Butyrate enhances mitochondrial function during oxidative stress in cell lines from boys with autism

Shannon Rose,Stephan Melnyk,Sirish C Bennuri,Rebecca Wynne,Stephen G Kahler,John C Slattery,Leanna Delhey,Marie Tippett,Richard E Frye,Derrick F Macfabe,Jakeira E Davis

doi:10.1038/s41398-017-0089-z

Abstract

Butyrate (BT) is a ubiquitous short-chain fatty acid (SCFA) principally derived from the enteric microbiome. BT positively modulates mitochondrial function, including enhancing oxidative phosphorylation and beta-oxidation and has been proposed as a neuroprotectant. BT and other SCFAs have also been associated with autism spectrum disorders (ASD), a condition associated with mitochondrial dysfunction. We have developed a lymphoblastoid cell line (LCL) model of ASD, with a subset of LCLs demonstrating mitochondrial dysfunction (AD-A) and another subset of LCLs demonstrating normal mitochondrial function (AD-N). Given the positive modulation of BT on mitochondrial function, we hypothesized that BT would have a preferential positive effect on AD-A LCLs. To this end, we measured mitochondrial function in ASD and age-matched control (CNT) LCLs, all derived from boys, following 24 and 48 h exposure to BT (0, 0.1, 0.5, and 1 mM) both with and without an in vitro increase in reactive oxygen species (ROS). We also examined the expression of key genes involved in cellular and mitochondrial response to stress. In CNT LCLs, respiratory parameters linked to adenosine triphosphate (ATP) production were attenuated by 1 mM BT. In contrast, BT significantly increased respiratory parameters linked to ATP production in AD-A LCLs but not in AD-N LCLs. In the context of ROS exposure, BT increased respiratory parameters linked to ATP production for all groups. BT was found to modulate individual LCL mitochondrial respiration to a common set-point, with this set-point slightly higher for the AD-A LCLs as compared to the other groups. The highest concentration of BT (1 mM) increased the expression of genes involved in mitochondrial fission (PINK1, DRP1, FIS1) and physiological stress (UCP2, mTOR, HIF1α, PGC1α) as well as genes thought to be linked to cognition and behavior (CREB1, CamKinase II). These data show that the enteric microbiome-derived SCFA BT modulates mitochondrial activity, with this modulation dependent on concentration, microenvironment redox state, and the underlying mitochondrial function of the cell. In general, these data suggest that BT can enhance mitochondrial function in the context of physiological stress and/or mitochondrial dysfunction, and may be an important metabolite that can help rescue energy metabolism during disease states. Thus, insight into this metabolic modulator may have wide applications for both health and disease since BT has been implicated in a wide variety of conditions including ASD. However, future clinical studies in humans are needed to help define the practical implications of these physiological findings.

Highlights

The human body houses a diverse ecosystem of microbes collectively referred to as the human microbiome
We examine the effect of reactive oxygen species (ROS) exposure on autism spectrum disorders (ASD) lymphoblastoid cell line (LCL) in reference to the CNT LCLs
In this study, when a subset of LCLs demonstrating mitochondrial dysfunction (AD-A) LCLs were exposed to butyric acid (BT) for 24 or 48 h, treatment with DMNQ to increase ROS increased the respiratory parameters linked to adenosine triphosphate (ATP) production to an equal amount or, in many cases, a higher amount than the control LCLs. This is consistent with our recent study where we demonstrated that treatment with DMNQ after prolonged exposure to a toxicant enhanced the respiratory parameters related to ATP production in autistic disorder (AD)-A but not AD-N LCLs84

Summary

Introduction

The human body houses a diverse ecosystem of microbes collectively referred to as the human microbiome. The enteric (gut) microbiota is an area of great interest since it accounts for approximately 99% of the human microbiome[4] and modulates the immune system[5], metabolism[6], receptor physiology[7], and gene expression[8,9]. The microbiome modulates host physiology through the production of metabolic mediators, including lipopolysaccharides, peptidoglycans, short-chain fatty acids (SCFA), neurotransmitters, and gaseous molecules[22,23,24]. PPA can modulate cell signaling[29,30], cell–cell interactions[31], gene expression[32,33], immune function[34], neurotransmitter synthesis and release[35], and mitochondrial[36] and lipid[37] metabolism. BT has positive effects in biological models of several important human diseases, including diabetes[43,44], neurodegenerative disorders[18,45], leukemia[46], lymphoma[47], and colorectal[48,49], breast[50,51], and pancreatic[52] cancers

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Discussion

Conclusion