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At the CDKN2A/B locus, three independent signals for type 2 diabetes risk are located in a noncoding region near CDKN2A. The disease-associated alleles have been implicated in reduced β-cell function, but the underlying mechanism remains elusive. In mice, β-cell-specific loss of Cdkn2a causes hyperplasia, while overexpression leads to diabetes, highlighting CDKN2A as a candidate effector transcript. Rare CDKN2A loss-of-function mutations are a cause of familial melanoma and offer the opportunity to determine the impact of CDKN2A haploinsufficiency on glucose homeostasis in humans. To test the hypothesis that such individuals have improved β-cell function, we performed oral and intravenous glucose tolerance tests on mutation carriers and matched control subjects. Compared with control subjects, carriers displayed increased insulin secretion, impaired insulin sensitivity, and reduced hepatic insulin clearance. These results are consistent with a model whereby CDKN2A loss affects a range of different tissues, including pancreatic β-cells and liver. To test for direct effects of CDKN2A-loss on β-cell function, we performed knockdown in a human β-cell line, EndoC-bH1. This revealed increased insulin secretion independent of proliferation. Overall, we demonstrated that CDKN2A is an important regulator of glucose homeostasis in humans, thus supporting its candidacy as an effector transcript for type 2 diabetes-associated alleles in the region.

Original publication

DOI

10.2337/db15-0602

Type

Journal article

Journal

Diabetes

Publication Date

02/2016

Volume

65

Pages

527 - 533

Keywords

Adolescent, Adult, Aged, Aged, 80 and over, Blood Glucose, Cell Line, Cell Proliferation, Female, Gene Knockdown Techniques, Genes, p16, Glucose Tolerance Test, Hepatobiliary Elimination, Homeostasis, Humans, Insulin, Insulin Resistance, Insulin-Secreting Cells, Male, Matched-Pair Analysis, Middle Aged, Mutation, Young Adult