Systemic and organ-specific anti-inflammatory effects of sodium-glucose cotransporter-2 inhibitors.

Inflammation plays an essential role and is a common feature in the pathogenesis of many chronic diseases. The exact mechanisms through which sodium-glucose cotransporter-2 (SGLT2) inhibitors achieve their much-acclaimed clinical benefits largely remain unknown. In this review, we detail the systemic and tissue- or organ-specific anti-inflammatory effects of SGLT2 inhibitors using evidence from animal and human studies. We discuss the potential pathways through which SGLT2 inhibitors exert their anti-inflammatory effects, including oxidative stress, mitochondrial, and inflammasome pathways. Finally, we highlight the need for further investigation of the extent of the contribution of the anti-inflammatory effects of SGLT2 inhibition to improvements in cardiometabolic and renal outcomes in clinical studies.

Time-Restricted Feeding Ameliorates Methionine-Choline Deficient Diet-Induced Steatohepatitis in Mice.

Non-alcoholic steatohepatitis (NASH) is an inflammatory form of non-alcoholic fatty liver disease (NAFLD), closely associated with disease progression, cirrhosis, liver failure, and hepatocellular carcinoma. Time-restricted feeding (TRF) has been shown to decrease body weight and adiposity and improve metabolic outcomes; however, the effect of TRF on NASH has not yet been fully understood. We had previously reported that inositol polyphosphate multikinase (IPMK) mediates hepatic insulin signaling. Importantly, we have found that TRF increases hepatic IPMK levels. Therefore, we investigated whether there is a causal link between TRF and IPMK in a mouse model of NASH, i.e., methionine- and choline-deficient diet (MCDD)-induced steatohepatitis. Here, we show that TRF alleviated markers of NASH, i.e., reduced hepatic steatosis, liver triglycerides (TG), serum alanine transaminase (ALT) and aspartate aminotransferase (AST), inflammation, and fibrosis in MCDD mice. Interestingly, MCDD led to a significant reduction in IPMK levels, and the deletion of hepatic IPMK exacerbates the NASH phenotype induced by MCDD, accompanied by increased gene expression of pro-inflammatory chemokines. Conversely, TRF restored IPMK levels and significantly reduced gene expression of proinflammatory cytokines and chemokines. Our results demonstrate that TRF attenuates MCDD-induced NASH via IPMK-mediated changes in hepatic steatosis and inflammation.

Time-restricted feeding ameliorates MCDD-induced steatohepatitis in mice.

Non-Alcoholic Steatohepatitis (NASH) is an inflammatory form of Non-Alcoholic Fatty Liver Disease (NAFLD), closely associated with disease progression, cirrhosis, liver failure, and hepatocellular carcinoma. Time-restricted feeding (TRF) has been shown to decrease body weight and adiposity and improve metabolic outcomes, however, the effect of TRF on NASH has not yet been fully understood. We had previously reported that inositol polyphosphate multikinase (IPMK) mediates hepatic insulin signaling. Importantly, we have found that TRF increases hepatic IPMK levels. Therefore, we investigated whether there is a causal link between TRF and IPMK in a mouse model of NASH, i.e., methionine and choline deficient diet (MCDD)-induced steatohepatitis. Here, we show that TRF alleviated markers of NASH, i.e., reduced hepatic steatosis, liver triglycerides (TG), serum alanine transaminase (ALT) and aspartate aminotransferase (AST), inflammation and fibrosis in MCDD mice. Interestingly, MCDD led to a significant reduction in IPMK levels, and the deletion of hepatic IPMK exacerbates the NASH phenotype induced by MCDD, accompanied by increased gene expression of pro-inflammatory chemokines. Conversely, TRF restored IPMK levels and significantly reduced gene expression of proinflammatory cytokines and chemokines. Our results demonstrate that TRF attenuates MCDD-induced NASH via IPMK-mediated changes in hepatic steatosis and inflammation.

Inositol polyphosphate multikinase modulates free fatty acids-induced insulin resistance in primary mouse hepatocytes.

Insulin resistance is a critical mediator of the development of nonalcoholic fatty liver disease (NAFLD). An excess influx of fatty acids to the liver is thought to be a pathogenic cause of insulin resistance and the development of NAFLD. Although elevated levels of free fatty acids (FFA) in plasma contribute to inducing insulin resistance and NAFLD, the molecular mechanism is not completely understood. This study aimed to determine whether inositol polyphosphate multikinase (IPMK), a regulator of insulin signaling, plays any role in FFA-induced insulin resistance in primary hepatocytes. Here, we show that excess FFA decreased IPMK expression, and blockade of IPMK decrease attenuated the FFA-induced suppression of protein kinase B (Akt) phosphorylation in primary mouse hepatocytes (PMH). Moreover, overexpression of IPMK prevented the FFA-induced suppression of Akt phosphorylation by insulin, while knockout of IPMK exacerbated insulin resistance in PMH. In addition, treatment with MG132, a proteasomal inhibitor, inhibits FFA-induced decrease in IPMK expression and Akt phosphorylation in PMH. Furthermore, treatment with the antioxidant N-acetyl cysteine (NAC) significantly attenuated the FFA-induced reduction of IPMK and restored FFA-induced insulin resistance in PMH. In conclusion, our findings suggest that excess FFA reduces IPMK expression and contributes to the FFA-induced decrease in Akt phosphorylation in PMH, leading to insulin resistance. Our study highlights IPMK as a potential therapeutic target for preventing insulin resistance and NAFLD.

Inositol polyphosphate multikinase modulates redox signaling through nuclear factor erythroid 2-related factor 2 and glutathione metabolism.

Maintenance of redox balance plays central roles in a plethora of signaling processes. Although physiological levels of reactive oxygen and nitrogen species are crucial for functioning of certain signaling pathways, excessive production of free radicals and oxidants can damage cell components. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling cascade is the key pathway that mediates cellular response to oxidative stress. It is controlled at multiple levels, which serve to maintain redox homeostasis within cells. We show here that inositol polyphosphate multikinase (IPMK) is a modulator of Nrf2 signaling. IPMK binds Nrf2 and attenuates activation and expression of Nrf2 target genes. Furthermore, depletion of IPMK leads to elevated glutathione and cysteine levels, resulting in increased resistance to oxidants. Accordingly, targeting IPMK may restore redox balance under conditions of cysteine and glutathione insufficiency.

IPMK modulates FFA-induced insulin resistance in primary mouse hepatocytes.

Insulin resistance is a critical mediator of the development of non-alcoholic fatty liver disease (NAFLD). An excess influx of fatty acids to the liver is thought to be a pathogenic cause of insulin resistance and the development of non-alcoholic fatty liver disease (NAFLD). Although elevated levels of free fatty acids (FFA) in plasma contribute to inducing insulin resistance and NAFLD, the molecular mechanism is not completely understood. This study aimed to determine whether inositol polyphosphate multikinase (IPMK), a regulator of insulin signaling, plays any role in FFA-induced insulin resistance in primary hepatocytes. Here, we show that excess FFA decreased IPMK expression, and blockade of IPMK decrease attenuated the FFA-induced suppression of Akt phosphorylation in primary mouse hepatocytes (PMH). Moreover, overexpression of IPMK prevented the FFA-induced suppression of Akt phosphorylation by insulin, while knockout of IPMK exacerbated insulin resistance in PMH. In addition, treatment with MG132, a proteasomal inhibitor, inhibits FFA-induced decrease in IPMK expression and Akt phosphorylation in PMH. Furthermore, treatment with the antioxidant N-Acetyl Cysteine (NAC) significantly attenuated the FFA-induced reduction of IPMK and restored FFA-induced insulin resistance in PMH. In conclusion, our findings suggest that excess FFA reduces IPMK expression and contributes to the FFA-induced decrease in Akt phosphorylation in PMH, leading to insulin resistance. Our study highlights IPMK as a potential therapeutic target for preventing insulin resistance and NAFLD.

Obesity and Overweight: Probing Causes, Consequences, and Novel Therapeutic Approaches Through the American Heart Association's Strategically Focused Research Network.

As the worldwide prevalence of overweight and obesity continues to rise, so too does the urgency to fully understand mediating mechanisms, to discover new targets for safe and effective therapeutic intervention, and to identify biomarkers to track obesity and the success of weight loss interventions. In 2016, the American Heart Association sought applications for a Strategically Focused Research Network (SFRN) on Obesity. In 2017, 4 centers were named, including Johns Hopkins University School of Medicine, New York University Grossman School of Medicine, University of Alabama at Birmingham, and Vanderbilt University Medical Center. These 4 centers were convened to study mechanisms and therapeutic targets in obesity, to train a talented cadre of American Heart Association SFRN-designated fellows, and to initiate and sustain effective and enduring collaborations within the individual centers and throughout the SFRN networks. This review summarizes the central themes, major findings, successful training of highly motivated and productive fellows, and the innovative collaborations and studies forged through this SFRN on Obesity. Leveraging expertise in in vitro and cellular model assays, animal models, and humans, the work of these 4 centers has made a significant impact in the field of obesity, opening doors to important discoveries, and the identification of a future generation of obesity-focused investigators and next-step clinical trials. The creation of the SFRN on Obesity for these 4 centers is but the beginning of innovative science and, importantly, the birth of new collaborations and research partnerships to propel the field forward.

IPMK modulates hepatic glucose production and insulin signaling.

Hepatic glucose production (HGP) is crucial for the maintenance of normal glucose homeostasis. Although hepatic insulin resistance contributes to excessive glucose production, its mechanism is not well understood. Here, we show that inositol polyphosphate multikinase (IPMK), a key enzyme in inositol polyphosphate biosynthesis, plays a role in regulating hepatic insulin signaling and gluconeogenesis both in vitro and in vivo. IPMK-deficient hepatocytes exhibit decreased insulin-induced activation of Akt-FoxO1 signaling. The expression of messenger RNA levels of phosphoenolpyruvate carboxykinase 1 (Pck1) and glucose 6-phosphatase (G6pc), key enzymes mediating gluconeogenesis, are increased in IPMK-deficient hepatocytes compared to wild type hepatocytes. Importantly, re-expressing IPMK restores insulin sensitivity and alleviates glucose production in IPMK-deficient hepatocytes. Moreover, hepatocyte-specific IPMK deletion exacerbates hyperglycemia and insulin sensitivity in mice fed a high-fat diet, accompanied by an increase in HGP during pyruvate tolerance test and reduction in Akt phosphorylation in IPMK deficient liver. Our results demonstrate that IPMK mediates insulin signaling and gluconeogenesis and may be potentially targeted for treatment of diabetes.

The Inositol Phosphate System-A Coordinator of Metabolic Adaptability.

All cells rely on nutrients to supply energy and carbon building blocks to support cellular processes. Over time, eukaryotes have developed increasingly complex systems to integrate information about available nutrients with the internal state of energy stores to activate the necessary processes to meet the immediate and ongoing needs of the cell. One such system is the network of soluble and membrane-associated inositol phosphates that coordinate the cellular responses to nutrient uptake and utilization from growth factor signaling to energy homeostasis. In this review, we discuss the coordinated interactions of the inositol polyphosphates, inositol pyrophosphates, and phosphoinositides in major metabolic signaling pathways to illustrate the central importance of the inositol phosphate signaling network in nutrient responses.

Dolutegravir Suppresses Thermogenesis via Disrupting Uncoupling Protein 1 Expression and Mitochondrial Function in Brown/Beige Adipocytes in Preclinical Models.

BACKGROUND: Antiretroviral therapy (ART) containing integrase strand transfer inhibitors (INSTIs) has been associated with weight gain in both ART initiation and switch studies, especially in women, but the underlying mechanisms are unclear. METHODS: The effects of dolutegravir (DTG) on food intake, energy expenditure, oxygen consumption in female mice, and gene expression from adipose tissues were assessed. Human and murine preadipocytes were treated with DTG either during differentiation into mature brown/beige adipocytes or postdifferentiation. Lipid accumulation, lipolysis, ß-adrenergic response, adipogenic markers, mitochondrial respiration, and insulin response were analyzed. RESULTS: Two-week administration of DTG to female mice reduced energy expenditure, which was accompanied by decreased uncoupling protein 1 (UCP1) expression in brown/beige adipose tissues. In vitro studies showed that DTG significantly reduced brown adipogenic markers, especially UCP1 in brown and beige adipocytes, whereas drugs from other classes did not. Furthermore, a loss of UCP1 by DTG led to a decrease in mitochondrial complex IV component, followed by a reduction in mitochondrial respiratory capacity and reduced insulin-stimulated glucose uptake. CONCLUSIONS: Our findings show that DTG targets UCP1 and mitochondrial functions in brown and beige adipocytes and disrupts thermogenic functions in preclinical models, providing the potential mechanisms by which DTG suppresses energy expenditure leading to weight gain.

Lipid accumulation and oxidation in glioblastoma multiforme.

Glioblastoma multiforme (GBM) is the most common and lethal primary malignant brain tumor in adults. Despite the multimodal standard treatments for GBM, the median survival is still about one year. Analysis of brain tissues from GBM patients shows that lipid droplets are highly enriched in tumor tissues while undetectable in normal brain tissues, yet the identity and functions of lipid species in GBM are not well understood. The aims of the present work are to determine how GBM utilizes fatty acids, and assess their roles in GBM proliferation. Treatment of U138 GBM cells with a monounsaturated fatty acid, oleic acid, induces accumulation of perilipin 2-coated lipid droplets containing triglycerides enriched in C18:1 fatty acid, and increases fatty acid oxidation. Interestingly, oleic acid also increases glucose utilization and proliferation of GBM cells. In contrast, pharmacologic inhibition of monoacylglycerol lipase attenuates GBM proliferation. Our findings demonstrate that monounsaturated fatty acids promote GBM proliferation via triglyceride metabolism, suggesting a novel lipid droplet-mediated pathway which may be targeted for GBM treatment.

Inositol polyphosphate multikinase is a metformin target that regulates cell migration.

Metformin has been shown to alter cell adhesion protein expression, which is thought to play a role in its observed antitumor properties. We found that metformin treatment down-regulated integrin ß1 concomitant with the loss of inositol polyphosphate multikinase (IPMK) in murine myocytes, adipocytes, and hepatocytes. To determine if IPMK was upstream of integrin ß1 expression, we examined IPMK-/- mouse embryonic fibroblast cells and found that integrins ß1 and ß3 gene expression was reduced by half, relative to wild-type cells, whereas focal adhesion kinase (FAK) activity and Rho/Rac/Cdc42 protein levels were increased, resulting in migration defects. Using nanonet force microscopy, we determined that cell:extracellular matrix adhesion and cell contractility forces were decreased, confirming the functional relevance of integrin and Rho protein dysregulation. Pharmacological studies showed that inhibition of both FAK1 and proline-rich tyrosine kinase 2 partially restored integrin ß1 expression, suggesting negative regulation of integrin ß1 by FAK. Together our data indicate that IPMK participates in the regulation of cell migration and provides a potential link between metformin and wound healing impairment.-Tu-Sekine, B., Padhi, A., Jin, S., Kalyan, S., Singh, K., Apperson, M., Kapania, R., Hur, S. C., Nain, A., Kim, S. F. Inositol polyphosphate multikinase is a metformin target that regulates cell migration.

Dexras1 Deletion and Iron Chelation Promote Neuroprotection in Experimental Optic Neuritis.

Dysregulation of iron metabolism, and resultant cytotoxicity, has been implicated in the pathogenesis of multiple sclerosis (MS) and other neurodegenerative processes. Iron accumulation promotes cytotoxicity through various mechanisms including oxidative stress and glutamate toxicity, and occurs in both MS patients and in the experimental autoimmune encephalomyelitis (EAE) model of MS. Divalent Metal Transporter1, a major iron importer in cells, is stimulated by signaling of Dexras1, a small G protein member of the Ras family. Dexras1 is activated by S-nitrosylation by nitric oxide (NO) produced by either inducible nitric oxide synthase in activated microglia/macrophages or neuronal nitric oxide synthase in neurons. Here we show Dexras1 exacerbates oxidative stress-induced neurodegeneration in experimental optic neuritis, an inflammatory demyelinating optic nerve condition that occurs in MS and EAE. Dexras1 deletion, as well as treatment with the iron chelator deferiprone, preserves vision and attenuates retinal ganglion cell (RGC) and axonal loss during EAE optic neuritis. These results suggest that iron entry triggered by NO-activated Dexras1 signaling is a potential mechanism of neuronal death in experimental optic neuritis. The current data suggest modulation of Dexras1 signaling and iron chelation are potential novel treatment strategies for optic neuritis and MS, and possibly other optic neuropathies as well.

Activation of AMPK by metformin improves withdrawal signs precipitated by nicotine withdrawal.

Cigarette smoking is the leading cause of preventable disease and death in the United States, with more persons dying from nicotine addiction than any other preventable cause of death. Even though smoking cessation incurs multiple health benefits, the abstinence rate remains low with current medications. Here we show that the AMP-activated protein kinase (AMPK) pathway in the hippocampus is activated following chronic nicotine use, an effect that is rapidly reversed by nicotine withdrawal. Increasing pAMPK levels and, consequently, downstream AMPK signaling pharmacologically attenuate anxiety-like behavior following nicotine withdrawal. We show that metformin, a known AMPK activator in the periphery, reduces withdrawal symptoms through a mechanism dependent on the presence of the AMPKα subunits within the hippocampus. This study provides evidence of a direct effect of AMPK modulation on nicotine withdrawal symptoms and suggests central AMPK activation as a therapeutic target for smoking cessation.

Reduced sterol regulatory element-binding protein (SREBP) processing through site-1 protease (S1P) inhibition alters oligodendrocyte differentiation in vitro.

The formation of the myelin membrane of the oligodendrocyte in the CNS is a fundamental process requiring the coordinated synthesis of many different components. The myelin membrane is particularly rich in lipids, however, the regulation of this lipid synthesis is not understood. In other cell types, including Schwann cells, the myelin-forming cells of the PNS, lipid synthesis is tightly regulated by the sterol regulatory element-binding protein (SREBP) family of transcription factors, but this has not been previously shown in oligodendrocytes. We investigated SREBPs' role during oligodendrocyte differentiation in vitro. Both SREBP-1 and SREBP-2 were expressed in oligodendrocyte precursor cells and differentiating oligodendrocytes. Using the selective site-1 protease (S1P) inhibitor PF-429242, which inhibits the cleavage of SREBP precursor forms into mature forms, we found that preventing SREBP processing inhibited process growth and reduced the expression level of myelin basic protein, a major component of myelin. Further, process extension deficits could be rescued by the addition of exogenous cholesterol. Blocking SREBP processing reduced mRNA transcription and protein levels of SREBP target genes involved in both the fatty acid and the cholesterol synthetic pathways. Furthermore, de novo levels and total levels of cholesterol synthesis were greatly diminished when SREBP processing was inhibited. Together these results indicate that SREBPs are important regulators of oligodendrocyte maturation and that perturbation of their activity may affect myelin formation and integrity. Cover Image for this issue: doi: 10.1111/jnc.13781.

Neuronal Activity-Induced Sterol Regulatory Element Binding Protein-1 (SREBP1) is Disrupted in Dysbindin-Null Mice-Potential Link to Cognitive Impairment in Schizophrenia.

Schizophrenia is a chronic debilitating neuropsychiatric disorder that affects about 1 % of the population. Dystrobrevin-binding protein 1 (DTNBP1 or dysbindin) is one of the Research Domain Constructs (RDoC) associated with cognition and is significantly reduced in the brain of schizophrenia patients. To further understand the molecular underpinnings of pathogenesis of schizophrenia, we have performed microarray analyses of the hippocampi from dysbindin knockout mice, and found that genes involved in the lipogenic pathway are suppressed. Moreover, we discovered that maturation of a master transcriptional regulator for lipid synthesis, sterol regulatory element binding protein-1 (SREBP1) is induced by neuronal activity, and is required for induction of the immediate early gene ARC (activity-regulated cytoskeleton-associated protein), necessary for synaptic plasticity and memory. We found that nuclear SREBP1 is dramatically reduced in dysbindin-1 knockout mice and postmortem brain tissues from human patients with schizophrenia. Furthermore, activity-dependent maturation of SREBP1 as well as ARC expression were attenuated in dysbindin-1 knockout mice, and these deficits were restored by an atypical antipsychotic drug, clozapine. Together, results indicate an important role of dysbindin-1 in neuronal activity induced SREBP1 and ARC, which could be related to cognitive deficits in schizophrenia.

Lysosomal iron modulates NMDA receptor-mediated excitation via small GTPase, Dexras1.

BACKGROUND: Activation of NMDA receptors can induce iron movement into neurons by the small GTPase Dexras1 via the divalent metal transporter 1 (DMT1). This pathway under pathological conditions such as NMDA excitotoxicity contributes to metal-catalyzed reactive oxygen species (ROS) generation and neuronal cell death, and yet its physiological role is not well understood. RESULTS: We found that genetic and pharmacological ablation of this neuronal iron pathway in the mice increased glutamatergic transmission. Voltage sensitive dye imaging of hippocampal slices and whole-cell patch clamping of synaptic currents, indicated that the increase in excitability was due to synaptic modification of NMDA receptor activity via modulation of the PKC/Src/NR2A pathway. Moreover, we identified that lysosomal iron serves as a main source for intracellular iron signaling modulating glutamatergic excitability. CONCLUSIONS: Our data indicates that intracellular iron is dynamically regulated in the neurons and robustly modulate synaptic excitability under physiological condition. Since NMDA receptors play a central role in synaptic neurophysiology, plasticity, neuronal homeostasis, neurodevelopment as well as in the neurobiology of many diseases, endogenous iron is therefore likely to have functional relevance to each of these areas.

Microsomal PGE2 synthase-1 regulates melanoma cell survival and associates with melanoma disease progression.

COX-2 and its product PGE2 enhance carcinogenesis and tumor progression, which has been previously reported in melanoma. As most COX inhibitors cause much toxicity, the downstream microsomal PGE2 synthase-1 (mPGES1) is a consideration for targeting. Human melanoma TMAs were employed for testing mPGES1 protein staining intensity and percentage levels, and both increased with clinical stage; employing a different Stage III TMA, mPGES1 intensity (not percentage) associated with reduced patient survival. Our results further show that iNOS was also highly expressed in melanoma tissues with high mPGES1 levels, and iNOS-mediated NO promoted mPGES1 expression and PGE2 production. An mPGES1-specific inhibitor (CAY10526) as well as siRNA attenuated cell survival and increased apoptosis. CAY10526 significantly suppressed tumor growth and increased apoptosis in melanoma xenografts. Our findings support the value of a prognostic and predictive role for mPGES1, and suggest targeting this molecule in the PGE2 pathway as another avenue toward improving melanoma therapy.

PKA-mediated phosphorylation of Dexras1 suppresses iron trafficking by inhibiting S-nitrosylation.

Dexras1 is a small GTPase and plays a central role in neuronal iron trafficking. We have shown that stimulation of glutamate receptors activates neuronal nitric oxide synthase, leading to S-nitrosylation of Dexras1 and a physiological increase in iron uptake. Here we report that Dexras1 is phosphorylated by protein kinase A (PKA) on serine 253, leading to a suppression of iron influx. These effects were directly associated with the levels of S-nitrosylated Dexras1, whereby PKA activation reduced Dexras1 S-nitrosylation in a dose dependent manner. Moreover, we found that adiponectin modulates Dexras1 via PKA. Hence these findings suggest the involvement of the PKA pathway in modulating glutamate-mediated ROS in neurons, and hint to a functional crosstalk between S-nitrosylation and phosphorylation.

Acyl-CoA-binding domain containing 3 modulates NAD+ metabolism through activating poly(ADP-ribose) polymerase 1.

NAD(+) plays essential roles in cellular energy homoeostasis and redox state, functioning as a cofactor along the glycolysis and citric acid cycle pathways. Recent discoveries indicated that, through the NAD(+)-consuming enzymes, this molecule may also be involved in many other cellular and biological outcomes such as chromatin remodelling, gene transcription, genomic integrity, cell division, calcium signalling, circadian clock and pluripotency. Poly(ADP-ribose) polymerase 1 (PARP1) is such an enzyme and dysfunctional PARP1 has been linked with the onset and development of various human diseases, including cancer, aging, traumatic brain injury, atherosclerosis, diabetes and inflammation. In the present study, we showed that overexpressed acyl-CoA-binding domain containing 3 (ACBD3), a Golgi-bound protein, significantly reduced cellular NAD(+) content via enhancing PARP1's polymerase activity and enhancing auto-modification of the enzyme in a DNA damage-independent manner. We identified that extracellular signal-regulated kinase (ERK)1/2 as well as de novo fatty acid biosynthesis pathways are involved in ACBD3-mediated activation of PARP1. Importantly, oxidative stress-induced PARP1 activation is greatly attenuated by knocking down the ACBD3 gene. Taken together, these findings suggest that ACBD3 has prominent impacts on cellular NAD(+) metabolism via regulating PARP1 activation-dependent auto-modification and thus cell metabolism and function.