Pharmacokinetic and pharmacodynamic properties of taspoglutide, a once-weekly, human GLP-1 analogue, after single-dose administration in patients with Type 2 diabetes.

AIMS: The study objectives were to evaluate the pharmacokinetic and pharmacodynamic properties, as well as safety and tolerability, of single doses of taspoglutide, a human glucagon-like peptide-1 (GLP-1) analogue. METHODS: In a double-blind, placebo-controlled study, 48 patients with Type 2 diabetes [mean age 56 +/- 7 years; mean body mass index (BMI) 30.4 +/- 3.0 kg/m(2)] inadequately controlled with metformin (< or = 2 g/day) were enrolled in three sequential cohorts; 12 patients in each cohort were randomized to a single subcutaneous injection of taspoglutide (1, 8 or 30 mg) and four received placebo. RESULTS: Plasma concentrations peaked within 24 h after injection and were sustained for > or = 14 days with all doses. In comparison with placebo, the 8- and 30-mg doses of taspoglutide significantly reduced glycaemic parameters, including 24-h blood glucose and 5-h postprandial glucose areas under the curve (AUCs), for up to 14 days with the 30-mg dose (P < 0.001). The most common adverse events, primarily gastrointestinal in nature, were dose-dependent and transient. CONCLUSIONS: A single dose of taspoglutide significantly improved glycaemic parameters in Type 2 diabetes patients for up to 14 days. The formulation was well tolerated and appears suitable for weekly administration.

Evaluation of acromegaly by measurement of 24-hourly urinary growth hormone excretion.

Twenty-four hourly urinary growth hormone excretion (24-h uGH) has been quantified using a combination of ultrafiltration and conventional immunoradiometric assay. Twenty-four hourly uGH was measured in 20 normal adults and in 42 patients with acromegaly (9 untreated, 28 treated but with above-normal IGF-I levels, and 5 treated and cured). The means and ranges were as follows: 3.7 (1-9) ng/24 h for normals and 160 (40-540), 66 (2-380) and 5.2 (4-8) ng/24 h for the three groups of acromegalic patients, respectively. Ten patients with pituitary adenomas without acromegaly had 24-h uGH within the normal range. Twenty-four hourly uGH therefore gives a clear differentiation between controls and untreated patients. Log-transformed values for subjects with acromegaly showed significant correlations between 24-h uGH and levels of IGF-I (r = 0.63, p < 0.01), fasting plasma GH (r = 0.92, p < 0.001) and plasma GH after glucose loading (r = 0.85, p < 0.001). Twenty-four hourly uGH was also determined in three acromegalic patients before and during SMS 201-995 therapy. Twenty-four hourly uGH reflected the corresponding changes in mean levels for hourly sampling over 12 h of plasma GH and IGF-I and in clinical signs after 3-6 months of therapy. The results of this study indicate that 24-h uGH is an accurate indicator of GH secretion in acromegalic patients and could therefore be used both in diagnosis and in monitoring the progress of therapy in these patients.

Protein kinase C activity and expression in normal and adenomatous human pituitaries.

Protein kinase C (PKC) activity and expression were measured in 54 adenomas (prolactin (PRL)-, growth hormone (GH)- and non-secreting), 1 of them obtained from a patient treated with the dopamine agonist bromocriptine and 2 from patients treated with the somatostatin analog octreotide. They were also measured in normal human and rat pituitaries. Total PKC activity was measured by incorporation of 32P into histones, and PKC expression by dot blot immunoquantification using purified PKC as a standard. Both enzyme activity and expression were higher in adenomatous pituitaries than in normal human or rat pituitaries. PKC expression in GH-secreting and non-secreting tumors was significantly higher than that in PRL-secreting tumors. Furthermore, it was significantly higher invasive tumors than in non-invasive tumors. In the 3 adenomas which were obtained from patients treated with bromocriptine or octreotide and which were used for PKC-activity measurement, particulate- and soluble-PKC activities were significantly lower than those measured in non-treated adenomas.

[EGF binding site number of rat anterior pituitary is increased by chronic administration with dopaminergic agonist, CV 205-502]. / Le nombre de sites EGF de l'antéhypophyse du rat est augmenté par l'administration chronique de l'agoniste dopaminergique, le CV 205-502.

In order to assess whether a chronic treatment with a dopamine agonist, CV205-502, could modulate anterior pituitary epidermal growth factor (EGF) binding sites, female Wistar rats were treated or not (controls) with CV205-502 0.25 mg/kg/day sc for 8 days. This treatment significantly reduced rats' pituitary weight and plasma prolactin levels when compared to controls (weight: 10.4 +/- 0.1 vs 11.1 +/- 0.1 mg, p less than 0.01; prolactin: 1.2 +/- 0.2 vs 4.9 +/- 0.5 ng/ml, p less than 0.01). These decreases were associated with a significant stimulation of the number of pituitary EGF binding sites Bmax: 16.7 +/- 2.3 vs 11.3 +/- 1.9 fmoles/mg proteins, p less than 0.01) with no significant effect on their affinity (Kd: 0.94 +/- 0.17 vs 0.95 +/- 0.14 nM). Therefore, the modulation of pituitary EGF binding sites might be one of the mechanisms by which the dopamine agonist, CV205-502, exerts its pharmacological effects on hormonal secretions and/or cell multiplication in the pituitary.

Cardiovascular effects of the somatostatin analog octreotide in acromegaly.

OBJECTIVE: To determine the cardiovascular effects of the somatostatin analog octreotide in patients with acromegaly. DESIGN: Prospective nonrandomized study. SETTING: Referral-based endocrinology clinic. PATIENTS: Seven patients with active acromegaly, three of whom had refractory congestive heart failure. The other four patients were free of symptoms associated with heart failure. INTERVENTIONS: All patients were treated with octreotide, 100 to 500 micrograms subcutaneously three times daily. The three patients with heart failure continued to receive cardiovascular therapy (angiotensin converting enzyme inhibitors, digitalis, diuretics). MEASUREMENTS AND MAIN RESULTS: During octreotide therapy, patients showed a rapid decrease in growth hormone and insulin-like growth factor 1 (IGF-1): Mean levels (+/- SD) fell from 28.1 +/- 32.7 micrograms/L to 5.2 +/- 8.3 micrograms/L and 740 +/- 126 micrograms/L to 372 +/- 64 micrograms/L, respectively (P less than 0.025). Plasma volume returned to normal and heart rate decreased significantly. In the four patients without heart failure, right-heart catheterization done before and after 3 months of octreotide therapy showed an 18.3% +/- 11% reduction in stroke volume and a return to normal of the cardiac index. The three patients with congestive heart failure, evaluated before and after 40 days and up to 2 years of therapy, showed a dramatic clinical improvement that was associated with an increase in stroke volume (by 24% to 51%). In these patients, the cardiac index remained in the normal range, filling pressures were markedly decreased, and pulmonary wedge pressure returned to normal. This improvement was sustained for up to 3 years in the two patients with heart failure who were receiving long-term treatment. CONCLUSION: The rapid and sustained cardiac improvement seen in our patients shows that octreotide therapy for patients with acromegaly may be highly beneficial, even in those patients with advanced cardiac failure.

Cyproterone acetate versus hydrocortisone treatment in late-onset adrenal hyperplasia.

Thirty late-onset adrenal hyperplasia patients consulting for isolated hirsutism were randomly divided into two groups; group 1 (n = 16) was treated with hydrocortisone in order to suppress androgen adrenal secretion, and group 2 (n = 14) received cyproterone acetate (CPA) antiandrogen therapy to inhibit peripheral androgen activity. The clinical and hormonal effects of each type of treatment were evaluated. Before treatment, the clinical and hormonal profiles of the two patient groups did not differ significantly. Excellent clinical evolution in terms of the regression of hirsutism was observed in the CPA-treated patients (54% decrease in the clinical score in 1 yr), in contrast with the slight decrease in hirsutism (26%) after hydrocortisone treatment. In hydrocortisone-treated patients, plasma androgen decreased to normal levels: testosterone from 3.05 +/- 1.45 to 1.46 +/- 0.42 nmol/L and delta 4-androstenedione from 13.6 +/- 4.1 to 6.33 +/- 1.47 nmol/L. Conversely, in CPA-treated patients, only a slight decrease in testosterone from 2.98 +/- 1.98 to 2.29 +/- 0.64 nmol/L and in delta 4-androstenedione from 12.9 +/- 5.9 to 9.86 +/- 2.23 nmol/L was observed. This slight decrease in plasma androgens contrasts with the rapid clinical improvement after CPA. These results emphasize the importance of peripheral receptivity to androgens in the clinical expression of hyperandrogenism. Moreover, they indicate that peripheral antiandrogen therapy may be more appropriate in late-onset adrenal hyperplasia patients than conventional adrenal inhibition using cortisone therapy.

Chronic treatment by the calcium channel blocker +/- PN 200-110 in the rat counteracts the stimulations of pituitary weight, prolactin release and pituitary C-kinase activity induced by a chronic estradiol treatment, in vivo.

In order to investigate whether a calcium channel blocker could modulate the protein kinase C activity in normal and estradiol pretreated rat pituitary, female Wistar rats were treated or not (controls) with +/- PN 200-110 (3 mg.kg-1.day-1, sc) for 8 days or with estradiol cervical implants for 8 or 15 days, alone or in combination with PN 200-110 the last 8 days. Estradiol treatment induced a significant increase in plasma prolactin levels and pituitary weight. PN 200-110 administered to normal rats did not modify these parameters, whereas it reduced the effects of the 15 days estradiol treatment on prolactin levels (53.1 +/- 4.9 vs 95.0 +/- 9.1 micrograms/l, p less than 0.0001) and pituitary weight (19.9 +/- 0.4 vs 23.0 +/- 0.6 mg, p less than 0.001), to values statistically comparable to those measured after 8 days of estradiol treatment. PN 200-110 alone did not induce any change in protein kinase C activity as compared with controls. In contrast, PN 200-110 treatment significantly counteracted the large increase in soluble activity and the decrease in the particulate one induced by estradiol between day 8 and day 15. We conclude that PN 200-110 opposed the stimulatory effects of chronic in vivo estradiol treatment on plasma prolactin levels and pituitary weight and that this regulation was related to a concomitant modulation of the protein kinase C activity.

Effect of oestradiol on dopamine receptors and protein kinase C activity in the rat pituitary: binding of oestradiol to pituitary membranes.

Oestradiol exerts an important modulatory influence on the release of prolactin which is accomplished partly through disruption of the inhibitory influence of dopamine. We have focused on the status of the anterior pituitary D2 dopamine receptor in female rats treated chronically with oestradiol or progesterone. A direct membrane effect of these steroids on the dopamine system was also investigated in vitro. Both steroids affected the status of the D2 receptor, oestradiol decreasing the number of sites in vitro and progesterone increasing it both in vitro and in vivo. The in vitro studies demonstrated that these steroids exert a direct membrane effect on the D2 receptor. These results correlated with an in vitro short-term physiological effect of oestradiol and progesterone on the dopaminergic inhibition of prolactin release, oestradiol decreasing it while progesterone had the opposite effect. Binding studies with [3H] oestradiol on pituitary membranes revealed a site for oestradiol of high affinity and low capacity, indicating that oestradiol's membrane effects could be mediated by a specific receptor. In vivo treatment with oestradiol also induces proliferation of prolactin-secreting cells (lactotrophs). We focused on the effect of oestradiol on protein kinase C activity, which is involved in both secretion and proliferation. In female rats treated with oestradiol total protein kinase C activity was increased by 74% (particulate 90%, soluble 71%) in comparison with controls. This effect was reversed by concomitant treatment with a dopamine agonist. Thus in the pituitary oestradiol and progesterone affect the characteristics of membrane components that are implicated in the physiological control of the cell. Whether these effects are post-transcriptional only or are also mediated through direct membrane mechanisms needs further investigation.

The stimulated C-kinase activity in estradiol-treated rat pituitaries is reduced by chronic treatment with the dopamine agonist CV 205-502.

To investigate whether the modulation of lactotrope cell multiplication and prolactin secretion in rat pituitary glands implicated the phosphoinositide C-kinase system, female Wistar rats were treated or not-with the dopamine agonist CV 205-502 or 8 days or with estradiol cervical implants for 8 for 15 days, alone or in combination with CV 205-502 for the last 8 days. CV 205-502 treatment induced a significant reduction in plasma PRL levels and in pituitary weights, whereas estradiol treatment induced a significant increase in both parameters. CV 205-502, in association with estradiol, counteracted estradiol stimulation of PRL levels and of pituitary weights. Total C-kinase activity in controls was 29.8 +/- 9.9 pmol 32phosphorus/min (N = 7, mean +/- SEM), mainly found in the soluble fraction (84%). When administered alone, CV 205-502 induced a significant reduction (-58%, p less than 0.02) in C-kinase activity in the particulate fraction with no modification in the soluble fraction. Both 8 and 15 days estradiol treatment induced a significant stimulation of total C-kinase activity, 74% and 155% respectively. When combined with estradiol, CV 205-502 significantly (p less than 0.02) counteracted the estradiol increase in total C-kinase activity, which was only 45% over control values. We conclude that treatment with a dopamine agonist and estradiol, which have antagonistic effects on the pituitary, exerts an opposite regulation of C-kinase activity. Whether this may be one of the mechanisms involved in their interaction on pituitary lactotropes remains to be determined.

Receptors and neurohormones in human pituitary adenomas.

In order to go further into the pathogenesis of human pituitary adenomas, we studied receptors for neurohormones (thyroliberin, TRH; dopamine, DA; somatostatin, SRIH), for estradiol and epidermal growth factor (EGF) thought to influence hormone secretion and/or cell growth. The following results were obtained: (1) the receptors listed above, with the exception of EGF receptors in the adenomas, are present in normal pituitary tissue and in prolactin (PRL)- and growth hormone (GH)-secreting adenomas; (2) they are functional and their affinities are not different in normal or tumoral tissues; (3) their density is variable and depends on the type of secreting adenoma (GH or PRL), the size of the tumor and the plasma level of the hormone which is secreted, and (4) in nonsecreting adenomas, only TRH receptors are found with characteristics identical to those observed in secreting adenomas. We also showed that TRH is contained in normal and tumoral pituitary tissues. TRH and SRIH are released in vitro from adenomatous cells in large amounts, suggesting their possible synthesis by the pituitary. In both cases a local regulation is observed. TRH release is stimulated in the presence of DA while SRIH is inhibited in the presence of TRH. This neuropeptide release may be implicated in the pituitary hormone regulation through a paracrine or an autocrine mechanism. Thus, the neurohormone receptors found in pituitary adenomas should be dependent on a more complex regulation than it has been envisaged till now.

Epidermal growth factor-binding sites, present in normal human and rat pituitaries, are absent in human pituitary adenomas.

To investigate the involvement of epidermal growth factor (EGF) and its receptor in the pathogenesis of human pituitary adenomas, we examined the presence of EGF-binding sites in normal rat and human pituitaries and in human PRL- and GH-secreting and nonsecreting pituitary adenomas. Using crude membrane preparations, specific binding for [125I] EGF was found in normal rat and human pituitaries. Equilibrium was reached at 25 C in 40 min. There was no change in the Kd values between male rats [Kd, 0.65 +/- 0.35 nM (mean +/- SD)] and female rats (Kd, 0.51 +/- 0.15 nM), while the maximum capacity was significantly higher (P less than 0.05) in male rats (21 +/- 8 fmol/mg protein) than in female rats (10 +/- 2 fmol/mg protein). Scatchard analysis of the data suggested the presence of a single class of binding sites. In the three normal human pituitaries tested, specific [125I]EGF binding was also demonstrated. However, both the Kd and the maximum capacity varied widely. Twenty-two human pituitary adenomas were tested, but no specific binding was detected in any of them. In addition to the binding experiments, a radioreceptor assay using rat liver membranes was developed to detect EGF or EGF-like material in extracts of six human pituitary adenomas (two of each type). No EGF activity was detected in any of the extracts. From these results, we conclude that EGF-binding sites are present in normal pituitary tissue, suggesting a physiological role for EGF in this tissue. Consequently, the reason(s) for the lack of EGF binding in pituitary adenoma membranes is not known.