L-Arginine (Blood Flow)

l-Arginine supplementation is a potential therapy for treating cardiovascular and metabolic diseases. However, the use of distinct l-arginine sources, intervened populations, and treatment regimens may have yielded confusion about their efficacy. This research constitutes a systematic review and meta-analysis summarizing the effects of l-arginine supplementation compared to placebo in individuals with cardiovascular disease (CVD), obesity, or diabetes. Eligibility criteria included randomized clinical trials and interventions based on oral supplementation of l-arginine with a minimum duration of three days; comparison groups consisted of individuals with the same disease condition receiving an oral placebo substance. The primary outcome was flow-mediated dilation, and secondary outcomes were nitrite/nitrate (NOx) rate and asymmetric dimethylarginine (ADMA). Statistical heterogeneity among studies included in the meta-analyses was assessed using the inconsistency index (I2). Fifty-four full-text articles from 3761 retrieved references were assessed for eligibility. After exclusions, 13 studies were included for data extraction. There was no difference in blood flow after post-ischemic hyperemia between the supplementation of l-arginine and placebo groups before and after the intervention period (standardized mean difference (SMD) = 0.30; 95% confidence intervals (CIs) = -0.85 to 1.46; I2 = 96%). Sensitivity analysis showed decreased heterogeneity when the studies that most favor arginine and placebo were removed, and positive results in favor of arginine supplementation were found (SMD = 0.59; 95% CIs = 0.10 to 1.08; I2 = 75%). No difference was found in meta-analytical estimates of NOx and ADMA responses between arginine or placebo treatments. Overall, the results indicated that oral l-arginine supplementation was not associated with improvements on selected variables in these patients (PROSPERO Registration: CRD42017077289).

BACKGROUND: Hypoxic-ischemic injury is thought to play a significant role in necrotizing enterocolitis (NEC). Nitric Oxide (NO) is the principal inhibitory neurotransmitter in the gut and is involved in regulation of mucosal blood flow and maintenance of mucosal integrity. NO is synthesized from L-arginine by NO synthases. Our primary objective was to determine the effectiveness of supplemental L-arginine versus placebo in prevention of NEC in preterm infants ≤ 34 weeks gestational age by systematic review of published randomized controlled trials (RCTs). METHODS: This review included RCTs in which L-arginine was administered as a supplement to neonates to prevent NEC. Searches were conducted in OVID MEDLINE, EMBASE, PubMed, and CINAHL from their dates of inception to July, 2014. Inclusion criteria were informed parental consent, neonates born at ≤ 34 weeks gestation, and birth weight ≤ 1500 g. Exclusion criteria included neonates with severe congenital anomalies and inborn errors of metabolism. Incidence of NEC was the primary outcome measure. Whole data were analyzed by RevMan 5.1 (Update Software, Oxford, UK). Outcome data were analyzed to determine risk ratios, number needed to treat, confidence intervals, and test for overall effect. RESULTS: Two trials including 425 neonates were eligible for this review. Of these, 235 neonates were included in the study. L-arginine had a 59% reduction in the incidence of stage II and III NEC (RR 0.41, 95% CI 0.20 to 0.85, NNT = 9) compared with placebo (P = 0.02). A similar finding was identified for all stages of NEC (60% reduction, RR 0.40, 95% CI 0.23 to 0.69, NNT = 5) (P = 0.001). At age 3 yrs, there was no significant difference between the 2 groups in terms of any neurodevelopmental disability (RR 0.65; 95% CI 0.23-1.83, P = 0.41). CONCLUSIONS: L-arginine supplementation appears to be protective in prevention of NEC in preterm infants and without any significant impact on neurodevelopmental outcomes at 36 months of corrected age. With the addition of the results of one more study to the literature, an intriguing role for L-arginine supplementation continues to gain support. However, large multi-centre RCTs are neede

BACKGROUND: Previous trials suggest that oral l-arginine administration affects endothelial function. However, most of these studies were small, the conclusions were inconsistent, and the precise effects are therefore debatable. OBJECTIVE: The objective was to assess the effect of oral l-arginine supplementation on endothelial function, as measured with the use of fasting flow-mediated dilation (FMD). DESIGN: We conducted a meta-analysis of randomized, placebo-controlled l-arginine supplementation trials that evaluated endothelial function. Trials were identified in PubMed, Cochrane Library, Embase, reviews, and reference lists of relevant papers. The weighted mean difference (WMD) was calculated for net changes in FMD by using random-effect models. Previously defined subgroup analyses and meta-regression analyses were performed to explore the influence of study characteristics. RESULTS: Thirteen trials were included and evaluated. Because there was only one long-term study, we focused on short-term effects of l-arginine (12 studies, 492 participants). In an overall pooled estimate, l-arginine significantly increased FMD (WMD: 1.98%; 95% CI: 0.47, 3.48; P = 0.01). Meta-regression analysis indicated that the baseline FMD was inversely related to effect size (regression coefficient = -0.55; 95% CI: -1.00, -0.1; P = 0.016). A subgroup analysis suggested that l-arginine supplementation significantly increased FMD when the baseline FMD levels were <7% (WMD: 2.56%; 95% CI: 0.87, 4.25; P = 0.003), but had no effect on FMD when baseline FMD was >7% (WMD: -0.27%; 95% CI: -1.52, 0.97; P = 0.67). CONCLUSION: Short-term oral l-arginine is effective at improving the fasting vascular endothelial function when the baseline FMD is low.

This study aimed to evaluate the effects of short-term oral L-arginine (ARG) supplementation on vascular parameters, nitric oxide (NO) concentration, and muscular performance during upper limb resistance exercise in healthy young men. A randomized, double-blind, crossover design was used with 16 recreationally trained men. Participants ingested ARG (3.2-9.6 g/day) or placebo for 4 days, separated by a 14-day washout. On the fourth day, they completed three sets of biceps curls at 65% of one-repetition maximum to concentric failure. Primary outcomes included total repetitions performed and fatigue ratio. Secondary outcomes comprised brachial artery diameter, peak systolic velocity, blood flow (velocity-time integral), vascular resistance index, plasma NO, and blood lactate concentrations. No significant differences were observed between ARG and placebo in muscular endurance (total repetitions, p = .305), volume load, or fatigue ratio. Plasma NO levels did not differ between conditions (p = .522). Although brachial artery diameter significantly increased 1-min postexercise in the ARG condition compared with placebo (p = .023), no differences were found for velocity-time integral, peak systolic velocity, resistance index, or blood pressure. Blood lactate concentrations rose after exercise in both groups, with a nonsignificant value in the ARG condition (p = .09 at 9-min postexercise). Short-term oral ARG supplementation did not enhance muscular endurance, systemic NO concentration, or vascular function during upper limb resistance exercise in healthy young men. Although a minor increase in brachial artery dilation was observed shortly after exercise, the effect was transient and insufficient to support meaningful ergogenic benefits.

BACKGROUND: Patients with type 2 diabetes (T2D) develop vascular complications due to arginine deficiency-induced microvascular endothelial dysfunction, which is related to the loss of muscle strength (MS) associated with aging. Thus, increased nitric oxide (NO)-mediated vasodilation may improve MS. We investigated the impact of the NO precursor citrulline on microvascular function (endothelial and muscle reactivity) and MS in T2D patients. METHODS: Sixteen participants with T2D (53-72 years, nine females) were randomized to citrulline supplementation (CITS, 6 g/day) or placebo for 4 weeks prior to an 8-week washout period, followed by the opposite supplement for 4 weeks in a crossover trial. Endothelial function (log-transformed reactive hyperemia index, LnRHI), forearm muscle reactivity (near-infrared spectroscopy-derived tissue oxygen index (TOI) reperfusion indices), plasma arginine levels (ARG), and handgrip strength (HGSrel) and calf MS (CMSrel) adjusted for body weight were measured at baseline and 4 weeks for each condition. RESULTS: CITS increased the LnRHI (∆0.11 ± 0.16 vs. ∆-0.08 ± 0.24, p < 0.05), TOI range (∆2.6 ± 3.3 vs. ∆-1.5 ± 4.8%, p < 0.01), TOI hyperemic response (∆1.2 ± 1.4 vs. ∆-0.6 ± 2.8%, p < 0.05), TOI 2 min area under the curve (∆154 ± 187 vs. ∆-41 ± 194%/s, p < 0.01), ARG (∆43 ± 28 vs. ∆1 ± 16μM/L, p < 0.001), CMS (∆1.5 ± 2.8 vs. ∆-0.3 ± 1.2 kg, p < 0.05), and CMSrel (∆0.02 ± 0.03 vs. ∆-0.01 ± 0.02 kg/kg, p < 0.01) compared to placebo. The improvements in LnRHI and CMSrel were correlated (r = 0.37, p < 0.05). CONCLUSIONS: This study showed that CITS improves microvascular endothelial function, muscle microvascular reactivity, and calf muscle strength in middle-aged and older patients with T2D.

Background: The dietary supplement citrulline might increase nitric oxide levels, leading to vasodilation and improved blood flow, potentially benefiting athletes' aerobic exercise performance. However, rapid oxidative impairment of the L-arginine/nitric oxide (NO) pathway limits these effects. This is countered by Bergamot Polyphenolic Fraction Gold® (BPFG), a strong natural antioxidant. To investigate L-citrulline + BPFG supplementation's effects, we performed a randomized, double-blind, placebo-controlled pilot trial on athletic performance and blood flow in trained athletes (cyclists). Methods: Random assignment of 90 male athletes resulted in nine different groups: placebo for Group 1, BPFG at 500 and 1000 mg daily for Groups 2 and 3, L-citrulline at 1000 and 2000 mg/daily for Groups 4 and 5, and the combination product of BPFG plus citrulline (N.O. Max) for Groups 6-9. Baseline and 3-month pre- and post-exercise biochemical, reactive vasodilation (RHI), and maximal oxygen consumption measurements were taken for all subjects. Results: Three months of the combination of BPFG and L-citrulline (N.O. Max) produced a significant synergistic effect, markedly increasing NO (p < 0.001 vs. placebo) release and RHI (p < 0.001 vs. placebo). Cardiorespiratory fitness improved significantly with the BPFG and L-citrulline combination, resulting in substantially higher VO2 max, VT1, VT2, and peak power and a significantly lower heart rate (p < 0.01 vs. placebo). No harmful adverse effects were observed. Conclusions: N.O. Max supplementation, providing beneficial effects on the antioxidant state and preserving the vascular endothelium might be a supplementation strategy to improve athletic performance and potentiate results. Given the small sample size, this study serves as a pilot, and further research is needed to validate these findings on a larger scale.

AIMS: Exercise has been shown to affect the nitric oxide (NO) pathway, which is involved in the pathophysiology of endothelial dysfunction in heart failure (HF) with reduced (HFrEF) and preserved ejection fraction (HFpEF). However, the effects of different exercise modes on NO metabolites in patients with HF are uncertain. METHODS AND RESULTS: Blood samples from two randomized controlled HF trials evaluating (i) high-intensity interval training (HIIT), (ii) moderate continuous training (MCT), or (iii) a control group (CG) in HFrEF (SMARTEX-HF) and HFpEF (OptimEx-Clin) were analysed for NO metabolites L-arginine, homoarginine (hArg), asymmetric and symmetric dimethylarginine (ADMA; SDMA). Metabolite plasma concentrations were compared between HFrEF and HFpEF at baseline and within each HF type after 3 months of supervised exercise training and a 12-month follow-up. Overall, 206 patients with HFrEF (61 ± 12 years, 18.9% females) and 160 with HFpEF (70 ± 8 years, 65.6% females) were investigated. Baseline hArg (1.74 ± 0.78 vs. 1.31 ± 0.69 µmol/L) and ADMA (0.68 ± 0.15 vs. 0.62 ± 0.09 µmol/L) were significantly higher in HFrEF (P < 0.001). NO metabolites showed several significant associations with markers of HF severity like exercise capacity (VO2peak) and NT-proBNP, but not with measures of endothelial function (reactive hyperaemia index, flow-mediated dilation). After 3 months of exercise and a 12-month follow-up, changes in metabolite plasma levels were not significantly different between study groups (HIIT, MCT, or CG) (pgroup×time > 0.05), neither in HFrEF nor HFpEF. CONCLUSION: Baseline NO metabolite profile was unfavourable in patients with HF and lower VO2peak or higher NT-proBNP. We did not find a significant influence of HIIT or MCT on NO metabolites at 3 and 12 months. Plain Language Summary: In our study, we measured the metabolites L-arginine, homoarginine, asymmetric and symmetric dimethylarginine (ADMA, SDMA), which are considered important regulators of the nitric oxide (NO) mediated endothelial function and associated with cardiovascular outcome, in patients with heart failure with reduced (HFrEF) or preserved ejection fraction (HFpEF) and investi

Women with endometriosis, an inflammatory disease, are at increased risk of cardiovascular disease and demonstrate impaired microvascular endothelial function, characterized by reduced nitric oxide (NO)-mediated vasodilation. In some clinical cohorts, nuclear factor-kappa B (NFκB) inhibition with salsalate improves endothelial function. We hypothesized that salsalate would improve cutaneous microvascular endothelial function in women with endometriosis. Following placebo or salsalate (3,000 mg·day-1 for 5 days), four intradermal microdialysis probes were placed in 11 women (33 ± 7 yr) with endometriosis. Local heating units (set to 33°C) and laser-Doppler flowmetry (red blood cell flux) probes were placed over the probes. Increasing doses of acetylcholine (ACh; dissolved in lactated Ringer's solution) were perfused, alone (control) or coperfused with: NG-nitro-l-arginine methyl ester (l-NAME), atorvastatin (statin), or l-NAME + statin (combo). Maximal vasodilation was then induced (local heat at 43°C + sodium nitroprusside perfusion). Data were normalized as percentage of maximal cutaneous vascular conductance (CVC%max red blood cell flux/mean arterial pressure). To measure macrovascular endothelial function, flow-mediated dilation (FMD) was additionally performed. During placebo, coperfusion with statin did not impact the CVC%max ACh dose-response (P = 0.93). Oral salsalate attenuated the CVC%max response to ACh perfusion alone (P < 0.01) but did not impact the l-NAME site (P = 0.09). Salsalate significantly augmented the CVC%max response of the statin site (P < 0.01) but did not affect the combo site response (P = 1.00). FMD was not different between treatments (P = 0.79). Salsalate treatment impairs vasodilation in the cutaneous microcirculation in women with endometriosis through non-NO-dependent mechanisms.NEW & NOTEWORTHY Our results show that oral salsalate treatment negatively impacts microvascular function but does not alter macrovascular function. In contrast to the majority of other clinical populations with endothelial dysfunction, salsalate treatment reduces microcirculatory function through non-NO-dependent mechanisms in women with endometriosis.

BACKGROUND: Postprandial vascular endothelial dysfunction is an early marker of atherosclerosis. Meal protein has been reported to reduce endothelial dysfunction in adults, and the effect could be mediated by the amino acid content. OBJECTIVES: This trial aims to assess the effect of a specifically designed plant-protein blend that contains high leucine, arginine, and cysteine on postprandial endothelial function in the elderly. METHODS: In a randomized, double-blind, 3-period crossover (2-wk washout), controlled trial, we compared the vascular effects of 3 high-saturated-fat high-sucrose (HFHS) meals containing either our specific plant-protein blend, or milk protein, or without added protein. The trial was conducted on 29 healthy adults aged >65 y presenting ≥2 cardiometabolic risk factors. Postprandial vascular function was evaluated at fasting, 3 h, and 5 h postprandially, using brachial flow-mediated dilation (FMD), hand microvascular reactivity (using Flowmetry Laser Doppler, FLD), and finger reactive hyperemia index (using Peripheral Arterial Tonometry, RHI). Immune cell count and gene expression in peripheral blood mononuclear cells (PBMCs) were also assessed postprandially. Data were analyzed using mixed linear models with repeated measurements on participants for meal composition and time of sampling. This trial was registered at clinicaltrials.gov as NCT04923555. RESULTS: FMD incremental AUC value decreased after meals (time effect P < 0.01), with no significant differences between meals. RHI also decreased with time (P < 0.01). PBMC count and monocyte chemoattractant protein-1 (MCP1), IL-1β, and IL-6 expression increased after meals showing postprandial endothelial activation (P < 0.05). Overall, meal composition had no effect on any of the postprandial changes (Ps>0.10). CONCLUSIONS: In healthy adults aged >65 y presenting cardiometabolic risk, adding protein to an HFHS challenge meal does not mitigate postprandial impairments in vascular endothelial function and inflammatory activation. Further studies are needed to explore the potential differences with younger adults.

AIM: This study aimed to investigate the acute effects of dietary nitrate ingestion through l-arginine supplementation or dehydrated beet consumption on endothelial function in chronic obstructive pulmonary disease (COPD) patients. The secondary outcome was to analyze arterial stiffness, plasma nitrate, and nitrate/protein concentration. METHODS: In this randomized crossover study, subjects with COPD underwent three series of supplementation: (1) l-arginine, (2) dehydrated beetroot, and (3) a placebo that appeared like the other supplements. Each intervention lasted 14 days, with a 7-day washout period between series. Participants underwent endothelial function assessment using flow-mediated dilatation (FMD), and plasma nitrate levels were measured at the end of each supplementation series. RESULTS: Seventeen subjects (twelve male) completed the study protocol. Only five subjects presented endothelial dysfunction (RHI ≤0.51) at baseline. The mean baseline characteristics included age 66.5 ± 9.4 years, BMI 27.5 ± 4.5 kg/m2, FEV1, 0.79 (0.67-1.06) L. There were no differences (p > 0.05) between the groups or from pre-to post-interventions for RHI and arterial stiffness index (AIx) values, as well as parameters of endothelium-dependent vasodilation, such as blood flow velocity (BFV), shear stress, shear rate, FMD (mm), and FMD%. There was also no differences (p > 0.05) between the groups or from pre-to post-interventions plasma nitrate levels. CONCLUSIONS: Acute dietary supplementation with nitrates, at the doses provided, did not show a significant improvement in endothelial function assessed by FMD, EndoPAT, or plasma nitrate levels in COPD. These findings suggest that a higher dose or prolonged supplementation might be required to achieve a therapeutic effect.

The transcriptional regulator nuclear factor-κB (NF-κB) is a mediator of endothelial dysfunction. Inhibiting NF-κB with salsalate is used to investigate inflammatory mechanisms contributing to accelerated cardiovascular disease risk. However, in the absence of disease, inhibition of NF-κB can impact redox mechanisms, resulting in paradoxically decreased endothelial function. This study aimed to measure microvascular endothelial function during inhibition of the transcriptional regulator NF-κB in reproductive-aged healthy women. In a randomized, single-blind, crossover, placebo-controlled design, nine healthy women were randomly assigned oral salsalate (1,500 mg, twice daily) or placebo treatments for 5 days. Subjects underwent graded perfusion with the endothelium-dependent agonist acetylcholine (ACh, 10-10 to 10-1 M, 33°C) alone and in combination with 15 mM NG-nitro-l-arginine methyl ester [l-NAME; nonselective nitric oxide (NO) synthase inhibitor] through intradermal microdialysis. Laser-Doppler flux was measured over each microdialysis site, and cutaneous vascular conductance (CVC) was calculated as flux divided by mean arterial pressure and normalized to site-specific maximum (CVC%max; 28 mM sodium nitroprusside + 43°C). The l-NAME sensitive component was calculated as the difference between the areas under the dose-response curves. During the placebo and salsalate treatments, the l-NAME sites were reduced compared with the control sites (both P < 0.0001). Across treatments, there was a significant difference between the control and l-NAME sites, where both sites shifted upward following salsalate treatment (both P < 0.0001), whereas the l-NAME-sensitive component was not different (P = 0.94). These data demonstrate that inhibition of the transcriptional regulator NF-κB improves cutaneous microvascular function in reproductive-aged healthy women through non-NO-dependent mechanisms.NEW & NOTEWORTHY The transcription factor nuclear factor-κB (NF-κB) regulates multiple aspects of innate and adaptive immunity by encoding for genes that participate in inflammation and impact endothelial function following NF-κB inhibition with salsalate treatment. Our results sh

We recently developed a novel keratin-derived protein (KDP) rich in cysteine, glycine, and arginine, with the potential to alter tissue redox status and insulin sensitivity. The KDP was tested in 35 human adults with type-2 diabetes mellitus (T2DM) in a 14-wk randomised controlled pilot trial comprising three 2×20 g supplemental protein/day arms: KDP-whey (KDPWHE), whey (WHEY), non-protein isocaloric control (CON), with standardised exercise. Outcomes were measured morning fasted and following insulin-stimulation (80 mU/m2/min hyperinsulinaemic-isoglycaemic clamp). With KDPWHE supplementation there was good and very-good evidence for moderate-sized increases in insulin-stimulated glucose clearance rate (GCR; 26%; 90% confidence limits, CL 2%, 49%) and skeletal-muscle microvascular blood flow (46%; 16%, 83%), respectively, and good evidence for increased insulin-stimulated sarcoplasmic GLUT4 translocation (18%; 0%, 39%) vs CON. In contrast, WHEY did not effect GCR (-2%; -25%, 21%) and attenuated HbA1c lowering (14%; 5%, 24%) vs CON. KDPWHE effects on basal glutathione in erythrocytes and skeletal muscle were unclear, but in muscle there was very-good evidence for large increases in oxidised peroxiredoxin isoform 2 (oxiPRX2) (19%; 2.2%, 35%) and good evidence for lower GPx1 concentrations (-40%; -4.3%, -63%) vs CON; insulin stimulation, however, attenuated the basal oxiPRX2 response (4%; -16%, 24%), and increased GPx1 (39%; -5%, 101%) and SOD1 (26%; -3%, 60%) protein expression. Effects of KDPWHE on oxiPRX3 and NRF2 content, phosphorylation of capillary eNOS and insulin-signalling proteins upstream of GLUT4 translocation AktSer437 and AS160Thr642 were inconclusive, but there was good evidence for increased IRSSer312 (41%; 3%, 95%), insulin-stimulated NFκB-DNA binding (46%; 3.4%, 105%), and basal PAK-1Thr423/2Thr402 phosphorylation (143%; 66%, 257%) vs WHEY. Our findings provide good evidence to suggest that dietary supplementation with a novel edible keratin protein in humans with T2DM may increase glucose clearance and modify skeletal-muscle tissue redox and insulin sensitivity within systems involving peroxiredoxins, antioxidant expression, and glucose uptake.

13. Food Funct. 2023 Aug 29;14(17):7959-7968. doi: 10.1039/d3fo02612d. The effect of microencapsulated watermelon rind (Citrullus lanatus) and beetroot (Beta vulgaris L.) ingestion on ischemia/reperfusion-induced endothelial dysfunction: a randomised clinical trial. Volino-Souza M(1)(2), Oliveir

Cisplatin is a chemotherapeutic drug that induces nephrotoxicity through inflammation and oxidative stress. Hydrogen sulfide (H2S) and nitric oxide (NO) are gaseous signaling molecules with cytoprotective potential in renal damage. The current study evaluated the nephroprotective potential of sodium hydrosulfide (NaHS), an H2S donor, and L-arginine, a NO precursor, against cisplatin-induced nephrotoxicity, even under NO synthase inhibition. Wistar rats were treated with cisplatin (5 mg/kg) to induce nephrotoxicity while administered with L-NG-nitro-L-arginine methyl (L-NAME), NaHS, and L-arginine either alone or in combination for 28 days. Renal function was assessed by monitoring various parameters, including body weight and urinary flow. Moreover, H2S, NO, creatinine level and clearance, blood urea nitrogen (BUN), electrolyte levels, and oxidative stress were monitored in body fluids. The findings revealed that L-NAME exacerbated cisplatin-induced nephrotoxicity, which was evident from reduced weights (P < .0001) and elevated urine output (P < .01), H2S (P < .0001), NO (P < .0001), creatinine (P < .01), and BUN (P < .0001) levels, along with reduced sodium and potassium (P < .0001) and elevated oxidative stress markers (P < .001) in plasma compared with healthy rats. The treatment with NaHS and L-arginine markedly protected against L-NAME + cisplatin-induced nephrotoxicity as the parameters were reinstated, including urine output (P < .01), H2S (P < .01), NO (P < .0001), creatinine (P < .05), and BUN (P < .01) levels compared with L-NAME + cisplatin rats. Moreover, coadministration of NaHS + L-arginine restored the sodium (P < .0001) and potassium (P < .01) levels in plasma and mitigated oxidative stress (P < .05). The results suggested that H2S and NO mitigated L-NAME + cisplatin-induced nephrotoxicity by ameliorating the L-NAME + cisplatin-induced oxidative stress. SIGNIFICANCE STATEMENT: The therapeutic validation of the mentioned agents would be beneficial in the treatment of renal dysfunction.

Myeloid-derived suppressor cells (MDSCs) play a crucial role in immunosuppression in tumor-bearing hosts. MDSCs express arginase-I and indoleamine 2,3-dioxygenase; they suppress T-cell function by reducing the levels of l-arginine and l-tryptophan, respectively. We examined the anticancer effects of supplementation of these amino acids in CT26 colon carcinoma-bearing mice. Oral supplementation of l-arginine or l-tryptophan (30 mg/mouse) did not affect tumor growth, whereas oral supplementation of d-arginine was lethal. Supplementation of l-arginine showed a tendency to augment the efficacy of cyclophosphamide (CP). CP reduced the proportions of granulocytic MDSCs and increased the proportions of monocytic MDSCs in the spleen and tumor tissues of CT26-bearing mice. l-Arginine supplementation alone did not affect the MDSC subsets. CP treatment tended to reduce the plasma levels of l-arginine in CT26-bearing mice and significantly increased the number of tumor-infiltrating CD8+ T cells. In addition, l-arginine supplementation significantly increased the proportions of tumor peptide-specific CD8+ T cells in draining lymph nodes. Importantly, additional supplementation of l-arginine significantly increased the number of cured mice that were treated with CP and anti-PD-1 antibody. Totally, l-arginine supplementation shows promise for boosting the therapeutic efficacy of chemoimmunotherapy. © 2020 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

In the pulmonary vasculature there is clearance of endothelin-1 from the circulation mediated by endothelin ETB receptors. This study explored the haemodynamic effects of endothelin-1 and its clearance in the pulmonary and hindquarter vasculature in anaesthetised rats. Carotid and pulmonary artery pressures and pulmonary and hindquarter blood flows were measured. In each rat, a single endothelin-1 or sarafotoxin S6C cumulative dose-response curve was generated with or without antagonist pretreatment (i.v.). Endothelin-1 caused an acute fall in MAP and rise in hindquarter vascular conductance (HVC) followed by a marked increase in MAP at 5 min with falls in HVC and pulmonary vascular conductance (PVC). Bosentan (10, 20 & 30 mg/kg) pretreatment caused dose-dependent inhibition of the MAP increase as well as PVC and HVC decreases to endothelin-1. Similarly, macitentan (30 mg/kg) or ambrisentan (10 mg/kg) caused significant block of responses to endothelin-1. Sarafotoxin S6C caused acute falls in MAP and increases in HVC and then small falls in PVC and HVC, all prevented by pretreatment with ETB antagonist BQ788 (1 mg/kg). Pretreatment with BQ788 enhanced endothelin-1 potency by 2.5-fold in PVC and 2.4-fold in HVC. With BQ788 and bosentan, the fall in HVC response was completely blocked, but there were residual MAP rises and PVC falls at the highest endothelin-1 dose. Our work confirms the role of ETB receptors in the pulmonary vasculature that decrease the circulating levels of endothelin-1. This has important consequences in selecting an appropriate ETA and ETB dual receptor antagonist to effectively block endothelin-1-mediated pulmonary vasoconstriction.

AIM: The objective was to evaluate the effects of nitric oxide (NO) and hydrogen sulfide (H2S) donors and possible interactions between these two systems in modulating gastric function. METHODS: Mice received saline, sodium nitroprusside (SNP), or sodium hydrosulfite (NaHS), and after 1 h, the animals were killed for immunofluorescence analysis of CSE or eNOS expressions, respectively. Other groups received saline, SNP, NaHS, Lawesson's reagent (H2S donor), PAG + SNP, L-NAME, L-NAME + NaHS, or L-NAME + Lawesson's reagent. Then, the gastric secretions (mucous and acid), gastric blood flow, gastric defense against ethanol, and gastric motility (gastric emptying and gastric contractility) were evaluated. RESULTS: SNP and NaHS increased the expression of CSE or eNOS, respectively. SNP or Lawesson's reagent did not alter gastric acid secretion but increased mucus production, and these effects reverted with PAG and L-NAME treatment, respectively. SNP or NaHS increased gastric blood flow and protected the gastric mucosa against ethanol injury, and these effects reverted with PAG and L-NAME treatments, respectively. SNP delayed gastric emptying when compared with saline, and PAG partially reversed this effect. NaHS accelerate gastric emptying, and L-NAME partially reversed this effect. SNP and NaHS alone induced gastric fundus and pylorus relaxation. However, pretreatment with PAG or L-NAME reversed these relaxant effects only in the pylorus but not in the gastric fundus. CONCLUSION: NO and H2S interact in gastric physiological functions, and this "cross-talk" is important in the control of mucus secretion, gastric blood flow, gastric mucosal defense, and gastric motility, but not in the control of basal gastric acid secretion.

BACKGROUND: Chronic supplementation with L-citrulline plus L-arginine has been shown to exhibit anti-atherosclerotic effects. However, the short-term action of this combination on the nitric oxide (NO)-cGMP pathway remains to be elucidated. The objective of the present study was to investigate the acute effects of a combination of oral L-citrulline and L-arginine on plasma L-arginine and NO levels, as well as on blood circulation. METHODS: Rats or New Zealand white rabbits were treated orally with L-citrulline, or L-arginine, or a combination of each at half dosage. Following supplementation, plasma levels of L-arginine, NOx, cGMP and changes in blood circulation were determined sequentially. RESULTS: L-Citrulline plus L-arginine supplementation caused a more rapid increase in plasma L-arginine levels and marked enhancement of NO bioavailability, including plasma cGMP concentrations, than with dosage with the single amino acids. Blood flow in the central ear artery in rabbits was also significantly increased by L-citrulline plus L-arginine administration as compared with the control. CONCLUSION: Our data show for the first time that a combination of oral L-citrulline and L-arginine effectively and rapidly augments NO-dependent responses at the acute stage. This approach may have clinical utility for the regulation of cardiovascular function in humans.

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) synthesis inhibitor and pro-inflammatory factor. We investigated the role of ADMA in rat gastric mucosa compromised through 30 min of gastric ischemia (I) and 3 h of reperfusion (R). These I/R animals were pretreated with ADMA with or without the combination of L-arginine, calcitonin gene-related peptide (CGRP) or a small dose of capsaicin, all of which are known to afford protection against gastric lesions, or with a farnesoid X receptor (FXR) agonist, GW 4064, to increase the metabolism of ADMA. In the second series, ADMA was administered to capsaicin-denervated rats. The area of gastric damage was measured with planimetry, gastric blood flow (GBF) was determined by H2-gas clearance, and plasma ADMA and CGRP levels were determined using ELISA and RIA. ADMA significantly increased I/R-induced gastric injury while significantly decreasing GBF, the luminal NO content, and the plasma level of CGRP. This effect of ADMA was significantly attenuated by pretreatment with CGRP, L-arginine, capsaicin, or a PGE2 analogue. In GW4064 pretreated animals, the I/R injury was significantly reduced and this effect was abolished by co-treatment with ADMA. I/R damage potentiated by ADMA was exacerbated in capsaicin-denervated animals with a further reduction of CGRP. Plasma levels of IL-10 were significantly decreased while malonylodialdehyde (MDA) and plasma TNF-α contents were significantly increased by ADMA. In conclusion, ADMA aggravates I/R-induced gastric lesions due to a decrease of GBF, which is mediated by a fall in NO and CGRP release, and the enhancement of lipid peroxidation and its pro-inflammatory properties.

BACKGROUND: Long-term inhibition of nitric oxide synthase by L-arginine analogues such as N(ω)-nitro-l-arginine methyl ester (L-NAME) has been shown to induce senescence in vitro and systemic hypertension and arteriosclerosis in vivo. We previously reported that plasminogen activator inhibitor-1 (PAI-1)-deficient mice (PAI-1(-/-)) are protected against L-NAME-induced pathologies. In this study, we investigated whether a novel, orally active PAI-1 antagonist (TM5441) has a similar protective effect against L-NAME treatment. Additionally, we studied whether L-NAME can induce vascular senescence in vivo and investigated the role of PAI-1 in this process. METHODS AND RESULTS: Wild-type mice received either L-NAME or L-NAME and TM5441 for 8 weeks. Systolic blood pressure was measured every 2 weeks. We found that TM5441 attenuated the development of hypertension and cardiac hypertrophy compared with animals that had received L-NAME alone. Additionally, TM5441-treated mice had a 34% reduction in periaortic fibrosis relative to animals on L-NAME alone. Finally, we investigated the development of vascular senescence by measuring p16(Ink4a) expression and telomere length in aortic tissue. We found that L-NAME increased p16(Ink4a) expression levels and decreased telomere length, both of which were prevented with TM5441 cotreatment. CONCLUSIONS: Pharmacological inhibition of PAI-1 is protective against the development of hypertension, cardiac hypertrophy, and periaortic fibrosis in mice treated with L-NAME. Furthermore, PAI-1 inhibition attenuates the arterial expression of p16(Ink4a) and maintains telomere length. PAI-1 appears to play a pivotal role in vascular senescence, and these findings suggest that PAI-1 antagonists may provide a novel approach in preventing vascular aging and hypertension.

Nitric oxide (NO) derived from endothelial nitric oxide synthase (eNOS) is a potent vasodilator and signaling molecule that plays essential roles in neovascularization. During limb ischemia, decreased NO bioavailability occurs secondary to increased oxidant stress, decreased L-arginine and tetrahydrobiopterin. This study tested the hypothesis that dietary cosupplementation with tetrahydrobiopterin (BH4), L-arginine and vitamin C acts synergistically to decrease oxidant stress, increase NO and thereby increase blood flow recovery after hindlimb ischemia. Rats were fed normal chow, chow supplemented with BH4 or L-arginine (alone or in combination) or chow supplemented with BH4 + L-arginine + vitamin C for 1 wk before induction of hindlimb ischemia. In the is-chemic hindlimb, cosupplementation with BH4 + L-arginine resulted in greater eNOS and phospho-eNOS (P-eNOS) expression, Ca(2+)-dependent NOS activity and NO concentration in the ischemic calf region (gastrocnemius), as well as greater NO concentration in the region of collateral arteries (gracilis). Rats receiving cosupplementation of BH4 + L-arginine led to greater recovery of foot perfusion and greater collateral enlargement than did rats receiving either agent separately. The addition of vitamin C to the BH4 + L-arginine regimen further increased these dependent variables. In addition, rats given all three supplements showed significantly less Ca(2+)-independent activity, less nitrotyrosine accumulation, greater glutathione (GSH)-to-glutathione disulfide (GSSG) ratio and less gastrocnemius muscle necrosis, on both macroscopic and microscopic levels. In conclusion, co-supplementation with BH4 + L-arginine + vitamin C significantly increased blood flow recovery after hindlimb ischemia by reducing oxidant stress, increasing NO bioavailability, enlarging collateral arteries and reducing muscle necrosis. Oral cosupplementation of BH4, L-arginine and vitamin C holds promise as a biological therapy to induce collateral artery enlargement.

BACKGROUND: Peripheral vascular disease in pre-diabetes may involve altered sympathetically-mediated vascular control. Thus, we investigated if pre-diabetes modifies baseline sympathetic Y(1)-receptor (Y(1)R) and α(1)-receptor (α(1)R) control of hindlimb blood flow (Q(fem)) and vascular conductance (VC). METHODS: Q(fem) and VC were measured in pre-diabetic ZDF rats (PD) and lean controls (CTRL) under infusion of BIBP3226 (Y(1)R antagonist), prazosin (α(1)R antagonist) and BIBP3226+prazosin. Neuropeptide Y (NPY) concentration and Y(1)R and α(1)R expression were determined from hindlimb skeletal muscle samples. RESULTS: Baseline Q(fem) and VC were similar between groups. Independent infusions of BIBP3226 and prazosin led to increases in Q(fem) and VC in CTRL and PD, where responses were greater in PD (p<0.05). The percent change in VC following both drugs was also greater in PD compared to CTRL (p<0.05). As well, Q(fem) and VC responses to combined blockade (BIBP3226+prazosin) were greater in PD compared to CTRL (p<0.05). Interestingly, an absence of synergistic effects was observed within groups, as the sum of the VC responses to independent drug infusions was similar to responses following combined blockade. Finally, white and red vastus skeletal muscle NPY concentration, Y(1)R expression and α(1)R expression were greater in PD compared to CTRL. CONCLUSIONS: For the first time, we report heightened baseline Y(1)R and α(1)R sympathetic control of Q(fem) and VC in pre-diabetic ZDF rats. In support, our data suggest that augmented sympathetic ligand and receptor expression in pre-diabetes may contribute to vascular dysregulation.

BACKGROUND: Many human studies report that nitric oxide (NO) improves sport performance. This is because NO is a potential modulator of blood flow, muscle energy metabolism, and mitochondrial respiration during exercise. L-Citrulline is an amino acid present in the body and is a potent endogenous precursor of L-arginine, which is a substrate for NO synthase. Here, we investigated the effect of oral L-citrulline supplementation on cycling time trial performance in humans. METHODS: A double-blind randomized placebo-controlled 2-way crossover study was employed. Twenty-two trained males consumed 2.4 g/day of L-citrulline or placebo orally for 7 days. On Day 8 they took 2.4 g of L-citrulline or placebo 1 h before a 4-km cycling time trial. Time taken to complete the 4 km cycle, along with power output/VO2 ratio (PO/VO2), plasma nitrite and nitrate (NOx) and amino acid levels, and visual analog scale (VAS) scores, was evaluated. RESULTS: L-Citrulline supplementation significantly increased plasma L-arginine levels and reduced completion time by 1.5 % (p < 0.05) compared with placebo. Moreover, L-citrulline significantly improved subjective feelings of muscle fatigue and concentration immediately after exercise. CONCLUSIONS: Oral L-citrulline supplementation reduced the time take to complete a cycle ergometer exercise trial. TRIAL REGISTRATION: Current Controlled Trials UMIN000014278.

BACKGROUND: The effects of antihypertensive agents on endothelial function have not been fully evaluated in human hypertension and data on the forearm circulation of humans are controversial. The aim of this study was (1) to evaluate the endothelial function in hypertensive patients (2) to investigate whether vitamin C administration has any benefit on the endothelial function and (3) to determine whether treatment with calcium antagonist improves endothelial dysfunction in hypertensive patients. METHODS: The endothelial function was estimated using venous occlusion plethysmography (VOP) in 8 hypertensive patients and 8 healthy volunteers. The patients in the hypertension group were treated with amlodipine, then examined again. The change of forearm blood flow (FBF) was measured with acetylcholine infusion through brachial artery and also with intra-arterial vitamin C. RESULTS: Forearm blood flow response to acetylcholine was significantly enhanced with intra-arterial infusion of vitamin C in hypertensive group before antihypertensive treatment. Co-infusion of L-NMMA, an inhibitor of nitric oxide synthase, blunted forearm blood flow response to acetylcholine. After treatment with amlodipine for 2 months in hypertensive group, endothelium-dependent vasorelaxation to acetylcholine was significantly improved compared to pretreatment, and vitamin C did not affect the improved endothelial function by amlodipine treatment. CONCLUSION: Vitamin C (acutely) and amlodipine (chronically) improved endothelial function in hypertensive patients. These results suggest that increased oxidative stress, at least in part, may be involved in the decreased endothelial function in hypertension.

The term "glycation compounds" comprises a wide range of structurally diverse compounds that are formed endogenously and in food via the Maillard reaction, a chemical reaction between reducing sugars and amino acids. Glycation compounds produced endogenously are considered to contribute to a range of diseases. This has led to the hypothesis that glycation compounds present in food may also cause adverse effects and thus pose a nutritional risk to human health. In this work, the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) summarized data on formation, occurrence, exposure and toxicity of glycation compounds (Part A) and systematically assessed potential associations between dietary intake of defined glycation compounds and disease, including allergy, diabetes, cardiovascular and renal disease, gut/gastrotoxicity, brain/cognitive impairment and cancer (Part B). A systematic search in Pubmed (Medline), Scopus and Web of Science using a combination of keywords defining individual glycation compounds and relevant disease patterns linked to the subject area of food, nutrition and diet retrieved 253 original publications relevant to the research question. Of these, only 192 were found to comply with previously defined quality criteria and were thus considered suitable to assess potential health risks of dietary glycation compounds. For each adverse health effect considered in this assessment, however, only limited numbers of human, animal and in vitro studies were identified. While studies in humans were often limited due to small cohort size, short study duration, and confounders, experimental studies in animals that allow for controlled exposure to individual glycation compounds provided some evidence for impaired glucose tolerance, insulin resistance, cardiovascular effects and renal injury in response to oral exposure to dicarbonyl compounds, albeit at dose levels by far exceeding estimated human exposures. The overall database was generally inconsistent or inconclusive. Based on this systematic review, the SKLM concludes that there is at present no convincing evidence for a causal association between dietary intake of glycation

BACKGROUND: There is a consistent association between exposure to air pollution and elevated rates of cardiopulmonary illnesses. As public health activities emphasize the paramount need to reduce exposure, it is crucial to examine strategies like the antioxidant diet that could potentially protect individuals who are unavoidably exposed. METHODS: A systematic search was performed in PubMed/Medline, EMBASE, CENTRAL, and ClinicalTrials.gov up to March 31, 2023, for clinical trials assessing dietary supplements against cardiovascular (blood pressure, heart rate, heart rate variability, brachial artery diameter, flow-mediated dilation, and lipid profile) or pulmonary outcomes (pulmonary function and airway inflammation) attributed to air pollution exposure. RESULTS: After reviewing 4681 records, 18 studies were included. There were contradictory findings on the effects of fish oil and olive oil supplementations on cardiovascular outcomes. Although with limited evidence, fish oil offered protection against pulmonary dysfunction induced by pollutants. Most studies on vitamin C did not find protective cardiovascular effects; however, the combination of vitamin C and E offered protective effects against pulmonary dysfunction but showed conflicting results for cardiovascular outcomes. Other supplements like sulforaphane, L-arginine, n-acetylcysteine, and B vitamins showed potential beneficial effects but need further research due to the limited number of existing trials. CONCLUSIONS: Although more research is needed to determine the efficacy and optimal dose of anti-inflammatory and antioxidant dietary supplements against air pollution toxicity, this low-cost preventative strategy has the potential to offer protection against outcomes of air pollution exposure. Copyright: © 2024 Ilaghi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

BACKGROUND: Acute ischemic stroke (AIS) is a leading cause of death and disability. AIS is caused by an embolus or thrombus that restricts blood flow to the brain tissue. Despite intravenous thrombolysis and endovascular thrombectomy, a substantial number of patients do not achieve effective reperfusion. Argatroban, a direct thrombin inhibitor, can potentially improve neurological outcomes in AIS patients. However, there are conflicting results in the medical literature regarding the efficacy and safety of argatroban in this context. OBJECTIVE: This study aims to evaluate the efficacy and safety of argatroban as monotherapy or adjunct therapy for acute ischemic stroke. METHODS: Five major databases (PubMed, Embase, Scopus, Web of Science, and Cochrane Library) were searched for randomized controlled trials (RCTs) that compared the efficacy and safety of using argatroban alone or in combination with recombinant tissue plasminogen activator (r-TPA) in the management protocol of the AIS. We used Review Manager Software (RevMan 5.4.1) for data analysis. RESULTS: We included 1393 patients from eight RCTs (of them, 726 were treated with argatroban alone or combined with r-TPA, while 667 received the placebo, standard therapy (standard treatments based on current guidelines including antihypertensive, antiplatelet agents, and statins) or endovascular r-TPA). Neither argatroban vs control nor argatroban with r-TPA vs r-TPA showed significant difference regarding the activity in daily living; (SMD= 1.69, 95% CI [-0.23, 3.61]; p = 0.09), (SMD= 0.99, 95% CI [-0.88, 2.86]; p = 0.30), respectively. Also, there was no significant difference in the National Institutes of Health Stroke Scale (NIHSS) score at seven days, the number of patients achieving modified Rankin Scale (mRS) of 0-1 or 0-2 at 90 days (p > 0.05). Argatroban did not significantly increase the risk of adverse events or symptomatic intracranial hemorrhage (ICH), or major systemic bleeding compared to control or r-TPA (p > 0.05) CONCLUSIONS: Argatroban does not demonstrate superior efficacy compared to placebo or standard therapy in terms of ADL, NIHSS and mRS outcomes. Importantly, argatroban does not significa

BACKGROUND/AIM OF THE STUDY: L-Arginine (L-Arg)/Nitric Oxide (NO) system is involved in the pathophysiology of relevant Obstetric conditions. This review aims at summarizing the effects of L-Arg supplementation in pregnancy looking at safety and efficacy. METHODS: We conducted a systematic review of the literature utilizing PubMed for studies published from inception to September 2022. The search included human and animal studies where L-Arg was supplemented pre-conceptionally or during pregnancy, by either oral or intravenous route. The main perinatal outcomes were focused. RESULTS: Among 1028 publications, 51 studies were eligible for inclusion, 25 were performed in women, and the remnant in animals. Compared to controls/placebo, the supplementation with L-Arg reduced the development of pre-eclampsia (four studies), decreased blood pressure, and reduced the need for antihypertensive drugs in women with Hypertensive Disorders of Pregnancy (HDP, eight studies). In women carrying growth retarded fetuses, L-Arg improved fetoplacental circulation, birth weight and neonatal outcomes (five studies), while in the case of threatened preterm birth, L-Arg reduced uterine contractions (two studies). In several animal species, L-Arg supplementation in pregnancy improved reproductive performance by increasing the litter number and size. Moreover, in pre-eclamptic and metabolic syndrome experimental models, maternal hypertension and fetal growth were improved. CONCLUSION: L-Arg displays biological activities in pregnancies complicated by HDP and growth restriction, both in women and animal models. L-Arg administration is safe and could be a candidate as an intervention beneficial to maternal and fetal outcomes, at least in moderate clinical disorders.

Gonzalez, AM and Trexler, ET. Effects of citrulline supplementation on exercise performance in humans: A review of the current literature. J Strength Cond Res 34(5): 1480-1495, 2020-L-citrulline, a nonessential amino acid found primarily in watermelon, has recently garnered much attention for its potential to augment L-arginine bioavailability, nitric oxide production, and exercise performance. Over the past decade, L-citrulline has received considerable scientific attention examining potentially ergogenic properties for both aerobic and anaerobic exercise performance. Thus, the purpose of this article is to summarize the theoretical rationale behind L-citrulline supplementation and to comprehensively review the available scientific evidence assessing the potential ergogenic value of L-citrulline supplementation on vascular function and exercise performance in humans. In addition, research that has investigated the potential synergistic effects of L-citrulline with other dietary ingredients (e.g., arginine, antioxidants, nitrates, and branched-chain amino acids) is reviewed. Oral L-citrulline and citrulline malate supplementation have shown to increase plasma citrulline and arginine concentrations, along with total nitrate and nitrite concentrations. Although blood flow enhancement is a proposed mechanism for the ergogenic potential of L-citrulline, evidence supporting acute improvements in vasodilation and skeletal muscle tissue perfusion after supplementation is scarce and inconsistent. Nevertheless, several studies have reported that L-citrulline supplementation can enhance exercise performance and recovery. Given the positive effects observed from some investigations, future studies should continue to investigate the effects of both acute and chronic supplementation with L-citrulline and citrulline malate on markers of blood flow and exercise performance and should seek to elucidate the mechanism underlying such effects.

BACKGROUND: Sepsis is life-threatening organ dysfunction because of a dysregulated host response to infection. Disturbed microvascular blood flow is associated with excess mortality and is a potential future target for interventions. This review addresses the evidence for pharmacological manipulation of the microcirculation in sepsis assessed by techniques that evaluate the sublingual microvasculature. METHODS: Systematic review using a published protocol. Eligibility criteria were studies of septic patients published from January 2000 to February 2018. Interventions were drugs aimed at improving perfusion. Outcome was improvement in microvascular flow using orthogonal polarization spectral, sidestream dark field, or incident dark field imaging (Grades of Recommendation, Assessment, Development, and Evaluation criteria used). RESULTS: Two thousand six hundred and six articles were screened and 22 included. (6 randomized controlled trials, 12 interventional, 3 observational, and 1 pilot, n = 572 participants). Multiple measurement techniques were described, including: automated analyses, subjective, and composite scoring systems. Norepinephrine was not found to improve microvascular flow (low-grade evidence, n = 6 studies); except in chronic hypertension (low, n = 1 study). Addition of arginine vasopressin or terlipressin to norepinephrine maintained flow while decreasing norepinephrine requirements (high, n = 2 studies). Neither dobutamine nor glyceryl trinitrate consistently improved flow (low, n = 6 studies). A single study (n = 40 participants) demonstrated improved flow with levosimendan (high). In a risk of bias assessment 16/16 interventional, pilot and observational studies were found to be high risk. CONCLUSIONS: There is no robust evidence to date that any one agent can reproducibly lead to improved microvascular flow. Furthermore, no study demonstrated outcome benefit of one therapeutic agent over another. Updated consensus guidelines could improve comparable reporting of measurements and reduce bias, to enable meaningful comparisons around the effects of individual pharmacological agents. Influence of Diet in Multiple Sclerosis: A Systematic Review.