APOΕ4 lowers energy expenditure in females and impairs glucose oxidation by increasing flux through aerobic glycolysis.

BACKGROUND: Cerebral glucose hypometabolism is consistently observed in individuals with Alzheimer's disease (AD), as well as in young cognitively normal carriers of the Ε4 allele of Apolipoprotein E (APOE), the strongest genetic predictor of late-onset AD. While this clinical feature has been described for over two decades, the mechanism underlying these changes in cerebral glucose metabolism remains a critical knowledge gap in the field. METHODS: Here, we undertook a multi-omic approach by combining single-cell RNA sequencing (scRNAseq) and stable isotope resolved metabolomics (SIRM) to define a metabolic rewiring across astrocytes, brain tissue, mice, and human subjects expressing APOE4. RESULTS: Single-cell analysis of brain tissue from mice expressing human APOE revealed E4-associated decreases in genes related to oxidative phosphorylation, particularly in astrocytes. This shift was confirmed on a metabolic level with isotopic tracing of 13C-glucose in E4 mice and astrocytes, which showed decreased pyruvate entry into the TCA cycle and increased lactate synthesis. Metabolic phenotyping of E4 astrocytes showed elevated glycolytic activity, decreased oxygen consumption, blunted oxidative flexibility, and a lower rate of glucose oxidation in the presence of lactate. Together, these cellular findings suggest an E4-associated increase in aerobic glycolysis (i.e. the Warburg effect). To test whether this phenomenon translated to APOE4 humans, we analyzed the plasma metabolome of young and middle-aged human participants with and without the Ε4 allele, and used indirect calorimetry to measure whole body oxygen consumption and energy expenditure. In line with data from E4-expressing female mice, a subgroup analysis revealed that young female E4 carriers showed a striking decrease in energy expenditure compared to non-carriers. This decrease in energy expenditure was primarily driven by a lower rate of oxygen consumption, and was exaggerated following a dietary glucose challenge. Further, the stunted oxygen consumption was accompanied by markedly increased lactate in the plasma of E4 carriers, and a pathway analysis of the plasma metabolome suggested an increase in aerobic glycolysis. CONCLUSIONS: Together, these results suggest astrocyte, brain and system-level metabolic reprogramming in the presence of APOE4, a 'Warburg like' endophenotype that is observable in young females decades prior to clinically manifest AD.

Impact of a Rapid Blood Culture Assay for Gram-Positive Identification and Detection of Resistance Markers in a Pediatric Hospital.

CONTEXT: Molecular diagnostics allow for rapid identification and detection of resistance markers of bloodstream infection, with a potential for accelerated antimicrobial optimization and improved patient outcomes. Although the impact of rapid diagnosis has been reported, studies in pediatric patients are scarce. OBJECTIVE: To determine the impact of a molecular blood-culture assay that identifies a broad-spectrum of pathogens and resistance markers in pediatric patients with gram-positive bloodstream infections. DESIGN: Data on the time to antimicrobial optimization, the length of hospitalization, and the hospital cost following implementation of a rapid assay were prospectively collected and compared with corresponding preimplementation data. RESULTS: There were 440 episodes from 383 patients included, 221 preimplementation episodes and 219 postimplementation episodes. Overall time to antimicrobial optimization was shortened by 12.5 hours (P = .006), 11.9 hours (P = .005) for bloodstream infections of Staphylococcus aureus specifically. Duration of antibiotics for those with probable blood-culture contamination with coagulase-negative staphylococci was reduced by 36.9 hours (P < .001). Median length of stay for patients admitted to general pediatric units was 1.5 days shorter (P = .04), and median hospital cost was $3757 (P = .03) less after implementation. For S aureus bloodstream infections, median length of stay and hospital cost were decreased by 5.6 days (P = .01) and $13,341 (P = .03), respectively. CONCLUSIONS: Implementation of molecular assay for the detection of gram-positive pathogens and resistance markers significantly reduced time to identification and resistance detection, resulting in accelerated optimization of therapy, shorter length of stay, and decreased health care cost.

A malachite green-based assay to assess glucan phosphatase activity.

With the recent discovery of a unique class of dual-specificity phosphatases that dephosphorylate glucans, we report an in vitro assay tailored for the detection of phosphatase activity against phosphorylated glucans. We demonstrate that, in contrast to a general phosphatase assay using a synthetic substrate, only phosphatases that possess glucan phosphatase activity liberate phosphate from the phosphorylated glucan amylopectin using the described assay. This assay is simple and cost-effective, providing reproducible results that clearly establish the presence or absence of glucan phosphatase activity. The assay described will be a useful tool in characterizing emerging members of the glucan phosphatase family.