Abstract Silkworm (Bombyx mori) 30K proteins are the major protein in the fifth instar larval hemolymph and possess multiple biological functions, such as inhibiting cell apoptosis induced by peroxide, virus or chemically and apolipoprotein functions. As a kind of insect apolipoprotein, they can bind with lipids and transport lipids inside insect larval hemolymph. Therefore it's very likely that silkworm 30K protein also has a similar function in mammalian cells, but it has not been reported so far. In order to study the effect of silkworm 30K apolipoprotein on lipid metabolism in mammalian cells, oleic acid (OA) and palmitic acid (PA) (OA∶PA=2∶1) solution was used to induce the normal human (Homo sapiens) liver cell line L-02 for 24 h to establish the fatty liver cell model in vitro. Then, the model was used to analyze the effects of these two kinds of silkworm 30K proteins, 30Kc6 and Lip-19G1, on lipid accumulation in liver cells. In order to understand the prevention function of these two proteins on lipid accumulation in liver cells, the normal liver cells were pretreated with 30Kc6 or Lip-19G1 protein before induction and then the cells were used to detect the lipid droplets IOD (integral optical density) value intracellular/total cell area by oil red O staining. The results showed that there was significant difference between 30Kc6 pretreatment group with control group (P＜0.05). However, there was no difference between Lip-19G1 pretreatment group with control groups. Morever, in order to understand the treatment effects of these two proteins on lipid accumulation in the fatty liver cells, the fatty liver cells were treated with 30Kc6 or Lip-19G1 protein, respectively. The fatty liver cells with 30Kc6 or Lip-19G1 protein treatment, the lipid droplets IOD value intracellular/ total cell area all reduced significantly compared with the cells without treatments (P＜0.01). These results showed that 30Kc6 had a certain inhibitory effects on the accumulation of lipid in human hepatic cells. Meanwhile, both 30Kc6 and Lip-19G1 proteins, could also reduce the accumulation of lipid droplet in fatty liver cells model. Therefore, this study will provide basic information for further study on the 30K apolipoprotein function and theoretical basis for new type of cholesterol drugs development.
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