Interpretive Summary: BHBA Metoformin Bovine Hepatocytes
By: Caitlin Vonderohe
When ruminants consume less energy than they are exerting, they are in a negative energy balance which can occur when they are experiencing physiological stress, late pregnancy, or early lactation. When ruminants are in a negative energy balance, they will mobilize non-esterified fatty acids and beta-hydroxy-buturic acid (BHBA) to meet the energetic demands of the animal, a condition called ketosis. Unfortunately, when BHBA is produced, the animal experiences systemic oxidative stress, enters an inflammatory state, and becomes predisposed to infectious disease. Metformin is currently used as the first line therapy for type II diabetes mellitus. Recent work has suggested that metformin activates AMPK, which blocks inflammatory pathways in cell culture, connecting metabolism to the innate immune system. Therefore, in a recent work published in the Journal of Animal Science, Xu et al. critically examined the effect of metformin on alleviating BHBA-induced inflammation in bovine hepatocytes.
Bovine hepatocytes were first treated with different doses of metformin, then exposed to BHBA levels commonly observed in cows experiencing ketosis. Various methods, including western blot, real-time quantitative PCR, chromatin precipitation, and immunofluorescence, were used to assess the activation of various pro- and anti-inflammatory pathways in hepatocytes. BHBA treatment resulted in greater expression of pro-inflammatory genes such as TNF-alpha, IL6, and IL1-beta, but this upregulation was prevented when cells were pretreated with metformin. Metformin treatment also blocked BHBA-mediated reductions in cellular proliferation. Additionally, cytokine protein expression, acetated histone 3 expression and relative levels of NAD/NADH allowed the authors to conclude the anti-inflammatory effects of metformin are mediated by the gene SIRT1 and the AMPK signaling pathway.
Overall, they successfully demonstrate that metformin can alleviate BHBA-induced inflammation by activating AMPK signaling which downregulates pro-inflammatory cytokines. This work demonstrates a novel mechanism of BHBA-induced hepatocellular inflammation and a potential target for ketosis therapy in the future.