Amino Acid Transport Research Articles

Regulatory Role of eIF2αK4 in Amino Acid Transporter Expression in Mouse Brain Capillary Endothelial Cells

Regulatory Role of eIF2αK4 in Amino Acid Transporter Expression in Mouse Brain Capillary Endothelial Cells

Ginsenoside-Enriched Extract from Black Ginseng Anti-Fatigue Effects by Improving Antioxidant Capacity and Mitochondrial Function

In this study, we investigated the anti-fatigue effects of black ginseng ginsenosides using exercise performance tests, serum analyses, and gene expression profiling. No significant differences in dietary intake or body weight were observed between groups. The low-dose black ginseng (LBG) group showed no significant improvements in swimming and rotating rod tests. In contrast, the medium (MBG)- and high-dose (HBG) groups showed notable increases in swimming time and significant improvements in the rotating rod test. All treatment groups exhibited longer running times, particularly the HBG group. Serum analysis revealed increased muscle and hepatic glycogen, catalase, and lactate dehydrogenase levels in the MBG and HBG groups, whereas lactate, lipid peroxide, and superoxide dismutase levels were decreased. Additionally, gene expression analysis showed significant upregulation of key antioxidant and mitochondrial function genes, including those encoding cationic amino acid transporter 2, stearoyl-CoA desaturase-2, nuclear respiratory factor 1, nuclear factor erythroid 2-related factor 2, mitochondrial transcription factor A, cytochrome c oxidase II, and NADH–ubiquinone oxidoreductase core subunit 1, particularly in the HBG group, indicating enhanced antioxidant capacity and improved mitochondrial function. These findings suggested that black ginseng ginsenosides effectively mitigated fatigue.

BIOM-37. EXPLORING L-TYPE AMINO ACID TRANSPORTER 1 (LAT1) AS A DIAGNOSTIC MARKER AND THERAPEUTIC TARGET IN MALIGNANT PERIPHERAL NERVE SHEATH TUMORS (MPNST)

Abstract OBJECTIVES Malignant peripheral nerve sheath tumors (MPNST) are aggressive soft tissue sarcomas that frequently arise from benign plexiform neurofibromas (PN). Approximately half of MPNST are associated with Neurofibromatosis type 1 (NF1). Despite partial elucidation of the molecular mechanisms underlying MPNST, diagnosis remains challenging, and prognosis is poor. Previously, we found that MPNST cells have elevated βIII-spectrin, a cytoskeletal protein involved in cell morphology and regulation of transporters, including L-type Amino Acid Transporter 1 (LAT1). LAT1 facilitates transport of large neutral amino acids and is upregulated in other cancer types. Our objective is to investigate LAT1 as a diagnostic marker and therapeutic target for MPNST. METHODS Gene and protein expression were determined by qPCR and WES protein analysis, respectively. The effect of shRNA knockdown of LAT1 in MPNST cells was assessed using IncuCyte proliferation assays as well as multiple mouse models. Tumor uptake of [18F] FDOPA, primarily transported by LAT1, in MPNST PDX tumors was assessed using PET/CT imaging. RESULTS LAT1 was expressed in MPNST (n=14) vs. benign PN tissues (n=6). Additionally, in human and murine MPNST cells, shRNA-mediated knockdown of LAT1 suppressed proliferation of MPNST cells in vitro and tumor growth in vivo. In a subcutaneous tumor growth model, intratumor injection of shLAT1 lentivirus reduced tumor volume to approximately 50% of control. Furthermore, uptake of [18F] FDOPA by LAT1 in MPNST PDX tumors was detected by PET/CT imaging. WU-356 PDX tissues exhibited higher LAT1 expression as well as increased uptake of [18F] FDOPA in tumors. Conversely, PET imaging showed significantly lower uptake of [18F] FDOPA in LAT1 knockdown tumors (p<0.05). CONCLUSIONS These results suggest that LAT1 promotes the growth and survival of MPNST cells. In addition, these findings demonstrate the potential use of LAT1 and the radiotracer [18F] FDOPA as a diagnostic biomarker in the management of MPNST.

CTNI-60. SAFETY LEAD-IN RESULTS FOR QBS10072S IN THE INDIVIDUAL SCREENING TRIAL OF INNOVATIVE GLIOBLASTOMA THERAPY (INSIGHT) TRIAL, A RANDOMIZED ADAPTIVE PLATFORM TRIAL FOR NEWLY DIAGNOSED MGMT UNMETHYLATED GLIOBLASTOMA

Abstract BACKGROUND QBS10072S, is a L-type amino acid transporter 1 (LAT-1) targeted alkylating agent that utilizes LAT1 as both a transport and targeting mechanism. QBS10072S can cross the blood-brain barrier, exhibits potential for cytotoxicity with a mechanism distinct from temozolomide and has low off-target effects. QBS10072S is being evaluated in the Individualized Screening Trial of Innovative Glioblastoma Therapy (INSIGhT) trial (NCT02977780), a randomized phase 2 adaptive multi-arm platform trial. METHODS Adult patients with newly diagnosed MGMT-unmethylated glioblastoma are eligible for INSIGhT. Since there is no safety data available for QBS10072S in combination with radiotherapy, a safety lead-in evaluation was conducted utilizing a 3 + 3 design. Starting dose for QBS10072S was 12mg/m2 in combination with radiation therapy and adjuvantly as monotherapy in 28 day cycles. Patients were monitored for dose-limiting toxicities (DLTs) to identify the maximum tolerated dose and recommended phase 2 dose (RP2D). RESULTS Nine patients were enrolled December 2022 to October 2023 for safety lead-in testing, and median age was 57 years (41-67) with 6 (66%) males, 6 (66%) patients with gross total resection, and median KPS 90 (range 80-100). Pharmacokinetic studies indicated that drug exposure was lower than prior studies, and three patients received 12mg/m2, 15mg/m2, and 18mg/m2, respectively, per dose escalation protocol. No DLTs nor adverse events leading to study drug discontinuation were reported during the evaluation period. Four patients had possible treatment-related CTCAE grade ≥ 3 toxicity including lymphopenia (n=3) and fatigue (n=1). The RP2D was determined to be 18mg/m2. Seven patients were discontinued from study treatment due to progressive disease and two patients remain on treatment. CONCLUSION QBS10072S, concurrent and adjuvant to radiation therapy, was well-tolerated in patients with newly diagnosed unmethylated MGMT glioblastoma. QBS10072S 18mg/m2 is being evaluated as a treatment arm in phase 2 testing in the ongoing INSIGhT trial.

Quantitative Structure-Property Relationship (QSPR) Modeling of Central Nervous System (CNS) Drug Activity using Molecular Descriptors

Background: L-type amino acid transporter-1 is a drug that stimulates the func-tions of the brain’s central nervous system. Membrane transporters have evolved, leading to a distinct approach in L-type amino acid transporter-1 drug delivery. One of the trans-porters used for transporting drugs across biological membranes is the L-type amino acid transporter-1. It is widely discussed in the medicinal field. Objectives: Numerous investigations indicate a close connection between the properties of alkanes and the diversity of central nervous system drugs in the brain, specifically log P and molecular weight. One important study that analyzes structural properties is focused on topological descriptors. Recently, topological indices have found application in the de-velopment of quantitative structure-activity relationships. These indices are correlated with the physicochemical properties of BCNS-acting drugs and their biological activity. Methods: The study employs significant methods of calculating topological indices: the edge set partition method and the Djokovi´c-Winkler relation (cut method) are utilized to calculate the values of these descriptors. Results: The results of distance and degree-based topological descriptors have been de-rived. The strong correlation between topological descriptors and the physicochemical properties of BCNS-acting drugs has been studied. Conclusions: This article identifies important topological features for various CNS medi-cations, aiming to support researchers in understanding the properties of molecules and their biological activity. Furthermore, we demonstrate how strongly these behaviors cor-respond to the physicochemical properties of central nervous system drugs.

SLC38A5 suppresses ferroptosis through glutamine-mediated activation of the PI3K/AKT/mTOR signaling in osteosarcoma

BackgroundSolute carrier family 38 member 5 (SLC38A5) is an amino acid transporter that plays a significant role in various cellular biological processes and may be involved in regulating the progression of tumors However, its function and underlying mechanism in osteosarcoma remain unexplored.MethodsUtilizing various database analyses and experiments, we have explored the dysregulation of SLC38A5 in osteosarcoma and its prognostic value. A series of in vitro functional experiments, including CCK-8, colony formation, wound healing, and transwell invasion assays, were conducted to evaluate the effects of SLC38A5 on the proliferation, migration, and invasion of osteosarcoma cells. Downstream pathways of SLC38A5 were explored through methods such as western blot and metabolic assays, followed by a series of validations. Finally, we constructed a subcutaneous xenograft tumor model in nude mice to explore SLC38A5 function in vivo.ResultsSLC38A5 is upregulated in osteosarcoma and is associated with poor prognosis in patients. Upregulation of SLC38A5 promotes proliferation, migration, and invasion of osteosarcoma cells, while the PI3K inhibitor BKM120 can counteract these effects. Additionally, silencing of SLC38A5 inhibits tumor growth in vivo. Mechanistically, SLC38A5 mediates the activation of the PI3K/AKT/mTOR signaling pathway by transporting glutamine, which subsequently enhances the SREBP1/SCD-1 signaling pathway, thereby suppressing ferroptosis in osteosarcoma cells.ConclusionSLC38A5 promotes osteosarcoma cell proliferation, migration, and invasion via the glutamine-mediated PI3K/AKT/mTOR signaling pathway and inhibits ferroptosis. Targeting SLC38A5 and the PI3K/AKT signaling axis may provide a meaningful therapeutic strategy for the future treatment of osteosarcoma.Graphical abstracts

Exposure to the antiretroviral drug dolutegravir impairs structure and neurogenesis in a forebrain organoid model of human embryonic cortical development

IntroductionFor many therapeutic drugs, including antiretroviral drugs used to treat people living with HIV-1 (PLWH), we have little data on the potential effects on the developing human brain due to limited access to tissue and historical constraints on the inclusion of pregnant populations in clinical trials. Human induced pluripotent stem cells (iPSCs) offer a new avenue to gain insight on how drugs may impact human cell types representative of the developing central nervous system. To prevent vertical transmission of HIV and promote the health of pregnant PLWH, antiretroviral therapy must be initiated and/or maintained throughout pregnancy. However, many antiretroviral drugs are approved for widespread use following clinical testing only in non-pregnant populations and there may be limited information on potential teratogenicity until pregnancy outcomes are evaluated. The integrase strand transfer inhibitor dolutegravir (DTG) is a frontline antiretroviral drug that is effective in viral suppression of HIV but was previously reported to be associated with a slight increase in the risk for neural tube defects in one study, although this has not been replicated in other cohorts.MethodsTo directly investigate the potential impact of DTG on human cortical neurogenesis, we measured the effects of daily drug exposure on the early stages of corticogenesis in a human iPSC-based forebrain organoid model. We quantified organoid size and structure and analyzed gene and protein expression to evaluate the impact of several doses of DTG on organoid development.ResultsWe observed deficits in organoid structure and impaired neurogenesis in DTG-treated organoids compared to vehicle-treated control organoids after 20 or 40 days in culture. Our highest dose of DTG (10 μM) resulted in significantly smaller organoids with a reduced density of neural rosette structures compared to vehicle-treated controls. Mechanistically, RNA-sequencing and immunohistological analysis suggests dysregulated amino acid transport and activation of the integrated stress response in the DTG-treated organoids, and functionally, a small molecule integrated stress response inhibitor (ISRIB) could partially rescue increased expression of proteins related to cell cycle regulation.DiscussionTogether, these results illustrate the potential for human iPSC-based strategies to reveal biological processes during neurogenesis that may be affected by therapeutic drugs and provide complementary data in relevant human cell types to augment preclinical investigations of drug safety during pregnancy.

Amino Acid Transport Dynamics in the Jejunum and Ileum in Rats: A Regional and Time-Course Analysis.

Postprandially, amino acids and di/tripeptides are thought to be primarily absorbed in the proximal small intestine. However, there have been no in vivo demonstrations of regional differences in amino acid transport dynamics between the proximal and distal small intestines. We monitored plasma amino acid responses in the jejunal and ileal mesenteric veins of rats after oral administration of a diet or an amino acid mixture (Experiment 1), and in the portal vein after direct administration of the amino acid mixture into the lumen of the jejunum or ileum (Experiment 2). In experiment 1, the total and some amino acid concentrations in the jejunal mesenteric vein were slightly higher than those in the ileal mesenteric vein after oral administration of the amino acid mixture, suggesting that the ileum actively transports luminal amino acids to the basolateral side, comparable to the jejunum. In experiment 2, portal amino acid concentrations were elevated to a greater extent after direct administration of the amino acid mixture into the ileal lumen than into the jejunal lumen. These results demonstrate regional differences in amino acid transport dynamics in vivo and suggest that the ileum has a higher capacity for transporting amino acids than the jejunum. Our findings highlight the importance of the ileum in postprandial amino acid absorption and metabolism.

Role of cholesterol in modulating brain hyperexcitability.

Cholesterol is a critical molecule in the central nervous system, and imbalances in the synthesis and metabolism of brain cholesterol can result in a range of pathologies, including those related to hyperexcitability. The impact of cholesterol on disorders of epilepsy and developmental and epileptic encephalopathies is an area of growing interest. Cholesterol cannot cross the blood-brain barrier, and thus the brain synthesizes and metabolizes its own pool of cholesterol. The primary metabolic enzyme for brain cholesterol is cholesterol 24-hydroxylase (CH24H), which metabolizes cholesterol into 24S-hydroxycholesterol (24HC). Dysregulation of CH24H and 24HC can affect neuronal excitability through a range of mechanisms. 24HC is a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptors and can increase glutamate release via tumor necrosis factor-α-dependent pathways. Increasing cholesterol metabolism can lead to dysfunction of excitatory amino acid transporter 2 and impair glutamate reuptake. Finally, overstimulation of NMDA receptors can further activate metabolism of cholesterol, leading to a vicious cycle of overactivation. All of these mechanisms increase extracellular glutamate and can lead to hyperexcitability. For these reasons, the cholesterol pathway represents a new potential mechanistic target for antiseizure medications. CH24H inhibition has been shown to decrease seizure behavior and improve survival in multiple animal models of epilepsy and could be a promising new mechanism of action for the treatment of neuronal hyperexcitability and developmental and epileptic encephalopathies.

Integrative Bioinformatics and Experimental Analysis of Curcumin's Role in Regulating Ferroptosis to Combat Osteoporosis

This study utilized bioinformatics and data mining techniques to explore the molecular mechanism of curcumin in treating osteoporosis (OP) through the lens of ferroptosis, thereby identifying novel therapeutic targets. The datasets GSE35958, GSE35956, GSE7429, and GSE7158 were obtained from the Gene Expression Omnibus (GEO) database. GSE35958 and GSE35956 were employed as training sets for data integration, while GSE7429 and GSE7158 served as independent validation sets. Through retrieval from the FerrDb database, iron death-related genes (FRGs) were identified, and the differentially expressed genes (DEGs) were intersected to obtain differentially expressed FRGs (DEFRGs). Subsequently, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted, followed by the construction of a Protein-Protein Interaction (PPI) network to identify Hub genes. The DGIdb database was utilized to predict candidate drugs associated with the Hub genes, and molecular docking and in vitro experiments confirmed that curcumin targets the Hub genes EGFR and PTGS2.Through in vitro testing of curcumin on BMSC cells, researchers examined cell vitality, iron death, osteogenic differentiation, mineralization, and the impact on EGFR and PTGS2 levels. The analysis yielded 2212 DEGs, 484 FRGs, with 45 FDEGs at the intersection. GO analysis revealed involvement in regulating mitochondrial proteins, amino acid transport across plasma membranes, and protein ubiquitination. KEGG pathway analysis indicated associations with iron death, FoxO signaling, mTOR signaling, cell aging, osteoclast differentiation, and GSH metabolism. Utilizing the MCC algorithm, five Hub genes were identified: MAPK3, PTGS2, TGFB1, CYBB, and EGFR, showing diagnostic potential for iron death. Curcumin displayed affinity for EGFR and PTGS2, mitigating iron-induced effects on BMSCs such as increased reactive oxygen species, Fe3+ levels, and decreased mitochondrial membrane potential. Furthermore, curcumin reversed these effects, suggesting EGFR and PTGS2 as targets for curcumin to inhibit BMSC ferroptosis and potentially delay osteoporosis development. Maintaining iron homeostasis and targeting BMSC ferroptosis could offer therapeutic avenues for iron overload-induced osteoporosis.

Modulation of SNARE-dependent exocytosis in astrocytes improves neuropathology in Huntington's disease

ABSTRACT Huntington's disease (HD) is a fatal, progressive neurodegenerative disorder. Prior studies revealed an increase in extracellular glutamate levels after evoking astrocytic SNARE-dependent exocytosis from cultured primary astrocytes from mutant huntingtin (mHTT)-expressing BACHD mice compared to control astrocytes, suggesting alterations in astrocytic SNARE-dependent exocytosis in HD. We used BACHD and dominant-negative (dn)SNARE mice to decrease SNARE-dependent exocytosis from astrocytes to determine whether reducing SNARE-dependent exocytosis from astrocytes could rescue neuropathological changes in vivo. We observed significant protection against striatal atrophy and no significant rescue of cortical atrophy in BACHD/dnSNARE mice compared to BACHD mice. Amino acid transporters are important for modulating the levels of extracellular neurotransmitters. BACHD mice had no change in GLT1 expression, decreased striatal GAT1 expression and increased levels of GAT3. There was no change in GAT1 after reducing astrocytic SNARE-dependent exocytosis, and increased GAT3 expression in BACHD mice was normalized in BACHD/dnSNARE mice. Thus, modulation of astrocytic SNARE-dependent exocytosis in BACHD mice is protective against striatal atrophy and modulates GABA transporter expression.

Enhancing the nutritional value of black soldier fly larvae through the nutrient amino acid transporter suppression in the excretion system

Abstract Larvae of the black soldier fly (Hermetia illucens, BSFL) are rich in valuable nutrients and offer a promising alternative protein source for animal feeds. Nonetheless, there is a pressing need to improve both the productivity and quality of BSFL to ensure the viability of BSFL products and facilitating the industrial production. To fulfil the needs of different animals, it is necessary to adjust the profile of essential amino acids (EAAs) in BSFL. Insects excrete surplus nutrients to maintain homeostasis; AAs are excreted by nutrient AA transporters (NATs) in the Malpighian tubules. We aimed to modify the composition of essential AAs by silencing the NAT in Malpighian tubules of BSFL (HiNATt). Silencing HiNATt resulted in a 77.3% increase in the total AA content while 56.2% decrease in body weight. Notably, the contents of some valuable essential AAs were strongly increased (histidine, 256.8%; valine, 198.1% in total compared to the intact larva). These results suggest that inhibiting the HiNATt function could modify the amount of accumulated EAAs. This finding opens a new avenue for producing BSFL with increased nutritional value as an alternative protein source.

Maternal Supplementation Spermidine During Gestation Improves Placental Angiogenesis and Reproductive Performance of High Prolific Sows.

Spermidine (SPD) is a widely recognized polyamine compound found in mammalian cells and plays a key role in various cellular processes. We propose that SPD may enhance placental vascular development in pregnant sows, leading to increased birth weight of piglets. Six hundred and nine sows at 60 days of gestation were randomly assigned into a basal diet (CON group), basal diet supplemented 10 mg/kg of SPD (SPD1 group), and basal diet supplemented 20 mg/kg of SPD (SPD2 group), respectively. Compared with the CON, SPD1 significantly increased the average number of healthy piglets per litter and the placental efficiency (P < 0.05), while the average number of mummified fetus per litter and the percentage of weak piglets significantly decreased (P < 0.05). In the plasma metabolomics, SPD content in plasma of sows (P = 0.075) and umbilical cord plasma of piglets (P = 0.078) had an increasing trend in response to SPD1. Furthermore, SPD1 increased the expression of the vascular endothelial cell marker protein, platelet endothelial cell adhesionmolecule-1 (PECAM-1/CD31) and the density of placental stromal vessels (P < 0.05). Moreover, as compared to CON, SPD2 significantly decreased the average number of mummified fetus per litter (P < 0.05), while the placental efficiency and the expression of amino acid transporter solute carrier (SLC) family 7, member7 (SLC7A7) and glucose transporters SLC2A2) and SLC5A4 in placental tissue significantly increased (P < 0.05). These results suggest that maternal supplementation of SPD during pregnancy increased healthy litter number, and promoted placental tissue development. Our findings provide evidence that maternal SPD has the potential to improve the production performance of sows.

Protein digestion and amino acid absorption mechanisms along the midgut of Musca domestica larvae

A model of protein digestion and peptide and amino acid absorption along the midgut of Musca domestica larvae was proposed and supported by RNA-Seq analyses, protein bioinformatics, microvillar-membrane-enriched midgut proteomics, and enzymatic activities. Peptidase genes are highly expressed in the posterior midgut (PM), whereas those for cathepsins have expression limited to the middle midgut (MM). MM has the lowest levels of gene expression of almost all peptidases but has high expression of genes for membrane-bound serine endopeptidases. The anterior midgut (AM) has intermediate expression values of serine endopeptidase and aminopeptidase (AP) genes and low expression of carboxypeptidases (CPs). Gene expression and peptidase activities were usually consistent for putative intracellular and membrane-bound enzymes. However, secreted peptidase gene expression and activities have divergent values, especially in the PM, which may be due to the countercurrent water flux causing enzyme recycling, thus decreasing their excretion. Data suggest that Trys and APs act in the AM. In the acidic MM, lysozymes kill microorganisms found in the diet, releasing proteins digested by cathepsins D, which may also digest Trys coming from the AM. Finally, highly active serine endopeptidases, CPs, dipeptidases, and APs complete protein digestion in PM. Absorption of peptides and amino acids coupled to protons may occur along the midgut, especially in PM, as occurs for facilitated amino acid transport. Absorption with sodium ions is probably restricted to AM and PM. Our findings provide valuable insights into the protein digestion and amino acid absorption mechanism in M. domestica larvae.

Symposium Review: The Impact of Fatty Acids as Bioactive Nutrients on the Development of Offspring

Fatty acids (FA) are normally considered a source of energy; however, some FA are essential nutrients with different biological functions such as ligands to membrane and nuclear receptors, and upon binding they modify cell function and transcript expression. The bioactive effects of the FA depend on the FA type and family (i.e., n-6 vs n-3). The FA effects on developmental programming have been studied in cattle and sheep with some similarities in the outcomes between species. Feeding n-3 FA during late gestation improves offspring production performance (i.e., milk yield in dairy cows and growth in beef cattle and sheep) compared with the offspring of dams supplemented with mono- and unsaturated FA or with offspring of dams with no FA supplementation. Also, there is a sexual dimorphism in the outcomes of n-3 FA supplementation, where the increase in growth due to n-3 FA seems to be more evident in males; but it might decrease growth in females. There are multiple assumptions as to how this physiological process occurs. Based on published literature, the developmental effect does not appear to be due to changes in hypothalamic regulations of dry matter intake and energy expenditure or liver and adipose tissue functions. The changes in offspring growth can be attributed to changes in gastrointestinal tract physiology, changes in immune response, or both, probably due to epigenetic changes in those tissues. Feeding n-3 FA in late gestation to the pregnant dam increases expression of amino acid transporters (mRNA and protein) in the offspring's duodenum, associated with changes in DNA methylation. Regarding immune function, the increase in offspring performance has been associated with decreased haptoglobin after weaning in calves or increases in lipid mediators, such as resolvin-D1 at birth. Omega-3 supplementation during late gestation affects offspring growth; changes in the offspring's gut and immune system biology can explain the sexual dysmorphism observed in changed body weight; however, we are unaware which of these basic mechanisms is responsible for the observed changes in biology.

The Regulation and Function of the Amino Acid Transporters LAT1, ASCT2, xCT in Urological Cancers

Amino acid transporters play pivotal roles in cancer biology, including in urological cancers. Among them, L-type amino acid transporter 1 (LAT1), alanine-serine-cysteine transporter 2 (ASCT2), and cystine-glutamate transporter (xCT) have garnered significant attention due to their involvement in various aspects of tumor progression and response to therapy. This review focuses on elucidating the regulation and functions of these amino acid transporters in urological cancers, including prostate, bladder, and renal cancers. Understanding the intricate regulatory mechanisms governing these amino acid transporters is essential for developing effective therapeutic strategies. Furthermore, exploring their interactions with signaling pathways and microenvironmental cues in the context of urological cancers may uncover novel therapeutic vulnerabilities. This comprehensive overview highlights the importance of amino acid transporters, particularly LAT1, ASCT2, and xCT, in urological cancers and underscores the potential of their inhibitors as therapeutic targets for improving patient outcomes.

Identification of genetic variants associated with exercise-induced atrial fibrillation in high-performing racehorses

Abstract Background Atrial fibrillation (AF) is the most common cardiac arrhythmia in athletes. Despite a lower burden of classical cardiovascular risk factors, the prevalence of AF in athletes is comparable to that in the general population of similar age (~13%, mean age 65.5), suggesting that exercise-induced AF may have different underlying mechanisms. The prevalence of AF in thoroughbred (TB) and standardbred (STB) racehorses is also relatively high (~5%), suggesting exercise as an independent risk factor. Due to selective breeding and complete control of pedigrees, racehorses are well-suited for genetic studies. Common and rare genetic variation explain a substantial part of AF variance, but no study has identified genetic variants associated with exercise-induced AF in any species. Objective In this project, we aimed to use the racehorse as a model to identify genetic variants associated with exercise-induced AF, and in a future study, possibly replicate the results in human athletes. Here we present preliminary results from the genome-wide association study (GWAS) of AF in racehorses. Methods We collected blood or hair samples from 181 STB and TB racehorses in which 71 had paroxysmal or persistent AF verified by ECG. We extracted DNA and performed whole-genome genotyping using a commercial equine genotyping platform (670k markers). We phased and imputed un-genotyped markers and increased the sample size of the control group, using publicly available equine data from similar breeds from the European Nucleotide Archive. We conducted a GWAS of 7.85 million markers in 71 cases and 296 controls using PLINK2 with covariates adjusted for population stratification, batch and sex. Results We identified one significant locus downstream of the protocadherin gene PCDH18 associated with AF in racehorses. The same locus has been associated with the ECG-trait P-wave terminal force in humans. Changes in P-wave terminal force is associated with increased atrial size, delayed interatrial conduction, left ventricular fibrosis and left atrial function, and considered a good predictor of AF occurrence. Several non-significant but interesting signals were also identified including the genes SLC6A15 (amino acid transport), MYBPH (myosin binding), MYF6 and MYOG (myoblast differentiation). Conclusion In these preliminary results, we have identified a new genetic locus associated with AF in racehorses. In addition, we have identified several candidate genes for further studies to elucidate the genetic background of exercise-induced AF. We aim to replicate our findings in a population of human athletes. Our results may aid the development of risk prediction tools for exercise-induced AF and new drugs for tailored treatment of AF in general.

Hydrolyzed protein formula improves the nutritional tolerance by increasing intestinal development and altering cecal microbiota in low-birth-weight piglets

BackgroundPrematurity or low birth weight (LBW), poses a significant challenge in global health. Exploring appropriate and effective nutritional interventions is crucial for the growth and development of LBW infants. Hydrolyzed protein formula has been suggested as a potential solution to prevent intestinal dysfunction and improve digestion and absorption in infants.ObjectivesThis study aimed to investigate the benefits of hydrolyzed protein formula on feeding intolerance, intestinal morphological development, and microbiota in a LBW piglet model.MethodsA total of 24 male piglets (3 d of age, 0.95–1.25 kg average BW) were assigned (8 pens/diet; 1 pigs/pen) into three dietary treatments and fed with a basic formula (BF), standard premature infant formula (SF) and hydrolyzed protein formula (HF) respectively, for 7 d. After the piglets sacrifice, growth performance, amino acid metabolism and intestinal morphology were assessed. 16S rRNA sequencing and microbial metabolic phenotypes analyzed the effects of different formula treatments on intestinal flora structure of LBW piglets.ResultsThe HF diet reduced the rates of diarrhea and milk vomiting were reduced by 20.44% (p &amp;gt; 0.05) and 58.44% (p &amp;gt; 0.05), and decreased the crypt depth in the ileum while increasing the ratio of villus height/crypt depth and the mRNA expressions of y+LAT1 and b0,+AT in the ileum (p &amp;lt; 0.05). HF increased the final body weight, serum Thr and essential amino acid contents, and CAT2 and b0,+AT mRNA expressions in ileal mucosa compared with the SF diet (p &amp;lt; 0.05). Microbiota sequencing results showed that the colonic microbial richness indices (Chao1, ACE, and observed species), the diversity indices (Shannon and Simpson), and the phyla Actinobacteriota, unidentified_Bacteria, Acidobacteriota and Actinobacteria, the genus Rubrobacter and RB41 were reduced (p &amp;lt; 0.05) in SF and HF groups. Microbial metabolic phenotypes analysis showed a reduction in the richness of biofilm-forming bacteria (p &amp;lt; 0.05).ConclusionIn summary, hydrolyzed protein formula had better nutrition and tolerance in LBW suckling piglets by improving amino acid transport and intestinal development, and regulating gut microbial communities.

Oligonol®, an Oligomerized Polyphenol from Litchi chinensis, Enhances Branched-Chain Amino Acid Transportation and Catabolism to Alleviate Sarcopenia

Branched-chain amino acids (BCAAs) are essential for muscle protein synthesis and are widely acknowledged for mitigating sarcopenia. Oligonol® (Olg), a low-molecular-weight polyphenol from Litchi chinensis, has also been found to attenuate sarcopenia by improving mitochondrial quality and positive protein turnover. This study aims to investigate the effect of Olg on BCAA-stimulated protein synthesis in sarcopenia. In sarcopenic C57BL/6 mice and senescence-accelerated mouse-prone 8 (SAMP8) mice, BCAAs were significantly decreased in skeletal muscle but increased in blood serum. Furthermore, the expressions of membrane L-type amino acid transporter 1 (LAT1) and branched-chain amino acid transaminase 2 (BCAT2) in skeletal muscle were lower in aged mice than in young mice. The administration of Olg for 8 weeks significantly increased the expressions of membrane LAT1 and BCAT2 in the skeletal muscle when compared with non-treated SAMP8 mice. We further found that BCAA deprivation via LAT1-siRNA in C2C12 myotubes inhibited the signaling of protein synthesis and facilitated ubiquitination degradation of BCAT2. In C2C12 cells mimicking sarcopenia, Olg combined with BCAA supplementation enhanced mTOR/p70S6K activity more than BCAA alone. However, blocked LAT1 by JPH203 reversed the synergistic effect of the combination of Olg and BCAAs. Taken together, changes in LAT1 and BCAT2 during aging profoundly alter BCAA availability and nutrient signaling in aged mice. Olg increases BCAA-stimulated protein synthesis via modulating BCAA transportation and BCAA catabolism. Combining Olg and BCAAs may be a useful nutritional strategy for alleviating sarcopenia.

Transcriptional Responses to Priority Effects in Nectar Yeast.

Priority effects, where the order and timing of species arrival influence the assembly of ecological communities, have been observed in a variety of taxa and habitats. However, the genetic and molecular basis of priority effects remains unclear, hindering a better understanding of when priority effects will be strong. We sought to gain such an understanding for the nectar yeast Metschnikowia reukaufii commonly found in the nectar of our study plant, the hummingbird-pollinated Diplacus (Mimulus) aurantiacus. In this plant, M. reukaufii can experience strong priority effects when it reaches flowers after other nectar yeasts, such as M. rancensis. After inoculation into two contrasting types of synthetic nectar simulating early arrival of M. rancensis, we conducted whole-transcriptome sequencing of 108 strains of M. reukaufii. We found that several genes were differentially expressed in M. reukaufii strains when the nectar had been conditioned by growth of M. rancensis. Many of these genes were associated with amino acid metabolism, suggesting that M. reukaufii strains responded molecularly to the reduction in amino acid availability caused by M. rancensis. Furthermore, investigation of expression quantitative trait loci (eQTLs) revealed that genes involved in amino acid transport and resistance to antifungal compounds were enriched in some genetic variants of M. reukaufii. We also found that gene expression was associated with population growth rate, particularly when amino acids were limited. These results suggest that intraspecific genetic variation in the ability of nectar yeasts to respond to nutrient limitation and direct fungal competition underpins priority effects in this microbial system.