The oral glucose tolerance test reveals a high frequency of both impaired glucose tolerance and undiagnosed Type 2 diabetes mellitus in primary hyperparathyroidism

AIMS

To evaluate the frequency of impaired glucose tolerance (IGT)and undiagnosed diabetes mellitus together with the indices of insulin resistance (IR) in primary hyperparathyroidism (pHPT).

METHODS

Out of 105 consecutive pHPT patients (F/M 78/27, asymptomatic/symptomatic 68/37, age (mean +/- s.d.) 60.7 +/- 12.7 years,body mass index 25.2 +/- 3.8 kg/m2, ionized calcium (iCa) 1.49 +/- 0.16 mmol/l,parathormone 200.4 +/- 233.9 pg/ml),59 without known diabetes mellitus and controls (n = 60) underwent an oral glucose tolerance test (OGTT, 75 g os). As indices of IR, homeostasis model assessment (HOMAIR)or OGTT data (insulin sensitivity index composite (ISI comp)) were evaluated.

RESULTS

In pHPT the prevalence of IGT (mean, 95% confidence intervals (CI), 40.7%, 27.8-53.6) was higher than in controls (25.0%, 13.7-36.3, P < 0.03). Similarly,the prevalence of undiagnosed diabetes mellitus was higher in pHPT(15.3%, 5.8-24.7) than in controls (5.0%, 0-10.7, P < 0.05). Moreover,the prevalence of IGT and undiagnosed diabetes was higher in pHPT than that previously reported in the general population of Northern Italy(8.5% and 3.2%, respectively). The indices showed that insulin resistance was higher in pHPT than in controls: HOMAIR (median, 95% CI,2.6, 2.5-3.9 vs. 1.7, 1.6-2.5, respectively; P < 0.003); ISI comp (3.5, 3.4-4.6 vs. 5.1, 4.9-7.2, respectively; P < 0.002).

CONCLUSIONS

Our data in a large and modern day pHPT series, with a preponderance of asymptomatic patients, confirm increased insulin resistance and pre-valence of IGT and undiagnosed diabetes.

Arginine reinstates the somatotrope responsiveness to intermittent growth hormone-releasing hormone administration in normal adults

It is well known that in normal adults the growth hormone (GH) response to GH-releasing hormone (GHRH) is inhibited by previous administration of the neurohormone. In 7 healthy volunteers (age 20-34 years) we studied the GH responses to two consecutive GHRH boluses (1 microgram/kg i.v. every 120 min) alone or coadministered with arginine (30 g i.v. over 30 min). The GH response to the first GHRH bolus (area under the curve, mean +/- SEM: 506.3 +/- 35.1 micrograms/l/h) was higher (p = 0.0001) than that to the second one (87.1 +/- 14.6 micrograms/l/h). The latter response was clearly increased (p = 0.0001) by coadministering arginine (980.5 +/- 257.5 micrograms/l/h). When every GHRH bolus was combined with arginine a marked potentiation of GH response to both boluses was found. However, the second combined administration of arginine and GHRH induced a GH increase which was lower compared to the first one (p = 0.016). In conclusion, our results show that arginine potentiates the GHRH-induced GH secretion preventing the lessening of somatotrope responsiveness to the neurohormone alone. As there is evidence that this phenomenon is due to an enhanced somatostatin release, these findings give further evidence of a somatostatin-suppressing effect of arginine.

Arginine potentiates the GHRH- but not the pyridostigmine-induced GH secretion in normal short children. Further evidence for a somatostatin suppressing effect of arginine

To investigate the mechanism underlying the GH-releasing effect of arginine (ARG), we studied the interactions of ARG (0.5 g/kg infused i.v. over 30 min) with GHRH (1 microgram/kg i.v.) and with pyridostigmine (PD, 60 mg orally) on GH secretion in 15 children and adolescents with familial short stature (5.1-15.4 years). In a group of eight subjects ARG induced a GH increase not statistically different to that observed after GHRH (peak, mean +/- SEM: 38.0 +/- 10.4 vs 64.0 +/- 14.4 mU/l). The combined administration of ARG and GHRH led to GH levels (101 +/- 15.2 mU/l) higher than those observed after GHRH (P less than 0.025) or ARG alone (P less than 0.001) and overlapping with those recorded after combined PD and GHRH administration (111 +/- 22.4 mU/l). In the other seven subjects, ARG and PD administration induced a similar GH response either when administered alone (25.2 +/- 13.6 and 27.8 +/- 4.0 mU/l, respectively) or in combination (33.8 +/- 5.4 mU/l). In conclusion, our results show that in children ARG administration potentiates GHRH- but not PD-induced GH increase. These findings agree with the hypothesis that the GH-releasing effect of both ARG and PD is mediated via the same mechanism, namely, by suppression of endogeneous somatostatin release. Combined administration of either ARG or PD with GHRH has a similar striking GH-releasing effect which is clearly higher than that of GHRH alone.

Relationships between IGF-I and age, gender, body mass, fat distribution, metabolic and hormonal variables in obese patients

OBJECTIVE

To compare insulin-like growth factor-I (IGF-I) concentrations in obese and normal subjects, and evaluate the possible relationships between IGF-I concentrations and demographic, anthropometric, metabolic and hormonal variables in obese patients.

SUBJECTS AND METHODS

286 obese outpatients (OB, 234 female and 52 male; age 18-71 y, body mass index (BMI) > 27 kg/m2) were recruited.

MEASUREMENTS

BMI, waist-to-hip ratio (WHR), serum basal and oral glucose tolerance test (OGTT)-stimulated glucose and insulin concentrations, IGF-I, basal growth hormone (GH), prolactin (PRL), androgens, thyrotropin (TSH), free triiodothyronine (fT3), free thyroxine (fT4), free fatty acids (FFA), triglycerides, total and high density lipoprotein (HDL)-cholesterol, 24h-urinary cortisol levels and blood pressure (BP) values were measured. IGF-I concentrations were also evaluated in a large population of 326 age-matched controls (controls, 228 women, 98 men; age 20-86 y, BMI < 25 kg/m2).

RESULTS

IGF-I concentrations were lower in OB than in controls (age-adjusted mean: 21.6 vs 23.6 nmol/L, P < 0.03). However, individual IGF-I concentrations in OB were within the age-adjusted normal range. In both groups, IGF-I concentrations were gender-independent, and showed a simple negative correlation with age (r = -0.47). In OB, univariate analysis also shows that IGF-I concentrations were negatively correlated with BMI (r = -0.33), but not WHR, with both basal (r = -0.16) and OGTT-stimulated glucose levels (r = -0.17), as well as FFA levels (r = -0.19), and with both diastolic and systolic BP (both r = -0.17). In OB women, IGF-I concentrations positively correlated with PRL (r = 0.31), testosterone (r = 0.30), androstenedione (r = 0.30), and dehydroepiandrosterone-sulfate (DHEAS) concentrations (r = 0.41). No correlation was found with other variables. The multiple regression analysis showed that IGF-I concentrations were inversely and independently related to age and BMI only.

CONCLUSIONS

In obesity, IGF-I concentrations are slightly reduced, but generally within the age-adjusted normal range. IGF-I concentrations in obesity show independent and negative relationships with age and BMI, but are not associated with fat distribution, insulin secretion, glucose tolerance, BP or risk indices for cardiovascular disease (CVD).

The GH/IGF-I axis in obesity: influence of neuro-endocrine and metabolic factors

In this review we propose an integrated neuro-endocrine-metabolic point of view on the alterations (adaptations?) of GH/IGF-1 axis in obesity, summarizing the evidence from the literature, particularly focusing the data on humans and adding where possible results from our studies in this field. It is well-known that GH secretion is deeply impaired in overweight patients: we reviewed the multiple mechanisms underlying this issue, considering either central (CNS-related, such as impairment of GHRH tone or increased somatostatin release) or peripheral (ie metabolic: insulin, free fatty acids, glucose) factors. A central point of the debate about GH insufficiency in obesity is if it represents a simple adaptive phenomenon or reflects a true impairment of the axis activity. Evaluation of IGF-I levels and generation in obesity was the mean used to address this question: a bulk of evidence on IGF-I balance in human obesity has been provided, but the matter is still uncertain and unsolved.

Arginine potentiates but does not restore the blunted growth hormone response to growth hormone-releasing hormone in obesity

A blunted growth hormone (GH) response to several stimuli, including growth hormone-releasing hormone (GHRH), has been shown in obesity. Arginine (ARG) has been demonstrated to potentiate the GHRH-induced GH increase in normal subjects, likely acting via inhibition of hypothalamic somatostatin release. To shed further light onto the mechanisms underlying the blunted GH secretion in obesity, we studied the effect of ARG (0.5 g/kg infused intravenously [IV] over 30 minutes) on both basal and GHRH (1 micron/kg IV)-stimulated GH secretion. Eight obese subjects (aged 26.4 +/- 3.9 years; body mass index, 39.0 +/- 1.9 kg/m2) and eight normal control volunteers (aged 27.0 +/- 1.7 years; body mass index, 22.3 +/- 0.5 kg/m2) were studied. In obese subjects, the GH response to both GHRH and ARG was lower (P less than .01 and P less than .002, respectively) than in controls. ARG potentiated the GH response to GHRH in obese patients (P less than .0003). However, in these patients, the GH secretion elicited by GHRH, even when coadministered with ARG, persisted at reduced levels (P less than .005) when compared with controls. Basal insulin-like growth factor-1 (IGF-1) levels did not significantly differ in obese subjects and in normal subjects (161.1 +/- 37.0 v 181.0 +/- 12.8 micrograms/L). In conclusion, ARG enhances the blunted GHRH-induced GH increase in obese patients, but the GH responses to ARG alone and to ARG + GHRH persist at lower levels than in normals. Thus, our results suggest the existence of a reduced pituitary GH pool in obesity.

Derangement of glucose metabolism in hyperparathyroidism

The derangement of glucose metabolism is found frequently in all forms of hyperparathyroidism. Both in primary (PHPT) and secondary hyperparathyroidism (SHPT) PTH excess is thought to be involved in deteriorating insulin sensitivity and secretion though their different clinical and pathophysiological conditions. In PHPT these abnormalities are related to a high frequency of Type 2 diabetes mellitus and also impaired glucose tolerance according to recent clinical studies, without differences between symptomatic and asymptomatic clinical presentation. In chronic renal failure (CRF), the disorders of glucose metabolism due to SHPT do not bear an increased risk for diabetes whereas they seem to be involved in the progression of atherosclerotic vascular damage which connotes CRF. Moreover, clinical and experimental studies have shown that vitamin D deficiency associated with glucose metabolism abnormalities favors the development of the metabolic syndrome. The potential for metabolic and cardiovascular harm related to hyperparathyroidism, especially PHPT, is the most interesting issue for clinical endocrinologists. This short review of the clinical and pathophysiological data of literature on glucose homeostasis disorders in hyperparathyroidism focuses on its potential clinical and therapeutic impact, particularly in the management of PHPT.

Androgen receptor functions as transcriptional repressor of cancer-associated fibroblast activation

The aging-associated increase of cancer risk is linked with stromal fibroblast senescence and concomitant cancer-associated fibroblast (CAF) activation. Surprisingly little is known about the role of androgen receptor (AR) signaling in this context. We have found downmodulated AR expression in dermal fibroblasts underlying premalignant skin cancer lesions (actinic keratoses and dysplastic nevi) as well as in CAFs from the 3 major skin cancer types, squamous cell carcinomas (SCCs), basal cell carcinomas, and melanomas. Functionally, decreased AR expression in primary human dermal fibroblasts (HDFs) from multiple individuals induced early steps of CAF activation, and in an orthotopic skin cancer model, AR loss in HDFs enhanced tumorigenicity of SCC and melanoma cells. Forming a complex, AR converged with CSL/RBP-Jκ in transcriptional repression of key CAF effector genes. AR and CSL were positive determinants of each other's expression, with BET inhibitors, which counteract the effects of decreased CSL, restoring AR expression and activity in CAFs. Increased AR expression in these cells overcame the consequences of CSL loss and was by itself sufficient to block the growth and tumor-enhancing effects of CAFs on neighboring cancer cells. As such, the findings establish AR as a target for stroma-focused cancer chemoprevention and treatment.

A model for recognition of polychlorinated dibenzo-p-dioxins by the aryl hydrocarbon receptor

Ligand binding by the aryl hydrocarbon receptor (AhR), a member of the bHLH-PAS family of transcriptional regulatory proteins, has been mapped to a region within the second 'PAS' domain, a conserved sequence motif first discovered in the Per-ARNT-Sim family of proteins. In addition to the bacterial photoactive yellow protein (PYP), which had been proposed as a structural prototype for the three dimensional fold of PAS domains, two crystal structures of the PAS domain have recently been determined: the human potassium channel HERG and the heme binding domain of the bacterial O(2) sensing FixL protein. The three structures reveal a highly conserved structural framework in evolutionary rather distant PAS domains, provide a more general view of how these domains can recognize their ligands and suggest a structure-function relationship that we exploited to build a three-dimensional model of the ligand binding domain (LBD) of the mouse aryl hydrocarbon receptor (mAhR). The model allowed us to putatively identify the residues responsible for the recognition of polychlorinated dibenzo-p-dioxins (PCDDs) by AhR receptors and to formulate an hypothesis on the signal transduction mechanism.

Metabolic modulation of the growth hormone-releasing activity of hexarelin in man

Hexarelin (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) is a new potent synthetic growth hormone (GH)-releasing hexapeptide. The mechanism of action of hexarelin in man has never been evaluated. Hexarelin may act directly on specific pituitary receptors and indirectly on the hypothalamus. To elucidate its mechanism of action in man, we studied the interaction of hexarelin with glucose and free fatty acids (FFA), two metabolic factors known to inhibit both basal and GH-releasing hormone (GHRH) stimulated GH secretion. Glucose is thought to inhibit GH secretion via stimulation of endogenous somatostatin release, whereas FFA could also act directly on somatotrope cells. Therefore, we investigated the effect of oral glucose (100 g) and lipid-heparin infusion (250 mL of a 10% lipid solution + 2,500 U heparin) on the GH response to a maximal dose (2 micrograms/kg intravenously [IV]) of hexarelin or GHRH in six normal men. Hexarelin elicited a clear-cut GH response (mean +/- SEM; peak, 62.6 +/- 8.0 micrograms/L) that was higher (P < .01) than that observed after GHRH (peak, 19.8 +/- 2.4 micrograms/L). Although similar increases in plasma glucose were observed with the two peptides, oral glucose almost abolished the GH response to GHRH (peak, 5.6 +/- 0.9 micrograms/L, P < .01) while only blunting the somatotrope response to hexarelin (peak, 38.4 +/- 7.9 micrograms/L, P < .05). Similarly, lipid-heparin infusion nearly abolished the GH response to GHRH (peak, 4.9 +/- 1.0 micrograms/L, P < .01) while only blunting the somatotrope response to hexarelin (peak, 34.2 +/- 4.5 micrograms/L, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Pyridostigmine partially restores the GH responsiveness to GHRH in normal aging

In 11 elderly normal subjects and in 17 young healthy subjects we studied the response of plasma growth hormone to GH-releasing hormone (GHRH(29), 1 microgram/kg iv) alone and preceded by pyridostigmine (120 mg orally 60 min before GHRH), a cholinesterase inhibitor likely able to suppress somatostatin release. The GH response to pyridostigmine alone was also examined. Basal plasma GH levels were similar in elderly and young subjects. In the elderly, GHRH induced a GH rise (AUC, median and range: 207.5, 43.5-444.0 micrograms.l-1.h-1) which was lower (p = 0.006) than that observed in young subjects (548.0, 112.5-2313.5 micrograms.l-1.h-1). The pyridostigmine-induced GH rise in the elderly was similar to that in young subjects (300.5, 163.0-470.0 vs 265.0, 33.0-514.5 micrograms.l-1.h-1). Pyridostigmine potentiated the GH responsiveness to GHRH in both elderly (437.5, 152.0-1815.5 micrograms.l-1.h-1; p = 0.01 vs GHRH alone) and young subjects (2140.0, 681.5-4429.5 micrograms.l-1.h-1; p = 0.0001 vs GHRH alone). However, the GH response to pyridostigmine + GHRH was significantly lower (p = 0.0001) in elderly than in young subjects. In conclusion, the cholinergic enhancement by pyridostigmine is able to potentiate the blunted GH response to GHRH in elderly subjects, inducing a GH increase similar to that observed after GHRH alone in young adults. This finding suggests that an alteration of somatostatinergic tone could be involved in the reduced GH secretion in normal aging. However, a decreased GH response to combined administration of pyridostigmine and GHRH in elderly subjects suggests that other abnormalities may coexist, leading to the secretory hypoactivity of somatotropes.

Effects of acipimox, an antilipolytic drug, on the growth hormone (GH) response to GH-releasing hormone alone or combined with arginine in obesity

Increased free fatty acid (FFA) levels of obese patients are likely involved in the pathogenesis of the growth hormone (GH) hyposecretion of obesity. To clarify their role, we studied the influence of inhibition of plasma FFA levels, induced by 500 mg oral acipimox (ACX), an antilipolytic drug, on the GH response to GH-releasing hormone (GHRH) alone or combined with arginine ([ARG] study A) in six normal women ([NS] aged 24 to 37 years; body mass index, 22.4 +/- 0.9 kg/m2) and six obese women ([OB] aged 21 to 40 years; body mass index 39.5 +/- 3.2 kg/m2). In a group of seven OB patients (aged 18 to 58 years; body mass index, 35.8 +/- 1.3 kg/m2), the effect of ACX on either GHRH- or GHRH+ARG-stimulated GH increase was also studied after a 4-day treatment with the same drug at 250 mg three times daily (study B). OB patients had baseline FFA levels higher than NS (0.77 +/- 0.06 v 0.44 +/- 0.09 mmol/L, P<.05). In study A, ACX reduced FFA levels to the same nadir in both groups (0.11 +/- 0.02 and 0.12 +/- 0.03 mmol/L, NS and OB subjects, respectively). In NS, ACX failed to significantly potentiate the GH response to either GHRH (1,371.9 +/- 425.2 v 1,001.8 +/- 229.0 micrograms/L x min) or GHRH+ARG (3558.4 +/- 1,513.7 v 3,045.9 +/- 441.8 micrograms/L x min), while in OB patients it increased the GH response to GHRH (797.6 +/- 277.3 v 353.8 +/- 136.7 micrograms/L x min, P<.01) and did not modify the response to ARG+GHRH (1,010.5 +/- 253.1 v 821.1 +/- 222.0 micrograms/L x min). In study B, ACX reduced FFA levels in OB patients (nadir, 0.09 +/- 0.04 mmol/L). This treatment strikingly increased the GH response to GHRH (1,734.0 +/- 725.4 v 271.5 +/- 112.8 micrograms/L x min, P<.01) and significantly potentiated that to ARG+GHRH (2,371.9 +/- 571.3 v 1,020.0 +/- 343.2 micrograms/L x min, P<.05). In conclusion, our present findings indicate that an acute reduction of plasma FFA levels in OB patients restores their somatotrope responsiveness, whereas it does not affect GH secretion in lean subjects. After prolonged treatment, ACX further improves GHRH-stimulated GH secretion in OB patients, suggesting that elevated FFA levels play a leading role in the GH hyposecretory state of obesity.

Insulin resistance is not coupled with defective insulin secretion in primary hyperparathyroidism

AIMS

An increased frequency of both impaired glucose tolerance and Type 2 diabetes mellitus (DM) has been reported in primary hyperparathyroidism (pHPT), thus we sought to investigate insulin sensitivity and insulin secretion in a large series of pHPT patients.

SUBJECTS AND METHODS

One hundred and twenty-two consecutive pHPT patients without known DM were investigated [age (mean +/- sd) 59.3 +/- 13.6 years, body mass index (BMI) 25.7 +/- 4.2 kg/m(2); serum calcium 2.8 +/- 0.25 mmol/l; PTH 203.2 +/- 145.4 ng/l]. Sixty-one control subjects were matched, according to the degree of glucose tolerance, in a 2 : 1 patient:control ratio. Fasting- and oral glucose tolerance test-derived estimates of insulin sensitivity and secretion were determined by means of the quantitative insulin sensitivity check index (QUICKI) and the insulin sensitivity index (ISI) composite.

RESULTS

Both the QUICKI and ISI composite were lower in pHPT patients than control subjects (P < 0.03 and P < 0.05, respectively) after adjusting for age, systolic blood pressure and BMI. Conversely, all insulin secretion estimates were significantly increased in pHPT patients than in control subjects (P < 0.04 and P < 0.03, respectively) and after adjusting for age, systolic blood pressure and BMI. Log serum calcium levels were negatively associated with the QUICKI and log ISI composite (R = -0.30, P = 0.001; R = -0.23, P = 0.020, respectively) in pHPT patients. Serum calcium levels significantly and independently contributed to impaired insulin sensitivity in multivariate analysis (QUICKI as dependent variable: beta = -0.31, P = 0.004, R(2) = 0.15; log ISI composite as dependent variable: beta = -0.29, P = 0.005, R(2) = 0.16).

CONCLUSIONS

Our study confirms a reduction in both basal and stimulated insulin sensitivity in primary hyperparathyroidism, in spite of increased insulin secretion. Moreover, our data show for the first time a significant relationship between hypercalcaemia and insulin sensitivity in this condition.

Relationships between dehydroepiandrosterone-sulphate and anthropometric, metabolic and hormonal variables in a large cohort of obese women

OBJECTIVE

The aim of the present study was to measure dehydroepiandrosterone-sulphate (DHEA-S) levels in obesity and assess the relationships between DHEA-S and anthropometric, metabolic and hormonal variables.

SUBJECTS AND METHODS

We evaluated the serum DHEA-S levels in 217 obese but otherwise normal female subjects (age (mean +/- SEM): 39.4 +/- 0.9, range 18-67 years, body mass index (BMI) = 36.1 +/- 0.4, range 27.1-57.1 kg/m2).

RESULTS

DHEA-S levels showed an age-dependent fall similar to that observed in normal women (n = 156, age 46.2 +/- 1.2, range 22-69 years, BMI < 25 kg/m2). Adjusting for age, obese women had mean DHEA-S levels higher than the control group (P < 0.02). In obese patients, DHEA-S levels were directly associated with serum testosterone, androstendione, IGF-I, fT3 levels and 24 h-urinary cortisol. On the other hand, DHEA-S levels were negatively associated with age, total cholesterol, triglycerides levels and systolic blood pressure. No correlation was found with BMI, waist:hip ratio, basal and post-OGTT insulin and glucose, free fatty acids, GH, PRL, fT4, TSH, SHBG levels or diastolic blood pressure. Multiple regression analysis indicated that in obese women, DHEA-S levels were associated negatively to age and positively to testosterone, androstendione and IGF-I levels and daily urinary cortisol. In a subgroup of 20 obese women, DHEA-S levels significantly (P < 0.001) fell after OGTT without any correlation with the insulin response.

CONCLUSIONS

The present results show that dehydroepiandrosterone-sulphate levels are not reduced in obesity, being slightly increased, particularly in young adulthood. Dehydroepiandrosterone-sulphate levels are positively and independently associated with androgen, 24-h urinary cortisol and IGF-I levels but do not seem associated with insulin levels or cardiovascular risk indices.

Interaction of free fatty acids and arginine on growth hormone secretion in man

We studied the interaction between free fatty acids (FFAs) and arginine (ARG) on basal and growth hormone (GH)-releasing hormone (GHRH)-stimulated GH secretion in 14 normal subjects. Compared with placebo, ARG induced a significant increase of GH secretion (334.0 +/- 157.5 v 36.9 +/- 27.6 micrograms/L/h, P < .05). The increased levels of FFAs (1.9 +/- 0.4 mEq/L), obtained by the infusion of a lipid-heparin emulsion, abolished the effect of ARG (55.8 +/- 45.6 v 334.0 +/- 157.5 micrograms/L/h, P < .05). GHRH-induced GH secretion was potentiated by ARG (2,009.9 +/- 463.2 v 922.0 +/- 244.4 micrograms/L/h, P < .05) and suppressed by lipid-heparin infusion (106.2 +/- 28.3 v 922.0 +/- 244.4 micrograms/L/h, P < .01). Moreover, the lipid-heparin infusion inhibited the potentiating effect of ARG on the GHRH-induced GH increase (527.9 +/- 113.6 v 2,009.9 +/- 463.2 micrograms/L/h, P < .01). These results confirm the strong inhibitory effect of FFAs on GH secretion, showing that they are even able to inhibit the potentiating effect of ARG on the GH response to GHRH. Since ARG likely acts via inhibition of hypothalamic somatostatin release, the inhibitory effect of FFAs on GH secretion could take place directly at the pituitary level and/or at the hypothalamic level, counteracting the effect of ARG.

Maximal secretory capacity of somatotrope cells in obesity: comparison with GH deficiency

OBJECTIVE

To evaluate the maximal secretory capacity of somatotrope cells in obesity and to compare it with that in hypopituitaric patients with GH deficiency.

DESIGN

Stimulation with GHRH. (1 microgram/kg i.v.), combined with arginine (ARG, 0.5 g/kg i.v.), which strongly potentiates the GH response to the neurohormone, likely inhibiting hypothalamic somatostatin. The reproducibility of the GH response to GHRH + ARG was evaluated in a second session.

SUBJECTS

Forty-five patients with simple obesity (OB 11 male and 34 female, age 40.5 +/- 1.8 y, BMI 38.8 +/- 1.1 kg/m2), 49 patients with hypopituitarism (GHD, 23 male and 26 female, 43.6 +/- 2.4 y, 24.7 +/- 0.7 kg/m2) and 44 normal young volunteers (NS, 25 male and 19 female, 33.8 +/- 1.0 y, 21.6 +/- 0.3 kg/m2) were studied.

MEASUREMENTS

GH levels were assayed by IRMA method, basally at -60 and 0 min, and than every 15 min up to +120 min. Basal IGF-I levels were assayed by RIA method, after acid-ethanol extraction.

RESULTS

IGF-I levels in OB were lower (P < 0.005) than those in NS but higher (P < 0.005) than those in GHD. Mean peak GH response to GHRH + ARG in OB was clearly lower than that in NS (P < 0.005) and higher (P < 0.005) than that in GHD. Sixty-percent OB and 100% GHD showed peak GH responses lower than the minimum normal limit in NS (16.5 micrograms/l) while 4% OB and only 53% GHD with GH responses lower than 3 micrograms/l, the limit under which GH replacement therapy of severe deficiency is allowed. Good intraindividual reproducibility of the GH response to GHRH + arginine test was present in all groups (OB: r = 0.78, P < 0.0001; GHD: r = 0.57, P < 0.003; NS: r = 0.74, P < 0.0001;.

CONCLUSIONS

The maximal secretory capacity of somatotrope cells is clearly less than normal in the obese but still more than is seen in GHD subjects. However, in about 50% of obese patients, the pituitary GH releasable pool overlaps with that of hypopituitaric patients with GH deficiency. Thus, even when the maximal secretory capacity of somatotrope cells is evaluated by a potent and reproducible provocative tests such as GHRH + arginine, overweight has to be taken in a great account as the cause of severely impaired GH response in patients with suspected GH deficiency.

The ULK3 Kinase Is Critical for Convergent Control of Cancer-Associated Fibroblast Activation by CSL and GLI

The connection between signaling pathways activating cancer-associated fibroblasts (CAFs) remains to be determined. Metabolic alterations linked to autophagy have also been implicated in CAF activation. CSL/RBPJ, a transcriptional repressor that mediates Notch signaling, suppresses the gene expression program(s), leading to stromal senescence and CAF activation. Deregulated GLI signaling can also contribute to CAF conversion. Here, we report that compromised CSL function depends on GLI activation for conversion of human dermal fibroblasts into CAFs, separately from cellular senescence. Decreased CSL upregulates the expression of the ULK3 kinase, which binds and activates GLI2. Increased ULK3 also induces autophagy, which is unlinked from GLI and CAF activation. ULK3 upregulation occurs in the CAFs of several tumor types, and ULK3 silencing suppresses the tumor-enhancing properties of these cells. Thus, ULK3 links two key signaling pathways involved in CAF conversion and is an attractive target for stroma-focused anti-cancer intervention.

Effects of short-term administration of low-dose rhGH on IGF-I levels in obesity and Cushing's syndrome: indirect evaluation of sensitivity to GH

OBJECTIVE

To verify the hypothesis of an increased sensitivity to GH in obesity (OB) and Cushing's syndrome (CS).

DESIGN

We studied the effects of short-term administration of low-dose rhGH on circulating IGF-I levels in patients with simple OB or CS and in normal subjects (NS).

METHODS

Nineteen women with abdominal OB aged (mean +/- s.e.m.) 38.2+/-3.1 years, body mass index 40.7+/-2.5 kg/m(2), waist to hip ratio 0.86+/-0.02, ten with CS (50.4+/-4.2 years, 29.7 +/- 3.3 kg/m(2)) and 11 NS (35.0+/-3.6 years, 20.5+/-0.5 kg/m(2)) underwent s.c. administration of 5 microg/kg per day rhGH at 2200 h for four days. Serum IGF-I, IGF-binding protein-3 (IGFBP-3), GH-binding protein (GHBP), insulin and glucose levels were determined at baseline and 12 h after the first and the last rhGH administration.

RESULTS

Basal IGF-I levels in NS (239.3+/-22.9 microg/l) were similar to those in OB (181.5+/-13.7 microg/l) and CS (229.0+/-29.1 microg/l). Basal IGFBP-3, GHBP and glucose levels in NS, OB and CS were similar while insulin levels in NS were lower (P<0.01) than those in OB and CS. In NS, the low rhGH dose induced a sustained rise of IGF-I levels (279.0+/-19.5 microg/l, P<0.001), a non-significant IGFBP-3 increase and no change in GHBP, insulin and glucose levels. In OB and CS, the IGF-I response to rhGH showed progressive increase (246.2+/-17.2 and 311.0+/-30.4 microg/l respectively, P<0.01 vs baseline). Adjusting by ANCOVA for basal values, rhGH-induced IGF-I levels in CS (299.4 microg/l) were higher than in OB (279.1 microg/l, P<0.01), which, in turn, were higher (P<0.05) than in NS (257.7 microg/l). In OB, but not in CS, IGFBP-3 and insulin levels showed slight but significant (P<0.05) increases during rhGH treatment, which did not modify glucose levels in any group; thus, in the OB patient group a significant fall in glucose/insulin ratio was observed.

CONCLUSIONS

Short-term treatment with low-dose rhGH has enhanced stimulatory effect on IGF-I levels in OB and, particularly, in hypercortisolemic patients. These findings support the hypothesis that hyperinsulinism and hypercortisolism enhance the sensitivity to GH in humans.

Cardiovascular risk and metabolic syndrome in primary hyperparathyroidism and their correlation to different clinical forms

Cardiometabolic disorders have been associated with primary hyperparathyroidism (PHPT), while the relationship of cardiovascular risk score (CRS) and metabolic syndrome (MS) with different clinical presentation of PHPT remains undefined. Our aim was to evaluate CRS, MS and its components in PHPT looking for their correlation to different clinical forms. In 68 consecutive PHPT patients and 68 matched controls, CRS, MS and its components were assessed to perform an observational case-control study at an ambulatory referral center for Bone Metabolism Diseases. Patients were stratified in symptomatic and asymptomatic PHPT; these latter were divided in high-risk and low-risk subgroups for end-organ damage. An increased proportion of PHPT patients had intermediate-high CRS and MS (mean, 95 % Confidence Interval (CI) 51.5 %, 39.6-63.3 and 20.6 %, 11.0-30.2, respectively, p < 0.02 vs. controls). Intermediate-high CRS was prevalent both in symptomatic and low-risk asymptomatic PHPT while MS resulted prevalent in low-risk asymptomatic but not in symptomatic PHPT. Type 2 DM, IFG, mixed dyslipidemia, hypertriglyceridemia, HDL-hypocholesterolemia, and LDL-hypercholesterolemia predominated in low-risk asymptomatic, while only LDL-hypercholesterolemia prevailed also in symptomatic PHPT. In patients and controls without cardiometabolic risk factors, HOMA-IR index was significantly increased in PHPT vs. controls (p < 0.03) and associated to total calcium (R = 0.73; p < 0.001). By multivariate analysis low-risk asymptomatic PHPT predicted MS after adjusting for age, sex, and BMI. Our data show an increased frequency of intermediate-high CRS both in symptomatic and low-risk asymptomatic PHPT while MS prevails in low-risk asymptomatic PHPT, supporting the potential for cardiovascular morbidity and mortality also in this form.

Convergent roles of ATF3 and CSL in chromatin control of cancer-associated fibroblast activation

Activation of cancer-associated fibroblasts (CAFs) promotes tumorigenesis. Kim et al. show that ATF3 and CSL converge in negative regulation of CAF activation through long-distance chromatin control. Bromodomain and extra-terminal (BET) inhibitors counteract the effects of ATF3 and CSL loss in CAF activation and cancer–stromal cell expansion.

Cancer-associated fibroblasts (CAFs) are important for tumor initiation and promotion. CSL, a transcriptional repressor and Notch mediator, suppresses CAF activation. Like CSL, ATF3, a stress-responsive transcriptional repressor, is down-modulated in skin cancer stromal cells, and Atf3 knockout mice develop aggressive chemically induced skin tumors with enhanced CAF activation. Even at low basal levels, ATF3 converges with CSL in global chromatin control, binding to few genomic sites at a large distance from target genes. Consistent with this mode of regulation, deletion of one such site 2 Mb upstream of IL6 induces expression of the gene. Observed changes are of translational significance, as bromodomain and extra-terminal (BET) inhibitors, unlinking activated chromatin from basic transcription, counteract the effects of ATF3 or CSL loss on global gene expression and suppress CAF tumor-promoting properties in an in vivo model of squamous cancer–stromal cell expansion. Thus, ATF3 converges with CSL in negative control of CAF activation with epigenetic changes amenable to cancer- and stroma-focused intervention.

Effect of the potentiation of cholinergic activity on the variability in individual GH response to GH-releasing hormone

In man the GH response to GHRH is highly variable and some normal subjects may be completely unresponsive to the neuropeptide. On the other hand, the potentiation of cholinergic activity by pyridostigmine (PD), a cholinesterase inhibitor, increases the GH response to GHRH, probably by inhibiting somatostatin release. The aim of this study was to assess the existence of intraindividual variability in the GH response to GHRH and verify the effects of PD treatment on inter- and intraindividual variability. Twenty normal adults (17 M and 3 F) and 10 normal prepubertal children (9 M and 1 F) underwent 2-5 administrations of 1 micrograms/kg GHRH on different days. Seven adults and all children also underwent 1-5 other tests in which GHRH was preceded (60 min before) by oral PD (120 mg in adults and 60 mg in children). The GH responses to GHRH were highly variable, not only within subjects but also in the same subject on different occasions (peak range; adults: 0.4-49.0 ng/ml; children: 2.4-50.0 ng/ml). PD always markedly increased the GH response to GHRH, even unmasking this response in 3 adults and 4 children hyporesponsive to the neuropeptide alone. However, the variability in the GH response was still present (adults: 27.2-108.5 ng/ml; children: 25.0-144.0 ng/ml), though reduced (adults: p = 0.0005; children: p = 0.0204). These data indicate that: i. A great inter- and intraindividual variability in the GH response to GHRH is present.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholinergic enhancement by pyridostigmine increases the insulin response to glucose load in obese patients but not in normal subjects

OBJECTIVE

To further investigate the role, if any, of acetylcholine and the parasympathetic nervous system in modulating beta-cell secretion in man.

DESIGN

Oral glucose load (OGTT, 100 g p.o. at 0 min) alone and preceded by pyridostigmine (PD, 120 mg p.o., 60 min before OGTT), a cholinesterase inhibitor, were administered on two different occasions, in random order, two or three days apart.

SUBJECTS

Ten women with central obesity (OB, body mass index (BMI): 34.2 +/- 2.1 kg/m2, waist to hip ratio (WHR): 0.83 +/- 0.01, aged 39.0 +/- 5.3y) and six normal women (NS, BMI: 22.7 +/- 1.9 kg/m2, WHR: 0.74 +/- 0.01, aged 37.1 +/- 4.8y) were studied.

MEASUREMENTS

Serum insulin, plasma glucose and plasma noradrenaline (NA) were measured at -60, -15 and 0 min, and then every 15 min up to +120 min. Insulin concentrations were measured in duplicate by immunoradiometric assay, glucose by glucose oxidase colorimetric method and NA was assayed after extraction with alumina using high performance liquid chromatography with electrochemical detection. Pulse rate (PR), systolic (SBP) and diastolic blood pressure (DBP) were also measured every 15 min during the tests by an automated cuff device.

RESULTS

OGTT raised glucose concentrations in OB and NS (incremental area: 420 +/- 44 vs 288 +/- 70 mmol/l. 2 h, respectively) without significant differences between groups (F = 0.6, P = ns). On the other hand, OB showed an insulin response to OGTT higher than NS (10,120 +/- 1074 vs 6692 +/- 1962 microU ml-1 2 h, respectively P < 0.01). After OGTT alone NA concentrations increased to the same extent in NS (peak vs basal: 1.40 +/- 0.16 vs 1.07 +/- 0.10 nmol/l, P < 0.05) and in OB (peak vs basal: 1.50 +/- 0.14 vs 1.04 +/- 0.18 nmol/l P < 0.05). Both in NS and in OB, PD administration failed to modify basal glucose and insulin (P = ns for both) as well as basal NA concentrations. In NS, the combined administration of PD and OGTT did not modify glucose and insulin responses compared to OGTT alone 335 +/- 65.4 mmol/l. 2h and 6348 +/- 1348 microU ml-1 2h, respectively) while in OB, PD significantly increased the insulin response to OGTT (14640 +/- 3030 microU ml-1 2h, P < 0.03), while the glucose response was not significantly different from OGTT alone (478 +/- 45 mmol/l. 2h). PD administration did not modify the NA response to OGTT, in NS or OB (P = ns). In both groups, pyridostigmine administration did not affect systolic or diastolic blood pressures, but decreased pulse rate to the same extent in NS (74 +/- 2 vs 66 +/- 2 beats/min, P < 0.05) and in OB (72 +/- 1 vs 67 +/- 2 beats/min, P < 0.05).

CONCLUSIONS

Our present data indicate that in man, as in animals, acetylcholine has a stimulatory influence on insulin secretion.

Comparison among the effects of arginine, a nitric oxide precursor, isosorbide dinitrate and molsidomine, two nitric oxide donors, on hormonal secretions and blood pressure in man

Arginine has well-known stimulatory effects on GH, PRL and insulin secretion in man but the mechanisms underlying these effects are still unclear. More recently, it has been demonstrated that arginine is the precursor of nitric oxide (NO) which mediates its vasodilatatory effect. Thus, it has been hypothesized that NO could also mediate the hormonal effects of arginine. To clarify this point, in seven normal young volunteers (7 normal male subjects, age 26-35 yr) we compared the effects of arginine hydrochloride (ARG, 0.5 g/kg iv over 30 min) on GH, PRL, insulin and glucose levels as well as on blood pressure, with those of isosorbide dinitrate (ISDN, 5 mg po) and molsidomine (MOLS, 4 mg po), two NO donors which possess well-known vasodilatatory effects. ARG infusion elicited a clear-cut GH increase (peak vs baseline 17.6 +/- 4.7 vs 2.7 +/- 0.8 (g/L, p < 0.01), PRL (20.6 +/- 2.8 vs 6.9 +/- 0.5 (g/L, p < 0.01) and insulin levels (31.4 +/- 5.7 vs 4.5 +/- 2.1 (U/L, p < 0.01) while induced a biphasic variation of plasma glucose levels with early increase (p < 0.01), followed by late decrease below basal values (p < 0.01). On the other hand, blood pressure was decreased by ARG (nadir vs baseline; systolic: 103 +/- 6 vs 112 +/- 3, p < 0.02 and diastolic 61 +/- 4 vs 72 +/- 2 mmHg, p < 0.02, respectively). ISDN and MOLS did not modify basal GH, PRL and insulin as well as glucose levels while induced a clear reduction in blood pressure (ISDN: nadir vs baseline; systolic: 94 +/- 4 vs 112 +/- 2, p < 0.02; diastolic 69 +/- 3 vs 80 +/- 2, p < 0.02; MOLS: systolic: 94 +/- 3 vs 113 +/- 2 p < 0.02; diastolic 63 +/- 4 vs 72 +/- 2, p < 0.02). The lowering effect of both ISDN and MOLS on both systolic and diastolic blood pressure levels was higher than that induced by ARG. The effect of the latter was, in turn, significantly different from that of placebo on diastolic levels only. In conclusion, our present date are against the hypothesis that NO mediates the stimulatory effects of arginine on GH, PRL and insulin secretion. On the other hand, our findings agree with the hypothesis that ARG has NO-mediated vasodilatatory effect able to decrease blood pressure in man.

Seasonality of birth in epilepsy: a Danish study

OBJECTIVES

A recent British epidemiological study, having found that the seasonality of birth in a large epileptic sample was significantly different from that of the general population, has pointed to neurodevelopmental disruption as the likely mechanism to cause at least part of the epilepsies of unknown aetiology. The aim of this study is to replicate the British study using a large Danish sample.

MATERIAL AND METHODS

The population studied is composed by all the 50,886 patients discharged from Danish Hospitals, with a diagnosis of epilepsy, in the period from 1977 to 1993. The seasonal pattern of birth in this sample has been compared, using regression methods, with all the live births in Denmark.

RESULTS

The results were strikingly similar to the British study, with a deficit of epileptic births in September and an excess during the winter months.

CONCLUSION

This study seems to confirm the seasonal presence in the environment of an aetiological factor(s) for epilepsy which acts in the perinatal period disrupting the neurodevelopment.

Assessment of GH/IGF-I axis in obesity by evaluation of IGF-I levels and the GH response to GHRH+arginine test

The GH response to provocative stimuli in obese is often as low as in panhypopituitaric patients with severe GHD; however, IGF-I levels are normal or slightly reduced. In 53 patients with simple obesity (11 M and 42 F, age: 40.3+/-1.6 yr, BMI: 39.1+/-1.0 Kg/m2), we evaluated the GH response to GHRH (1 microg/kg iv)+arginine (ARG, 0.5 g/kg iv), and total IGF-I levels. The mean (+/-SE) GH peak after GHRH+ARG was markedly lower (74% reduction, p<0.0001) in obese (16.8+/-2.0 microg/l) than in normal subjects (62.7+/-4.3 microg/l). IGF-I levels in obese patients (134.0+/-7.6 microg/l) were lower (33% reduction, p<0.001) than in normal subjects (200.8+/-5.7 microg/l). Taking into account the 3rd centile limit of normal response, the GH response to GHRH+ARG was reduced in 62.3% (33/53) of the obese patients, and 21.2% (7/33) of them had low IGF-I levels. Assuming the 1st centile limit, it was reduced in 33.9% (18/53) obese subjects, and 22% (4/18) of them had low IGF-I levels. Considering 3.0 microg/L as arbitrary cut-off, the GH response was reduced in 5.7% (3/53) of the obese patients, and still one of them had low IGF-I levels. Our findings: a) confirm that the secretory capacity of somatotroph cells is often deeply impaired in obesity; b) demonstrate that IGF-I assay generally rules out severe impairment of GH/IGF-I axis in obese patients with marked reduction of the GH secretion; c) indicate that the percentage of obese patients with concomitant reduction of GH secretion and IGF-I levels is not negligible. Thus, IGF-I assay should be routinely performed in obese patients; those presenting with low IGF-I levels should undergo further evaluation of their hypothalamo-pituitary function and morphology, particularly in the presence of empty sella.