Lipid Structure, Lipoprotein Transport, and Bile Acid Metabolism

Vocabulary practice flashcards covering lipid classes, bile acids and salts, apolipoproteins, lipoprotein metabolism, and dyslipidemia pharmacology.

Cholesterol

An endogenous, highly lipophilic lipid with a $\log(P)$ of $7.4$ and water solubility $<1\,\text{mg/L}$, present in blood up to $2\,\text{g/L}$, which functions in membrane structure, signaling, and bile acid synthesis.

Cholesteryl esters

A hydrophobic endogenous lipid class formed by attaching a variable fatty-acyl group to the hydroxyl group of cholesterol via an ester bond, making up $45\text{--}50\%$ of LDL particles.

Triglyceride

An endogenous lipid composed of glycerol esterified with three fatty acids, synthesized from glycerol 3-phosphate and acyl-CoA, and stored in adipose-cell cytosol as concentrated energy stores.

Phosphatidylcholine

An amphipathic phospholipid containing glycerol, two fatty-acyl groups, phosphate, and choline that forms lipid bilayers in cell membranes and monolayers on lipoprotein surfaces.

Cholic acid

One of the two major primary bile acids in humans (calculated $\log(P) = 3.0$), synthesized from cholesterol via 7-alpha-hydroxylase and conjugated to glycine or taurine.

Chenodeoxycholic acid

One of the two major primary bile acids in humans with a calculated $\log(P)$ of $4.1$, synthesized from cholesterol and converted to conjugated bile acids via amide linkages with glycine or taurine.

Glycocholate

The ionized glycine conjugate of cholic acid joined by an amide bond (calculated $\log(P) = 1.9$), identified as the major bile salt in human bile.

Taurocholate

The ionized taurine conjugate of cholic acid joined by an amide bond (calculated $\log(P) = 1.6$), characterized as a minor bile salt in human bile.

7-alpha-hydroxylase

The hepatic enzyme responsible for converting cholesterol to primary bile acids; it is regulated by negative feedback inhibition from returning bile salts.

Enterohepatic circulation

The pathway in which bile salts stored in the gallbladder and secreted into the small intestine are reabsorbed and returned to the liver through the portal vein.

Reverse cholesterol transport

The cardioprotective process mediated by HDL in which excess cholesterol is transported from extrahepatic peripheral tissues back to the liver.

LCAT (Lecithin-cholesterol acyl transferase)

An enzyme that participates in the esterification of free cholesterol into cholesteryl esters within HDL particles.

CETP (Cholesteryl ester transfer protein)

A plasma protein that mediates the transfer of cholesteryl esters between lipoproteins; its inhibition results in increased circulating HDL.

ApoB-100

The apolipoprotein recognized by hepatic LDL receptors to mediate the receptor-mediated endocytosis of LDL from the blood into the liver.

ApoC-II

An apolipoprotein essential for lipoprotein lipase recognition and activation; its deficiency results in hypertriglyceridemia.

ApoC-III

An apolipoprotein whose elevated levels are associated with the inhibition of lipoprotein lipase and its translation.

ApoE

An apolipoprotein whose defect hinders the catabolism of chylomicrons and VLDL, leading to elevations in both triglycerides and cholesterol.

Statins

A class of pharmaceutical agents that lower circulating cholesterol by directly blocking de novo cholesterol biosynthesis in the liver.

Ezetimibe

A drug that reduces plasma cholesterol levels by preventing dietary cholesterol absorption in the intestine.

Bile acid sequestrants

Therapeutic agents that bind bile salts in the intestine to prevent their reabsorption, thereby interrupting enterohepatic circulation.

PCSK9 inhibitors

Therapeutic agents that increase hepatic LDL receptor density to enhance LDL clearance from the bloodstream.

Fibrates

Lipid-lowering agents indicated in transport pathways to promote triglyceride hydrolysis.

Niacin

A lipid-modifying agent that lowers triglycerides by inhibiting lipolysis within adipose tissue.

Chylomicrons

Large lipoprotein particles composed of $80\text{--}95\%$ triglycerides that deliver dietary fats from the intestine, yielding remnants taken up by the liver.

Histamine

A supplemental chemical structure presented in Structure Card 09 for which no specific mechanisms, uses, or brands were supplied in the slides.