Distribution of autoantibodies to glutamic acid decarboxylase across the spectrum of diabetes mellitus seen in South Africa.
OBJECTIVE
This study investigated the association between glutamic acid decarboxylase antibodies (GAD-AB) and Type 1, Type 2, pancreatic and lipoatrophic diabetes mellitus (DM) in South African patients.


METHODS
Four groups were selected: group A, 100 Black Type 1 DM patients (age at onset < 35 years, body mass index (BMI) < 27 kg/m2 and insulin dependent within 1 year of presentation); group B, 80 Black Type 2 DM patients (age at onset > 35 years, BMI > 27 kg/m2 and controlled on oral hypoglycaemic agents for at least 1 year after presentation); group C, 10 patients of varying ethnicity with DM or impaired glucose tolerance secondary to chronic pancreatitis; group D, five patients of varying ethnicity with DM associated with total lipodystrophy. Fifty healthy Black control subjects were also studied (group E). Serum GAD-AB and random C-peptide levels were measured by radioimmunoassay.


RESULTS
Mean C-peptide concentration was significantly lower in Type 1 DM patients than Type 2 DM patients (P < 0.00001). Forty-four patients with Type 1 DM were GAD-AB-positive compared to two patients with Type 2 DM. Two control subjects were also GAD-AB-positive. No patient in the other groups had a titre > 1 U/ml. Type 1 DM patients who were GAD-AB-positive did not differ from those who were GAD-AB-negative for age at onset, duration of DM or C-peptide concentrations.


CONCLUSIONS
Auto-immune beta-cell destruction has an important role in the pathogenesis of Type 1 DM amongst African patients. However, Type 2 African DM patients and other diabetes subtypes are largely GAD-AB-negative.
Panz
V R
VR
Department of Medicine, University of the Witwatersrand Medical School, Johannesburg, South Africa. 014panz@chiron.wits.ac.za
Kalk
W J
WJ
Zouvanis
M
M
Joffe
B I
BI
D000328:Adult; D001323:Autoantibodies / Q000276:immunology*; D044383:Black People; D002096:C-Peptide / Q000097:blood; D003920:Diabetes Mellitus / Q000097:blood / Q000145:classification / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000276:immunology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000276:immunology; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010182:Pancreatic Diseases / Q000097:blood / Q000276:immunology; D011863:Radioimmunoassay; D013019:South Africa
D001323:Autoantibodies; D002096:C-Peptide; D005968:Glutamate Decarboxylase