Mortality prediction in stable hemodialysis patients is refined by YKL-40, a 40-kDa glycoprotein associated with inflammation.

Chronic inflammation contributes to increased mortality in hemodialysis (HD) patients. YKL-40 is a novel marker of inflammation, tissue remodeling, and highly expressed in macrophages inside vascular lesions. Elevated levels of YKL-40 have been reported for HD patients but how it integrates into the proinflammatory mediator network as a predictor of mortality remains elusive. We studied serum YKL-40, Interleukin-6 (IL-6), high-sensitivity C-reactive protein, monocyte chemotactic protein-1 (MCP-1), and interferon-gamma induced protein-10 (IP-10) in 475 chronic hemodialysis patients. Patients were followed for mortality for a median of 37 [interquartile range: 25-49] months and checked for interrelation of the measured mediators. To plot cumulative incidence functions, patients were stratified into terciles per YKL-40, IL-6, MCP-1, and IP-10 levels. Multivariable Cox regression models were built to examine associations of YKL-40, IP-10, and MCP-1 with all-cause and cause-specific mortality. Net reclassification improvement was calculated for the final models containing YKL-40 and IL-6. Increased YKL-40 was independently associated with age, IP-10, and IL-6 serum levels. After adjustment for demographic and laboratory parameters, comorbidities, and IL-6, only YKL-40 significantly improved risk prediction for all-cause (hazard ratio 1.4; 95% confidence interval 1.1-1.8) and cardiovascular mortality (hazard ratio 1.5; 95% confidence interval 1.03-2.2). Thus, in contrast to other biomarkers of aberrant macrophage activation, YKL-40 reflects inflammatory activity, which is not covered by IL-6. Mechanistic and prospective studies are needed to test for causal involvement of YKL-40 and whether it might qualify as a therapeutic target.

Biosensor analyses of serum autoantibodies: application to antiphospholipid syndrome and systemic lupus erythematosus.

Autoimmune disorders are rare human diseases characterized by the presence of circulating autoantibodies that bind the body's own structural compounds as target antigens. The detection of autoantibodies is important for the diagnostic process. Immunofluorescence and immunoassay methods do not allow a reliable characterization of binding characteristics. Therefore, novel analytical techniques should be considered. This review describes the application of surface plasmon resonance biosensor systems for the diagnosis of autoimmune disorders. The covalent attachment of native antigens to the sensor chip is a suitable method for obtaining highly reproducible analyses of autoantibodies, allowing the evaluation of kinetic rate and affinity constants, and it may enable the identification of disease-relevant autoantibodies linked to disease progression. The autoantibody microarray is another future-oriented technique. Patterns of differential antigen recognition should allow early diagnosis. This is due to the fact that a broad range of autoreactive B cell responses in autoimmune disorders can only be mirrored by including a sufficient number of antigens in a microarray format.

Unchanged androgen-binding properties of sex hormone-binding globulin in male patients with liver cirrhosis.

BACKGROUND: Men affected by liver cirrhosis frequently show clinical features of hypogonadism due to hormonal changes, in particular in the metabolism of 17beta-estradiol (E2) and testosterone (T). Sex hormone-binding globulin (SHBG), the major binding protein of these steroids in serum, is regularly elevated in such patients, with its androgen-binding properties possibly altered. In the present study, surface plasmon resonance biosensor techniques were used to determine whether the functional binding properties of this transporter are maintained in this pathology. METHODS: We selected 33 male patients with cirrhosis, Child-Pugh grade A or B, and 32 healthy males served as controls. Serum concentrations of T, E2, dehydroepiandrosterone sulfate (DHEAS) and SHBG were measured. In addition, ligand-binding properties of SHBG partially purified from sera of 23 cirrhotic patients and 20 controls were analyzed by a real-time biosensor technique using a surface-coated dihydrotestosterone derivative. RESULTS: The sensorgrams revealed that SHBG was fully bioactive in all samples investigated without any changes in binding kinetics. Moreover, total T concentrations were not significantly different in the cirrhotic patient sera (mean+/-SD 18.0+/-8.6 nmol/L) compared to controls (15.6+/-3.7; n.s.), whereas E2 was higher (152+/-60 vs. 96+/-29 pmol/L; p<0.0001) and DHEAS was lower (1493+/-1410 vs. 5099+/-2844 nmol/L; p<0.0001). CONCLUSIONS: Owing to elevated SHBG levels without changes in the steroid-binding properties in sera of cirrhotic male patients, free or bioavailable T concentrations are lower. This causes a shift of the hormonal balance in favor of E2, which exhibits a lower affinity for SHBG than androgens and accounts for the endocrine symptoms.

Immunoassay for sex hormone-binding globulin in undiluted serum is influenced by high-molecular-mass aggregates.

BACKGROUND: The new Elecsys chemiluminescence assay for measurement of homodimeric sex hormone-binding globulin (SHBG) was designed for use with undiluted serum, in contrast to other methods that require predilution. During assay development, unexpected calibration difficulties were observed that were attributable to particular biochemical properties of the highly concentrated SHBG in solution. METHODS: We used a surface plasmon resonance (SPR) biosensor, which enables biomolecular interaction analysis of SHBG, and size-exclusion chromatography for this investigation. The immunoassay was evaluated for imprecision, linearity, and suitability of the dilution medium, and the method was compared with an IRMA for SHBG. RESULTS: The SPR biosensor characterized the special protein properties of SHBG in various concentrations. Above 200 nmol/L there was a strong tendency toward formation of high-molecular-mass aggregates. This was also detectable by size-exclusion chromatography and could be reversed by simple dilution of the sample. On the basis of these results, the dynamic measuring range of the SHBG assay is restricted to 0.350-200 nmol/L. Assay evaluation on a 2010 analyzer revealed excellent precision (CV