Journal of applied physiology最新文献

{"title":"In vivo intracellular Ca²⁺ profiles after eccentric rat muscle contractions: addressing the mechanistic bases for repeated bout protection.","authors":"Ayaka Tabuchi, Yudai Kikuchi, Ryo Takagi, Yoshinori Tanaka, Daisuke Hoshino, David C Poole, Yutaka Kano","doi":"10.1152/japplphysiol.00164.2024","DOIUrl":"10.1152/japplphysiol.00164.2024","url":null,"abstract":"<p><p>Eccentric contractions (ECC) are accompanied by the accumulation of intracellular calcium ions ([Ca²⁺]_i) and induce skeletal muscle damage. Suppressed muscle damage in repeated bouts of ECC is well characterized; however, whether it is mediated by altered Ca²⁺ profiles remains unknown. We tested the hypothesis that repeated ECC suppresses Ca²⁺ accumulation via adaptations in Ca²⁺ regulation. Male Wistar rats were divided into two groups: ECC single bout (ECC-SB) and repeated bout (ECC-RB). Tibialis anterior (TA) muscles were subjected to ECC (40 times, 5 sets) once (ECC-SB) or twice 14 days apart (ECC-RB). Under anesthesia, the TA muscle was loaded with Ca²⁺ indicator Fura 2-AM, and the 340/380 nm ratio was evaluated as [Ca²⁺]_i. Ca²⁺ handling proteins were measured by Western blots. ECC induced [Ca²⁺]_i increase in both groups, but ECC-RB evinced a markedly suppressed [Ca²⁺]_i (Time: <i>P</i> < 0.01, Group: <i>P</i> = 0.0357). Five hours post-ECC, in contrast to the localized [Ca²⁺]_i accumulation in ECC-SB, ECC-RB exhibited lower and more uniform [Ca²⁺]_i (<i>P</i> < 0.01). In ECC-RB, mitochondria Ca²⁺ uniporter complex (MCU) components MCU and MICU2 were significantly increased pre-second ECC bout (<i>P</i> < 0.01), and both SERCA1 and MICU1 were better preserved after contractions (<i>P</i> < 0.01). Fourteen days after novel ECC, skeletal muscle mitochondrial Ca²⁺ regulating proteins were elevated. Following subsequent ECC, [Ca²⁺]_i accumulation and muscle damage were suppressed and SERCA1 and MICU1 preserved. These findings suggest that tolerance to a subsequent ECC bout is driven, at least in part, by enhanced mitochondrial and sarcoplasmic reticulum Ca²⁺ regulation.<b>NEW & NOTEWORTHY</b> We demonstrated a reduced [Ca²⁺]_i profile with suppressed muscle damage after a repeated bout of ECC in vivo: the ECC-induced immediate [Ca²⁺]_i increase was suppressed and the persistence of increased [Ca²⁺]_i with localized accumulation was diminished after repeated ECC. This effect occurred consonant with the upregulation of the mitochondrial Ca²⁺ uniporter complex and better preservation of SERCA1 and MICU1. These findings suggest that the mechanistic bases for repeated bout protection involve adaptation of Ca²⁺ regulation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1-12"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142639072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence on sex differences in sports performance.","authors":"Michael J Joyner, Sandra K Hunter, Jonathon W Senefeld","doi":"10.1152/japplphysiol.00615.2024","DOIUrl":"10.1152/japplphysiol.00615.2024","url":null,"abstract":"<p><p>Sex differences in sports performances continue to attract considerable scientific and public attention, driven in part by high profile cases of: <i>1</i>) biological male (XY) athletes who seek to compete in the female category after gender transition, and <i>2</i>) XY athletes with medical syndromes collectively known as disorders or differences of sex development (DSDs). In this perspective, we highlight scientific evidence that informs eligibility criteria and applicable regulations for sex categories in sports. There are profound sex differences in human performance in athletic events determined by strength, speed, power, endurance, and body size such that males outperform females. These sex differences in athletic performance exist before puberty and increase dramatically as puberty progresses. The profound sex differences in sports performance are primarily attributable to the direct and indirect effects of sex-steroid hormones and provide a compelling framework to consider for policy decisions to safeguard fairness and inclusion in sports.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"274-281"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142882038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of body posture on pulmonary diffusing capacity at rest and during exercise in endurance-trained and untrained individuals.","authors":"Andrew R Brotto, Stephanie de Waal, Andrew W D'Souza, Rhys I Beaudry, Cameron M Ehnes, Sophie É Collins, Desi P Fuhr, Sean van Diepen, Michael K Stickland","doi":"10.1152/japplphysiol.00447.2024","DOIUrl":"10.1152/japplphysiol.00447.2024","url":null,"abstract":"<p><p>Endurance-trained athletes exhibit a greater diffusing capacity for carbon monoxide (DLCO) at rest and during exercise as compared with untrained individuals; however, the mechanism(s) are unclear. The supine position translocates blood centrally and can be used to investigate DLCO responses independent of metabolic rate. We hypothesized that endurance-trained individuals would have a greater DLCO response to postural change at rest as compared with untrained and that the supine position would elicit a greater DLCO response as compared with the upright position during exercise in both groups. Fourteen endurance-trained (Trained) individuals (V̇o_2peak: 61.1 ± 4.4 mL·kg^-1·min^-1) and 14 untrained individuals (V̇o_2peak: 37.4 ± 3.0 mL·kg^-1·min^-1) completed DLCO maneuvers at rest and during exercise in the upright and supine position. At rest, there was a significant group-by-position interaction (<i>P</i> = 0.02) effect on DLCO with post hoc analysis determining DLCO increased from upright to supine position in Trained (<i>P</i> < 0.01), but not untrained (<i>P</i> = 0.58). There was no effect of position on exercising DLCO (<i>P</i> = 0.16) regardless of group; however, pulmonary capillary blood volume (V_C) was increased with supine exercise (<i>P</i> = 0.03). There was an apparent plateau in DLCO and V_C in the Trained group near-maximal exercise as Trained failed to increase DLCO (<i>P</i> = 0.25) and Vc (<i>P</i> = 0.46) up to near-maximal exercise. Trained individuals demonstrate greater DLCO recruitment with postural change at rest suggesting a greater ability to recruit/distend the pulmonary microvasculature. However, the supine position did not augment DLCO as compared with upright position in Trained individuals near-maximal exercise, suggesting a plateau may be reached at maximal exercise.<b>NEW & NOTEWORTHY</b> We demonstrate that the supine position increases resting DLCO significantly more in endurance-trained individuals as compared with untrained individuals. Furthermore, the supine position increases pulmonary capillary blood volume, but not diffusing capacity during exercise. Lastly, there was an apparent plateau in DLCO and V_C in the Trained group suggesting the pulmonary microvasculature may reach a morphological limit.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"301-310"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142835957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Respiratory muscle strength pre- and post-maximal apneas in a world champion breath-hold diver.","authors":"Joseph W Duke, Colin D Hubbard, Dario Vrdoljak, Geoff B Coombs, Andrew T Lovering, Ivan Drvis, Željko Dujić, Nikola Foretic","doi":"10.1152/japplphysiol.00671.2024","DOIUrl":"10.1152/japplphysiol.00671.2024","url":null,"abstract":"<p><p>Maximal static dry, that is, on land, apneas (breath-holds) result in severe hypoxemia and hypercapnia and have easy-going and struggle phases. During the struggle phase, the respiratory muscles involuntarily contract against the closed glottis in increasing frequency and magnitude, that is, involuntary breathing movements (IBMs). IBMs during maximal static apnea have been suggested to fatigue respiratory muscles, but this has yet to be measured. Thus, the purpose of this study was to quantify respiratory muscle strength pre- and post-apneas in an elite, world champion, world record-holding apneist. To do so, maximal inspiratory and expiratory pressure maneuvers (MIP and MEP, respectively) were performed pre- and post-apnea protocol, which included three preparatory apneas with 2.5-min rest. All preparatory apneas were ended after the participant reported 7-10 IBMs. Next, he performed three maximal static dry apneas with 5-min rest in between. The participant had maximal apneas lasting 363, 408, and 460 s. Including preparatory apneas, the participant's total apnea duration was 33.4 min in 57.0 min. Following the apnea protocol, that is, pre versus post, there was no change in MIP (-124.2 vs. -123.6 cmH₂O) or MEP (259.4 vs. 262.5 cmH₂O). These data, albeit in a single individual, suggest that respiratory muscle strength is not impacted by maximal static breath-holds. This could be the result of training and/or be a feature of this individual that allows him to excel in this sport.<b>NEW & NOTEWORTHY</b> Previous work has suggested that respiratory muscle fatigue may result from maximal breath-holds but this has not been measured. We measured respiratory muscle strength pre- and post-maximal apneas in a world champion breath-hold diver. We found no change in respiratory muscle strength following a series of apneas. This may be an adaptation of the diver's training or a feature of their physiology that allows them to be successful in this physiologically challenging sport.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"66-72"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Voluntary activation of maximal single and all finger power grip contractions.","authors":"Daanish Chauhan, Tivyan Aruneethan, Tina Tran, Jennifer Zarnett-Klein, Eshaan Shah, Sarira Behnia, Michael T Paris","doi":"10.1152/japplphysiol.00650.2024","DOIUrl":"10.1152/japplphysiol.00650.2024","url":null,"abstract":"<p><p>When all four fingers are engaged together during a grip strength contraction, the force produced by an individual finger is less than the force produced when it acts in isolation. The purpose of this study was to evaluate whether the reduced force output of a digit during an all-finger grip contraction is due to a decline in voluntary activation. Fifteen young adults (<i>n</i> = 7 females) completed voluntary contractions of the index finger in isolation and all fingers together in a dynamometer capable of separately recording forces from each finger during voluntary and electrically evoked contractions. The median and ulnar nerves were electrically stimulated simultaneously at the elbow to record individual finger flexion forces from doublet (100 Hz) pulses. Doublet stimulations were applied during and immediately following contractions at 50, 65, 85, and 100% maximal voluntary contraction (MVC) forces. Two-way ANOVAs were used to compare the effects of sex and finger (single vs. all) on flexion forces and voluntary activation. The index finger produced ∼25% more force when engaged in isolation compared with the all-finger contraction; however, there were no differences in voluntary activation between the single and all-finger MVCs (<i>P</i> = 0.344). The index finger force deficit was larger in females compared with males (34 vs. 18%, <i>P</i> = 0.030), but this was not explained by sex-related differences in voluntary activation. These data indicate that the additional force produced during single-finger contractions is not due to an alteration in voluntary activation, as all-finger contractions display near-maximal activation of each digit.<b>NEW & NOTEWORTHY</b> The deficit in finger flexion force when multiple digits are engaged is well characterized and often attributed to reduced motor unit activation. Using a custom-built, multifinger dynamometer, we report that the index-finger force deficit may not be related to a deficit in voluntary activation. Furthermore, the index-finger force deficit was greater in females compared with males, but this was also not related to sex-related differences in voluntary activation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"45-54"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142728910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flow-mediated dilation decreases in women, but not men, following mild acute intermittent hypoxia.","authors":"Sara E Mascone, Jacqueline K Limberg, Emily F Blake, Cynthia M Weiner, Lauren E Eagan, Shannon E Khan, Sushant M Ranadive","doi":"10.1152/japplphysiol.00513.2024","DOIUrl":"10.1152/japplphysiol.00513.2024","url":null,"abstract":"<p><p>Acute, intermittent exposure to mild hypoxia increases sympathetic nervous system activity, decreases arterial shear rate, and increases blood pressure (BP) in young men. Given that the BP-raising effects of intermittent hypoxia (IH) are less evident in young women, we sought to examine the influence of sex on macro- and microvascular function following IH. BP, macrovascular function [brachial artery flow-mediated dilation (FMD)], microvascular function [reactive hyperemia area under the curve (RHAUC)], and brachial artery shear rate [shear rate area under the curve (SRAUC)] were measured before and following 30 min of IH in 18 young adults (8 women, 23 ± 5 yr). IH elicited an average nadir blood oxygen saturation ([Formula: see text]) of 92 ± 3% (<i>P</i> < 0.0001 vs. baseline). In men, brachial systolic (bSBP; 116 ± 6 to 122 ± 7 mmHg, <i>P</i> = 0.001) and diastolic (bDBP; 116 ± 6 to 122 ± 7 mmHg, <i>P</i> = 0.001) BPs increased from baseline following IH. bSBP (110 ± 8 to 111 ± 7 mmHg, <i>P</i> = 0.67) and bDBP (64 ± 7 to 68 ± 7 mmHg, <i>P</i> = 0.12) were unchanged in women after IH. Men maintained macrovascular function after IH (ΔFMD: 0.75 ± 2.44%), whereas women exhibited a decline (ΔFMD: -3.09 ± 2.64%, <i>P</i> = 0.006 vs. men). Microvascular function and shear rate declined following IH independent of sex (RHAUC: 597 ± 306 to 467 ± 205 mL/min, <i>P</i> = 0.049; SRAUC: 1772 ± 907 to 1439 ± 596 s^-1, <i>P</i> = 0.040). Acute mild IH increases BP in healthy men but not women. In women, both micro- and macrovascular functions are lower following acute mild IH; in contrast, only microvascular function is lower in men. The sex-specific effects of IH on BP and macrovascular function may have important implications for the potential beneficial effects of IH.<b>NEW & NOTEWORTHY</b> The present study aimed to investigate the influence of sex on vascular responses to 30 min of acute, mild intermittent hypoxia. Men and women exhibited similar decreases in arterial shear rate and microvascular function after intermittent hypoxia. Although men exhibited increases in blood pressure but no changes in macrovascular function, women exhibited significant decreases in macrovascular function despite no changes in blood pressure. Sex may influence the potential hormetic effects of intermittent hypoxia.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"99-106"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11918295/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142828540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An acute bout of 4 × 4-min or 10 × 1-min HIIT improves β cell glucose sensitivity in postmenopausal females with type 2 diabetes: a secondary analysis.","authors":"J L Low, A Marcotte-Chénard, R Tremblay, H Islam, K Falkenhain, W M Mampuya, A Mari, A M McManus, E Riesco, J P Little","doi":"10.1152/japplphysiol.00777.2024","DOIUrl":"10.1152/japplphysiol.00777.2024","url":null,"abstract":"<p><p>Improvements in glycemic control following acute exercise are typically attributed to improved postexercise insulin sensitivity (IS) with comparatively little known about how acute exercise impacts β cell function, especially in postmenopausal females. We determined how two high-intensity interval training (HIIT) protocols, matched for total estimated energy expenditure, impact β cell function in postmenopausal females with type 2 diabetes. Thirteen postmenopausal females (70 ± 5 yr; 12 ± 7 yr since diagnosis, 80.9 ± 13.8 kg, 32.4 ± 5.6 kg·m²; HbA1c-49.8 ± 10.3 mmol/mol [6.7 ± 1.0]) living with type 2 diabetes were included in this semirandomized crossover trial. The trial involved an initial resting control condition followed by two HIIT conditions [4 × 4-min HIIT (HIIT4) and 10 × 1-min HIIT (HIIT10)] completed in a randomized order 2-4 days apart. β cell function (glucose sensitivity) and insulin sensitivity were determined from a 2-h mixed-meal tolerance test performed 2 h after rest or HIIT. Both HIIT4 and HIIT10 significantly improved β cell glucose sensitivity compared with control (15 pmol/min/m²/[mmol/L], [95% confidence interval (CI) 6, 23]; <i>P</i> = 0.002 and 16 pmol/min/m²/[mmol/L], [95% CI 7, 25]; <i>P</i> = 0.002, respectively), with no difference between HIIT protocols (1 [-8, 10], <i>P</i> = 0.79). There were no significant differences in IS metrics (Matsuda index, OGIS, Stumvoli, and QUICKI) between the conditions. An acute bout of 4 × 4-min or 10 × 1-min HIIT improves β cell glucose sensitivity in postmenopausal females living with type 2 diabetes. ClinicalTrials.gov: NCT04986345.<b>NEW & NOTEWORTHY</b> This is the first study to explore the effects of acute high-intensity interval training (HIIT) on β cell function in postmenopausal women with type 2 diabetes. Our crossover trial compares two HIIT protocols, matched for total estimated energy expenditure, examining their impacts on β cell function and insulin sensitivity. Despite the absence of an insulin-sensitizing effect, we show robust effects of HIIT on β-cell function, including an improvement in β-cell glucose sensitivity.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"311-317"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142853862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multidimensional assessment of exertional dyspnea in young healthy males and females who select unsatisfied inspiration at peak exercise.","authors":"Reid A Mitchell, Alanna S Hind, Olivia N Ferguson, Morgan Flynn, Jem I Arnold, Satvir S Dhillon, Neil D Eves, A William Sheel, Jordan A Guenette","doi":"10.1152/japplphysiol.00420.2024","DOIUrl":"10.1152/japplphysiol.00420.2024","url":null,"abstract":"<p><p>Historically, it was thought that healthy humans predominantly described their breathing as a sense of increased work or effort (W/E) during maximal exercise. However, emerging data show that many healthy adults select unpleasant dyspnea descriptors such as \"unsatisfied inspiration\" (UI), with relatively more females selecting UI than males. We hypothesized that males and females who select UI would report higher dyspnea intensity ratings during exercise, select more distressing dyspnea qualities post exercise, and have greater inspiratory constraints than those who do not. Sixty-four healthy, nonsmokers (32 males:32 females; 23 ± 5 yr) completed questionnaires, pulmonary function tests, and maximal incremental cycling with detailed dyspnea evaluation. Males in UI and non-UI subgroups reported similar Borg 0-10 dyspnea intensity ratings of W/E, UI, and unsatisfied expiration (UE) (all <i>P</i> > 0.05). Females in the UI subgroup reported significantly higher UI and UE ratings than females in the non-UI subgroup (both <i>P</i> < 0.01). Both UI subgroups reported greater air hunger, chest tightness, and mental breathing effort than non-UI participants (all <i>P</i> < 0.05). In males only, masculine gender was negatively correlated (ρ = -0.402, <i>P</i> = 0.02) and anxiety positively correlated (ρ = 0.363, <i>P</i> = 0.04) with submaximal UI ratings. Females with UI had smaller peak tidal volume (Vt) [1.74 (0.32) vs. 2.06 (0.33) L, <i>P</i> = 0.03] than non-UI females; and Vt was negatively correlated with submaximal (ρ = -0.496, <i>P</i> = 0.004) and peak (ρ = -0.495, <i>P</i> = 0.004) UI ratings in all females. There were no differences in Vt or correlations between Vt and dyspnea in male subgroups. Absolute lung volumes and psychosocial factors appear important in understanding sex differences in the perception of UI during exercise.<b>NEW & NOTEWORTHY</b> The mechanisms of sex-based differences in the sensation of unsatisfied inspiration (UI) in healthy humans during exercise are poorly understood. We found that females who selected UI at peak exercise had worse dyspnea intensity ratings throughout exercise. Both sexes who selected UI at peak exercise also reported more distressing dyspnea qualities post exercise. Psychosocial factors appeared to influence male dyspnea perception, whereas smaller absolute lung volumes correlated with worse UI ratings in females.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"73-88"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142769267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Myonuclear and satellite cell content of the vastus lateralis and soleus with 70 days of simulated microgravity and the NASA SPRINT exercise program.","authors":"Chad M Skiles, Gerard Boyd, Aaron Gouw, Ethan Robbins, Kiril Minchev, Jeffrey Ryder, Lori Ploutz-Snyder, Todd A Trappe, Scott Trappe","doi":"10.1152/japplphysiol.00468.2024","DOIUrl":"10.1152/japplphysiol.00468.2024","url":null,"abstract":"<p><p>We previously observed a range of whole muscle and individual slow and fast myofiber size responses (mean: +4 to -24%) in quadriceps (vastus lateralis) and triceps surae (soleus) muscles of individuals undergoing 70 days of simulated microgravity with or without the NASA SPRINT exercise countermeasures program. The purpose of the current investigation was to further explore, in these same individuals, the content of myonuclei and satellite cells, both of which are key regulators of skeletal muscle mass. Individuals completed 6° head-down-tilt bedrest (BR, <i>n</i> = 9), bedrest with resistance and aerobic exercise (BRE, <i>n</i> = 9), or bedrest with resistance and aerobic exercise and low-dose testosterone (BRE + T, <i>n</i> = 8). The number of myonuclei and satellite cells associated with each slow [myosin heavy chain (MHC) I] and fast (MHC IIa) myofiber in the vastus lateralis was not changed (<i>P</i> > 0.05) pre- to postbedrest within the BR, BRE, or BRE + T groups. Similarly, in the soleus, the number of myonuclei associated with each slow and fast myofiber, and the number of satellite cells associated with each slow myofiber were not changed (<i>P</i> > 0.05) pre- to postbedrest within the BR, BRE, or BRE + T groups. It appears that even with relatively large perturbations in muscle mass over a few months of simulated microgravity, or with partially or completely effective exercise countermeasures, human skeletal muscle tightly regulates the abundance of myonuclei and satellite cells. Thus, exercise countermeasures efficacy for skeletal muscle atrophy appears to be independent of myonuclei and satellite cell abundance.<b>NEW & NOTEWORTHY</b> This study showed that after 70 days of simulated microgravity, human skeletal muscle does not alter the number of nuclei or satellite cells associated with slow or fast myofibers in the two muscle groups most negatively influenced by microgravity exposure [i.e., quadriceps (vastus lateralis) and triceps surae (soleus)]. Furthermore, the efficacy of exercise countermeasures for maintaining the mass of these muscles does not appear to be related to the myocellular content of nuclei or satellite cells.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"195-202"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142800875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An IL-6 promoter variant (-174 G/C) augments IL-6 production and alters skeletal muscle transcription in response to exercise in mice.","authors":"L E Watson, C L MacRae, P Kallingappa, Y Cao, X Li, C P Hedges, R F D'Souza, N Fleming, K M Mellor, T L Merry","doi":"10.1152/japplphysiol.00391.2024","DOIUrl":"10.1152/japplphysiol.00391.2024","url":null,"abstract":"<p><p>Interleukin-6 (IL-6) is produced and secreted by skeletal muscle cells during exercise and plays an important role in mediating metabolic responses to exercise. The promoter region of the IL-6 gene contains a common genetic variant (-174 G/C, rs1800795), which may alter responses to exercise training. To isolate the impact of this gene variant on exercise-induced IL-6 expression and skeletal muscle transcription responses following exercise, we generated knock-in mice with a GG or variant CC genotype for the murine homolog of rs1800795. The overall gross metabolic phenotype of resting mice was similar between genotypes; however, following acute treadmill running, the variant CC genotype was associated with a greater increase in skeletal muscle <i>Il6</i> mRNA and circulating IL-6. Furthermore, we observed that mice with the variant CC genotype exhibited sex-specific differences in skeletal muscle master metabolism regulatory genes and had greater increases in genes controlling mitochondrial biogenesis in skeletal muscle post exercise. However, there was no effect of genotype on exercise-induced skeletal muscle glycogen depletion, circulating free fatty acids, blood glucose and lactate production, or exercise-responsive gene expression in subcutaneous fat. These findings suggest that the IL-6 promoter variant -174 G/C may result in enhanced skeletal muscle adaptations in response to exercise training and could mean that individuals with the \"C\" allele may more readily gain improvements in metabolic health in response to exercise training.<b>NEW & NOTEWORTHY</b> Interleukin-6 (IL-6) is produced and secreted by skeletal muscle during exercise and mediates metabolic responses to exercise. A common variant in the IL-6 promoter region (-174G/C) may alter responses to exercise training. Mice with the variant \"CC\" genotype exhibited higher skeletal muscle IL-6 mRNA and circulating IL-6 levels post exercise, as well as altered skeletal muscle gene transcription. This suggests that this variant might enhance muscle adaptations to exercise, potentially benefiting metabolic health.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"213-225"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142813285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}