ROHIT MAHAR

RESEARCH, TEACHING, or OTHER INTERESTS

Chemistry, Cancer Research, Multidisciplinary, Analytical Chemistry

Scopus Publications

Detecting altered hepatic lipid oxidation by MRI in an animal model of MASLD
Marc McLeod, Mario C. Chang, Anna Rushin, Mukundan Ragavan, Rohit Mahar, Gaurav Sharma, Arshee Badar, Anthony Giacalone, Max E. Glanz, Vinay R. Malut,et al.
Elsevier BV



Cyclodextrin in drug delivery: Exploring scaffolds, properties, and cutting-edge applications
Parbeen Singh and Rohit Mahar
Elsevier BV



DFT investigation of coupling constant anomalies in substituted β-lactams
Emily B. Crull, Alexei V. Buevich, Gary E. Martin, Rohit Mahar, Bo Qu, Chris H. Senanayake, Tadeusz F. Molinski, and R. Thomas Williamson
Wiley
Abstractβ‐lactams are a chemically diverse group of molecules with a wide range of biological activities. Having recently observed curious trends in 2JHH coupling values in studies on this structural class, we sought to obtain a more comprehensive understanding of these diagnostic NMR parameters, specifically interrogating 1JCH, 2JCH, and 2JHH, to differentiate 3‐ and 4‐monosubstituted β‐lactams. Further investigation using computational chemistry methods was employed to explore the geometric and electronic origins for the observed and calculated differences between the two substitution patterns.


Design and Discovery of Water-Soluble Benzooxaphosphole-Based Ligands for Hindered Suzuki-Miyaura Coupling Reactions with Low Catalyst Load
Arun D. R. Shada, Hari P. R. Mangunuru, Leila Terrab, Srinivasarao Tenneti, Nageswara Rao Kalikinidi, Santhosh Reddy Naini, Praveen Gajula, Emily B. Crull, Venumadhav Janganati, Raghavendra Kovvuri,et al.
American Chemical Society (ACS)
We report a new class of highly effective, benzooxaphosphole-based, water-soluble ligands in the application of Suzuki-Miyaura cross-coupling reactions for sterically hindered substrates in aqueous media. The catalytic activities of the coupling reactions were greatly enhanced by the addition of catalytic amounts of organic phase transfer reagents, such as tetraglyme and tetrabutylammonium bromide. The optimized general protocol can be conducted with a low catalyst load, thereby providing a practical solution for these reactions. The viability of this new Suzuki-Miyaura protocol was demonstrated with various substrates to generate important building blocks, including heterocycles, for the synthesis of biologically active compounds.


Exploring the Significance, Extraction, and Characterization of Plant-Derived Secondary Metabolites in Complex Mixtures
Ruchi Barthwal and Rohit Mahar
MDPI AG
Secondary metabolites are essential components for the survival of plants. Secondary metabolites in complex mixtures from plants have been adopted and documented by different traditional medicinal systems worldwide for the treatment of various human diseases. The extraction strategies are the key components for therapeutic development from natural sources. Polarity-dependent solvent-selective extraction, acidic and basic solution-based extraction, and microwave- and ultrasound-assisted extraction are some of the most important strategies for the extraction of natural products from plants. The method needs to be optimized to isolate a specific class of compounds. Therefore, to establish the mechanism of action, the characterization of the secondary metabolites, in a mixture or in their pure forms, is equally important. LC-MS, GC-MS, and extensive NMR spectroscopic strategies are established techniques for the profiling of metabolites in crude extracts. Various protocols for the extraction and characterization of a wide range of classes of compounds have been developed by various research groups and are described in this review. Additionally, the possible means of characterizing the compounds in the mixture and their uniqueness are also discussed. Hyphenated techniques are crucial for profiling because of their ability to analyze a vast range of compounds. In contrast, inherent chemical shifts make NMR an indispensable tool for structure elucidation in complex mixtures.


Inactivation of mitochondrial MUL1 E3 ubiquitin ligase deregulates mitophagy and prevents diet-induced obesity in mice
Lucia Cilenti, Jacopo Di Gregorio, Rohit Mahar, Fei Liu, Camilla T. Ambivero, Muthu Periasamy, Matthew E. Merritt, and Antonis S. Zervos
Frontiers Media SA
Obesity is a growing epidemic affecting millions of people worldwide and a major risk factor for a multitude of chronic diseases and premature mortality. Accumulating evidence suggests that mitochondria have a profound role in diet-induced obesity and the associated metabolic changes, but the molecular mechanisms linking mitochondria to obesity remain poorly understood. Our studies have identified a new function for mitochondrial MUL1 E3 ubiquitin ligase, a protein known to regulate mitochondrial dynamics and mitophagy, in the control of energy metabolism and lipogenesis. Genetic deletion of Mul1 in mice impedes mitophagy and presents a metabolic phenotype that is resistant to high-fat diet (HFD)-induced obesity and metabolic syndrome. Several metabolic and lipidomic pathways are perturbed in the liver and white adipose tissue (WAT) of Mul1(−/−) animals on HFD, including the one driven by Stearoyl-CoA Desaturase 1 (SCD1), a pivotal regulator of lipid metabolism and obesity. In addition, key enzymes crucial for lipogenesis and fatty acid oxidation such as ACC1, FASN, AMPK, and CPT1 are also modulated in the absence of MUL1. The concerted action of these enzymes, in the absence of MUL1, results in diminished fat storage and heightened fatty acid oxidation. Our findings underscore the significance of MUL1-mediated mitophagy in regulating lipogenesis and adiposity, particularly in the context of HFD. Consequently, our data advocate the potential of MUL1 as a therapeutic target for drug development in the treatment of obesity, insulin resistance, NAFLD, and cardiometabolic diseases.


Age-related differences in affective behaviors in mice: possible role of prefrontal cortical-hippocampal functional connectivity and metabolomic profiles
Marcelo Febo, Rohit Mahar, Nicholas A. Rodriguez, Joy Buraima, Marjory Pompilus, Aeja M. Pinto, Matteo M. Grudny, Adriaan W. Bruijnzeel, and Matthew E. Merritt
Frontiers Media SA
IntroductionThe differential expression of emotional reactivity from early to late adulthood may involve maturation of prefrontal cortical responses to negative valence stimuli. In mice, age-related changes in affective behaviors have been reported, but the functional neural circuitry warrants further investigation.MethodsWe assessed age variations in affective behaviors and functional connectivity in male and female C57BL6/J mice. Mice aged 10, 30 and 60 weeks (wo) were tested over 8 weeks for open field activity, sucrose preference, social interactions, fear conditioning, and functional neuroimaging. Prefrontal cortical and hippocampal tissues were excised for metabolomics.ResultsOur results indicate that young and old mice differ significantly in affective behavioral, functional connectome and prefrontal cortical-hippocampal metabolome. Young mice show a greater responsivity to novel environmental and social stimuli compared to older mice. Conversely, late middle-aged mice (60wo group) display variable patterns of fear conditioning and during re-testing in a modified context. Functional connectivity between a temporal cortical/auditory cortex network and subregions of the anterior cingulate cortex and ventral hippocampus, and a greater network modularity and assortative mixing of nodes was stronger in young versus older adult mice. Metabolome analyses identified differences in several essential amino acids between 10wo mice and the other age groups.DiscussionThe results support differential expression of ‘emotionality’ across distinct stages of the mouse lifespan involving greater prefrontal-hippocampal connectivity and neurochemistry.


Comprehensive isotopomer analysis of glutamate and aspartate in small tissue samples
Feng Cai, Divya Bezwada, Ling Cai, Rohit Mahar, Zheng Wu, Mario C. Chang, Panayotis Pachnis, Chendong Yang, Sherwin Kelekar, Wen Gu,et al.
Elsevier BV



Enrichment of hepatic glycogen and plasma glucose from H₂¹⁸O informs gluconeogenic and indirect pathway fluxes in naturally feeding mice
Margarida Coelho, Rohit Mahar, Getachew D. Belew, Alejandra Torres, Cristina Barosa, Fernando Cabral, Ivan Viegas, Amalia Gastaldelli, Vera M. Mendes, Bruno Manadas,et al.
Wiley
AbstractDeuterated water (2H2O) is a widely used tracer of carbohydrate biosynthesis in both preclinical and clinical settings, but the significant kinetic isotope effects (KIE) of 2H can distort metabolic information and mediate toxicity. 18O‐water (H218O) has no significant KIE and is incorporated into specific carbohydrate oxygens via well‐defined mechanisms, but to date it has not been evaluated in any animal model. Mice were given H218O during overnight feeding and 18O‐enrichments of liver glycogen, triglyceride glycerol (TG), and blood glucose were quantified by 13C NMR and mass spectrometry (MS). Enrichment of oxygens 5 and 6 relative to body water informed indirect pathway contributions from the Krebs cycle and triose phosphate sources. Compared with mice fed normal chow (NC), mice whose NC was supplemented with a fructose/glucose mix (i.e., a high sugar [HS] diet) had significantly higher indirect pathway contributions from triose phosphate sources, consistent with fructose glycogenesis. Blood glucose and liver TG 18O‐enrichments were quantified by MS. Blood glucose 18O‐enrichment was significantly higher for HS versus NC mice and was consistent with gluconeogenic fructose metabolism. TG 18O‐enrichment was extensive for both NC and HS mice, indicating a high turnover of liver triglyceride, independent of diet. Thus H218O informs hepatic carbohydrate biosynthesis in similar detail to 2H2O but without KIE‐associated risks.


Segmented Flow Strategies for Integrating Liquid Chromatography-Mass Spectrometry with Nuclear Magnetic Resonance for Lipidomics
Jiajun Lei, Rohit Mahar, Mario C. Chang, James Collins, Matthew E. Merritt, Timothy J. Garrett, and Richard A. Yost
American Chemical Society (ACS)
Building an accurate lipid inventory relies on coordinated information from orthogonal analytical capabilities. Integrating the familiar workflow of liquid chromatography (LC), high-resolution mass spectrometry (HRMS), and tandem mass spectrometry (MS/MS) with proton nuclear magnetic resonance spectroscopy (1H NMR) would be ideal for building that inventory. For absolute lipid structural elucidation, LC-HRMS/MS can provide lower-level structural information with superior sensitivity, while 1H NMR can provide invaluable higher-order structural information for the disambiguation of isomers with absolute chemical specificity. Digitization of the LC eluent followed by splitting the microfractions into two flow paths in a defined ratio for HRMS/MS and NMR would be the ideal strategy to permit correlation of the MS and NMR data as a function of chromatographic retention time. Here, we report an active segmentation platform to transform analytical flow rate LC eluent into parallel microliter segmented flow queues for high confidence correlation of the MS, MS/MS, and NMR data. The practical details in implementing this strategy to achieve an integrated LC-MS-NMR platform are presented, including the development of an active segmentation technology using a four-port two-way valve to transform the LC eluent into parallel segmented flows for online MS analysis followed by offline segment-specific 1H NMR and optimization of the detector response toward segmented flow. To demonstrate the practicality of this novel platform, it was tested using lipid mixture samples.


Bioactive Compounds from Aquatic Ecosystem
Surendra Puri, Rohit Mahar, and Gunjan Goswami
Springer Nature Singapore



Metabolic signatures associated with oncolytic myxoma viral infections
Rohit Mahar, Mukundan Ragavan, Mario C. Chang, Savannah Hardiman, Nissin Moussatche, Adam Behar, Rolf Renne, and Matthew E. Merritt
Springer Science and Business Media LLC
AbstractOncolytic viral therapy is a recent advance in cancer treatment, demonstrating promise as a primary treatment option. To date, the secondary metabolic effects of viral infection in cancer cells has not been extensively studied. In this work, we have analyzed early-stage metabolic changes in cancer cells associated with oncolytic myxoma virus infection. Using GC–MS based metabolomics, we characterized the myxoma virus infection induced metabolic changes in three cancer cell lines—small cell (H446) and non-small cell (A549) lung cancers, and glioblastoma (SFxL). We show that even at an early stage (6 and 12 h) myxoma infection causes profound changes in cancer cell metabolism spanning several important pathways such as the citric acid cycle, fatty acid metabolism, and amino acid metabolism. In general, the metabolic effects of viral infection across cell lines are not conserved. However, we have identified several candidate metabolites that can potentially serve as biomarkers for monitoring oncolytic viral action in general.


Synergistic Effect of β-Lapachone and Aminooxyacetic Acid on Central Metabolism in Breast Cancer
Mario C. Chang, Rohit Mahar, Marc A. McLeod, Anthony G. Giacalone, Xiumei Huang, David A. Boothman, and Matthew E. Merritt
MDPI AG
The compound β-lapachone, a naturally derived naphthoquinone, has been utilized as a potent medicinal nutrient to improve health. Over the last twelve years, numerous reports have demonstrated distinct associations of β-lapachone and NAD(P)H: quinone oxidoreductase 1 (NQO1) protein in the amelioration of various diseases. Comprehensive research of NQO1 bioactivity has clearly confirmed the tumoricidal effects of β-lapachone action through NAD+-keresis, in which severe DNA damage from reactive oxygen species (ROS) production triggers a poly-ADP-ribose polymerase-I (PARP1) hyperactivation cascade, culminating in NAD+/ATP depletion. Here, we report a novel combination strategy with aminooxyacetic acid (AOA), an aspartate aminotransferase inhibitor that blocks the malate-aspartate shuttle (MAS) and synergistically enhances the efficacy of β-lapachone metabolic perturbation in NQO1+ breast cancer. We evaluated metabolic turnover in MDA-MB-231 NQO1+, MDA-MB-231 NQO1−, MDA-MB-468, and T47D cancer cells by measuring the isotopic labeling of metabolites from a [U-13C]glucose tracer. We show that β-lapachone treatment significantly hampers lactate secretion by ~85% in NQO1+ cells. Our data demonstrate that combinatorial treatment decreases citrate, glutamate, and succinate enrichment by ~14%, ~50%, and ~65%, respectively. Differences in citrate, glutamate, and succinate fractional enrichments indicate synergistic effects on central metabolism based on the coefficient of drug interaction. Metabolic modeling suggests that increased glutamine anaplerosis is protective in the case of MAS inhibition.


Assessment of Tissue Specific Distribution and Seasonal Variation of Alkaloids in Alstonia scholaris
Rohit Mahar, Nagarajan Manivel, Sanjeev Kanojiya, Dipak K. Mishra, and Sanjeev K. Shukla
MDPI AG
Alstonia scholaris is a well-known source of alkaloids and widely recognized for therapeutic purposes to treat the ailments in human and livestock. However, the composition and production of alkaloids vary due to tissue specific metabolism and seasonal variation. This study investigated alkaloids in leaves, stems, trunk barks, fruits, and flowers of A. scholaris. The impact of seasonal changes on the production of alkaloids in the leaves of A. scholaris was also investigated. One and two-dimensional Nuclear Magnetic Resonance (NMR) experiments were utilized for the characterization of alkaloids and total eight alkaloids (picrinine, picralinal, akuammidine, 19 S scholaricine, 19,20 E vallesamine, Nb-demethylalstogustine N-Oxide, Nb-demethylalstogustine, and echitamine) were characterized and quantified. Quantitative and multivariate analysis suggested that the alkaloids content is tissue specific, illustrating the effect of plant tissue organization on alkaloidal production in A. scholaris. The results suggest that the best part to obtain alkaloids is trunk barks, since it contains 7 alkaloids. However, the best part for isolating picrinine, picralinal, akuammidine, 19 S scholaricine, and 19,20 E vallesamine is fruit, since it shows highest amount of these alkaloids. Undoubtedly, NMR and statistical methods are very helpful to differentiate the profile of alkaloids in A. scholaris.


Regulation of Metabolism by Mitochondrial MUL1 E3 Ubiquitin Ligase
Lucia Cilenti, Rohit Mahar, Jacopo Di Gregorio, Camilla T. Ambivero, Matthew E. Merritt, and Antonis S. Zervos
Frontiers Media SA
MUL1 is a multifunctional E3 ubiquitin ligase that is involved in various pathophysiological processes including apoptosis, mitophagy, mitochondrial dynamics, and innate immune response. We uncovered a new function for MUL1 in the regulation of mitochondrial metabolism. We characterized the metabolic phenotype of MUL1(−/−) cells using metabolomic, lipidomic, gene expression profiling, metabolic flux, and mitochondrial respiration analyses. In addition, the mechanism by which MUL1 regulates metabolism was investigated, and the transcription factor HIF-1α, as well as the serine/threonine kinase Akt2, were identified as the mediators of the MUL1 function. MUL1 ligase, through K48-specific polyubiquitination, regulates both Akt2 and HIF-1α protein level, and the absence of MUL1 leads to the accumulation and activation of both substrates. We used specific chemical inhibitors and activators of HIF-1α and Akt2 proteins, as well as Akt2(−/−) cells, to investigate the individual contribution of HIF-1α and Akt2 proteins to the MUL1-specific phenotype. This study describes a new function of MUL1 in the regulation of mitochondrial metabolism and reveals how its downregulation/inactivation can affect mitochondrial respiration and cause a shift to a new metabolic and lipidomic state.


Lipogenesis mediated by OGR1 regulates metabolic adaptation to acid stress in cancer cells via autophagy
Smitha Pillai, Iqbal Mahmud, Rohit Mahar, Crystal Griffith, Michael Langsen, Jonathan Nguyen, Jonathan W. Wojtkowiak, Pawel Swietach, Robert A. Gatenby, Marilyn M. Bui,et al.
Elsevier BV



Quantitative Analysis of Bioactive Carbazole Alkaloids in Murraya koenigii (L.) from Six Different Climatic Zones of India Using UPLC/MS/MS and Their Principal Component Analysis
Shiv Nandan, Sumit K. Singh, Pratibha Singh, Vikas Bajpai, Ashwanee K. Mishra, Trapti Joshi, Rohit Mahar, Sanjeev K. Shukla, Dipak K. Mishra, and Sanjeev Kanojiya
Wiley
AbstractMurraya koenigii (L.) Spreng (Curry leaf) is a commercially important medicinal plant in South Asia, containing therapeutically valuable carbazole alkaloids (CAs). Thus, the quantitative evaluation of these compounds from different climatic zones of India are an important aspect for quality assessment and economic isolation of targeted compounds from the plant. In this study, quantitative estimation of CAs among 34 Indian natural populations of M. koenigii was assessed using UPLC/MS/MS. The collected populations represent the humid subtropical, tropical wet & dry, tropical wet, semi‐arid, arid, and montane climatic zones of India. A total of 11 CAs viz. koenine‐I, murrayamine A, koenigine, koenimbidine, koenimbine, O‐methylmurrayamine A, girinimbine, mahanine, 8,8’’‐biskoenigine, isomahanimbine, and mahanimbine were quantified using multiple reaction monitoring (MRM) experiments within 5.0 min. The respective range for natural abundance of CAs were observed as 0.097–1.222, 0.092–5.014, 0.034–0.661, 0.010–1.673, 0.013–7.336, 0.010–0.310, 0.010–0.114, 0.049–5.288, 0.031–1.731, 0.491–3.791, and 0.492–5.399 mg/g in leaves of M. koenigii. The developed method shown linearity regression coefficient (r2>0.9995), LOD (0.003–0.248 ng/mL), LOQ (0.009–0.754 ng/mL), and the recovery was between 88.803–103.729 %. The bulk of these CAs were recorded in their highest concentrations in the humid subtropical zone, followed by the tropical wet & dry zones of India. Further, principal component analysis (PCA) was performed which differentiated the climatic zones according to the dominant and significant CAs contents within the populations. The study concludes that the method established is simple, rapid, with high sample throughput, and can be used as a tool for commercial purposes and quality control of M. koenigii.


Measuring nqo1 bioactivation using [²h<inf>7</inf>]glucose
Rohit Mahar, Mario C. Chang, and Matthew E. Merritt
MDPI AG
Treatment of cancers with β-lapachone causes NAD(P)H: quinone oxidoreductase 1 (NQO1) to generate an unstable hydroquinone that regenerates itself in a futile cycle while producing reactive oxygen species (ROS) in the form of superoxide and subsequently hydrogen peroxide. Rapid accumulation of ROS damages DNA, hyperactivates poly-ADP-ribose polymerase-I, causes massive depletion of NAD+/ATP, and hampers glycolysis. Cells overexpressing NQO1 subsequently die rapidly through an NAD+-keresis mechanism. Assessing changes in glycolytic rates caused by NQO1 bioactivation would provide a means of assessing treatment efficacy, potentially lowering the chemotherapeutic dosage, and reducing off-target toxicities. NQO1-mediated changes in glycolytic flux were readily detected in A549 (lung), MiaPaCa2 (pancreatic), and HCT-116 (colon) cancer cell lines by 2H-NMR after administration of [2H7]glucose. The deuterated metabolic products 2H-lactate and HDO were quantified, and linear relationships with glucose consumption for both products were observed. The higher concentration of HDO compared to 2H-lactate allows for more sensitive measurement of the glycolytic flux in cancer. Gas chromatography-mass spectrometry analysis agreed with the NMR results and confirmed downregulated energy metabolism in NQO1+ cells after β-lapachone treatment. The demonstrated method is ideal for measuring glycolytic rates, the effects of chemotherapeutics that target glycolysis, and has the potential for in vivo translation.


Deuterated water imaging of the rat brain following metabolism of [²H<inf>7</inf>]glucose
Rohit Mahar, Huadong Zeng, Anthony Giacalone, Mukundan Ragavan, Thomas H. Mareci, and Matthew E. Merritt
Wiley
PurposeTo determine whether deuterated water (HDO) generated from the metabolism of [2H7]glucose is a sensitive biomarker of cerebral glycolysis and oxidative flux.MethodsA bolus of [2H7]glucose was injected through the tail vein at 1.95 g/kg into Sprague‐Dawley rats. A 2H surface coil was placed on top of the head to record 2H spectra of the brain every 1.3 minutes to measure glucose uptake and metabolism to HDO, lactate, and glutamate/glutamine. A two‐point Dixon method based on a gradient‐echo sequence was used to reconstruct deuterated glucose and water (HDO) images selectively.ResultsThe background HDO signal could be detected and imaged before glucose injection. The 2H NMR spectra showed arrival of [2H7]glucose and its metabolism in a time‐dependent manner. A ratio of the HDO to glutamate/glutamine resonances demonstrates a pseudo–steady state following injection, in which cerebral metabolism dominates wash‐in of HDO generated by peripheral metabolism. Brain spectroscopy reveals that HDO generation is linear with lactate and glutamate/glutamine appearance in the appropriate pseudo–steady state window. Selective imaging of HDO and glucose is easily accomplished using a gradient‐echo method.ConclusionMetabolic imaging of HDO, as a marker of glucose, lactate, and glutamate/glutamine metabolism, has been shown here for the first time. Cerebral glucose metabolism can be assessed efficiently using a standard gradient‐echo sequence that provides superior in‐plane resolution compared with CSI‐based techniques.


¹⁵N-carnitine, a novel endogenous hyperpolarized MRI probe with long signal lifetime
Cornelius von Morze, John A. Engelbach, Galen D. Reed, Albert P. Chen, James D. Quirk, Tyler Blazey, Rohit Mahar, Craig R. Malloy, Joel R. Garbow, and Matthew E. Merritt
Wiley
PurposeThe purpose of this study was to investigate hyperpolarization and in vivo imaging of [15N]carnitine, a novel endogenous MRI probe with long signal lifetime.MethodsL‐[15N]carnitine‐d9 was hyperpolarized by the method of dynamic nuclear polarization followed by rapid dissolution. The T1 signal lifetimes were estimated in aqueous solution and in vivo following intravenous injection in rats, using a custom‐built dual‐tuned 15N/1H RF coil at 4.7 T. 15N chemical shift imaging and 15N fast spin‐echo images of rat abdomen were acquired 3 minutes after [15N]carnitine injection.ResultsEstimated T1 times of [15N]carnitine at 4.7 T were 210 seconds (in H2O) and 160 seconds (in vivo), with an estimated polarization level of 10%. Remarkably, the [15N]carnitine coherence was detectable in rat abdomen for 5 minutes after injection for the nonlocalized acquisition. No downstream metabolites were detected on localized or nonlocalized 15N spectra. Diffuse liver enhancement was detected on 15N fast spin‐echo imaging 3 minutes after injection, with mean hepatic SNR of 18 ± 5 at a spatial resolution of 4 × 4 mm.ConclusionThis study showed the feasibility of hyperpolarizing and imaging the biodistribution of HP [15N]carnitine.


ROS and hypoxia signaling regulate periodic metabolic arousal during insect dormancy to coordinate glucose, amino acid, and lipid metabolism
Chao Chen, Rohit Mahar, Matthew E. Merritt, David L. Denlinger, and Daniel A. Hahn
Proceedings of the National Academy of Sciences
Significance Organisms from bacterial spores, plant seeds, and invertebrate cysts to diapausing insects and mammalian hibernators dramatically suppress metabolism to save energy during dormant periods. Understanding regulatory mechanisms controlling metabolic depression provides insights into fundamental control of energy use during dormancy and offers perspectives that may allow artificial induction and breaking of dormancy. Some insects and mammalian hibernators show periodic arousal from metabolic depression during dormancy. We show that insects follow similar metabolic tactics during torpor and periodic arousal as mammalian hibernators, characterized by anaerobic metabolism during depression and aerobic metabolism during arousal, emphasizing fundamental similarities in metabolic regulation. Physiological levels of ROS regulate the switch from metabolic depression to periodic arousal thereby controlling substrate flow into the tricarboxylic acid cycle.


HDO production from [²H<inf>7</inf>]glucose Quantitatively Identifies Warburg Metabolism
Rohit Mahar, Patrick L. Donabedian, and Matthew E. Merritt
Springer Science and Business Media LLC
AbstractIncreased glucose uptake and aerobic glycolysis are striking features of many cancers. These features have led to many techniques for screening and diagnosis, but many are expensive, less feasible or have harmful side-effects. Here, we report a sensitive 1H/2H NMR method to measure the kinetics of lactate isotopomer and HDO production using a deuterated tracer. To test this hypothesis, HUH-7 hepatocellular carcinoma and AML12 normal hepatocytes were incubated with [2H7]glucose. 1H/2H NMR data were recorded for cell media as a function of incubation time. The efflux rate of lactate-CH3, lactate-CH2D and lactate-CHD2 was calculated as 0.0033, 0.0071, and 0.0.012 µmol/106cells/min respectively. Differential production of lactate isotopomers was due to deuterium loss during glycolysis. Glucose uptake and HDO production by HUH-7 cells showed a strong correlation, indicating that monitoring the HDO production could be a diagnostic feature in cancers. Deuterium mass balance of [2H7]glucose uptake to 2H-lactate and HDO production is quantitatively matched, suggesting increasing HDO signal could be used to diagnose Warburg (cancer) metabolism. Measuring the kinetics of lactate isotopomer and HDO production by 1H and 2H MR respectively are highly sensitive. Increased T1 of 2H-lactate isotopomers indicates inversion/saturation recovery methods may be a simple means of generating metabolism-based contrast.


Branched chain amino acids and carbohydrate restriction exacerbate ketogenesis and hepatic mitochondrial oxidative dysfunction during NAFLD
Muhammed S. Muyyarikkandy, Marc McLeod, Meghan Maguire, Rohit Mahar, Nathan Kattapuram, Christine Zhang, Chaitra Surugihalli, Vaishna Muralidaran, Kruthi Vavilikolanu, Clayton E. Mathews,et al.
Wiley
Mitochondrial adaptation during non‐alcoholic fatty liver disease (NAFLD) include remodeling of ketogenic flux and sustained tricarboxylic acid (TCA) cycle activity, which are concurrent to onset of oxidative stress. Over 70% of obese humans have NAFLD and ketogenic diets are common weight loss strategies. However, the effectiveness of ketogenic diets toward alleviating NAFLD remains unclear. We hypothesized that chronic ketogenesis will worsen metabolic dysfunction and oxidative stress during NAFLD. Mice (C57BL/6) were kept (for 16‐wks) on either a low‐fat, high‐fat, or high‐fat diet supplemented with 1.5X branched chain amino acids (BCAAs) by replacing carbohydrate calories (ketogenic). The ketogenic diet induced hepatic lipid oxidation and ketogenesis, and produced multifaceted changes in flux through the individual steps of the TCA cycle. Higher rates of hepatic oxidative fluxes fueled by the ketogenic diet paralleled lower rates of de novo lipogenesis. Interestingly, this metabolic remodeling did not improve insulin resistance, but induced fibrogenic genes and inflammation in the liver. Under a chronic “ketogenic environment,” the hepatocyte diverted more acetyl‐CoA away from lipogenesis toward ketogenesis and TCA cycle, a milieu which can hasten oxidative stress and inflammation. In summary, chronic exposure to ketogenic environment during obesity and NAFLD has the potential to aggravate hepatic mitochondrial dysfunction.


Quantitative µMRI and PLM study of rabbit humeral and femoral head cartilage at sub-10 µm resolutions
Syeda Batool, Rohit Mahar, Farid Badar, Austin Tetmeyer, and Yang Xia
Wiley
ABSTRACTThis study aimed to establish the baseline characteristics in humeral and femoral cartilage in rabbit, using quantitative magnetic resonance imaging (MRI) relaxation times (T2, T1ρ, and T1) at 9.75 and 70–82 µm pixel resolutions, and quantitative polarized light microscopy (PLM) measures (retardation, angle) at 1.0 and 4.0 µm pixel resolutions. Five intact (i.e., unopened) shoulder joints (the scapula and humeral heads) and three femoral heads of the hip joints from five healthy rabbits were imaged in MRI at 70–82 µm resolution. Thirteen cartilage‐bone specimens were harvested from these joints and imaged in µMRI at 9.75 µm resolution. Subsequently, quantitative PLM study of these specimens enabled the examination of the fibril orientation and organization in both intact joints and individual specimens. Quantitative MRI relaxation data and PLM fibril structural data show distinct features in tissue properties at different depths of cartilage, different in individual histological zones. The thicknesses of the histological zones in µMRI and PLM were successfully obtained. This is the first correlated and quantitative MRI and PLM study of rabbit cartilage at sub‐10 µm resolutions, which benefits future investigation of osteoarthritis using the rabbit model. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1052‐1062, 2020


Quantitative measurement of T2, T1ρ and T1 relaxation times in articular cartilage and cartilage-bone interface by SE and UTE imaging at microscopic resolution
Rohit Mahar, Syeda Batool, Farid Badar, and Yang Xia
Elsevier BV

RECENT SCHOLAR PUBLICATIONS

Detecting altered hepatic lipid oxidation by MRI in an animal model of MASLD
M McLeod, MC Chang, A Rushin, M Ragavan, R Mahar, G Sharma, ...
Cell Reports Medicine 5 (9) 2024



DFT investigation of coupling constant anomalies in substituted β‐lactams
EB Crull, AV Buevich, GE Martin, R Mahar, B Qu, CH Senanayake, ...
Magnetic Resonance in Chemistry 62 (8), 573-582 2024



Cyclodextrin in drug delivery: Exploring scaffolds, properties, and cutting-edge applications
P Singh, R Mahar
International Journal of Pharmaceutics, 124485 2024



Inactivation of mitochondrial MUL1 E3 ubiquitin ligase deregulates mitophagy and prevents diet-induced obesity in mice
L Cilenti, J Di Gregorio, R Mahar, F Liu, CT Ambivero, M Periasamy, ...
Frontiers in Molecular Biosciences 11, 1397565 2024



Age-related differences in affective behaviors in mice: possible role of prefrontal cortical-hippocampal functional connectivity and metabolomic profiles
M Febo, R Mahar, NA Rodriguez, J Buraima, M Pompilus, AM Pinto, ...
Frontiers in Aging Neuroscience 16, 1356086 2024



Exploring the significance, extraction, and characterization of plant-derived secondary metabolites in complex mixtures
R Barthwal, R Mahar
Metabolites 14 (2), 119 2024



Bioactive Compounds from Aquatic Ecosystem
S Puri, R Mahar, G Goswami
Current Status of Fresh Water Microbiology, 387-407 2023



Maturational Differences in Affective Behaviors Involves Changes in Frontal Cortical-Hippocampal Functional Connectivity and Metabolomic Profiles.
M Febo, R Mahar, NA Rodriguez, J Buraima, M Pompilus, AM Pinto, ...
Biorxiv: the Preprint Server for Biology 2023



Comprehensive isotopomer analysis of glutamate and aspartate in small tissue samples
F Cai, D Bezwada, L Cai, R Mahar, Z Wu, MC Chang, P Pachnis, C Yang, ...
Cell metabolism 35 (10), 1830-1843. e5 2023



Design and Discovery of Water-Soluble Benzooxaphosphole-Based Ligands for Hindered Suzuki–Miyaura Coupling Reactions with Low Catalyst Load
ADR Shada, HPR Mangunuru, L Terrab, S Tenneti, NR Kalikinidi, ...
Organic Letters 26 (14), 2751-2757 2023



Deuterium magnetic resonance imaging
P Donabedian, R Mahar, ME Merritt
US Patent App. 17/906,508 2023



Enrichment of hepatic glycogen and plasma glucose from H₂¹⁸O informs gluconeogenic and indirect pathway fluxes in naturally feeding mice
M Coelho, R Mahar, GD Belew, A Torres, C Barosa, F Cabral, I Viegas, ...
NMR in Biomedicine 36 (2), e4837 2023



Segmented Flow Strategies for Integrating Liquid Chromatography–Mass Spectrometry with Nuclear Magnetic Resonance for Lipidomics
J Lei, R Mahar, MC Chang, J Collins, ME Merritt, TJ Garrett, RA Yost
Analytical chemistry 95 (3), 1908-1915 2023



Segmented Flow Strategies for Integrating LC-MS with NMR for Lipidomics
J Lei, R Mahar, MC Chang, J Collins, ME Merritt, TJ Garrett, RA Yost
2022



Metabolic signatures associated with oncolytic myxoma viral infections
R Mahar, M Ragavan, MC Chang, S Hardiman, N Moussatche, A Behar, ...
Scientific Reports 12 (1), 12599 2022



Synergistic effect of -lapachone and aminooxyacetic acid on central metabolism in breast cancer.
MC Chang, R Mahar, MA McLeod, AG Giacalone, X Huang, ...
2022



Synergistic effect of β-lapachone and aminooxyacetic acid on central metabolism in breast cancer
MC Chang, R Mahar, MA McLeod, AG Giacalone, X Huang, ...
Nutrients 14 (15), 3020 2022



Assessment of Tissue Specific Distribution and Seasonal Variation of Alkaloids in Alstonia scholaris
R Mahar, N Manivel, S Kanojiya, DK Mishra, SK Shukla
Metabolites 12 (7), 607 2022



Investigating β-Lapachone Mediated Metabolic Disruption Using Stable Isotope Tracers
Mario C. Chang, Rohit Mahar, Matthew E. Merritt
The FASEB Journal 36 (S1) 2022



Lipogenesis mediated by OGR1 regulates metabolic adaptation to acid stress in cancer cells via autophagy
S Pillai, I Mahmud, R Mahar, C Griffith, M Langsen, J Nguyen, ...
Cell reports 39 (6) 2022

MOST CITED SCHOLAR PUBLICATIONS

Synthesis of triazolo isoquinolines and isochromenes from 2-alkynylbenzaldehyde via domino reactions under transition-metal-free conditions
RK Arigela, S Samala, R Mahar, SK Shukla, B Kundu
The Journal of Organic Chemistry 78 (20), 10476-10484 2013
Citations: 58



ROS and hypoxia signaling regulate periodic metabolic arousal during insect dormancy to coordinate glucose, amino acid, and lipid metabolism
C Chen, R Mahar, ME Merritt, DL Denlinger, DA Hahn
Proceedings of the National Academy of Sciences 118 (1), e2017603118 2021
Citations: 48



A metal-free tandem approach to prepare structurally diverse N-heterocycles: synthesis of 1, 2, 4-oxadiazoles and pyrimidinones
PK Gupta, MK Hussain, M Asad, R Kant, R Mahar, SK Shukla, K Hajela
New Journal of Chemistry 38 (7), 3062-3070 2014
Citations: 44



Rapid screening and quantitative determination of bioactive compounds from fruit extracts of Myristica species and their in vitro antiproliferative activity
R Pandey, R Mahar, M Hasanain, SK Shukla, J Sarkar, KB Rameshkumar, ...
Food Chemistry 211, 483-493 2016
Citations: 40



HDO production from [²H₇]glucose Quantitatively Identifies Warburg Metabolism
R Mahar, PL Donabedian, ME Merritt
Scientific reports 10 (1), 8885 2020
Citations: 37



Lipogenesis mediated by OGR1 regulates metabolic adaptation to acid stress in cancer cells via autophagy
S Pillai, I Mahmud, R Mahar, C Griffith, M Langsen, J Nguyen, ...
Cell reports 39 (6) 2022
Citations: 36



Pyranocarbazoles from Murraya koenigii (L.) Spreng. as antimicrobial agents
T Joshi, T Jain, R Mahar, SK Singh, P Srivastava, SK Shukla, DK Mishra, ...
Natural Product Research 32 (4), 430-434 2018
Citations: 34



Ruthenium (ii)-catalyzed C–H activation/C–N bond formation via in situ generated iminophosphorane as the directing group: construction of annulated pyridin-2 (1H)-ones
RK Arigela, R Kumar, T Joshi, R Mahar, B Kundu
RSC Advances 4 (101), 57749-57753 2014
Citations: 31



Identification of gallic acid based glycoconjugates as a novel tubulin polymerization inhibitors
K Upadhyaya, K Singh, A Arun, M Shukla, N Srivastava, R Ashraf, ...
Organic & biomolecular chemistry 14 (4), 1338-1358 2016
Citations: 30



Branched chain amino acids and carbohydrate restriction exacerbate ketogenesis and hepatic mitochondrial oxidative dysfunction during NAFLD
MS Muyyarikkandy, M McLeod, M Maguire, R Mahar, N Kattapuram, ...
The FASEB Journal 2020
Citations: 28



Synthesis of novel pyrimidine nucleoside analogues owning multiple bases/sugars and their glycosidase inhibitory activity
RK Thakur, A Mishra, KKG Ramakrishna, R Mahar, SK Shukla, ...
Tetrahedron 70 (45), 8462-8473 2014
Citations: 28



Deuterated water imaging of the rat brain following metabolism of [²H₇]glucose
R Mahar, H Zeng, A Giacalone, M Ragavan, TH Mareci, ME Merritt
Magnetic resonance in medicine 85 (6), 3049-3059 2021
Citations: 26



Quantitative measurement of T2, T1ρ and T1 relaxation times in articular cartilage and cartilage-bone interface by SE and UTE imaging at microscopic resolution
R Mahar, S Batool, F Badar, Y Xia
Journal of Magnetic Resonance 297, 76-85 2018
Citations: 24



Synthesis of S-(−)-5,6-Dihydrocanthin-4-ones via a Triple Cooperative Catalysis-Mediated Domino Reaction
SU Dighe, R Mahar, SK Shukla, R Kant, K Srivastava, S Batra
The Journal of Organic Chemistry 81 (11), 4751-4761 2016
Citations: 24



A Strategy for the Synthesis of Anthraquinone-Based Aryl-C-glycosides
N Anand, K Upadhyaya, A Ajay, R Mahar, SK Shukla, B Kumar, ...
The Journal of Organic Chemistry 78 (10), 4685-4696 2013
Citations: 22



Intramolecular C_sp²–C_sp² Friedel–Crafts Arylation: Substrate- and Condition-Controlled Divergent Synthesis of Fused-β-carbolines
SU Dighe, VD Yadav, R Mahar, SK Shukla, S Batra
Organic Letters 18 (23), 6010-6013 2016
Citations: 19



A strategy to access fused triazoloquinoline and related nucleoside analogues
K Upadhyaya, A Ajay, R Mahar, R Pandey, B Kumar, SK Shukla, ...
Tetrahedron 69 (40), 8547-8558 2013
Citations: 19



¹⁵N‐carnitine, a novel endogenous hyperpolarized MRI probe with long signal lifetime
C von Morze, JA Engelbach, GD Reed, AP Chen, JD Quirk, T Blazey, ...
Magnetic resonance in medicine 85 (4), 1814-1820 2021
Citations: 18



Facile ligand-free Pd-catalyzed tandem C–C/C–N coupling reaction: a novel access to highly diverse tetrazole tag isoindoline derivatives
M Sharma, I Khan, S Khan, R Mahar, SK Shukla, R Kant, PMS Chauhan
Tetrahedron Letters 56 (40), 5401-5408 2015
Citations: 13



Expedient base-mediated desulfitative dimethylamination, oxidation, or etherification of 2-(methylsulfanyl)-3, 5-dihydro-4H-imidazol-4-one scaffolds
S Khan, V Tyagi, R Mahar, V Bajpai, B Kumar, PMS Chauhan
Synthesis 45 (17), 2405-2412 2013
Citations: 13