[L-type fatty acid binding protein (L-FABP) and kidney disease]

Liver-type fatty acid binding protein (L-FABP) is expressed in the cytoplasm of human renal proximal tubules. Renal L-FABP expression is up-regulated and urinary excretion of renal L-FABP is increased by various stressors, such as urinary protein, hyperglycemia, tubular ischemia, toxins, and salt-sensitive hypertension, which lead to the progression of kidney disease. Urinary L-FABP levels accurately reflect the degree of tubulointerstitial damage and are strongly correlated with the prognosis of chronic kidney disease (CKD) patients in clinical studies. In patients with type I or type II diabetes, urinary L-FABP levels were reported to be significantly higher in patients with normal levels of urinary albumin than in those with microalbuminuria. Urinary L-FABP may be useful for the early detection of diabetic nephropathy. Furthermore, in a longitudinal study, a higher level of urinary L-FABP was found to be a risk factor for the progression of diabetic nephropathy. With respect to acute kidney disease (AKI), urinary L-FABP facilitates the early detection of AKI before an increase in serum creatinine. Therefore, urinary L-FABP was approved as a new tubular biomarker by the Ministry of Health, Labour and Welfare of Japan.