John J. B. Anderson

Biphasic Effects of Genistein on Bone Tissue in the Ovariectomized, Lactating Rat Model

Abstract The ovariectomized (OVX), lactating rat model has been used to investigate the skeletal effects of the plant estrogen, genistein, over a 14-day period. The OVX, lactating rat on a low-calcium diet loses slightly more than 50% of its bone mineral mass during the first 2 weeks of lactation, and we have demonstrated that estrogen treatment can significantly reduce the loss of femoral mass (ash weight). Following OVX, the rats were assigned to treatment or control groups (both placebo and positive control with estrogen replacement). The treatment groups received one of three doses of a genistein-rich preparation each day via the feed for 2 weeks, after which time the pups began to have an interest in solid feed. A positive control group received conjugated estrogen in the feed. The genistein doses were: low (0.5 mg/d); intermediate (1.6 mg/d); and high (5.0 mg/d). Measurements included ash weights of the femur, scanning electron microscopy (SEM) of the proximal tibia, and uterine weights. SEM results were as follows: (1) at the low dose genistein was approximately equally effective to estrogen in the retention of cancellous bone tissue, as reflected in the number and density of trabeculae in hemisections of the tibial subepiphyseal region, but at high doses genistein was less effective; and (2) rats treated with low-dose genistein, like estradiol, had rougher endosteal surfaces and smaller pores on these surfaces than untreated control rats. Mean ash weights of the entire femur were highest in the rats treated with the low dose compared to control rats (P < 0.05), and they were higher than ash weights of rats administered the intermediate or high doses of genistein. The mean ash weights of the femurs were consistent with the genistein effects on the tibias observed by SEM. In summary, a biphasic response to the genistein preparation was found in this OVX rat model. Interpretation of the results suggests that, at the low dose, genistein appears to be an agonist at the estrogen receptor locus, whereas at higher doses the genistein is less effective and may even have adverse effects on bone cells. These findings of a biphasic effect of genistein (i.e., an inverted U effect) are consistent with those of other recent reports in the literature on isolated bone cells and on reproductive tissues. In summary, lower doses of genistein from soy foods would be expected to act similarly to estrogens with a beneficial effect on bone tissue, but at high doses that are unlikely to be consumed in human diets, this soy derivative may have potentially adverse effects on bone cell functions and thereby on bone tissue.

Athletic Performance and Vitamin D

PURPOSE Activated vitamin D (calcitriol) is a pluripotent pleiotropic secosteroid hormone. As a steroid hormone, which regulates more than 1000 vitamin D-responsive human genes, calcitriol may influence athletic performance. Recent research indicates that intracellular calcitriol levels in numerous human tissues, including nerve and muscle tissue, are increased when inputs of its substrate, the prehormone vitamin D, are increased. METHODS We reviewed the worlds literature for evidence that vitamin D affects physical and athletic performance. RESULTS Numerous studies, particularly in the German literature in the 1950s, show vitamin D-producing ultraviolet light improves athletic performance. Furthermore, a consistent literature indicates physical and athletic performance is seasonal; it peaks when 25-hydroxy-vitamin D [25(OH)D] levels peak, declines as they decline, and reaches its nadir when 25(OH)D levels are at their lowest. Vitamin D also increases the size and number of Type II (fast twitch) muscle fibers. Most cross-sectional studies show that 25(OH)D levels are directly associated with musculoskeletal performance in older individuals. Most randomized controlled trials, again mostly in older individuals, show that vitamin D improves physical performance. CONCLUSIONS Vitamin D may improve athletic performance in vitamin D-deficient athletes. Peak athletic performance may occur when 25(OH)D levels approach those obtained by natural, full-body, summer sun exposure, which is at least 50 ng x mL(-1). Such 25(OH)D levels may also protect the athlete from several acute and chronic medical conditions.

1Phytoestrogens and bone

Abstract Practically all plant foods contain small amounts of the diverse phytoestrogen moleculesthat have the potential to improve health. Phytoestrogens, especially the soy-derived isoflavones, are receiving great scrutiny as food supplements for the purposes of both enhancing the health of tissues and preventing several common diseases, such as cardiovascular diseases, cancers of reproductive tissues and osteoporosis. Investigations of isoflavones, in particular, have recently become more prominent because of their oestrogenic activities. These actions may be as either partial oestrogen agonists or antioestrogens (inhibitors of natural oestrogen activity). For example, the isoflavones of soy, mainly genistein and daidzein, have been shown by at least three different laboratories to conserve bone in ovariectomized rodent models, and they probably have similar conservatory effects in higher mammalian species. Nevertheless, the only positive effects of phytoestrogens on bone observed so far in post-menopausal women have been small and limited to the lumbar vertebrae. Additional information on human studies currently in progress is needed before the efficacy of these preparations in human subjects is known.

The effects of phytoestrogens on bone

This review on the relationships between isoflavones and bone tissue covers the published reports of epidemiological and experimental studies of humans, animal models, isolated tissues, and cells in culture. The overriding conclusion is that, when provided at optimal dosages, isoflavones, particularly genistein and daidzein, have modest positive effects on bone tissue, i. e., improved bone mass. The in vivo doses of isoflavones required to achieve optimal bone effects in rodent models is typically 1000-fold greater than estradiol. In addition, at lower and higher doses than the optimal dose range, isoflavones have less positive effects on bone and thereby display a biphasic effect. Similar results on osteoblast-like bone cells in culture have been found in in vitro experiments of the effects of genistein, but not daidzein. In general, isoflavones derived from soybeans and their products have weak estrogenic agonistic properties when consumed by animals and humans at optimal doses, but deleterious effects may be observed at very high doses. Cell studies of genistein suggest that at high doses it contributes to the loss of normal cell functions, whereas daidzein at the same concentration has a beneficial effect on osteoblast-like cells. It is highly unlikely that human consumption would be so high from dietary sources to result in any adverse effects. In summary, isoflavones appear to have potential promise for maintaining or modestly improving bone mass of human subjects when consumed at optimal dosages.

Health potential of soy isoflavones for menopausal women

OBJECTIVE To review the current literature on the effects of soy isoflavones, one class of phyto-oestrogens, on cardiovascular diseases, osteoporosis, cancer and climacteric symptoms. DESIGN Many study designs were employed in the reports reviewed here, including prospective human trials, observational human studies, animal experiments and in vitro cell studies that explored the protective or preventive effects of soy isoflavones (genistein, daidzein and glycitein alone or mixed). SETTING Diverse settings were employed, depending on study design. SUBJECTS Human subjects, mostly menopausal or postmenopausal, were included, as were animal models and specific cell types. RESULTS The findings were: (i) isoflavones plus soy protein together were needed to obtain the highly significant beneficial results on blood lipids and arterial dimensions; (ii) isoflavone treatments alone at high doses (relative to above) consistently improved bone parameters in rodent ovariectomized models, but not in humans or primates; (iii) isoflavones were not consistent in exerting positive effects regarding the prevention or treatment of cancers of the mammary glands, uterus and colon; and (iv) the effects of isoflavones on climacteric symptoms were not clear-cut. CONCLUSIONS The promise of soy isoflavones reducing chronic disease risk seems to be non-uniform, with the most conclusive benefits occurring in the prevention of cardiovascular diseases, but other organ systems, such as skeletal and reproductive tissues, may also benefit from the consumption of soy and soy-derived products.

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.

Familial resemblance of radial bone mass between premenopausal mothers and their college-age daughters

SummaryThe influences of heredity and environmental factors on radial bone mass were evaluated in 84 premenopausal mothers with their biological daughters (ages 18–22). Mid- and distal radial bone mineral content (BMC) and density (BMD) were assessed using single-photon absorptiometry. As a group, the daughters (mean age 18.6 years) had 5–10% less bone mass at both the distal and midradial sites than their mothers (mean age 44.2 years). Familial resemblance estimates showed significant relationships between mothers and daughters for mid-and distal BMC and BMD after considering the influence of body mass index (BMI). Daughters with a maternal family history of osteoporosis had 6–7% lower but nonsignificant values of mid- (P=0.086) and distal BMC (P=0.075) compared to values of women with a negative family history, whereas mothers with a positive family history had 3–4% lower (NS) values of distal and mid-BMC compared to those of mothers with a negative family history after adjustment for BMI. Multiple regression analyses showed BMI to be the most important determinant of the bone values of the mothers, and both BMI and dietary calcium intake were found to be significant for the daughters. The findings of this study suggest that hereditary contributions from the mothers play an overwhelmingly critical role in the accrual of bone mass by their daughters by ages 18–22, but that environmental influences on bone consolidation during the premenopausal decades may be more important in promoting optimal (peak) bone mass and thereby may help to delay the postmenopausal onset of osteoporotic fractures.

Dietary factors in bone health of elderly lactoovovegetarian and omnivorous women.

The relationships between dietary factors and radial bone indices of omnivorous (n = 287) and lactoovovegetarian (n = 88) postmenopausal women were investigated. Bone mineral content (BMC) and bone density (BD) were determined at mid and distal radius sites using a Norland single-beam bone densitometer. A quantitative food frequency questionnaire assessed usual current and long-term intakes. Multiple regression analyses showed that 1) vegetarianism was a positive contributor (p less than 0.05) to Mid BMC, 2) protein was a positive contributor (p less than 0.02) to Mid and Distal BMC, 3) phosphorus was a negative contributor (p less than 0.10) to Mid and Distal BMC and Mid BD, and 4) current calcium was not a significant contributor to any of the bone indices after age, body mass index, energy, protein, P, and vegetarianism were accounted for in the models. Estimations of long-term Ca intake and other nutrients are necessary if relationships between diet and bone are to be identified at any age period using cross-sectional epidemiological methods.

Isoflavones regulate interleukin-6 and osteoprotegerin synthesis during osteoblast cell differentiation via an estrogen-receptor-dependent pathway.

The hypothesis tested in this in vitro study was that the expression and production of dietary isoflavone-mediated osteoclastogenesis-regulatory cytokines, such as interleukin-6 (IL-6) and osteoprotegerin (OPG), are related to the different levels of estrogen receptors expressed in two hFOB osteoblastic cell lines. OPG mRNA expression was significantly increased in both hFOB1.19 and hFOB/ER9 cells treated with 17 beta-estradiol, genistein, or daidzein at 10(-8)M in comparison to vehicle (control) (P<0.05). In both cell lines, the release of IL-6 was suppressed, while OPG production was enhanced by isoflavone treatments (P<0.05). The increased expression of OPG and decreased IL-6 production by isoflavones were dose-dependent. Responses to isoflavones were much stronger in hFOB/ER9 cells, which express the estrogen receptor 20 times higher than those in hFOB1.19 cells. After adding the ER binding blocker, ICI-182,780, the effects of isoflavones on OPG and IL-6 production disappeared. In summary, the inhibition by dietary isoflavones of IL-6 production and the stimulation of OPG appear to be mediated, at least in part, via a genomic pathway operating through estrogen receptors and gene expression mechanisms.

Osteoporosis prevention in premenopausal women: using a stage model approach to examine the predictors of behavior.

The precaution adoption process model was used to examine the predictors of 2 behaviors recommended to reduce the risk of developing osteoporosis: calcium consumption and weight-bearing exercise. A total of 452 premenopausal women completed a mailed questionnaire assessing stage in the precaution adoption process and 12 knowledge and attitudinal variables. Participants were also given an opportunity to request information about osteoporosis. In all, 11 of the 12 knowledge and attitudinal variables were associated with calcium stage; 8 were associated with exercise stage. Information requests were associated with both calcium and exercise stage. Findings provide substantial support for the precaution adoption process model and suggest that the model can be usefully applied in this area to increase understanding of why many women do not practice behaviors that could reduce their risk of developing osteoporosis.