Deleted in breast cancer–1 regulates SIRT1 activity and contributes to high-fat diet–induced liver steatosis in mice
Carlos Escande, … , Zhenkun Lou, Eduardo Nunes Chini
Carlos Escande, … , Zhenkun Lou, Eduardo Nunes Chini
Published January 11, 2010
Citation Information: J Clin Invest. 2010;120(2):545-558. https://doi.org/10.1172/JCI39319.
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Research Article Aging

Deleted in breast cancer–1 regulates SIRT1 activity and contributes to high-fat diet–induced liver steatosis in mice

Abstract

The enzyme sirtuin 1 (SIRT1) is a critical regulator of many cellular functions, including energy metabolism. However, the precise mechanisms that modulate SIRT1 activity remain unknown. As SIRT1 activity in vitro was recently found to be negatively regulated by interaction with the deleted in breast cancer–1 (DBC1) protein, we set out to investigate whether DBC1 regulates SIRT1 activity in vivo. We found that DBC1 and SIRT1 colocalized and interacted, and that DBC1 modulated SIRT1 activity, in multiple cell lines and tissues. In mouse liver, increased SIRT1 activity, concomitant with decreased DBC1-SIRT1 interaction, was detected after 24 hours of starvation, whereas decreased SIRT1 activity and increased interaction with DBC1 was observed with high-fat diet (HFD) feeding. Consistent with the hypothesis that DBC1 is crucial for HFD-induced inhibition of SIRT1 and for the development of experimental liver steatosis, genetic deletion of Dbc1 in mice led to increased SIRT1 activity in several tissues, including liver. Furthermore, DBC1-deficient mice were protected from HFD-induced liver steatosis and inflammation, despite the development of obesity. These observations define what we believe to be a new role for DBC1 as an in vivo regulator of SIRT1 activity and liver steatosis. We therefore propose that the DBC1-SIRT1 interaction may serve as a new target for therapies aimed at nonalcoholic liver steatosis.

Authors

Carlos Escande, Claudia C.S. Chini, Veronica Nin, Katherine Minter Dykhouse, Colleen M. Novak, James Levine, Jan van Deursen, Gregory J. Gores, Junjie Chen, Zhenkun Lou, Eduardo Nunes Chini

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Figure 3

DBC1 controls glucose-dependent SIRT1 activity in human hepatocytes.

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DBC1 controls glucose-dependent SIRT1 activity in human hepatocytes. (A)...
(A) HEPG2 cells were transfected with DBC1 siRNA, DBC1 siRNA plus control siRNA, and DBC1 siRNA plus SIRT1 siRNA. NAD-dependent SIRT1 activity was measured, and expressed as a percentage of control (nonspecific siRNA). The efficiency of transfection was confirmed by Western blot. (B) HEPG2 cells were transfected with DBC1 siRNA and DBC1; 5 mM nicotinamide was added 16 hours before fixation. Endogenous p53 acetylation levels were studied by immunofluorescence. Original magnification, ×600. (C) HEPG2 cells were cultured in serum-free media for 24 hours and then incubated for 24 hours in low (5 mM) or high (30 mM) glucose. SIRT1 activity was expressed in AFUs. n = 3. *P < 0.05, t test. (D) SIRT1 activity in HEPG2 cells transfected with DBC1 siRNA and then treated with high and low glucose as described in C. SIRT1 activity measured with DBC1 siRNA was normalized to the respective controls (nonspecific siRNA transfection) with high and low glucose. Data are shown as percent increase in SIRT1 activity over the respective controls (with high or low glucose, set as 100%). The fluorescence values in the control siRNA condition corresponded to 73 and 154 AFUs for cells in high and low glucose, respectively. Shown is 1 representative experiment of 3. The siRNA transfection efficiency was confirmed by Western blot. Except where indicated, data are mean ± SD.