Association of metabolic parameters and rs726344 in FNDC5 with serum irisin concentrations.
OBJECTIVE
Irisin has been suggested as a novel myokine with beneficial effects in rodents. However, previous data in humans showed conflicting results regarding its association with metabolic phenotypes and regulation of secretion. Furthermore, although an association of rs726344 in FNDC5 (fibronectin type III domain containing 5) coding for irisin with insulin sensitivity was reported, the effects of genetic variation at this locus on irisin serum levels have not been investigated, so far. Therefore, we investigated circulating irisin and the associations with rs726344 in a cohort of >1000 subjects.


METHODS
Irisin serum concentrations were measured with enzyme-linked immunosorbent assay. Associations with metabolic parameters including renal function, glucose and lipid metabolism, inflammation, as well as adipokine profiles, were assessed in regression models. Dynamic changes of serum irisin were investigated during oral glucose tolerance test (OGTT) in a subset of the cohort (n=136). rs726344 was genotyped in all subjects and analyzed for associations with serum irisin and traits of the metabolic syndrome.


RESULTS
Irisin was negatively associated with fat mass, fasting glucose and dyslipidemia but not with other adipokines. Moreover, irisin decreased during an OGTT in a subcohort comprising subjects with normal glucose tolerance, impaired fasting glucose, impaired glucose tolerance and type 2 diabetes mellitus. rs726344 was not associated with serum irisin levels or with other anthropometric and biochemical parameters.


CONCLUSIONS
Circulating irisin levels are associated with a beneficial metabolic profile but not with other adipokines and not with rs726344 in our cohort. Our data suggest a potential favorable role of irisin in the regulation of metabolism.
Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany.|Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
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http://orcid.org/0000-0003-1683-9276
T
Ebert
Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany.|Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
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S
Kralisch
Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany.|Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
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U
Wurst
Institute of Medical Informatics, Statistics and Epidemiology, University of Leipzig, Leipzig, Germany.|LIFE Research Center, University of Leipzig, Leipzig, Germany.
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M
Scholz
Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany.
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M
Stumvoll
Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
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P
Kovacs
Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany.|Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
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M
Fasshauer
Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany.|Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
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Tönjes
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D050218:Body Fat Distribution; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005353:Fibronectins / Q000097:blood* / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease / Q000453:epidemiology*; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007333:Insulin Resistance / Q000235:genetics*; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000453:epidemiology / Q000235:genetics; D008875:Middle Aged; D015203:Reproducibility of Results
D001786:Blood Glucose; C577593:FNDC5 protein, human; D005353:Fibronectins