Biology subjects

Narain, N. R.

Publications and source records attributed to Narain, N. R..

6 recordsLinked to original sources

bioRxiv2024

Amino Acid and Glucose Fermentation Maintain ATP Content in Mouse and Human Malignant Glioma Cells

Energy is necessary for tumor cell viability and growth. Aerobic glucose-driven lactic acid fermentation is a common metabolic phenotype seen in most cancers including malignant gliomas. This metabolic phenotype is linked to abnormalities in mitochondrial structure and function. A luciferin-luciferase bioluminescence ATP assay was used to measure the influence of amino acids, glucose, and oxygen on ATP content and viability in mouse (VM-M3 and CT-2A) and human (U-87MG) glioma cells that differed in cell biology, genetic background, and species origin. Oxygen consumption was measured using the Resipher system. Extracellular lactate and succinate were measured as end products of the glycolysis and glutaminolysis pathways, respectively. The results showed that: 1) glutamine was a source of ATP content irrespective of oxygen. No other amino acid could replace glutamine in sustaining ATP content and viability; 2) ATP content persisted in the absence of glucose and under hypoxia, ruling out substantial contribution through either glycolysis or oxidative phosphorylation (OxPhos) under these conditions; 3) Mitochondrial complex IV inhibition showed that oxygen consumption was not an accurate measure for ATP production through OxPhos. The glutaminase inhibitor, 6-diazo-5-oxo-L-norleucine (DON), reduced ATP content and succinate export in cells grown in glutamine. The data suggests that mitochondrial substrate level phosphorylation in the glutamine-driven glutaminolysis pathway contributes to ATP content in these glioma cells. A new model is presented highlighting the synergistic interaction between the high-throughput glycolysis and glutaminolysis pathways that drive malignant glioma growth and maintain ATP content through the aerobic fermentation of both glucose and glutamine. Summary statementMalignant gliomas, regardless of cell of origin or species, rely on fermentation mechanisms for ATP production due to OxPhos insufficiency. Glucose and glutamine together are necessary and sufficient for dysregulated tumor cell growth, whereas OxPhos is neither necessary nor sufficient.

cancer biology↗

bioRxiv2023

ScreenDMT reveals linoleic acid diols replicably associate with BMI and stimulate adipocyte calcium fluxes

Activating brown adipose tissue (BAT) improves systemic metabolism, making it a promising target for metabolic syndrome. BAT is activated by 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), which we previously identified to be inversely associated with BMI and which directly improves metabolism in multiple tissues. Here we profile plasma lipidomics from a cohort of 83 people and test which lipids association with BMI replicates in a concordant direction using our novel tool ScreenDMT, whose power and validity we demonstrate via mathematical proofs and simulations. We find that the linoleic acid diols 12,13-diHOME and 9,10-diHOME both replicably inversely associate with BMI and mechanistically activate calcium fluxes in mouse brown and white adipocytes in vitro, which implicates this pathway and 9,10-diHOME as candidate therapeutic targets. ScreenDMT can be applied to test directional mediation, directional replication, and qualitative interactions, such as identifying biomarkers whose association is shared (replication) or opposite (qualitative interaction) across diverse populations.

bioinformatics↗

bioRxiv2022

Residual Complex I activity supports glutamate catabolism and mtSLP via canonical Krebs cycle activity during acute anoxia without OXPHOS

Anoxia halts oxidative phosphorylation (OXPHOS) causing an accumulation of reduced compounds in mitochondrial matrix which impedes dehydrogenases. By simultaneously measuring oxygen concentration, NADH autofluorescence, mitochondrial membrane potential and ubiquinone reduction extent in organello in real-time, we show that Complex I utilized endogenous quinones to oxidize NADH under acute anoxia. Untargeted or [U-13C]glutamate-targeted metabolomic analysis of matrix and effluxed metabolites extracted during anoxia in the presence or absence of site-specific inhibitors of the electron transfer system inferred that NAD+ regenerated by Complex I is reduced by the 2-oxoglutarate dehydrogenase complex yielding succinyl-CoA supporting mitochondrial substrate-level phosphorylation (mtSLP), releasing succinate. Yet, targeted metabolomic analysis using [U-13C]malate also revealed concomitant succinate dehydrogenase reversal during anoxia yielding succinate by reducing fumarate, albeit to a small extent. Our results highlight the importance of quinone availability to Complex I oxidizing NADH, thus maintaining glutamate catabolism and mtSLP in the absence of OXPHOS.

biochemistry↗

bioRxiv2022

Serum metabolomic analysis of men on a low-carbohydrate diet for biochemically recurrent prostate cancer reveal the potential role of ketogenesis to slow tumor growth: A secondary analysis of the CAPS2 diet trial

BackgroundSystemic treatments for prostate cancer (PC) have significant side effects. Thus, newer alternatives with fewer side effects are urgently needed. Animal and human studies suggest the therapeutic potential of low carbohydrate diet (LCD) for PC. To test this possibility, Carbohydrate and Prostate Study 2 (CAPS2) trial was conducted in PC patients with biochemical recurrence (BCR) after local treatment to determine the effect of a 6-month LCD intervention vs. usual care control on PC growth as measured by PSA doubling time (PSADT). We previously reported the LCD intervention led to significant weight loss, higher HDL, and lower triglycerides and HbA1c with a suggested longer PSADT. However, the metabolic basis of these effects are unknown. MethodsTo identify the potential metabolic basis of effects of LCD on PSADT, serum metabolomic analysis was performed using baseline, month 3, and month 6 banked sera to identify the metabolites significantly altered by LCD and that correlated with varying PSADT. ResultsLCD increased the serum levels of ketone bodies, glycine and hydroxyisocaproic acid. Reciprocally, LCD reduced the serum levels of alanine, cytidine, asymmetric dimethylarginine (ADMA) and 2-oxobutanoate. As high ADMA level is shown to inhibit nitric oxide (NO) signaling and contribute to various cardiovascular diseases, the ADMA repression under LCD may contribute to the LCD-associated health benefit. Regression analysis of the PSADT revealed a correlation between longer PSADT with higher level of 2-hydroxybutyric acids, ketone bodies, citrate and malate. Longer PSADT was also associated with LCD reduced nicotinamide, fructose-1, 6-biphosphate (FBP) and 2-oxobutanoate. ConclusionThese results suggest a potential association of ketogenesis and TCA metabolites with slower PC growth and conversely glycolysis with faster PC growth. The link of high ketone bodies with longer PSADT supports future studies of ketogenic diets to slow PC growth.

cancer biology↗

bioRxiv2021

Identification and Validation of N-Acetylputrescine in Combination With Non-Canonical Clinical Features As a Parkinsons Disease Biomarker Panel

Parkinsons disease is a progressive neurodegenerative disorder in which loss of dopaminergic neurons in the substantia nigra results in a clinically heterogeneous group with variable motor and non-motor symptoms with a degree of misdiagnosis. Only 3-5% of sporadic Parkinsons patients present with genetic abnormalities, thus environmental, metabolic, and other unknown causes contribute to the pathogenesis of Parkinsons disease, which highlights the critical need for biomarkers. There could be a significant clinical benefit to treating Parkinsons disease at the earliest stage and identify at-risk populations once disease-modifying treatments are available. In the present study, we prospectively collected and analyzed plasma samples from 201 Parkinsons disease patients and 199 age-matched non-diseased controls. Multiomic and Bayesian artificial intelligence analysis of molecular and clinical data identified the diagnostic utility of N-acetyl putrescine (NAP) in combination with smell (B-SIT), depression/anxiety (HADS), and acting out dreams (RBD1Q) clinical measurements. The clinical and biomarker panel demonstrated an area under the curve, AUC = 0.9, positive predictive value, PPV = 0.91, and negative predictive value, NPV = 0.66 utilizing all four variables. The assessed diagnostic panel demonstrates combinatorial utility in diagnosing Parkinsons disease, allowing for an integrated interpretation of disease pathophysiology and highlighting the use of multi-tiered panels in neurological disease diagnosis.

neuroscience↗

bioRxiv2018

Multi-OMIC analysis of brain and serum from chronically-stressed mice reveals network disruptions in purine metabolism, fatty acid beta-oxidation, and antioxidant activity that are reversed by antidepressant treatment

Major depressive disorder (MDD) is a complex condition with unclear pathophysiology. Molecular disruptions within the periphery and limbic brain regions contribute to depression symptomatology. Here, we utilized a mouse chronic stress model of MDD and performed metabolomic, lipidomic, and proteomic profiling on serum plus several brain regions (ventral hippocampus, nucleus accumbens, and prefrontal cortex) of susceptible, resilient, and unstressed control mice. Proteomic analysis identified three serum proteins reduced in susceptible animals; lipidomic analysis detected differences in lipid species between resilient and susceptible animals in serum and brain; and metabolomic analysis revealed pathway dysfunctions of purine metabolism, beta oxidation, and antioxidants, which were differentially associated with stress susceptibility vs resilience by brain region. Antidepressant treatment ameliorated MDD-like behaviors and affected key metabolites within outlined networks, most dramatically in the ventral hippocampus. This work presents a resource for chronic stress-induced, tissue-specific changes in proteins, lipids, and metabolites and illuminates how molecular dysfunctions contribute to individual differences in stress sensitivity.

neuroscience↗