Citrulline: From metabolism to therapeutic use Bahri, Senda, Ph.D; Zerrouk, Naima, Pharm.D., Ph.D; Aussel, Christian, Pharm.D., Ph.D ...
Nutrition,
03/2013, Letnik:
29, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Abstract Citrulline possesses a highly specific metabolism that bypasses splanchnic extraction because it is not used by the intestine or taken up by the liver. The administration of citrulline may ...be used to deliver available nitrogen for protein homeostasis in peripheral tissues and as an arginine precursor synthesized de novo in the kidneys and endothelial and immune cells. Fresh research has shown that citrulline is efficiently transported across the intestinal luminal membrane by a set of transporters belonging to the B0,+ , L, and b0,+ systems. Several pharmacokinetic studies have confirmed that citrulline is efficiently absorbed when administered orally. Oral citrulline could be used to deliver arginine to the systemic circulation or as a protein anabolic agent in specific clinical situations, because recent data have suggested that citrulline, although not a component of proteins, stimulates protein synthesis in skeletal muscle through the mammalian target of rapamycin signaling pathway. Hence, citrulline could play a pivotal role in maintaining protein homeostasis and is a promising pharmaconutrient in nutritional support strategies for malnourished patients, especially in aging and sarcopenia.
Poloxamer 407 copolymer (ethylene oxide and propylene oxide blocks) shows thermoreversible properties, which is of the utmost interest in optimising drug formulation (fluid state at room temperature ...facilitating administration and gel state above sol-gel transition temperature at body temperature promoting prolonged release of pharmacological agents). Pharmaceutical evaluation consists in determining the rheological behaviour (flow curve or oscillatory studies), sol-gel transition temperature, in vitro drug release using either synthetic or physiological membrane and (bio)adhesion characteristics. Poloxamer 407 formulations led to enhanced solubilisation of poorly water-soluble drugs and prolonged release profile for many galenic applications (e.g., oral, rectal, topical, ophthalmic, nasal and injectable preparations) but did not clearly show any relevant advantages when used alone. Combination with other excipients like Poloxamer 188 or mucoadhesive polymers promotes Poloxamer 407 action by optimising sol-gel transition temperature or increasing bioadhesive properties. Inclusion of liposomes or micro(nano)particles in Poloxamer 407 formulations offers interesting prospects, as well. Besides these promising data, Poloxamer 407 has been held responsible for lipidic profile alteration and possible renal toxicity, which compromises its development for parenteral applications. In addition, new findings have demonstrated immuno-modulation and cytotoxicity-promoting properties of Poloxamer 407 revealing significant pharmacological interest and, hence, human trials are in progress to specify these potential applications.
Eur J Clin Invest 2012; 42 (3): 282–289
Background Sepsis considerably alters the intestinal barrier functions, which in turn modify the absorption and bioavailability of nutrients. However, the ...effects of septic shock on aminoacid (AAs) bioavailability are poorly documented. The aim of this study was to compare the bioavailability of citrulline, arginine and glutamine during endotoxemia.
Materials and methods Thirty‐six rats were randomised into two groups: control and lipopolysaccharides (LPS). The LPS group received an intraperitoneal injection of endotoxins (7·5 mg/kg). After 12 h, each group was again randomised into three subgroups, each of which received an oral bolus of citrulline, arginine or glutamine (5·7 mmol/kg). Blood samples were collected at various times from 0 to 600 min after AA administration. The concentrations of citrulline, arginine, glutamine and their metabolites arginine and ornithine were measured to determine pharmacokinetic parameters Area Under Curve (AUC), Cmax and Tmax.
Results The AUC values of citrulline decreased in LPS rats citrulline, control: 761 ± 67 and LPS: 508 ± 72 μmol min/mL (P = 0·02). Maximum concentrations of citrulline were also significantly decreased by endotoxemia (P = 0·01). The pharmacokinetic parameters of arginine and glutamine were not significantly modified by endotoxemia. The AUC value of arginine from citrulline conversion was diminished in endotoxemic rats. The other pharmacokinetic parameters of arginine were not significantly modified after arginine or citrulline supply in either group (control or LPS).
Conclusion Endotoxemia affects the bioavailability of AAs differently according to the amino acid considered. This feature may be important for nutritional strategy in ICU patients.
Dimethyl sulfoxide (DMSO) is usually used to solubilize poorly soluble drugs in permeation assays such as that using Caco2 enterocyte-like cells. The objective of this study was to evaluate the ...toxicity of DMSO on Caco2/TC7 cells and determinate the maximal concentration usable in permeation experiments. Caco2/TC7 cells were cultured for 21 d on 96-well plates for evaluation of toxicity. The determination of lactate dehydrogenase (LDH) release in cell supernatant and the measurement of Neutral Red (NR) uptake are used for cytotoxicity assays. DMSO solutions (0—100%) in Hank's balanced salt solution containing HEPES (25 mM), pH 7.4, were incubated with Caco-2/TC7 cells on 96 well plates. Caco2/TC7 cells were cultured on Transwell-Clear® inserts to evaluate the influence of DMSO on the apparent permeability of the paracellular marker mannitol. DMSO 10% did not induce any significant increase in LDH release whereas a significant increase in LDH activity (ANOVA, p<0.05) occurred at a DMSO concentration of 20 to 50%. NR incorporation in viable cells was statistically reduced by 27 to 36% at DMSO concentration of 20% up to 100% (ANOVA, p>0.05). No statistical difference (p<0.05) in apparent mannitol permeability was observed between the control and 10% DMSO groups. In conclusion, at concentrations of up to 10%, DMSO did not produce any significant alteration in apical membrane permeability or on cell-to-cell tight junctional complexes.
Saccharomyces boulardii is a nonpathogenic yeast with proven health benefits, some of them depending on its viability. However, the living yeast is sensitive to environmental conditions and its ...viability is less than 1% in the faeces after oral administration. Therefore, we assessed the survival conditions of S. boulardii in aqueous suspension and in its freeze-dried form and we formulated microspheres with the former and tablets with the latter in order to preserve the viability of the probiotic. While the viability of the yeast in aqueous suspension could be maintained for one year at −20 °C and +5 °C, increasing the temperature led to almost total mortality within 14 d at +40 °C and 4 d at +60 °C. The viability of the freeze-dried yeast was preserved for one year at +25 °C without moisture. With 75% relative humidity, the mortality was significant at 28 d at +25 °C and almost total within 1 d at +60 °C. In vitro, whereas less than 1% of non-encapsulated or non-tabletted S. boulardii survived after 120 min at pH 1.1, both formulations in microspheres and direct compression enabled to protect the yeast from degradation in HCl and to release it viable at pH 6.8. However, despite a similar release profile from both dosage forms, the compression led to a significant decrease in the viability of the freeze-dried yeast. In conclusion, although both formulations are efficient in protecting S. boulardii in acidic condition, microspheres provide a higher entrapment efficiency and a faster release of the viable probiotic in intestinal condition than matrix tablets.
Abstract Traumatic brain injury (TBI) is one of the most severe injuries encountered in intensive care units. TBI patients exhibit protein wasting and gastrointestinal dysfunction, which may be risk ...factors for a septic state. Specific nutritional support may be required for these patients, and we hypothesize that standard nutritional support does not allow restoration of the nutritional state of TBI patients. A well-validated rat model of TBI by fluid percussion was used. Rats were randomized into three groups: healthy rats receiving standard chow diet ad libitum (AL), rats sustaining TBI and receiving standard chow diet (TBI), and rats sustaining TBI and receiving a standard enteral diet (TBI-EN) for 4 days. TBI in rats was characterized by anorexia, body weight loss (AL: +15 +/- 5 g versus TBI: -11 +/- 4 g and TBI-EN: -8 +/- 4 g; p < 0.05), decrease in nitrogen balance (AL: 2.9 +/- 0.2 g versus TBI: 1.0 +/- 0.2 g and TBI-EN: 0.2 +/- 0.2 g, p < 0.05) associated with decrease in muscular protein content (extensor digitorum longus EDL: AL: 36 +/- 2 mg versus TBI: 26 +/- 3 mg and TBI-EN: 28 +/- 2 mg; p < 0.05), and intestinal atrophy (ileum: AL: 673 +/- 42 mg versus TBI: 442 +/- 23 mg and TBI-EN: 377 +/- 27 mg; p < 0.05). Interestingly, standard enteral nutrition was not effective in restoring any of these parameters. This work confirms that TBI is associated with profound nutritional alterations and has a major impact on nitrogen metabolism and on intestinal trophicity. It also demonstrates that using standard enteral nutrition cannot reverse this phenomenon. Thus, developing new nutritional strategies to cover TBI patients' specific nutritional requirements appears mandatory.
Summary Background & aims Citrulline is a major precursor of arginine by de novo synthesis in the kidneys. Oral citrulline supplementation may be beneficial in some clinical conditions. However, ...citrulline bioavailability depends on its intestinal absorption. Since the mechanism of citrulline transport across the intestine has not been established yet, this study was designed to characterize l -14 C-citrulline uptake by Caco-2 cells. Methods Caco-2 cells were cultured in a bicameral insert system. Inhibition studies were conducted in the presence of neutral, cationic, acidic and non-metabolized amino acids. We performed control inhibition studies for arginine uptake. Results Citrulline uptake was pH-independent whereas the uptake rate was reduced in the absence of Na+ . Kinetic analysis indicated the involvement of Na+ -dependent and Na+ -independent saturable transport components. For competition studies, both the transport components were markedly inhibited by large, small neutral and cationic amino acids. It was also noticed that specific inhibitor of system l BCH inhibited uptake. The inhibition profile of arginine transport was different from that of citrulline transport as arginine uptake was insensitive to BCH. Conclusions These characteristics suggest that system B0,+ might be responsible for the Na+ -dependent uptake of citrulline, whereas Na+ -independent uptake may include systems L and b0,+ . Our results show that systems involved in citrulline transport are partly different from those involved in arginine transport.
Best temperature for static liver graft storage is 1°C Charrueau, Christine, PhD; Neveux, Nathalie, PhD; Chaumeil, Jean-Claude, PhD ...
The Journal of surgical research,
04/2013, Letnik:
180, Številka:
2
Journal Article
Recenzirano
Abstract Background The best storage temperature in liver transplantation remains an unsolved question. Methods After storage for 24 h in University of Wisconsin solution at +4°C, +1°C, or −0.5°C, ...rat livers were subjected, or not, to 15 min of warm ischemia, rinsed with Ringer lactate, and subsequently reperfused with oxygenated Krebs-Henseleit buffer. Results In the presence of warm ischemia, for livers stored at +4°C, creatine kinase (CK) peaked at 21 ± 5 IU g−1 h−1 , hepatic resistance at 34,700 ± 1500 dyn s cm−5 , bile flow reached 18 ± 4 μL g−1 h−1 after 10 min, and oxygen consumption stabilized at about 25 μmol g−1 h−1 after 20 min. When livers were stored at +1°C, CK and hepatic resistance were lowered, bile production was 33 ± 6 μL g−1 h−1 ( P < 0.05 versus +4°C), and oxygen consumption was 105 ± 10 μmol g−1 h−1 ( P < 0.001). For livers stored at −0.5°C, results were not statistically different from those of the +1°C group except for bile flow, which was significantly lower. Without warm ischemia, the peak of CK ( P = 0.015) and the peak hepatic resistance ( P < 0.001) of the +4°C group were significantly increased compared with the +1°C or −0.5°C groups. However, no difference in bile flow or oxygen consumption was observed. The number of trypan blue-positive nonparenchymal cells ( P = 0.003) and the gain in liver weight during the reperfusion ( P = 0.015) were minimal after storage at +1°C. Conclusions Static storage at +1°C improved liver function compared with +4°C or −0.5°C. Main beneficial effect was observed with parameters reflecting sinusoidal cells injury.
Purpose
Although probiotics are of a major potential therapeutic interest, their efficacy is usually limited by poor bioavailability of viable microorganisms on site. The aim of this study was to ...protect the probiotic
Saccharomyces boulardii
from degradation in order to ensure a greater number of viable yeast in the colon.
Methods
Alginate microspheres coated with or not with chitosan were used to encapsulate the yeast by an extrusion method. The efficiency of encapsulation was assessed both
in vitro
and
in vivo
.
Results
In vitro
, less than 1% of the non-encapsulated probiotic survived after 120 min at pH 1.1, whereas the majority of encapsulated yeast cells remained entrapped within both types of microspheres. Further exposure to a pH 6.8 allowed the release of about 35% of viable yeasts.
In vivo
, the percentage of viable yeast excreted over 96 h after a single oral dose of 2 × 10
8
cfu/100 g in rats was 2.5% for non-encapsulated yeast and reached 13.3 and 9.0% of the dose administered for the uncoated and chitosan-coated microspheres, respectively.
Conclusions
Given the dose-dependent efficacy of
S. boulardii
and the efficiency of microencapsulation in protecting the yeast from degradation, alginate microspheres could be of great interest in therapeutic applications of the yeast.
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