The principal metabolic effect of metformin-an oral antihyperglycaemic agent-is the improvement in the sensitivity of peripheral tissues and liver to insulin. This study examined the effect of metformin monotherapy on antioxidative defence system activity in erythrocytes and plasma in diabetic patients. We studied the effect of metformin treatment on the activities of Cu, Zn-superoxide dismutase (EC 1. 15. 1. 1.), catalase (EC 1. 11. 1. 6.) and glutathione peroxidase (EC 1. 11. 1. 9.) in relation to lipid peroxidation products and reduced glutathione level in plasma and erythrocytes. In this study we also examined erythrocytes' susceptibility to H2O2-induced oxidative stress during metformin therapy. Although metformin monotherapy ameliorated the imbalance between free radical-induced increase in lipid peroxidation (by reducing the MDA level in both erythrocytes and plasma) and decreased plasma and cellular antioxidant defences (by increasing the erythrocyte activities of Cu, Zn, SOD, catalase and GSH level) and decreased erythrocyte susceptibility to oxidative stress, it had negligible effect to scavenge Fe ion-induced free radical generation in a phospholipid-liposome system.

Vitamin D deficiency could play an important role in the pathogenesis of type 2 diabetes mellitus (T2DM) as it may alter several crucial processes in the development of diabetes and its complications, such as pancreatic insulin secretion, peripheral insulin resistance, persistence of systemic „sterile” inflammation and immune activation. Vitamin D may also have an antioxidant effect through the inhibition of free radicals generation. The reported study was designed with eligible consecutively recruited patients with T2DM on standard metformin therapy (n=130), randomized in 1:1 ratio, considered to have undergone Vitamin D supplementation according to the guidelines proposed by the Endocrine Society, or to have continued with metformin only. The potential benefit was monitored through the influence on glycemia level, glycated haemoglobin (HbA1c), insulin resistance index (calculated as homeostatic model assessment; HOMA-IR), Castelli Risk Index I and Tryglicerides/Thiobarbituric acid-reactive substances (TG/TBARS) Index in a 6-month follow up period. Our study indicates that oral daily doses of vitamin D improve HbA1c levels over the 3-month and 6-month period, followed by a significant decrease in advanced oxidation protein products levels over the 3-month period when higher vitamin D doses are given. The effect of vitamin D on HOMA-IR index, malondialdehyde levels and TG/TBARS index was not statistically significant. Further investigation should consider defining the doses of vitamin D in patients with T2DM which may attenuate the oxidative stress risk, the risk of metabolic syndrome and the risk of related cardiovascular events.

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The aim of this cross-sectional study was to evaluate the cardiovascular risk in patients with subclinical hypothyroidism (SH) and metabolic syndrome (MetS) components. The study included 60 patients with SH and a control group of 60 healthy volunteers, gender and age matched, with normal thyroid-stimulating hormone (TSH) and free thyroxin (FT4) concentration. The following measurements were made in all participants: TSH, FT4, thyroid peroxidase antibodies, anti-thyroglobulin antibodies, body mass index (BMI), waist circumference, blood pressure, fasting plasma glucose, total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides (TG), TC/HDL cholesterol and LDL/HDL cholesterol ratio, basal insulin level and homeostatic model assessment insulin resistance (HOMA-IR) index. MetS was diagnosed according to the National Cholesterol Education Program Adult Treatment Panel III criteria. The results showed that the following indices were statistically significantly higher in the SH group: BMI (p < 0.05), diastolic blood pressure (p < 0.001), TC (p < 0.05), TG (p < 0.05) and basal insulin level (p < 0.05). Although MetS parameters were present in a higher per cent in the SH group, there was a significantly higher number of patients with hypertension and decreased HDL cholesterol (p < 0.05). More frequently, MetS was diagnosed in SH patients (46.67%) than in the control group (33.33%), although the difference was not statistically significant. These results indicated that the traditional cardiovascular risk factors were more frequently present in SH patients as compared to euthyroid participants. Our results did not confirm significantly higher presence of MetS in SH patients in comparison with euthyroid respondents.

Introduction: The performed study focused on determining the effect of vitamin D supplementation on enzymes involved in both inflammation and reactive oxygen species (ROS) production and ROS degradation in patients with type 2 diabetes mellitus (T2DM). Material and methods: The 6-month follow-up, randomized, controlled study included 140 patients with T2DM, ≥ 30 years old, with good metabolic control, treated with metformin and lifestyle advice only. All patients were randomly assigned to two groups (70 each). Patients from the first group (Intervention group) were assigned to receive vitamin D3 50 000 IU or 14 000 IU regarding their vitamin D baseline levels. Patients from the second (Metformin) group continued to receive only metformin during the 6-month study period. Results: After 6 months, the myeloperoxidase activity was significantly lower and gradually decreased in the Intervention group by about 40%, compared to the baseline measurement (p = 0.015) and compared to the Metformin group (p = 0.001). After 6 months, the xanthine oxidase (XO) activity decreased significantly in the Intervention group compared to the baseline and 3 rd month levels (p < 0.001). In the Metformin group there was also a significant decrease in XO after 6 months compared to baseline (p < 0.001) and the 3 rd month (p = 0.003). The catalase activity significantly increased within the Intervention group only when comparing the 3 rd and 6 th month (p = 0.027). Conclusions: Our study showed that vitamin D may improve endothelial dysfunction in patients with T2DM on metformin therapy by influencing two important factors implicated in the pathogenesis of diabetic complications-ROS production and inflammation, which can additionally contribute to a stable metabolic control during metformin therapy.