Sirtuin 1 (
SIRT1) has been reported to protect against
nonalcoholic fatty liver disease (
NAFLD) development. The mechanism of how
SIRT1 deacetylase activity affects
NAFLD has not been well investigated. The current investigation addressed the causal effect of systemic
SIRT1 activity on
NAFLD development and the underlying mechanism involved in both liver and mesenteric adipose tissue (MAT). Both
SIRT1 homozygous mice ablated the catalytic activity (sirt1Y/Y) and their corresponding wild type littermates (WT) were fed a high fat diet (HFD, 60% calories from fat) for 34weeks. Sirt1Y/Y mice showed significantly higher level of hepatic
triglyceride which was accompanied with higher levels of SREBP-1 and SCD1and decreased phosphorylation of LKB1 and AMPK in the liver. Compared with WT mice,
mRNA expression of lipogenic genes (lxrα,
srebp-1c, scd1 and fas) in the MAT increased significantly in sirt1Y/Y mice.
Fatty acid oxidation
biomarkers (acox1, acox3,
cpt, ucp1,
sirt3) in both liver and MAT were comparable between groups. Interestingly, we observed that in sirt1Y/Y mice, the
mRNA level of
hormone sensitive lipase (hsl), adipose
triglyceride lipase (atgl) and
perilipin-2 (plin-2), all involved in lipolysis, significantly increased in MAT, but not in epididymal adipose tissue. These changes positively correlated with circulating
free fatty acid (FFA) concentrations and higher hepatic
mRNA expression of cd36 for FFA uptake. The present study has provided novel evidence to suggest that under HFD-induced metabolic surplus, the lack of
SIRT1 catalytic activity promotes release of FFA from MAT and escalate
NAFLD by interfering with
lipid homeostasis in both liver and MAT.