The potential role of adiponectin- and resistin-like peptides in the regulation of lipid levels in the hemolymph of over-wintering adult females of Osmia bicornis

Abstract

The presence and potential role of adiponectin- and resistin-like peptides in mobilizing free lipids of hemolymph during over-wintering was studied in females of the European solitary red mason bee Osmia bicornis L. (Hymenoptera: Megachilidae). The levels of both peptides (as demonstrated both by RIA/ELISA and Western blots) were highest in fat body tissue homogenates during early pre-wintering (September) followed by a gradual and significant decline during wintering and post-wintering months (November-March). There was a gradual reduction of the lipid levels in hemolymph and adiponectin-like and resistin-like peptide content in fat body. Thus, the total lipid content in hemolymph and the adiponectin-like and resistin-like peptides in fat body homogenates was positively correlated. Our experiments also demonstrated that injections of various concentrations of fat body extracts as well as various doses of adiponectin and resistin increased the lipid levels in hemolymph in O. bicornis females at the three different periods of over-wintering time. In particular, injections of fat body extract and adiponectin resulted in the strongest mobilization of lipids especially in the first two periods of over-wintering: pre-wintering and wintering. Resistin also elicited an increase of lipid levels in hemolymph, but its effectiveness was lower compared to fat body extract and adiponectin. Taken together, our results strongly suggest the presence of adiponectin-like and resistin-like peptides in the fat body of O. bicornis and postulate a dynamic physiological role for these peptides during the process of over-wintering. © 2014 The Author(s).