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Biomedical subjects

J Kratzsch

Publications and source records attributed to J Kratzsch.

At least 19 recordsLinked to original sources
PubMed2006

Clinical and functional characteristics of the human Arg59Ter insulin-like growth factor i receptor (IGF1R) mutation: implications for a gene dosage effect of the human IGF1R.

CONTEXT: Signaling via the IGF-I receptor (IGF-IR) is crucial for normal prenatal and postnatal growth. The heterozygous IGF-IR mutation Arg59Ter resulted in reduced IGF-IR expression and represents haploinsufficiency of the human IGF1R gene. OBJECTIVE: We studied clinical and in vitro aspects of a human IGF1R gene dosage effect. We provide detailed clinical data on the two half-brothers and their mother with the Arg59Ter mutation. Arg59Ter and control fibroblasts were examined for functionality of IGF-I and insulin-stimulated receptor phosphorylation and signal transduction. RESULTS: The two brothers presented with primary microcephaly, mild mental retardation, and intrauterine as well as postnatal growth deficits. After GH therapy (30 microg/kg.d) for 24 months, the growth deficit in the propositus decreased by +1.0 sd. There was no clinical evidence for impaired glucose tolerance or hypoglycemia in all Arg59Ter subjects. In vitro, IGF-IR-deficient Arg59Ter cells expressed less IGF-IR and unchanged insulin receptor (IR) protein. Receptor autophosphorylation and phosphorylation of downstream protein kinase B/Akt exhibited resistance to IGF-I but showed an augmented response to insulin in Arg59Ter cells. Decreased IGF-IR content was accompanied by a reduction of IGF-IR/IR receptor hybrids, and therefore, increased levels of IR/IR homodimers probably explain increased insulin-stimulated receptor autophosphorylation and Akt phosphorylation. CONCLUSIONS: In vivo and in vitro IGF-I resistance in Arg59Ter subjects and fibroblasts indicates a human IGF1R gene dosage effect involving not only the IGF-IR, but also IGF-IR/IR hybrids. The abundance of both the IGF-IR protein and IGF-IR/IR hybrid receptors may have an impact on human growth, organ function, and glucose metabolism.

Body Weight↗
PubMed2006

Metabolic decompensation in children with type 1 diabetes mellitus associated with increased serum levels of the soluble leptin receptor.

OBJECTIVE: Type 1 diabetes mellitus (T1DM) leads to increased serum levels of the soluble leptin receptor (sOB-R) by an as yet unknown cellular mechanism. The aim of our study was to investigate potential metabolic factors that may be associated with the induction of the sOB-R release from its membrane receptor. MATERIALS AND METHODS: Twenty-five children (aged between 1.5 and 17.0 years) were studied at the onset of T1DM. Blood samples were collected before (n = 25), during the first 18 h (mean +/- S.D. 11.1 +/- 4.3 h, n = 16) and 92 h (47.5 +/- 22.5 h; n = 14) after beginning insulin therapy. Serum sOB-R and leptin levels were determined by in-house immunoassays. RESULTS: The sOBR-level and the molar sOB-R/leptin ratio were significantly higher before than after starting insulin treatment (P < 0.05). In contrast, leptin levels were significantly lower (P < 0.05) before insulin therapy. The correlation between sOB-R and blood glucose (r = 0.49; P < 0.05), as well as sOB-R with parameters of ketoacidosis, such as pH (r = -0.72), base excess (r = -0.70), and bicarbonate (r = -0.69) (P < 0.0001) at diagnosis of T1DM remained significant during the first 18 h of insulin treatment. Multiple regression analysis revealed that base excess predicted 41.0% (P < 0.001), age 16.4% (P < 0.05), and height SDS 13.9% (P < 0.01) of the sOB-R variance. CONCLUSIONS: Metabolic decompensation in children with new onset T1DM is associated with dramatic changes of the leptin axis; serum levels of sOB-R are elevated and of leptin are reduced. The molar excess of sOB-R over leptin (median 11.3) in this condition may contribute to leptin insensitivity. Upregulation of the soluble leptin receptor appears to be a basic mechanism to compensate for intracellular substrate deficiency and energy-deprivation state.

Adolescent↗
PubMed2005

Serum resistin levels of obese and lean children and adolescents: biochemical analysis and clinical relevance.

OBJECTIVE: It was hypothesized that resistin links obesity with diabetes, but this has not been studied in children and adolescents to date. PATIENTS: We determined serum resistin levels of 135 obese (body mass index, 32.0 +/- 6.2 kg/m2; age, 12.6 +/- 3.4 yr) and 201 lean children (body mass index, 18.7 +/- 2.4 kg/m2; age, 12.5 +/- 2.5 yr) by a newly developed and extensively evaluated in-house immunoassay. These results were controlled for their association with markers of puberty, obesity, and insulin sensitivity. RESULTS: The analytical evaluation of our assay revealed different resistin isoforms with major peaks of higher than 660 and 55 kDa in the size exclusion chromatography. Using this assay system we found no difference in the resistin levels of obese compared with lean subjects (P = 0.48). However, resistin was significantly higher in girls than in boys (6.74 +/- 2.42 vs. 5.79 +/- 2.45; P < 0.001). Interestingly, in both obese and lean children, resistin correlated with age (P < 0.01), Tanner stage, and testosterone and estradiol levels (P < 0.05). In contrast, no significant correlation was found with parameters of insulin resistance such as homeostasis model assessment, insulin sensitivity index, or insulin, proinsulin, and glucose concentrations in obese subjects. CONCLUSIONS: Resistin appears to be not the main link between obesity and insulin resistance in children and adolescents but because of its association with Tanner stage, it may be related to the maturation of children during pubertal development. Additionally, we have demonstrated the presence of different molecular isoforms of resistin in human blood, and this may raise problems in comparing data from diverse assay systems.

Adolescent↗
PubMed2005

Inverse changes in the serum levels of the soluble leptin receptor and leptin in neonates: relations to anthropometric data.

We aimed to evaluate the role of the soluble leptin receptor (sOB-R), the major leptin-binding protein in blood, for the regulation of growth and development of neonates. Therefore, human arterial and venous cord blood samples were taken from newborns of 45 healthy mothers to investigate correlations with anthropometric data. Furthermore, we compared changes in sOB-R and leptin in neonatal serum between postnatal d 1, 3, and 5. Cord blood levels of leptin (direct correlation) and the molar sOB-R/leptin ratio (inverse correlation) correlated significantly (P < 0.05) with weight, triceps, biceps, iliacal, and subscapular skinfolds at birth as well as on d 3 and 5 of life. During the first week of life, median leptin levels decreased significantly (P < 0.001) from 3.4 ng/ml in venous cord blood to 2.2 ng/ml in venous blood on d 1 after birth to 0.88 ng/ml on d 3 and 0.75 ng/ml on d 5. In contrast and most interestingly, median levels of sOB-R increased significantly (P < 0.001) from 14.5 ng/ml in cord blood to 18.9 ng/ml on d 1, 83 ng/ml on d 3, and 79.4 ng/ml on d 5. Consequently, the molar sOB-R/leptin ratio increased from 0.45 to 1.30 (d 1), 10.5 (d 3), and 13.7 (d 5) during the same period (P < 0.001). We found a remarkable postnatal change in the leptin-sOB-R axis with decreasing leptin and increasing sOB-R levels. Hence, the sOB-R may block leptin function by its competition with the membrane receptor for the ligand. These suppressive effects may be an important stimulus for energy uptake in the first week of life or in other conditions with a high energy demand.

Adolescent↗
PubMed2005

Circulating soluble leptin receptor, leptin, and insulin resistance before and after weight loss in obese children.

OBJECTIVE: To study the relationships between leptin, soluble leptin receptor (sOB-R), and insulin resistance in obese children before and after weight reduction. METHODS: We determined fasting serum leptin, sOB-R, and insulin resistance index (Homeostasis model assessment (HOMA)) in 36 obese children at baseline and 1 y later and compared them to 72 lean children matched for age, gender, and pubertal stage. The changes of leptin (Deltaleptin) and sOB-R (DeltasOB-R) over the 1 y period were correlated to the changes of HOMA (DeltaHOMA), the changes of weight status, and the changes of percentage body fat (Delta%BF) based on skinfold measurements. Multiple linear regression analyses were conducted for the dependent variables Deltaleptin and DeltasOB-R, including DeltaBMI and DeltaHOMA as independent variables adjusted for age, gender, and pubertal stage. Changes of leptin and sOB-R levels were analyzed in 11 obese children after they had lost weight substantially (decrease SDS-BMI>0.5) and compared to 11 obese children without substantial weight loss matched for age, gender, and pubertal stage. RESULTS: Obese children showed significantly (P<0.001) higher leptin and lower sOB-R levels. Deltaleptin correlated significantly to DeltaSDS-BMI (r=0.28, P<0.05), Delta%BF (r=0.44, P<0.05), and DeltaHOMA (r=0.42, P<0.01), while DeltasOB-R correlated significantly to DeltaSDS-BMI (r=-0.42, P<0.01) and Delta%BF (r=-0.47, P<0.01), but not to DeltaHOMA. In contrast to DeltasOB-R, Deltaleptin correlated significantly to DeltaHOMA (P=0.02) in multiple linear regression analysis. Substantial weight loss led to a significant increase in sOB-R (P=0.02) and to a decrease in HOMA (P=0.02). In children without substantial weight loss, there were no changes in sOB-R, while HOMA (P=0.04) and leptin (P=0.02) increased significantly. CONCLUSIONS: The decrease of sOB-R and the increase of leptin levels in obese children normalized after weight loss. Therefore, these changes are consequences rather than the cause of overweight. In contrast to sOB-R, leptin levels are associated with insulin resistance.

Adolescent↗
PubMed2005

Association of interleukin-6, C-reactive protein, interleukin-10 and adiponectin plasma concentrations with measures of obesity, insulin sensitivity and glucose metabolism.

Abnormal glucose tolerance is associated with subclinical chronic inflammation in patients with type 2 diabetes. The aim of this study was to investigate whether plasma concentrations of inflammatory markers are associated with measures of obesity, insulin sensitivity, and hyperglycemia. IL-6, adiponectin, CRP, and IL-10 plasma concentrations were evaluated in 142 patients with a wide range of obesity, insulin sensitivity and glucose tolerance. In parallel with the impairment of glucose tolerance, there was a significant increase in IL-6, and CRP, and a significant decrease in adiponectin and IL-10 plasma concentrations. There were significant correlations between the plasma concentrations of all inflammatory markers and % body fat, insulin sensitivity, and fasting plasma glucose. However, multivariate linear regression analysis identified insulin sensitivity as determined by glucose infusion rate during the steady state of an euglycemic-hyperinsulinemic clamp as the strongest predictor of adiponectin, CRP, IL-6, and IL-10 plasma concentrations. In addition, fasting plasma glucose was a significant determinant of adiponectin, CRP, and IL-6 plasma concentrations, whereas body fat content was only a significant predictor of CRP plasma concentration. In conclusion, our data suggest that abnormal inflammatory markers in patients with type 2 diabetes are primarily related to decreased insulin sensitivity.

Adiponectin↗
PubMed2005

Resistin gene 3'-untranslated region +62G-->A polymorphism is associated with hypertension but not diabetes mellitus type 2 in a German population.

OBJECTIVES: Resistin, a peptide hormone produced by adipocytes, has been associated with diabetes mellitus type 2 (DM-2) in some rodent models. In humans the exact function of resistin remains unknown. Some, but not all studies have found associations between polymorphisms in the resistin gene with DM-2. Recently a 3'-untranslated region +62G-->A polymorphism of the resistin gene has been associated with decreased risk for DM-2 and for hypertension in diabetics in a Chinese population. Purpose of the present study was to examine for the first time in a German Caucasian population the possible association between this polymorphism and DM-2, hypertension, lipoprotein levels, resistin levels as well as atherosclerosis. DESIGN, SETTING AND SUBJECTS: A total of 818 subjects participated in the study. The presence of the +62G-->A polymorphism of the resistin gene was investigated using polymerase chain reaction-restriction fragment length polymorphism in 384 subjects with DM-2 [224 men, 160 women, age 63.4 +/- 10.6 years, body mass index (BMI) 28.7 +/- 5.1 kg m(-2)] and in 434 nondiabetic age- and sex-matched control subjects (248 men, 186 women, age 64.4 +/- 6.5 years, BMI 26.5 +/- 3.7 kg m(-2)). RESULTS: Thirty-four subjects were found to be carrying the +62G-->A polymorphism in the control and 24 in the diabetic group (allelic frequencies 4% and 3.2% respectively). Subjects with DM-2 were not found to have a different frequency of the genotypes (93.75% and 6.258%, for GG:GA/AA respectively) than the control subjects (92.2% and 7.8% for GG:GA/AA respectively) (OR 0.75, 95% CI 0.44-1.3, P = 0.31). In the total cohort, carriers of the A allele had a higher prevalence of hypertension (OR 1.82, 95% CI 1.03-3.21, P = 0.039). When analysed separately, the control group showed a strong association between the presence of the A allele and hypertension (OR 2.92, 95% CI 1.38-6.15, P = 0.005), whilst no such association could be established in the diabetic group (OR 1.05, 95% CI 0.43-2.54, P = 0.92). Multiple regression analysis confirmed that the presence of the A variant is associated with hypertension in control but not in diabetic subjects, independent of age and BMI. The polymorphism had no significant influence on the presence of atherosclerotic disease, BMI, and on triglyceride, HDL and LDL cholesterol levels, both, in the control and the diabetic groups. There was no difference in the serum resistin levels between the 62G-->A variant carriers and noncarriers. CONCLUSIONS: In conclusion, the present data suggest that in a German Caucasian population the +62G-->A polymorphism of the resistin gene is associated with hypertension but not with DM-2.

Aged↗
PubMed2005

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↗
PubMed2004

Plasma levels of transforming growth factor-1beta and alpha2-macroglobulin before and after radical prostatectomy: association to clinicopathological parameters.

BACKGROUND: To study the levels of transforming growth factor-1beta (TGF-beta1) and of alpha2-macroglobulin (alpha2-M), a high affinity binding protein of TGF-beta1, in comparison to prostate-specific antigen (PSA) in prostate cancer (PCa) patients before and up to 12 months after prostatectomy, and to correlate the results with clinicopathological parameters. METHODS: Eighty-one patients who underwent radical prostatectomy for PCa were included in this study. Pre- and postoperatively, plasma levels of TGF-beta1, alpha2-M and PSA were measured in the same samples by ELISA, and were correlated with pathological parameters and clinical outcomes. RESULTS: The preoperative TGF-beta1 levels were significantly elevated as compared to the controls; they showed a positive correlation with the Gleason score. Patients with initial androgen-deprivation therapy had lower TGF-beta1 levels than untreated patients. Elevated concentrations of TGF-beta1 levelled off 12 months after prostatectomy approaching values of healthy individuals. Decreased plasma levels of total and transformed alpha2-M (proteinase-complexed form) were observed in PCa. Preoperative levels of TGF-beta1 but not of alpha2-M seem to be influenced by the body mass index (BMI). CONCLUSIONS: Elevated TGF-beta1 and decreased alpha2-M were consistently found in patients with PCa, and may be considered as risk factors for tumor development and progression. In comparison to PSA, the TGF-beta1 levels displayed a slow decline after radical prostatectomy; this indicates that TGF-beta1 is mainly produced outside the prostatic tissue. Since TGF-beta1 levels are influenced by the BMI, this indicates that PCa might be sensitive to diet.

Aged↗
PubMed2004

Priming with testosterone enhances stimulated growth hormone secretion in boys with delayed puberty.

BACKGROUND AND OBJECTIVE: Tests for growth hormone (GH) deficiency are not always helpful in the differential diagnosis of physiological delay of growth and puberty and GH deficiency. PATIENTS AND METHODS: To enhance diagnostic specificity, we used a single dose testosterone priming before repeating the arginine stimulation test in 26 boys with short stature and only early signs of puberty who failed to show an adequate response of serum GH in the first test. RESULTS: 77% (20/26 patients) increased their serum GH peak to more than 10 ng/ml, whereas six patients were still below this concentration. CONCLUSION: We propose that testosterone priming is a useful tool to distinguish between physiological delay of growth and puberty and GH deficiency and should be included in the diagnostic procedure.

Adolescent↗
PubMed2004

Increased serum soluble leptin receptor levels in children and adolescents with type 1 diabetes mellitus.

OBJECTIVE: We investigated whether or not serum levels of the soluble leptin receptor (sOB-R) and leptin are related to anthropometric and metabolic changes during pubertal development of children and adolescents with type 1 diabetes mellitus. DESIGN AND METHODS: Blood levels of sOB-R, leptin and HbA1C, as well as body-mass index (BMI), diabetes duration and daily insulin doses, were determined in 212 (97 girls; 115 boys) children with type 1 diabetes mellitus and compared with the sOB-R serum levels in 526 healthy children and adolescents. RESULTS: OB-R serum levels and parallel values of the molar ratio between sOB-R and leptin were significantly higher in children with diabetes than in normal children (P<0.05) in almost all investigated Tanner stages. Furthermore, in the entire group of patients, we demonstrated statistically significant correlations (P<0.02) between sOB-R and the duration of diabetes (r=0.30), HbA1c levels (r=0.32) and the insulin dose (r=0.18). Multiple-regression analysis revealed that HbA1c (12.4%), height (7.9%) and duration of diabetes (8.7%) contributed to 29% variance of sOB-R in diabetic children. CONCLUSIONS: Our data suggest that poor glycemic control in diabetes may lead to increased serum levels of sOB-R. This regulation of sOB-R appears to be independent of leptin, but may have an impact on leptin action. The consequently developing molar excess of sOB-R related to leptin could reduce leptin sensitivity and may, therefore, influence leptin-related anthropometric and metabolic abnormalities.

Adolescent↗
PubMed2003

Potential parameters for the detection of hGH doping.

The aim of our hGH application study with non-competitive athletes was the investigation of selected serum parameters from different processes affected by hGH. Fifteen athletes (age 21-33, mean 24) were treated with 0.06 IU hGH/kg BW per day or placebo (10 hGH, 5 placebo) respectively for 14 days. Blood samples were taken prior to, during and until 10 weeks after treatment. The concentrations of the following markers were determined in relevant serum samples: IGF-I, IGFBP-3, ALS, PIIINP, PINP, osteocalcin, and leptin. The IGF-I concentration increased rapidly within the hGH treatment group and showed significantly higher levels compared to baseline even 3 days after application. The response of the IGFBP-3 to the hGH applications was lower in comparison to IGF-I. The hGH group showed an increasing IGFBP-3 compared to baseline from day 4 till day 15. The response of PIIINP to hGH is clearly delayed compared to the IGF-I axis, but the PIIINP concentration remains on an increased level for a longer period (from day 4 until day 21). The time course and the extent of response varied strongly interindividually. PINP and osteocalcin showed only a small response to hGH applications. These parameters are characterised by a strong scattering of base values compared with the small response. In the hGH treatment group very different leptin concentrations were found at the beginning of the study, but after treatment decreasing leptin levels were observed in all cases. The determination of only one parameter will not be sufficient for detection of hGH abuse. A combination of markers by mathematical methods can be helpful to distinguish between placebo and hGH-treated athletes. By using the suggested discriminant function the data sets of hGH and placebo-treated athletes could be separated without false positive results.

Adult↗
PubMed2003

The soluble leptin receptor is crucial for leptin action: evidence from clinical and experimental data.

OBJECTIVE: The soluble leptin receptor (sOB-R) was recently identified as the main leptin-binding protein in human blood. The aim of our study was to elucidate the effects of physiologically relevant amounts of sOB-R on leptin-induced proliferation in a cell model. SUBJECTS AND MEASUREMENTS: To determine molar ratios between sOB-R and leptin in vivo, we measured both parameters in the serum of 529 healthy children and adolescents. For our in vitro cell model, mouse pre-B cells, transfected with the long form of the murine leptin receptor (BAF3/L46), were incubated with recombinant human leptin at two different basal levels (0.5 and 0.1 nM) and with the sOB-R at varying levels. The proliferative response of the cells was quantified by a (3)H-thymidine uptake assay. RESULTS: Significantly higher molar sOB-R/leptin ratios were observed during the first years of life, up to a 7.67-fold excess of sOB-R (quartiles: 4.43/10.27) in boys, compared to the states of prepuberty and puberty. An up to 10-fold molar excess of the sOB-R, reflecting the in vivo situation, resulted in a significant suppression of leptin action in the cell model. In contrast, gradually decreasing ratios of lower than two, as calculated during the progression of childhood and in early puberty, corresponded to proliferative rates in vitro as determined at basal leptin concentrations. CONCLUSION: At a distinct molar excess, sOB-R may suppress leptin action through inhibition of specific leptin binding to membrane-bound receptors in vitro. In vivo, sOB-R may further function to delay leptin clearance and increase the available leptin pool in the circulation. In the case of a massive excess of sOB-R, is it likely to be inhibitory to leptin interaction with the tissue membrane-bound OB-R.

Adolescent↗
PubMed2003

Relative abundance of growth hormone receptor isoforms in rhesus monkey tissues and human transformed lymphocytes.

The growth hormone receptor (GHR) is expressed as one active, full-sequence isoform and one truncated, inactive one that lacks the intracellular signaling domain. The aim of this study was to investigate the variation in the tissue expression of the full and truncated mRNA and protein. Epstein-Barr virus-transformed human B lymphocyte lines were established from 9 normal individuals with a height standard deviation score (SDS) of - 0.1 +/- 1.1 (mean +/- SD). Tissues were also collected from 3 Rhesus monkeys, whose GHR has 94.1 % homology with the human molecule. mRNA quantitation was determined by Real Time Quantitative PCR. Growth hormone receptor expression in transformed lymphocytes was also studied by fluorescence-activated cell sorter analysis. Both isoforms were expressed in transformed lymphocytes, but individual variation in the relative mRNA expression was small (truncated isoform percentage of total receptor mRNA: 17.1 +/- 4.4, mean +/- SD). There was no correlation between donors' height SDS and the expression of either isoform or the ratio between them. Protein expression by FACS analysis showed wider variation among the subjects; however, the relative ratio was similar in all the subjects. In monkey tissues, the truncated receptor showed a tissue-specific distribution. In conclusion, the expression of both isoforms in transformed lymphocytes from normal subjects shows small differences at the RNA or protein levels, and does not correlate with height SDS. Growth hormone splice isoforms show tissue specificity, suggesting local regulation of splicing. Tissues with relatively high expression of the truncated isoform are likely to be more resistant to the effects of GH due to the dominant negative effect of this isoform. In addition, the differential tissue expression might influence the levels of growth hormone binding protein in the immediate milieu of each tissue.

Adult↗
PubMed2003

Transcriptional and translational regulation of the splicing isoforms of the growth hormone receptor by glucocorticoids.

Glucocorticoids exert multiple effects on the growth hormone IGF-I axis. The GH receptor is expressed as an active, full-sequence molecule and a truncated, inactive one that lacks the intracellular signaling domain. We used the HuH7 human hepatoma cell line to investigate the effect of glucocorticoids on growth hormone receptor mRNA and protein expression. cDNA quantification was performed by Real Time Quantitative PCR. Growth hormone receptor expression at the protein level was studied by fluorescence-activated cell sorter analysis using specific polyclonal antibodies raised against the two isoform unique C-terminal sequences. Cells were treated with pharmacologic doses of dexamethasone (Dex 10 -7 - 10 -5 M) to assess its acute (1 hour or overnight) and chronic effects (7 days). Dex induced a dose-dependent increase of both the full (427 %) and truncated (180 %) mRNAs. At the protein level, Dex upregulated the full sequence more (183 %) than the truncated (126 %) protein. For a better understanding of this regulation system, cells were incubated with Dex 10 -6 M for 24 h in the absence or presence of a transcriptional inhibitor, actinomycin D, or a translational inhibitor, cycloheximide. Actinomycin D had no effect on Dex-induced upregulation, while cycloheximide blocked the truncated mRNA but not the full sequence mRNA upregulation, suggesting that this effect of glucocorticoids is a post-transcriptional event. After 7 days of chronic treatment, Dex induced a dose-dependent downregulation of the active receptor without any changes in the expression of the truncated isoform either at the mRNA or protein levels. We conclude that short-term glucocorticoid treatment results in an enhancement of the growth hormone receptor expression, while long-term treatment has a suppressive effect, through both transcriptional and translational mechanisms ultimately influencing both isoforms of the receptor.

Alternative Splicing↗
PubMed2003

A novel leptin receptor variant with a conservative amino acid substitution (I359 V) in body weight selected and unselected mouse lines.

Recently published results revealed linkage of obesity traits to a chromosomal region near the leptin receptor gene (Lepr) locus in high body weight selected big and fat DU6i mice. The purpose of this study was the search for variants of the Lepr gene in selected and unselected mouse lines as a candidate for different body composition traits. The complete Lepr cDNA sequence was analysed in DU6i mice. In addition, body weight, abdominal fat weight and serum leptin levels were measured in 42 day old, male mice of the strains DU6i, DUKs, Him : OF1 and DBA/2. Sequence comparison to the published wild type sequence revealed three silent mutations and an amino acid exchange (I359 V) in the C2 domain of the putative leptin binding site in the line DU6i. Compared to the high body weight selected mice also unselected lean control DUKs mice and Him : OF1 mice harbour the amino acid substitution, although they show significantly lower values for body weight, abdominal fat weight and serum leptin levels. Therefore, we assume that the mutation in the C2 domain of Lepr alone might not result in impaired leptin binding or signaling.

Amino Acid Sequence↗