title: Decreased activity of lecithin:cholesterol acyltransferase and hepatic lipase in chronic hypothyroid rats: implications for reverse cholesterol transport.
abstract: Chronic hypothyroidism is frequently associated with atherosclerosis due to increased cholesterol plasma levels; nevertheless, the contribution of impaired reverse cholesterol transport (RCT) in this process has not been completely elucidated. The aim of this study was to evaluate the effect of thyroidectomy (Htx) upon the main stages of RCT in rats. Plasma lipid alterations induced by thyroidectomy showed a slight, but significant, reduction of total plasma triglycerides, a 300% increase of LDL-cholesterol and a 25% decrease in HDL-cholesterol compared to control rats. We evaluated the first stage of RCT determining 3H-cholesterol efflux in Fu5AH cells. The capacity of HDL obtained from Htx rats to promote cholesterol efflux was similar to that of controls. Lecithin:cholesterol acyltransferase (LCAT) activity, the second stage and the driving force of RCT was 30% lower in Htx animals compared to controls, as determined by reconstituted HDL used as an external substrate. Lipoproteins are remodeled by hepatic lipase; the mean activity of this enzyme in postheparin plasma of Htx animals was reduced by 30% compared to controls, thus suggesting an impaired HDL remodeling by this enzyme in the hypothyroid status. In contrast, lipoprotein lipase activity in the Htx group was unchanged. In summary, this study demonstrates that chronic hypothyroidism in the rat induced an impaired RCT mainly at the cholesterol esterification, and HDL remodeling mediated by hepatic lipase. The latter probably results in an abnormal HDL structure, i.e. phospholipid enrichment, which contributes to decrease HDL-apo AI fractional catabolic rates.
authors.affiliation: Department of Nephrology, Instituto Nacional de Cardiología Ignacio Chávez, México.
authors.forename: Martha
authors.initials: M
authors.lastname: Franco
authors.forename: Graciela
authors.initials: G
authors.lastname: Castro
authors.forename: Luis
authors.initials: L
authors.lastname: Romero
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Regalado
authors.forename: Aida
authors.initials: A
authors.lastname: Medina
authors.forename: Claudia
authors.initials: C
authors.lastname: Huesca-Gómez
authors.forename: Serafín
authors.initials: S
authors.lastname: Ramírez
authors.forename: Luis F
authors.initials: LF
authors.lastname: Montaño
authors.forename: Carlos
authors.initials: C
authors.lastname: Posadas-Romero
authors.forename: Oscar
authors.initials: O
authors.lastname: Pérez-Méndez
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D002908:Chronic Disease; D007037:Hypothyroidism / Q000097:blood* / Q000201:enzymology* / Q000378:metabolism; D007863:Lecithin Cholesterol Acyltransferase Deficiency / Q000097:blood / Q000201:enzymology; D008049:Lipase / Q000097:blood / Q000172:deficiency*; D008055:Lipids / Q000097:blood; D008099:Liver / Q000378:metabolism; D008297:Male; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000097:blood*; D051381:Rats; D017208:Rats, Wistar; D013965:Thyroidectomy
chemical_list: D008055:Lipids; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase; D008049:Lipase