Oral administration of l-citrulline alters the vascular delivery of substances to rat skeletal muscles

Vascular endothelial function deteriorates with age and disease, and the production of vasodilator factors like nitric oxide (NO) decreases. The free amino acid l-citrulline increases vasodilation and blood flow through increased NO production. We examined the effects of oral l-citrulline administration on vascular delivery of substances to skeletal muscles. In Experiment 1, following oral l-citrulline administration and subsequent intravenous Evans blue dye (EBD) administration to rats, EBD levels delivered to skeletal muscles were measured after 60 min. In Experiment 2, plasma concentrations of amino acids and NOx, an indicator of vasodilation, were measured over time after oral l-citrulline administration. In Experiment 3, we measured EBD levels in skeletal muscles of streptozotocin-induced type 1 diabetic rats following l-citrulline administration. In these experiments, EBD levels in the soleus muscle were higher in the l-citrulline group than in the control group (19.9 ± 0.7 vs. 22.5 ± 1.9 μg/g tissue, p < 0.05). Plasma l-arginine, l-citrulline, and NOx levels were increased within 30 min after l-citrulline administration. EBD levels in the soleus and gastrocnemius muscles were higher in diabetic rats with l-citrulline administration (18.7 ± 2.2 vs. 25.0 ± 4.3 μg/g tissue, p < 0.05 and 8.0 ± 0.5 vs. 9.2 ± 0.8 μg/g tissue, p = 0.05, respectively). These data suggest that oral l-citrulline administration may increase the level of substances delivered to skeletal muscles by increasing the NO production in both normal and vascular endothelial dysfunction models.

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l-Citrulline (CIT) increases blood flow and induces vasorelaxation.

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CIT increased dye delivery to soleus but not gastrocnemius muscles in normal rats.

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CIT administration increased the blood levels of l-arginine and NOx.

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CIT led to higher dye delivery to soleus and gastrocnemius muscles in diabetic rats.

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CIT increase vascular delivery in skeletal muscles through increasing NO production.

Undigested low-methoxy pectin prevents diarrhea and induces colonic contraction during liquid-diet feeding in rats

OBJECTIVES

Dietary fibers, such as pectins, are blended in liquid diets (LDs) to prevent diarrhea; however, which type of pectin is more effective, along with its mechanism of action, remains unclear. This study aimed to investigate the gelling characteristics, fermentability, fecal properties, and motility of the colon during the administration of LDs blended with pectins.

METHODS

Male Sprague-Dawley rats were administered LDs containing high-methoxy pectin (HM), low-methoxy amidated pectin (LMA), low-methoxy pectin (LM), and very low-methoxy amidated pectin (VLMA) ad libitum. The amount of pectin in the feces was assessed by measuring galacturonic acid content. The contractile motility of the rats' descending colons was measured with a force transducer.

RESULTS

HM was well fermented, but VLMA was significantly less fermented. LM and LMA displayed intermediate fermentability. An LD that contained LM and VLMA gelled with calcium ions in artificial gastric juice did not cause diarrhea, as opposed to other pectin types. Contractile motility was significantly lower and stools were looser when pectin or calcium was excluded from the LD.

CONCLUSIONS

In the colon, LM or VLMA could form a water-holding gel with calcium ions to produce normal feces. The mechanical stimulation of the formed fecal mass might induce physiological colonic contractions.

Fecal imaging demonstrates that low-methoxyl pectin supplementation normalizes gastro-intestinal transit in mice given a liquid diet

This study has the following aims: (1) to confirm a methodology for a fecal indocyanine green (ICG) imaging test for measuring gastro-intestinal transit time (GITT); and (2) to compare GITT in mice given a liquid diet in which viscosity increases under acidic conditions to that in mice given stable liquid diets with comparable viscosity or regular chow. To address Aim 1, mice received ICG orally along with intraperitoneal injection of atropine in Study 1, and mice were given ICG orally with concurrent carmine red for Study 2. Fluorescence imaging of feces collected for 8 h thereafter was used to detect the first feces with fluorescence and thereby determine GITT. To address Aim 2, mice were fed ad libitum for 1 week with either liquid diet or regular chow for Study 3, or with liquid diet containing low-methoxyl (LM) pectin or high-methoxyl (HM) pectin, or regular chow for Study 4. GITT was then determined by fecal ICG imaging. Atropine delayed GITT in a dose-dependent manner. The GITT of ICG completely corresponded to that of carmine red (correlation coefficient, 1.00). The first ICG excretion in the loose/some diarrheal feces of mice given a liquid diet was seen at 170 min. Feces of mice given liquid diet were loose with LM pectin and loose/some diarrhea with HM pectin. GITT of mice given liquid diet with HM pectin was significantly delayed (280 min) compared to that of mice given liquid diet with LM pectin (111 min) or regular chow (130 min). Fecal imaging of ICG enables measurements of GITT. LM pectin supplementation in a liquid diet may normalize GITT in mice to that of a normal meal and may be associated with changes in fecal properties.

Efficacy of oral supplemental hydration for the prevention of contrast-induced nephropathy in rats

PURPOSE

To compare oral rehydration solution (ORS) with saline infusion for preventing contrast-induced nephropathy (CIN) in a rat model.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats (310-360 g) received intravenous indomethacin (10 mg/kg), N ^G-nitro-L-arginine methyl ester (10 mg/kg), and iohexol (10 mL/kg) to induce acute contrast-induced renal injury (CIN group); control rats received saline only. For hydration, rats received either continuous infusion (20 mL/kg/h) of saline or three oral doses (20 mL/kg each) of ORS. Acute renal injury was evaluated by assaying urine collected for 24 h beginning 2 h before the contrast injection, evaluating blood taken 22 h after the contrast injection, and examining the kidneys histopathologically.

RESULTS

Hydration with saline prevented only the contrast-induced increase in plasma creatinine, whereas ORS prevented deleterious changes in plasma creatinine, blood urea nitrogen, and creatinine clearance as well as in urinary protein, albumin, and N-acetyl-D-glucosaminidase concentrations. Histopathologic changes noted in the CIN group were diminished in both saline and ORS groups.

CONCLUSION

Both intravenous saline administration and oral hydration with ORS decreased the severity of CIN. Hydration with ORS was comparable to intravenous saline infusion in preventing CIN-associated abnormalities.

Detecting Enteral Nutrition Residues and Microorganism Proliferation in Feeding Tubes via Real-Time Imaging

BACKGROUND

Enteral nutrition (EN) residues that persist in feeding tubes provide substrates for microorganisms to proliferate and occlude the tubes. Visible EN residues in tubes are easily identified, but smaller residues can persist. We developed a new imaging technique to visualize EN residues and proliferation of microorganisms in feeding tubes.

MATERIALS AND METHODS

(1) Feeding tubes containing EN labeled with fluorescent dye and either with or without various types or amounts of thickeners were flushed once with water and then seeded with Pseudomonas aeruginosa Xen05 with recombinant luciferase DNA. (2) Because EN fluoresces intrinsically, EN in the feeding tubes without fluorescent dye was repeatedly flushed until the intrinsic fluorescence levels reached background levels. Fluorescent images of EN residues and bioluminescent images of microorganisms were acquired via an optical imaging system.

RESULTS

(1) Fluorescence images showed that the amount of EN residues increased at various sites in tubes depending on EN viscosity and the thickening agent, and bioluminescence images showed that microorganism proliferation was associated with a commensurate increase in EN residues. (2) The intrinsic fluorescence of EN also enabled the detection of EN residues in tubes even in the absence of fluorescence dye. Higher EN viscosity required more flushes to reach undetectable levels.

CONCLUSION

EN residues and microorganism proliferation in enteral feeding tubes were detected on fluorescence and bioluminescence images, respectively. This simplified approach allowed the real-time visualization of EN residues and microorganisms in feeding tubes.

Fluorescence imaging in vivo visualizes delayed gastric emptying of liquid enteral nutrition containing pectin

BACKGROUND

Semi-solidification by gelation or increased viscosity could slow the influx of liquid enteral nutrition (EN) into the small intestine. A liquid EN formula containing pectin that gels under acidic conditions such as those found in the stomach has been developed. A new near-infrared fluorescent imaging reagent was used to non-invasively acquire real time images of gastric emptying in a murine model in vivo. We postulated that the EN formula delays gastric emptying and tested this hypothesis using imaging in vivo.

METHODS

Male BALB/c mice were given an oral bolus injection of a liquid EN containing the fluorescence reagent GastroSense750 with or without pectin. The EN in the stomach was visualized in vivo at various intervals using a non-invasive live imaging system and fluorescent signals were monitored from the stomach, which was removed at 60 min after EN ingestion.

RESULTS

The fluorescence intensity of signals in stomachs in vivo and in resected stomachs was lower and attenuated over time in mice given EN without, than with pectin.

CONCLUSIONS

Adding a gelling agent such as pectin delayed the transit of liquid EN from the stomach. Fluorescence imaging can visualize the delayed gastric emptying of EN containing pectin.