The influence of insulin-like growth factor 1 on protein synthesis and degradation in skeletal muscle of rats with chronic renal failure
- VernacularTitle:胰岛素样生长因子-1对慢性肾功能不全大鼠骨骼肌蛋白质合成与分解的影响
- Author:
Xiulin, GAO
- Publication Type:Journal Article
- From:
Chinese Journal of Clinical Nutrition
2000;8(1):29-30
- CountryChina
- Language:Chinese
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Abstract:
Objective Patients with chronic renal failure (CRF) are frequently malnourished, skeletal muscle atrophy and protein depleted. Insulin-like growth factor 1 (IGF-1) is an anabolic hormone. The actions of IGF-1 on protein turnover were examined in skeletal muscle of rats with CRF and sham operated (SO), pair-fed controls. IGF-1 was extracted from serum and skeletal muscle and then measured by radio-immunoassay (RIA). Total tyrosine in the supernatant from the medium was measured fluorometrically and then basal protein synthesis rate and degradation rate in skeletal muscle were calculated. The results showed that IGF-1 levels in serum and in skeletal muscle in the CRF rats were 170.3 ± 16.4 ng/ml and 4.22 ± 1.03ng/grams respectively. These values were significantly lower than in the SO rats (410.4 ± 49.3ng/ml in serum and 6.93 + 1.41ng/grams in muscle, respectively, P<0.001 for each comparison). The basal protein synthesis rate in epitrochlearis muscle of the CRF rats (24.0 ± 2.1 nmol Tyr/grams per hour ) was significantly lower, by 22%, than that of SO, pair-fed rats (30.8 ± 2.4nmol Tyr/grams per hour,P<0.05). In contrast, the basal protein degradation rate in the epitrochlearis muscle of the CRF rats (234.4 ± 13.8nmol Tyr/grams per hour) was increased by 78% in comparison to SO rats (131.7 ± 8.4nmol Tyr/grams per hour, P< 0.001). Dose response curves of rhIGF-1 showed that the effects of rhIGF-1 On muscle protein synthesis and degradation in CRF rats were markedly attenuated as compared to their SO pair-fed controls. The enhancement in protein synthesis induced by increasing concentrations of rhIGF-1 (ranging from 25 to 500ng/ml) in CRF rats was only 25 to 44% of that in SO rats. Similarly, the suppressive effects of the various concentrations of rhlGF-1 on protein degradation in muscle from CRF rats were only 15 to 42% of those found in SO rats. These data indicate that there are impaired actions of rhIGF-1 on protein synthesis and degradation in skeletal muscle of rats with CRF. These findings suggest that the decreased IGF-1 levels in serum and in skeletal muscle, the resistance to the anabolie effects of IGF-1 on protein metabolism may be the main causes of reduced protein synthesis and enhaneed protein degradation in muscle, muscle atrophy and malnutrition in patients with CRF.
