Effects of 4 weeks recombinant human growth hormone administration on insulin resistance of skeletal muscle in rats.
OBJECTIVE
Effect of recombinant human growth hormone (rhGH) administration on lipid storage, and its subsequent effect on insulin sensitivity have not yet been adequately examined. Thus, we investigated the effects of rhGH treatment on muscle triglyceride (TG) and ceramide content, and insulin sensitivity after 4 weeks of rhGH administration in rats.


METHODS
Fourteen rats were randomly assigned to two groups: rhGH injection group (GH, n = 7) and saline injection group (CON, n = 7). GH received rhGH by subcutaneous injections (130 microg.kg(-1).day(-1), 6 days.week(-1)) for 4 weeks, while CON received saline injections that were equivalent in volume to GH group. Intramuscular TG and ceramide content and hepatic TG content were measured. To determine insulin sensitivity, oral glucose tolerance test (OGTT) and muscle incubation for glucose transport rate were performed in rats, and used as indicators of insulin sensitivity. We also examined plasma lipid profiles.


RESULTS
After 4 weeks of rhGH treatment, the GH group had higher muscle and liver TG contents than the CON (p < 0.05). Ceramide content in GH was significantly greater than that in CON (p < 0.05). GH also had higher plasma levels of FFA (p < 0.05), glucose and insulin responses during OGTT (p < 0.05), and lower glucose transport rates in submaximal insulin concentration (p < 0.05) as compared with CON. Results indicate that rhGH treatment is associated with insulin resistance in rats.


CONCLUSIONS
rhGH treatment elevated muscle TG and ceramide content, and hepatic TG content. Thus, elevation of these compounded by rhGH treatment could contribute to the development of insulin resistance in rats.
Park
Mi Jung
MJ
Department of Pediatrics, Sanggye Paik Hospital, Inje University School of Medicine, Seoul, Korea.
Jung
Su Ryun
SR
Jung
Hyun Lyung
HL
Craig
Bruce W
BW
Lee
Chong-Do
CD
Kang
Ho Youl
HY
D000818:Animals; D002518:Ceramides / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D019382:Human Growth Hormone / Q000008:administration & dosage*; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage; D014280:Triglycerides / Q000378:metabolism
D002518:Ceramides; D051275:Glucose Transporter Type 4; D011994:Recombinant Proteins; C495694:Slc2a4 protein, rat; D014280:Triglycerides; D019382:Human Growth Hormone; D005947:Glucose