Abnormal lipid droplets accumulation induced cognitive deficits in obstructive sleep apnea syndrome mice via JNK/SREBP/ACC pathway but not through PDP1/PDC pathway

The mechanisms of chronic intermittent hypoxia (CIH)-induced cognitive deficits remain unclear. Here, our study found that about 3 months CIH treatment induced lipid droplets (LDs) accumulation in hippocampal nerve and glia cells of C57BL/6 mice, and caused severe neuro damage including neuron lesions, neuroblast (NB) apoptosis and abnormal glial activation. Studies have shown that the neuronal metabolism disorders might contribute to the CIH induced-hippocampal impairment. Mechanistically, the results showed that pyruvate dehydrogenase complex E1ɑ subunit (PDHA1) and the pyruvate dehydrogenase complex (PDC) activator pyruvate dehydrogenase phosphatase 1 (PDP1) did not noticeable change after intermittent hypoxia. Consistent with those results, the level of Acetyl-CoA in hippocampus did not significantly change after CIH exposure. Interestingly, we found that CIH produced large quantities of ROS, which activated the JNK/SREBP/ACC pathway in nerve and glia cells. ACC catalyzed the carboxylation of Acetyl-CoA to malonyl-CoA and then more lipid acids were synthesized, which finally caused aberrant LDs accumulation. Therefore, the JNK/SREBP/ACC pathway played a crucial role in the cognitive deficits caused by LDs accumulation after CIH exposure. Additionally, LDs were peroxidized by the high level of ROS under CIH conditions. Together, lipid metabolic disorders contributed to nerve and glia cells damage, which ultimately caused behavioral dysfunction. An active component of Salvia miltiorrhiza, SMND-309, dramatically alleviated these injuries and improved cognitive deficits of CIH mice.

Biochemical and structural characterization of quizalofop-resistant wheat acetyl-CoA carboxylase

A novel nucleotide mutation in ACC1 resulting in an alanine to valine amino acid substitution in acetyl-CoA carboxylase (ACCase) at position 2004 of the Alopecurus myosuroides reference sequence (A2004V) imparts quizalofop resistance in wheat. Genotypes endowed with the homozygous mutation in one or two ACC1 homoeologs are seven- and 68-fold more resistant to quizalofop than a wildtype winter wheat in greenhouse experiments, respectively. In vitro ACCase activities in soluble protein extracts from these varieties are 3.8- and 39.4-fold more resistant to quizalofop with the homozygous mutation in either one or two genomes, relative to the wildtype. The A2004V mutation does not alter the specific activity of wheat ACCase, suggesting that this resistance trait does not affect the catalytic functions of ACCase. Modeling of wildtype and quizalofop-resistant wheat ACCase demonstrates that the A2004V amino acid substitution causes a reduction in the volume of the binding pocket that hinders quizalofop’s interaction with ACCase. Docking studies confirm that the mutation reduces the binding affinity of quizalofop. Interestingly, the models suggest that the A2004V mutation does not affect haloxyfop binding. Follow up in vivo and in vitro experiments reveal that the mutation, in fact, imparts negative cross-resistance to haloxyfop, with quizalofop-resistant varieties exhibiting higher sensitivity to haloxyfop than the wildtype winter wheat line.

Enhanced 3-Hydroxypropionic Acid Production From Acetate via the Malonyl-CoA Pathway in Corynebacterium glutamicum

Acetate is an economical and environmental-friendly alternative carbon source. Herein, the potential of harnessing Corynebacterium glutamicum as a host to produce 3-hydroxypropionic acid (3-HP) from acetate was explored. First, the expression level of malonyl-CoA reductase from Chloroflexus aurantiacus was optimized through several strategies, strain Cgz2/sod-N-C* showed an MCR enzyme activity of 63 nmol/mg/min and a 3-HP titer of 0.66 g/L in flasks. Next, the expression of citrate synthase in Cgz2/sod-N-C* was weakened to reduce the acetyl-CoA consumption in the TCA cycle, and the resulting strain Cgz12/sod-N-C* produced 2.39 g/L 3-HP from 9.32 g/L acetate. However, the subsequent deregulation of the expression of acetyl-CoA carboxylase genes in Cgz12/sod-N-C* resulted in an increased accumulation of intracellular fatty acids, instead of 3-HP. Accordingly, cerulenin was used to inhibit fatty acid synthesis in Cgz14/sod-N-C*, and its 3-HP titer was further increased to 4.26 g/L, with a yield of 0.50 g 3-HP/g-acetate. Finally, the engineered strain accumulated 17.1 g/L 3-HP in a bioreactor without cerulenin addition, representing the highest titer achieved using acetate as substrate. The results demonstrated that Corynebacterium glutamicum is a promising host for 3-HP production from acetate.

Deconstructing Methanosarcina acetivorans into an acetogenic archaeon

The reductive acetyl-coenzyme A (acetyl-CoA) pathway, whereby carbon dioxide is sequentially reduced to acetyl-CoA via coenzyme-bound C1 intermediates, is the only autotrophic pathway that can at the same time be the means for energy conservation. A conceptually similar metabolism and a key process in the global carbon cycle is methanogenesis, the biogenic formation of methane. All known methanogenic archaea depend on methanogenesis to sustain growth and use the reductive acetyl-CoA pathway for autotrophic carbon fixation. Here, we converted a methanogen into an acetogen and show that Methanosarcina acetivorans can dispense with methanogenesis for energy conservation completely. By targeted disruption of the methanogenic pathway, followed by adaptive evolution, a strain was created that sustained growth via carbon monoxide–dependent acetogenesis. A minute flux (less than 0.2% of the carbon monoxide consumed) through the methane-liberating reaction remained essential, indicating that currently living methanogens utilize metabolites of this reaction also for anabolic purposes. These results suggest that the metabolic flexibility of methanogenic archaea might be much greater than currently known. Also, our ability to deconstruct a methanogen into an acetogen by merely removing cellular functions provides experimental support for the notion that methanogenesis could have evolved from the reductive acetyl-coenzyme A pathway.

Acetyl-CoA mediated autoacetylation of fatty acid synthase in de novo lipogenesis

De novo lipogenesis (DNL) is a highly regulated metabolic process, which is known to be activated through transcriptional regulation of lipogenic genes, including fatty acid synthase (FASN). Unexpectedly, we find that the expression of FASN protein remains unchanged during Drosophila larval development when lipogenesis is hyperactive. Instead, acetylation modification of FASN is highly upregulated in fast-growing larvae. We further show that lysine K813 is highly acetylated in developing larvae, and its acetylation is required for upregulated FASN activity, body fat accumulation, and normal development. Intriguingly, K813 is rapidly autoacetylated by acetyl-CoA in a dosage-dependent manner, independent of known acetyltransferases. Furthermore, the autoacetylation of K813 is mediated by a conserved P-loop-like motif (N-xx-G-x-A). In summary, this work uncovers a novel role of acetyl-CoA-mediated autoacetylation of FASN in developmental lipogenesis and reveals a self-regulatory system that controls metabolic homeostasis by linking acetyl-CoA, lysine acetylation, and DNL.

PPARα−ACOT12 axis is responsible for maintaining cartilage homeostasis through modulating de novo lipogenesis

Here, in Ppara−/− mice, we found that an increased DNL stimulated the cartilage degradation and identified ACOT12 as a key regulatory factor. Suppressed level of ACOT12 was observed in cartilages of OA patient and OA-induced animal. To determine the role and association of ACOT12 in the OA pathogenesis, we generated Acot12 knockout (KO) (Acot12−/−) mice using RNA-guided endonuclease. Acot12−/− mice displayed the severe cartilage degradation with the stimulation of matrix MMPs and chondrocyte apoptosis through the accumulation of acetyl CoA. Delivery of acetyl CoA-conjugated chitosan complex into cartilage stimulated DNL and cartilage degradation. Moreover, restoration of ACOT12 into human OA chondrocytes and OA-induced mouse cartilage effectively rescued the pathophysiological features of OA by regulating DNL. Taken together, our study suggested ACOT12 as a novel regulatory factor in maintaining cartilage homeostasis and targeting ACOT12 could contribute to developing a new therapeutic strategy for OA.

Synthesis of Dolichols in Candida albicans Is Co-Regulated with Elongation of Fatty Acids

Protein glycosylation requires dolichyl phosphate as a carbohydrate carrier. Dolichols are α-saturated polyprenols, and their saturation in S. cerevisiae is catalyzed by polyprenyl reductase Dfg10 together with some other unknown enzymes. The aim of this study was to identify such enzymes in Candida. The Dfg10 polyprenyl reductase from S. cerevisiae comprises a C-terminal 3-oxo-5-alpha-steroid 4-dehydrogenase domain. Alignment analysis revealed such a domain in two ORFs (orf19.209 and orf19.3293) from C. albicans, which were similar, respectively, to Dfg10 polyprenyl reductase and Tsc13 enoyl-transferase from S. cerevisiae. Deletion of orf19.209 in Candida impaired saturation of polyprenols. The Tsc13 homologue turned out not to be capable of saturating polyprenols, but limiting its expression reduce the cellular level of dolichols and polyprenols. This reduction was not due to a decreased expression of genes encoding cis-prenyltransferases from the dolichol branch but to a lower expression of genes encoding enzymes of the early stages of the mevalonate pathway. Despite the resulting lower consumption of acetyl-CoA, the sole precursor of the mevalonate pathway, it was not redirected towards fatty acid synthesis or elongation. Lowering the expression of TSC13 decreased the expression of the ACC1 gene encoding acetyl-CoA carboxylase, the key regulatory enzyme of fatty acid synthesis and elongation.