bluuebunny/crossref_metadata_2025 huggingface dataset:
Blunted Increases in Skin Sympathetic Nerve Activity Contribute to the Attenuated Reflex Vasodilation in Aged Human Skin
Authors: Stanhewicz Anna E , Greaney Jody L , Alexander Lacy M , Kenney W. Larry
Published: November 2023

When core and skin temperatures are elevated, reflex cutaneous vasodilation is attenuated in human aging, even in the absence of overt cardiovascular disease or elevated cardiovascular disease risk factors. This diminished response is mediated, in part, by age‐associated alterations in endothelial function; however the relative contribution of altered skin sympathetic nervous system activity (SSNA) remains unclear. We hypothesized that 1) apparently healthy older (O) adults would demonstrate blunted SSNA responses to increased core temperature compared to young (Y) adults, and 2) that the decreased SSNA response would be associated with an attenuated cutaneous vasodilation. Reflex vasodilation was induced in 8 Y (24 ± 1 yrs; range = 20–29 yrs) and 8 O (68 ± 2 yrs; range = 60–79 yrs) adults using a water‐perfused suit to elevate esophageal temperature (Tes) by 1.0°C. SSNA (peroneal microneurography) and red cell flux (laser Doppler flowmetry) in the innervated dermatome (the dorsum of foot) were continuously measured. SSNA was normalized to, and expressed as, a percentage of baseline. Cutaneous vascular conductance (CVC) was calculated as flux/mean arterial pressure and expressed as a percentage of maximal CVC (local heating to 43°C). Reflex vasodilation was attenuated in O adults (O: 26±3 vs. Y: 56 ± 5 %CVCmax; p<0.001). During whole‐body heating, SSNA increased in both groups (p<0.05); however, the response was significantly blunted in O adults (O: Δ265 ± 79 vs. Y: Δ593 ± 73%; p=0.006). The increase in SSNA during heating was significantly correlated with cutaneous vasodilation in both Y (r2 = 0.97, p<0.001) and O (r2 = 0.92, p<0.001) adults throughout heating, with no age‐related differences in the slope of the linear regression between SSNA and %CVCmax (O: 0.06 ± 0.01 vs. Y: 0.07 ± 0.00; NS). These data demonstrate that age‐related impairments in reflex cutaneous vasodilation are mediated, in part, by a blunted efferent SSNA during hyperthermia.

Support or Funding Information

ACSM Research Endowment Grant
Thermotherapy Reduces Blood Pressure and Increases Leg Blood Flow in Patients With Symptomatic Peripheral Artery Disease
Authors: Roseguini Bruno Tesini , Neff Dustin , Kuhlenhoelter Alisha , Wong Brett , Motaganahalli Raghu
Published: November 2023

Peripheral arterial disease (PAD) is characterized by atherosclerotic obstruction of the arteries in the lower extremities and affects approximately 10% of individuals older than 65 years. The most common clinical presentation of PAD is intermittent claudication (IC), defined as leg pain caused by insufficient blood flow during walking. Despite the increasing prevalence of this condition, few non‐invasive therapies exist to improve vascular function and exercise tolerance in patients with IC. Recent studies demonstrated that repeated exposure to thermotherapy (TT) alleviates the symptoms of the disease, but the mechanisms by which TT exerts its clinical benefits remain elusive. We tested the hypothesis that application of leg thermotherapy (TT) using a water‐circulating garment system would increase leg blood flow and reduce blood pressure in patients with IC. Fourteen patients (age: 63±9 yrs) completed two experimental sessions, at least 72 hrs apart, in a randomized, cross‐over design. In the TT session, water at 48°C was circulated through the garment for 90 min, while thermoneutral water (33°C) was used in the control intervention. Leg skin temperature, core body temperature, heart rate and blood pressure were measured before, during and for 2 hrs following the interventions. A subset of 7 patients also underwent a protocol for the measurement of blood flow in the popliteal artery before and during 90 min of TT using phase contrast magnetic resonance imaging. Application of TT for 90 min induced marked increases from baseline in leg skin temperature (from 32.9±0.3 to 39.8±0.5°C, p<0.01) and HR (from 64±3 to 76±4 bpm, p<0.01) as well as a modest increase in core temperature (from 36.9±0.1 to 37.5±0.2°C, p<0.01). Compared to the control intervention, TT promoted a sustained reduction in systolic (~14 mmHg) and diastolic (~6 mmHg) blood pressure (p<0.05). In addition, TT application induced a marked increase in peak blood flow velocity (~92%), average velocity (~81%), and average blood flow per min (~97%) in the popliteal artery (p<0.01). These findings indicate that TT is a simple and effective strategy to reduce blood pressure and enhance leg blood flow in patients with IC.

Support or Funding Information

Indiana Clinical and Translational Science Institute Project Development Team
Daily Adaptive Changes in Blood Chemistry of Pigs Exposed to Heat Stress
Authors: Trejo Adriana Morales , Ibarra Nely , Castillo Gilberto , Pérez Misael , Castro Pedro , Avelar Ernesto , Cervantes Miguel
Published: November 2023

Animals and humans exposed to heat stress (HS) conditions may modify their physiology and metabolism to maintain homeostasis. In the dessert regions of the world, they have to adapt to great changes in ambient temperature (AT) within 24‐h periods, from thermo neutral (TN) AT early in the morning to stressful high AT in the afternoon. An experiment was conducted with six pigs (45 kg BW), individually housed, during the summer of Northwestern Mexico to analyze the impact of HS as well as the diurnal changes in AT on their blood chemistry. First, the pigs were housed under natural HS conditions (30.4 – 41.1° C, HS) during 14 d. Then, the pigs were moved to an air‐conditioned room (22.6–25.1 °C, TN) for two weeks. Blood samples were collected from the jugular vein of pigs at 0600, 1200 and 1600 h, during the last three days under HS, and again on the last day under TN conditions. Samples were processed to obtain serum in which blood chemistry parameters were analyzed. Heat stress reduced the serum concentration of cholesterol, total proteins, albumin, globulin, phosphorus, and Ala‐amino‐transferase (P<0.05); indirect bilirubin tended to reduce (P<0.10), and calcium tended to increase (P<0.10). As for the diurnal changes in AT, Ca SC decreased at 1200 and 1600 h (P<0.001) as compared with that at 0600; cholesterol also reduced at 1600 h compared to 0600 h (P<0.05). These changes indicate that HS animals modify their physiology and that some factors such as blood proteins, cholesterol and calcium are modified along the day in order to maintain pig homeostasis.

Support or Funding Information

CONACYT, México. Ciencia básica 2012, 00181348.
Menstrual Cycle Phase does not Influence Whole Body Heat Loss Responses During Exercise in the Heat
Authors: Dervis Sheila , Poirier Martin P. , Paull Gabrielle , Zhang Sarah Y. , Kenny Glen P.
Published: November 2023

Traditionally, female reproductive hormones (i.e., estrogen and progesterone) have been shown to independently influence local thermal responses during exercise in the heat. Consequently, studies examining thermal responses during exercise usually only test females during the early follicular phase of the menstrual cycle (i.e., first five days) when estrogen and progesterone are at their lowest levels. However, it remains unclear whether local thermal responses translate into comparable changes in whole‐body heat loss throughout the menstrual cycle. Therefore, we examined changes in whole‐body evaporative heat loss as determined using direct calorimetry in the early follicular (i.e., when both estrogen and progesterone levels are low), late follicular (i.e., when estrogen levels are high) and mid‐luteal (i.e., when both progesterone and estrogen levels are high) phases in young females (n=5, 21±2 years). Participants performed three 30‐min bouts of semi‐recumbent cycling at a fixed rate of metabolic heat production equal to 250 (Ex1), 325 (Ex2) and 415 W (Ex3) in the heat (40°C and 15% relative humidity), each bout followed by 15‐min of recovery. Whole‐body heat loss (evaporative and dry) and metabolic heat production were measured by direct and indirect calorimetry, respectively. Whole‐body heat content was calculated as the temporal summation of heat production and heat loss. Our preliminary results demonstrate that the combined rate of metabolic heat production and dry heat gain (i.e., net heat load) was similar between hormonal phases throughout the incremental intermittent exercise protocol (P>0.05). The rate of whole‐body evaporative heat loss measured during the early follicular (Ex1: 259±10 W, Ex2: 328±17 W, Ex3: 353±20 W), late follicular (Ex1: 248±27 W, Ex2: 306±36 W, Ex3: 337±31 W) and mid‐luteal phases (Ex1: 246±21 W, Ex2: 304±52 W, Ex3: 346±46 W) of the menstrual cycle were similar between phases for each exercise bout (P≥0.05). Accordingly, whole‐body heat content was also similar (early follicular: Ex1: 124±80 kJ, Ex2: 147±80 kJ, Ex3: 247±78 kJ; late follicular: Ex1: 125±27 kJ, Ex2: 139±17 kJ, Ex3: 180±59 kJ; mid‐luteal: Ex1: 121±28 kJ, Ex2: 147±39 kJ, Ex3: 213±49 kJ) (P>0.05). Our preliminary findings suggest that ovarian hormone fluctuations (i.e., estrogen and progesterone) during the menstrual cycle in young females do not influence whole‐body heat dissipation and therefore the amount of heat stored during exercise in the heat.

Support or Funding Information

Funding support: This study was supported by grants from the Natural Sciences and Engineering Research Council of Canada (Discover grant, RGPIN‐06313‐2014; Discovery Grants Program ‐ Accelerator Supplement, RGPAS‐462252‐2014; funds held by Dr. Glen P. Kenny).
The Effect of ETA and ETB Receptor Inhibition on Cutaneous Vasodilation and Sweating in Young Males During Rest and Exercise in the Heat
Authors: Singh Maya , Halili Lyra , Fujii Naoto , Kenny Glen P
Published: November 2023

During heat stress, increases in cutaneous blood flow and sweating are the main avenues by which a stable core body temperature can be maintained. However, the mechanisms underlying these responses remain elusive. Endothelin‐1 (ET‐1) is a powerful vasoconstrictor that can activate both endothelin A (ETA) and endothelin B (ETB) receptor subtypes, which contribute to the cutaneous vasodilation response induced by local skin heating. Additionally, both receptors are found on the human eccrine sweat glands. Given that ETA receptor activation can reduce nitric oxide (NO) bioavailability, which is known to augment both cutaneous vasodilation and sweating, we evaluated the hypothesis that the activation of ETA receptors may attenuate cutaneous vasodilation and sweating during heat stress. In this study, eight males (25 ± 4 years) performed an intermittent cycling protocol on a semi‐recumbent bicycle consisting of two 30 min bouts of moderate (40% VO2max) and high (75% VO2max) intensity exercise in the heat (35°C); separated by a 20‐ and 40‐ min recovery period respectively. Cutaneous vascular conductance (CVC, laser‐Doppler perfusion units/mean arterial pressure), normalized to maximal CVC, and sweat rate (ventilated capsule) were evaluated at four intradermal microdialysis forearm skin sites. Each site was perfused with either 1) lactated Ringer (Control), 2) 500 nM BQ‐123 (a selective ETA receptor blocker), 3) 300 nM BQ‐788 (a selective ETB receptor blocker), or 4) a combination of BQ‐123 and BQ‐788. During both exercise bouts, relative to Control (Exercise 1: 47 ± 8%max; Exercise 2: 62 ± 1%max), there were no between‐site differences in CVC (all P > 0.05). However, at the end of each recovery period, the blockade of ETA receptors (Recovery 1: 49 ± 4%max; Recovery 2: 49 ± 3%max) and the dual blockade of ETA and ETB receptors (Recovery 1: 49 ± 7%max; Recovery 2: 57 ± 8%max) augmented CVC in comparison to Control (Recovery 1: 33 ± 6%max; Recovery 2: 39 ± 5%max; P < 0.05). We observed no between‐site differences in sweat rate throughout the protocol from baseline rest to the end of the second recovery (all P > 0.05). We show that neither ETA nor ETB receptors modulate cutaneous perfusion and sweating during exercise in the heat. Furthermore, we demonstrate that activation of ETA receptors reduces cutaneous perfusion during passive heat stress after exercise in the heat.

Support or Funding Information

This study was supported by grants from the Natural Sciences and Engineering Research Council of Canada (Discover grant, RGPIN‐06313‐2014; Discovery Grants Program ‐ Accelerator Supplement, RGPAS‐462252‐2014; funds held by Dr. Glen P. Kenny).
Hypothermia/Rewarming Disrupts Excitation‐Contraction Coupling in Cardiomyocytes
Authors: Schaible Niccole , Han Young Soo , Hoang Thuy , Arteaga Grace , Tvieta Torkjel , Gary Sieck
Published: November 2023

Hypothermia/Rewarming (H/R) is poorly tolerated by the myocardium; however, the underlying intracellular basis of H/R‐induced cardiac injury remains elusive. We hypothesized that in cardiomyocytes, H/R leads to contractile dysfunction primarily through reduced Ca2+ sensitivity of the myofilaments. To test this hypothesis, isolated rat cardiomyocytes (13–15 cells from 6 rats per group) were electrically stimulated to evoke both cytosolic Ca2+ ([Ca2+]cyto) and contractile (sarcomere shortening) responses that were simultaneously measured using an IonOptix system. These measurements were subjected to the following temperature protocols: 1) hypothermia (15°C) followed by rewarming (35°C) or 2) time‐matched control (35°C). Contractile dysfunction after H/R was indicated by reduced shortening velocity and reduced extent of shortening of sarcomere length (SL) compared to time‐matched controls. Throughout hypothermia, basal [Ca2+]cyto increased and the duration of the evoked [Ca2+]cyto transients was prolonged. Phase‐loop plots of [Ca2+]cyto versus contraction in cells exposed to H/R indicate that Ca2+ sensitivity of contraction is reduced. Consistent with decreased Ca2+ sensitivity, we found that cardiac troponin I (cTnI) phosphorylation (measured by Western blot) increased after H/R. Our results support our overall hypothesis and suggest that reduced Ca2+ sensitivity and increased cTnI phosphorylation contributes to the altered excitation‐contraction coupling of cardiomyocytes following H/R. The clinical importance of our results brings focus to Ca2+ sensitivity as a plausible therapeutic target in treating patients exposed to accidental hypothermia.

Support or Funding Information

NIH Grant 5T32HL10535 (NSS)
Organ‐Specific Dietary Fatty Acid Uptake in Cold‐Acclimated Humans
Authors: Blondin Denis P. , Noll Christophe , Tingelstad Hans C. , Labbé Sébastien M. , Phoenix Serge , Guérin Brigitte , Turcotte Eric E , Richard Denis , Haman François , Carpentier André C
Published: November 2023

In rodents, brown adipose tissue (BAT) plays an important role in producing heat to defend against the cold and in taking up and dissipating energy from dietary fat (Bartelt et al. Nat Med, 2011). Recent investigations have shown that BAT in humans can also contribute to cold‐induced thermogenesis, but its role in dietary fat metabolism remains unclear. Dietary fat may be responsible for the postprandial accretion of triglycerides in lean tissues in individuals with pre‐diabetes (Labbé SM et al. Diabetes, 2012; Kunach M et al. Diabetes 2015), which impairs insulin sensitivity. Thus, the contribution of BAT to postprandial thermogenesis and dietary fat metabolism warrants further clarification. We used our well‐established positron emission tomography (PET) method with oral administration of 18F‐fluoro‐thiaheptadecanoic acid (18FTHA) and i.v. 11C‐acetate to determine the effect of BAT metabolic activation on organ‐specific dietary fatty acid uptake and partitioning in humans. Non‐cold acclimated healthy men took part in 2 metabolic studies before and after a 4‐week cold acclimation, previously shown to increase BAT oxidative capacity (Blondin et al. JCEM, 2014). A standard liquid meal containing the fatty acid PET tracer 18FTHA was given at the beginning, while 11C‐acetate was given at time 60 min during a 4‐h acute cold exposure. Preliminary results show that fractional dietary fatty acid uptake was greater in BAT, compared to muscle or subcutaneous white adipose tissue (0.31±0.009 min−1 vs. 0.009±0.003 min−1 and 0.018±0.008 min−1, respectively). However, increasing BAT oxidative capacity 2.9‐fold, through daily cold exposure over 4 weeks, did not increase BAT uptake of dietary fatty acids any further (0.31±0.009 min−1 vs. 0.021±0.006 min−1). Dietary fatty acid partitioning was significantly lower in BAT than in the liver and heart (0.37±0.12 SUVmean vs. 2.18±0.53 SUVmean and 1.01±0.30 SUVmean, respectively), but comparable to the levels seen in abdominal subcutaneous white adipose tissues (0.17.±0.05 SUVmean) and skeletal muscles (0.17.±0.04 SUVmean). These findings show that although cold‐stimulated BAT can contribute minimally to the clearance of dietary fatty acids in humans, dietary fatty acids are not the primary source of energy for the chronic cold acclimation‐induced increase in BAT oxidative metabolism.

Support or Funding Information

This research was supported by the Canadian Institutes of Health Research (OG‐3‐10‐2970‐AC) and the Natural Sciences and Engineering Research Council of Canada (RGPIN/326967‐2011).
Thermotherapy Application Increases The mRNA Expression of Angiogenic Factors in Human Skeletal Muscle
Authors: Roseguini Bruno Tesini , Kuhlenhoelter Alisha M. , Neff Dustin , Nie Yaohui , Wong Brett , Gavin Timothy P.
Published: November 2023

Treatment with thermotherapy (TT) reduces the clinical symptoms and improves exercise tolerance in patients with several chronic disease conditions, but the molecular mechanisms by which this therapy exerts its benefits remain poorly defined. We tested the hypothesis that a single session of TT increases systemic and skeletal muscle levels of angiogenic mediators in young individuals. Forty‐one healthy young subjects were recruited to participate in two separate studies (Study 1, n=18 and Study 2, n=23). A water‐circulating garment that covered both legs was used to apply TT or a control intervention on both studies. Water at 48°C was perfused through the garment for 90 min for TT application, while thermoneutral water (33°C) was used in the control intervention. In study 1, participants completed two experimental sessions (TT and control), at least 72 hrs apart, in a randomized, cross‐over design. Blood samples were taken before and 30 and 120 min following the completion of the trials for the determination of the percentage of circulating pro‐angiogenic cells (multiparametric flow‐cytometry) and the levels of inflammatory and angiogenic factors (multiplex immunoassays). In study 2, participants were randomly allocated to either a TT‐treated group (n=11) or to a control group (n=12). The treatments (TT or control) were applied for 90 min as described above. Biopsies were taken from the vastus lateralis muscle prior to and 30 and 120 min following the interventions. The mRNA expression of inflammatory and angiogenic factors and members of the heat shock protein family was determined using real‐time polymerase chain reaction. Application of TT for 90 min in study 1 had no effect on circulating levels of angiogenic cytokines and the percentage of bone marrow‐derived pro‐angiogenic cells (CD34+CD133+), but the levels of vasoconstrictor endothelin‐1 were lower 30 min after TT when compared to the control intervention (p<0.05). Conversely, in skeletal muscle (Study 2), TT evoked a transient increase in the mRNA expression of several important angiogenic factors and heat shock proteins. When compared to the control group, the change in mRNA expression from baseline of vascular endothelial growth factor, angiopoietin‐2, chemokines CCL2 and CX3CL1, the ratio of angiopoietin‐2/angiopoietin‐1 and the angiostatic factor platelet factor‐4 was higher (p<0.05) 30 min after the intervention in the TT‐treated group. Likewise, the expression of members of the heat shock protein family was up‐regulated 30 min after TT compared to control (p<0.05). The expression of the angiostatic transcription factor FoxO1 was lower in the TT group at 120 min following the end of intervention period (p=0.03). These novel findings indicate that TT is a simple, non‐invasive strategy to activate local angiogenic signaling and possibly promote vascular growth in skeletal muscle.
Effect of Combination Ice and Compression Socks on Resting Calf Blood Flow in Trained Male Athletes
Authors: Hudock Michael J , Keller Joshua L , Crecelius Anne R
Published: November 2023

Compression socks are common tools that are utilized in the realm of athletics. The purpose of the compression is to increase blood flow to the lower extremities, thereby increasing oxygen and energy sources needed for increased skeletal muscle function and/or recovery. Recently, a product has been marketed that combines the compression element and with cryotherapy, the goal being increased blood flow to the lower extremities while reducing inflammation post‐workout to quicken recovery. However, to our knowledge, direct measures of blood flow using this type of product have not been performed. Thus, this study looks at the effects of compression with and without cryotherapy on the blood flow of trained male athletes. The hypothesis was that compression would increase blood flow, ice would reduce it, and a combination of both would produce an intermediate result. Participants (n=5) were trained, having a body fat percentage that was not consider overweight and a minimum VO2max of 50 mL/kg/min. Those who met the criteria partook in four randomized trials during a single visit: control, compression, ice, and compression with ice. Calf blood flow (CBF; venous occlusion plethysmograph), skin temperature (temperature probe), heart rate (ECG), and blood pressure (sphygmomanometry) were monitored throughout each trial. As compared to control, compression alone decreased CBF (0.83±0.31 vs 1.66±0.33 ml/dl/min). Combined compression and ice resulted in similar CBF values (0.92±0.49 ml/dl/min) as the compression condition whereas the ice condition had minimal effect on CBF (1.39±0.48 ml/dl/min). Systemically, as per design, heart rate and blood pressure were relatively stable across all four trials. The present results indicate that compression, alone or in combination with ice do not increase CBF as measured by venous occlusion plethysmograph, at rest in trained males. Further, CBF was not attenuated during the ice alone condition. Taken together, the marketed effects of this product are questioned in the present experimental setup.

Support or Funding Information

University of Dayton Honors Program
Gender‐related Difference in Cardiac Autonomic Nervous Activity during Post‐Exercise Recovery
Authors: Liu Chia‐Hao , Wang Jong‐Shyan
Published: November 2023

The rate of post‐exercise cardio‐deceleration is used as an index of cardiac vagal reactivation. Analysis of heart rate variability (HRV) can provide useful information about autonomic control of the cardiovascular system. The purpose of this study was to investigate gender‐related difference on cardiac autonomic nervous activity during post‐exercise recovery. Twenty healthy males (age: 20.5±1.6 years; body mass index (BMI): 22.2±2.8 kg/m2) and 20 healthy females (age: 20.3±0.7 years; BMI: 20.2±2.5 kg/m2) performed the 3‐minutes step test using a novel virtual reality with bio‐sensing system. Cardiac autonomic modulation at rest and immediately after the exercise test were determined by spectral analysis of HRV. The results demonstrated that male subjects revealed less recovery HR after exercise, reflected by larger physical fitness index, compared to female subjects did. Although male subjects had higher normalized high frequency (nHF) (vagal activity) and SDNN than female subjects, no significant gender difference in the ratio of low frequency (LF) to high frequency (HF) power (sympathetic activity) was observed during post‐exercise recovery. Additionally, physical fitness index was positive associated with post‐exercise nHF level. Therefore, we conclude that healthy men may exhibit grander post‐exercise cardio‐deceleration by better cardiac vagal reactivation than healthy women.
Ethanol Feeding Reduces Circulating CTRP3 Levels
Authors: Fleming Christina Katelyn , Peterson Jonathan M
Published: November 2023

Alcohol‐induced fatty liver disease (AFLD), a leading cause of liver related mortalities, is an increasing public health concern resulting from excessive alcohol intake. C1q TNF Related Protein 3 (CTRP3), a novel adipokine, has been demonstrated to prevent diet‐induced fatty liver disease by acting directly on liver cells to increase lipid oxidation, reduce lipid synthesis, and ultimately protect the cells from alcohol‐induced damage/death. Effects on preventing alcohol‐induced fatty liver are unknown. Without current pharmaceutical treatments, this project is working towards identifying treatment to control this disease. This project's purpose was to determine if alcohol consumption reduced circulating CTRP3 levels. The CTRP3 transgenic mouse strain was developed along with a wild type control mouse strain that doesn't express the CTRP3 transgene. Acute and chronic ethanol feeding protocols were used in a mouse model. The mice were placed on a 10‐day ethanol diet before given a single dose gavage of ethanol. Serum was collected from mice at 0, 4, 8, and 24 hours after ethanol feeding. To test circulating CTRP3 levels, an immunoblot was conducted and the proteins were transferred to a membrane for analysis with antigens and chemiluminescence imaging. Both acute and chronic ethanol exposure displayed reduced circulating CTRP3 levels by ~30% and ~40%, respectively. Data analysis concluded that treatment with CTRP3 is a valid approach to pursue as a novel therapeutic for preventing alcoholic fatty liver disease. Elevated CTRP3 will prevent excessive diet‐induced hepatic triglyceride accumulation, thus exposing the clinical importance of CTRP3 as a relevant treatment for humans diagnosed with AFLD.
Repeated Binge‐Like Alcohol Intoxication Dysregulates Mesenteric Perilymphatic Adipose Tissue Lipogenic Gene Expression
Authors: Souza‐Smith Flavia M. , Song Kejing , Molina Patricia E
Published: November 2023

Visceral adipose tissue (VAT) inflammation is an important mediator of local insulin resistance (IR) and the consequent secretion of cytokines and adipokines may contribute to systemic IR. Repeated binge‐like alcohol intoxication (RBAI) episodes induce whole‐body IR and may potentially increase the risk for metabolic syndrome and type 2 diabetes. Previously we showed that RBAI promotes lymphatic vessels hyperpermeability leading to perilymphatic adipose tissue (PLAT – VAT isolated from blood vessels and lymphatic vessels) inflammatory milieu, impairs PLAT insulin signaling, and decreases circulating adiponectin levels. Based on a recognized shift from the traditional ‘glucocentric’ view of IR to a ‘lipocentric’ viewpoint we hypothesized that RBAI promotes impairment of PLAT lipid metabolism. Male Sprague‐Dawley rats received an intragastric bolus (intragastric catheter) of 2.5 g/kg/day of alcohol (12.5% alcohol w/v) or isocaloric dextrose in Vanilla Ensure (116 kcal/kg/day) for 3 days. PLAT was isolated 30 min or 24 h after the last alcohol or dextrose administration. PLAT gene expression of markers for peroxisome proliferator–activated receptor (PPAR‐γ), Diacylglycerol O‐AcylTransferase 1 (DGAT1), Fatty Acid Synthase (FAS), and Hormone‐Sensitive Lipase (HSL) was determined by Real Time PCR. PLAT isolated from RBAI rats at 24 h had decreased PPAR‐γ, DGAT1, and FAS but no significant alteration in HSL expression compared to dextrose‐treated time‐matched control animals. These results may suggest that RBAI impairs critical steps involved in PLAT lipid synthesis, which may in turn contribute to suppressed circulating adiponectin levels previously observed. We speculate that gut‐derived toxins leaking from lymphatic vessels into PLAT directly mediate these early alterations, reflecting lymphatic/PLAT crosstalk contributing to alcohol‐induced metabolic dysregulation.

Support or Funding Information

Supported by LSUHSC Department of Physiology.
Metformin Decreases Caveolin‐1 Expression in Differentiated Human Preadipocytes
Authors: Pfeifer Michaela A , Zhang Yuebo , Singh Prachi
Published: November 2023

Background

We have previously shown that increased caveolin‐1 expression impairs leptin‐dependent activation of cellular signaling pathways and may be responsible for attenuating leptin‐mediated increases in adiponectin expression in obesity. Further, insulin and leptin cellular signaling mechanisms are closely related such that molecules known to impair insulin signaling also alter leptin signaling. Conversely, known insulin‐sensitizing drugs may improve leptin‐signaling via reducing caveolin‐1 expression. We therefore tested the hypothesis that insulin‐sensitizing drugs decrease caveolin‐1 expression.

Methods

We used an in‐vitro approach to examine the effects of different insulin‐sensitizing drugs on caveolin‐1 expression. Human white preadipocytes were cultured to confluence and differentiated for 15 days. After differentiation, cells were then treated with increasing concentrations of pioglitazone (5–30 μM), troglitazone (10–30 μM), metformin (1–5 mM), or glimepiride (20–100 μM) for 24 hours. Caveolin‐1 protein expression was determined by Western blot analysis.

Results

Among the insulin‐sensitizers used in our experiment, only treatment with increasing concentrations of metformin resulted in a dose‐dependent decease in caveolin‐1 expression (P =0.007). Treatment with increasing concentration of troglitazone upregulated caveolin‐1 expression (p=0.005), while pioglitazone (p=0.5020) and glimepiride (p=0.0965) had no effect of caveolin‐1 protein expression.

Conclusions

Metformin reduces caveolin‐1 expression in differentiated human white preadipocytes. In obesity, caveolin‐1 expression is increased which may contribute to impaired leptin signaling. Therefore, metformin may be used to decrease caveolin‐1 expression and consequently improve leptin signaling and leptin‐dependent increases in adiponectin expression in obese individuals.

Support or Funding Information

Michaela Pfeifer was supported by the American Physiological Society Stride Summer Undergraduate Research Fellowship NHLBI 1 R25 HL115473‐01; Prachi Singh was supported by the American Heart Association Scientist Development Grant 11SDG7260046.
TonEBP/NFAT5 inhibits adipocyte differentiation via modulation of mitotic clonal expansion during early phase of differentiation in 3T3‐L1 cells
Authors: Kim Soo Jin , Kim Taehee , Choi Han Na , Kim Hyun‐Woo , Park Jin Bong , Jeon Byeong Hwa , Lee Sang Do
Published: November 2023

Obesity resulting from excessive accumulation of white adipose tissue is closely related to the chronic diseases such as diabetes, hyperlipidemia, and hypertension. White adipose mass is determined by the number and size of adipocytes. Preadipocyte like 3T3‐L1 cells undergo terminal differentiation manifested by formation of lipid droplets as well as adipocyte specific protein. TonEBP/NFAT5 belongs to the Rel family of transcription factors and plays important roles in the development and maintenance of kidney, immunity, arthritis, and cancer metastasis. Although the functions of TonEBP/NFAT5 during osteogenesis, chondrogenesis and myogenesis are reported recently, its role in the adipogenesis is not well known. In this study, we analyzed the role of TonEBP/NFAT5 in adipogenesis using 3T3‐L1 cells. TonEBP/NFAT5 expression was dramatically reduced during adipocyte differentiation of 3T3‐L1 cells. RNAi‐mediated knock down of TonEBP/NFAT5 facilitated adipogenesis. Whereas sustained expression of TonEBP/NFAT5 using adenovirus suppressed the formation of lipid droplet and the expression of FABP4, marker for terminally differentiated adipocytes. Also, TonEBP/NFAT5 inhibited the expression of PPARγ, master regulator of terminal adipocytes. TonEBP/NFAT5 suppressed adipogenesis in the early phase of the differentiation via modulation of Akt activity and mitotic clonal expansion. These results suggest that TonEBP/NFAT5 may be an important regulatory factor in the differentiation of adipocytes.

Support or Funding Information

This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (NRF‐2013R1A1A2060736, NRF‐2014R1A6A1029617)
Signatures of acylcarnitine and acyl‐CoA species suggest specific alterations of mitochondrial oxidation in mouse models of obesity and diabetes
Authors: Daniel Hannelore , Giesbertz Pieter , Mueller Katrin , Schomburg Dietmar
Published: November 2023

Obesity, insulin resistance and diabetes are characterized by changes in circulating plasma metabolite markers derived from amino acid and fatty acid metabolism including acylcarnitines (AC). In identifying organs and pathways as origins of the changes in plasma metabolites, we determined AC profiles in plasma and tissues from mouse models representing different stages of obesity and diabetes development. The leptin‐deficient ob/ob mouse served as a model for obesity associated with insulin resistance but pancreas hypertrophy whereas the db/db mouse is obese, insulin resistant with severe hyperglycemia and eventually pancreatic failure. A streptozotocin‐induced insulin‐deficient mouse was employed as a model for type I diabetes or end‐point stage type II diabetes with extreme hyperglycemia and ketosis. We used a sensitive LC‐MS/MS method to quantify around 45 AC derived from fatty acid and amino acid oxidation pathways. We furthermore determined concentrations of odd‐numbered fatty acids for which the metabolic origin is largely unknown. Since AC are derived from the conversion of acyl‐CoA we additionally determined a number of corresponding acyl‐CoA species in liver and assessed how they correlate with AC levels. Results displayed strong increases in AC derived from branched‐chain amino acid degradation in plasma and tissues of all mouse models, but most pronounced in streptozotocin‐treated animals. All mice also displayed increased levels of odd‐numbered AC in liver while dicarboxylic‐acylcarnitines derived from omega‐oxidation were strongly decreased in ob/ob and db/db mice. Correlations between AC and acyl‐CoA concentrations in liver were strongest for monocarboxylic metabolites, while dicarboxylic acylcarnitines like malonylcarnitine and succinylcarnitine showed no or negative correlations with their respective acyl‐CoA species. In summary, our analysis revealed major alterations in specific pathways of mitochondrial fatty acid and amino acid oxidation in the different mouse models during diabetes progression.
Early Improvements in Blood Lipid Profile and Vascular Alterations after Gastric Bypass Surgery Prior to Dramatic Weight Loss
Authors: Grogg Kristin , DeVallance Evan , Lemaster Kent , Hull Robert , Tabone Lawrence , Frisbee Jefferson , Chantler Paul
Published: November 2023

With 6.6% of adults in the U.S. classified as morbidly obese, excess bodyweight is now the sixth most significant risk factor contributing to the overall burden of disease, emerging as one of the most serious public health concerns in the 21st century. Bariatric surgery has been shown to eliminate comorbid conditions associated with obesity. The aim of this study is to evaluate the effect of weight reduction following laparoscopic Roux‐en Y gastric bypass (RYGB) on remodeling and improvements in arterial function, in addition to immediate reversal of metabolic deviations as weight is lost.

Patients that meet protocol inclusion criteria are invited to join the study during their 1 week pre‐operative clinical appointment. At this time patients are consented and instructed to lie supine for 10 minutes of quite relaxation. Patients then begin a sequence of non‐invasive examinations starting with a 12‐lead electrocardiogram, followed by an echocardiogram, carotid artery ultrasound, radial applanation tonometry, and endothelial function analysis using EndoPAT technology. Upon completion of the non‐invasive procedures a fasting blood sample is taken for analysis.

Preliminary findings show that RYGB results in significant body weight reduction (pre: 131.8 ±5.6 to post: 125 ±5.2 kg) in morbidly obese subjects, along with reductions in BMI (pre: 45.2 ±2.3 to post: 42.9 ± 2.2) and waist circumference (pre: 122.1 ±5.0 to post: 111.9 ± 3.2 cm) at the 1‐week time point. Decrease in body size and weight was aided by a reduction in low‐density lipoprotein (pre: 127 ±6.2 to post: 113 ±4.5 mg/dL), as well as suggested decreases in glucose levels. Such changes can be associated with an improvement of the lipid and glucose metabolism. However, these results appear before subjects have lost a substantial amount of weight (one week post‐operative), suggesting that noteworthy cardiovascular improvements post‐RYGB are achieved prior to the hypothesized weight‐related change. In addition, a number of improvements to the cardiovascular system were also marked at the 1‐week time point. Estimated left ventricular end systolic pressure and direct measure of left ventricular end systolic volume (pre: 66 ±4 to post: 55 ±3 mmHg) declined post‐GBS with an array of additional markers supporting alterations in central systolic blood pressure and myocardial oxygen demand. The data suggests that vascular changes are happening in the early stages of recovery, prior to dramatic weight loss, thus suggesting vascular modifications are a result of an alternate surgical benefit.
Substance P (SubP) is Sufficient to Induce Frequency Plasticity in Neonatal Rat Isolated Brainstem‐spinal cord Preparations in the Absence of Hypoxia
Authors: Johnson Stephen Mark , Watters Jyoti J , Kunz Morgan K , Gardner Alyssa N
Published: November 2023

The capacity for expressing respiratory neuroplasticity in neonates is poorly understood. One example is frequency plasticity, which is a persistent increase in breath frequency following a perturbation. Intermittent hypoxic exposures induce frequency plasticity in P14–P15 intact rats and in rhythmic medullary slices from neonatal P0–P7 mice. However, mutant mice lacking neurokinin‐1 receptors for which SubP is the endogenous ligand, do not express frequency plasticity following intermittent hypoxia, suggesting that SubP may be necessary for intermittent hypoxia‐induced frequency plasticity. Thus, we hypothesized that intermittent bath‐application of SubP is sufficient to induce frequency plasticity in isolated neonatal rat (P0–P3) brainstem‐spinal cord preparations. Intermittent SubP application (100 nM; 3 min on/7 min off; ×3 applications; n=13) to the entire brainstem‐spinal cord preparation increased burst frequency from 11.6 bursts/min (baseline) to 14.3 bursts/min (peak response). Burst frequency was still elevated to 12.7 and 12.1 bursts/min at 30 and 60 min following intermittent SubP exposure, indicating that acute SubP application induces a persistent effect. Respiratory burst frequency in time control experiments (n=13) was 11.5 bursts/min (baseline) and decreased by 25% over an equivalent time period. One bout of sustained SubP application (100 nM; 9 min; n=6) did not induce a persistent increase in respiratory burst frequency, suggesting a pattern sensitivity to this form of frequency plasticity. Likewise, intermittent SubP application at 10 (n=11) or 1.0 nM (n=7) did not induce frequency plasticity. Thus, intermittent SubP application is sufficient to induce frequency plasticity in a dose‐ and pattern‐dependent manner in the absence of hypoxia. Current studies are aimed at identifying if sexual dimorphisms exist, and understanding the role of inflammation in abrogating this form of frequency plasticity.

Support or Funding Information

Supported by R01 HL111598, the Vilas Family Foundation and a private donation.
Cervical Spinal Stimulation and Respiratory Recovery after Upper Cervical Spinal Cord Injury
Authors: Dale Erica Arden , Zhong Hui , Edgerton V Reggie
Published: November 2023

Over half of all spinal cord injuries (SCI) occur at the cervical level leading to disruption of bulbospinal pathways to respiratory motor neurons, respiratory muscle paralysis, and diminished breathing capacity. Of the 6,000 new cervical spinal injuries per year, ~20% will require mechanical ventilatory support. Even when mechanical ventilation is not necessary, breathing impairment greatly increases susceptibility to life‐threatening lung infections. In fact, the leading cause of morbidity and mortality in cervical SCI is respiratory impairment. In this study, rats were implanted with bilateral cervical (C4) stimulating electrodes and bilateral diaphragm EMG recording electrodes. Our previous data have shown that cervical spinal stimulation elicits evoked potentials and modulates diaphragm EMG (Dale et al., 2015). In this study, after obtaining baseline data, rats were given a C2 hemisection (C2HS). After recovery, rats were placed in either control (evoked potentials only; n=6) or Quipazine + stimulation (n=8) groups and were tested at 1, 2, and 4 weeks post‐C2HS. After eliciting spinal evoked potentials (SEP) of increasing intensity, rats received Quipazine (0.3mg/kg; IP), a broad‐spectrum serotonergic agonist, and diaphragm EMG was recorded for 20 min. Next, each rat received 3 bouts (interspersed with 5 min no stim) of cervical stimulation (bipolar) at increasing frequencies but at sub‐motor threshold intensity (5 min at 40Hz, 5min at 80Hz, and 5 min at 100Hz). Another set of SEPs was elicited upon stimulation completion. Our goal is to restore respiratory function in a rat model of cervical spinal injury by utilizing cervical spinal epidural electrical stimulation in combination with serotonergic agonists (e.g. quipazine). By inducing respiratory plasticity after synergistic modulation of the phrenic motor network (e.g. cervical epidural stimulation plus quipazine), we hypothesize that enhancing the contributions from spared motor neurons could be an avenue for preserving ventilatory capacity. This project may lead to novel therapies to extend and improve life for patients with cervical spinal cord injury by preserving breathing.

Support or Funding Information

Christopher and Dana Reeve Foundation and NIH U01EB007615
Electrophysiological properties of abdominal muscle‐projecting expiratory motoneurons of rats
Authors: da Silva Melina P. , Moraes Davi J.A. , Bonagamba Leni G.H. , Varanda Wamberto A. , Machado Benedito H.
Published: November 2023

Expiration is considered a passive process during resting breathing condition. There is a lack of information about the intrinsic electrophysiological properties of expiratory motoneurons and their possible changes in conditions in which the expiration becomes an active process, such as hypoxia. Considering that abdominal expiratory muscle activity depends on excitability of these motoneurons, here we aimed to characterize the electrophysiological properties of abdominal muscle‐projecting expiratory motoneurons combining retrograde tracer, immunofluorescence and whole cell patch clamp, in thoraco‐lumbar spinal cord slices from juvenile Wistar rats. Three different types of cholinergic expiratory motoneurons with similar capacitance were recorded: neurons with spontaneous action potentials whose resting potential hyperpolarizes (−65 ± 5 mV vs −69.7 ± 4 mV, n=9) and firing frequency decreases (8.5 ± 2 Hz vs 1.7 ± 1.3 Hz, n=9) after synaptic blockade. The passive properties of these motoneurons, such as input resistance and excitability, did not change after synaptic blockade (Ri = 0.16 ± 0.03 GΩ vs 0.13 ± 0.03 GΩ; Excitability = 40 ± 10 Hz vs 32 ± 11 Hz, n=9). The second group of motoneurons also exhibited spontaneous action potentials, but showed spike frequency adaptation, slowing or ceasing firing frequency during a maintained stimulus. Their membrane potential also hyperpolarized (−60 ± 1 mV vs −66 ± 1 mV, n=4) and firing frequency was abolished by synaptic blockade. On the other hand, no differences in the input resistance was observed (0.13 ± 0.01 GΩ vs 0.11 ± 0.01 GΩ, n=4). The third group did not show spontaneous action potential and synaptic blockade did not change membrane potential (−72.2 ± 2 mV vs −76 ± 3 mV, n=6) or input resistance (0.1 ± 0.04 GΩ vs 0.06 ± 0.02 GΩ, n=6). However, synaptic blockade decreased their intrinsic excitability. Overall, our data show that there are three different populations of abdominal muscle‐projecting expiratory motoneurons in rats, which may contribute to recruitment of expiratory muscles in different physiological and pathophysiological conditions.

Support or Funding Information

FAPESP, CAPES, CNPQ
Lung Mechanics and Structure in Aged C57BL/6x129 Mice
Authors: Elliott Jonathan E , Omar Tanya S , Mantilla Carlos B , Sieck Gary C
Published: November 2023

Aging‐related changes in lung mechanics of human subjects are characterized by a decrease in resistance and an increase in static compliance (decrease in elastic recoil). Together, these changes result in an increase in residual volume in the absence of an increase in total lung capacity. In C57BL/6x129 mice, it was reported that lung compliance increases with aging while elastic recoil pressure does not change. However, in these studies, “old” mice at 24 months of age were compared to “young” mice at 2 months of age, but at this younger age, alveologenesis is incomplete (completion does not occur until ~6 months of age). Accordingly, it remains to be established if the same aging‐related changes in lung mechanics are observed using fully developed adult C57BL/6x129 mice for comparison. To this end, we compared lung mechanics in C57BL/6x129 mice at 6 months (100% survival, n = 6), 18 months (90% survival, n = 6), and 24 months (75% survival, n = 6) of age. Respiratory system static mechanics (Resistance, Rrs; Compliance, Crs; Elastance, Ers) were assessed following tracheal intubation using the FlexiVent. There was a progressive aging‐related decrease in Rrs (6 month, 0.47 ± 0.02; 18 month, 0.41 ± 0.02; 24 month, 0.35 ± 0.02 cmH2O.s/ml), an increase in Crs (6 month, 0.046 ± 0.002; 18 month, 0.052 ± 0.002; 24 month, 0.062 ± 0.002 ml/cmH2O), and a decrease in Ers (6 month, 21.73 ± 1.19; 18 month, 19.30 ± 0.87; 24 month, 16.62 ± 1.25 cmH2O/ml). Additionally, lungs were fixed following tracheal instillation of 4% paraformaldehyde at 25 cmH2O. Thereafter, lungs were dehydrated, paraffin embedded, sectioned (6 μm thick), and stained (hematoxylin and eosin). Using standard stereological approaches, lung sections were analyzed in a uniform systematic but random fashion to assess alveolar morphology (measurement of average distance between alveolar walls based on mean linear intercept, Lm). There was a progressive aging‐related increase in Lm (6 month, 34 ± 2; 18 month, 40 ± 2; 24 month, 45 ± 2 μm) consistent with an aging‐related emphysematous‐like change in lung morphometry. Taken together, these results in appropriately aged C57BL/6x129 mice demonstrate an aging‐related change in lung mechanics and morphometry consistent with what is observed in aging humans. Therefore, the results of the present study confirm the use of rodent models for studying aging‐related changes in lung mechanics and morphometry.

Support or Funding Information

National Institute of Health grants R01‐AG044615 (CBM & GCS) and T32‐HL105355 (JEE).