Serum antibodies to collagen type IV and development of diabetic vascular complications in children with type 1 (insulin-dependent) diabetes mellitus. A longitudinal study

Serum Anti-Collagen IV IgM and IgG Antibodies as Indicators of Low Vascular Turnover of Collagen IV in Patients with Long-Term Complications of Type 2 Diabetes

Thickening of the vascular basement membrane (BM) is a fundamental structural change in the small blood vessels in diabetes. Collagen type IV (CIV) is a major component of the BMs, and monitoring the turnover of this protein in type 2 diabetes (T2D) can provide important information about the mechanisms of vascular damage. The aim of the study was through the use of non-invasive biomarkers of CIV (autoantibodies, derivative peptides, and immune complexes) to investigate vascular turnover of CIV in patients with long-term complications of T2D. We measured serum levels of these biomarkers in 59 T2D patients with micro- and/or macrovascular complications and 20 healthy controls using an ELISA. Matrix metalloproteinases-2 and -9 (MMP-2 and MMP-9) were also tested. In the T2D group, significantly lower levels of CIV markers and significantly higher levels of MMP-2 and MMP-9 were found compared to controls. A significant positive correlation was found between IgM antibody levels against CIV and MMP-2. These findings suggest that vascular metabolism of CIV is decreased in T2D with long-term complications and show that a positive linear relationship exists between MMP-2 levels and CIV turnover in the vascular wall.

Use of Glycated Hemoglobin (A1c) as a Biomarker for Vascular Risk in Type 2 Diabetes: Its Relationship with Matrix Metalloproteinases-2, -9 and the Metabolism of Collagen IV and Elastin

Background and objectives: HbA1c measurements may be useful not only in optimizing glycemic control but also as a tool for managing overall vascular risk in patients with diabetes. In the present study, we investigate the clinical significance of HbA1c as a biomarker for hyperglycemia-induced vascular damages in type 2 diabetes (T2D) based on the levels of matrix metalloproteinases-2, -9 (MMP-2, MMP-9), anti-collagen IV (ACIV), and anti-elastin (AE) antibodies (Abs) IgM, IgG, and IgA, and CIV-derived peptides (CIV-DP) reflecting collagen and elastin turnover in the vascular wall. The aim is to show the relationship of hyperglycemia with changes in the levels of vascular markers and the dynamics of this relationship at different degrees of glycemic control reported by HbA1c levels. Materials and Methods: To monitor elastin and collagen IV metabolism, we measured serum levels of these immunological markers in 59 patients with T2D and 20 healthy control subjects with an ELISA. Results: MMP-2, MMP-9, and the AEAbs IgA levels were significantly higher in diabetic patients than in control subjects, whereas those of the AEAbs IgM, ACIVAbs IgM, and CIV-DP were significantly lower. MMP-9 levels were significantly lower at HbA1c values >7.5%. Conclusions: A set of three tested markers (MMP-2, MMP-9, and AEAbs IgA) showed that vascular damages from preceding long-term hyperglycemia begin to dominate at HbA1c values ≥7.5%, which is the likely cut-point to predict increased vascular risk.

Serum anti-collagen type IV IgM antibodies and development of diabetic nephropathy in diabetics with essential hypertension

INTRODUCTION AND AIMS

Arterial hypertension and diabetic vascular complications are connected with an elevated degradation of elastic tissue. This process leads to an increased production of antibodies to collagen type IV (ACIV Abs). In the present investigation we studied whether the serum levels of antibodies (IgG, IgM and IgA) to collagen are related with microvascular complications.

MATERIAL AND METHODS

Serum levels of antibodies to collagen type IV (ACIV) IgG, IgM and IgA were measured using an ELISA method in 93 patients with type 2 diabetes mellitus and arterial hypertension (AH) (mean age 61.4 ±11.3 years, diabetes duration 9.88 ±3.12 years; hypertension duration 9.28 ±4.98). These values were compared to serum antibodies to CIV in 42 age and sex matched controls.

RESULTS

ACIV IgM antibodies levels in patients with AH and T2DM were statisticaly significantly higher than controls 0.178 (0.145÷0.220) vs. 0.142 (0.118÷0.173) (KW = 6.31; p = 0.01). Group 1 (patients with microvascular complications) showed significantly higher levels of ACIV IgM than controls 0.180 (0.136÷0.223) vs. 0.142 (0.118÷0.173) (KW = 5.03; p = 0.02). Patients from Group 2 showed statistically significantly higher levels of ACIV IgM than controls 0.176 (0.151÷0.202) vs. 0.142 (0.118÷0.173) (KW = 6.15; p = 0.01). ACIV IgM antibodies showed correlation with microalbuminuria (r = 0.21); (p = 0.04), BMI (r = 0.19); (p = 0.04), creatinine clearance (r = -0.36); (p = 0.01) and GFR (r = -0.34); (p = 0.02).

CONCLUSIONS

Our study showed an association between elevation of serum levels of ACIV IgM and development of diabetic nephropathy. We suggest that levels of ACIV IgM can be useful method for identfying a high risk for development of diabetic nephropathy.

Autoantibodies against basement membrane collagen type IV are associated with myocardial infarction

Background

Collagen type IV is the major constituent of basement membranes underlying endothelial cells and is important for endothelial cell attachment and function. Autoantibodies against native collagen type IV have been found in various autoimmune diseases. Oxidation of LDL in the vascular wall results in the formation of reactive aldehydes, which could modify surrounding matrix proteins. Like oxidized LDL, these modified matrix proteins are likely to induce immune responses. We examined whether autoantibodies against native or aldehyde-modified collagen type IV are associated with myocardial infarction.

Methods

IgM and IgG against native and aldehyde-modified collagen type IV were measured by ELISA in serum from 387 survivors of a first myocardial infarction and 387 age- and sex-matched controls.

Results

Post-infarction patients had significantly increased levels of IgM against native collagen type IV, and IgG against native collagen type IV was present at detectable level in 17% of patients as opposed to 7% of controls (p < 0.001). Controlling for major cardiovascular risk factors demonstrated that the presence of IgG against native collagen type IV was associated with myocardial infarction (OR 2.9 (1.6–5.4), p = 0.001). Similarly, subjects in the highest quartile of IgM against native collagen type IV had increased risk of having suffered myocardial infarction (OR 3.11 (1.8–5.4), p < 0.001) after adjusting for cardiovascular risk factors. In contrast, IgG against aldehyde-modified collagen type IV was decreased in myocardial infarction patients, but this association was not independent of established cardiovascular risk factors.

Conclusion

Autoantibodies against collagen type IV are associated with myocardial infarction independently of traditional cardiovascular risk factors.

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We measured native and MDA-collagen type IV IgM and IgG in MI patients and controls.

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Post-infarction patients had increased levels of IgM against native collagen type IV.

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Presence of IgG against native collagen type IV was associated with MI.

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In contrast, IgG against MDA-collagen type IV was decreased in MI patients.

Abnormal Savda syndrome: long-term consequences of emotional and physical stress on endocrine and immune activities in an animal model

OBJECTIVE

To investigate the relationship between emotional status, cold-dry environment and long-term immune responses to the stressors, and the potential pathological mechanisms between causative factors of abnormal Savda syndrome (ASS) and the susceptibility to disease; thus to clarify the ASS, and secondly to identify the optimal ASS animal model for further studies on traditional Uighur therapeutical formulations.

METHODS

Sixty mice were randomly and equally divided into 4 groups: control and 3 stress groups. The cold-dry environment was applied by keeping the mice in a climatic chamber. The emotional stress was induced by the application of the repeated electric foot-shocks in the electric foot-shock apparatus. The mice of the combined stress group underwent the repeated electric foot-shock treatment before being housed in the climatic chamber. The experimental routine was repeated for 21 days. In order to look into endocrine and immune stress responses, ELISA was used to determine the serum levels of the hormones corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), Beta-endorphin (β-END) and corticosterone (CORT), of the cytokines interleukin 2 (IL-2), interleukin 6 (IL-6), interferon-gamma (INF-γ) and tumor necrosis factor-alpha (TNF-α), and of the immunoglobulins immunoglobulin A (IgA), immunoglobulin M (IgM) and immunoglobulin G (IgG). Lymphocyte subsets were analyzed in duplicate in order to determine differences in the T cell ratio.

RESULTS

In the cold-dry environment group, the serum levels of CRH, ACTH and CORT were significantly higher than those of the control group, whereas serum β-END was not found significantly different. In both the repeated electric foot-shock group as well as in the combined stress group the serum levels of CRH, ACTH, β-END and CORT were significantly higher. Compared to the control animals, the serum concentration of INF-γ was significantly lower in all three different stress groups. The serum level of IL-2 was decreased in the combined stress group whereas the serum TNF-α level was significantly higher. The serum IgG level was significantly higher in all three stress groups, whereas the IgA level was lower in both chronic electric foot-shock group and combined stress group. The IgM level was found significantly higher in the combined stress group only. The percentage of CD4(+) cells in peripheral blood was dramatically decreased in mice exposed to colddry environment, chronic electric foot-shock and combined stress, whereas the percentage of the CD8(+) subset was not significantly different. The CD4(+)/CD8(+) ratios were markedly lower in both cold-dry environment group and combined stress group.

CONCLUSIONS

Combined stress can cause hyperactivity of the HPA axis, and an imbalance in the Th1/Th2 cell subset may contribute to illustrate the partial pathological mechanisms of ASS. This study identified this animal model of a combination of physical and emotional stress as an optimal model for further studies on ASS and relative therapies.

Densin and filtrin in the pancreas and in the kidney, targets for humoral autoimmunity in patients with type 1 diabetes

BACKGROUND AND AIM

The development of autoantibodies against antigens of the pancreatic islet cells is a typical phenomenon in patients with type 1 diabetes. The expression of densin, recently shown to be present in kidney podocytes, was explored in the pancreas. Additionally, we studied whether densin and filtrin, another molecule shared between the kidney podocytes and pancreatic islet cells, can act as autoantigens and whether autoantibodies against these can be detected in patients with type 1 diabetes.

METHODS

Expression of pancreatic densin was studied with reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence. Children and adolescents (n = 66) with type 1 diabetes and control subjects were analysed for densin autoantibodies (DAA) and filtrin autoantibodies (FAA) using radioimmunoprecipitation assay. The serum samples were obtained at the time of diagnosis and after a duration of 2, 5 and 10 years.

RESULTS

Densin expression was observed in the pancreas, localising to the beta cells. DAA were detected in 33% of the patients and the positivity was typically seen already at diagnosis. FAA were observed in 11% of the patients. The proportion of islet cell antibody (ICA) positive, GADA positive and protein tyrosine phosphatase-related islet antigen 2 antibody (IA-2A)-positive patients decreased during the follow-up period, and a similar trend was seen for DAA but not for FAA. Among the 14 patients with signs of renal injury, four tested positive for DAA and two for FAA.

CONCLUSIONS

Densin is a novel molecule shared by the kidney glomerular podocytes and pancreatic islet cells. Densin and filtrin can act as autoantigens, and autoantibodies against these can be detected in patients with type 1 diabetes.

Serum cobalt in children with essential hypertension

The effect of cobalt on the cardiovascular system is one of many aspects of cobalt metabolism in humans. Elastin and collagen are the main proteins of the vascular wall. The aims of this study were: 1) to determine serum cobalt concentrations in children with hypertension; and 2) to study the correlation between serum cobalt and some biological markers of the extracellular matrix of the vascular wall, i.e., anti-elastin and anti-collagen type IV antibodies. Patients showed statistically significant higher levels of systolic and diastolic blood pressure, and significantly lower serum cobalt concentrations, than controls. Children with hypertension showed significantly higher levels of total cholesterol (P = 0.0003) and collagen type IV IgM (P = 0.04). Collagen type IV IgG levels (P = 0.027) were lower than in controls. Serum cobalt in patients showed a correlation with systolic blood pressure (r = -0.44, P = 0.05), elastin IgM (r = 0.60, P = 0.007), and collagen type IV IgG (r = -0.46, P = 0.04). Our data suggest the existence of a correlation between changes in levels of serum cobalt, total cholesterol, anti-collagen type IV antibodies, and essential hypertension in children. This is the first study of serum cobalt in children with essential hypertension.

Serum fibrillin-antifibrillin immune complexes among diabetic children

The fibrillins are large glycoproteins components of 10-nm microfibrils found in the extracellular matrix of most tissues. Microfibrils play a role in elastic fiber assembly and serve to link cells to elastic fibers in the extracellular matrix. Fibrillin-1 (FBN-1) and -2 (FBN-2) are large, secreted glycoproteins known to be components of extracellular matrix microfibrils located in the vasculature, basement membrane, and various connective tissues and are often associated with a superstructure known as the elastic fiber. Anti-fibrillin antibodies found in some autoimmune diseases could form circulating immune complexes (CIC) with corresponding antigens. Type 1 (insulin-dependent) diabetes mellitus is an autoimmune disease leading to formation of different types of autoantibodies. To determine the possible presence of FBN-anti-FBN CIC (IgG and IgM) were studied by modified version of ELISA 35 children with Type 1 diabetes mellitus (mean age--12.37+/-3.77 years, diabetes duration 4+/-3.5 years). Eight of the diabetics had vascular complications. Twenty healthy children (mean age--11.58+/-2.89 years) were used as controls. Diabetics showed statistically significant higher levels of FBN-anti-FBN-2 CIC - IgG (0.303+/-0.076 vs. 0.252+/-0.029; p=0.029) and IgM (0.415+/-0.085 vs. 0.348+/-0.069; p=0.018) compared to the control group. FBN-anti-FBN-1 CIC IgM correlate with diabetes duration (r=0.52; p=0.0015) and BMI (r=0.33, p=0.053) while FBN-anti-FBN-1 CIC IgG correlate with serum Zinc (r=0.49, p=0.006). FBN-anti-FBN-2 CIC IgG correlate with microalbuminuria (r=0.65, p=0.0046) and retinopathy (r=0.61, p=0.0001). This study suggests that there may be a relationship of levels of FBN-anti-FBN-2 CIC IgG with the development of diabetic microangiopathy. Of course the number of the tested patients is limited for definitive conclusions. Although the meaning of these results is still being determined, the measurement of FBN-anti-FBN CIC may represent immunologic markers of FBN metabolism.

Detection of Free Antielastin Antibodies among Diabetic Children

Antibodies to elastin breakdown products are found in the serum of all human subjects and correlate with their respective serum peptide levels. The presence of these antielastin antibodies (AEAbs) and the corresponding antigens in circulation leads to the formation of circulating immune complexes (CICs). The aim of this study was to determine if the serum levels of free AEAbs (not bound in CICs) correlate with the development of vascular complications in diabetic children. To this end, we used a method for detecting immune complexes (complement inhibition factor [CIF]-enzyme-linked immunosorbent assay [ELISA]) in combination with an ELISA for detection of AEAbs. The levels of free immunoglobulin G (IgG) AEAbs were studied in the sera of 54 diabetic children (mean age 12.3+/-4 years; diabetes duration 5.2+/-3.7 years). Thirty-two of the children had vascular complications (group 1), and 22 were without vascular complications (group 2). Twenty healthy children (mean age 13.6+/-4.2 years) were used as controls. The diabetics showed statistically significant higher levels of free AEAbs (0.490 E492+/-0.244 E492 vs 0.307 E492+/-0.081 E492; p = .02) compared with the control group. In group 1, free AEAbs showed statistically significant higher levels than controls (0.523+/-0.269 vs 0.307+/-0.081; p = .016). Eighteen of 54 (33%) patients were positive for free AEAbs (13 of 32 [41%] in group 1 and 5 of 22 [22%] in group 2). Free AEAb levels in all diabetics showed a correlation with systolic blood pressure (r = .44; p = .01), diastolic blood pressure (r = .46; p = .009), total cholesterol (r = .33; p = .05), triglycerides (r= .38; p = .03), high-density lipoprotein (r= -.46; p = .009), serum fructose (r= .43; p = .001), and microalbuminuria (r= .41; p = .002). Patients who had vascular pathology showed a correlation of free AEAbs with microalbuminuria (r= .434; p= .026), serum fructose (r= .63; p = .0004), hemoglobin A1c (r= .392; p = .043), and triglycerides (r= .456; p = .025). These findings suggest that elevated levels of free IgG AEAbs are associated with the development of diabetic vascular complications in children.