Abstract

Sericin-derived oligopeptides (SDOs) from the Bombyx mori yellow silk cocoons show strong bioactive properties. However, clinical safety data on SDOs produced by specific enzymatic hydrolysis with a particular serine-rich (20.5%) and aspartic acid-rich (16.9%) composition is required to obtain regulatory approval as a novel food ingredient. This Phase 0 randomized, double-blind, placebo-controlled trial evaluated the short-term safety, tolerability, and gut microbiota effects of SDOs supplementation in healthy adults. Forty-two healthy volunteers were randomized (1:1:1) to receive daily doses of placebo, 0.9 g SDOs or 1.8 g SDOs for eight weeks. Primary safety endpoints included vital signs, hematology, and comprehensive clinical chemistry (renal and hepatic functions). Secondary outcomes included lipid profiles, oxidative stress markers (hs-CRP, TAC, SOD, MDA) and gut microbiota composition analyzed by 16S rRNA metagenome sequencing. Forty-one participants (97.6%) completed the study with high compliance (>98%). No serious adverse events were reported. All primary clinical parameters remained within clinically normal ranges, and no significant differences between groups were observed throughout the study (p > 0.05). No adverse effects on fasting blood glucose, lipid profiles or systemic oxidative stress were observed after SDOs supplementation. Importantly, 16S rRNA sequencing analysis showed that SDOs maintained gut microbial homeostasis throughout the 8-week intervention period, with Bacteroidetes and Firmicutes as the predominant phyla in the core community structure. Oral intake of enzymatically generated SDOs up to 1.8 g/day in healthy adults was well-tolerated with only occasional mild and transient gastrointestinal symptoms that did not appear to be dose-dependent. These first preliminary findings suggest a favorable safety profile for this unique peptide preparation, supporting its potential evaluation as a novel food ingredient and providing a reasonable basis for future, larger-scale trials to evaluate its efficacy in metabolic health.

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