Opposing actions of dehydroepiandrosterone and testosterone on insulin sensitivity. In vivo and in vitro studies of hyperandrogenic females

Fetal sex and the development of gestational diabetes mellitus in polycystic ovarian syndrome gravidae

BACKGROUND

Polycystic ovarian syndrome is characterized by elevated androgens and is a well-known risk factor for the occurrence of gestational diabetes mellitus. Androgens (particularly dehydroepiandrosterone-sulfate) are crucial for the development and characteristics of the male reproductive tract during fetal life, and fetal dehydroepiandrosterone-sulfate enters the placenta where it is metabolized and functions as an estrogen substrate. Given this unique sex-specific relationship with androgens and the association of serum dehydroepiandrosterone-sulfate concentration with insulin resistance, we hypothesized that metabolic comorbidities in pregnancy might differ by fetal sex in gravidae with polycystic ovarian syndrome, notably in those with infertility.

OBJECTIVE

This study aimed to evaluate the data in a large population-based database to explore if fetal sex was significantly associated with gestational diabetes mellitus in gravidae with infertility and polycystic ovarian syndrome after controlling for confounders.

STUDY DESIGN

This study was designed to evaluate the risk for the occurrence and rates of gestational diabetes mellitus among gravidae with infertility and a history of polycystic ovarian syndrome. We used a 2-hospital, single academic institution database comprising more than 30,000 subjects enrolled from September 2011 to June 2021 to identify all gravidae with diagnoses of infertility and polycystic ovarian syndrome at the time of delivery and to compare them with gravidae who lacked these comorbidities. Data on covariates, including but not limited to maternal age, body mass index, fetal sex, race, ethnicity, presence or absence of hypertensive disease, and presence or absence of gestational diabetes were identified. Unadjusted and adjusted odds rations were calculated.

RESULTS

We found a statistically significant association between fetal female sex and the development of gestational diabetes mellitus in gravidae with polycystic ovarian syndrome (odds ratio for female vs male, 2.13; 95% confidence interval, 1.06-4.32; P=.03). After adjusting for potential confounders identified in our univariate analyses, there continued to be a statistically significant association between female fetuses and the development of gestational diabetes mellitus (adjusted odds ratio for female vs male, 2.10; 95% confidence interval, 1.04-4.41; P=.04). In contrast, there was no significant association between fetal sex and the development of gestational diabetes mellitus in our similar analysis of gravidae without infertility and polycystic ovarian syndrome (P=.99).

CONCLUSION

Although the origin of gestational diabetes mellitus is multifactorial, we found that female fetal sex is associated with gestational diabetes mellitus in gravidae with infertility and polycystic ovarian syndrome but not in their comparative controls. Further research on the molecular mechanisms driving the association between female fetuses and the development of gestational diabetes mellitus in the context of maternal polycystic ovarian syndrome is warranted.

Adrenal Androgen Predictive Effects on Clinical and Metabolic Abnormalities of Polycystic Ovary Syndrome

OBJECTIVE

 To examine the possible effects of adrenal prohormones in the prediction of clinical and metabolic abnormalities in women with polycystic ovary syndrome (PCOS).

METHODS

 The present study enrolled 299 normal cycling non-PCOS, 156 normoandrogenemic, and 474 hyperandrogenemic women with PCOS. Baseline characteristics were compared using a chi-squared test or analysis of variance (ANOVA) as appropriate. The roles of adrenal prohormones and their ratios with total testosterone in predicting co-occurring morbidities in women PCOS were evaluated using univariate and multivariate logistic regression analyses.

RESULTS

 Adrenal hyperandrogenism per dehydroepiandrosterone sulfate (DHEAS) levels were found in 32% of women with PCOS. In non-PCOS women, dehydroepiandrosterone (DHEA) and its sulfate had no predictive role concerning clinical, anthropometric, and metabolic parameters. In PCOS women, mainly in the hyperandrogenemic group, DHEA showed to be a significant predictor against most anthropometric-metabolic index abnormalities (odds ratio [OR] = 0.36-0.97; p < 0.05), and an increase in triglycerides (TG) levels (OR = 0.76; p = 0.006). Dehydroepiandrosterone sulfate presented a few predictive effects regarding PCOS-associated disorders. In controls, DHEAS predicted against the increase in estimated average glucose (OR= 0.38; p = 0.036). In the normoandrogenic group, it predicted against elevation in the waist/hip ratio (WHR) (OR= 0.59; p = 0.042), and in hyperandrogenemic PCOS women, it predicted against abnormality in the conicity index (CI) (OR = 0.31; p = 0.028).

CONCLUSION

 Dehydroepiandrosterone was shown to be a better predictor of abnormal anthropometric and biochemical parameters in women with PCOS than DHEAS. Thus, regarding adrenal prohormones, DHEA measurement, instead of DHEAS, should be preferred in PCOS management. The effects of androgen prohormones on the prediction of PCOS abnormalities are weak.

Preconceptional, Gestational, and Lactational Exposure to an Unconventional Oil and Gas Chemical Mixture Alters Energy Expenditure in Adult Female Mice

Previous studies conducted in our laboratory have found altered adult health outcomes in animals with prenatal exposure to environmentally relevant levels of unconventional oil and gas (UOG) chemicals with endocrine-disrupting activity. This study aimed to examine potential metabolic health outcomes following a preconception, prenatal and postnatal exposure to a mixture of 23 UOG chemicals. Prior to mating and from gestation day 1 to postnatal day 21, C57BL/6J mice were developmentally exposed to a laboratory-created mixture of 23 UOG chemicals in maternal drinking water. Body composition, spontaneous activity, energy expenditure, and glucose tolerance were evaluated in 7-month-old female offspring. Neither body weight nor body composition differed in 7-month female mice. However, females exposed to 1.5 and 150 μg/kg/day UOG mix had lower total and resting energy expenditure within the dark cycle. In the light cycle, the 1,500 μg//kg/day group had lower total energy expenditure and the 1.5 μg/kg/day group had lower resting energy expenditure. Females exposed to the 150 μg/kg/day group had lower spontaneous activity in the dark cycle, and females exposed to the 1,500 μg/kg/day group had lower activity in the light cycle. This study reports for the first time that developmental exposure to a mixture of 23 UOG chemicals alters energy expenditure and spontaneous activity in adult female mice.

Adrenal hyperandrogenism does not deteriorate insulin resistance and lipid profile in women with PCOS

OBJECTIVE

The aim of this study was to investigate the impact of adrenal hyperandrogenism on insulin resistance and lipid profile in women with polycystic ovary syndrome (PCOS).

PATIENTS AND METHODS

We studied 372 women with PCOS according to the NIH criteria. 232 age- and BMI-matched women served as controls in order to define adrenal hyperandrogenism (DHEA-S >95th percentile). Then, patients with PCOS were classified into two groups: with adrenal hyperandrogenism (PCOS-AH, n = 108) and without adrenal hyperandrogenism (PCOS-NAH, n = 264). Anthropometric measurements were recorded. Fasting plasma glucose, insulin, lipid profile, sex hormone-binding globulin (SHBG) and androgen (TT, Δ4A, DHEA-S) concentrations were assessed. Free androgen index (FAI) and homeostatic model assessment-insulin resistance (HOMA-IR) index were calculated.

RESULTS

Women with PCOS-AH were younger than PCOS-NAH (P < 0.001), but did not differ in the degree and type of obesity. No differences were found in HOMA-IR, total cholesterol, HDL-c, LDL-c and triglyceride concentrations (in all comparisons, P > 0.05). These metabolic parameters did not differ between the two groups even after correction for age. Women with PCOS-AH had lower SHBG (29.2 ± 13.8 vs 32.4 ± 11.8 nmol/L, P = 0.025) and higher TT (1.0 ± 0.2 vs 0.8 ± 0.4 ng/mL, P = 0.05) and Δ4A (3.9 ± 1.2 vs 3.4 ± 1.0 ng/mL, P = 0.007) concentrations, as well as FAI (14.1 ± 8.0 vs 10.2 ± 5.0, P < 0.001). These results were confirmed by a multiple regression analysis model in which adrenal hyperandrogenism was negatively associated with age (P < 0.001) and SHBG concentrations (P = 0.02), but not with any metabolic parameter.

CONCLUSIONS

Women with PCOS and adrenal hyperandrogenism do not exhibit any deterioration in insulin resistance and lipid profile despite the higher degree of total androgens.

Relationship between serum DHEAS and oxidative stress levels of body mass index in healthy postmenopausal women

OBJECTIVES

Menopause is a natural step in the process of aging. Postmenopausal women have decreased levels of antioxidants and increased oxidative stress, the latter of which plays an important role in atherogenesis. The aim of the present study was to evaluate the relationship of the body mass index (BMI) with serum catalase activity, malondialdehyde (MDA), and dehydroepiandrosterone sulfate (DHEAS) levels in healthy postmenopausal women and estimate whether the MDA/DHEAS ratio is a possible marker of oxidative stress for determining cardiovascular risk in these women.

METHODS

We investigated serum catalase activity, MDA, and DHEAS levels, parity history, age, and BMI in 96 healthy postmenopausal women aged 50-82 years. The serum MDA levels and catalase activity were measured spectrophotometrically. The serum DHEAS levels were measured using an enzyme-linked immunosorbent assay. The ratio percentage of the serum DHEAS levels to serum MDA levels was designated as a biomarker for oxidative stress.

RESULTS

The mean BMI of the patients was 31.72 ± 6.16 kg/m(2) (range = 20.5-47.94). The MDA/DHEAS ratio was significantly decreased in patients with a BMI over 30 compared to that of patients with a BMI between 25 and 30 (P = 0.025). Moreover, BMI was positively correlated with serum DHEAS levels (r = 0.285, P < 0.01) and negatively correlated with the MDA/DHEAS ratio (r = -0.241, P < 0.05) in postmenopausal women. Furthermore, BMI was observed to be a potential predictor of the MDA/DHEAS ratio based on covariance analysis (P = 0.039).

CONCLUSIONS

Our results indicate that healthy, obese, postmenopausal women have a decreased MDA/DHEAS ratio. Additionally, BMI was observed to be a potential predictor of the MDA/DHEAS ratio.

The effect of androgens on ovarian follicle maturation: Dihydrotestosterone suppress FSH-stimulated granulosa cell proliferation by upregulating PPARγ-dependent PTEN expression

Intraovarian hyperandrogenism is one of the determining factors of follicular arrest in women with polycystic ovary syndrome (PCOS). Using androgenized rat models, we investigated the effects of androgens on metabolism, as well as on factors involved in follicular arrest and the reduced number of estrus cycles. The dihydrotestosterone (DHT)-treated rats had fewer estrus cycles, higher numbers of large arrested follicles and an increased in body weight gain compared with the dehydroepiandrostenedione (DHEA)- and placebo-treated rats. In cultured rat granulosa cells, DHT suppressed follicle stimulating hormone (FSH)-induced granulosa cell proliferation and increased the accumulation of cells in the G2/M phase. DHT decreased phosphorylated Akt (p-Akt) and cyclin D1 levels through increasing PTEN. DHT-promoted PTEN expression was regulated by peroxisome proliferator-activated receptor gamma (PPARγ) in granulosa cells. Meanwhile, in the large follicles of the DHT-treated rats, the expressions of PPARγ and PTEN were higher, but the expression of p-Akt and proliferating cell nuclear antigen (PCNA) were lower. Conclusively, DHT and DHEA produced differential effects on metabolism in prepubertal female rats like clinical manifestations of women with PCOS. DHT treatment may affect ovarian follicular maturation by altering granulosa cell proliferation through the regulation of enhancing PPARγ dependent PTEN/p-Akt expression in the granulosa cells.

High DHEAS/free testosterone ratio is related to better metabolic parameters in women with PCOS

AIMS

To demonstrate the effects of DHEAS/free testosterone (DHEAS/FT) ratio on metabolic parameters in women with and without polycystic ovary syndrome (PCOS).

METHODS

The data of 91 women with PCOS and 66 women in the control group were collected retrospectively.

RESULTS

DHEAS/FT of the control group was higher than that of PCOS group (684.93 ± 300.54 to 517.2 ± 300.8, p < 0.001). DHEAS/FT correlated with BMI (r = -0.352, p = 0.001), WHR (r = -0.371, p = 0.0219), LDL (r = -0.227, p = 0.031), HOMA-IR (r = -0.36, p = 0.001) and FAI (r = -0.639, p = 0.001) negatively and with HDL (r = 0.344, p = 0.001) and SHBG (r = 0.646, p = 0.001) positively. In the control group, DHEAS/FT correlated with BMI (r = -0.334, p = 0.007), CRP (r = -0.297, p = 0.016) and FAI (r = -0.399, p = 0.01) negatively.

CONCLUSIONS

High DHEAS/FT ratios are related to a better metabolic phenotype in women with PCOS and low levels can be used to detect women with PCOS that have a higher risk of metabolic problems.

Hyperandrogenemia in polycystic ovary syndrome: exploration of the role of free testosterone and androstenedione in metabolic phenotype

Objective

To evaluate the association between androstenedione, testosterone, and free testosterone and metabolic disturbances in polycystic ovary syndrome.

Methods

We analyzed the association between androstenedione, testosterone, and free testosterone and metabolic parameters in a cross-sectional study including 706 polycystic ovary syndrome and 140 BMI-matched healthy women. Polycystic ovary syndrome women were categorized into 4 groups: normal androstenedione and normal free testosterone (NA/NFT), elevated androstenedione and normal free testosterone (HA/NFT), normal androstenedione and elevated free testosterone (NA/HFT), elevated androstenedione and free testosterone (HA/HFT).

Results

Polycystic ovary syndrome women with elevated free testosterone levels (HA/HFT and NA/HFT) have an adverse metabolic profile including 2 h glucose, HbA1c, fasting and 2 h insulin, area under the insulin response curve, insulin resistance, insulin sensitivity index (Matsuda), triglycerides, total and high density lipoprotein cholesterol levels compared to NA/NFT (p<0.05 for all age- and BMI-adjusted analyses). In binary logistic regression analysis adjusted for age and BMI, odds ratio for insulin resistance was 2.78 (1.34–5.75, p = 0.006) for polycystic ovary syndrome women with HA/HFT compared to NA/NFT. We found no significantly increased risk of metabolic disorders in polycystic ovary syndrome women with HA/NFT. In multiple linear regression analyses (age- and BMI-adjusted), we found a significant negative association between androstenedione/free testosterone-ratio and area under the insulin response curve, insulin resistance, and total cholesterol/high density lipoprotein cholesterol-ratio and a positive association with Matsuda-index, and high density lipoprotein cholesterol (p<0.05 for all).

Conclusions

Polycystic ovary syndrome women with elevated free testosterone levels but not with isolated androstenedione elevation have an adverse metabolic phenotype. Further, a higher androstenedione/free testosterone-ratio was independently associated with a beneficial metabolic profile.

Gender-dependent associations of CDKN2A/2B, KCNJ11, POLI, SLC30A8, and TCF7L2 variants with type 2 diabetes in (North African) Tunisian Arabs

We investigated the impact of gender on T2DM association with confirmed susceptibility loci. CDKN2A/2B rs10811661, KCNJ11 rs5219, and TCF7L2 rs7903146 were associated with T2DM in females, while POLI rs488846 was associated with T2DM among males; the association of SLC30A8 rs13266634 and TCF7L2 rs4506565, rs12243326, and rs12255372 with T2DM was gender-independent.

Myostatin and its association with abdominal obesity, androgen and follistatin levels in women with polycystic ovary syndrome

STUDY QUESTION

What is the role of myostatin and its relationship with obesity, androgens and follistatin levels in women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWERS: The myostatin level was positively correlated to the risk of abdominal obesity, but negatively associated with circulating levels of dehydroepiandrosterone sulfate (DHEAS) and follistatin in women with PCOS.

WHAT IS KNOWN AND WHAT THIS PAPER ADDS

Myostatin is a well-known negative regulator of skeletal muscle and is involved in metabolism; however, little is known about the role of myostatin in women with PCOS. In this study, we found that the myostatin level was positively related to the risk of abdominal obesity, but negatively related to the circulating levels of DHEAS and follistatin in women with PCOS. Such a relationship might imply a potential regulatory role of androgens and follistatin in the metabolism of skeletal muscle in women with PCOS.

DESIGN

A cross-sectional case-control study.

PARTICIPANTS AND SETTING

A total of 239 untreated, consecutive women with PCOS and 38 healthy volunteer women without PCOS were enrolled and studied in a tertiary medical center.

MAIN RESULTS AND THE ROLE OF CHANCE

Myostatin level was higher in women with PCOS than those without PCOS (16.6±15.6 and 14.2±9.7, P=0.025), but were not significantly different between non-obese women with and without PCOS after considering the effect of obesity (P=0.09). Stepwise multivariate regression analysis in women revealed that only the presence of PCOS (β=0.256, P=0.0001), total testosterone (β=0.159, P=0.031), DHEAS (β=-0.188, P=0.0003) and follistatin (β=-0.171, P=0.0001) levels were left in the final model and were significantly related to the myostatin level after considering all the explanatory variables. By using stepwise multivariate regression analysis, the total testosterone levels (β=0.196, P=0.003) were positively, but the DHEAS (β=-0.196, P<0.0001) and follistatin (β=-0.151, P=0.0001) levels were negatively, related to myostatin levels in women with PCOS after adjustment for age, anthropometric measurements, insulin sensitivity index and hormonal profiles. The high myostatin level was associated with the increased risk of abdominal obesity after further adjusting the androgens and follistatin levels in women with PCOS.

LIMITATION, REASONS FOR CAUTION

This study is a cross-sectional case-control design, and therefore, cannot answer the cause-effect relationship among the androgens, follistatin and myostatin levels. The small sample size and non-obese control group may also limit the application of the conclusion of the present study to general population other than women with PCOS. In addition, lack of data regarding muscle mass is another limitation in this study that prevents clarification of the relationship between myostatin, lean mass and obesity and therefore restricts the clinical application of the results.

WIDER IMPLICATIONS OF THE FINDINGS

Future studies to investigate the efficacy of exercise and lifestyle modification in treating women with PCOS should consider the myostatin, follistatin and androgen levels as well as the effect of muscle mass and BMI.

STUDY FUNDING/COMPETING INTEREST

This study was supported by grants NSC97-2314-B002-079-MY3, NSC98-2314-B002-105-MY3 and NSC 100-2314-B002-027-MY3 from the National Science Council of Taiwan. There is no competing interest declared in this study.

Relative contributions of oligomenorrhea and hyperandrogenemia to the risk of metabolic syndrome in midlife women

CONTEXT

Young reproductive-age women with irregular menses and androgen excess are at high risk for unfavorable metabolic profile; however, recent data suggest that menstrual regularity and hyperandrogenism improve with aging in affected women approaching menopause.

OBJECTIVE

The objective of the study was to determine whether women with hyperandrogenemia (HA) and a history of oligomenorrhea (Oligo) are at an elevated risk for metabolic syndrome (MetS) at the early stages of menopausal transition.

METHODS

Baseline data from 2543 participants (mean age of 45.8 yr) in the Study of Women's Health Across the Nation were analyzed. Women with a lifetime history of more than one 3-month interval of nongestational and nonlactational amenorrhea were classified as having a history of Oligo. The highest tertile of serum testosterone was used to define HA. Women with normal serum androgens and eumenorrhea were used as the reference group. Logistic regression models generated adjusted odds ratios (AOR), controlling for age, ethnicity, body mass index, smoking, and study site.

RESULTS

Oligo was associated with MetS only when coincident with HA [AOR of 1.93 for Oligo and HA [95% confidence interval (CI) 1.17-3.17], AOR of 1.25 for Oligo and normal androgens (95% CI 0.81-1.93)]. In contrast, HA conferred a consistently significant risk for MetS, regardless of the menstrual frequency status [AOR of 1.48 for HA and eumenorrhea (95% CI 1.15-1.90)].

CONCLUSIONS

Our results suggest that HA but not history of Oligo is independently associated with the risk of prevalent MetS in pre- and perimenopausal women in their 40s.

Dehydroepiandrosterone reduces preadipocyte proliferation via androgen receptor

Several studies have suggested that both testosterone and dehydroepiandrosterone (DHEA) have weight-reducing and antidiabetic effects, especially in rodent studies; however, the precise mechanism of their action remains unclear. Here, we investigated the effect of DHEA on cell growth in adipose tissue. The appearance of senescence-associated β-galactosidase in stromal vascular fraction (SVF) isolated from Otsuka Long-Evans Tokushima fatty rats, an animal model of inherent obese type 2 diabetes, was prevented by DHEA administration. Next, the effects of DHEA and testosterone were compared in vivo and in vitro to evaluate whether these hormones influence cell growth in adipose tissue. Both DHEA and testosterone reduced body weight and epididymal fat weight equivalently when administered for 4 wk. To assess the effect of DHEA and testosterone on cell growth in adipose tissue, 5-bromo-2'-deoxyuridine (BrdU) uptake by SVF was measured. Quantification analysis of BrdU uptake by examining DNA isolated from each SVF revealed that treatment with DHEA and testosterone reduced cell replication. These results indicated that DHEA- and testosterone-induced decreased adiposity was associated with reduced SVF growth. Incubation with DHEA and testosterone equally decreased BrdU uptake by 3T3-L1 preadipocytes. Pretreatment with the androgen receptor (AR) inhibitor flutamide, but not the estrogen receptor inhibitor fulvestrant, abolished these effects. Knockdown of AR with siRNA also inhibited DHEA-induced decreases in BrdU uptake. These results suggest that DHEA-induced growth suppression of preadipocytes is mediated via AR. Therefore, both DHEA and testosterone similarly decrease adipocyte growth possibly via a common mechanism.

Heterogeneity of genetic associations of CDKAL1 and HHEX with susceptibility of type 2 diabetes mellitus by gender

We examined the genetic associations of previously identified sequence variants with type 2 diabetes mellitus (T2DM) and its potentially genetic heterogeneity by gender in a large-scale cohort. A total of 613 T2DM patients and 8221 control subjects from the Korea Association REsource (KARE) cohort were included in the analysis of genetic association of T2DM with 33 nucleotide polymorphic markers identified by previous studies. The association analysis was further conducted with data partitioned by gender. The association analysis resulted in five nucleotide sequence variants associated with the susceptibility of T2DM after Bonferonni correction (P < 0.0015). One was located near the gene of hematopoietically expressed homeobox (HHEX), and the others were all in the gene of cyclin-dependent kinase 5 regulatory subunit-associated protein 1-like 1 (CDKAL1). Further analysis revealed that the sequence variant (rs5015480) near HHEX and two SNPs (rs7756992 and rs9465871) in CDKAL1 were associated with the susceptibility of T2DM in females (P<0.005), but not in males (P>0.005). We suggested heterogeneous genetic associations of the T2DM susceptibility with the CDKAL1 and HHEX genes by gender.

High serum dehydroepiandrosterone sulfate is associated with phenotypic acne and a reduced risk of abdominal obesity in women with polycystic ovary syndrome

BACKGROUND

Women with polycystic ovary syndrome (PCOS) are known to have high prevalence of acne and elevated androgen levels. The current study aims to determine if dehydroepiandrosterone sulfate (DHEAS) level is associated with the presence of acne and reduced risk of abdominal obesity in women with PCOS, after considering the concurrent high testosterone level and insulin resistance (IR).

METHODS

Three hundred and eighteen untreated consecutive Taiwanese women with PCOS were enrolled. Phenotypic hyperandrogenism was recorded, and BMI, waist circumference, waist-to-hip ratio, lipid profiles, fasting glucose and insulin levels and hormone profiles were measured.

RESULTS

Women with acne were younger, had higher serum DHEAS levels (6.01 ± 3.45 versus 4.87 ± 2.49 μmol/l, P = 0.002) and a lower BMI (P = 0.0006), but comparable serum testosterone levels, in comparison with women without acne. The aggravating effect of elevated DHEAS on the risk of acne (odds ratio = 2.15, 95% confidence interval: 1.25-3.68, P = 0.005 for DHEAS cut-off of 6.68 μmol/l) still exited after adjustment for age and BMI. The DHEAS level was positively correlated with the testosterone level, but inversely related to waist circumference, waist-to-hip ratio, BMI, IR index, low-density lipoprotein-cholesterol and triglycerides. Women with PCOS in the highest quartile of DHEAS had the lowest risk of abdominal obesity after adjustment for age, IR, dyslipidemia, testosterone and estradiol levels.

CONCLUSIONS

Our results demonstrated the high serum DHEAS in women with PCOS was associated with the presence of acne and a significantly reduced risk of abdominal obesity, independent of serum testosterone concentration and IR.

Transcriptome and proteome expressions involved in insulin resistance in muscle and activated T-lymphocytes of patients with type 2 diabetes

We analyzed the genes expressed (transcriptomes) and the proteins translated (pro- teomes) in muscle tissues and activated CD4(+) and CD8(+) T-lymphocytes (T-cells) of five Type 2 diabetes (T2DM) subjects using Affymetrix microarrays and mass spectrometry, and compared them with matched non-diabetic controls. Gene expressions of insulin receptor (INSR), vitamin D receptor, insulin degrading enzyme, Akt, insulin receptor substrate-1 (IRS-1), IRS-2, glucose transporter 4 (GLUT4), and enzymes of the glycolytic pathway were decreased at least 50% in T2DM than in controls. However, there was greater than two-fold gene upregulation of plasma cell glycoprotein-1, tumor necrosis factor alpha (TNFalpha, and gluconeogenic enzymes in T2DM than in controls. The gene silencing for INSR or TNFalpha resulted in the inhibition or stimulation of GLUT4, respectively. Proteome profiles corresponding to molecular weights of the above translated transcriptomes showed different patterns of changes between T2DM and controls. Meanwhile, changes in transcriptomes and proteomes between muscle and activated T-cells of T2DM were comparable. Activated T-cells, analogous to muscle cells, expressed insulin signaling and glucose metabolism genes and gene products. In conclusion, T-cells and muscle in T2DM exhibited differences in expression of certain genes and gene products relative to non-diabetic controls. These alterations in transcriptomes and proteomes in T2DM may be involved in insulin resistance.

Dehydroepiandrosterone sulfate and insulin resistance in patients with polycystic ovary syndrome

OBJECTIVE

To test the hypothesis that increasing DHEAS levels is associated with improved insulin resistance in patients with polycystic ovary syndrome (PCOS).

DESIGN

Cross-sectional cohort analysis.

SETTING

Academic medical center.

PATIENT(S)

Three hundred fifty-two women with PCOS.

INTERVENTION(S)

Patients presenting for evaluation of symptoms related to androgen excess were evaluated physically and biochemically through laboratory analysis.

MAIN OUTCOME MEASURE(S)

Circulating DHEAS, total T, free T, sex hormone-binding globulin (SHBG), and 17-hydroxyprogesterone (17-OHP) levels, and calculated homeostasis model assessment of insulin resistance (HOMA-IR).

RESULT(S)

Bivariate analysis indicated that all parameters were associated with HOMA-IR, except 17-OHP and age, and confirmed a negative correlation between DHEAS and HOMA-IR. Multivariate analysis indicated that increases in DHEAS, SHBG, 17-OHP, and age were associated with decreasing HOMA-IR, whereas increases in free T, body mass index (BMI), and waist-to-hip ratio (WHR) were associated with increasing HOMA-IR. In decreasing order of importance, the following variables predicted insulin resistance: BMI > WHR > age > DHEAS > free T > SHBG > 17-OHP.

CONCLUSION(S)

DHEAS is negatively correlated to insulin resistance in patients with PCOS, and in our model ranked just behind other well-established predictors including BMI, WHR, and age. Whether this is due to a direct beneficial effect on insulin action by adrenal androgens such as DHEA, or whether DHEAS simply reflects the circulating levels of hyperinsulinemia, remains to be determined.

Gender-dependent effect of ageing on peripheral insulin action

The aim of the present study was to investigate the effect of both gender and age on insulin secretion, peripheral insulin effectiveness and insulin-receptor binding. Eighty healthy volunteers, 40 females of mean age 38.47 +/- 11.37 years and mean BMI 21.99 +/- 2.06 kg/m(2) and 40 males of mean age 34.87 +/- 11.22 years and mean BMI 22.65 +/- 2.31 kg/m(2), with normal glucose tolerance participated in the study. Peripheral insulin effectiveness was measured by the artificial endocrine pancreas, using the euglycaemic hyperinsulinaemic clamp technique and insulin-receptor binding on circulating mononuclear blood cells. Peripheral insulin sensitivity was significantly higher in females as compared to males (p < 0.001), while males demonstrated higher total number of insulin receptors (p < 0.0001) and number of high-affinity receptors (p < 0.01). Peripheral insulin sensitivity decreased with ageing in both males and females, the reduction in females being more pronounced (p < 0.05). In the group under 40 years, the females demonstrated significantly higher insulin sensitivity as compared to males (p < 0.001) and lower insulin-receptor binding. Over 40 years, females presented higher peripheral insulin sensitivity and higher insulin-receptor binding. The percentage of specifically bound insulin increased significantly with ageing in females and decreased in males. We consider that probably the higher androgen level in males affects the post-receptor processes in insulin action and despite the higher insulin-receptor binding, males have lower insulin sensitivity. The androgen levels in females increase with ageing, which could probably affect peripheral insulin sensitivity at the post-receptor level. In conclusion, our results demonstrate that when analysing peripheral insulin effectiveness and insulin-receptor binding, one should always consider both gender and age.

Insulin-sensitising agents: beyond thiazolidinediones

The global prevalence of Type 2 diabetes mellitus is increasing rapidly, at least in part as a function of obesity. The results of the United Kingdom Prospective Diabetes Study emphasise the importance of developing safe, efficacious new agents for the treatment of Type 2 diabetes. The pharmaceutical industry has recently focused on strategies to improve insulin resistance, particularly modulation of PPAR-gamma. Here we review current thinking on the mechanism of action of these agents, and consider future directions that may arise as a result of increasing understanding of the biology of these receptors and of insulin action. Studies of thiazolidinedione action in adipose tissue have revealed several novel adipocyte-derived hormones that may also be future pharmacological targets for increasing insulin sensitivity. The role of other hormones, such as cortisol and dehydroepiandrosterone, are also discussed in a therapeutic context, as are other novel approaches to the pharmacological management of patients with insulin resistance and Type 2 diabetes.

Very short term dehydroepiandrosterone treatment in female adrenal failure: impact on carbohydrate, lipid and protein metabolism

OBJECTIVE

In female adrenal insufficiency, dehydroepiandrosterone (DHEA) secretion is impaired and circulating androgen levels are severely reduced. We wanted to analyse the acute effects of physiological DHEA substitution on substrate metabolism.

DESIGN

We studied nine females with adrenal insufficiency after 9 days of oral DHEA replacement (50 mg/day) in a double-blind, placebo-controlled crossover study.

METHODS

Whole body and regional substrate metabolism was assayed in the basal state and during a euglycemic hyperinsulinemic glucose clamp by means of isotope dilution techniques (glucose, phenylalanine, tyrosine), indirect calorimetry and in situ lipolysis (microdialysis technique).

RESULTS

DHEA treatment normalized the levels of all androgens. Basal and insulin-stimulated total energy expenditure and rates of protein, lipid and glucose oxidation were unaffected by DHEA. Whole body turnover of glucose and protein were also unaffected by DHEA. Forearm breakdown of protein was reduced by insulin to the same extent after placebo and DHEA. Insulin sensitivity as expressed by the glucose infusion rate during the euglycemic clamp was similar after placebo and DHEA. Finally, the interstitial release of glycerol in adipose tissue was not significantly influenced by DHEA.

CONCLUSIONS

Short-term oral DHEA replacement in women with adrenal insufficiency was not associated with measurable changes in total or regional substrate metabolism.

Transcriptome and proteome expression in activated human CD4 and CD8 T-lymphocytes

T-lymphocytes (T-cells) are unique in that unlike monocytes, they have no insulin receptors, and are insulin insensitive, but upon activation with antigens develop insulin, IGF-1, and IL-2 receptors, and become insulin sensitive tissues. In vivo activation of these cells has now been demonstrated in patients with diabetic ketoacidosis. We analyzed the genomics and proteomics of activated and non-activated CD4+ and CD8+ T-cells of normal subjects using Affymetrix microarray gene chips and proteomes by SELDI-TOF mass spectrometry analysis. Genes for IL-2, insulin, and IGF-1 receptors were increased at least 2-fold in activated vs non-activated T-cells. Using an expression array containing the entire human genome of 39,500 genes, we evaluated approximately 27,000 genes relevant in physiologic and cellular ontologies. Of these, approximately 10,500 genes were increased in activated cells, compared to about 7,000, which were decreased, and approximately 9500, which were unchanged. Among activated ontologies were signal transduction pathways such as IRS-1, IRS-2, Akt, and glycolytic pathways. To our knowledge this is the first report of an hitherto unreported event. Possible implications of these processes are discussed in the light of their physiological significance.

Age-related insulin resistance: is it an obligatory finding? The lesson from healthy centenarians

It is widely known that advancing age is associated with impaired glucose handling. A unifying hypothesis explaining the relationship between aging and insulin resistance might encompass four main pathways, namely: (a) anthropometric changes (relative and absolute increase in body fat combined with a decline in fat free mass) which could be the anatomic substrate for explaining the reduction in active metabolic tissue; (b) environmental causes, mainly diet style and physical activity; (c) neuro-hormonal variations [decline in plasma dehydroepandrosterone sulphate (DHEAS) and IGF-1]; and finally (d) the rise in oxidative stress. Indeed previous studies have also investigated the occurrence and the degree of insulin resistance in healthy centenarians. Such data demonstrated that age-related insulin resistance is not an obligatory finding in the elderly and that healthy centenarians have a preserved insulin action compared to aged subjects. Why insulin action is preserved in centenarians is still not known. Nevertheless, a possible approach to the question is to outline the centenarians' anthropometric, endocrine and metabolic characteristics in order to design a clinical picture of such metabolic "successful aging". According to the remodeling theory of age, the preserved insulin action in centenarians might be the net result of the continuous adaptation of the body to the deleterious changes that occur over time. Nevertheless, only future longitudinal studies specifically designed to investigate the relationship between extreme old age and degree of insulin sensitivity will provide a conclusive answer with regard to the pathophysiology of adaptive metabolic changes occurring in the elderly.

Advancing age and insulin resistance: new facts about an ancient history

The relationship between advancing age and insulin resistance is widely known, but the cause(s) of such association are less well understood. Age-related changes in anthropometric characteristics and environmental factors (changes in diet habits and decline in physical activity) have been hypothesized as being among the main causes. More recently, the role of plasma insulin-like growth factor I (IGF-I), dehydroepiandrosterone sulphate (DHEAS) and tumour necrosis factor alpha (TNF-alpha) concentrations as well as the degree of oxidative stress have also been evaluated. As far as the anthropometric changes are concerned, a decline in fat-free mass and a relative or absolute increase in fat mass are common findings in aged subjects. Such changes are combined with a decline in plasma DHEAS and IGF-I concentration and a rise in plasma TNF-alpha concentrations and oxidative stress, which, in turn, may interact with the anthropometric changes determining the worsening in insulin-mediated glucose uptake. Finally, age-related environmental factors (changes in diet quality and decline in the degree of physical activity) might be a common factor allowing anthropometric factors and age-related remodelling to accelerate their negative impact on insulin action.

Changes in sex hormones during an oral glucose tolerance test in healthy premenopausal women

OBJECTIVE

To assess the effect of an acute elevation in circulating insulin on serum androgen levels in healthy obese women with different body-fat distributions.

DESIGN

Controlled clinical study.

SETTING

The Endocrinology Unit of an academic medical center.

PATIENT(S)

Seventy healthy premenopausal women participated: 27 women with upper-body obesity, 22 women with lower-body obesity, and 21 normal-weight women as controls.

INTERVENTION(S)

A 75-g oral glucose tolerance test (OGTT) was performed for all participants.

MAIN OUTCOME MEASURE(S)

Anthropometry and serum concentrations of glucose, insulin, free T, DHEAS, androstenedione, E2, and sex hormone-binding globulin (SHBG) at fasting, 60 minutes, and 120 minutes after oral glucose loading.

RESULT(S)

Although androgens and E2 levels in all three groups declined modestly, there were no statistically significant differences in response of the sex hormones to an OGTT in the two obese groups and normal-weight women. No correlation was found between changes in sex-hormone levels during an OGTT and insulin rise. Increased body mass index and more pronounced abdominal fat localization resulted in basal hyperinsulinemia, markedly exaggerated glucose-induced insulin levels, and hyperandrogenism, as was evident by significantly elevated free T and low SHBG serum levels.

CONCLUSION(S)

There were no statistically significant differences in androgen response to acute hyperinsulinemia during an OGTT between obese women with different regional fat distributions and lean controls.

Insulin and polycystic ovary syndrome: a new look at an old subject

In recent years the metabolic implications of polycystic ovary syndrome (PCOS) have received a great deal of attention; in fact 50% of women with PCOS are obese and a similar percentage of subjects was found to show exaggerated insulin secretion and reduced insulin-stimulated glucose uptake. The presence of these features in women with PCOS has profound clinical implications in terms of morbidity due to diabetes mellitus, dyslipidemia, hypertension and cardiovascular disease. Moreover, hyperinsulinemia has recently been proposed as a possible independent risk factor for endometrial and breast cancer. In the light of these considerations, the importance of metabolic screening in patients with PCOS in order to improve their quality of life cannot be underestimated. In this review we analyze all the clinical pathologies in which hyperinsulinemia of PCOS could be involved. Furthermore, in order to clarify the possible mechanisms leading to the insulin disorders of the syndrome, we review the available data about the insulin receptor abnormalities, as well as those concerning the insulin resistance and the exaggerated insulin secretion. Finally, we examine the main therapeutic strategies to ameliorate the insulinemic status of PCOS patients in order to potentially be able to prevent the long-term consequences of this syndrome.

Dehydroepiandrosterone decreases serum tumor necrosis factor-alpha and restores insulin sensitivity: independent effect from secondary weight reduction in genetically obese Zucker fatty rats

Dehydroepiandrosterone (DHEA) and its sulfate ester are the most abundant circulating adrenal steroids in humans. Administration of DHEA has been reported to have beneficial effects on obesity, hyperlipidemia, diabetes, and atherosclerosis in obese rodents, although its effects on insulin resistance have not been fully elucidated. In this study, the effects of DHEA treatment on insulin sensitivity were investigated in genetically obese Zucker rats, an animal model of insulin resistance, using the euglycemic clamp technique. After 0.4% DHEA was administered for 10 days to female obese Zucker rats aged 16 weeks, body weight and plasma insulin decreased and glucose disposal rate (GDR), which was normally reduced in obese rats, rose significantly compared with age- and sex-matched control obese rats. On the other hand, although the pair-fed obese rats also showed levels of weight reduction similar to those of DHEA-treated rats, the increase in GDR of DHEA-treated rats was significantly greater than in pair-fed rats, suggesting a direct ameliorating effect of DHEA on insulin sensitivity of obese rats. Serum concentration of tumor necrosis factor (TNF)-alpha, one of cytokines causing insulin resistance, was also reduced significantly in DHEA-treated, but not in pair-fed obese rats. In conclusion, our results suggest that DHEA treatment reduces body weight and serum TNF-alpha independently, and that both may ameliorate insulin resistance in obese Zucker fatty rats.

Insulin resistance and the polycystic ovary syndrome: mechanism and implications for pathogenesis

It is now clear that PCOS is often associated with profound insulin resistance as well as with defects in insulin secretion. These abnormalities, together with obesity, explain the substantially increased prevalence of glucose intolerance in PCOS. Moreover, since PCOS is an extremely common disorder, PCOS-related insulin resistance is an important cause of NIDDM in women (Table 3). The insulin resistance in at least 50% of PCOS women appears to be related to excessive serine phosphorylation of the insulin receptor. A factor extrinsic to the insulin receptor, presumably a serine/threonine kinase, causes this abnormality and is an example of an important new mechanism for human insulin resistance related to factors controlling insulin receptor signaling. Serine phosphorylation appears to modulate the activity of the key regulatory enzyme of androgen biosynthesis, P450c17. It is thus possible that a single defect produces both the insulin resistance and the hyperandrogenism in some PCOS women (Fig. 19). Recent studies strongly suggest that insulin is acting through its own receptor (rather than the IGF-I receptor) in PCOS to augment not only ovarian and adrenal steroidogenesis but also pituitary LH release. Indeed, the defect in insulin action appears to be selective, affecting glucose metabolism but not cell growth. Since PCOS usually has a menarchal age of onset, this makes it a particularly appropriate disorder in which to examine the ontogeny of defects in carbohydrate metabolism and for ascertaining large three-generation kindreds for positional cloning studies to identify NIDDM genes. Although the presence of lipid abnormalities, dysfibrinolysis, and insulin resistance would be predicted to place PCOS women at high risk for cardiovascular disease, appropriate prospective studies are necessary to directly assess this.

Nutrition, hormones, and breast cancer: is insulin the missing link?

Breast cancer incidence rates are high in societies with a Western lifestyle characterized by low levels of physical activity, and by an energy-dense diet rich in total and saturated fat and refined carbohydrates. Epidemiologic studies, so far mostly on postmenopausal women, have shown that breast cancer risk is increased in hyperandrogenic women, with decreased levels of plasma sex-hormone binding globulin, and with increased levels of testosterone and of free estrogens. This paper describes the role of hyperinsulinemia as a physiologic link between nutritional lifestyle factors, obesity, and the development of a hyperandrogenic endocrine profile, and reviews evidence that may or may not support the theory that chronic hyperinsulinemia is an underlying cause of breast cancer. An hypothesis is presented, stipulating that breast cancer risk is increased not only in hyperandrogenic postmenopausal women, but also in premenopausal women with mild hyperandrogenism and normal (ovulatory) menstrual cycles. The author suggests further investigation as to whether there is a positive association between risk of breast cancer before menopause and subclinical forms of the polycystic ovary syndrome (PCOS), and to what extent diet and physical activity during childhood, by modulating the degree of insulin resistance during adolescence, may or may not be determinants of a PCO-like hyperandrogenic endocrine profile persisting into adulthood.

More uniform diurnal blood glucose control and a reduction in daily insulin dosage on addition of glibenclamide to insulin in type 1 diabetes mellitus: role of enhanced insulin sensitivity

Combination therapy with insulin and sulphonylurea has gained acceptance in management of subjects with Type 2 (non-insulin-dependent) diabetes mellitus. However, its role in management of Type 1 (insulin-dependent) diabetes mellitus remains controversial. In this study, the effect of combination therapy with insulin and glibenclamide on metabolic control, daily insulin dosage, and insulin sensitivity was assessed in subjects with Type 1 diabetes mellitus. Ten men with Type 1 diabetes mellitus participated in a randomized, double-blind, crossover, clinical trial with three treatment regimens, namely (1) insulin alone, (2) insulin and placebo, (3) insulin and glibenclamide, each lasting 3 months. Combination therapy induced: (1) reduction in daily insulin dosage; (2) more uniform blood glucose control as reflected by a lower average 24 h blood glucose level, a smaller difference between mean preprandial and 2 h postprandial blood glucose concentrations, decreased 24 h urine glucose excretion, and a decline in number of hypoglycaemic events; (3) improved insulin sensitivity as expressed by more rapid plasma glucose disappearance rate, without a significant alteration in fasting plasma glucagon and 1h postprandial serum C-peptide levels; when compared with treatment with either insulin alone or with insulin and placebo. Therefore, it is apparent that the addition of glibenclamide to insulin reduces daily insulin dosage and renders a greater uniformity to diurnal blood glucose control, most probably secondary to enhancement of insulin sensitivity.

Excessive insulin receptor serine phosphorylation in cultured fibroblasts and in skeletal muscle. A potential mechanism for insulin resistance in the polycystic ovary syndrome

We investigated the cellular mechanisms of the unique disorder of insulin action found in the polycystic ovary syndrome (PCOS). Approximately 50% of PCOS women (PCOS-Ser) had a significant increase in insulin-independent beta-subunit [32P]phosphate incorporation (3.7-fold, P < 0.05 vs other groups) in skin fibroblast insulin receptors that was present in serine residues while insulin-induced tyrosine phosphorylation was decreased (both P < 0.05 vs other groups). PCOS skeletal muscle insulin receptors had the same abnormal phosphorylation pattern. The remaining PCOS women (PCOS-n1) had basal and insulin-stimulated receptor autophosphorylation similar to control. Phosphorylation of the artificial substrate poly GLU4:TYR1 by the PCOS-Ser insulin receptors was significantly decreased (P < 0.05) compared to control and PCOS-n1 receptors. The factor responsible for excessive serine phosphorylation appeared to be extrinsic to the receptor since no insulin receptor gene mutations were identified, immunoprecipitation before autophosphorylation corrected the phosphorylation defect and control insulin receptors mixed with lectin eluates from affected PCOS fibroblasts displayed increased serine phosphorylation. Our findings suggest that increased insulin receptor serine phosphorylation decreases its protein tyrosine kinase activity and is one mechanism for the post-binding defect in insulin action characteristic of PCOS.

Hyperandrogenic anovulation (PCOS): a unique disorder of insulin action associated with an increased risk of non-insulin-dependent diabetes mellitus

Polycystic ovary syndrome is the most common endocrine disorder in women of reproductive age. Recent prevalence estimates suggest that 5-10% of premenopausal women have the full-blown syndrome of hyperandrogenism, chronic anovulation, and polycystic ovaries. Evidence suggests that women with polycystic ovary syndrome have a unique disorder of insulin action and are at increased risk to develop non-insulin-dependent diabetes mellitus. Further, non-insulin-dependent diabetes mellitus in women with polycystic ovary syndrome has a substantially earlier age of onset (third to fourth decades) than it does in the general population (sixth to seventh decades). Studies assessing whether abnormalities in insulin action are intrinsic or secondary to the hormonal milieu have found that insulin-induced receptor autophosphorylation is markedly diminished in approximately 50% of polycystic ovary syndrome women. This defect is unique to women with polycystic ovary syndrome and is not seen in other common insulin-resistant states of obesity and non-insulin-dependent diabetes mellitus. In polycystic ovary syndrome women who have normal receptor autophosphorylation, it remains likely that signaling mechanisms downstream of the receptor are abnormal, since these women are also insulin resistant. This distinctive post-insulin-binding defect appears to be genetic, since it is present in cells removed from the in vivo environment for generations.

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.

Relationship between visceral fat, steroid hormones and insulin sensitivity in premenopausal obese women

OBJECTIVES

The relationships between visceral fat distribution, steroid hormones and peripheral insulin sensitivity were studied.

SETTING

All subjects were hospitalized in the Institute of Internal Medicine of the University of Verona, Italy.

SUBJECTS

Nineteen fertile obese women were studied with ages ranging from 18 to 53 years and body mass indexes ranging from 27.3 to 48.4.

INTERVENTION

Body fat distribution was evaluated by waist-to-hip circumference ratio and by computed tomography. The insulin tolerance test was used to evaluate peripheral insulin sensitivity. Glucose, insulin and C-peptide were measured in fasting conditions and during glucose load; total and free plasma testosterone and urinary cortisol excretion were also determined.

RESULTS

Significant correlations emerged between visceral adipose tissue and fasting glucose, insulin, and C-peptide, but not between visceral adipose tissue and total testosterone, free testosterone or urinary cortisol excretion. A negative correlation emerged between visceral adipose tissue and insulin sensitivity (r = -0.70; P < 0.01). No significant correlations were found between insulin sensitivity and age, body weight, body mass index, total adipose tissue, subcutaneous adipose tissue or waist-to-hip ratio. Total testosterone correlated with body weight, subcutaneous adipose tissue and total adipose tissue. Free testosterone and urinary cortisol excretion correlated positively with body weight, and negatively with age. No correlation was found between insulin sensitivity and total testosterone, free testosterone or urinary cortisol excretion. The correlation between visceral adipose tissue and insulin sensitivity remained significant even after adjusting for both age and the body mass index.

CONCLUSIONS

Our study shows that visceral fat is more closely associated with aberrations of insulin sensitivity than with obesity itself. Total testosterone, free testosterone and urinary cortisol excretion in our subjects do not seem to be associated with such aberrations.

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.

Enhanced adrenocortical activity as a contributing factor to diabetes in hyperandrogenic women

The high incidence of non-insulin-dependent diabetes mellitus (NIDDM) in women with polycystic ovarian syndrome (PCO) is believed to occur secondary to the insulin resistance associated with their androgenicity. In the present study, we have examined the interrelationships between glucose tolerance, androgenicity, and various in vivo and in vitro parameters of insulin sensitivity in 11 obese PCO patients with NIDDM, 14 PCO patients without diabetes, and 14 weight-matched controls. Both groups of PCO patients were hypertestosteronemic, hyperinsulinemic, and insulin-resistant when compared with a group of weight-matched controls. However, PCO patients with NIDDM differed from those without diabetes in that they had elevated basal and corticotropin-stimulated adrenal steroids (cortisol, dehydroepiandrosterone [DHEA], dehydroepiandrosterone sulfate [DHEAS]). The hyperglycemia of our diabetic patients was not related to their elevated testosterone levels or to their degree of insulin resistance, but was significantly and positively correlated with adrenal hypersecretion, which in turn was associated with postreceptor defects in insulin action. These findings would suggest that enhanced adrenocortical activity may be an important factor underlying the development of NIDDM in women with PCO.

Enhanced post-receptor insulin effects in women following dehydroepiandrosterone infusion

OBJECTIVE

We hypothesized that intravenous dehydroepiandrosterone (DHEA) would decrease insulin resistance in normal and insulin-resistant women.

METHODS

Five insulin-resistant women diagnosed as having polycystic ovaries (PCO) with elevated testosterone and normal dehydroepiandrosterone sulfate (DHEAS) with amenorrhea were recruited. Obese controls (OC) with normal menses and normal testosterone and DHEAS were recruited and matched to each PCO woman for age and weight. The PCO women had a mean testosterone of 3.2 +/- 0.4 nmol/L, fasting serum insulin level of 330 +/- 55 pmol/L, and DHEAS level of 3.4 +/- 1.3 mumol/L. An oral glucose tolerance test (OGTT) was performed at 8 AM after an overnight fast. A DHEA infusion (1 mg/hour for 17 hours) was begun at 6 PM and continued until the completion of the second OGTT performed the following morning at 8 AM. T-lymphocytes were drawn at 8 AM each morning.

RESULTS

The DHEA infusion had no significant effect on any of the in vivo indices of insulin sensitivity, ie, basal and OGTT insulin, C-peptide, and ratios of insulin/glucose. In vitro, DHEA significantly increased insulin binding to T-lymphocytes of PCO women but caused no significant change in OC women. There was, however, marked enhancement of T-lymphocyte pyruvate dehydrogenase (PDH) activities in both groups of study subjects following DHEA.

CONCLUSION

We conclude that a 17-hour infusion of DHEA enhanced T-lymphocyte insulin binding and PDH activity while producing no detectable improvements in in vivo indices of insulin sensitivity.

Hyperinsulinaemia, dyslipidaemia and exaggerated adrenal androgen response to adrenocorticotropin in male smokers

Insulin resistance and dyslipidaemia associated with smoking may result from increased secretion of anti-insulin hormones. We compared the pituitary-adrenocortical function using oral glucose tolerance, dexamethasone suppression and ACTH stimulation tests in smoking (n = 22) and non-smoking (n = 22) healthy males matched for age, body mass index, and waist-to-hip ratio. Smokers had lower HDL-cholesterol (p < 0.02), and higher triglyceride (p < 0.001), basal cortisol (p < 0.05), insulin (p < 0.05), and C-peptide (p < 0.02) levels, and a higher response of insulin and C-peptide to oral glucose (p < 0.005) than non-smokers, while the ACTH, cortisol, 17-hydroxyprogesterone, dehydroepiandrosterone, and androstenedione responses to oral glucose were similar in both groups. No differences were found in the response of cortisol, 17-hydroxyprogesterone, dehydroepiandrosterone, and androstenedione to dexamethasone. In contrast, the response of 17-hydroxyprogesterone (p = 0.04), dehydroepiandrosterone (p = 0.007), and androstenedione (p = 0.001) to ACTH was higher in smokers than non-smokers, while the increase in cortisol was of marginal significance (p = 0.07). In multiple regression analyses the dehydroepiandrosterone response to ACTH was a significant determinant of insulin, C-peptide, and triglyceride levels independent of physical activity, waist-to-hip ratio and HDL-cholesterol. Thus, smoking inhibits the adrenal 21-hydroxylase resulting in an increase in the production of adrenal androgens, which might contribute to the insulin resistance and dyslipidaemia in smokers.

Case report: amelioration of insulin resistance in diabetes with dehydroepiandrosterone

In hyperandrogenic females, the ratio of dehydroepiandrosterone (DHEA) to testosterone may be an important determinant of insulin sensitivity. This study involved changes in insulin sensitivity and glucose metabolism with therapeutic manipulation of DHEA (S)/testosterone in a female patient with non-insulin-dependent diabetes and hyperandrogenism. Therapeutic intervention included 1-month treatment with 0.25 mg dexamethasone at bedtime and 1-month dexamethasone + DHEA. Insulin sensitivity and glucose tolerance were assessed before and after each treatment regimen by examining: 1) fasting and oral glucose tolerance test glucose and insulin levels, 2) hypoglycemic response to intravenous insulin, and 3) erythrocyte insulin receptor binding. With dexamethasone alone, DHEAS, testosterone, and their ratio were reduced with a concomitant increase (30%) in oral glucose tolerance test insulin levels and a decrease (33%) in erythrocyte insulin binding. With DHEA + dexamethasone, the ratio of DHEAS/testosterone increased 16-fold along with a marked improvement in insulin sensitivity, as determined by a more than 30% reduction in fasting and oral glucose tolerance test insulin levels, a threefold stimulation of the rate of glucose disappearance with intravenous insulin, and a 30% increase in insulin binding. DHEA improved insulin sensitivity and reduced fasting and oral glucose tolerance test glucose levels and ameliorated the diabetic state. The ratio of DHEAS/testosterone is an important regulator of insulin sensitivity and glucose tolerance and that DHEA therapy may be beneficial in the treatment of certain forms of insulin resistance.

Direct relationship between elevated free testosterone and insulin resistance in hyperprolactinemic women

Women with hyperprolactinemia have been reported to have hyperandrogenemia and/or insulin resistance. However, little is known about the association of hyperandrogenemia and insulin resistance in these women. To investigate whether hyperandrogenemia and/or insulin resistance occur in hyperprolactinemic women, and to assess the relationship between them, we measured basal androgen level and both glucose and insulin levels after oral glucose administration in 20 hyperprolactinemic women and 7 female control subjects. Free testosterone level was higher and estradiol level lower in hyperprolactinemic women than in control subjects (p < 0.05), whereas dehydroepiandrosterone sulfate (DHEAS) and total testosterone levels were similar (p > 0.05). Both fasting glucose and insulin levels didn't differ in the two groups (p > 0.05). However, both serum glucose and insulin levels, after a 75 g glucose load, were significantly increased in hyperprolactinemic women, (p = 0.001, p < 0.001, respectively). In simple linear regression analysis in hyperprolactinemic women, only free testosterone level had a positive correlation with the incremental area under the insulin curve (insulin-IAU) (r = 0.47, p < 0.05). In multiple stepwise regression analysis, free testosterone level, mean blood pressure and DHEAS level were associated significantly with insulin-IAU (beta = 0.98, p < 0.0001; beta = 0.58, p = 0.002; beta = -0.67, p < 0.003, respectively). These results suggest that insulin resistance is closely related to elevated free testosterone level in hyperprolactinemic women.

Interrelation between plasma testosterone and plasma insulin in healthy adult men: the Telecom Study

Plasma insulin is a risk factor for diabetes mellitus and cardiovascular disease in men. We investigated the association between plasma testosterone and plasma insulin in an occupational sample of 1292 healthy adult men. Total plasma testosterone decreased with each decade of age and insulin increased with each decade of age. In these cross-sectional data, this significant graded inverse association between testosterone and insulin was independent of age. The association was reduced but not explained by the addition of obesity and subscapular skinfold to the model. Adjustment for alcohol consumption, cigarette smoking and plasma glucose did not materially alter the association. These results are the reverse of the positive association of androgens with insulin in women and suggest alternative possible explanations for the effect of hyperinsulinaemia on cardiovascular disease risk. Prospective studies will be necessary to determine the direction and causal nature of this association.