The retardation of vasculopathy induced by attenuation of insulin resistance in the corpulent JCR:LA-cp rat is reflected by decreased vascular smooth muscle cell proliferation in vivo.

Proliferation in vivo of vascular smooth muscle cells occurs early in the course of atherosclerosis. Cultured smooth muscle cells (SMCs) explanted from aortas of JCR:LA-cp corpulent rats known to exhibit metabolic derangements and insulin resistance typical of type II diabetes early in life and to develop atherosclerosis later in life exhibit increased proliferation compared with SMCs from lean, normal rats. Vascular smooth muscle proliferation in vitro was found to be positively and significantly correlated with plasma insulin levels in vivo. Proliferation of aortic SMCs from JCR:LA-cp cp/cp corpulent rats cultured in vitro exhibited increased proliferation in the presence of exogenous insulin. Exercise and diet, selected as interventions designed to ameliorate the insulin resistance and hyperinsulinemia in the JCR:LA-cp cp/cp rat, effectively lowered blood insulin levels and decreased subsequent proliferation in vitro of aortic SMCs explanted from these animals. The results indicate that assessment of proliferation of vascular smooth muscle cells ex vivo may provide insight into the presence and severity of atherogenicity in association with insulin resistance in diverse species under diverse circumstances. Accordingly, with appropriate controls, it may be possible to use SMC proliferation ex vivo as a marker of the extent to which an intervention such as administration of insulin sensitizers to experimental animals and human subjects results in a change in behavior of vessel wall elements potentially indicative of amelioration of atherogenicity and detectable as judged from reduced proliferative rates of the cells ex vivo when they have been harvested from vessels exposed to a milieu in which insulin resistance has been attenuated.