In spite of extensive research resulting in major advances in renal care including technological improvements of dialysis, the poor outcome of chronic kidney disease patients has only marginally been improved since the 1980s. It has thus become clear that new strategies are needed to move forward. There are now great expectations that increased knowledge about genetic characteristics combined with other biological markers will identify pathophysiological pathways involved in the initiation and progression of renal damage and that this in turn will help define tools for early disease intervention and personalized treatment strategies. Already, new methodologies have made it possible to study the heritable component of many kidney diseases, and it is probable that DNA-based diagnostics will be performed on a regular basis for many conditions in the near future. This article discusses basic genetic concepts and highlights some of the novel approaches available for genome-wide genetic analyses. We hope that it may serve as an introduction to the research field of what we call "nephrogenetics." A second article in this series will focus on the interpretation and evaluation of genetic association studies and how to make use of this information to improve patient care and outcomes.

P11 (S100A10) has been associated with the pathophysiology of depression both in human and rodent models. Different types of antidepressants have been shown to increase P11 levels in distinct brain regions and P11 gene therapy was recently proven effective in reversing depressive-like behaviours in mice. However, the molecular mechanisms that govern P11 gene expression in response to antidepressants still remain elusive. In this study we report decreased levels of P11, associated with higher DNA methylation in the promoter region, in the prefrontal cortex of the Flinders Sensitive Line (FSL) genetic rodent model of depression. This hypermethylated pattern was reversed to normal, as indicated by the control line, after chronic administration of escitalopram (a selective serotonin reuptake inhibitor; SSRI). The escitalopram-induced hypomethylation was associated with both an increase in P11 gene expression and a reduction in mRNA levels of two DNA methyltransferases that have been shown to maintain DNA methylation in adult forebrain neurons (Dnmt1 and Dnmt3a). In conclusion, our data further support a role for P11 in depression-like states and suggest that this gene is controlled by epigenetic mechanisms that can be affected by antidepressant treatment.

Low levels of circulating fetuin-A are associated with increased mortality in dialysis patients. This study aimed to examine a potential causative role for fetuin-A on mortality by investigating whether a functional polymorphism in the alpha2-Heremans-Schmid glycoprotein (AHSG) gene associates with mortality, and by estimating the causative effect of fetuin-A levels on mortality using a Mendelian randomization design. One thousand and forty-three incident dialysis patients were genotyped for the Thr256Ser polymorphism (rs4918) and followed up for 5 years; in 549 patients, serum fetuin-A levels were measured. Carriers of a serine allele displayed lower fetuin-A levels (-0.07 g/L per allele, P < 0.001). A small increased mortality risk was observed for the Thr/Ser and Ser/Ser genotype compared with the Thr/Thr genotype (HR 1.03, 95% CI 0.83-1.28 and HR 1.10, 95% CI 0.78-1.55, respectively). Using the AHSG genotype as an instrumental variable, the causative HR of fetuin-A levels on mortality was estimated as 1.01 per 0.1-g/L increase. Inflammation and diabetes partially modified the association of fetuin-A levels with outcome. The Thr256Ser polymorphism was weakly associated with mortality, and no causative effect of fetuin-A levels on this outcome was observed. Other risk factors, including inflammation and diabetes, might lead to lower fetuin-A levels, and/or modify the effect of low fetuin-A on mortality in end-stage renal disease patients.

HASH(0x27b1a2c0)

Objective. Anorexia is a common complication of chronic kidney disease (CKD), while novel animal and human data suggest a role for visfatin in regulating feeding behavior. We hypothesized that increased visfatin levels in CKD patients may be involved in the regulation of appetite and nutrient homeostasis. METHODS: This is a cross-sectional study where circulating visfatin levels were analysed in 246 incident CKD stage 5 patients starting dialysis therapy. The associations between visfatin (enzyme-linked immunosorbent assay, ELISA) and anthropometric and biochemical nutritional status, self-reported appetite, fasting serum amino acids (high-performance liquid chromatography) and circulating cytokine levels (ELISAs) were assessed. We also performed genotyping (Pyrosequencing(R)) of two polymorphisms (rs1319501 and rs9770242) in the visfatin gene. RESULTS: Serum visfatin concentrations were not associated with either body mass index or serum leptin. Across groups with worsening appetite, median visfatin levels were incrementally higher (P < 0.05). With increasing visfatin tertiles, patients proved to be more often anorectic (P < 0.05) and to have incrementally lower serum albumin, cholesterol and triglycerides as well as lower essential and non-essential serum amino acids (P < 0.05 for all). A polymorphism in the visfatin gene was associated with increased circulating visfatin levels and, at the same time, a higher prevalence of poor appetite (P < 0.05 for both). CONCLUSION: Our study suggests novel links between visfatin and anorexia in CKD patients. Based on recent studies, we speculate that high visfatin in CKD patients may constitute a counter-regulatory response to central visfatin resistance in uremia. Future studies should examine a putative role of visfatin as a regulator of nutrient homeostasis in uremia.

BACKGROUND & AIMS: Postoperative insulin resistance, resulting in hyperglycemia, is strongly associated to morbidity and mortality in surgical patients but the underlying mechanisms are unclear. As increasing data suggests a link between inflammation and insulin resistance, we aimed to evaluate if the expression of inflammatory and insulin signaling genes is regulated in skeletal muscle during surgery. METHODS: Eight patients (4 females, 63 [46-69] years, body mass index 25.5 [16.5-29.8]kg/m(2)) undergoing major abdominal surgery were included. Biopsies from m. rectus abdominis were obtained at the beginning and at the end of the operation. mRNA levels of 45 genes were analyzed. RESULTS: The time elapsed between the two biopsies was 224 (198-310)min. An increased (p<0.05) expression was noted for genes encoding both inflammatory mediators, such as interleukin 6, tumor necrosis factor, and nuclear factor of kappa light polypeptide gene enhancer in B cells, and metabolic regulators, such as peroxisome proliferator-activated receptor delta, while the analysis did not detect significant expression changes of the insulin signaling pathway genes. CONCLUSIONS: The observed gene expression changes in skeletal muscle during surgery occurred mainly in inflammatory pathways, suggesting a possible role for inflammation in the development of postoperative insulin resistance.

BACKGROUND: Visfatin, also known as pre-B-cell colony-enhancing factor 1 (PBEF-1), recently was shown to be secreted from adipocytes and have insulin-mimetic properties in mice. Because renal failure per se is associated with both increased levels of circulating peptides and marked insulin resistance, even in the absence of diabetes mellitus, we hypothesized that visfatin could be a factor linking inflammation, kidney disease, and insulin resistance in this patient group. METHODS: Altogether, we studied 189 patients with chronic kidney disease (CKD), comprising 149 patients with CKD stage 5 (glomerular filtration rate [GFR]< 15 mL/min; mean, 7 +/- 2 mL/min [<0.25 mL/s; mean, 0.12 +/- 0.03 mL/s]; 61% men; mean age, 54 +/- 12 years) and 40 patients with CKD stages 3 to 4 (GFR, 15 to 60 mL/min; mean, 33 +/- 21 mL/min [0.25 to 1.00 mL/s; mean, 0.55 +/- 0.35 mL/s]; 72% men; age, 59 +/- 15 years). We compared these with 30 randomly selected population controls (mean GFR, 85 +/- 16 mL/min [1.42 +/- 0.27 mL/s]; 69% men; age, 64 +/- 11 years). Serum visfatin was measured by using commercially available enzyme-linked immunosorbent assay, and we also performed genotyping of 3 verified polymorphisms in the visfatin gene (-423A/G,-1001T/G, and -1535C/T). Body fat was estimated by using dual-energy x-ray absorptiometry. RESULTS: Serum visfatin levels were greater in patients with CKD stage 5 (41.3 +/- 18.0 ng/mL) than in those with CKD stages 3 to 4 (34.0 +/- 9.8 ng/mL; P < 0.01 versus CKD stage 5) or healthy controls (29.3 +/- 8.1 ng/mL; P < 0.0001). However, there were no significant differences between patients with and without diabetes, and the significant differences in circulating visfatin levels between genotypes disappeared after adjustment for differences in age, sex, GFR, and serum albumin level. In univariate analysis, visfatin level correlated with levels of GFR (rho =-0.22; P = 0.001), interleukin 6 (IL-6; rho = 0.17; P = 0.01), high-sensitivity C-reactive protein (rho = 0.14; rho < 0.05), and soluble vascular cell adhesion molecule 1 (sVCAM-1; rho = 0.39; P < 0.0001), but not total or truncal fat mass, insulin resistance, or hemoglobin A(1c) level. High plasma visfatin level predicted mortality in patients with CKD, also after adjustment for age and sex (likelihood ratio, 18.2; P < 0.0001), but not after additional correction for GFR, sVCAM-1, serum albumin, and serum IL-6 levels. CONCLUSION: Circulating levels of the cytokine visfatin/PBEF-1 are influenced by renal function, but are not associated with fat mass or surrogate markers of insulin resistance in patients with CKD. Visfatin was associated independently with level of sVCAM-1, a marker of endothelial damage.

As the modern nephrology community continues to be burdened with growing numbers of patients with end-stage renal disease (ESRD) and exceptionally high mortality rates, it is obvious that progress in the development of preventive and therapeutic strategies has not been sufficient. This urges nephrologists to focus on the underlying mechanisms for ESRD morbidity and mortality, and in particular on cardiovascular disease (CVD), which is the major contributor to premature death in this patient group. The high prevalence of inflammation, vascular ossification, and oxidative stress in ESRD predisposes these patients to CVD. Because genetic risk factors may modulate the pathophysiologic response, genotype-phenotype association studies may provide ways of predicting individual disease progression and may shed some light on key regulatory pathways. Indeed, recent genetic association studies show that polymorphisms in candidate genes related to inflammatory signaling, vascular ossification, and oxidative stress response influence the uremic phenotype. DNA polymorphisms may also be used as nonconfounded tools in observational studies conducted to test causality, as stated by the mendelian randomization approach. To date, the collection of genetic data is no longer a limitation because genetic information is easily accessible in public databases and high-throughput genotyping technologies are available. Advanced bioinformatic tools are now warranted to facilitate the integration of accumulating genetic information with clinical and biochemical end points and, finally, to implement genotype-phenotype data in the care of patients with renal failure to better identify patients at high risk and to design novel personalized therapeutic and preventive strategies.

Background: Recently, adipose tissue was shown to contain macrophages capable of contributing to systemic inflammation and cardiovascular disease (CVD). Here, we investigate this putative relationship in patients with chronic kidney disease (CKD) by using the novel macrophage marker soluble (s)CD163. Methods: One hundred twenty patients with CKD stage 5 (mean glomerular filtration rate [GFR], 7 +/- 1 mL/min [0.12 +/- 0.02 mL/s; mean age, 53 +/- 1 years; 65% men), 38 patients with CKD stages 3 to 4 (mean GFR, 33 +/- 3 mL/min [0.55 +/- 0.05 mL/s]; mean age, 67 +/- 2 years; 68% men), and 28 healthy controls (mean GFR, 89 +/- 3 mL/min [1.48 +/- 0.05 mL/s]; mean age, 63 +/-2 years; 69% men) were characterized post hoc with a follow-up of up to 5 years (mean, 47 +/- 1 months). sCD163 levels, body composition (dual-energy x-ray absorptiometry), clinical parameters, and levels of circulating inflammatory markers (enzyme-linked immunosorbent assay) were assessed at baseline and, in a subset population, after 1 year of dialysis therapy (hemodialysis, n = 19; peritoneal dialysis, n = 30). Results: sCD163 level increased in patients with both severe (median, 4.3 mg/L; range, 1.3 to 23.4 mg/L) and moderate (median, 3.6 mg/L; range, 1.6 to 9.8 mg/L) CKD compared with controls (median, 2.6 mg/L; range, 0.8 to 7.6 mg/L; P < 0.001). Furthermore, sCD163 levels correlated with both truncal (rho = 0.17; P < 0.05) and total (rho = 0.17; P < 0.05) fat mass, as well as with all measured markers of inflammation and endothelial adhesion molecules. After 1 year, patients who increased body fat mass (average, 11%+/- 5% versus -5%+/- 5%; P < 0.05) also showed a significant increase in sCD163 levels (median, 2.2 versus -0.97 mg/L; P < 0.01). Finally, patients with sCD163 levels greater than 4.0 mg/L had a statistically significantly worse outcome than patients with sCD163 levels less than this value, even after adjustment for age, sex, and diabetes mellitus (chi-square = 19.98; P < 0.001). However, this effect was lost after adjustment for either inflammation or CVD. Conclusion: We show that increasing fat mass is associated with increasing levels of sCD163, a circulating marker of macrophages also associated with inflammatory biomarkers. We thus hypothesize that adipose tissue macrophages may have a role in the proinflammatory state observed in patients with renal disease. Finally, we propose the term "uremic-metabolic syndrome" to describe this state of increased adipose tissue signaling in patients with uremia, a phenomenon that may share some characteristics with the metabolic syndrome of obesity.