Metabolic Maturation Research Articles

Flexible nanofilms coated with aligned piezoelectric microfibers preserve the contractility of cardiomyocytes.

The use of engineered cardiac tissue for high-throughput drug screening/toxicology assessment remains largely unexplored. Here we propose a scaffold that mimics aspects of cardiac extracellular matrix while preserving the contractility of cardiomyocytes. The scaffold is based on a poly(caprolactone) (PCL) nanofilm with magnetic properties (MNF, standing for magnetic nanofilm) coated with a layer of piezoelectric (PIEZO) microfibers of poly(vinylidene fluoride-trifluoroethylene) (MNF+PIEZO). The nanofilm creates a flexible support for cell contraction and the aligned PIEZO microfibers deposited on top of the nanofilm creates conditions for cell alignment and electrical stimulation of the seeded cells. Our results indicate that MNF+PIEZO scaffold promotes rat and human cardiac cell attachment and alignment, maintains the ratio of cell populations overtime, promotes cell-cell communication and metabolic maturation, and preserves cardiomyocyte (CM) contractility for at least 12 days. The engineered cardiac construct showed high toxicity against doxorubicin, a cardiotoxic molecule, and responded to compounds that modulate CM contraction such as epinephrine, propranolol and heptanol.

Endothelial cell‐derived matrix promotes the metabolic functional maturation of hepatocyte via integrin‐Src signalling

The extracellular matrix (ECM) microenvironment is involved in the regulation of hepatocyte phenotype and function. Recently, the cell‐derived extracellular matrix has been proposed to represent the bioactive and biocompatible materials of the native ECM. Here, we show that the endothelial cell‐derived matrix (EC matrix) promotes the metabolic maturation of human adipose stem cell‐derived hepatocyte‐like cells (hASC‐HLCs) through the activation of the transcription factor forkhead box protein A2 (FOXA2) and the nuclear receptors hepatocyte nuclear factor 4 alpha (HNF4α) and pregnane X receptor (PXR). Reducing the fibronectin content in the EC matrix or silencing the expression of α5 integrin in the hASC‐HLCs inhibited the effect of the EC matrix on Src phosphorylation and hepatocyte maturation. The inhibition of Src phosphorylation using the inhibitor PP2 or silencing the expression of Src in hASC‐HLCs also attenuated the up‐regulation of the metabolic function of hASC‐HLCs in a nuclear receptor‐dependent manner. These data elucidate integrin‐Src signalling linking the extrinsic EC matrix signals and metabolic functional maturation of hepatocyte. This study provides a model for studying the interaction between hepatocytes and non‐parenchymal cell‐derived matrix.

Echinacea purpurea Extract Affects the Immune System, Global Metabolome, and Gut Microbiome in Wistar Rats

Echinacea purpurea extract, a traditional herbal food additive with dual-purpose of medicine and edible material, has been widely used for the treatment and prevention of various infectious diseases, especially for children, old aged and immunocompromised patients. Although there were numerous reports suggested E. purpurea possessed immunostimulatory and antibacterial effects in vitro, the mechanisms underlying remained to be elucidated. This study employed immunologic factors analysis, GC-TOFMS based metabolomics and 16S-rRNA-sequencing microbiome profiling technologies to explore the effects of E. purpurea on young rats, a physiological insufficient immunity status, by compared with pidotimod treatment on young rats and adult animals. E. purpurea treatment significantly increased IL-2, decreased IL-6 and affect immunoglobulins in the spleen of young rats, indicating its promotion of cellular immunity. Both the immunologic factors and the global metabolome of E. purpurea treated young rats were close to the status of mature individuals. Results of 16S-rRNA-sequencing of ileum content together with co-metabolism metabolites demonstrated that E. purpurea changed gut microbiota structure characteristically as a reducing Firmicutes phylum, especially Lactobacillus, and a rising Actinobacteria phylum including Bifidobacterium. The results were concluded that E. purpurea could potentially promote the maturation of immune and metabolism of immature rats, and also affect gut flora structure.

Microbial Composition of the Initial Colonization of Newborns.

Early-life interaction with indigenous intestinal microbes is a prerequisite for healthy immune and metabolic maturation. Human infants acquire their gut microbiota predominantly from the mother. A considerable inoculum of microbes is received by the neonate during vaginal delivery. Recent observations suggest that human gut colonization may be initiated prenatally by microbes in amniotic fluid, but the significance of this phenomenon remains unknown. After birth, neonatal gut colonization is guided by human milk factors, which selectively promote the growth of specific microbes, as well as by live microbes present in human milk. Aberrant gut colonization in early life has been associated with an increased risk of noncommunicable diseases in later life. Epidemiological and experimental studies suggest a causal relationship between early-life gut microbiota perturbations and disease risk. Perinatal antibiotic exposure, cesarean section delivery, postnatal antibiotic administration, and formula feeding, which may disrupt intestinal microecology, have been associated with disease development in later life. The modulation of gut microbiota in the perinatal period by pre- and probiotics, for example, may offer a means to reduce the risk of chronic diseases.

ERRγ Is Required for the Metabolic Maturation of Therapeutically Functional Glucose-Responsive β Cells

Pancreatic β cells undergo postnatal maturation to achieve maximal glucose-responsive insulin secretion, an energy intensive process. We identify estrogen-related receptor γ (ERRγ) expression as a hallmark of adult, but not neonatal β cells. Postnatal induction of ERRγ drives a transcriptional network activating mitochondrial oxidative phosphorylation, the electron transport chain, and ATP production needed to drive glucose-responsive insulin secretion. Mice deficient in β cell-specific ERRγ expression are glucose intolerant and fail to secrete insulin in response to a glucose challenge. Notably, forced expression of ERRγ in iPSC-derived β-like cells enables glucose-responsive secretion of human insulin invitro, obviating invivo maturation to achieve functionality. Moreover, these cells rapidly rescue diabetes when transplanted into β cell-deficient mice. These results identify a key role for ERRγ in β cell metabolic maturation, and offer a reproducible, quantifiable, and scalable approach for invitro generation of functional human β cell therapeutics.

The Effects of Oral Quercetin Supplementation on Splanchnic Glucose Metabolism in 1-Week-Old Calves Depend on Diet after Birth1–3

Background: Inadequate colostrum supply results in insufficient intake of macronutrients and bioactive factors, thereby impairing gastrointestinal development and the maturation of glucose metabolism in neonatal calves. The flavonoid quercetin has been shown to have health-promoting properties, including effects in diabetic animals. However, quercetin interacts with intestinal glucose absorption and might therefore exert negative effects in neonates.Objective: We evaluated the interaction between neonatal diet and quercetin feeding on splanchnic glucose metabolism in neonatal calves.Methods: Calves (n = 28) were assigned to 4 groups and fed either colostrum or a milk-based formula on days 1 and 2 and supplemented daily with 148 μmol quercetin aglycone/kg body weight [colostrum with quercetin (CQ+)/formula with quercetin (FQ+)] or without this substance [colostrum without quercetin (CQ−)/formula with quercetin (FQ−)] from days 2–8. From day 3 onward, all calves received milk replacer. A xylose absorption test was performed on day 3, and on day 7, blood samples were collected to study glucose first-pass uptake after [13C6]-glucose feeding and intravenous [6,6-2H2]-glucose bolus injection. Plasma concentrations of metabolites and hormones were measured by taking additional blood samples. A biopsy specimen of the liver was harvested on day 8 to measure the mRNA expression of gluconeogenic enzymes.Results: Higher postprandial plasma concentrations of glucose, lactate, urea, adrenaline, noradrenaline, insulin, and glucagon on day 7 in colostrum-fed calves indicate that metabolic processes were stimulated. Postabsorptive xylose and glucose plasma concentrations each increased by an additional 26%, and splanchnic glucose turnover decreased by 35% in colostrum-fed calves, suggesting improved glucose absorption and lower splanchnic glucose utilization in colostrum-fed calves. Quercetin supplementation resulted in higher noradrenaline concentrations and enhanced peak absorption and oxidation of [13C6]-glucose by 10%. Liver mitochondrial phosphoenolpyruvate carboxykinase mRNA abundance was reduced by 34% in colostrum-deprived calves.Conclusions: Feeding colostrum during the first 2 d of life is crucial for maturation of splanchnic glucose metabolism in calves. Supplementing quercetin improves gastrointestinal absorption capacity, particularly in colostrum-deprived calves.

Elucidating Metabolic Maturation in the Healthy Fetal Brain Using 1H-MR Spectroscopy.

(1)H-MRS provides a noninvasive way to study fetal brain maturation at the biochemical level. The purpose of this study was to characterize in vivo metabolic maturation in the healthy fetal brain during the second and third trimester using (1)H-MRS. Healthy pregnant volunteers between 18 and 40 weeks gestational age underwent single voxel (1)H-MRS. MR spectra were retrospectively corrected for motion-induced artifacts and quantified using LCModel. Linear regression was used to examine the relationship between absolute metabolite concentrations and ratios of total NAA, Cr, and Cho to total Cho and total Cr and gestational age. Two hundred four spectra were acquired from 129 pregnant women at mean gestational age of 30.63 ± 6 weeks. Total Cho remained relatively stable across the gestational age (r(2) = 0.04, P = .01). Both total Cr (r(2) = 0.60, P < .0001) as well as total NAA and total NAA to total Cho (r(2) = 0.58, P < .0001) increased significantly between 18 and 40 weeks, whereas total NAA to total Cr exhibited a slower increase (r(2) = 0.12, P < .0001). Total Cr to total Cho also increased (r(2) = 0.53, P < .0001), whereas total Cho to total Cr decreased (r(2) = 0.52, P < .0001) with gestational age. The cohort was also stratified into those that underwent MRS in the second and third trimesters and analyzed separately. We characterized metabolic changes in the normal fetal brain during the second and third trimesters of pregnancy and derived normative metabolic indices. These reference values can be used to study metabolic maturation of the fetal brain in vivo.

Transcriptional Pathways in cPGI2-Induced Adipocyte Progenitor Activation for Browning.

De novo formation of beige/brite adipocytes from progenitor cells contributes to the thermogenic adaptation of adipose tissue and holds great potential for the therapeutic remodeling of fat as a treatment for obesity. Despite the recent identification of several factors regulating browning of white fat, there is a lack of physiological cell models for the mechanistic investigation of progenitor-mediated beige/brite differentiation. We have previously revealed prostacyclin (PGI2) as one of the few known endogenous extracellular mediators promoting de novo beige/brite formation by relaying β-adrenergic stimulation to the progenitor level. Here, we present a cell model based on murine primary progenitor cells defined by markers previously shown to be relevant for in vivo browning, including a simplified isolation procedure. We demonstrate the specific and broad induction of thermogenic gene expression by PGI2 signaling in the absence of lineage conversion, and reveal the previously unidentified nuclear relocalization of the Ucp1 gene locus in association with transcriptional activation. By profiling the time course of the progenitor response, we show that PGI2 signaling promoted progenitor cell activation through cell cycle and adhesion pathways prior to metabolic maturation toward an oxidative cell phenotype. Our results highlight the importance of core progenitor activation pathways for the recruitment of thermogenic cells and provide a resource for further mechanistic investigation.

Executioner Caspase-3 and 7 Deficiency Reduces Myocyte Number in the Developing Mouse Heart.

Executioner caspase-3 and -7 are proteases promoting cell death but non-apoptotic roles are being discovered. The heart expresses caspases only during development, suggesting they contribute to the organ maturation process. Therefore, we aimed at identifying novel functions of caspases in heart development. We induced simultaneous deletion of executioner caspase-3 and -7 in the mouse myocardium and studied its effects. Caspase knockout hearts are hypoplastic at birth, reaching normal weight progressively through myocyte hypertrophy. To identify the molecular pathways involved in these effects, we used microarray-based transcriptomics and multiplexed quantitative proteomics to compare wild type and executioner caspase-deficient myocardium at different developmental stages. Transcriptomics showed reduced expression of genes promoting DNA replication and cell cycle progression in the neonatal caspase-deficient heart suggesting reduced myocyte proliferation, and expression of non-cardiac isoforms of structural proteins in the adult null myocardium. Proteomics showed reduced abundance of proteins involved in oxidative phosphorylation accompanied by increased abundance of glycolytic enzymes underscoring retarded metabolic maturation of the caspase-null myocardium. Correlation between mRNA expression and protein abundance of relevant genes was confirmed, but transcriptomics and proteomics indentified complementary molecular pathways influenced by caspases in the developing heart. Forced expression of wild type or proteolytically inactive caspases in cultured cardiomyocytes induced expression of genes promoting cell division. The results reveal that executioner caspases can modulate heart’s cellularity and maturation during development, contributing novel information about caspase biology and heart development.

Microbial-derived lithocholic acid and vitamin K2 drive the metabolic maturation of pluripotent stem cells-derived and fetal hepatocytes.

The liver is the main organ responsible for the modification, clearance, and transformational toxicity of most xenobiotics owing to its abundance in cytochrome P450 (CYP450) enzymes. However, the scarcity and variability of primary hepatocytes currently limits their utility. Human pluripotent stem cells (hPSCs) represent an excellent source of differentiated hepatocytes; however, current protocols still produce fetal-like hepatocytes with limited mature function. Interestingly, fetal hepatocytes acquire mature CYP450 expression only postpartum, suggesting that nutritional cues may drive hepatic maturation. We show that vitamin K2 and lithocholic acid, a by-product of intestinal flora, activate pregnane X receptor (PXR) and subsequent CYP3A4 and CYP2C9 expression in hPSC-derived and isolated fetal hepatocytes. Differentiated cells produce albumin and apolipoprotein B100 at levels equivalent to primary human hepatocytes, while demonstrating an 8-fold induction of CYP450 activity in response to aryl hydrocarbon receptor (AhR) agonist omeprazole and a 10-fold induction in response to PXR agonist rifampicin. Flow cytometry showed that over 83% of cells were albumin and hepatocyte nuclear factor 4 alpha (HNF4α) positive, permitting high-content screening in a 96-well plate format. Analysis of 12 compounds showed an R(2) correlation of 0.94 between TC50 values obtained in stem cell-derived hepatocytes and primary cells, compared to 0.62 for HepG2 cells. Finally, stem cell-derived hepatocytes demonstrate all toxicological endpoints examined, including steatosis, apoptosis, and cholestasis, when exposed to nine known hepatotoxins. Our work provides fresh insights into liver development, suggesting that microbial-derived cues may drive the maturation of CYP450 enzymes postpartum. Addition of these cues results in the first functional, inducible, hPSC-derived hepatocyte for predictive toxicology.

Maturation-Based Model of Arrhythmogenic Right Ventricular Dysplasia Using Patient-Specific Induced Pluripotent Stem Cells.

Cellular reprogramming of somatic cells to patient-specific induced pluripotent stem cells (iPSCs) enables in-vitro modeling of human cardiac disorders for pathogenic and therapeutic investigations. However, using iPSC-derived cardiomyocytes (iPSC-CMs) to model an adult-onset heart disease remains challenging because of the uncertainty regarding the ability of relatively immature iPSC-CMs to fully recapitulate adult disease phenotypes. Arrhythmogenic right ventricular dysplasia (ARVD) is an inherited cardiomyopathy characterized by pathological fibrofatty infiltration and cardiomyocyte (CM) loss predominantly in the right ventricle (RV), leading to heart failure and lethal arrhythmias. Over 50% of affected individuals have desmosome gene mutations, most commonly inPKP2encoding plakophilin-2. Using Yamanaka's pluripotent factors, we generated iPSC lines from ARVD patients withPKP2mutations. We first developed a method to induce metabolic maturation of iPSC-CMs and showed that induction of adult-like metabolic energetics from an embryonic/glycolytic state is essential to model an adult-onset cardiac disease using patient-specific iPSCs. Furthermore, we showed that coactivation of normal peroxisome proliferator-activated receptor (PPAR)-α and abnormal PPARγ pathways in ARVD iPSC-CMs resulted in exaggerated CM lipogenesis, CM apoptosis, Na(+)channel downregulation and defective intracellular calcium handling, recapitulating the pathological signatures of ARVD. Using this model, we revealed novel pathogenic insights that metabolic derangement in an adult-like metabolic milieu underlies ARVD pathologies, enabling us to propose novel disease-modifying therapeutic strategies.

Metabolic maturation, migration, and liver retention of CD4 single positive thymocytes and recent thymic emigrants (HEM4P.238)

Abstract CD4 or CD8 single positive (SP) thymocytes, recent thymic emigrants (RTEs), and peripheral naïve T cells represent three consecutive cell populations along T cell maturation program. Except for negative selection in SP thymocytes, the importance and the regulation of this maturation is not well understood. In particular, little is known about the transition from mature SP to RTE and key events of this transition during and after thymic egress. We identified the phenotype of CD4+ pre-RTEs, a population of SPs that has acquired the thymic egress capability. A pro-oxidant shift and an increase of mitochondria content was found in pre-RTEs when compared to SPs with less functional maturity. The elevation of intracellular ROS was involved in promoting the functional maturation of these young T cells. After egress, autoreactive CD4+ pre-RTEs were retained and some were activated in the liver. Education from secondary lymphoid organs were not required for hepatic retention but TCR-MHC interaction in the liver was important for the activation of CD4+ liver RTEs. When transferred into RAG-/- mice, liver but not lymph node RTEs caused T cell infiltration and severe pulmonary inflammation, suggesting that the liver may be the first checkpoint in the periphery to filter and retain autoreactive CD4+ RTEs that escape from negative selection. Together, our results emphasize the complexity of SP-RTE maturation and the impact of various lymphoid tissue microenvironments on this maturation.

Correction: Metabolic Maturation of White Matter Is Altered in Preterm Infants

Correction: Metabolic Maturation of White Matter Is Altered in Preterm Infants

Metabolic Maturation of White Matter Is Altered in Preterm Infants

Significant physiological switches occur at birth such as the transition from fetal parallel blood flow to a two-circuit serial system with increased arterial oxygenation of blood delivered to all organs including the brain. In addition, the extra-uterine environment exposes premature infants to a host of stimuli. These events could conceivably alter the trajectory of brain development in premature infants. We used in vivo magnetic resonance spectroscopy to measure absolute brain metabolite concentrations in term and premature-born infants without evidence of brain injury at equivalent post-conceptional age. Prematurity altered the developmental time courses of N-acetyl-aspartate, a marker for axonal and neuronal development, creatine, an energy metabolite, and choline, a membrane metabolite, in parietal white matter. Specifically, at term-equivalency, metabolic maturation in preterm infants preceded development in term infants, but then progressed at a slower pace and trajectories merged at ≈340–370 post-conceptional days. In parieto/occipital grey matter similar trends were noticed but statistical significance was not reached. The timing of white matter development and synchronization of white matter and grey matter maturation in premature-born infants is disturbed. This may contribute to the greater risk of long-term neurological problems of premature infants and to their higher risk for white matter injury.

Differential expression of NGF and BDNF in rat adipose depots during early development and adulthood

According to the current paradigm, the white adipose tissue (WAT) not only releases fatty acids, cholesterol, retinoids and other lipids stored in the adipocytes, but also produce and secrete numerous signaling proteins collectively termed adipokines. Among them are various cell growth factors such as nerve growth factor (NGF) and brain-derived growth factor (BDNF). While literature around obesity and its related diseases is abundant, we still do not know how WAT behaves during normal development. In the present study, we explored the expression of NGF and BDNF in the peripancreatic fat tissue (Ppf) and the epididymal fat tissue (Epf ) during a critical period for the metabolic maturation of male Wistar rats. At birth almost no abdominal WAT was observed in the rats. From day 15 to adulthood (2 months), it increased in weight. However, the adipocyte diameter was not different during the first month, compared to adulthood, indicating that the tissue growth in this stage was mostly hypertrophic, while in the second month we also observed hyperplasia of the adipocytes. We measured the production of the neutrophins NGF and BDNF by the abdominal WAT depots. We observed a significant reduction in the expression of NGF in Epf at 28d and two months. However, NGF expression in Ppf remained stable from postnatal 15d to adulthood, except for a nadir at 28d. On the other hand, we failed to detect BDNF during the first 2 months of life in Ppf, but it was expressed at detectable amounts in Epf, peaking at day 20. We do not know how these secretory changes influence the development of the cells and the surrounding tissues. However, in obesity the amount of WAT is increased, and it is necessary to understand the mechanisms of WAT growth in physiological state to identify with the unbalance in this tissue present in obesity. Adipobiology 2013; 5: 39-43.

Alterations in the equine oocyte and follicle associated with obesity and metabolic syndrome

Obesity is associated with disrupted reproductive cycles in mares, but the association between obesity and fertility has received minimal attention. In our first study, we hypothesized that mares with equine metabolic syndrome (EMS) have altered follicular environment compared to normal counterparts. Light-horse mares (11-27 yr) were classified as normal (CON; n1⁄412) or insulin resistant (EMS, n1⁄48) based on the reciprocal of the square root of insulin (RISQI) and modified insulin-to-glucose ratio (MIRG), with EMS having RISQI 5.50. Follicular fluid (FF), granulosa cells (GC), and oocytes were aspirated from dominant follicles 22-24 h after deslorelin and hCG administration. Blood was collected following an overnight fast for insulin (INS), leptin (LEP), adiponectin (ADIPO) and inflammatory cytokines. Expression for 32 genes, related to metabolism and follicle maturation, were assessed in GC. Concentrations of INS, LEP, ADIPO and cytokines were highly correlated in serum and FF (P<0.001). Insulin was lower in serum and FF of CON compared to EMS (P<0.001) while LEP and interleukin-1b tended to be lower in FF of CON (P1⁄40.07 and P1⁄40.10; respectively). Control mares had lower tumor necrosis factor-a in FF than EMS (P<0.05). Adiponectin was higher in serum and FF in CON vs. EMS (P<0.05). Gene expression for epiregulin was elevated (P<0.05) while tissue inhibitor of matrix metalloproteinase-2 tended to be lower (P1⁄40.09) in GC from CON vs. EMS. In a second study, we tested the hypotheses: 1) follicular fluid reflects systemic changes in metabolic hormones and metabolites, and 2) oocytes from obese mares have altered lipid content compared to mares

High-Density Lipoproteincholesterol, Reverse Cholesterol Transport, and Cardiovascular Risk: A Tale of Genetics?

Cholesterol deposition plays a central role in atherogenesis. The accumulation of lipid material is the result of an imbalance between the influx and efflux of cholesterol within the arterial wall. High levels of plasma low-density lipoprotein-cholesterol are considered the major mechanism responsible for the influx and accumulation of cholesterol in the arterial wall, while high-density lipoprotein (HDL)- cholesterol seems responsible for its efflux. The mechanism by which cholesterol is removed from extra-hepatic organs and delivered to the liver for its catabolism and excretion is called reverse cholesterol transport (RCT). Epidemiological evidence has associated high levels of HDL-cholesterol/ApoA-I with protection against atherosclerotic disease, but the ultimate mechanism(s) responsible for the beneficial effect is not well established. HDLs are synthesized by the liver and small intestine and released to the circulation as a lipid-poor HDL (nascent HDL), mostly formed by ApoA-I and phospholipids. Through their metabolic maturation, HDLs interact with the ABCA1 receptor in the macrophage surface increasing their lipid content by taking phospholipids and cholesterol from macrophages becoming mature HDL. The cholesterol of the HDLs is transported to the liver, via the scavenger receptor class B, type I, for further metabolization and excretion to the intestines in the form of bile acids and cholesterol, completing the process of RCT. It is clear that an inherited mutation or acquired abnormality in any of the key players in RCT mat affect the atherosclerotic process.

Metabolic Maturation of Auditory Neurones in the Superior Olivary Complex

Neuronal activity is energetically costly, but despite its importance, energy production and consumption have been studied in only a few neurone types. Neuroenergetics is of special importance in auditory brainstem nuclei, where neurones exhibit various biophysical adaptations for extraordinary temporal precision and show particularly high firing rates. We have studied the development of energy metabolism in three principal nuclei of the superior olivary complex (SOC) involved in precise binaural processing in the Mongolian gerbil (Meriones unguiculatus). We used immunohistochemistry to quantify metabolic markers for energy consumption (Na+/K+-ATPase) and production (mitochondria, cytochrome c oxidase activity and glucose transporter 3 (GLUT3)). In addition, we calculated neuronal ATP consumption for different postnatal ages (P0–90) based upon published electrophysiological and morphological data. Our calculations relate neuronal processes to the regeneration of Na+ gradients perturbed by neuronal firing, and thus to ATP consumption by Na+/K+-ATPase. The developmental changes of calculated energy consumption closely resemble those of metabolic markers. Both increase before and after hearing onset occurring at P12–13 and reach a plateau thereafter. The increase in Na+/K+-ATPase and mitochondria precedes the rise in GLUT3 levels and is already substantial before hearing onset, whilst GLUT3 levels are scarcely detectable at this age. Based on these findings we assume that auditory inputs crucially contribute to metabolic maturation. In one nucleus, the medial nucleus of the trapezoid body (MNTB), the initial rise in marker levels and calculated ATP consumption occurs distinctly earlier than in the other nuclei investigated, and is almost completed by hearing onset. Our study shows that the mathematical model used is applicable to brainstem neurones. Energy consumption varies markedly between SOC nuclei with their different neuronal properties. Especially for the medial superior olive (MSO), we propose that temporally precise input integration is energetically more costly than the high firing frequencies typical for all SOC nuclei.

Studying arrhythmogenic right ventricular dysplasia with patient-specific iPSCs

Cellular reprogramming of somatic cells to patient-specific induced pluripotent stem cells (iPSCs) enables in-vitro modelling of human genetic disorders for pathogenic investigations and therapeutic screens1–7. However, using iPSC-derived cardiomyocytes (iPSC-CMs) to model an adult-onset heart disease remains challenging due to the uncertainty regarding the ability of relatively immature iPSC-CMs to fully recapitulate adult disease phenotypes. Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited heart disease characterized by pathological fatty infiltration and cardiomyocyte loss predominantly in the right ventricle (RV)8, which is associated with life-threatening ventricular arrhythmias. Over 50% of affected individuals have desmosome gene mutations, most commonly in PKP2 encoding plakophilin-29. The median age at presentation of ARVD/C is 26 years8. We used Yamanaka’s methods1,10 to generate iPSC lines from fibroblasts of two patients with ARVD/C and PKP2 mutations11,12. Mutant PKP2 iPSC-CMs demonstrate abnormal plakoglobin nuclear translocation and decreased β-catenin activity13 in cardiogenic conditions; yet these abnormal features are insufficient to reproduce the pathological phenotypes of ARVD/C in standard cardiogenic conditions. Here we show that induction of adult-like metabolic energetics from an embryonic/glycolytic state and abnormal peroxisome proliferator-activated receptor-gamma (PPARγ) activation underlie the pathogenesis of ARVD/C. By coactivating normal PPAR-alpha (PPARα)-dependent metabolism and abnormal PPARγ pathway in beating embryoid bodies (EBs) with defined media, we established an efficient ARVD/C in-vitro model within two months. This model manifests exaggerated lipogenesis and apoptosis in mutant PKP2 iPSC-CMs. iPSC-CMs with a homozygous PKP2 mutation also displayed calcium-handling deficits. Our study is the first to demonstrate that induction of adult-like metabolism plays a critical role in establishing an adult-onset disease model using patient-specific iPSCs. Using this model, we revealed crucial pathogenic insights that metabolic derangement in adult-like metabolic milieu underlies ARVD/C pathologies, enabling us to propose novel disease-modifying therapeutic strategies.

Association of Lipoprotein Subfractions and Coronary Artery Calcium In Patient at Intermediate Cardiovascular Risk

More precise estimation of the atherogenic lipid parameters could improve identification of residual risk beyond what is possible using traditional lipid risk factors. The aim of the present study was to explore the association between advanced analysis of lipoprotein subfractions and the prevalence of coronary artery calcium. Consecutive participants at intermediate cardiovascular risk who were undergoing computed tomographic assessment of coronary calcium (calcium score) were included. Using a validated ultracentrifugation method (the vertical autoprofile II test), cholesterol in eluting lipoprotein subfractions [i.e., low- (LDL), very-low-, intermediate-, and high-density lipoprotein subclasses, lipoprotein (a), and predominant LDL distribution] was directly quantified. A total of 410 patients were included (29% women, mean age 57 years), of whom 297 (72.4%) had coronary artery calcium. LDL pattern B (predominance of small dense particles) emerged as an independent predictor of coronary calcium after adjustment for traditional risk factors (odds ratio 4.46, 95% confidence interval 1.19 to 16.7). However, after additional stratification for dyslipidemia, as defined by conventional lipid profiling, a statistically significant prediction was only retained for high-density lipoprotein subfraction 2 (odds ratio 3.45, 95% confidence interval 2.03 to 50.1) and "real" LDL (odds ratio 6.10, 95% confidence interval 1.26 to 23.41) in the normolipidemia group and for lipoprotein (a) (odds ratio 7.81, 95% confidence interval 1.41 to 43.5) in the dyslipidemic group. In conclusion, advanced assessment of the lipoprotein subfractions [i.e., LDL pattern B, high-density lipoprotein subfraction 2, "real" LDL, and lipoprotein (a)] using the vertical autoprofile II test provided additional information to that of conventional risk factors on the prevalence of coronary artery calcium in patients at intermediate cardiovascular risk.