[Improved quality of stored packed red blood cells by mechanical rinsing]

BACKGROUND

The transfusion of packed red blood cells (PRBC) is associated with various side effects, including storage damage to PRBCs. The cells change their structure, releasing potassium as well as lactate. Mechanical rinsing, available in many hospitals, is able to remove toxic substances and possibly minimizes the negative side effects of transfusion.

OBJECTIVE

The primary aim of our study was to improve the quality of PRBCs before transfusion. The effects of different washing solutions on PRBC quality were analyzed.

MATERIAL AND METHODS

This in vitro study compares 30 mechanically washed PRBCs. They were either processed with standard normal saline 0.9% (n = 15, N group) or a hemofiltration solution containing 4 mmol/l potassium (n = 15, HF group) by a mechanical rinsing device (Xtra, LivaNova, Munich, Germany). A subgroup analysis was performed based on the storage duration of the processed PRBCs (7, 14, 37 days). Samples were taken before washing (EKprä), immediately after washing (EKpost) and 10 h later (EKpost10h), after storage in the "wash medium" at room temperature. Concentrations of ATP (probability of survival in transfused erythrocytes), lactate, citrate and electrolytes (potassium, sodium, chloride, calcium) were tested.

RESULTS AND CONCLUSION

Mechanical rinsing improves pretransfusion quality of PRBC. Washing with a hemofiltration solution results in a more physiological electrolyte composition. Even 10 h after mechanical rinsing with a hemofiltration solution, the quality of 37-day-old PRBC is comparable to young PRBC that have been stored for 7 days and have not been washed. Washing stored PRBC increases the ATP content, which subsequently leads to an increased probability of survival of red cells after transfusion.

Tryptophan catabolism to serotonin and kynurenine in women undergoing in-vitro fertilization

This cross-sectional clinical study was designed to explore the impact of tryptophan-kynurenine and tryptophan-serotonin (5 HT) pathways on reproductive performance during in vitro fertilization (IVF). Paired serum and follicular fluid (FF) samples were obtained from 64 consecutive IVF patients. The analysis was done by using LC-MS/MS. Ovarian hyperstimulation resulted in decreased serum tryptophan (p<0.004), 5-HT (p<0.049) and kynurenine (p<0.001). FF levels of tryptophan (R=0.245, p<0.051), kynurenine (R=0.556, p<0.001) and 5-HT (R=0.523, p<0.001) were positively related to their respective serum levels. Clinical pregnancy was associated with higher serum 5-HT (p<0.045) and FF 5-HT (p<0.020) and lower kynurenine to 5-HT ratio (p<0.024). Chemical pregnancy was also positively related to FF 5-HT (R=0.362, p<0.024). Moreover, there was a direct relationship of the number of mature oocytes to the FF 5-HT (R=0.363, p<0.020) but it was inversely related to FF tryptophan to 5-HT and FF kynurenine to 5-HT ratios (R=-0.389, p<0.016 and R=-0.337, p<0.036, respectively). Multivariate logistic regression revealed that the number of mature oocytes was significantly influenced by FF 5-HT (?=0.473, p<0.001). In IVF patients ovarian hyperstimulation results in a reduction of the availability of tryptophan to catabolic pathways to kynurenine and 5-HT. Outcome measures improved significantly when 5-HT predominated over kynurenine.

Closing the gap - detection of clinically relevant von Willebrand disease in emergency settings through an improved algorithm based on rotational Thromboelastometry

Background

Hemorrhage and blood loss are still among the main causes of preventable death. Global hemostatic assays are useful point-of-care test (POCT) devices to rapidly detect cumulative effects of plasma factors and platelets on coagulation. Thromboelastography (TEG) and Thromboelastometry (ROTEM) are established methods in many anesthesiological departments for guided hemostatic treatment. However, von Willebrand disease remains undetected by standard ROTEM, especially during emergency care, despite being the most prevalent congenital hemostatic disorder.

Methods

In our monocentric cohort pilot study we focused on hemostatic challenges associated with von Willebrand disease. Twenty-seven patients with suspected von Willebrand disease were included. We modified the routine ROTEM assay by adding a preincubation with ristocetin and commercially available plasma-derived von Willebrand factor to identify clinically relevant von Willebrand disease (VWD).

Results

Addition of von Willebrand factor to the ristocetin assay of a VWD type 3 patient restored the reaction of the whole blood probe to match the response of a healthy person. Our modified ROTEM assay with ristocetin (Ricotem) showed that all high responders (n = 7) had VWD. In the low responder group (n = 16) – 10 of 16 had VWD and in the normal responder group (n = 5), 2 of 5 had mild type 1 VWD.

Conclusions

This new modification of the standard ROTEM assay enables the detection of otherwise unnoticed critical von Willebrand disease based on alterations in clot formation and might serve as a novel approach to reliably assess severe VWD patients by platelet-mediated blood clotting in an emergency setting. We recommend incorporating this new VWD-focused screening tool into the current ROTEM-based management algorithm of acute microvascular bleeding.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0672-8) contains supplementary material, which is available to authorized users.

Soluble ST2 regulation by rhinovirus and 25(OH)-vitamin D3 in the blood of asthmatic children

Paediatric asthma exacerbations are often caused by rhinovirus (RV). Moreover, 25(OH)-vitamin D3 (VitD3) deficiency during infancy was found associated with asthma. Here, we investigated the innate immune responses to RV and their possible modulation by 25(OH)-VitD3 serum levels in a preschool cohort of children with and without asthma. The innate lymphoid cell type 2 (ILC2)-associated marker, ST2, was found up-regulated in the blood cells of asthmatic children with low serum levels of 25(OH)-VitD3 in the absence of RV in their airways. Furthermore, in blood cells from control and asthmatic children with RV in their airways, soluble (s) ST2 (sST2) protein was found reduced. Asthmatic children with low 25(OH)-VitD3 in serum and with RV in vivo in their airways at the time of the analysis had the lowest sST2 protein levels in the peripheral blood compared to control children without RV and high levels of 25(OH)-VitD3. Amphiregulin (AREG), another ILC2-associated marker, was found induced in the control children with RV in their airways and low serum levels of 25(OH)-VitD3. In conclusion, the anti-inflammatory soluble form of ST2, also known as sST2, in serum correlated directly with interleukin (IL)-33 in the airways of asthmatic children. Furthermore, RV colonization in the airways and low serum levels of 25(OH)-VitD3 were found to be associated with down-regulation of sST2 in serum in paediatric asthma. These data indicate a counter-regulatory role of 25(OH)-VitD3 on RV-induced down-regulation of serum sST2 in paediatric asthma, which is relevant for the therapy of this disease.

Effect of maternal smoking on stress physiology in healthy neonates

OBJECTIVE

To assess the impact of maternal smoking during pregnancy (MSDP) on the neonatal hypothalamic-pituitary-adrenal axis.

STUDY DESIGN

In a prospective observational study, salivary cortisol and cortisone levels were measured at the fourth day of life during resting conditions and in response to a pain-induced stress event in healthy neonates whose mothers smoked cigarettes during each stage of pregnancy and compared with controls.

RESULTS

Neonates in the control group (n=70) exhibited a physiologic stress response with a significant increase in cortisol (1.3 to 2.1 ng ml^-1; P<0.05) and cortisone (11.8 to 17.8 ng ml^-1; P<0.05) from baseline levels, whereas in neonates from mothers who smoked (n=33), cortisol (0.9 to 0.8 ng ml^-1; P=0.77) and cortisone (11.5 to 13.0; P=0.19) stress response was not significantly different from baseline levels. A two-way analysis of variance confirmed these findings in both groups.

CONCLUSIONS

Healthy neonates whose mothers smoked during pregnancy show a blunted stress response on the fourth day of life. Thus, MSDP leads to a dysregulation of the HPA axis with continued effects in neonatal life. This might explain long-term consequences of MSDP such as overweight, diabetes mellitus and modification of blood pressure control mechanisms in adult life.

Nrf2-Keap1 pathway promotes cell proliferation and diminishes ferroptosis

Cancer cells are hallmarked by high proliferation and imbalanced redox consumption and signaling. Various oncogenic pathways such as proliferation and evading cell death converge on redox-dependent signaling processes. Nrf2 is a key regulator in these redox-dependent events and operates in cytoprotection, drug metabolism and malignant progression in cancer cells. Here, we show that patients with primary malignant brain tumors (glioblastomas, WHO °IV gliomas, GBM) have a devastating outcome and overall reduced survival when Nrf2 levels are upregulated. Nrf2 overexpression or Keap1 knockdown in glioma cells accelerate proliferation and oncogenic transformation. Further, activation of the Nrf2-Keap1 signaling upregulates xCT (aka SLC7A11 or system X_c⁻) and amplifies glutamate secretion thereby impacting on the tumor microenvironment. Moreover, both fostered Nrf2 expression and conversely Keap1 inhibition promote resistance to ferroptosis. Altogether, the Nrf2-Keap1 pathway operates as a switch for malignancy in gliomas promoting cell proliferation and resistance to cell death processes such as ferroptosis. Our data demonstrate that the Nrf2-Keap1 pathway is critical for cancer cell growth and operates on xCT. Nrf2 presents the Achilles’ heel of cancer cells and thus provides a valid therapeutic target for sensitizing cancer for chemotherapeutics.

ATF4 promotes angiogenesis and neuronal cell death and confers ferroptosis in a xCT-dependent manner

Activating transcription factor 4 (ATF4) is a critical mediator of metabolic and oxidative homeostasis and cell survival. ATF4 is elevated in response to diverse microenvironmental stresses, including starvation, ER stress damages and exposure to toxic factors. Here we show that ATF4 expression fosters the malignancy of primary brain tumors (WHO grade III and IV gliomas) and increases proliferation and tumor angiogenesis. Hence, ATF4 expression promotes cell migration and anchorage-independent cell growth, whereas siRNA-mediated knockdown of ATF4 attenuates these features of malignancy in human gliomas. Further experiments revealed that ATF4-dependent tumor promoting effects are mediated by transcriptional targeting the glutamate antiporter xCT/SCL7A11 (also known as system Xc^-). Thus, xCT is elevated as a consequence of ATF4 activation. We further found evidence that ATF4-induced proliferation can be attenuated by pharmacological or genetic xCT inhibition and ferroptosis inducers such as sorafenib, erastin and GPx4 inhibitor RSL3. Further, fostered xCT expression promotes cell survival and growth in ATF4 knockdown cells. Moreover, increased xCT levels ameliorate sorafenib and erastin-induced ferroptosis. Conversely, ATF4 knockdown renders cells susceptible for erastin, sorafenib and RSL3-induced ferroptosis. We further identified that ATF4 promotes tumor-mediated neuronal cell death which can be alleviated by xCT inhibition. Moreover, elevated ATF4 expression in gliomas promotes tumor angiogenesis. Noteworthy, ATF4-induced angiogenesis could be diminished by ferroptosis inducers erastin and by GPx4 inhibitor RSL3. Our data provide proof-of-principle evidence that ATF4 fosters proliferation and induces a toxic microenvironmental niche. Furthermore, ATF4 increases tumor angiogenesis and shapes the vascular architecture in a xCT-dependent manner. Thus, inhibition of ATF4 is a valid target for diminishing tumor growth and vasculature via sensitizing tumor cells for ferroptosis.

Change of the metabolomic profile during short-term mononuclear cell storage

BACKGROUND AND OBJECTIVES

Short-term storage of leukapheresis products used for immunotherapeutic mononuclear cell (MNC) products is a frequent event. The analysis of time-related metabolic patterns enables the characterization of storage-related effects in MNCs and the hypothesis-based optimization of the MNC medium.

MATERIALS AND METHODS

The MNC products from seven leukapheresis procedures were stored within a closed bag system for 48 h. Concentrations of amino acids, biogenic amines, phospho- and sphingolipids and hexoses in the medium were measured by targeted metabolomics. The viability of MNC subpopulations was assayed by Annexin V (AnV) and JC-1 staining.

RESULTS

Glucose depletion and a significant change of the acylcarnitine profile are early events within the first 24 h of storage. In contrast, for most amino acids, the maximum increase was observed at 48 h of storage as mirrored by an increase in the amino acid levels by a mean factor of 1·2 (1·3, 2·0) after 6 h (24 h, 48 h, respectively). This was except for the concentrations of glutamine and lysine, which did not change significantly. The taurine concentration showed a twofold increase within the first 24 h and remained constant thereafter. The steepest increase in AnV⁺ and 7-AAD⁺ CD4⁺ T cells was found between 24 and 48 h.

CONCLUSION

The time-course of apoptosis and metabolic patterns in the MNC products demonstrate that 24 h of storage is a decisive time-point, as afterwards key metabolic pathways showed nonlinear detrimental changes. Optimization of storage by supplementation of specific substrates demands therefore an early intervention.

A mouse organotypic tissue culture model for autosomal recessive congenital ichthyosis

BACKGROUND

Autosomal recessive congenital ichthyoses (ARCIs) are keratinization disorders caused by impaired skin barrier function. Mutations in the genes encoding the lipoxygenases 12R-LOX and eLOX-3 are the second most common cause of ARCIs. In recent years, human skin equivalents recapitulating the ARCI phenotype have been established.

OBJECTIVES

To develop a murine organotypic tissue culture model for ARCI.

METHODS

Epidermal keratinocytes were isolated from newborn 12R-LOX-deficient mice and cocultivated with mouse dermal fibroblasts embedded in a scaffold of native collagen type I.

RESULTS

With this experimental set-up the keratinocytes formed a well-organized multilayered stratified epithelium resembling skin architecture in vivo. All epidermal layers were present and the keratinocytes within showed the characteristic morphological features. Markers for differentiation and maturation indicated regular epidermal morphogenesis. The major components of epidermal structures were expressed, and were obviously processed and assembled properly. In contrast to their wild-type counterparts, 12R-LOX-deficient skin equivalents showed abnormal vesicular structures in the upper epidermal layers correlating with altered lipid composition and increased transepidermal water loss, comparable with 12R-LOX-deficient mice.

CONCLUSIONS

The mouse skin equivalents faithfully recapitulate the 12R-LOX-deficient phenotype observed in vivo, classifying them as appropriate in vitro models to study molecular mechanisms involved in the development of ARCI and to evaluate novel therapeutic agents. In contrast to existing human three-dimensional skin models, the generation of these murine models is not constrained by a limited supply of material and does not depend on in vitro expansion and/or genetic manipulations that could result in inadvertent genotypic and phenotypic alterations.

Cystatin C and neutrophil gelatinase-associated lipocalin: biomarkers for acute kidney injury after congenital heart surgery

QUESTIONS UNDER STUDY

To evaluate the diagnostic value of serum Cystatin C and urine neutrophil gelatinase-associated lipocalin (NGAL) for the detection of acute kidney injury in patients undergoing congenital heart surgery.

METHODS

Serial samples of serum Cystatin C and urine NGAL were collected from 139 consecutive patients with congenital heart defects aged 3 days to 30 years after admission to the intensive care unit, 2 and 6 hours after the end of cardiopulmonary bypass. Biomarker levels were compared to perioperative data retrospectively. Acute kidney injury was defined according to the paediatric-modified RIFLE classification.

RESULTS

According to the paediatric-modified RIFLE criteria 53% of patients developed evidence of acute kidney injury. Serum Cystatin C concentrations were strongly correlated with severity of acute kidney injury. Optimal sensitivity of 80% and specificity of 66% for the prediction of acute kidney injury occurred at a cut-off value of 0.995 mg/l, 2 hours after the end of cardiopulmonary bypass. The 2 hour urine NGAL concentration was significantly correlated to the duration of cardiopulmonary bypass, time of aortic cross clamping, and serum lactate concentration. Moreover a significant correlation was found between urine NGAL and both length of hospital stay and mechanical ventilation.

CONCLUSIONS

In patients after congenital heart surgery, urine NGAL indicates the damaging force of cardiopulmonary bypass and serum Cystatin C is a valuable predictive biomarker for resulting acute kidney injury.

The effect of valproate therapy on thrombin generation determined by calibrated automated thrombography

BACKGROUND

There is some evidence for coagulation disorders, e.g. decreased coagulation factor activity or thrombocytopenia, related to the use of antiepileptic drugs, mainly associated with valproate. The aim of our study was to evaluate the influence of valproate on thrombin generation.

METHOD

Patients with epilepsy receiving multiple anticonvulsant medications either with, or without, valproate were compared. The study group included 90 samples from patients with epilepsy, aged 1.3-20.1 years. Antiepileptic combination therapy without valproate was administered in 50 cases and therapy including valproate in 40 cases. The reference group consisted of 50 non-epileptic patients. Thrombin generation in platelet poor plasma was measured by calibrated automated thrombography.

RESULTS

No differences were measured for thrombin generation parameters between controls and patients without valproate therapy. In epileptic patients with valproate therapy, peak height and lag time were significantly lower in comparison to non-epileptic patients. In comparison to epileptic patients without valproate therapy, significant differences were found for lag time and peak time. Patients with valproate therapy had a significantly lower fibrinogen concentration. Platelet counts were decreased in a dose dependent manner.

CONCLUSION

No major differences in thrombin generation were found between children on antiepileptic therapy with and without valproate. The decreased fibrinogen levels result in shorter lag time and peak time.

11beta-hydroxysteroid dehydrogenase type 1 of the subcutaneous adipose tissue is dysregulated but not associated with metabolic disorders in adults born small for gestational age

INTRODUCTION

The mechanisms relating being born small for gestational age (SGA) and the later risk of metabolic disorders are not yet fully understood. Adipose 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) activity and expression have been positively associated with metabolic syndrome. In humans, no in vivo studies have explored 11beta-HSD1 activity and gene expression in sc adipose tissue of SGA subjects.

SUBJECTS AND METHODS

Thirty-nine subjects SGA (birth weight<10th percentile) were matched on gender and age with 36 subjects born appropriate for gestational age (AGA) (25th percentile<birth weight<75th percentile); the two groups were stratified according to body fat content into low-fat-mass (20 SGA and 18 AGA) and high-fat-mass (19 SGA and 18 AGA) subjects. Basal and stimulated activities of the 11beta-HSD1 enzyme were assessed in the effluent of microdialysis performed in the abdominal sc wall in vivo. mRNA expression was measured by real-time quantitative PCR.

RESULTS

Basal 11beta-HSD1 activity was comparable in both groups, whereas stimulated activity was lower in SGA subjects. A significant effect of body fat content on the stimulated 11beta-HSD1 activity was found in AGA but not in SGA subjects. 11beta-HSD1 expression was associated with body fat but not with birth weight.

CONCLUSION

The in vivo stimulated 11beta-HSD1 activity was decreased in subjects born SGA as compared with adults born AGA. 11beta-HSD1 gene expression was not associated with birth weight. It is therefore unlikely that local glucocorticoid metabolism in sc fat plays a major role in the development of the metabolic complications associated with being born SGA.

Effects of Various Dietary Amino Acid Preparations for Phenylketonuric Patients on the Metabolic Profiles along with Postprandial Insulin and Ghrelin Responses

AIM

We investigated the metabolic profiles along with insulin and ghrelin responses following ingestion of various amino acid (AA) substitutes commonly used in the treatment of phenylketonuria to study the effects of added macronutrients.

METHODS

Twenty healthy and 6 phenylketonuric adults ingested AA mixtures with or without carbohydrates and fat (Anamix, Easiphen, or p-am 3; 0.35 g AA/kg body weight); milk powder shakes were used for control purposes. Serum AA, glucose, urea, insulin, and ghrelin were measured over 5 h.

RESULTS

Peak AA concentrations were achieved at around 60 min postprandially for supplemented AA powders and control shakes, significantly later than for pure AA. Of interest, the mean Phe/Tyr ratio declined by 40-50% in phenylketonuric patients following intake of Easiphen, Anamix, or p-am 3. The insulin peaks, up to 500% as compared with baseline, occurred at 30 min and were approximately 100% higher after intake of AA plus macronutrients. Glucose and urea remained constant. Ghrelin showed a nadir at 60 min, followed by a rise leading to a 30% increase of initial concentrations for pure AA as compared with more constant levels for preparations with macronutrients.

CONCLUSION

An oral AA bolus together with macronutrients retards hyperaminoacidemia, displays a higher insulin secretion, normoglycemia, and more stable ghrelin concentrations, whereas the pure AA tested here exerted weaker anabolic effects.

Leptin and ghrelin expression in adipose tissues and serum levels in gastric banding patients

BACKGROUND

To determine how leptin and ghrelin are expressed in the adipose tissues of obese adults undergoing gastric banding (LAGB), and to correlate tissue expression with serum concentrations and parameters of the metabolic syndrome.

MATERIALS AND METHODS

A cross-sectional analysis of 92 patients: 61 obese patients with a body mass index (BMI) 49.2 +/- 1 kg m(-2) received LAGB, 20 patients underwent band exchange (BMI, 36.6 +/- 1.4 kg m(-2)) and 11 adult patients (BMI, 24.3 +/- 0.6 kg m(-2)) with fundoplication served as controls. Clinical data such as BMI and blood pressure were evaluated along with subcutaneous and visceral adipose tissue gene expression and fasting levels of leptin and ghrelin. Tissue transcripts were measured using real-time PCR, serum protein concentrations radio-immunologically.

RESULTS

Leptin gene expression was highest in the primary LAGB group and more pronounced in subcutaneous fat in both sexes (P < 0.0001). Serum leptin concentrations were highest in the LAGB group (P < 0.001), whereby women exhibited higher serum levels than men. Leptin concentrations correlated positively to expression in subcutaneous fat (P < 0.0001), and leptin expression was also correlated to BMI and systolic blood pressure. We detected ghrelin gene expression in both types of fat. The ghrelin mRNA amounts in adipose tissues were similar in both sexes and comparable within groups; serum concentrations were lower in patients with primary LAGB than in controls (P < 0.05).

CONCLUSIONS

Human adipose tissue expression of leptin is weight-course dependent and ghrelin is constitutional. Serum levels of leptin, but not of ghrelin, are indicative of an adaptive pattern of local gene expression in obese subjects undergoing weight reduction.

Salivary leptin induces increased expression of growth factors in oral keratinocytes

We investigated the influence of salivary leptin, purified by affinity chromatography, on the proliferation of human oral keratinocytes. Furthermore we determined the time- and dose-dependency of the incubation with salivary leptin on the production of epidermal growth factor (EGF) and keratinocyte growth factor (KGF), which are growth factors relevant to keratinocyte proliferation. The analysis was performed both intra- and extracellularly. The relationship between the three cytokines in cell proliferation was studied by successive blocking with specific antibodies. The incubation of oral keratinocytes with recombinant and native leptin led to a significantly increased, dose-dependent cell proliferation (P<0.001). A further significant increase in proliferation was observed after incubating the cells with sterile filtered saliva (P<0.001). The increase in proliferation could not be observed by simultaneous incubation with salivary leptin and specific antibodies against either leptin or KGF (P<0.001). We found a significant dose-dependency between leptin incubation and production of KGF and EGF at the RNA and protein level. Both cytokines were expressed intracellularly and released into the culture medium, where they could be quantified by ELISA. Furthermore, there was a dose- and time-dependent increase in the phosphorylation of STAT-1 and STAT-3, indicating that Ob-R(b) (the long form of the leptin receptor) expressed by the keratinocytes is functional. It is conceivable that the leptin-induced proliferation in keratinocytes is mediated by this signalling pathway. This is the first study to show a physiological role of salivary leptin as a growth factor for keratinocyte proliferation in the oral cavity. We could demonstrate its influence on the production of other growth factors essential for this proliferative effect. Based on the findings of our study we assume an important role for salivary leptin in wound healing within the vulnerable oral cavity.

Endocrine effects of food intake: insulin, ghrelin, and leptin responses to a single bolus of essential amino acids in humans

BACKGROUND

This study deals with the physiological effects of an oral bolus of essential amino acids (AA) on the secretion of insulin, ghrelin and leptin in fasting humans.

METHODS

12 healthy adults (age 18-40 years, 10 males, 2 females, body mass index 18.0-23.5 kg/m(2)) were included in our study. Seven fasted volunteers consumed an AA mixture (0.35 g/kg BW), 5 served as controls. Serum AA, glucose, albumin, urea and hormones were measured at 0, 15, 30 min and thereafter at 30-min intervals up to 5 h.

RESULTS

Glucose, albumin and urea remained constant, peak AA concentrations were achieved at 30 min for methionine (Met), at 60 min for all other AA. The insulin peak (533% compared to basal level, p < 0.01) at 30 min was earlier than the peaks of all AA except for Met. Ghrelin showed a continuous rise towards the end of the experiment leading to a 3-fold increase in initial concentrations in the study group (p < 0.001), significantly higher than in the control group (p < 0.05). In contrast, both groups exhibited almost constant leptin concentrations.

CONCLUSION

Our data indicate that an oral low-dose AA bolus not only causes considerable hyperaminoacidemia and hyperinsulinemia but is also accompanied by an increased ghrelin secretion in fasted humans. This may be a specific effect or may be due to the fact that a single bolus of AA is not a sufficient stimulus to induce satiety. Leptin, however, is not a key mediator in this setting.

Endocrine responses to the oral ingestion of a physiological dose of essential amino acids in humans

The response of insulin, human growth hormone (hGH), cortisol, leptin and ghrelin, in addition to various metabolic parameters, was measured at 10 minute intervals following the oral ingestion of a standardised physiological dose of essential amino acids (AA). Twenty-eight healthy male, fasted volunteers (aged 18-40 yrs, BMI 18.0-24.5 kg/m(2)) took part in the study; 13 volunteers in the AA group, nine subjects in an iso-caloric control group, and a further six subjects served as fasting controls. Twenty minutes after ingestion, insulin reached peak concentrations that were up to 500% higher than basal values (P<0.0001). The AA group and iso-caloric control group showed a similar insulin response. AA ingestion led to an increase in hGH secretion with maximum concentrations being 2100+/-1013% higher than the basal values (P<0.0001). In contrast, no changes in hGH concentrations were observed in the iso-caloric controls; in the fasting controls only a slight increase in hGH was found towards the end of the fasting period. While cortisol decreased significantly (P<0.01) during the study in the AA group, neither control group showed a significant change in this parameter. Changes in leptin levels remained insignificant in all three groups, whereas ghrelin showed a different profile in each of the three groups, i.e. a continuous rise towards the end of the study period (P<0.001) in the AA group, a less significant effect for the fasting group, and no effect at all in the iso-caloric control group. There was no significant correlation between the concentrations or the area under curve of the hormones measured in any of the groups. The endocrine data provided in this study indicate that a single bolus of essential AA in fasted individuals is associated with both anabolic and catabolic hormonal responses.

Differential distribution and expression of leptin and the functional leptin receptor in major salivary glands of humans

Leptin plays a central role in the regulation of food intake and energy expenditure in rodents. However, it has become clear that this hormone has more than only a satiety-inducing function, and that there are other sources of leptin, such as the central nervous system, placenta and the gastrointestinal tract in addition to adipose tIssue. Knowing about the important role of the salivary glands in food intake and digestion, it was the objective of the present study to investigate how leptin and its receptor are expressed and distributed in the major salivary glands of humans. We found leptin distributed throughout the major salivary glands with obvious intracellular concentrations in granula. In contrast, immunostaining for the leptin receptor was found exclusively in the membranes of the glandular cells. A high density of the leptin receptor was localised in the epithelia of the duct lumen. PCR analysis proved the autonomous expression of leptin by the salivary glands independently from adipocytes. Accordingly the long receptor isoform was expressed by any examined tIssue. In the light of recent findings of leptin influencing the growth of rodent salivary glands, the presence and distribution of leptin and its receptor suggests an autocrine role of salivary leptin within the glands.