Résumé
Excess energy is stored in adipose tissues in the form of triglycerides (TGs), which are hydrolyzed to free fatty acids(FFAs) to meet energy requirement under fasting conditions. In addition to thermogenesis and organ protection,the adipose tissue is now recognized as an important endocrine organ. The proteins secreted by adipocytes are termed as adipokines. Adipokines appear to be involved in such cellular processes as energy intake and energy expenditure,glucose and lipid metabolism,as well as anti- and pro-inflammatory effects via autocrine, paracrine and endocrine. At the systemic level, adipokines regulate various biological processes in target organs,including the brain,liver,muscle,vasculature,heart and pancreas, immune system, and others. Adipokines exert specific effects on glucose and lipid metabolism, including glucose metabolism (leptin, adiponectin, resistin), insulin sensitivity [leptin, adiponectin,zinc-α2-glycoprotein(ZAG)],adipogenesis [bone morphogenetic protein 4 (BMP4)] and other biological processes. However,a linkage between adipose tissue dysfunction and metabolic disorders needs further clarification. Altered expression or secretion of adipokines under adipose tissue dysfunction may contribute to a spectrum of obesity-associated diseases. Preclinical and clinical studies show that activating or inhibiting the signaling of specific adipokines could be an approach suitable to metabolic disease intervention. The current article reviews the effects of some adipokines on metabolism in order to deepen our understanding of the adipokines function.
Résumé
<p><b>OBJECTIVE</b>The expression of C/EBPalpha protein and mRNA during automatically activation process in primary cultures of HSCs were observed in order to explore its possible association with the proliferation and activation of HSCs.</p><p><b>METHODS</b>Immunocytochemistry, Western blot and RT-PCR were used to evaluated the expression of C/EBPalpha protein and mRNA; as well as the expression of alpha-SMA, Desmin, MMP2, type I procollagen (alpha1). The eukaryotic vector harboring the full length cDNA of C/EBPalpha was transfected into activated HSC, then immunocytochemistry was applied to confirm the transfection and evaluate the effect of transfection on the proliferation of HSC by calculating the PCNA-positive cells. The morphological changes of HSC were observed by use of phase-contrast microscope.</p><p><b>RESULTS</b>Constitutive expression of mRNA and protein of C/EBPalpha were detected in primarily cultured HSCs, and the protein was seen in both nuclei and cytoplasm with the latter being dominant. Their expression levels reached highest at day 2 of the culture, then decreased gradually when continually cultured to the day 4, 7, 10, on the other hand, the expression of alpha-SMA, MMP2 and ColI(alpha1) increased steadily. Transient transfection was verified by the fact that much more and stronger C/EBPalpha stain was observed in transfected HSCs than in void-vector transfected cells. In C/EBPalpha gene transfected HSCs, the number of PCNA-positive cells dramatically decreased compared with the void-vector transfected cells 24h after transfection. In addition, the C/EBPalpha gene transfected HSCs died 36 h after transfection, a few surviving cells became longer and thinner in morphology, however the void-vector transfected cells almost all remained alive.</p><p><b>CONCLUSIONS</b>C/EBPalpha was likely involved in the HSCs activation, and over-expressed C/EBPalpha by transfection had inhibitory influence on the proliferation of cultured rat HSCs.</p>