Development of endogenous glucocorticoids,mineralocorticoids and progestins in the human fetal and perinatal period

Summary Corticosteroids (CS) are known to be essential for fetal organ maturation and seem to play an important role in both the initiation of parturition and the postnatal adaptation of the human neonate. Pharmacologically, CS are widely used for enhancing fetal lung maturation prior to premature delivery. However, knowledge of endogenous CS and precursor levels throughout fetal and perinatal life and their response to exogenous CS is limited. Therefore, using automated liquid column chromatography plus specific radioimmunoassays, unconjugated aldosterone (Aldo), corticosterone (B), 11-deoxycorticosterone (DOC), progesterone (P), 17-hydroxyprogesterone (17-OHP), 11-deoxycortisol (S), cortisol (F) and cortisone (E) were simultaneously followed in 70 amniotic fluid (AF) control samples throughout pregnancy, and in cord and neonatal plasma longitudinally during the first week of life. From 14 to 38 weeks, AF levels of all measured steroids except E rose by 2 to 12-fold on the average (allP<0.001) but declined at term. E increased until 31–35 weeks (P<0.01), then remained almost constant until term. Cord levels of all steroids were substantially higher than those found in AF at term. While levels of the placentally derived steroids P, 17-OHP, DOC and E dropped sharply after birth by several orders of magnitude (P0.01) showing typical disappearance curves, the biologically most potent CS Aldo and F rose even further immediately after birth. Whereas Aldo levels declined from maxima about 100 times above normal adult levels at 6 h by almost 3-fold until day 7 (P<0.01), F (and also B) fluctuated considerably resembling a damped oscillation and, by day 7, reached mean levels less than half of those seen in later childhood. After betamethasone treatment of the mother, neonatal levels of Aldo and F were suppressed to 24–69% of normal until day 9, whereas those of the other steroids (except E) returned to normal during the first hours of life. Phenobarbital (PB) therapy of the mother led to decreased steroid levels in maternal and umbilical venous plasma at term, while umbilical arterial CS levels, notably those of Aldo and F (P<0.02), were increased when compared with untreated controls, indicating a stimulation of the most potent CS in the fetus after PB. The significance of the findings in view of fetoplacental function and fetal organ maturation is briefly discussed.Supported by a grant from the German Federal Ministry for Research and Technology (BMFT)Presented at the International Workshop on Perinatal and Pediatric Aspects of Clinical Pharmacology, Heidelberg, Federal Republic of Germany, 27–29 February 1980     

Ghrelin Suppresses Glucose-Stimulated Insulin Secretion and Deteriorates Glucose Tolerance in Healthy Humans

OBJECTIVE

The orexigenic gut hormone ghrelin and its receptor are present in pancreatic islets. Although ghrelin reduces insulin secretion in rodents, its effect on insulin secretion in humans has not been established. The goal of this study was to test the hypothesis that circulating ghrelin suppresses glucose-stimulated insulin secretion in healthy subjects.

RESEARCH DESIGN AND METHODS

Ghrelin (0.3, 0.9 and 1.5 nmol/kg/h) or saline was infused for more than 65 min in 12 healthy patients (8 male/4 female) on 4 separate occasions in a counterbalanced fashion. An intravenous glucose tolerance test was performed during steady state plasma ghrelin levels. The acute insulin response to intravenous glucose (AIRg) was calculated from plasma insulin concentrations between 2 and 10 min after the glucose bolus. Intravenous glucose tolerance was measured as the glucose disappearance constant (Kg) from 10 to 30 min.

RESULTS

The three ghrelin infusions raised plasma total ghrelin concentrations to 4-, 15-, and 23-fold above the fasting level, respectively. Ghrelin infusion did not alter fasting plasma insulin or glucose, but compared with saline, the 0.3, 0.9, and 1.5 nmol/kg/h doses decreased AIRg (2,152 ± 448 vs. 1,478 ± 2,889, 1,419 ± 275, and 1,120 ± 174 pmol/l) and Kg (0.3 and 1.5 nmol/kg/h doses only) significantly (P < 0.05 for all). Ghrelin infusion raised plasma growth hormone and serum cortisol concentrations significantly (P < 0.001 for both), but had no effect on glucagon, epinephrine, or norepinephrine levels (P = 0.44, 0.74, and 0.48, respectively).

CONCLUSIONS

This is a robust proof-of-concept study showing that exogenous ghrelin reduces glucose-stimulated insulin secretion and glucose disappearance in healthy humans. Our findings raise the possibility that endogenous ghrelin has a role in physiologic insulin secretion, and that ghrelin antagonists could improve β-cell function.Ghrelin has gained considerable attention over the last decade for its unique role in regulating mealtime hunger and lipid metabolism, as well as short- and long-term energy homeostasis (1–3). It is the only known circulating factor that promotes food intake and increases fat mass. Ghrelin is secreted mainly from the stomach and proximal small bowel, and stimulates growth hormone (GH) secretion (4–6), in addition to its effect on energy balance. In healthy subjects, plasma ghrelin levels rise progressively before meals and fall to a nadir within 1 hour after eating, with changes in plasma levels during meals varying two- to threefold (7–8). Under pathologic conditions associated with severe malnutrition and weight loss, such as anorexia nervosa (9), cancer, or cardiac cachexia (10–11), plasma total ghrelin levels are increased up to threefold compared with healthy individuals. Besides its well known effects on feeding behavior, fat mass, and GH secretion, ghrelin has recently been implicated in the regulation of glucose homeostasis (12–13).The GH secretagogue receptor (GHSR)-1a, also known as the ghrelin receptor, is widely distributed and has been localized to the hypothalamus, pituitary, liver, adipocyte, and pancreas (14–15). Both ghrelin and GHSR are expressed in human and rat pancreatic islets on both α- (16–17) and β-cells (18–19), and ghrelin is produced in a novel endocrine islet cell type that shares lineage with glucagon-secreting cells (20–21). Pancreatic ghrelin cells exist as the predominant cell type in fetal human islets, and expression in the pancreas during development significantly precedes its occurrence in the stomach (20). In animal mutant models, an early block in the differentiation of insulin-producing β cells leads to an enormous increase in ghrelin-producing ε cells, suggesting a developmental link between ghrelin and insulin (22). In vitro, ghrelin inhibits glucose-stimulated insulin secretion in a dose-dependent manner from cultured pancreata (23), isolated pancreatic islets (19,24), and immortalized β-cell lines (19,21), suggesting that it acts directly on β cells to achieve this effect. In experimental animals, both ghrelin released from pancreatic islets and exogenous ghrelin inhibit glucose-stimulated insulin secretion (16,24–26). Targeted gene deletion of ghrelin improves glucose tolerance and augments insulin secretion in ob/ob mice, suggesting a possible physiologic role which could be mediated by effects on islet function (27). Consistent with these findings, ghrelin gene deletion was shown to prevent glucose intolerance induced by a high-fat diet, an environmentally-induced model of hyperglycemia (26). Together, these findings indicate the potential of ghrelin blockade to prevent both genetically (ob gene)- and environmentally (high-fat diet)-induced glucose intolerance.The effect of ghrelin on insulin secretion in humans is controversial. Intravenous injection of ghrelin decreases plasma insulin and increases blood glucose in some studies, suggesting inhibition of insulin secretion (12,28). However, this finding has not been universally observed (29), and it is unclear whether such effects occur at physiologic or only pharmacologic doses of ghrelin. Prior studies performed in humans primarily assessed the impact of ghrelin on β-cell function in the fasting state, and there is little information on the effect of the peptide on stimulated insulin release. Therefore, the role of ghrelin in the regulation of glucose homeostasis in humans remains poorly understood.In this study, we determined the effect of ghrelin on glucose-stimulated insulin secretion and glucose tolerance. We infused acyl-ghrelin, the bioactive endogenous ligand of the GHSR-1a, at variable doses with the aim of raising plasma total ghrelin level to physiologic (less than twofold), supraphysiologic (two- to threefold) and pharmacologic (more than threefold) levels. An intravenous glucose tolerance test (IVGTT) was performed at steady state plasma ghrelin levels to determine the effect on glucose-stimulated insulin secretion and glucose tolerance in healthy, nonobese subjects.     

Pharmacokinetics and pharmacodynamics of GH: dependence on route and dosage of administration

OBJECTIVE: Pharmacokinetic and pharmacodynamic data after recombinant human GH (rhGH) administration in adults are scarce, but necessary to optimize replacement therapy and to detect doping. We examined pharmacokinetics, pharmacodynamics, and 20 kDa GH after injection of rhGH at different doses and routes of administration. DESIGN: Open-label crossover study with single boluses of rhGH. METHODS: Healthy trained subjects (10 males, 10 females) received bolus injections of rhGH on three occasions: 0.033 mg/kg s.c., 0.083 mg/kg s.c., and 0.033 mg/kg i.m. Concentrations of 22 and 20 kDa GH, IGF-I, and IGF-binding proteins (IGFBP)-3 were measured repeatedly before and up to 36 h after injection. RESULTS: Serum GH maximal concentration (Cmax) and area under the time-concentration curve (AUC) were higher after i.m. than s.c. administration of 0.033 mg/kg (Cmax 35.5 and 12.0 microg/l; AUC 196.2 and 123.8). Cmax and AUC were higher in males than in females (P < 0.01) and pharmacodynamic changes were more pronounced. IGFBP-3 concentrations showed no dose dependency. In response to rhGH administration, 20 kDa GH decreased in females and remained suppressed for 14-18 h (low dose) and 30 h (high dose). In males, 20 kDa GH was undetectable at baseline and throughout the study. CONCLUSIONS: After rhGH administration, pharmacokinetic parameters are mainly influenced by route of administration, whereas pharmacodynamic variables and 20 kDa GH concentrations are determined mainly by gender. These differences need to be considered for therapeutic use and for detection of rhGH doping.     

Hochdosierte Methotrexattherapie beim osteogenen Sarkom: Plasmapharmakokinetik zur Vorhersage der Toxizität

Zusammenfassung Bei 22 Patienten mit osteogenem Sarkom, die 103 hochdosierte Methotrexatinfusionen (6–8,5 g/m² in 4–6 h) erhielten, wurde mit einem eigenen spezifischen und rasch durchführbaren Radioimmunoassay die Plasmapharmakokinetik des Methotrexats untersucht. Bei nichttoxischen Verläufen lag die Plasmakonzentration nach 24 h unter 8,0 × 10^–6 mol/l, nach 48 h unter 8,0 × 10^–7 mol/l und nach 72 h unter 4,25 × 10^–7 mol/l. Alle Patienten mit 48 h-Werten über 1 × 10^–6 mol/l entwickelten schwere toxische Erscheinungen in Form von Knochenmarksdepression und Stomatitis, die durch eine verzögerte Ausscheidung des Methotrexats bedingt war. Der Anstieg des Serumkreatinins war kein zuverlässiges Kriterium für toxische Verläufe. Die Bestimmung der 48- und 72h-Methotrexat-Plasmakonzentrationen erwies sich als zuverlässiger Parameter zur Erfassung von Patienten mit drohender Toxizität. Sie ermöglicht somit, rechtzeitige therapeutische Maßnahmen, z.B. in Form einer zusätzlichen Leukovorintherapie zu ergreifen.Mit Unterstützung der Deutschen Krebshilfe, Bonn     

Atrial natriuretic peptide protects hepatocytes against damage induced by hypoxia and reactive oxygen. Possible role of intracellular free ionized calcium

Elevated concentrations of atrial natriuretic peptide reportedly mitigate acute renal failure in vivo and in the isolated perfused kidney (M. Nakamoto, J.I. Shapiro, P.F. Shanley, L. Chan & R.W. Shrier (1987) J. Clin. Invest. 80, 698-705; S.G. Shaw, J. Weidmann, J. Hodler, A. Zimmermann & A. Paternostro (1987) J. Clin. Invest. 80, 1232-1237). Since atrial natriuretic peptide has been shown to be a potent vasodilator, this beneficial effect may be due entirely to improved haemodynamics. To determine whether atrial natriuretic peptide also has a protective effect at the cellular level, rat hepatocyte cell cultures were treated with atrial natriuretic peptide prior to or after induction of cell damage by hypoxia (0.5% O2 for 4 h) or reactive oxygen (hypochlorous acid). Bleb formation, degradation of radiolabeled trichloroacetic acid-precipitable peptides, release of lactate dehydrogenase and trypan blue exclusion were used as indicators of cell damage. Atrial natriuretic peptide treatment distinctly protected the cell cultures against damage in both cases. This beneficial effect of atrial natriuretic peptide was partly mimicked by sodium nitroprusside, which, like atrial natriuretic peptide, largely increased the cellular cGMP content. 6-Anilino-5,8-quinolinedione (Ly 83583), an inhibitor of particulate guanylate cyclase, blocked the protective effect of atrial natriuretic peptide. Therefore a cGMP-mediated mechanism seems to be involved in the cytoprotective action of atrial natriuretic peptide. Fluorometric measurements using the Ca2+-sensitive dye Quin-2 showed that the elevation of intracellular Ca2+ after cellular insult by hypochlorous acid is prevented by atrial natriuretic peptide. These results suggest that atrial natriuretic peptide may attenuate hypoxic and toxic cell damage by increasing cGMP and reducing intracellular Ca2+.     

Etomidate: A selective adrenocortical 11β-hydroxylase inhibitor

Summary To investigate the adrenocortical suppression caused by the anesthetic etomidate, plasma levels of progesterone (P), 17-hydroxyprogesterone (17-OHP), 11-deoxycorticosterone (DOC), corticosterone (B), aldosterone (Aldo), 11-deoxycortisol (S), cortisol (F), and cortisone (E) were measured simultaneously before and after a short-term ACTH stimulation test in a 6.5-year-old boy whose convulsions could be kept under control only with constant etomidate infusions. During etomidate therapy, plasma levels of DOC and S were extremely elevated, the progestins P and 17-OHP were slightly elevated, whereas B and Aldo were in the lower normal range, and F and E were markedly decreased. A short-term ACTH stimulation test during etomidate infusion gave a blunted response of B, Aldo, F and E, whereas the level of DOC remained high and S even further increased. P and 17-OHP showed a positive response to ACTH. The ratios of B/DOC and F/S, which reflect adrenocortical 11-hydroxylase activity, were extremely decreased during etomidate and did not change after ACTH stimulation. In contrast, the ratios of DOC/P and S/17-OHP, which relect 21-hydroxylase activity, were elevated and remained elevated after ACTH stimulation. After discontinuation of etomidate therapy, all the baseline steroid levels were somewhat elevated, but responded normally to ACTH. These results demonstrate that etomidate causes a specific and reversible blockade of the 11-hydroxylation of adrenal steroid synthesis.Abbreviations P progesterone - DOC 11-deoxycorticosterone - B corticosterone - Aldo aldosterone - 170HP 17-hydroxyprogesterone - S 11-deoxycortisol - F cortisol - E cortisone - ACTH adrenocorticotrophic hormone Supported by a grant from the Deutsche Forschungsgemeinschaft     

Qualitative and quantitative changes in platelets after coronary-artery bypass surgery may help identify thrombotic complications and infections

Summary We studied the effect of coronary-artery bypass surgery on blood cells and platelets. Hematological parameters of eighty-three patients were measured by an automated cell counting and sizing analyzer. Sampling time was from 24 h prior to 10 days after surgery. During this time leukocytes and platelets showed characteristic changes in numbers and size, whereas red blood cells revealed no typical modifications. Even though it seems clear that changes of hematological parameters occur after bypass surgery, it is important to be aware of the actual extent of such changes. Therefore the data of 50 patients who had had no post-operative clinical complications were combined to generate diagrams of those parameters that had changed in a characteristic fashion. The diagrams showing average changes, and 99% confidence intervals in mean platelet volume and platelet count were able to identify seven (out of 7) cases with complications up to 48 h before clinical signs were apparent. Complications ranged from mild (3 cases with infections) to severe (4 cases with thrombosis, embolic thrombosis and/or reinfarction). Diagrams showing changes in leukocyte parameters were able to identify only two cases with infections. Even though the number of cases is yet small, the results suggest that surveillance of platelet parameters may be useful in postoperative care. Furthermore, this study was able to confirm the recent findings of Trowbridge and Martin [18] that an abnormal increase in platelet volume distribution width and low platelet counts found in patients with coronary heart disease may serve as good indicators for the prethrombotic state and the risk of myocardial infarction.Abbreviations MPV mean platelet volume - PDW platelet volume distribution width - RDW red blood cell distribution width - WBC white blood cells - RBC red blood cells