Dietary resveratrol alleviates liver and intestinal injury in ducks under cage rearing system

Abstract

Cage rearing is a promising farming method. However, our previous studies have demonstrated that changes in farming practices induce oxidative stress and inflammation in the liver and duodenum of ducks. Resveratrol (RES), a natural plant polyphenol, possesses antioxidant, anti-inflammatory, and cytoprotective properties. This study evaluated the alleviating effects of RES against cage-rearing-induced duck health problems, emphasizing the involvement of redox imbalance, inflammatory response, endoplasmic reticulum (ER) stress, apoptosis, and PI3K/AKT and MAPK/ERK pathways. A total of 120 healthy 12-week-old female ducks were transferred to a cage system and randomly assigned to two dietary RES groups with 6 replicates each (10 ducks per replicate), including basal diet + 0 mg/kg RES (control group, CON), and basal diet + 500 mg/kg RES (RES-treated group, RES). During the early stages (within 10 days) of cage rearing, blood, liver, and duodenal samples were collected for analysis. The results demonstrated that RES reduced histopathological damage in the liver and duodenum of cage-reared ducks. It also reduced serum albumin levels, increased serum aspartate aminotransferase and alanine aminotransferase levels, and enhanced antioxidant (increased CAT, GSH-Px, SOD, and T-AOC activities in the serum, liver, and duodenum, and reduced the increase in MDA) and anti-inflammatory properties (reduced pro-inflammatory cytokines interleukin (IL)-1β and IL-6 secretion and increased anti-inflammatory cytokine IL-4 levels). Additionally, quantitative real-time polymerase chain reaction revealed that RES intervention reversed the abnormal mRNA abundance of biomarkers associated with inflammatory injury (iNOS and COX2) in the liver, and ER stress (GRP78) and apoptosis (Bax and Bcl2) in the liver and duodenum of cage-reared ducks. Further analysis of key proteins in the PI3K/AKT and ERK MAPK signaling pathways revealed that RES promoted AKT phosphorylation in the liver and duodenum of cage-reared ducks and reduced cleaved caspase-3 protein content. Overall, RES prevents cage-rearing stimuli-induced liver and intestinal injury in ducks by enhancing liver function, improving antioxidant properties, inhibiting inflammation, ER stress, and apoptosis, and activating the PI3K/AKT signaling pathway.

Keywords: Cage rearing; Duck; Inflammation; Oxidative stress; Resveratrol.

Fig. 1

Representative photomicrographs of duck liver (A) and intestine (B) tissue sections (HE staining; magnification, 200 ×; scale bars, 100 μm). Inflammatory cell infiltration (black arrow); congestion (yellow arrow); hepatocyte degeneration with swollen cytosol, and loose and lightly stained cytoplasm (red arrow); cytoplasmic vacuolization (gray arrow); necrosis (green arrow); epithelial cell detachment (blue arrow).

Fig. 2

Effects of dietary RES supplementation on liver function in ducks reared in the cage system. Difference analysis was performed using an independent sample t-test between CON and RES groups for the same time of cage rearing. *P < 0.05 and **P < 0.01. Values are expressed as the mean ± SD (n = 6).

Fig. 3

Effects of RES on antioxidant levels in cage-reared ducks. (A–E) Serum antioxidant indices, (F–J) liver antioxidant indices, and (K–O) intestinal tissue antioxidant indices. Difference analysis was performed using an independent sample t-test between CON and RES groups for the same time of cage rearing. *P < 0.05 and **P < 0.01. Values are expressed as the mean ± SD (n = 6).

Fig. 4

Serum cytokine level of cage-reared ducks with RES supplementation. Difference analysis was performed using an independent sample t-test between CON and RES groups for the same time of cage rearing. *P < 0.05 and **P < 0.01. Values are expressed as the mean ± SD (n = 6).

Fig. 5

Effects of dietary RES supplementation on mRNA expression levels of iNOS, COX2, and GRP78 genes in cage-reared ducks. (A–C) liver. (D–F) duodenum. Difference analysis was performed using an independent sample t-test. *P < 0.05 and **P < 0.01. Values are expressed as the mean ± SD (n = 6).

Fig. 6

Effects of dietary RES supplementation on mRNA expression levels of Bax and Bcl2 genes in cage-reared ducks. (A-B) liver. (C-D) duodenum. Difference analysis was performed using an independent sample t-test. *P < 0.05 and **P < 0.01. Values are expressed as the mean ± SD (n = 6).

Fig. 7

RES induces AKT phosphorylation and suppresses specific cleavage of caspase-3 in the liver (A) and intestine (B) in cage-reared ducks. Difference analysis was performed using an independent sample t-test. *P < 0.05 and **P < 0.01. Values are expressed as the mean ± SD (n = 3).