Growth hormone and lipolysis: a reevaluation

Area of Science:

• Endocrinology
• Molecular Biology
• Biochemistry

Background:

• Previous research suggested clinical grade human growth hormone (hGH) lipolytic activity stemmed from an acidic peptide contaminant.
• This contaminant was believed to be the sole source of lipolysis in hGH preparations.

Purpose of the Study:

• To re-evaluate the lipolytic activity of highly purified human growth hormone (hGH).
• To investigate the lipolytic capacity of the purported acidic peptide contaminant.
• To determine if lipolytic activity is an intrinsic property of hGH.

Main Methods:

• Utilized clinical grade hGH preparations previously studied.
• Assessed lipolytic activity in the presence of dexamethasone and varying concentrations of hGH and peptide contaminant.
• Measured glycerol production as an indicator of lipolysis.
• Compared lipolytic response to purified hGH, acidic peptide, and bacterially synthesized hGH.
• Evaluated insulin-like response, refractoriness, and adipocyte binding characteristics of the acidic peptide.

Main Results:

• Highly purified hGH demonstrated delayed lipolytic activity in the presence of dexamethasone.
• The acidic peptide contaminant exhibited lipolytic activity equivalent to purified hGH.
• Both compounds showed similar effective concentrations and glycerol production increases.
• The acidic peptide displayed characteristics of hGH, including insulin-like effects and binding affinity.
• Lipolytic response to purified hGH was comparable to bacterially synthesized hGH.

Conclusions:

• Lipolytic activity appears to be an intrinsic property of human growth hormone (hGH).
• The acidic peptide contaminant is likely a variant of hGH.
• Previous claims attributing lipolysis solely to contaminants are refuted.
• The physiological significance of hGH-induced lipolysis requires further investigation.