Abstract
BackgroundAdiponectin is an adipokine, mainly produced by adipose tissue. It regulates several reproductive processes. The protein expression of the adiponectin system (adiponectin, its receptors, AdipoR1 and AdipoR2 and the APPL1 adaptor) in bovine ovary and its role on ovarian cells and embryo, remain however to be determined.MethodsHere, we identified the adiponectin system in bovine ovarian cells and embryo using RT-PCR, immunoblotting and immunohistochemistry. Furthermore, we investigated in vitro the effects of recombinant human adiponectin (10 micro g/mL) on proliferation of granulosa cells (GC) measured by [3H] thymidine incorporation, progesterone and estradiol secretions measured by radioimmunoassay in the culture medium of GC, nuclear oocyte maturation and early embryo development.ResultsWe show that the mRNAs and proteins for the adiponectin system are present in bovine ovary (small and large follicles and corpus luteum) and embryo. Adiponectin, AdipoR1 and AdipoR2 were more precisely localized in oocyte, GC and theca cells. Adiponectin increased IGF-1 10(-8) M-induced GC proliferation (P < 0.01) but not basal or insulin 10(-8) M-induced proliferation. Additionally, adiponectin decreased insulin 10(-8) M-induced, but not basal or IGF-1 10(-8) M-induced secretions of progesterone (P < 0.01) and estradiol (P < 0.05) by GC. This decrease in insulin-induced steroidogenesis was associated with a decrease in ERK1/2 MAPK phosphorylation in GC pre-treated with adiponectin. Finally, addition of adiponectin during in vitro maturation affected neither the percentage of oocyte in metaphase-II nor 48-h cleavage and blastocyst day 8 rates.ConclusionsIn bovine species, adiponectin decreased insulin-induced steroidogenesis and increased IGF-1-induced proliferation of cultured GC through a potential involvement of ERK1/2 MAPK pathway, whereas it did not modify oocyte maturation and embryo development in vitro.
Highlights
Adiponectin is an adipokine, mainly produced by adipose tissue
Results messenger RNA (mRNA) and protein expression of adiponectin system in bovine ovary and embryo RT-PCR analysis revealed the amplification of cDNAs corresponding to fragments of adiponectin (410 pb), AdipoR1 (550 pb), AdipoR2 (520 pb) in whole ovary, large and small follicles, corpus luteum, granulosa cells, cumulus cells from mature and immature cumulus-oocyte complexes (COC) and oocytes, as shown in adipose tissue used as a positive control (Fig. 1A)
Whereas adiponectin seemed to be less expressed in bovine freshisolated granulosa cells than in bovine primary-cultured granulosa cells from small follicles, the receptors AdipoR1 and AdipoR2 and the adaptor APPL1 were present at similar levels in the two cell types (Fig. 1B)
Summary
Adiponectin is an adipokine, mainly produced by adipose tissue. The protein expression of the adiponectin system (adiponectin, its receptors, AdipoR1 and AdipoR2 and the APPL1 adaptor) in bovine ovary and its role on ovarian cells and embryo, remain to be determined. Adiponectin is a hormone mainly produced by mature adipocytes and abundantly present in the circulation (2 to 20 μg/mL) in mammals [1,2]. This adipokine, known as Acrp, AdipoQ and GBP28, is a 30 kDa glycoprotein present in plasma as homomultimers, including trimers, hexamers and high molecular weight multimers [3]. Our team has found in rat [2], chicken [15] and human [16], that physiological levels of recombinant human adiponectin (rh adiponectin, 5 or 10 μg/ml) are able to increase progesterone and/or estradiol secretions in response to insulinlike growth factor-I (IGF-I) in cultured granulosa cells
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