Short‐term recovery of alpha‐lipoic acid on the intestine of <i>Megalobrama amblycephala</i> after ammonia stress

Abstract This study aimed to investigate the short‐term recovery effect of α ‐lipoic acid ( α ‐LA) on the intestine of juvenile Megalobrama amblycephala stressed by ammonia. Experimental fish with a body weight of 13.7 ± 1.6 g were exposed to ammonium chloride solutions at 0 (G1), 5.45 (G2) and 10.89 mg/L (G3), respectively, for 72 h. The fish were moved to aerated tap water to conduct the recovery experiment after ammonia stress. Each group was subdivided into three subgroups and fed three experimental diets containing 0, 0.6 or 1.2 g/kg α ‐LA for another 72 h. Intestinal samples after ammonia exposure and recovery were collected to analyse digestive and absorptive enzyme activities, histology and inflammation‐related gene expression. The results showed that compared with the control group, lipase, Na + , K + ‐ATPase, γ ‐GT and CK activities were significantly decreased at the 12th, 24th, 48th and 72nd hours under ammonia exposure ( p &lt; 0.05). Protease and amylase activities in stress groups also declined at the 24th, 48th and 72nd hours under ammonia exposure ( p &lt; 0.05). Meanwhile, TNF‐α, NF‐κB and IL‐1β mRNA levels significantly increased as ammonia concentrations increased at the same α ‐LA level ( p &lt; 0.05). However, protease, lipase, amylase, Na + , K + ‐ATPase, γ ‐GT and CK activities in G2 and G3 exhibited an upward trend with prolonged α ‐LA recovery. Diets supplemented with 0.6 and 1.2 g/kg α ‐LA increased the intestinal villus height and width in G2 ( p &lt; 0.05), decreased NF‐κB and IL‐1β expression levels in G3 ( p &lt; 0.05). Furthermore, the intestinal digestive and absorptive enzyme activities were positively correlated with dietary α ‐LA levels. In conclusion, dietary supplementation with α ‐LA restored the intestinal digestive and absorptive function and protected the intestine against ammonia‐induced stress.