Alterations in thyroid status modulate apolipoprotein, hepatic triglyceride lipase, and low density lipoprotein receptor in rats.
The influence of altered thyroid state is investigated on plasma apolipoprotein-A-I (apo-A-I), apo-B, and apo-E levels and on apo-A-I, apo-A-II, apo-B, apo-E, hepatic triglyceride lipase (HTGL), and low density lipoprotein (LDL) receptor mRNA levels in rat liver and intestine. Plasma total cholesterol and triglycerides are unchanged in hyperthyroid rats. Liver apo-A-I mRNA levels increase 3-fold, whereas intestinal apo-A-I mRNA levels remain constant. Plasma apo-A-I levels almost double after L-T4. Liver apo-B and apo-E and intestinal apo-B mRNA levels are not influenced by L-T4, but plasma apo-B and apo-E decrease significantly. In the liver, apo-A-II mRNA levels decrease, whereas LDL receptor mRNA levels increase more than 50%. HTGL mRNA is not influenced by L-T4. N-Propyl-thiouracil-induced hypothyroidism does not influence plasma triglycerides, but plasma cholesterol levels nearly double. Liver and intestinal apo-A-I mRNA levels and plasma apo-A-I concentrations remain constant after propylthiouracil treatment. Accompanying the increase in plasma apo-B, liver and intestinal apo-B mRNA concentrations rise by approximately 100% and 40%, respectively. Plasma apo-E increases nearly 2-fold, but liver, apo-A-II mRNA rises, whereas HTGL and LDL receptor mRNA levels decrease 20% and nearly 50%, respectively. In conclusion, thyroid hormones regulate rat apo-A-I and apo-A-II gene expression in opposite directions. Furthermore, the LDL receptor is regulated at the mRNA level, whereas HTGL gene expression is relatively resistant to alterations in thyroid status.
Staels
B
B
Laboratorium voor Experimentele Geneeskunde en Endocrinologie, Katholieke Universiteit, Leuven, Belgium.
Van Tol
A
A
Chan
L
L
Will
H
H
Verhoeven
G
G
Auwerx
J
J
D000818:Animals; D001053:Apolipoproteins / Q000097:blood / Q000235:genetics*; D005786:Gene Expression Regulation; D006980:Hyperthyroidism / Q000378:metabolism*; D007037:Hypothyroidism / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D008049:Lipase / Q000235:genetics*; D008055:Lipids / Q000097:blood; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D009693:Nucleic Acid Hybridization; D011441:Propylthiouracil; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011973:Receptors, LDL / Q000235:genetics*; D013974:Thyroxine
D001053:Apolipoproteins; D008055:Lipids; D012333:RNA, Messenger; D011973:Receptors, LDL; D011441:Propylthiouracil; D008049:Lipase; D013974:Thyroxine