Pregnancy and lactation, a challenge for the skeleton

In this review we discuss skeletal adaptations to the demanding situation of pregnancy and lactation. Calcium demands are increased during pregnancy and lactation, and this is effectuated by a complex series of hormonal changes. The changes in bone structure at the tissue and whole bone level observed during pregnancy and lactation appear to largely recover over time. The magnitude of the changes observed during lactation may relate to the volume and duration of breastfeeding and return to regular menses. Studies examining long-term consequences of pregnancy and lactation suggest that there are small, site-specific benefits to bone density and that bone geometry may also be affected. Pregnancy- and lactation-induced osteoporosis (PLO) is a rare disease for which the pathophysiological mechanism is as yet incompletely known; here, we discuss and speculate on the possible roles of genetics, oxytocin, sympathetic tone and bone marrow fat. Finally, we discuss fracture healing during pregnancy and lactation and the effects of estrogen on this process.

Soy isoflavones and cardiovascular disease epidemiological, clinical and -omics perspectives

Cardiovascular disease (CVD) mortality rates are lower in Asian countries where dietary patterns are very different from Western diet. A number of studies have linked these lower rates to the inclusion of soy products as a staple food in those countries. Soy is the richest dietary source of isoflavones, a type of phytoestrogen associated with many potentially beneficial effects. Isoflavone-containing soy protein consumption has been linked to reduced levels of LDL cholesterol in hypercholesterolemic patients. This effect is increased with the concomitant administration of isoflavones, and seems to be also complemented by the isoflavone capacity to restore the endothelial function in patients with weak and moderated endothelial dysfunction. The effects are variable depending on individuals� � � metabolism and in particular to their ability to convert daidzein to equol that seems to be restricted to approximately 1/3 of the population. Equol production has been indeed linked to a decreased arterial stiffness and antiatherosclerotic effects via NO production. Because the relevance of isoflavones consumption on the modulation of cardiovascular risk still remains unclear, this paper aims to review the existing knowledge on the biological activity of the isoflavones on the human cardiovascular system from an epidemiological, clinical and -omics point of view.

Calcium Intake, Vitamin D and Bone Health Status of Post-menopausal Chinese Women in Kuala Lumpur

Bone health status was investigated in 178 free-living Chinese post-menopausal women in Kuala Lumpur. Body mass index (BMI), body composition (using whole body DXA), calcium intake and serum 25-OH vitamin D status were measured along with biochemical markers of bone turnover, that is, pro-collagen Type 1 N-terminal peptide (P1NP), osteocalcin (OC) and C-telopeptide β cross link of Type 1 collagen (CTX- β). Bone mineral density (BMD) was measured using DXA (Hologic, USA) at the lumbar spine, femoral neck and total hip. Results showed that osteopenia was present in 50% of the subjects at the spine and 57.9% at the femoral neck. Osteoporosis was diagnosed in 10% of the subjects at both the femoral neck and spine. A total of 29.3% of the subjects had high levels of CTX- β. Mean serum level of 25-OH vitamin D was 60.4+15.6 nmol/L and 50.6% of the subjects had hypovitaminosis D (defined as < 50 nmol/l). Mean total calcium intake of the subjects was 497 + 233 mg, of which only 14% met the RNI for calcium with the additional intake of calcium supplements. Body fat was also significantly correlated (r=0.181, p< 0.05) with BMD at the spine but not BMD at the femoral neck. Lean body mass was positively correlated with BMD at the spine (r=0.289, p< 0.001) and femoral neck (r=0.295, p< 0.001). CTX-β was negatively correlated with BMD at the spine (r= -0.235, p< 0.001), whereas P1NP (r=-0.215, p< 0.001) and osteocalcin (r=-0.265, p< 0.001) were both negatively correlated with BMD at the femoral neck. Generally, the study found that women with osteopenia had higher levels of bone turnover markers, less lean body mass and lower calcium intake than women with normal BMD. In conclusion, this study demonstrated that the majority of free living Chinese post-menopausal women in Kuala Lumpur have low calcium intake, low 25-OH vitamin D status and low bone mass and elevated biochemical markers of bone turnover.

Influence of lifelong soy isoflavones consumption on bone mass in the rat

Soy isoflavones (IFs) have shown a bone-sparing effect through epidemiological studies in the Asian population. However, there is no evidence as to whether such protection would result from a lifelong exposure. We investigated the impact of an early exposure to IFs on bone status. Sixty female Wistar rats were fed either a standard diet (n=30) or the same food enriched with IFs (0.87 mg/g of diet) (n=30). After 1 month, they were allowed to mate, and were kept on the same regimen during the whole gestation and lactation periods. At weaning, female pups were each assigned to one of four nutritional groups; within each experimental group, animals were split into two groups, fed either the standard or the IF-rich diet. At 2, 3, 6, 12, 18, and 24 months after birth, 10 animals in each group were sacrificed. Femurs were collected for mechanical testing and bone mineral density (BMD) measurement. The rats perinatally or lifelong exposed to the IF-rich diet exhibited higher body weight and fat mass at 24 months of age. Peak bone mass was achieved between 6 and 12 months and did not differ between groups. In animals perinatally exposed to IF, BMD continued to increase. Thus, at 24 months, femoral total BMD (P<0.05), metaphyseal BMD (P<0.01), and failure load (P<0.05) were higher in the offspring born from mothers provided IF during pregnancy. Postnatal exposure alone did not improve bone parameters. This experiment provides evidence that perinatal exposure to phytoestrogens leads to a higher BMD later in life. It is suggested that these changes may have occurred as a consequence of programming effects, as has been shown for the endocrine and immune systems.

Hesperidin inhibits ovariectomized-induced osteopenia and shows differential effects on bone mass and strength in young and adult intact rats

The main aim of this study was to investigate the bone-sparing effect of hesperidin, one of the main flavonoid present in oranges, in two age groups of ovariectomized female rats, compared with their intact controls. Young (3 mo) and adult (6 mo) female Wistar rats were sham operated (SH) or ovariectomized (OVX) and then pair-fed for 90 days a casein-based diet supplemented or not with 0.5% hesperidin (Hp; n = 10/group). In older rats, Hp intake led to a partial inhibition of OVX-induced bone loss, whereas a complete inhibition was obtained in younger animals. At both ages, while plasma osteocalcin concentrations were unchanged, urinary excretion of deoxypyridinoline was reduced by Hp intake, suggesting that Hp was able to slow down bone resorption. Unexpectedly, in intact young rats, Hp consumption resulted in a significant increase in bone mineral density (BMD). Indeed, 6-mo-old HpSH rats had a similar BMD to 9-mo-old nontreated SH adult rats, suggesting an accelerated bone mass gain in the young rats. In contrast, in intact adult rats, Hp did not further increase BMD but did improve their bone strength. The results of this study show a protective effect of Hp on bone loss in OVX rats of both ages without uterine stimulation and accompanied by a lipid-lowering effect. The unexpected and intriguing findings obtained in intact rats showing improved BMD in young rats and improved femoral load in adult rats merit further investigation. The bone and lipid benefits of hesperidin make it an attractive dietary agent for the management of the health of postmenopausal women.

Modulation of soy isoflavones bioavailability and subsequent effects on bone health in ovariectomized rats: the case for equol

INTRODUCTION

Soy products are of particular interest because of their potential health benefits in a range of hormonal conditions, such as osteoporosis, due to their high content in phytoestrogens. Because equol, the main metabolite from soy isoflavones, is thought to be powerful, the present study was designated to evaluate the bone-sparing effects of equol by either providing the molecule through the diet or by eliciting its endogenous production by modulating intestinal microflora by short-chain fructooligosaccharides (sc-FOS) or live microbial (Lactobacillus casei) together with daidzein, its precursor.

METHODS

A comparison with daidzein and genistein was also performed. Rats (3 months old) were ovariectomised (OVX) or sham-operated (SH). Ovariectomised rats were randomly assigned to six experimental diets for 3 months: a control diet (OVX), the control diet supplemented with either genistein (G), or daidzein (D), or equol (E) at the level of 10 microg/g body weight/d. The remaining OVX rats were given daidzein at the dose of 10 mug/g body weight/d, simultaneously with short-chain FOS (Actilight, Beghin-Meiji) (D+FOS) or Lactobacillus casei (Actimel, Danone) (D+L). The SH rats were given the same control diet as OVX.

RESULTS

Genistein, daidzein or equol exhibited a bone sparing effect. Indeed, total femoral bone mineral density (BMD) was significantly enhanced (compared to that of OVX rats), as was the metaphyseal compartment. Bone strength was improved by E consumption, but not by genistein or daidzein given alone. As far as the FOS diet is concerned, the addition of prebiotics significantly raised efficiency of the daidzein protective effect on both femoral BMD and mechanical properties. The effects of lactobacillus were similar, except that the increase in metaphyseal-BMD was not significant.

CONCLUSION

In conclusion, long-term equol consumption, like genistein and daidzein, in the ovariectomized rat, provides bone sparing effects. Adding indigestible sugars, such as FOS or live microbial as L. casei, in the diet significantly improves daidzein protective effects on the skeleton.

Prevention of bone loss by phloridzin, an apple polyphenol, in ovariectomized rats under inflammation conditions

Aging and sex hormones related changes lead to inflammatory and oxidant conditions, which are involved in the pathogenesis of osteoporosis. Recent studies have suggested that polyphenols may exert a protective effect in such conditions. We assessed the effect of phloridzin (Phlo), a flavonoid exclusively found in apple, on bone metabolism in ovariectomized (OVX) or sham-operated (SH) rats with and without inflammation. Six-month-old Wistar rats were allocated to two equal groups that received either a control diet or a diet supplemented with 0.25% Phlo for 80 days. Three weeks before necropsy, inflammation was induced by subcutaneous injection of talc in 10 animals of each group. At necropsy, ovariectomy decreased both total (T-BMD) and metaphyseal (M-BMD) femoral bone mineral density (P < 0.01). Inflammation conditions, checked by an increase in the spleen weight and alpha1-acid glycoprotein concentration in OVX rats, exacerbated the decrease in T-BMD (g/cm2) (as well as M-BMD) observed in castrated animals (P < 0.05). Daily Phlo intake prevented ovariectomy-induced bone loss in conditions of inflammation as shown by T-BMD and M-BMD (P < 0.05). At the diaphyseal site, BMD was improved by Phlo in OVX rats with or without inflammation (P < 0.05). These results could be explained by changes in bone remodeling as the increased urinary deoxypyridinoline excretion in OVX and OVXinf animals was prevented by the polyphenol-rich diet (P < 0.001), while plasma osteocalcin concentration was similar in all experimental groups. In conclusion, Phlo consumption may provide protection against ovariectomy-induced osteopenia under inflammation conditions by improving inflammation markers and bone resorption.

Severe bone alterations under beta2 agonist treatments: bone mass, microarchitecture and strength analyses in female rats

AIMS

Beta2 adrenergic agonists are widely used in therapeutics and as doping agents by athletes. However, their effects on bone tissue, especially bone microarchitecture, remain poorly understood. Using three-dimensional (3D) microtomography, dual-energy X-ray absorptiometry, biomechanical testing and enzyme-linked immunosorbent assay, we evaluated the effects of two beta2 agonists, clenbuterol and salbutamol, on bone in growing rats.

METHODS

Twelve-week-old Wistar female rats (N = 39), divided in 3 groups, received during 6 weeks either salbutamol (4 mg/kg/day), clenbuterol (2 mg/kg/day) or normal saline (0.5 ml/kg/day) by subcutaneous injections.

RESULTS

After 6 weeks, the salbutamol and clenbuterol groups displayed lower bone mineral content (BMC), femoral length and cortical width than controls. Clenbuterol treatment further reduced bone mineral density. Bone microarchitecture was clearly altered by clenbuterol, as evidenced by lower trabecular number (-40.40%; P < 0.001), connectivity and trabecular bone volume (-42.85%; P < 0.001), leading to lower ultimate force. Clenbuterol significantly increased muscle mass (P < 0.01) and reduced fat mass when compared to controls. Salbutamol did not seem to have any effect on bone microarchitecture or body composition. Both beta2 agonists increased the bone resorption marker (C-terminal collagen crosslinks) without any change of a bone formation marker. At the end of the treatment, a drop in leptin was seen in the clenbuterol group only. Leptin levels were correlated with BMC (r = 0.69, P = 0.003).

CONCLUSION

These results confirm the deleterious effect of beta2 agonists on bone mass and show the negative effects of clenbuterol on trabecular bone microarchitecture. Bone loss occurred independently from muscle mass but was related to fat mass. A leptin-mediated effect on bone tissue seems likely. These pathophysiological effects may have important consequences in human therapeutics and doping.

Preventive effect of Abelmoschus manihot (L.) Medik. on bone loss in the ovariectomised rats

Because the biggest culprit in pathogenesis of osteoporosis is oestrogen deficiency, hormone replacement therapy remained the mainstay for prevention. However most of postmenopausal women are more inclined to use natural alternative. We thus investigated the ability of Abelmoschus manihot, a herbal medicine to prevent bone loss in ovariectomised rats. Female Wistar rats were sham operated (SH: 8) or ovariectomised (OVX: 24). On day 0, OVX rats were randomly assigned to groups as follows: eight received 10% Abelmoschus manihot leaves in their diet, eight were given 15% Abelmoschus manihot leaves and eight were untreated (OVX). Compounds were mixed with a soy protein-free diet and given orally for 3 months. At necropsy, bone mineral density (BMD) in the femur and in its metaphyseal zone was lower in OVX than SH (p<0.05). This osteopenia was prevented by consumption of the highest dose of Abelmoschus manihot leaves. Bone mineral content (BMC) in the total femur and its metaphyseal and diaphyseal subregions was improved, as well (p<0.05). This could be explained by a trend towards decreased bone resorption. The lowest dose did not elicit any significant effect. In conclusion, Abelmoschus manihot consumption, at the dose of 15% in the diet, provided bone-sparing effects by improving both BMD and BMC.

Fructooligosaccharides maximize bone-sparing effects of soy isoflavone-enriched diet in the ovariectomized rat

Isoflavones (IF) have been increasingly implicated for use in the prevention of osteoporosis. As their bioavailability could be improved by modulating intestinal microflora, the present study was undertaken to investigate whether IF and fructooligosaccharides (FOS), which are known to modify large-bowel flora and metabolism, may exhibit a cooperative bone-sparing effect. This work was carried out on 3-month-old Wistar rats assigned to 12 groups: 2 SH (sham-operated) and 10 OVX (ovariectomized). Animals received a diet for 90 days containing total IF (Prevastei HC, Central Soya) at 0 (OVX and SH), 10 (IF10), 20 (IF20), 40 (IF40), or 80 (IF80) microg/g body weight per day. FOS (Actilight, Beghin-Meiji) were orally given to half of the groups, (OVX FOS), (IF10 FOS), (IF20 FOS), (IF40 FOS), (IF80 FOS), and (SH FOS). Isoflavones exhibited a bone-sparing effect as soon as consumption reached 20 microg/g/day, whereas only the highest dose induced a weak uterotrophic activity. Indeed, total femoral bone mineral density (BMD) was significantly enhanced (compared with that of OVX rats), as was the metaphyseal compartment. Bone strength was improved as well. As far as the FOS diet is concerned, addition of prebiotics significantly raised the efficiency of the IF protective effect on both femoral BMD and mechanical properties. The trend toward higher BMD levels with the lowest IF dose (IF10) even reached a significant level when FOS were added. This effect could be explained by a reduced bone resorption. In conclusion, daily IF consumption prevented castration-induced osteopenia by decreasing bone resorption when given at 20, 40, or 80 microg (total isoflavones)/g/day. Simultaneous FOS consumption improved IF protective effect on the skeleton, with the lowest IF dose becoming efficient. Enhancement of IF bioavailability, following FOS fermentation, is probably involved.