RESUMO
Although the functions of adiponectin, a differentiated adipocyte-derived hormone, in regulating glucose and fatty acid metabolism are regulated by two subtypes of adiponectin receptors (AdipoRs; AdipoR1 and AdipoR2), those in ruminants remain unclear. Therefore we examined the messenger RNA (mRNA) expression levels of adiponectin and its receptors in various bovine tissues and mammary glands among different lactation stages, and the effects of lactogenic hormones (insulin, dexamethasone and prolactin) and growth hormone (GH) on mRNA expression of the AdipoRs in cultured bovine mammary epithelial cells (BMEC). AdipoRs mRNAs were widely expressed in various bovine tissues, but adiponectin mRNA expression was significantly higher in adipose tissue than in other tissues. In the mammary gland, although adiponectin mRNA expression was significantly decreased at lactation, AdipoR1 mRNA expression was significantly higher at peak lactation than at the dry-off stage. In BMEC, lactogenic hormones and GH upregulated AdipoR2 mRNA expression but did not change that of AdipoR1. In conclusion, adiponectin and its receptor mRNA were expressed in various bovine tissues and the adiponectin mRNA level was decreased during lactation. These results suggest that adiponectin and its receptors ware changed in mammary glands by lactation and that AdipoRs mRNA expression was regulated by different pathways in BMEC.
Assuntos
Adiponectina/genética , Adiponectina/metabolismo , Células Epiteliais/metabolismo , Regulação da Expressão Gênica , Hormônio do Crescimento/farmacologia , Glândulas Mamárias Humanas/citologia , Glândulas Mamárias Humanas/metabolismo , Prolactina/farmacologia , Animais , Bovinos , Células Cultivadas , Dexametasona/farmacologia , Feminino , Hormônio do Crescimento/fisiologia , Humanos , Insulina/farmacologia , Insulina/fisiologia , Lactação/genética , Lactação/fisiologia , Prolactina/fisiologia , RNA Mensageiro/metabolismo , Receptores de Adiponectina/genética , Receptores de Adiponectina/metabolismo , Teofilina/análogos & derivados , Regulação para CimaRESUMO
Adipocyte differentiation is an important aspect in energy homeostasis. Although the regulation of adipocyte differentiation is relatively well understood, the underlying molecular mechanism remains unclear. In this study, subcutaneous and epididymal adipose tissues were used to study the differential expression of associated genes. We found that the expression level of mouse homologue of rat prostatic androgen-repressed message-1 (mPARM-1) gene was higher in subcutaneous, perirenal and mesenteric adipose tissues than in epididymal adipose tissue. In mouse subcutaneous, perirenal, and mesenteric adipose tissues, the expression level of this gene was higher in adipocytes than in non-adipocyte cells, i.e. stromal-vascular cells. Furthermore, mPARM-1 mRNA expression was up-regulated in subcutaneous, mesenteric, and epididymal adipose tissues of mice fed a high-fat diet compared to those fed a normal-fat diet. Expression level of mPARM-1 mRNA increased in the early stage of the chemically induced adipocyte differentiation, preceding the increase in peroxisome proliferator-activated receptor-gamma 2 (PPAR-gamma2) mRNA. Tumor necrosis factor-alpha (TNF-alpha), an inhibitor of adipocyte differentiation, reduced the expression of mPARM-1 mRNA in differentiated 3T3-L1 cells and subsequently down-regulated the expression of adipogenic genes, including PPAR-gamma2, leptin and adipogenin. Moreover, knockdown of mPARM-1 expression with siRNA reduced lipid accumulation and the expression levels of PPAR-gamma2 and adipocyte protein 2 mRNAs, which suggest that the degree of adipocyte differentiation of 3T3-L1 cells has been reduced. These results indicate that mPARM-1 might be involved in the regulation of fat accumulation and adipocyte differentiation.