Alpha-melanocyte-stimulating hormone antagonizes the neuroendocrine effects of corticotropin-releasing factor and interleukin-1 alpha in the primate.

alpha-Melanocyte stimulating hormone (alpha-MSH), a peptide derived from POMC has previously been shown to antagonize the action of exogenously administered beta-endorphin (beta-EP) on pituitary PRL and LH release in the primate. In this study, we have tested the ability of alpha-MSH to block some of the acute pituitary effects of CRF and interleukin-1 alpha (IL-1 alpha), effects which are thought in part to result from the release of endogenous beta-EP. Experiments were performed in ovariectomized rhesus monkeys bearing a chronically implanted lateral ventricular cannula for peptide infusion. Peripheral blood samples for LH, cortisol, and PRL RIA were obtained at 15-min intervals during a 3-h control period when saline was infused into the ventricle, followed by a 5-h experimental period. CRF (15 micrograms/h) infused alone for 5 h caused a significant suppression of pulsatile LH release; by the fifth hour, LH secretion was reduced to 32.5 +/- 2.4% of the control saline infusion. The CRF-induced suppression of LH was prevented by coinfusion of alpha-MSH (60 micrograms/h); by the fifth hour LH was 89.0 +/- 3.6% of the control (P less than 0.05 vs. CRF alone). alpha-MSH also prevented the CRF-induced decrease in LH pulse frequency (P less than 0.05). IL-1 alpha (4.2 micrograms) was infused alone for 30 min or in combination with alpha-MSH (120 micrograms/h for 2 h). After IL-1 alpha alone, LH decreased to 30.1 +/- 2.4% of baseline at 5 h. This decrease was prevented by alpha-MSH; by 5 h LH was 101 +/- 5.1% of baseline (P less than 0.005 vs. IL-1 alpha alone). IL-1 alpha did not affect LH pulse frequency but pulse amplitude was reduced; this reduction was prevented by alpha-MSH (P less than 0.05). IL-1 alpha also stimulated PRL release. PRL rose from a mean baseline of 3.5 +/- 0.3 ng/ml to a peak of 13.8 +/- 2.7 ng/ml; after coinfusion of alpha-MSH the mean peak PRL response was only 4.4 +/- 1.5 ng/ml (P less than 0.001 vs. IL-1 alpha alone). After CRF infusion, cortisol increased to 136 +/- 7.9% of the mean morning baseline concentration. This increase was not prevented by alpha-MSH coinfusion; after CRF plus alpha-MSH, cortisol increased to 121 +/- 6.0% of baseline. In contrast, alpha-MSH prevented the IL-1 alpha-induced increase in cortisol: 167 +/- 15.5% vs. 91.7 +/- 8.3% (P less than 0.005).(ABSTRACT TRUNCATED AT 400 WORDS)     

Estrogen modulates the hypothalamic-pituitary-adrenal and inflammatory cytokine responses to endotoxin in women

Endotoxin stimulates the release of the inflammatory cytokines interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-alpha, which are potent activators of the hypothalamic-pituitary-adrenal (HPA) axis. Recent studies in the rodent and in the primate have shown that the HPA responses to endotoxin and IL-1 were enhanced by gonadectomy and attenuated by estradiol (E2) replacement. In addition, there is some evidence, in the rodent, that estrogen modulates inflammatory cytokine responses to endotoxin. To determine whether estrogen has similar effects in humans, we studied the cytokine and HPA responses to a low dose of endotoxin (2--3 ng/kg) in six postmenopausal women with and without transdermal E2 (0.1 mg) replacement. Mean E2 levels were 7.3 +/- 0.8 pg/mL in the unreplaced subjects and increased to 102 +/- 13 pg/mL after estrogen replacement. Blood was sampled every 20 min for 1--2 h before, and for 7 h after, iv endotoxin administration. Endotoxin stimulated ACTH, cortisol, and cytokine release in women with and without E2 replacement. E2 significantly attenuated the release of ACTH (P < 0.0001) and of cortisol (P = 0.02). Mean ACTH levels peaked at 190 +/- 91 pg/mL in the E2-replaced group vs. 411 +/- 144 pg/mL in the unreplaced women, whereas the corresponding mean cortisol levels peaked at 27 +/- 2.9 microg/dL with E2 vs. 31 +/- 3.2 microg/dL without E2. Estrogen also attenuated the endotoxin-induced release of IL-6 (P = 0.02), IL-1 receptor antagonist (P = 0.003), and TNF-alpha (P = 0.04). Mean cytokine levels with and without E2 replacement peaked at 341 +/- 94 pg/mL vs. 936 +/- 620 pg/mL for IL-6, 82 +/- 14 ng/mL vs. 133 +/- 24 ng/mL for IL-1 receptor antagonist, and 77 +/- 46 pg/mL vs. 214 +/- 87 pg/mL for TNF-alpha, respectively. We conclude that inflammatory cytokine and HPA responses to a low dose of endotoxin are attenuated in postmenopausal women receiving E2 replacement. These data show, for the first time in the human, that a physiological dose of estrogen can restrain cytokine and neuroendocrine responses to an inflammatory challenge.     

Alprazolam,a benzodiazepine,does not modify the ACTH and cortisol response to hCRH and AVP,but blunts the cortisol response to ACTH in humans

Alprazolam (AL), a benzodiazepine which activates gamma-amino butyrric acid (GABA)-ergic receptors, exerts a clear inhibitory effect on the activity of the hypothalamo-pituitary-adrenal (HPA) axis and is able to markedly reduce the ACTH response to metyrapone-induced inhibition of glucocorticoid feedback. It has been suggested that its inhibitory action could be regulated by CRH or AVP mediated mechanisms. However, the effect of benzodiazepines on the HPA response to CRH or AVP is contradictory. It has been shown that benzodiazepines have specific receptors on the adrenal gland but it is unclear if they mediate biological effects in humans. In order to further clarify the mechanisms underlying the inhibitory effect of benzodiazepine on HPA axis in humans, we studied the effect of AL (0.02 mg/kg po at -90 min) or placebo in 7 healthy young volunteers (7 female, age: 26-34 yr; wt: 50-58 kg, BMI 20-22 kg/m2) on: 1) the ACTH and cortisol responses to hCRH (2.0 microg/kg iv at 0 min) or AVP (0.17 U/kg im at 0 min); 2) the cortisol, aldosterone and DHEA responses to ACTH 1-24 (0.06 and 250 microg iv at 0 and 60 min, respectively). After placebo, the ACTH and cortisol responses to hCRH (peaks, mean+/-SE: 29.8+/-4.4 pg/ml and 199.3+/-19.6 microg/l) were similar to those recorded after AVP (31.7+/-6.5 pg/ml and 164.8+/-18.0 microg/l); the cortisol response to 0.06 microg ACTH (190.4+/-11.8 microg/l) was similar to that recorded after hCRH and AVP but lower (p<0.01) than that after 250 microg ACTH (260.6+/-17.4 microg/l). AL did not modify the ACTH response to both hCRH (42.5+/-7.1 pg/ml) and AVP (33.3+/-2.7 pg/ml), which even showed a trend toward increase. AL also failed to significantly modify the cortisol response to both hCRH (156.3+/-12.7 microg/l) and AVP (119.4+/-14.5 microg/l), which, on the other hand, showed a trend toward decrease. The cortisol peaks after 0.06 microg ACTH were significantly reduced (p<0.02) by AL pre-treatment (115.0+/-7.7 microg/l) which, in turn, did not modify the cortisol response to the subsequent ACTH bolus (214.7+/-16.6 microg/l). The DHEA and aldosterone responses to all the ACTH doses were not significantly modified by AL. In conclusion, these data show that the HPA response to AVP as well as to hCRH is refractory to the inhibitory effect of AL which, in turn, blunts the cortisol response to low ACTH dose. These findings suggest that both CRH- and AVP-mediated mechanisms could underlie the CNS-mediated inhibitory effect of AL on HPA axis; in the meantime, these results suggest that benzodiazepines could also act on adrenal gland by blunting the sensitivity of the fasciculata zone to ACTH.     

Neuroendocrine and metabolic effects of acute ghrelin administration in human obesity

Ghrelin stimulates appetite and plays a role in the neuroendocrine response to energy balance variations. Ghrelin levels are inversely associated with body mass index (BMI), increased by fasting and decreased by food intake, glucose load, insulin, and somatostatin. Ghrelin levels are reduced in obesity, a condition of hyperinsulinism, reduced GH secretion, and hypothalamus-pituitary-adrenal axis hyperactivity. We studied the endocrine and metabolic response to acute ghrelin administration (1.0 microg/kg i.v.) in nine obese women [OB; BMI (mean +/- SD) 36.3 +/- 2.3 kg/m(2)] and seven normal women (NW; BMI 20.3 +/- 1.7 kg/m(2)). Basal ghrelin levels in NW were higher than in OB (P < 0.05). In NW, ghrelin increased (P < 0.05) GH, prolactin (PRL), ACTH, cortisol, and glucose levels but did not modify insulin. In OB, ghrelin increased (P < 0.01) GH, PRL, ACTH, and cortisol levels. The GH response to ghrelin in OB was 55% lower (P < 0.02) than in NW, whereas the PRL, ACTH, and cortisol responses were similar. In OB, ghrelin increased glucose and reduced insulin (P < 0.05). Thus, obesity shows remarkable reduction of the somatotroph responsiveness to ghrelin, suggesting that ghrelin hyposecretion unlikely explains the impairment of somatotroph function in obesity. On the other hand, in obesity ghrelin shows preserved influence on PRL, ACTH, and insulin secretion as well as in glucose levels.     

Endotoxin and the hypothalamo-pituitary-adrenal (HPA) axis

Endotoxin is considered to be a systemic (immunological) stressor eliciting a prolonged activation of the hypothalamo-pituitary-adrenal (HPA) axis. The HPA-axis response after an endotoxin challenge is mainly due to released cytokines (IL-1, IL-6 and TNF-alpha) from stimulated peripheral immune cells, which in turn stimulate different levels of the HPA axis. Controversy exists regarding the main locus of action of endotoxin on glucocorticoid secretion, since the effect of endotoxin on this neuro-endocrine axis has been observed in intact animals and after ablation of the hypothalamus; however, a lack of LPS effect has been described at both pituitary and adrenocortical levels. The resulting increase in adrenal glucocorticoids has well-documented inhibitory effects on the inflammatory process and on inflammatory cytokine release. Therefore, immune activation of the adrenal gland by endotoxin is thought to occur by cytokine stimulation of corticosteroid-releasing hormone (CRH) production in the median eminence of the hypothalamus, which, in turn stimulates the secretion of ACTH from the pituitary. Acute administration of endotoxin stimulates ACTH and cortisol secretion and the release of CRH and vasopressin (AVP) in the hypophysial portal blood. During repeated endotoxemia, tolerance of both immune and HPA function develops, with a crucial role for glucocorticoids in the modulation of the HPA axis. A single exposure to a high dose of LPS can induce a long-lasting state of tolerance to a second exposure of LPS, affecting the response of plasma TNF-alpha and HPA hormones. Although there are gender differences in the HPA response to endotoxin and IL-1, these responses are enhanced by castration and attenuated by androgen and estrogen replacement. Estrogens attenuate the endotoxin-induced stimulation of IL-6, TNF-alpha and IL-1ra release and subsequent activation in postmenopausal women. There appears to be a temporal and functional relation between the HPA-axis response to endotoxin and nitric oxide formation in the neuro-endocrine hypothalamus, suggesting a stimulatory role for nitric oxide in modulating the HPA response to immune challenges.     

Effects of cortistatin-14 and somatostatin-14 on the endocrine response to hexarelin in humans

Cortistatin (CST)-14, a neuropeptide with high structural homology with somatostatine (SS)-14, binds all SS receptor subtypes but also shows activities not shared by SS. CST and SS are often co-expressed in the same neurons but are regulated by different stimuli. Moreover, CST, but not SS, also binds the GH secretagogue (GHS) receptor. We compared the effects of CST-14 and SS-14 (2.0 microg/kg/h i.v. from -30 to +90 min) on the endocrine response to hexarelin (HEX, 1.0 microg/kg i.v. at 0 min), a synthetic GHS, in 6 normal volunteers [age (mean+/-SEM): 28.7+/-2.9 yr; body mass index: 23.4+/-0.8 kg/m2]. GH, PRL, ACTH, cortisol, insulin and glucose levels were measured at each time point. CST-14 inhibited spontaneous GH secretion [delta-areas under curves (-AUC): -83.57+/-44.8 vs 2.3+/-2.7 microg/l/h, p<0.01] to the same extent of SS-14 (-186.1+/-162.9 microg/l/h, p<0.01). CST-14 as well as SS-14 also inhibited insulin secretion (p<0.05). The GH response to HEX was similarly inhibited by either CST-14 (AUC: 3814.1+/-924.2 vs 1212.9+/-379.8 microg/l/h, p<0.05) or SS-14 (720.9+/-158.6 microg/l/h, p<0.05). HEX significantly increased PRL, ACTH and cortisol levels but these responses were not modified by either CST-14 or SS-14. The effects of CST-14 and SS-14 on insulin and glucose levels were not modified by HEX. In conclusion, this study shows that CST-14 inhibits the GH response to HEX to the same extent of SS-14. Like SS-14, CST-14 also inhibits insulin secretion but both do not modify the stimulatory effects of HEX on lactotroph and corticotroph secretion. Thus, CST-14 exerts full SS-14 activity in humans.     

Melanocortin modulation of inflammatory cytokine and neuroendocrine responses to endotoxin in the monkey

alpha-MSH has potent antiinflammatory properties, but little is known about the specific melanocortin receptors (MC-Rs) that mediate these effects or about the role of the melanocortin system in modulating cytokine responses to an inflammatory challenge in the primate in vivo. We, therefore, studied the effects of infusion of the alpha-MSH agonist, [Nle(4),d-Phe(7)]-alpha-MSH (NDP-MSH); the alpha-MSH antagonist, SHU9119; and the selective MC3-R agonist, D-Trp8-gamma-MSH, compared with saline, on proinflammatory cytokine (TNF-alpha, IL-1beta, and IL-6), antiinflammatory cytokine [IL-10 and IL-1 receptor antagonist (IL-1ra)], and pituitary-adrenal responses to endotoxin in ovariectomized monkeys. In the first study NDP-MSH or SHU9119 was infused iv for 7 h starting at 0800 h, endotoxin was injected at 1000 h, and serial blood samples were collected (n = 6). NDP-MSH significantly attenuated proinflammatory cytokine responses to endotoxin. The area under the response curve (AUC) decreased by 61% for TNF-alpha (P = 0.02), 47% for IL-1beta (P = 0.02), and 41% for IL-6 (P = 0.04); there was no effect on IL-1ra or IL-10. SHU9119 did not affect proinflammatory cytokine responses, but decreased the IL-10 response by 31% (P = 0.03). NDP-MSH also attenuated ACTH (P < 0.001) and cortisol (P = 0.02) responses. In a second study, the effects of d-Trp8-gamma-MSH were similarly examined in seven monkeys. The AUC for IL-6 was decreased by 37% (P = 0.04) by d-Trp8-gamma-MSH; the AUC for IL-10 was increased by 22%, but this was not significant. However, the ratio of IL-6 to IL-10 was significantly decreased by d-Trp8-gamma-MSH (P = 0.04), consistent with a relatively more antiinflammatory cytokine environment. These results indicate that NDP-MSH can attenuate proinflammatory cytokine responses in the primate, consistent with previous studies in the rodent, and provide new evidence for a role for MC3-R in this process. Moreover, they show for the first time that SHU9119, a mixed MC3/4-R antagonist, can decrease the IL-10 response, establishing a physiological role for endogenous MSH in modulating the release of an antiinflammatory cytokine.     

Tyr-Ala-Hexarelin, a synthetic octapeptide, possesses the same endocrine activities of Hexarelin and GHRP-2 in humans

Hexarelin (HEX) and GHRP-2 are two synthetic hexapeptides, superanalogs of GHRP-6, belonging to GH secretagogue (GHS) family. GHS act via specific receptors at both the pituitary and the hypothalamic level to stimulate GH release both in animals and in humans. However, GHS also possess significant PRL- and ACTH/cortisol-releasing activity. Tyr-Ala-HEX as well as Tyr-Ala-GHRP-6 are, in turn, synthetic octapeptides generally used to perform binding studies because of their easy iodination. However, their endocrine activities have never been studied in humans. To clarify the endocrine activities of Tyr-Ala-HEX, in 7 young adult volunteers we compared the effects of the maximal effective dose of HEX (2.0 microg/kg i.v.) or GHRP-2 (2.0 microg/kg i.v.) with the same one of Tyr-Ala-HEX on GH, PRL, ACTH and cortisol levels. Basal GH, PRL, ACTH and cortisol levels in all testing sessions were similar. The administration of placebo did not modify hormonal levels. HEX and GHRP-2 administration induced the well known strong GH response (Cmax, mean+/-SE: 77.3+/-6.0 and 74.1+/-12.1 microg/l; AUC, mean+/-SE: 2596.7+/-251.1 and 2480.0+/-343.6 microg*min/l). These responses were similar to that induced by Tyr-Ala-HEX (63.7+/-18.5 microg/l; 1986.6+/-622.4 microg*min/l). Moreover, HEX, GHRP-2 and Tyr-Ala-HEX had the same significant stimulatory effect on PRL (14.9+/-2.5, 12.3+/-2.0 and 10.0+/-1.5 microg/l; 497.8+/-61.8, 480.4+/-66.9 and 415.8+/-58.5 microg*min/l), ACTH (48.0+/-10.1, 51.4+/-10.6 and 44.9+/-12.2 pg/ml; 1531.6+/-235.7, 1586.7+/-277.0 and 1338.1+/-164.5 pg*min/ml) and cortisol (179.9+/-10.0, 181.2+/-14.1 and 149.7+/-20.1 microg/l; 8465.0+/-406.6, 8689.2+/-788.1 and 6295.2+/-797.0 microg*min/l). Also the mean Tmax of the endocrine responses to HEX, GHRP-2 and Tyr-Ala-HEX were similar. In conclusion, the present results demonstrate that in humans Tyr-Ala-HEX is a GH secretagogue as potent as HEX and GHRP-2, two GHRP-6 superanalogs. Tyr-Ala-HEX also shares with HEX and GHRP-2 the same PRL- ACTH- and cortisol-releasing activity.     

Effect of recombinant human growth hormone (GH) replacement on the hypothalamic-pituitary-adrenal axis in adult GH-deficient patients

The aim of the study was to evaluate the hypothalamus-pituitary-adrenal (HPA) axis in patients (nine males, three females; mean age +/- sem 51 +/- 2 yr) with adult-onset GH deficiency (GHD) due to surgically treated pituitary tumors with preserved HPA function and without evidence of tumor recurrence before and during recombinant human (rh) GH replacement therapy (duration 31 +/- 6 months). HPA function was assessed by urinary free cortisol and morning serum cortisol levels as well as cortisol responses to 1 mug ACTH test (n = 7 patients) or insulin tolerance test (n = 5 patients) before and during rhGH therapy, the cut-off for the diagnosis of hypoadrenalism being a cortisol peak less than 18 microg/dl (<500 nmol/liter) after stimulatory tests. Serum cortisol and urinary free cortisol levels were significantly lower on therapy than before [7.6 +/- 0.8 vs. 11.5 +/- 0.9 microg/dl (208 +/- 22 vs. 317 +/- 24 nmol/liter), P < 0.01, and 19.6 +/- 2.5 vs. 32.2 +/- 3.2 microg per 24 h (54 +/- 7 vs. 89 +/- 9 nmol per 24 h), P < 0.05, respectively], whereas no change in cortisol-binding globulin levels was observed. Cortisol peak after either ACTH test or insulin tolerance test was lower on rhGH therapy than before [15.9 +/- 1.5 vs. 20.2 +/- 1.1 microg/dl (437 +/- 43 vs. 557 +/- 31), P = 0.01, and 13.1 +/- 2.6 vs. 20.4 +/- 1.4 microg/dl (362 +/- 71 vs. 564 +/- 37 nmol/liter), P = 0.03, respectively]. Accordingly, central hypoadrenalism was detected in nine of 11 patients. In conclusion, low GH and IGF-I levels, likely enhancing the conversion of cortisone to cortisol, may mask a condition of central hypoadrenalism. Therefore, the reassessment of HPA function in GHD patients during rhGH therapy is mandatory.     

Free fatty acids inhibit adrenocorticotropin and cortisol secretion stimulated by physical exercise in normal men

BACKGROUND: The basal circulating levels of ACTH and cortisol, but not the ACTH/cortisol response to hCRH, are significantly reduced by free fatty acid (FFA) infusion. OBJECTIVE: To verify whether FFA infusion modifies the ACTH/cortisol response to physical exercise, a well-known activator of the HPA axis at suprapituitary level. DESIGN: Exercise tests on a bicycle ergometer during infusion of a lipid-heparin emulsion (LHE) (experimental test) or normal saline (NaCl 0.9%) (control test). SETTING: Department of Cardiology at the University-Hospital. SUBJECTS: Seven healthy male subjects aged 25-33 years. INTERVENTIONS: On two mornings, at weekly intervals, LHE or saline were infused for 60 min; infusion started 10 min before exercise test on a bicycle ergometer, which lasted about 15 min. MAIN OUTCOME MEASURES: Circulating ACTH/cortisol levels and physiological variables during physical exercise. RESULTS: FFA levels (0.4 +/- 0.1 mEq/l) remained constant during control test, whereas they progressively rose (peak at 60 min, 2.7 +/- 1.0 mEq/l) during LHE infusion. Neither basal nor exercise-induced changes in physiological variables were modified by LHE infusion. Both ACTH and cortisol increased during exercise, with peak levels at 20 min and 30 min (control test: 103% and 42%, P < 0.001; experimental test: 28.5% and 18.6%, P < 0.05 higher than baseline, respectively). Both ACTH and cortisol responses were significantly lower in the experimental than in the control test (at 20 min P < 0.002 and at 30 min P < 0.05 for ACTH; at 20 min P < 0.05 and at 30 min, 40 min and 50 min P < 0.001 for cortisol). CONCLUSIONS: These data represent the first demonstration of an inhibitory action of increased circulating FFA levels on the HPA axis under stimulatory conditions (i.e. physical exercise, a challenge acting at suprapituitary level). In contrast, previous studies did not show FFA effects on the CRH-induced ACTH/cortisol response. Therefore, our data suggest negative effects of FFAs on the HPA axis at hypothalamic or higher centres in the central nervous system.     

Evidence for a positive correlation between serum cortisol levels and IL-1beta production by peripheral mononuclear cells in anorexia nervosa

A hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis has been reported in anorexia nervosa (AN), together with some immunological abnormalities, involving citokine - and particularly Tumor Necrosis-Factor-alpha (TNF-alpha) - production by polymorphonuclear cells. The ability of pro-inflammatory cytokines to activate the HPA axis is well known; however, there are no data demonstrating an interdependence between immunological and endocrine response in AN. To investigate the presence of a correlation between immune response and pituitary-adrenal function, plasma ACTH and serum cortisol concentrations were measured in 13 AN patients and in the same number of controls. TNF-alpha and interleukin (IL)-1beta production by ex-vivo unstimulated and LPS-stimulated peripheral mononuclear cells was also assessed. Circulating cortisol concentrations were higher (p<0.01) in AN (156.7 +/- 45.1 microg/l, mean +/- SD) than in controls (105.9 +/- 25.7 microg/l). Unstimulated IL-1beta release in supernatants of mononuclear cell cultures was slightly but not significantly higher in AN than in controls, while TNF-alpha release was similar in the two groups. A positive correlation was found between IL-1beta concentrations in unstimulated culture supranatants and serum cortisol levels in AN (r=0.782, p=0.002), while in normal subjects there was a trend toward a negative correlation; a slight positive correlation, while not significant, between IL-1beta and plasma ACTH, as well as between TNF-alpha and serum cortisol was also found in AN. These data suggest that the normal relationship between pro-inflammatory cytokines release, particularly IL-1beta, and cortisol secretion is deranged in AN.     

Hypothalamic-pituitary-adrenal activity in type 2 diabetes mellitus: role of autonomic imbalance

Symptomatic diabetic neuropathy has been found to be associated with hypothalamus-pituitary-adrenal (HPA) axis hyperfunction, but no data are available about HPA activity in diabetic patients with asymptomatic autonomic imbalance. To evaluate HPA axis activity in patients with type 2 diabetes mellitus (T2DM) in relation to the presence or the absence of subclinical parasympathetic or sympathetic neuronal dysfunction, we performed an observational study on 59 consecutive type 2 diabetic patients without chronic complications and/or symptoms of neuropathy or hypercortisolism. The following were measured: serum cortisol at 08:00 am and at midnight (F8 and F24, respectively), post-dexamethasone suppression cortisol, 24-hour urinary free cortisol (UFC), and morning corticotropin (ACTH). Deep-breathing (DB) and LS (LS) autonomic tests were performed to assess the parasympathetic function; postural hypotension test was performed to evaluate sympathetic activity. Patients were subdivided into 4 groups: subjects with parasympathetic failure (group A), sympathetic failure (group B), both para- and sympathetic failure (group C), and without autonomic failure (group D). Hypothalamus-pituitary-adrenal activity was increased in group A compared with group D (UFC, 48.6 +/- 21.4 vs 21.6 +/- 9.8 microg/24 h, P < .0001; ACTH, 27.0 +/- 8.6 vs 15.7 +/- 5.7 pg/dL, P < .01; F8, 20.4 +/- 4.5 vs 13.6 +/- 3.8 microg/dL, P < .05; post-dexamethasone suppression cortisol, 1.2 +/- 0.4 vs 0.8 +/- 0.6 microg/dL, P < .05, respectively) and group B (UFC, 26.3 +/- 11.0 microg/24 h, P < .0001; ACTH, 19.9 +/- 8.0 pg/dL, P < .05). Regression analysis showed that UFC levels were significantly associated with the deep-breathing test (beta = -0.40, P = .004) and tended to be associated with the lying-to-standing test (beta = -0.26, P = .065), whereas body mass index, glycated hemoglobin, and duration of disease were not. Type 2 diabetic patients with asymptomatic parasympathetic derangement have increased activity of HPA axis, related to the degree of the neuronal dysfunction.     

Development of pituitary-adrenal endocrine function in the marmoset monkey: infant hypercortisolism is the norm

Early life stress, involving activation of the hypothalamic-pituitary-adrenal (HPA) system, is associated with altered functioning of stress-related systems in adulthood. In the rat, postnatal development is characterized by low basal HPA activity and stress hyporesponsiveness, and infant exposure to atypical glucocorticoid levels leads to chronic alteration of HPA function and HPA-dependent peripheral and central processes. There have been few studies of primate HPA ontogeny, and here we report a study of changes in pituitary-adrenal function between birth and adulthood in the common marmoset monkey. In this simian primate, basal plasma ACTH and cortisol levels were actually elevated in neonates (ACTH, 141 +/- 28 pg/ml; cortisol, 1903 +/- 326 microg/dl) and wk 4 infants (ACTH, 114 +/- 9 pg/ml; cortisol, 290 +/- 8 microg/dl) relative to month 2 infants, juveniles (month 6), subadults (month 12), and adults (>2 yr; ACTH, 37 +/- 4 to 61 +/- 8 pg/ml; cortisol, 101 +/- 2 to 195 +/- 4 microg/dl). In contrast to older life stages, neonates lacked circadian change in their plasma cortisol levels, and this state of consistently high cortisol was associated with large adrenal glands in addition to high ACTH levels. Cerebrospinal fluid cortisol levels were, in accord with plasma levels, higher in wk 4 infants than in juveniles and subadults. In terms of stress response, month 2 infants demonstrated ACTH and cortisol peak stress responses similar to those at older life stages (infant stress cortisol, 185 +/- 36% of basal; subadult stress cortisol, 174 +/- 6% of basal); whereas infant ACTH recovery was also similar to that in older subjects, their cortisol poststress recovery was retarded. This primate, it is proposed, provides an excellent complementary model in which to test hypotheses derived from the rat model relating to HPA system ontogeny and the chronic effects and biomedical implications of hypercorticoidism during early life.     

The GH-releasing effect of ghrelin,a natural GH secretagogue,is only blunted by the infusion of exogenous somatostatin in humans

OBJECTIVE: Ghrelin, a 28-amino-acid peptide purified from the stomach and showing a unique structure with an n-octanoyl ester at the serine 3 residue, is a natural ligand of the GH secretagogue (GHS) receptor (GHS-R). Ghrelin strongly stimulates GH secretion in both animals and humans, showing a synergistic effect with GH-releasing hormone (GHRH) but no interaction with synthetic GHS. However, the activity of ghrelin as well as that of non-natural GHS is not fully specific for GH; ghrelin also induces a stimulatory effect on lactotroph and corticotroph secretion, at least in humans. DESIGN: To further clarify the mechanisms underlying the GH-releasing activity of this natural GHS, we studied the effects of somatostatin (SS, 2.0 microg/kg/h from -30 to +90 min) on the endocrine responses to ghrelin (1.0 microg/kg i.v. at 0 min) in seven normal young male volunteers [age (mean +/- SEM) 28.6 +/- 2.9 years; body mass index (BMI) 22.1 +/- 0.8 kg/m2]. In the same subjects, the effect of SS on the GH response to GHRH (1.0 microm/kg i.v. at 0 min) was also studied. MEASUREMENTS: Blood samples were taken every 15 min from -30 up to +120 min. GH levels were assayed at each time point in all sessions; PRL, ACTH and cortisol levels were assayed after ghrelin administration alone and during SS infusion. RESULTS: The GH response to ghrelin (hAUC0'-->120' 2695.0 +/- 492.6 microg min/l) was higher (P < 0.01) than that after GHRH (757.1 +/- 44.1 microg min/l). SS infusion almost abolished the GH response to GHRH (177.0 +/- 37.7 microg min/l, P < 0.01); the GH response to ghrelin was inhibited by SS (993.8 +/- 248.5 microg min/l, P < 0.01) but GH levels remained higher (P < 0.05) than with GHRH. Ghrelin induced significant increases in PRL, ACTH and cortisol levels and these responses were not modified by SS. CONCLUSIONS: Ghrelin, a natural GHS-R ligand, exerts a strong stimulatory effect on GH secretion in humans and this effect is only blunted by an exogenous somatostatin dose which almost abolishes the GH response to GHRH. The stimulatory effect of ghrelin on lactotroph and corticotroph secretion is refractory to exogenous somatostatin, indicating that these effects occur through pathways independent of somatostatinergic influence.     

Differential effects of estradiol on the adrenocorticotropin responses to interleukin-6 and interleukin-1 in the monkey.

Endotoxin and the inflammatory cytokines interleukin (IL)-1 and IL-6 are potent activators of the hypothalamic-pituitary-adrenal (HPA) axis. Although estradiol (E(2)) has been shown to enhance the HPA response to certain types of stress, previous studies in the rodent have shown that HPA responses to endotoxin and to IL-1 were enhanced by ovariectomy and attenuated by E(2). The mechanisms underlying these observations are unclear, but there is evidence that E(2) may have direct inhibitory effects on IL-6 synthesis and release. Because endotoxin and IL-1 both stimulate IL-6, it is possible that the E(2)-induced suppression of the HPA response to endotoxin and IL-1 results from decreased IL-6 release. We have therefore examined the ACTH response to IL-6 and IL-1beta in six ovariectomized rhesus monkeys with and without 3 weeks of E(2) replacement. In the first study, plasma ACTH levels peaked at 60 min after iv injection of 6 microg recombinant human IL-6. Both the ACTH response, over time, and the area under the ACTH response curve were significantly higher in the E(2)-treated animals (P < 0.05). The peak ACTH level was 66 +/- 16 pg/ml without E(2) vs. 161 +/- 69 pg/ml with E(2). In the second study, iv infusion of recombinant human IL-1beta (400 ng) produced plasma IL-6 levels comparable with those seen after IL-6 injection in the first study. In the IL-1 study, however, there was a significant attenuation of the ACTH response, over time, in the E(2)-treated animals (P < 0.001); the peak ACTH level was 83 +/- 34 pg/ml vs. 13 +/- 4.4 pg/ml after E(2). The IL-6 response was similarly attenuated (P < 0.001); the peak IL-6 level was 614 +/- 168 pg/ml vs. 277 +/- 53 pg/ml after E(2) treatment. Our results demonstrate that physiological levels of E(2) enhance the ACTH response to IL-6 but attenuate the ACTH response to IL-1. The attenuated ACTH response to IL-1 was accompanied by a blunted IL-6 response. Our results suggest that the blunted HPA response to IL-1 can be explained, at least in part, by E(2)-induced alterations in IL-6 release. It remains to be determined whether E(2) affects other inflammatory mediators that also participate in this process.     

Fat distribution in obese women is associated with subtle alterations of the hypothalamic–pituitary–adrenal axis activity and sensitivity to glucocorticoids

OBJECTIVES: Obesity with abdominal body fat distribution (A-BFD) and hypothalamic-pituitary-adrenal (HPA) axis activity are somehow linked, but the exact interactions still need clarification. Obese subjects display normal circulating plasma cortisol concentrations with normal circadian rhythms. However, when the HPA axis is pharmacologically challenged, body fat distribution matters and then A-BFD obese women differ from those with subcutaneous body fat distribution (P-BFD). We hypothesized that lower dose provocative and suppressive tests than those used to diagnose hypercortisolism of tumour origin or adrenal insufficiency would shed some light on the characteristics of the HPA axis activity in relation with body fat distribution. PATIENTS AND METHODS: Fifty premenopausal obese women were grouped according to their body fat mass distribution. Their plasma cortisol responses to (i) two low doses of dexamethasone (0.25 and 0.5 mg) with (ii) low dose of the ACTH analogue tetracosactrin (1 microg) were assessed. Salivary cortisol was also determined during the ACTH test. RESULTS: A-BFD differed from P-BFD women in terms of HPA axis responsiveness. They had comparatively: (i) increased nocturnal cortisol excretion (9.38 +/- 2.2 vs. 6.82 +/- 0.91 nmol/micromol creatinine, A-BFD vs. P-BFD, respectively, P = 0.03); (ii) increased salivary cortisol response to ACTH stimulation (1 microg) [salivary cortisol peak: 33.4 (14.1-129) vs. 28.5 (13.2-42.8) nmol/l; salivary AUC: 825 (235-44738) vs. 537 (69-1420) nmol/min/l; A-BFD vs. P-BFD, P = 0.04 for both]; and (iii) increased pituitary sensitivity to dexamethasone testing [postdexamethasone (0.25 mg) plasma cortisol levels: 163 (26-472) vs. 318 (26-652) nmol/l and postdexamethasone (0.5 mg) plasma cortisol levels: 26 (26-79) vs. 33 (26-402) nmol/l; A-BFD vs. P-BFD, P = 0.01 for both). CONCLUSIONS: These data demonstrate differences in the HPA axis activity and sensitivity to glucocorticoids between obese women differing in their body fat distribution, with both enhanced negative and positive feedback in those with abdominal obesity. Several mechanisms may explain these differences: central vs. peripheral hypotheses. Thus, abdominal obesity does not appear to be linked solely to one pathophysiological hypothesis.     

Leptin modulates inflammatory cytokine and neuroendocrine responses to endotoxin in the primate

Leptin, which plays a crucial role in regulating energy balance, can also modulate the inflammatory response. Although leptin-deficient rodents are more sensitive to the toxic effects of bacterial endotoxin, it is unknown if leptin can modulate inflammatory cytokine or neuroendocrine responses to inflammation in a primate model. We have therefore studied the effects of leptin on plasma cytokine and hypothalamic-pituitary-adrenal responses to endotoxin (5 microg iv) in nine ovariectomized rhesus monkeys. Human leptin (50 microg/h) or saline was infused iv for 16 h before and 4 h after endotoxin injection; mean plasma leptin increased from 3.6 +/- 1.0 ng/ml to 18 +/- 1.7 ng/ml (P < 0.001). Leptin infusion had no effect on baseline plasma cytokine and hormone levels before endotoxin injection. As expected, endotoxin stimulated TNF-alpha, IL-6, IL-1 receptor antagonist (IL-1ra), ACTH, and cortisol in the saline-infused animals (P < 0.001). There was a significant attenuation of the IL-6 (P < 0.005) and cortisol (P < 0.001) responses (repeated measures ANOVA) to endotoxin in the leptin-infused animals. There was a significant reduction (by paired analysis) in the responses of the leptin compared with saline-treated animals: 47% for TNF-alpha, 48% for IL-6, 30% for IL1ra, 42% for ACTH, and 22% for cortisol (P < 0.05). We conclude that an increase in circulating leptin, within the physiological range of our monkey colony, can blunt the inflammatory cytokine and hypothalamic-pituitary-adrenal responses to an inflammatory challenge. These results, coupled with our recent finding that endotoxin stimulates leptin release in the monkey, demonstrate that leptin can be both released in response to inflammatory cytokines and act to attenuate the responses to these cytokines.     

Mineralocorticoid receptor blockade by canrenoate increases both spontaneous and stimulated adrenal function in humans.

Animal studies indicate that mineralocorticoid receptors (MR) in the hippocampus play a major role in the glucocorticoid feedback control of the hypothalamo-pituitary-adrenal (HPA) axis. Specifically, MR mediate the proactive feedback of glucocorticoids in the maintenance of basal HPA activity. The stimulatory effect of intracerebroventricular and intrahippocampal MR blockade on the HPA axis in animals has been clearly shown, whereas the effect of systemic administration of mineralocorticoid antagonists in humans is still contradictory. To clarify this point, in seven normal young women (aged 25-32 yr; body mass index, 19.0-23.0 kg/m(2)) we studied the effects of canrenoate (CAN; 200 mg as iv bolus at 2000 h, followed by 200 mg infused in 500 mL saline over 4 h up to 2400 h) or placebo (saline, 1.0 mL as iv bolus at 2000 h, followed by 500 mL over 4 h up to 2400 h) on the spontaneous ACTH, cortisol, dehydroepiandrosterone (DHEA) and aldosterone secretion as well as on the ACTH, cortisol, and DHEA responses to human CRH (2.0 microg/kg as iv bolus at 2200 h) or arginine vasopressin (AVP; 0.17 U/kg as im bolus at 2200 h). Blood samples were taken every 15 min from 2000-2400 h. During placebo, spontaneous ACTH and cortisol levels showed progressive decreases (P < 0.05) from 2000-2400 h (baseline vs. nadir, mean +/- SEM, 2.0 +/- 0.3 vs. 1.4 +/- 0.2 pmol/L and 115.1 +/- 23.7 vs. 63.5 +/- 24.3 nmol/L), whereas DHEA and aldosterone levels did not change. CRH induced clear increases in ACTH, cortisol, and DHEA levels (peaks, mean +/- SEM, 7.1 +/- 1.1 vs. 1.6 +/- 0.2 pmol/L, 322.9 +/- 19.5 vs. 92.8 +/- 24.5 nmol/L, and 44.2 +/- 2.7 vs. 20.0 +/- 3.0 nmol/L; P < 0.05). Similarly, AVP elicited significant increases in ACTH, cortisol, and DHEA levels (3.8 +/- 0.3 vs. 1.5 +/- 0.1 pmol/L, 211.9 +/- 27.2 vs. 67.7 +/- 9.7 nmol/L, and 51.6 +/- 4.0 vs. 16.3 +/- 2.0 nmol/L; P < 0.05). During CAN treatment, ACTH, cortisol, and DHEA levels showed progressive rises, which begun at approximately 60 min and peaked between 2300 and 2400 h (ACTH, 3.4 +/- 0.4 vs. 1.1 +/- 0.3 pmol/L; cortisol, 314.5 +/- 49.6 vs. 123.3 +/- 13.2 nmol/L; DHEA, 52.0 +/- 8.8 vs. 21.0 +/- 2.3 nmol/L; P < 0.05 vs. baseline as well as vs. the same time points during placebo). Aldosterone secretion was not modified by CAN. The ACTH, cortisol, and DHEA responses to human CRH were enhanced by CAN (10.0 +/- 1.7 pmol/L, 462.2 +/- 36.9 nmol/L, and 66.3 +/- 8.8 nmol/L), although statistical significance (P < 0.05) was obtained for cortisol and DHEA only. Also the ACTH, cortisol and DHEA responses to AVP were amplified by CAN (8.0 +/- 2.6 pmol/L, 324.0 +/- 34.8 nmol/L, and 77.8 +/- 4.0 nmol/L); again, statistical significance (P < 0.05) was obtained for cortisol and DHEA only. In conclusion, our study shows that the blockade of MR by CAN significantly enhances the activity of the HPA axis in humans, indicating a physiological role for MR in its control. These results also suggest that the stimulatory effect of CAN on HPA axis is mediated by concomitant modulation of CRH and AVP release.     

alpha2-adrenoceptor regulation of the hypothalamic-pituitary-adrenocortical axis in obesity

BACKGROUND: Abdominal obesity is associated with hyper-responsiveness of the hypothalamic-pituitary-adrenocortical (HPA) axis to stimulatory neuropeptides and to stress. Catecholamines are involved in the regulation of the HPA axis, particularly during stress, via alpha-adrenoceptor modulation. DESIGN: In this study, we investigated the effects of pre-treatment with an alpha2-adrenoceptor agonist, clonidine (2 microg/kg over 10 minutes) and antagonist, yohimbine (0.125 mg/kg bolus, followed by 0. 001 mg/kg/minutes per 90 minutes infusion) on the HPA axis, measured by ACTH and cortisol response to combined CRH (human, 100 microg) plus AVP (0.3 IU) administration, and on noradrenalin (NA) and adrenalin (A) blood levels, in a group of obese women with abdominal (A-BFD) or peripheral (P-BFD) body fat distribution and in nonobese controls. RESULTS: During the control CRH + AVP test the ACTH but not the cortisol response was higher (P < 0.05) in obese A-BFD women than in controls, with minor and transient variations of NA levels. Neither the control test nor clonidine or yohimbine influenced basal or post CRH + AVP A concentrations. Clonidine pretreatment similarly and significantly decreased NA levels in all women and, compared to the control test, marginally influenced the ACTH response to CRH + AVP. Conversely, during yohimbine infusion NA levels steadily and similarly increased to values more or less double baseline values in all groups. Compared to the control test, however, the ACTH response to the CRH + AVP test performed during yohimbine infusion significantly decreased in the control subjects whereas a tendency to a further increase occurred in the obese groups and, specifically, in the A-BFD group significantly (P < 0.05) more than in the P-BFD group. CONCLUSIONS: This study shows that alpha2-adrenoceptor regulation of the HPA axis is different in obese and nonobese women, particularly in stressed conditions. We suggest that the abnormal ACTH response to CRH + AVP challenge with increased noradrenergic tone may represent a specific pathophysiological aspect of the abnormal response to stress or to other specific stimulatory factors in obese women, particularly those with abdominal body fat distribution.     

Neuromedin U partially mediates leptin-induced hypothalamo-pituitary adrenal (HPA) stimulation and has a physiological role in the regulation of the HPA axis in the rat

Intracerebroventricular (ICV) administration of the hypothalamic neuropeptide neuromedin U (NMU) or the adipostat hormone leptin increases plasma ACTH and corticosterone. The relationship between leptin and NMU in the regulation of the hypothalamo-pituitary adrenal (HPA) axis is currently unknown. In this study, leptin (1 nm) significantly increased the release of CRH from ex vivo hypothalamic explants by 207 +/- 8.4% (P < 0.05 vs. basal), an effect blocked by the administration of anti-NMU IgG. The ICV administration of leptin (10 mug, 0.625 nmol) increased plasma ACTH and corticosterone 20 min after injection [plasma ACTH (picograms per milliliter): vehicle, 63 +/- 20, leptin, 135 +/- 36, P < 0.05; plasma corticosterone (nanograms per milliliter): vehicle, 285 +/- 39, leptin, 452 +/- 44, P < 0.01]. These effects were partially attenuated by the prior administration of anti-NMU IgG. Peripheral leptin also stimulated ACTH release, an effect attenuated by prior ICV administration of anti-NMU IgG. We examined the diurnal pattern of hypothalamic NMU mRNA expression and peptide content, plasma leptin, and plasma corticosterone. The diurnal changes in hypothalamic NMU mRNA expression were positively correlated with hypothalamic NMU peptide content, plasma corticosterone, and plasma leptin. The ICV administration of anti-NMU IgG significantly attenuated the dark phase rise in corticosterone [corticosterone (nanograms per milliliter): vehicle, 493 +/- 38; NMU IgG, 342 +/- 47 (P < 0.05)]. These studies suggest that NMU may play a role in the regulation of the HPA axis and partially mediate leptin-induced HPA stimulation.