Journal of Advances in Biology & Biotechnology

This narrative review synthesizes findings from peer-reviewed literature retrieved from PubMed, Scopus, and Web of Science databases, focusing on studies published between 2000 and 2025 that investigate the effects of fucoidans and ulvans on gut microbiota, intestinal barrier function, and metabolic outcomes. The gut-metabolic axis, defined as the bidirectional relationship between the gut microbiota and host metabolism, is a paramount modulator of health and disease. Dysregulation of this axis is increasingly recognized in the pathophysiology of insulin resistance (IR) and type 2 diabetes mellitus (T2DM), conditions frequently driven by chronic low-grade systemic inflammation. A key mediator of this inflammatory state is metabolic endotoxemia, resulting from augmented intestinal permeability and translocation of lipopolysaccharide (LPS) into the systemic circulation. Among marine-derived bioactive compounds, brown seaweed fucoidans and green seaweed ulvans have attracted considerable attention for their capacity to modulate the gut-metabolic axis. These sulfated polysaccharides serve as prebiotics that selectively promote beneficial gut bacteria, including Lactobacillus, Bifidobacterium, and Akkermansia muciniphila, thereby enhancing short-chain fatty acid (SCFA) production. SCFAs, particularly butyrate, play essential roles in sustaining gut barrier integrity, modulating immune responses, and improving glucose homeostasis. Beyond their prebiotic effects, fucoidans and ulvans exert direct anti-inflammatory activities by inhibiting the NF-κB/MAPK signaling cascades and suppressing TLR4-mediated LPS recognition. Through these complementary mechanisms—gut ecosystem modulation, intestinal barrier reinforcement, and attenuation of inflammatory signaling—these algal polysaccharides represent a promising therapeutic strategy for metabolic disorders. Their potential applications extend to functional foods, nutraceuticals, and dietary supplements for the prevention and management of obesity, T2DM, and metabolic syndrome. However, it should be noted that the current evidence is predominantly derived from in vitro and animal studies, with limited clinical trials in human populations, underscoring the need for well-designed, long-term human intervention studies to validate their therapeutic efficacy and establish optimal dosing regimens.