Lactobacillus frumenti mediates energy production via fatty acid β-oxidation in the liver of early-weaned piglets

Background: Early-weaning of piglets is often accompanied by severe disorders, especially diarrhea. The gut microbiota and its metabolites play a critical role in the maintenance of the physiologic and metabolic homeostasis of the host. Our previous studies have demonstrated that oral administration of Lactobacillus frumenti improves epithelial barrier functions and confers diarrhea resistance in early-weaned piglets. However, the metabolic response to L. frumenti administration remains unclear. Then, we conducted simultaneous serum and hepatic metabolomic analyses in early-weaned piglets administered by L. frumenti or phosphate-buffered saline (PBS). Results: A total of 100 6-day-old crossbred piglets (Landrace x Yorkshire) were randomly divided into two groups and piglets received PBS (sterile, 2 mL) or L. frumenti (suspension in PBS, 10(8) CFU/mL, 2 mL) by oral administration once per day from 6 to 20 days of age. Piglets were weaned at 21 days of age. Serum and liver samples for metabolomic analyses were collected at 26 days of age. Principal components analysis (PCA) showed that L. frumenti altered metabolism in serum and liver. Numerous correlations (P < 0.05) were identified among the serum and liver metabolites that were affected by L. frumenti. Concentrations of guanosine monophosphate (GMP), inosine monophosphate (IMP), and uric acid were higher in serum of L. frumenti administration piglets. Pathway analysis indicated that L. frumenti regulated fatty acid and amino acid metabolism in serum and liver. Concentrations of fatty acid beta-oxidation related metabolites in serum (such as 3-hydroxybutyrylcarnitine, C4-OH) and liver (such as acetylcarnitine) were increased after L. frumenti administration. Conclusions: Our findings suggest that L. frumenti regulates lipid metabolism and amino acid metabolism in the liver of early-weaned piglets, where it promotes fatty acid beta-oxidation and energy production. High serum concentrations of nucleotide intermediates, which may be an alternative strategy to reduce the incidence of diarrhea in early-weaned piglets, were further detected. These findings broaden our understanding of the relationships between the gut microbiota and nutrient metabolism in the early-weaned piglets.