Clinical Characteristics, and Time Course of Pancreatic β-Cell Function and Glutamic Acid Decarboxylase Antibodies in Thai Patients with Adult-Onset Type 1 Diabetes: Distinction Between Patients of Rapid- and Slow-Onset

In order to study the clinical characteristics, time course of β cell function and glutamic acid decarboxylase antibodies (GAD₆₅Ab) in Thai patients with adult-onset Type 1 diabetes and to examine the distinctive features between patients with rapid-and slow-onset, 61 Thai patients with Type 1 diabetes who had age of disease onset at or after 20 years were studied. All patients were treated with insulin at the time of study and had fasting C-peptide levels ≤ 0.33 nmol/l. Twenty-six (42.6%) were in rapid-onset and 35 (57.4%) were in slow-onset groups. Fourty-four of 61(70.5%) were male. About three-fourths had body mass index (BMI) < 19 kg/m² at the time of insulin therapy. Only 7 of 61 (11.5%) patients had ketoacidosis at first presentation. Five patients had associated autoimmune thyroid disease and 10 (16.7%) patients had family history of diabetes in first-degree relatives. GAD₆₅Ab was positive in 31 patients (50.8%); 10 (38.5%) were in rapid-onset and 21 (60.0%) were in slow-onset groups. GAD₆₅Ab particularly of high levels were persistently elevated during 3 - 4 years follow-up period. The persistence of GAD₆₅Ab were not associated with changes in fasting C-peptide levels. At the time of insulin dependency, there were no distinctive clinical features between rapid- and slow-onset patients except higher fasting C-peptide (0.08 ± 0.08 vs. 0.14 ± 0.10 nmol/l; p = 0.023) and GAD₆₅Ab levels (19.6 ± 17.4 vs. 46.1 ± 49.7 U/ml; p = 0.036) in slow-onset patients. Fasting C-peptide levels of patients in the latter group were also demonstrated to be higher after 3 - 4 years of follow-up. In conclusion, most Thai patients with adult-onset Type 1 diabetes in this study were male and had significant degree of weight loss and lean BMI prior to insulin therapy. The presence of GAD₆₅Ab did not predict clinical features or rate of β cell loss. Patients in rapid-onset group had lower fasting C-peptide and GAD₆₅Ab levels than those of slow-onset group which confirms the slower process of β cell failure in the latter.

Key words

Type 1 Diabetes - Glutamic Acid Decarboxylase Antibodies - C-Peptide - Characteristic