Super-dosed butyrate induces a revisable metabolic paralysis through transient mitochondrial reprogramming in the gut-brain axis

Background and purposeSodium butyrate (SB) is a major product of gut microbiota with signaling activity in the human body. However, the toxic effect of SB remains largely unknown. This issue is addressed in current study. Experimental approachSB (0.3 - 2.5 g/kg) was administrated through a single peritoneal injection in mice. The core body temperature and mitochondrial function in the brain hypothalamus were monitored. Pharmacodynamics, targeted metabolomics, electron microscope, oxygen consumption rate and gene knockdown were employed to dissect the mechanism for the toxic effect. Key resultsThe temperature was reduced by SB (1.2 -2.5 g/kg) in a dose-dependent manner in mice for 2-4 hr. In the brain, the effect was associated with SB elevation and neurotransmitter (Glutamate and GABA) reduction. The mitochondria exhibited a transient volume expansion and crista loss in the hypothalamic neurons. ADP/ATP ratio was increased with accumulation of intermediate metabolites in the glycolysis, TCA cycle and pentose phosphate pathways. The mitochondrial protein, adenine nucleotide transporter (ANT), was activated for proton transportation leading to a transient potential collapse by proton leak. The SB activity was attenuated by ANT inhibition from gene knockdown or pharmacological blocker. The temperature drop was attenuated by i.p. injection of norepinephrine. The HDAC inhibitors, such as SAHA and pyruvate, did not exhibit the same effect. Conclusion and implicationsSuper-dosed SB generated an immediate and reversible toxic effect for inhibition of body temperature through transient mitochondrial reprogramming in the brain. The mechanism was quick activation of ANT proteins for the proton leak in mitochondria.