Supercritical CO₂ defatting and hydrolysis improve the bioactivity of Protaetia brevitarsis seulensis proteins against oxidative stress, inflammation, and muscle atrophy

This study evaluated the structural and functional properties of Protaetia brevitarsis seulensis larvae (PBS) subjected to hexane or supercritical CO₂ (SC-CO₂) defatting, followed by enzymatic hydrolysis. The untreated (W), hexane-defatted (H), and SC-CO₂-defatted (S) samples, and their respective hydrolysates (HH, SH), were compared. Defatting reduced particle size and improved uniformity, protein integrity and essential amino acids were better preserved with SC-CO₂ than hexane. SH had the highest amino acid content and antioxidant activity. In C2C12 myotubes, PBS-derived samples alleviated dexamethasone-induced muscle atrophy by increasing myotube diameter and reducing atrophy markers (Myostatin, MuRF-1, and Atrogin-1), with SH and HH outperforming the positive control. Moreover, PBS hydrolysates suppressed inflammatory cytokines (tumour necrosis factor-α, interleukin (IL)-1β, and IL-6) and improved insulin signaling by restoring Akt phosphorylation in palmitate-treated cells. Although the W group showed partial activity, its overall efficacy was limited compared with the pretreated samples. These findings suggest that SC-CO₂ defatting combined with enzymatic hydrolysis enhances the structural integrity and multifunctional bioactivity of PBS proteins, supporting their potential as sustainable functional ingredients with antioxidant, anti-inflammatory, and muscle-protective properties.