Grant R01 Research Articles

Climbing the Research Ladder: A 25-year Analysis of K-to-R Grant Conversion among Plastic Surgeons.

We evaluate the performance of plastic surgeons in converting National Institutes of Health K grants in early career to R grants intended for established investigators. We also investigate characteristics that may positively predict successful transition from K to R grants. K08, K23, and R01 (or equivalent) grants awarded to plastic surgeons and physicians within the departments of ophthalmology, dermatology, and neurosurgery were collected. Analyses of successful conversion rates from a K to an R grant between plastic surgeons and physicians within the selected departments were performed. Cross-sectional analysis of characteristics among identified plastic surgeons was completed via logistic regression to elucidate possible predictors of successful conversion. Comparison of pathway initiation rates demonstrate that plastic surgeons receive significantly fewer K grants relative to the size of their field when compared with other specialties (all P < 0.01). Of the analyzed plastic surgeons, 52.9% successfully converted to an R-series grant within 5.4 years of beginning their K-series grant. Conversion rates were not significantly different between plastic surgeons and physicians within the selected departments. Logistic regression analyses revealed that the time-adjusted mean relative citation ratio of K series-associated publications is a positive predictor of successful conversion (P = 0.047). With regard to increasing National Institutes of Health funding via the K-to-R pathway, we believe the field of plastic surgery could benefit from an increased effort to pursue a pathway of K-to-R conversion with a focus on quality over quantity when publishing articles associated with a K-series grant.

Postprandial metabolomics analysis reveals disordered serotonin metabolism in post-bariatric hypoglycemia.

Bariatric surgery is a potent therapeutic approach for obesity and type 2 diabetes but can be complicated by post-bariatric hypoglycemia (PBH). PBH typically occurs 1 to 3 hours after meals, in association with exaggerated postprandial levels of incretins and insulin. To identify mediators of disordered metabolism in PBH, we analyzed plasma metabolome in fasting state and 30 and 120 minutes after mixed meal in 3 groups: PBH (n = 13), asymptomatic post-RYGB (n = 10), and non-surgical controls (n = 8). In the fasting state, multiple tricarboxylic acid cycle intermediates and the ketone beta-hydroxybutyrate were increased by 30% to 80% in PBH vs. asymptomatic. Conversely, multiple amino acids (BCAA, tryptophan) and polyunsaturated lipids were reduced by 20% to 50% in PBH versus asymptomatic. Tryptophan-related metabolites, including kynurenate, xanthurenate, and serotonin, were reduced by 2- to 10-fold in PBH in fasting state. Postprandially, plasma serotonin was uniquely increased by 1.9-fold in PBH versus asymptomatic post-RYGB. In mice, serotonin administration lowered glucose and increased plasma insulin and GLP-1. Moreover, serotonin-induced hypoglycemia in mice was blocked by the nonspecific serotonin receptor antagonist cyproheptadine and the specific serotonin receptor 2 antagonist ketanserin. Together these data suggest that increased postprandial serotonin may contribute to the pathophysiology of PBH and provide a potential therapeutic target. NIH grant R01 DK121995, NIH grant P30 DK036836 (Diabetes Research Center grant, Joslin Diabetes Center), and Fundação de Amparo à Pesquisa do Estado de São Paulo-FAPESP grant 2018/22111-2.

Academic and Demographic Profile of Orthopaedic Vice Chairs of Research: Implications for Leadership.

Vice chairs (VCs) of research play an integral role in orthopaedic departments at academic medical centers; they strategically lead research efforts and support the research careers of faculty and trainees. To our knowledge, no analysis of orthopaedic VCs of research exists in the literature, and no similar analyses have been completed in other medical specialties. We aimed to investigate the academic and demographic characteristics of orthopaedic VCs of research. Doximity was used to identify orthopaedic residencies in the U.S. Personal and program websites were queried to identify VCs of research and collect academic and demographic characteristics. The Scopus database, the National Institutes of Health (NIH) RePORTER, and Google Scholar were used to obtain each investigator's Hirsch index (h-index) and the number and type of NIH grants awarded, respectively. Of the 207 orthopaedic residency programs identified, 71 (34%) had a named VC of research in the orthopaedic department. Of the top 50 medical schools, 42 were affiliated with such programs. Most VCs were men (89%). The racial and/or ethnic background of the majority of VCs was White (85%), followed by Asian (14%), and Black (1%). Most held the rank of professor (78%), followed by associate professor (18%), and assistant professor (4%). Over half were PhDs (55%), followed by MDs (37%) and MD/PhDs (8%). On average, the VCs had an h-index of 40.5. Furthermore, 65% had been awarded at least 1 NIH grant for their research, with 43% awarded at least 1 R01 grant. VCs of research develop research opportunities and shape the brand recognition of academic orthopaedic programs. Most orthopaedic VCs of research are men (89%); 85% each are White and have a rank of professor. Nearly half have been awarded at least 1 R01 grant from the NIH. This study outlines important academic and demographic characteristics among orthopaedic surgery VCs of research. Considering the mentorship aspect of their role, VCs of research have an opportunity to influence the diversity of incoming trainees in the field of academic orthopaedics.

Targeted inhibition of kisspeptin neurons reverses hyperandrogenemia and abnormal hyperactive LH secretion in a preclinical mouse model of polycystic ovary syndrome.

Do hyperactive kisspeptin neurons contribute to abnormally high LH secretion and downstream hyperandrogenemia in polycystic ovary syndrome (PCOS)-like conditions and can inhibition of kisspeptin neurons rescue such endocrine impairments? Targeted inhibition of endogenous kisspeptin neuron activity in a mouse model of PCOS reduced the abnormally hyperactive LH pulse secretion and hyperandrogenemia to healthy control levels. PCOS is a reproductive disorder characterized by hyperandrogenemia, anovulation, and/or polycystic ovaries, along with a hallmark feature of abnormal LH hyper-pulsatility, but the mechanisms underlying the endocrine impairments remain unclear. A chronic letrozole (LET; aromatase inhibitor) mouse model recapitulates PCOS phenotypes, including polycystic ovaries, anovulation, high testosterone, and hyperactive LH pulses. LET PCOS-like females also have increased hypothalamic kisspeptin neuronal activation which may drive their hyperactive LH secretion and hyperandrogenemia, but this has not been tested. Transgenic KissCRE+/hM4Di female mice or littermates Cre- controls were treated with placebo, or chronic LET (50 µg/day) to induce a PCOS-like phenotype, followed by acute (once) or chronic (2 weeks) clozapine-N-oxide (CNO) exposure to chemogenetically inhibit kisspeptin cells (n = 6 to 10 mice/group). Key endocrine measures, including in vivo LH pulse secretion patterns and circulating testosterone levels, were assessed before and after selective kisspeptin neuron inhibition and compared between PCOS groups and healthy controls. Alterations in body weights were measured and pituitary and ovarian gene expression was determined by qRT-PCR. Acute targeted inhibition of kisspeptin neurons in PCOS mice successfully lowered the abnormally hyperactive LH pulse secretion (P < 0.05). Likewise, chronic selective suppression of kisspeptin neuron activity reversed the previously high LH and testosterone levels (P < 0.05) down to healthy control levels and rescued reproductive gene expression (P < 0. 05). N/A. Ovarian morphology was not assessed in this study. Additionally, mouse models can offer mechanistic insights into neuroendocrine processes in PCOS-like conditions but may not perfectly mirror PCOS in women. These data support the hypothesis that overactive kisspeptin neurons can drive neuroendocrine PCOS-like impairments, and this may occur in PCOS women. Our findings complement recent clinical investigations using NKB receptor antagonists to lower LH in PCOS women and suggest that pharmacological dose-dependent modulation of kisspeptin neuron activity may be a valuable future therapeutic target to clinically treat hyperandrogenism and lower elevated LH in PCOS women. This research was supported by NIH grants R01 HD111650, R01 HD090161, R01 HD100580, P50 HD012303, R01 AG078185, and NIH R24 HD102061, and a pilot project award from the British Society for Neuroendocrinology. There are no competing interests.

Cracking the code: Can bibliometric attributes predict NIH R01 grant funding outcomes in gastrointestinal oncology? Exploring patterns from a five-year analysis.

9051 Background: The allocation of National Institutes of Health (NIH) R01 grants holds paramount importance for principal investigators in the field of scientific research. In this study, we explore the relationship between bibliometric attributes of principal investigators- specifically H-index, citations, publications, and seniority with the amount of NIH grant funding for R01 grants under gastrointestinal oncology from the fiscal years of 2018 to 2022. Understanding these interrelationships is crucial for researchers aiming to enhance their profiles to secure higher funding amounts from the NIH. Methods: The data was retrieved from the NIH RePORTER (Research Portfolio Online Reporting Tools Expenditure) using gastrointestinal oncology-related search terms from 2018-2022. The number of citations, publications, H-index, and seniority were obtained from Scopus. The bibliometric attributes of principal investigators were correlated with NIH grant funding amounts. Multiple regression analysis was employed to quantify the predictive power. Additionally, t-tests were performed to examine the significant differences in grant funding between high and low h-index groups. Results: A total of 1652 principal investigators who were awarded a gastrointestinal oncology related R01 grant were included in this study. The H-index consistently showcases a positive correlation with the amount of grant funding, reaching statistical significance in 2020 (H-index coefficient=1510.49, p value=0.07). Concurrently, t-tests emphasize the importance of H-index, illustrating that PI’s with high H-indexes (H-index &gt;42) secure significantly higher funding (average grant=$423,806, p=0.006 compared to those in the lower H-index group (average grant=$420,306, p=0.004). Conversely, citations showcased mixed results, with 2020 revealing a significant negative correlation (coefficient: -1.63, p= 0.04). Publications displayed a strong positive effect in 2021 (coefficient: 231.68, p value=0.10). Seniority exhibited varying impacts across years, notably a significant negative relationship in 2018 (coefficient: -3013.9, p=0.025). Conclusions: This study illuminates the complex interplay between PI’s bibliometric attributes and NIH grant funding outcomes. Notably, high h-index values consistently correlate with a higher funding amount for NIH grants. Although these insights contribute to a deeper understanding of the factors influencing NIH grants, further analysis should investigate additional variables that may significantly impact NIH grant funding.

Are we bridging the gap? A ten-year probe into NIH grants for early-career and independent investigators in oncology.

9010 Background: Ongoing gender disparities persist within National Institutes of Health (NIH) funding, specifically evident in NIH R01 grants within Oncology. A crucial aspect of addressing this issue involves a comprehensive investigation of discrepancies between early-career and independent principal investigators (PI). Here we present a ten-year analysis of gender distribution of early career vs. independent grants in the NIH under the field of Oncology. Methods: We implemented an R script utilizing NIH rePORTER, tidyverse, and janitor libraries for data retrieval. This script defined fields for retrieval which looped over fiscal years 2012 to 2022. The script executed API requests with criteria that included fiscal years, activity codes, and search terms that are relevant to oncology to extract grants from NIH rePORTER. We defined the early-career grant category to encompass the top 3 most active NIH K and F grants (K01,K08,K23, F31,F32,F33). In contrast, the independent research grant category included the top 3 most active NIH R grants (R01,R21,R35). The gender library was used to predict the gender of each principal investigator (PI) based on their first name. Ggplot and gtsummary packages were employed for data visualization and statistical analysis, automatically selecting appropriate tests based on data type. Results: Over the fiscal years 2012 to 2022, a total of 44,545 active early-career grants were funded by the NIH. Females (n = 24,243: 54.4% [95% CI:53.7%,55.0%]) surpassed their male counterparts (n = 20,302: 45.6% [95% CI:44.9%, 46.3%]) by holding more active early-career research grants. From 2012 to 2022, there was a significant upward trend that was noted in active early-career grants funded to females (1,818 to 2,969, p &lt; 0.01). Similarly, males exhibited a noteworthy increase in these grants when comparing 2012 to 2022 (1,780 to 1,986, p &lt; 0.001). Despite both genders experiencing an uptrend in active early-career NIH grants, females demonstrated a 48.3% increase, while males experienced a more modest 11.5% increase. In comparison, a total of 236,804 active independent research NIH grants were disbursed in the NIH R category from 2012 to 2022. Females (78,439: 33.1% [95% CI:32.7%,33.4%]) had fewer active independent NIH research grants compared to males (158,365: 66.9% [95% CI:66.6%,67.1%]). Males observed a 6.4% increase in independent NIH grants, rising from 14,419 to 15,343, while females exhibited a notable 48% increase, expanding from 6,193 to 9,195, from 2012 to 2022. Conclusions: In the realm of oncology, gender disparities are not evident among early career investigators as there were 53.7% of early career grants funded to females over the decade. Conversely, females accounted for only 33.3% of independent research grants. These observations emphasize the importance for targeted interventions to foster equal opportunities within the field of Oncology.

A Scholarly Dialog on Recent Trends in National Institutes of Health's Funding for the Thyroid Field.

Background: The National Institutes of Health (NIH) is the major funding agency for biomedical research in the United States. To initiate a scholarly dialog about research and career development in the thyroid field, here we reviewed recent trends in NIH funding for this area. We used the Research Portfolio Online Reporting Tool database to estimate the level of NIH extramural support during 2013-2022 (number of active grants/year and $amount/year weighed by the total number of active grants/year and $amount/year), provided by the NIH to the thyroid field. We determined that in 2013, the NIH supported ∼140 grants/year, totaling almost $50 million/year, the majority in the form of R01 grants. Within the thyroid field, support was evenly split between thyroid cancer and thyroid hormone metabolism and action subareas. In the subsequent years (2014-2022), the total number of active grants peaked at 150/year ($55 million) in 2014 but progressively decreased to about 100 active grants/year ($30 million) in 2022. This trend occurred while the NIH budget increased from $29 to $46 billion/year. Globally, the number of thyroid-related publications increased by ∼70% during the study period, and the fractional contribution of several countries remained relatively stable, except for China which increased by ∼600%. Remarkably, the fraction of thyroid-related publications in the United States sponsored by the NIH decreased from 5.5% to 3.1% of the global number. Conclusion: These results constitute a very concerning scenario for research and education in the thyroid field. We appeal to the NIH, the professional societies in endocrinology and thyroidology, and all other relevant stakeholders such as thyroid-related professionals and thyroid patients to engage in further discussions to identify the root causes of this trend and implement an action plan to stabilize and eventually reverse this situation.

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.

Deletion of Kcnj16 altered transcriptomic and metabolomic profiles of Dahl salt-sensitive rats

The essential role of inwardly rectifying K+ Channel Kir5.1 (encoded by the Kcnj16 gene) in renal salt handling and blood pressure control has been demonstrated in both human and animal models. However, the underlying mechanisms are still not fully understood. Here, we aimed to integrate transcriptomics and metabolomics to profile the comprehensive changes of genes and metabolites under the deletion of Kcnj16 in the Dahl salt-sensitive (SS) rat background to identify novel mechanisms. For the transcriptomics profiling, we performed RNA-sequencing on kidney cortex tissue of Kcnj16 knockout (KO) and wild-type (WT) SS rats (N=5 per group). For the metabolomics profiling, we performed untargeted metabolomics of kidney cortex tissue, plasma, and urine of KO (N=6) and WT (N=5) rats. Transcriptomics analysis revealed over 6,000 differentially expressed genes in KO rats compared to WT rats, with renin Ren (the gene encoding renin) being the most upregulated gene. Consistent with the phenotype observed in the KO rats, ingenuity pathway analysis (IPA) based on the transcriptomic profile predicted reduced blood pressure and kidney damage and increased ion transport. Canonical pathway analysis suggested activation of metabolic-related pathways [e.g., xenobiotic metabolism, tricarboxylic acid (TCA) cycle, phenylalanine degradation, etc.] and suppression of immune responses-related pathways [e.g., pathogen-induced cytokine storm signaling pathway, macrophage classical activation signaling pathway, nuclear factor of activated T cells (NFAT) pathway, etc.] in KO rats. Untargeted metabolomic analysis suggested distinct metabolic profiles of plasma, urine, and kidneys between WT and KO rats, with 219, 790, and 31 differentially expressed metabolites identified in plasma, urine, and kidney in KO rats compared to WT rats. Canonical pathway analysis identified spermine and spermidine degradation pathways in both plasma and urine and taurine biosynthesis pathways in both urine and kidney. Integration analysis based on transcriptomic and metabolomic profiles suggested an altered TCA cycle, amino acid, and reactive oxygen species metabolism. In conclusion, besides significantly altered ion transport, our transcriptomics and metabolomics data suggest significant suppressed immune responses-related and altered metabolic-related pathways in SS rats lacking Kir5.1, which provides new insights into the underlying mechanisms of the regulation of blood pressure and renal function by Kir5.1. This work is supported by National Institutes of Health Grants R35 HL135749 and R01 DK135644 (to A.S.), Department of Veteran Affairs grant I01 BX004024 (to A.S.), the American Physiological Society Postdoctoral Fellowship (to B.X.) and the American Society of Nephrology Dimitrios G. Oreopoulos Research Fellowship Award (to L.V.D.). 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.

Role for clock protein PER1 in cardiac adaption to salt-sensitive hypertension in male rats

The clock protein PERIOD1 (PER1) is known to regulate the transcription of many genes, impacting subsequent physiological responses and working with other proteins to establish rhythmicity in processes such as blood pressure regulation. Global PER1 knock-out (KO) in male rats is associated with increased severity of the salt-sensitive (SS) hypertensive phenotype in Dahl SS rats. Male PER1 KO SS rats demonstrated reduced amplitude of heart rate as well as altered renal electrolyte and fluid balance with accompanying changes in the expression of relevant genes in the kidney. However, little is known regarding changes in gene expression in cardiac tissue which may contribute to this phenotype. The goal of this study was to test the hypothesis that knockout of PER1 in SS rats results in altered gene expression in the heart. We selected the following genes due to their role in the clock protein complex and circadian control over blood pressure: Basic Helix-Loop-Helix ARNT Like 1 ( Bmal1), Cryptochrome 1 and 2 ( Cry1, Cry2), and Period 2 ( Per2). Given its role in compensatory natriuretic responses to pressure overload, we also assessed the gene Nppa which encodes atrial natriuretic peptide (ANP). In order to test this hypothesis, hearts were collected at 2 am (during the rat active period) from male Dahl SS control and PER1 KO rats following 3 weeks of high salt (4% NaCl) diet (n=5-6). Changes in expression of candidate genes were measured using quantitative real time RT-PCR. Genotype effects were assessed using unpaired student’s t test. PER1 KO SS male rats on high salt diet exhibited significantly decreased cardiac expression of in the clock genes Bmal1 (p&lt;0.0001), Cry1 (p=0.0007), and Cry2 (p=0.0094). Changes in Per2 expression were not apparent (p=0.1152). In contrast, PER1 KO rats exhibited significantly increased expression of Nppa (p=0.0017). Global PER1 knock-out in male SS rats results in hypertension associated with disrupted rhythms in heart rate. These changes are associated with reduction in expression of the genes encoding regulatory clock proteins Bmal1, Cry1, and Cry2, but not Per2. The decreased circadian gene expression in PER1 KO Dahl SS rats may contribute to the disrupted rhythms in heart rate. Increased ANP gene expression in the hearts of PER1 KO SS rats could serve as a compensatory mechanism to induce natriuresis. Thus, the data support the hypothesis that knockout of PER1 in SS rats alters gene expression in the heart. Together, these data illuminate a possible circadian-regulated pathway through which the heart and kidney communicate to respond to fluid and electrolyte imbalance in salt-sensitive hypertension. This work was supported by the National Institutes of Health grants R35 HL135789 (to AS), R01 DK109570 (to MLG and AS), R56DK128271 (to MLG), and Department of Veteran Affairs grants I01 BX004024 (to AS). 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.

In Vivo Silencing of Intestinal DMT1 Mitigates Iron Loading in β-thalassemia Intermedia (Hbbth3/+) Mice

β-thalassemia is an iron-loading anemia caused by homozygous mutations in the hemoglobin subunit beta gene. In β-thalassemia major, frequent blood transfusions and elevated absorption of dietary iron can lead to iron overload, which exacerbates pathological outcomes. Iron absorption is inappropriately high due to blunted expression of the iron-regulatory hormone hepcidin. Low hepcidin potentiates iron export from duodenal enterocytes by ferroportin (FPN); cellular iron depletion then secondarily increases expression of the iron importer, divalent metal-ion transporter 1 (DMT1). High expression of both transporters drives excessive iron absorption and ultimately, iron overload. In non-transfusion-dependent, β-thalassemia intermedia (βTI), hepcidin suppression and high iron absorption are the sole causes of iron loading. In this investigation, two parallel hypotheses were tested in βTI ( Hbbth3/+) mice: 1) Intestinal DMT1 drives elevated iron absorption and precipitates iron overload; and 2) In vivo silencing of intestinal DMT1 mitigates iron loading. Initial experiments revealed that intestine-specific ablation of DMT1 caused a pathophysiological shift from iron overload to an iron-deficiency phenotype with exacerbated anemia, thus proving that intestinal DMT1 is required for iron absorption in Hbbth3/+ mice. Subsequent studies utilized folic acid-coupled, ginger nanoparticle-derived lipid vectors to deliver functional DMT1 siRNAs to the duodenal epithelium of 4-week-old Hbbth3/+ mice daily for 16 days to assess the impact on iron loading. Knockdown of intestinal DMT1 blunted iron loading in Hbbth3/+ mice, thus supporting hypothesis 2. These notable experimental outcomes establish intestinal DMT1 as a plausible therapeutic target to mitigate iron overload in βTI and possibly other non-transfusion dependent, iron-loading anemias. This work was supported by grants R01 DK074867 from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and R01 DK109717 from NIDDK and the Offce of Dietary Supplements (to JFC). 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.

Enteric and Systemic Postprandial Lactate Shuttle Phases and Dietary Carbohydrate Carbon Flow

We interrogated the hypothesis of a Postprandial Lactate Shuttle (PLS) in young, healthy men and women (n=15). Participants reported to the lab (5:00 AM) following an overnight fast and had the forearm vein catheterized for primed continuous infusions of [6,6-2H]glucose and [3-13C]lactate stable isotope tracers. The contralateral hand vein was warmed and catharized for arterialized blood sampling. After a 90-minute (min) equilibration period participants underwent a 75 g oral glucose tolerance test (OGTT). Arterialized [lactate] rose from baseline (0.60sup&gt;). We estimate carbon flow from the OGTT from the rates of appearance of glucose, lactate and GNG from lactate. At 120-min the 75 g load was accounted for as follows: 29 g as blood lactate, 24 g of glucose from hepatic glucose release, 8 g of glucose from GNG, and 14 g withheld in the liver. Because blood [lactate] and Ra rose before [glucose] and Ra, evidence of an Enteric PLS is provided. Because secondary increments in blood [lactate] and Ra coincided with those of glucose, results are interpreted to indicate presence of a larger, secondary Systemic PLS phase. Antiquated ideas of lactate production due to hypoxia in skeletal muscles need to be supplanted because glycolysis proceeds to lactate in fully aerobic tissues, and because dietary carbohydrate is processed via lactate shuttling. In humans, lactate is a major vehicle for carbohydrate carbon distribution and metabolis. NIH grant R01 AG059715. 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.

Lipolysis and fat oxidation decrease during postprandial lactatemia

Circulating glycerol ([glycerol]) and free fatty acid ([FFA]) concentrations decrease and lactate concentration ([lactate]) increases in response to oral glucose consumption, but the effect of increased [lactate] on the rate of lipolysis is not known. We hypothesized that whole-body lipolytic (i.e., glycerol rate of appearance, Ra) and fat oxidation (FOx) rates would decrease following oral glucose consumption and inversely correlate with an increase in [lactate] above baseline levels (i.e., lactatemia) during both enteric (0–30 min) and systemic (60–120 min) phases of the postprandial lactate shuttle (PLS). Young, healthy men and women (n=15) reported to the lab following a 12-hour overnight fast and had the forearm vein catheterized for primed continuous infusion of [1,1,2,3,3-2H]glycerol. The contralateral hand vein was warmed and catheterized for arterialized blood sampling. After a 90-min equilibration period, participants underwent a 75 g oral glucose tolerance test (OGTT). Glycerol Ra was significantly lower at 5 min (1.92 ± 0.12 μmol·kg−1·min−1) and 30–120 min during the OGTT compared to baseline (2.06 ± 0.12 μmol·kg−1·min−1). [Glycerol] was significantly lower from baseline (69.19 ± 2.50 μM) at 30 min (50.58 ± 3.01 μM) after glucose consumption, then continued to decline thereafter. Similarly, [FFA] was significantly lower from baseline (464.71 ± 27.01 μM) at 30 min (247.14 ± 32.78 μM), then continued to decline. FOx was significantly lower from baseline (0.89 ± 0.05 kcal∙min−1) at 60 min (0.58 ± 0.05 kcal∙min−1) and remained steady from then on. Concurrently, [lactate] increased from baseline (0.59 ± 0.06 mM) and was significantly higher at 5 min (0.71 ± 0.06 mM) after glucose consumption, peaked at 15 min (1.09 ± 0.01 mM), reached a nadir at 30 min, then continued to rise thereafter. There was an overall inverse correlation (r = -0.71, p = 0.07) between glycerol Ra and [lactate] during the OGTT that was also present during the enteric phase (r = -0.45, p = 0.55). Similarly, there was overall an inverse correlation between FOx and [lactate] (r = -0.57, p = 0.17), but it was not present during the enteric phase (r = 0.93, p = 0.07). However, the correlations of both glycerol Ra and FOx with [lactate] approached linearity during the systemic phase (r = 0.99, p = 0.06). The reduction in glycerol Ra at 5 min indicates a rapid decrease in the rate of lipolysis following oral glucose consumption. The correlations suggest that lactatemia may influence both glycerol Ra and FOx by exerting an inhibitory effect, particularly during the systemic phase of the PLS. However, the lag in the decrease in FOx and opposing responses of glycerol Ra and [lactate] at 5 min suggests that lactatemia may have a greater role in inhibiting whole-body lipolysis in the postprandial period. Supported by NIH grant R01 AG059715 to GAB. 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.

Chlorpyrifos-Induced Airway Hyperreactivity in Rats Is Dependent on NK1 Receptor Signaling

Occupational and environmental exposures to organophosphorus pesticides (OP) are associated with increased asthma incidence. While the canonical mechanism of OP neurotoxicity is acetylcholinesterase (AChE) inhibition, we previously demonstrated that the OP chlorpyrifos (CPF) causes airway hyperreactivity (AHR) in adult rats 24 h after exposure at levels that do not significantly inhibit AChE. Here we further investigated the persistence of CPF-induced AHR at 7 days post-exposure and tested the hypothesis that neurogenic inflammation contributes to CPF-induced AHR. Eight-week-old male Sprague Dawley rats were administered 30 mg/kg CPF subcutaneously, and AHR was assessed at 24 h or 7 days post-exposure using a Flexivent mechanical ventilator during electrical stimulation of the vagus nerves. CPF significantly increased airway resistance and elastance at 24 h and 7 days post-exposure. The NK1 antagonist SR140333 was used to evaluate the involvement of substance P and its receptor NK1 in CPF-induced AHR. SR140333 was injected into rats 1 h before mechanical ventilation and vagal stimulation. NK1 receptor inhibition decreased vagally stimulated bronchoconstriction in CPF-exposed male animals to that observed in vehicle controls, at 24 h and 7 days post-CPF exposure. These data suggest that substance P signaling contributes to both acute and persistent CPF-induced AHR. These findings have significant implications for assessing the risk to human health and safety of CPF, and potentially other OPs, and indicate a potential new therapy for mitigating AHR in intoxicated individuals. This work was supported by the NIH (grants R01 ES017592 and T32 HL07013). 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.

Critical Environmental Limits for Middle-Aged Adults (PSU HEAT Project)

Critical environmental limits are the combinations of temperature and humidity above which heat balance cannot be maintained for a given metabolic heat production. Our lab has previously established critical environmental limits for young and older adults; however, these limits have yet to be established for middle-aged adults. The purpose of the present study was to (1) identify critical environmental limits for middle-aged adults, and (2) investigate age-related differences in critical environmental limits at a low metabolic rate reflecting activities of daily living across the adult age spectrum. Twenty-six older (71±5 yrs, 14F/12M), 36 middle aged (51±9 yrs, 26F/10M), and 27 young adults (23±3 yrs, 13F/14M) were exposed to progressive heat stress in a controlled environmental chamber during minimal activity. Progressive heat stress for the determination of critical environmental limits comprised either (1) constant dry-bulb (Tdb) temperature at 34°C with progressively increasing water vapor pressure (Pa) by 1 mmHg every 5 minutes (Pcrit trial), or (2) constant Pa at 12 mmHg with progressively increasing Tdb by 1°C every 5 minutes (Tcrit trial). Critical environmental limits in hot-dry environments were higher in young compared to middle aged (49.3±2.3 °C vs. 45.4±4.0 °C; p = 0.002) and older adults (49.3±2.3°C vs. 43.2±4.0°C; p &lt; 0.001), but were not different between middle aged and older adults (45.4±4.0 °C vs. 43.2±4.0°C; p = 0.125). Critical environmental limits in warm-humid conditions were lower in older adults compared to young (23.1±6.1 mmHg vs 31.7±1.5 mmHg, p &lt; 0.001) and middle aged (23.1±6.1 mmHg vs 29.0±5.1 mmHg, p = 0.004), but were not different between the young and middle aged (31.7±1.5 mmHg vs 29.0±5.1 mmHg, p = 0.220). Age was correlated with critical environmental limits in Tcrit (R2 = 0.34; p &lt; 0.001) and Pcrit (R2 = 0.51; p &lt; 0.001) trials based on linear and curvilinear regression, respectively. Critical environmental limits for middle aged adults performing minimal activity in warm-humid and hot-dry environments are intermediate to young and older adults. These data demonstrate an age-related decline in critical environmental limits that can be characterized by linear decline in hot-dry environments and by curvilinear decline in warm-humid environments. Supported by NIH Grant R01 AG067471. 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.

Age-Related Differences in the Onset of Cardiovascular Drift during Progressive Heat Stress (PSU HEAT Project)

As a result of the increasing duration, frequency, and severity of heat waves, older men and women are at greater risk for heat-related morbidity and mortality, with the majority of excess heat-related deaths attributed to increased cardiovascular strain associated with heat stress. PURPOSE: To (1) identify the environmental conditions (ambient temperature (Tdb) and humidity (rh)) at which heart rate (HR) begins to increase from equilibrium (i.e., the onset of cardiovascular drift), and (2) compare the environments in which cardiovascular drift begins relative to those at which a continuous rise in core temperature (Tc) is observed in young (Y), middle (MA), and older (O) adults. Methods: 26 Y (10 F; 19-29 yrs), 27 MA (21F; 40-64 yrs), and 19 O (7 F; 65-76 yrs) subjects were exposed to progressive heat stress in an environmental chamber at a low metabolic rate reflecting activities of daily living (159 ± 34 W) in a warm-humid (WH, 34-36°C, 50-80% rh) and a hot-dry (HD, 38°C-52°C, &lt;30% rh) environment. The environmental thresholds above which HR and Tc equilibrium could no longer be maintained were identified. Results: In WH environments, sustained increases in HR preceded the Tc inflection point in Y (73±5% rh vs. 81±5% rh; p&lt;0.001), MA (67±11% rh vs. 73±12% rh; p&lt;0.001), and O adults (53±11% rh vs. 57±12% rh; p=0.041). Similarly, in HD (15-20% rh) environments, the onset of cardiovascular drift preceded the Tc inflection point in Y (47±3°C vs. 49±3°C; p=0.004), MA (44±4°C vs. 46±4°C; p&lt;0.001), and O adults (42±5°C vs. 44±4°C; p=0.007). Additionally, in WH environments, cardiovascular drift began at lower combinations of Tdb and rh in O vs. Y subjects (34°C, 53±11% rh vs. 34°C, 73±5% rh; p&lt;0.001) and O vs. MA adults (34°C, 53±11% rh vs. 34°C, 67±11% rh; p=0.008). In HD environments, cardiovascular drift began at lower environments in MA vs. Y (44±4°C, 18% rh vs. 47±3°C, 15% rh; p=0.044) and O vs. Y (42±5°C, 20% rh vs. 47±3°C, 15% rh; p=0.006) CONCLUSION: These data suggest that cardiovascular drift, indicating increases in cardiovascular strain, occurs during compensable heat stress at metabolic rates reflecting activities of daily living in Y, MA, and O adults. Further, there is an age-associated shift in the onset of cardiovascular drift toward lower combinations of Tdb and rh. SIGNIFICANCE/NOVELTY: These results are the first to identify the specific environmental conditions at which increases in cardiovascular strain occur across the adult age spectrum. These findings provide concrete data for the development of safety guidelines and policy decisions to mitigate cardiovascular-related morbidity and mortality during impending heat events. Supported by NIA Grant T32 AG049676 (to R.M.C.) and NIH Grant R01 AG067471 (to W.L.K.). 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.

Chloroquine Affects Frequency-Dependent Endocytosis in Diaphragm Muscle of Old Mice

Chloroquine is an antimalarial agent commonly used as an autophagy inhibitor by preventing autolysosomal fusion. Autophagy is an important cellular process through which defective cytoplasmic structures are recycled and degraded that has been implicated in aging neuromuscular effects. We recently showed that acute chloroquine treatment blunts the maximal forces generated by the diaphragm muscle, likely by impairing neuromuscular transmission generally consistent with aging effects in the diaphragm muscle. In addition, old mice show increased accumulation of autophagy proteins in phrenic motor neurons, consistent with impaired autophagy flux. In the present study, we hypothesized that chloroquine treatment results in accumulation of bulk endosomes pre-synaptically. Each hemidiaphragm with attached phrenic nerve was excised from 24-month-old male and female C57BL/6 mice to evaluate frequency dependent (0 vs 80 Hz stimulation) uptake of the styryl dye FM4-64, given that 80-Hz stimulation frequency induces bulk endocytosis after synaptic vesicle retrieval. Diaphragm-phrenic nerve preparations were incubated in 5 μM FM4-64 for 1 h prior to 6-min nerve stimulation (0.5 ms supramaximal pulses in 80 Hz, 200 ms trains delivered at 40% duty cycle) followed by a 5-min post-stimulation incubation. FM4-64 uptake at diaphragm neuromuscular junctions (NMJs) was measured using confocal microscopy. Preparations were randomly assigned to co-incubation with chloroquine (50 μM) or vehicle (Rees-Simpson solution). There was minimal FM4-64 uptake in the absence of phrenic nerve stimulation, consistent with the activity-dependent uptake of the styryl dye. With 80 Hz stimulation, high levels of FM4-64 uptake were evident in both the chloroquine and vehicle-treated groups without significant differences across groups. FM4-64 fluorescence was evident throughout the presynpatic terminal with few areas of dense accumulation, consistent with retention of endosomes. There was no evidence of greater endosome accumulation with chloroquine treatment. Of note, a slight increase in FM4-64 uptake was evident in the chloroquine treated groups compared to vehicle in the non-stimulated NMJs. These results are consistent with FM4-64 uptake reflecting bulk endocytosis that mainly occurs during high frequency stimulation. The impairment in autophagy flux following chloroquine treatment is expected to result in endosome accumulation but it is possible that the stimulation protocol was insuffcient to elucidate this possibility. Collectively, the findings of this study are consistent with impaired autophagy at diaphragm presynaptic terminals which may underlie neuromuscular deficits observed in old age. Supported by NIH grant R01 AG057052 and the Mayo Clinic. 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.

Novel Use of 1-methylhistamine as a Biomarker of the Histamine Response to Exercise

Histamine is released within skeletal muscle during exercise, promoting a sustained post-exercise vasodilation and contributing to adaptive responses to exercise training. Tracking this response is complicated by the short half-life and localization of histamine, requiring invasive methods such as intramuscular microdialysis or arteriovenous catheterization. Surrogates based on regional blood flow to assess post-exercise vasodilation require skilled use of expensive equipment, such as ultrasonography. These approaches may not be available in many research or athletic settings. Therefore, we explored the use of 1-methylhistamine (1-MH), a primary metabolite of histamine, as a novel biomarker of histamine’s release in response to aerobic and resistance exercise. We hypothesized that urinary 1-MH production would increase following exercise and that it would be positively correlated with post-exercise femoral artery blood flow and vascular conductance. Six healthy (1F, 5M; 22±4y; 24.3±1.9 kg·m2) trained participants (VO2peak: 51.8±7.7 ml·kg−1·min−1; back squat 1-repetition maximum, 1-RM: 1.66±0.27 kg·bodyweight−1) completed two exercise sessions separated by 1-wk: Aerobic, 30-min of cycling exercise at 70% VO2peak; Resistance, 6 sets of 10 repetitions of back squat exercise at 70% 1-RM. Femoral artery blood flow and vascular conductance were measured and venous blood samples were obtained before, immediately after, and throughout 2-h of post-exercise recovery. Urine was collected during the 24-h before and 2-, and 24-h post-exercise. Histamine and 1-MH concentrations were measured via high-performance liquid chromatography. Results are presented as mean ± SD and were compared by repeated-measures ANOVA and Pearson’s correlations. Blood flow increased immediately after exercise vs before (Aerobic: 442±60 vs 184±58 mL·min−1, p&lt;0.05; Resistance: 626±190 vs 194±54 mL·min−1, p&lt;0.05) and remained elevated 30-min into recovery (Aerobic: 273±63, p&lt;0.05; Resistance: 396±99 mL·min−1, p&lt;0.05). The area under the curve for blood flow after exercise tended to be greater following resistance (16117±5504 mL) vs aerobic (8732±5360 mL, p=0.06) exercise. When averaged across exercise modes, urine 1-MH production was elevated 2-h post-exercise vs before (23.6±15.9 vs 9.2±5.9 μg/h, p&lt;0.05). Urine 1-MH production tended to correlate with percent elevation in femoral artery blood flow (r=0.59, p=0.09) and correlated with the percent elevation in vascular conductance following exercise (r=0.53, p&lt;0.05). These results demonstrate that both aerobic and resistance exercise elicit a histamine response and support the utility of urinary 1-MH production as a biomarker of histamine’s release in response to exercise. Supported by NIH grant R01 AG072805. 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.

Hyperglycemia Induces Remodeling of Nitric Oxide Synthase Activity in Glomerular Podocytes

Background: The regulation of glomerular filtration is influenced by the renin-angiotensin system (RAS) and the release of nitric oxide (NO) by glomerular cells. Several studies suggest that NO levels in glomeruli decrease as renal pathology develops, and restoring NO levels can be beneficial for glomerular function. Despite these findings, the expression of nitric oxide synthase (NOS) subunits in podocytes, particularly under pathological conditions, still requires further investigation. We hypothesized that decreased NO bioavailability in diabetes and hyperglycemia is linked to pathological NOS remodeling, thus influencing redox balance in podocytes and promoting renal damage. Methods: Live-cell confocal imaging was used to investigate NO production and the distribution of NOS in both control and hyperglycemic conditions. First, we used immortalized human podocytes (obtained from M. Saleem lab) loaded with the DAF-FM fluorescent marker in control and hyperglycemic (exposed to high glucose for 12 hours) conditions. Next, freshly isolated glomeruli from Type 2 Diabetic Nephropathy (T2DN) and Wistar male rats (age 26-30 weeks) were used to confirm our data ex vivo. NO production was monitored following Angiotensin II (Ang II) stimulation, and the distribution of NOS was determined using specific NOS1 and NOS2 commercially available inhibitors (Nω-Propyl-L-arginine hydrochloride and L-NIL, respectively). One-way ANOVA (OriginPro) was used for statistical analysis. Results: Upon application of Ang II, rapid NO production was observed in cultured and Wistar rats isolated glomeruli podocytes. The release of NO was blocked by preincubation with corresponding inhibitors targeting NOS. Our findings reveal that NOS1 primarily contributes to signaling in healthy podocytes, accounting for 69±5% of the total NO response, while the remaining NO production mediated by the RAS is attributed to NOS2 (39±5%). In diabetic conditions, the maximal amplitude of NO production mediated by Ang II was decreased by 22±10% compared to the control (one-way ANOVA, n≥24, p&lt;0.001). Furthermore, high glucose conditions significantly altered NOS distribution in podocytes, where NOS2 signaling became predominant (89±7% of the total NO response), and the contribution of NOS1 became less significant. Conclusions: The changes in the distribution of NO sources could be associated with heightened oxidative and nitrosative stress, promoting renal damage. Our research demonstrates that in diabetes, NOS2 activity becomes predominant, potentially playing a direct role in advancing pathological processes in podocytes. Revealing the mechanisms of this fundamental pathway in the glomerulus impacts our progress toward new treatment and preventive measures for diabetic kidney disease development. This research was supported by National Institutes of Health Grants R01 DK126720 (to OP), R01 DK129227 (to AS and OP), and R01 DK115749 (to KS), US Department of Veteran Affairs grants I01CX002391 (to JHL), I01CX001248 (JCO) and I01 BX004024 (to AS). 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.