Nutrient regulation of the mTOR complex 1 signaling pathway

Leucyl-tRNA synthetase 1 is required for proliferation of TSC-null cells

Uncontrolled cell proliferation associated with cancer depends on the functional abrogation of at least one of tumor suppressor. In response to nutrient cue, tuberous sclerosis complex (TSC) works as a tumor suppressor which inhibits cell growth via negative regulation of the mammalian target of rapamycin complex (mTORC1). However, the regulation mechanism of nutrient-dependent cell proliferation in TSC-null cells remains unclear. Here, we demonstrate that leucine is required for cell proliferation through the activation of leucyl-tRNA synthetase (LARS1)-mTORC1 pathway in TSC-null cells. Cell proliferation and survival were attenuated by LARS1 knock-down or inhibitors in TSC-null cells. In addition, either rapamycin or LARS1 inhibitors significantly decreased colony formation ability while their combined treatment drastically attenuated it. Taken together, we suggest that LARS1 inhibitors might considered as novel tools for the regression of tumor growth and proliferation in TSC-null tumor cells which regrow upon discontinuation of the mTORC1 inhibition.

Amino Acids Supplementation for the Milk and Milk Protein Production of Dairy Cows

Simple Summary

The composition of milk not only has nutritional implications, but is also directly related to the income of dairy producers. As regards milk’s composition, concerns around milk protein have emerged from the increased consumption of casein products. The synthesis of proteins in milk is a highly complex and high-cost process, because the conversion efficiency of dietary protein to milk protein is very low in dairy cows. Thus, some studies have increased milk protein by using protein supplements or a single amino acid (AA) supply. AAs are the building blocks of protein, and can also stimulate the protein synthetic pathway. This review mainly concerns the use of AAs for producing milk protein in high-producing dairy cows, particularly with methionine, lysine, and histidine. Understanding the mechanisms of AAs will help to promote milk protein synthesis in the dairy industry.

Abstract

As the preference of consumers for casein products has increased, the protein content of milk from dairy cows is drawing more attention. Protein synthesis in the milk of dairy cows requires a proper supply of dietary protein. High protein supplementation may help to produce more milk protein, but residues in feces and urine cause environmental pollution and increase production costs. As such, previous studies have focused on protein supplements and amino acid (AA) supply. This review concerns AA nutrition for enhancing milk protein in dairy cows, and mainly focuses on three AAs: methionine, lysine, and histidine. AA supplementation for promoting protein synthesis is related to the mammalian target of rapamycin (mTOR) complex and its downstream pathways. Each AA has different stimulating effects on the mTOR translation initiation pathway, and thus manifests different milk protein yields. This review will expand our understanding of AA nutrition and the involved pathways in relation to the synthesis of milk protein in dairy cows.

Use of deuterium oxide (2H2O) to assess muscle protein synthesis in juvenile red drum (Sciaenops ocellatus) fed complete, and valine-deficient diets

The use of ²H₂O in tank water to assess protein synthesis rates in fish is a relatively novel methodology that could allow for a better understanding of the effects of particular nutritional and environmental variables on rates of protein accretion. As such, this study involved an assessment and comparison of protein synthesis rates in the muscle of juvenile red drum fed a control diet (nutritionally complete) versus a valine (Val)-deficient diet. Six groups of 12 juvenile red drum, initially weighing ~ 4.5 g/fish, were stocked in six separate 38-L aquaria operating as a recirculating system. Fish were acclimatized to experimental conditions for 2 weeks while being fed the control diet. Just prior to initiating the protein synthesis assay, one aquarium of fish was fed the control diet while a second aquarium of fish was fed the Val-deficient diet. Immediately after consuming the experimental diets, each group of fish was moved to an independent aquarium containing ²H₂O, and the fractional synthetic rate (FSR) of protein synthesis was obtained at 12, 24, 36 and 48 h after feeding by collecting two fish per treatment at each time point. This protein synthesis assay procedure was performed in three separate sessions, and considered as replicates over time (n = 3) for fish fed the control or Val-deficient diets immediately before initiating the session. Results indicated that a one-time feeding of a diet deficient in Val significantly reduced protein synthesis rates in the muscle of red drum. In addition, a significant effect of time after feeding was found, where observed FSR values peaked at 12 h after feeding and decreased as time progressed. In conclusion, deuterium methodologies were applicable to red drum, and this approach had the sensitivity to assess differences in protein synthesis rates when dietary perturbations were introduced.

Graduate Student Literature Review: Mitochondrial adaptations across lactation and their molecular regulation in dairy cattle

As milk production in dairy cattle continues to increase, so do the energetic and nutrient demands on the dairy cow. Difficulties making the necessary metabolic adjustments for lactation can impair lactation performance and increase the risk of metabolic disorders. The physiological adaptations to lactation involve the mammary gland and extramammary tissues that coordinately enhance the availability of precursors for milk synthesis. Changes in whole-body metabolism and nutrient partitioning are accomplished, in part, through the bioenergetic and biosynthetic capacity of the mitochondria, providing energy and diverting important substrates, such as AA and fatty acids, to the mammary gland in support of lactation. With increased oxidative capacity and ATP production, reactive oxygen species production in mitochondria may be altered. Imbalances between oxidant production and antioxidant activity can lead to oxidative damage to cellular structures and contribute to disease. Thus, mitochondria are tasked with meeting the energy needs of the cell and minimizing oxidative stress. Mitochondrial function is regulated in concert with cellular metabolism by the nucleus. With only a small number of genes present within the mitochondrial genome, many genes regulating mitochondrial function are housed in nuclear DNA. This review describes the involvement of mitochondria in coordinating tissue-specific metabolic adaptations across lactation in dairy cattle and the current state of knowledge regarding mitochondrial-nuclear signaling pathways that regulate mitochondrial proliferation and function in response to shifting cellular energy need.

A Time-Course Comparison of Skeletal Muscle Metabolomic Alterations in Walker-256 Tumour-Bearing Rats at Different Stages of Life

Cancer cachexia is a severe wasting condition that needs further study to find ways to minimise the effects of damage and poor prognosis. Skeletal muscle is the most impacted tissue in cancer cachexia; thus, elucidation of its metabolic alterations could provide a direct clue for biomarker research and be applied to detect this syndrome earlier. In addition, concerning the significant changes in the host metabolism across life, this study aimed to compare the metabolic muscle changes in cachectic tumour-bearing hosts at different ages. We performed ¹H-NMR metabolomics in the gastrocnemius muscle in weanling and young adult Walker-256 tumour-bearing rats at different stages of tumour evolution (initial, intermediate, and advanced). Among the 49 metabolites identified, 24 were significantly affected throughout tumour evolution and 21 were significantly affected regarding animal age. The altered metabolites were mainly related to increased amino acid levels and changed energetic metabolism in the skeletal muscle, suggesting an expressive catabolic process and diverted energy production, especially in advanced tumour stages in both groups. Moreover, these changes were more severe in weanling hosts throughout tumour evolution, suggesting the distinct impact of cancer cachexia regarding the host's age, highlighting the need to adopting the right animal age when studying cancer cachexia.

Serum biochemical parameters and amino acids metabolism are altered in piglets by early-weaning and proline and putrescine supplementations

The study was to investigate the effect of early-weaning stress and proline (Pro) and putrescine (Put) supplementations on serum biochemical parameters and amino acids (AA) metabolism in suckling and post-weaning pigs. Blood and small intestinal mucosa were harvested from suckling piglets at 1, 7, 14, and 21 d of age and piglets on d 1, 3, 5, and 7 after weaning at 14 d of age, as well as from piglets received oral administration of Pro and Put from 1 to 14 d old. In suckling piglets, the serum glucose, albumin and total cholesterol levels were increased (P < 0.05) with increasing age, whereas the serum globulin, urea nitrogen (BUN), alkaline phosphatase (ALP) and aspartate aminotransferase (AST) levels were lowered (P < 0.05). The concentrations of most serum AA and the AA transporters related gene expressions were highest in 7-d-old piglets (P < 0.05), whereas the phosphorylation status of the mammalian target of the rapamycin (mTOR) signaling pathway in the small intestine increased in piglets from 1 to 21 d old (P < 0.05). Weaning at 14 d old increased (P < 0.05) the BUN and triglycerides levels in serum, as well as jejunal solute carrier family 7 member 6 (SLC7A6), ileal SLC36A1 and SLC1A1 mRNA abundances at d 1 or 3 post-weaning. Weaning also inhibited (P < 0.05) the phosphorylation levels of mTOR and its downstream ribosomal protein S6 kinase 1 (S6K1) and 4E-binding protein-1 (4EBP1) in the small intestine of weanling pigs. Oral administration of Put and Pro decreased (P < 0.05) serum ALP levels and increased (P < 0.05) intestinal SLC36A1 and SLC1A1 mRNA abundances and mTOR pathway phosphorylation levels in post-weaning pigs. Pro but not Put treatment enhanced (P < 0.05) serum Pro, arginine (Arg) and glutamine (Gln) concentrations of weaning-pigs. These findings indicated that early-weaning dramatically altered the biochemical blood metabolites, AA profile and intestinal mTOR pathway activity, and Pro and Put supplementations improved the AA metabolism and transportation as well as activated the intestinal mTOR pathway in weanling-pigs. Our study has an important implication for the broad application of Pro and Put in the weaning transition of piglets.

Effects of L-Histidine and Sodium Acetate on β-Casein Expression in Nutrient-Restricted Bovine Mammary Epithelial Cells

Simple Summary

Nutrient restriction is known to decrease the milk production and milk quality of dairy cows. However, providing cows with abundant nutrients also has a disadvantage because it will increase feed costs. Under such a situation, the use of feed additives can be a good strategy to reduce the feed cost. The objective of this study was to investigate the effects of histidine and sodium acetate on β-casein expression in nutrient-restricted bovine mammary epithelial cells. The results indicate that histidine has the potential to increase the β-casein levels in bovine mammary cells when the nutrient is restricted, suggesting that histidine is a potential feed additive for cows in a nutrient-insufficient environment.

Abstract

Nutrient restriction is a challenging condition for the mammary glands of dairy cows. In this condition, supplementing amino acids and energy sources might be a good strategy to improve the concentration of one of the most important caseins in bovine milk. Therefore, the objective of this study was to investigate the effects of L-histidine (His) and sodium acetate (Ace) in a nutrient-restricted (NR) immortalized bovine mammary epithelial cell line (MAC-T cells). The treatments for the MAC-T cells are as follows: experiment (1) 0–5% diluted basal medium; experiment (2) supplementation of 0–9.6 mM of His or Ace in NR or normal conditions; experiment (3) supplementation of 0–9.6 mM of Ace plus 0.15 mM of His in NR or normal conditions. The 1% diluted medium showed no significant effect on the cell viability with the basal medium; thus, it was selected as the NR condition. The relative expression of β-casein was significantly increased in the NR condition with the inclusion of 0.15 mM His alone or with Ace compared to that in control. The supplementation of Ace increased the β-casein level under normal conditions. However, it did not change the expression of β-casein under the NR condition. The results suggest that His has the potential to increase the β-casein expression under the NR condition.

Dietary Selenium Regulates microRNAs in Metabolic Disease: Recent Progress

Selenium (Se) is an essential element for the maintenance of a healthy physiological state. However, due to environmental and dietary factors and the narrow safety range of Se, diseases caused by Se deficiency or excess have gained considerable traction in recent years. In particular, links have been identified between low Se status, cognitive decline, immune disorders, and increased mortality, whereas excess Se increases metabolic risk. Considerable evidence has suggested microRNAs (miRNAs) regulate interactions between the environment (including the diet) and genes, and play important roles in several diseases, including cancer. MiRNAs target messenger RNAs to induce changes in proteins including selenoprotein expression, ultimately generating disease. While a plethora of data exists on the epigenetic regulation of other dietary factors, nutrient Se epigenetics and especially miRNA regulated mechanisms remain unclear. Thus, this review mainly focuses on Se metabolism, pathogenic mechanisms, and miRNAs as key regulatory factors in Se-related diseases. Finally, we attempt to clarify the regulatory mechanisms underpinning Se, miRNAs, selenoproteins, and Se-related diseases.

Is targeting autophagy mechanism in cancer a good approach? The possible double-edge sword effect

Autophagy is a conserved cellular process required to maintain homeostasis. The hallmark of autophagy is the formation of a phagophore that engulfs cytosolic materials for degradation and recycling to synthesize essential components. Basal autophagy is constitutively active under normal conditions and it could be further induced by physiological stimuli such as hypoxia, nutrient starvation, endoplasmic reticulum stress,energy depletion, hormonal stimulation and pharmacological treatment. In cancer, autophagy is highly context-specific depending on the cell type, tumour microenvironment, disease stage and external stimuli. Recently, the emerging role of autophagy as a double-edged sword in cancer has gained much attention. On one hand, autophagy suppresses malignant transformation by limiting the production of reactive oxygen species and DNA damage during tumour development. Subsequently, autophagy evolved to support the survival of cancer cells and promotes the tumourigenicity of cancer stem cells at established sites. Hence, autophagy is an attractive target for cancer therapeutics and researchers have been exploiting the use of autophagy modulators as adjuvant therapy. In this review, we present a summary of autophagy mechanism and controlling pathways, with emphasis on the dual-role of autophagy (double-edged sword) in cancer. This is followed by an overview of the autophagy modulation for cancer treatment and is concluded by a discussion on the current perspectives and future outlook of autophagy exploitation for precision medicine.

Lifetime Impact of Cow's Milk on Overactivation of mTORC1: From Fetal to Childhood Overgrowth, Acne, Diabetes, Cancers, and Neurodegeneration

The consumption of cow's milk is a part of the basic nutritional habits of Western industrialized countries. Recent epidemiological studies associate the intake of cow's milk with an increased risk of diseases, which are associated with overactivated mechanistic target of rapamycin complex 1 (mTORC1) signaling. This review presents current epidemiological and translational evidence linking milk consumption to the regulation of mTORC1, the master-switch for eukaryotic cell growth. Epidemiological studies confirm a correlation between cow's milk consumption and birthweight, body mass index, onset of menarche, linear growth during childhood, acne vulgaris, type 2 diabetes mellitus, prostate cancer, breast cancer, hepatocellular carcinoma, diffuse large B-cell lymphoma, neurodegenerative diseases, and all-cause mortality. Thus, long-term persistent consumption of cow's milk increases the risk of mTORC1-driven diseases of civilization. Milk is a highly conserved, lactation genome-controlled signaling system that functions as a maternal-neonatal relay for optimized species-specific activation of mTORC1, the nexus for regulation of eukaryotic cell growth, and control of autophagy. A deeper understanding of milk´s impact on mTORC1 signaling is of critical importance for the prevention of common diseases of civilization.

Energy sensors in drug addiction: A potential therapeutic target

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

Understanding the complex role of mTORC as an intracellular critical mediator of whole-body metabolism in anorexia nervosa: A mini review

Anorexia nervosa (AN) is a kind of malnutrition resulting from chronic self-induced starvation. The reported associated endocrine changes (adaptive and non-adaptive) include hypothalamic amenorrhea, a nutritionally acquired growth hormone resistance with low insulin like growth factor-1 (IGF-1) secretion, relative hypercortisolemia, decreased leptin and insulin concentrations, and increased ghrelin, Peptide YY (PYY) and adiponectin secretion. The combined effect of malnutrition and endocrinopathy may have deleterious effects on multi-organs including bone, gonads, thyroid gland, and brain (neurocognition, anxiety, depression, and other psychopathologies). The mammalian target of rapamycin (mTOR) is a kinase that in humans is encoded by the mTOR gene. Recent studies suggest an important role of mTOR complex in integration of nutrient and hormone signals to adjust energy homeostasis. In this review, we tried to elucidate the role/s of mTOR as critical mediator of the cellular response in anorexia nervosa. (www.actabiomedica.it)

Maternal Protein Restriction Increases Autophagy in the Pancreas of Newborn Rats

A maternal low-protein diet increases the susceptibility of offspring to type 2 diabetes by inducing alterations in β cell mass and function. However, the mechanism of this pancreas injury remains poorly understood. The present study aimed to assess whether autophagy is altered in the pancreas of intrauterine growth restriction (IUGR). In addition, the autophagy associated mammalian target of rapamycin complex 1 (mTORC1) signaling and endoplasmic reticulum (ER) stress were further evaluated in the pancreas. The maternal protein restriction IUGR rat model was established as the IUGR group, and assessed alongside normal newborn rats (CON group). Then, the levels of autophagy markers were assessed by transmission electron microscopy, immunofluorescence, quantitative real-time PCR (qRT-PCR) and Western blot, respectively. In addition, mTORC1 signaling effectors were evaluated by Western blot; ER stress was quantitated by immunohistochemistry, qRT-PCR and Western blotting. Compared with the control group, the IUGR group showed increased levels of the autophagy markers LC3II and Beclin1, with decreased mTORC1 signaling activity. In addition, ER stress was confirmed in β cells of the IUGR group. These findings provided evidence that maternal protein restriction enhances autophagy in newborn pancreas, where ER stress was also induced in β cells, which might effect the pancreas development.

Effects of dietary betaine supplementation on biochemical parameters of blood and testicular oxidative stress in Hu sheep

Betaine, a highly valuable feed additive, has been observed to alter the distribution of protein and fat in the bodies of ruminants and to exhibit strong antioxidant properties. However, the effects of dietary betaine supplementation on the biochemical parameters of blood and on testicular oxidative stress remain unknown. This study aimed to investigate the effects of dietary betaine supplementation on lipid metabolism, immunity, and testicular oxidative status in Hu sheep. Experimental sheep (n=3, three sheep per group) were fed betaine-containing diets, a basal diet supplemented with 0 g/day (control group), 1 g/day (B1), and 3 g/day betaine (B2). There were no differences in the serum concentrations of triglycerides and cholesterol in Hu sheep receiving diets supplemented with betaine. The ratio of basophils significantly increased in the B1 and B2 groups. ELISA (enzyme-linked immunosorbent assay) results showed that testicular superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity were significantly higher, whereas malondialdehyde (MDA) content significantly decreased, after feeding betaine-supplemented diets. qPCR results showed that the mRNA expression levels of CAT, SOD2, and GSH-Px were significantly upregulated in both the B1 and B2 groups compared to those in the control group. Furthermore, the expression of proliferating cell nuclear antigen (PCNA) was significantly lower in the testes of betaine-treated Hu sheep than in the control group. Moreover, LKB1 (liver kinase B1) expression significantly increased, and mRNA expression of AMPK (AMP-activated serine/threonine protein kinase) significantly decreased in the B1 group. The relative gene expression of mTOR (mechanistic target of rapamycin) was significantly higher in the B2 group than in the control group. RAPTOR expression significantly increased in the B1 group. Western blot revealed that the ratio of P-mTOR and mTOR significantly increased after feeding betaine-supplemented diets. In conclusion, betaine supplementation improved serum lipid metabolism, immune response, and increased the testicular antioxidant capacity of Hu sheep, which might be regulated via mTOR signaling pathway.

Nutrients and Pathways that Regulate Health Span and Life Span

Both life span and health span are influenced by genetic, environmental and lifestyle factors. With the genetic influence on human life span estimated to be about 20–25%, epigenetic changes play an important role in modulating individual health status and aging. Thus, a main part of life expectance and healthy aging is determined by dietary habits and nutritional factors. Excessive or restricted food consumption have direct effects on health status. Moreover, some dietary interventions including a reduced intake of dietary calories without malnutrition, or a restriction of specific dietary component may promote health benefits and decrease the incidence of aging-related comorbidities, thus representing intriguing potential approaches to improve healthy aging. However, the relationship between nutrition, health and aging is still not fully understood as well as the mechanisms by which nutrients and nutritional status may affect health span and longevity in model organisms. The broad effect of different nutritional conditions on health span and longevity occurs through multiple mechanisms that involve evolutionary conserved nutrient-sensing pathways in tissues and organs. These pathways interacting each other include the evolutionary conserved key regulators mammalian target of rapamycin, AMP-activated protein kinase, insulin/insulin-like growth factor 1 pathway and sirtuins. In this review we provide a summary of the main molecular mechanisms by which different nutritional conditions, i.e., specific nutrient abundance or restriction, may affect health span and life span.

L-type amino acid transporter 1 promotes proliferation and invasion of human chorionic trophoblast and choriocarcinoma cells through mTORC1

L-type amino acid transporter 1 (LAT1) is a neutral amino acid transporter expressed in trophoblast giant cells onembryonic day 8 in mice. LAT1 is responsible for metabolism in blastocysts and cancer cells. Despite research concerning the aberrant high expression and indispensable function of LAT1 in various cancers, little is known about the role of LAT1 in regulating the behaviors of human trophoblast cells under different physiological and pathological conditions. The HTR8-SVneo human trophoblast cell line and JEG-3 and JAR choriocarcinoma cell lines are used as models for trophoblast cell biological research. The proliferation and apoptosis of these cells were assayed using the CCK-8 assay and flow cytometry, respectively. Transwell-chambers were used to observed migration and invasion of the cells. Immunofluorescent staining, western blot, and RT-PCR assays were used to determine the possible mechanism of LAT1 on human trophoblast cell behaviors with small interfering RNA or signal agonists and antagonist treatments. LAT1 was expressed in the trophoblast and choriocarcinoma cells. LAT1 was involved in regulating behaviors of these cells, such as cell proliferation, apoptosis, migration, and invasion. Detailed results suggested that LAT1 modulated trophoblast cell functions by mediation of mTORC1 signaling pathways. Our results implicate LAT1 as a very important regulator in human trophoblast cell behaviors at the maternal-fetal interface.

Emendation of autophagic dysfuction in neurological disorders: a potential therapeutic target

BACKGROUND

Neurological disorders have been continuously contributing to the global disease burden and affect millions of people worldwide. Researchers strive hard to extract out the ultimate cure and serve for the betterment of the society, and yet the treatments available provide only symptomatic relief. Aging and abnormal mutations seem to be the major culprits responsible for neurotoxicity and neuronal death. One of the major causes of these neurological disorders that has been paid utmost attention recently, is Autophagic Dysfunction.

AIM

The aim of the study was to understand the autophagic process, its impairment in neurological disorders and targeting the impairments as a therapeutic option for the said disorders.

METHODS

For the purpose of review, we carried out an extensive literature study to excerpt the series of steps involved in autophagy and to understand the mechanism of autophagic impairment occurring in a range of neurodegenerative and neuropsychiatric disorders like Parkinson, Alzheimer, Depression, Schizophrenia, Autism etc. The review also involved the exploration of certain molecules that can help in triggering the compromised autophagic members.

RESULTS

We found that, a number of genes, proteins, receptors and transcription factors interplay to bring about autophagy and plethora of neurological disorders are associated with the diminished expression of one or more autophagic member leading to inhibition of autophagy.

CONCLUSION

Autophagy is a significant process for the removal of misfolded, abnormal, damaged protein aggregates and nonfunctional cell organelles in order to suppress neurodegeneration. Therefore, triggering autophagy could serve as an important therapeutic target to treat neurological disorders.

Focus on the Multimodal Role of Autophagy in Rheumatoid Arthritis

Autophagy exerts its dual role in eukaryotic cells and exerts its cytoprotective action through degradation mechanism and by regulating catabolic processes which results in elimination of pathogens. Under suitable conditions, autophagy is associated with recycling of cytoplasmic components which causes regeneration of energy whereas deregulated autophagy exerts its implicated role in development and pathogenesis of auto-immune diseases such as rheumatoid arthritis. The immune, innate, and adaptive responses are regulated through the development, proliferation, and growth of lymphocytes. Such innate and adaptive responses can act as mediator of arthritis; along with this, stimulation of osteoclast-mediated bone resorption takes place via transferring citrullinated peptides towards MHC (major histocompatibility complex) compartments, thereby resulting in degradation of bone. Processes such as apoptosis resistance are also regulated through autophagy. In this review, the current knowledge based on role of autophagy in pathogenesis of rheumatoid arthritis is summarized along with proteins associated.

Quantitative genetic screening reveals a Ragulator-FLCN feedback loop that regulates the mTORC1 pathway

Forward genetic screens in mammalian cell lines, such as RNAi and CRISPR-Cas9 screens, have made major contributions to the elucidation of diverse signaling pathways. Here, we exploited human haploid cells as a robust comparative screening platform and report a set of quantitative forward genetic screens for identifying regulatory mechanisms of mTORC1 signaling, a key growth control pathway that senses diverse metabolic states. Selected chemical and genetic perturbations in this screening platform, including rapamycin treatment and genetic ablation of the Ragulator subunit LAMTOR4, revealed the known core mTORC1 regulatory signaling complexes and the intimate interplay of the mTORC1 pathway with lysosomal function, validating the approach. In addition, we identified a differential requirement for LAMTOR4 and LAMTOR5 in regulating the mTORC1 pathway under fed and starved conditions. Furthermore, we uncovered a previously unknown "synthetic-sick" interaction between the tumor suppressor folliculin and LAMTOR4, which may have therapeutic implications in cancer treatment. Together, our study demonstrates the use of iterative "perturb and observe" genetic screens to uncover regulatory mechanisms driving complex mammalian signaling networks.

Mislocalization of TORC1 to Lysosomes Caused by KIF11 Inhibition Leads to Aberrant TORC1 Activity

While the growth factors like insulin initiate a signaling cascade to induce conformational changes in the mechanistic target of rapamycin complex 1 (mTORC1), amino acids cause the complex to localize to the site of activation, the lysosome. The precise mechanism of how mTORC1 moves in and out of the lysosome is yet to be elucidated in detail. Here we report that microtubules and the motor protein KIF11 are required for the proper dissociation of mTORC1 from the lysosome upon amino acid scarcity. When microtubules are disrupted or KIF11 is knocked down, we observe that mTORC1 localizes to the lysosome even in the amino acid-starved situation where it should be dispersed in the cytosol, causing an elevated mTORC1 activity. Moreover, in the mechanistic perspective, we discover that mTORC1 interacts with KIF11 on the motor domain of KIF11, enabling the complex to move out of the lysosome along microtubules. Our results suggest not only a novel way of the regulation regarding amino acid availability for mTORC1, but also a new role of KIF11 and microtubules in mTOR signaling.

Does high dietary protein intake contribute to the increased risk of developing prediabetes and type 2 diabetes?

Insulin resistance is a complex metabolic disorder implicated in the development of many chronic diseases. While it is generally accepted that body mass loss should be the primary approach for the management of insulin resistance-related disorders in overweight and obese individuals, there is no consensus among researchers regarding optimal protein intake during dietary restriction. Recently, it has been suggested that increased plasma branched-chain amino acids concentrations are associated with the development of insulin resistance and type 2 diabetes. The exact mechanism by which excessive amino acid availability may contribute to insulin resistance has not been fully investigated. However, it has been hypothesised that mammalian target of rapamycin (mTOR) complex 1 hyperactivation in the presence of amino acid overload contributes to reduced insulin-stimulated glucose uptake because of insulin receptor substrate (IRS) degradation and reduced Akt-AS160 activity. In addition, the long-term effects of high-protein diets on insulin sensitivity during both weight-stable and weight-loss conditions require more research. This review focusses on the effects of high-protein diets on insulin sensitivity and discusses the potential mechanisms by which dietary amino acids can affect insulin signalling. Novelty: Excess amino acids may over-activate mTOR, resulting in desensitisation of IRS-1 and reduced insulin-mediated glucose uptake.

Polyunsaturated fatty acid deficiency affects sulfatides and other sulfated glycans in lysosomes through autophagy-mediated degradation

Metabolic changes in sulfatides and other sulfated glycans have been related to various diseases, including Alzheimer's disease (AD). However, the importance of polyunsaturated fatty acids (PUFA) in sulfated lysosomal substrate metabolism and its related disorders is currently unknown. We investigated the effects of deficiency or supplementation of PUFA on the metabolism of sulfatides and sulfated glycosaminoglycans (sGAGs) in sulfatide-rich organs (brain and kidney) of mice. A PUFA-deficient diet for over 5 weeks significantly reduced the sulfatide expression by increasing the sulfatide degradative enzymes arylsulfatase A and galactosylceramidase in brain and kidney. This sulfatide degradation was clearly associated with the activation of autophagy and lysosomal hyperfunction, the former of which was induced by suppression of the Erk/mTOR pathway. A PUFA-deficient diet also activated the degradation of sGAGs in the brain and kidney and that of amyloid precursor proteins in the brain, indicating an involvement in general lysosomal function and the early developmental process of AD. PUFA supplementation prevented all of the above abnormalities. Taken together, a PUFA deficiency might lead to sulfatide and sGAG degradation associated with autophagy activation and general lysosomal hyperfunction and play a role in many types of disease development, suggesting a possible benefit of prophylactic PUFA supplementation.

Phytogenic feed- and water-additives improve feed efficiency in broilers via modulation of (an)orexigenic hypothalamic neuropeptide expression

Fueled by consumer preference for natural and antibiotic-free products, phytogenics have become the fastest growing segment of the animal feed additives. Yet, their modes of action are not fully understood. This study was undertaken to determine the effect of 5 phytogenics (3 feed- and 2 water-supplements) on the growth performance of commercial broilers, and their potential underlying molecular mechanisms. Day-old male Cobb 500 chicks (n = 576) were randomly assigned into 48 pens consisting of 6 treatments (Control; AVHGP; SCP; BHGP; AVSSL; SG) in a complete randomized design (12 birds/pen, 8 pens/treatment, 96 birds/treatment). Chicks had ad libitum access to feed and water. Individual body weight (BW) was recorded weekly and feed intake was measured daily. Core body temperatures were continuously recorded using thermo-loggers. At d 35, hypothalamic tissues were excised from the thermo-logger-equipped chickens (n = 8 birds/treatment) to determine the expression of feeding-related neuropeptides. Both feed (AVHGP, SCP, BHGP) and water-supplemented (AVSSL, SG) phytogenics significantly improved feed efficiency (FE) compared to the control birds. This higher FE was achieved via a reduction in core body temperature and improvement of market BW, without changes in feed intake in broilers supplemented with phytogenic water additives as compared to the control group. Broilers fed dietary phytogenics, however, attained higher feed efficiency via a reduction in feed intake while maintaining similar BW as the control group. At the molecular levels, the effects of the phytogenic water additives seemed to be mediated by the activation of the hypothalamic AgRP-ORX-mTOR-S6k1 and inhibition of CRH pathways. The effect of the phytogenic feed additives appeared to be exerted through the activation of AdipoQ, STAT3, AMPK, and MC1R pathways. This is the first report describing the likely central mechanisms through which phytogenic additives improve the growth performance and feed efficiency in broilers.

Si-Wei-Qing-Gan-Tang Improves Non-Alcoholic Steatohepatitis by Modulating the Nuclear Factor-κB Signal Pathway and Autophagy in Methionine and Choline Deficient Diet-Fed Rats

Si-Wei-Qing-Gan-Tang (SWQGT) is a Chinese medicine formula that is widely used as a folk remedy of herbal tea for the treatment of chronic hepatitis, like non-alcoholic steatohepatitis (NASH), around Ganzhou City (Jiangxi province, China). However, the underlying mechanisms of this formula against NASH are still unknown. This study aimed to explore the effect and mechanisms of SWQGT against NASH. A network pharmacology approach was used to predict the potential mechanisms of SWQGT against NASH. Then a rat model of NASH established by feeding the methionine and choline deficient (MCD) diet was used to verify the effect and mechanisms of SWQGT on NASH in vivo. SWQGT (1 g/kg/d and 3 g/kg/d) were given by intragastric administration. Body weight, liver weight, serum biochemical indicators, liver triglyceride and total cholesterol were all measured. Tumor necrosis factor-α (TNF-α), Interleukin (IL)-1β, IL-6 levels in the livers were evaluated using ELISA. Hematoxylin and eosin (HE) and Oil Red O staining were used to determine histology, while western blot was used to assess the relative expression levels of the nuclear factor-κB (NF-κB) pathway- and autophagy-related proteins. Functional and pathway enrichment analyses revealed that SWQGT obviously influenced inflammation-related signal pathways in NASH. Furthermore, in vivo experiment showed that SWQGT caused a reduction in liver weight and liver index of MCD diet-fed rats. The formula also helped to reduce hepatomegaly and improve pathological liver changes and hepatic steatosis. SWQGT likewise reduced liver TNF-α, IL-1β, and IL-6 levels and down-regulated p-NF-κB p65, p-p38 MAPK, p-MEK1/2, p-ERK1/2, p-mTOR, and p62, while up-regulating p-ULK1 and LC3II protein expression levels. SWQGT could improve NASH in MCD diet-fed rats, and this effect may be associated with its down-regulation of NF-κB and activation of autophagy.

Effects of diet supplementation with rumen-protected betaine on carcass characteristics and fat deposition in growing lambs

This study evaluated the effects of dietary rumen-protected betaine (RPB) supplementation on the fat deposition of lambs. Sixty Hu sheep were randomly divided into 5 groups. The lambs were fed a control diet (CON) or diets supplemented with 1.1 g/d unprotected betaine (UPB), 1.1 g/d RPB, 2.2 g/d RPB or 3.3 g/d RPB for 70 days. Compared with UPB, the abdominal fat in 2.2 g/d RPB supplemented group was decreased (P < .05). Compared with CON and UPB, the fat contents in longissimus dorsi (LD) of RPB treatments were increased (P < .01). With increasing of RPB levels, the fat content in the LD was quadratically increased (P < .05). Compared with CON, genes expression of PI3K, mTOR and S6K1 in the LD of RPB treatments were up-regulated (P < .05). In conclusion, RPB supplementation decreased the abdominal fat in lambs but increased the fat content in lamb meat, and this effect might be regulated by mTOR signaling.

Phenylalanine and valine differentially stimulate milk protein synthetic and energy-mediated pathway in immortalized bovine mammary epithelial cells

Studies on promoting milk protein yield by supplementation of amino acids have been globally conducted. Nevertheless, there is a lack of knowledge of what pathways affected by individual amino acid in mammary epithelial cells that produce milk in practice. Phenylalanine (PHE) and valine (VAL) are essential amino acids for dairy cows, however, researches on mammary cell levels are still lacking. Thus, the aim of this study was conducted to evaluate the effects of PHE and VAL on milk protein synthesis-related and energy-mediated cellular signaling in vitro using immortalized bovine mammary epithelial (MAC-T) cells. To investigate the effects of PHE and VAL, the following concentrations were added to treatment medium: 0, 0.3, 0.6, 0.9, 1.2, and 1.5 mM. The addition of PHE or VAL did not adversely affect cell viability compared to control group. The concentrations of cultured medium reached its maximum at 0.9 mM PHE and 0.6 mM VAL (p < 0.05). Therefore, aforementioned 2 treatments were analyzed for proteomics. Glucose transporter 1 and mammalian target of rapamycin mRNA expression levels were up-regulated by PHE (166% and 138%, respectively) (p < 0.05). Meanwhile, sodium-dependent neutral amino acids transporter type 2 (ASCT2) and β-casein were up-regulated by VAL (173% in ASCT2, 238% in and 218% in β-casein) (p < 0.05). A total of 134, 142, and 133 proteins were detected in control group, PHE treated group, and VAL treated group, respectively. Among significantly fold-changed proteins, proteins involved in translation initiation or energy metabolism were detected, however, expressed differentially between PHE and VAL. Thus, pathway analysis showed different stimulatory effects on energy metabolism and transcriptional pathways. Collectively, these results showed different stimulatory effects of PHE and VAL on protein synthesis-related and energy-mediated cellular signaling in MAC-T cells.

Role of autophagy during the replication and pathogenesis of common mosquito-borne flavi- and alphaviruses

Arboviruses that are transmitted to humans by mosquitoes represent one of the most important causes of febrile illness worldwide. In recent decades, we have witnessed a dramatic re-emergence of several mosquito-borne arboviruses, including dengue virus (DENV), West Nile virus (WNV), chikungunya virus (CHIKV) and Zika virus (ZIKV). DENV is currently the most common mosquito-borne arbovirus, with an estimated 390 million infections worldwide annually. Despite a global effort, no specific therapeutic strategies are available to combat the diseases caused by these viruses. Multiple cellular pathways modulate the outcome of infection by either promoting or hampering viral replication and/or pathogenesis, and autophagy appears to be one of them. Autophagy is a degradative pathway generally induced to counteract viral infection. Viruses, however, have evolved strategies to subvert this pathway and to hijack autophagy components for their own benefit. In this review, we will focus on the role of autophagy in mosquito-borne arboviruses with emphasis on DENV, CHIKV, WNV and ZIKV, due to their epidemiological importance and high disease burden.

Rap1-GTPases control mTORC1 activity by coordinating lysosome organization with amino acid availability

The kinase mTOR complex 1 (mTORC1) promotes cellular growth and is frequently dysregulated in cancers. In response to nutrients, mTORC1 is activated on lysosomes by Rag and Rheb guanosine triphosphatases (GTPases) and drives biosynthetic processes. How limitations in nutrients suppress mTORC1 activity remains poorly understood. We find that when amino acids are limited, the Rap1-GTPases confine lysosomes to the perinuclear region and reduce lysosome abundance, which suppresses mTORC1 signaling. Rap1 activation, which is independent of known amino acid signaling factors, limits the lysosomal surface available for mTORC1 activation. Conversely, Rap1 depletion expands the lysosome population, which markedly increases association between mTORC1 and its lysosome-borne activators, leading to mTORC1 hyperactivity. Taken together, we establish Rap1 as a critical coordinator of the lysosomal system, and propose that aberrant changes in lysosomal surface availability can impact mTORC1 signaling output.

Cross-Talk Between the Tumor Microenvironment, Extracellular Matrix, and Cell Metabolism in Cancer

The extracellular matrix (ECM) is a complex network of secreted proteins which provides support for tissues and organs. Additionally, the ECM controls a plethora of cell functions, including cell polarity, migration, proliferation, and oncogenic transformation. One of the hallmarks of cancer is altered cell metabolism, which is currently being exploited to develop anti-cancer therapies. Several pieces of evidence indicate that the tumor microenvironment and the ECM impinge on tumor cell metabolism. Therefore, it is essential to understand the contribution of the complex 3D microenvironment in controlling metabolic plasticity and responsiveness to therapies targeting cell metabolism. In this mini-review, we will describe how the tumor microenvironment and cancer-associated fibroblasts dictate cancer cell metabolism, resulting in increased tumor progression. Moreover, we will define the cross-talk between nutrient signaling and the trafficking of the ECM receptors of the integrin family. Finally, we will present recent data highlighting the contribution of nutrient scavenging from the microenvironment to support cancer cells growth under nutrient starvation conditions.

Effects of dietary valine supplementation during late gestation on the reproductive performance and mammary gland development of gilts

Background

Mammary gland development during late gestation in gilts is a major factor that alters the composition of colostrum and growth performance of piglets. Plasma valine is taken up and metabolized extensively by the mammary gland; however, the effects of valine on mammary gland development during late gestation are still unclear. Thirty primiparous gilts were divided into three treatment groups (n = 10) and received one of the three diets starting on day 75 of gestation until the day of farrowing. The total dietary valine to lysine ratio of the three diets was 0.63 (LV), 0.73 (MV), and 0.93 (HV), respectively.

Results

Dietary valine supplementation during late gestation did not affect (P > 0.05) the litter size and weight at farrowing; however, the piglet weight and average daily gain at weaning were linearly increased (P < 0.05) as the dietary valine increased. The highest piglet weight at weaning was observed when the gilts were provided the HV diet. Dietary valine supplementation linearly elevated (P < 0.05) protein, fat and solids-not-fat and some free amino acids content in colostrum. The concentration of prolactin in plasma of gilts was linearly increased in response to valine supplementation at days 1 and 10 of lactation (P < 0.05). Furthermore, with increasing dietary valine allowance, a linear increase (P < 0.05) was observed in the area of the lumen of alveolus and the content of DNA, RNA, and total protein in the mammary tissues at day 1 of lactation. Moreover, the protein expression of cyclin D1, p-mTOR, p-S6, and p-4EBP1 was also linearly increased (P < 0.05) in the mammary tissue at day 1 of lactation. However, no difference (P > 0.05) was observed in the indices related to mammary development and the mTOR signaling pathway at day 21 of lactation.

Conclusion

The results revealed that increasing the total dietary valine to lysine ratio to 0.93 during late gestation significantly enhances the piglet weight and average daily gain at weaning probably due to improved development of mammary gland.

AMPK-mTOR pathway is involved in glucose-modulated amino acid sensing and utilization in the mammary glands of lactating goats

Background

The local supply of energy-yielding nutrients such as glucose seems to affect the synthesis of milk components in the mammary gland (MG). Thus, our study was conducted to investigate the effects of locally available MG glucose supply (LMGS) on amino acid (AA) sensing and utilization in the MG of lactating dairy goats. Six dosages of glucose (0, 20, 40, 60, 80, and 100 g/d) were infused into the MG through the external pudendal artery to investigate the dose-dependent changes in mammary AA uptake and utilization (Exp.1) and the changes in mRNA and protein expression of the AMPK-mTOR pathway (Expt.2).

Results

In Exp.1, total milk AA concentration was highest when goats were infused with 60 g/d glucose, but lower when goats were infused with 0 and 100 g/d glucose. Increasing LMGS quadratically changed the percentages of α_S2-casein and α-lactalbumin in milk protein, which increased with infusions from 0 to 60 g/d glucose and then decreased with infusions between 60 and 100 g/d glucose. The LMGS changed the AA availability and intramammary gland AA utilization, as reflected by the mammary AA flux indexes. In Exp.2, the mRNA expression of LALBA in the MG increased quadratically with increasing LMGS, with the highest expression at dose of 60 g/d glucose. A high glucose dosage (100 g/d) activated the general control nonderepressible 2 kinase, an intracellular sensor of AA status, resulting in a reduced total milk AA concentration.

Conclusions

Our new findings suggest that the lactating MG in dairy goats may be affected by LMGS through regulation of the AA sensory pathway, AA utilization and protein synthesis, all being driven by the AMPK-mTOR pathway.

T cell Metabolism in Lupus

Abnormal T cell responses are central to the development of autoimmunity and organ damage in systemic lupus erythematosus. Following stimulation, naïve T cells undergo rapid proliferation, differentiation and cytokine production. Since the initial report, approximately two decades ago, that engagement of CD28 enhances glycolysis but PD-1 and CTLA-4 decrease it, significant information has been generated which has linked metabolic reprogramming with the fate of differentiating T cell in health and autoimmunity. Herein we summarize how defects in mitochondrial dysfunction, oxidative stress, glycolysis, glutaminolysis and lipid metabolism contribute to pro-inflammatory T cell responses in systemic lupus erythematosus and discuss how metabolic defects can be exploited therapeutically.

Leucine promotes the growth of squabs by increasing crop milk protein synthesis through the TOR signaling pathway in the domestic pigeon (Columba livia)

Leucine (Leu) plays a critical regulatory role in protein synthesis, however, the effects and molecular mechanisms of Leu on crop milk protein in the domestic pigeons (Columba livia) are still unknown. Therefore, the study aimed to investigate the effects of dietary Leu supplementation on crop milk protein synthesis and the growth performance of squabs and the possible underlying mechanism. A total of 240 pairs of breeding pigeons (1102.3 ± 9.5 g/pair) were randomly assigned to 1 of 5 treatments, including a positive control (PC) diet that had adequate crude protein (crude protein, CP = 18%; Leu = 1.30%), a negative control (NC) diet that was low in CP (CP = 16%, Leu = 1.30%), and NC diets supplemented with Leu at 0.15%, 0.45%, or 1.05%. Compared with the NC diet, 0.15 to 0.45% Leu supplementation decreased BW loss and increased relative crop weight, crop thickness, and protein levels in the crop tissue and milk of breeding pigeons. However, dietary supplementation with 1.05% Leu inhibited ADFI in breeding pigeons. Dietary supplementation with 0.15 to 0.45% Leu decreased the mortality rate and increased the BW, eviscerated yield, and breast muscle yield of young squabs. The protein expression levels of the target of rapamycin (TOR), ribosomal protein S6 kinase 1 (S6K1), ribosomal protein S6 kinase (S6), eukaryotic initiation factor 4E binding protein 1 (4EBP1), and eukaryotic translation initiation factor 4E (eIF4E) were upregulated in the crop tissue of breeding pigeons in PC, 0.15% and 0.45% Leu-supplemented groups. Collectively, these results indicated that 0.15 to 0.45% Leu supplementation could decrease BW loss, increase milk protein synthesis in the crop of breeding pigeons, and enhance the survival rate and growth performance of young squabs through the TOR signaling pathway.

Podocyte hypertrophic stress and detachment precedes hyperglycemia or albuminuria in a rat model of obesity and type2 diabetes-associated nephropathy

Type2 diabetes-associated nephropathy is the commonest cause of renal failure. Mechanisms responsible are controversial. Leptin-deficient hyperphagic Zucker (fa/fa) rats were modeled to test the hypothesis that glomerular enlargement drives podocyte hypertrophic stress leading to accelerated podocyte detachment, podocyte depletion, albuminuria and progression. By 6weeks, prior to development of either hyperglycemia or albuminuria, fa/fa rats were hyperinsulinemic with high urinary IGF1/2 excretion, gaining weight rapidly, and had 1.6-fold greater glomerular volume than controls (P < 0.01). At this time the podocyte number per glomerulus was not yet reduced although podocytes were already hypertrophically stressed as shown by high podocyte phosphor-ribosomal S6 (a marker of mTORC1 activation), high urinary pellet podocin:nephrin mRNA ratio and accelerated podocyte detachment (high urinary pellet podocin:aquaporin2 mRNA ratio). Subsequently, fa/fa rats became both hyperglycemic and albuminuric. 24 hr urine albumin excretion correlated highly with decreasing podocyte density (R2 = 0.86), as a consequence of both increasing glomerular volume (R2 = 0.70) and decreasing podocyte number (R2 = 0.63). Glomerular podocyte loss rate was quantitatively related to podocyte detachment rate measured by urine pellet mRNAs. Glomerulosclerosis occurred when podocyte density reached <50/106um3. Reducing food intake by 40% to slow growth reduced podocyte hypertrophic stress and "froze" all elements of the progression process in place, but had small effect on hyperglycemia. Glomerular enlargement caused by high growth factor milieu starting in pre-diabetic kidneys appears to be a primary driver of albuminuria in fa/fa rats and thereby an under-recognized target for progression prevention. Progression risk could be identified prior to onset of hyperglycemia or albuminuria, and monitored non-invasively by urinary pellet podocyte mRNA markers.

Seryl-tRNA synthetase is involved in methionine stimulation of β-casein synthesis in bovine mammary epithelial cells

Despite the well-characterised mechanisms of amino acids (AA) regulation of milk protein synthesis in mammary glands (MG), the underlying specific AA regulatory machinery in bovine MG remains further elucidated. As methionine (Met) is one of the most important essential and limiting AA for dairy cows, it is crucial to expand how Met exerts its regulatory effects on dairy milk protein synthesis. Our previous work detected the potential regulatory role of seryl-tRNA synthetase (SARS) in essential AA (EAA)-stimulated bovine casein synthesis. Here, we investigated whether and how SARS participates in Met stimulation of casein production in bovine mammary epithelial cells (BMEC). With or without RNA interference against SARS, BMEC were treated with the medium in the absence (containing all other EAA and devoid of Met alone)/presence (containing 0·6 mm of Met in the medium devoid of Met alone) of Met. The protein abundance of β-casein and members of the mammalian target of rapamycin (mTOR) and general control nonderepressible 2 (GCN2) pathways was determined by immunoblot assay after 6 h treatment, the cell viability and cell cycle progression were determined by cell counting and propidium iodide-staining assay after 24 h treatment, and protein turnover was determined by l-[ring-3H5]phenylalanine isotope tracing assay after 48 h treatment. In the absence of Met, there was a general reduction in cell viability, total protein synthesis and β-casein production; in contrast, total protein degradation was enhanced. SARS knockdown strengthened these changes. Finally, SARS may work to promote Met-stimulated β-casein synthesis via affecting mTOR and GCN2 routes in BMEC.

Valine supplementation during late pregnancy in gilts increases colostral protein synthesis through stimulating mTOR signaling pathway in mammary cells

Mammary gland development during late pregnancy in sows is a major factor affecting the composition of colostrum and milk and the pre-weaning growth of piglets, while valine is essential for protein and nitrogen metabolism in mammary gland of sow. However, the effects of valine and its underlying mechanism on mammary gland development during late pregnancy are still unclear. Here, we hypothesized that dosage of dietary valine during late pregnancy will affect protein synthesis of colostrum in gilts. The results showed that supplementation of valine during late pregnancy significantly increased content of protein (P < 0.01), fat (P = 0.02) and solids-non-fat (P = 0.04) in colostrum. Our in vitro study also confirmed that valine supplementation increased protein synthesis and cell proliferation in porcine mammary epithelial cells (PMEC). Furthermore, these changes were associated with elevated phosphorylation levels of mammalian target of rapamycin (mTOR), and ribosomal protein S6 kinase (S6) and eukaryotic initiation factor 4E-binding protein-1 (4EBP1) in valine-supplemented cells, which could be effectively blocked by the antagonists of mTOR. These findings indicated that valine enhanced mammary gland development and protein synthesis in colostrum via the mTOR signaling pathway. These results, using an in vivo and in vitro model, helped to understand the beneficial effects of dietary valine supplementation on gilts.

New advances in the management of pulmonary sarcoidosis

Sarcoidosis is a highly variable granulomatous multisystem syndrome. It affects individuals in the prime years of life; both the frequency and severity of sarcoidosis are greater in economically disadvantaged populations. The diagnosis, assessment, and management of pulmonary sarcoidosis have evolved as new technologies and therapies have been adopted. Transbronchial needle aspiration guided by endobronchial ultrasound has replaced mediastinoscopy in many centers. Advanced imaging modalities, such as fluorodeoxyglucose positron emission tomography scanning, and the widespread availability of magnetic resonance imaging have led to more sensitive assessment of organ involvement and disease activity. Although several new insights about the pathogenesis of sarcoidosis exist, no new therapies have been specifically developed for use in the disease. The current or proposed use of immunosuppressive medications for sarcoidosis has been extrapolated from other disease states; various novel pathways are currently under investigation as therapeutic targets. Coupled with the growing recognition of corticosteroid toxicities for managing sarcoidosis, the use of corticosteroid sparing anti-sarcoidosis medications is likely to increase. Besides treatment of granulomatous inflammation, recognition and management of the non-granulomatous complications of pulmonary sarcoidosis are needed for optimal outcomes in patients with advanced disease.

Impact of nutrient overload on metabolic homeostasis

Nutrient overload occurs worldwide as a consequence of the modern diet pattern and the physical inactivity that sometimes accompanies it. Cells initiate multiple protective mechanisms to adapt to elevated intracellular metabolites and restore metabolic homeostasis, but irreversible injury to the cells can occur in the event of prolonged nutrient overload. Many studies have advanced the understanding of the different detrimental effects of nutrient overload; however, few reports have made connections and given the full picture of the impact of nutrient overload on cellular metabolism. In this review, detailed changes in metabolic and energy homeostasis caused by chronic nutrient overload, as well as their associations with the development of metabolic disorders, are discussed. Overnutrition-induced changes in key organelles and sensors rewire cellular bioenergetic pathways and facilitate the shift of the metabolic state toward biosynthesis, thereby leading to the onset of various metabolic disorders, which are essentially the downstream manifestations of a misbalanced metabolic equilibrium. Based on these mechanisms, potential therapeutic targets for metabolic disorders and new research directions are proposed.

Long noncoding RNA BFAL1 mediates enterotoxigenic Bacteroides fragilis-related carcinogenesis in colorectal cancer via the RHEB/mTOR pathway

Long noncoding RNAs (lncRNAs) contribute to many steps in carcinogenesis and often serve as biomarkers or therapeutic targets for tumor diagnosis and therapy. Although the role of lncRNAs in tumor formation is becoming clear, whether lncRNAs mediate gut microbiota-induced colorectal cancer (CRC) is largely unknown. Enterotoxigenic Bacteroides fragilis (ETBF) is a well-known tumor-inducing bacterium in the human gut; however, its tumorigenic effect remains to be explored. In the present study, we revealed the mechanism by which a lncRNA participates in gut bacteria-induced carcinogenesis: Bacteroides fragilis-associated lncRNA1 (BFAL1) in CRC tissues mediates ETBF carcinogenesis. BFAL1 was highly expressed in CRC tissues compared with that in adjacent normal tissues. In vitro, BFAL1 was upregulated in ETBF-treated CRC cells. Mechanistically, ETBF promoted tumor growth via BFAL1 by activating the Ras homolog, which is the MTORC1 binding/mammalian target of the rapamycin (RHEB/mTOR) pathway. Furthermore, BFAL1 regulated RHEB expression by competitively sponging microRNAs miR-155-5p and miR-200a-3p. Clinically, both high expression of BFAL1 and high abundance of ETBF in CRC tissues predicted poor outcomes for patients with CRC. Thus, BFAL1 is a mediator of ETBF-induced carcinogenesis and may be a potential therapeutic target for ETBF-induced CRC.

Exercise regulates lipid droplet dynamics in normal and fatty liver

Lipids droplets (LD) are dynamics organelles that accumulate neutral lipids during nutrient surplus. LD alternates between periods of growth and consumption through regulated processes including as de novo lipogenesis, lipolysis and lipophagy. The liver is a central tissue in the regulation of lipid metabolism. Non-Alcoholic Fatty Liver Diseases (NAFLD) is result of the accumulation of LD in liver. Several works have been demonstrated a positive effect of exercise on reduction of liver fat. However, the study of the exercise on liver LD dynamics is far from being understood. Here we investigated the effect of chronic exercise in the regulation of LD dynamics using a mouse model of high fat diet-induced NAFLD. Mice were fed with a high-fat diet or control diet for 12 weeks; then groups were divided into chronic exercise or sedentary for additional 8 weeks. Our results showed that exercise reduced fasting glycaemia, insulin and triacylglycerides, also liver damage. However, exercise did not affect the intrahepatic triacylglycerides levels and the number of LD but reduced their size. In addition, exercise decreased the SREBP-1c levels, without changes in lipolysis, mitochondrial proteins or autophagy/lipophagy markers. Unexpectedly in the control mice, exercise increased the number of LD, also PLIN2, SREBP-1c, FAS, ATGL, HSL and MTTP levels. Our findings show that exercise rescues the liver damage in a model of NAFLD reducing the size of LD and normalizing protein markers of de novo lipogenesis and lipolysis. Moreover, exercise increases proteins associated to LD dynamics in the control mice.

Dairy Products: Is There an Impact on Promotion of Prostate Cancer? A Review of the Literature

This review of the literature aims to study potential associations between high consumption of milk and/or dairy products and prostate cancer (PC). Literature is scarce, yet there is a direct relationship between mTORC1 activation and PC; several ingredients in milk/dairy products, when in high concentrations, increase signaling of the mTORC1 pathway. However, there are no studies showing an unequivocal relationship between milk products PC initiation and/or progression. Three different reviews were conducted with articles published in the last 5 years: (M1) PC and intake of dairy products, taking into account the possible mTORC1signaling mechanism; (M2) Intake of milk products and incidence/promotion of PC; (M3) mTORC1 activation signaling pathway, levels of IGF-1 and PC; (M4) mTORC pathway and dairy products. Of the 32 reviews identified, only 21 met the inclusion criteria and were analyzed. There is little scientific evidence that directly link the three factors: incidence/promotion of PC, intake of dairy products and PC, and PC and increased mTORC1 signaling. Persistent hyper-activation of mTORC1 is associated with PC promotion. The activity of exosomal mRNA in cellular communication may lead to different impacts of different types of milk and whether or not mammalian milks will have their own characteristics within each species. Based on this review of the literature, it is possible to establish a relationship between the consumption of milk products and the progression of PC; we also found a possible association with PC initiation, hence it is likely that the intake of dairy products should be reduced or minimized in mens' diet.

Association analysis between feed efficiency and expression of key genes of the avTOR signaling pathway in meat-type ducks

Genes involved in the target of rapamycin (TOR) signaling pathway are implicated in nutrient translation, cell proliferation and differentiation, and anabolism, which can affect both growth and feed intake. However, the role of TOR signaling in the regulation of feed intake and feed efficiency in poultry is not clear. In the present study, a total of 1000 ducks, of similar initial weight, were chosen and transferred to individual cages to determine their residual feed intake (RFI) from the age of 21 to 42 days. Subsequently, 60 ducks, which were divided into high (HRFI) and low (LRFI) groups according to their RFI, were chosen to analyze the TOR signaling activities in the liver. The differential expression level of genes involved in the TOR signaling pathway was assayed by the real-time polymerase chain reaction. In the liver, the expression of AKT, avTOR, avLST8, and S6K1 was significantly higher in LRFI ducks than in HRFI ducks; avTOR and AKT were negatively associated with the feed conversion ratio and RFI. Furthermore, PI3K was moderately positively associated with AKT; AKT was strongly positively associated with PI3K, avTOR, avLST8, and S6K1; and avTOR was strongly positively associated with S6K1. In conclusion, the activation of avTOR signaling in the liver of LRFI ducks might be ascribed to higher energy state or more active nutrient transport (amino acids), or both, than those in the liver of HRFI ducks. The results of the present study indicate that AKT and avTOR of TOR signaling might be used as candidate genes to assess molecular regulation of feed efficiency.

Septin6 regulates cell growth and casein synthesis in dairy cow mammary epithelial cells via mTORC1 pathway

This research paper addresses the hypothesis that Septin6 is a key regulatory factor influencing amino acid (AA)-mediated cell growth and casein synthesis in dairy cow mammary epithelial cells (DCMECs). DCMECs were treated with absence of AA (AA-), restricted concentrations of AA (AAr) or normal concentrations of AA (AA+) for 24 h. Cell growth, expression of CSN2 and Septin6 were increased in response to AA supply. Overexpressing or inhibiting Septin6 demonstrated that cell growth, expression of CSN2, mTOR, p-mTOR, S6K1 and p-S6K1 were up-regulated by Septin6. Furthermore, overexpressing or inhibiting mTOR demonstrated that the increase in cell growth and expression of CSN2 in response to Septin6 overexpression were inhibited by mTOR inhibition, and vice versa. Our hypothesis was supported; we were able to show that Septin6 is an important positive factor for cell growth and casein synthesis, it up-regulates AA-mediated cell growth and casein synthesis through activating mTORC1 pathway in DCMECs.

Mutant p53 and Cellular Stress Pathways: A Criminal Alliance That Promotes Cancer Progression

The capability of cancer cells to manage stress induced by hypoxia, nutrient shortage, acidosis, redox imbalance, loss of calcium homeostasis and exposure to drugs is a key factor to ensure cancer survival and chemoresistance. Among the protective mechanisms utilized by cancer cells to cope with stress a pivotal role is played by the activation of heat shock proteins (HSP) response, anti-oxidant response induced by nuclear factor erythroid 2-related factor 2 (NRF2), the hypoxia-inducible factor-1 (HIF-1), the unfolded protein response (UPR) and autophagy, cellular processes strictly interconnected. However, depending on the type, intensity or duration of cellular stress, the balance between pro-survival and pro-death pathways may change, and cell survival may be shifted into cell death. Mutations of p53 (mutp53), occurring in more than 50% of human cancers, may confer oncogenic gain-of-function (GOF) to the protein, mainly due to its stabilization and interaction with the above reported cellular pathways that help cancer cells to adapt to stress. This review will focus on the interplay of mutp53 with HSPs, NRF2, UPR, and autophagy and discuss how the manipulation of these interconnected processes may tip the balance towards cell death or survival, particularly in response to therapies.

Muscle and serum metabolomes are dysregulated in colon-26 tumor-bearing mice despite amelioration of cachexia with activin receptor type 2B ligand blockade

Cancer-associated cachexia reduces survival, which has been attenuated by blocking the activin receptor type 2B (ACVR2B) ligands in mice. The purpose of this study was to unravel the underlying physiology and novel cachexia biomarkers by use of the colon-26 (C26) carcinoma model of cancer cachexia. Male BALB/c mice were subcutaneously inoculated with C26 cancer cells or vehicle control. Tumor-bearing mice were treated with vehicle (C26+PBS) or soluble ACVR2B either before (C26+sACVR/b) or before and after (C26+sACVR/c) tumor formation. Skeletal muscle and serum metabolomics analysis was conducted by gas chromatography-mass spectrometry. Cancer altered various biologically functional groups representing 1) amino acids, 2) energy sources, and 3) nucleotide-related intermediates. Muscle metabolomics revealed increased content of free phenylalanine in cancer that strongly correlated with the loss of body mass within the last 2 days of the experiment. This correlation was also detected in serum. Decreased ribosomal RNA content and phosphorylation of a marker of pyrimidine synthesis revealed changes in nucleotide metabolism in cancer. Overall, the effect of the experimental C26 cancer predominated over blocking ACVR2B ligands in both muscle and serum. However, the level of methyl phosphate, which was decreased in muscle in cancer, was restored by sACVR2B-Fc treatment. In conclusion, experimental cancer affected muscle and blood metabolomes mostly independently of blocking ACVR2B ligands. Of the affected metabolites, we have identified free phenylalanine as a promising biomarker of muscle atrophy or cachexia. Finally, the decreased capacity for pyrimidine nucleotide and protein synthesis in tumor-bearing mice opens up new avenues in cachexia research.

Influence of Normal Aging on Brain Autophagy: A Complex Scenario

Misfolded proteins are pathological findings in some chronic neurodegenerative disorders including Alzheimer's, Parkinson's, and Huntington's diseases. Aging is a major risk factor for these disorders, suggesting that the mechanisms responsible for clearing misfolded proteins from the brain, the ubiquitin-proteasome system and the autophagy-lysosomal pathway, may decline with age. Although autophagic mechanisms have been found to decrease with age in many experimental models, whether they do so in the brain is unclear. This review examines the literature with regard to age-associated changes in macroautophagy and chaperone-mediated autophagy (CMA) in the central nervous system (CNS). Beclin 1, LC3-II, and the LC3-II/LC3-I ratio have frequently been used to examine changes in macroautophagic activity, while lamp2a and HSPA8 (also known as hsc70) have been used to measure CMA activity. Three gene expression analyses found evidence for an age-related downregulation of macroautophagy in human brain, but no published studies were found of age-related changes in CMA in human brain, although cerebrospinal fluid concentrations of HSPA8 were reported to decrease with age. Most studies of age-related changes in brain autophagy in experimental animals have found age-related declines in macroautophagy, and macroautophagy is necessary for normal lifespan in Caenorhabditis elegans, Drosophila, and mice. However, the few studies of age-related changes in brain CMA in experimental animals have produced conflicting results. Investigations of the influence of aging on macroautophagy in experimental animals in systems other than the CNS have generally found an age-related decrease in Beclin 1, but conflicting results for LC3-II and the LC3-II/LC3-I ratio, while CMA decreases with age in most models. CONCLUSION: while indirect evidence suggests that brain autophagy may decrease with normal aging, this issue has not been investigated sufficiently, particularly in human brain. Measuring autophagic activity in the brain can be challenging because of differences in basal autophagic activity between experimental models, and the inability to include lysosomal inhibitors when measuring the LC3-II/LC3-I ratio in postmortem specimens. If autophagy does decrease in the brain with aging, then pharmacological interventions and/or lifestyle alterations to slow this decline could reduce the risk of developing age-related neurodegenerative disorders.

Rab5 GTPases are required for optimal TORC2 function

Target of rapamycin complex-2 (TORC2), a conserved protein kinase complex, is an indispensable regulator of plasma membrane homeostasis. In budding yeast (Saccharomyces cerevisiae), the essential downstream effector of TORC2 is protein kinase Ypk1 and its paralog Ypk2. Muk1, a Rab5-specific guanine nucleotide exchange factor (GEF), was identified in our prior global screen for candidate Ypk1 targets. We confirm here that Muk1 is a substrate of Ypk1 and demonstrate that Ypk1-mediated phosphorylation stimulates Muk1 function in vivo. Strikingly, yeast lacking its two Rab5 GEFs (Muk1 and Vps9) or its three Rab5 paralogs (Vps21/Ypt51, Ypt52, and Ypt53) or overexpressing Msb3, a Rab5-directed GTPase-activating protein, all exhibit pronounced reduction in TORC2-mediated phosphorylation and activation of Ypk1. Vps21 coimmunoprecipitates with TORC2, and immuno-enriched TORC2 is less active in vitro in the absence of Rab5 GTPases. Thus, TORC2-dependent and Ypk1-mediated activation of Muk1 provides a control circuit for positive (self-reinforcing) up-regulation to sustain TORC2-Ypk1 signaling.

Short-term lactation and mammary metabolism responses in lactating goats to graded removal of methionine from an intravenously infused complete amino acid mixture

To investigate the possible pathways of Met deficiency to depress milk protein synthesis, 4 lactating goats fitted with jugular vein, mammary vein, and carotid artery catheters and transonic blood flow detectors on the external pudic artery were used in a 4 × 4 Latin square experiment. Goats were fasted for 24 h followed by a 9-h intravenous infusion of an AA mixture plus glucose. Milk yield was recorded and samples were taken in h 2 to 8 of the infusion period, and mammary biopsy was performed in the last hour. Treatments were graded removal of Met from the infused AA mixture to achieve Met content in the infusate of 100 (complete), 60, 30, or 0% of that in casein. Graded Met removal decreased yield of milk, milk protein, and lactose linearly and tended to decrease yield of milk fat linearly. Milk protein yield decreased to 82, 78, and 69% that of complete mixture infusion, respectively, when the 60, 30, and 0% Met infusate was infused. Circulating Met decreased linearly with graded Met removal. Arterial and venous Met decreased to 36 and 23% that of complete mixture infusion, respectively, when all Met was removed out of the mixture. Concomitant with the decreased circulating concentration was a similar increase in mammary Met affinity as reflected by the linearly increased mammary Met clearance rate. The increased affinity plus the linearly increased mammary blood flow totally offset the negative effect of decreased circulating Met concentration on mammary Met uptake. The overall result was similar mammary Met uptakes across treatments ranging from 285.9 to 339.5 μmol/h. Mammary uptakes of the other AA measured were generally not affected by treatments except for a linearly decreased Thr uptake and a trend of linearly increased Glu uptake. Consistent with the behavior of an AA mainly catabolized in the liver and mainly used for protein synthesis in peripheral tissues, mammary uptake to milk output ratios of Met measured in the present study ranged from 1.25 to 1.49 and was not affected by treatments. For the other AA measured, the ratio of Thr was linearly decreased and that of Glu was linearly increased by graded Met removal. Graded Met removal linearly elevated circulating urea N and glucose concentrations, indicating enhanced whole-body catabolism of AA and hepatic gluconeogenesis. Treatments had no significant effects on circulating insulin, growth hormone, and the other hormones and metabolites measured. Phosphorylation status of eIF4E binding protein 1 tended to decrease linearly and that of p70S6k was linearly decreased by graded Met removal, indicating depressed signal in the intracellular mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway. In conclusion, results of the present study indicated that the mTORC1 pathway and whole-body AA catabolism rather than mammary uptake appeared the drivers for changes in milk protein synthesis in response to varying Met supply.

Ex vivo organotypic culture system of precision-cut slices of human pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, which is mainly due to late diagnosis and profound resistance to treatment. The latter is to a large extent attributed to the tumor stroma that is exceedingly prominent in PDAC and engages in complex interactions with the cancer cells. Hence, relevant preclinical models of PDAC should also include the tumor stroma. We herein describe the establishment and functional validation of an ex vivo organotypic culture of human PDAC that is based on precision-cut tissue slices from surgical specimens and reproducibly recapitulates the complex cellular and acellular composition of PDAC, including its microenvironment. The cancer cells, tumor microenvironment and interspersed remnants of nonneoplastic pancreas contained in these 350 µm thick slices maintained their structural integrity, phenotypic characteristics and functional activity when in culture for at least 4 days. In particular, tumor cell proliferation persisted and the grade of differentiation and morphological phenotype remained unaltered. Cultured tissue slices were metabolically active and responsive to rapamycin, an mTOR inhibitor. This culture system is to date the closest surrogate to the parent carcinoma and harbors great potential as a drug sensitivity testing system for the personalized treatment of PDAC.