Regulation of the mTOR complex 1 pathway by nutrients, growth factors, and stress

Sensing and Signaling of Methionine Metabolism

Availability of the amino acid methionine shows remarkable effects on the physiology of individual cells and whole organisms. For example, most cancer cells, but not normal cells, are hyper dependent on high flux through metabolic pathways connected to methionine, and diets restricted for methionine increase healthy lifespan in model organisms. Methionine's impact on physiology goes beyond its role in initiation of translation and incorporation in proteins. Many of its metabolites have a major influence on cellular functions including epigenetic regulation, maintenance of redox balance, polyamine synthesis, and phospholipid homeostasis. As a central component of such essential pathways, cells require mechanisms to sense methionine availability. When methionine levels are low, cellular response programs induce transcriptional and signaling states to remodel metabolic programs and maintain methionine metabolism. In addition, an evolutionary conserved cell cycle arrest is induced to ensure cellular and genomic integrity during methionine starvation conditions. Methionine and its metabolites are critical for cell growth, proliferation, and development in all organisms. However, mechanisms of methionine perception are diverse. Here we review current knowledge about mechanisms of methionine sensing in yeast and mammalian cells, and will discuss the impact of methionine imbalance on cancer and aging.

Downregulation of miR-96-5p Inhibits mTOR/NF-κb Signaling Pathway via DEPTOR in Allergic Rhinitis

BACKGROUND

This study aims to investigate the regulatory effect of microRNA-96-5p (miR-96-5p) in the pathophysiological process of allergic rhinitis (AR).

METHODS

Nasal mucosal tissue samples were collected from AR patients and healthy controls. An in vitro AR model was established by stimulating human nasal epithelial cells (HNECs) with interleukin (IL)-13. The expressions of target genes and proteins were measured by qPCR, Western blot, or ELISA. Dual-luciferase reporter assay and pull-down assay were performed to confirm the interaction between miR-96-5p and DEP domain-containing mammalian target of rapamycin-interacting protein (DEPTOR).

RESULTS

The level of miR-96-5p was increased while the expression of DEPTOR was decreased in AR patients. The expressions of proinflammatory cytokines were markedly increased and the mammalian target of rapamycin (mTOR)/NF-κB pathway was activated in HNECs following IL-13 stimulation. miR-96-5p downregulation alleviated the stimulated function by IL-13. DEPTOR was the target of miR-96-5p. Knockdown of DEPTOR reversed the function of miR-96-5p inhibitor on IL-13-stimulated HNECs.

CONCLUSIONS

The current study showed that miR-96-5p and DEPTOR were aberrantly expressed in AR nasal mucosa. miR-96-5p knockdown inhibited the production of inflammatory cytokines and the activation of mTOR/NF-κB pathway via targeting DEPTOR. These findings suggested that miR-96-5p might be used as a diagnostic marker and therapeutic target for the treatment of AR.

Inhibition of mitochondrial complex II in neuronal cells triggers unique pathways culminating in autophagy with implications for neurodegeneration

Mitochondrial dysfunction and neurodegeneration underlie movement disorders such as Parkinson’s disease, Huntington’s disease and Manganism among others. As a corollary, inhibition of mitochondrial complex I (CI) and complex II (CII) by toxins 1-methyl-4-phenylpyridinium (MPP⁺) and 3-nitropropionic acid (3-NPA) respectively, induced degenerative changes noted in such neurodegenerative diseases. We aimed to unravel the down-stream pathways associated with CII inhibition and compared with CI inhibition and the Manganese (Mn) neurotoxicity. Genome-wide transcriptomics of N27 neuronal cells exposed to 3-NPA, compared with MPP⁺ and Mn revealed varied transcriptomic profile. Along with mitochondrial and synaptic pathways, Autophagy was the predominant pathway differentially regulated in the 3-NPA model with implications for neuronal survival. This pathway was unique to 3-NPA, as substantiated by in silico modelling of the three toxins. Morphological and biochemical validation of autophagy markers in the cell model of 3-NPA revealed incomplete autophagy mediated by mechanistic Target of Rapamycin Complex 2 (mTORC2) pathway. Interestingly, Brain Derived Neurotrophic Factor (BDNF), which was elevated in the 3-NPA model could confer neuroprotection against 3-NPA. We propose that, different downstream events are activated upon neurotoxin-dependent CII inhibition compared to other neurotoxins, with implications for movement disorders and regulation of autophagy could potentially offer neuroprotection.

Effect of Feeding Wet Feed or Wet Feed Fermented by Bacillus licheniformis on Growth Performance, Histopathology and Growth and Lipid Metabolism Marker Genes in Broiler Chickens

The present study evaluated the effect of three feeding methods (dry feed, wet feed or wet feed fermented with Bacillus licheniformis) on the growth performance, intestinal histomorphometry and gene expression of the lipid metabolism- and growth-related genes of broiler chickens. A total of 360 one-day-old Cobb-500 broiler chicks were randomly allotted into three groups containing four replicates with 30 birds each. The first group (control) was fed a dry mash basal diet. The second and third groups were fed wet feed and fermented wet feed. The final body weight and weight gain were reduced (p < 0.01) in the wet feed group, while they did not differ between the fermented wet feed and dry feed groups. Feed intake was not altered, and feeding on wet feed significantly (p < 0.01) increased the feed-to-gain ratio compared to the remaining groups. No differences between the three feeding methods in carcass characteristics, blood biochemistry and nutrient digestibility were observed except for crude protein digestibility, which was increased (p < 0.01) in the fermented wet feed group. Duodenal and ileal villi heights were elevated in birds fed fermented wet feeds, while crypt depth was not altered. The expression fold of IGF-1, GH and m-TOR genes in the pectoral muscle of birds fed wet feed was decreased (p < 0.05), while myostatin gene expression was elevated. Feeding on wet feed reduced the hepatic gene expression of PPARγ and increased that of FAS. In conclusion, wet feed negatively affected the broiler chickens' efficiency under heat stress; however, fermenting the wet feed with Bacillus licheniformis improved feed utilization and birds' performance compared to the dry feed group.

The combination of ginger powder and zinc supplement improves the fructose-induced metabolic syndrome in rats by modulating the hepatic expression of NF-κB, mTORC1, PPAR-α SREBP-1c, and Nrf2

Although studies have shown that ginger, as an herbal remedy and zinc are able to improve inflammation, oxidative stress, autophagy, and metabolism of lipid and glucose, their molecular mechanisms are unknown. Therefore, this study was aimed to examine the therapeutic effects of ginger with zinc supplement for eight weeks on fructose-induced metabolic syndrome (MS). Ninety-six adult male Sprague Dawley rats (220 g ± 20) were randomly assigned to twelve controlled and treated groups. After the last treatment session, the level of lipid profiles, glucose, insulin, and leptin as metabolic factors and liver enzymes as biomarkers to evaluate liver function in serum were measured. The level of antioxidant enzymes and lipid peroxidation to evaluate the oxidative status and the TNF-α level as a biomarker to assess the state of inflammation in liver were also measured. The level of zinc along with the expression of NF-κB, mTORC1, PPAR-α, SREBP-1c, and Nrf2 in liver was also evaluated. The level of metabolic factors and liver enzymes in serum along with lipid peroxidation and TNF-α in liver increased; zinc and antioxidant enzymes levels decreased in rats with MS compared to control rats (p < .05). The hepatic expression of SREBP-1c, NF-κB and mTORC1 were upregulated and the expression of PPAR-α and Nrf2 were downregulated in rats with MS compared to control rats (p < .05). Treatment with different doses of ginger, zinc, and the combination of them could improve metabolic, inflammatory oxidative stress factors, and expression of the above genes in rats with MS compared to the MS group (p < .05). It can be concluded that ginger, zinc, and the combination of them could improve oxidative damage, inflammation, and autophagy induced by fructose and could adjust the glucose and lipid metabolism and the homeostasis of zinc in rats with MS. PRACTICAL APPLICATIONS: Due to the increasing prevalence of metabolic diseases, the use of plant compounds such as ginger has attracted widespread attention. Ginger as an herbal remedy with predominant pharmacological properties due to its availability, cheapness, and lack of side effects is also very popular for the treatment of metabolic disorders in folk medicine. Moreover, enhancing its medicinal properties with supplements such as zinc can be widely welcomed. This study was actually performed with the aim of investigating the effects of ginger + zinc supplement on MS. The results showed that the ginger + zinc supplement could improve oxidative damage, inflammation, and autophagy caused by fructose and adjust the glucose and lipid metabolism and the homeostasis of zinc in rats with MS. The results of this study support the hypothesis that ginger can be used as a very suitable option for the production of medicinal supplements to maintain human health.

Metallothionein 1 Overexpression Does Not Protect Against Mitochondrial Disease Pathology in Ndufs4 Knockout Mice

Mitochondrial diseases (MD), such as Leigh syndrome (LS), present with severe neurological and muscular phenotypes in patients, but have no known cure and limited treatment options. Based on their neuroprotective effects against other neurodegenerative diseases in vivo and their positive impact as an antioxidant against complex I deficiency in vitro, we investigated the potential protective effect of metallothioneins (MTs) in an Ndufs4 knockout mouse model (with a very similar phenotype to LS) crossed with an Mt1 overexpressing mouse model (TgMt1). Despite subtle reductions in the expression of neuroinflammatory markers GFAP and IBA1 in the vestibular nucleus and hippocampus, we found no improvement in survival, growth, locomotor activity, balance, or motor coordination in the Mt1 overexpressing Ndufs4-/- mice. Furthermore, at a cellular level, no differences were detected in the metabolomics profile or gene expression of selected one-carbon metabolism and oxidative stress genes, performed in the brain and quadriceps, nor in the ROS levels of macrophages derived from these mice. Considering these outcomes, we conclude that MT1, in general, does not protect against the impaired motor activity or improve survival in these complex I-deficient mice. The unexpected absence of increased oxidative stress and metabolic redox imbalance in this MD model may explain these observations. However, tissue-specific observations such as the mildly reduced inflammation in the hippocampus and vestibular nucleus, as well as differential MT1 expression in these tissues, may yet reveal a tissue- or cell-specific role for MTs in these mice.

Mitochondrial transformations in the aging human placenta

Mitochondria play a key role in homeostasis and are central to one of the leading hypotheses of aging, the free radical theory. Mitochondria function as a reticulated network, constantly adapting to the cellular environment through fusion (joining), biogenesis (formation of new mitochondria), and fission (separation). This adaptive response is particularly important in response to oxidative stress, cellular damage, and aging, when mitochondria are selectively removed through mitophagy, a mitochondrial equivalent of autophagy. During this complex process, mitochondria influence surrounding cell biology and organelles through the release of signaling molecules. Given that the human placenta is a unique organ having a transient and somewhat defined life span of ∼280 days, any adaption or dysfunction associated with mitochondrial physiology as a result of aging will have a dramatic impact on the health and function of both the placenta and the fetus. Additionally, a defective placenta during gestation, resulting in reduced fetal growth, has been shown to influence the development of chronic disease in later life. In this review we focus on the mitochondrial adaptions and transformations that accompany gestational length and share similarities with age-related diseases. In addition, we discuss the role of such changes in regulating placental function throughout gestation, the etiology of gestational complications, and the development of chronic diseases later in life.

Loss of hepatic aldolase B activates Akt and promotes hepatocellular carcinogenesis by destabilizing the Aldob/Akt/PP2A protein complex

Loss of hepatic fructose-1, 6-bisphosphate aldolase B (Aldob) leads to a paradoxical up-regulation of glucose metabolism to favor hepatocellular carcinogenesis (HCC), but the upstream signaling events remain poorly defined. Akt is highly activated in HCC, and targeting Akt is being explored as a potential therapy for HCC. Herein, we demonstrate that Aldob suppresses Akt activity and tumor growth through a protein complex containing Aldob, Akt, and protein phosphatase 2A (PP2A), leading to inhibition of cell viability, cell cycle progression, glucose uptake, and metabolism. Interestingly, Aldob directly interacts with phosphorylated Akt (p-Akt) and promotes the recruitment of PP2A to dephosphorylate p-Akt, and this scaffolding effect of Aldob is independent of its enzymatic activity. Loss of Aldob or disruption of Aldob/Akt interaction in Aldob R304A mutant restores Akt activity and tumor-promoting effects. Consistently, Aldob and p-Akt expression are inversely correlated in human HCC tissues, and Aldob down-regulation coupled with p-Akt up-regulation predicts a poor prognosis for HCC. We have further discovered that Akt inhibition or a specific small-molecule activator of PP2A (SMAP) efficiently attenuates HCC tumorigenesis in xenograft mouse models. Our work reveals a novel nonenzymatic role of Aldob in negative regulation of Akt activation, suggesting that directly inhibiting Akt activity or through reactivating PP2A may be a potential therapeutic approach for HCC treatment.

PI3K/AKT/mTOR signaling in gastric cancer: Epigenetics and beyond

PI3K/AKT/mTOR pathway is one of the most important signaling pathways involved in normal cellular processes. Its aberrant activation modulates autophagy, epithelial-mesenchymal transition, apoptosis, chemoresistance, and metastasis in many human cancers. Emerging evidence demonstrates that some infections as well as epigenetic regulatory mechanisms can control PI3K/AKT/mTOR signaling pathway. In this review, we focused on the role of this pathway in gastric cancer development, prognosis, and metastasis, with an emphasis on epigenetic alterations including DNA methylation, histone modifications, and post-transcriptional modulations through non-coding RNAs fluctuations as well as H. pylori and Epstein-Barr virus infections. Finally, we reviewed different molecular targets and therapeutic agents in clinical trials as a potential strategy for gastric cancer treatment through the PI3K/AKT/mTOR pathway.

Effects of nonylphenol induced oxidative stress on apoptosis and autophagy in rat ovarian granulosa cells

Nonylphenol (NP) is a kind of environmental endocrine disruptors which is generally recognized to cause female reproductive toxicity, but its basic mechanism has not been fully elucidated. In this study, granulosa cells (GCs) were treated with 0-70 μM NP for 24 h, the cell viability of GCs was reduced significantly, as well as increased cell apoptosis with G2/M arrest. Furthermore, NP significantly induced autophagy and the production of reactive oxygen species (ROS). However, these phenomenons were inhibited by blocking the production of ROS with N-Acetyl-l-cysteine (NAC) administration. Intriguingly, the inhibition of autophagy with 3-Methyladenine (3-MA) could enhance the apoptosis induced by NP. Moreover, the down regulating of p-Akt/Akt, p-mTOR/mTOR and subsequent up-regulation of p-AMPK/AMPK induced by NP can be rescued by pretreatment of NAC. Our findings suggested that NP promotes rat ovarian GCs apoptosis and autophagy simultaneously, which may involve the activation of ROS-dependent Akt/AMPK/mTOR pathway. Whatever, the activation of autophagy is likely to develop a protective mechanism to improve the apoptosis of rat ovarian GCs induced by NP.

The endocrinological component and signaling pathways associated to cardiac hypertrophy

Although myocardial growth corresponds to an adaptive response to maintain cardiac contractile function, the cardiac hypertrophy is a condition that occurs in many cardiovascular diseases and typically precedes the onset of heart failure. Different endocrine factors such as thyroid hormones, insulin, insulin-like growth factor 1 (IGF-1), angiotensin II (Ang II), endothelin (ET-1), catecholamines, estrogen, among others represent important stimuli to cardiomyocyte hypertrophy. Thus, numerous endocrine disorders manifested as changes in the local environment or multiple organ systems are especially important in the context of progression from cardiac hypertrophy to heart failure. Based on that information, this review summarizes experimental findings regarding the influence of such hormones upon signalling pathways associated with cardiac hypertrophy. Understanding mechanisms through which hormones differentially regulate cardiac hypertrophy could open ways to obtain therapeutic approaches that contribute to prevent or delay the onset of heart failure related to endocrine diseases.

Identification of Dietary Phytochemicals Capable of Enhancing the Autophagy Flux in HeLa and Caco-2 Human Cell Lines

Autophagy is a major degradation system for intracellular macromolecules. Its decline with age or obesity is related to the onset and development of various intractable diseases. Although dietary phytochemicals are expected to enhance autophagy for preventive medicine, few studies have addressed their effects on the autophagy flux, which is the focus of the current study. Herein, 67 dietary phytochemicals were screened using a green fluorescent protein (GFP)-microtubule-associated protein light chain 3 (LC3)-red fluorescent protein (RFP)-LC3ΔG probe for the quantitative assessment of autophagic degradation. Among them, isorhamnetin, chrysoeriol, 2,2',4'-trihydroxychalcone, and zerumbone enhanced the autophagy flux in HeLa cells. Meanwhile, analysis of the structure-activity relationships indicated that the 3'-methoxy-4'-hydroxy group on the B-ring in the flavone skeleton and an ortho-phenolic group on the chalcone B-ring were crucial for phytochemicals activities. These active compounds were also effective in colon carcinoma Caco-2 cells, and some of them increased the expression of p62 protein, a typical substrate of autophagic proteolysis, indicating that phytochemicals impact p62 levels in autophagy-dependent and/or -independent manners. In addition, these compounds were characterized by distinct modes of action. While isorhamnetin and chrysoeriol enhanced autophagy in an mTOR signaling-dependent manner, the actions of 2,2',4'-trihydroxychalcone and zerumbone were independent of mTOR signaling. Hence, these dietary phytochemicals may prove effective as potential preventive or therapeutic strategies for lifestyle-related diseases.

DEPTOR is a direct p53 target that suppresses cell growth and chemosensitivity

DEP-domain containing mTOR-interacting protein (DEPTOR), a natural mTOR inhibitor, has essential roles in several processes, including cell growth, metabolism, apoptosis, and immunity. DEPTOR expression has been shown to be diversely controlled at transcriptional levels in cell- and context-specific manners. However, whether there is a general mechanism for the regulation of DEPTOR expression remains largely unknown. Here, we report that DEPTOR is a downstream target of the tumor suppressor, p53, whose activity is positively correlated with DEPTOR expression both in vitro in cell cultures and in vivo in mouse tissues. Mechanistically, p53 directly binds to the DEPTOR promoter and transactivates its expression. Depletion of the p53-binding site on the DEPTOR promoter by CRISPR-Cas9 technology decreases DEPTOR expression and promotes cell proliferation and survival by activating AKT signaling. Importantly, inhibition of AKT by small molecular inhibitors or genetic knockdown abrogates the induction of cell growth and survival induced by deletion of the p53-binding region on the DEPTOR promoter. Furthermore, p53, upon activation by the genotoxic agent doxorubicin, induces DEPTOR expression, leading to cancer cell resistance to doxorubicin. Together, DEPTOR is a direct p53 downstream target and contributes to p53-mediated inhibition of cell proliferation, survival, and chemosensitivity.

A combination of growth factors and cytokines alter preimplantation mouse embryo development, foetal development and gene expression profiles

Within the maternal tract, the preimplantation embryo is exposed to an array of growth factors (GFs) and cytokines, most of which are absent from culture media used in clinical IVF. Whilst the addition of individual GFs and cytokines to embryo culture media can improve preimplantation mouse embryo development, there is a lack of evidence on the combined synergistic effects of GFs and cytokines on embryo development and further foetal growth. Therefore, in this study, the effect of a combined group of GFs and cytokines on mouse preimplantation embryo development and subsequent foetal development and gene expression profiles was investigated. Supplementation of embryo culture media with an optimised combination of GFs and cytokines (0.05 ng/ml vascular endothelial GF, 1 ng/ml platelet-derived GF, 0.13 ng/ml insulin-like GF 1, 0.026 ng/ml insulin-like GF 2 and 1 ng/ml granulocyte colony-stimulating factor) had no effect on embryo morphokinetics but significantly increased trophectoderm cell number (P = 0.0002) and total cell number (P = 0.024). Treatment with this combination of GFs and cytokines also significantly increased blastocyst outgrowth area (P &lt; 0.05) and, following embryo transfer, increased foetal weight (P = 0.027), crown-rump length (P = 0.017) and overall morphological development (P = 0.027). RNA-seq analysis of in vitro derived foetuses identified concurrent alterations to the transcriptional profiles of liver and placental tissues compared with those developed in vivo, with greater changes observed in the GF and cytokine treated group. Together these data highlight the importance of balancing the actions of such factors for the regulation of normal development and emphasise the need for further studies investigating this prior to clinical implementation.

Eukaryotic translation initiation factors as promising targets in cancer therapy

The regulation of the translation of messenger RNA (mRNA) in eukaryotic cells is critical for gene expression, and occurs principally at the initiation phase which is mainly regulated by eukaryotic initiation factors (eIFs). eIFs are fundamental for the translation of mRNA and as such act as the primary targets of several signaling pathways to regulate gene expression. Mis-regulated mRNA expression is a common feature of tumorigenesis and the abnormal activity of eIF complexes triggered by upstream signaling pathways is detected in many tumors, leading to the selective translation of mRNA encoding proteins involved in tumorigenesis, metastasis, or resistance to anti-cancer drugs, and making eIFs a promising therapeutic target for various types of cancers. Here, we briefly outline our current understanding of the biology of eIFs, mainly focusing on the effects of several signaling pathways upon their functions and discuss their contributions to the initiation and progression of tumor growth. An overview of the progress in developing agents targeting the components of translation machinery for cancer treatment is also provided.

PTH(1‑34) activates the migration and adhesion of BMSCs through the rictor/mTORC2 pathway

The ability of intermittent parathyroid hormone (1-34) [PTH(1-34)] treatment to enhance bone-implant osseo-integration was recently demonstrated in vivo. However, the mechanisms through which PTH (1-34) regulates bone marrow-derived stromal cells (BMSCs) remain unclear. The present study thus aimed to investigate the effects of PTH(1-34) on the migration and adhesion of, and rictor/mammalian target of rapamycin complex 2 (mTORC2) signaling in BMSCs. In the present study, BMSCs were isolated from Sprague-Dawley rats treated with various concentrations of PTH(1-34) for different periods of time. PTH(1-34) treatment was performed with or without an mTORC1 inhibitor (20 nM rapamycin) and mTORC1/2 inhibitor (10 µM PP242). Cell migration was assessed by Transwell cell migration assays and wound healing assays. Cell adhesion and related mRNA expression were investigated through adhesion assays and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively. The protein expression of chemokine receptors (CXCR4 and CCR2) and adhesion factors [intercellular adhesion molecule 1 (ICAM-1), fibronectin and integrin β1] was examined by western blot analysis. The results revealed that various concentrations (1, 10, 20, 50 and 100 nM) of PTH(1-34) significantly increased the migration and adhesion of BMSCs, as well as the expression of CXCR4, CCR2, ICAM-1, fibronectin and integrin β1. In addition, the p-Akt and p-S6 levels were also upregulated by PTH(1-34). BMSCs subjected to mTORC1/2 signaling pathway inhibition or rictor silencing exhibited a markedly reduced PTH-induced migration and adhesion, while no such effect was observed for the BMSCs subjected to mTORC1 pathway inhibition or raptor silencing. These results indicate that PTH(1-34) promotes BMSC migration and adhesion through rictor/mTORC2 signaling in vitro. Taken together, the results of the present study reveal an important mechanism for the therapeutic effects of PTH(1-34) on bone-implant osseointegration and suggest a potential treatment strategy based on the effect of PTH(1-34) on BMSCs.

Evaluation of Kaempferol as AKT Dependent mTOR Regulator via Targeting FKBP-12 in Hepatocellular Carcinoma: An In silico Approach

Background:

Hepatocellular carcinomas (HCCs) are inherently chemotherapy-resistant tumors with about 30-50% activation of PI3K/Akt/mTOR pathway, and this pathway is not aberrant in normal cells. Therefore, targeting the PI3K/Akt/mTOR pathway has become a promising strategy in drug designing to combat liver cancer. Recently, many studies with phytochemicals suggest few classes of compounds, especially flavonoids, to be useful in down-regulating the PI3K/Akt/mTOR pathway corresponding to HCC. In the present study, an attempt is made to explore flavonoids, from which the best mTORC1 inhibitor against hepatocellular carcinoma is selected using computational molecular modeling.

Methods:

In the present study, we performed a virtual screening method with phytochemicals of flavonoid category. To ensure proper bioavailability and druggability, pharmacokinetic and interaction parameters have been used to screen the molecules. The target protein molecules have been selected from the RCSB. The interaction studies have been conducted using Biovia Discovery Studio client version 17.2.0.1.16347 and the pharmacokinetic predictions have been made through ADMET SAR. The responsiveness towards the regulation of the mTOR pathway varies from person to person, demanding a pharmacogenomic approach in the analysis. The genetic variants (Single Nucleotide Variants-SNVs) corresponding to the mutations have been identified.

Results and Discussion:

The study identified phytoconstituents with better interaction with receptor FKBP12, a Rapamycin binding domain which is the target of Rapamycin and its analogues for mTORC1 inhibition in HCC. Another protein, ‘AKT serine/threonine-protein kinase’ has been identified, which is associated with activation of mTORC1. The molecular interaction studies (docking studies) and ADMET (absorption, distribution, metabolism, excretion and toxicity) analysis were used to identify the affinity between selected phytoconstituents as mTORC1 inhibitor against Hepatocellular carcinoma. The docking studies support Kaempferol to be a potential ligand with docking score values of 33.4 (3CQU-3D structure of AKT1)] and 27.3 (2FAP-3D structure of FRB domain of mTOR) respectively as compared to that of standard drug Everolimus with 24.4 (3CQU-3D structure of AKT1) and 20.1 (2FAP-3D structure of FRB domain of mTOR) respectively. Docking studies along with ADMET results show that Kaempferol has favorable drug likeliness properties and binds to the same active site (site1) of the targeted proteins (3CQU-3D structure of AKT1) and (2FAP-3D structure of FRB domain of mTOR) where the standard drug Everolimus is known to bind.

Conclusion:

The study exhibited that Kaempferol had a better binding affinity towards the receptor FKBP12, a Rapamycin Binding Domain and AKT serine/threonine-protein kinase resulting in its better efficacy in the mTORC1 inhibition as when compared with standard drug Everolimus against HCC. To the best of our knowledge, no studies have been reported on Kaempferol as mTORC1 inhibitor against Hepatocellular carcinoma.

The Double-Edge Sword of Autophagy in Cancer: From Tumor Suppression to Pro-tumor Activity

During tumorigenesis, cancer cells are exposed to a wide variety of intrinsic and extrinsic stresses that challenge homeostasis and growth. Cancer cells display activation of distinct mechanisms for adaptation and growth even in the presence of stress. Autophagy is a catabolic mechanism that aides in the degradation of damaged intracellular material and metabolite recycling. This activity helps meet metabolic needs during nutrient deprivation, genotoxic stress, growth factor withdrawal and hypoxia. However, autophagy plays a paradoxical role in tumorigenesis, depending on the stage of tumor development. Early in tumorigenesis, autophagy is a tumor suppressor via degradation of potentially oncogenic molecules. However, in advanced stages, autophagy promotes the survival of tumor cells by ameliorating stress in the microenvironment. These roles of autophagy are intricate due to their interconnection with other distinct cellular pathways. In this review, we present a broad view of the participation of autophagy in distinct phases of tumor development. Moreover, autophagy participation in important cellular processes such as cell death, metabolic reprogramming, metastasis, immune evasion and treatment resistance that all contribute to tumor development, is reviewed. Finally, the contribution of the hypoxic and nutrient deficient tumor microenvironment in regulation of autophagy and these hallmarks for the development of more aggressive tumors is discussed.

Polyphenolic Proanthocyanidin-B2 suppresses proliferation of liver cancer cells and hepatocellular carcinogenesis through directly binding and inhibiting AKT activity

The well-documented anticarcinogenic properties of natural polyphenolic proanthocyanidins (OPC) have been primarily attributed to their antioxidant and anti-inflammatory potency. Emerging evidence suggests that OPC may target canonical oncogenic pathways, including PI3K/AKT; however, the underlying mechanism and therapeutic potential remain elusive. Here we identify that proanthocyanidin B2 (OPC-B2) directly binds and inhibits AKT activity and downstream signalling, thereby suppressing tumour cell proliferation and metabolism in vitro and in a xenograft and diethyl-nitrosamine (DEN)-induced hepatocellular carcinoma (HCC) mouse models. We further find that OPC-B2 binds to the catalytic and regulatory PH domains to lock the protein in a closed conformation, similar to the well-studied AKT allosteric inhibitor MK-2206. Molecular docking and dynamic simulation suggest that Lys297 and Arg86 are critical sites of OPC-B2 binding; mutation of Lys297 or Arg86 to alanine completely abolishes the antitumor effects of OPC-B2 but not MK-2206. Together, our study reveals that OPC-B2 is a novel allosteric AKT inhibitor with potent anti-tumour efficacy beyond its antioxidant and anti-inflammatory properties.

Tip60 Phosphorylation at Ser 99 Is Essential for Autophagy Induction in Bombyx mori

Tip60, a key histone acetyltransferase of the MYST family and member of the nuclear multimeric protein complex (NuA4), regulates the activity and stability of proteins involved in the cell cycle, DNA damage responses, autophagy, etc. However, the function and regulatory mechanism of Tip60 homolog in Bombyx mori are not elucidated. In the present study, Bombyx Tip60 (BmTip60) was functionally identified. Developmental profiles showed that the protein levels and nuclear localization of BmTip60 peaked in fat body during the larval–pupal metamorphosis when autophagy was intensive; simultaneously, the BmTip60 protein migrated to form an upper band as detected by Western blot. Interestingly, the upper band of BmTip60 was reduced by λ-phosphatase treatment, indicating that it was a phosphorylated form of BmTip60. Results showed that BmTip60 was promoted by starvation but not 20-hydroxyecdysone treatment. Transcription factor AMP-activated protein kinase (AMPK) affected by starvation was pivotal for BmTip60 protein migration. In addition, one mammalian phosphorylation site was identified in BmTip60 at Ser99, the constitutive-activation mutation of Ser99 to Asp99 but not its inactive mutation to Ala99 significantly upregulated autophagy, showing the critical role of phosphorylation at Ser99 for BmTip60-mediated autophagy. In conclusion, the starvation-AMPK axis promotes BmTip60 in B. mori, which was requisite for autophagy induction. These results reveal a regulatory mechanism of histone acetyltransferase Tip60 homologs by phosphorylation in insects, and sheds light on further related studies of acetylation regulation.

Association of mTOR pathway with risk of gastric cancer in male smoker with potential prognostic significance

Aberrant expression of mTOR signaling pathway is significantly associated with gastric cancer. However, the effect of smoking on mTOR expression and its downstream signaling molecules in gastric cancer has not been explored. Our study aims to investigate the effect of smoking on p-mTOR and its correlation with various downstream targets and survival of the smoker and never-smoker in advanced gastric cancer patients. Forty-one smokers and 41 never-smokers patient sample with the advanced gastric carcinoma were chosen for this study. Immunohistochemistry and western blot analysis were performed to check the expression of p-mTOR and its downstream targets. The correlation of p-mTOR with its downstream targets was analyzed by linear regression analysis in Graph Pad Prism software. Survivability analysis was examined by Kaplan-Meier method with log rank test in SPSS. High expression of p-mTOR and its downstream targets were observed in advanced gastric cancer smoker patients as compared to never-smokers by immunohistochemistry and western blot analysis. Results revealed that over expressed p-mTOR in smoker patients were positively correlated with its downstream targets (P < 0.05) and poor survival (P = 0.034). Over expression of p-mTOR in gastric cancer male smoker patients had the worse outcome.

The Target of Rapamycin Signalling Pathway in Ageing and Lifespan Regulation

Ageing is a complex trait controlled by genes and the environment. The highly conserved mechanistic target of rapamycin signalling pathway (mTOR) is a major regulator of lifespan in all eukaryotes and is thought to be mediating some of the effects of dietary restriction. mTOR is a rheostat of energy sensing diverse inputs such as amino acids, oxygen, hormones, and stress and regulates lifespan by tuning cellular functions such as gene expression, ribosome biogenesis, proteostasis, and mitochondrial metabolism. Deregulation of the mTOR signalling pathway is implicated in multiple age-related diseases such as cancer, neurodegeneration, and auto-immunity. In this review, we briefly summarise some of the workings of mTOR in lifespan and ageing through the processes of transcription, translation, autophagy, and metabolism. A good understanding of the pathway's outputs and connectivity is paramount towards our ability for genetic and pharmacological interventions for healthy ageing and amelioration of age-related disease.

Energy metabolism: A newly emerging target of BMP signaling in bone homeostasis

Energy metabolism is the process of generating energy (i.e. ATP) from nutrients. This process is indispensable for cell homeostasis maintenance and responses to varying conditions. Cells require energy for growth and maintenance and have evolved to have multiple pathways to produce energy. Both genetic and functional studies have demonstrated that energy metabolism, such as glucose, fatty acid, and amino acid metabolism, plays important roles in the formation and function of bone cells including osteoblasts, osteocytes, and osteoclasts. Dysregulation of energy metabolism in bone cells consequently disturbs the balance between bone formation and bone resorption. Metabolic diseases have also been reported to affect bone homeostasis. Bone morphogenic protein (BMP) signaling plays critical roles in regulating the formation and function of bone cells, thus affecting bone development and homeostasis. Mutations of BMP signaling-related genes in mice have been reported to show abnormalities in energy metabolism in many tissues, including bone. In addition, BMP signaling correlates with critical signaling pathways such as mTOR, HIF, Wnt, and self-degradative process autophagy to coordinate energy metabolism and bone homeostasis. These findings will provide a newly emerging target of BMP signaling and potential therapeutic strategies and the improved management of bone diseases. This review summarizes the recent advances in our understanding of (1) energy metabolism in regulating the formation and function of bone cells, (2) function of BMP signaling in whole body energy metabolism, and (3) mechanistic interaction of BMP signaling with other signaling pathways and biological processes critical for energy metabolism and bone homeostasis.

The mTORC1 inhibitor rapamycin and the mTORC1/2 inhibitor AZD2014 impair the consolidation and persistence of contextual fear memory

RATIONALE

The mechanistic target of rapamycin (mTOR) kinase mediates various long-lasting forms of synaptic and behavioural plasticity. However, there is little information concerning the temporal pattern of mTOR activation and susceptibility to pharmacological intervention during consolidation of contextual fear memory. Moreover, the contribution of both mTOR complex 1 and 2 together or the mTOR complex 1 downstream effector p70S6K (S6K1) to consolidation of contextual fear memory is unknown.

OBJECTIVE

Here, we tested whether different timepoints of vulnerability to rapamycin, a first generation mTOR complex 1 inhibitor, exist for contextual fear memory consolidation and persistence. We also sought to characterize the effects of dually inhibiting mTORC1/2 as well as S6K1 on fear memory formation and persistence.

METHODS

Rapamycin was injected systemically to mice immediately, 3 h, or 12 h after contextual fear conditioning, and retention was measured at different timepoints thereafter. To determine the effects of a single injection of the dual mTROC1/2 inhibitor AZD2014 after learning on memory consolidation and persistence, a dose-response experiment was carried out. Memory formation and persistence was also assessed in response to the S6K1 inhibitor PF-4708671.

RESULTS

A single systemic injection of rapamycin immediately or 3 h, but not 12 h, after learning impaired the formation and persistence of contextual fear memory. AZD2014 was found, with limitations, to dose-dependently attenuate memory consolidation and persistence at the highest dose tested (50 mg/kg). In contrast, PF-4708671 had no effect on consolidation or persistence.

CONCLUSION

Our results indicate the need to further understand the role of mTORC1/2 kinase activity in the molecular mechanisms underlying memory processing and also demonstrate that the effects of mTORC1 inhibition at different timepoints well after learning on memory consolidation and persistence.

Amino acid-dependent control of mTORC1 signaling: a variety of regulatory modes

The mechanistic target of rapamycin complex 1 (mTORC1) is an essential regulator of cell growth and metabolism through the modulation of protein and lipid synthesis, lysosome biogenesis, and autophagy. The activity of mTORC1 is dynamically regulated by several environmental cues, including amino acid availability, growth factors, energy levels, and stresses, to coordinate cellular status with environmental conditions. Dysregulation of mTORC1 activity is closely associated with various diseases, including diabetes, cancer, and neurodegenerative disorders. The discovery of Rag GTPases has greatly expanded our understanding of the regulation of mTORC1 activity by amino acids, especially leucine and arginine. In addition to Rag GTPases, other factors that also contribute to the modulation of mTORC1 activity have been identified. In this review, we discuss the mechanisms of regulation of mTORC1 activity by particular amino acids.

Light-emitting diode irradiation induces AKT/mTOR-mediated apoptosis in human pancreatic cancer cells and xenograft mouse model

The beneficial effects of light-emitting diode (LED) irradiation have been reported in various pathologies, including cancer. However, its effect in pancreatic cancer cells remains unclear. Herein, we demonstrated that blue LED of 460 nm regulated pancreatic cancer cell proliferation and apoptosis by suppressing the expression of apoptosis-related factors, such as mutant p53 and B-cell lymphoma 2 (Bcl-2), and decreasing the expression of RAC-β serine/threonine kinase 2 (AKT2), the phosphorylation of protein kinase B (AKT), and mammalian target of rapamycin (mTOR). Blue LED irradiation also increased the levels of cleaved poly-(ADP-ribose) polymerase (PARP) and caspase-3 in pancreatic cancer cells, while it suppressed AKT2 expression and inhibited tumor growth in xenograft tumor tissues. In conclusion, blue LED irradiation suppressed pancreatic cancer cell and tumor growth by regulating AKT/mTOR signaling. Our findings indicated that blue LEDs could be used as a nonpharmacological treatment for pancreatic cancer.

Searching for the Mechanisms of Mammalian Cellular Aging Through Underlying Gene Regulatory Networks

Aging attracts the attention throughout the history of humankind. However, it is still challenging to understand how the internal driving forces, for example, the fundamental building blocks of life, such as genes and proteins, as well as the environments work together to determine longevity in mammals. In this study, we built a gene regulatory network for mammalian cellular aging based on the experimental literature and quantify its underlying driving force for the dynamics as potential and flux landscape. We found three steady-state attractors: a fast-aging state attractor, slow-aging state attractor, and intermediate state attractor. The system can switch from one state attractor to another driven by the intrinsic or external forces through the genetics and the environment. We identified the dominant path from the slow-aging state directly to the fast-aging state. We also identified the dominant path from slow-aging to fast-aging through an intermediate state. We quantified the evolving landscape for revealing the dynamic characteristics of aging through certain regulation changes in time. We also predicted the key genes and regulations for fast-aging and slow-aging through the analysis of the stability for landscape basins. We also found the oscillation dynamics between fast-aging and slow-aging and showed that more energy is required to sustain such oscillations. We found that the flux is the dynamic cause and the entropy production rate the thermodynamic origin of the phase transitions or the bifurcations between the three-state phase and oscillation phase. The landscape quantification provides a global and physical approach to explore the underlying mechanisms of cellular aging in mammals.

The Impact of Diet on Breast Cancer Outcomes

PURPOSE OF REVIEW

Breast cancer is the most common cancer in women, yet conclusive evidence of the effects of dietary modification in breast cancer survivors is lacking. Here, we summarize the literature and highlight important data regarding the association between dietary interventions and breast cancer outcomes.

RECENT FINDINGS

Long-term follow-up and secondary analysis of the Women's Health Initiative study demonstrated a significant improvement in overall survival for women who were randomized to the low-fat diet pattern compared with those in the usual-diet group. Dietary quality as measured by Healthy Eating Index score was also associated with both a decrease in cancer-specific mortality and overall mortality. Despite current evidence on the role of diet and nutrition in breast cancer outcomes, conclusive data to translate current findings to clinical practice is lacking and requires multidisciplinary prospective research to advance the field.

Effect of long-term dietary probiotic Lactobacillus reuteri 1 or antibiotics on meat quality, muscular amino acids and fatty acids in pigs

This study investigated effects of 175-d dietary treatment with Lactobacillus reuteri 1 (LR1) or antibiotics (olaquindox and aureomycin) on the longissimus thoracis (LT) of pigs. Results showed that antibiotics decreased pork quality by increasing drip loss, shear force, and altering myofiber characteristics including diameter, cross-sectional area and myosin heavy chain isoforms compared to LR1. Pigs fed antibiotics had lower muscle contents of free glutamic acid, inosinic acid, and higher glutamine compared to pigs fed the controls and LR1 diets (P ≤ .05). Furthermore, antibiotics decreased free isoleucine, leucine, methionine in LT compared to the control (P ≤ .05). Compared to antibiotics, LR1 likely improved protein synthesis by modulating expression of amino acid transport and ribosomal protein S6 kinase 1 (S6K1) genes, and altered fatty acid profile by regulating metabolic pathways. Overall, LR1 improved pork quality compared to antibiotics by decreasing drip loss and shear force, increasing inosinic acid and glutamic acid that may improve flavor, and altering muscle fiber characteristics.

Embryonic response to high beta-hydroxybutyrate (BHB) levels in postpartum dairy cows

Cows at the beginning of lactation often do not meet their energy needs by feeding and therefore mobilize body fat, which produces ketone bodies, including β-hydroxybutyrate (BHB). They are nevertheless usually inseminated around 60 d postpartum, when they are still in this characteristic period of energy deficit. The aim of this study was to observe the effects of negative energy balance on embryo quality and to identify ways to improve the fertility of dairy cows. Holstein cows (n = 18) grouped as high or low BHB based on blood measurement at day 45 postpartum were estrus-synchronized and treated with follicle-stimulating hormone to obtain multiple follicle development, induced to ovulate and inseminated with sexed semen around day 60 postpartum. Of the 290 embryos collected over 16 mo, 159 were of quality I to IV. Based on microarray analysis of gene expression, exposure to an energy deficit metabolic environment (high BHB) during early development appeared to modify signaling by the mTOR and sirtuins pathways in the embryo, implying mitochondrial dysfunction and inhibition of transcription, leading to slower cell division, thus programming the embryo to be more energy efficient. Altered methylation markers suggested that such coping mechanisms might persist into adulthood.

Role of Cyclin-Dependent Kinase 1 in Translational Regulation in the M-Phase

Cyclin dependent kinase 1 (CDK1) has been primarily identified as a key cell cycle regulator in both mitosis and meiosis. Recently, an extramitotic function of CDK1 emerged when evidence was found that CDK1 is involved in many cellular events that are essential for cell proliferation and survival. In this review we summarize the involvement of CDK1 in the initiation and elongation steps of protein synthesis in the cell. During its activation, CDK1 influences the initiation of protein synthesis, promotes the activity of specific translational initiation factors and affects the functioning of a subset of elongation factors. Our review provides insights into gene expression regulation during the transcriptionally silent M-phase and describes quantitative and qualitative translational changes based on the extramitotic role of the cell cycle master regulator CDK1 to optimize temporal synthesis of proteins to sustain the division-related processes: mitosis and cytokinesis.

Leukocyte Nucleolus and Anisakis pegreffii-When Falling Apart Means Falling in Place

The view of the nucleolus as a mere ribosomal factory has been recently expanded, highlighting its essential role in immune and stress-related signalling and orchestrating. It has been shown that the nucleolus structure, formed around nucleolus organiser regions (NORs) and attributed Cajal bodies, is prone to disassembly and reassembly correlated to various physiological and pathological stimuli. To evaluate the effect of parasite stimulus on the structure of the leukocyte nucleolus, we exposed rat peripheral blood mononuclear cells (PBMC) to the crude extract of the nematode A. pegreffii (Anisakidae), and compared the observed changes to the effect of control (RPMI-1640 media), immunosuppressive (MPA) and immunostimulant treatment (bacterial lipopolysaccharide (LPS) and viral analogue polyinosinic:polycytidylic acid (poly I:C)) by confocal microscopy. Poly I:C triggered the most accentuated changes such as nucleolar fragmentation and structural unravelling, LPS induced nucleolus thickening reminiscent of cell activation, while MPA induced disassembly of dense fibrillar and granular components. A. pegreffii crude extract triggered nucleolar segregation, expectedly more enhanced in treatment with a higher dose. This is the first evidence that leukocyte nucleoli already undergo structural changes 12 h post-parasitic stimuli, although these are likely to subside after successful cell activation.

Enzyme Replacement Therapy Can Reverse Pathogenic Cascade in Pompe Disease

Pompe disease, a deficiency of glycogen-degrading lysosomal acid alpha-glucosidase (GAA), is a disabling multisystemic illness that invariably affects skeletal muscle in all patients. The patients still carry a heavy burden of the disease, despite the currently available enzyme replacement therapy. We have previously shown that progressive entrapment of glycogen in the lysosome in muscle sets in motion a whole series of “extra-lysosomal” events including defective autophagy and disruption of a variety of signaling pathways. Here, we report that metabolic abnormalities and energy deficit also contribute to the complexity of the pathogenic cascade. A decrease in the metabolites of the glycolytic pathway and a shift to lipids as the energy source are observed in the diseased muscle. We now demonstrate in a pre-clinical study that a recently developed replacement enzyme (recombinant human GAA; AT-GAA; Amicus Therapeutics) with much improved lysosome-targeting properties reversed or significantly improved all aspects of the disease pathogenesis, an outcome not observed with the current standard of care. The therapy was initiated in GAA-deficient mice with fully developed muscle pathology but without obvious clinical symptoms; this point deserves consideration.

mTOR-Myc axis drives acinar-to-dendritic cell transition and the CD4+ T cell immune response in acute pancreatitis

The inflammatory response in acute pancreatitis (AP) is associated with acinar-to-dendritic cell transition. The CD4+ T-cell-mediated adaptive immune response is necessary for pancreatic inflammatory damage. However, the effect of acinar-to-dendritic cell transition on the CD4+ T-cell response and the regulatory mechanism remain undefined. A mouse animal model of AP was established by repeated intraperitoneal injection of CAE. The mTOR inhibitor rapamycin was administered before AP induction. Primary acinar cells were isolated and co-incubated with subsets of differentiated CD4+ T cells. The expression of DC-SIGN was also assessed in pancreatic tissues from human AP patients. We found acinar cells expressed DC-SIGN and displayed the phenotype of dendritic cells (DCs), which promoted the differentiation of naive CD4+ T cells into CD4+/IFN-γ+ Th1 and CD4+/IL-17A+ Th17 cells in pancreatic tissues during AP. DC-SIGN was the target gene of Myc. The mTOR inhibitor rapamycin inhibited AP-induced DC-SIGN expression, CD4+ Th1/Th17 cell differentiation and the pro-inflammatory response via Myc. Acinar cells expressed DC-SIGN in pancreatic tissues of human patients with AP. In conclusion, acinar-to-dendritic cell transition is implicated in the CD4+ T-cell immune response via mTOR-Myc-DC-SIGN axis, which might be an effective target for the prevention of local pancreatic inflammation in AP.

A suppressive oligodeoxynucleotide expressing TTAGGG motifs modulates cellular energetics through the mTOR signaling pathway

Immune-mediated inflammation must be down-regulated to facilitate tissue remodeling during homeostatic restoration of an inflammatory response. Uncontrolled or over-exuberant immune activation can cause autoimmune diseases, as well as tissue destruction. A151, the archetypal example of a chemically synthesized suppressive oligodeoxynucleotide (ODN) based on repetitive telomere-derived TTAGGG sequences, was shown to successfully down-regulate a variety of immune responses. However, the degree, duration and breadth of A151-induced transcriptome alterations remain elusive. Here, we performed a comprehensive microarray analysis in combination with Ingenuity Pathway Analysis (IPA) using murine splenocytes to investigate the underlying mechanism of A151-dependent immune suppression. Our results revealed that A151 significantly down-regulates critical mammalian target of rapamycin (mTOR) activators (Pi3kcd, Pdpk1 and Rheb), elements downstream of mTOR signaling (Rps6ka1, Myc, Stat3 and Slc2a1), an important component of the mTORC2 protein complex (Rictor) and Mtor itself. The effects of A151 on mTOR signaling were dose- and time-dependent. Moreover, flow cytometry and immunoblotting analyses demonstrated that A151 is able to reverse mTOR phosphorylation comparably to the well-known mTOR inhibitor rapamycin. Furthermore, Seahorse metabolic assays showed an A151 ODN-induced decrease in both oxygen consumption and glycolysis implying that a metabolically inert state in macrophages could be triggered by A151 treatment. Overall, our findings suggested novel insights into the mechanism by which the immune system is metabolically modulated by A151 ODN.

Influence of dietary replacement of fish meal with fish soluble meal on growth and TOR signaling pathway in juvenile black sea bream (Acanthopagrus schlegelii)

An 8-week feeding trial was conducted to evaluate the effect of replacement of fish meal (FM) with fish soluble meal (FSM) on growth performance, feed utilization and expression of genes involved in TOR signaling pathway for juvenile black sea bream (Acanthopagrus schlegelii). Six isonitrogenous (41%) and isolipidic diets were prepared to contain graded levels of FSM which replaced 0% (control diet), 10%, 20%, 30%, 40% and 60% protein from FM. Triplicate groups of 20 fish with initial weight 0.51 ± 0.01 g were fed with experimental diets twice daily to apparent satiation. The results showed significant differences in growth performance and feed utilization among all treatments, final body weight (FBW), percent weight gain (PWG), specific growth rate (SGR) and protein efficiency ratio (PER) significantly increased with dietary replacement levels of FM with FSM increasing from 0% to 40% (P < 0.05), PWG, SGR and PER were significantly reduced when replacement of FM with FSM further increased from 40% to 60%. Based on PWG against replacement levels of FM with FSM, A two-slope broken-line model analysis indicated that the optimal replacement of FM with FSM is to be 42.59%. Moreover, the lowest feed conversion ratio (FCR) was observed in fish fed the 40% FSM replacement diet. Muscle amino acid profile in muscle revealed that total essential amino acids, arginine and threonine were significantly influenced by replacement levels of FSM, while there was no significant difference in NEAA among all treatments. The hematological indices were not affected by the replacement levels of FM with FSM. The relative expression levels of irs-1, pi3k, akt, igf-1, s6k1 and tor were up-regulated when replacement levels of FM with FSM increased from 0% to 40%, and higher values were observed in fish fed with 40% FSM replacement diet compared to those fed the other diets. However, relative expression of 4e-bp2 was down-regulated when replacement levels of FM with FSM increased from 0% to 40% (P < 0.05). In summary, the results of present study indicated that FSM could be a viable alternative protein source for black sea bream, dietary FSM supplementation could improve growth and up-regulate the relative expression of irs-1, pi3k, akt, igf-1, s6k1 genes related to TOR signaling pathway in liver of juvenile black sea bream.

Modulating EGFR-MTORC1-autophagy as a potential therapy for persistent fetal vasculature (PFV) disease

Persistent fetal vasculature (PFV) is a human disease that results from failure of the fetal vasculature to regress normally. The regulatory mechanisms responsible for fetal vascular regression remain obscure, as does the underlying cause of regression failure. However, there are a few animal models that mimic the clinical manifestations of human PFV, which can be used to study different aspects of the disease. One such model is the Nuc1 rat model that arose from a spontaneous mutation in the Cryba1 (crystallin, beta 1) gene and exhibits complete failure of the hyaloid vasculature to regress. Our studies with the Nuc1 rat indicate that macroautophagy/autophagy, a process in eukaryotic cells for degrading dysfunctional components to ensure cellular homeostasis, is severely impaired in Nuc1 ocular astrocytes. Further, we show that CRYBA1 interacts with EGFR (epidermal growth factor receptor) and that loss of this interaction in Nuc1 astrocytes increases EGFR levels. Moreover, our data also show a reduction in EGFR degradation in Nuc1 astrocytes compared to control cells that leads to over-activation of the mechanistic target of rapamycin kinase complex 1 (MTORC1) pathway. The impaired EGFR-MTORC1-autophagy signaling in Nuc1 astrocytes triggers abnormal proliferation and migration. The abnormally migrating astrocytes ensheath the hyaloid artery, contributing to the pathogenesis of PFV in Nuc1, by adversely affecting the vascular remodeling processes essential to regression of the fetal vasculature. Herein, we demonstrate in vivo that gefitinib (EGFR inhibitor) can rescue the PFV phenotype in Nuc1 and may serve as a novel therapy for PFV disease by modulating the EGFR-MTORC1-autophagy pathway.

ABBREVIATIONS

ACTB: actin, beta; CCND3: cyclin 3; CDK6: cyclin-dependent kinase 6; CHQ: chloroquine; COL4A1: collagen, type IV, alpha 1; CRYBA1: crystallin, beta A1; DAPI: 4'6-diamino-2-phenylindole; EGFR: epidermal growth factor receptor; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFAP: glial fibrillary growth factor; KDR: kinase insert domain protein receptor; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MKI67: antigen identified by monoclonal antibody Ki 67; MTORC1: mechanistic target of rapamycin kinase complex 1; PARP: poly (ADP-ribose) polymerase family; PCNA: proliferating cell nuclear antigen; PFV: persistent fetal vasculature; PHPV: persistent hyperplastic primary vitreous; RPE: retinal pigmented epithelium; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase, polypeptide 1; SQSTM1/p62: sequestome 1; TUBB: tubulin, beta; VCL: vinculin; VEGFA: vascular endothelial growth factor A; WT: wild type.

RICTOR/mTORC2 affects tumorigenesis and therapeutic efficacy of mTOR inhibitors in esophageal squamous cell carcinoma

Dysregulation of mTORC1/mTORC2 pathway is observed in many cancers and mTORC1 inhibitors have been used clinically in many tumor types; however, the mechanism of mTORC2 in tumorigenesis is still obscure. Here, we mainly explored the potential role of mTORC2 in esophageal squamous cell carcinoma (ESCC) and its effects on the sensitivity of cells to mTOR inhibitors. We demonstrated that RICTOR, the key factor of mTORC2, and p-AKT (Ser473) were excessively activated in ESCC and their overexpression is related to lymph node metastasis and the tumor-node-metastasis (TNM) phase of ESCC patients. Furthermore, we found that mTORC1/ mTORC2 inhibitor PP242 exhibited more efficacious anti-proliferative effect on ESCC cells than mTORC1 inhibitor RAD001 due to RAD001-triggered feedback activation of AKT signal. Another, we demonstrated that down-regulating expression of RICTOR in ECa109 and EC9706 cells inhibited proliferation and migration as well as induced cell cycle arrest and apoptosis. Noteworthy, knocking-down stably RICTOR significantly suppresses RAD001-induced feedback activation of AKT/PRAS40 signaling, and enhances inhibition efficacy of PP242 on the phosphorylation of AKT and PRAS40, thus potentiates the antitumor effect of RAD001 and PP242 both in vitro and in vivo. Our findings highlight that selective targeting mTORC2 could be a promising therapeutic strategy for future treatment of ESCC.

SHMT2 Promotes Liver Regeneration Through Glycine-activated Akt/mTOR Pathway

BACKGROUND

The development of liver transplantation (LT) is increasingly being limited by the unavailability of liver grafts. Unique regenerative capacity of liver in response to injuries makes living-donor liver transplantation (LDLT) a feasible strategy to meet clinical demands. Serine hydroxymethyl-transferase 2 (SHMT2) serves as the key enzyme in the biosynthesis of glycine. Glycine affects the activity of mammalian target of rapamycin (mTOR), which is important for cellular growth and proliferation. In this study, the effects of SHMT2 on mouse liver regeneration were investigated using a classical partial hepatectomy (PH) model.

METHODS

In vivo, PH was performed on mice with or without knockdown of SHMT2. In vitro, SHMT2 was overexpressed in primary hepatocytes, which were cultured in customized Dulbecco's modified eagle media and LY294002 (an Akt inhibitor). Relevant indexes of liver regeneration, cell proliferation, and Akt/mTOR signal pathways were analyzed.

RESULTS

After PH, the expression levels of SHMT2 fluctuated with time and knockdown of SHMT2 in vivo lowered the regenerative ability of liver, with reduced glycine levels compared to the scramble group. In addition, overexpression of SHMT2 in hepatocytes boosted glycine production while enhancing Akt/mTOR pathway activity. These results were validated by the application of LY294002 in vitro.

CONCLUSIONS

SHMT2 can contribute to liver regeneration after PH, and this is likely related to the activation of Akt/mTOR signaling pathway by its metabolic product, glycine, in hepatocytes. These results might have therapeutic implications for the prognosis of patients undergoing hepatic resection or transplantation.

Lipid Metabolism in Development and Progression of Hepatocellular Carcinoma

: Metabolic reprogramming is critically involved in the development and progression of cancer. In particular, lipid metabolism has been investigated as a source of energy, micro-environmental adaptation, and cell signalling in neoplastic cells. However, the specific role of lipid metabolism dysregulation in hepatocellular carcinoma (HCC) has not been widely described yet. Alterations in fatty acid synthesis, β-oxidation, and cellular lipidic composition contribute to initiation and progression of HCC. The aim of this review is to elucidate the mechanisms by which lipid metabolism is involved in hepatocarcinogenesis and tumour adaptation to different conditions, focusing on the transcriptional aberrations with new insights in lipidomics and lipid zonation. This will help detect new putative therapeutic approaches in the second most frequent cause of cancer-related death.

Metabolic Regulation and Related Molecular Mechanisms in Various Stem Cell Functions

Recent studies on the mechanisms that link metabolic changes with stem cell fate have deepened our understanding of how specific metabolic pathways can regulate various stem cell functions during the development of an organism. Although it was originally thought to be merely a consequence of the specific cell state, metabolism is currently known to play a critical role in regulating the self-renewal capacity, differentiation potential, and quiescence of stem cells. Many studies in recent years have revealed that metabolic pathways regulate various stem cell behaviors (e.g., selfrenewal, migration, and differentiation) by modulating energy production through glycolysis or oxidative phosphorylation and by regulating the generation of metabolites, which can modulate multiple signaling pathways. Therefore, a more comprehensive understanding of stem cell metabolism could allow us to establish optimal culture conditions and differentiation methods that would increase stem cell expansion and function for cell-based therapies. However, little is known about how metabolic pathways regulate various stem cell functions. In this context, we review the current advances in metabolic research that have revealed functional roles for mitochondrial oxidative phosphorylation, anaerobic glycolysis, and oxidative stress during the self-renewal, differentiation and aging of various adult stem cell types. These approaches could provide novel strategies for the development of metabolic or pharmacological therapies to promote the regenerative potential of stem cells and subsequently promote their therapeutic utility.

Regulation of insulin resistance and glucose metabolism by interaction of PIM kinases and insulin receptor substrates

Insulin resistance is caused by various environmental and genetic factors leading to a number of serious health issues. Due to its multifactorial origin, molecular characterization may provide better tools for its effective treatment. On molecular level, dysregulation of signaling pathway by insulin receptor substrates (IRSs) is one of the most common reasons of this disease. IRSs are regulated by >50 serine/threonine kinases, which may have positive or negative effects on insulin sensitivity. Among these serine/threonine kinases, PIM kinases have garnered much attention as they not only affect insulin sensitivity by phosphorylating IRSs directly and/or indirectly but also alter the activities of their downstream molecules like PI3K, AKT, and mTOR. In this review, interactions of PIM kinases with IRSs and their downstream proteins and their action mechanism in the regulation of insulin resistance are elaborated. Furthermore, this review offers fundamental understandings of the role of PIM kinases in this signaling pathway.

Fyn Kinase: A Potential Therapeutic Target in Acute Kidney Injury

Acute kidney injury (AKI) is a common disease with a complex pathophysiology which significantly contributes to the development of chronic kidney disease and end stage kidney failure. Preventing AKI can consequently reduce mortality, morbidity, and healthcare burden. However, there are no effective drugs in use for either prevention or treatment of AKI. Developing therapeutic agents with pleiotropic effects covering multiple pathophysiological pathways are likely to be more effective in attenuating AKI. Fyn, a non-receptor tyrosine kinase, has been acknowledged to integrate multiple injurious stimuli in the kidney. Limited studies have shown increased Fyn transcription level and activation under experimental AKI. Activated Fyn kinase propagates various downstream signaling pathways associated to the progression of AKI, such as oxidative stress, inflammation, endoplasmic reticulum stress, as well as autophagy dysfunction. The versatility of Fyn kinase in mediating various pathophysiological pathways suggests that its inhibition can be a potential strategy in attenuating AKI.

Oxidative Stress Triggers Selective tRNA Retrograde Transport in Human Cells during the Integrated Stress Response

In eukaryotes, tRNAs are transcribed in the nucleus and exported to the cytosol, where they deliver amino acids to ribosomes for protein translation. This nuclear-cytoplasmic movement was believed to be unidirectional. However, active shuttling of tRNAs, named tRNA retrograde transport, between the cytosol and nucleus has been discovered. This pathway is conserved in eukaryotes, suggesting a fundamental function; however, little is known about its role in human cells. Here we report that, in human cells, oxidative stress triggers tRNA retrograde transport, which is rapid, reversible, and selective for certain tRNA species, mostly with shorter 3′ ends. Retrograde transport of tRNA^SeC, which promotes translation of selenoproteins required to maintain homeostatic redox levels in cells, is highly efficient. tRNA retrograde transport is regulated by the integrated stress response pathway via the PERK-REDD1-mTOR axis. Thus, we propose that tRNA retrograde transport is part of the cellular response to oxidative stress.

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Oxidative stress triggers nuclear import of cytoplasmic tRNAs

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Import is selective for certain tRNAs

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Import requires activation of the unfolded protein response and inhibition of mTOR via REDD1

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tRNA nuclear import is a component of the integrated stress response

p-Coumaric acid prevents obesity via activating thermogenesis in brown adipose tissue mediated by mTORC1-RPS6

Brown adipose tissue (BAT) has long been recognized as an energy-consuming organ and a possible target for combating metabolism disorder. Although numerous studies have demonstrated the ability of phytochemical phenolic acids to improve obesity by activating BAT, the underlying mechanism or mechanism therein remain obscure. In this study, diet-induced obese mice, genetically obese mice, and C3H10T1/2 cells were used to examine the effects of p-Coumaric acid (CA) on metabolism profiles. The results showed that CA prevented metabolic syndromes in the two mice models through the activation of BAT. This phenomenon was closely linked to the upregulation of uncoupling protein 1 (UCP1) and the accelerated burning of fatty acids and glucose, which consequently enhanced the energy expenditure and thermogenesis. Similar results were also obtained in vitro. Importantly, these effects were mediated by the mammalian target of rapamycin complex 1 (mTORC1)-RPS6 pathway. These findings reveal, to the best of our knowledge for the first time, the close correlation between mTORC1-RPS6 and BAT-mediated thermogenesis, and, in addition, the key role played by mTORC1-RPS6 in mediating phenolic acids-induced activation of BAT, thus preventing obesity.

Interleukin-22 drives a metabolic adaptive reprogramming to maintain mitochondrial fitness and treat liver injury

Rationale: Interleukin 22 (IL-22) is an epithelial survival cytokine that is at present being explored as therapeutic agents for acute and chronic liver injury. However, its molecular basis of protective activities remains poorly understood. Methods: Here we demonstrate that IL-22 inhibits the deteriorating metabolic states induced by stimuli in hepatocytes. Utilizing cell biological, molecular, and biochemical approaches, we provide evidence that IL-22 promotes oxidative phosphorylation (OXPHOS) and glycolysis and regulates the metabolic reprogramming related transcriptional responses. Results: IL-22 controls metabolic regulators and enzymes activity through the induction of AMP-activated protein kinase (AMPK), AKT and mammalian target of rapamycin (mTOR), thereby ameliorating mitochondrial dysfunction. The upstream effector lncRNA H19 also participates in the controlling of these metabolic processes in hepatocytes. Importantly, amelioration of liver injury by IL-22 through activation of metabolism relevant signaling and regulation of mitochondrial function are further demonstrated in cisplatin-induced liver injury and steatohepatitis. Conclusions: Collectively, our results reveal a novel mechanism underscoring the regulation of metabolic profiles of hepatocytes by IL-22 during liver injury, which might provide useful insights from the bench to the clinic in treating and preventing liver diseases.

Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment

Hepatitis C virus (HCV) infection is the major risk factor for liver cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of HCC initiation, growth, and metastasis appear to be highly complex due to the decade-long interactions between the virus, immune system, and overlapping bystander effects of host metabolic liver disease. The lack of a readily accessible animal model system for HCV is a significant obstacle to understand the mechanisms of viral carcinogenesis. Traditionally, the primary prevention strategy of HCC has been to eliminate infection by antiviral therapy. The success of virus elimination by antiviral treatment is determined by the SVR when the HCV is no longer detectable in serum. Interferon-alpha (IFN-α) and its analogs, pegylated IFN-α (PEG-IFN-α) alone with ribavirin (RBV), have been the primary antiviral treatment of HCV for many years with a low cure rate. The cloning and sequencing of HCV have allowed the development of cell culture models, which accelerated antiviral drug discovery. It resulted in the selection of highly effective direct-acting antiviral (DAA)-based combination therapy that now offers incredible success in curing HCV infection in more than 95% of all patients, including those with cirrhosis. However, several emerging recent publications claim that patients who have liver cirrhosis at the time of DAAs treatment face the risk of HCC occurrence and recurrence after viral cure. This remains a substantial challenge while addressing the long-term benefit of antiviral medicine. The host-related mechanisms that drive the risk of HCC in the absence of the virus are unknown. This review describes the multifaceted mechanisms that create a tumorigenic environment during chronic HCV infection. In addition to the potential oncogenic programming that drives HCC after viral clearance by DAAs, the current status of a biomarker development for early prediction of cirrhosis regression and HCC detection post viral treatment is discussed. Since DAAs treatment does not provide full protection against reinfection or viral transmission to other individuals, the recent studies for a vaccine development are also reviewed.

Lipotoxicity, Nutrient-Sensing Signals, and Autophagy in Diabetic Nephropathy

Diabetic nephropathy is a leading cause of proteinuria, kidney fibrosis, and subsequent end-stage renal disease. The renal prognosis of diabetic patients with refractory proteinuria is extremely poor. Therefore, identification of novel therapeutic targets to combat this serious condition and improve renal prognosis is urgently necessary. In diabetic patients, in addition to blood glucose levels, serum levels of free fatty acids (FFAs) are chronically elevated, even during postprandial periods. Of the various types of FFAs, saturated FFAs are highly cytotoxic and their levels are elevated in the serum of patients with diabetes. Thus, an increase in saturated FFAs is currently thought to contribute to proximal tubular cell damage and podocyte injury in diabetic nephropathy. Therefore, protecting both types of kidney cells from saturated FFA-related lipotoxicity may become a novel therapeutic approach for diabetic patients with refractory proteinuria. Interestingly, accumulating evidence suggests that controlling intracellular nutrient signals and autophagy can ameliorate the FFA-related kidney damage. Here, we review the evidence indicating possible mechanisms underlying cell injury caused by saturated FFAs and cell protective roles of intracellular nutrient signals and autophagy in diabetic nephropathy.

Simultaneous inhibition of atypical protein kinase‑C and mTOR impedes bladder cancer cell progression

Despite enormous scientific advancements in cancer treatment, there is a need for research to combat cancer, particularly bladder cancer. Drugs once proved to be effective in treating bladder cancer have shown reduced efficacy; hence, the cancer recurrence rate is increasing. To overcome this situation, several strategies have been considered, including the development of novel active drugs or modification of existing therapeutic regimens by combining two or more existing drugs. In recent years, atypical protein kinase Cs (PKCs), phospholipid-dependent serine/threonine kinases, have been considered as a central regulator of various cancer-associated signaling pathways, and they control cell cycle progression, tumorigenesis and metastasis. Additionally, the biologically crucial mTOR signaling pathway is altered in numerous types of cancer, including bladder cancer. Furthermore, despite independent activation, atypical PKC signaling can be triggered by mTOR. The present study examined whether the concurrent inhibition of atypical PKCs and mTOR using a combination of novel atypical PKC inhibitors (ICA-I, an inhibitor of PKC-ι; or ζ-Stat, an inhibitor of PKC-ζ) and rapamycin blocks bladder cancer progression. In the present study, healthy bladder MC-SV-HUCT2 and bladder cancer TCCSUP cells were tested and subjected to a WST1 assay, western blot analysis, immunoprecipitation, a scratch wound healing assay, flow cytometry and immunofluorescence analyses. The results revealed that the combination therapy induced a reduction in human bladder cancer cell viability compared with control and individual atypical PKC inhibitor and rapamycin treatment. Additionally, the concurrent inhibition of atypical PKCs and mTOR retards the migration of bladder cancer cells. These findings indicated that the administration of atypical PKC inhibitors together with rapamycin could be a useful therapeutic option in treating bladder cancer.