Protective effects of dietary dimethyl itaconate supplementation on oxidative stress, inflammation, and apoptosis in broilers under chronic heat stress

This study was conducted to evaluate the effects of dietary dimethyl itaconate (DI) supplementation on oxidative stress, inflammation, and apoptosis in broilers under chronic heat stress (HS). Twenty-one-day-old male Ross 308 broilers (n = 120) were randomly allocated to 5 groups: a control group, HS group, HS + 50 mg/kg DI group, HS + 150 mg/kg DI group, and HS + 200 mg/kg DI group. The birds in the control group received the basal diets and were maintained at 21 ± 1 °C for 24 h daily. The birds in the HS group and HS + DI groups were raised at 32 ± 1 °C for 8 h daily and received basal diets containing DI at the indicated dose (0, 50, 150, or 200 mg/kg). The results showed that the contents of alanine aminotransferase, aspartate aminotransferase, and malondialdehyde (MDA) in serum were markedly elevated by exposure to chronic HS (P < 0.01), and this elevation was alleviated by 150 and 200 mg/kg DI supplementation (P < 0.05). Chronic HS-induced declines (P < 0.05) in total antioxidant capacity (T-AOC) and activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in serum were markedly attenuated after 200 mg/kg DI treatment in broilers (P < 0.05). Moreover, broilers subjected to chronic HS exhibited higher contents of MDA, protein carbonyl, and hydrogen peroxide (P < 0.01), but lower T-AOC and activities of antioxidant enzymes (P < 0.05), as well as reduced inhibition of superoxide and hydroxyl free radicals (P < 0.01) in the liver compared to the control group; these changes were effectively mitigated by treatment with 200 mg/kg DI in broilers (P < 0.05). In addition, 50-200 mg/kg DI effectively ameliorated chronic HS-stimulated upregulation of the mRNA levels of pro-inflammatory mediators in the livers of broilers (P < 0.01). Dietary supplementation with 150 and 200 mg/kg DI significantly alleviated chronic HS challenge-induced upregulation of the mRNA levels of Bcl-2-associated X, caspase 3, and caspase 9 (P < 0.01), but downregulation of Bcl-2 mRNA levels (P < 0.01) in broilers (P < 0.05). Importantly, chronic HS-induced downregulation of the mRNA or protein levels of nuclear factor (erythroid-derived 2)-like 2 (NRF-2), NADPH quinone acceptor oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), SOD2, or glutathione-S-transferases (GST) (P < 0.01) was markedly improved by 150 and 200 mg/kg DI (P < 0.05). The above results indicated that DI can ameliorate oxidative stress, inflammation, and apoptosis in broilers under chronic HS.