Klein, H. H.

Matthaei, S.

Ries, W.

Scriba, Peter Christian

English

Open Access LMU

504 A Abstracts the influence of physical activity on glucoregulation depends on in- tensity of exercise. 253. Activation of insulin-receptor-kinase in intact HIRc and hepatoma G2-cells: Effect of dexamethasone H. H. Klein ~, W. Riesl~ S. Matthaei 2and P. C. Scriba 1. Departments ofInternal Medicine, ~University of Liibeck and 2University of Ham- burg, FRG We have studied the ffect of a pretreatment with dexamethasone (D) on insulin (1)-binding and I-activation of insulin receptor kinase (IRK) in intact HIRc-cells (Ratl-fibroblasts expressing human 1-re- ceptor, provided by Dr. A. Ullrich, Genentech) and hepatoma G2-cells (HG2-cells). Cells were preineubated with (+ D) or without ( -  D) 100 nmol/I D for48 h. Fresh medium with 0, 10, or 500 ng/ml I was then added to the cells for 30 min to activate cellular IRK. l- receptors were isolated and immunoprecipitated in the presence of kinase and phosphatase inhibitors. IRK-activity towards histone that was then measured at 0.5 Izmol/l 3Zp-ATP reflected the activity state of the receptors while the cells were intact. In HIRe-cells +D the number of I-receptors was reduced by 58+5% (p<0.01). In HG2-cells, no D-effect on binding was found. D increased the l-ef- fect on IRK-activity (expressed as femtomol P into histone/pmol I-binding activity/rain +SEM) in HIRc-cells at a submaximal (10 ng/ ml; -D :  19.4-+1.6, +D:  37.8+2.4; p<0.01) and at a maximally effective I-concentration (500 ng/ml; - D: 61.0 + 7.4, + D: 83.3 -+ 8.7; p<0.01). A comparable increase was obsetwed in HG2-cells. Conclusions: (1) D reduces the number of l-receptors in HIRe, but not in HG2-cells, (2) D increases I-activation of IRK in both HIRc and HG2 cells. (3) Our data indicate that D could lead to an amplifi- cation of the I-signalling into the cell by increasing IRK-activity. This may explain previously described permissive ffects of D on biological actions of 1. 254. The effect of omega-3 fatty acids on insulin binding and action in normal and hereditary hypertriglyceridaemic rats fed a high sucrose diet I. Klime~, M. Fickovfi, E. Svfibov~, A. Vrfina, P, Bohov, ~.Zorfid, L. Sikurova, V. Balfi2 and L. Macho. Institute of Experimental Endo- crinology, Bratislava, Institute of Clinical and Experimental Medi- cine, Prague and Research Institute of Gerontology, Malacky, Czechoslovakia To clarify mechanisms of beneficial effects of omega-3 fatty acids (w-3 FA) on glycide and lipid metabolism we investigated the out- come of 24 days administration of w-3 FA rich fish oil (FIe) on se- rum triglycerides (TG), glucose (G) and insulin (1). I binding (B) and action (A) in liver and fat tissue in normal and hypertriglyceridaemic (HTG) rats fed sucrose (SR) diet (70 cal%), In HIG rats, SR feeding further increased fasting TG levels (1.4_+0.1 vs 3.5_+0.7 mmol-I -), p<0.01) abolished by F Ie  treatment, l levels (34.7+4.9 ~U.ml 1) increased further on SR (61.2+_8.7, p<0.01) along with G (6.10_+ 0.04 vs 7.72_+0.29 mmol. 1 I. p < 0.001) suggesting worsening of IA. F Ie  kept I and G within their baselines. F Ie  raised w-3 FA content in liver (14.34+1.32 vs 18.58_+1.8 weight%) and adipocyte mem- branes accompanied by increased hepatocyte membrane fluidity (0.550 + 0.002 vs 0.508 -+ 0.007, p < 0.005). F Ie  increased IB in adipo- cytes (0.43 _+ 0.008 vs 0.83 + 0.04 femtomol- 10- ~ cells, p < 0.02) with no effect in liver. In fat tissue F Ie  enhanced IA (incorporation of 14-C-glucose into lipids). Comparable data were generated in nor- mal rats. F Ie  treatment inhibited SR-induced HTG in both animal models and prevented the suggested worsening of IA. This probably concerns fat tissue as F Ie  did not affect IB or IA in liver regardless of the change in hepatocyte fluidity. 255. A mutation in the insulin receptor causes insulin resistance and leprechaunism M. P. Klinkhamer, W. M611er, H. M. J. Krans and J. A. Maassen. Syl- vius Laboratories and Department of Endocrinology and Metabolic Diseases, University of Leiden, The Netherlands We have recently described a leprechaun patient with severe insulin resistance. Cultured fibroblasts of the patient showed 2-deoxyglu- cose-uptake stimulation by insulin of 1.2-fold compared to 1.7-fold in control fibroblasts. The resistance was related to a malfunction of the insulin receptor as concluded from the absence of significant in- sulin binding to the patient's cells and an impaired insulin stimu- lation of/3 subunit autophosphorylation. Molecular cloning and se- quencing of insulin-receptor cDNA of the patient showed a homozygous leucine-to-proline mutation in the a subunit of the re- ceptor. This mutation is located outside the regions known to be in- volved in insulin binding and tyrosine kinase. However, it seems to inhibit the transduction of the insulin-binding signal, generated on the insulin-binding site of the a subunit, to the tyrosine-kinase do- main on the/3 subunit. By means of DNA amplification techniques we tbund that the lhmily members are heterozygous for this muta- tion, These individuals have only one allele coding for a functional insulin receptor. As a result the insulin-binding levels are only 30% of the control levels. Oral glucose tolerance tests show increased in- sulin levels but low normal glucose levels. These findings indicate that an insulin-binding defect is not sufficient o induce Type 2 (non- insulin-dependent) diabetes. 256. T cell.dependent class 11 MHC antigen expression i duced by streptozotocin C. Klinkhammer, C. Dohle and H. Gleichmann. Clinical Depart- mcnt, Diabetes Research Institute, Heinrich-Heine-University, Dtisseldorf, FRG T lymphocytes can be sensitised specifically by streptozotocin (STZ). We aimed at analysing the effects of STZ on class lI MHC expres- sion in vivo. Subcutaneous injection of STZ led to prominent induc- tion of class II antigens in multiple organs of BALB/c mice. By an immunoperoxidase method on cryo-cut sections Ia ntigens were evaluated with monoclonal antibodies detecting LA d, antibodies with specificity for la k were used as controls. Treatment with STZ re- sulted in definite, yet transient increases of class II-positive cells within days in the pancreas, liver, heart and kidney, but not the brain. Pancreatic B cells, however, were devoid of class II antigen positivity, These immune phenomena were T cell-dependent as as- sessed in tissues from BALB/cJ nu/nu recipients and their +/nu  counterparts. The upward regulation of cellular class II antigen ex- pression by STZ is presumed to ensue local release of lymphokines. The intriguing concept of T cell activation by class II-positive beta cells still remains to be proven. 257. Platelet alpha granule release of growth factors in diabetic patient and non-diabetic subjects with non-healing wounds D.R. Knighton, V.D. Fiegel, K.L. Atkinson, B.G. Penner and J. B. Penland. Department of Surgery, University of Minnesota, USA Platelet alpha-granules contain several growth factors (GF): platelet- derived growth factor (PDGF), platelet-derived angiogenesis factor (PDAF), platelet-derived pidermal growth factor (PDEGF), platelet factor 4 (PF4), and transforming rowth factor-B (TGFB). Beta thromboglobulin (B-TG) is also found in the alpha granule. Patients with non-healing wounds had blood sampled for preparation of platelct GF according to published techniques. B-TG was measured by radioimmunoassay, PDGF by ELISA, mitogenic index by H 3 thymidine incorporation i to Balb 3T3 cells, and capillary endotheli- al chemotaxis by modified Boyden chamber technique. Patient diag- nosis included diabetes mellitus, peripheral vascular disease (PVD), decubitus ulcer (DU), surgical wound dehiscence (SURG), radiation burn (RB), and venous tasis (VS). Seven patients with diabetes mel- litus had B-TG=I67_+0A7ng/ml, mitogenic index (MI)=2.5+ 0.17, PDGF = 42.7 _+ 4.9 ng/ml, and capillary endothelial chemotaxis (CEC) of 2.8 _+ 0.54 x control. All 20 control wound patients had lower values. B-TG was significantly higher than all groups (p < 0.05), MI was greater than PVD and DU (p<0.05) and PDGF val- ues were uniformly higher (/7 < 0.05). CEC was not statistically dif- ferent. Platelets from diabetic wound patients have high levels of al- pha granule GF necessary for wound repair. A local block in GF release or enhanced degradation may be present at the wound site. 258. Autoimmune and metabolic risk markers in siblings of Type 1 (in- sulin-dependent) diabetic probands M. Knip, J. Karjalainen, P. Lautala, R. Lounamaa, H.K. Akerblom and the Study Group on Childhood Diabetes in Finland. Depart- ment of Pediatrics, University of Oulu, Children's Hospital, Univer- sity of Helsinki; National Public Health Institute, Helsinki and all paediatric departments i  Finland To evaluate the relationship between autoimmune and metabolic risk markers for Type 1 (insulin-dependent) diabetes we analysed the oc- currence of conventional (IF-ICA) and complement-fixing cytoplas- mic islet cell antibodies (CF-ICA) and insulin autoantibodies (IAA) in siblings between 3 19 years of age of all newly diagnosed iabetic children younger than 15 years participating in a nationwide study. Twenty-three of 514 (4.5%) were positive for IF-1CA, 19 (3.7%) for CF-ICA and 5/589 (0.9%) ibr IAA at the presentation of diabetes in 

Activstion of insulin-receptor-kinase in intact HIRc and hepatoma G2-cells: Effect of dexamethasone

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Activstion of insulin-receptor-kinase in intact HIRc and hepatoma G2-cells: Effect of dexamethasone

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