Harald H Klein
Research interests
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InterestsDiabetes, Hypertension, Diabetes Complications, Obesity, Insulin Resistance, Neuroendocrine Tumors, Osteoporosis, Osteoporotic Fractures, Postmenopausal Osteoporosis, Rheumatoid Arthritis
Publications
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6.55Impact points
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6.55Impact points
The proteomic signature of insulin-resistant human skeletal muscle reveals increased glycolytic and decreased mitochondrial enzymes.
Diabetologia. 04/2012; 55(4):1114-27.
The molecular mechanisms underlying insulin resistance in skeletal muscle are incompletely understood. Here, we aimed to obtain a global picture of changes in protein abundance in skeletal muscle in obesity and type 2 diabetes, and those associated with whole-body measures of insulin action. Skeleta... [more] The molecular mechanisms underlying insulin resistance in skeletal muscle are incompletely understood. Here, we aimed to obtain a global picture of changes in protein abundance in skeletal muscle in obesity and type 2 diabetes, and those associated with whole-body measures of insulin action. Skeletal muscle biopsies were obtained from ten healthy lean (LE), 11 obese non-diabetic (OB), and ten obese type 2 diabetic participants before and after hyperinsulinaemic-euglycaemic clamps. Quantitative proteome analysis was performed by two-dimensional differential-gel electrophoresis and tandem-mass-spectrometry-based protein identification. Forty-four protein spots displayed significant (p < 0.05) changes in abundance by at least a factor of 1.5 between groups. Several proteins were identified in multiple spots, suggesting post-translational modifications. Multiple spots containing glycolytic and fast-muscle proteins showed increased abundance, whereas spots with mitochondrial and slow-muscle proteins were downregulated in the OB and obese type 2 diabetic groups compared with the LE group. No differences in basal levels of myosin heavy chains were observed. The abundance of multiple spots representing glycolytic and fast-muscle proteins correlated negatively with insulin action on glucose disposal, glucose oxidation and lipid oxidation, while several spots with proteins involved in oxidative metabolism and mitochondrial function correlated positively with these whole-body measures of insulin action. Our data suggest that increased glycolytic and decreased mitochondrial protein abundance together with a shift in muscle properties towards a fast-twitch pattern in the absence of marked changes in fibre-type distribution contribute to insulin resistance in obesity with and without type 2 diabetes. The roles of several differentially expressed or post-translationally modified proteins remain to be elucidated.
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1.13Impact points
Long-term graft function of cryostored alginate encapsulated rat islets.
European journal of medical research. 09/2011; 16(9):396-400.
Microencapsulation of pancreatic islets before transplantation is a promising approach to enable graft function in an immunocompetent recipient without immunosuppression. However, the insufficient availability of allogenic islet tissue is a major problem. One concept to overcome these shortcomings i... [more] Microencapsulation of pancreatic islets before transplantation is a promising approach to enable graft function in an immunocompetent recipient without immunosuppression. However, the insufficient availability of allogenic islet tissue is a major problem. One concept to overcome these shortcomings is the cryopreservation of encapsulated allogenic islets. Recently, we reported a gentle cryopreservation protocol for rat islets encapsulated in an alginate-based microcapsule system. Here, we report for the first time long-term transplantation data of these cryopreserved microencapsulated islets. We detected a stable graft function for more than 12 month (experiments still continuing) after transplantation of 2500 cryopreserved microencapsulated CD rat islets in streptozotocin-diabetic Wistar rats. Moreover, the glucose clearance rate during an IPGTT was well preserved up to 56 weeks after transplantation. In addition, hyperglycemic blood glucose levels after removal of rat islet grafts 12 and 56 weeks after transplantation confirmed the efficacy of the encapsulated islets. Finally, the retrieved encapsulated rat islets responded well with a 7-fold increase of insulin secretion to a glucose stimulus (12 and 56 weeks). In conclusion, our study demonstrates for the first time that cryopreservation of encapsulated rat islets is possible without substantial losses on graft function for a very long time.
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4.40Impact points
Protection from diabetes development by single-chain antibody-mediated delivery of a NF-κB inhibitor specifically to β-cells in vivo.
American journal of physiology. Endocrinology and metabolism. 04/2011; 301(1):E83-90.
Recently, we reported the generation of single-chain antibodies (SCAs) highly specific for rodent and human β-cells. Our current report describes the generation of a fusion protein of one of these SCAs (SCA B1) with a NF-κB essential modifier (NEMO)-binding domain (NBD) peptide, thereby creating a s... [more] Recently, we reported the generation of single-chain antibodies (SCAs) highly specific for rodent and human β-cells. Our current report describes the generation of a fusion protein of one of these SCAs (SCA B1) with a NF-κB essential modifier (NEMO)-binding domain (NBD) peptide, thereby creating a selective inhibitor of NF-κB activation in β-cells. The SCA B1-NBD fusion protein was cloned in the pIRES-EGFP, expressed in bacteria, and purified by metal affinity chromatography; the newly generated complex was then administered intravenously to rodents and evaluated for its ability to protect β-cells against cytokines in vitro and diabetogenic agents in vivo. First, it was shown clearly that our SCA B1-NBD fusion protein binds highly selective to CD rat β-cells in vivo. Second, we observed that SCA B1-mediated in vivo delivery of the NBD peptide completely blocked IL-1β + IFNγ- and TNFα + IFNγ-mediated induction of NF-κB as well as islet dysfunction in culture. Finally, repeated intravenous injection of SCA B1-NBD prior to multiple low-dose administration of streptozotocin in CD mice not only induced a striking resistance to diabetes development but also preserved β-cell mass. In conclusion, our data show for the first time that a SCA B1-NBD fusion peptide reliably protects β-cells against cytokines in vitro and allows protection from diabetes development in CD mice in vivo.
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0.34Impact points
[New differential therapy of type 2 diabetes].
Der Internist. 03/2011; 52(4):395-6, 398-404.
A variety of different drugs with distinct approaches are available for the treatment of type 2 diabetes. Different treatment options, as well as new developments, are needed, since an acceptable quality of glucose control often requires drug combinations. Furthermore, type 2 diabetes is known as a ... [more] A variety of different drugs with distinct approaches are available for the treatment of type 2 diabetes. Different treatment options, as well as new developments, are needed, since an acceptable quality of glucose control often requires drug combinations. Furthermore, type 2 diabetes is known as a heterogeneous disease that is characterized by different phases and individual characteristics, such as risk profiles and contraindications. In particular the impact of antihyperglycemic therapies on cardiovascular risk, body weight and the risk for hypoglycemia is important, but also the consideration of other co-morbidities, occupational and social aspects plays a role. So far, each therapeutic step is based on lifestyle-interventions and, if possible, metformin. Dipeptidylpeptidase 4 (DPP 4) inhibitors und glucagon-like peptid 1 (GLP 1) mimetics represent a new important tool in the differential therapy of type 2 diabetes. The advantage of incretin-based concepts is an improvement of glucose quality without induction of hypoglycemia and additional weight gain. It is, however, still not known, whether these advantages will still be seen in end point studies, e. g. concerning the cardiovascular risk.
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2.16Impact points
Preserved insulin secretion capacity and graft function of cryostored encapsulated rat islets.
Regulatory peptides. 10/2010; 166(1-3):135-8.
Encapsulation of pancreatic islets before transplantation enables survival and function in an immunocompetent recipient without immunosuppression. However, the insufficient availability of allogenic islet tissue is a major problem. One concept to overcome these shortcomings is the cryopreservation o... [more] Encapsulation of pancreatic islets before transplantation enables survival and function in an immunocompetent recipient without immunosuppression. However, the insufficient availability of allogenic islet tissue is a major problem. One concept to overcome these shortcomings is the cryopreservation of microencapsulated allogenic islets, to allow their unlimited collection and use on demand. Therefore, this report outlines the development of a cryopreservation protocol for CD rat islets encapsulated in an alginate-based microcapsule-system. We determined RPMI-medium plus 10% FCS as freezing medium, equilibration at 0°C for 15 min with the cryoprotectant dimethyl sulfoxide (DMSO; final concentration 2.0M), and a stepwise removal of DMSO by sucrose dilution after thawing, as best protocol for cryopreservation of encapsulated islets. Importantly, the cryopreserved encapsulated islets showed post thawing in vitro an insulin increase upon a glucose challenge comparable to that of non-cryopreserved encapsulated islets. Moreover, a stable graft function without the need of immunosuppression was detected after transplantation of 2500 cryopreserved encapsulated CD rat islets in streptozotocin-diabetic Wistar rats. Finally, the glucose clearance rate during an IPGTT 4 weeks after transplantation was comparable to that of rats transplanted with non-cryopreserved encapsulated islets. In conclusion, our study demonstrates for the first time that cryopreservation of encapsulated rat islets is possible without substantial losses on graft function. Future studies will now have to carry on this approach to human islets, aiming to apply such a bioartificial pancreas consisting of cryopreserved encapsulated islets in humans.
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6.55Impact points
In vitro phage display in a rat beta cell line: a simple approach for the generation of a single-chain antibody targeting a novel beta cell-specific epitope.
Diabetologia. 04/2010; 53(7):1384-94.
The aim of the present study was to evaluate in vitro phage display in a beta cell line as a novel strategy for the isolation of beta cell-specific agents/biomarkers. A single-chain antibody (SCA) library was pre-incubated with AR42J cells in order to eliminate SCAs with exocrine binding properties.... [more] The aim of the present study was to evaluate in vitro phage display in a beta cell line as a novel strategy for the isolation of beta cell-specific agents/biomarkers. A single-chain antibody (SCA) library was pre-incubated with AR42J cells in order to eliminate SCAs with exocrine binding properties. It was then panned against INS-1 cells to select beta cell-targeted antibodies. By these means, we isolated a novel antibody, SCA B5, that binds rapidly (6.0 min) and with a 450-fold higher specificity to beta cells relative to exocrine cells. We estimated for SCA B5 a binding affinity in the low micromol/l range and 858 binding sites per beta cell. Confocal microscopy showed binding to the beta cell surface and confirmed subsequent internalisation. Moreover, staining of rat and human pancreatic tissue sections with SCA B5 suggests that the target epitope is presented in pancreatic beta cells of different origins. Infrared imaging revealed that labelling of beta cells with tracer SCA B5 is strictly dependent on beta cell mass. With competition assays we excluded insulin, glutamate decarboxylase, C-peptide and islet amyloid polypeptide as SCA B5 targets. In accordance with these predictions, SCA B5 homed in vivo highly selectively to normal beta cells and dysfunctional beta cells of diabetic rats. Moreover, accumulation of radioactively labelled SCA B5 in the pancreas was reduced by 80% after pre-injection with unlabelled SCA B5, thereby confirming the specific uptake in the pancreas. We report a simple strategy for the generation of an SCA targeting a novel beta cell-specific epitope.
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6.20Impact points
Necrotizing fasciitis of the back musculature as a complication of acquired perforating collagenosis in diabetes mellitus.
The Journal of clinical endocrinology and metabolism. 01/2010; 95(1):11-2.
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2.87Impact points
Effects of a short-term improvement in glycaemic control on skin microvascular dysfunction in Type 1 and Type 2 diabetic patients.
Diabetic medicine : a journal of the British Diabetic Association. 10/2009; 26(9):880-6.
AIMS: To investigate whether Type 1 and Type 2 diabetic patients differ in the effects of short-term improvement in glycaemic control on skin microvascular dysfunction. METHODS: Fourteen Type 1 and 14 Type 2 diabetic patients admitted to hospital to improve glycaemic control were investigated. Two a... [more] AIMS: To investigate whether Type 1 and Type 2 diabetic patients differ in the effects of short-term improvement in glycaemic control on skin microvascular dysfunction. METHODS: Fourteen Type 1 and 14 Type 2 diabetic patients admitted to hospital to improve glycaemic control were investigated. Two age- and sex-matched groups of non-diabetic subjects served as controls. Capillary blood cell velocity (CBV) was assessed at the dorsal middle phalangeal area of the ring finger at rest and after 3-min arterial occlusion using laser Doppler anemometry. RESULTS: Comparing the measurements before and after improvement in glycaemic control, there were no significant changes in peak CBV, time to peak CBV and vasomotion amplitudes in Type 1 and Type 2 diabetic patients. On admission to hospital, time to peak CBV was prolonged in Type 1 (20.9 +/- 2.9 vs. 12.3 +/- 1.6 s, P = 0.003) and Type 2 diabetic patients (20.6 +/- 2.6 vs. 11.9 +/- 1.3 s, P = 0.021) compared with control subjects. After improvement in glycaemic control, there was no significant difference in time to peak CBV between Type 1 diabetic patients and their control subjects (17.8 +/- 4.2 vs. 12.3 +/- 1.6 s, P = 0.535). In Type 2 diabetic patients, the time to peak CBV increased non-significantly. CONCLUSIONS: Short-term improvement in glycaemic control did not appear to reverse microcirculatory dysfunction in Type 1 and Type 2 diabetes. However, there was an improvement of the delayed reactive hyperaemia in Type 1 diabetic patients.
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8.51Impact points
Generation of novel single-chain antibodies by phage-display technology to direct imaging agents highly selective to pancreatic {beta}- or {alpha}-cells in vivo.
Diabetes. 08/2009;
Objective: Non-invasive determination of pancreatic beta-cell mass in vivo has been hampered by the lack of suitable beta-cell specific imaging agents. This report outlines an approach for the development of novel ligands homing selectively to islet-cells in vivo. Research Design and Methods: In ord... [more] Objective: Non-invasive determination of pancreatic beta-cell mass in vivo has been hampered by the lack of suitable beta-cell specific imaging agents. This report outlines an approach for the development of novel ligands homing selectively to islet-cells in vivo. Research Design and Methods: In order to generate agents specifically binding to pancreatic islets, a phage-library was screened for single-chain-antibodies (SCAs) on rat islets using two different approaches: (1) The library was injected into rats in vivo, and islets were isolated after a circulation time of 5 minutes. (2) Pancreatic islets were directly isolated, and the library was panned in the islets in vitro. Subsequently, the identified SCAs were extensively characterized in vitro and in vivo. Results: We report the generation of SCAs that bind highly selective to either beta- or alpha-cells. These SCAs are internalised by target cells, disappear rapidly from the vasculature and exert no toxicity in vivo. Specific binding to beta- or alpha-cells was detected in cell-lines in vitro, in rats in vivo, and in human tissue in situ. Electron microscopy demonstrated binding of SCAs to the endoplasmatic reticulum and the secretory granules. Finally, in a biodistribution study the labeling intensity derived from [(125)I]-labeled SCAs after i.v. administration in rats strongly predicted the beta-cell mass and was inversely related to the glucose excursions during an intraperitoneal glucose tolerance test. Conclusions: Our data provide strong evidence that the presented SCAs are highly specific for pancreatic beta-cells and enable imaging and quantification in vivo.
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1.69Impact points
Influence of the duration of type 2 diabetes on early functional and morphological markers of atherosclerosis compared to the impact of coexisting classic cardiovascular risk factors.
Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association. 05/2008; 116(5):298-304.
AIM: The increased incidence of atherosclerotic macrovascular disease in type 2 diabetic patients is associated both with diabetes specific factors and coexisting classic cardiovascular risk factors as components of the metabolic syndrome. The aim of this study was to investigate the association bet... [more] AIM: The increased incidence of atherosclerotic macrovascular disease in type 2 diabetic patients is associated both with diabetes specific factors and coexisting classic cardiovascular risk factors as components of the metabolic syndrome. The aim of this study was to investigate the association between the duration of diabetes and early functional and morphological markers of atherosclerosis compared to the impact of coexisting cardiovascular risk factors such as hypertension, dyslipoproteinemia and cigarette smoking. METHODS: 63 type 2 diabetic patients and 25 non-diabetic control subjects were investigated. Lumen diameter of the brachial artery was measured by high-resolution ultrasound at rest and after 5-min suprasystolic arterial compression. Endothelium-independent dilatation of the brachial artery was measured 4 min after sublingual administration of 400 mug of glycerol trinitrate (GTN). Percentage change of arterial lumen diameter during reactive hyperemia (FMD%) and after GTN administration (GTN%) relative to the baseline measurements were calculated. The intima-media thickness (IMT) of the common carotid artery was measured bilaterally and averages were calculated. RESULTS: FMD% (3.8+/-0.8% vs. 6.9+/-0.9%; p<0.01) and GTN% (5.6+/-0.7% vs. 14.9+/-1.7%; p<0.01) were reduced in the diabetic patients compared to their control subjects. IMT was increased in diabetic patients compared to their controls (0.82+/-0.02 mm vs. 0.62+/-0.02 mm; p<0.01). The age-adjusted diabetes duration was inversely related to FMD% (r=-0.27; p=0.016). On multiple regression analysis including packyears, hypertension, hypercholesterolemia, and hypertriglyceridemia, only diabetes duration remained a significant independent determinant of FMD. GTN% and IMT were not associated with diabetes duration, packyears, hypertension, hypercholesterolemia, and hypertriglyceridemia when all variables were taken into account. CONCLUSION: The present data lend support to the suggestion that diabetic specific factors compared to coexisting cardiovascular risk factors such as hypertension, hyperlipoproteinemia, and smoking are of major importance for the pathogenesis of endothelial dysfunction in type 2 diabetes, because only the diabetes duration was shown to be related to endothelium-dependent vasodilation when all variables were taken into account.
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Iodothyronine antibodies are not correlated with prevalence or prognosis of non-thyroidal illness syndrome
European Congress of Endocrinology 2008, Berlin, Germany; 05/2008
Patients suffering from critical illness usually exhibit a characteristic functional state of thyrotropic feedback control that is referred to as non-thyroidal illness syndrome (NTIS). Today, there are still important questions unsolved, e.g. regarding the interdependence of immunological and endocr... [more] Patients suffering from critical illness usually exhibit a characteristic functional state of thyrotropic feedback control that is referred to as non-thyroidal illness syndrome (NTIS). Today, there are still important questions unsolved, e.g. regarding the interdependence of immunological and endocrine functions in critical illness. Therefore, in the context of the prospective AQUA FONTIS study we investigated 164 patients that were treated in medical, surgical and heart surgical intensive care units (ICUs) of the Bergmannsheil university hospitals in Bochum, Germany. Here, we examined the titres of antibodies reacting with thyroxine (T4-ab) and triiodothyronine (T3-ab) that were determined 24 h after admission to the ICU, and investigated their correlation with parameters of thyroid homeostasis, length of stay in hospital (LOSIH) or ICU (LOSICU) and survival of patients. All patients exhibited Gaussian distributed antibody titres that were in the normal range for healthy volunteers. Moreover, the titres didn’t correlate with functional characteristics like thyrotroph thyroid hormone sensitivity index (TTSI) as a parameter for the central component of NTIS, or sum activity of 5′-deiodinase as a marker for impaired deiodination. Again, antibody titres didn’t exhibit correlation with survival, LOSIH or LOSICU, in the latter two cases even if only the subgroup of surviving patients was considered. In conclusion, despite of immunological activation, e.g. in case of sepsis, antibodies directed against T3 or T4 are not elevated among critically ill patients nor do they play a role in the prognosis of the disease. Endocrine Abstracts (2008) 16 P821
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1.49Impact points
Microvascular dysfunction in rheumatoid arthritis assessed by laser Doppler anemometry: relationship to soluble adhesion molecules and extraarticular manifestations.
Rheumatology international. 01/2008; 28(2):145-52.
In search of a noninvasive diagnostic test for rheumatoid vasculitis (RV), this study addressed the questions whether changes in capillary blood cell velocity (CBV) detected by laser Doppler anemometry in patients with rheumatoid arthritis (RA) were correlated with the levels of soluble adhesion mol... [more] In search of a noninvasive diagnostic test for rheumatoid vasculitis (RV), this study addressed the questions whether changes in capillary blood cell velocity (CBV) detected by laser Doppler anemometry in patients with rheumatoid arthritis (RA) were correlated with the levels of soluble adhesion molecules and whether cutaneous flow abnormalities may reflect extraarticular manifestations in RA. In 31 RA patients and 20 patients with osteoarthritis (OA), CBV was measured in the skin above the left ring finger at rest and after 3-min arterial occlusion. Serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble E-selectin (sE-selectin), and soluble P-selectin (sP-selectin) were assessed by enzyme linked immunosorbent assay. Peak CBV was reduced in RA patients compared to OA patients (0.42 +/- 0.07 mm/s vs. 0.70 +/- 0.13 mm/s; P = 0.013). Both CBV during rest and reactive hyperemia were not correlated with the levels of soluble adhesion molecules. There were no significant differences in resting or peak CBV between RA patients with or without extraarticular manifestations. The lack of an inverse correlation between the levels of soluble adhesion molecules and CBV during rest and reactive hyperemia contradicts the assumption that inflammatory vascular damage indicated by increased levels of soluble adhesion molecules was the main reason for the impairment of microcirculation. The present results do not suggest that cutaneous flow abnormalities may reflect extraarticular manifestations in RA.
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0.34Impact points
[New concepts in the treatment of type 2 diabetes]
Der Internist. 08/2007; 48(7):698, 700-7.
The development of a variety of new substances will considerably expand the therapeutic choices in the treatment of type 2 diabetes. In 2006, the endocannabinoid receptor blocker Rimonabant has been approved for the treatment of type 2 diabetes in Germany.This compound has led to significant reducti... [more] The development of a variety of new substances will considerably expand the therapeutic choices in the treatment of type 2 diabetes. In 2006, the endocannabinoid receptor blocker Rimonabant has been approved for the treatment of type 2 diabetes in Germany.This compound has led to significant reductions of body weight along with improvements of HbA1c levels and lipid profiles, but the lack of health insurance coverage limits its large scale use in germany. In April 2007, the first members of the GLP 1 analogues/incretin mimetics (exenatide, Byetta) and DPP 4 inhbitors (sitagliptin, Januvia) have become available for the treatment of type 2 diabetes in Germany. Both drugs have significantly lowered HbA1c levels in clinical studies. In addition, the incretin mimetics have caused a progressive reduction of body weight, while the DPP 4 inhibitors have been rather weight neutral. Sitagliptin can be administered orally, whereas exenatide has to be injected subcutaneously. Neither the DPP 4 inhibitors, nor the incretin mimetics have led to the development of hypoglycaemia, unless combined with sulfonylureas. Overall, the introduction of these new drug classes will certainly broaden our therapeutic choices in the management of type 2 diabetes. The long-term effects of these drugs on the development of diabetic complications in long-term trials remains to be awaited.
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0.47Impact points
[Therapeutic management of acral manifestations of systemic sclerosis]
Medizinische Klinik (Munich, Germany : 1983). 04/2007; 102(3):209-18.
Acral manifestations of systemic sclerosis include Raynaud's phenomenon, calcinosis cutis, and sclerodactyly. In the later stages of the disease, contractures of the skin and joints as well as obliterative vasculopathy leading to digital ulcers and necrotic lesions may occur. Patients with acral... [more] Acral manifestations of systemic sclerosis include Raynaud's phenomenon, calcinosis cutis, and sclerodactyly. In the later stages of the disease, contractures of the skin and joints as well as obliterative vasculopathy leading to digital ulcers and necrotic lesions may occur. Patients with acral manifestations of systemic sclerosis are ideally treated by a team that includes a rheumatologist, dermatologist, hand surgeon, physiotherapist, and, eventually, a psychologist. Calcium channel antagonists, alpha(1)-adrenergic blockade with prazosin, and prostacyclin analogs were proven to be effective in the treatment of scleroderma-related Raynaud's phenomenon. Losartan, an angiotensin II receptor inhibitor, and fluoxetine, a selective serotonin reuptake inhibitor, have been beneficial for systemic sclerosis-associated Raynaud's phenomenon in pilot studies. Parenteral prostacyclin analogs, e. g., iloprost, can be recommended as first-line treatment of ischemic digital ulcers. When prostacyclin analogs fail, the phosphodiesterase type 5 inhibitor sildenafil can be tried to improve ulcer healing. Bosentan, an endothelin receptor antagonist, may prevent new digital ulcers. At present, there are no medical agents agreed to be generally effective in the reduction of calcinotic deposits or cutaneous fibrosis, although some drugs have been identified as potentially beneficial. Surgical treatment of acral manifestations consists of excision or curettage of symptomatic calcific deposits, digital sympathectomy, arterial reconstruction, and amputation in rare cases. Flexion contractures of the proximal interphalangeal joints, with secondary hyperextension of the metacarpophalangeal joints, can be treated by arthrodesis of the proximal interphalangeal joints and resection arthroplasty or prostheses at the metacarpophalangeal joints to improve hand function.
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2.16Impact points
Synthesis and evaluation of a glibenclamide glucose-conjugate: a potential new lead compound for substituted glibenclamide derivatives as islet imaging agents.
Regulatory peptides. 04/2007; 139(1-3):122-7.
The search for novel SUR1-ligands originates from the idea to influence the in vivo behaviour by adding new structural moieties to the glibenclamide structure while preserving its binding affinity. Important application of novel conjugates might be their use as radioactively labelled tracer probes i... [more] The search for novel SUR1-ligands originates from the idea to influence the in vivo behaviour by adding new structural moieties to the glibenclamide structure while preserving its binding affinity. Important application of novel conjugates might be their use as radioactively labelled tracer probes in the non-invasive investigation of the islet mass. It is known that the imaging quality of a tracer could be improved by increasing its hydrophilicity, which leads to a reduced plasma protein binding and diminished the unspecific uptake by various organs. In this study the glucose molecule was chosen as a substitute of glibenclamide to enhance hydrophilicity. As expected glucose conjugation leads to a 12-fold increase of the hydrophilicity. In vitro evaluation showed that the conjugate binds with high affinity to SUR1. Interestingly, in vivo the hypoglycaemic action of the conjugate was of significant shorter duration compared to glibenclamide. In accordance, the conjugate was cleared much faster from the blood stream, due to a significant lower plasma protein binding. In conclusion, glycosylation proved to be a powerful tool for the development of a high affinity glibenclamide ligand with completely different pharmacodynamics. Therefore, the glucose-conjugate could be a potential lead compound for the design of substituted glibenclamide derivatives as islet imaging ligands.
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2.86Impact points
Calpain inhibition impairs glycogen syntheses in HepG2 hepatoma cells without altering insulin signaling.
The Journal of endocrinology. 04/2007; 193(1):45-51.
Calpains are a family of non-lysosomal cytoplasmatic cysteine proteases. Since calpain 10 (CAPN10), a member of the calpain family of proteases, has been found to represent a putative diabetes susceptibility gene, it was argued that calpains may be involved in the development of type 2 diabetes. The... [more] Calpains are a family of non-lysosomal cytoplasmatic cysteine proteases. Since calpain 10 (CAPN10), a member of the calpain family of proteases, has been found to represent a putative diabetes susceptibility gene, it was argued that calpains may be involved in the development of type 2 diabetes. The functional role of calpains in insulin signaling and/or insulin action is, however, not clear. We investigated the effects of the calpains 1 and 2 inhibitor PD151746 on insulin signaling and insulin action in human hepatoma G2 cells (HepG2). HepG2 cells were incubated without (-PD) or with (+PD) 5.33 micromol/l PD151746 for different times and then stimulated with 100 nmol/l insulin for 0 (t(0)), 5 (t(5)), 15 (t(15)), 30 (t(30)), 45 (t(45)), and 60 (t(60)) min. After solubilization of the cells, insulin receptor kinase activity, tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), IRS-1-associated phosphatidylinositol-3 kinase (PI3-kinase), PI3-kinase activity, Thr(308) phosphorlyation of Akt, amount of protein tyrosine phosphatase-epsilon (PTPepsilon), and glycogen synthase activity were determined. Incubation with PD151746 resulted in a significant reduction of insulin-stimulated glycogen synthesis compared with cells not pre-incubated with the calpain inhibitor (-PD: t(0), 4.90 +/- 1.20%; t(5), 5.90 +/- 1.02%; t(15), 5.29 +/- 0.95%; t(30), 5.60 +/- 1.10%; t(45), 5.52 +/- 0.90%; t(60), 5.67 +/- 0.97%;+PD: t(0), 4.56 +/- 1.10%; t(5), 6.16 +/- 1.05%; t(15), 7.52 +/- 1.09%; t(30), 7.68 +/- 1.10%; t(45), 8.28 +/- 0.89%; t(60), 7.69 +/- 0.98%; P < 0.05). Incubation with PD151746 significantly increased the protein amount of PTPepsilon in the cells after 12 h (-PD: t(1), 0.85 +/- 0.18 RU (Relative unit); t(8), 0.87 +/- 0.18 RU; t(12), 0.9 +/- 0.13 RU; +PD: t(1), 0.92 +/- 0.21 RU; t(8), 1.1 +/- 0.15 RU; t(12), 1.34 +/- 0.16 RU; P < 0.05). Calpain inhibition with PD151746 had no effect on the insulin stimulation of the investigated insulin signaling parameters. These results in HepG2 cells suggest that calpains play a role in the hepatic regulation of insulin-stimulated glycogen synthesis independent of the PI3-kinase/Akt signaling pathway.
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0.59Impact points
[Oral antidiabetic therapy]
Deutsche medizinische Wochenschrift (1946). 01/2007; 131 Suppl 8:S264-7.
Consistent antihyperglycaemic treatment for preventing vascular complications in type 2 diabetes mellitus (2DM) often require the application of several measures. The basis of such treatment should be dietary changes and increased physical exercise. The target of antiglycemic treatment is the reduct... [more] Consistent antihyperglycaemic treatment for preventing vascular complications in type 2 diabetes mellitus (2DM) often require the application of several measures. The basis of such treatment should be dietary changes and increased physical exercise. The target of antiglycemic treatment is the reduction of HbA1c to below 6.5%. Regular monitoring of HbA1c every 2-6 months is reasonable in order to recognize therapeutic failure early and adapt treatment accordingly. Metformin is the drug of first choice for the oral treatment of 2DM, once possible contraindications having been excluded. The advantage of glinides, compared with sulfonylureas, is mainly in allowing greater dietary flexibility. Although not finally decided, there are ever fewer objections against combined metformin and sulphonylurea treatment. The current guidelines of the (British)National Institute for Clinical Excellence (NICE) specifically recommend this combination treatment. There are pointers to glitazone having protective effects in 2DM beyond its blood-sugar lowering action. However, the clinical significance of these effects requires confirmation. If adequate blood-sugar reduction cannot be achieved with oral medication it is important to initiate insulin administration as soon as possible.
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0.47Impact points
[Endosonography -- an additional diagnostic possibility in the differentiation between the two common types of primary hyperaldosteronism]
Medizinische Klinik (Munich, Germany : 1983). 02/2006; 101(1):65-8.
BACKGROUND: Primary aldosteronism is an important and one of the few potentially curable forms of secondary hypertension. The distinction between aldosterone-producing adenoma (APA) and idiopathic adrenal hyperplasia (IHA) may be difficult, but establishing the correct diagnosis is essential because... [more] BACKGROUND: Primary aldosteronism is an important and one of the few potentially curable forms of secondary hypertension. The distinction between aldosterone-producing adenoma (APA) and idiopathic adrenal hyperplasia (IHA) may be difficult, but establishing the correct diagnosis is essential because surgery is only effective in patients with adrenal adenoma. CASE REPORT: The case of a 65-year-old man with long-term hypertension due to an APA is reported. The routine laboratory tests displayed an elevated plasma aldosterone/renin quotient as well as an elevated 24-h urinary excretion of aldosterone and its metabolites. The serum aldosterone concentration did not decrease normally in the saline suppression test. The posture testing demonstrated an increase in aldosterone. These facts might lead to the conclusion of an IHA. Magnetic resonance imaging (MRI) of the adrenal glands revealed no abnormalities. Because of the unusual combination of laboratory findings and radiologic results an endosonographic examination of the adrenal glands was performed which yielded a unilateral adrenal adenoma. With establishing this diagnosis, curative surgery became possible. CONCLUSION: This case demonstrates that in the differential diagnosis of primary aldosteronism, endosonography is more important than previously discussed. It may be helpful in the differentiation of an unusual constellation of laboratory and radiologic findings.
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1.69Impact points
The beta3-adrenergic agonist CL316,243 inhibits insulin signaling but not glucose uptake in primary human adipocytes.
Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association. 10/2005; 113(8):418-22.
Insulin resistance and obesity are central components of the metabolic syndrome which has become the leading cause of cardiovascular morbidity and mortality worldwide. Direct interactions of the beta (3)-adrenoceptor system with adipocyte signaling and function in humans remain poorly understood. Ho... [more] Insulin resistance and obesity are central components of the metabolic syndrome which has become the leading cause of cardiovascular morbidity and mortality worldwide. Direct interactions of the beta (3)-adrenoceptor system with adipocyte signaling and function in humans remain poorly understood. However, this might have important consequences for the regulation of energy homeostasis and insulin resistance in states of hyperinsulinemia and sympatho-adrenergic overactivity. We therefore investigated beta (3)-adrenoceptor-mediated effects on insulin signaling and glucose uptake in mammary adipocytes of healthy women that underwent breast reduction surgery. Glucose uptake was strongly induced by insulin stimulation. This was paralleled by robust induction of insulin receptor kinase activity, insulin receptor substrate-1-associated phosphatidylinositol-3 kinase activity, and protein kinase B phosphorylation. Treatment with the beta (3)-adrenoceptor-selective agonist CL316,243 alone, neither induced alterations in the early insulin signaling cascade nor changed the basal level of glucose uptake. By contrast, pretreatment with the beta (3)-adrenoceptor agonist inhibited the insulin-induced insulin receptor substrate-1-associated phosphatidylinositol-3 kinase activity by 50 % and protein kinase B phosphorylation by 40 % without affecting insulin receptor kinase activity upstream. However, on the functional level insulin-induced glucose uptake remained unchanged by beta (3)-adrenoceptor stimulation. Our data demonstrate an insulin receptor-independent negative influence of beta (3)-adrenoceptor stimulation on proximal insulin signaling. This inhibition is apparently dissociated from glucose uptake in human adipocytes.
Following (9)
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Johannes W. Dietrich
Ruhr-Universität Bochum -
Lehnhardt Marcus
BG-Traumacenter Bergmannsheil Bochum -
Wolfgang Schechinger
Bioavid Diagnostics -
Steffen Hering
Krankenhaus Bietigheim -
Nora Prochnow
Ruhr-Universität Bochum
