Leucine Supplementation in a Chronically Protein-Restricted Diet Enhances Muscle Weight and Postprandial Protein Synthesis of Skeletal Muscle by Promoting the mTOR Pathway in Adult Rats

Low protein intake causes a decrease in protein deposition in most animal tissues. The purpose of this study was to investigate whether leucine supplementation would increase the synthesis rate of protein and muscle weight in adult rats, which chronically consume only 58.8% of their protein requirements. Thirty-six male Sprague-Dawley rats were assigned to one of three dietary treatments including a 20% casein diet (CON), a 10% casein + 0.44% alanine diet (R), and a 10% casein + 0.87% leucine diet (RL). After a 10 d dietary treatment, plasma amino acid levels were measured after feeding, the gastrocnemius muscles and soleus muscles were harvested and weighed, and the fractional synthesis rate (FSR) and mammalian target of rapamycin (mTOR) signaling proteins in skeletal muscle were measured. Regarding the plasma amino acid level, the RL group had the highest concentration of leucine (P < 0.05) and the lowest concentration of isoleucine (P < 0.05) among the three groups, and the CON group had a lower concentration of valine (P < 0.05) than the R and RL groups. Compared with the R and RL groups, the CON group diet significantly increased (P < 0.05) feed intake, protein synthesis rate, and the phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and decreased the weight of abdominal adipose. Compared with the R group, the RL group significantly increased in gastrocnemius muscle weight, protein synthesis rate, and phosphorylation of both ribosomal protein S6 kinase 1 (S6K1) and 4E-BP1. In conclusion, when protein is chronically restricted in adult rat diets, leucine supplementation moderately improves body weight gain and increases muscle protein synthesis through mTOR activation

Validating Accuracy of Rayleigh-Wave Dispersion Extracted from Ambient Seismic Noise Via Comparison with Data from a Ground-Truth Earthquake

In order to validate the accuracy of estimated Green’s functions (EGFs), which are widely used in ambient seismic noise tomography, a broadband seismograph was installed in the epicentral area of an M 5 earthquake, with ground‐truth location from Interferometric Synthetic Aperture Radar observations. EGFs between this station and permanent stations are compared with surface waves excited by the earthquake. The group velocity dispersion measured from EGFs at large interstation distances (∼1000  km or longer) are consistent with measurements from the earthquake, and the EGFs from symmetric noise correlation functions (NCFs) are usually more accurate. At shorter interstation distances (300–1000 km), the match between noise and earthquake dispersion is good for most stations, although we observed mismatch for a few stations. The mismatch is probably caused by low signal‐to‐noise ratio of NCFs or nondiffusive noise wavefield at short distances