What is Apolipoprotein A-II?

Apolipoprotein A-II (ApoA-II) is the second most abundant protein component of HDL (High-Density Lipoprotein) after ApoA-I.

• Synthesized in the liver

• Present mainly in HDL particles

• Influences HDL metabolism and function

Normal Reference Range

• Approximately 20–40 mg/dL
  (May vary slightly by laboratory.)

Clinical Significance

1️⃣ Role in HDL Metabolism

ApoA-II:

• Stabilizes HDL structure

• Modulates activity of enzymes such as:

  • LCAT (Lecithin–Cholesterol Acyltransferase)

  • Hepatic lipase

• Influences HDL particle size and remodeling

2️⃣ Cardiovascular Disease (CVD)

The role of ApoA-II in atherosclerosis is complex:

• Some studies suggest protective effects

• Others show neutral or mildly pro-atherogenic effects

Unlike ApoA-I, ApoA-II is not as strong a predictor of cardiovascular risk.

However:

• Altered ApoA-II levels may indicate dysfunctional HDL.

3️⃣ Metabolic Syndrome & Diabetes

Changes in ApoA-II levels are observed in:

• Type 2 diabetes mellitus

• Insulin resistance

• Obesity

• Hypertriglyceridemia

May reflect abnormalities in HDL metabolism.

4️⃣ Liver Disease

Since ApoA-II is synthesized in the liver:

• ↓ Levels in severe liver disease

• Useful as an indirect marker of hepatic synthetic function

5️⃣ Amyloidosis

Certain mutations in ApoA-II are associated with:

• Hereditary amyloidosis

• Amyloid deposition in tissues

Rare but clinically significant.