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Key Points Diabetic nephropathy has severe individual and societal consequences, owing to its high morbidity, mortality and health-care costs Despite the availability of anti-glycaemic, renoprotective and antihypertensive agents, diabetes mellitus remains the most common cause of end-stage renal disease in developed countries New biomarkers that can identify patients at risk of diabetic nephropathy are needed, as well as new agents that directly target the pathogenic pathways of diabetic nephropathy Growing evidence suggests that the complement system has a pathogenic role in the development of diabetic nephropathy Mannose-binding protein is a strong biomarker of diabetic nephropathy in patients with type 1 diabetes mellitus (T1DM) and T2DM; H-ficolin might be useful to identify patients with T1DM at risk of persistent microalbuminuria Inhibiting specific components of the complement system might be an effective therapeutic strategy to treat diabetic nephropathy An increasing body of evidence points toward a role for the complement system in the pathogenesis of diabetic nephropathy. Here, Allan Flyvbjerg describes the underlying experimental and clinical evidence and discusses how the association between complement activation and diabetic nephropathy might facilitate the identification of new biomarkers of disease progression and targets for therapeutic intervention. The development of type 1 and type 2 diabetes mellitus has a substantial negative impact on morbidity and mortality and is responsible for substantial individual and socioeconomic costs worldwide. One of the most serious consequences of diabetes mellitus is the development of diabetic angiopathy, which manifests clinically as microvascular and macrovascular complications. One microvascular complication, diabetic nephropathy, is the most common cause of end-stage renal disease in developed countries. Although several available therapeutic interventions can delay the onset and progression of diabetic nephropathy, morbidity associated with this disease remains high and new therapeutic approaches are needed. In addition, not all patients with diabetes mellitus will develop diabetic nephropathy and thus new biomarkers are needed to identify individuals who will develop this life-threatening disease. An increasing body of evidence points toward a role of the complement system in the pathogenesis of diabetic nephropathy. For example, circulating levels of mannose-binding lectin (MBL), a pattern recognition molecule of the innate immune system, have emerged as a robust biomarker for the development and progression of this disease, and evidence suggests that MBL, H-ficolin, complement component C3 and the membrane attack complex might contribute to renal injury in the hyperglycaemic mileu. New approaches to modulate the complement system might lead to the development of new agents to prevent or slow the progression of diabetic nephropathy.

Diabetic angiopathy is among the most serious consequences of diabetes mellitus owing to its impact on quality of life, morbidity, mortality and burden to health-care systems. This Review discusses data that support a role of dysregulation of components of the complement system and the tumor necrosis factor superfamily in the development of diabetic angiopathy. Among the most serious consequences of diabetes mellitus is the development of diabetic angiopathy, of which the clinical features are cardiovascular disease, retinopathy, nephropathy and neuropathy. Diabetic kidney problems affect up to one third of all patients with diabetes mellitus and are a major cause of end-stage renal failure. Although a huge number of pharmaceutical interventions are available today, diabetic angiopathy remains a leading cause of mortality and morbidity in diabetes mellitus, therefore, an urgent need exists to develop new therapeutic strategies. Recent data support the hypothesis that dysregulation of the complement system and of members of the tumor necrosis factor (TNF) superfamily may be involved in the development of diabetic vascular complications. The mannose-binding lectin pathway—an overall regulatory component of the complement system—is a particularly promising biomarker as it is directly involved in the development of diabetic angiopathy. In addition, two components of the TNF superfamily, namely TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) and osteoprotegerin, may be involved in the pathogenesis of diabetic angiopathy. Several ways of specifically manipulating the complement and TNF superfamily systems already exist, but whether or not these drugs provide new targets for intervention for late diabetic complications is still to be revealed. Key Points The development of diabetic angiopathy has serious individual and societal consequences because of the substantial impact on morbidity and mortality Despite lifestyle changes and drug intervention against hyperglycemia, hypertension and dyslipidemia, microvascular and macrovascular complications are still a clinical problem in patients with diabetes mellitus An ongoing need exists to develop better risk markers of diabetic angiopathy and drugs that act more specifically Emerging evidence supports a role of the complement system and of members of the tumor necrosis factor superfamily in the pathogenesis of diabetic vascular complications Mannose-binding lectin and osteoprotegerin are strong and independent biomarkers of microvascular and macrovascular complications in diabetes mellitus Agonists and antagonists against components of the complement system and the tumor necrosis factor superfamily may prove effective in the treatment of diabetic vascular complications

The incidence and prevalence of diabetes mellitus (DM) continue to grow markedly throughout the world, due primarily to the increase in type 2 DM (T2DM). Although improvements in DM and hypertension management have reduced the proportion of diabetic individuals who develop chronic kidney disease (CKD) and progress to end-stage renal disease (ESRD), the sheer increase in people developing DM will have a major impact on dialysis and transplant needs. This KDIGO conference addressed a number of controversial areas in the management of DM patients with CKD, including aspects of screening for CKD with measurements of albuminuria and estimated glomerular filtration rate (eGFR); defining treatment outcomes; glycemic management in both those developing CKD and those with ESRD; hypertension goals and management, including blockers of the renin–angiotensin–aldosterone system; and lipid management.

Increasing evidence has suggested an independent association between periodontitis and a range of comorbidities, for example cardiovascular disease, type 2 diabetes, rheumatoid arthritis, osteoporosis, Parkinson's disease, Alzheimer's disease, psoriasis, and respiratory infections. Shared inflammatory pathways are likely to contribute to this association, but distinct causal mechanisms remain to be defined. Some of these comorbid conditions may improve by periodontal treatment, and a bidirectional relationship may exist, where, for example, treatment of diabetes can improve periodontal status. The present article presents an overview of the evidence linking periodontitis with selected systemic diseases and calls for increased cooperation between dentists and medical doctors to provide optimal screening, treatment, and prevention of both periodontitis and its comorbidities.

The role of vascular endothelial growth factor (VEGF) in renal pathophysiology. Vascular endothelial growth factor (VEGF) is an endothelial-specific growth factor that promotes endothelial cell proliferation, differentiation and survival, mediates endothelium-dependent vasodilatation, induces microvascular hyperpermeability and participates in interstitial matrix remodeling. In the kidney, VEGF expression is most prominent in glomerular podocytes and in tubular epithelial cells, while VEGF receptors are mainly found on preglomerular, glomerular, and peritubular endothelial cells. The role of VEGF in normal renal physiology is essentially unknown. The absence of prominent effects of VEGF blockade in normal experimental animals suggests a limited function during homeostasis, although a role in the formation and maintenance of glomerular capillary endothelial fenestrations has been suggested. VEGF and its receptors are up-regulated in experimental animals and humans with type 1 and type 2 diabetes. Inhibition of VEGF has beneficial effects on diabetes-induced functional and structural alterations, suggesting a deleterious role for VEGF in the pathophysiology of diabetic nephropathy. VEGF is required for glomerular and tubular hypertrophy and proliferation in response to nephron reduction, and loss of VEGF is associated with the development of glomerulosclerosis and tubulointerstitial fibrosis in the remnant kidney. No firm conclusions on the role of VEGF in minimal change or membranous glomerulonephritis can be drawn. VEGF may be an essential mediator of glomerular recovery in proliferative glomerulonephritis. Glomerular and tubulointerstitial repair in thrombotic microangiopathy and cyclosporin nephrotoxicity may also be VEGF-dependent. In conclusion, VEGF is required for growth and proliferation of glomerular and peritubular endothelial cells. While deleterious in some, it may contribute to recovery in other forms of renal diseases.

The adipocyte-secreted protein adiponectin is associated with insulin sensitivity in observational studies. We aimed to evaluate whether this relationship is causal using a Mendelian randomization approach. In a sample of Swedish men aged 71 years (n = 942) from the Uppsala Longitudinal Study of Adult Men (ULSAM), insulin sensitivity (M/I ratio) was measured by the euglycemic insulin clamp. We used three genetic variants in the ADIPOQ locus as instrumental variables (IVs) to estimate the potential causal effect of adiponectin on insulin sensitivity and compared these with results from conventional linear regression. The three ADIPOQ variants, rs17300539, rs3774261, and rs6444175, were strongly associated with serum adiponectin levels (all P ≤ 5.3 × 10−9) and were also significantly associated with M/I ratio in the expected direction (all P ≤ 0.022). IV analysis confirmed that genetically determined adiponectin increased insulin sensitivity (β = 0.47–0.81, all P ≤ 0.014) comparable with observational estimates (β = 0.50, all Pdifference ≥ 0.136). Adjustment for BMI and waist circumference partly explained the association of both genetically determined and observed adiponectin levels with insulin sensitivity. The observed association between higher adiponectin levels and increased insulin sensitivity is likely to represent a causal relationship partly mediated by reduced adiposity.

Aims/hypothesis In diabetes, advanced glycation end-products (AGEs) and the AGE precursor methylglyoxal (MGO) are associated with endothelial dysfunction and the development of microvascular complications. In this study we used a rat model of diabetes, in which rats transgenically overexpressed the MGO-detoxifying enzyme glyoxalase-I (GLO-I), to determine the impact of intracellular glycation on vascular function and the development of early renal changes in diabetes. Methods Wild-type and Glo1 -overexpressing rats were rendered diabetic for a period of 24 weeks by intravenous injection of streptozotocin. Mesenteric arteries were isolated to study ex vivo vascular reactivity with a wire myograph and kidneys were processed for histological examination. Glycation was determined by mass spectrometry and immunohistochemistry. Markers for inflammation, endothelium dysfunction and renal dysfunction were measured with ELISA-based techniques. Results Diabetes-induced formation of AGEs in mesenteric arteries and endothelial dysfunction were reduced by Glo1 overexpression. Despite the absence of advanced nephrotic lesions, early markers of renal dysfunction (i.e. increased glomerular volume, decreased podocyte number and diabetes-induced elevation of urinary markers albumin, osteopontin, kidney-inflammation-molecule-1 and nephrin) were attenuated by Glo1 overexpression. In line with this, downregulation of Glo1 in cultured endothelial cells resulted in increased expression of inflammation and endothelium dysfunction markers. In fully differentiated cultured podocytes incubation with MGO resulted in apoptosis. Conclusions/interpretation This study shows that effective regulation of the GLO-I enzyme is important in the prevention of vascular intracellular glycation, endothelial dysfunction and early renal impairment in experimental diabetes. Modulating the GLO-I pathway therefore may provide a novel approach to prevent vascular complications in diabetes.

The Metabolic Syndrome Is Frequent in Klinefelter’s Syndrome and Is Associated With Abdominal Obesity and Hypogonadism Anders Bojesen , MD, PHD 1 2 , Kurt Kristensen , MD, PHD 3 , Niels H. Birkebaek , MD, PHD 3 , Jens Fedder , MD, PHD 4 , Leif Mosekilde , MD, DMSCI 5 , Paul Bennett , MD 6 , Peter Laurberg , MD, DMSCI 7 , Jan Frystyk , MD, DMSCI 1 , Allan Flyvbjerg , MD, DMSCI 1 , Jens S. Christiansen , MD, DMSCI 1 and Claus H. Gravholt , MD, DMSCI 1 1 Medical Department M, Endocrinology and Diabetes, and Medical Research Laboratories, Clinical Institute, Aarhus University Hospital, Aarhus, Denmark 2 Department of Clinical Genetics, Vejle Hospital, Vejle, Denmark 3 Department of Pediatrics, Aarhus University Hospital, Skejby Hospital, Aarhus, Denmark 4 Fertility Clinic and Scientific Unit, Braedstrup Hospital, Braedstrup, Denmark 5 Medical Department C, Aarhus University Hospital, Aarhus, Denmark 6 Department of Clinical Biochemistry, Statens Serum Institut, Copenhagen, Denmark 7 Department of Endocrinology, Aalborg University Hospital, Aalborg, Denmark Address correspondence and reprint requests to Anders Bojesen, MD, Medical Department M, Endocrinology and Diabetes, Aarhus University Hospital, Noerrebrogade 42-44, DK-8000, Aarhus C, Denmark. E-mail: anders.bojesen{at}dadlnet.dk Abstract OBJECTIVE —Klinefelter’s syndrome is associated with an increased prevalence of diabetes, but the pathogenesis is unknown. Accordingly, the aim of this study was to investigate measures of insulin sensitivity, the metabolic syndrome, and sex hormones in patients with Klinefelter’s syndrome and an age-matched control group. RESEARCH DESIGN AN METHODS —In a cross-sectional study, we examined 71 patients with Klinefelter’s syndrome, of whom 35 received testosterone treatment, and 71 control subjects. Body composition was evaluated using dual-energy X-ray absorptiometry scans. Fasting blood samples were analyzed for sex hormones, plasma glucose, insulin, C-reactive protein (CRP), and adipocytokines. We analyzed differences between patients with untreated Klinefelter’s syndrome and control subjects and subsequently analyzed differences between testosterone-treated and untreated Klinefelter’s syndrome patients. RESULTS —Of the patients with Klinefelter’s syndrome, 44% had metabolic syndrome (according to National Cholesterol Education Program/Adult Treatment Panel III criteria) compared with 10% of control subjects. Insulin sensitivity (assessed by homeostasis model assessment 2 modeling), androgen, and HDL cholesterol levels were significantly decreased, whereas total fat mass and LDL cholesterol, triglyceride, CRP, leptin, and fructosamine levels were significantly increased in untreated Klinefelter’s syndrome patients. In treated Klinefelter’s syndrome patients, LDL cholesterol and adiponectin were significantly decreased, whereas no difference in body composition was found in comparison with untreated Klinefelter’s syndrome patients. Multivariate analyses showed that truncal fat was the major determinant of metabolic syndrome and insulin sensitivity. CONCLUSIONS —The prevalence of metabolic syndrome was greatly increased, whereas insulin sensitivity was decreased in Klinefelter’s syndrome. Both correlated with truncal obesity. Hypogonadism in Klinefelter’s syndrome may cause an unfavorable change in body composition, primarily through increased truncal fat and decreased muscle mass. Testosterone treatment in Klinefelter’s syndrome only partly corrected the unfavorable changes observed in untreated Klinefelter’s syndrome, perhaps due to insufficient testosterone doses. ATPIII, Adult Treatment Panel III BFtr, truncal fat CRP, C-reactive protein DEXA, dual-energy X-ray absorptiometry FPG, fasting plasma glucose FSH, follicle-stimulating hormone HOMA, homeostasis model assessment HOMA2%S, HOMA of insulin sensitivity IMAT, intermuscular adipose tissue LBM, lean body mass LH, luteinizing hormone NCEP, National Cholesterol Education Program SHBG, sex hormone–binding globulin SMM, skeletal muscle mass TBF, total body fat Footnotes The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C Section 1734 solely to indicate this fact. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. Accepted April 18, 2006. Received January 20, 2006. DIABETES CARE

Adiponectin exerts anti-inflammatory and antiatherogenic effects and appears to protect against arteriosclerosis. Accordingly, an association between low concentrations of plasma adiponectin and cardiovascular (CV) disease has been demonstrated in several studies. In contrast, elevated plasma adiponectin has been associated with increased mortality and an increasing number of major adverse CV events (MACE). Because of these conflicting results, the true role of adiponectin remains to be elucidated. In the Copenhagen City Heart Study, we prospectively followed up 5,624 randomly selected men and women from the community without CV disease. Plasma adiponectin was measured at the beginning of the study. The median follow-up time was 7.8 years (interquartile range 7.3 to 8.3). The end point was all-cause mortality (n = 801), and the combined end point was MACE, consisting of CV mortality or nonfatal myocardial infarction or ischemic stroke (n = 502). High adiponectin was inversely associated with an increasing number of traditional CV risk factors (p <0.0001). The geometric mean adiponectin concentrations were 10.0 mg/L (95% confidence interval [CI] 9.7 to 10.4) for persons with no CV risk factors present versus 8.1 mg/L (95% CI 7.8 to 8.4) for persons with 4 CV risk factors. After adjustment for confounding risk factors by Cox regression analysis, adiponectin remained an independent predictor of death and MACE. The hazard ratio for each increase in adiponectin of 5 mg/L for death and MACE was 1.20 (95% CI 1.14 to 1.27; p <0.0001) and 1.14 (95% CI 1.05–1.23; p <0.0001), respectively. In conclusion, an increasing number of risk factors for CV disease is associated with decreased plasma adiponectin. High plasma adiponectin independently predicted death and MACE in a large community-based population. These results have confirmed the dual expression indicated by previous studies.