title: Possible human leukocyte antigen-mediated genetic interaction between type 1 and type 2 Diabetes.
abstract: We assessed the prevalence of families with both type 1 and type 2 diabetes in Finland; and we studied, in patients with type 2 diabetes, the association between a family history of type 1 diabetes, glutamic acid decarboxylase (GAD) antibodies (GADab), and type 1 diabetes-associated human leukocyte antigen (HLA) DQB1-genotypes. Further, in mixed type 1/type 2 diabetes families, we investigated whether sharing an HLA haplotype with a family member with type 1 diabetes influenced the manifestation of type 2 diabetes. Among 695 families ascertained through the presence of more than 1 patient with type 2 diabetes, 100 (14%) also had members with type 1 diabetes. Type 2 diabetic patients from the mixed families had, more often, GADab (18% vs. 8%, P < 0.0001) and DQB1*0302/X genotype (25% vs. 12%, P = 0.005) than patients from families with only type 2 diabetes; but they had a lower frequency of DQB1*02/0302 genotype, compared with adult-onset type 1 patients (4% vs. 27%, P < 0.0001). In the mixed families, the insulin response to oral glucose load was impaired in patients who had HLA class II risk haplotypes, either DR3(17)-DQA1*0501-DQB1*02 or DR4*0401/4-DQA1*0301-DQB1*0302, compared with patients without such haplotypes (P = 0.016). This finding was independent of the presence of GADab. We conclude that type 1 and type 2 diabetes cluster in the same families. A shared genetic background with a patient with type 1 diabetes predisposes type 2 diabetic patients both to autoantibody positivity and, irrespective of antibody positivity, to impaired insulin secretion. The findings support a possible genetic interaction between type 1 and type 2 diabetes mediated by the HLA locus.
authors.affiliation: Diabetes and Endocrine Research Laboratory, Department of Endocrinology, Lund University, S-20502 Malmö, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: E
authors.initials: E
authors.lastname: Lindholm
authors.forename: P
authors.initials: P
authors.lastname: Almgren
authors.forename: A
authors.initials: A
authors.lastname: Gustafsson
authors.forename: C
authors.initials: C
authors.lastname: Forsblom
authors.forename: L
authors.initials: L
authors.lastname: Groop
authors.forename: T
authors.initials: T
authors.lastname: Tuomi
mesh_terms: D001323:Autoantibodies / Q000097:blood; D002096:C-Peptide / Q000097:blood; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000235:genetics* / Q000276:immunology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000235:genetics* / Q000276:immunology*; D005260:Female; D005387:Finland; D005838:Genotype; D005951:Glucose Tolerance Test; D005968:Glutamate Decarboxylase / Q000276:immunology; D006681:HLA-D Antigens / Q000235:genetics*; D006683:HLA-DQ Antigens / Q000235:genetics; D059848:HLA-DQ alpha-Chains; D059866:HLA-DQ beta-Chains; D015803:HLA-DR3 Antigen / Q000235:genetics; D015804:HLA-DR4 Antigen / Q000235:genetics; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged
chemical_list: D001323:Autoantibodies; D002096:C-Peptide; D006681:HLA-D Antigens; D006683:HLA-DQ Antigens; D059848:HLA-DQ alpha-Chains; D059866:HLA-DQ beta-Chains; C069050:HLA-DQA1 antigen; C069051:HLA-DQB1 antigen; D015803:HLA-DR3 Antigen; D015804:HLA-DR4 Antigen; D007328:Insulin; D005968:Glutamate Decarboxylase