Lipid Sensing by Mammalian Target of Rapamycin

Mammalian target of Rapamycin (mTOR) is a protein kinase that integrates nutrient and growth factor signals to promote cellular growth and proliferation. mTOR exists in two complexes - mTORC1 and mTORC2 that are distinguished by their binding partners and signaling inputs. mTORC1 is responsive to growth factors, amino acids and glucose and is associated with Raptor; whereas, mTORC2 is responsive primarily to growth factors and is associated with Rictor. Raptor and Rictor confer substrate specificity to mTORC1 and mTORC2 respectively. Phosphatidic acid (PA), a lipid second messenger and a central metabolite for membrane phospholipid biosynthesis, is required for the stability and activation of both mTORC1 and mTORC2. The negatively charged head group of PA interacts with positively charged Lys and Arg residues in the FRB (FK-506 binding protein–12 (FKBP12)-rapamycin binding) domain of mTOR and stabilizes the mTOR complexes. The PA-binding site on mTOR is highly conserved from yeast to humans – indicating the importance of PA for mTOR function. While much is known about the role of amino acid sensing by mTOR, much less is known how mTOR responds to other essential nutrients needed for cell growth. An under-appreciated component of serum needed for cell growth is lipids that are used for the synthesis of membranes and organelles. Because of an increased utilization of exogenous lipids by KRas-driven cancer cells, we examined the effect of exogenously supplied lipids on mTORC1 and mTORC2 in KRas-driven cancer cells. We demonstrate that both mTORC1 and mTORC2 are responsive to dietary unsaturated fatty acids through the de novo synthesis of PA. Fatty acids entering the cell are activated through an ATP dependent linking of Coenzyme A (CoA) by Acyl-CoA synthetase, and thereby shunting them towards de novo PA synthesis. We find that a specific isoform of Acyl-CoA synthetase longchain (ACSL)-5 is overexpressed in KRas-driven cancer cells. Genetic ablation of ACSL5 inhibits oleate-mediated activation of mTORC1 and mTORC2 through reduction in levels of PA. Further, inhibition of ACSL5 leads to a G1 cell cycle arrest in Ras driven cells. The activation of mTOR by oleic acid was also dependent on lysophosphatidic acid acyltransferase that adds the CoA-charged fatty acid to 1-acylglycerol-3-phosphate to generate PA. Of significance, the glycerol-3-phosphate that gets acylated to PA was derived by reduction of the glycolytic intermediate dihydroxyacetone phosphate – indicating that glucose is also sensed by mTOR via PA. In response to lipids, we observed that mTORC2 co-localizes with the mitochondrial fraction where it activates downstream targets to regulate mitochondrial metabolism. While it has long been appreciated that mTOR is a sensor of amino acids, this study reveals that mTOR also senses the presence of lipids and glucose via production of PA

Vacancy-mediated mechanism of nitrogen substitution in carbon nanotubes

Nitrogen substitution reaction in a graphene sheet and carbon nanotubes of different diameter are investigated using the generalized tight-binding molecular dynamics method. The formation of a vacancy in curved graphene sheet or a carbon nanotube is found to cause a curvature dependent local reconstruction of the surface. Our simulations and analysis show that vacancy mediated N substitution (rather than N chemisorption) is favored on the surface of nanotubes with diameter larger than 8 nm. This predicted value of the critical minimum diameter for N incorporation is confirmed by experimental results presented on nitrogen-doped multiwalled nanotubes with [approximate]5 at. % nitrogen prepared by the thermal chemical vapor deposition process

Analysis of Blood Flow through Viscoelastic Blood Vessel

Analysis of viscoelastic material can be done through ansys multi physics software. For modelling viscoelastic materials, prony series coefficients had been generated from the stress relaxation data (shear modulus vs. time) using prony series curve fitting. Also, Ansys was used to study the fluid interaction on viscoelastic materials. First blood vessel was modelled using geometric modeller and it is exported to ansys and using prony series curve fitting, viscoelastic properties are given to the blood vessel. Blood flow was modelled in CFX. Two way coupling was established between Ansys and CFX. And the boundary conditions such as pressure pulse and mass flow rate was given to the blood flow. Then the model was solved in CFX. And the variation of pressure, von mises stress and total mesh displacement along the length of blood vessel is plotted

Switching and Rectification in Carbon-Nanotube Junctions

Multi-terminal carbon-nanotube junctions are under investigation as candidate components of nanoscale electronic devices and circuits. Three-terminal "Y" junctions of carbon nanotubes (see Figure 1) have proven to be especially interesting because (1) it is now possible to synthesize them in high yield in a controlled manner and (2) results of preliminary experimental and theoretical studies suggest that such junctions could exhibit switching and rectification properties. Following the preliminary studies, current-versus-voltage characteristics of a number of different "Y" junctions of single-wall carbon nanotubes connected to metal wires were computed. Both semiconducting and metallic nanotubes of various chiralities were considered. Most of the junctions considered were symmetric. These computations involved modeling of the quantum electrical conductivity of the carbon nanotubes and junctions, taking account of such complicating factors as the topological defects (pentagons, heptagons, and octagons) present in the hexagonal molecular structures at the junctions, and the effects of the nanotube/wire interfaces. A major component of the computational approach was the use of an efficient Green s function embedding scheme. The results of these computations showed that symmetric junctions could be expected to support both rectification and switching. The results also showed that rectification and switching properties of a junction could be expected to depend strongly on its symmetry and, to a lesser degree, on the chirality of the nanotubes. In particular, it was found that a zigzag nanotube branching at a symmetric "Y" junction could exhibit either perfect rectification or partial rectification (asymmetric current-versus-voltage characteristic, as in the example of Figure 2). It was also found that an asymmetric "Y" junction would not exhibit rectification

Study on clinical profile, scoring systems and outcomes of obstetric patients in our intensive care unit

Background: Obstetric patients in ICU, pose a clinical challenge to intensivists and obstetricians. The objective of our study was to evaluate the incidence, indications and interventions in these patients. Secondly to assess whether clinical scores can help to estimate severity of the condition, predict mortality and morbidity in these patients.Methods: It was a retrospective observational study including all antepartum and postpartum patients admitted to ICU between January 2018 to June 2020.Results: Majority of patients needing ICU care were in the antepartum period (82.8%). Multigravida (55.2%) and unbooked cases (60.4%) constituted a major proportion of patients. Hypertensive disorders of pregnancy followed by sepsis amounted for common etiologies. Transfusions (43.2%), ventilatory support (26%) followed by inotropic support (14.9%) were the interventions required in the majority number of patients. Maternal mortality rate was 2.23%. Out of the clinical scores, OEWS (Obstetric early warning score) was a better modality to assess the severity of the disease and the need for ICU care.Conclusions: A multidisciplinary approach and close coordinated care of obstetric patients can reduce the maternal mortality rate. Early identification of critically ill obstetric patients using clinical scores can help us in triaging patients to high dependency units/ICU. OEWS is a very simple score which helps us in identifying patients needing intensive care

Inhibiting glutamine utilization creates a synthetic lethality for suppression of ATP citrate lyase in KRas-driven cancer cells

Metabolic reprogramming is now considered a hallmark of cancer cells. KRas-driven cancer cells use glutaminolysis to generate the tricarboxylic acid cycle intermediate α -ketoglutarate via a transamination reaction between glutamate and oxaloacetate. We reported previously that exogenously supplied unsaturated fatty acids could be used to synthesize phosphatidic acid–a lipid second messenger that activates both mammalian target of rapamycin (mTOR) complex 1 (mTORC1) and mTOR complex 2 (mTORC2). A key target of mTORC2 is Akt–a kinase that promotes survival and regulates cell metabolism. We report here that mono- unsaturated oleic acid stimulates the phosphoryla tion of ATP citrate lyase (ACLY) at the Akt phosphorylation site at S455 in an mTORC2 dependent manner. Inhibition of ACLY in KRas-driven cancer cells in the absence of serum resulted in loss of cell viability. We examined the impact of glutamine (Gln) deprivation in combination with inhibition of ACLY on the viability of KRas-driven cancer cells. While Gln deprivation was somewhat toxic to KRas- driven cancer cells by itself, addition of the ACLY inhibitor SB-204990 increased the loss of cell viability. However, the transaminase inhibitor aminooxyace tate was minimally toxic and the combination of SB-204990 and aminooxtacetate led to significant loss of cell viability and strong cleavage of poly-ADP ribose polymerase–indicating apoptotic cell death. This effect was not observed in MCF7 breast cancer cells that do not have a KRas mutation or in BJ-hTERT human fibroblasts which have no oncogenic mutation. These data reveal a synthetic lethality between inhibition of glutamate oxaloacetate transaminase and ACLY inhibition that is specific for KRas-driven cancer cells and the apparent metabolic reprogramming induced by activating mutations to KRa

Conservation Laws and Integrability of a One-dimensional Model of Diffusing Dimers

We study a model of assisted diffusion of hard-core particles on a line. The model shows strongly ergodicity breaking : configuration space breaks up into an exponentially large number of disconnected sectors. We determine this sector-decomposion exactly. Within each sector the model is reducible to the simple exclusion process, and is thus equivalent to the Heisenberg model and is fully integrable. We discuss additional symmetries of the equivalent quantum Hamiltonian which relate observables in different sectors. In some sectors, the long-time decay of correlation functions is qualitatively different from that of the simple exclusion process. These decays in different sectors are deduced from an exact mapping to a model of the diffusion of hard-core random walkers with conserved spins, and are also verified numerically. We also discuss some implications of the existence of an infinity of conservation laws for a hydrodynamic description.Comment: 39 pages, with 5 eps figures, to appear in J. Stat. Phys. (March 1997

Amino Acids and mTOR Mediate Distinct Metabolic Checkpoints in Mammalian G1 Cell Cycle

Objective In multicellular organisms, cell division is regulated by growth factors (GFs). In the absence of GFs, cells exit the cell cycle at a site in G1 referred to as the restriction point (R) and enter a state of quiescence known as G0. Additionally, nutrient availability impacts on G1 cell cycle progression. While there is a vast literature on G1 cell cycle progression, confusion remains – especially with regard to the temporal location of R relative to nutrient-mediated checkpoints. In this report, we have investigated the relationship between R and a series of metabolic cell cycle checkpoints that regulate passage into S-phase. Methods We used double-block experiments to order G1 checkpoints that monitor the presence of GFs, essential amino acids (EEAs), the conditionally essential amino acid glutamine, and inhibition of mTOR. Cell cycle progression was monitored by uptake of [3H]-thymidine and flow cytometry, and analysis of cell cycle regulatory proteins was by Western-blot. Results We report here that the GF-mediated R can be temporally distinguished from a series of late G1 metabolic checkpoints mediated by EAAs, glutamine, and mTOR – the mammalian/mechanistic target of rapamycin. R is clearly upstream from an EAA checkpoint, which is upstream from a glutamine checkpoint. mTOR is downstream from both the amino acid checkpoints, close to S-phase. Significantly, in addition to GF autonomy, we find human cancer cells also have dysregulated metabolic checkpoints. Conclusion The data provided here are consistent with a GF-dependent mid-G1 R where cells determine whether it is appropriate to divide, followed by a series of late-G1 metabolic checkpoints mediated by amino acids and mTOR where cells determine whether they have sufficient nutrients to accomplish the task. Since mTOR inhibition arrests cells the latest in G1, it is likely the final arbiter for nutrient sufficiency prior to committing to replicating the genome

Beneficial impacts of biochar as a potential feed additive in animal husbandry

In the last decade, biochar production and use have grown in popularity. Biochar is comparable to charcoal and activated charcoal because it is a pyrogenic carbonaceous matter made by pyrolyzing organic carbon-rich materials. There is a lack of research into the effects of adding biochar to animal feed. Based on the reviewed literature, including its impact on the adsorption of toxins, blood biochemistry, feed conversion rate, digestion, meat quality, and greenhouse gas emissions, adding biochar to the diet of farm animals is a good idea. This study compiles the most important research on biochar's potential as a supplement to the diets of ruminants (including cows and goats), swine, poultry, and aquatic organisms like fish. Biochar supplementation improves animal growth, haematological profiles, meat, milk and egg yield, resistance to illnesses (especially gut pathogenic bacteria), and reduced ruminant methane emission. Biochar's strong sorption capacity also helps efficiently remove contaminants and poisons from the animals' bodies and the farm surroundings where they are raised. Animal farmers are predicted to make greater use of biochar in the future. Biochar could potentially be of value in the healthcare and human health fields; hence research into this area is encouraged. The present review highlights the potential benefits of biochar as an additive to animal feed and demonstrates how, when combined with other environmentally friendly practices, biochar feeding can extend the longevity of animal husbandry