[7] The encoded apolipoprotein AI, is a 28.1 kDa protein composed of 243 amino acids; 21 peptides have been observed through mass spectrometry data.

[8][9] Due to alternative splicing, there exists multiple transcript variants of APOA1, including at least one which encodes a Apo-AI preprotein.

[7] Apolipoprotein AI is the major protein component of high density lipoprotein (HDL) particles in plasma.

[18] Paradoxically, carriers of this mutation have very low HDL-C (HDL-cholesterol) levels, but no increase in the risk of heart disease, often living to age 100 or older.

[20] Apo-AI Milano has also been shown in small clinical trials to have a statistically significant effect in reducing (reversing) plaque build-up on arterial walls.

[21][23] A study from 2008 describes two novel susceptibility haplotypes, P2-S2-X1 and P1-S2-X1, discovered in ApoAI-CIII-AIV gene cluster on chromosome 11q23, which confer approximately threefold higher risk of coronary heart disease in normal[24] as well as in the patients having type 2 diabetes mellitus.

[30] Apolipoprotein AI and ApoE interact epistatically to modulate triglyceride levels in coronary heart disease patients.

It was concluded, that this regulation happens on transcription level: calcitriol alters yet unknown coactivators or corepressors, resulting in repression of APOA1 promoter activity.

[32] Exercise or statin treatment may cause an increase in HDL-C levels by inducing Apo-AI production, but this depends on the G/A promoter polymorphism.