Effects of the new C1q/TNF-related protein (CTRP-3) "cartonectin" on the adipocytic secretion of adipokines.
BACKGROUND
Cartonectin (collagenous repeat-containing sequence of 26-kDa protein; CORS-26) was described as a new adipokine of the C1q/TNF molecular superfamily C1q/TNF-related protein-3 (CTRP-3), secreted by the adipocytes of mice and humans. The receptor and function of cartonectin are unknown and the recombinant protein is not commercially available.


OBJECTIVE
To investigate the effects of recombinant cartonectin on the secretion of adipokines such as adiponectin, leptin, and resistin from adipocytes of human and murine origin. The effect of the BMI of the adipocyte donor was also investigated.


METHODS
Human adipocytes from pooled lean and preobese healthy individuals and murine 3T3-L1 adipocytes were used for stimulation experiments. Recombinant cartonectin was expressed in insect H5 cells. Adipokine secretion was measured using enzyme-linked immunosorbent assay. In addition, western blot analysis and luciferase reporter gene assays were employed.


RESULTS
Cartonectin (1, 10, 50, and 250 ng/ml) in higher doses stimulates the secretion of adiponectin and resistin from murine adipocytes. This effect is not caused by an induction of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) protein expression, as confirmed by western blot analysis. Also, luciferase reporter gene assay revealed that cartonectin failed to induce luciferase activity at the peroxisome proliferator-activated receptor responsive element site containing the adiponectin/luciferase promoter fragment. Human adipocytes from lean individuals secrete higher amounts of adiponectin and leptin when compared with adipocytes of individuals with a preobesity BMI (25-30 kg/m(2)). Cartonectin failed to stimulate adiponectin or leptin secretion from human adipocytes, irrespective of the BMI value.


CONCLUSIONS
Cartonectin is a new adipokine that differentially regulates the secretion of classical adipokines, with marked differences between the human and the murine systems. These effects are species-dependent, while basal adipokine secretion is influenced by the BMI.
Wölfing
Britta
B
Department of Internal Medicine I, University of Regensburg, Regensburg, Germany.
Buechler
Christa
C
Weigert
Johanna
J
Neumeier
Markus
M
Aslanidis
Charalampos
C
Schöelmerich
Juergen
J
Schäffler
Andreas
A
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D054392:Adipokines / Q000235:genetics / Q000378:metabolism*; D052242:Adiponectin / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D015992:Body Mass Index; D004797:Enzyme-Linked Immunosorbent Assay; D017930:Genes, Reporter; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D020738:Leptin / Q000378:metabolism; D051379:Mice; D047495:PPAR gamma / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000378:metabolism; D052243:Resistin / Q000378:metabolism; D013045:Species Specificity; D050507:Subcutaneous Fat, Abdominal / Q000378:metabolism*; D048069:Tumor Necrosis Factors / Q000378:metabolism*
C499918:ADIPOQ protein, human; D054392:Adipokines; D052242:Adiponectin; C499919:Adipoq protein, mouse; C506069:C1QTNF3 protein, human; D015850:Interleukin-6; D020738:Leptin; D047495:PPAR gamma; C499624:RETN protein, human; D011994:Recombinant Proteins; D052243:Resistin; C499623:Retn protein, mouse; D048069:Tumor Necrosis Factors