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Ketogenic diet dampens excitatory neurotransmission by shrinking synaptic vesicle pools.

Ketogenic diet (KD) is used for the treatment of drug-resistant childhood epilepsy and has been proposed to improve outcomes in neurodegenerative diseases. However, the mechanisms by which KD alters brain circuitry remain unclear. Here, we investigated the impact of KD on hippocampal function through integrative analysis of gene expression and neurotransmission. We found that KD induces extensive transcriptional reprogramming, including altered expression of numerous synaptic genes. Proteomic and genomic profiling revealed significant changes in histone modifications, particularly at promoters of KD-regulated genes. Electrophysiological recordings showed that KD reduces excitatory synaptic gain and short-term plasticity at CA3-CA1 synapses, dampening the summation of excitatory inputs and enhancing the summation of inhibitory inputs. These functional changes were driven, in part, by a reduction in the readily releasable vesicle pool at excitatory synapses under KD. Together, our findings demonstrate that KD drives transcriptional remodeling of hippocampal circuits, leading to synaptic adaptations that may underlie its anti-epileptic and neuroprotective effects.

Animals

Bioassay procedure for the detection of mutagenic metabolites in human urine with the use of sister chromatid exchange analysis.

A short-term bioassay system for the detection of activated mutagenic metabolites in urine from humans exposed to promutagens was described. Human diploid fibroblasts were grown in medium containing 5--20% urine from smokers, from nonsmokers, and from individuals undergoing cyclophosphamide (Cp) chemotherapy for treatment of cancer. The cells were then subjected to sister chromatid exchange (SCE) analysis. Activated Cp metabolic products in urine specimens produced up to a ten-fold increase in SCE's over preinjection SCE levels for the same individuals. Linear dose-response curves over a urine concentration range from 5 to 20% in culture medium were obtained from cells grown in urine specimens from 7 nonsmokers and 8 cigarette smokers. This test system proved to be sensitive to ambient exposure levels of environmental mutagens and demonstrated that urine from smokers was significantly more mutagenic than was urine from nonsmokers. Replicate experiments showed highly reproducible SCE values for each individual as well as for average SCE values for each group of subjects. The ability of this bioassay system to detect trace mutagenic activity in human urine reproducibly makes it an attractive choice for the monitoring of humans who have been exposed to environmental and/or industrial mutagens.

Adult

Gut metagenome and plasma metabolome profiles in older adults suggest pyruvate metabolism as a link between sleep quality and frailty.

Poor sleep quality is associated with increased frailty in older adults, but the role of the gut microbiome in this relationship remains unclear. Here, gut metagenome and plasma metabolome were profiled in 1,225 individuals aged 62-96 years. Poor sleep quality was associated with reduced abundances of potential probiotics such as Faecalibacterium prausnitzii and elevated abundances of pathobionts. A gut microbiome sleep quality index (GMSI) was developed to quantify microbial balance related to better sleep quality; higher GMSI scores were inversely associated with frailty and related clinical traits. Pyruvate metabolism emerged as a key microbial pathway linking sleep quality to frailty, with features such as F. prausnitzii abundance and microbial pyridoxal 5'-phosphate biosynthesis implicated in this connection. These findings deepen our understanding of microbiome-metabolome pathways related to sleep quality and frailty in aging and provide a valuable resource for future longitudinal and interventional studies.

Humans

Longevity of cardiac and skeletal muscle proteins is dependent on tissue and subcellular compartmentation patterns.

Myocytes are exceptionally long-lived cells that must maintain proteome integrity over decades while adjusting for changes in functional output and metabolic demand. We used in vivo stable isotope labeling combined with mass spectrometry proteomics and correlated multi-isotope imaging mass spectrometry to quantify and visualize protein turnover across cardiac, fast-twitch, and slow-twitch skeletal muscles, creating a resource of hundreds of individual protein turnover rates from each tissue. We found that cardiac muscle has the highest rate of protein turnover, followed by slow-twitch skeletal muscle and then fast-twitch skeletal muscle, and that these different rates of protein turnover are driven by different levels of muscle use, rather than myosin isoform composition. We also identified protein age heterogeneity at the myofiber and sarcomere levels. These findings uncover fundamental principles of muscle protein maintenance and have broad implications for understanding cellular aging, muscle disease, and the design of therapeutic strategies targeting muscle protein turnover.

Animals

TCF25 serves as a nutrient sensor to orchestrate metabolic adaptation and cell death by enhancing lysosomal acidification under glucose starvation.

Cells adapt to nutrient limitation by activating catabolic and inhibiting anabolic pathways, yet prolonged stress may lead to cell death. How cells orchestrate metabolic adaptation and cell death to nutrient stress is poorly understood. We conduct a genome-wide CRISPR-Cas9 screen to identify regulators in glucose-starvation-induced cell death and find a group of genes in lysosomal pathway is enriched following glucose starvation. We focus on one candidate gene, Transcriptional Factor 25 (TCF25). We find TCF25 enhances lysosomal acidification by targeting V-ATPase, promoting autophagy and ATP generation under glucose starvation. However, prolonged glucose starvation constitutively activates ferritinophagy via TCF25, increasing lysosomal membrane permeability (LMP) and leading to lysosome-dependent cell death (LDCD). Knocking out TCF25 or V-ATPase components prevents cell death. Furthermore, TCF25 deficiency protects mice from hepatic ischemia-reperfusion injury. Our findings identify TCF25 as a crucial nutrient sensor that regulates lysosomal activity, offering potential therapeutic targets for metabolic and ischemic disorders.

Lysosomes

The Myo2 adaptor Ldm1 and its receptor Ldo16 mediate actin-dependent lipid droplet motility.

Organelle motility enables strategic cellular reorganizations. In yeast, this process depends on the actin cytoskeleton, type V myosin motor proteins, and organelle-specific myosin adaptor proteins. While the myosin adaptors for most organelles are known, the coupling of myosin to lipid droplets (LDs), the cellular lipid storage organelles, remained enigmatic. Using genome-wide screening, we identified Ldm1 (lipid droplet motility 1/Yer085c) as a myosin adaptor. Ldm1 binds to the globular tail domain of the myosin Myo2 and to the LD surface protein Ldo16 to enable actin-dependent LD motility. Ldo16 has additional roles in LD contact sites to the vacuole and the endoplasmic reticulum, suggesting a coordination of LD motility and organelle tethering. Ldm1 has a second role in mitochondrial transport, and elevated Ldm1 levels rescue defects of the mitochondrial Myo2-adaptors Mmr1/Ypt11. Our work identifies the molecular machinery for LD motility and contributes to a comprehensive understanding of acto-myosin-based cellular reorganization.

Lipid Droplets

Intermembrane coupling between Bcl-xL and the IP3 receptor supports local Ca2+ transfer at ER-mitochondrial contacts.

Bcl-xL, an anti-apoptotic Bcl-2 family protein, engages laterally with Bak/Bax in the outer mitochondrial membrane (OMM) to inhibit apoptosis and interacts with the IP3 receptor Ca2+ channels (IP3Rs) in the endoplasmic reticulum (ER) membrane to control Ca2+ release. It is unknown if OMM-localized Bcl-xL can also interact in trans with IP3Rs at ER-mitochondrial contacts to form a tethering complex that supports IP3R-mediated local Ca2+ transfer from ER to mitochondria. We establish that IP3R-mitochondria Ca2+ signal propagation depends on Bcl-xL. By targeting Bcl-xL specifically to different subcellular compartments, we find that OMM-localized Bcl-xL increases the efficacy of ER-mitochondrial Ca2+ transfer without changing ER Ca2+ release, despite attenuating mitochondrial Ca2+ uptake. We find interaction between Bcl-xL and each IP3R isoform occurring at the mitochondria and a complex formed by OMM-localized Bcl-xL and IP3Rs. OMM Bcl-xL interacts with IP3Rs in trans at ER-mitochondrial contacts to optimize local Ca2+ signal propagation into the mitochondria.

Bcl-xL

PANAMA-enabled high-sensitivity dual nanoflow LC-MS metabolomics and proteomics analysis.

High-sensitivity nanoflow liquid chromatography (nLC) is seldom employed in untargeted metabolomics because current sample preparation techniques are inefficient at preventing nanocapillary column performance degradation. Here, we describe an nLC-based tandem mass spectrometry workflow that enables seamless joint analysis and integration of metabolomics (including lipidomics) and proteomics from the same samples without instrument duplication. This workflow is based on a robust solid-phase micro-extraction step for routine sample cleanup and bioactive molecule enrichment. Our method, termed proteomic and nanoflow metabolomic analysis (PANAMA), improves compound resolution and detection sensitivity without compromising the depth of coverage as compared with existing widely used analytical procedures. Notably, PANAMA can be applied to a broad array of specimens, including biofluids, cell lines, and tissue samples. It generates high-quality, information-rich metabolite-protein datasets while bypassing the need for specialized instrumentation.

Proteomics

Use of human-liver microsomes from kidney-transplant donors for the induction of chromatid aberrations and sister-chromatid exchanges by means of pre-carcinogens in Chinese hamster cells in vitro.

Samples of two human livers taken during operation of kidney donor patients were processed for microsome fractions and used for metabolization of cyclophosphamide (CP) and dimethylnitrosamine (DMN) in combination with the NADPH-generating system. Rat-liver microsomes were checked for comparison. Induction of chromatid aberrations and sister-chromatid exchanges in a newly isolated clone of Chinese hamster fibroblasts served as indicators of activity. Human S-9 fractions standardized on protein content showed strong variations of CP and DMN activation. Whereas liver microsomes of one patient (who also suffered from Gaucher's disease) were highly active for both pre-carcinogens and metabolized DMN at the same level as the uninduced rat-liver microsomes, the S-9 fraction from the second patient failed to activate CP, but was distinctly positive for DMN. It is suggested that samples of liver and other organs of renal transplant donors might be a practicable source of freshly prepared human microsome fractions usable in biochemical, genetic and carcinogenetic studies. Problems concerning the extrapolation of results are discussed.

Biotransformation

Sucrose metabolism in resting-cell suspensions of caries associated and non-caries-associated dental plaque.

Small specimens of cariogenic plaque (CP) and non-cariogenic plaque (NCP) from the same tooth were individually dispersed in buffer, divided equally, and incubated for 45 min with [(14)C]sucrose uniformly labeled either in the glucosyl moiety or the fructosyl moiety. Sucrose metabolism was analyzed periodically during an anaerobic incubation at 37 degrees C. Radiochemical techniques were devised to analyze formation of lactic acid, soluble extracellular polysaccharide, total cell-bound and insoluble products, intracellular polysaccharide, lactic acid from intracellular polysaccharide catabolism, insoluble extracellular glucan, CO(2), total volatile acids, individual volatile acids, and rates of sucrose consumption. The contribution of the glucosyl and fructosyl moieties of sucrose to each metabolic by-product was determined. All of the metabolic data were adjusted to the size of the plaque specimens as determined by colony-forming units, Coulter counter particle counts, and fluorometric protein analyses. Both types of dental plaque transformed from 70 to 80% of the consumed sucrose into lactic acid and cell-bound and insoluble products, primarily intracellular polysaccharide and extracellular glucan. Volatile acids accounted for most of the remaining by-products. CP metabolized significantly more sucrose than NCP and consequently produced significantly higher levels of each metabolic by-product. High levels of Streptococcus mutans were found in CP (averaging 40% of colony-forming units), whereas it was virtually absent in NCP. Actinomyces and S. sanguis levels were distinctly higher in NCP. NCP harbored more anaerobes and dextranase-forming microorganisms than CP.

Actinomyces

Proteomic analysis illustrates the potential involvement of dysregulated ribosome-related pathways and disrupted metabolism during retinoic acid-induced cleft palate development.

Recent studies have unveiled disrupted metabolism in the progression of cleft palate (CP), a congenital anomaly characterized by defective fusion of facial structures. Nonetheless, the precise composition of this disrupted metabolism remains elusive, prompting us to identify these components and elucidate primary metabolic irregularities contributing to CP pathogenesis. We established a murine CP model by retinoic acid (RA) treatment and analyzed control and RA-treated embryonic palatal tissues by LC-MS-based proteomic approach. We identified 220 significantly upregulated and 224 significantly downregulated proteins. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that these differentially expressed proteins (DEPs) were involved in translation, ribosome assembly, mitochondrial function, mRNA binding, as well as key metabolic pathways like oxidative phosphorylation (OXPHOS), glycolysis/gluconeogenesis, and amino acid biosynthesis. These findings suggest that dysregulated ribosome-related pathways and disrupted metabolism play a critical role in CP development. Protein-protein interaction analysis using the STRING database revealed a tightly connected network of DEPs. Furthermore, we identified the top 10 hub proteins in CP using the Cytohubba plugin in Cytoscape. These hub proteins, including RPL8, RPS11, ALB, PA2G4, RPL23, RPS6, CCT7, EGFR, HSPD1, and RPS28, are potentially key regulators of CP pathogenesis. In conclusion, our comprehensive proteomic analysis provides insights into the molecular alterations associated with RA-induced CP in Kun Ming mice. These findings suggest potential therapeutic targets and pathways to understand and prevent congenital craniofacial anomalies.

Cleft Palate

Excretion patterns of alkylating metabolites in urine following cyclophosphamide treatment of tumor patients: influence of application route, dosage, liver and kidney function.

The excretion patterns of cyclophosphamide (CP) in urine were studied in 54 tumor patients aged between 21 and 61 years, using the nitrobenzyl-pyridine (NBP) reaction, with regard to the route of application (i.v., i.m. or oral), the CP dose and the functional state of the liver and kidney. The studies were carried out in nephrectomized patients and patients with liver affections caused by the basic disease, in particular with malignant lymphomas and mammary carcinomas. The following results were obtained: 1. There exists a direct relationship between the dose of CP applied and the quantitative excretion of alkylating metabolites in urine. According to these studies in which the patients received up to 2.8 g CP/m2 body surface, the upper CP dose was limited by the generally toxic side effects rather than by the metabolization rate. 2. At comparable CP doses the route of application (i.v., i.m. or oral) has no appreciable influence on the excreted NBP activity. 3. Disorders of the liver function without signs of icterus are not a contraindication to CP treatment. 4. The functional failure of one kidney has no statistically significant influence on the excretion of alkylating metabolites in urine.

Administration, Oral

"Metabolic" action potentials in Acetabularia.

The transient depolarizations in Acetabularia which fulfill the essential criteria of an action potential (all-or-none characteristics, triggering by depolarization, propagation, etc.) are investigated. These action potentials are analyzed by conductance measurements and voltage clamp experiments on the basis of the analog circuit of the membrane (Gradmann, D. 1975, J. Membrane Biol. 25:183). It is concluded that these action potentials do not arise by permeability changes of the passive diffusion channels, but by the active pathway of the electrogenic pump, which consists of a voltage source EP of about --20 mV in series with two nonlinear conducting elements P1 and P2, the latter and EP being shunted by a large quasi capacity CP of some mF cm-2. The nonlinear current-voltage relationship of the carrier system (P1) is not changed during the action potential but has an effect on its time course. However, the elements P2 and CP, which probably reflect metabolic entities, are suggested to control the action potentials.

Acetabularia

Analog circuit of the Acetabularia membrane.

The high membrane potential of Acetabularia (Em=-170mV) is due to an electrogenic pump in parallel with the passive diffusion system (Ed=-80mV) which could be studied separately in the cold, when the pump is blocked. Electrical measurements under normal conditions show that the pump pathway consists of its electromotive force Ep with two elements P1 and P2 in series; P2 is shunted by a large capacitance (Cp=3mF cm-2). The nonlinear current-voltage relationship of P1 (light- and temperature-sensitive) could be determined separately; it reflects the properties of a carrier-mediated electrogenic pump. The value of Ep(-190 mV) indicates a stoichiometry of 2:1 between electrogenically transported charges and ATP. The electrical energy normally stored in Cp, compares well with the metabolic energy, stored in the ATP pool. The nonlinear current-voltage relationship of P2 (attributed to phosphorylating reactions) is also sensitive to light and temperature and is responsible for the region of negative conductance of the overall current-voltage relationship. The power of the pump (1 muW cm-2) amounts to some percent of the total energy turnover. The high Cl- fluxes (1 nmol cm-2 sec-1) and the electrical properties of the plasmalemma are not as closely related as assumed previously. For kinetic reasons, a direct and specific Cl- pathway between the vacuole and outside is postulated to exist.

Acetabularia

Feeding habits and their physiological determinants. Relationships between consumer's preference for sweetness of drinks and certain physiological parameters.

Investigations determining the preferred saccharose concentration in drinks (CP(S)), gustatory threshold values, blood glucose level, basal metabolism rate and body weight index (im) were carried out with 83 cadets, aged 21--23 years. CP(S) was directly proportional to the gustatory threshold for sweet tastee, blood glucose level and basal metabolism and the correlation found in all three cases was statistically significant (p less than 0.01). The accuracy of CP(S) estimation by cadets was strictly related to their threshold difference for sweet tast depending also on smoking.

Adult

Utilization of blood-borne and intramuscular substrates during continuous and intermittent exercise in man.

1. Substrate utilization in the legs during bicycle exercise was studied in five subjects when performing intermittent intense exercise (15 sec work--15 sec rest) as well as continuous exercise during 60 min, with an almost identical average power output and oxygen uptake in both situations. 2. Muscle biopsies were obtained from vastus lateralis at rest, during, and after exercise in order to determine intramuscular lipid and carbohydrate utilization. The contribution from blood-borne substrates to total oxidative metabolism was determined by arterial-femoral venous (a-fv) differences for oxygen, FFA, glucose, and lactate and leg blood flow. 3. Intermittent and continuous exercise revealed a similar glycogen depletion and the intramuscular lactate accumulation was rather small. A similar uptake of blood-borne substrate (FFA, glucose) was found in both situations whereas a release of lactate only was observed in intermittent exercise. 4. ATP and CP levels oscillated between work and rest periods in intermittent exercise but were not resynthesized to resting levels at the end of the rest periods. The mainly aerobic energy release during each work period in intermittent exercise is partly caused by myoglobin functioning as an oxygen store; this factor was calculated to be more important than ATP and CP or lactate level oscillations. 5. The metabolic response to intermittent exercise was found to be similar to that found in continuous exercise with approximately the same average power output and oxygen uptake. This indicates that some factor in the intermediary metabolism, for instance citrate, functions as a regulator retarding glycolysis and favouring lipid utilization and an aerobic energy release in intermittent exercise.

Adenosine Triphosphate

Host genetics predominates over gut microbiota in serum copper levels in boars.

Copper is an essential trace element in numerous biological processes; maintaining its homeostasis is crucial for pig health and productivity. In this study, we employed a mixed-effects model to investigate the contributions of host genetics, gut microbiota, and their interactions with serum copper levels in pigs. We further explored potential candidate genes and microbiota associated with copper metabolism. The results demonstrated that host genetics exert a dominant influence on serum copper regulation compared to the effects of the gut microbiota. Furthermore, genome-wide association analysis identified 4 candidate genes, CPHL1, CP, NCEH1, and PDE10A, strongly linked to copper metabolism. By applying multiple association approaches, 10 bacterial genera, such as Blautia, Lachnospiraceae UCG-008, and Ruminococcaceae UCG-007 were found to be significantly correlated with serum copper levels. This research offers novel insights into the genetic and microbial determinants of copper variation in pigs, establishing a foundation for future genetic and microbiota-based strategies aimed at enhancing copper homeostasis and overall livestock health.

Animals

Creatine phosphate in rat blood platelets.

Creatine phosphate (CP) was found in rat platelets by an assay method devised to increase the specificity and sensitivity. In this method, radioactivity of [14C]ATP was measured after the reaction of CP with [14C]ADP in the presence of creatine kinase. The mean value of the CP content in rat platelets was 24.8 nmoles per 10(9) platelets. Since the molar ratio of CP and ATP was 1:2.6, it is probable that CP plays a role in the energy metabolism of rat platelets.

Adenosine Diphosphate