The (TAAAA)n polymorphism of the SHBG gene in men with the metabolic syndrome

Low serum Sex Hormone-Binding Globulin (SHBG) has been proposed as an indicator of the Metabolic Syndrome (MS) and cardiovascular disease in men. On the other hand, the (TAAAA)n repeat polymorphism in the SHBG gene has been shown to affect SHBG levels. The possible role of this polymorphism in the MS was examined in the present study.

The study population consisted of 83 men with MS aged 54.9±14.8 years and 166 healthy men of the same age. The diagnosis of MS was based on the criteria proposed by the National Cholesterol Education Program - Third Adult Treatment Panel (NCEP-ATP III). The waist circumference was recorded and blood samples were obtained after overnight fasting for biochemical and hormonal tests. The SHBG(TAAAA)N polymorphism was genotyped in peripheral blood leucocytes.

Genotype analysis for the (TAAAA)n polymorphism of the SHBG gene in the patients and controls identified 6 alleles having 6-11 TAAAA repeats. Patients with MS had more frequently short-allele genotypes (with 6/6, 6/7, 6/8, 7/7, 7/8 or 8/8 tandem repeats) compared to controls (53% vs. 39.8%, p=0.047). In the entire study population, men homozygous for the 6 TAAAA repeat allele had lower SHBG levels (p=0.01) and higher waist circumference (p=0.006) than men heterozygous or non-carriers of this allele.

Short SHBG(TAAAA)N allele genotypes may play a role in the development of the MS. The mechanism of this contribution remains unclear.