Regulatory Effects of Myo‐Inositol on Carbohydrate Metabolism and Low‐Salinity Adaptation in Pacific White Shrimp (Penaeus vannamei)

Abstract

This study investigated how dietary myo‐inositol affects osmoregulation, carbohydrate and lipid metabolism, immunity, and antioxidant properties in Penaeus vannamei under long‐term low‐salinity conditions. A two‐factor (2 × 3) orthogonal approach was used with three different concentrations of dietary myo‐inositol (0, 1,200, and 2,000 mg/kg) at two dietary carbohydrate levels: normal carbohydrate or high carbohydrate (HC). Six experimental diets were formulated, and a feeding trial was carried out for 42 days. The interaction of myo‐inositol with an HC diet significantly improved shrimp survival, weight gain, and specific growth rates. Dietary myo‐inositol increased the contents of Na+, K+, and Ca2+ in the serum and reduced the ion loss caused by low‐salinity stress. In addition, a lack of myo‐inositol can lead to loosening of gill filament connections and thinning or disappearance of the cuticle. However, myo‐inositol supplementation protected the structural and functional integrity of the shrimp gills and significantly enhanced the ion transport capacity (P < 0.05). Two‐factor analysis showed that myo‐inositol concentration was affected by dietary carbohydrate levels, and an HC diet enhanced myo‐inositol biosynthesis in shrimp gills (P < 0.05). The concentrations of myo‐inositol are highest in the gills and lowest in the liver and pancreas. Moreover, dietary myo‐inositol can improve the immune function and antioxidant capacity of P. vannamei. The results also indicated that under sustained low‐salinity stress, high levels of carbohydrates cannot relieve the stress caused by low‐salinity conditions and can even affect the healthy growth of P. vannamei. Under HC levels, adding dietary myo‐inositol significantly improved glycogen and lipid deposition in hepatopancreas tissue and enhanced carbohydrate utilization and osmotic adjustment ability in P. vannamei under chronic low‐salinity stress.