Physiological Reports

Objectives To examine the acute effects of a single bout of high-intensity interval training (HIIT) on fetal blood flow distribution during the third trimester of pregnancy. Methods Thirty-four healthy pregnant participants (mean age 31.6 years, standard deviation (SD) 4.1; gestational week 33.8 (SD 0.4) completed eight 30-second high-intensity cycling work-bouts interspersed with 2-minute rest periods. Fetal heart rate (FHR), maternal blood pressure, and Doppler-derived blood flow indices in the middle cerebral artery, umbilical artery and vein, and ductus venosus were assessed before and after exercise. We estimated fetal liver blood flow and the ratio of umbilical vein flow to ductus venosus. Maternal heart rate (HR) and FHR were recorded throughout exercise. Paired t-tests compared pre- and post-exercise values. Results No significant changes were observed in fetal blood flow indices or distribution following exercise. Average maternal HR and FHR during the work-bouts were 158 bpm (SD 16) and 152 bpm (SD 12), respectively. Following HIIT, maternal systolic blood pressure increased by 5 mmHg (95% CI 1 to 8, p=.014), maternal HR by 22 bpm (95% CI 15 to 28, p<.001), and FHR by 13 bpm (95% CI 10 to 17, p<.001). We recorded 16 instances of FHR above normal range during HIIT. Conclusion A single HIIT session in late pregnancy increased maternal blood pressure and HR and transiently elevated FHR but did not affect fetal blood flow indices or distribution. Brief episodes of fetal tachycardia were observed but appeared to be clinically insignificant. Future research should investigate the effects of repeated HIIT exposure during pregnancy.

Myocyte Enhancer Factor 2D (Mef2D) is a member of the Mef2 family. As a transcription factor, Mef2D regulates the expression of genes that impinge on cellular viability, tissue development, and fuel metabolism in a tissue dependent manner. Mef2D is expressed in the beta-cell, and overexpression and knockdown have been shown to modulate glucose stimulated insulin secretion. We sought to understand the role of Mef2D on beta-cell function and survival. To determine the function of Mef2D in the beta-cell, we built overexpression and knockdown INS-1 832/13 cell lines. We determined the effect of Mef2D overexpression or knockdown on mitochondrial respiration, insulin secretion, cell survival, and gene expression. Our data demonstrates that Mef2D knockdown enhances mitochondrial respiration, insulin secretion, and cell survival. Conversely, Mef2D overexpression inhibits mitochondrial respiration, insulin secretion, and cell survival. We demonstrate that some of this effect is due to modulated expression of the mitochondrial gene mtND6. These findings demonstrate that Mef2D overexpression is detrimental to beta-cell function and that Mef2D knockdown is beneficial. These data suggest that Mef2D may be a viable target to enhance functional beta-cell mass as a treatment for Type 1 and Type 2 Diabetes.

General anesthetics enable invasive experimentation but can affect cardiovascular and respiratory physiology, biasing preclinical outcomes. We compared five anesthetic regimens in adult male Wistar rats, tribromoethanol (TBE, 250 mg/kg i.p.), chloral hydrate (CH, 400 mg/kg i.p.), ketamine-xylazine (KX, 80/10 mg/kg i.p.), thiopental (TP, 80 mg/kg i.p.), and isoflurane (ISO, 4% induction, 2% maintenance), to investigate integrated cardiorespiratory and biochemical markers. Femoral arterial catheterization allowed continuous blood pressure (BP) and derived heart rate (HR) recordings, while ventilation was assessed through pletysmography at baseline (awake), during induction, and recovery phases of anesthesia. Variability was evaluated in the time and frequency domains, including HR, systolic blood pressure (SBP), and spontaneous baroreflex sensitivity. In an independent cohort of rats, butyrylcholinesterase (BChE), CK-MB, cTnI, and LDH were measured. Baseline BP was unchanged by TBE and TP, whereas all anesthetics affected HR. Minute ventilation and breathing frequency were reduced with all agents, while tidal volume decreased with KX and TBE only. LDH and cTnI were unaffected, BChE was reduced by KX, TBE, and ISO, and CK-MB increased with CH and KX. Variability analysis showed that all anesthetics depressed pulse-interval and SBP variability and shifted spectral power toward higher frequencies, while baroreflex sensitivity and effectiveness were consistently reduced. During recovery, KX and TP restored most variability indices, whereas CH, TBE, and ISO showed persistent suppression. These findings highlight distinct profiles of cardiovascular depression and biomarker responses across anesthetics and underscore the importance of accounting for autonomic variability when selecting different anesthetics in experimental protocols. HighlightsO_LIFive anesthetic regimens were tested in rats. C_LIO_LIAll anesthetics reduced ventilation, and KX and TBE also reduced tidal volume. C_LIO_LICH and KX increased CKMB, while KX, TBE and ISO reduced BChE. C_LIO_LIAll anesthetics reduced blood pressure variability and baroreflex sensitivity. C_LIO_LIVariability recovered with TP and KX, whereas CH, TBE and ISO showed persistent suppression. C_LI

Right ventricular failure (RVF) is a serious disease with a high mortality but no effective pharmacologic treatments. We reported RVF was reversed by chronic treatment with an 1A-adrenergic receptor (1A-AR) agonist. Recent studies suggest mitochondrial dysfunction contributes to RVF. Therefore, we investigated if reversal of RVF by chronic 1A-AR agonist treatment involved improved mitochondrial function. A mouse model of RVF caused by pulmonary artery constriction (PAC) for 2 wk was chronically treated for a further 2 wk. with a low dose of the 1A-AR agonist A61603 (10 ng/kg/day) or vehicle (no drug control). RV dysfunction was assessed from the fractional shortening of the RV outflow tract (RVOT FS). RVOT FS for sham controls (46.5 {+/-} 1.3 %, n = 9) was reduced 4 wk after PAC (27.6 {+/-} 1.5 %, n = 13, P < 0.0001), but was higher after PAC plus 2 wk A61603 treatment (34.5 {+/-} 0.6 %, n = 14, P < 0.001). RV myocardial respiration rate (O2 consumption) for sham controls (776 {+/-} 51 pM/s/mg, n = 9) was reduced 4 wk after PAC (493 {+/-} 28 pM/s/mg, n = 15, P <0.0001), but was higher after PAC plus 2 wk A61603 treatment (634 {+/-} 30 pM/s/mg, n = 11, P <0.05). RV myocardial ATP level for sham controls (3.3 {+/-} 0.1 mM, n = 10) was reduced 4 wk after PAC (1.9 {+/-} 0.1 mM, n = 6, P < 0.0001), but was higher after PAC plus 2 wk A61603 treatment (2.6 {+/-} 0.13 mM, n = 7, P < 0.01). In conclusion, reversal of RVF after chronic A61603 treatment involved reversal of mitochondrial dysfunction. Consistent with our previous studies, this study suggests that the 1A-AR is a therapeutic target to treat RVF. HighlightsRV failure is reported to involve mitochondrial dysfunction which might impair RV contraction by decreasing cardiomyocyte ATP level. Using the pulmonary artery constriction model of RV failure, we found that chronic treatment with an 1A-adrenergic receptor agonist increased RV myocardial respiration rate, increased RV myocardial ATP level, and increased RV function. These findings suggest that the 1A-adrenergic receptor is a therapeutic target for treating RV failure, and that the mechanism involves improved RV cardiomyocyte bioenergetic status.

ObjectivesThis study aimed to compare exercise-induced changes in serum and salivary concentrations of cardiac troponin-I (cTnI) in athletes during and after a marathon. MethodsThirty-six male runners were recruited. Eighteen participants in group 1 completed a marathon (42.195 km), while eighteen participants in group 2 did not undergo this exercise. Blood and saliva samples were collected at twelve different time points and then analyzed for cTnI using an immunoassay. ResultsBiphasic cTnI release into the circulation was observed during and after the marathon. Moreover, a similar pattern of biphasic cTnI elevation was found in saliva. In group 1, salivary and serum concentrations of cTnI first peaked after 60 min of exercise (0.67{+/-}0.08 ng/mL and 0.76{+/-}0.07 ng/mL), decreased slightly towards the end of the marathon (0.40{+/-}0.06 ng/mL and 0.46{+/-}0.06 ng/mL), and then reached a second, higher peak 4 h post-exercise (0.72{+/-}0.09 ng/mL and 0.82{+/-}0.09 ng/mL), returning to baseline by 48 h after marathon completion (0.16{+/-}0.04 ng/mL and 0.18{+/-}0.04 ng/mL). In group 2, there were no time-dependent changes in cTnI concentrations in both saliva and serum. Deming regression and Passing-Bablok regression demonstrated that there was proportional agreement between salivary and serum levels of cTnI in both groups at all twelve time points. The Bland-Altman method revealed that there was a negative differential bias but no proportional bias in the data. ConclusionsDocumenting a similar, biphasic pattern of cTnI elevations in saliva and serum during and after the marathon provides a reliable non-invasive alternative without requiring a blood draw.

Obesity is the most common cause of hypertension. We have previously shown that high levels of circulating leptin in diet-induced obese (DIO) mice induced hypertension by increasing expression of Transient Receptor Potential Melastatin-subfamily member 7 (TRPM7) in the carotid bodies (CB). In addition, we demonstrated in rat PC12 cells that leptin increases Trpm7 gene expression by inducing CpG site-specific demethylation within the 5 regulatory region containing a signal transducer and activator of transcription 3 (STAT3) binding site. This leptin-induced Trpm7 upregulation was prevented by inhibition of JAK-STAT3 signaling. Based on these findings, we hypothesized that reversing region-specific methylation at the Trpm7 promoter in the CB could attenuate obesity-associated hypertension. Compared with lean controls, DIO mice exhibited increased Trpm7 expression and the STAT3- binding site-specific promoter demethylation in the CB. Administration of methylated DNA oligonucleotides targeting the STAT3 binding site attenuated CpG site-specific DNA demethylation and reduced Trpm7 transcription in the CB of DIO mice. This intervention resulted in decreased carotid sinus nerve activity and reduced arterial blood pressure, especially during the light phase. Our results suggest that targeted modulation of CpG site-specific DNA methylation at the Trpm7 promoter using DNA oligonucleotide may represent a novel therapeutic strategy for obesity-induced hypertension.

We investigated effects of three aerobic exercise interventions, varying in amount and intensity with durations of 8-9-months on small RNA (smRNA) expression and regulatory pathways in skeletal muscle and plasma from 120 participants. Using untargeted smRNA sequencing focused on miRNAs and piRNAs, adjusting for demographics and bodyweight, we identified 124 muscle smRNAs altered by exercise amount and 15 by intensity, and 47 plasma smRNAs altered by intensity and one by amount. These smRNAs were enriched in metabolic, transcriptional, translational, and cell cycle pathways. Exercise-induced changes in several smRNAs-six from muscle and five from plasma-and exercise-induced reduction in body weight, aligned with improvement in insulin sensitivity (p<0.05). These findings demonstrate tissue-specific regulation of smRNAs by exercise and identify potential candidates for exercise mimetics to modulate muscle insulin sensitivity.

Short-term heat acclimation (HA) induces cardiovascular and fluid-regulatory adaptations, but its impact on markers of renal tubular injury and acute kidney injury risk (AKI) during exercise-heat stress remains unclear. Fourteen healthy endurance athletes were randomised to five days of isothermic HA (HOT; n = 7; 32 {degrees}C, 70% relative humidity; target core temperature [&ge;]38.5 {degrees}C), or matched exercise in thermoneutral conditions (TEMP, n = 7). Heat stress tests (HST; 45 min cycling at 32 {degrees}C, 70% RH) were performed pre- and post-intervention. Blood biomarkers of kidney tubular stress (NGAL, KIM-1), fluid-regulation (copeptin, serum osmolality) and sympathetic activity (plasma normetanephrine) were measured at rest and immediately post-HST. HA reduced resting heart rate (-8 {+/-} 5 bpm, p = 0.007, d = 1.0), increased plasma volume (+7.3 {+/-} 5.1%, p = 0.022) and sweat loss (+500 {+/-} 539 mL, p = 0.018, d = 1.1). Copeptin rose during the pre-intervention HST in both groups (HOT: +11 {+/-} 6; TEMP: +12 {+/-} 13 pmol{middle dot}L-1, p < 0.05), but not post-intervention. NGAL increased only in TEMP during HST1 (+45 {+/-} 29 g{middle dot}L-1, p = 0.030), while KIM-1 remained unchanged. No group x time interactions were observed for any biomarkers (p > 0.05). Five days of HA improved cardiovascular and thermoregulatory responses but did not alter renal stress markers or fluid-regulatory responses during exercise in the heat. These findings suggest short-term HA enhances heat tolerance without reducing acute renal biomarker responses under hot, humid conditions. New & NoteworthyFive days of isothermic heat acclimation improved cardiovascular and thermoregulatory responses, related to a lower resting heart rate, plasma volume expansion, and greater sweat loss. However, these benefits did not reduce renal tubular stress markers (NGAL, KIM-1), fluid-regulatory strain (copeptin), or sympathetic activity (normetanephrine) during exercise in the heat. Short-term heat acclimation lowers cardiovascular strain but does not mitigate renal biomarker responses, suggesting kidney stress risk remains unchanged in hot, humid conditions.

Perinatal opioid exposure is a prevalent clinical concern linked to respiratory instability and adverse infant outcomes. The opioid buprenorphine is prescribed as a medication for opioid use disorder during pregnancy and used to treat neonatal opioid withdrawal syndrome, yet its direct effects on neonatal control of breathing have not been examined. Here, we asked how acute buprenorphine exposure affects breathing at rest, and during chemoreceptor stimulation. Using dual-chamber head-out plethysmography, we measured pulmonary ventilation rate ([V]I) and metabolic rate in awake male and female Sprague-Dawley neonatal rats on postnatal days 4-5 (P4-5) during eupnea and a hypoxic-hypercapnic (HH) challenge. The effects of buprenorphine and two opioid receptor antagonists, naloxone hydrochloride, or peripherally restricted naloxone methiodide, were assessed using a repeated measures design. [V]I during eupnea and HH were markedly depressed following buprenorphine administration. Buprenorphine reduced [V]O2 and [V]CO2 and produced ventilatory equivalents for O2 and CO2 consistent with frank hypoventilation, driven by reduced breathing frequency and tidal volume (VT). When administered after buprenorphine, neither naloxone hydrochloride nor naloxone methiodide could rescue the buprenorphine-mediated hypoventilation in eupnea or during HH. In contrast, pre-treatment with either naloxone hydrochloride or naloxone methiodide attenuated buprenorphine-induced hypoventilation by preserving VT. These findings demonstrate that neonatal protective chemoreceptor reflexes are depressed by buprenorphine and suggest that pre-treatment with a peripheral opioid receptor antagonist could mitigate buprenorphine-induced hypoventilation without inducing opioid withdrawal. Key PointsO_LIAcute buprenorphine exposure significantly depressed pulmonary ventilation rate ([V]I) during eupnea and hypoxic hypercapnia (HH) in awake neonatal rats. C_LIO_LIBuprenorphine-induced hypoventilation was driven by reduced tidal volume (VT) and breathing frequency. C_LIO_LIBuprenorphine also reduced oxygen consumption ([V]O2) and carbon dioxide production ([V]CO2). C_LIO_LINaloxone given after buprenorphine failed to reverse hypoventilation. C_LIO_LIIn contrast, pre-treatment with either naloxone hydrochloride or peripherally restricted naloxone methiodide mitigated buprenorphine-induced hypoventilation by preserving VT. C_LI

This study examined the utility of HRV detrended fluctuation analysis alpha-1 (DFA1) to assess readiness-to-train and exercise durability under varying acute training loads. Nineteen trained cyclists completed two 20-minute time-trials (TT) under rested and fatigued conditions. DFA1 was measured during a standardized warm-up (WU), 20-min TT, and standardized cool-down (CD). Power output (PO) and DFA1 responses were compared across conditions, and associations with performance and fitness (W/kg) were examined. DFA1 values declined with increasing WU and CD exercise intensity (p<0.001) and were significantly attenuated following the 20-min TT (p<0.001). While DFA1 profiles did not differ significantly between rested and fatigued conditions, lower pre-TT DFA1 was associated with reduced TT performance (p=0.022; r=0.55), suggesting relevance to training readiness. Additionally, an 18% decline in DFA1 between 10- and 20-min during the TT (p=0.031), and lower post-TT values at matched intensities were observed (p<0.001), indicating physiological perturbation from the 20-min TT. Fitter participants exhibited lower DFA1 values during the 20-min TT (p<0.001; r=-0.77), suggesting a greater capacity to sustain physiological stress. While DFA1 is responsive to exercise intensity and stress, offering potential to assess training readiness and durability, more robust fatigue protocols are needed to validate DFA1 as training load monitoring tool.

BackgroundCalcitonin gene related peptide (CGRP) hyperpolarizes pulmonary arterial smooth muscle cells (SMCs) and endothelial cells (ECs) through PKA-dependent activation of KATP channels. CGRP can diminish the severity of pulmonary fibrosis (PF), however, the effects on vascular signaling were poorly defined. We hypothesized that hyperpolarization to CGRP would be augmented in a mouse model of PF. MethodsPF was induced in male and female C57BL/6 mice by intratracheal delivery of bleomycin (3 wk), with saline used as control (sham). Pulmonary arteries (PAs; 100-150 {micro}m diameter) were cannulated and pressurized to 16 cmH2O, and endothelial tubes were studied in complementary experiments to eliminate the influence of SMCs. Membrane potential (Vm) was recorded continuously using intracellular microelectrodes. Responses were also evaluated in isolated lungs preconstricted with U46619 ([~]10 mmHg). ResultsPF led to greater indices of PH in males vs. females. Isolated lungs and PAs from male PF mice had enhanced vasodilation and hyperpolarization of Vm to CGRP, although no effect was observed in females. The greater vasodilation and hyperpolarization of SMCs to CGRP in males persisted in endothelium-disrupted PAs and during treatment with L-NAME indicating that ECs are not required for greater responsiveness to CGRP. With no effect on resting Vm, inhibition of KATP channels or PKA significantly attenuated hyperpolarization of SMCs and ECs, attenuated vasodilation to CGRP in PAs, and eliminated differences between groups in males. Direct activation of PKA, but not KATP, evoked greater Vm hyperpolarization and vasodilation in PF vs. sham PAs and lungs. Although no difference in sensory nerves was observed in fibrotic mice, perivascular nerve stimulation evoked greater vasodilation in PAs. ConclusionsIn a mouse model of PF, CGRP-dependent hyperpolarization of pulmonary arterial SMCs and ECs is augmented through increased PKA-dependent activation of KATP channels leading to increased vasodilator sensitivity.

Hypoxemia occurs in intermittent forms, such as obstructive sleep apnea, and in continuous forms, such as at high altitude, and is increasingly recognized as a modulator of cardiometabolic risk. Although hypoxemia alters postprandial glucose and lipid metabolism, its effects on ketone bodies remain unclear. Using a randomized crossover design, we examined whether six hours of normoxemia or intermittent hypoxemia (15 hypoxemic cycles/hour targeting [~]85% peripheral oxyhemoglobin saturation with 100% medical-grade nitrogen) alters plasma {beta}-hydroxybutyrate (BHB) concentrations in 12 young adult females (mean [SD]: 21 [3] years) following a high-fat meal (33% of estimated daily energy requirements; 59% of calories from fat). In a follow-up session, a subset (n = 8) completed six hours of continuous hypoxemia (fraction of inspired oxygen [~]12.0% in a normobaric chamber). Postprandial data were analyzed using baseline-adjusted linear mixed-effects models, with Bonferroni post hoc tests. A time x condition interaction (P = 0.010) indicated that BHB concentrations at 360 minutes were higher during continuous hypoxemia (0.247 mmol/L; 95% CI: 0.218-0.275) than normoxemia (0.176 mmol/L; 95% CI: 0.153-0.200; PBonferroni = 0.029) and intermittent hypoxemia (0.163 mmol/L; 95% CI: 0.139-0.186; PBonferroni = 0.002), representing increases of 13.0% and 14.2% in estimated marginal means, respectively. This response was accompanied by higher postprandial plasma glucose and triglyceride concentrations during continuous hypoxemia than during normoxemia and intermittent hypoxemia (PBonferroni [&le;] 0.002), despite similar plasma insulin and non-esterified fatty acid responses across conditions (P [&ge;] 0.081). These findings indicate that continuous hypoxemia increases late postprandial plasma BHB concentrations in young adult females. New FindingsO_ST_ABSWhat is the central question of this study?C_ST_ABSWhat are the effects of normoxemia, intermittent hypoxemia, and continuous hypoxemia on plasma {beta}-hydroxybutyrate (BHB) concentrations in young adult females after a high-fat meal? What is the main finding and its importance?Compared to normoxemia, young adult females showed higher postprandial plasma BHB concentrations during continuous hypoxemia, but not during intermittent hypoxemia, despite similar changes in plasma concentrations of two main regulators of BHB production (non-esterified fatty acids and insulin) across experimental conditions. These findings suggest that continuous hypoxemia modifies postprandial BHB concentrations through mechanisms not fully explained by circulating non-esterified fatty acids or insulin concentrations alone.

Abstract Purpose: MyotonPRO (MTP) and time-harmonic elastography (THE) are increasingly used to assess muscle mechanical properties, yet they operate on fundamentally different physical principles. MTP measures composite MTP stiffness (N/m) through surface oscillations, while THE quantifies intrinsic shear modulus (THE stiffness, kPa) via propagating shear waves. This study aimed at systematically compare MTP and THE measurements in the vastus lateralis muscle across different contraction intensities and examine how the skin layer and subcutaneous fat (SLSF) thickness influence their relationship. Methods: Twenty-six healthy adults (15 males, 11 females; age 25 [SD 4] years) underwent MTP and THE measurements of the vastus lateralis at rest and during isometric contractions at 15% and 30% maximal voluntary contraction (MVC). Effects of contraction intensities on tissue properties were assessed using univariate analyses of variance with repeated measures. Associations between the different outcomes of THE and MTP technologies were explored using Pearson's correlations and partial correlation coefficients separately for each contraction intensity with adjustment of the SLSF thickness of participants. Results: Both technologies detected contraction intensity-dependent stiffening across all outcomes (p < 0.001). THE stiffness increased from 5.3 [1.2] kPa at rest to 15.6 [6.1] kPa at 30% MVC; THE wave attenuation increased from 0.83 [0.19] to 1.42 [0.36] s/m while MTP stiffness increased from 337.3 [49.3] N/m at rest to 529.4 [160.7] N/m at 30% MVC. Correlations between modalities were weak and condition-dependent. THE wave attenuation did not significantly correlate with any MTP outcome across conditions. Conclusion: MTP and THE detect contraction-induced stiffening through fundamentally different physical mechanisms and should not be regarded as interchangeable. Their correlation is modest at rest and breaks down (or reverses) during active contraction, with subcutaneous fat as a key modifying factor. Clinical trial number: Not applicable.

RationaleAutonomic dysfunction is a hallmark of sepsis pathophysiology, yet its quantification remains challenging. Multiscale entropy (MSE) derived from heart rate variability (HRV) offers a dynamic measure of physiological complexity and may serve as a biomarker of early deterioration associated with subsequent organ failure, vasopressor escalation, or mortality. ObjectiveTo determine whether MSE computed across multiple temporal scales during the first 24 hours of Intensive Care Unit (ICU) admission is associated with short-term mortality and longer-term organ dysfunction in patients with sepsis, and whether these relationships vary across vasopressor exposure. Unlike prior studies that focused on short-term HRV metrics, we applied MSE across multiple temporal scales and incorporated these features into machine learning models to evaluate their prognostic utility in septic shock. MethodsThis retrospective cohort study included adult ICU sepsis patients at Emory University Hospital from January 2016 to December 2019. Of 2,076 eligible patients, 958 were propensity matched into two cohorts: fluids-only and fluids-plus-vasopressor, with norepinephrine as the primary vasopressor. High-resolution electrocardiogram (ECG) waveforms were analyzed to compute MSE across 20 temporal scales. Machine learning models using (1) MSE features alone and (2) MSE combined with demographic and vital sign data (MSE-DV) were compared against traditional HRV measures based model and severity of illness scores for predicting outcomes. Model performance was assessed using the area under the receiver operating characteristic curve (AUROC), with a primary outcome of mortality at day 7 and secondary outcome of persistent organ dysfunction at day 28. ResultsIn the fluids-plus-vasopressor cohort, MSE-based models demonstrated superior predictive performance for 7-day mortality (AUROC 0.84) compared to severity of illness scores (AUROC 0.64). MSE-DV models also predicted organ dysfunction including 28-day renal (AUROC 0.75), neurological (AUROC 0.79), and respiratory (AUROC 0.71) dysfunction. Patients receiving second-line and third-line vasopressors and corticosteroids exhibited progressively lower MSE values, particularly at mid-range and long-range scales. ConclusionMSE features in the first 24 hours of ICU stay predict mortality and organ dysfunction with higher discrimination than traditional severity of illness scores. Future work should validate these findings, assess longitudinal MSE trends, and race-specific autonomic patterns to refine predictive models.

Exercise affects the immune function and induces pro- and anti-inflammatory effects. The alterations concerning the immune system linked to physical activity have been documented across various studies with complex exercise tests. However, the characterization of the non-pathological, exercise-induced immunological stress regulation is highly relevant in numerous clinical and non-clinical areas for a better understanding of normal physiological adaptations and differentiation from non-healthy adaptations. Thus, it is valuable and necessary to establish simple immune-metabolic response triggering exercise tests for use in clinical and non-clinical settings. The aim of this study was to examine the effects of the 1-minute sit-to-stand test (STST) on immune-metabolic stress indices and to determine whether it elicits a sufficiently high intensity to qualify as an anaerobic exercise test, thereby supporting its application in investigating exercise-induced immunological stress regulation. 28 study participants performed the 1-minute STST. Capillary blood was taken 20 and 10 minutes before the test, immediately after, and 5, 10, 15, 30, and 45 minutes after exercise. Lactate, glucose and blood counts were determined. Lactate concentration increased significantly immediately after the STST (p < 0.001) and remained significantly elevated until 45 minutes post-exercise. Glucose concentration was significantly decreased after 10 minutes post-exercise (p < 0.05) and again 30 and 45 minutes post-exercise (p < 0.01 for both). Leucocyte count increased significantly post-exercise (p < 0.001) and returned to baseline levels 30 minutes afterwards. Lymphocyte and granulocyte count increased significantly after the test (p < 0.001 for both) and lymphocyte count slightly decreased below baseline values 30 minutes post-exercise (p = 0.07) while granulocyte count remained significantly elevated (p < 0.05). Furthermore, decreased NLR (p < 0.001) and SII (p < 0.01) immediately after the test and increased levels of NLR, SII and SIRI post-exercise could be observed. The 1-minute STST caused an increase in lactate level above the anaerobic threshold, therefore the test can be evaluated as an anaerobic exercise test. Furthermore, it was demonstrated that the STST induced shifts in leucocyte, lymphocyte, and granulocyte counts, which means that even a short intense anaerobic exercise, such as the STST causes changes in immune cell counts and therefore, the test is suitable for analyzing the exercise-induced immunological stress response.

The population of kisspeptin neurons located in the rostral periventricular area of the third ventricle (RP3V) is thought to have a key role in generating the GnRH surge that triggers ovulation. Using a modified GCaMP fibre photometry procedure, we have been able to record the in vivo population activity of RP3VKISS neurons across the estrous cycle of female mice. A marked increase in GCaMP activity was detected beginning on the afternoon of proestrus that lasted in total for 13{+/-}1 hours. This was comprised of slow baseline oscillations with a period of 91{+/-}4 min and associated with high frequency rapid transients. Very little oscillating baseline or transient activity was detected at other stages of the estrous cycle. Concurrent blood sampling showed that the peak of the LH surge occurred 3.5{+/-}1.1 h after the first baseline RP3VKISS neuron baseline oscillation on the afternoon of proestrus. The time of onset of RP3VKISS neuron oscillations varied between mice and across subsequent proestrous stages in the same mice. To assess the impact of estradiol on RP3VKISS neuron activity, mice were ovariectomized and given an incremental estradiol replacement regimen. Minimal patterned GCaMP activity was found in OVX mice, and this was not changed acutely by any of the estradiol treatments. However, on the afternoon of the expected LH surge, the same oscillating baseline activity with associated transients occurred for 7.1{+/-}0.5 h. These observations reveal an unexpected prolonged oscillatory pattern of RP3VKISS neuron activity that is dependent on estrogen and underlies the preovulatory LH surge as well as potentially other facets of reproductive behavior.

Salt-sensitive hypertension, a condition in which the blood pressure (BP) increases with an increase in salt intake, is influenced by behavioral, genetic, and environmental factors. Salt sensitivity is associated with variants of the G protein-coupled receptor kinase 4{gamma} (GRK4{gamma}) and the renal sodium bicarbonate cotransporter 2 (NBCe2), encoded by the solute carrier family 4 member 5 (SLC4A5). The R>65L variant (rs2960306) of human GRK4 (hGRK4{gamma} 65L) contributes to salt sensitivity through a signaling pathway and gene-gene interaction with SLC4A5. Global expression of GRK4{gamma} 65L in transgenic mice results in salt-sensitive hypertension, due in part to an increase in endogenous GRK4 and angiotensin type 1 receptor (AT1R) expression. Grk4 knockout (Grk4-/-) mice have decreased blood pressure and are salt-resistant. The expression of hGRK4{gamma} 65L only in the kidney of Grk4-/- mice increases BP in response to a high salt diet. The renal expression of SLC4A5 is increased in hGRK4{gamma} 65L transgenic mice, relative to mice expressing wild-type (WT) human GRK4 (hGRK4 65L), without endogenous mGrk4. Human renal proximal tubule cells (hRPTCs) endogenously expressing GRK4 WT and SLC4A5 WT, SLC4A5 variants, GRK4 65L, and both GRK4 65L and SLC4A5 variants were studied. SLC4A5 expression is increased in hRPTCs expressing GRK4 65L and in cells expressing both GRK4 65L and SLC4A5 variants compared with GRK4 WT and SLC4A5 WT. Luminal and basolateral sodium transport in hRPTCs is increased in the presence of both hGRK4 65L and SLC4A5 variants. GRK4 interacts with nuclear histone deacetylases (HDACs). Mice expressing hGRK4 65L only in the kidney have decreased expression but increased phosphorylation of HDAC1. HDAC1 expression is decreased and HDAC1 but not HDAC2 phosphorylation is increased in hRPTCs expressing both hGRK4 65L and SLC4A5 variants. The presence of hGRK4{gamma} 65L decreased HDAC1 expression but increased AT1R expression in the kidneys of mice on high salt diet. Our results show that GRK4{gamma} 65L causes salt-sensitive hypertension by increasing renal SLC4A5 and AT1R expressions by inhibiting the HDAC1 pathway.

Exercise provides broad health benefits, including improved emotional well-being and cognitive function. Emerging evidence suggests that exercising at different times during the day can have differential effects. However, how circadian phase and sex influence behavioral and physiological responses to exercise remains unclear. To address this question, we examined male and female wild-type mice maintained in either regular (REG, lights on/off at 7AM/7PM) or inverted (INV, lights off/on at 10AM/10PM) light cycles. Mice were then subjected to daily 20-min group swimming exercise sessions at ZT2-3 for 3 weeks. Exercised and sedentary controls mice were then subjected to an open field test (OFT) and blood corticosterone (CORT) measurements 24 hours post-exercise. We quantified several behaviors during swimming: escape attempts, floating, climbing and collisions. We also identified a novel swimming behavior: floating with only nostrils-above-water events (NAWEs). We found that expression of these behaviors was differentially modulated by sex, light-cycle and their interaction. Notably, behavioral differences were more pronounced in REG mice (rest phase). REG mice also lost weight after exercise and had elevated CORT levels compared to mice kept in INV conditions (active phase). Interestingly, OFT behaviors showed significant differences primarily in INV mice, particularly females, when comparing exercised vs sedentary groups. Our novel findings reveal that circadian rhythms and sex significantly interact to shape swimming exercise and stereotyped behaviors in mice. This emphasizes the need to consider the animals circadian phase when designing preclinical studies to match intended behavioral and physiological outcomes. HIGHLIGHTSCircadian phase and sex jointly shape swimming behavior patterns. Newly identified swimming behavior is more prevalent during rest-phase Restphase exercise produced stronger behavioral and physiological effects. Rest-phase exercise resulted in weight loss and elevated stress markers. Active-phase exercised females showed the strongest open field behavioral differences.

New FindingsWhat is the central question of this study? Are adaptations elicited by combined flywheel resistance and aerobic exercise influenced by habitual physical activity levels in patients with chronic kidney disease? What is the main finding and its importance? Combined flywheel resistance and aerobic exercise promote clinically meaningful improvements in muscle size, power output, and physical function in patients with chronic kidney disease. Those not meeting the weekly moderate intensity physical activity recommendations experienced greater increases in power output compared to those who were physically active whereas no differences in the magnitude of improvements in physical function were observed between physical activity levels. Physical inactivity is common in chronic kidney disease (CKD) and is associated with poor neuromuscular and functional outcomes. Whether habitual physical activity (PA) influences adaptations to structured exercise in CKD remains unclear. This study examined if adaptations to combined flywheel resistance and aerobic exercise (FRE+AE) differed based on self-reported PA in Veterans with CKD stages 3-4. Twenty older male Veterans with CKD stages 3-4 (mean eGFR 37.9 {+/-} 10.2 mL/min/1.73 m{superscript 2}) were randomized to six weeks of FRE+AE (n=11) or health education (EDU; n=9). Participants were classified as meeting (Meets PA) or below (Low PA) weekly moderate intensity PA recommendations using the 7-day Physical Activity Recall. Outcomes included vastus lateralis muscle thickness (VL MT), knee extensor power output (60{degrees}{middle dot}s-1 and 180{degrees}{middle dot}s-1), gait speed (GS), and five-repetition sit-to-stand (STS). FRE+AE increased VL MT (p=0.030), power output at 180{degrees}/s (p=0.021), GS (p=0.001), and reduced STS time (p=0.012), with significant between-group differences versus EDU for VL MT (p=0.009) and GS (p=0.028). Low PA experienced greater increases in power output at 60{degrees}{middle dot}s-1 (Hedges g; Low PA=0.44, Meets PA=0.25) and 180{degrees}{middle dot}s-1 (Hedges g; Low PA=1.38, Meets PA=0.38) compared to Meets PA after FRE+AE. Conversely, Meets PA had greater improvements in GS (Hedges g; Low PA=0.93, Meets PA=1.29) and STS (Hedges g; Low PA=-0.72, Meets PA=-2.20) compared to Low PA. Six weeks of FRE+AE produced clinically meaningful neuromuscular and functional improvements in Veterans with CKD stages 3-4 irrespective of PA level, supporting FRE+AE as a feasible intervention in this population.

Background: Exercise-based cardiac rehabilitation (CR) improves peak oxygen uptake ([V]O2peak) in patients with coronary heart disease (CHD); however, whether women and men exhibit similar adaptations across the steps of O2 transport remains unknown. We aimed to compare the ventilatory and circulatory determinants of [V]O2peak changes between women and men with CHD following a structured exercise training program. Methods: A total of 28 women (27%) and 75 men (73%) with CHD, matched for age, body mass index, and [V]O2peak (% predicted), underwent maximal cardiopulmonary exercise testing (CPET) before and after 12 weeks of CR. [V]O2peak and minute ventilation ([V]E) were measured breath by breath. Heart rate and cardiac output ([Q]c)were assessed non-invasively using impedance cardiography. Exercise efficiency ({Delta}[V]O2/{Delta}W), alveolar ventilation ([V]A), ventilatory efficiency (OUES), O2 pulse, arteriovenous oxygen content difference (C(a-[v])O2) and gross muscular efficiency (W) were calculated using standard equations. Mixed model analyses (sex x time) were used to compare training-induced changes between sexes. Results: At baseline, values of [V]O2peak (absolute and normalized by fat free mass), [V]E, [V]A, O2 pulse, C(a-[v])O2, {Delta}[V]O2/{Delta}W, W were significantly lower in women than in men with CHD (group effect, p<0.01). [V]O2peak normalized by fat-free mass improved similarly in both sexes after CR (p<0.0001, no significant sex x time interaction). Pulmonary convection ([V]E, [V]A), ventilatory efficiency (OUES), circulatory convection ([Q]c, cardiac index, O2 pulse), and peripheral gross muscular efficiency (W) all improved similarly after CR in women and men (effect sizeXtime effect, p<0.05, no significant group x time interaction). The prevalence of responder categories did not differ between sexes (p=0.826). Conclusion: Women and men with CHD demonstrated equivalent O2 transport phenotype adaptations after CR, with comparable improvements across the O2 transport chain (pulmonary, circulatory, and peripheral determinants of [V]O2peak).