Protein Supplementation Enhances the Effects of Intermittent Loading on Skeletal Muscles by Activating the mTORC1 Signaling Pathway in a Rat Model of Disuse Atrophy.

Inactivity leads to skeletal muscle atrophy, whereas intermittent loading (IL) during hind limb unloading (HU) attenuates muscle atrophy. However, the combined effects of IL and protein supplementation on disuse muscle atrophy are unclear. Therefore, we investigated the effects of IL and a high-protein oral nutritional supplement (HP) during HU on skeletal muscle mass and protein synthesis/breakdown. Male F344 rats were assigned to the control (CON), 14-day HU (HU), IL during HU (HU + IL), and IL during HU followed by HP administration (2.6 g protein/kg/day; HU + IL + HP) groups. Soleus and gastrocnemius muscles were sampled 30 min after the last IL and HP supplementation. HU decreased relative soleus and gastrocnemius muscle masses. Relative muscle masses and p70 ribosomal protein S6 kinase/ribosomal protein S6 phosphorylation in soleus and gastrocnemius muscles were higher in the HU + IL group than the HU group and further higher in the HU + IL + HP group than the HU + IL group in gastrocnemius muscle. Therefore, protein administration plus IL effectively prevented skeletal muscle atrophy induced by disuse, potentially via enhanced activation of targets downstream of mammalian target of rapamycin complex 1 (mTORC1) signaling pathway.

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.

Enteral feeding with low-methoxyl pectin accelerates colonic anastomosis healing in rats.

OBJECTIVE: Enteral feeding with pectin has proven beneficial for anastomosis healing in rats. The aim of this study was to investigate the effects of low-methoxyl pectin (LMP) or high-methoxyl pectin (HMP), on colonic anastomosis healing in rats. METHODS: Male Sprague-Dawley rats (age 7 wk) were fed liquid diets containing LMP, HMP, or no pectin (pectin-free [PF]) for 14 d (n = 10/group). The rats underwent colonic anastomosis surgery on day 7 and were sacrificed on day 14. Bursting pressure, breaking strength, and salt-soluble hydroxyproline at the anastomosis site were used as indices of anastomosis healing. Short-chain fatty acids (SCFAs) in the cecal contents were analyzed. RESULTS: Breaking strength was higher in the LMP group than in the other two groups (P < 0.001). The salt-soluble hydroxyproline content was higher in LMP group than in the PF group (P < 0.01). Bursting pressure did not differ among the three groups. The LMP group produced normal, formed stools, whereas watery stools were observed in HMP and PF groups throughout the experimental period. Cecal SCFAs were highest in LMP group. CONCLUSIONS: These results suggest that LMP promotes healing of colonic anastomosis more effectively than HMP, which may be explained by the mechanical stresses generated by the movement of normally formed stool though the colon.

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.

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.