Evaluation of L-arginine reactivity in comparison with flow-mediated dilatation and intima-media thickness

Antioxidant, anti-inflammatory, and anti-fibrotic properties of olive leaf extract protect against L-arginine induced chronic pancreatitis in the adult male albino rat

Chronic pancreatitis (CP) is an inflammatory disease affects the pancreas with upcoming fibrosis and notable parenchymal destruction. CP poses a high risk for pancreatic carcinoma. The present study aimed to investigate, for the first time up to our knowledge, the effect of olive leaf extract on L-arginine induced CP with referral to some of its underlying mechanisms. Forty adult male albino rats were divided equally into four groups; control, olive leaf extract treated (200 mg/kg orally once daily), CP group (300 mg L-arginine/100 g body weight intraperitoneally, once daily for 3 weeks then every 3 days for the subsequent 3 weeks), and CP treated with olive leaf extract group. At the end of the experiment, body weight, serum glucose, serum insulin, homeostatic model assessment of insulin resistance (HOMA-IR), serum amylase and lipase as well as tissue superoxide dismutase (SOD), and malondialdehyde (MDA) levels were assessed. Pancreatic tissues were subjected to histological and immuno-histochemical studies. The CP group revealed significant decrease in body weight and increase in serum glucose, serum insulin, HOMA-IR score, serum amylase, and serum lipase levels. Significant increase in MDA level and decrease in SOD level were detected. Marked degenerative changes and fibrosis were detected. Upregulation of alpha smooth muscle actin (α-SMA), transforming growth factor beta (TGF-β), caspase-3, and interleukin-6 (IL-6) immunoreactions were implicated in CP pathogenesis. Olive leaf extract alleviated all the examined parameters via its-antioxidant, anti-inflammatory, and anti-fibrotic properties. Olive leaf extract can protect against CP and restore pancreatic functions.

Escitalopram improves neural functional prognosis and endothelial dysfunction in patients with acute cerebral infarction

BACKGROUND

Escitalopram is one of the most commonly used SSRIs at present, which has the characteristics of quick onset, less interactions with other drugs, and relative safety.

OBJECTIVE

This study aims to investigate the effects of escitalopram on neural functional prognoses and endothelial dysfunction after acute ischemic stroke.

METHODS

One hundred eligible patients afflicted with acute ischemic stroke were randomized into two groups: control and treatment groups. Patients in the treatment group received escitalopram in addition to the basic therapies in the control group over a period of 90 days. Neurological deficits were quantified using the National Institutes of Health Stroke Scale (NIHSS) score and Barthel index (BI) score, cognitive impairment was determined using the Mini-Mental State Examination (MMSE) score, depressive symptoms were measured using the 17-item Hamilton Depression Rating Scale (HAMD). Furthermore, post-stroke depression (PSD) was defined based on the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition), with a HAMD score ≥17. Flow-mediated vascular dilatation (FMD) of the brachial artery was use as a surrogate indicator for endothelial dysfunction assessment with ultrasound.

RESULTS

The mean NIHSS and HAMD scores on day 90 after treatment were significantly lower in the treatment group than in the control group (2.17±0.36 vs. 4.24±0.85; 5.81±1.35 vs. 10.43±4.91; P < 0.01), while the mean BI score and FMD were significantly higher in the treatment group (93.08±6.23 vs. 79.64±7.56, P < 0.01; 8.71±2.35 vs. 5.83±1.21, P < 0.05) than in the control group. The improvement in MMSE score was not significantly different between the two groups.

CONCLUSIONS

Treatment with escitalopram early after ischemic stroke can improve neural functional prognoses and endothelial dysfunction. Escitalopram had less side effects, which is worthy of clinical prophylactic application.

Arginine impairs endothelial and executive function in older subjects with cardiovascular risk

Neurovascular coupling, the relationship between cerebral blood flow and neuronal activity, is attenuated in patients with impaired executive function. We tested the hypothesis that peripheral vascular function may associate with executive function in older subjects with cardiovascular risk factors and that treatment with the antioxidant L-arginine would improve both vascular and executive function. Nineteen subjects with type 2 diabetes mellitus and/or controlled hypertension were enrolled. Subjects were treated with L-arginine or placebo for 4 days in a randomized, double-blinded, cross-over study. Brachial artery vascular function, peripheral artery tonometry, and Trail Making Test Part B testing were performed on day 1 and day 4 during each condition. L-arginine significantly reduced the digital reactive hyperemia index, and the comparison of changes against placebo was significant (P = .01). With executive function testing, we observed a significant interaction between treatment and order. Restricting the analysis to the first treatment period, subjects treated with placebo decreased their Trail Making Test Part B times by 57.3 ± 52.5 seconds from day 1 to day 4 (P = .01) while those treated with arginine had no significant change (6.4 ± 18.4 seconds worse, P = .37). In addition, L-arginine was associated with increased mean arterial pressure from 88 ± 9 mm Hg to 92 ± 11 mm Hg, which trended toward significance. L-arginine treatment worsened digital microvascular and executive function in older subjects with cardiovascular risk factors. These data further support a link between vascular and executive function.

l-arginine and l-NMMA for assessing cerebral endothelial dysfunction in ischaemic cerebrovascular disease: A systematic review

Endothelial dysfunction (ED), in particular cerebral ED, may be an essential biomarker for ischaemic cerebrovascular disease. However, there is no consensus on methods to best estimate cerebral ED. In this systematic review, we evaluate the use of l-arginine and N^G -monomethyl-l-arginine (l-NMMA) for assessment of cerebral ED. A systematic search of PubMed, EMBASE and the Cochrane Library was done. We included studies investigating cerebrovascular response to l-arginine or l-NMMA in human subjects with vascular risk factors or ischaemic cerebrovascular disease. Seven studies (315 subjects) were eligible according to inclusion and exclusion criteria. Studies investigated the effect of age (n=2), type 2 diabetes mellitus (DM) (n=1), cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) (n=1), leukoaraiosis (n=1), and prior ischaemic stroke or transient ischaemic attack (TIA) (n=2) on cerebral ED. Most studies applied transcranial Doppler to quantify cerebral ED. Endothelium-dependent vasodilatation (EDV) induced by l-arginine was impaired in elderly and subjects with leukoaraiosis, but enhanced in CADASIL patients. Studies including subjects with prior ischaemic stroke or TIA reported both enhanced and impaired EDV to l-arginine. Responses to l-NMMA deviated between subjects with type 2 DM and the elderly. We found only few studies investigating cerebral endothelial responses to l-arginine and l-NMMA in subjects with vascular risk factors or ischaemic cerebrovascular disease. Inconsistencies in results were most likely due to variations in methods and included subject populations. In order to use cerebral ED as a prognostic marker, further studies are required to evaluate the association to cerebrovascular disease.

Cerebral endothelial function determined by cerebrovascular reactivity to L-arginine

Endothelium forms the inner cellular lining of blood vessels and plays an important role in many physiological functions including the control of vasomotor tone. Cerebral endothelium is probably one of the most specific types but until recently it was impossible to determine its function. In this review, the role of cerebrovascular reactivity to L-arginine (CVR-L-Arg) for assessment of cerebral endothelial function is discussed. L-Arginine induces vasodilatation through enhanced production of nitric oxide (NO) in the cerebral endothelium. Transcranial Doppler sonography is used for evaluation of cerebral blood flow changes. The method is noninvasive, inexpensive, and enables reproducible measurements. CVR-L-Arg has been compared to flow-mediated dilatation as a gold standard for systemic endothelial function and intima-media thickness as a marker for morphological changes. However, it seems to show specific cerebral endothelial function. So far CVR-L-Arg has been used to study cerebral endothelial function in many pathological conditions such as stroke, migraine, etc. In addition CVR-L-Arg has also proven its usefulness in order to show potential improvement after pharmacological interventions. In conclusion CVR-L-Arg is a promising noninvasive research method that could provide means for evaluation of cerebral endothelial function in physiological and pathological conditions.

Decreased reactivity of skin microcirculation in response to L-arginine in later-onset type 1 diabetes

OBJECTIVE

The aim of our study was to evaluate the vasodilatory effect of l-arginine infusion on the skin microcirculation and to assess the relationship between this effect and the presence of microangiopathy in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Capillaroscopy was performed before and after l-arginine infusion in 48 diabetic patients (26 women and 22 men; age, 39.8 ± 6.3 years) and 24 volunteers free of any chronic disease (13 women and 11 men; age, 38.0 ± 6.7 years). The skin microcirculation reactivity, as expressed by the percentage of area covered by capillaries (coverage) and the distance between capillaries (distance), and the relationship between microcirculation reactivity and the presence of microangiopathic complications were assessed.

RESULTS

The distance before l-arginine infusion was significantly lower in patients than in controls (221 [153-311] vs. 240 [185-356] µm; P = 0.02) and did not differ after l-arginine infusion (223.5 [127-318] vs. 242.5 [181-341] µm; P = 0.27). The difference between the coverage values obtained before and after l-arginine infusion (Δcoverage) was significantly different from zero in the control group but not in the diabetes group. Patients with later onset of diabetes were characterized by decreased skin microcirculation reactivity when compared with patients with earlier onset of diabetes (-1.18 [-5.07 to 11.60] vs. 1.36 [-6.00 to 8.06]; P = 0.02) despite the higher prevalence of retinopathy in patients with earlier onset of diabetes (64% vs. 26%; P = 0.02).

CONCLUSIONS

Skin microvascular reactivity is impaired in patients with later onset of type 1 diabetes. Capillaroscopy with l-arginine infusion is useful for the identification of skin microangiopathy in type 1 diabetes.

L-arginine reactivity in cerebral vessels after severe traumatic brain injury

OBJECTIVES

Traumatic brain injury (TBI) causes an early reduction of cerebral blood flow (CBF). The purpose was to study cerebrovascular endothelial function by examining the reactivity of cerebral vessels to L-arginine.

METHODS

Fifty-one patients with severe TBI were prospectively studied by measuring cerebral hemodynamics before and after the administration of L-arginine, 300 mg/kg at 12 hours and at 48 hours after injury. These hemodynamic measurements, using transcranial Doppler techniques, included internal carotid flow volume as an estimate of hemispheric CBF, flow velocity in intracranial vessels, CO(2) reactivity, and dynamic pressure autoregulation using thigh cuff deflation and carotid compression methods. Changes in the hemodynamics with L-arginine administration were analyzed using a general linear mixed model.

RESULTS

L-arginine produced no change in mean arterial pressure, intracranial pressure, or brain oxygenation. Overall, L-arginine induced an 11.3% increase in internal carotid artery flow volume (P=0.0190). This increase was larger at 48 hours than at 12 hours (P=0.0045), and tended to be larger in the less injured hemisphere at both time periods. The response of flow velocity in the intracranial vessels was similar, but smaller differences with administration of L-arginine were observed. There was a significant improvement in CO(2) reactivity with L-arginine, but no change in dynamic pressure autoregulation.

DISCUSSION

The low response of the cerebral vessels to L-arginine at 12 hours post-injury with improvement at 48 hours suggests that dysfunction of cerebrovascular endothelium plays a role in the reduced CBF observed after TBI.

The effect of allopurinol on the cerebral vasculature of patients with subcortical stroke; a randomized trial

AIMS

New preventative strategies for stroke are required. One promising strategy is uric acid reduction and xanthine oxidase inhibition with allopurinol. We sought to investigate whether allopurinol improves cerebrovascular reactivity (CVR) following subcortical stroke.

METHODS

We performed a randomized, double-blind, controlled study to investigate the effect of a 3-month course of 300 mg allopurinol once daily vs. placebo on CVR in individuals with recent (within 6 months) subcortical stroke. Participants were randomized on a 1:1 basis. CVR was defined as the percentage change in middle cerebral artery flow velocity following an intravenous injection of 15 mg kg(-1) of acetazolamide. Our primary end-point was the CVR difference between baseline and 3 months. Secondary end-points included measures of peripheral vascular reactivity and blood markers of inflammation and endothelial activation.

RESULTS

We enrolled 50 participants; 45 completed the protocol. Baseline serum urate was 0.35 mmol l(-1) (SD 0.1) and 0.34 mmol l(-1) (SD 0.1) in the allopurinol and placebo groups, respectively. There were no serious adverse events related to treatment. CVR did not change following treatment with allopurinol [median CVR change 0.89% after allopurinol (n = 20) and -0.68% after placebo (n = 25); 95% confidence interval for estimated difference in medians -13.4, 25.5, P = 0.64]. Urate was significantly lowered by allopurinol but no change in other secondary end-points was seen.

CONCLUSION

Xanthine oxidase inhibition with allopurinol has previously been shown to improve cerebrovascular function, but no benefit was seen in this study. It may therefore be that previous encouraging findings will not translate into important clinical benefits.