This project, in part, represents an extension of work previously reported as Project Numbers Z01 DK69037, Z01 DK069097 and Z01 DK069000. It also reports on continuation of work previously reported under Project Numbers DK069036-23, DK069063-17, and DK069100-06. All work related to diabetic kidney disease, except for the genetics of diabetic kidney disease, is now reported under this single project. In the last year, we demonstrated that higher plasma bradykinin and related peptide concentrations measured before the onset of clinical diabetic kidney disease in Caucasians with type 1 diabetes was associated with preservation of kidney structure, suggesting that elevations of these kinin concentrations may reflect beneficial adaptive responses to early kidney structural changes in diabetic kidney disease. Similarly, we found that a higher serum concentration of serum amyloid A was associated with reduced risk of end-stage kidney disease in American Indians with type 2 diabetes and early diabetic kidney disease. In both cases, higher concentrations of these biomarkers are associated with more rapid progression of diabetic kidney disease if measured later in the disease. These observations suggest that mechanisms which suppress these beneficial effects or promote the harmful effects of these markers may enhance prediction of progressive diabetic kidney disease and provide new therapeutic targets. We found that a routine white blood cell count and differential provide clinically relevant information about the risk of diabetic kidney disease in American Indians and in Caucasians with type 2 diabetes. Lymphocytes and neutrophils, which together represent >90% of white blood cells, had the strongest associations with structural lesions of diabetic kidney disease and with loss of kidney function. Neutrophil and lymphocyte fractions and the neutrophil:lymphocyte ratio each modestly but significantly improved prediction of kidney function loss over traditional risk factors. The value of these white blood cell parameters may be enhanced by combining them with other markers of inflammation, especially those localized predominantly to the kidneys. We observed that lower concentrations of a set of urine metabolites that are implicated in reduced mitochondrial function are associated with kidney structural lesions in American Indians with type 2 diabetes and may serve as biomarkers for early glomerular lesions in diabetic kidney disease. We also identified 77 CpG sites measured in blood that were strongly associated with the progression of diabetic kidney disease among individuals with chronic kidney disease at baseline. These findings have implications for the pathogenesis of diabetic kidney disease, suggesting that epigenetic modification of pathways affecting apoptosis and kidney fibrosis is an important contributor to the disease. These results suggest that DNA methylation measured in peripheral blood cells may provide a useful, easily measured biomarker for assessing the risk of diabetic kidney disease. In the past year, we explored the relationship between exposure to persistent organic pollutants, including polychlorinated biphenyls and pesticides, and the risk of progressive diabetic kidney disease. We observed that polychlorinated biphenyls with less than four chlorine atoms were associated with an increased risk of end-stage kidney disease in an American Indian population with type 2 diabetes. Given the extent of exposure to these toxic substances in many parts of the world, further study of these exposures is warranted. Our systems biology efforts continue to yield interesting findings. We found that ORAI store-operated channels exist in human proximal tubules and that impairment of the ORAI channel expression or channel activity leads to a decreased albumin absorption by proximal tubular cells and results in proteinuria. In another study, we applied an integrated strategy that combines genome-wide intrarenal gene expression profiling, quantitative morphometric analysis, and clinical outcomes data analysis, to explore potential novel pathways underlying early-stage structural changes in diabetic kidney disease. Transcripts related to cortical interstitial fractional volume (VvInt) measured on kidney biopsy showed significant enrichment for inflammatory mechanisms and for substrate metabolic processes in the renal tubule. The association of VvInt-linked genes with long-term clinical outcomes, including increasing urine albumin excretion and declining glomerular filtration rate validated the relevance of the early-stage processes to progression of more advanced diabetic kidney disease. This approach may enhance our ability to identify urinary markers of intrarenal disease processes active in patients who have minimal or clinically undetected diabetic kidney disease. Finally, we continue to publish from our consortial and professional society work. We published several papers under the auspices of the International Society of Nephrology outlining a roadmap for the future of kidney disease research and management over the next 10 years, outlining goals and topics of importance as well as strategies for accomplishing those goals. We published several papers with the CKD Biomarkers Consortium describing various urine biomarkers and their relationship with progressive kidney and cardiovascular disease. We also published a paper examining the role of serum filtration markers as predictors of the same health outcomes.
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