Efficacy of Silkworm Pupae Extract on Muscle Strength and Mass in Middle-Aged and Older Individuals: A Randomized, Double-Blind, Placebo-Controlled Trial.

OBJECTIVES: We investigated the efficacy and safety of silkworm pupae extract (SWP) consumption for 12 weeks on muscle mass and strength in middle-aged and older individuals with relatively low skeletal muscle mass who do regular low-intensity exercise. DESIGN: A randomized double-blinded placebo-controlled trial. PARTICIPANTS: The study was conducted with 54 participants with relatively low skeletal muscle mass (SMM) (64.4 ± 6.1 years; body mass index, 23.8 ± 2.4 kg/m2). INTERVENTION AND MEASUREMENTS: Participants were randomly assigned to one of two groups: 1000 mg of SWP/day plus regular exercise (SWP group, n=27) or placebo plus regular exercise (placebo group, n=27). All participants were required to engage in 30-60 minutes/day of walking for ≥3 days/week for 12 weeks. The primary outcome was knee extension/flexion strength (Nm), measured at the velocity of 60°/s. Secondary outcomes included body composition, biomarkers (creatine kinase and creatinine), handgrip strength, and quality of life questionnaire. RESULTS: Both the intention-to-treat (ITT) and per-protocol (PP) analyses revealed no significant impact of SWP on knee strength compared to the placebo group over 12 weeks. On the other hand, the SWP group had significantly greater increases in right-handgrip strength by 1.94 kg (95% CI: 0.08-3.79; p = 0.041) and left-handgrip strength by 1.83 kg (0.25-3.41; p = 0.024) compared to the placebo group in the ITT population, after 12 weeks. Moreover, in the PP population, the SWP group revealed an even greater increase in right-handgrip strength by 2.07 kg (0.15-3. 98; p = 0.035) and left-handgrip strength by 2.21 kg (0.60-3.83; p = 0.008) for the 12-week period. However, this study resulted in a failure to detect significant differences in the body composition, biomarkers, quality of life questionnaire, physical activity, and caloric intake between the groups. None of the participants in the SWP group experienced any significant adverse events. In the placebo group, two participants experienced urticaria and allergic side effects, leading to their withdrawal from the study and two exhibited elevated levels of liver enzyme and increased diastolic blood pressure, respectively at 12 weeks. CONCLUSION: SWP, in addition to low-intensity exercise, may enhance handgrip strengths in middle-aged and older adults with relatively lower SMM. Future studies need to use a large sample size over longer periods to validate our findings. This trial was registered at clinicaltrials.gov as NCT04994054.

Structural characteristics and properties of the regenerated silk fibroin prepared from formic acid.

Structural characteristics and thermal and solution properties of the regenerated silk fibroin (SF) prepared from formic acid (FU) were compared with those of SF from water (AU). According to the turbidity and shear viscosity measurement, SF formic acid solution was stable and transparent, no molecular aggregations occurred. The sample FU exhibited the beta-sheet structure, while AU random coil conformation using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry. The effects of methanol treatment on samples were also examined. According to the measurement of crystallinity (XRD) and crystallinity index (FTIR), the concept of long/short-range ordered structure formation was proposed. Long-range ordered crystallites are predominantly formed for methanol treated SF film while SF film cast from formic acid favors the formation of short-range ordered structure. The relaxation temperatures of SF films measured by dynamic thermomechanical analysis supported the above mechanism due to the sensitivity of relaxation temperature on the short-range order.