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Biomedical subjects

W Arlt

Publications and source records attributed to W Arlt.

At least 19 recordsLinked to original sources

Linking Antley-Bixler syndrome and congenital adrenal hyperplasia: a novel case of P450 oxidoreductase deficiency.

The Antley-Bixler syndrome (ABS) is a multiple congenital malformation syndrome with craniosynostosis, radiohumeral synostosis, femoral bowing, choanal atresia or stenosis, joint contractures, urogenital abnormalities and, often, early death. Autosomal recessive and dominant inheritance have been postulated, as has fluconazole teratogenesis. Mutations in POR (P450 (cytochrome) oxidoreductase, an essential electron donor to enzymes participating in cholesterol biosynthesis), have been identified in some patients with the ABS phenotype. Recent evidence suggests that these mutations cause attenuated steroid hydroxylation, which in turn, causes congenital adrenal hyperplasia (CAH) with ambiguous genitalia in both sexes and glucocorticoid deficiency. Here, we report on a new patient with findings of both ABS and CAH that further illustrates how low maternal estriol at prenatal screening can serve as a marker steroid facilitating early diagnosis.

Abnormalities, Multiple↗

Hyperbranched polymers as drug carriers: microencapsulation and release kinetics.

The aim of this work was to study the feasibility of hyperbranched polymers as drug carriers by employing different microparticle formation methods and the influence of loading methods on release kinetics. Commercially available hyperbranched polyester (Perstorp) and three polyesteramides (DSM) were loaded with the pharmaceutical acetaminophen. The gas antisolvent precipitation (GAS), the coacervation, and the particles from gas saturated solutions (PGSS) are among conventional processes that were used to prepare microparticles of drug-loaded hyperbranched polyesters for the first time. For preparing solid dispersions of drug-loaded hyperbranched polyesteramides the solvent method was applied. Infrared (IR) and differential thermal analysis (DTA) studies suggest that acetaminophen is partly dissolved in the polymer matrix and partly crystallized outside the polymer matrix. For acetaminophen-loaded polyesters prepared by the GAS method, the presence of free drugs is predominant when compared to microparticles prepared by the coacervation method. This event disappears for microparticles prepared by the PGSS method. Moreover, the release of drug from drug-loaded Bol-GAS is biphasic, where the initial burst (48%), indicating the presence of unincorporated drugs, is followed by a slow-release phase, suggesting the diffusion of drug through polymer matrices. The release of drugs from drug-loaded Bol-PGSS do not show this behavior since the drug is better dissolved or dispersed in polymer matrices. In the case of drug-loaded polyesteramides, coevaporates prepared from 3 hyperbranched structures (H1690, H1200, and H1500) using the solvent method result in different release kinetics. The hydrophobic characteristic of hyperbranched polyesteramide H1500 shows the biphasic release kinetic whereas the drug released from hydrophilic matrices H1690 and H1200 exhibits fast release comparable to that of pure drug.

Acetaminophen↗

[Hypopituitarism].

Hypopituitarism is usually caused by tumours of the hypothalamus-pituitary region, but may also arise as the consequence of pituitary inflammation, infiltration or hypoperfusion. Tumour mass reduction by surgical intervention or following drug treatment may improve pituitary function. However, neurosurgical tumour resection and radiation therapy may lead to a permanent manifestation of hypopituitarism. Diagnosis is established by endocrine testing, revealing the characteristic low serum concentrations of both peripheral hormone and associated regulatory hormone of pituitary origin. Hypopituitarism may involve from one to all endocrine axes regulated by the pituitary (in order of frequency: growth hormone deficiency>secondary hypogonadism>secondary hypothyroidism>secondary adrenal failure). The treatment of permanent hypopituitarism consists of replacement of the peripheral hormones (hydrocortisone, DHEA, thyroxine, testosterone or oestradiol, growth hormone). Quality of life is impaired in a considerable number of patients with hypopituitarism and mortality is increased, mostly due to cardiovascular and cerebrovascular causes, but also as a consequence of recurrent respiratory infections. Long-term care and monitoring of patients with hypopituitarism requires the experienced endocrinologist.

Adrenal Insufficiency↗

[Adrenal crisis. Diagnostic and therapeutic management of acute adrenal cortex insufficiency].

Acute adrenal insufficiency is a rare but life-threatening disorder that develops as a result of inadequate adrenal steroid production. Early diagnosis is key for effective and life-saving treatment of the affected patients. The main clinical features are non-specific, thus often leading to misdiagnosis and invasive diagnostic work up, in particular in patients with previously unknown disease. Adrenal crisis in patients with known chronic adrenal insufficiency is nowadays rare, but can only be prevented by structured patient education on stress-related glucocorticoid dose adjustment. Outcome of adrenal crisis is crucially determined by the physician's clinical competence and immediate initiation of specific treatment.

Acute Disease↗

Study of feed temperature control of chromatography using computional fluid dynamics simulation.

Recently preparative high-performance liquid chromatography (HPLC) has been used more and more frequently to separate drugs and natural substances. However, large-scale HPLC easily tends to reduce the yield and purity of the product. Hydrodynamic and heat factors play an important roles. Generally, in a large-scale HPLC column, the tracer profile inside column will take on a parabolic shape because of the distributor, which will impact the separation performance of the column. With the inlet temperature suitably lower than the wall temperature, this situation could be improved to some extent. In this work, some experiments were conducted using HPLC, with a column 10 cm in diameter to determine the optimal temperature difference between wall and inlet temperatures. The wall temperature was fixed at about 30 degrees C and the inlet temperature varied from 15 to 30 degrees C. The flow-rate of the eluent, methanol, was 300 ml/min. The experimental result was simulated using CFD software FLUENT 4.4.4. The simulated temperature field fitted the experimental one very well and the simulated flow, temperature and tracer distribution inside column could provide good explanation of separation performance under different conditions. In addition, the simulation could at least approximately predict the optimal temperature difference.

Chromatography, High Pressure Liquid↗

Thiazolidinediones but not metformin directly inhibit the steroidogenic enzymes P450c17 and 3beta -hydroxysteroid dehydrogenase.

Androgen biosynthesis requires 3beta-hydroxysteroid dehydrogenase type II (3betaHSDII) and the 17alpha-hydroxylase and 17,20-lyase activities of cytochrome P450c17. Thiazolidinedione and biguanide drugs, which are used to increase insulin sensitivity in type 2 diabetes, lower serum androgen concentrations in women with polycystic ovary syndrome. However, it is unclear whether this is secondary to increased insulin sensitivity or to direct effects on steroidogenesis. To investigate potential actions of these drugs on P450c17 and 3betaHSDII, we used "humanized yeast" that express these steroidogenic enzymes in microsomal environments. The biguanide metformin had no effect on either enzyme, whereas the thiazolidinedione troglitazone inhibited 3betaHSDII (K(I) = 25.4 +/- 5.1 microm) and both activities of P450c17 (K(I) for 17alpha-hydroxylase, 8.4 +/- 0.6 microm; K(I) for 17,20-lyase, 5.3 +/- 0.7 microm). The action of troglitazone on P450c17 was competitive, but it was mainly a noncompetitive inhibitor of 3betaHSDII. The thiazolidinediones rosiglitazone and pioglitazone exerted direct but weaker inhibitory effects on both P450c17 and 3betaHSDII. These differential effects of the thiazolidinediones do not correlate with their effects on insulin sensitivity, suggesting that distinct regions of the thiazolidinedione molecule mediate these two actions. Thus, thiazolidinediones inhibit two key enzymes in human androgen synthesis contributing to their androgen-lowering effects, whereas metformin affects androgen synthesis indirectly, probably by lowering circulating insulin concentrations.

3-Hydroxysteroid Dehydrogenases↗

Mutation of proline 409 to arginine in the meander region of cytochrome p450c17 causes severe 17 alpha-hydroxylase deficiency.

We elucidated the molecular basis of 17 alpha-hydroxylase deficiency in a Chinese patient with male pseudohermaphroditism. The patient is a compound heterozygote, carrying two different mutant alleles in the CYP17 gene. The first mutation, g.6333--6341delGACTCTTTCA, located in exon 8, was reported in a Thai patient living in a rural village in Thailand. We suggest that g.6333--6341delGACTCTTTCA may be a prevalent mutation causing P450c17 deficiency in Southeast Asia. The second mutation is a missense mutation, g.5582C>G, located in exon 7, changing the codon 409 from CCG to CGG, and changing the coded amino acid from proline to arginine, i.e., P409R. This proline residue is conserved in P450c17 of other species and other human P450 proteins. Site-directed mutagenesis, in vitro expression, and functional analysis of the P409R mutant in COS-1 cells show that it has a complete lack of 17 alpha-hydroxylase activity. The proline residue probably causes a turn in the meander region of P450c17, and we hypothesize, by comparison to homologous proteins, that the change in the protein conformation may abolish heme incorporation or may prevent P450c17 from interacting with electron donors.

Adolescent↗

Octreotide LAR treatment throughout pregnancy in an acromegalic woman.

We report a 24-year-old woman with active acromegaly despite pituitary surgery and irradiation who received continuous octreotide LAR treatment for the control of GH excess throughout her pregnancy. The patient delivered a healthy girl following an uneventful pregnancy. Despite a substantial materno-fetal transfer of octreotide, postnatal development was normal with length parameters around the 50th percentile at 3 months of age. In almost all previously described cases (n = 13) octreotide was stopped after the diagnosis of pregnancy was established. No side-effects of mother or fetus have been reported. Octreotide treatment in pregnancy seems to be feasible and safe. Due to the still-limited number of reported cases, the potential benefits of octreotide treatment should be weighed carefully against its possible risks.

Acromegaly↗

Dehydroepiandrosterone supplementation in healthy men with an age-related decline of dehydroepiandrosterone secretion.

Serum dehydroepiandrosterone declines with age. Whether this represents a harmful deficiency or an age-related adaptation is not known. Dehydroepiandrosterone replacement in adrenal insufficiency, a state of pathological loss of dehydroepiandrosterone production, improves well-being, mood, and sexuality. To determine the effects of dehydroepiandrosterone in healthy men with a physiological, age-related decline in serum dehydroepiandrosterone sulfate, we conducted a double blind cross-over study in 22 healthy male volunteers (age range, 50-69 yr) with endogenous dehydroepiandrosterone sulfate levels below 4.1 micromol/liter (1500 ng/ml) receiving 4 months of dehydroepiandrosterone (50 mg/d) and 4 months of placebo treatment in random order, with a 1-month washout period. Dehydroepiandrosterone treatment increased serum dehydroepiandrosterone and dehydroepiandrosterone sulfate to concentrations usually found in young men. Circulating androgen levels did not change; however, androgen metabolites increased, indicating enhanced peripheral androgen synthesis. At baseline, psychometric assessment revealed normal well-being and sexuality scores. After 4 months of dehydroepiandrosterone, no effect on sexuality was observed, whereas some mood scores improved slightly, but were not significantly different from scores after placebo. Compared with placebo, dehydroepiandrosterone had no effect on serum lipids, bone markers, body composition, or exercise capacity. Thus, in contrast to previous findings in adrenal insufficiency, we found no obvious benefit of 4 months of dehydroepiandrosterone supplementation in healthy men with a physiological decline of dehydroepiandrosterone production.

Affect↗

Dehydroepiandrosterone replacement in women with adrenal insufficiency: effects on body composition, serum leptin, bone turnover, and exercise capacity.

Studies in animals and humans using supraphysiological doses of dehydroepiandrosterone (DHEA) reported significant changes in body composition and carbohydrate metabolism. To investigate the metabolic action of a physiological DHEA replacement dose, we studied 24 women with adrenal insufficiency (AI; mean +/- SD age, 42.3 +/- 9.3 yr; duration of disease, 9.2 +/- 8.4 yr; body mass index, 23.4 +/- 4.0 kg/m(2)) in a double blind, placebo-controlled, randomized, cross-over design. They received 50 mg DHEA/day and placebo orally for 4 months each, with a 1 -month washout period. Measurements included fasting serum glucose, insulin, leptin, bone markers, anthropometric parameters determined by bioimpedance analysis, and exercise capacity as assessed by an incremental cycling test. DHEA did not induce any change in body mass index (placebo vs. DHEA, 23.3 +/- 4.1 vs. 23.2 +/- 3.9 kg/m(2); P = 0.39), parameters of body composition, or exercise capacity. However, compared with placebo, DHEA replacement led to a significant decrease in serum leptin (absolute change after 4 months, DHEA vs. placebo, -5.3 +/- 8.0 vs. 1.1 +/- 5.7 ng/mL; P = 0.01). This is most likely the result of the DHEA-induced normalization of circulating androgens. DHEA had no effect on fasting glucose, insulin, or the glucose/insulin ratio. Compared with placebo, serum osteocalcin increased slightly, but significantly, during DHEA treatment (absolute change after 4 months DHEA vs. placebo, +1.6 +/- 5.3 vs. -1.2 +/- 6.2 ng/mL; P = 0.02). However, urinary cross-links excretion did not change. In conclusion, replacement of DHEA in a physiological dose in patients with pathological DHEA deficiency does not have a significant effect on carbohydrate metabolism, body composition, or exercise capacity. The biological relevance of the changes in leptin and osteocalcin levels remains to be determined.

Adrenal Insufficiency↗

Optimization of simulated moving bed plants with low efficient stationary phases: separation of fructose and glucose.

An optimization procedure for simulated moving bed (SMB) plants with low efficient stationary phases is presented. The new aspect is that the desorbent consumption can be cut by 70% by running the plant with lower internal liquid flows and a corresponding larger switch time while the productivity is kept constant. This concept was validated by the separation of fructose and glucose in water on a calcium resin with an eight-column SMB plant. The separation can be predicted well by a true moving bed (TMB) and a simulated moving bed simulation. Adsorption isotherms were determined up to 300 kg/m3 for glucose and 500 kg/m3 for fructose from 25 to 80 degrees C. Experimental SMB runs were performed over a wide range of feed concentrations (10-350 kg/m3) and temperatures (25-80 degrees C). The strong influence of the delay volume is pointed out. For an experimental run with high feed concentration a complete set of data is presented. To reduce biological growth separation at 80 degrees C is recommended.

Fructose↗

Influence of oral dehydroepiandrosterone (DHEA) on urinary steroid metabolites in males and females.

Oral dehydroepiandrosterone (DHEA) replacement therapy may have a multitude of potential beneficial effects and exerts its action mainly via peripheral bioconversion to androgens (and estrogens). A daily dose of 50-mg DHEA has been shown by us and others to restore low endogenous serum DHEA concentrations to normal youthful levels followed by an increase in circulating androgens and estrogens. As the hepatic first-pass effect may lead to a non physiological metabolism of DHEA after oral ingestion we studied the influence of two single DHEA doses (50 and 100 mg) on the excretion of steroid metabolites in 14 elderly males [age 58.8+/-5.1 years (mean +/- SEM)] with endogenous DHEAS levels <1500 ng/ml and in 9 healthy females (age 23.3+/-4.1 years) with transient suppression of endogenous DHEA secretion induced by dexamethasone (dex) pretreatment (4x0.5 mg/day/4 days). Urinary steroid profiles in the elderly males were compared to the steroid patterns found in 15 healthy young men (age 28.9+/-5.1 years). In the females the results were compared to their individual baseline excretion without dex pretreatment. Urinary steroid determinations were carried out by semiautomatic capillary gas-liquid chromatography. In both genders DHEA administration induced significant increases in urinary DHEA (females: baseline vs. 50 mg vs. 100 mg: 361+/-131 vs. 510+/-264 vs. 1541+/-587 microg/day; males: placebo vs. 50 mg vs. 100 mg: 434+/-154 vs. 1174+/-309 vs. 4751+/-1059 microg/day) as well as in the major DHEA metabolites androsterone (A) and etiocholanolone (Et). Fifty mg DHEA led to an excretion of DHEA and its metabolites only slightly above baseline levels found in young females and in young men, respectively, whereas 100 mg induced clearly supraphysiological values. After 50 mg DHEA the ratios of urinary DHEA metabolites (A/DHEA, Et/DHEA) were not significantly different between elderly males vs. young male volunteers and young healthy females versus their individual baseline levels. In conclusion, an oral dose of 30 to 50 mg DHEA restores a physiological urinary steroid profile in subjects with DHEA deficiency without evidence for a relevant hepatic first-pass effect on urinary metabolites.

Administration, Oral↗

Oral glucose tolerance testing but not intravenous glucose administration uncovers hyper-responsiveness of hypothalamo-pituitary-adrenal axis in patients with adrenal incidentalomas.

OBJECTIVE: Modern imaging techniques are detecting adrenal incidentalomas with increasing frequency. Recent data suggests food-dependent hypercortisolism in a subgroup of patients with bilateral macronodular hyperplasia due to aberrant adrenal responsiveness to gastric inhibitory polypeptide (GIP). We studied the putative influence of food intake on the hypothalamo-pituitary-adrenal (HPA) axis in patients with adrenal incidentalomas and possible mediation by GIP. PATIENTS AND MEASUREMENTS: We examined 15 mildly obese patients with adrenal incidentalomas, eight healthy, lean subjects, and seven obese patients with the metabolic syndrome, who were matched for body weight and age. Each individual underwent oral glucose tolerance testing (OGTT, 75 g glucose), i.v. glucose administration (IVGTT, 30 g glucose over 1 h) and i.v. glucose plus GIP infusion (body weight adapted leading to physiological postprandial GIP serum levels) on three occasions. Plasma glucose, ACTH and cortisol were measured from blood samples taken every 15 minutes from time - 30 minutes to + 75 minutes. RESULTS: OGTT, i.v. glucose administration and GIP infusion led to comparable glucose values within the groups. In contrast to normal subjects and patients with the metabolic syndrome, patients with adrenal incidentalomas had significantly higher mean cortisol values after oral glucose intake as compared to i.v. glucose administration or GIP infusion. The increase in cortisol levels was preceded by a corresponding ACTH increase. No significant effect of GIP administration on cortisol or on ACTH secretion could be detected. CONCLUSIONS: Patients with adrenal incidentalomas showed an abnormal responsiveness of the pituitary-adrenal axis to oral glucose administration. The cortisol peaks in these patients seemed to be ACTH-mediated and were not induced by GIP.

Adenoma↗

Enzymatic activities of P450c17 stably expressed in fibroblasts from patients with the polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting approximately 5-10% of women of reproductive age. The clinical features of PCOS include oligo/anovulation, hyperandrogenemia, and hyperinsulinemia. Because P450c17 is the single enzyme catalyzing both 17alpha-hydroxylase and 17,20-lyase activities in the ovary and adrenal, some have suggested that defects in P450c17 may cause the hyperandrogenism of PCOS. Previous studies have shown that serine hyperphosphorylation of P450c17 increases the enzyme's 17,20-lyase activity, thereby favoring androgen production, and that serine phosphorylation of the insulin receptor beta-chain (IR-beta) inhibits IR-beta tyrosine phosphorylation, causing insulin resistance in vitro. We previously suggested that a gain of function mutation in a single serine kinase might cause the hyperandrogenism and insulin resistance observed in PCOS patients by excessive phosphorylation of both P450c17 and IR-beta. To test this hypothesis, we obtained fibroblasts from nine previously studied patients: three controls, three PCOS patients with normal levels of IR-beta serine phosphorylation, and three PCOS patients with increased levels of IR-beta serine phosphorylation. Initial studies showed that such skin fibroblasts could not be transfected effectively by calcium phosphate, diethylaminoethyl-dextran, lipofection or adenovirus procedures. Therefore, we employed a retroviral infection system to stably express human P450c17 in the primary cultures of fibroblast cells from the PCOS patients and controls and measured the resulting 17alpha-hydroxylase and 17,20-lyase activity. The cells were analyzed in a blinded fashion until the study was complete. The 17alpha-hydroxylase and 17,20-lyase activities in each cell line correlated well with the amount of P450c17 protein expressed, but there was no correlation between either enzymatic activity (or their ratio) with the clinical phenotype of the cells' donors even when results were corrected for the number of P450c17 complementary DNA inserts per cell line. Overnight incubation with 1 micromol/L insulin also did not affect enzymatic activity. Thus, we were unable to find evidence for the hypothesis that in PCOS a single abnormal kinase hyperphosphorylates both IR-beta, causing insulin resistance, and P450c17, causing hyperandrogenism. However, because fibroblasts do not normally express either P450c17 or the accessory proteins needed for its optimal activity, these results cannot exclude a role for serine phosphorylation in the hyperandrogenism and insulin resistance of PCOS.

Adolescent↗

Adrenocortical function in patients with macrometastases of the adrenal gland.

OBJECTIVE: Metastases of the adrenal gland are a frequent finding in patients with malignant tumors like bronchogenic carcinoma or breast cancer. Only limited and conflicting data on adrenocortical function in these patients are available. DESIGN: Cross-sectional study. METHODS: We investigated the impact of adrenal macrometastases on adrenocortical function in a series of 28 tumor patients using the ACTH(1-24) stimulation test and dexamethasone suppression test. Seven normal controls (Con), eleven patients without adrenal metastases (No Met), eight patients with unilateral (Uni Met) and nine patients with bilateral adrenal metastases (Bil Met) were investigated. RESULTS: The prevalence of adrenal insufficiency was low in our study population, with only two of nine patients with bilateral metastases having subclinical adrenocortical insufficiency. In the remaining patients with uni- or bilateral metastases, baseline and stimulated cortisol concentrations were higher than in controls and cancer patients without metastases (baseline cortisol (in nmol/l): Con: 307+/-33.2 vs Uni Met: 440+/-53.5, and Bil Met: 637.6+/-92.1, P=0.04 by ANOVA; cortisol 60 min after ACTH(1-24): Con: 794.6+/-41.2 vs Uni Met: 990.8+/-92.9, and Bil Met: 1151.4+/-155.5, P=0.03 by ANOVA). Simultaneously, baseline and stimulated serum aldosterone concentrations were significantly blunted in the tumor groups. CONCLUSIONS: Adrenal insufficiency is infrequent and develops only in patients with bilateral metastases. However, the majority of patients have activation of the hypothalamic-pituitary-adrenal axis despite adrenal metastases with strongly elevated cortisol concentrations.

Adrenal Cortex↗