How does mTOR sense glucose starvation? AMPK is the usual suspect

Differential regulation of expression of the protein kinases DYRK1A and DYRK1B in cancer cells

The protein kinases DYRK1A and DYRK1B are pivotal regulators of cell cycle progression by promoting cell cycle exit into quiescence. DYRK1B appears to play a more important role in cancer cell quiescence than DYRK1A, as evidenced by its overexpression or copy number variations in human tumour samples. Nonetheless, the stimuli driving DYRK1B upregulation and the potential divergence in expression patterns between DYRK1A and DYRK1B remain largely elusive. In the present study, we scrutinized the regulatory pathways modulating DYRK1B expression relative to DYRK1A in PANC-1 and A549 cancer cell lines across varying conditions. Serum deprivation, pharmacological mTOR inhibition and increased cell density resulted in the differential upregulation of DYRK1B compared to DYRK1A. We then aimed to assess the role of protein kinases MST1 and MST2, which are key transmitters of cell density dependent effects. Unexpectedly, exposure to the MST1/2 inhibitor XMU-MP-1 resulted in increased DYRK1B levels in A549 cells. Further investigation into the off-target effects of XMU-MP-1 unveiled the inhibition of Aurora kinases (AURKA and AURKB) as a potential causative factor. Consistently, AURK inhibitors VX-680 (tozasertib), MLN8237 (alisertib), AZD1152-HQPA (barasertib) resulted in the upregulation of DYRK1B expression in A549 cells. In summary, our findings indicate that the expression of DYRK1A and DYRK1B is differentially regulated in cancer cells and reveal that the kinase inhibitor XMU-MP-1 increases DYRK1B expression likely through off target inhibition of Aurora kinases.

Exploring the anti-cancer potential of SGLT2 inhibitors in breast cancer treatment in pre-clinical and clinical studies

The link between type 2 diabetes mellitus (T2DM) and an increased risk of breast cancer (BC) has prompted the exploration of novel therapeutic strategies targeting shared metabolic pathways. This review focuses on the emerging evidence surrounding the potential anti-cancer effects of sodium-glucose cotransporter-2 (SGLT2) inhibitors in the context of BC. Preclinical studies have demonstrated that various SGLT2 inhibitors, such as canagliflozin, dapagliflozin, ipragliflozin, and empagliflozin, can inhibit the proliferation of BC cells, induce apoptosis, and modulate key cellular signaling pathways. These mechanisms include the activation of AMP-activated protein kinase (AMPK), suppression of mammalian target of rapamycin (mTOR) signaling, and regulation of lipid metabolism and inflammatory mediators. The combination of SGLT2 inhibitors with conventional treatments, including chemotherapy and radiotherapy, as well as targeted therapies like phosphoinositide 3-kinases (PI3K) inhibitors, has shown promising results in enhancing the anti-cancer efficacy and potentially reducing treatment-related toxicities. The identification of specific biomarkers or genetic signatures that predict responsiveness to SGLT2 inhibitor therapy could enable more personalized treatment selection and optimization, particularly for challenging BC subtypes [e, g., triple negative BC (TNBC)]. Ongoing and future clinical trials investigating the use of SGLT2 inhibitors, both as monotherapy and in combination with other agents, will be crucial in elucidating their translational potential and guiding their integration into comprehensive BC care. Overall, SGLT2 inhibitors represent a novel and promising therapeutic approach with the potential to improve clinical outcomes for patients with various subtypes of BC, including the aggressive and chemo-resistant TNBC.

Excitatory amino acid transporter supports inflammatory macrophage responses

Excitatory amino acid transporters (EAATs) are responsible for excitatory amino acid transportation and are associated with auto-immune diseases in the central nervous system and peripheral tissues. However, the subcellular location and function of EAAT2 in macrophages are still obscure. In this study, we demonstrated that LPS stimulation increases expression of EAAT2 (coded by Slc1a2) via NF-κB signaling. EAAT2 is necessary for inflammatory macrophage polarization through sustaining mTORC1 activation. Mechanistically, lysosomal EAAT2 mediates lysosomal glutamate and aspartate efflux to maintain V-ATPase activation, which sustains macropinocytosis and mTORC1. We also found that mice with myeloid depletion of Slc1a2 show alleviated inflammatory responses in LPS-induced systemic inflammation and high-fat diet induced obesity. Notably, patients with type II diabetes (T2D) have a higher level of expression of lysosomal EAAT2 and activation of mTORC1 in blood macrophages. Taken together, our study links the subcellular location of amino acid transporters with the fate decision of immune cells, which provides potential therapeutic targets for the treatment of inflammatory diseases.

Neuroprotective Effect of Clemastine Improved Oligodendrocyte Proliferation through the MAPK/ERK Pathway in a Neonatal Hypoxia Ischemia Rat Model

Neonatal hypoxic-ischemic encephalopathy is the most common cause of long-term disability in term neonates, and white matter injury is the primary cause of cerebral palsy. Therapies that focus on the neuroprotection of myelination and oligodendrocyte proliferation could potentially ameliorate long-lasting neurological impairments after hypoxic-ischemic encephalopathy. Clemastine, a histamine H1 antagonist, has been shown to exert neuroprotective effects in multiple sclerosis and spinal cord injury by promoting oligodendrogenesis and re-myelination. In this study, we demonstrated the neuroprotective effects of clemastine in our rat model of neonatal hypoxic-ischemic brain injury. Animals received a single intraperitoneal injection of either vehicle or clemastine (10 mg/kg) for 6 consecutive days. Our results showed a significant reduction in white matter loss after treatment, with a clear effect of clemastine on oligodendrocytes, showing a significant increase in the number of Olig2+ cells. We characterized the MAPK/ERK pathway as a potential mechanistic pathway underlying the neuroprotective effects of clemastine. Altogether, our results demonstrate that clemastine is a potential compound for the treatment of hypoxic-ischemic encephalopathy, with a clear neuroprotective effect on white matter injury by promoting oligodendrogenesis.

Challenges of Spatially Resolved Metabolism in Cancer Research

Stable isotope-resolved metabolomics comprises a critical set of technologies that can be applied to a wide variety of systems, from isolated cells to whole organisms, to define metabolic pathway usage and responses to perturbations such as drugs or mutations, as well as providing the basis for flux analysis. As the diversity of stable isotope-enriched compounds is very high, and with newer approaches to multiplexing, the coverage of metabolism is now very extensive. However, as the complexity of the model increases, including more kinds of interacting cell types and interorgan communication, the analytical complexity also increases. Further, as studies move further into spatially resolved biology, new technical problems have to be overcome owing to the small number of analytes present in the confines of a single cell or cell compartment. Here, we review the overall goals and solutions made possible by stable isotope tracing and their applications to models of increasing complexity. Finally, we discuss progress and outstanding difficulties in high-resolution spatially resolved tracer-based metabolic studies.

Glucose deprivation triggers DCAF1-mediated inactivation of Rheb-mTORC1 and promotes cancer cell survival

Low glucose is a common microenvironment for rapidly growing solid tumors, which has developed multiple approaches to survive under glucose deprivation. However, the specific regulatory mechanism remains largely elusive. In this study, we demonstrate that glucose deprivation, while not amino acid or serum starvation, transactivates the expression of DCAF1. This enhances the K48-linked polyubiquitination and proteasome-dependent degradation of Rheb, inhibits mTORC1 activity, induces autophagy, and facilitates cancer cell survival under glucose deprivation conditions. This study identified DCAF1 as a new cellular glucose sensor and uncovered new insights into mechanism of DCAF1-mediated inactivation of Rheb-mTORC1 pathway for promoting cancer cell survival in response to glucose deprivation.

Glucose starvation causes ferroptosis-mediated lysosomal dysfunction

Lysosomes, the hub of metabolic signaling, are associated with various diseases and participate in autophagy by supplying nutrients to cells under nutrient starvation. However, their function and regulation under glucose starvation remain unclear and are studied herein. Under glucose starvation, lysosomal protein expression decreased, leading to the accumulation of damaged lysosomes. Subsequently, cell death occurred via ferroptosis and iron accumulation due to DMT1 degradation. GPX4, a key factor in ferroptosis inhibition located on the outer membrane of lysosomes, accumulated in lysosomes, especially under glucose starvation, to protect cells from ferroptosis. ALDOA, GAPDH, NAMPT, and PGK1 are also located on the outer membrane of lysosomes and participate in lysosomal function. These enzymes did not function effectively under glucose starvation, leading to lysosomal dysfunction and ferroptosis. These findings may facilitate the treatment of lysosomal-related diseases.

mTORC1 regulates cell survival under glucose starvation through 4EBP1/2-mediated translational reprogramming of fatty acid metabolism

Energetic stress compels cells to evolve adaptive mechanisms to adjust their metabolism. Inhibition of mTOR kinase complex 1 (mTORC1) is essential for cell survival during glucose starvation. How mTORC1 controls cell viability during glucose starvation is not well understood. Here we show that the mTORC1 effectors eukaryotic initiation factor 4E binding proteins 1/2 (4EBP1/2) confer protection to mammalian cells and budding yeast under glucose starvation. Mechanistically, 4EBP1/2 promote NADPH homeostasis by preventing NADPH-consuming fatty acid synthesis via translational repression of Acetyl-CoA Carboxylase 1 (ACC1), thereby mitigating oxidative stress. This has important relevance for cancer, as oncogene-transformed cells and glioma cells exploit the 4EBP1/2 regulation of ACC1 expression and redox balance to combat energetic stress, thereby supporting transformation and tumorigenicity in vitro and in vivo. Clinically, high EIF4EBP1 expression is associated with poor outcomes in several cancer types. Our data reveal that the mTORC1-4EBP1/2 axis provokes a metabolic switch essential for survival during glucose starvation which is exploited by transformed and tumor cells.

Glucose hypometabolism prompts RAN translation and exacerbates C9orf72-related ALS/FTD phenotypes

The most prevalent genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia is a (GGGGCC)n nucleotide repeat expansion (NRE) occurring in the first intron of the C9orf72 gene (C9). Brain glucose hypometabolism is consistently observed in C9-NRE carriers, even at pre-symptomatic stages, but its role in disease pathogenesis is unknown. Here, we show alterations in glucose metabolic pathways and ATP levels in the brains of asymptomatic C9-BAC mice. We find that, through activation of the GCN2 kinase, glucose hypometabolism drives the production of dipeptide repeat proteins (DPRs), impairs the survival of C9 patient-derived neurons, and triggers motor dysfunction in C9-BAC mice. We also show that one of the arginine-rich DPRs (PR) could directly contribute to glucose metabolism and metabolic stress by inhibiting glucose uptake in neurons. Our findings provide a potential mechanistic link between energy imbalances and C9-ALS/FTD pathogenesis and suggest a feedforward loop model with potential opportunities for therapeutic intervention.

TFE3-SLC36A1 axis promotes resistance to glucose starvation in kidney cancer cells

Higher demand for nutrients including glucose is characteristic of cancer. "Starving cancer" has been pursued to curb tumor progression. An intriguing regime is to inhibit glucose transporter GLUT1 in cancer cells. In addition, during cancer progression, cancer cells may suffer from insufficient glucose supply. Yet, cancer cells can somehow tolerate glucose starvation. Uncovering the underlying mechanisms shall shed insight into cancer progression and benefit cancer therapy. TFE3 is a transcription factor known to activate autophagic genes. Physiological TFE3 activity is regulated by phosphorylation-triggered translocation responsive to nutrient status. We recently reported TFE3 constitutively localizes to the cell nucleus and promotes cell proliferation in kidney cancer even under nutrient replete condition. It remains unclear whether and how TFE3 responds to glucose starvation. In this study, we show TFE3 promotes kidney cancer cell resistance to glucose starvation by exposing cells to physiologically relevant glucose concentration. We find glucose starvation triggers TFE3 protein stabilization through increasing its O-GlcNAcylation. Furthermore, through an unbiased functional genomic study, we identify SLC36A1, a lysosomal amino acid transporter, as a TFE3 target gene sensitive to TFE3 protein level. We find SLC36A1 is overexpressed in kidney cancer, which promotes mTOR activity and kidney cancer cell proliferation. Importantly, SLC36A1 level is induced by glucose starvation through TFE3, which enhances cellular resistance to glucose starvation. Suppressing TFE3 or SLC36A1 significantly increases cellular sensitivity to GLUT1 inhibitor in kidney cancer cells. Collectively, we uncover a functional TFE3-SLC36A1 axis that responds to glucose starvation and enhances starvation tolerance in kidney cancer.

Application of Aptamer-SERS Nanotags for Unveiling the PD-L1 Immunomarker Progression Correlated to the Cell Metabolic Bioprocess

In recent years, the expression and progression of programmed cell death ligand 1 (PD-L1) as an immunomarker in the context of a cell metabolic environment has gained significant attention in cancer research. However, intercellular bioprocesses that control the dynamics of PD-L1 have been largely unexplored. This study aimed to explore the cell metabolic states and conditions that govern dynamic variations of PD-L1 within the cell metabolic environment using an aptamer-based surface-enhanced Raman scattering (SERS) approach. The aptamer-SERS technique offers a sensitive, rapid, and powerful analytical tool for targeted and nondestructive detection of an immunomarker with high sensitivity and specificity. By combining aptamer-SERS with cell state profiling, we investigated the modulation in PD-L1 expression under different metabolic states, including glucose deprivation, metabolic coenzyme activity, and altered time/concentration-based cytokine availability. The most intriguing features in our findings include the cell-specific responses, cell differentiation by revealing distinct patterns, and dynamics of PD-L1 in different cell lines. Additionally, the time-dependent variations in PD-L1 expression, coupled with the dose-dependent relationship between glucose concentration and PD-L1 levels, underscore the complex interplay between immune checkpoint regulation and cellular metabolism. Therefore, this work demonstrates the advantages of using highly-sensitive and specific aptamer-SERS nanotags for investigating the immune checkpoint dynamics and related metabolic bioprocess.

AMPK-mTORC1 pathway mediates hepatic IGFBP-1 phosphorylation in glucose deprivation: a potential molecular mechanism of hypoglycemia-induced impaired fetal growth

Mechanisms underlying limitations in glucose supply that restrict fetal growth are not well established. IGF-1 is an important regulator of fetal growth and IGF-1 bioavailability is markedly inhibited by IGFBP-1 especially when the binding protein is hyperphosphorylated. We hypothesized that the AMPK-mTORC1 pathway increases IGFBP-1 phosphorylation in response to glucose deprivation. Glucose deprivation in HepG2 cells activated AMPK and TSC2, inhibited mTORC1 and increased IGFBP-1 secretion and site-specific phosphorylation. Glucose deprivation also decreased IGF-1 bioavailability and IGF-dependent activation of IGF-1R. AICAR (an AMPK activator) activated TSC2, inhibited mTORC1, and increased IGFBP-1 secretion/phosphorylation. Further, siRNA silencing of either AMPK or TSC2 prevented mTORC1 inhibition and IGFBP-1 secretion and phosphorylation in glucose deprivation. Our data suggest that the increase in IGFBP-1 phosphorylation in response to glucose deprivation is mediated by the activation of AMPK/TSC2 and inhibition of mTORC1, providing a possible mechanistic link between glucose deprivation and restricted fetal growth.

The potential of short-chain fatty acid epigenetic regulation in chronic low-grade inflammation and obesity

Obesity and chronic low-grade inflammation, often occurring together, significantly contribute to severe metabolic and inflammatory conditions like type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. A key player is elevated levels of gut dysbiosis-associated lipopolysaccharide (LPS), which disrupts metabolic and immune signaling leading to metabolic endotoxemia, while short-chain fatty acids (SCFAs) beneficially regulate these processes during homeostasis. SCFAs not only safeguard the gut barrier but also exert metabolic and immunomodulatory effects via G protein-coupled receptor binding and epigenetic regulation. SCFAs are emerging as potential agents to counteract dysbiosis-induced epigenetic changes, specifically targeting metabolic and inflammatory genes through DNA methylation, histone acetylation, microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). To assess whether SCFAs can effectively interrupt the detrimental cascade of obesity and inflammation, this review aims to provide a comprehensive overview of the current evidence for their clinical application. The review emphasizes factors influencing SCFA production, the intricate connections between metabolism, the immune system, and the gut microbiome, and the epigenetic mechanisms regulated by SCFAs that impact metabolism and the immune system.

Novel 4th-generation phytase improves broiler growth performance and reduces woody breast severity through modulation of muscle glucose uptake and metabolism

The objective of the present study was to determine the effect of a novel (4th generation) phytase supplementation as well as its mode of action on growth, meat quality, and incidence of muscle myopathies. One-day old male broilers (n = 720) were weighed and randomly allocated to 30 floor pens (24 birds/pen) with 10 replicate pens per treatment. Three diets were fed from hatch to 56- days-old: a 3-phase corn-soy based diet as a positive control (PC); a negative control (NC) formulated to be isocaloric and isonitrogenous to the PC and with a reduction in Ca and available P, respectively; and the NC supplemented with 2,000 phytase units per kg of diet (NC + P). At the conclusion of the experiment, birds fed with NC + P diet were significantly heavier and had 2.1- and 4.2-points better feed conversion ratio (FCR) compared to birds offered NC and PC diets, respectively. Processing data showed that phytase supplementation increased live weight, hot carcass without giblets, wings, tender, and skin-on drum and thigh compared to both NC and PC diets. Macroscopic scoring showed that birds fed the NC + P diet had lower woody breast (WB) severity compared to those fed the PC and NC diets, however there was no effect on white striping (WS) incidence and meat quality parameters (pH, drip loss, meat color). To delineate its mode of action, iSTAT showed that blood glucose concentrations were significantly lower in birds fed NC + P diet compared to those offered PC and NC diets, suggesting a better glucose uptake. In support, molecular analyses demonstrated that the breast muscle expression (mRNA and protein) of glucose transporter 1 (GLUT1) and glucokinase (GK) was significantly upregulated in birds fed NC + P diet compared to those fed the NC and PC diets. The expression of mitochondrial ATP synthase F0 subunit 8 (MT-ATP8) was significantly upregulated in NC + P compared to other groups, indicating intracellular ATP abundance for anabolic pathways. This was confirmed by the reduced level of phosphorylated-AMP-activated protein kinase (AMPKα1/2) at Thr172 site, upregulation of glycogen synthase (GYS1) gene and activation of mechanistic target of rapamycin and ribosomal protein S6 kinase (mTOR-P70S6K) pathway. In conclusion, this is the first report showing that in-feed supplementation of the novel phytase improves growth performance and reduces WB severity in broilers potentially through enhancement of glucose uptake, glycolysis, and intracellular ATP production, which used for muscle glycogenesis and protein synthesis.

Advances and Challenges in Cell Biology for Cultured Meat

Cultured meat is an emerging biotechnology that aims to produce meat from animal cell culture, rather than from the raising and slaughtering of livestock, on environmental and animal welfare grounds. The detailed understanding and accurate manipulation of cell biology are critical to the design of cultured meat bioprocesses. Recent years have seen significant interest in this field, with numerous scientific and commercial breakthroughs. Nevertheless, these technologies remain at a nascent stage, and myriad challenges remain, spanning the entire bioprocess. From a cell biological perspective, these include the identification of suitable starting cell types, tuning of proliferation and differentiation conditions, and optimization of cell-biomaterial interactions to create nutritious, enticing foods. Here, we discuss the key advances and outstanding challenges in cultured meat, with a particular focus on cell biology, and argue that solving the remaining bottlenecks in a cost-effective, scalable fashion will require coordinated, concerted scientific efforts. Success will also require solutions to nonscientific challenges, including regulatory approval, consumer acceptance, and market feasibility. However, if these can be overcome, cultured meat technologies can revolutionize our approach to food.

AMPK role in epilepsy: a promising therapeutic target?

Epilepsy is a complex and multifaceted neurological disorder characterized by spontaneous and recurring seizures. It poses significant therapeutic challenges due to its diverse etiology and often-refractory nature. This comprehensive review highlights the pivotal role of AMP-activated protein kinase (AMPK), a key metabolic regulator involved in cellular energy homeostasis, which may be a promising therapeutic target for epilepsy. Current therapeutic strategies such as antiseizure medication (ASMs) can alleviate seizures (up to 70%). However, 30% of epileptic patients may develop refractory epilepsy. Due to the complicated nature of refractory epilepsy, other treatment options such as ketogenic dieting, adjunctive therapy, and in limited cases, surgical interventions are employed. These therapy options are only suitable for a select group of patients and have limitations of their own. Current treatment options for epilepsy need to be improved. Emerging evidence underscores a potential association between impaired AMPK functionality in the brain and the onset of epilepsy, prompting an in-depth examination of AMPK's influence on neural excitability and ion channel regulation, both critical factors implicated in epileptic seizures. AMPK activation through agents such as metformin has shown promising antiepileptic effects in various preclinical and clinical settings. These effects are primarily mediated through the inhibition of the mTOR signaling pathway, activation of the AMPK-PI3K-c-Jun pathway, and stimulation of the PGC-1α pathway. Despite the potential of AMPK-targeted therapies, several aspects warrant further exploration, including the detailed mechanisms of AMPK's role in different brain regions, the impact of AMPK under various conditional circumstances such as neural injury and zinc toxicity, the long-term safety and efficacy of chronic metformin use in epilepsy treatment, and the potential benefits of combination therapy involving AMPK activators. Moreover, the efficacy of AMPK activators in refractory epilepsy remains an open question. This review sets the stage for further research with the aim of enhancing our understanding of the role of AMPK in epilepsy, potentially leading to the development of more effective, AMPK-targeted therapeutic strategies for this challenging and debilitating disorder.

p300 nucleocytoplasmic shuttling underlies mTORC1 hyperactivation in Hutchinson-Gilford progeria syndrome

The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth, metabolism and autophagy. Multiple pathways modulate mTORC1 in response to nutrients. Here we describe that nucleus-cytoplasmic shuttling of p300/EP300 regulates mTORC1 activity in response to amino acid or glucose levels. Depletion of these nutrients causes cytoplasm-to-nucleus relocalization of p300 that decreases acetylation of the mTORC1 component raptor, thereby reducing mTORC1 activity and activating autophagy. This is mediated by AMP-activated protein kinase-dependent phosphorylation of p300 at serine 89. Nutrient addition to starved cells results in protein phosphatase 2A-dependent dephosphorylation of nuclear p300, enabling its CRM1-dependent export to the cytoplasm to mediate mTORC1 reactivation. p300 shuttling regulates mTORC1 in most cell types and occurs in response to altered nutrients in diverse mouse tissues. Interestingly, p300 cytoplasm-nucleus shuttling is altered in cells from patients with Hutchinson-Gilford progeria syndrome. p300 mislocalization by the disease-causing protein, progerin, activates mTORC1 and inhibits autophagy, phenotypes that are normalized by modulating p300 shuttling. These results reveal how nutrients regulate mTORC1, a cytoplasmic complex, by shuttling its positive regulator p300 in and out of the nucleus, and how this pathway is misregulated in Hutchinson-Gilford progeria syndrome, causing mTORC1 hyperactivation and defective autophagy.

Short-term feed restriction induces inflammation and an antioxidant response via cystathionine-β-synthase and glutathione peroxidases in ruminal epithelium from Angus steers

Decreased intake is induced by stressors such as parturition, transportation, dietary transitions, and disease. An important function of one-carbon metabolism (OCM) is to produce the antioxidant glutathione to help reduce oxidative stress. Although various components of OCM are expressed in the bovine rumen and small intestine, the relationship between reduced feed intake, OCM, and antioxidant mechanisms in gut tissues is unknown. This study aimed to assess alterations in immune and antioxidant pathways in ruminal epithelium due to acute feed restriction (FR). Seven group-housed ruminally cannulated Angus steers (663 ± 73 kg body weight, 2 yr old) had ad libitum access to a finishing diet (dry-rolled corn, corn silage, modified wet distiller's grains) during 15 d of a pre-FR period (PRE). Subsequently, steers were moved to a metabolism barn with tie stalls and individually fed at 25% of estimated intake in PRE for 3 d (FR period, FRP). This was followed by 15 d of recovery (POST) during which steers had ad libitum access to the same diet as in PRE and FRP. Plasma and ruminal tissue biopsies were collected during each period. Plasma free fatty acid and IL1-β concentrations were higher (P ≤ 0.03) in FRP than PRE or POST. The mRNA abundance of the proinflammatory genes tumor necrosis factor, toll-like receptor 2 (TLR2), and TLR4 in the ruminal epithelium peaked (P < 0.05) at FRP and remained higher at POST. These responses agreed with the higher (P < 0.05) abundance of phosphorylated (p)-MAPK (an inflammation activator) and p-EEF2 (translational repressor) in FRP than PRE and POST. Although ruminal glutathione peroxidase (GPX) enzyme activity did not increase at FRP compared with PRE and POST, protein abundance of GPX1 and GPX3 along with the antioxidant response regulator NFE2L2 were highest (P < 0.01), and the activity of cystathionine-beta synthase tended (P = 0.06) to be highest during FR. Although FR had minimal negative effects on tissue integrity-related genes (only filamin A was downregulated), it led to a systemic inflammatory response and triggered inflammation and antioxidant mechanisms within the ruminal epithelium. Thus, deploying anti-inflammatory and antioxidant mechanisms via molecules that feed into OCM (e.g., dietary methyl donors such as methionine, choline, betaine, and folate) could potentially counteract the stressors associated with FR.

TorS - Reframing a rational for type 2 diabetes treatment

The mammalian target of rapamycin complex 1 syndrome (Tors), paradigm implies an exhaustive cohesive disease entity driven by a hyperactive mTORC1, and which includes obesity, type 2 diabetic hyperglycemia, diabetic dyslipidemia, diabetic cardiomyopathy, diabetic nephropathy, diabetic peripheral neuropathy, hypertension, atherosclerotic cardiovascular disease, non-alcoholic fatty liver disease, some cancers, neurodegeneration, polycystic ovary syndrome, psoriasis and other. The TorS paradigm may account for the efficacy of standard-of-care treatments of type 2 diabetes (T2D) in alleviating the glycaemic and non-glycaemic diseases of TorS in T2D and non-T2D patients. The TorS paradigm may generate novel treatments for TorS diseases.

Myotube growth is associated with cancer-like metabolic reprogramming and is limited by phosphoglycerate dehydrogenase

The Warburg effect links growth and glycolysis in cancer. A key purpose of the Warburg effect is to generate glycolytic intermediates for anabolic reactions, such as nucleotides → RNA/DNA and amino acids → protein synthesis. The aim of this study was to investigate whether a similar 'glycolysis-for-anabolism' metabolic reprogramming also occurs in hypertrophying skeletal muscle. To interrogate this, we first induced C2C12 myotube hypertrophy with IGF-1. We then added 14C glucose to the differentiation medium and measured radioactivity in isolated protein and RNA to establish whether 14C had entered anabolism. We found that especially protein became radioactive, suggesting a glucose → glycolytic intermediates → non-essential amino acid(s) → protein series of reactions, the rate of which was increased by IGF-1. Next, to investigate the importance of glycolytic flux and non-essential amino acid synthesis for myotube hypertrophy, we exposed C2C12 and primary mouse myotubes to the glycolysis inhibitor 2-Deoxy-d-glucose (2DG). We found that inhibiting glycolysis lowered C2C12 and primary myotube size. Similarly, siRNA silencing of PHGDH, the key enzyme of the serine biosynthesis pathway, decreased C2C12 and primary myotube size; whereas retroviral PHGDH overexpression increased C2C12 myotube size. Together these results suggest that glycolysis is important for hypertrophying myotubes, which reprogram their metabolism to facilitate anabolism, similar to cancer cells.

Epigenome wide association study in peripheral blood of pregnant women identifies potential metabolic pathways related to gestational diabetes

Gestational diabetes mellitus (GDM) increases the risk of developing metabolic disorders in both pregnant women and their offspring. Factors such as nutrition or the intrauterine environment may play an important role, through epigenetic mechanisms, in the development of GDM. The aim of this work is to identify epigenetic marks involved in the mechanisms or pathways related to gestational diabetes. A total of 32 pregnant women were selected, 16 of them with GDM and 16 non-GDM. DNA methylation pattern was obtained from Illumina Methylation Epic BeadChip, from peripheral blood samples at the diagnostic visit (26-28 weeks). Differential methylated positions (DMPs) were extracted using ChAMP and limma package in R 2.9.10, with a threshold of FDR <0.05, deltabeta >|5|% and B >0. A total of 1.141 DMPs were found, and 714 were annotated in genes. A functional analysis was performed, and we found 23 genes significantly related to carbohydrate metabolism. Finally, a total of 27 DMPs were correlated with biochemical variables such as glucose levels at different points of oral glucose tolerance test, fasting glucose, cholesterol, HOMAIR and HbA1c, at different visits during pregnancy and postpartum. Our results show that there is a differentiated methylation pattern between GDM and non-GDM. Furthermore, the genes annotated to the DMPs could be implicated in the development of GDM as well as in alterations in related metabolic variables.

The Influence of Coffee on Reducing Metabolic Dysfunction-Associated Steatotic Liver Disease in Patients With Type 2 Diabetes: A Review

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a liver disease characterized by hepatic fat accumulation associated with various severities of inflammation and scarring. As studies explore specialized treatments, emerging evidence suggests a potential protective effect of coffee consumption. Consumption of coffee or its components, such as caffeine and/or chlorogenic acid (CA), can reduce markers of liver injury and induce a myriad of other health benefits. However, there is limited research on patients with both MASLD and type 2 diabetes (T2D). Current research suggests that patients with MASLD are at greater risk of developing T2D and future liver-related complications and vice versa. Given that both MASLD and T2D are global burdens, the present literature review analyzes current research to identify trends and determine if coffee can be a viable treatment for MASLD patients with T2D. Results indicate that coffee consumption may protect against MASLD in T2D patients who are overweight/obese through a declined rate of weight gain, inhibition of the mammalian target of rapamycin (mTOR) gene, and insignificant changes to the gut microbiome. More longitudinal research on human subjects is needed to establish a causal relationship between coffee consumption and MASLD alleviation.

Impaired Autophagic Flux in Glucose-Deprived Cells: An Outcome of Lysosomal Acidification Failure Exacerbated by Mitophagy Dysfunction

Autophagy dysfunction is associated with human diseases and conditions including neurodegenerative diseases, metabolic issues, and chronic infections. Additionally, the decline in autophagic activity contributes to tissue and organ dysfunction and aging-related diseases. Several factors, such as down-regulation of autophagy components and activators, oxidative damage, microinflammation, and impaired autophagy flux, are linked to autophagy decline. An autophagy flux impairment (AFI) has been implicated in neurological disorders and in certain other pathological conditions. Here, to enhance our understanding of AFI, we conducted a comprehensive literature review of findings derived from two well-studied cellular stress models: glucose deprivation and replicative senescence. Glucose deprivation is a condition in which cells heavily rely on oxidative phosphorylation for ATP generation. Autophagy is activated, but its flux is hindered at the autolysis step, primarily due to an impairment of lysosomal acidity. Cells undergoing replicative senescence also experience AFI, which is also known to be caused by lysosomal acidity failure. Both glucose deprivation and replicative senescence elevate levels of reactive oxygen species (ROS), affecting lysosomal acidification. Mitochondrial alterations play a crucial role in elevating ROS generation and reducing lysosomal acidity, highlighting their association with autophagy dysfunction and disease conditions. This paper delves into the underlying molecular and cellular pathways of AFI in glucose-deprived cells, providing insights into potential strategies for managing AFI that is driven by lysosomal acidity failure. Furthermore, the investigation on the roles of mitochondrial dysfunction sheds light on the potential effectiveness of modulating mitochondrial function to overcome AFI, offering new possibilities for therapeutic interventions.

Increasing glutathione levels by a novel posttranslational mechanism inhibits neuronal hyperexcitability

Glutathione (GSH) depletion, and impaired redox homeostasis have been observed in experimental animal models and patients with epilepsy. Pleiotropic strategies that elevate GSH levels via transcriptional regulation have been shown to significantly decrease oxidative stress and seizure frequency, increase seizure threshold, and rescue certain cognitive deficits. Whether elevation of GSH per se alters neuronal hyperexcitability remains unanswered. We previously showed that thiols such as dimercaprol (DMP) elevate GSH via post-translational activation of glutamate cysteine ligase (GCL), the rate limiting GSH biosynthetic enzyme. Here, we asked if elevation of cellular GSH by DMP altered neuronal hyperexcitability in-vitro and in-vivo. Treatment of primary neuronal-glial cerebrocortical cultures with DMP elevated GSH and inhibited a voltage-gated potassium channel blocker (4-aminopyridine, 4AP) induced neuronal hyperexcitability. DMP increased GSH in wildtype (WT) zebrafish larvae and significantly attenuated convulsant pentylenetetrazol (PTZ)-induced acute 'seizure-like' swim behavior. DMP treatment increased GSH and inhibited convulsive, spontaneous 'seizure-like' swim behavior in the Dravet Syndrome (DS) zebrafish larvae (scn1Lab). Furthermore, DMP treatment significantly decreased spontaneous electrographic seizures and associated seizure parameters in scn1Lab zebrafish larvae. We investigated the role of the redox-sensitive mammalian target of rapamycin (mTOR) pathway due to the presence of several cysteine-rich proteins and their involvement in regulating neuronal excitability. Treatment of primary neuronal-glial cerebrocortical cultures with 4AP or l-buthionine-(S,R)-sulfoximine (BSO), an irreversible inhibitor of GSH biosynthesis, significantly increased mTOR complex I (mTORC1) activity which was rescued by pre-treatment with DMP. Furthermore, BSO-mediated GSH depletion oxidatively modified the tuberous sclerosis protein complex (TSC) consisting of hamartin (TSC1), tuberin (TSC2), and TBC1 domain family member 7 (TBC1D7) which are critical negative regulators of mTORC1. In summary, our results suggest that DMP-mediated GSH elevation by a novel post-translational mechanism can inhibit neuronal hyperexcitability both in-vitro and in-vivo and a plausible link is the redox sensitive mTORC1 pathway.

Effect of Glucose Supplementation on Apoptosis in the Pectoralis major of Chickens Raised under Thermoneutral or Heat Stress Environment

Reduced feed intake during heat stress (HS) disrupts glucose homeostasis, thereby resulting in endoplasmic reticulum (ER) stress and triggering apoptosis in chickens. We hypothesize that glucose supplementation could reduce apoptosis in chickens raised under HS. This study comprised 456 28-day-old broiler chickens randomly assigned to four treatment combinations under glucose supplementation and HS. The treatments were TN0, TN6, HS0, and HS6 with two glucose levels (0% and 6%) and two temperature levels (25 °C (thermoneutral-TN) and 35 °C (8.00 AM to 8.00 PM, (HS)). After 7 days post-HS, the blood glucose level for the HS6 group was higher than for TN0, TN6, and HS0. We studied the mRNA expression of genes and caspase-3 activity in the four experimental groups. The expressions of GCN2, ATF4, CHOP, and FOXO3a increased during HS regardless of glucose supplementation, while PERK and MAFbx increased only under HS with glucose supplementation. We show that under TN conditions, glucose supplementation led to a significant increase in cellular apoptosis in the Pectoralis (P.) major. However, under HS with glucose, the level of apoptosis was similar to that of chickens raised under TN conditions with no glucose supplementation. The utility of glucose to curtail apoptosis under HS should be tested under other intense models of HS.

Alteration of the embryonic microenvironment and sex-specific responses of the preimplantation embryo related to a maternal high-fat diet in the rabbit model

The maternal metabolic environment can be detrimental to the health of the offspring. In a previous work, we showed that maternal high-fat (HH) feeding in rabbit induced sex-dependent metabolic adaptation in the fetus and led to metabolic syndrome in adult offspring. As early development representing a critical window of susceptibility, in the present work we aimed to explore the effects of the HH diet on the oocyte, preimplantation embryo and its microenvironment. In oocytes from females on HH diet, transcriptomic analysis revealed a weak modification in the content of transcripts mainly involved in meiosis and translational control. The effect of maternal HH diet on the embryonic microenvironment was investigated by identifying the metabolite composition of uterine and embryonic fluids collected in vivo by biomicroscopy. Metabolomic analysis revealed differences in the HH uterine fluid surrounding the embryo, with increased pyruvate concentration. Within the blastocoelic fluid, metabolomic profiles showed decreased glucose and alanine concentrations. In addition, the blastocyst transcriptome showed under-expression of genes and pathways involved in lipid, glucose and amino acid transport and metabolism, most pronounced in female embryos. This work demonstrates that the maternal HH diet disrupts the in vivo composition of the embryonic microenvironment, where the presence of nutrients is increased. In contrast to this nutrient-rich environment, the embryo presents a decrease in nutrient sensing and metabolism suggesting a potential protective process. In addition, this work identifies a very early sex-specific response to the maternal HH diet, from the blastocyst stage.

Regulation of Transporters for Organic Cations by High Glucose

Endogenous positively charged organic substances, including neurotransmitters and cationic uremic toxins, as well as exogenous organic cations such as the anti-diabetic medication metformin, serve as substrates for organic cation transporters (OCTs) and multidrug and toxin extrusion proteins (MATEs). These proteins facilitate their transport across cell membranes. Vectorial transport through the OCT/MATE axis mediates the hepatic and renal excretion of organic cations, regulating their systemic and local concentrations. Organic cation transporters are part of the remote sensing and signaling system, whose activity can be regulated to cope with changes in the composition of extra- and intracellular fluids. Glucose, as a source of energy, can also function as a crucial signaling molecule, regulating gene expression in various organs and tissues. Its concentration in the blood may fluctuate in specific physiological and pathophysiological conditions. In this work, the regulation of the activity of organic cation transporters was measured by incubating human embryonic kidney cells stably expressing human OCT1 (hOCT1), hOCT2, or hMATE1 with high glucose concentrations (16.7 mM). Incubation with this high glucose concentration for 48 h significantly stimulated the activity of hOCT1, hOCT2, and hMATE1 by increasing their maximal velocity (Vmax), but without significantly changing their affinity for the substrates. These effects were independent of changes in osmolarity, as the addition of equimolar concentrations of mannitol did not alter transporter activity. The stimulation of transporter activity was associated with a significant increase in transporter mRNA expression. Inhibition of the mechanistic target of rapamycin (mTOR) kinase with Torin-1 suppressed the transporter stimulation induced by incubation with 16.7 mM glucose. Focusing on hOCT2, it was shown that incubation with 16.7 mM glucose increased hOCT2 protein expression in the plasma membrane. Interestingly, an apparent trend towards higher hOCT2 mRNA expression was observed in kidneys from diabetic patients, a pathology characterized by high serum glucose levels. Due to the small number of samples from diabetic patients (three), this observation must be interpreted with caution. In conclusion, incubation for 48 h with a high glucose concentration of 16.7 mM stimulated the activity and expression of organic cation transporters compared to those measured in the presence of 5.6 mM glucose. This stimulation by a diabetic environment could increase cellular uptake of the anti-diabetic drug metformin and increase renal tubular secretion of organic cations in an early stage of diabetes.

Antitumor Activity of Metformin Combined with Locoregional Therapy for Liver Cancer: Evidence and Future Directions

This article aimed to examine the effect of metformin use on improving outcomes after liver-directed therapy in patients with HCC and identify future directions with the adjuvant use of and potential therapeutic agents that operate on similar mechanistic pathways. Databases were queried to identify pertinent articles on metformin's use as an anti-cancer agent in HCC. Eleven studies were included, with five pre-clinical and six clinical studies. The mean overall survival (OS) and progression-free survival were both higher in the locoregional therapy (LRT) + metformin-treated groups. The outcome variables, including local tumor recurrence rate, reduction in HCC tumor growth and size, tumor growth, proliferation, migration and invasion of HCC cells, HCC cell apoptosis, DNA damage, and cell cycle arrest, showed favorable outcomes in the LRT + metformin-treated groups compared with LRT alone. This systemic review provides a strong signal that metformin use can improve the tumor response after locoregional therapy. Well-controlled prospective trials will be needed to elucidate the potential antitumor effects of metformin and other mTOR inhibitors.

Cell starvation regulates ceramide-induced autophagy in mouse preimplantation embryo development

Ceramide induces autophagy upon starvation via downregulation of nutrient transporters. To elucidate the mechanism by which starvation regulates autophagy in mouse embryos, the present study investigated nutrient transporter expression and the effect of C2-ceramide on in vitro embryo development, apoptosis, and autophagy. The transcript levels of the glucose transporters Glut1 and Glut3 were high at the 1- and 2-cell stages, and gradually decreased at the morula and blastocyst (BL) stages. Similarly, expression of the amino acid transporters L-type amino transporter-1 (LAT-1) and 4F2 heavy chain (4F2hc) gradually decreased from the zygote to the BL stage. Upon ceramide treatment, expression of Glut1, Glut3, LAT-1, and 4F2hc was significantly reduced at the BL stage, while expression of the autophagy-related genes Atg5, LC3, and Gabarap and synthesis of LC3 were significantly induced. Ceramide-treated embryos exhibited significantly reduced developmental rates and total cell numbers per blastocyst, and increased levels of apoptosis and expression of Bcl2l1 and Casp3 at the BL stage. Ceramide treatment significantly decreased the average mitochondrial DNA copy number and mitochondrial area at the BL stage. In addition, ceramide treatment significantly decreased mTOR expression. These results suggest that ceramide-induced autophagy promotes apoptosis by following downregulation of nutrient transporters during mouse embryogenesis.

Inhibition of protein translation under matrix-deprivation stress in breast cancer cells

Matrix-deprivation stress leads to cell-death by anoikis, whereas overcoming anoikis is critical for cancer metastasis. Work from our lab and others has identified a crucial role for the cellular energy sensor AMPK in anoikis-resistance, highlighting a key role for metabolic reprogramming in stress survival. Protein synthesis is a major energy-consuming process that is tightly regulated under stress. Although an increase in protein synthesis in AMPK-depleted experimentally-transformed MEFs has been associated with anoikis, the status and regulation of protein translation in epithelial-origin cancer cells facing matrix-detachment remains largely unknown. Our study shows that protein translation is mechanistically abrogated at both initiation and elongation stages by the activation of the unfolded protein response (UPR) pathway and inactivation of elongation factor eEF2, respectively. Additionally, we show inhibition of the mTORC1 pathway known for regulation of canonical protein synthesis. We further functionally assay this inhibition using SUnSET assay, which demonstrates repression of global protein synthesis in MDA-MB-231 and MCF7 breast cancer cells when subjected to matrix-deprivation. In order to gauge the translational status of matrix-deprived cancer cells, we undertook polysome profiling. Our data revealed reduced but continuous mRNA translation under matrix-deprivation stress. An integrated analysis of transcriptomic and proteomic data further identifies novel targets that may aid cellular adaptations to matrix-deprivation stress and can be explored for therapeutic intervention.

Glucose Hypometabolism Prompts RAN Translation and Exacerbates C9orf72-related ALS/FTD Phenotypes

The most prevalent genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia is a (GGGGCC)n nucleotide repeat expansion (NRE) occurring in the first intron of the C9orf72 gene (C9). Brain glucose hypometabolism is consistently observed in C9-NRE carriers, even at pre-symptomatic stages, although its potential role in disease pathogenesis is unknown. Here, we identified alterations in glucose metabolic pathways and ATP levels in the brain of asymptomatic C9-BAC mice. We found that, through activation of the GCN2 kinase, glucose hypometabolism drives the production of dipeptide repeat proteins (DPRs), impairs the survival of C9 patient-derived neurons, and triggers motor dysfunction in C9-BAC mice. We also found that one of the arginine-rich DPRs (PR) can directly contribute to glucose metabolism and metabolic stress. These findings provide a mechanistic link between energy imbalances and C9-ALS/FTD pathogenesis and support a feedforward loop model that opens several opportunities for therapeutic intervention.

mTORC1 syndrome (TorS): unified paradigm for diabetes/metabolic syndrome

'Glucolipotoxicity' and 'insulin resistance' are claimed to drive type 2 diabetes (T2D) and the non-glycemic diseases of the metabolic syndrome (MetS) (obesity, dyslipidemia, hypertension). In line with that, glycemic and/or insulin control are considered to be primary goal in treating T2D/MetS. However, recent standard-of-care (SOC) treatments of T2D, initially designed to control T2D hyperglycemia, appear now to alleviate the cardio-renal and non-glycemic diseases of T2D/MetS independently of glucose lowering and insulin resistance, and in non-T2D patients altogether, calling for an alternative unifying pathophysiology/treatment paradigm for T2D/MetS. This opinion article proposes to replace the current 'glucolipotoxic/insulin-resistance' paradigm of T2D/MetS with an 'mammalian target of rapamycin complex 1 (mTORC1) syndrome' (TorS) paradigm, implying an exhaustive cohesive disease entity driven by an upstream hyperactive mTORC1, and which includes diabetic hyperglycemia, diabetic dyslipidemia, hypertension, diabetic macrovascular and microvascular disease, non-alcoholic fatty liver disease, some cancers, neurodegeneration, polycystic ovary syndrome (PCOS), psoriasis, and others. The TorS paradigm may account for the insulin-resistant glycemic context of TorS, combined with response to insulin of the non-glycemic diseases of TorS. The TorS paradigm may account for the efficacy of current antidiabetic SOC treatments in diabetic and nondiabetic patients. Most importantly, the TorS paradigm may generate novel treatments for TorS.

Resveratrol attenuates staphylococcal enterotoxin B-activated immune cell metabolism via upregulation of miR-100 and suppression of mTOR signaling pathway

Acute Respiratory Distress Syndrome (ARDS) is triggered by a variety of insults, such as bacterial and viral infections, including SARS-CoV-2, leading to high mortality. In the murine model of ARDS induced by Staphylococcal enterotoxin-B (SEB), our previous studies showed that while SEB triggered 100% mortality, treatment with Resveratrol (RES) completely prevented such mortality by attenuating inflammation in the lungs. In the current study, we investigated the metabolic profile of SEB-activated immune cells in the lungs following treatment with RES. RES-treated mice had higher expression of miR-100 in the lung mononuclear cells (MNCs), which targeted mTOR, leading to its decreased expression. Also, Single-cell RNA-seq (scRNA seq) unveiled the decreased expression of mTOR in a variety of immune cells in the lungs. There was also an increase in glycolytic and mitochondrial respiration in the cells from SEB + VEH group in comparison with SEB + RES group. Together these data suggested that RES alters the metabolic reprogramming of SEB-activated immune cells, through suppression of mTOR activation and its down- and upstream effects on energy metabolism. Also, miR-100 could serve as novel potential therapeutic molecule in the amelioration of ARDS.

AMPK-dependent phosphorylation of the GATOR2 component WDR24 suppresses glucose-mediated mTORC1 activation

The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth in response to amino acid and glucose levels. However, how mTORC1 senses glucose availability to regulate various downstream signalling pathways remains largely elusive. Here we report that AMP-activated protein kinase (AMPK)-mediated phosphorylation of WDR24, a core component of the GATOR2 complex, has a role in the glucose-sensing capability of mTORC1. Mechanistically, glucose deprivation activates AMPK, which directly phosphorylates WDR24 on S155, subsequently disrupting the integrity of the GATOR2 complex to suppress mTORC1 activation. Phosphomimetic Wdr24S155D knock-in mice exhibit early embryonic lethality and reduced mTORC1 activity. On the other hand, compared to wild-type littermates, phospho-deficient Wdr24S155A knock-in mice are more resistant to fasting and display elevated mTORC1 activity. Our findings reveal that AMPK-mediated phosphorylation of WDR24 modulates glucose-induced mTORC1 activation, thereby providing a rationale for targeting AMPK-WDR24 signalling to fine-tune mTORC1 activation as a potential therapeutic means to combat human diseases with aberrant activation of mTORC1 signalling including cancer.

Increased mTOR Signaling and Impaired Autophagic Flux Are Hallmarks of SARS-CoV-2 Infection

The COVID-19 (Coronavirus Disease 2019), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), severely affects mainly individuals with pre-existing comorbidities. Here our aim was to correlate the mTOR (mammalian/mechanistic Target of Rapamycin) and autophagy pathways with the disease severity. Through western blotting and RNA analysis, we found increased mTOR signaling and suppression of genes related to autophagy, lysosome, and vesicle fusion in Vero E6 cells infected with SARS-CoV-2 as well as in transcriptomic data mining of bronchoalveolar epithelial cells from severe COVID-19 patients. Immunofluorescence co-localization assays also indicated that SARS-CoV-2 colocalizes within autophagosomes but not with a lysosomal marker. Our findings indicate that SARS-CoV-2 can benefit from compromised autophagic flux and inhibited exocytosis in individuals with chronic hyperactivation of mTOR signaling.

Queueing theory model of mTOR complexes' impact on Akt-mediated adipocytes response to insulin

A queueing theory based model of mTOR complexes impact on Akt-mediated cell response to insulin is presented in this paper. The model includes several aspects including the effect of insulin on the transport of glucose from the blood into the adipocytes with the participation of GLUT4, and the role of the GAPDH enzyme as a regulator of mTORC1 activity. A genetic algorithm was used to optimize the model parameters. It can be observed that mTORC1 activity is related to the amount of GLUT4 involved in glucose transport. The results show the relationship between the amount of GAPDH in the cell and mTORC1 activity. Moreover, obtained results suggest that mTORC1 inhibitors may be an effective agent in the fight against type 2 diabetes. However, these results are based on theoretical knowledge and appropriate experimental tests should be performed before making firm conclusions.

SGLT-2 Inhibitors in Cancer Treatment-Mechanisms of Action and Emerging New Perspectives

A new group of antidiabetic drugs, sodium-glucose cotransporter 2 inhibitors (SGLT-2 inhibitors), have recently been shown to have anticancer effects and their expression has been confirmed in many cancer cell lines. Given the metabolic reprogramming of these cells in a glucose-based model, the ability of SGLT-2 inhibitors to block the glucose uptake by cancer cells appears to be an attractive therapeutic approach. In addition to tumour cells, SGLT-2s are only found in the proximal tubules in the kidneys. Furthermore, as numerous clinical trials have shown, the use of SGLT-2 inhibitors is well-tolerated and safe in patients with diabetes and/or heart failure. In vitro cell culture studies and preclinical in vivo studies have confirmed that SGLT-2 inhibitors exhibit antiproliferative effects on certain types of cancer. However, the mechanisms of this action remain unclear. Even in those tumour cell types in which SGLT-2 is present, there is sometimes an SGLT-2-independent mechanism of anticancer action of this group of drugs. This article presents the current state of knowledge of the potential mechanisms of the anticancer action of SGLT-2 inhibitors and their possible future application in clinical oncology.

Vasorin Deletion in C57BL/6J Mice Induces Hepatocyte Autophagy through Glycogen-Mediated mTOR Regulation

Abnormal vasorin (Vasn) expression occurs in multiple diseases, particularly liver cancers. Vasn knockout (KO) in mice causes malnutrition, a shortened life span, and decreased physiological functions. However, the causes and underlying mechanisms remain unknown. Here, we established Vasn KO C57BL/6J mice by using the CRISPR/Cas9 system. The animals were weighed, and histology, immunohistochemistry, electronic microscopy, and liver function tests were used to examine any change in the livers. Autophagy markers were detected by Western blotting. MicroRNA (miRNA) sequencing was performed on liver samples and analyses to study the signaling pathway altered by Vasn KO. Significant reductions in mice body and liver weight, accompanied by abnormal liver function, liver injury, and reduced glycogen accumulation in hepatocytes, were observed in the Vasn KO mice. The deficiency of Vasn also significantly increased the number of autophagosomes and the expression of LC3A/B-II/I but decreased SQSTM1/p62 levels in hepatocytes, suggesting aberrant activation of autophagy. Vasn deficiency inhibited glycogen-mediated mammalian target of rapamycin (mTOR) phosphorylation and activated Unc-51-like kinase 1 (ULK1) signaling, suggesting that Vasn deletion upregulates hepatocyte autophagy through the mTOR-ULK1 signaling pathway as a possible cause of diminished life span and health. Our results indicate that Vasn is required for the homeostasis of liver glycogen metabolism upstream of hepatocyte autophagy, suggesting research values for regulating Vasn in pathways related to liver physiology and functions. Overall, this study provides new insight into the role of Vasn in liver functionality.

Mechanism and Therapeutic Targets of c-Jun-N-Terminal Kinases Activation in Nonalcoholic Fatty Liver Disease

Non-alcoholic fatty liver (NAFL) is the most common chronic liver disease. Activation of mitogen-activated kinases (MAPK) cascade, which leads to c-Jun N-terminal kinase (JNK) activation occurs in the liver in response to the nutritional and metabolic stress. The aberrant activation of MAPKs, especially c-Jun-N-terminal kinases (JNKs), leads to unwanted genetic and epi-genetic modifications in addition to the metabolic stress adaptation in hepatocytes. A mechanism of sustained P-JNK activation was identified in acute and chronic liver diseases, suggesting an important role of aberrant JNK activation in NASH. Therefore, modulation of JNK activation, rather than targeting JNK protein levels, is a plausible therapeutic application for the treatment of chronic liver disease.

ABCA8 inhibits breast cancer cell proliferation by regulating the AMP activated protein kinase/mammalian target of rapamycin signaling pathway

ATP-binding cassette (ABC) subfamily A member 8 (ABCA8) has been reported to play a vital role in cancer development. Our study aimed to explore the role and the molecular mechanism of ABCA8 in breast cancer (BC) progression. GSE65194, GSE15852, and GSE45827 datasets were used to identify differentially expressed genes (DEGs) in BC. The diagnosis and prognosis value were determined using ROC curve analysis and Kaplan-Meier plotter, respectively. The relationship between ABCA8 expression and clinicopathological features in BC was analyzed by TCGA. Co-expressed genes of ABCA8 in BC were screened out through GEPIA and subjected to KEGG pathway enrichment analysis. Cell proliferation was evaluated by CCK-8 and EdU incorporation assays. Proliferating cell nuclear antigen (PCNA) expression and the changes of the AMP activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway were measured by western blot analysis. Totally 4 overlapping DEGs were identified and all reduced in BC samples. ABCA8 with high diagnostic and prognostic values was selected for further exploration. Low ABCA8 expression was correlated with clinicopathological features in BC patients. ABCA8 overexpression inhibited BC cell proliferation. The top 20 co-expressed genes of ABCA8 were identified by GEPIA and significantly enriched in AMPK signaling pathway. Inhibition of AMPK/mTOR pathway reversed the suppressive effect of ABCA8 on BC cell growth. These results suggested that ABCA8 overexpression repressed BC cell proliferation through regulating the AMPK/mTOR signaling pathway.

Fluorescence Imaging of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor Resistance in Non-Small Cell Lung Cancer

Simple Summary

Lung cancer is the leading cause of cancer-related deaths, with a low (<21%) 5-year survival rate. Lung cancer is often driven by the misfunction of molecules on the surface of cells of the epithelium, which orchestrate mechanisms by which these cells grow and proliferate. Beyond common non-specific treatments, such as chemotherapy or radiotherapy, among molecular-specific treatments, a number of small-molecule drugs that block cancer-driven molecular activity have been developed. These drugs initially have significant success in a subset of patients, but these patients systematically develop resistance within approximately one year of therapy. Substantial efforts towards understanding the mechanisms of resistance have focused on the genomics of cancer progression, the response of cells to the drugs, and the cellular changes that allow resistance to develop. Fluorescence microscopy of many flavours has significantly contributed to the last two areas, and is the subject of this review.

Abstract

Non-small cell lung cancer (NSCLC) is a complex disease often driven by activating mutations or amplification of the epidermal growth factor receptor (EGFR) gene, which expresses a transmembrane receptor tyrosine kinase. Targeted anti-EGFR treatments include small-molecule tyrosine kinase inhibitors (TKIs), among which gefitinib and erlotinib are the best studied, and their function more often imaged. TKIs block EGFR activation, inducing apoptosis in cancer cells addicted to EGFR signals. It is not understood why TKIs do not work in tumours driven by EGFR overexpression but do so in tumours bearing classical activating EGFR mutations, although the latter develop resistance in about one year. Fluorescence imaging played a crucial part in research efforts to understand pro-survival mechanisms, including the dysregulation of autophagy and endocytosis, by which cells overcome the intendedly lethal TKI-induced EGFR signalling block. At their core, pro-survival mechanisms are facilitated by TKI-induced changes in the function and conformation of EGFR and its interactors. This review brings together some of the main advances from fluorescence imaging in investigating TKI function and places them in the broader context of the TKI resistance field, highlighting some paradoxes and suggesting some areas where super-resolution and other emerging methods could make a further contribution.

NOT JUST CALORIC RESTRICTION: A COMPLEX APPROACH TO PROLONG LIFESPAN AND IMPROVE QUALITY OF LIFE

Aging is an urgent healthcare issue in view of the rapid growth of the proportion of older persons. Searching for reliable aging biomarkers and prolonging lifespan are increasingly important scientific directions. Experimental gerontology helps to explore fundamental facts which are not always applicable in clinical scenarios. As an example, caloric restriction is one of the key interventions that prolongs laboratory animals’ lifespan and ameliorates some, but not all, aging biomarkers in humans. Consequences of overeating such as obesity, insulin resistance, type 2 diabetes, and metabolic syndrome are taking their toll with aging, making caloric restriction a hot topic in gerontology and geriatrics. Nevertheless, caloric restriction is not widely applicable in view of poor adherence to and limitations of strict diets. Drugs mimicking caloric restrictions, the so-called caloric restriction mimetics, are developed to overcome these limitations. Caloric restriction alone is not a panacea since metabolic pathways are complex and not responsive to a single intervention. Fasting and exercising are additional options for reducing effects of excessive intake of calories. Arguably, physical activity significantly improves the quality of life at old age and delays the onset of overt insulin resistance and associated diseases. Thus, developing optimal fasting and exercising schemes is becoming increasingly important. Such interventions are confounded by a number of factors, including circadian and other biorhythms and baseline metabolic activity. It is justifiable to test fasting and exercising in experimental animals to reveal numerous confounding factors. A hypothesis in this article points to the role of complex interventions such as moderate and balanced diet, intermittent fasting, and physical exercise adjusted to circadian rhythms for prolonging life and improving quality of life. The hypothesis may shed light on fundamental mechanisms of aging and perspectives of anti-aging drug therapies.

Biological significance of MYC and CEBPD coamplification in urothelial carcinoma: Multilayered genomic, transcriptional and posttranscriptional positive feedback loops enhance oncogenic glycolysis

BACKGROUND AND PURPOSE

The aim of this study is to decipher the underlying mechanisms of CCAAT/enhancer-binding protein delta (CEBPD)-enhanced glycolysis as well as the biological significance of CEBPD and MYC coamplification in urothelial carcinoma (UC).

METHODS

In vitro analyses were conducted to examine the effects of altered CEBPD or MYC expression on UC cells. The in vivo effects of CEBPD overexpression in a high-glucose environment on tumour growth were investigated in xenografted induced diabetic severe combined immunodeficiency/beige mice. Data mining was used to cross-validate the associations between CEBPD and MYC copy number and transcriptional expression, quantitative reverse transcription-polymerase chain reaction, immunohistochemistry, chromogenic in situ hybridization, and in situ hybridization targeting microRNA were performed on 635 UC patient samples and xenograft samples. UC patient survival in relation to diabetes was validated by using the National Health Insurance Research Database.

RESULTS

CEBPD and MYC coamplification (29.6%) occurred at a high frequency, MYC expression promoted chromosomal instability, facilitating CEBPD copy number gain and expression. CEBPD promoted glucose uptake and lactate production by upregulating SLC2A1 and HK2, leading to mitochondrial fission, increased extracellular acidification rate and decreased oxygen consumption rate to fuel cell growth. CEBPD upregulated HK2 expression through multiple regulation pathways including MYC stabilization, suppression of FBXW7 transactivation and MYC-independent transcriptional suppression of hsa-miR-429. Clinical and xenografted experiments confirmed the growth advantage of CEBPD in relation to glucose metabolic dysregulation and the significant correlations between the expression of these genes.

CONCLUSIONS

We confirmed that CEBPD has an oncogenic role in UC by activating AKT signalling and initiating metabolic reprogramming from mitochondrial oxidative phosphorylation to glycolysis to satisfy glucose addiction. These novel CEBPD- and MYC-centric multilayered positive feedback loops enhance cancer growth that could complement theranostic approaches.

Targeting of the tumor immune microenvironment by metformin

Stimulating antitumor immunity is an attractive idea for suppressing tumors. CD4 + and CD8 + T cells as well as natural killer cells (NK) are the primary antitumor immune cells in the tumor microenvironment (TME). In contrast to these cells, regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), cancer-associated fibroblasts (CAFs), and tumor-associated macrophages (TAMs) release several molecules to suppress antitumor immunity and stimulate cancer cell invasion and proliferation. Adjuvant treatment with certain nontoxic agents is interesting to boost antitumor immunity. Metformin, which is known as an antidiabetes drug, can modulate both antitumor and protumor immune cells within TME. It has the ability to induce the proliferation of CD8 + T lymphocytes and NK cells. On the other hand, metformin attenuates polarization toward TAMs, CAFs, and Tregs. Metformin also may stimulate the antitumor activity of immune system cells, while it interrupts the positive cross-talk and interactions between immunosuppressive cells and cancer cells. The purpose of this review is to explain the basic mechanisms for the interactions and communications between immunosuppressive, anti-tumoral, and cancer cells within TME. Next, we discuss the modulating effects of metformin on various cells and secretions in TME.

Maternal Metformin Treatment during Gestation and Lactation Improves Skeletal Muscle Development in Offspring of Rat Dams Fed High-Fat Diet

Maternal high-fat (HF) diet is associated with offspring metabolic disorder. This study intended to determine whether maternal metformin (MT) administration during gestation and lactation prevents the effect of maternal HF diet on offspring’s skeletal muscle (SM) development and metabolism. Pregnant Sprague-Dawley rats were divided into four groups according to maternal diet {CHOW (11.8% fat) or HF (60% fat)} and MT administration {control (CT) or MT (300 mg/kg/day)} during gestation and lactation: CH-CT, CH-MT, HF-CT, HF-MT. All offspring were weaned on CHOW diet. SM was collected at weaning and 18 weeks in offspring. Maternal metformin reduced plasma insulin, leptin, triglyceride and cholesterol levels in male and female offspring. Maternal metformin increased MyoD expression but decreased Ppargc1a, Drp1 and Mfn2 expression in SM of adult male and female offspring. Decreased MRF4 expression in SM, muscle dysfunction and mitochondrial vacuolization were observed in weaned HF-CT males, while maternal metformin normalized them. Maternal metformin increased AMPK phosphorylation and decreased 4E-BP1 phosphorylation in SM of male and female offspring. Our data demonstrate that maternal metformin during gestation and lactation can potentially overcome the negative effects of perinatal exposure to HF diet in offspring, by altering their myogenesis, mitochondrial biogenesis and dynamics through AMPK/mTOR pathways in SM.

Synthetic mRNAs; Their Analogue Caps and Contribution to Disease

The structure of synthetic mRNAs as used in vaccination against cancer and infectious diseases contain specifically designed caps followed by sequences of the 5′ untranslated repeats of β-globin gene. The strategy for successful design of synthetic mRNAs by chemically modifying their caps aims to increase resistance to the enzymatic deccapping complex, offer a higher affinity for binding to the eukaryotic translation initiation factor 4E (elF4E) protein and enforce increased translation of their encoded proteins. However, the cellular homeostasis is finely balanced and obeys to specific laws of thermodynamics conferring balance between complexity and growth rate in evolution. An overwhelming and forced translation even under alarming conditions of the cell during a concurrent viral infection, or when molecular pathways are trying to circumvent precursor events that lead to autoimmunity and cancer, may cause the recipient cells to ignore their differential sensitivities which are essential for keeping normal conditions. The elF4E which is a powerful RNA regulon and a potent oncogene governing cell cycle progression and proliferation at a post-transcriptional level, may then be a great contributor to disease development. The mechanistic target of rapamycin (mTOR) axis manly inhibits the elF4E to proceed with mRNA translation but disturbance in fine balances between mTOR and elF4E action may provide a premature step towards oncogenesis, ignite pre-causal mechanisms of immune deregulation and cause maturation (aging) defects.

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

The Glucosylceramide Synthase Inhibitor PDMP Causes Lysosomal Lipid Accumulation and mTOR Inactivation

For many years, the biology of glycosphingolipids was elucidated with the help of glucosylceramide synthase (GCS) inhibitors such as 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP). Additionally, PDMP gained interest because of its chemosensitizing effects. Several studies have successfully combined PDMP and anti-cancer drugs in the context of cancer therapy. However, the mechanism of action of PDMP is not fully understood and seems to go beyond glycolipid inhibition. Here, we used a functionalized sphingosine analogue (pacSph) to investigate the acute effects of PDMP on cellular sphingolipid distribution and found that PDMP, but not other GCS inhibitors, such as ND-DNJ (also called Miglustat), induced sphingolipid accumulation in lysosomes. This effect could be connected to defective export from lysosome, as monitored by the prolonged lysosomal staining of sphingolipids as well as by a delay in the metabolic conversion of the pacSph precursor. Additionally, other lipids such as lysobisphosphatidic acid (LBPA) and cholesterol were enriched in lysosomes upon PDMP treatment in a time-dependent manner. We could further correlate early LBPA enrichment with dissociation of the mechanistic target of rapamycin (mTOR) from lysosomes followed by nuclear translocation of its downtream target, transcription factor EB (TFEB). Altogether, we report here a timeline of lysosomal lipid accumulation events and mTOR inactivation arising from PDMP treatment.