| Adipose tissue has long been considered to be a passive, inactive tissue. However, it is now widely accepted that adipose tissue secretes a number of peptide hormones including leptin, tumor necrosis factor-alpha (TNF-α), adiponectin and resistin etc, which affect insulin action and energy homeostasis. These newly discovered functions have changed our view that adipose tissue is no longer considered only as an energy storage tissue but as a major endocrine organ.TNF-α is a multifunctional cytokine. TNF-α exists as a 26kDa membrane-bound precursor(mTNF-α), which can be processed at the cell surface by a TNF-α-converting enzyme (TACE) to genernate a 17-kDa soluble form (sTNF-α). Much effort has been focused recently on understanding the role of tumor necrosis factor-a (TNF-α) in regulating fat metabolism and insulin action in rodents and humans, however, there are few reports in domestic animals. Furthermore, to my knowledge, previous few studies distinguished the functions of mTNF-α from that of sTNF-α.Resistin is a member of the newjy discovered cysteine-rich secretory protein family. Some studies demonstrated that resistin had an inhibitory effect on adipose conversion. Therefore, resistin is speculated to be a feedback regulator of adipogenesis and a signal to restrict adipose tissue formation. It is just a start about the study of resistin actions, in particular about the relationship between resistin and lipolysis pathway.In the present study, we employ genetically obese and lean pigs as subjects. Through semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) and Western blotting analysis, we performed the following studies: firstly, we determined the levels of TNF-a expression in adipose tissue of different growth-stage genetically lean and obese pigs; secondly, to analyze whether the expression patternbetween TNF-α receptor (TNFR) or TACE and TNF-α is consistent or not, we examined the levels of TNF-α receptor (TNFR) and TACE in adipose tissue or other tissues from different growth-stage pigs; thirdly, to study the relationship among mTNF-α, sTNF-α and TACE as well as the relationship between them and fat deposition, we analyzed the changes of the levels of mTNF-α, sTNF-α and TACE in adipose tissue from feeding-restricted group(FR) and control group(C); fourthly, to know the characteristic of resistin expression in pigs, we determined the levels of resistin mRNA and protein in adipose tissue of different growth-stage genetically lean and obese pigs; fifthly, to understand the relationship between resistin and fat deposition, we examined the adipose amount of resistin at different time points of feeding restriction for pigs;sixthly, to know whether TNF-α and resistin regulate lipolysis via cAMP pathway, we analyzed the variations of TNF-α and resistin as well as some parameters associated with lipolysis pathway after body-weight reduction in feeding-restricted obese pigs; finally, we localized resistin expression in the cell types from pig adipose tissue.On basis of the results of our experiments, we draw a few following conclusions: 1) TNF-α, TNFR, TACE and resistin could be expressed in adipose tissue of pigs, furthermore, the levels of their expression were positively associated with fat deposition; 2) The decrease of fat deposition result in the reduction of TNF-α and resistin as well as some parameters associated with lipolysis pathway, suggesting the possible association between the two adipocytekines and lipolysis pathway; 3) TACE might play the important regulation in the ratio of mTNF-α to sTNF-α; 4) resistin was expessed not only in adipocytes but also in non-fat cells, indicating other biology actions of resistin.
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