The prevalence of diabetes worldwide has been steadily increasing over the past 20 years. In 1997 it was estimated to be 124 million, 1 in 2015 it was estimated to be 415 million among 20–70 year olds, and this is expected to rise to 642 million by 2040. 2 In the UK, an estimated 4 million people have diabetes either diagnosed or undiagnosed. 2 This represents a significant burden on health care resources, 3 particularly given that type 2 diabetes (T2D) is associated with comorbidities including obesity, 4 cardiovascular disease, 5 chronic kidney disease 6 and neuropathy. 7 T2D is a complex disorder, caused by a combination of environmental and genetic factors. 8 Before the first genomewide association study (GWAS) was conducted for T2D in 2007, 9 very few genetic loci were known to be involved with T2D. However, linkage and candidate-gene association studies have often failed to replicate findings through lack of power and inadequate knowledge of the underlying biological pathways. 10, 11