American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

Spinal cord injury (SCI) disrupts supraspinal autonomic pathways that regulate cardiovascular function, producing marked blood pressure instability and contributing to secondary injury in peripheral organs. The kidney is particularly vulnerable to these disturbances because renal blood flow (RBF) depends on tightly regulated interactions between neural, myogenic, and vascular control mechanisms. However, how SCI level and chronicity alter dynamic renal autoregulation remains poorly defined. Here, we investigated the effects of high- and low-thoracic SCI on renal hemodynamic control using in vivo blood pressure and RBF recordings in female mice. Hemodynamics were assessed at baseline and during acute sympathetic stimulation induced by norepinephrine (NE; 10 g/kg, i.v.) at 24 h and 4 wk following spinal cord transection at thoracic level 3 (T3) or thoracic level 10 (T10). Time-domain analyses quantified systolic blood pressure recovery, while frequency-domain analyses were used to resolve myogenic and sympathetic contributions to RBF regulation. High-thoracic SCI caused marked disruption of renal vascular responses to acute hypertension, producing paradoxical increases in RBF during NE-induced pressure elevations and sustained reductions in baseline and evoked RBF activity within frequency ranges associated with myogenic and sympathetic vasomotion. These impairments were most pronounced during the chronic phase of injury, consistent with loss of dynamic autoregulatory control and vascular remodeling. In contrast, low-thoracic SCI preserved baseline renal vasomotor activity and demonstrated recovery of dynamic autoregulatory responses over time. These findings identify SCI level and chronicity as critical determinants of renal microvascular regulation and demonstrate that high-thoracic SCI produces persistent autonomic-vascular uncoupling. This disruption of dynamic renal autoregulation represents a previously underappreciated mechanism of secondary organ vulnerability following neurotrauma.

Background The relative contributions of molecular size, electrostatic charge, and filtration rate to glomerular transport remain controversial. We hypothesized that glomerular sieving data contain a limited number of underlying transport modes that can be identified directly from experimental measurements. Methods Glomerular sieving coefficients were measured in anesthetized rats using neutral and anionic polysucrose during baseline conditions and glucagon-induced hyperfiltration. Data were analyzed using aligned-rank two-factor ANOVA, nonlinear mixed-effects regression of an electrostatic distributed two-pore model, pairwise correlation analysis, and principal component analysis. Results Hyperfiltration reduced the sieving of small and intermediate polysucrose molecules, whereas anionic polysucrose exhibited lower sieving coefficients than neutral polysucrose over a broad range of molecular sizes. An electrostatic distributed two-pore model accurately reproduced the observed effects of filtration rate and molecular charge and yielded an effective pore-wall charge density of 5.4 mC/m2 (95% confidence interval, 4.5 to 6.6). Pairwise correlation analysis revealed strong coupling between neighboring molecular sizes throughout the entire measured size range. Principal component analysis of the 2.5-8.0 nm size-selective region showed that the first principal component explained 96.3% of the variance and the first two principal components explained 99.9% of the variance. Separate analyses of the 2.5-5.0 nm and 5.0-8.0 nm transport regions showed that the first principal component explained 99.4% and 89.5% of the variance, respectively. Conclusions Glomerular sieving curves exhibited a highly constrained low-dimensional structure despite differences in molecular charge, filtration rate, and individual animals. The observed transport structure was consistent with distinct small-pore and large-pore transport domains and enabled highly effective principal component-based denoising of experimental sieving data.

The carotid body (CB) is the key peripheral oxygen sensor. CB mitochondria are hypothesised to be uniquely adapted with unusually low intrinsic oxygen affinity which, in association with nitric oxide (NO) and reactive oxygen species signalling, enables acute responsiveness to hypoxia. However, CB mitochondrial physiology or intrinsic oxygen affinity have never been measured directly. We sought to address this key gap by isolating sheep CB mitochondria and comprehensively characterising their phenotype and contrasting them to a non-oxygen sensing tissue, left ventricular myocardium (LV). High resolution respirometry, liquid chromatography mass spectrometry, enzymatic assays and in silico modelling were used to characterise mitochondrial content, aerobic capacity, oxygen affinity, complex subunit abundance and activity, H2O2 production and NO sensitivity in ovine CB and LV. Mitochondrial oxygen affinity (P50 = 0.089 mmHg) was lower in the CB than the LV (P50 = 0.058 mmHg; p = 0.005). Whilst mitochondrial content was lower in the CB, CB mitochondria had higher respiratory rates and enzymatic activity than LV. H2O2 production and NO sensitivity were similar in the two tissues. While intrinsic mitochondrial oxygen affinity is slightly lower in the oxygen sensing CB than in the non-oxygen sensing LV, this difference is small. Hence, any role of mitochondria in CB oxygen sensing is not due to an intrinsic difference in the O2 affinity of cytochrome oxidase due to differential expression of its subunits. Instead, this work suggests that differences in O2 affinity in vivo are secondary to other factors, perhaps including NO, that alter mitochondrial O2 affinity.

Cyclooxygenase-1 (COX-1) is classically regarded as a constitutive enzyme that produces eicosanoids with housekeeping functions, but recent evidence indicates that it may also be involved in the acute phase of severe systemic inflammation. There is evidence indicating that COX-1 is selectively activated in the spleen via post-translational mechanisms early the course of LPS-induced systemic inflammation. However, the mechanistic link between COX-1 and the spleen has not yet been demonstrated in direct experiments. The present study was conducted to fill this gap. The effects of the COX-1 inhibitor SC-560 on the LPS-induced severity triad (hypotension, hypothermia and acidosis) were evaluated in rats subjected to splenectomy or in sham-operated controls. In the sham-operated group, SC-560 significantly attenuated the severity triad independently of changes in plasma cytokines (TNF and IL-1{beta}). In the splenectomized rats, SC-560 completely lost its ability to attenuate the hypotension and the acidosis induced by LPS. The effect of SC-560 on LPS-induced hypothermia was also impaired by splenectomy, though not completely. We then conducted a lipidomic screening to identify which COX-1-derived eicosanoids might be responsible for mediating the severity triad. Based on spleen-blood correlations, the screening identified PGE2 and PGD2 as putative candidates. In conclusion, the present study provides direct evidence for a mechanistic link between the spleen and COX-1 in the mediation of severity in systemic inflammation, and identifies PGE2 and PGD2 as putative candidates involved.

Heart rate (HR) and its variability (HRV), mediated by the autonomic nervous system are key indicators of diving physiology and behavioral state, in vertebrates. However, these indicators remain understudied in cetaceans due to the technical challenges of recording electrocardiograms (ECGs) underwater. To overcome these challenges, we developed a waterproof device based on an all-in-one suction-cup that integrate an ECG-accelerometer logger with bipolar electrodes. Using this device, we obtained high-resolution ECG signals in bottlenose dolphins (Tursiops truncatus, n=8), belugas (Delphinapterus leucas, n=2), and orcas (Orcinus orca, n=1) during breathing and apnea. This approach allowed us to highlight species-specific features of the ECG waveform, consistent with a biphasic T wave in the three species of cetaceans and a bifid P wave unique to belugas, which were independent from the respiration state. Resting surface HRs were 70 {+/-} 4 bpm in dolphins, 51 {+/-} 1 bpm in belugas, and 50 {+/-} 2 bpm in the orca and exhibited pronounced oscillation related to the mechanism of respiratory sinus arrhythmia. As expected, short apneas ([~] 1 min) induced bradycardia in all three species (53 {+/-} 5, 33 {+/-} 3, and 37 {+/-} 2 bpm, respectively). In dolphins this bradycardia was coupled with a significant decrease of the coefficient of variability of RR intervals, one of the indices of HRV. Moreover, we were surprised to observe HR oscillations throughout apnea, suggesting a persistent fluctuation of autonomic modulation. Thus, to better understand autonomic modulation in cetaceans we employed food (fishes, squids, gelatin, etc.) as a strong rewarding stimulus. For that we compared HR and HRV during 2-min of food deprivation versus continuous feeding periods. In dolphins, food deprivation produced no significant change in HR or HRV from resting surface values, whereas continuous feeding decreased HR of about 20 % and increased HRV metrics (StDRR, CVRR, RMSSD). Belugas showed similar responses, with a HR decline of about 40 % and an increase HRV indices. These findings established baseline HR and HRV parameters during breathing or apnea for three cetacean species and demonstrate that autonomic responses to appetitive stimuli can be non-invasively quantified, validating a novel tool to investigate cetacean cardiovascular physiology and environmental perception.

Stress-related psychiatric disorders and inflammatory bowel diseases share high co-morbidity and contribute to the symptom severity of one another. In mice, ten days of Chronic Social Defeat Stress (CSDS) is sufficient to reduce gut microbiome diversity and the relative abundance of Firmicutes, which are hallmarks of inflammatory bowel diseases. However, mechanisms by which stress causes gut microbiome dysbiosis are largely unknown. Here, we demonstrate that pharmacologically inhibiting {beta}-adrenergic receptors (ARs), which are activated by (nor)adrenaline during stress, mitigates gut dysbiosis otherwise caused by CSDS. Compared to vehicle-treated mice following CSDS, propranolol-treated mice displayed a modest increase in sociability, increased alpha diversity, and increased abundance of anaerobic commensal Clostridia. Abundance of short-chain fatty acid-producing anaerobic Firmicutes abundance correlated with sociability following CSDS across all treatments. Pharmacologically blocking -ARs during stress increased subsequent sociability, but had little effect on gut microbiome composition. Together, our findings support the hypothesis that {beta}-AR activation contributes to stress-induced changes of the gut microbiome. One Sentence SummaryPharmacologically inhibiting beta-adrenergic receptors during chronic stress mitigates reductions in anaerobic, short-chain fatty acid-producing bacteria in the gut.

Climate-driven warming is challenging the physiological limits of aquatic ectotherms, with cardiac performance emerging as one of the key determinants of thermal tolerance. Cardiac function relies on mitochondrial ATP production, and mitochondrial dysfunction has been linked to cardiac failure at critical temperatures. However, mitochondria are plastic and may represent a target for interventions aimed at improving thermal tolerance in fish. Exercise training improves whole-animal performance in fish, including cardiac thermal performance, and improves mitochondrial function in other taxa. However, its effects on the thermal sensitivity of cardiac mitochondria remain unknown. This study investigated whether exercise-training alters cardiac mitochondrial performance at optimal and critical temperatures in rainbow trout Oncorhynchus mykiss. Farmed rainbow trout were subjected to a four-week exercise training regime, while control fish remained under standard rearing conditions. Cardiac mitochondrial respiration was assessed in permeabilised heart fibres at 16{degrees}C (optimal growth temperature) and 26{degrees}C (temperature associated with cardiac arrhythmia) and several biochemical and nuclear indicators were measured. No significant differences were detected between treatments for any measured variable. However, trained fish generally exhibited higher maximal respiratory capacities and respiratory control ratios, particularly at the elevated temperature, suggesting subtle improvements in mitochondrial function despite considerable inter-individual variation. Temperature influenced mitochondrial performance, increasing proton leak and reducing coupling efficiency. These findings demonstrate that cardiac mitochondrial function is thermally sensitive and represents a potential targeted for improving thermal resilience in aquaculture species.

BackgroundDietary sodium restriction is a common nutritional and physiological challenge that activates electrolyte-conserving endocrine pathways, but its impact on systemic lipid metabolism remains incompletely defined. We examined whether short-term dietary sodium deprivation alters the circulating lipidome and identifies lipid signatures of metabolic adaptation. MethodsMale Sprague-Dawley rats were maintained on sodium-sufficient (NaS) or sodium-deprived (NaD) diets for 7 days (n=3 per group). Serum lipids were profiled by untargeted LC-MS/MS in positive and negative ion modes. Lipidomic differences were evaluated using class-level and species-level analyses, principal component analysis, volcano plots, heatmaps, and pathway-oriented interpretation. ResultsNaD rats exhibited a distinct serum lipidomic profile compared with NaS controls, indicating global remodeling of circulating lipid composition. Sodium deprivation produced class-specific and species-resolved changes, including selective depletion of subsets of neutral lipid species, prominent wax ester remodeling, increased phosphatidylcholine and lysophosphatidylcholine abundance, and altered acylcarnitine profiles. These signatures are consistent with coordinated changes in lipid storage, membrane phospholipid turnover, and mitochondrial fatty-acid handling. ConclusionsDietary sodium deprivation induces coordinated serum lipidome remodeling in rats, supporting the concept that nutritional electrolyte status can influence systemic lipid metabolism. These exploratory findings identify sodium deprivation as a metabolic stressor linked to neutral lipid mobilization, phospholipid remodeling, and altered mitochondrial substrate handling, and provide a foundation for future mechanistic studies.

Background: Despite the common use of local heating and intradermal microdialysis perfusion of acetylcholine (ACh) to probe cutaneous endothelium and nitric oxide (NO)-dependent dilation, sex differences in microvascular responsiveness to these stimuli in healthy young adults remain incompletely understood. Methods: Cutaneous vasodilation was assessed in response to local heating to 39{degrees}C and 42{degrees}C and graded perfusion of ACh (10-10 to 10-1 mol/L) alone or concurrently with 15 mM NG-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor) using laser-Doppler flowmetry coupled with intradermal microdialysis in 80 young adults (40 females). Results: Local heating to 42{degrees}C elicited greater endothelium- and NO-dependent dilation than heating to 39{degrees}C in both groups (p<0.001), but no sex differences were observed at either temperature (p=0.65). ACh-induced endothelium-dependent dilation also was not different between sexes (p=0.08), but the NO-dependent component was greater in females than in males (p=0.01). In young females, menstrual cycle day (range: day 2-33) was not associated with endothelium- or NO-dependent dilation in response to any stimulus (all p[&ge;]0.19), regardless of hormonal contraceptive use. Conclusions: Taken together, these findings suggest that sex differences in microvascular NO bioavailability in healthy young adults depend on the stimulus used to elicit cutaneous vasodilation and, in females, microvascular endothelium- and NO-dependent dilation are not meaningfully influenced by menstrual cycle phase.

Skeletal muscles secrete a variety of cytokines in response to inflammatory stimuli such as lipopolysaccharide (LPS); however, the contributions of resident macrophages or other non-muscle cells to the secretory responses are not well understood. To determine the potential impact of resident macrophages to inflammatory cytokine production, we tested the LPS responsiveness of isolated mouse soleus muscle when a critical toll receptor adapter protein (Myd88) was knocked down only in myeloid-derived cells within the muscle (e.g. resident macrophages). The phenotype is referred to as LyzMyd88-/- ; the litter mate controls were Myd88fl/fl. In solei from LyzMyd88-/- mice, cytokine secretory rates for interleukin-6 (IL-6) and keratinocyte-derived cytokine (KC, CXCL1) were significantly reduced to 56.3%, and 60.6% of control, respectively, over the first hour of LPS exposure. In the second hour, secretion of granulocyte colony stimulating factor (G-CSF), IL-6, KC(CXCL1) and monocyte chemoattractant protein-1 (MCP-1, CCL2) were greatly elevated by 5-10-fold in both phenotypes compared to the first hour. However, only MCP-1 secretion was decreased to 70.6% of control in the second hour. We also tested the secretory response to buffer containing 1% sterile mouse plasma because dilute plasma is known to amplify the responses of macrophages to LPS. Treatment with 1% plasma alone affected baseline measures of some cytokines but resulted in no further increases in secretion during either hour of exposure. However, small and gradual increases in secretory rates were observed for several cytokines over the study period, with or without plasma, with the largest responses seen in IL-6 and KC. Overall, the results are consistent with a significant early contribution of myeloid-derived, resident immune cells to the cytokine secretory responses of intact oxidative skeletal muscle. In addition, small quantities of plasma in the buffer have no independent stimulatory effects on cytokine secretion

Anthelmintic resistance in cyathostomins is escalating worldwide, threatening equine health and highlighting the need for sustainable, ecology based parasite control strategies. Chicory (Cichorium intybus, Puna II) has emerged as a promising antiparasitic forage, yet its broader effects on the equine holobiont, parasites, microbiota, and host physiology remain poorly understood. We conducted a 32 day longitudinal grazing trial in young horses to assess how chicory affects parasitological outcomes, gut microbial ecology, nemabiome composition, behaviour, and host physiological and immune responses. Twenty-six naturally infected Anglo-Arabian horses were monitored weekly, with 13 grazing a chicory-based sward and 13 grazing a permanent pasture. Clinical parameters, body weight, and serum biochemistry remained stable across treatments, indicating that chicory was well tolerated. Immune profiles showed limited variation, although IL 10 increased in chicory fed horses, suggesting subtle immune modulation. Behavioural observations revealed no signs of discomfort and indicated slightly enhanced social interactions in the chicory group. Chicory grazing produced a marked reduction in cyathostomin egg excretion, accompanied by species specific shifts in nemabiome composition. Several cyathostomin taxa, including Cylicocyclus ashworthi, C. leptostomus, and C. nassatus, declined in chicory fed horses, whereas certain Cylicostephanus spp increased, indicating differential sensitivity rather than uniform suppression. Concomitantly, chicory induced profound ecological changes in the gut microbiota, including reduced alpha diversity, increased beta dispersion, and destabilised individual microbial trajectories. Several bacterial lineages, particularly Oscillospiraceae, Clostridiaceae, Lachnospiraceae, and Bacteroidales, were differentially enriched, reflecting a functional reorganisation of the intestinal ecosystem. Together, these findings demonstrate that chicory reduces parasite fitness, reshapes nemabiome composition, and alters gut microbial ecology while maintaining host physiological stability. Chicory thus emerges as a promising ecological tool for parasite control, capable of modulating the equine holobiont in ways that complement and potentially reduce reliance on conventional anthelmintic strategies. However, because its effects on gut microbial ecology remain uncertain, and may include shifts resembling dysbiosis, future studies are needed to monitor microbial dynamics more closely and clarify the long term ecological consequences of chicory grazing.

Pulmonary arterial hypertension (PAH) is a devastating disease with poor outcome affecting relatively young subjects. The arachidonic acid (AA) metabolite, 15-hydroxyeicosatetraenoic acid (15-HETE), has been implicated in the pathogenesis of hypoxia-induced PAH. We tested the hypothesis that genetic deletion of GPR39, the target receptor for 15-HETE, will attenuate PAH. We subjected wild-type (WT) and GPR39 KO to 4 weeks of hypoxia versus normoxia, after which right ventricular and systemic hemodynamics were measured. Immunohistochemistry of lung was performed for pulmonary arteriolar thickness as well as capillary and pericyte density. Lung tissue was also analyzed for AA and 15-HETE levels as well as signaling events (mRNA and protein levels) downtream of GPR39 activation. Unlike WT mice, GPR39 KO mice did not develop PAH. They also exhibited markedly less pulmonary ateriolar remodeling and greater pulmonary capillary density. mRNA expression of genes in the Gq, Gs and G12/13 pathways were upregulated in the WT mice while GPR39 KO hypoxic showed no change in these genes. WT and not GPR39 KO hypoxic mice exhibited enhanced AKT phosphorylation. Downstream of the phosphatidylinositol 3-kinase-AKT pathway, endothelial nitric oxide synthetase was upregulated in both WT hypoxia and GPR39 KO hypoxia mice, while sonic hedgehog was upregulated only in WT hypoxia mice. We conclude that hypoxia-induced aberrant signaling is markedly attenuated with genetic deletion of GPR39, which is associated with less pulmonary arteriolar remodeling and greater capillary density, thus preventing PAH. These results suggest that pharmacological inhibition of GPR39 may offer a novel treatment for PAH.

Premature ovarian insufficiency (POI) significantly impacts quality of life, yet the immediate cognitive landscape and lived experience of younger women remain under-researched. In 125 young women (aged 19-48; 66 with idiopathic POI, 59 age-matched controls), we examined self-reported cognitive distress and symptom burden within the POI cohort and compared objective global and domain-specific cognitive performance between groups. Objective accuracy scores were derived from six online tasks (Cognitron) and combined into a robust global measure. Within the POI cohort, there were significant differences in symptom burden domains ({chi}(3) = 61.90, p<0.001), with psychological and sexual symptoms reported at a significantly higher intensity than physical and vasomotor symptoms (all p<0.001). Furthermore, the standardised magnitude of perceived cognitive distress (56.20%) was significantly greater than that of overall symptom burden (42.00%, p<0.001). Case-control comparisons revealed no significant differences in global cognitive performance (p=0.615), yet the POI cohort performed significantly less accurate than controls in verbal analogical reasoning (-0.86 SD, 95% CI: -1.52, -0.20, p = 0.011). The findings highlight an urgent need for comprehensive emotional and psychosexual support in POI care. Additionally, the presence of high cognitive distress alongside localised objective deficits demonstrates that cognitive health monitoring must be proactive in early adulthood, especially given their established long-term risks for later-life cognitive decline and dementia.

RationaleThere is no effective pharmacotherapy for obesity hypoventilation syndrome (OHS). Intranasal leptin augments the hypercapnic ventilatory response (HCVR), attenuates upper airway obstruction, and increases ventilation during sleep in diet-induced obese (DIO) mice. Respiratory effects of leptin can be attenuated by serotonergic antagonists. ObjectivesTo establish if serotonergic innervation of the hypoglossal motoneurons (XII MN) mediates effects of leptin on OHS. MethodsWe examined effects of intranasal leptin on the HCVR, sleep architecture, arousal latency, flow limited (obstructed) and non-flow limited breathing, genioglossus muscle (GG) activity and metabolic rate across sleep/wake states in the presence and absence of serotonergic neurons innervating XII MN in DIO Sert-flp mice expressing FlpO recombinase in the serotonergic neurons. These mice were transfected into the XII MN with retrograde adeno-associated virus carrying either FlpO-dependent caspase or control yellow fluorescent protein (YFP). Measurements and Main ResultsControl YFP virus was densely localized to the serotonergic neurons of the medullary raphe (MR), but not the dorsal raphe (DR), and these neurons were ablated by caspase. Leptin enhanced the HCVR, increased arousal latency in males, but not in females, and these effects were abolished by caspase. Neither leptin nor caspase affected sleep architecture or metabolic rate. Leptin increased GG activity awake and during NREM sleep, attenuated pharyngeal obstruction and increased minute ventilation in NREM and REM sleep. All effects of leptin were abolished by the FlpO-dependent caspase. ConclusionsLeptin treats OHS by stimulating MR serotonergic neurons, which project to XII MN and stimulate pharyngeal muscles during sleep.

Background: Cutaneous microvascular responses to local heating and acetylcholine perfusion are widely used to assess nitric oxide (NO)-mediated endothelium-dependent dilation in human health and disease. Despite the increasingly common usage of these approaches, no studies have directly compared responses to these stimuli within individuals. Therefore, we assessed endothelium- and NO-dependent dilation in 80 young adults (40 males/40 females; 22{+/-}3 years) to determine the extent to which microvascular responses to these endothelium-dependent stimuli are comparable within an individual. Methods: We examined cutaneous vascular conductance responses to (1) standardized local heating protocols to 39{degrees}C and 42{degrees}C, and (2) graded infusions of acetylcholine (10-10-10-1 M) alone or with 15 mM NG-nitro-l-arginine methyl ester (L-NAME; NO synthase inhibitor). Endothelium- and NO-dependent dilation were calculated and expressed in multiple ways based on commonly published analyses to allow for a thorough comparison within and between each stimulus. Results: Local heating-induced endothelium- and NO-dependent dilation were lower at 39{degrees}C compared with 42{degrees}C (P<0.001). The magnitude of local heating-induced endothelium-dependent dilation was significantly related to the NO-dependent contribution of that response at 39{degrees}C (R2= 0.79) and 42{degrees}C (R2= 0.56). Local heating-induced NO-dependent dilation at 39{degrees}C was not related to that at 42{degrees}C (P>0.05). Acetylcholine-induced endothelium- and NO-dependent dilation were not related to local heating-induced responses (all P>0.05). Conclusions: These data demonstrate that while local heating and acetylcholine perfusion produce robust endothelium- and NO-dependent cutaneous vasodilation, these responses are not comparable within an individual.

Background: Hormone therapy (HT) has not consistently reduced atherosclerotic cardiovascular disease (ASCVD) events in post-menopausal women, yet the underlying mechanisms remain poorly understood. Methods: Female Ldlr-/- mice with established atherosclerosis were subjected to surgical menopause and treated with 17{beta}-estradiol (E2) following lipid normalization. Studies were performed in aging and young mice. To determine whether inflammation mediates the age-dependent response to HT, a cohort of aging mice underwent transplantation with Ifn{gamma}-/-bone marrow (BM) before hormone treatments. Metabolic parameters, HDL function, systemic inflammation, atherosclerotic burden, liver metabolic and oxidative stress signaling, and hepatic estrogen receptor signaling were evaluated. Results: In aging mice, menopause E2 treatment failed to reduce established atherosclerosis as shown in sham operated mice during lipid normalization. Instead, E2 treatment increased circulating IFN{gamma} and IL-6, impaired HDL antioxidant and cholesterol efflux functions, and promoted inflammatory and vulnerable plaque phenotypes. Suppression of inflammation through Ifn{gamma}-/-BM transplantation restored HDL function and significantly reduced atherosclerosis in E2-treated aging mice. In contrast to aging mice, young mice exhibited reduced systemic and plaque inflammation, improved HDL functions, and regression of atherosclerosis following E2 treatment. Liver RNA sequencing and qPCR validation identified activation of inflammatory, oxidative stress, and lipid metabolic pathways in aging E2-treated mice, which were largely attenuated following Ifn{gamma}-/- bone marrow transplantation as well as in young mice. Compared to young mice, aging mice presented hepatic estrogen receptor remodeling characterized by reduced estrogen receptor (ER) expression and increased G-protein coupled estrogen receptor (GPER) expression. Constitutive GPER activation was accompanied by induction of NOX1-dependent oxidative stress, which was further exacerbated by E2 treatment, leading to persistent inflammation. Conclusions: The cardiovascular effects of estrogen therapy are fundamentally age dependent. Aging shifts estrogen signaling toward hepatic oxidative stress and inflammation through increased GPER. While E2 treatment preserves both metabolic and cardiovascular protection in young mice, aging exacerbates GPER-NOX1-mediated oxidative stress, resulting in impaired HDL function and persistent residual ASCVD risk. These findings identify inflammation-driven, non-lipid mechanisms as potential therapeutic targets to improve cardiovascular outcomes during hormone therapy in postmenopausal women.

Consumption of high fat diet (HFD) is linked to reduced cardiac vagal motor output, a main contributor to progression of cardiovascular disease. HFD for 15 days increases extrasynaptic or tonic gamma aminobutyric acid (GABA) current in cardiac projecting neurons in the dorsal motor nucleus of the vagus (CVNDMV), which contributes to dampening cardiac parasympathetic output. However, the mechanism underlying this increased inhibition is unknown. Here, we hypothesize that increased activity of protein kinase C {delta} isoform (PKC{delta}) enhances tonic GABA current in CVNDMV after HFD. Whole-cell patch-clamp recording of retrogradely labeled CVNDMV demonstrated that pan inhibition of PKC activity with GFX, and isoform specific inhibition of PKC{delta} with rottlerin normalize 15-day HFD-induced increases in tonic GABA current, suggesting that PKC{delta} mediates enhanced tonic inhibition. This effect persisted in the presence of dynasore, a clathrin-mediated endocytosis blocker, indicating that the normalization effect of PKC{delta} inhibition on tonic current in HFD is likely independent of clathrin-mediated endocytosis. Furthermore, no differences in PKC{delta} mRNA or protein expression were observed between NFD and HFD, suggesting a post-translational mechanism underpinning increased tonic GABA current after 15 days of HFD. Altogether, this study provides evidence that HFD-induces increased PKC{delta} activity, but not expression, leading to increased tonic GABAergic inhibition in CVNDMV. This increase PKC{delta} activity could explain the cardiac vagal motor output dampening in CVD and be developed into treatments targeting PKC{delta} for CVD.

White, beige and brown adipocytes store energy as lipids, secrete hormones and produce heat, playing an important role in the regulation of energy balance through not completely defined mechanisms. We investigate herein the impact of the almost complete absence of mature adipocytes (severe lipoatrophy) in the determination of energy balance (energy intake and expenditure) and homeothermy in mice. For this, mice with severe lipoatrophy induced by adipocyte deletion of peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) (PPAR{gamma} flox adiponectin-Cre) and littermate controls (PPAR{gamma} flox) were evaluated for energy balance, thermoneutral zone, core body temperature, locomotor activity, and gene expression profiles at different ambient temperatures. Severely lipoatrophic mice are heavier, hypermetabolic and hyperphagic and feature a widened thermoneutral zone, lower ambulatory activity, and metabolic inflexibility at both 23 and 17{degrees}C, along with unstable thermal behavior characterized by hyperthermia at 30{degrees}C, normothermia at 23{degrees}C, and bouts of hypothermia at 17{degrees}C. Noteworthy, lipoatrophic mice hypermetabolism at 30{degrees}C is not due to thyroid hormones, impaired insulation or increased body and lean masses and is not altered by pharmacological blockade of either {beta}-adrenergic receptor signaling with propranolol or skeletal muscle sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCA) and sarcolipin (SLN)-mediated calcium cycling with dantrolene, but is partially attenuated by pharmacological inhibition of acetyl-CoA carboxylase (ACC) and de novo lipogenesis with ND-630. In conclusion, severe lipoatrophy causes hypermetabolism and hyperthermia at 30{degrees}C partly through the activation of liver de novo fatty acid synthesis.

After myocardial infarction (MI), pathological autonomic remodeling, including vagal dysfunction and sympathoexcitation, occurs and predisposes to ventricular arrhythmias (VT/VF). The underlying factors that drive this remodeling, including the observed neuroinflammation and glial activation, remain unknown. We hypothesized that sympathetic nociceptive afferents underlie this remodeling post-MI. Epidural resiniferatoxin (RTX, to ablate sympathetic cardiac afferent neurons) vs. saline was administered in pigs prior to MI and autonomic and electrophysiological effects assessed four to six weeks post-infarction. Acute effects of afferent ablation after chronic MI were also assessed in a separate group of animals. Baroreflex sensitivity and vagal tone, as measured by parasympathetic neuronal activity and cardiac nociceptive responses, were improved in infarcted animals which received epidural RTX prior to MI. These animals also demonstrated reduced spinal cord inflammation and glial activation, downregulation of circulating stress and inflammatory pathways, and stabilization of electrophysiological parameters, with reduced VT/VF-inducibility. Epidural RTX after chronic MI also acutely restored vagal function and decreased VT/VF. These data suggest that cardiac spinal nociceptive afferents directly contribute to VT/VF susceptibility and MI-induced autonomic remodeling, including oxidative stress, inflammation, glial activation, and reduced vagal function, providing novel insights into the causal role of these afferents in driving sympathovagal imbalance after MI.

Background Ischemic heart failure (IHF) has been shown to impair contractility and disrupt sarcomere function in the left ventricle. Left ventricular failure can cause left atrial dysfunction, which is associated with a greater risk of patient mortality. Despite this, the biochemical and biomechanical characteristics of the left atrium in IHF remain obscure. Methods Myocardial mechanical properties were measured using permeabilized muscle isolated from the left ventricle (LV) and left atrium (LA) of donors and patients with IHF. Tissue homogenates from these samples were used to measure titin and myosin isoforms as well as the phosphorylation of sarcomeric regulatory proteins. Histology was used to quantify fibrosis in the patients' left ventricle and left atrium. Results Length-dependent changes in Ca2+-sensitivity were blunted in LV myocardium from patients with IHF. LA myocardium did not show robust length-dependence of Ca2+-dependent force. The calcium sensitivity of both LA and LV myocardium was increased in IHF. The maximum force generated by LV but not LA myocardium was decreased in IHF. LA myocardial samples exhibited faster contractile kinetics than LV samples, irrespective of disease. Troponin I phosphorylation decreased in both chambers with IHF. Conclusions Left atrial IHF myocardium maintained contractile force and displayed increases in calcium sensitivity, which may allow for increased LA contraction under pathological conditions. The increases in calcium sensitivity observed in ischemic myocardium of both chambers are likely driven by decreased phosphorylation of troponin I, which alters thin filament regulation. Conversely, thick filament properties of the left ventricle, such as thick filament protein isoforms and phosphorylation of myosin binding protein-C, displayed chamber-specific differences independent of disease state. These biochemical changes may explain the chamber-specific differences in kinetics and length-dependent properties. Collectively, these biophysical and biochemical data suggest LA remodeling in IHF may assist in increasing LV end-diastolic volume to maintain adequate cardiac output.