Evidence shows that
trimethylamine (TMA)/
trimethylamine-N-oxide (
TMAO) is closely related to
non-alcoholic fatty liver disease (
NAFLD). The conversion of TMA to
TMAO is mainly catalyzed by
flavin-containing
monooxygenases 3 (
FMO3) and
FMO1. In this study, we explored the role of TMA in the process of
NAFLD. The human
NAFLD liver
puncture data set GSE89632 and rat
TMAO gene chip GSE135856 was downloaded for gene differential expression analysis. Besides,
oleic acid (OA) combined with
palmitate were used to establish high-fat cell model. TMA,
TMAO and FMO1-siRNA were used to stimulate L02 cells. Contents of
free fatty acid (FFA),
triglyceride (TG),
TMAO,
FMO1 and unfolded protein response (UPR) related
proteins GRP78, XBP1, Derlin-1 were detected. Our results showed that
FMO1 and PEG10 were important in the progression of
NAFLD. Immunohistochemistry showed that
FMO1 in
NAFLD liver was increased. In addition, the contents of FFA, TG,
FMO1 expression, and
TMAO were significantly increased after OA + palmitate and TMA stimulation. However, after silencing
FMO1 with
siRNA, the expressions of these molecules were decreased. Besides, the
protein levels of
GRP78, XBP1, Derlin-1 were increased after
TMAO treatment (all P < 0.05). In Conclusion, high fat and TMA could induce the expression of
FMO1 and its metabolite
TMAO. When
FMO1 is silenced, the effects of high fat and TMA on
TMAO are blocked. And the role of
TMAO in
NAFLD may be through the activation of UPR.