Dehydroepiandrosterone: the "missing link" between hyperinsulinemia and atherosclerosis?

Dehydroepiandrosterone (DHEA) and aging

Dehydroepiandrosterone sulfate (DHEAS) is the most abundant circulating steroid hormone in humans and can readily be converted to its parent steroid DHEA by tissue sulfatases. Yet, a biologic function for these steroids has not been defined. The link between DHEA and aging has been raised by: (1) its well documented age-related decline, and (2) a preventive effect of DHEA on numerous age-related illnesses: ischemic heart-disease, cognitive impairment, immunodeficiency, malignancies, osteoporosis. These effects have been suggested by epidemiological studies in humans. Animal studies support a protective effect of DHEA on these age-related diseases. However, it remains unknown whether these results in animals can be transposed in humans, because adrenal secretion of DHEA seems to be particular to primates. In humans, only a few studies have been performed. The effects of oral supplementation with DHEA have, so far, focused on the possible metabolic effects of DHEA. A few studies have shown: the absence of any side-effects; no change in body-weight; conflicting results on body-composition and lipids and no effect on insulin-tolerance. The latest study showed a beneficial effect on well-being but these results need to be confirmed.

Induction of steroidogenic enzyme genes by insulin and IGF-I in cultured adult human adrenocortical cells

Insulin and the insulin-like growth factors (IGFs) have multiple role in gene expression in steroidogenic cells. We investigated the regulation of steroidogenic enzyme gene expression by insulin and IGF-I in primary cultures of human adrenocortical cells from donors of ages 19-77 years. The effects of insulin and IGF-I observed here were independent of age and sex of the donor. After 5 days in serum-containing medium, cultures were exposed to insulin or IGF-I together with cyclic AMP analogs or ACTH in serum-free defined medium. Insulin and IGF-I at physiological concentrations increased mRNA levels for 17 alpha-hydroxylase and type II 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in the absence of cyclic AMP or ACTH. They had lesser effects on 21-hydroxylase and cholesterol side-chain cleavage enzyme mRNA levels and were3 without effect on 11 beta-hydroxylase mRNA. All steroidogenic enzyme mRNAs were strongly increased by cyclic AMP or ACTH, and this increase was potentiated by insulin or IGF-I. These effects of insulin and IGF-I were accompanied by decreases in the ratio of dehydroepiandrosterone/cortisol synthesized from pregnenolone by the cultures. Induction of steroidogenic enzyme genes in adult human adrenocortical cells by insulin and IGF-I is unlikely to occur by means of a cyclic AMP-dependent mechanism. These data increase the evidence for an important regulation of steroidogenesis by these hormones.

The relationship of natural androgens to coronary heart disease in males: a review

Published studies dealing with the relationship between circulating levels of testosterone and dehydroepiandrosterone (sulfate) (DHEA(S)) and coronary heart disease (CHD) in males, as well as corresponding experimental animal studies are reviewed. One randomized intervention study, eight prospective and 30 cross-sectional studies have evaluated this relationship. In the intervention study, testosterone undecanoate given orally significantly improved angina pectoris in 62 patients with CHD as compared to placebo. No significant association between serum testosterone and CHD was reported in the prospective studies, whereas those studies concerning DHEAS found either no or an inverse association with CHD. Of 30 cross-sectional studies, 18 reported reduced concentrations of testosterone (primarily), and/or DHEA(S) in CHD patients as compared to normals, 11 found similar circulating levels of these androgens in controls and patients with CHD, and one study found elevated levels of DHEA(S) in patients. Animal studies (six male rabbits and one in male chicks) suggest an anti-atherogenic effect of testosterone and DHEA. In conclusion, one intervention, eight cohort and several cross-sectional studies suggest either a neutral or a favourable effect of testosterone and DHEA(S) on CHD in males.

Dehydroepiandrosterone reduces plasma plasminogen activator inhibitor type 1 and tissue plasminogen activator antigen in men

Dehydroepiandrosterone (DHEA) may help prevent heart disease in men. To test the hypothesis that DHEA might exert its effects by enhancing endogenous fibrinolytic potential, a double-blind, placebo-controlled study was conducted that assessed the effects of DHEA administration on plasma plasminogen activator inhibitor type 1 (PAI-1) and tissue plasminogen activator (tPA) antigen. Eighteen men received 50 mg DHEA orally and 16 men received a placebo capsule thrice daily for 12 days. Serum DHEA-sulfate and plasma PAI-1 and tPA antigen were measured before and after treatment. In the DHEA group, serum DHEA-sulfate (from 7.5 +/- 1.2 micromol/L to 20.2 +/- 1.5 micromol/L (P < 0.0001), androstenedione (from 2.6 +/- 0.2 nmol/L to 4.0 +/- 0.4 nmol/L; P < 0.005) and estrone (from 172 +/- 21 pmol/L to 352 +/- 28 pmol/L; P < 0.005) increased, whereas plasma PAI-1 (from 55.4 +/- 3.8 ng/mL to 38.6 +/- 3.3 ng/mL; P < 0.0001) and tPA antigen (from 8.1 +/- 1.9 ng/mL to 5.4 +/- 1.3 ng/mL; P < 0.0005) decreased. In the placebo group, serum DHEA-sulfate declined slightly from 8.0 +/- 3.3 micromol/L to 7.3 +/- 3.4 micromol/L (P < 0.05), but no other measured steroid changed. Plasma PAI-1 and tPA antigen did not change in the placebo group. These findings suggest that DHEA administration reduces plasma PAI-1 and tPA antigen concentrations in men.

Dehydroepiandrosterone inhibits human platelet aggregation in vitro and in vivo

The hypothesis has been advanced that the adrenal steroids dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) exert antiatherogenic and cardioprotective actions. Platelet activation has also been implicated in atherogenesis. To determine if DHEA and DHEAS affect platelet activation, the effects of these steroids on platelet aggregation were assessed both in vitro and in vivo. When DHEAS was added to pooled platelet-rich plasma before the addition of the agonist arachidonate, either the rate of platelet aggregation was slowed or aggregation was completely inhibited. Inhibition of platelet aggregation by DHEA was both dose- and time-dependent. Inhibition of platelet aggregation by DHEA was accompanied by reduced platelet thromboxane B2 (TxB2) production. Inhibition of platelet aggregation by DHEA was also demonstrated in vivo. In a randomized, double-blind trial, 10 normal men received either DHEA 300 mg (n = 5) or placebo capsule (n = 5) orally three times daily for 14 days. In one man in the DHEA group arachidonate-stimulated platelet aggregation was inhibited completely during DHEA administration, whereas in three other men in the DHEA group the rate of platelet aggregation was prolonged, and the sensitivity and responsiveness to agonist were reduced. None of the men in the placebo group manifested any change in platelet activity. These findings suggest that DHEA retards platelet aggregation in humans. Inhibition of platelet activity by DHEA may contribute to the putative antiatherogenic and cardioprotective effects of DHEA.

Dehydroepiandrosterone and body fat

Dehydroepiandrosterone sulfate (DHEA-S) is the most abundant circulating adrenal steroid in man, yet its physiologic role and that of its parent compound DHEA are unknown. Age-related decreases in DHEA in association with increases in obesity, insulin resistance, and atherosclerosis are well known. Recent investigations in lower mammals (which do not secrete DHEA) have suggested that DHEA (or its metabolites) may function as an antiobesity agent in these models of obesity independent of food intake. Proposed mechanisms for the decrease in fat mass and lower weight gain when DHEA is given orally include increases in futile cycling and peroxisomal beta-oxidation and decreases in de novo lipogenesis. Alterations in the availability of reducing equivalents for lipid synthesis do not appear to explain this decrease. Changes in pancreatic insulin secretion or insulin sensitivity may also be responsible for some of these effects. Studies in humans have failed to demonstrate a beneficial effect of DHEA on body composition or energy expenditure at either pharmacologic or physiologic replacement doses for 1-3 months. Administration of DHEA to men or women has also not been shown to alter insulin sensitivity as measured by the minimal model or the euglycemic clamp technique. The effect of DHEA on peroxisomal beta-oxidation and de novo lipogenesis is not known. We conclude that a significant role for DHEA in the pharmacologic treatment of human obesity is unlikely.

A review of dehydroepiandrosterone (DHEA)

Dehydroepiandrosterone (DHEA) is quantitatively the most abundant hormone in humans and mammals, with a wide variety of physiological effects, including major regulatory effects upon the immune system. Two of the most striking aspects of DHEA are a steady decline in DHEA with age and a significant deficiency in DHEA in patients with several major diseases, including cancer, atherosclerosis, and Alzheimer's disease. The hormone is secreted in a non-sulfated (DHEA) and sulfated form (DHEA-S). The two are apparently interchangeable, and it appears likely that its physiological effects are achieved by derivative molecules that have yet to be identified.

Hyperinsulinaemia and decreased plasma levels of dehydroepiandrosterone sulfate in premenopausal women with coronary heart disease

OBJECTIVES

The purpose of the study was to establish plasma levels of insulin, ovarian sex hormones and dehydroepiandrosterone sulfate (DHEA-S) and to evaluate their correlations with lipids in premenopausal women with angiographically demonstrated coronary stenosis.

DESIGN

Differences in plasma levels of insulin, ovarian sex hormones, DHEA-S and lipids between groups were compared by analysis of variance.

SETTING

From January 1993 until December 1993 patients were diagnosed in the Outpatient Clinic of the Department of Endocrinology Medical Centre for Postgraduate Education, Warsaw.

SUBJECTS

Premenopausal women with normal oral glucose tolerance test (OGTT) results, with and without coronary stenosis were studied: 21 women after acute myocardial infarction with angiographically demonstrated coronary stenosis (women with CHD), and 14 women with chest pain, a positive exercise test without significant changes of coronary arteries on coronarography (women with normal coronarography, NC). The control group consisted of nine, healthy women with no risk factors for CHD.

MAIN OUTCOME MEASURES

In premenopausal women with CHD, the decreased plasma level of DHEA-S and hyperinsulinaemia were anticipated.

RESULTS

In women with CHD, the plasma levels of DHEA-S (926.5 +/- 83 ng mL-1) were significantly lower than those in women with NC (1375.7 +/- 181 ng mL-1) and in healthy controls (1984 +/- 127 ng mL-1), P < 0.02 and P < 0.001, respectively. The fasting insulin and insulin response to an OGTT in women with CHD and with NC was higher than in healthy subjects. A significant decrease of high-density lipoprotein (HDL) cholesterol, HDL-2 cholesterol and apolipoprotein A-I, and an increase of total cholesterol, low-density lipoprotein cholesterol C and apolipoprotein B levels in women with CHD compared to healthy controls were observed. A negative correlation between fasting insulin and the plasma levels of DHEA-S was established.

CONCLUSION

In premenopausal women, hyperinsulinaemia and decreased DHEA-S levels may contribute to the development of coronary atherosclerosis.

Endogenous sex hormones: impact on lipids, lipoproteins, and insulin

Estrogen use has been reported to decrease triglyceride and low-density lipoprotein cholesterol (LDL-C) and increase high-density lipoprotein cholesterol (HDL-C). Estrogen use increases the secretion of large, very low-density lipoprotein cholesterol (VLDL-C) and also stimulates the uptake of VLDL-C by the liver and increases the catabolism of LDL-C in the liver. Sex hormones may affect several enzymes involved in the metabolism of HDL-C and triglyceride and may also affect lipolysis. In both pre- and postmenopausal women, several studies have shown that increased glucose and insulin concentrations are associated with increased free testosterone and decreased sex hormone binding globulin. The temporal direction of this relationship in premenopausal women is not clear, however. In contrast to women, increased androgen concentrations in men do not seem to be associated with increased cardiovascular risk factors, although testosterone concentrations are associated with increased HDL-C and decreased insulin concentrations. Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) appear to be associated with improved cardiovascular risk factors in men, but this connection in women is less clear.

Sex-specific action of insulin to acutely increase the metabolic clearance rate of dehydroepiandrosterone in humans

To test the hypothesis that insulin acutely enhances the metabolic clearance rate (MCR) of dehydroepiandrosterone in humans, the effect of a short-term insulin infusion on the MCR of dehydroepiandrosterone was assessed in 10 men and 7 women. After an overnight fast, dehydroepiandrosterone was infused at 3.47 mumol/h for 6.5 h. At 240 min, a hyperinsulinemic-euglycemic clamp was begun by infusing insulin at 21.5 pmol/kg per min for 2.5 h. MCR of dehydroepiandrosterone was calculated at baseline (210-240 min) and during the insulin infusion (360-390 min). A control study was conducted at least 1 wk later, in which 0.45% saline was substituted for the hyperinsulinemic-euglycemic clamp. During the insulin clamp study, serum insulin rose from 34 +/- 2 to 1084 +/- 136 pmol/liter (P = 0.0001) in men and from 40 +/- 5 to 1357 +/- 175 pmol/liter (P = 0.0003) in women, while serum glucose remained constant in both groups. MCR of dehydroepiandrosterone rose in men during the insulin infusion from 2443 +/- 409 to 3599 +/- 500 liters/24 h (P = 0.003), but did not change during the control saline infusion. In contrast, MCR of dehydroepiandrosterone in women did not change in the insulin clamp study during insulin infusion (2526 +/- 495 liters/24 h at baseline vs. 2442 +/- 491 liters/24 h during insulin infusion; P = 0.78). These findings suggest that insulin acutely increases the MCR of dehydroepiandrosterone in men but not in women.

Obesity-induced diabetes (diabesity) in C57BL/KsJ mice produces aberrant trans-regulation of sex steroid sulfotransferase genes

The diabetes (db) gene is a recessive obesity mutation in the mouse capable of producing diabetes only through interaction with heretofore undefined modifiers in the genetic background of certain inbred strains. Here we identify the genetic map locations of androgen and estrogen sulfotransferase genes important in maintaining the balance of active sex steroids in the liver. The Std locus encoding dehydroepiandrosterone sulfotransferase was mapped to proximal Chromosome 7, and the Ste locus encoding estrogen sulfotransferase was mapped to Chromosome 5. The db mutation in the diabetes-susceptible C57BL/KsJ strain aberrantly regulated mRNA transcript levels from these two loci. Hepatic Ste mRNA transcripts were increased from undetectable levels in normal males and females to high levels in db/db mice of both sexes. An anomalous suppression of Std transcription was observed in db/db females, but not in normal females. These reciprocal changes in mRNA concentrations in mutant females were reflected by an induction of a high affinity estrogen sulfotransferase activity and a concomitant loss of dehydroepiandrosterone sulfotransferase activity. These db gene-elicited effects were specific for the sex steroid sulfotransferases since other potential sex steroid metabolizing enzymes (phenol sulfotransferase, sex steroid sulfohydrolase, and UDP-glucuronyltransferase) were unaffected. These aberrant changes would virilize hepatic metabolism in females by increasing the ratio of active androgens to estrogens. In human females, non-insulin-dependent diabetes mellitus often develops when visceral obesity and hyperinsulinemia are associated with hyperandrogenization. This study demonstrates that background modifier genes interacting deleteriously with an obesity mutation are not necessarily defective alleles. Rather, some are functional genes whose regulation has been altered by pleiotropic effects of the obesity gene.

Decreased testosterone and dehydroepiandrosterone sulfate concentrations are associated with increased insulin and glucose concentrations in nondiabetic men

Although many studies indicate that increased androgenicity is associated with insulin resistance and hyperinsulinemia in both premenopausal and postmenopausal women, relatively few data are available on this relationship in men. We examined the association of sex hormone-binding globulin (SHBG), total and free testosterone, dehydroepiandrosterone sulfate (DHEA-SO4), and estradiol to glucose and insulin concentrations before and during an oral glucose tolerance test in 178 men from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Total and free testosterone and DHEA-SO4 were significantly inversely associated with insulin concentrations. Free testosterone and DHEA-SO4 were also significantly inversely correlated with glucose concentrations. SHBG was weakly positively associated with glucose concentrations. Estradiol was not related to glucose or insulin concentrations. After adjustment for age, obesity, and body fat distribution, insulin concentrations remained significantly inversely correlated with free testosterone (r = -.23), total testosterone (r = -.21), and DHEA-SO4 (r = -.21; all P < .01). In conclusion, we observed that increased testosterone and DHEA-SO4 are associated with lower insulin concentrations in men. This is in striking contrast to women, where increased androgenicity is associated with insulin resistance and hyperinsulinemia.

Interrelationships between intraabdominal fat and total serum testosterone levels in obese women

Thirty-six women aged 18 to 52 years with body mass indexes (BMIs) between 27 and 52 were studied. Visceral and subcutaneous fat areas and body fat were evaluated by computerized tomography with a single scan at the IV-V lumbar vertebra level. Glucose, insulin, and C-peptide levels were measured before and after a glucose load. Total and free serum testosterone and 24-hour urinary cortisol excretion were measured. A stepwise multiple regression equation showed the visceral to subcutaneous fat area ratio to be the most powerful predictor for glucose alterations both during fasting and after a glucose load, and showed BMI to be the most powerful predictor for insulin and C-peptide levels. Total serum testosterone, after matching for age and BMI, demonstrates a significant negative correlation with visceral fat area. We conclude that in obese women, as in men, intraabdominal fat negatively correlates with serum testosterone levels.