Hippocampal heat shock protein 25 expression in streptozotocin-induced diabetic mice

Hippocampal abnormalities are believed to increase the risk of cognitive decline in diabetic patients. The underlying mechanism is unknown, but both hyperglycemia and oxidative stress have been implicated. Cellular stresses induce the expression of heat shock protein 25 (HSP25) and this results in cytoprotection. Our aim was to assess hippocampal expression of HSP25 in experimental diabetes. Mice were rendered diabetic by streptozotocin injection. Ten weeks after diabetes onset hippocampal HSP25 expression was studied by immunoblotting and immunohistochemistry (IHC). Expression of glial fibrillary acidic protein, nitrotyrosine, iNOS, HSP72, HSP90, and Cu/Zn superoxide dismutase (SOD) was assessed by either IHC or immunoblotting, Cu/Zn-SOD activity by enzymatic assay, and malondialdehyde (MDA) content by colorimetric assay. Hippocampal HSP25 was significantly increased in diabetic as compared to non-diabetic animals and localized predominantly within the pyramidal neurons layer of the CA1 area. This was paralleled by overexpression of nitrotyrosine, iNOS, SOD expression/activity, and enhanced MDA content. In experimental diabetes, HSP25 is overexpressed in the CA1 pyramidal neurons in parallel with markers of oxidative stress.

ANTI-HSP60 and ANTI-HSP70 antibody levels and micro/ macrovascular complications in type 1 diabetes: the EURODIAB Study

OBJECTIVES

The heat shock proteins 60 and 70 (HSP60, HSP70) play an important role in cytoprotection. Under stress conditions they are released into the circulation and elicit an immune response. Anti-HSP60 and anti-HSP70 antibody levels have been associated with cardiovascular disease. Type 1 diabetes is associated with a greatly increased risk of micro- and macrovascular complications. Therefore, we investigated whether anti-HSP60 and anti-HSP70 antibody levels were associated with micro- and macrovascular complications in type 1 diabetic patients.

DESIGN

A cross-sectional nested case-control study from the EURODIAB Study of 531 type 1 diabetic patients was performed.

SUBJECTS

Cases (n = 363) were defined as those with one or more complications of diabetes; control subjects (n = 168) were all those with no evidence of any complication. We measured anti-HSP60 and anti-HSP70 antibody levels and investigated their cross-sectional associations with diabetic complications.

RESULTS

Anti-HSP70 antibody levels were significantly greater in control than in case subjects, whereas anti-HSP60 antibody levels were similar in the two groups. In logistic regression analysis, anti-HSP70 levels in the upper quartiles were associated with a 47% reduced odds ratio of micro/macrovascular complications, independently of conventional risk factors, markers of inflammation and endothelial dysfunction [odds ratio (OR) = 0.53, 95% confidence intervals (CI): 0.28-1.02].

CONCLUSIONS

In this large cohort of type 1 diabetic subjects, we found an independent and inverse association between serum anti-HSP70 antibody levels and diabetic micro/macrovascular complications. This suggests that anti-HSP70 antibody levels may be a novel marker of protection from chronic diabetic complications.

Monocyte chemoattractant protein-1 has prosclerotic effects both in a mouse model of experimental diabetes and in vitro in human mesangial cells

AIMS/HYPOTHESIS

Diabetic nephropathy is characterised by mesangial extracellular matrix accumulation. Monocyte chemoattractant protein-1 (MCP-1), a chemokine promoting monocyte infiltration, is upregulated in the diabetic glomerulus. We performed in vitro and in vivo studies to examine whether MCP-1 may have prosclerotic actions in the setting of diabetes, presumably via its receptor, chemokine (C-C motif) receptor 2 (CCR2), which has been described in mesangial cells.

METHODS

Human mesangial cells were exposed to recombinant human (rh)-MCP-1 (100 ng/ml) for 12, 24 and 48 h and to rh-MCP-1 (10, 100 and 200 ng/ml) for 24 h. Fibronectin, collagen IV and transforming growth factor, beta 1 (TGF-beta1) protein levels were measured by ELISA and pericellular polymeric fibronectin levels by western blotting. The intracellular mechanisms were investigated using specific inhibitors for CCR2, nuclear factor kappa B (NF-kappaB), p38 mitogen-activated protein kinase and protein kinase C, and an anti-TGF-beta1 blocking antibody. In both non-diabetic and streptozotocin-induced diabetic mice that were deficient or not in MCP-1, glomerular fibronectin accumulation was examined by immunohistochemistry, while cortical Tgf-beta1 (also known as Tgfb1) and fibronectin mRNA and protein levels were examined by real-time PCR and western blotting.

RESULTS

In mesangial cells, MCP-1 binding to CCR2 induced a 2.5-fold increase in fibronectin protein levels at 24 h followed by a rise in pericellular fibronectin, whereas no changes were seen in collagen IV production. MCP-1-induced fibronectin production was TGF-beta1- and NF-kappaB-dependent. In diabetic mice, loss of MCP-1 diminished glomerular fibronectin protein production and both renal cortical Tgf-beta1 and fibronectin mRNA and protein levels.

CONCLUSIONS/INTERPRETATION

Our in vitro and in vivo findings indicate a role for the MCP-1/CCR2 system in fibronectin deposition in the diabetic glomerulus, providing a new therapeutic target for diabetic nephropathy.

The MCP-1/CCR2 system has direct proinflammatory effects in human mesangial cells

Both inflammatory and haemodynamic factors have been implicated in the pathogenesis of diabetic and other progressive glomerulopathies. Mesangial cell exposure to mechanical stretch induces both intercellular adhesion molecule 1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) expression. CC Chemokine receptor 2 (CCR2), the cognate MCP-1 receptor, has been recently demonstrated in human mesangial cells (HMCs). We tested whether MCP-1 binding to CCR2 affects ICAM-1 expression in HMCs and, secondly, if stretch-induced ICAM-1 is mediated by MCP-1 via an autocrine mechanism. Serum-deprived HMCs were exposed to either rh-MCP-1 (0.1-1-10-50-100 ng/ml) or mechanical stretch in the presence and in the absence of RS102895, a specific CCR2 inhibitor. ICAM-1 expression was assessed both by immunofluorescence and cytofluorimetry. Monocyte-HMC interaction was tested by adhesion assay. CCR2 expression was studied by reverse transcriptase-polymerase chain reaction, immunoblotting, and flow cytometry. HMCs exposure to rh-MCP-1 induced a significant twofold increase in ICAM-1 expression at 24 h, leading to enhanced monocyte adhesion. This effect occurred via the CCR2 receptor as CCR2 was expressed in HMCs and CCR2 blockade prevented ICAM-1 upregulation. Stretch-induced ICAM-1 expression was not altered by CCR2 blockade and stretch significantly reduced CCR2 mRNA and protein expression via an MCP-1-independent mechanism. In conclusion, stretch and MCP-1 independently induce ICAM-1 expression in HMCs. Stretch-induced CCR2 downregulation may favour MCP-1 paracrine activity.

Glutathione levels in patients with erectile dysfunction, with or without diabetes mellitus

The reduced form of glutathione (GSH) is the most important cell antioxidant and is also an essential cofactor for nitric oxide (NO) synthase that synthesizes NO from l-arginine. Reduced levels of GSH, due both to a hyperglycaemia-induced increase of free radical production and to a decrease of NADPH levels [like in diabetes mellitus (DM)], can hamper the endothelial cell functions. This condition may play an important role in the aetiology of some clinical signs, like erectile dysfunction (ED). The aim of this study was to test the hypothesis that GSH concentration is reduced in patients with ED and type 2 diabetes mellitus. We studied 111 male patients with ED: 64 with diabetes (ED/DM) and 47 without diabetes (ED/wDM); 20 patients with diabetes but without ED (DM) and 26 male normal subjects as a control group (C). The GSH red blood cell concentration was significantly lower in ED than in C (X +/- SD; 1782.12 +/- 518.02 vs. 2269.20 +/- 231.56 mumol/L, p < 0.001). In particular, GSH was significantly reduced in ED/DM vs. ED/wDM (1670.74 +/- 437.68 vs. 1930.63 +/- 581.01 micromol/L, p < 0.01). In DM, GSH was significantly lower than in C and significantly higher than in ED/DM (2084.20 +/- 118.14 vs. 2269.20 +/- 231.56 and vs. 1670.74 +/- 437.68 micromol/L, p < 0.002 and p < 0.001 respectively). GSH showed a negative correlation with fasting glucose concentrations (r = -0.34, p < 0.01) and with the duration of DM (r = -0.25, p < 0.05). A GSH depletion can lead to a reduction of NO synthesis, thus impairing vasodilation in the corpora cavernosa.

Prior gestational hyperglycemia: a long-term predictor of the metabolic syndrome

Little is known about the association between prior gestational hyperglycemia of different severity and the subsequent risk for the metabolic syndrome. Eighty-one women with prior gestational diabetes mellitus (GDM), 25 with one abnormal value at the oral glucose tolerance test (OGTT), and 65 with normal OGTT were studied after a mean of 8.5 yr from the index pregnancy. Patients with prior gestational hyperglycemia (both one abnormal value at the OGTT and GDM) showed a worse metabolic pattern than subjects with gestational normoglycemia [respectively higher values of body mass index (BMI), waist, blood pressure, serum glucose, insulin, C-peptide, homeostatic model assessment (HOMA), fibrinogen and lower levels of HDL-cholesterol]. Prevalence of the metabolic syndrome and its components was 2-4-fold higher in women with prior gestational hyperglycemia (and 10-fold higher if pre-pregnancy obesity coexisted) when compared to normoglycemic controls; in a Cox proportional hazard model, after adjustments for age and pre-pregnancy BMI, gestational hyperglycemia and pre-pregnancy BMI predicted subsequent metabolic syndrome [respectively: hazard ratio (HR)=4.26 and HR=1.21] and most of its components. In the same model, the highest quartile of fasting serum glucose at the OGTT of the index pregnancy was significantly associated to the metabolic syndrome and its components. Gestational hyperglycemia and fasting glucose values were also associated to subsequent fibrinogen values, but not to albumin excretion rates. In young adult women, prior gestational hyperglycemia (particularly abnormal fasting glucose values), above all in combination with pre-pregnancy obesity, anticipates a subsequent syndrome at high cardiovascular risk and, possibly, a mild chronic inflammatory response.

A clinically orientated approach increases the efficiency of screening for latent autoimmune diabetes in adults (LADA) in a large clinic-based cohort of patients with diabetes onset over 50 years

AIMS

To assess if a clinically orientated approach improves screening for latent autoimmune diabetes in adults (LADA) in patients developing diabetes over age 50.

METHODS

From a clinic-based cohort of 3327 patients with Type 2 DM diagnosed over age 50 we recruited those with at least one feature suggestive of insulin deficiency: (i) fasting blood glucose > or = 15 mmol/l and/or HbA(1c) > or = 10% in spite of adequate compliance to diet and treatment; (ii) decreasing body weight > or = 10% in the previous 3 months in spite of constant diet; (iii) BMI < 25 mg/kg(2). A control group of 240 patients not presenting any of the previous criteria was randomly selected from the out-patient clinic.

RESULTS

We identified 220 (6.6%) patients, of whom 70 were positive for glutamic acid decarboxylase antibodies (GADA) and/or islet cell antibodies (ICA), giving a prevalence of LADA of 31.8% (95% CI 25.7-38.4). In contrast, no patient randomly selected from the remaining cohort had marker positivities. With respect to patients negative for both ICA and GADA, those who were positive had lower C-peptide values (0.53 +/- 0.51 vs. 0.88 +/- 0.42 nmol/l, P < 0.001); the lowest levels were found in patients in whom both antibodies were positive. In linear regression analysis, variables independently associated with fasting C-peptide were GADA (beta = -0.25, P < 0.001), ICA (beta = -0.15, P = 0.04), BMI (beta = 0.03, P < 0.001) and duration of diabetes (beta = -0.02, P < 0.001).

CONCLUSION

This study shows that: (i) a clinically orientated approach increases the efficiency of a screening programme for LADA, so that one in three screened patients are classified correctly; (ii) ICA and GADA positivity were negatively associated with residual beta-cell function, independent of BMI and duration of the disease; (iii) positivity for both ICA and GADA identifies patients with the lowest residual beta-cell function.

Clinical characteristics and outcome of pregnancy in women with gestational hyperglycaemia with and without antibodies to beta-cell antigens

AIMS

To evaluate the prevalence of beta-cell autoantibodies in women with gestational diabetes and impaired glucose tolerance, and identify clinical characteristics differentiating hyperglycaemic patients with and without autoantibodies.

METHODS

One hundred and twenty-three pregnant patients with gestational diabetes, 84 with impaired glucose tolerance and 290 with normoglycaemia were evaluated for anti-islet cell antibodies, glutamic acid decarboxylase (GAD) autoantibodies, and the components of the metabolic syndrome.

RESULTS

Autoantibody positivity was 8.9%, 17.9% and 0.3% in patients with diabetes, impaired tolerance and normoglycaemia, respectively. Hyperglycaemic patients with autoantibodies had lower body mass index, waist, weight gain at the time of the screening test and a lower percentage of previous pregnancies than those without autoantibodies. In addition, their fasting insulin values were significantly lower and inversely related to the presence of autoantibodies (odds ratio (OR) = 0.64; 95% confidence interval (CI) 0.42-0.96), the lowest values being found in anti-GAD+ patients. Autoantibody-positive women with diabetes were more frequently treated with insulin than negative patients (OR = 7.21; 95% CI 1.85-28.08).

CONCLUSIONS

Autoantibody-positive women with gestational hyperglycaemia displayed fewer features of insulin resistance and required more frequent insulin therapy than negative women and presumably had presymptomatic Type 1 diabetes. If this conclusion is corroborated by the follow-up of larger series, clinical and immunological distinction of types of gestational hyperglycaemia would be useful.

Anti-CD38 autoantibodies: characterisation in new-onset type I diabetes and latent autoimmune diabetes of the adult (LADA) and comparison with other islet autoantibodies

AIMS/HYPOTHESIS

Serum anti-CD38 autoantibodies (aAbs) have been reported in 17 to 19% of patients with long-standing Type I (insulin-dependent) diabetes mellitus and Type II (non-insulin-dependent) diabetes mellitus. Whether these aAbs are also found in new-onset Type I diabetes and in Latent Autoimmune Diabetes in Adults (LADA) is not known, as is their relationship with conventional islet aAbs.

METHODS

These issues were addressed by studying new-onset Type I and LADA diabetic cohorts with a recently developed anti-CD38 enzymatic immuno-assay.

RESULTS

Anti-CD38 aAb prevalence among new-onset Type I patients (3.8%) was lower than previously found in long-standing Type I diabetes (11.7%, as defined with the 97.5 percentile cutoff; p=0.01), suggesting a late appearance of these aAbs. Among LADA patients, 14.9% were anti-CD38(+). Anti-CD38 were only associated with anti-GAD aAbs in new-onset Type I diabetes. Although the CD38 target molecule was expressed in human pancreatic islets, anti-CD38 aAbs did not contribute to the islet cell antibody (ICA) immunofluorescence reactivity. All the positive sera analysed for Ca(2+) release were found to mobilise it. In agreement with these agonistic features, anti-CD38(+) new-onset Type I patients showed higher fasting C-peptide values as compared to negative counterparts; the association was stronger when the analysis was limited to the agonistic anti-CD38(+) sera. A similar trend was found among LADA patients.

CONCLUSION/INTERPRETATION

Anti-CD38 aAbs are distinct markers of islet autoimmunity which are more prevalent in long-standing disease, as opposed to the other known islet aAbs. Their in vitro agonistic properties could be operating in vivo as well, as they identify sub-groups of patients with higher residual beta-cell function.

The possible role of autoimmunity in the pathogenesis of diabetes in B-thalassemia major

OBJECTIVE

To evaluate the possible role of autoimmunity in the pathogenesis of diabetes associated with B-thalassemia, we studied a cohort of 53 B-thalassemic individuals, under long term blood transfusion, that included twelve patients with diabetes (22.6%).

MATERIAL AND METHODS

To evaluate the activation of an autoimmune response, individuals were tested for islet cell antibodies (ICA), glutamic acid decarboxylase (GAD) autoantibodies, insulin autoantibodies (IAA) and serum anti-nuclear antibodies (ANA).

RESULTS

Nine of the total B-thalassemic population (16.98%) were ICA-positive. The frequency of ICA-positive subjects among thalassemic individuals was higher than in the general population. Five (41.6%) of the ICA-positive individuals were diabetic. Of these, three were serum C-peptide-negative (<0.21 nmol/l). HLA class II typing of our thalassemic population did not reveal significantly different allelic frequencies with respect to the control population.

CONCLUSIONS

Our study demonstrates evidence of immune system activation against pancreatic B-cells in B-thalassemia and we propose that iron deposition may, through oxidative damage, act as an environmental factor that triggers the autoimmune response. Therefore, we speculate that pancreatic autoimmunity may contribute to selective B-cells damage in the pathogenesis of diabetes associated with B-thalassemia.