Background
GLP‐1 (glucagon‐like peptide‐1) receptor agonists exert beneficial long‐term effects on cardiovascular and renal outcomes. In humans, the natriuretic effect of GLP‐1 depends on GLP‐1 receptor interaction, is accompanied by suppression of angiotensin II, and is independent of changes in renal plasma flow. In rodents, angiotensin II constricts vasa recta and lowers medullary perfusion. The current randomized, controlled, crossover study was designed to test the hypothesis that GLP‐1 increases renal medullary perfusion in healthy humans.

Methods and Results
Healthy male participants (n=10, aged 27±4 years) ingested a fixed sodium intake for 4 days and were examined twice during a 1‐hour infusion of either GLP‐1 (1.5 pmol/kg per minute) or placebo together with infusion of 0.9% NaCl (750 mL/h). Interleaved measurements of renal arterial blood flow, oxygenation (R2*), and perfusion were acquired in the renal cortex and medulla during infusions, using magnetic resonance imaging. GLP‐1 infusion increased medullary perfusion (32±7%, P<0.001) and cortical perfusion (13±4%, P<0.001) compared with placebo. Here, NaCl infusion decreased medullary perfusion (−5±2%, P=0.007), whereas cortical perfusion remained unchanged. R2* values increased by 3±2% (P=0.025) in the medulla and 4±1% (P=0.008) in the cortex during placebo, indicative of decreased oxygenation, but remained unchanged during GLP‐1. Blood flow in the renal artery was not altered significantly by either intervention.

Conclusions
GLP‐1 increases predominantly medullary but also cortical perfusion in the healthy human kidney and maintains renal oxygenation during NaCl loading. In perspective, suppression of angiotensin II by GLP‐1 may account for the increase in regional perfusion.