Improvement of cardiovascular risk markers by pioglitazone is independent from glycemic control: results from the pioneer study.

OBJECTIVES: This study was performed to assess whether the anti-inflammatory and antiatherogenic effects of pioglitazone suggested by animal experiments are reproducible in man and independent from improvements in metabolic control. BACKGROUND: Type 2 diabetes is associated with increased cardiovascular risk. METHODS: A total of 192 patients were enrolled into a six-month, prospective, open-label, controlled clinical study. They were randomized to receive either pioglitazone (45 mg) or glimepiride (1 to 6 mg, with the intent to optimize therapy). Biochemical and clinical markers to assess therapeutic effects included HbA1c, fasting glucose, insulin, adiponectin, lipids, high-sensitivity C-reactive protein (hsCRP), intracellular adhesion molecule, vascular cell adhesion molecule, vascular endothelial growth factor, fibrinogen, von Willebrand factor, matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein (MCP)-1, soluble CD40 ligand, and carotid intima-media thickness (IMT). RESULTS: The study was completed by 173 patients (66 female, 107 male; age [+/- SD]: 63 +/- 8 years; disease duration: 7.2 +/- 7.2 years; HbA1c: 7.5 +/- 0.9%; pioglitazone arm: 89 patients). A comparable reduction in HbA1c was seen in both groups (p < 0.001). In the pioglitazone group, reductions were observed for glucose (p < 0.001 vs. glimepiride group at end point), insulin (p < 0.001), low-density lipoprotein/high-density lipoprotein ratio (p < 0.001), hsCRP (p < 0.05), MMP-9 (p < 0.05), MCP-1 (p < 0.05), and carotid IMT (p < 0.001), and an increase was seen in high-density lipoprotein (p < 0.001) and adiponectin (p < 0.001). Spearman ranks analysis revealed only one correlation between the reduction in cardiovascular risk parameters and the improvement in the metabolic parameters (MMP-9 and fasting blood glucose, p < 0.05) CONCLUSIONS: This prospective study gives evidence of an anti-inflammatory and antiatherogenic effect of pioglitazone versus glimepiride. This effect is independent from blood glucose control and may be attributed to peroxisome proliferator-activated receptor gamma activation.

IRIS II study: intact proinsulin is confirmed as a highly specific indicator for insulin resistance in a large cross-sectional study design.

BACKGROUND: The cross-sectional IRIS-II study tried to assess the prevalence of insulin resistance and macrovascular disease in orally treated patients with Type 2 diabetes. METHODS: In total, 4,270 patients were enrolled into the study (2,146 male, 2,124 female; mean +/- SD age 63.9 +/- 11.1 years; body mass index 30.1 +/- 5.5 kg/m2; duration of disease 5.4 +/- 5.6 years; hemoglobin A1c 6.8 +/- 1.3%). The study consisted of a single morning visit with completion of a standardized questionnaire and collection of a fasting blood sample. RESULTS: The mean intact proinsulin value was 11.4 +/- 12.4 pmol/L (normal range < 10 pmol/L). Homeostasis model assessment resulted in 1,147 insulin-sensitive patients (26.9%) and 3,123 patients (73.1%) with insulin resistance. Of the latter patients 1,465 (34.3% of all patients) had also elevated intact proinsulin values, while 1,658 (38.8%) had no proinsulin elevation. In contrast, 1,042 (24.4%) of the insulin-sensitive patients had normal intact proinsulin, and only 105 (2.4%) had elevated intact proinsulin concentrations (chi2 test P < 0.0001). A specificity of 93.2% (sensitivity 46.9%) was calculated for elevated intact proinsulin as an indirect marker for insulin resistance. Of the 1,451 patients treated with sulfonylurea 52% had elevated intact proinsulin values and increased prevalence of cardiovascular complications (odds ratio 1.45). CONCLUSION: Type 2 patients with elevated fasting intact proinsulin values can be regarded as being insulin resistant. The results confirm that fasting intact proinsulin is a suitable measure for beta-cell dysfunction and insulin resistance in type 2 diabetes and may be used to support therapeutic decisions.

Repetitive hypoxia increases lipid loading in human macrophages-a potentially atherogenic effect.

Obstructive sleep apnea (OSA) is characterized by repetitive episodes of hypoxia and is associated with an increase in cardiovascular disease. We, therefore, investigated the effect of repetitive hypoxia on two key early events in atherogenesis; lipid loading in foam cells and monocyte adhesion to endothelial cells. Human macrophages were loaded with acetylated low-density lipoproteins. During lipid loading, the cells were exposed to 30 min cycles of 2%/21% oxygen or control (room air, 5% CO(2) incubator). Human umbilical vein endothelial cells (HUVECs) were also exposed to 30 min cycles of repetitive hypoxia or control conditions and monocyte adhesion measured. Cell adhesion molecules E-selectin, ICAM-1 and VCAM-1 were measured by ELISA. Repetitive hypoxia increased cholesteryl ester uptake by macrophages (127+/-5% compared to controls; p=0.003). By contrast, monocyte adhesion to HUVECs and cell adhesion molecule expression were unchanged by exposure to repetitive hypoxia, compared to controls (p >0.1). Repetitive hypoxia, at levels relevant to tissues such as the arterial wall, enhances lipid uptake into human macrophages. This may contribute to accelerated atherosclerosis in OSA patients.

IRIS II Study: Sensitivity and specificity of intact proinsulin, adiponectin, and the proinsulin/adiponectin ratio as markers for insulin resistance.

OBJECTIVE: This study was performed to compare the specificity and sensitivity of intact proinsulin, adiponectin, and their ratio (proinsulin/adiponectin) in the prediction of insulin resistance as assessed by the homeostasis model assessment (HOMA) score (> or =2 = resistant). RESEARCH DESIGN AND METHODS: Using a cross-sectional approach, 500 orally treated patients with type 2 diabetes (272 women, 238 men; mean +/- SD age, 64.8 +/- 11.6 years; hemoglobin A1c, 7.0 +/- 1.5%; disease duration, 5.8 +/- 6.1 years) were investigated. Various cutoffs for body mass index-adjusted adiponectin and proinsulin/adiponectin were compared with the established cutoff value of 10 pmol/L for fasting proinsulin. RESULTS: Fasting proinsulin correlated more closely with the HOMA score (r = 0.560, P < 0.001) than fasting adiponectin (r = -0.204, P < 0.001) or proinsulin/adiponectin (r = 0.355, P < 0.001). For proinsulin, specificity and sensitivity for insulin resistance in correlation to the HOMA score results were 96% and 70%, respectively. At a comparable specificity level to proinsulin, adiponectin did not reach a comparable sensitivity (14%), while the proinsulin/adiponectin ratio almost reached the same sensitivity (65%). Overall, patients with elevated proinsulin had a higher prevalence of micro- and macrovascular disease [odds ratio 1.47 (adiponectin, 1.08; proinsulin/ adiponectin, 1.48) and 1.34 (adiponectin, 1.32; proinsulin/adiponectin, 1.27), respectively]. CONCLUSIONS: Elevation of fasting intact proinsulin seems to be the more specific marker for insulin resistance and increased cardiovascular risk than suppression of fasting adiponectin. Formation of the ratio does not lead to a further increase in the predictive value.

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.

Nitric oxide does not mediate the vasodilation of early human pregnancy.

BACKGROUND: In early pregnancy, a substantial drop in arterial blood pressure occurs, that might be attributed to enhanced vascular nitric oxide synthesis. We investigated whether nitric oxide mediates the vasodilation that occurs in early human pregnancy. METHODS: Resting and stimulated forearm vascular resistance were measured (venous occlusion plethysmograph) in six women at 10 +/- 3 weeks of uncomplicated pregnancy and in the same women 7 +/- 5 weeks after elective termination of pregnancy. Forearm vascular resistance was also measured in six non-pregnant, healthy controls. RESULTS: Resting forearm vascular resistance was similar during pregnancy (33 +/- 16 arbitrary units (AU)), after pregnancy (31 +/- 10 AU) and in controls (41 +/- 13 AU, P > 0.05). The decreases in forearm vascular resistance to intrabrachial infusions of acetylcholine (2 and 20 microg/min), serotonin (10 and 100 ng/min) and sodium nitroprusside (1 and 2.5 microg/min) were similar in all groups. The nitric oxide synthase inhibitor NG-monomethyl-L-arginine (16 micromol/min) produced similar increases in vascular resistance in pregnant women (38 +/- 17 AU), after pregnancy (36 +/- 14 AU) and in control subjects (42 +/- 8 AU, P = NS). CONCLUSIONS: These results indicate that neither basal nor stimulated nitric oxide levels are altered in the forearm circulation during first trimester pregnancy.