Читать книгу Handbook of Diabetes - Rudy Bilous - Страница 67

Evidence for a genetic basis for type 2 diabetes comes from a clear familial aggregation, but it does not segregate in a classic Mendelian fashion. About 10% of patients with type 2 diabetes have a similarly affected sibling. The concordance rate for identical twins is variously estimated to be 33–90% (17–37% in non‐identical twins), but the interpretation of this is difficult because siblings may have similar lifestyles and diets. Thus, the explanation for the high concordance may be environmental rather than genetic.

Unlike type 1, type 2 diabetes is not associated with genes in the HLA region. So far, 19 gene variants have been described and validated as being associated with type 2 diabetes. Of these, the strongest is TCF7L2; 15% of European adults carry two copies of the abnormal gene and they have double the lifetime risk of developing type 2 diabetes compared to the 40% who carry no copies. Carriers of the T risk allele have impaired insulin secretion and enhanced hepatic glucose output. Nearly all of the other described genes affect either β cell mass or function; few appear to have potential effects on insulin resistance.