Etiologic significance of defects in cholesterol, phospholipid, and bile acid metabolism in the liver of patients with intrahepatic calculi

Abstract

Intrahepatic calculi, highly prevalent in the Far East, including Japan, are characterized clinically by chronic proliferative cholangitis with frequent stone recurrences. Intrahepatic calculi consist of 2 groups, i.e., brown pigment stones, including a high cholesterol content, and cholesterol stones, with the former predominating. To gain insights into the pathogenesis of intrahepatic calculi, cholesterol and bile acid biosynthesis, as well as alterations in intracellular transport and/or canalicular secretion of phospholipid and bile acid were investigated in liver of patients with intrahepatic calculi. Enzyme activities of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase were increased (12.8 ؎ 1.9 pmol/min/mg protein, mean ؎ SEM vs. 5.5 ؎ 0.4 in controls; P < .01) and cholesterol 7␣-hydroxylase activities were decreased (1.3 ؎ 0.4 vs. 4.9 ؎ 0.6; P < .01) in liver specimens of patients with brown pigment stones. In addition, messenger RNA (mRNA) levels of multidrug resistance P-glycoprotein 3 (MDR3 Pgp) and phosphatidylcholine transfer protein (PCTP) were markedly low in the liver specimens compared with the levels in specimens of control subjects, gallbladder stone patients, and patients with obstructive cholestasis. The protein levels and the immunohistochemical staining were decreased for MDR3 Pgp and PCTP in the liver. Consistently, the concentrations of phospholipid were markedly reduced in the hepatic bile from both affected and unaffected hepatic segments. In patients with intrahepatic calculi, biliary cholesterol supersaturation and the formation of cholesterol-rich brown pigment as well as cholesterol stones may be attributed to decreased hepatic transport and biliary secretion of phospholipids, in the setting of increased cholesterogenesis and decreased bile acid synthesis. (HEPATOLOGY 2001;33:1194-1205

Interacting Proteins Dictate Function of the Minimal START Domain Phosphatidylcholine Transfer Protein/StarD2

“…The Them2 antibody was described above, and a rabbit anti-human PC-TP antibody was previously described (19). HEK 293T cells were rinsed three times with PBS and fixed for 20 min in 4% paraformaldehyde.…”

Impaired response of biliary lipid secretion to a lithogenic diet in phosphatidylcholine transfer protein-deficient mice

“…Liver cytosol was prepared by homogenizing 300 mg of tissue in ice-cold buffer containing 0.25 M sucrose, 10 mM Tris, pH 7.35, 1 mM EDTA, 5 mM DTT, and Complete™ protease inhibitor (Roche, Indianapolis, IN). Samples were then centrifuged at 100,000 g for 1 h at 4 Њ C. Equal amounts of cytosolic proteins (75 g) were subjected to SDS-PAGE, transferred onto nitrocellulose membranes, and probed using a polyclonal antibody to PC-TP (21). Visualization was by enhanced chemiluminescence using goat anti-rabbit horseradish peroxidase-conjugated secondary antibody (Bio-Rad, Hercules, CA).…”

A polymorphism in New Zealand inbred mouse strains that inactivates phosphatidylcholine transfer protein

“…Egg yolk PC, brain phosphatidylserine (PS) and bovine heart cardiolipin were from Avanti Polar Lipids (Alabaster, AL). L L-a-1-Palmitoyl-2-linoleoyl-[linoleoyl- [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C] PC (50 mCi/mmol) was from NEN Life Science Products (Boston, MA) and [1a,a(n)- 3 H] and cholesteryl oleate (44 Ci/mmol) was from Amersham Biosciences (GE Healthcare Bio-Sciences Corp., Piscataway, NJ).…”