Fatty acid-binding proteins as plasma markers of tissue injury

Mortality risk assessment and the role of thrombolysis in pulmonary embolism

Acute venous thromboembolism remains a frequent disease, with an incidence ranging between 23 and 69 cases per 100,000 population per year. Of these patients, approximately one-third present with clinical symptoms of acute pulmonary embolism (PE) and two-thirds with deep venous thrombosis (DVT). Recent registries and cohort studies suggest that approximately 10% of all patients with acute PE die during the first 1 to 3 months after diagnosis. Overall, 1% of all patients admitted to hospitals die of acute PE, and 10% of all hospital deaths are PE-related. These facts emphasize the need to better implement our knowledge on the pathophysiology of the disease, recognize the determinants of death or major adverse events in the early phase of acute PE, and most importantly, identify those patients who necessitate prompt medical, surgical, or interventional treatment to restore the patency of the pulmonary vasculature.

Highly sensitive recombinant antibodies capable of reliably differentiating heart-type fatty acid binding protein from noncardiac isoforms

During recent times, heart-type fatty acid binding protein (hFABP) has gained increasing credence as a promising cardiac biomarker. This is largely due to its rapid myocardial release and subsequent clearance kinetics, which are superior to those of myoglobin and offer an earlier diagnostic window than the troponins. Realization of its full diagnostic and prognostic potential is dependent on accessibility to robust hFABP-specific assays. Here we describe a rational strategy for generation and screening of hFABP-specific avian-derived recombinant antibodies. These antibodies were confirmed to be exquisitely specific for hFABP, with no cross-reactivity observed in a representative panel of the most homologous non-heart-type FABP isoforms. All of the antibodies tested exhibited single-figure nanomolar affinities, and their analytical potential was demonstrated in a simple inhibition enzyme-linked immunosorbent assay (ELISA) format that returned an impressive limit of quantitation (LOQ) value of 1.9 ng/ml. The cumulative results underline the potential value of these antibodies as enabling reagents for use in a variety of immunodiagnostic configurations.

Automated heart-type fatty acid-binding protein assay for the early diagnosis of acute myocardial infarction

We compared an automated quantitative heart-type fatty acid-binding protein (H-FABP) assay with other cardiac-marker assays to examine its usefulness as an early diagnostic marker of acute myocardial infarction (AMI). Serum samples for cardiac troponin T (cTnT), creatine kinase-MB isozyme (CK-MB), myoglobin, and H-FABP were obtained from 64 patients with AMI and 53 patients with other conditions (control group). H-FABP was measured by using 2 immunoassays, the H-FABP enzyme-linked immunosorbent assay (ELISA; Biocheck, Foster City, CA) and the H-FABP latex turbidimetric immunoassay (LTIA; HBI, Anyang, Korea). Sensitivities of assays for cTnT, CK-MB, myoglobin, H-FABP (by ELISA), H-FABP (by LTIA), and electrocardiogram (ECG) for the diagnosis of AMI at hospital admission were 39.1%, 59.4%, 64.1%, 68.7%, 70.3%, and 54.7%, respectively. Specificities of cTnT, CK-MB, myoglobin, H-FABP (by ELISA), H-FABP (by LTIA), and ECG were 98.1%, 71.7%, 81.1%, 77.4%, 90.6%, and 92.5%, respectively. The automated H-FABP (by LTIA) is superior to cTnT, CK-MB, myoglobin, and H-FABP (by ELISA) tests for the diagnosis of AMI in patients admitted within 4 hours from the onset of chest pain.

Intestinal-FABP and liver-FABP: Novel markers for severe abdominal injury

OBJECTIVES

Fatty acid-binding proteins (FABPs) have relatively high tissue concentrations and low plasma concentrations and are released into the circulation following organ injury. We explored the utility of intestinal-(I)-FABP and liver-(L)-FABP for the diagnosis of abdominal injury in patients with multiple trauma.

METHODS

This prospective study included 102 trauma patients and 30 healthy volunteers. Plasma I-FABP and L-FABP levels were measured in the emergency department (ED) by enzyme-linked immunosorbent assay (ELISA). Forty-one patients suffered from serious or severe abdominal trauma (Abbreviated Injury Score [AIS] code "ai" for abdominal injury, AISai > or = 3) and nine were moderately abdominally injured (AISai < 3). Fifty-two had no abdominal injury.

RESULTS

Median I-FABP and L-FABP levels in the AISai > or = 3 group (516 pg/mL and 135 ng/mL, respectively) were significantly higher compared to the AISai < 3 group (154 pg/mL and 13 ng/mL, respectively) or those without abdominal injury (207 pg/mL and 21 ng/mL, respectively) or normal controls (108 pg/mL and 13 ng/mL, respectively). The cutoff to distinguish the ai > or = 3 is 359 pg/mL for I-FABP and 54 ng/mL for L-FABP, with 93% specificity and 75% sensitivity for I-FABP and 93% and 82% for L-FABP, respectively.

CONCLUSIONS

High I-FABP and L-FABP levels correlate with relevant severity of abdominal tissue damage in patients with multiple trauma. I-FABP and L-FABP could be useful as markers for the early detection of significant abdominal injury in acute multiple trauma and identify patients who require rapid intervention.

The intestinal fatty acid binding protein diagnosing gut dysfunction in acute pancreatitis: a pilot study

OBJECTIVES

To study the use of intestinal fatty acid binding protein (I-FABP) in diagnosing gut dysfunction in patients with acute pancreatitis (AP).

METHODS

Thirty-two patients with AP onset within 7 days were enrolled in our study. The severity of disease and the gut dysfunction were evaluated as follows: on admission, on the seventh day of disease attack, and on the third day after enteral nutrition. Serum levels of I-FABP, citrulline, and C-reactive protein (CRP) and the lactulose and mannitol absorption ratio in urine were measured in parallel.

RESULTS

The serum level of I-FABP increased on admission, and it was more pronounced in severe attacks. All patients had increased gut dysfunction score, serum level of CRP, and urine level of lactulose and mannitol absorption ratio with decreased serum level of citrulline. A positive correlation was found between the following pairs of measurement on admission: serum level of I-FABP and gut dysfunction score, serum level of I-FABP and Acute Physiology and Chronic Health Evaluation II score, I-FABP and serum level of CRP, and serum level of I-FABP and the length of ICU stay. A reverse correlation between the serum level of I-FABP and the serum level of citrulline was found.

CONCLUSIONS

The serum level of I-FABP can be used for assessing the gut dysfunction and disease severity of AP.

Urinary intestinal fatty acid-binding protein concentration predicts extent of disease in necrotizing enterocolitis

PURPOSE

Urinary intestinal fatty acid-binding protein (i-FABP), a marker of intestinal mucosal cell damage, has recently been proposed as a clinically useful measure in the early detection of necrotizing enterocolitis (NEC). However, there are no data on urinary i-FABP in more advanced (Bell stage II /III) NEC. The aim of this study was to test the use of urinary i-FABP in surgical NEC.

METHODS

Urine was collected every 24 hours from infants with Bell stage II/III NEC admitted to a surgical Neonatal Intensive Care Unit. Clinical, laboratory, and surgical data were collected concurrently. Urinary i-FABP was quantified by enzyme-linked immunosorbent assay and expressed as picograms per nanomole creatinine (median [range]). Results are presented as median (range) and compared by Mann-Whitney test and by linear regression.

RESULTS

There was a trend toward an increase in i-FABP:Cr in infants with NEC (controls, 1.0 [0.4-1.3], vs NEC, 2.1 [0.39-35.1], P = .055). Urinary i-FABP:Cr was significantly higher in infants with extensive disease (7.4 pg/mmol [2.1-35.0 pg/mmol]) than in those with focal disease (1.1 pg/mmol [0.3-1.7 pg/mmol]), P = .002. In addition, i-FABP:Cr was less than the previously suggested 2 pg/mmol cutoff in 6 of 16 infants with NEC, 5 of whom had focal disease. Urinary i-FABP:Cr decreased during both successful nonoperative management (P < .0001) and after surgery in the operated group.

CONCLUSIONS

In this pilot study, urinary i-FABP was associated with extensive disease in infants with NEC requiring surgery. Further work, in a larger number of patients, is required to investigate the applicability of urinary i-FABP as a marker of intestinal damage and as an adjunct to current indications for surgical intervention in infants with NEC.

Non-invasive assessment of barrier integrity and function of the human gut

Over the past decades evidence has been accumulating that intestinal barrier integrity loss plays a key role in the development and perpetuation of a variety of disease states including inflammatory bowel disease and celiac disease, and is a key player in the onset of sepsis and multiple organ failure in situations of intestinal hypoperfusion, including trauma and major surgery. Insight into gut barrier integrity and function loss is important to improve our knowledge on disease etiology and pathophysiology and contributes to early detection and/or secondary prevention of disease. A variety of tests have been developed to assess intestinal epithelial cell damage, intestinal tight junction status and consequences of intestinal barrier integrity loss, i.e. increased intestinal permeability. This review discusses currently available methods for evaluating loss of human intestinal barrier integrity and function.

Pathological and physiological hypertrophies are regulated by distinct gene programs

BACKGROUND

This study aims to investigate changes that occur during progression and establishment of physiological and pathological cardiac hypertrophy, by microarray technology and functional annotations.

DESIGN AND METHODS

Myocardial infarction leading to heart failure was induced in rats, with animals killed 1, 3, 7, 14, 42, and 92 days after coronary artery ligation. A second group was subjected to daily treadmill exercise and killed 1, 4, 24, and 48 h after a single exercise bout, or after 28 or 56 days of exercise training.

RESULTS

Physiological hypertrophy was associated with less transcriptional alternation than pathological hypertrophy, indicating that posttranscriptional and translational regulation may be more important. The main difference between the two types of hypertrophy was that myocardial infarction was associated with downregulation of genes related to fatty acid metabolism, whereas no such change occurred after exercise training. Thus, fatty acid metabolism may distinguish adverse maladaptive hypertrophy from beneficial adaptive hypertrophy.

CONCLUSION

This study points to specific genes and gene classes related to biological processes that may be important in these well-characterized rat models of physiological and pathological cardiac hypertrophy.

Point-of-care test of heart-type fatty acid-binding protein for the diagnosis of early acute myocardial infarction

AIM

To investigate the efficacies of point-of-care test of heart-type fatty-acid binding protein (H-FABP) and its combinations with the conventional biomarkers in the diagnosis of early acute myocardial infarction (AMI).

METHODS

227 patients suspected of AMI were consecutively recruited in two centers. Biomarkers including H-FABP, myoglobin (MYO), creatine kinase-myocardial band (CK-MB) and cardiac troponin T (cTnT) were determined simultaneously at admission. AMI was defined according to the universal definition of myocardial infarction. Chi-Square test was adopted for the analysis.

RESULTS

In patients presenting within 12 h of symptom onset, the sensitivity of H-FABP[93.0% (95% CI: 86.6%-96.9%)] was significantly higher than that of initial CK-MB [67.5% (95% CI: 58.1%-76.0%), P<0.0001], cTnT [69.3% (95%CI: 60.0%-77.6%), P<0.0001] and MYO [68.6% (95% CI: 54.1%-80.9%), P<0.05]. The negative predictive value of H-FABP [92.8% (95%CI: 86.3%-96.8%)] was significantly higher than that of initial CK-MB [74.7% (95% CI: 66.8%-81.5%), P<0.001] and cTnT [75.9% (95% CI: 68.1%-82.6%), P<0.001]. The sensitivity of H-FABP+cTnT combination [94.7% (95% CI: 88.9%-98.0%)] was significantly higher than that of admission cTnT [69.3% (95% CI: 60.0%-77.6%), P<0.0001], CK-MB+cTnT [75.4% (95% CI: 66.5%-83.0%), P<0.0001] and MYO+CK-MB+cTnT [74.5% (95% CI: 60.4%-85.7%), P<0.05]. The negative predictive value of H-FABP+cTnT [94.5% (95% CI: 88.4%-98.0%] was significantly higher than that of initial cTnT [75.9% (95% CI: 68.1%-82.6%), P<0.001] and CK-MB+cTnT [79.1% (95% CI: 71.2%-85.6%), P<0.001]. Subgroup analysis showed that the superiorities of both the sensitivities and the negative predictive values of H-FABP and H-FABP+cTnT combination occurred only in patients who presented within 6 h of the symptom onset.

CONCLUSION

Point-of-care test of H-FABP can be used as a valuable biomarker to detect or exclude an early-stage AMI. Combining H-FABP and cTnT provides the best performance for early AMI diagnosis.

Biomarkers in pulmonary arterial hypertension

Despite recent advances in medical treatment, pulmonary arterial hypertension (PAH) continues to be associated with high morbidity and mortality. While the diagnosis is established via a right heart catheterisation, current non-invasive measures of disease severity and response to treatment used in clinical practice are the 6-min walk distance and the World Health Organization functional class. Although both parameters correlate with disease severity and prognosis, they have significant limitations. A major shortcoming in assessing PAH is lack of standardised, non-invasive, objective parameters that function as biomarkers to help assess the severity and prognosis of disease and to follow patients' response to treatment. In this article, we will review current knowledge on potential biomarkers associated with diagnosis, prognosis and response to treatment of PAH. Most biomarkers are either being evaluated for potential use in clinical practice, or being used as research tools.

Clinical assessment of ischemia-modified albumin and heart fatty acid-binding protein in the early diagnosis of non-ST-elevation acute coronary syndrome in the emergency department

OBJECTIVES

Heart fatty acid-binding protein (h-FABP) and ischemia-modified albumin (IMA) have recently been evaluated, but to the best of our knowledge, no study has reported an analysis of these two markers for the detection of early myocardial infarction and myocardial ischemia in a large cohort of consecutive patients presenting to an emergency department (ED). This study evaluates the diagnostic accuracy and the clinical utility of h-FABP and IMA for non-ST-segment elevation acute coronary syndrome (ACS) diagnosis in the first hour of management in an ED.

METHODS

In a prospective 11-month study, 677 patients admitted to the ED with chest pain and suspected non-ST-segment elevation ACS were enrolled. On presentation, blood samples were obtained for the measurement of the biomarkers h-FABP (immunodetection with CardioDetect) and IMA (albumin cobalt-binding test). Two physicians, blinded to the results of the markers, independently categorized patients as having or not having non-ST-segment elevation ACS.

RESULTS

Of the 677 patients who were prospectively recruited, non-ST-segment elevation ACS was diagnosed in 185 (27.3%). While IMA was not predictive of the ACS diagnosis (odds ratio [OR] = 1.23; 95% CI = 0.87 to 1.81), h-FABP was predictive of ACS diagnosis (OR = 4.65; 95% CI = 2.39 to 9.04) with specificity at 96.8% (95% CI = 95.4% to 98.1%) and sensitivity at 13.5% (95% CI = 10.9% to 16.1%). However, h-FABP did not add significant additional information to a predictive model that included the usual diagnostic tools for non-ST-elevation ACS management (p = 0.40).

CONCLUSIONS

In this study on a large cohort of patients admitted to an ED for chest pain, IMA and h-FABP did not provide valuable information for ACS diagnosis.

Comparison of usefulness of heart-type fatty acid binding protein versus cardiac troponin T for diagnosis of acute myocardial infarction

We aimed to assess the additive diagnostic value of measuring the serum levels of soluble human heart-type fatty acid binding protein (H-FABP) in the early diagnosis of acute myocardial infarction (AMI) in unselected patients with chest pain. A total of 97 consecutive patients with acute ischemic-type chest pain were prospectively enrolled and classified according to the American Heart Association/American College of Cardiology guidelines. The test characteristics of H-FABP and cardiac troponin T serum levels at admission revealed a greater sensitivity of H-FABP in the first 4 hours of symptoms (86% vs 42%, p <0.05). Combining H-FABP and cardiac troponin T also improved the sensitivity in the detection of AMI (97% vs 71%, p <0.05) but demonstrated a greater misclassification rate (25% vs 9%, p <0.05). The specificity of H-FABP was poor (65%, 95% confidence interval 58% to 71%). Receiver operating characteristics revealed a poor performance of H-FABP in patients with non-ST-elevation myocardial infarction. Classification tree analysis demonstrated that an H-FABP-related improvement in the early definite rule-out of AMI (reduction of false-negative rate from 11% to 3%) was at the expense of an increase in the false-positive rate to 5%. In conclusion, measurement of H-FABP, in addition to cardiac troponin T, serum levels within the first 4 hours of symptoms improves the sensitivity and negative predictive value for the detection of AMI at the cost of test accuracy and precision, especially in patients with non-ST-elevation myocardial infarction.

Urinary biomarkers for the detection of renal injury

Despite the well-known limitations, currently the most widely used biomarkers for the early detection of chronic kidney disease or acute kidney injury are proteinuria, serum creatinine, and blood urea nitrogen. All of these are less than optimal and tend to focus attention on later stages of injury when therapies may be less effective. Recently, there has been a great surge of interest in identifying novel biomarkers that can be easily detected in the urine that can diagnose renal injury at the earliest stages. A variety of methods have been employed to identify these biomarkers including transcriptomics, proteomics, metabolomics, lipidomics, and gene arrays. Currently, several candidate biomarkers have been identified and studied in different renal injury states. These include kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, and fatty-acid binding proteins (FABPs). This review will highlight the current state of knowledge of these biomarkers as well as the limitation of these biomarkers in the early diagnosis of renal injury.

Serum heart type fatty acid binding protein levels in metabolic syndrome

Heart type fatty acid binding protein (H-FABP) is a major cytoplasmic low-molecular weight protein and released into the circulation when the myocardium is injured. Previous studies have demonstrated that H-FABP is closely associated with acute coronary syndrome, hypertrophic and dilated cardiomyopathy, heart failure, stroke, obstructive sleep apnea syndrome, pulmonary embolism. The aim of this study was to investigate serum H-FABP value in the patients with metabolic syndrome (MetS). We measured serum H-FABP levels in 55 consecutive patients with MetS, and 73 age-matched control subjects by using a sandwich enzyme-linked immunosorbent assay. Serum H-FABP levels were significantly higher in patients with MetS than in control subjects 18.37 ± 13.0 and 7.9 ± 6.5 ng/ml, respectively, (P < 0.001). Serum H-FABP levels were significantly higher in patients with diabetic MetS than in without diabetic MetS, 24.0 ± 10.2 and 13.9 ± 12.6 ng/ml, respectively, (P: 0,003). There were statistically significant differences between patients without diabetic MetS and control subjects, 13.8 ± 12.6 and 7.9 ± 6.5 ng/ml, respectively, (P = 0.023). Patients with MetS have an increased risk of death from cardiovascular diseases. H-FABP seems to be a marker that will enable the detection of cardiac injury in the early asymptomatic period in patients with MetS.

Urinary liver-type fatty acid-binding protein predicts adverse outcomes in acute kidney injury

Acute kidney injury (AKI) is a common condition with significant associated morbidity and mortality. The insensitivity and non-specificity of traditional markers of renal dysfunction prevent timely diagnosis, estimation of the severity of renal injury, and the administration of possible therapeutic agents. Here, we determine the prognostic ability of urinary liver-type fatty acid-binding protein (L-FABP), and further characterize its sensitivity and specificity as a biomarker of AKI. Initial western blot studies found increased urinary L-FABP in patients with confirmed AKI. A more extensive cross-sectional study found significant increases in urinary L-FABP, normalized to urinary creatinine, in 92 patients with established AKI compared with 62 patients without clinical evidence of AKI. In hospitalized patients, the diagnostic performance of urinary L-FABP for AKI, assessed by the area under the receiver operating characteristic curve, was 0.93. This compares favorably with other established biomarkers of AKI such as kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, N-acetyl-beta-glucosaminidase, and interleukin-18. Our study shows that age-adjusted urinary L-FABP levels were significantly higher in patients with poor outcome, defined as the requirement for renal replacement therapy or the composite end point of death or renal replacement therapy.

A systematic review of serologic tests in the diagnosis of necrotizing enterocolitis

BACKGROUND

Although many serologic markers have been suggested for diagnosis of necrotizing enterocolitis, there is little consensus on which of these is potentially clinically useful. Our aims were (i) to systematically review circulating markers that are potentially useful in the diagnosis of NEC and (ii) to compare the relative performance of each serologic marker of NEC by pooling estimates of marker accuracies and presenting their combined diagnostic accuracies.

METHODS

We undertook a systematic review of the literature to identify studies that reported serologic markers at the time of diagnosis of necrotizing enterocolitis. Where possible, we constructed 2-by-2 tables of diagnostic accuracy from each article, if 2 or more studies investigated the same test, their results were meta-analyzed by pooling estimates of sensitivity, specificity, likelihood ratio for positive index test (LR+), likelihood ratio for negative index test (LR-), diagnostic odds ratio, and their corresponding 95% confidence intervals.

RESULTS

Twenty-five articles provided information on serology at the time of diagnosis of necrotizing enterocolitis. Of these, it was possible to construct diagnostic accuracy tables from 16 articles and to combine data from studies that used C-reactive protein, intestinal fatty acid binding protein, and platelet-activating factor. Of these C-reactive protein was a sensitive but nonspecific marker for necrotizing enterocolitis, whereas platelet-activating factor and intestinal fatty acid binding protein were both sensitive and specific.

CONCLUSIONS

Most serologic markers of necrotizing enterocolitis have been used in too few studies to evaluate their use. Of those tests that have been tested repeatedly, platelet-activating factor and intestinal fatty acid binding protein are potentially useful, although their use must be further tested in larger prospective studies.

Neurochemical biomarkers in the differential diagnosis of movement disorders

In recent years, the neurochemical analysis of neuronal proteins in cerebrospinal fluid (CSF) has become increasingly accepted for the diagnosis of neurodegenerative dementia diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease. CSF surrounds the central nervous system, and in the composition of CSF proteins one finds brain-specific proteins that are prioritized from blood-derived proteins. Levels of specific CSF proteins could be very promising biomarkers for central nervous system diseases. We need the development of more easily accessible biomarkers, in the blood. In neurodegenerative diseases with and without dementia, studies on CSF and blood proteins have investigated the usefulness of biomarkers in differential diagnosis. The clinical diagnoses of Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration still rely mainly on clinical symptoms as defined by international classification criteria. In this article, we review CSF biomarkers in these movement disorders and discuss recent published reports on the neurochemical intra vitam diagnosis of neurodegenerative disorders (including recent CSF alpha-synuclein findings).

A pilot study on the noninvasive evaluation of intestinal damage in celiac disease using I-FABP and L-FABP

BACKGROUND AND GOALS

In the clinical management of celiac disease, new noninvasive tools for evaluation of intestinal damage are needed for diagnosis and for follow-up of diet effects. Fatty acid binding proteins (FABP) are potentially useful for this purpose as these are small cytosolic proteins present in enterocytes and sensitive markers for intestinal mucosal damage. First, the distribution and microscopic localization of FABP in the healthy human intestine was examined. Second, levels of circulating FABP were measured in patients with celiac disease before and after introducing a gluten-free diet (GFD) and in healthy controls.

STUDY

The distribution and microscopic localization of FABP in normal human intestinal tissue was assessed using surgical intestinal specimens of 39 patients. Circulating levels of intestinal (I)-FABP and liver (L)-FABP were determined in 26 healthy volunteers and 13 patients with biopsy proven celiac disease. Ten of these patients were reevaluated within 1 year after starting GFD.

RESULTS

I-FABP and L-FABP are predominantly present in the small intestine, mainly the jejunum. Moreover, FABP are expressed in cells on the upper part of the villi, the initial site of destruction in celiac disease. Circulating levels of FABP are significantly elevated in untreated patients with biopsy proven celiac disease compared with healthy controls (I-FABP: 784.7 pg/mL vs. 172.7 pg/mL, P<0.001; L-FABP: 48.4 ng/mL vs. 10.4 ng/mL, P<0.001). In response to GFD, these concentrations normalize.

CONCLUSIONS

Results of this pilot study strongly suggest that FABP can be used as a noninvasive method for assessment of intestinal damage in celiac disease. Besides an additional role in the diagnosis of celiac disease, FABP potentially enable noninvasive monitoring of the GFD effects.

Identification of cardiac myosin-binding protein C as a candidate biomarker of myocardial infarction by proteomics analysis

Acute myocardial infarction (AMI) is a common cause of death for which effective treatments are available provided that diagnosis is rapid. The current diagnostic gold standards are circulating cardiac troponins I and T. However, their slow release delays diagnosis, and their persistence limits their utility in the identification of reinfarction. The aim was to identify candidate biomarkers of AMI. Isolated mouse hearts were perfused with oxygenated protein-free buffer, and coronary effluent was collected after ischemia or during matched normoxic perfusion. Effluents were analyzed using proteomics approaches based on one- or two-dimensional initial separation. Of the 459 proteins identified after ischemia with one-dimensional separation, 320 were not detected in the control coronary effluent. Among these were all classic existing biomarkers of AMI. We also identified the cardiac isoform of myosin-binding protein C in its full-length form and as a 40-kDa degradation product. This protein was not detected in the other murine organs examined, increased markedly with even trivial myocardial infarction, and could be detected in the plasma after myocardial infarction in vivo, a profile compatible with a biomarker of AMI. Two-dimensional fluorescence DIGE of ischemic and control coronary effluents identified more than 200 asymmetric spots verified by swapping dyes. Once again existing biomarkers of injury were confirmed as well as posttranslational modifications of antioxidant proteins such as peroxiredoxins. Perfusing hearts with protein-free buffers provides a platform of graded ischemic injury that allows detailed analysis of protein release and identification of candidate cardiac biomarkers like myosin-binding protein C.

Prognostic value of combination of heart-type fatty acid-binding protein and ischemia-modified albumin in patients with acute coronary syndromes and normal troponin T values

Recent studies have suggested that heart-type fatty acid-binding protein (H-FABP) may detect ongoing myocardial damage involved in the progression of acute coronary syndromes (ACS). This study was prospectively designed to examine whether the combination of H-FABP, a marker for ongoing myocardial damage, and ischemia-modified albumin (IMA), a marker for myocardial ischemia, would effectively diagnose patients with ACS. H-FABP values above 1.5 microg/l can be correctly measured via an ELISA and 6 microg/l is the currently used cut-off value (1-3). We measured serum H-FABP and IMA of 108 patients on admission within 12 hr after onset of chest pain and normal troponin T. serum samples from ACS group (n=82) had decreased capacity of ACB [64 (61-67) U/ml] compared with non-ACS ischemic chest pain group (n=26) samples [75 (71-78) U/ml] (P<0.05). The combination of IMA and H-FABP usually had better sensitivity [96.3% (92.2-100%)] (P<0.05) and accuracy [92.6 (87.7-97.5%)] (P<0.05) than when individually used. Thus, the combination of H-FABP and IMA measurements after initiation of chest pain may be highly effective for risk stratification in patients with ACS and normal cardiac troponin T.

Brain-type and liver-type fatty acid-binding proteins: new tumor markers for renal cancer?

BACKGROUND

Renal cell carcinoma (RCC) is the most common renal neoplasm. Cancer tissue is often characterized by altered energy regulation. Fatty acid-binding proteins (FABP) are involved in the intracellular transport of fatty acids (FA). We examined the level of brain-type (B) and liver-type (L) FABP mRNA and the protein expression profiles of both FABPs in renal cell carcinoma.

METHODS

Paired tissue samples of cancerous and noncancerous kidney parts were investigated. Quantitative RT-PCR, immunohistochemistry and western blotting were used to determine B- and L-FABP in tumor and normal tissues. The tissue microarray (TMA) contained 272 clinico-pathologically characterized renal cell carcinomas of the clear cell, papillary and chromophobe subtype. SPSS 17.0 was used to apply crosstables (chi2-test), correlations and survival analyses.

RESULTS

B-FABP mRNA was significantly up-regulated in renal cell carcinoma. In normal tissue B-FABP mRNA was very low or often not detectable. RCC with a high tumor grading (G3 + G4) showed significantly lower B-FABP mRNA compared with those with a low grading (G1 + G2). Western blotting analysis detected B-FABP in 78% of the cases with a very strong band but in the corresponding normal tissue it was weak or not detectable. L-FABP showed an inverse relationship for mRNA quantification and western blotting. A strong B-FABP staining was present in 52% of the tumor tissues contained in the TMA. In normal renal tissue, L-FABP showed a moderate to strong immunoreactivity in proximal tubuli. L-FABP was expressed at lower rates compared with the normal tissues in 30.5% of all tumors. There was no correlation between patient survival times and the staining intensity of both FABPs.

CONCLUSION

While B-FABP is over expressed in renal cell carcinoma in comparison to normal renal tissues L-FABP appears to be reduced in tumor tissue. Although the expression behavior was not related to the survival outcome of the RCC patients, it can be assumed that these changes indicate fundamental alterations in the fatty metabolism in the RCC carcinogenesis. Further studies should identify the role of both FABPs in carcinogenesis, progression and with regard to a potential target in RCC.

Serum 99th centile values for two heart-type fatty acid binding protein assays

Background

We have previously demonstrated that heart-type fatty acid binding protein (H-FABP) is an independent prognostic marker for survival after acute coronary syndrome (ACS). This study aimed to define the 99th centile values for H-FABP as determined with two different assays, and to study the relationship with age, gender and renal function.

Methods

H-FABP was measured on redundant routine outpatient samples using the MARKIT-M (Dainippon) and the Evidence Investigator (Randox) assays.

Results

Two hundred and forty-two subjects with Siemens Ultra-TnI value <0.045 μg/L (99th centile) were studied. In all, 174 subjects had estimated glomerular filtration rate (eGFR) >60 mL/min. The 99th centile values for subjects with eGFR >60 mL/min for the Evidence Investigator H-FABP were 5.3 and 5.8 μg/L and for the MARKIT-M H-FABP were 8.3 and 9.1 μg/L in female and male subjects, respectively. There is an increase in H-FABP with age in subjects with normal renal function for both assays. Gender comparison showed no significant difference for either assay. Comparison of samples showed that subjects with eGFR <60 mL/min showed a median increase of 0.71 μg/L with Evidence Investigator assay and 1.09 μg/L with MARKIT-M assay compared with subjects with eGFR >60 mL/min. Calibration differences were confirmed by cross measurement of calibrators and recombinant H-FABP.

Conclusions

We have defined the 99th centile values for H-FABP in a population of primary and secondary care outpatients that can be used to risk stratify patients with ACS. We have confirmed that H-FABP increases with renal dysfunction and age, but have not confirmed the gender difference previously reported.

Qualification of cardiac troponin I concentration in mouse serum using isoproterenol and implementation in pharmacology studies to accelerate drug development

Cardiac troponin I is a useful biomarker of myocardial injury, but its use in mice and application to early drug discovery are not well described. The authors investigated the relationship between cTnI concentration in serum and histologic lesions in heart tissue from mice treated with isoproterenol (ISO). Cardiac TnI concentrations in serum increased in a dose-dependant manner and remained increased twenty-four to forty-eight hours after a single administration of isoproterenol. Increased cTnI concentration was of greater magnitude and longer duration than increased fatty acid binding protein 3 concentration, aspartate aminotransferase activity, and creatine kinase activity in serum. Isoproterenol-induced increases in cTnI concentrations were both greater and more sustained in BALB/c than in CD1 mice and correlated with incidence and severity of lesions observed in heart sections from both strains. In drug development studies in BALB/c mice with novel kinase inhibitors, cTnI concentration was a reliable stand-alone biomarker of cardiac injury and was used in combination with measurements of in vivo target inhibition to demonstrate an off-target contribution to cardiotoxicity. Additional attributes, including low cost and rapid turnaround time, made cTnI concentration in serum invaluable for detecting cardiotoxicity, exploring structure-activity relationships, and prioritizing development of compounds with improved safety profiles early in drug discovery.

Transient postprandial ischemia is associated with increased intestinal fatty acid binding protein in patients with chronic gastrointestinal ischemia

BACKGROUND

Chronic gastrointestinal ischemia (CGI) is still a difficult diagnosis to make. Currently, the only diagnostic with an acceptable sensitivity for actual mucosal ischemia is gastrointestinal tonometry. However, tonometry is a cumbersome and invasive diagnostic test. We are in need of a more simple, noninvasive test for diagnosing mucosal ischemia. A sensitive and early serum marker could be of great use in this setting. The aim of this study was to evaluate the use of promising serum markers for mucosal ischemia [intestinal fatty acid binding protein (I-FABP), D-lactate, and lipopolysaccharide] and compared findings with corresponding gastrointestinal tonometry measurements.

METHODS

Patients referred for evaluation of CGI were included. All patients had visualization of abdominal arteries and gastrointestinal tonometry. Before, during, and after tonometry blood samples were drawn for measurements of serum markers.

RESULTS

Forty-nine patients were eligible for evaluation. CGI was diagnosed in 24 (49%) patients. The baseline measurements showed a significant increase in I-FABP before exercise tonometry in the abnormal-response groups compared with the normal-response group, respectively, 0.45 and 1.3 microg/l (P=0.04). An abnormal response on meal tonometry was associated with increased I-FABP levels, 1, 2, and 4 h after tonometry, compared with the patients with a normal response, respectively, 1.26, 1.11, and 0.58 microg/l (P=0.048, 0.01, and 0.03). The measurements of D-lactate and lipopolysaccharide were undetectable, or low, at all different points of time.

CONCLUSION

Transient postprandial mucosal ischemia, as detected with gastrointestinal tonometry, is associated with increased I-FABP levels, indicating epithelial damage. Late markers for mucosal ischemia remained negative.

High-fat nutrition reduces hepatic damage following exposure to bacterial DNA and hemorrhagic shock

BACKGROUND/AIMS

Bacterial infection combined with hypotension results in exacerbation of the inflammatory response with release of interferon (IFN) gamma. This excessive inflammation may lead to development of hepatic damage and liver failure. This study investigates the effect of dietary lipids on release of IFN-gamma and development of hepatic damage following exposure to synthetic bacterial DNA (CpG-ODN) and hemorrhagic shock.

METHODS

Rats were exposed to CpG-ODN 18h before hemorrhagic shock. Samples were taken 4h following shock. High-fat nutrition was administered at 18h, 2h and 45min before induction of shock.

RESULTS

Enteral high-fat strongly reduced circulating IFN-gamma (0.2ng/ml, P<0.01) following exposure to CpG-ODN and hemorrhagic shock compared with fasted rats (2.7ng/ml). Concomitantly, plasma L-FABP was reduced (437+/-22ng/ml, P<0.01), and F-actin distribution was preserved. Furthermore, high-fat nutrition reduced apoptosis in the liver and preserved expression of the hepatoprotective protein ABIN-1. Interestingly, administration of anti-IFN-gamma antibodies was associated with reduced expression of ABIN-1.

CONCLUSIONS

This study shows that enteral high-fat reduces IFN-gamma and decreases CpG-enhanced liver injury following hemorrhagic shock. Administration of high-fat nutrition may be an important new therapeutic strategy to reduce liver damage in a clinical setting of bacterial infection combined with hypotension.

Serum levels of adipocyte fatty acid-binding protein (AFABP) are increased in chronic haemodialysis (CD)

OBJECTIVE

Adipocyte fatty acid-binding protein (AFABP) was recently introduced as an adipocyte-expressed factor, serum levels of which independently correlate with the development of the metabolic syndrome and cardiovascular disease in humans. In the current study, we investigated renal elimination of this protein by comparing circulating AFABP levels in patients on chronic haemodialysis (CD) with controls. We hypothesized that if renal filtration is a significant route of elimination of AFABP, it would accumulate in CD patients.

PATIENTS AND MEASUREMENTS

AFABP was determined by ELISA in control (n = 60) and CD (n = 60) patients and correlated to clinical and biochemical measures of renal function, glucose and lipid metabolism, as well as inflammation, in both groups.

RESULTS

Median serum AFABP levels were more than 10-fold higher in CD patients (510.9 +/- 294.7 microg/l) as compared to controls (44.3 +/- 35.2 microg/l). Furthermore, CD independently predicted AFABP concentrations in multiple regression analysis. In addition, body mass index and free fatty acids were independently associated with circulating AFABP.

CONCLUSIONS

Renal filtration appears as an important route of elimination of AFABP. Future studies should elucidate whether this adipocyte-expressed factor contributes to the increased risk of cardiovascular disease found in end-stage renal disease.

Serum adipocyte-fatty acid binding protein discriminates patients with permanent and temporary body weight loss

Adipocyte-fatty acid binding protein (A-FABP) is a biomarker of adiposity and metabolic syndrome. The aim of our work was to investigate the effect of weight reduction on serum A-FABP value. In the study, we analyzed a group of 189 probands suffering from obesity (102 women and 87 men; aged 57.3+/-12 years) initially, after a 3-month low-fat diet and once again 3 months after the termination of the diet for serum A-FABP, insulin, glucose, total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides. Basal biomarker concentrations were typical of the metabolic syndrome, and moreover A-FABP correlated with Quicki and BMI. We observed a reduction in BMI in 145 subjects who were divided into two subgroups: A-with persistent BMI reduction even after 6 months, B-with BMI reduction after 3 months and its regress after 6 months. Individuals with rise or no BMI difference were signed as subgroup C. In subgroup A, A-FABP level increased and returned to the earlier level (42.3 vs 68.3 vs 37.1 microg/l) and correlated with the markers of the metabolic syndrome. In subgroup B, A-FABP level increased less significantly, however elevated A-FABP level persisted for 6 months (41.9 vs 53.6 vs 50.7 microg/l). Subgroup C (n=54) showed no difference in A-FABP after 3-month diet and after next 3 months. The A-FABP value correlated with the some components of the metabolic syndrome. In conclusion, we describe that serum A-FABP might be a prognostic marker of body weight loss suggesting a preventive therapeutic intervention.

Rapid reversal of human intestinal ischemia-reperfusion induced damage by shedding of injured enterocytes and reepithelialisation

Background

Intestinal ischemia-reperfusion (IR) is a phenomenon related to physiological conditions (e.g. exercise, stress) and to pathophysiological events (e.g. acute mesenteric ischemia, aortic surgery). Although intestinal IR has been studied extensively in animals, results remain inconclusive and data on human intestinal IR are scarce. Therefore, an experimental harmless model for human intestinal IR was developed, enabling us to clarify the sequelae of human intestinal IR for the first time.

Methods and Findings

In 30 patients undergoing pancreatico-duodenectomy we took advantage of the fact that in this procedure a variable length of jejunum is removed. Isolated jejunum (5 cm) was subjected to 30 minutes ischemia followed by reperfusion. Intestinal Fatty Acid Binding Protein (I-FABP) arteriovenous concentration differences across the bowel segment were measured before and after ischemia to assess epithelial cell damage. Tissue sections were collected after ischemia and at 25, 60 and 120 minutes reperfusion and stained with H&E, and for I-FABP and the apoptosis marker M30. Bonferroni's test was used to compare I-FABP differences. Mean (SEM) arteriovenous concentration gradients of I-FABP across the jejunum revealed rapidly developing epithelial cell damage. I-FABP release significantly increased from 290 (46) pg/ml before ischemia towards 3,997 (554) pg/ml immediately after ischemia (p<0.001) and declined gradually to 1,143 (237) pg/ml within 1 hour reperfusion (p<0.001). Directly after ischemia the intestinal epithelial lining was microscopically normal, while subepithelial spaces appeared at the villus tip. However, after 25 minutes reperfusion, enterocyte M30 immunostaining was observed at the villus tip accompanied by shedding of mature enterocytes into the lumen and loss of I-FABP staining. Interestingly, within 60 minutes reperfusion the epithelial barrier resealed, while debris of apoptotic, shedded epithelial cells was observed in the lumen. At the same time, M30 immunoreactivity was absent in intact epithelial lining.

Conclusions

This is the first human study to clarify intestinal IR induced cell damage and repair and its direct consequences. It reveals a unique, endogenous clearing mechanism for injured enterocytes: rapid detachment of damaged apoptotic enterocytes into the lumen. This process is followed by repair of the epithelial continuity within an hour, resulting in a normal epithelial lining.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

Liver-type fatty acid-binding protein and lipid transport

Liver-type fatty acid-binding protein (L-FABP), a member of the genetically related cytosolic fatty acid binding protein (FABP) family, has both similar and different function and conformation compared with other family members. L-FABP, which is mainly found in liver and small intestine, participates in transporting fatty acids and combining a variety of hydrophobic group and is associated with many diseases. In recent years, the transfer mechanism of L-FABP was attracting great attention, and the research methods were developed from in vitro to in vivo, and from cell molecular level to gene ablation animals. Although a part of the mechanism has been revealed, the research should be continued to demonstrate it in deepth and resolve some new questions. This article aims to review the characteristics, conformation and in vivo study status of L-FABP.

Cardiac dysfunction and cell damage across clinical stages of severity in growth-restricted fetuses

OBJECTIVE

The purpose of this study was to assess cardiac function and cell damage in intrauterine growth-restricted (IUGR) fetuses across clinical Doppler stages of deterioration.

STUDY DESIGN

One hundred twenty appropriate-for-gestational-age and 81 IUGR fetuses were classified in stages 1/2/3 according umbilical artery present/absent/reversed end-diastolic blood flow, respectively. Cardiac function was assessed by modified-myocardial performance index, early-to-late diastolic filling ratios, cardiac output, and cord blood B-type natriuretic peptide; myocardial cell damage was assessed by heart fatty acid-binding protein, troponin-I, and high-sensitivity C-reactive protein.

RESULTS

Modified-myocardial performance index, blood B-type natriuretic peptide, and early-to-late diastolic filling ratios were increased in a stage-dependent manner in IUGR fetuses, compared with appropriate-for-gestational-age fetuses. Heart fatty acid-binding protein levels were higher in IUGR fetuses at stage 3, compared with control fetuses. Cardiac output, troponin-I, and high-sensitivity C-reactive protein did not increase in IUGR fetuses at any stage.

CONCLUSION

IUGR fetuses showed signs of cardiac dysfunction from early stages. Cardiac dysfunction deteriorates further with the progression of fetal compromise, together with the appearance of biochemical signs of cell damage.

A-FABP--a biomarker associated with the metabolic syndrome and/or an indicator of weight change?

OBJECTIVE

Adipocyte fatty acid-binding protein (A-FABP) is a plasma biomarker recently associated with the metabolic syndrome. The aim of these studies was to investigate changes of A-FABP during profound weight loss induced by laparoscopic adjustable gastric banding (LAGB).

METHODS AND PROCEDURES

In study one, 29 severely obese female subjects were examined before and 1 year after surgical treatment. A subgroup of 10 patients was investigated in 3-month intervals. Metabolic parameters were determined using standard methods, and A-FABP was detected using a commercially available enzyme-linked immunosorbent assay.

RESULTS

Mean weight loss after 1 year was 24.9 kg (P < 0.001), mainly due to a decrease in fat mass. Metabolic parameters improved substantially. However, serum A-FABP remained stable. In study two, a subgroup of 10 patients was examined quarterly to determine the time course of A-FABP changes. Quarterly measurements of serum A-FABP were significantly higher than baseline levels with the highest A-FABP value after the first 3 months, where patients had highest weight loss.

DISCUSSION

Our results in study one show that A-FABP serum levels are positively associated with body weight and fat mass. However, 1 year after pronounced weight loss A-FABP levels remained unchanged. In study two, time course analyses revealed maximum increase of serum A-FABP in parallel to highest weight loss, which allows to suppose that A-FABP is not only a biomarker of the metabolic syndrome in the steady state, but also a marker of weight changes in dynamic situations.

Fatty acid-binding proteins: role in metabolic diseases and potential as drug targets

Lipids are vital components of many biological processes and crucial in the pathogenesis of numerous common diseases, but the specific mechanisms coupling intracellular lipids to biological targets and signalling pathways are not well understood. This is particularly the case for cells burdened with high lipid storage, trafficking and signalling capacity such as adipocytes and macrophages. Here, we discuss the central role of lipid chaperones--the fatty acid-binding proteins (FABPs)--in lipid-mediated biological processes and systemic metabolic homeostasis through the regulation of diverse lipid signals, and highlight their therapeutic significance. Pharmacological agents that modify FABP function may provide tissue-specific or cell-type-specific control of lipid signalling pathways, inflammatory responses and metabolic regulation, potentially providing a new class of drugs for diseases such as obesity, diabetes and atherosclerosis.

Heart-type Fatty acid-binding protein in Acute Myocardial infarction Evaluation (FAME): background and design of a diagnostic study in primary care

BACKGROUND

Currently used biomarkers for cardiac ischemia are elevated in blood plasma after a delay of several hours and therefore unable to detect acute coronary syndrome (ACS) in a very early stage. General practitioners (GPs), however, are often confronted with patients suspected of ACS within hours after onset of complaints. This ongoing study aims to evaluate the added diagnostic value beyond clinical assessment for a rapid bedside test for heart-type fatty-acid binding protein (H-FABP), a biomarker that is detectable as soon as one hour after onset of ischemia.

METHODS

Participating GPs perform a blinded H-FABP rapid bedside test (Cardiodetect) in patients with symptoms suggestive of ACS such as chest pain or discomfort at rest. All patients, whether referred to hospital or not, undergo electrocardiography (ECG) and venapunction for a plasma troponin test within 12-36 hours after onset of complaints. A final diagnosis will be established by an expert panel consisting of two cardiologists and one general practitioner (blinded to the H-FABP test result), using all available patient information, also including signs and symptoms. The added diagnostic value of the H-FABP test beyond history taking and physical examination will be determined with receiver operating characteristic curves derived from multivariate regression analysis.

CONCLUSION

Reasons for presenting the design of our study include the prevention of publication bias and unacknowledged alterations in the study aim, design or data-analysis. To our knowledge this study is the first to assess the diagnostic value of H-FABP outside a hospital-setting. Several previous hospital-based studies showed the potential value of H-FABP in diagnosing ACS. Up to now however it is unclear whether these results are equally promising when the test is used in primary care. The first results are expected in the end of 2008.

Fabp3 as a biomarker of skeletal muscle toxicity in the rat: comparison with conventional biomarkers

Fatty acid binding protein 3 (Fabp3) has been used as a serological biomarker of cardiac injury, but its utility as a preclinical biomarker of injury to skeletal muscle is not well described. Fabp3 concentrations were determined for tissues from Sprague-Dawley rats and found to occur at highest concentrations in cardiac muscle and in skeletal muscles containing an abundance of type I fibers, such as the soleus muscle. Soleus is also a primary site of skeletal muscle (SKM) injury caused by lipid-lowering peroxisome proliferator-activated receptor alpha (PPAR-alpha) agonists. In rats administered repeat doses of a PPAR-alpha agonist, the kinetics and amplitude of plasma concentrations of Fabp3 were consistent with plasma compound concentrations and histopathology findings of swollen, hyalinized, and fragmented muscle fibers with macrophage infiltration. Immunohistochemical detection of Fabp3 revealed focal depletion of Fabp3 protein from injured SKM fibers which is consistent with increased serum Fabp3 concentrations in treated rats. We then assessed the predictivity of serological Fabp3 for SKM necrosis in short duration toxicology studies. Rats were treated with various doses of 27 different compounds, and the predictivity of serological biomarkers was assessed relative to histology in individual rats and in treatment groups. Under these study conditions, Fabp3 was the most useful individual biomarker based on concordance, sensitivity, positive and negative predictive values, and false negative rate. In addition, the combination of Fabp3 and aspartate aminotransferase (AST) had greater diagnostic value than the conventional combination of creatine kinase-MM isoenzyme (CK) and AST.