Insulin inhibits adrenal 17,20-lyase activity in man

Effects of intraperitoneal insulin versus subcutaneous insulin administration on sex hormone-binding globulin concentrations in patients with type 1 diabetes mellitus

AIMS

Elevated sex hormone-binding globulin (SHBG) concentrations have been described in patients with type 1 diabetes mellitus (T1DM), probably due to low portal insulin concentrations. We aimed to investigate whether the route of insulin administration, continuous intraperitoneal insulin infusion (CIPII), or subcutaneous (SC), influences SHBG concentrations among T1DM patients.

METHODS

Post hoc analysis of SHBG in samples derived from a randomized, open-labeled crossover trial was carried out in 20 T1DM patients: 50% males, mean age 43 (±13) years, diabetes duration 23 (±11) years, and hemoglobin A1c (HbA1c) 8.7 (±1.1) (72 (±12) mmol/mol). As secondary outcomes, testosterone, 17-β-estradiol, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were analyzed.

RESULTS

Estimated mean change in SHBG was -10.3nmol/L (95% CI: -17.4, -3.2) during CIPII and 3.7nmol/L (95% CI: -12.0, 4.6) during SC insulin treatment. Taking the effect of treatment order into account, the difference in SHBG between therapies was -6.6nmol/L (95% CI: -17.5, 4.3); -12.7nmol/L (95% CI: -25.1, -0.4) for males and -1.7nmol/L (95% CI: -24.6, 21.1) for females, respectively. Among males, SHBG and testosterone concentrations changed significantly during CIPII; -15.8nmol/L (95% CI: -24.2, -7.5) and -8.3nmol/L (95% CI: -14.4, -2.2), respectively. The difference between CIPII and SC insulin treatment was also significant for change in FSH 1.2U/L (95% CI: 0.1, 2.2) among males.

CONCLUSIONS

SHBG concentrations decreased significantly during CIPII treatment. Moreover, the difference in change between CIPII and SC insulin therapy was significant for SHBG and FSH among males. These findings support the hypothesis that portal insulin administration influences circulating SHBG and sex steroids.

Increased clearance of cortisol by 5beta-reductase in a subgroup of women with adrenal hyperandrogenism in polycystic ovary syndrome

OBJECTIVE

Increased peripheral metabolism of cortisol may explain compensatory ACTH-dependent adrenal steroidogenesis and hence hyperandrogenism in polycystic ovary syndrome (PCOS). Previous studies have described an increased 5alpha-reduction of cortisol or impaired regeneration of cortisol by 11beta-HSD1 in PCOS. However, these observations may be confounded by obesity. Moreover, the relationship between alterations in cortisol metabolism and the extent of adrenal androgen hyper-secretion in response to ACTH has not been established. This study aimed to examine the association between cortisol metabolism and ACTH-dependent adrenal hyperandrogenism in PCOS, independently of obesity.

DESIGN

We compared 90 PCOS women (age 18-45 yr) stratified by adrenal androgen responses to ACTH1-24 and 45 controls matched for age and body weight.

METHODS

PCOS women were stratified as normal responders (NR), intermediate responders (IR), and high responders (HR) to 250 microg ACTH1-24: NR (no.=27) had androstenedione and DHEA responses within 2 SD of the mean in controls; IR (no.=43) had DHEA responses >2 SD above controls; HR (no.=20) had both androstenedione and DHEA responses >2 SD above controls.

RESULTS

All groups were similar for age, body weight, and body fat distribution. Basal testosterone, androstenedione, and 5alpha-dihydrotestosterone plasma levels were similarly elevated among the 3 groups of PCOS compared with controls, whereas basal DHEA-S was higher in HR (2.8+/-1.2 microg/ml) and IR (2.4+/-1.1 microg/ml) than in NR (1.8+/-0.8 microg/ml) and controls (1.7+/-0.6 microg/ml). The HR group had the lowest basal plasma cortisol levels (101+/-36 ng/ml vs IR 135+/-42 ng/ml, NR 144+/-48 ng/ml, and controls 165+/-48 ng/ml; all p<0.01), but the greatest cortisol response to ACTH1-24 (Delta(60-0)cortisol 173+/-60 ng/ml vs IR 136+/-51 ng/ml, NR 114+/-50 ng/ml, and controls 127+/-50 ng/ml; all p<0.01), and the highest urinary excretion of total and 5beta-reduced cortisol metabolites (eg 5beta-tetrahydrocortisol/ cortisol ratio 25.2+/-15.3 vs IR 18.8+/-10.7, NR 19.7+/-11.4, and controls 17.2+/-13.7; all p<0.05). There were no differences in urinary excretion of 5alpha-reduced cortisol metabolites or in 5alpha-dihydrotestosterone/testosterone ratio between groups.

CONCLUSIONS

Adrenal androgen excess in PCOS is associated with increased inactivation of cortisol by 5beta-reductase that may lower cortisol blood levels and stimulate ACTH-dependent steroidogenesis.

Effect of insulin and testosterone on androgen production and transcription of SULT2A1 in the NCI-H295R adrenocortical cell line

OBJECTIVE

To determine changes in adrenal androgen (AA) production, and transcription of dehydroepiandrosterone (DHEA) sulfotransferase (SULT2A1) in the NCI-H295R human adrenocortical cell line in response to insulin and testosterone, an environment mimicking the polycystic ovary syndrome state.

DESIGN

In vitro experiment using NCI-H295R adrenocortical cell lines.

SETTING

Academic medical center.

PATIENT(S)

NCI-H295R human adrenocortical cell line.

INTERVENTION(S)

The transcriptional activity of SULT2A1 and adrenal steroid production was quantified after exposure to various treatments (e.g., forskolin, insulin, testosterone, and combinations thereof).

MAIN OUTCOME MEASURE(S)

Quantification of mRNA for DHEA sulfotransferase (SULT2A1) by real-time reverse transcription-polymerase chain reaction and measurement of steroid production by radioimmunoassay.

RESULT(S)

Testosterone decreased DHEAS and cortisol, and increased DHEA secretion by H295R cells; the inhibitory effects of testosterone on DHEAS and cortisol production were augmented by insulin. There was a trend toward an increase in the transcription of SULT2A1 by insulin and testosterone.

CONCLUSION(S)

Testosterone and insulin appear to be modulators of adrenal androgen production in this human adrenocortical cell model. These results suggest that testosterone may augment DHEA secretion in the human adrenal, although they do not support the role of this sex steroid or insulin on the elevated DHEAS levels frequently observed in polycystic ovary syndrome.

Steroids in adult men with type 1 diabetes: a tendency to hypogonadism

OBJECTIVE

To compare steroids and their associations in men with type 1 diabetes and healthy control subjects.

RESEARCH DESIGN AND METHODS

We studied 52 adult men with type 1 diabetes without microvascular complications, compared with 53 control subjects matched for age and BMI. Steroids and their binding globulins were assessed in a single venous blood sample and a 24-h urine sample.

RESULTS

In adult men with type 1 diabetes, total testosterone did not differ from healthy control subjects, but sex hormone-binding globulin (SHBG) (42 [14-83] vs. 26 [9-117] nmol/l, P < 0.001), cortisol-binding globulin (CBG; 0.87 +/- 0.17 vs. 0.73 +/- 0.10 nmol/l, P < 0.001), and cortisol levels (0.46 +/- 0.16 vs. 0.39 +/- 0.14 nmol/l, P < 0.01) were higher. The free testosterone index was lower (60 [17-139] vs. 82 [24-200], P < 0.001), and the calculated free testosterone was slightly lower (497 [115] vs. 542 [130], P < 0.064), but the pituitary-gonadal axis was not obviously affected in type 1 diabetes. The calculated free serum cortisol was not different, and 24-h urinary free cortisol excretion was lower in type 1 diabetes (121 [42-365] vs. 161 [55-284] nmol/24 h, P < 0.009). Testosterone was mainly associated with SHBG. Estimated portal insulin was a contributor to SHBG in control subjects but not in type 1 diabetes. Cortisol was associated with CBG. HbA(1c) contributed to CBG in men with diabetes but not in control subjects, whereas estimated portal insulin did not contribute.

CONCLUSIONS

Adult men with fairly controlled type 1 diabetes without complications who are treated with subcutaneous insulin have a tendency to hypogonadism, as reflected by lower free testosterone levels in the presence of similar total testosterone levels and higher SHBG levels.

Three-month treatment with metformin or dexfenfluramine does not modify the effects of diet on anthropometric and endocrine-metabolic parameters in abdominal obesity

Abdominal obesity is connoted by hyperinsulinism and insulin insensitivity, a trend toward glucose intolerance, hypoactivity of GH/IGF-I axis and alterations of hypothalamo-pituitary-adrenal (HPA) axis. It has been hypothesized that treatment with metformin (MET) and dexfenfluramine (DEX) could counteract those endocrine-metabolic alterations. Thus, we studied the effects of 3-month treatment with MET or DEX on anthropometric (BMI, WHR, FM and FFM), metabolic (basal and OGTT-induced glucose) and hormonal variables (IGF-I, DHEA-S, androstendione, testosterone, fT3, fT4, TSH, basal and OGTT-induced insulin) as well as on blood pressure in 28 normotensive patients with abdominal obesity (OB, 3 M, 25 F; 47.5+/-1.5 yr [mean+/-SE], BMI 35.4+/-1.1 kg/m2, WHR 0.98+/-0.04 and 0.86+/-0.07, in M and F, respectively). All patients were on balanced hypocaloric diet (1400 Kcal/day). Patients were randomly assigned to treatment with MET (no.=10, 500 mg twice daily po) or DEX (no.=10, 15 mg thrice daily po) or placebo (no.=8). Before treatment all groups had similar anthropometric, metabolic and hormonal values. After 3-month treatment with MET, DEX or placebo, weight, BMI and WHR reductions were similar in all groups (p<0.05 vs baseline in either group). In each group FFM/FM ratio showed non significant trend toward increase. No significant variations in metabolic and endocrine variables were recorded in each group after 1 and 3-month treatment. However, glucose tolerance, OGTT-induced insulin response, glucose/insulin ratio showed a similar trend toward improvement in all groups, while IGF-I, 24 h urinary cortisol, DHEA-S, androstendione, testosterone, thyroid hormone and TSH levels did not show any variation. Significant (p<0.02) and similar reductions of DBP, but not of SBP, levels were found in all groups. In conclusion, our findings demonstrate that, at least after 3-month treatment, metformin and dexfenfluramine do not modify the effects of diet on anthropometric, metabolic and hormonal parameters as well as on blood pressure in patients with abdominal obesity.

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.