Ghrelin interacts with human plasma lipoproteins.

Area of Science:

• Biochemistry
• Endocrinology
• Lipid Metabolism

Background:

• Ghrelin, a stomach-derived peptide hormone, stimulates appetite and growth hormone secretion.
• Ghrelin exists in acylated (octanoylated) and des-acyl forms in human blood.
• Previous studies identified esterases like butyrylcholinesterase in human serum and carboxylesterase in rat serum responsible for ghrelin desoctanoylation.

Purpose of the Study:

• To investigate the role of lipoprotein-associated enzymes in ghrelin desoctanoylation.
• To determine how lipoproteins influence the transport of circulating ghrelin.

Main Methods:

• Analysis of ghrelin desoctanoylation in contact with various plasma subfractions, including low-density lipoproteins (LDLs) and lipoprotein-poor plasma.
• Identification of enzymes responsible for ghrelin hydrolytic activity in these subfractions.
• Assessment of ghrelin's association with different classes of lipoproteins: triglyceride-rich lipoproteins (TRLs), high-density lipoproteins (HDLs), very high-density lipoproteins (VHDLs), and LDLs.

Main Results:

• Ghrelin desoctanoylation predominantly occurred with LDLs and lipoprotein-poor plasma.
• Butyrylcholinesterase and platelet-activating factor acetylhydrolase were identified as key enzymes in these processes.
• Ghrelin associates with TRLs, HDLs, VHDLs, and LDLs; acylation is crucial for TRL and LDL interaction, while HDLs and VHDLs bind both acylated and des-acyl forms.

Conclusions:

• Lipoprotein-associated enzymes play a significant role in ghrelin desoctanoylation.
• Lipoproteins, particularly TRLs and LDLs, are involved in transporting acylated ghrelin.
• HDLs and VHDLs transport both acylated and des-acyl ghrelin, interacting via ghrelin's terminal parts.