Dehydroepiandrosterone inhibits intracellular calcium release in beta-cells by a plasma membrane-dependent mechanism

Steroids, steroid associated substances and gestational diabetes mellitus

As gestational diabetes mellitus (GDM) is both a frequent and serious complication, steroid levels in pregnancy are extremely elevated and their role in pregnancy is crucial, this review focuses on the role of steroids and related substances in the GDM pathophysiology. Low SHBG levels are associated with insulin resistance and hyperinsulinemia, while also predicting a predisposition to GDM. Other relevant agents are placental hormones such as kisspeptin and CRH, playing also an important role beyond pregnancy, but which are synthesized here in smaller amounts in the hypothalamus. These hormones affect both the course of pregnancy as well as the synthesis of pregnancy steroids and may also be involved in the GDM pathophysiology. Steroids, whose biosynthesis is mainly provided by the fetal adrenal glands, placenta, maternal adrenal glands, and both maternal and fetal livers, are also synthesized in limited amounts directly in the pancreas and may influence the development of GDM. These substances involve the sulfated Δ5 steroids primarily acting via modulating different ion channels and influencing the development of GDM in different directions, mostly diabetogenic progesterone and predominantly anti-diabetic estradiol acting both in genomic and non-genomic way, androgens associated with IR and hyperinsulinemia, neuroactive steroids affecting the pituitary functioning, and cortisol whose production is stimulated by CRH but which suppresses its pro-inflammatory effects. Due to the complex actions of steroids, studies assessing their predominant effect and studies assessing their predictive values for estimating predisposition to GDM are needed.

Dehydroepiandrosterone on metabolism and the cardiovascular system in the postmenopausal period

Dehydroepiandrosterone (DHEA), mostly present as its sulfated ester (DHEA-S), is an anabolic hormone that naturally declines with age. Furthermore, it is the most abundant androgen and estrogen precursor in humans. Low plasma levels of DHEA have been strongly associated with obesity, insulin resistance, dyslipidemia, and high blood pressure, increasing the risk of cardiovascular disease. In this respect, DHEA could be regarded as a promising agent against metabolic syndrome (MetS) in postmenopausal women, since several age-related metabolic diseases are reported during aging. There are plenty of experimental evidences showing beneficial effects after DHEA therapy on carbohydrate and lipid metabolism, as well as cardiovascular health. However, its potential as a therapeutic agent appears to attract controversy, due to the lack of effects on some symptoms related to MetS. In this review, we examine the available literature regarding the impact of DHEA therapy on adiposity, glucose metabolism, and the cardiovascular system in the postmenopausal period. Both clinical studies and in vitro and in vivo experimental models were selected, and where possible, the main cellular mechanisms involved in DHEA therapy were discussed. Schematic representation showing some of the general effects observed after administration DHEA therapy on target tissues of energy metabolism and the cardiovascular system. ↑ represents an increase, ↓ represents a decrease, - represents a worsening and ↔ represents no change after DHEA therapy.

Role of Androgens in Female Genitourinary Tissue Structure and Function: Implications in the Genitourinary Syndrome of Menopause

INTRODUCTION

Genitourinary conditions in women increase in prevalence with age. Androgens are prerequisite hormones of estrogen biosynthesis, are produced in larger amounts than estrogens in women, and decrease throughout adulthood. However, research and treatment for genitourinary complaints have traditionally focused on estrogens to the exclusion of other potential hormonal influences.

AIM

To summarize and evaluate the evidence that androgens are important for maintaining genitourinary health in women and that lack of androgenic activity can contribute to the development of symptoms of the genitourinary syndrome of menopause.

METHODS

The role of androgens in the pathophysiology, diagnosis, and treatment of genitourinary syndrome of menopause was discussed by an international and multidisciplinary panel during a consensus conference organized by the International Society for the Study of Women's Sexual Health. A subgroup further examined publications from the PubMed database, giving preference to clinical studies or to basic science studies in human tissues.

MAIN OUTCOME MEASURES

Expert opinion evaluating trophic and functional effects of androgens, their differences from estrogenic effects, and regulation of androgen and estrogen receptor expression in female genitourinary tissues.

RESULTS

Androgen receptors have been detected throughout the genitourinary system using immunohistochemical, western blot, ligand binding, and gene expression analyses. Lower circulating testosterone and estradiol concentrations and various genitourinary conditions have been associated with differential expression of androgen and estrogen receptors. Supplementation of androgen and/or estrogen in postmenopausal women (local administration) or in ovariectomized animals (systemic administration) induces tissue-specific responses that include changes in androgen and estrogen receptor expression, cell growth, mucin production, collagen turnover, increased perfusion, and neurotransmitter synthesis.

CONCLUSION

Androgens contribute to the maintenance of genitourinary tissue structure and function. The effects of androgens can be distinct from those of estrogens or can complement estrogenic action. Androgen-mediated processes might be involved in the full or partial resolution of genitourinary syndrome of menopause symptoms in women. Traish AM, Vignozzi L, Simon JA, et al. Role of Androgens in Female Genitourinary Tissue Structure and Function: Implications in the Genitourinary Syndrome of Menopause. Sex Med Rev 2018;6:558-571.

Dehydroepiandrosterone-sulfate (DHEAS) promotes MIN6 cells insulin secretion via inhibition of AMP-activated protein kinase

Derived from adrenal cortical, dehydroepiandrosterone-sulfate (DHEAS) is a precursor to androgens and estrogens, with various bioactivities. Although it has the property of anti-diabetes, the long-term effect of DHEAS on insulin secretion in beta-cells is still unclear. In this study, the effect of DHEAS on the insulin secretion activity in MIN6 cell lines in vitro was assessed. Insulin biosynthesis and secretion were stimulated by DHEAS for 24h. DHEAS inhibited the AMPK activation and upregulated the expression of ACC-1. These findings indicate that DHEAS may exert prominent stimulatory effects on insulin secretion partly via AMPK inhibition and ACC-1 upregulation.

Adrenarche and middle childhood

Middle childhood, the period from 6 to 12 years of age, is defined socially by increasing autonomy and emotional regulation, somatically by the development of anatomical structures for subsistence, and endocrinologically by adrenarche, the adrenal production of dehydroepiandrosterone (DHEA). Here I suggest that DHEA plays a key role in the coordinated development of the brain and body beginning with middle childhood, via energetic allocation. I argue that with adrenarche, increasing levels of circulating DHEA act to down-regulate the release of glucose into circulation and hence limit the supply of glucose which is needed by the brain for synaptogenesis. Furthermore, I suggest the antioxidant properties of DHEA may be important in maintaining synaptic plasticity throughout middle childhood within slow-developing areas of the cortex, including the insula, thamalus, and anterior cingulate cortex. In addition, DHEA may play a role in the development of body odor as a reliable social signal of behavioral changes associated with middle childhood.

Dehydroepiandrosterone-induced phosphorylation and translocation of FoxO1 depend on the mineralocorticoid receptor

In humans, dehydroepiandrosterone (DHEA), with its sulfate, is the most abundant adrenal steroid, whereas the rat adrenals are not capable of synthesizing this steroid. Circulating concentrations of DHEA sulfate lie in the millimolar range and those of DHEA in the subnanomolar range. DHEA exerts protective potential during vascular remodeling, although the underlying mechanisms of this protection are imperfectly defined. We hypothesized that physiological doses of DHEA alter signaling pathways that are of central importance for vascular integrity. We exposed human endothelial cells, vascular smooth muscle cells, and fibroblasts to DHEA (10(-6) to 10(-10) mol/L) and observed a dose- and time-dependent increase of extracellular signal-regulated kinases 1 and 2 activation. Similar results were observed in rat vascular smooth muscle cells. In addition, in rat vascular smooth muscle cells, we found altered phosphorylation and cellular translocation of the transcription factor FoxO1. Pharmacological blockade of the mineralocorticoid receptor (MR) with eplerenone or small interfering RNA-mediated MR-silencing prevented DHEA-induced extracellular signal-regulated kinase 1/2 phosphorylation and its effects on FoxO1. Of note, in a cell-based MR transactivation assay, we did not find any agonist effect of DHEA on MR activity. We conclude that DHEA induces early signaling events in vascular cells that might underlie the DHEA-mediated protection against vasculopathies. These effects are dependent on the MR, although the finding that DHEA fails to act as a direct MR agonist suggests that additional signaling proteins are involved. In this regard, DHEA may either interact with coeffectors to modify MR activity or serves as a ligand for a yet unknown receptor that might transactivate the MR.

Sex steroids effects on the endocrine pancreas

The endocrine pancreas is central in the physiopathology of diabetes mellitus. Nutrients and hormones control endocrine pancreatic function and the secretion of insulin and other pancreatic islet hormones. Although the pancreas is not usually considered as a target of steroids, increasing evidence indicates that sex steroid hormones modify pancreatic islet function. The biological effects of steroid hormones are transduced by both, classical and non-classical steroid receptors that in turn produce slow genomic and rapid non-genomic responses. In this review, we focused on the effects of sex steroid hormones on endocrine pancreatic function, with special emphasis in animal studies.

Fasting-induced hepatic production of DHEA is regulated by PGC-1alpha, ERRalpha, and HNF4alpha

The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1alpha is involved in the coordinate induction of changes in gene expression in the liver that enable a homeostatic response to alterations in metabolic state, environmental cues, and nutrient availability. In exploring the specific pathways under PGC-1alpha regulation in the liver, we have made the surprising observation that this coactivator can induce the expression of CYP11A1 and CYP17A1, key rate-limiting enzymes involved in the initial steps of steroidogenesis. Both of these enzymes function to produce C(19)-steroids, converting cholesterol into pregnenolone, and then to dehydroepiandrosterone (DHEA). Estrogen-related receptor (ERR)-alpha mediates PGC-1alpha's induction of CYP11A1 and binds within the first intron of the CYP11A1 gene. Both ERR-alpha and hepatocyte nuclear factor-4alpha are required for PGC-1alpha-mediated induction of CYP17A1, and specific binding sites for these receptors have been identified in the regulatory regions of this gene. The potential physiological significance of these observations was highlighted in rats where fasting induced hepatic expression of PGC-1alpha and CYP17A1 and was associated with an increase in hepatic levels of DHEA. These data suggest that DHEA could be playing a role as an intracellular signaling molecule involved in modulating hepatic activity in response to fasting conditions.

Hydrocortisone treatment in girls with congenital adrenal hyperplasia inhibits serum dehydroepiandrosterone sulfate and affects the GH-IGF-I system

Sex hormones are modulators of the GH/ IGF-I system. We have hypothesized that the inhibition of DHEAS in treated girls with congenital adrenal hyperplasia (CAH) might affect this modulation. We analyzed serum IGF-I, IGFBP-3 and DHEAS in 17 prepubertal (Pp) and 32 pubertal (Pu) girls with CAH, under hydrocortisone replacement therapy, in the presence of normal (Gr1) or high (Gr2) serum testosterone (T) and androstenedione (A) levels. All groups had appropriate normal controls. Serum DHEAS in patients with CAH was significantly lower than in the respective controls (p < 0.04), except for Pp CAH Gr2. Serum IGF-I, but not serum IGFBP-3, in CAH subgroups was significantly higher than in the respective controls (p < 0.05), except for Pp CAH Gr2. It is concluded that glucocorticoid treatment of girls with CAH results in hypofunction of the adrenal zona reticularis. Low levels of serum DHEAS could be involved in the regulation of IGF-I biological response in target tissues. Additional studies are necessary to confirm these findings.

Dehydroepiandrosterone stimulates endothelial proliferation and angiogenesis through extracellular signal-regulated kinase 1/2-mediated mechanisms

Dehydroepiandrosterone (DHEA) activates a plasma membrane receptor on vascular endothelial cells and phosphorylates ERK 1/2. We hypothesize that ERK1/2-dependent vascular endothelial proliferation underlies part of the beneficial vascular effect of DHEA. DHEA (0.1-10 nm) activated ERK1/2 in bovine aortic endothelial cells (BAECs) by 15 min, causing nuclear translocation of phosphorylated ERK1/2 and phosphorylation of nuclear p90 ribosomal S6 kinase. ERK1/2 phosphorylation was dependent on plasma membrane-initiated activation of Gi/o proteins and the upstream MAPK kinase because the effect was seen with albumin-conjugated DHEA and was blocked by pertussis toxin or PD098059. A 15-min incubation of BAECs with 1 nm DHEA (or albumin-conjugated DHEA) increased endothelial proliferation by 30% at 24 h. This effect was not altered by inhibition of estrogen or androgen receptors or nitric oxide production. There was a similar effect of DHEA to increase endothelial migration. DHEA also increased the formation of primitive capillary tubes of BAECs in vitro in solubilized basement membrane. These rapid DHEA-induced effects were reversed by the inhibition of either Gi/o-proteins or ERK1/2. Additionally, DHEA enhanced angiogenesis in vivo in a chick embryo chorioallantoic membrane assay. These findings indicate that exposure to DHEA, at concentrations found in human blood, causes vascular endothelial proliferation by a plasma membrane-initiated activity that is Gi/o and ERK1/2 dependent. These data, along with previous findings, define an important vascular endothelial cell signaling pathway that is activated by DHEA and suggest that this steroid may play a role in vascular function.

New functional aspects of the neuroendocrine marker secretagogin based on the characterization of its rat homolog

Secretagogin is a recently cloned human beta-cell-expressed EF-hand Ca(2+)-binding protein. Converging evidence indicates that it exerts Ca(2+) sensor activity and is involved in regulation of insulin synthesis and secretion. To obtain a potent tool for the extension of its functional analysis in rat in vitro systems, we cloned the rat homolog of human secretagogin. Using comparative sequence analysis, immunostaining, and immunoblotting, we demonstrated a high degree of sequence homology and similar tissue expression patterns of human and rat secretagogin. Highest rat secretagogin expression levels were found in pancreatic beta-cells. On the basis of newly generated anti-rat secretagogin antibodies, we established a rat secretagogin-specific sandwich capture ELISA and demonstrated release of secretagogin from viable Rin-5F cells. Dexamethasone treatment of Rin-5F cells resulted in an increased secretagogin release rate, which was inversely correlated with insulin secretion. In contrast, the secretagogin transcription rate was markedly reduced. This resulted in a decreased intracellular secretagogin content under the influence of dexamethasone. Sucrose gradient cell fractionation analysis of Rin-5F cells confirmed the predominant cytosolic localization of secretagogin, with only limited association of secretagogin with insulin granules. The loss of intracellular secretagogin after dexamethasone treatment affected predominantly the insulin granule-associated secretagogin fractions. The sequence homology and the comparable tissue expression patterns of human and rat secretagogin indicate conserved intracellular functions. The effects of dexamethasone on the total secretagogin content in Rin-5F cells and on its intracellular distribution might result in an impaired Ca(2+) sensitivity of dexamethasone-treated insulin-secreting cells.