Rats subcutaneously implanted with AH109A
hepatoma cells show
hyperlipidemia with high concentrations of serum
triglyceride and nonesterified
fatty acid, suppression of
lipoprotein lipase (LPL), and elevation of
hormone-sensitive lipase (HSL) activities during the growth of the
hepatoma. Supplementation of the diet with
sulfur amino acids such as
L: -methionine (Met) and
L: -cystine (Cys) improved
hyperlipidemia by restoring LPL and HSL activities. In the present study, we have attempted to examine the effects of
sulfur amino acids on the activity and
mRNA level of LPL and the activity of HSL using 3T3-L1 cells, which are known to differentiate to adipocytes. The adipocytes were incubated with various concentrations of Met, Cys or
L: -cysteine (CysH) in the absence or presence of
tumor necrosis factor-alpha (
TNF-alpha). LPL activity was suppressed by
TNF-alpha. In the absence of
TNF-alpha, Met, Cys and CysH did not change the LPL activity. In the presence of
TNF-alpha, Met and Cys significantly increased the LPL activity, and Met also enhanced the LPL
mRNA level. HSL activity was also suppressed by
TNF-alpha. In the absence of
TNF-alpha, Met enhanced the HSL activity. In the presence of
TNF-alpha, Met, Cys and CysH suppressed the HSL activity.
Sulfur amino acids such as Met, Cys and CysH affected the LPL activity,
mRNA level, and HSL activity in 3T3-L1 adipocytes. Some of these effects of
sulfur amino acids were different between LPL and HSL, between the absence and the presence of
TNF-alpha, and between 3T3-L1 adipocytes and the adipose tissue from rats.