This study investigated preventive effects of whey protein fermented with Lactobacillus gasseri IM13 (FWP) on dexamethasone-(DEX) induced muscle atrophy. Whey protein (WP) was fermented with 9 Lactobacillus strains, isolated from infant feces, (L. reuteri 3B03, L. gasseri 5R01, 5R13, IM13, IR13, L. plantarum 11B02, L. rhamnosus IM14, IM18, IM19) which have high tolerance to bile salts and acid, and adherable ability to the intestine. The proteolytic activity of strains and antioxidant activities of fermented WP were synergistically improved by fermentation. In particular, L. gasseri IM13 exhibited potent proteolytic activity against WP, and WP fermented with L. gasseri showed strong reducing power and radical scavenging activities. The viable cell count, degree of hydrolysis, pH, and antioxidant activities were estimated every 3 fermentation hours to identify fermentation characteristic. During fermentation, L. gasseri IM13 grew consecutively and then pH value decreased as lactic acid contents increased. As the amount of free amino acids in whey is restricted, the continuous growth of L. gasseri IM13 depends on proteolysis enzymes and the degree of hydrolysis in WP increased over fermentation time. In addition, the anti-oxidative activities were the highest when fermentation was progressed for 45 h. Whole genome sequence of L. gasseri IM13 was analyzed and identified its functional characteristics. The genome data was compared with other 4 Lactobacillus strains and expressed by phylogenetic tree, dendrogram, and Venn diagram. The novelty of IM13 was confirmed based on genome data
To evaluate the preventive effect on muscle atrophy, FWP was pre-treated on DEX-stimulated C2C12 mouse muscle cells. DEX treatment induced muscle atrophy by inhibiting histological changes in myotubes (reduction in the diameter and nuclei formation), creatine kinase activity, and myogenic regulatory messenger RNA (mRNA) expression. The results showed the pretreatment with WP and FWP alleviated inhibition of myogenesis by DEX, and FWP indicated significantly higher preventive effects compared to WP. Moreover, FWP markedly down-regulated the expression of muscle atrophy genes mediated by the ubiquitin-proteasome and autophagy-lysosome systems stimulated by DEX. Similarly, FWP pretreatment showed significantly higher protective effects on DEX-triggered mRNA expression of muscle atrophy gene compared to WP pretreatment. These findings suggest that the administration of FWP could prevent DEX-induced muscle atrophy by up-regulating myogenesis and down-regulating muscle protein degradation, and thus has the potential to play preventive roles in the management of muscle atrophy.