Type 1 diabetes in insulin-treated adult-onset diabetic subjects.
The frequency of autoimmune features was compared in adult-onset diabetic subjects either requiring insulin treatment within 12 months of diagnosis or progressing to insulin therapy after a latency of at least 5 years. Adult-onset insulin-treated diabetic subjects were sampled from the population-based Canterbury Diabetes Registry (n = 1580). There were 237 (15%) registrants who met the study criteria of age < 75 years at 1 January 1993, age at diagnosis of diabetes > or = 45 years and duration of diabetes between 5 and 15 years; 101 subjects commenced insulin 5-15 years after diagnosis (group 1) and 80 subjects commenced insulin within 1 year of diagnosis (group 2). C-peptide levels, islet cell antibodies (ICA) and antibodies against glutamic acid decarboxylase (anti-GAD) were determined in all individuals from group 1 (n = 27) and group 2 (n = 23) who agreed to be recruited to the study. The group 1 and group 2 samples did not differ significantly in their demographic characteristics, nor were they different from the two groups from which they were drawn (mean age, 64.2 years; age at diagnosis, 53.5 years; duration of diabetes, 10.7 years; body mass index, 28.6 kg/m2). Overall, 12 of the 50 (24%) study subjects tested positive for anti-GAD; 43% (10) of group 2 subjects were anti-GAD positive compared with only 7.4% (2) of group 1 subjects (P < 0.01). Postprandial C-peptide levels were significantly lower in group 2 subjects compared with group 1 subjects (627 vs 1124 pM, P < 0.05). All subjects were ICA negative. These observations suggest that autoimmune destruction of beta-cells explains early requirement for insulin in adult-onset diabetes.
Willis
J
J
Lipid and Diabetes Research Group, Hagley Building, Christchurch Hospital, New Zealand. jwillis@chmeds.ac.nz
Scott
R
R
Brown
L
L
Zimmet
P
P
MacKay
I
I
Rowley
M
M
D017668:Age of Onset; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D003922:Diabetes Mellitus, Type 1 / Q000145:classification* / Q000175:diagnosis / Q000188:drug therapy*; D003924:Diabetes Mellitus, Type 2 / Q000145:classification* / Q000175:diagnosis / Q000188:drug therapy; D003937:Diagnosis, Differential; D005968:Glutamate Decarboxylase / Q000276:immunology; D006801:Humans; D007328:Insulin / Q000627:therapeutic use*; D007515:Islets of Langerhans / Q000276:immunology; D008875:Middle Aged
D001323:Autoantibodies; D002096:C-Peptide; D007328:Insulin; C024211:islet cell antibody; D005968:Glutamate Decarboxylase