Search

Recent clinical trials in people with type 2 diabetes have demonstrated beneficial actions on heart and kidney outcomes following treatment with GLP-1RAs. In part, these actions are consistent with improved glucose control and significant weight loss. But GLP-1RAs may also have additive benefits by improving postprandial dysmetabolism. In diabetes, dysregulated postprandial nutrient excursions trigger inflammation, oxidative stress, endothelial dysfunction, thrombogenicity, and endotoxemia; alter hormone levels; and modulate cardiac output and regional blood and lymphatic flow. In this perspective, we explore the actions of GLP-1RAs on the postprandial state and their potential role in end-organ benefits observed in recent trials. Treatment with GLP-1RAs has been associated with beneficial actions on heart and kidney outcomes in recent clinical trials. Beyond improvements in glucose control and significant weight loss, Thomas et al. argue that the GLP-1RAs may also have additive benefits by improving postprandial dysmetabolism in people with type 2 diabetes. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease commonly is associated with an increased risk of cardiovascular disease. There are traditional common risk factors for both conditions including hypertension and poor glycemic control. However, it is likely that there are other pathophysiological mechanisms that explain the clinical phenomenon of increased cardiovascular disease in diabetic patients with chronic kidney and vice versa. Current management of both conditions includes aggressive glucose and blood pressure control. The protective role of treating dyslipidemia has been shown for cardiovascular disease, but the results for renal disease are not as clear. The advent of new classes of glucose-lowering agents such as sodium glucose co-transporter2 inhibitors and glucagon-like peptide-1 agonists has resulted in impressive effects on both cardiovascular and renal disease in diabetes. However, how these drugs act independently of glucose lowering to confer both kidney and cardiovascular protection has not been fully elucidated. Nevertheless, these new treatments provide optimism for reducing both microvascular and macrovascular complications in diabetes, which represent the major causes of morbidity and premature mortality in this condition. [ABSTRACT FROM AUTHOR]

Background: The consumption of advanced glycation end products (AGEs) has increased because of modern food processing and has been linked to the development of type 2 diabetes in rodents. Objective: We determined whether changing dietary AGE intake could modulate insulin sensitivity and secretion in healthy, overweight individuals. Design: We performed a double-blind, randomized, crossover trial of diets in 20 participants [6 women and 14 men; mean ± SD body mass index (in kg/m²): 29.8 ± 3.7]. Isoenergetic- and macronutrient-matched diets that were high or low in AGE content were alternately consumed for 2 wk and separated by a 4-wk washout period. At the beginning and end of each dietary period, a hyperinsulinemiceuglycemic clamp and an intravenous glucose tolerance test were performed. Dietary, plasma and urinary AGEs N∈-(carboxymethyl) lysine (CML), N∈-(carboxyethyl)lysin (CEL), and methylglyoxal-derived hydroimadazolidine (MG-H1) were measured with the use of mass spectrometry. Results: Participants consumed less CML, CEL, and MG-H1 during the low-AGE dietary period than during the high-AGE period (all P < 0.05), which was confirmed by changes in urinary AGE excretion. There was an overall difference in insulin sensitivity of -22.1 mg ⋅ kg-1 ⋅ min-1 between diets (P = 0.001). Insulin sensitivity increased by 1.3 mg ⋅ kg-1 ⋅ min-1 after the low-AGE diet (P = 0.004), whereas it showed a tendency to decrease by 0.8 mg ⋅ kg-1 ⋅ min-1 after the high-AGE diet (P = 0.086). There was no difference in body weight or insulin secretion between diets (P = NS). Conclusions: A diet that is low in AGEs may reduce the risk of type 2 diabetes by increasing insulin sensitivity. Hence, a restriction in dietary AGE content may be an effective strategy to decrease diabetes and cardiovascular disease risks in overweight individuals. This trial was registered at clinicaltrials.gov as NCT00422253. [ABSTRACT FROM AUTHOR]

Background This study aimed at investigating the effects of genetic angiotensin-converting enzyme (ACE) 2 deficiency on glucose homeostasis in the pancreas and skeletal muscle and their reversibility following ACE inhibition. Procedures ACE2 -knockout and C57bl6J mice were placed on a standard diet (SD) or a high-fat diet (HFD) for 12 weeks. An additional group of ACE2 -knockout mice was fed a SD and treated with the ACE inhibitor, perindopril (2 mg kg − 1 day − 1 ). Glucose and insulin tolerance tests, indirect calorimetry measurements and EchoMRI were performed. Non-esterfied ‘free’ fatty acid oxidation rate in skeletal muscle was calculated by measuring the palmitate oxidation rate. β-cell mass was determined by immunostaining. Insulin, collectrin, glucose transporter protein, and peroxisome proliferator-activated receptor-γ expression were analysed by RT-PCR. Markers of mithocondrial biogenesis/content were also evaluated. Main Findings ACE2 -knockout mice showed a β-cell defect associated with low insulin and collectrin levels and reduced compensatory hypertrophy in response to a HFD, which were not reversed by perindopril. On the other hand, ACE2 deficiency shifted energy metabolism towards glucose utilization, as it increased the respiratory exchange ratio, reduced palmitate oxidation and PCG-1α expression in the skeletal muscle, where it up-regulated glucose transport proteins. Treatment of ACE2 -knockout mice with perindopril reversed the skeletal muscle changes, suggesting that these were dependent on Angiotensin II (Ang II). Principal Conclusions ACE2 -knockout mice display a β-cell defect, which does not seem to be dependent on Ang II but may reflect the collectrin-like action of ACE2. This defect seemed to be compensated by the fact that ACE2 -knockout mice shifted their energy consumption towards glucose utilisation via Ang II. [ABSTRACT FROM AUTHOR]

Abstract: Decreased gene expression of heat shock protein 72 (HSP72) in skeletal muscle is associated with insulin resistance in humans. We aimed to determine whether HSP72 protein expression in insulin-sensitive tissues is related to criterion standard measures of adiposity and insulin resistance in a young healthy human population free of hyperglycemia. Healthy participants (N = 17; age, 30 ± 3 years) underwent measurement of body composition (dual-energy x-ray absorptiometry), a maximum aerobic capacity test (V̇o 2max), an oral glucose tolerance test, and a hyperinsulinemic-euglycemic clamp (M) to access insulin sensitivity. Skeletal muscle and subcutaneous adipose tissue biopsies were obtained by percutaneous needle biopsy. HSP72 protein expression in skeletal muscle was inversely related to percentage body fat (r = −0.54, P < .05) and remained significant after adjustment for age and sex (P < .05). Insulin sensitivity was also related to HSP72 protein expression in skeletal muscle (r = 0.52, P < .05); however, this relationship disappeared after adjustment for percentage body fat (P = .2). In adipose tissue, HSP72 protein expression was not related to adiposity or insulin sensitivity. Physical activity and aerobic fitness did not show any association with HSP72 protein expression in either tissue studied. A lower expression of HSP72 protein in human skeletal muscle was associated with increased adiposity and decreased insulin sensitivity in healthy individuals. These findings are consistent with rodent data suggesting that HSP72 stimulates fat oxidation with consequent reduction in fat storage and adiposity. [ABSTRACT FROM AUTHOR]

Summary: Diabetic nephropathy is a major cause of morbidity and mortality in diabetic patients. Two key mechanisms implicated in the development of diabetic nephropathy include advanced glycation and oxidative stress. Advanced glycation is the irreversible attachment of reducing sugars onto amino groups of proteins to form advanced glycation end products (AGEs). AGE modification of proteins may lead to alterations in normal function by inducing cross-linking of extracellular matrices. Intracellular formation of AGEs also can cause generalized cellular dysfunction. Furthermore, AGEs can mediate their effects via specific receptors, such as the receptor for AGE (RAGE), activating diverse signal transduction cascades and downstream pathways, including generation of reactive oxygen species (ROS). Oxidative stress occurs as a result of the imbalance between ROS production and antioxidant defenses. Sources of ROS include the mitochondria, auto-oxidation of glucose, and enzymatic pathways including nicotinamide adenine dinucleotide phosphate reduced (NAD[P]H) oxidase. Beyond the current treatments to treat diabetic complications such as the optimization of blood pressure and glycemic control, it is predicted that new therapies designed to target AGEs, including AGE formation inhibitors and cross-link breakers, as well as targeting ROS using novel highly specific antioxidants, will become part of the treatment regimen for diabetic renal disease. [ABSTRACT FROM AUTHOR]

Advanced glycation end-products (AGEs) contribute to the development and progression of diabetic kidney disease. Several different strategies have been developed to prevent the accumulation of AGEs in experimental diabetes, many of which have proved highly effective in attenuating renal damage in experimental models, even the absence of blood glucose control. These data suggests that if AGEs can be directly treated, some of the complications of diabetes may also be prevented. [Copyright &y& Elsevier]

Reports on the estimated number of people worldwide who will have diabetes by the year of 2025, according to the World Health Organization. Percentage of newly diagnosed patients with type 2 diabetes; Development of diabetic nephropathy; Total number of people with type 1 diabetes.

The tubulointerstitium in progressive diabetic kidney disease: More than an aftermath of glomerular injury? Although the glomerulus, particularly the mesangium, has been the focus of intense investigation in diabetes, tubulointerstitial injury is also a major feature of diabetic nephropathy and an important predictor of renal dysfunction. The renal tubule in diabetes is subject to both direct and indirect pathogenetic influences as a consequence of its position in the nephron and its resorptive function. On exposure to glucose, proximal tubular cells elaborate vasoactive hormones, including angiotensin II and injurious cytokines such as transforming growth factor-β (TGF-β), as well as extracellular matrix proteins. In turn, angiotensin II may further increase TGF-β expression in both proximal tubular and interstitial cells, thus amplifying the stimulus to fibrogenesis in the renal tubulointerstitium. In addition to these mostly direct influences, the renal tubule, particularly its proximal segment, is exposed to glomerular effluent. In the diabetic state, this includes large quantities of advanced glycation end products and glucose and, at later stages in the evolution of diabetic nephropathy, protein, all of which are factors that may induce TGF-β expression and fibrosis. Diabetic nephropathy should therefore be viewed as a disease affecting the entire nephron. Continued exploration into tubulointerstitial disease in addition to glomerular injury in diabetes may help provide further insights into the pathogenesis of diabetic nephropathy and additional targets for therapeutic intervention. [ABSTRACT FROM AUTHOR]

Comments on the prevention of end-stage renal disease (ESRD) in the U.S. Factors contributing to the decline in the renal function rate; Proportion of time spent on conservative therapy; Cost of ESRD treatment.

Editorial. Examines the role of growth factors in the development and progression of renal disease. Relationship between insulin-like growth factor-1 and vascular endothelial growth factor; Activation of the nonreceptor tyrosine kinase pathways by a diverse range of mitogens.

The mechanisms involved in expansion of the tubulointerstitial compartment of the kidney in individuals with diabetes are not well understood. Given that tubulointerstitial damage is an important predictor of progression to end-stage kidney disease in most forms of chronic kidney disease it is imperative to gain a greater understanding of the processes involved. With this in mind, a very clear objective for the scientific content of this meeting was to spend more than half the program outside the comfort zone of nephrology, gaining insights from sources such as neurodegenerative and mitochondrial diseases, stem cells, cancer and high-level computing to reconstruct organ systems. The meeting also aimed to place the new concepts presented in the context of current knowledge in diabetic kidney disease and the milestones achieved to date in this area. The presenters were all extremely generous, giving not only their time, but also showing a large proportion of unpublished data to stimulate discussions, questions and innovation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cardiovascular disease (CVD) has many risk factors contributing to development. [•] Advanced glycation endproducts (AGEs) contribute to many pathologies of CVD. [•] Mitochondrial dysfunction (mito-stress) facilitates pathological events. [•] Targeting of both AGEs and mito-stress may hold the key to CVD treatment. [ABSTRACT FROM AUTHOR]

Abstract: Glycated proteins/advanced glycation endproducts contribute to the development of diabetic complications but the precise pathway from glycated proteins to complications is still being delineated. The ezrin, radixin and moesin protein family is a new class of advanced glycation endproduct-binding protein and we hypothesize that advanced glycation endproducts mediate some of their detrimental effects leading to diabetic complications by inhibiting ezrin''s actions. Our previous study revealed that glycated proteins bind to the N-terminal domain of ezrin (aa 1–324) and this study further defines the ezrin binding epitope. Binding of glycated albumin to recombinant N-ezrin deletion constructs (aa 1–280, 1–170 and 1–144) and glutathione-S-transferase-N-ezrin fusion proteins, (aa 200–324 and 270–324) was analysed using ligand and far Western blotting, and surface plasmon resonance. Glycated albumin binding was markedly reduced on removal of amino acids 280–324, while binding was preserved in the fusion proteins. A series of peptides based on residues 280–324 was synthesized and those containing residues 277–299 of ezrin bound maximally. Peptide binding to glycated albumin was glycation-specific. An ezrin peptide (aa 277–299) dose-dependently reversed the inhibitory effect of glycated albumin on ezrin (1–324) phosphorylation in vitro, suggesting that binding of advanced glycation endproducts to ezrin changes the conformation of the latter sufficiently to alter binding interactions distant from the advanced glycation endproduct-binding site. This may have consequences for subcellular ezrin localization and signalling pathways. Altogether, these studies provide important structural knowledge for developing peptide antagonists that may be therapeutically useful in preventing advanced glycation endproduct:ezrin interactions in diabetes. [Copyright &y& Elsevier]

Calcium channel blockers, either amlodipine or mibefradil, ameliorate renal injury in experimental diabetes. Background. Diabetic nephropathy is associated with increased albuminuria and accmulation of extracellular matrix proteins within the kidney. Clinical studies have shown some beneficial effects of calcium channel blockers (CCB) on diabetic nephropathy, even though they are generally considered to be less renoprotective than agents that interrupt the renin angiotensin system. However, effects of CCBs on renal injury, and in particular, expression of extracellular matrix proteins in a model of normotensive diabetic nephropathy, are poorly characterized. Methods. Experimental diabetes was induced by injection of streptozocin in Sprague-Dawley rats. Amlodipine, a CCB which blocks the L channel, and mibefradil, a CCB blocking the T as well as the L channels, were given to diabetic rats for six months. Albumin excretion rate (AER), pathologic injury, and expression of the extracellular matrix proteins, collagen I, and fibronectin were assessed. Results. Increased AER in diabetic rats (13.2 ×/÷1.3 mg/d, geometric mean ×/÷ tolerance factor) was attenuated by either amlodipine (3.2 ×/÷ 1.4 mg/d) or mibefradil (2.6 ×/÷ 1.4 mg/d). Increased glomerulosclerosis and tubulointerstitial injury in diabetic animals were attenuated by amlodipine and mibefradil. There was increased collagen accmulation in the kidney of diabetic rats as assessed by picro-sirius red staining. Gene expression of both collagen I and fibronectin were also increased in the kidneys from diabetic animals, as assessed by reverse transcription-polymerase chain reaction (RT-PCR). These markers of fibrosis were attenuated by treatment with either amlodipine or mibefradil. Blood pressure in diabetic rats (136 ± 2 mm Hg) was modestly reduced by amlodipine (126 ± 3 mm Hg) but not by mibefradil treatment (134 ± 3 mm Hg). Conclusion. Calcium channel blockers attenuated albuminuria, pathologic injury, and accmulation of extracellular matrix proteins in this normotensive model of diabetic nephropathy. These findings suggest that CCBs may be useful in preventing pathologic injury in the diabetic kidney. [ABSTRACT FROM AUTHOR]

Effect of diabetes and aminoguanidine therapy on renal advanced glycation end-product binding. Background. Advanced glycation end-products (AGEs) have been implicated in the pathogenesis of diabetic nephropathy, and aminoguanidine (AG) has been shown to decrease the accumulation of AGEs in the diabetic kidney. Methods. This study investigates changes in AGE binding associated with diabetes in the rat kidney using in vitro and in vivo autoradiographic techniques. Male Sprague-Dawley rats were randomized into control and diabetic groups with and without AG treatment and were sacrificed after three weeks. Frozen kidney sections (20 μm) were incubated with [125I]-AGE-RNase or [125I]-AGE-BSA. To localize the AGE binding site, in vivo autoradiography was performed by injection of 15 μCi of [125I]-AGE-BSA into the abdominal aorta of the rat. Results. Low-affinity binding sites specific for AGEs in the renal cortex (IC50 = 0.28 μm) were detected by in vitro autoradiography. There was a significant increase in [125I]-AGE binding in the diabetic kidney, which was prevented by AG treatment. Emulsion autoradiography revealed that binding was localized primarily to proximal tubules in the renal cortex. Renal AGE levels, as assessed by fluorescence or by radioimmunoassay, were increased after three weeks of diabetes. This increase was attenuated by AG therapy. Conclusions. AGE binding sites are present within the proximal tubules of the kidney and appear to be modulated by endogenous AGE levels. It remains to be determined if these binding sites represent receptors involved in clearance of AGEs or are linked to pathogenic pathways that lead to the development of diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Methylglyoxal (MGO) is a reactive glucose metabolite linked to diabetic cardiovascular disease (CVD). MGO levels surge during intermittent hyperglycemia. We hypothesize that these MGO spikes contribute to atherosclerosis, and that pyridoxamine as a MGO quencher prevents this injury. To study this, we intravenously injected normoglycemic 8-week old male C57Bl6 ApoE-/- mice with normal saline (NS, n = 10) or 25 µg MGO for 10 consecutive weeks (MGO iv , n = 11) with or without 1 g/L pyridoxamine (MGO iv +PD, n = 11) in the drinking water. We measured circulating immune cells by flow cytometry. We quantified aortic arch lesion area in aortic roots after Sudan-black staining. We quantified the expression of inflammatory genes in the aorta by qPCR. Intermittent MGO spikes weekly increased atherosclerotic burden in the arch 1.8-fold (NS: 0.9 ± 0.1 vs 1.6 ± 0.2 %), and this was prevented by pyridoxamine (0.8 ± 0.1 %). MGO iv spikes increased circulating neutrophils and monocytes (2-fold relative to NS) and the expression of ICAM (3-fold), RAGE (5-fold), S100A9 (2-fold) and MCP1 (2-fold). All these changes were attenuated by pyridoxamine. This study suggests that MGO spikes damages the vasculature independently of plasma glucose levels. Pyridoxamine and potentially other approaches to reduce MGO may prevent excess cardiovascular risk in diabetes [Display omitted] [ABSTRACT FROM AUTHOR]

Smooth muscle cell (SMC) proliferation and fibrosis contribute to the development of advanced atherosclerotic lesions. Oxidative stress caused by increased production or unphysiological location of reactive oxygen species (ROS) is a known major pathomechanism. However, in atherosclerosis, in particular under hyperglycaemic/diabetic conditions, the hydrogen peroxide-producing NADPH oxidase type 4 (NOX4) is protective. Here we aim to elucidate the mechanisms underlying this paradoxical atheroprotection of vascular smooth muscle NOX4 under conditions of normo- and hyperglycaemia both in vivo and ex vivo . Following 20-weeks of streptozotocin-induced diabetes, Apoe −/− mice showed a reduction in SM-alpha-actin and calponin gene expression with concomitant increases in platelet-derived growth factor (PDGF), osteopontin (OPN) and the extracellular matrix (ECM) protein fibronectin when compared to non-diabetic controls. Genetic deletion of Nox4 ( Nox4 −/ − Apoe −/− ) exacerbated diabetes-induced expression of PDGF, OPN, collagen I, and proliferation marker Ki67. Aortic SMCs isolated from NOX4-deficient mice exhibited a dedifferentiated phenotype including loss of contractile gene expression, increased proliferation and ECM production as well as elevated levels of NOX1-associated ROS. Mechanistic studies revealed that elevated PDGF signalling in NOX4-deficient SMCs mediated the loss of calponin and increase in fibronectin, while the upregulation of NOX1 was associated with the increased expression of OPN and markers of proliferation. These findings demonstrate that NOX4 actively regulates SMC pathophysiological responses in diabetic Apoe −/− mice and in primary mouse SMCs through the activities of PDGF and NOX1. [ABSTRACT FROM AUTHOR]

Unlabelled: Glucose lowering medication use among patients with type 2 diabetes and advanced renal disease (eGFR<60) in a large multinational outcome trial (TREAT) is assessed. We demonstrate statistically significant differences regionally in use of metformin at lower eGFR and increasing reliance upon insulin with/without other medications at low eGFR.Introduction: As renal disease advances, most of the oral anti-diabetic agents requiring renal clearance must be reduced or discontinued. The potential for prolonged hypoglycemia, fluid/volume overload and congestive heart failure may complicate medication choices. In order to evaluate patterns of glycemia management we describe glucose lowering medication use among patients with advanced renal disease and type 2 diabetes in a large multinational outcome trial designed to focus on patients with eGFR<60 in order to commence a dialog on best practices. We felt that analysis of this data would be able to describe regional variations in treatment within a multinational trial in order to understand potential outcome differences attributed to complications.Results: The patients entering this study had moderate glycemic control. Insulin therapy either alone (32%) or in combination with other agents (17%) reflected a shift towards insulin use in those subjects with decreased renal function when compared with standard populations with normal kidney function. The use of multiple oral agents, or oral agents plus insulin was quite common. While gender did not appear to play a role in medication choices, there were significant regional variations. For example, oral agents were used more in North America compared with other regions (Latin America, Australia/Western Europe, Russia/Eastern Europe). Patients enrolled at more advanced ages were less likely to be on a regimen of rapid-acting insulin alone consistent with recommendations that suggest a preference for longer-acting preparations in the geriatric population (1). Higher degrees of obesity were associated more complex treatment regimens. Despite this population being at high risk for cardiovascular events, the use of beta blockers (50%), statins (64%) and aspirin (48%) were relatively low, especially in the group that did not require medications to achieve adequate glycemic control.Conclusions: Current attempts to compare strategies for diabetes therapy must control for baseline demographic group differences influencing treatment choice. Future recommendations for glycemic control in patients with Grade 3 or higher chronic kidney disease require additional studies, with matched populations. We suggest that evaluation of studies similar to TREAT will assist in determining the optimal therapeutic regimens for populations with moderate to severe renal dysfunction, a condition in which repeated hospitalizations for fluid overload/heart failure add to the high cost of diabetes care. [ABSTRACT FROM AUTHOR]

Objective/Rationale Both the renin-angiotensin system (RAS) and the receptor for advanced glycation end products (RAGE) potentiate diabetes-associated atherosclerosis (DAA). We assessed the effectiveness of concomitant RAS and RAGE inhibition on DAA. Methods Diabetic (5 x 55 mg/kg streptozotocin daily) and non-diabetic male RAGE/apolipoprotein E double knockout (RAGE/apoE DKO) mice were treated with quinapril (30 mg/kg/day) for 20 weeks. At the end of the study aortic plaques were assessed. Results Diabetic RAGE/apoE DKO showed significantly less plaque area than diabetic apoE KO mice. Plaque deposition was almost abolished in quinapril treated diabetic RAGE/apoE DKOs, with significant attenuation of vascular collagen deposition, nitrotyrosine staining, and reduced macrophage infiltration. Expression of the advanced glycation end product receptor 3 (galectin 3) was also significantly reduced. Conclusion Concomitant inhibition of RAS and RAGE signalling almost completely inhibited the development of experimental DAA. A dual therapeutic approach may be a superior strategy for the treatment of diabetic macrovascular disease. [ABSTRACT FROM AUTHOR]

Renal fibrosis results from excessive accumulation of extracellular matrix mainly driven by transforming growth factor-β1 (TGF-β1). Certain microRNAs have been implicated in this disease, and here we examine the role of let-7b. Rat proximal tubular epithelial cells (NRK52E) were treated with TGF-β1 for 3 days to assess the expression of markers of fibrosis and let-7b. These factors were also assessed in two mouse models representing early and more advanced diabetic nephropathy and in the non-diabetic adenine-induced renal fibrosis model. TGF-β1 downregulated the expression of let-7b and induced fibrogenesis in NRK52E cells. Ectopic expression of let-7b repressed TGF-β1 receptor 1 (TGFBR1) expression directly by targeting the two let-7b binding sites in the 3'-untranslated region of that gene, reduced expression of extracellular matrix proteins, decreased SMAD3 activity, and attenuated the profibrotic effects of TGF-β1. Knockdown of let-7b elevated TGFBR1 expression and mimicked some of the profibrotic effects of TGF-β1. Consistent with these observations, let-7b expression was also reduced in models of both diabetic and non-diabetic renal fibrosis with the upregulation of TGFBR1. Thus, let-7b microRNA represents a potential new target for the treatment of renal fibrosis in diabetic and non-diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Abstract: Chronic overconsumption of a Western diet has been identified as a major risk factor for diabetes, yet precisely how each individual component contributes to defects in glucose homeostasis independent of consumption of other macronutrients remains unclear. Eight-week-old male Sprague Dawley rats were randomized to feeding with one of six semi-pure diets: control, processed (high advanced glycation end products/AGE), high protein, high dextrose (glucose polymer), high in saturated fat (plant origin), or high in saturated fat (animal origin). After chronic feeding for 24 weeks, body composition was determined by bioelectrical impedance spectroscopy and glucose homeostasis was assessed. When compared to the control and high AGE diets, excess consumption of the diet high in saturated fat (animal source) increased body weight and adiposity, and decreased insulin sensitivity, as defined by HOMA IR, impaired skeletal muscle insulin signaling and insulin hypersecretion in the context of increased circulating glucagon-like peptide (GLP-1). Compared to the control diet, chronic consumption of the high AGE, protein or dextrose diet increased fasting plasma glucose, decreased fasting plasma insulin and insulin secretion. These diets also reduced circulating GLP-1 concentrations. These data suggest that individual components of a western diet have differential effects in modulating glucose homeostasis and adiposity. These data provide clear evidence of a link between over-consumption of a western diet and the development of diabetes. [Copyright &y& Elsevier]

The effect of intensive glucose control on major kidney outcomes in type 2 diabetes remains unclear. To study this, the ADVANCE trial randomly assigned 11,140 participants to an intensive glucose-lowering strategy (hemoglobin A1c target 6.5% or less) or standard glucose control. Treatment effects on end-stage renal disease ((ESRD), requirement for dialysis or renal transplantation), total kidney events, renal death, doubling of creatinine to above 200 μmol/l, new-onset macroalbuminuria or microalbuminuria, and progression or regression of albuminuria, were then assessed. After a median of 5 years, the mean hemoglobin A1c level was 6.5% in the intensive group, and 7.3% in the standard group. Intensive glucose control significantly reduced the risk of ESRD by 65% (20 compared to 7 events), microalbuminuria by 9% (1298 compared to 1410 patients), and macroalbuminuria by 30% (162 compared to 231 patients). The progression of albuminuria was significantly reduced by 10% and its regression significantly increased by 15%. The results were almost identical in analyses taking account of potential competing risks. The number of participants needed to treat over 5 years to prevent one ESRD event ranged from 410 in the overall study to 41 participants with macroalbuminuria at baseline. Thus, improved glucose control will improve major kidney outcomes in patients with type 2 diabetes. [ABSTRACT FROM AUTHOR]

Abstract: Aims: To asses differences in treatment effects of a fixed combination of perindopril–indapamide on major clinical outcomes in patients with type 2 diabetes across subgroups of cardiovascular risk. Methods: 11,140 participants with type 2 diabetes, from the ADVANCE trial, were randomized to perindopril–indapamide or matching placebo. The Framingham equation was used to calculate 5-year CVD risk and to divide participants into two risk groups, moderate–high risk (<25% and no history of macrovascular disease), very high risk (>25% and/or history of macrovascular disease). Endpoints were macrovascular and microvascular events. Results: The mean age of participants was 66 years (42.5% female). 1000 macrovascular and 916 microvascular events were recorded over follow-up of 4.3 years. Relative treatment effects were similar across risk groups, (all P-values for heterogeneity ≥0.38). Hazard ratios for combined macro- and microvascular events were 0.89 (0.77–1.03) for the moderate-high risk and 0.92 (0.81–1.03) for the very high risk. Absolute treatment effects tended to be greater in the high risk groups although differences were not statistically significant (P >0.05). Conclusions: Relative effects of blood pressure lowering with perindopril–indapamide on cardiovascular outcomes were similar across risk groups whilst absolute effects trended to be greater in the high risk group. [Copyright &y& Elsevier]

Abstract: Cardiovascular benefits of ubiquinone have been previously demonstrated, and we administered it as a novel therapy in an experimental model of type 2 diabetic nephropathy. db/db and dbH mice were followed for 10weeks, after randomization to receive either vehicle or ubiquinone (CoQ10; 10mg/kg/day) orally. db/db mice had elevated urinary albumin excretion rates and albumin:creatinine ratio, not seen in db/db CoQ10-treated mice. Renal cortices from db/db mice had lower total and oxidized CoQ10 content, compared with dbH mice. Mitochondria from db/db mice also contained less oxidized CoQ10(ubiquinone) compared with dbH mice. Diabetes-induced increases in total renal collagen but not glomerulosclerosis were significantly decreased with CoQ10 therapy. Mitochondrial superoxide and ATP production via complex II in the renal cortex were increased in db/db mice, with ATP normalized by CoQ10. However, excess renal mitochondrial hydrogen peroxide production and increased mitochondrial membrane potential seen in db/db mice were attenuated with CoQ10. Renal superoxide dismutase activity was also lower in db/db mice compared with dbH mice. Our results suggest that a deficiency in mitochondrial oxidized CoQ10 (ubiquinone) may be a likely precipitating factor for diabetic nephropathy. Therefore CoQ10 supplementation may be renoprotective in type 2 diabetes, via preservation of mitochondrial function. [Copyright &y& Elsevier]

Intervention in the renin-angiotensin-aldosterone-system (RAAS) is associated with slowing the progressive loss of renal function. During initiation of therapy, however, there may be an acute fall in glomerular filtration rate (GFR). We tested whether this initial fall in GFR reflects a renal hemodynamic effect and whether this might result in a slower decline in long-term renal function. We performed a post hoc analysis of the Reduction of Endpoints in Non-Insulin-Dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan (RENAAL) trial. Patients assigned to losartan had a significantly greater acute fall in estimated (eGFR) during the first 3 months compared to patients assigned to placebo, but a significantly slower long-term mean decline of eGFR thereafter. A large interindividual difference, however, was noticed in the acute eGFR change. When patients were divided into tertiles of initial fall in eGFR, the long-term eGFR slope calculated from baseline was significantly higher in patients with an initial fall compared to those with an initial rise. When eGFR decline was calculated from 3 months to the final visit, excluding the initial effect, patients with a large initial fall in eGFR had a significant lower long-term eGFR slope compared to those with a moderate fall or rise. This relationship was independent of other risk markers or change in risk markers for progression of renal disease such as blood pressure and albuminuria. Thus, the greater the acute fall in eGFR, during losartan treatment, the slower the rate of long-term eGFR decline. Hence, interpretation of trial results relying on slope-based GFR outcomes should separate the initial drug-induced GFR change from the subsequent long-term effect on GFR. [ABSTRACT FROM AUTHOR]

Obesity is highly prevalent in Western populations and is considered a risk factor for the development of renal impairment. Interventions that reduce the tissue burden of advanced glycation end-products (AGEs) have shown promise in stemming the progression of chronic disease. Here we tested if treatments that lower tissue AGE burden in patients and mice would improve obesity-related renal dysfunction. Overweight and obese individuals (body mass index (BMI) 26-39 kg/m2) were recruited to a randomized, crossover clinical trial involving 2 weeks each on a low- and a high-AGE-containing diet. Renal function and an inflammatory profile (monocyte chemoattractant protein-1 (MCP-1) and macrophage migration inhibitory factor (MIF)) were improved following the low-AGE diet. Mechanisms of advanced glycation-related renal damage were investigated in a mouse model of obesity using the AGE-lowering pharmaceutical, alagebrium, and mice in which the receptor for AGE (RAGE) was deleted. Obesity, resulting from a diet high in both fat and AGE, caused renal impairment; however, treatment of the RAGE knockout mice with alagebrium improved urinary albumin excretion, creatinine clearance, the inflammatory profile, and renal oxidative stress. Alagebrium treatment, however, resulted in decreased weight gain and improved glycemic control compared with wild-type mice on a high-fat Western diet. Thus, targeted reduction of the advanced glycation pathway improved renal function in obesity. [ABSTRACT FROM AUTHOR]

Cell division autoantigen 1 (CDA1) modulates cell proliferation and transforming growth factor-β (TGF-β) signaling in a number of cellular systems; here we found that its levels were elevated in the kidneys of two animal models of diabetic renal disease. The localization of CDA1 to tubular cells and podocytes in human kidney sections was similar to that seen in the rodent models. CDA1 small interfering RNA knockdown markedly attenuated, whereas its overexpression increased TGF-β signaling, modulating the expression of TGF-β, TGF-β receptors, connective tissue growth factor, collagen types I, III, IV, and fibronectin genes in HK-2 cells. CDA1 and TGF-β together were synergistic in stimulating TGF-β signaling and target gene expression. CDA1 knockdown effectively blocked TGF-β-stimulated expression of collagen genes. This was due to its ability to modulate the TGF-β type I, but not the type II, receptor, leading to increased phosphorylation of Smad3 and extracellular signal-regulated kinase mitogen-activated protein kinase. Furthermore, the Smad3 inhibitor, SIS3, markedly attenuated the activities of CDA1 in stimulating TGF-β signaling as well as gene expression of collagens I, III, and IV. Thus, our in vitro and in vivo findings show that CDA1 has a critical role in TGF-β signaling in the kidney. [ABSTRACT FROM AUTHOR]

The accumulation of advanced glycation end products is thought to be a key factor in the initiation and progression of diabetic nephropathy. Here we determined whether the size of the ligands for the receptor for advanced glycation end products (RAGEs) that were present in the serum of patients with type 2 diabetes modulates their pathogenic potential. Serum was collected from control subjects and patients with type 2 diabetes with varying degrees of renal disease (normo-, micro-, or macroalbuminuria). The titers of the RAGE ligands N-carboxymethyllysine (CML), S100A, S100B, and high-mobility group box 1 (HMGB1) were measured by enzyme-linked immunosorbent assay in serum as well as in pooled size-fractionated serum. We also measured cellular binding of serum fractions to mesangial cells transfected with RAGE and examined the downstream signaling pathways. Circulating CML was increased in patients with type 2 diabetes, whereas HMGB1 was decreased. S100A8, S100BA9, and soluble RAGE were unchanged. The high-molecular-weight (over 50 kDa) serum fraction contained the greatest proportion of RAGE ligands, with all immunoreactivity and cellular binding observed only with serum fractions over 30 kDa. High-molecular-weight serum from macroalbuminuric patients showed greater RAGE binding capacity, modulation of cell-surface RAGE expression, increased phospho-protein kinase C-α, and p65 nuclear factor κB DNA-binding activity, which were competitively inhibited by soluble RAGE or CML neutralizing antibodies. These data show that ligands that activate RAGE present in the circulation of patients with type 2 diabetes and nephropathy are predominantly of high molecular weight. [ABSTRACT FROM AUTHOR]

We previously reported that overexpression of cell division autoantigen 1 (CDA1) in HeLa cells arrests cell growth and inhibits DNA synthesis at S-phase (1). Here we show that CDA1- induced arrest of cell growth is accompanied by increases in protein and mRNA levels of the cyclin-dependent kinase (Cdk) inhibitor protein, p21Waf1/CiP1 (p21). Both p21 induction and cell growth arrest are reversed when CDA1 expression is inhibited. CDA1 also increases p53 protein, but not its mRNA, in a time- and dose-dependent manner. MDM2, a ubiquitin ligase regulating p53 degradation, is inactivated by CDA1, suggesting that p53 protein accumulation is due to decreased protein degradation. Knockdown of p53, using siRNA targeting two sites of p53 mRNA, abrogates transcriptional induction of p21 by CDA1. Deletion of the p53 responsive element in the distal region of p21 promoter attenuates promoter activity in response to CDA1. DNA damage caused by camptothecin treatment increases mRNA and protein levels of CDA1, accompanied by induction of p53. The DNA damage-induced p53 induction is markedly attenuated by CDA1 knockdown. CDA1 induces phosphorylation of ERK1/2(p44/42), an activity blocked by PD98059 and U0126, inhibitors of the upstream kinase MEK1/2. The MEK inhibitors also block induction of p21 mRNA and abrogate p21 promoter activity stimulated by CDA1. Cell cycle kinases, Cdk1, -2, -4, and -6 are inhibited by CDA1 overexpression. We conclude that CDA1 induces p53- and MEK/ERK1/2 MAPK-dependent expression of p21 by acting through the p53 responsive element in the p21 promoter and that this contributes to its antiproliferative activity. [ABSTRACT FROM AUTHOR]

Abstract: Experimental hyperglycemia produces a marked hypertrophic response in rat mesenteric arteries, accompanied by activation of Na/H exchange (NHE) in medial smooth muscle. This study asked if other vascular beds are similarly affected by examining the hypertrophic and NHE response of the basilar artery. Sections of mesenteric and basilar arteries from adult rats were analysed by standard morphometric techniques at 1 and 3 weeks after streptozotocin injection. NHE activity was assessed as changes in intracellular pH in isolated intact vessels using concurrent myography and fluorescence spectroscopy. Mesenteric arteries showed a significant increase in lumenal (47%), medial (51%) and adventitial (17%) area. In contrast, these parameters were not increased in basilar arteries from the same set of animals. Maximal NHE activity was significantly increased at 1 week (24%) and 3 weeks (20%) in mesenteric arteries, but in basilar arteries there was no change in basal intracellular pH, maximal NHE activity or kinetic properties of the transporter. NHE plays a central role in vascular changes in diabetes. As the mesenteric hypertrophy is amenable to therapeutic intervention these findings add further to the potential of NHE as a therapeutic target for ameliorating vascular disease in diabetes. [Copyright &y& Elsevier]

Increased tubular organic ion clearance following chronic ACE inhibition in patients with type 1 diabetes.Background.The tubular excretion of creatinine significantly contributes to its clearance. Administration of an angtiotensin-converting enzyme (ACE) inhibitor is associated with increased organic ion clearance in experimental diabetes. This study examines the effect and implications of chronic ACE inhibition on renal organic ion excretion in patients with type 1 diabetes.Methods.Samples were obtained from the Melbourne Diabetic Nephropathy Study Group (MDNSG) that randomized patients to receive perindopril (N= 11), nifedipine (N= 11), or placebo (N= 8). Albumin excretion rate, creatinine clearance, and isotopic glomerular filtration rate (GFR) were assessed at baseline and after 24 months. In addition, the clearance of the endogenous cations N-methylynicotinamide (NMN), creatinine, and the anion hippurate were determined by high-performance liquid chromatography (HPLC).Results.Following treatment with the ACE inhibitor, perindopril, renal clearance of NMN was increased (+96%) (P<0.05). There was no difference in patients treated with nifedipine (P= 0.25) and NMN clearance fell in the placebo-treated patients (−26%) (P<0.05). Changes in NMN clearance were unaffected after adjusting for the effects of perindopril on GFR. However, they were attenuated after adjusting for hippurate clearance, a marker of renal blood flow. This effect of perindopril on NMN clearance was seen in both men and women, regardless of baseline clearance and was correlated with reduced albuminuria following perindopril treatment.Conclusion.Organic ion clearance is increased in patients with diabetes following chronic ACE inhibition. This is consistent with experimental models showing increased ion transporter expression and improved tubular blood flow, following blockade of the renin-angiotensin system (RAS). These findings may have implications for the interpretation of creatinine-based indices in patients with diabetes. [ABSTRACT FROM AUTHOR]

AGEs activate mesangial TGF-β–Smad signaling via an angiotensin II type I receptor interaction.Background.The renin-angiotensin system (RAS) and the accumulation of advanced glycation end products (AGEs) have been implicated in the pathogenesis of diabetic nephropathy. Whether there is a functional interaction between the RAS and AGEs in diabetic nephropathy is not known. In this study, we investigated whether AGEs could activate autocrine angiotensin II (Ang II) signaling and subsequently induce transforming growth factor-β (TGF-β)–Smad signaling in cultured rat mesangial cells.Methods.The intracellular formation of reactive oxygen species (ROS) was detected using the fluorescent probe CM-H2DCFDA. Ang II was measured by radioimmunoassay. TGF-β released into media was quantitatively analyzed in an enzyme-linked immunosorbent assay (ELISA). Smad2, p27Kip1 (p27), fibronectin, and receptor for AGEs (RAGE) protein expression were determined by Western blot analysis. TGF-β–inducible promoter activity was analyzed by a luciferase assay. DNA synthesis was evaluated by 5-bomo-2′-deoxyuridine (BrdU) incorporation and de novo protein synthesis was determined by[3H]leucine incorporation.Results.AGEs increased intracellular ROS generation in mesangial cells, and this effect was significantly inhibited by an antiserum against RAGE. AGEs also were found to stimulate Ang II production in a time- and dose-dependent manner, which was completely prevented by an antioxidant,N-acetylcysteine (NAC). AGE-induced TGF-β overproduction was completely blocked by candesartan, an Ang II type 1 receptor (AT1R) antagonist. Both candesartan and neutralizing antibody against TGF-β completely prevented AGEs-induced Smad2 phosphorylation and TGF-β–inducible promoter activity. Furthermore, AGEs were found to inhibit DNA synthesis and to stimulate de novo protein synthesis and fibronectin production in association with up-regulation of p27. All of these phenomena were completely prevented by candesartan or a polyclonal antibody against TGF-β.Conclusion.The present study suggests that AGE-RAGE–mediated ROS generation activates TGF-β–Smad signaling and subsequently induces mesangial cell hypertrophy and fibronectin synthesis by autocrine production of Ang II. This pathway may provide an important link between metabolic and haemodynamic factors in promoting the development and progression of diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Low-molecular-weight AGEs are associated with GFR and anemia in patients with type 2 diabetes. Background. Advanced glycation end products (AGEs) are implicated in the development and progression of diabetic nephropathy. We examined the predictors of low-molecular-weight (LMW) AGEs in a cross-sectional survey of 604 patients with type 2 diabetes in a single clinic. Methods. A clinical history and results of routine blood and urine testing were obtained for all patients over a 2-year period. Fluorescent LMW AGEs were estimated in serum samples taken concurrently, using an established flow injection method. Predictors of LMW AGEs were identified using multiple regression analysis. Results. LMW AGEs were 34% higher in patients with diabetes than nondiabetic volunteers from the same community ( P < 0.001). Independent predictors for LMW AGEs in patients with diabetes were glomerular filtration rate (GFR) and hemoglobin (both P < 0.001). While patients with renal impairment and anemia had the highest levels of LMW AGEs, both GFR and hemoglobin remained predictive when patients with a serum creatinine or hemoglobin within the “normal range” were analyzed separately. Patients with hyperfiltration had significantly lower LMW AGEs than those with normal renal function. Gender was also a significant independent predictor of LMW AGEs in patients without anemia. However, LMW AGEs were not associated with metabolic control or the presence of macrovascular disease. Conclusion. Circulating levels of LMW AGEs are elevated in patients with diabetes, especially those with impaired renal function or anemia. These findings extend the evidence for an association between AGEs and progressive renal injury in patients with type 2 diabetes. Whether LMW AGEs contribute to, or are a marker of, renal damage needs to be established by prospective studies. [ABSTRACT FROM AUTHOR]

Proteinuria, a target for renoprotection in patients with type 2 diabetic nephropathy: Lessons from RENAAL. Background. Proteinuria or albuminuria is an established risk marker for progressive renal function loss. Albuminuria can be effectively lowered with antihypertensive drugs that interrupt the renin-angiotensin system (RAS). We investigated whether albuminuria could not only serve as a marker of renal disease, but also function as a monitor of the renoprotective efficacy of RAS intervention by the angiotensin II (Ang II) antagonist, losartan, in patients with diabetic nephropathy. Methods. The data from the RENAAL (Reduction in End Points in Noninsulin-Dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan) study, a double-blind, randomized trial, were used to examine the effects of losartan on the renal outcome [i.e., the primary composite end point of doubling of serum creatinine, end-stage renal disease (ESRD) or death] in 1513 type 2 diabetic patients with nephropathy. We examined the effect of the degree of albuminuria at baseline, initial antiproteinuric response to therapy, and the degree of remaining (residual) albuminuria on renal outcome (either the primary composite end point of RENAAL or ESRD). We also evaluated the contribution to renal protection of the antiproteinuric effect of losartan independently of changes in blood pressure. Results. Baseline albuminuria is almost linearly related to renal outcome, and is the strongest predictor among all measured well-known baseline risk parameters. [ABSTRACT FROM AUTHOR]

Angiotensin-converting enzyme (ACE) is a zinc metalloproteinase and a key regulator of the renin–angiotensin system (RAS). ACE2 is a newly described enzyme identified in rodents and humans with a more restricted distribution than ACE, and is found mainly in heart and kidney. ACE2 cleaves a single residue from angiotensin I (Ang I) to generate Ang 1–9, and degrades Ang II, the main effector of the RAS, to the vasodilator Ang 1–7. The importance of ACE2 in normal physiology and pathophysiological states is largely unknown. ACE2 might act in a counter-regulatory manner to ACE, modulating the balance between vasoconstrictors and vasodilators within the heart and kidney, and playing a significant role in regulating cardiovascular and renal function. [Copyright &y& Elsevier]

Effects of the combination of an angiotensin II antagonist with an HMG-CoA reductase inhibitor in experimental diabetes. Background. Angiotensin II type 1 (AT1) receptor antagonists and 3-hydroxy-3-methylglutaryl conenzyme A (HMG-CoA) reductase inhibitors have been shown to confer renoprotection. However, the renal effects of the combination of an AT1 receptor antagonist and an HMG-CoA reductase inhibitor in experimental diabetes are unknown. Methods. Diabetes was induced by injection of streptozotocin in Wistar rats. Diabetic rats were randomly treated with losartan, an AT1 receptor antagonist, or simvastatin, an HMG-CoA reductase inhibitor, as well as the combination of both for eight weeks. Albumin excretion rate (AER) and plasma concentrations of blood urea nitrogen (BUN), creatinine, cholesterol, and triglycerides were measured. Renal injury was evaluated. Immunohistochemical staining of transforming growth factor β1 (TGFβ1) and vascular endothelial growth factor (VEGF) were performed. Results. Increased AER in diabetic rats was attenuated by treatment with either losartan or simvastatin and further reduced by the combination of the two. Elevated plasma concentrations of BUN and creatinine were only reduced by the combination. There was no significant difference in plasma concentrations of cholesterol and triglycerides between control and diabetic rats and neither was influenced by losartan or simvastatin. Kidney pathologic injury was attenuated by losartan, but not simvastatin, compared to diabetic animals. Overexpression of TGFβ1 and VEGF was observed in the glomeruli of diabetic rats and was attenuated by losartan, simvastatin, or the combination of both to a similar level. Conclusion. The combination of an angiotensin antagonist with an HMG-CoA reductase inhibitor confers superiority over monotherapies on renal function, as assessed by prevention of albuminuria and rise in plasma BUN and creatinine. However, no advantage of combination... [ABSTRACT FROM AUTHOR]

Discusses the isolation of advanced glycation end-binding proteins from diabetic rat kidneys. Purification of the proteins by cation exchange; Inhibition of the ability of cells to produce tubules; Potential for therapeutic intervention in prevention or treatment of diabetic complications.