Branched-chain amino acids from plants and the metabolic syndrome: pathways and pharmacological applications.

Background: Metabolic syndrome (MetS) affects approximately 1.54 billion adults worldwide and is characterized by central obesity, insulin resistance, hypertension, and dyslipidemia. Chronic low-grade inflammation is central to the development of MetS. A global shift toward a plant-based diet has prompted a reevaluation of the differing impacts of protein sources on metabolic health. Objective: The purpose of this review is to provide a systematic overview of how BCAAs from plant sources may modulate chronic inflammatory processes and improve individual components of MetS by analyzing their sources, bioavailability (including both digestibility and absorptive efficiency), metabolism, and modes of action compared to animal-based BCAAs. Results: Dietary plant-derived BCAAs are abundant and have acceptable bioaccessibility. Legumes, whole grains, and microalgae contain significant levels of BCAAs. Processing technologies such as fermentation, heat treatment, and extrusion enhance BCAA content in food products. Germination and enzymatic hydrolysis can significantly improve digestibility. Preclinical evidence from cell-based and rodent studies indicates that plant-derived BCAAs exert multi-target regulation of chronic inflammation, including modulation of mTORC1 signaling, suppression of the NF-κB pathway, potential regulation of the NLRP3 inflammasome, and beneficial interactions with gut microbiota. Their comparatively slower absorption kinetics relative to animal-derived BCAAs offer a mechanistic rationale for avoiding chronic mTORC1 hyperactivation, although direct human evidence confirming these specific mechanistic pathways remains limited and requires further clinical validation. Large prospective cohort studies suggest that substituting animal proteins with plant sources is associated with an approximately 8-12% lower risk of all-cause and cardiovascular mortality, although the certainty of this evidence is limited by residual confounding inherent in observational designs. RCT evidence (moderate certainty by GRADE) demonstrates improved glycemic control, lipid profiles, and body composition with plant-based dietary patterns, particularly in individuals with type 2 diabetes or metabolic syndrome. The "BCAA paradox" can be explained by the differing kinetics of absorption, matrix effects, and gut microbiota interactions between plant and animal sources. Conclusion: Plant-based BCAAs hold great potential for the prevention and treatment of MetS, owing to their low saturated fat content, abundant dietary fiber, polyphenolic antioxidant capacity, and beneficial effects on gut microbiota. Future studies should focus on precision nutrition, long-term clinical trials, and optimal dosing regimens. Translating mechanistic knowledge into dietary recommendations is essential for managing MetS.