Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) is expressed in not only adipocytes and macrophages but also peritubular capillaries in the normal kidney. We recently demonstrated that ectopic expression of FABP4, but not FABP1 known as liver FABP (L-FABP), in the glomerulus is associated with progression of proteinuria and renal dysfunction. However, urinary excretion of FABP4 has not been investigated.
Subjects who participated in the Tanno-Sobetsu Study, a study with a population-based cohort design, in 2011 (n = 392, male/female: 166/226) were enrolled. Urinary FABP4 (U-FABP4) and urinary albumin-to-creatinine ratio (UACR) were measured. Change in estimated glomerular filtration rate (eGFR) was followed up one year later.
In 93 (23.7%) of the 392 subjects, U-FABP4 level was below the sensitivity of the assay. Subjects with undetectable U-FABP4 were younger and had lower UACR and higher eGFR levels than subjects with measurable U-FABP4. U-FABP4 level was positively correlated with age, systolic blood pressure and levels of serum FABP4 (S-FABP4), triglycerides, hemoglobin A1c (HbA1c), urinary FABP1 (U-FABP1) and UACR (r = 0.360, p<0.001). Age, S-FABP4, U-FABP1 and UACR were independent predictors of U-FABP4. On the other hand, systolic blood pressure, HbA1c and U-FABP4 were independently correlated with UACR. Reduction in eGFR after one year was significantly larger in a group with the highest tertile of baseline U-FABP4 than a group with the lowest tertile.
Citation: Okazaki Y, Furuhashi M, Tanaka M, Mita T, Fuseya T, Ishimura S, et al. (2014) Urinary Excretion of Fatty Acid-Binding Protein 4 is Associated with Albuminuria and Renal Dysfunction. PLoS ONE 9(12): e115429. https://doi.org/10.1371/journal.pone.0115429
Editor: Ines Armando, Universtiy of Maryland School of Medicine, United States of America
Received: September 17, 2014; Accepted: November 23, 2014; Published: December 15, 2014
Copyright: © 2014 Okazaki et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper.
Funding: M.F. has been supported by grants from JSPS KAKENHI, Takeda Science Foundation, Ono Medical Research Foundation, Akiyama Life Science Foundation, Suhara Memorial Foundation, Takeda Medical Research Foundation, and Japan Diabetes Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Fatty acid-binding proteins (FABPs) are proteins of about 14–15 kDa in size that can reversibly bind to hydrophobic ligands, such as long chain fatty acids, with high affinity and coordinate lipid responses in cells , . FABPs have been proposed to facilitate the transport of lipids to specific compartments in the cell. Among FABPs, FABP1, known as liver FABP (L-FABP), is expressed in proximal tubular epithelial cells in the kidney . It has been reported that urinary FABP1 reflects damage of proximal tubular epithelial cells ,  and predicts progression of renal dysfunction , .
FABP4, also known as adipocyte FABP (A-FABP) or aP2, is expressed in both adipocytes and macrophages and plays important roles in the development of insulin resistance and atherosclerosis –. It has been shown that a small-molecule specific FABP4 inhibitor would be a novel strategy to prevent and treat type 2 diabetes mellitus and atherosclerosis . Recent studies also showed that FABP4 is one of the novel adipocyte-derived bioactive molecules referred to as adipokines  and that elevated circulating FABP4 level is associated with obesity, insulin resistance, hypertension, cardiac dysfunction and atherosclerosis –.
Other than adipocytes and macrophages, it has been reported that FABP4 is expressed in endothelial cells of capillaries and small veins, but not arteries, in several mouse and human tissues including the heart and kidney , . Recently, we demonstrated that ectopic FABP4 expression in the glomerulus is associated with progression of proteinuria and renal dysfunction . However, significance of urinary excretion of FABP4 has not been elucidated. We here investigated the association between urinary excretion of FABP4 and renal function in the Tanno-Sobetsu study, a prospective cohort study.
The Tanno-Sobetsu Study is a study with a population-based cohort design recruiting residents of two rural towns, Tanno and Sobetsu, in Hokkaido and includes voluntarily annual health examination and follow-up survey. Of subjects who participated in the Tanno-Sobetsu Study, a total of 392 subjects (male/female: 166/226) in Sobetsu Town were enrolled for the present analyses in 2011. This study conformed to the principles outlined in the Declaration of Helsinki and was performed with the approval of the ethical committee of Sapporo Medical University. Written informed consent was received from all of the subjects.
Medical check-ups were performed between 06:00 h and 09:00 h after an overnight fast. After measuring anthropometric parameters, blood pressure was measured twice consecutively on the upper arm using an automated sphygmomanometer (HEM-907, Omron Co., Kyoto, Japan) with subjects in a seated resting position, and average blood pressure was used for analysis. Body mass index (BMI) was calculated as body weight (in kilograms) divided by the square of body height (in meters). Peripheral venous blood and urine samples were obtained from study subjects after physical examination. The serum, plasma and urine samples were analyzed immediately or stored at −80°C until biochemical analyses.
Concentrations of FABP4 in serum (S-FABP4) and urine (U-FABP4) and FABP1 in urine (U-FABP1) were measured using commercially available enzyme-linked immunosorbent assay kits of FABP4 (Biovendor R&D, Modrice, Czech Republic) and FABP1 (CIMIC Co., Tokyo, Japan). The accuracy, precision and reproducibility of the kits have been described previously , . Levels of U-FABP4 and U-FABP1 were normalized by urine creatinine level (µg/gCr).
Fasting plasma insulin was measured by a radioimmunoassay method. Creatinine (Cr) and lipid profiles, including total cholesterol, high-density lipoprotein (HDL) cholesterol and triglycerides, were determined by enzymatic methods. Low-density lipoprotein (LDL) cholesterol level was calculated by the Friedewald equation. Hemoglobin A1c (HbA1c) was determined by a latex coagulation method and was expressed in national glycohemoglobin standardization program (NGSP) scale. High-sensitivity C-reactive protein (hsCRP) was measured by a nephelometry method. HOMA-R, an indicator of insulin resistance, was calculated by the previously reported formula: insulin (µU/ml) × glucose (mg/dl)/405. Urinary albumin-to-creatinine ratio (UACR; mg/gCr) was used as a marker of microalbuminuria. Estimated glomerular filtration rate (eGFR) was calculated by an equation for Japanese : eGFR (mL/min/1.73 m2) = 194×Cr(−1.094)×age(−0.287) ×0.739 (if female). For assessing yearly decline of eGFR, change in eGFR was calculated: eGFR in 2012 – eGFR in 2011.
Numeric variables are expressed as means ±SD or medians (interquartile ranges). The distribution of each parameter was tested for its normality using the Shapiro-Wilk W test, and non-normally distributed parameters were logarithmically transformed. Differences in parameters between two groups were tested by the unpaired t test. The correlation between two variables was evaluated using Pearson's correlation coefficient. One-way analysis of variance and Tukey-Kramer post hoc test were used for detecting significant differences in data among three groups. Multiple linear regression analysis was performed to identify independent determinants of U-FABP4, UACR and change in eGFR. A p value of less than 0.05 was considered statistically significant.
Characteristics of the study subjects
Basal characteristics of the study subjects are shown in Table 1. Female subjects had significantly smaller waist circumference, lower levels of glucose and Cr and higher levels of total cholesterol, HDL cholesterol, LDL cholesterol and S-FABP4 than did male subjects. The underlying diseases were hypertension (n = 206, 52.6%), diabetes mellitus (n = 49, 12.5%), dyslipidemia (n = 92, 23.5%), ischemic heart disease (n = 19, 4.8%) and stroke (n = 8, 2.0%). Of the 392 subjects, 123 (31.4%) were not on any medication.
Association of urinary FABP4 level with clinical characteristics
In 93 (23.7%) of the 392 subjects (male/female: 50/43), U-FABP4 level was below the sensitivity of the assay (i.e., <0.1 ng/ml). In the other 299 subjects, U-FABP4 could be determined and its level normalized by urinary Cr ranged from 0.01 to 38.6 µg/gCr. As shown in Table 2, subjects with undetectable levels of U-FABP4 were younger and had lower levels of triglycerides, S-FABP4, UACR and U-FABP1 and higher level of eGFR than subjects with measurable U-FABP4.
The level of U-FABP4 was significantly correlated with S-FABP4 (r = 0.280, p<0.001) (Table 3). In contrast to S-FABP4, which was significantly correlated with BMI (r = 0.480, p<0.001) and waist circumference (r = 0.402, p<0.001), U-FABP4 was not correlated with BMI or waist circumference. U-FABP4 was negatively correlated with insulin level (r = −0.115, p = 0.04) and positively correlated with age (r = 0.255, p<0.001), systolic blood pressure (r = 0.189, p = 0.001) and levels of triglycerides (r = 0.115, p = 0.04), HbA1c (r = 0.124, p = 0.03), UACR (r = 0.360, p<0.001; Fig. 1) and U-FABP1 (r = 0.534, p<0.001) (Table 3). Stepwise regression analysis using the correlated parameters revealed that age, S-FABP4, UACR and U-FABP1 were independent predictors of U-FABP4 (Table 3). A subsequent multiple regression analysis showed that age, S-FABP4, UACR and U-FABP1 were independently correlated with U-FABP4, explaining 40.2% of the variance in this measure (R2 = 0.402) (Table 3).
Logarithmically transformed urinary albumin-to-creatinine ratio (UACR) was plotted against logarithmically transformed urinary FABP4 (U-FABP4) for each subject with detectable U-FABP4 level (n = 299). There was a significant correlation between the two parameters (r = 0.360, p<0.001).
UACR was negatively correlated with eGFR and positively correlated with age, systolic blood pressure, diastolic blood pressure and levels of triglycerides, glucose, HbA1c, blood urea nitrogen, S-FABP4 (r = 0.244, p<0.001), U-FABP1 (r = 0.254, p<0.001) and U-FABP4 (r = 0.360, p<0.001; Fig. 1) (Table 4). In stepwise regression analysis using the correlated parameters, age, systolic blood pressure, HbA1c and U-FABP4 were selected as independent predictors of UACR, and a subsequent multiple regression analysis showed that systolic blood pressure, HbA1c and U-FABP4 were independently correlated with UACR, explaining a total of 21.2% of the variance in this measure (R2 = 0.212) (Table 4). Furthermore, U-FABP4 was an independent predictor for UACR after adjustment of age, gender, systolic blood pressure, HbA1c, eGFR, S-FABP4 and U-FABP1.
Of the 392 study subjects, 325 subjects received follow up re-examination one year later (i.e., in 2012). The re-examined subjects were divided according to tertile of U-FABP4 or U-FABP1 at baseline: low (1st tertile, T1), middle (2nd tertile, T2) and high (3rd tertile, T3) U-FABP groups. Of note, the subjects with undetectable U-FABP4 were assigned as low (T1) U-FABP4 group. As shown in Fig. 2A, reduction in eGFR was significantly larger in the high-U-FABP4 group than in the low-U-FABP4 group. Similarly, the high-U-FABP1 group showed larger reduction in eGFR than did the low- and middle-U-FABP1 groups (Fig. 2B).
A, B. Of the 392 recruited subjects, 325 subjects could be followed up in 2012, and change in eGFR from 2011 to 2012 (mL/min/1.73 m2/year) shown by box plots was compared among three groups divided by tertiles of urinary FABP4 (U-FABP4) (A) and urinary FABP1 (U-FABP1) (B). Tertile of U-FABP4 consists of low (T1<0.04 µg/gCr, n = 108), middle (0.04≤T2<0.30 µg/gCr, n = 108), and high (T3≥0.30 µg/gCr, n = 109) groups. Tertile of U-FABP1 consists of low (T1<4.27 µg/gCr, n = 108), middle (4.27≤T2<7.15 µg/gCr, n = 108), and high (T3≥7.15 µg/gCr, n = 109) groups. *P<0.05, **P<0.001.
Change in eGFR was negatively correlated with baseline UACR (r = −0.154, p = 0.005), eGFR (r = −0.323, p<0.001), U-FABP1 (r = −0.140, p = 0.029) and U-FABP4 (r = −0.140, p = 0.011) but was not correlated with S-FABP4 (r = 0.024, p = 0.655). Multiple regression analysis showed that U-FABP4 was an independent predictor for change in eGFR after adjustment of age, gender and baseline eGFR. However, U-FABP4 was not selected as an independent determinant of change in eGFR when UACR or U-FABP1 was additionally incorporated into the adjustment.
This is the first report regarding significance of urinary FABP4 level in a general population. In normal kidneys, FABP4 is expressed in endothelial cells of the tubulointerstitial peritubular capillary (PTC) and vein in both the cortex and medulla, but not in glomerular or arterial endothelial cells, under a normal physiological condition . Interestingly, FABP4 was markedly and ectopically up-regulated in endothelial cells regenerating after endothelial balloon denudation in the pig coronary artery . We recently demonstrated that FABP4 was remarkably expressed in the glomerulus in patients with strong inflammatory disorders of capillaries . Furthermore, the level of FABP4 expression in the glomerulus was significantly higher in patients with endothelial proliferative lesions than in those without the lesions in IgA nephropathy. These findings indicate that ectopic expression of FABP4 in glomerular endothelial cells is associated with local inflammation in the glomerulus. In the previous study , we also demonstrated the association between increased glomerular FABP4 area, which was expressed in glomerular endothelial cells and macrophages, and decline in eGFR. Furthermore, the present study showed an association of high level of U-FABP4 with larger decline in eGFR (Fig. 2A). Taken together, U-FABP4 could be a novel biomarker of glomerular damage.
FABP4 is thought to be a non-secretory protein since it lacks typical signal peptides , . However, recent studies have shown that FABP4 is released from adipocytes , ,  and that serum concentration of FABP4 is associated with obesity, insulin resistance, diabetes, hypertension, cardiac dysfunction, atherosclerosis and inflammatory markers –, . We and others showed that elevation of serum FABP4 was a novel predictor of cardiovascular prognosis –. Furthermore, a recent study revealed that FABP4 secreted from adipocytes controlled hepatic glucose production, leading to insulin resistance as an adipokine both in vivo and in vitro . In addition, there is the possibility that circulating FABP4 has untoward effects on the vascular endothelium since a recent study showed that exogenous FABP4 inhibited endothelial nitric oxide synthase (eNOS) expression and its activation in human umbilical vascular endothelial cells . In the present study, U-FABP4 was weakly correlated with S-FABP4 but not with BMI or waist circumference, while S-FABP was significantly correlated with BMI and waist circumference, suggesting that main source of U-FABP4 is derived from ectopic expression of glomerular FABP4 rather than increased adiposity and that locally increased FABP4 in the glomerulus affects renal dysfunction.
It has been reported that FABP4 expression is not detected in podocytes , . An understanding of the role of podocytes as a glomerular filtration barrier has been advanced in the past decade . However, the importance of glomerular endothelial cells in the pathogenesis of proteinuria has received attention recently , . Loss of the glycocalyx in glomerular endothelial cells was shown to promote passage of albumin across the glomerular filtration barrier , . Glomerular endothelial cell damage preceded podocyte injury in different types of renal injuries and decreased eNOS , , . Interestingly, a study  showed that FABP4 expression decreased phosphorylation of eNOS and NO production in microvascular endothelial cells, contributing to endothelial dysfunction. Thus, there is the possibility that glomerular FABP4, which is up-regulated by endothelial damage, compromises NO production, leading to a vicious cycle of glomerular injury and increase in protein permeability.
It has been reported that U-FABP1 reflects damage of proximal tubular epithelial cells ,  and predicts progression of renal dysfunction , . Significance of U-FABP1 and U-FABP4 would be different, since it has been suggested that U-FABP4 reflects damage of glomerular damage . In the present study, U-FABP4 was positively correlated with U-FABP1 (r = 0.534, p<0.001) (Table 3). Although UACR was positively correlated with U-FABP4 and U-FABP1 (Table 4), only U-FABP4, but not U-FABP1, was selected as an independent predictor of UACR in a stepwise regression analysis (Table 4), suggesting that U-FABP4 is potentially more sensitive predictor of albuminuria, especially in a population-based cohort.
There are some limitations of this study. First, it is not possible to critically address the causal relationship between U-FABP4 and renal dysfunction since we did not perform intervention for reducing glomerular FABP4. Second, U-FAPB4 was not measurable in nearly one-fourth of the subjects. Thus, the relationship between U-FAPB4 and albuminuria might not be generalized to the overall population. This issue needs to be re-examined if sensitivity of U-FABP4 assay is improved. In addition, some of subjects in the present study might have several drugs, including angiotensin II receptor blockers ,  and statin , which have been reported to affect circulating FABP4 concentrations. Therefore, such drugs might modulate urinary excretion of FABP4. Lastly, since all study subjects were Japanese, whether the present findings can be generalized to other ethnicities remains unclear.
In conclusion, urinary FABP4 level is independently correlated with level of albuminuria and possibly predicts yearly decline of eGFR. U-FABP4 would be a novel biomarker of glomerular damage.
Conceived and designed the experiments: MF MT KS. Performed the experiments: YO MF MT T. Mita TF SI YW KH. Analyzed the data: YO MF SI HA HO HY SS. Wrote the paper: MF MT T. Miura.
- 1. Furuhashi M, Hotamisligil GS (2008) Fatty acid-binding proteins: role in metabolic diseases and potential as drug targets. Nat Rev Drug Discov 7:489–503.
- 2. Furuhashi M, Ishimura S, Ota H, Miura T (2011) Lipid chaperones and metabolic inflammation. Int J Inflam 2011:642612.
- 3. Maatman RG, van de Westerlo EM, van Kuppevelt TH, Veerkamp JH (1992) Molecular identification of the liver- and the heart-type fatty acid-binding proteins in human and rat kidney. Use of the reverse transcriptase polymerase chain reaction. Biochem J 288 (Pt 1):285–290.
- 4. Kamijo-Ikemori A, Sugaya T, Kimura K (2006) Urinary fatty acid binding protein in renal disease. Clin Chim Acta 374:1–7.
- 5. Noiri E, Doi K, Negishi K, Tanaka T, Hamasaki Y, et al. (2009) Urinary fatty acid-binding protein 1: an early predictive biomarker of kidney injury. Am J Physiol Renal Physiol 296:F669–679.
- 6. Araki S, Haneda M, Koya D, Sugaya T, Isshiki K, et al. (2013) Predictive effects of urinary liver-type fatty acid-binding protein for deteriorating renal function and incidence of cardiovascular disease in type 2 diabetic patients without advanced nephropathy. Diabetes Care 36:1248–1253.
- 7. Mou S, Wang Q, Li J, Shi B, Ni Z (2012) Urinary excretion of liver-type fatty acid-binding protein as a marker of progressive kidney function deterioration in patients with chronic glomerulonephritis. Clin Chim Acta 413:187–191.
- 8. Hotamisligil GS, Johnson RS, Distel RJ, Ellis R, Papaioannou VE, et al. (1996) Uncoupling of obesity from insulin resistance through a targeted mutation in aP2, the adipocyte fatty acid binding protein. Science 274:1377–1379.
- 9. Makowski L, Boord JB, Maeda K, Babaev VR, Uysal KT, et al. (2001) Lack of macrophage fatty-acid-binding protein aP2 protects mice deficient in apolipoprotein E against atherosclerosis. Nat Med 7:699–705.
- 10. Maeda K, Cao H, Kono K, Gorgun CZ, Furuhashi M, et al. (2005) Adipocyte/macrophage fatty acid binding proteins control integrated metabolic responses in obesity and diabetes. Cell Metab 1:107–119.
- 11. Furuhashi M, Fucho R, Gorgun CZ, Tuncman G, Cao H, et al. (2008) Adipocyte/macrophage fatty acid-binding proteins contribute to metabolic deterioration through actions in both macrophages and adipocytes in mice. J Clin Invest 118:2640–2650.
- 12. Furuhashi M, Tuncman G, Gorgun CZ, Makowski L, Atsumi G, et al. (2007) Treatment of diabetes and atherosclerosis by inhibiting fatty-acid-binding protein aP2. Nature 447:959–965.
- 13. Cao H, Sekiya M, Ertunc ME, Burak MF, Mayers JR, et al. (2013) Adipocyte lipid chaperone AP2 is a secreted adipokine regulating hepatic glucose production. Cell Metab 17:768–778.
- 14. Xu A, Wang Y, Xu JY, Stejskal D, Tam S, et al. (2006) Adipocyte fatty acid-binding protein is a plasma biomarker closely associated with obesity and metabolic syndrome. Clin Chem 52:405–413.
- 15. Xu A, Tso AW, Cheung BM, Wang Y, Wat NM, et al. (2007) Circulating adipocyte-fatty acid binding protein levels predict the development of the metabolic syndrome: a 5-year prospective study. Circulation 115:1537–1543.
- 16. Tso AW, Xu A, Sham PC, Wat NM, Wang Y, et al. (2007) Serum adipocyte fatty acid binding protein as a new biomarker predicting the development of type 2 diabetes: a 10-year prospective study in a Chinese cohort. Diabetes Care 30:2667–2672.
- 17. Yeung DC, Xu A, Cheung CW, Wat NM, Yau MH, et al. (2007) Serum adipocyte fatty acid-binding protein levels were independently associated with carotid atherosclerosis. Arterioscler Thromb Vasc Biol 27:1796–1802.
- 18. Ota H, Furuhashi M, Ishimura S, Koyama M, Okazaki Y, et al. (2012) Elevation of fatty acid-binding protein 4 is predisposed by family history of hypertension and contributes to blood pressure elevation. Am J Hypertens 25:1124–1130.
- 19. Ishimura S, Furuhashi M, Watanabe Y, Hoshina K, Fuseya T, et al. (2013) Circulating levels of fatty acid-binding protein family and metabolic phenotype in the general population. PLoS ONE 8:e81318.
- 20. Fuseya T, Furuhashi M, Yuda S, Muranaka A, Kawamukai M, et al. (2014) Elevation of circulating fatty acid-binding protein 4 is independently associated with left ventricular diastolic dysfunction in a general population. Cardiovasc Diabetol 13:126.
- 21. Elmasri H, Karaaslan C, Teper Y, Ghelfi E, Weng M, et al. (2009) Fatty acid binding protein 4 is a target of VEGF and a regulator of cell proliferation in endothelial cells. FASEB J 23:3865–3873.
- 22. Iso T, Maeda K, Hanaoka H, Suga T, Goto K, et al. (2013) Capillary endothelial fatty acid binding proteins 4 and 5 play a critical role in fatty acid uptake in heart and skeletal muscle. Arterioscler Thromb Vasc Biol 33:2549–2557.
- 23. Tanaka M, Furuhashi M, Okazaki Y, Mita T, Fuseya T, et al. (2014) Ectopic expression of fatty acid-binding protein 4 in the glomerulus is associated with proteinuria and renal dysfunction. Nephron Clin Paract [doi: ]10.1159/000368412]. (in press).
- 24. Kamijo A, Kimura K, Sugaya T, Yamanouchi M, Hikawa A, et al. (2004) Urinary fatty acid-binding protein as a new clinical marker of the progression of chronic renal disease. J Lab Clin Med 143:23–30.
- 25. Matsuo S, Imai E, Horio M, Yasuda Y, Tomita K, et al. (2009) Revised equations for estimated GFR from serum creatinine in Japan. Am J Kidney Dis 53:982–992.
- 26. Lee MY, Tse HF, Siu CW, Zhu SG, Man RY, et al. (2007) Genomic changes in regenerated porcine coronary arterial endothelial cells. Arterioscler Thromb Vasc Biol 27:2443–2449.
- 27. Mita T, Furuhashi M, Hiramitsu S, Ishii J, Hoshina K, et al. (2014) FABP4 is secreted from adipocytes by adenyl cyclase-PKA- and guanylyl cyclase-PKG-dependent lipolytic mechanisms. Obesity [doi: ]10.1002/oby.20954]. (in press).
- 28. Terra X, Quintero Y, Auguet T, Porras JA, Hernandez M, et al. (2011) FABP 4 is associated with inflammatory markers and metabolic syndrome in morbidly obese women. Eur J Endocrinol 164:539–547.
- 29. Furuhashi M, Ishimura S, Ota H, Hayashi M, Nishitani T, et al. (2011) Serum fatty acid-binding protein 4 is a predictor of cardiovascular events in end-stage renal disease. PLoS ONE 6:e27356.
- 30. von Eynatten M, Breitling LP, Roos M, Baumann M, Rothenbacher D, et al. (2012) Circulating adipocyte fatty acid-binding protein levels and cardiovascular morbidity and mortality in patients with coronary heart disease: a 10-year prospective study. Arterioscler Thromb Vasc Biol 32:2327–2335.
- 31. Chow WS, Tso AW, Xu A, Yuen MM, Fong CH, et al. (2013) Elevated circulating adipocyte-fatty acid binding protein levels predict incident cardiovascular events in a community-based cohort: a 12-year prospective study. J Am Heart Assoc 2:e004176.
- 32. Aragones G, Saavedra P, Heras M, Cabre A, Girona J, et al. (2012) Fatty acid-binding protein 4 impairs the insulin-dependent nitric oxide pathway in vascular endothelial cells. Cardiovasc Diabetol 11:72.
- 33. Brinkkoetter PT, Ising C, Benzing T (2013) The role of the podocyte in albumin filtration. Nat Rev Nephrol 9:328–336.
- 34. Satchell SC, Braet F (2009) Glomerular endothelial cell fenestrations: an integral component of the glomerular filtration barrier. Am J Physiol Renal Physiol 296:F947–956.
- 35. Sun YB, Qu X, Zhang X, Caruana G, Bertram JF, et al. (2013) Glomerular endothelial cell injury and damage precedes that of podocytes in adriamycin-induced nephropathy. PLoS ONE 8:e55027.
- 36. Toyoda M, Najafian B, Kim Y, Caramori ML, Mauer M (2007) Podocyte detachment and reduced glomerular capillary endothelial fenestration in human type 1 diabetic nephropathy. Diabetes 56:2155–2160.
- 37. Yuen DA, Stead BE, Zhang Y, White KE, Kabir MG, et al. (2012) eNOS deficiency predisposes podocytes to injury in diabetes. J Am Soc Nephrol 23:1810–1823.
- 38. Gilkeson GS, Mashmoushi AK, Ruiz P, Caza TN, Perl A, et al. (2013) Endothelial nitric oxide synthase reduces crescentic and necrotic glomerular lesions, reactive oxygen production, and MCP1 production in murine lupus nephritis. PLoS ONE 8:e64650.
- 39. Lee MY, Li H, Xiao Y, Zhou Z, Xu A, et al. (2011) Chronic administration of BMS309403 improves endothelial function in apolipoprotein E-deficient mice and in cultured human endothelial cells. Br J Pharmacol 162:1564–1576.
- 40. Miyoshi T, Doi M, Hirohata S, Kamikawa S, Usui S, et al. (2011) Olmesartan reduces arterial stiffness and serum adipocyte fatty acid-binding protein in hypertensive patients. Heart Vessels 26:408–413.
- 41. Furuhashi M, Mita T, Moniwa N, Hoshina K, Ishimura S, et al. (2014) Angiotensin II receptor blockers decrease serum concentration of fatty acid-binding protein 4 in patients with hypertension. Hypertens Res (in press).
- 42. Karpisek M, Stejskal D, Kotolova H, Kollar P, Janoutova G, et al. (2007) Treatment with atorvastatin reduces serum adipocyte-fatty acid binding protein value in patients with hyperlipidaemia. Eur J Clin Invest 37:637–642.