Oral Administration of Silk Peptide Enhances the Maturation and Cytolytic Activity of Natural Killer Cells

Silk peptide, the hydrolysate of silk protein derived from cocoons, has been employed as a biomedical material and is believed to be safe for human use. Silk peptide display various bioactivities, including anti-inflammatory, immune-regulatory, anti-tumor, anti-viral, and anti-bacterial. Although earlier investigations demonstrated that silk peptide stimulates macrophages and the production of pro-inflammatory cytokines, its effect on natural killer (NK) cell function has not yet been explored. In this study, we initially confirmed that silk peptide enhances NK cell activity in vitro and ex vivo. To assess the modulatory activity of silk peptide on NK cells, mice were fed various amounts of a silk peptide-supplemented diet for 2 months and the effects on immune stimulation, including NK cell activation, were evaluated. Oral administration of silk peptide significantly enhanced the proliferation of mitogen- or IL-2-stimulated splenocytes. In addition, oral silk peptide treatment enhanced the frequency and degree of maturation of NK cells in splenocytes. The same treatment also significantly enhanced the target cell cytolytic activity of NK cells, which was determined by cell surface CD107a expression and intracellular interferon-γ expression. Finally, oral administration of silk peptide stimulated T helper 1-type cytokine expression from splenic lymphocytes. Collectively, our results suggest that silk peptide potentiates NK cell activity in vivo and could be used as a compound for immune-modulating anti-tumor treatment.

Anti-diabetic effect of acid hydrolyzed silk peptides via cytoprotection of pancreas beta-cells and up-regulation of glucose uptake in muscle cells / 동물의과학연구지

In this study, we observed anti-diabetic effects of acid hydrolyzed silk peptides, where the amount of peptides in the total amino acid mixture was strictly regulated. Using in vitro diabetes models, silk peptide-containing amino acid mixtures of 5.60% (G5), 11.30% (G10), 14.50% (G15), and 20.50% (G20) were examined separately in order to determine whether they have biological activities. According to our results, a cytoprotective effect was observed following treatment of interleukin-1beta in RINm5f pancreas beta-cells. As a consequence, Bax, a pro-apoptotic gene, was down-regulated, while Bcl-2, a pro-survival gene, was retained at normal level. Results of the 4',6-diamidino-2-phentylindole (DAPI) staining assay confirmed that G20 has a better cytoprotective effect. Insulin release from RINm5f cells showed a significant increase following treatment with G5-G20, suggesting that silk peptide effectively regulated and induced insulin production. Single treatment with G5-G20 resulted in enhanced glucose uptake in L6 skeletal muscle cells. In addition, a higher amount of each group inhibited the activity of alpha-glucosidase. In summary, these data suggest that silk peptide may have an anti-diabetic effect through protection of pancreas beta-cells and enhancement of insulin release, which showed a close association with Type 1 diabetes mellitus (DM), and can improve glucose uptake, which was the major target for therapy of Type 2 diabetes. Taken together, we concluded that acid hydrolyzed silk peptides can be used effectively for control of blood sugar metabolism via improvement of the problematic indices of Type 1 and Type 2 DM.

The Effects of Programmed Dietary System of a Mixture of Natural Supplements on the Composition, Serum Lipids and the Leptin Levels / 대한지역사회영양학회지

This study was to investigate the effects of a silk peptide, and prune and raspberry mixture on the body fat, serum lipid composition and fat distribution in Korean women during the time they received these supplements. During the 4 month period of this research (June to October, 2002), 75 women (average age 22.9 yr) were selected as subjects. Their nutrient intake was investigated by use of a questionnaire and the 24-hour recall method. Antropometric assessments of the subjects were investigated by using the SBIA Method (Segmental Bioimpedance Assay, Inbody 3.0). The results were as follows: their mean body weight was 59.3 kg, their mean body height was 161.7 cm and their mean Basal Metabolic Indices (BMI) was 22.7. The status of their dietary fiber intake significantly increased (p<0.05) after use of the supplements. Their body fat significantly decreased following the 3rd stage of supplementation (p<0.05), and their percent of body fat signiflcantly decreased after supplementation (p<0.05). Their triceps and suprailiac circumference significantly decreased following the 3rd stage of supplementation (p<0.05). Their waist circumferences and waist-hip ratios (WHR) significantly decreased after both the 2nd and 3rd stage of supplementation (p<0.05). Their total cholesterol significantly decreased following the 3rd stage of supplementation, as compared to their baseline results and those obtained following the 1st stage of supplementation (p<0.05). Their LDL-cholesterol and LDL/HDL ratios significantly decreased following the 3rd stage of supplementation, as compared to their baseline results and those obtained following the 1st stage of supplementation (p<0.05). Their 4-HNE and total antioxidant statuses significantly decreased following the 2nd and 3rd stage of supplementation, as compared to their baseline results and those obtained following the 1st stage of supplementation (p<0.05). Their 2nd stage supplementation results were significantly negatively correlated with their triceps measurements and WHR (p<0.05). Their 3rd stage supplementation results were significantly negatively correlated with their anterior thigh measurements (p<0.05). The above results show that prune, raspberry, silk peptide and dietary fiber supplementation to a routine diet improves body fat distribution, total cholesterol, and triglyceride levels. The decrease of abdominal fat and WHR were especially noteworthy. This implies a decrease of risk factors.