title: Proteomic and functional characterization of endogenous adiponectin purified from fetal bovine serum.
abstract: Adiponectin is a plasma protein exclusively secreted from fat tissue. Many recent pharmacological studies suggest that recombinant adiponectin has multiple therapeutic potentials for obesity-related metabolic disorders, including type 2 diabetes, dyslipidemia, insulin resistance and atherosclerosis. However, the physiological relevance of these findings remains to be further established. In the present study, we have purified endogenous adiponectin from fetal bovine serum and characterized its post-translational modifications and physiological functions in animal models. Endogenous bovine serum adiponectin consists predominantly of full-length proteins that form multiple oligomeric complexes, including trimers, hexamers and higher molecular species. Two-dimensional gel electrophoresis revealed that bovine serum adiponectin exists as multiple post-translationally modified isoforms with distinct molecular weight and isoelectric point. Further analysis using mass spectrometry and Edman degradation sequencing demonstrated that five conserved lysine residues (Lys 28, 60, 63, 72 and 96) within the collagenous domain of bovine adiponectin are hydroxylated and glycosylated by a glucosyl alpha(1-2)galactosyl group. Injection of endogenous bovine adiponectin into C57 mice potently decreased circulating glucose levels and enhanced lipid clearance after a high fat meal. Chronic administration of this protein for a period of two weeks significantly increased insulin sensitivity and glucose tolerance, and depleted hepatic lipid accumulation in high-fat fed mice. These results provide direct evidence that endogenous bovine adiponectin is a physiological hormone that can regulate lipid and glucose metabolism.
authors.affiliation: Center for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.forename: Winifred P S
authors.initials: WP
authors.lastname: Wong
authors.forename: Johannes F G
authors.initials: JF
authors.lastname: Vliegenthart
authors.forename: Gerrit J
authors.initials: GJ
authors.lastname: Gerwig
authors.forename: Karen S L
authors.initials: KS
authors.lastname: Lam
authors.forename: Garth J S
authors.initials: GJ
authors.lastname: Cooper
authors.forename: Aimin
authors.initials: A
authors.lastname: Xu
mesh_terms: D052242:Adiponectin; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D006031:Glycosylation; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood* / Q000737:chemistry* / Q000302:isolation & purification*; D007525:Isoelectric Focusing; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism; D014357:Trypsin / Q000737:chemistry
chemical_list: D052242:Adiponectin; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; D014280:Triglycerides; D014357:Trypsin; D005947:Glucose; D008239:Lysine