L-carnitine and taurine synergistically inhibit the proliferation and osteoblastic differentiation of vascular smooth muscle cells.
OBJECTIVE
To investigate the synergistic action of L-carnitine (LC) and taurine (TAU) on the proliferation and osteoblastic differentiation of vascular smooth muscle cells (VSMCs).


METHODS
DNA and protein synthesis of VSMCs were assessed using scintillation counting. Alkaline phosphatase (ALP) activity and calcium content were determined to investigate the effects of LC and TAU on the osteoblastic differentiation and mineralization of VSMCs. TAU uptake by VSMCs was assayed. RNA interference was used to down-regulate the expression of the TAU transporter (TAUT) in rat VSMCs.


RESULTS
LC and TAU synergistically inhibited the proliferation and beta-glycerophosphate (beta-GP)-induced osteoblastic differentiation of VSMCs as evidenced by the decreased [(3)H]thymidine incorporation, ALP activity and calcium deposition. Furthermore, LC stimulated the TAU uptake and TAUT expression in VSMCs. Suppression of TAUT with short hairpin RNA (shRNA) abolished the synergistic action of LC and TAU in VSMCs.


CONCLUSIONS
The synergistic inhibitory action of LC and TAU on the proliferation and osteoblastic differentiation of VSMCs is attributable to the up-regulation of TAUT expression and TAU uptake by LC.
Institute of Metabolism and Endocrinology, the Second Xiang-Ya Hospital, Central South University, Changsha, China.
Hui
H
Xie
Bing
B
Yang
Xin-min
XM
Zhou
Feng-lin
FL
Song
Jian-ming
JM
Li
Kang
K
Zhou
Wen
W
Hu
Yi-qun
YQ
Peng
Si-yuan
SY
Tang
Ling-qing
LQ
Yuan
Si-yuan
SY
Xiong
Xiao-bo
XB
Liao
D000818:Animals; D050197:Atherosclerosis / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002331:Carnitine / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007930:Leucine / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology; D051381:Rats; D013654:Taurine / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D000099247:Taurine Transporters
D002118:Calcium; D002331:Carnitine; D004247:DNA; D007930:Leucine; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D013654:Taurine; D013936:Thymidine; D000099247:Taurine Transporters