Identification of Binding Sites on Human Serum Albumin for Somapacitan, a Long-Acting Growth Hormone Derivative.

Somapacitan, a human growth hormone derivative that binds reversibly to albumin, was investigated for human serum albumin (HSA) and HSA domain binding. Isothermal titration calorimetry (ITC) binding profiles showed high-affinity binding (∼100-1000 nM) of one somapacitan molecule and low-affinity binding (∼1000-10000 nM) of one to two somapacitan molecules to HSA. The high-affinity site was identified in HSA domain III using size exclusion chromatography (SEC) and ITC. SEC studies showed that the neonatal Fc receptor shields one binding site for somapacitan, indicating its position in domain III. A crystal structure of somapacitan in complex with HSA optimized for neonatal Fc receptor binding, having four amino acid residue replacements, identified a low-affinity site in fatty acid-binding site 6 (domain II). Surface plasmon resonance (SPR) showed these replacements affect the kinetics of the high-affinity binding site. Furthermore, small-angle X-ray scattering and SPR brace two somapacitan-binding sites on HSA.

Pharmacokinetics and Pharmacodynamics of Once-Weekly Somapacitan in Children and Adults: Supporting Dosing Rationales with a Model-Based Analysis of Three Phase I Trials.

BACKGROUND: Somapacitan, a long-acting growth hormone (GH) derivative, has been well-tolerated in children with GH deficiency (GHD) and adults (healthy and adult GHD), in phase I, single- and multiple-dose trials, respectively, and has pharmacokinetic and pharmacodynamic properties supporting a once-weekly dosing regimen. OBJECTIVE: In the absence of a multiple-dose phase I trial in children with GHD, the aim was to develop a pharmacokinetic/pharmacodynamic model to predict somapacitan exposure and insulin-like growth factor-I (IGF-I) response after once-weekly multiple doses in both children and adults with GHD. METHODS: Pharmacokinetic/pharmacodynamic models were developed from pharmacokinetic and IGF-I profiles in three phase I trials of somapacitan (doses: healthy adults, 0.01-0.32 mg/kg; adult with GHD, 0.02-0.12 mg/kg; children with GHD, 0.02-0.16 mg/kg) using non-linear mixed-effects modeling. Pharmacokinetics were described using a non-linear one-compartment model with dual first- and zero-order absorption through a transit compartment, with saturable elimination. IGF-I profiles were described using an indirect response pharmacokinetic/pharmacodynamic model, with sigmoidal-effect relationship. RESULTS: The non-linear pharmacokinetic and IGF-I data were well-described in order to confidently predict pharmacokinetic/pharmacodynamic profiles after multiple doses in adults and children with GHD. Body weight was found to be a significant covariate, predictive of the differences observed in the pharmacokinetics and pharmacodynamics between children and adults. Weekly dosing of somapacitan provided elevated IGF-I levels throughout the week, despite little or no accumulation of somapacitan, in both adults and children with GHD. CONCLUSION: This analysis of somapacitan pharmacokinetic/pharmacodynamic data supports once-weekly dosing in adults and children with GHD. TRIAL REGISTRATION: ClinicalTrials.gov identifier numbers NCT01514500, NCT01706783, NCT01973244.

A useful model to compare human and mouse growth hormone gene chromosomal structure, expression and regulation, and immune tolerance of human growth hormone analogues.

Human (h) pituitary growth hormone (GH) is both physiologically and clinically important. GH reaches its highest circulatory levels in puberty, where it contributes to energy homeostasis and somatogenic growth. GH also helps to maintain tissues and organs and, thus, health and homeostasis. A reduction in the rate of hGH production begins in middle age but if GH insufficiency occurs this may result in tissue degenerative and metabolic diseases. As a consequence, hGH is prescribed under conditions of GH deficiency and, because of its lipolytic activity, stimulation of hGH release has also been used to treat obesity. However, studies of normal GH production and particularly synthesis versus secretion are not feasible in humans as they require sampling normal pituitaries from living subjects. Furthermore, human (or primate) GH structure and, as such, regulation and potential function, is distinct from non-primate rodent GH. As a result, most information about hGH regulation comes from measurements of secreted levels of GH in humans. Thus, partially humanized hGH transgenic mice, generated containing fragments of human chromosome 17 that include the intact hGH gene locus and many thousands of flanking base pairs as well as the endogenous mouse (m) GH gene provide a potentially useful model. Here we review this mouse model in terms of its ability to allow comparison of hGH versus mGH gene expression, and specifically: (i) GH locus structure as well as regulated and rhythmic expression; (ii) their ability to model a clinical assessment of hGH production in response to overeating and hyperinsulinemia as well as a possible effect of exercise, and (iii) their hGH-related immune tolerance and thus potential for testing hGH-related analogue immunogenicity.

Somapacitan, a once-weekly reversible albumin-binding GH derivative, in children with GH deficiency: A randomized dose-escalation trial.

OBJECTIVE: To evaluate the safety, local tolerability, pharmacodynamics and pharmacokinetics of escalating single doses of once-weekly somapacitan, a reversible, albumin-binding GH derivative, vs once-daily GH in children with GH deficiency (GHD). DESIGN: Phase 1, randomized, open-label, active-controlled, dose-escalation trial (NCT01973244). PATIENTS: Thirty-two prepubertal GH-treated children with GHD were sequentially randomized 3:1 within each of four cohorts to a single dose of somapacitan (0.02, 0.04, 0.08 and 0.16 mg/kg; n=6 each), or once-daily Norditropin® SimpleXx® (0.03 mg/kg; n=2 each) for 7 days. MEASUREMENTS: Pharmacokinetic and pharmacodynamic profiles were assessed. RESULTS: Adverse events were all mild, and there were no apparent treatment-dependent patterns in type or frequency. Four mild transient injection site reactions were reported in three of 24 children treated with somapacitan. No antisomapacitan/anti-human growth hormone (hGH) antibodies were detected. Mean serum concentrations of somapacitan increased in a dose-dependent but nonlinear manner: maximum concentration ranged from 21.8 ng/mL (0.02 mg/kg dose) to 458.4 ng/mL (0.16 mg/kg dose). IGF-I and IGFBP-3, and change from baseline in IGF-I standard deviation score (SDS) and IGFBP-3 SDS, increased dose dependently; greatest changes in SDS values were seen for 0.16 mg/kg. IGF-I SDS values were between -2 and +2 SDS, except for peak IGF-I SDS with 0.08 mg/kg somapacitan. Postdosing, IGF-I SDS remained above baseline levels for at least 1 week. CONCLUSIONS: Single doses of once-weekly somapacitan (0.02-0.16 mg/kg) were well tolerated in children with GHD, with IGF-I profiles supporting a once-weekly treatment profile. No clinically significant safety/tolerability signals or immunogenicity concerns were identified.

Pasireotide for the Medical Management of Feline Hypersomatotropism.

BACKGROUND: Feline hypersomatotropism (HST) is a cause of diabetes mellitus in cats. Pasireotide is a novel multireceptor ligand somatostatin analog that improves biochemical control of humans with HST. HYPOTHESIS/OBJECTIVES: Pasireotide improves biochemical control of HST and diabetes mellitus in cats. ANIMALS: Hypersomatotropism was diagnosed in diabetic cats with serum insulin-like growth factor-1 (IGF-1) concentration >1,000 ng/mL by radioimmunoassay and pituitary enlargement. METHODS: Insulin-like growth factor 1 was measured and glycemic control assessed using a 12-hour blood glucose curve on days 1 and 5. On days 2, 3, and 4, cats received 0.03 mg/kg pasireotide SC q12h. IGF-1, insulin dose, and estimated insulin sensitivity (product of the area under the blood glucose curve [BGC] and insulin dose) were compared pre- and post treatment. Paired t-tests or Wilcoxon signed rank tests were employed for comparison where appropriate; a linear mixed model was created to compare BGC results. RESULTS: Insulin-like growth factor 1 decreased in all 12 cats that completed the study (median [range] day 1: 2,000 ng/mL [1,051-2,000] and day 5: 1,105 ng/mL [380-1,727], P = .002, Wilcoxon signed rank test). Insulin dose was lower on day 5 than on day 1 (mean reduction 1.3 [0-2.7] units/kg/injection, P = .003, paired t-test). The product of insulin dose and area under the BGC was lower on day 5 than day 1 (difference of means: 1,912; SD, 1523; u × mg/dL × hours, P = .001; paired t-test). No clinically relevant adverse effects were encountered. CONCLUSIONS: Short-acting pasireotide rapidly decreased IGF-1 in cats with HST and insulin-dependent diabetes. The decrease in IGF-1 was associated with increased insulin sensitivity.

N-terminal mono-PEGylation of growth hormone antagonist: correlation of PEG size and pharmacodynamic behavior.

Growth hormone antagonist (GHA), an analog of growth hormone (GH), can inhibit GH action and treat acromegaly. However, GHA suffers from a short plasma half-life of 15-20 min that has limited its clinical application. PEGylation, conjugation with polyethylene glycol (PEG), can increase the plasma half-life of GHA. Single PEG attachment (mono-PEGylation) at N-terminus of GHA has the advantages of product homogeneity and minimization of the bioactivity loss. Conjugation of large PEG molecule may increase the plasma half-life but could potentially decrease the bioactivity of GHA, due to the steric shielding effect of PEG. Thus, N-terminal mono-PEGylation of GHA with 20 kDa and 40 kDa PEG were used to look for a balance of the two competing factors. Sedimentation velocity analysis suggested that 40 kDa PEG was more efficient than 20 kDa PEG to elongate the molecular shape of the conjugate. As reflected by marginal suppression of insulin-like growth factor I (IGF-I), GHA conjugated with 40 kDa PEG was statistically indistinguishable from the saline solution that could not inhibit GH action. In contrast, GHA conjugated with 20kDa PEG can apparently inhibit GH action, as reflected by IGF-I suppression of 30-43%. Thus, our work demonstrated the effective therapeutic potency of N-terminally mono-PEGylated GHA.

Multiple biosynthetic trafficking routes for apically secreted proteins in MDCK cells.

Many newly synthesized membrane proteins traverse endocytic intermediates en route to the surface in polarized epithelial cells; however, the biosynthetic itinerary of secreted proteins has not been elucidated. We monitored the trafficking route of two secreted proteins with different apical sorting signals: the N-glycan-dependent cargo glycosylated growth hormone (gGH) and Ensol, a soluble version of endolyn whose apical sorting is independent of N-glycans. Both proteins were observed to colocalize in part with apical recycling endosome (ARE) markers. Cargo that lacks an apical targeting signal and is secreted in a nonpolarized manner did not localize to the ARE. Expression of a dominant-negative mutant of myosin Vb, which disrupts ARE export of glycan-dependent membrane proteins, selectively inhibited apical release of gGH but not Ensol. Fluorescence recovery after photobleaching (FRAP) measurements revealed that gGH in the ARE was less mobile than Ensol, consistent with tethering to a sorting receptor. However, knockdown of galectin-3 or galectin-4, lectins implicated in apical sorting, had no effect on the rate or polarity of gGH secretion. Together, our results suggest that apically secreted cargoes selectively access the ARE and are exported via differentially regulated pathways.

Long-acting pegylated human GH in children with GH deficiency: a single-dose, dose-escalation trial investigating safety, tolerability, pharmacokinetics and pharmacodynamics.

OBJECTIVE: GH replacement therapy currently requires daily injections, which may be inconvenient and distressing for young patients. This study determined the safety, tolerability, pharmacokinetics and pharmacodynamics of escalating single doses of a pegylated GH (NNC126-0083) developed for once-weekly administration, in children with GH deficiency (GHD). DESIGN AND METHODS: Thirty children (age ≥6 and ≤12 years, weight ≥16 kg) were randomised to NNC126-0083 or daily GH treatment. The subjects discontinued their daily GH treatment 7-9 days before receiving NNC126-0083 at 0.01, 0.02, 0.04 or 0.06 mg protein/kg (n=22) or seven once-daily doses of GH at 0.035 mg protein/kg (n=8). RESULTS: NNC126-0083 was well tolerated, and no short-term safety or local tolerability issues were identified. After NNC126-0083 treatment, dose-dependent IGF1 increases were evident for maximum concentration (C(max)), but not area under the curve (AUC(0)(-)(168 h)). Mean values for IGF1 AUC(0)(-)(168 h)/168 h and C(max) were higher for GH than for NNC126-0083, although the difference was not statistically significant for cohort's 0.06 mg protein/kg. At 0.06 mg protein/kg, the resulting IGF1 response began subsiding at ∼3 days post-dose. CONCLUSION: Single doses of long-acting NNC126-0083 were safe and well tolerated in children with GHD. Increased IGF1 levels were observed in all NNC126-0083 dose groups; however, a satisfactory once-weekly IGF1 profile was not reached within the NNC126-0083 dose levels administered.

Pegylated long-acting human growth hormone possesses a promising once-weekly treatment profile, and multiple dosing is well tolerated in adult patients with growth hormone deficiency.

BACKGROUND: Recombinant human GH (rhGH) replacement therapy in children and adults currently requires daily sc injections for several years or lifelong, which may be both inconvenient and distressing for patients. NNC126-0083 is a pegylated rhGH developed for once-weekly administration. OBJECTIVES: Our objective was to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple doses of NNC126-0083 in adult patients with GH deficiency (GHD). SUBJECTS AND METHODS: Thirty-three adult patients with GHD, age 20-65 yr, body mass index 18.5-35.0 kg/m(2), and glycated hemoglobin of 8.0% or below. Fourteen days before randomization, subjects discontinued daily rhGH. NNC126-0083 (0.01, 0.02, 0.04, and 0.08 mg/kg) was given sc once weekly for 3 wk (NNC126-0083 for six subjects and placebo for two subjects). Blood samples were collected up to 168 h after the first and up to 240 h after the third dosing. Physical examination, antibodies, and local tolerability were assessed. RESULTS: NNC126-0083 was well tolerated with no difference in local tolerability compared with placebo and with no signs of lipoatrophy. A more than dose-proportional exposure was observed at the highest NNC126-0083 dose (0.16 mg protein/kg). Steady-state pharmacokinetics seemed achieved after the second dosing. A clear dose-dependent pharmacodynamic response in circulating IGF-I levels was observed [from a predose mean (SD) IGF-I SD score of -3.2 (1.7) to peak plasma concentration of -0.5 (1.3), 1.6 (1.3), 2.1 (0.5), and 4.4 (0.9) in the four dose groups, respectively]. CONCLUSION: After multiple dosing of NNC126-0083, a sustained pharmacodynamic response was observed. NNC126-0083 has the potential to serve as an efficacious, safe, and well-tolerated once-weekly treatment of adult patients with GHD.

Effects of reproductive stage, GH, and 11-ketotestosterone on expression of growth differentiation factor-9 in the ovary of the eel, Anguilla australis.

In order to study the regulation of the growth differentiation factor-9 (gdf9) gene in a primitive teleost with semelparous life history, we cloned a cDNA encoding shortfinned eel Gdf9, expressed a partial peptide in Escherichia coli, and raised an antiserum to evaluate changes in Gdf9 expression during its pituitary homogenate-induced reproductive cycle. The effects of in vivo and in vitro exposure to the androgen 11-ketotestosterone (11-KT), known to affect previtellogenic (PV) oocyte growth, were also determined. Furthermore, we investigated whether Gdf9 expression was metabolically gated by treating PV fish with recombinant GH in vivo. Immunoreactive proteins of ca. 52 and 55 kDa were identified by western blot analysis. Gdf9 message and protein were most abundant in PV oocytes, and peaked slightly earlier for mRNA than for protein. Captivity resulted in reduced gdf9 mRNA levels, which were restored following pituitary homogenate treatment. As oocytes progressed through induced oogenesis, Gdf9 expression decreased. Neither 11-KT nor GH treatment affected gdf9 mRNA levels in PV fish, although GH could partially restore handling- or captivity-induced decreases in gdf9 mRNA levels. Semelparous eels thus show an expression pattern of Gdf9 during oogenesis that is similar to that seen in other vertebrates, that appears responsive to handling or captivity stress, and whose control remains to be elucidated.

Improving the pharmacokinetics/pharmacodynamics of prolactin, GH, and their antagonists by fusion to a synthetic albumin-binding peptide.

To prolong the circulation half-life of human prolactin (hPRL), human GH (hGH), and their competitive antagonists, hPRL-G129R and hGH-G120R, we examined the effects of fusing a serum albumin-binding peptide (SA20) to their amino- or carboxyl-terminus. Fusion of the SA20 peptide to the amino-terminus of the ligands was less detrimental upon their ability to induce or inhibit signal transduction and cell proliferation in vitro than fusion to the carboxyl-terminus. Pharmacokinetic (PK) studies in mice revealed that the half-life of SA20-hPRL and SA20-hGH was prolonged and their clearance was reduced in comparison with hPRL and hGH. Pharmacodynamic (PD) studies in 8-week-old female mice revealed that lobuloalveolar development in mammary glands was greater in all three groups (daily, every 2 days, or every third day over a 12-day period) of mice treated with SA20-hPRL (4 mg/kg) compared with hPRL (3.59 mg/kg). Similarly, daily administration (i.p.) of SA20-hGH (8 mg/kg) or hGH (7.15 mg/kg) to 23-day-old female mice over a 40-day period revealed the superiority of SA20-hGH over hGH as measured by weight gain, body length, and lobuloalveolar development in the mammary glands. These findings indicate that SA20 modification of hPRL, hGH, and their respective antagonists improves their PK/PD properties.

Growth hormone isoforms.

Human growth hormone (GH) is a heterogeneous protein hormone consisting of several isoforms. The sources of this heterogeneity reside at the level of the genome, mRNA splicing, post-translational modification and metabolism. The GH gene cluster on chromosome 17q contains 2 GH genes (GH1 or GH-N and GH2 or GH-V) in addition to 2(-3) genes encoding the related chorionic somatomammotropin. Alternative mRNA splicing of the GH1 transcript yields two products: 22K-GH (the principal pituitary GH form) and 20K-GH. Post-translationally modified GH forms include N(alpha)-acylated, deamidated and glycosylated monomeric GH forms, as well as both non-covalent and disulfide-linked oligomers up to at least pentameric GH. GH fragments generated in the course of peripheral metabolism may be measured in immunoassays for GH. The GH-N gene is expressed in the pituitary, the GH-V gene in the placenta. Secretion of pituitary GH forms is pulsatile under control from the hypothalamus, whereas secretion of placental GH-V is tonic and rises progressively in maternal blood during the 2nd and 3rd trimester. Pituitary GH forms are co-secreted during a secretory pulse; no isoform-specific stimuli have been identified. There are minor differences in somatogenic and metabolic bioactivity among the GH isoforms, depending on species and assay system used. Both 20K-GH and GH-V have poor lactogenic activity. Oligomeric GH forms have variably diminished bioactivity compared to monomeric forms. GH isoforms cross-react in most immunoassays, but assays specific for 22K-GH, 20K-GH and GH-V have been developed. The metabolic clearance of 20K-GH and GH oligomers is delayed compared to that of 22K-GH. The heterogeneous mixture of GH isoforms in blood is further complicated by the presence of two GH-binding proteins, which form complexes with GH; isoform proportions also vary depending on the lag time from a secretory pulse because of different half-lives. GH forms excreted in the urine reflect monomeric GH isoforms in blood, but constitute only a minute fraction of the GH production rate. The heterogeneity of GH is one important reason for the notorious disparity among assay results. It also presents an opportunity for distinguishing endogenous from exogenous GH.

The circadian clock components CRY1 and CRY2 are necessary to sustain sex dimorphism in mouse liver metabolism.

In mammals, males and females exhibit anatomical, hormonal, and metabolic differences. A major example of such sex dimorphism in mouse involves hepatic drug metabolism, which is also a noticeable target of circadian timekeeping. However, whether the circadian clock itself contributes to sex-biased metabolism has remained unknown, although several daily output parameters differ between sexes in a number of species, including humans. Here we show that dimorphic liver metabolism is altered when the circadian regulators Cryptochromes, Cry1 and Cry2, are inactivated. Indeed, double mutant Cry1(-/-) Cry2(-/-) male mice that lack a functional circadian clock express a number of sex-specific liver products, including several cytochrome P450 enzymes, at levels close to those measured in females. In addition, body growth of Cry-deficient mice is impaired, also in a sex-biased manner, and this phenotype goes along with an altered pattern of circulating growth hormone (GH) in mutant males, specifically. It is noteworthy that hormonal injections able to mimic male GH pulses reversed the feminized gene expression profile in the liver of Cry1(-/-) Cry2(-/-) males. Altogether, our observations suggest that the 24-h clock paces the dimorphic ultradian pulsatility of GH that is responsible for sex-dependent liver activity. We thus conclude that circadian timing, sex dimorphism, and liver metabolism are finely interconnected.

[18F-fluoro-L-DOPA PET-CT imaging combined with genetic analysis for optimal classification and treatment in a child with severe congenital hyperinsulinism]. / Estudio PET-TC con 18F-fluoro-L-DOPA combinado con el análisis genético para la optimización de la clasificación y tratamiento de un niño con hiperinsulinismo congénito grave.

BACKGROUND: Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycaemia in infancy. The differential diagnosis between focal and diffuse forms of CHI is of great importance when planning surgery. The aim of this article is to show the first case of focal CHI diagnosed in Spain using PET-CT imaging combined with genetic analysis. METHODS: A 13 month child with CHI and normal conventional radiological investigations treated with diazoxide, diet control and feeding by gastrostomy is presented. Genetic analysis of ABCC8 and KCNJ11 genes and PET-TAC using 18F-fluoro-L-DOPA were performed. RESULTS: A pathological mutation (G111R) in the paternal allele of ABCC8 was detected. PET-CT scanning using 18F-fluoro-L-DOPA showed a focus of high uptake in the body of the pancreas compatible with adenoma that was hystopathologically confirmed. After surgical resection the patient is asymptomatic without needing either pharmacological treatment or dietetic control. CONCLUSIONS: The combination of genetic analysis and 18F-fluoro-L-DOPA PET-TAC shows a great potential for the identification, location and guideline for surgery in CHI.

Activation of growth hormone receptors by growth hormone and growth hormone antagonist dimers: insights into receptor triggering.

GH binds dimerized GH receptors (GHRs) to form a trimolecular complex and induces downstream signaling events. The mechanism by which GH binding converts the inactive predimerized GHR to its active signaling conformation is uncertain. GH has no axis of symmetry. Its interaction with GHR is mediated by two asymmetric binding sites on GH, each with distinct affinity. Site 1 is of high affinity and is thought to mediate the first binding step. Mutation of binding site 2 (as in the human GH mutant, G120R) disrupts the second binding but leaves site 1 binding intact. G120R is a GH antagonist; it binds only one GHR and thus fails to signal, and it prevents productive GHR binding by normal GH. We previously demonstrated that prolactin receptor signaling was achieved by a dimeric version of a prolactin antagonist. We now employ assays of cellular signaling and receptor conformational changes to examine whether GH molecules harboring two site 1 regions can trigger GHR activation. We used recombinantly produced GH-GH and G120R-G120R dimers in which monomers in tandem are connected by a short linker peptide. Rabbit GHR-expressing human fibrosarcoma cells (C14) were treated with GH, G120R, GH-GH, or G120R-G120R. As expected, GH and GH-GH, but not G120R, induced GHR disulfide linkage, as assessed by anti-GHR blotting of cell extracts resolved by SDS-PAGE under nonreducing conditions. Disulfide linkage of GHRs reflects attainment of the active signaling conformation. Likewise, GH and GH-GH, but not G120R, caused Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5) activation. Notably, G120R-G120R, despite its lack of an intact site 2 in either dimer partner, also promoted GHR disulfide linkage and JAK2 and STAT5 activation, albeit less potently than either GH or GH-GH. Time-course responses of the three agonists were similar in terms of JAK2 and STAT5 activation. Pretreatment of cells with our conformation-sensitive inhibitory monoclonal antibody, anti-GHR ext-mAb, prevented ligand-induced receptor activation for all three agonists. GHR was also rendered less immunoprecipitable by anti-GHR ext-mAb after treatment with these agonists. These results are important in that they indicate that a ligand with two intact binding sites 1 causes GHR to adopt similar conformational changes as does GH and thus triggers activation of JAK2 and downstream signaling. Furthermore, we infer that there is substantial flexibility in the GHR extracellular domain, such that it productively accommodates GH dimers that are much larger than GH.

Growth hormone receptor mRNA expression in non-functioning and somatotroph pituitary adenomas: implications for growth hormone substitution therapy?

The use of growth hormone (GH) in patients with GH deficiency induced by pituitary adenoma is widely accepted, but the safety of this mitogenic hormone, particularly in patients with residual tumor after neurosurgery, continues to be a concern. Since the mitogenic potency of GH is dependent upon the presence of the GH receptor (GH-R) and the subsequent IGF-1/IGF receptor (IGF-1-R) system we investigated the expression of the members of the growth hormone cascade in endocrine inactive and GH-producing pituitary adenomas. Tissue specimens of 18 clinically non-functioning pituitary adenomas and 6 GH-producing adenomas were collected following transsphenoidal surgery while normal cadaver pituitary glands served as controls. After RNA extraction, semi-quantitative RT-PCR amplification with specific primers for GH, GH-R, IGF-1 and IGF-1-R was performed. Applying this sensitive RT-PCR based approach, GH-R expression was demonstrated in all normal pituitaries, most inactive adenomas (94%), and the majority of GH-producing adenomas (66%). Both IGF-1 and IGF-1-R mRNA was detectable in the majority of inactive (72% and 77%, respectively) and somatotrophic adenomas (83% and 83%). While IGF-1-R mRNA was expressed in all normal pituitary specimen studied, IGF-1 was detectable in only 55% of them. In summary, expression of members of the GH-IGF-1 cascade could be demonstrated in a substantial subset of patients with non-functioning and GH-producing pituitary adenomas. These factors might serve as a substrate for the transduction of mitogenic effects of GH on remnant pituitary tumors during GH replacement therapy. Therefore, GH therapy should be carefully considered and patients on GH therapy kept under close observation.

Growth hormone secretagogue (GHS) analogue, hexarelin stimulates GH from peripheral lymphocytes.

The role of growth hormone releasing hormone (GHRH) and growth hormone releasing peptide-6 (GHRP-6) analogue hexarelin was investigated in the regulation of GH production from lymphocytes. Porcine and bovine blood mononuclear cells were separated using density gradient centrifugation method by layering the whole blood or buffy coat cells on lymphodex. Cells were incubated for 3 or 5 days with or without phytohemagglutinin (PHA-M), GHRH, GHRP-6 analogue hexarelin, somatostatin or GHRH + hexarelin. Growth hormone was fractionated from supernatants by gel chromatography and further concentrated by lyophilization at - 20 degrees C. A nearly two fold increase in basal secretion of GH (porcine: 3.5 +/- 0.1 ng/ml, bovine: 3.2 +/- 0.2 ng/ml) was achieved by GHRH and hexarelin at concentrations of 0.1, 1.0, 10 and 100 nM in both porcine and bovine cells. Lymphocytic GH release was also stimulated in response to PHA-M (10 micro g/well). Neither a dose dependent nor a synergistic nor an additive effect was apparent on GH secretion from lymphocytes. GHRH stimulated lymphocytic GH secretion, whereas, somatostatin had no effect. This study reports for the first time that hexarelin stimulates the secretion of GH from peripheral lymphocytes.

[Preoperative administration of a slow releasing somatostatin analog (SR-lanreotide, BIM 23014) in patients with acromegaly in the course of GH-releasing adenoma]. / Przedoperacyjne zastosowanie analogu somatostatyny o przedluzonym dzialaniu (SR-Lanreotide, BIM 23014) u pacjentów z akromegalia w przebiegu makrogruczolaka przysadki.

To evaluate the therapeutic efficacy of slow releasing analogue of somatostatin (SR-Lanreotide) in the pretreatment for GH-releasing adenomas, especially macroadenomas. During the last four years (between January 1996 and December 1999) the authors carried out 382 transsphenoidal operations for to various lesions. There were 169 acromegalic patients in this group. 82 of them received, as pretreatment, the slow releasing analogue of somatostatin (SR-Lanreotide, BIM 23014) in a dose of 30 mg every 14 days for 3 months (6 injections). There were 55 women and 27 men (range 25-68, mean age 44.8 years, SD +/- 10 years) operated on by one experienced neurosurgeon. The concentrations of serum GH--70.5 micrograms/l (range 5.3-500 micrograms/l, SD +/- 83.9 micrograms/l) and IGF-I--1302 micrograms/l (range 610-2030 micrograms/l, SD +/- 360.7 micrograms/l) were high. Out of these 82 patients 79 had macroadenomas with suprasellar and parasellar extension. The volume of the tumours was calculated according to the formula of Di Chiro-Nelson. The mean volume of the tumour was 4146.9 mm3 (range 213.5-38595.3 mm3, SD +/- 5675.9 mm3). The response to the pretreatment suppression of the serum GH, IGF-I level and shrinkage of the tumours--were evaluated before surgery. Second MR examination was performed in 38 pretreated patients. During the Lanreotide treatment mean serum GH level decreased from 70.5 to 15.6 micrograms/l (p < 0.0001), mean serum IGF-I concentration decreased from 1302 to 787 micrograms/l and mean volume of the tumour decreased from 5662 to 2326 mm3 (p < 0.0001). During surgery, tumours were observed to be softer, had liquid consistency and were easier removed. 57 patient (69.5%) who underwent surgery had GH below 5 micrograms/l and were cured. Transsphenoidal microsurgical resection of pituitary adenomas is the primary treatment for acromegaly. Lanreotide pretreatment significantly decreased mean serum GH and IGF-I level, shrinks the tumour and make it much softer and easier to be removed.

1H NMR structural analysis of human ghrelin and its six truncated analogs.

Human ghrelin, the first recognized natural ligand of growth hormone secretagogue growth hormone secretagogue receptors (GHS-Rs) (M. Kojima, H. Hosada, Y. Date, M. Nakazato, H. Matsuo, and K. Kangawa, Nature, 1999, Vol. 402, pp. 656-660), consists of 28 amino acids of which Ser3 is modified by n-octanoylation. This new peptide hormone has been implicated not only in regulation of the GH secretion but also in regulation of food intake. The discovery of ghrelin opens up more opportunities to study the relationship of ghrelin with metabolic diseases. Until now, only mass spectometry analysis has been reported on the structure of ghrelin. NMR analysis is a suitable way to study if any tertiary structure of unbound ghrelin is present in solution. NMR studies were carried out on human ghrelin and its five truncated analogs. The full-length ghrelin and its fragments exhibited random coil behavior in aqueous solution. Additional studies were carried out on the shortest active segment of human ghrelin, which consists of the first five amino acids of the ghrelin sequence (M. A. Bednarek, S. D. Feighner, S.-S. Pong, K. K. McKee, D. L. Hreniuk, M. V. Silva, V. A. Warrem, A. D. Howard, L. H. Y. Van der Ploeg, and J. V. Heck, Journal of Medical Chemistry, 2000, Vol. 43, pp. 4370-4376), to compare the spectral features with their counterparts in the full-length ghrelin. The NMR data showed behavior similar to ghrelin except for two additional nuclear Overhauser effects (NOEs) between the Phe4 NH and the protons of the beta-methylene of Ser3. CD on human ghrelin and its short active analog in water were indicative of random coil peptides. Molecular modeling based on NMR data was carried out to probe which structural features were similar to growth hormone-releasing peptide-6 (GHRP-6), a hexapeptide that binds to GHS-R releasing GH and stimulating food intake. Modeling suggested some similarities, but they were not of a nature to account for binding properties of these compounds.