Physiological Reports

We measured plasma levels of fibrinogen, plasminogen, tissue plasminogen activator (t-PA) and plasminogen activation inhibitor 1 (PAI-1) in blood from 37 patients with severe coronavirus disease-19 (COVID-19) and 23 controls. PAI-1, t-PA and fibrinogen levels were significantly higher in the COVID-19 group. Increased levels of PAI-1 likely result in lower plasmin activity and hence decreased fibrinolysis. These observations provide a partial explanation for the fibrin- mediated increase in blood viscosity and hypercoagulability that has previously been observed in COVID-19. Our data suggest that t-PA administration may be problematic, but that other interventions designed to enhance fibrinolysis might prove useful in the treatment of the coagulopathy that is often associated with severe COVID-19.

The increase in plasma volume [~]24 hours post-exercise may act as an erythropoietic signal, but this mechanisms responsiveness to different exercise prescription variables is poorly understood. The purpose of this study was to determine the impact of high-intensity interval exercise duration on plasma volume and related responses. On separate days, 16 healthy, recreationally active participants (n=8 males; n=8 females) performed four (4x4) or eight intervals (8x4) consisting of 4 min at 105% critical power with 3 min recovery. Venous blood samples collected before, immediately after, and 24 hours after each HIIT session were used to measure hemoglobin concentration and hematocrit to calculate plasma volume changes. Erythropoietic and plasma volume regulating hormone concentrations were measured using ELISA kits. Plasma volume decreased immediately after both protocols (4x4: -4.4{+/-}3.5%, p<0.05; 8x4: -4.4{+/-}3.6%, p<0.05) but was only significantly elevated above baseline 24 hours after the 8x4 protocol (4x4: +1.0{+/-}7.1%, p>0.05; 8x4: +5.6{+/-}4.6%, p<0.05). Erythropoietin concentration ([EPO]) was higher than baseline 24 hours after the HIIT protocols (4x4: Pre vs 24 h post: 6.5{+/-}3.1 vs. 7.1{+/-}3.3 mIU/mL; 8x4: 6.9{+/-}3.7 vs. 7.3{+/-}3.7 mIU/mL; main effect of time, p<0.05) with no difference between protocols (p>0.05). [Aldosterone] was elevated immediately post-exercise after both protocols (4x4: Pre vs 0 h post: 295{+/-}151 vs. 544{+/-}259 pg/mL; 8x4: 335{+/-}235 vs. 821{+/-}553 pg/mL), but the 8x4 protocol caused a larger increase (interaction effect, p<0.05). That post-exercise hypervolemia may be exercise duration-dependent but is not required for increases in circulating EPO has important implications for endurance training aiming to increase oxygen delivery to active tissues. NEWS AND NOTEWORTHYThis study is the first to show that both a common HIIT protocol length (4 x 4 min) and an extended HIIT protocol (8 x 4 min) similarly increased [erythropoietin] 24 h after exercise, despite only the extended protocol transiently increasing plasma volume. Previous works have investigated plasma volume regulation following different HIIT durations, but not explored links to erythropoietic signalling. This studys findings have relevance for understanding the physiology of exercise-induced erythropoiesis.

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.

Little is known about the prognostic value of out-of-clinic biometric monitoring of cardiovascular function in chronic kidney disease (CKD). Using real-world sampling strategies, a mean ({+/-}SD) of 50.3{+/-}9.3 hours of ECG recordings from wearable BioPatch ECG devices was collected in a cohort consisting of 458 participants from seven Chronic Renal Insufficiency Cohort (CRIC) centers. The presence of diabetes was associated with a 7.4 ms lower Standard Deviation of NN Intervals (SDNN) compared to non-diabetic participants (p=0.001). Multivariable linear regression revealed that participants without proteinuria (uPCR<0.2) had a 5.15 ms higher SDNN compared to participants with proteinuria (uPCR[&ge;]0.2, p=0.027). Cosinor modeling suggested differences in SDNN acrophase quartiles for diabetes (p=0.02), history of cardiovascular disease (p=0.003), eGFR (p=0.04), systolic blood pressure (p=0.04), and beta blocker use (p=0.0002). In the spline analysis, the SDNN curve differed between participants with and without cardiovascular disease (p=0.0005). This study assembled the largest dataset to date of SDNN as an index for heart rate variability from wearable digital health technology in the CRIC. The study demonstrates that several clinical and demographic factors are associated with SDNN in participants with CKD. This sets the stage to determine the predictiveness of time-specific HRV metrics for future clinical outcomes.

Recent studies have emphasized the importance of the nitric oxide synthase (NOS)-independent, nitrate (NO3-) [-&gt;] nitrite (NO2-) [-&gt;] nitric oxide (NO) pathway in skeletal muscle. In particular, it has been hypothesized that this pathway is especially active in type II, or fast-twitch, muscle fibers, necessitating greater NO3- and NO2- storage. We therefore measured NO3- and NO2- concentrations in the predominantly fast-twitch vastus lateralis and predominantly slow-twitch soleus muscles of rats. Contrary to the above hypothesis, we found that NO3- and NO2- concentrations were 3.4-fold and 1.8-fold higher, respectively, in the soleus. On the other hand, NO signaling (i.e., cyclic guanosine monophosphate (cGMP) level) was comparable in the two muscles. Although the physiological significance of these observations remains to be determined, we speculate that NO production via the NO3- [-&gt;] NO2- [-&gt;] NO pathway is normally higher in slow-twitch muscles, thus helping compensate for their inherently lower NOS activity.

PurposeModerate-intensity exercise has beneficial effects for individuals with CKD. However, it is unclear whether intermittent exercise (IE) has a different effect on renal haemodynamics compared to continuous exercise (CE). This study aimed to compare the effects of intermittent or continuous exercise on renal haemodynamics and renal injury during moderate-intensity exercise. MethodsTen males underwent IE or CE to consider the effect of exercise on renal haemodynamics during moderate-intensity exercise. Renal haemodynamic assessment and blood-sampling were conducted before exercise (pre) and immediately (post 0), 30-min (post 30), and 60-min (post 60) after exercise. Urine-sampling was conducted in pre, post 0 and post 60. ResultsThere was no condition-by-time interaction (p = 0.073), condition (p = 0.696), or time (p = 0.433) effects regarding renal blood flow. There was a condition-by-time interaction effect regarding noradrenaline concentrations (p = 0.037). Moreover, both conditions significantly increased noradrenaline concentration at post 0 (IE: p = 0.003, CE: p < 0.001) and remained significantly higher in post 30 (p < 0.001) and post 60 (p < 0.001). Significant difference was found in noradrenaline concentrations at post 0 when comparing IE and CE (399 {+/-} 119 vs. 552 {+/-} 224 pg/ml, p = 0.037). Urinary neutrophil gelatinase-associated lipocalin concentrations increased at post 60 (p = 0.009), but none of them exceeded the cutoff values for the definition of renal damage. Other renal injury biomarkers showed a similar pattern. ConclusionThese findings suggest that IE has a similar effect on renal haemodynamics and function, and AKI biomarkers compared to CE.

Ventricular remodeling is one of the primary adaptive mechanisms in response to long-term mechanical overload in diabetes. In addition to cardiomyocyte hypertrophy, alterations in noncardiomyocyte compartments [e.g. extracellular matrix (ECM)] are an essential process in the remodeling of ventricle during diabetes. Integrins that link the ECM and intracellular cytoskeleton function as mechanotransducers to translate the mechanical force to intracellular signals. We hypothesize that mechanotransduction mechanisms are altered in diabetic cardiomyopathy mouse hearts. To test this hypothesis, force and intracellular calcium ([Ca2+]i) measurements on papillary muscle fibers were investigated in adult mouse cardiomyocytes from normal (non-db) and type 2 diabetic (db/db) mice. In addition, atomic force microscopy (AFM) was used to measure adhesion force between integrin receptors and ECM protein fibronectin (FN) by quantifying the unbinding force required to break FN-cardiomyocytes (integrin) bonds. In db/db mice, the peak active force decreased at 71% or 73% while the peak of [Ca2+]i decreased at 64% and 68% at 1 Hz or 2 Hz. In the presence of the FN (35 nM), active force was increased significantly by 40-50% in db/db mice. Furthermore, increased active force in the presence of FN was associated with 26-42% increase in [Ca2+]i at all giving stimulations of 1 Hz and 2 Hz in db/db mice, respectively. The increased effects on force and [Ca2+]i caused by FN were greater in ventricular muscles from db/db mice than from non-db mice. The unbinding force between FN (2.7 M) coated AFM probes and cardiomyocyte in db/db was 52% higher than non-db (58.3 {+/-} 0.3 pN vs 38.6 {+/-} 0.9 pN. p < 0.05). The binding probability of FN-cardiomyocytes, calculated as number of force curves with adhesion / number of total force curves sampled, was significantly reduced by 30% in db/db cardiomyocytes when compared to normal. In addition, the cell stiffness, representing changes in Ca2+ signaling and cytoskeletal reorganization, was 19% increase in db/db cardiomyocytes. The presented data indicate that dynamic changes of the mechanical properties of integrin-ECM interactions may contribute to impaired intracellular Ca2+ signaling and myofilament activation in the diabetic cardiomyopathy.

The impact of testosterone therapy on hormone cycles, exercise capacity, and physiology of transmasculine individuals is not well understood. Existing studies report limited metrics at large time intervals between data collection. Here, we collect high-resolution temporal data from a single amateur trans male triathlete over a time period of 13 months-including one baseline month and twelve months on testosterone therapy-to characterize hormone, strength, body composition, aerobic, and training load profiles. Daily urine hormone monitoring revealed that progesterone and luteinizing hormone are the clearest metrics to predict cessation of menses. After one year, the participant increased lean body mass by 12%, average hand grip strength by 13%, jump height by 16%, and average knee isometric strength by 15%, but, in contrast with prior research, did not lose fat mass or show changes in isokinetic knee strength. While absolute VO2 max increased by 10%, relative VO2 max (e.g., normalized to body mass) only increased during corresponding peaks in training load. We provide guidelines to monitor trans males during testosterone therapy and recommendations to scale this case study to a larger population.

Sickle cell disease (SCD) is a systemic hematological disease. Various genotypes of the disease exist; however, the two most common include hemoglobin SS (Hgb SS) and hemoglobin SC (Hgb SC) disease. Hgb SC is typically considered a less severe genotype; however, some patients with SC disease still have significant complications. Ektacytometry is utilized to measure red blood cell deformability in sickle cell patients and may help identify patients at risk for severe disease. We described a patient with genotype hemoglobin SC with a more severe phenotype, who we show to have very rigid red blood cells via ektacytometry.

We have previously shown that fresh frozen plasma (FFP) and fibrinogen have protective effects in mice with hemorrhagic shock through restoration of endothelial syndecan-1 and reversal of endothelial injury. In the current study, we tested the hypothesis that a combined model of abdominal sepsis and hemorrhagic shock would induce endothelial syndecan-1 shedding and lung injury which could be attenuated by both FFP and fibrinogen. C57BL/6 mice underwent cecal ligation and puncture (CLP) followed by hemorrhagic shock (HS) and fluid resuscitation with lactated Ringers (LR), fibrinogen (5 mg/mouse), and FFP, all at 1X shed blood volume. After 24 hours, lung tissues and plasma were harvested for assays. CLP+HS induced an increase in alveolar thickness and decreases in lung syndecan-1 and lung neutrophil granule-enzymes (myeloperoxidase, neutrophil elastase, and MMP9), with reciprocal elevations in plasma syndecan-1 and plasma neutrophil granule-enzymes (myeloperoxidase, neutrophil elastase, and MMP9). All these alterations were significantly attenuated by FFP but not by fibrinogen. Additionally, CLP+HS-induced hypotension at 24 hours was partially reversed by FFP but not by fibrinogen. FFP administration inhibits CLP+HS-induced neutrophil degranulation to prevent syndecan-1 shedding and lung injury. The current study supports that FFP has therapeutic benefit in a combined septic and hemorrhage shock model.

Fibroblast growth factor 21 (FGF21) is a biomarker that has been linked to metabolic health. This study was conducted to examine the relationship between FGF21 and its purported upstream regulators and downstream targets in healthy humans. Male and female participants completed three study visits. During visit 1 anthropometrics were measured and a VO2peak test was conducted on a stationary bike. During visits 2 and 3 resting metabolic rate, heart rate, and blood pressure were recorded and a blood sample was taken. Results from visits 2 and 3 were averaged before statistical analysis. Additionally, participants completed a food frequency questionnaire to detail typical diet over the previous month and had three days of measured physical activity and sleep. Moderate correlations between FGF21 and measured sleep (r = 0.34, p = 0.05), saturated fat intake (r = -0.37, p = 0.04), and blood urea nitrogen levels (r = -0.47, p = 0.01) were observed. Additionally, greater intensities of daily physical activity were associated with lower FGF21 levels. Serum FGF21 levels may be influenced by lifestyle variables such as sleep and physical activity, diet, and other circulating biomarkers. Highlights- FGF21 is positively correlated with sleep in healthy humans. - Sugar intake is positively correlated with FGF21 concentrations in humans. - Blood urea nitrogen concentrations are negatively correlated with FGF21 in humans.

Obesity alters protein metabolism in skeletal muscle, and although exercise and amino acids act synergistically to regulate muscle anabolism in healthy humans, this interaction may be impaired in obesity. We examined whether acute aerobic exercise alters amino acid-stimulated muscle protein synthesis during the immediate postexercise period in subjects with obesity. Sixteen sedentary adults with a body mass index >30 kg/m2 underwent stable-isotope tracer infusion studies to determine mixed-muscle fractional synthesis rate (FSR) in the basal (fasted) state and under two experimental conditions: eight subjects received an amino acid infusion (AA), while another eight performed 45 min of cycling at [~]65% heart rate reserve immediately prior to the amino acid infusion (EX+AA). Amino acid infusion significantly increased muscle protein FSR in AA (P < 0.0001). In contrast, no significant increase was observed in EX+AA (P > 0.05), and the amino acid-stimulated increase in muscle protein FSR in EX+AA was 78% lower than that in the AA (P < 0.01). Amino acid infusion increased plasma amino acid concentrations in both conditions (P < 0.05); however, plasma concentrations of essential and branched-chain amino acids, including leucine, were lower in the EX+AA condition (P < 0.05). Changes in muscle protein FSR were positively associated with plasma leucine concentrations during the amino acid infusion (P < 0.05). These findings suggest that, in humans with obesity, aerobic exercise may abolish amino acid-stimulated muscle protein synthesis during the immediate postexercise period, with implications when considering nutritional strategies designed to optimize muscle anabolism in this population. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/732200v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1c9d4e3org.highwire.dtl.DTLVardef@1b7c399org.highwire.dtl.DTLVardef@18a99aborg.highwire.dtl.DTLVardef@6ed880_HPS_FORMAT_FIGEXP M_FIG C_FIG

Synthetic membrane stabilizers, such as poloxamer 188 (P188), have great promise in the treatment of Duchenne muscular dystrophy and other diseases associated with disrupted membranes. The aim of this study was to assess the efficacy of P188 to limit myocardial damage in models of muscular dystrophy subjected to highly injurious stress. These studies use male and female mdx and {beta}-sarcoglycan null ({beta}-SG-/-) mice subjected to an isoproterenol stress protocol in the presence or absence of P188. We show that P188 provides a significant level of protection to male mdx hearts from the isoproterenol induced injury. Surprisingly, we find that P188 has no protective actions in female mdx mice or in {beta}-SG-/- mice of either sex. These results suggest that the mechanism of action of P188 is more complicated than previously thought. The presence of sex differences in the absence of dystrophin is not consistent with a model of P188 working by biophysical restoration of membrane integrity. Furthermore, the absence of protective effects of P188 in {beta}-SG-/- myocardium indicates that there are important differences in the mechanisms of membrane damage in hearts lacking dystrophin and hearts lacking the sarcoglycan complex. Developing a better understanding of these differences will be important in the development of therapies for dystrophic cardiomyopathy and other forms of heart disease.

Impaired microvascular function is a hallmark of pre-diabetes. With development of atherosclerosis this impaired microvascular function can result in diminished capacity for ambulation and is a risk factor for Type 2 Diabetes. Dynamic changes in vascular tone are determined, in large part, by the eNOS/NO/cGMP axis. We used gain of function of the eNOS/NO/cGMP axis in diet-induced obese (DIO) mice and reduced function in lean mice to test the hypothesis that functionality of this vascular control mechanism parallels the benefits of an exercise training regimen. DIO mice have lower exercise capacity than lean mice and were used for pharmacological gain of function. The PDE-5a inhibitor - sildenafil - increases cGMP and was administered to DIO mice daily. In sedentary mice, we find that sildenafil does not improve exercise capacity. In contrast, it amplifies the microcirculatory effects of exercise training. Sildenafil synergizes with exercise training to improve performance during an incremental exercise test. Improved exercise performance was accompanied by increased skeletal muscle capillary flow velocity and capillary density measured via intravital microscopy. Loss of function was tested in lean mice hemizygous for endothelial cell (EC) specific eNOS creating an EC-eNOS knockdown (KD). EC-eNOS KD decreases capillary density and exercise tolerance in sedentary mice; however, it did not prevent exercise-training induced improvements in endurance capacity. These data show that 1) increasing cGMP with sildenafil enhances microcirculatory function and exercise work tolerance that results from training; 2) eNOS KD does not prevent the microcirculatory or improvements in exercise tolerance with training. PDE-5a inhibitors combined with physical exercise are a potential mechanism for improving ambulation in patients with circulatory limitations.

Chronic angiotensin II (AngII) infusion is an experimental model that induces hypertension in rodents. The natriuresis, diuresis, and blood pressure responses differ between males and females, perhaps unexpectedly, given the rodent kidney, which plays a key role in blood pressure regulation, exhibit marked sex differences. Those sex differences include morphology, hemodynamics, and, under healthy (undrugged) conditions, solute and electrolyte transporter abundance. Notably, compared to the male rat nephron, the female rat nephron exhibits lower Na+/H+ exchanger 3 (NHE3) activity along the proximal tubule, but higher Na+ transporter activities along the distal segments. AngII infusion-induced hypertension induces a pressure natriuretic response that reduces NHE3 activity and shifts Na+ transport capacity downstream, to different extents in the two sexes. The goals of this study are (i) to understand how the sexually dimorphic responses differentially impact segmental electrolyte transport following a 14- day AngII infusion, and (ii) to identify and explain any sex differences in the effects of loop diuretics, thiazide diuretics, and K+-sparing diuretics. To achieve those goals, we developed sex-specific computational models of renal epithelial transport of electrolytes and water. Model simulations suggest that the NHE3 downregulation in the proximal tubule is a major contributor to natriuresis and diuresis in hypertension, with a stronger effect in males. Due to the downstream shift of Na+ transport load in hypertension, all three diuretic classes are predicted to induce stronger natriuretic and diuretic effects under hypertension compared to normotension, especially in females. New and NoteworthySex differences in the prevalence of hypertension are found in humans and animal models. The kidney, which plays an important role in blood pressure regulation, exhibits sex differences in morphology, hemodynamics, and membrane transporter distributions. This computational modeling study provides insights into how the sexually dimorphic responses to a 14-day angiotensin II infusion differentially impact segmental electrolyte transport. Simulations results also explain sex differences in the effects of loop diuretics, thiazide diuretics, and K+-sparing diuretics.

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.

Angiotensin converting enzyme 2 (ACE2) is an enzyme that limits activity of the renin-angiotensin system (RAS) and also serves as a receptor for the SARS-CoV-2 Spike (S) protein. Binding of S protein to ACE2 causes internalization which activates local RAS. ACE2 is on the X chromosome and its expression is regulated by sex hormones. In this study, we defined ACE2 mRNA abundance and examined effects of S protein on ACE2 activity and/or angiotensin II (AngII) levels in pivotal tissues (lung, adipose) from male and female mice. In lung, ACE2 mRNA abundance was reduced following gonadectomy (GDX) of male and female mice and was higher in XX than XY mice of the Four Core Genotypes (FCG). Reductions in lung ACE2 mRNA abundance by GDX occurred in XX, but not XY FCG female mice. Lung mRNA abundance of ADAM17 and TMPRSS2, enzymes that shed cell surface ACE2 and facilitate viral cell entry, was reduced by GDX in male but not female mice. For comparison, adipose ACE2 mRNA abundance was higher in female than male mice and higher in XX than XY FCG mice. Adipose ADAM17 mRNA abundance was increased by GDX of male and female mice. S protein reduced ACE2 activity in alveolar type II epithelial cells and 3T3-L1 adipocytes. Administration of S protein to male and female mice increased lung AngII levels and decreased adipose ACE2 activity in male but not female mice. These results demonstrate that sex differences in ACE2 expression levels may impact local RAS following S protein exposures.

Obesity is a significant health concern worldwide, increasing the risk for type 2 diabetes mellitus (T2DM) and cardiovascular disease. Studies have found various vascular anomalies, abnormal heart rhythm, and impaired electro-mechanical coupling in patients with diabetes. Research on non-diabetic obese individuals has shown that besides diabetes-related complications, obesity itself raises the risk of developing cardiovascular disease. Recent studies have revealed a decrease in the speed of electrical signal conduction in the heart, along with slight gap junction dysfunction, which is insufficient to explain the observed impediment of impulse conduction. Its still unclear whether this impairment is due to obesity-related fat toxicity or diabetes-related factors. Our study aimed to investigate the ventricular action potential parameters and voltage-gated Na+ (INa) and Ca2+ (I(Ca, L)) currents in Zucker fatty (ZF) rats in comparison to Zucker diabetic fatty (ZDF) rats, a well-established model of obesity and T2DM. Ventricular myocytes were enzymatically isolated from 25-30-week-old Zucker rats. Resting and action potentials were recorded from isolated left ventricular myocytes using a {beta}-escin perforated patch clamp in current-clamp mode; INa and I(Ca, L) were recorded using whole-cell patch clamp techniques. Ventricular myocytes from ZF rats showed higher excitability and faster upstroke velocity. ZF rats also had a larger density of INa. Conversely, ZDF rats had decreased INa which correlated with a reduced velocity of the action potential upstroke. There were no changes in the density or voltage sensitivity of I(Ca, L) among the three groups of animals. In conclusion, obesity alone and obesity accompanied by DM have distinct effects on the action potential waveform, INa density and excitability of ventricular myocytes in a rat model of T2DM.

BackgroundLow bone mass is common in adults with thalassemia (Thal) and sickle cell disease (SCD), though disease-specific artifacts may contribute to inaccuracies in bone mineral density (BMD) assessment. Trabecular bone score (TBS), an indicator of bone quality, is not susceptible to these challenges and may improve fracture risk prediction. MethodsA retrospective chart review was conducted in patients with Thal or SCD who had at least one spine BMD scan by DXA performed in the past 10 years. The most recent scan was reanalyzed for bone quality using TBS Insight (Medimaps v 3.0.2) with abnormal defined as TBS <1.20. Fracture prevalence was determined by patient report with medical record validation. Patients were compared to healthy controls who participated in previous research. ResultsData was abstracted from 126 patients with Thal (31.7{+/-}11.9 yrs, 51% Male), 170 with SCD (24.6{+/-}13.5 yrs, 43% Male), and 64 controls (25.9{+/-}8.0 yrs, 17% Male). Low bone mass was observed in 63% of Thal compared with 36% of SCD and 3% of controls (p<0.001); while only 15% of patients had abnormal TBS. History of fracture was present in 35.6% of Thal and 22.9% of SCD; of which 15.7% were fragility fractures. After adjusting for age and hypogonadism, low bone mass was associated with an increased overall fracture prevalence (OR: 1.8, 95% CI: 1.03, 3.23; p=0.041), but not with fragility fracture. In contrast, abnormal bone quality was strongly associated with fragility fracture after adjustment for age, sex, and BMI (OR: 11.4, 95% CI: 2.2, 59.1, p=0.004). ConclusionsBone quality by TBS may be a valuable tool in predicting the risk of fragility fractures in young adults with hemoglobinopathies and should be considered when making decisions for anti-resorptive therapy in those with low BMD naive to fracture or where disease-specific artifacts complicate accurate spine assessment by BMD alone.

BackgroundHyponatremia is the most frequent electrolyte disturbance in hospitalized patients, yet assessing volume status remains a diagnostic challenge. The Venous Excess Ultrasound (VExUS) system has been proposed as a noninvasive method to evaluate volume overload and guide management. However, data on its clinical impact in hypoosmolar hyponatremia are limited. ObjectiveTo investigate whether the VExUS system can support the management of acute hypoosmolar hyponatremia, detect discrepancies with physical examination in assessing volume status, and predict clinical outcomes. MethodsThis single-center observational study included adult inpatients with moderate or severe hypoosmolar hyponatremia (plasma sodium <=130 mEq/L). Patients underwent a standard clinical evaluation (history and physical examination) and a VExUS-based ultrasound assessment of at least two venous regions (inferior vena cava, hepatic veins, portal vein, or renal veins). Internal jugular vein measurements were used when feasible. The treating physicians of the patients were blinded to the ultrasound findings. Serum sodium levels were measured at 24, 48, and 96 hours. Treatments were based on existing clinical guidelines, and any changes in therapy were documented. ResultsTwenty-eight patients were enrolled, and two were excluded due to inadequate ultrasound data or new-onset cirrhosis. VExUS classification differed from clinical examination in 65.4 percent of patients (17 of 26), yet these discrepancies did not lead to significant differences in serum sodium trends or management changes at 24, 48, or 96 hours (p>0.05). Only four patients required therapeutic adjustments within 24 hours, and one displayed discrepant volume classifications. The VExUS system showed limited ability to distinguish euvolemia in patients with SIADH and demonstrated minimal correlation with laboratory parameters such as NT-proBNP and CA-125. ConclusionsWhile ultrasound assessment is noninvasive and potentially useful, this study found that discrepancies in VExUS-based volume status classification did not significantly alter clinical outcomes or treatment strategies in hospitalized patients with hypoosmolar hyponatremia. The VExUS method should not replace standard complementary evaluations recommended by hyponatremia guidelines, although it may have a niche role when ruling in or out hypervolemia in selected cases.