Surplus fatty acid synthesis increases oxidative stress in adipocytes and lnduces lipodystrophy.

Adipocytes are the primary sites for fatty acid storage, but the synthesis rate of fatty acids is very low. The physiological significance of this phenomenon remains unclear. Here, we show that surplus fatty acid synthesis in adipocytes induces necroptosis and lipodystrophy. Transcriptional activation of FASN elevates fatty acid synthesis, but decreases NADPH level and increases ROS production, which ultimately leads to adipocyte necroptosis. We identify MED20, a subunit of the Mediator complex, as a negative regulator of FASN transcription. Adipocyte-specific male Med20 knockout mice progressively develop lipodystrophy, which is reversed by scavenging ROS. Further, in a murine model of HIV-associated lipodystrophy and a human patient with acquired lipodystrophy, ROS neutralization significantly improves metabolic disorders, indicating a causal role of ROS in disease onset. Our study well explains the low fatty acid synthesis rate in adipocytes, and sheds light on the management of acquired lipodystrophy.

[Silencing MSH3 expression enhances cisplatin sensitivity of human tongue cancer cells].

OBJECTIVE: To explore the effect of MSH3 knock-down on sensitivity of tongue cancer cells to cisplatin. METHODS: Three small interfering RNA (siRNA) fragments targeting MSH3 CDS region were synthesized and transfected into CAL27 cells via Lipofectamine. Real-time PCR and Western blotting were used to assess the efficiency of MSH3 silencing. MTS, apoptosis staining and cell immunofluorescence assay were used to examine the cisplatin sensitivity, apoptosis and DNA repair of transfected CAL27 cells. RESULTS: s One of the 3 siRNAs was found to significantly reduce the expression of MSH3 protein in CAL27 cells (P<0.05). MTS assay showed that MSH3 silencing resulted in an significant reduction of IC50 of cisplatin from 21.32 to 13.95 µmol/L (P<0.05) and increased the apoptotic index of the exposed cells from 4.23∓1.27 to 11.32∓1.82 (P<0.05). Immunofluorescence assay demonstrated that silencing MSH3 markedly reduced the number of γ-H2AX foci. CONCLUSION: Silencing MSH3 can significantly increase cisplatin sensitivity of tongue cancer cells, the mechanism of which involves mainly attenuation of repair of DNA double-strand damage in the cells.