Metabolic Sensor Research Articles

Long-Term Hypercaloric Diet Consumption Exacerbates Age-Induced Dysmetabolism and Carotid Body Dysfunction: Beneficial Effects of CSN Denervation.

Carotid bodies (CBs) are metabolic sensors whose dysfunction is involved in the genesis of dysmetabolic states. Ageing induces significant alterations in CB function also prompting to metabolic deregulation. On the other hand, metabolic disease can accelerate ageing processes. Taking these into account, we evaluated the effect of long-term hypercaloric diet intake and CSN resection on age-induced dysmetabolism and CB function. Experiments were performed in male Wistar rats subjected to 14 or 44 weeks of high-fat high-sucrose (HFHSu) or normal chow (NC) diet and subjected to either carotid sinus nerve (CSN) resection or a sham procedure. After surgery, the animals were kept on a diet for more than 9 weeks. Metabolic parameters, basal ventilation, and hypoxic and hypercapnic ventilatory responses were evaluated. CB type I and type II cells, HIF-1α and insulin receptor (IR), and GLP-1 receptor (GLP1-R)-positive staining were analyzed by immunofluorescence. Ageing decreased by 61% insulin sensitivity in NC animals, without altering glucose tolerance. Short-term and long-term HFHSu intake decreased insulin sensitivity by 55 and 62% and glucose tolerance by 8 and 29%, respectively. CSN resection restored insulin sensitivity and glucose tolerance. Ageing decreased spontaneous ventilation, but short-term or long-term intake of HFHSu diet and CSN resection did not modify basal ventilatory parameters. HFHSu diet increased hypoxic ventilatory responses in young and adult animals, effects attenuated by CSN resection. Ageing, hypercaloric diet, and CSN resection did not change hypercapnic ventilatory responses. Adult animals showed decreased type I cells and IR and GLP-1R staining without altering the number of type II cells and HIF-1α. HFHSu diet increased the number of type I and II cells and IR in young animals without significantly changing these values in adult animals. CSN resection restored the number of type I cells in HFHSu animals and decreased IR-positive staining in all the groups of animals, without altering type II cells, HIF-1α, or GLP-1R staining. In conclusion, long-term hypercaloric diet consumption exacerbates age-induced dysmetabolism, and both short- and long-term hypercaloric diet intakes promote significant alterations in CB function. CSN resection ameliorates these effects. We suggest that modulation of CB activity is beneficial in exacerbated stages of dysmetabolism.

Electro‐metabolic signaling in heart: how local blood flow is regulated

How local blood flow is controlled in heart has proved a mystery after decades of extensive investigation by many research groups. Multiple metabolic products and factors have been suggested to affect coronary blood flow and to contribute its regulation. Nevertheless, how this blood flow is regulated and shown to be responsive to metabolic need remains unclear. Our new observations provided compelling evidence for electro‐metabolic signaling (Zhao et al. PNAS 2020) that originates in ventricular myocytes and is conducted to capillary endothelial cells and then to contractile smooth muscle cells and pericytes. This hypothesis posits that the metabolic sensors are the contractile myocytes themselves and the information distribution system is an electrical network composed of the same capillaries that distribute the oxygen‐rich blood. The “valves” that open to permit more blood to flow to the needy myocytes or close to slow the flow are contractile smooth muscle cells on the end‐arterioles and also the contractile pericytes attached to the capillary endothelial cells and end‐arterioles. Each of these critical elements communicate with the other electrically in a functioning EMS communication system because gap junctions (or the equivalent) connect them. As cardiac myocytes carry out pressure‐volume work, they consume ATP and produce elevated ADP. This leads to a decline in [ATP] and an increase in [ADP], actions that lead to the opening of KATP channels which are hugely abundant in the cardiac myocytes and which drive EMS. This produces a time‐averaged hyperpolarization of the cardiac action potential (AP) which produces a low‐pass filtered hyperpolarization in the neighboring EMS network. To confirm and extend our hypothesis and observations, additional studies have been conducted on perfused and pressurized mouse cardiac papillary muscle preparations to investigate how signals from cardiac myocytes are sent through the neighboring capillaries to the contractile elements. Specifically, gap junction permeable dye (lucifer yellow, LY), was used to trace the intercellular conduction pathway and cdh5‐GCaMP8 mice were used to evaluate the effect of myocyte voltage on capillary endothelial cells function. Optogenetic experiments with channel‐rhodopsin was also used to evaluate the intercellular signals from capillary endothelial cells to pericytes, vascular smooth muscle cells and cardiac myocytes. Our results show that when LY was injected into the cardiac myocytes it was also observed in the neighboring capillaries. Hyperpolarization of cardiac myocyte was also shown to hyperpolarize capillary endothelial cells. These investigations provide stunning and compelling support for electro‐metabolic signaling and lay the foundation for advanced investigations of its dynamic role in health and disease.

SLC3A2 N‐glycosylation and alternate evolutionary trajectories for amino acid metabolism

Cancer and other proliferative diseases are driven by cooperative rewiring of growth signaling and metabolism, where posttranslational modifications to proteins play a critical role in maintaining the disease state. Most PTMs require metabolites as donor substrates, providing underappreciated link between metabolism and signaling. Protein N‐glycosylation and Golgi remodeling of N‐glycan on receptor kinases, T cell receptor, glucagon receptor, and glucose transporters provides feedback between signaling and metabolism. In turn, N‐glycosylation requires uridine diphosphate N‐acetylglucosamine (UDP‐GlcNAc), generated by the hexosamine biosynthesis pathway (HBP) from glucose, glutamine and acetyl‐CoA, where the flux of these substrates into UDP‐GlcNAc are in competition with glycolysis, glutaminolysis and fatty‐acid turnover. Thus, N‐glycan branching, a pathway of N‐acetylglucosaminyltransferases (MGAT1, 2, 4 and 5, avian 6) in the Golgi, is a sensor of central metabolism.In a search for additional glycoproteins that link metabolism, N‐glycosylation and signaling, we identified SLC3A2 (4F2hc, CD98),an adaptor to amino acid (AA) transporters SLC7A5‐11, ‐13 which stabilizes cell surface residency. The SLC3A2*SLC7A5 exchanger imports essential AA that stimulate mTOR signaling and anabolic metabolism, while SLC3A2*SLC7A11 supports glutathione synthesis and mitigation of oxidative stress. Analysis of SLC3A2 N‐glycans revealed stable site‐specific profiles of Golgi remodeling, with the exception of the conserved N365 where branching and poly‐N‐acetyllactosamine content were sensitive to the insertion of lost ancestral sites and to HBP. The N‐glycans are positioned to promote galectin‐mediated clustering with N‐glycosylated Na++/AA symporters and enhance diffusion‐limited flux between exchangers and AA /Na+ symporters. In a successful experiment of Nature, SLC3A2 has been deleted in Neoaves, a clade representing 95% of Ave species that are adapted for flapping flight, the most metabolically intense form of vertebrate locomotion. Neoaves have also acquired a unique N‐glycan branching specificity GnT‐VI (Mgat6, Q9DGD1), which may support an alternate clustering of N‐glycosylated transporters. KEAP1, and four SLC7A family exchangers are also absent, and two others have duplicated, consistent with a shift in metabolic imperatives of Neoaves. The fate of these genes in Primates, Neoaves and Naked mole rat highlights the tension between metabolic rates and oxidative stress that govern lifestyle and longevity.

Galectin‐3 Regulates Oxidant Stress in Obesity

ObjectiveInvestigate the mechanism by which overexpression of Galectin‐3 (GAL3) in the endothelium of obese mice contributes to excess reactive oxygen species (ROS) production and subsequent vascular dysfunction.Methodsdb/db mice, a well‐characterized model of human obesity, were crossed with mice lacking GAL3, a receptor for advanced glycation end products, to generate lean and obese mice with and without GAL3 deletion. Metabolic and cardiovascular endpoints were assessed by mRNA and protein expression in freshly isolated microvascular endothelial cells, microvascular reactivity assessed by pressure myography, and ROS production assessed by dihydroethidium (DHE) staining. Other previously characterized db/db colonies were utilized to further elucidate the mechanistic contributions of GAL3, including mice harboring deletions of NADPH Oxidase I (NOX1), Myostatin (MSTN), and Protein Tyrosine Phosphatase 1B (PTP1B).ResultsDeletion of GAL3 in obese mice had no observable effect on anatomical, metabolic, or plasma phenotype, except for normalizing levels of plasma ROS as evidenced by decrease in thiobarbituric acid reactive substances (TBARS). Obese mice exhibited profound endothelial dysfunction, which was rescued by deletion of GAL3. Our data demonstrate that NOX1, the predominant source of endothelial superoxide production, is significantly downregulated by GAL3 deletion, thereby restoring endothelial function and ameliorating endothelial ROS production in obesity. Furthermore, we demonstrate that GAL3‐mediated NOX1 overexpression is amenable to improvements in metabolic status, such as lowering blood glucose with metformin, improving glucose handling by augmenting muscle mass through deletion of MSTN, or improving insulin signaling through deletion of PTP1B.ConclusionTaken together, these data demonstrate that the overproduction of superoxide by endothelial NOX1 is regulated by the metabolic sensor GAL3 in obesity, leading to endothelial dysfunction and subsequent cardiovascular disease. This pathway presents an attractive target for therapeutic intervention to break the link between aberrant metabolism in obesity and its corresponding vascular pathologies.

Pyruvate kinase, a metabolic sensor powering glycolysis, drives the metabolic control of DNA replication

BackgroundIn all living organisms, DNA replication is exquisitely regulated in a wide range of growth conditions to achieve timely and accurate genome duplication prior to cell division. Failures in this regulation cause DNA damage with potentially disastrous consequences for cell viability and human health, including cancer. To cope with these threats, cells tightly control replication initiation using well-known mechanisms. They also couple DNA synthesis to nutrient richness and growth rate through a poorly understood process thought to involve central carbon metabolism. One such process may involve the cross-species conserved pyruvate kinase (PykA) which catalyzes the last reaction of glycolysis. Here we have investigated the role of PykA in regulating DNA replication in the model system Bacillus subtilis.ResultsOn analysing mutants of the catalytic (Cat) and C-terminal (PEPut) domains of B. subtilis PykA we found replication phenotypes in conditions where PykA is dispensable for growth. These phenotypes are independent from the effect of mutations on PykA catalytic activity and are not associated with significant changes in the metabolome. PEPut operates as a nutrient-dependent inhibitor of initiation while Cat acts as a stimulator of replication fork speed. Disruption of either PEPut or Cat replication function dramatically impacted the cell cycle and replication timing even in cells fully proficient in known replication control functions. In vitro, PykA modulates activities of enzymes essential for replication initiation and elongation via functional interactions. Additional experiments showed that PEPut regulates PykA activity and that Cat and PEPut determinants important for PykA catalytic activity regulation are also important for PykA-driven replication functions.ConclusionsWe infer from our findings that PykA typifies a new family of cross-species replication control regulators that drive the metabolic control of replication through a mechanism involving regulatory determinants of PykA catalytic activity. As disruption of PykA replication functions causes dramatic replication defects, we suggest that dysfunctions in this new family of universal replication regulators may pave the path to genetic instability and carcinogenesis.

MitoQ Inhibits Human Breast Cancer Cell Migration, Invasion and Clonogenicity.

Simple SummarySolid tumors comprise metabolically hostile areas adjacent to metabolically friendly ones, and their distribution fluctuates in space and time. Selection pressure is maximal in hostile areas where cancer cells develop at least four survival strategies: to adapt themselves, to modify the microenvironment, to hibernate metabolically, and to escape. Escape marks the transition from a localized to an invasive tumor that may ultimately disseminate remotely, forming metastases. Based on the hypothesis that mitochondria are metabolic sensors that control these responses, we previously established that mitochondrial superoxide is a pro-metastatic intracellular signaling agent. Here, we tested MitoQ, a mitochondria-targeted ROS inactivator that already successfully passed Phase I safety clinical trials, as a potential inhibitor of the early steps of the metastatic cascade. Using human breast cancer cells as models in anticipation of preclinical and clinical assays, we report that MitoQ inhibits cancer cell migration, invasion, clonogenicity, sphere formation and spheroid stability.To successfully generate distant metastases, metastatic progenitor cells must simultaneously possess mesenchymal characteristics, resist to anoïkis, migrate and invade directionally, resist to redox and shear stresses in the systemic circulation, and possess stem cell characteristics. These cells primarily originate from metabolically hostile areas of the primary tumor, where oxygen and nutrient deprivation, together with metabolic waste accumulation, exert a strong selection pressure promoting evasion. Here, we followed the hypothesis according to which metastasis as a whole implies the existence of metabolic sensors. Among others, mitochondria are singled out as a major source of superoxide that supports the metastatic phenotype. Molecularly, stressed cancer cells increase mitochondrial superoxide production, which activates the transforming growth factor-β pathway through src directly within mitochondria, ultimately activating focal adhesion kinase Pyk2. The existence of mitochondria-targeted antioxidants constitutes an opportunity to interfere with the metastatic process. Here, using aggressive triple-negative and HER2-positive human breast cancer cell lines as models, we report that MitoQ inhibits all the metastatic traits that we tested in vitro. Compared to other mitochondria-targeted antioxidants, MitoQ already successfully passed Phase I safety clinical trials, which provides an important incentive for future preclinical and clinical evaluations of this drug for the prevention of breast cancer metastasis.

Sulfide Oxidation Evidences the Immediate Cellular Response to a Decrease in the Mitochondrial ATP/O2 Ratio.

The present article will not attempt to deal with sulfide per se as a signaling molecule but will aim to examine the consequences of sulfide oxidation by mitochondrial sulfide quinone reductase in mammalian cells. This oxidation appears first as a priority to avoid self-poisoning by endogenous sulfide and second to occur with the lowest ATP/O2 ratio when compared to other mitochondrial substrates. This is explained by the injection of electrons in the respiratory chain after complex I (as for succinate) and by a sulfur oxidation step implying a dioxygenase that consumes oxygen but does not contribute to mitochondrial bioenergetics. Both contribute to increase cellular oxygen consumption if sulfide is provided below its toxic level (low µM). Accordingly, if oxygen supply or respiratory chain activity becomes a limiting factor, small variations in sulfide release impact the cellular ATP/ADP ratio, a major metabolic sensor.

Lactiplantibacillus plantarum K8-based paraprobiotics prevents obesity and obesity-induced inflammatory responses in high fat diet-fed mice

This study was conducted to investigate the effect of the paraprobiotics, lactic acid bacteria lysates (LAB-P) prepared from Lactiplantibacillus plantarum K8, on obesity and obesity-induced inflammatory responses in high-fat diet (HFD)-fed mice. LAB-P (100 mg/kg) significantly decreased the HFD-induced increase in weight by approximately 20% compared to that in the HFD control. This result was accompanied by a decrease in adipose weight/size. The white adipose tissue weight of epididymis, subcutaneous inguinal region, and mesentery were decreased by 36%, 20%, and 40%, respectively, in LAB-P (100 mg/kg)-administered mice. The size of the epididymal white adipose tissue-derived adipocytes was reduced by 41%. The LAB-P-mediated reduction in adipose tissues was associated with downregulation of adipogenic factors, such as peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα). In addition, LAB-P administration reduced total cholesterol and low-density lipoprotein levels by 23% and 42%, respectively, with a 55% reduction in lactate dehydrogenase levels. Stromal vascular fraction-derived adipose tissue macrophages were favorably regulated by LAB-P administration; the expression of CD11c, an inflammatory marker, was reduced by 30%, and that of CD206, an anti-inflammatory marker, was increased by 9-fold. These results were shown to correlated with the inhibition of proinflammatory cytokines (IL-1β and IL-6) and downregulation of NF-κB expression. Furthermore, LAB-P administration suppressed HFD-induced fatty liver by activating AMPKα, an energy metabolic sensor. This study indicates that LAB-P effectively prevents HFD-induced obesity and obesity-induced inflammatory responses and serves a valuable basic work for utilizing LAB-P as functional food ingredient to preventing obesity and treating obesity-associated inflammatory diseases.

Sperm histone H3 lysine 4 tri-methylation serves as a metabolic sensor of paternal obesity and is associated with the inheritance of metabolic dysfunction

ObjectiveParental environmental exposures can strongly influence descendant risks for adult disease. How paternal obesity changes the sperm chromatin leading to the acquisition of metabolic disease in offspring remains controversial and ill-defined. The objective of this study was to assess (1) whether obesity induced by a high-fat diet alters sperm histone methylation; (2) whether paternal obesity can induce metabolic disturbances across generations; (3) whether there could be cumulative damage to the sperm epigenome leading to enhanced metabolic dysfunction in descendants; and (4) whether obesity-sensitive regions associate with embryonic epigenetic and transcriptomic profiles. Using a genetic mouse model of epigenetic inheritance, we investigated the role of histone H3 lysine 4 methylation (H3K4me3) in the paternal transmission of metabolic dysfunction. This transgenic mouse overexpresses the histone demethylase enzyme KDM1A in the developing germline and has an altered sperm epigenome at the level of histone H3K4 methylation. We hypothesized that challenging transgenic sires with a high-fat diet would further erode the sperm epigenome and lead to enhanced metabolic disturbances in the next generations. MethodsTo assess whether paternal obesity can have inter- or transgenerational impacts, and if so to identify potential mechanisms of this non-genetic inheritance, we used wild-type C57BL/6NCrl and transgenic males with a pre-existing altered sperm epigenome. To induce obesity, sires were fed either a control or high-fat diet (10% or 60% kcal fat, respectively) for 10–12 weeks, then bred to wild-type C57BL/6NCrl females fed a regular diet. F1 and F2 descendants were characterized for metabolic phenotypes by examining the effects of paternal obesity by sex, on body weight, fat mass distribution, the liver transcriptome, intraperitoneal glucose, and insulin tolerance tests. To determine whether obesity altered the F0 sperm chromatin, native chromatin immunoprecipitation-sequencing targeting H3K4me3 was performed. To gain insight into mechanisms of paternal transmission, we compared our sperm H3K4me3 profiles with embryonic and placental chromatin states, histone modification, and gene expression profiles. ResultsObesity-induced alterations in H3K4me3 occurred in genes implicated in metabolic, inflammatory, and developmental processes. These processes were associated with offspring metabolic dysfunction and corresponded to genes enriched for H3K4me3 in embryos and overlapped embryonic and placenta gene expression profiles. Transgenerational susceptibility to metabolic disease was only observed when obese F0 had a pre-existing modified sperm epigenome. This coincided with increased H3K4me3 alterations in sperm and more severe phenotypes affecting their offspring. ConclusionsOur data suggest sperm H3K4me3 might serve as a metabolic sensor that connects paternal diet with offspring phenotypes via the placenta. This non-DNA-based knowledge of inheritance has the potential to improve our understanding of how environment shapes heritability and may lead to novel routes for the prevention of disease. This study highlights the need to further study the connection between the sperm epigenome, placental development, and children's health. Summary sentencePaternal obesity impacts sperm H3K4me3 and is associated with placenta, embryonic and metabolic outcomes in descendants.

VDAC1: a structural interface between primary cilia and metabolism?

The primary cilium (PC), a ubiquitous microtubule (MT)-based organelle that protrudes from the apical surface of most human cells, is essential for transducing signals required for growth control. Many cancers exhibit near- complete loss of cilia during the early stages of oncogenic transformation. Our lab recently showed that the hypoxia-induced cleaved form of the mitochondrial outer membrane channel VDAC1 (VDAC1-ΔC) is a critical regulator of both glycolysis and ciliogenesis. Our current work aims to delineate the molecular mechanisms involved in the cross-talk between mitochondria and ciliogenesis regulation for PC to serve as an intrinsic metabolic sensor capable of creating a tumor permissive microenvironment.

ASIC1a senses lactate uptake to regulate metabolism in neurons

Lactate is a major metabolite largely produced by astrocytes that nourishes neurons. ASIC1a, a Na+ and Ca2+-permeable channel with an extracellular proton sensing domain, is thought to be activated by lactate through chelation of divalent cations, including Ca2+, Mg2+ and Zn2+, that block the channel pore. Here, by monitoring lactate-evoked H+ and Ca2+ transport in cultured mouse cortical and hippocampal neurons, we find that stereo-selective neuronal uptake of L-lactate results in rapid intracellular acidification that triggers H+ extrusion to activate plasma membrane ASIC1a channels, leading to propagating Ca2+ waves into the cytosol and mitochondria. We show that lactate activates ASIC1a at its physiological concentrations, far below that needed to chelate divalent cations. The L-isomer of lactate exerts a much greater effect on ASIC1a-mediated activity than the d-isomer and this stereo-selectivity arises from lactate transporters, which prefer the physiologically common L-lactate. The lactate uptake in turn results in intracellular acidification, which is then followed by a robust acid extrusion. The latter response sufficiently lowers the pH in the vicinity of the extracellular domain of ASIC1a to trigger its activation, resulting in cytosolic and mitochondrial Ca2+ signals that accelerate mitochondrial respiration. Furthermore, blocking ASIC1a led to a robust mitochondrial ROS production induced by L-lactate. Together our results indicate that ASIC1a is a metabolic sensor, which by sensing extracellular pH drop triggered by neuronal lactate uptake with subsequent proton extrusion, transmits a Ca2+ response that is propagated to mitochondria to enhance lactate catabolism and suppress ROS production.

Real-time metabolic heat-based specific growth rate soft sensor for monitoring and control of high molecular weight hyaluronic acid production by Streptococcus zooepidemicus.

This present investigation addressing the metabolic bottleneck in synthesis of high MW HA by Streptococcus zooepidemicus and illustrates the application of calorimetric fed-batch control of µ at a narrower range. Feedforward (FF) and feedback (FB) control was devised to improve the molecular weight (MW) of HA production by S. zooepidemicus. Metabolic heat measurements (Fermentation calorimetry) were modeled to decipher real-time specific growth rate, [Formula: see text] was looped into the PID circuit, envisaged to control [Formula: see text] to their desired setpoint values 0.05 [Formula: see text], 0.1 [Formula: see text], and 0.15 [Formula: see text] respectively. Similarly, a predetermined exponential feed rate irrespective of real-time µ was carried out in FF strategy. The developed FB strategy established a robust control capable of maintaining the specific growth rate (µ) close to the [Formula: see text] value with a minimal tracking error. Exponential feed rate carried out with a lowest [Formula: see text] of 0.05 [Formula: see text] showed an improved MW of HA to 2.98 MDa and 2.94 MDa for the FF and FB-based control strategies respectively. An optimal HA titer of 4.73g/L was achieved in FF control strategy at [Formula: see text]. Superior control of µ at low [Formula: see text] value was observed to influence HA polymerization positively by yielding an improved MW and desired polydispersity index (PDI) of HA. PID control offers advantage over conventional fed-batch method to synthesize HA at an improved MW. Calorimetric signal-based µ control by PID negates adverse effects due to the secretion of other end products albeit maintaining regular metabolic activities. KEY POINTS: First report to compare HA productivities by feedforward and feedback control strategy. Inherent merits of regulating µ at narrower range were entailed. Relationship between operating µ and HA molecular weight was discussed.

Multistability in Macrophage Activation Pathways and Metabolic Implications.

Macrophages are innate immune cells with a dynamic range of reversible activation states including the classical pro-inflammatory (M1) and alternative anti-inflammatory (M2) states. Deciphering how macrophages regulate their transition from one state to the other is key for a deeper understanding of inflammatory diseases and relevant therapies. Common regulatory motifs reported for macrophage transitions, such as positive or double-negative feedback loops, exhibit a switchlike behavior, suggesting the bistability of the system. In this review, we explore the evidence for multistability (including bistability) in macrophage activation pathways at four molecular levels. First, a decision-making module in signal transduction includes mutual inhibitory interactions between M1 (STAT1, NF-KB/p50-p65) and M2 (STAT3, NF-KB/p50-p50) signaling pathways. Second, a switchlike behavior at the gene expression level includes complex network motifs of transcription factors and miRNAs. Third, these changes impact metabolic gene expression, leading to switches in energy production, NADPH and ROS production, TCA cycle functionality, biosynthesis, and nitrogen metabolism. Fourth, metabolic changes are monitored by metabolic sensors coupled to AMPK and mTOR activity to provide stability by maintaining signals promoting M1 or M2 activation. In conclusion, we identify bistability hubs as promising therapeutic targets for reverting or blocking macrophage transitions through modulation of the metabolic environment.

Kir6.1/K-ATP channel in astrocytes is an essential negative modulator of astrocytic pyroptosis in mouse model of depression.

Rationale: Astrocyte dysfunction is one of the important pathological mechanisms of depression. Stress contributes to the onset of depression. As metabolic stress sensor, Kir6.1-contaning K-ATP channel (Kir6.1/K-ATP) is prominently expressed in astrocytes. However, the involvement of Kir6.1/K-ATP channel in depression remains obscure.Methods: Astrocyte-specific Kir6.1 knockout mice were used to prepare two mouse models of depression to explore the role of astrocytic Kir6.1/K-ATP channel in depression. Primary astrocytes were cultured to reveal the underlying mechanism for Kir6.1-regulated astrocytic pyroptosis.Results: We identified that chronic stress reduced the astrocytic Kir6.1 expression in hippocampus of mice. We further observed astrocyte-specific knockout of Kir6.1 induced depressive-like behaviors in mice. Moreover, we found that astrocytic Kir6.1 deletion increased NLRP3-mediated astrocytic pyroptosis in response to stress. Mechanistically, Kir6.1 associated with NLRP3, and this interaction prevented the assembly and activation of NLRP3 inflammasome, thereby inhibition of astrocytic pyroptosis. More importantly, VX-765, an effective and selective inhibitor for NLRP3 inflammasome, could reverse the astrocytic pyroptosis and rescue the deterioration of behaviors in astrocytic Kir6.1 knockout mice.Conclusions: Our findings illustrate that Kir6.1/K-ATP channel in astrocytes is an essential negative modulator of astrocytic pyroptosis and plays a crucial role in depression and suggest that astrocytic Kir6.1/K-ATP channel may be a promising therapeutic target for depression.

Glucose and Serum Deprivation Led to Altered Proliferation, Differentiation Potential and AMPK Activation in Stem Cells from Human Deciduous Tooth.

Stem cell therapy is an evolving treatment strategy in regenerative medicine. Recent studies report stem cells from human exfoliated deciduous teeth could complement the traditional mesenchymal stem cell sources. Stem cells from human exfoliated deciduous teeth exhibit mesenchymal characteristics with multilineage differentiation potential. Mesenchymal stem cells are widely investigated for cell therapy and disease modeling. Although many research are being conducted to address the challenges of mesenchymal stem cell therapy in clinics, most of the studies are still in infancy. Host cell microenvironment is one of the major factors affecting the homing of transplanted stem cell and understanding the factors affecting the fate of stem cells of prime important. In this study we aimed to understand the effects of serum deprivation in stem cells derived from human deciduous tooth. Our study aimed to understand the morphological, transcriptional, cell cycle and stemness based changes of stem cells in nutrient deprived medium. Our results suggest that stem cells in nutrient deprived media undergo low proliferation, high apoptosis and changed the differentiation potential of the stem cells. Serum deprived mesenchymal stem cells exhibited enhanced chondrogenic differentiation potential and reduced osteogenic differentiation potential. Moreover, the activation of key metabolic sensor AMP-activated kinase (AMPK) leads to activation of transcription factors such as FOXO3, which leads to an S phase quiescence. Serum deprivation also enhanced the expression of stemness related genes Sox2 and c-Myc.

Clusterin is involved in mediating the metabolic function of adipose SIRT1

SummarySIRT1 is a metabolic sensor regulating energy homeostasis. The present study revealed that mice with selective overexpression of human SIRT1 in adipose tissue (Adipo-SIRT1) were protected from high-fat diet (HFD)-induced metabolic abnormalities. Adipose SIRT1 was enriched at mitochondria-ER contacts (MERCs) to trigger mitohormesis and unfolded protein response (UPRmt), in turn preventing ER stress. As a downstream target of UPRmt, clusterin was significantly upregulated and acted together with SIRT1 to regulate the protein and lipid compositions at MERCs of adipose tissue. In mice lacking clusterin, HFD-induced metabolic abnormalities were significantly enhanced and could not be prevented by overexpression of SIRT1 in adipose tissue. Treatment with ER stress inhibitors restored adipose SIRT1-mediated beneficial effects on systemic energy metabolism. In summary, adipose SIRT1 facilitated the dynamic interactions and communications between mitochondria and ER, via MERCs, in turn triggering a mild mitochondrial stress to instigate the defense responses against dietary obesity-induced metabolic dysfunctions.

INDY-From Flies to Worms, Mice, Rats, Non-Human Primates, and Humans.

I’m Not Dead Yet (Indy) is a fly homologue of the mammalian SLC13A5 (mSLC13A5) plasma membrane citrate transporter, a key metabolic regulator and energy sensor involved in health, longevity, and disease. Reduction of Indy gene activity in flies, and its homologs in worms, modulates metabolism and extends longevity. The metabolic changes are similar to what is obtained with caloric restriction (dietary restriction). Similar effects on metabolism have been observed in mice and rats. As a citrate transporter, INDY regulates cytoplasmic citrate levels. Indy flies heterozygous for a P-element insertion have increased spontaneous physical activity, increased fecundity, reduced insulin signaling, increased mitochondrial biogenesis, preserved intestinal stem cell homeostasis, lower lipid levels, and increased stress resistance. Mammalian Indy knockout (mIndy-KO) mice have higher sensitivity to insulin signaling, lower blood pressure and heart rate, preserved memory and are protected from the negative effects of a high-fat diet and some of the negative effects of aging. Reducing mIndy expression in human hepatocarcinoma cells has recently been shown to inhibit cell proliferation. Reduced Indy expression in the fly intestine affects intestinal stem cell proliferation, and has recently been shown to also inhibit germ cell proliferation in males with delayed sperm maturation and decreased spermatocyte numbers. These results highlight a new connection between energy metabolism and cell proliferation. The overrall picture in a variety of species points to a conserved role of INDY for metabolism and health. This is illustrated by an association of high mIndy gene expression with non-alcoholic fatty liver disease in obese humans. mIndy (mSLC13A5) coding region mutations (e.g., loss-of-function) are also associated with adverse effects in humans, such as autosomal recessive early infantile epileptic encephalopathy and Kohlschütter−Tönz syndrome. The recent findings illustrate the importance of mIndy gene for human health and disease. Furthermore, recent work on small-molecule regulators of INDY highlights the promise of INDY-based treatments for ameliorating disease and promoting healthy aging.

Interaction of DBC1 with polyoma small T antigen promotes its degradation and negatively regulates tumorigenesis

Deleted in Breast Cancer 1 (DBC1) is an important metabolic sensor. Previous studies have implicated DBC1 in various cellular functions, notably cell proliferation, apoptosis, histone modification, and adipogenesis. However, current reports about the role of DBC1 in tumorigenesis are controversial and designate DBC1 alternatively as a tumor suppressor or a tumor promoter. In the present study, we report that polyoma small T antigen (PyST) associates with DBC1 in mammalian cells, and this interaction leads to the posttranslational downregulation of DBC1 protein levels. When coexpressed, DBC1 overcomes PyST-induced mitotic arrest and promotes the exit of cells from mitosis. Using both transient and stable modes of PyST expression, we also show that cellular DBC1 is subjected to degradation by LKB1, a tumor suppressor and cellular energy sensor kinase, in an AMP kinase-independent manner. Moreover, LKB1 negatively regulates the phosphorylation as well as activity of the prosurvival kinase AKT1 through DBC1 and its downstream pseudokinase substrate, Tribbles 3 (TRB3). Using both transient transfection and stable cell line approaches as well as soft agar assay, we demonstrate that DBC1 has oncogenic potential. In conclusion, our study provides insight into a novel signaling axis that connects LKB1, DBC1, TRB3, and AKT1. We propose that the LKB1–DBC1–AKT1 signaling paradigm may have an important role in the regulation of cell cycle and apoptosis and consequently tumorigenesis.

The role of lipid metabolism in shaping the expansion and the function of regulatory T cells.

Metabolic inflammation, defined as a chronic low-grade inflammation, is implicated in numerous metabolic diseases. In recent years, the role of regulatory T cells (Tregs) as key controllers of metabolic inflammation has emerged, but our comprehension on how different metabolic pathways influence Treg functions needs a deeper understanding. Here we focus on how circulating and intracellular lipid metabolism, in particular cholesterol metabolism, regulates Treg homeostasis, expansion, and functions. Cholesterol is carried through the bloodstream by circulating lipoproteins (chylomicrons, very low-density lipoproteins, low-density lipoproteins). Tregs are equipped with a wide array of metabolic sensors able to perceive and respond to changes in the lipid environment through the activation of different intracellular pathways thus conferring to these cells a crucial metabolic and functional plasticity. Nevertheless, altered cholesterol transport, as observed in genetic dyslipidemias and atherosclerosis, impairs Treg proliferation and function through defective cellular metabolism. The intracellular pathway devoted to the cholesterol synthesis is the mevalonate pathway and several studies have shown that this pathway is essential for Treg stability and suppressive activity. High cholesterol concentrations in the extracellular environment may induce massive accumulation of cholesterol inside the cell thus impairing nutrients sensors and inhibiting the mevalonate pathway. This review summarizes the current knowledge regarding the role of circulating and cellular cholesterol metabolism in the regulation of Treg metabolism and functions. In particular, we will discuss how different pathological conditions affecting cholesterol transport may affect cellular metabolism in Tregs.

Berberine inhibits pancreatic intraepithelial neoplasia by inhibiting glycolysis via the adenosine monophosphate -activated protein kinase pathway

Most cases of pancreatic cancer develop in patients with chronic pancreatitis (CP). Berberine is natural product that exhibits anti-tumor effects in various types of cancer and is used in traditional Chinese medicine. In this study, we demonstrated that berberine inhibited the development of pancreatic intraepithelial neoplasia (PanIN) in an in vivo CP model and an in vitro acinar-to-ductal metaplasia model. As berberine may inhibit glycolysis during the development of PanIN, we measured indicators of glycolysis. Quantitative reverse transcription polymerase chain reaction and western blotting assays revealed that berberine activated the adenosine monophosphate-activated protein kinase (AMPK) pathway. This demonstrated that berberine suppressed glycolysis by targeting AMPK, a key metabolic sensor. Furthermore, berberine acted via the AMPK–hypoxia-inducible factor 1 alpha pathway to achieve suppression of PanIN. These findings show that berberine is a potential therapeutic candidate for preventing the progression of CP to PanIN.