Haymond M W, Horber F F, Mauras N
Department of Pediatrics, Nemours Children's Clinic, Jacksonville, FL 32241.
Horm Res. 1992;38 Suppl 1:73-5. doi: 10.1159/000182574.
Human growth hormone (rhGH) increases estimates of whole-body protein synthesis, but has little effect on rates of proteolysis in both the postabsorptive state and during meal absorption. In addition, rhGH stimulates protein synthesis in skeletal muscle tissue. In contrast, insulin decreases estimates of whole-body and forearm proteolysis while decreasing or, in the presence of infused (or ingested) amino acids, sustaining estimates of protein synthesis. Using high-dose prednisone as a controlled model for protein catabolism in normal volunteers, high-dose rhGH together with prednisone prevents the protein catabolic effects of prednisone alone. GH is thought to mediate its effects via the generation of insulin-like growth factor I (IGF-I). However, high rates of infusion of rhIGF-I induce hypoglycemia and decrease estimates of whole body proteolysis, suggestive of a predominant insulin-like effect. When rhIGF-I is infused at a rate that achieves plasma IGF-I concentrations similar to those observed during rhGH treatment and yet avoids hypoglycemia, estimates of proteolysis and protein synthesis were not affected in the absence or presence of prednisone treatment. Thus, the mechanism of action of rhGH on body protein metabolism remains to be elucidated. However, rhGH alone or in combination with rhIGF-I may provide a new management strategy in a variety of protein catabolic conditions in humans.
人生长激素（rhGH）可提高全身蛋白质合成的估计值，但对空腹状态和进餐吸收期间的蛋白水解速率影响甚微。此外，rhGH可刺激骨骼肌组织中的蛋白质合成。相比之下，胰岛素可降低全身和前臂的蛋白水解估计值，同时在输注（或摄入）氨基酸时，降低或维持蛋白质合成的估计值。以高剂量泼尼松作为正常志愿者蛋白质分解代谢的对照模型，高剂量rhGH与泼尼松联合使用可预防泼尼松单独使用时的蛋白质分解代谢作用。生长激素被认为是通过生成胰岛素样生长因子I（IGF-I）来介导其作用的。然而，高剂量输注rhIGF-I会导致低血糖，并降低全身蛋白水解的估计值，提示其具有主要的胰岛素样作用。当以达到与rhGH治疗期间观察到的血浆IGF-I浓度相似且避免低血糖的速率输注rhIGF-I时，无论是否进行泼尼松治疗，蛋白水解和蛋白质合成的估计值均不受影响。因此，rhGH对机体蛋白质代谢的作用机制仍有待阐明。然而，单独使用rhGH或与rhIGF-I联合使用可能为人类多种蛋白质分解代谢状况提供一种新的治疗策略。
