Phosphatidylethanolamine Biosynthesis Research Articles

Mitochondrial bioenergetics stimulates autophagy for pathological MAPT/Tau clearance in tauopathy neurons

ABSTRACT Hyperphosphorylation and aggregation of MAPT (microtubule-associated protein tau) is a pathogenic hallmark of tauopathies and a defining feature of Alzheimer disease (AD). Pathological MAPT/tau is targeted by macroautophagy/autophagy for clearance after being sequestered within autophagosomes, but autophagy dysfunction is indicated in tauopathy. While mitochondrial bioenergetic deficits have been shown to precede MAPT/tau pathology in tauopathy brains, it is unclear whether energy metabolism deficiency is involved in the pathogenesis of autophagy defects. Here, we reveal that stimulation of anaplerotic metabolism restores defective oxidative phosphorylation (OXPHOS) in tauopathy neurons which, strikingly, leads to pronounced MAPT/tau clearance by boosting autophagy functionality through enhancements of mitochondrial biosynthesis and supply of phosphatidylethanolamine for autophagosome biogenesis. Furthermore, early anaplerotic stimulation of OXPHOS elevates autophagy activity and attenuates MAPT/tau pathology, thereby counteracting memory impairment in tauopathy mice. Taken together, our study sheds light on a pivotal role of mitochondrial bioenergetic deficiency in tauopathy-related autophagy defects and suggests a new therapeutic strategy to prevent the buildup of pathological MAPT/tau in AD and other tauopathy diseases. Abbreviation: AA: antimycin A; AD, Alzheimer disease; ATP, adenosine triphosphate; AV, autophagosome/autophagic vacuole; AZ, active zone; Baf-A1: bafilomycin A1; CHX, cycloheximide; COX, cytochrome c oxidase; DIV, days in vitro; DRG, dorsal root ganglion; ETN, ethanolamine; FRET, Förster/fluorescence resonance energy transfer; FTD, frontotemporal dementia; Gln, glutamine; HA: hydroxylamine; HsMAPT/Tau, human MAPT; IMM, inner mitochondrial membrane; LAMP1, lysosomal-associated membrane protein 1; LIs, lysosomal inhibitors; MDAV, mitochondria-derived autophagic vacuole; MmMAPT/Tau, murine MAPT; NFT, neurofibrillary tangle; OCR, oxygen consumption rate; Omy: oligomycin; OXPHOS, oxidative phosphorylation; PPARGC1A/PGC-1alpha: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PE, phosphatidylethanolamine; phospho-MAPT/tau, hyperphosphorylated MAPT; PS, phosphatidylserine; PISD, phosphatidylserine decarboxylase;SQSTM1/p62, sequestosome 1; STX1, syntaxin 1; SYP, synaptophysin; Tg, transgenic; TCA, tricarboxylic acid; TEM, transmission electron microscopy.

Novel biallelic PISD missense variants cause spondyloepimetaphyseal dysplasia with disproportionate short stature and fragmented mitochondrial morphology.

Biallelic variants in PISD cause a phenotypic spectrum ranging from short stature with spondyloepimetaphyseal dysplasia (SEMD) to a multisystem disorder affecting eyes, ears, bones, and brain. PISD encodes the mitochondrial-localized enzyme phosphatidylserine decarboxylase. The PISD precursor is self-cleaved to generate a heteromeric mature enzyme that converts phosphatidylserine to the phospholipid phosphatidylethanolamine. We describe a 17-year-old male patient, born to unrelated healthy parents, with disproportionate short stature and SEMD, featuring platyspondyly, prominent epiphyses, and metaphyseal dysplasia. Trio genome sequencing revealed compound heterozygous PISD variants c.569C>T; p.(Ser190Leu) and c.799C>T; p.(His267Tyr) in the patient. Investigation of fibroblasts showed similar levels of the PISD precursor protein in both patient and control cells. However, patient cells had a significantly higher proportion of fragmented mitochondria compared to control cells cultured under basal condition and after treatment with 2-deoxyglucose that represses glycolysis and stimulates respiration. Structural data from the PISD orthologue in Escherichia coli suggest that the amino acid substitutions Ser190Leu and His267Tyr likely impair PISD's autoprocessing activity and/or phosphatidylethanolamine biosynthesis. Based on the data, we propose that the novel PISD p.(Ser190Leu) and p.(His267Tyr) variants likely act as hypomorphs and underlie the pure skeletal phenotype in the patient.

Skeletal muscle PGC-1α remodels mitochondrial phospholipidome but does not alter energy efficiency for ATP synthesis.

Exercise training is thought to improve the mitochondrial energy efficiency of skeletal muscle. Some studies suggest exercise training increases the efficiency for ATP synthesis by oxidative phosphorylation (OXPHOS), but the molecular mechanisms are unclear. We have previously shown that exercise remodels the lipid composition of mitochondrial membranes, and some of these changes could contribute to improved OXPHOS efficiency (ATP produced by O2 consumed or P/O). Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) is a transcriptional co-activator that coordinately regulates exercise-induced adaptations including mitochondria. We hypothesized that increased PGC-1α activity is sufficient to remodel mitochondrial membrane lipids and promote energy efficiency. Mice with skeletal muscle-specific overexpression of PGC-1α (MCK-PGC-1α) and their wildtype littermates were used for this study. Lipid mass spectrometry and quantitative PCR were used to assess muscle mitochondrial lipid composition and their biosynthesis pathway. The abundance of OXPHOS enzymes was determined by western blot assay. High-resolution respirometry and fluorometry analysis were used to characterize mitochondrial bioenergetics (ATP production, O2 consumption, and P/O) for permeabilized fibers and isolated mitochondria. Lipidomic analyses of skeletal muscle mitochondria from wildtype and MCK-PGC-1α mice revealed that PGC-1α increases the concentrations of cone-shaped lipids such as phosphatidylethanolamine (PE), cardiolipin (CL), and lysophospholipids, while decreases the concentrations of phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidic acid (PA). However, while PGC-1α overexpression increased the abundance of OXPHOS enzymes in skeletal muscle and the rate of O2 consumption (JO2), P/O values were unaffected with PGC-1α in permeabilized fibers or isolated mitochondria. Collectively, overexpression of PGC-1α promotes the biosynthesis of mitochondrial PE and CL but neither PGC-1α nor the mitochondrial membrane lipid remodeling induced in MCK-PGC-1α mice is sufficient to increase the efficiency for mitochondrial ATP synthesis. These findings suggest that exercise training may increase OXPHOS efficiency by a PGC-1α-independent mechanism, and question the hypothesis that mitochondrial lipids directly affect OXPHOS enzymes to improve efficiency for ATP synthesis.

Exploring the metabolic implications of blue light exposure during daytime in rats

Excessive exposure to light is a global issue. Artificial light pollution has been shown to disrupt the body's natural circadian rhythm. To investigate the impacts of light on metabolism, we studied Sprague-Dawley rats chronically exposed to red or blue light during daytime or nighttime. Rats in the experimental group were exposed to extended light for 4 hours during daytime or nighttime to simulate the effects of excessive light usage. Strikingly, we found systemic metabolic alterations only induced by blue light during daytime. Furthermore, we conducted metabolomic analyses of the cerebrospinal fluid, serum, heart, liver, spleen, adrenal, cerebellum, pituitary, prostate, spermatophore, hypothalamus and kidney from rats in the control and blue light exposure during daytime. Significant changes in metabolites have been observed in cerebrospinal fluid, serum, hypothalamus and kidney of rats exposed to blue light during daytime. Metabolic alterations observed in rats encompassing pyruvate metabolism, glutathione metabolism homocysteine degradation, phosphatidylethanolamine biosynthesis, and phospholipid biosynthesis, exhibit analogous patterns to those inherent in specific physiological processes, notably neurodevelopment, cellular injury, oxidative stress, and autophagic pathways. Our study provides insights into tissue-specific metabolic changes in rats exposed to blue light during the daytime and may help explain potential mechanisms of photopathogenesis.

Gestational testosterone excess early to mid-pregnancy disrupts maternal lipid homeostasis and activates biosynthesis of phosphoinositides and phosphatidylethanolamines in sheep

Gestational hyperandrogenism is a risk factor for adverse maternal and offspring outcomes with effects likely mediated in part via disruptions in maternal lipid homeostasis. Using a translationally relevant sheep model of gestational testosterone (T) excess that manifests maternal hyperinsulinemia, intrauterine growth restriction (IUGR), and adverse offspring cardiometabolic outcomes, we tested if gestational T excess disrupts maternal lipidome. Dimensionality reduction models following shotgun lipidomics of gestational day 127.1 ± 5.3 (term 147 days) plasma revealed clear differences between control and T-treated sheep. Lipid signatures of gestational T-treated sheep included higher phosphoinositides (PI 36:2, 39:4) and lower acylcarnitines (CAR 16:0, 18:0, 18:1), phosphatidylcholines (PC 38:4, 40:5) and fatty acids (linoleic, arachidonic, Oleic). Gestational T excess activated phosphatidylethanolamines (PE) and PI biosynthesis. The reduction in key fatty acids may underlie IUGR and activated PI for the maternal hyperinsulinemia evidenced in this model. Maternal circulatory lipids contributing to adverse cardiometabolic outcomes are modifiable by dietary interventions.

Metabolomics profile and machine learning prediction of treatment responses in immune thrombocytopenia: A prospective cohort study.

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by antibody-mediated platelet destruction and impaired platelet production. The mechanisms underlying ITP and biomarkers predicting the response of drug treatments are elusive. We performed a metabolomic profiling of bone marrow biopsy samples collected from ITP patients admission in a prospective study of the National Longitudinal Cohort of Hematological Diseases. Machine learning algorithms were conducted to discover novel biomarkers to predict ITP patient treatment responses. From the bone marrow biopsies of 91 ITP patients, we quantified a total of 4494 metabolites, including 1456 metabolites in the positive mode and 3038 metabolites in the negative mode. Metabolic patterns varied significantly between groups of newly diagnosed and chronic ITP, with a total of 876 differential metabolites involved in 181 unique metabolic pathways. Enrichment factors and p-values revealed the top metabolically enriched pathways to be sphingolipid metabolism, the sphingolipid signalling pathway, ubiquinone and other terpenoid-quinone biosynthesis, thiamine metabolism, tryptophan metabolism and cofactors biosynthesis, the phospholipase D signalling pathway and the phosphatidylinositol signalling system. Based on patient responses to five treatment options, we screened several metabolites using the Boruta algorithm and ranked their importance using the random forest algorithm. Lipids and their metabolism, including long-chain fatty acids, oxidized lipids, glycerophospholipids, phosphatidylcholine and phosphatidylethanolamine biosynthesis, helped differentiate drug treatment responses. In conclusion, this study revealed metabolic alterations associated with ITP in bone marrow supernatants and a potential biomarker predicting the response to ITP.

Betaine and I-LG may have a predictive value for ATB: A causal study in a large European population.

To analyze the causal relationship between 486 human serum metabolites and the active tuberculosis (ATB) in European population. In this study, the causal relationship between human serum metabolites and the ATB was analyzed by integrating the genome-wide association study (GWAS). The 486 human serum metabolites were used as the exposure variable, three different ATB GWAS databases in the European population were set as outcome variables, and single nucleotide polymorphisms were used as instrumental variables for Mendelian Randomization. The inverse variance weighting was estimated causality, the MR-Egger intercept to estimate horizontal pleiotropy, and the combined effects of metabolites were also considered in the meta-analysis. Furthermore, the web-based MetaboAnalyst 6.0 was engaged for enrichment pathway analysis, while R (version 4.3.2) software and Review Manager 5.3 were employed for statistical analysis. A total of 21, 17, and 19 metabolites strongly associated with ATB were found in the three databases after preliminary screening (P < 0.05). The intersecting metabolites across these databases included tryptophan, betaine, 1-linoleoylglycerol (1-monolinolein) (1-LG), 1-eicosatrienoylglycerophosphocholine, and oleoylcarnitine. Among them, betaine (I2 = 24%, P = 0.27) and 1-LG (I2 = 0%, P = 0.62) showed the lowest heterogeneity among the different ATB databases. In addition, the metabolic pathways of phosphatidylethanolamine biosynthesis (P = 0.0068), methionine metabolism (P = 0.0089), betaine metabolism (P = 0.0205) and oxidation of branched-chain fatty acids (P = 0.0309) were also associated with ATB. Betaine and 1-LG may be biomarkers or auxiliary diagnostic tools for ATB. They may provide new guidance for medical practice in the early diagnosis and surveillance of ATB. In addition, by interfering with phosphatidylethanolamine biosynthesis, methionine metabolism, betaine metabolism, oxidation of branched-chain fatty acids, and other pathways, it is helpful to develop new anti-tuberculosis drugs and explore the virulence or pathogenesis of ATB at a deeper level, providing an effective reference for future studies.

Biallelic PI4KA mutations Disrupt B Cell Mitochondrial Metabolism and Cause Hypogammaglobulinemia

Introduction Biallelic mutations in the PI4KA gene cause PI4KA-related disorder, a novel condition with neurological (limb spasticity, developmental delay, intellectual disability, seizures, ataxia, nystagmus), gastrointestinal (GI; inflammatory bowel disease [IBD] and multiple intestinal atresia [MIA]) and immunological manifestations. PI4KA encodes phosphatidylinositol (PI) 4-kinase alpha, which catalyzes the first step of phosphoinositide metabolism, phosphorylating PI to PI4P (phosphatidylinositol 4-phosphate). Phosphoinositides collectively have fundamental signalling roles in the plasma membrane and other organelles. We collected comprehensive clinical and laboratory data on 13 patients and performed a multiomic strategy, combining transcriptome, proteome, lipidome and metabolome analyses of three patients' EBV-transformed cell lines to unravel the burden of B cell deficiency in PI4KA-related disorder and define the role of PI4KA in B cells. Results Recurrent or severe infections (8/13) and GI (either gastroesophageal reflux disease, MIA or IBD; 6/13) manifestations were frequent. Thyroid disease (either hypo- or hyperthyroidism; 2/13), juvenile idiopathic arthritis (JIA; 1/13) and non-Hodgkin lymphoma (1/13) were reported. At last follow up 11 patients were alive. Ten had either hypogammaglobulinemia, decreased absolute numbers of B cells or decreased B cell subsets. B cell subsets showed increased transitional (4/7), decreased naive (2/7) and decreased switched memory (4/7) B cells. B cell proliferation to T independent mitogens, specifically IgM + CpG or pokeweed, was impaired in 2/2. T-cell (either CD3+, CD4+ or CD8+) lymphopenia was detected in 4/13. T-cell proliferation was maintained in 5/5. NK cells were decreased in 6/13. Ig replacement therapy (4/13) and immunosuppressive treatment (due to JIA [1/13] or IBD [2/13]) were given. Lipidome analysis showed that different glycerophospholipids profile (i.e., phosphatidylcholine [PC], phosphatidylethanolamines [PE] and phosphatidylserine [PS]) was altered. Metabolome analysis and pathway enrichment analysis confirmed impaired phosphatidylethanolamine biosynthesis and additionally showed altered PIP metabolism and mitochondrial dysfunction (i.e., beta-oxidation of short and long fatty acids). Although the total number of mitochondria was not affected, the mitochondrial activity was significantly reduced. Integration analyses of proteomics, metabolomic and lipidomic data reveals biochemical mechanisms underlying biallelic PI4KA mutation. In particular, dysregulation of metabolic enzymes and pathways involved in glutathione metabolism and tricarboxylic acid cycle was found (Fig. 1). These metabolic impairments ultimately impacted on oxidative phosphorylation, thus disrupting mitochondrial integrity. Gene set enrichment analysis of differentially expressed genes suggested a skewing towards naive B cell gene sets. Pathways enrichment analysis of transcriptome and proteome showed enrichment in B cell receptor (BCR) pathway and complex, PI3K/mTOR pathway and phospholipids metabolism. PI4P and its metabolite PI(4,5)P2 are determinants of PM identity, specifically controlling cytoskeletal dynamics. Deranged basal actin organization was reverted after anti-IgM stimulation. Hyperactivation of PI3K targets (pAKT473, p4EBP1 and pS6) was observed. Dysregulation of RABGAP1, RAB8B and LAMP3 mRNA prompted us to investigate autophagy. Indeed, LC3 was increased either in the presence or absence of chloroquine, showing that PI4KA mutations enhanced autophagosome formation and inhibited its degradation. Conclusion Overall, by altering the production of several key lipids, biallelic PI4KA mutations disrupt B cell metabolism causing mitochondrial dysfunction, mTOR hyperactivation, increased autophagy and deranged cytoskeleton organization. PI4KA-related disorder is a novel syndromic inborn error of immunity causing B cell deficiency and hypogammaglobulinemia. Figure 1. Integration of proteomics, metabolomics and lipidomics reveals biochemical mechanisms underlying biallelic PI4KA mutations.

Parkinson's Disease and the Heart: Studying Cardiac Metabolism in the 6-Hydroxydopamine Model.

Parkinson's-disease (PD) is an incurable, age-related neurodegenerative disease, and its global prevalence of disability and death has increased exponentially. Although motor symptoms are the characteristic manifestations of PD, the clinical spectrum also contains a wide variety of non-motor symptoms, which are the main cause of disability and determinants of the decrease in a patient's quality of life. Noteworthy in this regard is the stress on the cardiac system that is often observed in the course of PD; however, its effects have not yet been adequately researched. Here, an untargeted metabolomics approach was used to assess changes in cardiac metabolism in the 6-hydroxydopamine model of PD. Beta-sitosterol, campesterol, cholesterol, monoacylglycerol, α-tocopherol, stearic acid, beta-glycerophosphoric acid, o-phosphoethanolamine, myo-inositol-1-phosphate, alanine, valine and allothreonine are the metabolites that significantly discriminate parkinsonian rats from sham counterparts. Upon analysis of the metabolic pathways with the aim of uncovering the main biological pathways involved in concentration patterns of cardiac metabolites, the biosynthesis of both phosphatidylethanolamine and phosphatidylcholine, the glucose-alanine cycle, glutathione metabolism and plasmalogen synthesis most adequately differentiated sham and parkinsonian rats. Our results reveal that both lipid and energy metabolism are particularly involved in changes in cardiac metabolism in PD. These results provide insight into cardiac metabolic signatures in PD and indicate potential targets for further investigation.

Megaconial congenital muscular dystrophy due to CHKB gene variants, the first report of thirteen Iranian patients

Megaconial congenital muscular dystrophy (OMIM: 602,541) related to CHKB gene mutation is a newly defined rare autosomal recessive disorder, with multisystem involvement presenting from the neonatal period to adolescence. Choline kinase beta, lipid transport enzyme, catalyzes the biosynthesis of phosphatidylcholine and phosphatidylethanolamine, two major components of the mitochondrial membrane, on which respiratory enzyme activities are dependent. CHKB gene variants lead to loss-of-function of choline kinase b and lipid metabolism defects and mitochondrial structural changes. To date, many megaconial congenital muscular dystrophy cases due to CHKB gene variants have been reported worldwide. We describe thirteen Iranian megaconial congenital muscular dystrophy cases related to CHKB gene variants, including clinical presentations, laboratory and muscle biopsy findings, and novel CHKB gene variants. The most common symptoms and signs included intellectual disability, delayed gross-motor developmental milestones, language skills problems, muscle weakness, as well as autistic features, and behavioral problems. Muscle biopsy examination showed the striking finding of peripheral arrangements of large mitochondria in muscle fibers and central sarcoplasmic areas devoid of mitochondria. Eleven different CHKB gene variants including six novel variants were found in our patients. Despite the rarity of this disorder, recognition of the multisystem clinical presentations combined with characteristic findings of muscle histology can properly guide to genetic evaluation of CHKB gene.

Doxorubicin inhibits phosphatidylserine decarboxylase and confers broad-spectrum antifungal activity.

As phospholipids of cell membranes, phosphatidylethanolamine (PE) and phosphatidylserine (PS) play crucial roles in glycerophospholipid metabolism. Broadly, some phospholipid biosynthesis enzymes serve as potential fungicide targets. Therefore, revealing the functions and mechanism of PE biosynthesis in plant pathogens would provide potential targets for crop disease control. We performed analyses including phenotypic characterizations, lipidomics, enzyme activity, site-directed mutagenesis, and chemical inhibition assays to study the function of PS decarboxylase-encoding gene MoPSD2 in rice blast fungus Magnaporthe oryzae. The Mopsd2 mutant was defective in development, lipid metabolism, and plant infection. The PS level increased while PE decreased in Mopsd2, consistent with the enzyme activity. Furthermore, chemical doxorubicin inhibited the enzyme activity of MoPsd2 and showed antifungal activity against 10 phytopathogenic fungi including M. oryzae and reduced disease severity of two crop diseases in the field. Three predicted doxorubicin-interacting residues are important for MoPsd2 functions. Our study demonstrates that MoPsd2 is involved in de novo PE biosynthesis and contributes to the development and plant infection of M. oryzae and that doxorubicin shows broad-spectrum antifungal activity as a fungicide candidate. The study also implicates that bacterium Streptomyces peucetius, which biosynthesizes doxorubicin, could be potentially used as an eco-friendly biocontrol agent.

Structural basis for catalysis of human choline/ethanolamine phosphotransferase 1

Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are two primary components of the eukaryotic membrane and play essential roles in the maintenance of membrane integrity, lipid droplet biogenesis, autophagosome formation, and lipoprotein formation and secretion. Choline/ethanolamine phosphotransferase 1 (CEPT1) catalyzes the last step of the biosynthesis of PC and PE in the Kennedy pathway by transferring the substituted phosphate group from CDP-choline/ethanolamine to diacylglycerol. Here, we present the cryo-EM structures of human CEPT1 and its complex with CDP-choline at resolutions of 3.7 Å and 3.8 Å, respectively. CEPT1 is a dimer with 10 transmembrane segments (TMs) in each protomer. TMs 1-6 constitute a conserved catalytic domain with an interior hydrophobic chamber accommodating a PC-like density. Structural observations and biochemical characterizations suggest that the hydrophobic chamber coordinates the acyl tails during the catalytic process. The PC-like density disappears in the structure of the complex with CDP-choline, suggesting a potential substrate-triggered product release mechanism.

PECT1, a rate-limiting enzyme in phosphatidylethanolamine biosynthesis, is involved in the regulation of stomatal movement in Arabidopsis.

An Arabidopsis mutant displaying impaired stomatal responses to CO2 , cdi4, was isolated by a leaf thermal imaging screening. The mutated gene PECT1 encodes CTP:phosphorylethanolamine cytidylyltransferase. The cdi4 exhibited a decrease in levels and a defect in light-induced stomatal opening as well as low-CO2 -induced stomatal opening. We created RNAi lines in which PECT1 was specifically repressed in guard cells. These lines are impaired in their stomatal responses to low-CO2 concentrations or light. Fungal toxin fusicoccin (FC) promotes stomatal opening by activating plasma membrane H+ -ATPases in guard cells via phosphorylation. Arabidopsis H+ -ATPase1 (AHA1) has been reported to be highly expressed in guard cells, and its activation by FC induces stomatal opening. The cdi4 and PECT1 RNAi lines displayed a reduced stomatal opening response to FC. However, similar to in the wild-type, cdi4 maintained normal levels of phosphorylation and activation of the stomatal H+ -ATPases after FC treatment. Furthermore, the cdi4 displayed normal localization of GFP-AHA1 fusion protein and normal levels of AHA1 transcripts. Based on these results, we discuss how PECT1 could regulate CO2 - and light-induced stomatal movements in guard cells in a manner that is independent and downstream of the activation of H+ -ATPases.

Segmental hair metabolomics analysis in pregnant women with pregnancy complications

Pregnancy complications, as preeclampsia (PE) and HELLP syndrome, occurring with similar pathophysiological mechanisms, have adverse effects on the health of both mother and fetus during pregnancy and thereafter, they are leading causes of maternal and fetal morbidity and mortality. The hair metabolome has been recognized as a valuable source of information in pregnancy research, as it provides stable metabolite information to be able to assist with studying biomarkers or metabolic mechanisms of pregnancy and its complications. The aim of this study was to investigate the hair metabolome profile of pregnant women with PE, HELLP syndrome and healthy women. Hair samples of new-borns' mothers (patients and controls) were investigated segmentally relevant to each trimester using a proper sample preparation and gas chromatography-mass spectrometry (GC-MS) to identify robust biomarkers that can be useful for screening, early detection, follow-up and treatment of PE and HELLP syndrome, the etiology of which are still unknown. The results showed a significant change in the metabolome profiles of the patient and control groups regarding the trimesters. A striking decrease was observed in all 100 metabolites investigated in the patient group (p < 0.000). The metabolic pathways associated with significant metabolites have also been investigated, and the most affected pathways were observed to be the urea cycle, glycine, serine, aspartate, methionine and purine metabolism, ammonia cycle, and phosphatidylethanolamine biosynthesis. The found metabolites provide us with extensive data on the ability to establish biomarkers for predicting, early detection and monitoring of PE.

Two Different Phospholipases C, Isc1 and Pgc1, Cooperate To Regulate Mitochondrial Function.

The absence of Isc1, the yeast homologue of mammalian neutral sphingomyelinase type 2, leads to severe mitochondrial dysfunction. We show that the deletion of another type C phospholipase, the phosphatidylglycerol (PG)-specific phospholipase Pgc1, rescues this defect. Phosphatidylethanolamine (PE) levels and cytochrome c oxidase activity, which were reduced in isc1Δ cells, were restored to wild-type levels in the pgc1Δ isc1Δ mutant. The Pgc1 substrate PG inhibited the in vitro activities of Isc1 and the phosphatidylserine decarboxylase Psd1, an enzyme crucial for PE biosynthesis. We also identify a mechanism by which the balance between the current demand for PG and its consumption is controlled. We document that the product of PG hydrolysis, diacylglycerol, competes with the substrate of PG-phosphate synthase, Pgs1, and thereby inhibits the biosynthesis of excess PG. This feedback loop does not work in the absence of Pgc1, which catalyzes PG degradation. Finally, Pgc1 activity is partially inhibited by products of Isc1-mediated hydrolysis. The described functional interconnection of the two phospholipases contributes significantly to lipid homeostasis throughout the cellular architecture. IMPORTANCE In eukaryotic cells, mitochondria are constantly adapting to changes in the biological activity of the cell, i.e., changes in nutrient availability and environmental stresses. We propose a model in which this adaptation is mediated by lipids. Specifically, we show that mitochondrial phospholipids regulate the biosynthesis of cellular sphingolipids and vice versa. To do this, lipids move by free diffusion, which does not require energy and works under any condition. This model represents a simple way for the cell to coordinate mitochondrial structure and performance with the actual needs of overall cellular metabolism. Its simplicity makes it a universally applicable principle of cellular regulation.

Fat body phospholipid state dictates hunger-driven feeding behavior.

Diet-induced obesity leads to dysfunctional feeding behavior. However, the precise molecular nodes underlying diet-induced feeding motivation dysregulation are poorly understood. The fruit fly is a simple genetic model system yet displays significant evolutionary conservation to mammalian nutrient sensing and energy balance. Using a longitudinal high-sugar regime in Drosophila, we sought to address how diet-induced changes in adipocyte lipid composition regulate feeding behavior. We observed that subjecting adult Drosophila to a prolonged high-sugar diet degrades the hunger-driven feeding response. Lipidomics analysis reveals that longitudinal exposure to high-sugar diets significantly alters whole-body phospholipid profiles. By performing a systematic genetic screen for phospholipid enzymes in adult fly adipocytes, we identify Pect as a critical regulator of hunger-driven feeding. Pect is a rate-limiting enzyme in the phosphatidylethanolamine (PE) biosynthesis pathway and the fly ortholog of human PCYT2. We show that disrupting Pect activity only in the Drosophila fat cells causes insulin resistance, dysregulated lipoprotein delivery to the brain, and a loss of hunger-driven feeding. Previously human studies have noted a correlation between PCYT2/Pect levels and clinical obesity. Now, our unbiased studies in Drosophila provide causative evidence for adipocyte Pect function in metabolic homeostasis. Altogether, we have uncovered that PE phospholipid homeostasis regulates hunger response.

Megaconial congenital muscular dystrophy due to novel CHKB variants: a case report and literature review

BackgroundCholine kinase beta (CHKB) catalyzes the first step in the de novo biosynthesis of phosphatidyl choline and phosphatidylethanolamine via the Kennedy pathway. Derangement of this pathway might also influence the homeostasis of mitochondrial membranes.Autosomal recessive CHKB mutations cause a rare form of congenital muscular dystrophy known as megaconial congenital muscular dystrophy (MCMD).Case presentationWe describe a novel proband presenting MCMD due to unpublished CHKB mutations. The patient is a 6-year-old boy who came to our attention for cognitive impairment and slowly progressive muscular weakness. He was the first son of non-consanguineous healthy parents from Sri Lanka. Neurological examination showed proximal weakness at four limbs, weak osteotendinous reflexes, Gowers’ maneuver, and waddling gate. Creatine kinase levels were mildly increased. EMG and brain MRI were normal. Left quadriceps skeletal muscle biopsy showed a myopathic pattern with nuclear centralizations and connective tissue increase. Histological and histochemical staining suggested subsarcolemmal localization and dimensional increase of mitochondria. Ultrastructural analysis confirmed the presence of enlarged (“megaconial”) mitochondria. Direct sequencing of CHKB identified two novel defects: the c.1060G > C (p.Gly354Arg) substitution and the c.448-56_29del intronic deletion, segregating from father and mother, respectively. Subcloning of RT-PCR amplicons from patient’s muscle RNA showed that c.448-56_29del results in the partial retention (14 nucleotides) of intron 3, altering physiological splicing and transcript stability. Biochemical studies showed reduced levels of the mitochondrial fission factor DRP1 and the severe impairment of mitochondrial respiratory chain activity in patient’s muscle compared to controls.ConclusionsThis report expands the molecular findings associated with MCMD and confirms the importance of considering CHKB variants in the differential diagnosis of patients presenting with muscular dystrophy and mental retardation. The clinical outcome of MCMD patients seems to be influenced by CHKB molecular defects. Histological and ultrastructural examination of muscle biopsy directed molecular studies and allowed the identification and characterization of an intronic mutation, usually escaping standard molecular testing.

Bilayer Forming Phospholipids as Targets for Cancer Therapy.

Phospholipids represent a crucial component for the structure of cell membranes. Phosphatidylcholine and phosphatidylethanolamine are two phospholipids that comprise the majority of cell membranes. De novo biosynthesis of phosphatidylcholine and phosphatidylethanolamine occurs via the Kennedy pathway, and perturbations in the regulation of this pathway are linked to a variety of human diseases, including cancer. Altered phosphatidylcholine and phosphatidylethanolamine membrane content, phospholipid metabolite levels, and fatty acid profiles are frequently identified as hallmarks of cancer development and progression. This review summarizes the research on how phospholipid metabolism changes over oncogenic transformation, and how phospholipid profiling can differentiate between human cancer and healthy tissues, with a focus on colorectal cancer, breast cancer, and non-small cell lung cancer. The potential for phospholipids to serve as biomarkers for diagnostics, or as anticancer therapy targets, is also discussed.

Cord Blood Metabolomics and Autism Spectrum Disorder

IntroductionAutism spectrum disorder (ASD) has increased dramatically in prevalence and incidence in recent years (1:59 in the US, CDC). With prenatal and/or genetic origins, early detection and intervention are critical to improve outcomes. Few studies have assessed perinatal biomarkers for later development of ASD. We hypothesize that cord blood plasma‐based metabolomics will differentiate infants who would later be diagnosed with ASD and typically developing (TD) controls.MethodsBanked cord blood plasma samples and clinical data from the Iowa Maternal Fetal Tissue Bank were used. Samples were analyzed via gas chromatography and mass spectrometry (GC‐MS) and relative MS signal intensity of a maximum of was quantified ratiometrically. All metabolites were normalized to internal controls (succinate) to account for effects of extraction, derivatization, and/or loading. Ratiometric levels of each metabolite were compared by t‐test between ASD and control groups. Results P&lt;0.01 are reported given the pilot nature of this small study. Metabolite set enrichment analysis (MSEA) was performed against human libraries. Significantly altered metabolites were compared to a tertiary sample of cord blood from individuals later diagnosed with attention deficit hyperactivity disorder (ADHD) to determine specificity for ASD.Results91 metabolites were detected and analyzed. Homocysteine (fold change [FC]: 1.411; p=0.017), Myristic acid (FC: 1.221; p=0.084), Pentadecanoic acid (FC: 1.256; p=0.093) were increased in ASD samples, while L‐Isoleucine (FC: 0.858; p=0.047), L‐Threonine (FC: 0.7131; p=0.068), O‐Phosphoethanolamine (FC: 0.704; p=0.070), and 2‐Hydroxybutyric acid (FC: 0.615; p=0.073) were decreased. Of these, only pentadecanoic was also significantly changed in ADHD samples (FC: 1.514; p=0.002). MSEA revealed enrichment of homocysteine degradation (p=0.017), catecholamine biosynthesis (p=0.048), threonine and 2‐Oxobutanoate degradation (p=0.068), Phosphatidylcholine Biosynthesis (p=0.070), and Phosphatidylethanolamine Biosynthesis (p=0.070) in ASD cord blood samples.ConclusionWe found that cord blood plasma metabolomics reveals intriguing and specific differences between ASD and control samples. While some of differences are supported by evidence, these alterations have not previously been extended to the prenatal period. Future work will investigate concordance with maternal blood metabolomics to determine maternal‐fetal pathways.

Temperature sensitivity of Notch signaling underlies species-specific developmental plasticity and robustness in amniote brains

Ambient temperature significantly affects developmental timing in animals. The temperature sensitivity of embryogenesis is generally believed to be a consequence of the thermal dependency of cellular metabolism. However, the adaptive molecular mechanisms that respond to variations in temperature remain unclear. Here, we report species-specific thermal sensitivity of Notch signaling in the developing amniote brain. Transient hypothermic conditions increase canonical Notch activity and reduce neurogenesis in chick neural progenitors. Increased biosynthesis of phosphatidylethanolamine, a major glycerophospholipid components of the plasma membrane, mediates hypothermia-induced Notch activation. Furthermore, the species-specific thermal dependency of Notch signaling is associated with developmental robustness to altered Notch signaling. Our results reveal unique regulatory mechanisms for temperature-dependent neurogenic potentials that underlie developmental and evolutionary adaptations to a range of ambient temperatures in amniotes.