The Effect Of Native And Oxidized High Density Lipoprotein On The Transcription Of MSRG In HepG2 Cells

A novel gene was cloned and temporarily named as metabolism syndrome-related gene (MSRG). To understand the relationship between MSRG and MS and the function of MSRG, our lab has been doing series of studies on the factors which can affect the transcription of MSRG. In the present study, we firstly established the method for quantification of the mRNA level of MSRG in HepG2 cells and found that MSRG, compared with the mRNA level ofβ-actin, was a lowly transcribed gene. Then, we investigated the effects of native high density lipoprotein (N-HDL) and oxidized high density lipoprotein (OX-HDL) on the transcription of MSRG in HepG2 cells. When HepG2 cells were incubated with 0mg/L, 25mg/L, 50mg/L, and 100mg/L of N-HDL or 0mg/L, 25mg/L, and 50mg/L of OX-HDL, the transcription of MSRG in the cells had a tendency to decrease with the increase of the lipoproteins. Compared with that in the cells incubated with 0mg/L of N-HDL, the transcription level was significantly decreased in the cells that were incubated with 50mg/L and 100 mg/L of N-HDL (p＜0.05). There was also a significant decrease of the transcription of MSRG in HepG2 cells, which were incubated with 25mg/L and 50mg/L OX-HDL, compared with that in cells incubated with 0mg/L of OX-HDL. Although not significantly, when compared with that in cells incubated with 100mg/L N-HDL, the transcription level was increased in the cells incubated by 200mg/L of N-HDL. The transcription in the cells incubated with 100mg/L or 200mg/L of OX-HDL was higher than that in cells incubated with 50mg/L of OX-HDL(p＜0.05). Incubated with 100mg/L N-HDL for Oh, 6h, 12h, and 24h or with 100mg/L OX-HDL for Oh, 6h, and 12h, the cells had a decreasing tendency to transcribe MSRG. The transcription in the cells, cultured by N-HDL for 6h, 12h, 24h, and 36h, was lower than that in cells incubated by N-HDL for 0h(p＜0.05). Compared with that in the cells cultured by OX-HDL for Oh, the transcription was decreased in the cells incubated with OX-HDL for 6h and 12h(p＜0.05). Between the cells incubated with N-HDL for 36h and exposed to N-HDL for 24h, the difference of MSRG transcription was not significant(p＞0.05). The transcription was significantly increased in the cells incubated with OX-HDL for 24h and 36h, compared with that in cells cultured by OX-HDL for 12h(p＜0.05). After incubation with 100mg/L N-HDL or OX-HDL for 12h separately, the levels of MSRG in the cells incubated with N-HDL or OX-HDL were decreased significantly compared with control (p＜0.05). The transcription of MSRG in the cells between the N-HDL and OX-HDL groups were not significant. In the medium, the levels of total cholesterol and triglyceride in N-HDL group and the level of total cholesterol in OX-HDL group were increased compared with control (p＜0.05). The levels of glycogen, total cholesterol, and triglyceride in cells were not significantly changed among control, N-HDL, and OX-HDL groups.The results suggest that both N-HDL and OX-HDL can influence the transcription of MSRG in HepG2 cells. When incubated with N-HDL or OX-HDL, the transcription of MSRG had a tendency to decrease with the increasing of lipoprotein concentration and length of lipoprotein incubation time. After reaching the lowest level, the transcription of MSRG had a tendency to increase with the continuous rising of lipoprotein concentration and incubation time. The ability of N-HDL to inhibit the transcription of MSRG was stronger than OX-HDL.