Resistance exercise with anti-inflammatory foods attenuates skeletal muscle atrophy induced by chronic inflammation

Long-term stimulation by implanted pacemaker enables non-atrophic treatment of bilateral vocal fold paresis in a human-like animal model

A wide variety of treatments have been developed to improve respiratory function and quality of life in patients with bilateral vocal fold paresis (BVFP). One experimental method is the electrical activation of the posterior cricoarytenoid (PCA) muscle with a laryngeal pacemaker (LP) to open the vocal folds. We used an ovine (sheep) model of unilateral VFP to study the long-term effects of functional electrical stimulation on the PCA muscles. The left recurrent laryngeal nerve was cryo-damaged in all animals and an LP was implanted except for the controls. After a reinnervation phase of six months, animals were pooled into groups that received either no treatment, implantation of an LP only, or implantation of an LP and six months of stimulation with different duty cycles. Automated image analysis of fluorescently stained PCA cross-sections was performed to assess relevant muscle characteristics. We observed a fast-to-slow fibre type shift in response to nerve damage and stimulation, but no complete conversion to a slow-twitch-muscle. Fibre size, proportion of hybrid fibres, and intramuscular collagen content were not substantially altered by the stimulation. These results demonstrate that 30 Hz burst stimulation with duty cycles of 40% and 70% did not induce PCA atrophy or fibrosis. Thus, long-term stimulation with an LP is a promising approach for treating BVFP in humans without compromising muscle conditions.

Intestinal-targeted nanotubes-in-microgels composite carriers for capsaicin delivery and their effect for alleviation of Salmonella induced enteritis

Salmonella is a word-wide food-borne pathogen, which can cause severe enteritis and intestinal microbiota imbalance. Capsaicin (Cap), a food-based bioactive ingredient, has antibacterial and anti-inflammatory properties. However, its low solubility, low bioavailability and the irritation to digestive tract greatly limit its applications. Here, an intestinal responsively "nanotubes-in-microgel" composite carrier was constructed by capturing α-lactalbumin (α-lac) nanotubes in low-methoxy pectin microgels (LMP-NT) (52 μm). Cap was loaded in such system via hydrophobic interaction with a loading capacity of 38.02 mg/g. The LMP microgels remained stable and protected NT/Cap from early releasing in the gastric condition. It showed an excellent mucoadhesive capacity, which can prolong the intestinal retention up to 12 h and control release NT/Cap in intestine. Afterward, NT/Cap could penetrate across the mucus layer deeply and enter the intestinal villi epithelial cells efficiently. LMP-NT microgels achieved a mucoadhesive-to-penetrating transition in response to intestinal pH, improving the epithelium absorption and the in vivo bioavailability of Cap. Oral administration of LMP-NT/Cap could effectively alleviate enteritis caused by Salmonella infection and maintain the homeostasis of gut microbiota. Overall, this work suggested that LMP-NT composite microgels were promising for intestine-targeted and oral delivery of hydrophobic bioactive food compounds.

Inorganic Iron Supplementation Rescues Hematological Insufficiency Even Under Intense Exercise Training in a Mouse Model of Iron Deficiency with Anemia

Iron deficiency anemia (IDA) due to malnutrition and/or blood loss is a common condition, especially in women of reproductive age. Intense exercise can induce anemia via an inflammatory response, but whether intense exercise affects the efficacy of iron supplementation to treat IDA is unclear. Here, we show in a mouse model of IDA that acute intense swimming increased IL-6 levels in the blood, but did not affect the maximum elevation of plasma iron following oral administration of 0.5 mg/kg Bw iron. However, compared with the control group without intense exercise, acute intense swimming was associated with a significant decrease in plasma iron 2 and 4 h after iron loading that could be attributed to rapid iron absorption in peripheral tissues. In the chronic experiment, IDA mice administered 0.36, 1.06, or 3.2 mg/kg Bw iron per day that were subjected to 11 intense swimming sessions over 3 weeks showed significantly decreased recovery levels for hemoglobin and red blood cell count during the early phase of the experimental period. At the end of the experimental period, significant, dose-dependent effects of iron, but not the main effect of intense exercise, were seen for recovery of hemoglobin and red blood cell counts, consistent with the acute exercise study. These results suggested that intense exercise in the presence of IDA does not inhibit iron absorption from the gastrointestinal tract and that iron supplementation can enhance the recovery process even after intense exercise.

Pulsed ultrasound prevents lipopolysaccharide-induced muscle atrophy through inhibiting p38 MAPK phosphorylation in C2C12 myotubes

OBJECTIVE

Inflammation contributes to skeletal muscle atrophy via protein degradation induced by p38 mitogen-activated protein kinase (MAPK) phosphorylation. Meanwhile, pulsed ultrasound irradiation provides the mechanical stimulation to the target tissue, and has been reported to show anti-inflammatory effects. This study investigated the preventive effects of pulsed ultrasound irradiation on muscle atrophy induced by lipopolysaccharide (LPS) in C2C12 myotubes.

METHODS

C2C12 myotubes were used in this research. The pulsed ultrasound (a frequency of 3 MHz, duty cycle of 20%, intensity of 0.5 W/cm²) was irradiated to myotube before LPS administration.

RESULTS

The LPS increased phosphorylation of p38 MAPK and decreased the myofibril and myosin heavy chain protein (P < 0.05), followed by atrophy in C2C12 myotubes. The pulsed ultrasound irradiation attenuated p38 MAPK phosphorylation and myotube atrophy induced by LPS (P < 0.05).

CONCLUSIONS

Pulsed ultrasound irradiation has the preventive effects on inflammation-induced muscle atrophy through inhibiting phosphorylation of p38 MAPK.

α-Hydroxyisocaproic Acid Decreases Protein Synthesis but Attenuates TNFα/IFNγ Co-Exposure-Induced Protein Degradation and Myotube Atrophy via Suppression of iNOS and IL-6 in Murine C2C12 Myotube

There is ongoing debate as to whether or not α-hydroxyisocaproic acid (HICA) positively regulates skeletal muscle protein synthesis resulting in the gain or maintenance of skeletal muscle. We investigated the effects of HICA on mouse C2C12 myotubes under normal conditions and during cachexia induced by co-exposure to TNFα and IFNγ. The phosphorylation of AMPK or ERK1/2 was significantly altered 30 min after HICA treatment under normal conditions. The basal protein synthesis rates measured by a deuterium-labeling method were significantly lowered by the HICA treatment under normal and cachexic conditions. Conversely, myotube atrophy induced by TNFα/IFNγ co-exposure was significantly improved by the HICA pretreatment, and this improvement was accompanied by the inhibition of iNOS expression and IL-6 production. Moreover, HICA also suppressed the TNFα/IFNγ co-exposure-induced secretion of 3-methylhistidine. These results demonstrated that HICA decreases basal protein synthesis under normal or cachexic conditions; however, HICA might attenuate skeletal muscle atrophy via maintaining a low level of protein degradation under cachexic conditions.

Fermented milk retains beneficial effects on skeletal muscle protein anabolism after processing by centrifugation and supernatant removal

Lactobacillus-fermented milk can stimulate anabolic effects in skeletal muscle. Fermented milk containing Lactobacillus produces aqueous molecules, such as free AA and lactate. This study aimed to investigate how processing fermented milk by centrifugation and removal of supernatant affects AA absorption and postprandial skeletal muscle protein synthesis (MPS) when mice are fed fermented milk. We gavaged male Sprague-Dawley rats with skim milk (S), fermented milk (F), or processed fermented milk (P), and examined the total AA content in portal vein blood (reflecting AA absorption) and plantaris muscle MPS at 30, 60, and 90 min following administration. Relative to fasted rats, at 30 min the total AA concentration in portal vein blood from rats in the P groups was significantly higher, followed by F and S, respectively. The MPS rates were higher for the F or P groups compared with the S group. Phosphorylation levels of p70S6 kinase in the P and F groups were significantly higher than those for the S group 30 min after administration, although the level of Akt phosphorylation was similar among the groups. These results suggested that fermentation improves AA absorption that in turn enhances postprandial MPS via Akt-independent mechanisms, and that processed fermented milk retains these favorable effects on MPS.

L-Glutamine and Physical Exercise Prevent Intestinal Inflammation and Oxidative Stress Without Improving Gastric Dysmotility in Rats with Ulcerative Colitis

The aim of this study was to evaluate the effects of glutamine supplementation or exercise on gastric emptying and intestinal inflammation in rats with ulcerative colitis (UC). Strength exercise consisted of jump training 4 × 10 repetitions/5 days a week/8 weeks with progressive overload. Endurance exercise consisted of swimming without overload for a period of 1 h a day/5 days a week/8 weeks. Another group (sedentary) of animals was supplemented with L-glutamine (1 g/kg of body weight) orally for 8 weeks before induction of UC. Colitis was induced by intra-colonic administration of 1 mL of 4% acetic acid. We assessed gastric emptying, macroscopic and microscopic scoring, oxidative stress markers, and IL-1β, IL-6, and (TNF-α) levels. The UC significantly increased (p < 0.05) the gastric emptying compared with the saline control group. We observed a significantly decrease (p < 0.05) in body weight gain in UC rats compared with the control groups. Both exercise interventions and L-glutamine supplementation significantly prevented (p < 0.05) weight loss compared with the UC group. Strength and endurance exercises significantly prevented (p < 0.05) the increase of microscopic scores and oxidative stress (p < 0.05). L-glutamine supplementation in UC rats prevented hemorrhagic damage and improved oxidative stress markers (p < 0.05). Strength and endurance exercises and glutamine decreased the concentrations of inflammatory cytokines IL-1β, IL-6, and TNF-α compared with the UC group (p < 0.05). Strength and endurance exercises and L-glutamine supplementation prevented intestinal inflammation and improved cytokines and oxidative stress levels without altering gastric dysmotility in rats with UC.

Repeated stretch-shortening contraction of the triceps surae attenuates muscle atrophy and liver dysfunction in a rat model of inflammation

NEW FINDINGS

What is the central question of this study? Is stretch-shortening contraction effective to attenuate skeletal muscle atrophy and hepatic dysfunction in a rat model of peptidoglycan-polysaccharide (PG-PS)-induced inflammation (PG-PS rat)? What are the main findings and their importance? Stretch-shortening contraction attenuates skeletal muscle atrophy in the trained leg and increases circulating interleukin-10 in PG-PS rats. Stretch-shortening contraction also ameliorates liver dysfunction in PG-PS rats, possibly via increased blood interleukin-10. These findings are important because they suggest that stretch-shortening contraction is effective to maintain liver function in addition to exercised skeletal muscle mass.

ABSTRACT

Stretch-shortening contraction (SSC) is an effective modality to improve skeletal muscle mass. However, the beneficial effects of SSC in the presence of chronic inflammation remain unclear. Here, we imposed five SSC sessions unilaterally on the triceps surae in young female Lewis rats. Rats were injected with vehicle or peptidoglycan-polysaccharide (PG-PS) to induce long-lasting inflammation. The PG-PS reduced gastrocnemius muscle mass in both legs, but that of the SSC-trained leg was significantly greater than that of the contralateral leg. Circulating pro-inflammatory cytokines, such as IL-1β, were significantly increased by PG-PS injection, even if carrying out SSC. The circulating anti-inflammatory cytokine IL-10 increased with SSC in both healthy and inflammatory conditions. Stretch-shortening contraction also prevented increases in serum aspartate aminotransferase activity and plasma free phenylalanine concentration induced by PG-PS, in comparison to the control resistance exercise consisting of isometric contractions. Moreover, aspartate aminotransferase and phenylalanine concentrations demonstrated a significant and negative correlation with IL-10/IL-1β values (r = -0.61, P = 0.017, and r = -0.66, P = 0.008, respectively). These results suggest that SSC training is effective to reduce both muscle atrophy and the hepatic dysfunction induced by PG-PS, mediated, at least in part, through an increase in circulating IL-10.