Recording-2025-02-07T07:06:16.035Z

Introduction to Lipid Lowering Medications

  • Purpose: To decrease cholesterol and triglyceride levels in the body.

  • Common Classes: Statins and fibrates.

  • Other Medications: Bile acid resins, niacin (Vitamin B3), ezetimibe, PCSK9 inhibitors.

Importance of Cholesterol

  • Function: Critical component of cell membranes and has roles in synthesizing steroid hormones, vitamin D, and bile.

  • Sources of Cholesterol:

    • Dietary: Obtained from food (e.g., fats from fries).

    • Endogenous: Synthesized by the liver.

Cholesterol Absorption and Transport

  • Process:

    1. Dietary fats and cholesterol are absorbed in the small intestine.

    2. They are packaged into lipoproteins (water-soluble) to be transported in the bloodstream.

  • Lipoproteins:

    • Chylomicrons: Largest and least dense; transport dietary cholesterol from intestines to lymphatic system and bloodstream.

Cholesterol Synthesis in the Liver

  • Mavalinate Pathway:

    • Begins with two acetyl CoA molecules joining via acetyl CoA acyl transferase to form four-carbon acetyl acetyl CoA.

    • Combined by HMG CoA synthase into HMG CoA (six-carbon).

    • HMG CoA reductase converts HMG CoA into mevalonate (rate-limiting step).

  • Outcome: Mevalonate is a precursor to cholesterol.

Lipoprotein Types and Functions

  • VLDL (Very Low-Density Lipoproteins):

    • Packaged with triglycerides and cholesterol; transport to body tissues.

    • After delivering triglycerides, they become LDL.

  • LDL (Low-Density Lipoproteins):

    • Smaller, denser; deliver cholesterol to peripheral tissues.

  • HDL (High-Density Lipoproteins):

    • Small but dense; transport excess cholesterol back to the liver.

    • Function: Opposes the role of LDL in cholesterol transport.

Implications of LDL Levels

  • Cholesterol Buildup:

    • Excess LDL leads to cholesterol accumulation in tissues, particularly the endothelium of blood vessels.

    • Results in the formation of plaques, increasing the risk of cardiovascular diseases (strokes, myocardial infarctions, peripheral vascular disease).

Miscellaneous Lipid Lowering Agents

1. Bile Acid Resins

  • Examples: Cholestyramine, Cholestopol, Cholesevelam.

  • Mechanism:

    • Bind to bile acids in the intestine, preventing their reabsorption.

    • Induces liver to produce more bile salts from cholesterol.

    • Increases LDL receptor numbers, enhancing LDL uptake and lowering cholesterol.

  • Use: Often combined with statins; primarily lower LDL.

  • Side Effects: Gastrointestinal upset, decreased absorption of fat-soluble vitamins (A, D, E, K).

2. Niacin (Vitamin B3)

  • Mechanism:

    • Inhibits lipoprotein lipase in adipose tissue, reducing free fatty acid release.

    • Leads to decreased VLDL and LDL levels.

    • Can moderately increase HDL.

  • Side Effects: Flushing (red face and itching), hyperglycemia, elevated uric acid levels.

3. Ezetimibe

  • Mechanism:

    • Blocks Niemann-Pick C1-like 1 (NPC1L1) protein, reducing cholesterol absorption in the intestine.

    • Does not affect VLDL or HDL levels.

  • Use: Typically combined with statins.

  • Side Effects: Gastrointestinal upset, rare liver damage.

4. PCSK9 Inhibitors

  • Examples: Ilyrolcumab, Evolocumab.

  • Mechanism:

    • Antibodies that bind PCSK9 protein, preventing degradation of LDL receptors.

    • Increases LDL receptor availability, reducing LDL levels in the bloodstream and moderately affecting VLDL and HDL.

  • Administration: Injection every 2-4 weeks.

  • Side Effects: Muscle pain, neurocognitive effects (delirium, dementia).

Conclusion

  • Significance: A vital role in managing cholesterol levels and preventing cardiovascular diseases through various mechanisms.

  • Combination Therapies: Often used together to enhance efficacy and target different pathways in lipid metabolism.