Exposure to flaxseed and its purified lignan reduces bone strength in young but not older male rats

A comprehensive review of the health benefits of flaxseed oil in relation to its chemical composition and comparison with other omega-3-rich oils

Flaxseed (Linum usitatissimum L) is an ancient perennial plant species regarded as a multipurpose plant owing to its richness in omega-3 polyunsaturated fatty acids (PUFA) including α-linolenic acid (ALA). The extensive biochemical analysis of flaxseed resulted in the identification of its bioactive, i.e., lignans with potential application in the improvement of human health. Flaxseed oil, fibers, and lignans exert potential health benefits including reduction of cardiovascular disease, atherosclerosis, diabetes, cancer, arthritis, osteoporosis, and autoimmune and neurological disorders that have led to the diversification of flaxseed plant applications. This comprehensive review focuses on flaxseed oil as the major product of flaxseed with emphasis on the interrelationship between its chemical composition and biological effects. Effects reviewed include antioxidant, anti-inflammatory, antimicrobial, anticancer, antiulcer, anti-osteoporotic, cardioprotective, metabolic, and neuroprotective. This study provides an overview of flaxseed oil effects with the reported action mechanisms related to its phytochemical composition and in comparison, to other PUFA-rich oils. This study presents the most updated and comprehensive review summarizing flaxseed oil's health benefits for the treatment of various diseases.

Flaxseed extract reduces tissue accumulation and enhances urinary excretion of chondroitin sulphate in the rat: a possible new path in substrate reduction therapy for mucopolysaccharidosis

CONTEXT

Chondroitin 6 sulphate (C6S) is a glycosaminoglycan (GAG) whose accumulation is notable in mucopolysaccharidosis type IVA and VII. Flaxseed, Linum usitatissimum L. (Linaceae) (FS), is reported to have comparable properties to those of soybean, a source of genistein, a potential new treatment for MPSs.

OBJECTIVE

We assess the effect of total ethanol flaxseed extract (EFSE) in an animal model of C6S accumulation.

MATERIALS AND METHODS

The study was performed in adult male Wistar rats (n = 24) for 15 successive days. The animals were divided into four groups: (1) control injected with physiological saline buffer, (2) intoxicated rats injected intraperitoneally with C6S, (3) intoxicated with C6S and treated with EFSE, and (4) treated with EFSE. All groups were subjected to histopathological and biochemical studies. The antioxidant and phytochemical properties of EFSE were examined.

RESULTS

Dry EFSE contains total phenols (6.28 mg EAG/g), condensed tannins (2.98 mg ECAT/g) and flavonoids (0.44 mg ECAT/g) with high antioxidant potential [RPE (IC₅₀ = 8.37 ± 0.176), DPPH (IC₅₀ = 12.79 ± 0.273)]. The LD₅₀ is higher than 5000 mg/kg. The histopathological examination showed an accumulation of C6S in the C6S intoxicated group, which disappeared in the C6S-EFSE treated group. GAGs assays showed an increased excretion in the C6S intoxicated group and increased excretion of 14% in the C6S-EFSE group compared to the C6S group.

DISCUSSION AND CONCLUSIONS

EFSE showed significant potential for chelation. Its use for the treatment of GAG accumulation could be suggested and generalized to a larger study population.

A mechanistic review of chinese medicine polyphenols on bone formation and resorption

Bone reconstruction includes a steady state system of bone formation and bone absorption. This tight coupling requires subtle coordination between osteoblasts and osteoclasts. If this balance is broken, it will lead to bone mass loss, bone density reduction, and bone metabolic diseases, such as osteoporosis. Polyphenols in Chinese herbal medicines are active ingredients in plant extracts with high safety and few side effects, and they can play a role in affecting bone formation and bone resorption. Some of these have estrogen-like effects and can better target bone health in postmenopausal women. The purpose of this review is to provide comprehensive information on the mechanisms underlying the relationship between traditional Chinese medicine polyphenols and bone formation or bone resorption.

C-Type Natriuretic Peptide Plays an Anti-Inflammatory Role in Rat Epididymitis Induced by UPEC

Human epididymitis is mainly caused by retrograde urinary tract infection with uropathogenic Escherichia coli (UPEC). This disease is an important factor (accounting for 20-30%) causing male infertility. C-type natriuretic peptide (CNP), a protein composed of 22 amino acids, is proved to play an immunoregulatory role in respiratory and cardiovascular systems. CNP is expressed extremely high in the epididymis, but whether CNP plays the same role in acute epididymitis is unclear. At first, we established an acute caput epididymitis model in rats with UPEC and treated them with CNP to measure inflammatory damage. Then RNA-seq transcriptome technology was used to reveal potential signal pathways. Secondly, the turbidity and activity of UPEC were assessed using a microplate reader and the amount of UPEC by agar plates after incubation with CNP. Thirdly, macrophages in caput epididymis were tested by immunohistochemistry (IHC). Meanwhile, lipopolysaccharide (LPS) with or without CNP was used to stimulate the macrophage (RAW264.7) in vitro and to detect the expression level of pro-inflammatory factors. Finally, the macrophage (RAW264.7) was treated with CNP, 8-Br-cGMP [cyclic guanosinc monophosphate (cGMP) analog] and KT5823 [protein kinase G (PKG) inhibitor], and the expression level of nuclear factor-k-gene binding (NF-kB) signal pathway was examined. The results showed that the damage of epididymis induced by UPEC as well as the pro-inflammatory factors could be alleviated significantly with CNP treatment. CNP could inhibit the activity and numbers of bacteria in both in vivo and in vitro experiments. Moreover, CNP repressed the invasion, and the expression of pro-inflammatory factors (such as NF-kB, IL-1β, IL-6, TNF-α) in macrophages and its effect could be inhibited by KT5823. Therefore, we drew a conclusion from the above experiments that CNP alleviates the acute epididymitis injury induced by UPEC. On one hand, CNP could inhibit the growth of UPEC. On the other hand, CNP could decrease invasion and inflammatory reaction of macrophages; the mechanism was involved in inhibiting NF-kB signal pathway through the cGMP/PKG in macrophages. This research would open up the possibility of using CNP as a potential treatment for epididymitis.

Effect of hydroalcoholic extract of flaxseed on bone mineral density in Wistar rats using digital radiography

Background:

Given that the world's population is aging, the problems associated with osteoporosis and related fractures are increasing. The aim of the study was to evaluate the effect of flaxseed extract on bone mineral density (BMD) in Wistar rats using digital radiography.

Methods:

In this experimental study, 25 male and 25 female Wistar rats were randomly divided into 5 groups: 1. Control, 2. Calcium and vitamin D (Ca/VitD), 3. 100 mg/kg flaxseed, 4. 200 mg/kg flaxseed, and 5. 400 mg/kg flaxseed. Then, the animals were kept for thirty days. Maxillary and mandibular BMD as well as serum levels of calcium, vitamin D and phosphorus were measured at baseline and after 30 days of keeping the rats.

Results:

The results showed that serum levels of calcium and phosphorus were not significantly different in all five groups before and after 30 days. Serum levels of vitamin D were significantly higher in the group receiving Ca/vit D (with a mean of 61.6±15.8 in the male group and 85±12.9 in the female group) as compared with other groups (P<0.001). The highest level of change in maxillary and mandibular bone density was in 200 mg/kg flaxseed group with a mean difference of 24.5±6.1 and 26.5±3.1, respectively, which was significant in comparison with the control and Ca/vit D groups (p<0.001) .

Conclusion:

Flaxseed extract is more effective in increasing bone density than the group receiving Ca/vit D. The mandibular and maxillary BMD was higher in the group receiving 200 mg/kg flaxseed compared to the group receiving Ca/vit D (p<0.001).

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.

Role of ABCG2 in transport of the mammalian lignan enterolactone and its secretion into milk in Abcg2 knockout mice

Lignans are phytoestrogens that are metabolized by the gut microbiota to enterodiol and enterolactone, the main biologically active enterolignans. Substantial interindividual variation in plasma concentration and urinary excretion of enterolignans has been reported, this being determined, at least in part, by the intake of lignan precursors, the gut microbiota, and the host's phase 2 conjugating enzyme activity. However, the role of ATP-binding cassette (ABC) transporters in the transport and disposition of enterolactone has not been reported so far. Active transport assays using parental and Madin-Darby canine kidney epithelial cells transduced with murine and human ABCG2 showed a significant increase in apically directed translocation of enterolactone in transduced cells, which was confirmed by using the selective ABCG2 inhibitor Ko143. In addition, enterolactone also inhibited transport of the antineoplastic agent mitoxantrone as a model substrate, with inhibition percentages of almost 40% at 200 μM for human ABCG2. Furthermore, the endogenous levels in plasma and milk of enterolactone in wild-type and Abcg2((-/-)) knockout female mice were analyzed. The milk/plasma ratio decreased significantly in the Abcg2((-/-)) phenotype, as compared with the wild-type mouse group (0.4 ± 0.1 as against 6.4 ± 2.6). This paper is the first to report that enterolactone is a transported substrate and therefore most probably a competitive inhibitor of ABCG2, which suggests it has a role in the interindividual variations in the disposition of enterolactone and its secretion into milk. The inhibitory activity identified provides a solid basis for further investigation in possible food-drug interactions.

Flaxseed enhances the beneficial effect of low-dose estrogen therapy at reducing bone turnover and preserving bone microarchitecture in ovariectomized rats

Our previous research showed greatest protection to vertebral bone mineral density and strength in ovariectomized (OVX) rats when lignan- and α-linolenic acid-rich flaxseed (FS) is combined with low-dose estrogen therapy (LD) compared with either treatment alone. This study determined the effects of combined FS+LD on serum and tissue markers of bone turnover and microarchitecture to explain our previous findings. Three-month-old OVX rats were randomized to negative control (NEG), FS, LD or FS+LD for 2 or 12 weeks, meaningful time points for determining effects on markers of bone metabolism and bone structure, respectively. Ground FS was added to the AIN-93M diet (100 g/kg diet) and LD (0.42 μg 17β-estradiol/(kg body weight·day)) was delivered by subcutaneous implant. Sham rats were included as positive control. Bone formation (e.g., osteocalcin), bone resorption (e.g., tartrate-resistant acid phosphatase-5β (TRAP-5β)), as well as osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANKL) were analyzed from the 2-week study by commercial assays (serum) and (or) histology (vertebra). Vertebral bone microarchitecture was measured from the 12-week study using microcomputed tomography. In serum, FS+LD and LD induced lower TRAP-5β and osteocalcin, and higher OPG and OPG/RANKL ratio versus NEG and FS (p < 0.05). In vertebrae, FS+LD induced higher OPG and lower osteocalcin versus NEG (p < 0.01) and did not differ from LD and FS. FS+LD improved bone microarchitecture versus NEG, FS, and LD (p < 0.05). In conclusion, FS+LD protects bone tissue because of a reduction in bone turnover. However, elucidating the distinctive action of FS+LD on bone turnover compared with LD requires further investigation.

Investigating the role of polyunsaturated fatty acids in bone development using animal models

Incorporating n-3 polyunsaturated fatty acids (PUFA) in the diet may promote the development of a healthy skeleton and thereby reduce the risk of developing osteoporosis in later life. Studies using developing animal models suggest lowering dietary n-6 PUFA and increasing n-3 PUFA intakes, especially long chain n-3 PUFA, may be beneficial for achieving higher bone mineral content, density and stronger bones. To date, the evidence regarding the effects of α-linolenic acid (ALA) remain equivocal, in contrast to evidence from the longer chain products, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This review reports the results of investigations into n-3 PUFA supplementation on bone fatty acid composition, strength and mineral content in developing animal models as well as the mechanistic relationships of PUFA and bone, and identifies critical areas for future research. Overall, this review supports a probable role for essential (ALA) and long chain (EPA and DHA) n-3 PUFA for bone health. Understanding the role of PUFA in optimizing bone health may lead to dietary strategies that promote bone development and maintenance of a healthy skeleton.

Effects of a safflower tea supplement on antioxidative status and bone markers in postmenopausal women

We conducted this study to examine the effects of safflower seed granular tea containing physiologically active polyphenols on antioxidative activities and bone metabolism. Forty postmenopausal women ages 49 to 64-years were recruited from Daegu and Gyeongbuk and were randomly assigned to either a safflower tea supplement (Saf-tea) group (n = 27) or a placebo group (n = 13). The Saf-tea group received 20 g of safflower seed granule tea per day containing a 13% ethanol extract of defatted safflower seeds, whereas the placebo group received a similar type of tea that lacked the ethanol extract. No significant changes in nutrient intake for either the placebo or Saf-tea groups were observed before or after the study period, except vitamin A intake increased after 6 months in the Saf-tea group. Dietary phytoestrogen intakes were similar in the Saf-tea group (60.3 mg) and placebo group (52.5 mg). Significant increases in plasma genistein and enterolactone were observed in the Saf-tea group. After 6 months of supplementation, serum levels of antioxidant vitamins such as α-tocopherol and ascorbic acid increased significantly, and TBARS levels decreased in the Saf-tea group compared to the placebo group. Serum osteocalcin levels were reduced (P < 0.05) in the Saf-tea group after 6 months, whereas serum osteocalcin did not change in the placebo group. Urinary deoxypyridinoline/creatinine excretion was not different between the two groups at baseline, and did not change in either group after 6 months. Bone mineral density decreased significantly in the placebo group (P < 0.01) but not in the supplemented group. It was concluded that polyphenols (72 mg/day), including serotonin derivatives, in the Saf-tea had both antioxidant and potential bone protecting effects in postmenopausal women without liver toxicity.

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.

Estradiol-17beta and linseed meal interact to alter visceral organ mass and hormone concentrations from ovariectomized ewes

To evaluate the estrogenic potential of secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on visceral organ mass, IGF-I, and thyroid hormone (T(3) and T(4)) concentrations, 48 multiparous, ovariectomized ewes (54.6 +/- 1.1 kg) were used in a 3 x 4 factorial arrangement. Main effects were length of LSM feeding (0, 1, 7, or 14 d) and length of exposure to estradiol-17beta (E(2)) implant (0, 6, or 24 h prior to tissue collection). Implanting ewes with E(2) for 24h increased liver mass relative to empty body weight (EBW; g/kg EBW) compared with ewes implanted for 0 or 6 h (P <or= 0.03), whereas feeding LSM for 14 d decreased liver mass compared with ewes fed LSM for 1 or 7 d (P <or= 0.02). There was an LSM x E(2) interaction (P = 0.01) for duodenal mass (g/kg EBW), LSM, and E(2) tended (P = 0.07) to influence the stomach complex mass; however, ileal mass was not affected. Neither LSM nor E(2) affected (P >or= 0.12) CYP2C or CYP3A mRNA expression or cellularity of the liver. Exogenous E(2) influenced circulating concentrations of IGF-I, T(3), and T(4). The estrogenic or anti-estrogenic potential of LSM is dependent upon the tissue, exposure to E(2), and the duration of LSM feeding. Feeding LSM during gestation, lactation, or during the grow-finish phase warrants further investigation.

A randomized controlled trial of the effects of flaxseed lignan complex on metabolic syndrome composite score and bone mineral in older adults

A randomized double-blind placebo controlled study design was used to assess the effects of flaxseed lignan complex supplementation during exercise training on a metabolic syndrome composite score and osteoporosis risk in older adults. A total of 100 subjects (>or=50 years) were randomized to receive flaxseed lignan (543 mg.day-1 in a 4050 mg complex) or placebo while completing a 6 month walking program (30-60 min.day-1, 5-6 days.week-1). Fasting serum glucose, triacylglycerol (TAG), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein cholesterol, total cholesterol, interleukin-6, and tumor necrosis factor-alpha were measured every 2 months, while body composition, bone mineral density, and resting blood pressure were assessed at baseline and at 6 months. A composite Z score of 6 risk factors for metabolic syndrome (fasting glucose, HDL cholesterol, TAG, abdominal adiposity, blood pressure, and inflammatory cytokines) was calculated at baseline and at 6 months. Men taking placebo increased metabolic syndrome composite Z score (p < 0.05), but there were no changes in the other groups. A significant group x sex x time interaction was noted for TAG (p = 0.017) and diastolic blood pressure (p = 0.046), with men taking flaxseed lignan decreasing diastolic blood pressure relative to men taking placebo, and men taking placebo increasing TAG relative to men taking flax lignan. There were no differences between groups for change in bone measures, body composition, lipoproteins, or cytokines. Males taking the flaxseed lignan complex reduced metabolic syndrome score relative to men taking placebo, but a similar trend was not seen in females. Flaxseed lignan had no effect on bone mineral density or content, body composition, lipoproteins, glucose, or inflammation.

Effect of estrogenic compounds (estrogen or phytoestrogens) combined with exercise on bone and muscle mass in older individuals

Exercise has a beneficial effect on bone, possibly by stimulating estrogen receptor alpha. Because estrogen up-regulates this receptor, estrogen therapy combined with exercise training may be optimal for increasing bone mineral density. Studies combining estrogen therapy and exercise training in postmenopausal women show mixed results, but indicate that the combination of interventions may be more effective for increasing bone mass than either intervention alone. Plant-like estrogens (i.e phytoestrogens such as soy isoflavones) may act as weak estrogen agonists or antagonists, have small beneficial effects on bone, and may interact with exercise for increasing bone mineral density. Phytoestrogen derived from flaxseed (flax lignans) has not been evaluated as extensively as soy isoflavones and thus its effect on bone is difficult to determine. Estrogen or soy isoflavones given to postmenopausal women results in a small increase in lean tissue mass that may be mediated through estrogen receptor alpha on muscle or through decreased inflammation.

Intake of dietary phytoestrogen and indices of antioxidant and bone metabolism of pre- and post-menopausal Korean women

A group of 101 women, aged 40-65 years consisted of 48 premenopausal subjects and 53 postmenopausal ones living in Daegu and Gyeongbuk area in Korea were evaluated with their general characteristics, lifestyle factors, nutrient and phytoestrogen intakes, blood and urinary indices concerning antioxidant status and bone metabolism. Body mass index (BMI), waist hip ratio (WHR) and systolic blood pressure (SBP) of the postmenopausal women were significantly higher (23.8, 0.86, and 126.9 mmHg, respectively) than those of the premenopausal women (22.6, 0.82, and 115.9 mmHg; respectively). Nutrient intakes of the postmenopausal and premenopausal groups were not different except lower fat intake and higher dietary fiber and iron intakes in the postmenopausal group. Daily total phytoestrogen intake was significantly higher in the postmenopausal group (48.54 mg) than the premenopausal (31.41 mg) and was resulted mostly from higher intakes of daidzein and genistein from soy and soy products (45.42 mg vs 28.91 mg). Serum genistein level and excretion of enterolactone, major lignan metabolite, were not very different between the two groups. Serum retinal and α- tocopherol levels were higher in the postmenopausal group but TBARS levels were not different between the two groups. Serum osteocalcin (7.18 ng/mL) and urinary deoxypyridinoline (7.15 nmol/mmol creatinine), in the postmenopausal group were significantly higher than those in the premenopausal group (4.80 ng/mL, 5.95 nmol/mmol creatinine). Urinary excretion of enterolactone was positively correlated with serum osetocalcin in premenopausal women and serum genistein negatively correlated with the urinary DPD in postmenopausal women. Dietary phytoestrogen intake was negatively correlated with serum level of TBARS in all subjects. It is concluded that the effect of total phytoestrogen intake is beneficial on body antioxidant status in all middle-aged women regardless of menopause but the effect on bone metabolism appears different by the type of the phytoestrogen and the menopausal state.

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.

AAPH-mediated antioxidant reactions of secoisolariciresinol and SDG

Secoisolariciresinol (SECO ) is the major lignan found in flaxseed (Linum usitatissimum L.) and is present in a polymer that contains secoisolariciresinol diglucoside (SDG ). SECO, SDG and the polymer are known to have a number of health benefits, including reduction of serum cholesterol levels, delay in the onset of type II diabetes and decreased formation of breast, prostate and colon cancers. The health benefits of SECO and SDG may be partially attributed to their antioxidant properties. To better understand their antioxidant properties, SECO and SDG were oxidized using 2,2'-azobis(2-amidinopropane), an in vitro model of radical scavenging. The major lignan radical-scavenging oxidation products and their formation over time were determined. SDG was converted to four major products, which were the result of a phenoxyl radical intermediate. One of these products, a dimer of SDG, decomposed under the reaction conditions to form two of the other major products, and . SECO was converted to five major products, two of which were also the result of a phenoxyl radical intermediate. The remaining products were the result of an unexpected alkoxyl radical intermediate. The phenol oxidation products were stable under the reaction conditions, whereas two of the alcohol oxidation products decomposed. In general, only one phenol group on the lignans was oxidized, suggesting that the number of phenols per molecule may not predict radical scavenging antioxidant ability of lignans. Finally, SECO is a superior antioxidant to SDG, and it may be that the additional alcohol oxidation pathway contributes to its greater antioxidant ability.

Flaxseed oil and bone development in growing male and female mice

Flaxseed is being increasingly incorporated into foods as a result of its proposed health benefits. Combined with the fact that bone is sensitive to dietary changes in fatty acids, the optimization of bone metabolism during childhood may be influenced by altering the type and amounts of fatty acids consumed. The effects of whole flaxseed or its purified lignan on bone development have been investigated, but positive and/or negative effects of flaxseed oil (FO), rich in alpha-linolenic acid (ALA), on bone development have not been reported. The objective of this study was to elucidate the effects of a 10% FO diet on indices of bone health, including bone mass and biomechanical bone strength. Male and female mice were fed either a 10% flaxseed oil (FO) or a 10% corn oil (CO) diet from postnatal day (PND) 28 until PND 91. Male and female mice fed FO converted ALA to eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) as indicated by significantly higher serum EPA and DHA; however, serum cytokines (interleukin-1beta, interleukin-6, tumor necrosis factor-alpha) with the potential to modulate bone metabolism did not significantly differ among groups. As expected, serum linoleic acid and arachidonic acid were significantly lower among mice fed FO. Feeding FO diet did not result in a higher or lower bone mass or stronger or weaker femurs and lumbar vertebra than in mice fed CO diet in either gender, suggesting that the level of ALA attainable in a 10% flaxseed oil diet is safe with regard to bone development in growing mice.

A western-style diet reduces bone mass and biomechanical bone strength to a greater extent in male compared with female rats during development

Evidence from epidemiological and animal-feeding trials suggests that a western-style diet that is high in fat, and low in Ca, vitamin D and folic acid may result in low bone mass and poor bone quality: this leads to an increased risk of fragility fracture. The overall objective of the present study was to determine the effect of feeding a western-style diet (low in Ca (0.4 g/kg diet, Ca:P ratio 1:10), cholecalciferol (3 microg/kg diet), folic acid (0.23 mg/kg diet) and fibre (20 g/kg diet), and high in fat (200 g/kg diet)) for 17 weeks on bone mineral content (BMC) and the biomechanical bone strength of rat femurs. A secondary objective was to determine whether femurs from male and female rats (seven to eight rats per group) respond differently to the western-style diet. Male and female rats weighing 150-180 g were fed a western-style diet or a control diet for 17 weeks. At the end of the feeding trial, femur BMC was measured by ashing, and biomechanical properties were determined by three-point bending. Femur BMC and the majority of biomechanical properties measured were lower (P<0.05) among male and female rats fed a western-style diet compared with a control diet, despite similar weight gain and final body weight within genders. However, the western-style diet had a greater negative effect on femur BMC and biomechanical strength properties among male rats compared with females. This may be because male rats experienced greater overall body growth, as assessed by weight gain, than female rats, and suggests that the nutrient composition of the western-style diet did not support the development of strong femurs.

Biomechanical bone strength and bone mass in young male and female rats fed a fish oil diet

The study objective was to determine if male and female rats fed a diet rich in fish oil had femurs and vertebrae that were stronger and more resistant to fracture than rats not fed omega-3 long chain polyunsaturated fatty acids. Weanling rats were randomized to a control or a fish oil diet for 5 weeks. Feeding fish oil to males had no effect on biomechanical strength properties of femurs and vertebrae as measured by three point bending and compression, respectively. In contrast, females fed fish oil had reduced length growth and a lower vertebral peak load. These effects may have been partly mediated by a lower food intake but were not associated with differences in serum IGF-I, estradiol or urinary calcium. The effect of consuming a fish oil diet into later adulthood should be investigated to determine if femur strength is also affected among females.

Flaxseed increased alpha-linolenic and eicosapentaenoic acid and decreased arachidonic acid in serum and tissues of rat dams and offspring

The effects of dietary flaxseed (FS), and defatted flaxseed meal (FLM) on serum and tissue fatty acid profiles were investigated. Pregnant Sprague-Dawley rats were fed AIN-93 based diets balanced in calories, fat, nitrogen, and fiber. Diets contained 0, 20%, 40% FS or 13% or 26% FLM by weight. The control, FS and FLM diets differed in linoleic acid to alpha-linolenic acid (ALA) fatty acid ratio. These diets were fed continuously during gestation, suckling period and 8 weeks post-weaning (F(1)). FS fatty acids were bioavailable and metabolized by pregnant and F(1) rats. ALA and eicosapentaenoic acid increased; linoleic and arachidonic acid decreased; and docosahexaeonic acid was unchanged in serum, 'gastric milk' and liver of FS and FLM-fed pregnant and F(1) rats. FS more than FLM, changed fatty acids profiles, but FLM and 40% FS significantly reduced serum cholesterol. Dietary 40% FS may have increased oxidative stress as evidenced by a reduction in liver vitamin E.

Effects of flaxseed and defatted flaxseed meal on reproduction and development in rats

Flaxseed, a rich source of reportedly beneficial n-3 fatty acid and phytoestrogens, has not been thoroughly tested for reproductive effects. High levels of flaxseed (FS, 20 or 40%) or defatted flaxseed meal (FLM, 13 or 26%) added to AIN-93 diet were evaluated in a two-phase study: dosed during gestation only or during gestation and maturation in a lifetime study. At cesarean section on gestation day 20, neither FS nor FLM affected fertility, body weight gain, litter size, or fetal development. FLM, but not FS, decreased gestation length. The offspring of dams allowed to litter were observed to postnatal day (PND) 21 or 90. Neither FS nor FLM affected PND 21 survival indices of F1 pups. FS (20 and 40%), but not FLM, increased the anogenital index (AGI) of F1 females at PND 21. The AGI of F1 males was not affected by either FS or FLM. FLM (13 and 26%), but not FS, delayed puberty in F1 males. Age and weight at the onset of puberty in females were not affected by FS or FLM. FS and FLM caused dose-related increases in the number of F1 females with irregular estrous cycles. During PND 21-90, F1 females fed 20% FS, 13% FLM, or 26% FLM gained more weight than the controls. FS and FLM decreased thymus/body weight and thymus/brain weight ratios in weanling F1 males and females. FS and FLM decreased liver/body weight and liver/brain weight ratios in weanling F1 females, and 26% FLM decreased the same two ratios in F1 males. In conclusion, FS did not affect fetal development but did affect indices of postnatal development such as the estrous cycle.

Modulation of essential (n-6):(n-3) fatty acid ratios alters fatty acid status but not bone mass in piglets

Dietary (n-6) and (n-3) fatty acids have been implicated as important regulators of bone metabolism. The main objective of this research was to define the response of whole-body growth, fatty acid status and bone mass to a reduced dietary (n-6):(n-3) fatty acid ratio. A secondary objective was to determine whether there is an amount of fat x fatty acid ratio interaction for these outcomes. Piglets (n = 32) were randomized to 1 of 4 diets: group 1: [30 g fat/L + (n-6):(n-3) ratio 4.5:1]; group 2: [30 g fat/L + (n-6):(n-3) ratio 9.0:1]; group 3: [60 g fat/L + (n-6):(n-3) ratio 4.5:1]; and group 4: [60 g fat/L + (n-6):(n-3) ratio 9.0:1]. After 21 d, outcomes assessed included growth, fatty acid status and bone mass and metabolism. Growth and bone mass did not differ among the four groups nor did arachidonic acid (AA as g/100 g fatty acids) in plasma, adipose and brain. Piglets fed diets 1 and 3 with the lower (n-6):(n-3) ratio had lower liver AA (P < 0.001). Those fed diets 1 and 2 containing 30 g fat/L had lower docosahexaenoic acid (DHA as g/100 g fatty acids) in liver (P < 0.001), plasma (P = 0.019) and adipose tissue (P = 0.045). However, piglets fed diets 1 and 3 had higher (P < 0.001) brain DHA than those fed diets with a higher (n-6):(n-3) ratio. Higher plasma DHA was associated with less bone resorption (r = -0.44, P = 0.01). Therefore, elevation of dietary (n-3) fatty acids supports growth and fatty acid status while not compromising bone mass. The results may be of relevance to the nutritional management of preterm infants whose DHA status is often too low and bone resorption too high.

Exposure to purified lignan from flaxseed (Linum usitatissimum) alters bone development in female rats

Due to the potential oestrogenic effects of secoisolariciresinol diglycoside (SDG), the mammalian lignan precursor in flaxseed (Linum usitatissimum), we hypothesized that exposure to purified SDG during early life would have a positive effect on developing bone. This present study determined whether exposure to SDG purified from flaxseed during suckling via mother's milk or continuously to adolescence (postnatal day (PND) 50) or adulthood (PND 132) increased bone mineral content (BMC) or bone strength in female rat offspring. Offspring were exposed to basal diet (BD) or one of two doses of SDG (50S, 100S) equivalent to that in a 50 or 100 g flaxseed/kg diet during lactation only or through to PND 50 or 132. At PND 50 and 132, femurs were analysed for BMC by dual energy X-ray absorptiometry and biomechanical strength by a 3-point bending test. Compared with BD group, rats exposed to continuous 50S or 100S diet had stronger femurs at PND 50 without changes in BMC. At PND 132 there were no differences in femur strength despite the fact that continuous exposure to BD resulted in a higher BMC than rats exposed to 100S during lactation only or to 50S or 100S during lactation through to adulthood. In conclusion, female rat bone is more sensitive to the oestrogen-like action of lignans during early life when endogenous levels of sex hormones are low, but by adulthood the improved bone strength does not persist. Importantly, exposure to purified lignan does not have negative effects on bone strength.