title: Serum chemerin levels vary with time of day and are modified by obesity and tumor necrosis factor-{alpha}.
abstract: Chemerin is an adipokine with important regulatory roles in adipogenesis. In humans, serum total chemerin (i.e. prochemerin plus chemerin) levels are positively associated with body mass index and metabolic syndrome. However, the mechanisms that increase serum chemerin concentration are unknown. We hypothesized that chronic low-grade inflammation that occurs in obesity promotes chemerin production by adipocytes. Consistent with this, TNFalpha treatment of 3T3-L1 adipocytes increased bioactive chemerin levels in the cell media as detected using a CMKLR1 cell-based bioassay. This effect was blocked by the protein synthesis inhibitor cycloheximide and protein secretion inhibitor brefeldin A, indicating that TNFalpha may enhance prochemerin synthesis and secretion from adipocytes. In vivo, TNFalpha produced a time-dependent increase in serum total chemerin and bioactive chemerin. Bioactive chemerin was produced by primary mouse adipocytes and hepatocytes. Only primary adipocyte-derived chemerin was responsive to TNFalpha regulation implicating adipocytes as a potential source of elevated serum chemerin after TNFalpha exposure in vivo. In lean mice, serum total chemerin levels oscillated with peak levels occurring during daytime and trough levels at night. Comparatively, leptin- and leptin receptor-deficient obese mice, which have elevated adipose tissue expression of TNFalpha, displayed elevated serum total chemerin levels with an enhanced oscillatory pattern. In summary, our novel results identified TNFalpha as a positive regulator of adipocyte-derived chemerin. We corroborate the finding of elevated chemerin in obese humans by identifying elevated serum levels of total chemerin in two obese mouse models with a corresponding alteration in the rhythmic pattern of serum chemerin levels.
authors.affiliation: College of Pharmacy, Dalhousie University, 5968 College Street, Halifax, Nova Scotia, Canada B3H 3J5.
authors.forename: Sebastian D
authors.initials: SD
authors.lastname: Parlee
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Ernst
authors.forename: Shanmugam
authors.initials: S
authors.lastname: Muruganandan
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Sinal
authors.forename: Kerry B
authors.initials: KB
authors.lastname: Goralski
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D020126:Brefeldin A / Q000494:pharmacology; D002478:Cells, Cultured; D018925:Chemokines; D002630:Chemotactic Factors / Q000097:blood*; D003513:Cycloheximide / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood*; D051379:Mice; D018345:Mice, Knockout; D009765:Obesity / Q000503:physiopathology*; D016133:Polymerase Chain Reaction; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology*
chemical_list: D018925:Chemokines; D002630:Chemotactic Factors; D036341:Intercellular Signaling Peptides and Proteins; D011500:Protein Synthesis Inhibitors; D014409:Tumor Necrosis Factor-alpha; C523686:chemerin protein, mouse; D020126:Brefeldin A; D003513:Cycloheximide