In humans, the natriuretic effect of GLP-1 depends on GLP-1 receptor interaction, is independent of changes in renal blood flow, renin, ANP, and aldosterone but is accompanied by suppression of angiotensin II (ANGII). The mechanism by which GLP-1 reduces ANGII independently of changes in renin is not clarified. It was hypothesized that GLP-1 suppresses renin substrate, angiotensinogen, in plasma.
To test this proposal, we measured arterial angiotensinogen concentration in biobanked plasma samples from healthy males during a 3-hour GLP-1 infusion that induced natriuresis (1). Samples were from a study with fixed sodium intake where eight healthy men were examined twice in random order during a 3-hour infusion of either GLP-1(1.5 pmol kg-1 min-1) or vehicle together with an intravenous infusion of 0.9% NaCl (750 mL/hour). Arterial plasma angiotensinogen was measured in plasma by dilution (1:200) and addition of excess exogenous human renin (Inst. of Biological Standards UK). After prolonged incubation, ANGI was quantified by radioimmunoassay. Intraassay variation was 9-12%.
Arterial plasma angiotensinogen and renin levels decreased similarly and modestly (~15 and ~30%, respectively) after NaCl infusion during both studies whereas ANGII levels decreased significantly (~25%) only during GLP-1 infusion.
Suppression of plasma angiotensinogen is less likely to account for GLP-1-mediated ANGII suppression in healthy young males. In perspective, GLP-1 could enhance pathways of ANGII degradation rather than inhibit its formation.
1. Asmar A et al. Extracellular fluid volume expansion uncovers a natriuretic action of GLP-1: a functional GLP-1-renal axis in man. J Clin Endocrinol Metab. 2019 Jul 1;104(7):2509-2519.
B.L.Jensen: None. A.Asmar: Research Support; Novo Nordisk A/S.
