Growth hormone-mediated breakdown of body fat: effects of GH on lipases in adipose tissue and skeletal muscle of old rats fed different diets.
Lipid storage and breakdown is mainly controlled by lipoprotein lipase and hormone-sensitive lipase. The aim of this work was to elucidate whether growth hormone mediated loss of adipose tissue involves a concerted action on tissue lipases, and to what degree such events are modulated by dietary regimen. Twelve-month-old rats fed first a high-fat diet or a low-fat diet for 14 weeks were injected with saline or growth hormone (4 mg/kg/d) for four days or three weeks in different combinations with either high- or low-fat diets. In adipose tissue, growth hormone generally inhibited lipoprotein lipase and also attenuated the inhibiting effect of insulin on hormone-sensitive lipase activity. Growth hormone treatment combined with restricted high-fat feeding reduced the activity of both lipases in adipose tissue and stimulated hormone-sensitive lipase in muscle. Generally, plasma levels of free fatty acids, glycerol and cholesterol were reduced by growth hormone, and in combination with restricted high-fat feeding, triglyceride levels improved too. We conclude that growth hormone inhibits lipid storage in adipose tissue by reducing both lipoprotein lipase activity and insulin's inhibitory action on hormone-sensitive lipase. We also propose that growth hormone's effects on tissue lipases and blood lipids are modulated by dietary regimen.
Johansen
T
T
Dept. of Pharmacology 3, Novo Nordisk, Malov, Denmark. thuj@novonordisk.com
Richelsen
B
B
Hansen
H S
HS
Din
N
N
Malmlöf
K
K
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000367:Age Factors; D000704:Analysis of Variance; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002250:Carbon Radioisotopes; D004041:Dietary Fats / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D008055:Lipids / Q000097:blood; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012588:Scintillation Counting; D002787:Sterol Esterase / Q000037:antagonists & inhibitors / Q000378:metabolism
D002250:Carbon Radioisotopes; D004041:Dietary Fats; D007328:Insulin; D008055:Lipids; D013006:Growth Hormone; D002787:Sterol Esterase; D008071:Lipoprotein Lipase