Lipid Profile and Cardiovascular Risk

Lipoproteins & Metabolism - Fat Shuttles & Cycles

• Lipoproteins: Lipid carriers (Triglycerides - TG, Cholesterol).
  • Chylomicrons (CM): Dietary TG transport. Key Apos: B-48, C-II, E.
  • VLDL: Endogenous TG transport. Key Apos: B-100, C-II, E.
  • IDL: VLDL remnant, LDL precursor. Key Apos: B-100, E.
  • LDL: Cholesterol to tissues ("Bad"). Key Apo: B-100.
  • HDL: Reverse cholesterol transport ("Good"). Key Apo: A-I.
• Key Players & Pathways:
  • LPL (Lipoprotein Lipase): TG hydrolysis in CM/VLDL; activated by ApoC-II.
  • LCAT (Lecithin-Cholesterol Acyltransferase): HDL maturation; activated by ApoA-I.
  • CETP (Cholesteryl Ester Transfer Protein): Exchanges CE for TG between HDL & VLDL/LDL.
  • ApoE: Ligand for hepatic uptake of CM remnants & IDL.

⭐ ApoE4 isoform: linked to ↑LDL-C, accelerated atherosclerosis, and ↑Cardiovascular Disease (CVD) risk. ApoE2 is associated with Type III hyperlipoproteinemia; ApoE3 is common/neutral.

Lipid Profile Components - Decoding the Numbers

• Total Cholesterol (TC): Overall cholesterol. Desirable: <200 mg/dL.
• LDL-C (Low-Density Lipoprotein Cholesterol): "Bad" cholesterol. Optimal: <100 mg/dL.
  • Calculated by Friedewald formula: $LDL‑C = TC - HDL‑C - (TG/5)$ mg/dL (if TG <400 mg/dL).
• HDL-C (High-Density Lipoprotein Cholesterol): "Good" cholesterol. Protective: >60 mg/dL. Low (risk factor): <40 mg/dL.
• Triglycerides (TG): Normal: <150 mg/dL.
• VLDL-C (Very Low-Density Lipoprotein Cholesterol): Estimated as $TG/5$ mg/dL.
• Non-HDL Cholesterol: $TC - HDL‑C$. Secondary target. Desirable: <130 mg/dL.

⭐ Friedewald Formula Inaccuracy: Not valid if Triglycerides (TG) >400 mg/dL, chylomicrons present (non-fasting sample), or in Type III dyslipidemia (dysbetalipoproteinemia).

Dyslipidemias & Atherogenesis - When Lipids Rebel

• Dyslipidemia: Abnormal blood lipid concentrations (↑LDL-C, ↑Total Cholesterol, ↑Triglycerides, ↓HDL-C) that are key drivers for atherosclerosis.
  • Classified as Primary (genetic, e.g., Familial Hypercholesterolemia) or Secondary (due to lifestyle, diabetes, hypothyroidism, nephrotic syndrome).
  • Desirable Levels: LDL-C < 100 mg/dL (ideal < 70 or < 55 for very high-risk); HDL-C > 40 (Men) / > 50 (Women) mg/dL; Triglycerides < 150 mg/dL.
• Atherogenesis: The step-wise pathological process of plaque formation within arterial walls.

![Atherosclerotic plaque development stages](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Biochemistry_Clinical_Biochemistry_Lipid_Profile_and_Cardiovascular_Risk/dc491909-4ede-4af5-84d5-59acf4676acb.png)
> ⭐ Lp(a), or Lipoprotein(a), is an independent, genetically determined risk factor for atherosclerotic cardiovascular disease (ASCVD), enhancing both atherogenesis and thrombotic risk.

CVD Risk & Management (India Focus) - Guarding the Heart

• Key Risk Factors (India Specific):
  • Modifiable: Dyslipidemia (↑LDL-C, ↑Triglycerides, ↓HDL-C), Hypertension, Diabetes Mellitus, Smoking, Central Obesity (Waist: Men >90cm, Women >80cm), Physical inactivity, Unhealthy diet, ↑Lipoprotein(a) (>50mg/dL high risk).
  • Non-Modifiable: Advancing Age, Family Hx of premature CVD, Male sex.