Dr. Youngil Lee

PURPOSE: Maternal and postnatal overnutrition has been linked to an increased risk of cardiometabolic diseases in offspring. This study investigated the impact of adult-onset voluntary wheel running to counteract cardiometabolic risks in female offspring exposed to a life-long high-fat, high-sucrose (HFHS) diet.

METHODS: Dams were fed either a HFHS or a low-fat, low-sucrose (LFLS) diet starting from 8 weeks prior to pregnancy and continuing throughout gestation and lactation. Offspring followed their mothers' diets. At 15 weeks of age, they were divided into sedentary (Sed) or voluntary wheel running (Ex) groups, resulting in four groups: LFLS/Sed (n = 10), LFLS/Ex (n = 5), HFHS/Sed (n = 6), HFHS/Ex (n = 5). Cardiac function was assessed at 25 weeks, with tissue collection at 26 weeks for mitochondrial respiratory function and protein analysis. Data were analyzed using two-way ANOVA.

RESULTS: While maternal HFHS diet did not affect the offspring's body weight at weaning, continuous HFHS feeding post-weaning resulted in increased body weight and adiposity, irrespective of the exercise regimen. HFHS/Sed offspring showed increased left ventricular wall thickness and elevated expression of enzymes involved in fatty acid transport (CD36, FABP3), lipogenesis (DGAT), glucose transport (GLUT4), oxidative stress (protein carbonyls, nitrotyrosine), and early senescence markers (p16, p21). Their cardiac mitochondria displayed lower oxidative phosphorylation (OXPHOS) efficiency and reduced expression of OXPHOS complexes and fatty acid metabolism enzymes (ACSL5, CPT1B). However, HFHS/Ex offspring mitigated these effects, aligning more with LFLS/Sed offspring.

CONCLUSIONS: Adult-onset voluntary wheel running effectively counteracts the detrimental cardiac effects of a lifelong HFHS diet, improving mitochondrial efficiency, reducing oxidative stress, and preventing early senescence. This underscores the significant role of physical activity in mitigating diet-induced cardiometabolic risks.

[Purpose] Endurance exercise induces muscle fiber-type shifting and autophagy; however, the potential role of autophagy in muscle fiber-type transformation remains unclear. This study examined the relationship between muscle fiber-type shifting and autophagy in the soleus (SOL) and extensor digitorum longus (EDL) muscles, which are metabolically discrete muscles.[Methods] Male C57BL/6J mice were randomly assigned to sedentary control (CON) and exercise (EXE) groups. After 1 week of acclimation to treadmill running, the mice in the EXE group ran at 12-15 m/min, 60 min/day, 5 days/week for 6 weeks. All mice were sacrificed 90 min after the last exercise session, and the targeted tissues were rapidly dissected. The right side of the tissues was used for western blot analysis, whereas the left side was subjected to immunohistochemical analysis.[Results] Endurance exercise resulted in muscle fiber-type shifting (from type IIa to type I) and autophagy (an increase in LC3-II) in the SOL muscle. However, muscle fiber-type transformation and autophagy were not correlated in the SOL and EDL muscles. Interestingly, in contrast to the canonical autophagy signaling pathways, our study showed that exercise-induced autophagy concurs with enhanced anabolic (increased p-AKTSer473/AKT and p-mTOR/mTORSer2448 ratios) and suppressed catabolic (reduced p-AMPKThr172/AMPK ratio) states.[Conclusion] Our findings demonstrate that chronic endurance exercise-induced muscle fiber-type transformation and autophagy occur in a muscle-specific manner (e.g., SOL). More importantly, our study suggests that endurance training-induced SOL muscle fiber-type transition may underlie metabolic modulations caused by the AMPK and AKT/mTOR signaling pathways rather than autophagy.

Background: Sudden cardiac death in young athletes is a rare and tragic occurrence. A pre-participation physical examination (PPE) is widely used to identify athletes who might be at risk of sudden cardiac death. High school athletes in Escambia, Okaloosa, Santa Rosa, and Walton counties in Florida undergo annual sports physicals through a local sports medicine outreach program. A resting electrocardiogram (ECG) was implemented during the 2022 PPE. The aim of this study was to document the efficacy of implementing ECGs and to highlight the cardiac abnormalities identified in young athletes as part of a 1-d PPE.
Methods: In total, 1,357 high school athletes (males = 879 and females = 478; age, 15.1 ± 1.3 years) completed a resting 12-lead ECG. These were interpreted by cardiologists using the International Criteria, with abnormal results being further investigated before final sports clearance. Descriptive statistics regarding ECG findings were analyzed.
Results: Twenty-three ECGs (1.7%) were classified as “abnormal” and were referred for further testing. Of these, 14 athletes were cleared to participate in sports, and 6 declined further evaluation. Three athletes, all males, were not cleared for sports participation. Of these, 2 athletes presented with Wolf-Parkinson-White syndrome (0.15%), and 1 athlete (0.10%) presented with dilated cardiomyopathy.
Conclusion: Adding ECG screening as part of a single-day PPE can be used as a tool in identifying cardiac abnormalities among young athletes. To our knowledge, this is the highest number of athletes screened during a PPE in 1 d nationwide.

Context : Latency is a reliable temporal metric used to evaluate sensorimotor integration of the fibularis longus (FL) and fibularis brevis (FB) during lateral ankle sprain perturbations. Currently, no clinical recommendations exist to select appropriate thresholds to evaluate the closed-loop reflex response of the lateral ankle musculature. The purpose of this study was to assess threshold value on latency of the FL and FB during an unanticipated inversion perturbation that simulates the mechanism of a lateral ankle sprain.
Design : Descriptive laboratory study.
Methods : Twenty healthy adults with no history of lateral ankle sprain injury completed an unanticipated single-leg drop landing onto a 25° laterally inclined force platform from a height of 30 cm. Surface electromyography recorded muscle activity data from the FL and FB during the inversion perturbation. Latency was identified at points where muscle activity exceeded 2, 5, and 10 SD above the average muscle activity 200 milliseconds prior to foot contact, and compared across threshold value using a 1-way analysis of variance ( P < .05).
Results : The 2 SD threshold was significantly shorter than both 5 SD and 10 SD thresholds for the FL ( P < .01) and FB ( P < .01). Likewise, the 5 SD threshold was significantly shorter than the 10 SD thresholds for FL ( P = .004) and FB ( P = .003).
Conclusions : More sensitive thresholds results in a shorter closed-loop reflexive response compared to the more rigorous thresholds. We recommend that selection of the appropriate threshold to identify latency of the lateral ankle musculature should be based on the device used to simulate a lateral ankle sprain and the ankle inversion velocity produced during the ankle inversion perturbation.

Background: Sudden cardiac death in young athletes is a rare and tragic occurrence. A preparticipation physical examination (PPE) is widely used to identify athletes who might be at risk of sudden cardiac death. High school athletes in Escambia, Okaloosa, Santa Rosa, and Walton counties in Florida undergo annual sports physicals through a local sports medicine outreach program. A resting electrocardiogram (ECG) was implemented during the 2022 PPE. The aim of this study was to document the efficacy of implementing ECGs and to highlight the cardiac abnormalities identified in young athletes as part of a 1-d PPE.
Methods: In total, 1,357 high school athletes (males = 879 and females = 478; age, 15.1 ± 1.3 years) completed a resting 12-lead ECG. These were interpreted by cardiologists using the International Criteria, with abnormal results being further investigated before final sports clearance. Descriptive statistics regarding ECG findings were analyzed.
Results: Twenty-three ECGs (1.7%) were classified as " abnormal " and were referred for further testing. Of these, 14 athletes were cleared to participate in sports, and 6 declined further evaluation. Three athletes, all males, were not cleared for sports participation. Of these, 2 athletes presented with Wolf-Parkinson-White syndrome (0.15%), and 1 athlete (0.10%) presented with dilated cardiomyopathy.
Conclusion: Adding ECG screening as part of a single-day PPE can be used as a tool in identifying cardiac abnormalities among young athletes. To our knowledge, this is the highest number of athletes screened during a PPE in 1 d nationwide.

IntroductionMetabolic disorder promotes premature senescence and poses more severe cardiac dysfunction in females than males. Although endurance exercise (EXE) has been known to confer cardioprotection against metabolic diseases, whether EXE-induced cardioprotection is associated with mitigating senescence in females remains unknown. Thus, the aim of the present study was to examine metabolic disorder-induced cardiac anomalies (cellular senescence, metabolic signaling, and autophagy) using a mouse model of obese/type 2 diabetes induced by a high-fat/high-fructose (HFD/HF) diet.MethodsFemale C57BL/6 mice (10 wk old) were assigned to three groups (n = 11/group): normal diet group (CON), HFD/HF group, and HFD/HF diet + endurance exercise (HFD/HF + EXE) group. Upon confirmation of hyperglycemia and overweight after 12 wk of HFD/HF diet, mice assigned to HFD/HF + EXE group started treadmill running exercise (60 min center dot d(-1), 5 d center dot wk(-1) for 12 wk), with HFD/HF diet continued.ResultsEXE ameliorated HFD/HF-induced body weight gain and hyperglycemia, improved insulin signaling and glucose transporter 4 (GLUT4) levels, and counteracted cardiac disruption. EXE reversed HFD/HF-induced myocyte premature senescence (e.g., prevention of p53, p21, p16, and lipofuscin accumulation), resulting in suppression of a senescence-associated secretory phenotype such as inflammation (tumor necrosis factor alpha and interleukin-1 beta) and oxidative stress (protein carbonylation). Moreover, EXE restored HFD/HF-induced autophagy flux deficiency, evidenced by increased LC3-II concomitant with p62 reduction and restoration of lysosome function-related proteins (LAMP2, CATHEPSIN L, TFEB, and SIRT1). More importantly, EXE retrieved HFD/HF-induced apoptosis arrest (e.g., increased cleaved CASPASE3, PARP, and TUNEL-positive cells).ConclusionsOur study demonstrated that EXE-induced antisenescence phenotypes, autophagy restoration, and promotion of propitiatory cell removal by apoptosis play a crucial role in cardiac protection against metabolic distress-induced cardiac disruption.

Introduction and aim: Non-alcoholic fatty liver disease (NAFLD) is one of the most common diseases in the United States. Metabolic distress (obese diabetes) is the main causative element of NAFLD. While there is no cure for NAFLD, endurance exercise (EEx) has emerged as a therapeutic strategy against NAFLD. However, mechanisms of EXE-induced hepatic protection especially in female subjects remain unidentified. Thus, the aim of the study is to examine molecular mechanisms of EXE-induced hepatic protection against diet-induced NAFLD in female mice. Material and methods: Nine-week-old female C57BL/6J mice were randomly divided into three groups: normal-diet control group (CON, n=11); high-fat diet/high-fructose group (HFD/HF, n=11); and HFD/HF+EEx group (HFD/HF+EEx, n=11). The mice assigned to HFD/HF and HFD/HF+EEx groups were fed with HFD/HF for 12 weeks, after which the mice assigned to the EEx group began treadmill exercise for 12 weeks, with HFD/HF continued. Results: EEx attenuated hepatic steatosis, reduced de novo lipogenesis (reduction in ATP -Citrate-Lyase and diacylglycerol-O-acyltransferase 1), and enhanced mitochondrial biogenesis and fatty-acid activation (oxidative phosphorylation enzymes and Acyl-CoA synthetase1). Also, EEx prevented upregulation of gluconeogenic proteins (glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphatase, and phosphoenolpyruvate-carboxykinase1), premature senescence (suppression of p53, p22, and p16, tumor-necrosis-factor-alpha, and interleukin-1 beta, and oxidative stress), and autophagy deficiency. Furthermore, EXE reversed apoptosis arrest (cleaved cysteine-dependent-aspartate-directed protease3 and Poly-(ADP-ribose)-polymerase1). Conclusion: EEx-mediated reparations of metabolic and redox imbalance (utilization of pentose phosphate pathway), and autophagy deficiency caused by metabolic distress critically contribute to preventing/delaying severe progression of NAFLD. Also, EEx-induced anti-senescence and cell turnover are crucial protective mechanisms against NAFLD. (C) 2022 Fundacion Clinica Medica Sur, A.C. Published by Elsevier Espana, S.L.U.

Doxorubicin (DOX) is a potent chemotherapeutic agent widely used for various types of cancer; however, its accumulation causes myotoxicity and muscle atrophy. Endurance exercise (EXE) has emerged as a vaccine against DOX-induced myotoxicity. However, potential molecular mechanisms of EXE-mediated myocyte protection for the unfavorable muscle phenotype remain unelucidated. In addition, most studies have identified the short-term effects of DOX and EXE interventions, but studies on the prolonged EXE effects used as adjuvant therapy for chronic DOX treatment are lacking. Twelve-week-old adult male C57BL/6J mice were assigned to four groups: sedentary treated with saline (SED-SAL, n = 10), endurance exercise treated saline (EXE-SAL, n = 10), sedentary treated with doxorubicin (SED-DOX, n = 10), and endurance exercise treated with doxorubicin (EXE-DOX, n = 10). Mice were intraperitoneally injected with DOX (5 mg/kg) or saline five times biweekly for eight weeks, while a treadmill running exercise was performed. Body composition was assessed and then soleus muscle tissues were excised for histological and biochemical assays. Our data showed that DOX aggravated body composition, absolute soleus muscle mass, and distinct pathological features; also, TOP2B upregulation was linked to DOX-induced myotoxicity. We also demonstrated that EXE-DOX promoted mitochondrial biogenesis (e.g., citrate synthase). However, no alterations in satellite cell activation and myogenesis factors in response to DOX and EXE interventions were observed. Instead, SED-DOX promoted catabolic signaling cascades (AKT-FOXO3 alpha-MuRF-1 axis), whereas EXE-DOX reversed its catabolic phenomenon. Moreover, EXE-DOX stimulated basal autophagy. We showed that the EXE-mediated catabolic paradigm shift is likely to rescue impaired muscle integrity. Thus, our study suggests that EXE can be recommended as an adjuvant therapy to ameliorate DOX-induced myotoxicity.

Autophagy/mitophagy, a cellular catabolic process necessary for sustaining normal cellular function, has emerged as a potential therapeutic strategy against numerous obstinate diseases. In this regard, endurance exercise (EXE)-induced autophagy/ mitophagy (EIAM) has been considered as a potential health-enriching factor in various tissues including the brain; however, underlying mechanisms of EIAM in the brain has not been fully defined yet. This study investigated the molecular signaling nexus of EIAM pathways in the cortex of the brain.C57BL/6 young male mice were randomly assigned to a control group(CON, n=12) and an endurance exercise group (EXE, n=12). Our data demonstrated that exercise-induced autophagy coincided with an enhanced anabolic state (p-AKT, p-mTOR, and p-p70S6K); furthermore, mitophagy concurred with enhanced mitochondrial turnover: increases in both fission (DRP1, BNIP3, and PINK1) and fusion (OPA1 and MFN2) proteins. In addition, neither oxidative stress nor sirtuins (SIRT) 1 and 3 were associated with EIAM; instead, the activation of AMPK as well as a JNK-BCL2 axis was linked to EIAM promotion. Collectively, our results demonstrated that EXE-induced anabolic enrichment did not hinder autophagy/mitophagy and that the concurrent augmentation of mitochondrial fusion and fusion process contributed to sustaining mitophagy in the cortex of the brain. Our findings suggest that the EXE-induced concomitant potentiation of the catabolic and anabolic state is a unique molecular mechanism that simultaneously contributes to recycling and rebuilding the cellular structure, leading to upholding healthy cellular environment. Thus, the current study provides a novel autophagy/mitophagy mechanism, from which groundbreaking pharmacological strategies of autophagy can be developed.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.