The role of the hypothalamus-gut microbiota in the pathogenesis of periparturient fatty liver disease in dairy cows.

During the periparturient period, dairy cows experience negative energy balance due to reduced feed intake, leading to adipose tissue breakdown, liver damage, and fat accumulation. This study examined the gut-liver-brain axis to explore the link between fatty liver disease, changes in hypothalamic appetite-related neurons, and microbiome shifts in dairy cows. Thirty cows were monitored, with daily DMI recordings and blood sampling. Postpartum brain, liver, and ileal contents were collected from 10 selected cows, divided into two groups: H-DMI (slight DMI decrease) and L-DMI (severe DMI decrease). The L-DMI group of cows exhibited higher plasma NEFA, BHBA, ALT, and AST levels, along with severe hepatic steatosis and lipid accumulation. Transcriptome sequencing of the hypothalamic arcuate nucleus (ARC) revealed decreased expression of Hypocretin Neuropeptide Precursor (HCRT), orexin-A (OX-A), Orexin Receptor Type 1 (OX1R), and Cannabinoid Receptor 1 (CB1) in the L-DMI group, while Pro-opiomelanocortin (POMC) and Melanocortin 4 Receptor (MC4R) expression increased. Metagenomic analysis of ileal contents showed reduced abundance of Ruminococcus spp. in the L-DMI group, which may be associated with fatty liver disease (FL). Integrated omics analysis showed that increased MC4R expression was correlated with the elevated abundance of bacteria such as Akkermansia glycaniphila, and reduced abundance of species such as Methanobrevubacter thaueri and Ruminococcus spp. Decreased HCRT expression was also linked to Akkermansia glycaniphila. In conclusion, these changes may affect DMI through the OX-A/POMC pathway, with neurological and gut microbiome alterations potentially leading to appetite suppression, negative energy balance, and the development of fatty liver disease.