| Nerve growth factor (NGF) is discorvered by Rita Levi-Montalcini in the early 1950's. Substantial evidence has accumulated that NGF not only plays an important role in neurotrophin but also acts on non-neuronal cells. Today , the action of NGF on non-neuronal cells have the focus of people's attention. Recently, some studies have demonstrated that NGF is synthesized and released by white adipose tissue. White adipose tissue is an active endocrine organ secreting a wide range of hormones and other protein factors, collectively referred to as adipokines. And adipokines play an important role in obesity and related diseases. In addition, studies have indicated that NGF may inhibit appetite centrally. Thus we speculate that NGF may play a role in obesity.Excessive fuel is stored within adipocyte in the form of triacylglycerols when energy balance is negative, which results in obesity. In the cellularity, it appears that the number of adipocyte increases and cell volume extends. Preadipocytes in the adipose tissue have the potential to proliferate and differentiate into mature adipocyte. It is recognized that the excessive proliferation and differentiation of preadipocyte is a significant part in obesity. 3T3-L1 is a preadipocyte line which is origin of the embryo of Swiss mice. 3T3-L1 preadipocyte line can differentiate into mature adipocyte and simulate the function of adipose tissue in vivo, thus it is applied extensively. Study has demonstrated that NGF expression is examined in 3T3-L1 preadipocyte before and after the induction of differentiation into adipocyte, and the rate of expression falls markedly after induction, being lowest at days 2 and 4 postinduction. Therefore we speculate that NGF may involve in proliferation and differentiation of 3T3-L1 preadipocyte.In this study, we detecked the expression of NGFmRNA in hypothalamus , brain stem and adipose tissue of obese rats by RT-PCR and observed the effect of NGF on proliferation and differentiation of 3T3-L1 cells to study the relation between NGF and obesity.In first part, obese rat models were established by feeding high-fat diet to SD rats for 16 weeks. Most of rats were proved to develop obesity by detecting weight, Lee's index and serum lipid. NGFmRNA was detected by RT-PCR in brain (hypothalamus, brain stem) and the major white adipose tissue depots (subcutaneous, omental, perirenal, epididymal) of rats. The result was that there was no different production of NGFmRNA in hypothalamus and brain stem in two groups (P>0.05); NGFmRNA production of four adipose tissue was higher in obese rats than in control rats (P<0.05, P<0.01).In second part, 3T3-L1 preadipocyte were cultured with increasing concentrations of NGF (0, 10μg/L, 100μg/L, 1000μg/L) and after 48h cell proliferation was determined by MTT spectrophotometry. The results showed that the absorbance at 490nm of 3T3-L1 preadipocyte decreased by 17.4%, 26.1%, 34.7% (P<0.01) in the groups of 10μg/L, 100μg/L, 1000μg/L NGF. Differentiation of the cells was initiated after confluence by incubation for 2 days in culture medium containing 0.5mmol/L 3-isobutyl-1-methylxanthine, 1.0μmol/L dexamethasone, 10mg/L insulin and increasing concentrations of NGF (0, 10μg/L, 100μg/L, 1000μg/L). At day 8 postinduction, cell differentiation was determined by Oil Red O staining. The result showed that the lipid droplet content of cell in 10μg/L, 100μg/L, 1000μg/L NGF group was about 58%, 56%, 52% respectively as much as control group(P<0.001).The study indicates that NGF may correlate with obesity, and may inhibit the development of obesity. |
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