Slow Phenotype Research Articles

Developmental and environmental effects on VTC2-dependent leaf ascorbate accumulation and functions.

In nature, environmental conditions strongly fluctuate, frequently subjecting plants to periods of immediate photo-oxidative stress. The small molecule ascorbate allows plants to cope with such stress conditions. Ascorbate scavenges reactive oxygen species and enables the rapid and full induction of photoprotective non-photochemical quenching (NPQ). NPQ is dependent on zeaxanthin (Zx), which requires ascorbate as the electron donor during its synthesis by the violaxanthin de-epoxidase. The VTC2 gene encodes for one of two isoforms of GDP-L-galactose phosphorylase, the rate-controlling enzyme of ascorbate biosynthesis. In the current study, by including a newly identified vtc2 allele, we found that loss of VTC2 depleted ascorbate mainly from the mature leaves and thereby limited NPQ specifically in this tissue. Growth in fluctuating light and controlled climate suppressed the slow NPQ induction phenotype of vtc2 mature leaves to some degree. This was concurrent with a constitutively higher accumulation of zeaxanthin under this condition. When plants were shifted to natural conditions, with strongly fluctuating light and temperature, the ascorbate deficient mature leaves of vtc2 bleached. Together, our results reveal developmental and environmental effects on VTC2-dependent ascorbate accumulation and function.

Differential distribution of NAT2 polymorphisms and NAT2 acetylator phenotypes among indigenous populations of the Brazilian Amazon.

We report, for the first time, the distribution of four no-function NAT2 single nucleotide polymorphisms and inferred NAT2 acetylator phenotypes in three indigenous groups (Munduruku, Paiter-Suruí, and Yanomami), living in reservation areas in the Brazilian Amazon. Two hundred and seventy-six participants from three indigenous groups (92 for each group) were included and genotyped for four NAT2 polymorphisms (rs1801279, rs1801280, rs1799930, and rs1799931) by the TaqMan system. Minor Allele Frequency (MAF) was determined and NAT2 acetylator phenotypes were inferred. NAT2 rs1801279G>A was absent in all cohorts; rs1799930G>A was absent in Yanomami and rare (MAF 0.016) in Munduruku and Paiter-Suruí; MAF of rs1801280T>C ranged five-fold (0.092-0.433), and MAF of rs1799931G>A varied between 0.179 and 0.283, among the three groups. The distribution of NAT2 phenotypes differed significantly across cohorts; the prevalence of the slow acetylator phenotype ranged from 16.3% in Yanomami to 33.3% in Munduruku to 48.9% in Paiter-Suruí. This three-fold range of variation is of major clinical relevance because the NAT2 slow phenotype is associated with higher risk of hepatotoxicity with antituberculosis chemotherapy and high incidence rates of tuberculosis and burden of latent infection among Munduruku, Paiter-Surui, and Yanomami peoples. According to the frequency of the NAT2 slow acetylator phenotype, the estimated number of individuals needed to be genotyped to prevent one additional event of hepatotoxicity range from 31 (Munduruku) to 39 (Paiter-Surui) and to 67 (Yanomami). The rs1801279 polymorphism was not found in any of the cohorts, while the MAF of the other polymorphisms showed significant variation between the cohorts. The difference in the prevalence of the NAT2 slow acetylator phenotype, which is linked to isoniazid-induced hepatotoxicity, was observed in the different study cohorts.

Association of renal biomarkers with fast progressor phenotype and related outcomes in anterior circulation large vessel occlusion stroke.

Renal dysfunction is a known predictor of long-term functional dependency after anterior circulation large vessel occlusion (ACLVO) stroke. However, the impact of renal dysfunction on early infarct growth rate (IGR) has not been previously demonstrated. The objective of this study was to define the association of creatinine-based renal biomarkers with fast or slow progressor phenotypes and related clinical outcomes in ACLVO stroke. This retrospective study examined patients with acute intracranial internal carotid artery or middle cerebral artery-M1 occlusions admitted between 2014 and 2019. Patients were included if they received baseline CT perfusion (CTP) or MRI on presentation within 24 h of estimated stroke onset. Infarct growth rate (IGR) was determined by ischemic core volume on CTP or MRI divided by time from stroke onset to imaging. IGR was used to stratify fast progressor (IGR ≥10 mL/h) and slow progressor (IGR < 10 mL/h) status. Renal dysfunction was assessed based on serum creatinine and estimated glomerular filtration rate (eGFR) on presenting laboratories. Logistic regression models, adjusted for significant covariates, identified independent associations between renal dysfunction biomarkers, progressor status, and clinical outcomes based on modified Rankin Scale (mRS) at 90 days. Among 230 patients with ACLVO, 29% were fast progressors, with median serum creatinine levels higher than slow progressors (1.1 vs. 0.9 mg/dL, p < 0.05) and lower median eGFR (66.2 vs. 69.0 mL/min/1.73m2, p < 0.05). Elevated creatinine (≥1.2 mg/dL) was independently associated with fast progressor status (adjusted OR 2.37, 95% CI 1.18-4.77), worse 90-day mRS (adjusted OR 1.88, 95% CI 1.01-3.51) and mortality (adjusted OR 2.57, 95% CI 1.14-5.79). Reduced eGFR (<60 mL/min/1.73m2) was independently associated with fast progressor status (adjusted OR 2.38, 95% CI 1.14-4.94), but not with 90-day mRS or mortality. Serum creatinine-based biomarkers of renal dysfunction were associated with fast progressor phenotype of ACLVO stroke, and worse clinical outcomes, which may help identify such patients earlier during emergency evaluation for expedited access to EVT. Future prospective studies are warranted to confirm and test implementation of these findings.

6404 Iodide Metabolism Anomalies in Patients with Thyroid Cancer; A Case Series

Abstract Disclosure: G.I. Uwaifo: None. Thyroid cancer is often treatable and often involves iodine ablation therapy. Iodine based imaging and/or therapy can be complicated in patients with abnormal iodide metabolism. We present two patients with thyroid cancer and disparate abnormal iodide metabolism. Case 1 is a 35 yr old Caucasian lady with papillary thyroid cancer (PTC) stage 1 with no metastases. After total thyroidectomy and prior to I-131 remnant ablation she had a contrast Chest CT for shortness of breath. A month after serum iodine was elevated (545 Ug/L; 40—92). 24 hr urine iodine levels was also elevated; (2,300Ug/day; 150-500). She denied dietary intake of iodine rich foods. Ablation was postponed and she commenced a strict “zero” iodine diet. Despite this and despite having no further contrast imaging serum and urinary iodine remain elevated for nearly 3 yrs. Further history indicated episodes of sensitivity to several medications and Cytochrome P450 genetic profiling revealed two polymorphisms of CYP P450 2C19 and 2D6 associated with slow drug metabolizer phenotype. 34 months after her Chest CT with serum iodine of 127Ug/L and 24 hr Urine iodine of 652 she had radio iodine-ablation (RIA) with 130Mci of I-131. She had post treatment dysgeusia and parotitis. She remains on a low iodine diet and is presumably cured. Case 2 is a 66 yr old Caucasian man referred for second opinion regarding therapeutic options for known metastatic PTC with metastases to thoracic spine and lungs. He was diagnosed with follicular variant PTC 7 yrs ago. He had total thyroidectomy and repeated RIAs with a total accumulated dose of ∼ 850Mci and last RIA 3 yrs ago. His latest two whole body I-131 scans were -ve despite elevated thyroglobulins and metastatic disease. He was unable to tolerate sorefanib. He is on thyroid hormone repletion and quarterly denosumab. Contrast PET-CT scan a week prior showed extensive metastatic disease and thyroglobulins in the 300—650 ng/ml range. Work up for repeat whole body I-131 scan revealed curiously that serum iodine was 46 Ug/L (40-92) despite his recent contrast study and this was confirmed on two repeats. 24 hr urine iodine was reduced; 87 ug/day (150-500) and he had a typical diet with no excess intake of goitrogens. Based on history of often needing significantly higher doses of medications like opioids, anesthetics and sedatives cytochrome P450 genetic profile obtained showed two polymorphisms (of CYP P450 2C-19 and CVPs 3A4 +3A5) associated with fast metabolizer phenotype. Given his unusually rapid iodine clearance the utility of any further iodine based imaging and/or therapy was deemed dubious. His current management continues without change. We present two patients with extremes of iodine metabolic processing that had clinical management significance. Careful evaluation of ambient iodine status of patients is an important part of the preparation of thyroid cancer patients for iodine based imaging and/or therapy. Presentation: 6/1/2024

Brain energy metabolism as an underlying basis of slow and fast cognitive phenotypes in honeybees.

In the context of slow-fast behavioral variation, fast individuals are hypothesized to be those who prioritize speed over accuracy while slow individuals are those which do the opposite. Since energy metabolism is a critical component of neural and cognitive functioning, this predicts such differences in cognitive style to be reflected at the level of the brain. We tested this idea in honeybees by first classifying individuals into slow and fast cognitive phenotypes based on a learning assay and then measuring their brain respiration with high-resolution respirometry. Our results broadly show that inter-individual differences in cognition are reflected in differences in brain mass and accompanying energy use at the level of the brain and the whole animal. Larger brains had lower mass-specific energy usage and bees with larger brains had a higher metabolic rate. These differences in brain respiration and brain mass were, in turn, associated with cognitive differences, such that bees with larger brains were fast cognitive phenotypes whereas those with smaller brains were slow cognitive phenotypes. We discuss these results in the context of the role of energy in brain functioning and slow-fast decision making and speed accuracy trade-off.

CYP3A4 Poor and Intermediate Metabolizers Have a Higher Rate of Steroid-Induced Intraocular Pressure Response.

Evaluate the relationship between CYP3A4 phenotype, the gene encoding the enzyme that metabolizes exogenous steroids, and the rate of steroid-induced intraocular pressure (IOP) response. Lymphocyte-derived DNA sequencing of CYP3A4 from 10073 patients was completed using the PGRN-Seq assay. Subjects with CYP3A4 intermediate metabolizer or slower phenotypes were identified and compared with controls matched by age, race, and sex. All subjects had at least 3 eye exams with at least an exam while on topical/systemic/local steroid in any body location except the eye. Patients with pre-existing glaucoma or glaucoma suspects were excluded. Of the 10,073 patients, there were 63 patients who had CYP3A4 poor or intermediate metabolizer phenotype. Of the 63 patients, 22 had documented steroid use. Fifty-nine percent (13/22) of patients with CYP3A4 poor/intermediate metabolizer had a steroid-induced IOP response of 3mmHg or more, significantly higher compared with 23% (5/22) of matched controls ( P =0.031). Although more poor/intermediate metabolizers were steroid responders, the average IOP elevation in steroid responders in both groups was similar (5.0±2.5mmHg in CYP3A4 poor/intermediate metabolizers compared with 4.1±2.1mmHg in controls, P =0.327). Family history of glaucoma was similar in both groups (7/22 vs. 8/22, P =1.0). Reduced CYP3A4 phenotypes may help identify patients at a higher risk of steroid-induced IOP elevation.

T-Allele Carriers of Mono Carboxylate Transporter One Gene Polymorphism rs1049434 Demonstrate Altered Substrate Metabolization during Exhaustive Exercise.

Polymorphism rs1049434 characterizes the nonsynonymous exchange of adenosine (A) by thymidine (T) in the gene for monocarboxylate transporter 1 (MCT1). We tested whether T-allele carriers of rs1049434 demonstrate increased accumulation of markers of metabolic strain. Physically active, healthy, young male subjects (n = 22) conducted a power-matched one-legged cycling exercise to exhaustion. Metabolic substrates in capillary blood, selected metabolic compounds, and indices for the slow oxidative phenotype of vastus lateralis muscle were quantified in samples collected before and after exercise. The genotypes of the rs1049434 polymorphism were determined with polymerase chain reactions. One-legged exercise affected the concentration of muscle metabolites entering the tricarboxylic acid cycle, such as acetyl-co-enzyme A (+448%) and acetyl-L-carnitine (+548%), muscle glycogen (-59%), and adenosine monophosphate (-39%), 30 min post-exercise. Exercise-related variability in the muscular concentration of glycogen, long-chain acyl co-enzyme As and a triglyceride, nicotinamide adenine dinucleotide (NADH), and adenosine monophosphate (AMP) interacted with rs1049434. T-allele carriers demonstrated a 39% lesser reduction in glycogen after exercise than non-carriers when NADH increased only in the non-carriers. Muscle lactate concentration was 150% higher, blood triacyl-glyceride concentration was 53% lower, and slow fiber percentage was 20% lower in T-allele carriers. The observations suggest a higher anaerobic glycolytic strain during exhaustive exercise and a lowered lipid handling in T-allele non-carriers.

CYP2B6 and ABCB1 genotypes predict methadone plasma exposure among patients on maintenance therapy against opioid addictions in Tanzania.

Methadone maintenance therapy (MMT) exhibits significant variability in pharmacokinetics and clinical response, partly due to genetic variations. However, data from sub-Saharan African populations are lacking. We examined plasma methadone variability and pharmacogenetic influences among opioid-addicted Tanzanian patients. Patients attending MMT clinics (n = 119) in Tanzania were genotyped for common functional variants of the CYP3A4, CYP3A5, CYP2A6, CYP2B6, CYP2C19, CYP2D6, ABCB1, UGT2B7 and SLCO1B1 genotypes. Trough plasma concentrations of total methadone, S-methadone (S-MTD) and R-methadone (R-MTD), with their respective metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The methadone-to-EDDP metabolic ratio (MMR) was used to categorize the phenotype. The proportions of MMR-predicted ultrarapid, extensive, intermediate and slow methadone metabolizer phenotypes were 2.5%, 58.2%, 23.7% and 15.6%, respectively. CYP2B6 genotype significantly correlated with S-methadone (P = .006), total methadone (P = .03), and dose-normalized methadone plasma concentrations (P = .001). Metabolic ratios of R-methadone (R-MTD/R-EDDP), S-methadone (S-MTD/S-EDDP), and total methadone (MMR) were significantly higher among patients homozygous for defective variants (*6 or *18) than heterozygous or CYP2B6*1/*1 genotypes (P < .001). The metabolic ratio for S-MTD and total methadone was significantly higher among ABCB1c.3435T/T than in the C/C genotype. No significant effect of CYP2D6, CYP2C19, CYP3A4, CYP3A5, CYP2A6, UGT2B7 and SLCO1B1 genotypes on S-methadone, R-methadone, or total methadone was observed. Approximately one in six opioid-addicted Tanzanian patients are methadone slow metabolizers, influenced by genetic factors. Both the CYP2B6 and ABCB1 genotypes are strong predictors of methadone metabolic capacity and plasma exposure. Further investigation is needed to determine their predictive value for methadone treatment outcomes and to develop genotype-based dosing algorithms for safe and effective therapy.

Proteomic reference map for sarcopenia research: mass spectrometric identification of key muscle proteins located in the sarcomere, cytoskeleton and the extracellular matrix.

Sarcopenia of old age is characterized by the progressive loss of skeletal muscle mass and concomitant decrease in contractile strength. Age-related skeletal muscle dysfunctions play a key pathophysiological role in the frailty syndrome and can result in a drastically diminished quality of life in the elderly. Here we have used mass spectrometric analysis of the mouse hindlimb musculature to establish the muscle protein constellation at advanced age of a widely used sarcopenic animal model. Proteomic results were further analyzed by systems bioinformatics of voluntary muscles. In this report, the proteomic survey of aged muscles has focused on the expression patterns of proteins involved in the contraction-relaxation cycle, membrane cytoskeletal maintenance and the formation of the extracellular matrix. This includes proteomic markers of the fast versus slow phenotypes of myosin-containing thick filaments and actin-containing thin filaments, as well as proteins that are associated with the non-sarcomeric cytoskeleton and various matrisomal layers. The bioanalytical usefulness of the newly established reference map was demonstrated by the comparative screening of normal versus dystrophic muscles of old age, and findings were verified by immunoblot analysis.

Effect of blood flow restriction and electrical muscle stimulation on human glycemic response to a glucose challenge.

To determine whether reduced tissue oxygen availability through blood flow restriction (BFR) alone, or in combination with electrically induced muscle contractions, can improve glucose clearance after an acute glucose challenge. In a randomized crossover design, 21 young participants (females: 12) were allocated to perform 1) electrical muscle stimulation (EMS), 2) BFR, 3) EMS + BFR or 4) no treatment (control). Participants completed each condition immediately preceding a 2h oral glucose tolerance test (100g). Primary analyses were performed on the glucose area under the curve (AUC) at time points 0-30, 30-120, and 0-120min. Secondary analyses were performed on glycemic responses based on biological sex and estimated muscle phenotype. Compared to the control (322±25mM∙min), the 0-30min AUC was reduced following EMS (293±22mM∙min, p = 0.0004), and EMS + BFR (298±36mM∙min., p = 0.006), whereas BFR in isolation did not differ (306±30mM∙min, p = 0.1). The 30-120 and 0-120min glucose AUCs were similar across conditions. Based on effect size from the control conditions, our secondary analysis suggests different 0-30min glycemic responses after EMS + BFR between females (dz = 0.206) vs. males (dz = 1.461) and/or slow (dz = 0.426) vs. fast (dz = 1.075) muscle phenotype. Reducing tissue oxygen availability with BFR did not augment the effects of EMS in the overall group; however, we provide preliminary data to suggest possible sex and/or muscle phenotypic responses in glycemic regulation with these modalities.

Alterations in neuromuscular junction morphology with ageing and endurance training modulate neuromuscular transmission and myofibre composition.

Both ageing and exercise training affect the neuromuscular junction (NMJ) structure. Morphological alterations in the NMJ have been considered to influence neuromuscular transmission and myofibre properties, but the direct link between the morphology and function has yet to be established. We measured the neuromuscular transmission, myofibre composition and NMJ structure of 5-month-old (young) and 24-month-old untrained (aged control) and trained (aged trained) mice. Aged trained mice were subjected to 2 months of endurance training before the measurement. Neuromuscular transmission was evaluated in vivo as the ratio of ankle plantar flexion torque evoked by the sciatic nerve stimulation to that by direct muscle stimulation. The torque ratio was significantly lower in aged mice than in young and aged trained mice at high-frequency stimulations, showing a significant positive correlation with voluntary grip strength. The degree of pre- to post-synaptic overlap of the NMJ was also significantly lower in aged mice and positively correlated with the torque ratio. We also found that the proportion of fast-twitch fibres in the soleus muscle decreased with age, and that age-related denervation occurred preferentially in fast-twitch fibres. Age-related denervation and a shift in myofibre composition were partially prevented by endurance training. These results suggest that age-related deterioration of the NMJ structure impairs neuromuscular transmission and alters myofibre composition, but these alterations can be prevented by structural amelioration of NMJ with endurance training. Our findings highlight the importance of the NMJ as a major determinant of age-related deterioration of skeletal muscles and the clinical significance of endurance training as a countermeasure. KEY POINTS: The neuromuscular junction (NMJ) plays an essential role in neuromuscular transmission and the maintenance of myofibre properties. We show that neuromuscular transmission is impaired with ageing but recovered by endurance training, which contributes to alterations in voluntary strength. Neuromuscular transmission is associated with the degree of pre- to post-synaptic overlap of the NMJ. Age-related denervation of fast-twitch fibres and a shift in myofibre composition toward a slower phenotype are partially prevented by endurance training. Our study provides substantial evidence that age-related and exercise-induced alterations in neuromuscular transmission and myofibre properties are associated with morphological changes in the NMJ.

Temporal expression of mitochondrial life cycle markers during acute and chronic overload of rat plantaris muscles.

Skeletal muscle hypertrophy is generally associated with a fast-to-slow phenotypic adaptation in both human and rodent models. Paradoxically, this phenotypic shift is not paralleled by a concomitant increase in mitochondrial content and aerobic markers that would be expected to accompany a slow muscle phenotype. To understand the temporal response of the mitochondrial life cycle (i.e., biogenesis, oxidative phosphorylation, fission/fusion, and mitophagy/autophagy) to hypertrophic stimuli, in this study, we used the functional overload (FO) model in adult female rats and examined the plantaris muscle responses at 1 and 10weeks. As expected, the absolute plantaris muscle mass increased by ∼12 and 26% at 1 and 10weeks following the FO procedure, respectively. Myosin heavy-chain isoform types I and IIa significantly increased by 116% and 17%, respectively, in 10-week FO plantaris muscles. Although there was a general increase in protein markers associated with mitochondrial biogenesis in acute FO muscles, this response was unexpectedly sustained under 10-week FO conditions after muscle hypertrophy begins to plateau. Furthermore, the early increase in mito/autophagy markers observed under acute FO conditions was normalized by 10weeks, suggesting a cellular environment favoring mitochondrial biogenesis to accommodate the aerobic demands of the plantaris muscle. We also observed a significant increase in the expression of mitochondrial-, but not nuclear-, encoded oxidative phosphorylation (OXPHOS) proteins and peptides (i.e., humanin and MOTS-c) under chronic, but not acute, FO conditions. Taken together, the temporal response of markers related to the mitochondrial life cycle indicates a pattern of promoting biogenesis and mitochondrial protein expression to support the energy demands and/or enhanced neural recruitment of chronically overloaded skeletal muscle.

Juvenile amyotrophic lateral sclerosis caused by a mutation in the SPTLC2 gene: case presentation

Juvenile amyotrophic lateral sclerosis (ALS) is a rare group of motor neuron diseases, with the age of onset up to 25 years. Juvenile ALS more commonly has genetic origin vs. sporadic forms of ALS that develop in adulthood. Genetic analysis of these cases with early onset makes it possible to identify the genes responsible for the disease. Here we present a case of a rare variant of juvenile ALS caused due to the SPTLC2 gene mutation.&#x0D; Cases with early disease onset are characterized by slow progression and variable phenotype, which often makes accurate diagnosis challenging. Therefore patients with combined upper and lower motor neuron disorders aged under 25 years should undergo comprehensive examination, in particular to identify gene mutations.

Evaluating interactions of polygenic risk scores and NAT2 genotypes with tobacco smoking in bladder cancer risk.

Tobacco smoking is the most important risk factor for bladder cancer. Previous studies have identified the N-acetyltransferase (NAT2) gene in association with bladder cancer risk. The NAT2 gene encodes an enzyme that metabolizes aromatic amines, carcinogens commonly found in tobacco smoke. In our study, we evaluated potential interactions of tobacco smoking with NAT2 genotypes and polygenic risk score (PRS) for bladder cancer, using data from the UK Biobank, a large prospective cohort study. We used Cox proportional hazards models to measure the strength of the association. The PRS was derived using genetic risk variants identified by genome-wide association studies for bladder cancer. With an average of 10.1 years of follow-up of 390 678 eligible participants of European descent, 769 incident bladder cancer cases were identified. Current smokers with a PRS in the highest tertile had a higher risk of developing bladder cancer (HR: 6.45, 95% CI: 4.51-9.24) than current smokers with a PRS in the lowest tertile (HR: 2.41, 95% CI: 1.52-3.84; P for additive interaction = <.001). A similar interaction was found for genetically predicted metabolizing NAT2 phenotype and tobacco smoking where current smokers with the slow NAT2 phenotype had an increased risk of developing bladder cancer (HR: 5.70, 95% CI: 2.64-12.30) than current smokers with the fast NAT2 phenotype (HR: 3.61, 95% CI: 1.14-11.37; P for additive interaction = .100). Our study provides support for considering both genetic and lifestyle risk factors in developing prevention measures for bladder cancer.

Lnc-Malat1 promotes slow myofiber-type transformation through sponging miR-129-5p in C2C12 myotubes

Long non-coding metastasis-associated lung adenocarcinoma transcript (lnc-Malat1) emerges as a novel regulator in skeletal muscle development, while its function and the related mechanism is not fully revealed yet. In this study, knockdown of lnc-Malat1 by siRNA significantly inhibited the expression of myoblast marker genes (MyHC, MyoD, and MyoG) and slow muscle fiber marker genes (MyHC I), together with repressed expression of mitochondria-related genes COX5A, ACADM, CPTA1, FABP3, and NDUFA1. Overexpression of lnc-Malat1 exerted an opposite effect, promoting myoblast differentiation and slow muscle fiber formation. Dual luciferase reporter assay revealed a direct interaction between lnc-Malat1 and miR-129-5p, and overexpression of lnc-Malat1 significantly inhibited miR-129-5p expression, thereby elevating the expression of Mef2a, miR-129-5p target protein. In addition, enforced expression of lnc-Malat1 restored the inhibitory effect of miR-129-5p on myoblast differentiation and MyHC I expression. Taken together, our results suggest that lnc-Malat1 promotes myoblast differentiation, and maintains the slow muscle fiber phenotype via adsorbing miR-129-5p.

DPPA3-HIF1α axis controls colorectal cancer chemoresistance by imposing a slow cell-cycle phenotype

Tumor relapse is linked to rapid chemoresistance and represents a bottleneck for cancer therapy success. Engagement of a reduced proliferation state is a non-mutational mechanism exploited by cancer cells to bypass therapy-induced cell death. Through combining functional pulse-chase experiments in engineered cells and transcriptomic analyses, we identify DPPA3 as a master regulator of slow-cycling and chemoresistant phenotype in colorectal cancer (CRC). We find a vicious DPPA3-HIF1α feedback loop that downregulates FOXM1 expression via DNA methylation, thereby delaying cell-cycle progression. Moreover, downregulation of HIF1α partially restores a chemosensitive proliferative phenotype in DPPA3-overexpressing cancer cells. In cohorts of CRC patient samples, DPPA3 overexpression acts as a predictive biomarker of chemotherapeutic resistance that subsequently requires reduction in its expression to allow metastatic outgrowth. Our work demonstrates that slow-cycling cancer cells exploit a DPPA3/HIF1α axis to support tumor persistence under therapeutic stress and provides insights on the molecular regulation of disease progression.

O70 | Identification of fast and slow CYP2D15 metabolizer phenotypes in dogs using dextromethorphan as a probe

Journal of Veterinary Pharmacology and TherapeuticsVolume 46, Issue S1 p. 62-63 ORAL PRESENTATIONS O70 | Identification of fast and slow CYP2D15 metabolizer phenotypes in dogs using dextromethorphan as a probe First published: 11 June 2023 https://doi.org/10.1111/jvp.13236Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume46, IssueS1Special Issue: 15th International Congress of the European Association for Veterinary Pharmacology and Toxicology held Bruges, Belgium, July 2–5, 2023June 2023Pages 62-63 RelatedInformation

Physiologically Based Pharmacokinetic Modeling for Multiple Oral Administration Labetalol in Pregnant Women.

Labetalol has an irreplaceable role in treating Hypertensive disorders of pregnancy (HDP), a common disease during pregnancy with a prevalence of 5.2-8.2%. However, there were big differences in dosage regimens between various guidelines. A physiologically-based pharmacokinetics (PBPK) model was established and validated to evaluate the existing oral dosage regimens, and to compare the difference in plasma concentration between pregnant and non-pregnant women. First, non-pregnant woman models with specific plasma clearance or enzymatic metabolism (UGT1A1, UGT2B7, CYP2C19) were established and validated. For CYP2C19, slow, intermediate, and rapid metabolic phenotypes were considered. Then, a pregnant model with proper structure and parameters adjustment was established and validated against the multiple oral administration data. The predicted labetalol exposure captured the experimental data well. The following simulations with criteria lowering 15mmHg blood pressure (corresponding to around 108ng/ml plasma labetalol) found that the maximum daily dosage in the Chinese guideline may be insufficient for some severe HDP patients. Moreover, similar predicted steady-state trough plasma concentration was found between the maximum daily dosage in the American College of Obstetricians and Gynecologists (ACOG) guideline, 800mg Q8h and a regimen of 200mg Q6h. Simulations comparing non-pregnant and pregnant women found that the difference in labetalol exposure highly depended on the CYP2C19 metabolic phenotype. In summary, this work initially established a PBPK model for multiple oral administration of labetalol for pregnant women. This PBPK model may lead to personalized labetalol medication in the future.

Abstract TP177: Comparison Of Baseline Serum Glucose Concentration Between Fast And Slow Progressor Phenotypes Of Anterior Circulation Large Vessel Occlusion Stroke

Introduction: The determinants of fast and slow progressor phenotypes of infarct growth in anterior circulation large vessel occlusion (ACLVO) remain poorly understood. Previous studies have shown a potential link between baseline serum glucose and acute infarct growth. We assessed whether presenting serum glucose is independently associated with fast or slow progression of infarct growth in ACLVO stroke. Methods: Retrospective analysis of patients with acute stroke due to intracranial ICA or proximal MCA occlusion across two comprehensive stroke centers from 2014-2019. Baseline CTP or MRI were obtained within 24hours of stroke onset. Fast progressors (ischemic core &gt; 70ml, 0-6 h) and slow progressors (&lt;/= 30ml, 6-24 h) were identified. Serum glucose levels were compared in two groups: fast vs. non-fast progressors (0-6 h), slow vs. non-slow progressors (6-24 h). Mann-Whitney test was used for univariate group comparisons. Pearson correlation tested the association between serum glucose and infarct growth rate (core volume / time of stroke onset to imaging). Results: A total of 350 participants were included (n=178 imaged &lt; 6 hours of stroke onset; n=172 imaged at 6-24 hours of stroke onset). Amongst early presenters, the median glucose was 127 mg/dL for fast progressors (n=32) versus 122 mg/dL in non-fast progressors (n=146), p=0.45. Amongst late presenters, the median glucose was 122 mg/dL for slow progressors versus 133 in non-slow progressors (p=0.085). The correlation between serum glucose concentration and infarct growth rate was 0.03 (p=0.57). Conclusion: While a numerical trend suggesting lower glucose levels was observed in slow progressors, no significant correlation between hyperacute serum glucose and infarct growth rate was established.

A Human iPSC Model Reveals Specific Upregulation of Linker Histone H1-0 in ETV6::RUNX1+ Preleukemia and B Cell Precursor Acute Lymphoblastic Leukemia

The ETV6::RUNX1 translocation is the most common chromosomal rearrangement associated with pediatric B cell precursor acute lymphoblastic leukemia (BCP-ALL). As previously shown, ETV6::RUNX1 leads to a distinct clinically silent preleukemic state in utero that manifests in impaired early B cell differentiation. Acquisition of secondary oncogenic mutations gives rise to overt leukemia in 0.2% of children carrying ETV6::RUNX1. In-depth characterization of ETV6::RUNX1+ preleukemia is essential to gain an understanding of leukemic transformation and develop preventive strategies. Here, we identify dysregulation of the epigenetic regulator H1-0 in ETV6::RUNX1+ preleukemia and BCP-ALL. Utilizing CRISPR/Cas9 genome editing, we generated monoclonal ETV6::RUNX1+ human induced pluripotent stem cell (hiPSC) lines with stable ETV6::RUNX1 expression driven by the endogenous ETV6 promoter. To assess the preleukemic setting mediated by ETV6::RUNX1, we performed RNA sequencing (RNA-seq) analysis of ETV6::RUNX1+ and matching wild-type (WT) hiPSCs of two donors. We identified 20 differentially expressed genes in ETV6::RUNX1+ hiPSCs of both donors compared to the respective WT hiPSCs (up: 15, down: 5, absolute fold change ≥ 2, p ≤ 0.05). Interestingly, our RNA-seq analysis revealed consistent upregulation of H1-0 (mean: 2.43-fold), a linker histone involved in chromatin remodeling, cell proliferation and differentiation. Elevated H1-0 levels in the ETV6::RUNX1+ hiPSC lines were confirmed by quantitative real-time PCR and immunoblot (Figure 1A). To determine H1-0 levels in ETV6::RUNX1+ B cell precursors, we analyzed published gene expression microarray and RNA-seq data sets. Both ETV6::RUNX1+ CD34+ cells (n = 10) derived from umbilical cord blood (Polak et al. Haematologica 2019) and ETV6::RUNX1+ CD34+CD19+ cells (n = 4) generated by hematopoietic differentiation of hiPSCs (Böiers et al. Developmental Cell 2018) showed significant upregulation of H1-0 compared to the respective control cells lacking ETV6::RUNX1 (unpaired t-test, p = 0.0087 and p = 0.0076, respectively). Additionally, we differentiated ETV6::RUNX1+ and WT hiPSCs into CD34+CD45+ hematopoietic progenitor cells and performed single-cell RNA-seq analysis. We identified coexpression of H1-0 with cyclin-dependent kinase inhibitor genes CDKN1A and CDKN1B, indicating a slow or non-cycling phenotype of H1-0+ cells. Next, we examined H1-0 mRNA levels in gene expression data sets of pediatric and adult leukemia patients (St. Jude PeCan database (n = 876), Jerchel et al. Haematologica 2018 (n = 654), MILE study (n = 1299)). H1-0 expression was found to be significantly elevated in ETV6::RUNX1+ BCP-ALL patient samples compared to other leukemia entities, especially TCF3::PBX1+ ALL (ordinary one-way ANOVA, p ≤ 0.0001), KMT2A rearranged ALL (p ≤ 0.0001) and chronic lymphoblastic leukemia (CLL, p ≤ 0.0001). Strikingly, H1-0 expression was 22.37-fold lower in CLL compared to ETV6::RUNX1+ BCP-ALL (Figure 1B). This observation prompted us to investigate H1-0 expression in B cell developmental stages using published data sets. Interestingly, we found that H1-0 levels decrease during early B cell development in both normal bone marrow (Black et al. Nucleic Acids Research 2018) and umbilical cord blood-derived cells (Novershtern et al. Cell 2011). Additionally, analysis of single-cell RNA-seq data of early B cell precursors derived from healthy bone marrow (Mehtonen et al. Genome Medicine 2020) and fetal liver (Developmental Cell Atlas Newcastle University) revealed that relative numbers of H1-0 expressing cells per differentiation state decreased along the pseudotime B cell development trajectory. Taken together, our study identifies H1-0 upregulation as a specific alteration present already at the ETV6::RUNX1+ preleukemic state. High H1-0 expression was associated with slower proliferation and increased stemness. This phenotype might explain the persistence of in utero generated preleukemic ETV6::RUNX1+ clones residing in the bone marrow of approximately 5% of healthy children for years. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal