Evaluation of selected parameters of the antioxidative system in patients with type 2 diabetes in different periods of metabolic compensation

Parameters of glycemic control and their relationship with zinc concentrations in blood and with superoxide dismutase enzyme activity in type 2 diabetes patients

OBJECTIVE

This study assessed the relationship between the parameters of glycemic control, and zinc concentrations in blood and superoxide dismutase enzyme activity in type 2 diabetes patients.

SUBJECTS AND METHODS

Seventy-three individuals, aged between 25 and 59 years, were divided into the experimental group (type 2 diabetes patients, n = 36) and control group (n = 37). Plasma and erythrocyte zinc concentrations, superoxide dismutase activity, and parameters of glycemic control were analyzed.

RESULTS

Mean plasma zinc concentration was 74.1 ± 10.7 µg/dL and 68.8 ± 9.6 µg/dL, erythrocyte zinc concentration was 48.1 ± 9.5 µg/gHb and 41.2 ± 8.0 µg/gHb, and superoxide dismutase activity was 2248.9 ± 300.0 U/gHb and 2059.6 ± 285.4 U/gHb, in the experimental group and the control group, respectively (p < 0.05).

CONCLUSION

Type 2 diabetes patients showed a positive response to oxidative stress due to adequate zinc concentration in blood and increased activity of superoxide dismutase, and the enzyme was influenced by serum insulin.

Chemical and functional changes of human insulin by in vitro incubation with blood from diabetic patients in oxidative stress

Oxidative stress damage to biomolecules has been implicated in several diseases including diabetes mellitus. In the present study, we investigated the effect of oxidative stress in whole blood (WB) from diabetic patients (n = 60) on recombinant human insulin. Insulin was incubated with WB obtained from diabetic patients (DP) who had hyperglycemia (>300 mg/dL) or from 41 healthy volunteers (HV). Whole blood of DP, unlike WB of HV, induced higher values of formazan (142%), dityrosines (279%), and carbonyls (58%) in the insulin residues. Interestingly, the insulin modified by WB of DP showed less hypoglycemic activity in rat (30%) in comparison with insulin incubated with WB of HV. The incubation of insulin in WB from DP induces chemical changes in insulin and a decrease in its biological activity, events that might be associated with the high levels of oxidative stress markers found in the plasma of these patients.

HSP 70 and atherosclerosis--protector or activator?

BACKGROUND

Atherosclerosis and its complications represent the leading cause of morbidity and mortality. Heat shock protein 70 (HSP70) protects cellular elements from injury by reducing oxidation, inflammation and apoptosis and by refolding damaged proteins. HSP70 improves viability of stressed vascular smooth muscle cells, possibly via its chaperone functions. It has been proposed that the response mounted against bacterial HSPs results in an autoimmune reaction, which has the potential to cause complement-mediated endothelial injury, and hence accelerate atherogenesis.

OBJECTIVE

to examine the roles of HSPs in atherosclerosis.

METHODS

A literature review.

RESULTS/CONCLUSIONS

The role of HSPs in atherosclerosis is controversial. HSP60 probably acts as an autoantigen, and may trigger both cell- and antibody-mediated immune responses, while HSP70 is likely to be involved in cytoprotection. The significance of this inverse relation between HSP70 and atherosclerosis has not yet been elucidated. Whether HSPs will become therapeutic targets remains to be established.

Coronary artery atherosclerosis in patients with the initial and the early stage of chronic renal failure

The recent clinical data indicate that the initial and the early stages of chronic renal failure (CRF) may lead to increased incidence of cardiovascular complications and increased extent of coronary artery disease (CAD). This retrospective study was aimed to determine the effects of coexisting diabetes mellitus type 2 (DM-2) and the extent of atherosclerosis in coronary vessels in patients with mildly reduced kidney function (glomerular filtration rate GFR = 89–60 ml/min) and moderately reduced kidney function (GFR = 59–30 ml/min). The study patients included 53 subjects with creatinine concentration above 120 μmol/l as a cut-off level for the initial stage and compensated CRF. The distributions of coronary artery stenosis were also analysed with respect to DM-2 coexistence and levels of haemoglobin glikolised (HbA1c). The odds ratio of pathological changes in coronary arteries in patients with GFR = 44–30 ml/min, with respect to the number of affected vessels — only one, more than one or more than two — were 7.22, 4.90 and 3.55, respectively. In CRF patients with GFR = 60–89 ml/min the odds ratio of one, more than one and more than two vessels with stenosis and CAD was 1.93, 1.70 and 1.53, respectively. DM-2 was not related to the risk of significant coronary artery stenosis and did not enhance the pre-existing changes in the study setting. Our results demonstrate that the initial and the early stages of CRF were significant risk factors for coronary stenoses and for enhancing the pre-existing changes.

Alterations in the high density lipoprotein phenotype and HDL-associated enzymes in subjects with metabolic syndrome

Patients with metabolic syndrome (MetS) usually have low high density lipoprotein cholesterol (HDL-C) levels. We determined the HDL distribution profile as well as the HDL-related lipoprotein associated phospholipase A(2) (HDL-LpPLA(2)) and paraoxonase-1 (PON1) activities in subjects with MetS (n = 189) but otherwise healthy. Age and sex-matched individuals (n = 166) without MetS served as controls. The lower HDL-C concentration in MetS patients was due to a reduction in both large and small HDL subclasses (P < 0.001 and P < 0.05, respectively). As the number of MetS components increased, the HDL phenotype comprised of a greater percentage of small HDL-3 and less large HDL-2 subclasses, resulting in a decreased HDL-2/HDL-3 ratio (P < 0.001 for all trends). Multivariate analysis revealed that HDL-2 levels and the HDL-2/HDL-3 ratio significantly and independently correlated with HDL-C (positively) and TG (negatively) levels. HDL-3 concentration significantly and independently positively correlated with HDL-C and TG levels. HDL-LpPLA(2) activity was decreased in MetS patients (P < 0.01), a phenomenon that may contribute to the defective antiatherogenic activity of HDL in MetS. PON1 activity did not differ between groups. We conclude that MetS, in addition to the decrease in HDL-C concentration, is associated with alterations in the HDL phenotype, which is comprised of a greater percentage of small HDL subclasses. Furthermore, HDL-LpPLA(2) activity is decreased in MetS patients.

Carvedilol modifies antioxidant status of patients with stable angina

The aim of this study was to evaluate the effect of carvedilol on the enzymatic antioxidative defence and plasma antioxidative activity in patients with stable angina. The study comprised 30 patients, aged 37-49 years with stable angina. Patients received carvedilol in escalating doses of 12.5 mg/24 h, 25 mg/24 h, and 50 mg/24 h for 4 weeks each. The control group was matched for age and gender, and consisted of 12 healthy volunteers, aged 39-49 years. Blood samples were collected from the cubital vein before and 4, 8 and 12 weeks after the therapy from the patients and once from the control group. For all the subjects, the superoxide dismutase (SOD-1), glutathione peroxidase (GSH-Px), catalase (CAT) activities in the erythrocytes and the antioxidant activity of the blood plasma were determined. The enzymatic antioxidative defence was significantly decreased in patients with stable angina in comparison to the healthy subjects. During the carvedilol therapy, an increase in the SOD-1, GSH-Px and CAT activities was observed. Moreover, 8 and 12 weeks after carvedilol therapy, the GSH-Px activity did not differ significantly from that observed in the group of healthy subjects. Carvedilol also increased the plasma antioxidative activity in patients with stable angina, but its level remained significantly lower than in the control group. In conclusion, carvedilol enhances antioxidant defense mechanisms in patients with chronic stable angina pectoris.