Para-Tyrosine Supplementation Improves Insulin- and Liraglutide- Induced Vasorelaxation in Cholesterol-Fed Rats.

Former data of our workgroup indicated that the accumulation of oxidized amino acids (meta- and ortho-tyrosine) due to oxidative stress may play an important role in the impaired insulininduced vasoactive properties of different arterial segments. There are evidences, that incorporation of these amino acids into cellular proteins leads to certain hormonal resistances, which might be restored by supplementation with the physiologic isoform, para-tyrosine. Rats in the control group were kept on a regular diet, rats in the cholesterol-fed group received high-fat diet, while the third group of rats received high-fat diet with para-tyrosine supplementation for 16 weeks. Plasma cholesterol level was significantly higher in the cholesterol-fed group, while the level of cholesterol in the cholesterol+para-tyrosine group did not differ significantly from that of the controls. Plasma level of insulin after glucose stimulation was decreased in the cholesterol-fed group, while that in the para-tyrosine supplemented group did not differ significantly from the controls. Vascular para-, meta- and ortho-tyrosine content was measured with HPLC. Elevated vascular meta-tyrosine/para-tyrosine ratio of cholesterol fed rats could be avoided by para-tyrosine supplementation. Vascular response of the thoracic aorta to insulin and liraglutide was assessed by a DMT multi-myograph. Cholesterol feeding resulted in vascular insulin-and liraglutide resistance, which was restored by para-tyrosine supplementation. Incorporation of the oxidative stress induced pathological tyrosine isoforms leads to vascular-hormone-resistances. We show that the physiological amino acid para-tyrosine is capable of restoring hypercholesterolemia-induced increased meta-tyrosine content of the vascular wall, thus attenuating functional vascular damage.

[Pathology and diagnostic opportunities of lower limb compartment syndrome]. / Az alsó végtagi compartment-syndroma kórtana és diagnosztikai lehetoségei.

BACKGROUND: The indication for the surgical treatment of lower limb compartment syndrome mostly depends on the clinical signs, which can be uncertain and often delayed, resulting in a late and insufficient intervention. AIM: In this study, the progression of compartment syndrome was monitored with the measurement of intracompartmental pressure and tissue oxygen saturation. MATERIALS AND METHODS: 16 patients (12 male and 4 female; mean age: 62,7 years) underwent acute lower limb revascularization surgery due to critical (more than 4 hour) limb ischaemia. The indications were the following: 5 iliac artery embolisms and 11 femoral artery occlusions. After revascularization, significant lower limb oedema and swelling were detected. To monitor the elevated intracompartmental pressure (ICP), KODIAG pressure meter was used. Tissue oxygen saturation (StO2) was measured with near-infrared-spectroscopy. RESULTS: In 12 cases the IPC exceeded the critical 40 mmHg. In these patients, StO2 was 50-53%, in spite of the successful re-canalisation. An urgent, semi-open fasciotomy was performed in these cases. In four patients, the clinical picture suggested compartment syndrome. However, the measured parameters did not indicate surgical intervention (ICP: 25-35 mmHg, StO2: normal). SUMMARY: In addition to the empirical guidelines, we describe an evidence based surgical intervention strategy for lower limb compartment syndrome. Our results and advised parameter intervals help the clinicians to decide between conservative and operative treatment of the disease.

Cardioprotective action of urocortin in early pre- and postconditioning.

Pre- and postconditioning are powerful endogenous adaptive phenomenon of the organism whereby different stimuli enhance the tolerance against various types of stress. Urocortin (Ucn), member of the corticotropin-releasing factor (CRF) family has potent effects on the cardiovascular system. The aim of this article was to investigate the action of Ucn on cultured cardiomyocytes in the process of pre- and postconditioning. Isolated neonatal rat ventricular myocytes were preconditioned with adenosine, simulated ischemia, and Ucn (10-min treatment followed by 10-min reperfusion/recovery). For detecting the effect of alternative types of preconditioning, necrosis enzyme (lactate dehydrogenase [LDH]) release, vital staining (trypan blue), and ratio of apoptosis/necrosis were examined after cardiac cells were exposed to 3-h sustained ischemia and 2-h reperfusion. Same parameters were measured in the postconditioned groups (30- or 60-min ischemia followed by postconditioning with 10-min ischemic stimulus or Ucn and 2-h reperfusion). Cells exposed to 3-h ischemia followed by 2-h reperfusion were shown as control. Our results show that LDH release a number of trypan blue-stained dead cells and the ratio of apoptotized and necrotized cells was decreased in all preconditioned groups compared with control group. In postconditioned groups LDH content of culture medium, trypan blue-positive cardiomyocytes, and the rate of apoptotic/necrotic cells was reduced contrasted with non-postconditioned group. We can conclude that preconditioning with Ucn induced such a powerful cell protective effect as adenosine and ischemia. Furthermore, postconditioning with Ucn after 60-min ischemia was more cardioprotective than ischemic postconditioning.

Expression and protective role of heme oxygenase-1 in delayed myocardial preconditioning.

In the study the authors aimed to demonstrate the expression and protective effect of heme oxygenase-1 (HO-1) in the delayed preconditioning (PC) on cultured myocardiac cells. Neonatal rat cardiac myocytes were exposed to ischemic (ischemic medium [IM] for 20 min) and pharmacological (adenosine, epinephrine, opioid) PC. Twenty-four hours later cells were subjected to a simulated ischemia (SI)--culturing for 3 h in IM, followed by 2-h reperfusion in normal medium--and then lactate dehydrogenase (LDH), live/death ratio, and apoptosis were measured. For demonstrating the protective role of HO-1, its enzymatic activity was competitively inhibited by administration of zinc protoporphyrin IX (ZnPPIX), and HO-1 synthesis was blocked with HO-1 siRNA. Cells in control group were cultured under normoxic conditions. In SI group, cells underwent only an SI without PC. HO-1 expression in all of the groups was demonstrated with immunostaining. Our results showed a significant decrease of LDH release, apoptosis, and cell death in PC groups versus SI group, which has been risen in ZnPPIX- and HO-1 siRNA-treated groups. HO-1 immunostaining showed an appreciable HO-1 expression in PC groups, which was abolished with HO-1 siRNA administration, but not in ZnPPIX group. The results therefore suggest that HO-1 expression increases in both ischemic and pharmacological PC, and HO-1 has cellular protective effect against cell death and apoptosis in ischemia-reperfusion-induced oxidative injury.

[Oxidative stress and leukocyte activation after lower limb revascularization surgery]. / Alsóvégtagi revaszkularizációs mutéteket követo oxidatív stressz vizsgálata.

The authors aimed to study of oxidative stress and thrombocyte function in the perioperative interval following the revascularization surgery of lower limb. The prospective randomised study involved 10 patients whose surgical interventions were indicated by lower limb embolism, thrombosis or abdominal aorta aneurysm, and 10 healthy volunteers were also involved in the study. Peripheral blood samples were collected before, and after the surgery (2, 24 hours and one week). The maximal free radical production and lag time of the free radical production of activated leukocytes were measured, and leukocyte adhesion molecules (CD11a and CD18) signing leucocyte activation were determined as well. Endogenous antioxidant defence status, reduced glutathione (GSH), total thiol-groups (-SH), SOD activity and thrombocyte function were investigated in platelet rich plasma and in whole blood. White blood cell count and free radical production was significantly higher in patients group before surgery than in healthy group (in case of the free radical production the difference proved to be 10 times (p < 0.01)) and elevated continuously during the observation time. The CD11a and CD18 expression of the granulocytes significantly decreased right after the revascularization, but with a gradual elevation, until the 7th day they exceed the ischaemic value. GSH concentration decreased significantly 2 and 24 hours after surgery and total thiol groups (-SH) followed the same kinetics. SOD activity was significantly lower in patients group haemolysates before surgery when it was measured in healthy groups (p < 0.01) and decreased further significantly 24 hours after the surgery (p < 0.01 vs. before surgery). Suppressed thrombocyte aggregation was detected in platelet rich plasma and in whole blood during the observation excepted the one week samples, where a highly significant elevation in ADP and collagen induced aggregation were observed. Our results show a great alteration in the antioxidant-prooxidant balance and the insufficiency of platelet aggregation's inhibition after peripheral vessel closure and revascularization intervention. We suggest the monitoring of the antioxidant status and thrombocyte function of patients going to underwent surgical intervention and if it necessary the therapeutic help.

Intestinal ischemic preconditioning in rats and NF-kappaB activation.

Cold preservation prior to small-bowel transplantation can moderate tissue injury, although it is unable to protect the bowel graft from acute reperfusion injury. One method to reduce oxidative stress is ischemic preconditioning (IPC). The limited data regarding IPC of the bowel encouraged us to investigate the key factor in this process, i.e., the activation of nuclear factor-kappa binding (NF-kB) in bowel tissue. The intestine was preconditioned by various cycles of IPC on rats. Activation of NF-kB was detected by a chemiluminescence-based ELISA method. Our findings showed that NF-kB level was elevated significantly 30 min after IPC. One hour following IPC, NF-kB decreased to control level; 2 h after IPC, the level significantly increased again. These changes were independent of the number of IPC cycles. Our experiments with various IPC cycles revealed that even a very short IPC cycle was able to activate the IPC cascade in small-bowel tissue.

Comparison of the extrapancreatic action of BRX-220 and pioglitazone in the high-fat diet-induced insulin resistance.

UNLABELLED: A new Biorex molecule, BRX-220, has been shown to be effective in animal models of diabetic neuro- and retinopathy. Recent in vitro studies showed that it might also have an insulin-sensitizing action. Therefore, the effect of BRX-220 on insulin sensitivity was compared with the action of pioglitazone (PGZ) in high fat (HF) diet-induced insulin resistance (IR) of rats. METHODS: Male Wistar rats were fed for 3 weeks a standard chow (PD) or the HF (70-cal%) diet. The HF-fed rats were also given daily BRX-220 (20 mg/kg BW) or PGZ (6 mg/kg BW) by gavage. In vivo insulin action was assessed by the euglycemic hyperinsulinemic clamp. Glucose, insulin, FFA, triglyceride (TG), and glycerol levels in blood were also measured, as well as tissue TG content. RESULTS: Increased levels of fed TG in circulation after HF diet (PD: 2.0+/-0.2 vs. HF: 5.0+/-0.8 mmol/L) were partially corrected by BRX-220 (HF + BRX: 3.8+/-0.3) and normalized by PGZ (HF + PGZ: 2.6+/-0.3). Both molecules prevented the increase in fed serum FFA levels after HF diet (PD: 0.5+/-0.06; HF: 1.8+/-0.2 mmol/L), with a more pronounced effect of PGZ (HF + BRX: 1.2+/-0.1; HF + PGZ: 0.7+/-0.06). Tissue TG levels increased significantly in response to HF feeding in both liver (HF: 16+/-3.0; PD: 6.4+/-1.1 micromol/g) and skeletal muscle (HF: 7.7+/-1.2; PD: 2.4+/-0.4). This increase was completely normalized by both agents in the liver (HF + BRX: 8.8+/-0.8; HF + PGZ: 8.8+/-1.0), and only partially in the skeletal muscles. HF diet-induced in vivo IR (PD: 25.4+/-0.5; HF: 15.7+/-0.5 mg/kg/min) was significantly reduced by BRX-220 (HF + BRX: 18.7+/-0.3) and PGZ (HF + PGZ: 22.8+/-0.4) treatment. CONCLUSIONS: (1) Subchronic administration of BRX-220 leads to an improvement of in vivo insulin action. (2) This insulin-sensitizing effect is, however, not as pronounced as that of PGZ. (3) It is accompanied by a decrease of circulating TG and FFA levels in the postprandial state and (4) by lower TG content in liver and skeletal muscle.

Effect of BRX-220 against peripheral neuropathy and insulin resistance in diabetic rat models.

Bimoclomol (BML), a symptomatic antidiabetic agent, has been developed by Biorex R & D Co. to treat diabetic neuropathy and retinopathy. BRX-220, an orally active member of the BRX family, has been developed to treat diabetic complications and insulin resistance (IR) as a follow-up compound. The effect of BRX-220 on peripheral neuropathy was examined in rats with diabetes (type 1) induced by administration of a beta-cell toxin, streptozotocin (STZ, 45 mg/kg iv). Nerve functions were evaluated by electrophysiological measurements of muscle motor and sensory nerve conduction velocities (MNCV and SNCV, respectively). MNCV and SNCV decreased in diabetic rats by 25% (p < 0.001). A 1-month preventive treatment with BRX-220 (2.5, 5, 10, and 20 mg/kg po) dose-dependently improved diabetes-related deficits in MNCV (51.3%, 71.3%, 86.1%, and 91.3%) and SNCV (48.9%, 68.5%, 86.1%, and 93.2%). Insulin sensitivity was measured using the insulin tolerance test (ITT), both in STZ diabetic and in Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). Severe IR was detected in STZ diabetic and ZDF rats. This resistance was significantly (p < 0.05) reduced by BRX-220 treatment.