Dietary supplementation of thiamine down-regulates the expression of mitophagy and endoplasmic reticulum stress-related genes in the rumen epithelium of goats during high-concentrate diet feeding

Several studies have demonstrated that high-concentrate (HC) diet with thiamine supplementation can alleviate rumen epithelium inflammation and protecting the barrier function in goats. This study aimed to investigate the effects of dietary supply of thiamine on mitophagy and endoplasmic reticulum stress (ERS) during high-concentrate diet feeding. Twenty-four Boer goats (35.62 ± 2.4 kg) were used in this study, goats were subsequently assigned to 3 treatment groups (8 goats in each group) as follows: a low-concentrate diet (CON; concentrate: forage 30:70), a high-concentrate diet (HC; concentrate: forage 70:30) and high-concentrate diet with 200 mg thiamine/kg DMI (HCT; concentrate: forage 70:30) for 12 weeks. Compared with the HC group, the goats of HCT group had a markedly higher final weight, net weight gain, and average daily gain (ADG). The blood physiological and biochemical results showed that the HCT group expressed a lower the content of lymphocytes and leukocytes but a higher total protein and monocytes compared with that of HC group. The rumen epithelial mitochondrial membrane potential change (ΔΨm), relative mitochondrial DNA (mtDNA) content, adenosine triphosphate (ATP) level, together with the activities of the respiratory complexes I, III, and IV were markedly higher in the HCT group relative to HC ones. Relative to the HC group, the unc-51 like autophagy activating kinase 1 (ULK1), microtubule-associated protein 1 light chain 3 (LC3), autophagy-related 5 (ATG5), autophagy related 7 (ATG7), Beclin1, PTEN induced putative kinase 1 (PINK1), PERK (PKR-Endoplasmic Reticulum Kinase), activating transcription factor 4 (ATF4), activating transcription factor 6 (ATF6), X-box binding protein 1 (XBP1), heat shock 70 kDa protein 5 (HSPA5), DNA damage-inducible transcript 3 (DDIT3) and DNA damage-inducible transcript 4 (DDIT4) mRNA levels were decreased, but the breast cancer 1 (BRCA1), ataxia telangiectasia mutated (ATM), heat shock factor binding protein 1 (HSBP1) were increased in rumen epithelium of the HCT group. The results of transmission electron micrographs showed that the cell structure of the HCT group was higher integrity than that in the HC group, and the damage degree of mitochondria as well as endoplasmic reticulum being lower than the HC group. These results demonstrated that dietary thiamine could enhance rumen epithelial integrity by suppressing the responses of ERS and mitophagy during long-term HC diet feeding.HIGHLIGHTS This study is the first to demonstrate that the reduction of inflammatory response is related to the down-regulation of autophagy and endoplasmic reticulum stress in goats. Thiamine has good anti-inflammatory and anti-oxidation properties, which can be applied in intensive industry to reduce the negative effects caused by long-term high-concentrate diet.