bluuebunny/crossref_metadata_2025 huggingface dataset:
Butyrate ameliorates Paneth cell defects, total inflammation, and epithelial cell apoptosis during mitochondrial dysfunction driven by Prohibitin 1-deficiency
Authors: Alula Kibrom , Dowdell Alexander , Lee Scott , Colgan Sean , Theiss Arianne
Published: May 2023

Introduction: Prohibitin 1 (PHB1) is a mitochondrial chaperone protein important for maximal activity of the electron transport chain. PHB1 deficiency in intestinal epithelial cells (IECs) or specifically in Paneth cells (PCs) induces epithelial mitochondrial dysfunction, PC defects, gut microbiota dysbiosis, and spontaneous ileitis in mice by 20 weeks-of-age. Dysbiotic gut microbiota has been implicated in inflammatory bowel diseases and is associated with the decreased abundance of short chain fatty acids (SCFAs; acetate, propionate, and butyrate)-producing bacteria. SCFAs play a significant role in reducing intestinal inflammation and enhancing epithelial barrier dysfunction. We tested the hypothesis that luminal SCFA levels were decreased in mice with PHB1 deficiency and that supplementation of SCFAs will ameliorate intestinal inflammation during mitochondrial dysfunction driven by loss of PHB1. Methods: Ileal luminal contents were collected from Phb1fl/fl (control) and Phb1iΔIEC (Phb1-deficient in IECs) mice at 20 weeks of age and SCFAs were measured by gas chromatography-mass spectrometry. Phb1iΔIEC and Phb1fl/fl littermate mice were treated with 20 mM butyrate dissolved in their drinking water from 16 to 20 weeks-of-age and PC defects were measured by antimicrobial peptide expression (Lysozyme, Cryptdin 3, Cryptdin 5, and Ang4) and Lysozyme staining allocation into secretory granules. Ileitis was measured by histological scoring and pro-inflammatory cytokine expression. To test epithelial intrinsic responses, ileal crypt enteroids derived from Phb1iΔIEC and Phb1fl/fl littermate mice were treated with 200 μg/ml healthy ileal stool lysates (from Phb1fl/fl mice) or dysbiotic stool lysates (from Phb1iΔIEC mice) for 16 hours with or without 0.05 mM butyrate, 0.5 mM propionate, 0.5 mM acetate, alone or in combination. Enteroid viability and apoptosis were measured by morphological change and cleaved Caspase 3 expression. Results: Butyrate was significantly decreased in ileal stool of Phb1iΔIEC mice. Butyrate supplementation in Phb1iΔIEC mice protected against ileitis and PC defects. Dysbiotic stool lysate decreased viability and increased apoptosis in Phb1-deficient enteroids that were prevented by butyrate supplementation. Conclusion: Mitochondrial health in IECs cells is crucial for healthy gut microbiota composition and for epithelial defense when the microbiome becomes dysbiotic. Butyrate rescues IECs from insults caused by dysbiotic gut microbiota during mitochondrial dysfunction driven by PHB1 deletion.

Funding: APS Postdoctoral Fellowship

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
The loss of hepatic PPARα prompts fatty liver disease-induced hypertension and cardiovascular disease
Authors: Badmus Olufunto , Kipp Zachary Kipp , Bates Evelyn , da Silva Alexandre , Taylor Lucy , Martinez Genesee , Hinds Terry , Stec David
Published: May 2023

Non-alcoholic fatty liver disease (NAFLD) often clusters with obesity, diabetes, and hyperlipidemia. For unknown reasons, the leading cause of death in patients with NAFLD is cardiovascular disease (CVD). Most preclinical models of NAFLD are induced by high-fat diet feeding that induces obesity and glucose intolerance, each provoking CVD independent of changes in hepatic fat. To determine the role of NAFLD in the promotion of CVD, independent of changes in body weight and insulin sensitivity, we utilized our hepatocyte-specific PPARα knockout ( Ppara HepKO ) and littermate control ( Ppara fl / fl ) mice. After 30 weeks on a standard diet, male Ppara HepKO mice exhibited elevated hepatic fat content compared to littermates as measured by Echo MRI (11.95 ± 1.4 vs. 3.74 ± 1.4%, p<0.05), hepatic triglycerides (1.4 ± 0.10 vs. 0.3 ± 0.01mM, p<0.05), and Oil Red O staining, despite body weight, fasting blood glucose, and insulin levels being the same as controls. The Ppara HepKO mice also displayed elevated mean arterial blood pressure (121 ± 4 vs. 108 ± 2 mmHg, p<0.05), impaired diastolic function, and adverse cardiac remodeling consisting of dilated cardiomyopathy. The mice with the loss of hepatic PPARα displayed alterations in vascular stiffness, including increased pulsatility index, resistive index, and intima-media thickness in the abdominal aorta and carotid artery, which was corroborated with reduced kinase signaling in the aortas of the Ppara HepKO mice. Our findings indicate that hepatic PPARα is vital in protecting the cardiovascular system via a liver-specific mechanism. Also, the  Ppara HepKO mice are possibly a novel model for studying NAFLD-induced CVD.

This work was supported by National Institute of Health R01DK126884, and the National Heart, Lung and Blood Institute P01 HL05197-11 (D.E.S) and the National Institute of General Medical Sciences P20GM104357-02.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Understanding myocardial contractility comprehensively through multiple dimensions
Authors: Geloian Gorune , Kuang Serena
Published: May 2023

Myocardial contractility (MC) is commonly defined in a vague matter as the intrinsic contractile property of cardiac muscle, or its ability to generate force and shorten. This understanding is insufficient. In this abstract, we propose that MC should be comprehensively conceptualized through multiple dimensions, (i.e., it is not merely intrinsic and it is more than an ability) through logical analysis as follows. First, when conceptualizing MC in medical physiology, it is no doubt that force (F) and velocity (V) of muscle shortening are two aspects of the muscle’s ability. Both F and V are dependent on afterload, an extrinsic factor. This extrinsic factor-dependency indicates the following: 1) muscle contraction exhibits adaptability, i.e., muscles are intelligent when interacting with extrinsic factors and only produce F and/or V appropriate to the given extrinsic factor(s); and 2) what is intrinsic is not ability (F and/or V), but capacity (including FC and VC) which is truly independent of extrinsic factors. An ability is always a fraction of capacity and a result of adaptability; capacity (FC and VC, although not quantifiable so far, but theoretically present) is the ultimate source of ability (F and V) which can be experimentally quantified. Second, it is well known that F is determined by at least two aspects: a component (F_FS) governed by the Frank-Starling Law (i.e., the force-length relationship) and a component (F_Ca) by the level of intracellular Ca2+ transient during cross bridge cycles that determines the actual number of cross-bridges binding to thin filaments. A gap in current medical physiology education is that when introducing muscle physiology, the Frank-Starling law that determines F_FS is always introduced, but when presenting MC specifically, quite often, the contribution of F_FS to F is ignored and only F_Ca (i.e., inotropism) is included. Finally, V can also be at least subdivided into the rate of Ca2+ releasing into the cytoplasm (V_Ca) from the sarcoplasmic reticulum as well as the rate of ATP hydrolysis catalyzed by the myosin heads (V_ATP). In conclusion, MC is a complex concept, which needs to be described through multiple dimensions including but not limited to its capacity, adaptability, and ability. The capacity can be further differentiated into Fc and Vc, and ability into F and V, both of which having at least two subdimensions, respectively: F_FS and F_Ca; V_Ca, and V_ATP.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
UBR1 Mediates ACE2 Ubiquitination and Hypertension in Male Mice
Authors: Elgazzaz Mona , Nuzzo Anna , Restivo Luke , Miao Kevin , Lazartigues Eric
Published: May 2023

Angiotensin-II is one of the main players in the renin angiotensin system (RAS). It mediates vasoconstriction and inflammation through binding to angiotensin-II receptor 1 (AT1R). Conversely, angiotensin converting enzyme 2 (ACE2) counteracts the vasopressor effect of Ang-II/AT1R by converting Ang-II to Ang (1-7). We previously reported that in hypertension, Ang-II mediates ACE2 internalization and ubiquitination. Recently, we identified UBR1, an E3 ubiquitin protein ligase, as a potential ubiquitinase modulating ACE2 expression. While UBR1 deletion has been linked to impaired neurogenesis and cardiovascular development, there is no study that has assessed the role of UBR1 in cardiovascular regulation. Here, we aimed to investigate the role of UBR1 in hypertension. C57BI/6J mice (3-month-old, M=8, F=6) were implanted with subcutaneous osmotic pumps containing Ang-II (600 ng/kg/min) for 4 weeks and BP monitored by telemetry. UBR1 protein expression was upregulated in the hypothalamus of hypertensive male mice but not in females (Mean ±SEM: 3.3 ±0.6 vs.1.1 ±0.1; fold change to GAPDH; p<0.05) while ACE2 was reduced (1.5 ±0.2 vs. 4.1 ±0.3; p<0.05). In vitro, human aortic endothelial cells (HAEC) treated with Ang-II (100 nM) also showed an increase in UBR1 protein expression compared to vehicle (72.5 ±3.4 vs. 39.4 ±3.4 fold change to tubulin; p<0.05) and a parallel reduction in ACE2 (3.5 ±0.1 vs. 25.2 ±1.7; p<0.05). Conversely, HAEC treated with UBR1 siRNA and Ang-II exhibited a reversal of Ang-II-induced ACE2 downregulation (42.6 ±1.2 vs. 3.5 ±0.1 p<0.05). To further confirm the role of UBR1 in mediating hypertension, C57BI/6J male mice (3-month-old, n=10/group) were injected with either UBR1 small hairpin RNA (shRNA) or scrambled shRNA bilaterally in the paraventricular nucleus of the hypothalamus. After 4 weeks, BP was recorded before and 2 weeks after Ang-II infusion, as above. Baseline mean arterial pressure (MAP) was not different in UBR1 shRNA-treated mice compared to controls (MAP: 102.7 ±4.1 vs. 108.4 ±2.3 mmHg). Interestingly, UBR1 shRNA-treated mice showed a blunted Ang-II mediated hypertension compared to scramble shRNA group (MAP: 131.7 ±3.7 vs. 146.3±5.1 mmHg, student t test, p<0.05) suggesting that UBR1 plays a critical role in neurogenic hypertension. In summary, hypertension is associated with upregulation of UBR1 and a parallel downregulation of ACE2, while knockdown of UBR1 resulted in reduced hypertension to Ang-II infusion. We conclude that UBR1 upregulation in hypertension might contribute to ACE2 ubiquitination and a reduction of its compensatory activity.

NHLBI HL150592- Veterans Affairs Merit Award BX004294

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Compliance and Elasticity in Medical Physiology: Confusion and Clarification
Authors: Laban Nora , Dawood Radwa , Kuang Serena
Published: May 2023

The concepts of compliance and elasticity are both used in medical physiology to describe how a soft tissue reacts to an external force. In general, compliance is defined as ΔV/ΔP (a change in volume (V)/a change in pressure(P)), but the interpretations of this definition are inconsistent. When compliance is addressed, the definition of elasticity is not presented, so the relationship between compliance and elasticity is not addressed, which causes confusion in students’ learning of the two concepts. The goals of this study are 1) draw attention to the inconsistent definitions through an analysis of teaching materials; 2) eliminate the confusion by supplementing the missing information to provide a complete picture of the two related concepts; and 3) illustrate how these concepts should be applied to 1-D and 3-D deformation in soft tissues. Results are as follows. 1) Inconsistent interpretations of compliance: Among 16 medical physiology textbooks and 2 USMLE Step 1 review books analyzed regarding the heart, arteries and vein, 33% of books claim compliance related to elasticity (without showing how), 22% to stiffness, 44% to distensibility, and 17% to capacitance. 2) The missing content but essential to medical physiology: In material science, Young’s/elastic modulus (E) and Bulk’s modulus (K) measure the elasticity for 1-D and 3-D materials respectively. Their relationship with compliance are formally addressed and mathematically illustrated via the following equations: E= σ/ε, where E is elastic modulus, σ is stress, and ε is strain; and K= - ΔP/(ΔV/V0), where K is Bulk’s modulus, and V0 is initial volume, and ΔP/(ΔV/V0) is compression. 3) During a vessel’s constriction, a point in the vessel’s wall moves in a 1-D dimension, so in dealing with arteries and veins, the first equation applies. The second equation applies to the heart due to the 3-D change of the heart. In conclusion, adding the following essential information eliminates the confusion about compliance and elasticity: 1) Definitions of Young’s and Bulk’s moduli to address soft tissues elasticity with 1-D and 3-D deformations and 2) The mathematical reciprocal relationship between a type of compliance and its corresponding modulus.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Tonicity Can Be Expressed in Multiple Ways
Authors: Kuang Serena , Li Xiaonan , Yang Xiaoqi , Walter Stefan
Published: May 2023

We have provided a definition for tonicity1 to eliminate many issues with the concept2-4 in physiology education and proposed that there are multiples ways to express tonicity1. In this abstract, we prove this hypothesis using logical reasoning. OC0 (the initial osmotic concentration in a solution compartment (S) before osmosis occurs)5 is the key term to be used. If person A and B are playing a game and score 12 and 8 points, respectively, there are many ways (narrative or quantitative) to express the result of the game, such as “A won the game,” “B lost the game,” “A earned 4 more points than B,” “B had 4 points less than A,” “12 to 8” or “3 to 2.” Osmosis in an osmosis system (S1-m-S2) can be viewed as a water-competing game between OC0 (S1) and OC0 (S2) across the membrane (m). If OC0 (S1) and OC0 (S2) equal 300 and 250 (mOsm/L), respectively, then the tonicity between S1 and S2 can be expressed as “S1 is hypertonic to S2.” This also means that any expressions that mean “S1 is hypertonic to S2” are alternate ways to express tonicity, including 300:250, 6:5, Δ OC0 = 300 – 250 = 50 (mOsm/L), π (S1): π (S2), and Δ π = π (S1) - π (S2). These multiple expressions are not exclusive. Among these ways, “00:250” is most informative. Just like A and B can only own their points (12 and 8) and the score (12 to 8) can only be owned by the game, as we have addressed previously1, S1 and S2 own their points (OC0 (S1) and OC0 (S2)) and the owner of the water-competing game (S1-m-S2), not any solution owns tonicity. A tiny difference between the scores of “12:8” and “300:250” or “ Δ π ” is the following: “12:8” shows the result of the game, “300:250” predicts the result of osmosis or “ Δ π ” shows the result of osmosis. In fact, Δ π is the only accurate definition in a list of inconsistent, elusive definitions of tonicity in the literature we presented in a past work2. As long as the truth of tonicity is clear, the multiple expressions of it can be developed without confusion. Hence, it is incorrect to refer to “a solution’s tonicity” or “the tonicity of a solution,” as is commonly seen in the literature and causes great confusion1. References: Kuang et al., The concept of tonicity: Problems and resolutions [Abstract], The FASEB Journal, 2020 34(S1); Kuang et al., A resolution for the inconsistency in the definitions of tonicity [Abstract], The FASEB Journal, 2022 36(S1); Kuang et al., Resolutions to the problems caused by introducing both osmolarity and effective osmolarity [Abstract], The FASEB Journal, 2022 36(S1); Kuang et al., Origin of the term “isotonic” [Abstract], The FASEB Journal, 2022 36(S1); Kuang et al., The concept of osmolarity: Problems and resolutions [Abstract], The FASEB Journal, 2020 34(S1).

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
How to Study Osmosis If the Membrane Water Moves Across Is Nonideal
Authors: Kuang Serena , Yang Xiaoqi , Li Xiaonan
Published: May 2023

In our past works, we introduced two fundamental osmosis systems (a simple S-m-H2O and a composite S1-m-S2) to study osmosis1,2, where m is a selectively permeable membrane that separates two fluid compartments. A composite S1-m-S2 can be deconstructed into two simple osmosis systems (S1-m-H2O and H2O-m-S2)1,2. When applying these two fundamental osmosis systems, a given m can either be permeable to water only (an ideal m) or its permeability to one species of non-charged solute particles (SP, e.g., urea) can be ignored. If m' represents a nonideal membrane whose permeability to urea cannot be ignored, then a new research question emerges: how can osmosis be studied in S-m'-H2O and S1-m'-S2, respectively? This abstract provides the answers by logical reasoning. First, S-m'-H2O can be viewed as the overlap of a pure osmosis system with an ideal m (S-m-H2O) and a permeant SP (pSP), urea diffusion system: S-m'-H2O = S-m-H2O + Surea-m'-H2O, so that osmosis and urea diffusion can be studied separately. The former is governed by van ’t Hoff’s law and the latter by Fick’s law. Second, similarly, S1-m'-S2 = S1-m-S2 + S1urea-m'-S2urea. Third, the effect of urea diffusion on osmosis depends on several conditions: 1) In S-m'-H2O, urea diffusion and osmosis are always in opposite directions, so urea diffusion reduces the resulting osmotic pressure (π). 2) In S1-m'-S2, if S1 is hypertonic to S2 and [urea]S1 > [urea]S2, then the diffusion and osmosis are in opposite directions, so the diffusion reduces the resulting osmotic pressure gradient (Δ π). 3) If S1 is hypotonic to S2 and [urea]S1 > [urea]S2, then osmosis and diffusion are in the same direction, so the diffusion augments the resulting Δ π. In conclusion: 1) Deconstruction of an osmosis system that has a nonideal m' allows separate studies of osmosis and pSP diffusion, respectively. 2) The effect of pSP diffusion on osmosis needs to be differentiated according to the type of osmosis systems and the direction of osmosis and pSP diffusion. 3) While the simple S-m-H2O and composite S1-m-S2 are fundamental osmosis systems, S-m'-H2O and S1-m'-S2 are complex passive membrane transport systems that transport both water and pSP. 4) If a given nonideal m' is permeable to two types of pSP (e.g., urea and glucose), then the diffusion system needs to be further deconstructed into a urea diffusion system and a glucose diffusion system. References: Kuang et al., The concept of osmolarity: Problems and resolutions [Abstract], The FASEB Journal, 2020 34(S1); Kuang et al., The concept of tonicity: Problems and resolutions [Abstract], The FASEB Journal, 2020 34(S1).

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Chronic cannabigerol administration lowers blood pressure in phenotypically normal mice
Authors: Vernail Victoria , Bingaman Sarah , Raup-Konsavage Wesley , Vrana Kent , Arnold Amy
Published: May 2023

Cannabigerol (CBG), the precursor of the major cannabinoid compounds synthesized from Cannabis sativa L., has emerged as a novel potential therapeutic target due to its lack of psychoactive effects and efficacy at reducing pain and inflammation in animal models. Despite this, little is known about the safety of CBG, including its impact on cardiovascular function. Our laboratory recently showed that acute CBG administration lowers blood pressure, by over 20 mmHg, in phenotypically normal male mice via an α2-adrenoreceptor mechanism, which could suggest the need for caution in using this compound in healthy individuals. In this study, we tested the hypothesis that CBG can also lower blood pressure in mice when administered chronically. To test this hypothesis, four male C57BL/6J mice were implanted with radiotelemetry probes at 8-10 weeks of age and allowed to recover for 10 days. This approach allows for continuous measurement of blood pressure, heart rate, and locomotor activity in conscious animals. Baseline blood pressure and heart rate were recorded for 24-hours prior to drug treatment. Mice were then administered CBG at a dose previously found to acutely lower blood pressure (10 mg/kg, intraperitoneal) for 14 days, with vital signs recorded for 24-hours at the end of treatment. We found that chronic CBG reduced 24-hour systolic blood pressure by ~5 mmHg (129±3 mmHg baseline vs. 124±2 mmHg post-CBG; p=0.040 via paired t-test), with similar trends for diastolic and mean blood pressure. This depressor effect was accompanied by a significant decrease in heart rate (581±15 bpm baseline vs. 502±19 bpm post-CBG; p=0.003), with no effect on locomotor activity. These overall findings suggest that chronic CBG may produce a small, but significant, decrease in blood pressure in phenotypically normal male mice. The magnitude of chronic CBG depressor effects was smaller than previously observed for acute administration. This could reflect multiple mechanisms including a2-adrenoreceptor desensitization or baroreflex buffering, but this remains to be tested. Regardless, these findings may provide caution for potential hypotensive effects of CBG under normotensive conditions.

Funding sources: PA Options for Wellness and Penn State Medical Marijuana Academic Clinical Research Center

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Treatment with PFKFB3 inhibitor potentially improves diastolic function and arterial stiffness in PHD2ECKO mice
Authors: Williams Quinesha , Zeng Heng , Besanson Jessie , Cantrell Aubrey , Chen Jian-Xiong
Published: May 2023

AIMS: Arterial stiffness is a central factor of cardiovascular disease states and etiologies, such as hypertension and heart failure. Currently there is no available therapy to effectively target arterial stiffness. An oxygen sensing protein, prolyl hydroxylase domain-2 (PHD), is an emerging novel target for vascular remodeling. Previous studies have shown that specific deletion of PHD2 in the endothelium (PHD2ECKO) results in upregulation of hypoxia inducible factor (HIF), a crucial regulator of oxygen homeostasis. HIF affects several pathways, such as angiogenesis and energy metabolism. A glycolytic enzyme, 6-phosphofructo-2-kinase/fructose 2,6-biphosphatase 3 (PFKFB3), produces fructose 2,6-biphosphate. This metabolite allosterically activates phosphofructokinase 1 (PFK1), a rate-limiting enzyme of glycolysis. This study investigates the effects of PFKFB3 inhibition on PHD2ECKO mice using (2E)-3-(3-Pyridinyl)-1-(4-pyridinyl)-2-propen-1-one [3PO]. We hypothesize that treatment with 3PO will attenuate arterial stiffness in PHD2ECKO mice, thus leading to significant improvement in cardiac function. METHODS AND RESULTS: PHD2ECKO and PHD2f/f mice were injected with 3PO (25mg/kg/day) for 14 days i.p. Echocardiographic measurements were performed prior to treatment and at 2 weeks of treatment with 3PO. Blood pressure measurements were performed for three consecutive days of week one and week two.Echocardiography showed improvement of diastolic function in PHD2ECKO mice post-treatment with 3PO. This was exhibited by significant reductions in diastolic diameter and diastolic volume. Pulse wave velocity (PWV) is decreased, while coronary reserve flow (CFR) is increased post-treatment of the PFKFB3 inhibitor. Though these results are not significant, this notably shows some improvement in arterial stiffness. Blood pressure measurements showed improvements in systolic and diastolic blood pressure for PHD2ECKO mice. Systolic and diastolic blood pressure significantly decreased post-treatment of 3PO. CONCLUSIONS: Inhibition of PFKFB3 in endothelium PHD2 deficient mice improves diastolic cardiac function. Though insignificant, there was an improvement of arterial stiffness. Results showed a slight increase in CRF and decrease in PWV. This suggests that the glycolytic pathway can be a therapeutic target in cardiac function and arterial stiffness.

This work was supported by National Institute of General Medical Sciences and National Heart, Lung, and Blood Institute (R01HL151536, JX Chen), the National Heart, Lung, and Blood Institute (R56HL164321, H. Zeng).

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
The cardioprotective effects of Empagliflozin in Doxorubicin-induced endoplasmic reticulum (ER) stress
Authors: Malik Akshi , Bagchi Ashim , Jassal Davinder , Singal Pawan
Published: May 2023

The use of doxorubicin (Dox) in cancer patients carries the risk of cardiotoxicity which is associated with an excessive production of reactive oxygen species as well as an imbalance in the redox state affecting mitochondrial functioning, ER homeostasis and protein folding. An accumulation of misfolded proteins triggers the unfolded protein response (UPR) known as ER stress. Subsequently ER-stress induced apoptosis results in loss of cardiomyocytes. Despite clinical trials indicating the benefits of an antidiabetic drug, Empagliflozin (EMPA) in reducing cardiovascular deaths and hospitalization rate in heart failure patients, it remains uncertain whether EMPA exerts a cardioprotective effect on Dox-induced cardiomyopathy (DIC). Herein, we aimed to investigate the effects of EMPA on Dox-induced ER stress and cardiomyopathy. In isolated adult rat cardiomyocytes, Dox (10μM, 24hrs) induced oxidative stress causing the activation of inflammation markers as well as ER-stress markers. Interestingly, EMPA (500nM, 24hrs) treatment prior to Dox was able to reduce oxidative stress; inflammatory markers (IL-1β, TNFα, and TGFβ), and significantly increased the expression of STAT-3. Dox-induced ER-stress activated ER transmembrane proteins and upregulated the expression of various genes, including X-box binding protein 1 (XBP1). The splicing of XBP1 mRNA on Dox treatment generated spliced XBP1 and subsequently up-regulated chaperones like glucose regulated protein 94 (GRP94), glucose regulated protein 78 (GRP78), and/or protein disulfide-isomerase (PDI). These Dox-induced changes in the upregulation of ER stress proteins were blunted by EMPA. EMPA also promoted expression of inositol requiring kinase 1α (IRE1α) which helped in maintaining ER homeostasis. Additionally, EMPA treatment, down-regulated caspase-12 and caspase-3 activation as well as phosphorylation of c-JUN NH2-terminal kinase (JNK), thereby promoting cardiomyocyte survival. These cardioprotective effects of EMPA on the reduction of ER stress in an in-vitro DIC model suggests its therapeutic potential that can occur independent of the effects related to diabetes. Thus, EMPA may contribute to improvements in cardiac damage during Dox mediated stress and inflammation. The recognition of Dox-induced cardiotoxicity as well as a dire need for a cardioprotective agent to be administered in conjunction with Dox is evident and EMPA may prove to be such an agent.

Supported by CANUSA grant.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Mitochondrial Ca2+ dynamics differ between the left and right ventricles in murine and porcine hearts
Authors: Sung Jae Hwi , Villanueva Hector , Igualador Ariadna , Prins Kurt , Liu Julia
Published: May 2023

Despite their differences in metabolism, mechanics, and developmental origin, the right ventricle (RV) is often assumed to function similarly to the left ventricle (LV). Specifically, though Ca2+ transport into mitochondria is well established to play a crucial role in matching cardiac energy production to demand, little is known regarding whether mitochondrial Ca2+ (mtCa2+) handling is distinct in the RV and LV. Our objective was to test the hypothesis that the regulation of mtCa2+ differs in the RV and LV. By isolating mitochondria from RV and LV free wall tissues from wild-type mice and healthy pigs, we compared several parameters indicative of Ca2+-regulated mitochondrial function. Basal mtCa2+ levels were higher in RV mitochondria than in LV mitochondria. When successive boluses of Ca2+ were administered to isolated mitochondria, RV mitochondria took up fewer Ca2+ boluses, showing lower Ca2+ retention capacity. RV mitochondria displayed relatively more protein carbonylation, suggesting oxidative stress. Interestingly, ATP production rate was higher in RV mitochondria relative to LV mitochondria; however, only LV mitochondria exhibited an increase in ATP production rate in the presence of Ca2+. We also compared the protein expression of the subunits of the mitochondrial Ca2+ uniporter complex (MCUC) and the mitochondrial Na+/Ca2+ exchanger (NCLX) and found that levels of the MCUC subunit Essential MCU Regulator (EMRE) and NCLX were higher in the LV than the RV, potentially facilitating more dynamic Ca2+ transport in and out of LV mitochondria. Collectively, these data suggest that mtCa2+ is calibrated to higher but more static levels in the RV, whereas in the LV basal mtCa2+ is lower to ensure dynamic range for physiological stimuli to increase mitochondrial bioenergetics, corresponding to the larger changes in workload experienced by the LV.

This study was supported by the National Institutes of Health (1K22HL137901 to Julia C. Liu) and by the Department of Integrative Biology and Physiology (to Jae Hwi Sung).

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Caloric adequacy normalizes brain tissue protein turnover in a rat brain injury model
Authors: Curl Casey , Leija Robert , Peck Austin , Arevalo Jose , Osmond Adam , Doung Justin , Miller Benjamin , Horning Michael , Brooks George
Published: May 2023

Traumatic brain injury (TBI) is a leading cause for hospitalization in America, often having long lasting effects including increased morbidity, mortality and cognitive deficits post recovery. Based on Standard of Care (SOC) treatment, TBI patients are grossly underfed, yet it is unclear how underfeeding effects protein turnover post-TBI. Thus, we designed a study to elucidate the effects of TBI and caloric restriction (CR) on protein dynamics post-TBI. Hypothesis: We hypothesize that TBI would elicit an increased fractional synthesis rate (FSR) in all brain tissue as compared to control, ad libitum (AL) fed animals, while CR would suppress FSR. Thus, we predicted that the CR+TBI animals would have an elevated FSR over CR control but suppressed compared to AL+TBI animals. Methods: Deuterium oxide was used to measure FSR 13-day post TBI in multiple tissues [skeletal muscle, heart, right and left cerebellum, right and left cortex and hippocampus] of Sprague Dawley rats, AL fed control (AL-Con: n=3), AL+TBI (n=6), or CR+TBI (n=5) and CR-Control (n=6). Tissue homogenates were fractionated to isolate the mitochondrial fraction, and cytoplasmic/sarcoplasmic fraction. Pentafluorobenzyl bromide derivatized alanine samples were measured by GC-MS to evaluate ions with m/z 448, 449, 450. FSR was determined using the m/z ion ratios and MIDA. We found that TBI significantly increased FSR over control animals in the left and right cortex (p≤0.05) and suppressed FSR in the cerebellum (p≤0.05). We found that CR in conjunction with TBI caused an increased FSR in the mitochondrial, cytosolic, and whole tissue of the cortical regions of the brain compared to CR control animals (p≤0.05). The increased FSR found with the CR-TBI group was mitigated with ad lib feeding, exhibiting caloric adequacy mitigates the effects of TBI in cortical and cerebral brain regions. This research shows evidence that caloric restriction has a negative impact on brain healing post-TBI.

This project was funded by a grant to GAB from the PAC 12 athletic association (CAL-Brooks-17-02)

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Calcitriol regulates skeletal muscle primary fibroblast proliferation, transition to myofibroblast, and Smad signaling-associated fibrogenesis
Authors: Srikuea Ratchakrit , Hirunsai Muthita
Published: May 2023

To repair damaged muscle, extracellular matrix remodeling that relies on function of fibroblasts plays crucial role in skeletal muscle healing and functional recovery. Currently, several lines of evidence suggest skeletal muscle is a vitamin D-target tissue. Nevertheless, non-calcemic action of calcitriol (the active form of vitamin D3) on the regulation of fibrogenesis process involving in fibrosis development after skeletal muscle injury has not been reported. Herein, cultured primary fibroblasts isolated from skeletal muscle of male C57BL/6 mice (age 1-month-old, n=6) were treated with calcitriol and compared its effect with antifibrotic agent suramin. Cell proliferation was evaluated using BrdU incorporation assay. Transition of fibroblast to myofibroblast and TGF-β1/Smad signaling were investigated using immunocytochemistry and western blot analysis. The results revealed that calcitriol and suramin treatment significantly decreased primary fibroblast proliferation via reduction of cell number in the S-phase of cell cycle. However, anti-proliferative effect of calcitriol was diminished after the cells were co-treated with TGF-β1. TGF-β1 treatment induced transition of fibroblast to myofibroblast through significantly increased α-smooth muscle actin (α-SMA) and p-Smad2/3 protein expression along with altered cellular organization of intermediate filament vimentin. Although calcitriol able to suppress α-SMA and p-Smad2/3 protein expression levels in TGF-β1-treated cells, it showed differential effects compared with suramin that significantly suppressed cell proliferation and decreased transcription factor related to fibrogenic determination (TCF4). Altogether, these findings reveal calcitriol action on the regulation of primary fibroblast proliferation, transition of fibroblast to myofibroblast, and Smad signaling-associated fibrogenesis. Additionally, TGF-β1 stimulation directly affects anti-proliferative effect of calcitriol on skeletal muscle fibroblasts that could modulate calcitriol action on fibrogenesis process of skeletal muscle after injury.

This research project was supported by Mahidol University under the New Discovery and Frontier Research Grant (NDFR 23/2564 to R.S.) and the CIF and CNI grant, Faculty of Science, Mahidol University (to R.S.).

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Immune, metabolic, and renal effects of post-wean BPF exposure in BUF/Mna female rats
Authors: Wagner Valerie , Holl Katie , Clark Karen , Reho John , Dwinell Melinda , Solberg Woods Leah , Lehmler Hans-Joachim , Raff Hershel , Grobe Justin , Kwitek Anne
Published: May 2023

Exposure to endocrine-disrupting chemicals (EDCs) increases the risk of obesity and related cardiometabolic disorders. Bisphenol F (BPF), an EDC that affects the thyroid, reproductive health, and immune cell function, is a common substitute for bisphenol A (BPA) and is used in manufacturing polycarbonates and consumer products. EDC exposure effects likely vary in the population, indicating gene x EDC interactions; however, genetic risk factors interacting with EDCs are unknown. In vivo toxicity studies performed in isogenic or genetically undefined outbred models may obscure or overemphasize exposure outcomes and do not address significant variability in population-level effects. These limitations can be avoided by studying the N/NIH Heterogeneous Stock (HS) rats, an outbred population derived from eight founder inbred strains readily amenable to genetic study. We hypothesize that BPF-induced metabolic disease has underlying genetic risk, which can be identified using HS rats and their founding inbred strains. We previously demonstrated that post-wean BPF exposure increases body growth and adiposity in male HS rats. We evaluated the metabolic impact of post-weaning BPF exposure in BUF/Mna rats, one of the HS-founding inbred strains that has genetic risks for thymic hyperplasia and focal segmental glomerulosclerosis. Weanling littermate pairs of male and female BUF rats were randomly exposed to either vehicle (0.1% EtOH) or 1.125 mg BPF/L in 0.1% EtOH for 10 weeks in drinking water. Metabolic measures, tissues, urine, and feces were taken. Males exposed to BPF did not differ from vehicle control. In females, BPF exposure did not change body composition or body weight gain; however, examination of two metabolic cage time points found that BPF females had decreased energy efficiency (weight gained/calorie absorbed) compared to vehicle control. There was an energy balance disruption in BPF females with increased 24 hr distance traveled and decreased resting metabolic rate compared to vehicle females. Also, BPF females had increased thymus and kidney mass compared to vehicle females. Our preliminary data indicate that post-wean BPF exposure affects immune, metabolic, and renal phenotypes in BUF rats in a sex-specific manner. These results suggest that BPF exacerbates inherent organ dysfunction in a genetically susceptible HS-founding inbred strain. This work supports BPF exposure as a metabolic disease risk factor and indicates that the HS rat will be a useful model for dissecting gene x BPF interactions on metabolic health.

NIH T32 GM008629, NIH P30 ES005605, NIH R24 OD024617.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
The high ventricular function in the shortfin mako shark (Isurus oxyrinchus)
Authors: Lai N Chin , Head Brian , Lai Yin , Tresguerres Martin , Tang Tong
Published: May 2023

The shortfin mako sharks ( Isurus oxyrinchus) belongs to the family Lamnidae, which is a group of high performance regional endothermic elasmobranch fishes that has metabolic rates (47.4±8 ml/kg/min) higher than ectothermic elasmobranchs, and also rivals that of mammals. As in all elasmobranchs, the mako sharks do not possess direct cardiac sympathetic innervation to elevate cardiac performance, but it still retains an ancient design of a capacious semi-rigid pericardium (5.4±0.6 ml/kg) likely to accommodate its large atrial diastolic volume. This study test the hypothesis that the increase in cardiac output in the mako is influenced by a strong positive lusitrophic effect that serves to increase stroke volume, which in turn invokes the Frank-Starling’s effects. The objectives is to show differences in the physiology and biochemical properties between mako (Is) and an ectothermic blue shark ( Prioance glauca, Pg), both are oceanic species and share similar life history. Echocardiography showed a higher early to late filling velocity ratio (p=0.036) in the Is (0.92±0.16, [n=15]) than in Pg (0.45±0.04, [9]). The early time velocity integral is also greater in Is (8.8±2.4 cm, [15]) vs Pg (6.8±0.8 cm [9]) indicating a stronger conduit filling imparted by the energy from previous systole in Is. However, basal cAMP (Is: 31±12 [7] vs Pg: 31±1 [3] fmol/min/μg) and stimulated cAMP with isoproterenol+GTPγS (Is: 65±21 [7] vs Pg: 59±7 [3] fmol/min/μg) activity are similar in both groups. This suggests that the differences in ventricular contractility are not through the classic adrenergic signaling pathway involving adenylyl cyclases, but likely through the mechanical stretching of the myofibrils from diastole. Caveolin distribution of the ventricular tissues following sucrose density gradient shows a higher degree of Caveolin-1/3 in the buoyant fraction and little in the in the heavy fraction in both shark species indicating an absence of t-tubules. However, Is shows a remarkably high amount of buoyant Cav-1/3 fraction compared to Pg. We posit that the high fraction abundance of Cav-1/3 provides a gateway for corticotropin-releasing factor, such as urotensin I or possibly an ancestral precursor of urocortin, which has been shown to elevate heart function in mammals.

The study is supported by NSF IBN93-16621. No disclosure.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Electrophysiological properties and phenotype of the expiratory lateral parafacial neurons of rats
Authors: Magalhães Karolyne , da Silva Melina , Mecawi Andre , Paton Julian , Machado Benedito , Moraes Davi
Published: May 2023

Active expiration is essential for increasing pulmonary ventilation during high chemical drive (hypercapnia). Several studies demonstrated that the lateral aspect of the parafacial (pFL) region, which contains expiratory neurons, drives abdominal muscles during active expiration in response to hypercapnia. However, the electrophysiological properties and synaptic mechanisms determining the activity of pFL expiratory neurons and the specific conditions for their emergence are not fully understood. Therefore, using whole-cell electrophysiology and single-cell qRT-PCR techniques, we evaluated the intrinsic electrophysiological properties, the phenotype, and the respiratory-related synaptic inputs to the pFL expiratory neurons, as well as the mechanisms for the expression of their expiratory activity under conditions of hypercapnia induced active expiration in in situ preparations of juvenile rats. We also evaluated whether these neurons possess intrinsic CO2/[H+] sensitivity. All recorded pFL expiratory neurons were glutamatergic. In normocapnia, GABAergic and glycinergic inhibition during inspiration and expiration suppressed the activity of excitatory pFL expiratory neurons. In hypercapnia, these neurons escape glycinergic inhibition and generate burst discharges at the end of expiration. Post-inhibitory rebound, CaV3.2 isoform of T-type Ca2+ channels, and intracellular [Ca2+] contribute to their expiratory activity. Hypercapnia/hypocapnia or acidosis/alkalosis did not affect the activity of pFL expiratory neurons, indicating that these neurons do not possess intrinsic CO2 and pH sensitivity. Additionally, ion channels/receptors (TASK or GPR4) related to CO2/[H+] sensitivity were not expressed by pFL expiratory neurons. In conclusion, the intrinsic electrophysiological properties and post-synaptic disinhibition of glutamatergic neurons both play essential roles in generating the expiratory oscillations in the pFL region during hypercapnia in rats.

FAPESP and CNPq

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Gut microbial metabolite delta - valerobetaine (VB) influences energy metabolism by altering fat utilization and satiety-related hormones in mice
Authors: Kim Jiyoung , Naudin Crystal , Liu Ken , Parcha Kim , Dawson Paul , Jones Rheinallt , Neish Andrew
Published: May 2023

There is mounting evidence that the gut microbiota exerts profound influences on systemic homeostasis and metabolism, including effects on host energy metabolism, fatty acid oxidation, and obesity. However, we know little about how the microbiota mechanistically influences these aspects of host biology. Previously, we used mass spectrometry-based metabolomics platforms to demonstrate remarkable differences in the metabolite composition in the hepatic mitochondria of germ-free (GF) and conventional mice and identified Δ-valerobetaine (VB) as a key discriminative molecule. VB was undetectable in GF mice but present in conventional mice. We showed that VB is produced by specific bacterial species and inhibited mitochondrial fatty acid oxidation by suppression of the carnitine shuttle. VB administration to GF and conventional mice increased visceral fat mass and exacerbated hepatic steatosis with a Western-style diet but not a chow control diet and can thus function as a microbiota-derived obesogen. Here we show that VB impacts the physiological aspects of energy metabolism. VB reduces the Oxygen consumption rate (OCR) in HEPG2 cells and alters mitochondria-related protein markers (PGC1α, AMPKα, TFAM) suggesting changes in VB can alter the function of mitochondria. To evaluate whole animal consequences, we utilized the CLAMS-HC metabolic cage system to measure the respiratory exchange ratio (RER) in conventional mice. We found that western diet-fed animals treated with VB (IP 50mg/kg) for a week significantly increased RER compared to control groups on the same diet, whereas there was no impact of VB on regular chow diet-fed animals. Higher RER indicates the usage of glucose rather than the usage of fat, thus shifting the resources to produce energy and enhancing the accumulation/retention of adipose tissue. We also found a significant increase in food intake among VB-treated animals regardless of diet. We further investigated the impact of VB on energy-regulating hormones from serum and found a significant alteration in leptin and ghrelin levels. These data suggest VB alters energy utilization in a diet-dependent fashion possibly through regulating energy satiety hormones. Manipulation of VB levels by changing the intake of dietary precursors, or with VB-producing bacterial taxa, may provide therapeutic approaches to disorders of energy/lipid metabolism.

This project has been funded by U.S. NIH R01 AI64462.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.