Fatty Acid Binding Proteins (FABPs), is a family of ten proteins named by the first tissues in which they were discovered (adipose, liver, heart, intestine, etc).  The most predominant functions for this family of proteins are related to their binding capacity for long-chain fatty acids (LCFAs) and other fat soluble molecules.  Through their binding capacity, FABPs are known to be critical for fatty acid uptake and intracellular transport, but also in important for regulation of lipid metabolism and cellular signaling.   These functions point to FABPs to be cytoprotectants to fatty acid oxidative stressors.

Specifically, Liver Fatty Acid Binding Protein (L-FABP), also called FABP1 (or FABP-1), is a 14 kDa protein that comprises 2-11% of the cytosolic protein of normal hepatocytes.  It is also expressed in tubular kidney cells, the aveolar epithelium of the lung and intestinal tissue.

FABP1 in Lipid Metabolism Research and Drug Development Studies
FABP1 levels and function are of interest to groups researching lipid metabolism.  PPARs are key regulators of lipid metabolism proteins (including FABP1 expression) and a binding partner of FABP1.  Thus, drugs that target PPARs ultimately influence FABP1 levels.

  • PPAR-1 agonists are fibrates, a class of drugs used in the treatment of dyslipidemia. Fibrates are often used in combination with other drugs, mainly statins, and effectively lower serum triglycerides and raise serum HDL-cholesterol levels. These PPAR-alpha agonists may carry therapeutic value for the treatment of non-alcoholic fatty liver disease (NASH).
  • PPAR-1 antagonists promote inflamed cell phenotypes and inflamed tumor microenvironment.

Lower levels of FABP1 in the liver leaves hepatocytes susceptible to the effects of lipid oxidation, however, higher levels of FABP1 may promote lipid accumulation.  Thus, FABP1 regulation likely acts as a control dial for many lipid and inflammation related diseases.

FABP1 as a Biomarker
Independent of its function, FABP1 has been identified as a useful biomarker in the areas of liver and kidney disease research.  Due to its small size, FABP1 is sensitive and early biomarker protein for liver and tubular kidney cell damage in vivo and in vitro.  When cells are damaged, cytosolic contents leak out of the cell into the serum.  Smaller biomarker proteins are often detected in circulation faster than the larger biomarker proteins typically used to study liver and kidney activity (ALT, AST, Albumin, NAG).

In the kidney, L-FABP is excreted in urine due to ischemia (or low capillary blood flow) and oxidative stress on renal tubule, before progression of tissue damage.  This is useful for early detection of renal damage accompanying tubular dysfunction.

In the liver, L-FABP is a sensitive marker of rapid hepatocyte lysis (toxicology assays and detection of liver damage during or after transplantation).  This could be a useful biomarker for early detection of NAFLD/NASH and other liver disease or transplantation research.

FABP1 can be a useful biomarker to researchers studying:

  • kidney disease: diabetic nephropathy, renal hypoxic stress, chronic kidney disease, acute kidney injury, cardiorenal syndrome
  • liver disease: cholesteric liver disease, drug-induced liver injury or DILI, NASH, hepatocellular carcinoma or HCC, alcoholic liver disease, cirrhosis, hepatic porphyria, liver transplantation and liver regeneration, chronic Hepatitis C
  • metabolic diseases: metabolic syndrome, diabetes, obesity
  • digestive disorders: intestinal ischemic syndrome
  • systemic inflammation

Diapharma’s FABP1 (L-FABP) ELISA Product Offerings:
Human FABP1 (L-FABP) High Sensitivity ELISA Kit Urine (from CMIC Holdings, Japan)
Human FABP1 (L-FABP) High Sensitivity ELISA Kit Serum (coming fall 2019)