Diabetes mellitus (DM) has become the world’s third major disease after tumors and cardiovascular disease. With the exploitation of marine biological resources, the efficacy of using polysaccharides isolated from marine organisms in blood glucose regulation has received widespread attention. Some marine polysaccharides can reduce blood glucose by inhibiting digestive enzyme activity, eliminating insulin resistance, and regulating gut microbiota. These polysaccharides are mainly fucose-containing sulphated polysaccharides from algae and sea cucumbers. It follows that the hypoglycemic activity of marine fucosyl-polysaccharides is closely related to their structure, such as their sulfate group, monosaccharide composition, molecular weight and glycosidic bond type. However, the structure of marine fucosyl-polysaccharides and the mechanism of their hypoglycemic activity are not yet clear. Therefore, this review comprehensively covers the effects of marine fucosyl-polysaccharides sources, mechanisms and the structure–activity relationship on hypoglycemic activity. Moreover, the potential regulatory effects of fucosyl-polysaccharides on vascular complications caused by hyperglycemia are also summarized in this review. This review provides rationales for the activity study of marine fucosyl-polysaccharides and new insights into the high-value utilization of marine biological resources.

Low molecular weight galactomannan (LMGM) alleviated diarrhea symptoms within two hours post-treatment, promoted intestinal water absorption, and regulated gut microbiota.

High viscosity of alginate means a relatively low substrate concentration, which limits the efficiency of hydrolysis, resulting in one of the main challenges for the large-scale production of alginate oligosaccharides (AOS). In this study, a pilot-scale degradation product (PSDP) of the recombinant enzyme 102C300C-Vgb was produced for the first time at a substrate concentration of up to 20% sodium alginate. The optimal conditions for SA digestion were: enzyme dosage of 25 U/g, enzymatic temperature of 45 °C, enzymatic pH of 7.0, and enzymatic time of 24 h. Under these conditions, the yield of enzymatic hydrolysis was consistently in the range of 69% to 70%. The average molecular weight (Mw) of PSDP was 1496.36 Da, mainly containing oligosaccharides with degrees of polymerization ranging from 2 to 4. The low-Mw PSDP was subsequently applied in the diet of sea cucumber Stichopus japonicus. The results showed that the body wall weight of S. japonicus increased significantly after 40 days of feeding with a 0.09% PSDP-supplemented diet. Furthermore, PSDP-supplemented diet significantly increased the thickness of the serosal and submucosal layers and the width folds of mucosa of the sea cucumber gut. The abundance of pathogenic bacteria was reduced effectively, and that of beneficial bacteria increased significantly after being fed with PSDP. The results demonstrated that PSDP can serve as a digestive health enhancer for sea cucumbers, promoting their healthy growth.

Sea cucumber viscera by-products are abundant but remain underutilized. Although the development of umami peptides from marine by-products has been well-reported, sea cucumber viscera have received less attention. In this study, an umami-rich hydrolysate was prepared from sea cucumber viscera through synergistic dual-enzyme hydrolysis. Under optimal conditions, the co-hydrolysis using Flavourzyme and aminopeptidase yielded extraction rates of 69.38% for solids, 67.29% for protein, and 66.96% for total sugar, and produced a 1.75-fold higher umami signal intensity (electronic tongue) than the single-enzyme (Flavourzyme) hydrolysate. The target umami fraction was enriched through sensory-guided separation combined with ultrafiltration and ion-exchange chromatography. Thirty-three umami peptides, predominantly derived from actin hydrolysis, were identified in this fraction via peptidomics and virtual screening. Based on docking simulations against the umami receptor T1R1/T1R3, two peptides (DFLDDGPG and SDTGNFGF) with the lowest docking scores were selected. The predictions revealed that two peptides bind to the T1R3 subunit via hydrogen bonds and π-related interactions. The umami-enhancing effect of peptide DFLDDGPG in salty systems was demonstrated by a trained panel (n = 10) across concentration ranges of 0.1–1.0 mg/mL peptide and 0.1–1.0% NaCl, with a positive correlation validated by RSM and ANOVA (p < 0.05). This study identified novel umami peptides from sea cucumber by-products as promising candidates for natural, low-sodium flavor enhancers.