Exp Clin Endocrinol Diabetes 2013; 121(05): 310-317
DOI: 10.1055/s-0032-1333299
Article
© Georg Thieme Verlag KG Stuttgart · New York

Regulation and Function of C1Q/TNF-related Protein-5 (CTRP-5) in the Context of Adipocyte Biology

A. Schmid*
1   Department of Internal Medicine I, Regensburg University Hospital, Germany
,
A. Kopp*
1   Department of Internal Medicine I, Regensburg University Hospital, Germany
,
C. Aslanidis
2   Institute of Clinical Chemistry and Laboratory Medicine, Regensburg University Hospital, Germany
,
M. Wabitsch
3   Division of Pediatric Endocrinology and Diabetes, Department of Pediatrics and Adolescent Medicine, University of Ulm, Germany
,
M. Müller
1   Department of Internal Medicine I, Regensburg University Hospital, Germany
,
A. Schäffler
1   Department of Internal Medicine I, Regensburg University Hospital, Germany
› Author Affiliations
Further Information

Publication History

received 15 October 2012
first decision 18 December 2012

accepted 07 January 2013

Publication Date:
21 February 2013 (online)

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Abstract

Background and aim:

The C1q/TNF-related protein (CTRP) family represents a growing family of adiponectin paralogous proteins. CTRP-5 was detected in adipose tissue of mice and plays a role in the context of the metabolic syndrome. It was the aim to investigate the detailed expression profile of CTRP-5 in a variety of adipocytic cells and to determine whether CTRP-5 circulates in human serum. Moreover, regulation and function of CTRP-5 was studied in the context of adipocyte biology.

Material and methods:

CTRP-5 serum levels were measured in 50 healthy subjects by ELISA. Genotype analysis was performed by direct sequencing in 200 probands. CTRP-5 mRNA and protein expression was analyzed by RT-PCR, real-time RT-PCR and Western blot. Recombinant CTRP-5 and fatty acids were used for stimulation experiments in 3T3-L1 adipocytes. siRNA-mediated knockdown of CTRP-3 was performed during adipocyte differentiation.

Results:

CTRP-5 mRNA and protein was strongly expressed in a wide variety of human and murine adipocytic cells and was induced during adipocyte differentiation. Saturated fatty acids increased CTRP-5 expression in adipocytes. siRNA-mediated cellular knockdown of CTRP-3 in adipocytes resulted in an upregulation of CTRP-5 expression. CTRP-5 inhibited the release of resistin and adiponectin dose-dependently. CTRP-5 circulates abundantly in human sera with a broad interindividual variation. The SNP 1014 T/A was not associated with type 2 diabetes mellitus in 200 Caucasian probands.

Conclusions:

CTRP-5 might be a novel adipokine that circulates abundantly in human sera. CTRP-5 is functionally involved in adipocyte biology and there might exist a counter-regulatory connection with its family member, CTRP-3.

* Both authors contributed equally.