Calcitonin and estrogens

Pyroptosis mediates osteoporosis via the inflammation immune microenvironment

Osteoporosis represents a systemic imbalance in bone metabolism, augmenting the susceptibility to fractures among patients and emerging as a notable mortality determinant in the elderly population. It has evolved into a worldwide concern impacting the physical well-being of the elderly, imposing a substantial burden on both human society and the economy. Presently, the precise pathogenesis of osteoporosis remains inadequately characterized and necessitates further exploration. The advancement of osteoporosis is typically linked to the initiation of an inflammatory response. Cells in an inflammatory environment can cause inflammatory death including pyroptosis. Pyroptosis is a recently identified form of programmed cell death with inflammatory properties, mediated by the caspase and gasdermin families. It is regarded as the most inflammatory form of cell death in contemporary medical research. Under the influence of diverse cytokines, macrophages, and other immune cells may undergo pyroptosis, releasing inflammatory factors, such as IL-1β and IL-18. Numerous lines of evidence highlight the pivotal role of pyroptosis in the pathogenesis of inflammatory diseases, including cancer, intestinal disorders, hepatic conditions, and cutaneous ailments. Osteoporosis progression is frequently associated with inflammation; hence, pyroptosis may also play a role in the pathogenesis of osteoporosis to a certain extent, making it a potential target for treatment. This paper has provided a comprehensive summary of pertinent research concerning pyroptosis and its impact on osteoporosis. The notion proposing that pyroptosis mediates osteoporosis via the inflammatory immune microenvironment is advanced, and we subsequently investigate potential targets for treating osteoporosis through the modulation of pyroptosis.

The regulatory role of PI3K in ageing-related diseases

Ageing is a physiological/pathological process accompanied by the progressive damage of cell function, triggering various ageing-related disorders. Phosphatidylinositol 3-kinase (PI3K), which serves as one of the central regulators of ageing, is closely associated with cellular characteristics or molecular features, such as genome instability, telomere erosion, epigenetic alterations, and mitochondrial dysfunction. In this review, the PI3K signalling pathway was firstly thoroughly explained. The link between ageing pathogenesis and the PI3K signalling pathway was then summarized. Finally, the key regulatory roles of PI3K in ageing-related illnesses were investigated and stressed. In summary, we revealed that drug development and clinical application targeting PI3K is one of the focal points for delaying ageing and treating ageing-related diseases in the future.

Soy Isoflavones Ameliorate Metabolic and Immunological Alterations of Ovariectomy in Female Wistar Rats: Antioxidant and Estrogen Sparing Potential

Hormone replacement therapy (HRT) can alleviate estrogen deficiency symptoms especially during menopause. The present study aimed at investigating the effect of soy isoflavones as HRT on immunological and bone health-related parameters with a special focus on the interactions between immunological status and metabolism. Thirty healthy cyclic female Wistar rats were used in this experiment. Ten females were sham-operated, and 20 females were subjected to ovariectomy. Overiectomized (OVX) female rats were randomly divided into 2 groups: the control group (G1, OVX/casein) was fed a casein-based diet, and the second group (G2, OVX/soy) was fed a high soy isoflavone diet. Both groups were compared to a sham-operated group (G3, sham/casein). Treatments continued for 7 weeks. Feed intake, weight gain, and lymphoid organ relative weights were recorded. Some metabolic, immunological, and bone health-related parameters were measured. Moreover, nitric oxide (NO), malondialdehyde (MDA), and total antioxidant capacity (TAC) were determined. Bone histopathology and immunohistochemistry to estrogen receptor alpha (ERα) were done. Feeding soy to OVX females reduced feed intake, weight gain, relative lymphoid organ weight, and T-lymphocytes transformation. Soy isoflavone administration normalized nearly all metabolic and immunological parameters to a level comparable to the sham group via oxidative stress amelioration and bone ERα promotion. Soy isoflavones seemed to be good HRT in estrogen deprivation which modulated the appetite, weight gain, lipid profile, proinflammation, and bone turnover.

The cyclic AMP-dependent protein kinase A pathway is involved in progesterone effects on calcitonin secretion from TT cells

It is well known that gonadal steroid hormones influence the level of plasma calcitonin (CT), but the mechanism by which progesterone affects CT secretion is not clear. Immortalized TT cells are a reliable model system for studying the endocrine function of human parafollicular cells. In the present study, the effects of progesterone on CT secretion were examined in TT cells. TT cells were incubated in medium containing vehicle (DMSO), progesterone or BSA-progesterone for 60 or 150 min, and then the levels of CT in the medium, progesterone receptors, cAMP accumulation and CT mRNA expression were measured. To study the correlation between progesterone effects and the cAMP-dependent protein kinase A (PKA) pathway, cell lysates or cells in 24-well plates were treated with either vehicle or progesterone plus RU486, SQ22536, KT5720, or 3-isobutyl-1-methylxanthine. Then, adenylyl cyclase and protein kinase A (PKA) activities were measured in the cell lysates, and the CT levels were measured in the medium from the 24-well plate. The activated cAMP response element binding protein (P-CREB) was also measured by immunofluorescence. Administration of 1 microM progesterone or 500 nM BSA-progesterone increased the secretion of CT by 381% and 100%, respectively. Progesterone receptors A and B were downregulated by progesterone treatment. The cAMP concentration, adenylyl cyclase and PKA activity, CT mRNA expression, and nuclear P-CREB concentrations all showed an increase after progesterone treatment. RU486, SQ22536 and KT5720 inhibited the progesterone-stimulated effects. These results suggest that a cAMP-dependent PKA pathway is involved in progesterone-stimulated effects on CT secretion from TT cells.

Chronic Estradiol Exposure Modulates Thyroid Structure and Decreases T4 and T3 Serum Levels in Middle-Aged Female Rats

OBJECTIVES

In human medicine, estrogen is applied in prevention and treatment of health problems associated with the menopause. The aim of this study was to examine the effects of chronic estradiol dipropionate (EDP) treatment on thyroid gland structure and function in middle-aged female rats.

METHODS

At 14 months of age, Wistar rats received 0.625 mg EDP/kg b.w./day intraperitoneally for 2 weeks. The peripheral and central zones of the thyroid were stereologically analyzed and the following morphometric parameters determined: volume density of follicles, follicular epithelium, interstitium and colloid, epithelial height and the index of activation rate. Serum levels of TSH, T4 and T3 were determined by ELISA.

RESULTS

EDP treatment led to significant decreases in volume densities of follicles and follicular epithelium, epithelial height and index of activation rate (by 11%, p < 0.05; 23%, p < 0.005; 11%, p < 0.05 and 21%, p < 0.05, respectively) in comparison to control values. Hyperplasia of thyroid follicular cells was noticed in 25% of EDP-treated animals. Serum levels of T4 and T3 were decreased (by 33%, p < 0.005 and 28%, p < 0.001, respectively), but TSH concentration was not significantly different from that of the controls.

CONCLUSION

Chronic estradiol treatment significantly decreased volume density and height of centrally located follicular epithelium, follicular activation index and serum level of total thyroid hormones in middle-aged rats.

The thyroid C cells of ovariectomized rats treated with estradiol

The structure and function of thyroid C cells were studied in ovariectomized (Ovx) adult female rats without and after chronic treatment with estradiol dipropionate (EDP). A peroxidase-antiperoxidase method was applied for localization of calcitonin (CT) in the C cells. Morphometric changes in their volume, nuclei, and relative volume density were evaluated in comparison with sham-operated control rats using a stereological method. The number of C cells was calculated. CT content in the sera was determined by radioimmunoassay. Ovariectomy (Ovx) led to a 21% increase in body weight ( P<0.005), while treatment of Ovx rats with EDP decreased body weight by 25% ( P<0.01). The immunoreactivity for CT in C cells of the Ovx rats was markedly increased. Significant decreases in the volume of C cells (by 13%; P<0.05) and serum CT (by 45%) were recorded, while the C cell number increased by 59% ( P<0.05) in relation to the corresponding controls. The treatment of Ovx rats with EDP caused conspicuous degranulation of the C cells. The cellular volume was increased by 11% and serum CT by 36% in comparison with Ovx animals. At the same time a decrease in C cell number by 29% ( P<0.05) was evident. It may be concluded that estradiol deficiency after Ovx reduced the synthesis and release of CT, while chronic treatment of these animals with EDP had a positive effect on the secretory activity of thyroid C cells.

Meta-analyses of therapies for postmenopausal osteoporosis. V. Meta-analysis of the efficacy of hormone replacement therapy in treating and preventing osteoporosis in postmenopausal women

OBJECTIVE

To review the effect of hormone replacement therapy (HRT) on bone density and fractures in postmenopausal women.

DATA SOURCE

We searched MEDLINE and EMBASE from 1966 to 1999, the Cochrane Controlled Register, citations of relevant articles, and proceedings of international meetings for eligible randomized controlled trials. We contacted osteoporosis investigators to identify additional studies, and primary authors for unpublished data.

STUDY SELECTION

We included 57 studies that randomized postmenopausal women to HRT or a control (placebo or calcium/vitamin D) and were of at least 1 yr in duration. Seven of these studies reported fractures.

DATA ABSTRACTION

For each study, three independent reviewers assessed the methodological quality and abstracted the data.

DATA SYNTHESIS

HRT showed a trend toward reduced incidence of vertebral fractures [relative risk (RR) 0.66, 95% confidence interval (CI) 0.41-1.07; 5 trials] and nonvertebral fractures (RR 0.87, 95% CI 0.71-1.08; 6 trials). HRT had a consistent effect on bone mineral density (BMD) at all sites. The difference between HRT and control in the percent change in bone density at 2 yr was 6.76 (5.83, 7.89; 21 trials) at the lumbar spine and 4.53 (3.68, 5.36; 14 trials) and 4.12 (3.45, 4.80; 9 trials) at the forearm and femoral neck, respectively.

CONCLUSIONS

HRT has a consistent, favorable and large effect on bone density at all sites. The data show a nonsignificant trend toward a reduced incidence in vertebral and nonvertebral fractures.

Age-related differences in the secretion of calcitonin in female rats

The mechanism that causes hypercalcitonemia in female rats and is associated with aging was investigated. Young (3 mo), adult (8 mo), middle-aged (12 mo), and old (21 mo) rats were infused with CaCl2 and were bled from a jugular catheter after a CaCl2 challenge. To mimic some of the hormonal changes caused by aging, the anterior pituitary (AP)-grafted ovariectomized rats with hyperprolactinemic syndrome were used to mimic the physiological status of aging. The rat thyroid gland was incubated with or without ovine prolactin (oPRL; 40 or 80 ng/ml) at 37 degreesC for 30 min. Old rats possessed the lowest levels of plasma estradiol and progesterone yet had the highest levels of plasma prolactin and calcitonin (CT) compared with young, adult, and middle-aged rats. The basal release of thyroid CT in vitro in thyroid glands gradually increased with age. Compared with cortex (CX)-grafted rats, the AP-grafted rats possessed higher levels of plasma PRL, basal and CaCl2-induced levels of plasma CT, and the release of thyroid CT in thyroid glands. After stimulation with oPRL, the in vitro release of thyroid CT increased in both CX- and AP-grafted rats. These results suggest that the hypersecretion of CT in old rats is due at least in part to hyperprolactinemia.

Meta-analysis about efficacy of anti-resorptive drugs in post-menopausal osteoporosis

OBJECTIVE

The purpose of this study was to compare the effect of three groups of anti-resorptive drugs in post-menopausal osteoporosis.

DATA SOURCES

We collected data covering the period between 1983 and 1995, by first using MEDLINE. References retrieved were scanned further to identify additional papers.

STUDY SELECTION

Only randomized studies evaluating bone mass by means of dual-photon or dual energy densitometry over a period of 1 year were accepted.

DATA EXTRACTION

Studies were arranged into three drug groups. We used densitometry results after 1 year in all treatment or control groups. Factors which might interfere with the results were recorded for subsequent separate analysis.

DATA SYNTHESIS

The MEDLINE search identified almost 25,000 studies. On reading the abstracts, 275 trials appeared to be controlled trials and original copies were retrieved for detailed analysis. A total of 31 articles which satisfied the inclusion criteria were identified. The first meta-analysis included studies which compared oestrogens and placebo, and the global effect-size was 0.54 (95% CI 0.34, 0.73). The second meta-analysis compared calcitonins with placebo and produced an effect-size of 0.41 (95% CI 0.21, 0.61) The third analysis compared bisphosphonates and placebo and showed an effect-size of 0.87 (95% CI 0.68, 1.07). Only oestrogen dose affected the results found.

CONCLUSIONS

Bisphosphonates had the greatest effect on bone mass in post-menopausal osteoporosis.

A systematic review of the skeletal effects of estrogen therapy in postmenopausal women. I. An assessment of the quality of randomized trials published between 1977 and 1995

PURPOSE

To examine the quality of published randomized controlled trials of the effects of estrogen treatment on fracture risk and measures of bone mass.

DATA SOURCES

Articles on estrogen treatment for osteoporosis published between 1977 and 1995 were identified by searching Medline and Excerpta Medica databases and bibliographies of original papers and published reviews.

STUDY SELECTION

Studies selected were randomized controlled trials of the efficacy of estrogens in preventing loss of bone mass or fractures in postmenopausal women.

DATA EXTRACTION

Data extraction and quality assessment were performed in duplicate, with assistance of a manual. Raters were blinded as to authors and their affiliations and the publication details.

RESULTS

Of 99 eligible randomized controlled trials published between 1977 and 1995, eight included no extractable data, and 23 contained results that were published in duplicate. Total quality scores increased over time, but this was accounted for by improvements only in the measurement technologies used to estimate bone mineral content or density. There was no improvement in the quality of randomization methods, the extent to which withdrawals were accounted for, or in the baseline comparability of treated and control patients. Neither sample sizes nor durations of follow-up increased over time.

CONCLUSIONS

This body of literature fails to address whether estrogen therapy reduces fracture rates, and does not allow for comparison of the effects of different active therapies on change in bone density. Although there were improvements in the techniques for estimating bone mass and delivering estrogen treatment, the studies published in the 1990s were no more informative for making clinical or policy decisions than those published in the 1970s.

A systematic review of the skeletal effects of estrogen therapy in postmenopausal women. II. An assessment of treatment effects

PURPOSE

To combine the results of randomized controlled trials to provide overall estimates of the effect of estrogen treatment on fracture rates and measures of bone mass.

DATA SOURCES

Articles on estrogen treatment for osteoporosis published between 1977 and 1995 were identified.

STUDY SELECTION

Studies selected were randomized controlled trials of the efficacy of estrogens in preventing loss of bone mass or fractures in postmenopausal women.

DATA EXTRACTION

Data extraction and quality assessment were performed in duplicate, with assistance of a manual. Raters were blinded as to authors and their affiliations and the publication details. With estimates of bone mass, the treatment effect size was defined as the difference in the mean annual change in bone mass between the treatment and control groups divided by the pooled standard deviation for change. In the case of fractures, efficacy was measured as the reduction in the numbers of individuals experiencing new fractures with treatment. Effect sizes were pooled using the random effects model.

RESULTS

Thirty-seven studies met the criteria for inclusion in the systematic review. Only one small secondary prevention trial contained evaluable data on vertebral fractures. This study found a fracture relative risk of 0.63 (95% confidence interval, CI 0.28-1.43) with estrogen treatment. There was more information on the effects of treatment on bone mass. Overall effect sizes ranged between 0.5 and 2.5 standard deviation (SD) units for change. A dose-response relationship was apparent but high doses of estrogens were not associated with effect sizes greater than those observed with recommended doses. There was no significant difference in efficacy between transdermal and oral administration of estrogens. Pooling of paired data from secondary prevention studies indicated that treatment effect sizes were smaller at the hip (0.92, 95% CI 0.3-1.5 SD units) than at the spine (2.1, 95% CI 0.9-3.3 SD units). No significant effects of co-intervention with calcium, progestogens or androgens were seen, although an additive effect of higher doses of calcium could not be ruled out.

CONCLUSIONS

Clear-cut effects of estrogens in attenuating the postmenopausal decline in estimated bone mass were apparent in this literature. However, the trials were short-term and provide inadequate evidence on the effects of treatment on fracture risk.

Effects of ovarian steroid hormones and thyroxine on calcitonin secretion in pregnant rats

In the present study, the roles of ovarian steroid hormones and thyroxine (T4) in regulating the secretion of calcitonin (CT) in pregnant rats were examined. The levels of plasma progesterone, pre- and post-CaCl2 plasma CT, and recovery time of plasma CT and calcium after calcium challenge were greatest in midterm pregnant rats. The levels of basal plasma progesterone, CT, calcium, and recovery time of plasma CT after calcium challenge were less in late pregnant rats, but basal plasma estradiol was highest in late pregnancy. The concentrations of plasma T4 were gradually decreased in rats during pregnancy. Regardless of the presence of estradiol, administration of progesterone in ovariectomized (Ovx) rats resulted in an increase of plasma T4 as well as the basal and calcium-induced secretion of CT. Administration of estradiol alone did not alter the CaCl2-induced levels but decreased the post-CaCl2 levels of plasma calcium in Ovx rats. The basal levels of plasma CT were decreased in Ovx rats treated with T4. These results suggest that the hypercalcitoninemia in midterm pregnant rats is due to an increased secretion of progesterone. Hypocalcitoninemia in late pregnant rats, however, is due in part to lower plasma calcium.

Influence of estrogens on calcitonin secretion

In this study we investigated the calcitonin (CT) pattern both in basal conditions and after calcium infusion before and one month after oophorectomy in 17 premenopausal women. In addition, 13 oophorectomized women were randomly allocated to two groups, one given hormone replacement treatment and the other untreated, and CT response to hypercalcemia was reevaluated one year later. CT response to calcium infusion was significant only before oophorectomy and one year after estrogen-progestogen treatment, whereas there was no response one month after oophorectomy or after one year without hormone replacement therapy. Our data indicate that both estrogen secretion and replacement treatment may be important factors in CT response.