A comparison effects of l-citrulline and l-arginine against cyclosporine-induced blood pressure and biochemical changes in the rats

OBJECTIVE

The use of cyclosporine A (CsA) is associated with different adverse effects including hypertension and nephrotoxicity. The present study aimed to compare the inhibitory effects of l-arginine &l-citrulline on CsA-induced blood pressure and biochemical changes in the serum of rats.

METHODS

Thirty-six rats were divided into 6 groups received daily: (1) 1ml distilled water, (2) 200mg/kg l-citrulline IP, (3) 25mg/kg CsA SC, (4) CsA+l-citrulline with the same dose of the former groups, (5) 200mg/kg l-arginine IP and (6) l-arginie+CsA with the same doses of group 4 for 7 days.

RESULTS

The changes in the blood pressure, heart rate, creatinine, BUN, glucose and C-reactive protein (CRP) of the serum were determined in the treated animals. Significant (p<0.001) increase was shown in the blood pressure and heart rate of CsA treated rats compared to the control group. There were also a significant (p<0.05) increase in the creatinine, BUN and glucose, but a decrease in the CRP value in the CsA-treated group. However, l-citrulline significantly (p<0.001) inhibited the changes in the blood pressure and heart rate in CsA-treated as well as it was able to reduce blood pressure in non-treated group significantly (p<0.01). l-citrulline also inhibited the increased levels of BUN and creatinine induced by CsA, while, l-arginine was able to prevent the increased blood pressure and creatinine occurs after administration of CsA.

CONCLUSIONS

These findings suggest that the l-citrulline is more efficient than l-arginine against the adverse effects induced by cyclosporine.

Oral nitrate and citrulline decrease blood pressure and increase vascular conductance in young adults: a potential therapy for heart failure

Purpose

Both inorganic nitrate and citrulline are known to alter the arginine–nitric oxide–nitrate system to increase the bioavailability of nitric oxide with potential benefits in the treatment of heart failure. However, their effects on cardiac electrical activity, vascular compliance and peripheral conductance are less well understood. This study examined the effect of nitrate and citrulline on cardiac electrical activity and blood flow.

Methods

Young adult subjects (n = 12) were recruited to investigate the effects of acute oral nitrate consumption (8 mg/kg) and chronic citrulline consumption (3 g/day) on cardiac electrical activity measured by ECG recording and blood pressure. Blood flow and vascular compliance were measured by IR-plethysmography at the thumb and the hallux.

Results

Nitrate (p < 0.05) and citrulline (p < 0.01) consumption both decreased diastolic blood pressure but had no effect on either pulse pressure or rate-pressure product (NS for both). Citrulline also decreased systolic pressure (p < 0.01). Nitrate and citrulline both decreased vascular compliance (p < 0.05 for both) prior to isometric grip exercise, but this was increased for nitrate following exercise (NS). Citrulline decreased R–R interval 9 % (p < 0.05) at rest and increased heart rate (p < 0.05) in addition to significantly decreasing pulse transit duration (6 %; p < 0.05). QRS duration was also decreased by 5 % for citrulline (p < 0.05) with the reduction in R–R interval.

Conclusion

Both nitrate and citrulline supplementation decreased vascular tone at rest but citrulline also altered sympathovagal balance to increase sympathetic tone. We suggest that both oral nitrate and citrulline may be suitable adjuvants for patients with heart failure to improve peripheral tissue oxygenation.

Oral supplementation with a combination of L-citrulline and L-arginine rapidly increases plasma L-arginine concentration and enhances NO bioavailability

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.

Effects of Oral L-Citrulline Supplementation on Lipoprotein Oxidation and Endothelial Dysfunction in Humans with Vasospastic Angina

BACKGROUND

Decreased nitric oxide (NO) bioavailability and increased lipid oxidation are associated with progressive endothelial dysfunction. L-Citrulline, the effective precursor of L-arginine which is essential as a substrate for endothelial NO synthase (eNOS), is effective in enhancing NO-dependent signaling. However, little is known about the efficacy of L-citrulline supplementation on lipoprotein oxidation and endothelial dysfunction.

METHODS

Twenty-two patients (aged 41 - 64 years old) diagnosed with vasospastic angina with flow-mediated dilation (FMD) of the brachial artery (< 5.5 %) received 800 mg/day of L-citrulline for 8 weeks. FMD (%), blood NOx, asymmetric dimethylarginine (ADMA), small dense LDL, oxidized lipids, amino acids concentrations were measured before and after supplementation.

RESULTS

Compared with baseline values, FMD (%) was significantly improved at 4 and 8 weeks as well as at 4 weeks after the end of intake. L-Citrulline supplementation caused a significant lowering of plasma ADMA levels. Plasma L-arginine/ADMA ratio and NOx levels rose markedly throughout the study period. Moreover, significant reductions of serum oxidized LDL and lectin-like oxidized LDL receptor 1 (LOX-1) ligand containing ApoB (LAB), an indicator of the biological activity of oxidized lipoprotein binding to LOX-1, were observed after L-citrulline intake.

CONCLUSIONS

L-Citrulline supplementation improves endothelial dysfunction, probably due to potentiating NO-dependent reactions and decreasing the state of lipoprotein oxidation in humans.

The effects of short term L-citrulline supplementation on wave reflection responses to cold exposure with concurrent isometric exercise

BACKGROUND

Supplementation with L-citrulline (L-cit) has shown attenuating effects on blood pressure (BP) and pulse-wave-reflection responses (augmentation index (AIx)) to local exposure to cold, but the potential cardioprotective effects of L-cit during whole-body cold exposure with concurrent exercise are poorly understood. We hypothesized that L-cit would attenuate the BP and AIx responses to cold exposure and isometric handgrip (IHG) exercise.

METHODS

Sixteen healthy males with a mean age of 23±3 years volunteered for a study of the effect of L-cit on the BP and AIx responses to cold exposure and IHG exercise. Experiments were conducted inside an environmental chamber in cold conditions (4 ºC). Radial waveforms were obtained in duplicates and averaged through applanation tonometry. After 5 minutes of measurements made at rest in the supine position (RES), after the finalization of the exercise about the subjects were evaluated in non exercise condition that were basically the same as the RES. After initial measurements in cold conditions, subjects were randomized to receive either a placebo (Maltodextrin, PL) or L-cit (100mg/kg) for 14 days, followed by a 14-day washout period and then a 14-day regimen of the other agent. Subjects were re-evaluated after each treatment period.

RESULTS

At RES, there was a significant treatment-by-time interaction for brachial systolic BP (BSBP; P < 0.01), aortic systolic BP (ASBP; P < 0.01), and AIx (P < 0.05), such that L-cit decreased BSBP (-11±2mm Hg; P < 0.01), ASBP (-10±2mm Hg; P < 0.05), and AIx (-2±2%; P < 0.05) as compared with their respective values before the intervention. During IHG, BSBP, ASBP, and AIx were increased (P < 0.05) as compared with their values at RES, but these responses were unaffected by either of the study treatments.

CONCLUSIONS

L-citrulline may be a feasible adjuvant treatment for decrease the BP and AIx responses induced by cold. Further research is warranted to evaluate the impact of cold exposure and exercise on cardiovascular risk in clinical populations.

Recombinant human arginase toxicity in mice is reduced by citrulline supplementation

Human recombinant arginase I cobalt coupled to polyethylene glycol 5000 (HuArg I [Co]-PEG5000) achieved potent in vitro depletion of arginine from tissue culture medium and cytotoxicity to many cancer cell lines. The recombinant enzyme also produced tumor growth inhibition of hepatocellular carcinoma and pancreatic carcinoma xenografts. Although these results were promising, the therapeutic index was narrow. Toxicities were seen in normal cells in tissue culture. In vivo normal tissue injury occurred at doses twice the effective dose. The current study was conducted to define, in greater detail, the maximum tolerated dose (MTD), pharmacodynamics, and dose-limiting toxicities (DLTs) of twice-weekly intraperitoneal HuArg I [Co]-PEG5000 in Balb/c mice. Animal weight and survival were monitored, serum arginine levels measured, and complete blood cell counts, chemistries, necropsies, and histologies were performed. In addition, methods to ameliorate the HuArg I [Co]-PEG5000 adverse effects were tested. Supplemental l-citrulline was given concurrently with the arginase drug. The HuArg I [Co]-PEG5000 MTD in mice was 5 mg/kg twice weekly, and DLTs included weight loss and marrow necrosis. No other organ damage or changes in blood cell counts or chemistries were observed. Arginase reduced serum arginine levels from 60 µM to 4 to 6 µM. Supplemental l-citrulline given per os or daily subcutaneously reduced and delayed toxicities, and l-citrulline given twice daily subcutaneously completely prevented animal toxicities. On the basis of these results, we hypothesize that HuArg I [Co]-PEG5000, particularly with supplemental l-citrulline, may be an attractive therapeutic agent for argininosuccinate synthetase-deficient tumors.