Effect of dehydroepiandrosterone on glucose uptake in cultured human fibroblasts

Pigment epithelium-derived factor (PEDF) represses the glucose transporter 1 (GLUT1) mRNA expression and may be a potential therapeutic agent in psoriasis: a case-control and experimental study

We investigated the whole blood GLUT1 mRNA expression and serum pigment epithelium-derived factor (PEDF), interleukin-6 (IL-6), fetuin-A, and pentraxin-3 (PTX3) levels in psoriatic patients and tested their correlations with the severity of psoriasis using the psoriasis area and severity index (PASI) score. Also, we tested the GLUT1 mRNA expression after an in vitro treatment of human skin fibroblast (HSF) cell lines with PEDF. The case-control part of the study recruited 74 participants (44 psoriatic patients and 30 healthy volunteers). Whole blood GLUT1 mRNA fold changes were estimated by RT-PCR, and serum PEDF, IL-6, fetuin-A, and PTX3 levels were measured by ELISA kits. In the experimental part, the HSF cell lines were treated with different concentrations of PEDF for different times to test its effect on the GLUT1 mRNA expression. The whole blood GLUT 1 expression significantly increased in psoriatic patients and correlated positively with serum IL-6, fetuin-A, PTX3 levels and with the severity of psoriasis while negatively with serum PEDF levels. The PEDF-treated HSF cell lines showed a time- and dose-dependent decline in the GLUT 1 mRNA expression. The whole blood GLUT 1 mRNA is a non-invasive biomarker that is associated with the severity of psoriasis. PEDF represses GLUT 1 expression and may be a potential therapeutic agent in psoriasis.Trial registration: ClinicalTrials.gov Identifier: NCT04242082.

Sex-specific effects of dehydroepiandrosterone (DHEA) on glucose metabolism in the CNS

DHEA is a neuroactive steroid, due to its modulatory actions on the central nervous system (CNS). DHEA is able to regulate neurogenesis, neurotransmitter receptors and neuronal excitability, function, survival and metabolism. The levels of DHEA decrease gradually with advancing age, and this decline has been associated with age related neuronal dysfunction and degeneration, suggesting a neuroprotective effect of endogenous DHEA. There are significant sex differences in the pathophysiology, epidemiology and clinical manifestations of many neurological diseases. The aim of this study was to determine whether DHEA can alter glucose metabolism in different structures of the CNS from male and female rats, and if this effect is sex-specific. The results showed that DHEA decreased glucose uptake in some structures (cerebral cortex and olfactory bulb) in males, but did not affect glucose uptake in females. When compared, glucose uptake in males was higher than females. DHEA enhanced the glucose oxidation in both males (cerebral cortex, olfactory bulb, hippocampus and hypothalamus) and females (cerebral cortex and olfactory bulb), in a sex-dependent manner. In males, DHEA did not affect synthesis of glycogen, however, glycogen content was increased in the cerebral cortex and olfactory bulb. DHEA modulates glucose metabolism in a tissue-, dose- and sex-dependent manner to increase glucose oxidation, which could explain the previously described neuroprotective role of this hormone in some neurodegenerative diseases.

Neurosteroid dehydroepiandrosterone enhances activity and trafficking of astrocytic GLT-1 via σ1 receptor-mediated PKC activation in the hippocampal dentate gyrus of rats

Neurosteroid dehydroepiandrosterone (DHEA) has been reported to exert a potent neuroprotective effect against glutamate-induced excitotoxicity. However, the underlying mechanism remains to be elucidated. One of the possible mechanisms may be an involvement of astrocytic glutamate transporter subtype-1 (GLT-1) that can quickly clear spilled glutamate at the synapse to prevent excitotoxicity. To examine the effect of DHEA on GLT-1 activity, we measured synaptically induced glial depolarization (SIGD) in the dentate gyrus (DG) of adult rats by applying an optical recording technique to the hippocampal slices stained with voltage-sensitive dye RH155. Bath-application of DHEA for 10 min dose-dependently increased SIGD without changing presynaptic glutamate releases, which was sensitive to the GLT-1 blocker DHK. Patch-clamp recordings in astrocytes showed that an application of 50 μM DHEA increased glutamate-evoked inward currents (Iglu) by approximately 1.5-fold, which was dependent on the GLT-1 activity. In addition, the level of biotinylated GLT-1 protein in the surface of astrocytes was significantly elevated by DHEA. The DHEA-increased SIGD, Iglu, and GLT-1 translocation to the cell surface were blocked by the σ₁ R antagonist NE100 and mimicked by the σ₁ R agonist PRE084. DHEA elevated the phosphorylation level of PKC in a σ₁ R-dependent manner. Furthermore, the PKC inhibitor chelerythrine could prevent the DHEA-increased SIGD, Iglu, and GLT-1 translocation. Collectively, present results suggest that DHEA enhances the activity and translocation to cell surface of astrocytic GLT-1 mainly via σ₁ R-mediated PKC cascade.

Long-Term Administration of Dehydroepiandrosterone Accelerates Glucose Catabolism via Activation of PI3K/Akt-PFK-2 Signaling Pathway in Rats Fed a High-Fat Diet

Dehydroepiandrosterone (DHEA) has a fat-reducing effect, while little information is available on whether DHEA regulates glucose metabolism, which would in turn affect fat deposition. To investigate the effects of DHEA on glucose metabolism, rats were administered a high-fat diet containing either 0 (HCG), 25 (HLG), 50 (HMG), or 100 (HHG) mg·kg^-1 DHEA per day via gavage for 8 weeks. Results showed that long-term administration of DHEA inhibited body weight gain in rats on a high-fat diet. No statistical differences in serum glucose levels were observed, whereas hepatic glycogen content in HMG and HHG groups and muscle glycogen content in HLG and HMG groups were higher than those in HCG group. Glucokinase, malate dehydrogenase and phosphofructokinase-2 activities in HMG and HHG groups, pyruvate kinase and succinate dehydrogenase activities in HMG group, and pyruvate dehydrogenase activity in all DHEA treatment groups were increased compared with those in HCG group. Phosphoenolpyruvate carboxykinase and glycogen phosphorylase mRNA levels were decreased in HMG and HHG groups, whereas glycogen synthase-2 mRNA level was increased in HMG group compared with those in HCG. The abundance of Glut2 mRNA in HMG and HHG groups and Glut4 mRNA in HMG group was higher than that in HCG group. DHEA treatment increased serum leptin content in HMG and HHG groups compared with that in HCG group. Serum insulin content and insulin receptor mRNA level in HMG group and insulin receptor substrate-2 mRNA level in HMG and HHG group were increased compared with those in HCG group. Furthermore, Pi3k mRNA level in HMG and Akt mRNA level in HMG and HHG groups were significantly increased than those in HCG group. These data showed that DHEA treatment could enhance glycogen storage and accelerate glucose catabolism in rats fed a high-fat diet, and this effect may be associated with the activation of PI3K/Akt-PFK-2 signaling pathway.

Effect of dehydroepiandrosterone on cell growth and mitochondrial function in TM-3 cells

Dehydroepiandrosterone (DHEA), a major steroid hormone, decreases with age, and this reduction has been shown to be associated with physical health. In the present study, the effect of DHEA on cell growth and mitochondrial function was investigated using TM-3 cells, a Leydig cell line. The growth of TM-3 cells exposed to 100 μM DHEA for 24h was inhibited due to cell cycle arrest, primarily in the S and G2/M phases, and this effect was caused by decreased activity of glucose-6-phosphate dehydrogenase (G6PD) and reduced expression of cyclinA and cyclinB mRNA. A novel finding was that DHEA improved TM-3 cell viability in a markedly time-dependent manner. Although no differences were observed in the configuration or number of TM-3 cell mitochondria following DHEA treatment, mitochondrial membrane permeability and the activity of succinate dehydrogenase (SDH) increased subsequent to 24h treatment of cells with 100 μM DHEA. Overall, the data demonstrate that DHEA inhibited TM-3 cell growth by decreasing G6PD activity and the expression of cyclin mRNAs, whereas it improved TM-3 cell viability by increasing mitochondrial membrane permeability and the activity of SDH. This could be one of mechanisms of DHEA exerts its biological function.

The effect of dehydroepiandrosterone (DHEA) on renal function and metabolism in diabetic rats

Dehydroepiandrosterone (DHEA) is an endogenous steroid hormone involved in a number of biological actions in humans and rodents, but its effects on renal tissue have not yet been fully understood. The aim of this study is to assess the effect of DHEA treatment on diabetic rats, mainly in relation to renal function and metabolism. Diabetic rats were treated with subcutaneous injections of a 10mg/kg dose of DHEA diluted in oil. Plasma glucose and creatinine, in addition to urine creatinine, were quantified espectophotometrically. Glucose uptake and oxidation were quantified using radioactive glucose, the urinary Transforming Growth Factor β(1) (TGF-β(1)) was assessed by enzyme immunoassay, and the total glutathione in the renal tissue was also measured. The diabetic rats displayed higher levels of glycemia, and DHEA treatment reduced hyperglycemia. Plasmatic creatinine levels were higher in the diabetic rats treated with DHEA, while creatinine clearance was lower. Glucose uptake and oxidation were lower in the renal medulla of the diabetic rats treated with DHEA, and urinary TGF-β(1), as well as total gluthatione levels, were higher in the diabetic rats treated with DHEA. DHEA treatment was not beneficial to renal tissue, since it reduced the glomerular filtration rate and renal medulla metabolism, while increasing the urinary excretion of TGF-β(1) and the compensatory response by the glutathione system, probably due to a mechanism involving a pro-oxidant action or a pro-fibrotic effect of this androgen or its derivatives. In conclusion, this study reports that DHEA treatment may be harmful to renal tissue, but the mechanisms of this action have not yet been fully understood.

Endocrine alterations in response to calorie restriction in humans

This review focuses on research involving calorie restriction (CR) in humans and the resulting changes observed in endocrine and neuroendocrine systems. Special emphasis is given to the clinical science studies designed to investigate the effects of controlled, high-quality, energy-restricted diets on both biomarkers of longevity and on the development of chronic diseases of human aging. Prolonged CR has been shown to extend both the median and maximal lifespan in a variety of lower species such as yeast, worms, fish, rats and mice. The biological mechanisms of this lifespan extension via CR are not fully elucidated, but possibly involve significant alterations in energy metabolism, oxidative damage, insulin sensitivity and functional changes in both neuroendocrine and autonomic nervous systems. Most of the difficulty in characterizing the systemic endocrine and neuroendocrine changes with aging and CR is due to the limited capability to collect large and multiple blood samples from small animals, which are usually shorter lived, and hence the most studied. Ongoing studies of prolonged CR in humans are now making it possible to analyze changes in the "biomarkers of aging" to unravel some of the mechanisms of its anti-aging phenomenon. With the incremental expansion of research endeavors in the area of energy restriction, data on the effects of CR in non-human primates and human subjects are becoming more accessible. Detailed analyses from controlled human trials involving long-term CR will allow investigators to link observed alterations from body composition and endocrine systems down to changes in molecular pathways and gene expression, with their possible effects on aging.

Effect of dehydroepiandrosterone on insulin sensitivity in Otsuka Long-Evans Tokushima-fatty rats

In order to clarify the effect of dehydroepiandrosterone (DHEA) on improvement of insulin resistance, we examined the effects of overexpression of wild-type protein kinase C-zeta (wt-PKCzeta)/3-phosphoinositide-dependent protein kinase-1 (wt-PDK1) and kinase-inactive PKCzeta/PDK1 (DeltaPKCzeta/DeltaPDK1) on DHEA-induced [(3)H]2-deoxyglucose (DOG) uptake using the electroporation method in rat adipocytes. Overexpression of wt-PKCzeta and wt-PDK1 significantly increased in DHEA-induced [(3)H]2-DOG uptake. Wortmannin completely suppressed DHEA-induced [(3)H]2-DOG uptake in wt-PKCzeta- and wt-PDK1-transfected adipocytes. Overexpression of neither DeltaPKCzeta nor DeltaPDK1 increased DHEA-induced [(3)H]2-DOG uptake. Otsuka Long-Evans fatty rats (OLETF), animal models of type 2 diabetes, and Long-Evans Tokushima rats (LETO) as control, were treated with 0.4% DHEA for 2 weeks. Insulin-induced [(3)H]2-DOG uptakes, activations of PI 3-kinase and PKCzeta of adipocytes were significantly increased in DHEA-treated OLETF rats. Moreover, plasma glucose levels in OLETF rats after treatment with DHEA for 2 weeks were significantly lower than treatment without DHEA, but not in LETO rats. These results indicate that DHEA treatment may improve glucose tolerance through a PI 3-kinase-PKCzeta pathway and downregulates adiposity in OLETF rats.

Two years of treatment with dehydroepiandrosterone does not improve insulin secretion, insulin action, or postprandial glucose turnover in elderly men or women

To determine if dehydroepiandrosterone (DHEA) replacement improves insulin secretion, insulin action, and/or postprandial glucose metabolism, 112 elderly subjects with relative DHEA deficiency ingested a labeled mixed meal and underwent a frequently sampled intravenous glucose tolerance test before and after 2 years of either DHEA or placebo. Despite restoring DHEA sulphate concentrations to values observed in young men and women, the changes over time in fasting and postprandial glucose concentrations, meal appearance, glucose disposal, and endogenous glucose production were identical to those observed after 2 years of placebo. The change over time in postmeal and intravenous glucose tolerance test insulin and C-peptide concentrations did not differ in men treated with DHEA or placebo. In contrast, postmeal and intravenous glucose tolerance test change over time in insulin and C-peptide concentrations were greater (P < 0.05) in women after DHEA than after placebo. However, since DHEA tended to decrease insulin action, the change over time in disposition indexes did not differ between DHEA- and placebo-treated women, indicating that the slight increase in insulin secretion was a compensatory response to a slight decrease in insulin action. We conclude that 2 years of replacement of DHEA in elderly men and women does not improve insulin secretion, insulin action, or the pattern of postprandial glucose metabolism.

Dehydroepiandrosterone and human adipose tissue

OBJECTIVE

The aim of this study was to investigate whether DHEA alters the proliferation and differentiation of human sc and visceral adipose cells in primary cultures.

METHOD

Sc and omental adipose tissue was obtained from 10 female donors aged 36+/-3.6 yr with a body mass index (BMI) of 33+/-3.21 kg/m2. Stromal vascular cells were isolated and cultured using modified procedures described by Entenmann and Hauner. For the proliferation assay, stromal-vascular cells from sc and visceral adipose tissue cultures were fed with proliferation media containing 0, 25 or 100 microM DHEA for 3 days. At the end of this treatment period, two type cultures were prepared for determining their metabolic activity using the sulforhodamine B staining procedure.

RESULTS

The metabolic activity of proliferating human visceral adipose tissue was higher than sc adipose tissue. The activity of proliferating human visceral tissue cultures decreased more than the sc tissue as the level of DHEA in the cultures was increased.

CONCLUSIONS

These data suggest that DHEA predominantly influences the proliferation and differentiation of human omental adipose tissue.

Dehydroepiandrosterone increases β-cell mass and improves the glucose-induced insulin secretion by pancreatic islets from aged rats

The effect of dehydroepiandrosterone (DHEA) on pancreatic islet function of aged rats, an animal model with impaired glucose-induced insulin secretion, was investigated. The following parameters were examined: morphological analysis of endocrine pancreata by immunohistochemistry; protein levels of insulin receptor, IRS-1, IRS-2, PI 3-kinase, Akt-1, and Akt-2; and static insulin secretion in isolated pancreatic islets. Pancreatic islets from DHEA-treated rats showed an increased beta-cell mass accompanied by increased Akt-1 protein level but reduced IR, IRS-1, and IRS-2 protein levels and enhanced glucose-stimulated insulin secretion. The present results suggest that DHEA may be a promising drug to prevent diabetes during aging.

Effects of dehydroepiandrosterone on gluconeogenic enzymes and glucose uptake in human hepatoma cell line, HepG2

Dehydroepiandrosterone (DHEA), the most abundant human adrenal steroid, improves insulin sensitivity and obesity in human and model animals. In a previous study, we reported that orally administered DHEA suppresses the elevated activities of hepatic gluconeogenic enzymes like glucose-6-phosphatase (G6Pase) in C57BL/KsJ-db/db mice. However, the molecular mechanisms by which DHEA ameliorates insulin resistance are not clearly understood. In the present study, we cultured the human hepatoma cell line HepG2 with DHEA and measured the enzyme activity and protein expression of G6Pase to investigate the direct effect of DHEA on glucose metabolism in hepatocytes. DHEA significantly suppressed both the activity and protein expression of G6Pase. Moreover, DHEA decreased the gene expression of G6Pase and phosphoenolpyruvate carboxykinase, both of which were maximal at 1 microM DHEA, whereas the mRNA level of glucose-6-phosphate translocase was unchanged. Furthermore, DHEA enhanced 2-deoxyglucose uptake, although its effect was much smaller than that of insulin. These results suggest that DHEA may act at multiple steps in the regulation of glucose metabolism in the liver.

Adrenopause

Dehydroepiandrosterone(DHEA) and DHEA-S are steroids that are abundantly produced by the adrenal gland. Plasma concentrations of DHEA and DHEA-S increase during adrenarche but decrease steadily after puberty. Although DHEA and DHEA-S have few intrinsic androgenic actions, they have recently attracted widespread attention due to their beneficial anti-aging effects. We clarified the beneficial effects of DHEA as an anti-aging steroid with regard to its stimulation of the immune system and its anti-diabetes, anti-atherosclerosis, anti-dementia (neurosteroid), anti-obesity and anti-osteoporosis effects. There are two possible biochemical and molecular mechanisms: direct action via the DHEA receptor on the target gene; and indirect action. We identified a high affinity of DHEA binding in human T-lymphocytes by searching for the target genes that are induced in activated T-lymphocytes in the presence of DHEA, determined the gene sequence and named DHEA-induced dual p38-specific phosphatase (DDSP). DDSP transgenic mice have been created to identify the anti-aging effects of DDSP. The conversion of DHEA to estrone by cytochrome P450 aromatase in primary cultured human osteoblasts was clarified. We are currently undertaking an open trial of DHEA replacement therapy.

The phosphatidylinositol/AKT/atypical PKC pathway is involved in the improved insulin sensitivity by DHEA in muscle and liver of rats in vivo

DHEA improves insulin sensitivity and has anti-obesity effect in animal models and men. However, the molecular mechanisms by which DHEA improves insulin action have not been clearly understood. In the present study, we examined the protein levels and phosphorylation state of insulin receptor (IR), IRS-1 and IRS-2, the association between IRSs and PI3K and SHP2, the insulin-induced IRSs associated PI 3-kinase activities, and the phosphorylation status of AKT and atypical PKCzeta/lambda in the liver and the muscle of 6 month-old Wistar rats treated with DHEA. There was no change in IR, IRS-1 and IRS-2 protein levels in both tissues of treated rats analysed by immunoblotting. On the other hand, insulin-induced IRS-1 tyrosine phosphorylation was increased in both tissues while IRS-2 tyrosyl phosphorylation was increased in liver of DHEA treated group. The PI3-kinase/AKT pathway was increased in the liver and the PI3K/atypical PKCzeta/lambda pathway was increased in the muscle of DHEA treated rats. These data indicate that these regulations of early steps of insulin action may play a role in the intracellular mechanism for the improved insulin sensitivity observed in this animal model.

Dehydroepiandrosterone stimulates glucose uptake in human and murine adipocytes by inducing GLUT1 and GLUT4 translocation to the plasma membrane

Dehydroepiandrosterone (DHEA) has been shown to modulate glucose utilization in humans and animals, but the mechanisms of DHEA action have not been clarified. We show that DHEA induces a dose- and time-dependent increase in glucose transport rates in both 3T3-L1 and human adipocytes with maximal effects at 2 h. Exposure of adipocytes to DHEA does not result in changes of total GLUT4 and GLUT1 protein levels. However, it does result in significant increases of these glucose transporters in the plasma membrane. In 3T3-L1 adipocytes, DHEA increases tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and IRS-2 and stimulates IRS-1- and IRS-2-associated phosphatidylinositol (PI) 3-kinase activity with no effects on either insulin receptor or Akt phosphorylation. In addition, DHEA causes significant increases of cytosolic Ca(2+) concentrations and a parallel activation of protein kinase C (PKC)-beta(2). The effects of DHEA are abrogated by pretreatment of adipocytes with PI 3-kinase and phospholipase C gamma inhibitors, as well as by inhibitors of Ca(2+)-dependent PKC isoforms, including a specific PKC-beta inhibitor. Thus, DHEA increases glucose uptake in both human and 3T3-L1 adipocytes by stimulating GLUT4 and GLUT1 translocation to the plasma membrane. PI 3-kinase, phospholipase C gamma, and the conventional PKC-beta(2) seem to be involved in DHEA effects.

Interacting mediators of allostasis and allostatic load: towards an understanding of resilience in aging

Individual differences in the aging process can be conceptualized as an accumulation of wear and tear of daily experiences and major life stressors that interact with the genetic constitution and predisposing early life experiences. The neuroendocrine system, autonomic nervous system, and immune system are mediators of adaptation to challenges of daily life, referred to as allostasis, meaning "maintaining stability through change." Physiological mediators such as adrenalin from the adrenal medulla, glucocorticoids from the adrenal cortex, and cytokines from cells of the immune system act upon receptors in various tissues and organs to produce effects that are adaptive in the short run but can be damaging if the mediators are not shut off when no longer needed. When release of the mediators is not efficiently terminated, their effects on target cells are prolonged, leading to other consequences that may include receptor desensitization and tissue damage. This process has been named "allostatic load," and it refers to the price the tissue or organ pays for an overactive or inefficiently managed allostatic response. Therefore, allostatic load refers to the "cost" of adaptation. This article discusses the mediators of allostasis and their contributions to allostatic load as well as their role in resilience of the aging organism to stressful experiences.

Mechanism of action of anti-aging DHEA-S and the replacement of DHEA-S

The plasma ACTH and cortisol levels do not change during aging. On the other hand, the plasma dehydroepiandrosterone sulfate (DHEA-S) changes remarkably during aging. Before puberty, the plasma DHEA-S level both in males and females is very low, however, it rapidly increases at puberty, and thereafter significantly decreases both linearly and age-dependently. Cytochrome P450c17 has two enzyme activities, 17-alpha-hydroxylase and 17,20-lyase. Cortisol is synthesized by 17-alpha-hydroxylase, and DHEA is synthesized by 17,20-lyase. The mechanism of dissociation of cortisol and DHEA synthesis in aging depends on another regulator of 17,20-lyase of cytochrome P450c17 such as cytochrome P450 reductase. We demonstrated significant decrease in cytochrome P450 reductase activity in bovine aged adrenal glands. We clarified the beneficial effects of DHEA as an anti-aging steroid based on both in vitro and in vivo experiments, such as the stimulatory effect of immune system, anti-diabetes mellitus, anti-atherosclerosis, anti-dementia (neurosteroid), anti-obesity and anti-osteoporosis. It is very important to identify the mechanism of action of DHEA. We clarified the conversion of DHEA to estrone by cytochrome P450 aromatase in primary cultured human osteoblasts. We indentified high affinity of DHEA binding with K(d)=6.6 nM in antigen and DHEA stimulated human T lymphocytes. We searched for the target genes that are specifically induced in activated T lymphocytes in the presence of DHEA by subtractive hybridization screening for differentially expressed transcripts. The double blind, randomized human replacement therapies utilizing DHEA are also reviewed.

Dehydroepiandrosterone (DHEA) stimulates glucose uptake in rat adipocytes: activation of phospholipase D

We examined the effect of dehydroepiandrosterone (DHEA) on glucose uptake and phospholipase D (PLD) activation in rat adipocytes. DHEA (1 microM) provoked a twofold increase in [3H]2-deoxyglucose (DG) uptake for 30 min. Incorporation of [3H]glycerol into diacylglycerol was increased 150% above basal level for 20 min after stimulation with 1 microM DHEA. DHEA increased PLD activity, measured by the incorporation into [3H]phosphatidylethanol in [3H]palmitate labelled rat adipocytes, or by [3H]choline release in [methyl-(3)H]choline labeled rat adipocytes. Our results suggest that DHEA stimulates glucose uptake with activation of PLD in rat adipocytes.

DHEA inhibits cell growth and induces apoptosis in BV-2 cells and the effects are inversely associated with glucose concentration in the medium

Dehydroepiandrosterone (DHEA), a major steroid secreted by the adrenal gland which decreases with age after adolescence, is available as a nutritional supplement. DHEA is known to have antiproliferative effects but the mechanism is unclear. In this study using BV-2 cells, a murine microglial cell line, we investigated the effect of DHEA on cell viability and the interaction between DHEA and glucose concentrations in the medium. We showed that DHEA inhibited cell viability and G6PD activity in a dose-dependent manner and that the effect of DHEA on cell viability was inversely associated with glucose concentrations in the medium, i.e. lowered glucose strongly enhanced the inhibition of cell viability by DHEA. DHEA inhibited cell growth by causing cell cycle arrest primarily in the G0--G1 phase, and the effect was more pronounced at zero glucose (no glucose added, G0) than high glucose (4.5 mg/ml of the medium, G4.5). Glucose deprivation also enhanced apoptosis induced by DHEA. At G4.5, DHEA did not induce formation of DNA ladder until it reached 200 microM. However, at G0, 100 microM DHEA was able to induce apoptosis, as evidenced by the formation of DNA ladder, elevation of histone-associated DNA fragmentation and increase in cells positively stained with annexin V-FITC and annexin V-FITC/propidium iodide. The interactions between DHEA and glucose support the contention that DHEA exerts its antiproliferative effects through alteration of glucose metabolism, possibly by inhibition of G6PD activity leading to decreased supply of ribose-5-phosphate for synthesis of DNA and RNA. Although DHEA is only antiproliferative at pharmacological levels, our results indicate that its antiproliferative effect can be enhanced by limiting the supply of glucose such as by energy restriction. In addition, the present study shows that glucose concentration is an important factor to consider when studying the antiproliferative and toxicological effects of DHEA.

Androstenediol stimulates myelopoiesis and enhances resistance to infection in gamma-irradiated mice

The ionizing radiation-induced hemopoietic syndrome is characterized by defects in immune function and increased mortality due to infections and hemorrhage. Since the steroid 5-androstene-3beta, 17beta-diol (5-androstenediol, AED) modulates cytokine expression and increases resistance to bacterial and viral infections in rodents, we tested its ability to promote survival after whole-body ionizing radiation in mice. In unirradiated female B6D2F1 mice, sc AED elevated numbers of circulating neutrophils and platelets and induced proliferation of neutrophil progenitors in bone marrow. In mice exposed to whole-body (60)Co gamma-radiation (3 Gy), AED injected 1 h later ameliorated radiation-induced decreases in circulating neutrophils and platelets and marrow granulocyte-macrophage colony-forming cells, but had no effect on total numbers of circulating lymphocytes or erythrocytes. In mice irradiated (0, 1 or 3 Gy) and inoculated four days later with Klebsiella pneumoniae, AED injected 2 h after irradiation enhanced 30-d survival. Injecting AED 24 h before irradiation or 2 h after irradiation increased survival to approximately the same extent. In K. pneumoniae-inoculated mice (irradiated at 3-7 Gy) and uninoculated mice (irradiated at 8-12 Gy), AED (160 mg/kg) injected 24 h before irradiation significantly promoted survival with dose reduction factors (DRFs) of 1.18 and 1.26, respectively. 5-Androstene-3beta-ol-17-one (dehydroepiandrosterone, DHEA) was markedly less efficacious than AED in augmenting survival, indicating specificity. These results demonstrate for the first time that a DHEA-related steroid stimulates myelopoiesis, and ameliorates neutropenia and thrombocytopenia and enhances resistance to infection after exposure of animals to ionizing radiation.

Accelerated conversion of dehydroepiandrosterone sulfate to estrogen in a patient with Crow-Fukase syndrome and diabetes mellitus

About 28% of patients with the Crow-Fukase syndrome exhibit glucose intolerance which may be induced by low serum levels of dehydroepiandrosterone (DHEA). We report a patient with the Crow-Fukase syndrome who exhibited non-insulin dependent diabetes mellitus (NIDDM) worsened prior to admission. He received the DHEA sulfate (DHEA-S) infusion test to evaluate aromatase activity. This patient exhibited an increase in aromatase activity measured by the conversion of the intravenously loaded DHEA-S to estrogen, and low serum levels of DHEA and DHEA-S. These abnormalities returned to nearly normal during the administration of prednisolone, 60 mg per day. No adverse effect on his diabetes was observed during the corticosteroid treatment. Five control patients with diabetes but without the Crow-Fukase syndrome showed no increase in the conversion of DHEA-S to estrogen, which suggests that aromatase activity is normal in diabetes. The increase in aromatase activity in our patient may have led to a low serum concentration of DHEA that in turn caused glucose intolerance and a deterioration of the diabetes prior to admission. Glucocorticoid therapy may be beneficial in Crow-Fukase syndrome to improve the distorted metabolism of DHEA with no adverse effect on the diabetes.

Dehydroepiandrosterone and related steroids alter 3T3-L1 preadipocyte proliferation and differentiation

The purpose of the present study was to determine if the anti-adipogenic effects of dehydroepiandrosterone (DHEA) are mediated solely by DHEA or by one or more of its downstream metabolites. In Experiment 1, preconfluent proliferating cultures of 3T3-L1 preadipocytes were incubated for either 24 or 72 h with 0, 1, 5 or 25 microM DHEA, DHEA sulfate (DHEAS), testosterone, estrone and 17beta-estradiol. Pregnenolone, a precursor of DHEA(S), was also tested at these concentrations. After 24 h of incubation, DHEAS, 17beta-estradiol and estrone at the 1 microM level stimulated preadipocyte proliferation. In contrast, DHEA and 17beta-estradiol at the 25 microM level attenuated proliferation to a greater extent than all other steroids. After 72 h of incubation, DHEA and 17beta-estradiol at the 25 microM level attenuated proliferation to a greater extent than all other steroids. In Experiment 2, post-confluent cultures of differentiating 3T3-L1 preadipocytes were incubated for 6 days with 0, 5, 30, or 60 microM levels of these steroids. Preadipocyte differentiation, as assessed by lipid content and glycerol-3-phosphate dehydrogenase activity, decreased markedly when treated with 30 and 60 microM DHEA, 17beta-estradiol, estrone and pregnenolone. In contrast, DHEAS had no impact on preadipocyte proliferation or differentiation. These results suggest that the anti-adipogenic actions of DHEA in adipose tissue may be mediated, in part, by one or more of its distal metabolites, including 17beta-estradiol.

Dehydroepiandrosterone attenuates preadipocyte growth in primary cultures of stromal-vascular cells

The purpose of this study was to determine whether the antiobesity actions of dehydroepiandrosterone (DHEA) are due to an influence on preadipocyte proliferation and/or differentiation in primary cultures of pig and rat stromal-vascular (SV) cells. Pig SV cells were isolated from dorsal subcutaneous adipose tissue of 7-day-old pigs. For the proliferation assays, pig SV cells were grown for 4 days in plating medium containing DHEA at 0, 15, 50, or 150 microM. For the differentiation assays, pig SV cells were grown in plating medium for 3 days and then switched to a serum-free medium containing DHEA at 0, 15, 50, or 150 microM for the next 6 days. Rat SV cells were isolated from inguinal fat pads of 5-wk-old male rats. Rat SV cells were exposed to DHEA at 0, 5, 25, or 75 microM during proliferation. For the differentiation assays, rat SV cells were grown for 8 days in a serum-free medium containing DHEA at 0, 5, 25, or 75 microM. Preadipocyte differentiation [lipid staining, glycerol-3-phosphate dehydrogenase (GPDH) activity] and proliferation (preadipocyte-specific antigen staining) decreased with increasing levels of DHEA in cultures of pig SV cells. In cultures of rat SV cells, preadipocyte differentiation (lipid staining, GPDH activity) and proliferation ([3H]thymidine incorporation) were decreased in the 25 and 75 microM DHEA groups compared with the control and 5 microM DHEA groups. The level of expression of CCAAT enhancer binding protein-alpha, a master regulator of adipogenesis, in cultures of pig SV cells treated with 150 microM DHEA was 38% of control cultures. These data support the hypothesis that DHEA directly attenuates adipogenesis via attenuation of preadipocyte proliferation and differentiation.

Rat pancreatic islet and RINm5F cell responses to epiandrosterone, dehydroepiandrosterone and interleukin-1 beta

Epiandrosterone (EA), dehydroepiandrosterone (DHEA), and their sulfate (-S) and acetate (-A) conjugates were investigated for effects on isolated pancreatic islets and RINm5F insulinoma cells. Interleukin-1 beta (IL-1 beta) inhibited glucose-stimulated insulin release in cultured islets, but the presence of EA, EA-A, and to a lesser extent EA-S, preserved the secretory response. IL-1 beta also increased islet nitrite production, which was antagonized by EA and EA-A, but not by EA-S. EA, EA-A, DHEA, and DHEA-A, but not EA-S and DHEA-S inhibited glucose-stimulated insulin release from islets. This response may be related to the inhibition of glucose transport by EA, EA-A, DHEA, DHEA-A, and DHEA-S, as observed in RINm5F cells. EA, EA-A, DHEA, and DHEA-A also inhibited glucose metabolism in RINm5F cells, whereas EA-S and DHEA-S had no effect. EA, EA-A, DHEA, and DHEA-A, but not the sulfate conjugates, also inhibited RINm5F cell IL-1 beta-induced nitric oxide synthase (iNOS) activity. IL-1 beta also increased cytosolic Cu/Zn-superoxide dismutase (SOD) and mitochondrial Mn-SOD in RINm5F cells. EA inhibited RINm5F cell Cu/Zn-SOD in the presence and absence of IL-1 beta, whereas EA-S increased basal enzyme activity and did not affect the IL-1 beta response. EA did not affect basal Mn-SOD activity and inhibited IL-1 beta-stimulated activity, whereas EA-S was without effect. IL-1 beta had no effect on catalase activity in RINm5F cells, whereas EA, EA-A, and DHEA-A inhibited catalase activity. Thus, EA and DHEA and their acetate congeners protected the beta-cell from the inhibitory effects of IL-1 beta, and inhibited glucose transport and oxidation, and inducible nitricoxide synthase expression. EA and DHEA also had profound effects on Cu/Zn-SOD, which may alter the toxic effects of hydrogen peroxide generation in beta-cells.

Inhibition of migration and proliferation of vascular smooth muscle cells by dehydroepiandrosterone sulfate

Dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S) are the most abundant steroids in humans, and their serum concentrations progressively decrease with age. Although relationships between DHEA(-S) and many age-related illnesses have been postulated, the mechanisms for their effects remain unknown, and specific receptors for these molecules have not been identified. In this paper, to investigate the role of DHEA(-S) in atherogenesis, we studied the proliferation and migration of a rabbit vascular smooth muscle cell line, SM-3, in the presence of DHEA(-S). Cellular proliferation was inhibited by DHEA-S, and to a lesser extent by DHEA. Modified Boyden's chamber assays revealed that DHEA-S inhibited the migration of SM-3 cells toward PDGF-BB. In cell attachment assays, DHEA-S inhibited the attachment of SM3 cells to fibronectin. It was suggested that the inhibitory effect of DHEA-S for SM-3 proliferation and migration was due to the decreased interaction with fibronectin. Scatchard analysis revealed the presence of two populations of DHEA-S binding sites in the nuclear fraction, and a smaller number in the cytosolic fraction. Since the dissociation constant of the higher affinity site was similar to the serum DHEA-S concentration in humans (Kd = 5.8 microM), this binding site could be functional under physiologic conditions. These findings suggest that there may be receptor-mediated anti-atherogenic actions of DHEA-S.

Disturbances in insulin secretion and sensitivity in women with the polycystic ovary syndrome

Insulin resistance, defined as a diminished effect of a given dose of insulin on glucose homeostasis, is a highly prevalent feature of women with PCOS. Insulin resistance in PCOS is closely associated with an increase in truncal-abdominal fat mass, elevated free fatty acid levels, increased androgens, particularly free testosterone through reduced SHBG levels, and anovulation. The causes for insulin resistance in PCOS are still unknown. One line of evidence suggests that an increase in truncal-abdominal fat mass and subsequently increased free fatty acid levels induce insulin resistance in women with PCOS. Increased effects of corticosteroids and a relative reduction in oestrogen and progesterone seem to be involved in the aberrant body fat distribution. Conversely, there are also results supporting primary, genetic target cell defects as a cause of insulin resistance in PCOS. An explanation for these seemingly contradictory results could be that the group of women with PCOS is heterogeneous with respect to the primary event in carbohydrate/insulin disturbances. Also insulin secretion in PCOS is characterized by heterogeneity. At one end of the spectrum is a large subgroup of mainly obese women with reduced insulin secretion, which appears to result from failure of the beta cells to compensate for insulin resistance in susceptible women, resulting in glucose intolerance and NIDDM. In the insulin-resistant patients with normal glucose tolerance, most of the hyperinsulinaemia is probably due to secondarily increased insulin secretion and decreased insulin degradation. However, a component of the increased first-phase insulin release is not due to measurable insulin resistance. Notably, this is also found in lean women with normal insulin sensitivity, and is not reversed after weight reduction, in contrast to the findings for insulin resistance. The implications of this enhanced insulin release are not fully clear, but it may tentatively be associated with carbohydrate craving and subsequently increased risks for development of obesity and insulin resistance. It may represent a primary disturbance of insulin secretion in PCOS or may be associated with the perturbed steroid balance in anovulation. The insulin-androgen connection in PCOS appears to be amplified by several different mechanisms, notably in both directions, the initiating event probably varying between individuals. Thus insulin increases the biological availability of potent steroids, primarily testosterone, through the suppression of SHBG synthesis. Insulin is also involved as a progonadotrophin in ovarian steroidogenesis, with the possible net result of interfering with ovulation and/or increasing ovarian androgen production in states of hyperinsulinaemia. Conversely, testosterone may indirectly contribute to insulin resistance through facilitating free fatty acid release from abdominal fat, but perhaps also through direct muscular effects at higher serum levels. It seems likely that this constitution, presumably genetic, would provide evolutionary advantages in times of limited nutrition, given the energy-saving effects of insulin resistance. Hypothetically, hyperinsulinaemia (primary) could provide a stimulus to ensure intake of nourishment, but unlimited food supplies could in some cases initiate a vicious 'anabolic' circle, in which several of the proposed amplifying mechanisms between insulin and androgens--in both directions--could take part.