Urinary liver-type fatty acid binding protein as a useful biomarker in chronic kidney disease.

BACKGROUND: We reported that urinary L-FABP reflected the progression of chronic kidney disease (CKD). This study is aimed to evaluate the clinical significance of urinary liver type fatty acid binding protein (L-FABP) as a biomarker for monitoring CKD. METHODS: Urinary L-FABP was measured using human L-FABP ELISA kit (CMIC.Co., Ltd., Tokyo, Japan). The relations between urinary L-FABP and clinical parameters were evaluated in non-diabetic CKD (n = 48) for a year. In order to evaluate the influence of serum L-FABP derived from liver upon urinary L-FABP, both serum and urinary L-FABP were simultaneously measured in patients with CKD (n = 73). RESULTS: For monitoring CKD, the cut-off value in urinary L-FABP was determined as 17.4 microg/g.cr. by using a receiver operating characteristics (ROC) curve. Renal function deteriorated significantly more in patients with 'high' urinary L-FABP (n = 36) than in those with 'low' L-FABP (n = 12). The decrease in creatinine clearance was accompanied by an increase in urinary L-FABP, but not in urinary protein. Serum L-FABP in patients with CKD was not correlated with urinary L-FABP. CONCLUSION: Urinary excretion of L-FABP increases with the deterioration of renal function. Serum L-FABP did not influence on urinary L-FABP. Urinary L-FABP may be a useful clinical biomarker for monitoring CKD.

Clinical evaluation of urinary excretion of liver-type fatty acid-binding protein as a marker for the monitoring of chronic kidney disease: a multicenter trial.

To confirm the clinical usefulness of the measurement of urinary liver-type fatty acid-binding protein (L-FABP) in chronic kidney disease (CKD), we carried out a multicenter trial. Clinical markers were measured in patients with nondiabetic CKD (n = 48) every 1 to 2 months for a year. We divided patients retrospectively into progression (n = 32) and nonprogression (n = 16) groups on the basis of the rate of disease progression, then assessed several clinical markers. Initially creatinine clearance (Ccr) was similar in the 2 groups; however, the urinary L-FABP level was significantly higher in the former group than in the latter (111.5 vs 53 microg/g creatinine, P < .001). For the monitoring CKD, we set the cutoff values for urinary L-FABP and urinary protein at 17.4 microg/g creatinine and 1.0 g/g creatinine, respectively. Urinary L-FABP was more sensitive than urinary protein in predicting the progression of CKD (93.8% and 68.8%, respectively). However, urinary protein showed greater specificity than did urinary L-FABP (93.8% and 62.5%, respectively). Over time, the progression of CKD tended to correlate with changes in urinary L-FABP (r = - .32, P < .05), but not in urinary protein (r = .18, not significant). The dynamics of urinary protein differed from that of urinary L-FABP, which increased as Ccr declined. Urinary L-FABP is more sensitive than urinary protein in predicting the progression of CKD. Urinary excretion of L-FABP increases with the deterioration of kidney function. Urinary L-FABP is therefore a useful clinical marker in the monitoring of CKD.

Urinary excretion of liver fatty acid-binding protein in health-check participants.

BACKGROUND: Messenger RNA of liver fatty acid-binding protein (L-FABP) is expressed in proximal tubules of the kidney, and a certain amount is excreted into urine. We analyzed factors relating to the urinary L-FABP excretion in health-check participants. METHODS: We measured L-FABP in the first morning urine by ELISA in 715 men and 193 women 30-79 years of age who entered a 2-day hospitalized health checkup program. In addition to the routine physical examination and laboratory tests, plasma high-sensitivity C-reactive protein (HSCRP) was assayed. RESULTS: In 150 healthy subjects, urinary L-FABP averaged 3.6 +/- 0.2 microg/g creatinine, whereas the values were significantly increased in patients with hypertension (5.2 +/- 0.4, P = 0.010), diabetes mellitus (5.5 +/- 0.5, P < 0.001), and chronic hepatitis (5.8 +/- 1.0, P = 0.022). Urinary L-FABP excretion was significantly greater in women than in men when the value was related to creatinine. In regression analysis in men, urinary L-FABP was positively correlated with fasting plasma glucose (r = 0.103, P = 0.033) and plasma HSCRP (r = 0.135, P = 0.006). CONCLUSIONS: It is suggested that renal production and urinary excretion of L-FABP are increased in situations in which arteriosclerosis is promoted, such as hypertension, diabetes mellitus, and cardiovascular inflammation.

Urinary excretion of fatty acid-binding protein reflects stress overload on the proximal tubules.

Urinary excretion of human liver-type fatty acid-binding protein (hL-FABP), which is expressed in human proximal tubules and engaged in free fatty acid (FFA) metabolism, was reported to reflect the clinical prognosis of chronic kidney disease. Here we have investigated the pathophysiological significance of hL-FABP in a model of protein overload nephropathy. Because L-FABP is not expressed in the wild-type mice, we generated hL-FABP chromosomal gene transgenic (Tg) mice. Tg mice were intraperitoneally injected with bovine serum albumin (BSA) replete with FFAs (r-BSA group) or FFA-depleted BSA (d-BSA group). The r-BSA group developed significantly more severe tubulointerstitial damage than did the d-BSA group. Renal expression of the hL-FABP gene was more up-regulated, and urinary excretion of hL-FABP was significantly higher, in the r-BSA group than in the d-BSA group. Furthermore, compared with their wild-type littermates injected with r-BSA, the number of infiltrated macrophages was significantly attenuated in Tg mice injected with it on day 28. In patients with kidney disease (n = 50), urinary hL-FABP was correlated with both urinary protein and the severity of tubulointerstitial injury. In conclusion, our experimental model suggests that urinary excretion of hL-FABP reflects stresses, such as urinary protein overload, on the proximal tubules. The clinical observations support this hypothesis.

Urinary fatty acid-binding protein as a new clinical marker of the progression of chronic renal disease.

Previous studies have indicated that in massive proteinuria, free fatty acids (FFAs) bound to albumin were overloaded in the proximal tubule and exacerbated tubulointerstitial damage. Liver-type fatty acid-binding protein (L-FABP) is an intracellular carrier protein of FFAs that is expressed in the proximal tubule of human kidney. We sought to evaluate urinary L-FABP as a clinical marker in chronic renal disease. Urinary L-FABP was measured in patients with nondiabetic chronic renal disease (n = 120) with the use of a newly established ELISA method. We then monitored these patients for 15 to 51 months. Clinical data were analyzed with multivariate analysis. Urinary L-FABP was correlated with urinary protein, urinary alpha(1)-microglobulin, and serum creatinine concentrations. Urinary L-FABP at the start of follow-up (F = 17.1, r =.36, P <.0001) was selected as a significant clinical factor correlated with the progression rate, defined as a slope of a reciprocal of serum creatinine over time. We next selected the patients with mild renal dysfunction (n = 35) from all 120 patients and divided them into 2 groups according to progression rate: the progression group (n = 22) and the nonprogression group (n = 13). Serum creatinine and urinary protein concentrations and blood pressure at the start of follow-up were higher in the progression group than in the nonprogression group, although we detected no significant difference between the 2 groups. Urinary L-FABP was significantly higher in the former group than in the latter (P <.05). The results showed that urinary L-FABP reflected the clinical prognosis of chronic renal disease. Urinary L-FABP may be a clinical marker that can help predict the progression of chronic glomerular disease.

[Urinary fatty acid binding protein as a new clinical marker for the progression of chronic renal disease].

BACKGROUND: As free fatty acids are loaded into the proximal tubule during various kinds of stresses and become cytotoxic, they may play an important role in the progression of renal disease. The proximal tubular epithelial cells express liver-type fatty acid binding protein(L-FABP), an intracellular carrier protein of fatty acids. We hypothesized that urinary L-FABP reflected stresses on the proximal tubule and thus presents a new clinical marker for the progression of renal disease. METHODS: ELISA for L-FABP was established and relations between urinary L-FABP and clinical parameters from non-diabetic chronic renal disease (n = 120) were evaluated. RESULTS: Laboratory data revealed a correlation between urinary L-FABP and urinary protein (F = 22.7), urinary alpha 1-microglobulin (F = 13.9) and serum creatinine (F = 11.4). Notably only urinary L-FABP at the start of follow-up (F = 17.1) was selected as a significant clinical factor correlated with the progression rate defined as a slope of a reciprocal of serum creatinine over time. The results indicated that urinary L-FABP was correlated with the clinical prognosis of renal disease. CONCLUSION: Urinary L-FABP is a new clinical marker for predicting the progression of chronic glomerular disease.