Effect of L-Citrulline Supplementation on Blood Pressure: a Systematic Review and Meta-Analysis of Clinical Trials

Assessment of Registered Clinical Trial Designs: Comparison of L-Arginine and/or L-Citrulline Interventions for Hypertension

BACKGROUND

L-Arginine (Arg) is an essential amino acid and a precursor for the synthesis of vascular nitric oxide, while L-Citrulline is a non-essential amino acid substrate for increasing L-arginine. Both L-arginine and L-Citrulline in translational studies may acutely lower the blood pressure. Current meta-analysis for L-arginine or L-Citrulline interventions in blood pressure have identified significant heterogeneity. Clinical trial evidence for L-arginine or L-Citrulline in chronic blood pressure reduction in the general population requires an examination of trial designs, as not all translational studies may have influenced vascular reactivity. Our aims are to explore whether L-arginine and L-citrulline intervention trials in chronic blood pressure consider standardized end points relevant to the general adult populations.

METHODS

A step-wise search on clinicaltrials.gov, the U.S. Library of Medicine registry for clinical trials, was performed including the following keyword search parameters: "completed" "L-Citrulline" "L-arginine" trial", and "adults", involving "blood pressure" reduction as a primary end point in adult humans.

RESULTS

Of the forty-four completed trials, only five were included for analysis. Following the careful evaluation of trial design, we observed heterogeneity across participant inclusion criteria (population sample size, age range, sex), interventional design (dosages, duration), and primary outcomes, measured with respect to changes in diastolic or systolic blood pressure.

CONCLUSION

In conclusion, there is a lack of robust trial design evidence to suggest that L-arginine or L-Citrulline, based on current RCTs in the general population, have an overall positive effect on vascular endothelial reactivity and a beneficial chronic blood pressure-lowering effect. Indeed, conclusions drawn from human meta-analysis studies have been heterogenous between studies, which may be attributed to study design heterogeneity, including differences in sample population, age, and blood pressure at the time of entry. Inconsistencies in the study design poses a challenge for systematic reviews and meta-analysis to accurately assess the effect size and impact of L-arginine or L-citrulline on both systolic and diastolic blood pressure.

The Role of Diet in the Prevention of Hypertension and Management of Blood Pressure: An Umbrella Review of Meta-Analyses of Interventional and Observational Studies

High blood pressure (BP) is a major pathological risk factor for the development of several cardiovascular diseases. Diet is a key modifier of BP, but the underlying relationships are not clearly demonstrated. This is an umbrella review of published meta-analyses to critically evaluate the wide range of dietary evidence from bioactive compounds to dietary patterns on BP and risk of hypertension. PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials were searched from inception until October 31, 2021, for relevant meta-analyses of randomized controlled trials or meta-analyses of observational studies. A total of 175 publications reporting 341 meta-analyses of randomized controlled trials (145 publications) and 70 meta-analyses of observational studies (30 publications) were included in the review. The methodological quality of the included publications was assessed using Assessment of Multiple Systematic Reviews 2 and the evidence quality of each selected meta-analysis was assessed using NutriGrade. This umbrella review supports recommended public health guidelines for prevention and control of hypertension. Dietary patterns including the Dietary Approaches to Stop Hypertension and the Mediterranean-type diets that further restrict sodium, and moderate alcohol intake are advised. To produce high-quality evidence and substantiate strong recommendations, future research should address areas where the low quality of evidence was observed (for example, intake of dietary fiber, fish, egg, meat, dairy products, fruit juice, and nuts) and emphasize focus on dietary factors not yet conclusively investigated.

Metabolomics Applied to Cord Serum in Preeclampsia Newborns: Implications for Neonatal Outcomes

Preeclampsia (PE) is one of the leading causes of maternal and perinatal morbidity and mortality. However, it is still uncertain how PE affects neonate metabolism. We conducted an untargeted metabolomics analysis of cord blood to explore the metabolic changes in PE neonates. Umbilical cord serum samples from neonates with preeclampsia (n = 29) and non-preeclampsia (non-PE) (n = 32) pregnancies were analyzed using the UHPLC-QE-MS metabolomic platform. Different metabolites were screened, and pathway analysis was conducted. A subgroup analysis was performed among PE neonates to compare the metabolome between appropriate-for-gestational-age infants (n = 21) and small-for-gestational-age (SGA) infants (n = 8). A total of 159 different metabolites were detected in PE and non-PE neonates. Creatinine, N4-acetylcytidine, sphingomyelin (D18:1/16:0), pseudouridine, uric acid, and indolelactic acid were the most significant differential metabolites in the cord serum of PE neonates. Differential metabolite levels were elevated in PE neonates and were involved in the following metabolic pathways: glycine, serine, and threonine metabolism; sphingolipid, glyoxylate, and dicarboxylate metabolism; and arginine biosynthesis. In PE neonates, SGA neonates showed increased levels of hexacosanoyl carnitine and decreased abundance of 3-hydroxybutyric acid and 3-sulfinoalanine. Taurine-related metabolism and ketone body-related pathways were mainly affected. Based on the UHPLC-QE-MS metabolomics analysis, we identified the metabolic profiles of PE and SGA neonates. The abundance of metabolites related to certain amino acid, sphingolipid, and energy metabolism increased in the umbilical cord serum of PE neonates.

l-Citrulline supplementation during pregnancy improves perinatal and postpartum maternal vascular function in a mouse model of preeclampsia

Preeclampsia is a spontaneously occurring pregnancy complication diagnosed by new-onset hypertension and end-organ dysfunction with or without proteinuria. This pregnancy-specific syndrome contributes to maternal morbidity and mortality and can have detrimental effects on fetal outcomes. Preeclampsia is also linked to increased risk of maternal cardiovascular disease throughout life. Despite intense investigation of this disorder, few treatment options are available. The aim of this study was to investigate the potential therapeutic effects of maternal l-citrulline supplementation on pregnancy-specific vascular dysfunction in the male C57BL/6J × female C57BL/6J C1q-/- preeclampsia-like mouse model. l-Citrulline is a nonessential amino acid that is converted to l-arginine to promote smooth muscle and blood vessel relaxation and improve nitric oxide (NO)-mediated vascular function. To model a preeclampsia-like pregnancy, female C57BL/6J mice were mated to C1q-/- male mice, and a subset of dams was supplemented with l-citrulline throughout pregnancy. Blood pressure, systemic vascular glycocalyx, and ex vivo vascular function were investigated in late pregnancy, and postpartum at 6 and 10 mo of age. Main findings show that l-citrulline reduced blood pressure, increased vascular glycocalyx volume, and rescued ex-vivo vascular function at gestation day 17.5 in this preeclampsia-like model. The vascular benefit of l-citrulline also extended postpartum, with improved vascular function and glycocalyx measures at 6 and 10 mo of age. l-Citrulline-mediated vascular improvements appear, in part, attributable to NO pathway signaling. Taken together, l-citrulline supplementation during pregnancy appears to have beneficial effects on maternal vascular health, which may have translational implications for improved maternal cardiovascular health.

Citrulline, Biomarker of Enterocyte Functional Mass and Dietary Supplement. Metabolism, Transport, and Current Evidence for Clinical Use

L-Citrulline is a non-essential but still important amino acid that is released from enterocytes. Because plasma levels are reduced in case of impaired intestinal function, it has become a biomarker to monitor intestinal integrity. Moreover, oxidative stress induces protein citrullination, and antibodies against anti-citrullinated proteins are useful to monitor rheumatoid diseases. Citrullinated histones, however, may even predict a worse outcome in cancer patients. Supplementation of citrulline is better tolerated compared to arginine and might be useful to slightly improve muscle strength or protein balance. The following article shall provide an overview of L-citrulline properties and functions, as well as the current evidence for its use as a biomarker or as a therapeutic supplement.

The Effects of Magnesium Supplementation on Lipid Profile Among Type 2 Diabetes Patients: a Systematic Review and Meta-analysis of Randomized Controlled Trials

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the effects of magnesium (Mg) supplementation on the lipid profile in type 2 diabetes (T2DM) patients. Web of Science, Scopus, PubMed, and Embase databases were searched to infinity until 30 January 2020. Weighted mean differences (WMD) were pooled using a random-effects model. Heterogeneity, sensitivity analysis, and publication bias were reported using standard methods. The pooled analysis of 12 randomized controlled trial s indicated that Mg administration led to significant reduction of serum low-density lipoprotein (LDL) levels (p = 0.006). However, our results revealed that Mg supplementation did not have any effect on triglycerides (TG), total cholesterol (TC), and high-density lipoprotein (HDL) serum concentrations among T2DM patients in comparison with the control group. Subgroup analysis based on duration of study suggested that more than 12 weeks of Mg supplementation significantly decreased the serum TC levels (p = 0.002). Subgroup analysis comparing the dose of intervention indicated that Mg supplementation less than 300 mg significantly decreased the serum LDL concentrations (p < 0.001), while more than 300 mg of Mg supplementation significantly increased the serum HDL levels (p = 0.026). In a subgroup analysis comparing the type of intervention, it displayed that inorganic Mg supplementation decreased the LDL (p < 0.001) and TC (p = 0.003) levels, while organic Mg supplementation showed no difference. Mg supplementation has a beneficial effect on lowering LDL level in T2DM patients. However, we have to note that any research performed so far is not sufficient for making robust guidelines to use Mg supplementation in clinical practice.

The Effects of Magnesium Supplementation on Blood Pressure and Obesity Measure Among Type 2 Diabetes Patient: a Systematic Review and Meta-analysis of Randomized Controlled Trials

In this study, we aimed to systematically review the literature to evaluate the effects of magnesium (Mg) supplementation on blood pressure (BP) and obesity measure among patients with type 2 diabetes mellitus (T2DM). Major electronic databases of Web of Science, the Cochrane library, PubMed, and Scopus were searched completely from the inception until 15 October 2019 to identify randomized clinical trials (RCTs) pertaining to the topic of interest. All outcomes were pooled using a random-effects model and expressed as weighted mean differences (WMD) with 95% confidential intervals (CI). Heterogeneity, sensitivity analysis, and publication bias were also assessed using standard methods. The pooled analysis of five RCTs showed that Mg supplementation did not affect body weight (WMD: - 0.01 kg, 95% CI: - 0.36 to 0.33), BMI (WMD: - 0.07, 95% CI: - 0.18 to 0.04), and waist circumference (WMD: 0.12, 95% CI: - 1.24 to 1.48) in T2DM patients compared to the control groups of the patients who received placebo. However, pooling seven RCTs together showed significant reduction of systolic blood pressure (WMD: - 5.78 mmHg, 95% CI: - 11.37 to - 0.19) and diastolic blood pressure (WMD: - 2.50 mmHg, 95% CI: - 4.58 to - 0.41) in T2DM patients. Furthermore, subgroup analysis by dose of intervention, intervention duration, and type of intervention suggested that Mg supplementation for > 12 weeks, in doses higher than 300 mg/day or inorganic forms, could significantly decrease both systolic and diastolic BP in T2DM patients. Based on the findings, Mg supplementation has beneficial effects on BP in type 2 diabetes patients independent of body weight status. However, further investigations are needed to provide more reliable evidences.

Effects of artichoke on blood pressure: A systematic review and meta-analysis

PURPOSE

Clinical trials considering the effects of artichoke supplementation on blood pressure have yielded different and contradictory outcomes. Thus, a systematic review and meta-analysis were performed to assess effects of artichoke administration on blood pressure.

METHODS

Related studies were detected by searching the Cochrane Library, PubMed, Embase and Scopus databases up to 15 March 2020. Weighted Mean Differences (WMD) were pooled using a random-effects model. Heterogeneity, sensitivity analyses, and publication bias were evaluated using standard methods.

RESULTS

Pooled analysis of eight randomized controlled trials revealed that artichoke supplementation did not have an effect on systolic blood pressure (SBP), (WMD: -0.77 mmHg, 95 % CI: -2.76 to 1.22) or diastolic blood pressure (DBP) (WMD: -0.11 mmHg, 95 % CI: -1.72 to 1.50) when compared to the placebo group. However, subgroup analyses based on health status suggested that artichoke administration among hypertensive patients may significantly reduce SBP (WMD: -3.19 mmHg, 95 % CI: -3.32 to -3.06) and DBP (WMD: -2.33 mmHg, 95 % CI: -2.23 to -2.43), but no such reduction was found in NAFLD patients. Furthermore, our results indicated that artichoke supplementation for 12 weeks led to a significantly decreased DBP (WMD: -2.33 mmHg, 95 % CI: -2.43 to -2.23), but 8 weeks of intervention did not (WMD: 0.80 mmHg, 95 % CI: -1.06 to 2.66).

CONCLUSION

Artichoke supplementation may potentially lead to SBP and DBP reduction in hypertensive patients. In addition, artichoke supplementation for 12 weeks may significantly improve DBP.

The effect of barberry (Berberis vulgaris L.) supplementation on blood pressure: A systematic review and meta-analysis of the randomized controlled trials

OBJECTIVE

We identified and quantified the results of randomized clinical trials by examining the effect of barberry supplementation on blood pressure.

METHODS

We conducted a comprehensive search in the medical bibliographic database up to May 2020 on randomized clinical trials investigating the effect of barberry supplementation on adult blood pressure. Intensive literature searches and data extraction according to a prefixed scheme was performed independently by two investigators.

RESULTS

Through 5 randomized clinical trial studies, 350 subjects with 175 cases for the intervention group and 175 cases for control group were included in our study. The intervention period ranged from 4 to 12 weeks. In general, barberry supplementation did not have a significant effect on systolic blood pressure (WMD: -4.15 mmHg; 95 % CI: -10.3, 1.99, P = 0.185) and diastolic blood pressure (WMD: -1.22 mmHg; 95 % CI: -6.26, 3.82, P = 0.635). Our study was heterogeneous and subgroup analysis did not eliminate heterogeneity.

CONCLUSION

Totally, based on this study, we cannot conclude that barberry supplementation has beneficial effects on blood pressure. Also, all included studies had limitations such as different in geographical situations, Dietary of participants, health conditions, and pharmacological forms of berberis. Therefore, further study in this area is recommended.

Effects of Cynara scolymus L. on glycemic indices:A systematic review and meta-analysis of randomized clinical trials

OBJECTIVES

Cynara scolymus L. (common artichoke) and its products have been considered as potential phytotherapeutic agents for various conditions, such as cardiovascular, hepatic and gastric diseases, among others. Until now, the effects of artichoke and artichoke products administration on glycemic indices have not been sufficiently appraised. The present study evaluated the effects of artichoke and artichoke products administration on the glycemic indices.

METHODS

Clinical trials were identified in the Cochrane Library, PubMed, Embase and Scopus databases; to infinity until 15 March 2020. Weighted mean differences (WMD) were pooled using a random-effects model. Heterogeneity, sensitivity analysis and publication bias were reported using standard methods.

RESULTS

Pooled analysis of nine Randomized controlled trials (RCTs), demonstrated that the administration of artichoke and artichoke products led to a significant reduced fasting blood sugar (FBS) (WMD: -5.28 mg/dl, 95 % CI: -8.95, -1.61; p = 0.005). However, other glycemic indeces including fasting insulin (WMD: -0.45 μIU/dL, 95 % CI: -1.14, 0.25; p = 0.20), HOMA-IR (MD: -0.25, 95 % CI: -0.57, 0.07; p = 0.12) or Hemoglobin A1c (HbA1c) (WMD: -0.09, 95 % CI: -0.20, 0.02; p = 0.09) did not alter after the administration of artichoke and artichoke products. A subgroup analysis comparing the kind of intervention, revealed that just the supplementation of artichoke and artichoke products, in a noco-supplementation form, was efficacy for the reduction of Homeostatic model assessment of insulin resistance (HOMA-IR) (WMD: -0.52, 95 % CI: -0.85, -0.19; p = 0.002).

CONCLUSIONS

The supplementation of artichoke and artichoke products can significantly reduce the FBS concentrations in humans. Moreover, these outcomes suggested that just the supplementation of artichoke and artichoke products is more effective in the reduction of HOMA-IR levels than the co-supplementation form. However, additional clinical trials with longer study periods are necessitated to obtain a robust conclusion for producing new guidelines as part of a healthy diet.

Amino Acids and Developmental Origins of Hypertension

During pregnancy, amino acids are important biomolecules that play essential roles in fetal growth and development. Imbalanced amino acid intake during gestation may produce long-term morphological or functional changes in offspring, for example, developmental programming that increases the risk of developing hypertension in later life. Conversely, supplementation with specific amino acids could reverse the programming processes in early life, which may counteract the rising epidemic of hypertension. This review provides an overview of the evidence supporting the importance of amino acids during pregnancy and fetal development, the impact of amino acids on blood pressure regulation, insight from animal models in which amino acids were used to prevent hypertension of developmental origin, and interactions between amino acids and the common mechanisms underlying development programming of hypertension. A better understanding of the pathophysiological roles of specific amino acids and their interactions in developmental programming of hypertension is essential so that pregnant mothers are able to benefit from accurate amino acid supplementation during pregnancy in order to prevent hypertension development in their children.

The beneficial effects of nutraceuticals and natural products on small dense LDL levels, LDL particle number and LDL particle size: a clinical review

Cardiovascular diseases (CVDs) are globally the major causes of morbidity and mortality. Evidence shows that smaller and denser low-dense lipoprotein (sdLDL) particles are independent atherogenic risk factors for CVD due to their greater susceptibility to oxidation, and permeability in the endothelium of arterial walls. sdLDL levels are an independent risk factor and of more predictive value than total LDL-C for the assessment of coronary artery disease and metabolic syndrome. Functional food ingredients have attracted significant attention for the management of dyslipidemia and subsequently increase cardio-metabolic health. However, to date there is no study that has investigated the effect of these bioactive natural compounds on sdLDL levels. Therefore, the aim of the present review is to summarize the evidence accrued on the effect of special dietary ingredients such as omega-3 polyunsaturated fatty acids, nutraceuticals and herbal medicines on the levels of sdLDL, LDL particle number, and LDL particle size. Based on the results of the existing clinical trials this review suggests that natural products such as medicinal plants, nutraceuticals and omega-3 fatty acids can be used as adjunct or complementary therapeutic agents to reduce sdLDL levels, LDL particle numbers or increase LDL particle size and subsequently may prevent and treat CVD, with the advantage that theses natural agents are generally safe, accessible, and inexpensive.

Effect of oral L-citrulline on brachial and aortic blood pressure defined by resting status: evidence from randomized controlled trials

Background

Experimental evidence indicates that oral L-citrulline (L-Cit) may reduce resting blood pressure (BP) as well as BP responses to exercise and cold exposure (non-resting). However, results from human intervention trials are inconsistent. This study aims to summarize the clinical evidence regarding the effects of L-Cit supplementation on brachial systolic blood pressure (SBP), brachial diastolic blood pressure (DBP), in addition to aortic SBP and aortic DBP at rest and non-resting conditions.

Methods

Multiple databases including PubMed, Embase, Cochrane library, Web of Science, and Clinical Trials were searched systematically. Randomized controlled trials of human participants were quantitatively meta-analyzed.

Results

Fourteen trials contained in eight studies were available for quantitative syntheses for brachial BP. Results showed that L-Cit supplementation significantly reduced both brachial SBP (− 4.490 mmHg, 95% CI: − 7.332 to − 1.648, P = 0.002) and brachial DBP (− 3.629 mmHg, 95% CI: − 5.825 to − 1.434, P = 0.001). Nine of the trials were meta-analyzed for aortic BP which showed that L-Cit intervention significantly reduced aortic SBP (− 6.763 mmHg, 95% CI: − 10.991 to − 2.534, P = 0.002), but not aortic DBP (− 3.396 mmHg, 95% CI: − 7.418 to 0.627, P = 0.098). The observed reducing effects of L-Cit appeared stronger for non-resting than for resting brachial SBP (P for difference = 0.044).

Conclusion

L-Cit supplementation significantly decreased non-resting brachial and aortic SBP. Brachial DBP was significantly lowered by L-Cit regardless of resting status. Given the relatively small number of available trials in the stratified analyses and the potential limitations of these trials, the present findings should be interpreted cautiously and need to be confirmed in future well-designed trials with a larger sample size.

The Effects of Oral l-Arginine and l-Citrulline Supplementation on Blood Pressure

Nitric oxide (NO) is a well-known vasodilator produced by the vascular endothelium via the enzyme endothelial nitric oxide synthase (eNOS). The inadequate production of NO has been linked to elevated blood pressure (BP) in both human and animal studies, and might be due to substrate inaccessibility. This review aimed to investigate whether oral administration of the amino acids l-arginine (Arg) and l-citrulline (Cit), which are potential substrates for eNOS, could effectively reduce BP by increasing NO production. Both Arg and Cit are effective at increasing plasma Arg. Cit is approximately twice as potent, which is most likely due to a lower first-pass metabolism. The current data suggest that oral Arg supplementation can lower BP by 5.39/2.66 mmHg, which is an effect that is comparable with diet changes and exercise implementation. The antihypertensive properties of Cit are more questionable, but are likely in the range of 4.1/2.08 to 7.54/3.77 mmHg. The exact mechanism by which Cit and Arg exert their effect is not fully understood, as normal plasma Arg concentration greatly exceeds the Michaelis constant (K_m) of eNOS. Thus, elevated plasma Arg concentrations would not be expected to increase endogenous NO production significantly, but have nonetheless been observed in other studies. This phenomenon is known as the "l-arginine paradox".

Effect of chronic nitrate and citrulline supplementation on vascular function and exercise performance in older individuals

Increased nitric oxide (NO) bioavailability may improve exercise performance and vascular function. It remains unclear whether older adults who experience a decreased NO bioavailability may benefit from chronic NO precursor supplementation. This randomised, double-blind, trial aims to assess the effect of chronic NO precursor intake on vascular function and exercise performance in older adults (60-70 years old). Twenty-four healthy older adults (12 females) performed vascular function assessment and both local (knee extensions) and whole-body (incremental cycling) exercise tests to exhaustion before and after one month of daily intake of a placebo (PLA) or a nitrate-rich salad and citrulline (N+C, 520mg nitrate and 6g citrulline) drink. Arterial blood pressure (BP) and stiffness, post-ischemic, hypercapnic and hypoxic vascular responses were evaluated. Prefrontal cortex and quadriceps oxygenation was monitored by near-infrared spectroscopy. N+C supplementation reduced mean BP (-3.3mmHg; p=0.047) without altering other parameters of vascular function and oxygenation kinetics. N+C supplementation reduced heart rate and oxygen consumption during submaximal cycling and increased maximal power output by 5.2% (p<0.05), but had no effect on knee extension exercise performance. These results suggest that chronic NO precursor supplementation in healthy older individuals can reduce resting BP and increase cycling performance by improving cardiorespiratory responses.