Ipriflavone inhibits bone resorption in intact and ovariectomized rats

Ipriflavone suppresses NLRP3 inflammasome activation in host response to biomaterials and promotes early bone healing

AIM

Emerging studies have shown that immune response to biomaterial implants plays a central role in bone healing. Ipriflavone is clinically used for osteoporosis. However, the mechanism of ipriflavone in immune response to implants in early stages of osseointegration remains unclear. In this study, we aimed to investigate the potential role of ipriflavone in early bone healing process and uncover the underlying mechanism.

MATERIALS AND METHODS

We carried out histological examination as well as analysis of proinflammatory cytokines and NLRP3 inflammasome activation in a tibial implantation mouse model with intra-peritoneal injection of ipriflavone. In addition, we explored the mechanism of ipriflavone in the regulation of NLRP3 inflammasome activation in macrophages.

RESULTS

In vivo, ipriflavone ameliorated host inflammatory response related to NLRP3 inflammasome activation at implantation sites, characterized by reductions of inflammatory cell infiltration and proinflammatory cytokine interleukin-1β levels. Ipriflavone treatment also showed beneficial effects on early osseointegration. Further investigations of the molecular mechanism showed that the suppression of NLRP3 inflammasome acts upstream of NLRP3 oligomerization through abrogating the production of reactive oxygen species.

CONCLUSIONS

These results revealed an anti-inflammatory role of ipriflavone in NLRP3 inflammasome activation through improving mitochondrial function. This study provides a new strategy for the development of immune-regulated biomaterials and treatment options for NLRP3-related diseases.

Effects of isoflavone interventions on bone mineral density in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials

Isoflavones have a structure similar to 17β-estradiol, so they may be useful to postmenopausal women in preventing bone loss related to estrogen deficiency. The present study integrated the findings from 63 randomized controlled trials and found that isoflavone interventions may have benefits in the prevention and treatment of menopause-related osteoporosis.

PURPOSE

This study aimed to determine the efficacy of isoflavone interventions on bone density outcomes and the safety of isoflavone interventions in postmenopausal women by means of systematic review and meta-analysis.

METHODS

A systematic search was performed on three databases (PubMed, Scopus, and Cochrane Library). Included studies were limited to randomized controlled trials (RCTs) assessing the effects of isoflavone intervention on bone mineral density (BMD) in postmenopausal women. Mean difference (MD) in BMD or relative risk for adverse outcomes was used as a summary effect measure; pooled-effect estimates were calculated using a random-effects model.

RESULTS

A total of 63 RCTs, involving 6427 postmenopausal women, were included in the meta-analysis. Statistically significant differences in BMD at the last follow-up visit between the two groups (isoflavones vs. control) were found at the lumbar spine (MD = 21.34 mg/cm², 95% CI = 8.21 to 34.47 mg/cm², p = 0.001), the femoral neck (MD = 28.88 mg/cm², 95% CI = 15.05 to 42.71 mg/cm², p < 0.0001), and the distal radius (MD = 19.27 mg/cm², 95% CI = 5.65 to 32.89 mg/cm², p = 0.006). The positive effects in improved BMD were primarily associated with two formulations, i.e., genistein 54 mg/day and ipriflavone 600 mg/day. Isoflavone interventions were generally safe and well tolerated.

CONCLUSION

Isoflavone interventions, genistein (54 mg/day) and ipriflavone (600 mg/day) in particular, have beneficial effects on BMD outcomes and are safe in postmenopausal women. They may be considered as a complementary or alternative option in the prevention and treatment of menopause-related osteoporosis.

The efficacy and safety of ipriflavone in postmenopausal women with osteopenia or osteoporosis: A systematic review and meta-analysis

OBJECTIVES

Ipriflavone (IP) is one of the over-the-counter drugs and found in foods, which is available for prevention of osteoporosis (OP) since 1989 in over 22 countries. Although some clinical trials have suggested that IP is appropriate for treatment of OP, there continues to be controversy regarding the efficacy and safety due to some contradictory reports. With the wide usage of IP for osteoporotic women, there is a critical need for evaluation of the evidence for IP in clinical practice.

METHODS AND MATERIALS

We searched randomized control trials (RCTs) in PubMed, CENTRAL and CNKI which used the regimen of IP in postmenopausal women with osteopenia or OP. The efficacy referred to the absolute change and relative change in bone mineral density (BMD) and bone turnover markers. The safety profiles were associated with adverse events and the number of subject withdrawals due to adverse reactions.

RESULTS

Eleven RCTs (n = 1605) met the eligibility criteria were included. The increase of the BMD in lumbar spine of the IP group is greater than that of the placebo group (random effect model: SMD = 0.36; 95%CI= (0.09, 0.62)). For safety profile, most frequent reactions are gastrointestinal symptoms, but withdrawals due to adverse reactions are similar in both the IP group and placebo control at the same time intervals.

CONCLUSIONS

IP significantly increases BMD and has inhibitory effect on bone resorption markers in postmenopausal women with osteopenia or OP. Gastrointestinal symptoms may occur, but adverse drug withdrawal events were not statistically increased when compared with placebo group.

3-Piperidylethoxypterocarpan: A potential bone anabolic agent that improves bone quality and restores trabecular micro-architecture in ovariectomized osteopenic rats

A series of new 6H-benzofuro[3, 2-c]chromenes (BFC, pterocarpans) with structure-activity relationships were investigated for their potential use in osteoporosis treatment. One of the BFCs 3-piperidylethoxypterocarpan 20 promotes osteoblast differentiation and mineralization at a dose as low as 1 pM via activation of ER/P38MAPK/BMP-2 pathway. When evaluated for in-vivo osteogenic activity in female Sprague-Dawley rats, BFC 20 increased bone mineral density and new bone formation, compared with control at 1.0 and 10.0 mg/kg/body weight by oral gavage for 30 days. The compound was devoid of any uterotrophic effect and led to the new bone formation in adult ovariectomized osteopenic rats. BFC 20 compound also inhibited bone resorption by reducing Ovx induced increase in urinary CTx, thus exhibiting both bone anabolic and anti-catabolic action. Finally, BFC 20 treatment to Ovx rats led to improved trabecular microarchitectural restoration and exhibited therapeutic potential as a dual acting anti-osteoporotic agent for the management of osteoporosis.

Effect of isoflavone soy protein supplementation on endometrial thickness, hyperplasia, and endometrial cancer risk in postmenopausal women: a randomized controlled trial

OBJECTIVE

This study aims to determine whether long-term isoflavone soy protein (ISP) supplementation affects endometrial thickness and rates of endometrial hyperplasia and cancer in postmenopausal women.

METHODS

In this randomized, double-blind, placebo-controlled trial, 350 postmenopausal women aged 45 to 92 years were randomized to a total daily dose of 154 mg of ISP or a milk protein-matched placebo for a 3-year period. Women with a surgically absent uterus were excluded from the analysis (final study population, N = 224). The main outcome measures were as follows: mean change in endometrial thickness on transvaginal ultrasound from baseline until up to 36 months of follow-up and the incidence of endometrial sampling, endometrial hyperplasia, and endometrial cancer.

RESULTS

A total of 666 visits among 224 participants were evaluated. Treatment groups did not significantly differ on the mean baseline or on-trial changes in endometrial thickness. Of the 103 placebo-treated participants, 7 (6.8%) underwent endometrial biopsy; 6 (85.7%) of these biopsies were benign. One woman in the placebo group was diagnosed with complex endometrial hyperplasia with atypia and underwent hysterectomy. The pathology result from this surgical operation was stage IB endometrial cancer. Of the 121 participants in the soy group, 9 (7.4%) underwent endometrial biopsy. The results were benign in all nine cases (100%). Although the rate of hyperplasia/malignancy was higher in the placebo group (14.3% vs 0%), the difference was not statistically significant.

CONCLUSIONS

Three-year ISP supplementation has no effect on endometrial thickness or on the rates of endometrial hyperplasia and cancer in postmenopausal women.

Effect of intermittent PTH (1-34) on posterolateral spinal fusion with iliac crest bone graft in an ovariectomized rat model

SUMMARY

Intermittent treatment with high-dose parathyroid hormone (PTH) enhances the quantity and quality of the fusion callus and reduces healing time of posterolateral spinal fusion with autologous iliac bone grafts in ovariectomized osteoporotic female Sprague-Dawley rats. Intermittent PTH (1-34) could be an appropriate adjunctive therapy for osteoporotic patients undergoing posterolateral intertransverse process fusion.

INTRODUCTION

The study was designed to test the hypothesis that intermittent administration of PTH improves spinal fusion rates in a randomized controlled, ovariectomized osteoporotic rat spinal fusion model.

METHODS

Thirty-six 10-week-old Sprague-Dawley rats were ovariectomized and underwent bilateral posterolateral L4-L5 spinal fusion with autologous iliac bone graft 6 weeks later. The experimental (PTH) group (18 rats) received daily subcutaneously administered injections of PTH (1-34) at 30 μg/kg/day starting on the day of operation. The control group (18 rats) received a subcutaneously administered injection of normal saline of the same volume. Nine rats from each group were sacrificed at 4 and 6 weeks. After sacrifice, the L4-L5 vertebral segments were removed and analyzed by plain radiographs, μ-CT, histomorphometry, and serum bone metabolism marker.

RESULTS

The PTH group had a significantly higher fusion rate and X-ray fusion score than the control group at 4 and 6 weeks (p < 0.05). μ-CT and histological analysis showed that the fusion bone volume and cortical thickness for the PTH group were significantly higher than those for the control group at 4 and 6 weeks (p < 0.05). Metabolic marker analysis also showed significant difference between the two groups. The serum osteocalcin was significantly higher in the PTH group at 4 and 6 weeks, and levels of N-terminal peptide of type I collagen were significantly higher at 4 weeks (p < 0.05).

CONCLUSION

Intermittent treatment with high-dose PTH enhances the quantity of the fusion callus and reduces the healing time of posterolateral spinal fusion with autologous iliac bone grafts in ovariectomized osteoporotic female Sprague-Dawley rats.

Mutagenicity of ipriflavone in vivo and in vitro

Ipriflavone (7-isopropoxy-isoflavone) is a semisynthetic isoflavone derivative from daidzein and prescribed to prevent and treat osteoporosis in postmenopausal women. In the present study, ipriflavone was investigated with regard to their cytotoxic and mutagenic effects using the micronucleus assay (MN) in vivo on cells of bone marrow and peripheral blood of Swiss albino mice and the micronucleus test with the cytokinesis-blocked micronucleus assay (CBMN assay) on human peripheral blood lymphocytes. The studies were performed in mice with three dosages of the drug, 1.71, 8.57 and 42.85 mg/kg bw in single oral exposure, and for two dosages, 5 and 10 μg/mL in the CBMN assay. Ipriflavone, in the dosages tested, did not differ from controls neither in the induction of MN nor induced cytotoxicity to cells in the in vivo test. However, in the CBMN assay, the concentration of 10 μg/mL induced a statistically significant increase in MN formation and decreased cell proliferation, demonstrating to be mutagenic and cytotoxic at this concentration.

Effect of tetracalcium dimagnesium phytate on bone characteristics in ovariectomized rats

The aim was to evaluate the influence of dietary Ca-Mg-phytate consumption on the bone characteristics of ovariectomized rats, an animal model for postmenopausal osteoporosis. Twenty ovariectomized female Wistar rats were randomly assigned to two groups fed, respectively, with a non-phytate diet (AIN-76A) or the same diet enriched with 1% phytate (as the calcium magnesium salt, phytin). After 12 weeks of feeding the rats were sacrificed, and both femoral bones and L4 vertebra were removed from each rat. Bone mass, length, width, volume, and mineral density were measured, and the phosphorus, calcium, magnesium, and zinc contents of bones were determined. Deoxypyridinoline (a bone resorption marker) was measured in urine, and osteocalcin (a bone formation marker) was measured in serum. The calcium and phosphorus contents and bone mineral density were significantly higher in both femoral bones and L4 vertebra for phytate-treated rats in comparison to rats in the non-phytate group. Deoxypyridinoline was significantly increased in rats in the non-phytate treatment group. Ca-Mg-phytate consumption reduces bone mineral density loss due to estrogen deficiency. Thus, phytate exhibits effects similar to those of bisphosphonates on bone resorption and may be of use in the primary prevention of osteoporosis if larger studies in humans confirm these findings.

Effects of phyto-oestrogens on tissues

Recent investigations on the effects of phyto-oestrogens on various tissues have revealed that these diverse molecules may improve human health, particularly by protecting against certain chronic diseases. After a brief examination of the food sources, structures, and general cellular actions of the major phyto-oestrogens, current research findings on cardiovascular disease, skeletal tissues, and reproductive cancers are reviewed. Phyto-oestrogen concentrations in blood may be maintained at high levels in those consuming soyabean (Glycine max)-based food daily at several meals and exert their effects on target cells through either genomic effects via the classical oestrogen receptors or non-genomic effects mediated by membrane-bound oestrogen receptors or other cellular proteins. The expression of oestrogen receptor (OR) subtypes alpha (a) and beta (beta) varies across tissues, and cells that preferentially express OR-beta, which may include bone cells, are more likely to respond to phyto-oestrogens. Conversely, reproductive tissues contain relatively more OR-a and may, thus, be differently affected by phyto-oestrogens. Soyabean phyto-oestrogens appear to prevent the progression of atherosclerosis through multiple interactions, including lowering of plasma lipids and lipoproteins, increased vasodilatation and, possibly, decreased activation of blood platelets and vascular smooth muscle cells. However, a favourable impact on cardiovascular disease morbidity and mortality by a soyabean-enriched western-type diet remains to be shown, and unresolved questions remain regarding dose and form of the phyto-oestrogens in relation to risks and benefits. The isoflavones of soyabean have been shown consistently to have bone-retentive effects in animal studies by several investigators using rodent models, although intakes must be above a relatively high threshold level for a lengthy period of time, and little or no extra benefit is observed with intakes above this threshold level. The reports of modest or no effects on prevention of bone loss in human and non-human primate studies respectively, may be due to the limited doses tested so far. The relationship between soyabean-food intake and cancer risk has been more extensively investigated than for any other disease, but with less certainty about the benefits of long-term consumption of phyto-oestrogen-containing foods on prevention of cancer. The observations that breast and prostate cancer rates are lower in Asian countries, where soyabean foods are consumed at high levels, and the high isoflavone content of soyabeans have led to examination of the potential protective effects of phyto-oestrogens. Establishing diet-cancer relationships has proved difficult, in part because of the conflicting data from various studies of effects of soyabean-diets on cancer. Epidemiological evidence, though not impressive, does suggest that soyabean intake reduces breast cancer risk. The isoflavone genistein has a potent effect on breast cancer cells in vitro, and early exposure of animals to genistein has been effective in reducing later development of mammary cancer. Thus, continuous consumption of soyabean foods in early life and adulthood may help explain the low breast cancer mortality rates in Asian countries. Although the evidence for a protective effect against prostate cancer may be slightly more supportive, more research is needed before any firm conclusions can be made about the phyto-oestrogen-cancer linkages.

Anabolic agents and the bone morphogenetic protein pathway

A major unmet need in the medical field today is the availability of suitable treatments for the ever-increasing incidence of osteoporosis and the treatment of bone deficit conditions. Although therapies exist which prevent bone loss, the options are extremely limited for patients once a substantial loss of skeletal bone mass has occurred. Patients who have reduced bone mass are predisposed to fractures and further morbidity. The FDA recently approved PTH (1-34) (Teriparatide) for the treatment of postmenopausal osteoporosis after both preclinical animal and clinical human studies indicated it induces bone formation. This is the only approved bone anabolic agent available but unfortunately it has limited use, it is relatively expensive and difficult to administer. Consequently, the discovery of low cost orally available bone anabolic agents is critical for the future treatment of bone loss conditions. The intricate process of bone formation is co-ordinated by the action of many different bone growth factors, some stored in bone matrix and others released into the bone microenvironment from surrounding cells. Although all these factors play important roles, the bone morphogenetic proteins (BMPs) clearly play a central role in both bone cartilage formation and repair. Recent research into the regulation of the BMP pathway has led to the discovery of a number of small molecular weight compounds as candidate bone anabolic agents. These agents may usher in a new wave of more innovative and versatile treatments for osteoporosis as well as orthopedic and dental indications.

The effect of soy protein and soy isoflavones on calcium metabolism in postmenopausal women: a randomized crossover study

BACKGROUND

Evidence suggests that soy isoflavones act as estrogen agonists and have beneficial skeletal effects, but the effects on calcium metabolism in humans are not known.

OBJECTIVE

This study tested whether soybean isoflavones, soy protein, or both alter calcium metabolism in postmenopausal women.

DESIGN

Calcium metabolism in 15 postmenopausal women was studied by using metabolic balance and kinetic modeling in a randomized, crossover design of three 1-mo controlled dietary interventions: soy protein isolate enriched with isoflavones (soy-plus diet), soy protein isolate devoid of isoflavones (soy-minus diet), and a casein-whey protein isolate (control diet).

RESULTS

There was no significant difference between the diets in net acid excretion (P = 0.12). Urinary calcium excretion was significantly (P < 0.01) less with consumption of either of the soy diets (soy-plus diet: 85 +/- 34 mg/d; soy-minus diet: 80 +/- 34 mg/d) than with consumption of the control diet (121 +/- 63 mg/d), but fractional calcium absorption was unaffected by treatment. Endogenous fecal calcium was significantly (P < 0.01) greater with consumption of the soy-minus diet than with consumption of the other diets. Total fecal calcium excretion, bone deposition and resorption, and calcium retention were not significantly affected by the dietary regimens.

CONCLUSIONS

The lower urinary calcium seen with the consumption of an isolated soy protein than with that of an isolated milk protein was not associated with improved calcium retention. This finding reinforces the importance of evaluating all aspects of calcium metabolism. Soy isoflavones did not significantly affect calcium metabolism.

Quercetin suppresses bone resorption by inhibiting the differentiation and activation of osteoclasts

Although quercetin has suppressed bone resorption in several animal studies, its target cells and the mechanism of its action related to bone resorption has not been fully elucidated. We investigated the effect of quercetin on the differentiation and activation of osteoclasts. We used cocultures of mouse spleen cells and ST2 cells, and cultures of osteoclast progenitor cells [M-CSF-dependent (MD) cells from mouse bone marrow and murine monocytic RAW 264 (RAW) cells]. Quercetin dose-dependently inhibited osteoclast-like (OCL) cell formation at 2-5 microM concentration in both the coculture and MD cell culture. Quercetin inhibited the increase of tartrate-resistant acid phosphatase (TRAP) activity of mononuclear preosteoclasts (pOCs) induced by receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL) in both MD and RAW cell cultures. Quercetin reversely induced the disruption of actin rings in OCLs. Quercetin also suppressed both pit formation induced by osteoclasts on dentine slices and PTH-stimulated (45)Ca release in mouse long bone cultures. These results suggest that osteoclast progenitors as well as mature osteoclasts, are quercetin's target cells in relation to bone resorption, and that quercetin's suppressive effect on bone resorption results from both its inhibitory effect on the differentiation of osteoclast progenitor cells into pOCs and from its disruptive effect on actin rings in mature osteoclasts.

Prevention of osteopaenia by phyto-oestrogens: animal studies

Osteoporosis has become a major public health problem. Because the biggest culprit in the process of bone loss is oestrogen deficiency, hormone replacement therapy remains the mainstay for prevention, but prophylaxis by this means is limited. Phyto-oestrogens deserve special mention because emerging data support the suggestion that these weakly oestrogenic compounds, present in plants, may prevent bone loss associated with the menopause and thus represent a potential alternative therapy for a range of hormone-dependent conditions, including postmenopausal symptoms. A substantial body of work in animal models in the past few years has provided convincing data for significant improvements in bone mass and other endpoints following feeding with soya. Thus, phyto-oestrogens appear to have potential promise for maintaining or modestly improving bone mass of human subjects when consumed at optimal dosages. However, we must appreciate the limits of the information reached before extrapolating to man and we need to gather more data before health professionals can actively advocate the increased consumption of soya. Indeed, it will be important further to characterise the physiological effects of phyto-oestrogens and their margins of safety.

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

Soy intake and the maintenance of peak bone mass in Hong Kong Chinese women

Our previous study on bone health among premenopausal women showed that bone mass consolidation is attained by the early 30s, and small loss of spinal bone mineral density (SBMD) occurs soon after peak bone mass attainment. Recent interest has been shown in the potential beneficial effects of phytoestrogens on bone health. However, data are lacking, particularly in Asian women. This study aims to investigate the effect of soy isoflavones intake on the maintenance of peak bone mass in a cohort of 132 women aged 30-40 years who were followed up for 3 years. Baseline measurements of SBMD (L2-L4) were obtained using dual-energy X-ray densitometry, and dietary intake of soy foods and other key nutrients, including dietary calcium, were obtained through a quantitative food frequency method. Information on body measurements; physical activity (PA), weight-bearing activity in particular; age of menarche; and number of pregnancies were obtained at baseline. Repeated measurements of SBMD were obtained yearly for a further 3 years with an average follow-up time of 38 months. Analyses were performed on 116 subjects with at least three SBMD measurements (at baseline, 3-year follow-up, and at least one measurement during follow-up). The individual SBMD regression slope was computed for each of the subjects. Soy isoflavones consumption was categorized as quartiles of intake. We observed a significant difference in the SBMD individual regression slopes between women belonging to the fourth and first soy isoflavones intake quartiles. The positive effect of soy isoflavones on SBMD remained after adjusting for age and body size (height, weight, and bone area). Multiple linear regression analysis including the other known covariates (lean body mass, PA, energy adjusted calcium, and follow-up time) showed that soy isoflavones, together with these variables, accounted for 24% of the variances of the SBMD individual regression slope. This longitudinal study shows that soy intake had a significant effect on the maintenance of SBMD in women aged 30-40 years. The effects of phytoestrogens on bone health should be explored further in a population with habitual dietary soy but low calcium intake.

The effect of an ipriflavone-containing supplement on urinary N-linked telopeptide levels in postmenopausal women

Osteoporosis is a significant health concern to our aging population. We report here the results of a pilot placebo-controlled trial of a dietary supplement containing ipriflavone, calcium, and vitamin D on a urinary marker of bone breakdown in postmenopausal women. Seven postmenopausal women not currently receiving hormone replacement therapy received either an ipriflavone-containing supplement or placebo for 3 months. Urinary N-linked telopeptides, a marker of bone breakdown, declined by 29% in those receiving the supplement, whereas an increase in this marker was observed in the group receiving the placebo. No changes were observed in salivary hormone measurements. Although our sample size was small, to the best of our knowledge, this is the first report that demonstrates changes in N-linked telopeptide levels as a result of consuming an ipriflavone-containing product. Our findings confirm those of other researchers that demonstrate the usefulness of ipriflavone at slowing the progression of bone loss and suggest that measuring N-linked telopeptides may be a useful tool to assess therapeutic efficacy.