Advanced glycation end product (AGE) formation may contribute to the progression of atherosclerosis, particularly in diabetes. The present study explored atherosclerosis in streptozotocin-induced diabetic apolipoprotein E-deficient (apoE؊/؊) mice that were randomized (n ‫؍‬ 20) to receive for 20 weeks no treatment, the AGE cross-link breaker ALT-711, or the inhibitor of AGE formation aminoguanidine (AG). A sixfold increase in plaque area with diabetes was attenuated by 30% with ALT-711 and by 40% in AG-treated mice. Regional distribution of plaque demonstrated no reduction in plaque area or complexity within the aortic arch with treatment, in contrast to the thoracic and abdominal aortas, where significant attenuation was seen. Diabetes-associated accumulation of AGEs in aortas and plasma and decreases in skin collagen solubility were ameliorated by both treatments, in addition to reductions in the vascular receptor for AGE. Collagenassociated reductions in the AGEs carboxymethyllysine and carboxyethyllysine were identified with both treatments. Diabetes was also accompanied by aortic accumulation of total collagen, specifically collagens I, III, and IV, as well as increases in the profibrotic cytokines transforming growth factor-␤ and connective tissue growth factor and in cellular ␣-smooth muscle actin. Attenuation of these changes was seen in both treated diabetic groups. ALT-711 and AG demonstrated the ability to reduce vascular AGE accumulation in addition to attenuating atherosclerosis in these diabetic mice.

Background-It remains controversial whether specific blockade of the renin-angiotensin system confers superior antiatherosclerotic effects over other antihypertensive agents in diabetes. Therefore, the aim of this study was to compare equihypotensive doses of the angiotensin II subtype 1 (AT 1 ) receptor blocker irbesartan with the calcium antagonist amlodipine on diabetes-induced plaque formation in the apolipoprotein E (apoE)-null mouse and to explore molecular and cellular mechanisms linked to vascular protection. Methods and Results-Diabetes was induced by injection of streptozotocin in 6-week-old apoE-null mice. Diabetic animals were randomized to no treatment, irbesartan, or amlodipine for 20 weeks. Diabetes was associated with an increase in plaque area and complexity in the aorta in association with a significant increase in aortic AT 1 receptor expression, cellular proliferation, collagen content, macrophage-and ␣-smooth muscle actin-positive cell infiltration, as well as an increased expression of platelet-derived growth factor-B (PDGF-B), monocyte chemoattractant protein-1 (MCP-1), and vascular cell adhesion molecule-1 (VCAM-1). Irbesartan but not amlodipine treatment attenuated the development of atherosclerosis, collagen content, cellular proliferation, and macrophage infiltration as well as diabetes-induced AT 1 receptor, PDGF-B, MCP-1, and VCAM-1 overexpression in the aorta despite similar blood pressure reductions by both treatments. Conclusions-Diabetes-associated atherosclerosis is ameliorated by AT 1 receptor blockade but not by calcium channel antagonism, providing further evidence for the vascular renin-angiotensin system playing a pivotal role in the development and acceleration of atherosclerosis in diabetes.

Abstract. Hyperlipidemia not only may be relevant to cardiovascular disease in diabetes but may also play a role in the development and progression of diabetic nephropathy. Furthermore, there is increasing evidence that advanced glycation end products (AGE) play an important role in diabetic renal disease. The objectives of this study were first to characterize renal injury in diabetic apolipoprotein E knockout (apo E-KO) mice and second to explore the role of AGE in the development and progression of renal disease in this model. Diabetes was induced by injection of streptozotocin in 6-wk-old apo E-KO mice. Diabetic animals received no treatment or treatment with the inhibitor of AGE formation aminoguanidine (1 g/kg per d) or the cross-link breaker [4,5-dimethyl-3-(2-oxo2-phenylethyl)-thiazolium chloride] ALT-711, which cleaves preformed AGE (20 mg/kg per d) for 20 wk. Nondiabetic apo E-KO mice as well as nondiabetic and diabetic C57BL/6 mice served as controls. Compared with nondiabetic apo E-KO mice, induction of diabetes in apo E-KO mice resulted in accelerated renal injury characterized by albuminuria and glomerular and tubulointerstitial injury. These abnormalities were associated with increased expression of collagen type I and type IV and transforming growth factor-␤1 (TGF-␤1), increased ␣-smooth muscle actin immunostaining and macrophage infiltration, and increased serum and renal AGE. The two treatments, which attenuated renal AGE accumulation in a disparate manner, were associated with less albuminuria, structural injury, macrophage infiltration, TGF-␤1, and collagen expression. The accelerated renal injury that was observed in diabetic apo E-KO mice was attenuated by approaches that inhibit renal AGE accumulation.

In the diabetic kidney, clinical as well as experimental observations have shown an upregulation of growth factors such as PDGF. These studies, however, were not designed to address whether upregulation of PDGF is merely a manifestation of diabetic renal injury or whether PDGF plays an active role in the pathophysiology of diabetic nephropathy. The objectives of this study were first to assess whether PDGF-dependent pathways are involved in the development of diabetic nephropathy and second to determine the effects of PDGF receptor antagonism on this disorder and associated molecular and cellular processes. This study used the diabetic apolipoprotein E-knockout (apoE-KO) mouse, a recently described model of accelerated diabetic nephropathy. Diabetes was induced by injection of streptozotocin in 6-wk-old apoE-KO mice.

Although metabolic derangement plays a central role in diabetic nephropathy, a better understanding of secondary mediators of injury may lead to new therapeutic strategies. Expression of macrophage migration inhibitory factor (MIF) is increased in experimental diabetic nephropathy, and increased tubulointerstitial mRNA expression of its receptor, CD74, has been observed in human diabetic nephropathy. Whether CD74 transduces MIF signals in podocytes, however, is unknown. Here, we found glomerular and tubulointerstitial CD74 mRNA expression to be increased in Pima Indians with type 2 diabetes and diabetic nephropathy. Immunohistochemistry confirmed the increased glomerular and tubular expression of CD74 in clinical and experimental diabetic nephropathy and localized glomerular CD74 to podocytes. In cultured human podocytes, CD74 was expressed at the cell surface, was upregulated by high concentrations of glucose and TNF-␣, and was activated by MIF, leading to phosphorylation of extracellular signal-regulated kinase 1/2 and p38. High glucose also induced CD74 expression in a human proximal tubule cell line (HK2). In addition, MIF induced the expression of the inflammatory mediators TRAIL and monocyte chemoattractant protein 1 in podocytes and HK2 cells in a p38-dependent manner. These data suggest that CD74 acts as a receptor for MIF in podocytes and may play a role in the pathogenesis of diabetic nephropathy.