Diabetes and Dyslipidemia

Abstract

Background —Clinical observations suggest that transplant coronary artery disease (TxCAD) is immunologically mediated but may be accelerated by metabolic derangements. We developed a rat model of heterotopic heart transplantation in the presence of diabetes and dyslipidemia to further study their role in TxCAD development. Methods and Results —Major histocompatibility complex–mismatched strains of inbred rats underwent heterotopic heart transplantation (ACI-to-Lewis allografts). Diabetes (DM) was induced by streptozotocin injection (80 mg/kg) after transplantation; dyslipidemia was worsened by feeding of a 60% high-fructose diet (+F). Allograft transplants were divided into four groups: (1) +DM/+F; (2) +DM/−F; (3) −DM/+F; and (4) −DM/−F. Isograft transplants (Lewis to Lewis, +DM/±F) were controls. All animals received daily cyclosporine (5 mg/kg). Grafts surviving >30 days were evaluated for TxCAD on histological sections and graded 0 to 5 for intimal thickness. All streptozotocin-treated animals were diabetic within 2 weeks, with fourfold increases in plasma glucose concentrations versus nondiabetics. Severe TxCAD was observed in diabetic allografts only. The mean grade of TxCAD in diabetic allografts was 3.2±0.5 versus 1.1±0.4 in diabetic isografts ( P <0.03) and zero TxCAD in nondiabetic allografts ( P ≤0.0001). Fructose feeding resulted in a 1.5-fold higher triglyceride and a 1.3-fold higher cholesterol level versus the regular diet (−F) but showed no independent contribution to the development of TxCAD. Conclusions —These findings suggest that metabolic derangements associated with diabetes play an important role in TxCAD development in heterotopic ACI-to-Lewis rat heart transplantation. In this model of TxCAD in major histocompatibility complex–mismatched, diabetic, and dyslipidemic rats, immunologic and metabolic mechanisms that contribute to TxCAD can be further delineated and approaches to its prevention assessed.