Although the role of
mechanistic target of rapamycin complex 1 (
mTORC1) in lipid metabolism has been the subject of previous research, its function in
chylomicron production is not known. In this study, we created three stable human colorectal
adenocarcinoma Caco-2 cell lines exhibiting normal, low, or high
mTORC1 kinase activity, and used these cells to investigate the consequences of manipulating
mTORC1 activity on enterocyte differentiation and
chylomicron-like particle production. Constitutively active
mTORC1 induced Caco-2 cell proliferation and differentiation (as judged by
alkaline phosphatase activity) but weakened transepithelial electrical resistance (TEER). Repressed
mTORC1 activity due to the knockdown of RPTOR significantly decreased the expression of lipogenic genes FASN, DGAT1, and DGAT2,
lipoprotein assembly genes
APOB and
MTTP, reduced
protein expression of
APOB,
MTTP, and FASN, downregulated the gene expression of very long-chain
fatty acyl-CoA ligase (FATP2),
acyl-CoA binding protein (
DBI), and prechylomicron transport vesicle-associated
proteins VAMP7 (
vesicle-associated membrane protein 7) and SAR1B (secretion associated
Ras related GTPase 1B) resulting in the repression of
apoB-containing
triacylglycerol-rich
lipoprotein secretion. Exposure of Caco-2 cells harboring a constitutively active
mTORC1 to
short-chain fatty acid derivatives, R-α-
lipoic acid and
4-phenylbutyric acid, downregulated
chylomicron-like particle secretion by interfering with the lipidation and assembly of the particles, and concomitantly repressed
mTORC1 activity with no change to Raptor abundance or PRAS40 (Thr246) phosphorylation. R-α-
lipoic acid and
4-phenylbutyric acid may be useful to mitigate intestinal
lipoprotein overproduction and associated postprandial
inflammation.