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

Cinnamaldehyde supplementation acts as an insulin mimetic compound improving glucose metabolism during adolescence, but not during adulthood, in healthy male rats

PURPOSE

Adolescence is a critical period of increased vulnerability to nutritional modifications, and adolescents may respond differently from adults to dietary intake and nutraceuticals. Cinnamaldehyde, a major bioactive compound of cinnamon, improves energy metabolism, as has been shown in studies conducted primarily in adult animals. We hypothesized that cinnamaldehyde treatment may have a higher impact on the glycemic homeostasis of healthy adolescent rats than on healthy adult rats.

METHODS

Male adolescent (30 days) or adult (90 days) Wistar rats received cinnamaldehyde (40 mg/kg) for 28 days by gavage. The oral glucose tolerance test (OGTT), liver glycogen content, serum insulin concentration, serum lipid profile, and hepatic insulin signaling marker expression were evaluated.

RESULTS

Cinnamaldehyde-treated adolescent rats showed less weight gain (P = 0.041), improved OGTT (P = 0.004), increased expression of phosphorylated IRS-1 (P = 0.015), and a trend to increase phosphorylated IRS-1 (P = 0.063) in the liver of adolescent rats in the basal state. None of these parameters was modified after treatment with cinnamaldehyde in the adult group. Cumulative food intake, visceral adiposity, liver weight, serum insulin, serum lipid profile, hepatic glycogen content, and liver protein expression of IRβ, phosphorylated IRβ, AKT, phosphorylated AKT, and PTP-1B in the basal state were similar between both age groups.

CONCLUSION

In a healthy metabolic condition, cinnamaldehyde supplementation affects glycemic metabolism in adolescent rats while promoting no changes in adult rats.

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.

Greater Consumption of Total and Individual Lignans and Dietary Fibers Were Significantly Associated with Lowered Risk of Hip Fracture-A 1:1 Matched Case-Control Study among Chinese Elderly Men and Women

The study aims to examine the association of dietary intake of lignans with the risk of hip fractures in Chinese older adults. This was a 1:1 age- and gender- matched case−control study. Dietary survey was conducted by face-to-face interviews using a 79-item validated food frequency questionnaire. Habitual intake of total and individual lignans (matairesinol, secoisolariciresinol, pinoresinol, and lariciresinol) was estimated based on the available lignans databases. Conditional logistic regression was used to examine the relationship of dietary total and individual lignans, lignan-rich foods (vegetables, fruits, nuts, and cereals) and dietary fibers with the risk of hip fracture. A total of 1070 pairs of hip fracture incident cases and controls were recruited. Compared with the lowest quartile, the highest quartile group showed a reduced hip fracture risk by 76.3% (0.237, 95% CI: 0.103−0.544, Ptrend < 0.001) for total lignans, and 62.5% (0.375, 95% CI: 0.194−0.724, Ptrend = 0.001) for dietary fibers. Similar findings were observed for individual lignans, the estimated enterolactone level, as well as lignans from vegetables and nuts. We concluded that greater consumption of total and individual lignans, and lignan-rich foods were significantly associated with decreased risk of hip fracture.

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.

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.

Psoralea corylifoliaExtract Ameliorates Experimental Osteoporosis in Ovariectomized Rats

We evaluated the protective effect of Psoralea corylifolia L. (PCL) extract on the ovariectomized (OVX) rat model. The biochemical markers of bone turnover, calcium metabolism, and calcium balance were examined. PCL extract (25 mg or 50 mg/kg body weight/day) was orally administrated to OVX rats for 3 months. PCL extract did not alter weight gain or uterus weight in OVX rats. PCL extract significantly increased serum Ca (calcium) levels ( p < 0.05, vs. OVX group) as well as decreased urinary Ca excretion ( p < 0.05 vs. OVX group) in OVX rats. The upregulation of serum osteocalcin level by ovariectomy was suppressed by treatment with PCL extract in rats ( p < 0.05, vs. OVX group). PCL extract increased bone mineral density at 50 mg/kg body weight/day in OVX rats ( p < 0.05, vs. OVX group). Our results indicate that orally administrated PCL extract can decrease urinary calcium excretion and decrease serum osteocalcin in OVX rats, resulting in positive effects on bone mineral density as well as bone formation. In conclusion, our studies showed that PCL might be a potential candidate for treatment of postmenopausal osteoporosis.

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.

Hydroxycinnamic acids are ester-linked directly to glucosyl moieties within the lignan macromolecule from flaxseed hulls

In flaxseed hulls, lignans are present in an oligomeric structure. Secoisolariciresinol diglucoside (SDG), ester-linked to hydroxy-methyl-glutaric acid (HMGA), forms the backbone of this lignan macromolecule. The hydroxycinnamic acids p-coumaric acid glucoside (CouAG) and ferulic acid glucoside (FeAG) are also part of the lignan macromolecule. However, their position and type of linkage are still unknown. The aim of this study was to investigate how CouAG and FeAG are linked within the lignan macromolecule from flaxseed hulls. Fragments of the lignan macromolecule were obtained by partial saponification. After isolation of the fragments by preparative RP-HPLC, several key structures were identified by MS and NMR. Within the lignan macromolecule, CouAG is attached to the C-6 position of a glucosyl moiety of SDG. FeA is linked to the C-2 position of a glucosyl moiety of SDG. FeAG is ester-linked within the lignan macromolecule with its carboxyl group, but it remains unclear whether FeAG links to the C-2 or C-6 position of SDG. Attachment of HMGA to the glucosyl moiety of CouAG or FeAG was not observed. The results clearly show that within the lignan macromolecule, the hydroxycinnamic acids are linked directly via an ester bond to the glucosyl moiety of SDG.

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.

Genistein alone and in combination with the mammalian lignans enterolactone and enterodiol induce estrogenic effects on bone and uterus in a postmenopausal breast cancer mouse model

The use of phytoestrogens, such as isoflavones and lignans, for treatment of postmenopausal breast cancer is increasing, but their effects on bone and other major organs are not clear. While the isoflavone genistein (GEN) has been shown to prevent or slow the loss of bone mineral density (BMD), the effect of lignans enterodiol (END) and enterolactone (ENL) are unknown. In this study, we determined in ovariectomized mice with human MCF-7 breast tumor xenografts the effects of the lignans, and GEN, alone and in combination, on bone and uterus. Mice with established MCF-7 tumors were fed a basal diet (AIN-93G), divided into 5 groups, and given daily subcutaneous injections (10 mg/kg body weight) of either ENL, END, GEN, a mixture of these compounds (MIX), or vehicle as a negative control for 22 weeks. Results showed that GEN acts estrogenically in both the uterus and bone by increasing the uterus weight, femur BMD, and femur biomechanical strength (yield load), while the lignans do not. However, treatment with MIX induced minimal effects on femur biomechanical strength parameters but significantly increased uterus weight. A significant positive correlation was observed between MCF-7 tumor volume and femur BMD and biomechanical strength parameters (femur peak load and yield load) but not with uterus weight, suggesting that the uterus may respond differently to phytoestrogens compared to MCF-7 tumors and bone. It is concluded that GEN induces beneficial effects on bone but has adverse effects on tumors and uterus in this model of postmenopausal breast cancer. The lignans do not exert adverse effects on any tissue, however, when combined with GEN, they exert an adverse effect on the uterus.

Effect of ethanol extract of Lepidium meyenii Walp. on osteoporosis in ovariectomized rat

Maca (Lepidium meyenii Walp.) is a cruciferous plant from the Andes of Peru. The root of Maca is traditionally employed for its supposed properties in aphrodisiacs and improving fertility, it also has been widely used to help alleviate the symptoms of menopause. The purpose of this study was to evaluate the effect of ethanol extract of Maca on postmenopausal osteoporosis in ovariectomized rats. Female Sprague-Dawley rats were divided into four groups: Sham-operated and ovariectomized groups were fed with equivolume of distilled water, and the remaining ovariectomized groups were orally administrated with ethanol extract of Maca at 0.096 and 0.24 g/kg for 28 weeks. The findings derived from the basis of bone mineral density, biomechanical, biochemical and histopathological parameters indicated that higher dose of ethanol extract of Maca was effective in the prevention of estrogen deficient bone loss.

Increase in bone mass and bone strength by Sambucus williamsii HANCE in ovariectomized rats

Herbal Sambucus williamsii HANCE (SWH) is a folk medicine with a long history of safe use for treatment of bone fractures and joint diseases in China. The present study was designed to investigate if SWH extract could be used for treatment of postmenopausal osteoporosis. SWH extracts (30 or 60 mg/100 g body weight/d) were orally administrated to four-months-old ovariectomized (OVX) rats for 3 months. SWH extracts did not alter weight gain and uterus weight in OVX rats. SWH extracts significantly increased serum Ca levels (p<0.05, vs. OVX control group) as well as decreased urinary Ca excretion (p<0.01, vs. OVX control group) in OVX rats. The upregulation of serum alkaline phosphatase, serum osteocalcin as well as urinary deoxypyridinoline levels by OVX was suppressed by treatment with SWH extracts in rats (p<0.05, vs. OVX control group). SWH extract increased the stiffness of femur at both dosage (p<0.05, vs. OVX control group) and increased tibial bone mineral density at 60 mg/100 g body weight/d (p<0.05, vs. OVX control group) in OVX rats. Our results indicate that orally administrated SWH extracts can decrease urinary calcium excretion and bone turnover rate in OVX rats, resulting in positive effects on biomechanical strength of bone and bone mineral density. This study is the first to report that SWH could be considered as a potential candidate for management of postmenopausal osteoporosis. Then in vitro experiments were performed to determine the potential molecular mechanism of the anti-osteoporotic effect of SWH. Results suggested that chloroform fraction and ethyl acetate fraction of SWH can inhibit osteoclastogenesis osteoclast by modulating the expression of osteoprotegrin (OPG) and receptor activator of NF-kappaB ligand (RANKL) mRNA in osteoblastic UMR 106 cells. Both of them increased OPG mRNA and decreased RANKL mRNA expression, resulting in a dose-dependent increase in OPG/RANKL mRNA ratio (p<0.01, vs. vehicle-treated). Taken together, SWH treatment can effectively suppress the OVX-induced increase in bone turnover and its effects might be mediated by a decrease in osteoclastogenesis.

In vivo anti-osteoporotic activity of isotaxiresinol, a lignan from wood of Taxus yunnanensis

Isotaxiresinol, the main lignan isolated from the water extract of wood of Taxus yunnanensis, was investigated for its effect on bone loss, on serum biochemical markers for bone remodeling and on uterine tissue, using ovariectomized (OVX) rats as the model of postmenopausal osteoporosis. After oral administration of isotaxiresinol (50 and 100mg/kg/d) for 6 weeks, bone mineral content (BMC) and bone mineral density (BMD) in total and cortical bones were increased as compared to those of OVX control rats, and decreases of three bone strength indexes induced by OVX surgery were prevented. Serum biochemical markers for bone remodeling revealed that isotaxiresinol slightly increased bone formation and significantly inhibited bone resorption without side effect on uterine tissue. These results suggest that isotaxiresinol may be useful for treatment of postmenopausal osteoporosis, especially for prevention of bone fracture induced by estrogen deficiency.

Dietary lignins are precursors of mammalian lignans in rats

The mammalian lignans enterolactone (ENL) and enterodiol, commonly found in human plasma and urine, are phytoestrogens that may contribute to the prevention of breast cancer and coronary heart disease. They are formed by the conversion of dietary precursors such as secoisolariciresinol and matairesinol lignans by the colonic microflora. The identification of lignins, cell-wall polymers structurally related to lignans, as precursors of mammalian lignans is reported here for the first time. In study 1, rats were fed rye or wheat bran (15% diet) for 5 d. Untreated brans and brans extracted with solvents to remove lignans were compared. ENL was estimated in urine samples collected for 24 h by time-resolved fluoroimmunoassay. ENL urinary excretion was reduced from 18.6 to 5.3 nmol/d (n=8; P<0.001) when lignans were removed from rye bran and from 30.5 to 6.2 nmol/d (P<0.001) when they were removed from wheat bran. These results suggest that lignins, embedded in the cell wall and retained in the bran during solvent extraction, account for 26-32% of the ENL formed from cereal brans. In study 2, rats were fed a deuterated synthetic lignin (0.2% diet) together with wheat bran (15%) for 3 d. The detection of deuterated ENL by LC-tandem MS in urine (20 nmol/d) clearly confirms the conversion of lignin into mammalian lignans. More research is warranted to determine the bioavailability of lignins in the human diet.

Isoflavones with supplemental calcium provide greater protection against the loss of bone mass and strength after ovariectomy compared to isoflavones alone

Although hormone replacement therapy (HRT) and calcium (Ca) supplementation preserve bone mass more when combined, there is a growing concern over the safety of HRT that necessitates thorough investigation of effective, alternative treatments for bone loss. While plant-derived estrogen-like compounds such as isoflavones preserve bone, it is not known whether isoflavones and Ca supplementation attenuate losses in bone mass and strength to a greater extent when combined. This study compared the effects of an isoflavone extract + high Ca to isoflavone extract or high Ca alone on preservation of bone mineral density (BMD) and biomechanical strength in ovariectomized (ovx) rats. Rats were sham-operated (n = 10) or ovx (n = 40). Shams were fed a 0.2% Ca diet. Ovx rats were randomized to a 0.2% Ca diet alone (OVX) or with isoflavone extract (IE; 1.6 g/kg diet) or to a high Ca diet (Ca; 2.5%) alone or a high Ca diet with the isoflavone extract (IE + Ca) for 8 weeks. BMD of femur and lumbar spine were measured by dual-energy X-ray absorptiometry. The biomechanical strength of femurs and individual vertebra was measured by three-point bending and compression testing, respectively. The average food intake was lowest (P < 0.05) among sham and IE groups and greatest (P < 0.05) among the OVX group. Final body weight was lowest (P < 0.05) among shams and highest (P < 0.05) among the OVX group while IE + Ca were lighter (P < 0.05) than all ovx groups. Femur and vertebra BMD was greater (P < 0.05) among IE + Ca and sham rats compared to IE, Ca, or OVX rats. Although there were differences in femur BMD among groups, biomechanical properties at the femur midpoint did not differ among groups, possibly due to the lack of cortical bone loss at this site. Conversely, vertebra biomechanical strength was greater (P < 0.05) among IE + Ca and Ca alone groups compared to IE alone. Uterine weight was higher (P < 0.05) among shams than OVX and IE with no difference among shams, Ca, or IE + Ca rats, suggesting that the isoflavones did not have an uterotrophic effect. In conclusion, isoflavones combined with high Ca are more protective against the loss of femur and vertebra BMD than isoflavones or high Ca diet alone.

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.

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.