Project Summary/Abstract This project will build a new kidney biopsy cohort to characterize the molecular, morphometric, and metabolic features of diabetic kidney disease (DKD) over the modern clinical course of type 1 diabetes (T1D). Landmark kidney biopsy studies have enhanced our understanding of DKD pathogenesis. However, advances in continuous glucose monitoring and automated insulin delivery have changed diabetes management and the clinical course of DKD in T1D. Moreover, innovation in molecular methods to interrogate kidney tissue, such as single-cell RNA sequencing (scRNA-seq), allows characterization of DKD at a resolution not previously possible. Based on published work and our preliminary data, we hypothesize that perturbed kidney energetics and hypoxia are central metabolic pathways in the development of DKD in T1D. We will test this hypothesis by creating a unique new longitudinal kidney biopsy cohort (N=100) spanning the critical duration of T1D over which DKD initiates and progresses (5-30 years) and leveraging our existing vanguard biopsy cohort (N=30). Normative kidney biopsy data will be provided from our existing cohort of healthy controls (N=20), the Kidney Precision Medicine Project (KPMP), and additional living kidney donor biopsies. We will implement state-of- the-art molecular (scRNA-seq) and morphometric interrogation of kidney tissue and rigorous metabolic phenotyping. Specifically, we aim to: (1) define differences in kidney energetics and hypoxia over the course of T1D; (2) test associations of the transcriptomic signatures of hypoxia with the structural lesions and clinical manifestations of progressive DKD; and (3) explore the mechanistic correlates of perturbed kidney energetics and hypoxia within a subset of participants with T1D with repeat kidney biopsies. This work will help define the role of perturbed energetics and hypoxia in DKD as well as risk factors for and consequences of kidney hypoxia in T1D. This study will also generate a valuable repository of data, biosamples, and kidney tissue for further analysis of DKD in T1D, made publicly available through the KPMP platform.