Novel DYRK1A Inhibitor Rescues Learning and Memory Deficits in a Mouse Model of Down Syndrome

Down syndrome (DS) is a complex genetic disorder associated with substantial physical, cognitive, and behavioral challenges. Due to better treatment options for the physical co-morbidities of DS, the life expectancy of individuals with DS is beginning to approach that of the general population. However, the cognitive deficits seen in individuals with DS still cannot be addressed pharmacologically. In young individuals with DS, the level of intellectual disability varies from mild to severe, but cognitive ability generally decreases with increasing age, and all individuals with DS have early onset Alzheimer’s disease (AD) pathology by the age of 40. The present study introduces a novel inhibitor for the protein kinase DYRK1A, a key controlling kinase whose encoding gene is located on chromosome 21. The novel inhibitor is well characterized for use in mouse models and thus represents a valuable tool compound for further DYRK1A researc

Discovery of a Redox Thiol Switch: Implications for Cellular Energy Metabolism

The redox-based modifications of cysteine residues in proteins regulate their function in many biological processes. The gas molecule H2S has been shown to persulfidate redox sensitive cysteine residues resulting in an H2S-modified proteome known as the sulfhydrome. Tandem Mass Tags (TMT) multiplexing strategies for large-scale proteomic analyses have become increasingly prevalent in detecting cysteine modifications. Here we developed a TMT-based proteomics approach for selectively trapping and tagging cysteine persulfides in the cellular proteomes. We revealed the natural protein sulfhydrome of two human cell lines, and identified insulin as a novel substrate in pancreatic beta cells. Moreover, we showed that under oxidative stress conditions, increased H2S can target enzymes involved in energy metabolism by switching specific cysteine modifications to persulfides. Specifically, we discovered a Redox Thiol Switch, from protein S-glutathioinylation to S-persulfidation (RTSGS). We propose that the RTSGS from S-glutathioinylation to S-persulfidation is a potential mechanism to fine tune cellular energy metabolism in response to different levels of oxidative stress

Increased Glucose Availability Sensitizes Pancreatic Cancer to Chemotherapy

Pancreatic Ductal Adenocarcinoma (PDAC) is highly resistant to chemotherapy. Effective alternative therapies have yet to emerge, as chemotherapy remains the best available systemic treatment. However, the discovery of safe and available adjuncts to enhance chemotherapeutic efficacy can still improve survival outcomes. We show that a hyperglycemic state substantially enhances the efficacy of conventional single- and multi-agent chemotherapy regimens against PDAC. Molecular analyses of tumors exposed to high glucose levels reveal that the expression of GCLC (glutamate-cysteine ligase catalytic subunit), a key component of glutathione biosynthesis, is diminished, which in turn augments oxidative anti-tumor damage by chemotherapy. Inhibition of GCLC phenocopies the suppressive effect of forced hyperglycemia in mouse models of PDAC, while rescuing this pathway mitigates anti-tumor effects observed with chemotherapy and high glucose

Triheptanoin alters [U- 13 C 6 ]-glucose incorporation into glycolytic intermediates and increases TCA cycling by normalizing the activities of pyruvate dehydrogenase and oxoglutarate dehydrogenase in a chronic epilepsy mouse model

Triheptanoin is anticonvulsant in several seizure models. Here, we investigated changes in glucose metabolism by triheptanoin interictally in the chronic stage of the pilocarpine mouse epilepsy model. After injection of [U- C ]-glucose (i.p.), enrichments of C in intermediates of glycolysis and the tricarboxylic acid (TCA) cycle were quantified in hippocampal extracts and maximal activities of enzymes in each pathway were measured. The enrichment of C glucose in plasma was similar across all groups. Despite this, we observed reductions in incorporation of C in several glycolytic intermediates compared to control mice suggesting glucose utilization may be impaired and/or glycogenolysis increased in the untreated interictal hippocampus. Triheptanoin prevented the interictal reductions of C incorporation in most glycolytic intermediates, suggesting it increased glucose utilization or – as an additional astrocytic fuel – it decreased glycogen breakdown. In the TCA cycle metabolites, the incorporation of C was reduced in the interictal state. Triheptanoin restored the correlation between C enrichments of pyruvate relative to most of the TCA cycle intermediates in “epileptic” mice. Triheptanoin also prevented the reductions of hippocampal pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase activities. Decreased glycogen breakdown and increased glucose utilization and metabolism via the TCA cycle in epileptogenic brain areas may contribute to triheptanoin's anticonvulsant effects

Time Course of Hepatic Gluconeogenesis During Hindlimb Suspension Unloading

New Findings: • What is the central question of this study? The rate of liver gluconeogenesis during hindlimb suspension unloading has not been determined. • What is the main finding and its importance? Hepatic gluconeogenesis is significantly increased under conditions of hindlimb suspension unloading, which simulates the muscular atrophy occurring during spaceflight. This finding supports earlier hypothesis. This metabolic shift in the living animal warrants further study. The goal of this work was to determine the time-dependent changes in fractional hepatic gluconeogenesis (GNG) during conditions of hindlimb suspension unloading (HSU), a \u27ground-based\u27 method for inducing muscular atrophy to simulate space flight. We hypothesized that GNG would increase in HSU conditions as a result of metabolic shifts in the liver and skeletal muscle. A significant and progressive atrophy was observed in the soleus (30, 47 and 55%) and gastrocnemius muscles (0, 15 and 17%) after 3, 7 and 14 days of HSU, respectively. Fractional hepatic GNG was determined following the incorporation of deuterium from deuterated water (2H2O) into C-H bonds of newly synthesized glucose after an 8 h fast. Enrichment of plasma glucose with 2H was measured using the classic method of Landau et al. (the \u27hexamethylenetetramine (HMT) method\u27), based on specific 2H labelling of glucose carbons, and the novel method of Chacko et al. (\u27average method\u27), based on the assumption of equal 2H enrichment on all glucose carbons (except C2). After 3 days of HSU, fractional GNG was significantly elevated in the HSU group, as determined by either method (∼13%, P \u3c 0.05). After 7 and 14 days of HSU, gluconeogenesis was not significantly different. Both analytical methods yielded similar time-dependent trends in gluconeogenic rates, but GNG values determined using the average method were consistently lower (∼30%) than those found by the HMT method. To compare and validate the average method against the HMT method further, we starved animals for 13 h to allow for hepatic GNG to contribute 100% to endogenous glucose production. The HMT method yielded 100% GNG, while the average method yielded GNG of ∼70%. As both methods used the same values of precursor enrichment, we postulated that the underestimation of gluconeogenic rate was as a result of differences in the measurements of product enrichment (2H labelling of plasma glucose). This could be explained by the following factors: (i) loss of deuterium via exchange between acetate and glucose; (ii) interference caused by fragment m/z 169, representing multiple isobaric species; and (iii) interference from other sugars at m/z 169. In conclusion, HSU caused a time-dependent increase in hepatic gluconeogenesis, irrespective of the analytical methods used. © 2012 The Authors. Experimental Physiology © 2012 The Physiological Society

Growth deficits in cystic fibrosis mice begin in utero prior to IGF-1 reduction.

Growth deficits are common in cystic fibrosis (CF), but their cause is complex, with contributions from exocrine pancreatic insufficiency, pulmonary complications, gastrointestinal obstructions, and endocrine abnormalities. The CF mouse model displays similar growth impairment despite exocrine pancreatic function and in the absence of chronic pulmonary infection. The high incidence of intestinal obstruction in the CF mouse has been suggested to significantly contribute to the observed growth deficits. Previous studies by our group have shown that restoration of the cystic fibrosis transmembrane conductance regulator (CFTR) in the intestinal epithelium prevents intestinal obstruction but does not improve growth. In this study, we further investigate growth deficits in CF and gut-corrected CF mice by assessing insulin-like growth factor 1 (IGF-1). IGF-1 levels were significantly decreased in CF and gut-corrected CF adult mice compared to wildtype littermates and were highly correlated with weight. Interestingly, perinatal IGF-1 levels were not significantly different between CF and wildtype littermates, even though growth deficits in CF mice could be detected late in gestation. Since CFTR has been suggested to play a role in water and nutrient exchange in the placenta through its interaction with aquaporins, we analyzed placental aquaporin expression in late-gestation CF and control littermates. While significant differences were observed in Aquaporin 9 expression in CF placentas in late gestation, there was no evidence of placental fluid exchange differences between CF and control littermates. The results from this study indicate that decreased IGF-1 levels are highly correlated with growth in CF mice, independent of CF intestinal obstruction. However, the perinatal growth deficits that are observed in CF mice are not due to decreased IGF-1 levels or differences in placenta-mediated fluid exchange. Further investigation is necessary to understand the etiology of early growth deficits in CF, as growth has been shown to be a significant factor in disease outcomes

ADEMA: An Algorithm to Determine Expected Metabolite Level Alterations Using Mutual Information

<div><p>Metabolomics is a relatively new “omics” platform, which analyzes a discrete set of metabolites detected in bio-fluids or tissue samples of organisms. It has been used in a diverse array of studies to detect biomarkers and to determine activity rates for pathways based on changes due to disease or drugs. Recent improvements in analytical methodology and large sample throughput allow for creation of large datasets of metabolites that reflect changes in metabolic dynamics due to disease or a perturbation in the metabolic network. However, current methods of comprehensive analyses of large metabolic datasets (metabolomics) are limited, unlike other “omics” approaches where complex techniques for analyzing coexpression/coregulation of multiple variables are applied. This paper discusses the shortcomings of current metabolomics data analysis techniques, and proposes a new multivariate technique (ADEMA) based on mutual information to identify expected metabolite level changes with respect to a specific condition. We show that ADEMA better predicts De Novo Lipogenesis pathway metabolite level changes in samples with Cystic Fibrosis (CF) than prediction based on the significance of individual metabolite level changes. We also applied ADEMA's classification scheme on three different cohorts of CF and wildtype mice. ADEMA was able to predict whether an unknown mouse has a CF or a wildtype genotype with 1.0, 0.84, and 0.9 accuracy for each respective dataset. ADEMA results had up to 31% higher accuracy as compared to other classification algorithms. In conclusion, ADEMA advances the state-of-the-art in metabolomics analysis, by providing accurate and interpretable classification results.</p> </div

Cholestenoic Acid Is an Important Elimination Product of Cholesterol in the Retina: Comparison of Retinal Cholesterol Metabolism with That in the Brain

This is the first comprehensive investigation of oxysterol levels in the human retina and retinal pigment epithelium that establishes the major mechanism for enzymatic cholesterol elimination from the posterior part of the eye