Diabetes Care, Vol 20, Issue 8 1304-1309, Copyright © 1997 by American Diabetes Association
Diabetic retinopathy, promoter (4G/5G) polymorphism of PAI-1 gene, and PAI-1 activity in Pima Indians with type 2 diabetes
DK Nagi, LJ McCormack, V Mohamed-Ali, JS Yudkin, WC Knowler and PJ Grant
National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, Arizona, USA.
OBJECTIVE: To examine the relationship between plasma plasminogen activator
inhibitor 1 (PAI-1) activity and PAI-1 gene (4G/5G) polymorphism and
diabetic retinopathy in Pima Indians with type 2 diabetes. RESEARCH DESIGN
AND METHODS: We studied 171 Pima Indians with type 2 diabetes between the
ages of 30-70 years in a population-based epidemiological survey. Plasma
PAI-1 activity was measured by a spectrophotometric assay and PAI-1 4G/5G
promoter genotype by the polymerase chain reaction (PCR) using
allele-specific primers. Retinopathy was assessed by ophthalmoscopy after
pupillary dilation and classified as any retinopathy or as nonproliferative
and proliferative. RESULTS: Retinopathy was present in 70 (41%) subjects,
and 4 (2.3%) subjects had proliferative retinopathy. Plasma PAI-1 activity
was not significantly different among subjects with and without retinopathy
(17.1 +/- vs. 19.7 +/- 9.1 arbitrary units (AU)/ml, P = 0.09). PAI-1
activity was negatively correlated with duration of diabetes (rs = -0.18, P
= 0.02). In a logistic regression analysis controlled for age, sex, BMI,
and duration of diabetes, any retinopathy was significantly associated with
fasting plasma glucose concentrations (P < 0.05), 2-h postload glucose
(P = 0.02), and HbA1c (P = 0.008), but not with PAI-1 activity (P = 0.48).
The prevalence of retinopathy in the three genotype groups differed
significantly (4G/4G, 4G/5G, and 5G/5G were 44, 49, and 24%, respectively;
chi 2 = 8.22, df = 2, P = 0.016) and remained significant after controlling
for age, sex, BMI, duration of diabetes, glycated hemoglobin, and urine
albumin-to-creatine ratio in a logistic regression analysis. The odds
ratios for retinopathy in subjects with 4G/4G and 4G/5G, compared with the
5G/5G genotype, were 2.0 and 3.1, respectively. CONCLUSIONS: Although
diabetic retinopathy in Pima Indians with type 2 diabetes is not associated
with PAI-1 activity, subjects with the 4G/4G and 4G/5G genotype had a
higher prevalence of retinopathy compared with 5G/5G PAI-1genotype. These
preliminary findings indicate that in Pima Indians with type 2 diabetes,
presence of the 4G allele of the PAI-1 gene was associated with a higher
risk of diabetic retinopathy.