Influence of α-Linolenic Acid on the Intestinal Barrier Integrity and Intestinal Antioxidant Status in Broilers

Abstract

This study aimed to investigate the beneficial effects of α-linolenic acid (ALA) on intestinal barrier function and antioxidant status in broilers, along with the associated molecular mechanisms. 320 one-day-old Arbor Acres broilers were randomly divided into four groups, each with eight replicates, and fed diets with 0 (control), 200, 400, and 600 mg of ALA/kg for 42 days. ALA supplementation did not significantly affect the broilers' overall growth performance. Supplementing diets with 400 and 600 mg/kg of ALA significantly enhanced (p < 0.05) jejunal and ileal villus height, the jejunal villus height to crypt depth ratio, and ileal mRNA expression and protein levels of Zonula occludens-1 (ZO-1) and occludin in broilers on Day 42. Broilers fed diets containing 600 mg/kg of ALA exhibited significantly increased (p < 0.05) serum catalase (CAT) activity, total antioxidant capacity (T-AOC), and jejunal and ileal activities of CAT and total superoxide dismutase (T-SOD), alongside reduced malondialdehyde (MDA) concentrations in serum, jejunum, and ileum on Days 21 and 42, compared to the control group. Supplementing 600 mg/kg of ALA significantly increased (p < 0.05) the mRNA expressions of CAT, SOD1, NRF2, and HO-1, along with the protein levels of cytoplasmic and nuclear NRF2 and HO-1 in the jejunum and ileum on Days 21 and 42. These findings demonstrate the protective effects of ALA in improving intestinal health in broilers. The underlying mechanisms may involve enhancing intestinal barrier integrity by increasing tight junction protein abundance and boosting intestinal antioxidant capacity by elevating antioxidant enzyme activity and activating the NRF2 pathway. In conclusion, our results showed that 600 mg/kg of ALA was identified as the optimal concentration for improving intestinal barrier function and antioxidant status in broilers, highlighting its potential for protecting intestinal health through ALA-based interventions.

Keywords: broiler; growth performance; intestinal antioxidant status; intestinal barrier function; α‐linolenic acid.

FIGURE 1

Influence of ALA on the intestinal morphology of broilers. Values are means (n = 8), with the standard errors appearing as vertical bars. ^a,bMeans within a row with different letters differ significantly (P < 0.05). (A) The images of jejunal and ileal tissues on Day 21; (B–D) the jejunal and ileal villus height, crypt depth, and the ratio of those on Day 21; (E) the images of jejunal and ileal tissues on Day 42; (F–H) the jejunal and ileal villus height, crypt depth, and the ratio of those on Day 42.

FIGURE 2

Influence of ALA on the relative protein expression of ZO‐1 and occludin in the jejunum and ileum of broilers. Values were presented as mean with standard errors appearing as vertical bars. ^a,bMeans with different letters differ significantly among the groups (p < 0.05). (AH) The jejunal and ileal protein expression of ZO‐1 and occludin (n = 3), the jejunal (A, C) and ileal (B, D) protein expression of ZO‐1 and occludin on Day 21, the jejunal (E, G) and ileal (F, H) protein expression of ZO‐1 and occludin on Day 42. (I–L) The jejunal and ileal mRNA expression of ZO‐1 and occludin on Days 21 and 42 (n = 8). ZO‐1, Zonula occludens‐1.

FIGURE 3

Influence of ALA on the activities of antioxidant enzymes of broilers. Values are means (n = 8), with the standard errors appearing as vertical bars. ^a,bMeans within a row with different letters differ significantly (p < 0.05). (A–D) Serum activities of antioxidant enzymes of broilers on Day 21; (E–H) The jejunal and ileal activities of antioxidant enzymes of broilers on Day 21; (I–L) The jejunal and ileal activities of antioxidant enzymes of broilers on Day 42. CAT, catalase; MDA, malondialdehyde; T‐AOC, total antioxidant capacity; T‐SOD, total superoxide dismutase.

FIGURE 4

Influence of ALA on the mRNA abundance of antioxidant enzymes and NRF2 pathway in the jejunum and ileum of broilers on Days 21 and 42. Values are means (n = 8), with the standard errors appearing as vertical bars. ^a,bMeans within a row with different letters differ significantly (p < 0.05). (A–D) The jejunal and ileal mRNA abundance of antioxidant enzymes and NRF2 pathway of broilers on Day 21; (E–H) The jejunal and ileal mRNA abundance of antioxidant enzymes and NRF2 pathway of broilers on Day 42. CAT, catalase; HO‐1, heme oxygenase 1; NRF2, nuclear factor erythroid 2‐related factor 2; SOD1, superoxide dismutase 1.

FIGURE 5

Influence of ALA on the relative protein expression of NRF2 and HO‐1 in the jejunum and ileum of broilers. Values were presented as mean with standard errors appeared by vertical bars (n = 3). ^a,bMeans with different letters differ significantly among the groups (p < 0.05). (A–E) The jejunal (A) and ileal (B) protein expression of Nucl‐NRF2, Cyto‐NRF2, and HO‐1 on Day 21; (F–J) The jejunal (F) and ileal (G) protein expression of Nucl‐NRF2, Cyto‐NRF2, and HO‐1 on Day 42. Nucl‐NRF2, Nuclear factor erythroid 2‐related factor 2; Cyto‐NRF2, cytoplasmic nuclear factor erythroid 2‐related factor 2; HO‐1, heme oxygenase 1.