319-OR: Renoprotective Effects of Glucagon and Incretin Agonist Combinations Mediated by Macula Densa Cells

Introduction & Objective: Recent therapeutic advances in diabetic nephropathy (DN) including GLP-1 analogs are promising, however more efficient treatments are needed with improved mechanistic understanding of their mode of action. Glucagon (GCG), GLP-1 and GIP receptors (R) are expressed in the kidney. Macula densa (MD) cells play central roles in controlling renal hemodynamics and tissue remodeling. This study aimed to examine the renoprotective effects of GCG w/without incretin analogs.

Methods: Intravital multiphoton imaging (MPM) was used to detect acute or chronic effects of GCG (long-acting IUB288) w/wo GLP-1 and GIP on afferent (AA) and efferent arteriole (EA) blood flow, single nephron glomerular filtration rate (SNGFR), MD cell calcium, nitric oxide (NO, using DAF-FM diacetate iv), mitochondrial function (using MitoTracker Red iv) in wild-type or Sox2-GCaMP5, Ren1d or Cdh5-Confetti mice (for genetic cell fate tracking) in control and STZ model of type I DN, and in MD cells in vitro.

Results: MPM revealed intense, selective MD cell labeling with AF647-conjugated GCG injected iv. GCG induced acute, two-fold increases in cell calcium only in MD cells. GCGR was 7.64-fold enriched in MD vs control cell transcriptome. Acute GCG treatment significantly increased MD cell protein synthesis, NO production, mitochondrial metabolism, AA/EA blood flow, protected glomerular hemodynamics from vasoconstrictor challenge. These effects were preserved or augmented when given in combination with incretin analogs including the GCG/GLP-1/GIP triagonist TG208, in chronic treatments and DN. Chronic GCG treatment induced a trend towards augmented tissue remodeling by resident progenitor cells.

Conclusion: MD-specific functional expression of GCGR is linked to improved cell metabolism, vasodilation, renal hemodynamics and tissue repair. MD cell targeting is an important novel mode of action of GCG that may be combined with incretin analogs for greater therapeutic effect in DN.