Glycolysis-Mediated Activation of v-ATPase by Nicotinamide Mononucleotide Ameliorates Lipid-Induced Cardiomyopathy by Repressing the CD36-TLR4 Axis.

BACKGROUND: Chronic overconsumption of lipids followed by their excessive accumulation in the heart leads to cardiomyopathy. The cause of lipid-induced cardiomyopathy involves a pivotal role for the proton-pump vacuolar-type H+-ATPase (v-ATPase), which acidifies endosomes, and for lipid-transporter CD36, which is stored in acidified endosomes. During lipid overexposure, an increased influx of lipids into cardiomyocytes is sensed by v-ATPase, which then disassembles, causing endosomal de-acidification and expulsion of stored CD36 from the endosomes toward the sarcolemma. Once at the sarcolemma, CD36 not only increases lipid uptake but also interacts with inflammatory receptor TLR4 (Toll-like receptor 4), together resulting in lipid-induced insulin resistance, inflammation, fibrosis, and cardiac dysfunction. Strategies inducing v-ATPase reassembly, that is, to achieve CD36 reinternalization, may correct these maladaptive alterations. For this, we used NAD+ (nicotinamide adenine dinucleotide)-precursor nicotinamide mononucleotide (NMN), inducing v-ATPase reassembly by stimulating glycolytic enzymes to bind to v-ATPase. METHODS: Rats/mice on cardiomyopathy-inducing high-fat diets were supplemented with NMN and for comparison with a cocktail of lysine/leucine/arginine (mTORC1 [mechanistic target of rapamycin complex 1]-mediated v-ATPase reassembly). We used the following methods: RNA sequencing, mRNA/protein expression analysis, immunofluorescence microscopy, (co)immunoprecipitation/proximity ligation assay (v-ATPase assembly), myocellular uptake of [3H]chloroquine (endosomal pH), and [14C]palmitate, targeted lipidomics, and echocardiography. To confirm the involvement of v-ATPase in the beneficial effects of both supplementations, mTORC1/v-ATPase inhibitors (rapamycin/bafilomycin A1) were administered. Additionally, 2 heart-specific v-ATPase-knockout mouse models (subunits V1G1/V0d2) were subjected to these measurements. Mechanisms were confirmed in pharmacologically/genetically manipulated cardiomyocyte models of lipid overload. RESULTS: NMN successfully preserved endosomal acidification during myocardial lipid overload by maintaining v-ATPase activity and subsequently prevented CD36-mediated lipid accumulation, CD36-TLR4 interaction toward inflammation, fibrosis, cardiac dysfunction, and whole-body insulin resistance. Lipidomics revealed C18:1-enriched diacylglycerols as lipid class prominently increased by high-fat diet and subsequently reversed/preserved by lysine/leucine/arginine/NMN treatment. Studies with mTORC1/v-ATPase inhibitors and heart-specific v-ATPase-knockout mice further confirmed the pivotal roles of v-ATPase in these beneficial actions. CONCLUSION: NMN preserves heart function during lipid overload by preventing v-ATPase disassembly.

Phospholipase D Mediates Glutamine-Induced mTORC1 Activation to Promote Porcine Intestinal Epithelial Cell Proliferation.

BACKGROUND: The intestinal epithelium is one of the fastest self-renewal tissues in the body, and glutamine plays a crucial role in providing carbon and nitrogen for biosynthesis. In intestinal homeostasis, phosphorylation-mediated signaling networks that cause altered cell proliferation, differentiation, and metabolic regulation have been observed. However, our understanding of how glutamine affects protein phosphorylation in the intestinal epithelium is limited, and identifying the essential signaling pathways involved in regulating intestinal epithelial cell growth is particularly challenging. OBJECTIVES: This study aimed to identify the essential proteins and signaling pathways involved in glutamine's promotion of porcine intestinal epithelial cell proliferation. METHODS: Phosphoproteomics was applied to describe the protein phosphorylation landscape under glutamine treatment. Kinase-substrate enrichment analysis was subjected to predict kinase activity and validated by qRT-PCR and Western blotting. Cell Counting Kit-8, glutamine rescue experiment, chloroquine treatment, and 5-fluoro-2-indolyl deschlorohalopemide inhibition assay revealed the possible underlying mechanism of glutamine promoting porcine intestinal epithelial cell proliferation. RESULTS: In this study, glutamine starvation was found to significantly suppress the proliferation of intestinal epithelial cells and change phosphoproteomic profiles with 575 downregulated sites and 321 upregulated sites. Interestingly, phosphorylation of eukaryotic initiation factor 4E-binding protein 1 at position Threonine70 was decreased, which is a crucial downstream of the mechanistic target of rapamycin complex 1 (mTORC1) pathway. Further studies showed that glutamine supplementation rescued cell proliferation and mTORC1 activity, dependent on lysosomal function and phospholipase D activation. CONCLUSION: In conclusion, glutamine activates mTORC1 signaling dependent on phospholipase D and a functional lysosome to promote intestinal epithelial cell proliferation. This discovery provides new insight into regulating the homeostasis of the intestinal epithelium, particularly in pig production.

Folate depletion induces erythroid differentiation through perturbation of de novo purine synthesis.

Folate, an essential vitamin, is a one-carbon acceptor and donor in key metabolic reactions. Erythroid cells harbor a unique sensitivity to folate deprivation, as revealed by the primary pathological manifestation of nutritional folate deprivation: megaloblastic anemia. To study this metabolic sensitivity, we applied mild folate depletion to human and mouse erythroid cell lines and primary murine erythroid progenitors. We show that folate depletion induces early blockade of purine synthesis and accumulation of the purine synthesis intermediate and signaling molecule, 5'-phosphoribosyl-5-aminoimidazole-4-carboxamide (AICAR), followed by enhanced heme metabolism, hemoglobin synthesis, and erythroid differentiation. This is phenocopied by inhibition of folate metabolism using the inhibitor SHIN1, and by AICAR supplementation. Mechanistically, the metabolically driven differentiation is independent of mechanistic target of rapamycin complex 1 (mTORC1) and adenosine 5'-monophosphate-activated protein kinase (AMPK) and is instead mediated by protein kinase C. Our findings suggest that folate deprivation-induced premature differentiation of erythroid progenitor cells is a molecular etiology to folate deficiency-induced anemia.

Stearic acid promotes lipid synthesis through CD36/Fyn/FAK/mTORC1 axis in bovine mammary epithelial cells.

Stearic acid (C18:0, SA) is a saturated long-chain fatty acid (LCFA) that has a prominent function in lactating dairy cows. It is obtained primarily from the diet and is stored in the form of triacylglycerol (TAG) molecules. The transmembrane glycoprotein cluster of differentiation 36 (CD36) is also known as fatty acid translocase, but whether SA promotes lipid synthesis through CD36 and FAK/mTORC1 signaling is unknown. In this study, we examined the function and mechanism of CD36-mediated SA-induced lipid synthesis in bovine mammary epithelial cells (BMECs). SA-enriched supplements enhanced lipid synthesis and the FAK/mTORC1 pathway in BMECs. SA-induced lipid synthesis, FAK/mTORC1 signaling, and the expression of lipogenic genes were impaired by anti-CD36 and the CD36-specific inhibitor SSO, whereas overexpression of CD36 effected the opposite results. Inhibition of FAK/mTORC1 by TAE226/Rapamycin attenuated SA-induced TAG synthesis, inactivated FAK/mTORC1 signaling, and downregulated the lipogenic genes PPARG, CD36, ACSL1, SCD, GPAT4, LIPIN1, and DGAT1 at the mRNA and protein levels in BMECs. By coimmunoprecipitation and yeast two-hybrid screen, CD36 interacted directly with Fyn but not Lyn, and Fyn bound directly to FAK; FAK also interacted directly with TSC2. CD36 linked FAK through Fyn, and FAK coupled mTORC1 through TSC2 to form the CD36/Fyn/FAK/mTORC1 signaling axis. Thus, stearic acid promotes lipogenesis through CD36 and Fyn/FAK/mTORC1 signaling in BMECs. Our findings provide novel insights into the underlying molecular mechanisms by which LCFA supplements promote lipid synthesis in BMECs.

Glutamine deficiency drives transforming growth factor-ß signaling activation that gives rise to myofibroblastic carcinoma-associated fibroblasts.

Tumor-promoting carcinoma-associated fibroblasts (CAFs), abundant in the mammary tumor microenvironment (TME), maintain transforming growth factor-ß (TGF-ß)-Smad2/3 signaling activation and the myofibroblastic state, the hallmark of activated fibroblasts. How myofibroblastic CAFs (myCAFs) arise in the TME and which epigenetic and metabolic alterations underlie activated fibroblastic phenotypes remain, however, poorly understood. We herein show global histone deacetylation in myCAFs present in tumors to be significantly associated with poorer outcomes in breast cancer patients. As the TME is subject to glutamine (Gln) deficiency, human mammary fibroblasts (HMFs) were cultured in Gln-starved medium. Global histone deacetylation and TGF-ß-Smad2/3 signaling activation are induced in these cells, largely mediated by class I histone deacetylase (HDAC) activity. Additionally, mechanistic/mammalian target of rapamycin complex 1 (mTORC1) signaling is attenuated in Gln-starved HMFs, and mTORC1 inhibition in Gln-supplemented HMFs with rapamycin treatment boosts TGF-ß-Smad2/3 signaling activation. These data indicate that mTORC1 suppression mediates TGF-ß-Smad2/3 signaling activation in Gln-starved HMFs. Global histone deacetylation, class I HDAC activation, and mTORC1 suppression are also observed in cultured human breast CAFs. Class I HDAC inhibition or mTORC1 activation by high-dose Gln supplementation significantly attenuates TGF-ß-Smad2/3 signaling and the myofibroblastic state in these cells. These data indicate class I HDAC activation and mTORC1 suppression to be required for maintenance of myCAF traits. Taken together, these findings indicate that Gln starvation triggers TGF-ß signaling activation in HMFs through class I HDAC activity and mTORC1 suppression, presumably inducing myCAF conversion.

Membrane vesicles from Lactobacillus johnsonii delay osteoarthritis progression via modulating macrophage glutamine synthetase/mTORC1 axis.

AIMS: The manipulation of macrophage recruitment and their shift in the M1/M2 ratio is a promising approach to mitigate osteoarthritis (OA). Nevertheless, the current clinical medication available for OA is only palliative and may result in undesirable outcomes. Hence, it is urgent to explore alternative disease-modifying drug supplement that are both safer and more effective in OA treatment, like probiotic and probiotic-derived membrane vesicles. METHODS: The synovial inflammation and cartilage damage in collagenase-induced OA (CIOA) mice were observed using haematoxylin and eosin, saffron O-solid green and immunohistochemical staining. Bipedal balance test and open field test were conducted to determine the effectiveness of L. johnsonii-derived membrane vesicles (LJ-MVs) in reducing joint pain of CIOA mice. Additionally, Transwell, western blot, and immunological testing were used to examine the effect of LJ-MVs on macrophage migration and reprogramming. Furthermore, a 4D label-free proteomic analysis of LJ-MVs and their parent bacterium was performed, and the glutamine synthetase (GS)/mTORC1 axis in macrophage was verified by western blot. RESULTS: L. johnsonii and its membrane vesicles, LJ-MVs, exhibit a novel ability to mitigate inflammation, cartilage damage, and pain associated with OA. This is achieved by their ability to impede macrophage migration, M1-like polarization, and inflammatory mediators secretion, while simultaneously promoting the M2/M1 ratio in synovial macrophages. The mechanism underlying this effect involves the modulation of macrophage GS/mTORC1 pathway, at least partially. SIGNIFICANCE: Owing to their probiotic derivation, LJ-MVs will be a more dependable and potent disease-modifying drugs for the prevention and therapy of OA in the long run.

Hyperbaric oxygen treatment increases intestinal stem cell proliferation through the mTORC1/S6K1 signaling pathway in Mus musculus.

BACKGROUND: Hyperbaric oxygen treatment (HBOT) has been reported to modulate the proliferation of neural and mesenchymal stem cell populations, but the molecular mechanisms underlying these effects are not completely understood. In this study, we aimed to assess HBOT somatic stem cell modulation by evaluating the role of the mTOR complex 1 (mTORC1), a key regulator of cell metabolism whose activity is modified depending on oxygen levels, as a potential mediator of HBOT in murine intestinal stem cells (ISCs). RESULTS: We discovered that acute HBOT synchronously increases the proliferation of ISCs without affecting the animal's oxidative metabolism through activation of the mTORC1/S6K1 axis. mTORC1 inhibition by rapamycin administration for 20 days also increases ISCs proliferation, generating a paradoxical response in mice intestines, and has been proposed to mimic a partial starvation state. Interestingly, the combination of HBOT and rapamycin does not have a synergic effect, possibly due to their differential impact on the mTORC1/S6K1 axis. CONCLUSIONS: HBOT can induce an increase in ISCs proliferation along with other cell populations within the crypt through mTORC1/S6K1 modulation without altering the oxidative metabolism of the animal's small intestine. These results shed light on the molecular mechanisms underlying HBOT therapeutic action, laying the groundwork for future studies.

PUM1 Promotes Tumor Progression by Activating DEPTOR-Meditated Glycolysis in Gastric Cancer.

RNA-binding proteins (RBPs) play essential roles in tumorigenesis and progression, but their functions in gastric cancer (GC) remain largely elusive. Here, it is reported that Pumilio 1 (PUM1), an RBP, induces metabolic reprogramming through post-transcriptional regulation of DEP domain-containing mammalian target of rapamycin (mTOR)-interacting protein (DEPTOR) in GC. In clinical samples, elevated expression of PUM1 is associated with recurrence, metastasis, and poor survival. In vitro and in vivo experiments demonstrate that knockdown of PUM1 inhibits the proliferation and metastasis of GC cells. In addition, RNA-sequencing and bioinformatics analyses show that PUM1 is enriched in the glycolysis gene signature. Metabolomics studies confirm that PUM1 deficiency suppresses glycolytic metabolism. Mechanistically, PUM1 binds directly to DEPTOR mRNA pumilio response element to maintain the stability of the transcript and prevent DEPTOR degradation through post-transcriptional pathway. PUM1-mediated DEPTOR upregulation inhibits mTORC1 and alleviates the inhibitory feedback signal transmitted from mTORC1 to PI3K under normal conditions, thus activating the PI3K-Akt signal and glycolysis continuously. Collectively, these results reveal the critical epigenetic role of PUM1 in modulating DEPTOR-dependent GC progression. These conclusions support further clinical investigation of PUM1 inhibitors as a metabolic-targeting treatment strategy for GC.

Methionine supplementation spares body protein by regulating the expression of mTORC1 downstream factors in rats fed a soy protein diet with sufficient sulfur amino acids: a pilot study.

Dietary supplementation with methionine and threonine spares body protein in rats fed a low protein diet, but the effect is not observed for other essential amino acids. Although the requirement for sulfur amino acids is relatively high in rodents, the precise mechanisms underlying protein retention are not fully understood. The aim of this study was to explore whether the activation of mammalian target of rapamycin complex 1 (mTORC1) downstream factors in skeletal muscle by supplementation with threonine and/or methionine contributes to protein retention under sufficient cystine requirement. Male Sprague-Dawley rats were freely fed a 0% protein diet for 2 weeks. These experimental rats were then fed a restricted diet (14.5 g/day) containing 12% soy protein supplemented with both cystine and, methionine and threonine (MT), methionine (M), threonine (T), or neither (NA) (n = 8) for an additional 12 days. Two additional groups were freely fed a diet containing 0% protein or 20% casein as controls (n = 6). Body weight and gastrocnemius muscle weight were higher, and blood urea nitrogen and urinary nitrogen excretion were lower, in the M and MT groups than in the T and NA groups, respectively. p70 S6 kinase 1 abundance was higher, and eukaryotic translation initiation factor 4E-binding protein 1 abundance and mRNA levels were lower, in the skeletal muscles of the M and MT groups. These results suggest that methionine regulates mTORC1 downstream factors in skeletal muscle, leading to spare body protein in rats fed a low protein diet meeting cystine requirements.

Core Target and Key Signal Pathway of Xiaoluo in the Treatment of Thyroid Cancer.

Context: At present, hormone therapy and surgery are the main treatments for thyroid cancer, and they have a quick effect but a high recurrence rate. Also, the side effects are significant. it's extremely urgent to explore treatments that can take into account both therapeutic benefits and side effects. Objective: The study intended to explore whether Xiaoluo has an inhibitory effect on the proliferation of thyroid-cancer cells in vitro and to examine the core target and key signaling pathway of Xiaoluo in the treatment of thyroid cancer, using the thyroid-cancer cell line SW579. Design: The research team performed an in-vitro study. Setting: The study took place at the College of Pharmacy at Harbin University of Commerce in Harbin, China. Outcome Measures: The research team used a Western blot analysis to detect the expression of apoptosis proteins-B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and Caspase-3-and the activity related to the signaling pathways phosphoinositide 3-kinase (PI3K)/ protein kinase B (AKT)/ mammalian target of rapamycin 1 (mTORC1). The team measured optical densities and inhibition rates for the 1, 2, 5, 10, and 15 mg/mL Xiaokuo groups and for a negative control group. The research team measured apoptosis, expression of Bcl-2, Bax, and Caspase-3, and expression of P13K, AKT, and mTor for the 10 µmol/L LY294002, 10 mg/mL Xiaoluo, 100 ng/mL IGF-1, and 100 ng/mL IGF-1+10 mg/mL Xiaoluo groups and for the blank control group. Results: The inhibition of SW579 cell proliferation increased with each increase in the Xiaoluo concentration from 1-15 mg/mL, and the inhibition rate reached 49.63% when the concentration was 15 mg/ml. The Xiaoluo group's late and total apoptosis rates were significantly higher (both P < .01) than those of the blank control group. The Xiaoluo group's expression of the Bcl-2 protein was significantly lower (P < .05), and its expressions of Bax and Caspase-3 were significantly higher (both P < .01) than those of the blank control group. The Xiaoluo group's expressions of P-PI3K, P-Akt, and P-MTOR were significantly lower than those of the blank group (all P < .01). These findings were comparable to those that occurred with use of the PI3K/AKT/mTORC1 signaling pathway inhibitor LY294002. Conclusions: Xiaoluo exerts its antithyroid-cancer effects through the induction of apoptosis in thyroid cancer cells through the inhibition of the PI3K/AKT/mTORC1 signaling pathway. Xiaoluo may serve as a potential therapeutic agent for the treatment of thyroid cancer.

A High Dose of Calcitriol Inhibits Glycolysis and M2 Macrophage Polarization in the Tumor Microenvironment by Repressing mTOR Activation: in vitro and Molecular Docking Studies.

BACKGROUND/AIMS: Macrophages interact with tumor cells within the tumor microenvironment (TME), which plays a crucial role in tumor progression. Cancer cells also can instruct macrophages to facilitate the spread of cancer and the growth of tumors. Thus, modulating macrophages-cancer cells interaction in the TME may be therapeutically beneficial. Although calcitriol (an active form of vitamin D) has anticancer properties, its role in TME is unclear. This study examined the role of calcitriol in the regulation of macrophages and cancer cells in the TME and its influence on the proliferation of breast cancer cells. METHODS: We modeled the TME, in vitro, by collecting conditioned medium from cancer cells (CCM) and macrophages (MCM) and culturing each cell type separately with and without (control) a high-dose (0.5 µM) calcitriol (an active form of vitamin D). An MTT assay was used to examine cell viability. Apoptosis was detected using FITC (fluorescein isothiocyanate) annexin V apoptosis detection kit. Western blotting was used to separate and identify proteins. Quantitative real-time PCR was used to analyze gene expression. Molecular docking studies were performed to evaluate the binding type and interactions of calcitriol to the GLUT1 and mTORC1 ligand-binding sites. RESULTS: Calcitriol treatment suppressed the expression of genes and proteins implicated in glycolysis (GLUT1, HKII, LDHA), promoted cancer cell apoptosis, and reduced viability and Cyclin D1gene expression in MCM-induced breast cancer cells. Additionally, calcitriol treatment suppressed mTOR activation in MCM-induced breast cancer cells. Molecular docking studies further showed efficient binding of calcitriol with GLUT1 and mTORC1. Calcitriol also inhibited CCM-mediated induction of CD206 and increased TNFα gene expression in THP1-derived macrophages. CONCLUSION: The results suggest that calcitriol may impact breast cancer progression by inhibiting glycolysis and M2 macrophage polarization via regulating mTOR activation in the TME and warrants further investigation in vivo.

Combination of the LARS1 Inhibitor, BC-LI-0186 with a MEK1/2 Inhibitor Enhances the Anti-Tumor Effect in Non-Small Cell Lung Cancer.

PURPOSE: The mammalian target of rapamycin complex 1 (mTORC1) regulates cell growth and proliferation by growth factor coordination and amino acid availability. Leucyl-tRNA synthetase 1 (LARS1) senses the intracellular leucine concentration and mediates amino acid-induced activation of mTORC1. Thus, LARS1 inhibition could be useful in cancer treatment. However, the fact that mTORC1 can be stimulated by various growth factors and amino acids suggests that LARS1 inhibition alone has limitations in inhibiting cell growth and proliferation. We investigated the combined effects of BC-LI-0186, a LARS1 inhibitor, and trametinib, an MEK inhibitor, on non-small cell lung cancer (NSCLC). Materials and Methods: Protein expression and phosphorylation were observed by immunoblotting, and genes differentially expressed between BC-LI-0186-sensitive and -resistant cells were identified by RNA sequencing. The combined effect of the two drugs was inferred from the combination index values and a xenograft model. RESULTS: LARS1 expression was positively correlated with mTORC1 in NSCLC cell lines. BC-LI-0186 treatment of A549 and H460 cells maintained in media supplemented with fetal bovine serum revealed paradoxical phosphorylation of S6 and activation of mitogen- activated protein kinase (MAPK) signaling. Compared with BC-LI-0186-sensitive cells, -resistant cells showed enrichment of the MAPK gene set. The combination of trametinib and BC-LI-0186 inhibited the phosphorylation of S6, MEK, and extracellular signal-regulated kinase and their synergistic effects were confirmed in a mouse xenograft model. CONCLUSION: The combination of BC-LI-0186 and trametinib inhibited the non-canonical mTORC1-activating function of LARS1. Our study demonstrated a new therapeutic approach for NSCLC without targetable driver mutations.

Non-Essential Amino Acid Availability Influences Proteostasis and Breast Cancer Cell Survival During Proteotoxic Stress.

Protein homeostasis (proteostasis) regulates tumor growth and proliferation when cells are exposed to proteotoxic stress, such as during treatment with certain chemotherapeutics. Consequently, cancer cells depend to a greater extent on stress signaling, and require the integrated stress response (ISR), amino acid metabolism, and efficient protein folding and degradation pathways to survive. To define how these interconnected pathways are wired when cancer cells are challenged with proteotoxic stress, we investigated how amino acid abundance influences cell survival when Hsp70, a master proteostasis regulator, is inhibited. We previously demonstrated that cancer cells exposed to a specific Hsp70 inhibitor induce the ISR via the action of two sensors, GCN2 and PERK, in stress-resistant and sensitive cells, respectively. In resistant cells, the induction of GCN2 and autophagy supported resistant cell survival, yet the mechanism by which these events were induced remained unclear. We now report that amino acid availability reconfigures the proteostasis network. Amino acid supplementation, and in particular arginine addition, triggered cancer cell death by blocking autophagy. Consistent with the importance of amino acid availability, which when limited activates GCN2, resistant cancer cells succumbed when challenged with a potentiator for another amino acid sensor, mTORC1, in conjunction with Hsp70 inhibition. IMPLICATIONS: These data position amino acid abundance, GCN2, mTORC1, and autophagy as integrated therapeutic targets whose coordinated modulation regulates the survival of proteotoxic-resistant breast cancer cells.

l-Type amino acid transporter 1 in hypothalamic neurons in mice maintains energy and bone homeostasis.

Hypothalamic neurons regulate body homeostasis by sensing and integrating changes in the levels of key hormones and primary nutrients (amino acids, glucose, and lipids). However, the molecular mechanisms that enable hypothalamic neurons to detect primary nutrients remain elusive. Here, we identified l-type amino acid transporter 1 (LAT1) in hypothalamic leptin receptor-expressing (LepR-expressing) neurons as being important for systemic energy and bone homeostasis. We observed LAT1-dependent amino acid uptake in the hypothalamus, which was compromised in a mouse model of obesity and diabetes. Mice lacking LAT1 (encoded by solute carrier transporter 7a5, Slc7a5) in LepR-expressing neurons exhibited obesity-related phenotypes and higher bone mass. Slc7a5 deficiency caused sympathetic dysfunction and leptin insensitivity in LepR-expressing neurons before obesity onset. Importantly, restoring Slc7a5 expression selectively in LepR-expressing ventromedial hypothalamus neurons rescued energy and bone homeostasis in mice deficient for Slc7a5 in LepR-expressing cells. Mechanistic target of rapamycin complex-1 (mTORC1) was found to be a crucial mediator of LAT1-dependent regulation of energy and bone homeostasis. These results suggest that the LAT1/mTORC1 axis in LepR-expressing neurons controls energy and bone homeostasis by fine-tuning sympathetic outflow, thus providing in vivo evidence of the implications of amino acid sensing by hypothalamic neurons in body homeostasis.

Pharmacological vitamin C inhibits mTOR signaling and tumor growth by degrading Rictor and inducing HMOX1 expression.

Pharmacological vitamin C (VC) is a potential natural compound for cancer treatment. However, the mechanism underlying its antitumor effects remains unclear. In this study, we found that pharmacological VC significantly inhibits the mTOR (including mTORC1 and mTORC2) pathway activation and promotes GSK3-FBXW7-mediated Rictor ubiquitination and degradation by increasing the cellular ROS. Moreover, we identified that HMOX1 is a checkpoint for pharmacological-VC-mediated mTOR inactivation, and the deletion of FBXW7 or HMOX1 suppresses the regulation of pharmacological VC on mTOR activation, cell size, cell viability, and autophagy. More importantly, it was observed that the inhibition of mTOR by pharmacological VC supplementation in vivo produces positive therapeutic responses in tumor growth, while HMOX1 deficiency rescues the inhibitory effect of pharmacological VC on tumor growth. These results demonstrate that VC influences cellular activities and tumor growth by inhibiting the mTOR pathway through Rictor and HMOX1, which may have therapeutic potential for cancer treatment.

α-hederin regulates glucose metabolism in intestinal epithelial cells by increasing SNX10 expression.

BACKGROUND: Sorting nexin 10 (SNX10) has recently been identified as a critical regulator of colorectal carcinogenesis, whose deletion promoted cell proliferation and survival in human CRC cells, and promoted colorectal tumor growth and upregulated amino-acid metabolism in mice. However, what happens when silencing SNX10 in normal human intestinal epithelial cells (IECs) remains unknown, and no drugs targeting SNX10 have been reported. Here, we first investigated the biological function and underlying mechanisms of SNX10 in normal human IECs, and found that α-hederin, a pentacyclic triterpenoid saponin, has a regulatory effect on SNX10 expression. PURPOSE: This study aimed to explore the function of SNX10 in IECs to provide a new target for the prevention and treatment of malignant transformation and the intervention mechanism of α-hederin for further development of potential novel agents targeting SNX10. METHODS: The transfection approach was used to construct SNX10 stable knockdown cells. Cell proliferation was detected by CCK8, clone formation, EdU, flow cytometry, and wound healing assays. Enzyme activity assays for glucose metabolism, qRT-PCR, western blotting, and immunofluorescence staining were performed to investigate the protein expression of signaling pathways. RESULTS: Silencing SNX10 promoted cell proliferation and cycle transition in IECs and increased the activity of key enzymes involved in glucose metabolism. Moreover, DEPDC5 expression was significantly decreased following SNX10 knockdown, followed by activation of the mTORC1 pathway. α-hederin reversed the accelerated cell proliferation, cycle progression, and glucose metabolic activity, as well as the activated mTORC1 pathway caused by SNX10 knockdown, by notably increasing SNX10 expression in a dose-dependent manner. CONCLUSION: We first reported that knockdown of SNX10 in normal human IECs promoted cell proliferation and activated glucose metabolism by activating the mTORC1 pathway. Meanwhile, we first found that α-hederin down-regulated glucose metabolism activity and slowed cell proliferation by increasing SNX10 expression in IECs.

Knockdown of regulatory associated protein of TOR (raptor) in hypothalamus-stimulated folliculogenesis and induced ovarian cysts.

CONTEXT: Mammalian target of rapamycin complex 1 (mTORC1) is an essential sensor that regulates fundamental biological processes like cell growth, proliferation and energy metabolism. The treatment of disease by sirolimus, a mTORC1 inhibitor, causes adverse effects, such as female fertility disorders. AIMS: The objective of the study was to decipher the reproductive consequences of a downregulation of mTORC1 in the hypothalamus. METHODS: The reduced expression of mTORC1 was induced after intracerebroventricular injection of lentivirus expressing a short hairpin RNA (shRNA) against regulatory associated protein of TOR (raptor) in adult female mice (ShRaptor mice). KEY RESULTS: The ShRaptor mice were fertile and exhibited a 15% increase in the litter size compared with control mice. The histological analysis showed an increase in antral, preovulatory follicles and ovarian cysts. In the hypothalamus, the GnRH mRNA and FSH levels in ShRaptor mice were significantly elevated. CONCLUSIONS: These results support the hypothesis that mTORC1 in the central nervous system participates in the regulation of female fertility and ovarian function by influencing the GnRH neuronal activity. IMPLICATIONS: These results suggest that a lower mTORC1 activity directly the central nervous system leads to a deregulation in the oestrous cycle and an induction of ovarian cyst development.

Influence of protein source (cricket, pea, whey) on amino acid bioavailability and activation of the mTORC1 signaling pathway after resistance exercise in healthy young males.

PURPOSE: New dietary proteins are currently introduced to replace traditional animal protein sources. However, not much is known about their bioaccessibility and ability to stimulate muscle protein synthesis compared to the traditional protein sources. We aimed to compare effects of ingesting a protein bolus (0.25 g/kg fat free mass) of either cricket (insect), pea, or whey protein on circulating amino acid levels and activation of the mTORC1 signaling pathway in the skeletal muscle at rest and after exercise. METHODS: In a randomized parallel controlled trial, young males (n = 50) performed a one-legged resistance exercise followed by ingestion of one of the three protein sources. Blood samples were collected before and in the following 4 h after exercise. Muscle biopsies were obtained at baseline and after 3 h from the non-exercised and exercised leg. RESULTS: Analysis of blood serum showed a significantly higher concentration of amino acids after ingestion of whey protein compared to cricket and pea protein. No difference between protein sources in activation of the mTORC1 signaling pathway was observed either at rest or after exercise. CONCLUSION: Amino acid blood concentration after protein ingestion was higher for whey than pea and cricket protein, whereas activation of mTORC1 signaling pathway at rest and after exercise did not differ between protein sources. TRIAL REGISTRATION NUMBER: Clinicaltrials.org ID NCT04633694.

[Ethoxysanguinarine directly targets CIP2A to inhibit proliferation and induce autophagy of SGC7901/DDP cells].

This study aims to investigate the effect of ethoxysanguinarine(Eth) on cisplatin(DDP)-resistant human gastric cancer cells and decipher the underlying mechanism. The human gastric cancer cell line SGC7901 and the DDP-resistant cell line SGC7901/DDP were used as the cell models. Western blot was employed to determine the expression levels of multidrug resistance-related proteins, and methyl thiazolyl tetrazolium(MTT) assay to detect the proliferation of SGC7901 and SGC7901/DDP cells exposed to DDP. After treatment with different concentrations of Eth, the proliferation of SGC7901 and SGC7901/DDP cells was detected by MTT assay, trypan blue exclusion assay, colony formation assay, and high-content imaging and analysis system. The apoptosis of SGC7901/DDP cells was detected by flow cytometry with Annexin V-FITC/PI staining. GFP-LC3 transfection was carried out to detect the effect of Eth on the autophagy of SGC7901/DDP cells. The expression levels of the multidrug resistance-related protein P-glycoprotein(P-gp), the apoptosis-related proteins [caspase-9, caspase-3, and poly(ADP-ribose) polymerase(PARP)], the autophagy-related protein light chain 3-Ⅱ(LC3-Ⅱ), the key effectors [mammalian target of rapamycin(mTOR), 70 kDa ribosomal protein S6 kinase(P70 S6 K), and 4 E binding protein 1(4 E-BP1)] of the mammalian target of rapamycin complex 1(mTORC1) signaling pathway, cancerous inhibitor of protein phosphatase 2A(CIP2A), and protein kinase B(Akt) were measured by Western blot. The mRNA level of CIP2A in the SGC7901/DDP cells exposed to Eth for 24 h was analyzed by RT-qPCR. After SGC7901/DDP cells were transfected with CIP2A expression vector pcDNA3.1-HA-CIP2A and treated with different concentrations of Eth, MTT assay was used to determine the prolife-ration of SGC7901/DDP cells and Western blot to detect the expression levels of related proteins. The interaction sites of Eth and CIP2A were predicted by molecular docking. The affinity between Eth and CIP2A was determined by drug affinity responsive target stability(DARTS) assay. The pharmacokinetic properties and drug-like activity of Eth were predicted by SwissADME. The results indicated that SGC7901/DDP cells were more sensitive to Eth than SGC7901 cells. Eth significantly inhibited proliferation and colony formation and changed the morphology, roundness, and area of SGC7901/DDP cells. Eth treatment caused the nucleus shrinking and significantly increased the apoptosis rate of the cells. Furthermore, Eth down-regulated the expression of caspase-9 and caspase-3 precursors and promoted the cleavage of PARP, which suggested that Eth induced the apoptosis of SGC7901/DDP cells. The GFP-LC3 in Eth-treated cells showed speckled aggregation. The up-regulated expression of LC3-Ⅱ by Eth indicated that Eth activated the autophagy of SGC7901/DDP cells. Eth down-regulated the expression of P-gp, the phosphorylation of mTOR, P70 S6K, and 4E-BP1, the expression of CIP2A, and the phosphorylation of Akt. Additionally, it increased the activity of PP2A, and had no significant effect on the expression of CIP2A in SGC7901/DDP cells. CIP2A overexpression antagonized the inhibition of cell proliferation and the activation of autophagy by Eth. Molecular docking suggested that Eth bound to CIP2A. The results of DARTS assay further proved the above binding effect. Eth has potential drug-like activity. The above results demonstrated that Eth inhibited the proliferation, induced the apoptosis, and activated the autophagy of SGC7901/DDP cells by targeting CIP2A and then down-regulating PP2A/mTORC1 signaling pathway. This study provided a new target for the treatment of cisplatin-resistant gastric cancer.

Retinoic Acid Increases Cellular Cholesterol in Leishmania donovani-Infected Macrophages in an mTOR-Independent Manner.

Infection with Leishmania donovani reduces cellular cholesterol and thus deprives the host cells by inhibiting its synthesis and uptake. Changes in cholesterol levels increase the chance of attachment and internalization of L. donovani in macrophages (Mϕ). Retinoic acid (RA), an important micronutrient, restores the lysosomal uptake of cholesterol in L. donovani-infected Mϕ. Importantly, mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) increases the cellular cholesterol level by increasing expression of sterol regulatory element-binding protein 2 (SREBP2). Whether the efficacy of RA in L. donovani-infected Mϕ is mediated by mTOR is not yet established. Moreover, there are contradicting reports suggesting potential activation and inhibition of mTOR in L. donovani-infected Mϕ. Intrigued by this, we attempted to understand the RA-mediated restoration of cholesterol as well as the possible roles of mTORC1, if any. Our findings suggest that L. donovani infection impairs the synthesis of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), uptake of low-density lipoprotein receptor (LDLR), and secretion of ATP-binding cassette transporter (ABCA1) in Mϕ. L. donovani infection possibly impairs mTORC1 formation, as it inhibits the expression of regulatory-associated protein of mammalian target of rapamycin (RAPTOR). Importantly, all these are restored upon RA supplementation. RA also restores the levels of SREBP2 in L. donovani-infected Mϕ, resulting in increased cellular cholesterol and thus reducing the parasite burden. When mTORC1 was inhibited, RA exerted a similar response in L. donovani-infected Mϕ; i.e., it restored cholesterol levels and reduced the parasite burden. In summary, RA restores cholesterol levels in L. donovani-infected Mϕ and reduces the parasite burden in an mTOR-independent manner. IMPORTANCE People who reside in regions where leishmaniasis is endemic and who lack proteins, iron, zinc, and vitamin A in their diet are more prone to develop visceral leishmaniasis (VL) as a full-blown disease. Vitamin A deficiency favors the development of a parasitic infection in the human host, and the WHO recommends administering 200,000-IU doses to VL patients on admission. Additionally, Leishmania entry and its survival inside the host are achieved by utilizing host cholesterol, as all trypanosomatids lack de novo synthesis of sterol. We have already shown that RA regulates cellular cholesterol levels associated with an efficient immune response. A deficiency of retinoic acid (RA) favors the parasite in Leishmania donovani-infected macrophages by downregulating the immune response. In the present work, we observed that RA restores cellular cholesterol levels in Leishmania donovani-infected macrophages. This study proposes using RA as an immune potentiator along with standard therapy.