Metabolic Sensor Research Articles

Barley microRNAs as metabolic sensors for soil nitrogen availability

Barley (Hordeum vulgare) is one of the most important crops in the world, ranking 4th in the worldwide production. Crop breeders are facing increasing environmental obstacles in the field, such as drought, salinity but also toxic over fertilization which not only impacts quality of the grain but also an yield. One of the most prevalent mechanisms of gene expression regulation in plants is microRNA-mediated silencing of target genes. We identified 13 barley microRNAs and 2 microRNAs* that are nitrogen excess responsive. Four microRNAs respond only in root, eight microRNAs only in shoot and one displays broad response in roots and shoots. We demonstrate that 2 microRNAs* are induced in barley shoot by nitrogen excess. For all microRNAs we identified putative target genes and confirmed microRNA-guided cleavage sites for ten out of thirteen mRNAs. None of the identified microRNAs or their target genes is known as nitrogen excess responsive. Analysis of expression pattern of thirteen target mRNAs and their cognate microRNAs showed expected correlations of their levels. The plant microRNAs analyzed are also known to respond to nitrogen deprivation and exhibit the opposite expression pattern when nitrogen excess/deficiency conditions are compared. Thus, they can be regarded as metabolic sensors of the regulation of nitrogen homeostasis in plants.

Modulation of Renal Injury by Variable Expression of Myo-Inositol Oxygenase (MIOX) via Perturbation in Metabolic Sensors.

Obesity is associated with perturbations in cellular energy homeostasis and consequential renal injury leading to chronic renal disease (CKD). Myo-inositol oxygenase (MIOX), a tubular enzyme, alters redox balance and subsequent tubular injury in the settings of obesity. Mechanism(s) for such adverse changes remain enigmatic. Conceivably, MIOX accentuates renal injury via reducing expression/activity of metabolic sensors, which perturb mitochondrial dynamics and, if sustained, would ultimately contribute towards CKD. In this brief communication, we utilized MIOX-TG (Transgenic) and MIOXKO mice, and subjected them to high fat diet (HFD) administration. In addition, ob/ob and ob/MIOXKO mice of comparable age were used. Mice fed with HFD had increased MIOX expression and remarkable derangements in tubular injury biomarkers. Decreased expression of p-AMPKα (phospho AMP-activated protein kinase) in the tubules was also observed, and it was accentuated in MIOX-TG mice. Interestingly, ob/ob mice also had decreased p-AMPKα expression, which was restored in ob/MIOXKO mice. Parallel changes were observed in Sirt1/Sirt3 (silent mating type information regulation 2 homolog), and expression of other metabolic sensors, i.e., PGC-1α (Peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and Yin Yang (YY-1). In vitro experiments with tubular cells subjected to palmitate-BSA and MIOX-siRNA had results in conformity with the in vivo observations. These findings link the biology of metabolic sensors to MIOX expression in impaired cellular energy homeostasis with exacerbation/amelioration of renal injury.

Abstract B51: Adaptation to oncogene-induced metabolic stress by MondoA (MLXIP) drives common acute lymphoblastic leukemia (cALL) malignancy

Abstract MondoA (also known as MLXIP, MAX-like protein X interacting protein) is a metabolic stress sensor and a proglycolytic transcription factor potentially involved in metabolic addiction features of leukemia and the Warburg effect. MondoA dimerizes with MLX within the MYC interactome and promotes longevity in C. elegans (Johnson et al., 2014). The MYC interactome comprises the MYC/MAX/MNT/MLX/MLXIP transcription factor network: Its key players MYC, MNT and MLXIP differentially mediate proliferation, differentiation, or metabolism by heterodimerization with MAX or MLX. We previously described MondoA to promote malignancy of common precursor B-cell acute lymphoblastic leukemia (cALL). MondoA knockdown (MKD) in cALL cell lines in xenografted mice reduced the number of leukemic blasts (Sipol, 2014). Here we report that MondoA high expression was observed in ALL subtypes with no MYC overexpression. RNA-sequencing data of 132 primary ALL bone marrow samples confirmed the inverse correlation of MYC and MondoA. Interestingly, in subgroups of ALL with low MYC expression and high MondoA (cALL with BCR-ABL, cALL with TCF3-PBX, cALL with ETV6-RUNX1, and cALL with hyperdiploid karyotype), metabolic gene sets did not appear as upregulated. In contrast, cALL samples with high MYC expression and low MondoA (proB-ALL with MLL rearrangements and B-ALL with IGH-MYC fusion gene) demonstrated upregulation of pathways for oxidative phosphorylation and fatty acid metabolism in addition to targets of E2F, G2M checkpoints, and MYC targets. Using CRISPR/CAS9-mediated knockout (MKO), we demonstrate that MondoA dials down MYC-induced metabolic stress and increases leukemia stress resistance. By limiting mitochondrial pyruvate dehydrogenase (PDH) activity in PDHK1 (pyruvate dehydrogenase kinase 1)-dependent manner, MondoA decreases oxidative phosphorylation. In line with limiting effect of MondoA on oxidative phosphorylation, we observed that MondoA decreases ROS generation in B cells. In conclusion, MondoA is restricting MYC-target gene expression to promote leukemia cell survival by facilitating glycolysis and adaption to oxidative stress. MondoA limits pyruvate availability for the TCA cycle by decreasing PDH activity, thus ensuring consistent glycolytic flux, mediating the Warburg effect, and insuring integrity of leukemia metabolism and ROS balancing in response to oncogene activation. Citation Format: Alexandra Sipol, Erik Hameister, Andreas Petry, Agnes Görlach, Jürgen Ruland, Guenther Richter, Stefan Burdach, Poul Sorensen. Adaptation to oncogene-induced metabolic stress by MondoA (MLXIP) drives common acute lymphoblastic leukemia (cALL) malignancy [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B51.

Energy sensors in drug addiction: A potential therapeutic target.

Addiction is defined as the repeated exposure and compulsive seek of psychotropic drugs that, despite the harmful effects, generate relapse after the abstinence period. The psychophysiological processes associated with drug addiction (acquisition/expression, withdrawal, and relapse) imply important alterations in neurotransmission and changes in presynaptic and postsynaptic plasticity and cellular structure (neuroadaptations) in neurons of the reward circuits (dopaminergic neuronal activity) and other corticolimbic regions. These neuroadaptation mechanisms imply important changes in neuronal energy balance and protein synthesis machinery. Scientific literature links drug-induced stimulation of dopaminergic and glutamatergic pathways along with presence of neurotrophic factors with alterations in synaptic plasticity and membrane excitability driven by metabolic sensors. Here, we provide current knowledge of the role of molecular targets that constitute true metabolic/energy sensors such as AMPK, mTOR, ERK, or KATP in the development of the different phases of addiction standing out the main brain regions (ventral tegmental area, nucleus accumbens, hippocampus, and amygdala) constituting the hubs in the development of addiction. Because the available treatments show very limited effectiveness, evaluating the drug efficacy of AMPK and mTOR specific modulators opens up the possibility of testing novel pharmacotherapies for an individualized approach in drug abuse.

Abstract A03: Preconception paternal DDT exposure and programming of metabolic dysfunction and breast cancer in offspring

Abstract The pesticide dichlorodiphenyltrichloroethane or DDT was widely used in agriculture or to combat insect-borne diseases until the 1970s in the United States and the 1980s in Europe. It continues to be used in developing countries to combat malaria or illegally to protect crops. Because of its prolonged half-life, DDT is a persistent environmental pollutant that still can detected in the American population, particularly in minorities and recent immigrants. Epidemiologic studies have shown that early-life (in utero and early childhood) exposure to DDT is associated with a four-fold increase in breast cancer risk in women, and these findings are supported by animal studies. While maternal DDT exposure in pregnancy has been linked to breast cancer in offspring, the effects of paternal DDT exposure on their progeny’s breast cancer development have not been investigated. Environmental exposures can induce epigenetic changes in paternal sperm and affect the risk of disease in their offspring. Here, we evaluated the effects of preconception exposure to DDT on the male sperm epigenome and programming of offspring’s susceptibility to breast cancer, using a mouse model. Male mice were exposed to DDT (1.7mg/kg body weight) by oral gavage in the preconception window. DDT and control-vehicle (CO) males were then used for sperm collection or housed with female mice, with free access to a standard chow diet, for three days. Pregnancy onset was assessed by the presence of a vaginal plug. The weight and number of pups per litter were determined two days after birth. Pups were weaned at 21 days of age and fed a standard chow diet for the extent of the study. Offspring were weighed weekly and used to study metabolic parameters. Mammary tumors were induced by administration of 15mg of medroxyprogesterone to six-week-old female offspring, followed by oral administration of 1mg 7,12-dimethylbenz[a]anthracene once a week for 3 weeks. RNA extracted from sperm CO and DDT males was used for small RNA-seq analysis. Preconception exposure to DDT altered small noncoding RNAs (e.g., miRNAs and tRNAs) in paternal sperm. In line with that, offspring of DDT-exposed fathers had a significant decrease in birth and weaning weights compared to controls. Further, DDT offspring showed metabolic dysfunction. Compared to CO, female offspring of DDT fathers had significantly accelerated breast tumor growth and a nonsignificant increase in mammary tumor incidence and shorter tumor latency. These tumor phenotypes were linked to mammary tissue inhibition of AMPK, a central metabolic sensor, and increased mTOR activity. In conclusion, our findings support a role for DDT exposure from the paternal lineage in metabolic dysfunction and increased breast cancer development in the offspring. Defining the mechanism by which paternal exposures to EDC such as DDT can promote breast cancer development in offspring is critical to identifying early detection/preventive approaches or treatments for this malignancy in a subset of women. Citation Format: Raquel Santana da Cruz, Hong Cao, Camile Fontelles, Apsra Nasir, Volkan Tekam, M. Idalia Cruz, Lu Jin, Sonia de Assis. Preconception paternal DDT exposure and programming of metabolic dysfunction and breast cancer in offspring [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A03.

OGT suppresses S6K1-mediated macrophage inflammation and metabolic disturbance

Enhanced inflammation is believed to contribute to overnutrition-induced metabolic disturbance. Nutrient flux has also been shown to be essential for immune cell activation. Here, we report an unexpected role of nutrient-sensing O-linked β-N-acetylglucosamine (O-GlcNAc) signaling in suppressing macrophage proinflammatory activation and preventing diet-induced metabolic dysfunction. Overnutrition stimulates an increase in O-GlcNAc signaling in macrophages. O-GlcNAc signaling is down-regulated during macrophage proinflammatory activation. Suppressing O-GlcNAc signaling by O-GlcNAc transferase (OGT) knockout enhances macrophage proinflammatory polarization, promotes adipose tissue inflammation and lipolysis, increases lipid accumulation in peripheral tissues, and exacerbates tissue-specific and whole-body insulin resistance in high-fat-diet-induced obese mice. OGT inhibits macrophage proinflammatory activation by catalyzing ribosomal protein S6 kinase beta-1 (S6K1) O-GlcNAcylation and suppressing S6K1 phosphorylation and mTORC1 signaling. These findings thus identify macrophage O-GlcNAc signaling as a homeostatic mechanism maintaining whole-body metabolism under overnutrition.

The SGLT2 inhibitor canagliflozin suppresses lipid synthesis and interleukin-1 beta in ApoE deficient mice.

Sodium-glucose cotransporter 2 inhibitors such as canagliflozin lower blood glucose and reduce cardiovascular events in people with type 2 diabetes through mechanisms that are not fully understood. Canagliflozin has been shown to increase the activity of the AMP-activated protein kinase (AMPK), a metabolic energy sensor important for increasing fatty acid oxidation and energy expenditure and suppressing lipogenesis and inflammation, but whether AMPK activation is important for mediating some of the beneficial metabolic effects of canagliflozin has not been determined. We, therefore, evaluated the effects of canagliflozin in female ApoE-/- and ApoE-/-AMPK β1-/- mice fed a western diet. Canagliflozin increased fatty acid oxidation and energy expenditure and lowered adiposity, blood glucose and the respiratory exchange ratio independently of AMPK β1. Canagliflozin also suppressed liver lipid synthesis and the expression of ATP-citrate lyase, acetyl-CoA carboxylase and sterol response element-binding protein 1c independently of AMPK β1. Canagliflozin lowered circulating IL-1β and studies in bone marrow-derived macrophages indicated that in contrast with the metabolic adaptations, this effect required AMPK β1. Canagliflozin had no effect on the size of atherosclerotic plaques in either ApoE-/- and ApoE-/-AMPK β1-/- mice. Future studies investigating whether reductions in liver lipid synthesis and macrophage IL-1β are important for the cardioprotective effects of canagliflozin warrant further investigation.

Intestinal mir-794 responds to nanopolystyrene by linking insulin and p38 MAPK signaling pathways in nematode Caenorhabditis elegans.

Caenorhabditis elegans is sensitive to toxicity of environmental pollutants. The alteration in expression of mir-794, a microRNA (miRNA) molecule, mediated a protective response to nanopolystyene (100nm) at predicted environmental concentration (1μg/L) in nematodes. However, the underlying molecular basis for mir-794 function in regulating the response to nanopolystyrene remains largely unclear. In this study, we found that intestinal overexpression of mir-794 caused the susceptibility to nanopolystyrene toxicity, suggesting that mir-794 acted in the intestine to regulate the response to nanopolystyrene. Intestinal overexpression of mir-794 further decreased the expressions of daf-16 encoding a FOXO transcriptional factor in insulin signaling pathway, skn-1 encoding a Nrf transcriptional factor in p38 MAPK signaling pathway, and mdt-15 encoding a lipid metabolic sensor acting downstream of SKN-1 in nanopolystyrene exposed nematodes. Meanwhile, intestinal overexpression of mir-794 could suppress the resistance of nematodes overexpressing intestinal daf-16, skn-1, or mdt-15 containing the corresponding 3' untranslated region (3' UTR) to nanopolystyrene toxicity. Therefore, DAF-16, SKN-1, and MDT-15 acted as the downstream targets of intestinal mir-794 to regulate the response to nanopolystyrene. In the intestine, DAF-16 functioned synergistically with SKN-1 or MDT-15 to regulate the response to nanopolystyrene. Our results suggested that the intestinal mir-794 provided an important epigenetic regulation mechanism to control the response to nanopolystyrene by linking insulin and p38 MAPK signaling pathways in nematodes.

AMPK activation in pregnant human myometrial arteries from high-altitude and intrauterine growth-restricted pregnancies.

High-altitude (>2,500 m) residence increases the incidence of intrauterine growth restriction (IUGR) due, in part, to reduced uterine artery blood flow and impaired myometrial artery (MA) vasodilator response. A role for the AMP-activated protein kinase (AMPK) pathway in protecting against hypoxia-associated IUGR is suggested by genomic and transcriptomic studies in humans and functional studies in mice. AMPK is a hypoxia-sensitive metabolic sensor with vasodilatory properties. Here we hypothesized that AMPK-dependent vasodilation was increased in MAs from high versus low-altitude (<1,700 m) Colorado women with appropriate for gestational age (AGA) pregnancies and reduced in IUGR pregnancies regardless of altitude. Vasoreactivity studies showed that, in AGA pregnancies, MAs from high-altitude women were more sensitive to vasodilation by activation of AMPK with A769662 due chiefly to increased endothelial nitric oxide production, whereas MA responses to AMPK activation in the low-altitude women were endothelium independent. MAs from IUGR compared with AGA pregnancies had blunted vasodilator responses to acetylcholine at high altitude. We concluded that 1) blunted vasodilator responses in IUGR pregnancies confirm the importance of MA vasodilation for normal fetal growth and 2) the increased sensitivity to AMPK activation in AGA pregnancies at high altitude suggests that AMPK activation helped maintain MA vasodilation and fetal growth. These results highlight a novel mechanism for vasodilation of MAs under conditions of chronic hypoxia and suggest that AMPK activation could provide a therapy for increasing uteroplacental blood flow and improving fetal growth in IUGR pregnancies.NEW & NOTEWORTHY Intrauterine growth restriction (IUGR) impairs infant well- being and increases susceptibility to later-in-life diseases for mother and child. Our study reveals a novel role for AMPK in vasodilating the myometrial artery (MA) from women residing at high altitude (>2,500 m) with appropriate for gestational age pregnancies but not in IUGR pregnancies at any altitude.

Relevance of SIRT1-NF-κB Axis as Therapeutic Target to Ameliorate Inflammation in Liver Disease.

Inflammation is an adaptive response in pursuit of homeostasis reestablishment triggered by harmful conditions or stimuli, such as an infection or tissue damage. Liver diseases cause approximately 2 million deaths per year worldwide and hepatic inflammation is a common factor to all of them, being the main driver of hepatic tissue damage and causing progression from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH), cirrhosis and, ultimately, hepatocellular carcinoma (HCC). The metabolic sensor SIRT1, a class III histone deacetylase with strong expression in metabolic tissues such as the liver, and transcription factor NF-κB, a master regulator of inflammatory response, show an antagonistic relationship in controlling inflammation. For this reason, SIRT1 targeting is emerging as a potential strategy to improve different metabolic and/or inflammatory pathologies. In this review, we explore diverse upstream regulators and some natural/synthetic activators of SIRT1 as possible therapeutic treatment for liver diseases.

Lipid metabolic sensors of MDT-15 and SBP-1 regulated the response to simulated microgravity in the intestine of Caenorhabditis elegans

Caenorhabditis elegans is a useful animal model to determine the underlying mechanism for the response to simulated microgravity. In this study, we employed C. elegans as an animal model to investigate the role of lipid metabolic sensors in regulating the response to simulated microgravity. Among the lipid metabolic sensors, simulated microgravity treatment could increase the expressions of sbp-1 and mdt-15. RNAi knockdown of sbp-1 or mdt-15 induced a susceptibility to toxicity of simulated microgravity, suggesting the alteration in SBP-1 and MDT-1 mediated a protective response to simulated microgravity. Tissue-specific activity analysis demonstrated that both MDT-15 and SBP-1 could act in the intestine to regulate the response to simulated microgravity. Genetic interaction analysis further indicated that intestinal MDT-15 acted upstream of SBP-1 to regulate the response to simulated microgravity. During the control of response to simulated microgravity, fatty acyl CoA desaturase FAT-6 was identified as the downstream target of intestinal SBP-1. Therefore, the identified signaling cascade of MDT-15-SBP-1-FAT-6 suggested the important function of lipid metabolic sensors in mediating a novel intestinal signaling pathway to regulate the response to simulated microgravity in nematodes.

Residual Glucose Taste in T1R3 Knockout but not TRPM5 Knockout Mice

Knockout (KO) mice missing the sweet taste receptor subunit T1R3 or the signaling protein TRPM5 have greatly attenuated sweetener preferences. Yet both types of KO mice develop preferences for glucose but not fructose in 24-h tests, which has been attributed to the postoral reinforcing actions of glucose. Here we probed for residual sugar taste sensitivity in KO mice. Unlike wildtype (WT) mice, food-restricted T1R3 KO and TRPM5 KO mice displayed little attraction for 8% glucose and 8% fructose in 1-min, two-bottle choice tests. However, in 1-h tests about half of the T1R3 KO mice displayed a significant preference for glucose over fructose (78-84%), while WT mice showed either no or weak preferences (41-56%) for glucose. Following one-bottle training sessions, WT mice display greater glucose preferences although still weaker than those observed in T1R3 KO mice. In contrast, TRPM5 KO mice were indifferent to sugars in 1-h tests but developed a strong preference for glucose over fructose in 24-h tests. T1R3 taste cells contain the sodium glucose cotransporter 1 (SGLT1) and the ATP-gated K+ (KATP) metabolic sensor, which may mediate the unlearned glucose preference displayed by T1R3 KO mice. Unlike WT mice, many T1R3 KO mice strongly preferred glucose to a non-metabolizable glucose analog (α-methyl-D-glucopyranoside, MDG) in initial 1-h choice tests. Glucose and MDG are both ligands for SGLT1 which indicates that SGLT1 sensing does not mediate the glucose preference of T1R3 KO mice. Instead, KATP sensing and/or other oral sensors are implicated. The MDG findings also argue against postoral sensing as the primary source of the initial glucose preference displayed by T1R3 KO mice. Why only half of the T1R3 KO mice showed this preference in 1-h tests remains to be determined. All T1R3 KO mice preferred glucose to fructose in 24-h tests, which appears to be due to both oral and postoral glucose sensing.

AMP-activated protein kinase in the grass carp Ctenopharyngodon idellus: Molecular characterization, tissue distribution and mRNA expression in response to overwinter starvation stress.

Adenosine monophosphate-activated protein kinase (AMPK) is the main energy sensor in mammals, but limited information is available regarding its role as an energy sensor in nutrient-restricted fish particularly in period of overwinter starvation. The present study aimed to investigate the role of AMPK in the grass carp Ctenopharyngodon idellus through characterization of AMPK full-length cDNAs and the measurement of transcriptional activity in response to overwinter starvation. AMPK is a heterotrimeric serine/threonine kinase that consists of a catalytic alpha (α) subunit complexed with two regulatory subunits, beta (β) and gamma (γ). In our study, we identified nine isoforms of the AMPK family in grass carp and obtained their complete coding sequences (CDS). In the grass carp, the α subunit is encoded by two isoforms (α1 and α2). The β and γ subunits are encoded by three (β1a, β1b, β2) and four isoforms (γ1, γ2a, γ2b, γ3), respectively. AMPK isoforms in grass carp possess structural features similar to mammalian AMPK and exhibit a high degree of homology with other fish and vertebrate AMPK sequences. The mRNA of nine grass carp AMPK isoforms were found to be expressed in a wide range of tissues in vivo, but the abundance of each AMPK mRNA demonstrated a tissue-dependent expression pattern, indicating that they might be key complexes playing the role of energy metabolism sensors during overwinter starvation conditions. Compared to expression levels in control fish (week 0), the expression of various AMPK isoforms significantly increased in the hepatopancreas of fish exposed to 1week or more of overwinter starvation conditions as follows: week 1 (AMPK α1 and AMPK α2), week8 (AMPK β1b and AMPK γ2b), week 12 (AMPK β2 and AMPK γ1), and week 16 (AMPK β1a, AMPK γ2a, and AMPK γ3). Additionally, compared to expression levels in control fish (week 0), the expression of various AMPK isoforms significantly increased in the adipose tissue of fish exposed to 1week or more of overwinter starvation conditions as follows: week 1(AMPK β1a and AMPK β1b), week 4 (AMPK α1, AMPK α2, AMPK γ1, AMPK γ2b and AMPK γ3), and week 8 (AMPK β2 and AMPK γ2a). Further in vitro analysis revealed that the mRNA levels of AMPK isoforms in hepatocytes (AMPK α1, AMPK α2, AMPK β1a, AMPK β1b, AMPK β2, AMPK γ2b and AMPK γ3) and adipocytes (AMPK γ2a, AMPK γ2b and AMPK γ3) changed significantly with in the first 24h of exposure to the overwinter starvation conditions. These findings confirm that nine AMPK subunits are present in grass carp and that all encode proteins with conserved functional domains. The nine AMPK subunits are all regulated at the transcriptional levels to manage excess energy expenditure during overwinter starvation stress.

Activin-A limits Th17 pathogenicity and autoimmune neuroinflammation via CD39 and CD73 ectonucleotidases and Hif1-α–dependent pathways

In multiple sclerosis (MS), Th17 cells are critical drivers of autoimmune central nervous system (CNS) inflammation and demyelination. Th17 cells exhibit functional heterogeneity fostering both pathogenic and nonpathogenic, tissue-protective functions. Still, the factors that control Th17 pathogenicity remain incompletely defined. Here, using experimental autoimmune encephalomyelitis, an established mouse MS model, we report that therapeutic administration of activin-A ameliorates disease severity and alleviates CNS immunopathology and demyelination, associated with decreased activation of Th17 cells. In fact, activin-A signaling through activin-like kinase-4 receptor represses pathogenic transcriptional programs in Th17-polarized cells, while it enhances antiinflammatory gene modules. Whole-genome profiling and in vivo functional studies revealed that activation of the ATP-depleting CD39 and CD73 ectonucleotidases is essential for activin-A-induced suppression of the pathogenic signature and the encephalitogenic functions of Th17 cells. Mechanistically, the aryl hydrocarbon receptor, along with STAT3 and c-Maf, are recruited to promoter elements on Entpd1 and Nt5e (encoding CD39 and CD73, respectively) and other antiinflammatory genes, and control their expression in Th17 cells in response to activin-A. Notably, we show that activin-A negatively regulates the metabolic sensor, hypoxia-inducible factor-1α, and key inflammatory proteins linked to pathogenic Th17 cell states. Of translational relevance, we demonstrate that activin-A is induced in the CNS of individuals with MS and restrains human Th17 cell responses. These findings uncover activin-A as a critical controller of Th17 cell pathogenicity that can be targeted for the suppression of autoimmune CNS inflammation.

SUN-261 Deletion of Hepatic Kisspeptin Results in Abnormal Glucose Metabolism in Female Mice

Kisspeptin is a hypothalamic protein critical for neuroendocrine control of pubertal development and fertility and is modulated by nutritional signals. Kisspeptin has been localized to specific neurons located in the arcuate and anteroventral periventricular (AVPV) nuclei of the hypothalamus and is secreted to control GnRH mediated pubertal maturation and reproduction. Kisspeptin has also been localized to peripheral tissues including the liver, fat, gonads, intestine and placenta, although its role in these tissues is unclear. The objective of current study is to define the role of hepatic kisspeptin as a metabolic sensor. A floxed Kiss1 mouse has been developed, and ablation of liver-specific Kiss1 was achieved in two to three month old Kiss1f/f male and female mice given a single tail vein injection of thyroid hormone-binding globulin (TBG) promoter-driven Cre recombinase adeno-associated virus (AAV-CRE). A control group of Kiss1f/f male and female mice received an injection of AAV-GFP, expressing green fluorescent protein. Two weeks after injection, a glucose tolerance test (GTT) was performed followed by an insulin tolerance test. To determine whether changes had occurred in the reproductive axis, estrous cyclicity was assessed by daily vaginal smears and estrous cycle phases determined by vaginal cytology. Mice were euthanized four weeks post-injection and tissues were collected for RNA extraction and gene expression analysis via qRT-PCR. As expected, qRT-PCR data showed absence of Kiss1 expression in the liver of AAV-CRE mice compared to AAV-GFP mice with no changes in kisspeptin gene expression were noted in the ovary, testes, spleen, pancreas, arcuate or AVPV. Estrous cyclicity was also not affected by viral ablation of hepatic Kiss1. Elevated fasting glucose and glucose intolerance in the GTT were found in AAV-CRE compared to AAV-GFP females (P < 0.05). No differences in AAV-CRE and AAV-GFP male mice were found, indicating the importance of Kiss1 in glucose homeostasis in females. The insulin tolerance test was not statistically different between groups or treatments. Further research is required to elucidate the mechanism by which hepatic kisspeptin alters glucose metabolism in mice in a sexually-dimorphic fashion.

OR14-07 Association Between Placental Glucose Uptake and Protein O-Glcnacylation and Birth Outcomes in Obese Non-Diabetic Mothers

Increased transport of nutrients such as glucose, across the placenta, has been linked to abnormal fetal growth and pregnancy complications in obese non-diabetic mothers (1); however, the underlying mechanisms are poorly understood. We hypothesized that in placenta, the metabolic and nutrient sensor O-GlcNAc transferase (OGT), highly sensitive to glucose flux through the hexosamine biosynthetic pathway (HBP), responds to maternal obesogenic environment by increasing O-GlcNAc post-translational modification of nucleocytoplasmic proteins in the placenta altering fetal growth trajectories. Tissue biopsies were isolated from placentas collected at term from 26 non-diabetic mothers alongside routine biochemistry and anthropometric data (maternal fasting glucose, glycated hemoglobin (HbA1c), early pregnancy body weight (BMI) and birth weight). OGT and glucose transporter 1 (GLUT1) protein expression as well as tissue levels of O-GlcNAcylation were determined by immunoblotting using specific antibodies. The BeWo choriocarcinoma cell line was also used as an in vitro model of trophoblast to test the effect of high glucose and GLUT1 silencing on the OGT activity by immunoblotting. Maternal BMI was positively correlated to birth weight centile (BWC) (p=0.0130, R2=0.231), maternal fasting glucose (p=0.0177, R2=0.221) and HbA1c levels (p= 0.0156, R2=0.229) as well as placental OGT protein expression (p=0.0294, R2=0.183). The latter was positively associated to the levels of protein O-GlcNAcylation (p=0.0023, R2=0.326). Interestingly, GLUT1 protein levels were positively correlated to BWC (p=0.0056, R2=0.279) and strongly correlated to protein O-GlcNAcylation (p<0.0001, R2=0.507), suggesting an increase in the placental flux of glucose. In agreement with findings in placenta biopsies, in BeWo cells total protein O-GlcNAcylation levels were altered by cell exposure to different glucose levels (5 mM vs 15 mM, p<0.01). This was prevented by downregulating OGT or GLUT1 expression (p<0.001) using gene silencing. In addition, OGT protein levels were negatively associated to AMP-activated protein kinase (AMPK) activation (p=0.0005, R2=0.402) in placenta biopsies identifying a novel cross-talk between two placental nutrient sensors, OGT and AMPK, previously shown in other tissues (2). Accordingly, the silencing of OGT promoted the activation of AMPK (p<0.01) and its downstream target acetyl-CoA carboxylase (ACC) (p<0.01) in BeWo cells, as demonstrated by increased phosphorylation of residues Thr172 and Ser79 for AMPK and ACC respectively. Such obesity-associated cross talk between metabolic and nutrient sensors might disrupt multiple cellular pathways involved in fetal development and growth.

Remodeling Translation Primes CD8+ T-cell Antitumor Immunity.

The requisites for protein translation in T cells are poorly understood and how translation shapes the antitumor efficacy of T cells is unknown. Here we demonstrated that IL15-conditioned T cells were primed by the metabolic energy sensor AMP-activated protein kinase to undergo diminished translation relative to effector T cells. However, we showed that IL15-conditioned T cells exhibited a remarkable capacity to enhance their protein translation in tumors, which effector T cells were unable to duplicate. Studying the modulation of translation for applications in cancer immunotherapy revealed that direct ex vivo pharmacologic inhibition of translation elongation primed robust T-cell antitumor immunity. Our work elucidates that altering protein translation in CD8+ T cells can shape their antitumor capability.

A metabolic sensor controls pathologic ILC2 function to regulate airway inflammation

Abstract Employing models of allergen exposure, pathogen infection, and chronic inflammation, research in the Monticelli lab is examining how the innate immune system responds to tissue-specific cues to modulate cellular metabolism in order to coordinately regulate resolution of inflammation and promotion of tissue homeostasis at the body’s barrier surfaces. Our recent findings indicate that subsets of innate lymphoid cells (ILCs) utilize distinct metabolic pathways to fuel their proliferation and activation, and that this bioenergetic re-wiring influences their proinflammatory and tissue protective functions. Ongoing studies are examining how particular cell-extrinsic signals (such as cytokines) and cell-intrinsic factors (such as enzymes and transcription factors) control this metabolic reprogramming. In new unpublished studies, we’ve found that lung-resident ILC2s upregulate expression of the metabolic ‘sensor’ transcription factor aryl hydrocarbon receptor (Ahr) upon activation with select airway allergens. Genetic or pharmacologic manipulation of Ahr signaling in murine models directly regulated ILC2 responses during airway inflammation, suggesting that ILC2-intrinsic sensing of Ahr ligand metabolites is critical for protection versus progression of innate immune lung disease pathogenesis.

Elevated Glucose and Insulin Levels Decrease DHA Transfer across Human Trophoblasts via SIRT1-Dependent Mechanism.

Gestational diabetes mellitus (GDM) results in reduced docosahexaenoic acid (DHA) transfer to the fetus, likely due to placental dysfunction. Sirtuin-1 (SIRT1) is a nutrient sensor and regulator of lipid metabolism. This study investigated whether the high glucose and insulin condition of GDM regulates DHA transfer and expression of fatty acid transporters and if this effect is related to SIRT1 expression and function. Syncytialized primary human trophoblasts were treated with and without glucose (25 mmol/L) and insulin (10−7 mol/L) for 72 h to mimic the insulin-resistance conditions of GDM pregnancies. In control conditions, DHA transfer across trophoblasts increased in a time- and dose-dependent manner. Exposure to GDM conditions significantly decreased DHA transfer, but increased triglyceride accumulation and fatty acid transporter expression (CD36, FABP3, and FABP4). GDM conditions significantly suppressed SIRT1 mRNA and protein expression. The SIRT1 inhibitor decreased DHA transfer across control trophoblasts, and recombinant SIRT1 and SIRT1 activators restored the decreased DHA transport induced by GDM conditions. The results demonstrate a novel role of SIRT1 in the regulation of DHA transfer across trophoblasts. The suppressed SIRT1 expression and the resultant decrease in placental DHA transfer caused by high glucose and insulin levels suggest new insights of molecular mechanisms linking GDM to fetal DHA deficiency.

The roles of GRP81 as a metabolic sensor and inflammatory mediator.

GPR81 (also named as HCA1) is a member of a subfamily of orphan G-protein coupled receptors (GPCRs), coupled to Gi -type G proteins. GPR81 was discovered in 2001 and identified as the only known endogenous receptor of lactate under physiological conditions in 2008, which opened a new field of research on how lactate may act as a signal moleculealong with the GPR81 expression in the roles of metabolic process and inflammatory response. Recent studies showed that the physiological functions of GPR81 include lipid metabolism in adipose tissues, metabolic excitability in the brain, cellular development, and inflammatory response modulation. These findings may reveal a novel therapeutic strategy to treatclinical,metabolic, and inflammatory diseases. This article will summarize past research on GPR81, including its characteristics of distribution and expression, functional residues, pharmacological, and physiological agonists, involvementin signal transduction, and pharmacological applications.