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BMC Med. 2019 Aug 23;17(1):165. doi: 10.1186/s12916-019-1392-8.

Persistent C-peptide secretion in Type 1 diabetes and its relationship to the genetic architecture of diabetes.

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Usher Institute of Population Health and Informatics, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9AG, UK.
Usher Institute of Population Health and Informatics, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9AG, UK.
Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital Campus, Crewe Road, Edinburgh, UK.
Medical School, University of Exeter, Exeter, UK.
Center for Public Health Genomics, University of Virginia, Charlottesville, USA.
Medical School, University of Dundee, Dundee, UK.
Metabolic Unit, Western General Hospital, Edinburgh, UK.
Royal Infirmary of Edinburgh, Edinburgh, UK.
Diabetes Centre, Victoria Hospital, Kirkaldy, UK.
Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK.
David Matthews Diabetes Centre, Monklands Hospital, Airdrie, UK.
Glasgow Caledonian University, Glasgow, UK.
NHS Highland Diabetes Centre, Inverness, UK.



The objective of this cross-sectional study was to explore the relationship of detectable C-peptide secretion in type 1 diabetes to clinical features and to the genetic architecture of diabetes.


C-peptide was measured in an untimed serum sample in the SDRNT1BIO cohort of 6076 Scottish people with clinically diagnosed type 1 diabetes or latent autoimmune diabetes of adulthood. Risk scores at loci previously associated with type 1 and type 2 diabetes were calculated from publicly available summary statistics.


Prevalence of detectable C-peptide varied from 19% in those with onset before age 15 and duration greater than 15 years to 92% in those with onset after age 35 and duration less than 5 years. Twenty-nine percent of variance in C-peptide levels was accounted for by associations with male gender, late age at onset and short duration. The SNP heritability of residual C-peptide secretion adjusted for gender, age at onset and duration was estimated as 26%. Genotypic risk score for type 1 diabetes was inversely associated with detectable C-peptide secretion: the most strongly associated loci were the HLA and INS gene regions. A risk score for type 1 diabetes based on the HLA DR3 and DQ8-DR4 serotypes was strongly associated with early age at onset and inversely associated with C-peptide persistence. For C-peptide but not age at onset, there were strong associations with risk scores for type 1 and type 2 diabetes that were based on SNPs in the HLA region but not accounted for by HLA serotype.


Persistence of C-peptide secretion varies widely in people clinically diagnosed as type 1 diabetes. C-peptide persistence is influenced by variants in the HLA region that are different from those determining risk of early-onset type 1 diabetes. Known risk loci for diabetes account for only a small proportion of the genetic effects on C-peptide persistence.


Age at diagnosis; C-Peptide; Cross-sectional studies; Diabetes mellitus type 1; Genetics; Insulin secretion

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