Caucasian versus African-American differences in orosomucoid: potential implications for therapy

Area of Science:

• Pharmacogenetics
• Biochemistry
• Clinical Chemistry

Background:

• Orosomucoid (ORM) is a key plasma protein involved in drug binding.
• Understanding racial variations in ORM is crucial for personalized medicine.
• Previous research has not fully elucidated ORM differences across racial groups or their impact on drug interactions.

Purpose of the Study:

• To investigate potential racial disparities in orosomucoid (ORM) serum concentrations and allele frequencies.
• To examine the influence of ORM phenotype on the binding of quinidine and lidocaine.
• To correlate ORM variants with the unbound fraction of these drugs.

Main Methods:

• Prospective, nonrandomized study involving healthy Caucasian and African-American volunteers.
• Orosomucoid (ORM) concentrations measured using Laurell-Rocket immunoelectrophoresis.
• ORM allele typing performed via isoelectric focusing and immunoblotting.
• Drug concentrations (total and unbound) quantified using fluorescence polarization immunoassays and ultrafiltration.

Main Results:

• No significant differences in the frequency of common ORM alleles between racial groups.
• Mean total ORM concentration was significantly lower in Caucasians compared to African-Americans (p=0.01).
• A higher unbound fraction of quinidine was observed with the ORM 1-S phenotype (p=0.009).
• No significant association found between ORM phenotype and lidocaine unbound fraction.

Conclusions:

• African-Americans exhibit higher mean total orosomucoid (ORM) concentrations than Caucasians.
• Specific ORM variants, particularly ORM 1-S, significantly influence quinidine binding.
• These findings highlight the importance of considering ORM phenotype in drug therapy, especially for quinidine, across different racial groups.