Tretowicz, M. M. | bioRxiv Science

bioRxiv2025

Integrated Multi-Omics Mapping of Mitochondrial Dysfunction and Substrate Preference in Barth Syndrome Cardiac Tissue

Barth syndrome (BTHS) is a rare X-linked recessively inherited disorder caused by variants in the TAFAZZIN gene, leading to impaired conversion of monolysocardiolipin (MLCL) into mature cardiolipin (CL). Accumulation of MLCL and CL deficiency are diagnostic markers for BTHS. Clinically, BTHS includes cardiomyopathy, skeletal myopathy, neutropenia, and growth delays. Severely affected patients may require early cardiac transplants due to unpredictable cardiac phenotypes. The pathophysiological mechanisms of BTHS are poorly understood, and treatments remain symptomatic. This study analyzed heart samples from five pediatric male BTHS patients (5 months-15 years) and compared them to tissues from 24 non-failing donors (19-71 years) using an integrated omics method combining metabolomics, lipidomics, and proteomics. The analysis confirmed changes in diagnostic markers (CL and MLCL), severe mitochondrial alterations, metabolic shifts, and elevated heart-failure markers. It also revealed significant interindividual differences among BTHS patients. With this study describe a powerful analytical tool for the in-depth analysis of metabolic disorders and a solid foundation for the understanding of BTHS disease phenotypes in cardiac tissues.

molecular biology↗

bioRxiv2025

Kynurenine and NAD+ Pathways are Associated with Macrophage Content and Polarization in Carotid Plaques

Background and AimsMetabolism dictates macrophage function and plays a central role in atherosclerotic plaque progression. The kynurenine pathway, which metabolizes the majority of the essential amino acid tryptophan, plays a pivotal role in regulating immune responses and supporting NAD+ synthesis, essential for cellular energy metabolism. Higher circulating kynurenine levels are associated with cardiovascular disease, yet their role in atherosclerotic plaques is unclear. This study aims to investigate the underlying mechanisms driving increased kynurenine concentrations in plaques and to determine whether kynurenine serves as a mere biomarker of low-grade inflammation or reflects specific macrophage-driven metabolic alterations that could position it as a potential therapeutic target. MethodsWe used histological and transcriptomic data from two biobanks: the Athero Express Biobank (AE; n=91) and Maastricht human plaque study (MaasHPS, n= 26). Macrophages were identified through CD68 staining in AE, and M1/M2-like macrophage subtypes were distinguished by iNOS/CD68 and arginase/CD68 expression in MAASHPS. Primary human monocyte-derived cultured macrophages were polarized into M1- and M2-like phenotypes for using IFN-{gamma} and IL-4, respectively. Tryptophan, kynurenine and/or NAD+ concentrations in plaques were quantified usingliquid chromatography and metabolomics analyses. ResultsKynurenine concentrations were significantly higher in plaques with greater macrophage density (p = 0.023). Transcriptomic analysis in AE revealed upregulation of IDO2, AFMID, and KYNU in plaques with increased macrophage infiltration (p < 0.05), but not IDO1 (p = 0.16). In the MAASHPS biobank, higher IDO1, KYNU, and KMO expression correlated negatively with M2 marker positive macrophages (p < 0.001), while HAAO correlated positively (p < 0.01). In vitro, M1-like macrophages showed increased IDO1 and reduced QPRT expression compared to M2-like macrophages. We found that this disruption in kynurenine pathway gene expression led to decreased NAD+ concentrations in M1-like macrophages compared to M2-like macrophages in vitro. ConclusionHigher kynurenine levels in atherosclerotic plaques are increased by the increased presence of M1 macrophages, likely driven by both an increased IDO1 activity and reduced QPRT gene expression. This leads to decreased concentrations of NAD+, potentially determining the phenotype of the macrophages. Future studies should address whether modulation of the kynurenine pathway restores NAD+ metabolism and leads to a decrease in inflammation and an increased stable plaque phenotype.

immunology↗