Evidence for causal effects of neuropsychiatric conditions on risk of venous thromboembolism: A univariable and multivariable Mendelian randomization study

BACKGROUND

Substantial observational evidence suggests an association between neuropsychiatric conditions and venous thromboembolism (VTE). However, the causal relationship between these two conditions requires further investigation. Therefore, we used a two-sample Mendelian randomization (MR) approach to assess the bidirectional causal effects between four neuropsychiatric conditions and VTE, deep vein thrombosis, and pulmonary embolism (PE).

METHODS

Genetic variants associated with four neuropsychiatric conditions (ie, schizophrenia, major depressive disorder [MDD], bipolar disorder, and epilepsy) and VTE, deep vein thrombosis, and PE were selected. Bidirectional univariable and multivariable MR methods were applied to evaluate the causal relationships among these conditions. The primary causal estimates were obtained using the inverse variance weighted method with multiplicative random effects, supplemented by MR Egger regression, weighted median, simple mode, and weighted mode. Sensitivity analysis was conducted using the MR pleiotropy residual sum, funnel plots, and outlier (MR pleiotropy and residual sum and outlier) method.

RESULTS

Univariable MR results showed that genetic susceptibility to MDD increases the risk of VTE and PE (VTE: odds ratio [OR], 1.25; 95% confidence interval [CI], 1.08-1.46; P = .004; PE: OR, 1.36; 95% CI, 1.09-1.69; P = .006) and that PE has an adverse causal effect on MDD (OR, 1.02; 95% CI, 1.00-1.04; P = .026). Adjustment for confounders such as obesity, sleep duration, smoking, physical activity, and alcohol consumption revealed that increased genetic susceptibility to MDD is also associated with VTE and PE.

CONCLUSIONS

Our results suggest that genetic susceptibility to MDD might have an adverse causal effect on the risk of VTE and PE and that PE has a reverse causal effect on MDD. Prevention and early diagnosis of depression are crucial in the management of VTE and PE.

Enteric Nervous System Striped Patterning and Disease: Unexplored Pathophysiology

The enteric nervous system (ENS) controls gastrointestinal (GI) motility, and defects in ENS development underlie pediatric GI motility disorders. In disorders such as Hirschsprung's disease (HSCR), pediatric intestinal pseudo-obstruction (PIPO), and intestinal neuronal dysplasia type B (INDB), ENS structure is altered with noted decreased neuronal density in HSCR and reports of increased neuronal density in PIPO and INDB. The developmental origin of these structural deficits is not fully understood. Here, we review the current understanding of ENS development and pediatric GI motility disorders incorporating new data on ENS structure. In particular, emerging evidence demonstrates that enteric neurons are patterned into circumferential stripes along the longitudinal axis of the intestine during mouse and human development. This novel understanding of ENS structure proposes new questions about the pathophysiology of pediatric GI motility disorders. If the ENS is organized into stripes, could the observed changes in enteric neuron density in HSCR, PIPO, and INDB represent differences in the distribution of enteric neuronal stripes? Here, we review mechanisms of striped patterning from other biological systems and propose how defects in striped ENS patterning could explain structural deficits observed in pediatric GI motility disorders.

Advances in Brain-Gut-Microbiome Interactions: A Comprehensive Update on Signaling Mechanisms, Disorders, and Therapeutic Implications

The complex, bidirectional interactions between the brain, the gut, and the gut microbes are best referred to as the brain gut microbiome system. Animal and clinical studies have identified specific signaling mechanisms within this system, with gut microbes communicating to the brain through neuronal, endocrine, and immune pathways. The brain, in turn, modulates the composition and function of the gut microbiota through the autonomic nervous system, regulating gut motility, secretion, permeability, and the release of hormones impacting microbial gene expression. Perturbations at any level of these interactions can disrupt the intricate balance, potentially contributing to the pathogenesis of intestinal, metabolic, neurologic, and psychiatric disorders. Understanding these interactions and their underlying mechanisms holds promise for identifying biomarkers, as well as novel therapeutic targets, and for developing more effective treatment strategies for these complex disorders. Continued research will advance our knowledge of this system, with the potential for improved understanding and management of a wide range of disorders. This review provides an update on the current state of knowledge regarding this system, with a focus on recent advancements and emerging research areas.

The GRADE Working Group and CINeMA approaches provided inconsistent certainty of evidence ratings for a network meta-analysis of opioids for chronic noncancer pain

OBJECTIVES

Assessment of the certainty of evidence (CoE) from network meta-analysis is critical to convey the strength of inferences for clinical decision-making. Both the GRADE (Grading of Recommendations Assessment, Development and Evaluation) Working Group (GWG) and the Confidence in Network Meta-Analysis (CINeMA) framework have been designed to assess the CoE of treatment effects informed by network meta-analysis; however, the concordance of results is uncertain.

STUDY DESIGN AND SETTING

We assessed the CoE for treatment effects of individual opioids on pain relief and physical functioning from a network meta-analysis for chronic noncancer pain using the GWG approach and the CINeMA framework. Both approaches evaluate the CoE as high, moderate, low or very low. We quantified the number of discrepant CoE ratings between approaches and the magnitude of the difference (ie, one level, two levels, or three levels).

RESULTS

Across 105 comparisons among individual opioids for pain relief, the GWG and CINeMA approaches provided different CoE ratings in 34% of cases (36 of 105). Across 66 comparisons for physical functioning, there was discordance in 17% of cases (11 of 66). All discrepancies were separated by one level. The CINeMA framework typically provided lower CoE ratings compared to the GWG approach, predominantly because of differences in the assessment of transitivity and heterogeneity.

CONCLUSION

Our findings suggest there are differences between the CoE ratings provided by the GWG and CINeMA approaches when applied to network meta-analyses. Further research is needed to replicate or refute our findings in other network meta-analyses and assess the implications for clinical decision-making.

Single-cell transcriptome atlas of Drosophila gastrula 2.0

During development, positional information directs cells to specific fates, leading them to differentiate with their own transcriptomes and express specific behaviors and functions. However, the mechanisms underlying these processes in a genome-wide view remain ambiguous, partly because the single-cell transcriptomic data of early developing embryos containing accurate spatial and lineage information are still lacking. Here, we report a single-cell transcriptome atlas of Drosophila gastrulae, divided into 77 transcriptomically distinct clusters. We find that the expression profiles of plasma-membrane-related genes, but not those of transcription-factor genes, represent each germ layer, supporting the nonequivalent contribution of each transcription-factor mRNA level to effector gene expression profiles at the transcriptome level. We also reconstruct the spatial expression patterns of all genes at the single-cell stripe level as the smallest unit. This atlas is an important resource for the genome-wide understanding of the mechanisms by which genes cooperatively orchestrate Drosophila gastrulation.

Psyllium Fiber Protects Against Colitis Via Activation of Bile Acid Sensor Farnesoid X Receptor

BACKGROUND & AIMS

Fiber-rich foods promote health, but mechanisms by which they do so remain poorly defined. Screening fiber types, in mice, revealed psyllium had unique ability to ameliorate 2 chronic inflammatory states, namely, metabolic syndrome and colitis. We sought to determine the mechanism of action of the latter.

METHODS

Mice were fed grain-based chow, which is naturally rich in fiber or compositionally defined diets enriched with semi-purified fibers. Mice were studied basally and in models of chemical-induced and T-cell transfer colitis.

RESULTS

Relative to all diets tested, mice consuming psyllium-enriched compositionally defined diets were markedly protected against both dextran sulfate sodium- and T-cell transfer-induced colitis, as revealed by clinical-type, histopathologic, morphologic, and immunologic parameters. Such protection associated with stark basal changes in the gut microbiome but was independent of fermentation and, moreover, maintained in mice harboring a minimal microbiota (ie, Altered Schaedler Flora). Transcriptomic analysis revealed psyllium induced expression of genes mediating bile acid (BA) secretion, suggesting that psyllium's known ability to bind BA might contribute to its ability to prevent colitis. As expected, psyllium resulted in elevated level of fecal BA, reflecting their removal from enterohepatic circulation but, in stark contrast to the BA sequestrant cholestyramine, increased serum BA levels. Moreover, the use of BA mimetics that activate the farnesoid X receptor (FXR), as well as the use of FXR-knockout mice, suggested that activation of FXR plays a central role in psyllium's protection against colitis.

CONCLUSIONS

Psyllium protects against colitis via altering BA metabolism resulting in activation of FXR, which suppresses pro-inflammatory signaling.

Ending genetic essentialism through genetics education

Genetic concepts are regularly used in arguments about racial inequality. This review summarizes research about the relationship between genetics education and a particular form of racial prejudice known as genetic essentialism. Genetic essentialism is a cognitive form of prejudice that is used to rationalize inequality. Studies suggest that belief in genetic essentialism among genetics students can be increased or decreased based on what students learn about human genetics and why they learn it. Research suggests that genetics education does little to prevent the development of genetic essentialism, and it may even exacerbate belief in it. However, some forms of genetics education can avert this problem. In particular, if instructors teach genetics to help students understand the flaws in genetic essentialist arguments, then it is possible to reduce belief in genetic essentialism among biology students. This review outlines our knowledge about how to accomplish this goal and the research that needs to be done to end genetic essentialism through genetics education.

US private payers' perspectives on insurance coverage for genome sequencing versus exome sequencing: A study by the Clinical Sequencing Evidence-Generating Research Consortium (CSER)

PURPOSE

There is limited payer coverage for genome sequencing (GS) relative to exome sequencing (ES) in the U.S. Our objective was to assess payers' considerations for coverage of GS versus coverage of ES and requirements payers have for coverage of GS. The study was conducted by the NIH-funded Clinical Sequencing Evidence-Generating Research Consortium (CSER).

METHODS

We conducted semi-structured interviews with representatives of private payer organizations (payers, N = 12) on considerations and evidentiary and other needs for coverage of GS and ES. Data were analyzed using thematic analysis.

RESULTS

We described four categories of findings and solutions: demonstrated merits of GS versus ES, enhanced methods for evidence generation, consistent laboratory processes/sequencing methods, and enhanced implementation/care delivery. Payers see advantages to GS vs. ES and are open to broader GS coverage but need more proof of these advantages to consider them in coverage decision-making. Next steps include establishing evidence of benefits in specific clinical scenarios, developing quality standards, ensuring transparency of laboratory methods, developing clinical centers of excellence, and incorporating the role of genetic professionals.

CONCLUSION

By comparing coverage considerations for GS and ES, we identified a path forward for coverage of GS. Future research should explicitly address payers' conditions for coverage.

Use of Sodium-Glucose Cotransporter-2 Inhibitors in Renal Transplant Patients With Diabetes: A Brief Review of the Current Literature

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are a novel class of oral hypoglycemic agents commonly prescribed in type 2 diabetes (T2D). They have been shown to slow the progression of diabetic nephropathy and improve cardiovascular outcomes in high-risk individuals, although major cardiovascular and renal outcome clinical trials have excluded renal transplant patients. The aim of this review was to determine the outcomes and safety with use of SGLT2 inhibitors in renal transplant patients with diabetes. We conducted a review of randomized controlled trials, cohort studies, case series and case reports that assessed use of SGLT2 inhibitors in patients post-renal transplant with either pre-existing T2D or new-onset diabetes after transplant. The outcomes assessed included blood pressure, renal allograft function (estimated glomerular filtration rate), proteinuria (urinary albumin-to-creatinine ratio), glycemic control, body weight and adverse effects. A total of 9 studies, which included 144 patients, were reviewed. SGLT2 inhibitor use in renal transplant patients demonstrates either a small or nonsignificant reduction in blood pressure and results in overall stable renal allograft function. It also results in modest improvement in glycemic control as well as weight reduction. The incidence of adverse effects is low and reversible, as reported in previous nontransplant clinical trials. Overall, our findings suggest beneficial outcomes with no significant adverse effects or complications with the use of SGLT2 inhibitors in renal transplant patients with diabetes; however, these findings are based on small trials, and thus well-designed trials in this population are warranted.

The antitumor capacity of mesothelin-CAR-T cells in targeting solid tumors in mice

Since the approval of chimeric antigen receptor (CAR) T cell therapy targeting CD19 by the FDA, CAR-T cell therapy has received increasing attention as a new method for targeting tumors. Although CAR-T cell therapy has a good effect against hematological malignancies, it has been less effective against solid tumors. In the present study, we selected mesothelin (MSLN/MESO) as a target for CAR-T cells because it is highly expressed by solid tumors but only expressed at low levels by normal tissues. We engineered a third generation MSLN-CAR comprising a single-chain variable fragment (scFv) targeting MSLN (MSLN-scFv), a CD8 transmembrane domain, the costimulatory domains from CD28 and 4-1BB, and the activating domain CD3ζ. In vitro, MSLN-CAR-T cells killed various solid tumor cell lines, demonstrating that it could specifically kill MSLN-positive cells and release cytokines. In vivo, we investigated the effects of MSLN-CAR-T cell therapy against ovarian, breast, and colorectal cancer cell-line-derived xenografts (CDX) and MSLN-positive colorectal and gastric cancer patient-derived xenografts (PDX). MSLN-CAR decreased the growth of MSLN-positive tumors concomitant with significantly increased T cells and cytokine levels compared to the control group. These results indicated that modified MSLN-CAR-T cells could be a promising therapeutic approach for solid tumors.

Molecular Mechanism of RNA Recognition by Zinc-Finger Antiviral Protein

Zinc-finger antiviral protein (ZAP) is a host antiviral factor that specifically restricts a wide range of viruses. ZAP selectively binds to CG-dinucleotide-enriched RNA sequences and recruits multiple RNA degradation machines to degrade target viral RNA. However, the molecular mechanism and structural basis for ZAP recognition of specific RNA are not clear. Here, we report the crystal structure of the ZAP N-terminal domain bound to a CG-rich single-stranded RNA, providing the molecular basis for its specific recognition of a CG dinucleotide and additional guanine and cytosine. The four zinc fingers of ZAP adopt a unique architecture and form extensive interactions with RNA. Mutations of both protein and RNA at the RNA-ZAP interacting surface reduce the in vitro binding affinity and cellular antiviral activity. This work reveals the molecular mechanism of ZAP recognition of specific target RNA and also provides insights into the mechanism by which ZAP coordinates downstream RNA degradation processes.

The association of histological progression with biochemical response to ursodeoxycholic acid in primary biliary cholangitis

Primary biliary cholangitis (PBC) is currently diagnosed at an early stage; therefore, the number of patients with PBC without symptoms at the time of diagnosis is increasing. However, up to 30% of patients with PBC exhibit the suboptimal response to ursodeoxycholic acid (UDCA) and are at high risk of end-stage liver disease. Obeticholic acid is an approved second-line therapy for patients with PBC that are refractory to UDCA. Novel surrogate endpoints are required to identify individuals eligible for second-line therapies. An inadequate biochemical response to UDCA is a useful predictor of poor outcomes in patients with PBC. In addition to UDCA effects on biochemical parameters, histological outcomes could be considered as candidate surrogate endpoints. Alterations in liver histology are used as surrogate endpoints in clinical studies. However, current staging systems are insufficient to determine PBC disease severity and progression because of the pathological heterogeneity of the disease. Histological features at baseline and biochemical response to UDCA treatment can affect the disease course of PBC. Therefore, novel surrogate endpoints must be represented by parameters characterized by histological outcomes and treatment responses in PBC. In this review, we discuss the existing histological parameters and newly created factors to identify patients with PBC who are at a high risk of developing end-stage liver disease and, consequently, the potential need for additional treatments.

Identification of a Repair-Supportive Mesenchymal Cell Population during Airway Epithelial Regeneration

Tissue regeneration requires coordinated and dynamic remodeling of stem and progenitor cells and the surrounding niche. Although the plasticity of epithelial cells has been well explored in many tissues, the dynamic changes occurring in niche cells remain elusive. Here, we show that, during lung repair after naphthalene injury, a population of PDGFRα⁺ cells emerges in the non-cartilaginous conducting airway niche, which is normally populated by airway smooth muscle cells (ASMCs). This cell population, which we term “repair-supportive mesenchymal cells” (RSMCs), is distinct from conventional ASMCs, which have previously been shown to contribute to epithelial repair. Gene expression analysis on sorted lineage-labeled cells shows that RSMCs express low levels of ASMC markers, but high levels of the pro-regenerative marker Fgf10. Organoid co-cultures demonstrate an enhanced ability for RSMCs in supporting club-cell growth. Our study highlights the dynamics of mesenchymal cells in the airway niche and has implications for chronic airway-injury-associated diseases.

Moiseenko et al. explore the dynamics of mesenchymal cells in the peribronchial niche in response to airway injury. They identify a population of mesenchymal cells located in close proximity to airway smooth muscle cells (ASMCs). This population, termed “repair-supportive mesenchymal cells” (RSMCs), is recruited to facilitate airway epithelial regeneration.

Impact of Maternal HbA1c Levels ≤6% and Race in Nondiabetic Pregnancies on Birthweight and Early Neonatal Hypoglycemia

OBJECTIVE

To evaluate whether pregnancy glycated hemoglobin (HbA1c) levels of ≤6% and maternal race impacts neonatal hypoglycemia and birthweight, and whether diabetes and beta blocker use during pregnancy additively impacts neonatal outcomes.

STUDY DESIGN

Retrospective chart review of 4769 infants born at ≥34 weeks; 21 482 glucose measurements were assessed. Predefined groups were infants born to mothers without documented pregnancy conditions (group N), prenatal exposure of beta blockers (group B), diabetes (group D), or both (group DB).

RESULTS

In group N, both in Caucasian (Caucasian, n = 1756; β = 2.6, P < .001) and African American (n = 1872; β = 2.2, P = .002) race, there was a direct relationship between pregnancy HbA1c levels and birthweight. HbA1c (aOR 1.8; 95% CI [1.3-2.5]) levels, maternal race, prematurity, cesarean delivery, and birth weight predicted hypoglycemia. Each 0.1% increase in HbA1c levels between 4.8 and 6 increased the odds of neonatal hypoglycemia by 6.4% in African American (β 0.62, SE 0.22, P = .01) and by 12.0% in Caucasian (β 1.13, SE 0.23 P < .001) population. The odds of neonatal hypoglycemia were 1.7 (group B), 2.1 (group D), and 3.1 (group DB) times higher compared with group N.

CONCLUSIONS

Pregnancy HbA1c levels between 4.8% and 6.0% considered acceptable during pregnancy impacts neonatal hypoglycemia and birthweight especially in Caucasian race. A third trimester HbA1c >5.2 is a potential risk factor for neonatal hypoglycemia, especially in preterm infants. Although we report new findings on the relationship between maternal HbA1c levels and neonatal outcomes, a prospective study is required to validate our findings and determine "optimal" HbA1C levels during pregnancy.

Vitamin D Clinical Pharmacology: Relevance to COVID-19 Pathogenesis

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Integrating Old and New Paradigms of G1/S Control

The Cdk-Rb-E2F pathway integrates external and internal signals to control progression at the G1/S transition of the mammalian cell cycle. Alterations in this pathway are found in most human cancers, and specific cyclin-dependent kinase Cdk4/6 inhibitors are approved or in clinical trials for the treatment of diverse cancers. In the long-standing paradigm for G1/S control, Cdks inactivate the retinoblastoma tumor suppressor protein (Rb) through phosphorylation, which releases E2F transcription factors to drive cell-cycle progression from G1 to S. However, recent observations in the laboratory and clinic challenge central tenets of the current paradigm and demonstrate that our understanding of the Rb pathway and G1/S control is still incomplete. Here, we integrate these new findings with the previous paradigm to synthesize a current molecular and cellular view of the mammalian G1/S transition. A more complete and accurate understanding of G1/S control will lead to improved therapeutic strategies targeting the cell cycle in cancer.

Pandemic Preparedness: Developing Vaccines and Therapeutic Antibodies For COVID-19

The SARS-CoV-2 pandemic that causes COVID-19 respiratory syndrome has caused global public health and economic crises, necessitating rapid development of vaccines and therapeutic countermeasures. The world-wide response to the COVID-19 pandemic has been unprecedented with government, academic, and private partnerships working together to rapidly develop vaccine and antibody countermeasures. Many of the technologies being used are derived from prior government-academic partnerships for response to other emerging infections.

Synthetic mRNA Encoding VEGF-A in Patients Undergoing Coronary Artery Bypass Grafting: Design of a Phase 2a Clinical Trial

Therapeutic angiogenesis may improve outcomes in patients with coronary artery disease undergoing surgical revascularization. Angiogenic factors may promote blood vessel growth and regenerate regions of ischemic but viable myocardium. Previous clinical trials of vascular endothelial growth factor A (VEGF-A) gene therapy with DNA or viral vectors demonstrated safety but not efficacy. AZD8601 is VEGF-A₁₆₅ mRNA formulated in biocompatible citrate-buffered saline and optimized for high-efficiency VEGF-A expression with minimal innate immune response. EPICCURE is an ongoing randomized, double-blind, placebo-controlled study of the safety of AZD8601 in patients with moderately decreased left ventricular function (ejection fraction 30%–50%) undergoing elective coronary artery bypass surgery. AZD8601 3 mg, 30 mg, or placebo is administered as 30 epicardial injections in a 10-min extension of cardioplegia. Injections are targeted to ischemic but viable myocardial regions in each patient using quantitative ¹⁵O-water positron emission tomography (PET) imaging (stress myocardial blood flow < 2.3 mL/g/min; resting myocardial blood flow > 0.6 mL/g/min). Improvement in regional and global myocardial blood flow quantified with ¹⁵O-water PET is an exploratory efficacy outcome, together with echocardiographic, clinical, functional, and biomarker measures. EPICCURE combines high-efficiency delivery with quantitative targeting and follow-up for robust assessment of the safety and exploratory efficacy of VEGF-A mRNA angiogenesis (ClinicalTrials.gov: NCT03370887).

Insufficient Evidence for "Autism-Specific" Genes

Despite evidence that deleterious variants in the same genes are implicated across multiple neurodevelopmental and neuropsychiatric disorders, there has been considerable interest in identifying genes that, when mutated, confer risk that is largely specific for autism spectrum disorder (ASD). Here, we review the findings and limitations of recent efforts to identify relatively “autism-specific” genes, efforts which focus on rare variants of large effect size that are thought to account for the observed phenotypes. We present a divergent interpretation of published evidence; discuss practical and theoretical issues related to studying the relationships between rare, large-effect deleterious variants and neurodevelopmental phenotypes; and describe potential future directions of this research. We argue that there is currently insufficient evidence to establish meaningful ASD specificity of any genes based on large-effect rare-variant data.

Neuro-immune Interactions in the Tissues

The ability of the nervous system to sense environmental stimuli and to relay these signals to immune cells via neurotransmitters and neuropeptides is indispensable for effective immunity and tissue homeostasis. Depending on the tissue microenvironment and distinct drivers of a certain immune response, the same neuronal populations and neuro-mediators can exert opposing effects, promoting or inhibiting tissue immunity. Here, we review the current understanding of the mechanisms that underlie the complex interactions between the immune and the nervous systems in different tissues and contexts. We outline current gaps in knowledge and argue for the importance of considering infectious and inflammatory disease within a conceptual framework that integrates neuro-immune circuits both local and systemic, so as to better understand effective immunity to develop improved approaches to treat inflammation and disease.

Heart Transplantation in Children with Mitochondrial Disease

OBJECTIVES

To compare the outcomes and comorbidities of children with mitochondrial disease undergoing heart transplantation with children without mitochondrial disease.

STUDY DESIGN

Using a unique linkage between the Pediatric Health Information System and Scientific Registry of Transplant Recipients databases, pediatric heart transplantation recipients from 2002 to 2016 with a diagnosis of cardiomyopathy were included. Post heart transplantation survival and morbidities were compared between patients with and without mitochondrial disease.

RESULTS

A total of 1330 patients were included, including 47 (3.5%) with mitochondrial disease. Survival after heart transplantation was similar between patients with and without mitochondrial disease over a median follow-up of 4 years. Patients with mitochondrial disease were more likely to have a stroke after heart transplantation (11% vs 3%; P = .009), require a longer duration of mechanical ventilation after heart transplantation (3 days vs 1 day; P < .001), and have a longer intensive care unit stay after heart transplantation (10 vs 6 days; P = .007). The absence of a hospital readmission within the first post-transplant year was similar among patients with and without mitochondrial disease (61.7% vs 51%; P = .14). However, patients with mitochondrial disease who were readmitted demonstrated a longer length of stay compared with those without (median, 14 days vs 8 days; P = .03).

CONCLUSIONS

Patients with mitochondrial disease can successfully undergo heart transplantation with survival comparable with patients without mitochondrial disease. Patients with mitochondrial disease have greater risk for post-heart transplantation morbidities including stroke, prolonged mechanical ventilation, and longer intensive care unit and readmission length of stay. These results suggest that the presence of mitochondrial disease should not be an absolute contraindication to heart transplantation in the appropriate clinical setting.

γ-6-Phosphogluconolactone, a Byproduct of the Oxidative Pentose Phosphate Pathway, Contributes to AMPK Activation through Inhibition of PP2A

The oxidative pentose phosphate pathway (oxiPPP) contributes to cell metabolism through not only the production of metabolic intermediates and reductive NADPH but also inhibition of LKB1-AMPK signaling by ribulose-5-phosphate (Ru-5-P), the product of the third oxiPPP enzyme 6-phosphogluconate dehydrogenase (6PGD). However, we found that knockdown of glucose-6-phosphate dehydrogenase (G6PD), the first oxiPPP enzyme, did not affect AMPK activation despite decreased Ru-5-P and subsequent LKB1 activation, due to enhanced activity of PP2A, the upstream phosphatase of AMPK. In contrast, knockdown of 6PGD or 6-phosphogluconolactonase (PGLS), the second oxiPPP enzyme, reduced PP2A activity. Mechanistically, knockdown of G6PD or PGLS decreased or increased 6-phosphogluconolactone level, respectively, which enhanced the inhibitory phosphorylation of PP2A by Src. Furthermore, γ-6-phosphogluconolactone, an oxiPPP byproduct with unknown function generated through intramolecular rearrangement of δ-6-phosphogluconolactone, the only substrate of PGLS, bound to Src and enhanced PP2A recruitment. Together, oxiPPP regulates AMPK homeostasis by balancing the opposing LKB1 and PP2A.