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Biomedical subjects

J Kratzsch

Publications and source records attributed to J Kratzsch.

At least 73 records · Page 4Linked to original sources
PubMed1998

Human leptin forms complexes with alpha 2-macroglobulin which are recognized by the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein.

OBJECTIVE: To identify binding proteins of leptin in human plasma. METHODS: Binding was evaluated by electrophoresis, size exclusion chromatography (SEC), Western blotting, and radioisotope labeling. Quantification of leptin and the different forms of alpha2-macroglobulin (alpha2-M) was performed by ELISA. RESULTS: Leptin interacts with the proteinase inhibitor, alpha2-M. 125I-labeled leptin specifically binds to the transformed inhibitor, which arises by reaction with proteinases or with reactive primary amines. No leptin binding was observed to the native alpha2-M, which abundantly occurs in plasma. The complex formation between leptin and alpha2-M was found to proceed within minutes and was stable, as it resisted separation by SEC and electrophoresis. The Kd of the complex was 2.14 +/- 0.78 micromol/l. Complex formation with transformed alpha2-M did not interfere with the immunological determination of leptin in plasma. The leptin-alpha2-M complex was found to be recognized by the alpha2-M receptor/low density lipoprotein receptor-related protein. By computer analysis, a simple model is presented showing that the degree of transformation of alpha2-M may significantly influence the leptin concentration in blood. CONCLUSIONS: The proteinase inhibitor, alpha2-M, may act as a leptin-binding protein in human plasma. Binding of leptin to transformed alpha2-M and its rapid clearance by the alpha2-M receptor may significantly influence the bioavailability of leptin in human plasma.

Adult↗
PubMed1997

Increased serum GHBP levels in obese pubertal children and adolescents: relationship to body composition, leptin and indicators of metabolic disturbances.

OBJECTIVE: The serum concentration of the high-affinity growth hormone-binding protein (GHBP) is increased in obesity but the mechanisms are poorly understood. This study assessed the physiological mechanisms involved in the regulation of GHBP in adiposity. SUBJECTS AND MEASUREMENTS: We tested a number of obesity specific parameters for their association with GHBP. In this study, 199 normal or overweight children and adolescents (101 boys, 98 girls, aged (mean +/- s.d.): 13.7 +/- 2.3 y) underwent an anthropometric evaluation (circumference measurements and bioimpedance analysis) combined with blood withdrawal for the measurement of insulin-like growth factor-I (IGF-I), insulin, leptin and GHBP (by specific RIA), uric acid, triglycerides and cholesterol. RESULTS: By linear regression analysis GHBP correlated significantly (P < 0.001) with percent body fat mass (r = 0.71), waist (r = 0.73) and hip (r = 0.69) circumference, weight (r = 0.61) waist hip ratio (WHR) (r = 0.54), as well as with the serum concentrations of leptin (r = 0.64), uric acid (r = 0.54), insulin (r = 0.45), LDL-cholesterol (r = 0.43), cholesterol (r =0.33), LDL/HDL ratio (r = 0.47), triglycerides (r = 0.30) and with height standard deviations scores (SDS) (r = 0.23). Age, gender and pubertal stage had no impact on GHBP. In a multiple regression analysis containing age and gender, as well as the anthropometric variables, percent fat mass and waist circumference, as independent variables, associations between GHBP and leptin (P < 0.001), cholesterol (P < 0.01), LDL-cholesterol (P = 0.01), LDL/HDL ratio (P = 0.02), triglycerides (P = 0.01) remained significant. In a final model using the stepwise analysis involving age, gender and all the independent predictors of GHBP, waist circumference (P < 0.001), accounted for 49.5% of the 60.0% total variability in GHBP, while the implication of leptin (P < 0.001), age (P < 0.01) and cholesterol (P < 0.05) increased the predicted variability for 7.5%, 1.9%, and 1.0%, respectively. Serum GHBP was significantly reduced in a subgroup of 104 overweight or obese patients during a diet-induced weight loss programme, the coefficient of correlation between GHBP and leptin after (r = 0.45, P < 0.001) and before weight reduction (r = 0.41, P < 0.001) were comparable. CONCLUSION: Waist circumference, an indicator of abdominal body fat mass, is a major determinant of GHBP levels during childhood, while leptin may be one candidate for a signal linking adipocytes to the growth hormone receptor related GHBP release. Additionally, elevated serum levels of GHBP may reflect metabolic disturbances of adiposity.

Adolescent↗
PubMed1997

Measurement of serum exon 3-retaining growth hormone-binding protein in children and adolescents by radioimmunoassay.

Recently described assays for the determination of growth hormone-binding protein (GHBP) show a wide variety of normal ranges. Their results depend on the assay design and in the case of ligand-immunofunctional assay (LIFA), probably also on the binding characteristics, i.e. epitope specificity and affinity of the employed antibody. These facts underline the necessity to look for more accurate and specific assays. In this report we describe an accurate and simple radioimmunoassay (RIA) which allows the specific quantitation of the exon 3-retaining GHBP isoform (E3-GHBP). Data of the E3-GHBP RIA were compared to those of a LIFA measuring undifferentiated functional forms of GHBP. Our results demonstrate significant relationships between GHBP and age, BMI and IGF-I as determined by RIA and by LIFA in normal children and adolescents (n = 115, p < 0.001). Moreover, BMI is the only regulating factor of GHBP for both methods as shown by multiple regression analysis (p < 0.001). All our data suggest a qualitatively paralleled regulation of E3-GHBP and undifferentiated functional GHBP forms. This finding was confirmed by a good correlation between RIA and LIFA data (r = 0.74, p < 0.001). Children with idiopathic short stature (ISS, n = 47) had significantly lower GHBP levels than normal controls (n = 58) measured by the E3-GHBP RIA (p < 0.0001) and by LIFA (p < 0.01). We conclude that (1) ISS children may have a structural or quantitative defect at the level of the GHR, and (2) the highly specific assay for E3-GHBP immunoreactivity provides a sensitive diagnostic tool in conditions with partial GH insensitivity.

Adolescent↗
PubMed1996

Growth hormone-binding protein related immunoreactivity is regulated by the degree of insulinopenia in diabetes mellitus.

OBJECTIVE: Derangements in the GH/IGF axis are common in patients with diabetes mellitus. In insulin-dependent diabetes mellitus (IDDM), these disturbances seem to be due to a partial defect in GH action on its own receptor or via a post-receptor defect. In non-insulin-dependent diabetes mellitus (NIDDM), data are limited, and the regulation of the GH receptor (GHR) remains unclear. However, animal studies with diabetic rats demonstrated that the GHR density may be influenced by insulin disposal at the hepatocyte. With respect to this hypothesis we studied the relation between peripheral insulin status and the serum GH-binding protein (GHBP), which reflects indirectly the GHR density in the tissues. Patients with IDDM were compared to a NIDDM group as well as to a group of healthy subjects. DESIGN AND PATIENTS: Basal blood samples for the determination of serum GHBP, GH, and IGF-I were obtained from patients with IDDM (n = 27), subjects with NIDDM (n = 112) and healthy controle (n = 42). Insulin, proinsulin, C-peptide and IGF-binding protein 1 (IGFBP-1) serum levels were used to estimate the insulin status in diabetic patients. RESULTS: GHBP serum levels were significantly lower in patients with IDDM than in either NIDDM or controls (P < 0.001). Conversely, the IGF-I levels were reduced in both groups of diabetics. A subgroup of hypoinsulinaemic NIDDM patients showed significantly decreased GHBP concentrations (P < 0.05) compared to the NIDDM sub-group with hyperinsulinaemia. Furthermore, GHBP levels were significantly decreased in insulin-treated patients with NIDDM compared to either non-insulin-requiring subjects or normal controls (P < 0.05). A significant direct relation was found between levels of GHBP and total insulin dose (P < 0.01) in patients with IDDM. In the NIDDM group, GHBP was correlated with proinsulin (P < 0.001), C-peptide (P < 0.01), Insulin (P < 0.05) and inversely with IGFBP-1 (P < 0.001). Multiple linear regression analysis indicated a significant contribution of proinsulin and IGFBP-1 to the variation of GHBP. CONCLUSIONS: Decreased GHBP levels in IDDM as well as in NIDDM correlate with insulinopenia. Since the degree of insulinopenia depends on the capability of the beta-cells to secrete proinsulin, C-peptide and insulin, we hypothesize that these hormones at least partially influence the serum level of GHBP. Low GHBP levels may reflect a reduced GH receptor density and a concomitant GH insensitivity, which leads to an impaired IGF generation in insulin-deficient patients.

Adult↗
PubMed1996

Insulin-like growth factor-I and alpha 2-macroglobulin in seminal plasma correlate with semen quality.

Insulin-like growth factor-I (IGF-I) and alpha 2-macroglobulin (alpha 2-M) are believed to be involved in the development of germ cells. IGF-I is mainly controlled by concentrations of human growth hormone (HGH), influences cell proliferation and differentiation and its action is mediated by insulin-like growth factor-binding proteins (IGFBP), placental protein 14 (PP14) and prostate-specific antigen (PSA). alpha 2-M acts as a broad spectrum proteinase inhibitor and a binding protein for many cytokines and hormones, e.g. inhibin and activin. This study was designed to identify concentrations of these molecules in seminal plasma in normal semen samples of healthy men, correlations with semen quality, the relationship of IGF-I and alpha 2-M with factors affecting male fertility, and whether vasectomy influences the concentrations of these molecules. Concentrations of IGF-I and alpha 2-M in human seminal plasma were related to semen quality, basal concentrations of HGH, testosterone, IGFBP-3, soluble fibronectin receptor (sFNR), PSA and PP14 in seminal plasma and to serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Commercially available assays were used to analyse 69 semen samples of various quality and 11 post-vasectomy samples. IGF-I concentrations in seminal plasma were significantly correlated with the percentage of morphologically normal spermatozoa (r = 0.748, P = 0.00001) and sperm concentration (r = 0.301, P = 0.011), but negatively correlated with serum FSH (r = -0.506, P = 0.00006) and PSA in seminal plasma (r = -0.388, P = 0.00009). Total alpha 2-M was significantly correlated with sperm count (r = 0.423, P = 0.0005), percentage of progressively motile spermatozoa (r = 0.444, P = 0.00019), quality of motility (sperm motile efficiency, r = 802, P = 0.00001) and straight line velocity (r = 0.411, P = 0.0013). Correlation between the sperm concentration and HGH in seminal plasma was weak (r = 0.287, P = 0.015). Vasectomy reduced the concentration of total alpha 2-M (P = 0.00008) and HGH (P = 0.0068) in the seminal plasma; IGF-I was also reduced after vasectomy when the total ejaculate amount was considered. Thus IGF-I and alpha 2-M are significant for the germ cell development: IGF-I in the maturation of spermatozoa and alpha 2-M in progressive motility.

Follicle Stimulating Hormone↗
PubMed1996

Transformed alpha 2-macroglobulin as a low-affinity growth hormone-binding protein.

Human growth hormone (GH) forms complexes with the purified proteinase inhibitor, alpha 2-macroglobulin (alpha 2-M). This inhibitor occurs in two different forms in serum, known as native and transformed alpha 2-M. It has been clearly demonstrated, using chromatography and electrophoresis combined with autoradiography, that human GH binds specifically to the transformed inhibitor and not to the native protein. The binding was characterized as being mainly non-covalent and involved specific binding sites present only in the transformed inhibitor molecule. Binding analysis, using an immunoprecipitation technique, revealed that GH possesses two different types of binding sites, with dissociation constants of 0.49 +/- 0.12 mumol/l and 61 +/- 8 mumol/l for the high- and low-affinity binding site, respectively. Distribution analysis of 125I-labelled GH in whole plasma suggests that the hormone is bound to two different proteins: first, to the high-affinity GH-binding protein (GHBP) and, second, to the low-affinity GHBP, identified as transformed alpha 2-macroglobulin.

Carrier Proteins↗
PubMed1995

Regulation of growth hormone (GH), insulin-like growth factor (IGF)I, IGF binding proteins -1, -2, -3 and GH binding protein during progression of liver cirrhosis.

The aim of this study was to investigate the regulation of various proteins of the GHIGF axis during progression of liver failure and to search for potential prognostic markers of functional hepatic reserve. Serum levels of growth hormone (GH) and high affinity growth hormone binding protein (GHBP), insulin-like growth factor I (IGF-I) and IGF binding proteins (IGFBP) -1, -2 and -3 were determined in patients with liver cirrhosis. A continuous decline in the concentrations of IGF-I, IGFBP-3 and serum GH-binding activity (GHBP) was observed during progression of cirrhosis and the data correlated significantly with choline esterase, total serum protein and the Child score. In addition, GHBP showed a significant correlation with the enzymatic activity of glutamate dehydrogenase or transaminases and seems so to be influenced by the degree of liver cell damage. In contrast, IGFBP-1 and IGFBP-2 levels were significantly elevated in preterminal disease suggesting an upregulatory mechanism is still effective in this situation. Only when liver function had markedly deteriorated, the serum levels of these two parameters decreased again, possibly due to an impaired synthesis. The excellent correlation between the serum levels of IGF-I (r = -0.64, p < 0.001) or IGFBP-3 (r = -0.67, p < 0.001) and the Child score index suggests that they reflect the hepatic functions just as conventional indicators. For an appropriate interpretation of the liver function the measurement of the growth related peptides can be a valuable tool to estimate pathological alteration in the functional hepatic reserve or in the glucose homeostasis.

Adolescent↗
PubMed1995

Identification of transformed alpha 2-macroglobulin as a growth hormone-binding protein in human blood.

We have found that the human GH forms complexes with the purified proteinase inhibitor, alpha 2-macroglobulin. This inhibitor occurs in two different forms in human blood, known as native and transformed alpha 2-macroglobulin. It could be clearly demonstrated by chromatography and electrophoresis combined with autoradiography that the GH binds specifically to the transformed inhibitor, but not to the native protein. The binding was characterized as being mainly noncovalent to specific binding sites present only in the transformed inhibitor molecule. Binding analysis using antibody precipitation technique revealed two different classes of binding sites with dissociation constants of 0.49 +/- 0.12 and 61 +/- 8 mumol/L for high and low affinity binding sites, respectively. Distribution analysis of 125I-labeled GH in whole plasma suggested that the hormone is bound to different proteins: 1) to the high affinity GH-binding protein, and 2) to the low affinity GH-binding protein identified as transformed alpha 2-macroglobulin.

Chromatography, Gel↗
PubMed1995

Growth hormone-binding protein-related immunoreactivity in the serum of patients with acromegaly is regulated inversely by growth hormone concentration.

In this report we describe a newly developed radioimmunoassay (RIA) for the determination of the high-affinity growth hormone-binding protein (GHBP) in human blood. Using this RIA for the measurement of GHBP in serum of 29 patients with acromegaly, decreased concentrations were found compared to the normal range, depending on the activity of the disease. Growth hormone-binding protein was correlated inversely to log GH (r = -0.7, p < 0.001). A weaker relationship was shown between the GHBP activity determined in a functional assay based on charcoal separation and log GH (r = -0.51, p < 0.01). While insulin-like growth factor I (IGF-I) and IGF binding protein 3 (IGFBP-3) were correlated directly to log GH (r = 0.77 and r = 0.66, p < 0.001), an inverse and weaker relationship was evident between GHBP measured by RIA and IGF-I or IGFBP-3 (r = -0.61 and r = -0.57, p < 0.01). In contrast, no correlation could be detected between data of the functional GHBP assay and IGF-I or IGFBP-3.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1993

Measurement of insulin-like growth factor I (IGF-I) in normal adults, patients with liver cirrhosis and acromegaly: experience with a new competitive enzyme immunoassay.

A competitive enzyme immunoassay for the determination of human insulin-like growth factor I in microtiter plates was established. Using a polyclonal antiserum raised in rabbits against hIGF-I ovalbumin conjugate the assay system was able to detect IGF-I at a range of 12-800 pg/well with a sensitivity of 10 pg/well. It showed a low (< 0.5%) cross reactivity with hIGF-II. The serum concentrations of IGF-I found by EIA agreed well with those found in a conventional RIA (r = 0.965, p < 0.001). Effects of age and sex on IGF-I levels were studied in 260 normal adults. There was no evidence for sex differences but a steep decline of values from the third to the fourth and from the eight to the ninth decade, respectively. To asses the diagnostic capability of the IGF-I determination in liver cirrhosis, 71 sera of patients classified according to Child classes (A-C) were measured. Although significantly diminished concentrations were found in class B vs A and in class C vs B, the diagnostic sensitivity in cross-sectional examinations proved to be low (class A: 0.33, class B: 0.67). Only in the case of extensively destroyed liver parenchyma (Child C: 0.94) IGF-I was a good indicator of impaired hepatocellular capacity. In 29 patients with acromegaly serum IGF-I levels were investigated. All patients with active acromegaly showed increased IGF-I levels. In contrast, in inactive or weakly active acromegaly values were considerably lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1993

Clinical studies of IGFBP-2 by radioimmunoassay.

A specific radioimmunoassay for human IGFBP-2 was developed using a polyclonal antiserum directed against a partial sequence (hIGFBP-2(176-190)). The tracer was prepared by radioiodination of a [Tyr]o-hIGFBP-2(176-190) derivative. The assay was used to study IGFBP-2 levels in numerous clinical and experimental situations. There was little circadian fluctuations of serum level which showed a marked age-dependence with high levels at birth and senescence and low levels during puberty. Decreased IGFBP-2 levels were present in untreated insulin-dependent diabetes mellitus (IDDM), in acromegaly and during dexamethasone suppression test. GH deficiency, fasting, IGF-I administration to patients with GH receptor deficiency, hepatic failure and insulinomas caused a moderate increase of serum IGFBP-2. Markedly elevated levels were found in chronic renal failure, non-islet cell tumour induced hypoglycemia and leukaemias. The fact that all possible relationships between insulin secretion and IGFBP-2 levels could be identified suggests that insulin is not a major regulator. In general, there was an inverse relationship with serum IGFBP-3 (except IDDM) and IGFBP-2 levels were high in situations where free IGF-II should be expected to be high. The tentative conclusion would therefore be that free IGF-II is a major regulator of circulating IGFBP-2.

Animals↗
PubMed1990

Stress-related changes of saliva cortisol in VDU operators.

In the field of work physiology, catecholamines and cortisol are used as strain indicators, because their production is increased in stressing work situations. Short-term stress cannot be ascertained by measuring catecholamines in urine. We studied the excretion of cortisol in saliva during short-term stress. We examined 77 healthy subjects who worked at a video display unit (VDU) for 30 min. They had to carry out a task with high speed and accuracy demands. Saliva specimens were taken before and after VDU work. Saliva cortisol levels were determined by means of a sensitive enzyme immunoassay (EIA). Additionally physiological parameters (heart rate, blood pressure, respiratory rate) and task performance were measured, and the subjects were asked about their feelings of stress and psychovegetative disorders. Saliva cortisol concentrations were significantly increased after 30 min of VDU work. Heart rate, blood pressure and respiratory rate were also increased during the task. In persons with high heart rate and blood pressure levels saliva cortisol increased significantly stronger during VDU work than in persons with lower heart rate and blood pressure levels. The results indicate that saliva cortisol is a useful strain indicator in short-term stress situations.

Adult↗
PubMed1990

A sensitive sandwich enzyme immunoassay for measurement of insulin on microtiter plates.

A sensitive enzyme immunoassay for the measurement of insulin in human sera on microtiter plates was established. The assay is based on the sandwich technique with guinea pig anti-insulin IgG adsorbed at microtiter plate wells, human insulin as standard and the same anti-insulin IgG labeled with horseradish peroxidase. Standards used cover a range from 0 to 1200 pmol/l with a detection limit of 10 pmol/l. Coefficients of variation between 3-7% for intraassay precision and 5-11% for interassay precision were obtained over the concentration range of 80-1000 pmol/l. The correlation of EIA-data with those of a commercially available double antibody radioimmunoassay (r = 0.98) could be expressed by the equation: EIA = 0.97 RIA - 57 pmol/l. Normal fasting serum insulin concentrations in healthy subjects ranged from 11-165 pmol/l. In subjects with potentially diminished basal values concentrations of 10-79 pmol/l were determined. The insulin response in oral glucose tolerance tests of children was discussed, who had a constitutional tall stature or Turner's syndrome, respectively.

Adult↗