TY - JOUR
T1 - Neutral endopeptidase 24.11 is important for the degradation of both endogenous and exogenous glucagon in anesthetized pigs
AU - Trebbien, Ramona
AU - Klarskov, L.
AU - Olesen, M.
AU - Holst, J. J.
AU - Carr, R. D.
AU - Deacon, C. F.
PY - 2004
Y1 - 2004
N2 - Glucagon has a short plasma t(1/2) in vivo, with renal extraction playing a major role in its elimination. Glucagon is degraded by neutral endopeptidase (NEP) 24.11 in vitro, but the physiological relevance of NEP 24.11 in glucagon metabolism is unknown. Therefore, the influence of candoxatril, a selective NEP inhibitor, on plasma levels of endogenous and exogenous glucagon was examined in anesthetized pigs. Candoxatril increased endogenous glucagon concentrations, from 6.3 +/- 2.5 to 20.7 +/- 6.3 pmol/l [COOH-terminal (C)-RIA, P <0.05]. During glucagon infusion, candoxatril increased the t(1/2) determined by C-RIA (from 3.0 &PLUSMN; 0.5 to 17.0 &PLUSMN; 2.5 min, P <0.005) and midregion (M)-RIA (2.8 +/- 0.5 to 17.0 +/- 3.0 min, P <0.01) and reduced metabolic clearance rates (MCR; 19.1 &PLUSMN; 3.2 to 9.4 &PLUSMN; 2.0 ml.kg(-1).min(-1), P <0.02, C-RIA; 19.2 +/- 4.8 to 9.0 +/- 2.3 ml.kg-(1).min(-1), P <0.05, M-RIA). However, neither t(1/2) nor MCR determined by NH2-terminal (N)-RIA were significantly affected (t(1/2), 2.7 &PLUSMN; 0.4 to 4.5 &PLUSMN; 1.6 min; MCR, 30.3 &PLUSMN; 6.4 to 28.5 &PLUSMN; 9.0 ml.kg(-1).min(-1)), suggesting that candoxatril had no effect on NH2-terminal degradation but leads to the accumulation of NH2-terminally truncated forms of glucagon. Determination of arteriovenous glucagon concentration differences revealed that renal glucagon extraction was reduced (but not eliminated) by candoxatril (from 40.4 &PLUSMN; 3.8 to 18.6 &PLUSMN; 4.1%, P <0.02, C-RIA; 29.2 +/- 3.1 to 14.7 +/- 2.2%, P <0.02, M-RIA; 26.5 &PLUSMN; 4.0 to 19.7 &PLUSMN; 3.5%, P <0.06, N-RIA). Femoral extraction was reduced by candoxatril when determined by C-RIA (from 22.7 +/- 2.4 to 8.0 +/- 5.1%, P <0.05) but was not changed significantly when determined using M- or N-RIAs (10.0 &PLUSMN; 2.8 to 4.7 &PLUSMN; 3.7%, M-RIA; 10.5 &PLUSMN; 2.5 to 7.8 &PLUSMN; 4.2%, N-RIA). This study provides evidence that NEP 24.11 is an important mediator of the degradation of both endogenous and exogenous glucagon in vivo.
AB - Glucagon has a short plasma t(1/2) in vivo, with renal extraction playing a major role in its elimination. Glucagon is degraded by neutral endopeptidase (NEP) 24.11 in vitro, but the physiological relevance of NEP 24.11 in glucagon metabolism is unknown. Therefore, the influence of candoxatril, a selective NEP inhibitor, on plasma levels of endogenous and exogenous glucagon was examined in anesthetized pigs. Candoxatril increased endogenous glucagon concentrations, from 6.3 +/- 2.5 to 20.7 +/- 6.3 pmol/l [COOH-terminal (C)-RIA, P <0.05]. During glucagon infusion, candoxatril increased the t(1/2) determined by C-RIA (from 3.0 &PLUSMN; 0.5 to 17.0 &PLUSMN; 2.5 min, P <0.005) and midregion (M)-RIA (2.8 +/- 0.5 to 17.0 +/- 3.0 min, P <0.01) and reduced metabolic clearance rates (MCR; 19.1 &PLUSMN; 3.2 to 9.4 &PLUSMN; 2.0 ml.kg(-1).min(-1), P <0.02, C-RIA; 19.2 +/- 4.8 to 9.0 +/- 2.3 ml.kg-(1).min(-1), P <0.05, M-RIA). However, neither t(1/2) nor MCR determined by NH2-terminal (N)-RIA were significantly affected (t(1/2), 2.7 &PLUSMN; 0.4 to 4.5 &PLUSMN; 1.6 min; MCR, 30.3 &PLUSMN; 6.4 to 28.5 &PLUSMN; 9.0 ml.kg(-1).min(-1)), suggesting that candoxatril had no effect on NH2-terminal degradation but leads to the accumulation of NH2-terminally truncated forms of glucagon. Determination of arteriovenous glucagon concentration differences revealed that renal glucagon extraction was reduced (but not eliminated) by candoxatril (from 40.4 &PLUSMN; 3.8 to 18.6 &PLUSMN; 4.1%, P <0.02, C-RIA; 29.2 +/- 3.1 to 14.7 +/- 2.2%, P <0.02, M-RIA; 26.5 &PLUSMN; 4.0 to 19.7 &PLUSMN; 3.5%, P <0.06, N-RIA). Femoral extraction was reduced by candoxatril when determined by C-RIA (from 22.7 +/- 2.4 to 8.0 +/- 5.1%, P <0.05) but was not changed significantly when determined using M- or N-RIAs (10.0 &PLUSMN; 2.8 to 4.7 &PLUSMN; 3.7%, M-RIA; 10.5 &PLUSMN; 2.5 to 7.8 &PLUSMN; 4.2%, N-RIA). This study provides evidence that NEP 24.11 is an important mediator of the degradation of both endogenous and exogenous glucagon in vivo.
U2 - 10.1152/ajpendo.00353.2003
DO - 10.1152/ajpendo.00353.2003
M3 - Journal article
SN - 0193-1849
VL - 287
SP - E431-E438
JO - AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
JF - AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
IS - 3
ER -