Diabetes and Our Genes

Type 1 diabetes (T1D) and T2D which affect approximately 200 million adults worldwide are diseases characterized by hyperglycemia. Diabetes results from metabolic consequences of beta cell dysfunction and/or the inability of insulin to properly regulate levels of blood glucose. Approximately 90% to 95% of the affected individuals are afflicted with T2D. Although T1D and T2D have some common clinical features, these diseases are the results of different biological mechanisms. T1D, which is the result of autoimmune destruction of the beta cells of the pancreas, typically presents in childhood. Human leukocyte antigen locus is the major susceptibility locus for T1D. T2D which occurs by reduced insulin secretion due to abnormalities in pancreatic beta cell function or decreased beta cell mass, typically presents in adults older than 40 years of age. Although there are some genetic similarities that exist between T1D and T2D, studies support the fact that these are two distinct diseases. Also, there is another type of diabetes existing: latent autoimmune diabetes in adults. Environmental and genetic factors play role in the etiology of diabetes. There is a strong evidence for the genetic contribution that includes concordance rates that are higher in monozygotic twins when compared to dizygotic twins. It has been proven to be more challenging to identify the genes for T2D. But emerging of non-hypothesis-driven molecular genetics techniques such as Genome-Wide Association Studies and next generation sequencing have given great opportunity to find disease related loci. Maturity-onset diabetes of the young (MODY) which is a special form of diabetes occasionally seen in patients before the age of 25 and is inherited in an autosomal dominant fashion. The prevalence of MODY has been estimated to be 2-5% of all diabetes cases. The patients in this group have mutations in the limited number of the genes such as HNF1A and GCK. As a result, diabetes has different subtypes all of which have different genetic backgrounds.