Ghigo E, Ceda G P, Valcavi R, Goffi S, Zini M, Mucci M, Valenti G, Cocchi D, Müller E E, Camanni F
Dipartimento di Fisiopatologia Clinica, Università di Torino, Italy.
J Endocrinol Invest. 1994 Feb;17(2):113-7. doi: 10.1007/BF03347695.
Reportedly, the responsiveness of somatotrope cells to GHRH is reduced in elderly humans but it is totally restored by arginine (ARG) which likely acts by inhibiting hypothalamic release of somatostatin. As this effect was observed after infusion of high doses of the amino acid, in this study, we compared the effect of iv administration of 30, 10 and 5 g ARG(group A, B and C, respectively) as well as oral administration of 8 g ARG(group D) on the GH response to 1 microgram/kg i.v.GHRH in 27 healthy elderly subjects (11 M and 16 F, age 70-86 yr, BMI 21-25 kg/m2). In group A (n = 7) 30 g i.v. ARG strikingly enhanced the GHRH-induced GH rise (peak, mean +/- SE: 41.5 +/- 4.4 vs 11.7 +/- 5.3 micrograms/L, p < 0.05). Similarly, in group B (n = 6) and D (n = 7) 10 g i.v. and 8 g oral ARG enhanced the GH response to GHRH (20.9 +/- 4.7 vs 8.3 +/- 2.8 micrograms/L, p < 0.03 and 31.0 +/- 5.3 vs 11.4 +/- 3.4 micrograms/L, p < 0.03, respectively). In contrast, in group C (n = 7) 5 g i.v. ARG failed to modify the GHRH-induced GH rise (6.0 +/- 1.6 vs 3.5 +/- 0.9 micrograms/L). The GH responses to GHRH alone did not significantly differ amongst groups; the GH responses to GHRH and ARG were not significantly different among groups A, B and D and were greater than the GH response in group C. These results show that the GH response to GHRH in elderly subjects is enhanced even by low iv doses of arginine and by the orally administered amino acid, the lowest effective dose being 8 g. Moreover, they imply that the combined administration of GHRH and arginine may be a useful approach to restore the impaired function of the GH-IGF axis in aging.
据报道，老年人中生长激素细胞对生长激素释放激素（GHRH）的反应性降低，但精氨酸（ARG）可使其完全恢复，精氨酸可能通过抑制下丘脑生长抑素的释放发挥作用。由于在输注高剂量氨基酸后观察到了这种效应，在本研究中，我们比较了静脉注射30g、10g和5g ARG（分别为A组、B组和C组）以及口服8g ARG（D组）对27名健康老年人（11名男性和16名女性，年龄70 - 86岁，体重指数21 - 25kg/m²）静脉注射1μg/kg GHRH后生长激素（GH）反应的影响。在A组（n = 7）中，静脉注射30g ARG显著增强了GHRH诱导的GH升高（峰值，平均值±标准误：41.5±4.4 vs 11.7±5.3μg/L，p < 0.05）。同样，在B组（n = 6）和D组（n = 7）中，静脉注射10g和口服8g ARG增强了对GHRH的GH反应（分别为20.9±4.7 vs 8.3±2.8μg/L，p < 0.03和31.0±5.3 vs 11.4±3.4μg/L，p < 0.03）。相比之下，在C组（n = 7）中，静脉注射5g ARG未能改变GHRH诱导的GH升高（6.0±1.6 vs 3.5±0.9μg/L）。各组单独对GHRH的GH反应无显著差异；A组、B组和D组对GHRH和ARG联合的GH反应无显著差异，且大于C组的GH反应。这些结果表明，即使是低剂量静脉注射精氨酸和口服精氨酸也能增强老年受试者对GHRH的GH反应，最低有效剂量为8g。此外，它们意味着联合使用GHRH和精氨酸可能是恢复衰老过程中受损的GH - IGF轴功能的一种有用方法。
