Biology subjects

Koleini, N.

Publications and source records attributed to Koleini, N..

4 recordsLinked to original sources

bioRxiv2026

Reduced Myocardial Serine Synthesis Impairs Functional, Metabolic, and Redox Adaptations to Cardiac Stress

BackgroundImpaired myocardial metabolism is a defining feature of heart failure, but many defective pathways and mechanisms remain to be identified. Prior studies find phosphoglycerate kinase and its synthesized product 3-phospho-glycerate required for the serine synthetic pathway (SSP) are reduced in human HFpEF myocardium. As serine is also provided exogenously, the impact of SSP reduction is uncertain. Here, we tested if and how SSP decline coupled to phosphoglycerate dehydrogenase (PHGDH) impacts cardiomyocyte (CM) and whole heart metabolic remodeling and stress responses. MethodsStudies were performed in isolated CMs and mice with CM-selective knock-down of PHGDH. Using pharmacological inhibition or genetic silencing of PHGDH, we tested their impact on CM one-carbon metabolism pathways, cell hypertrophic responses, mitochondrial respiration, and in vivo functional, structural, and metabolic adaptations to pressure-overload stress. ResultsIn CMs, PHGDH inhibition caused dose-dependent serine depletion linearly coupled with cytotoxicity, accompanied by NAD/NADH and GSH/GSSG imbalance, reduced ATP, and disruption of one-carbon and nucleotide metabolites. Stable-isotope tracing revealed distinct metabolic fates of glucose-derived (SSP) versus exogenous serine. Exogenous serine did not rescue PHGDH-deficient CMs, whereas combined ribose and an anti-oxidant (DTT) attenuated injury and reduced nucleotide pools. PHGDH suppression reduced amino acid abundance, impaired nascent protein synthesis, and blunted endothelin-1-induced hypertrophic and mitochondrial respiration. In vivo, cardiomyocyte-specific PHGDH heterozygous mice (PHGDH+/-) had no basal phenotype, but amplified chamber dilation, dysfunction, fibrosis, and mortality 4 weeks after transverse aortic constriction (TAC). Corresponding increases in amino acids, one-carbon metabolites, nucleotides, and TCA-cycle intermediates in wild-type TAC hearts were significantly blunted in PHGDH+/- hearts. ConclusionsCardiomyocyte SSP is a critical regulator of redox balance, one-carbon metabolism, purine synthesis, amino acid homeostasis, and growth-related pathways required for cardiac adaptation to pressure overload. It is non-redundant with exogenous serine by providing distinct influences on key metabolic pathways and is a potential therapeutic target.

molecular biology↗

bioRxiv2025

Characterization of the cardiac proteome of wild-type transthyretin amyloidosis cardiomyopathy

IntroductionMyocardial accumulation of the protein transthyretin (TTR) can result in amyloid TTR cardiomyopathy (ATTR-CM), a form of restrictive heart disease with limited therapies and still generally poor clinical outcomes. The mechanisms by which TTR fibril accumulation elicits cardiac toxicity at the protein level remain largely unknown. Accordingly, we performed untargeted proteomics of ventricular myocardium from patients with ATTR-CM versus controls. MethodsMyocardial tissue from non-failing (NF) controls (n=7) and ATTR-CM (n=4) were assayed by mass spectrometry. HFrEF, HCM, and HFpEF proteomics were acquired from published databases. ResultsA total of 539/7093 (7.6% of total) proteins were found to be differentially expressed in ATTR-CM, 227/359 (42%) upregulated and 312/539 (58%) downregulated. Gene ontology pathway analysis found that downregulated proteins were enriched for oxidative phosphorylation and mitochondrial protein translation pathways, while upregulated proteins were enriched for enhanced endocytosis and intracellular vesicle mediated transport. The latter is not observed in other forms of heart failure. We further identify a profound downregulation of sarcomere protein content, which is also not seen in other cardiomyopathies. ConclusionThe ATTR-CM myocardial proteome identifies endocytosis and intracellular transport as uniquely upregulated processes, whereas sarcomere protein content is uniquely downregulated. Both maybe potential therapeutic targets.

molecular biology↗

bioRxiv2025

Macrophages Lacking TSC2 have mTORC1-dependent GPNMB Augmentation Ameliorating Cardiac Ischemia-Reperfusion Injury

IntroductionMacrophages (M{Phi}) modulate both myocardial inflammatory and reparative phases following ischemia-reperfusion (I/R) injury. The mechanistic target of rapamycin (mTOR) is thought to play an important role in M{Phi} phenotype and functionality, but studies report conflicting net influences suggesting dependence on disease context and downstream signaling. Here, we tested the impact of M{Phi} with constitutive mTORC1 activation induced by targeted deletion of tuberous sclerosis complex 2 (TSC2) on cardiac responses to I/R injury. Methods/ResultsMyeloid TSC2 depleted (M{Phi}TSC2-/-) mice were generated by crossing Lys2Cre x TSC2flx/flx. Bone-marrow derived M{Phi}TSC2-/- vs control M{Phi} had basal increased mTORC1 and reduced mTORC2 activity. M{Phi}TSC2-/- were differentially responsive to stimulation by lipopoly- saccharide/IFN-{gamma} or IL-4 in vitro, and all disparities were prevented by rapamycin confirming the model. In vivo, M{Phi}TSC2-/- mice were strongly protected against I/R injury, with minimal change in ejection fraction, less LV dilation, hypertrophy, lung edema, or activation of stress/pro fibrotic genes. Mice pre-treated with anti-LY6G Ab to deplete neutrophils were still similarly protected, suggesting that the impact was primarily related to M{Phi}. M{Phi}TSC2-/- mice had less myocardial pro- inflammatory macrophages (CCR2+MHC-IIhi), LY6C+ monocytes, neutrophils, and CD8+ T cells 5 days post-I/R, and fewer CCR2+ but more CCR2- M{Phi} 2 weeks post I/R. Both M{Phi}TSC2-/- in vitro and in vivo post I/R phenotypes were converted to WT by rapamycin, supporting mTORC1 dependence. Lastly, synthesis of glycoprotein nonmetastatic melanoma protein B (GPNMB), a principally M{Phi} anti-inflammatory secreted protein protective against myocardial infarction was enhanced in M{Phi}TSC2-/- macrophages and hearts following I/R in an mTORC1 dependent manner. Conclusion: Constitutive macrophage-specific mTORC1 activation via TSC2 deletion reduces pro-inflammatory cell infiltration, increases GPNMB protein expression and preserves heart function following I/R injury. Rapamycin eliminates these effects. These results identify a cardioprotective mTORC1-GPNMB signaling nexus in M{Phi} in vivo.

immunology↗

bioRxiv2024

ATP Citrate Lyase Supports Cardiac Function and NAD+/NADH Balance And Is Depressed in Human Heart Failure

BackgroundATP-citrate lyase (ACLY) converts citrate into acetyl-CoA and oxaloacetate in the cytosol. It plays a prominent role in lipogenesis and fat accumulation coupled to excess glucose, and its inhibition is approved for treating hyperlipidemia. In RNAseq analysis of human failing myocardium, we found ACLY gene expression is reduced; however the impact this might have on cardiac function and/or metabolism has not been previously studied. As new ACLY inhibitors are in development for cancer and other disorders, such understanding has added importance. MethodsCardiomyocytes, ex-vivo beating hearts, and in vivo hearts with ACLY inhibited by selective pharmacologic (BMS303141, ACLYi) or genetic suppression, were studied. Regulation of ACLY gene/protein expression, and effects of ACLYi on function, cytotoxicity, tricarboxylic acid (TCA)-cycle metabolism, and redox and NAD+/NADH balance were assessed. Mice with cardiac ACLY knockdown induced by AAV9-acly-shRNA or cardiomyocyte tamoxifen-inducible Acly knockdown were studied. ResultsAcly gene expression was reduced more in obese patients with heart failure and preserved EF (HFpEF) than HF with reduced EF. In vivo pressure-overload and in vitro hormonal stress increased ACLY protein expression, whereas it declined upon fatty-acid exposure. Acute ACLYi (1-hr) dose-dependently induced cytotoxicity in adult and neonatal cardiomyocytes, and caused substantial reduction of systolic and diastolic function in myocytes and ex-vivo beating hearts. In the latter, ATP/ADP ratio also fell and lactate increased. U13C-glucose tracing revealed an ACLY-dependent TCA-bypass circuit in myocytes, where citrate generated in mitochondria is transported to the cytosol, metabolized by ACLY and then converted to malate to re-enter mitochondria, bypassing several NADH-generating steps. ACLYi lowered NAD+/NADH ratio and restoring this balance ameliorated cardiomyocyte toxicity. Oxidative stress was undetected with ACLYi. Adult hearts following 8-weeks of reduced cardiac and/or cardiomyocyte ACLY downregulation exhibited ventricular dilation and reduced function that was prevented by NAD augmentation. Cardiac dysfunction from ACLY knockdown was worse in hearts subjected to sustained pressure-overload, supporting a role in stress responses. ConclusionsACLY supports normal cardiac function through maintenance of the NAD+/NADH balance and is upregulated by hemodynamic and hormonal stress, but depressed by lipid excess. ACLY levels are most reduced in human HFpEF with obesity potentially worsening cardio-metabolic reserve.

molecular biology↗