Haptoglobin phenotypes and gene frequencies in unipolar major depression

Studies from the authors' laboratory have shown that major depression is accompanied by significantly increased plasma concentrations of positive acute-phase proteins such as haptoglobin. Haptoglobin is characterized by a molecular variation with three known phenotypes (Hp 1-1, Hp 2-1, and Hp 2-2). This study investigated haptoglobin plasma levels and phenotype and gene frequencies in unipolar major depression.

Haptoglobin plasma levels of 22 healthy volunteers, 32 patients with minor depression, and 72 patients with major depression were determined by means of a laser nephelometric method. Haptoglobin phenotyping of these 126 subjects and 200 healthy blood donors was also carried out.

The patients with major depression exhibited significantly higher haptoglobin plasma levels than the healthy comparison subjects and the patients with minor depression. Subjects with the haptoglobin phenotype Hp 2-2 had significantly lower haptoglobin levels than the phenotype Hp 1-1 and Hp 2-1 carriers. The frequencies of haptoglobin phenotypes Hp 2-1 (61.1%) and Hp 2-2 (20.8%) in the patients with major depression were significantly higher and lower, respectively, than the frequencies in the normal population (i.e., the blood donors: 48.0% and 37.0%, respectively). The frequency of the Hp-1 gene was significantly greater in the patients with major depression (48.6%) than in the normal population (39.0%).

Major depression is characterized by a hyperhaptoglobinemia that is largely independent of haptoglobin phenotypes. This altered distribution of haptoglobin phenotypes and genes suggests that genetic variation on chromosome 16 may be associated with that illness.