Postprandial response of salivary ghrelin and leptin to carbohydrate uptake.
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Adolescent↗
Biomedical subjects
M Gröschl
Publications and source records attributed to M Gröschl.
Development of a novel compact sonicator for cell disruption.
Ultrasound microbial cell disrupters operating at around 20 kHz are often physically large and, due to significant heating, can be unsuitable for small sample volumes where biochemical integrity of the extracted product is required. Development of a compact device based on a 63.5-mm diameter, 6.5-mm thick tubular transducer for rapid cell disruption in small-volume samples in a high-intensity acoustic cavitation field with minimal temperature rises is described here. Suspensions of Saccharomyces cerevisiae were exposed to cavitation for various times in the compact device and a 20-kHz probe sonicator. Cell disruption was assessed by protein release and by staining. Yeast cell disruption was greater in the novel 267-kHz sonicator than in the 20-kHz probe sonicator for the same exposure time. A 1-dimensional (1-D) transfer matrix model analysis for piezoelectric resonators was applied to an axial cross-section of the tubular sonicator to predict frequencies of mechanical resonance in the sample volume associated with maximum acoustic pressure. Admittance measurements identified frequencies of electrical resonance. Ultrasonic cavitation noise peaks were detected by a hydrophone at both the mechanical and electrical resonances. Cell breakage efficiency was twice as great in terms of protein released per dissipated watt at the mechanical resonance predicted by the model, compared to those at the electrical resonance frequencies. The results form a basis for rational design of an ultrasound cell disruption technique for small-volume samples.
Erythrocytes↗
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.
Cell Proliferation↗
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.
Administration, Oral↗
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.
Autocrine Communication↗
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.
Administration, Oral↗
Spontaneous nocturnal leptin secretion in children with myelomeningocele and growth hormone deficiency.
OBJECTIVE: To examine the spontaneous leptin secretion in patients with myelomeningocele (MMC) and growth hormone deficiency (GHD). METHODS: Serum leptin levels were studied in 10 prepubertal MMC patients with GHD (CA 6.2 +/- 0.5 years), 10 patients with idiopathic GHD (IGHD; CA 7.6 +/- 0.7 years) and 12 children with normal variant short stature (NVSS; CA 7.6 +/- 0.5 years). Mean BMI (kg/m(2)) values of the groups did not differ significantly. Nocturnal leptin levels were analyzed over 10 h (blood samples every 20 min) and measured by specific radioimmunoassay. RESULTS: Mean leptin concentrations did not correlate with BMI in MMC patients. Nocturnal leptin secretion of MMC patients was significantly different to those of children with IGHD and NVSS. Morning leptin levels did not decline as observed in both other groups. CONCLUSION: Since all groups were matched for BMI values, we suggest a hypothalamic dysregulation of leptin secretion in MMC patients.
Body Composition↗
Relationship between salivary progesterone, 17-hydroxyprogesterone, and cortisol levels throughout the normal menstrual cycle of healthy postmenarcheal girls.
OBJECTIVE: To determine the usefulness of salivary P and 17 alpha-hydroxyprogesterone (17-OHP) for the assessment of ovarian function. In addition, salivary cortisol (F) levels were measured to assess the role of the adrenal cortex throughout the menstrual cycle. DESIGN: Prospective study. SETTING: Outpatients in hospital for children and adolescents. PATIENT(S): Thirty young women with regular menstrual cycles. INTERVENTION(S): Saliva collection in the early morning from day 1 of menstrual bleeding until next menses. MAIN OUTCOME MEASURE(S): Salivary P, 17-OHP, and F measured by RIAs. RESULT(S): During days 1-12 of the follicular phase, P and 17-OHP levels remained unchanged (P: 9-29.3 pg/mL; 17-OHP: 8-31 pg/mL). Thereafter, P increased exponentially from day 13 onward, reaching a plateau (mean +/- SEM, 70.1 +/- 9.0 pg/mL) between day 16 and 20, followed by a constant decrease until end of the cycle. The 17-OHP levels increased between day 14 and 17 (maximum: 45.8 +/- 4.5 pg/mL), decreasing rapidly thereafter. The F levels remained unchanged (follicular: 7.5 +/- 1.1 ng/mL; luteal 7.2 +/- 1.1 ng/mL). There was a significant correlation between P and 17-OHP (r(2) = 0.43; P<.001). When calculating ratios of P/F and 17-OHP/F, linear regression yielded a much stronger correlation (r(2) = 0.74; P<.001), although F did not show any correlation to P or 17-OHP. CONCLUSION(S): Changes in salivary 17-OHP levels throughout the menstrual cycle reflect ovarian but not adrenal function.
17-alpha-Hydroxyprogesterone↗
Stability of salivary steroids: the influences of storage, food and dental care.
We studied influences of dental care, food and storage on the reproducibility of salivary steroid levels. Cortisol (F), 17OH-progesterone (17OHP) and Progesterone (P) were measured using adapted commercial radioimmunoassays. Saliva samples of healthy adults (n = 15; m:8; f:7) were collected directly before and after dental care, and directly before and after breakfast with various foodstuffs. A second experiment investigated stability of steroids under different storage conditions. Four series of identical saliva portions (I: Native saliva; II: Centrifuged saliva; III: Saliva with trifluor acetate (TFA); IV: Saliva with 0.5% NaN(3)) were stored at room temperature and at 4 degrees C for up to three weeks. To demonstrate influences of repeated thawing and re-freezing of saliva on steroid values, saliva samples (n = 15) were divided into identical portions. These portions were frozen and re-thawed up to 5 times before measurement. Neither dental care nor intake of bread or milk effected the reproducibility of F, 170HP, and P. Steroid levels decreased significantly in the course of three weeks under different storage conditions (P < 0.001). This decrease was clinically relevant from the second week onward, with exception of NaN(3) treated samples. After repeated freezing and re-thawing 17OHP and P decreased slightly (about 5%). Only F decreased significantly after the third thawing (P < 0.001). The results show the usefulness of standardized handling of saliva samples for improving reproducibility and reliability of salivary steroid measurements.
17-alpha-Hydroxyprogesterone↗
A study of the spatial organisation of microbial cells in a gel matrix subjected to treatment with ultrasound standing waves.
Retention and manipulation of microbial cells through exploitation of ultrasonic forces has been reported as a novel cell immobilisation technique. The spatial ordering of yeast cells, within suspensions subjected to an ultrasonic standing wave field, was analysed for the first time. A technique, based on 'freezing' the spatial arrangement using polymer gelation was developed. The resultant gel was then sectioned and examined using microscopic techniques. Light Microscopy confirmed the presence of specific regions in the ultrasonic field, where the cells are organised into bands corresponding to the standing waves' pressure nodal planes. Computer Image Analysis measurement of several physical parameters associated with this cell distribution matched the values derived from the theoretical model. The spatial cell-cell re-arrangement within each band and uneven distribution along the nodal planes have been analysed by Scanning Electron Microscopy. These results complement the ongoing study of the process of immobilisation of microbial cells by ultrasound standing waves.
Cells, Immobilized↗
Identification of leptin in human saliva.
Leptin is produced predominantly in adipose tissue but has recently also been found in gastric mucosa. It has been shown that the oral application of leptin induces neuronal activity in the brain stem of rodents. The objective of the present study was to identify this hormone in human saliva and to examine the production and stability of salivary leptin. We have demonstrated production of leptin in salivary glands and oral mucosa by RT-PCR, its storage by immunocytochemistry, and the release of the peptide by RIA. Chromatographic analysis and immunoblotting confirmed the identity of leptin. There is a strong linear correlation (r2 = 0.78) between leptin concentrations from simultaneously collected saliva and plasma samples (n = 61). Stimulation of saliva flow increases total leptin secretion up to 3-fold (P < 0.001). As to the stability of leptin in gastric fluid, we found the peptide was not degraded above pH 3.5. Additionally, salivary leptin remains stable up to 5 d at 4 C. With regard to the presence of leptin receptors in gastric mucosa, we suggest salivary leptin as being a possible ligand for gastric leptin receptors. Furthermore, the determination of leptin in saliva allows for noninvasive sample collection.
Adult↗
Renal loss of leptin in patients with nephrotic syndrome.
OBJECTIVE: In humans, short term changes of serum leptin lead to alterations in food intake and energy expenditure. The objective of the present study was to relate urine leptin concentrations with the extent of proteinuria in patients with nephrotic syndrome (NS). A second goal was to investigate the impact of potential urinary leptin losses on serum leptin concentrations and body composition. DESIGN AND METHODS: Seventeen patients with proteinuria were compared with twenty patients with remission of NS and ten healthy children. Leptin was measured by radioimmunoassay. RESULTS: Urinary leptin excretion in proteinuric patients was significantly higher than in non-proteinuric patients with and without NS and in healthy controls (2.64+/-0.034 microg/g creatinine, 0.026+/-0.05 microg/g creatinine, and 0.073+/-0.11 microg/g creatinine respectively; P<0.001 and P<0.01 respectively compared with controls). Urine leptin positively correlated with urine IgG concentration (P=0.013, r2=0.36) in the proteinuric group. No difference in serum leptin values could be demonstrated between the three groups. CONCLUSIONS: In summary, our data demonstrate a significant leptin excretion in children with severe proteinuria. Proteinuria, however, does not lead to changes in serum leptin, suggesting that the significant loss of leptin is compensated for by sustained up-regulation of leptin production.
Adolescent↗
Viability of plant cell suspensions exposed to homogeneous ultrasonic fields of different energy density and wave type.
Exposure of Petunia hybrida cell suspensions to ultrasound at a frequency of 2.43 MHz in a standing wave field at an energy density of 70 Jm-3 (pressure amplitude of 0.78 MPa) decreased their mean viability to 35% after 20 min of sonication. A comparison of propagating wave and standing wave treatments at equal frequency (2.15 MHz) and energy density (8.5 Jm-3) showed, in the first case, a rapid decline in mean viability of cells (to 30% after 10 min of sonication) and, in the second case, a retaining of the initial viability (95%), respectively. Cells sonicated 4 days after subculture were more sensitive than cells sonicated 2 or 6 days after transfer to new culture medium. It was concluded that cellular viability depends primarily on the acoustic energy density, the exposure time, and the mechanical properties of the cells determined by age. As a consequence of the trapping of cells in the anti-node planes of the standing wave, propagating wave fields reduced cellular viability compared with standing wave fields at equal energy density.
Cell Survival↗
Variability of leptin values measured from different sample matrices.
Leptin concentrations are usually determined in serum or EDTA-treated plasma. Our aim was to evaluate the precision and accuracy of leptin measurement from serum and various kinds of plasma. Blood samples were collected from healthy volunteers and divided into aliquots of serum and plasma with administration of K(2)-EDTA, citrate, fluoride and lithium-heparinate, respectively. Leptin concentrations were measured by a specific radioimmunoassay. There were clear differences between the leptin values from the different matrices. The coefficient of variation (CV) was highest in serum samples (CV: 11.9 %) and very low in K(2)-EDTA-treated plasma samples (CV: 5.3%). Leptin measurements from serum yielded significantly lower results than the respective K(2)-EDTA-treated plasma samples (p < 0.05). The measurement in Li-heparinate-treated plasma revealed similar results to that in K(2)-EDTA-treated plasma. The lowest CV was determined in fluoride-treated plasma (5.2%). A higher CV was determined in citrate-treated plasma (5.8%) and the values were about 25% lower than in the respective K(2)-EDTA-treated plasma samples (p < 0.0001). Lower leptin measurements in citrate-treated plasma may partially, but not in total, be a consequence of dilution by anticoagulating additives. Because of the low CV K(2)-EDTA- and Li-heparinate-treated plasma samples appear most reliable for the measurement of leptin. The usage of these sample matrices is therefore recommended.
Adult↗
A novel ultrasonic resonance field device for the retention of animal cells.
This article describes two types of flow-through cell retention devices based on the concept of layered piezoelectric resonators. A single-chamber device is compared to a novel optimized steam-sterilizable prototype ultrasonic cell separator with improved acoustic design and an integrated cooling circuit, eliminating the problem of local temperature increase caused by the high amplitudes necessary to achieve the separation of animal cells with low acoustic contrast. This setup yields highly reproducible results and is ideal for studying the long-term effects of ultrasonic sound fields and separation efficiency. The novel two-chamber system has the potential for scaleability due to the reduction in thermal and acoustic flow, increased field stability, and separation efficiency. Finally, the effect of power input on separation and cell viability is reported. Such flow-through cell retention systems could be used as systems to retain biomass within the fermentor or as a substitute for centrifugation, with the major advantage of eliminating high-speed rotational motion.
Animals↗
Selective retention of viable cells in ultrasonic resonance field devices.
A double-chamber ultrasonic resonance field device was used for the separation and retention of animal cells. By controlling operational parameters such as flow and power input, the device can retain viable cells more efficiently, allowing for selective removal of nonviable cells and cell debris. A simple model describing the forces acting on spherical particles in a sound field (primary radiation force, Bernoulli force, secondary radiation force) is presented. Field stability increases with decreasing average flow rates and increasing power input. At very high field stability, as achieved with low flow rates and high power input, the selectivity for viable cells is reduced, due to the efficient retention of all types of particles. At high flow rates and resulting low field stability, selectivity is also reduced, due to poor separation efficiency, resulting in equally low retention of viable cells, nonviable cells, and cell debris.
Animals↗