Genetic Background of Diabetes Mellitus(Series "Treatment of Diabetes Mellitus" (7))

In clinical practice, genetic information is not necessary in a therapeutic plan; however, the information is very important when we need to determine a diagnosis, prognosis, or recurrence of a disease among relatives of a patient. The genetic background of diabetes mellitus contains two different forms. The first one is the causative genes in autosomal dominant type of diabetes (maturity onset diabetes of the young; MODY), and the second is the susceptibility polymorphisms in type 2 diabetes. MODY is a monogenic disease; therefore, the classical linkage analysis works perfectly to identify a causative gene using a large pedigree (RW family). Six kinds of genes are identified as MODY genes, in which 5 are transcription factors. Transcription factors have brought a new aspect of pathophysiology in diabetes mellitus and promoted us to study the its relationships with diabetes during the last 10 years. Now, we know that MODY has extra pancreatic phenotype such as kidney cysts, genital malformations, liver diseases, or other disease in addition to diabetes. Polymorphism in the MODY genes also acts as susceptibility genes for type 2 diabetes. In this paper, we introduce the relationship of MODY gene and the phenotype of Japanese MODY subjects. We also include the current genetic studies on type 2 diabetes mellitus