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H Kolb

Publications and source records attributed to H Kolb.

At least 37 records · Page 2Linked to original sources
PubMed2003

[Pilot study of controlled retrospective analysis (retrolective study design) of care for type 2 diabetics since 1990].

BACKGROUND AND OBJECTIVE: There are few data on the quality of care received by patients with type 2 diabetes under routine conditions and only a few long-term studies that investigated the influence of treatment strategies on the development of clinical endpoints. It was the aim of this study, using retrospectively obtained data, to determine whether it is possible to document over a 10 year period the treatment design and clinical end-points in type 2 diabetics under the care of general practitioners. PATIENTS AND METHODS: General practitioners were randomly selected and informed by independent collaborating monitors about the aim of the study and data documentation. At a second visit by a monitor the completed data forms were audited and entered into a database. Course of treatment was documented by 21 general practitioners, two of them diabetes specialists, for all patients in whom, between 1.1.1990 and 31.12.1993, type 2 diabetes had been diagnosed for the first time (n=455; 251 females, 204 males, mean age 61,5 years). Continuous complete documentation of the course of treatment in the given practice was obtained in 85% of patients over a mean observation period of 8,7 years. 45 myocardial infarcts in 40 patients (9%), 42 strokes in 37 patients (8%), blindness in seven eyes of five patients (1,5%) and 19 amputations (4,2%) were recorded; 72 patients died (15,8%). CONCLUSION: The data of this pilot study indicate that detailed analysis of treatment quality can be obtained in a sizeable cohort, using of a well controlled retrospective (retrolective) study design.

Adult↗
PubMed2003

A wheat-based, diabetes-promoting diet induces a Th1-type cytokine bias in the gut of NOD mice.

Dietary antigens are candidate environmental factors in the pathogenesis of type 1 diabetes. In the non-obese diabetic (NOD) mouse, an animal model of type 1 diabetes, cereal-based diets promote disease development, whereas the diets based on hydrolysed proteins or non-diabetogenic proteins are protective. The hypothesis that diabetogenic diets modulate the cytokine balance in the gut was tested. NOD mice were fed with NTP-2000 (mainly a wheat-based milk-free diet) or Prosobee (a semi-purified hypoallergenic diet based on soy protein isolate) or Prosobee plus casein (milk protein fraction). The mRNA levels of IFN-gamma, IL-10, TNF-alpha, TGF-beta, and inducible NO synthase in the small intestine and the Peyer's patches were determined by semi-quantitative RT-PCR. Mice fed on the cereal-based NTP-2000 diet expressed higher levels of the Th1-type and pro-inflammatory markers IFN-gamma, TNF-alpha, and inducible NO synthase mRNA compared to the Prosobee-fed animals. The expression of the counterregulatory cytokines IL-10 and TGF-beta was unaffected. This resulted in a significant bias of the intestinal cytokine balance towards T helper cell type 1 after feeding NTP-2000. The cytokine mRNA levels in the gut-associated Peyer's patches were not affected. Thus, modulation of gut immunoreactivity by diet may contribute to disease development in NOD mice.

Animal Feed↗
PubMed2002

A multi-centre, blinded international trial of the effect of A(1) and A(2) beta-casein variants on diabetes incidence in two rodent models of spontaneous Type I diabetes.

AIMS/HYPOTHESIS: The diabetes-inducing potential of cows' milk is still debated and there is no consensus on the diabetogenicity of individual milk proteins. A(1)-beta-casein has been associated with increased diabetes frequency in ecological studies and in NOD mice. Our aim was to ascertain whether A(1)-beta-casein was more diabetogenic than A(2) and to test the diabetogenicity of a milk-free diet in animals representing different forms of spontaneous Type I (insulin-dependent) diabetes mellitus. METHODS: Defined diets were coded and shipped to laboratories in New Zealand (NOD/NZ), Canada (BB) and the UK (NOD/Ba). Base diets were Pregestimil (PG) and ProSobee (PS). Purified fractions of whole casein (WC), A(1)or A(2)-beta-casein were added at 10%. A milk-free, wheat-predominant, NTP-2000 diet was the control. Animals were fed from weaning up to 150 or 250 days, and insulitis, diabetes frequency and expression of pancreatic cytokines were assessed. RESULTS: Diabetes incidence was highest in three locations in animals fed NTP-2000. PG and PS diets were protective except for NOD/Ba mice fed PG+WC where incidence was similar to NTP-2000. A(1) and A(2) diets were protective in both models, but A(1) beta-casein was slightly more diabetogenic in PS-fed BB rats. The New Zealand study was confounded by an infection. CONCLUSION/INTERPRETATION: A milk-free, wheat-predominant diet was highly diabetogenic in three widely separate locations in both animal models. A previous result that A(1) beta-casein was more diabetogenic than A(2) beta-casein in NOD mice was not confirmed; both beta-casein variants were protective in BB rats and NOD mice. Whole Casein promoted diabetes in NOD/Ba but protected BB showing that unique diabetes haplotypes react differently to dietary proteins. A(1)- was more diabetogenic than A(2)-beta-casein only in PS-fed BB rats. Neither the analysis of insulitis nor of pancreatic cytokine gene expression showed a difference between A(1) or A(2) beta-casein fed animals. Milk caseins are unlikely to be exclusive promoters of Type I diabetes, but could enhance the outcome of diabetes in some cases. Other diet components such as wheat could be more important promoters of Type I diabetes.

Animals↗
PubMed2002

Impaired glucose tolerance is associated with increased serum concentrations of interleukin 6 and co-regulated acute-phase proteins but not TNF-alpha or its receptors.

AIMS/HYPOTHESIS: A population-based sample was studied to define immune abnormalities in individuals at risk of Type II (non-insulin-dependent) diabetes mellitus because of impaired glucose tolerance. METHODS: A total of 1653 individuals aged 55 to 74 years participated in a population based survey in Southern Germany (KORA Survey 2000). Those without a history of diabetes were subjected to an OGTT. Randomly selected subjects with IGT ( n=80) were compared with non-diabetic control subjects ( n=77) and patients with Type II diabetes ( n=152) of the same population-based sample after matching for age and sex. Immune parameters were analysed in serum with rigidly evaluated ELISA. RESULTS: Serum pro-inflammatory cytokine interleukin 6 (IL-6) concentrations were higher in subjects with IGT and Type II diabetes than in the control subjects (median 1.8 and 2.5 vs 0.8 pg/ml, p<0.0001). Soluble IL-6 receptors potentiate IL-6 bioactivity and their concentrations were mildly increased in Type II diabetes ( p<0.05). These immune changes seem relevant because IL-6 dependent acute-phase proteins C-reactive protein, serum amyloid A protein and fibrinogen were also increased in IGT and Type II diabetes. Circulating concentrations of TNF-alpha and its two receptors sTNF-R60 and sTNF-R80 were not increased in IGT subjects compared with the control subjects. CONCLUSION/INTERPRETATION: Our study shows systemic up-regulation of selected inflammatory mediators in patients with Type II diabetes and IGT. The pattern observed is non-random and fits with an IL-6 associated rather than TNF-alpha associated response.

Acute-Phase Proteins↗
PubMed2002

Immunoregulation during disease progression in prediabetic NOD mice: inverse expression of arginase and prostaglandin H synthase 2 vs. interleukin-15.

Non-obese diabetic (NOD) mice spontaneously develop insulin dependent diabetes due to autoimmune destruction of beta-cells. The progression of insulitis can be accelerated and synchronized in the pancreas by a single injection of 250 mg/kg cyclophosphamide. In this study, we will report on three immune mediators that were not known to be expressed during insulitis until now. Early insulitis in ten-week-old female NOD mice was associated with strong expression of prostaglandin H synthase 2 in the pancreas and of arginase, an antagonist enzyme of the inducible NO synthase. After acceleration of insulitis progression by cyclophosphamide, expression of the two enzymes was downregulated within 24 h. There was strong concomitant upregulation of IL-15 gene expression that preceded lymphocyte invasion of islets and a rise of IFN-gamma mRNA levels by several days. The comparison of individual pancreata showed that the expression of IL-12 and IL-18 mRNA closely correlated with levels of IL-15 gene expression. We conclude that arginase and prostaglandin H synthase 2 expression is associated with peri-insulitis, while IL-15 is a candidate cytokine in driving destructive insulitis, as it elicits Th1-cytotoxic responses in lymphoid as well as in non-lymphoid immune cells and is unusually resistant to downregulation by antagonistic cytokines. This is the first report on arginase, prostaglandin H synthase 2 and IL-15 expression in pancreatic lesions of prediabetic NOD mice.

Animals↗
PubMed2002

A murine interleukin-4-Ig fusion protein regulates the expression of Th1- and Th2-specific cytokines in the pancreas of NOD mice.

Interleukin (IL)-4 is a key cytokine in T-helper type 2 (Th2) immune response. We have constructed a dimeric IL-4 molecule consisting of the murine IL-4 and the murine Fc part of IgG2a. We first tested the biological activity of the chimeric protein by in vitro studies using isolated murine spleen cells. IL-4-Ig was found to downregulate LPS-induced IFN-gamma and TNF-alpha production. The immunomodulatory potential of the fusion protein was also analyzed in non-obese diabetic (NOD) mice, an animal model for human type 1 diabetes. Female NOD mice aged 10 weeks were treated once with cyclophosphamide to accelerate and synchronize the progression of insulitis. Treatment with IL-4-Ig induced strong modulation of the pancreatic cytokine balance. Expression was downregulated for both Th1-specific cytokine IFN-gamma and the Th2-specific cytokine IL-10. IL-12p40 expression was only slightly affected. Interestingly, infiltration increased in the islets of IL-4-Ig-treated animals, and therefore did not correlate with the decreased IFN-gamma expression. Hence, IL-4-Ig did not prevent the progression from peri- to intra-insulitis, but suppressed inflammatory cytokine production. In most experiments, the biological activity of IL-4-Ig and IL-4 was comparable. We conclude that treatment with the chimeric protein IL-4-Ig effectively downregulates Th1 responses but simultaneously augments intra-islet infiltration.

Animals↗
PubMed2001

Dominant role of intercellular adhesion molecule-1 in the pathogenesis of autoimmune diabetes in non-obese diabetic mice.

Intercellular adhesion molecule (ICAM)-1 is involved in forming the immunological synapse. The contribution of ICAM-1 to immune responses is not critical because mice with a disrupted ICAM-1 gene do not have grossly abnormal immune reactivity. Here we report on the surprising finding that diabetes-prone NOD mice with a disrupted ICAM-1 gene (ICAM-1(-/-)) are completely protected from disease development. While 64% of ICAM-1(+/+) and 44% of ICAM-1(+/-) female NOD mice developed overt diabetes until 310 days old, no ICAM-1(-/-) NOD mice became hyperglycaemic. Histological examinations revealed minor infiltration around pancreatic islets of ICAM1(-/-) NOD mice. Administration of cyclophosphamide caused a progression to severe islet destruction in ICAM-1(+/+) NOD mice within 10 days. In contrast, ICAM-1(-/-) mice showed only mild insulitis. Furthermore, ICAM-1(+/+) NOD mice showed an increase of IFN-gamma, interleukin (IL)-12p40 and IL-12p35 pancreatic mRNA levels, leading to an increased ratio of IFN-gamma: IL-4 and IL-12p40: IL-12p35 expression. In contrast, ICAM-1(-/-) NOD mice did not upregulate IFN-gamma or IL-12p40 gene expression but maintained IL-4 and increased IL-12p35 gene expression. These results identify a dominant and non-redundant role of ICAM-1 in the development of autoimmune diabetes.

Animals↗
PubMed2001

Disease resistant, NOD-related strains reveal checkpoints of immunoregulation in the pancreas.

The autoimmune diabetic NOD mouse serves as a model for human type 1 diabetes. Disease development is due to islet beta cell destruction in the context of immune cell infiltration of islets and inflammatory changes throughout the pancreas. In the present study we tried to identify immune reactivity patterns in the pancreas associated with diabetes resistance in NOD-related mouse strains. The pancreata of diabetes-prone female NOD/LtJ, NOD/Bom and of genetically related but diabetes-resistant strains; NOR, NON, NON.NOD-H2g7, NOD.NON-H-2nbl were obtained at the age of 70 days for semiquantitative analysis of insulitis and of mRNA expression by reverse transcriptase PCR. In addition, the response to a single dose of cyclophosphamide for synchronizing and accelerating the progression of insulitis was determined. The progression of insulitis and immune gene expression in response to cyclophosphamide revealed characteristic differences between the six strains. NOD/LtJ and NOD/Bom mice were found significantly to upregulate pancreatic IL-12p40 and IL-18 expression after cyclophosphamide treatment, followed by an increase in IFN-gamma mRNA levels. In contrast, the two MHC-haplotype H-2nbl expressing strains either up-regulated neither IL-12/IL-18 nor IFN-gamma gene expression. The two strains sharing MHC haplotype H-2g7 expression with NOD did respond to cyclophosphamide with IL-12p40/IL-18 gene expression. However, NON.NOD-H-2g7 mice failed to progress to IFN-gamma gene expression. NOR mice progressed to IFN-gamma expression but exhibited sustained IL-4 gene expression. Only severe intra-insulitis was associated with the expression of inducible NO synthase. The comparison of diabetes-prone and diabetes-resistant strains revealed three checkpoints of immune regulation in the pancreas. The earliest checkpoint is the induction of an IL-12p40/IL-18 response in innate immune or antigen-presenting cells. The next level of control is at the induction of IFN-gamma gene expression, and a third checkpoint is the maintenance or loss of antagonistic Th2 type reactions.

Animals↗
PubMed2001

Does partial preservation of residual beta-cell function justify immune intervention in recent onset Type I diabetes?

Immune intervention seems to offer the prospect of preventing or reversing the hyperglycaemic phase of Type I (insulin-dependent) diabetes mellitus. A number of prevention trials have been undertaken before disease onset but the logistics of such trials are prohibitive. More rapid and less expensive means of testing new therapies are needed and the current emphasis is therefore on intervention after diagnosis to salvage residual beta-cell function. At present, because restoration of normal metabolism seems unattainable, such interventions are tested against their ability to maintain C-peptide production over the first months or years of diabetes.

C-Peptide↗
PubMed2001

Localization of neurotransmitters and calcium binding proteins to neurons of salamander and mudpuppy retinas.

We wished to identify the different types of retinal neurons on the basis of their content of neuroactive substances in both larval tiger salamander and mudpuppy retinas, favored species for electrophysiological investigation. Sections and wholemounts of retinas were labeled by immunocytochemical methods to demonstrate three calcium binding protein species and the common neurotransmitters, glycine, GABA and acetylcholine. Double immunostained sections and single labeled wholemount retinas were examined by confocal microscopy. Immunostaining patterns appeared to be the same in salamander and mudpuppy. Double and single cones, horizontal cells, some amacrine cells and ganglion cells were strongly calbindin-immunoreactive (IR). Calbindin-IR horizontal cells colocalized GABA. Many bipolar cells, horizontal cells, some amacrine cells and ganglion cells were strongly calretinin-IR. One type of horizontal cell and an infrequently occurring amacrine cell were parvalbumin-IR. Acetylcholine as visualized by ChAT-immunoreactivity was seen in a mirror-symmetric pair of amacrine cells that colocalized GABA and glycine. Glycine and GABA colocalized with calretinin, calbindin and occasionally with parvalbumin in amacrine cells.

Acetylcholine↗
PubMed2000

Choline acetyltransferase is found in terminals of horizontal cells that label with GABA, nitric oxide synthase and calcium binding proteins in the turtle retina.

In this study, we discriminated the various types of horizontal cell in the turtle retina on their content of neuroactive substances. Double label immunocytochemistry was performed on sectioned and wholemount retina using antisera to neural- and endothelial-nitric oxide synthase (nNOS, and eNOS), calretinin (CR), calbindin (CB), gamma-aminobutyric acid (GABA) and choline acetyltransferase (ChAT). H1 cells and their axon terminals label with CR, CB and GABA. Only H1 axon terminals label with eNOS. H2 cells contain CB, CR, nNOS and GABA maybe in their dendrites. H3 cells label only with nNOS. The localization of nNOS in the H2 and H3 cells is a novel finding. None of these antibodies labels H4 cells. The photoreceptor subtypes have been differentiated by different intensity of labeling with CB. The accessory member of the double cone is less intensely labeled with CB than the principal member and rods and blue cones do not appear to label at all. ChAT-IR is located in terminal boutons of H1 and H2 horizontal cells and H1 axon terminals and these boutons contact rods and all spectral types of cones. Clearly, GABA is present in H1 horizontal cells and may be used in neurotransmission between horizontal cells and possibly for feedback pathways to photoreceptors. The evidence of nNOS immunoreactivity in H2 and H3 horizontal cells, combined with available physiological evidence, suggests that NO may be involved in electrical coupling and/or modulation of synaptic input to these types of cells. Furthermore, our results raise the possibility that cholinergic synaptic transmission may occur from horizontal cell processes to photoreceptors in the outer plexiform layer of the turtle retina.

Animals↗
PubMed2000

Natural resistance of human beta cells toward nitric oxide is mediated by heat shock protein 70.

Human beta cells exhibit increased resistance against nitric oxide (NO) radicals as compared with rodent islet cells. Here we tested whether endogenous heat shock protein 70 (hsp70) accounts for the resistance of human cells. Stable transfection of the human beta cell line CM with an antisense hsp70 mRNA-expressing plasmid (ashsp70) caused selective suppression (>95%) of spontaneously expressed hsp70 but not of hsc70 or GRP75 protein. ashsp70 transfection abolished the resistance of CM cells to the NO donors (Z)-1- (2-(2-aminoethyl)-N-(2-ammonioethyl)amino)diazen-1-ium -1,2-diolate and sodium nitroprusside and increased the proportions of necrotic cells 3-5-fold (p < 0.05) and of apoptotic cells about 2-fold (p < 0.01). Re-induction of hsp70 expression by heat shock re-established resistance to NO toxicity. hsp70 did not exert its protective effect at the level of membrane lipid integrity because radical induced lipid peroxidation appeared independent of hsp70 expression. However, after NO exposure only hsp70-deficient cells showed significantly decreased mitochondrial activity, by 40-80% (p < 0.01). These results suggest a key role of hsp70 in the natural resistance of human beta cells against NO induced injury, by preserving mitochondrial function. These findings provide important implications for the development of beta cell protective strategies in type 1 diabetes and islet transplantation.

Animals↗
PubMed2000

p38-dependent enhancement of cytokine-induced nitric-oxide synthase gene expression by heat shock protein 70.

Heat shock protein (hsp) 70 protects cells against stress by means of its ability to chaperone denatured proteins and to modulate stress-activated signaling pathways. Because inflammatory processes are often accompanied by hsp expression and because stress and cytokines share several signaling pathways, we investigated the possibility that hsp70 might modulate the cellular response to cytokines. We found that stable cell clones overexpressing hsp70, or cells shortly after transfection with hsp70, produced 2 times more nitric oxide and inducible nitric-oxide synthase (iNOS) protein and mRNA in response to cytokines than control cells expressing undetectable amounts of hsp70. Since mitogen-activated protein kinases participate in the activation of iNOS by cytokines, we investigated whether hsp70 affected the activation of these signaling pathways. hsp70 overexpression led to a specific enhancement of the activation of the p38 pathway by cytokines, producing little or no effect on the activation of extracellular signal-regulated kinase or Jun N-terminal kinase. Blocking p38 activity with SB203580 totally abolished the enhancing effect of hsp70 on cytokine-induced endogenous iNOS mRNA accumulation or transcription of an iNOS promoter-driven luciferase gene, while having little effect on the cytokine response observed in control cells. We conclude that the p38 pathway acts as an enhancing factor in the activation of iNOS by cytokines and that hsp70 can modulate the cellular response to cytokines by acting on signaling elements upstream of p38.

Animals↗