N-acetylaspartate catabolism determines cytosolic acetyl-CoA levels and histone acetylation in brown adipocytes

Abstract

Histone acetylation depends on the abundance of nucleo-cytoplasmic acetyl-CoA. Here, we present a novel route for cytoplasmic acetyl-CoA production in brown adipocytes. N-acetylaspartate (NAA) is a highly abundant brain metabolite catabolized by aspartoacylase yielding aspartate and acetate. The latter can be further used for acetyl-CoA production. Prior to this work, the presence of NAA has not been described in adipocytes. Here, we show that accumulation of NAA decreases the brown adipocyte phenotype. We increased intracellular NAA concentrations in brown adipocytes via media supplementation or knock-down of aspartoacylase and measured reduced lipolysis, thermogenic gene expression, and oxygen consumption. Combinations of approaches to increase intracellular NAA levels showed additive effects on lipolysis and gene repression, nearly abolishing the expression of Ucp1, Cidea, Prdm16, and Ppara. Transcriptome analyses of aspartoacylase knock-down cells indicate deficiencies in acetyl-CoA and lipid metabolism. Concordantly, cytoplasmic acetyl-CoA levels and global histone H3 acetylation were decreased. Further, activating histone marks (H3K27ac and H3K9ac) in promoters/enhancers of brown marker genes showed reduced acetylation status. Taken together, we present a novel route for cytoplasmic acetyl-CoA production in brown adipocytes. Thereby, we mechanistically connect the NAA pathway to the epigenomic regulation of gene expression, modulating the phenotype of brown adipocytes.

Liver p53 is stabilized upon starvation and required for amino acid catabolism and gluconeogenesis

“…cDNA was prepared using cDNA‐Synthese Kit H Plus (Peqlab) and diluted to 1 ng/ml. Quantitative PCR (qPCR) was done as previously described (52) on a Bio‐Rad CFX cycler with SYBR Green chemistry (Bio‐Rad, Hercules, CA, USA). Primer sequences are listed in Supplemental Table S4.…”

“…Clear supernatant was used to measure protein concentration with a bicinchoninic acid assay (Thermo Fisher Scientific). Immunoblotting was performed as previously described (19, 52). The following antibodies were used: human p53 (sc‐126; Santa Cruz Biotechnology, Santa Cruz, CA, USA), mouse p53 (2524; Cell Signaling Technology, Danvers, MA, USA), β‐actin (ab6276; Abcam, Cambridge, MA, USA), ras‐related nuclear protein, (RAN) (610340; BD Biosciences, San Jose, CA, USA), cyclin‐dependent kinase inhibitor 1A (CDKN1A; p21) (2947; Cell Signaling Technology), and AMPK/ acetyl‐CoA carboxylase 1 (ACC1) total and phosphorylated from Cell Signaling Technology (9957; AMPK and ACC1 antibody sampler kit).…”

Redirecting N-acetylaspartate metabolism in the central nervous system normalizes myelination and rescues Canavan disease

“…Although our understanding of ASPA in peripheral organs is limited (26,48,49) and astrocyterestricted expression shows preclinical disease rescue, clinical translation might benefit from ubiquitous ASPA expression. This is primarily based on the observation of high ASPA expression levels in peripheral organs (3).…”

“…Although ASPA mutations are responsible for CD, the physiologic and pathomechanistic roles of NAA are still unknown. Current hypotheses for the homeostasis of NAA in the CNS cover a wide spectrum of functions, including molecular water pump (24), acetate donor for myelin lipids (25), histone acetylation (26), and neuronal differentiation (27). Understanding how NAA metabolism is coordinated in neurons and glial cells has been another major challenge.…”

Epigenetic Regulation of the Thermogenic Adipose Program

“…In this regard, a recent study established that N-acetyl aspartate (NAA), generated by acetylation of aspartate using acetyl-CoA, regulates thermogenic gene expression and lipolysis. NAA affects acetyl-CoA levels and thus histone acetylation in brown adipocytes [73]. Interestingly, in BAT, an increase in NAD + levels affects Sirt1 activity to activate transcription of thermogenic genes, including PGC1α, and enhances oxidative metabolism [74].…”