Down-regulation of osteoclast differentiation by daidzein via caspase 3

Unlocking daidzein's healing power: Present applications and future possibilities in phytomedicine

BACKGROUND

Cancer is one of the leading causes of death and a great threat to people around the world. Cancer treatment modalities include surgery, radiotherapy, chemotherapy, radiochemotherapy, hormone therapy, and immunotherapy. The best approach is to use a combination of several types. Among the treatment methods mentioned above, chemotherapy is frequently used, but its activity is hampered by the development of drug resistance and many side effects. In this regard, the use of medicinal plants has been discussed, and in recent decades, the use of isolated phytochemicals came into the focus of interest. By critically evaluating the available evidence and emphasizing the unique perspective offered by this review, we provide insights into the potential of daidzein as a promising therapeutic agent, as well as outline future research directions to optimize its efficacy in clinical settings.

PURPOSE

To summarized the therapeutic potential of daidzein, an isoflavone phytoestrogen in the management of several human diseases with the focuses on the current status and future prospects as a therapeutic agent.

METHODS

Several search engines, including PubMed, GoogleScholar, and ScienceDirect, were used, with the search terms "daidzein", "daidzein therapeutic potential", or individual effects. The study included all peer-reviewed articles. However, the most recent publications were given priority.

RESULTS

Daidzein showed protective effects against malignant diseases such as breast cancer, prostate cancer but also non-malignant diseases such as diabetes, osteoporosis, and cardiovascular diseases. Daidzein activates multiple signaling pathways leading to cell cycle arrest and apoptosis as well as antioxidant and anti-metastatic effects in malignant cells. Moreover, the anticancer effects against different cancer cells were more prominent and discussed in detail.

CONCLUSIONS

In short, daidzein represents a promising compound for drug development. The comprehensive potential anticancer activities of daidzein through various molecular mechanisms and its therapeutic/clinical status required further detail studies.

A Review of the Phytochemistry and Bioactivity of Clover Honeys (Trifolium spp.)

This review covers a comprehensive overview of the phytoconstituents and bioactivities reported to date for clover honeys produced from various Trifolium spp. against the backdrop of a more general discussion of the chemistry and bioactivity of these important agricultural species. While research into the phytochemical composition of various honeys and their associated bioactivities is growing, this review demonstrates that the literature to date has seen only a limited number of studies on clover honeys. Surprisingly, there appear to be no comparative data on the concentration of flavonoids in general or isoflavonoids specifically in different clover honeys, although the latter have been identified as a main group of bioactive compounds in red clover plants. Based on the findings of this review, the presence of phytoestrogenic isoflavonoids (e.g., formononetin, biochanin A, genistein, daidzein, glycitein) in clover plants and, by extension, in clover honeys should be further investigated, specifically of clover species outside the three popular perennial clovers (red, white and alsike clovers) to exploit new opportunities of potential benefit to both the pharmaceutical and apiculture industries.

Soy isoflavones alleviate periodontal destruction in ovariectomized rats

OBJECTIVE

The purpose of this study was to investigate whether soy isoflavone supplementation is effective in preventing periodontal destruction exacerbated by estrogen deficiency (ED) and its potential mechanism.

BACKGROUND

The progression of periodontitis is affected by host factors, such as smoking, diabetes mellitus, and steroid use. Bone loss in periodontitis can be aggravated by ED.

METHODS

A rat model of experimental periodontitis (EP) with ED was established by silk ligature and inoculation with Porphyromonas gingivalis, and some EP rats were subjected to bilateral ovariectomy (OVX). The treatment groups received an intravenous injection of 17-β-estradiol (E₂ B) or soy isoflavones (SI) by gavage. The rats were euthanized, and the maxillary jaws, gingiva, and serum were harvested. Tight junction protein and interleukin (IL)-17 expression, reactive oxygen species (ROS) level, and periodontal destruction were assessed. In addition, we determined whether grainyhead-like 2 (GRHL2) is required for enhancing the epithelial barrier by SI in an in vitro P. gingivalis infection model.

RESULTS

Estrogen deficiency impaired the expression of genes encoding tight junction proteins in the gingiva, increased IL-17 level, and accelerated alveolar bone resorption. SI treatment alleviated tight junction protein expression, decreased IL-17 and ROS levels, and prevented the absorption of alveolar bone. Furthermore, GRHL2 expression was significantly induced by SI in human oral keratinocytes-1 (HOK-1) cells; GRHL2 knockdown impaired the expression of OCLN and ZO-1 induced by SI treatment.

CONCLUSION

Soy isoflavones alleviates periodontitis in OVX rats, as observed by the increased expression of tight junction proteins, and reduced IL-17 level and alveolar bone loss. The in vitro studies suggested that the enhancement of oral epithelial barrier by SI treatment was partially dependent on GRHL2.

Analysis of the molecular mechanisms by flavonoids with potential use for osteoporosis prevention or therapy

BACKGROUND

Osteoporosis is the most common skeletal disorder worldwide. Flavonoids have the potential to alleviate bone alterations in osteoporotic patients with the advantage of being safer and less expensive than the conventional therapies.

OBJECTIVE

The main objective is to analyze the molecular mechanisms triggered in bone by different subclasses of flavonoids. In addition, this review provides an up-to-date overview on the cellular and molecular aspects of osteoporotic bones versus healthy bones, and a brief description of some epidemiological studies indicating that flavonoids could be useful for osteoporosis treatment.

METHODS

The PubMed database was searched in the range of years 2001- 2021 using the keywords osteoporosis, flavonoids, and their subclasses such as flavones, flavonols, flavanols, isoflavones, flavanones and anthocyanins, focusing the data on the molecular mechanisms triggered in bone.

RESULTS

Although flavonoids comprise many compounds that differ in structure, their effects on bone loss in postmenopausal women or in ovariectomized-induced osteoporotic animals are quite similar. Most of them increase bone mineral density and bone strength, which occur through enhancement of osteoblastogenesis and osteoclast apoptosis, decrease in osteoclastogenesis as well as increase in neovascularization on the site of the osteoporotic fracture.

CONCLUSION

Several molecules of signaling pathways are involved in the effect of flavonoids on osteoporotic bone. Whether all flavonoids have a common mechanism or they act as ligands of estrogen receptors remain to be established. More clinical trials are necessary to know better their safety, efficacy, delivery and bioavailability in humans, as well as comparative studies with conventional therapies.

Effect of pinocembrin isolated from Alpinia zerumbet on osteoblast differentiation

Bone mass is regulated by osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Osteoporosis is a bone metabolism disorder in which bone mass decreases due to increased bone resorption rather than bone formation. We focused on the traditional plant Alpinia zerumbet in Okinawa, Japan, and searched for promising compounds for the prevention and treatment of osteoporosis. Pinocembrin isolated from the leaves of A. zerumbet showed enhanced alkaline phosphatase (ALP) activity and mineralization and increased mRNA expression of osteoblast-related genes Alp and Osteocalcin (Ocn) in MC3T3-E1 cells. Pinocembrin increased the mRNA expression of Runx2 and Osterix, which are important transcription factors in osteoblast differentiation, and the mRNA expression of Dlx5 and Msx2, which are enhancers of these transcription factors. The bone morphogenetic protein (BMP) antagonist noggin, its receptor kinase inhibitor LDN-193189 and p38 MAPK inhibitor SB203580 attenuated pinocembrin-promoted ALP activity. Pinocembrin increased the mRNA of Bmp-2 and its target gene Id1. In addition, the estrogen receptor (ER) inhibitor ICI182780 suppressed pinocembrin-stimulated ALP activity. Pinocembrin may increase BMP-2 expression via ER. Then, the BMP-2 promotes osteoblast specific genes expression and mineralization through both Smad-dependent and independent pathway following Runx2 and Osterix induction. Our findings suggest that pinocembrin has bone anabolic effects and may be useful for the prevention and treatment of bone metabolic diseases such as osteoporosis.

Synthesis and biological activities of drugs for the treatment of osteoporosis

Osteoporosis is an asymptomatic progressive disease. With the improvement of people's living standard and the aging of population, osteoporosis and its fracture have become one of the main diseases threatening the aging society. The serious medical and social burden caused by this has aroused wide public concern. Osteoporosis is listed as one of the three major diseases of the elderly. At present, the drugs for osteoporosis include bone resorption inhibitors and bone formation promoters. The purpose of these anti-osteoporosis drugs is to balance osteoblast bone formation and osteoclast bone resorption. With the development of anti-osteoporosis drugs, new anti osteoporosis drugs have been designed and synthesized. There are many kinds of new compounds with anti osteoporosis activity, but most of them are concentrated on the original drugs with anti osteoporosis activity, or the natural products with anti-osteoporosis activity are extracted from the natural products for structural modification to obtain the corresponding derivatives or analogues. These target compounds showed good ALP activity in vitro and in vivo, promoted osteoblast differentiation and mineralization, or had anti TRAP activity, inhibited osteoclast absorption. This work attempts to systematically review the studies on the synthesis and bioactivity of anti-osteoporosis drugs in the past 10 years. The structure-activity relationship was discussed, which provided a reasonable idea for the design and development of new anti-osteoporosis drugs.

Betulin Suppresses Osteoclast Formation via Down-Regulating NFATc1

Osteoporosis is a disease characterized by osteoclast-mediated low bone mass. The modulation of osteoclasts is important for the prevention or therapeutic treatment of loss of bone mass. Osteoclasts, which are bone-resorbing multinucleated cells, are differentiated from the hematopoietic stem cell monocyte/macrophage lineage by Receptor activator of nuclear factor kappa-B ligand (RANKL) expressed from osteoblasts and stromal cells. RANKL signaling ultimately activates nuclear factor of activated T Cells 1 (NFATc1), which is a master transcription factor in osteoclastogenesis. Betulin, a lupine type pentacyclic triterpenoid, was isolated from the bark of Betula platyphylla. Betulin inhibited RANKL-mediated osteoclast differentiation by downregulating NFATc1. Betulin may serve as a useful structural scaffold in the therapeutic agent development to prevention/treatment the osteoclast-mediated bone disorder.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Inhibitory effect of a genistein derivative on pigmentation of guinea pig skin

This study demonstrated the mechanisms of the inhibitory effects of GD against UVB-induced pigmentation in guinea pig skin.

Daidzein increases OPG/RANKL ratio and suppresses IL-6 in MG-63 osteoblast cells

Daidzein is a major dietary source of isoflavones found in Leguminosae, and belongs to the family of diphenolic compounds. The estrogenic effects of daidzein to prompt bone formation and prevent bone resorption have been observed in animal models and cultured cells. In our study, we studied the effects of daidzein, raloxifene and E₂ on expression of the osteoblast-produced bone regulatory factors OPG, RANKL and IL-6 in human osteoblastic MG-63 cells. Results suggest that treatment with daidzein, raloxifene and E₂ increased the levels of OPG and decreased those of RANKL and IL-6. The effects of daidzein on OPG and RANKL expression are mediated by both ERα and ERβ but those on IL-6 production primarily by ERα. Moreover, daidzein may promote activation of the classic estrogen response element (ERE) pathway through increasing ERα, ERβ and steroid hormone receptor coactivator (SRC)-1 expression. E₂ was also able to enhance transcription derived from the ERE, while raloxifene has no effect on it. Raloxifene increased ERα protein and gene expression levels but had no effect on ERβ protein and gene expression at 0.1μM. E₂ was found significantly increased the protein and mRNA levels of SRC-1, while raloxifene has no effect on it compared with control. This ability of daidzein to affect osteoblastic cells makes it a good candidate for the treatment of bone loss in postmenopausal women.

Effects of Scytosiphon lomentaria on osteoblastic proliferation and differentiation of MC3T3-E1 cells

BACKGROUND/OBJECTIVES

Bone formation and bone resorption continuously occur in bone tissue to prevent the accumulation of old bone, this being called bone remodeling. Osteoblasts especially play a crucial role in bone formation through the differentiation and proliferation. Therefore, in this study, we investigated the effects of Scytosiphon lomentaria extract (SLE) on osteoblastic proliferation and differentiation in MC3T3-E1 cells.

MATERIALS/METHODS

A cell proliferation assay, alkaline phosphatase (ALP) activity assay, alizarin red staining and protein expression analysis of osteoblastic genes were carried out to assess the osteoblastic proliferation and differentiation.

RESULTS

The results indicated that treatment of SLE promoted the proliferation of MC3T3-E1 cells and improved ALP activity. And, SLE treatment significantly promoted mineralized nodule formation compared with control. In addition, cells treated with SLE significantly upregulated protein expression of ALP, type 1 collagen, bone morphogenetic protein 2, runt-related transcription factor 2, osterix, and osteoprotegerin.

CONCLUSIONS

The results demonstrate that SLE promote differentiation inducement and proliferation of osteoblasts and, therefore may help to elucidate the transcriptional mechanism of bone formation and possibly lead to the development of bone-forming drugs.

Pomegranate Peel Extract Prevents Bone Loss in a Preclinical Model of Osteoporosis and Stimulates Osteoblastic Differentiation in Vitro

The nutritional benefits of pomegranate have attracted great scientific interest. The pomegranate, including the pomegranate peel, has been used worldwide for many years as a fruit with medicinal activity, mostly antioxidant properties. Among chronic diseases, osteoporosis, which is associated with bone remodelling impairment leading to progressive bone loss, could eventually benefit from antioxidant compounds because of the involvement of oxidative stress in the pathogenesis of osteopenia. In this study, with in vivo and ex vivo experiments, we investigated whether the consumption of pomegranate peel extract (PGPE) could limit the process of osteopenia. We demonstrated that in ovariectomized (OVX) C57BL/6J mice, PGPE consumption was able to significantly prevent the decrease in bone mineral density (-31.9%; p < 0.001 vs. OVX mice) and bone microarchitecture impairment. Moreover, the exposure of RAW264.7 cells to serum harvested from mice that had been given a PGPE-enriched diet elicited reduced osteoclast differentiation and bone resorption, as shown by the inhibition of the major osteoclast markers. In addition, PGPE appeared to substantially stimulate osteoblastic MC3T3-E1 alkaline phosphatase (ALP) activity at day 7, mineralization at day 21 and the transcription level of osteogenic markers. PGPE may be effective in preventing the bone loss associated with ovariectomy in mice, and offers a promising alternative for the nutritional management of this disease.

Combined Effects of Soy Isoflavones and β-Carotene on Osteoblast Differentiation

Soy isoflavones, genistein, daidzein and its metabolite equol, as well as β-carotene have been reported to be effective for maintaining bone health. However, it remains to be elucidated whether combining soy isoflavones with β-carotene is beneficial to bone formation. This study investigated the combined effect of soy isoflavones and β-carotene on the differentiation of MC3T3-E1 preosteoblastic cells. Daidzein and genistein alone did not affect cell growth but increased alkaline phosphatase (ALP) activity. Beta-carotene alone inhibited cell growth and markedly enhanced ALP activity. Soy isoflavones combined with β-carotene resulted in higher ALP activity than treatment with isoflavones or β-carotene alone. We observed significant main effects of β-carotene on the enhanced expression of Runx2, ALP, and ostepontin mRNA, whereas there was a significant main effect of soy isoflavones on the expression of osterix mRNA. To investigate how β-carotene affected osteoblast differentiation, MC3T3-E1 cells were treated with retinoic acid receptor (RAR) pan-antagonist combined with β-carotene. Osteopontin and ALP mRNA expression levels, which were increased following treatment with β-carotene, were significantly suppressed by the RAR pan-antagonist. This suggests treatment with β-carotene enhanced early osteoblastic differentiation, at least in part via RAR signaling. These results indicate that a combination of isoflavones and β-carotene may be useful for maintaining a positive balance of bone turnover by inducing osteoblast differentiation.

Novel inhibitors of RANKL-induced osteoclastogenesis: Design, synthesis, and biological evaluation of 6-(2,4-difluorophenyl)-3-phenyl-2H-benzo[e][1,3]oxazine-2,4(3H)-diones

A series of novel 6-(2,4-difluorophenyl)-3-phenyl-2H-benzo[e][1,3]oxazine-2,4(3H)-dione derivatives were synthesized and evaluated for their inhibitory effects on osteoclast activities by using TRAP-staining assay. Among the tested compounds, 3d and 3h exhibited more potent osteoclast-inhibitory activities than the lead compound NDMC503 (a ring-fused structure of NDMC101), as reported in our previous study. Both 3d and 3h exhibited two-fold increase in activity compared to NDMC503. In addition, our biological results indicated that 3d and 3h could suppress RANKL-induced osteoclastogenesis-related marker genes, such as NFATc1, c-fos, TRAP, and cathepsin K. Notably, 3d could significantly attenuate the bone-resorbing activity of osteoclasts in the pit formation assay. Thus, this study might provide a new class of lead structures that warrant further development as potential anti-resorptive agents.

Daidzein pretreatment improves survival in mouse model of sepsis

BACKGROUND

The aim of the present study was to assess the effect of seven days daidzein pretreatment in cecal ligation and puncture (CLP) model of sepsis.

METHODS

We assessed the survival benefit of daidzein and its effect on lung injury in CLP-induced sepsis in mice and determined the bacterial load in peritoneal fluid, blood, and lung homogenates. Tumor necrosis factor α (TNF-α) and corticosterone levels were measured by enzyme-linked immunosorbent assay; relative mRNA expression was estimated by real-time polymerase chain reaction, and standard biochemical techniques were used to measure nitrite level, myeloperoxidase activity, and vascular permeability.

RESULTS

Daidzein pretreatment for seven days at a dose of 1 mg/kg body weight subcutaneously increased the survival time of septic mice. Daidzein decreased the bacterial load in peritoneal fluid, blood, and lungs, reduced the tumor necrosis factor α and nitrite level in plasma, and partially suppressed lung injury by reducing vascular permeability and myeloperoxidase activity in septic mice. Further, it restored the relative mRNA expressions of inducible nitric oxide synthase, glucocorticoid receptor α, and glucocorticoid receptor β genes in septic lungs were restored by daidzein pretreatment.

CONCLUSIONS

Daidzein pretreatment for 7 d in sepsis increased the survival time in mice, which may be relate to decrease in bacterial load, anti-inflammatory effect, and protection from lung injury.

Novel daidzein analogs enhance osteogenic activity of bone marrow-derived mesenchymal stem cells and adipose-derived stromal/stem cells through estrogen receptor dependent and independent mechanisms

INTRODUCTION

Osteoporosis is a disease characterized by low bone mineral density (BMD) and increased risk of fractures. Studies have demonstrated the use of phytoestrogens, or plant-derived estrogens, such as genistein and daidzein, to effectively increase osteogenic activity of bone marrow-derived mesenchymal stem cells (BMSCs). Herein, the effects of daidzein analogs on the osteogenic differentiation efficiency of human BMSC and adipose-derived stromal/stem cells (ASC) were explored.

METHODS

BMSCs and ASCs underwent osteogenic differentiation in the presence of vehicle, 17β-estradiol (E2), phytoestrogens, or daidzein analogs. Cells were stained for alkaline phosphatase (ALP) enzymatic activity, calcium deposition by alizarin red s, and phosphate mineralization by silver nitrate. Gene expression analysis was conducted on cells treated with daidzein analogs.

RESULTS

Cells treated with E2, daidzein, or genistein increased calcium deposition by 1.6-, 1.5-, and 1.4-fold, respectively, relative to vehicle-treated BMSCs and 1.6-, 1.7-, and 1.4-fold relative to vehicle-treated ASCs, respectively. BMSCs treated with daidzein analog 2c, 2g, and 2l demonstrated a 1.6-, 1.6-, and 1.9-fold increase in calcium deposition relative to vehicle-treated BMSCs, respectively, while ASCs treated with daidzein analog 2c, 2g, or 2l demonstrated a 1.7-, 2.0-, and 2.2-fold increase in calcium deposition relative to vehicle-treated ASCs, respectively. Additional analysis with BMSCs and ASCs was conducted in the more efficient compounds: 2g and 2l. ALP activity and phosphate mineralization was increased in 2g- and 2l-treated cells. The analysis of lineage specific gene expression demonstrated increased expression of key osteogenic genes (RUNX2, c-FOS, SPARC, DLX5, SPP1, COL1A1, IGF1, SOST, and DMP1) and earlier induction of these lineage specific genes, following treatment with 2g or 2l, relative to vehicle-treated cells. Estrogen receptor (ER) inhibitor studies demonstrated that ER antagonist fulvestrant inhibited the osteogenic differentiation of 2g in BMSCs and ASCs, while fulvestrant only attenuated the effects of 2l, suggesting that 2l acts by both ER dependent and independent pathways.

CONCLUSIONS

These studies provide support for exploring the therapeutic efficacy of daidzein derivatives for the treatment of osteoporosis. Furthermore, the patterns of gene induction differed following treatment with each daidzein analog, suggesting that these daidzein analogs activate distinct ER and non-ER pathways to induce differentiation in BMSCs and ASCs.

Positive skeletal effects of cladrin, a naturally occurring dimethoxydaidzein, in osteopenic rats that were maintained after treatment discontinuation

Effects of cladrin treatment and withdrawal in osteopenic rats were studied. Cladrin improved trabecular microarchitecture, increased lumbar vertebral compressive strength, augmented coupled remodeling, and increased bone osteogenic genes. A significant skeletal gain was maintained 4 weeks after cladrin withdrawal. Findings suggest that cladrin has significant positive skeletal effects.

INTRODUCTION

We showed that a standardized extract of Butea monosperma preserved trabecular bone mass in ovariectomized (OVx) rats. Cladrin, the most abundant bioactive compound of the extract, promoted peak bone mass achievement in growing rats by stimulating osteoblast function. Here, we studied the effects of cladrin treatment and withdrawal on the osteopenic bones.

METHODS

Adult female Sprague-Dawley rats were OVx and left untreated for 12 weeks to allow for significant estrogen deficiency-induced bone loss, at which point cladrin (1 and 10 mg/kg/day) was administered orally for another 12 weeks. Half of the rats were killed at the end of the treatments and the other half at 4 weeks after treatment withdrawal. Sham-operated rats and OVx rats treated with PTH or 17β-estradiol (E2) served as various controls. Efficacy was evaluated by bone microarchitecture using microcomputed tomographic analysis and fluorescent labeling of bone. qPCR and western blotting measured mRNA and protein levels in bone and uterus. Specific ELISA was used for measuring levels of serum PINP and urinary CTx.

RESULTS

In osteopenic rats, cladrin treatment dose dependently improved trabecular microarchitecture, increased lumbar vertebral compression strength, bone formation rate (BFR), cortical thickness (Cs.Th), serum PINP levels, and expression of osteogenic genes in bones; and reduced expression of bone osteoclastogenic genes and urinary CTx levels. Cladrin had no uterine estrogenicity. Cladrin at 10 mg/kg maintained acquired skeletal gains 4 weeks after withdrawal.

CONCLUSION

Cladrin had positive skeletal effects in osteopenic rats that were maintained after treatment withdrawal.

Antiresorptive activity of bacillus-fermented antler extracts: inhibition of osteoclast differentiation

Antlers have been traditionally used for thousands of years as a natural product with medicinal and pharmaceutical properties. In developing healthy foods, Bacillus-mediated fermentation is widely used to enhance the biological activity of nutrients in foods. Recently, fermentation was shown to enhance the osteogenic activity of antlers. This study aimed to elucidate the antiresorptive activity of Bacillus-fermented antler and its mode of action. We found that Bacillus-fermented antler extract strongly inhibited osteoclast differentiation by downregulating the expression and activity of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1). This extract also inhibited the activation of phospholipase C γ 2 (PLC γ 2), a signaling molecule that could regulate NFATc1 transcriptional activity. This suggested that Bacillus-fermented antler extract could inhibit PLC γ 2-NFATc1 signaling required for bone resorption and cell fusion. Consequently, Bacillus-fermented antler extract might benefit osteoclast-related disorders, including osteoporosis; furthermore, it may improve gastrointestinal activity.

Vitamin D interactions with soy isoflavones on bone after menopause: a review

Vitamin D is known to increase Ca absorption in adults. However, the threshold vitamin D status to benefit Ca absorption is lower than the target vitamin D status for higher bone mineral density and lower fracture risk, pointing to another pathway for vitamin D to benefit bone. One possibility is by affecting osteoblast and osteoclasts directly. Vitamin D-related bone metabolism may also be affected by soy isoflavones, which selectively bind to the estrogen receptor β and may reduce bone loss in postmenopausal women. We discuss a possible synergistic effect of soy isoflavones and vitamin D on bone by affecting osteoblast and osteoclast formation and activity in postmenopausal women.

Effects of different doses of ferutinin on bone formation/resorption in ovariectomized rats

This study analyzes the effects of different doses of ferutinin on bone loss caused by estrogen deficiency in ovariectomized rats, in comparison with estradiol benzoate. Thirty female Sprague-Dawley rats were ovariectomized and treated for 30 days from the day after ovariectomy. Static/dynamic histomorphometric analyses were performed on trabecular and cortical bone of lumbar vertebrae and femurs. Very low weight increments were recorded only in all F-OVX groups, with respect to the others. Although the great differences in weight, that could imply a decrease of bone mass in F-OVX groups compared to the control ovariectomized group (C-OVX), trabecular bone in lumbar vertebrae did not show significant differences, suggesting that ferutinin, opposing estrogen deficiency, inhibits bone resorption. Newly formed cortical bone was always low in all F-OVX groups and high in C-OVX, suggesting that it is mainly devoted in answering mechanical demands. In contrast, in distal femoral metaphyses, trabecular bone was reduced and the number of osteoclasts was increased in C-OVX with respect to all other groups, suggesting that it is mainly devoted in answering metabolic demands; moreover, ferutinin dose of 2 mg/kg seemed to be more effective than the lower doses used and estrogens, particularly in those skeletal regions with higher metabolic activity. Our results suggest that the role of ferutinin in preventing osteoporosis caused by estrogen deficiency is expressed in decreasing bone erosion; moreover, in all F-OVX groups bone turnover is very low and seems correlated to the trivial body weight increase, which, in turn, depends on ferutinin treatment.

Antioxidant profile of Trifolium pratense L

In order to examine the antioxidant properties of five different extracts of Trifolium pratense L. (Leguminosae) leaves, various assays which measure free radical scavenging ability were carried out: 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, superoxide anion and nitric oxide radical scavenger capacity tests and lipid peroxidation assay. In all of the tests, only the H2O and (to some extent) the EtOAc extracts showed a potent antioxidant effect compared with BHT and BHA, well-known synthetic antioxidants. In addition, in vivo experiments were conducted with antioxidant systems (activities of GSHPx, GSHR, Px, CAT, XOD, GSH content and intensity of LPx) in liver homogenate and blood of mice after their treatment with extracts of T. pratense leaves, or in combination with CCl4. Besides, in the extracts examined the total phenolic and flavonoid amounts were also determined, together with presence of the selected flavonoids: quercetin, luteolin, apigenin, naringenin and kaempferol, which were studied using a HPLC-DAD technique. HPLC-DAD analysis showed a noticeable content of natural products according to which the examined Trifolium pratense species could well be regarded as a promising new source of bioactive natural compounds, which can be used both as a food supplement and a remedy.

Fisetin Inhibits Osteoclast Differentiation via Downregulation of p38 and c-Fos-NFATc1 Signaling Pathways

The prevention or therapeutic treatment of loss of bone mass is an important means of improving the quality of life for patients with disorders related to osteoclast-mediated bone loss. Fisetin, a flavonoid dietary ingredient found in the smoke tree (Continus coggygria), exhibits various biological activities, but its effect on osteoclast differentiation is unknown. In this study, fisetin dose-dependently inhibited the RANKL-induced osteoclast differentiation with downregulation of the activity or expression of p38, c-Fos, and NFATc1 signaling molecules. The p38/c-Fos/NFATc1-regulated expression of genes required for cell fusion and bone resorption, such as DC-STAMP and cathepsin K, was also inhibited by fisetin. Considering the rescue of fisetin's inhibitory action by NFATc1 over-expression, the cascade of p38-c-Fos-NFATc1 could be strongly involved in the inhibitory effect of fisetin on osteoclast differentiation. Furthermore, fisetin inhibited the bone-resorbing activity of mature osteoclasts. In conclusion, fisetin may be of use in the treatment of osteoclast-related disorders, including osteoporosis.

Daidzein administration positively affects thyroid C cells and bone structure in orchidectomized middle-aged rats

SUMMARY

Thyroid C cells hormone, calcitonine, inhibits bone resorption. We have demonstrated that daidzein treatment of orchidectomized rats (model for osteoporosis) stimulated C cells and increased trabecular bone mass. These results suggest that, besides direct action, daidzein may also affect bone structure indirectly through enhancement of thyroid C cell activity.

INTRODUCTION

Thyroid C cells produce calcitonin (CT) which acts as an inhibitor of bone resorption. In this study, the influence of daidzein treatment on thyroid C cells, bone structure, and bone function in orchidectomized (Orx) middle-aged rats was investigated.

METHODS

Sixteen-month-old Wistar rats were divided into Orx and sham-operated (SO) groups. Half the Orx rats were given subcutaneous injections of daidzein (30 mg/kg b.w./day) for 3 weeks. CT-immunopositive thyroid C cells were morphometrically analyzed. The metaphyseal region of the proximal tibia was measured histomorphometrically, and cancellous bone area (B.Ar), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were calculated. Serum samples were analyzed for CT and osteocalcin (OC), calcium (Ca) and phosphorus concentrations, and urine samples for Ca levels.

RESULTS

Treatment of Orx animals with daidzein significantly increased volume of C cells compared to the Orx rats. Daidzein also enhanced B.Ar, Tb.Th, and Tb.N and reduced Tb.Sp. The serum OC and urinary Ca concentrations decreased significantly in comparison with the Orx group.

CONCLUSIONS

These findings indicate that daidzein treatment stimulates thyroid C cells, increase trabecular bone mass, and decrease bone turnover in Orx middle-aged rats, which is the model of male osteoporosis.

Medicarpin inhibits osteoclastogenesis and has nonestrogenic bone conserving effect in ovariectomized mice

Medicarpin, a pterocarpan class of naturally occurring benzopyran furanobenzene compound was synthesized in gram scale to investigate its effects on murine bone cells and in ovariectomized (OVx) mice. Medicarpin, at as low as 10(-10)M suppressed osteoclastogenesis in bone marrow cells (BMCs). Medicarpin-induced apoptosis of mature osteoclasts isolated from long bones. Effects of medicarpin in osteoclasts appear to be independent of estrogen receptor (ER) activation as ICI 180,782 failed to abrogate its effects on osteoclasts. In calvarial osteoblasts, medicarpin (10(-10)M) blocked nuclear factor kappaB (NF-kappaB) signaling assessed by tumor necrosis factor alpha (TNFalpha)-stimulated nuclear translocation of p65 subunit of NF-kappaB. Medicarpin also inhibited the expression of TNFalpha in mouse calvarial osteoblasts. This effect was ER dependent as ICI 180,782 reversed the suppressive effect of medicarpin on TNFalpha mRNA levels in osteoblasts. In addition, like 17beta-estradiol, presence of medicarpin inhibited TNFalpha-induced upregulation of interleukin-1, and -6 mRNA levels in osteoblasts. In co-cultures consisting of calvarial osteoblasts and BMCs, presence of medicarpin increased osteoprotegerin (OPG)/receptor activator of NF-kappaB ligand (RANKL) ratio and reduced mRNA levels of osteoclast markers including tartrate-resistant acid phosphatase and RANK. OVx mice administered medicarpin (10.0mgkg(-1)day(-1)) orally for 30days had reduced formation of osteoclasts but increased formation of osteoprogenitor cells in BMCs compared with OVx+vehicle group. Medicarpin treatment to OVx mice maintained parameters of trabecular microarchitecure. Medicarpin exhibited no uterine estrogenicity. Our findings point towards direct and indirect inhibitory effects of medicarpin on osteoclastogenesis in vitro that contribute to its bone sparing effect in OVx mice.

Absorption of calcium from milk and tempeh consumed by postmenopausal Malay women using the dual stable isotope technique

Assessment of calcium bioavailability from non-dairy foods containing moderate amounts of calcium is especially important in populations that have habitually low dairy consumption. Absorption of calcium from milk and tempeh (a traditional fermented soy product) was compared in a sample of Malay subjects. A randomized, crossover design was utilized to assess calcium absorption in 20 postmenopausal women from either a glass of milk (114 g) or from a meal of tempeh (206 g); each containing 130 mg calcium. At each study of Phase 1 (mid-July) and Phase 2 (mid-August), intravenous (42)Ca and oral (44)Ca were administered and calcium absorption was measured in 24-h urine collections post-dosing; with a 1-month washout period between phases. Absorption of calcium from tempeh did not differ significantly from milk (36.9 +/- 10.6% vs. 34.3 +/- 8.6%, respectively). Due to differences in the calcium content of tempeh, four servings of this product would be needed to get the same amount of absorbed calcium as that obtained from a 4-ounce glass of milk. Tempeh may provide readily available calcium for this population of women at risk for low bone mass.

Saurolactam inhibits osteoclast differentiation and stimulates apoptosis of mature osteoclasts

The receptor activator of nuclear factor-kappaB ligand (RANKL) plays a critical role in the differentiation and bone resorptive activity of osteoclasts. Recently, the development of anti-resorptive agents from natural substances has become a subject of interest. Therefore, we evaluated the effects of 222 natural compounds on the RANKL-induced tartrate-resistance acid phosphatase (TRAP; a marker for osteoclast differentiation) activity and multinucleated osteoclast formation in RAW264.7 murine macrophage cells. We found that saurolactam was one of the compounds inhibiting the RANKL-induced osteoclastogenesis; it significantly inhibited the RANKL-induced TRAP activity and formation of multinucleated osteoclasts without any cytotoxicity. Interestingly, saurolactam prevented RANKL-induced activation of MAP kinases and NF-kappaB, and mRNA expression of osteoclast-related genes and transcription factors (c-Fos, Fra-2, and NFATc1). We also observed the inhibitory effect of saurolactam on the differentiation of mouse bone marrow-derived macrophages into osteoclasts. Furthermore, saurolactam inhibited the bone resorptive activity of mature osteoclasts with the induction of apoptotic signaling cascade and the inhibition of survival signaling pathways such as c-Src/PI3K/Akt, Ras/ERK, and JNK/c-Jun. In conclusion, although further studies are needed to determine the precise mechanism and biological efficacy of saurolactam in osteoclast-mediated bone disorders, our results demonstrate that saurolactam potentially inhibits osteoclast differentiation by preventing the activation of MAP kinases and transcription factors that consequently affect the regulation of genes required for osteoclastogenesis, and the bone resorptive activity of mature osteoclasts by inhibiting osteoclast survival-related signaling pathways and triggering the apoptotic signaling cascade.

Apigenin Induces Apoptosis through a Mitochondria/Caspase-Pathway in Human Breast Cancer MDA-MB-453 Cells

In this study, we investigated the mechanistic role of the caspase cascade in extrinsic and intrinsic apoptosis induced by apigenin, which has been targeted as a candidate in the development of noncytotoxic anticancer medicines. Treatment with apigenin (1–100 µM) significantly inhibited the proliferation of MDA-MB-453 human breast cancer cells in a dose- and time-dependent manner with IC₅₀ values of 59.44 and 35.15 µM at 24 and 72 h, respectively. This inhibition resulted in the induction of apoptosis and the release of cytochrome c in cells exposed to apigenin at its 72 h IC₅₀. Subsequently, caspase-9, which acts in mitochondria-mediated apoptosis, was cleaved by apigenin. In addition, apigenin activated caspase-3, which functions downstream of caspase-9. The apigenin-induced activation of caspase-3 was accompanied by the cleavage of capases-6, -7, and -8. These results are supported by evidence showing that the activity patterns of caspases-3, -8, and -9 were similar. The present study supports the hypothesis that apigenin-induced apoptosis involves the activation of both the intrinsic and extrinsic apoptotic pathways.

Trifolium L.--a review on its phytochemical and pharmacological profile

Plants from the genus Trifolium have been used in traditional medicine by many cultures. In Turkish folk medicine, for example, some Trifolium species are used for their expectorant, analgesic, antiseptic properties and also to treat rheumatic aches. Some species are also grown as pasture crops for animals in the Mediterranean. The high quercetin concentration and soyasaponin occurrence make the seeds of some Trifolium species a potential source of health beneficial phytochemicals for use in human nutrition. However, Trifolium pratense has also gained popularity due to research into its use for the treatment for menopausal symptoms. This paper provides an overview of the phytochemical and pharmacological profile of Trifolium species.

Equol induces apoptosis through cytochrome c-mediated caspases cascade in human breast cancer MDA-MB-453 cells

This study investigated the role of the caspase activation cascade in extrinsic and intrinsic apoptosis induced by equol in human breast cancer MDA-MB cells. First, the antiproliferative effect of equol was determined in cells treated with 1-100 microM equol for 24, 48, and 72h. Equol significantly inhibited cell proliferation in a dose-dependent manner (p<0.05). Exposure to 50 or 100 microM equol for 72h strongly promoted apoptosis. Under the same conditions, remarkable cytochrome c release was observed. Subsequently, caspase-9, which acts in mitochondria-mediated apoptosis, was cleaved by equol at high concentrations, but caspase-8 activation of receptor-mediated apoptosis was not observed. At both equol concentrations, the caspase-8 and -9 activity assays showed similar patterns. In addition, equol treatment activated caspase-3, which is downstream from caspase-9, and this was accompanied by the cleavage of capase-6 and -7. Activation of these caspases leads to increased activation of PARP, lamin, and ICAD. This study suggests that equol induces the intrinsic pathway of apoptosis via caspase-9 and cytochrome c, independent of caspase-8, in human breast cancer MDA-MB-453 cells.

Daidzein causes cell cycle arrest at the G1 and G2/M phases in human breast cancer MCF-7 and MDA-MB-453 cells

We examined the mechanisms by which daidzein inhibits the growth of breast cancer cells. First, we investigated its antiproliferative effects in MCF-7 and MDA-MB-453 cells exposed to 1-100 microM daidzein for 24, 48, or 72 h. Daidzein significantly inhibited cell proliferation in a dose- and time-dependent manner (p<0.05) and resulted in significant cell cycle arrest in the G1 and G2/M phases after 72 h of treatment at concentrations over 5 and 10 microM in MCF-7 and MDA-MB-453 cells, respectively (p<0.05). In addition, daidzein caused the accumulation of cells in sub-G0 phase in a dose-dependent manner in MDA-MB-453 (p<0.05), but not MCF-7, cells. As another biomarker of apoptosis induction, caspase-9 activity was significantly increased by daidzein in both cells. To investigate the effects of daidzein on the proteins regulating cell cycle arrest, cells were treated with 100 microM daidzein for 72 h. Similar changes in the expression of regulatory proteins were detected in both cells. Daidzein treatment resulted in decreases in cyclin D, CDK2, and CDK4, whereas the expression of CDK6 and cyclin E was unchanged. The protein expression of CDK1 related to the G2/M phase decreased markedly with daidzein treatment, whereas slight expression of cyclins A and B occurred. Daidzein treatment increased the expression of the CDK inhibitors p21(Cip1) and p57(Kip2), but not that of p27(Kip1). Thus, daidzein exerts its anticancer effects in human breast cancer cells via cell cycle arrest at the G1 and G2/M phases.

Baicalein inhibits osteoclast differentiation and induces mature osteoclast apoptosis

In bone remodeling, an imbalance caused by increased bone resorption over bone formation leads to adult skeletal diseases such as osteoporosis. Therefore, the development of anti-resorptive agents has still gained more interest. In this study, using cell-based assay systems in RAW264.7 murine macrophage cells, we found that baicalein significantly inhibited the receptor activator of NF-kappaB ligand (RANKL)-induced tartrate-resistance acid phosphatase (TRAP) activity and the formation of multinucleated osteoclasts in a dose-dependent manner. Interestingly, baicalein inhibited RANKL-induced activation of signaling molecules (Akt, ERK/MAP kinase and NF-kappaB) and mRNA expression of osteoclast-associated genes (TRAP, matrix metalloproteinase 9 and c-Src) and another transcription factors (c-Fos, Fra-2 and NFATc1). In addition, baicalein inhibited the bone resorptive activity of mature osteoclasts by inducing apoptosis. The inhibitory effects of baicalein on the formation of mouse bone marrow macrophage-derived osteoclasts and their bone resorptive activity were also observed. In conclusion, although further studies are needed to determine its biological efficacy and precise mechanism in bone, the present results demonstrated that baicalein has a potential to inhibit osteoclast differentiation and induce mature osteoclast apoptosis.

Soy phytoestrogens: impact on postmenopausal bone loss and mechanisms of action

Due to their ability to mimic the actions of mammalian estrogens, soy phytoestrogens have been proposed as potential therapeutic agents to aid in preventing postmenopausal bone loss. In vitro, phytoestrogens promote osteoblastogenesis and inhibit osteoclastogenesis. Although a relatively large number of intervention studies have been undertaken in animals and humans, the efficacy of phytoestrogens as bone-protective agents in vivo remains unclear. Differences in the bioactivities of individual phytoestrogens, differences in phytoestrogen metabolism and bioavailability within different study populations, and imprecise reporting of the dose of phytoestrogens administered in intervention studies may have contributed to the disparity in study findings.

Dietary isoflavones act on bone marrow osteoprogenitor cells and stimulate ovary development before influencing bone mass in pre-pubertal piglets

Food containing soybeans provide isoflavone phytoestrogens that can preserve bone mass in postmenopausal women, and prevent bone loss in ovariectomized rats. But their effects on bone remain unclear, particularly on bone formation during growth. Two groups of eight pre-pubertal piglets were fed a basal or an isoflavone-enriched (S800) diet for 6 weeks. The S800 diet contained 800 mg SoyLifetrade mark/kg, providing 2.8 mg isoflavones/kg body weight/day. Several bones were collected and tested for bone strength and density. Bone marrow was collected from humeri together with blood samples and genital tracts. The plasma concentrations of isoflavones were increased in the pigs fed S800, but growth rate, body weight, plasma bone markers, bone mineral density, and strength were all unaffected. In contrast, cultured stromal cells from S800 pigs had more alkaline phosphatase-rich cells and mineralized nodules, secreted more osteocalcin, osteoprotegerin and RANK-L, synthesized more osteoprotegerin, and RANK-L. Cultured mononucleated nonadherent bone marrow cells from S800 pigs developed fewer tartrate-resistant acid phosphatase mononucleated cells (osteoclast progenitors) when cultured with 1,25(OH)(2)D(3), and resorbed a smaller area of dentine slices. Freshly isolated bone marrow osteoclast progenitors from S800 pigs had more caspase-3 cleavage activity, and synthesized less RANK. Both osteoclast and osteoblast progenitors had ERalpha and ERbeta, whose syntheses were stimulated by the S800 diet. The S800 piglets had heavier ovaries with more follicles, but their uterus weight was unaffected. We conclude that dietary isoflavones have no detectable effect on the bone mass of growing female piglets, but act on bone marrow osteoprogenitors via ERs--mainly ERbeta, and stimulate ovary development.

Enhancing Effect of Daidzein on the Differentiation and Mineralization in Mouse Osteoblast-like MC3T3-E1 Cells

The effect of daidzein, an important isoflavone, on the differentiation and mineralization in MC3T3-E1 cells, a mouse calvaria osteoblast-like cell line, was investigated. The MTT assay, the alizarin red S and von Kossa staining, the measurement of calcium (Ca) and phosphorus (P) concentrations by inductively coupled plasma-atomic emission spectrometry and the nitrophenol liberation method were used to determine the cell proliferation, mineralization and intracellular alkaline phosphatase (ALP) activity, respectively. Daidzein enhanced the cell proliferation after the culture for 2 days and the effect reached maximum on day 6. ALP activity and cellular Ca and P contents were increased time- and dose-dependently when the cells were treated with daidzein in the presence of disodium beta-glycerophosphate and L-ascorbic acid. Differentiation of the cells to the mature osteoblasts was prompted under incubation in the presence of daidzein for 21 days, by the time the mineralized nodules formed. The calcium depositions of the cells by alizarin red S staining were increased significantly after the culture with daidzein as long as 28 days. It has been demonstrated that daidzein may be able to enhance the bone differentiation and mineralization and prompt the bone formation in the early growing stage and the late growing stage of osteoblasts.

Dietary polyphenols and the prevention of diseases

Polyphenols are the most abundant antioxidants in the diet and are widespread constituents of fruits, vegetables, cereals, dry legumes, chocolate, and beverages, such as tea, coffee, or wine. Experimental studies on animals or cultured human cell lines support a role of polyphenols in the prevention of cardiovascular diseases, cancers, neurodegenerative diseases, diabetes, or osteoporosis. However, it is very difficult to predict from these results the effects of polyphenol intake on disease prevention in humans. One of the reasons is that these studies have often been conducted at doses or concentrations far beyond those documented in humans. The few clinical studies on biomarkers of oxidative stress, cardiovascular disease risk factors, and tumor or bone resorption biomarkers have often led to contradictory results. Epidemiological studies have repeatedly shown an inverse association between the risk of myocardial infarction and the consumption of tea and wine or the intake level of some particular flavonoids, but no clear associations have been found between cancer risk and polyphenol consumption. More human studies are needed to provide clear evidence of their health protective effects and to better evaluate the risks possibly resulting from too high a polyphenol consumption.

Phytoestrogens derived from red clover: an alternative to estrogen replacement therapy?

The benefits of plant extracts from soy and red clover as alternatives to conventional hormone replacement therapy (HRT) have been debated in the past. Here, an attempt has been made to summarize the biochemical and pharmacological data in the light of clinical aspects. Red clover and soy extracts contain isoflavones, which have a high affinity to estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta), progesterone receptor (PR) and androgen receptor (AR). The higher affinity to ERbeta compared to ERalpha has been used as an explanation why red clover extracts function as food additives to treat menopausal disorders and may reduce risk of breast cancer. Biochemical analysis shows that these representatives of phytoestrogens have multiple actions beside selective estrogen receptor modulator (SERM)-activity. They act as selective estrogen enzyme modulators (SEEMs), have antioxidant activity and interact with transcription factors such as NF-kappaB. Furthermore, it is indicated that they have protective effects on osteoporosis and the cardiovascular system. Currently 40-50mg of isoflavones (biochanin A, daidzein, formononetin and genistein) are recommended as daily dose. This recommendation is based on the daily intake of phytoestrogens in a traditional Japanese diet.

Modulation of osteoclastogenesis in porcine bone marrow cultures by quercetin and rutin

Flavonols, in contrast to soybean isoflavones, are the most abundant phytoestrogens in western diets, being present in onions, beans, fruits, red wine, and tea. They may protect against atherosclerosis, inhibit certain cancer cell types, and reduce bone resorption. The most widely distributed flavonol is quercetin, which occurs mainly as its glycoside, rutin, but data are very scarce regarding the precise mechanism of action of these compounds on bone-resorbing cells at concentrations similar to those detected in human plasma. We have therefore investigated the effects of nanomolar concentrations of quercetin and rutin on the development and activity of osteoclasts in vitro compared with the effects of 17beta-estradiol. Nonadherent porcine bone marrow cells were cultured on dentine slices in the presence of 10 nM 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), with or without 10 nM quercetin, 10 nM rutin or 10 nM 17beta-estradiol for 11 days. Multinuclear TRAP+ cells that resorbed dentine (osteoclasts) developed in the presence of 1,25(OH)2D3, but their number was significantly reduced by quercetin, rutin, and 17beta-estradiol (P < 0.05). Like 17beta-estradiol, both flavonols also significantly reduced resorption (P<0.05) as assessed by the size of pits resorbed on dentine slices. Osteoclasts and osteoclast progenitors contained estrogen receptor alpha (ERalpha), ERbeta, and RANK proteins. Both flavonols increased nuclear ERbeta protein and decreased ERalpha protein of osteoclast progenitors. Moreover, rutin reduced RANK protein, whereas 17beta-oestradiol and quercetin promoted apoptosis by cleavage of caspase-8 and caspase-3. All the effects of flavonols were reversed by 1 microM ICI 182,780, an estrogen antagonist. Thus, the anti-resorbing properties of flavonols are mainly mediated by ER proteins through the inhibition of RANK protein or the activation of caspases.

Inhibition of 17beta-hydroxysteroid dehydrogenases by phytoestrogens: comparison with other steroid metabolizing enzymes

Effects of phytoestrogens on human health have been reported for decades. These include not only beneficial action in cancer prevention but also endocrine disruption in males. Since then many molecular mechanisms underlying these effects have been identified. Targets of phytoestrogens comprise steroid receptors, steroid metabolising enzymes, elements of signal transduction and apoptosis pathways, and even the DNA processing machinery. Understanding the specific versus pleiotropic effects of selected phytoestrogens will be crucial for their biomedical application. This review will concentrate on the influence of phytoestrogens on 17beta-hydroxysteroid dehydrogenases from a comparative perspective with other steroid metabolizing enzymes.

Soy isoflavones may protect against orchidectomy-induced bone loss in aged male rats

Evidence from several studies suggests that soy protein and/or its isoflavones may have beneficial effects on bone in postmenopausal women and animal models who have osteoporosis. The present study examined the dose-dependent effects of soy isoflavones in the context of soy protein or casein on the male skeleton. Thirteen-month-old male Fisher 344 rats were orchidectomized (ORX; 5 groups) or sham-operated (Sham; 1 group) and immediately placed on dietary treatments for 180 days. Diets were semi-purified and the protein source was either casein (Sham and ORX; controls), casein with two added doses of isoflavones (Iso1; 600 mg/kg diet and Iso2; 1200 mg/kg diet), soy protein with normal isoflavones content (Soy; 600 mg/kg diet), or soy protein with added isoflavones (Soy+; 1200 mg/kg diet). A 7% loss of whole body bone mineral density (BMD) was observed due to orchidectomy; however, the ORX induced BMD loss was significantly reduced to 4.3 and 4.7 % with the Soy and Soy+, respectively. Both doses of isoflavones in conjunction with casein also reduced the loss of whole body BMD, albeit not significantly different from ORX control animals. Trabecular bone histomorphometric analysis of the proximal tibia further supported the bone-sparing role of soy isoflavones as indicated by higher percent bone volume and trabecular number, and lower trabecular separation. We conclude that isoflavones exert modest beneficial effects on the male skeleton whether provided with casein or a soy protein.