Four-dimensional lipidomics profiling in X-linked adrenoleukodystrophy using trapped ion mobility mass spectrometry.

Lipids play pivotal roles in an extensive range of metabolic and physiological processes. In recent years, the convergence of trapped ion mobility spectrometry and MS has enabled 4D-lipidomics, a highly promising technology for comprehensive lipid analysis. 4D-lipidomics assesses lipid annotations across four distinct dimensions-retention time, collisional cross section, m/z (mass-to-charge ratio), and MS/MS spectra-providing a heightened level of confidence in lipid annotation. These advantages prove particularly valuable when investigating complex disorders involving lipid metabolism, such as adrenoleukodystrophy (ALD). ALD is characterized by the accumulation of very-long-chain fatty acids (VLCFAs) due to pathogenic variants in the ABCD1 gene. A comprehensive 4D-lipidomics strategy of ALD fibroblasts demonstrated significant elevations of various lipids from multiple classes. This indicates that the changes observed in ALD are not confined to a single lipid class and likely impacts a broad spectrum of lipid-mediated physiological processes. Our findings highlight the incorporation of mainly saturated and monounsaturated VLCFA variants into a range of lipid classes, encompassing phosphatidylcholines, triacylglycerols, and cholesterol esters. These include ultra-long-chain fatty acids with a length of up to thirty carbon atoms. Lipid species containing C26:0 and C26:1 were the most frequently detected VLCFA lipids in our study. Furthermore, we report a panel of 121 new candidate biomarkers in fibroblasts, exhibiting significant differentiation between controls and individuals with ALD. In summary, this study demonstrates the capabilities of a 4D-lipid profiling workflow in unraveling novel insights into the intricate lipid modifications associated with metabolic disorders like ALD.

PCYT2 deficiency in Saarlooswolfdogs with progressive retinal, central, and peripheral neurodegeneration.

We investigated a syndromic disease comprising blindness and neurodegeneration in 11 Saarlooswolfdogs. Clinical signs involved early adult onset retinal degeneration and adult-onset neurological deficits including gait abnormalities, hind limb weakness, tremors, ataxia, cognitive decline and behavioral changes such as aggression towards the owner. Histopathology in one affected dog demonstrated cataract, retinal degeneration, central and peripheral axonal degeneration, and severe astroglial hypertrophy and hyperplasia in the central nervous system. Pedigrees indicated autosomal recessive inheritance. We mapped the suspected genetic defect to a 15 Mb critical interval by combined linkage and autozygosity analysis. Whole genome sequencing revealed a private homozygous missense variant, PCYT2:c.4A>G, predicted to change the second amino acid of the encoded ethanolamine-phosphate cytidylyltransferase 2, XP_038402224.1:(p.Ile2Val). Genotyping of additional Saarlooswolfdogs confirmed the homozygous genotype in all eleven affected dogs and demonstrated an allele frequency of 9.9% in the population. This experiment also identified three additional homozygous mutant young dogs without overt clinical signs. Subsequent examination of one of these dogs revealed early-stage progressive retinal atrophy (PRA) and expansion of subarachnoid CSF spaces in MRI. Dogs homozygous for the pathogenic variant showed ether lipid accumulation, confirming a functional PCYT2 deficiency. The clinical and metabolic phenotype in affected dogs shows some parallels with human patients, in whom PCYT2 variants lead to a rare form of spastic paraplegia or axonal motor and sensory polyneuropathy. Our results demonstrate that PCYT2:c.4A>G in dogs cause PCYT2 deficiency. This canine model with histopathologically documented retinal, central, and peripheral neurodegeneration further deepens the knowledge of PCYT2 deficiency.

Human ovarian aging is characterized by oxidative damage and mitochondrial dysfunction.

STUDY QUESTION: Are human ovarian aging and the age-related female fertility decline caused by oxidative stress and mitochondrial dysfunction in oocytes? SUMMARY ANSWER: We found oxidative damage in oocytes of advanced maternal age, even at the primordial follicle stage, and confirmed mitochondrial dysfunction in such oocytes, which likely resulted in the use of alternative energy sources. WHAT IS KNOWN ALREADY: Signs of reactive oxygen species-induced damage and mitochondrial dysfunction have been observed in maturing follicles, and even in early stages of embryogenesis. However, although recent evidence indicates that also primordial follicles have metabolically active mitochondria, it is still often assumed that these follicles avoid oxidative phosphorylation to prevent oxidative damage in dictyate arrested oocytes. Data on the influence of ovarian aging on oocyte metabolism and mitochondrial function are still limited. STUDY DESIGN, SIZE, DURATION: A set of 39 formalin-fixed and paraffin-embedded ovarian tissue biopsies were divided into different age groups and used for immunofluorescence analysis of oxidative phosphorylation activity and oxidative damage to proteins, lipids, and DNA. Additionally, 150 immature oocytes (90 germinal vesicle oocytes and 60 metaphase I oocytes) and 15 cumulus cell samples were divided into different age groups and used for targeted metabolomics and lipidomics analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: Ovarian tissues used for immunofluorescence microscopy were collected through PALGA, the nationwide network, and registry of histo- and cytopathology in The Netherlands. Comprehensive metabolomics and lipidomics were performed by liquid-liquid extraction and full-scan mass spectrometry, using oocytes and cumulus cells of women undergoing ICSI treatment based on male or tubal factor infertility, or fertility preservation for non-medical reasons. MAIN RESULTS AND THE ROLE OF CHANCE: Immunofluorescence imaging on human ovarian tissue indicated oxidative damage by protein and lipid (per)oxidation already at the primordial follicle stage. Metabolomics and lipidomics analysis of oocytes and cumulus cells in advanced maternal-age groups demonstrated a shift in the glutathione-to-oxiglutathione ratio and depletion of phospholipids. Age-related changes in polar metabolites suggested a decrease in mitochondrial function, as demonstrated by NAD+, purine, and pyrimidine depletion, while glycolysis substrates and glutamine accumulated, with age. Oocytes from women of advanced maternal age appeared to use alternative energy sources like glycolysis and the adenosine salvage pathway, and possibly ATP which showed increased production in cumulus cells. LIMITATIONS, REASONS FOR CAUTION: The immature oocytes used in this study were all subjected to ovarian stimulation with high doses of follicle-stimulating hormones, which might have concealed some age-related differences. WIDER IMPLICATIONS OF THE FINDINGS: Further studies on how to improve mitochondrial function, or lower oxidative damage, in oocytes from women of advanced maternal age, for instance by supplementation of NAD+ precursors to promote mitochondrial biogenesis, are warranted. In addition, supplementing the embryo medium of advanced maternal-age embryos with such compounds could be a treatment option worth exploring. STUDY FUNDING/COMPETING INTEREST(S): The study was funded by the Amsterdam UMC. The authors declare to have no competing interests. TRIAL REGISTRATION NUMBER: N/A.

Adaptations of the 3T3-L1 adipocyte lipidome to defective ether lipid catabolism upon Agmo knockdown.

Little is known about the physiological role of alkylglycerol monooxygenase (AGMO), the only enzyme capable of cleaving the 1-O-alkyl ether bond of ether lipids. Expression and enzymatic activity of this enzyme can be detected in a variety of tissues including adipose tissue. This labile lipolytic membrane-bound protein uses tetrahydrobiopterin as a cofactor, and mice with reduced tetrahydrobiopterin levels have alterations in body fat distribution and blood lipid concentrations. In addition, manipulation of AGMO in macrophages led to significant changes in the cellular lipidome, and alkylglycerolipids, the preferred substrates of AGMO, were shown to accumulate in mature adipocytes. Here, we investigated the roles of AGMO in lipid metabolism by studying 3T3-L1 adipogenesis. AGMO activity was induced over 11 days using an adipocyte differentiation protocol. We show that RNA interference-mediated knockdown of AGMO did not interfere with adipocyte differentiation or affect lipid droplet formation. Furthermore, lipidomics revealed that plasmalogen phospholipids were preferentially accumulated upon Agmo knockdown, and a significant shift toward longer and more polyunsaturated acyl side chains of diacylglycerols and triacylglycerols could be detected by mass spectrometry. Our results indicate that alkylglycerol catabolism has an influence not only on ether-linked species but also on the degree of unsaturation in the massive amounts of triacylglycerols formed during in vitro 3T3-L1 adipocyte differentiation.

An autosomal dominant neurological disorder caused by de novo variants in FAR1 resulting in uncontrolled synthesis of ether lipids.

PURPOSE: In this study we investigate the disease etiology in 12 patients with de novo variants in FAR1 all resulting in an amino acid change at position 480 (p.Arg480Cys/His/Leu). METHODS: Following next-generation sequencing and clinical phenotyping, functional characterization was performed in patients' fibroblasts using FAR1 enzyme analysis, FAR1 immunoblotting/immunofluorescence, and lipidomics. RESULTS: All patients had spastic paraparesis and bilateral congenital/juvenile cataracts, in most combined with speech and gross motor developmental delay and truncal hypotonia. FAR1 deficiency caused by biallelic variants results in defective ether lipid synthesis and plasmalogen deficiency. In contrast, patients' fibroblasts with the de novo FAR1 variants showed elevated plasmalogen levels. Further functional studies in fibroblasts showed that these variants cause a disruption of the plasmalogen-dependent feedback regulation of FAR1 protein levels leading to uncontrolled ether lipid production. CONCLUSION: Heterozygous de novo variants affecting the Arg480 residue of FAR1 lead to an autosomal dominant disorder with a different disease mechanism than that of recessive FAR1 deficiency and a diametrically opposed biochemical phenotype. Our findings show that for patients with spastic paraparesis and bilateral cataracts, FAR1 should be considered as a candidate gene and added to gene panels for hereditary spastic paraplegia, cerebral palsy, and juvenile cataracts.

Functional analysis of thirty-four suspected pathogenic missense variants in ALDH5A1 gene associated with succinic semialdehyde dehydrogenase deficiency.

Deficiency of succinate semialdehyde dehydrogenase (SSADH; aldehyde dehydrogenase 5a1 (ALDH5A1), OMIM 271980, 610045), the second enzyme of GABA degradation, represents a rare autosomal-recessively inherited disorder which manifests metabolically as gamma-hydroxybutyric aciduria. The neurological phenotype includes intellectual disability, autism spectrum, epilepsy and sleep and behavior disturbances. Approximately 70 variants have been reported in the ALDH5A1 gene, half of them being missense variants. In this study, 34 missense variants, of which 22 novel, were evaluated by in silico analyses using PolyPhen2 and SIFT prediction tools. Subsequently, the effect of these variants on SSADH activity was studied by transient overexpression in HEK293 cells. These studies showed severe enzymatic activity impairment for 27 out of 34 alleles, normal activity for one allele and a broad range of residual activities (25 to 74%) for six alleles. To better evaluate the alleles that showed residual activity above 25%, we generated an SSADH-deficient HEK293-Flp-In cell line using CRISPR-Cas9, in which these alleles were stably expressed. This model proved essential in the classification as deficient for one out of the seven studied alleles. For 8 out of 34 addressed alleles, there were discrepant results among the used prediction tools, and/or in correlating the results of the prediction tools with the functional data. In case of diagnostic urgency of missense alleles, we propose the use of the transient transfection model for confirmation of their effect on the SSADH catalytic function, since this model resulted in fast and robust functional characterization for the majority of the tested variants. In selected cases, stable transfections can be considered and may prove valuable.

ENCORE: a practical implementation to improve reproducibility and transparency of computational research.

Reproducibility of computational research is often challenging despite established guidelines and best practices. Translating these guidelines into practical applications remains difficult. Here, we present ENCORE, an approach to enhance transparency and reproducibility by guiding researchers in how to structure and document a computational project. ENCORE builds on previous efforts in computational reproducibility and integrates all project components into a standardized file system structure. It utilizes pre-defined files as documentation templates, leverages GitHub for software versioning, and includes an HTML-based navigator. ENCORE is designed to be agnostic to the type of computational project, data, programming language, and ICT infrastructure, and does not rely on specific software tools. We also share our group's experience using ENCORE, highlighting that the most significant challenge to the routine adoption of approaches like ours is the lack of incentives to motivate researchers to dedicate sufficient time and effort to ensure reproducibility.

Lipidomic biomarkers in plasma correlate with disease severity in adrenoleukodystrophy.

BACKGROUND: X-linked adrenoleukodystrophy (ALD) is a neurometabolic disorder caused by pathogenic variants in ABCD1 resulting very long-chain fatty acids (VLCFA) accumulation in plasma and tissues. Males can present with various clinical manifestations, including adrenal insufficiency, spinal cord disease, and leukodystrophy. Female patients typically develop spinal cord disease and peripheral neuropathy. Predicting the clinical outcome of an individual patient remains impossible due to the lack of genotype-phenotype correlation and predictive biomarkers. METHODS: The availability of a large prospective cohort of well-characterized patients and associated biobank samples allowed us to investigate the relationship between lipidome and disease severity in ALD. We performed a lipidomic analysis of plasma samples from 24 healthy controls, 92 male and 65 female ALD patients. RESULTS: Here we show that VLCFA are incorporated into different lipid classes, including lysophosphatidylcholines, phosphatidylcholines, triglycerides, and sphingomyelins. Our results show a strong association between higher levels of VLCFA-containing lipids and the presence of leukodystrophy, adrenal insufficiency, and severe spinal cord disease in male ALD patients. In female ALD patients, VLCFA-lipid levels correlate with X-inactivation patterns in blood mononuclear cells, and higher levels are associated with more severe disease manifestations. Finally, hematopoietic stem cell transplantation significantly reduces, but does not normalize, plasma C26:0-lysophosphatidylcholine levels in male ALD patients. Our findings are supported by the concordance of C26:0-lysophosphatidylcholine and total VLCFA analysis with the lipidomics results. CONCLUSIONS: This study reveals the profound impact of ALD on the lipidome and provides potential biomarkers for predicting clinical outcomes in ALD patients.

X-linked adrenoleukodystrophy (ALD) affects the brain, spinal cord, and adrenal glands. ALD is caused by too many very long-chain fatty acids (VLCFAs) in the body. We don't know how ALD progresses in individual patients. We have analyzed blood samples from male and female ALD patients. We found that certain changes in fatty acid (or lipid) composition are associated with more severe symptoms. Our findings may lead to new ways to predict which symptoms are likely to change over time and to monitor the effectiveness of treatment. This research increases our understanding of ALD and may improve patient care in the future.

A conserved complex lipid signature marks human muscle aging and responds to short-term exercise.

Studies in preclinical models suggest that complex lipids, such as phospholipids, play a role in the regulation of longevity. However, identification of universally conserved complex lipid changes that occur during aging, and how these respond to interventions, is lacking. Here, to comprehensively map how complex lipids change during aging, we profiled ten tissues in young versus aged mice using a lipidomics platform. Strikingly, from >1,200 unique lipids, we found a tissue-wide accumulation of bis(monoacylglycero)phosphate (BMP) during mouse aging. To investigate translational value, we assessed muscle tissue of young and older people, and found a similar marked BMP accumulation in the human aging lipidome. Furthermore, we found that a healthy-aging intervention consisting of moderate-to-vigorous exercise was able to lower BMP levels in postmenopausal female research participants. Our work implicates complex lipid biology as central to aging, identifying a conserved aging lipid signature of BMP accumulation that is modifiable upon a short-term healthy-aging intervention.

DHA Shortage Causes the Early Degeneration of Photoreceptors and RPE in Mice With Peroxisomal ß-Oxidation Deficiency.

Purpose: Patients deficient in peroxisomal ß-oxidation, which is essential for the synthesis of docosahexaenoic acid (DHA, C22:6n-3) and breakdown of very-long-chain polyunsaturated fatty acids (VLC-PUFAs), both important components of photoreceptor outer segments, develop retinopathy present with retinopathy. The representative mouse model lacking the central enzyme of this pathway, multifunctional protein 2 (Mfp2-/-), also show early-onset retinal decay and cell-autonomous retinal pigment epithelium (RPE) degeneration, accompanied by reduced plasma and retinal DHA levels. In this study, we investigated whether DHA supplementation can rescue the retinal degeneration of Mfp2-/- mice. Methods: Mfp2+/- breeding pairs and their offspring were fed a 0.12% DHA or control diet during gestation and lactation and until sacrifice. Offspring were analyzed for retinal function via electroretinograms and for lipid composition of neural retina and plasma with lipidome analysis and gas chromatography, respectively, and histologically using retinal sections and RPE flatmounts at the ages of 4, 8, and 16 weeks. Results: DHA supplementation to Mfp2-/- mice restored retinal DHA levels and prevented photoreceptor shortening, death, and impaired functioning until 8 weeks. In addition, rescue of retinal DHA levels temporarily improved the ability of the RPE to phagocytose outer segments and delayed the RPE dedifferentiation. However, despite the initial rescue of retinal integrity, DHA supplementation could not prevent retinal degeneration at 16 weeks. Conclusions: We reveal that the shortage of a systemic supply of DHA is pivotal for the early retinal degeneration in Mfp2-/- mice. Furthermore, we report that adequate retinal DHA levels are essential not only for photoreceptors but also for RPE homeostasis.

Alterations in ether lipid metabolism and the consequences for the mouse lipidome.

Alkylglycerol monooxygenase (AGMO) and plasmanylethanolamine desaturase (PEDS1) are enzymes involved in ether lipid metabolism. While AGMO degrades plasmanyl lipids by oxidative cleavage of the ether bond, PEDS1 exclusively synthesizes a specific subclass of ether lipids, the plasmalogens, by introducing a vinyl ether double bond into plasmanylethanolamine phospholipids. Ether lipids are characterized by an ether linkage at the sn-1 position of the glycerol backbone and they are found in membranes of different cell types. Decreased plasmalogen levels have been associated with neurological diseases like Alzheimer's disease. Agmo-deficient mice do not present an obvious phenotype under unchallenged conditions. In contrast, Peds1 knockout mice display a growth phenotype. To investigate the molecular consequences of Agmo and Peds1 deficiency on the mouse lipidome, five tissues from each mouse model were isolated and subjected to high resolution mass spectrometry allowing the characterization of up to 2013 lipid species from 42 lipid subclasses. Agmo knockout mice moderately accumulated plasmanyl and plasmenyl lipid species. Peds1-deficient mice manifested striking changes characterized by a strong reduction of plasmenyl lipids and a concomitant massive accumulation of plasmanyl lipids resulting in increased total ether lipid levels in the analyzed tissues except for the class of phosphatidylethanolamines where total levels remained remarkably constant also in Peds1 knockout mice. The rate-limiting enzyme in ether lipid metabolism, FAR1, was not upregulated in Peds1-deficient mice, indicating that the selective loss of plasmalogens is not sufficient to activate the feedback mechanism observed in total ether lipid deficiency.

Freedom from paroxysmal atrial fibrillation after successful pulmonary vein isolation with pulmonary vein ablation catheter-phased radiofrequency energy: 2-year follow-up and predictors of failure.

AIMS: In patients with paroxysmal atrial fibrillation (PAF) the pattern of atrial fibrillation (AF) episodes and the total AF burden, may be related to the efficacy of pulmonary vein isolation (PVI). We evaluated (pre)-procedural factors explaining the long-term outcome after PVI, using a ring-shaped multielectrode ablation catheter [pulmonary vein ablation catheter (PVAC)]. METHODS AND RESULTS: A total of 120 consecutive patients with PAF were treated with the PVAC. The patients' histories were obtained by a questionnaire and the clinical charts. Follow-up was performed at 3, 6, 12, 18, and 24 months with serial electrocardiogram, and multiple day Holter at 6, 12, and 24 months, as well as event recording in case of unexplained palpitations. At 1 year, 66 of 120 (55%, 95% confidence interval (CI) [46-63%]) patients were free of any left atrial (LA) arrhythmia without class I or III anti-arrhythmics after a single procedure. At 2 years, freedom from LA arrhythmia slightly declined further to 58 of 119 (49%, 95% CI [40-58%]). The only pre-procedural predictor of long-term success was a shorter duration of the longest episode of AF (hazard ratio (HR) 0.77 95% CI [0.64-0.92]). The only procedural predictor of long-term success was no need for direct current cardioversion (DCCV) for AF (HR 0.36 95% CI [0.21-0.61]). Since other characteristics in these PAF patients were very homogeneous, no further clinical predictors were observed. CONCLUSION: Freedom from LA arrhythmia after PVI for PAF with PVAC is 49% after 2-year follow-up, with little decline between year 1 and 2. Predictors of long-term failure were a longer duration of the longest episode of AF in the pre-procedural questionnaire, and a procedural DCCV for AF.

Safety of pulmonary vein isolation and left atrial complex fractionated atrial electrograms ablation for atrial fibrillation with phased radiofrequency energy and multi-electrode catheters.

AIMS: Recently, a multi-electrode catheter system using phased radiofrequency (RF) energy was developed specifically for atrial fibrillation (AF) ablation: the pulmonary vein ablation catheter (PVAC), the multi-array septal catheter (MASC), and the multi-array ablation catheter (MAAC). Initial results of small trials have been promising: shorter procedure times and low adverse event rates. In a large single-centre registry, we evaluated the adverse events associated with multi-electrode ablation catheter procedures with PVAC alone, or combined with MASC and MAAC. METHODS AND RESULTS: In all, 634 consecutive patients with AF had 663 procedures with multi-electrode ablation catheters, 502 patients with the PVAC alone, 128 patients with PVAC/MASC/MAAC, 29 redo procedures with the PVAC or PVAC/MASC/MAAC, and 4 patients had a complicated transseptal puncture. Major and minor adverse events during 6 month follow-up were registered. In 15 cases (2.3%), major adverse events were seen within the first month after the procedure. These included complicated transseptal puncture (4), stroke (2), transient ischaemic attack (5), acute coronary syndrome (2), femoral pseudoaneurysm (1), and arteriovenous fistulae (1). Minor adverse events were seen in 10.7% at 6 months, mostly due to femoral haematoma (3.9%), and non-significant PV stenosis (5.2%). There was no difference in the occurrence of major adverse events between PVAC alone, or PVAC/MASC/MAAC ablation. CONCLUSION: Ablation with phased RF and multi-electrode catheters is accompanied by a major adverse event rate of 2.3% within 1 month and a minor event rate of 10.7% at 6 months.

Arrhythmia detection after atrial fibrillation ablation: value of incremental monitoring time.

BACKGROUND: After pulmonary vein isolation (PVI), patients need to be followed to analyze the effect of the treatment. We evaluated the influence of the duration of Holter monitoring on the detection of arrhythmia recurrences after a single PVI at 12 months. METHODS: Consecutive patients with paroxysmal atrial fibrillation (AF) underwent successful PVI with phased radiofrequency and pulmonary vein ablation catheter. Follow-up was performed with electrocardiogram at 3, 6, and 12 months and 7-day Holter at 12 months. Symptomatic patients received additional event recording. The 7-day Holters at 12 months were evaluated for documented left atrial tachyarrhythmia recurrences, and each individual day with AF was categorized. RESULTS: At 12 months after the procedure, 21 of the 96 (22%) patients had AF on their 7-day Holter. In the patients with AF recurrence, there was an increase in sensitivity from 53% of a 1-day Holter up to 88% with 4-day Holter, and 100% of a 7-day Holter. Monitoring with duration of less than 4 days resulted in significantly less detection of patients with AF compared to 7-day Holter. CONCLUSIONS: A 4-day Holter at 12 months has an 88% sensitivity for arrhythmia detection, and appears to provide a sufficient monitoring time. Prolonging the monitoring time to 7 days does not significantly increase the yield.

Cell Type-Selective Loss of Peroxisomal ß-Oxidation Impairs Bipolar Cell but Not Photoreceptor Survival in the Retina.

Retinal degeneration is a common feature in peroxisomal disorders leading to blindness. Peroxisomes are present in the different cell types of the retina; however, their precise contribution to retinal integrity is still unclear. We previously showed that mice lacking the central peroxisomal ß-oxidation enzyme, multifunctional protein 2 (MFP2), develop an early onset retinal decay including photoreceptor cell death. To decipher the function of peroxisomal ß-oxidation in photoreceptors, we generated cell type selective Mfp2 knockout mice, using the Crx promotor targeting photoreceptors and bipolar cells. Surprisingly, Crx-Mfp2-/- mice maintained photoreceptor length and number until the age of 1 year. A negative electroretinogram was indicative of preserved photoreceptor phototransduction, but impaired downstream bipolar cell signaling from the age of 6 months. The photoreceptor ribbon synapse was affected, containing free-floating ribbons and vesicles with altered size and density. The bipolar cell interneurons sprouted into the ONL and died. Whereas docosahexaenoic acid levels were normal in the neural retina, levels of lipids containing very long chain polyunsaturated fatty acids were highly increased. Crx-Pex5-/- mice, in which all peroxisomal functions are inactivated in photoreceptors and bipolar cells, developed the same phenotype as Crx-Mfp2-/- mice. In conclusion, the early photoreceptor death in global Mfp2-/- mice is not driven cell autonomously. However, peroxisomal ß-oxidation is essential for the integrity of photoreceptor ribbon synapses and of bipolar cells.

The Platelet Lipidome Is Altered in Patients with COVID-19 and Correlates with Platelet Reactivity.

BACKGROUND: Activated platelets have been implicated in the proinflammatory and prothrombotic phenotype of coronavirus disease 2019 (COVID-19). While it is increasingly recognized that lipids have important structural and signaling roles in platelets, the lipidomic landscape of platelets during infection has remained unexplored. OBJECTIVE: To investigate the platelet lipidome of patients hospitalized for COVID-19. METHODS: We performed untargeted lipidomics in platelets of 25 patients hospitalized for COVID-19 and 23 noninfectious controls with similar age and sex characteristics, and with comparable comorbidities. RESULTS: Twenty-five percent of the 1,650 annotated lipids were significantly different between the groups. The significantly altered part of the platelet lipidome mostly comprised lipids that were less abundant in patients with COVID-19 (20.4% down, 4.6% up, 75% unchanged). Platelets from COVID-19 patients showed decreased levels of membrane plasmalogens, and a distinct decrease of long-chain, unsaturated triacylglycerols. Conversely, platelets from patients with COVID-19 displayed class-wide higher abundances of bis(monoacylglycero)phosphate and its biosynthetic precursor lysophosphatidylglycerol. Levels of these classes positively correlated with ex vivo platelet reactivity-as measured by P-selectin expression after PAR1 activation-irrespective of disease state. CONCLUSION: Taken together, this investigation provides the first exploration of the profound impact of infection on the human platelet lipidome, and reveals associations between the lipid composition of platelets and their reactivity. These results warrant further lipidomic research in other infections and disease states involving platelet pathophysiology.

Biallelic variants in TAMM41 are associated with low muscle cardiolipin levels, leading to neonatal mitochondrial disease.

Mitochondrial disorders are clinically and genetically heterogeneous, with variants in mitochondrial or nuclear genes leading to varied clinical phenotypes. TAMM41 encodes a mitochondrial protein with cytidine diphosphate-diacylglycerol synthase activity: an essential early step in the biosynthesis of phosphatidylglycerol and cardiolipin. Cardiolipin is a mitochondria-specific phospholipid that is important for many mitochondrial processes. We report three unrelated individuals with mitochondrial disease that share clinical features, including lethargy at birth, hypotonia, developmental delay, myopathy, and ptosis. Whole exome and genome sequencing identified compound heterozygous variants in TAMM41 in each proband. Western blot analysis in fibroblasts showed a mild oxidative phosphorylation (OXPHOS) defect in only one of the three affected individuals. In skeletal muscle samples, however, there was severe loss of subunits of complexes I-IV and a decrease in fully assembled OXPHOS complexes I-V in two subjects as well as decreased TAMM41 protein levels. Similar to the tissue-specific observations on OXPHOS, cardiolipin levels were unchanged in subject fibroblasts but significantly decreased in the skeletal muscle of affected individuals. To assess the functional impact of the TAMM41 missense variants, the equivalent mutations were modeled in yeast. All three mutants failed to rescue the growth defect of the Δtam41 strains on non-fermentable (respiratory) medium compared with wild-type TAM41, confirming the pathogenicity of the variants. We establish that TAMM41 is an additional gene involved in mitochondrial phospholipid biosynthesis and modification and that its deficiency results in a mitochondrial disorder, though unlike families with pathogenic AGK (Sengers syndrome) and TAFAZZIN (Barth syndrome) variants, there was no evidence of cardiomyopathy.

Pulmonary vein isolation and left atrial complex-fractionated atrial electrograms ablation for persistent atrial fibrillation with phased radio frequency energy and multi-electrode catheters: efficacy and safety during 12 months follow-up.

AIMS: Ablation for persistent atrial fibrillation (AF) remains a difficult and time-consuming procedure with varying degrees of success. We evaluated the long-term effects of a novel approach for ablation of persistent AF using multi-electrode catheters. METHODS AND RESULTS: In 89 patients with longstanding persistent AF (>1 year), multi-electrode ablation was performed with a pulmonary vein ablation catheter (PVAC), a multi-array septal catheter (MASC), and a multi-array ablation catheter (MAAC) for ablation of complex-fractionated atrial electrograms (CFAE) at the septum, left atrial (LA) roof, floor, posterior wall, and mitral isthmus. Follow-up was performed at 6 and 12 months with electrocardiogram, 7 days Holter, and occasionally ambulant event recordings. Average procedure and fluoroscopy times were 112 ± 32 and 21 ± 10 min. The pre-specified endpoint of pulmonary vein isolation and LA CFAE ablation was reached in all patients. No procedural complications were observed. At 12 months after a single treatment 44 of 89 (49%) remained in sinus rhythm, including direct current cardioversion in 12 patients. At 12 months, after a redo PVAC/MASC/MAAC, an additional 6 of 15 patients (40%) were free of AF. In 18 of 89 (20%) patients AF was changed to paroxysmal. CONCLUSIONS: In this single centre study, ablation for longstanding persistent AF with the PVAC/MASC/MAAC resulted in 56% freedom of AF at 1 year after 1.2 ± 0.4 procedures. This approach is time efficient and has a favourable safety profile.