Comparison of Low and High-dose Growth Hormone Administration on Muscle Ceramide Contents and Insulin Resistance in Rats
Hyung Lyung Jung1, Jong Sik Ryu1, Sang Yeong Kim1, Young Taek Doo2 and Ho Youl Kang11Department of Physical Education, Kyungpook National University, Daegu, Republic of Korea.
2Department of Physical Therapy, Gwangju Woman’s University, Gwangju, Republic of Korea.
Corresponding Author E-mail: hokang@knu.ac.kr
Abstract: We evaluated the effects of low- and high- dosage growth hormone (GH) administration on muscle ceramide contents and insulin resistance in rats. 24 rats were randomly assigned to three groups: low dosage GH injection group (L/GH, n = 8), high dosage GH injection group (H/GH, n = 8) and saline injection group (CON, n = 8). GH groups received GH by subcutaneous injections (L/GH; 65 μg/kg/day, H/GH; 130 μg/kg/day, 6 days/week) for 4 weeks, while CON received saline injections that were equivalent in volume to L/GH group. At the end of 4-week treatments, plasma lipids, insulin and glucose levels were measured. Glucose transporter 4 protein (GLUT-4) and ceramide contents were determined in muscle while triglyceride contents were determined in both muscle and liver. Rate of glucose uptake was determined under submaximal and non- insulin conditions during the epitrochlearis incubation. After 4 weeks of GH injection, H/GH had significantly higher plasma FFA levels (p < 0.05), but L/GH did not have it compared to CON. Plasma insulin levels were significantly lower in H/GH and glucose level in H/GH was higher than CON group (p < 0.05). Muscle ceramide, muscle and liver triglyceride contents were significantly greater in H/GH than CON, but those were not significantly different between L/GH and CON. Glucose transport rate under submaximal insulin condition was significantly lower in H/GH group than CON group (p < 0.05), but L/GH was not different from CON. Therefore, results of this study suggested that the deterioration of muscle insulin resistance due to GH treatment is strongly associated with the elevated TG and ceramide contents due to high GH administration dosage in rats.
Keywords: Growth Hormone; Muscle Triglyceride, Liver Triglyceride; Ceramide; Glucose Transport Rate; Insulin Resistance Back to TOC