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- Title
Role of growth hormone in regulating lipolysis, proteolysis, and hepatic glucose production during fasting.
- Authors
Sakharova, Alla A; Horowitz, Jeffrey F; Surya, Sowmya; Goldenberg, Naila; Harber, Matthew P; Symons, Kathy; Barkan, Ariel
- Abstract
<bold>Context: </bold>Fasting is associated with suppressed insulin and augmented GH secretion. The involvement of each mechanism in the regulation of fuel mobilization during fasting is unknown.<bold>Objective: </bold>To ascertain the role of GH in the regulation of the rates of lipolysis, proteolysis, and hepatic glucose production (HGP) during the physiological daily feed/fast cycle and after 2 d of complete fasting, we used a model of selective GH suppression by the administration of GHRH receptor antagonist (GHRH-A).<bold>Design and Setting: </bold>We conducted an open label in-patient study in the General Clinical Research Center at the University of Michigan.<bold>Participants: </bold>Six healthy, nonobese volunteers participated.<bold>Main Outcome Measures: </bold>We assessed 24-h plasma GH concentration and rates of lipolysis, proteolysis, and HGP using stable isotope techniques after an overnight fast and after 2 d of fasting.<bold>Results: </bold>GHRH-A suppressed plasma GH by about 65% during the fed state (P = 0.015) but did not alter the rates of lipolysis, proteolysis, or HGP. Fasting for 2 d suppressed plasma insulin concentration by about 80% and elevated plasma GH about 4-fold (both P < 0.01). This was accompanied by a doubling in the rate of lipolysis, an approximately 40% increase in proteolysis, and an approximately 30% decline in HGP (all P < 0.05). Preventing the fasting-induced increase in GH with GHRH-A largely abolished the increase in the rate of lipolysis. GHRH-A also augmented the fasting-induced reduction in HGP but did not alter proteolysis.<bold>Conclusions: </bold>Endogenous GH plays a very limited metabolic role during the daily feed/fast cycle but is essential for the increased lipolytic rate found with more prolonged fasting.
- Subjects
PROTEIN metabolism; CELL receptors; COMPARATIVE studies; GENETIC disorders; GLUCOSE; LIPID metabolism disorders; LIVER; RESEARCH methodology; MEDICAL cooperation; RESEARCH; RESEARCH funding; EVALUATION research; HUMAN growth hormone
- Publication
Journal of Clinical Endocrinology & Metabolism, 2008, Vol 93, Issue 7, p2755
- ISSN
0021-972X
- Publication type
journal article
- DOI
10.1210/jc.2008-0079