Short-term effects of Subacute ruminal acidosis on ferroptosis and iron metabolism in the livers of lactating sheep fed a high-grain diet.

Abstract

Subacute ruminal acidosis can cause liver injury in ruminants. Ferroptosis, an iron-dependent cell death, is involved in many liver diseases. This study aimed to investigate ferroptosis in SARA-induced liver injury and explore the changes in hepatic iron metabolism. Twelve ruminally cannulated, lactating Hu sheep (parities: 2 or 3; BW: 50.6 ± 4.0 kg; 18.8 ± 3.6 d in milk; MY: 0.52 ± 0.08 kg/d; mean ± SD) were divided into 2 groups (n = 6/group) and fed a low-grain diet (LG group, grain: forage = 3: 7, 24.89% starch and 40.66% NDF) or a high-grain diet (HG group, grain: forage = 7: 3, 38.64% starch and 24.41% NDF) for 8 wk. Weekly, rumen pH was measured 10 min before feeding and 1, 2, 3, 4, 5, 6, and 8 h post-feeding. On d 57, all sheep were slaughtered after collecting the hepatic vein blood, and liver tissue was collected. The high-grain diet significantly decreased rumen pH compared with the low-grain diet; the rumen pH on d 56 in the HG group was <5.6 at 1, 2, 3, and 4 h after feeding. Plasma concentrations of LPS, MDA, IL-1β, and IL-6 at 4 h post-feeding increased, while glutathione (GSH) and glutathione peroxidase 4 (GPX4) decreased. Moreover, lipid reactive oxygen species (lipid ROS), ferrous ion, and MDA were elevated, whereas GSH was decreased in the liver of the HG group. For ferroptosis-related proteins, feeding a high-grain diet led to increased acyl-CoA synthetase long-chain family member 4 (ACSL4) and arachidonate 15-lipoxygenase (ALOX15) and decreased GPX4 and solute carrier family 7 member 11 (SLC7A11). For ferritinophagy-related proteins, high-grain diet feeding decreased ferritin heavy chain 1 (FTH1) and increased nuclear receptor coactivator 4 (NCOA4) and microtubule-associated protein 1 light chain 3 II (MAP1LC3-II). Regarding iron metabolism, increased protein expression of nuclear mothers against decapentaplegic homolog1/5/8 (SMAD1/5/8) and hepcidin, decreased protein expression of ferroportin (FPN), and iron deposits were observed in the liver of the HG group. Furthermore, feeding high-grain diets also increased inflammatory signaling-related proteins IL-6 and phospho-signal transducer and activator of transcription 3 (p-STAT3). Taken together, this study suggests that SARA induced liver injury and ferroptosis. Enhanced ferritinophagy, disordered iron metabolism, and elevated inflammatory response may mediate ferroptosis in the livers of sheep fed a high-grain diet.