Predoctoral Fellowship Research Articles

A whole-food, plant-based intensive lifestyle intervention improves glycaemic control and reduces medications in individuals with type 2 diabetes: a randomised controlled trial

Abstract Aims/hypothesis We conducted the largest and longest clinical trial comparing a whole-food, plant-based intervention with standard medical care (SMC) in individuals with type 2 diabetes. Methods We randomised (parallel-arm; computerised 1:1 randomisation ratio) 169 adults aged 18–75 years with type 2 diabetes in the Marshall Islands to an intensive whole-food, plant-based intervention with moderate exercise (PB+Ex) or SMC for 24 weeks. The PB+Ex intervention included 12 weeks of meals, exercise sessions and group classes. Primary outcomes were glycaemic control (HbA1c, glucose, insulin and HOMA-IR) and glucose-lowering medication use. Secondary outcomes included lipids, blood pressure, heart rate and C-reactive protein. Only lab analysts were blinded. Results Compared with SMC (n=90 randomised; n=70 analysed), the PB+Ex (n=79 randomised; n=66 analysed) intervention decreased HbA1c by an additional 14 mmol/mol (1.3%) at week 12 (−22 vs −7 mmol/mol [−2.0% vs −0.7%]; p<0.0001) and 8 mmol/mol (0.7%) at week 24 (−16 vs −8 mmol/mol [−1.4% vs −0.7%]; p=0.01). Concomitantly, 63% of medicated PB+Ex participants reduced their glucose-lowering medications (vs 24%; p=0.006), and 23% of PB+Ex participants with a baseline HbA1c <75 mmol/mol (<9%) achieved remission. Additionally, the PB+Ex intervention reduced weight (−2.7 kg; p<0.0001), C-reactive protein (−11 nmol/l; p=0.005) and cardiovascular medication use compared with SMC. At intermediate timepoints, it improved glucose, insulin, HOMA-IR, cholesterol, triglycerides and heart rate, but not at week 24. Conclusions/interpretation A whole-food, plant-based lifestyle intervention was more effective for improving glycaemic control than SMC. It also reduced the need for diabetes and cardiovascular medications and induced diabetes remission in some participants. Therefore, it is an effective, evidence-based lifestyle option for individuals with type 2 diabetes. Trial registration ClinicalTrials.gov NCT03862963 Funding This research was funded by the Department of the Army (W81XWH-05-1-0547). CJH received support through a National Institutes of Health Predoctoral T32 Obesity Fellowship (T32 HL105349). Graphical Abstract

Diet-induced obesity mediated through Estrogen-Related Receptor α is independent of intestinal function.

Obesity has become an epidemic, prompting advances in therapies targeting this condition. Estrogen-related receptor α (ESRRA), a transcription factor, plays pivotal roles in energy metabolism across diverse tissues. Studies have demonstrated that loss of Esrra leads to fat malabsorption and resistance to diet-induced obesity. However, the reliance of these studies on germline Esrra mutants overlooks the tissue-specific implications of ESRRA in diet-induced obesity. Notably, Esrra exhibits high expression in the gastrointestinal (GI) tract relative to other tissues. Given the critical role of the GI tract in dietary lipid metabolism, this study employs mouse genetics and genomics approaches to dissect the specific impact of intestinal ESRRA along with investigating its role in diet-induced obesity.

Equity Spotlight: Emma Hogan

Emma Hogan is a Computer Science and Engineering PhD student at UC San Diego and a Ford Foundation Predoctoral Fellow.

#1408 Dehydration cannot substitute for any of the triple whammy drugs to cause acute kidney injury

Abstract Background and Aims Polymedication in patients with chronic diseases, such as hypertension, can lead to undesired drug interactions. The combination of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) with diuretics and non-steroidal anti-inflammatory drugs (NSAIDs) can cause triple whammy (TW)-induced acute kidney injury (TW-AKI). Up to 9% of hypertensive patients used NSAIDs in combination with ACEIs / ARBs and diuretics. AKI has a mortality rate of 40% and TW increases the risk of AKI by 30% compared to the combination of only two drugs. In addition, TW-AKI is associated with other risk factors such as dehydration, which may exacerbate the injury. Consequently, the aim of our study was to determine whether dehydration combined with two of the TW drugs could induce AKI in an in vivo experimental model. Method Three months old male Spontaneously Hypertensive Rats (SHR) were divided into four experimental groups: control group (CT); TW group (TW), which received four days of double therapy with trandolapril and furosemide, followed by a triple therapy for two days with trandolapril, furosemide and ibuprofen; trandolapril and ibuprofen group (T+I), which received four days of trandolapril followed by two days of trandolapril and ibuprofen; furosemide and ibuprofen group (F+I), which received four days of furosemide followed by two days of furosemide and ibuprofen; and trandolapril and furosemide group (T+F), which received six days of trandolapril and furosemide. All groups were subjected to a 60-70% water restriction of basal intake (i.e. 15 mL/day) to generate mild dehydration. Blood and urine samples were collected at baseline (B), day 4 and day 6. Blood pressure was measured at baseline and day 4. Renal function was assessed by plasma creatinine, plasma urea and creatinine clearance, and hydration status was determined by plasma osmolarity and water balance (i.e. water intake minus urine flow). Results Under basal conditions, all rats were hypertensive. The combination of trandolapril and furosemide significantly reduced the mean blood pressure on day 4 (p = 0.0066), while trandolapril or furosemide alone did not achieve these decreases. After four days of water restriction to 15 mL/day, all groups showed mild dehydration with a decrease in water balance and an increase in plasma osmolarity by. Plasma creatinine and plasma urea values were only increased on day 6 in the TW group (p = 0.0009 and p = 0.02, respectively). Creatinine clearance was also clearly reduced in the TW group (p = 0.0004). F+I and T+F groups showed slight decreases in creatinine clearance at day 6, as well as slight increases in plasma urea. However, these changes were not as pronounced as those observed in the TW group. Conclusion In our in vivo model of TW-AKI, mild dehydration cannot replace any of the TW drugs, although it appears that combination of F+I and T+F in dehydrated rats slightly alter plasma urea and creatinine clearance values at day 6, suggesting that this condition maintained over time might lead to the development of AKI. Funding This research was funded by grants from Instituto de Salud Carlos III (ISCIII), Ministerio de Ciencia e Innovación (PI21/01226 and PI21/00548 co-funded by the European Union; and RICORS2040, RD21/0005/0004, co-funded by the European Union—NextGenerationEU, Mecanismo para la Recuperación y la Resiliencia (MRR)) and from Consejería de Educación, Junta de Castilla y León (IES160P20), co-funded by FEDER funds. Noelia Diaz-Morales is recipient of a Juan de la Cierva-Formación postdoctoral contract (FJC2020-043205-I) funded by MCIN/AEI/10.13039/501100011033 and the European Union “NextGenerationEU/PRTR”. Eva M. Baranda-Alonso is recipient of a predoctoral fellowship from the Junta de Castilla y Leon (Spain) and the European Social Fund from the European Commission.

#1413 High performance of ACLARA calculator of rat creatinine clearance for the chronic follow up of renal function

Abstract Background and Aims A neural network-based calculator to estimate rat creatinine clearance (ClCr), as a measurement of the glomerular filtration rate (GFR), from paired plasma creatinine concentration and body weight data has been recently developed [1]. Like human GFR estimating formulae, ACLARA averts long experimental procedures and reduces animal stress (by obviating the use of individual isolation in metabolic cages). This tool is publicly available for free use among the scientific community (https://idal.uv.es/aclara/). When collated with experimentally measured ClCr, ACLARA performs very well at comparing experiments in the whole, showing almost identical behavior of all experimental groups and conditions. Yet, ACLARA was trained mostly with data from short experiments involving acute changes in renal function, and from young rats. Fewer data from older animals was included in the development of the calculator. Thus, its field performance on longer evolution of renal function in adult rats has not yet been sufficiently validated. Accordingly, the aim of this work was to deepen in the assessment of ACLARA in the long-term evolution of rat ClCr. Method The evolution of measured (mClCr) versus ACLARA-estimated ClCr (eClCr) was compared at different time points over a period of 3 months in 20 male Wistar rats with chronic renal damage and 8 age-matched controls. In total, 176 data pairs of mClCr and eClCr were obtained. On the one hand, mClCr was determined by the usual experimental procedure [2]. Briefly, rats were allocated in metabolic cages to obtain 24-hour urine samples and urine flow (UF). Creatinine concentration was measured in the urine (Cru) and plasma (Crp) by a colorimetric assay based on the Jaffe's reaction, and mCrCl was then calculated as Cru x UF / Crp. On the other hand, eClCr was estimated with the ACLARA calculator from the corresponding Crp and body weight data. A Pearson's correlation study between mClCr and eClCr was carried out. Results Our results reveal that the information provided by the 90-day evolution of mClCr and eClCr is virtually identical at the whole experiment level (see Fig. 1). Furthermore, ACLARA seems to provide slightly more coherent and homogeneous information, as the considerable experimental error introduced by urine collection is averted in eClCr but present in mClCr. At the individual data level, ACLARA-estimated values are slightly lower than the corresponding measurements. The correlation between mClCr and eClCr was highly significant (r Pearson= 0.83; p < 0.0001). Conclusion ACLARA shows high performance at estimating CrCl in rats of growing age. Our results support its use also in chronic studies in which renal function must be evaluated. Funding This research was funded by grants from Instituto de Salud Carlos III (ISCIII), Ministerio de Ciencia e Innovación (PI21/01226 and PI21/00548 co-funded by the European Union; and RICORS2040, RD21/0005/0004, co-funded by the European Union – NextGenerationEU, Mecanismo para la Recuperación y la Resiliencia (MRR)) and from Consejería de Educación, Junta de Castilla y León (IES160P20), co-funded by FEDER funds. Joana Mercado-Hernández is recipient of a predoctoral fellowship from the Junta de Castilla y Leon (Spain) and the European Social Fund from the European Commission.

Renal Function and Transporters in the Na/K-ATPase α1S/S Mouse Model of High Affnity for Cardiotonic Steroids

Genetic ablation of ATP1A1 in the mouse renal proximal tubule (RPT) revealed that Na/K-ATPase (NKA) α1 tonically inhibits sodium and water reabsorption. Mechanistically, findings in KO mouse RPT and renal epithelial cells were consistent with a prevalent role of a NKA/Src-dependent downregulation of Na+/H+ exchanger 3 (NHE3). Pharmacologically, functional activation of this pathway has been obtained in vitro and ex vivo using low concentrations of NKA archetypal ligands cardiotonic steroids (CTS). However, the physiological implication of an activation of the endogenous CTS (eCTS)/NKA/Src on renal transporters including NHE3 has not been explored. We assessed the renal impact of CTS/NKA α1 receptor activation by comparing mice expressing the naturally resistant NKA α1 and age-matched mice genetically engineered to express a mutated NKA α1 with high affnity for CTS (R111Q/D122N double substitution). Mice obtained from established colonies at the University of Cincinnati were a gift from Dr. Jerry Lingrel. CTS-sensitive (α1S/S) male mice aged 3-6 months on a C57Bl6 background and age-matched controls (α1R/R) were used. Mice were born with a normal Mendelian ratio, with no observable difference between α1S/S and α1R/R. Renal Na/K-ATPase inhibitory dose-response curve to the CTS ouabain was shifted to the left, as expected, and occurred without detectable change of total renal NKA activity, NKA α1 or β1 protein contents. Metabolic cage studies revealed that increased α1 sensitivity to CTS resulted in a significant increase in urine output in α1S/S mice compared to age-matched α1R/R controls (3.9±0.3 vs. 2.4±0.2 ml/24h; n=6, p<0.01). Consistent with an activation of the NKA/Src receptor by eCTS, western blot analyses of renal cortical preparation revealed an increased phosphorylation of NKA α1 at Y260 (Src target residue) and decreased NHE3 content (43.6 %; n=5, p<0.01). RNA-seq analysis of whole kidneys from α1S/S and α1R/R littermate mice using the Illumina NovaSeq 6000 system (Novogene) and Volcano Plot (DEG data using Python) further showed differential expression of 296 genes (147 upregulated and 149 downregulated). Gene Set Enrichment Analysis (GSEA) using the WebGestalt toolkit showed that the altered pathways were mostly involved in solute transport. Taken together, these results provide genetic evidence of the physiological role of eCTS/NKAα1 on renal function in the intact mouse. Increased affnity to eCTS is suffcient to lead to an activation of NKAα1/Src, a downregulation of NHE3, and transcriptional regulation of renal transporters associated with increased urine output. This work was supported by AHA, Predoctoral fellowship #19PRE34450095, NIH DK129937, and NIH Grant P20GM103434 to the West Virginia IDeA Network of Biomedical Research Excellence. This is the full abstract presented at the American Physiology Summit 2024 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.

Adaptations to maternal WSD-feeding and metformin use on fetal islets from non-human primate offspring

Given the current increased prevalence of diabetes in pregnancy, the potential relative risks and benefits of oral glycemic agents on the developing offspring should be evaluated and considered. Metformin (Met) is a common oral glycemic agent prescribed in pregnancy that is not metabolized, but is renally excreted and actively transported across the placenta. Thus, the developing fetus is exposed to near equivalent maternal adult doses with subsequent risk of adverse consequences. Using a non-human primate model of maternal overnutrition, our group previously demonstrated that developmental exposure to a Western-style diet (WSD) results in an inappropriate increase in glucose-stimulated insulin secretion and changes in expression of several ion channels involved in insulin secretion in islets from juvenile offspring. Given that maternal overnutrition results in an excess energy supply to the developing fetus while Met inhibits mitochondrial respiration, we hypothesize that maternal WSD-feeding and Met will result in maladaptive beta-cell function in the fetus. Static insulin secretion assays on islets from chow (CD) and WSD +/- Met-exposed offspring show no differences in glucose-stimulated insulin secretion. Nevertheless, islets from a mWSD+Met-exposed fetus showed lower oxygen consumption and extracellular acidification rate relative to mWSD+placebo fetal islets, suggesting that maternal diet influences fetal programming and adaptation to Met in fetal islets. Therefore, we predict that the metabolic response to intrauterine Met exposure differs depending on the maternal diet. Elucidation of the mechanisms mediating adaptations to maternal diet and Met exposure during development may provide insight on interventions to avoid beta-cell failure in the offspring as they age. All nonhuman primate studies were supported in part by the Oregon National Primate Research Center grant P51 OD011092 from the National Institutes of Health/Offce of the Director. D.T.C. was supported by the Vanderbilt University Training Program in Molecular Endocrinology (5T32 DK563-30) and a predoctoral fellowship from the NIH/NIDDK (1F31 DK135164).T.A.D., C.E.M., K.M.A., J.E.F., P.K., and M.G. were supported by NIH/NIDDK Grants R24 DK090964 and R01 DK128187. This is the full abstract presented at the American Physiology Summit 2024 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.

Endothelial Hemoglobin Alpha Mediates Iron Regulation of Endothelial Nitric Oxide

Iron deficiency anemia (IDA) is a common comorbidity in cardiovascular disease. Previous clinical studies have found iron deficiency anemia (IDA) increases endothelial NO signaling and attributed this change to the reduction in circulating hemoglobin. However, it has been shown in ex vivo preparations that endothelial NO signaling is unaffected by the presence of erythrocytes suggesting changes in circulating hemoglobin do not alter NO signaling. Our lab has previously shown the hemoglobin-α (Hbα) is expressed in the endothelium of small arteries and scavenges NO. We hypothesized endothelial Hbα, rather than blood hemoglobin is responsible for the increased NO signaling in IDA. We first tested this hypothesis in a mouse model of IDA in which we were able to replete vascular iron stores. Male and female C57BL/6 mice were fed an iron deficient (2-6 ppm Fe) or nutrient matched control diet (48 ppm Fe) beginning at weaning. IDA mice underwent phlebotomies (10% blood volume) at 9 and 11 weeks old. To restore vascular iron stores, a subset of IDA mice received a single i.p. injection of iron dextran (FeDex; 20 mg/kg) at 12 weeks. All measurements were taken one week later. As expected, IDA mice had low blood hemoglobin, and FeDex did not rescue the anemia but did rescue vascular iron stores as measured by ferritin light chain protein. To investigate NO signaling, we used laser speckle contrast imaging to measure changes in in vivo blood flow in response to the NO synthase inhibitor L-NAME. The magnitude of the response to L-NAME is an indicator of NO signaling. IDA mice exhibited an exaggerated response to L-NAME indicating increased NO signaling. FeDex treatment restored the L-NAME response back to control levels suggesting reduced vascular iron stores, rather than the anemia itself increased NO signaling. In order to investigate the role of endothelial Hbα, we repeated these studies in endothelial specific Hbα knockout mice (Hba1fl/fl-Cdh5-CreERT2+). Lack of endothelial Hbα did not prevent the increased response to L-NAME in IDA mice but did prevent the rescue by FeDex. This suggests a model in which endothelial Hba participates in regulating NO in response to iron but not the increased NO in IDA. Because Hbα does not explain the initial increase in NO, we have begun investigating other anemia-associated NO stimulators. Erythropoetin (EPO) is known to stimulate NO production in endothelial cells and is elevated in our anemia model regardless of FeDex treatment. Future work will investigate the role of EPO in regulating NO in IDA. University of Virginia Basic and Translational Research Training Grant T32 007284 (LSD, MAL, SAL); NIH HL088554; LaunchPad; Lipedema Foundation; AHA Predoctoral Fellowship (MAL). This is the full abstract presented at the American Physiology Summit 2024 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.

Exploring a Role for Gut Microbiota to Modulate Aldosterone

Hypertension is associated with an increased risk of mortality for numerous conditions including heart disease, diabetes, and renal disease (D. Aune, Biomed Res Int, 2021). Hypertension is often viewed as idiopathic and treatment is seldom aimed at addressing an underlying mechanism; however, a recent study indicates that primary aldosteronism is an underappreciated cause of idiopathic hypertension (J. Brown, Ann Intern Med, 2020). Here, we investigate for the first time the influence of gut microbiota on aldosterone regulation. To pursue this, we used C57Bl/6 mice (n=20; males) housed in the Johns Hopkins Animal Care Facility and fed a specific pathogen-free diet. Whole blood from submandibular cheek bleeds were collected into K2EDTA-treated tubes at baseline and mice were allowed to recover. Mice were then treated with antibiotics (ABX; 1g/L ampicillin, 1g/L neomycin, and 0.5g/L vancomycin) in their drinking water ad libitum for a total of 7 days to dramatically suppress gut microbes. Whole blood via submandibular cheek bleeds were collected after 24hrs, and at day 7 on ABXs. Mice were sacrificed on day 7 of ABX. Plasma samples from baseline, 24hrs on ABX and 7 days on ABX were used to determine aldosterone concentration and plasma renin activity (PRA) via ELISA. In addition, 24hr urine samples were collected at baseline and at day 7 on ABXs. Statistics were calculated using paired, one-way ANOVA; data below are mean ± SD. Our results demonstrate that plasma aldosterone and PRA, as well as urine aldosterone, were significantly increased from baseline to 7 days on ABX treatment (plasma aldo (pg/mL): 295.1 ± 164.8 vs 634.9 ± 290.4, p= 0.0197; plasma PRA (ng Ang-1/mL/hr): 191.8 ± 137.6 vs 325.9 ± 141.5, p= 0.0108; urine aldo (pg/mL): 2019 ± 322.1 vs 2668 ± 292.0, p = 0.0047). However, there was no significant difference in plasma aldosterone from baseline to 24hrs on ABX treatment (295.1 ± 164.8 vs 434.5 ± 245.3, p= 0.1047). In contrast, we observed a significant increase in angiotensin I from baseline to 24hrs on ABX treatment (191.8 ± 137.6 vs 355.8 ± 139.6, p=0.0041), and this increase was sustained until day 7 (325.9 ± 141.5 vs baseline, p=0.0108). Preliminary data suggest aldosterone is also increased in the plasma of germ-free mice (without gut microbes) compared to conventionalized controls (750.4 ± 265.0, n= 6, vs 314.4 ± 260.3, n=4, p=0.0667), implying that gut microbiota normally act to suppress plasma aldosterone. Taken together, we demonstrate that in the absence of gut microbiota, plasma aldosterone, urine aldosterone, and PRA are significantly increased. Understanding how gut microbes influence aldosterone levels could provide valuable insights into the development and treatment of hypertension. This knowledge may open new avenues for therapeutic interventions, such as probiotics or dietary modifications, to help regulate blood pressure. William Townsend Porter Predoctoral Fellowship from the American Physiological Society (BNM), Johns Hopkins Post-baccalaureate Research Education Program (PREP; R25GM109441 to ADM), the NIDDK Diabetic Complications Consortium (RRID:SCR_001415m www.diacomp.org, grants DK076169 and DK 115255 (subaward to JLP)) and American Heart Association Established Investigator Award (to JLP). This is the full abstract presented at the American Physiology Summit 2024 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.

Cellular Mechanisms for pH Regulation and Energy Metabolism in Sharks and Rays

Similar to mammalian kidney distal tubule cells, specialized shark and ray gill epithelial cells maintain blood pH homeostasis. These shark and ray gill cells are either enriched with the Na+/K+-ATPase (NKA) and responsible for acid secretion or enriched for the vacuolar H+-ATPase (VHA) and responsible for base secretion. Moreover, both cell types contain abundant mitochondria and glycogen, and glycogen content decreases in active acid-base regulatory cells in vivo. Additional experiments with isolated gill cells in vitro show that glycogen coincides with the subcellular localization of NKA and VHA. Under control conditions, glycogen and NKA are at the cell membrane of acid-secreting cells while glycogen and VHA are in the cytoplasm of base-secreting cells. During exposure to alkalosis, NKA and glycogen localization remains unchanged in acid-secreting cells; however, both VHA and glycogen translocate to the cell membrane of base-secreting cells. Interestingly, this process is prevented by pharmacological inhibition of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC). This suggests a novel mechanism, a coupling of glycogen metabolism with acid-base regulation that sustains ATPase function during sudden periods of increased energy demand. Since VHA, sAC, and glycogen are evolutionarily widespread, this mechanism is likely to apply broadly to other organisms and systems, perhaps including chronic kidney disease. APS Porter Predoctoral Fellowship and National Science Foundation Postdoctoral Research Fellowship in Biology #1709911 to JR, National Science Foundation Grant IOS 1354181 to MT. This is the full abstract presented at the American Physiology Summit 2024 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.

Functional profiling of resident cells during vascular aging

Introduction: Depending on surrounding cell types, substrate mechanics, and chemical agonists, vascular cell types – including endothelial (ECs) and smooth muscle cells (VSMC) — modulate their behavior to maintain homeostasis. Aging perturbs this homeostasis resulting in EC and SMC dysfunction, marked by impaired barrier integrity and pathological ECM remodeling. Endothelial-to-mesenchymal transition (EndMT) in ECs and “dedifferentiation” of VSMCs towards a synthetic phenotype are phenomenon under investigation as cellular drivers of the widespread dysregulation seen with aging. The overall goal of this project is to understand the effect of cross-talk between ECM and growth factor signaling on vascular cell plasticity during aging. Materials and Methods: Human aortic endothelial cells (HAECs) were seeded onto transwell inserts after seven days treatment with or without TGF-β. After growing to confluence on the insert, cells were subjected to a FITC-dextran transwell assay. A parallel group of cells was seeded onto fibronectin coated glass-bottom dishes and stained for the expression of focal adhesion proteins and cell-type markers. Mouse aortic smooth muscle cells (maSMCs) were isolated from C57Bl6 mice at 3 (young), 6 (early middle-aged; EMA), 9 (middle-age; MA), or greater than 18 months of age (old). Cells were seeded onto dye-quenched (DQ) collagen type I (Col-I) substrate before gain of fluorescence was measured in proximity to the cell as well as in the surrounding media. A parallel group of cells were allowed to grow in media containing FITC Col-I, and gain of fluorescence was measured in proximity to the cells. Each cell type (3M, 6M, 9M, and 18M) in both experiments (DQ and FITC) were further treated with MMP inhibitor, TG2 inhibitor and TGF-β1 to measure their impacts on Col-I turnover. Results: Barrier function was not impaired in ECs cultured with TGF-β1, relative to their untreated counterparts. Mouse aortic SMCs isolated from older mice had decreased rates of Col-I cleavage and were more susceptible to MMP inhibition than their younger counterparts. Conclusions: maSMCs from older mice have lower Col-I turnover than their younger counterparts. This is consistent with bulk tissue behavior, as it is well known that relative collagen levels increase in the elastic vasculature as we age. TGF-β1 treatment did not have an effect on permeability of 4kd FITC-dextran, it is feasible that there will be an impact on the larger 70kd fragments. Travis Brady is supported by the NASEM Ford Foundation Pre-doctoral Fellowship. This is the full abstract presented at the American Physiology Summit 2024 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.

Sex-Based Differences in Proximal Tubule Endocytic Capacity in Mice

Women are more protected from acute kidney injury, and chronic kidney disease (CKD) in women progresses more slowly to end-stage renal disease compared to men. CKD involves changes in the integrity of the glomerular barrier function with consequent proteinuria. The kidney proximal tubule (PT) normally reclaims albumin and other filtered proteins via receptor-mediated endocytosis facilitated by the multiligand receptors megalin and cubilin. PT health, and ultimately kidney function, is impacted by the uptake of excess albumin and by nephrotoxic drugs that enter cells in a megalin/cubilin dependent manner. Recent transcriptomic studies in mice have shown differences in the expression of megalin and cubilin between males and females and across the S1, S2, and S3 sub-segments that comprise the PT. Additionally, reduced reabsorption of water and salt by the PT has been demonstrated in female rodents. These differences in PT receptor expression and functionality likely contribute to sex-based differences in PT endocytic capacity. To determine if there are sex-based differences in the recovery of filtered proteins by the PT, urine and kidney tissue were collected from five male and five female 13-week-old C57BL/6 mice. Urinary albumin was quantified by ELISA. Kidneys were processed for Western blotting and immunofluorescence staining. We used imaging-based approaches to quantify the expression and distribution of albumin, megalin, and cubilin in SGLT2-positive S1 and SGLT2-negative, OAT1-positive S2 segments. Under normal conditions, S1 had greater intensity of subapical albumin staining in both males and females. However, females had greater intensity of albumin staining in S2 normalized to S1 compared to males. Female mice had lower levels of urinary albumin excretion when normalized to creatinine than males. Female mice had greater expression of total megalin (1.5x) and cubilin (1.4x) and decreased expression of NHE3 (0.7x) in the kidney cortex. Male and female mice had similar levels of megalin expression and surface localization in S1, however female mice had greater expression and surface localization of megalin in S2. Males had greater colocalization of megalin with lysosomal marker, LAMP1. In both males and females, the colocalization of megalin with LAMP1 decreased from S1 to S2. Together, these data suggest that, at baseline in female mice, S2 has greater endocytic capacity and contributes more to the uptake of normally filtered albumin than in males. This increased capacity could explain the reduced urinary excretion of albumin observed in rodent injury models and in women with CKD. Current studies are focused on incorporating these sex-based differences into a multiscale mathematical model of protein uptake along the length of the PT. National Institutes of Health: T32 DK007052, F31 DK121394, R01 DK125049, R01 DK118726, R01 DK083785, S10 OD021627, S10 OD028596, U54 DK137329, ASN Foundation for Kidney Research Pre-Doctoral Fellowship Award. This is the full abstract presented at the American Physiology Summit 2024 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 Sex-based Differences in Chemoreflex during Recovery from Acute Lung Injury

Introduction- Sex-specific patterns in respiratory conditions, such as asthma, COPD, cystic fibrosis, obstructive sleep apnea, and idiopathic pulmonary fibrosis, have been previously documented. Animal models of acute lung injury (ALI) have offered insights into sex differences, with male mice exhibiting distinct lung edema and vascular leakage compared to female mice. Our lab has provided evidence that the peripheral (or carotid body) chemoreflex is sensitized in male rats during the recovery from bleomycin-induced ALI, but whether sex-based chemoreflex changes occur post-ALI in not known. To bridge this gap, our current study employed the bleomycin-induced ALI animal model to investigate sex-based differences in chemoreflex activation during the recovery of ALI. Methods- ALI was induced using a single intra-tracheal instillation of bleomycin (bleo) (day 1). Resting fR (respiratory frequency) was measured at pre-bleo, day 7 (D7) post-bleo, and 1 month (1 mth) post-bleo time points. The chemoreflex response to hypoxia (10% O2, 0% CO2) and normoxic-hypercapnia (21% O2, 5% CO2) were measured before bleo administration (pre-bleo) time point and 1 month (1 mth) post-bleo using whole-body plethysmography. Apnea-hypopnea Index (AHI), post-sigh apneas, and sighs were measured at each time point. Results- Resting fR: There were no significant differences in resting fR, either at pre-bleo time point or at day 7 (D7) post-bleo between male and female rats. At 1 mth post-bleo, the resting fR was partially restored in both sexes but the recovery towards normal ranges of resting fR was significantly slower in male rats compared to female rats. AHI, post-sigh apneas, and sighs: At the pre-bleo and 1 mth post-bleo time points, there were no significant differences in AHI, post-sigh apneas, and sighs between male and female rats. However, at D7 post-bleo, the male rats exhibited a higher AHI than female rats; Chemoreflex sensitivity: Both male and female rats exhibited a sensitized chemoreflex activation to hypoxia and normoxic-hypercapnia with no significant differences between sexes. Discussion- Our study showed a sex difference in resting ventilatory parameters including resting fR and AHI post ALI. On the other hand, we did not find any sex difference in chemoreflex sensitization at 1 mth post-bleo. This research contributes to a better understanding of sex-based variations in lung disorders. This study was supported by NIH grant R01 HL-152160 and in part, by NIH grants R01 HL-121012 and R01 HL126796. H-JW was also supported by Margaret R. Larson Professorship in Anesthesiology. IZ was partially supported by the Theodore F. Hubbard Foundation. KK was supported by the AHA predoctoral fellowship -AHA award #903872 by the American Heart Association. This is the full abstract presented at the American Physiology Summit 2024 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.

Cardiomyocyte-specific deletion of adhesion G protein-coupled receptor F5 (ADGRF5) increases susceptibility to stress and arrhythmia

G-Protein Coupled Receptors (GPCR) represent the largest family of cell surface receptors in the human body and serve as targets for more than 30% of all approved drugs. Adhesion GPCRs (AGPCR) are an understudied GPCR family containing numerous extracellular domains that interact with extracellular proteins, including many known mediators of cardiac remodeling responses to pathologic stress. However, their relative expression in the heart and impact on cardiac function normally or during disease has been largely unstudied. To address this, we evaluated RNASeq-attained AGPCR expression from left ventricular (LV) samples of adult mice, of which Adgrf5 was one of the most highly expressed. Notably, decreased ADGRF5 expression is observed across numerous failing human LV tissue GEO datasets, and C57BL6/J mice subjected to transaortic constriction (TAC) surgery to induce pressure overload-induced HF also displayed reduced LV Adgrf5 expression by 12 weeks post-TAC. Analysis of published single cell (sc)-RNASeq datasets confirmed Adgrf5 expression in cardiomyocytes (CM), which also decreased following TAC in mice and in CM from failing human hearts. To investigate the impact of CM-specific ADGRF5 on cardiac function and remodeling normally or during disease progression, we crossed floxed ADGRF5 (ADGRF5f/f) and αMHC-Cre mice to generate constitutive, CM-specific ADGRF5 knockout mice (F5cmKO). These mice display normal cardiac structure and function at 12 weeks of age versus αMHC-Cre mice, as assessed via echocardiography, gravimetrics and immunohistochemistry. However, F5cmKO mice develop cardiac dysfunction, maladaptive remodeling, and increased mortality over time, even in the absence of pathologic insult, suggesting a homeostatic function of CM-specific ADGRF5. Following TAC surgery, F5cmKO mice display similar outcomes including enhanced cardiac dysfunction with accelerated remodeling and increased mortality. To attain mechanistic insight into these outcomes, we performed RNA-sequencing on LV tissue of 12-week-old F5cmKO mice, identifying and subsequently validating Scn1b as significantly upregulated in F5cmKO CM. Scn1b encodes for the β subunits of voltage-gated sodium channels (Scnβ1/β1B), which regulate gating and kinetics of Nav1.5 as well as adhesive CM-CM interactions, disruption of which could lead to arrhythmias. Indeed, conscious electrocardiogram (ECG) readings via telemetry indicated F5cmKO mice had a high burden of premature ventricular contractions (PVC), including ventricular tachycardia associated with cardiac enlargement. Using a combination of luciferase and fluorescence resonance energy transfer (FRET) reporters and gene expression analyses in neonatal rat ventricular myocytes (NRVM), we confirmed that ADGRF5 controls Scn1b expression in a Gαq/11 protein-dependent manner. In all, we have discovered that loss of CM-specific ADGRF5 leads to increased Scn1b expression with enhanced susceptibility to stress, arrythmias and sudden death, thus may provide a novel GPCR target to promote the maintenance of cardiac rhythm. AHA Predoctoral Fellowship 834906 to J.M.E. P01 HL147841 to D.T. This is the full abstract presented at the American Physiology Summit 2024 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.

NADPH oxidase-derived reactive oxygen species regulates adipose tissue lipolysis in humans

There is mounting evidence suggesting that reactive oxygen species (ROS) generated by NADPH oxidase (NOX) regulate physiological processes, as NOX has been shown to promote increases in lipolysis in cultured adipocytes. PURPOSE: To determine the mechanisms by which NOX stimulates adipose tissue lipolysis. METHODS: Young healthy females (n = 17; mean ± SD; age: 21.7 ± 5 years; body mass index: 22.2 ± 3.8 kg/m2) participated in this study. Participants underwent microdialysis and hyperinsulinemic-euglycemic clamp (clamp) procedures. Three microdialysis probes were inserted into subcutaneous abdominal adipose tissue to monitor local adipose tissue ROS (H2O2) production and lipolysis (as indicated by dialysate glycerol). To determine whether NOX stimulates lipolysis via distinct signaling pathways, microdialysis probes were perfused with either isoproterenol (Iso; β-adrenergic agonist to stimulate canonical lipolysis signaling) or atrial natriuretic peptide (ANP to stimulate non-canonical lipolysis signaling), then perfused with a local NOX inhibitor (apocynin). A control probe was perfused with apocynin but without any agonists of lipolysis. The microdialysis procedures were then repeated under hyperinsulinemic conditions during the same study visit. RESULTS: In the fasted state, dialysate H2O2 concentrations were lower in the control and Iso probes upon apocynin perfusion (control probe without apocynin: 1.06 ± 0.5 μM, with apocynin: 0.62 ± 0.2 μM; p = 0.005; Iso probe without apocynin: 1.01 ± 0.4 μM, with apocynin: 0.66 ± 0.2 μM; p = 0.003). Apocynin perfusion did not alter dialysate H2O2 concentrations in the ANP probe under the fasted state (p = 0.11). Dialysate glycerol concentrations did not change upon apocynin perfusion under any of the microdialysis probe conditions in the fasted state (p > 0.05). During the clamp, apocynin perfusion resulted in lower dialysate H2O2 concentrations in the three conditions (control probe without apocynin: 1.22 ± 0.6 μM, with apocynin: 0.75 ± 0.3 μM; p = 0.03; Iso probe without apocynin: 1.55 ± 0.8 μM, with apocynin: 0.79 ± 0.3 μM; p = 0.01; ANP probe without apocynin: 1.55 ± 0.6 μM, with apocynin: 0.92 ± 0.3 μM; p = 0.03). Dialysate glycerol concentrations were lower in the Iso probe upon apocynin perfusion during the clamp (Iso probe without apocynin: 124.7 ± 38 μM, with apocynin: 90.9 ± 25 μM; p = 0.003). CONCLUSIONS: This study presents adipose tissue NOX as a source of in vivo ROS production in human participants. In addition, we reveal a novel mechanism of NOX in adipose tissue function whereby NOX exerts increases in β-adrenergic-mediated lipolysis during hyperinsulinemia. Our findings highlight the roles of ROS as signaling mediators and suggest that an imbalance between NOX activity and insulin action on adipose tissue could negatively affect systemic fatty acid metabolism. Porter Pre-doctoral Fellowship from the American Physiological Society and an NIH National Research Service Award (F31HL154642). This is the full abstract presented at the American Physiology Summit 2024 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.

Activation of Piezo-1 Prevents Human Microvascular Endothelial Dysfunction During Acute Inhibition of Ceramide Formation

Despite the well-known damaging effects of elevated intracellular ceramides on human microvascular function, our recent work has shown that inhibition of ceramide formation through neutral sphingomyelinase (NSmase) promotes endothelial dysfunction in arterioles from healthy adults, manifested as endothelial production of hydrogen peroxide (H2O2), rather than nitric oxide (NO), in response to flow (flow-induced dilation; FID). Recent evidence suggests that ceramide prevents inactivation of Piezo-1, a shear-sensitive Ca2+ channel and inhibition of Piezo-1 reduces endothelial nitric oxide synthase (eNOS) activation in response to flow. Together, we hypothesized that ceramide-induced Piezo-1 activation is required to maintain NO-mediated FID in human microvessels and thus agonism of Piezo-1 during NSmase inhibition will prevent endothelial dysfunction. Arterioles (100-250μm) from healthy adults were dissected from discarded surgical adipose tissue. Vessels were cannulated in organ chambers, pre-constricted with endothelin-1, and changes in internal diameter in response to increases in flow were measured with videomicroscopy. Peroxy yellow 1 (PY1) fluorescent probe was used to assess endothelial H2O2 production in human umbilical vein endothelial cells (HUVECs). Mean% maximal dilation or fluorescent intensity±SE with two-way repeated measures ANOVA is reported. FID was preserved with Piezo-1 agonism (Yoda-1, 1μM, 30min) during NSmase inhibition (GW4869 4μM, 30min; 73±16.8, n=4 vs control 73±8.2, n=9; p>0.05), however FID was diminished in the presence of the eNOS inhibitor L-NAME (100μM; -2.6±11.3, n=5; p<0.05). A similar switch to NO-mediated FID was seen with C2-ceramide (5μM)+GW4869 (70.1±9.7 vs +L-NAME -3±9.7, n=4 both; p<0.05). NSmase inhibition increased H2O2 production in HUVECs (5.2±7.4 vs 83.0±31.6, n=6; p<0.05), an effect that was diminished with Yoda-1 (5.1±7.5, n=4; p<0.05) and C2-ceramide (10.7±9.2, n=5; p<0.05). These data suggest a role for Piezo-1 in NSmase-induced NO-signaling and provide mechanistic insight into how ceramide may exert beneficial effects within the human microvasculature. This research is supported by the National Institute of Health (NHLBI) R01HL160752 (JKF) and the American Heart Association (AHA) Predoctoral Fellowship 909315 (GSK). This is the full abstract presented at the American Physiology Summit 2024 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.

Sglt2-independent effects of gliflozins on proximal tubule function

Background: Beyond glycemic control, Sglt2 inhibitors (Sglt2i) have protective effects on renal function. Sglt2i-mediated reductions in Na+ reabsorption have been suggested to protect PT cells from damage. The mechanisms responsible for renoprotection are unknown and have been suggested to involve inhibition of NHE3 leading to reduced ATP-dependent tubular workload and mitochondrial oxygen consumption. NHE3 activity is also important for regulation of endosomal pH, and the effects of Sglt2i on endocytic function are unknown. Aim of this study: to dissect the direct and immediate effects of SGLT2i on PT cell functions using opossum kidney (OK) PT cells, which represents a powerful physiologically-relevant system model. Methods: We tested the direct effects of Sglt2i on Na+-dependent fluid transport and endocytic uptake in a highly differentiated cell culture model that recapitulates the morphology, metabolism, and high endocytic and transport capacity of PT cells in vivo. The effect of gliflozins on albumin uptake and on fluid transport was quantified in OK PT cells. The effect of canagliflozin vs the NHE3 inhibitor S3226 on early endosome pH in OK cells was measured using fluorescence ratio imaging. Effects of gliflozins, NHE3 inhibitors, and AMPK pathway perturbants were determined by immunoblotting. 10 week-old male C57BL/6 mice were given canagliflozin or empagliflozin by oral gavage daily following vehicle gavage. Urine was collected via metabolic cages at baseline and after 24 h and 48h. Creatinine and albumin were measured by ELISA. Results: Canagliflozin but not empagliflozin reduced fluid transport across cell monolayers and inhibited endocytic uptake of albumin. These effects were independent of glucose and occurred at clinically relevant concentrations of drug. Canagliflozin did not affect endosomal pH, and albumin uptake was further reduced when added together with the selective NHE3 inhibitor S3226. Additionally, canagliflozin did not alter NHE3 phosphorylation when added alone, but prevented the reduction in phosphorylation caused by the selective NHE3 inhibitor S3226. Mice given a single dose of canagliflozin excreted twice as much urine over 24 h compared with empagliflozin-treated animals, suggesting that off-target effects of canagliflozin contribute significantly to reduced Na+-dependent fluid transport in vivo. Conclusions: Canagliflozin reduces fluid transport and albumin uptake in PT cells via effects on mitochondrial function upstream of the AMPK/mTOR axis. Sglt2i-mediated reductions in Na+-dependent fluid transport in the PT are secondary to reduced mitochondrial function and are not NHE3-specific. ASN Pre-doctoral fellowship Award, National Institutes of Health: R01 DK118726, R01 DK125049, S10 OD021627, Dialysis Clinic Inc. This is the full abstract presented at the American Physiology Summit 2024 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.

GCLM Expression Drives Macrophage Efferocytosis

Atherosclerosis, a chronic inflammatory disease characterized by the accumulation of lipids, apoptotic cells (ACs), and fibrous elements within the arterial wall, can lead to plaque rupture, one of the most common causes of death in cardiovascular disease (CVD). Rupture prone plaques, characterized by large necrotic cores and thin fibrous caps, lead to acute luminal thrombosis resulting in myocardial infarctions (MI) and strokes. AC accumulation coupled with deficiency in their clearance, results in necrotic core formation. Macrophages are responsible for clearing ACs through efferocytosis; however, as atherosclerosis progresses efferocytosis is impaired. AC accumulation leads to chronic inflammation driven by reactive oxygen species production that disrupts cellular redox balance. Glutathione (GSH), the main antioxidant in the body, maintains redox balance; however, it fails to do so in atherosclerosis. Reports have shown a single nucleotide polymorphism (SNP) in the promoter region of the modifier subunit of GCL (GCLM), a rate limiting enzyme responsible for de novo synthesis of GSH, limits its transcription under oxidative stress and is associated with increased risk of MI. Moreover, deletion of GCLM shows an increase in atherosclerotic plaque area and necrotic core, however it remains unknown how GCLM contributes to necrotic core formation and increased CVD incidence. Methods: Bone marrow derived macrophages from WT, Het, and KO GCLM mutant mice and peripheral blood mononuclear cells (PBMCs) from blood donors were isolated and used for efferocytosis and protein assays. PBMCs and atherosclerosis plaque sections were used for SNP genotyping and in situ efferocytosis assays. Results: Efferocytosis impairment correlated with decreased GCLM expression in mice. The presence of a SNP in GCLM significantly decreases efferocytosis in vitro as well as in situ in stage 5 human plaques. Conclusion: These results suggest that loss of GCLM in macrophages impairs primary and secondary efferocytosis in mice. This is corroborated with the inhibition of GSH synthesis. We also observed an impairment in efferocytosis in human macrophages with the presence of the risk allele in GCLM. Malcolm Feist Pre-doctoral Fellowship, Center of Cardiovascular Diseases and Sciences. This is the full abstract presented at the American Physiology Summit 2024 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.

Plasma Branched-Chain Fatty Acids Reflect Dairy-Fat Intake in a Pilot Clinical Trial in Individuals with Prediabetes

Epidemiological studies often rely on fatty acid (FA) biomarkers of dairy-fat intake to represent diet history and to establish associations with cardiometabolic risk factors. However, a more robust body of direct research is needed to validate the currently utilized FA biomarkers as accurate representations of dairy-fat intake. Thus, our objectives were to i) compare the plasma FA profile of individuals with prediabetes following the consumption of a diet with full-fat (3.25%) yogurt (FFY diet) or non-fat yogurt (NFY diet) to evaluate their validity of currently utilized biomarkers and ii) identify additional FAs to serve as potential biomarkers. We hypothesized that the proportion of the unique dairy-derived FAs including odd-chain FAs (13:0, 15:0, 17:0, 19:0, 21:0, 23:0), branched-chain FAs ( iso-13:0, anteiso-13:0, iso-14:0, iso-15:0, anteiso-15:0, iso-16:0, iso-17:0, anteiso-17:0, iso-18:0), and the trans-FAs 16:1 trans-9 and 18:1 trans-11 would increase in plasma total lipids following the consumption of three daily servings of full-fat yogurt for three weeks. Our 8-week randomized, double-masked, controlled crossover study included six men and seven women aged 45-75 years old. Each experimental diet period, NFY diet and FFY diet, was three weeks in length. The arithmetic difference in fat (8% energy) between the NFY diet (30% fat) and the FFY diet (38% fat) was solely due to the dairy fat in the full-fat yogurt. Following each experimental diet period, fasting plasma samples were taken and analyzed for FA composition of plasma total lipids using gas-liquid chromatography. Consumption of the FFY diet resulted in no change in the proportion of total odd-chain FAs or the individual FAs 16:1 trans-9 and 18:1 trans-11, but the proportion of total branched-chain FAs was greater in response to the FFY diet ( P < 0.01). For individual odd-chain and branched-chain FAs, the proportions of iso-17:0 and anteiso-17:0 were greater in response to the FFY diet ( P < 0.01 for both); however, there were no differences in anteiso-15:0 or iso-15:0 proportions by diet. Results from this pilot trial suggest that commonly utilized FA biomarkers may not be suffciently robust to represent dairy-fat intake. Branched-chain FAs should be further explored for alternatives. Funding for this project was provided by National Dairy Council Nutrition Research Funding, a USDA Agriculture and Food Research Initiative National Institute of Food and Agriculture Predoctoral Fellowship, and a fellowship from the University of Vermont’s Food Systems Research Center. This is the full abstract presented at the American Physiology Summit 2024 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.

Ischemic Conditioning Reduces Neuromuscular Fatigability During Dynamic Exercise Post Stroke

INTRODUCTION: In addition to baseline muscle weakness, stroke survivors often demonstrate increased neuromuscular fatigability (an acute exercise-induced reduction in power, hereafter referred to as fatigability), which limits endurance during functional tasks. Ischemic conditioning (IC) is a non-invasive and easy-to-administer intervention that can reduce fatigability in stroke survivors during a sustained isometric contraction of their paretic knee extensors. However, IC’s effects on fatigability during dynamic contractions are unknown, despite the greater relevance to everyday activities. Additionally, fatigability is known to be task specific. Thus, the purpose of this study was to quantify the effects of IC on fatigability (percent reduction in power) during dynamic contractions of the paretic knee extensors in stroke survivors. We hypothesized that fatigability would be less after a single session of IC versus IC-sham treatment in stroke survivors. Methods: Eight stroke survivors (66 ± 6 years of age, 6 male) performed 60 maximal voluntary concentric contractions (1 every 4 seconds) with their paretic knee extensors against a resistance of 30% of their maximal voluntary isometric contraction torque through a 60-degree range of motion after receiving a single session of IC and IC-sham treatment on two separate days. IC consisted of 5 sets of 5-minute upper thigh blood flow occlusion at 225 mmHg (25 mmHg for IC-sham) with 5 minutes of no occlusion between each set. The order of the 2 sessions was randomized. All participants visited the laboratory on a different day for functional measurements (Fugl-Meyer Assessment, 10-meter walk test, and 6-minute walk test). Reduction in power was calculated as the difference between the highest average power output from 5 consecutive contractions within the first 15 contractions and the average power output from the last 5 contractions. A paired t-test was used to compare if fatigability during dynamic exercise would differ between the 2 sessions after IC and IC-sham treatment. Pearson correlation was performed to determine the relationship between the difference in fatigability (after IC versus IC-sham treatment) and functional measurements. Results: After a single session of IC treatment, stroke survivors were less fatigable compared to IC-sham treatment (21.9 ± 19.2% power reduction vs. 29.4 ± 19.0%, p = 0.016). Improvement in fatigability after IC versus IC-sham treatment was positively correlated with Fugl-Meyer Assessment lower extremity motor score ( r = 0.82, p = 0.013). CONCLUSION: These preliminary results indicate that IC could serve as a potential intervention to reduce fatigability during dynamic exercise in stroke survivors, especially those who are mildly affected by stroke. Funding Source: American Heart Association Predoctoral Fellowship (903373, ZZ) and Eunice Kennedy Shriver National Institute of Child Health and Human Development R01 Grant (HD099340, AH & MD). This is the full abstract presented at the American Physiology Summit 2024 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.