Fibroblast growth factor-19: development, analytical characterization and clinical evaluation of a new ELISA test.

OBJECTIVE: Since fibroblast growth factor 19 (FGF-19) is a potent metabolic regulator that influences glucose and lipid homeostasis, our aim was to develop an ELISA assay for measuring FGF-19 in human serum and to investigate its concentrations in healthy volunteers and patients suffering from metabolic syndrome. MATERIAL AND METHODS: A sandwich ELISA method was developed for quantitative determination of human FGF-19 in serum samples. Blood pressure, waist circumference, FGF-21 serum levels, serum cholesterol, triacylglycerols, HDL-cholesterol, LDL-cholesterol, insulin, glucose, adiponectin, uric acid, creatinine, hs-CRP and calculated BMI and Quicki insulin sensitivity index were measured in 153 healthy volunteers and 66 persons with metabolic syndrome. RESULTS: Neither sex nor age influenced FGF-19 serum concentration in the healthy volunteers. Probands with metabolic syndrome had 65 % lower FGF-19 serum values than the healthy ones (medians 158.6 versus 242.4 ng/L; p<0.01). FGF-19 correlated with glucose (r = -0.35, p<0.01), HDL (r = 0.24, p = 0.045), triacylglycerols (r = -0.19, p = 0.05) and with a number of other risk factors for metabolic syndrome (r = -0.28, p = 0.01). When adjusted to the concentrations of triacylglycerols, BMI and glucose, and finally to all data pertinent to FGF-19 (according to correlation analysis), our data indicate that FGF-19 is an independent marker of metabolic syndrome. CONCLUSIONS: The present study demonstrates the analytical properties of the ELISA FGF-19 assay and its usefulness when studying the metabolic syndrome. Serum concentrations of FGF-19 could be new key predictors of metabolic syndrome and thereby even a new negative risk factor of atherosclerosis.

Lipocalin-2: development, analytical characterization, and clinical testing of a new ELISA.

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.

Proguanylin: development, analytical characterization, and clinical testing of a new ELISA.

The aim of our work was to develop an assay for the determination of proguanylin in human blood, and investigate its levels in healthy volunteers and donors suffer from hypertension often accompanied by body sodium accumulation and plasma volume expansion. We developed and evaluated the sandwich ELISA method for the quantitative determination of human proguanylin in serum samples. We conducted also the pilot study on individuals with hypertension and oh healthy probands and measured proguanylin serum levels, serum and urine sodium and creatinine levels. In the study on 256 healthy volunteers we demonstrated that women have significantly higher values of proguanylin than men (medians 12.7 vs. 9.6 ng/ml, p < 0.01) and proguanylin values increased with age of individuals (p < 0.01). Futhermore, we tested 17 individuals with hypertension and found that probands with anamnesi of hypertension had higher proguanylin values than healthy individuals from the first study (medians 16.2 vs. 11.3 ng/ml, p < 0.01). Both of groups did not differ in sex or age. Proguanylin values correlated with the systolic blood pressure (r = 0.41, p < 0.01), sodium fraction excretion (r = 0.72, p < 0.01) and serum sodium (r = -0.39, p < 0.01). No significant correlation we found with serum proguanylin and creatinine. In the group of 9 healthy probands we demonstrated the existence of a diurnal rhythm of proguanylin with its maximum in the evening hours (between 6-10 p.m.). The pilot study supports the hypothesis about the role of proguanylin in sodium metabolism and its possible importance for hypertension disorder. Further research is necessary to confirm our findings in individuals with hypertension with different medication in order to assess proguanylin value as a risk predictor of accelerated hypertension, and to classify individuals with hypertension for variuos types of diuretic therapy.