INS VNTR allelic variation and dynamic insulin secretion in healthy adult non-diabetic Caucasian subjects

Aims To elucidate the relationship between the human insulin gene INS VNTR regulatory polymorphism and insulin secretion. The polymorphism arises from tandem repetition of 14-15bp oligonucleotides. In Caucasians, repeat number varies from 26 to over 200, with two main and discrete allele size classes: class I (26-63 repeats) and class III (141-209 repeats). Class I allele homozygosity is associated with elevated risk of developing Type 1 diabetes, while the class III allele has been associated with increased risk of Type 2 diabetes, polycystic ovary syndrome (PCOS) and with larger size at birth, which may influence development of adult disease. Methods Thirty-one healthy adult subjects with normal glucose tolerance, underwent an intravenous glucose tolerance test with one minute sampling. Seventeen. subjects were homozygous for class I alleles (14 excluding individuals carrying alleles associated with parent-of-origin effects and heterogeneity in allele transmission) and 14 homozygous for class III alleles. The groups were well matched. Results No significant differences in amount or rate of insulin secretion, or beta cell function were detected between the two groups. There was a difference in pattern of pulsatile insulin secret-ion with more 9-minute oscillations in class I homozygotes (P < 0.026). The after-load glucose concentration was also higher in subjects with class I alleles (P < 0.03). Conclusions These results warrant further analysis of possible association between allelic variation of the INS VNTR and the pulsatility of insulin secretion.