José A.M. De Carvalho

Diabetic nephropathy: Traditional to proteomic markers

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes and it is defined as a rise in the urinary albumin excretion (UAE) rate and abnormal renal function. Currently, changes in albuminuria are considered a hallmark of onset or progression of DN. However, some patients with diabetes have advanced renal pathological changes and progressive kidney function decline even if urinary albumin levels are in the normal range, indicating that albuminuria is not the perfect marker for the early detection of DN. The present article provides an overview of the literature reporting some relevant biomarkers that have been found to be associated with DN and that potentially may be used to predict the onset and/or monitor the progression of nephropathy. In particular, biomarkers of renal damage, inflammation, and oxidative stress may be useful tools for detection at an early stage or prediction of DN. Proteomic-based biomarker discovery represents a novel strategy to improve diagnosis, prognosis and treatment of DN; however, proteomics-based approaches are not yet available in most of the clinical chemistry laboratories. The use of a panel with a combination of biomarkers instead of urinary albumin alone seems to be an interesting approach for early detection of DN, including markers of glomerular damage (e.g., albumin), tubular damage (e.g., NAG and KIM-1), inflammation (e.g., TNF-α) and oxidative stress (e.g., 8-OHdG) because these mechanisms contribute to the development and outcomes of this disease.

Assessment of Inflammatory and Oxidative Biomarkers in Obesity and Their Associations with Body Mass Index

The aim of this study was to evaluate the inflammatory and oxidative biomarkers’ levels in obese subjects and their associations with body mass index (BMI), in order to investigate the role of these biomarkers in obesity. Fasting glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, apolipoprotein A, apolipoprotein B, albumin, urinary albumin, creatinine, glomerular filtration rate, interleukin-6 (IL-6), nitrate/nitrite (NOx), and ischemia-modified albumin (IMA) were measured in 93 subjects divided according to different BMI. IL-6, urinary albumin, and IMA levels were significantly higher in obese subjects. However, the levels of NOx were significantly lower in this population. Significant correlations between BMI and IL-6 (r = 0.326, P = 0.002), NOx (r = −0.249, P = 0.021), urinary albumin (r = 0.270, P = 0.008), and IMA (r = 0.286, P = 0.005) were reported. We have shown an increase of IL-6, urinary albumin, and IMA combined with lower levels of NOx in obese patients and an association between of these biomarkers with BMI, suggesting a possible interplay of oxidative stress, inflammation, and endothelial dysfunction state in obesity.

Association between DNA strand breakage and oxidative, inflammatory and endothelial biomarkers in type 2 diabetes

Evidence has been presented recently that type 2 diabetes patients have an increased level of DNA damage. This DNA damage could be associated with oxidative, inflammatory, and endothelial biomarkers and could represent a possible indication of injury in the endothelium and induction of inflammation in type 2 diabetes. To confirm this possible association, DNA strand breakage was evaluated by use of the comet assay and its association with oxidative, inflammatory, and endothelial biomarkers in type 2 diabetes patients. A case-control study (30 healthy controls and 32 subjects with type 2 diabetes) was performed to evaluate the association between DNA damage and NOx (nitrate/nitrite), interleukin-6 (IL-6), urinary albumin, fasting glucose, and glycated hemoglobin (HbA(1c)) levels. Type 2 diabetes patients presented higher DNA damage than control subjects, higher levels of IL-6 and urinary albumin, and lower NOx. Significant correlations between DNA damage and NOx (r=-0.303, p=0.016), IL-6 (r=0.845, p<0.001), urinary albumin (r=0.496, p<0.001), fasting glucose (r=0.449, p<0.001), and HbA(1c) (r=0.575, p<0.001) were reported. Our findings showed an increase of DNA damage in type 2 diabetes especially in those patients with poor glycemic control and associations among NOx, IL-6 and urinary albumin levels with DNA damage.

Urinary kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin as indicators of tubular damage in normoalbuminuric patients with type 2 diabetes.

OBJECTIVES Renal dysfunction has been reported in normoalbuminuric patients, demonstrating the necessity to improve the diagnostic and prognostic tools for diabetic kidney disease (DKD) investigation. Therefore, the aim of this study was to investigate whether the urinary levels of neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) are increased in type 2 diabetes mellitus (DM) patients with normal or mildly increased albuminuria. DESIGN AND METHODS In this study, 117 type 2 DM patients classified into three groups according to urinary albumin/creatinine ratio (uACR): uACR<10mg/g creatinine, uACR 10-30mg/g creatinine and uACR>30mg/g creatinine were enrolled. Urinary concentrations of KIM-1 (uKIM-1) and NGAL (uNGAL) were measured. RESULTS uKIM-1 levels increased progressively from uACR<10mg/g creatinine (69.0±20.8pg/ml) to uACR 10-30mg/g creatinine (106.1±41.2pg/ml) and to uACR>30mg/g creatinine (166.0±31.9pg/ml) (P<0.001). In addition, uNGAL levels increased progressively from uACR<10mg/g creatinine (29.5±8.8ng/ml) to uACR 10-30mg/g creatinine (51.7±10.9ng/ml) and to uACR>30mg/g creatinine (71.0±9.6ng/ml) (P<0.001) patients. Similarly, both uKIM-1 and uNGAL adjusted by urinary creatinine were increased in patients with uACR 10-30mg/g creatinine. Significant and positive correlations were observed between uACR, uKIM-1 and uNGAL. CONCLUSIONS uKIM-1 and uNGAL were increased in type 2 DM patients with normal or mildly increased albuminuria, which indicates that tubular and glomerular injuries may be occurring even at the earliest stage of DKD.

Assessment of urinary γ-glutamyltransferase and alkaline phosphatase for diagnosis of diabetic nephropathy.

BACKGROUND Urinary biomarkers of tubular damage can be useful for early diagnosis of diabetic nephropathy. Thus, the aim of this study was to test the diagnostic accuracy of the urinary excretion of γ-glutamyltransferase (GGT) and alkaline phosphatase (ALP) for diagnosis of diabetic nephropathy (DN). METHODS Fasting glucose, fructosamine, serum creatinine, glomerular filtration rate (GFR), serum uric acid, serum albumin, and urinary albumin, creatinine, GGT and ALP were assessed in 74 type 2 diabetic patients without nephropathy and 38 type 2 diabetic patients with nephropathy. RESULTS Urinary GGT and ALP were threefold higher in type 2 diabetic patients with nephropathy. Significant correlations were observed between urinary albumin and GGT (r=0.439, P<0.001) and urinary albumin and ALP (r=0.305, P<0.01). Areas under the curve for GGT and ALP were 0.7696 (P<0.001) and 0.7233 (P<0.001), respectively. At a cut-off value of 72U/g creatinine, GGT demonstrated a sensitivity of 96.0% and a specificity of 52.6%. At a cut-off value of 20U/g creatinine, ALP demonstrated a sensitivity and specificity of 83.8% and 36.8%, respectively. CONCLUSIONS Urinary GGT and ALP have potential value in the diagnosis of nephropathy in type 2 diabetic patients, but GGT has a slightly higher ability to discriminate nephropathy than ALP.

An Alternative Pathway Through the Fenton Reaction for the Formation of Advanced Oxidation Protein Products, a New Class of Inflammatory Mediators

The accumulation of advanced oxidation protein products (AOPPs) has been linked to several pathological conditions, and their levels are formed during oxidative stress as a result of reactions between plasma proteins and chlorinated oxidants produced by myeloperoxidase (MPO). However, it was suggested that the generation of this mediator of inflammation may also occur via an MPO-independent pathway. The aim of this study was to induce the formation of AOPPs in vitro through Fenton reaction and to investigate whether this generation could be counteracted by N-acetylcysteine (NAC) and fructose-1,6-bisphosphate (FBP). The complete Fenton system increased the AOPPs levels and both NAC and FBP were capable of inhibiting the formation of Fenton reaction-induced AOPPs. These data provide a new hypothesis about another pathway of AOPPs formation, as well as report that NAC and FBP may be good candidates to neutralize pro-inflammatory and pro-oxidant effects of AOPPs in several diseases.

Oxidative DNA damage is associated with inflammatory response, insulin resistance and microvascular complications in type 2 diabetes

Urinary markers of nucleic acid oxidation may be useful biomarkers in diabetes. It has been demonstrated that T2DM patients have an increased level of oxidative DNA damage; however, it is unclear whether increased DNA damage may be related to a greater degree of inflammation and insulin resistance. Thus, the aim of this present study was to investigate the relation of the impact of oxidative DNA damage, assessed by urinary 8-OHdG, on the levels of inflammatory cytokines, as well as insulin resistance. In addition, we also investigated the diagnostic ability of urinary 8-OHdG in the identification of microvascular complications in T2DM.A case-control study, enrolling 22 healthy controls and 54 subjects with T2DM, was performed to evaluate the relation between oxidative DNA damage and interleukin-6 (IL-6), IL-1,tumor necrosis factor-alpha (TNF-α), IL-10, and Homeostasis Model Assessment (HOMA-IR) index. T2DM patients presented higher urinary 8-OHdG, IL-6, IL-1, TNF-α levels and HOMA-IR, and lower IL-10 levels than control subjects. Moreover, urinary 8-OHdG levels were significantly higher in the group T2DM with microvascular complications when compared to the without complications. The areas under the curve for urinary 8-OHdG and urinary albumin were, respectively, 0.836 (P<0.001) and 0.786 (P=0.002). Thus, urinary 8-OHdG has a slightly higher ability to discriminate microvascular complications in T2DM compared with urinary albumin. It was also demonstrated that T2DM patients with higher median of urinary 8-OHdG had significantly elevated levels of IL-6, TNF-α and HOMA-IR, and decreased IL-10 levels. Our findings showed that T2DM patients with higher urinary 8-OHdG levels showed a greater inflammatory degree and higher insulin resistance. It is possible to speculate that T2DM patients present a cascade of events as increasing metabolic abnormalities such as insulin resistance and inflammatory activation, as well as increased ROS generation factors that may contribute directly to greater oxidative DNA damage.

In vitro oxidation of fibrinogen promotes functional alterations and formation of advanced oxidation protein products, an inflammation mediator.

Fibrinogen (FB) is a soluble blood plasma protein and is a key molecule involved in coagulation. Oxidative modification of proteins, such as the formation of advanced oxidation protein products (AOPP), a heterogeneous family of protein compounds structurally modified and derived from oxidative stress, may be associated with the pathophysiology of a number of chronic inflammatory diseases. Therefore, the aim of this study was to determine whether the formation of this mediator of inflammation occurs from FB and whether its generation is associated with structural changes. Results of the present study suggest that the oxidation of FB may provoke the formation of AOPP, which in turn, may promote functional alterations in FB, thus causing changes in its structural domains and increasing its procoagulant activity.

Urinary inflammatory cytokines as indicators of kidney damage in type 2 diabetic patients

BACKGROUND The aim of this study was to investigate whether urinary levels of interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) are altered in normoalbuminuric patients with type 2 diabetes mellitus (T2DM), and whether these cytokines are able to identify diabetic kidney disease (DKD) among these patients. METHODS This study included 125 T2DM patients classified into 3 groups according to urinary albumin/creatinine ratio (uACR): uACR <10mg/g creatinine, uACR 10-30mg/g creatinine and uACR >30mg/g creatinine. Urinary inflammatory cytokines were measured. RESULTS The urinary IL-6 concentrations increased from uACR <10 (97.2±26.4pg/ml) to uACR 10-30 (113.6±28.0pg/ml) and to uACR >30mg/g creatinine (163.5±25.6pg/ml) (P<0.05 and P<0.001, respectively) patients. The urinary IL-10 concentrations decreased in these uACR ranges [100.0 (58.0-141.0) pg/ml vs. 62.0 (54.5-71.5) pg/ml vs. 42.0 (32.0-48.0) pg/ml] (P<0.05 and P<0.001, respectively). All urinary cytokines demonstrated good ability to identify DKD (areas under curves >0.9). CONCLUSIONS Urinary inflammatory cytokines, especially IL-6 and IL-10, may assist in the identification of DKD in T2DM patients, even in the absence of micro- and macroalbuminuria.

An automated technique for the measurement of the plasma glutathione reductase activity and determination of reference limits for a healthy population.

*Corresponding author: Rafael Noal Moresco, Universidade Federal de Santa Maria, Centro de Ci ê ncias da Sa ú de, Departamento de An á lises Cl í nicas e Toxicol ó gicas, Avenida Roraima 1000, Pr é dio 26, Sala 1401, 97105-900, Santa Maria, RS, Brazil, Phone: + 55 55 32208941, Fax: + 55 55 32208018, E-mail: rnmoresco@yahoo.com.br Carine L. Hermes: Laborat ó rio de Bioqu í mica Cl í nica , Departamento de An á lises Cl í nicas e Toxicol ó gicas, Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil; and Programa de P ó s-Gradua ç ã o em Ci ê ncias Farmac ê uticas , Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil Bruna S. Hausen: Laborat ó rio de Bioqu í mica Cl í nica , Departamento de An á lises Cl í nicas e Toxicol ó gicas, Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil; and Programa de P ó s-Gradua ç ã o em Ci ê ncias Farmac ê uticas , Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil Manuela B. Sangoi: Laborat ó rio de Bioqu í mica Cl í nica , Departamento de An á lises Cl í nicas e Toxicol ó gicas, Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil ; and Programa de P ó s-Gradua ç ã o em Ci ê ncias Farmac ê uticas , Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil Ta í s C. Almeida: Laborat ó rio de Bioqu í mica Cl í nica , Departamento de An á lises Cl í nicas e Toxicol ó gicas, Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil; and Programa de P ó s-Gradua ç ã o em Ci ê ncias Farmac ê uticas , Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil Jos é A.M. De Carvalho: Laborat ó rio de Bioqu í mica Cl í nica , Departamento de An á lises Cl í nicas e Toxicol ó gicas, Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil ; and Programa de P ó s-Gradua ç ã o em Ci ê ncias Farmac ê uticas , Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil Patr í cia Gomes: Programa de P ó s-Gradua ç ã o em Nanoci ê ncias , Centro Universit á rio Franciscano, Santa Maria, RS , Brazil Rafael N. Moresco: Laborat ó rio de Bioqu í mica Cl í nica , Departamento de An á lises Cl í nicas e Toxicol ó gicas, Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil ; and Programa de P ó s-Gradua ç ã o em Ci ê ncias Farmac ê uticas , Centro de Ci ê ncias da Sa ú de, Universidade Federal de Santa Maria, Santa Maria, RS , Brazil