In chicken ovary the adiponectin

In chicken ovary, the adiponectin gene was found to be mainly expressed in theca cells and is suggested to exert a paracrine or autocrine effect on ovarian steroidogenesis (Chabrolle et al., 2007). A limited number of studies have revealed the effect of adiponectin on ovarian steroidogenesis or its association with polycystic ovarian syndrome (PCOS) in women. In porcine follicular cells, adiponectin was found to increase steroidogenic acute regulatory protein (StAR) transcript abundance but reduces cytochrome P450 aromatase expression (Ledoux et al., 2006). Similarly, adiponectin is suggested to exert an inhibitory effect on bovine theca cell steroidogenesis (Lagaly et al., 2008). Adiponectin decreased insulin-induced steroidogenesis and increased insulin-like growth factor-1-induced proliferation of cultured bovine granulosa cells through a potential involvement of mitogen-activated protein kinase (MAPK)-Erk1/2 pathway (Maillard et al., 2010). Adiponectin HMW isoform is selectively reduced in women with PCOS, independent of body mass index and insulin resistance (Aroda et al., 2008, O’Connor et al., 2010). Overall, adiponectin and its receptors appear to be involved in steroidogenesis in the mammalian ovary.
Summary and conclusions Our studies revealed that the chicken adiponectin mRNA sequence shares only 65–68% homology to mammalian adiponectin cDNA, although the deduced amino ion channel sequence of chicken adiponectin contained 22 glycine-X-Y repeats (where X and Y represent any amino acid) at the N-terminal end as found in mammalian adiponectin. We also found that adiponectin is expressed in a variety of tissues in the chicken with the greatest expression in adipose tissue. Using gel filtration column chromatography and Western blot analysis, adiponectin in chicken plasma and adipose tissue was found to be predominantly a multimeric HMW isoform that is larger than 669kDa mass. Mass spectrometric analysis of chicken adiponectin revealed the presence of several post-translational modifications to the lysine and proline residues in the collagenous domain. An enzyme immunoassay developed and validated for quantifying plasma adiponectin in chickens revealed that plasma adiponectin levels ranged between 4 and 10μg/ml in broiler chickens. Chicken adiponectin receptors, AdipoR1 and AdipoR2 appear to have seven distinct hydrophobic regions representing seven transmembrane domains while their cDNA sequences were 76–83% identical to the respective mammalian sequences. Both AdipoR1 and AdipoR2 mRNA were found to be expressed in adipose tissue, liver, anterior pituitary gland, diencephalon, skeletal muscle, kidney, spleen, ovary, and blood. Using anti-chicken adiponectin, AdipoR1, or AdipoR2 antibodies, adiponectin-, AdipoR1-, AdipoR2-ir cells were localized in the broiler breeder chicken testis. Furthermore, testicular AdipoR1 and AdipoR2 mRNA abundance were found to be significantly higher in adult chickens compared to prepubertal chickens, suggesting that sexual maturation is likely associated with an up-regulation of testicular AdipoR1 and AdipoR2 gene expression. We are currently elucidating the biological functions of avian adiponectin and its importance to avian growth and reproduction.
Acknowledgments