Cyclosporin A (CyA) was fed to male Wistar rats in a dose of 5, 10 or 50 mg/kg b.wt. for 7 days. In another experimental procedure 10 mg/kg b.wt. CyA was given for 7 days combined with Diltiazem (DIL) 6.25 mg/kg b.wt. once daily ip. Glucose stimulated insulin secretion from the isolated perfused pancreas was investigated in these animals. Total insulin secretion (ng/50 min) was not affected after feeding 5 mg/kg b.wt. CyA, but was significantly decreased with 10 and 50 mg/kg b.wt. CyA. The biphasic insulin secretion was reduced after 5 mg/kg b.wt. CyA during the initial peak (0-10 min) but not during the second peak (10-50 min), whereas after 10 and 50 mg/kg b.wt. CyA both peaks nearly reached base-line levels. DIL markedly increased the initial peak (0-10 min) after feeding CyA 10 mg/kg b.wt., whereas the second peak was not affected. Our results demonstrate a toxic effect of CyA on the pancreatic B-cell, which might be partly abolished by calcium-antagonists.

We have studied the impact of liquid diets formulated for complete or supplemental enteral nutrition of type II, non insulin-dependent (NIDDM) diabetics on carbohydrate homeostasis. To achieve this, liquid formula tolerance tests were performed in NIDDM patients under an oral treatment regimen with a combination of diet plus glibenclamide (7 men, 3 women, age: 56 +/- 11 years; mean body mass index of 26.2 +/- 3.6 kg/m2). After an overnight fast, each patient received the usual morning medication and, thereafter, ingested formula diet in randomized order with 10 day intervals between tests. 500 ml were administered of either a standard liquid diet (Biosorb Sonde), a fibre containing diet (Biosorb Plus Sonde), or a carbohydrate modified, fructose containing "diabetes" diet (Fresubin Diabetes) (carbohydrate contents of approximately equal to 60 g, respectively). Blood samples were collected over 180 min. Considering minor variations in the nutritional values of the diets, IR-insulin, IR-C-peptide, IR-glucose-dependent insulinotropic polypeptide (GIP), and IR-glucagon-like peptide. 1 (GLP-1) in plasma did not significantly differ between the study groups. After ingestion of Biosorb Sonde area under the curve glucose was greater than that seen after uptake of fibre containing or carbohydrate modified, i.e. fructose containing "liquid diabetes diets". All diets challenged the entero-insular axis in non-insulin dependent diabetics to a comparable extent. This data does not support the contention to employ special "diabetes" formulas for enteral nutrition of patients with NIDDM.

Regelmäßige Referenten: H. E. Adamek, Ludwigshafen; U. R. Fölsch, Kiel; C. Folwaczny, München; V. Keim, Leipzig; Kellner, München; M. Müller-Schilling, Heidelberg; H. Messmann, Augsburg; H. H.-J. Schmidt, Berlin; W. E. Schmidt, Bochum; A. Stallmach, Homburg; C. P. Strassburg, Hannover; H. Witt, Berlin; B. Simon, Marburg.

HISTORY AND CLINICAL FINDINGS:A 47-year-old man with a known and substituted vitamin B12 deficiency presented with increasing symptoms associated with orthostatic hypotension, neck pain and micturitional and visual disturbances.CLINICAL AND LABORATORY TESTS:Catecholamines were strongly reduced in plasma and urine.DIAGNOSIS, TREATMENT AND CLINICAL COURSE:A pure autonomic failure was diagnosed and therapy with fludrocortisone, yohimbine and erythropoetine was started. Symptoms with the exception of micturitional disturbances improved strongly.CONCLUSIONS:Multiple-drug treatment of pure autonomic failure is successful. The prognosis is good.

Conarello SL, Li Z, Ronan J et al. Mice lacking dipeptidyl peptidase IV are protected against obesity and insulin resistance. Proc Natl Acad Sci USA 2003; 100: 6825-6830

Mucus secretion of the airways is under the control of a variety of intracellular second messenger systems. Cyclic nucleotides such as cGMP, coupled to the recently discovered nitric oxide system, and cAMP are of outstanding interest in this respect. The present study used the modified Ussing chamber technique and mucins labelled with (35)SO(4) to investigate mucus secretion in the rat trachea to clarify the contribution of these different second messenger systems to the control of mucin secretion.A variety of drugs affecting either the generation or the breakdown of the respective cyclic nucleotides were used. Neither drugs interfering with nitric oxide synthase nor the phosphodiesterase isoenzyme responsible for cGMP breakdown nor cGMP analogues were able to affect mucus secretion. In contrast, stimulation of adenylate cyclase or inhibition of the respective phosphodiesterase resulted in a potent increase of mucus secretion. In conclusion, we failed to show the involvement of the nitric oxide/cGMP system, whereas the cAMP system seems to be a very efficient regulator of mucus secretion in the rat trachea.

Glucagon-like peptide-1-(7---36) amide (GLP-1) is a potent incretin hormone secreted from distal gut. It stimulates basal and glucose-induced insulin secretion and proinsulin gene expression. The present study tested the hypothesis that GLP-1 may modulate insulin receptor binding. RINm5F rat insulinoma cells were incubated with GLP-1 (0.01-100 nM) for different periods (1 min-24 h). Insulin receptor binding was assessed by competitive ligand binding studies. In addition, we investigated the effect of GLP-1 on insulin receptor binding on monocytes isolated from type 1 and type 2 diabetes patients and healthy volunteers. In RINm5F cells, GLP-1 increased the capacity and affinity of insulin binding in a time- and concentration-dependent manner. The GLP-1 receptor agonist exendin-4 showed similar effects, whereas the receptor antagonist exendin-(9---39) amide inhibited the GLP-1-induced increase in insulin receptor binding. The GLP-1 effect was potentiated by the adenylyl cyclase activator forskolin and the stable cAMP analog Sp-5, 6-dichloro-1-beta-D-ribofuranosyl-benzimidazole-3', 5'-monophosphorothioate but was antagonized by the intracellular Ca(2+) chelator 1,2-bis(0-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM. Glucagon, gastric inhibitory peptide (GIP), and GIP-(1---30) did not affect insulin binding. In isolated monocytes, 24 h incubation with 100 nM GLP-1 significantly (P<0.05) increased the diminished number of high-capacity/low-affinity insulin binding sites per cell in type 1 diabetics (9,000+/-3,200 vs. 18,500+/-3,600) and in type 2 diabetics (15,700+/-2,100 vs. 28,900+/-1,800) compared with nondiabetic control subjects (25,100+/-2,700 vs. 26,200+/-4,200). Based on our previous experiments in IEC-6 cells and IM-9 lymphoblasts indicating that the low-affinity/high-capacity insulin binding sites may be more specific for proinsulin (Jehle, PM, Fussgaenger RD, Angelus NK, Jungwirth RJ, Saile B, and Lutz MP. Am J Physiol Endocrinol Metab 276: E262-E268, 1999 and Jehle, PM, Lutz MP, and Fussgaenger RD. Diabetologia 39: 421-432, 1996), we further investigated the effect of GLP-1 on proinsulin binding in RINm5F cells and monocytes. In both cell types, GLP-1 induced a significant increase in proinsulin binding. We conclude that, in RINm5F cells and in isolated human monocytes, GLP-1 specifically increases the number of high-capacity insulin binding sites that may be functional proinsulin receptors.

BackgroundInsulin‐like growth factors (IGF) and their corresponding receptors and binding proteins are important in carcinogenesis for several tumours, but their expression pattern in the functionally and biologically heterogeneous human neuroendocrine tumours of the gastroenteropancreatic tract is largely unknown.Materials and methodsThis study searched for the mRNA expression patterns of components of the IGF system: IGF‐1 and IGF‐2, IGF receptors 1 and 2 (IGF‐1R, IGF‐2R), IGF‐binding proteins 1–6 (IGFBP1–6)) in the most frequent human gastroenteropancreatic neuroendocrine tumours (gastrinomas, insulinomas, tumours associated with carcinoid syndrome and functionally inactive tumours) employing reverse transcriptase‐polymerase chain reaction (RT‐PCR).ResultsIn the 37 tumour samples analysed (nine gastrinomas, 10 insulinomas, nine tumours associated with carcinoid syndrome and nine functionally inactive tumours) IGFBP‐2 was found in all tumour samples while the IGFBP‐1 was expressed only at low frequency (10–22%) among the four tumour types. The IGF‐2R was predominantly expressed in gastrinomas. Among the four tumour types the expression of IGF‐1R, IGF‐2R and IGFBP‐6 varied significantly. In addition, 12 pairs of significantly coexpressed IGF system components were detected (IGF‐1 ↔ IGF‐1R, IGF‐1 ↔ IGF‐2R, IGF‐1 ↔ IGFBP‐3, IGF‐1 ↔ IGFBP‐6, IGFBP‐3 ↔ IGF‐1R, IGFBP‐6 ↔ IGF‐1R, IGFBP‐1 ↔ IGF‐2R, IGFBP‐3 ↔ IGF‐2R, IGFBP‐5 ↔ IGF‐2R, IGFBP‐3 ↔ IGFBP‐5, IGFBP‐3 ↔ IGFBP‐6, IGFBP‐5 ↔ IGFBP‐6).ConclusionsThe described differences of the expression patterns of the IGF system components in neuroendocrine tumour subtypes suggest tumour type‐dependent different pathways in tumour growth control by IGF system components.

Somatostatin is a hormone that regulates the function of several exocrine and endocrine glands. The peptide mediates its actions via five different receptors. These proteins are expressed in a tissue-specific manner. Somatostatin receptors are also present in neuroendocrine gastroenteropancreatic tumors. Two long-acting somatostatin analogues, octreotide and lanreotide, are recognized by the receptor subtypes 2 and 5. Excessive hormone secretion in carcinoid syndrome can be controlled by these drugs. In addition, at least a subgroup of patients with carcinoid syndromes respond with delayed tumor growth during octreotide therapy. In the future, the availability of the somatostatin receptor cDNAs will allow the development of specific and even more potent receptor analogues.

Tachykinins like substance P (SP), neurokinin A (NKA), neurokinin B (NKB) differentially stimulate airway mucus secretion with the following rank order of potency in rat trachea: SP>NKA>NKB. These differential actions are most likely due to different affinities to the tachykinin receptors, termed neurokinin (NK)(1), NK(2)and NK(3). In this study we characterized the receptor subtype responsible for the differential secretagogue effects in rat trachea by means of selective receptor antagonists and receptor agonists.SR 140333 [NK(1)-antagonist] completely inhibited SP action (283,29+/-21, 12%-->84,53+/-4, 09%; P<0,01) and significantly reduced the effects of NKA (179,08+/-17,34%-->118,86+/-6,7%; P<0,01) and NKB (171,89+/-5, 75%-->109,5+/-4,11%; P<0,01). SR 48968 [NK(2)-antagonist] did not affect SP action, but reduced the effects of NKA and NKB. SR 142801 [NK(3)-antagonist] did not change any effect of SP, NKA or NKB. [Sar(9)]SP (NK(1)-agonist) caused strong dose-dependent secretagogue effects similar to SP, [betaAla(8)]NKA (NK(2)-agonist) showed only slight and [Pro(7)]NKB (NK(3)-agonist) no effects. The present data suggest that the secretagogue effects elicited by tachykinins in rat trachea are mediated via NK(1)receptors.

BackgroundHuman gastroenteropancreatic neuroendocrine tumours are functionally and biologically heterogeneous, but their exact growth factor receptor expression pattern, important for onco‐ and carcinogenesis, remains unknown.MethodsThis study searched for the mRNA expression pattern of six tyrosine‐ and serine/threonine kinase receptors [hepatocyte growth factor (HGFR), fibroblast growth factor (FGFR), epidermal growth factor (EGFR), insulin‐like growth factor (IGF)‐1R, transforming growth factor (TGF)‐βR1, TGF‐βR2] together with the five somatostatin receptors in human gastroenteropancreatic neuroendocrine tumours (gastrinomas, insulinomas, tumours with carcinoid syndrome, functionally inactive neuroendocrine tumours) using reverse transcriptase‐polymerase chain reaction (RT‐PCR).ResultsEGF receptor was expressed almost exclusively in gastrinomas. Among the four tumour subtypes, expression frequencies of the somatostatin receptors 1 and 5, HGF‐, IGF‐1‐, TGF‐βR1, TGF‐βR2 and the EGF‐receptor varied significantly.ConclusionsIn spite of the common cellular origin of these tumours, differences in growth factor receptor expression suggest the existence of different pathways during tumour subtype development.

We have previously demonstrated that cholecystokinin (CCK) stimulates significant cAMP accumulation in HEK-293 cells expressing human CCK-A receptors while causes little of no significant cAMP response via CCK-B receptors.Substitution of Leu-81 to Art, or Ser-82 to Asn in the first intraceUnlar loop (ICL-1) of CCK,BR, resulted in significant increases in cAMP production.Aim: The role of cAMP in CCK-mediated cell growth and proliferation has not been fully characterized in HEK-293 cells.To further explore the functional ramifications of cAMP signaling induced by CCK in this cell system, we examined the mitogenic response of CCK-AR or the ICL-1 CCK-BR mutants cell lines to CCK.Methods: Cells grown on multi-well plates were treated with CCK at varying concentrations in serum-free DME/FI2 media for DNA synthesis, or in 0.5% fetal bovine serum for cell numbers.Forskolin alone or in conjunction with 1 mM IBMX was used as positive control of cAMP activation.DNA synthesis was measured by tritiated-thymidine incorporation into TCA-insoluble fraction after 24 h.Cell numbers were counted by microscopic examination of viable cells stained by trypan blue over a 7 day period.Results and Conclusion: CCK inhibited DNA synthesis in cells expressing CCK-AR and CCK-BR ICL-I mutants capable of cAMP production in a dose dependent manner.In contrast, CCK-BR wild type or mutant L85M that exhibited little or no cAMP increase were not sensitive to inhibition by CCK up to 100 nM.Cell numbers were significantly reduced by CCK in CCK-AR, CCK-BR mutants LS1R and $82N, to 8, 30 and 15% of their respective controls after 7 days.Forskolin up to 10 tiM alone had no significant inhibitory effect but caused dose-depandant inhibition of DNA synthesis in the presence of 1 mM IBMX in all HEK-293 cell lines tested.In addition, combination of CCK and forskolin]IBMX caused significent inhibition of DNA synthesis by wild type CCK-BR cells.These data suggest that inhibition of cell growth by CCK in transfected HEK-293 cells may require the involvement of cAMP and its down-stream signals.

Wagner, U., D. Bredenbröker, B. Storm, B. Tackenberg, H-C. Fehmann and P. von Wichert. Effects of VIP and related peptides on airway mucus secretion from isolated rat trachea. Peptides 19(2) 241-245, 1998.—Vasoactive intestinal polypeptide (VIP) is known as an important regulator of airway function. It has been suggested that VIP is involved in the pathogenesis of asthma due to its relaxant effects on smooth muscles. The present study was designed to characterize the effects of the peptides of the VIP family on airway mucus secretion. The peptides VIP, PHI, PACAP-27, PACAP-38, GLP-I, exendin-4, helodermin, helospectin I and helospectin II were investigated using isolated rat trachea. Data show that PACAP-27 is the most potent stimulator of airway mucus secretion (225% stimulation). The rank order of potency was PACAP-27 > VIP > helospectin II > PHI > exendin-4 = helodermin = helospectin I = PACAP-38. The addition of the protease inhibitor thiorphan enhanced the effects of PHI and helodermin, but not of the other peptides. These data show that the peptides of the VIP family stimulate airway mucus secretion differently.