The fixed combination of pioglitazone and metformin improves biomarkers of platelet function and chronic inflammation in type 2 diabetes patients: results from the PIOfix study.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is characterized by a proinflammatory and procoagulant condition. This study investigates the impact of a pioglitazone plus metformin therapy on biomarkers of inflammation and platelet activation in comparison to a treatment with glimepiride plus metformin. METHODS: The study was designed as a multicenter, randomized, double-blinded two-arm trial. Patients with T2DM and dyslipidemia under metformin monotherapy with hemoglobin A1c value between 6.5% and 9.0% were eligible for trial participation. Blood was drawn at baseline and after 24 weeks of treatment from patients of five centers. Markers of inflammation and thrombocyte function (soluble CD40 ligand, thromboxane, vWillebrand factor, adhesion molecules, clotting reaction) were evaluated subsequently in a central laboratory. RESULTS: A total of 46 patients were included in the final analyses. Mean (± standard deviation) age was 58.5 ± 9.0 years (13 women, 33 men; disease duration 6.3 ± 5.0 years; body mass index 32.0 ± 4.8 kg/m(2)). A total of 25 patients were treated with pioglitazone plus metformin, and 21 patients were in the glimepiride arm. There was a significant decline of E-selectin (-3.7 ± 4.8 ng/ml, p < .001 versus baseline), vWillebrand factor (-19.5 ± 32.0%, p < .05), and high-sensitivity C-reactive protein concentrations (-1.08 ± 0.91 mg/liter, p < .05) in the metformin + pioglitazone arm only (metformin + glimepiride, -0.5 ± 3.4 ng/ml, +1.4 ± 33.2%, + 0.08 ± 0.72 mg/liter, respectively, all not significant). Also, all other surrogate markers for platelet function and inflammation showed slight improvements in the metformin + pioglitazone arm but not in the metformin + glimepiride arm. CONCLUSIONS: The fixed metformin + pioglitazone combination treatment showed an overall improvement of laboratory surrogate markers, indicating improvement of platelet function and of chronic systemic inflammation, which was not seen with metformin + glimepiride.

Pioglitazone in addition to metformin improves erythrocyte deformability in patients with Type 2 diabetes mellitus.

The aim of the present study was to compare the effect of PIO (pioglitazone) or GLIM (glimepiride) on erythrocyte deformability in T2DM (Type 2 diabetes mellitus). The study covered 23 metformin-treated T2DM patients with an HbA1c (glycated haemoglobin) >6.5%. Patients were randomized to receive either PIO (15 mg, twice a day) or GLIM (1 mg, twice a day) in combination with metformin (850 mg, twice a day) for 6 months. Blood samples were taken for the measurement of fasting glucose, HbA1c, fasting insulin, intact proinsulin, adiponectin and Hct (haematocrit). In addition, the erythrocyte EI (elongation index) was measured using laser diffractoscopy. Both treatments significantly improved HbA1c levels (PIO, -0.9+/-1.1%; GLIM, -0.6+/-0.4%; both P<0.05) and resulted in comparable HbA1c levels after 6 months (PIO, 6.5+/-1.2%; GLIM, 6.2+/-0.4%) Treatment with PIO reduced fasting insulin levels (-8.7+/-15.8 milli-units/l; P=0.098), intact proinsulin levels (-11.8+/-9.5 pmol/l; P<0.05) and Hct (-1.3+/-2.3%; P=0.09), whereas adiponectin levels increased (8.2+/-4.9 microg/ml; P<0.05). No significant change in these parameters was observed during GLIM treatment. PIO improved the EI, resulting in a significant increase in EI at all physiological shear stress ranges (0.6-6.0 Pa; P<0.05). The improvement in EI correlated with the increase in adiponectin levels (r=0.74; P<0.001), and inversely with intact proinsulin levels (r=-0.47; P<0.05). This is the first study showing an improvement in EI during treatment with PIO, which was associated with an increase in adiponectin and a decrease in intact proinsulin levels, but independent of glycaemic control.

Differences in the results and interpretation of oxidized LDL cholesterol by two ELISA assays--an evaluation with samples from the PIOstat study.

BACKGROUND: The oxidized LDL-particles (oxLDL) are considered to be an important driving factor in the pathophysiology of arteriosclerosis. Few methods exist today to directly determine oxLDL in human plasma. We evaluated the plausibility of results derived from a new ELISA (Immundiagnostik, Bensheim, Germany) in comparison to a different ELISA test (Mercodia, Uppsala, Sweden). METHODS: Samples from a previous prospective, randomized study comparing the effects of pioglitazone with simvastatin on chronic systemic inflammation were measured at baseline and endpoint with both tests. Both drugs are known to have a decreasing effect on circulating small dense oxLDL levels. RESULTS: In total, 84 patients without diabetes mellitus were included into this analysis (45 female, 39 male, age(mean +/- SD): 58+/- 8 years). With the Mercodia ELISA, a decrease in oxLDL was seen with simvastatin only (Mean +/- SD: 54.2 +/- 12.5 U/L at baseline vs. 42.9 +/- 12.9 U/L at endpoint; p < 0.001, pioglitzone: 53.8 +/- 13.2 U/L vs. 54.3 +/- 15.254 U/L, n.s.). In contrast, a decrease of oxLDL was observed with the new ELISA for both drugs (simvastatin 65.1 +/- 21.8 ng/mL vs. 52.7 +/- 19.8 ng/mL; pioglitazone: 72.8 +/- 26.1 ng/ml vs. 57.9 +/- 22.1 ng/ml, p < 0.01 vs. baseline in both cases). CONCLUSION: Determination of oxLDL with the Mercodia method lead to lower results and detected only the changes with simvastatin. While statins decrease the overall number of oxLDL particles, pioglitazone predominantly changes the size and LDL composition leading to larger particles with lower oxidation. In our study, the Immundiagnostik ELISA but not the competitive method confirmed the expected efficacy of PPARgamma-activation in decreasing the oxidation of LDL particles.

Peripheral leptin levels in narcoleptic patients.

BACKGROUND: Narcolepsy is a severe sleep disorder that in most patients is characterized by the deficiency of central orexin. Clinically, narcolepsy is associated with obesity. Currently, there is a literature controversy about the potential alteration of leptin levels in narcoleptic patients. Theoretically, diminished leptin levels could partially contribute to the observed overweight of patients. Two studies have reported decreased leptin levels, whereas a larger, recent study failed to detect differences between patients and controls. METHODS: To help settle the controversy, we have measured peripheral leptin levels in 42 narcoleptic patients and in 31 body mass index-matched controls. RESULTS: No significant differences in leptin levels between the groups were observed. Mean leptin levels were 16.0 +/- 14.9 ng/mL in the narcoleptic men and 30.4 +/- 17.8 ng/mL in the narcoleptic women. The corresponding values for the controls were 21.2 +/- 17.0 ng/mL (P = 0.49, men) and 33.9 +/- 16.9 ng/mL (P = 0.31, women). In addition, no correlation was found between leptin levels and clinical symptomatology in the narcoleptic patients. CONCLUSIONS: Taken together, the data argue against a major deterioration of leptin secretion in narcoleptic patients.

Relaxin expression correlates significantly with serum fibrinogen variation in response to antidiabetic treatment in women with type 2 diabetes mellitus.

AIM: Diabetes is associated with aberrant coagulation. Relaxin, an insulin-like peptide hormone, is a candidate to be involved in the underlying molecular mechanisms. Therefore, the present study investigated the correlation of relaxin expression with fibrinogen levels in diabetes patients undergoing oral antidiabetic treatment. METHOD: In total, 192 type 2 diabetes patients were enrolled into the study. The patients were randomized to receive either pioglitazone or glimepiride for 26 weeks. Blood was drawn at baseline and at the end of the study to measure the concentrations of relaxin and fibrinogen with an enzyme-linked immunosorbent assay and a turbimetric method, respectively. In addition, platelets were counted at both time points. RESULTS: Total datasets were available from 161 patients (age 62.5 +/- 8.1 years, mean +/- standard deviation; 58 women, 103 men). The median initial parameter concentrations were: relaxin, 27.4 pg/ml (range 0.4 - 380 pg/ml); fibrinogen, 3.0 g/l (range 1.1 - 7.9 g/l); platelets, 217,000/microl (range 51,000 - 547 000/microl). The data were analyzed according to the increase or decrease of each parameter after therapy compared with baseline. There was a significant correlation of relaxin variation with fibrinogen variation, seen particularly in the female subgroup (p < 0.05). The correlation was independent of the antidiabetic medication. CONCLUSION: The data suggest that there is a correlation between fibrinogen levels and relaxin expression. Relaxin may exert its cardioprotective properties after pathologic fibrinogen increase. This regulation may be affected by diabetes. As a consequence, cardiovascular risk may increase in women with aberrant relaxin functionality.

Relaxin expression correlates significantly with serum changes in VEGF in response to antidiabetic treatment in male patients with type 2 diabetes mellitus.

Recent studies indicate that relaxin as well as VEGF possess cardioprotective properties. This study aimed to determine the association of relaxin with VEGF in patients with type 2 diabetes. We therefore analyzed samples from a recent study showing the benefits of anti-diabetic treatment on cardiovascular risk markers independently from glycemic control. VEGF, relaxin and markers of endothelial dysfunction, s-ICAM-1 and s-VCAM-1, were compared after 26 +/- 2 weeks of antidiabetic treatment with pioglitazone or glimepiride with their base line values. A total of 151 data sets (patients age, 62.7 +/- 8.1 years, diabetes duration, 6.8 +/- 6.6 years, 57 women, 94 men) were available for the analysis. Baseline values were in median, relaxin: 27.4 pg/mL 125% quartile 15.8; 75% quartile: 45.21, s-ICAM-1: 294 ng/mL [25% quartile: 260; 75% quartile: 331], s-VCAM-1: 677 ng/mL [25% quartile: 589; 75% quartile 871], VEGF: 350 pg/mL [25% quartile: 251; 75% quartile: 514]. Parameter variation after therapy showed a significant correlation of relaxin expression with VEGF expression (p = 0.02) in the entire study group. The correlation was seen in the subgroup of male patients (p < 0.01) but did not reach significance in the female patients (p = 0.71). No further correlation was observed analyzing the other investigated parameters. Our data suggest that relaxin may exert its cardioprotective action possibly via VEGF increase, particularly in men. In women, other pathways may superimpose this effect. In conclusion, our study supports the hypothesis of different regulating pathways and effects of relaxin in men and women also in patients with type 2 diabetes.

The beta-specific protein kinase C inhibitor ruboxistaurin (LY333531) suppresses glucose-induced adhesion of human monocytes to endothelial cells in vitro.

AIMS: Strong evidence shows that late diabetic complications in diabetes mellitus are substantially related to an increased synthesis of diacylglycerol with a subsequent activation of protein kinase C (PKC) beta. Several studies have shown that specific inhibition of the PKC isoform beta by ruboxistaurin is able to attenuate the development of microvascular complications under diabetic conditions. The aim of this in vitro study was to investigate the effect of ruboxistaurin on glucose-induced adhesion of monocytes to endothelial cells, representing one of the first pivotal steps in the course of atherogenesis. METHODS: Human umbilical venous endothelial cells were isolated and cultured to confluence in microtiter plates. After coincubation with monocytes in the presence of 0, 10, or 400 ng ruboxistaurin to achieve PKC beta-specific and -unspecific PKC inhibition, cells were fixed and monocyte adhesion was determined by means of a standardized chemiluminescence assay. Expression of adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin) was also measured by chemiluminescence methods. RESULTS: Adhesion of monocytes to endothelial cells cultured under hyperglycemic conditions (27.7 mM glucose) was increased by 30.9 +/- 5.1% (p < 0.001) versus endothelial cells cultured under normoglycemic (NG) conditions (5.5 mM). Pretreatment of endothelial cells with 10 nM (PKC beta-specific concentration) and 400 nM (PKC beta-unspecific concentration) led to a significant reduction of glucose-induced adhesion of monocytes to endothelial cells that was statistically not different from endothelial adhesion under NG conditions (-7.2 +/- 3.1 and -8.1 +/- 2.6%, respectively; not significant vs NG). A nonsignificant tendency to lower the expression of adhesion molecules was seen with 10 ng of ruboxistaurin. CONCLUSIONS: We conclude that monocyte adhesion to endothelial cells under hyperglycemic conditions is at least mediated by PKC beta activation. Ruboxistaurin is able to suppress this monocyte adhesion even in a PKC beta-specific concentration. Further studies should evaluate these potential effects of ruboxistaurin in vivo.

Evaluation of human resistin assays with serum from patients with type 2 diabetes and different degrees of insulin resistance.

Resistin is a peptide hormone encoded at the RSTN gene that since its detection in mice is considered to be an important link between obesity and insulin resistance. However, the study reports and especially the human data are contradictory and require further investigation. The purpose of this study was to evaluate three commercially available resistin ELISAs with different target epitopes (Phoenix, Belmont, CA, USA (PH); Biovendor, Brno, Czech Republic (BV); and Immundiagnostik, Bensheim, Germany (ID)) from a laboratory and clinical perspective. All three assays successfully passed the standardized technical validation procedure, with an inter- and intra-assay variability below 10% and 15%, respectively. They proved to be different with regard to calibration and reference ranges, which may be linked to the different antibody specificities. The clinical evaluation was performed with fasting serum samples from 78 patients with type 2 diabetes (43 female, 35 male, age (mean +/- SD, range): 67 +/- 10, (41-86) years; BMI: 29.2 +/- 4.2 (21.6-41.9) kg/m2). Insulin resistance was calculated from the fasting insulin and glucose values by means of the HOMA analysis. Intact proinsulin served as comparative laboratory marker for insulin resistance. The mean resistin values of patients without insulin resistance were slightly higher (PH: 9.5 +/- 2.8 ng/ml; BV: 4.1 +/- 4.0 ng/ml; ID: 3.8 +/- 9.0 ng/ml) than the mean values of the resistant patients (PH: 9.0 +/- 1.7 ng/ml, n.s.; BV: 3.8 +/- 1.3 ng/ml, n.s.; ID: 0.8 +/- 1.0 ng/ml, p<0.05). Intact proinsulin levels correlated well with the HOMA score values (r = 0.64, p<0.001). No correlation was seen between any of the resistin assays and any of the other clinical or laboratory observation parameters collected, such as BMI, age, disease duration, triglycerides, LDL, HDL, insulin, glucose, or intact proinsulin. In conclusion, the resistin assays showed good technical quality, but the diagnostic value remains still unclear. It may, however, be concluded from this study that at least in cross-sectional epidemiological investigations, fasting human resistin concentrations are not significantly correlating with any clinical measure for insulin resistance.

Clinical and laboratory evaluation of specific chemiluminescence assays for intact and total proinsulin.

Measurement of proinsulin is an important tool in the assessment of pancreatic beta cell function in patients with type 2 diabetes. The goal of this study was to perform a technical and clinical evaluation of two specific chemiluminescence assays (CLIA) for the determination of intact and total proinsulin in comparison to a radioimmunoassay (RIA) method for the measurement of total proinsulin. A total of 191 serum samples from patients with type 2 diabetes were used to perform a regression analysis. The total proinsulin CLIA showed higher proinsulin levels than the two other proinsulin assays (mean +/- SD: 55.9 +/- 58.1 pmol/l, p < 0.001 in both cases). The intact proinsulin CLIA (22.5 +/- 20.9 pmol/l) gave lower values than the RIA for total proinsulin (31.9 +/- 25.4 pmol/l, p < 0.001 vs. CLIA, r = 0.948). The RIA has a 95% cross-reactivity to des31,32-proinsulin, which is secreted during the process of beta cell deterioration. The intact proinsulin CLIA has virtually no cross-reactivity with des31,32-proinsulin (1.4%) and is therefore more specific for intact proinsulin than the RIA. This test does not measure further degradation products, in contrast to the total proinsulin CLIA. The CLIA is, therefore, more specific for total proinsulin measurement than the RIA. Both CLIAs could be performed much faster (4 hours) than the RIA method (75 hours/ 4 days). In conclusion, the CLIA methods show improved qualitative outcomes, higher specificity and several technical advantages over the RIA method.

Evaluation of a new fully automated one-step C-peptide chemiluminescence assay (LIAISON C-Peptid).

The determination of C-peptide, a 31 amino acid fragment of proinsulin which is a byproduct of insulin formation, is used as a marker for insulin secretion. Clinically, the determinations are performed to detect autonomous insulinoma, factitious hypoglycemia, and in general to assess the function of beta-cells in patients with diabetes mellitus. The analysis is frequently performed by radioimmunoassays (RIA), which have several disadvantages, for instance the use of radioactivity and time and resource requirements. We performed an evaluation of a new fully automated chemiluminescence assay (LIAISON C-Peptid, Byk-Sangtec) at two clinical sites, in Germany and Italy, with regard to imprecision and clinical relevance of the obtained data, and the correlation with a standard RIA method and another chemiluminescence test. The new assay showed a good correlation with the RIA (r = 0.950) and the chemiluminescence assay (r = 0.967). The intra-assay variability and inter-assay variability was 3.5% and 8.7% in Germany, and 2.4% and 9.6% in Italy. The clinical evaluation of samples derived from 19 oral glucose tolerance tests, 13 insulin suppression tests, and 2 insulin secretion stimulation tests revealed a clinical specificity of 100%, i.e. all cases resulted in the same clinical diagnosis with all tests. With regard to the practical performance of the assays, the new chemiluminescence test, as a single-step fully automated method, offered the advantage of being a non-radioactive, less complex and much faster method than the RIA and also had timely advantages over the comparative chemiluminescence test. In general, the new LIAISON chemiluminescence assay compared favorably with the RIA and comparative chemiluminescence test and offers an attractive alternative for C-peptide analysis.