Growth factor signalling in the regulation of α-cell fate.

Glucagon plays critical roles in regulating glucose homeostasis, mainly by counteracting the effects of insulin. Consequently, the dysregulated glucagon secretion that is evident in type 2 diabetes has significant implications in the pathophysiology of the disease. Glucagon secretion from pancreatic α-cells has been suggested to be modulated by blood glucose, signals from the nervous system and endocrine components. In addition to these regulators, intraislet factors acting in a paracrine manner from neighbouring ß-cells are emerging as central modulator(s) of α-cell biology. One of the most important of these paracrine factors, insulin, modulates glucagon secretion. Indeed, the α-cell-specific insulin receptor knockout (αIRKO) mouse manifests hypersecretion of glucagon in the postprandial stage and exhibits defective secretion in fasting-induced hypoglycaemia, together mimicking the α-cell defects observed in type 2 diabetes. Interestingly, αIRKO mice display a progressive increase in ß-cell mass and a concomitant decrease in α-cells. Lineage trace analyses reveal that the new ß-cells originate, in part, from the insulin receptor-deficient α-cells indicating a critical role for α-cell insulin signalling in determining ß-cell origin. Our studies also reveal that glucagon-like peptide-1 (GLP-1) treatment of αIRKO mice suppresses glucagon secretion despite absence of functional insulin receptors precluding a role for insulin in GLP-1 action on α-cells in this model. These findings highlight the significance of insulin signalling in the regulation of α-cell biology.

Association of soluble CD40 ligand with carotid atherosclerosis in Japanese type 1 diabetic patients.

AIMS/HYPOTHESIS: It has recently been shown that the soluble form of CD40 ligand (sCD40L) interacts with CD40 on vascular cells, leading to a variety of proinflammatory responses, and that serum sCD40L levels can be a predictive marker of cardiovascular events. The aim of this study was to estimate sCD40L levels in type 1 diabetic patients to examine a possible association with carotid atherosclerosis. SUBJECTS AND METHODS: Human sCD40L levels in serum and intima-media thickness (IMT) of carotid artery were examined in 80 Japanese type 1 diabetic patients (27 men and 53 women, age 22.8+/-3.4 years (mean+/-SD), duration of diabetes 13.2+/-6.1 years) and 20 healthy age-matched non-diabetic individuals. RESULTS: Serum sCD40L levels were significantly (p=0.0185) higher in subjects with type 1 diabetes (2.10+/-1.33 ng/ml) compared with non-diabetic subjects (1.35+/-0.88 ng/ml). The greatest IMT (Max-IMT) and averaged IMT (Mean-IMT) were also significantly greater in patients with type 1 diabetes than in control subjects (0.73+/-0.14 vs 0.64+/-0.07 mm, p=0.0041, 0.63+/-0.09 vs 0.57+/-0.06 mm, p=0.0066, respectively). Levels of sCD40L were statistically significantly associated with Max-IMT (r=0.383, p<0.001) and Mean-IMT (r=0.275, p=0.0058). Furthermore, stepwise multivariate regression analyses demonstrated that sCD40L is a determinant of both Max- and Mean-IMT, independently of conventional risk factors. CONCLUSIONS/INTERPRETATION: It is suggested that increased levels of serum sCD40L are associated with accelerated atherosclerotic change observed in young patients with type 1 diabetes.

Increased stress protein ORP150 autoantibody production in Type 1 diabetic patients.

AIMS: Various genetic and environmental stresses interfere with protein folding in the endoplasmic reticulum (ER), which leads to the induction of ER stress. It has recently been reported that ER stress is involved in the development of diabetes in diabetic animal models. The aim of this study is to estimate ER stress levels in Type 1 diabetic patients. METHODS: We recruited Type 1 diabetic patients undergoing periodic follow-up examinations (n = 91) and healthy non-diabetic individuals (n = 37), and measured their serum anti-oxygen-related protein (ORP)150 autoantibody levels. RESULTS: Anti-ORP150 autoantibody levels in Type 1 diabetic patients were significantly higher compared with those in healthy non-diabetic subjects. Furthermore, the serum autoantibody levels in Type 1 diabetic patients correlated with HbA(1c) (F > 3.0, P = 0.079), indicating that hyperglycaemia itself induces ER stress in diabetes. CONCLUSIONS: Anti-ORP150 autoantibody levels in Type 1 diabetic patients are higher compared with non-diabetic subjects, suggesting that ER stress is increased in Type 1 diabetes.

Use of immunohistochemical procedures in diagnosing angiosarcoma. Evaluation of 98 cases.

BACKGROUND: Differential diagnosis of angiosarcoma, predominantly showing a non- or poorly vasoformative proliferation from other types of sarcomas, poorly differentiated carcinomas, and amelanotic melanoma, is often problematic. METHODS: The use of antibodies directed against Factor VIII-related antigen (FVIIIRA), Ulex europaeus lectin type 1 (UEA-1), CD31, and vascular endothelial growth factor (VEGF) in the diagnosis of angiosarcoma was examined in 98 cases of autopsy-proven angiosarcoma diagnosed during 1974-1990 in a survey of 178 Japanese hospitals. Reactivity of angiosarcoma cells for epithelial membrane antigen, cytokeratin, and melanoma cell antigen (HMB45) also was examined. RESULTS: Histologic specimens were formed exclusively by vasoformative areas in 32 cases and combined vasoformative and varying extents of non- or poorly vasoformative areas in another 66 cases. In vasoformative areas, the proliferating cells showed a diffuse positive reaction in the cytoplasm and/or cell surface for anti-FVII-IRA in 82 (84%) of 98 cases, for anti-CD31 in 78 (80%), and for UEA-1 in 69 (70%). In non- or poorly vasoformative areas, the positivity rate for FVIIIRA, CD31, and UEA-1 was 29%, 62%, and 46%, respectively. A positive reaction was found for either one of three endothelial markers in the non- or poorly vasoformative areas of 57 cases (86%). Epithelial membrane antigen and anticytokeratin antibody were positive in 4 and 11 cases, respectively, in the vasoformative areas and in 3 and 14 cases, respectively, in non- or poorly vasoformative areas with a simultaneous positive reaction for either one of three endothelial cell markers. None of the proliferating cells showed a positive reactivity for HMB45. The positivity rates of the angiosarcoma cells for each marker were different according to the primary tumor sites. The angiosarcoma cells in non- or poorly vasoformative areas showed the lowest positivity rate for anti-FVIIIRA in the heart (9%) and for anti-CD31 in the extremities (17%) and the highest positivity rate for anticytokeratin in the trunk (60%). Ulex europaeus lectin type 1 had almost the same reactivity rate (30-56%) in every organ. Angiosarcoma cells in 13 (36%) of 36 biopsy specimens and 8 (14%) of 56 autopsy specimens were positive for the anti-VEGF antibody. CONCLUSION: These findings suggest that the combined use of endothelial cell markers including FVIIIRA, UEA-1, and CD31 is useful in the diagnosis of angiosarcoma, especially in cases exclusively with a non- or poorly vasoformative pattern.