Growth Hormone Signaling in Vivo in Humans
|First Received Date ICMJE||August 6, 2007|
|Last Updated Date||August 6, 2007|
|Start Date ICMJE||September 2005|
|Primary Completion Date||Not Provided|
|Current Primary Outcome Measures ICMJE
||GH-receptor signaling [ Time Frame: hours ]|
|Original Primary Outcome Measures ICMJE||Same as current|
|Change History||No Changes Posted|
|Current Secondary Outcome Measures ICMJE
||Insulin sensitivity [ Time Frame: hours ]|
|Original Secondary Outcome Measures ICMJE||Same as current|
|Current Other Outcome Measures ICMJE||Not Provided|
|Original Other Outcome Measures ICMJE||Not Provided|
|Brief Title ICMJE||Growth Hormone Signaling in Vivo in Humans|
|Official Title ICMJE||Growth Hormone (GH) Signaling in Vivo in Human Muscle and Adipose Tissue: Impact of Insulin, Substrate Background and gh Receptor Blockade|
Objective: GH induces insulin resistance in muscle and fat and in vitro data indicate that this may involve crosstalk between the signaling pathways of the two hormones.
Aim: To investigate GH and insulin signaling in vivo in human muscle and fat tissue in response to GH, GH receptor blockade and insulin stimulation..
The molecular mechanisms by which GH promotes insulin antagonism are still unclear. Stimulation of lipolysis could be of importance since high plasma FFA levels have been shown to interfere with insulin receptor signaling via inhibition of insulin-stimulated insulin receptor substrate (IRS)-1 associated phosphatidylinositol (PI) 3-kinase activity in human skeletal muscle, resulting in a decreased GLUT4 translocation and glucose transport (6). A recent study, however, was unable to document a suppression in the insulin-stimulated activity of either IRS-1 associated PI 3-kinase or the serin/threonin kinase Akt after GH administration to healthy humans, despite induction of lipolysis and insulin resistance (7). Other studies have shown that acute GH exposure induces insulin resistance in skeletal muscle rapidly and before the subsequent rise in plasma FFA (1;7;8). These observations indicate that GH may cause insulin resistance via a non-FFA mediated mechanism.
The predominant GH signal transduction cascade comprises activation of the GHR dimer, phosphorylation of JAK2 and subsequently activation of Stat5. The intact JAK2/Stat5 pathway is necessary for normal statural growth (9). There is animal and in vitro evidence to suggest that insulin and GH share post-receptor signaling pathways (10). Convergence has been reported at the levels of Stat5 and SOCS3 as well as on protein kinases comprising the major IR signaling pathway; IRS 1/2, PI 3-kinase, Akt and ERK 1/2 (11-14).
Pegvisomant is a GH analog and a competitive reversible GH receptor antagonist, which blocks peripheral GH signal transduction (15). Pegvisomant has been shown to inhibit the necessary conformational change of the GHR dimer and thus constitutes an optimal negative control in GH signaling studies.
The aim of this work was to further study GH signal transduction pathways in vivo in muscle and adipose tissue from healthy subjects in response to acute and more prolonged GH exposure as well as during hyperinsulinemia. The design also included administration of pegvisomant in an attempt to correct for spontaneous GH secretion.
|Study Type ICMJE||Interventional|
|Study Phase||Not Provided|
|Study Design ICMJE||Allocation: Randomized
Endpoint Classification: Pharmacodynamics Study
Intervention Model: Crossover Assignment
Masking: Single Blind
Primary Purpose: Basic Science
|Condition ICMJE||Intracellular Signaling Peptides and Proteins|
|Study Arm (s)||
* Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
|Recruitment Status ICMJE||Completed|
|Completion Date||April 2006|
|Primary Completion Date||Not Provided|
|Eligibility Criteria ICMJE||
|Ages||20 Years to 40 Years|
|Accepts Healthy Volunteers||Yes|
|Contacts ICMJE||Contact information is only displayed when the study is recruiting subjects|
|Location Countries ICMJE||Denmark|
|NCT Number ICMJE||NCT00512473|
|Other Study ID Numbers ICMJE||20050113|
|Has Data Monitoring Committee||No|
|Responsible Party||Not Provided|
|Study Sponsor ICMJE||University of Aarhus|
|Collaborators ICMJE||Not Provided|
|Information Provided By||University of Aarhus|
|Verification Date||August 2007|
ICMJE Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP