Summary
Activity of plasminogen activator inhibitor-1 (PAI-1), a potent inhibitor of fibrinolysis,
is raised in non-insulin-dependent diabetes mellitus (NIDDM) and may contribute to
excess macrovascular disease. We investigated the association of PAI-1 activity with
NIDDM in Pima Indians, a racial group with low risk of coronary artery disease, but
in whom the impact of NIDDM on the occurrence of coronary artery disease is similar
to other racial groups. We studied 308 (136 nondiabetic, 172 diabetic) Pima Indians
from Arizona, and 138 (98 nondiabetic, 40 diabetic) South Asians and 129 (80 non-diabetic,
49 diabetic) Europeans living in North London. PAI-1 activity was measured by a spectrophotometric
assay, and insulin, intact proinsulin and des 31,32 proinsulin concentrations were
measured employing highly specific monoclonal antibody-based assays. Compared with
non-diabetic subjects, PAI-1 activity was significantly higher in subjects with NIDDM
among South Asians (22.8 ± 7.3 vs. 17.4 ± 6.9 AU/ml, p <0.001) and Europeans (23.1
± 6.6 vs. 16.5 ± 6.1 AU/ml, p <0.001) but not among Pima Indians (19.5 ± 9.6 vs. 18.5
± 8.6 AU/ml, ns). The association of PAI-1 activity with diabetes remained statistically
significant when controlled for age, sex, body mass index and waist-hip ratio, serum
triglyceride and fasting insulin concentrations in South Asians (p <0.001) and Europeans
(p <0.001). The relationships of PAI-1 activity with clinical and biochemical variables
were similar in the three racial groups other than for fasting and 2 h plasma glucose
concentrations which were significantly associated with PAI-1 activity in South Asians
(partial r = 0.32 and 0.31) and Europeans (partial r = 0.44 and 0.50) but not in Pima
Indians (partial r = 0.11 and 0.15). In Pima Indians with NIDDM, PAI-1 activity was
similar in those treated with sulphonylureas, insulin, or no drugs for diabetes. In
conclusion, the association of PAI-1 with diabetes differs in racial groups who are
at different risk of NIDDM and ischaemic heart disease. Previously reported differences
in the prevalence of ischaemic heart disease between diabetic and non-diabetic Pima
Indians, and between non-diabetic subjects from the three racial groups, are unlikely
to be due to differences in PAI-1 activity.