Submitted on July 6, 2004
Accepted on December 14, 2004
Heritability of Free and Receptor Bound Leptin in Normal Twins
Jens Jordan1*, Georg Brabant2, Marina Brinsuk1, Jens Tank1, Rudiger Horn2, Friedrich C Luft1, and Andreas Busjahn3
1 Franz Volhard Clinical Research Center, Medical Faculty of the Charite and Helios Klinikum, Berlin, Germany
2 Department of Endocrinology, Medizinische Hochschule Hannover, Hannover, Germany
3 HealthTwiSt GmbH, Berlin, Germany
* To whom correspondence should be addressed. E-mail: jordan{at}fvk.charite-buch.de.
Free and receptor-bound leptin may be regulated by different mechanisms. Genes that influence the concentration of these fractions may have an important functional bearing. We determined circulating leptin receptor concentrations, bound as well as free leptin concentrations, and body composition in 24 monozygotic (MZ) and in 22 dizygotic (DZ) twin pairs. Bound leptin and
leptin receptor concentrations were inversely correlated with body fat content. Free leptin concentrations were directly correlated with body fat content. The correlations in age and sex adjusted free leptin, bound leptin and
leptin receptor concentrations were higher between MZ
twins than between DZ twins. Adjusted heritability (h2) estimates were 0.28 for free leptin, 0.73 for bound leptin, and 0.55 for leptin receptor. The genetic correlation with body fat was -.58 for the leptin receptor, -.20 for bound leptin, and 0.93 for free leptin. Our data are consistent with a strong genetic influence on leptin receptor and bound leptin and a weaker genetic influence on free leptin concentrations. The same genes that lower bound leptin and leptin receptor concentrations may increase fat mass or vice versa.
