Oxidant Status and Lipid Composition of Erythrocyte Membranes in Patients with Type 2 Diabetes, Chronic Liver Damage, and a Combination of Both Pathologies

There is an important set of cirrhotic and diabetic patients that present both diseases. However, information about metabolic and cellular blood markers that are altered, in conjunction or distinctively, in the 3 pathological conditions is scarce. The aim of this project was to evaluate several indicators of prooxidant reactions and the membrane composition of blood samples (serum and red blood cells (RBCs)) from patients clinically classified as diabetic (n=60), cirrhotic (n=70), and diabetic with liver cirrhosis (n=25) as compared to samples from a similar population of healthy individuals (n=60). The results showed that levels of TBARS, nitrites, cysteine, and conjugated dienes in the RBC of cirrhotic patients were significantly increased. However, the coincidence of diabetes and cirrhosis partially reduced the alterations promoted by the cirrhotic condition. The amount of total phospholipids and cholesterol was greatly enhanced in the patients with both pathologies (between 60 and 200% according to the type of phospholipid) but not in the patients with only one disease. Overall, the data indicate that the cooccurrence of diabetes and cirrhosis elicits a physiopathological equilibrium that is different from the alterations typical of each individual malady

Increased erythrocytes by-products of arginine catabolism are associated with hyperglycemia and could be involved in the pathogenesis of type 2 diabetes mellitus.

Diabetes mellitus (DM) is a worldwide disease characterized by metabolic disturbances, frequently associated with high risk of atherosclerosis and renal and nervous system damage. Here, we assessed whether metabolites reflecting oxidative redox state, arginine and nitric oxide metabolism, are differentially distributed between serum and red blood cells (RBC), and whether significant metabolism of arginine exists in RBC. In 90 patients with type 2 DM without regular treatment for diabetes and 90 healthy controls, paired by age and gender, we measured serum and RBC levels of malondialdehyde (MDA), nitrites, ornithine, citrulline, and urea. In isolated RBC, metabolism of L-[(14)C]-arginine was also determined. In both groups, nitrites were equally distributed in serum and RBC; citrulline predominated in serum, whereas urea, arginine, and ornithine were found mainly in RBC. DM patients showed hyperglycemia and increased blood HbA1C, and increased levels of these metabolites, except for arginine, significantly correlating with blood glucose levels. RBC were observed to be capable of catabolizing arginine to ornithine, citrulline and urea, which was increased in RBC from DM patients, and correlated with an increased affinity for arginine in the activities of putative RBC arginase (Km = 0.23±0.06 vs. 0.50±0.13 mM, in controls) and nitric oxide synthase (Km = 0.28±0.06 vs. 0.43±0.09 mM, in controls). In conclusion, our results suggest that DM alters metabolite distribution between serum and RBC, demonstrating that RBC regulate serum levels of metabolites which affect nitrogen metabolism, not only by transporting them but also by metabolizing amino acids such as arginine. Moreover, we confirmed that urea can be produced also by human RBC besides hepatocytes, being much more evident in RBC from patients with type 2 DM. These events are probably involved in the specific physiopathology of this disease, i.e., endothelial damage and dysfunction

A Single Zidovudine (AZT) Administration Delays Hepatic Cell Proliferation by Altering Oxidative State in the Regenerating Rat Liver

The 3′-azido-3′-deoxythymidine or Zidovudine (AZT) was the first antiretroviral drug used in the treatment of HIV patients, which has good effectiveness but also hepatotoxic side effects that include cell cycle arrest and oxidative/nitrative mitochondrial damage. Whether such an oxidative damage may affect the proliferative-regenerative capacity of liver remains to be clearly specified at doses commonly used in the clinical practice. In this study, we described the oxidative-proliferative effect of AZT administered at a common clinical dose in rat liver submitted to 70% partial hepatectomy (PH). The results indicate that AZT significantly decreased DNA synthesis and the number of mitosis in liver subjected to PH in a synchronized way with the promotion of organelle-selective lipid peroxidation events (especially those observed in plasma membrane and cytosolic fractions) and with liver enzyme release to the bloodstream. Then at the dose used in clinical practice AZT decreased liver regeneration but stimulates oxidative events involved during the proliferation process in a way that each membrane system inside the cell preserves its integrity in order to maintain the cell proliferative process. Here, the induction of large amounts of free ammonia in the systemic circulation could become a factor capable of mediating the deleterious effects of AZT on PH-induced rat liver regeneration

The role of oxidant stress and gender in the erythrocyte arginine metabolism and ammonia management in patients with type 2 diabetes.

ObjectivesTo study the differences in the levels of nitrogen metabolites, such as ammonia and nitric oxide and the correlations existing among them in both red blood cells (RBCs) and serum, as well as the possible differences by gender in healthy subjects and patients with type 2 Diabetes Mellitus (DM).Design and methodsThis cross-sectional study included 80 patients diagnosed with type 2 DM (40 female and 40 male patients) and their corresponding controls paired by gender (40 female and 40 male). We separated serum and RBC and determined metabolites mainly through colorimetric and spectrophotometric assays. We evaluated changes in the levels of the main catabolic by-products of blood nitrogen metabolism, nitric oxide (NO), and malondialdehyde (MDA).ResultsHealthy female and male controls showed a differential distribution of blood metabolites involved in NO metabolism and arginine metabolism for the ornithine and urea formation. Patients with DM had increased ammonia, citrulline, urea, uric acid, and ornithine, mainly in the RBCs, whereas the level of arginine was significantly lower in men with type 2 DM. These findings were associated with hyperglycemia, glycosylated hemoglobin (Hb A1C), and levels of RBC's MDA. Furthermore, most of the DM-induced alterations in nitrogen-related metabolites appear to be associated with a difference in the RBC capacity for the release of these metabolites, thereby causing an abrogation of the gender-related differential management of nitrogen metabolites in healthy subjects.ConclusionsWe found evidence of a putative role of RBC as an extra-hepatic mechanism for controlling serum levels of nitrogen-related metabolites, which differs according to gender in healthy subjects. Type 2 DM promotes higher ammonia, citrulline, and MDA blood levels, which culminate in a loss of the differential management of nitrogen-related metabolites seen in healthy women and men

Formation and release of (¹⁴C)-citrulline, (¹⁴C)-ornithine and of (¹⁴C)-urea after incubation with (¹⁴C)-arginine in RBC from control subjects and patients with type 2 diabetes mellitus.

<p>The results are expressed as the mean ± SD for levels of produced and released, in nmols per mL, of radio-labeled citrulline, ornithine, and urea, after incubation with (¹⁴C)-arginine, quantified in supernatants, or in the RBC pellets obtained from control healthy volunteers (n = 30) and in patients with type 2 diabetes mellitus (n = 30). Statistics: *p<0.01 as compared to healthy controls.</p

Clinical parameters of control subjects and patients with type 2 DM.

<p>The results are expressed as means ± SD. Abbreviations: BMI, body mass index; TG, triacylglycerols, and hs-CRP, high-sensitive C-reactive protein. Statistics: *p<0.01 as compared to healthy controls.</p

Serum and RBC levels of MDA, arginine, and nitrites from blood obtained from control subjects and patients with type 2 diabetes mellitus.

<p>The results are expressed as the mean ± SD for levels of blood MDA (panel A), arginine (panel B), or blood nitrites (panel C) in RBC samples from control healthy volunteers (n = 90) and in patients with type 2 diabetes mellitus (n = 90). Symbols indicating each experimental group at the top of the panels. Statistics: *p<0.01 against control values (healthy subjects).</p

Overview of the possible metabolic pathways for arginine in RBC and their interaction with endothelial cells.

<p>Enzymatic routes that can probably directly use or produce arginine, ornithine, urea, or citrulline in the RBC. Key to abbreviations: Arg: arginase; eNOS: endothelial nitric oxide synthase; NO: nitric oxide; NOS: nitric oxide synthase, and OCT: ornithine carbamoyl transferase.</p

Effect of added arginine on its own release and that of MDA, and rate of RBC hemolysis from control subjects and patients with type 2 diabetes mellitus.

<p>The results are expressed as the mean ± SD for levels of released arginine (panel A) and MDA (panel B), in RBC samples from control healthy volunteers (n = 30) and in patients with type 2 diabetes mellitus (n = 30). Panel C shows the rate of hemolysis obtained in each preparation. Start of the incubation at 37°C in the presence of increasing arginine concentrations is indicated by the upper arrow. Symbols indicating each experimental group at the top of the panels. Statistics: *p<0.01 against control basal values (zero) and **p<0.01 vs. the basal metabolite value (zero) in samples from DM patients.</p

Serum and RBC levels of citrulline, ornithine, and urea from blood obtained from control subjects and patients with type 2 diabetes mellitus.

<p>The results are expressed as the mean ± SD for levels of blood citrulline (panel A), ornithine (panel B), or blood urea (panel C) in RBC samples from control healthy volunteers (n = 90) and in patients with type 2 diabetes mellitus (n = 90). Symbols indicating each experimental group at the top of the panels. Statistics as indicated in Fig. 1.</p