흰쥐에서 연령이 골격근의 당 대사에 미치는 영향

Effect of Age on Glucose Metabolism of Skeletal Muscle in Rats

연령에 따른 내당능의 감소 발생여부를 Sprague-Dawley종 흰쥐 수컷을 실험동물로 하여 연구한 결과는 다음과 같다. 연령에 따른 몸무게 변화는 1개월에서 2개월 사이에는 급격한 증가를 보였으며 2개월에서 4개월까지는 완만한 증가를 그 후 8개월까지는 미미하였다. 절식상태에서 혈당량(mg/dl)은 성장기군에서 $92{\pm}8.9$였으며 성숙기군에서는 $106{\pm}13.6$으로 성장기군에 비해 높았으며 인슐린 농도 또한 성숙기군에서 높았다. 체중 100mg당 180mg의 당을 부하한 내당능 검사에서도 성숙기군에서는 성장기군에 비해 당내성의 감소현상을 나타내었다. 당부하 검사시 동시에 측정한 혈장 인슐린 농도는 첫 30분에는 성장기군에서 높았으나, 120분에는 성숙기군에서 높은 값을 나타내었다. Soleus근의 당 섭취능은 성숙기군에서 성장기군보다 낮았으나 통계적으로 유의한 차이는 없었다. 인슐린 첨가에 의한 당 섭취능의 변화양상은 성숙기군과 성장기군 사이에 특별한 차이를 발견할 수 없었다.

Background: It is doubtful that aging causes deteriorated glucose metabolism and insulin resistance of skeletal muscle. Some researchers had different results about it. So we have studied the mechanism responsible for the abnormal glucose tolerance associated with aging in rapidly growing and matured rats. Materials and Methods: Animals were used S.D. rats. Growing rats were 7 weeks old (BW: 160-190 gm) and matured rats were 28 weeks old (BW: 420-525 gm). Results: Fasting blood glucose and plasma insulin levels were significantly elevated in matured rat compared with growing rats. And during oral glucose tolerance test the glucose level was also significantly elevated in matured rats. These results confirmed an insulin resistant state of aging. Insulin levels at 30 minutes of oral glucose tolerance test was significantly elevated in growing rat. But at 120 minutes it was maintained at higher level in matured rats than in growing rats. It suggested the possibility of increased insulin secretion by initial stimulation of beta-cells in growing rats, and increased secretion and decreased catabolic rate of insulin in matured rats. Glucose uptake rate of soleus muscle in matured rats was lower than that of growing rats, but the difference was not statistically significant. The dose(insulin)-responsive(glucose uptake) curve of soleus muscle was only slightly deviated to the right side. Conclusion: Glucose metabolism of rat skeletal muscle was worsened by aging. The data of glucose uptake experiments suggested the possibility of insulin resistance of skeletal muscle in matured rats. but the mechanism of insulin resistance of skeletal muscle need further studies.