Chemistry of Lipids

Study Notes

Lipids can be classified into triacylglycerol, phospholipids, and cholesterol.
Free fatty acids can be found in tissues and are transported in serum bound to the protein albumin.

Eicosanoids are chemical messengers synthesized in the cells where their physiological activity is expressed.
Prostaglandins are among the most potent biological substances known, with slight structural differences giving them highly distinct biological effects.
Prostaglandins can induce smooth muscle contraction, lower blood pressure, and contribute to the inflammatory response.
Aspirin and other nonsteroidal anti-inflammatory agents inhibit the synthesis of prostaglandins by inhibiting cyclooxygenase.
Thromboxane stimulates constriction and clotting of platelets, while prostacyclin has the opposite effect, promoting vasodilation and inhibiting platelet aggregation.
Certain prostaglandins are involved in the induction of labor and other reproductive processes.
Leukotrienes promote constriction of bronchi associated with asthma.

HDL (good cholesterol) carries cholesterol from tissues to the liver.
Chylomicrons carry dietary triacylglycerols from the intestine.
LDL (bad cholesterol) carries cholesterol from the liver to tissues.
Lipoprotein(a) (Lp(a)) is structurally and metabolically distinct from other lipoproteins, with prothrombotic, proinflammatory, and proatherogenic properties.
High plasma concentrations of Lp(a) are associated with an increased risk of cardiovascular diseases.

Cholesterol is a derived lipid, formed from acetyl-CoA, with 27 carbon atoms.
Vitamin D is formed from 7-dehydrocholesterol when exposed to ultraviolet radiation.
Bile acids are formed in the liver and are composed of 80% cholesterol.
Adrenocortical hormones and sex hormones are steroid hormones formed from cholesterol.

Excess oxidized LDL leads to the formation of fatty streaks (foam cells) in the subintimal space.
Foam cells separate endothelial cells, exposing them to blood, which leads to plaques and thrombus formation.
Thrombus formation can lead to complete occlusion of the lumen, eventually causing acute myocardial infarction (AMI) or cerebrovascular accident (CVA).