Nikša Turk

Detection of autoantibodies against advanced glycation endproducts and AGE-immune complexes in serum of patients with diabetes mellitus

Advanced glycation of protein causes their immunogenicity. The evidence that advanced glycation endproducts (AGEs) have antigenic properties has led to a hypothesis that the AGE structure found in vivo may exert an autoimmune response. In the present study, we showed the sera of diabetic patients as well as of nondiabetic individuals to contain autoantibodies to epitopes of AGE structures. Contrary to what might be expected, we observed lower AGE antibody titers in diabetic subjects, and postulated that the antibodies against AGEs form immune complexes in vivo, hampering their determination. The existence of immune complexes containing AGE moiety was established by two independent criteria: (a) serum AGE-immune complexes (AGE-IC) were detected by enzyme-linked immunosorbent assay (ELISA) using an immunochemical bridge; and (b) soluble AGE-IC were precipitated from serum by polyethylene glycol and analyzed. We demonstrated the presence of circulating AGE-IC in sera, predominantly in the sera of diabetic subjects. We also found an inverse correlation between serum AGE level and AGE-IC (r=-0.8, P<0.000), indicating the serum level of AGEs to decline with an increasing presence of AGE-IC. The content of AGE in soluble immune complexes was significantly higher in diabetic patients than in control subjects (3.51+/-1.9 vs. 1.89+/-1.0 microgEq/ml (P<0.00004), and correlated inversely with free antibodies (r=-0.26, P<0.01). Interactions of AGE autoantibodies with AGE as a continuously produced antigen result in the formation of AGE-immune complexes that may play a role in the atherogenic processes.

Initial disease course and treatment in an inflammatory bowel disease inception cohort in Europe: The ECCO-EpiCom cohort

Background:The EpiCom cohort is a prospective, population-based, inception cohort of inflammatory bowel disease (IBD) patients from 31 European centers covering a background population of 10.1 million. The aim of this study was to assess the 1-year outcome in the EpiCom cohort. Methods:Patients were followed-up every third month during the first 12 (±3) months, and clinical data, demographics, disease activity, medical therapy, surgery, cancers, and deaths were collected and entered in a Web-based database (www.epicom-ecco.eu). Results:In total, 1367 patients were included in the 1-year follow-up. In western Europe, 65 Crohn’s disease (CD) (16%), 20 ulcerative colitis (UC) (4%), and 4 IBD unclassified (4%) patients underwent surgery, and in eastern Europe, 12 CD (12%) and 2 UC (1%) patients underwent surgery. Eighty-one CD (20%), 80 UC (14%), and 13 (9%) IBD unclassified patients were hospitalized in western Europe compared with 17 CD (16%) and 12 UC (8%) patients in eastern Europe. The cumulative probability of receiving immunomodulators was 57% for CD in western (median time to treatment 2 months) and 44% (1 month) in eastern Europe, and 21% (5 months) and 5% (6 months) for biological therapy, respectively. For UC patients, the cumulative probability was 22% (4 months) and 15% (3 months) for immunomodulators and 6% (3 months) and 1% (12 months) for biological therapy, respectively in the western and eastern Europe. Discussion:In this cohort, immunological therapy was initiated within the first months of disease. Surgery and hospitalization rates did not differ between patients from eastern and western Europe, although more western European patients received biological agents and were comparable to previous population-based inception cohorts.

Rat tissue collagen modified by advanced glycation: correlation with duration of diabetes and glycemic control.

Abstract Collagenous proteins are especially prone to nonenzymatic glycation, because they contain several dibasic amino acid residues with free amino groups, have a very slow turnover rate, and are exposed to ambient levels of glucose. The aim of this study was to determine the time-dependent course of advanced glycation process in diabetic rats in relation to glycemic control and duration of diabetes, compared to age-matched controls. Immunochemical assay with antibodies to advanced glycation end products (AGE) was first developed to qualitatively detect and quantify the AGE formed in rat tendon and aortic collagen. Individual collagen samples were extracted by extensive pepsin and collagenase digestion. The amount of AGE was measured by competitive ELISA and results were expressed as AGE U/mg collagen. Diabetic rats showed a significant increase in AGE content in aortic collagen at 20 weeks (n=6, 206.6 ± 16.7 U/mg collagen) compared with that measured at 4 and 12 weeks (n=6, 110 ± 12.8 U/mg collagen, and n=13, 184.9 ± 12.3 U/mg collagen at 4 and 12 weeks, respectively; p < 0.001 between 20 weeks and 4 weeks; p < 0.01 between 20 weeks and 12 weeks). The amount of AGE in tendon collagen of diabetic rats increased from 1.9 ± 0.38 U/mg at 4 weeks to 11.2 ± 6.1 U/mg collagen at 20 weeks, p < 0.001. Considerable disparity was observed in the intensity of glycation between aortic and tendon collagen. AGE-content per mg of aortic collagen was several-fold to that found in tendon collagen (p < 0.001). To investigate the effect of glycemic control on the advanced glycation process, total aortic AGE-collagen content was compared between untreated diabetic rats (D; n=13, 184.9 ± 12.3 U/mg) and diabetic rats treated for 12 weeks with insulin (DI; n=6, 133.9 ± 10.7 U/mg), or phlorizin (DP; n=6, 132.4 ± 8.9 U/mg), or by a combination of insulin/phlorizin (DIP; n=6, 124.3 ± 6.5 U/mg). In spite of therapy used, all groups of diabetic animals had a significantly higher aortic AGE-collagen content than those in the nondiabetic control group (C: n=8, 104.6 ± 14.9 U/mg) of the same age (D, DI, DP, DIP vs. C, p < 0.001). Comparison between the mean levels of glycated hemoglobin (D: 5.62 ± 0.38 % vs.C: 1.7 ± 0.05 %) and mean AGE levels in the studied group of animals yielded a very good exponential correlation (r = 0.89, p < 0.001). Glycation-derived late-stage collagen modification was detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and by immunoblotting confirmed to contain (an) AGE-structure(s). Our study provides strong immunochemical evidence of AGE formation in vivo during hyperglycemia, and of their temporal association with structural alterations of extracellular matrix proteins. The advanced glycation process is retarded and reduced in intensity, but not completely abolished, by glycemia regulation with, or independently of, insulin.

Proinflammatory cytokines and receptor activator of nuclear factor kappaB-ligand/osteoprotegerin associated with bone deterioration in patients with Crohn´s disease

Objectives The high incidence of bone disease and the increasing evidence of Crohns disease (CD) bone decline in corticosteroid users and nonusers suggest that bone metabolism is affected by inflammatory process. The aim of the study was to compare serum levels of proinflammatory cytokines, markers of bone turnover and regulatory molecules of osteoclast biogenesis, receptor activator of nuclear factor κB-ligand (RANKL) and osteoprotegerin (OPG), between naïve and long-standing CD patients. Methods The study included 95 CD patients, 15 of them with newly diagnosed and previously untreated CD. The spine and hip bone mineral density was measured by dual-energy X-ray absorptiometry. Biochemical markers were determined by immunoassay. Results Osteopenia was recorded at diagnosis in 53% of naïve patients and osteoporosis was found in 26% of long-standing CD patients. The newly diagnosed patients showed correlation between TNF-&agr; and soluble RANKL (sRANKL) (r=0.5; P=0.04), and this positive relationship characterized the study population as a whole (r=0.3; P=0.003). Analysis of the OPG and sRANKL relationship showed absence of correlation in patients with healthy skeleton, whereas an inverse correlation was found in those with osteopenia (r=−0.31; P=0.033) and osteoporosis (r=−0.48; P=0.028). In naïve patients with reduced T score, the correlation between sRANKL and OPG was highly inverse (r=−0.8; P=0.02) and these patients were characterized by lower BMI, significantly higher level of proinflammatory cytokines, elevated C-reactive protein, and increased activity of free sRANKL and OPG. Conclusion Bone disease that accompanies CD at diagnosis suggests that bone metabolism is affected by the underlying inflammatory process per se, as probably confirmed by our finding of the central proinflammatory cytokine TNF-&agr; being strongly associated with the osteoclastogenic mediator RANKL, and inversely with bone density.

Temporal association between lens protein glycation and cataract development in diabetic rats

Abstract In an attempt to shed more light on the relation between the glycation process and structural protein alterations, we followed the formation of glycated products in the lenses of hyperglycaemic Wistar rats during a period of 5 months following alloxan diabetes inducement. The study groups included non-diabetic (control), untreated diabetic rats (D), and diabetic rats receiving insulin alone or in combination with phlorizin, an inhibitor of renal tubular glucose transport. Lenses were removed at 4 and 20 weeks, and advanced glycation products in alkali-soluble lens proteins were determined by their characteristic spectrofluorescence (emission at 385 nm with excitation of 335 nm). In 20-week untreated diabetic rats as compared to control rats, a significant increase was observed in the fluorescence level (3.25±1.02 vs 1.61±0.17 FU/mg, P<0.001), while in 4-week animals the increase was from 1.26±0.11 FU/mg in controls to 1.80±0.25 FU/mg in diabetics (P<0.001). Daily treatment of 20-week diabetic rats with insulin alone (2.46±0.48 FU/mg) or in combination with phlorizin (2.30±0.26 FU/mg) did not significantly influence lens fluorescence level. The amount of glucose-bound ketoamine linkage was estimated after acid hydrolysis as released 5-hydroxymethylfurfural (HMF). In 20-week controls, it was slightly higher than in 4-week controls (0.57±0.31 vs 0.41±0.20 nmol HMF/mg, respectively). The diabetic group showed a significant increase, however. In 4-week diabetics, a level of 1.07±0.36 nmol HMF/mg was found, while in 20-week animals the glycated protein amount rose to 2.46±0.79 nmol HMF/mg. In addition to the increases in glycated content with continuing diabetic hyperglycaemia, significant changes in protein composition of alkali-soluble lenses developed. The SDS-PAGE pattern showed an appearance of protein polymers of heterogeneous size (C 4 weeks 3.0±1.1% vs C 20 weeks 17.9±2.9%; D 4 weeks 7.3±2.1% vs D 20 weeks 19.8±3.6%) and the proteins of high molecular weight (HMW) failed to penetrate into the gel. Only a small amount of these HMW proteins was present in controls (C 20 weeks 2.5±1.2%) and short-term diabetes (D 4 weeks 0.8±0.2%), whereas in long-term untreated diabetes there was a dramatic increase (D 20 weeks 30.5±3.2%) with a corresponding decrease in other peaks. All diabetic animals from this group had macroscopically detectable cataractous lenses. Treatment with insulin or insulin/phlorizin followed the HMW protein level of the untreated animals (28.2±4.0% or 27.08±3.3% vs 30.52±3.32%)

Products of advanced glycation in patients with type 2 diabetes and vascular disease.

Background: Non-enzymatic glycation leading to advanced glycation endproduct (AGE) formation is thought to contribute to vascular pathology. In the present study, AGEs and anti-AGE antibodies in free and immune complex-bound form were assayed in the serum of diabetic (DMCAD) (n = 69) and nondiabetic (n = 78) patients with coronary artery disease (CAD) and in control subjects (n = 47) free from vascular disease. Methods: A blocking enzyme-linked immunosorbent assay (ELISA) was used to test immunoreactivity against AGE epitope(s) and a competitive ELISA was used to measure total AGE content. Results: Anti-AGE immunoreactivity was significantly higher in diabetic than in control subjects (P = 0.045). Although a wide range of anti-AGE antibody titres were observed in nondiabetic CAD patients, there was no significant difference from those of control subjects. Both diabetic and nondiabetic CAD patients had a higher concentration of circulating immune complexes containing the AGE moiety as antigen than did control subjects (DMCAD versus control, P = 0.041; CAD versus control, P = 0.047). Study patients showed a positive correlation between serum AGE and AGE-immune complexes (DM, r = 0.29, P = 0.014; CAD, r = 0.26, P = 0.019), whereas no such correlation was recorded in controls (r = 0.08, P = 0.89). Conclusion: To our knowledge, this is the first study demonstrating increased AGE-immune complexes in patients with CAD, either with or without diabetes, suggesting that AGE-immune complexes might be involved in the atherosclerotic process, either as the result of it or as part of the pathophysiologic process.

Health care and patients' education in a European inflammatory bowel disease inception cohort: An ECCO-EpiCom study

BACKGROUND AND AIMS The EpiCom study and inception cohort was initiated in 2010 in 31 centers from 14 Western and 8 Eastern European countries, covering a 10.1million person background population. Our aim was to investigate whether there is a difference between Eastern and Western Europe in health care and education of patients with inflammatory bowel disease (IBD). METHODS A quality of care (QoC) questionnaire was developed in the EpiCom group consisting of 16 questions covering 5 items: time interval between the onset of symptoms and diagnosis, information, education, empathy and access to health care providers. RESULTS Of 1,515 patients, 947 (217 east/730 west) answered the QoC questionnaire. Only 23% of all patients had knowledge about IBD before diagnosis. In Eastern Europe, significantly more patients searched out information about IBD themselves (77% vs. 68%, p<0.05), the main source was the Internet (92% vs. 88% p=0.23). In Western Europe, significantly more patients were educated by nurses (19% vs. 1%, p<0.05), while in Eastern Europe, gastroenterologists were easier to contact (80% vs. 68%, p<0.05). CONCLUSION Health care differed significantly between Eastern and Western Europe in all items, but satisfaction rates were high in both geographic regions. Because of the low awareness and the rising incidence of IBD, general information should be the focus of patient organizations and medical societies. In Western Europe IBD nurses play a very important role in reducing the burden of patient management.

Relationship of methylglyoxal-adduct biogenesis to LDL and triglyceride levels in diabetics

AIMS Protein glycation leading to advanced glycation-endproducts (AGE) is enhanced in diabetes by increased blood glucose and collateral endogenous production of reactive α-dicarbonyls. Among AGE precursors, methylglyoxal (MG) is considered as one of the key intermediates. We hypothesized it to be a common product of both carbonyl and oxidative stress, and investigated its biogenesis in relation to glycemic and lipid status in diabetic patients. METHODS Serum and urine MG-adducts were measured by competitive immunofluorometric assay in 83 diabetic and 20 healthy subjects. KEY FINDINGS A significant association of MG-adducts serum level with LDL (r=0.31;p=0.003) was observed. A correlation between LDL-c, HDL-C and PPG as independent variables and serum MG-adducts as a dependent variable was found (p<0.014) using multiple stepwise regression, whereas urine albumin/creatinine ratio was independently associated with urine MG-adducts. LDL cut-off >3.0mmol/l discriminated patients with higher serum MG-adducts (p=0.0052), although there was no between-subgroup difference in glycemic control. Patients on statin therapy had a lower MG-adduct level. The positive relationship between LDL-c and MG-adducts (r=0.38;p=0.042) was noted in patients free of statin treatment, whereas an inverse tendency was found in the statin-treated subgroup. SIGNIFICANCE Significant relationship between LDL and MG-adduct production, as well as tight correlation between triglycerides and urinary MG-adduct excretion suggest that the lipoxidation and glyceraldehyde-3-phosphate route, along with the glycolytic pathway, might be an important source of MG generation. The glycotoxin methylglyoxal seems to be a common factor linking hyperglycemia and intensive lipolysis, two dominant metabolic changes in diabetes.

Humoral SPARC/osteonectin protein in plasma cell dyscrasias

The matricellular protein SPARC (secreted protein acidic and rich in cysteine)/osteonectin was determined in patients with multiple myeloma and related disease to assess the hypothesized role of SPARC as a possible marker of tumor burden and disease progression. Soluble SPARC was measured by competitive enzyme-linked immunosorbent assay (ELISA) in plasma of 42 patients, including sequential measurements in individual patients, and in 20 healthy controls. SPARC values were heterogeneous in multiple myeloma patients showing a decline from baseline levels recorded in controls (456±195 vs 600±63 ng/ml, p=0.00023). A SPARC showed a significant positive correlation with platelet count (r=0.72, p=0.000000, n=42), hemoglobin (r=0.52, p=0.00037, n=42), and IgG level (r=0.43, p=0.0085, n=42) and negative correlation with β2-microglobulin (r=−0.46, p=0.0023, n=42), aspartate aminotransferase (AST) (r=−0.42, p=0.0061, n=41), interleukin (IL)-6 (r=−0.41, p=0.008, n=42), lactate dehydrogenase (LDH) (r=−0.36, p=0.02, n=41), and percentage of plasma cells in bone marrow aspirate (r=−0.34, p=0.029, n=42). No correlation was found between SPARC and “M” component or disease stage. Investigations performed during the course of disease, including sequential measurements in individual patients, showed a trend to downregulation by disease progression, with the lowest level recorded in the terminal stage (217±107 ng/ml, n=11). Patients with established osteolytic lesions had lower plasma SPARC at diagnosis (309±197 vs 581±293, p=0.021), which correlated with osteocalcin by disease progression (r=0.31, p=0.026). The results of this pilot study revealed abnormalities in the level of humoral SPARC in multiple myeloma and an overall trend to downregulation in the advanced stage of the disease. The regulation of SPARC seems to be opposite to the markers of tumor burden and of aggressive multiple myeloma phenotype.

Simultaneous analysis of mitotane and its main metabolites in human blood and urine samples by SPE‐HPLC technique

Adrenocortical carcinoma (ACC) is a rare malignancy with an incompletely understood pathogenesis and a poor prognosis. The adrenalytic activity of mitotane has made it the most important single drug in the treatment of ACC. Unfortunately, the exact mechanism of mitotane action is still unknown. It is believed that mitotane belongs to the class of drugs that require metabolic transformation by cytochrome P450 for therapeutic action; therefore determination of plasma levels of not only mitotane but also its metabolites would help in carrying out the treatment. The objective of this work was to develop and validate an SPE-HPLC method for simultaneous determination of mitotane and its metabolites in different biological fluids. The sample preparation consisted of a solid-phase extraction on a Discovery DSC(18) cartridge, while analysis of extracts was performed on a Symmetry C(18) column. The usefulness of the proposed method was confirmed by analysis of plasma, red cell and urine samples from patient chronically treated with 1.5 g of mitotane. The patient involved in this study had a high plasma concentration of mitotane and none of the investigated metabolites were found. In order to investigate whether the polymorphism of CYP2C9 and CYP2C19 enzymes could be related to the metabolism of mitotane, RT-PCR analysis was performed.