Dietary myo-inositol ameliorates chronic iron salt toxicity in Litopenaeus vannamei: Insights from growth, histopathology, antioxidant capacity, apoptosis, microbiome, and metabolome

Iron (Fe) toxicity poses a significant challenge in aquaculture, affecting the health, metabolism, and microbial ecology of Litopenaeus vannamei . This study investigated the protective effects of myo-inositol (MI) supplementation against Fe-induced toxicity by integrating microbiome and metabolomic analyses. L. vannamei with the initial weight of 0.30 ± 0.00 g were chronically exposed to Fe salts levels without Fe and MI (N), with Fe and without MI (Fe), with Fe and 800 mg/kg MI (FeMI1), and with Fe and 1600 mg/kg MI (FeMI2) for 60 days. Results demonstrated that dietary MI significantly improved the growth performance in shrimp exposed to Fe salts, including increased weight gain ( P = 0.005), specific growth rate ( P = 0.005), and reduction in feed conversion ratio ( P < 0.001). Exposure to Fe salts significantly increased Fe accumulation in the muscle and hepatopancreas tissues ( P < 0.05). Fe exposure also elevated the expression of apoptosis-related genes ( caspase3, caspase8, p53, Bax ), and histopathological damage while suppressing antioxidant enzyme activities (CAT, T-AOC, MnSOD, GSH-Px, AK; P < 0.05). Intestinal microbiota analysis revealed Fe-induced dysbiosis, characterized by a reduction in beneficial bacterial populations in the genus ( Motilimonas ) and microbial diversity. MI supplementation alleviated these negative effects by enhancing antioxidant responses, modulating immune-metabolic pathways, and restoring intestinal microbial balance. Metabolomic analysis identified significant alterations in key metabolites, including serotonin, S-adenosyl- L -homocysteine, and propionic acid, while correlation heatmaps revealed strong associations between these metabolites and microbiota at the phylum level. Firmicutes, Chloroflexi, and Acidobacteriota were positively correlated with antioxidant-related metabolites, whereas Bacteroidota showed a negative correlation with sclareol. This integrated approach shows that MI regulates key metabolic pathways linked to oxidative stress and cellular defence. Overall, these findings suggest that MI supplementation is a promising dietary strategy to mitigate Fe-induced toxicity in L. vannamei , contributing to improved aquaculture sustainability. • Fe exposure increased metal bioaccumulation in L. vannamei hepatopancreatic tissues. • MI reduced Fe-induced toxicity by boosting antioxidant and reducing apoptosis. • Digestive enzymes improved significantly with MI dietary supplementation. • MI protected hepatopancreas and intestine from Fe-induced tissue damage. • MI restored intestinal microbial richness altered by Fe exposure.