Mechanisms of haptoglobin protection against hemoglobin peroxidation triggered endothelial damage.

Extracellular hemoglobin (Hb) has been recognized as a disease trigger in hemolytic conditions such as sickle cell disease, malaria, and blood transfusion. In vivo, many of the adverse effects of free Hb can be attenuated by the Hb scavenger acute-phase protein haptoglobin (Hp). The primary physiologic disturbances that can be caused by free Hb are found within the cardiovascular system and Hb-triggered oxidative toxicity toward the endothelium has been promoted as a potential mechanism. The molecular mechanisms of this toxicity as well as of the protective activities of Hp are not yet clear. Within this study, we systematically investigated the structural, biochemical, and cell biologic nature of Hb toxicity in an endothelial cell system under peroxidative stress. We identified two principal mechanisms of oxidative Hb toxicity that are mediated by globin degradation products and by modified lipoprotein species, respectively. The two damage pathways trigger diverse and discriminative inflammatory and cytotoxic responses. Hp provides structural stabilization of Hb and shields Hb's oxidative reactions with lipoproteins, providing dramatic protection against both pathways of toxicity. By these mechanisms, Hp shifts Hb's destructive pseudo-peroxidative reaction to a potential anti-oxidative function during peroxidative stress.

Methylation levels of sodium-iodide symporter (NIS) promoter in benign and malignant thyroid tumors with reduced NIS expression.

DNA methylation regulates gene expression. Aberrant methylation plays an important role in human tumorigenesis. We have previously detected reduced NIS mRNA expression in thyroid tumors as compared to non-tumor tissues. Thus, in this study we investigated whether the methylation of the CpG-island located in the NIS gene promoter was associated with reduced mRNA expression in thyroid tumors. Methylation levels of 30 pairs of samples from 10 benign and 20 malignant thyroid tumors (T) along with matched non-tumor (NT) areas were determined by semiquantitative methylation specific-PCR. NIS methylation was detected in all samples. Methylation levels and frequencies did not differ between the groups and were not associated with BRAF mutational status. Highest methylation levels and frequencies were detected in the 5' region of the CpG-island decreasing toward the 3' end. Intraindividual analysis (T versus NT) showed high tumor methylation levels in 40 % of the samples in the benign group and 30 % in the malignant group, associated with low NIS mRNA expression. No quantitative correlation was detected between methylation levels and mRNA expression in any the groups. The results of this study showed that methylation of NIS promoter is a very frequent event in both benign and malignant tumors as well as in their surrounding tissues, and characterized a non-homogeneous methylation pattern along the CpG island. Therefore, further investigations involving other sites that may be implicated in methylation regulation of NIS expression are warranted.

Oral ingestion of a hydrolyzed gelatin meal in subjects with normal weight and in obese patients: Postprandial effect on circulating gut peptides, glucose and insulin.

Gut hormones [ghrelin, peptide YY (PYY) and glucagon-like peptide-1 (GLP-1)] are an important group of hormones that target appetite control. They are released from endocrine L cells of the small bowel in proportion to the volume, components and calories in a meal. In the current study, 20 g of gelatin (flavored and sweetened) were given to obese patients (n=12) and lean subjects (n=10). Subsequently, plasma samples were collected at-30- minute intervals up to 180 minutes and glucose, insulin, PYY, GLP-1 and ghrelin were assayed using specific and sensitive immunofluorometric and radioimmunoassays. As expected, obese patients had normal serum glucose levels, higher serum insulin, and lower plasma concentration of ghrelin at all times compared to lean subjects. GLP-1 plasma levels were significantly elevated at 60 minutes, peaking at 120 minutes in obese patients and lean subjects. As a consequence, there was a significant rise in serum insulin levels with a significantly higher peak level at 60 min (obese) and 30 min (lean). There were no significant changes in PYY plasma concentrations and no correlation was found between body mass index and concentrations of ghrelin, PYY and GLP-1 in the group of obese patients. In conclusion, a single gelatin meal induces a rise in plasma GLP-1 followed by an increase in serum levels of insulin. These findings may be applied to maximize satiety in obese patients as a means of improving adherence to calorie-controlled diets as well as provide better control of diabetic patients.

Peripheral blood levels of thyroglobulin mRNA and serum thyroglobulin concentrations after radioiodine ablation of multinodular goiter with or without pre-treatment with recombinant human thyrotropin.

We investigated the effect of therapeutic doses of radioiodine (RAI) on peripheral serum messenger thyroglobulin RNA (Tg mRNA) and serum thyroglobulin (sTg) in patients with multinodular goiter (MNG) preceded or not by treatment with recombinant human TSH (rhTSH). Fourteen patients with large MNG (91-542 ml) received RAI (550-2960 MBq). Half of the patients received 0.45 mg of rhTSH prior to the treatment (RAI+rhTSH group) and half did not (RAI group). Patients' blood samples were collected before and 24, 48, and 72 h; 7 and 30 days; and 6, 9, and 12 months after RAI treatment. Serum Tg was measured by immunoradiometric assay, serum anti-Tg by radioimmunoassay, and quantification of circulating Tg mRNA was performed by real-time PCR. The shrinkage of MNG volume was documented by serial computed tomography (CT) scans before, 6 and 12 months after RAI. Peak Tg mRNA and sTg were reached earlier in the RAI+rhTSH group (24 h and 48 h) than in the RAI group (7 days). Both declined after the peak and the lowest levels were observed at 12 months. The mean reduction of the thyroid volume was 19.8% (RAI group) and 30.3% (RAI+rhTSH group) at 6 months (ns) and 32.8% RAI and 52.5% (RAI+rhTSH group) at 12 months (p<0.05). After RAI treatment there was a significant and positive correlation between goiter volume and sTg only in the RAI group (r=0.7; p=0.032). Serum anti-Tg had a transitory and relatively small elevation in 3 and 2 patients, respectively, in the RAI and RAI+rhTSH groups. We concluded that after RAI ablation of MNG there is a rapid release of Tg into the serum possibly from the colloid, which is followed by an elevation of serum Tg mRNA that may be due to an increased release of follicular cells into the blood stream. Both phenomena are enhanced by the use of rhTSH before RAI treatment as a consequence of a more effective and prolonged radiation exposure of the thyroid follicles.