Dietary Arecoline Supplementation Enhances Flesh Quality, Muscle Growth, and Protein Deposition in Grass Carp (Ctenopharyngodon idella): Insights Into TOR and FOXO Signaling Pathways.

Arecoline is an alkaloid isolated from the plant betel nut, which exerts a wide range of physiological effects by stimulating muscarinic receptors. To explore the effect of arecoline on the flesh quality of fish, grass carp were fed different levels of arecoline (0, 0.5, 1.0, 1.5, 2.0, and 2.5 mg/kg diet) for 63 days. Key findings demonstrated that arecoline significantly alleviated postmortem pH decline, reduced cooking losses, and decreased lactic acid content. It also enhanced the nutritional value of muscle by increasing the content of essential amino acids (EAAs) and polyunsaturated fatty acids (PUFAs). Moreover, it improved muscle flavor characteristics by increasing the content of amino acids associated with umami. Additionally, appropriate levels of arecoline increased muscle fiber diameter, the frequency of fibers with diameters greater than 50 μm, and the mRNA levels of myogenic regulatory factors (MRFs). These findings suggest that arecoline promotes muscle growth in grass carp. We further found that dietary arecoline may promote muscle protein deposition through protein synthesis and the ubiquitin-proteasome pathway (UPP). Our findings provide novel evidence that arecoline improves fish flesh quality. These findings offer practical insights for aquaculture nutrition and highlight arecoline's potential as a functional feed additive.