Lipocalin-2: Development, Analytical Characterization, and Clinical Testing of a New ELISA

Abstract

Lipocalin-2 (also known as neutrophil gelatinase-associated lipocalin [NGAL]) has been described as a promising marker of metabolic syndrome associated with inflammation. The aim of our work was to develop an assay for the determination of lipocalin-2 in human serum and to investigate its levels in healthy volunteers and donors suffering from metabolic syndrome. We also conducted a pilot study on individuals with metabolic syndrome and on healthy probands and measured lipocalin-2 in these individuals. We developed and evaluated the sandwich ELISA method for the quantitative determination of human lipocalin-2 in serum samples. We measured blood pressure, waist circumference, serum cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, insulin, glucose, creatinine, hs-CRP, and adiponectin and calculated the BMI and Quicki insulin sensitivity index. In the study on 153 healthy volunteers, we showed that sex and age are not determinative for lipocalin-2 serum values. Furthermore, we tested 45 individuals with metabolic syndrome; values of lipocalin-2 did not differ (78.8 vs. 80.0 microg/l, p =0.56) from the data of healthy individuals from the first study. Neither group differed with regard to sex or age. Lipocalin-2 correlated with alanine aminotransferase (ALT) (r=-0.3, p<0.01) aspartate aminotransferase (AST) (r=-0.3, p<0.01), cholesterol (r=-0.21, p=0.047), creatinine (r=0.19, p=0.05), and high-sensitivity C-reactive protein (hs-CRP) (r=0.22, p=0.036). No significant correlation was found between serum lipocalin-2 and BMI, waist circumference, blood pressure, triglycerides, HDL, Quicki, or the number of metabolic syndrome components. When study patients with metabolic syndrome were further stratified according to the number of components of metabolic syndrome, serum concentrations of lipocalin-2 did not differ. The results presented demonstrate the analytical competence of the lipocalin-2 assay. However, we assumed that lipocalin-2 is not a routinely usable marker of metabolic syndrome or obesity. The association between serum lipocalin-2 and obesity or metabolic syndrome was not validated in our study.

Quantitation of serum angiopoietin-like proteins 3 and 4 in a Finnish population sample

“…There are several basic residue-rich regions in ANGPTL 3 and 4, both in N-and C-terminal regions that could mediate the binding of these proteins at the sites important for LPL activity. For ANGPTL3, good agreement with previous reports showing that ANGPTL3 is present in the circulation at a higher concentration (224 ng/ml) compared with ANGPTL4 (1.73 ng/ ml) ( 22,23 ). Although some differences exist in the values reported for ANGPTL 3 and 4, these probably are due to differences in method standardization, population samples, and/or the antibodies used.…”

Weight loss in prepubertal obese children is associated with a decrease in adipocyte fatty-acid-binding protein without changes in lipocalin-2: a 2-year longitudinal study

“…A previous study in adults showed higher concentrations of plasmatic lipocalin-2 in obese subjects (10), but these results have not been corroborated by other authors (27). It is noteworthy that, despite obtaining clear differences between obese and lean children in our studied cohorts, lipocalin-2 levels were not related to BMI and waist circumference.…”

Effect of Obesity on Circulating Adipokines and Their Expression in Omental Adipose Tissue of Female Bariatric Surgery Patients

“…However, Jun et al, (2011) found no effect of global ablation of lipocalin-2 on obesity-mediated insulin resistance in vivo. In obese humans no statistically significant effect of BMI was found on circulating levels of lipocalin-2 (Stejskal et al, 2008) and this was confirmed by . Furthermore lipocalin-2 was found in and released almost exclusively by the nonfat cells rather than the fat cells isolated from human omental adipose tissue .…”