Browsing by Author "Lim, Kenneth"

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    A Randomized Control Trial of Ravulizumab for Treatment of Patients With COVID-19 Infection and Kidney Injury
    (Elsevier, 2022) Memon, Aliza A.; Ahmed, Hasban; Li, Yi; Wongboonsin, Janewit; Hundert, Joshua; Benoit, Stefanie; Chaudhari, Advika; Sher, Jawad; Ghimire, Pratima; Hopkins, Rebecca; Patel, Jay; Stegman, Melinda; Lim, Kenneth; Azzi, Jamil; Siedlecki, Andrew M.; Medicine, School of Medicine
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    Cardiovascular Functional Changes in Chronic Kidney Disease: Integrative Physiology, Pathophysiology and Applications of Cardiopulmonary Exercise Testing
    (Frontiers, 2020-09-15) Lim, Kenneth; McGregor, Gordon; Coggan, Andrew R.; Lewis, Gregory D.; Moe, Sharon M.; Medicine, School of Medicine
    The development of cardiovascular disease during renal impairment involves striking multi-tiered, multi-dimensional complex alterations encompassing the entire oxygen transport system. Complex interactions between target organ systems involving alterations of the heart, vascular, musculoskeletal and respiratory systems occur in Chronic Kidney Disease (CKD) and collectively contribute to impairment of cardiovascular function. These systemic changes have challenged our diagnostic and therapeutic efforts, particularly given that imaging cardiac structure at rest, rather than ascertainment under the stress of exercise, may not accurately reflect the risk of premature death in CKD. The multi-systemic nature of cardiovascular disease in CKD patients provides strong rationale for an integrated approach to the assessment of cardiovascular alterations in this population. State-of-the-art cardiopulmonary exercise testing (CPET) is a powerful, dynamic technology that enables the global assessment of cardiovascular functional alterations and reflects the integrative exercise response and complex machinery that form the oxygen transport system. CPET provides a wealth of data from a single assessment with mechanistic, physiological and prognostic utility. It is an underutilized technology in the care of patients with kidney disease with the potential to help advance the field of cardio-nephrology. This article reviews the integrative physiology and pathophysiology of cardio-renal impairment, critical new insights derived from CPET technology, and contemporary evidence for potential applications of CPET technology in patients with kidney disease.
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    Effect of kidney donation on bone mineral metabolism
    (Public Library of Science, 2020-07-07) Hiemstra, Thomas F.; Smith, Jane C.; Lim, Kenneth; Xu, Dihua; Kulkarni, Shreya; Bradley, J. Andrew; Paapstel, Kaido; Schoenmakers, Inez; Bradley, John R.; Tomlinson, Laurie; McEniery, Carmel M.; Wilkinson, Ian B.; Medicine, School of Medicine
    Kidney donation results in reductions in kidney function and lasting perturbations in phosphate homeostasis, which may lead to adverse cardiovascular sequelae. However, the acute effects of kidney donation on bone mineral parameters including regulators of calcium and phosphate metabolism are unknown. We conducted a prospective observational controlled study to determine the acute effects of kidney donation on mineral metabolism and skeletal health. Biochemical endpoints were determined before and after donation on days 1, 2 and 3, 6 weeks and 12 months in donors and at baseline, 6 weeks and 12 months in controls. Baseline characteristic of donors (n = 34) and controls (n = 34) were similar: age (53±10 vs 50±14 years, p = 0.33), BMI (26.3±2.89 vs 25.9±3.65, p = 0.59), systolic BP (128±13 vs 130±6 mmHg, p = 0.59), diastolic BP (80±9 vs 81±9 mmHg, p = 0.68) and baseline GFR (84.4±20.2 vs 83.6±25.2 ml/min/1.73m2, p = 0.89). eGFR reduced from 84.4±20.2 to 52.3±17.5 ml/min/1.73m2 (p<0.001) by day 1 with incomplete recovery by 12 months (67.7±22.6; p = 0.002). Phosphate increased by day 1 (1.1(0.9–1.2) to 1.3(1.1–1.4) mmol/L, p <0.001) but declined to 0.8(0.8–1.0) mmol/L (p<0.001) before normalizing by 6 weeks. Calcium declined on day 1 (p = 0.003) but recovered at 6 weeks or 12 months. PTH and FGF-23 remained unchanged, but α-Klotho reduced by day 1 (p = 0.001) and remained low at 6 weeks (p = 0.02) and 1 year (p = 0.04). In this study, we conclude that kidney donation results in acute disturbances in mineral metabolism characterised by a reduced phosphate and circulating α-Klotho concentration without acute changes in the phosphaturic hormones FGF23 and PTH.
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    Epimeric vitamin D and cardiovascular structure and function in advanced CKD and after kidney transplantation
    (Oxford University Press, 2024) Arroyo, Eliott; Leber, Cecilia A.; Burney, Heather N.; Li, Yang; Li, Xiaochun; Lu, Tzong-shi; Jones, Glenville; Kaufmann, Martin; Ting, Stephen M. S.; Hiemstra, Thomas F.; Zehnder, Daniel; Lim, Kenneth; Medicine, School of Medicine
    Background: 25-hydroxyvitamin D can undergo C-3 epimerization to produce 3-epi-25(OH)D3. 3-epi-25(OH)D3 levels decline in chronic kidney disease (CKD), but its role in regulating the cardiovascular system is unknown. Herein, we examined the relationship between 3-epi-25(OH)D3, and cardiovascular functional and structural endpoints in patients with CKD. Methods: We examined n = 165 patients with advanced CKD from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) study cohort, including those who underwent kidney transplant (KTR, n = 76) and waitlisted patients who did not (NTWC, n = 89). All patients underwent cardiopulmonary exercise testing and echocardiography at baseline, 2 months and 12 months. Serum 3-epi-25(OH)D3 was analyzed by liquid chromatography-tandem mass spectrometry. Results: Patients were stratified into quartiles of baseline 3-epi-25(OH)D3 (Q1: <0.4 ng/mL, n = 51; Q2: 0.4 ng/mL, n = 26; Q3: 0.5-0.7 ng/mL, n = 47; Q4: ≥0.8 ng/mL, n = 41). Patients in Q1 exhibited lower peak oxygen uptake [VO2Peak = 18.4 (16.2-20.8) mL/min/kg] compared with Q4 [20.8 (18.6-23.2) mL/min/kg; P = .009]. Linear mixed regression model showed that 3-epi-25(OH)D3 levels increased in KTR [from 0.47 (0.30) ng/mL to 0.90 (0.45) ng/mL] and declined in NTWC [from 0.61 (0.32) ng/mL to 0.45 (0.29) ng/mL; P < .001]. Serum 3-epi-25(OH)D3 was associated with VO2Peak longitudinally in both groups [KTR: β (standard error) = 2.53 (0.56), P < .001; NTWC: 2.73 (0.70), P < .001], but was not with left ventricular mass or arterial stiffness. Non-epimeric 25(OH)D3, 24,25(OH)2D3 and the 25(OH)D3:24,25(OH)2D3 ratio were not associated with any cardiovascular outcome (all P > .05). Conclusions: Changes in 3-epi-25(OH)D3 levels may regulate cardiovascular functional capacity in patients with advanced CKD.
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    FGF23 and Cardiovascular Structure and Function in Advanced Chronic Kidney Disease
    (Wolters Kluwer, 2022-07-05) Halim, Arvin; Burney, Heather N.; Li, Xiaochun; Li, Yang; Tomkins, Claudia; Siedlecki, Andrew M.; Lu, Tzong-shi; Kalim, Sahir; Thadhani, Ravi; Moe, Sharon; Ting, Stephen M.S.; Zehnder, Daniel; Hiemstra, Thomas F.; Lim, Kenneth; Medicine, School of Medicine
    Background: Fibroblast growth factor 23 (FGF23) is a bone-derived phosphatonin that is elevated in chronic kidney disease (CKD) and has been implicated in the development of cardiovascular disease. It is unknown whether elevated FGF23 in CKD is associated with impaired cardiovascular functional capacity, as assessed by maximum exercise oxygen consumption (VO2Max). We sought to determine whether FGF23 is associated with cardiovascular functional capacity in patients with advanced CKD and after improvement of VO2Max by kidney transplantation. Methods: We performed secondary analysis of 235 patients from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) cohort, which recruited patients with stage 5 CKD who underwent kidney transplantation or were waitlisted and hypertensive controls. All patients underwent cardiopulmonary exercise testing (CPET) and echocardiography and were followed longitudinally for 1 year after study enrollment. Results: Patients across FGF23 quartiles differed in BMI (P=0.004) and mean arterial pressure (P<0.001) but did not significantly differ in sex (P=0.5) or age (P=0.08) compared with patients with lower levels of FGF23. Patients with higher FGF23 levels had impaired VO2Max (Q1: 24.2±4.8 ml/min per kilogram; Q4: 18.6±5.2 ml/min per kilogram; P<0.001), greater left ventricular mass index (LVMI; P<0.001), reduced HR at peak exercise (P<0.001), and maximal workload (P<0.001). Kidney transplantation conferred a significant decline in FGF23 at 2 months (P<0.001) before improvement in VO2Max at 1 year (P=0.008). Multivariable regression modeling revealed that changes in FGF23 was significantly associated with VO2Max in advanced CKD (P<0.001) and after improvement after kidney transplantation (P=0.006). FGF23 was associated with LVMI before kidney transplantation (P=0.003), however this association was lost after adjustment for dialysis status (P=0.4). FGF23 was not associated with LVMI after kidney transplantation in all models. Conclusions: FGF23 levels are associated with alterations in cardiovascular functional capacity in advanced CKD and after kidney transplantation. FGF23 is only associated with structural cardiac adaptations in advanced CKD but this was modified by dialysis status, and was not associated after kidney transplantation.
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    Impaired arterial vitamin D signaling occurs in the development of vascular calcification
    (PLOS, 2020-11-19) Lim, Kenneth; Molostvov, Guerman; Lubczanska, Maria; Fletcher, Simon; Bland, Rosemary; Hiemstra, Thomas F.; Zehnder, Daniel; Medicine, School of Medicine
    Conflicting data exists as to whether vitamin D receptor agonists (VDRa) are protective of arterial calcification. Confounding this, is the inherent physiological differences between human and animal experimental models and our current fragmented understanding of arterial vitamin D metabolism, their alterations in disease states and responses to VDRa's. Herein, the study aims to address these problems by leveraging frontiers in human arterial organ culture models. Human arteries were collected from a total of 24 patients (healthy controls, n = 12; end-stage CKD, n = 12). Cross-sectional and interventional studies were performed using arterial organ cultures treated with normal and calcifying (containing 5mmol/L CaCl2 and 5mmol/L β-glycerophosphate) medium, ex vivo. To assess the role of VDRa therapy, arteries were treated with either calcitriol or paricalcitol. We found that human arteries express a functionally active vitamin D system, including the VDR, 1α-hydroxylase and 24-hydroxylase (24-OHase) components and these were dysregulated in CKD arteries. VDRa therapy increased VDR expression in healthy arteries (p<0.01) but not in CKD arteries. Arterial 1α-OHase (p<0.05) and 24-OHase mRNA and protein expression were modulated differentially in healthy and CKD arteries by VDRa therapy. VDRa exposure suppressed Runx2 and MMP-9 expression in CKD arteries, however only paricalcitol suppressed MMP-2. VDRa exposure did not modulate arterial calcification in all organ culture models. However, VDRa reduced expression of senescence associated β-galactosidase (SAβG) staining in human aortic-smooth muscle cells under calcifying conditions, in vitro. In conclusion, maladaptation of arterial vitamin D signaling components occurs in CKD. VDRa exposure can exert vasculo-protective effects and seems critical for the regulation of arterial health in CKD.
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    Initiation of Dialysis Is Associated With Impaired Cardiovascular Functional Capacity.
    (AHA, 2022-07-19) Arroyo, Eliott; Umukoro, Peter E.; Burney, Heather N.; Li, Yang; Li, Xiaochun; Lane, Kathleen A.; Sher, S. Jawad; Lu, Tzong-Shi; Moe, Sharon M.; Moorthi, Ranjani; Coggan, Andrew R.; McGregor, Gordon; Hiemstra, Thomas F.; Zehnder, Daniel; Lim, Kenneth; Kinesiology, School of Health and Human Sciences
    Background The transition to dialysis period carries a substantial increased cardiovascular risk in patients with chronic kidney disease. Despite this, alterations in cardiovascular functional capacity during this transition are largely unknown. The present study therefore sought to assess ventilatory exercise response measures in patients within 1 year of initiating dialysis. Methods and Results We conducted a cross-sectional study of 241 patients with chronic kidney disease stage 5 from the CAPER (Cardiopulmonary Exercise Testing in Renal Failure) study and from the intradialytic low-frequency electrical muscle stimulation pilot randomized controlled trial cohorts. Patients underwent cardiopulmonary exercise testing and echocardiography. Of the 241 patients (age, 48.9 [15.0] years; 154 [63.9%] men), 42 were predialytic (mean estimated glomerular filtration rate, 14 mL·min·1.73 m), 54 had a dialysis vintage ≤12 months, and 145 had a dialysis vintage >12 months. Dialysis vintage ≤12 months exhibited a significantly impaired cardiovascular functional capacity, as assessed by oxygen uptake at peak exercise (18.7 [5.8] mL·min·kg) compared with predialysis (22.7 [5.2] mL·min·kg; <0.001). Dialysis vintage ≤12 months also exhibited reduced peak workload, impaired peak heart rate, reduced circulatory power, and increased left ventricular mass index (<0.05 for all) compared with predialysis. After excluding those with prior kidney transplant, dialysis vintage >12 months exhibited a lower oxygen uptake at peak exercise (17.0 [4.9] mL·min·kg) compared with dialysis vintage ≤12 months (18.9 [5.9] mL·min·kg; =0.033). Conclusions Initiating dialysis is associated with a significant impairment in oxygen uptake at peak exercise and overall decrements in ventilatory and hemodynamic exercise responses that predispose patients to functional dependence. The magnitude of these changes is comparable to the differences between low-risk New York Heart Association class I and higher-risk New York Heart Association class II to IV heart failure.
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    Integrin α 5 Is Regulated by miR-218-5p in Endothelial Progenitor Cells
    (Wolters Kluwer, 2022) Liu, Jialing; Li, Yi; Lyu, Lingna; Xiao, Liang; Memon, Aliza A.; Yu, Xin; Halim, Arvin; Patel, Shivani; Osman, Abdikheyre; Yin, Wenqing; Jiang, Jie; Naini, Said; Lim, Kenneth; Zhang, Aifeng; Williams, Jonathan D.; Koester, Ruth; Qi, Kevin Z.; Fucci, Quynh-Anh; Ding, Lai; Chang, Steven; Patel, Ankit; Mori, Yutaro; Chaudhari, Advika; Bao, Aaron; Liu, Jia; Lu, Tzong-Shi; Siedlecki, Andrew; Medicine, School of Medicine
    Kidney endothelial cells are sensitive to hypoxic injury. This cell type expresses integrin α5 (ITGA5), which is essential to the Tie2 signaling cascade. The microRNA miR-218 is known to increase after hypoxia, but the microRNA’s role in regulating ITGA5 protein synthesis is unclear. In this study, the authors found that miR-218-5p specifically binds to ITGA5 mRNA in human kidney-derived endothelial progenitor cells (EPCs). In an animal model of ischemia/reperfusion injury, cells pretreated with an miR-218-5p mimic were delivered efficiently, whereas an animal model containing an miR-218-2 deletion specific to angioblasts resulted in kidney dysgenesis and impaired migration of mouse kidney-derived EPCs. Understanding the regulation of prominent signaling pathways in EPCs may inform optimization of therapeutic techniques for addressing kidney endothelial cell injury.
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    Kidney disease and congenital heart disease: Partnership for life
    (Frontiers Media, 2022-08-19) El Sayegh, Skye; Ephrem, Georges; Wish, Jay B.; Moe, Sharon; Lim, Kenneth; Medicine, School of Medicine
    The literature on the relationship between kidney and cardiovascular diseases is continuously expanding. Scientists have elucidated many of the neurohormonal and hemodynamic pathways involved in cardiorenal disease. However, little is known about kidney disease in patients with congenital heart disease. Given advances in the medical and surgical care of this highly complex patient population, survival rates have dramatically improved leading to a higher percentage of adults living with congenital heart disease. Accordingly, a noticeable increase in the prevalence of kidney disease is appreciated in these patients. Some of the main risk factors for developing chronic kidney disease in the adult congenital heart disease population include chronic hypoxia, neurohormonal derangements, intraglomerular hemodynamic changes, prior cardiac surgeries from minimally invasive to open heart surgeries with ischemia, and nephrotoxins. Unfortunately, data regarding the prevalence, pathophysiology, and prognosis of chronic kidney disease in the adult congenital heart disease population remain scarce. This has led to a lack of clear recommendations for evaluating and managing kidney disease in these patients. In this review, we discuss contemporary data on kidney disease in adults with congenital heart disease in addition to some of the gaps in knowledge we face. The article highlights the delicate interaction between disease of the heart and kidneys in these patients, and offers the practitioner tools to more effectively manage this vulnerable population.
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    Klotho and the Treatment of Human Malignancies
    (MDPI, 2020-06-23) Sachdeva, Aishani; Gouge, Jerome; Kontovounisios, Christos; Nikolaou, Stella; Ashworth, Alan; Lim, Kenneth; Chong, Irene; Medicine, School of Medicine
    Klotho was first discovered as an anti-ageing protein linked to a number of age-related disease processes, including cardiovascular, renal, musculoskeletal, and neurodegenerative conditions. Emerging research has also demonstrated a potential therapeutic role for Klotho in cancer biology, which is perhaps unsurprising given that cancer and ageing share similar molecular hallmarks. In addition to functioning as a tumour suppressor in numerous solid tumours and haematological malignancies, Klotho represents a candidate therapeutic target for patients with these diseases, the majority of whom have limited treatment options. Here, we examine contemporary evidence evaluating the anti-neoplastic effects of Klotho and describe the modulation of downstream oncogenic signalling pathways, including Wnt/β-catenin, FGF, IGF1, PIK3K/AKT, TGFβ, and the Unfolded Protein Response. We also discuss possible approaches to developing therapeutic Klotho and consider technological advances that may facilitate the delivery of Klotho through gene therapy.