Indirect Suppression of Pulsatile LH Secretion by CRH Neurons in the Female Mouse

Acute stress is a potent suppressor of pulsatile luteinizing hormone (LH) secretion, but the mechanisms through which corticotrophin-releasing hormone (CRH) neurons inhibit gonadotropin-releasing hormone (GnRH) release remain unclear. The activation of paraventricular nucleus (PVN) CRH neurons with Cre-dependent hM3Dq in Crh-Cre female mice resulted in the robust suppression of pulsatile LH secretion. Channelrhodopsin (ChR2)-assisted circuit mapping revealed that PVN CRH neuron projections existed around kisspeptin neurons in the arcuate nucleus (ARN) although many more fibers made close appositions with GnRH neuron distal dendrons in the ventral ARN. Acutely prepared brain slice electrophysiology experiments in GnRH- green fluorescent protein (GFP) mice showed a dose-dependent (30 and 300 nM CRH) activation of firing in ~20% of GnRH neurons in both intact diestrus and ovariectomized mice with inhibitory effects being uncommon (<8%). Confocal GCaMP6 imaging of GnRH neuron distal dendrons in acute para-horizontal brain slices from GnRH-Cre mice injected with Cre-dependent GCaMP6s adeno-associated viruses demonstrated no effects of 30 to 300 nM CRH on GnRH neuron dendron calcium concentrations. Electrophysiological recordings of ARN kisspeptin neurons in Crh-Cre,Kiss1-GFP mice revealed no effects of 30 -300 nM CRH on basal or neurokinin B-stimulated firing rate. Similarly, the optogenetic activation (2-20 Hz) of CRH nerve terminals in the ARN of Crh-Cre,Kiss1-GFP mice injected with Cre-dependent ChR2 had no effect on kisspeptin neuron firing. Together, these studies demonstrate that PVN CRH neurons potently suppress LH pulsatility but do not exert direct inhibitory control over GnRH neurons, at their cell body or dendron, or the ARN kisspeptin neuron pulse generator in the female mouse.

Psychosomatic symptoms during South East Asian haze crisis are related to changes in cerebral hemodynamics

OBJECTIVES

Forest fires in South Asia lead to widespread haze, where many healthy individuals develop psychosomatic symptoms. We investigated the effects of haze exposure on cerebral hemodynamics and new symptoms. We hypothesised that vasoactive substances present in the haze, would lead to vasodilation of cerebral vasculature, thereby altering cerebral hemodynamics, which in turn may account for new psychosomatic symptoms.

METHODS

Seventy-four healthy volunteers were recruited, and serial transcranial Doppler (TCD) ultrasonography was performed to record blood flow parameters of bilateral middle cerebral arteries (MCA). The first TCD was performed in an air-conditioned environment. It was repeated outdoors after the participants spent 30-minutes in the haze environment. The prevailing level of pollutant standards index (PSI) was recorded. Appropriate statistical analyses were performed to compare cerebral hemodynamics at baseline and after haze exposure in all participants. Subgroup analyses were then employed to compare the findings between symptomatic and asymptomatic participants.

RESULTS

Study participants' median age was 30 years (IQR 26-34), and new psychosomatic symptoms were reported by 35 (47.3%). There was a modest but significant decrease in pulsatility index (PI) and resistivity index (RI) in the left MCA after haze exposure (PI: p = 0.026; RI: p = 0.021). When compared to baseline parameters, haze exposure resulted in significantly lower mean PI (p = 0.001) and RI (p = 0.001) in symptomatic patients, but this difference was not present in asymptomatic patients (PI: p = 0.919; RI: p = 0.970).

CONCLUSION

Haze causes significant alterations in cerebral hemodynamics in susceptible individuals, probably responsible for various psychosomatic symptoms. The prognostic implications and health effects of haze require evaluation in a larger study.

Progesterone Suppression of Luteinizing Hormone Pulse Frequency in Adolescent Girls With Hyperandrogenism: Effects of Metformin

CONTEXT

Polycystic ovary syndrome (PCOS) and adolescent hyperandrogenism (HA) are characterized by rapid luteinizing hormone (LH) pulse frequency. This partly reflects impaired gonadotropin-releasing hormone pulse generator (hypothalamic) sensitivity to progesterone (P4) negative feedback. We assessed whether metformin may improve P4 sensitivity in adolescent HA, for which it is prescribed widely.

OBJECTIVE

To test the hypothesis that metformin improves hypothalamic P4 sensitivity in adolescent HA.

DESIGN

Nonrandomized, interventional trial.

SETTING

Academic clinical research unit.

PARTICIPANTS

Ten adolescent girls with HA.

INTERVENTION

The girls underwent LH sampling every 10 minutes for 11 hours, at study baseline and after 7 days of oral P4 and estradiol (E2). Participants then took metformin (1 g twice daily) for 9.4 to 13.7 weeks, after which participants again underwent frequent LH sampling before and after 7 days of oral P4 and E2 (while continuing metformin). Total and free testosterone (T) and fasting insulin were assessed at each admission. At admissions 1 and 3, 2-hour oral glucose tolerance tests were performed.

MAIN OUTCOME MEASURE

Metformin-related change in hypothalamic P4 sensitivity index [percent change in LH pulse frequency (before vs after P4 and E2) divided by day 7 P4 level].

RESULTS

Free T levels decreased by 29% with metformin (P = 0.0137). Measures of hyperinsulinemia and P4 sensitivity index did not significantly change with metformin use.

CONCLUSION

Short-term metformin use improved biochemical hyperandrogenemia, but did not improve hypothalamic sensitivity to P4 suppression, in adolescent girls.

Comparison between transdermal nitroglycerin and sildenafil citrate in intrauterine growth restriction: effects on uterine, umbilical and fetal middle cerebral artery pulsatility indices

OBJECTIVES

To evaluate the effects of transdermal nitroglycerin (GTN) and sildenafil citrate on Doppler velocity waveforms of the uterine (UtA), umbilical (UA) and fetal middle cerebral (MCA) arteries in pregnancies with intrauterine growth restriction (IUGR).

METHODS

This was a prospective study of 35 singleton pregnancies (gestational age, 24-31 weeks) with IUGR and abnormal UtA and UA Doppler waveforms. We compared maternal arterial blood pressure and Z-scores of the pulsatility index (PI) of UtA, UA and fetal MCA before and after application of a transdermal GTN patch (average dose, 0.4 mg/h), oral sildenafil citrate (50 mg) or placebo. Statistical analysis was performed by ANOVA for paired samples.

RESULTS

There was a significant decrease in UtA-PI after application of GTN (21.0%) and sildenafil citrate (20.4%). A significant reduction in UA-PI was also observed for both GTN (19.1%) and sildenafil citrate (18.2%). There was no difference in UtA- and UA-PI when the GTN and sildenafil groups were compared. No changes in Doppler velocimetry were observed in the placebo group and no significant change in MCA-PI was observed in any group. Maternal arterial blood pressure decreased with administration of both GTN and sildenafil citrate in those with pre-eclampsia.

CONCLUSION

The use of transdermal GTN or sildenafil citrate in pregnancies with IUGR is associated with a significant reduction in both UtA and UA Doppler PI, as well as maternal arterial blood pressure. Neither drug affected the MCA-PI. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Increasing LH pulsatility in women with hypothalamic amenorrhoea using intravenous infusion of Kisspeptin-54

BACKGROUND

Hypothalamic amenorrhea (HA) is the one of the most common causes of period loss in women of reproductive age and is associated with deficient LH pulsatility. High-dose kisspeptin-54 acutely stimulates LH secretion in women with HA, but chronic administration causes desensitization. GnRH has paradoxical effects on reproductive activity; we therefore hypothesized that a dose-dependent therapeutic window exists within which kisspeptin treatment restores the GnRH/LH pulsatility in women with HA.

AIM

The aim of the study was to determine whether constant iv infusion of kisspeptin-54 temporarily increases pulsatile LH secretion in women with HA.

METHODS

Five patients with HA each underwent six assessments of LH pulsatility. Single-blinded continuous iv infusion of vehicle or kisspeptin-54 (0.01, 0.03, 0.10, 0.30, or 1.00 nmol/kg/h) was administered. The LH pulses were detected using blinded deconvolution.

RESULTS

Kisspeptin increased LH pulsatility in all patients with HA, with peak responses observed at different doses in each patient. The mean peak number of pulses during infusion of kisspeptin-54 was 3-fold higher when compared with vehicle (number of LH pulses per 8 h: 1.6 ± 0.4, vehicle; 5.0 ± 0.5, kisspeptin-54, P < .01 vs vehicle). The mean peak LH pulse secretory mass during kisspeptin-54 was 6-fold higher when compared with vehicle (LH pulse secretory mass in international units per liter: 3.92 ± 2.31, vehicle; 23.44 ± 12.59, kisspeptin-54; P < .05 vs vehicle).

CONCLUSIONS

Kisspeptin-54 infusion temporarily increases LH pulsatility in women with HA. Furthermore, we have determined the dose range within which kisspeptin-54 treatment increases basal and pulsatile LH secretion in women with HA. This work provides a basis for studying the potential of kisspeptin-based therapies to treat women with HA.

[Study of the effect of colloidal solution of silver nanoparticles on parameters of cardio- and hemo-dynamics in rabbits]

Metal nanoparticles and silver nanoparticles in particular are extensively studied recently considering their prominent antimicrobial properties. Nevertheless, their toxicity aspects and probable side effects remain not well studied. In this article the results of study of the influence of silver nanoparticles onto a cardiovascular system in an in vivo experiment were provided, changes in parameters of cardio- and hemodynamics were defined, and the principles of such influence were identified. Dose-dependent effect of these nanoparticles was established when administered in dose of 4.3 mg/kg three times and 20 mg/kg once.

[Influence of iron nanoparticles on cardiac performance and hemodynamics in rabbits after intravenous administration in acute experiment]

Iron nanoparticles are possessed by high potential in the creation of effective and safe antianemic drugs due to the enhanced biological activity of metal nanoparticles. As a step of intravenous dosage form development the study of short-term effects of iron nanoparticles on the cardiovascular system is important. Dose-dependent changes of systemic hemodynamics' parameters were established in acute experiment on rabbits after several intravenous injections of zero-valent iron nanoparticles solution.

Estradiol regulates GH-releasing peptide's interactions with GH-releasing hormone and somatostatin in postmenopausal women

OBJECTIVE

Estrogen stimulates pulsatile secretion of GH, via mechanisms that are largely unknown. An untested hypothesis is that estradiol (E₂) drives GH secretion by amplifying interactions among GH-releasing hormone (GHRH), somatostatin (SS), and GH-releasing peptide (GHRP).

DESIGN

The design comprised double-blind randomized prospective administration of transdermal E₂ vs placebo to healthy postmenopausal women (n=24) followed by pulsatile GHRH or SS infusions for 13 h overnight with or without continuous GHRP2 stimulation.

METHODS

End points were mean concentrations, deconvolved secretion, and approximate entropy (ApEn; a regularity measure) of GH.

RESULTS

By generalized ANOVA models, it was observed that E₂ vs placebo supplementation: i) augmented mean (13-h) GH concentrations (P=0.023), GHRH-induced pulsatile GH secretion over the first 3 h (P=0.0085) and pulsatile GH secretion over the next 10 h (P=0.054); ii) increased GHRP-modulated (P=0.022) and SS-modulated (P<0.001) GH ApEn; and iii) did not amplify GHRH/GHRP synergy during pulsatile GH secretion. By linear regression, E₂ concentrations were found to be positively correlated with GH secretion during GHRP2 infusion (P=0.022), whereas BMI was found to be negatively correlated with GH secretion during GHRH (P=0.006) and combined GHRH/GHRP (P=0.015) stimulation. E₂ and BMI jointly determined triple (combined l-arginine, GHRH, and GHRP2) stimulation of GH secretion after saline (R²=0.44 and P=0.003) and pulsatile GHRH (R²=0.39 and P=0.013) infusions.

CONCLUSION

In summary, in postmenopausal women, E₂ supplementation augments the amount (mass) and alters the pattern (regularity) of GH secretion via interactions among GHRH, SS, GHRP, and BMI. These outcomes introduce a more complex model of E₂ supplementation in coordinating GH secretion in aging women.

A single injection of kisspeptin-54 temporarily increases luteinizing hormone pulsatility in healthy women

BACKGROUND

Kisspeptin is a novel hypothalamic peptide which stimulates endogenous gonadotrophin releasing hormone (GnRH) secretion. A single subcutaneous bolus injection of kisspeptin-54 increases circulating luteinizing hormone (LH) levels in women, but its acute effects on LH pulsatility are not known.

AIMS

To investigate the effects of a single subcutaneous (sc) injection of kisspeptin-54 administration on LH pulsatility in healthy female volunteers.

METHODS

Six healthy female adult volunteers underwent 10-minute blood sampling for serum LH measurement for 8 h during the follicular phase of menstrual cycle. Sc bolus injection of saline or kisspeptin-54 (0·15, 0·30 or 0·60 nmol/kg) was administered 4 h after commencing the study. A previously described, blinded deconvolution method was used to detect LH pulses.

RESULTS

Mean number of LH pulses was increased significantly following 0·30 and 0·60 nmol/kg kisspeptin-54 when compared with saline (mean increase in number of LH pulses per 4 h, following injection: -0·17 ± 0·54, saline; +2·33 ± 0·56, 0·30 nmol/kg kisspeptin-54, P < 0·05 vs saline; +2·33 ± 0·80, 0·60 nmol/kg kisspeptin-54, P < 0·05 vs saline). LH pulse secretory mass increased following injection of 0·60 nmol/kg in five of six subjects, but the mean change in all subjects was non-significant when compared with saline (mean increase in pulse secretory mass in IU/l following injection: +0·35 ± 0·40, saline; +2·61 ± 1·17, 0·60 nmol/kg kisspeptin-54, P = 0·10 vs saline).

CONCLUSIONS

A single injection of kisspeptin-54 temporarily stimulates the number of LH pulses in healthy women. Further studies are required to investigate the therapeutic potential of kisspeptin-54 injection to restore LH pulsatility in patients with reproductive disorders caused by impaired GnRH secretion.

The effect of flow acceleration on the cyclic variation of blood echogenicity under pulsatile flow

It has been shown that the echogenicity of blood varies during a flow cycle under pulsatile flow both in vitro and in vivo. In general, the echogenicity of flowing whole blood increases during the early systole phase and then reduces to a minimum at late diastole. While it has been postulated that this cyclic variation is associated with the dynamics of erythrocyte aggregation, the mechanisms underlying this increasing echogenicity with flow velocity remain uncertain. The effect of flow acceleration has also been proposed as an explanation for this phenomenon, but no specific experiments have been conducted to test this hypothesis. In addition, the influence of ultrasonic attenuation on the cyclic variation of echogenicity requires clarification. In the present study, a Couette flow system was designed to simulate blood flowing with different acceleration patterns, and the flow velocity, attenuation, and backscattering coefficient were measured synchronously from 20%- and 40%-hematocrit porcine whole blood and erythrocyte suspensions using 35-MHz ultrasound transducers. The results showed ultrasonic attenuation exerted only minor effects on the echogenicity of blood under pulsatile flow conditions. Cyclic variations of echogenicity were clearly observed for whole blood with a hematocrit of 40%, but no variations were apparent for erythrocyte suspensions. The echogenicity did not appear to be enhanced when instantaneous acceleration was applied to flowing blood in any case. These findings show that flow acceleration does not promote erythrocyte aggregation, even when a higher peak velocity is applied to the blood. Comparison of the results obtained with different accelerations revealed that the cyclic variation in echogenicity observed during pulsatile blood flow may be jointly attributable to the effect of shear rate and the distribution of erythrocyte on aggregation.

Kisspeptin restores pulsatile LH secretion in patients with neurokinin B signaling deficiencies: physiological, pathophysiological and therapeutic implications

Pulsatile gonadotropin-releasing hormone (GnRH) is crucial to normal reproductive function and abnormalities in pulse frequency give rise to reproductive dysfunction. Kisspeptin and neurokinin B (NKB), neuropeptides secreted by the same neuronal population in the ventral hypothalamus, have emerged recently as critical central regulators of GnRH and thus gonadotropin secretion. Patients with mutations resulting in loss of signaling by either of these neuroendocrine peptides fail to advance through puberty but the mechanisms mediating this remain unresolved. We report here that continuous kisspeptin infusion restores gonadotropin pulsatility in patients with loss-of-function mutations in NKB (TAC3) or its receptor (TAC3R), indicating that kisspeptin on its own is sufficient to stimulate pulsatile GnRH secretion. Moreover, our findings suggest that NKB action is proximal to kisspeptin in the reproductive neuroendocrine cascade regulating GnRH secretion, and may act as an autocrine modulator of kisspeptin secretion. The ability of continuous kisspeptin infusion to induce pulsatile gonadotropin secretion further indicates that GnRH neurons are able to set up pulsatile secretion in the absence of pulsatile exogenous kisspeptin.

Sex steroids, GHRH, somatostatin, IGF-I, and IGFBP-1 modulate ghrelin's dose-dependent drive of pulsatile GH secretion in healthy older men

CONTEXT

Ghrelin is a potent endogenous stimulator of GH secretion. However, clinical factors that regulate ghrelin dose-responsiveness are incompletely defined.

OBJECTIVE

The aim of the study was to test the multipathway hypothesis that testosterone (T) and estradiol, GHRH, and somatostatin (SS) jointly modulate ghrelin's action.

DESIGN/PARTICIPANTS/SETTING

Healthy older men (n = 21) participated in a double-blind, prospectively randomized, placebo (Pl)-controlled study in a Clinical Translational Research Center.

INTERVENTIONS

To create a range of sex-steroid milieus, men received leuprolide + Pl (n = 10) or leuprolide + T addback (n = 11). Sixteen to 21 d later, subjects received three separate randomly ordered overnight constant i.v. infusions of saline, GHRH, and SS. Interactions between the peptide clamp and ghrelin were tested by superimposed injections of four randomly ordered bolus i.v. doses of ghrelin (0.03, 0.135, 0.60, and 2.7 μg/kg). GH was measured every 10 min, and GH responses were assessed by nonlinear dose-response analysis. Linear associations were assessed by stepwise regression.

OUTCOME MEASURES/RESULTS

The descending numerical order of ghrelin efficacy (maximal GH secretory-burst mass; micrograms/liter) was 107 (GHRH + Pl), 104 (GHRH + T), 73 (saline + T), 73 (SS + T), 60 (saline + Pl), and 52 (SS + Pl) [means], wherein SS + T exceeded SS + Pl. GHRH and IGF binding protein-1 augmented, whereas IGF-I attenuated ghrelin potency. Age and IGF-I decreased ghrelin/GHRH synergy. Ghrelin sensitivity was independent of interventions.

CONCLUSIONS

These studies introduce composite regulatory effects of sex hormones, GHRH, SS, IGF binding protein-1, and IGF-I on ghrelin dose-responsiveness, suggesting multipathway modulation of GH-secretagogue action.

Effect of letrozole on uterine artery Doppler flow indices prior to first-trimester termination of pregnancy: a randomized controlled trial

OBJECTIVE

We previously demonstrated that a sequential regimen of letrozole and misoprostol resulted in a marked reduction in the serum estradiol concentration and in a higher efficacy of first-trimester termination of pregnancy than misoprostol alone. The aim of this study was to evaluate the effect of letrozole on uterine artery Doppler flow indices during early pregnancy.

METHODS

This was a randomized controlled trial. Thirty women requesting termination of pregnancy up to 63 days' gestation were randomized into two groups: a letrozole group receiving 10 mg of letrozole, daily, for 3 days, and a control group receiving a placebo for 3 days. Serum estradiol, progesterone and human chorionic gonadotropin (hCG) concentrations were measured before drug administration and then daily for 6 days. Ultrasound scanning for fetal viability and measurement of the pulsatility (PI) and resistance (RI) indices of the uterine arteries was performed before drug administration, and then on day 3 and day 7 after starting letrozole or placebo. All pregnancies were terminated by surgical evacuation on day 7 or day 8.

RESULTS

Uterine artery PI and RI decreased significantly in the letrozole group, but not in the control group. Serum estradiol concentrations were significantly lower in the letrozole group than in the control group from day 2 onwards. Serum progesterone and hCG concentrations were comparable for the two groups throughout the 7 days. There were significantly more women in the letrozole group with vaginal bleeding.

CONCLUSION

We have demonstrated that the use of letrozole in the first trimester of pregnancy suppresses serum estradiol levels but results in an increase in blood flow to the uterus. Further studies should be carried out to elucidate the mechanism of letrozole pretreatment in medical abortion.

How drugs influencing central blood pressure prevent atherosclerosis complications?

Although the differences between central and peripheral blood pressure (BP) have been known for decades, the consequences of decision-making based on peripheral rather than central BP have only recently been recognized. Central PP is closer to the heart, coronary and carotid arteries, which are the most important sites of cardiovascular events. The influence of cyclic stretch (owing to cyclic changes in BP) on the arterial wall has been documented at every stage of atherosclerosis development. Apart from mediating atherosclerosis progression and plaque instability, the pulsatile component of BP is the main mechanism leading to plaque rupture and, consequently, to acute coronary syndromes and other vascular complications. Latest evidence suggests that the effect of some antihypertensive drugs on central BP (especially on central pulse pressure) is greater when compared with the effect on peripheral pressure, especially if systolic or pulse pressure are measured. Recently, a new group of drugs (advanced glycation end products cross-link breakers) were developed which have ability to decrease pulsatile component of blood pressure. The principal goal of the present review is to update the latest advances in this field.

Chunghyul-Dan (Qingxie-Dan) Improves Arterial Stiffness in Patients with Increased baPWV

Arterial stiffness is an important, independent determinant of cardiovascular risk. Pulse wave velocity (PWV) has been used as a valuable index of arterial stiffness and as a surrogate marker for atherosclerosis. Chunghyul-dan (CHD) has anti-hyperlipidemic activity, anti-inflammatory activity and anti-atherogenic effects. To determine its clinical effect on increased arterial stiffness, we examined whether CHD improves arterial stiffness in patients with increased brachial-ankle PWV (baPWV). Thirty-five subjects with increased baPWV (> 1400 cm/sec) were recruited and randomized to a treatment group (20 subjects) or a control group (15 subjects). The treatment group was administered CHD at a dose of 600 mg three times a day for 8 weeks, and the control group received no medication (observation only). baPWV was assessed using a pulse pressure analyzer at baseline and after 8 weeks. Blood pressure and serum lipid profile were monitored in the treatment group. Our results indicate that baPWV was lowered significantly in the treatment group after 8 weeks of medication ( p < 0.05), but not in the control group. Moreover, there were no significant changes in blood pressure and serum lipids profile except triglyceride level suggesting that the effect is largely independent of CHD's lipid-lowering effect or a blood pressure change. In conclusion, CHD appears to improve arterial stiffness in patients with increased PWV.

The effects of low-dose fluvastatin and valsartan combination on arterial function: a randomized clinical trial

BACKGROUND

Ageing progressively diminishes arterial functions, even in the absence of traditional risk factors. Our aim was to explore whether age-related arterial changes in middle-aged males could be reversed using short-term, low-dose fluvastatin/valsartan combination intervention.

METHODS

Forty apparently healthy, middle-aged males (43.3 ± 5.8 years) were recruited in a double-blind, randomised intervention. Individuals received either 10mg fluvastatin/20mg valsartan daily or placebo over 30 days. The brachial artery flow mediated dilation (FMD), pulse wave velocity (PWV) and common carotid artery β-stiffness were assessed at baseline and after 30 days, and again 5-10 months after therapy discontinuation.

RESULTS

Arterial function variables significantly improved after 30 days of intervention; FMD improved by 167.7% (P<0.001), PWV by 10.9% (P<0.05) and β-stiffness by 18.8% (P<0.01), whereas no changes were obtained in the placebo group. The favourable outcomes in the intervention group were accompanied by a significant decrease of high sensitivity-C reactive protein levels (1.8-fold; P<0.05). In contrast, lipids and blood pressure remained unchanged. Surprisingly, the beneficial arterial effects were still present to a substantial degree 7 months after completing intervention (remaining % of initial improvement: FMD 82.1%, PWV 69.5% and β-stiffness 68.5%), but declined substantially after 10 months.

CONCLUSION

Our results indicate that age-related arterial changes, at least in middle-aged males, can be reversed. Short-term treatment with a low-dose fluvastatin/valsartan combination resulted in a large and long lasting improvement of arterial function.

Angiotensin converting enzyme inhibitors effect on arterial stiffness and wave reflections: a meta-analysis and meta-regression of randomised controlled trials

OBJECTIVE

Several studies have assessed the effect of angiotensin converting enzyme inhibitors (ACEIs) on arterial stiffness and wave reflections as measured by pulse wave velocity (PWV) and augmentation index (AIx), respectively. We conducted a meta-analysis to investigate this effect in comparison to placebo and to other antihypertensive agents. Additionally, we investigated this effect when ACEIs are combined with other antihypertensive agents and in comparison to a combination of antihypertensive agents.

METHODS

MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were searched from inception to May 2011 on randomised controlled trials (RCTs) which assessed the effect of ACEIs on arterial stiffness vs. placebo or no treatment and ACEIs vs. angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs), β-blockers and diuretics. RCTs which assessed the effect of ACEIs combined with other antihypertensives or compared ACEIs with a combination of antihypertensives were also sought. Data from included RCTs were pooled with use of fixed and random effects meta-analysis of the weighted mean change differences between the comparator groups. Heterogeneity across studies was assessed with the I(2) statistic.

RESULTS

In 5 trials including 469 patients, treatment with ACEIs (n=227) vs. placebo (n=216) significantly reduced PWV (pooled mean change difference -1.69, 95% C.I. -2.05, -1.33, p<0.00001 with insignificant heterogeneity). In 9 trials which included 378 patients, treatment with ACEIs (n=178) insignificantly reduced PWV when compared with other antihypertensives (ARBs, CCBs, β-blockers, diuretics and a combination of ACEI and ARB) (n=220) (pooled mean change difference -0.19, 95% C.I. -0.59, 0.21, p=0.36, I(2)=0%). ACEI effect on AIx in comparison to placebo was assessed in 7 trials. Treatment with ACEIs significantly reduced AIx (pooled mean change difference -3.79, 95% C.I. -5.96, -1.63, p=0.0006) with significant heterogeneity. In 7 trials, treatment with ACEIs significantly reduced AIx when compared with other antihypertensives (pooled mean change difference -1.84, 95% C.I. -3, -0.68, p=0.002, I(2)=32%, p for heterogeneity=0.11). However, this effect was only significant when compared with β-blockers (pooled mean change difference -1.6, 95% C.I. -2.84, -0.36, p=0.01). Mean BP differences between baseline and end of treatment did not predict the treatment (ACEI) induced changes in PWV.

CONCLUSIONS

ACEIs reduce PWV and AIx which are markers of arterial stiffness and wave reflections in patients with different pathological conditions. However, due to the lack of high quality and properly powered RCTs, it is not clear whether ACEIs are superior to other antihypertensive agents in their effect on arterial stiffness. The ability of ACEIs to reduce arterial stiffness (PWV) seems to be independent of its ability to reduce BP.

Effects of lowering dialysate calcium concentrations on arterial stiffness in patients undergoing hemodialysis

BACKGROUND/AIMS

We assessed changes in hemodynamic and arterial stiffness parameters following reductions of dialysate calcium concentrations in patients undergoing hemodialysis.

METHODS

In this prospective study, 20 patients on maintenance hemodialysis (10 females, 10 males) with dialysate calcium concentrations of 1.75 mmol/L were enrolled. At the start of the study, the dialysate calcium level was lowered to 1.50 mmol/L. Serial changes in biochemical, hemodynamic, and arterial stiffness parameters, including pulse wave velocity (PWV) and augmentation index (AIx), were assessed every 2 months for 6 months. We also examined changes in the calcification-inhibitory protein, serum fetuin-A.

RESULTS

During the 6-month study period, serum total calcium and ionized calcium decreased consistently (9.5 ± 1.0 to 9.0 ± 0.7, p = 0.002 vs. 1.3 ± 0.1 to 1.1 ± 0.1, p = 0.035). Although no apparent changes in blood pressure were observed, heart-femoral PWW (hf-PWV) and AIx showed significant improvement (p = 0.012, 0.043, respectively). Repeated-measures ANOVA indicated a significant effect of lowering dialysate calcium on hf-PWV (F = 4.58, p = 0.004) and AIx (F = 2.55, p = 0.049). Accompanying the change in serum calcium, serum fetuin-A levels significantly increased (95.8 ± 45.8 pmol/mL at baseline to 124.9 ± 82.2 pmol/mL at 6 months, p = 0.043).

CONCLUSIONS

Lowering dialysate calcium concentration significantly improved arterial stiffness parameters, which may have been associated with upregulation of serum fetuin-A.

Cetrorelix suppresses the preovulatory LH surge and ovulation induced by ovulation-inducing factor (OIF) present in llama seminal plasma

BACKGROUND

The purpose of the study was to determine if the effect of llama OIF on LH secretion is mediated by stimulation of the hypothalamus or pituitary gland.

METHODS

Using a 2-by-2 factorial design to examine the effects of OIF vs GnRH with or without a GnRH antagonist, llamas with a growing ovarian follicle greater than or equal to 8 mm were assigned randomly to four groups (n = 7 per group) and a) pre-treated with 1.5 mg of GnRH antagonist (cetrorelix acetate) followed by 1 mg of purified llama OIF, b) pre-treated with 1.5 mg of cetrorelix followed by 50 micrograms of GnRH, c) pre-treated with a placebo (2 ml of saline) followed by 1 mg of purified llama OIF or d) pre-treated with a placebo (2 ml of saline) followed by 50 micrograms of GnRH. Pre-treatment with cetrorelix or saline was given as a single slow intravenous dose 2 hours before intramuscular administration of either GnRH or OIF. Blood samples for LH measurement were taken every 15 minutes from 1.5 hours before to 8 hours after treatment. The ovaries were examined by ultrasonography to detect ovulation and CL formation. Blood samples for progesterone measurement were taken every-other-day from Day 0 (day of treatment) to Day 16.

RESULTS

Ovulation rate was not different (P = 0.89) between placebo+GnRH (86%) and placebo+OIF groups (100%); however, no ovulations were detected in llamas pre-treated with cetrorelix. Plasma LH concentrations surged (P < 0.01) after treatment in both placebo+OIF and placebo+GnRH groups, but not in the cetrorelix groups. Maximum plasma LH concentrations and CL diameter profiles did not differ between the placebo-treated groups, but plasma progesterone concentrations were higher (P < 0.05), on days 6, 8 and 12 after treatment, in the OIF- vs GnRH-treated group.

CONCLUSION

Cetrorelix (GnRH antagonist) inhibited the preovulatory LH surge induced by OIF in llamas suggesting that LH secretion is modulated by a direct or indirect effect of OIF on GnRH neurons in the hypothalamus.

[Effects of a neuroleptic analgesia with acepromazine on the blood perfusion of the canine kidney. Examination using the sonographic recordable blood circulation parameters of resistance index and pulsatility index]

OBJECTIVE

Kidney failure after anaesthesia constitutes a serious clinical complication. A number of patients suffer from compensated kidney insufficiency, which may be transformed into an acute kidney insufficiency through additional stress, such as an operation and anaesthesia. The aim of the present study was to investigate the effects of a neurolept analgesia with acepromazine on sonographically accessible blood perfusion parameters.

MATERIAL AND METHODS

Following anaesthesia with acepromazine/l-methadone (0.1 mg/kg BW acepromazine, 0.5 mg/kg BW l-methadone) a sonographic examination of the left kidney was performed in 19 clinically healthy foxhound and beagle dogs. Every 5 minutes resistance index and pulsatility index as well as invasive blood pressure were measured and digitally recorded.

RESULTS

Within 5 minutes after induction of anaesthesia a transient increase of the mean arterial blood pressure occurred. After 10 minutes the blood pressure decreased to the initial value and remained essentially constant to the end of the investigation. Resistance index and pulsatility index showed a similar behaviour: After a small initial decrease during the first 5 minutes both parameters displayed a significant increase. This rise was very pronounced up to approximately 15 minutes and then flattened significantly until the end of the test period after 30 minutes. The values corresponded to those found in vessel stenosis.

CONCLUSION AND CLINICAL RELEVANCE

Due to the described changes this type of anaesthesia should not be used in dogs with nephropathy, even though the results of this experimental study might not be necessarily transferable to the clinical patient.

Endothelin-1 effects on spontaneous oscillations in choroidal arterioles

PURPOSE

This study characterizes the effects of endothelin-1 (ET-1) on the perfusion pressure of the choroidal vasculature using in situ perfused isolated rabbit eyes.

METHODS

Rabbit external ophthalmic arteries (n = 12) in a head-mounted preparation were cannulated and perfused with warmed tyrode. The three-way polypropylene catheter was further connected to a pressure transducer and the effect of intraluminal pressure as a measure of total vascular resistance was assessed. Response curves to intra-arterial injections of ET-1 (group A; n = 6) and to an intravitreal injection followed by an intra-arterial injection of ET-1 (group B; n = 6) were obtained. Data were studied using paired t-test and fast Fourier transform.

RESULTS

Before any drugs were administered, spontaneous oscillations were observed in the 12 rabbit models. In group A, ET-1 induced a short and weak vasodilating effect followed by a strong and long-lasting vasoconstrictor tone. Vasomotion became more evident, showing a higher frequency and shorter amplitude of oscillations. In group, B the intravitreal injection produced no significant changes in registered pressure or vasomotion characteristics. The intra-arterial injection produced effects similar to those observed in group A.

CONCLUSION

Our study has three main findings: (i) the choroidal vasculature demonstrated spontaneous oscillations in perfusion pressure in basal conditions in all rabbit eye models; (ii) ET-1 applied intra-arterially induced a short drop in perfusion pressure followed by a long withstanding contraction; and (iii) intra-arterial ET-1 modulated the frequency and amplitude of the spontaneous oscillations, causing a faster rate of pulsatility.

Membrane-initiated actions of estradiol (E2) in the regulation of LH secretion in ovariectomized (OVX) ewes

BACKGROUND

We demonstrated that E2 conjugated to BSA (E2BSA) induces a rapid membrane-initiated inhibition of LH secretion followed hours later by a slight increase in LH secretion. Whether these actions of E2BSA are restricted to the pituitary gland and whether the membrane-initiated pathway of E2BSA contributes to the up-regulation of the number of GnRH receptors during the positive feedback effect of E2 were evaluated here. We have shown that the suppression of LH secretion induced by E2 and E2BSA is the result of a decreased responsiveness of the pituitary gland to GnRH. In this study we further tested the ability of E2BSA to decrease the responsiveness of the pituitary gland to GnRH under the paradigm of the preovulatory surge of LH induced by E2.

METHODS

For the first experiment GnRH and LH secretions were determined in samples of pituitary portal and jugular blood, respectively, in ewes treated with 12 mg E2BSA. In the second experiment, the number of GnRH receptors was quantified in ewes 12 h after administration of 25 micrograms E2 (the expected time for the increase in the number of GnRH receptors and the positive feedback effect of E2 in LH secretion) or 12 mg E2BSA. In the third experiment, the preovulatory-like surge of LH was characterized in ewes injected with 25 micrograms E2 alone or followed 8 h later (before the beginning of the LH surge) with 60 mg E2BSA.

RESULTS

a) the decrease in LH secretion induced by E2BSA was not accompanied by changes in the pulsatile pattern of GnRH, b) E2BSA increased the number of GnRH receptors, and c) the presence of E2BSA in E2-treated ewes delayed the onset, reduced the length, and decreased the amount of LH released during the preovulatory surge of LH.

CONCLUSIONS

a) the rapid suppression of LH secretion induced by E2BSA is mediated only via a direct action on the pituitary gland, b) E2 acting via a membrane-initiated pathway contributes to increase the number of GnRH receptors and, c) administration of E2BSA near the beginning of the pre-ovulatory surge of LH delays and reduces the magnitude of the surge.

Effect of a gonadotropin releasing hormone analog on cerebral hemodynamics in premenopausal women

BACKGROUND

Impaired reactivity of cerebral blood vessels is associated with increased risk of stroke. Female sex hormones have vasoactive effects in a number of vascular beds but their effects upon the cerebral circulation are not well understood. Ultrasound techniques allow us to examine the ability of intracranial vessels to dilate in response to a pharmacological stimulus (the carbonic anhydrase inhibitor acetazolamide). We studied intracranial hemodynamics in a group of premenopausal women before and after induction of a temporary hypoestrogenic state.

METHODS

We examined middle cerebral artery mean flow velocity, common and internal carotid artery pulsatility index and cerebrovascular reactivity to acetazolamide (CVR) in a group of women undergoing treatment for menstrual disorders. Volunteers underwent ultrasound examination during the follicular phase of the menstrual cycle and after completing treatment with gonadotropin releasing hormone (GnRH, goserelin 3.6 mg) administered subcutaneously every 28 days for 12 weeks. The study was conducted in a prospective, single-blind fashion and analyzed using parametric comparisons of means to examine change in intracranial hemodynamic parameters between pre- and postmenopausal states.

RESULTS

Twelve premenopausal women aged 37.2+/-7 years and without overt vascular disease completed the protocol. GnRH reduced serum estrogen concentration (215.6+/-122 pg/ml vs. 82.4+/-12 pg/ml, p=0.0047) but this was not associated with a change in CVR (145+/-19% and 146+/-14% for follicular and post-GnRH studies, respectively (p=0.6). No significant changes in blood pressure, internal carotid or middle cerebral artery pulsatility or mean flow velocity were observed between time points.

CONCLUSION

Neither resting cerebral hemodynamics nor reactivity of cerebral resistance vessels to a potent vasodilatory stimulus changed when the circulating concentration of estradiol was artificially decreased using a GnRH agonist. Induction of a hypoestrogenic state does not appear to influence cerebral vasodilatory capacity in the short term.

Pre- versus postmenopausal age, estradiol, and peptide-secretagogue type determine pulsatile growth hormone secretion in healthy women: studies using submaximal agonist drive and an estrogen clamp

CONTEXT

GH-releasing peptide (GHRP), GHRH, and somatostatin are physiological regulators of pulsatile GH secretion.

HYPOTHESIS

Age, independently of abdominal visceral fat (AVF) and basal (nonpulsatile) GH secretion, damps pulsatile GH secretion driven by physiological (rather than pharmacological) amounts of GHRP and GHRH in an experimentally controlled estradiol (E(2)) milieu.

DESIGN AND SETTING

A prospectively randomized, double-blind parallel-cohort study was conducted at an academic medical center.

PARTICIPANTS

Community-dwelling healthy premenopausal (PRE, age 24 +/- 0.8 yr, n = 20) and postmenopausal (POST, age 63 +/- 1.8 yr, n = 22) women participated in the study.

INTERVENTIONS

Gonadal-axis down-regulation with leuprolide was followed by randomized addback of placebo or transdermal E(2) and separate-day iv bolus injections of a half-maximally stimulatory dose of GHRP-2 or GHRH (each 0.33 mug/kg).

ANALYSIS

Three-way analysis of covariance included main factors age, E(2) status, and secretagogue type and covariates AVF and basal GH secretion.

RESULTS

Submaximally stimulated pulsatile GH secretion was positively determined by PRE vs. POST age (P < 0.001), E(2) repletion vs. depletion (P = 0.001) and GHRP-2 vs. GHRH stimulation (P < 0.001), after adjustment for AVF and basal secretion. E(2) vs. placebo elevated fasting mean GH concentrations in both PRE and POST women (P = 0.006) but increased basal (nonpulsatile) GH secretion in PRE only (P = 0.002). PRE vs. POST age prolonged GHRH-driven GH secretory bursts by 36% (P = 0.006).

CONCLUSION

PRE vs. POST age, E(2) availability, and physiological peptide drive are triple determinants of pulsatile GH secretion independently of abdominal visceral fat and nonpulsatile GH secretion in healthy women.

Decreased expression of A-kinase anchoring protein 150 in GT1 neurons decreases neuron excitability and frequency of intrinsic gonadotropin-releasing hormone pulses

The frequency of intrinsic pulsatile GnRH secretion from endogenous GnRH neurons and GT1 GnRH cell lines is stimulated by increased intracellular cAMP levels. The downstream molecules comprising the cAMP signaling pathway are organized in microdomains by a family of scaffolding proteins, A-kinase anchoring proteins (AKAPs). These molecules tether protein kinase A, cAMP-specific phosphodiesterases, phosphatases to known substrates. In neurons AKAP150 organizes many of the signaling molecules known to regulate the excitability and intrinsic pulsatile activity of GnRH neurons. AKAP150 was expressed in both the GT1-1 and GT1-7 cells. We determined the role of AKAP150 in coordinating GT1-1 cell excitability and intrinsic GnRH pulsatile secretion by lowering AKAP150 levels with a small interfering RNA (siRNA) adenovirus construct to AKAP150 (Ad-AKAP150-siRNA). Infection with Ad-AKAP150-siRNA specifically decreased AKAP150 mRNA levels by 74% and protein levels by 53% relative to uninfected cells or cells infected with a luciferase control adenovirus siRNA vector. In GT1 cells, spontaneous Ca(2+) oscillations, an index of neuron excitability, are stimulated by increased levels of intracellular cAMP and lowered by decreased levels. The frequency of spontaneous Ca(2+) oscillations in Ad-AKAP150-siRNA-treated GT1-1 cells decreased by 47.2% relative to controls. A dramatic decrease in the number of spontaneous GnRH pulses was also observed after infection with Ad-AKAP150-siRNA. The interpulse interval increased to 143 +/- 20.25 min in Ad-AKAP150-siRNA infected cells from 32.2 +/- 7.3 min in luciferase control adenovirus siRNA vector-infected cells. These data demonstrate an important role of AKAP150 in coordinating signaling events regulating the frequency of intrinsic pulsatile GnRH secretion.

Estradiol and progesterone-induced slowing of gonadotropin-releasing hormone pulse frequency is not reversed by subsequent administration of mifepristone

Subsequent to suppression of LH (GnRH) pulse frequency by progesterone (P) and estradiol (E(2)), LH pulse frequency remains slow for 7 days after P withdrawal if mid-luteal E(2) concentrations are maintained. This may reflect an ability of E(2) to potentiate the suppressive effects of low P levels. We explored this notion in a similar experimental paradigm by administering a P-receptor antagonist (mifepristone) after P withdrawal while continuing E(2). Studies were performed in seven ovulatory, non-obese women. Transdermal E(2) (0.2 mg/day) and oral micronized P (100 mg every 8 h) were started within 24 h of the LH surge and continued for 10 days. Subjects then underwent a 13-h blood sampling protocol for determination of LH pulse characteristics and various hormone concentrations. Oral P was then discontinued, and oral mifepristone (50, 100, or 200 mg daily) and transdermal E(2) (0.2 mg/day) were administered for 7 days, after which the above sampling protocol was repeated. Results with all mifepristone doses were similar and therefore pooled. Mean LH, LH amplitude, and mean FSH markedly decreased after 7 days of mifepristone, but LH pulse frequency did not change (3.3 +/- 1.5 vs. 2.4 +/- 1.5 pulses/13 h). Prolactin and androstenedione increased between the first and second admissions, with no changes in E(2), cortisol, testosterone, or DHEAS. In conclusion, blockade of P action by mifepristone does not reverse a suppressed LH pulse frequency within 7 days when E(2) concentrations are maintained, suggesting that P withdrawal alone may not explain the luteal-follicular increase of GnRH pulse frequency.

Ocular haemodynamic changes after single treatment with photodynamic therapy assessed with non-invasive techniques

PURPOSE

To investigate in patients with neovascular age-related macular degeneration (ARMD) the changes in ocular perfusion caused by single treatment with photodynamic therapy (PDT) by different non-invasive methods; to evaluate correlations between relative changes of ocular haemodynamic parameters after PDT among each other and compared to morphological parameters; and to assess this in relation to early changes of visual acuity.

METHODS

STUDY POPULATION

17 consecutive patients with subfoveal choroidal neovascularization (CNV) caused by ARMD scheduled for PDT without previous PDT treatment (four patients with predominantly classic CNV and 13 patients with occult CNV).

OBSERVATION PROCEDURES

best-corrected visual acuity (before PDT, 6 and 8 weeks after PDT), fundus photography, fluorescein angiography, haemodynamic measurements with laser Doppler flowmetry (LDF), laser interferometry and ocular blood flow (OBF) tonometry (baseline and 1, 2, 6 and 8 weeks after treatment).

MAIN OUTCOME MEASURES

choroidal blood flow (CHBF), fundus pulsation amplitude (FPA), pulsatile ocular blood flow (POBF), visual acuity. Changes smaller than 20% were considered clinically irrelevant.

RESULTS

Ocular haemodynamic parameters did not change significantly in the follow-up period. Changes of haemodynamic parameters showed no correlation to treatment spot, morphological changes or visual acuity. Changes of visual acuity were comparable to results of earlier studies.

CONCLUSION

Single treatment with PDT did not modify ocular blood flow parameters above 20% as assessed with different non-invasive methods.

Regulation of basal, pulsatile, and entropic (patterned) modes of GH secretion in a putatively low-somatostatin milieu in women

Somatostatin (SS) released by hypothalamic neurons inhibits GH exocytosis noncompetitively. Therefore, we postulated that attenuation of GH feedback-induced SS outflow would help to unmask covariates of endogenous secretagogue drive. To this end, 42 healthy pre- and postmenopausal women were randomly assigned to receive leuprolide plus estradiol (E(2)) or leuprolide plus placebo. A putatively low-SS milieu was imposed by L-arginine infusion. Deconvolution and regularity analyses were applied to 6-h GH concentration-time profiles. By two-way ANOVA, age negatively (P < 0.001) and E(2) positively (P = 0.001) determined pulsatile GH secretion in the presumptively SS-deficient milieu (P < 0.001). Comparable effects were exerted on the mass of GH secreted per burst per unit distribution volume (age P = 0.001, E(2) P < 0.001, overall P < 0.001). E(2) alone predicted basal (nonpulsatile) GH secretion (P = 0.004). Stepwise forward-selection multivariate regression demonstrated that age (P = 0.0017) and E(2) (P = 0.0002) together explained 46% of intersubject variability in pulsatile GH secretion (P < 0.001) and fully replaced the negative univariate effect of abdominal visceral fat (r(2) = 0.32, P < 0.001). Moreover, age and E(2) (but not AVF) interacted to supervise GH regularity (P = 0.007). We conclude that age and E(2) availability individually and together constitute primary predictors of basal, pulsatile, and patterned GH secretion in an inferentially feedback-silenced context in healthy women. Therefore, both factors must be considered in framing hypotheses of endogenous GH drive.

Relative effects of estrogen, age, and visceral fat on pulsatile growth hormone secretion in healthy women

Growth hormone (GH) secretion is subject to complex regulation. How pre- and postmenopausal age (PRE, POST), estradiol (E(2)) availability, and abdominal visceral fat (AVF) jointly affect peptidyl-secretagogue drive of GH secretion is not known. To this end, healthy PRE (n = 20) and POST (n = 22) women underwent a low- vs. high-E(2) clamp before receiving a continuous intravenous infusion of GH-releasing hormone (GHRH) or GH-releasing peptide (GHRP-2). According to analysis of covariance, PRE and POST women achieved age-independent hypo- and euestrogenemia under respective low- and high-E(2) clamps. All four of age (P < 0.001), E(2) status (P = 0.006), secretagogue type (P < 0.001), and an age x peptide interaction (P = 0.014) controlled pulsatile GH secretion. Independently of E(2) status, POST women had lower GH responses to both GHRH (P = 0.028) and GHRP-2 (P < 0.001) than PRE women. Independently of age, GHRP-2 was more stimulatory than GHRH during low E(2) (P = 0.011) and high E(2) (P < 0.001). Stepwise forward-selection multivariate analysis revealed that computerized tomographic estimates of AVF explained 22% of the variability in GHRH action (P = 0.002), whereas age and E(2) together explained 60% of the variability in GHRP-2 drive (P < 0.001). These data establish that age, estrogen status, and AVF are triple covariates of continuous peptide-secretagogue drive of pulsatile GH secretion in women. Each factor must be controlled for to allow valid comparisons of GH-axis activity.

The effects of continuous combined oral estradiol and norethisterone on pulsatility index in internal carotid and uterine arteries in early postmenopausal Taiwanese women---a preliminary study

OBJECTIVE

This study analyzed whether continuous combined oral estradiol and norethisterone had any effect on the pulsatility index (PI) of the internal carotid and uterine arteries in Taiwanese early postmenopausal women.

MATERIALS AND METHODS

A group of 40 healthy postmenopausal women with no history of hormone therapy (HT) participated in this study and were randomly subdivided into two groups: HT treatment group (n = 20) and placebo group (n = 20). PI was evaluated with color Doppler ultrasound at the beginning of the study and after 4 months of HT (2 mg 17beta-estradiol + 1 mg norethisterone acetate) or placebo.

RESULTS

There was no significant change in the PI of the internal carotid and the uterine arteries after 4 months of HT.

CONCLUSION

This HT regimen showed no significant negative impact on vascular resistance in Taiwanese early postmenopausal women. Results are compatible with the updated recommendations on HT stating that there is little cardiovascular risk when HT is initiated within a few years of the menopause.

Elevated Glucose Attenuates Agonist- and Flow-Stimulated Endothelial Nitric Oxide Synthase Activity in Microvascular Retinal Endothelial Cells

Impaired vasoactive release of opposing vasodilator and vasoconstrictor mediators due to endothelial dysfunction is integral to the pathogenesis of diabetic retinopathy. The aim of this study was to determine the effect of hyperglycemia on the expression of endothelial nitric oxide synthase (eNOS) and the release of nitric oxide (NO) in bovine microvascular retinal endothelial cells (BRECs) under both static (basal and acetylcholine stimulated) and flow (laminar shear stress [10 dynes/cm2 and pulsatile flow 0.3 to 23 dynes/cm2) conditions using a laminar shear apparatus and an in vitro perfused transcapillary culture system. The activity and expression of eNOS, measured by nitrate levels and immunoblot, respectively, were determined following exposure of BRECs to varying concentrations of glucose and mannitol (0 to 25 mM). Under static conditions the expression of eNOS decreased significantly following exposure to increasing concentrations of glucose when compared to osmotic mannitol controls and was accompanied by a significant dose-dependent decrease in nitrate levels in conditioned medium. The acetylcholine stimulated increase in NO release (2.0 +/- 0.3-fold) was significantly reduced by 55% +/- 5% and 65% +/- 4.5% following exposure to 16 and 25 mM glucose, respectively, when compared to osmotic controls. In parallel studies, glucose significantly inhibited both laminar shear stress and pulsatile flow-induced activity when compared to mannitol. We conclude that hyperglycemia impairs agonist- and flow-dependent release of NO in retinal microvascular endothelial cells and may thus contribute to the vascular endothelial dysfunction and impaired autoregulation of diabetic retinopathy.

Misoprostol administration in first-trimester pregnancies with embryonic demise reduces uterine arterial blood flow

OBJECTIVES

This study was designed to evaluate the effect of misoprostol on the blood flow in uterine arteries of pregnant women with first-trimester embryonic demise.

METHODS

Transvaginal ultrasonographic Doppler examinations (resistance index, pulsatility index, systolic/diastolic ratio) of the uterine arteries in 61 pregnant women were performed before misoprostol administration and 90 min later. Following baseline Doppler measurements, each woman received 200 microg misoprostol intravaginally and 200 microg misoprostol orally.

RESULTS AND CONCLUSION

All Doppler indices increased significantly after misoprostol administration (p < 0.0001), suggesting an increase in flow resistance.

The Influence of Calcineurin Inhibitors on Pulse Wave Velocity in Renal Transplant Recipients

BACKGROUND

Pulse wave velocity (PWV) is a marker of the arterial wall stiffness and independent cardiovascular risk factor in hemodialysis patients. Cyclosporine A (CyA) and tacrolimus (TAC) are known to differ in the influence on cardiovascular risk factors in renal transplant recipients. Recent studies suggest that CyA may decrease arterial compliance. The aim of the study was to assess the influence of CyA and TAC on the PWV and arterial wall stiffness in renal transplant recipients.

METHODS

The study population consisted of two groups of cadaveric renal transplant recipients, 76 patients each, matched for age, sex, blood pressure, body mass index, and length of the post-transplant follow-up. PWV between carotid and femoral artery was measured using a Complior device. Fasting blood was sampled for serum creatinine, lipid profile, uric acid, glucose, and C-reactive protein.

RESULTS

Aortic pulse wave velocity -- a marker of increased arterial stiffness -- was significantly higher in CyA group compared with TAC group (9.33 +/- 2.10 vs. 8.54 +/- 1.35, respectively; p < 0.01). Uric acid, total cholesterol, triglycerides, and LDL-cholesterol concentrations were significantly higher in CyA group. Significant correlations were found between PWV and age, systolic and diastolic blood pressure, and fasting glucose in the CyA group, but only between PWV and age in TAC group.

CONCLUSION

CyA-based immunosuppressive therapy is associated with an unfavorable profile of cardiovascular risk factors and increased arterial stiffness in renal transplant recipients.

Valsartan Reduces Serum Cystatin C and the Renal Vascular Resistance in Patients with Essential Hypertension

A high level of albuminuria and increased renal vascular resistance are associated with hypertensive renal damage. In this study, the authors investigated the effect of the angiotensin II receptor blocker, valsartan, on renal function and intrarenal hemodynamics in non-diabetic patients with essential hypertension. A prospective three-month study of the effects of valsartan, 40-80 mg/day, was performed in 30 hypertensive patients. As an assessment of renal function, serum creatinine, urine albumin/creatinine (Alb/Cr) ratio, and serum cystatin C levels were evaluated. Doppler ultrasonography of the kidney was performed for the evaluation of renal hemodynamics. Peak-systolic, end-diastolic, and mean velocities of interlobar arteries were evaluated, and the pulsatility index (PI) and resistive index (RI) were calculated. It was determined that patients with microalbuminuria had higher levels of serum cystatin C, PI, and RI compared to patients without microalbuminuria. Valsartan treatment significantly reduced systolic and diastolic blood pressure and decreased the Alb/Cr ratio. Serum creatinine was not changed, whereas serum cystatin C levels were significantly reduced. Valsartan treatment significantly decreased the PI in all patients and both PI and RI in patients with microalbuminuria. These results suggest that the angiotensin II receptor blocker, valsartan, is able to improve renal function by reducing renal vascular resistance in hypertensive patients, especially in patients with microalbuminuria, and may prevent future renal failure in patients with essential hypertension.

Modulation of gonadotropin-releasing hormone pulse generator sensitivity to progesterone inhibition in hyperandrogenic adolescent girls--implications for regulation of pubertal maturation

CONTEXT

Adult women with polycystic ovary syndrome (PCOS) have decreased GnRH pulse generator sensitivity to progesterone (P)-mediated slowing. This defect is androgen mediated because it is reversed with androgen receptor blockade. Adolescent hyperandrogenism often precedes PCOS.

OBJECTIVE

The aim of the study was to evaluate GnRH pulse generator sensitivity to P-mediated slowing in normal and hyperandrogenic girls.

DESIGN

We conducted a controlled interventional study.

SETTING

The study was conducted in a general clinical research center.

PARTICIPANTS

A total of 26 normal control (NC) and 26 hyperandrogenic (HA) girls were studied.

INTERVENTION

Frequent blood sampling was performed for 11 h to assess LH pulse frequency before and after 7 d of oral estradiol and P.

MAIN OUTCOME MEASURE

We measured the slope of the percentage reduction in LH pulse frequency as a function of d 7 P (slope).

RESULTS

Overall, Tanner 3-5 HA subjects were less sensitive to P-mediated slowing than Tanner 3-5 NC (slope, 4.7 +/- 3.4 vs. 10.3 +/- 7.7; P = 0.006). However, there was variability in the responses of HA subjects; 15 had P sensitivities within the range seen in NC, whereas nine were relatively P insensitive. The two groups had similar testosterone levels. Fasting insulin levels were higher in P-insensitive HA girls (39.6 +/- 30.6 vs. 22.2 +/- 13.9 microIU/ml; P = 0.02), and there was an inverse relationship between fasting insulin and P sensitivity in HA girls (P = 0.02). Tanner 1-2 NC had lower testosterone levels and were more P sensitive than Tanner 3-5 NC (slope, 19.3 +/- 5.8; P = 0.04).

CONCLUSIONS

Hyperandrogenism is variably associated with reduced GnRH pulse generator sensitivity to P-mediated slowing during adolescence. In addition to androgen levels, insulin resistance may modulate P sensitivity.

Organizational actions of postnatal estradiol in female sheep treated prenatally with testosterone: programming of prepubertal neuroendocrine function and the onset of puberty

Prenatal testosterone (T) exposure defeminizes reproductive neuroendocrine function in female sheep, although the LH surge dysfunctions are initially less severe in gonadally intact females than in females subject to neonatal ovariectomy and estradiol (E) replacement. Because prepubertal ovarian production of E differs quantitatively and qualitatively from chronic E replacement, we tested the hypothesis that postnatal E exacerbates the consequences of prenatal T on the positive, but not the negative, steroid feedback controls of GnRH secretion. Our approach was to characterize prepubertal sensitivity to E negative feedback, the onset and maintenance of progestagenic cycles, and the LH surge response in ovary intact, prenatally untreated (control), and T-treated (T) sheep that were exposed postnatally to only endogenous E, or exposed to excess E by s.c. implant. Sensitivity to E negative feedback was reduced in T females, but excess postnatal E did not further increase LH pulse frequency. Excess E prevented ovarian cycles in several control females, and increased cycle irregularity in T females. However, the LH surge mechanism was functional in all control females (regardless of postnatal E exposure) and in some T females without excess E, but nonfunctional in T females with excess E. These findings suggest that postnatal E does not program increased resistance to E negative feedback, but excess postnatal E does disrupt other mechanisms required for ovarian cyclicity. We conclude that in this precocial species, prenatal steroids are sufficient to program controls of tonic LH secretion, but the LH surge mechanism is susceptible to further programming by postnatal E.

Decrease of brachial-ankle pulse wave velocity in female subclinical hypothyroid patients during normalization of thyroid function: a double-blind, placebo-controlled study

OBJECTIVE

Subclinical hypothyroidism affects 5-15% of the general population, is especially prevalent in females, and may be associated with increased morbidity from cardiovascular disease, although it remains controversial. We recently reported a significant increase in the brachial-ankle pulse wave velocity (baPWV), a parameter of arterial stiffening and an independent predictor of cardiovascular events, in subclinical hypothyroidism without thyroiditis. The current study was performed to assess changes in baPWV in female subclinical hypothyroidism with autoimmune chronic thyroiditis (Hashimoto's disease) after restoration of normal thyroid function.

METHODS

In a randomized placebo-controlled study, 95 female subclinical hypothyroid patients were monitored for changes in baPWV before and after levothyroxine (l-T(4)) replacement therapy. Changes in baPWV were also measured in 42 age-matched normal female subjects.

RESULTS

The baseline baPWV values in patients with subclinical hypothyroidism were significantly higher than in normal subjects. With attainment of euthyroidism, baPWV showed a significant decrease from 1776.7+/-86.0 to 1674.3+/-79.2 cm/s (P=0.006) in patients treated with l-T(4), but the changes in baPWV and TSH were not correlated. The change in baPWV was significantly and negatively correlated with age and baseline pulse pressure, but multiple regression analysis revealed that these parameters failed to be associated with the change in baPWV.

CONCLUSIONS

Sustained normalization of thyroid function during l-T(4) replacement therapy significantly decreases baPWV in female subclinical hypothyroid patients with autoimmune chronic thyroiditis, suggesting the improvement of arterial stiffening and, consequently, possible prevention of cardiovascular disease.

Psychosocial stress inhibits amplitude of gonadotropin-releasing hormone pulses independent of cortisol action on the type II glucocorticoid receptor

Our laboratory has developed a paradigm of psychosocial stress (sequential layering of isolation, blindfold, and predator cues) that robustly elevates cortisol secretion and decreases LH pulse amplitude in ovariectomized ewes. This decrease in LH pulse amplitude is due, at least in part, to a reduction in pituitary responsiveness to GnRH, caused by cortisol acting via the type II glucocorticoid receptor (GR). The first experiment of the current study aimed to determine whether this layered psychosocial stress also inhibits pulsatile GnRH release into pituitary portal blood. The stress paradigm significantly reduced GnRH pulse amplitude compared with nonstressed ovariectomized ewes. The second experiment tested if this stress-induced decrease in GnRH pulse amplitude is mediated by cortisol action on the type II GR. Ovariectomized ewes were allocated to three groups: nonstress control, stress, and stress plus the type II GR antagonist RU486. The layered psychosocial stress paradigm decreased GnRH and LH pulse amplitude compared with nonstress controls. Importantly, the stress also lowered GnRH pulse amplitude to a comparable extent in ewes in which cortisol action via the type II GR was antagonized. Therefore, we conclude that psychosocial stress reduces the amplitude of GnRH pulses independent of cortisol action on the type II GR. The present findings, combined with our recent observations, suggest that the mechanisms by which psychosocial stress inhibits reproductive neuroendocrine activity at the hypothalamic and pituitary levels are fundamentally different.

[Clinical study of arterial rigidity. Part II. Remodeling of vessels in arterial hypertension and metabolic syndrome. possibilities of correction with drugs]

In the second part of the review we present data on vascular remodeling in arterial hypertension and metabolic syndrome with analysis of factors and mechanisms influencing pulse wave propagation velocity in these diseases. We also consider possibilities of correction of remodeling of vessels with contemporary antihypertensive drugs.

Uterine ultrasonographic changes during endometriosis treatment: a comparison between levonorgestrel-releasing intrauterine devices and a gonadotropin-releasing hormone agonist

We compared the effects of levonorgestrel-releasing intrauterine devices (LNG-IUD) and a gonadotropin-releasing hormone agonist (GnRHa) on uterine volume, uterine arteries pulsatility index (PI) and endometrial thickness before and after six months of endometriosis treatment. Sixty women aged 18-40 y were allocated randomly to one of two groups: LNG-IUDs were inserted in 30 women, and GnRHa monthly injections were performed on the other 30. All 60 women were submitted to transvaginal 2-D ultrasound scans on the day that the treatment started and then six months later. Measurements of uterine arteries PI, uterine volume and endometrial thickness were performed at both evaluations. The use of LNG-IUDs significantly decreased endometrial thickness (pre = 6.08 +/- 3.00 mm, post = 2.7 +/- 0.98 mm; mean +/- SD), as did the use of GnRHa (pre = 6.96 +/- 3.82 mm, post = 3.23 +/- 2.32 mm). The uterine volume decreased in the GnRHa group (pre = 86.67 +/- 28.38 cm(3), post = 55.27 +/- 25.52 cm(3)), but not in the LNG-IUD group (pre = 75.77 +/- 20.88 cm(3), post = 75.97 +/- 26.62 cm(3)). Uterine arteries PI increased for both groups; however, the increase was higher in the GnRHa group (0.99 +/- 0.84 vs. 0.38 +/- 0.84, p = 0.007; PI increase in GnRHa and in LNG-IUD groups, respectively). In conclusion, levonorgestrel released directly onto the endometrium by the LNG-IUD induced smaller uterine changes than did the hypoestrogenism induced by GnRHa. Nevertheless, both promoted similar effects on endometrial thickness.

Secretagogues govern GH secretory-burst waveform and mass in healthy eugonadal and short-term hypogonadal men

BACKGROUND

GH pulses are putatively initiated by hypothalamic GH-releasing hormone (GHRH), amplified by GH-releasing peptide (GHRP), and inhibited by somatostatin (SS).

OBJECTIVE

To ascertain how secretagogues control the waveform (time evolution of release rates) as well as the mass of secretory bursts.

DESIGN

We quantified the shape of GH secretory bursts evoked by continuous combined i.v. infusion of maximally effective doses of GHRH and GHRP-2, and by bolus injection of each peptide after delivering L-arginine to restrain hypothalamic SS release in 12 healthy young men.

METHODS

A mathematically verified and experimentally validated variable-waveform deconvolution model was applied to intensively sampled GH time series.

RESULTS

The secretory-burst mode (time from burst onset to maximal secretion) was 19+/-0.69 min during saline infusion, and fell to a) 10.4+/-3.0 min during constant dual stimulation with GHRH/GHRP-2 (P<0.01), b) 14.6+/-1.8 min after l-arginine/GHRH (P<0.025), and c) 15.0+/-1.0 min after l-arginine/GHRH (P<0.01). Secretagogues augmented the mass of GH secreted in pulses by 44-, 42-, and 16-fold respectively, over saline (2.2+/-0.81 microg/l per h; P<0.001 for each). Pulse number and variability were unaffected. Applying the same methodology to ten other young men with acute leuprolide-induced hypogonadism yielded comparable waveform and mass estimates.

CONCLUSION

The present analyses in men demonstrate that peptidyl secretagogues modulate not only the magnitude but also the time course of the GH-release process in vivo independently of the short-term sex-steroid milieu.

Atorvastatin improves arterial stiffness in normotensive normolipidaemic persons with type 2 diabetes

Increased arterial stiffness is an independent predictor of cardiovascular disease and mortality in middle-aged and olderadults. We measured arterial stiffness by pulse wave velocity (PWV)in brachial-ankle segments by automated oscillometry in 71 normotensive and normolipidaemic subjects with type 2 diabetes (40 males and 31 females). 57 patients (whose baPWV was more than 1400 cm/second) were randomised into two groups, group A (n=29) were given 10 mg atorvastatin daily for 6 months and group B (n=28) were given placebo. After 6 months, atorvastatin group had significant improvement in brachial-ankle pulse wave velocity (baPWV) (1712.03 +/- 349.9 cm/second versus 1558.81 +/- 303.26 cm/ second, p< 0.05). Though the placebo group showed some improvement (1692.03 +/- 425.15 cm/second versus 1636.78 +/- 425.1 cm/second) it was not statistically significant. Despite correlation was noted between baPWV and systolic blood pressure (SBP), there was no significant correlation between the mean baPWV and duration of diabetes, body mass index (BMI), waist circumference, waist-hip ratio (WHR), waist to height ratio (WHtR), glycated haemoglobin (HbA1c), LDL, HDL cholesterol and spot urine albumin creatinine ratio (ACR) at the baseline. The decrement of LDL-cholesterol is correlated with the decrement of the baPWV in the atorvastatin group only (p<0.01).

Twenty-four hour continuous ghrelin infusion augments physiologically pulsatile, nycthemeral, and entropic (feedback-regulated) modes of growth hormone secretion

BACKGROUND

Ghrelin is a 28-amino acid acylated peptide that potentiates GHRH stimulation and opposes somatostatin inhibition acutely. Whether prolonged ghrelin administration can sustain physiological patterns of GH secretion remains unknown.

HYPOTHESIS

Continuous delivery of ghrelin will amplify physiological patterns of GH secretion over 24 h.

SUBJECTS

Men and women ages 29-69 yr, body mass indices 23-52 kg/m2, were included in the study.

LOCATION

The study was performed at an academic medical center.

METHODS

Twenty-four hour continuous sc infusion of saline vs. ghrelin (1 microg/kg.h) with frequent sampling was examined. Deconvolution and entropy analyses were performed.

OUTCOMES

IGF-I concentrations were determined. Basal, pulsatile, nycthemeral, and entropic measures of GH secretion were calculated.

RESULTS

Ghrelin infusion compared with saline infusion for 24 h elevated (median) acylated ghrelin, GH, and IGF-I concentrations by 8.1-fold (P < 0.001),11-fold (P < 0.001), and 1.4-fold (P = 0.002). GH secretory-burst mass and frequency increased by 6.6-fold (P = 0.004) and 1.7-fold (P < 0.001), respectively, resulting in a 12-fold increase in pulsatile GH secretion (P < 0.001). Interpulse variability decreased significantly (P = 0.046), whereas GH secretory-burst shape and half-life did not change. The amplitude of the nycthemeral GH rhythm increased by 3.4-fold (P < 0.001), and GH patterns became more irregular (higher approximate entropy P < 0.001). Combining GHRH with ghrelin was not an additive in driving GH secretion.

CONCLUSIONS

Continuous ghrelin infusion for 24 h elevates acylated ghrelin, GH and IGF-I concentrations, and stimulates pulsatile, nycthemeral, and entropic modes of GH secretion. The consistency of outcomes in a heterogeneous cohort of adults suggests potentially broad utility of this physiological secretagogue in hyposomatotropic states.

Acylated ghrelin inhibits spontaneous luteinizing hormone pulsatility and responsiveness to naloxone but not that to gonadotropin-releasing hormone in young men: evidence for a central inhibitory action of ghrelin on the gonadal axis

CONTEXT

Recent evidence suggests that ghrelin exerts a negative modulation on the gonadal axis. Ghrelin was reported to suppress LH secretion in both animal and human models. Moreover, acylated ghrelin (AG) also decreases the LH responsiveness to GnRH in vitro.

OBJECTIVE

The objective of the study was to evaluate the effects of AG infusion on spontaneous and stimulated gonadotropin secretion.

DESIGN, PARTICIPANTS, AND INTERVENTION

In seven young healthy male volunteers (age mean +/- sem 26.4 +/- 2.6 yr), we evaluated LH and FSH levels every 15 min during: 1) iv isotonic saline infusion; 2) iv saline followed by AG; LH and FSH response to GnRH (100 microg iv as a bolus), 3) alone and 4) during AG infusion; LH and FSH response to naloxone (0.1 mg/kg iv as a slow bolus), 5) alone and 6) during AG infusion.

RESULTS

Significant LH but not FSH pulses were recorded in all subjects under saline infusion. AG infusion inhibited LH levels [area under the curve((240-480)): 415.8 +/- 69.7 mIU/ml.min during AG vs. 744.6 +/- 120.0 mIU/ml.min during saline, P < 0.02] and abolished LH pulsatility. No change in FSH secretion was recorded. The LH and FSH responses to GnRH during saline were not affected by AG administration. However, AG inhibited the LH response to naloxone [area under the curve ((120-210)): 229.9 +/- 39.3 mIU/ml.min during AG vs. 401.1 +/- 44.6 mIU/ml.min during saline, P < 0.01]. FSH levels were not modified by naloxone alone or in combination with AG.

CONCLUSIONS

AG inhibits both spontaneous LH pulsatility and the LH response to naloxone. Because AG does not affect the LH response to GnRH, these findings indicate that the ghrelin system mediates central inhibition of the gonadal axis.

The effect of levothyroxine on arterial stiffness and lipid profile in patients with subclinical hypothyroidism

BACKGROUND

The influence of treatment for subclinical hypothyroidism (SCH) on cardiovascular morbidity and mortality, arterial stiffness, and lipid profile has not been elucidated yet. The aim of this study was to evaluate the effect of levothyroxine on arterial stiffness, lipid profile, and inflammation.

METHODS

The study included 30 patients with SCH. Patients were treated with levothyroxine and were assessed at baseline and at 1, 4, and 7 months. Blood samples were taken for lipid profile and highly sensitive C-reactive protein (hs-CRP). Arterial stiffness was evaluated by augmentation index (AIx). In conditions that cause arterial stiffness, the pulse wave traveling from the periphery to the heart reaches the heart during systole, resulting in augmentation of the central pressure. This increase, calculated as the AIx, is a good expression of central aortic pressure.

RESULTS

After accomplishing euthyroidism, the AIx decreased from 17.2 +/- 8.3 to 14.3 +/- 6.5 (p < 0.01) and AIx percentage decreased from 36.2 +/- 11.5 to 33.2 +/- 9.1 (p = 0.03). Systolic blood pressure (SBP) decreased from 134.7 +/- 20 to 127.6 +/- 13.7 mmHg (p < 0.01). In those patients whose AIx decreased, low-density lipoprotein (LDL) levels decreased by 0.4 +/- 0.96 mmol/L compared to the patients whose AIx did not decrease and LDL increased by 0.62 +/- 1.48 mmol/L (p = 0.057). Total cholesterol decreased by 0.72 +/- 1.64 mmol/L in the patients whose AIx decreased and increased by 1 +/- 2.53 mg/dL in the patients whose AIx did not improve (p = 0.06).

CONCLUSIONS

In patients with SCH, treatment with levothyroxine had a significant beneficial effect on arterial stiffness and SBP, and no effect on lipid profile or hs-CRP.

An increase in kisspeptin-54 release occurs with the pubertal increase in luteinizing hormone-releasing hormone-1 release in the stalk-median eminence of female rhesus monkeys in vivo

The G-protein coupled receptor GPR54 and its ligand, KiSS-1-derived peptide kisspeptin-54, appear to play an important role in the mechanism of puberty. This study measures the release of kisspeptin-54 in the stalk-median eminence (S-ME) during puberty and examines its potential role in the pubertal increase in LHRH-1 release in female rhesus monkeys. First, developmental changes in release of kisspeptin-54 and LHRH-1 were assessed in push-pull perfusate samples obtained from the S-ME of prepubertal, early pubertal, and midpubertal female rhesus monkeys. Whereas LHRH-1 levels in 10-min intervals had been measured previously for other experiments, kisspeptin-54 levels in 40-min pooled samples were newly measured by RIA. The results indicate that a significant increase in kisspeptin-54 release occurred in association with the pubertal increase in LHRH-1 release and that a nocturnal increase in kisspeptin-54 release was already observed in prepubertal monkeys and continued through the pubertal period. Second, we measured kisspeptin-54 release in the S-ME of midpubertal monkeys at 10-min intervals using a microdialysis method. Kisspeptin-54 release in the S-ME was clearly pulsatile with an interpulse interval of about 60 min, and approximately 75% of kisspeptin-54 pulses were correlated with LHRH-1 pulses. Finally, the effect of kisspeptin-10 on LHRH-1 release was examined with the microdialysis method. Kisspeptin-10 infusion through a microdialysis probe significantly stimulated LHRH-1 release in a dose-dependent manner. Collectively, the results are consistent with the hypothesis that kisspeptin plays a role in puberty.

Short-term treatment with L-arginine prevents the smoking-induced impairment of endothelial function and vascular elastic properties in young individuals

BACKGROUND

L-arginine, the substrate for endothelial nitric oxide synthase, is essential for normal endothelial function. Aim of the present study was to investigate in healthy smokers the effect of a short-term daily L-arginine administration on vascular function.

METHODS

We studied the effect of a 3-day oral administration of L-arginine in 10 healthy smokers (24.3+/-0.73 years old) on 3 occasions (day , day 1 and day 3). The study was carried out on two separate arms, one with L-arginine (7 gr/d) and one with placebo according to a randomized, placebo-controlled, double-blind, cross-over design. Measurements were carried out before, immediately after (Sm0) and 20 min after (Sm20) cigarette smoking. Endothelial function was evaluated by flow-mediated dilatation (FMD) of the brachial artery. Carotid-femoral pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) as a measure of arterial wave reflections.

RESULTS

Compared to placebo, L-arginine led to an increase of FMD (p<0.05 at day 2), indicating a favorable effect on endothelial function, which however lost significance at day 3. l-arginine induced a progressive decrease of PWV and AIx at both day 2 and day 3 (p<0.01 vs baseline for all). L-arginine blunted the acute smoking-induced increase of AIx at both day 1 (p<0.05) and day 3 (p<0.01), and there was a trend to protect the smoking-induced change of PWV at day 3 (p<0.1).

CONCLUSIONS

Short-term daily administration of L-arginine improves arterial performance in healthy smokers and abrogates the smoking-induced increase in arterial stiffness and wave reflections in these individuals.

Oestrogen-dependent stimulation of luteinising hormone release by galanin-like peptide in female rats

Galanin-like peptide (GALP), a ligand for three types of galanin receptor, is reported to have a role in regulating luteinising hormone (LH) release in male rodents and primates, but its role in LH release in female rodents remains controversial. The present study was conducted to test whether GALP has a stimulatory role in regulating LH secretion in female rats. The effect of i.c.v. infusion of GALP (5 nmol) on pulsatile LH release was investigated in Wistar-Imamichi strain female rats, or lean and obese Zucker rats. In oestradiol-17beta (oestradiol)-primed ovariectomised (OVX) Wistar-Imamichi female rats, i.c.v. infusion of GALP caused a gradual increase in LH release for the first 1.5 h after the infusion followed by an increased LH pulse frequency during the next 1.5 h, resulting in a significant increase in the mean LH concentrations and baseline levels of LH pulses throughout the sampling period and in the frequency of LH pulses at the last half of the period compared to vehicle-treated controls. The stimulatory effect of GALP was oestrogen-dependent because the same GALP treatment did not affect LH release in OVX rats in the absence of oestradiol. In lean Zucker rats, LH pulses were found in oestradiol-primed OVX individuals and central GALP infusion increased mean LH concentrations in the last half of the period. By contrast, few LH pulses were found in oestradiol-primed OVX obese Zucker rats reportedly with lower hypothalamic GALP expression. Central GALP infusion caused an apparent but transient increase in LH release, resulting in the significant increase in all pulse parameters of LH pulses compared to vehicle-treated controls in the first half of the sampling period. These results suggest that hypothalamic GALP is likely involved in stimulating GnRH/LH release, and that the stimulatory effect of GALP on LH release is oestrogen-dependent in female rats.

High dose treatment with angiotensin II receptor blocker in patients with hypertension: Differential effect of tissue protection versus blood pressure lowering

Aggressive inhibition of renin-angiotensin-aldosterone system may provide the best cardiovascular protection. We examined the effect of different doses of angiotensin II receptor blocker, Candesartan, on arterial elasticity, inflammatory and metabolic parameters in hypertensive patients with multiple cardiovascular risk factors. 69 hypertensive patients were randomized into three groups: group 1 included patients treated with high doses of Candesartan (32 mg), group 2 included patients treated with conventional doses of Candesartan (16 mg), group 3 included patients that received antihypertensive treatment other that angiotensin II type-1 receptor blockers (ARBs) or angiotensin-converting enzyme inhibitors (ACEIs). Patients were evaluated for lipid profile, HbA1C, insulin, C-peptide, hs-CRP, aldosterone, renin and Homeostasis model assessment-insulin resistance (HOMA-IR). Arterial elasticity was evaluated using pulse wave contour analysis method (HDI CR 2000, Eagan, Minnesota). In patients treated with high doses of Candesartan: large artery elasticity index (LAEI) increased from 8.6+/-2.8 to 16.6+/-5.1 ml/mm Hg x 100 after 6 months of treatment (p<0.0001). Small artery elasticity index (SAEI) increased from 2.7+/-1.3 to 5.9+/-2.8 ml/mm Hg x 100 (p<0.0001). Systemic vascular resistance (SVR) decreased from 1881.5+/-527.5 to 1520.9+/-271.8 (p<0.0006). In patients treated with conventional doses of Candesartan: LAEI index increased from 11.0+/-3.5 to 14.4+/-3.2 ml/mm Hg x 100 (p<0.0001). SAEI increased during the study from 3.7+/-1.4 to 5.4+/-2.1 ml/mm Hg x 100 (p<0.0001). SVR decreased from 1699.8+/-327.6 to 1400.7+/-241 (p<0.0001). In the control group: neither LAE nor SAE improved during the treatment period. Although similar reduction in blood pressure was observed in all three groups, both LAE and SAE improved only in patients treated by ARBs. Treatment with high doses of Candesartan improves arterial stiffness to a greater extent than conventional doses of Candesartan, despite comparable changes in blood pressure.