing a significant increase in systemic estrogen activity. Preliminary evidence suggests that flax lignans and perhaps other phytoestrogens may have potential in this regard.

Lignans and tamoxifen, alone or in combination, reduce human breast cancer cell adhesion, invasion and migration in vitro

Flaxseed has been shown to reduce the metastasis of estrogen receptor negative (ER-) human breast cancer in nude mice. This study determined whether enterodiol (ED) and enterolactone (EL), metabolites of plant lignans exceptionally rich in flaxseed, and tamoxifen (TAM), alone or in combination, can influence the various steps of metastasis, that is, breast cancer cell adhesion, invasion and migration, of two ER- human breast cancer cell lines, MDA-MB-435 and MDA-MB-231. The inhibition by ED, EL or TAM (1-5 microM) of cell adhesion to Matrigel or extracellular matrices, fibronectin, laminin, and type IV collagen, as well as cell invasion was dose dependent in both cell lines. When ED, EL and TAM were combined at 1 microM, a greater inhibitory effect on cell adhesion and invasion was observed than with either compound alone. ED and EL at doses of 0.1-10 microM reduced cell migration, but TAM had no effect at 0.1 and 1 microM, and exhibited a stimulatory effect at 10 microM. It is concluded that lignans and TAM, alone or in combination, can inhibit the steps involved in the metastasis cascade. Although more investigations are required, the study also suggests that the intake of the lignan-rich flaxseed may not antagonize the effect of TAM in ER- breast cancer cells.

A low-fat, whole-food vegan diet, as well as other strategies that down-regulate IGF-I activity, may slow the human aging process

A considerable amount of evidence is consistent with the proposition that systemic IGF-I activity acts as pacesetter in the aging process. A reduction in IGF-I activity is the common characteristic of rodents whose maximal lifespan has been increased by a wide range of genetic or dietary measures, including caloric restriction. The lifespans of breeds of dogs and strains of rats tend to be inversely proportional to their mature weight and IGF-I levels. The link between IGF-I and aging appears to be evolutionarily conserved; in worms and flies, lifespan is increased by reduction-of-function mutations in signaling intermediates homologous to those which mediate insulin/IGF-I activity in mammals. The fact that an increase in IGF-I activity plays a key role in the induction of sexual maturity, is consistent with a broader role for-IGF-I in aging regulation. If down-regulation of IGF-I activity could indeed slow aging in humans, a range of practical measures for achieving this may be at hand. These include a low-fat, whole-food, vegan diet, exercise training, soluble fiber, insulin sensitizers, appetite suppressants, and agents such as flax lignans, oral estrogen, or tamoxifen that decrease hepatic synthesis of IGF-I. Many of these measures would also be expected to decrease risk for common age-related diseases. Regimens combining several of these approaches might have a sufficient impact on IGF-I activity to achieve a useful retardation of the aging process. However, in light of the fact that IGF-I promotes endothelial production of nitric oxide and may be of especial importance to cerebrovascular health, additional measures for stroke prevention-most notably salt restriction-may be advisable when attempting to down-regulate IGF-I activity as a pro-longevity strategy.

Dietary flaxseed inhibits human breast cancer growth and metastasis and downregulates expression of insulin-like growth factor and epidermal growth factor receptor

Recent studies indicate that diets rich in phytoestrogens and n-3 fatty acid have anticancer potential. This study determined the effect of flaxseed (FS), the richest source of lignans and alpha-linolenic acid, on growth and metastasis of established human breast cancer in a nude mice model. Estrogen receptor-negative human breast cancer cells, MDA-MB-435, were injected into the mammary fat pad of mice (Ncr nu/nu) fed a basal diet (BD). At Week 8, mice were randomized into two diet groups, such that the groups had similar tumor size and body weight. One continued on the BD, while the other was changed to BD supplemented with 10% FS, until sacrifice at Week 15. A significant reduction (P < 0.05) in tumor growth rate and a 45% reduction (P = 0.08) in total incidence of metastasis were observed in the FS group. Lung metastasis incidence was 55.6% in the BD group and 22.2% in the FS group, while the lymph node metastasis incidence was 88.9% in the BD group and 33.3% in the FS group (P < 0.05). Mean tumor number (tumor load) of total and lymph node metastasis was significantly lower in the FS than in the BD group (P < 0.05). Metastatic lung tumor number was reduced by 82%, and a significantly lower tumor trend (P < 0.01) was observed in the FS group. Lung weight, which also reflects metastatic tumor load, in the FS group was reduced by 20% (P < 0.05) compared with the BD group. Immunohistochemical study showed that Ki-67 labeling index and expression of insulin-like growth factor I and epithelial growth factor receptor in the primary tumor were lower in the FS (P < 0.05) than in the BD group. In conclusion, flaxseed inhibited the established human breast cancer growth and metastasis in a nude mice model, and this effect is partly due to its downregulation of insulin-like growth factor I and epidermal growth factor receptor expression.

Non-nutrient bioactive substances of pulses

Pulses supply many bioactive substances found in minor amounts in food, but which may have significant metabolic and/or physiological effects. These compounds have long been classified as antinutritional factors, but many studies have reconsidered their impact on health. Some could play a role in the prevention of the major diseases of affluent societies. As these compounds can be beneficial or adverse, depending on conditions, an assessment of their various physiological effects is necessary to determine whether they should be preserved or eliminated in each main nutritional situation.

Mammalian phytoestrogens: enterodiol and enterolactone

The mammalian phytoestrogens enterodiol (END) and enterolactone (ENL) are produced in the colon by the action of bacteria on the plant precursors matairesinol (MAT), secoisolariciresinol (SECO), their glycosides, and other precursors in the diet. Both END and ENL have been shown to possess weakly estrogenic and antiestrogenic activities, and it has been suggested that the high production of these antiestrogenic mammalian lignans in the gut may serve to protect against breast cancer in women and prostate cancer in men. Various in vitro experiments suggested END and ENL significantly inhibited the growth of human colon tumor cells, and the E2-induced proliferation of MCF-7 breast cancer cells was inhibited by ENL. The protective effects of mammalian lignans may be due to their ability to compete with E2 for the type II estrogen receptor, to induce sex hormone binding globulin (SHBG), to inhibit placental aromatase, and to act as antioxidants. This review mainly deals with the chemistry, quantitative analysis, biological properties and health effects of END and ENL.

Biosynthetic pathway to the cancer chemopreventive secoisolariciresinol diglucoside-hydroxymethyl glutaryl ester-linked lignan oligomers in flax (Linum usitatissimum) seed

Application of stable and radioisotope precursor/tracer experiments resulted in the identification of various phenylpropanoid, monolignol, and lignan metabolites involved in the biosynthesis of the cancer chemopreventive secoisolariciresinol diglucoside (SDG; 1)-containing ester-linked "polymer(s)" in flax (Linum usitatissimum) seed. Individual analysis of size-segregated flax seed capsules at five early stages of their development provided a metabolic profile of intermediates leading to "biopolymer" biosynthesis. The use of (1)H and (13)C NMR and HRMS analyses resulted in the identification of 6a-HMG (hydroxymethyl glutaryl) SDG (17) and 6a,6a'-di-HMG SDG (18) as the two major components of the ester-linked "biopolymer(s)". Based on metabolic tracer analyses and relative radioisotopic incorporations throughout each of these five stages of seed development, a biochemical pathway is proposed from phenylalanine to SDG (1), with subsequent mono- and di-substitutions of SDG (1) with HMG CoA. These metabolites then serve as precursors for formation of the SDG-HMG ester-linked oligomers. Results from this study will facilitate future isolation and characterization of the proteins and enzymes involved in biosynthesis of the SDG-HMG ester-linked oligomers in flax seed.