Fibrinolytic system proteins in blood and arterial walls [1±6] have been implicated in atherogenesis and in the macroangiopathy typical of non-insulindependent diabetes mellitus (NIDDM). Impairment of fibrinolysis may lead to accumulation of microthrombi that may induce or exacerbate atherogenesis. High concentrations of plasminogen activator inhibitor type-1 (PAI-1) and attenuated fibrinolytic activity are seen in human subjects with obesity, NID-DM, or both [7±10]. Obesity and particularly early stage NIDDM are also characterized by increased concentrations of immunoreactive insulin (IRI) evident in plasma. Several observations suggest a causal connection between hyperinsulinaemia, insulin resistance and impaired fibrinolysis in blood [7±10]. However, the temporal relationships between hyperinsulinaemia, hypertriglyceridaemia, and impaired fibrinolytic system capacity secondary to increased PAI-1 in blood and the onset of macroangiopathy have not yet been elucidated. Accordingly, we studied JCR:LA-cp (corpulent) rats, animals genetically predisposed to develop severe insulin resistance with hyperinsulinaemia, hyperlipidaemia, obesity, and subsequent macroangiopathy [11±14].The JCR:LA-cp atherosclerosis-prone rat strain is one in which many aspects of early NIDDM and atherogenesis are simulated [11±14]. This strain incorporates an autosomal recessive cp (corpulent) gene and JCR:LA-cp rats homozygous for the cp gene (cp/ cp) are obese, insulin resistant, and hypertriglyceridaemic [13]. Heterozygous ( + /cp) and homozygous Diabetologia (1998) Summary Increased concentrations of plasminogen activator inhibitor type-1 (PAI-1) in blood and attenuated fibrinolytic activity, hypertriglyceridaemia, and insulin resistance are common in subjects with obesity and non-insulin-dependent diabetes mellitus who are at markedly increased risk for coronary artery disease. To clarify potentially causal relationships between these phenomena, we studied JCR:LA-cp rats, animals that are insulin resistant and prone to vasculopathy. Blood and aortas were obtained from lean and corpulent animals at 1, 2, 4, 6, and 9 months of age. The homozygous corpulent rats were hyperinsulinaemic and hypertriglyceridaemic at all ages tested. Increased activity of PAI-1 was present in blood from corpulent animals at 1, 6, and 9 months of age. Positive correlations were observed between blood PAI-1 and both insulin and triglycerides. As judged from results with aortic rings in in vitro culture, the increased PAI-1 in blood was anteceded by increased expression of PAI-1 in arterial walls. Thus, changes indicative of inhibition of the fibrinolytic system capacity precede gross atherosclerosis.[ Diabetologia (1998)
41: 141±147]Keywords Atherosclerosis, diabetes, hyperinsulinaemia, hypertriglyceridaemia, plasminogen activator inhibitor-1.Received: 8 July 1997 and in revised form: 23 September 1997Corresponding author: Dr. P. M. Absher, Department of Medicine, Given Building, Room C-323, University of Vermont College of Medicine, Burlington, VT 05405,...