Abstract Atrial fibrillation represents a prevalent cardiac arrhythmia whose pathogenic mechanisms remain incompletely understood. Here, we identify impaired atrial lymphangiogenesis as a critical determinant in atrial fibrillation pathogenesis. Analysis of human left atrial appendage specimens reveals decreased lymphatic vessel density in atrial fibrillation patients compared to those in sinus rhythm. Mechanistically, we demonstrate that epicardial adipose tissues from atrial fibrillation patients secrete kynurenic acid, which acts via GPR35 to disrupt lymphatic endothelial cell metabolism and mitochondrial homeostasis, ultimately promoting endothelial-to-mesenchymal transition. Using an organotypic culture system, we show that epicardial adipose tissue -derived factors directly impair lymphatic vessel formation. In vivo studies utilizing angiotensin II-induced and high-fat diet male mouse models confirm the critical role of lymphatic dysfunction in atrial fibrillation susceptibility. Therapeutic interventions promoting lymphangiogenesis, either through VEGFC administration or weight loss intervention by LY3437943 (the novel triple GIP, GLP-1, and glucagon receptor agonist), significantly attenuate atrial fibrillation inducibility. These findings establish lymphatic dysfunction as a novel pathogenic mechanism in atrial fibrillation and highlight lymphatic vessel formation as a promising therapeutic target.

Optimal function of beige adipocytes is essential for energy balance and metabolic homeostasis. We previously identified that cholinergic receptor nicotinic α2 subunit (CHRNA2) mediates a beige fat selective signaling in mice and humans. Here, we investigate the molecular composition of CHRNA2-containing nicotinic acetylcholine receptors (nAChRs) in beige adipocytes and its impact on whole-body metabolism. Expression levels of cholinergic receptor nicotinic β2 subunit (CHRNB2) and CHRNA2 positively correlate within murine and human beige adipocytes, and both nAChRs are regulated by a spectrum of beige fat regulators. CHRNB2 is essential for the response to nAChR agonists in beige adipocytes. CHRNB2 partial agonists, a family of drugs clinically used for smoking cessation, activate both murine and human beige adipocytes. Mice deficient in Chrnb2, with both whole-body knockout or adipocyte-specific deletion, exhibit compromised adaptive thermogenesis in subcutaneous fat and more aggravated metabolic dysfunction after challenge with high-fat-diet feeding compared with control mice, underscoring the importance of the nAChR signaling in maintaining energy balance. This cholinergic signaling declines in subcutaneous fat with aging. These findings indicate CHRNB2 forms a functional receptor with CHRNA2 in beige adipocytes and highlight their potential as therapeutic targets against metabolic disorders. ARTICLE HIGHLIGHTS:Beige adipocyte activity, mediated by CHRNA2, significantly influences adipose function and systemic metabolism. The CHRNB2 subunit forms a functional receptor with CHRNA2 and is essential for the response to nicotinic acetylcholine receptor agonists in beige adipocytes. Deletion of Chrnb2 in mice compromises the adaptive response to cold in subcutaneous adipose tissue and renders exacerbated metabolic dysfunction due to diet-induced obesity. This cholinergic signaling within subcutaneous adipose tissue declines with aging. CHRNB2 partial agonists, a family of drugs clinically used for smoking cessation, activate both murine and human beige adipocytes.

Fine-tuning of lipid metabolism in adipose tissue is crucial for maintaining energy homeostasis and metabolic health. Beyond total metal abundance, the intracellular distribution of metal ions represents a fundamental yet largely unexplored regulatory layer of cellular metabolism. Here, we demonstrate that ZIP13/SLC39A13, originally identified as an intracellular zinc transporter, regulates the subcellular distribution of iron. This function limits iron-dependent reactive oxygen species production, thereby restraining excessive cAMP/PKA signaling in mature adipocytes. Consequently, ZIP13 suppresses β-adrenergic receptor-stimulated lipolysis in subcutaneous white adipose tissue, as well as thermogenesis in brown adipose tissue. Notably, ZIP13 exhibits a context-dependent shift in substrate utilization during adipocyte differentiation, transitioning from zinc transport in preadipocytes to iron transport in mature adipocytes. In humans, ZIP13 mutations cause spondylocheirodysplastic Ehlers-Danlos syndrome with lipoatrophy, supporting the physiological relevance of intracellular metal distribution in metabolic regulation. Together, these findings establish intracellular metal distribution—rather than total metal abundance—as a fundamental principle governing cellular metabolism.

Fasciolosis is a major cause of food-borne parasitic zoonosis. It primarily affects ruminants but also infects humans. Clinically, it is characterized by abnormal liver images with prominent eosinophilia. We herein report a 77-year-old Japanese livestock farmer, who experienced fasciolosis reinfection. Environmental investigation of his residence revealed that both intermediate host snails and sika deer, a natural final host, inhabited his house. In addition, cattle were infected with Fasciola. Based on these findings, we concluded that his work place was accidentally contaminated with Fasciola metacercariae.

Background: Postoperative atrial fibrillation (POAF) is associated with short- and long-term morbidity and mortality. However, the ability of the epicardial adipocyte to regulate POAF remains poorly understood. Objectives: The authors investigated the possible role of human epicardial adipocyte-derived adipokines in the regulation of the myocardial redox state and POAF. Methods: The authors prospectively studied 274 patients who underwent scheduled open-heart surgery. Finally, 149 patients without known atrial fibrillation were enrolled and divided into POAF and non-POAF groups. Epicardial adipose tissue biopsies and isolated preadipocytes were used to explore the important secretable adipokines associated with POAF. Results: POAF occurred in 53 (35.6%) patients. Genome-wide expression profiling of background-matched differentiated preadipocytes representing the POAF or non-POAF groups and quantitative polymerase chain reaction validation as a biological replicate using all cohort samples revealed that only SPARCL1 was significantly downregulated in the POAF group. SPARCL1 messenger RNA expression in differentiated preadipocytes correlated with SPARCL1 protein concentration in the preadipocyte culture medium. SPARCL1 attenuated angiotensin II-induced oxidative stress in neonatal rat myocytes. Coculture of human induced pluripotent stem cell-derived atrial cardiomyocyte with the differentiated preadipocyte revealed that the preadipocytes derived from non-POAF patients suppressed myocardial oxidative stress. Low SPARCL1 expression in human epicardial differentiated preadipocytes was associated with a higher risk of long-term adverse cardiovascular events after surgery. Conclusions: These findings suggested that the SPARCL1, derived from epicardial differentiated preadipocytes, may be an important paracrine adipokine that regulates POAF and subsequent cardiovascular outcomes by improving myocardial redox state.

Background:Risk stratification for ventricular fibrillation (VF) in patients with Brugada syndrome (BrS) remains a significant clinical challenge. Atrial fibrillation (AF) is relatively common in BrS, suggesting arrhythmogenic abnormalities in both the atria and ventricles. The purpose of this study was to investigate the relationship between P-waveforms and VF occurrence in patients with BrS. Method:Eighty-two patients with BrS were retrospectively evaluated and classified into two groups based on the occurrence of VF during the overall clinical course: VF occurrence (n = 34) and VF nonoccurrence (n = 48). The relationship between VF occurrence and parameters on 12-lead electrocardiogram (ECG) at the initial visit, prior to any drug administration, was analyzed. Results:During a median follow-up of 75.0 months, VF occurred in 23 patients, including 19 recurrent and four new cases. Multivariable logistic regression identified notched P-wave as an independent risk factor for VF occurrence in all models (odds ratios 6.45-8.45; all p < 0.01). Depending on the model, symptomatic BrS, early repolarization pattern, and fragmented QRS were also independently associated with VF. Kaplan-Meier analysis showed a significantly lower incidence of VF in patients with BrS who have neither a history of VF nor a notched P-wave (p < 0.0001). Conclusions:Notched P-wave on 12-lead ECG is a significant risk factor for the occurrence of VF in patients with BrS. Notched P-wave in patients with BrS may indicate the presence of an underlying arrhythmogenic substrate predisposing to VF.

BACKGROUND:Vericiguat, an oral soluble guanylate cyclase stimulator, is a novel therapeutic agent for patients with heart failure with reduced ejection fraction; however, the detailed cardioprotective mechanism remains unclear. We aimed to explore the mechanism of the effect of vericiguat on the myocardium, particularly focusing on oxidative stress, using in vivo and in vitro experiments. METHODS AND RESULTS:Male 8-week-old mice were divided into a control group, angiotensin II (AngII) infusion group, and AngII infusion with low- or high-dose vericiguat treatment group. After 14 days of treatment, vericiguat did not affect the systolic or diastolic blood pressure increase caused by AngII infusion. AngII-induced cardiac hypertrophy and fibrosis in the left ventricle (LV) were significantly ameliorated by high-dose vericiguat treatment. AngII-induced O2-overproduction and upregulation of messenger RNA levels of Nppa, Nppb, Myh7, Col1a1, Col3A1, and Tgfb1 in the LV were significantly attenuated by vericiguat in a dose-dependent manner. Incubation of neonatal rat cardiomyocytes using vericiguat and AngII revealed that preceding incubation with vericiguat directly reduced AngII-induced cardiomyocyte O2-production and cardiac hypertrophy-associated gene expression. In addition, AngII-induced phosphorylation of ERK 1/2 or p38 MAPK was significantly attenuated by the incubation with vericiguat. CONCLUSIONS:Our study demonstrated that vericiguat suppresses myocardial oxidative stress via the regulation of ERK 1/2 or p38 MAPK signaling, leading to antihypertrophic/fibrotic effects.

Background During the early phase of the coronavirus disease 2019 (COVID-19) pandemic, a global reduction in hospitalizations for acute myocardial infarction (AMI) was observed. Generally, patients experienced increased severity of AMI with delays in time from symptom onset to treatment during the pandemic. However, the impact of the COVID-19 pandemic on in-hospital mortality among patients with AMI remains unclear. This study aimed to compare the long-term prognosis of patients with AMI during the COVID-19 pandemic to that observed in the pre-pandemic period and to evaluate the influence of the COVID-19 pandemic on the prognosis of patients with AMI. Methods We reviewed the data of patients admitted to our hospital for AMI treatment between April 1, 2018, and March 31, 2021. The time from admission to major adverse cardiac events (MACE), as well as the time from admission to all-cause death, were examined between the pandemic period (April 1, 2020, to March 31, 2021) and the pre-pandemic period (April 1, 2018, to March 31, 2020). Results Eighty patients were included in the study, and those admitted during the pandemic exhibited a higher likelihood of advanced age, lower levels of LDL-cholesterol, and a reduced prevalence of hypertension. The 2.5-year MACE-free survival and overall survival rates between the patients during the pre-pandemic and pandemic periods were not significantly different. Conclusion The long-term prognosis of patients with AMI during the COVID-19 pandemic remains unclear. In this study, we reported that the 2.5-year MACE-free survival and overall survival rates of the patients with AMI admitted during the COVID-19 pandemic were not significantly different from those during the pre-pandemic period. The impact of the COVID-19 pandemic on the prognosis of patients with AMI appears to vary according to the study population.

Background: We have previously reported the advantages of a prehospital 12-lead electrocardiography system (P-ECG) for ST-segment elevation myocardial infarction (STEMI) patients (Circ Rep 2019; Circ J 2022, 2023). Since 2020 with Coronavirus disease 2019 (COVID-19), the patient transport situation has changed dramatically. We investigated how patient transport was changed by COVID-19. The effect of prehospital electrocardiography (ECG) was also evaluated. Methods and Results: Recent urban STEMI patients who received primary percutaneous coronary intervention (PCI) using P-ECG were assigned to a P-ECG group (n=87; age 69 +/- 14 years), and comparable urban STEMI patients not using P-ECG were assigned to a Conventional group (n=87; age 71 +/- 13 years). The pre-COVID-19 period is defined as the period before the pandemic began, and the COVID-19 period is the time thereafter. In the Conventional group, first medical contact (FMC)-to-reperfusion time (110 +/- 45 vs. 90 +/- 31 min; P=0.025) and door-to-reperfusion time (89 +/- 41 vs. 70 +/- 29min; P=0.015) in the COVID-19 period were significantly longer than in the pre-COVID-19 period. However, in the P-ECG group, there was no difference in FMC-to-reperfusion time and door-to-reperfusion time between the 2 periods. In the Conventional group, Killip class (2.0 +/- 1.3 vs. 1.1 +/- 0.5; P=0.001) and left ventricular ejection fraction (49 +/- 12 vs. 57 +/- 9.0%; P=0.002) were significantly poorer in the COVID-19 period than in the pre-COVID-19 period. However, in the P-ECG group, there was no significant difference between the 2 periods. Conclusions: During the COVID-19 pandemic, P-ECG might have provided advantages for patient transport and outcomes in urban STEMI patients.

BACKGROUND:The prognosis of patients with acute myocardial infarction (AMI) in the initial stage of the coronavirus disease 2019 (COVID-19) outbreak has been reported globally. However, the reports on the prognosis of patients with AMI after the initial stage of the pandemic are limited worldwide. METHODS:This retrospective observational study utilized data from the electronic medical records system of the Oita University Hospital. This study encompassed patients who were hospitalized at our hospital for AMI treatment between April 2018 and June 2022. The study period was categorized into the following three periods: the pre-pandemic period (April 2018 to March 2020), the first phase of the pandemic (April 2020 to March 2021), and the second phase of the pandemic (April 2021 to June 2022). The primary outcome was the duration from the initial admission for AMI treatment to the onset of major adverse cardiac events (MACE). The secondary outcome was the duration from the initial admission for AMI treatment to death from any cause. These outcomes were compared among patients with AMI admitted during the three periods. RESULTS:The one-year MACE-free survival rates did not differ significantly among the three periods (p = 0.146), whereas the one-year overall survival rates were significantly different (p = 0.022). Univariate Cox regression analysis showed that patients with AMI had poorer overall survival in the second phase of the COVID-19 pandemic compared to the pre-pandemic period (hazard ratio {HR}: 4.92, 95% confidence interval {CI}: 1.27-19.09, p = 0.021). However, multiple regression analysis did not show significant differences in the overall survival of patients with AMI across the three periods (HR: 2.77, 95% CI: 0.59-12.96, p = 0.196). CONCLUSION:The long-term impact of the COVID-19 pandemic on the prognosis of patients with AMI remains unclear. Further research is required to clarify the long-term impact by using larger cohorts that include pre-hospital data.

Abstract Background Cardiac lymphatic systems play an important role in maintaining myocardial fluid homeostasis during inflammation. We have recently reported the epicardial adipose tissue (EAT)-derived factor induces inflammation and fibrosis in atrial myocardium, which lead to atrial fibrillation (AF). However, the direct effect of EAT on the cardiac lymphatic endothelial cells (LECs) remains unknown. Objective To elucidate the effect of EAT on cardiac LECs, as one of the potential causes of AF. Methods Human EAT samples were collected from 18 consecutive patients with or without AF patients during cardiovascular surgery. They were categorized into the sinus rhythm (SR) group (n=9, 72.7±8.6 years) and the AF group (n=9, 73.3±7.4 years). Preadipocytes were extracted from EAT by homogenization and collagenase treatment, and cultured to confluence. After differentiation to mature adipocytes, cell culture supernatant was collected, and cultured with human LECs. Cell permeability was measured by using FITC-dextran assay. Tube forming ability was analyzed by seeding LECs on the extracellular matrix gels. Metabolomic profiling of LECs was performed by GC-MS system. Results RT-PCR analysis revealed that cell culture supernatant from mature adipocytes of AF patients significantly increased mRNA expression of mesenchymal marker, TAGLN/SM22a (p<0.01) in human LECs, whereas mRNA expression of lymphatic endothelial markers, LYVE1 (p=0.0552) and PROX1 (p=0.0231) were decreased in human LECs, compared to those from mature adipocytes of SR patients. These data suggest cell culture supernatant from mature adipocytes of AF patients highly induce endothelial-to-mesenchymal transition (EndMT) of LECs. When assessing the endothelial barrier function by using FITC-dextran, cell culture supernatant from mature adipocytes of AF patients significantly decreased cell barrier function (p<0.01) compared to those from mature adipocytes of SR patients. Furthermore, cell culture supernatant from mature adipocytes of AF patients significantly decreased the tube forming ability of LECs (p<0.01) compared to those from mature adipocytes of SR patients. To assess the metabolomic changes in human LECs by EAT-secretome, we conducted the GC/MS analysis. Cell culture supernatant from mature adipocytes of AF patients significantly decreased several amino acids including branched-chain amino acid (BCAA; valine, leucine and isoleucine), compared to those from mature adipocytes of SR patients. Conclusion Our study with human EAT and LECs demonstrated that EAT-secretome from AF patients altered metabolomic profile in LECs, and highly caused EndMT in LECs, leading to impaired barrier function and the tube forming ability. Defects of lymphangiogenesis could be a therapeutic target for atrial cardiomyopathy.

BACKGROUND Typical left bundle branch block (LBBB) shows 2 peaks of the R wave, which reflect activation reaching the interventricular septum (R) and posterolateral wall (R') sequentially. OBJECTIVE The purpose of this study was to investigate the relationship among R-R' interval (RR'), mechanical dyssynchrony, extent of viable myocardium, and long-term outcomes in cardiac resynchronization therapy (CRT) candidates. METHODS The study enrolled 49 patients (34 men; mean age: 69 +/- 11 years) with LBBB who received CRT. The LBBB definition used requires the presence of mid-QRS notching in leads V-1, V-2, V-5, V-6, I, and aVL. Baseline evaluations were QRS duration (QRSd) and RR' measured from the 12-lead electrocardiogram; eyeball dyssynchrony (apical rocking and septal flash) and opposing-wall delay by speckle tracking from echocardiography, and extent of viable myocardium assessed by thallium-201 single-photon emission computed tomography. Primary outcomes included the combination of all-cause death and heart failure-related hospitalization. RESULTS RR' predicted volumetric response better than QRSd (area under the curve 0.73 vs 0.67, respectively). The long RR' group (>= 48 ms) revealed more frequent eyeball dyssynchrony and significantly greater radial (SL) and circumferential dyssynchrony (AP and SL) and %viable segment than the short RR' group. In multivariate regression analysis, only RR' >= 48 ms was independently associated with higher event-free survival rates following CRT (hazard ratio 0.21; P = .014). CONCLUSION These findings suggest that RR' in complete LBBB was associated with mechanical dyssynchrony, extent of viable myocardium, and long-term outcomes following CRT.

Human mutations in neuropeptide Y (NPY) have been linked to high body mass index but not altered dietary patterns1. Here we uncover the mechanism by which NPY in sympathetic neurons2,3 protects from obesity. Imaging of cleared mouse brown and white adipose tissue (BAT and WAT, respectively) established that NPY+ sympathetic axons are a smaller subset that mostly maps to the perivasculature; analysis of single-cell RNA sequencing datasets identified mural cells as the main NPY-responsive cells in adipose tissues. We show that NPY sustains the proliferation of mural cells, which are a source of thermogenic adipocytes in both BAT and WAT4-6. We found that diet-induced obesity leads to neuropathy of NPY+ axons and concomitant depletion of mural cells. This defect was replicated in mice with NPY abrogated from sympathetic neurons. The loss of NPY in sympathetic neurons whitened interscapular BAT, reducing its thermogenic ability and decreasing energy expenditure before the onset of obesity. It also caused adult-onset obesity of mice fed on a regular chow diet and rendered them more susceptible to diet-induced obesity without increasing food consumption. Our results indicate that, relative to central NPY, peripheral NPY produced by sympathetic nerves has the opposite effect on body weight by sustaining energy expenditure independently of food intake.

Metabolic diseases are caused by a prolonged energy imbalance, and adipose tissue is known to be the main contributor. We previously reported that ZIP13, an Slc39a transporter whose deficiency causes Ehlers-Danlos syndrome spondylocheirodysplastic type 3 associated with lipoatrophy, inhibits the adipocyte browning pathway by modulating intracellular zinc status. The precise mechanisms of how ZIP13 regulates the homeostasis of adipose tissue remain unclear and therefore, we investigated the role of ZIP13 in mature adipocytes using adipocyte-specific Zip13 -deficient mice. We herein demonstrate that these mice show accelerated lipolysis and reduced respiratory exchange ratio. In addition, abundance of iron and zinc balance were altered during differentiation in normal adipocytes, whereas iron distribution was substantially affected in Zip13 -deficient adipocytes, which downregulated PDE activity and enhanced β-adrenergic receptor signaling pathways. Importantly, we confirmed that ZIP13 could transport both zinc and iron, using the Xenopus oocyte transport system and in silico structural dynamics simulations, and that the defect in iron distribution perturbs proper lipolysis. Together, these results illustrate that ZIP13 acts as a key regulator for lipolysis in adipocytes via the proper use of metals, and that the ZIP13-iron axis plays an important role in regulation of lipid metabolism. ### Competing Interest Statement The authors have declared no competing interest. * RER : respiratory exchange ratio HFD : high-fat-diet STD : standard diet ER : endoplasmic reticulum PKA : protein kinase A ICP-MS : inductively coupled plasma mass spectrometry EDSSPD3 : Ehlers-Danlos syndrome spondylocheirodysplastic type 3 NEFA : nonesterified fatty acid MT : metallothionein PDE : phosphodiesterase 4F2hc : 4F2 cell-surface antigen heavy chain SVF : stromal vascular fraction IRP2 : iron regulatory protein 2 TfR : transferrin receptor Fth1 : ferritin heavy chain FTL : ferritin light chain NAC : N-acetylcysteine FACS : fluorescence-activated cell sorting WAT : white adipose tissue.

Abstract Background Fibrofatty changes in the myocardium of the right ventricular (RV) to right ventricular outflow tract (RVOT) in patients with Brugada syndrome (BrS) may contribute to ventricular conduction delay and ultimately in the development of ventricular fibrillation (VF). In patients with atrial fibrillation (AF), inflammatory infiltration of epicardial adipose tissue (EAT) into the atrial muscle, along with reduced quantity and quality of EAT, has been demonstrated to be associated with the development of AF. We hypothesized that EAT in the RVOT from the RV in patients with BrS may lead to organic abnormalities in the ventricular muscle, resulting in VF. Purpose The purpose of this study was to evaluate the quantity and quality of EAT in patients with BrS using cardiac computed tomography (CT) and to determine the relationship with the occurrence of VF. Methods We retrospectively evaluated 61 of 82 patients with BrS regularly followed in our outpatient clinic from January 2000 to December 2023, who underwent cardiac CT scans. Patients were divided into two groups: those with VF events during follow-up (VF event group) and those without events (VF non-event group). Patient background, various parameters, volume of epicardial adipose tissue (EAT), and CT values from cardiac CT scans were compared between the two groups. EAT volume and CT values were measured for the entire heart and four specific regions: right ventricle (RV-EAT), right ventricular outflow tract (RVOT) to pulmonary artery bifurcation (RVOT-EAT), left ventricle (LV-EAT), and the left coronary artery main trunk circumference (LV summit-EAT) were measured for four specific sites. Results Median age at first diagnosis of BrS was 43 years, 98% were male patients, 41 patients (71%) had symptomatic BrS, and 18 patients (31%) had a family history. During a median follow-up of 72 months (30-136 months), 22 patients (38%) had VF events, including 2 arrhythmic sudden deaths. The median time from diagnosis to the first VF event was 14.3 months (4.3-24.5 months). The VF event group had more overall EAT volume (98.3 cm3 [range: 77.4 to 120.3 cm3] vs. 70.1 cm3 [range: 53.8 to 98.0 cm3], P=0.02) and significantly more RV-EAT volume (18.4 cm3 [range: 11.5 to 28.0 cm3] vs. 11.0 cm3 [range: 7.9 to 18.3 cm3], P=0.008). The CT value of RV-EAT was significantly lower in the VF event group (-83.1±6.1 vs -78.0±6.2, P=0.003), although the RV-EAT/LV-EAT density ratio was not different between the two groups (1.01±0.05 vs 0.99±0.07, P=0.14). On the other hand, the density ratio of RVOT-EAT/LV-EAT was significantly lower in the VF event group (0.95±0.08 vs. 1.00±0.08, P=0.03). Conclusions EAT analysis via CT in patients with BrS revealed that those experiencing VF events during follow-up tended to exhibit greater RV-EAT volume, lower CT values of RV-EAT, and higher CT values of RVOT-EAT density. These findings suggest EAT involvement in VF occurrence in patients with BrS.

Endothelial dysfunction may trigger coronary spastic angina (CSA). However, the risk factors for CSA in young patients remain unclear. This study aimed to investigate the age-dependent role of serum uric acid levels in patients with CSA. We enrolled 423 patients who underwent an ergonovine tolerance test during coronary angiography for the CSA evaluation. We categorized the patients as (1) young (age ≤ 65 years) CSA-positive (n = 33), (2) young CSA-negative (n = 138), (3) elderly (age > 66 years) CSA-positive (n = 42), and (4) elderly CSA-negative (n = 210) groups. In the young groups, the smoker proportion (57.6 vs. 38.4

Choline is an essential nutrient for cellular metabolism, including the biosynthesis of phospholipids, neurotransmitters, and one-carbon metabolism. A critical step of choline catabolism is the mitochondrial import and synthesis of chorine-derived methyl donors, such as betaine. However, the underlying mechanisms and the biological significance of mitochondrial choline catabolism remain insufficiently understood. Here, we report that a mitochondrial inner-membrane protein SLC25A48 controls mitochondrial choline transport and catabolism in vivo. We demonstrate that SLC25A48 is highly expressed in brown adipose tissue and required for whole-body cold tolerance, thermogenesis, and mitochondrial respiration. Mechanistically, choline uptake into the mitochondrial matrix via SLC25A48 facilitates betaine synthesis and one-carbon metabolism. Importantly, cells lacking SLC25A48 exhibited reduced synthesis of purine nucleotides and failed to initiate the G1-to-S phase transition, thereby leading to cell death. Taken together, the present study identified SLC25A48 as a mitochondrial carrier that mediates choline import and plays a critical role in mitochondrial respiratory capacity, purine nucleotide synthesis, and cell survival.

The Ras homology (Rho) family of GTPases serves various functions, including promotion of cell migration, adhesion, and transcription, through activation of effector molecule targets. One such pair of effectors, the Rho‐associated coiled‐coil kinases (ROCK1 and ROCK2), induce reorganization of actin cytoskeleton and focal adhesion through substrate phosphorylation. Studies on ROCK knockout mice have confirmed that ROCK proteins are essential for embryonic development, but their physiological functions in adult mice remain unknown. In this study, we aimed to examine the roles of ROCK1 and ROCK2 proteins in normal adult mice. Tamoxifen (TAM)‐inducible ROCK1 and ROCK2 single and double knockout mice (ROCK1flox/flox and/or ROCK2flox/flox;Ubc‐CreERT2) were generated and administered a 5‐day course of TAM. No deaths occurred in either of the single knockout strains, whereas all of the ROCK1/ROCK2 double conditional knockout mice (DcKO) had died by Day 11 following the TAM course. DcKO mice exhibited increased lung tissue vascular permeability, thickening of alveolar walls, and a decrease in percutaneous oxygen saturation compared with noninducible ROCK1/ROCK2 double‐floxed control mice. On Day 3 post‐TAM, there was a decrease in phalloidin staining in the lungs in DcKO mice. On Day 5 post‐TAM, immunohistochemical analysis also revealed reduced staining for vascular endothelial (VE)‐cadherin, β‐catenin, and p120‐catenin at cell–cell contact sites in vascular endothelial cells in DcKO mice. Additionally, VE‐cadherin/β‐catenin complexes were decreased in DcKO mice, indicating that ROCK proteins play a crucial role in maintaining lung function by regulating cell–cell adhesion.