Hyperfiltration (HF) is a state of high glomerular filtration rate (GFR) observed in early diabetes that damages glomeruli, resulting in an iterative process of increasing filtration load on fewer and fewer remaining functional glomeruli. To delineate underlying cellular mechanisms of damage induced by HF, transcriptional profiles of kidney biopsies from Pima Indians with type 2 diabetes with or without early-stage diabetic kidney disease (DKD) were grouped into two HF categories based on annual iothalamate GFR measurements. Twenty-six participants with a peak GFR measurement within two years of biopsy were categorized as the HF group, and 26 in whom biopsy preceded peak GFR by >2 years were considered pre-HF. The HF group had higher hemoglobin A1c, higher urine albumin-to-creatinine ratio, increased glomerular basement membrane width and lower podocyte density compared to the pre-HF group. A glomerular 1240-gene transcriptional signature identified in the HF group was enriched for endothelial stress response signaling genes, including from endothelin-1, tec-kinase and TGF-β1 pathways, with the majority of the transcripts mapped to endothelial and inflammatory cell clusters in kidney single cell transcriptional data. This analysis reveals molecular pathomechanisms contributing to development of HF and early DKD and involving putative ligand-receptor pairs and downstream intracellular targets linked to cellular crosstalk between endothelial and mesangial cells.
Molecular Programs of Glomerular Hyperfiltration in Early Diabetic Kidney Disease
