Dehydroepiandrosterone Stimulation of Osteoblastogenesis in Human MSCs Requires IGF-I Signaling

Dioscorea esculenta Intake with Resistance Training Improves Muscle Quantity and Quality in Healthy Middle-Aged and Older Adults: A Randomized Controlled Trial

Resistance training and Dioscorea esculenta intake have a positive effect on muscle. Therefore, we aimed to determine whether 12-week Dioscorea esculenta intake combined with resistance exercise more effectively improves muscle quantity, quality, and cardiometabolic parameters in healthy middle-aged and older adults. This study is a double-blind trial with 66 volunteers (21 males/45 females; age 53 ± 5 years; body weight 61 ± 11 kg; BMI 24 ± 4 kg) who were randomly divided into four groups: sedentary-control with placebo (Sed and PL) or Dioscorea (Sed and Dio) and resistance training with placebo (RT and PL) or Dioscorea (RT and Dio). Resistance training sessions using elastic bands were performed 3 days/week for a 12-week period. Dioscorea esculenta tablets were ingested at 2000 mg/day once per day. The RT and Dio group showed greater improvements in the femoris muscle's thickness, echo intensity for the rectus femoris (index of muscle quality), and the five times sit-to-stand test compared to that of the Sed and PL group; the echo intensity in the RT and Dio group further improved compared to those in the Sed and Dio, and RT and PL groups (p < 0.05). The circulating levels of C1q (a potential biomarker of muscle fibrosis) in the RT and Dio group were significantly lower than those in the Sed and PL, and Sed and Dio groups (p < 0.05). Chronic Dioscorea esculenta intake combined with low-intensity resistance exercise may more effectively improve muscle quantity and quality indices in healthy middle-aged and older adults.

Structure-function of DHEA binding proteins

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA) and its sulfated metabolite DHEA-S are the most abundant circulating steroids and are precursors for active sex steroid hormones, estradiol and testosterone. DHEA has a broad range of reported effects in the central nervous system (CNS), cardiovascular system, adipose tissue, kidney, liver, and in the reproductive system. The mechanisms by which DHEA and DHEA-S initiate their biological effects are diverse. DHEA and DHEA-S may directly bind to plasma membrane (PM) receptors, including a DHEA-specific, G-protein coupled receptor (GPCR) in endothelial cells; various neuroreceptors, e.g., aminobutyric-acid-type A (GABA(A)), N-methyl-d-aspartate (NMDA) and sigma-1 (S1R) receptors (NMDAR and SIG-1R). DHEA and DHEA-S directly bind the nuclear androgen and estrogen receptors (AR, ERα, or ERβ) although with significantly lower binding affinities compared to the steroid hormones, e.g., testosterone, dihydrotestosterone, and estradiol, which are the cognate ligands for AR and ERs. Thus, extra-gonadal metabolism of DHEA to the sex hormones must be considered for many of the biological benefits of DHEA. DHEA also actives GPER1 (G protein coupled estrogen receptor 1). DHEA activates constitutive androstane receptor CAR (CAR) and proliferator activated receptor (PPARα) by indirect dephosphorylation. DHEA affects voltage-gated sodium and calcium ion channels and DHEA-2 activates TRPM3 (Transient Receptor Potential Cation Channel Subfamily M Member 3). This chapter updates our previous 2018 review pertaining to the physiological, biochemical, and molecular mechanisms of DHEA and DHEA-S activity.

Generation of Functional Immortalized Human Corneal Stromal Stem Cells

In addition to their therapeutic potential in regenerative medicine, human corneal stromal stem cells (CSSCs) could serve as a powerful tool for drug discovery and development. Variations from different donors, their isolation method, and their limited life span in culture hinder the utility of primary human CSSCs. To address these limitations, this study aims to establish and characterize immortalized CSSC lines (imCSSC) generated from primary human CSSCs. Primary CSSCs (pCSSC), isolated from human adult corneoscleral tissue, were transduced with ectopic expression of hTERT, c-MYC, or the large T antigen of the Simian virus 40 (SV40T) to generate imCSSC. Cellular morphology, proliferation capacity, and expression of CSSCs specific surface markers were investigated in all cell lines, including TNFAIP6 gene expression levels in vitro, a known biomarker of in vivo anti-inflammatory efficacy. SV40T-overexpressing imCSSC successfully extended the lifespan of pCSSC while retaining a similar morphology, proliferative capacity, multilineage differentiation potential, and anti-inflammatory properties. The current study serves as a proof-of-concept that immortalization of CSSCs could enable a large-scale source of CSSC for use in regenerative medicine.

Dehydroepiandrosterone status and efficacy of dehydroepiandrosterone supplementation for bone health in anorexia nervosa: A systematic review and meta-analysis

OBJECTIVE

This study was designed to determine the status of dehydroepiandrosterone (DHEA) in women with anorexia nervosa (AN) and to assess the efficacy of DHEA supplementation as a treatment for bone health in women with AN.

METHOD

Studies were retrieved from the PubMed, Embase, Cochrane Library, MEDLINE, and Scopus databases from inception to February 14, 2022. Observational studies that compared serum DHEA levels between women with AN and healthy controls were included for meta-analysis, and randomized controlled trials (RCTs) that evaluated the effects of DHEA supplementation on bone mass were reviewed.

RESULTS

Meta-analysis of 15 cross-sectional studies revealed that patients with AN had significantly elevated serum DHEA levels (mean difference (MD) = 311.63 ng/dl; 95% confidence interval (CI), 78.01-545.25) and reduced DHEAS levels (MD = -24.90 μg/dl; 95% CI, -41.72 to -8.07) compared with healthy controls. A systematic review of seven RCTs found that DHEA monotherapy does not improve bone mineral density (BMD) compared with placebo after adjusting for weight gain. While the combination of DHEA and conjugated oral contraceptives has led to increased bone strength and decreased bone loss, the beneficial effect appears to be limited to older adolescents and adults with closed physes. Potential detrimental effects on BMD were identified in younger adolescents with open physes in one study.

DISCUSSION

Due to the lack of apparent benefit of DHEA in women with AN and its potential detrimental effect on BMD in young patients with AN, current evidence does not support the use of DHEA.

PUBLIC SIGNIFICANCE

This study demonstrates that women with anorexia nervosa have abnormal levels of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS), which have been suggested by previous studies to play a role in the development of low bone density in this condition. However, current evidence does not support the use of DHEA as a treatment to preserve bone health in patients with anorexia nervosa given the lack of clear benefit following its use and also because of a potential detrimental effect on bone mineral density in young patients with anorexia nervosa.

Generation of Mesenchymal Cell Lines Derived from Aged Donors

Background: Mesenchymal stromal cells (MSCs) have the capacity for self-renewal and multi-differentiation, and for this reason they are considered a potential cellular source in regenerative medicine of cartilage and bone. However, research on this field is impaired by the predisposition of primary MSCs to senescence during culture expansion. Therefore, the aim of this study was to generate and characterize immortalized MSC (iMSC) lines from aged donors. Methods: Primary MSCs were immortalized by transduction of simian virus 40 large T antigen (SV40LT) and human telomerase reverse transcriptase (hTERT). Proliferation, senescence, phenotype and multi-differentiation potential of the resulting iMSC lines were analyzed. Results: MSCs proliferate faster than primary MSCs, overcome senescence and are phenotypically similar to primary MSCs. Nevertheless, their multi-differentiation potential is unbalanced towards the osteogenic lineage. There are no clear differences between osteoarthritis (OA) and non-OA iMSCs in terms of proliferation, senescence, phenotype or differentiation potential. Conclusions: Primary MSCs obtained from elderly patients can be immortalized by transduction of SV40LT and hTERT. The high osteogenic potential of iMSCs converts them into an excellent cellular source to take part in in vitro models to study bone tissue engineering.

TMT-Based Proteomic Explores the Influence of DHEA on the Osteogenic Differentiation of hBMSCs

Dehydroepiandrosterone (DHEA) has been revealed to implicate in facilitating osteoblast differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and inhibiting osteoporosis (OP). However, the underlying molecular mechanism remains largely unknown. Here, we induced osteogenic differentiation of hBMSCs derived from elders using an osteogenic induction medium with or without DHEA. The results showed that osteogenic induction medium (OIM) with DHEA could significantly promote the proliferation and osteogenic differentiation of hBMSCs than OIM alone. By using a Tandem Mass Tag (TMT) labeling and liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology, we screened out 604 differentially expressed proteins (DEPs) with at least one unique peptide were identified [524: OIM vs. complete medium (CM), and 547: OIM+DHEA vs. CM], among these proteins, 467 DEPs were shared in these two different comparative groups. Bioinformatic analysis revealed these DEPs are mainly enriched in metabolic pathways. Interestingly, the expression levels of the DEPs in the metabolic pathways showed a more noticeable change in the OIM+DHEA vs. CM group than OIM vs. CM group. Moreover, the protein-protein interaction (PPI) network analysis revealed that three potential proteins, ATP5B, MT-CYB, and MT-ATP6, involved in energy metabolism, might play a key role in osteogenic differentiation induced by OIM+DHEA. These findings offer a valuable clue for us to better understand the underlying mechanisms involved in osteoblast differentiation of hBMSCs caused by DHEA and assist in applying DHEA in hBMSCs-based therapy for osteogenic regeneration.

Association of urinary free cortisol with bone formation in patients with mild autonomous cortisol secretion

CONTEXT

Mild autonomous cortisol secretion (ACS) is associated with an increased risk of vertebral fractures (VFx). However, the influence of this condition on bone turnover or its association with mild ACS is still controversial.

OBJECTIVE

This study aimed to evaluate the impact of mild ACS on bone quality among patients living with the disease.

DESIGN AND SETTING

A retrospective study was conducted using data from 55 mild ACS and 12 nonfunctioning adrenal tumour (NFT) patients who visited Chiba University Hospital, Japan, from 2006 to 2018.

PATIENTS AND MAIN OUTCOME MEASURES

We analysed clinical features and bone-related factors, including bone mineral density (BMD) and VFx, performed blood tests to assess bone metabolism markers in patients with mild ACS and NFT, and assessed the associations between bone-related markers and endocrinological parameters in patients with mild ACS.

RESULTS

No significant differences between mild ACS and NFT patients were observed with respect to the presence or absence of VFx and BMD. Urinary free cortisol (UFC) was higher in mild ACS patients with VFx than those without (p = .037). The T-score and young adult mean (YAM) of the BMD of the femoral neck in mild ACS patients with a body mass index <25 were positively correlated with dehydroepiandrosterone sulphate levels (ρ: 0.42, p = .017; ρ: 0.40, p = .024, respectively). Pearson's correlation analysis showed that bone-specific alkaline phosphatase was negatively correlated with UFC in the patients with mild ACS (ρ: -0.37, p = .026).

CONCLUSIONS

These results suggest that urinary free cortisol may be useful for predicting bone formation in mild ACS patients.

DHEA inhibits proliferation, migration and alters mesenchymal-epithelial transition proteins through the PI3K/Akt pathway in MDA-MB-231 cells

Cancer is one of the leading causes of death worldwide, and breast cancer is the most common among women. Dehydroepiandrosterone (DHEA), the most abundant steroid hormone in human serum, inhibits proliferation and migration of breast cancer cells, modulating the expression of proteins involved in mesenchymal-epithelial transition (MET). However, the underlying molecular mechanisms are not fully understood. DHEA effects on the triple-negative breast cancer cell line MDA-MB-231 (mesenchymal stem-like) could be exerted by binding to receptors tyrosine kinase (RTKs) and signaling through MEK/ERK and/or PI3K/Akt pathways. In this study, MDA-MB-231 cells were exposed to DHEA in the presence of pharmacological inhibitors of these pathways and a siRNA against PIK3CA gene, which blocks PI3K pathway. Cell proliferation was measured by crystal violet staining, migration by the wound healing and transwell assays, and MET protein expression by western blot. A xenograft tumor growth in nude mice (nu^-/nu^-) using a siRNA against PI3K was also performed. Results showed that neither of the inhibitors used reverted the antiproliferative activity of DHEA. However, wortmannin and LY294002, inhibitors of the PI3K/Akt pathway, abolished the up- and down-regulation of E- and N-cadherin expression respectively, and inhibition of migration induced by DHEA in MDA-MB-231 cells. The siRNA that blocks the PI3K pathway, abolished the effects of DHEA on proliferation, migration, MET proteins expression and the growth of tumors in nude mice. In conclusion, these results suggest that PI3K/Akt pathway participates in the effects of DHEA on breast cancer cells.

Effects of Dioscorea esculenta intake with resistance training on muscle hypertrophy and strength in sprint athletes

Androgen hormones are important compounds related to body composition and exercise performance in athletes. The intake of Dioscorea esculenta, known as lesser yam, contains diosgenin and resistance training have been shown to normalize the secretion of androgen hormones. This study aimed to clarify the level of androgen hormone secretion and the effects of Dioscorea esculenta intake with resistance training on muscle hypertrophy and strength in athletes. First, in a cross-sectional study, we compared the serum androgen hormone [dehydroepiandrosterone (DHEA), testosterone, and 5α-dihydrotestosterone (DHT)] levels between sprint athletes (n = 15) and non-athletes (n = 15). Second, in an 8-week intervention study, sprint athletes were randomly divided into 2 groups: resistance training with placebo (n = 8) or with Dioscorea esculenta (2,000 mg/day) intake (n = 7). The serum DHEA, free testosterone, and DHT levels were lower in athletes than in non-athletes. Dioscorea esculenta intake combined with resistance training increased the arm fat-free mass, the 1 repetition maximum of deadlift and snatch, and the serum DHEA, free testosterone, and DHT levels, compared with resistance training and placebo intake. The results suggested that Dioscorea esculenta intake combined with resistance training has further effects on muscle hypertrophy and strength in athletes by restoring secretion of androgen hormones.

DHEA in bone: the role in osteoporosis and fracture healing

Dehydroepiandrosterone (DHEA) is a metabolic intermediate in the biosynthesis of estrogens and androgens with a past clouded in controversy and bold claims. It was once touted as a wonder drug, a fountain of youth that could cure all ailments. However, in the 1980s DHEA was banned by the FDA given a lack of documented health benefits and long-term use data. DHEA had a revival in 1994 when it was released for open market sale as a nutritional supplement under the Dietary Supplement Health and Safety Act. Since that time, there has been encouraging research on the hormone, including randomized controlled trials and subsequent meta-analyses on various conditions that DHEA may benefit. Bone health has been of particular interest, as many of the metabolites of DHEA are known to be involved in bone homeostasis, specifically estrogen and testosterone. Studies demonstrate a significant association between DHEA and increased bone mineral density, likely due to DHEA's ability to increase osteoblast activity and insulin like growth factor 1 (IGF-1) expression. Interestingly, IGF-1 is also known to improve fracture healing, though DHEA, a potent stimulator of IGF-1, has never been tested in this scenario. The aim of this review is to discuss the history and mechanisms of DHEA as they relate to the skeletal system, and to evaluate if DHEA has any role in treating fractures.

Fibroblast growth factor 23 counters vitamin D metabolism and action in human mesenchymal stem cells

Chronic kidney disease (CKD) is associated with elevated circulating fibroblast growth factor 23 (FGF23), impaired renal biosynthesis of 1α,25-dihydroxyvitamin D (1α,25(OH)₂D), low bone mass, and increased fracture risk. Our previous data with human mesenchymal stem cells (hMSCs) indicated that vitamin D metabolism in hMSCs is regulated as it is in the kidney and promotes osteoblastogenesis in an autocrine/paracrine manner. In this study, we tested the hypothesis that FGF23 inhibits vitamin D metabolism and action in hMSCs. hMSCs were isolated from discarded marrow during hip arthroplasty, including two subjects receiving hemodialysis and a series of 20 subjects (aged 49-83 years) with estimated glomerular filtration rate (eGFR) data. The direct in vitro effects of rhFGF23 on hMSCs were analyzed by RT-PCR, Western immunoblot, and biochemical assays. Ex vivo analyses showed positive correlations for both secreted and membrane-bound αKlotho gene expression in hMSCs with eGFR of the subjects from whom hMSCs were isolated. There was downregulated constitutive expression of αKlotho, but not FGFR1 in hMSCs obtained from two hemodialysis subjects. In vitro, rhFGF23 countered vitamin D-stimulated osteoblast differentiation of hMSCs by reducing the vitamin D receptor, CYP27B1/1α-hydroxylase, biosynthesis of 1α,25(OH)₂D₃, and signaling through BMP-7. These data demonstrate that dysregulated vitamin D metabolism in hMSCs may contribute to impaired osteoblastogenesis and altered bone and mineral metabolism in CKD subjects due to elevated FGF23. This supports the importance of intracellular vitamin D metabolism in autocrine/paracrine regulation of osteoblast differentiation in hMSCs.

Iron Overload Associated Endocrine Dysfunction Leading to Lower Bone Mineral Density in Thalassemia Major

CONTEXT

Patients with thalassemia major (TM) have a lower bone mineral density (BMD) and higher risk of fracture than the general population. The possible mechanisms include anemia, iron overload, malnutrition, and hormonal deficiency, but these have not been thoroughly investigated.

OBJECTIVE

To identify major mineral and hormonal factors related to BMD in adult TM patients to provide human evidence for the proposed mechanisms.

DESIGN

Retrospective study.

SETTING

Referral center.

PATIENTS

Twenty-nine patients with β-TM, aged 23 to 44 years who were followed-up during 2017 to 2018 were enrolled.

OUTCOME MEASUREMENTS

Endocrine profiles, including thyroid, parathyroid, and pituitary function, glucose, vitamin D, calcium, phosphate, and fibroblast growth factor 23 (FGF23) were obtained. The relationships among the above parameters, body height, fractures, and BMD were analyzed.

RESULTS

Abnormal BMD was observed in 42.9% of women and 23.1% of men. The mean final heights of women and men were 3.7 cm and 7.3 cm lower than the mean expected values, respectively. Fracture history was recorded in 26.7% of women and 35.7% of men. BMD was negatively correlated with parathyroid hormone, FGF23, thyrotropin, and glycated hemoglobin (HbA1c) levels, and positively correlated with testosterone, IGF-1, and corticotropin levels (all P < .05). Moreover, hypothyroidism was associated with lower BMD in both the lumbar spine (P = .024) and the femoral neck (P = .004). Patients with hypothyroidism had a higher percentage of abnormal BMD (P = .016).

CONCLUSION

Hypothyroidism, higher HbA1c, and lower adrenocorticotropin were predictors of abnormal BMD in patients with β-TM. Whether the correction of these factors improves BMD warrants further research.

Dehydroepiandrosterone (DHEA) and its Sulphate (DHEAS) in Alzheimer's Disease

BACKGROUND

Neurosteroids Dehydroepiandrosterone (DHEA) and Dehydroepiandrosterone Sulphate (DHEAS) are involved in many important brain functions, including neuronal plasticity and survival, cognition and behavior, demonstrating preventive and therapeutic potential in different neuropsychiatric and neurodegenerative disorders, including Alzheimer's disease.

OBJECTIVE

The aim of the article was to provide a comprehensive overview of the literature on the involvement of DHEA and DHEAS in Alzheimer's disease.

METHODS

PubMed and MEDLINE databases were searched for relevant literature. The articles were selected considering their titles and abstracts. In the selected full texts, lists of references were searched manually for additional articles.

RESULTS

We performed a systematic review of the studies investigating the role of DHEA and DHEAS in various in vitro and animal models, as well as in patients with Alzheimer's disease, and provided a comprehensive discussion on their potential preventive and therapeutic applications.

CONCLUSION

Despite mixed results, the findings of various preclinical studies are generally supportive of the involvement of DHEA and DHEAS in the pathophysiology of Alzheimer's disease, showing some promise for potential benefits of these neurosteroids in the prevention and treatment. However, so far small clinical trials brought little evidence to support their therapy in AD. Therefore, large-scale human studies are needed to elucidate the specific effects of DHEA and DHEAS and their mechanisms of action, prior to their applications in clinical practice.

Usefulness of Mesenchymal Cell Lines for Bone and Cartilage Regeneration Research

The unavailability of sufficient numbers of human primary cells is a major roadblock for in vitro repair of bone and/or cartilage, and for performing disease modelling experiments. Immortalized mesenchymal stromal cells (iMSCs) may be employed as a research tool for avoiding these problems. The purpose of this review was to revise the available literature on the characteristics of the iMSC lines, paying special attention to the maintenance of the phenotype of the primary cells from which they were derived, and whether they are effectively useful for in vitro disease modeling and cell therapy purposes. This review was performed by searching on Web of Science, Scopus, and PubMed databases from 1 January 2015 to 30 September 2019. The keywords used were ALL = (mesenchymal AND ("cell line" OR immortal*) AND (cartilage OR chondrogenesis OR bone OR osteogenesis) AND human). Only original research studies in which a human iMSC line was employed for osteogenesis or chondrogenesis experiments were included. After describing the success of the immortalization protocol, we focused on the iMSCs maintenance of the parental phenotype and multipotency. According to the literature revised, it seems that the maintenance of these characteristics is not guaranteed by immortalization, and that careful selection and validation of clones with particular characteristics is necessary for taking advantage of the full potential of iMSC to be employed in bone and cartilage-related research.

Mechanisms of Action of Dehydroepiandrosterone

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA) and its sulfated metabolite DHEA-S are the most abundant steroids in circulation and decline with age. Rodent studies have shown that DHEA has a wide variety of effects on liver, kidney, adipose, reproductive tissues, and central nervous system/neuronal function. The mechanisms by which DHEA and DHEA-S impart their physiological effects may be direct actions on plasma membrane receptors, including a DHEA-specific, G-protein-coupled receptor in endothelial cells; various neuroreceptors, e.g., aminobutyric-acid-type A, N-methyl-d-aspartate (NMDA), and sigma-1 (S1R) receptors; by binding steroid receptors: androgen and estrogen receptors (ARs, ERα, or ERβ); or by their metabolism to more potent sex steroid hormones, e.g., testosterone, dihydrotestosterone, and estradiol, which bind with higher affinity to ARs and ERs. DHEA inhibits voltage-gated T-type calcium channels. DHEA activates peroxisome proliferator-activated receptor (PPARα) and CAR by a mechanism apparently involving PP2A, a protein phosphatase dephosphorylating PPARα and CAR to activate their transcriptional activity. We review our recent study showing DHEA activated GPER1 (G-protein-coupled estrogen receptor 1) in HepG2 cells to stimulate miR-21 transcription. This chapter reviews some of the physiological, biochemical, and molecular mechanisms of DHEA and DHEA-S activity.

Synergistic effect of 1α,25-dihydroxyvitamin D3 and 17β-estradiol on osteoblast differentiation of pediatric MSCs

Vitamin D is essential for mineral homeostasis and contributes to bone metabolism by stimulating osteoblast differentiation of marrow stromal cells (MSCs). In this study, we used MSCs from pre-pubertal girls and boys to test the hypothesis that 1α,25(OH)₂D and 17β-estradiol have synergistic effects on these MSCs, and what mechanism is involved. With IRB approval, we isolated MSCs from discarded excess iliac marrow graft from children undergoing alveolar cleft repair. Plasma was available from 8 female (9.3±0.2years) and 8 male (9.6±0.1years) subjects for hormone assays [25(OH)D, total testosterone, 17β-estradiol, estrone, DHEA-S, Growth Hormone, IGF-I]. RT-PCR was used for gene expression. Alkaline phosphatase (ALP) activity was used to measure osteoblast differentiation at day 7; alizarin red was used to measure matrix mineralization at day 21. All subjects were pre-pubertal based on their hormone levels. Serum 25(OH)D levels ranged from 13.1 to 26.4ng/mL, with 75% below 20ng/mL. Constitutive gene expression of VDR and ERα, β varied from subject to subject with no association with sex or serum chemistries. In osteoblastogenic medium, 1α,25(OH)₂D₃ (10nM) increased ALP activity by 36% (p<0.05) in MSCs; 10nM of E2 was not stimulatory but the combination of 1α,25(OH)₂D₃ and E2 increased ALP 151% (p<0.05 vs. control) and by 84.5% (p<0.05 vs. 1α,25(OH)₂D3 alone). The combination of 1α,25(OH)₂D₃ and E2 significantly increased mineralization 11-fold, compared with either agent alone. Twenty-four hour treatment with 1α,25(OH)₂D₃ (10nM) or E2 (10nM) upregulated each other's receptor by as much as 5.8-fold for ERα and 2.9-fold for the VDR. In summary, 1α,25(OH)₂D3 stimulated osteoblast differentiation and matrix mineralization with MSCs from pre-pubertal subjects, with a synergistic effect of E2, mediated by upregulated receptor levels, at least in part. These studies add new information about the regulation of human osteoblast differentiation, effects of 1α,25(OH)₂D₃ and E2 on MSCs, and the importance of vitamin D for skeletal health.

Dehydroepiandrosterone and Bone

In humans, dehydroepiandrosterone (DHEA), secreted mainly from the adrenal cortex, and its sulfate ester, DHEAS, are the most abundant circulating steroids. DHEA/DHEAS possess pleiotropic effects in human aging, bone, metabolic diseases, neurologic function/neurodegenerative diseases, cancer, immune system and disorders, cardiovascular diseases, diabetes, muscle function, sexual dysfunction, and other health conditions. The age-related reduced levels of DHEA and DHEAS are associated with bone mineral density measures of osteopenia and osteoporosis. Clinical, epidemiological, and experimental studies indicate that DHEA replacement therapy may be beneficial for bone health through its inhibition of skeletal catabolic IL-6 and stimulation of osteoanabolic IGF-I-mediated mechanisms. Studies with primary cultures of human bone marrow-derived mesenchymal stem cells (hMSCs) were used to show that DHEA stimulates osteoblastogenesis. The in vitro stimulation of both osteoblastogenesis and IGF-I gene expression by DHEA in hMSCs requires IGF-I receptor, PI3K, p38 MAPK, or p42/44 MAPK signaling pathways. The in vitro inhibition of IL-6 secretion in hMSCs by DHEA was more consistent and extensive than by estradiol or dihydrotestosterone. In summary, evidence from us and others indicates that DHEA may be useful for treating bone diseases through its inhibition of skeletal catabolic IL-6 and stimulation of anabolic IGF-I-mediated mechanisms.

Inhibition of Osteoblast Function by Brucella abortus is Reversed by Dehydroepiandrosterone and Involves ERK1/2 and Estrogen Receptor

Brucella abortus induces an inflammatory response that stimulates the endocrine system resulting in the secretion of cortisol and dehydroepiandrosterone (DHEA). Osteoarticular brucellosis is the most common presentation of the active disease in humans, and we have previously demonstrated that B. abortus infection inhibits osteoblast function. We aimed to evaluate the role of cortisol and DHEA on osteoblast during B. abortus infection. B. abortus infection induces apoptosis and inhibits osteoblast function. DHEA treatment reversed the effect of B. abortus infection on osteoblast by increasing their proliferation, inhibiting osteoblast apoptosis, and reversing the inhibitory effect of B. abortus on osteoblast differentiation and function. By contrast, cortisol increased the effect of B. abortus infection. Cortisol regulates target genes by binding to the glucocorticoid receptor (GR). B. abortus infection inhibited GRα expression. Cell responses to cortisol not only depend on GR expression but also on its intracellular bioavailability, that is, dependent on the activity of the isoenzymes 11β-hydroxysteroid dehydrogenase (HSD) type-1, 11β-HSD2 (which convert cortisone to cortisol and vice versa, respectively). Alterations in the expression of these isoenzymes in bone cells are associated with bone loss. B. abortus infection increased 11β-HSD1 expression but had no effect on 11β-HSD2. DHEA reversed the inhibitory effect induced by B. abortus infection on osteoblast matrix deposition in an estrogen receptor- and ERK1/2-dependent manner. We conclude that DHEA intervention improves osteoblast function during B. abortus infection making it a potential candidate to ameliorate the osteoarticular symptoms of brucellosis.

Chronic kidney disease and vitamin D metabolism in human bone marrow-derived MSCs

Vitamin D that is synthesized in the skin or is ingested undergoes sequential steps of metabolic activation via a cascade of cytochrome P450 enzymatic hydroxylations in the liver and kidney to produce 1α,25-dihydroxyvitamin D (1α,25(OH)2 D). There are many tissues that are able to synthesize 1α,25(OH)2 D, but the biological significance of extrarenal hydroxylases is unresolved. Human marrow-derived mesenchymal stem cells (marrow stromal cells, hMSCs) give rise to osteoblasts, and their differentiation is stimulated by 1α,25(OH)2 D. In addition to being targets of 1α,25(OH)2 D, hMSCs can synthesize it; on the basis of those observations, we further examined the local autocrine/paracrine role of vitamin D metabolism in osteoblast differentiation. Research with hMSCs from well-characterized subjects provides an innovative opportunity to evaluate the effects of clinical attributes on the regulation of hMSCs. Like the renal 1α-hydroxylase, the enzyme in hMSCs is constitutively decreased with age and chronic kidney disease (CKD); both are regulated by PTH1-34, insulin-like growth factor 1, calcium, 1α,25(OH)2 D, 25(OH)D, and fibroblast growth factor 23. CKD is associated with impaired renal biosynthesis of 1α,25(OH)2 D, low bone mass, and increased fracture risk. Studies with hMSCs from CKD patients or aged subjects indicate that circulating 25(OH)D may have an important role in osteoblast differentiation on vitamin D metabolism and action in hMSCs.

The Association between Dehydroepiandrosterone Sulfate (DHEA-S) and Bone Mineral Density in Korean Men and Women

Background

The relationship between dehydroepiandrosterone sulfate (DHEA-S) and bone mineral density (BMD) is controversial. And findings of most studies that have investigated this relationship are restricted to postmenopausal women. In this study, we investigated the relationship between serum DHEA-S and BMD in both men and women.

Methods

This cross-sectional study evaluated a total of 294 healthy Korean participants through a medical examination program. And a subgroup of 154 participants was subjected to a longitudinal analysis. We measured BMD by dual energy X-ray absorptiometry and assayed DHEA-S by a chemiluminescent immunoassay.

Results

We evaluated the association between serum DHEA-S concentration and BMD at the femur trochanter after adjusting for cofounders such as age, body mass index, lifestyle factors, serum cortisol level, serum insulin-like growth factor 1 (IGF-1) level, and sex. Through our longitudinal study, we found that the changes in BMD at the total spine, at the femur neck, and at the femur trochanter were all smaller in the ΔDHEA-S <0 group than in the ΔDHEA-S >0 group.

Conclusions

We found that there was a positive correlation between serum DHEA-S and femur BMD, which suggests that controlling serum DHEA-S levels may retard age-related BMD reduction in Koreans.

Novel mechanisms for DHEA action

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA), secreted by the adrenal cortex, gastrointestinal tract, gonads, and brain, and its sulfated metabolite DHEA-S are the most abundant endogeneous circulating steroid hormones. DHEA actions are classically associated with age-related changes in cardiovascular tissues, female fertility, metabolism, and neuronal/CNS functions. Early work on DHEA action focused on the metabolism to more potent sex hormones, testosterone and estradiol, and the subsequent effect on the activation of the androgen and estrogen steroid receptors. However, it is now clear that DHEA and DHEA-S act directly as ligands for many hepatic nuclear receptors and G-protein-coupled receptors. In addition, it can function to mediate acute cell signaling pathways. This review summarizes the molecular mechanisms by which DHEA acts in cells and animal models with a focus on the 'novel' and physiological modes of DHEA action.