Developing effective screening strategies in multiple endocrine neoplasia type 1 (MEN 1) on the basis of clinical and sequencing data of German patients with MEN 1.

BACKGROUND: Multiple-endocrine-neoplasia-type-1 (MEN1) is an autosomal-dominant inherited disorder characterized by the combined occurrence of primary hyperparathyroidism (pHPT), gastroenteropancreatic neuroendocrine tumors (GEP), adenomas of the pituitary gland (APA), adrenal cortical tumors (ADR) and other tumors. As the tumors appear in an unpredictable schedule, uncertainty about screening programs is persisting. OBJECTIVE: To optimize screening and to analyze possible differences in sporadic versus familial cases. METHODS: We analyzed data of 419 individuals including 306 MEN-1 patients (138 isolated and168 familial cases out of 102 unrelated families). RESULTS: A total of 683 tumors occurred consisting of 273 pHPT, 138 APA, 166 GEP, 57 ADR, 24 thymic- and bronchial-carcinoids as well as 25 neoplasms of other tissues. The age-related penetrance was determined as 10%, 35%, 67%, 81% and 100% at 20, 30, 40, 50 and 65 years respectively. Although pHPT being the most frequent first manifestation (41%), also GEP (22%) or APA (21%) were found to be the first presentation. APA occurred significantly more frequent (p<0,05) in isolated (n=138) than in familial (n=168) cases, whereas GEP showed a tendency to occur more often in familial cases. Genotype/phenotype correlation in 140 clinically affected MEN-1 cases showed a tendency for truncating mutations, especially nonsense mutations to be associated to GEP and carcinoids of the lungs and thymus. CONCLUSION: In view of the morbidity and frequency in familial cases an effective screening programme should aim at an early diagnosis of GEP particularly when truncating, especially nonsense mutations are found.

Using skin models to assess the effects of a pre-work cream. Methodological aspects and perspective of the industry.

BACKGROUND: There is a basic necessity to understand the mechanisms of the protective effects of pre-work creams. Additionally a lot of workplace-related irritants cannot be tested with the existing in vivo methods due to their toxicological profile. As a consequence, there is a need for additional in vitro models for testing pre-work creams. OBJECTIVE: An in vitro skin model test was developed to evaluate the protective mechanism of a pre-work cream. METHODS: The efficacy of 3 products was assessed by an in vivo test (repetitive occlusive irritation test) and then 3-dimensional skin model tests were carried out. RESULTS: In vivo test results demonstrate that the best protection against sodium dodecyl sulfate is offered by a multiple emulsion. In the case of a skin model test, sodium dodecyl sulfate led to cell damage, an increase in proinflammatory markers and some barrier lipids. The pre-work cream increased the content of skin lipids, without inducing irritation or cell death. CONCLUSION: Skin models support the understanding of the interaction of irritants and pre-work creams. Because they are in vitro models, there are no limitations regarding the selection of irritants, which offers numerous opportunities to test a broad range of workplace irritants.

Low serum levels of testosterone in men with minimal traumatic hip fractures.

Sex steroids are essential for accretion and maintenance of bone mass. Their importance for osteoporotic fractures in men, however, are undefined. We determined circulating levels of testosterone (T), non-SHBG-bound T (bT), free testosterone (FT), oestradiol (E2), intact parathormone (iPTH), 25-OH-vitamin D (25(OH)D), and trabecular bone mineral density at spinal level (tBMD) by single quantitative computed tomography (QCT), respectively, in elderly men 1-3.5 months after minimal traumatic hip fractures (MTHF, age=75+/-10 ys, n=27). A group of patients with non-immobilising stroke (S; age=73+/-8 ys, n=12) served as controls. Men with known secondary osteoporosis were excluded from the study. Furthermore, serum levels of T and E2 were compared to healthy controls aged 20-30 years (n=138) and 60-80 years (n=110). In addition a literature-based analysis of studies on testosterone in men hip fractures were conducted. Mean tBMD of men with MTFH (52.7+/-17.6 mg/cm3, T-score=- 4.5+/-0.6) was significantly lower than in men with S (78+/-16.3 mg/cm3, T-score=- 3.5+/-0.8). Significant differences of the means between both groups were observed for T, bT, and FT but not for E2, 25(OH)D, and iPTH, respectively. About 90 % of men with MTHF had T serum levels 2 SD below the mean of young controls. This proportion reduced to 30 % if compared with serum levels of 60-80-year-old healthy men whereas men after S remained well within the normal range adjusted for age. Mean serum levels of iPTH were within the normal range (1-6.8 pmol/l); 25(OH)D serum levels were at the lower end of the normal control levels (30-190 nmol/l). There was an inverse relationship between iPTH and 25(OH)D (r=- 0,4; p<0,03). In conclusion, low serum T is common in men with MTHF and only partly due to age. It appears to be a primary factor in fragility fractures in men and not simply secondary to morbidity following the fracture. In view of the scarce and inconsistent data published on this issue (1 longitudinal and 6 cross-sectional studies) the present study supports the patho-physiological relevance of low serum testosterone for the occurrence of MTHF in men.

Using skin models to assess the effects of a protection cream on skin barrier function.

BACKGROUND: There is a basic necessity to understand the mechanisms of the protective effects of emulsions. This would promote the development of protective cosmetics and therefore improve the prevention and treatment of occupational skin diseases. However, for such studies, no reliable skin model is available. OBJECTIVE: An in vitro skin model test was developed to evaluate the protective mechanism of cosmetic ingredients. METHODS: The efficacy of three products was assessed by an in vivo test (Repetitive Occlusive Irritation Test) and then 3-dimensional skin model tests were carried out. RESULTS: In vivo test results demonstrate that the best protection against sodium dodecyl sulphate is offered by a multiple emulsion. In the case of a skin model test, sodium dodecyl sulphate led to cell damage, an increase in pro-inflammatory markers and some barrier lipids. The multiple emulsion increased the content of skin lipids, without inducing irritation or cell death. CONCLUSION: Skin models react similarly to sodium dodecyl sulphate compared to human skin and therefore they are suitable to study barrier repair after sodium dodecyl sulphate damage. It is likely that the superior protective effect of the multiple emulsion in vivo is based on the increased amount of skin barrier lipids.

Sex steroids and body composition in men with cystic fibrosis.

OBJECTIVE: Delayed sexual maturation and low body weight is common in cystic fibrosis (CF). Concomitant data on sex hormones and concomitant body composition are lacking in men with CF. DESIGN: Cross-sectional study. SUBJECTS AND METHODS: Serum levels of testosterone, 17beta-oestradiol (E(2)), 25-hydroxyvitamin D (25(OH)D), sex hormone-binding globulin (SHBG) and LH were measured by RIA and total and regional lean body mass (LBM), fat body mass (FBM), bone mineral content and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry, in men with CF (n=40; age 24.7+/-5.4 years) and age-matched healthy controls (n=28; age 25.7+/-3.7). Only men without acute disease exacerbation or systemic glucocorticoid treatment were included. RESULTS: Mean levels of hormonal serum parameters differed significantly between healthy controls (testosterone=20.2+/-5.5 nmol/l; E(2)=95.0+/-20.2 pmol/l; 25(OH)D=62.8+/-28.3 nmol/l) and patients (testosterone=15.9+/-4.1 nmol/l; E(2)=60.7+/-19.4 pmol/l; 25(OH)D=39.5+/-17.8 nmol/l; P<0.001) while no difference was found for SHBG or LH. Eleven (for E(2), 19 of 40, for 25(OH)D, 20 of 40) out of 40 patients had serum testosterone levels 2 s.d. below the mean of normal. Men with CF showed a relative shift from FBM to LBM and a different body fat distribution compared with healthy controls (P<0.01). Testosterone was not correlated with weight, total or regional LBM or FBM, but significantly with BMD (r=0.32; P<0.05) independently from body height and 25(OH)D levels. E(2) was correlated with regional and total FBM (r=0.48; P<0.05). In a multiple regression analysis of the joint effect of testosterone and body components on E(2), a testosterone-independent effect was found for FBM. CONCLUSIONS: CF patients with stable disease have moderately reduced serum testosterone levels. This might already imply detrimental effects on bone. The change in LBM of patients appears to have no direct association with sex hormone levels while low FBM might cause reduced net conversion of serum testosterone to E(2) with possible effects on FBM distribution.

[Reversible blindness caused by an invasive prolactinoma]. / Reversible Erblindung durch ein invasives Prolaktinom.

HISTORY: A 40-year-old man presented with severe headache, nausea and acute blindness. A CT-scan of the skull revealed a huge tumor along the basis of the skull. The patient was referred to our clinic for diagnostic and therapeutic evaluation. INVESTIGATIONS: MRT showed a large right-sided paramedian tumour displacing the brain stem with signs of increased intracranial pressure. Routine laboratory tests were normal except a normochromic anaemia. Endocrine tests demonstrated partial hypopituitarism with alteration of the somatotropic, gonadotropic and corticotropic axis and moderate hyperprolactinaemia. TREATMENT AND COURSE: On the day of admission a transnasal biopsy was taken. The preliminary histopathological diagnosis was a low differentiated carcinoma. Because of this diagnosis and because of the infiltrative tumour growth an operation was not performed but emergency irradiation was begun and dopamine agonist therapy was started because of hyperprolactinaemia. Several days later the final microscopic diagnosis of the transnasal biopsy specimen was reported to be an invasive prolactinoma. Under dopamine agonist therapy prolactin levels rose to a maximum of 6460 ng/ml to decline thereafter to normal values, and the visual disturbances recovered. After 5 weeks of therapy considerable shrinkage of the tumor was demonstrated by MRT. CONCLUSION: The differential diagnosis of acute visual deterioration caused by a large tumour along the basis of the skull includes an invasive prolactinoma. The diagnosis is made by demonstrating grossly elevated prolactin levels. To avoid falsely low prolactin measurements, caused by a hook-effect in the prolactin assay, serum dilution is mandatory in the diagnostic work-up. In the case of a prolactinoma medical treatment with dopamine receptor agonists is the therapy of choice because it causes rapid tumour shrinkage and symptomatic improvement in most patients, so that irradition of the tumour is not indicated. As dopamine agonist therapy is rapidly effective and well tolerated, it should be started even in case of doubt to lose no time until final diagnosis.

Hepatitis C and the leptin system: bound leptin levels are elevated in patients with hepatitis C and decrease during antiviral therapy.

BACKGROUND: Serum leptin levels are elevated in alcoholic liver cirrhosis and thus might be involved in the anorexia and hypermetabolism often seen in those patients. We hypothesized that the leptin system is modulated in patients with hepatitis C and might be affected by antiviral therapy. The aim of this study was to investigate the different leptin components in serum of patients with hepatitis C before, during and after interferon alpha and ribavirin therapy and in controls. METHODS: 25 patients (11 female, 14 male) with chronic hepatitis C were compared with body mass index, gender and age-matched controls (n = 25). Patients were treated with interferon alpha alone (3 MU tiw) or in combination with ribavirin for 6-12 months. Free leptin and bound leptin levels were measured using specific radioimmunoassays before interferon therapy, at 12 weeks of therapy and after 3 months of follow-up. RESULTS: Free leptin levels were higher in female than in male subjects, both for patients (P < 0.01) and controls (P < 0.05). Bound leptin levels were elevated in both female (P < 0.05) and male (P < 0.001) patients compared to controls. No alteration of free leptin levels was found during therapy, whereas bound leptin levels decreased after 3 months of therapy (P < 0.005) and re-increased to the baseline levels 3 months after therapy was stopped. Responder but not non-responder had decreased bound leptin levels (P < 0.01) comparing pre- and posttreatment levels. However, no significant correlations were determined between any of the leptin components to virus load, ALT, TNF alpha receptor levels (sTNFR-75, sTNFR-55) and histopathology at any time point. CONCLUSION: Since no correlation was found between the different leptin components and any of the inflammatory markers, the decrease in bound leptin levels during antiviral therapy suggests either a direct interferon-dependent effect on the leptin system or an alteration of other leptin secretagogues.

Induction of autoantibodies to the adrenal cortex and pancreatic islet cells by interferon alpha therapy for chronic hepatitis C.

BACKGROUND/AIMS: Interferon alpha (IFN-alpha) therapy for chronic hepatitis C may trigger induction of autoimmunity against several organs. Immune reactions against distinct adrenocortical protein antigens involved in adrenal autoimmune disease have not been reported to date. Therefore, we investigated the development of highly sensitive and specific adrenal autoantibodies in patients with chronic hepatitis C in response to IFN-alpha treatment. In addition, we studied induction of pancreatic islet and thyroid autoantibodies. PATIENTS/METHODS: Sera of 75 patients (42 males, 33 females; mean age 47 (13) years) were analysed before, during, and after IFN-alpha therapy (9-18x10(6) IE/week; mean duration 8.3 (3.5) months). Autoantibodies (Abs) to adrenal 21-hydroxylase (21OH-Abs), and to islet glutamic acid decarboxylase (GAD65-Abs) and protein tyrosine phosphatase (IA2-Abs) were determined by a radiobinding assay using (35)S labelled protein generated by an in vitro translation system. Thyroid antibodies were measured by a commercially available ELISA. RESULTS: Thirteen of 75 patients were initially positive for some of the autoantibodies. During or after IFN-alpha therapy, 3/62 initially negative patients (4.8%) developed 21OH-Abs. GAD65-Abs or IA2-Abs appeared in 5/62 and 1/62 patients, respectively (9.7% in total). In 12/62 patients (19.4%), thyroid specific antibodies appeared. In none of the 21OH-Ab positive subjects was adrenal dysfunction observed, and no patient with islet autoantibodies developed diabetes mellitus or impaired glucose tolerance. CONCLUSIONS: IFN-alpha induces 21OH-Abs in some cases, while islet and thyroid specific autoantibodies are more frequently found. However, our results indicate for the first time that the adrenal cortex also has to be considered as a potential target of IFN-alpha related autoimmunity.

Estradiol levels in psychotic disorders.

Estradiol has been postulated to constitute a protective factor for schizophrenia, which could provide women at risk to experience a psychotic episode with a relative protection in phases of high estradiol levels, i.e. before menopause and during the peri- and postovulatory phases of their cycle. Women suffering from schizophrenia have been reported to show significantly lower estradiol levels than the normal population and to experience first onset or recurrence of a psychotic episode significantly more often in low estrogen phases of the cycle with low estradiol levels. We examined estradiol levels in an open prospective study in 43 women admitted with a diagnosis of an acute psychotic episode and could confirm these findings for schizophrenia as well as other psychotic disorders. Only 28% of the women exhibited estradiol and progesterone levels indicating a peri- or postovulatory phase and all of the estradiol levels on admission were either within the lower part of the cycle-dependent normal range or below normal; comparison with a control group of healthy volunteers and patients admitted with different psychiatric diagnoses confirmed their estradiol levels to be significantly higher. However, when splitting this control group, the statistical difference would only hold between the study group of psychotic patients and the healthy control group. The group of patients with other diagnoses than a psychotic episode fell in between of the other two groups and did not differ significantly from either. Thus, an unspecific effect, i.e. a hypothalamic downregulation due to the stress of acute hospitalization must be born in mind when assessing hormone levels in acutely psychotic women.

Postoperative altered plasma growth hormone levels--a predictor for postoperative complications? A case report.

We compared the onset of predictors for postoperative complications (lactate, total T2 (tT2), total T4 (tT4) and cortisone) retrospectively with the onset of altered growth hormone (GH) concentration in a patient who had had a lethal postoperative outcome and in 13 patients who were without postoperative complications for a period of 24 hours postoperatively. Compared with the values of the patients without postoperative complications, GH values were elevated (68-fold) 1 h after surgery to 103 ng/ml and lactate was increased (12-fold) to 12.7 mmol/l at 6 h postoperatively in the patient with the lethal outcome. The other parameters measured (tT3, tT4 and cortisone) showed no rapid alteration during the first hours postoperatively. This case report suggests that the rapid postoperative onset of raised GH concentration in plasma may be an earlier marker for postoperative complications than the 'established' predictors.

[A young woman with neurofibromatosis 1 (Recklinghausen disease), abdominal tumor and hypertension]. / Eine junge Patientin mit Neurofibromatose Typ 1 (Morbus Recklinghausen), Unterbauchtumor und Hypertonus.

HISTORY AND ADMISSION FINDINGS: A 38-year-old woman, known to have type 1 neurofibromatosis (NF1; von Recklinghausen's disease) and recurrence of a malignant haemangiopericytoma in the lower abdomen developed hypertension. She also had headaches and marked perspiration. Physical examination revealed tachycardia and paleness of the distal digits, in addition to multiple neurofibromas and café-au-lait spots. INVESTIGATIONS: A tumour was found in the region of the right adrenal gland, in addition to the known haemangiopericytoma. The levels of epinephrine and dopamine were elevated, suggesting an orthotopic phaeochromocytoma as the cause of the hypertension. Mutation analysis confirmed the neurofibromatosis by demonstrating a splice mutation of the NF1 gene in exon 8. She also was found to have emphysema of the right upper and middle lobes of the lung. TREATMENT AND COURSE: Because of the extensive local changes the recurrent haemangiopericytoma was only partially resected. At the same time a right adrenalectomy was performed without complication. However, the patient's postoperative recovery was slow, but she was now normotensive. Planned radiotherapy was omitted because of her poor general state. Instead she was given weekly palliative chemotherapy with adriamycin, with little improvement. She died several weeks later from the malignancy. CONCLUSION: This case emphasizes that in a patient with NF1 a phaeochromocytoma must be considered as a possible cause of hypertension. It is likely that the patient's emphysema was associated with the NF1, while the haemangiopericytoma was presumably unconnected with the NF1.

Free and bound leptin levels during human pregnancy.

Leptin is a hormone secreted from adipocytes and trophoblasts which might influence energy metabolism during gestation. In this study we evaluated the course of free and bound leptin levels in 22 healthy pregnant women and compared these values to those in non-pregnant women matched for body mass index (BMI) and age. Serum concentrations of both leptin components and plasma levels of estradiol, progesterone, insulin, non-esterified fatty acids and glucose were measured at each trimester. The BMI increased from the first to the second trimester (22.8 +/- 3.1 and 24.7 +/- 2.9, respectively; p < 0.05) and remained stable thereafter (third trimester 25.3 +/- 2.9 kg/m2). Free leptin and bound leptin did not differ between patients and controls in the first trimester of pregnancy. Free leptin levels increased from the first (122 (60)) to the second trimester (181 (60) pmol/l; p < 0.05) and remained constant (third trimester 181 (76) pmol/l; difference between second and third trimesters, NS). Bound leptin increased from the second (0.43 (0.16)) to the third trimester (0.57 (0.21) nmol/l; p < 0.05). Only bound leptin was higher in the patient group in the third trimester compared to controls (p < 0.01). Our findings of a shift in free leptin to bound leptin in late pregnancy may indicate different physiological roles for both components. Free leptin may reflect maternal fat stores, whereas bound leptin may regulate maternal metabolism via central effects on food intake and energy expenditure.

Energetic requirement of carbachol-induced Ca2+ signaling in single mouse beta-cells.

Insulin secretion is under multifactorial control by glucose and neurohumoral factors like acetylcholine (ACH), which activate the Ca2+/phospholipase C signaling pathway. All insulin secretagogues elevate cytosolic free Ca2+ ([Ca2+]i) that is central to the stimulation of insulin secretion. The actions of ACH on [Ca2+]i are glucose dependent but the metabolic steps involved are only partly understood. Here we have characterized the metabolic steps by which glucose exerts its synergistic effects on ACH-linked Ca2+-signals. [Ca2+]i was measured in single fura-2 loaded beta-cells. The ACH analog carbachol (3 microM) caused rise in [Ca2+]i that was strongly dependent on the extracellular glucose concentration ranging from 0-10 mM. Iodoacetate, which blocks glycolysis, thereby preventing the generation of NADH and ATP from glucose metabolism, and rotenone or antimycin, which inhibit complex 1 and 2 of the mitochondrial respiratory chain, respectively, inhibited in glucose (6 mM) the carbachol-induced Ca2+ signal to a similar extent as glucose deprivation. This demonstrates that glucose metabolism and generation of ATP through oxidative phosphorylation of energy rich substrates like NADH and FADH2 are required for carbachol-induced Ca2+ signals. While sodium arsenate, which prevents net glycolytic production of ATP without inhibiting glycolysis, had no significant effect on the carbachol-induced Ca2+-signal, the mitochondrial pyruvate transport inhibitor alpha-cyano-4-hydroxycinnamate and the Krebs cycle inhibitor monofluoroacetate strongly suppressed the rise in [Ca2+]i elicited by carbachol. While pyruvate was ineffective, methyl pyruvate, a membrane-permeant pyruvate analog, and alpha-ketoisocaproate in combination with glutamine, which are both substrates for mitochondrial ATP production, could restore the carbachol-induced Ca2+ signal in glucose-free medium. These data demonstrate for the first time that Krebs cycle metabolism of glucose and ATP formation through oxidative phosphorylation is critical for the glucose dependency of ACH-linked Ca2+-signals in mouse beta-cells, and they suggest that mitochondrial metabolism plays a key role in the interactive regulation of beta-cells by neurohumoral factors activating the Ca2+/phospholipase C signaling pathway.

An unusual cause of retrograde ejaculation and hypertension.

A 39-year-old man presented with a 1-year history of retrograde ejaculation and a 10-year history of drug-resistant hypertension. Diagnostic abdominal ultrasound revealed an open bladder neck during the filling phase and a retroperitoneal tumor. After surgical excision histology revealed an extra-adrenal pheochromocytoma, which should be included in the differential diagnosis of patients presenting with retrograde ejaculation and hypertension.

Determinants of within-subject variation of fasting serum leptin concentrations in healthy subjects.

The hormone leptin is considered to contribute to body weight regulation through modulation of feeding behavior and energy expenditure. The aim of the present study was 1) to assess the day-to-day within-subject variation (biovariability) of serum leptin concentrations in healthy subjects and 2) to investigate whether this variation is associated with food intake, exercise, anthropometric measurements or various metabolic covariates (insulin, C-peptide and glucagon, glucose, lactate, 3-hydroxybutyrate (3-OHB), triglycerides, non-esterified-fatty acids and glycerol). Serum leptin levels were taken daily on 12 consecutive days after an overnight fast in 12 healthy subjects with a mean (SD) age of 22.7 (1.5) yr. and a BMI of 22.8 (1.6) kg/m2. Food intake, exercise, anthropometric measurements and various metabolic covariates were also determined during this period. The overall mean of serum leptin concentration was 33.3 pmol/L with a within-subject SD range of 27-41 pmol/L and a between-subject SD range of 18-61 pmol/L. The within-subject variance of serum leptin as a proportion of total variance was 9.5%. Within-subject variation of serum leptin concentrations is small in relation to between-subject variation in healthy, normal weight subjects. This has implications for the power of interventional or prospective studies. In men, 6.7% of the variation in serum leptin concentration was associated with body weight measured on the same day (p= 0.037). In women, however, 66% of the variation was negatively associated with 3-OHB measured on both the same and the previous day (p=0.0003 and 0.002), and positively associated with triglyceride concentration measured on the previous day (p=0.0017) and insulin measured on the same day (p=0.0002). Within-subject associations in women could be due to phasic changes in unmeasured variables, possibly related to the menstrual cycle or might suggest that energy balance may exert a delayed influence on serum leptin levels, with plasma 3-OHB and triglycerides acting as markers for the state of the fat stores that regulate leptin secretion. The differences between the genders remain unexplained, however.

Free serum leptin but not bound leptin concentrations are elevated in patients with end-stage renal disease.

BACKGROUND: Leptin is a 16-kDa protein that is thought to be a regulator of food intake and body weight. Although total serum leptin levels have been reported to be elevated in obese and normal weight patients with end-stage renal disease (ESRD), it is not known whether serum-free leptin concentrations are also increased in patients with ESRD with no apparent nutritional problems. Furthermore, there are no data on how different dialysis modes (high-flux haemodiafiltration and low-flux dialysis) influence serum leptin subfractions. METHODS: We measured fasting serum free and bound leptin levels in three groups of male subjects: patients on haemodiafiltration with high flux dialysers (n=11), patients on haemodialysis with low-flux dialysers (n=17) and healthy age (61+/-8 years) and BMI (23.8+/-3.1 kg/m(2)) matched control subjects (n=28). Both leptin components were determined before and after a single dialysis session. RESULTS: Body mass indices were correlated with serum free leptin levels in both patients (r=0.69, P<0.001) and controls (r=0.77, P<0.001). Mean (SD) serum free leptin levels were significantly higher in ESRD patients than in control subjects (91+/-33 vs 41+/- 21 pmol/l; P<0.01). Bound leptin levels did not differ in both groups (0.67+/-0.12 vs 0.56+/-0.11 nmol/l, NS). Elevated serum-free leptin levels in ESRD patients could be reduced by haemodiafiltration with high-flux membranes, but not with low-flux haemodialysis membranes. The former led to a reduction of initial serum free leptin values to 76+/-17% (P<0.01), whereas bound leptin remained unaffected. CONCLUSION: Serum-free leptin levels are elevated in ESRD without any apparent effect on body weight. In contrast, serum bound leptin levels remain stable, thus central feedback regulation via the bound form of the hormone may serve as an alternative explanation in the regulation of food intake and energy expenditure in chronic patients on haemodialysis with no apparent nutritional problems.

A study on the genetics of obesity: influence of polymorphisms of the beta-3-adrenergic receptor and insulin receptor substrate 1 in relation to weight loss, waist to hip ratio and frequencies of common cardiovascular risk factors.

Beta-3-adrenergic receptor (beta-3-AR) and insulin receptor substrate 1 (IRS-1) have been implicated in the pathogenesis of obesity and in obesity related increase in insulin resistance which is associated with, among other diseases, dyslipidemia and type 2 diabetes mellitus. We studied 210 white female Caucasian obese subjects, who underwent a formal weight loss program (Optifast). We examined the association between mutations of the IRS-1 gene at codon 972, mutations of the beta-3-AR gene at codon 64, and the combination of both mutations with the degree of weight loss, waist to hip ratio and the prevalence of hypertension, dyslipidemia and type 2 diabetes mellitus. Twenty-four women (11.4%) were polymorph only for the beta-3-AR mutation, 23 women (10.9%) only for the IRS-1 mutation, and 6 subjects (2.9%) were polymorph for both alleles. No patient displayed a homozygous polymorphism. Similar frequencies of these polymorphisms were observed when the 100 non-obese control women were tested (14.0, 15.0, 3.0, respectively). After 13 weeks of weight loss the group with multiple polymorph alleles had lost less of their weight than the obese controls without mutation (Delta BMI 5.32+/-0.18 versus 6.12+/-0.2 kg/m2, p<0.05). In this group, the frequency of type 2 diabetes (66.7%) was significantly higher than in the obese control group without mutations (16.7%, p=0.008). Our findings suggest there is a synergy between the polymorphisms of Trp64Arg beta-3-AR and Gly972Arg IRS-1 in Caucasian German obese women leading to a decreased weight loss. This seems to be accompanied with an increased frequency of type 2 diabetes.

Free and protein bound leptin are distinct and independently controlled factors in energy regulation.

AIMS/HYPOTHESIS: Leptin exerts important regulating effects on energy homeostasis and could have a central role in our understanding of obesity, diabetes mellitus and the metabolic syndrome. Leptin circulates in a free and protein bound form. The aim of the present study was to test whether both fractions of the leptin system can be selectively regulated and thus serve independent physiological roles. METHODS: Using specific radioimmunoassays we measured both leptin components in relation to BMI in healthy subjects before and after weight reduction and in hyperthyroid patients during correction of thyrotoxicosis. In the latter group body composition and resting energy expenditure was monitored. In addition, we measured serum and cerebrospinal fluid concentrations of free and bound leptin in patients with neurological disorders. RESULTS: Under all conditions free leptin concentrations reflected body fat mass. Bound leptin concentrations decreased during weight reduction but also after treatment of hyperthyroidism despite an increase in fat mass. Direct measurement of resting energy expenditure and bound leptin in hyperthyroid patients and under thyrostatic treatment showed a significant positive correlation of both variables. In contrast to free leptin whose transport into the cerebrospinal fluid appears to be saturated at low physiological concentrations of serum free leptin, bound leptin concentrations in the cerebrospinal fluid increased in parallel to serum concentrations over the whole physiologically relevant range. CONCLUSION/INTERPRETATION: Our data indicate a distinct role of free and bound leptin in the feedback regulating energy intake and expenditure and could have important implications for our understanding of the physiology and pathophysiology of leptin-dependent signalling.

Tolbutamide and diazoxide modulate phospholipase C-linked Ca(2+) signaling and insulin secretion in beta-cells.

Arginine vasopressin (AVP), bombesin, and ACh increase cytosolic free Ca(2+) and potentiate glucose-induced insulin release by activating receptors linked to phospholipase C (PLC). We examined whether tolbutamide and diazoxide, which close or open ATP-sensitive K(+) channels (K(ATP) channels), respectively, interact with PLC-linked Ca(2+) signals in HIT-T15 and mouse beta-cells and with PLC-linked insulin secretion from HIT-T15 cells. In the presence of glucose, the PLC-linked Ca(2+) signals were enhanced by tolbutamide (3-300 microM) and inhibited by diazoxide (10-100 microM). The effects of tolbutamide and diazoxide on PLC-linked Ca(2+) signaling were mimicked by BAY K 8644 and nifedipine, an activator and inhibitor of L-type voltage-sensitive Ca(2+) channels, respectively. Neither tolbutamide nor diazoxide affected PLC-linked mobilization of internal Ca(2+) or store-operated Ca(2+) influx through non-L-type Ca(2+) channels. In the absence of glucose, PLC-linked Ca(2+) signals were diminished or abolished; this effect could be partly antagonized by tolbutamide. In the presence of glucose, tolbutamide potentiated and diazoxide inhibited AVP- or bombesin-induced insulin secretion from HIT-T15 cells. Nifedipine (10 microM) blocked both the potentiating and inhibitory actions of tolbutamide and diazoxide on AVP-induced insulin release, respectively. In glucose-free medium, AVP-induced insulin release was reduced but was again potentiated by tolbutamide, whereas diazoxide caused no further inhibition. Thus tolbutamide and diazoxide regulate both PLC-linked Ca(2+) signaling and insulin secretion from pancreatic beta-cells by modulating K(ATP) channels, thereby determining voltage-sensitive Ca(2+) influx.