Linda Hilsted

Proton-Pump Inhibitor Therapy Induces Acid-Related Symptoms in Healthy Volunteers After Withdrawal of Therapy

BACKGROUND & AIMS Rebound acid hypersecretion (RAHS) has been demonstrated after 8 weeks of treatment with a proton-pump inhibitor (PPI). If RAHS induces acid-related symptoms, this might lead to PPI dependency and thus have important implications. METHODS A randomized, double-blind, placebo-controlled trial with 120 healthy volunteers was conducted. Participants were randomized to 12 weeks of placebo or 8 weeks of esomeprazole 40 mg/d followed by 4 weeks with placebo. The Gastrointestinal Symptom Rating Scale (GSRS) was filled out weekly. A score of >2 on 1 of the questions regarding heartburn, acid regurgitation, or dyspepsia was defined as a clinically relevant acid-related symptom. RESULTS There were no significant differences between groups in GSRS scores at baseline. GSRS scores for acid-related symptoms were significantly higher in the PPI group at week 10 (1.4 +/- 1.4 vs 1.2 +/- 0.9; P = .023), week 11 (1.4 +/- 1.4 vs 1.2 +/- 0.9; P = .009), and week 12 (1.3 +/- 1.2 vs 1.0 +/- 0.3; P = .001). Forty-four percent (26/59) of those randomized to PPI reported > or = 1 relevant, acid-related symptom in weeks 9-12 compared with 15% (9/59; P < .001) in the placebo group. The proportion reporting dyspepsia, heartburn, or acid regurgitation in the PPI group was 13 of 59 (22%) at week 10, 13 of 59 (22%) at week 11, and 12 of 58 (21%) at week 12. Corresponding figures in the placebo group were 7% at week 10 (P = .034), 5% at week 11 (P = .013), and 2% at week 12 (P = .001). CONCLUSIONS PPI therapy for 8 weeks induces acid-related symptoms in healthy volunteers after withdrawal. This study indicates unrecognized aspects of PPI withdrawal and supports the hypothesis that RAHS has clinical implications.

Childhood Exposure to Phthalates: Associations with Thyroid Function, Insulin-like Growth Factor I, and Growth

Background Phthalates are widely used chemicals, and human exposure is extensive. Recent studies have indicated that phthalates may have thyroid-disrupting properties. Objective We aimed to assess concentrations of phthalate metabolites in urine samples from Danish children and to investigate the associations with thyroid function, insulin-like growth factor I (IGF-I), and growth. Methods In 845 children 4–9 years of age, we determined urinary concentrations of 12 phthalate metabolites and serum levels of thyroid-stimulating hormone, thyroid hormones, and IGF-I. Results Phthalate metabolites were detected in all urine samples, of which monobutyl phthalate was present in highest concentration. Phthalate metabolites were negatively associated with serum levels of free and total triiodothyronine, although statistically significant primarily in girls. Metabolites of di(2-ethylhexyl) phthalate and diisononyl phthalate were negatively associated with IGF-I in boys. Most phthalate metabolites were negatively associated with height, weight, body surface, and height gain in both sexes. Conclusions Our study showed negative associations between urinary phthalate concentrations and thyroid hormones, IGF-I, and growth in children. Although our study was not designed to reveal the mechanism of action, the overall coherent negative associations between urine phthalate and thyroid and growth parameters may suggest causative negative roles of phthalate exposures for child health.

Measurement of precursors for α-amidated hormones by radioimmunoassay of glycine-extended peptides after trypsin-carboxypeptidase B cleavage

Using fragment 5-17 of human gastrin-17 extended with glycine at the C-terminus as hapten, three of six rabbits produced high-titer, high-avidity antisera specific for glycine-extended gastrins. In combination with trypsin and carboxypeptidase B cleavage, radioimmunoassays based on these antisera measured progastrins in some extra-antral tissues and certain malignant tumors. The results show that sequential cleavage with trypsin and carboxypeptidase B followed by radioimmunoassay of glycine-extended peptides is a rapid and accurate procedure for measurement of biosynthetic precursors of alpha-amidated peptide hormones. Moreover, the procedure seems promising in the search for tumor markers.

Oxyntomodulin (glicentin-(33-69)): pharmacokinetics, binding to liver cell membranes, effects on isolated perfused pig pancreas, and secretion from isolated perfused lower small intestine of pigs

The pharmacokinetics of purified synthetic oxyntomodulin were studied after infusing it into euglycaemic pigs at two rates. The elimination of the peptide from plasma was characterized by two components, a fast one (t1/2 7.2 +/- 0.6 min) and a slow one (t1/2 20.4 +/- 3.8 min) (mean +/- S.E.M., n = 7). The metabolic clearance rate was independent of infusion rate (6.96 +/- 0.99 vs 7.44 +/- 0.98 ml/kg . min (mean +/- S.E.M., n = 7). The synthetic peptide bound to pig hepatic glucagon receptors, but with approximately 2% of the affinity of glucagon, and showed insulinotropic and somatostatinotropic effects when infused into isolated perfused pig pancreases at concentrations higher than 10(-10) M. A dose-dependent increase was also shown for pancreatic glucagon output. A naturally occurring peptide, identified as oxyntomodulin by gel filtration and HPLC, was released into the circulation from the pig lower small intestinal mucosa upon intraluminal administration of glucose, and represented 25 +/- 3.8% of the secreted glucagon-like immunoreactivity. 11 +/- 2.3% of the secreted glucagon-like immunoreactivity was indistinguishable from glucagon itself upon gel filtration; thus at least 36% of the glucagon-like immunoreactivity secreted from the intestinal mucosa is already in an active form.

On the accuracy of radioimmunological determination of somatostatin in plasma

We performed the following experiments to evaluate the accuracy of our newly developed radioimmunoassay for somatostatin: (1) Recovery of synthetic somatostatin added to human, porcine, and canine plasma with or without extraction with 67% acetone or 76% ethanol, using 3 different region-specific antibodies and, where applicable, 125I-labelled Tyr-1- or Tyr-11-substituted somatostatin or 125I-N-Tyr-somatostatin as tracers. The recovery of somatostatin corrected for losses inherent in the extraction procedure was close to 100%, and independent of species, antibody and tracer. Somatostatin 1-28 was extracted slightly less efficiently. Unextracted plasma interfered massively in the assay. (2) Pharmacokinetic experiments with infusion of somatostatin into 14 pigs and determination of metabolic clearance rate (MCR) and T-1/2. MCR was 27-38 ml/kg per min, independent of infusion rate (6.1 or 13 pmol/kg per min), extraction procedure or tracer. T-1/2 was 1.9 min. The infused somatostatin was not measurable in unextracted plasma. (3) Characterization of endogenous and exogenous, labelled and unlabelled somatostatin 1-14 in human plasma, using Sephadex G-50 columns at pH 7.5 and 9.0. Human plasma showed excess immunoreactivity eluting at the void volume whereas synthetic somatostatin was recovered quantitatively at the position of marker somatostatin when added to the plasma. The immunoreactivity of the tracers was decreased (125I-Tyr-11-somatostatin) or abolished (125I-N-Tyr- or 125I-Tyr-1-somatostatin) after incubation with plasma or void volume fractions of plasma subjected to gel filtration. Extracted plasma did not contain void volume immunoreactivity, but like whole plasma, small amounts of components which coeluted with intact somatostatin.

The Zollinger-Ellison syndrome and mismeasurement of gastrin.

BACKGROUND & AIMS Zollinger-Ellison syndrome (ZES) is characterized by hypersecretion of gastric acid, severe peptic ulcerations in the upper small intestine, and diarrhea. It is usually diagnosed by measuring increased levels of gastrin in plasma. METHODS We examined the accuracy of commercial kits to measure gastrin (7 radioimmunoassays and 5 enzyme-linked immunosorbent assays), using plasma from 40 patients suspected or known to have ZES. Each sample was analyzed using the 12 kits and a reference assay that measures bioactive gastrin in plasma, irrespective of size and amino acid derivatization. Known concentrations of peptides with identical sequences to circulating gastrins were also assessed by all assays. Molecular patterns in plasma from patients with ZES were examined by chromatography and monitored by kits that measure false-low or false-high concentrations of gastrin. RESULTS Failure to diagnose gastrinomas has serious consequences. Four kits found false-low concentrations of gastrin in 20% to 80% of the patients. Specificity assessment showed that the antibodies used in these kits bound only gastrin-17. Three kits found false-high concentrations of gastrin, because the reagents had increased reactions to sulfated gastrins or to unspecific factors in plasma. Thus, only 5 of 12 kits tested accurately measure plasma concentrations of gastrin. CONCLUSIONS Seven of 12 tested commercial kits inaccurately measure plasma concentrations of gastrin; these assays used antibodies with inappropriate specificity that were insufficiently validated. Misdiagnosis of gastrinoma based on lack of specificity of assays for gastrin results in ineffective or inappropriate therapy for patients with ZES.

Effect of peripherally administered ghrelin on gastric emptying and acid secretion in the rat.

Ghrelin is a gut peptide that is secreted from the stomach and stimulates food intake. There are ghrelin receptors throughout the gut and intracerebroventricular ghrelin has been shown to increase gastric acid secretion. The aim of the present study was to examine the effects of peripherally administered ghrelin on gastric emptying of a non-nutrient and nutrient liquid, as well as, basal and pentagastrin-stimulated gastric acid secretion in awake rats. In addition, gastric contractility was studied in vitro. Rats equipped with a gastric fistula were subjected to an intravenous infusion of ghrelin (10-500 pmol kg(-1) min(-1)) during saline or pentagastrin (90 pmol kg(-1) min(-1)) infusion. After administration of polyethylene glycol (PEG) 4000 with 51Cr as radioactive marker, or a liquid nutrient with (51)Cr, gastric retention was measured after a 20-min infusion of ghrelin (500 pmol kg(-1) min(-1)). In vitro isometric contractions of segments of rat gastric fundus were studied (10(-9) to 10(-6) M). Ghrelin had no effect on basal acid secretion, but at 500 pmol kg(-1) min(-1) ghrelin significantly decreased pentagastrin-stimulated acid secretion. Ghrelin had no effect on gastric emptying of the nutrient liquid, but significantly increased gastric emptying of the non-nutrient liquid. Ghrelin contracted fundus muscle strips dose-dependently (pD2 of 6.93+/-0.7). Ghrelin IV decreased plasma orexin A concentrations and increased plasma somatostatin concentrations. Plasma gastrin concentrations were unchanged during ghrelin infusion. Thus, ghrelin seems to not only effect food intake but also gastric motor and secretory function indicating a multifunctional role for ghrelin in energy homeostasis.

Neuropeptide Y in guinea pig, rabbit, rat and man. Identical amino acid sequence and oxidation of methionine-17.

Neuropeptide Y (NPY) was isolated and characterised from acid-ethanol extracts of rabbit and guinea pig brain. In both instances the chromatographic purification was a two-step procedure of gel filtration followed by reverse-phase high-performance liquid chromatography. The amino acid sequence of rabbit and guinea pig NPY was found to be identical to human and rat NPY as deduced from the cDNA structures. With the exception of the porcine peptide, all mammalian NPYs characterised to date have a methionine residue in position 17. This methionine residue is readily oxidized as indicated by the high degree of spontaneous oxidation of peptides found in the rabbit and guinea pig brain extracts and in NPY extracted from a rat phaeochromocytoma cell line. It is concluded that NPY is among the most highly conserved peptides and that NPYs containing methionine in position 17 are prone to oxidation.

Sex Hormone-Binding Globulin Levels Predict Insulin Sensitivity, Disposition Index and Cardiovascular Risk During Puberty

OBJECTIVE Early puberty is associated with increased risk of subsequent cardiovascular disease. Low sex hormone–binding globulin (SHBG) levels are a feature of early puberty and of conditions associated with increased cardiovascular risk. The aim of the present study was to evaluate SHBG as a predictor of glucose metabolism and metabolic risk during puberty. RESEARCH DESIGN AND METHODS This was a cross-sectional study on 132 healthy Caucasian children and adolescents evaluated by an oral glucose tolerance test, a dual-energy X-ray absorptiometry scan, direct oxygen uptake measurement during cycle ergometry, and fasting blood samples. RESULTS SHBG levels declined with advancement of puberty in both boys (P < 0.001) and girls (P = 0.019). SHBG was significantly positively associated with insulin sensitivity in boys (P < 0.001) and girls (P < 0.001). In addition, SHBG was a strong predictor of insulin sensitivity (P = 0.001) and the only predictor of the disposition index (P = 0.031) after adjustment for puberty, fat mass, and aerobic fitness. SHBG was significantly negatively associated with metabolic risk (P = 0.032) and with hypersensitive C-reactive protein levels (P = 0.030) after adjustment for relevant confounders. CONCLUSIONS SHBG was a strong predictor of insulin sensitivity and metabolic risk during puberty. Thus, we hypothesize that SHBG integrates the marked changes in glucose metabolism and body composition that occur during the pubertal transition.

Why glucocorticoid withdrawal may sometimes be as dangerous as the treatment itself

Glucocorticoid therapy is widely used, but withdrawal from glucocorticoids comes with a potential life-threatening risk of adrenal insufficiency. Recent case reports document that adrenal crisis after glucocorticoid withdrawal remains a serious problem in clinical practice. Partly due to difficulties in inter-study comparison the true prevalence of glucocorticoid-induced adrenal insufficiency is unknown, but it might be somewhere between 46 and 100% 24h after glucocorticoid withdrawal, 26-49% after approximately one week, and some patients show prolonged suppression lasting months to years. Adrenal insufficiency might therefore be underdiagnosed in clinical practice. Clinical data do not permit accurate estimates of a lower limit of glucocorticoid dose and duration of treatment, where adrenal insufficiency will not occur. Due to individual variation, neither the glucocorticoid dose nor the duration of treatment can be used reliably to predict adrenal function after glucocorticoid withdrawal. Also the recovery rate of the adrenal glands shows individual variation, which may be why there is currently insufficient evidence to prove the efficacy and safety of different withdrawal regimens. Whether a patient with an insufficient response to an adrenal stimulating test develops clinically significant adrenal insufficiency depends on the presence of stress and resulting glucocorticoid demand and it is thus totally unpredictable and can change relative fast. Adrenal insufficiency should therefore always be taken seriously. Individual variation in hypothalamic-pituitary-adrenal axis function might be due to differences in glucocorticoid sensitivity and might be genetic. Further awareness of the potential side effect of withdrawal of glucocorticoid and further research are urgently needed.