Candidate: I am a physician-scientist seeking to discover diagnostic solutions to the problems of diabetes mellitus and kidney disease. I completed a Ph. D. working on the role of adiponectin in hepatic insulin sensitivity. My interest i the diagnostic challenges of diabetes mellitus led me to a residency in clinical pathology to gain expertise in clinical assay development. I have developed assays for serum adiponectin, bioavailable 25-hydroxyvitamin D, and serum carbamylated albumin (%C-Alb) that is akin to """"""""hemoglobin A1c for uremia,"""""""" whose values are correlated to blood urea and are predictive of mortality in patients on dialysis. I am the Assistant Medical Director in the Department of Pathology at Beth Israel Deaconess Medical Center and an Instructor of Pathology at Harvard Medical School;the majority of my time is protected for research. My clinical position is uniquely synergistic with my research goals. My short term goals are to pursue an intensive period of research training through the K08 program, use this time to complete my assay project, gain experience in animal model experiments and coursework in clinical investigation, and obtain sufficient preliminary data to support application for an independent research award. My long-term goals are to continue translational research in assay development, focusing on understanding the pathophysiology of uremia, and addressing the challenges of diagnosis, prevention, and management of kidney disease and diabetes mellitus. My long-term career goals will require additional training in clinical investigation in order for me to become an effective translational investigator. I have established mentoring relationships with Drs. Ananth Karumanchi and Ravi Thadhani, two prominent senior investigators in the fields of preeclampsia and kidney disease. Environment: My affiliations with BIMDC and Harvard Medical School place me within a research environment that is second to none. My department has provided me with independent laboratory space and mass spectrometer instrumentation for the execution of assay development and performance for my project, my clinical and research laboratories are located in the BIDMC main hospital complex within the Longwood Medical Area of Boston. Longwood is also home to the Harvard School of Public Health where I will pursue training in human subjects research and biostatistics. Among the resources available to me include support from the Harvard CTSC. If I am granted K08 support I will be eligible to enroll in clinical research coursework through the Harvard School of Public Health's Summer Program in Clinical Effectiveness and pursue an MPH degree. My departmental chair Jeffrey Saffitz has gone to great lengths to provide a nurturing research environment for young investigators. Research: Protein carbamylation by urea-derived cyanate may contribute to the complications of chronic and end stage kidney disease (ESRD). We hypothesized that protein carbamylation is determined by the balance between time-averaged urea concentrations and cyanate scavengers such as free amino acids. Here, we report discovery of a specific carbamylation site in human albumin and methods to measure carbamylated albumin (%C-Alb) using liquid chromatography and tandem mass spectrometry. When we analyzed %C-Alb in patient samples we found that %C-Alb was elevated in ESRD patients who died during the first year of hemodialysis compared to survivors, and elevated %C-Alb levels were significantly associated with all-cause mortality (hazard ratio 3.76, P=0.0002). Although %C-Alb levels were positively correlated to average blood urea concentrations as expected, we found equally strong negative correlations between %C-Alb and concentrations of many serum amino acids. These results suggested that amino acid deficiencies in hemodialysis patients may contribute to protein carbamylation, and that amino acid supplements could be used in the treatment of hemodialysis patients in order to inhibit protein carbamylation and its sequelae. Previous animal model studies have shown that urea contributes directly to atherosclerosis and uremic cardiomyopathy, but it is unknown whether this is due to carbamylation. Previous studies have also shown that carbamylation inhibits the actions of thiol antioxidants. Increased oxidative stress has been linked to chronic kidney disease, atherosclerosis, and uremic cardiomyopathy, but it is unknown whether carbamylation is a significant contributor to uremia-associated oxidative stress and its cardiovascular pathology. We recently published these results in the journals Science Trans. Med. And CJASN, and we are currently following up on these studies through a pilot clinical trial testing the effects of amino acid carbamylation scavengers on protei carbamylation in hemodialysis patients. In this proposal we seek to further our understanding of the effects of urea on the heart, and test various specific treatments for """"""""hypercarbamylation."""""""" Specific Aim 1 will test whether carbamylation directly contributes to atherosclerosis using a mouse model of kidney failure and atherogenesis.
Specific Aim 2 will test whether carbamylation directly contributes to myocardial fibrosis, hypertrophy, and remodeling using a rat model of kidney failure, and whether urea activates cardiomyocyte oxidative stress signaling pathways.
Specific Aim 3 will test whether amino acid supplements or other carbamylation scavengers can reduce carbamylation and ameliorate uremia-associated heart disease.
Specific Aim 4 will test whether a thiol antioxidant, alpha lipoic acid, can reduce carbamylation and oxidative stress, and ameliorate uremia-associated heart disease.
Chronic kidney disease affects an estimated 5%-10% of adults, and the vast majority of these patients die of cardiovascular disease even before they ever require hemodialysis. Chronic uremia associated with kidney failure causes modifications of proteins and amino acids (carbamylation). This proposal will test whether carbamylation contributes to myocardial oxidative stress, atherosclerosis, and heart failure in rodents, and whether amino acid or antioxidant treatments are able to reduce carbamylation and uremia-associated heart disease.
|Kalim, Sahir; Trottier, Caitlin A; Wenger, Julia B et al. (2016) Longitudinal Changes in Protein Carbamylation and Mortality Risk after Initiation of Hemodialysis. Clin J Am Soc Nephrol :|
|Berg, Anders H; Powe, Camille E; Evans, Michele K et al. (2015) 24,25-Dihydroxyvitamin d3 and vitamin D status of community-dwelling black and white Americans. Clin Chem 61:877-84|
|Kalim, Sahir; Ortiz, Guillermo; Trottier, Caitlin A et al. (2015) The Effects of Parenteral Amino Acid Therapy on Protein Carbamylation in Maintenance Hemodialysis Patients. J Ren Nutr 25:388-92|
|Drechsler, Christiane; Kalim, Sahir; Wenger, Julia B et al. (2015) Protein carbamylation is associated with heart failure and mortality in diabetic patients with end-stage renal disease. Kidney Int 87:1201-8|
|Kalim, Sahir; Karumanchi, S Ananth; Thadhani, Ravi I et al. (2014) Protein carbamylation in kidney disease: pathogenesis and clinical implications. Am J Kidney Dis 64:793-803|