Reducing branched-chain amino acids improves cardiac stress response in mice by decreasing histone H3K23 propionylation.

Identification of branched-chain amino acid (BCAA) oxidation enzymes in the nucleus led us to predict that they are a source of the propionyl-CoA that is utilized for histone propionylation and, thereby, regulate gene expression. To investigate the effects of BCAAs on the development of cardiac hypertrophy and failure, we applied pressure overload on the heart in mice maintained on a diet with standard levels of BCAAs (BCAA control) versus a BCAA-free diet. The former was associated with an increase in histone H3K23-propionyl (H3K23Pr) at the promoters of upregulated genes (e.g., cell signaling and extracellular matrix genes) and a decrease at the promoters of downregulated genes (e.g., electron transfer complex [ETC I-V] and metabolic genes). Intriguingly, the BCAA-free diet tempered the increases in promoter H3K23Pr, thus reducing collagen gene expression and fibrosis during cardiac hypertrophy. Conversely, the BCAA-free diet inhibited the reductions in promoter H3K23Pr and abolished the downregulation of ETC I-V subunits, enhanced mitochondrial respiration, and curbed the progression of cardiac hypertrophy. Thus, lowering the intake of BCAAs reduced pressure overload-induced changes in histone propionylation-dependent gene expression in the heart, which retarded the development of cardiomyopathy.

Histone H3K9 butyrylation is regulated by dietary fat and stress via an Acyl-CoA dehydrogenase short chain-dependent mechanism.

OBJECTIVE: We previously reported that ß-oxidation enzymes are present in the nucleus in close proximity to transcriptionally active promoters. Thus, we hypothesized that the fatty acid intermediate, butyryl-CoA, is the substrate for histone butyrylation and its abundance is regulated by acyl-CoA dehydrogenase short chain (ACADS). The objective of this study was to determine the genomic distribution of H3K9-butyryl (H3K9Bu) and its regulation by dietary fat, stress, and ACADS and its impact on gene expression. METHODS AND RESULTS: Using genome-wide chromatin immunoprecipitation-sequencing (ChIP-Seq), we show that H3K9Bu is abundant at all transcriptionally active promoters, where, paradoxically, it is most enriched in mice fed a fat-free vs high-fat diet. Deletion of fatty acid synthetase (FASN) abolished H3K9Bu in cells maintained in a glucose-rich but not fatty acid-rich medium, signifying that fatty acid synthesis from carbohydrates substitutes for dietary fat as a source of butyryl-CoA. A high-fat diet induced an increase in ACADS expression that accompanied the decrease in H3K9Bu. Conversely, the deletion of ACADS increased H3K9Bu in human cells and mouse hearts and reversed high-fat- and stress-induced reduction in promoter-H3K9Bu, whose abundance coincided with diminished stress-regulated gene expression as revealed by RNA sequencing. In contrast, H3K9-acetyl (H3K9Ac) abundance was minimally impacted by diet. CONCLUSION: Promoter H3K9 butyrylation is a major histone modification that is negatively regulated by high fat and stress in an ACADS-dependent fashion and moderates stress-regulated gene expression.

Adiponectin enhances the bioenergetics of cardiac myocytes via an AMPK- and succinate dehydrogenase-dependent mechanism.

Adiponectin is one of the most abundant circulating hormones, which through adenosine monophosphate-activated protein kinase (AMPK), enhances fatty acid and glucose oxidation, and exerts a cardioprotective effect. However, its effects on cellular bioenergetics have not been explored. We have previously reported that 5-aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside (AICAR, an AMPK activator) enhances mitochondrial respiration through a succinate dehydrogenase (SDH or complex II)-dependent mechanism in cardiac myocytes, leading us to predict that Adiponectin would exert a similar effect via activating AMPK. Our results show that Adiponectin enhances basal mitochondrial oxygen consumption rate (OCR), ATP production, and spare respiratory capacity (SRC), which were all abolished by the knockdown of AMPKγ1, inhibition of SDH complex assembly, via the knockdown of the SDH assembly factor 1 (Sdhaf1), or inhibition of SDH activity. Additionally, Adiponectin alleviated hypoxia-induced reductions in OCR and ATP production, in a Sdhaf1-dependent manner, whereas overexpression of Sdhaf1 confirmed its sufficiency for mediating these effects. Importantly, the levels of holoenzyme SDH under the various conditions correlated with OCR. We also show that the effects of Adiponectin, AMPK, Sdhaf1, as well as, SDH complex assembly all required sirtuin 3 (Sirt3). In conclusion, Adiponectin potentiates mitochondrial bioenergetics via promoting SDH complex assembly in an AMPK-, Sdhaf1-, and Sirt3-dependent fashion in cardiac myocytes.

Novel, Broadly Reactive Anticapsular Antibodies against Carbapenem-Resistant Klebsiella pneumoniae Protect from Infection.

Carbapenem-resistant (CR) sequence type 258 (ST258) Klebsiella pneumoniae has become an urgent health care threat, causing an increasing number of high-mortality infections. Its resistance to numerous antibiotics and threat to immunocompromised patients necessitate finding new therapies to combat these infections. Previous successes in the laboratory, as well as the conservation of capsular polysaccharide (CPS) among the members of the ST258 clone, suggest that monoclonal antibody (MAb) therapy targeting the outer polysaccharide capsule of K. pneumoniae could serve as a valuable treatment alternative for afflicted patients. Here, we isolated several IgG antibodies from mice inoculated with a mixture of CR K. pneumoniae CPS conjugated to anthrax protective antigen. Two of these MAbs, 17H12 and 8F12, bind whole and oligosaccharide epitopes of the CPS of clade 2 ST258 CR K. pneumoniae, which is responsible for the most virulent CR K. pneumoniae infections in the United States. These antibodies were shown to agglutinate all clade 2 strains and were also shown to promote extracellular processes killing these bacteria, including biofilm inhibition, complement deposition, and deployment of neutrophil extracellular traps. Additionally, they promoted opsonophagocytosis and intracellular killing of CR K. pneumoniae by human-derived neutrophils and cultured murine macrophages. Finally, when mice were intratracheally infected with preopsonized clade 2 CR K. pneumoniae, these MAbs reduced bacterial dissemination to organs. Our data suggest that broadly reactive anticapsular antibodies and vaccines against clade 2 ST258 CR K. pneumoniae are possible. Such MAbs and vaccines would benefit those susceptible populations at risk of infection with this group of multidrug-resistant bacteria.IMPORTANCE Carbapenem-resistant Klebsiella pneumoniae is an enteric bacterium that has been responsible for an increasing number of deadly outbreaks and hospital-acquired infections. The pathogen's resistance to numerous antibiotics, including new drugs, leaves few therapeutic options available for infected patients, who often are too sick to fight the infection themselves. Immunotherapy utilizing monoclonal antibodies has been successful in other medical fields, and antibodies targeting the outer polysaccharide capsule of these bacteria could be a valuable treatment alternative. This study presents two anticapsular antibodies, 17H12 and 8F12, that were found to be protective against the most virulent carbapenem-resistant K. pneumoniae clinical strains. These antibodies are shown to promote the killing of these strains through several extracellular and intracellular processes and prevent the spread of infection in mice from the lungs to distal organs. Thus, they could ultimately treat or protect patients infected or at risk of infection by this multidrug-resistant bacterium.