Obesity is a major global health burden that is linked to type 2 diabetes, cardiovascular disease, and metabolic syndrome. Chitosan oligosaccharides (COS) are bioactive compounds that are derived from the depolymerization of the chitosan in crustacean shells and are promising candidates for natural anti-adipogenesis effects. However, there is incomplete understanding of the molecular mechanisms by which structurally defined low-molecular-weight COS modulates adipogenic transcription networks and global transcriptional reprogramming. MALDI-TOF (matrix-assisted laser desorption/ionization time-of-flight) mass spectrometry and ¹³C NMR spectroscopy indicated a predominance of dimeric species (DP2) at m/z 344.79, which represents a lower molecular weight fraction and is proposed to improve the membrane permeability and intracellular bioavailability of COS. In a 3T3-L1 preadipocyte model, COS treatment at concentrations of 320–1280 µg/mL dose-dependently reduced intracellular lipid accumulation, triglyceride content, and adipocyte maturation while enhancing lipolysis and insulin-mediated glucose uptake. Western blot analysis indicated dose-dependent downregulation of PPARγ and C/EBPα. Transcriptomic RNA-seq analysis indicated large-scale transcriptional reprogramming with the altered expression of genes involved in PPAR signaling, PI3K-Akt, AMPK, insulin signaling, and fatty acid metabolism pathways among differentially expressed genes. These findings demonstrate that COS suppresses adipogenesis through the coordinated modulation of adipogenic transcription factors and multiple metabolic signaling pathways. The results support its potential as a promising natural compound but warrant preclinical investigation in the context of obesity and metabolic disorders.

Holothuria scabra has long been acknowledged in traditional medicine for its therapeutic properties. The transforming growth factor-beta (TGF-β) superfamily is crucial in regulating cellular processes, including differentiation, proliferation, and immune responses. This study marks the first exploration of the gene expression localization, sequence conservation, and functional roles of H. scabra TGF-β proteins, specifically activin (HolscActivin), inhibin (HolscInhibin), and the TGF-β receptor (HolscTGFBR), across various organs. In situ hybridization indicated that HolscActivin and HolscInhibin are expressed in the intestine, respiratory tree, ovary, testis, and inner body wall. This suggests their roles in nutrient absorption, gas exchange, reproduction, and extracellular matrix remodeling. Notably, HolscTGFBR demonstrated a similar tissue-specific expression pattern, except for its absence in the respiratory tree. Bioinformatics analysis reveals that HolscTGFBR shares significant sequence similarity with HomsaTGFBR, especially in regions essential for signal transduction and inhibition. Molecular docking results indicate that HolscActivin may promote receptor activation, while HolscInhibin functions as a natural antagonist, reflecting the signaling mechanisms of human TGF-β proteins. Interestingly, cross-species ternary complex docking with human TGF-β receptors further supports these findings, showing that HolscActivin moderately engages the receptors, whereas HolscInhibin exhibits strong binding, suggestive of competitive inhibition. These results indicate that H. scabra TGF-β proteins retain the structural and functional features of vertebrate TGF-β ligands, supporting their potential applications as natural modulators in therapeutic and functional food development.

Crustacean shell waste from the seafood industry represents an underutilized food waste with the potential to produce chitosan and chitosan oligosaccharides (COS), with promising applications in bone regeneration. However, the molecular mechanisms of COS during osteogenic differentiation remain uncharacterized. In this study, chitosan was extracted from mud crab (Scylla olivacea) shell waste and COS was prepared from chitosan by acid hydrolysis and then characterized by FT-IR and FESEM, confirming the chitosan backbone and a degree of deacetylation (DD) exceeding 80%. The COS treatment in the concentration range of 5–320 µg/mL significantly enhanced MC3T3-E1 pre-osteoblast proliferation without cytotoxicity, and it increased alkaline phosphatase (ALP) activity, extracellular matrix mineralization, and Runx2/osterix (OSX) expression. Transcriptomics of pre-osteoblasts treated with COS at 320 µg/mL for 21 days identified 19,643 differentially expressed genes, revealing coordinated activation of multiple osteogenesis-related signaling pathways, including ECM–integrin/focal adhesion, PI3K-Akt/MAPK, TGF-β/BMP, Wnt/β-catenin, and parathyroid hormone (PTH) synthesis. These findings demonstrate that marine-derived COS promotes osteoblast differentiation through the coordinated activation of multiple signaling pathways, providing the first comprehensive transcriptomic characterization of MC3T3-E1 pre-osteoblast directly treated with COS during osteogenic differentiation. Therefore, this study supports the use of COS as a promising bioactive oligosaccharide for bone regeneration and osteoporosis management, and further in vivo and clinical studies are recommended.