Disparate Effects of Diabetes and Hyperlipidemia on Experimental Kidney Disease.

It is well established that diabetes is the major cause of chronic kidney disease worldwide. Both hyperglycemia, and more recently, advanced glycation endproducts, have been shown to play critical roles in the development of kidney disease. Moreover, the renin-angiotensin system along with growth factors and cytokines have also been shown to contribute to the onset and progression of diabetic kidney disease; however, the role of lipids in this context is poorly characterized. The current study aimed to compare the effect of 20 weeks of streptozotocin-induced diabetes or western diet feeding on kidney disease in two different mouse strains, C57BL/6 mice and hyperlipidemic apolipoprotein (apo) E knockout (KO) mice. Mice were fed a chow diet (control), a western diet (21% fat, 0.15% cholesterol) or were induced with streptozotocin-diabetes (55 mg/kg/day for 5 days) then fed a chow diet and followed for 20 weeks. The induction of diabetes was associated with a 3-fold elevation in glycated hemoglobin and an increase in kidney to body weight ratio regardless of strain (p < 0.0001). ApoE deficiency significantly increased plasma cholesterol and triglyceride levels and feeding of a western diet exacerbated these effects. Despite this, urinary albumin excretion (UAE) was elevated in diabetic mice to a similar extent in both strains (p < 0.0001) but no effect was seen with a western diet in either strain. Diabetes was also associated with extracellular matrix accumulation in both strains, and western diet feeding to a lesser extent in apoE KO mice. Consistent with this, an increase in renal mRNA expression of the fibrotic marker, fibronectin, was observed in diabetic C57BL/6 mice (p < 0.0001). In summary, these studies demonstrate disparate effects of diabetes and hyperlipidemia on kidney injury, with features of the diabetic milieu other than lipids suggested to play a more prominent role in driving renal pathology.

Diabetes Reduces Severity of Aortic Aneurysms Depending on the Presence of Cell Division Autoantigen 1 (CDA1).

Diabetes is a negative risk factor for aortic aneurysm, but the underlying explanation for this phenomenon is unknown. We have previously demonstrated that cell division autoantigen 1 (CDA1), which enhances transforming growth factor-ß signaling, is upregulated in diabetes. We hypothesized that CDA1 plays a key role in conferring the protective effect of diabetes against aortic aneurysms. Male wild-type, CDA1 knockout (KO), apolipoprotein E (ApoE) KO, and CDA1/ApoE double-KO (dKO) mice were rendered diabetic. Whereas aneurysms were not observed in diabetic ApoE KO and wild-type mice, 40% of diabetic dKO mice developed aortic aneurysms. These aneurysms were associated with attenuated aortic transforming growth factor-ß signaling, reduced expression of various collagens, and increased aortic macrophage infiltration and matrix metalloproteinase 12 expression. In the well-characterized model of angiotensin II-induced aneurysm formation, concomitant diabetes reduced fatal aortic rupture and attenuated suprarenal aortic expansion, changes not seen in dKO mice. Furthermore, aortic CDA1 expression was downregulated ∼70% within biopsies from human abdominal aortic aneurysms. The identification that diabetes is associated with upregulation of vascular CDA1 and that CDA1 deletion in diabetic mice promotes aneurysm formation provides evidence that CDA1 plays a role in diabetes to reduce susceptibility to aneurysm formation.

Angiotensin II type 2 receptor (AT2R) in renal and cardiovascular disease.

Angiotensin II (Ang II) is well-considered to be the principal effector of the renin-angiotensin system (RAS), which binds with strong affinity to the angiotensin II type 1 (AT1R) and type 2 (AT2R) receptor subtype. However, activation of both receptors is likely to stimulate different signalling mechanisms/pathways and produce distinct biological responses. The haemodynamic and non-haemodynamic effects of Ang II, including its ability to regulate blood pressure, maintain water-electrolyte balance and promote vasoconstriction and cellular growth are well-documented to be mediated primarily by the AT1R. However, its biological and functional effects mediated through the AT2R subtype are still poorly understood. Recent studies have emphasized that activation of the AT2R regulates tissue and organ development and provides in certain context a potential counter-regulatory mechanism against AT1R-mediated actions. Thus, this review will focus on providing insights into the biological role of the AT2R, in particular its actions within the renal and cardiovascular system.

The angiotensin II type 2 receptor agonist Compound 21 is protective in experimental diabetes-associated atherosclerosis.

AIMS/HYPOTHESIS: Angiotensin II is well-recognised to be a key mediator in driving the pathological events of diabetes-associated atherosclerosis via signalling through its angiotensin II type 1 receptor (AT1R) subtype. However, its actions via the angiotensin II type 2 receptor (AT2R) subtype are still poorly understood. This study is the first to investigate the role of the novel selective AT2R agonist, Compound 21 (C21) in an experimental model of diabetes-associated atherosclerosis (DAA). METHODS: Streptozotocin-induced diabetic Apoe-knockout mice were treated with vehicle (0.1 mol/l citrate buffer), C21 (1 mg/kg per day), candesartan cilexetil (4 mg/kg per day) or C21 + candesartan cilexetil over a 20 week period. In vitro models of DAA using human aortic endothelial cells and monocyte cultures treated with C21 were also performed. At the end of the experiments, assessment of plaque content and markers of oxidative stress, inflammation and fibrosis were conducted. RESULTS: C21 treatment significantly attenuated aortic plaque deposition in a mouse model of DAA in vivo, in association with a decreased infiltration of macrophages and mediators of inflammation, oxidative stress and fibrosis. On the other hand, combination therapy with C21 and candesartan (AT1R antagonist) appeared to have a limited additive effect in attenuating the pathology of DAA when compared with either treatment alone. Similarly, C21 was found to confer profound anti-atherosclerotic actions at the in vitro level, particularly in the setting of hyperglycaemia. Strikingly, these atheroprotective actions of C21 were completely blocked by the AT2R antagonist PD123319. CONCLUSIONS/INTERPRETATION: Taken together, these findings provide novel mechanistic and potential therapeutic insights into C21 as a monotherapy agent against DAA.

Mouse Models for Studying Diabetic Nephropathy.

Diabetic nephropathy (DN) is a term used to describe kidney damage cause by diabetes. With DN as one of the leading causes of end-stage renal disease worldwide, there is a strong need for appropriate animal models to study DN pathogenesis and develop therapeutic strategies. To date, most experiments are carried out in mouse models as opposed to other species for several reasons including lower cost, ease of handling, and easy manipulation of the mouse genome to generate transgenic and knockout animals. This unit provides detailed insights and technical knowledge in setting up one of the most widely used models of DN, the streptozotocin (STZ)-induced model. This model has been extensively exploited to study the mechanism of diabetic renal injury. The advantages and limitations of the STZ model and the availability of other genetic models of DN are also discussed.

AT2R agonist, compound 21, is reno-protective against type 1 diabetic nephropathy.

The hemodynamic and nonhemodynamic effects of angiotensin II on diabetic complications are considered to be primarily mediated by the angiotensin II type 1 receptor subtype. However, its biological and functional effect mediated through the angiotensin II type 2 receptor subtype is still unclear. Activation of the angiotensin II type 2 receptors has been postulated to oppose angiotensin II type 1 receptor-mediated actions and thus attenuate fibrosis. This study aimed to elucidate the reno-protective role of the novel selective angiotensin II type 2 receptor agonist, Compound 21, in an experimental model of type 1 diabetic nephropathy. Compound 21 treatment significantly attenuated diabetes mellitus-induced elevated levels of cystatin C, albuminuria, mesangial expansion, and glomerulosclerosis in diabetic mice. Moreover, Compound 21 markedly inhibited the expression of various proteins implicated in oxidative stress, inflammation, and fibrosis, in association with decreased extracellular matrix production. These findings demonstrate that monotherapy of Compound 21 is protective against the progression of experimental diabetic nephropathy by inhibiting renal oxidative stress, inflammation, and fibrosis.

Role of bone-marrow- and non-bone-marrow-derived receptor for advanced glycation end-products (RAGE) in a mouse model of diabetes-associated atherosclerosis.

RAGE (receptor for advanced glycation end-products) is expressed on multiple cell types implicated in the progression of atherosclerosis and plays a role in DAA (diabetes-associated atherosclerosis). The aim of the present study was to determine the relative role of either BM (bone marrow)- or non-BM-derived RAGE in the pathogenesis of STZ (streptozotocin)-induced DAA. Male ApoE (apolipoprotein E)-null (ApoE-/-:RAGE+/+) and ApoE:RAGE-null (ApoE-/-:RAGE-/-) mice at 7 weeks of age were rendered diabetic with STZ. At 8 weeks of age, ApoE-/- and ApoE-/-:RAGE-/- control and diabetic mice received BM from either RAGE-null or RAGE-bearing mice, generating various chimaeras. After 10 and 20 weeks of diabetes, mice were killed and gene expression and atherosclerotic lesion formation were evaluated respectively. Deletion of RAGE in either the BM cells or non-BM cells both resulted in a significant attenuation in DAA, which was associated with reduced VCAM-1 (vascular cell adhesion molecule-1) expression and translated into reduced adhesion in vitro. In conclusion, the results of the present study highlight the importance of both BM- and non-BM-derived RAGE in attenuating the development of DAA.

Novel pathways and therapies in experimental diabetic atherosclerosis.

Diabetic subjects are at a greater risk of developing major vascular complications due to abnormalities pertinent to the diabetic milieu. Current treatment options achieve significant improvements in glucose levels and blood pressure control, but do not necessarily prevent or retard diabetes-mediated macrovascular disease. In this review, we highlight several pathways that are increasingly being appreciated as playing a significant role in diabetic vascular injury. We focus particularly on the advanced glycation end product/receptor for advanced glycation end product (AGE/RAGE) axis and its interplay with the nuclear protein HMGB1. We discuss evidence implicating a significant role for the renin-angiotensin system, urotensin II and PPAR, as well as the importance of proinflammatory mediators and oxidative stress in cardiovascular complications. The specific targeting of these pathways may lead to novel therapies to reduce the burden of diabetic vascular complications.

The pleiotropic actions of rosuvastatin confer renal benefits in the diabetic Apo-E knockout mouse.

Diabetic nephropathy is a leading cause of end-stage renal disease. Statins may exert renoprotective effects independently of lipid-lowering properties. We investigated the pleiotropic effects of rosuvastatin on renal structure and function in streptozotocin diabetic apolipoprotein-E knockout (Apo-E(-/-)) mice, a model of progressive nephropathy in which dyslipidemia is resistant to statin treatment. These effects were compared with those observed with conventional renin-angiotensin system blockade (candesartan) or combined treatment. Nondiabetic and diabetic Apo-E(-/-) mice were randomized to no treatment or treatment with candesartan (2.5 mg/kg), rosuvastatin (5 mg/kg), or their combination per gavage for 20 wk. Urine and blood samples were collected for assessment of albuminuria, creatinine clearance, plasma lipids, glucose, and glycated hemoglobin. Renal sclerosis was analyzed on paraffin-embedded kidney sections stained with periodic acid-Schiff. Renal expression of collagen IV, fibronectin and advanced glycation end products (AGEs), receptor for advanced glycation and products (RAGE), NADPH oxidase 4 (NOX4), and nitrotyrosine was assessed by real-time PCR and/or immunohistochemistry. Diabetes-induced albuminuria was not affected by rosuvastatin and combination treatment but was prevented by candesartan. Diabetes resulted in increased creatinine clearance, which was not modified by the treatments. Rosuvastatin and/or candesartan prevented diabetes-associated renal extracellular matrix accumulation. Rosuvastatin reduced accumulation of AGEs and expression of RAGE, NOX4, and nitrotyrosine. In conclusion, in the diabetic Apo-E(-/-) mouse, rosuvastatin confers renal benefits that are independent of lipid lowering and equivalent or greater to those observed with candesartan. The combination treatment is not superior to monotherapies.

Regulation of pro-inflammatory and pro-fibrotic factors by CCN2/CTGF in H9c2 cardiomyocytes.

Connective tissue growth factor (CTGF), also known as CCN2, is implicated in fibrosis through both extracellular matrix (ECM) induction and inhibition of ECM degradation. The role of CTGF in inflammation in cardiomyocytes is unknown. In some mesenchymal cell systems, CTGF mediates effects through TGF-beta or tyrosine kinase cell surface receptor, TrkA, signalling. In this study, cellular mechanisms by which CTGF regulates pathways involved in fibrosis and inflammation were explored. Murine H9c2 cardiomyocytes were treated with recombinant human (rh)CTGF and ECM formation gene expression: fibronectin, collagen type -I and -III and ECM degradation genes: TIMP-1, TIMP-2 and PAI-1 were found to be induced. CTGF treatment also increased pro-inflammatory cytokines TNF-alpha, IL-6, MCP-1 and IL-8. CTGF upregulated TGF-beta1 mRNA and rapidly induced phosphorylation of TrkA. The CTGF-induced pro-fibrotic and pro-inflammatory effects were blocked by anti-TGF-beta neutralizing antibody and Alk 5 inhibitor (SB431542). A specific blocker of TrkA activation, k252a, also abrogated CTGF-induced effects on fibrosis and gene expresison of MCP-1 and IL-8, but not TNF-alpha or IL-6. Collectively, this data implicates CTGF in effects on pro-fibrotic genes and pro-inflammatory genes via TGF-beta pathway signalling and partly through TrkA.

Adverse effects of high glucose and free fatty acid on cardiomyocytes are mediated by connective tissue growth factor.

Diabetic cardiomyopathy is characterized by interstitial fibrosis and cardiomyocyte hypertrophy and apoptosis. Also known as CCN2, connective tissue growth factor (CTGF) is implicated in the fibrosis; however, whether it contributes to cardiomyocytes changes and adverse effects of high glucose and lipids on these cells remains unknown. Hearts from streptozotocin-induced diabetic rats had elevated CTGF and changes of pathological myocardial hypertrophy, fibrosis, and cardiomyocyte apoptosis. Rat H9c2 cardiomyocytes were then treated with recombinant human (rh)CTGF, high glucose, or the saturated free fatty acid palmitate. Each reagent induced cell hypertrophy, as indicated by the ratio of total protein to cell number, cell size, and gene expression of cardiac hypertrophy marker genes atrial natriuretic peptide (ANP), and alpha-skeletal actin. Each treatment also caused apoptosis measured by increased caspase3/7 activity, apoptotic cells by transferase-mediated dUTP nick end labeling (TUNEL) assay, and lower viable cell number. Further studies showed CTGF mRNA was rapidly induced by high glucose and palmitate in H9c2 cells and in mouse neonatal cardiomyocyte primary cultures. small interfering RNA against CTGF blocked the high glucose and palmitate induction of hypertrophy and apoptosis. In addition, these CTGF effects were through the tyrosine kinase A (TrkA) receptor with tyrosine kinase activity, which has previously been implicated in CTGF signaling: TrkA was phosphorylated by CTGF, and a specific TrkA blocker abrogated CTGF-induced effects on hypertrophy and apoptosis. For the first time in any system, fatty acid is newly identified as a regulator of CTGF, and this work implicates autocrine CTGF as a mediator of adverse effects of high glucose and fatty acids in cardiomyocytes.

Eplerenone does not attenuate diabetes-associated atherosclerosis.

BACKGROUND: It has been suggested that aldosterone, with its known pro-inflammatory and profibrotic actions, may play a key role in the development and progression of atherosclerosis. METHOD: In this study, the ability of aldosterone antagonism to reduce atherosclerosis in experimental diabetes was assessed. Diabetes was induced in ApoE knockout mice with streptozotocin, and the mice were treated with the specific aldosterone antagonist, eplerenone, in their feed over 20 weeks (approximately 200 mg/kg per day). RESULT: En face analysis revealed that eplerenone treatment was unable to attenuate atherosclerosis as assessed by percentage lesion area quantitation in the aortae of these mice compared with untreated diabetic mice (diabetic, 10.7 +/- 1.1; diabetic + eplerenone, 8.8 +/- 1.2%). In contrast, we observed a significant, more than 50% decrease in percentage of plaque area in the nondiabetic control groups. Despite this lack of effect in the diabetic mice, eplerenone treatment was associated with reduced cytosolic superoxide production. However, aortic transcript levels of key molecules implicated in diabetes-associated atherogenesis, such as monocyte chemoattractant protein-1 and vascular cell adhesion molecule-1, were not significantly attenuated by eplerenone. CONCLUSION: These findings suggest that eplerenone treatment may not be as antiatherosclerotic in the diabetic context.

Linking diabetes and atherosclerosis.

Cardiovascular diseases are the major causes of morbidity and mortality in people with diabetes. Macroangiopathy in diabetes is manifested by more accelerated and progressive atherosclerosis, which is more widely distributed. The pathogenesis of this accelerated atherosclerosis is multifactorial and includes very complex interactions. Several abnormalities - such as hyperglycemia, dyslipidemia, hypertension, endothelial dysfunction, renin-angiotensin system activation and chronic subclinical inflammation - all appear to play important roles in the development of diabetes-induced atherosclerosis. Treatment of the residual risk, other than glycemia, blood pressure and low-density lipoprotein cholesterol, remains important as the rate of diabetes increases worldwide. A synergistic multifactorial approach against both conventional cardiovascular risk factors and emerging risk factors, such as vasoactive systems, the AGE-RAGE axis, novel proteins, such as TRAIL, and the complement system, as well as oxidative stress and inflammation, may be a promising way to prevent macrovascular disease in diabetes. In this review we focus on the major causes and mechanisms of atherosclerotic disease in patients with diabetes and highlight emerging targets for therapeutic intervention.

Rodent models of streptozotocin-induced diabetic nephropathy.

Streptozotocin-induced pancreatic injury is commonly used for creating rodent models of type 1 diabetes which develop renal injury with similarities to human diabetic nephropathy. This model can be established in genetically modified rodents for investigating the role of molecular mechanisms and genetic susceptibility in the development of diabetic nephropathy. In this report, the authors describe and compare the current protocols being used to establish models of diabetic nephropathy in rat and mouse strains using streptozotocin. The authors also list some of the histological criteria and biochemical measurements which are being used to validate these models. In addition, our review explains some of the key aspects involved in these models, including the impact of streptozotocin-dosage, uninephrectomy, hypertension and genetically modified strains, which can each affect the development of disease and the interpretation of findings.

Lack of the antioxidant enzyme glutathione peroxidase-1 accelerates atherosclerosis in diabetic apolipoprotein E-deficient mice.

BACKGROUND: Recent clinical studies have suggested a major protective role for the antioxidant enzyme glutathione peroxidase-1 (GPx1) in diabetes-associated atherosclerosis. We induced diabetes in mice deficient for both GPx1 and apolipoprotein E (ApoE) to determine whether this is merely an association or whether GPx1 has a direct effect on diabetes-associated atherosclerosis. METHODS AND RESULTS: ApoE-deficient (ApoE-/-) and ApoE/GPx1 double-knockout (ApoE-/- GPx1-/-) mice were made diabetic with streptozotocin and aortic lesion formation, and atherogenic pathways were assessed after 10 and 20 weeks of diabetes. Aortic proinflammatory and profibrotic markers were determined by both quantitative reverse-transcription polymerase chain reaction analysis after 10 weeks of diabetes and immunohistochemical analysis after 10 and 20 weeks of diabetes. Sham-injected nondiabetic counterparts served as controls. Atherosclerotic lesions within the aortic sinus region, as well as arch, thoracic, and abdominal lesions, were significantly increased in diabetic ApoE-/- GPx1-/- aortas compared with diabetic ApoE-/- aortas. This increase was accompanied by increased macrophages, alpha-smooth muscle actin, receptors for advanced glycation end products, and various proinflammatory (vascular cell adhesion molecule-1) and profibrotic (vascular endothelial growth factor and connective tissue growth factor) markers. Quantitative reverse-transcription polymerase chain reaction analysis showed increased expression of receptors for advanced glycation end products (RAGE), vascular cell adhesion molecule-1, vascular endothelial growth factor, and connective tissue growth factor. Nitrotyrosine levels were significantly increased in diabetic ApoE-/- GPx1-/- mouse aortas. These findings were observed despite upregulation of other antioxidants. CONCLUSIONS: Lack of functional GPx1 accelerates diabetes-associated atherosclerosis via upregulation of proinflammatory and profibrotic pathways in ApoE-/- mice. Our study provides evidence of a protective role for GPx1 and establishes GPx1 as an important antiatherogenic therapeutic target in patients with or at risk of diabetic macrovascular disease.

Increased atherosclerosis following treatment with a dual PPAR agonist in the ApoE knockout mouse.

OBJECTIVE: Recent reports have suggested that dual peroxisome proliferator-activated receptor (PPAR) alpha/gamma agonists are associated with adverse cardiovascular events. This study aimed to investigate the actions of the non-thiazolidinedione PPARalpha/gamma agonist, compound 3q, on plaque development in the apolipoprotein E knockout (apoE KO) mouse, a recognised model of accelerated plaque development. METHODS: Six-week-old male apoE KO mice were randomised to receive the dual PPARalpha/gamma agonist, compound 3q (3 mg/kg/day), the PPARgamma agonist, rosiglitazone (20 mg/kg/day), the PPARalpha agonist, gemfibrozil (100 mg/kg/day) by gavage or no treatment for 20 weeks (n=12/group). RESULTS: Gemfibrozil and rosiglitazone significantly reduced lesion area. However, compound 3q was associated with a three-fold increase in total plaque area (versus control p<0.001). This was associated with an upregulation of markers of plaque instability including vascular cell adhesion molecule-1 (3.5-fold, p<0.001), P-selectin (3.4-fold, p<0.001) monocyte chemoattractant protein-1 (3.4-fold; p<0.001) as well as the scavenger receptor, CD36 (2-fold, p<0.01). These disparate effects were observed with the dual PPAR agonist despite lowering LDL cholesterol and improving insulin sensitivity to a similar extent to PPARalpha and gamma agonists used individually. CONCLUSION: The finding of increased atherogenesis following a dual PPARalpha/gamma agonist is consistent with recent clinical findings. These data provide an important framework for further exploring the potential utility and safety of combinatorial approaches.

A 1,3-diacylglycerol-rich oil induces less atherosclerosis and lowers plasma cholesterol in diabetic apoE-deficient mice.

OBJECTIVE: Recent studies have demonstrated that 1,3-diacylglycerol (1,3-DAG) has several metabolic advantages over triacylglycerol (TAG) in humans and in animal models despite both oils having a similar fatty acid composition. In our current study, we have examined the effects of long-term feeding of a 1,3-DAG-rich oil on the dyslipidemia and atherosclerosis in the experimental model of the diabetic apolipoprotein E (apoE)-deficient mouse that develops accelerated atherosclerosis. METHODS AND RESULTS: Diets containing 1,3-DAG-rich oil or TAG oil were administered to control non-diabetic apoE-dificient and diabetic apoE-deficient mice for 20 weeks. In diabetic apoE-deficient mice, 1,3-DAG reduced the extent of atherosclerotic lesions in the aortic arch and thoracic aorta by 37 and 44%, respectively, compared to TAG. Further, in diabetic apoE-deficient mice, plasma total cholesterol and triglyceride levels were significantly lower in the 1,3-DAG-fed group than in the TAG-fed group. This occurred partially through an apparent reduction in the size of triglyceride-rich lipoproteins but not apparently by reducing the number of lipoprotein particles. By contrast the control non-diabetic apoE-deficient mice showed no differential responses to the type of oil at least over 20 weeks. CONCLUSIONS: We have demonstrated that dietary 1,3-DAG-rich oil reduced atherosclerosis in diabetic apoE-deficient mice, and was associated with reduction in plasma cholesterol especially within larger triglyceride-rich lipoproteins.

PPAR-alpha and -gamma agonists attenuate diabetic kidney disease in the apolipoprotein E knockout mouse.

BACKGROUND: Peroxisome proliferator-activated receptor (PPAR)-alpha and PPAR-gamma agonists are widely used in diabetes. In addition to their effects on lipid and glucose homeostasis, these agents have been postulated to have independent renoprotective actions. In the current study, we assess the efficacy of the PPAR-alpha agonist, gemfibrozil, the PPAR-gamma agonist rosiglitazone and the non-thiazolidinedione PPAR-alpha/gamma coagonist, compound 3q, on kidney structure and function in streptozotocin-treated apolipoprotein E knockout mice. METHODS: Control and streptozotocin-diabetic mice were randomized to receive rosiglitazone (20 mg/kg/day), gemfibrozil (100 mg/kg/day), or compound 3q (3 mg/kg/day) by gavage, or no treatment for a period of 20 weeks. Renal fibrosis was assessed by standard histology and collagen IV immunohistochemistry. Kidney function was assessed by urinary albumin excretion and creatinine clearance. RESULTS: Diabetes in this model was associated with an increase in glomerulosclerosis, tubulointerstitial fibrosis and increased collagen IV deposition in the glomeruli and tubules. All three agents significantly attenuated glomerulosclerosis, tubulointerstitial expansion and collagen IV deposition. The increase in albuminuria and the decline in kidney function associated with diabetes in this model were also attenuated by each of these agents, with no superiority observed among various treatment groups. These renoprotective effects were observed in the absence of changes in glucose, insulin or lipid levels or a reduction in blood pressure. CONCLUSIONS: Combined with their independent anti-atherosclerotic actions, and their important effects on dyslipidaemia and insulin resistance, PPAR agonists may be useful for the prevention of diabetic complications, including kidney disease, even in type 1 diabetes.

Diabetes mellitus-associated atherosclerosis: mechanisms involved and potential for pharmacological invention.

While diabetes mellitus is most often associated with hypertension, dyslipidemia, and obesity, these factors do not fully account for the increased burden of cardiovascular disease in patients with the disease. This strengthens the need for comprehensive studies investigating the underlying mechanisms mediating diabetic cardiovascular disease and, more specifically, diabetes-associated atherosclerosis. In addition to the recognized metabolic abnormalities associated with diabetes mellitus, upregulation of putative pathological pathways such as advanced glycation end products, the renin-angiotensin system, oxidative stress, and increased expression of growth factors and cytokines have been shown to play a causal role in atherosclerotic plaque formation and may explain the increased risk of macrovascular complications. This review discusses the methods used to assess the development of atherosclerosis in the clinic as well as addressing novel biomarkers of atherosclerosis, such as low-density lipoprotein receptor-1. Experimental models of diabetes-associated atherosclerosis are discussed, such as the streptozocin-induced diabetic apolipoprotein E knockout mouse. Results of major clinical trials with inhibitors of putative atherosclerotic pathways are presented. Other topics covered include the role of HMG-CoA reductase inhibitors and fibric acid derivatives with respect to their lipid-altering ability, as well as their emerging pleiotropic anti-atherogenic actions; the effect of inhibiting the renin-angiotensin system by either ACE inhibition or angiotensin II receptor antagonism; the effect of glycemic control and, in particular, the promising role of thiazolidinediones with respect to their direct anti-atherogenic actions; and newly emerging mediators of diabetes-associated atherosclerosis, such as advanced glycation end products, vascular endothelial growth factor and platelet-derived growth factor. Overall, this review aims to highlight the observation that various pathways, both independently and in concert, appear to contribute toward the pathology of diabetes-associated atherosclerosis. Furthermore, it reflects the need for combination therapy to combat this disease.