Erdinc Cakir

Systemic Markers of Lipid Peroxidation and Antioxidants in Patients with Nonalcoholic Fatty Liver Disease

OBJECTIVES:The aim of the present study was to examine the systemic parameters of oxidative stress and antioxidants in patients with nonalcoholic fatty liver disease and investigate the relationship between these parameters and clinical and biochemical outcomes.METHODS:Fifty-one male patients with nonalcoholic fatty liver disease (group I), 30 age-matched and body mass index (BMI)-matched healthy male subjects, and 30 age-matched male patients with chronic viral hepatitis (group II) were enrolled in the study.RESULTS:Increased systemic levels of malondialdehyde and depletion of antioxidants such as coenzyme Q10, CuZn-superoxide dismutase, and catalase activity were observed in group I. Coenzyme Q10 and CuZn-superoxide dismutase correlated negatively with increasing necroinflammatory activity and fibrosis. Body fat was negatively associated with plasma coenzyme Q10 levels, while an inverse association was found between plasma catalase levels and TG. However, LDL was positively associated with plasma malondialdehyde levels. CuZn-superoxide dismutase levels were negatively associated with glucose, insulin, and HOMA-IR. In addition, the levels of CuZn-superoxide dismutase correlated significantly in a negative manner with BMI.CONCLUSIONS:Our results concerning correlations suggest that disturbances in BMI, body fat, and lipid metabolism may contribute to altered oxidative status in NAFLD, and insulin resistance may be related to decreased antioxidants in NAFLD as well as products of lipid peroxidation. However, although our results suggest interesting correlations, this different mostly “weak” relationships must be taken with caution.

Short-Term Treatment with Sevelamer Increases Serum Fetuin-A Concentration and Improves Endothelial Dysfunction in Chronic Kidney Disease Stage 4 Patients

BACKGROUND AND OBJECTIVES Vascular calcification and endothelial dysfunction contribute to the development of cardiovascular disease in patients with chronic kidney disease (CKD). Sevelamer, a non-calcium-based phosphate binder, has been shown to attenuate cardiovascular calcification in CKD patients, although the exact mechanism has not been clarified. This study was designed to investigate the effect of short-term sevelamer treatment on both serum fetuin-A concentrations and endothelial dysfunction seen in CKD patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Fifty nondiabetic stage 4 CKD patients whose phosphate levels were > or =5.5 mg/dl were enrolled in this 8-wk randomized prospective study. Thirty-six healthy volunteers served as matched controls. Patients were treated with either sevelamer (n = 25, 12 males) or calcium acetate (n = 25, 13 males). Fetuin-A, high-sensitivity C-reactive protein, Ca x PO4 product, flow-mediated dilation (FMD), insulin, and homeostasis model assessment (HOMA) were obtained at baseline and after the treatment period. RESULTS As expected, CKD patients had significantly lower levels of fetuin-A and FMD, and significantly higher levels of intact parathyroid hormone, Ca x PO4 product, and high-sensitivity C-reactive protein than controls (P < 0.001 for all). The use of sevelamer led to a significant increase in the fetuin-A concentration with improvement in FMD, whereas no significant difference was observed in the calcium acetate group. In a multiple regression analysis, FMD levels were independently related to fetuin-A both before (beta = 0.63, P < 0.001) and after (beta = 0.38, P = 0.004) treatment. CONCLUSIONS This small, randomized, prospective study shows that short-term sevelamer treatment significantly increases fetuin-A levels and improves FMD in nondiabetic stage 4 CKD patients.

Endothelial dysfunction in type-2 diabetics with early diabetic nephropathy is associated with low circulating adiponectin

BACKGROUND Type-2 diabetes and diabetic kidney disease have additive effects on cardiovascular risk. Furthermore, the degree of proteinuria is an independent predictor of mortality in this patient group. We hypothesized that altered kidney clearance and/or metabolism of vasoactive peptides occurring during proteinuria could link early diabetic nephropathy to cardio vascular disease (CVD). METHODS We performed a cross-sectional study of 85 incident patients (51 +/- 5 years, 49 males) with type-2 diabetes and 38 age- and sex-matched controls. We further divided patients by the presence of minor (<500 mg/day; n = 40) or severe (>/=500 mg/day; n = 45) proteinuria. Clinical and anthropometric data, along with ultrasonographic flow-mediated dilatation (FMD) of the brachial artery and carotid intima-media thicknesses (CIMT), were recorded in each group. Circulating NAMPT/visfatin, adiponectin (normalized to BMI), AHSG/fetuin-A and hsCRP levels were also measured using commercial ELISA. RESULTS Plasma NAMPT/visfatin, CIMT, HOMA index and hsCRP levels were all significantly higher in diabetics than in control subjects, and all but CIMT correlated with proteinuria (rho = 0.46; P < 0.001, rho = 0.54; P > 0.05, rho = 0.32; P = 0.003, rho = 0.76; P < 0.001, respectively). FMD, adiponectin and AHSG/fetuin-A levels were significantly lower, and negatively correlated with proteinuria (rho = -0.54; P < 0.001, rho = -0.56; P < 0.001, rho = -0.48; P < 0.001, respectively). In a multivariate regression analysis, the degrees of proteinuria (r(2) = -0.32, P = 0.04) and plasma levels of NAMPT/visfatin (r(2) = -0.33, P = 0.006) were independently related to FMD. CONCLUSIONS The present study suggests that the presence of proteinuria, regardless of the degree of renal function impairment, is an important predictor of endothelial dysfunction in early diabetic nephropathy and that it is associated with altered circulating levels of NAMPT/visfatin and adiponectin.

Elevated plasma homocysteine concentrations as a predictor of steatohepatitis in patients with non‐alcoholic fatty liver disease

Background:  Although steatosis is common in patients with severe hyperhomocysteinemia due to deficiency of cystathionine β‐synthase, there are no satisfactory data on homocysteine concentrations in patients with non‐alcoholic fatty liver disease. The main aim of the present study was to evaluate the clinical significance of plasma homocysteine concentrations in patients with non‐alcoholic fatty liver disease.

ADMA Levels Correlate with Proteinuria, Secondary Amyloidosis, and Endothelial Dysfunction

Asymmetric dimethyl-arginine (ADMA), a residue of the proteolysis of arginine-methylated proteins, is a potent inhibitor of nitric oxide synthesis. The increased protein turnover that accompanies proteinuric secondary amyloidosis may increase circulating levels of ADMA, and this may contribute to endothelial dysfunction. We performed a cross-sectional study of 121 nondiabetic proteinuric patients with normal GFR (including 39 patients with nephrotic-range proteinuria and secondary amyloidosis) and 50 age-, sex-, and BMI-matched healthy controls. The proteinuric patients had higher levels of serum ADMA, symmetric dimethyl-arginine (SDMA), high-sensitivity C-reactive protein (hsCRP), and insulin resistance (homeostasis model assessment index) than controls. Compared with controls, brachial artery flow-mediated dilatation (FMD), serum L-Arginine, and the L-Arginine/ADMA ratio were significantly lower among proteinuric patients, suggesting greater endothelial dysfunction. When patients with secondary amyloidosis were compared with patients with glomerulonephritis who had similar levels of proteinuria, those with amyloidosis had higher ADMA and SDMA levels and lower L-Arginine/ADMA ratios and FMD measurements (P < 0.001 for all). Finally, even after adjusting for confounders, ADMA level correlated with both proteinuria and the presence of secondary amyloidosis, and was an independent predictor of FMD. We propose that ADMA synthesis may be increased in chronic kidney disease, especially in secondary amyloidosis, and this may explain part of the mechanism by which proteinuria increases cardiovascular morbidity and mortality.

Endothelial functions improve with decrease in asymmetric dimethylarginine (ADMA) levels after renal transplantation.

Background. Chronic kidney disease (CKD) is associated with increased cardiovascular events. The relationships between the markers of inflammation and endothelial dysfunction were investigated both before and after living donor kidney transplantation. Methods. Twenty-seven renal transplant patients were studied. Eleven patients (six male, five female) were on cyclosporine A, whereas 16 patients (nine male, seven female) were treated with tacrolimus based regimes. Twenty-seven subjects (12 males, 15 females) were studied as controls. Plasma adiponectin, high sensitive C reactive protein (hsCRP), Asymetric dimethyl arginine (ADMA) levels were studied before transplantation and on days 1, 3, 7, 14, and 28. The brachial artery flow mediated dilatation (FMD) was studied before transplantation and on the 28th day. Results. Serum hsCRP and ADMA levels decreased significantly from the first posttransplantation day on each measurement (P<0.001 for all) while the decrement of plasma adiponectin started in the third day (P<0.001 for all). The FMD was lower in the patients than the control group (P<0.001) and improved significantly in the 28th day of transplantation (P<0.001). Conclusions. The results indicate that ADMA is associated with FMD in CKD both before and after kidney transplantation. Endothelial functions improve at the very beginning of the posttransplantation period with accompanying reduction in ADMA and hsCRP levels.

Serum Uric Acid Level and Endothelial Dysfunction in Patients with Nondiabetic Chronic Kidney Disease

Background: An elevated serum uric acid level is strongly associated with endothelial dysfunction and inflammation, both of which are common in chronic kidney disease (CKD). We hypothesized that endothelial dysfunction in subjects with CKD would correlate with uric acid levels. Materials and Methods: We evaluated the association between serum uric acid level and ultrasonographic flow-mediated dilatation (FMD) in 263 of 486 patients with recently diagnosed CKD (stage 3–5) (48% male, age 52 ± 12 years). To minimize confounding, 233 patients were excluded because they were diabetic, had established cardiovascular complications or were taking drugs (renin-angiotensin system blockers, statins) interfering with vascular function. Results: Serum uric acid level was significantly increased in all stages of CKD and strongly correlated with estimated glomerular filtration rate (eGFR-MDRD); FMD was inversely associated with serum uric acid (r = –0.49, p < 0.001). The association of serum uric acid with FMD remained after adjustment for age, gender, smoking, LDL cholesterol, eGFR, high-sensitivity C-reactive protein, systolic blood pressure, proteinuria, and homeostatic model assessment index (β = –0.27, p < 0.001). Conclusion: Increased serum uric acid is an independent predictor of endothelial dysfunction in subjects with CKD.

The effects of thyroxine replacement on the levels of serum asymmetric dimethylarginine (ADMA) and other biochemical cardiovascular risk markers in patients with subclinical hypothyroidism

Background  The relationship between subclinical hypothyroidism (SH) and cardiovascular disease (CVD) is still under debate. The purpose of the present study was to evaluate plasma total homocysteine (tHcy), high sensitive C‐reactive protein (hsCRP), small dense low‐density lipoprotein (sdLDL), l‐arginine and asymmetric dimethylarginine (ADMA) concentrations and their relationship to nitric oxide (NO) production, measured as plasma nitrite‐plus‐nitrate (NOx) concentration, in patients with SH before and after thyroxine replacement therapy and compared with control group values.

Serum Fetuin-A Concentration and Endothelial Dysfunction in Chronic Kidney Disease

Background: Defective endothelial function, an initial step in the development of atherosclerotic plaque, is prevalent in moderate to advanced chronic kidney disease (CKD). In this study, the investigators hypothesized that fetuin-A, a calcification inhibitor, is a novel risk factor for the development of endothelial dysfunction in patients. Methods: 198 nondiabetic patients with a mean age of 44.0 ± 12.4 years and with different stages of CKD were studied. In addition to a detailed metabolic panel, flow-mediated dilatation assessed by high-resolution brachial ultrasonography was performed to determine endothelial dysfunction. Carotid intima-media thickness was also estimated by ultrasonography. Serum fetuin-A concentrations were determined by using a human ELISA method. Results: Endothelial dysfunction was observed in all stages (1–5) of CKD and worsened in parallel to the reduction in estimated glomerular filtration rate. Serum fetuin-A concentrations were also found to be decreased in all but stage 1 CKD. On multiple regression analysis, endothelial dysfunction was independently associated with fetuin-A (β = 0.745, p < 0.001) and intact parathyroid hormone concentrations (β = –0.216, p < 0.001). Conclusion: These data in a selected cohort of CKD patients indicate that fetuin-A may be one of the contributing factors for the development of endothelial dysfunction in CKD patients.

Serum uric acid independently predicts cardiovascular events in advanced nephropathy.

Background: Chronic kidney disease (CKD) is associated with increased risk for cardiovascular (CV) disease and is also associated with elevated uric acid, which is emerging as a nontraditional CV risk factor. We therefore evaluated uric acid as a risk factor for CV disease in subjects presenting to nephrologists with CKD who were not on medications known to alter endothelial function. Methods: 303 subjects with stage 3–5 CKD were followed for a mean of 39 months (range 6–46) and assessed for fatal and nonfatal CV events. Hyperuricemia was defined as uric acid >6.0 mg/dl for women and >7.0 mg/dl for men. In addition to other CV risk factors, endothelial function (flow-mediated dilatation), inflammatory markers (hsCRP), and insulin resistance (HOMA index and fasting insulin levels) were included in the analysis. We evaluated the association between uric acid and flow-mediated dilatation with linear regression. The impact of uric acid on composite CV events was assessed with Cox regression analysis. Results: Of a total of 303 patients, 89 had normouricemia and 214 had hyperuricemia. Both fatal (32 of 214 vs. 1 of 89 subjects) and combined fatal and nonfatal (100 of 214 vs. 13 of 89 subjects) CV events were more common in subjects with hyperuricemia compared with normal uric acid levels, and this was independent of estimated glomerular filtration rate, traditional CV risk factors including diabetes, hypertension and BMI, and nontraditional risk factors (hsCRP and endothelial function). The 46-month survival rate was 98.7% in the group with low uric acid compared to 85.8% in patients with high uric acid (p = 0.002). Conclusions: Hyperuricemia is an independent risk factor for CV events in subjects presenting with CKD who are not on medications known to alter endothelial function.