Elevated Vascular Level of ortho-Tyrosine Contributes to the Impairment of Insulin-Induced Arterial Relaxation.

Previous studies have shown that in diabetes mellitus, insulin-induced relaxation of arteries is impaired and the level of ortho-tyrosine (o-Tyr), an oxidized amino acid is increased. Thus, we hypothesized that elevated vascular level of o-Tyr contributes to the impairment of insulin-induced vascular relaxation. Rats were fed with o-Tyr for 4 weeks. Insulin-induced vasomotor responses of isolated femoral artery were studied using wire myography. Vascular o-Tyr content was measured by HPLC, whereas immunoblot analyses were preformed to detect eNOS phosphorylation. Sustained oral supplementation of rats with o-Tyr increased the content of o-Tyr in the arterial wall and significantly reduced the relaxations to insulin. Sustained supplementation of cultured endothelial cells with o-Tyr increased the incorporation of o-Tyr and mitigated eNOS Ser (1 177) phosphorylation to insulin. Increasing arterial wall o-Tyr level attenuates insulin-induced relaxation - at least in part - by decreasing eNOS activation. Elevated level of o-Tyr could be an underlying mechanism for vasomotor dysfunction in diabetes mellitus

Role of Ryanodine Type 2 Receptors in Elementary Ca 2+ Signaling in Arteries and Vascular Adaptive Responses

Background: Hypertension is the major risk factor for cardiovascular disease, the most common cause of death worldwide. Resistance arteries are capable of adapting their diameter independently in response to pressure and flow-associated shear stress. Ryanodine receptors (RyRs) are major Ca2+-release channels in the sarcoplasmic reticulum membrane of myocytes that contribute to the regulation of contractility. Vascular smooth muscle cells exhibit 3 different RyR isoforms (RyR1, RyR2, and RyR3), but the impact of individual RyR isoforms on adaptive vascular responses is largely unknown. Herein, we generated tamoxifen-inducible smooth muscle cell-specific RyR2-deficient mice and tested the hypothesis that vascular smooth muscle cell RyR2s play a specific role in elementary Ca2+ signaling and adaptive vascular responses to vascular pressure and/or flow. Methods and Results: Targeted deletion of the Ryr2 gene resulted in a complete loss of sarcoplasmic reticulum-mediated Ca2+-release events and associated Ca2+-activated, large-conductance K+ channel currents in peripheral arteries, leading to increased myogenic tone and systemic blood pressure. In the absence of RyR2, the pulmonary artery pressure response to sustained hypoxia was enhanced, but flow-dependent effects, including blood flow recovery in ischemic hind limbs, were unaffected. Conclusions: Our results establish that RyR2-mediated Ca2+-release events in VSCM s specifically regulate myogenic tone (systemic circulation) and arterial adaptation in response to changes in pressure (hypoxic lung model), but not flow. They further suggest that vascular smooth muscle cell-expressed RyR2 deserves scrutiny as a therapeutic target for the treatment of vascular responses in hypertension and chronic vascular diseases

Exenatide induces aortic vasodilation increasing hydrogen sulphide, carbon monoxide and nitric oxide production

BACKGROUND: It has been reported that GLP-1 agonist exenatide (exendin-4) decreases blood pressure. The dose-dependent vasodilator effect of exendin-4 has previously been demonstrated, although the precise mechanism is not thoroughly described. Here we have aimed to provide in vitro evidence for the hypothesis that exenatide may decrease central (aortic) blood pressure involving three gasotransmitters, namely nitric oxide (NO) carbon monoxide (CO), and hydrogen sulphide (H2S). METHODS: We determined the vasoactive effect of exenatide on isolated thoracic aortic rings of adult rats. Two millimetre-long vessel segments were placed in a wire myograph and preincubated with inhibitors of the enzymes producing the three gasotransmitters, with inhibitors of reactive oxygen species formation, prostaglandin synthesis, inhibitors of protein kinases, potassium channels or with an inhibitor of the Na+/Ca2+-exchanger. RESULTS: Exenatide caused dose-dependent relaxation of rat thoracic aorta, which was evoked via the GLP-1 receptor and was mediated mainly by H2S but also by NO and CO. Prostaglandins and superoxide free radical also play a part in the relaxation. Inhibition of soluble guanylyl cyclase significantly diminished vasorelaxation. We found that ATP-sensitive-, voltage-gated- and calcium-activated large-conductance potassium channels are also involved in the vasodilation, but that seemingly the inhibition of the KCNQ-type voltage-gated potassium channels resulted in the most remarkable decrease in the rate of vasorelaxation. Inhibition of the Na+/Ca2+-exchanger abolished most of the vasodilation. CONCLUSIONS: Exenatide induces vasodilation in rat thoracic aorta with the contribution of all three gasotransmitters. We provide in vitro evidence for the potential ability of exenatide to lower central (aortic) blood pressure, which could have relevant clinical importance

Immunnefelometria és nagy teljesítményű folyadékkromatográfia a microalbuminuria vizsgálatában. Újonnan javasolt határértékek vizsgálata = Analysis of microalbuminuria with immunonephelometry and high performance liquid chromatography. Evaluation of new criteria

Mind a hipertónia, mind a 2-es típusú diabetes mellitus jelentős tényező a népesség halálozásában. Mindkét betegség károsítja az endothelt, aminek korai jele a microalbuminuria, amelyet szűrővizsgálatként tesztcsíkkal, diagnosztikus vizsgálatként immunológiai alapú módszerekkel, illetve nagy teljesítményű folyadékkromatográfiával lehet mérni. Ez utóbbi segítségével az ún. nem immunreaktív albuminforma is kimutatható. Célkitűzés: A szerzők célkitűzése immunnefelometriával microalbuminuriára negatív, diabéteszes és hipertóniás, illetve nem diabéteszes hipertóniás betegek albuminürítésének vizsgálata volt nagy teljesítményű folyadékkromatográfiával. Továbbá célul tűzték ki a microalbuminuria megállapításához használt jelenlegi kritériumok (albumin-kreatinin hányados: férfiaknál ≥2,5 mg/mmol, nőknél ≥3,5 mg/mmol) és a közelmúltban megjelent Heart Outcomes Prevention Evaluation tanulmány által javasolt új kritériumok (nem diabéteszesekben, immunológiai módszerrel ≥0,7 mg/mmol, nagy teljesítményű folyadékkromatográfiás módszerrel ≥3,1 mg/mmol, diabéteszesekben immunológiai módszerrel ≥1,4 mg/mmol, nagy teljesítményű folyadékkromatográfiával ≥5,2 mg/mmol) használhatóságának vizsgálatát is. Módszer: Szűrővizsgálattal microalbuminuriára negatív 469 egyén vizeletének vizsgálata történt meg immunnefelometriás módszerrel. Az így is negatívakat vizsgálták tovább nagy teljesítményű folyadékkromatográfián alapuló, a méretkizárásos kromatográfia elvén működő Accumin™ Kit-tel. Eredmények: Nagy teljesítményű folyadékkromatográfiával átlagosan háromszor nagyobb albuminürítést mértek, mint immunnefelometriával. Az intraindividuális variációs koefficiens a két módszerrel nem különbözött (37 ± 31% és 40 ± 31%, p = 0,869; immunnefelometria és nagy teljesítményű folyadékkromatográfia; átlag ± szórás). A jelenlegi albumin-kreatinin hányadoson alapuló kritériumokat használva, az immunológiai módszerrel negatív egyének nagy teljesítményű folyadékkromatográfiával 43%-ban bizonyultak pozitívnak. Ha a Heart Outcomes Prevention Evaluation tanulmány új kritériumait használták, 14,5%-ra csökkent az immunnefelometriával negatív, nagy teljesítményű folyadékkromatográfiával pozitívak aránya; nagy teljesítményű folyadékkromatográfiával microalbuminuria-pozitívak száma elsősorban a diabéteszes és hipertóniás csoportban csökkent (49% és 7,5%), míg a nem diabéteszes hipertóniás csoportban kevésbé (37% és 26,5%). A hagyományos kritériumrendszerben logisztikus regressziós vizsgálat során a legerősebb kockázati faktornak a férfinem bizonyult. Az immunnefelometriával microalbuminuriára negatív egyének 28%-ában nagy teljesítményű folyadékkromatográfiával kimondható a microalbuminuria diagnózisa a jelen szakmai szabályok szerint. Következtetések: Az immunológiai módszerekkel microalbuminuriára negatív egyének közel harmadában nagy teljesítményű folyadékkromatográfiával kimondható a microalbuminuria diagnózisa, amihez továbbra is szükséges a háromszori vizeletvizsgálat. A Heart Outcomes Prevention Evaluation tanulmány által megállapított új kritériumok sem a diabéteszes és hipertóniás betegekre, sem a nem diabéteszes hipertóniás betegekre nem alkalmazhatók jól. Nem lehet figyelmen kívül hagyni a microalbuminuria-pozitivitás legjelentősebb prediktorát, a nemet. | Introduction: Hypertension as well as type 2 diabetes mellitus is a major factor in population mortality. Both diseases damage the endothelium, the early sign of which is microalbuminuria, which can be screened by dipstick and can be diagnosed by using immuno-based and high performance liquid chromatography methods. Using high performance liquid chromatography, the non-immunoreactive albumin can be detected as well. Aims: The authors aimed at the examination of albuminuria in the case of immunonephelometrically negative patients with high performance liquid chromatography, in diabetic and hypertensive and non-diabetic hypertensive populations. The authors also wanted to compare the present (albumin-creatinine ratio: male: ≥2.5 mg/mmol, female: ≥3.5 mg/mmol) and a new criteria of the Heart Outcomes Prevention Evaluation study (patients without diabetes: immunological method, ≥0.7 mg/mmol; high performance liquid chromatography, ≥3.1 mg/mmol; individuals with diabetes: immunological method, ≥1.4 mg/mmol; high performance liquid chromatography, ≥5.2 mg/mmol) of microalbuminuria. Methods: Examination of fresh urines of 469 microalbuminuria negative patients by dipstick were performed by immunonephelometry. Patients, who were microalbuminuria negative by immunonephelometry as well, were further analyzed by high performance liquid chromatography using the Accumin™ Kit, based on size-exclusion chromatography. Results: Three times higher albuminuria were found with high performance liquid chromatography than with immunonephelometry. The intraindividual coefficient of variation did not differ in the two methods (37 ± 31% vs. 40 ± 31%, p = 0.869; immunonephelometry vs. high performance liquid chromatography; mean ± standard deviation). Using the present criteria for microalbuminuria, 43% of immunonephelometrically negative patients proved to be microalbuminuric by high performance liquid chromatography. Using the new criteria of the Heart Outcomes Prevention Evaluation study, the rate of microalbuminuria positivity among the immunonephelometrically negative patients decreased to 14.5% by high performance liquid chromatography and the decrease in the number of microalbuminuria positive cases by high performance liquid chromatography could be observed mainly in the diabetic and hypertensive group (49% vs. 7.5%), while slighter decrease could be observed in the non-diabetic hypertensive group (37% vs. 26.5%). Applying the traditional criteria, the strongest predictor was the male gender by the logistic regression analysis. In 28% of microalbuminuria negative patients by immunonephelometry the diagnosis of microalbuminuria can be established using high performance liquid chromatography. Conclusions: Almost in one-third of microalbuminuria negative patients by immunonephelometry the diagnosis of microalbuminuria can be established by high performance liquid chromatography for which diagnosis three constitutive urine examinations are still needed. New criteria determined by the Heart Outcomes Prevention Evaluation study can be used neither in case of diabetic and hypertensive patients, nor in the case of non-diabetic hypertensive patients. The gender as the most important predictor of microalbuminuria cannot be ignored