Associations between haptoglobin polymorphism, lipids, lipoproteins and inflammatory variables

The haptoglobin allele frequencies and the phenotype distribution were dete rmined in 741 male Caucasian workers, aged 35 to 59 years. The association of the haptoglobin polymorphism with various clinical and biochemical param eters was investigated. Furthermore a possible interaction with the apo E p olymorphism on lipid and lipoprotein traits was analysed. The frequency of Hpl and Hp2 was found to be 0.401 and 0.599, respectively. The observed dis tribution of Hp types (Hp 1-1, 15.5%; Hp 2-1, 49.3%; Hp 2-2, 35.2%) was in Hardy-Weinberg equilibrium. Age, body mass index, smoking, alcohol intake a nd blood pressure were comparable between the three Hp groups. Subjects wit h Hp 2-2 had significantly higher serum total and free cholesterol concentr ation compared to those in other haptoglobin types (P = 0.006 and P = 0.003 ). Similarly, apo B levels were significantly higher among Hp 2-2 individua ls (P = 0.02). No significant differences were demonstrated between the Hp phenotypes in HDL cholesterol, apo A-I, apo E, Lp(a), cholesteryl esters, f ibrinogen and C-reactive protein concentrations, although for the latter an increase was noticed in Hp 2-2. The effects of Hp type and apo E type on L p(a) and on fret: cholesterol levels were found to be significantly multipl icative, with the highest free cholesterol values observed in subjects havi ng Hp 2-2 and the apo epsilon 4 allele. Significantly lower Lp(a) levels we re observed in individuals carrying Hp 1-1 and an epsilon 2 allele than in subjects without the epsilon 2 allele. In conclusion, haptoglobin polymorph ism may play an important role in the regulation of lipoprotein metabolism and could contribute to the risk of coronary heart disease. Larger samples are needed to clarify the clinical relevance of the gene-gene (Hp-apo E) in teraction on lipids and lipoproteins. (C) 1999 Elsevier Science Ireland Ltd . All rights reserved.